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1

MARKOV CHAIN APPROXIMATIONS FOR TRANSITION DENSITIES OF LEVY PROCESSES  

E-Print Network (OSTI)

MARKOV CHAIN APPROXIMATIONS FOR TRANSITION DENSITIES OF L´EVY PROCESSES ALEKSANDAR MIJATOVI for the existence of transition densities of X, we establish sharp convergence rates of the normalised probability class with applications in diverse areas such as mathematical finance, risk management, insurance

2

Crystallization of polyethylene by modified weighted density approximation(MWDA)  

E-Print Network (OSTI)

In this article, we use the modified weighted density approximation to study the crystallization of polyethylene. We also use a direct correlation function of polyethylene based on RISM theory. The free energy of a polyethylene is calculated using density functional theory. The crystallization and solid and liquid density are calculated and finally compared with the prism simulation and experimental results. That shown the result obtained by MWDA is in better agreement, compared with the experimental result than the prism.

Razeghizadeh, Alireza; Lavafpour, Farhad

2015-01-01T23:59:59.000Z

3

Crystallization of polyethylene by modified weighted density approximation(MWDA)  

E-Print Network (OSTI)

In this article, we use the modified weighted density approximation to study the crystallization of polyethylene. We also use a direct correlation function of polyethylene based on RISM theory. The free energy of a polyethylene is calculated using density functional theory. The crystallization and solid and liquid density are calculated and finally compared with the prism simulation and experimental results. That shown the result obtained by MWDA is in better agreement, compared with the experimental result than the prism.

Alireza Razeghizadeh; Vahdat Rafee; Farhad Lavafpour

2015-02-07T23:59:59.000Z

4

Generalized local-density approximation for spherical potentials  

Science Journals Connector (OSTI)

An alternative density functional for the spherical approximation of cell potentials is formulated. It relies on overlapping atomic spheres for the calculation of the kinetic energy, similar to the atomic sphere approximation (ASA), however, a shape correction is used that has the same form as the interstitial treatment in the nonoverlapping muffin-tin (MT) approach. The intersite Coulomb energy is evaluated using the Madelung energy as computed in the MT approach, while the on-site Coulomb energy is calculated using the ASA. The Kohn-Sham equations for the functional are then solved self-consistently. The ASA is known to give poor elastic constants and good point defect energies. Conversely the MT approach gives good elastic constants and poor point defect energies. The proposed new functional maintains the simplicity of the spherical potentials found in the ASA and MT approaches, but gives good values for both elastic constants and point defects. This solution avoids a problem, absent in the ASA but suffered by the MT approximation, of incorrect distribution of site charges when charge transfer is large. Relaxation of atomic positions is thus facilitated. Calculations confirm that the approach gives similar elastic constants to the MT approximation, and defect formation energies similar to those obtained with ASA.

X.-G. Zhang and D. M. C. Nicholson

1999-08-15T23:59:59.000Z

5

A mesh-free convex approximation scheme for KohnSham density functional theory  

E-Print Network (OSTI)

A mesh-free convex approximation scheme for Kohn­Sham density functional theory Phanish: Convex approximation scheme Mesh-free methods Kohn­Sham Density functional theory Maximum-entropy a b s t r a c t Density functional theory developed by Hohenberg, Kohn and Sham is a widely accepted

Ortiz, Michael

6

Double-hybrid density-functional theory with meta-generalized-gradient approximations  

E-Print Network (OSTI)

Double-hybrid density-functional theory with meta-generalized-gradient approximations Sidi Ould-parameter double-hybrid density-functional theory [K. Sharkas, J. Toulouse, and A. Savin, J. Chem. Phys. 134 of the most accurate approximations for electronic-structure calculations within density- functional theory

Paris-Sud XI, Université de

7

Approximating Probability Density Functions with Mixtures of Truncated Exponentials  

E-Print Network (OSTI)

). Thus, the parameters to be estimated are a 0k , a 1k , a 2k ,a 3k , b (j) 1k ,b (j) 2k and b (j) 3k . Define ? ? (k) (x;? mk ) (abbreviated ? ? (k) (x)) as the initial MTE approximation for PDF f X (x) in interval D k .To estimate the parameters ? mk... = {a 0mk ,a 1mk ,a 2mk ,a 3mk ,b (j) 1mk ,b (j) 2mk ,b (j) 3mk } in (1), the discrete approximation to KL divergence between the standard PDF and the MTE approximation is minimized sub- ject to continuity, probability mass and non-negativity constraints...

Cobb, Barry R.; Shenoy, Prakash P.; Rumi, Rafael

2004-07-01T23:59:59.000Z

8

Density-functional theory of nonuniform classical liquids: An extended modified weighted-density approximation  

E-Print Network (OSTI)

Density-functional theory of nonuniform classical liquids: An extended modified weighted-density the approximationstreat long-rangeand short-rangepotentials. I. INTRODUCTION The density-functional theory of nonuniform of density- functional theory to the problem of freezing of classical liquids,4 and in particular

Likos, Christos N.

9

Range-separated density-functional theory with random phase approximation: Detailed formalism and illustrative applications  

E-Print Network (OSTI)

Range-separated density-functional theory with random phase approximation: Detailed formalism-body theory, we present the details of a formally exact adiabatic-connection fluctuation-dissipation density-functional´an, Phys. Rev. Lett. 102, 096404 (2009). Range-separated density-functional theory approaches combining

Boyer, Edmond

10

The low-energy nuclear density of states and the saddle point approximation  

E-Print Network (OSTI)

The nuclear density of states plays an important role in nuclear reactions. At high energies, above a few MeV, the nuclear density of states is well described by a formula that depends on the smooth single particle density of states at the Fermi surface, the nuclear shell correction and the pairing energy. In this paper we present an analysis of the low energy behaviour of the nuclear density of states using the saddle point approximation and extensions to it. Furthermore, we prescribe a simple parabolic form for excitation energy, in the low energy limit, which may facilitate an easy computation of level densities.

Sanjay K. Ghosh; Byron K. Jennings

2001-07-30T23:59:59.000Z

11

Modeling of free electronic state density in hydrogenic plasmas based on nearest neighbor approximation  

SciTech Connect

Most conventional atomic models in a plasma do not treat the effect of the plasma on the free-electron state density. Using a nearest neighbor approximation, the state densities in hydrogenic plasmas for both bound and free electrons were evaluated and the effect of the plasma on the atomic model (especially for the state density of the free electron) was studied. The model evaluates the electron-state densities using the potential distribution formed by the superposition of the Coulomb potentials of two ions. The potential from one ion perturbs the electronic state density on the other. Using this new model, one can evaluate the free-state density without making any ad-hoc assumptions. The resulting contours of the average ionization degree, given as a function of the plasma temperature and density, are shifted slightly to lower temperatures because of the effect of the increasing free-state density.

Nishikawa, Takeshi, E-mail: nishikawa.takeshi@okayama-u.ac.jp [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan)

2014-07-15T23:59:59.000Z

12

Generalized local-density approximation and one-dimensional finite uniform electron gases  

E-Print Network (OSTI)

We explicitly build a generalized local-density approximation (GLDA) correlation functional based on one-dimensional (1D) uniform electron gases (UEGs). The fundamental parameters of the GLDA \\textemdash a generalization of the widely-known local-density approximation (LDA) used in density-functional theory (DFT) \\textemdash are the electronic density $\\rho$ and a newly-defined two-electron local parameter called the hole curvature $\\eta$. The UEGs considered in this study are finite versions of the conventional infinite homogeneous electron gas and consist of $n$ electrons on a infinitely thin wire with periodic boundary conditions. We perform a comprehensive study of these finite UEGs at high, intermediate and low densities using perturbation theory and quantum Monte Carlo calculations. We show that the present GLDA functional yields accurate estimates of the correlation energy for both weakly and strongly correlated one-dimensional systems and can be easily generalized to higher-dimensional systems.

Loos, Pierre-Franois

2014-01-01T23:59:59.000Z

13

Superfluid Local Density Approximation: A Density Functional Theory Approach to the Nuclear Pairing Problem  

E-Print Network (OSTI)

I describe the foundation of a Density Functional Theory approach to include pairing correlations, which was applied to a variety of systems ranging from dilute fermions, to neutron stars and finite nuclei. Ground state properties as well as properties of excited states and time-dependent phenomena can be achieved in this manner within a formalism based on microscopic input.

Aurel Bulgac

2012-04-10T23:59:59.000Z

14

Secrets of the Greatest Snow on Earth  

Science Journals Connector (OSTI)

State license plates and tourism brochures boast that Utah ski areas receive the greatest snow on Earth, but is there really anything special about Utah's snow? Often it is argued in ski industry brochures that Utah's snow is the greatest ...

W. James Steenburgh; Trevor I. Alcott

2008-09-01T23:59:59.000Z

15

Double-hybrid density-functional theory with meta-generalized-gradient approximations  

SciTech Connect

We extend the previously proposed one-parameter double-hybrid density-functional theory [K. Sharkas, J. Toulouse, and A. Savin, J. Chem. Phys. 134, 064113 (2011)] to meta-generalized-gradient-approximation (meta-GGA) exchange-correlation density functionals. We construct several variants of one-parameter double-hybrid approximations using the Tao-Perdew-Staroverov-Scuseria (TPSS) meta-GGA functional and test them on test sets of atomization energies and reaction barrier heights. The most accurate variant uses the uniform coordinate scaling of the density and of the kinetic energy density in the correlation functional, and improves over both standard Kohn-Sham TPSS and second-order Mller-Plesset calculations.

Souvi, Sidi M. O., E-mail: sidi.souvi@irsn.fr; Sharkas, Kamal; Toulouse, Julien, E-mail: julien.toulouse@upmc.fr [Sorbonne Universits, UPMC Univ Paris 06, UMR 7616, Laboratoire de Chimie Thorique, F-75005 Paris (France) [Sorbonne Universits, UPMC Univ Paris 06, UMR 7616, Laboratoire de Chimie Thorique, F-75005 Paris (France); CNRS, UMR 7616, Laboratoire de Chimie Thorique, F-75005 Paris (France)

2014-02-28T23:59:59.000Z

16

Transverse exchange energy in relativistic density-functional calculations: An alternative approximation  

Science Journals Connector (OSTI)

The large error of the local-density approximation for the transverse photon-electron or Breit interaction is analyzed, transforming the Breit interaction into a sum of terms suitable to be handled in a nonrelativistic formalism: the local approximation for each of these terms is built up and an alternative expression for the relativistic exchange energy is proposed. Calculations using this expression are made for atoms ranging throughout the periodic table and the results show a sharp improvement when compared to those obtained by the previous approximation.

Mauro Boero and Pietro Cortona

1994-02-01T23:59:59.000Z

17

The slowly varying density approximation for the surface tension and surface energy of  

Science Journals Connector (OSTI)

We present a detailed study of the validity of the slowly varying density approximation to calculate the surface tension and the surface energy of Lennard-Jones fluids. To do so, we consider three explicit analytical expressions for the radial distribution function of the liquid phase, including one proposed by our research group, together with very accurate expressions for the liquid and vapour densities, also proposed by ourselves. The calculation of the surface tension from the direct correlation function using the PercusYevick and the hypernetted-chain approximations is also considered. Finally, our results are compared with those obtained by other authors by computer simulation, and also with those estimated via the general expressions (i.e., not in the ambit of the approximation studied here). We demonstrate that although the slowly varying density approximation is in good agreement with more complex expressions near the critical point, it is not adequate to calculate the surface energy and the surface tension of Lennard-Jones fluids at every temperature.

A Mulero; C Galn; F Cuadros

2003-01-01T23:59:59.000Z

18

Fundamental gaps with approximate density functionals: The derivative discontinuity revealed from ensemble considerations  

SciTech Connect

The fundamental gap is a central quantity in the electronic structure of matter. Unfortunately, the fundamental gap is not generally equal to the Kohn-Sham gap of density functional theory (DFT), even in principle. The two gaps differ precisely by the derivative discontinuity, namely, an abrupt change in slope of the exchange-correlation energy as a function of electron number, expected across an integer-electron point. Popular approximate functionals are thought to be devoid of a derivative discontinuity, strongly compromising their performance for prediction of spectroscopic properties. Here we show that, in fact, all exchange-correlation functionals possess a derivative discontinuity, which arises naturally from the application of ensemble considerations within DFT, without any empiricism. This derivative discontinuity can be expressed in closed form using only quantities obtained in the course of a standard DFT calculation of the neutral system. For small, finite systems, addition of this derivative discontinuity indeed results in a greatly improved prediction for the fundamental gap, even when based on the most simple approximate exchange-correlation density functional the local density approximation (LDA). For solids, the same scheme is exact in principle, but when applied to LDA it results in a vanishing derivative discontinuity correction. This failure is shown to be directly related to the failure of LDA in predicting fundamental gaps from total energy differences in extended systems.

Kraisler, Eli; Kronik, Leeor [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100 (Israel)] [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100 (Israel)

2014-05-14T23:59:59.000Z

19

Thermally-assisted-occupation density functional theory with generalized-gradient approximations  

SciTech Connect

We extend the recently proposed thermally-assisted-occupation density functional theory (TAO-DFT) [J.-D. Chai, J. Chem. Phys. 136, 154104 (2012)] to generalized-gradient approximation (GGA) exchange-correlation density functionals. Relative to our previous TAO-LDA (i.e., the local density approximation to TAO-DFT), the resulting TAO-GGAs are significantly superior for a wide range of applications, such as thermochemistry, kinetics, and reaction energies. For noncovalent interactions, TAO-GGAs with empirical dispersion corrections are shown to yield excellent performance. Due to their computational efficiency for systems with strong static correlation effects, TAO-LDA and TAO-GGAs are applied to study the electronic properties (e.g., the singlet-triplet energy gaps, vertical ionization potentials, vertical electron affinities, fundamental gaps, and symmetrized von Neumann entropy) of acenes with different number of linearly fused benzene rings (up to 100), which is very challenging for conventional electronic structure methods. The ground states of acenes are shown to be singlets for all the chain lengths studied here. With the increase of acene length, the singlet-triplet energy gaps, vertical ionization potentials, and fundamental gaps decrease monotonically, while the vertical electron affinities and symmetrized von Neumann entropy (i.e., a measure of polyradical character) increase monotonically.

Chai, Jeng-Da, E-mail: jdchai@phys.ntu.edu.tw [Department of Physics, Center for Theoretical Sciences, and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)] [Department of Physics, Center for Theoretical Sciences, and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

2014-05-14T23:59:59.000Z

20

Self-Consistent Fermi-Liquid Properties and Density of States for Nuclear Many-Body Approximations  

Science Journals Connector (OSTI)

......Properties and Density of States for Nuclear Many-Body Approximations...compression modulus, symmetry energy and Landau parameters. We...Fermi surface by discussing nuclear matter approximations in terms...observable to be determined from nuclear many-body approximations......

Hiroshi Uechi

1991-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Uniform electron gases. II. The generalized local density approximation in one dimension  

SciTech Connect

We introduce a generalization (gLDA) of the traditional Local Density Approximation (LDA) within density functional theory. The gLDA uses both the one-electron Seitz radius r{sub s} and a two-electron hole curvature parameter ? at each point in space. The gLDA reduces to the LDA when applied to the infinite homogeneous electron gas but, unlike the LDA, it is also exact for finite uniform electron gases on spheres. We present an explicit gLDA functional for the correlation energy of electrons that are confined to a one-dimensional space and compare its accuracy with LDA, second- and third-order Mller-Plesset perturbation energies, and exact calculations for a variety of inhomogeneous systems.

Loos, Pierre-Franois, E-mail: pf.loos@anu.edu.au; Ball, Caleb J.; Gill, Peter M. W., E-mail: peter.gill@anu.edu.au [Research School of Chemistry, Australian National University, Canberra ACT 0200 (Australia)] [Research School of Chemistry, Australian National University, Canberra ACT 0200 (Australia)

2014-05-14T23:59:59.000Z

22

Oak Ridge Removes Laboratory's Greatest Source of Groundwater...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Removes Laboratory's Greatest Source of Groundwater Contamination Oak Ridge Removes Laboratory's Greatest Source of Groundwater Contamination May 1, 2012 - 12:00pm Addthis Workers...

23

Approximating probability density functions in hybrid Bayesian networks with mixtures of truncated exponentials  

E-Print Network (OSTI)

be marginalized in closed form. This allows propagation to be done exactly using the Shenoy-Shafer architecture for computing marginals, with no restrictions on the construction of a join tree. This paper presents MTE potentials that approximate standard PDF...

Cobb, Barry R.; Shenoy, Prakash P.; Rumi, Rafael

2006-09-01T23:59:59.000Z

24

Improved approximation algorithms for low-density instances of the Minimum Entropy Set Cover Problem  

Science Journals Connector (OSTI)

Abstract We study the approximability of instances of the minimum entropy set cover problem, parameterized by the average frequency of a random element in the covering sets. We analyze an algorithm combining a greedy approach with another one biased towards large sets. The algorithm is controlled by the percentage of elements to which we apply the biased approach. The optimal parameter choice leads to improved approximation guarantees when average element frequency is less than e.

Cosmin Bonchi?; Gabriel Istrate

2014-01-01T23:59:59.000Z

25

Oak Ridge Removes Laboratory's Greatest Source of Groundwater  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Oak Ridge Removes Laboratory's Greatest Source of Groundwater Oak Ridge Removes Laboratory's Greatest Source of Groundwater Contamination Oak Ridge Removes Laboratory's Greatest Source of Groundwater Contamination May 1, 2012 - 12:00pm Addthis Workers remove the 4,000-gallon Tank W-1A, which was ORNL’s greatest source of groundwater contamination. Workers remove the 4,000-gallon Tank W-1A, which was ORNL's greatest source of groundwater contamination. Workers load boxes containing contaminated soil that surrounded Tank W-1A. Workers load boxes containing contaminated soil that surrounded Tank W-1A. The 6,500-pound Tank W-1A is shipped away from ORNL. The 6,500-pound Tank W-1A is shipped away from ORNL. Workers remove the 4,000-gallon Tank W-1A, which was ORNL's greatest source of groundwater contamination. Workers load boxes containing contaminated soil that surrounded Tank W-1A.

26

Oak Ridge Removes Laboratory's Greatest Source of Groundwater  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Oak Ridge Removes Laboratory's Greatest Source of Groundwater Oak Ridge Removes Laboratory's Greatest Source of Groundwater Contamination Oak Ridge Removes Laboratory's Greatest Source of Groundwater Contamination May 1, 2012 - 12:00pm Addthis Workers remove the 4,000-gallon Tank W-1A, which was ORNL’s greatest source of groundwater contamination. Workers remove the 4,000-gallon Tank W-1A, which was ORNL's greatest source of groundwater contamination. Workers load boxes containing contaminated soil that surrounded Tank W-1A. Workers load boxes containing contaminated soil that surrounded Tank W-1A. The 6,500-pound Tank W-1A is shipped away from ORNL. The 6,500-pound Tank W-1A is shipped away from ORNL. Workers remove the 4,000-gallon Tank W-1A, which was ORNL's greatest source of groundwater contamination. Workers load boxes containing contaminated soil that surrounded Tank W-1A.

27

Density functional theory for the description of spherical non-associating monomers in confined media using the SAFT-VR equation of state and weighted density approximations  

SciTech Connect

As a first step of an ongoing study of thermodynamic properties and adsorption of complex fluids in confined media, we present a new theoretical description for spherical monomers using the Statistical Associating Fluid Theory for potential of Variable Range (SAFT-VR) and a Non-Local Density Functional Theory (NLDFT) with Weighted Density Approximations (WDA). The well-known Modified Fundamental Measure Theory is used to describe the inhomogeneous hard-sphere contribution as a reference for the monomer and two WDA approaches are developed for the dispersive terms from the high-temperature Barker and Henderson perturbation expansion. The first approach extends the dispersive contributions using the scalar and vector weighted densities introduced in the Fundamental Measure Theory (FMT) and the second one uses a coarse-grained (CG) approach with a unique weighted density. To test the accuracy of this new NLDFT/SAFT-VR coupling, the two versions of the theoretical model are compared with Grand Canonical Monte Carlo (GCMC) molecular simulations using the same molecular model. Only the version with the CG approach for the dispersive terms provides results in excellent agreement with GCMC calculations in a wide range of conditions while the FMT extension version gives a good representation solely at low pressures. Hence, the CG version of the theoretical model is used to reproduce methane adsorption isotherms in a Carbon Molecular Sieve and compared with experimental data after a characterization of the material. The whole results show an excellent agreement between modeling and experiments. Thus, through a complete and consistent comparison both with molecular simulations and with experimental data, the NLDFT/SAFT-VR theory has been validated for the description of monomers.

Malheiro, Carine; Mendiboure, Bruno; Plantier, Frdric; Miqueu, Christelle [Universit Pau et Pays Adour, CNRS, TOTAL - UMR 5150 LFC-R Laboratoire des Fluides Complexes et leurs Rservoirs, BP 1155 PAU, F-64013 (France)] [Universit Pau et Pays Adour, CNRS, TOTAL - UMR 5150 LFC-R Laboratoire des Fluides Complexes et leurs Rservoirs, BP 1155 PAU, F-64013 (France); Blas, Felipe J. [Departamento de Fsica Aplicada, and Centro de Fsica Terica y Matemtica FIMAT, Universidad de Huelva, 21071 Huelva (Spain)] [Departamento de Fsica Aplicada, and Centro de Fsica Terica y Matemtica FIMAT, Universidad de Huelva, 21071 Huelva (Spain)

2014-04-07T23:59:59.000Z

28

What the World's Greatest Energy Managers Do Differently  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

the World's GREATEST the World's GREATEST Energy Managers Do Differently? Nasr Alkadi, PhD, CEM U.S. DOE Advanced Manufacturing Office (AMO) Tuesday Webcast for Industry Role of an Energy Manager July 10, 2012 Oak Ridge National Laboratory (ORNL) is DOE's Largest Science and Energy Laboratory  World's most powerful open scientific computer  Operating the world's most intense pulsed neutron source and a world-class research reactor  $1.4B budget  4,550 employees  4,000 research guests annually  $500M invested in modernization  Nation's most diverse energy portfolio  Nation's largest

29

Panama Canal One of the Greatest Engineering Feats of the  

E-Print Network (OSTI)

Panama Canal One of the Greatest Engineering Feats of the 20th Century #12;Panama Problem So, what's the Panama Problem? Treacherous trip around Cape Horn, the southernmost tip of South America Countless number;History - The French Attempt February 1, 1881 - France begins work on Panama Canal French Plan: dig

Provancher, William

30

Insulating gap in the transition-metal oxides: A calculation using the local-spin-density approximation with the on-site Coulomb U correlation correction  

Science Journals Connector (OSTI)

The electron-electron correlation has been considered by using the local-spin-density approximation (LSDA) with on-site Coulomb interaction (LSDA+U) in the first-principles discrete variational cluster method. Based on the correction to LSDA, we have carried out the self-consistent electronic-structure calculations for the strongly correlated electronic systems of NiO, CoO, and FeO. In contrast to LSDA, the LSDA+U calculations reveal the experimentally observed antiferromagnetic and insulating ground state. The values of the energy gap and the magnetic moment for these compounds are in good agreement with experimental results. The calculations suggest that the energy gap changes from the Mott-Hubbard characters for the early-3d-transition-metal monoxide to charge-transfer character for the late-3d-transition-metal monoxide.

Pan Wei and Zheng Qing Qi

1994-04-15T23:59:59.000Z

31

e/a classification of HumeRothery Rhombic Triacontahedron-type approximants based on all-electron density functional theory calculations  

SciTech Connect

There are three key electronic parameters in elucidating the physics behind the HumeRothery electron concentration rule: the square of the Fermi diameter (2kF)2, the square of the critical reciprocal lattice vector and the electron concentration parameter or the number of itinerant electrons per atom e/a. We have reliably determined these three parameters for 10 Rhombic Triacontahedron-type 2/12/12/1 (N?=?680) and 1/11/11/1 (N?=?160162) approximants by making full use of the full-potential linearized augmented plane wave-Fourier band calculations based on all-electron density-functional theory. We revealed that the 2/12/12/1 approximants Al13Mg27Zn45 and Na27Au27Ga31 belong to two different sub-groups classified in terms of equal to 126 and 109 and could explain why they take different e/a values of 2.13 and 1.76, respectively. Among eight 1/11/11/1 approximants Al3Mg4Zn3, Al9Mg8Ag3, Al21Li13Cu6, Ga21Li13Cu6, Na26Au24Ga30, Na26Au37Ge18, Na26Au37Sn18 and Na26Cd40Pb6, the first two, the second two and the last four compounds were classified into three sub-groups with ?=?50, 46 and 42; and were claimed to obey the e/a?=?2.30, 2.102.15 and 1.701.80 rules, respectively.

Mizutani, U.; Inukai, M.; Sato, H.; Zijlstra, E.S.; Lin, Q.

2014-05-16T23:59:59.000Z

32

Electronic band structure of LiInSe2: A first-principles study using the Tran-Blaha density functional and GW approximation  

Science Journals Connector (OSTI)

Abstract Using first-principles theoretical techniques within density functional theory and many-body perturbation theory we investigated the structural and electronic properties of two LiInSe2 crystal modifications, orthorhombic (?-NaFeO2-type) and tetragonal (CuFeS2-type), focusing on the interband transitions and band gaps. It is found that the Tran-Blaha (TB09) functional predicts LiInSe2 to be a direct-gap semiconductor with a significantly larger band gap as compared with that from common local-density and gradient-corrected functionals. The most accurate values of the fundamental energy gaps are calculated within quasiparticle GW approximation and found to be 2.95eV for the orthorhombic phase and 2.85eV for the tetragonal one, with equal pressure coefficients of 63meV/GPa. Our theoretical results eliminate the uncertainty in the band gap of LiInSe2. Moreover, the data obtained define the upper limit of the band gap of solid solutions (Cu,Li)InSe2 and (Ag,Li)InSe2, which can be of interest for applications in optoelectronics.

A.V. Kosobutsky; Yu.M. Basalaev

2014-01-01T23:59:59.000Z

33

Question of the Week: What Change Has Made the Greatest Difference in the  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Change Has Made the Greatest Difference Change Has Made the Greatest Difference in the Efficiency of Your Home? Question of the Week: What Change Has Made the Greatest Difference in the Efficiency of Your Home? January 29, 2009 - 10:24am Addthis Many of our readers have commented on changes, both large and small, that they've made to improve the comfort and energy efficiency of their homes. The changes that will make the greatest difference can vary depending on your location, the age of your home, and the improvements needed, but tell us: What change have you made that has made the greatest difference in improving the comfort and efficiency of your home? E-mail your responses to the Energy Saver team at consumer.webmaster@nrel.gov. Addthis Related Articles Question of the Week: What Change Has Made the Greatest Difference in the Efficiency of Your Home?

34

Question of the Week: What Change Has Made the Greatest Difference in the  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Change Has Made the Greatest Difference Change Has Made the Greatest Difference in the Efficiency of Your Home? Question of the Week: What Change Has Made the Greatest Difference in the Efficiency of Your Home? January 29, 2009 - 10:24am Addthis Many of our readers have commented on changes, both large and small, that they've made to improve the comfort and energy efficiency of their homes. The changes that will make the greatest difference can vary depending on your location, the age of your home, and the improvements needed, but tell us: What change have you made that has made the greatest difference in improving the comfort and efficiency of your home? E-mail your responses to the Energy Saver team at consumer.webmaster@nrel.gov. Addthis Related Articles Question of the Week: What Change Has Made the Greatest Difference in the Efficiency of Your Home?

35

Exploring the limit of accuracy for density functionals based on the generalized gradient approximation: Local, global hybrid, and range-separated hybrid functionals with and without dispersion corrections  

SciTech Connect

The limit of accuracy for semi-empirical generalized gradient approximation (GGA) density functionals is explored by parameterizing a variety of local, global hybrid, and range-separated hybrid functionals. The training methodology employed differs from conventional approaches in 2 main ways: (1) Instead of uniformly truncating the exchange, same-spin correlation, and opposite-spin correlation functional inhomogeneity correction factors, all possible fits up to fourth order are considered, and (2) Instead of selecting the optimal functionals based solely on their training set performance, the fits are validated on an independent test set and ranked based on their overall performance on the training and test sets. The 3 different methods of accounting for exchange are trained both with and without dispersion corrections (DFT-D2 and VV10), resulting in a total of 491508 candidate functionals. For each of the 9 functional classes considered, the results illustrate the trade-off between improved training set performance and diminished transferability. Since all 491508 functionals are uniformly trained and tested, this methodology allows the relative strengths of each type of functional to be consistently compared and contrasted. The range-separated hybrid GGA functional paired with the VV10 nonlocal correlation functional emerges as the most accurate form for the present training and test sets, which span thermochemical energy differences, reaction barriers, and intermolecular interactions involving lighter main group elements.

Mardirossian, Narbe; Head-Gordon, Martin, E-mail: mhg@cchem.berkeley.edu [Department of Chemistry, University of California, Berkeley and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California, Berkeley and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2014-05-14T23:59:59.000Z

36

Fish Species of Greatest Conservation Need in Iowa's Nonwadeable Rivers: Distribution, Relative Abundance, and Influences from  

E-Print Network (OSTI)

Fish Species of Greatest Conservation Need in Iowa's Nonwadeable Rivers: Distribution, Relative of fish species of greatest conservation need in Iowa's nonwadeable rivers. · Evaluate the influence of potential movement barriers and anthropogenic stressors on fish distributions in Iowa's nonwadeable rivers

Koford, Rolf R.

37

Climate change is one of the greatest threats facing us today. CICERO's mission  

E-Print Network (OSTI)

Climate change is one of the greatest threats facing us today. CICERO's mission is to provide reliable and comprehensive knowledge about all aspects of the climate change problem. Foto: Scanpix #12;Climate change is one of the greatest threats facing us today. CICERO's mission is to provide reliable

Johansen, Tom Henning

38

Marine Biodiversity and Conservation "One of the greatest scientific challenges facing society today is understanding,  

E-Print Network (OSTI)

Marine Biodiversity and Conservation "One of the greatest scientific challenges facing society W L T O N Director, Center for Marine Biodiversity and Conservation, Scripps Institution the way in conducting the research essential for under- standing and conserving marine biodiversity

Levin, Lisa

39

STUDENT GOVERNMENT ASSOCIATION The Student Government Association, or "SGA", has the greatest student representative  

E-Print Network (OSTI)

_____________________________________________________________________________ STUDENT GOVERNMENT ASSOCIATION The Student Government Association, or "SGA", has the greatest student representative authority on campus. The Student Government Association receives a $4.50 per student per quarter student-assessed fee

Selmic, Sandra

40

Electronic structure of La2CuO4 and YBa2Cu3O6: A local-spin-density approximation with on-site Coulomb-U correlation calculations  

Science Journals Connector (OSTI)

The electron-electron correlation has been considered by using the local-spin-density approximation (LSDA) with on-site Coulomb interaction in the first-principles discrete variational cluster method. Based on the correction to LSDA, we have carried out self-consistent electronic-structure calculations for the strongly correlated electronic systems of La2CuO4 and YBa2Cu3O6. In contrast to LSDA, the LSDA+U calculations reveal the experimentally observed antiferromagnetic and insulating ground state. The energy gap for these compounds is of a charge-transfer character, and the values of the energy gap and Cu magnetic moment are in good agreement with experiments. The orbital character of the states near the Fermi level in La2CuO4 and YBa2Cu3O6 is discussed and a comparison with experiments is made.

Pan Wei and Zheng Qing Qi

1994-05-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Fast Approximate Convex Decomposition  

E-Print Network (OSTI)

Approximate convex decomposition (ACD) is a technique that partitions an input object into "approximately convex" components. Decomposition into approximately convex pieces is both more efficient to compute than exact convex decomposition and can...

Ghosh, Mukulika

2012-10-19T23:59:59.000Z

42

Gedanken densities and exact constraints in density functional theory  

SciTech Connect

Approximations to the exact density functional for the exchange-correlation energy of a many-electron ground state can be constructed by satisfying constraints that are universal, i.e., valid for all electron densities. Gedanken densities are designed for the purpose of this construction, but need not be realistic. The uniform electron gas is an old gedanken density. Here, we propose a spherical two-electron gedanken density in which the dimensionless density gradient can be an arbitrary positive constant wherever the density is non-zero. The Lieb-Oxford lower bound on the exchange energy can be satisfied within a generalized gradient approximation (GGA) by bounding its enhancement factor or simplest GGA exchange-energy density. This enhancement-factor bound is well known to be sufficient, but our gedanken density shows that it is also necessary. The conventional exact exchange-energy density satisfies no such local bound, but energy densities are not unique, and the simplest GGA exchange-energy density is not an approximation to it. We further derive a strongly and optimally tightened bound on the exchange enhancement factor of a two-electron density, which is satisfied by the local density approximation but is violated by all published GGA's or meta-GGAs. Finally, some consequences of the non-uniform density-scaling behavior for the asymptotics of the exchange enhancement factor of a GGA or meta-GGA are given.

Perdew, John P. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States) [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States); Ruzsinszky, Adrienn; Sun, Jianwei [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States)] [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Burke, Kieron [Department of Chemistry and Department of Physics, University of California, Irvine, California 92697 (United States)] [Department of Chemistry and Department of Physics, University of California, Irvine, California 92697 (United States)

2014-05-14T23:59:59.000Z

43

Retrocommissioning's Greatest Hits  

E-Print Network (OSTI)

and maintenance of buildings. Although owners' priorities for RCX projects may vary, it typically focuses on energy-using equipment such as lighting, HVAC, refrigeration, and the related controls. This paper highlights key findings from several of PECI...

Haasl, T.; Potter, A.; Irvine, L.

2001-01-01T23:59:59.000Z

44

Density and pair-density scaling for deriving the Euler equation in density-functional and pair-density-functional theory  

SciTech Connect

A link between density and pair density functional theories is presented. Density and pair density scaling are used to derive the Euler equation in both theories. Density scaling provides a constructive way of obtaining approximations for the Pauli potential. The Pauli potential (energy) of the density functional theory is expressed as the difference of the scaled and original exchange-correlation potentials (energies).

Nagy, A. [Department of Theoretical Physics, University of Debrecen, H-4010 Debrecen (Hungary)

2011-09-15T23:59:59.000Z

45

Bethe free-energy approximations for disordered quantum systems  

E-Print Network (OSTI)

Given a locally consistent set of reduced density matrices, we construct approximate density matrices which are globally consistent with the local density matrices we started from when the trial density matrix has a tree structure. We employ the cavity method of statistical physics to find the optimal density matrix representation by slowly decreasing the temperature in an annealing algorithm, or by minimizing an approximate Bethe free energy depending on the reduced density matrices and some cavity messages originated from the Bethe approximation of the entropy. We obtain the classical Bethe expression for the entropy within a naive (mean-field) approximation of the cavity messages, which is expected to work well at high temperatures. In the next order of the approximation, we obtain another expression for the Bethe entropy depending only on the diagonal elements of the reduced density matrices. In principle, we can improve the entropy approximation by considering more accurate cavity messages in the Bethe approximation of the entropy. We compare the annealing algorithm and the naive approximation of the Bethe entropy with exact and approximate numerical simulations for small and large samples of the random transverse Ising model on random regular graphs.

I. Biazzo; A. Ramezanpour

2014-07-08T23:59:59.000Z

46

Approximation Algorithms Tandy Warnow  

E-Print Network (OSTI)

size and 1 / . #12;Approximation algorithms for: Minimum Vertex Cover (finding a set of vertices-SAT 3-SAT DIR-HAM-CYCLEINDEPENDENT SET VERTEX COVER GRAPH 3-COLOR HAM-CYCLE TSP SUBSET-SUM SCHEDULINGPLANAR 3-COLOR SET COVER NP-Completeness by definition of NP-completeness #12;NP-hard Optimization

Warnow,Tandy

47

DENSITY FUNCTIONAL THEORY OF FIELD THEORETICAL SYSTEMS  

E-Print Network (OSTI)

DENSITY FUNCTIONAL THEORY OF FIELD THEORETICAL SYSTEMS E. Engel Inst. fur Theor. Physik background of relativistic density functional theory is emphasized and its consequences for relativistic Kohn-Sham equations are shown. The local density approximation for the exchange energy functional is reviewed

Engel, Eberhard

48

Ions in solution: Density corrected density functional theory (DC-DFT)  

SciTech Connect

Standard density functional approximations often give questionable results for odd-electron radical complexes, with the error typically attributed to self-interaction. In density corrected density functional theory (DC-DFT), certain classes of density functional theory calculations are significantly improved by using densities more accurate than the self-consistent densities. We discuss how to identify such cases, and how DC-DFT applies more generally. To illustrate, we calculate potential energy surfaces of HOCl{sup ?} and HOH{sub 2}O complexes using various common approximate functionals, with and without this density correction. Commonly used approximations yield wrongly shaped surfaces and/or incorrect minima when calculated self consistently, while yielding almost identical shapes and minima when density corrected. This improvement is retained even in the presence of implicit solvent.

Kim, Min-Cheol; Sim, Eunji, E-mail: esim@yonsei.ac.kr [Department of Chemistry and Institute of Nano-Bio Molecular Assemblies, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul 120-749 (Korea, Republic of)] [Department of Chemistry and Institute of Nano-Bio Molecular Assemblies, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Burke, Kieron [Department of Chemistry, University of California, Irvine, California 92697 (United States)] [Department of Chemistry, University of California, Irvine, California 92697 (United States)

2014-05-14T23:59:59.000Z

49

Quantum critical benchmark for density functional theory  

E-Print Network (OSTI)

Two electrons at the threshold of ionization represent a severe test case for electronic structure theory. A pseudospectral method yields a very accurate density of the two-electron ion with nuclear charge close to the critical value. Highly accurate energy components and potentials of Kohn-Sham density functional theory are given, as well as a useful parametrization of the critical density. The challenges for density functional approximations and the strength of correlation are also discussed.

Paul E. Grabowski; Kieron Burke

2014-08-09T23:59:59.000Z

50

Time-dependent density-functional theory for open systems  

E-Print Network (OSTI)

By introducing the self-energy density functionals for the dissipative interactions between the reduced system and its environment, we develop a time-dependent density-functional theory formalism based on an equation of motion for the Kohn-Sham reduced single-electron density matrix of the reduced system. Two approximate schemes are proposed for the self-energy density functionals, the complete second order approximation and the wide-band limit approximation. A numerical method based on the wide-band limit approximation is subsequently developed and implemented to simulate the steady and transient current through various realistic molecular devices. Simulation results are presented and discussed.

Xiao Zheng; Fan Wang; Chi Yung Yam; Yan Mo; GuanHua Chen

2007-02-27T23:59:59.000Z

51

Algorithms for Polytope Covering and Approximation, and for Approximate  

E-Print Network (OSTI)

@research.att.com Abstract This paper gives an algorithm for polytope covering: let L and U be sets of points in RdAlgorithms for Polytope Covering and Approximation, and for Approximate Closest-point Queries draft , comprising n points altogether. A cover for L from U is a set C U with L a subset of the convex hull of C

Clarkson, Kenneth L.

52

Algorithms for Polytope Covering and Approximation, and for Approximate  

E-Print Network (OSTI)

@research.att.com Abstract This paper gives an algorithm for polytope covering : let L and U be sets of points in R dAlgorithms for Polytope Covering and Approximation, and for Approximate Closest-point Queries draft , comprising n points altogether. A cover for L from U is a set C #26; U with L a subset of the convex hull

Clarkson, Kenneth L.

53

Algorithms for Polytope Covering and Approximation, and for Approximate  

E-Print Network (OSTI)

an algorithm for polytope covering: let L and U be sets of points in Rd, comprising n points altogether Algorithms for Polytope Covering and Approximation, and for Approximate. A cover for L from U is a set C U with L a subset of the convex hull of C. Suppose c

Clarkson, Kenneth L.

54

Buoyancy-generated variable-density turbulence  

SciTech Connect

Both a one-point (engineering) and a two-point (spectral) model are tested against numerical data. Deficiencies in these variable-density models are disucssed and modifications are suggested. Attention is restricted to turbulent interactions of two miscible, incompressible Newtonian fluids of different densities. Departures from the limits of validity of the Boussinesq approximation are examined. Results of the buoyancy-generated turbulence are compared with variable-density model predictions. 3 figs, 6 refs.

Sandoval, D.L. [Los Alamos National Lab., NM (United States)]|[Washington Univ. (United States); Clark, T.T. [Los Alamos National Lab., NM (United States); Riley, J.J. [Washington Univ. (United States)

1996-06-01T23:59:59.000Z

55

Forward approximation and backward approximation in fuzzy rough sets  

Science Journals Connector (OSTI)

Abstract It is general to obtain rules by attribute reduction in fuzzy information systems. Instead of obtaining rules by attribute reduction, which may have a negative effect on inducting good rules, the objective of this paper is to extract rules without computing attribute reducts. Forward and backward approximations in fuzzy rough sets are first defined, and their important properties are discussed. Two algorithms based on forward and backward approximations, namely, mine rules based on the forward approximation (MRBFA) and mine rules based on the backward approximation (MRBBA), are proposed for rule extraction. The two algorithms are evaluated by several data sets from the UC Irvine Machine Learning Repository. The experimental results show that both MRBFA and MRBBA achieve better classification performances than the method based on attribute reduction.

Yi Cheng

2015-01-01T23:59:59.000Z

56

Approximation Algorithms for Covering Problems  

E-Print Network (OSTI)

?-approximation for general CIP with {0, 1} variables [24].details of an extension to CIP with general upper bounds onCovering Integer Programs ( CIP ). Given a non-negative cost

Koufogiannakis, Christos

2009-01-01T23:59:59.000Z

57

The Born-Oppenheimer Approximation  

Science Journals Connector (OSTI)

In physics and chemistry the Born-Oppenheimer approximation is a very important method for...1). It is based on the important fact that the molecular Schrdinger operator contains one small parameter, the ratio k

J. M. Combes; P. Duclos; R. Seiler

1981-01-01T23:59:59.000Z

58

Gluon Condensate in Pion Superfluid beyond Mean Field Approximation  

E-Print Network (OSTI)

We study gluon condensate in a pion superfluid, through calculating the equation of state of the system in the Nambu-Jona-Lasinio model. While in mean field approximation the growing pion condensate leads to an increasing gluon condensate, meson fluctuations reduce the gluon condensate and the broken scalar symmetry can be smoothly restored at finite isospin density.

Yin Jiang; Pengfei Zhuang

2011-03-04T23:59:59.000Z

59

Ancilla Approximable Quantum State Transformations  

E-Print Network (OSTI)

We consider the transformations of quantum states obtainable by a process of the following sort. Combine the given input state with a specially prepared initial state of an auxiliary system. Apply a unitary transformation to the combined system. Measure the state of the auxiliary subsystem. If (and only if) it is in a specified final state, consider the process successful, and take the resulting state of the original (principal) system as the result of the process. We review known information about exact realization of transformations by such a process. Then we present results about approximate realization of finite partial transformations. We consider primarily the issue of approximation to within a specified positive epsilon, but we also address the question of arbitrarily close approximation.

Andreas Blass; Yuri Gurevich

2014-03-30T23:59:59.000Z

60

Quasiclassical Born-Oppenheimer approximations  

E-Print Network (OSTI)

We discuss several problems in quasiclassical physics for which approximate solutions were recently obtained by a new method, and which can also be solved by novel versions of the Born-Oppenheimer approximation. These cases include the so-called bouncing ball modes, low angular momentum states in perturbed circular billiards, resonant states in perturbed rectangular billiards, and whispering gallery modes. Some rare, special eigenstates, concentrated close to the edge or along a diagonal of a nearly rectangular billiard are found. This kind of state has apparently previously escaped notice.

Oleg Zaitsev; R. Narevich; R. E. Prange

2000-09-29T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

1 Density Functional Theory for Emergents Robert O. Jones  

E-Print Network (OSTI)

1 Density Functional Theory for Emergents Robert O. Jones Peter-Gr¨unberg-Institut PGI-1 and German the widespread use of density functional (DF) theory in materials science and chemistry and the physical insight as basic variable 3 3 An "approximate practical method" 5 4 Density functional formalism 7 4.1 Single

62

The dynamics of variable-density turbulence  

SciTech Connect

The dynamics of variable-density turbulent fluids are studied by direct numerical simulation. The flow is incompressible so that acoustic waves are decoupled from the problem, and implying that density is not a thermodynamic variable. Changes in density occur due to molecular mixing. The velocity field, is in general, divergent. A pseudo-spectral numerical technique is used to solve the equations of motion. Three-dimensional simulations are performed using a grid size of 128{sup 3} grid points. Two types of problems are studied: (1) the decay of isotropic, variable-density turbulence, and (2) buoyancy-generated turbulence in a fluid with large density fluctuations. In the case of isotropic, variable-density turbulence, the overall statistical decay behavior, for the cases studied, is relatively unaffected by the presence of density variations when the initial density and velocity fields are statistically independent. The results for this case are in quantitative agreement with previous numerical and laboratory results. In this case, the initial density field has a bimodal probability density function (pdf) which evolves in time towards a Gaussian distribution. The pdf of the density field is symmetric about its mean value throughout its evolution. If the initial velocity and density fields are statistically dependent, however, the decay process is significantly affected by the density fluctuations. For the case of buoyancy-generated turbulence, variable-density departures from the Boussinesq approximation are studied. The results of the buoyancy-generated turbulence are compared with variable-density model predictions. Both a one-point (engineering) model and a two-point (spectral) model are tested against the numerical data. Some deficiencies in these variable-density models are discussed and modifications are suggested.

Sandoval, D.L.

1995-11-01T23:59:59.000Z

63

Approximate Method for the Free Energy  

Science Journals Connector (OSTI)

......Articles Approximate Method for the Free Energy Akihide Oguchi Department of Physics...a lower bound of the Helmholtz free energy in the statistical physics. A new approximate expression of the free energy is obtained. This approximate......

Akihide Oguchi

1976-11-01T23:59:59.000Z

64

Approximate convex decomposition and its applications  

E-Print Network (OSTI)

in representations with an unmanageable number of components. In this work, we have developed an approximate technique, called Approximate Convex Decomposition (ACD), which decomposes a given polygon or polyhedron into "approximately convex" pieces that may provide...

Lien, Jyh-Ming

2009-05-15T23:59:59.000Z

65

The dynamics of variable-density turbulence  

SciTech Connect

The dynamics of variable-density turbulent fluids are studied by direct numerical simulation. The flow is incompressible so that acoustic waves are decoupled from the problem, and implying that density is not a thermodynamic variable. Changes in density occur due to molecular mixing. The velocity field is, in general, divergent. A pseudo-spectral numerical technique is used to solve the equations of motion. Three-dimensional simulations are performed using a grid size of 128{sup 3} grid points. Two types of problems are studied: (1) the decay of isotropic, variable-density turbulence, and (2) buoyancy-generated turbulence in a fluid with large density fluctuations (such that the Boussinesq approximation is not valid). In the case of isotropic, variable-density turbulence, the overall statistical decay behavior, for the cases studied, is relatively unaffected by the presence of density variations when the initial density and velocity fields are statistically independent. The results for this case are in quantitative agreement with previous numerical and laboratory results. In this case, the initial density field has a bimodal probability density function (pdf) which evolves in time towards a Gaussian distribution. The pdf of the density field is symmetric about its mean value throughout its evolution. If the initial velocity and density fields are statistically dependent, however, the decay process is significantly affected by the density fluctuations. For this case, the pdf of the density becomes asymmetric about its mean value during the early stages of its evolution. It is argued that these asymmetries in the pdf of the density field are due to different entrainment rates, into the mixing region, that favor the high speed fluid.

Sandoval, D.L.

1995-11-01T23:59:59.000Z

66

Approximating Metal-Insulator Transitions  

E-Print Network (OSTI)

We consider quantum wave propagation in one-dimensional quasiperiodic lattices. We propose an iterative construction of quasiperiodic potentials from sequences of potentials with increasing spatial period. At each finite iteration step the eigenstates reflect the properties of the limiting quasiperiodic potential properties up to a controlled maximum system size. We then observe approximate metal-insulator transitions (MIT) at the finite iteration steps. We also report evidence on mobility edges which are at variance to the celebrated Aubry-Andre model. The dynamics near the MIT shows a critical slowing down of the ballistic group velocity in the metallic phase similar to the divergence of the localization length in the insulating phase.

C. Danieli; K. Rayanov; B. Pavlov; G. Martin; S. Flach

2014-05-06T23:59:59.000Z

67

Approximations to Brueckner theory for nucleon-nucleus collisions  

Science Journals Connector (OSTI)

The concept of quasiparticles has been very fruitful for the development of theories of many-body systems of strongly interacting particles. A central problem for a quantitative treatment is the interaction between the quasiparticles (the effective interaction between particles). The Brueckner reaction matrix theory and the Jastrow variational approach have been used extensively, especially for nuclei. Our present concern is the collisions between nuclei. An exact calculation of the effective interaction between the nucleons is then extremely complicated. Only the simplest extreme, the nucleon-nucleus optical potential, can be treated fully. Approximate treatments are called for. The present paper investigates some approximations to the Brueckner theory. We are primarily interested in the imaginary part of the one-body (one-nucleon) mean field, as it relates to the damping of collective motion. Of special interest is the increase at low density. Comparisons with Skyrme forces show that they exaggerate this density dependence.

H.S. Khler

1984-01-01T23:59:59.000Z

68

Energy density of variational states  

Science Journals Connector (OSTI)

We show, in several important and general cases, that a low variational energy density of a trial state is possible even when the trial state represents a different phase from the ground state. Specifically, we ask whether the ground-state energy density of a Hamiltonian whose ground state is in phase A can be approximated to arbitrary accuracy by a wave function, which represents a different phase B. We show this is indeed the case when A has discrete symmetry breaking order in one dimension or topological order in two dimensions, while B is disordered. We argue that, if reasonable conditions of physicality are imposed upon the trial wave function, then this is not possible when A has discrete symmetry breaking in dimensions greater than one and B is symmetric. Some other situations are also discussed.

Leon Balents

2014-12-08T23:59:59.000Z

69

Effects of the boussinesq approximation on the results of strongly-buoyant plume calculations  

SciTech Connect

Nearly all mathematical models which are commonly used to predict the dispersion of chimney gases in the atmosphere or heated water discharges in the aquatic environment employ the so-called boussinesq approximation. It is part of this approximation that density variations appear solely in the buoyancy term of the momentum equation and are neglected in all other terms.

Schatzmann, M.; Policastro, A.J.

1984-01-01T23:59:59.000Z

70

Rough Set Approximations in Formal Concept Analysis  

E-Print Network (OSTI)

Rough Set Approximations in Formal Concept Analysis Y.Y. Yao, Yaohua Chen Department of Computer}@cs.uregina.ca Abstract-- An important topic of rough set theory is the approximation of undefinable sets or concepts of approximation operators. In this paper, the notion of rough set approximations is introduced into formal concept

Yao, Yiyu

71

Validity of the shape-independent approximation for Bose-Einstein condensates  

Science Journals Connector (OSTI)

The validity of the shape-independent approximation is studied for three trapped atoms. By comparing the total ground-state energy calculated using pseudopotentials in the Hartree-Fock approximation to the exact ground-state energy, the shape-independent approximation is shown to agree quantitatively only in the low-density limit. It is also shown using configuration interaction that a Dirac ? function is not suitable as a replacement for the two-body interaction in exact theories.

B. D. Esry and Chris H. Greene

1999-08-01T23:59:59.000Z

72

Laboratory Density Functionals  

E-Print Network (OSTI)

We compare several definitions of the density of a self-bound system, such as a nucleus, in relation with its center-of-mass zero-point motion. A trivial deconvolution relates the internal density to the density defined in the laboratory frame. This result is useful for the practical definition of density functionals.

B. G. Giraud

2007-07-26T23:59:59.000Z

73

How to Calculate Molecular Column Density  

E-Print Network (OSTI)

The calculation of the molecular column density from molecular spectral (rotational or ro-vibrational) transition measurements is one of the most basic quantities derived from molecular spectroscopy. Starting from first principles where we describe the basic physics behind the radiative and collisional excitation of molecules and the radiative transfer of their emission, we derive a general expression for the molecular column density. As the calculation of the molecular column density involves a knowledge of the molecular energy level degeneracies, rotational partition functions, dipole moment matrix elements, and line strengths, we include generalized derivations of these molecule-specific quantities. Given that approximations to the column density equation are often useful, we explore the optically thin, optically thick, and low-frequency limits to our derived general molecular column density relation. We also evaluate the limitations of the common assumption that the molecular excitation temperature is con...

Mangum, Jeffrey G

2015-01-01T23:59:59.000Z

74

Diffusion Approximation of Radiative Transfer Problems with Guillaume Bal \\Lambda Leonid Ryzhik y  

E-Print Network (OSTI)

propagation. The radiative transport equation for the evolution of the average phase space energy density a Ryzhik y September 16, 1998 Abstract We derive the diffusion approximation of transport equations with discontinuities at interfaces. The transport equations model the energy density of acoustic waves. The waves

Bal, Guillaume

75

The benchmark of gutzwiller density functional theory in hydrogen systems  

SciTech Connect

We propose an approximate form of the exchange-correlation energy functional for the Gutzwiller density functional theory. It satisfies certain physical constraints in both weak and strong electron correlation limits. We benchmark the Gutzwiller density functional approximation in the hydrogen systems, where the static correlation error is shown to be negligible. The good transferability is demonstrated by applications to the hydrogen molecule and some crystal structures.

Yao, Y.; Wang, Cai-Zhuang; Ho, Kai-Ming

2012-02-23T23:59:59.000Z

76

Symmetric Density Functionals  

E-Print Network (OSTI)

Variations in distinct restricted spaces of wave functions generate distinct density functionals. In particular, angular momentum projected Slater determinants define a new density functional, compatible simultaneously with angular momentum quantum number and mean field descriptions.

B. G. Giraud

2005-07-13T23:59:59.000Z

77

Density measurements Viscosity measurements  

E-Print Network (OSTI)

Density measurements Viscosity measurements Temperature measurements Pressure measurements Flow rate measurements Velocity measurements Sensors How to measure fluid flow properties ? Am´elie Danlos Ravelet Experimental methods for fluid flows: an introduction #12;Density measurements Viscosity

Ravelet, Florent

78

ORIGINAL ARTICLE Approximate Truth and Descriptive Nesting  

E-Print Network (OSTI)

ORIGINAL ARTICLE Approximate Truth and Descriptive Nesting Jeffrey Alan Barrett Received: 7 July. This paper presents a notion of local probable approximate truth in terms of descriptive nesting relations

Barrett, Jeffrey A.

79

Multi topological approximations of rough set theory  

Science Journals Connector (OSTI)

In this paper, we generalise Pawlak's approximation spaces to topological approximation spaces. These topological approximation spaces are generated using many topological notions such as regular open sets, semi-open sets, pre-open sets, ?-open sets, ?-open sets and ?-open sets and others. The basic definitions and properties of these topological approximation spaces are introduced and sufficiently illustrated. We put all topological generalisations in one generalisation called m-generalisation spaces.

A.S. Salama; O.G. El-Barbary

2013-01-01T23:59:59.000Z

80

Approximation Algorithms for Maximization Problems arising in  

E-Print Network (OSTI)

Approximation Algorithms for Maximization Problems arising in Graph Partitioning Thesis for the M of size k that maximizes : Max­k­Vertex Cover : the weight of edges incident with vertices in U . Max a number of approximation algorithms based on linear and semidefinite programming, and obtain approximation

Langberg, Michael

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Direct Observation of Born-Oppenheimer Approximation  

E-Print Network (OSTI)

Direct Observation of Born-Oppenheimer Approximation Breakdown in Carbon Nanotubes Adam W of the theoretically predicted breakdown of the Born-Oppenheimer approximation in individual single-walled carbon nanotubes. The Born-Oppenheimer (BO) or adiabatic approximation is widely used to simplify the very complex

Cronin, Steve

82

Mathematical Analysis of Born{Oppenheimer Approximations  

E-Print Network (OSTI)

Mathematical Analysis of Born{Oppenheimer Approximations George A. Hagedorn and Alain Joye concerning Born{Oppenheimer approximations in molecular quantum mechanics. Introduction The goal of this paper is to review rigorous mathematical results concerning Born{Oppenheimer approximations. We make

Hagedorn, George A.

83

Truth approximation via abductive belief change  

Science Journals Connector (OSTI)

......in Model-Based Reasoning and Abduction Truth approximation via abductive belief change...of belief change, on the one hand, and truth approximation, construed as increasing...or beliefs does lead them closer to the truth, and hence tracks truth approximation......

Gustavo Cevolani

2013-12-01T23:59:59.000Z

84

Density functional theory for self-bound systems  

E-Print Network (OSTI)

The density functional theory is extended to account for self-bound systems. To this end the Hohenberg-Kohn theorem is formulated for the intrinsic density and a Kohn-Sham like procedure for an $N$--body system is derived using the adiabatic approximation to account for the center of mass motion.

Nir Barnea

2007-11-06T23:59:59.000Z

85

High density effective theory on the lattice  

E-Print Network (OSTI)

Long-range interactions in finite density QCD necessitate a non-perturbative approach in order to reliably map out the key features and spectrum of the QCD phase diagram. However, the complex nature of the fermion determinant in this sector prohibits the use of established Monte Carlo techniques that utilize importance sampling. Whilst significant progress has been made in the low density, high temperature region, this remains a considerable challenge at mid to high density. At large chemical potential, QCD can be approximated using high density effective theory which is free from the sign problem at leading order. We investigate the implementation of this theory on the lattice in conjunction with existing re-weighting techniques.

A. Dougall

2007-10-08T23:59:59.000Z

86

Unambiguous exchange-correlation energy density Kieron Burke,a)  

E-Print Network (OSTI)

density approximation LDA , the conventional form is eXC unif (r) , the exchange-correlation energy the following definition of an energy density: eXC wave fn. r d3 r P r,r r r 2 r r 1 2 2 r,r s r,r r r , 2 whereUnambiguous exchange-correlation energy density Kieron Burke,a) Federico G. Cruz, and Kin-Chung Lam

Burke, Kieron

87

Density scaling and anisotropy in supersonic MHD turbulence  

E-Print Network (OSTI)

We study the statistics of density for supersonic turbulence in a medium with magnetic pressure larger than the gaseous pressure. This study is motivated by molecular cloud research. Our simulations exhibit clumpy density structures, which contrast increases with the Mach number. At 10 Machs densities of some clumps are three orders of magnitude higher than the mean density. These clumps give rise to flat and approximately isotropic density spectrum corresponding to the random distribution of clumps in space. We claim that the clumps originate from our random, isotropic turbulence driving. When the contribution from those clumps is suppressed by studying logarithm of density, the density statistics exhibit scale-dependent anisotropy consistent with the models where density structures arise from shearing by Alfv\\'en waves. It is noteworthy that originally such models were advocated for the case of low-Mach, nearly incompressible turbulence.

A. Beresnyak; A. Lazarian; J. Cho

2005-02-25T23:59:59.000Z

88

Moving boundary approximation for curved streamer ionization fronts: Solvability analysis  

Science Journals Connector (OSTI)

The minimal density model for negative streamer ionization fronts is investigated. An earlier moving boundary approximation for this model consisted of a kinetic undercooling type boundary condition in a Laplacian growth problem of Hele-Shaw type. Here we derive a curvature correction to the moving boundary approximation that resembles surface tension. The calculation is based on solvability analysis with unconventional features, namely, there are three relevant zero modes of the adjoint operator, one of them diverging; furthermore, the inner-outer matching ahead of the front must be performed on a line rather than on an extended region; and the whole calculation can be performed analytically. The analysis reveals a relation between the fields ahead and behind a slowly evolving curved front, the curvature and the generated conductivity. This relation forces us to give up the ideal conductivity approximation, and we suggest to replace it by a charge neutrality approximation. This implies that the electric potential in the streamer interior is no longer constant but solves a Laplace equation; this leads to a Muskat-type problem.

Fabian Brau, Benny Davidovitch, and Ute Ebert

2008-11-21T23:59:59.000Z

89

Validity of several approximations for the turbulent buoyant jet in a stagnant neutrally-stratified ambient  

SciTech Connect

A series of approximations are usually made in deriving integral model equations for the dispersion of a round turbulent buoyant jet into a stagnant neutrally-stratified ambient fluid. The magnitudes of differences in model predictions caused by making four of these approximations are calculated as a function of the initial densimetric Froude number and the initial relative density difference. The four approximations studied are (1) the Boussinesq approximation, (2) the use of a common Gaussian width for both mean axial velocity and mean temperature (or concentration) excess, (3) the neglect of fluctuation-correlation terms, and (4) the assumption of a linear relationship between excess density and excess temperature (or concentration). The four approximations are studied singly and then cumulatively as the predictions of the two models, one with and one without all approximations, are compared to seven low Froude number data cases. Results show that the Boussinesq approximation produces percentage differences in predictions which are about half of the initial relative density difference expressed in percentage. Use of a common Gaussian width for velocity and temperature produces differences from 6% to 30% depending on the entrainment assumption used. Fluctuation correlation effects rarely exceed 8%. Lastly, at Froude numbers below about 10 the correct nonlinear equation of state must often be used for heated waste jets to acheive accurate results, and the correct air equation of state may also be needed for low Froude number heated air jets, depending on the initial diameter and velocity.

Ponce, T.C.

1982-01-01T23:59:59.000Z

90

A long-range-corrected density functional that performs well for both ground-state properties and time-dependent density functional theory  

E-Print Network (OSTI)

and time-dependent density functional theory excitation energies, including charge-transfer excited states energies within time-dependent density functional theory, is systematically evaluated, and optimal values. THEORETICAL BACKGROUND Generalized gradient approximations GGAs in density functional theory DFT are quite

Herbert, John

91

Estimate sequence methods: extensions and approximations  

E-Print Network (OSTI)

Aug 11, 2009 ... Estimate sequence methods: extensions and approximations ... or both, and draw some guidelines on the design of further estimate sequence...

Michel Baes

2009-08-11T23:59:59.000Z

92

Born-Oppenheimer approximation in open systems  

E-Print Network (OSTI)

We generalize the standard Born-Oppenheimer approximation to the case of open quantum systems. We define the zeroth order Born-Oppenheimer approximation of an open quantum system as the regime in which its effective Hamiltonian can be diagonalized with fixed slowly changing variables. We then establish validity and invalidity conditions for this approximation for two kinds of dissipations--the spin relaxation and the dissipation of center-of-mass motion. As an example, the Born-Oppenheimer approximation of a two-level open system is analyzed.

X. L. Huang; X. X. Yi

2009-09-16T23:59:59.000Z

93

Born-Oppenheimer approximation in open systems  

Science Journals Connector (OSTI)

We generalize the standard Born-Oppenheimer approximation to the case of open quantum systems. We define the zeroth-order Born-Oppenheimer approximation for an open quantum system as the regime in which its effective Hamiltonian can be diagonalized with fixed slowly changing variables. We then establish validity and invalidity conditions for this approximation for two types of dissipationsthe spin relaxation and the dissipation of center-of-mass motion. As an example, the Born-Oppenheimer approximation for a two-level open system is analyzed.

X. L. Huang and X. X. Yi

2009-09-11T23:59:59.000Z

94

An approximate global solution of Einstein's equations for a finite body  

E-Print Network (OSTI)

We obtain an approximate global stationary and axisymmetric solution of Einstein's equations which can be considered as a simple star model: a self-gravitating perfect fluid ball with constant mass density rotating in rigid motion. Using the post-Minkowskian formalism (weak-field approximation) and considering rotation as a perturbation (slow-rotation approximation), we find approximate interior and exterior (asymptotically flat) solutions to this problem in harmonic and quo-harmonic coordinates. In both cases, interior and exterior solutions are matched, in the sense of Lichnerowicz, on the surface of zero pressure to obtain a global solution. The resulting metric depends on three arbitrary constants: mass density, rotational velocity and the star radius at the non-rotation limit. The mass, angular momentum, quadrupole moment and other constants of the exterior metric are determined by these three parameters. It is easy to show that this type of fluid cannot be a source of the Kerr metric

J. A. Cabezas; J. Martin-Martin; A. Molina; E. Ruiz

2006-11-02T23:59:59.000Z

95

Density functional theory of electrowetting  

E-Print Network (OSTI)

The phenomenon of electrowetting, i.e., the dependence of the macroscopic contact angle of a fluid on the electrostatic potential of the substrate, is analyzed in terms of the density functional theory of wetting. It is shown that electrowetting is not an electrocapillarity effect, i.e., it cannot be consistently understood in terms of the variation of the substrate-fluid interfacial tension with the electrostatic substrate potential, but it is related to the depth of the effective interface potential. The key feature, which has been overlooked so far and which occurs naturally in the density functional approach is the structural change of a fluid if it is brought into contact with another fluid. These structural changes occur in the present context as the formation of finite films of one fluid phase in between the substrate and the bulk of the other fluid phase. The non-vanishing Donnan potentials (Galvani potential differences) across such film-bulk fluid interfaces, which generically occur due to an unequal partitioning of ions as a result of differences of solubility contrasts, lead to correction terms in the electrowetting equation, which become relevant for sufficiently small substrate potentials. Whereas the present density functional approach confirms the commonly used electrocapillarity-based electrowetting equation as a good approximation for the cases of metallic electrodes or electrodes coated with a hydrophobic dielectric in contact with an electrolyte solution and an ion-free oil, a significantly reduced tendency for electrowetting is predicted for electrodes coated with a dielectric which is hydrophilic or which is in contact with two immiscible electrolyte solutions.

Markus Bier; Ingrid Ibagon

2014-02-10T23:59:59.000Z

96

The Observer Algorithm for Visibility Approximation  

E-Print Network (OSTI)

other algorithms do. We test this algorithm in several settings: rural, mountainous and urban areasThe Observer Algorithm for Visibility Approximation Per-Magnus OLSSON a and Patrick DOHERTY present a novel algorithm for visibility approximation that is sub- stantially faster than ray casting

Doherty, Patrick

97

APPROXIMATE TAXI FARES From Midway -$35  

E-Print Network (OSTI)

APPROXIMATE TAXI FARES From Midway - $35 From O'Hare - $60 From Downtown - $35 MIDWAY Midway International Airport is approximately eight miles west of the University of Chicago campus. Midway is easily transportation, shuttle, car, and taxi. FROM MIDWAY AIRPORT Follow the airport signs to the CTA Orange Line

Issa, Naoum

98

Optimal Tree Approximation with Wavelets Richard Baraniuk  

E-Print Network (OSTI)

simply represented: the energy from a singularity localizes along one branch of the tree (see Figure 1Optimal Tree Approximation with Wavelets Richard Baraniuk Department of Electrical and Computer on trees and point out that an optimal tree approximant exists and is easily computed. The optimal tree

99

Rough Set Approximations in Formal Concept Analysis  

E-Print Network (OSTI)

Rough Set Approximations in Formal Concept Analysis Yiyu Yao and Yaohua Chen Department of Computer}@cs.uregina.ca Abstract. A basic notion shared by rough set analysis and formal concept anal- ysis is the definability to each other based on defin- ability. In this paper, the notion of rough set approximations is introduced

Yao, Yiyu

100

Chiral dynamics and peripheral transverse densities  

SciTech Connect

In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M{sub {pi}}{sup -1}) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two--pion threshold at timelike t = 4 M{ sub {pi}}{sup 2}, which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M{sub {pi}}{sup -1}) and the "molecular" region b = O(M{sub N}{sup 2}/M{sub {pi}}{sup 3}); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N{ sub c} limit of QCD; (e) quantify the region of transverse distances where the chiral components of the densities are numerically dominant; (f) calculate the chiral divergences of the b{sup 2}-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M{sub {pi}} -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes.

Granados, Carlos G. [Uppsala University (Sweden); Weiss, Christian [JLAB, Newport News, VA (United States)

2014-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Prediction for Max-Stable Processes via an Approximated Conditional Density  

E-Print Network (OSTI)

for a river in western Colorado. Figure 2 displays the maximum ozone readings at 29 sites in a region of North A. Davis2 Philippe Naveau3 1 Department of Statistics Colorado State University, Fort Collins, CO

Cooley, Dan

102

Approximating the Conditional Density Given Large Observed Values via a Multivariate Extremes Framework, with Application to  

E-Print Network (OSTI)

model for the angular measure, we apply our method to nitrogen dioxide measurements in metropolitan mea- sure, Air pollution, Nitrogen dioxide monitoring. 1 Introduction and Motivation Nitrogen dioxide

Cooley, Dan

103

Inner magnetosphere plasma densities  

E-Print Network (OSTI)

The radio plasma imager (RPI) on the IMAGE satellite performs radio sounding in the magnetosphere, transmitting coded signals stepping through the frequency range of interest and receiving the returned echoes. The measurements provide the echo amplitude as a function of frequency and echo delay time on a so-called plasmagram. A newly developed algorithm inverts THE echo traces on a plasmagram to electron density spatial distributions. Based on these observed density distributions, an empirical model is constructed to describe the two-dimensional density distribution in the inner magnetosphere.

Reinisch, B W

2002-01-01T23:59:59.000Z

104

The Boussinesq approximation in rapidly rotating flows  

E-Print Network (OSTI)

In the classical formulation of the Boussinesq approximation centrifugal buoyancy effects related to differential rotation, as well as strong vortices in the flow, are neglected. However, these may play an important role in rapidly rotating flows, such as in astrophysical and geophysical applications, and also in turbulent convection. We here provide a straightforward approach resulting in a Boussinesq-type approximation that consistently accounts for centrifugal effects. We further compare our new approach to the classical one in fluid flows confined between two differentially heated and rotating cylinders. The results justify the need of using the proposed approximation in rapidly rotating flows.

Lopez, Jose M; Avila, Marc

2013-01-01T23:59:59.000Z

105

Alternative separation of exchange and correlation in density-functional theory R. Armiento*  

E-Print Network (OSTI)

Alternative separation of exchange and correlation in density-functional theory R. Armiento.245120 PACS number s : 71.15.Mb, 31.15.Ew Kohn-Sham KS density-functional theory1 DFT is a successful scheme on this approach by creating and deploying a local-density-approximation-type XC functional. Hence, this work

Armiento, Rickard

106

PHYSICAL REVIEW C 77, 064308 (2008) Effective shell model Hamiltonians from density functional theory: Quadrupolar and  

E-Print Network (OSTI)

for mapping a self-consistent mean-field theory (also known as density functional theory) onto a shell-state solution of this density functional theory at the Hartree-Fock plus BCS level, an effective shell-consistent mean-field (SCMF) approximation [1], also known as density functional theory (DFT

Bertsch George F.

107

Introduction to Density Functional Theory and Exchange-Correlation Energy Functionals  

E-Print Network (OSTI)

Introduction to Density Functional Theory and Exchange-Correlation Energy Functionals R. O. Jones.jones@fz-juelich.de Density functional calculations of cohesive and structural properties of molecules and solids can the theory and discuss the local density approximations basic to most applications, and we discuss ways

108

A Density Functional Theory Study of Hydrogen Adsorption in MOF-5 Tim Mueller and Gerbrand Ceder*  

E-Print Network (OSTI)

A Density Functional Theory Study of Hydrogen Adsorption in MOF-5 Tim Mueller and Gerbrand Ceder initio molecular dynamics in the generalized gradient approximation to density functional theory to store hydrogen with sufficient gravimetric and volumetric densities to be economi- cally practical

Ceder, Gerbrand

109

Approximate Stokes Drift Profiles in Deep Water  

Science Journals Connector (OSTI)

A deep-water approximation of the Stokes drift velocity profile is explored as an alternative to the monochromatic profile. The alternative profile investigated relies on the same two quantities required for the monochromatic profile, namely, the ...

yvind Breivik; Peter A. E. M. Janssen; Jean-Raymond Bidlot

2014-09-01T23:59:59.000Z

110

Quasiclassical Approximation for Slow Neutron Scattering  

Science Journals Connector (OSTI)

......Approximation for Slow Neutron Scattering Takeo Nishigori Department...formula for the differential scattering cross section of a slow neutron is derived along the line...of Spherical Rotors and Neutron Scattering Juichiro Hama and Tuto......

Takeo Nishigori

1970-06-01T23:59:59.000Z

111

Rough Approximate Operators: Axiomatic Rough Set Theory  

Science Journals Connector (OSTI)

In rough set theory, the upper and lower approximations are ... are two abstract operators acting on the power set of U, the universe of discourse. ... The proof is an easy application of point set topology. Simi...

T. Y. Lin; Qing Liu

1994-01-01T23:59:59.000Z

112

On the Born-Oppenheimer approximation  

Science Journals Connector (OSTI)

We discuss the validity of the Born-Oppenheimer approximation for molecular levels. It is shown...1/4...and prescriptions are given for their calculation. In particular to fourth order some adiabatic corrections ...

J. M. Combes

1975-01-01T23:59:59.000Z

113

NONLINEAR APPROXIMATIONS FOR ELECTRONIC STRUCTURE CALCULATIONS  

E-Print Network (OSTI)

NONLINEAR APPROXIMATIONS FOR ELECTRONIC STRUCTURE CALCULATIONS G. BEYLKIN AND T. S. HAUT Abstract. We present a new method for electronic structure calculations based on novel algorithms for nonlinear numerical calculus suitable for electronic structure calculations. For any spatial orbital

Beylkin, Gregory

114

Approximate inference in Gaussian graphical models  

E-Print Network (OSTI)

The focus of this thesis is approximate inference in Gaussian graphical models. A graphical model is a family of probability distributions in which the structure of interactions among the random variables is captured by a ...

Malioutov, Dmitry M., 1981-

2008-01-01T23:59:59.000Z

115

A fresh look at the adhesion approximation  

E-Print Network (OSTI)

I report on a systematic derivation of the phenomenological ``adhesion approximation'' from gravitational instability together with a brief evaluation of the related status of analytical modeling of large-scale structure.

Thomas Buchert

1997-11-04T23:59:59.000Z

116

Testing the accuracy of radiative cooling approximations in SPH simulations  

E-Print Network (OSTI)

Hydrodynamical simulations of star formation have stimulated a need to develop fast and robust algorithms for evaluating radiative cooling. Here we undertake a critical evaluation of what is currently a popular method for prescribing cooling in SPH simulations, i.e. the polytropic cooling due originally to Stamatellos et al. This method uses the local density and potential to estimate the column density and optical depth to each particle and then uses these quantities to evaluate an approximate expression for the net radiative cooling. We evaluate the algorithm by considering both spherical and disc-like systems with analytic density and temperature structures. In spherical systems, the total cooling rate computed by the method is within around 20 for the astrophysically relevant case of opacity dominated by ice grains and is correct to within a factor of order unity for a range of opacity laws. In disc geometry, however, the method systematically under-estimates the cooling by a large factor at all heights i...

Wilkins, Daniel R

2011-01-01T23:59:59.000Z

117

An improved proximity force approximation for electrostatics  

SciTech Connect

A quite straightforward approximation for the electrostatic interaction between two perfectly conducting surfaces suggests itself when the distance between them is much smaller than the characteristic lengths associated with their shapes. Indeed, in the so called 'proximity force approximation' the electrostatic force is evaluated by first dividing each surface into a set of small flat patches, and then adding up the forces due two opposite pairs, the contributions of which are approximated as due to pairs of parallel planes. This approximation has been widely and successfully applied in different contexts, ranging from nuclear physics to Casimir effect calculations. We present here an improvement on this approximation, based on a derivative expansion for the electrostatic energy contained between the surfaces. The results obtained could be useful for discussing the geometric dependence of the electrostatic force, and also as a convenient benchmark for numerical analyses of the tip-sample electrostatic interaction in atomic force microscopes. - Highlights: Black-Right-Pointing-Pointer The proximity force approximation (PFA) has been widely used in different areas. Black-Right-Pointing-Pointer The PFA can be improved using a derivative expansion in the shape of the surfaces. Black-Right-Pointing-Pointer We use the improved PFA to compute electrostatic forces between conductors. Black-Right-Pointing-Pointer The results can be used as an analytic benchmark for numerical calculations in AFM. Black-Right-Pointing-Pointer Insight is provided for people who use the PFA to compute nuclear and Casimir forces.

Fosco, Cesar D. [Centro Atomico Bariloche, Comision Nacional de Energia Atomica, R8402AGP Bariloche (Argentina) [Centro Atomico Bariloche, Comision Nacional de Energia Atomica, R8402AGP Bariloche (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo, R8402AGP Bariloche (Argentina); Lombardo, Fernando C. [Departamento de Fisica Juan Jose Giambiagi, FCEyN UBA, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina) [Departamento de Fisica Juan Jose Giambiagi, FCEyN UBA, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); IFIBA (Argentina)] [Argentina; Mazzitelli, Francisco D., E-mail: fdmazzi@cab.cnea.gov.ar [Centro Atomico Bariloche, Comision Nacional de Energia Atomica, R8402AGP Bariloche (Argentina); Departamento de Fisica Juan Jose Giambiagi, FCEyN UBA, Facultad de Ciencias Exactas y Naturales, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina)

2012-08-15T23:59:59.000Z

118

Extended quasiparticle approximation and Brueckner theory  

Science Journals Connector (OSTI)

The time-dependent Greens function method provides a basic theory for nuclear dynamics and heavy-ion collisions. The spectral function plays an important role in this theory containing information on correlations in the medium. These are usually neglected by using a quasiparticle approximation. In order to evaluate this particular approach it is important to establish in the static limit a link between this method and other traditional nuclear many-body theories such as the Brueckner approach. Using a self-consistent T-matrix approximation for the self-energy in the Greens-function approach, treating particles and holes on equal footing, the self-energy can be obtained and compared with the Brueckner expression. In the quasiparticle limit it contains terms up to and analogous to the Brueckner second order rearrangement energy. In an extended quasiparticle approximation (EQP) which does not violate the sum rule for the spectral function the Brueckner third-order rearrangement energy can also be reproduced. The latter approximation constitutes a bridge between the Brueckner and Greens-function methods. It assumes small absorption (and energy dependence) of the mean field. Some numerical estimates of the different approximation schemes that we discuss are shown. An iteration scheme for applying the EQP approximation is suggested.

H. S. Khler and Rudi Malfliet

1993-09-01T23:59:59.000Z

119

The problem of the universal density functional and the density matrix functional theory  

SciTech Connect

The analysis in this paper shows that the Hohenberg-Kohn theorem is the constellation of two statements: (i) the mathematically rigorous Hohenberg-Kohn lemma, which demonstrates that the same ground-state density cannot correspond to two different potentials of an external field, and (ii) the hypothesis of the existence of the universal density functional. Based on the obtained explicit expression for the nonrel-ativistic particle energy in a local external field, we prove that the energy of the system of more than two non-interacting electrons cannot be a functional of the inhomogeneous density. This result is generalized to the system of interacting electrons. It means that the Hohenberg-Kohn lemma cannot provide justification of the universal density functional for fermions. At the same time, statements of the density functional theory remain valid when considering any number of noninteracting ground-state bosons due to the Bose condensation effect. In the framework of the density matrix functional theory, the hypothesis of the existence of the universal density matrix functional corresponds to the cases of noninteracting particles and to interaction in the Hartree-Fock approximation.

Bobrov, V. B., E-mail: vic5907@mail.ru; Trigger, S. A., E-mail: satron@mail.ru [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2013-04-15T23:59:59.000Z

120

Limit cycle analysis of nuclear coupled density-wave oscillations  

SciTech Connect

Recent tests at commercial boiling water reactors (BWRs) have demonstrated the existence of limit cycles for nuclear coupled density-wave oscillations (NCDWOs) at off-normal conditions. This paper presents the application of a simplified nonlinear BWR core model to determine the potential magnitude and limiting mechanisms of severe NCDWOs, and an approximate determination of the limit cycle using singular perturbation analysis. In this model, the point kinetics equation with infinite-delayed approximation and linear reactivity feedback to both fuel temperature and coolant density is used. This model correctly predicts the magnitude of the Vermont Yankee power oscillations.

Ward, M.E.; Lee, J.C.

1986-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Diffusion Approximation of Radiative Transfer Problems with Guillaume Bal \\Lambda Leonid Ryzhik y  

E-Print Network (OSTI)

Ryzhik y Abstract We derive the diffusion approximation of transport equations with discontinuities at interfaces. The transport equations model the energy density of acoustic waves. The waves are reflected in the high frequency regime by a radiative transfer equation. This model has been first proposed

Ryzhik, Lenya

122

Density Inhomogeneities and Electron Mobility in Supercritical Xenon  

NLE Websites -- All DOE Office Websites (Extended Search)

Density Inhomogeneities and Electron Mobility in Supercritical Xenon Density Inhomogeneities and Electron Mobility in Supercritical Xenon Richard A. Holroyd, Kengo Itoh, and Masaru Nishikawa J. Chem. Phys. 118, 706-710 (2003) [Find paper at Scitation] Abstract: The low-field mobility of electrons in supercritical Xe has been measured isothermally as a function of density above the critical temperature (289.7 K). At 293 K the mobility varies from a high of 890 cm2/Vs at 9.2 x 1021 atoms/cm3 to a minimum value of 4.6 cm2/Vs at a density of 3.5 x 1021 atoms/cm3, which is just below the critical density. The density dependence of the mobility is reasonably well predicted by the deformation potential model if the adiabatic compressibility is used to characterize the electron-medium interactions. Approximate agreement indicates that

123

Density | OpenEI  

Open Energy Info (EERE)

Density Density Dataset Summary Description This dataset is part of a larger internal dataset at the National Renewable Energy Laboratory (NREL) that explores various characteristics of large solar electric (both PV and CSP) facilities around the United States. This dataset focuses on the land use characteristics for solar facilities that are either under construction or currently in operation. Source Land-Use Requirements for Solar Power Plants in the United States Date Released June 25th, 2013 (5 months ago) Date Updated Unknown Keywords acres area average concentrating solar power csp Density electric hectares km2 land land requirements land use land-use mean photovoltaic photovoltaics PV solar statistics Data application/vnd.openxmlformats-officedocument.spreadsheetml.sheet icon Master Solar Land Use Spreadsheet (xlsx, 1.5 MiB)

124

Single-Nucleon Densities  

NLE Websites -- All DOE Office Websites (Extended Search)

Densities Densities This web page presents single-nucleon densities calculated for a variety of nuclei in the range A=2-10 with some preliminary results for A=11,12. These are from variational Monte Carlo calculations (VMC) using the Argonne v18 two-nucleon and Urbana X three-nucleon potentials (AV18+UX). (Urbana X is intermediate between the Urbana IX and Illinois-7 models; it has the form of UIX supplemented with a two-pion S-wave piece, while the strengths of its terms are taken from the IL7 model. It does NOT have the three-pion-ring term of IL7.) These VMC wave functions are the starting trial functions for a number of recent Green's function Monte Carlo (GFMC) calculations: Brida, et al., Phys. Rev. C 84, 024319 (2011); McCutchan, et al., Phys. Rev. C 86, 024315 (2012);

125

Molecular Binding Energies from Partition Density Functional Theory  

SciTech Connect

Approximate molecular calculations via standard Kohn-Sham density functional theory are exactly reproduced by performing self-consistent calculations on isolated fragments via partition density functional theory [P. Elliott, K. Burke, M. H. Cohen, and A. Wasserman, Phys. Rev. A 82, 024501 (2010)]. We illustrate this with the binding curves of small diatomic molecules. We find that partition energies are in all cases qualitatively similar and numerically close to actual binding energies. We discuss qualitative features of the associated partition potentials.

Nafziger, J.; Wu, Q.; Wasserman, A.

2011-12-21T23:59:59.000Z

126

Early Type Galaxy Core Phase Densities  

E-Print Network (OSTI)

Early type galaxies, ellipticals and S0's, have two distinct core density profiles, either a power law or nearly flat in projection. The two core types are distributed with substantial overlap in luminosity, radius, mass and velocity dispersion, however, the cores separate into two distinct distributions in their coarse grain phase density, Q_0 = rho/sigma^3,suggesting that dynamical processes played a dominant role in their origin. The transition phase density separating the two elliptical types is approximately 0.003 M_sun pc^-3 km^-3 s^3,. The Q_0*M_c^2 vs M_c diagram shows that globular clusters, nuclear star clusters and power-law cores fall on what is likely a "collisional" sequence of inspiralling globular clusters. on which the relative core mass excess varies as the bulk stellar mass to the -0.34+/-0.08 power, close to predictions, albeit with a correlation coefficient of -0.46. Both power-law and cored galaxies lie on a single sequence of approximately Q_0 ~r_c^-2.2, suggesting that transport proces...

Carlbeg, Raymond

2014-01-01T23:59:59.000Z

127

Density Functional Theory for Superconductors  

E-Print Network (OSTI)

Density Functional Theory for Superconductors LATHIOTAKIS, A. MARQUES, 1,2,3 LU DERS, L. FAST, 2004 words: theory superconductors; density functional theory; critical temperature; exchange matter physics theoretical chemistry is density functional theory (DFT). foundations were established mid

Gross, E.K.U.

128

Relativistic Nuclear Energy Density Functionals  

Science Journals Connector (OSTI)

......research-article Articles Relativistic Nuclear Energy Density Functionals Dario Vretenar...196, 2012 137 Relativistic Nuclear Energy Density Functionals Dario Vretenar...and P. Ring 2. Relativistic nuclear energy density functionals Even though......

Dario Vretenar; Tamara Niksic; Peter Ring

2012-10-01T23:59:59.000Z

129

Energy in density gradient  

E-Print Network (OSTI)

Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindric configuration. This is of practical importance for drift wave instability in various plasmas, and in particular in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit ...

Vranjes, J

2015-01-01T23:59:59.000Z

130

Multiple density layered insulator  

DOE Patents (OSTI)

A multiple density layered insulator for use with a laser is disclosed wh provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation.

Alger, Terry W. (Tracy, CA)

1994-01-01T23:59:59.000Z

131

Nuclear relativistic hartree-fock approximation with effective pions  

SciTech Connect

The effect of an interaction between the {sigma}- and {pi}-meson fields, as well as that of the mixture of pseudoscalar (PS) and pseudovector (PV) couplings for the {pi}N vertex on the shell structure of finite nuclei are analyzed in the framework of different nonlinear nuclearmodels based on the relativistic Hartree-Fock approximation. For the case of a dominant {pi}N PV coupling, it is found that if the {sigma}-{pi} interaction generates an effective pion mass increasing with the nuclear density, the unrealistic effect of pions on the shell structure can be strongly reduced, keeping, roughly, the contribution of pions to the total binding energy. The {pi}N PS coupling increases slightly the spin-orbit splittings and the binding energy of the single-particle levels.

Marcos, S., E-mail: marcoss@unican.es; Lopez-Quelle, M.; Niembro, R. [Universidad de Cantabria (Spain); Savushkin, L. N. [St. Petersburg University for Telecommunications (Russian Federation)

2012-12-15T23:59:59.000Z

132

Coherent quasiparticle approximation cQPA and nonlocal coherence  

E-Print Network (OSTI)

We show that the dynamical Wigner functions for noninteracting fermions and bosons can have complex singularity structures with a number of new solutions accompanying the usual mass-shell dispersion relations. These new shell solutions are shown to encode the information of the quantum coherence between particles and antiparticles, left and right moving chiral states and/or between different flavour states. Analogously to the usual derivation of the Boltzmann equation, we impose this extended phase space structure on the full interacting theory. This extension of the quasiparticle approximation gives rise to a self-consistent equation of motion for a density matrix that combines the quantum mechanical coherence evolution with a well defined collision integral giving rise to decoherence. Several applications of the method are given, for example to the coherent particle production, electroweak baryogenesis and study of decoherence and thermalization.

Matti Herranen; Kimmo Kainulainen; Pyry M. Rahkila

2009-12-14T23:59:59.000Z

133

Approximating European Options by Rebate Barrier Options  

E-Print Network (OSTI)

When the underlying stock price is a strict local martingale process under an equivalent local martingale measure, Black-Scholes PDE associated with an European option may have multiple solutions. In this paper, we study an approximation for the smallest hedging price of such an European option. Our results show that a class of rebate barrier options can be used for this approximation, when its rebate and barrier are chosen appropriately. An asymptotic convergence rate is also achieved when the knocked-out barrier moves to infinity under suitable conditions.

Song, Qingshuo

2011-01-01T23:59:59.000Z

134

Stochastic Approximation and Its Application in MCMC  

E-Print Network (OSTI)

) is known as observational noise, which is de ned as follows: t+1 = H t+1( t; xt+1) h t+1( t); In 1951, Robin and Monro introduced the so-called Robbins - Monro algorithm (1951) to solve the integration equation and the algorithm works as follows...: Algorithm 1.1.1. Stochastic Approximation 1 a. Generate Xt+1 g t(x), where t indexes the iteration. b. Set t+1 = t + atH( t; Xt+1), where at is the gain factor. This Robbins a^ Monro algorithm is the most popular stochastic approximation method used...

Cheng, Yichen

2013-05-31T23:59:59.000Z

135

Boussinesq approximation of the Cahn-Hilliard-Navier-Stokes equations  

Science Journals Connector (OSTI)

We use the Cahn-Hilliard approach to model the slow dissolution dynamics of binary mixtures. An important peculiarity of the Cahn-Hilliard-Navier-Stokes equations is the necessity to use the full continuity equation even for a binary mixture of two incompressible liquids due to dependence of mixture density on concentration. The quasicompressibility of the governing equations brings a short time-scale (quasiacoustic) process that may not affect the slow dynamics but may significantly complicate the numerical treatment. Using the multiple-scale method we separate the physical processes occurring on different time scales and, ultimately, derive the equations with the filtered-out quasiacoustics. The derived equations represent the Boussinesq approximation of the Cahn-Hilliard-Navier-Stokes equations. This approximation can be further employed as a universal theoretical model for an analysis of slow thermodynamic and hydrodynamic evolution of the multiphase systems with strongly evolving and diffusing interfacial boundaries, i.e., for the processes involving dissolution/nucleation, evaporation/condensation, solidification/melting, polymerization, etc.

Anatoliy Vorobev

2010-11-12T23:59:59.000Z

136

Communication: Random phase approximation renormalized many-body perturbation theory  

SciTech Connect

We derive a renormalized many-body perturbation theory (MBPT) starting from the random phase approximation (RPA). This RPA-renormalized perturbation theory extends the scope of single-reference MBPT methods to small-gap systems without significantly increasing the computational cost. The leading correction to RPA, termed the approximate exchange kernel (AXK), substantially improves upon RPA atomization energies and ionization potentials without affecting other properties such as barrier heights where RPA is already accurate. Thus, AXK is more balanced than second-order screened exchange [A. Grneis et al., J. Chem. Phys. 131, 154115 (2009)], which tends to overcorrect RPA for systems with stronger static correlation. Similarly, AXK avoids the divergence of second-order Mller-Plesset (MP2) theory for small gap systems and delivers a much more consistent performance than MP2 across the periodic table at comparable cost. RPA+AXK thus is an accurate, non-empirical, and robust tool to assess and improve semi-local density functional theory for a wide range of systems previously inaccessible to first-principles electronic structure calculations.

Bates, Jefferson E.; Furche, Filipp, E-mail: filipp.furche@uci.edu [Department of Chemistry, University of California, Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025 (United States)] [Department of Chemistry, University of California, Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025 (United States)

2013-11-07T23:59:59.000Z

137

APPROXIMATION ALGORITHMS FOR CLUSTERING A Dissertation  

E-Print Network (OSTI)

develop new algorithmic techniques that will find application in a wide range of settings. We consider problems such as the stochastic versions of the set cover, vertex cover, and facility location problemsAPPROXIMATION ALGORITHMS FOR CLUSTERING PROBLEMS A Dissertation Presented to the Faculty

Swamy, Chaitanya

138

Symbolic Test Selection Based on Approximate Analysis  

E-Print Network (OSTI)

Symbolic Test Selection Based on Approximate Analysis Bertrand Jeannet, Thierry J´eron, Vlad Rusu}@irisa.fr Abstract. This paper addresses the problem of generating symbolic test cases for testing the conformance. The challenge we consider is the selection of test cases according to a test purpose, which is here a set

Paris-Sud XI, Université de

139

Approximate Relational Reasoning by Stochastic Propositionalization  

E-Print Network (OSTI)

Approximate Relational Reasoning by Stochastic Propositionalization Nicola Di Mauro, Teresa M fold recognition Nicola Di Mauro · Teresa M.A. Basile · Stefano Ferilli · Floriana Esposito Department.com c Springer-Verlag Berlin Heidelberg 2010 #12;82 N. Di Mauro et al. and drug design are relational

Di Mauro, Nicola

140

Correcting the diffusion approximation at the boundary  

E-Print Network (OSTI)

, 2011 The diffusion approximation to the radiative transport equation applies for light that has solutions of the radiative transport equation to evaluate each of their accuracy. Nonetheless, nearly all transport equation · I þ aI þ sLI ¼ 0; ð1:1? governs continuous light propagation in tissues [1

Kim, Arnold D.

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Approximating the Permanent with Belief Propagation  

E-Print Network (OSTI)

, then use Bethe free energy to approximate this partition function. After deriving some speedups to standard, not to mention relatively high polynomial running times that discourage their usage in practical applications-connected networks such as trees. In certain special loopy graph cases, including graphs with a single loop

Huang, Bert

142

Approximated Distributions of Sampling Inequality Indices  

Science Journals Connector (OSTI)

Often, in finite samples, the true level of the confidence intervals for natural estimators of inequality indices belonging to the Gini family differs greatly from their nominal level, which is based on the asymptotic confidence limits. This paper ... Keywords: Gini index family, Gram-Charlier approximation, Monte Carlo experiment, algebraic computer software, income distribution

Paola Palmitesta; Corrado Provasi; Cosimo Spera

1999-06-01T23:59:59.000Z

143

Approximate Inference and Protein-Folding  

E-Print Network (OSTI)

Approximate Inference and Protein-Folding Chen Yanover and Yair Weiss School of Computer Science Side-chain prediction is an important subtask in the protein-folding problem. We show that #12;nding algorithms, including a widely used protein-folding software (SCWRL). 1 Introduction Inference in graphical

Weiss, Yair

144

The Density of States in Dilute Solid Solutions  

Science Journals Connector (OSTI)

...relative to its value in the pure solvent, is derived. It is shown to...density of states in the pure solvent. The result, which follows...laborious derivation by means of Green function techniques. An application...approximate evaluation of the Green function method, is amended...

1966-01-01T23:59:59.000Z

145

An improved thin film approximation to accurately determine the optical conductivity of graphene from infrared transmittance  

SciTech Connect

This work presents an improved thin film approximation to extract the optical conductivity from infrared transmittance in a simple yet accurate way. This approximation takes into account the incoherent reflections from the backside of the substrate. These reflections are shown to have a significant effect on the extracted optical conductivity and hence on derived parameters as carrier mobility and density. By excluding the backside reflections, the error for these parameters for typical chemical vapor deposited (CVD) graphene on a silicon substrate can be as high as 17% and 45% for the carrier mobility and density, respectively. For the mid- and near-infrared, the approximation can be simplified such that the real part of the optical conductivity is extracted without the need for a parameterization of the optical conductivity. This direct extraction is shown for Fourier transform infrared (FTIR) transmittance measurements of CVD graphene on silicon in the photon energy range of 3707000?cm{sup ?1}. From the real part of the optical conductivity, the carrier density, mobility, and number of graphene layers are determined but also residue, originating from the graphene transfer, is detected. FTIR transmittance analyzed with the improved thin film approximation is shown to be a non-invasive, easy, and accurate measurement and analysis method for assessing the quality of graphene and can be used for other 2-D materials.

Weber, J. W.; Bol, A. A. [Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Sanden, M. C. M. van de [Department of Applied Physics, Eindhoven University of Technology, Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Dutch Institute for Fundamental Energy Research (DIFFER), Nieuwegein (Netherlands)

2014-07-07T23:59:59.000Z

146

Model calculations for electronic densities of states in heavy-fermion systems  

Science Journals Connector (OSTI)

The influence of the lattice on the density of states for conduction-band andf-electrons in heavy fermion and mixed valent systems has been calculated from an extension of the non-crossing approximation to the la...

H. Keiter; P. Schnenberg

1990-01-01T23:59:59.000Z

147

Exchange-correlation energy from pairing matrix fluctuation and the particle-particle random phase approximation  

SciTech Connect

Despite their unmatched success for many applications, commonly used local, semi-local, and hybrid density functionals still face challenges when it comes to describing long-range interactions, static correlation, and electron delocalization. Density functionals of both the occupied and virtual orbitals are able to address these problems. The particle-hole (ph-) Random Phase Approximation (RPA), a functional of occupied and virtual orbitals, has recently known a revival within the density functional theory community. Following up on an idea introduced in our recent communication [H. van Aggelen, Y. Yang, and W. Yang, Phys. Rev. A 88, 030501 (2013)], we formulate more general adiabatic connections for the correlation energy in terms of pairing matrix fluctuations described by the particle-particle (pp-) propagator. With numerical examples of the pp-RPA, the lowest-order approximation to the pp-propagator, we illustrate the potential of density functional approximations based on pairing matrix fluctuations. The pp-RPA is size-extensive, self-interaction free, fully anti-symmetric, describes the strong static correlation limit in H{sub 2}, and eliminates delocalization errors in H{sub 2}{sup +} and other single-bond systems. It gives surprisingly good non-bonded interaction energies competitive with the ph-RPA with the correct R{sup ?6} asymptotic decay as a function of the separation R, which we argue is mainly attributable to its correct second-order energy term. While the pp-RPA tends to underestimate absolute correlation energies, it gives good relative energies: much better atomization energies than the ph-RPA, as it has no tendency to underbind, and reaction energies of similar quality. The adiabatic connection in terms of pairing matrix fluctuation paves the way for promising new density functional approximations.

Aggelen, Helen van [Department of Inorganic and Physical Chemistry, Ghent University, Ghent (Belgium) [Department of Inorganic and Physical Chemistry, Ghent University, Ghent (Belgium); Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Yang, Yang [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States)] [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Yang, Weitao [Department of Chemistry and Department of Physics, Duke University, Durham, North Carolina 27708 (United States)] [Department of Chemistry and Department of Physics, Duke University, Durham, North Carolina 27708 (United States)

2014-05-14T23:59:59.000Z

148

Vibrational Superposition States Without Rotating Wave Approximation  

E-Print Network (OSTI)

We propose a scheme to generate superpositions of coherent states for the vibrational motion of a laser cooled trapped-ion. It is based on the interaction with a standing wave making use of the counter-rotating terms, i.e. not applying the rotating wave approximation. We also show that the same scheme can be exploited for quantum state measurement, i.e. with the same scheme non-classical states may be reconstructed

Mancini, S; Tombesi, P

2000-01-01T23:59:59.000Z

149

Limit theorems for stochastic approximation algorithms  

E-Print Network (OSTI)

We prove a central limit theorem applicable to one dimensional stochastic approximation algorithms that converge to a point where the error terms of the algorithm do not vanish. We show how this applies to a certain class of these algorithms that in particular covers a generalized P\\'olya urn model, which is also discussed. In addition, we show how to scale these algorithms in some cases where we cannot determine the limiting distribution but expect it to be non-normal.

Renlund, Henrik

2011-01-01T23:59:59.000Z

150

Covering based approximation a new type approach  

Science Journals Connector (OSTI)

The rough set theory, proposed by Pawlak is termed as basic (traditional) rough set theory and it has been extended in many directions. Covering based rough set is one of the extensions of the basic rough set theory. A covering is a generalisation of notion of partitioned rough set (Pawalk rough set) introduced by W. Zakowski. In this article it is introduced a new type of covering-based rough set in which both lower and upper approximation operators are improved.

Debadutta Mohanty

2010-01-01T23:59:59.000Z

151

Automating Logic Rectification by Approximate SPFDs  

Science Journals Connector (OSTI)

In the digital VLSI cycle, a netlist is often modified to correct design errors, perform small specification changes or implement incremental rewiring-based optimization operations. Most existing automated logic rectification tools use a small set of ... Keywords: SAT-based algorithm, approximate SPFD, digital VLSI cycle, design errors, incremental rewiring-based optimization operations, automated logic rectification tools, predefined logic transformations, memory/time explosion problem

Yu-Shen Yang; S. Sinha; A. Veneris; R. K. Brayton

2007-01-01T23:59:59.000Z

152

VISCOSITY AND RELAXATION APPROXIMATIONS FOR HYPERBOLIC SYSTEMS OF CONSERVATION LAWS  

E-Print Network (OSTI)

VISCOSITY AND RELAXATION APPROXIMATIONS FOR HYPERBOLIC SYSTEMS deal with the approximation of conservation * *laws via viscosity or relaxation. The following topics are covered: The general structure of viscosity and relaxation approximations is discu

Tzavaras, Athanasios E.

153

Nonlinear adaptive control using radial basis function approximants  

E-Print Network (OSTI)

The purpose of this research is to present an adaptive control strategy using the radial basis function approximation method. Surface approximation methods using radial basis function approximants will first be discussed. The Hamiltonian dynamical...

Petersen, Jerry Lee

1993-01-01T23:59:59.000Z

154

Knapsack Problems with Sigmoid Utilities: Approximation Algorithms via Hybrid Optimization$  

E-Print Network (OSTI)

Knapsack Problems with Sigmoid Utilities: Approximation Algorithms via Hybrid Optimization$ Vaibhav with sigmoid utilities. We merge approximation algorithms from discrete optimization with algorithms from continuous optimization to develop approximation algorithms for these NP-hard problems with sigmoid utilities

Bullo, Francesco

155

High Energy Density Capacitors  

SciTech Connect

BEEST Project: Recapping is developing a capacitor that could rival the energy storage potential and price of todays best EV batteries. When power is needed, the capacitor rapidly releases its stored energy, similar to lightning being discharged from a cloud. Capacitors are an ideal substitute for batteries if their energy storage capacity can be improved. Recapping is addressing storage capacity by experimenting with the material that separates the positive and negative electrodes of its capacitors. These separators could significantly improve the energy density of electrochemical devices.

None

2010-07-01T23:59:59.000Z

156

The Monte Carlo Independent Column Approximations Conditional Random Noise: Impact on Simulated Climate  

Science Journals Connector (OSTI)

The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average radiative fluxes is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. Results for five experiments are used ...

P. Risnen; H. W. Barker; J. N. S. Cole

2005-11-01T23:59:59.000Z

157

Accurate Ground-State Energies of Solids and Molecules from Time-Dependent Density-Functional Theory  

E-Print Network (OSTI)

-dissipation theorem with time-dependent density- functional theory. The key ingredient is a renormalization scheme be obtained from time- dependent density-functional theory (TDDFT) through the Dyson equation ð? ¼ KS ð? þ KS density-functional theory (DFT), one needs a rather involved approximation for the xc energy in order

Thygesen, Kristian

158

Density-functional theory of freezing of quantum liquids at zero temperature using exact liquid-state linear response  

E-Print Network (OSTI)

Density-functional theory of freezing of quantum liquids at zero temperature using exact liquid the shortcomings of the currently popular density-functional approximate theories to describe 3d freezing distances. S0163-1829 97 04310-5 I. INTRODUCTION The modern density-functional theory DFT , which

Likos, Christos N.

159

Density Functional Theory with Correct Long-Range Asymptotic Behavior Roi Baer1,* and Daniel Neuhauser2,  

E-Print Network (OSTI)

Density Functional Theory with Correct Long-Range Asymptotic Behavior Roi Baer1,* and Daniel within density functional theory (DFT) which spawns a class of approximations leading to correct long.043002 PACS numbers: 31.15.Ew, 31.15.Ne, 31.25.Eb, 71.15.Mb Density functional theory (DFT) [1,2] is an in

Baer, Roi

160

Generalized Polya urns via stochastic approximation  

E-Print Network (OSTI)

We collect, survey and develop methods of (one-dimensional) stochastic approximation in a framework that seems suitable to handle fairly broad generalizations of Polya urns. To show the applicability of the results we determine the limiting fraction of balls in an urn with balls of two colors. We consider two models generalizing the Polya urn, in the first one ball is drawn and replaced with balls of (possibly) both colors according to which color was drawn. In the second, two balls are drawn simultaneously and replaced along with balls of (possibly) both colors according to what combination of colors were drawn.

Renlund, Henrik

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Charge Density Wave Compounds  

NLE Websites -- All DOE Office Websites (Extended Search)

Fisher Research Group Fisher Research Group Layered Chalcogenides 29 February 2008 Controlling the Wave by Brad Plummer, SLAC Communications Stanford University researchers working in part at SSRL have discovered a novel set of properties pertaining to a compound of materials called tritellurides. These compounds, composed of three atoms of tellurium and a single atom of one of the rare earth elements, demonstrate unique electronic properties that can be controlled by altering the temperature of the material. The tritellurides display phenomena known as charge density waves (CDW). In a normal conductive metal, electrons persist in a "sea" wherein they are evenly distributed and equally available, or conductive. A CDW occurs under certain circumstances and causes the electrons to clump together, lowering their availability, and thereby lowering the compound's conductivity. Tellurium, when crystallized into quasi-two-dimensional planes and combined with rare earth elements, produces a material with CDWs that can be manipulated and controlled.

162

Nuclear energy density optimization  

Science Journals Connector (OSTI)

We carry out state-of-the-art optimization of a nuclear energy density of Skyrme type in the framework of the Hartree-Fock-Bogoliubov theory. The particle-hole and particle-particle channels are optimized simultaneously, and the experimental data set includes both spherical and deformed nuclei. The new model-based, derivative-free optimization algorithm used in this work has been found to be significantly better than standard optimization methods in terms of reliability, speed, accuracy, and precision. The resulting parameter set unedf0 results in good agreement with experimental masses, radii, and deformations and seems to be free of finite-size instabilities. An estimate of the reliability of the obtained parameterization is given, based on standard statistical methods. We discuss new physics insights offered by the advanced covariance analysis.

M. Kortelainen; T. Lesinski; J. Mor; W. Nazarewicz; J. Sarich; N. Schunck; M. V. Stoitsov; S. Wild

2010-08-13T23:59:59.000Z

163

Incorporation of particle collisions in the time-dependent Hartree-Fock approximation  

SciTech Connect

In the time-dependent Hartree-Fock (TDHF) approximation, particles interact only through the mean field, and the collisions between particles are not included. Previously, we formulated the extended time-dependent Hartree-Fock (ETDHF) approximation to include particle collisions in terms of a temporal variation of the occupation probability n/sub lambda/ for the single-particle states. In the simplest approximation, the single-particle potential is modified only through the particle density which depends on n/sub lambda/. We wish to refine the extended TDHF approximation by studying how particle collisions affect the single-particle potential. We find that it acquires two second-order contributions which are state-dependent and are the generalization of the core polarization and correlation contributions one encounters in the study of the nucleon-nucleus optical potentials. In consequence, concepts such as energy-dependent single-particle potentials and effective masses may be properly introduced in the extended TDHF approximation. We also wish to review the conservation of energy in the ETDHF approximation. We find that the total energy should include a second-order contribution due to correlations arising from particle collisions.

Wong, C.Y.

1982-01-01T23:59:59.000Z

164

Density Functional Theory for Superconductors  

E-Print Network (OSTI)

Density Functional Theory for Superconductors N. N. LATHIOTAKIS,1,2 M. A. L. MARQUES,1,2,3 M. LU; density functional theory; critical temperature; exchange and correlation; phonon and theoretical chemistry is density functional theory (DFT). Its foundations were established in the mid-1960s

Gross, E.K.U.

165

Embedding of the Brueckner Approximation in the Extended Jastrow Scheme  

Science Journals Connector (OSTI)

A nonperturbative derivation of the Brueckner approximation to the ground-state energy of nuclear matter (with standard choice of hole and particle energies) is given within the framework of the method of correlated basis functions. The structure of the factor-cluster (FIY) expansion of the expectation value of the Hamiltonian with respect to a trial function incorporating short-range correlations in a general fashion, is analyzed for a uniform extended medium of fermions. With a special choice of correlated wave function, the Brueckner approximation is extracted from the FIY expansion by selective summation of two-body combination terms to all orders in the smallness parameter ? associated, in this case, with both Brueckner-Bethe-Goldstone and FIY energy expansions. A reexamination of the numerical comparison of conventional Brueckner and Jastrow methods carried out earlier for two simple models of nuclear matter leads to the conclusion that it is inadvisable, at least in a Jastrow calculation satisfying the average Pauli condition, to incorporate the O(?) contribution of the analog of the dispersion correction of reaction-matrix theory without at the same time including the O(?) contribution of the analog of the Bethe-Faddeev term. For the uniform extended medium for the Jastrow choice of wave function, there is a formal cancellation of these two three-body contributions, the scale of this cancellation being governed by the size of ?. In the numerical example considered, ? is about 0.22 and the cancellation goes something like +14 MeV-15 MeV=-1 MeV. These findings, when juxtaposed with the standard Brueckner results for the simple models in question, suggest that a departure from the standard prescription of hole and particle energies in reaction-matrix theory may be necessary when ? is sizeable-as in liquid He3 and the high-density neutron gas, as well as equilibrium nuclear matter described with some potentials.

J. W. Clark and M. L. Ristig

1973-05-01T23:59:59.000Z

166

Understanding the NMR shifts in paramagnetic transition metal oxides using density functional theory calculations  

E-Print Network (OSTI)

obvious. In this paper, we show by means of density functional theory DFT calcula- tions that a rationalUnderstanding the NMR shifts in paramagnetic transition metal oxides using density functional functional theory DFT calculations in the generalized gradient approximation. For each compound, we calculate

Ceder, Gerbrand

167

Calculation of hyperfine coupling constants of radicals by density-functional theory  

Science Journals Connector (OSTI)

Hyperfine coupling constants for small radicals have been calculated using the density-functional theory with a gradient-corrected (GC) local-spin-density approximation (LSDA). The agreement between the calculated and observed results is fairly good. The GC-LSDA is essential to calculate the isotropic hyperfine coupling constants for ? radicals. For ? radicals, the simple LSDA also leads to relatively good results.

Nobuhiko Ishii and Tatsuo Shimizu

1993-08-01T23:59:59.000Z

168

Density-Dependence of Two-Body Interactions Beyond the Mean-Field Approximation. Part 1: Generalized Brueckner G-Matrix in the Local Approximation  

E-Print Network (OSTI)

This paper has been merged with the preprint nucl-th/0210057. The combined version is accepted for publication is Phys. Rev. C

T. Duguet; P. Bonche

2002-10-17T23:59:59.000Z

169

Approximation method for spin- Ising models  

Science Journals Connector (OSTI)

An approximation for calculating the thermodynamic properties of spin- Ising models is described. The method is based on the formulation of Kramers and Wannier for the square lattice, and involves expressing the free energy in terms of the limiting maximum eigenvalue of a matrix sequence which represents the contribution from a single spin of the lattice. The application of this formulation to various two- and three-dimensional lattices shows that many of these are characterized by an identically structured matrix sequence with exactly two nonvanishing elements in each row and column. To explore the potential of using this similarity and its simplicity for analyzing Ising models we consider the two-dimensional square lattice in an external field and approximate the doubly infinite lattice by a semi-infinite one consisting of n(?10) infinitely long rows. Calculations are carried out and compared with (1) Onsager's formula for the free energy, (2) the Onsanger-Yang formula for the spontaneous magnetization, and (3) values calculated from series. Except for the region around the critical point where the correlation length exceeds n lattice spacings, substantial agreementto better than 12 places of decimals in some casesis obtained. As an additional measure of the potential of this method, a value for the critical exponent ? is computed by the extrapolation of the magnetization along the critical isotherm. The result is found to be in excellent agreement with the known value for ?.

Solomon Gartenhaus

1983-02-01T23:59:59.000Z

170

An Improved Approximation Algorithm For Vertex Cover with Hard Capacities  

E-Print Network (OSTI)

An Improved Approximation Algorithm For Vertex Cover with Hard Capacities #3; Rajiv Gandhi y Eran-hard as it generalizes the well-known vertex cover problem. Previously, approximation algorithms with an approximation version of this problem is at least as hard as set cover; in addition, they developed a 3-approximation

Srinivasan, Aravind

171

On the mathematical treatment of the Born-Oppenheimer approximation.  

E-Print Network (OSTI)

On the mathematical treatment of the Born-Oppenheimer approximation. Thierry Jecko AGM, UMR 8088 du the main ideas used by mathematicians to show the accuracy of the Born-Oppenheimer approximation of the approximation in Chemistry. We contribute in this way to the discussion on the Born-Oppenheimer approximation

Paris-Sud XI, Université de

172

A comparison of approximate models for radiation in gas turbines  

Science Journals Connector (OSTI)

Approximate equations for radiative heat transfer equations coupled to an equation for the temperature are stated and a comparative numerical study of the different approximations is given. The approximation methods considered here range from moment methods to simplified PN-approximations. Numerical experiments and comparisons in different space dimensions and for various physical situations are presented.

M. Frank; M. Seaid; A. Klar; R. Pinnau; G. Thommes; J. Janicka

2004-01-01T23:59:59.000Z

173

Collective Modes in a Superfluid Neutron Gas within the Quasiparticle Random-Phase Approximation  

E-Print Network (OSTI)

We study collective excitations in a superfluid neutron gas at zero temperature within the quasiparticle random phase approximation. The particle-hole residual interaction is obtained from a Skyrme functional, while a separable interaction is used in the pairing channel which gives a realistic density dependence of the pairing gap. In accordance with the Goldstone theorem, we find an ungapped collective mode (analogous to the Bogoliubov-Anderson mode). At low momentum, its dispersion relation is approximately linear and its slope coincides with the hydrodynamic speed of sound calculated with the Skyrme equation of state. The response functions are compared with those obtained within the Landau approximation. We also compute the contribution of the collective mode to the specific heat of the neutron gas, which is relevant for the thermodynamic properties of the inner crust of neutron stars.

Nol Martin; Michael Urban

2015-01-05T23:59:59.000Z

174

Energy-Density Enhancement of Carbon-Nanotube-Based Supercapacitors with Redox Couple in Organic Electrolyte  

Science Journals Connector (OSTI)

Energy-Density Enhancement of Carbon-Nanotube-Based Supercapacitors with Redox Couple in Organic Electrolyte ... The redox molecule also contributes to increasing the cell capacitance by a faradaic redox reaction, and therefore the energy density of the supercapacitor can be significantly increased. ... More specifically, the addition of redox-active decamethylferrocene in an organic electrolyte results in an approximately 27-fold increase in the energy density of carbon-nanotube-based supercapacitors. ...

Jinwoo Park; Byungwoo Kim; Young-Eun Yoo; Haegeun Chung; Woong Kim

2014-11-16T23:59:59.000Z

175

The Approximability Behaviour of Some Combinatorial Problems with Respectto the Approximability of a Class of Maximum Independent Set Problems  

Science Journals Connector (OSTI)

We prove that the existence of a polynomial time ?-approximation algorithm (where ? < 1 is a fixed constant) for a class of independent set problems, leads to a polynomial time approximation algorithm with approximation ratio strictly ... Keywords: NP-complete problem, convex programming, independent set, polynomial time approximation algorithm, quadratic programming, vertex covering

Marc Demange; Vangelis Th. Paschos

1997-05-01T23:59:59.000Z

176

Effects of the symmetry energy on properties of neutron star crusts near the neutron drip density  

E-Print Network (OSTI)

We study the effects of the symmetry energy on the neutron drip density and properties of nuclei in neutron star crusts. The nonuniform matter around the neutron drip point is calculated by using the Thomas--Fermi approximation with the relativistic mean-field model. The neutron drip density and the composition of the crust are found to be correlated with the symmetry energy and its slope. We compare the self-consistent Thomas--Fermi approximation with other treatments of surface and Coulomb energies and find that these finite-size effects play an essential role in determining the equilibrium state at low density.

S. S. Bao; J. N. Hu; Z. W. Zhang; H. Shen

2014-10-03T23:59:59.000Z

177

Symmetry energy effects on properties of neutron star crusts around the neutron drip density  

E-Print Network (OSTI)

We study the effects of the symmetry energy on the neutron drip density and properties of nuclei in neutron star crusts. The nonuniform matter around the neutron drip point is calculated using the Thomas--Fermi approximation with the relativistic mean-field model. The neutron drip density and the composition of the crust are found to be correlated with the symmetry energy and its slope. We compare the self-consistent Thomas--Fermi approximation with other treatments of surface and Coulomb energies, and find that these finite-size effects play an essential role in determining the equilibrium state at low density.

Bao, S S; Zhang, Z W; Shen, H

2014-01-01T23:59:59.000Z

178

Semiclassical approximation to supersymmetric quantum gravity  

SciTech Connect

We develop a semiclassical approximation scheme for the constraint equations of supersymmetric canonical quantum gravity. This is achieved by a Born-Oppenheimer type of expansion, in analogy to the case of the usual Wheeler-DeWitt equation. The formalism is only consistent if the states at each order depend on the gravitino field. We recover at consecutive orders the Hamilton-Jacobi equation, the functional Schroedinger equation, and quantum gravitational correction terms to this Schroedinger equation. In particular, the following consequences are found: (i) the Hamilton-Jacobi equation and therefore the background spacetime must involve the gravitino, (ii) a (many-fingered) local time parameter has to be present on super Riem {sigma} (the space of all possible tetrad and gravitino fields) (iii) quantum supersymmetric gravitational corrections affect the evolution of the very early Universe. The physical meaning of these equations and results, in particular, the similarities to and differences from the pure bosonic case, are discussed.

Kiefer, Claus; Lueck, Tobias; Moniz, Paulo [Institut fuer Theoretische Physik, Universitaet zu Koeln, Zuelpicher Strasse 77, 50937 Cologne (Germany); Astronomy Unit, School of Mathematical Sciences, Queen Mary College, University of London, Mile End Road, London E1 4NS (United Kingdom)

2005-08-15T23:59:59.000Z

179

Adiabatic Approximation, Semiclassical Scattering, and Unidirectional Invisibility  

E-Print Network (OSTI)

The transfer matrix of a possibly complex and energy-dependent scattering potential can be identified with the $S$-matrix of a two-level time-dependent non-Hermitian Hamiltonian H(t). We show that the application of the adiabatic approximation to H(t) corresponds to the semiclassical description of the original scattering problem. In particular, the geometric part of the phase of the evolving eigenvectors of H(t) gives the pre-exponential factor of the WKB wave functions. We use these observations to give an explicit semiclassical expression for the transfer matrix. This allows for a detailed study of the semiclassical unidirectional reflectionlessness and invisibility. We examine concrete realizations of the latter in the realm of optics.

Ali Mostafazadeh

2014-01-17T23:59:59.000Z

180

Heat flow in the postquasistatic approximation  

SciTech Connect

We apply the postquasistatic approximation to study the evolution of spherically symmetric fluid distributions undergoing dissipation in the form of radial heat flow. For a model that corresponds to an incompressible fluid departing from the static equilibrium, it is not possible to go far from the initial state after the emission of a small amount of energy. Initially collapsing distributions of matter are not permitted. Emission of energy can be considered as a mechanism to avoid the collapse. If the distribution collapses initially and emits one hundredth of the initial mass only the outermost layers evolve. For a model that corresponds to a highly compressed Fermi gas, only the outermost shell can evolve with a shorter hydrodynamic time scale.

Rodriguez-Mueller, B. [Computational Science Research Center, College of Sciences, San Diego State University, San Diego, California (United States); Peralta, C. [Deutscher Wetterdienst, Frankfurter Strasse 135, 63067 Offenbach (Germany); School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia); Barreto, W. [Centro de Fisica Fundamental, Facultad de Ciencias, Universidad de Los Andes, Merida (Venezuela, Bolivarian Republic of); Rosales, L. [Laboratorio de Fisica Computacional, Universidad Experimental Politecnica, 'Antonio Jose de Sucre', Puerto Ordaz (Venezuela, Bolivarian Republic of)

2010-08-15T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Heat flow in the postquasistatic approximation  

E-Print Network (OSTI)

We apply the postquasistatic approximation to study the evolution of spherically symmetric fluid distributions undergoing dissipation in the form of radial heat flow. For a model which corresponds to an incompressible fluid departing from the static equilibrium, it is not possible to go far from the initial state after the emission of a small amount of energy. Initially collapsing distributions of matter are not permitted. Emission of energy can be considered as a mechanism to avoid the collapse. If the distribution collapses initially and emits one hundredth of the initial mass only the outermost layers evolve. For a model which corresponds to a highly compressed Fermi gas, only the outermost shell can evolve with a shorter hydrodynamic time scale.

B. Rodrguez-Mueller; C. Peralta; W. Barreto; L. Rosales

2010-05-10T23:59:59.000Z

182

Improved association in a classical density functional theory for water  

SciTech Connect

We present a modification to our recently published statistical associating fluid theory-based classical density functional theory for water. We have recently developed and tested a functional for the averaged radial distribution function at contact of the hard-sphere fluid that is dramatically more accurate at interfaces than earlier approximations. We now incorporate this improved functional into the association term of our free energy functional for water, improving its description of hydrogen bonding. We examine the effect of this improvement by studying two hard solutes (a hard hydrophobic rod and a hard sphere) and a Lennard-Jones approximation of a krypton atom solute. The improved functional leads to a moderate change in the density profile and a large decrease in the number of hydrogen bonds broken in the vicinity of the hard solutes. We find an improvement of the partial radial distribution for a krypton atom in water when compared with experiment.

Krebs, Eric J.; Schulte, Jeff B.; Roundy, David [Department of Physics, Oregon State University, Corvallis, Oregon 97331 (United States)] [Department of Physics, Oregon State University, Corvallis, Oregon 97331 (United States)

2014-03-28T23:59:59.000Z

183

Generation of Gaussian Density Fields  

E-Print Network (OSTI)

This document describes analytical and numerical techniques for the generation of Gaussian density fields, which represent cosmological density perturbations. The mathematical techniques involved in the generation of density harmonics in k-space, the filtering of the density fields, and the normalization of the power spectrum to the measured temperature fluctuations of the Cosmic Microwave Background, are presented in details. These techniques are well-known amongst experts, but the current literature lacks a formal description. I hope that this technical report will prove useful to new researchers moving into this field, sparing them the task of reinventing the wheel.

Hugo Martel

2005-06-22T23:59:59.000Z

184

Density Functional Theory (DFT) Simulated Annealing (SA)  

E-Print Network (OSTI)

. . . . . . . . 9 2009 #12;! " # $ % & - " # $ %' ! " # # $ % & # ( # " ) Density Functional Theory) % Lattice-Boltzmann (LBM) #12;! " # $ % & - " # $ %' ! " # # $ % & # ( # " ) Density Functional Theory (DFT;! " # $ % & - " # $ %' ! " # # $ % & # ( # " ) Density Functional Theory (DFT) Simulated Annealing (SA) Monte Carlo &$ ' ' (GCMC

185

Approximate von Neumann entropy for directed graphs  

Science Journals Connector (OSTI)

In this paper, we develop an entropy measure for assessing the structural complexity of directed graphs. Although there are many existing alternative measures for quantifying the structural properties of undirected graphs, there are relatively few corresponding measures for directed graphs. To fill this gap in the literature, we explore an alternative technique that is applicable to directed graphs. We commence by using Chung's generalization of the Laplacian of a directed graph to extend the computation of von Neumann entropy from undirected to directed graphs. We provide a simplified form of the entropy which can be expressed in terms of simple node in-degree and out-degree statistics. Moreover, we find approximate forms of the von Neumann entropy that apply to both weakly and strongly directed graphs, and that can be used to characterize network structure. We illustrate the usefulness of these simplified entropy forms defined in this paper on both artificial and real-world data sets, including structures from protein databases and high energy physics theory citation networks.

Cheng Ye; Richard C. Wilson; Csar H. Comin; Luciano da F. Costa; Edwin R. Hancock

2014-05-12T23:59:59.000Z

186

Femtolensing: Beyond the Semi-Classical Approximation  

E-Print Network (OSTI)

Femtolensing is a gravitational lensing effect in which the magnification is a function not only of the positions and sizes of the source and lens, but also of the wavelength of light. Femtolensing is the only known effect of $(10^{-13}-10^{-16} M_{\\sun})$ dark-matter objects and may possibly be detectable in cosmological gamma-ray burst spectra. We present a new and efficient algorithm for femtolensing calculations in general potentials. The physical-optics results presented here differ at low frequencies from the semi-classical approximation, in which the flux is attributed to a finite number of mutually coherent images. At higher frequencies, our results agree well with the semi-classical predictions. Applying our method to a point-mass lens with external shear, we find complex events that have structure at both large and small spectral resolution. In this way, we show that femtolensing may be observable for lenses up to $10^{-11}$ solar masses, much larger than previously believed. Additionally, we discuss the possibility of a search for femtolensing of white dwarfs in the LMC at optical wavelengths.

A. Ulmer; J. Goodman

1994-06-13T23:59:59.000Z

187

Nuclear matter at high temperature and low net baryonic density  

SciTech Connect

We study the effect of the {sigma}-{omega} mesons interaction on nucleon-antinucleon matter properties. This interaction is employed in the context of the linear Walecka model to discuss the behavior of this system at high temperature and low net baryonic density regime. The field equations are solved in the relativistic mean-field approximation and our results show that the phase transition pointed out in the literature for this regime is eliminated when the meson interaction are considered.

Costa, R. S.; Duarte, S. B. [Centro Brasileiro de Pesquisas Fisicas-CBPF, Rua Dr. Xavier Sigaud, 150 Urca 22290-180, Rio de Janeiro, RJ (Brazil); Oliveira, J. C. T. [Departamento de Fisica, Universidade Federal de Roraima, Campus do Paricarana, s/n, 69310-270, Boa Vista, RR (Brazil); Rodrigues, H. [Centro Federal de Educacao Tecnologica do Rio de Janeiro, Av. Maracana, 249 Maracana 20271-110, Rio de Janeiro, RJ (Brazil); Chiapparini, M. [Instituto de Fisica, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier, 524 Maracana, Rio de Janeiro, RJ (Brazil)

2010-11-12T23:59:59.000Z

188

Analysis of the Independent Particle Model approach to Nuclear Densities  

E-Print Network (OSTI)

We present an analysis of the use of the Darwin-Fowler approximation in connection with the statistical IPM, by comparing the results of our recent studies with the occupation number approach (OCN) and some traditional statistical independent particle model (IPM) approaches. The analysis of level density works based on the statistical IPM reveals that the use of the the Darwin-Fowler approximation, in some of them, is theoretically inconsistent and some of their results should rather be considered as theoretical coincidences with other consistent approaches, than proofs of their validity. We conclude that, in general, the use of the Darwin-Fowler approximation with the statistical IPM should be used criteriously or, if possible, avoided altogether and suggest that the combinatorial IPM approaches have important advantages over the other models and formalisms analyzed in this paper, especially regarding the consistency of the microscopic description of the nuclear structure and dynamics of non highly excited systems.

F. B. Guimaraes

2012-08-31T23:59:59.000Z

189

Set Covering and Network Optimization: Dynamic and Approximation Algorithms  

E-Print Network (OSTI)

Set Covering and Network Optimization: Dynamic and Approximation Algorithms Orestis A. Telelis summarize our results on development and analysis of approximation and dynamic algorithms for set covering and network optimization problems. The results include probabilistic analysis of set covering algorithms

Kouroupetroglou, Georgios

190

VISCOSITY AND RELAXATION APPROXIMATIONS FOR HYPERBOLIC SYSTEMS OF CONSERVATION LAWS  

E-Print Network (OSTI)

VISCOSITY AND RELAXATION APPROXIMATIONS FOR HYPERBOLIC SYSTEMS OF CONSERVATION LAWS Athanasios E. Tzavaras Abstract. These lecture notes deal with the approximation of conservation laws via viscosity or relaxation. The following topics are covered: The general structure of viscosity and relaxation

Tzavaras, Athanasios E.

191

Approximate Linear Programming for Firstorder MDPs Scott Sanner  

E-Print Network (OSTI)

, the bounds that we derive for approximation error apply equally to all domain instantiations (i.eApproximate Linear Programming for First­order MDPs Scott Sanner University of Toronto Department

Sanner, Scott

192

Three fast computational approximation methods in hypersonic aerothermodynamics  

E-Print Network (OSTI)

Three fast computational approximation methods in hypersonic aerothermodynamics V.V. Riabov* Rivier analyzed to study nonequilibrium hypersonic viscous flows near blunt bodies. These approximations allow; Nonequilibrium hypersonic flows 1. Introduction Numerous methods [1,2] that require significant computational

Riabov, Vladimir V.

193

The Hadley Circulation and the Weak Temperature Gradient Approximation  

Science Journals Connector (OSTI)

The weak temperature gradient (WTG) approximation is applied to simple shallow-water models of the Hadley circulation. While it is difficult to formally justify the use of the WTG approximation for this problem, the derived WTG solutions are ...

L. M. Polvani; A. H. Sobel

2002-05-01T23:59:59.000Z

194

An approximate thermal analysis of Stirling engine regenerators  

Science Journals Connector (OSTI)

This paper approximates the transport phenomena in a Stirling engine regenerator to aid its practical design. The...

S. H. Park; Y. -S. Lee

1993-06-01T23:59:59.000Z

195

Bond selective chemistry beyond the adiabatic approximation  

SciTech Connect

One of the most important challenges in chemistry is to develop predictive ability for the branching between energetically allowed chemical reaction pathways. Such predictive capability, coupled with a fundamental understanding of the important molecular interactions, is essential to the development and utilization of new fuels and the design of efficient combustion processes. Existing transition state and exact quantum theories successfully predict the branching between available product channels for systems in which each reaction coordinate can be adequately described by different paths along a single adiabatic potential energy surface. In particular, unimolecular dissociation following thermal, infrared multiphoton, or overtone excitation in the ground state yields a branching between energetically allowed product channels which can be successfully predicted by the application of statistical theories, i.e. the weakest bond breaks. (The predictions are particularly good for competing reactions in which when there is no saddle point along the reaction coordinates, as in simple bond fission reactions.) The predicted lack of bond selectivity results from the assumption of rapid internal vibrational energy redistribution and the implicit use of a single adiabatic Born-Oppenheimer potential energy surface for the reaction. However, the adiabatic approximation is not valid for the reaction of a wide variety of energetic materials and organic fuels; coupling between the electronic states of the reacting species play a a key role in determining the selectivity of the chemical reactions induced. The work described below investigated the central role played by coupling between electronic states in polyatomic molecules in determining the selective branching between energetically allowed fragmentation pathways in two key systems.

Butler, L.J. [Univ. of Chicago, IL (United States)

1993-12-01T23:59:59.000Z

196

Density Log | Open Energy Information  

Open Energy Info (EERE)

Density Log Density Log Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Technique: Density Log Details Activities (6) Areas (6) Regions (0) NEPA(0) Exploration Technique Information Exploration Group: Downhole Techniques Exploration Sub Group: Well Log Techniques Parent Exploration Technique: Well Log Techniques Information Provided by Technique Lithology: provides data on the bulk density of the rock surrounding the well Stratigraphic/Structural: Stratigraphic correlation between well bores. Hydrological: Porosity of the formations loggesd can be calculated for the Density log andprovide an indication potential aquifers. Thermal: Cost Information Low-End Estimate (USD): 0.4040 centUSD 4.0e-4 kUSD 4.0e-7 MUSD 4.0e-10 TUSD / foot Median Estimate (USD): 0.6868 centUSD

197

Improved Approximation Algorithms for the Partial Vertex Cover Problem  

E-Print Network (OSTI)

Improved Approximation Algorithms for the Partial Vertex Cover Problem Eran Halperin 1? and Aravind words and phrases. Partial vertex cover, approximation algorithms, semide#12;nite programming edges are covered. Just as for the vertex cover problem, 2-approximation algorithms are known

Srinivasan, Aravind

198

An Improved Approximation Algorithm For Vertex Cover with Hard Capacities  

E-Print Network (OSTI)

of this problem is at least as hard as set cover; they have also developed a 3-approximation algorithm cover problem. Key Words and Phrases: Approximation algorithms, capacitated covering, set cover, vertexAn Improved Approximation Algorithm For Vertex Cover with Hard Capacities (Extended Abstract) Rajiv

Khuller, Samir

199

A Local 2-approximation Algorithm for the Vertex Cover Problem  

E-Print Network (OSTI)

A Local 2-approximation Algorithm for the Vertex Cover Problem Matti °Astrand, Patrik Flor.lastname}@cs.helsinki.fi Abstract. We present a distributed 2-approximation algorithm for the minimum vertex cover problem and Johnson's [2] list. In a centralised setting, the polynomial-time approximability of the vertex cover

Suomela, Jukka

200

A Parallel Algorithm for Approximating the Minimum Cycle Cover  

E-Print Network (OSTI)

approximation algorithm for the problem of finding a minimum cycle cover. A cycle cover is a set of cycles cover [1, 7, 8]. The basis for our approximation algorithm is a routine to find a maximal set of edgeA Parallel Algorithm for Approximating the Minimum Cycle Cover Philip Klein \\Lambda Aiken

Yang, Junfeng

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

An Improved Approximation Algorithm For Vertex Cover with Hard Capacities  

E-Print Network (OSTI)

as hard as set cover; they have also developed a 3-approximation algorithm for the unweighted version. We Words and Phrases: Approximation algorithms, capacitated covering, set cover, vertex cover, linearAn Improved Approximation Algorithm For Vertex Cover with Hard Capacities (Extended Abstract) Rajiv

Srinivasan, Aravind

202

Viscosity and Relaxation Approximation for Hyperbolic Systems of Conservation Laws  

E-Print Network (OSTI)

Viscosity and Relaxation Approximation for Hyperbolic Systems of Conservation Laws Athanasios E with the approximation of conservation laws via viscosity or relaxation. The following topics are covered: The general structure of viscosity and relaxation approximations is discussed, as suggested by the second law

Tzavaras, Athanasios E.

203

SUBTRACTING A BEST RANK-1 APPROXIMATION MAY INCREASE TENSOR RANK  

E-Print Network (OSTI)

SUBTRACTING A BEST RANK-1 APPROXIMATION MAY INCREASE TENSOR RANK Alwin Stegeman Heymans Institute, fax: +33 4 92 94 28 98, pcomon@unice.fr ABSTRACT Is has been shown that a best rank-R approximation be solved by consecutively computing and substracting best rank-1 approximations. The reason

Paris-Sud XI, Université de

204

On the mathematical treatment of the Born-Oppenheimer approximation.  

E-Print Network (OSTI)

On the mathematical treatment of the Born-Oppenheimer approximation. Thierry Jecko AGM, UMR 8088 du the main ideas used by mathematicians to show the accuracy of the Born-Oppenheimer approximation in this way to the discussion on the Born-Oppenheimer approximation initiated in [SW]. The paper neither

205

On the mathematical treatment of the Born-Oppenheimer approximation.  

E-Print Network (OSTI)

On the mathematical treatment of the Born-Oppenheimer approximation. Thierry Jecko AGM, UMR 8088 du the main ideas used by mathematicians to show the accuracy of the Born-Oppenheimer approximation in this way to the discussion on the Born-Oppenheimer approximation initiated in [SW1]. The paper neither

Paris-Sud XI, Université de

206

Smoluchowski-Kramers approximation in the case of variable friction  

E-Print Network (OSTI)

We consider the small mass asymptotics (Smoluchowski-Kramers approximation) for the Langevin equation with a variable friction coefficient. The limit of the solution in the classical sense does not exist in this case. We study a modification of the Smoluchowski-Kramers approximation. Some applications of the Smoluchowski-Kramers approximation to problems with fast oscillating or discontinuous coefficients are considered.

Mark Freidlin; Wenqing Hu

2012-03-03T23:59:59.000Z

207

Rough Set Approximations in Formal Concept Analysis and Knowledge Spaces  

E-Print Network (OSTI)

Rough Set Approximations in Formal Concept Analysis and Knowledge Spaces Feifei Xu1,2 , Yiyu Yao2 a generalized definition of rough set approximations, based on a subsystem of subsets of a universe. The sub set approximations. 1 Introduction Rough set theory [6, 7] is an extension of the set theory with two

Yao, Yiyu

208

Approximation of conic sections by curvature continuous quartic Bzier curves  

Science Journals Connector (OSTI)

In this paper we propose two approximation methods of conic section by quartic Bezier curves. These are the extensions of the quartic Bezier approximations of circular arcs presented in Ahn and Kim (1997) [1] and Kim and Ahn (2007) [10] to conic cases. ... Keywords: Approximation order, Conic section, Curvature continuity, Hausdorff distance, Quartic Bzier curves, Spline

Young Joon Ahn

2010-10-01T23:59:59.000Z

209

Linear response of homogeneous nuclear matter with energy density functionals  

E-Print Network (OSTI)

Response functions of infinite nuclear matter with arbitrary isospin asymmetry are studied in the framework of the random phase approximation. The residual interaction is derived from a general nuclear Skyrme energy density functional. Besides the usual central, spin-orbit and tensor terms it could also include other components as new density-dependent terms or three-body terms. Algebraic expressions for the response functions are obtained from the Bethe-Salpeter equation for the particle-hole propagator. Applications to symmetric nuclear matter, pure neutron matter and asymmetric nuclear matter are presented and discussed. Spin-isospin strength functions are analyzed for varying conditions of density, momentum transfer, isospin asymmetry, and temperature for some representative Skyrme functionals. Particular attention is paid to the discussion of instabilities, either real or unphysical, which could manifest in finite nuclei.

Pastore, A; Navarro, J

2014-01-01T23:59:59.000Z

210

Linear response of homogeneous nuclear matter with energy density functionals  

E-Print Network (OSTI)

Response functions of infinite nuclear matter with arbitrary isospin asymmetry are studied in the framework of the random phase approximation. The residual interaction is derived from a general nuclear Skyrme energy density functional. Besides the usual central, spin-orbit and tensor terms it could also include other components as new density-dependent terms or three-body terms. Algebraic expressions for the response functions are obtained from the Bethe-Salpeter equation for the particle-hole propagator. Applications to symmetric nuclear matter, pure neutron matter and asymmetric nuclear matter are presented and discussed. Spin-isospin strength functions are analyzed for varying conditions of density, momentum transfer, isospin asymmetry, and temperature for some representative Skyrme functionals. Particular attention is paid to the discussion of instabilities, either real or unphysical, which could manifest in finite nuclei.

A. Pastore; D. Davesne; J. Navarro

2014-12-07T23:59:59.000Z

211

Communication: Self-interaction correction with unitary invariance in density functional theory  

SciTech Connect

Standard spin-density functionals for the exchange-correlation energy of a many-electron ground state make serious self-interaction errors which can be corrected by the Perdew-Zunger self-interaction correction (SIC). We propose a size-extensive construction of SIC orbitals which, unlike earlier constructions, makes SIC computationally efficient, and a true spin-density functional. The SIC orbitals are constructed from a unitary transformation that is explicitly dependent on the non-interacting one-particle density matrix. When this SIC is applied to the local spin-density approximation, improvements are found for the atomization energies of molecules.

Pederson, Mark R., E-mail: mark.pederson@science.doe.gov [Office of Basic Energy Sciences, SC22.1, U.S. Department of Energy, Washington, DC 20585 (United States); Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Ruzsinszky, Adrienn [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States)] [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Perdew, John P. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States) [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States)

2014-03-28T23:59:59.000Z

212

Bose-Einstein condensation and Silver Blaze property from the two-loop $?$-derivable approximation  

E-Print Network (OSTI)

We extend our previous investigation of the two-loop $\\Phi$-derivable approximation to finite chemical potential $\\mu$ and discuss Bose-Einstein condensation (BEC) in the case of a charged scalar field with $O(2)$ symmetry. We show that the approximation is renormalizable by means of counterterms which are independent of both the temperature and the chemical potential. We point out the presence of an additional skew contribution to the propagator as compared to the $\\mu=0$ case, which comes with its own gap equation (except at Hartree level). We solve this equation together with the field equation, and the usual longitudinal and transversal gap equations to find that the transition is second order, in agreement with recent lattice results to which we compare. We also discuss a general criterion an approximation should obey for the so-called Silver Blaze property to hold, and we show that any $\\Phi$-derivable approximation at finite temperature and density obeys this criterion if one chooses a UV regularization that does not cut off the Matsubara sums.

Gergely Mark; Urko Reinosa; Zsolt Szp

2014-10-26T23:59:59.000Z

213

Taming Density Functional Theory by Coarse-Graining  

E-Print Network (OSTI)

The standard (``fine-grained'') interpretation of quantum density functional theory, in which densities are specified with infinitely-fine spatial resolution, is mathematically unruly. Here, a coarse-grained version of DFT, featuring limited spatial resolution, and its relation to the fine-grained theory in the $L^1\\cap L^3$ formulation of Lieb, is studied, with the object of showing it to be not only mathematically well-behaved, but consonant with the spirit of DFT, practically (computationally) adequate and sufficiently close to the standard interpretation as to accurately reflect its non-pathological properties. The coarse-grained interpretation is shown to be a good model of formal DFT in the sense that: all densities are (ensemble)-V-representable; the intrinsic energy functional $F$ is a continuous function of the density and the representing external potential is the (directional) functional derivative of the intrinsic energy. Also, the representing potential $v[\\rho]$ is quasi-continuous, in that $v[\\rho]\\rho$ is continuous as a function of $\\rho$. The limit of coarse-graining scale going to zero is studied to see if convergence to the non-pathological aspects of the fine-grained theory is adequate to justify regarding coarse-graining as a good approximation. Suitable limiting behaviors or intrinsic energy, densities and representing potentials are found. Intrinsic energy converges monotonically, coarse-grained densities converge uniformly strongly to their low-intrinsic-energy fine-grainings, and $L^{3/2}+L^\\infty$ representability of a density is equivalent to the existence of a convergent sequence of coarse-grained potential/ground-state density pairs.

Paul E. Lammert

2010-08-10T23:59:59.000Z

214

Energetics of a fluid under the Boussinesq approximation  

E-Print Network (OSTI)

This paper presents a theory describing the energy budget of a fluid under the Boussinesq approximation: the theory is developed in a manner consistent with the conservation law of mass. It shows that no potential energy is available under the Boussinesq approximation, and also reveals that the work done by the buoyancy force due to changes in temperature corresponds to the conversion between kinetic and internal energy. This energy conversion, however, makes only an ignorable contribution to the distribution of temperature under the approximation. The Boussinesq approximation is, in physical oceanography, extended so that the motion of seawater can be studied. This paper considers this extended approximation as well. Under the extended approximation, the work done by the buoyancy force due to changes in salinity corresponds to the conversion between kinetic and potential energy. It also turns out that the conservation law of mass does not allow the condition $\

Maruyama, Kiyoshi

2014-01-01T23:59:59.000Z

215

Eddington-inspired Born-Infeld gravity: nuclear physics constraints and the validity of the continuous fluid approximation  

SciTech Connect

In this paper we investigate the classical non-relativistic limit of the Eddington-inspired Born-Infeld theory of gravity. We show that strong bounds on the value of the only additional parameter of the theory ?, with respect to general relativity, may be obtained by requiring that gravity plays a subdominant role compared to electromagnetic interactions inside atomic nuclei. We also discuss the validity of the continuous fluid approximation used in this and other astrophysical and cosmological studies. We argue that although the continuous fluid approximation is expected to be valid in the case of sufficiently smooth density distributions, its use should eventually be validated at a quantum level.

Avelino, P.P., E-mail: ppavelin@fc.up.pt [Centro de Astrofsica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)

2012-11-01T23:59:59.000Z

216

Large two-dimensional electronic systems: Self-consistent energies and densities at low cost  

Science Journals Connector (OSTI)

We derive a self-consistent local variant of the Thomas-Fermi approximation for (quasi-) two-dimensional (2D) systems by localizing the Hartree term. The scheme results in an explicit orbital-free representation of the electron density and energy in terms of the external potential, the number of electrons, and the chemical potential determined upon normalization. We test the method over a variety 2D nanostructures by comparing to the Kohn-Sham 2D local-density approximation (LDA) calculations up to 600 electrons. Accurate results are obtained in view of the negligible computational cost. We also assess a local upper bound for the Hartree energy.

E. Rsnen; S. Pittalis; G. Bekio?lu; I. Makkonen

2013-01-31T23:59:59.000Z

217

Optimization Online - Fast Approximations for Online Scheduling of ...  

E-Print Network (OSTI)

Jun 19, 2014 ... Fast Approximations for Online Scheduling of Outpatient Procedure Centers. Berg(bberg2 ***at*** gmu.edu) Denton(btdenton ***at***...

Berg

2014-06-19T23:59:59.000Z

218

On Low Rank Matrix Approximations with Applications to Synthesis ...  

E-Print Network (OSTI)

a given matrix by a matrix of specified (low rank) in the uniform norm. ... Note that in the existing literature on low rank approximation of matrices the empha-.

2011-05-23T23:59:59.000Z

219

L^p Bernstein Inequalities and Radial Basis Function Approximation  

E-Print Network (OSTI)

on scattered data This dissertation follows the style of the Journal of Approximation Theory. 2 sites. F.J. Narcowich and J.D. Ward have made signi cant contributions to this eld studying approximation on compact manifolds where the data sites are allowed... on scattered data This dissertation follows the style of the Journal of Approximation Theory. 2 sites. F.J. Narcowich and J.D. Ward have made signi cant contributions to this eld studying approximation on compact manifolds where the data sites are allowed...

Ward, John P.

2012-10-19T23:59:59.000Z

220

E-Print Network 3.0 - approximation descriptions microscopiques...  

NLE Websites -- All DOE Office Websites (Extended Search)

de l'approximation locale. Ce calcul est entirement... :lpmmc.grenoble.cnrs.frspip.php?article404 Description : Les polaritons de cavit sont des quasiparticules hybrides...

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Finding approximately rank-one submatrices with the nuclear norm ...  

E-Print Network (OSTI)

Nov 8, 2010 ... Abstract: We propose a convex optimization formulation with the nuclear norm and $\\ell_1$-norm to find a large approximately rank-one...

Xuan Vinh Doan

2010-11-08T23:59:59.000Z

222

Better approximation guarantees for job-shop scheduling  

SciTech Connect

Job-shop scheduling is a classical NP-hard problem. Shmoys, Stein & Wein presented the first polynomial-time approximation algorithm for this problem that has a good (polylogarithmic) approximation guarantee. We improve the approximation guarantee of their work, and present further improvements for some important NP-hard special cases of this problem (e.g., in the preemptive case where machines can suspend work on operations and later resume). We also present NC algorithms with improved approximation guarantees for some NP-hard special cases.

Goldberg, L.A.; Paterson, M. [Univ. of Warwick, Conventry (United Kingdom); Srinivasan, A. [National Univ. of Singapore (Singapore)] [and others

1997-06-01T23:59:59.000Z

223

Revisiting density functionals for the primitive model of electric double layers  

SciTech Connect

Density functional theory (DFT) calculations are typically based on approximate functionals that link the free energy of a multi-body system of interest with the underlying one-body density distributions. Whereas good performance is often proclaimed for new developments, it is difficult to vindicate the theoretical merits relative to alternative versions without extensive comparison with the numerical results from molecular simulations. Besides, approximate functionals may defy statistical-mechanical sum rules and result in thermodynamic inconsistency. Here we compare systematically several versions of density functionals for ionic distributions near a charged surface using the primitive model of electric double layers. We find that the theoretical performance is sensitive not only to the specific forms of the density functional but also to the range of parameter space and the precise properties under consideration. In general, incorporation of the thermodynamic sum rule into the DFT calculations shows significant improvements for both electrochemical properties and ionic distributions.

Jiang, Jian [Department of Chemical and Environmental Engineering and Department of Mathematics, University of California, Riverside, California 92521 (United States) [Department of Chemical and Environmental Engineering and Department of Mathematics, University of California, Riverside, California 92521 (United States); Department of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Cao, Dapeng, E-mail: jwu@engr.ucr.edu, E-mail: doug@chem.byu.edu, E-mail: caodp@mail.buct.edu.cn [Department of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)] [Department of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Henderson, Douglas, E-mail: jwu@engr.ucr.edu, E-mail: doug@chem.byu.edu, E-mail: caodp@mail.buct.edu.cn [Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 (United States)] [Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 (United States); Wu, Jianzhong, E-mail: jwu@engr.ucr.edu, E-mail: doug@chem.byu.edu, E-mail: caodp@mail.buct.edu.cn [Department of Chemical and Environmental Engineering and Department of Mathematics, University of California, Riverside, California 92521 (United States)] [Department of Chemical and Environmental Engineering and Department of Mathematics, University of California, Riverside, California 92521 (United States)

2014-01-28T23:59:59.000Z

224

USING CUMULATIVE NUMBER DENSITIES TO COMPARE GALAXIES ACROSS COSMIC TIME  

SciTech Connect

Comparing galaxies across redshifts at fixed cumulative number density is a popular way to estimate the evolution of specific galaxy populations. This method ignores scatter in mass accretion histories and galaxy-galaxy mergers, which can lead to errors when comparing galaxies over large redshift ranges (?z > 1). We use abundance matching in the ?CDM paradigm to estimate the median change in cumulative number density with redshift and provide a simple fit (+0.16 dex per unit ?z) for progenitors of z = 0 galaxies. We find that galaxy descendants do not evolve in the same way as galaxy progenitors, largely due to scatter in mass accretion histories. We also provide estimates for the 1? range of cumulative number densities corresponding to galaxy progenitors and descendants. Finally, we discuss some limits on cumulative number density comparisons, which arise due to difficulties measuring physical quantities (e.g., stellar mass) consistently across redshifts. A public tool to calculate cumulative number density evolution for galaxies, as well as approximate halo masses, is available online.

Behroozi, Peter S.; Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford, CA 94305 (United States)] [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford, CA 94305 (United States); Marchesini, Danilo [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)] [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Muzzin, Adam [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)] [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Papovich, Casey [Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States)] [Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Stefanon, Mauro [Physics and Astronomy Department, University of Missouri, Columbia, MO 65211 (United States)] [Physics and Astronomy Department, University of Missouri, Columbia, MO 65211 (United States)

2013-11-01T23:59:59.000Z

225

Cosmic density and velocity fields in Lagrangian perturbation theory  

E-Print Network (OSTI)

A first- and second-order relation between cosmic density and peculiar-velocity fields is presented. The calculation is purely Lagrangian and it is derived using the second-order solutions of the Lagrange-Newton system obtained by Buchert & Ehlers. The procedure is applied to two particular solutions given generic initial conditions. In this approach, the continuity equation yields a relation between the over-density and peculiar-velocity fields that automatically satisfies Euler's equation because the orbits are derived from the Lagrange-Newton system. This scheme generalizes some results obtained by Nusser et al. (1991) in the context of the Zel'dovich approximation. As opposed to several other reconstruction schemes, in this approach it is not necessary to truncate the expansion of the Jacobian given by the continuity equation in order to calculate a first- or second-order expression for the density field. In these previous schemes, the density contrast given by (a) the continuity equation and (b) Euler's equation are mutually incompatible. This inconsistency arises as a consequence of an improper handling of Lagrangian and Eulerian coordinates in the analysis. Here, we take into account the fact that an exact calculation of the density is feasible in the Lagrangian picture and therefore an accurate and consistent description is obtained.

Mikel Susperregi; Thomas Buchert

1997-08-04T23:59:59.000Z

226

Stationary nature of the density-functional free energy: Application to accelerated multiple-scattering calculations  

Science Journals Connector (OSTI)

The number of operations required for conventional density-functional algorithms grows as the cube of the number of atoms, N. For large systems the computing requirements are unattainable. To overcome this limitation it is acceptable to approximate those variables with respect to which the free energy is stationary. We show that the stationarity of the free energy with respect to electron density, one-electron potential, chemical potential, occupation function, and temperature allows for very useful approximations leading to rapid and accurate determination of the free energy. Here we discuss approximations involved in calculating the finite temperature electron density needed to evaluate the Harris-Foulkes free energy. Of particular importance are (1) an electron density at each site that is based on exact solution of the Poisson equation combined with a solution of the multiple-scattering problem in which only scattering from a small cluster of sites surrounding the site in question is retained and (2) an approximate occupation function having a finite number of poles in the complex energy plane. The intention is to develop, within density-functional theory, an O(N) scalable first-principles scheme, based on spatially local multiple-scattering methods, for calculating free energies of large systems.

D. M. C. Nicholson; G. M. Stocks; Y. Wang; W. A. Shelton; Z. Szotek; W. M. Temmerman

1994-11-15T23:59:59.000Z

227

Rock Density | Open Energy Information  

Open Energy Info (EERE)

form form View source History View New Pages Recent Changes All Special Pages Semantic Search/Querying Get Involved Help Apps Datasets Community Login | Sign Up Search Page Edit with form History Facebook icon Twitter icon » Rock Density Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Technique: Rock Density Details Activities (2) Areas (2) Regions (0) NEPA(0) Exploration Technique Information Exploration Group: Lab Analysis Techniques Exploration Sub Group: Rock Lab Analysis Parent Exploration Technique: Rock Lab Analysis Information Provided by Technique Lithology: Density of different lithologic units. Stratigraphic/Structural: Hydrological: Thermal: Cost Information Low-End Estimate (USD): 10.001,000 centUSD 0.01 kUSD 1.0e-5 MUSD 1.0e-8 TUSD / sample

228

Density functional theory of freezing for soft interactions in two dimensions  

E-Print Network (OSTI)

A density functional theory of two-dimensional freezing is presented for a soft interaction potential that scales as inverse cube of particle distance. This repulsive potential between parallel, induced dipoles is realized for paramagnetic colloids on an interface, which are additionally exposed to an external magnetic field. An extended modified weighted density approximation which includes correct triplet correlations in the liquid state is used. The theoretical prediction of the freezing transition is in good agreement with experimental and simulation data.

Sven van Teeffelen; Christos N. Likos; Norman Hoffmann; Hartmut Lwen

2006-04-18T23:59:59.000Z

229

Density changes in amorphous Pd{sub 80}Si{sub 20} during low temperature ion irradiation  

SciTech Connect

Density changes in amorphous Pd{sub 80}Si{sub 20} during ion irradiation below 100K were detected by in situ HVEM measurements of the changes in specimen length as a function of ion fluence. A decrease in mass density as a function of the ion fluence was observed. The saturation value of the change in mass density was determined to be approximately -1.2%.

Schumacher, G.; Birtcher, R.C.; Rehn, L.E.

1994-11-01T23:59:59.000Z

230

Semi-exact concentric atomic density fitting: Reduced cost and increased accuracy compared to standard density fitting  

SciTech Connect

A local density fitting scheme is considered in which atomic orbital (AO) products are approximated using only auxiliary AOs located on one of the nuclei in that product. The possibility of variational collapse to an unphysical attractive electron state that can affect such density fitting [P. Merlot, T. Kjrgaard, T. Helgaker, R. Lindh, F. Aquilante, S. Reine, and T. B. Pedersen, J. Comput. Chem. 34, 1486 (2013)] is alleviated by including atom-wise semidiagonal integrals exactly. Our approach leads to a significant decrease in the computational cost of density fitting for HartreeFock theory while still producing results with errors 25 times smaller than standard, nonlocal density fitting. Our method allows for large HartreeFock and density functional theory computations with exact exchange to be carried out efficiently on large molecules, which we demonstrate by benchmarking our method on 200 of the most widely used prescription drug molecules. Our new fitting scheme leads to smooth and artifact-free potential energy surfaces and the possibility of relatively simple analytic gradients.

Hollman, David S. [Center for Computational Quantum Chemistry, University of Georgia, 1004 Cedar St., Athens, Georgia 30602 (United States) [Center for Computational Quantum Chemistry, University of Georgia, 1004 Cedar St., Athens, Georgia 30602 (United States); Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061 (United States); Schaefer, Henry F. [Center for Computational Quantum Chemistry, University of Georgia, 1004 Cedar St., Athens, Georgia 30602 (United States)] [Center for Computational Quantum Chemistry, University of Georgia, 1004 Cedar St., Athens, Georgia 30602 (United States); Valeev, Edward F. [Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061 (United States)

2014-02-14T23:59:59.000Z

231

THE DEPENDENCE OF STAR FORMATION EFFICIENCY ON GAS SURFACE DENSITY  

SciTech Connect

Studies by Lada et al. and Heiderman et al. have suggested that star formation mostly occurs above a threshold in gas surface density {Sigma} of {Sigma}{sub c} {approx} 120 M{sub Sun} pc{sup -2} (A{sub K} {approx} 0.8). Heiderman et al. infer a threshold by combining low-mass star-forming regions, which show a steep increase in the star formation rate per unit area {Sigma}{sub SFR} with increasing {Sigma}, and massive cores forming luminous stars which show a linear relation. We argue that these observations do not require a particular density threshold. The steep dependence of {Sigma}{sub SFR}, approaching unity at protostellar core densities, is a natural result of the increasing importance of self-gravity at high densities along with the corresponding decrease in evolutionary timescales. The linear behavior of {Sigma}{sub SFR} versus {Sigma} in massive cores is consistent with probing dense gas in gravitational collapse, forming stars at a characteristic free-fall timescale given by the use of a particular molecular tracer. The low-mass and high-mass regions show different correlations between gas surface density and the area A spanned at that density, with A {approx} {Sigma}{sup -3} for low-mass regions and A {approx} {Sigma}{sup -1} for the massive cores; this difference, along with the use of differing techniques to measure gas surface density and star formation, suggests that connecting the low-mass regions with massive cores is problematic. We show that the approximately linear relationship between dense gas mass and stellar mass used by Lada et al. similarly does not demand a particular threshold for star formation and requires continuing formation of dense gas. Our results are consistent with molecular clouds forming by galactic hydrodynamic flows with subsequent gravitational collapse.

Burkert, Andreas [University Observatory Munich, Scheinerstrasse 1, D-81679 Munich (Germany); Hartmann, Lee, E-mail: burkert@usm.lmu.de, E-mail: lhartm@umich.edu [Department of Astronomy, University of Michigan, 830 Dennison, 500 Church St., Ann Arbor, MI 48109-1042 (United States)

2013-08-10T23:59:59.000Z

232

DENSITY LIMITS IN TOROIDAL PLASMAS MARTIN GREENWALD  

E-Print Network (OSTI)

(RFP) ---- Spheromaks and FRCs · Physics basis for density limit ---- Neutrals ---- Radiation models as fast terminations · Spheromak and FRC don't have density limit data operation at "optimized" density

Greenwald, Martin

233

Polynomialtime approximation algorithms for the Ising model \\Lambda  

E-Print Network (OSTI)

Polynomial­time approximation algorithms for the Ising model \\Lambda Mark Jerrum and Alistair, Scotland November 1989 (revised December 1991) Abbreviated title: Approximation algorithms for the Ising evaluates the partition function of an arbitrary ferromagnetic Ising system to any specified degree

Sinclair, Alistair

234

On the Oberbeck-Boussinesq approximation on unbounded domains  

E-Print Network (OSTI)

On the Oberbeck-Boussinesq approximation on unbounded domains Eduard Feireisl and Maria E. Schonbek Abstract We study the Oberbeck-Boussinesq approximation describing the mo- tion of an incompressible, heat that the total energy of any solution of the resulting Oberbeck-Boussinesq system tends to zero with growing time

Schonbek, Maria

235

Generalizing the Boussinesq Approximation to Stratified Compressible Flow  

E-Print Network (OSTI)

Generalizing the Boussinesq Approximation to Stratified Compressible Flow Dale R. Durran a Akio The simplifications required to apply the Boussinesq approximation to compressible flow are compared with those compressible fluid with the Boussinesq continuity equation has led to the development of several different sets

236

Dynamic Enthalpy, Conservative Temperature, and the Seawater Boussinesq Approximation  

E-Print Network (OSTI)

Dynamic Enthalpy, Conservative Temperature, and the Seawater Boussinesq Approximation WILLIAM R (Manuscript received 8 June 2009, in final form 27 August 2009) ABSTRACT A new seawater Boussinesq system of the full system. The seawater Boussinesq approximation simplifies the mass con- servation equation to $ Á u

Young, William R.

237

Lecture 20: Approximate algorithms Outline of this Lecture  

E-Print Network (OSTI)

for approximation algorithms. ffl Vertex­cover problem. ffl Traveling­salesman problem. 1 #12; Introduction Many. Another example is we are looking for a maximum size independent set (IS). An approximate algorithm; Vertex­cover Vertex Cover: A vertex cover of a graph G is a set of vertices such that every edge in G

Wu, Dekai

238

Lecture 20: Approximate algorithms Outline of this Lecture  

E-Print Network (OSTI)

for approximation algorithms. Vertex-cover problem. Traveling-salesman problem. 1 #12;Introduction Many. Another example is we are looking for a maximum size independent set (IS). An approximate algorithm Cover: A vertex cover of a graph is a set of vertices such that every edge in is incident

Wu, Dekai

239

10 -Approximation Algorithm for a Generalization of the Weighted  

E-Print Network (OSTI)

A 2 1 10 -Approximation Algorithm for a Generalization of the Weighted Edge-Dominating Set Problem consider a natural strategy, reducing edge-dominating set to edge cover. Our main result is a simple 2 1 10 -approximation algorithm for the weighted edge-dominating set problem, improving the existing ratio, due

Parekh, Ojas

240

Parametric Optimization of Artificial Neural Networks for Signal Approximation Applications  

E-Print Network (OSTI)

Parametric Optimization of Artificial Neural Networks for Signal Approximation Applications J. Lane.thames@gatech.edu randal.abler@gatech.edu dirk.schaefer@me.gatech.edu ABSTRACT Artificial neural networks are used to solve set of configuration parameters for artificial neural networks such that the network's approximation

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Fast Vectorless Power Grid Verification Using an Approximate Inverse Technique  

E-Print Network (OSTI)

Fast Vectorless Power Grid Verification Using an Approximate Inverse Technique Nahi H. Abdul Ghani Department of ECE University of Toronto Toronto, Ontario, Canada f.najm@utoronto.ca ABSTRACT Power grid Aids General Terms Performance, Algorithms, Verification Keywords Power grid, voltage drop, approximate

Najm, Farid N.

242

Neural Network-Based Accelerators for Transcendental Function Approximation  

E-Print Network (OSTI)

Neural Network-Based Accelerators for Transcendental Function Approximation Schuyler Eldridge accelerators has the potential to sustain the his- toric energy and performance improvements of computing systems. We propose the use of NN-based accelerators to approximate mathematical functions in the GNU C

Joshi, Ajay

243

Born-Oppenheimer approximation for a harmonic molecule  

E-Print Network (OSTI)

We apply the Born-Oppenheimer approximation to a harmonic diatomic molecule with one electron. We compare the exact and approximate results not only for the internal degrees of freedom but also for the motion of the center of mass. We address the problem of identical nuclei and discuss other applications of the model and its limitations.

Francisco M. Fernandez

2008-10-13T23:59:59.000Z

244

The Born-Oppenheimer Approximation C. David Sherrill  

E-Print Network (OSTI)

The Born-Oppenheimer Approximation C. David Sherrill School of Chemistry and Biochemistry Georgia as a product of nuclear and elec- tronic terms, (r, R) = (r)(R). We thus introduce the Born-Oppenheimer that the total wavefunction is given as (r; R)(R). The Born-Oppenheimer approximation rests on the fact

Sherrill, David

245

Parallel algorithms for approximation of distance maps on parametric surfaces  

E-Print Network (OSTI)

results demonstrate up to four orders of magnitude improvement in execution time compared to the state(n) numerical algorithm for first-order approximation of geodesic distances on geometry images, where n charts, parallel algorithms, GPU, SIMD 1. INTRODUCTION Approximation of geodesic distances on curved

Kimmel, Ron

246

APPROXIMATE HAMILTON DECOMPOSITIONS OF ROBUSTLY EXPANDING REGULAR DIGRAPHS  

E-Print Network (OSTI)

APPROXIMATE HAMILTON DECOMPOSITIONS OF ROBUSTLY EXPANDING REGULAR DIGRAPHS DERYK OSTHUS and is a robust outexpander has an approximate decomposition into edge-disjoint Hamilton cycles, i.e. G contains a set of r -o(r) edge-disjoint Hamilton cycles. Here G is a robust outexpander if for every set S which

Osthus, Deryk

247

Probabilistic Rough Set Approximations Yiyu (Y.Y.) Yao  

E-Print Network (OSTI)

Probabilistic Rough Set Approximations Yiyu (Y.Y.) Yao Department of Computer Science University have been applied to the theory of rough set in sev- eral forms, including decision-theoretic analysis and rough inclusion functions, we revisit probabilistic rough set approximation operators and present

Yao, Yiyu

248

ROUGH SET APPROXIMATIONS: A CONCEPT ANALYSIS POINT OF VIEW  

E-Print Network (OSTI)

ROUGH SET APPROXIMATIONS: A CONCEPT ANALYSIS POINT OF VIEW Yiyu Yao University of Regina, Regina and content of data, definable concepts, lower and upper ap- proximations, rough set approximations Contents 1. Conclusion Bibliography Biographical Sketches Summary Rough set theory was proposed by Pawlak for analyzing

Yao, Yiyu

249

Relational Interpretations of Neighborhood Operators Rough Set Approximation Operators  

E-Print Network (OSTI)

Relational Interpretations of Neighborhood Operators and Rough Set Approximation Operators Y.Y. Yao and rough set approximations using the more familiar notion of binary relations. A special class of neigh sets, partitions, coverings. 1 INTRODUCTION The theory of rough sets is motivated by practical needs

Yao, Yiyu

250

Absolute Approximation of Tukey Depth: Theory and Experiments  

E-Print Network (OSTI)

Absolute Approximation of Tukey Depth: Theory and Experiments Dan Chen School of Computer Science¨ur Theoretische Informatik Abstract A Monte Carlo approximation algorithm for the Tukey depth problem in high. Keywords: Tukey depth, computational geometry 1. Introduction Tukey depth is also known as location depth

Morin, Pat

251

HEREDITARY APPROXIMATION PROPERTY W. B. JOHNSON AND A. SZANKOWSKI  

E-Print Network (OSTI)

HEREDITARY APPROXIMATION PROPERTY W. B. JOHNSON AND A. SZANKOWSKI Abstract. If X is a Banach space approximation property, trace formula. Johnson was supported in part by NSF DMS-0500292, DMS-1001321, and the U.S.-Israel Binational Science Foundation. 1 #12;2 W. B. JOHNSON AND A. SZANKOWSKI (S) Is there a HAPpy space that has

Johnson, William B.

252

Energy Content of Colliding Plane Waves using Approximate Noether Symmetries  

E-Print Network (OSTI)

This paper is devoted to study the energy content of colliding plane waves using approximate Noether symmetries. For this purpose, we use approximate Lie symmetry method of Lagrangian for differential equations. We formulate the first-order perturbed Lagrangian for colliding plane electromagnetic and gravitational waves. It is shown that in both cases, there does not exist

M. Sharif; Saira Waheed

2011-09-19T23:59:59.000Z

253

Approximate Dynamic Programming for High Dimensional Resource Allocation Problems  

E-Print Network (OSTI)

the dimensionality of these variables is in the ten thousand to one million range. We describe an approximation in Section II by presenting a simple but general model for the management of discrete resources. Section III describes an algorithmic strategy using the principles of approximate dynamic programming. Section IV

Powell, Warren B.

254

Open problems in nuclear density functional theory  

E-Print Network (OSTI)

This note describes five subjects of some interest for the density functional theory in nuclear physics. These are, respectively, i) the need for concave functionals, ii) the nature of the Kohn-Sham potential for the radial density theory, iii) a proper implementation of a density functional for an "intrinsic" rotational density, iv) the possible existence of a potential driving the square root of the density, and v) the existence of many models where a density functional can be explicitly constructed.

B. G. Giraud

2009-11-30T23:59:59.000Z

255

Nuclear energy density optimization: Shell structure  

Science Journals Connector (OSTI)

Background: Nuclear density functional theory is the only microscopical theory that can be applied throughout the entire nuclear landscape. Its key ingredient is the energy density functional.

M. Kortelainen; J. McDonnell; W. Nazarewicz; E. Olsen; P.-G. Reinhard; J. Sarich; N. Schunck; S. M. Wild; D. Davesne; J. Erler; A. Pastore

2014-05-15T23:59:59.000Z

256

Transformations for densities Linear transformations  

E-Print Network (OSTI)

' & $ % Lecture 28 Transformations for densities Linear transformations 1-1 differentiable functions General transformations Expectation of a function 1 #12;' & $ % Transformations for discrete transformation of a U[0, 1] · Take X U[0, 1], so that fX(x) = 1 0 0 and set Y

Adler, Robert J.

257

Definition: Density Log | Open Energy Information  

Open Energy Info (EERE)

Density Log Density Log Jump to: navigation, search Dictionary.png Density Log Density logging is a well logging tool that can provide a continuous record of a formation's bulk density along the length of a borehole. In geology, bulk density is a function of the density of the minerals forming a rock (i.e. matrix) and the fluid enclosed in the pore spaces.[1] View on Wikipedia Wikipedia Definition Density logging is a well logging tool that can provide a continuous record of a formation's bulk density along the length of a borehole. In geology, bulk density is a function of the density of the minerals forming a rock and the fluid enclosed in the pore spaces. This is one of three well logging tools that are commonly used to calculate porosity, the other two being sonic logging and neutron porosity logging

258

Variational Fermihypernetted-chain approximation [FHNC/?(r)] calculations with ?z-dependent correlations in liquid He3  

Science Journals Connector (OSTI)

The ground state of liquid He3 at zero temperature is approximated by a Jastrow two-body trial wave function including ?z-dependent correlations. The variational calculations are performed in the framework of the Fermi-hypernetted-chain (FHNC) approximation, and the elementary diagrams are estimated with two different extensions of the interpolating equation approach [FHNC/?(r)] [Fabrocini and Rosati, Nuovo Cimento D 1, 615 (1982)]. A comparison with a variational Monte Carlo calculation [Krten and Clark, Phys. Rev. B 30, 1342 (1984)] shows good agreement for the expectation values of the total, kinetic, and potential energies. The increase of the total energy over a ?z-independent calculation, working with a semioptimized correlation function, is approximately 0.2 K at the equilibrium density for both Lennard-Jones and Aziz HFDHE2 potentials.

F. Arias de Saavedra and E. Buendra

1990-10-01T23:59:59.000Z

259

Beyond chemical accuracy: The pseudopotential approximation in diffusion Monte Carlo calculations of the HCP to BCC phase transition in beryllium  

E-Print Network (OSTI)

Motivated by the disagreement between recent diffusion Monte Carlo calculations and experiments on the phase transition pressure between the ambient and beta-Sn phases of silicon, we present a study of the HCP to BCC phase transition in beryllium. This lighter element provides an oppor- tunity for directly testing many of the approximations required for calculations on silicon and may suggest a path towards increasing the practical accuracy of diffusion Monte Carlo calculations of solids in general. We demonstrate that the single largest approximation in these calculations is the pseudopotential approximation. After removing this we find excellent agreement with experiment for the ambient HCP phase and results similar to careful calculations using density functional theory for the phase transition pressure.

Shulenburger, Luke; Desjarlais, M P

2015-01-01T23:59:59.000Z

260

Finite-density effective sigma meson mass in chiral models  

Science Journals Connector (OSTI)

Properties of chirally-invariant models of nuclear matter are calculated with the relativistic Hartree approximation. Our emphasis is on the behavior of the effective ? meson mass. We find that the effective ? mass does not scale with the effective nucleon mass, which in these calculations is proportional to the expectation value of the ? field, i.e., the chiral order parameter. These results suggest that a decrease in the effective ? mass with increasing nucleon density is not a generic feature of chiral models. We also find that the incompressibility of nuclear matter is lower for those models with higher effective ? masses.

David K. Griegel and Thomas D. Cohen

1989-03-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Nonsingular Formulation of the Brueckner Approximation for an Infinite Fermi System  

Science Journals Connector (OSTI)

In the approximation neglecting any but single pair correlations, singularities of the reaction matrix render Brueckner's integral for the average energy per particle a singular integral. Several attempts to overcome this difficulty have been unsuccessful. By considering the infinite Fermi system to be a limit of finite systems, it is shown that the correct result merely involves replacing Brueckner's ordinary integral over diagonal reaction matrix elements by a principal value integral. In a finite system the level shift of a Bethe-Goldstone state differs from the diagonal reaction matrix element by a normalization factor which does not approach unity uniformly in the integration variable as the volume becomes infinite. In the neighborhood of a singularity the expression for the two-particle energy shift takes the form cy(y2+cU-1), where y is the unperturbed energy measured from the singularity, c is the square of a matrix element, and U is the quantization volume. Hence as U?? the sum over the energy y indeed approaches a principal value integral. An alternative derivation, employing a modified reaction matrix for which there is no difference between level shift and matrix element, leads to the same result. The general derivations are preceded by a soluble example.The connection of the Brueckner approximation with a phase-shift approximation for low-density systems is discussed. Some corrections to the higher order terms in existing derivations of the "separation method" expansion of the Brueckner reaction matrix are given.

Richard L. Becker

1962-08-15T23:59:59.000Z

262

Full-potential calculations using the generalized gradient approximation: Structural properties of transition metals  

Science Journals Connector (OSTI)

The equilibrium volumes and bulk moduli of nonmagnetic 3d, 4d, and 5d transition metals have been calculated using a full-potential linear-muffin-tin-orbitals (FP-LMTO) method and the generalized gradient approximation (PW91) of Perdew and Wang [in Electronic Structure of Solids 1991, edited by P. Ziesche and H. Eschrig (Akademie Verlag, Berlin, 1991), Vol. 11]. The gradient-corrected FP-LMTO results are found to be superior to the corresponding local-density approximation (LDA) results in all transition-metal series. Furthermore, the atomic-spheres approximation (ASA) is found to yield larger equilibrium volumes and smaller bulk moduli than the FP method. The inaccuracies introduced by the ASA are of the same magnitude as the gradient corrections, suggesting that a FP treatment is important for gradient-corrected calculations. Excellent agreement with experiment is found for the c/a ratios of the hcp metals using both the LDA and the PW91, while for the fcc-bcc structural energy differences of 4d metals disagreement with semiempirical estimates remains.

V. Ozoli? and M. Krling

1993-12-15T23:59:59.000Z

263

Excitations and benchmark ensemble density functional theory for two electrons  

SciTech Connect

A new method for extracting ensemble Kohn-Sham potentials from accurate excited state densities is applied to a variety of two-electron systems, exploring the behavior of exact ensemble density functional theory. The issue of separating the Hartree energy and the choice of degenerate eigenstates is explored. A new approximation, spin eigenstate Hartree-exchange, is derived. Exact conditions that are proven include the signs of the correlation energy components and the asymptotic behavior of the potential for small weights of the excited states. Many energy components are given as a function of the weights for two electrons in a one-dimensional flat box, in a box with a large barrier to create charge transfer excitations, in a three-dimensional harmonic well (Hooke's atom), and for the He atom singlet-triplet ensemble, singlet-triplet-singlet ensemble, and triplet bi-ensemble.

Pribram-Jones, Aurora; Burke, Kieron [Department of Chemistry, University of California-Irvine, Irvine, California 92697 (United States)] [Department of Chemistry, University of California-Irvine, Irvine, California 92697 (United States); Yang, Zeng-hui; Ullrich, Carsten A. [Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211 (United States)] [Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211 (United States); Trail, John R.; Needs, Richard J. [Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom)] [Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom)

2014-05-14T23:59:59.000Z

264

Non-perturbative calculation of molecular magnetic properties within current-density functional theory  

SciTech Connect

We present a novel implementation of KohnSham density-functional theory utilizing London atomic orbitals as basis functions. External magnetic fields are treated non-perturbatively, which enable the study of both magnetic response properties and the effects of strong fields, using either standard density functionals or current-density functionalsthe implementation is the first fully self-consistent implementation of the latter for molecules. Pilot applications are presented for the finite-field calculation of molecular magnetizabilities, hypermagnetizabilities, and nuclear magnetic resonance shielding constants, focusing on the impact of current-density functionals on the accuracy of the results. Existing current-density functionals based on the gauge-invariant vorticity are tested and found to be sensitive to numerical details of their implementation. Furthermore, when appropriately regularized, the resulting magnetic properties show no improvement over standard density-functional results. An advantage of the present implementation is the ability to apply density-functional theory to molecules in very strong magnetic fields, where the perturbative approach breaks down. Comparison with high accuracy full-configuration-interaction results show that the inadequacies of current-density approximations are exacerbated with increasing magnetic field strength. Standard density-functionals remain well behaved but fail to deliver high accuracy. The need for improved current-dependent density-functionals, and how they may be tested using the presented implementation, is discussed in light of our findings.

Tellgren, E. I., E-mail: erik.tellgren@kjemi.uio.no; Lange, K. K.; Ekstrm, U.; Helgaker, T. [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway)] [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway); Teale, A. M., E-mail: andrew.teale@nottingham.ac.uk [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway); School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Furness, J. W. [School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)] [School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

2014-01-21T23:59:59.000Z

265

Joint density-functional theory for electronic structure of solvated systems  

E-Print Network (OSTI)

We introduce a new form of density functional theory for the {\\em ab initio} description of electronic systems in contact with a molecular liquid environment. This theory rigorously joins an electron density-functional for the electrons of a solute with a classical density-functional theory for the liquid into a single variational principle for the free energy of the combined system. A simple approximate functional predicts, without any fitting of parameters to solvation data, solvation energies as well as state-of-the-art quantum-chemical cavity approaches, which require such fitting.

Sahak Petrosyan; Jean-Francois Briere; David Roundy; T. A. Arias

2007-02-09T23:59:59.000Z

266

Effect of electron density profile on power absorption of high frequency electromagnetic waves in plasma  

SciTech Connect

Considering different typical electron density profiles, a multi slab approximation model is built up to study the power absorption of broadband (0.75-30 GHz) electromagnetic waves in a partially ionized nonuniform magnetized plasma layer. Based on the model, the power absorption spectra for six cases are numerically calculated and analyzed. It is shown that the absorption strongly depends on the electron density fluctuant profile, the background electron number density, and the collision frequency. A potential optimum profile is also analyzed and studied with some particular parameters.

Xi Yanbin; Liu Yue [MOE Key Laboratory of Materials Modification by Laser, Electron, and Ion Beams, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

2012-07-15T23:59:59.000Z

267

Improved approximate formulas for flux from cylindrical and rectangular sources  

SciTech Connect

This report provides two new approximate formulas for the flux at detector points outside the radial and axial extensions of a homogeneous cylindrical source and improved approximate formulas for the flux at points opposite rectangular surface sources. These formulas extend the range of geometries for which analytic approximations may be used by shield design engineers to make rapid scoping studies and check more extensive calculations for reasonableness. These formulas can be used to support skeptical, independent evaluations and are also valuable teaching tools for introducing shield designers to complex shield analyses.

Wallace, O.J.; Bokharee, S.A.

1993-03-01T23:59:59.000Z

268

AdS/CFT correspondence beyond its supergravity approximation  

E-Print Network (OSTI)

We will study the AdS/CFT correspondence beyond its supergravity approximation by deforming an effective field theory on AdS by string length scale effects. We will explicitly show that the conformal dimensions of both the relevant and the irrelevant operators receive correction from these string theory effects going beyond its supergravity approximation. However, as is expected from the full string theory on AdS (not just its supergravity approximation) being dual to the $\\mathcal{N}=4$ super-Yang-Mills theory, the conformal dimension of marginal operators do not receive any such corrections.

Mir Faizal; Ahmed Farag Ali; Ali Nassar

2014-05-18T23:59:59.000Z

269

Jacek Dobaczewski Density functional theory and energy  

E-Print Network (OSTI)

Jacek Dobaczewski Density functional theory and energy density functionals in nuclear physics Jacek Functional #12;Jacek Dobaczewski Mean-Field Theory Density Functional Theory · mean-field one? Density Functional Theory: A variational method that uses observables as variational parameters. #12;Jacek

Dobaczewski, Jacek

270

Cumulative sum quality control for calibrated breast density measurements  

SciTech Connect

Purpose: Breast density is a significant breast cancer risk factor. Although various methods are used to estimate breast density, there is no standard measurement for this important factor. The authors are developing a breast density standardization method for use in full field digital mammography (FFDM). The approach calibrates for interpatient acquisition technique differences. The calibration produces a normalized breast density pixel value scale. The method relies on first generating a baseline (BL) calibration dataset, which required extensive phantom imaging. Standardizing prospective mammograms with calibration data generated in the past could introduce unanticipated error in the standardized output if the calibration dataset is no longer valid. Methods: Sample points from the BL calibration dataset were imaged approximately biweekly over an extended timeframe. These serial samples were used to evaluate the BL dataset reproducibility and quantify the serial calibration accuracy. The cumulative sum (Cusum) quality control method was used to evaluate the serial sampling. Results: There is considerable drift in the serial sample points from the BL calibration dataset that is x-ray beam dependent. Systematic deviation from the BL dataset caused significant calibration errors. This system drift was not captured with routine system quality control measures. Cusum analysis indicated that the drift is a sign of system wear and eventual x-ray tube failure. Conclusions: The BL calibration dataset must be monitored and periodically updated, when necessary, to account for sustained system variations to maintain the calibration accuracy.

Heine, John J.; Cao Ke; Beam, Craig [Cancer Prevention and Control Division, Moffitt Cancer Center, 12902 Magnolia Drive, Tampa, Florida 33612 (United States); Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, 1603 W. Taylor St., Chicago, Illinois 60612 (United States)

2009-12-15T23:59:59.000Z

271

INTRODUCTION TO THE VARIATIONAL DENSITY MATRIX METHOD AND ITS APPLICATION TO DENSE HYDROGEN  

E-Print Network (OSTI)

\\GammafiE s \\Psi s (R)\\Psi s (R 0 ) (1) is needed to compute the thermal averages of operators hOi = Tr [Oae] Tr [ae] : (2) At the first level, this many body density matrix may be approximated

Militzer, Burkhard

272

Efficient k?p method for the calculation of total energy and electronic density of states  

Science Journals Connector (OSTI)

An efficient method for calculating the electronic structure in large systems with a fully converged Brillouin zone sampling is presented. The method is based on a k?p-like approximation developed in the framework of the density-functional perturbation theory. The reliability and efficiency of the method are demonstrated in test calculations on Ar and Si supercells.

Marcella Iannuzzi and Michele Parrinello

2001-11-15T23:59:59.000Z

273

Electron density estimations derived from spacecraft potential measurements on Cluster in tenuous plasma regions  

E-Print Network (OSTI)

in the solar wind, the magnetosheath, and the plasmashere by the use of CIS ion density and WHISPER electron, in operation from early 2001 in a high inclination orbit, have provided data over nearly half of the 11-year are in the magnetotail from approximately beginning of July to end of October, and the high inclination orbit makes

California at Berkeley, University of

274

Stable relativistic/charge-displacement channels in ultrahigh power density (?1021 W/cm3) plasmas  

Science Journals Connector (OSTI)

...mankind with an origin that predates the Stone Age. From the use of a wooden club to the contemporary production of vigorous thermonuclear environments, the achievable power density (W/cm 3 ) has been advanced by approximately a factor of 20 orders of magnitude...

A. B. Borisov; J. W. Longworth; K. Boyer; C. K. Rhodes

1998-01-01T23:59:59.000Z

275

JAMES E. HANSEN World's Greatest Crime against Humanity and Nature  

E-Print Network (OSTI)

's nuclear plants for billions of years, once fast reactors are operational. Thus we can stop mining uranium decades in the future as easily available uranium is used up. Nuclear reactors can also be made more to stay, existing in more than 30 nations. Uranium sieved from the ocean can power all of the world

Hansen, James E.

276

Peer Exchange Calls Inspire New Lessons Learned Greatest Hits  

Energy.gov (U.S. Department of Energy (DOE))

A new Lessons Learned: Peer Exchange Calls resource summarizes top takeaways shared by Better Buildings Residential Network members, from tips to collaborating with utilities to cost-effective...

277

What the World's GREATEST Energy Managers Do Differently  

Energy.gov (U.S. Department of Energy (DOE))

This presentation describes some tips and practices to help energy managers understand the goal, build a coalition, and sustain momentum.

278

Question of the Week: What are Your Greatest Energy Concerns...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

in a winter coat inside my house all winter. What other options do I have to reduce heat loss in a place that I don't own? Posted by: Kendra | September 10, 2008 at 02:18 PM...

279

Parton Densities at the LHC  

E-Print Network (OSTI)

This contribution to the Italian "Workshop sui Monte Carlo, la Fisica e le Simulazioni a LHC", held at LNF, Frascati, in February, May and October 2006, summarises the status of parton density functions (PDF's) and the impact of their uncertainties on the LHC physics. Emphasis is given to methods of contraining PDF's using LHC data. Moreover, the advantages of the so-called PDF reweighting technique, which enables to quickly estimate PDF uncertainties with Monte Carlo events, are also presented.

A. Tricoli; for the ATLAS Collaboration

2008-08-19T23:59:59.000Z

280

Electronic density-of-states of amorphous vanadium pentoxide films: Electrochemical data and density functional theory calculations  

SciTech Connect

Thin films of V{sub 2}O{sub 5} were prepared by sputter deposition onto transparent and electrically conducting substrates and were found to be X-ray amorphous. Their electrochemical density of states was determined by chronopotentiometry and displayed a pronounced low-energy peak followed by an almost featureless contribution at higher energies. These results were compared with density functional theory calculations for amorphous V{sub 2}O{sub 5}. Significant similarities were found between measured data and computations; specifically, the experimental low-energy peak corresponds to a split-off part of the conduction band apparent in the computations. Furthermore, the calculations approximately reproduce the experimental band gap observed in optical measurements.

Lykissa, Iliana; Li, Shu-Yi; Granqvist, Claes G.; Niklasson, Gunnar A., E-mail: gunnar.niklasson@angstrom.uu.se [Department of Engineering Sciences, The ngstrm Laboratory, Uppsala University, P.O. Box 534, SE-75121 Uppsala (Sweden); Ramzan, Muhammad [Department of Physics and Astronomy, The ngstrm Laboratory, Uppsala University, P.O. Box 516, SE-75120 Uppsala (Sweden); Chakraborty, Sudip; Ahuja, Rajeev [Department of Physics and Astronomy, The ngstrm Laboratory, Uppsala University, P.O. Box 516, SE-75120 Uppsala (Sweden); Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden)

2014-05-14T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Adaptive Gaussian Predictive Process Approximation Surya T Tokdar  

E-Print Network (OSTI)

exploration of Gaussian process models, including Bayesian treatments. For theoreti- cal details on commonAdaptive Gaussian Predictive Process Approximation Surya T Tokdar Duke University Abstract We address the issue of knots selection for Gaussian predictive process methodology. Predictive process

West, Mike

282

Approximation Algorithms for 2-Stage Stochastic Scheduling Problems  

Science Journals Connector (OSTI)

There has been a series of results deriving approximation algorithms for 2-stage discrete stochastic optimization problems, in which the probabilistic component of the input is given by means of "black box", from which the algorithm "learns" the distribution ...

David B. Shmoys; Mauro Sozio

2007-06-01T23:59:59.000Z

283

Approximate Dynamic Programming with Affine ADDs Scott Sanner  

E-Print Network (OSTI)

Approximate Dynamic Programming with Affine ADDs Scott Sanner NICTA and ANU Canberra, Australia and Multiagent Systems (AAMAS 2010), van der Hoek, Kaminka, Lespérance, Luck and Sen (eds.), May, 10­14, 2010

Sanner, Scott

284

On the mathematical treatment of the Born-Oppenheimer approximation  

E-Print Network (OSTI)

Motivated by a paper by B.T. Sutcliffe and R.G. Woolley, we present the main ideas used by mathematicians to show the accuracy of the Born-Oppenheimer approximation for molecules. Based on mathematical works on this approximation for molecular bound states, in scattering theory, in resonance theory, and for short time evolution, we give an overview of some rigourous results obtained up to now. We also point out the main difficulties mathematicians are trying to overcome and speculate on further developments. The mathematical approach does not fit exactly to the common use of the approximation in Physics and Chemistry. We criticize the latter and comment on the differences, contributing in this way to the discussion on the Born-Oppenheimer approximation initiated by B.T. Sutcliffe and R.G. Woolley. The paper neither contains mathematical statements nor proofs. Instead we try to make accessible mathematically rigourous results on the subject to researchers in Quantum Chemistry or Physics.

Thierry Jecko

2014-04-24T23:59:59.000Z

285

Numerical Test of Born-Oppenheimer Approximation in Chaotic Systems  

E-Print Network (OSTI)

We study the validity of the Born-Oppenheimer approximation in chaotic dynamics. Using numerical solutions of autonomous Fermi accelerators, we show that the general adiabatic conditions can be interpreted as the narrowness of the chaotic region in phase space.

Jeong-Bo Shim; Mahir S. Hussein; Martina Hentschel

2009-08-04T23:59:59.000Z

286

The local potential approximation in the background field formalism  

E-Print Network (OSTI)

Working within the familiar local potential approximation, and concentrating on the example of a single scalar field in three dimensions, we show that the commonly used approximation method of identifying the total and background fields, leads to pathologies in the resulting fixed point structure and the associated spaces of eigenoperators. We then show how a consistent treatment of the background field through the corresponding modified shift Ward identity, can cure these pathologies, restoring universality of physical quantities with respect to the choice of dependence on the background field, even within the local potential approximation. Along the way we point out similarities to what has been previously found in the f(R) approximation in asymptotic safety for gravity.

I. Hamzaan Bridle; Juergen A. Dietz; Tim R. Morris

2014-03-20T23:59:59.000Z

287

APPROXIMATE HARTREE TYPE WAVE FUNCTIONS AND MATRIX ELEMENTS FOR...  

Office of Scientific and Technical Information (OSTI)

APPROXIMATE HARTREE TYPE WAVE FUNCTIONS AND MATRIX ELEMENTS FOR THE K AND L SHELLS OF ATOMS AND IONS Re-direct Destination: Temp Data Fields Meyerott, R.E. Temp Data Storage 3:...

288

Human sciences The human sciences database contains approximately 254 academic  

E-Print Network (OSTI)

Human sciences The human sciences database contains approximately 254 academic journals and statistical reports on the following subjects: (comparative literature, theology, history and geography, education, psychology, arts, languages and Library Science) Social sciences The social sciences database

289

Testing and Comparing the Modified Anomalous Diffraction Approximation  

Science Journals Connector (OSTI)

The modified anomalous diffraction approximation (MADA) is used to predict absorption and extinction in water and ice clouds, but it does not predict the scattering phase function or asymmetry parameter g. In conjunction with g parameterizations, ...

David L. Mitchell; Anthony J. Baran; W. P. Arnott; C. Schmitt

2006-11-01T23:59:59.000Z

290

Bounds for the adiabatic approximation with applications to quantum computation  

SciTech Connect

We present straightforward proofs of estimates used in the adiabatic approximation. The gap dependence is analyzed explicitly. We apply the result to interpolating Hamiltonians of interest in quantum computing.

Jansen, Sabine; Ruskai, Mary-Beth; Seiler, Ruedi [Institut fuer Mathematik, TU Berlin, MA 7-2, Strasse des 17, Juni 136, D-10623 Berlin (Germany); Department of Mathematics, Tufts University, Medford, Massachusetts 02155 (United States); Institut fuer Mathematik, TU Berlin, MA 7-2, Strasse des 17, Juni 136, D-10623 Berlin (Germany)

2007-10-15T23:59:59.000Z

291

Revisiting the energetics of the ocean in Boussinesq approximation  

Science Journals Connector (OSTI)

Following a suggestion by Tailleux (2012), a consistent formulation of internal energy, the first law of thermodynamics, and the thermodynamic potentials for an ocean in Boussinesq approximation with a non-linear equation of state is given. A ...

Carsten Eden

292

The BornOppenheimer approximation: A toy version  

Science Journals Connector (OSTI)

The BornOppenheimer approximation which is central to the physics and chemistry of molecules and solids is illustrated by a one-dimensional toy model that is easily solved.

Gautam Gangopadhyay; Binayak Dutta-Roy

2004-01-01T23:59:59.000Z

293

CoulombBornOppenheimer approximation in PsH scattering  

Science Journals Connector (OSTI)

To improve the Coulomb-Born approximation (CBA) theory of ionization in positronium (Ps) and atom scattering, the effect of exchange is introduced. The nine-dimensional exchange amplitude for ionization of Ps in ...

Hasi Ray

2006-02-01T23:59:59.000Z

294

Approximation algorithms for grammar-based data compression  

E-Print Network (OSTI)

This thesis considers the smallest grammar problem: find the smallest context-free grammar that generates exactly one given string. We show that this problem is intractable, and so our objective is to find approximation ...

Lehman, Eric (Eric Allen), 1970-

2002-01-01T23:59:59.000Z

295

Automating Logic Rectification by Approximate SPFDs Yu-Shen Yang  

E-Print Network (OSTI)

Automating Logic Rectification by Approximate SPFDs Yu-Shen Yang Dept. of ECE University of Toronto changes or implement incremental rewiring-based optimization operations. Most existing automated logic

Veneris, Andreas

296

Regularity and approximation of systems arising in electromagnetic interrogation of  

E-Print Network (OSTI)

Regularity and approximation of systems arising in electromagnetic interrogation of dielectric describes the electromagnetic interrogation of dielectric materials. We address the well describing the electromagnetic in- terrogation of dielectric materials. Let E and H be the intensities

297

Approximate translation : media, narrative, and experience in urban design  

E-Print Network (OSTI)

Approximate translation is developed as a design process through which the place-embedded history of an urban environment can be understood, allowing for better design and intervention in that urban environment. Generally, ...

Crisman, Jonathan

2013-01-01T23:59:59.000Z

298

High energy light scattering in the generalized eikonal approximation  

Science Journals Connector (OSTI)

The generalized eikonal approximation method is applied to the study of light scattering by a dielectric medium. In this method, the propagation of light inside the medium is assumed...

Chen, Tuan W

1989-01-01T23:59:59.000Z

299

A constantfactor approximation algorithm for the kmedian problem  

E-Print Network (OSTI)

that this result is best possible via a reduction from the set cover problem. # moses@cs.stanford.edu. StanfordA constant­factor approximation algorithm for the k­median problem Moses Charikar # Sudipto Guha­factor approximation algorithm for the metric k­median prob­ lem. The k­median problem is one of the most well

Keinan, Alon

300

The time-dependent Born-Oppenheimer approximation  

E-Print Network (OSTI)

We explain why the conventional argument for deriving the time-dependent Born-Oppenheimer approximation is incomplete and review recent mathematical results, which clarify the situation and at the same time provide a systematic scheme for higher order corrections. We also present a new elementary derivation of the correct second-order time-dependent Born-Oppenheimer approximation and discuss as applications the dynamics near a conical intersection of potential surfaces and reactive scattering.

Gianluca Panati; Herbert Spohn; Stefan Teufel

2007-12-28T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Kohn-Sham Kinetic Energy Density in the Nuclear and Asymptotic Regions: Deviations from the Von Weizs\\"acker Behavior and Applications to Density Functionals  

E-Print Network (OSTI)

We show that the Kohn-Sham positive-definite kinetic energy (KE) density significantly differs from the von Weizs\\"acker (VW) one at the nuclear cusp as well as in the asymptotic region. At the nuclear cusp, the VW functional is shown to be linear and the contribution of p-type orbitals to the KE density is theoretically derived and numerically demonstrated in the limit of infinite nuclear charge, as well in the semiclassical limit of neutral large atoms. In the latter case, it reaches 12 of the KE density. In the asymptotic region we find new exact constraints for meta Generalized Gradient Approximation (meta-GGA) exchange functionals: with an exchange enhancement factor proportional to $\\sqrt{\\alpha}$, where $\\alpha$ is the common meta-GGA ingredient, both the exchange energy density and the potential are proportional to the exact ones. In addition, this describes exactly the large-gradient limit of quasi-two dimensional systems.

Della Sala, F; Constantin, L A

2014-01-01T23:59:59.000Z

302

Definition: Power density | Open Energy Information  

Open Energy Info (EERE)

density density Jump to: navigation, search Dictionary.png Power density The rate of energy flow (power) per unit volume, area or mass. Common metrics include: horsepower per cubic inch, watts per square meter and watts per kilogram.[1][2] View on Wikipedia Wikipedia Definition Power density (or volume power density or volume specific power) is the amount of power (time rate of energy transfer) per unit volume. In energy transformers like batteries, fuel cells, motors, etc. but also power supply units or similar, power density refers to a volume. It is then also called volume power density which is expressed as W/m. Volume power density is sometimes an important consideration where space is constrained. In reciprocated internal combustion engines, power density- power per swept

303

Electronic density of states in amorphous zirconium alloys  

Science Journals Connector (OSTI)

We have produced amorphous Zr-Rh, Zr-Ru, and Zr-Re films by means of rf diode cosputtering techniques. Measurements were made of the superconducting transition temperature Tc, the normal resistivity ?, and upper critical field Hc2. From ? and (dHc2dT)Tc we determined the dressed density of states at the Fermi level N*=N(1+?), where ? is the electron-phonon coupling constant and N is the bare density of states. For Zr-Rh and Zr-Re, N* exhibited an approximately linear decrease as the Zr fraction decreased. For Zr-Ru alloys the behavior was more complex. Estimating N for Zr-Rh alloys, we find it to be approximately the same in magnitude and composition dependence as the N for Zr-Cu alloys. We calculate the magnitude and composition dependence of N for Zr-Rh and Zr-Cu alloys with the use of a simple model and obtain good agreement with the experimental results.

F. P. Missell; S. Frota-Pessa; J. Wood; J. Tyler; J. E. Keem

1983-02-01T23:59:59.000Z

304

Estimation of Density of Biodiesel  

Science Journals Connector (OSTI)

In addition, the numeric value for coefficient e is very small (?0.00001) and the nd(ave) of most biodiesels are not greater than 2. Therefore, the product of e nd(ave) can be neglected without affecting the accuracy of the calculation and eq 30 is good for estimation of density of biodiesel. ... Interestingly, the %AAD for mixed biodiesel (0.38) is lower than those of pure (0.41%) and total biodiesels. ... (21) The model cannot differentiate a mixed biodiesel from pure biodiesels. ...

Suriya Phankosol; Kaokanya Sudaprasert; Supathra Lilitchan; Kornkanok Aryusuk; Kanit Krisnangkura

2014-06-16T23:59:59.000Z

305

Ensemble density variational methods with self- and ghost-interaction-corrected functionals  

SciTech Connect

Ensemble density functional theory (DFT) offers a way of predicting excited-states energies of atomic and molecular systems without referring to a density response function. Despite a significant theoretical work, practical applications of the proposed approximations have been scarce and they do not allow for a fair judgement of the potential usefulness of ensemble DFT with available functionals. In the paper, we investigate two forms of ensemble density functionals formulated within ensemble DFT framework: the Gross, Oliveira, and Kohn (GOK) functional proposed by Gross et al. [Phys. Rev. A 37, 2809 (1988)] alongside the orbital-dependent eDFT form of the functional introduced by Nagy [J. Phys. B 34, 2363 (2001)] (the acronym eDFT proposed in analogy to eHF ensemble Hartree-Fock method). Local and semi-local ground-state density functionals are employed in both approaches. Approximate ensemble density functionals contain not only spurious self-interaction but also the so-called ghost-interaction which has no counterpart in the ground-state DFT. We propose how to correct the GOK functional for both kinds of interactions in approximations that go beyond the exact-exchange functional. Numerical applications lead to a conclusion that functionals free of the ghost-interaction by construction, i.e., eDFT, yield much more reliable results than approximate self- and ghost-interaction-corrected GOK functional. Additionally, local density functional corrected for self-interaction employed in the eDFT framework yields excitations energies of the accuracy comparable to that of the uncorrected semi-local eDFT functional.

Pastorczak, Ewa [Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, ul. Wroblewskiego 15, 93-590 Lodz (Poland)] [Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, ul. Wroblewskiego 15, 93-590 Lodz (Poland); Pernal, Katarzyna, E-mail: pernalk@gmail.com [Institute of Physics, Lodz University of Technology, ul. Wolczanska 219, 90-924 Lodz (Poland)] [Institute of Physics, Lodz University of Technology, ul. Wolczanska 219, 90-924 Lodz (Poland)

2014-05-14T23:59:59.000Z

306

Full charge-density scheme with a kinetic-energy correction: Application to ground-state properties of the 4d metals  

Science Journals Connector (OSTI)

We present a full charge-density technique to evaluate total energies from the output of self-consistent linear muffin-tin orbitals (LMTO) calculations in the atomic-sphere approximation (ASA). The Coulomb energy is calculated exactly from the complete, nonspherically symmetric charge density defined within nonoverlapping, space-filling Wigner-Seitz cells; the exchange-correlation energy is evaluated by means of the local-density approximation or the generalized gradient approximation applied to the complete charge-density; and the ASA kinetic energy is corrected for the nonspherically symmetric charge density by a gradient expansion. The technique retains most of the simplicity and the computational efficiency of the LMTO-ASA method, and calculations of atomic volumes and elastic constants of the 4d elements show that it has the accuracy of full-potential methods.

L. Vitos; J. Kollr; H. L. Skriver

1997-05-15T23:59:59.000Z

307

Combining Density Functional Theory and Density Matrix Functional Theory Daniel R. Rohr1  

E-Print Network (OSTI)

Combining Density Functional Theory and Density Matrix Functional Theory Daniel R. Rohr1 , Julien and CNRS, 4 place Jussieu, 75252 Paris, France We combine density-functional theory with density cleavage is an ubiquitous process for chemistry. Density-matrix functional theory (DMFT) (see, e.g., Refs

Paris-Sud XI, Université de

308

Variational principles with Pad approximants for tearing mode analysis  

SciTech Connect

Tearing modes occur in several distinct physical regimes, and it is often important to compute the inner layer response for these modes with various effects. There is a need for an approximate and efficient method of solving the inner layer equations in all these regimes. In this paper, we introduce a method of solving the inner layer equations based on using a variational principle with Pad approximants. For all the regimes considered, the main layer equations to be solved are inhomogeneous, and Pad approximants give a convenient and efficient method of satisfying the correct asymptotic behavior at the edge of the layer. Results using this variational principlePad approximant method in three of these regimes is presented. These regimes are the constant-? resistive-inertial (RI) regime, the constant-? viscoresistive regime, and the non-constant-? inviscid tearing regime. The last regime includes the constant-? RI regime and the inertial regime. The results show that reasonable accuracy can be obtained very efficiently with Pad approximants having a small number of parameters.

Cole, Andrew J. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)] [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Finn, John M. [Applied Mathematics and Plasma Physics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)] [Applied Mathematics and Plasma Physics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)

2014-03-15T23:59:59.000Z

309

Quasipotential Equation Corresponding to the Relativistic Eikonal Approximation  

Science Journals Connector (OSTI)

A three-dimensional Lippmann-Schwinger-type equation for the elastic scattering amplitude and the corresponding homogeneous Schrdinger equation for the two-particle bound states are studied. The potential is defined as an infinite power series in the coupling constant which fits the perturbative expansion of the on-energy-shell scattering amplitude. The approximate equation obtained by keeping only the lowest-order term in the potential is local and has the following properties: (i) The scattering amplitude yields the relativistic eikonal approximation for large energies or small exchanged mass and momentum transfer; (ii) for the Coulomb problem the approximate equation is exactly soluble and leads to a relativistic Balmer formula including the fine-structure splitting.

I. T. Todorov

1971-05-15T23:59:59.000Z

310

The Monte Carlo Independent Column Approximation Model Intercomparison  

NLE Websites -- All DOE Office Websites (Extended Search)

The Monte Carlo Independent Column Approximation Model Intercomparison The Monte Carlo Independent Column Approximation Model Intercomparison Project (McMIP) Barker, Howard Meteorological Service of Canada Cole, Jason Meteorological Service of Canada Raisanen, Petri Finnish Meteorological Institute Pincus, Robert NOAA-CIRES Climate Diagnostics Center Morcrette, Jean-Jacques European Centre for Medium-Range Weather Forecasts Li, Jiangnan Canadian Center for Climate Modelling Stephens, Graeme Colorado State University Vaillancourt, Paul Environment Canada Oreopoulos, Lazaros JCET/UMBC and NASA/GSFC Siebesma, Pier KNMI Los, Alexander KNMI Clothiaux, Eugene The Pennsylvania State University Randall, David Colorado State University Iacono, Michael Atmospheric & Environmental Research, Inc. Category: Radiation The Monte Carlo Independent Column Approximation (McICA) method for

311

Scalar Nature of the Nuclear Density Functional  

E-Print Network (OSTI)

Because of the rotational invariance of the nuclear Hamiltonian, there exists a density functional for nuclei that depends only on two scalar densities. Practical calculations boil down to radial, one-dimensional ones.

B. G. Giraud

2008-01-22T23:59:59.000Z

312

Risk Bounds for Mixture Density Estimation  

E-Print Network (OSTI)

In this paper we focus on the problem of estimating a bounded density using a finite combination of densities from a given class. We consider the Maximum Likelihood Procedure (MLE) and the greedy procedure described by ...

Rakhlin, Alexander

2004-01-27T23:59:59.000Z

313

Biodiesel Density: Experimental Measurements and Prediction Models  

Science Journals Connector (OSTI)

Density is an important biodiesel parameter, with impact on fuel quality. Predicting density is of high relevance for a correct formulation of an adequate blend of raw materials that optimize the cost of biodiesel fuel production while allowing the ...

Maria Jorge Pratas; Samuel V. D. Freitas; Mariana B. Oliveira; Slvia C. Monteiro; lvaro S. Lima; Joo A. P. Coutinho

2011-04-19T23:59:59.000Z

314

Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric nuclear matter based on improved approximation schemes  

E-Print Network (OSTI)

We present Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric nuclear matter which are based on improved approximations schemes. The potential matrix elements have been adapted for isospin asymmetric nuclear matter in order to account for the proton-neutron mass splitting in a more consistent way. The proton properties are particularly sensitive to this adaption and its consequences, whereas the neutron properties remains almost unaffected in neutron rich matter. Although at present full Brueckner calculations are still too complex to apply to finite nuclei, these relativistic Brueckner results can be used as a guidance to construct a density dependent relativistic mean field theory, which can be applied to finite nuclei. It is found that an accurate reproduction of the Dirac-Brueckner-Hartree-Fock equation of state requires a renormalization of these coupling functions.

E. N. E. van Dalen; C. Fuchs; Amand Faessler

2006-12-14T23:59:59.000Z

315

Complete equation of state for neutron stars using the relativistic Hartree-Fock approximation  

SciTech Connect

We construct the equation of state in a wide-density range for neutron stars within relativistic Hartree-Fock approximation. The properties of uniform and nonuniform nuclear matter are studied consistently. The tensor couplings of vector mesons to baryons due to exchange contributions (Fock terms) are included, and the change of baryon internal structure in matter is also taken into account using the quark-meson coupling model. The Thomas-Fermi calculation is adopted to describe nonuniform matter, where the lattice of nuclei and the neutron drip out of nuclei are considered. Even if hyperons exist in the core of a neutron star, we obtain the maximum neutron-star mass of 1.95M{sub ?}, which is consistent with the recently observed massive pulsar, PSR J1614-2230. In addition, the strange vector (?) meson also plays a important role in supporting a massive neutron star.

Miyatsu, Tsuyoshi; Cheoun, Myung-Ki [Department of Physics, Soongsil University, Seoul 156-743 (Korea, Republic of); Yamamuro, Sachiko; Nakazato, Ken'ichiro [Department of Physics, Faculty of Science and Technology, Tokyo University of Science (TUS), Noda 278-8510 (Japan)

2014-05-02T23:59:59.000Z

316

Stellar electron-capture rates calculated with the finite-temperature relativistic random-phase approximation  

E-Print Network (OSTI)

We introduce a self-consistent microscopic theoretical framework for modelling the process of electron capture on nuclei in stellar environment, based on relativistic energy density functionals. The finite-temperature relativistic mean-field model is used to calculate the single-nucleon basis and the occupation factors in a target nucleus, and $J^{\\pi} = 0^{\\pm}$, $1^{\\pm}$, $2^{\\pm}$ charge-exchange transitions are described by the self-consistent finite-temperature relativistic random-phase approximation. Cross sections and rates are calculated for electron capture on 54,56Fe and 76,78Ge in stellar environment, and results compared with predictions of similar and complementary model calculations.

YiFei Niu; Nils Paar; Dario Vretenar; Jie Meng

2011-04-09T23:59:59.000Z

317

Solution of the Schrodinger equation for the inverse-square potential using Pade approximants  

E-Print Network (OSTI)

to J@(x) Order of the approximant which approximates J (x) to a relative o -4- error less than 10 44 Order of the approximant which approximates Jl(x) to a relative -4 error less than 10 10 Order of the approximant which approximates J4(x) to a... relative -4- error less than 10 Figure Page Order of the approximant which approximates J&(x) to a relative error less than 10 ? 4 4c 12 14 Relative error in the 4, 4 approximant to J. (x) Relative error in the 4, 4 approximant to J4 (x) 4r...

Golden, Jack Emitt

1972-01-01T23:59:59.000Z

318

approximately 200 megawatts (MWs) of power from TCEP, making  

NLE Websites -- All DOE Office Websites (Extended Search)

approximately 200 megawatts (MWs) of power from TCEP, making approximately 200 megawatts (MWs) of power from TCEP, making it the first U.S. purchase by a utility of low-carbon power from a commercial-scale, coal-based power plant with carbon capture. The 400-MW TCEP plant is a first-of-its-kind integrated gasification combined cycle (IGCC) poly-generation facility capable of capturing 90 percent of the carbon dioxide (CO 2 ) it produces. The $2.4-billion plant was a third round selection under DOE's Clean Coal Power Initiative

319

Improved approximation algorithm for the jump number of interval orders  

Science Journals Connector (OSTI)

Abstract The jump number problem for posets is to find a linear extension in which the number of incomparable adjacent pairs is minimized. In this paper the class of interval orders is considered. Three 3/2-approximation algorithms for this problem have been known for some time. By a previous work of Mitas, the problem may be reformulated as a subgraph packing task. We prove that the problem reduces also to a set cover task, and we establish an improved bound of 1.484 to the approximation ratio of the jump number on interval orders.

Przemys?aw Krysztowiak

2013-01-01T23:59:59.000Z

320

Optimal approximation of harmonic growth clusters by orthogonal polynomials  

SciTech Connect

Interface dynamics in two-dimensional systems with a maximal number of conservation laws gives an accurate theoreticaI model for many physical processes, from the hydrodynamics of immiscible, viscous flows (zero surface-tension limit of Hele-Shaw flows), to the granular dynamics of hard spheres, and even diffusion-limited aggregation. Although a complete solution for the continuum case exists, efficient approximations of the boundary evolution are very useful due to their practical applications. In this article, the approximation scheme based on orthogonal polynomials with a deformed Gaussian kernel is discussed, as well as relations to potential theory.

Teodorescu, Razvan [Los Alamos National Laboratory

2008-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


321

The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers  

E-Print Network (OSTI)

The optically thin critical densities and the effective excitation densities to produce a 1 K km/s (or 0.818 Jy km/s $(\\frac{\

Shirley, Yancy L

2015-01-01T23:59:59.000Z

322

Time Dependent Density Functional Theory An introduction  

E-Print Network (OSTI)

Time Dependent Density Functional Theory An introduction Francesco Sottile LSI, Ecole Polytechnique) Time Dependent Density Functional Theory Palaiseau, 26 May 2014 1 / 62 #12;Outline 1 Introduction: why and Resources Francesco Sottile (ETSF) Time Dependent Density Functional Theory Palaiseau, 26 May 2014 2 / 62

Botti, Silvana

323

Density functional theory George F. Bertsch  

E-Print Network (OSTI)

Density functional theory George F. Bertsch #3; Institute for Nuclear Theory and Department of Physics University of Tsukuba Tsukuba 305-8577 Japan Abstract Density functional theory is a remarkably Time-dependent density functional theory: the equations 34 A Optical properties

Bertsch George F.

324

DENSITY FUNCTIONAL THEORY, THE MODERN TREATMENT OF  

E-Print Network (OSTI)

DENSITY FUNCTIONAL THEORY, THE MODERN TREATMENT OF ELECTRON CORRELATIONS E.K.U. Gross and Stefan The basic idea of density functional theory is to describe a many-electron system exclusively and completely-consistent scheme, known as the Kohn-Sham scheme [2], is the heart of modern density functional theory

Gross, E.K.U.

325

On Approximating the Translational Velocity of Vortex Rings  

E-Print Network (OSTI)

from this configuration and the system scaling. Here, the accuracy of this approximation is presented orifice in a flat plate contain a converging radial component of velocity. For both configurations. By this definition, the piston velocity is the average jet velocity passing through the orifice independent

Mohseni, Kamran

326

The Exemplar Breakpoint Distance for nontrivial genomes cannot be approximated  

E-Print Network (OSTI)

The Exemplar Breakpoint Distance for non­trivial genomes cannot be approximated Guillaume Blin 1 ­ France guillaume.fertin@univ­nantes.fr Abstract. A promising and active field of comparative genomics con­ sists in comparing two genomes by establishing a one­to­one correspon­ dence (i.e., a matching) between

Fertin, Guillaume

327

Incorporating Velocity Shear into the Magneto-Boussinesq Approximation  

E-Print Network (OSTI)

Motivated by consideration of the solar tachocline, we derive, via an asymptotic procedure, a new set of equations incorporating velocity shear and magnetic buoyancy into the Boussinesq approximation. We demonstrate, by increasing the magnetic field scale height, how these equations are linked to the magneto-Boussinesq equations of Spiegel and Weiss (1982).

Bowker, Jordan A; Kersal, Evy

2014-01-01T23:59:59.000Z

328

Improved approximation algorithms for a capacitated facility location problem  

E-Print Network (OSTI)

that ordinary randomized rounding rarely generates a feasible solution to the associated set covering problemImproved approximation algorithms for a capacitated facility location problem Fabi'an A. Chudak. There is a set of demand locations that require service from facilities; there is a set of locations at which

Keinan, Alon

329

CS 105: Algorithms (Grad) Approximation Algorithms (continued) Feb 21, 2005  

E-Print Network (OSTI)

.g. Clique. = O(log n), e.g. Set Cover. = O(1), e.g. Vertex Cover. Page 1 of 7 #12;CS 105: Algorithms (Grad Algorithms: Vertex Cover 1.1 Introduction to Approximation Algorithms There are several optimization problems (TSP) - finding a minimum cost tour of all cities � Vertex Cover - find minimum set of vertex

Chakrabarti, Amit

330

Geometric and capacitated set cover Exact and approximation algorithms for  

E-Print Network (OSTI)

Geometric and capacitated set cover ' & $ % Exact and approximation algorithms for geometric and capacitated set cover problems Piotr Berman Pennsylvania State University Marek Karpinski Bonn University Andrzej Lingas Lund University July 22, 2010 COCOON 2010 Page 1 #12;Geometric and capacitated set cover

Berman, Piotr

331

LP-Based Approximation Algorithms for Reliable Resource Allocation  

Science Journals Connector (OSTI)

......technique for analyzing the minimum set cover problem. For a special case of RRA...technique for analyzing the minimum set cover problem. For a special case of RRA...UFL can be easily reduced from the set cover problem [18] that is hard to approximate......

Kewen Liao; Hong Shen

2014-01-01T23:59:59.000Z

332

CP-networks: semantics, complexity, approximations and extensions  

E-Print Network (OSTI)

CP-networks: semantics, complexity, approximations and extensions F. Rossi, K. B. Venable Dept Constraint Computation Centre, University College Cork Cork, Ireland tw@4c.ucc.ie July 23, 2002 Abstract CP-networks are an elegant and compact qualitative framework for ex- pressing preferences. Unfortunately, reasoning with CP

Walsh, Toby

333

A fast approximation technique for power grid analysis  

Science Journals Connector (OSTI)

In this paper, we present a fast approximation algorithm for computing IR drops in a VLSI power grid. Assuming that the grid does not have pathological defects, the algorithm can estimate IR drops to within 5% average error, with a run time of less than ...

Mysore Sriram

2011-01-01T23:59:59.000Z

334

New approximation algorithms for minimum cycle bases of graphs  

Science Journals Connector (OSTI)

We consider the problem of computing an approximate minimum cycle basis of an undirected edge-weighted graph G with m edges and n vertices; the extension to directed graphs is also discussed. In this problem, a {0, 1} incidence vector ...

Telikepalli Kavitha; Kurt Mehlhorn; Dimitrios Michail

2007-02-01T23:59:59.000Z

335

An Example of Uniform Approximation near a Caustic  

Science Journals Connector (OSTI)

In the region inside a caustic having two rays through each point ray acoustics approximates a sound field due to a point harmonic source of frequency ? by e?Im(T1)[A1ei?T 1+A2e(i?T 2+ir/2) ]. When the caustic is smooth Ludwig approximates the field everywhere by a constant times e i?? [B 1 Ai (?? 2 3 ?)?i? ? 1 2 B 2 Ai ?(?? 1 2 ?)] where Ai is the usual Airy function. An example of Ludwig's approximation is presented in parameterless form for the unbounded layered medium having speed c(z)?=?z ? 1 2 . This approximation of course agrees with ray theory on the source side of the caustic rises to a large but finite value near the caustic and exhibits exponential decay on the other side of the caustic. For the record the results are expressed in horizontal range x and depth z with the source at x = 0 z = z 0: T n ?=?( 2 3 )[??+?(???1) n ?] 1 2 [????(??1?) n ?/2] where ? = z + z 0 and r2 = 4zz0 ? x2; An ?2 = 2r(? + (? 1) n ?); 2? = ? ? R where R 2 = (z ? z 0)2 + x 2 3? 1 2 ?=???+?R ; B 1 2 ?=?2?? 1 3 /(rR 2 ) and B 2 ?=?? ? 1 2 /R .

1974-01-01T23:59:59.000Z

336

Managing Approximate Models in Evolutionary Aerodynamic Design Optimization  

E-Print Network (OSTI)

Managing Approximate Models in Evolutionary Aerodynamic Design Optimization Yaochu Jin yaochu jin­ mization problems that are discontinuous, multi­modal and multi­objective [1, 2]. Aerodynamic structural to high complexity of the aerodynamic analysis and large number of evaluations needed in the evolutionary

Coello, Carlos A. Coello

337

Gerla Giangiacomo Fuzzy logic. Mathematical tools for approximate reasoning. (English)  

E-Print Network (OSTI)

the author's approach to fuzzy control. Based upon a certain version of fuzzified logical programming, viz. Herbrand models for fuzzy logics, the author interprets lists of fuzzy control rules by fuzzy logicGerla Giangiacomo Fuzzy logic. Mathematical tools for approximate reasoning. (English) [B] Trends

Gerla, Giangiacomo

338

On the mathematical treatment of the Born-Oppenheimer approximation  

SciTech Connect

Motivated by the paper by Sutcliffe and Woolley [On the quantum theory of molecules, J. Chem. Phys. 137, 22A544 (2012)], we present the main ideas used by mathematicians to show the accuracy of the Born-Oppenheimer approximation for molecules. Based on mathematical works on this approximation for molecular bound states, in scattering theory, in resonance theory, and for short time evolution, we give an overview of some rigorous results obtained up to now. We also point out the main difficulties mathematicians are trying to overcome and speculate on further developments. The mathematical approach does not fit exactly to the common use of the approximation in Physics and Chemistry. We criticize the latter and comment on the differences, contributing in this way to the discussion on the Born-Oppenheimer approximation initiated by Sutcliffe and Woolley. The paper neither contains mathematical statements nor proofs. Instead, we try to make accessible mathematically rigourous results on the subject to researchers in Quantum Chemistry or Physics.

Jecko, Thierry, E-mail: thierry.jecko@u-cergy.fr [AGM, UMR 8088 du CNRS, Universit de Cergy-Pontoise, Dpartement de mathmatiques, site de Saint Martin, 2 avenue Adolphe Chauvin, F-95000 Pontoise (France)] [AGM, UMR 8088 du CNRS, Universit de Cergy-Pontoise, Dpartement de mathmatiques, site de Saint Martin, 2 avenue Adolphe Chauvin, F-95000 Pontoise (France)

2014-05-15T23:59:59.000Z

339

Decoupling electrons and nuclei without the Born-Oppenheimer approximation  

E-Print Network (OSTI)

Decoupling electrons and nuclei without the Born-Oppenheimer approximation Patrick Cassam. The EN-GMFCI is a new paradigm for quantum chemistry that bypasses the tradi- tional Born-Oppenheimer (BO;1 Introduction The Born-Oppenheimer (BO) potential energy surface (PES) is one of the main paradigm of quantum

Paris-Sud XI, Université de

340

Preprint UC Davis Math 199930 A continuum approximation for the  

E-Print Network (OSTI)

Preprint UC Davis Math 1999­30 A continuum approximation for the excitations of the (1; 1 and Shannon Starr Department of Mathematics University of California, Davis Davis, CA 95616­8633, USA bolina, with an appropriate scaling, the energy of low­ lying excitations of the (1; 1; : : : ; 1) interface in the d

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

HEREDITARY APPROXIMATION PROPERTY W. B. JOHNSON AND A. SZANKOWSKI  

E-Print Network (OSTI)

HEREDITARY APPROXIMATION PROPERTY W. B. JOHNSON AND A. SZANKOWSKI Abstract. If X is a Banach space, trace formula. Johnson was supported in part by NSF DMS-0500292, DMS-1001321, and the U.S.-Israel Binational Science Foundation. 1 #12;2 W. B. JOHNSON AND A. SZANKOWSKI subsymmetric basis unless

Johnson, William B.

342

Approximate inference for spatial functional data on massively parallel processors  

Science Journals Connector (OSTI)

With continually increasing data sizes, the relevance of the big n problem of classical likelihood approaches is greater than ever. The functional mixed-effects model is a well established class of models for analyzing functional data. Spatial functional ... Keywords: Functional data analysis, Functional mixed-effects model, GPU, Gaussian processes, Likelihood analysis, Operator approximations

Lars Lau Rakt; Bo Markussen

2014-04-01T23:59:59.000Z

343

Approximate hedging problem with transaction costs in stochastic volatility markets  

E-Print Network (OSTI)

Approximate hedging problem with transaction costs in stochastic volatility markets Thai Huu Nguyen stochastic volatility markets with transaction costs using a new form for enlarged volatility in Leland between the present setting and high frequency markets with transaction costs. Possibilities to improve

Paris-Sud XI, Université de

344

Approximating the Probability of an Itemset being Nele Dexters  

E-Print Network (OSTI)

gives a statistical approach to the success probability Sl, the probability that a set consisting of lApproximating the Probability of an Itemset being Frequent Nele Dexters University of Antwerp algorithms, the probability that an itemset is a candidate and the probability that a set is frequent (a

Antwerpen, Universiteit

345

Approximate Minimum-Energy Multicasting in Wireless Ad Hoc Networks  

E-Print Network (OSTI)

and a set of destination nodes, the problem is to build a minimum-energy multicast tree for the requestApproximate Minimum-Energy Multicasting in Wireless Ad Hoc Networks Weifa Liang, Senior Member, IEEE Abstract--A wireless ad hoc network consists of mobile nodes that are equipped with energy

Liang, Weifa

346

Expressive Power and Approximation Errors of Restricted Boltzmann Machines  

E-Print Network (OSTI)

#12;Expressive Power and Approximation Errors of Restricted Boltzmann Machines Guido F. Montufar1 Boltzmann Machines (RBMs) depending on the number of units that they contain, and which are representative Machine (RBM) [23, 10] is a learning system con- sisting of two layers of binary stochastic units

347

Di usion Approximation of Radiative Transfer Equations in a Channel  

E-Print Network (OSTI)

direction. 1 #12; 1 Introduction Radiative transport equations were #12;rst used to describe the propagationDi#11;usion Approximation of Radiative Transfer Equations in a Channel Guillaume Bal Department by a di#11;usion equation. However, the thickness of the crust is of the order of the transport mean free

Bal, Guillaume

348

Numerical study on the validity of the diffusion approximation  

E-Print Network (OSTI)

of photons can be accurately modeled by the radiative transport equation (RTE).9,10 Because and the radiative transport as implemented by Monte Carlo simulation in the cases of point and ball sources. Our of the difficulties in handling the RTE directly, the diffusion approximation to the transport equation has been

Virginia Tech

349

Approximate Bayesian Computations Done Exactly: Towards a Thousand Human Genomes  

E-Print Network (OSTI)

Approximate Bayesian Computations Done Exactly: Towards a Thousand Human Genomes Principal of California, Irvine, USA January 28, 2011 Abstract Currently, 1000 whole human genomes are being sequenced. It is becoming exceedingly difficult to extract critical information from such extensive population-level genomic

Sainudiin, Raazesh

350

Rough Set Approximation Framework for Smarter Vertical Handovers  

E-Print Network (OSTI)

2010 Rough Set Approximation Framework for Smarter Vertical Handovers Nalin ChakooO, Saewoong to support seamless mobility. In this paper, we propose rough set based decision framework for vertical handoff in heterogeneous networks. We apply fuzzy decision to fuzzy-rough set which gives us the advantage

Bahk, Saewoong

351

The BornOppenheimer Approximation to the Wave Operators  

Science Journals Connector (OSTI)

We apply the BornOppenheimer approximation to a scattering problem. We consider a diatomic molecule with short-range potential separating into two atoms. Using our earlier mathematical results we construct a leading order expansion to the wave operator for this scattering channel. We comment on limitation and possible extensions of this work.

Armin Kargol

1999-01-01T23:59:59.000Z

352

Self-similar and charged spheres in the diffusion approximation  

E-Print Network (OSTI)

We study spherical, charged and self--similar distributions of matter in the diffusion approximation. We propose a simple, dynamic but physically meaningful solution. For such a solution we obtain a model in which the distribution becomes static and changes to dust. The collapse is halted with damped mass oscillations about the absolute value of the total charge.

Barreto, W

1999-01-01T23:59:59.000Z

353

Improved Approximations for Max Set Splitting and Max NAE SAT  

E-Print Network (OSTI)

Improved Approximations for Max Set Splitting and Max NAE SAT #3; Jiawei Zhang and Yinyu Ye y Nanjing, 210093, P.R.China August 16, 2000, Revised January 22, 2001. #3; This research was supported Fudan University, Shanghai, R.R.China. z This work was done while the author was visiting Computational

Ye, Yinyu

354

Aerodynamic Focusing Of High-Density Aerosols  

SciTech Connect

High-density micron-sized particle aerosols might form the basis for a number of applications in which a material target with a particular shape might be quickly ionized to form a cylindrical or sheet shaped plasma. A simple experimental device was built in order to study the properties of high-density aerosol focusing for 1#22; m silica spheres. Preliminary results recover previous findings on aerodynamic focusing at low densities. At higher densities, it is demonstrated that the focusing properties change in a way which is consistent with a density dependent Stokes number.

Ruiz, D. E.; Fisch, Nathaniel

2014-02-24T23:59:59.000Z

355

Different approximations of shallow fluid flow over an obstacle  

SciTech Connect

Three different sets of shallow water equations, representing different levels of approximation are considered. The numerical solutions of these different equations for flow past bottom topography in several different flow regimes are compared. For several cases the full Euler solutions are computed as a reference, allowing the assessment of the relative accuracies of the different approximations. Further, the differences between the dispersive shallow water (DSW) solutions and those of the highly simplified, hyperbolic shallow water (SW) equations is studied as a guide to determining what level of approximation is required for a particular flow. First, the Green-Naghdi (GN) equations are derived as a vertically-integrated rational approximation of the Euler equations, and then the generalized Boussinesq (gB) equations are obtained under the further assumption of weak nonlinearity. A series of calculations, each assuming different values of a set of parameters{emdash}undisturbed upstream Froude number, and the height and width of the obstacle, are then presented and discussed. In almost all regions of the parameter space, the SW and DSW theories yield different results; it is only when the flows are entirely subcritical or entirely supercritical and when the obstacles are very wide compared to the depth of the fluid that the SW and DSW theories are in qualitative and quantitative agreement. It is also found that while the gB solutions are accurate only for small bottom topographies (less than 20{percent} of the undisturbed fluid depth), the GN solutions are accurate for much larger topographies (up to 65{percent} of the undisturbed fluid depth). The limitation of the gB approximation to small topographies is primarily due to the generation of large amplitude upstream propagating solitary waves at transcritical Froude numbers, and is consistent with previous analysis. (Abstract Truncated)

Nadiga, B.T.; Margolin, L.G. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Smolarkiewicz, P.K. [National Center for Atmospheric Research, Boulder, Colorado 80307 (United States)] [National Center for Atmospheric Research, Boulder, Colorado 80307 (United States)

1996-08-01T23:59:59.000Z

356

Investigating the Dynamics and Density Evolution of Returning Plasma Blobs from the 2011 June 7 Eruption  

E-Print Network (OSTI)

This work examines infalling matter following an enormous Coronal Mass Ejection (CME) on 2011 June 7. The material formed discrete concentrations, or blobs, in the corona and fell back to the surface, appearing as dark clouds against the bright corona. In this work we examined the density and dynamic evolution of these blobs in order to formally assess the intriguing morphology displayed throughout their descent. The blobs were studied in five wavelengths (94, 131, 171, 193 and 211 \\AA) using the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA), comparing background emission to attenuated emission as a function of wavelength to calculate column densities across the descent of four separate blobs. We found the material to have a column density of hydrogen of approximately 2 $\\times$ 10$^{19}$ cm$^{-2}$, which is comparable with typical pre-eruption filament column densities. Repeated splitting of the returning material is seen in a manner consistent with the Rayleigh-Taylor instability. Furthe...

Carlyle, Jack; van Driel-Gesztelyi, Lidia; Innes, Davina; Hillier, Andrew; Matthews, Sarah

2014-01-01T23:59:59.000Z

357

Shift in the longitudinal sound velocity due to sliding charge-density waves  

Science Journals Connector (OSTI)

The nonlinear conductivity observed for moderate electric fields in NbSe3, TaS3, (TaS4)2I, and K0.3MoO3 below the charge-density-wave-transition is believed to be due to the sliding of the charge-density waves. The sliding motion leads to a Doppler shift of the x-ray diffraction peaks, but this effect has not yet been resolved. We show here that besides the Doppler shift, a sliding incommensurate charge-density wave causes a change in the longitudinal sound velocity of the crystal that is linear in the charge-density-wave velocity. The resulting anisotropic shift is estimated in a mean-field approximation and found to be experimentally observable.

S. N. Coppersmith and C. M. Varma

1984-09-15T23:59:59.000Z

358

Transport Energy Use and Population Density  

NLE Websites -- All DOE Office Websites (Extended Search)

Transport Energy Use and Population Density Transport Energy Use and Population Density Speaker(s): Masayoshi Tanishita Date: July 1, 2004 - 10:00pm Location: Bldg. 90 Seminar Host/Point of Contact: Jonathan Sinton After Peter Newman and Jeffrey Kenworthy published "Cities and Automobile Dependence" in 1989, population density was brought to public attention as an important factor to explain transport mobility and energy use. However, several related issues still remain open: Is an increase in population density more effective than rising gas prices in reducing transport energy use? How much does per capita transport energy use change as population density in cities changes? And what kind of factors influence changes in population density? In this presentation, using city-level data in the US, Japan and other countries, the population-density elasticity of

359

cross-sections with a density-dependent Brueckner-Hartree-Fock NN interaction  

E-Print Network (OSTI)

In the calculation of the K +-nucleus cross sections, the coupling of the mesons exchanged between the K + and the target nucleons to the polarization of the Fermi and Dirac seas has been taken into account. This polarization has been calculated in the one-loop approximation but summed up to all orders (RPA approximation). For this calculation a density-dependent Brueckner-Hartree-Fock NN interaction providing a good description of both nuclear matter and finite nuclei has been used. The agreement with experiment is considerably improved. PACS numbers: 25.80.Nv, 21.30.+y, 21.60.Jz, 24.10.Jv

J. C. Caillon; J. Labarsouque; Centre Detudes Nuclaires De Bordeaux-gradignan; Universit Bordeaux I

1994-01-01T23:59:59.000Z

360

Development and scale-up of the low density core process for Ti-64  

SciTech Connect

The Low Density Core (LDC) process is a method for making metallic structures with solid surfaces covering a porous core. The development of the LDC process for making Ti-64 sheet based structures is described. Sheets {approximately}2000 x 1200 x 4 mm{sup 3} have been made with {approximately}40 vol.% core porosity levels, and several forming techniques have been demonstrated. The LDC billet breakdown and forming behavior was found to be similar to conventional Ti-64 processes, so LDC Ti-64 sheet has the advantage that it can be fabricated into structures using well-established methods.

Schwartz, D.S.; Shih, D.S.; Lederich, R.J.; Martin, R.L.; Deuser, D.A. [Boeing Co., St. Louis, MO (United States)

1998-12-31T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Dot Density Maps Dot density maps, or dot maps, portray the geographic distribution of discrete phenomena  

E-Print Network (OSTI)

Dot Density Maps Dot density maps, or dot maps, portray the geographic distribution of discrete for representing geographic patterns. Dot density maps are particularly useful for understanding global distribution of the mapped phenomenon and comparing relative densities of different regions on the map. Dot

Klippel, Alexander

362

KH Computational Physics-2009 Density Functional Theory (DFT) Density Functional Theory  

E-Print Network (OSTI)

KH Computational Physics- 2009 Density Functional Theory (DFT) Density Functional Theory of interacting particles. Kristjan Haule, 2009 ­2­ #12;KH Computational Physics- 2009 Density Functional Theory functional of n. Kristjan Haule, 2009 ­3­ #12;KH Computational Physics- 2009 Density Functional Theory (DFT

Haule, Kristjan

363

Population Density Population density (persons per square kilometer) layers, for 1990  

E-Print Network (OSTI)

Population Density Africa Population density (persons per square kilometer) layers, for 1990 the 12 population density classes. Source information: http://sedac.ciesin.columbia.edu/gpw/. ´ Robinson://sedac.ciesin.columbia.edu/place/ Publish Date: 03/13/07 0 1,000 km Population Density 2000 0 Persons \\ Sq.Km 0-2 Persons \\ Sq.Km 2

Columbia University

364

Electron and Negative Ion Densities in C(2)F(6) and CHF(3) Containing Inductively Coupled Discharges  

SciTech Connect

Electron and negative ion densities have been measured in inductively coupled discharges containing C{sub 2}F{sub 6} and CHF{sub 3}. Line integrated electron density was determined using a microwave interferometer, negative ion densities were inferred using laser photodetachment spectroscopy, and electron temperature was determined using a Langmuir probe. For the range of induction powers, pressures and bias power investigated, the electron density peaked at 9 x 10{sup 12} cm{sup -2} (line-integrated) or approximately 9 x 10{sup 11} cm{sup -3}. The negative ion density peaked at approximately 1.3 x 10{sup 11} cm{sup -3}. A maximum in the negative ion density as a function of induction coil power was observed. The maximum is attributed to a power dependent change in the density of one or more of the potential negative ion precursor species since the electron temperature did not depend strongly on power. The variation of photodetachment with laser wavelength indicated that the dominant negative ion was F{sup -}. Measurement of the decay of the negative ion density in the afterglow of a pulse modulated discharge was used to determine the ion-ion recombination rate for CF{sub 4}, C{sub 2}F{sub 6} and CHF{sub 3} discharges.

HEBNER,GREGORY A.; MILLER,PAUL A.

1999-12-07T23:59:59.000Z

365

Excitation energies of molecules within time-independent density functional theory  

SciTech Connect

Recently proposed exchange energy functional for excited-states is tested for obtaining excitation energies of diatomic molecules. The functional is the ground-state counterpart of the local-density approximation, the modified local spin density (MLSD). The MLSD functional is tested for the N{sub 2} and CO diatomic molecules. The excitation energy obtained with the MLSD functional for the N{sub 2} molecule is in close vicinity to that obtained from the exact exchange orbital functional, Krieger, Li and Iafrate (KLI). For the CO molecule, the departure in excitation energy is observed and is due to the overcorrection of self-interaction.

Hemanadhan, M., E-mail: hemanadh@iitk.ac.in; Harbola, Manoj K., E-mail: hemanadh@iitk.ac.in [Department of Physics, Indian Institute of Technology Kanpur, Kanpur-208016 (India)

2014-04-24T23:59:59.000Z

366

projects are valued at approximately $67 million (including $15 million  

NLE Websites -- All DOE Office Websites (Extended Search)

projects are valued at approximately $67 million (including $15 million projects are valued at approximately $67 million (including $15 million in non-Federal cost sharing) over four years. The overall goal of the research is to develop carbon dioxide (CO 2 ) capture and separation technologies that can achieve at least 90 percent CO 2 removal at no more than a 35 percent increase in the cost of electricity. The projects, managed by FE's National Energy Technology Laboratory (NETL), include: (1) Linde, LLC, which will use a post-combustion capture technology incorporating BASF's novel amine-based process at a 1-megawatt electric (MWe) equivalent slipstream pilot plant at the National Carbon Capture Center (NCCC) (DOE contribution: $15 million); (2) Neumann Systems Group, Inc., which will design, construct, and test a patented NeuStreamTM absorber at the Colorado

367

Exploring approximations to the GW self-energy ionic gradients  

E-Print Network (OSTI)

The accuracy of the many-body perturbation theory GW formalism to calculate electron-phonon coupling matrix elements has been recently demonstrated in the case of a few important systems. However, the related computational costs are high and thus represent strong limitations to its widespread application. In the present study, we explore two less demanding alternatives for the calculation of electron-phonon coupling matrix elements on the many-body perturbation theory level. Namely, we test the accuracy of the static Coulomb-hole plus screened-exchange (COHSEX) approximation and further of the constant screening approach, where variations of the screened Coulomb potential W upon small changes of the atomic positions along the vibrational eigenmodes are neglected. We find this latter approximation to be the most reliable, whereas the static COHSEX ansatz leads to substantial errors. Our conclusions are validated in a few paradigmatic cases: diamond, graphene and the C60 fullerene. These findings open the way f...

Faber, C; Attaccalite, C; Cannuccia, E; Duchemin, I; Deutsch, T; Blase, X

2015-01-01T23:59:59.000Z

368

Studies in Interpolation and Approximation of Multivariate Bandlimited Functions  

E-Print Network (OSTI)

&M University in partial ful llment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Co-Chairs of Committee, Thomas Schlumprecht N. Sivakumar Committee Members, Joel Zinn William Johnson Fred Dahm Head of Department, Albert...{Chairs of Advisory Committee: Dr. Thomas Schlumprecht Dr. N. Sivakumar The focus of this dissertation is the interpolation and approximation of multi- variate bandlimited functions via sampled (function) values. The rst set of results investigates polynomial...

Bailey, Benjamin Aaron

2012-10-19T23:59:59.000Z

369

A randomised approximation algorithm for the hitting set problem  

Science Journals Connector (OSTI)

Abstract Let H = ( V , E ) be a hypergraph with vertex set V and edge set E , where n : = | V | and m : = | E | . Let l be the maximum size of an edge and ? be the maximum vertex degree. A hitting set (or vertex cover) in H is a subset of V in which all edges are incident. The hitting set problem is to find a hitting set of minimum cardinality. It is known that an approximation ratio of l can be achieved easily. On the other hand, for constant l, an approximation ratio better than l cannot be achieved in polynomial time under the unique games conjecture (Khot and Regev, 2008 [17]). Thus breaking the l-barrier for significant classes of hypergraphs is a complexity-theoretically and algorithmically interesting problem, which has been studied by several authors (Krivelevich, 1997 [18], Halperin, 2000 [12], Okun, 2005 [23]). We propose a randomised algorithm of hybrid type for the hitting set problem, which combines LP-based randomised rounding, graphs sparsening and greedy repairing and analyse it for different classes of hypergraphs. For hypergraphs with ? = O ( n 1 4 ) and l = O ( n ) we achieve an approximation ratio of l ( 1 ? c ? ) , for some constant c > 0 , with constant probability. For the case of hypergraphs where l and ? are constants, we prove a ratio of l ( 1 ? l ? 1 8 ? ) . The latter is done by analysing the expected size of the hitting set and using concentration inequalities. Moreover, for quasi-regularisable hypergraphs, we achieve an approximation ratio of l ( 1 ? n 8 m ) . We show how and when our results improve over the results of Krivelevich, Halperin and Okun.

Mourad El Ouali; Helena Fohlin; Anand Srivastav

2014-01-01T23:59:59.000Z

370

Topologies and approximation operators induced by binary relations  

E-Print Network (OSTI)

Rough set theory is an important mathematical tool for dealing with uncertain or vague information. This paper studies some new topologies induced by a binary relation on universe with respect to neighborhood opera- tors. Moreover, the relations among them are studied. In additionally, lower and upper approximations of rough sets using the binary relation with respect to neighborhood operators are studied and examples are given.

Nurettin Bagirmaz; A. Fatih Ozcan Hatice Tasbozan; Ilhan Icen

2014-05-09T23:59:59.000Z

371

Product-state Approximations to Quantum Ground States  

E-Print Network (OSTI)

The local Hamiltonian problem consists of estimating the ground-state energy (given by the minimum eigenvalue) of a local quantum Hamiltonian. First, we show the existence of a good product-state approximation for the ground-state energy of 2-local Hamiltonians with one or more of the following properties: (1) high degree, (2) small expansion, or (3) a ground state with sublinear entanglement with respect to some partition into small pieces. The approximation based on degree is a surprising difference between quantum Hamiltonians and classical CSPs (constraint satisfaction problems), since in the classical setting, higher degree is usually associated with harder CSPs. The approximation based on low entanglement, in turn, was previously known only in the regime where the entanglement was close to zero. Since the existence of a low-energy product state can be checked in NP, the result implies that any Hamiltonian used for a quantum PCP theorem should have: (1) constant degree, (2) constant expansion, (3) a "volume law" for entanglement with respect to any partition into small parts. Second, we show that in several cases, good product-state approximations not only exist, but can be found in polynomial time: (1) 2-local Hamiltonians on any planar graph, solving an open problem of Bansal, Bravyi, and Terhal, (2) dense k-local Hamiltonians for any constant k, solving an open problem of Gharibian and Kempe, and (3) 2-local Hamiltonians on graphs with low threshold rank, via a quantum generalization of a recent result of Barak, Raghavendra and Steurer. Our work introduces two new tools which may be of independent interest. First, we prove a new quantum version of the de Finetti theorem which does not require the usual assumption of symmetry. Second, we describe a way to analyze the application of the Lasserre/Parrilo SDP hierarchy to local quantum Hamiltonians.

Fernando G. S. L. Brando; Aram W. Harrow

2014-12-15T23:59:59.000Z

372

The Local Potential Approximation for the Brueckner G-matrix  

E-Print Network (OSTI)

The Brueckner G-matrix for a slab of nuclear matter is analyzed in the singlet $^1S$ and triplet $^3S+^3D$ channels. The complete Hilbert space is split into two domains, the model subspace $S_0$, in which the two-particle propagator is calculated explicitly, and the complementary one, $S'$, in which the local potential approximation is used. This kind of local approximation was previously found to be quite accurate for the $^1S$ pairing problem. A set of model spaces $S_0(E_0)$ with different values of the cut-off energy $E_0$ is considered, $E_0$ being the upper limit for the single-particle energies of the states belonging to $S_0$. The independence of the G-matrix of $E_0$ is assumed as a criterion of validity of the local potential approximation. Such independence is obtained within few percent for $E_0=10 \\div 20$ MeV for both the channels under consideration.

M. Baldo; U. Lombardo; E. E. Saperstein; M. V. Zverev

2001-04-16T23:59:59.000Z

373

Nonlocal independent pixel approximation: Direct and inverse problems  

SciTech Connect

The independent pixel approximation (IPA), which treats radiative properties of each pixel independently by using standard plane-parallel calculations preserves scale-invariance found in the analyses of the horizontal variability of liquid water in marine stratocumulus clouds. Several studies, however, report a violation of scale-invariance in LANDSAT cloud radiance fields that are much smoother than cloud structure on small scales. This shows a limitation of IPA on small scales: it is unable to simulate the smooth small-scale behavior that is due to the horizontal photon transport. This paper introduces a nonlocal independent pixel approximation (NIPA) that extends the IPA by incorporating empirically the smoothing effects of horizontal interpixel fluxes through a convolution product of the IPA and an approximate Green function for radiative transfer. The authors also address the inverse problem of cloud optical depth retrieval from satellite data, showing how NIPA can be used to overcome the limitations of current IPA-based methods at small scales.

Marshak, A. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Climate and Radiation Branch] [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Climate and Radiation Branch; [Univ. of Maryland Baltimore County, Baltimore, MD (United States). Joint Center for Earth Systems Technology; Davis, A. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Climate and Radiation Branch] [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Climate and Radiation Branch; [Science Systems and Applications, Inc., Lanham, MD (United States); Cahalan, R.F.; Wiscombe, W. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Climate and Radiation Branch] [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Climate and Radiation Branch

1998-01-01T23:59:59.000Z

374

Quartz resonator fluid density and viscosity monitor  

DOE Patents (OSTI)

A pair of thickness-shear mode resonators, one smooth and one with a textured surface, allows fluid density and viscosity to be independently resolved. A textured surface, either randomly rough or regularly patterned, leads to trapping of liquid at the device surface. The synchronous motion of this trapped liquid with the oscillating device surface allows the device to weigh the liquid; this leads to an additional response that depends on liquid density. This additional response enables a pair of devices, one smooth and one textured, to independently resolve liquid density and viscosity; the difference in responses determines the density while the smooth device determines the density-viscosity product, and thus, the pair determines both density and viscosity.

Martin, Stephen J. (Albuquerque, NM); Wiczer, James J. (Albuquerque, NM); Cernosek, Richard W. (Albuquerque, NM); Frye, Gregory C. (Cedar Crest, NM); Gebert, Charles T. (Albuquerque, NM); Casaus, Leonard (Bernalillo, NM); Mitchell, Mary A. (Tijeras, NM)

1998-01-01T23:59:59.000Z

375

Discussion on the energy content of the galactic dark matter Bose-Einstein condensate halo in the Thomas-Fermi approximation  

E-Print Network (OSTI)

We show that the galactic dark matter halo, considered composed of an axionlike particles Bose-Einstein condensate \\cite{pir12} trapped by a self-graviting potential \\cite{boh07}, may be stable in the Thomas-Fermi approximation since appropriate choices for the dark matter particle mass and scattering length are made. The demonstration is performed by means of the calculation of the potential, kinetic and self-interaction energy terms of a galactic halo described by a Boehmer-Harko density profile. We discuss the validity of the Thomas-Fermi approximation for the halo system, and show that the kinetic energy contribution is indeed negligible.

J. C. C. de Souza; M. O. C. Pires

2014-01-23T23:59:59.000Z

376

Density gradient free electron collisionally excited X-ray laser  

DOE Patents (OSTI)

An operational X-ray laser (30) is provided that amplifies 3p-3s transition X-ray radiation along an approximately linear path. The X-ray laser (30) is driven by a high power optical laser. The driving line focused optical laser beam (32) illuminates a free-standing thin foil (34) that may be associated with a substrate (36) for improved structural integrity. This illumination produces a generally cylindrically shaped plasma having an essentially uniform electron density and temperature, that exists over a long period of time, and provides the X-ray laser gain medium. The X-ray laser (30) may be driven by more than one optical laser beam (32, 44). The X-ray laser (30) has been successfully demonstrated to function in a series of experimental tests.

Campbell, Edward M. (Pleasanton, CA); Rosen, Mordecai D. (Berkeley, CA)

1989-01-01T23:59:59.000Z

377

Density gradient free electron collisionally excited x-ray laser  

DOE Patents (OSTI)

An operational x-ray laser is provided that amplifies 3p-3s transition x-ray radiation along an approximately linear path. The x-ray laser is driven by a high power optical laser. The driving line focused optical laser beam illuminates a free-standing thin foil that may be associated with a substrate for improved structural integrity. This illumination produces a generally cylindrically shaped plasma having an essentially uniform electron density and temperature, that exists over a long period of time, and provides the x-ray laser gain medium. The x-ray laser may be driven by more than one optical laser beam. The x-ray laser has been successfully demonstrated to function in a series of experimental tests.

Campbell, E.M.; Rosen, M.D.

1984-11-29T23:59:59.000Z

378

Considering Air Density in Wind Power Production  

E-Print Network (OSTI)

In the wind power production calculations the air density is usually considered as constant in time. Using the CIPM-2007 equation for the density of moist air as a function of air temperature, air pressure and relative humidity, we show that it is worth taking the variation of the air density into account, because higher accuracy can be obtained in the calculation of the power production for little effort.

Farkas, Zn

2011-01-01T23:59:59.000Z

379

Considering Air Density in Wind Power Production  

E-Print Network (OSTI)

In the wind power production calculations the air density is usually considered as constant in time. Using the CIPM-2007 equation for the density of moist air as a function of air temperature, air pressure and relative humidity, we show that it is worth taking the variation of the air density into account, because higher accuracy can be obtained in the calculation of the power production for little effort.

Zn Farkas

2011-03-11T23:59:59.000Z

380

Dark Matter Density in Disk Galaxies  

E-Print Network (OSTI)

I show that the predicted densities of the inner dark matter halos in LCDM models of structure formation appear to be higher than estimates from real galaxies and constraints from dynamical friction on bars. This inconsistency would not be a problem for the LCDM model if physical processes that are omitted in the collisionless collapse simulations were able to reduce the dark matter density in the inner halos. I review the mechanisms proposed to achieve the needed density reduction.

J. A. Sellwood

2008-07-12T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Exact and approximate differential renormalization-group generators  

Science Journals Connector (OSTI)

In dealing with critical phenomena of complex systems that simulate realistic materials, the full structure of the renormalization group is often unnecessarily cumbersome. For approximate calculations and for systems with special properties, specialized generators are simpler to apply. We derive several such exact and approximate differential generators and solve a number of interesting practical problems to illustrate this approach: (i) We derive a new approximate differential generator based on the Wilson incomplete-integration generator. Using this generator we calculate for an n-component spin system the eigenvalues (critical-point exponents) associated with a critical point of arbitrary order O and "propagator exponent" ?? to first order in the expansion parameter ?O(??)=d+O(??-d); this extends previous work for ??=2, O arbitrary; ???2, O=2 (long-rang forces); and ??=4, O=2 (the "Lifshitz point"). Our results agree with those obtainable using an approximate generator based on the Wegner-Houghton equation. The cases ??=2L (L a positive integer ?2) describe the onset of helical ordering for which | k?|?(-p)?k, where ?k=12(L-1)+o(?O2(2L)) and p parametrizes the hypersurface of critical points. For p>0, the ordered phase is uniform; for p<0 there is spiral order. The point p=0, at which such nonuniform ordering commences, we term a generalized Lifshitz point of Lifschitz character L. (ii) We consider the full Wilson and Wegner-Houghton generators in the paired spin-momenta limit and the n?? limit for even-order critical points. These limiting generators are identical for both full generators. This demonstrates that at least in these cases the Wilson and Wegner-Houghton generators agree exactly, without recourse to perturbation theory. These simple exact generators should provide "anchors" for calculations of exponents for higher-order critical points. (iii) We derive approximate generators which are suitable for compressible magnetic systems and more general systems with constraints for which the spin momenta are grouped in any arbitrary manner. We apply this to the case of a simple compressible magnet model and obtain the exact renormalization-group trajectories to order ? with ???2(2)=4-d.

J. F. Nicoll; T. S. Chang; H. E. Stanley

1976-03-01T23:59:59.000Z

382

Weighted-density functionals for cavity formation and dispersion energies in continuum solvation models  

E-Print Network (OSTI)

Continuum solvation models enable efficient first principles calculations of chemical reactions in solution, but require extensive parametrization and fitting for each solvent and class of solute systems. Here, we examine the assumptions of continuum solvation models in detail and replace empirical terms with physical models in order to construct a minimally-empirical solvation model. Specifically, we derive solvent radii from the nonlocal dielectric response of the solvent from ab initio calculations, construct a closed-form and parameter-free weighted-density approximation for the free energy of the cavity formation, and employ a pair-potential approximation for the dispersion energy. We show that the resulting model with a single solvent-independent parameter: the electron density threshold ($n_c$), and a single solvent-dependent parameter: the dispersion scale factor ($s_6$), reproduces solvation energies of organic molecules in water, chloroform and carbon tetrachloride with RMS errors of 1.1, 0.6 and 0....

Sundararaman, Ravishankar; Arias, T A

2014-01-01T23:59:59.000Z

383

Ionic density distributions near the charged colloids: Spherical electric double layers  

SciTech Connect

We have studied the structure of the spherical electric double layers on charged colloids by a density functional perturbation theory, which is based both on the modified fundamental-measure theory for the hard spheres and on the one-particle direct correlation functional (DCF) for the electronic residual contribution. The contribution of one-particle DCF has been approximated as the functional integration of the second-order correlation function of the ionic fluids in a bulk phase. The calculated result is in very good agreement with the computer simulations for the ionic density distributions and the zeta potentials over a wide range of macroion sizes and electrolyte concentrations, and compares with the results of Yu et al. [J. Chem. Phys. 120, 7223 (2004)] and modified Poisson-Boltzmann approximation [L. B. Bhuiyan and C. W. Outhwaite, Condens. Matter Phys. 8, 287 (2005)]. The present theory is able to provide interesting insights about the charge inversion phenomena occurring at the interface.

Kim, Eun-Young; Kim, Soon-Chul, E-mail: sckim@andong.ac.kr [Department of Physics, Andong National University, Andong 760-749 (Korea, Republic of)] [Department of Physics, Andong National University, Andong 760-749 (Korea, Republic of)

2013-11-21T23:59:59.000Z

384

Double-hybrid density-functional theory applied to molecular crystals  

E-Print Network (OSTI)

We test the performance of a number of two- and one-parameter double-hybrid approximations, combining semilocal exchange-correlation density functionals with periodic local second-order M{\\o}ller-Plesset (LMP2) perturbation theory, for calculating lattice energies of a set of molecular crystals: urea, formamide, ammonia, and carbon dioxide. All double-hybrid methods perform better on average than the corresponding Kohn-Sham calculations with the same functionals, but generally not better than standard LMP2. The one-parameter double-hybrid approximations based on the PBEsol density functional gives lattice energies per molecule with an accuracy of about 6 kJ/mol, which is similar to the accuracy of LMP2. This conclusion is further verified on molecular dimers and on the hydrogen cyanide crystal.

Sharkas, Kamal; Maschio, Lorenzo; Civalleri, Bartolomeo

2014-01-01T23:59:59.000Z

385

Ground state properties and high pressure behavior of plutonium dioxide: Systematic density functional calculations  

E-Print Network (OSTI)

Plutonium dioxide is of high technological importance in nuclear fuel cycle and is particularly crucial in long-term storage of Pu-based radioactive waste. Using first-principles density-functional theory, in this paper we systematically study the structural, electronic, mechanical, thermodynamic properties, and pressure induced structural transition of PuO$_{2}$. To properly describe the strong correlation in the Pu $5f$ electrons, the local density approximation$+U$ and the generalized gradient approximation$+U$ theoretical formalisms have been employed. We optimize the $U$ parameter in calculating the total energy, lattice parameters, and bulk modulus at the nonmagnetic, ferromagnetic, and antiferromagnetic configurations for both ground state fluorite structure and high pressure cotunnite structure. The best agreement with experiments is obtained by tuning the effective Hubbard parameter $U$ at around 4 eV within the LDA$+U$ approach. After carefully testing the validity of the ground state, we further in...

Zhang, Ping; Zhao, Xian-Geng

2010-01-01T23:59:59.000Z

386

Density-functional study of water adsorption on the PuO2(110) surface  

Science Journals Connector (OSTI)

Water adsorption on a PuO2(110) surface is studied using a periodic model with both the local-density approximation (LDA) and the generalized gradient approximation (GGA) of density-functional theory. The 60 core electrons of the Pu atom are represented by a relativistic effective core potential, and scalar relativistic effects have been incorporated into the valence orbitals. Both molecular and dissociative configurations of the adsorbate H2O are considered at one molecular layer coverage. For molecular water adsorption, LDA calculations indicate binding only at the top site, whereas the GGA indicates no binding for any site. Dissociative adsorption is found to be energetically more favorable than molecular adsorption, in agreement with experimental observations. The effects on the geometric and electronic structures influenced by water adsorption are investigated.

Xueyuan Wu and Asok K. Ray

2002-01-30T23:59:59.000Z

387

Toward understanding the exchange-correlation energy and total-energy density functionals  

Science Journals Connector (OSTI)

If an accurate ground-state electron density ?0 for a system is known, it is shown from calculations on atoms that a strikingly good estimate for the total electronic energy of atoms is provided by the formula E[?0]=tsumi?i-(1-1/N)J[?0], where N is the number of electrons, J[?0] is the classical Coulomb repulsion energy for ?0, and the ?i are the Kohn-Sham orbital energies determined by the Zhao-Morrison-Parr procedure [Phys. Rev. A 50, 2138 (1994)] for implementation of the Levy-constrained search determination of the Kohn-Sham kinetic energy. The surprising accuracy of this formula is attributed to the fact that the exchange-correlation functional is equal to -J/N plus a functional that behaves as if it were approximately homogeneous, of degree 1 in the electron density. A corresponding exact formula is given, and various approximate models are constructed.

Robert G. Parr and Swapan K. Ghosh

1995-05-01T23:59:59.000Z

388

Global hybrids from the semiclassical atom theory satisfying the local density linear response  

E-Print Network (OSTI)

We propose global hybrid approximations of the exchange-correlation (XC) energy functional which reproduce well the modified fourth-order gradient expansion of the exchange energy in the semiclassical limit of many-electron neutral atoms and recover the full local density approximation (LDA) linear response. These XC functionals represent the hybrid versions of the APBE functional [Phys. Rev. Lett. 106, 186406, (2011)] yet employing an additional correlation functional which uses the localization concept of the correlation energy density to improve the compatibility with the Hartree-Fock exchange as well as the coupling-constant-resolved XC potential energy. Broad energetical and structural testings, including thermochemistry and geometry, transition metal complexes, non-covalent interactions, gold clusters and small gold-molecule interfaces, as well as an analysis of the hybrid parameters, show that our construction is quite robust. In particular, our testing shows that the resulting hybrid, including 20\\% o...

Fabiano, E; Cortona, P; Della Sala, F

2015-01-01T23:59:59.000Z

389

Density Measurements of Argonne Premium Coal Samples  

Science Journals Connector (OSTI)

Density Measurements of Argonne Premium Coal Samples ... Constitution of Illinois No. 6 Argonne Premium Coal: A Review ... Constitution of Illinois No. 6 Argonne Premium Coal: A Review ...

He Huang; Keyu Wang; David M. Bodily; V. J. Hucka

1995-01-01T23:59:59.000Z

390

Some challenges for Nuclear Density Functional Theory  

E-Print Network (OSTI)

We discuss some of the challenges that the DFT community faces in its quest for the truly universal energy density functional applicable over the entire nuclear chart.

T. Duguet; K. Bennaceur; T. Lesinski; J. Meyer

2006-06-20T23:59:59.000Z

391

3-D capacitance density imaging system  

DOE Patents (OSTI)

A three-dimensional capacitance density imaging of a gasified bed or the like in a containment vessel is achieved using a plurality of electrodes provided circumferentially about the bed in levels and along the bed in channels. The electrodes are individually and selectively excited electrically at each level to produce a plurality of current flux field patterns generated in the bed at each level. The current flux field patterns are suitably sensed and a density pattern of the bed at each level determined. By combining the determined density patterns at each level, a three-dimensional density image of the bed is achieved. 7 figs.

Fasching, G.E.

1988-03-18T23:59:59.000Z

392

High Energy Density Ultracapacitors | Department of Energy  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Program, and Vehicle Technologies Program Annual Merit Review and Peer Evaluation es038smith2011p.pdf More Documents & Publications High Energy Density Ultracapacitors High...

393

E-Print Network 3.0 - approximate solution method Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

numerical solution of partial differential... , Meshfree Approximation Methods with Matlab, Lecture Notes, IIT, 2005. Other required material... data approximation with radial...

394

S-truncated Functions and Rough Sets in Approximation and Classification of Bottleneck Polygons.  

E-Print Network (OSTI)

??Some collections of two-dimensional points form very irregular shapes, which cannot be approximated by standard curves without making large errors. We approximate the sets of (more)

Rakus-Andersson, Elisabeth

2005-01-01T23:59:59.000Z

395

Linear-response calculation in the time-dependent density functional theory  

SciTech Connect

Linear response calculations based on the time-dependent density-functional theory are presented. Especially, we report results of the finite amplitude method which we have recently proposed as an alternative and feasible approach to the (quasiparticle-)random-phase approximation. Calculated properties of the giant resonances and low-energy E1 modes are discussed. We found a universal linear correlation between the low-energy E1 strength and the neutron skin thickness.

Nakatsukasa, Takashi; Inakura, Tsunenori; Avogadro, Paolo; Ebata, Shuichiro; Sato, Koichi; Yabana, Kazuhiro [RIKEN Nishina Center, Wako-shi 351-0198, Japan and Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); RIKEN Nishina Center, Wako-shi 351-0198 (Japan); Departimento di Fisica, Universita degli Studi di Milano, via Celoria 16, 20133 Milan (Italy) and RIKEN Nishina Center, Wako-shi 351-0198 (Japan); Center for Nuclear Study, University of Tokyo, Bunkyo-ku, 113-0033, Japan and RIKEN Nishina Center, Wako-shi 351-0198 (Japan); RIKEN Nishina Center, Wako-shi 351-0198 (Japan); Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan) and RIKEN Nishina Center, Wako-shi 351-0198 (Japan)

2012-11-12T23:59:59.000Z

396

Particle-vibration coupling within covariant density functional theory  

E-Print Network (OSTI)

Covariant density functional theory, which has so far been applied only within the framework of static and time dependent mean field theory is extended to include Particle-Vibration Coupling (PVC) in a consistent way. Starting from a conventional energy functional we calculate the low-lying collective vibrations in Relativistic Random Phase Approximation (RRPA) and construct an energy dependent self-energy for the Dyson equation. The resulting Bethe-Salpeter equation in the particle-hole ($ph$) channel is solved in the Time Blocking Approximation (TBA). No additional parameters are used and double counting is avoided by a proper subtraction method. The same energy functional, i.e. the same set of coupling constants, generates the Dirac-Hartree single-particle spectrum, the static part of the residual $ph$-interaction and the particle-phonon coupling vertices. Therefore a fully consistent description of nuclear excited states is developed. This method is applied for an investigation of damping phenomena in the spherical nuclei with closed shells $^{208}$Pb and $^{132}$Sn. Since the phonon coupling terms enrich the RRPA spectrum with a multitude of $ph\\otimes$phonon components a noticeable fragmentation of the giant resonances is found, which is in full agreement with experimental data and with results of the semi-phenomenological non-relativistic approach.

E. Litvinova; P. Ring; V. Tselyaev

2007-05-08T23:59:59.000Z

397

TECHNICAL NOTES Efficacy of the Implied Approximation in the Identification  

E-Print Network (OSTI)

+ kA2 * k b U + k2 A3 * k + k2 A4 * k h b 2 where air density; U mean wind velocity; B=2b bridge deck configuration of the bridge deck; h and displacement of the bridge deck section in the vertical and torsional Xinzhong Chen1 and Ahsan Kareem2 Abstract: Structural motion induced aerodynamic forces on bridges

Chen, Xinzhong

398

Chirality dependence of the density-of-states singularities in carbon nanotubes S. Reich and C. Thomsen  

E-Print Network (OSTI)

approach and yields the energy splitting for an arbitary chiral angle in metallic nanotubes. SemiconductingChirality dependence of the density-of-states singularities in carbon nanotubes S. Reich and C-of-states singularities in single-walled car- bon nanotubes. Our approximation goes beyond the lowest-order, isotropic

Nabben, Reinhard

399

Condition on the KohnSham kinetic energy and modern parametrization of the ThomasFermi density  

E-Print Network (OSTI)

; published online 20 January 2009 We study the asymptotic expansion of the neutral-atom energy as the atomic-correlation energy, EXC n , must be approximated. But a direct, orbital-free DFT could be constructed if onlyCondition on the Kohn­Sham kinetic energy and modern parametrization of the Thomas­Fermi density

Burke, Kieron

400

Microinstabilities in weak density gradient tokamak systems  

SciTech Connect

A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient.

Tang, W.M.; Rewoldt, G.; Chen, L.

1986-04-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Density Estimation Trees in High Energy Physics  

E-Print Network (OSTI)

Density Estimation Trees can play an important role in exploratory data analysis for multidimensional, multi-modal data models of large samples. I briefly discuss the algorithm, a self-optimization technique based on kernel density estimation, and some applications in High Energy Physics.

Anderlini, Lucio

2015-01-01T23:59:59.000Z

402

Density of simulated americium/curium melter feed solution  

SciTech Connect

Vitrification will be used to stabilize an americium/curium (Am/Cm) solution presently stored in F-Canyon for eventual transport to Oak Ridge National Laboratory and use in heavy isotope production programs. Prior to vitrification, a series of in-tank oxalate precipitation and nitric/oxalic acid washes will be used to separate these elements and lanthanide fission products from the bulk of the uranium and metal impurities present in the solution. Following nitric acid dissolution and oxalate destruction, the solution will be denitrated and evaporated to a dissolved solids concentration of approximately 100 g/l (on an oxide basis). During the Am/Cm vitrification, an airlift will be used to supply the concentrated feed solution to a constant head tank which drains through a filter and an in-line orifice to the melter. Since the delivery system is sensitive to the physical properties of the feed, a simulated solution was prepared and used to measure the density as a function of temperature between 20 to 70{degrees} C. The measured density decreased linearly at a rate of 0.0007 g/cm3/{degree} C from an average value of 1.2326 g/cm{sup 3} at 20{degrees} C to an average value of 1.1973g/cm{sup 3} at 70{degrees} C.

Rudisill, T.S.

1997-09-22T23:59:59.000Z

403

Moduli-space approximation for BPS brane worlds  

Science Journals Connector (OSTI)

We develop the moduli-space approximation for the low energy regime of Bogomolnyi-Prasad-Sommerfield (BPS) branes with a bulk scalar field to obtain an effective four-dimensional action describing the system. An arbitrary BPS potential is used and account is taken of the presence of matter in the branes and small supersymmetry breaking terms. The resulting effective theory is a bi-scalar tensor theory of gravity. In this theory, the scalar degrees of freedom can be stabilized naturally without the introduction of additional mechanisms other than the appropriate BPS potential. We place observational constraints on the shape of the potential and the global configuration of branes.

Gonzalo A. Palma and Anne-Christine Davis

2004-11-11T23:59:59.000Z

404

Breakdown of the Dipole Approximation in Strong-Field Ionization  

E-Print Network (OSTI)

We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10$^{13}$ W/cm$^2$. Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semi-classical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as origin of our observations.

Ludwig, A; Mayer, B W; Phillips, C R; Gallmann, L; Keller, U

2014-01-01T23:59:59.000Z

405

Breakdown of the Dipole Approximation in Strong-Field Ionization  

E-Print Network (OSTI)

We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10$^{13}$ W/cm$^2$. Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semi-classical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as origin of our observations.

A. Ludwig; J. Maurer; B. W. Mayer; C. R. Phillips; L. Gallmann; U. Keller

2014-08-11T23:59:59.000Z

406

Density functional theory for carbon dioxide crystal  

SciTech Connect

We present a density functional approach to describe the solid?liquid phase transition, interfacial and crystal structure, and properties of polyatomic CO{sub 2}. Unlike previous phase field crystal model or density functional theory, which are derived from the second order direct correlation function, the present density functional approach is based on the fundamental measure theory for hard-sphere repulsion in solid. More importantly, the contributions of enthalpic interactions due to the dispersive attractions and of entropic interactions arising from the molecular architecture are integrated in the density functional model. Using the theoretical model, the predicted liquid and solid densities of CO{sub 2} at equilibrium triple point are in good agreement with the experimental values. Based on the structure of crystal-liquid interfaces in different planes, the corresponding interfacial tensions are predicted. Their respective accuracies need to be tested.

Chang, Yiwen; Mi, Jianguo, E-mail: mijg@mail.buct.edu.cn; Zhong, Chongli [State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China)

2014-05-28T23:59:59.000Z

407

Density of Spray-Formed Materials  

SciTech Connect

Spray Forming is an advanced materials processing technology that transforms molten metal into a near-net-shape solid by depositing atomized droplets onto a substrate. Depending on the application, the spray-formed material may be used in the as-deposited condition or it may undergo post-deposition processing. Regardless, the density of the as-deposited material is an important issue. Porosity is detrimental because it can significantly reduce strength, toughness, hardness and other properties. While it is not feasible to achieve fully-dense material in the as-deposited state, density greater than 99% of theoretical density is possible if the atomization and impact conditions are optimized. Thermal conditions at the deposit surface and droplet impact angle are key processing parameters that influence the density of the material. This paper examines the factors that contribute to porosity formation during spray forming and illustrates that very high as-deposited density is achieved by optimizing processing parameters.

Kevin M. McHugh; Volker Uhlenwinkel; Nils Ellendr

2008-06-01T23:59:59.000Z

408

Neutral depletion and the helicon density limit  

SciTech Connect

It is straightforward to create fully ionized plasmas with modest rf power in a helicon. It is difficult, however, to create plasmas with density >10{sup 20} m{sup ?3}, because neutral depletion leads to a lack of fuel. In order to address this density limit, we present fast (1 MHz), time-resolved measurements of the neutral density at and downstream from the rf antenna in krypton helicon plasmas. At the start of the discharge, the neutral density underneath the antenna is reduced to 1% of its initial value in 15 ?s. The ionization rate inferred from these data implies that the electron temperature near the antenna is much higher than the electron temperature measured downstream. Neutral density measurements made downstream from the antenna show much slower depletion, requiring 14 ms to decrease by a factor of 1/e. Furthermore, the downstream depletion appears to be due to neutral pumping rather than ionization.

Magee, R. M.; Galante, M. E.; Carr, J. Jr.; Lusk, G.; McCarren, D. W.; Scime, E. E. [West Virginia University, Morgantown, West Virginia 26506 (United States)] [West Virginia University, Morgantown, West Virginia 26506 (United States)

2013-12-15T23:59:59.000Z

409

Non-BornOppenheimer nuclear and electronic densities for a three-particle HookeCoulomb model  

Science Journals Connector (OSTI)

Abstract Non-BornOppenheimer, nBO, one-particle nuclear and electron densities for a HookeCoulomb model of a three-body system are presented. These densities are obtained using exact closed-form analytic solutions to this problem as well as variational solutions. Moreover, the densities are calculated using different reference points, such as the global center of mass [cm], the geometric centers between both identical [gc12] and non-identical particles [cm13], and the location of the non-identical particle [p3]. It is shown that the topology of these nBO densities depends upon the choice of the reference points. This result is in turn used to argue that in a nBO regime the topological properties of the one-particle density cannot be univocally correlated with molecular structure, in the way it is done for the BornOppenheimer approximation.

C.G. Rodrguez; A.S. Urbina; F.J. Torres; D. Cazar; E.V. Ludea

2013-01-01T23:59:59.000Z

410

Approximation algorithms for the partition vertex cover problem  

Science Journals Connector (OSTI)

Abstract We consider a natural generalization of the Partial Vertex Cover problem. Here an instance consists of a graph G = ( V , E ) , a cost function c : V ? Z + , a partition P 1 , , P r of the edge set E, and a parameter k i for each partition P i . The objective is to find a minimum cost set of vertices which cover at least k i edges from the partition P i . We call this the Partition-VC problem. In this paper, we give matching upper and lower bound on the approximability of this problem. Our algorithm is based on a novel LP relaxation for this problem. This LP relaxation is obtained by adding knapsack cover inequalities to a natural LP relaxation of the problem. We show that this LP has integrality gap of O ( log ? r ) , where r is the number of sets in the partition of the edge set. We also extend our result to more general settings. For example we consider a problem where additionally edges have profits, and we would like to pick a minimum cost set of vertices which cover edges of total profit at least ? i for each partition P i . We call this the Knapsack Partition Vertex Cover problem. We give an O ( log ? r ) approximation algorithm for this problem as well.

Suman K. Bera; Shalmoli Gupta; Amit Kumar; Sambuddha Roy

2014-01-01T23:59:59.000Z

411

Lower crustal density estimation using the density-slowness relationship: a preliminary study  

E-Print Network (OSTI)

-facies metamorphic rocks. Velocity-density data was compiled from the literature for pressures greater than 600 MPa and linear fits of density on slowness were made. No correction was made for the effect of temperature. Densities were then estimated for a number...

Jones, Gary Wayne

2012-06-07T23:59:59.000Z

412

Testing the kinetic energy functional: Kinetic energy density as a density functional  

E-Print Network (OSTI)

is to the exchange-correlation energy as a functional of the density. A large part of the total energy, the kinetic contexts. For finite systems these forms integrate to the same global ki- netic energy, but they differTesting the kinetic energy functional: Kinetic energy density as a density functional Eunji Sim

Burke, Kieron

413

Expancel Foams: Fabrication and Characterization of a New Reduced Density Cellular Material for Structural Applications  

SciTech Connect

This study was initiated to produce a low-density centering medium for use in experiments investigating the response of materials to shock-loading. While the main drivers for material selection were homogeneity, dimensional stability, performance and cost, other secondary requirements included fine cell size, the ability to manufacture 5--10 cm-sized parts and an extremely compressed development time. The authors chose a non-traditional methodology using a hollow, expandable, polymeric microballoon material system called Expancel{reg_sign}. These microballoons are made from a copolymer of polyacrylonitrile (PAN) and polymethacrylonitrile (PMAN) and use iso-pentane as the blowing agent. The average diameter (by volume) of the unexpanded powder is approximately 13 {micro}m, while the average of the expanded powder is 35--55 {micro}m, with a few large microballoons approaching 150--200 p.m. A processing method was developed that established a pre-mixed combination of unexpanded and expanded Expancel at a ratio such that the tap (or vibration) density of the mixed powders was the same as that desired of the final part. Upon heating above the tack temperature of the polymer, this zero-rise approach allowed only expansion of the unexpanded powder to fill the interstices between the pre-expanded balloons. The mechanical action of the expanding powder combined with the elevated processing temperature yielded flee-standing and mechanically robust parts. Although mechanical properties of these foams were not a key performance requirement, the data allowed for the determination of the best temperature to heat the samples. Processing the foam at higher temperatures enhanced both modulus and strength. The maximum allowable temperature was limited by dimensional stability and shrinkback considerations. Tomographic analysis of foam billets revealed very flat density profiles. Parts of any density between the low density expanded powder (approximately 0.013 g/cm{sup 3}) and the higher density unexpanded powder (approximately 0.5 g/cm{sup 3}) can be produced using this technique. The extremely wide range of accessible densities, ease of processing, relatively inexpensive materials, uniformity of the density, scaleable nature of the process should make this technology highly competitive for a variety of Defense Programs and commercial applications.

L. Whinnery; S. Goods; B. Even

2000-08-01T23:59:59.000Z

414

Effect of low density H-mode operation on edge and divertor plasma parameters  

SciTech Connect

We present a study of the impact of H-mode operation at low density on divertor plasma parameters on the DIII-D tokamak. The line-average density in H-mode was scanned by variation of the particle exhaust rate, using the recently installed divertor cryo-condensation pump. The maximum decrease (50%) in line-average electron density was accompanied by a factor of 2 increase in the edge electron temperature, and 10% and 20% reductions in the measured core and divertor radiated power, respectively. The measured total power to the inboard divertor target increased by a factor of 3, with the major contribution coming from a factor of 5 increase in the peak heat flux very close to the inner strike point. The measured increase in power at the inboard divertor target was approximately equal to the measured decrease in core and divertor radiation.

Maingi, R. [Oak Ridge Associated Universities, Inc., TN (United States); Mioduszewski, P.K. [Oak Ridge National Lab., TN (United States); Cuthbertson, J.W. [Sandia National Labs., Albuquerque, NM (United States)] [and others

1994-07-01T23:59:59.000Z

415

Full charge-density calculation of the surface energy of metals  

Science Journals Connector (OSTI)

We have calculated the surface energy and the work function of the 4d metals by means of an energy functional based on a self-consistent, spherically symmetric atomic-sphere potential. In this approach the kinetic energy is calculated completely within the atomic-sphere approximation (ASA) by means of a spherically symmetrized charge density, while the Coulomb and exchange-correlation contributions are calculated by means of the complete, nonspherically symmetric charge density within nonoverlapping, space-filling Wigner-Seitz cells. The functional is used to assess the convergence and the accuracy of the linear-muffin-tin-orbitals (LMTO) method and the ASA in surface calculations. We find that the full charge-density functional improves the agreement with recent full-potential LMTO calculations to a level where the average deviation in surface energy over the 4d series is down to 10%.

L. Vitos; J. Kollr; H. L. Skriver

1994-06-15T23:59:59.000Z

416

Density Prediction of Uranium-6 Niobium Ingots  

SciTech Connect

The densities of uranium-6 niobium (U-Nb) alloys have been compiled from a variety of literature sources such as Y-12 and Rocky Flats datasheets. We also took advantage of the 42 well-pedigreed, homogeneous baseline U-Nb alloys produced under the Enhanced Surveillance Program for density measurements. Even though U-Nb alloys undergo two-phase transitions as the Nb content varies from 0 wt. % to 8 wt %, the theoretical and measured densities vary linearly with Nb content. Therefore, the effect of Nb content on the density was modeled with a linear regression. From this linear regression, a homogeneous ingot of U-6 wt.% Nb would have a density of 17.382 {+-} 0.040 g/cc (95% CI). However, ingots produced at Y-12 are not homogeneous with respect to the Nb content. Therefore, using the 95% confidence intervals, the density of a Y-12 produced ingot would vary from 17.310 {+-} 0.043 g/cc at the center to 17.432 {+-} 0.039 g/cc at the edge. Ingots with larger Nb inhomogeneities will also have larger variances in the density.

D.F.Teter; P.K. Tubesing; D.J.Thoma; E.J.Peterson

2003-04-15T23:59:59.000Z

417

Tokamak Equilibria with Reversed Current Density  

Science Journals Connector (OSTI)

Observations of nearly zero toroidal current in the central region of tokamaks (the current hole) raises the question of the existence of toroidal equilibria with very low or reversed current in the core. The solutions of the Grad-Shafranov equilibrium equation with hollow toroidal current density profile including negative current density in the plasma center are investigated. Solutions of the corresponding eigenvalue problem provide simple examples of such equilibrium configurations. More realistic equilibria with toroidal current density reversal are computed using a new equilibrium problem formulation and computational algorithm which do not assume nested magnetic surfaces.

A. A. Martynov; S. Yu. Medvedev; L. Villard

2003-08-21T23:59:59.000Z

418

Instabilities in the Nuclear Energy Density Functional  

E-Print Network (OSTI)

In the field of Energy Density Functionals (EDF) used in nuclear structure and dynamics, one of the unsolved issues is the stability of the functional. Numerical issues aside, some EDFs are unstable with respect to particular perturbations of the nuclear ground-state density. The aim of this contribution is to raise questions about the origin and nature of these instabilities, the techniques used to diagnose and prevent them, and the domain of density functions in which one should expect a nuclear EDF to be stable.

M. Kortelainen; T. Lesinski

2010-02-05T23:59:59.000Z

419

Non-power law behavior of the radial profile of phase-space density of halos  

SciTech Connect

We study the pseudo phase-space density, ?(r)/?{sup 3}(r), of ?CDM dark matter halos with and without baryons (baryons+DM, and pure DM), by using the model introduced in Del Popolo (2009), which takes into account the effect of dynamical friction, ordered and random angular momentum, baryons adiabatic contraction and dark matter baryons interplay. We examine the radial dependence of ?(r)/?{sup 3}(r) over 9 orders of magnitude in radius for structures on galactic and cluster of galaxies scales. We find that ?(r)/?{sup 3}(r) is approximately a power-law only in the range of halo radius resolved by current simulations (down to 0.1% of the virial radius) while it has a non-power law behavior below the quoted scale, with inner profiles changing with mass. The non-power-law behavior is more evident for halos constituted both of dark matter and baryons while halos constituted just of dark matter and with angular momentum chosen to reproduce a Navarro-Frenk-White (NFW) density profile, are characterized by an approximately power-law behavior. The results of the present paper lead to conclude that density profiles of the NFW type are compatible with a power-law behavior of ?(r)/?{sup 3}(r), while those flattening to the halo center, like those found in Del Popolo (2009) or the Einasto profile, or the Burkert profile, cannot produce radial profile of the pseudo-phase-space density that are power-laws at all radii. The results argue against universality of the pseudo phase-space density and as a consequence argue against universality of density profiles constituted by dark matter and baryons as also discussed in Del Popolo (2009)

Popolo, A. Del, E-mail: adelpopolo@oact.inaf.it [Dipartimento di Fisica e Astronomia, University Of Catania, Viale Andrea Doria 6, 95125 Catania (Italy)

2011-07-01T23:59:59.000Z

420

Shear Viscosity in the Post-quasistatic Approximation  

E-Print Network (OSTI)

We apply the post-quasi--static approximation, an iterative method for the evolution of self-gravitating spheres of matter, to study the evolution of anisotropic non-adiabatic radiating and dissipative distributions in General Relativity. Dissipation is described by viscosity and free-streaming radiation, assuming an equation of state to model anisotropy induced by the shear viscosity. We match the interior solution, in non-comoving coordinates, with the Vaidya exterior solution. Two simple models are presented, based on the Schwarzschild and Tolman VI solutions, in the non--adiabatic and adiabatic limit. In both cases the eventual collapse or expansion of the distribution is mainly controlled by the anisotropy induced by the viscosity.

C. Peralta; L. Rosales; B. Rodr guez-Mueller; W. Barreto

2010-03-09T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

On Corrections to the Born-Oppenheimer Approximation  

E-Print Network (OSTI)

This report presents a new approach for treating the coupling of electrons and nuclei in quantum mechanical calculations for molecules and condensed matter. It includes the standard "Born-Oppenheimer approximation" as a special case but treats both adiabatic and non-adiabatic corrections using perturbation theory. The adiabatic corrections include all terms that do not explicitly involve the nuclear wavefunctions, so that the nuclei move on a single electronic potential surface. The non-adiabatic corrections, which allow the nuclei to move on more than one potential surface, include coupling between the electronic and nuclear wavefunctions. The method is related to an approach first proposed by Born and Huang, but it differs in the methodology and in the definition of the electronic wavefunctions and potential surfaces. A simple example is worked out to illustrate the mechanics of the technique. The report also includes a review of previous work.

Gerald I. Kerley

2013-06-24T23:59:59.000Z

422

Finite Approximations to Quantum Physics: Quantum Points and their Bundles  

E-Print Network (OSTI)

There exists a physically well motivated method for approximating manifolds by certain topological spaces with a finite or a countable set of points. These spaces, which are partially ordered sets (posets) have the power to effectively reproduce important topological features of continuum physics like winding numbers and fractional statistics, and that too often with just a few points. In this work, we develop the essential tools for doing quantum physics on posets. The poset approach to covering space quantization, soliton physics, gauge theories and the Dirac equation are discussed with emphasis on physically important topological aspects. These ideas are illustrated by simple examples like the covering space quantization of a particle on a circle, and the sine-Gordon solitons.

A. P. Balachandran; G. Bimonte; E. Ercolessi; P. Teotonio-Sobrinho

1993-10-04T23:59:59.000Z

423

Quantifier elimination for approximate Beals-Kartashova factorization  

E-Print Network (OSTI)

The only known constructive factorization algorithm for linear partial differential operators (LPDOs) is Beals-Kartashova (BK) factorization \\cite{bk2005}. One of the most interesting features of BK-factorization: at the beginning all the first-order factors are constructed and afterwards the factorization condition(s) should be checked. This leads to the important application area - namely, numerical simulations which could be simplified substantially if instead of computation with one LPDE of order $n$ we will be able to proceed computations with $n$ LPDEs all of order 1. In numerical simulations it is not necessary to fulfill factorization conditions exactly but with some given accuracy, which we call approximate factorization. The idea of the present paper is to look into the feasibility of solving problems of this kind using quantifier elinination by cylindrical algebraic decomposition.

Elena Kartashova; Scott McCallum

2007-01-07T23:59:59.000Z

424

ANALYTIC APPROXIMATION OF CARBON CONDENSATION ISSUES IN TYPE II SUPERNOVAE  

SciTech Connect

I present analytic approximations for some issues related to condensation of graphite, TiC, and silicon carbide in oxygen-rich cores of supernovae of Type II. Increased understanding, which mathematical analysis can support, renders researchers more receptive to condensation in O-rich supernova gases. Taking SN 1987A as typical, my first analysis shows why the abundance of CO molecules reaches an early maximum in which free carbon remains more abundant than CO. This analysis clarifies why O-rich gas cannot oxidize C if {sup 56}Co radioactivity is as strong as in SN 1987A. My next analysis shows that the CO abundance could be regarded as being in chemical equilibrium if the CO molecule is given an effective binding energy rather than its laboratory dissociation energy. The effective binding energy makes the thermal dissociation rate of CO equal to its radioactive dissociation rate. This preserves possible relevance for the concept of chemical equilibrium. My next analysis shows that the observed abundances of CO and SiO molecules in SN 1987A rule out frequent suggestions that equilibrium condensation of SUNOCONs has occurred following atomic mixing of the He-burning shell with more central zones in such a way as to reproduce roughly the observed spectrum of isotopes in SUNOCONs while preserving C/O > 1. He atoms admixed along with the excess carbon would destroy CO and SiO molecules, leaving their observed abundances unexplained. The final analysis argues that a chemical quasiequilibrium among grains (but not gas) may exist approximately during condensation, so that its computational use is partially justified as a guide to which mineral phases would be stable against reactions with gas. I illustrate this point with quasiequilibrium calculations by Ebel and Grossman that have shown that graphite is stable even when O/C >1 if prominent molecules are justifiably excluded from the calculation of chemical equilibrium.

Clayton, Donald D., E-mail: claydonald@gmail.com [Department of Physics and Astronomy, Clemson University, Clemson, SC (United States)

2013-01-01T23:59:59.000Z

425

Quantum Algorithms for Approximating the Effective Resistances in Electrical Networks  

E-Print Network (OSTI)

The theory of electrical network has many applications in algorithm design and analysis. It is an important task to compute the basic quantities about electrical networks, such as electrical flows and effective resistances, as quickly as possible. Classically, to compute these quantities, one basically need to solve a Laplacian linear system, and the best known algorithms take $\\tilde{O}(m)$ time, where $m$ is the number of edges. In this paper, we present two quantum algorithms for approximating the effective resistance between any two vertices in an electrical network. Both of them have time complexity polynomial in $\\log{n}$, $d$, $c$, $1/\\phi$ and $1/\\epsilon$, where $n$ is the number of vertices, $d$ is the maximum degree of the vertices, $c$ is the ratio of the largest to the smallest edge resistance, $\\phi$ is the expansion of the network, and $\\epsilon$ is the relative error. In particular, when $d$ and $c$ are small and $\\phi$ is large, our algorithms run very fast. In contrast, it is unknown whether classical algorithms can solve this case very fast. Furthermore, we prove that the polynomial dependence on the inverse expansion (i.e. $1/\\phi$) is necessary. As a consequence, our algorithms cannot be significantly improved. Finally, as a by-product, our second algorithm also produces a quantum state approximately proportional to the electrical flow between any two vertices, which might be of independent interest. Our algorithms are based on using quantum tools to analyze the algebraic properties of graph-related matrices. While one of them relies on inverting the Laplacian matrix, the other relies on projecting onto the kernel of the weighted incidence matrix. It is hopeful that more quantum algorithms can be developed in similar way.

Guoming Wang

2013-11-08T23:59:59.000Z

426

wave power density | OpenEI  

Open Energy Info (EERE)

power density power density Dataset Summary Description This project estimates the naturally available and technically recoverable U.S. wave energy resources, using a 51-month Wavewatch III hindcast database developed especially for this study by National Oceanographic and Atmospheric Administration's (NOAA's) National Centers for Environmental Prediction. For total resource estimation, wave power density in terms of kilowatts per meter is aggregated across a unit diameter circle. Source Electric Power Research Institute (EPRI) Date Released December 05th, 2011 (2 years ago) Date Updated Unknown Keywords EPRI MHK NREL ocean Virginia Tech wave wave power density Data application/pdf icon Download Full Report (pdf, 8.8 MiB) Quality Metrics Level of Review Some Review Comment

427

Viscosity and Density of Reference Fluid.  

E-Print Network (OSTI)

??The viscosity and density of bis(8-methylnonyl) benzene-1,2- dicarboxylate {diisodecyl phthalate (DIDP)}, with a nominal viscosity at T = 298 K and p = 0.1 MPa (more)

Almotari, Masaed Moti M

2006-01-01T23:59:59.000Z

428

Separation of carbon nanotubes in density gradients  

DOE Patents (OSTI)

The separation of single-walled carbon nanotubes (SWNTs), by chirality and/or diameter, using centrifugation of compositions of SWNTs in and surface active components in density gradient media.

Hersam, Mark C. (Evanston, IL); Stupp, Samuel I. (Chicago, IL); Arnold, Michael S. (Northbrook, IL)

2012-02-07T23:59:59.000Z

429

Density controlled carbon nanotube array electrodes  

DOE Patents (OSTI)

CNT materials comprising aligned carbon nanotubes (CNTs) with pre-determined site densities, catalyst substrate materials for obtaining them and methods for forming aligned CNTs with controllable densities on such catalyst substrate materials are described. The fabrication of films comprising site-density controlled vertically aligned CNT arrays of the invention with variable field emission characteristics, whereby the field emission properties of the films are controlled by independently varying the length of CNTs in the aligned array within the film or by independently varying inter-tubule spacing of the CNTs within the array (site density) are disclosed. The fabrication of microelectrode arrays (MEAs) formed utilizing the carbon nanotube material of the invention is also described.

Ren, Zhifeng F. (Newton, MA); Tu, Yi (Belmont, MA)

2008-12-16T23:59:59.000Z

430

Separation of carbon nanotubes in density gradients  

DOE Patents (OSTI)

The separation of single-walled carbon nanotubes (SWNTs), by chirality and/or diameter, using centrifugation of compositions of SWNTs in and surface active components in density gradient media.

Hersam, Mark C. (Evanston, IL); Stupp, Samuel I. (Chicago, IL); Arnold, Michael S. (Northbrook, IL)

2010-02-16T23:59:59.000Z

431

LANDAU'S NECESSARY DENSITY CONDITIONS FOR LCA GROUPS  

E-Print Network (OSTI)

LANDAU'S NECESSARY DENSITY CONDITIONS FOR LCA GROUPS KARLHEINZ GR�OCHENIG, GITTA KUTYNIOK's conditions to the setting of locally compact abelian (LCA) groups, relying in an analogous way on the basics

Seip, Kristian

432

LANDAU'S NECESSARY DENSITY CONDITIONS FOR LCA GROUPS  

E-Print Network (OSTI)

LANDAU'S NECESSARY DENSITY CONDITIONS FOR LCA GROUPS KARLHEINZ GR¨OCHENIG, GITTA KUTYNIOK's conditions to the setting of locally compact abelian (LCA) groups, relying in an analogous way on the basics

Kutyniok, Gitta

433

Fact #661: February 7, 2011 Population Density  

Energy.gov (U.S. Department of Energy (DOE))

The density of the population in the U.S., measured as the number of people per square mile, affects the way goods and people are transported. The newly released 2010 Census data show that, on a...

434

Electron densities from the Brueckner Doubles method  

Science Journals Connector (OSTI)

The concept of the Brueckner orbital is examined, following a resurgence of ... distinction between Self Consistent Field, Natural and Brueckner orbitals are discussed. Total electron densities are ... are studie...

Caroline M. van Heusden; Rika Kobayashi; Roger D. Amos

1993-07-01T23:59:59.000Z

435

Coal fractionation by density for coking purposes  

Science Journals Connector (OSTI)

Scarce coal with good coking properties may be obtained by separating less valuable coal into different density fractions. The use of valuable fractions released in enrichment ensures optimal coking-batch composi...

S. G. Gagarin

2010-09-01T23:59:59.000Z

436

On coherence in parametric density estimation  

Science Journals Connector (OSTI)

......1990 research-article Miscellanea On coherence in parametric density estimation J...KullbackLeibler directed divergence has this coherence property whereas the corresponding symmetric...estimation is also discussed. Admissibility|Coherence|Kullback-Leibler divergence|Predictive......

J. AITCHISON

1990-12-01T23:59:59.000Z

437

Alpha track density using a semiconductor detector  

E-Print Network (OSTI)

of factors including variation in the initial dielectric thickness, and other undefined parameters. In addition, the resultant radon concentration reading is dependent upon the calibration factor used to interpret the track density reading. Obtaining...

Hamilton, Ian Scott

2012-06-07T23:59:59.000Z

438

High Energy Density Ultracapacitors | Department of Energy  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Merit Review and Peer Evaluation Meeting, June 7-11, 2010 -- Washington D.C. es038smith2010o.pdf More Documents & Publications High Energy Density Ultracapacitors High...

439

High Energy Density Ultracapacitors | Department of Energy  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Merit Review and Peer Evaluation Meeting, May 18-22, 2009 -- Washington D.C. esp22smith.pdf More Documents & Publications High Energy Density Ultracapacitors High Energy...

440

Buoyancy-generated variable-density turbulence  

SciTech Connect

Because of the importance of turbulence mixing in many applications, a number of turbulence mixing models have been proposed for variable- density flows. These engineering models (one- point statistical models) typically include the transport of the turbulent kinetic energy and the turbulent energy dissipation rate (i.e., k - {epsilon} models). The model presented by Besnard, Harlow, Rauenzahn and Zemach (1992) (herein referred to as BHRZ) is a one-point model intended to describe variable-density turbulent flows. Transport equations for the Reynolds stress tensor, R{sub ij}, and the turbulent energy dissipation rate, the density-velocity correlation, a{sub i}, and the density-specific volume correlation, b are derived. This model employs- techniques and concepts from incompressible, constant- density turbulence modeling and incorporates ideas from two-phase flow models. Clark and Spitz (1994) present a two-point model for variable-density turbulence. Their derivation is based on transport equations that, are based 0481 on two-point- generalizations of R{sub ij}, a{sub ij}, and b. These equations are Fourier transformed with respect to the separation distance between the two points. Transport equations are derived for R{sub ij}, a{sub i}, b. As in the one-point model, this model contains many ad-hoc assumptions and unknown model coefficients that must be determined by comparison with experimental and numerical data. However, the two-point formalism requires fewer equilibrium assumptions then does a single-point model. Our primary concern in this paper lies in the nonlinear processes of turbulence and the influence of large density variations (not within the Boussinesq limit) on these processes. To. isolate the effects of variable-density on the turbulence we restrict our flow to be incompressible, statistically homogeneous buoyancy-generated. turbulence. To our knowledge there have not been any simulations reported for this problem.

Sandoval, D.L.; Clark, T.T.; Riley, J.J.

1996-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
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441

Origin of Tokamak Density Limit Scalings  

Science Journals Connector (OSTI)

The onset criterion for radiation driven islands [P.?H. Rebut and M. Hugon, Plasma Physics and Controlled Nuclear Fusion Research 1984: Proc. 10th Int. Conf. London, 1984, (IAEA, Vienna, 1985), Vol.2] in combination with a simple cylindrical model of tokamak current channel behavior is consistent with the empirical scaling of the tokamak density limit [M. Greenwald, Nucl. Fusion 28, 2199 (1988)]. Many other unexplained phenomena at the density limit are consistent with this novel physics mechanism.

D. A. Gates and L. Delgado-Aparicio

2012-04-20T23:59:59.000Z

442

The Chemistry of Atherogenic High Density Lipoprotein  

E-Print Network (OSTI)

TRL Bouyant triglyceride-rich lipoprotein C18 Carbon tail of eighteen atoms CE Capillary electrophoresis CETP Cholesterol ester transfer protein CM Chylomicrons CsCdY dicesium cadmium ethylenediaminetetraacetic acid CAD Coronary artery disease CVD... Cardiovascular disease DGU Density gradient ultracentrifugation I-DGU Immunospecific-density gradient ultracentrifugation DMSO Dimethyl sulfoxide DS Dextran sulfate dTRL Dense triglyceride rich lipoprotein EDTA Ethyelenediaminetetraacetic acid HDL High...

Moore, D'Vesharronne J.

2012-07-16T23:59:59.000Z

443

Bone Mineral Density in Women with Depression  

Science Journals Connector (OSTI)

...illness and the normal women were individually matched for age, body-mass index, and menstrual status; women with many of the risk factors associated with decreased bone mineral density were excluded; dual-energy x-ray absorptiometry was used to measure bone density at the spine, hip, and radius; and bone... Major depression is a complex disorder reflecting genetic, developmental, and environmental factors. Although its pathophysiology is not clearly understood, depression is associated with hypothalamic dysfunction specifically, hypercortisolism, the ...

Michelson D.; Stratakis C.; Hill L.

1996-10-17T23:59:59.000Z

444

Kinetic and electron-electron energies for convex sums of ground state densities with degeneracies and fractional electron number  

SciTech Connect

Properties of exact density functionals provide useful constraints for the development of new approximate functionals. This paper focuses on convex sums of ground-level densities. It is observed that the electronic kinetic energy of a convex sum of degenerate ground-level densities is equal to the convex sum of the kinetic energies of the individual degenerate densities. (The same type of relationship holds also for the electron-electron repulsion energy.) This extends a known property of the Levy-Valone Ensemble Constrained-Search and the Lieb Legendre-Transform refomulations of the Hohenberg-Kohn functional to the individual components of the functional. Moreover, we observe that the kinetic and electron-repulsion results also apply to densities with fractional electron number (even if there are no degeneracies), and we close with an analogous point-wise property involving the external potential. Examples where different degenerate states have different kinetic energy and electron-nuclear attraction energy are given; consequently, individual components of the ground state electronic energy can change abruptly when the molecular geometry changes. These discontinuities are predicted to be ubiquitous at conical intersections, complicating the development of universally applicable density-functional approximations.

Levy, Mel, E-mail: ayers@mcmaster.ca, E-mail: mlevy@tulane.edu [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States) [Department of Chemistry, Duke University, Durham, North Carolina 27708 (United States); Department of Physics, North Carolina A and T State University, Greensboro, North Carolina 27411 (United States); Department of Chemistry, Tulane University, New Orleans, Louisiana 70118 (United States); Anderson, James S. M.; Zadeh, Farnaz Heidar; Ayers, Paul W., E-mail: ayers@mcmaster.ca, E-mail: mlevy@tulane.edu [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario (Canada)

2014-05-14T23:59:59.000Z

445

Ionic Asymmetry and Solvent Excluded Volume Effects on Spherical Electric Double Layers: A Density Functional Approach  

SciTech Connect

In this article we present a classical density functional theory for electrical double layers of spherical macroions that extends the capabilities of conventional approaches by accounting for electrostatic ion correlations, size asymmetry and excluded volume effects. The approach is based on a recent approximation introduced by Hansen-Goos and Roth for the hard sphere excess free energy of inhomogeneous fluids (J. Chem. Phys. 124, 154506). It accounts for the proper and efficient description of the effects of ionic asymmetry and solvent excluded volume, especially at high ion concentrations and size asymmetry ratios including those observed in experimental studies. Additionally, we utilize a leading functional Taylor expansion approximation of the ion density profiles. In addition, we use the Mean Spherical Approximation for multi-component charged hard sphere fluids to account for the electrostatic ion correlation effects. These approximations are implemented in our theoretical formulation into a suitable decomposition of the excess free energy which plays a key role in capturing the complex interplay between charge correlations and excluded volume effects. We perform Monte Carlo simulations in various scenarios to validate the proposed approach, obtaining a good compromise between accuracy and computational cost. We use the proposed computational approach to study the effects of ion size, ion size asymmetry and solvent excluded volume on the ion profiles, integrated charge, mean electrostatic potential, and ionic coordination number around spherical macroions in various electrolyte mixtures. Our results show that both solvent hard sphere diameter and density play a dominant role in the distribution of ions around spherical macroions, mainly for experimental water molarity and size values where the counterion distribution is characterized by a tight binding to the macroion, similar to that predicted by the Stern model.

Medasani, Bharat; Ovanesyan, Zaven; Thomas, Dennis G.; Sushko, Maria L.; Marucho, Marcelo

2014-05-29T23:59:59.000Z

446

Enskog theory for polydisperse granular mixtures. II. Sonine polynomial approximation  

Science Journals Connector (OSTI)

The linear integral equations defining the Navier-Stokes (NS) transport coefficients for polydisperse granular mixtures of smooth inelastic hard disks or spheres are solved by using the leading terms in a Sonine polynomial expansion. Explicit expressions for all the NS transport coefficients are given in terms of the sizes, masses, compositions, density, and restitution coefficients. In addition, the cooling rate is also evaluated to first order in the gradients. The results hold for arbitrary degree of inelasticity and are not limited to specific values of the parameters of the mixture. Finally, a detailed comparison between the derivation of the current theory and previous theories for mixtures is made, with attention paid to the implication of the various treatments employed to date.

Vicente Garz; Christine M. Hrenya; James W. Dufty

2007-09-10T23:59:59.000Z

447

Kudzu (Pueraria montana) community responses to herbicides, burning, and high-density loblolly pine  

SciTech Connect

Kudzu is an aggressive, nonnative vine that currently dominates an estimated 810,000 ha of mesic forest communities in the eastern United States. To test an integrated method of weed control, abundances of kudzu and other plant species were compared during 4 yr after six herbicide treatments (clopyralid, triclopyr, metsulfuron, picloram 1 2,4-D, tebuthiuron, and a nonsprayed check), in which loblolly pines were planted at three densities (0, 1, and 4 seedlings m22) to induce competition and potentially delay kudzu recovery. This split-plot design was replicated on each of the four kudzu-dominated sites near Aiken, SC. Relative light intensity (RLI) and soil water content (SWC) were measured periodically to identify mechanisms of interference among plant species. Two years after treatment (1999), crown coverage of kudzu averaged , 2% in herbicide plots compared with 93% in the nonsprayed check, and these differences were maintained through 2001, except in clopyralid plots where kudzu cover increased to 15%. In 2001, pine interference was associated with 33, 56, and 67% reductions in biomass of kudzu, blackberry, and herbaceous vegetation, respectively. RLI in kudzu-dominated plots (4 to 15% of full sun) generally was less than half that of herbicide-treated plots. SWC was greatest in tebuthiuron plots, where total vegetation cover averaged 26% compared with 77 to 111% in other plots. None of the treatments eradicated kudzu, but combinations of herbicides and induced pine competition delayed its recovery.

T.B. Harrington; L.T. Rader-Dixon; J.W. Taylor, Jr.

2003-11-01T23:59:59.000Z

448

Nuclear energy density optimization: Shell structure  

E-Print Network (OSTI)

Nuclear density functional theory is the only microscopical theory that can be applied throughout the entire nuclear landscape. Its key ingredient is the energy density functional. In this work, we propose a new parameterization UNEDF2 of the Skyrme energy density functional. The functional optimization is carried out using the POUNDerS optimization algorithm within the framework of the Skyrme Hartree-Fock-Bogoliubov theory. Compared to the previous parameterization UNEDF1, restrictions on the tensor term of the energy density have been lifted, yielding a very general form of the energy density functional up to second order in derivatives of the one-body density matrix. In order to impose constraints on all the parameters of the functional, selected data on single-particle splittings in spherical doubly-magic nuclei have been included into the experimental dataset. The agreement with both bulk and spectroscopic nuclear properties achieved by the resulting UNEDF2 parameterization is comparable with UNEDF1. While there is a small improvement on single-particle spectra and binding energies of closed shell nuclei, the reproduction of fission barriers and fission isomer excitation energies has degraded. As compared to previous UNEDF parameterizations, the parameter confidence interval for UNEDF2 is narrower. In particular, our results overlap well with those obtained in previous systematic studies of the spin-orbit and tensor terms. UNEDF2 can be viewed as an all-around Skyrme EDF that performs reasonably well for both global nuclear properties and shell structure. However, after adding new data aiming to better constrain the nuclear functional, its quality has improved only marginally. These results suggest that the standard Skyrme energy density has reached its limits and significant changes to the form of the functional are needed.

M. Kortelainen; J. McDonnell; W. Nazarewicz; E. Olsen; P. -G. Reinhard; J. Sarich; N. Schunck; S. M. Wild; D. Davesne; J. Erler; A. Pastore

2013-12-06T23:59:59.000Z

449

Approximation algorithms for a geometric set cover problem  

Science Journals Connector (OSTI)

Given a finite set of straight line segments S in R 2 and some k ? N , is there a subset V of points on segments in S with | V | ? k such that each segment of S contains at least one point in V ? This is a special case of the set covering problem where the family of subsets given can be taken as a set of intersections of the straight line segments in S . Requiring that the given subsets can be interpreted geometrically this way is a major restriction on the input, yet we have shown that the problem is still strongly NP-complete [5]. In light of this result, we studied the accuracy of two polynomial-time approximation algorithms along with a third heuristic based algorithm which return segment coverings. We obtain certain theoretical results, and in particular we show that the performance ratio for each of these algorithms is unbounded, in general. Despite this, our experimental results suggest that the cases where this ratio exceeds 2 are rare for reasonable methods of placing segments. This is evidence that these polynomial-time algorithms solve the problem accurately in practice.

Valentin E. Brimkov; Andrew Leach; Jimmy Wu; Michael Mastroianni

2012-01-01T23:59:59.000Z

450

Planar F-Deletion: Approximation and Optimal FPT Algorithms  

E-Print Network (OSTI)

Let F be a finite set of graphs. In the F-Deletion problem, we are given an n-vertex, m-edge graph G and an integer k as input, and asked whether at most k vertices can be deleted from G such that the resulting graph does not contain a graph from F as a minor. F-Deletion is a generic problem and by selecting different sets of forbidden minors F, one can obtain various fundamental problems such as Vertex Cover, Feedback Vertex Set or Treewidth t-Deletion. In this paper we obtain a number of generic algorithmic results about Planar F-Deletion, when F contains at least one planar graph. The highlights of our work are - A randomized O(nm) time constant factor approximation algorithm for the optimization version of Planar F-Deletion. - A randomized O(2^{O(k)} n) time parameterized algorithm for Planar F-Deletion when F is connected. Here a family F is called connected if every graph in F is connected. The algorithm can be made deterministic at the cost of making the polynomial factor in the running time n\\log^2 n ...

Fomin, Fedor; Misra, Neeldhara; Saurabh, Saket

2012-01-01T23:59:59.000Z

451

Generalized approximations of reflection coefficients in orthorhombic media  

Science Journals Connector (OSTI)

Reflection coefficients of qP- (quasi-P) and qS- (quasi-S) incident waves in orthorhombic media can be explicitly expressed by means of impedance matrices. In this paper, we extend previous studies and derive the generalized and linearized equations of reflectivity for all four types of waves in the symmetry-axis plane. These approximations have sufficient accuracy over a wide range of angles, therefore they are suitable for characterizing the seismic amplitude responses of unconventional resources. For example, they can be applied to represent the amplitude variation with offset for shale gas or coalbed methane reservoirs with strong anisotropy and complicated symmetry. Reduced equations are then derived in a transverse isotropic medium with a vertical symmetry axis (VTI) or a horizontal axis (HTI) for the anisotropic amplitude inversion. They retain higher accuracy than the corresponding previously published expressions at a strongly anisotropic interface, because they include the second-order terms of anisotropic parameters contrast. Numerical analyses on the inverse problem using different linearized expressions show the practical value of the new derived expressions in the joint inversion of the qPqP- and qPqS-waves for elastic parameters and anisotropic parameters.

Feng Zhang; Xiangyang Li

2013-01-01T23:59:59.000Z

452

ORBITAL-FREE KINETIC-ENERGY DENSITY FUNCTIONAL THEORY  

E-Print Network (OSTI)

Chapter 5 ORBITAL-FREE KINETIC-ENERGY DENSITY FUNCTIONAL THEORY Yan Alexander Wang and Emily A Theory (DFT), there was the Thomas-Fermi (TF) model, which uses the electron density ¢¡ r£ (a function-dependent DFT Density-Functional Theory DI density-independent DM1 first-order reduced density matrix EDF energy

Wang, Yan Alexander

453

A Bayesian Probability Calculus for Density Matrices  

E-Print Network (OSTI)

One of the main concepts in quantum physics is a density matrix, which is a symmetric positive definite matrix of trace one. Finite probability distributions are a special case where the density matrix is restricted to be diagonal. Density matrices are mixtures of dyads, where a dyad has the form uu' for any any unit column vector u. These unit vectors are the elementary events of the generalized probability space. Perhaps the simplest case to see that something unusual is going on is the case of uniform density matrix, i.e. 1/n times identity. This matrix assigns probability 1/n to every unit vector, but of course there are infinitely many of them. The new normalization rule thus says that sum of probabilities over any orthonormal basis of directions is one. We develop a probability calculus based on these more general distributions that includes definitions of joints, conditionals and formulas that relate these, i.e. analogs of the theorem of total probability, various Bayes rules for the calculation of posterior density matrices, etc. The resulting calculus parallels the familiar 'classical' probability calculus and always retains the latter as a special case when all matrices are diagonal. Whereas the classical Bayesian methods maintain uncertainty about which model is 'best', the generalization maintains uncertainty about which unit direction has the largest variance. Surprisingly the bounds also generalize: as in the classical setting we bound the negative log likelihood of the data by the negative log likelihood of the MAP estimator.

Manfred K. Warmuth; Dima Kuzmin

2014-08-09T23:59:59.000Z

454

Extreme density-driven delocalization error for a model solvated-electron system  

SciTech Connect

Delocalization (or charge-transfer) error is one of the scarce but spectacular failures of density-functional theory. It is particularly apparent in extensively delocalized molecules, and manifests in the calculation of bandgaps, reaction barriers, and dissociation limits. Even though delocalization error is always present in the self-consistent electron density, the differences from reference densities are often quite subtle and the error tends to be driven by the exchange-correlation energy expression. In this article, we propose a model system (the Kevan model) where approximate density functionals predict dramatically different charge distributions because of delocalization error. The model system consists of an electron trapped in a water hexamer and is a finite representation of an experimentally observed class of solids: electrides. The Kevan model is of fundamental interest because it allows the estimation of charge transfer error without recourse to fractional charge calculations, but our results are also relevant in the context of the modeling of confined electrons in density-functional theory.

Johnson, Erin R., E-mail: ejohnson29@ucmerced.edu; Otero-de-la-Roza, A., E-mail: aoterodelaroza@ucmerced.edu; Dale, Stephen G., E-mail: sdale@ucmerced.edu [Chemistry and Chemical Biology, School of Natural Sciences, University of California, Merced, 5200 North Lake Road, Merced, California 95343 (United States)

2013-11-14T23:59:59.000Z

455

Stochastic Biasing and Galaxy-Mass Density Relation in the Weakly Non-linear Regime  

E-Print Network (OSTI)

It is believed that the biasing of the galaxies plays an important role for understanding the large-scale structure of the universe. In general, the biasing of galaxy formation could be stochastic. Furthermore, the future galaxy survey might allow us to explore the time evolution of the galaxy distribution. In this paper, the analytic study of the galaxy-mass density relation and its time evolution is presented within the framework of the stochastic biasing. In the weakly non-linear regime, we derive a general formula for the galaxy-mass density relation as a conditional mean using the Edgeworth expansion. The resulting expression contains the joint moments of the total mass and galaxy distributions. Using the perturbation theory, we investigate the time evolution of the joint moments and examine the influence of the initial stochasticity on the galaxy-mass density relation. The analysis shows that the galaxy-mass density relation could be well-approximated by the linear relation. Compared with the skewness of the galaxy distribution, we find that the estimation of the higher order moments using the conditional mean could be affected by the stochasticity. Therefore, the galaxy-mass density relation as a conditional mean should be used with a caution as a tool for estimating the skewness and the kurtosis.

A. Taruya; J. Soda

1998-09-16T23:59:59.000Z

456

E-Print Network 3.0 - approximate half-intensity widths Sample...  

NLE Websites -- All DOE Office Websites (Extended Search)

linear time algorithm for computing a (1+)-approximation to the minimum width 2-slab cover of P... a set P of n points in IR3 , one can maintain an -approximate minimum width...

457

Low-rank approximations with sparse factors II: penalized methods with discrete Newton-like iterations  

E-Print Network (OSTI)

H. Zha, and H. Simon. Low-rank Approximations with Sparse5) H. Simon and H. Zhao Low-rank matrix approximation usingZhang. Matrices with low-rank-plus-shift structure: partial

Simon, Horst

2011-01-01T23:59:59.000Z

458

A simulationapproximation approach to sample size planning for high-dimensional classification studies  

Science Journals Connector (OSTI)

......simulation-approximation approach to sample size...Environmental Science, Policy, Management, University...challenging. The approach developed here...approximation approaches to different...Environmental Science, Policy, & Management, University......

Perry de Valpine; Hans-Marcus Bitter; Michael P. S. Brown; Jonathan Heller

2009-07-01T23:59:59.000Z

459

E-Print Network 3.0 - approximate l-state solutions Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

where C... 'o','x','+'. Omit C for a connected graph. APPROXIMATE SOLUTIONS The matlab commands eul, rk2, and rk4 can be used... to obtain approximate solutions of the ......

460

High-Energy-Density Plasmas, Fluids  

NLE Websites -- All DOE Office Websites (Extended Search)

High-Energy-Density Plasmas, Fluids High-Energy-Density Plasmas, Fluids /science-innovation/_assets/images/icon-science.jpg High-Energy-Density Plasmas, Fluids National security depends on science and technology. The United States relies on Los Alamos National Laboratory for the best of both. No place on Earth pursues a broader array of world-class scientific endeavors. TRIDENT target chamber Sasi Palaniyappan, right, and Rahul Shah left inside a target chamber where the TRIDENT short pulse laser is aimed at a very thin diamond- foil target, a fraction of a micrometer thick. The laser delivers a power on target of 150 Terawatts focused into a 7 micrometer spot, yielding laser brilliance over 100 times more intense than needed to make the target electrons fully relativistic. These experiments test novel methods of producing intense

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


461

Neutron Matter from Low to High Density  

E-Print Network (OSTI)

Neutron matter is an intriguing nuclear system with multiple connections to other areas of physics. Considerable progress has been made over the last two decades in exploring the properties of pure neutron fluids. Here we begin by reviewing work done to explore the behavior of very low density neutron matter, which forms a strongly paired superfluid and is thus similar to cold Fermi atoms, though at energy scales differing by many orders of magnitude. We then increase the density, discussing work that ties the study of neutron matter with the determination of the properties of neutron-rich nuclei and neutron-star crusts. After this, we review the impact neutron matter at even higher densities has on the mass-radius relation of neutron stars, thereby making contact with astrophysical observations.

Gandolfi, Stefano; Carlson, J

2015-01-01T23:59:59.000Z

462

RPA calculation of $K^+$-nucleus cross-sections with a density-dependent Brueckner-Hartree-Fock NN interaction  

E-Print Network (OSTI)

In the calculation of the $K^+$-nucleus cross sections, the coupling of the mesons exchanged between the $K^+$ and the target nucleons to the polarization of the Fermi and Dirac seas has been taken into account. This polarization has been calculated in the one-loop approximation but summed up to all orders (RPA approximation). For this calculation a density-dependent Brueckner-Hartree-Fock NN interaction providing a good description of both nuclear matter and finite nuclei has been used. The agreement with experiment is considerably improved.

J. C. Caillon; J. Labarsouque

1994-06-21T23:59:59.000Z

463

E-Print Network 3.0 - approximate kinetic equations Sample Search...  

NLE Websites -- All DOE Office Websites (Extended Search)

equation. Reactor kinetics and Summary: equations, prompt jump approximation; subcritical reactor kinetics, circulating fuel reactor dynamics 5... solution to neutron...

464

Approximation Order Equivalence Properties of Manifold-Valued Data Subdivision Schemes  

E-Print Network (OSTI)

, is there an approximation operator Ah = Ah;r,R that maps samples of any f : R M on a grid of size h to an approximant fh on Curves and Surfaces (Avignon, France, June 29-July 5, 2006.) and further discussed in a mini, is there an approximation operator Ah = Ah;r,R that maps samples of any f : R M on a grid of size h to an approximant fh

Yu, Thomas P.-Y.

465

A Time-Dependent BornOppenheimer Approximation with Exponentially Small Error Estimates  

Science Journals Connector (OSTI)

...We present the construction of an exponentially accurate time-dependent BornOppenheimer approximation for molecular quantum mechanics.

George A. Hagedorn; Alain Joye

2001-11-01T23:59:59.000Z

466

Hall viscosity, spin density, and torsion  

E-Print Network (OSTI)

We investigate the relationship between Hall viscosity, spin density and response to geometric torsion. For the most general effective action for relativistic gapped systems, the presence of non-universal terms implies that there is no relationship between torsion response and Hall viscosity. We also consider free relativistic and non-relativistic microscopic actions and again verify the existence of analogous non-universal couplings. Explicit examples demonstrate that torsion response is unrelated to both Hall viscosity and spin density. We also argue that relativistic gapped theories must have vanishing Hall viscosity in Lorentz invariant vacuums.

Geracie, Michael; Roberts, Matthew M

2014-01-01T23:59:59.000Z

467

Density Perturbations in the Ekpyrotic Scenario  

E-Print Network (OSTI)

We study the generation of density perturbations in the ekpyrotic scenario for the early universe, including gravitational backreaction. We expose interesting subtleties that apply to both inflationary and ekpyrotic models. Our analysis includes a detailed proposal of how the perturbations generated in a contracting phase may be matched across a `bounce' to those in an expanding hot big bang phase. For the physical conditions relevant to the ekpyrotic scenario, we re-obtain our earlier result of a nearly scale-invariant spectrum of energy density perturbations. We find that the perturbation amplitude is typically small, as desired to match observation.

Justin Khoury; Burt A. Ovrut; Paul J. Steinhardt; Neil Turok

2001-09-06T23:59:59.000Z

468

Josephson oscillations of charge density waves  

SciTech Connect

The formation of charge density waves in solids was originally proposed as a possible mechanism for superconductivity by Froehlich. Although the experimentally discovered materials with charge density waves (CDW)s are found to have finite resistivity as a result of impurity pinning, they nevertheless reveal many interesting features including motion which is analogous to a resistively shunted Josephson junction of superconductors. The noise spectrum of CDW systems is reviewed with particular emphasis on interactions with normal as well as magnetic impurities. Future prospects for observing an amplitude variation of the noise signals induced by a magnetic field are proposed.

Ruvalds, J.; Tua, P.F.

1985-01-01T23:59:59.000Z

469

Low density, microcellular foams, preparation, and articles  

DOE Patents (OSTI)

A microcellular low-density foam of poly(4-methyl-1-pentene) particularly useful for forming targets for inertial confinement fusion has been developed. Articles made from the foam have been machined to tolerances of 0.0001 inch, although the densities of the fragile foam are low (about 10 to about 100 mg/cc) and the cell sizes are small (about 10 to about 30 ..mu..m). Methods for forming the foam and articles are given. The yield strength of the foam of the invention is higher than was obtained in other structures of this same material.

Young, A.T.

1982-03-03T23:59:59.000Z

470

Energy and Momentum Density in Field Theory  

Science Journals Connector (OSTI)

It is shown that the energy density commutator condition in its simplest form is valid for interacting spin 0, , 1 field systems, but not for higher spin fields. The action principle is extended, for this purpose, to arbitrary coordinate frames. There is a discussion of four categories of fields and some explicit consideration of spin 32 as the simplest example that gives additional terms in the energy density commutator. As the fundamental equation of relativistic quantum field theory, the commutator condition makes explicit the greater physical complexity of higher spin fields.

Julian Schwinger

1963-04-15T23:59:59.000Z

471

Calculation of nuclear spin-spin coupling constants using frozen density embedding  

SciTech Connect

We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between {sup 199}Hg and {sup 13}C upon coordination of dimethylsulfoxide solvent molecules.

Gtz, Andreas W., E-mail: agoetz@sdsc.edu [San Diego Supercomputer Center, University of California San Diego, 9500 Gilman Dr MC 0505, La Jolla, California 92093-0505 (United States); Autschbach, Jochen [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000 (United States)] [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000 (United States); Visscher, Lucas, E-mail: visscher@chem.vu.nl [Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, Theoretical Chemistry, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)] [Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, Theoretical Chemistry, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)

2014-03-14T23:59:59.000Z

472

Galaxy ecology: groups and low-density environments in the SDSS and 2dFGRS  

E-Print Network (OSTI)

We analyse the observed correlation between galaxy environment and H-alpha emission line strength, using volume-limited samples and group catalogues of 24968 galaxies drawn from the 2dF Galaxy Redshift Survey (Mb<-19.5) and the Sloan Digital Sky Survey (Mr<-20.6). We characterise the environment by 1) Sigma_5, the surface number density of galaxies determined by the projected distance to the 5th nearest neighbour; and 2) rho1.1 and rho5.5, three-dimensional density estimates obtained by convolving the galaxy distribution with Gaussian kernels of dispersion 1.1 Mpc and 5.5 Mpc, respectively. We find that star-forming and quiescent galaxies form two distinct populations, as characterised by their H-alpha equivalent width, EW(Ha). The relative numbers of star-forming and quiescent galaxies varies strongly and continuously with local density. However, the distribution of EW(Ha) amongst the star-forming population is independent of environment. The fraction of star-forming galaxies shows strong sensitivity to the density on large scales, rho5.5, which is likely independent of the trend with local density, rho1.1. We use two differently-selected group catalogues to demonstrate that the correlation with galaxy density is approximately independent of group velocity dispersion, for sigma=200-1000 km/s. Even in the lowest density environments, no more than ~70 per cent of galaxies show significant H-alpha emission. Based on these results, we conclude that the present-day correlation between star formation rate and environment is a result of short-timescale mechanisms that take place preferentially at high redshift, such as starbursts induced by galaxy-galaxy interactions.

Michael Balogh; Vince Eke; Chris Miller; Ian Lewis; Richard Bower; Warrick Couch; Robert Nichol; Joss Bland-Hawthorn; Ivan K. Baldry; Carlton Baugh; Terry Bridges; Russell Cannon; Shaun Cole; Matthew Colless; Chris Collins; Nicholas Cross; Gavin Dalton; Roberto De Propris; Simon P. Driver; George Efstathiou; Richard S. Ellis; Carlos S. Frenk; Karl Glazebrook; Percy Gomez; Alex Gray; Edward Hawkins; Carole Jackson; Ofer Lahav; Stuart Lumsden; Steve Maddox; Darren Madgwick; Peder Norberg; John A. Peacock; Will Percival; Bruce A. Peterson; Will Sutherland; Keith Taylor

2004-01-05T23:59:59.000Z

473

A Time{Dependent Born{Oppenheimer Approximation with Exponentially Small Error Estimates  

E-Print Network (OSTI)

A Time{Dependent Born{Oppenheimer Approximation with Exponentially Small Error Estimates George A{ Oppenheimer approximation for molecular quantum mechanics. We study molecular systems whose electron masses. The small parameter that governs the approximation is the usual Born{Oppenheimer expansion parameter #15

Joye, Alain

474

A Time--Dependent Born--Oppenheimer Approximation with Exponentially Small Error Estimates  

E-Print Network (OSTI)

A Time--Dependent Born--Oppenheimer Approximation with Exponentially Small Error Estimates George A--dependent Born-- Oppenheimer approximation for molecular quantum mechanics. We study molecular systems whose parameter that governs the approximation is the usual Born--Oppenheimer expansion parameter #, where # 4

Hagedorn, George A.

475

Motivation Green's functions The GW Approximation The Bethe-Salpeter Equation Introduction to Green's functions  

E-Print Network (OSTI)

Motivation Green's functions The GW Approximation The Bethe-Salpeter Equation Introduction to Green=whiteMotivation Green's functions The GW Approximation The Bethe-Salpeter Equation Outline 1 Motivation 2 Green's functions 3 The GW Approximation 4 The Bethe-Salpeter Equation #12;bg=whiteMotivation Green's functions

Botti, Silvana

476

Duality, Conjugacy and Adjointness of Approximation Operators in Covering Based Rough Sets  

E-Print Network (OSTI)

Duality, Conjugacy and Adjointness of Approximation Operators in Covering Based Rough Sets Mauricio approximation operators in covering-based rough sets. In this paper, we establish relationships between the most for the generalized rough set model based on a binary relation. Key words: rough sets, coverings, approximations

Granada, Universidad de

477

Time Dependent Density Functional Theory Application to Extended Systems  

E-Print Network (OSTI)

Time Dependent Density Functional Theory Application to Extended Systems Francesco Sottile Facility (ETSF) Donostia, 25 July 2007 Time Dependent Density Functional Theory Francesco Sottile #12 Density Functional Theory Francesco Sottile #12;Linear Periodic systems ALDA The Quest for the Holy

Botti, Silvana

478

Mechanical constraints enhance electrical energy densities of soft dielectrics  

E-Print Network (OSTI)

Mechanical constraints enhance electrical energy densities of soft dielectrics Lin Zhang, Qiming, the dielectric will breakdown electrically. The breakdown limits the electrical energy density of the dielectric electric fields and thus increase their electrical energy densities. The mechanical constraints suppress

Ferrari, Silvia

479

High-power-density spot cooling using bulk thermoelectrics  

E-Print Network (OSTI)

3D electrothermal model, the cooling power densities of themax , and increasing the cooling power densities 224 times.the advantages of high cooling power densities and is less

Zhang, Y; Shakouri, A; Zeng, G H

2004-01-01T23:59:59.000Z

480

neutron density. The neutron density (nn) of the source was modeled by solving the simul-  

E-Print Network (OSTI)

neutron density. The neutron density (nn) of the source was modeled by solving the simul- taneousT is the thermal neutron velocity, l is the decay constant, Ns is the s-process abun- dance, bs� is the maxwellian-averaged neutron capture cross-section, and t0 is the average neutron exposure (21). The branching decay of 186Re

West, Stuart

Note: This page contains sample records for the topic "greatest density approximately" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


481

On the Determination of the Mean Cosmic Matter Density and the Amplitude of Density Fluctuations  

E-Print Network (OSTI)

The cosmological implications from a new estimate of the local X-ray galaxy cluster abundance are summarized. The results are then compared to independent observations. It is suggested that `low' values for the mean cosmic matter density and the amplitude of mass density fluctuations currently do not appear unreasonable observationally.

Thomas H. Reiprich

2002-07-02T23:59:59.000Z

482

Novel and Optimized Materials Phases for High Energy Density...  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Novel and Optimized Materials Phases for High Energy Density Batteries Novel and Optimized Materials Phases for High Energy Density Batteries 2013 DOE Hydrogen and Fuel Cells...

483

TEMPO-based Catholyte for High Energy Density Nonaqueous Redox...  

NLE Websites -- All DOE Office Websites (Extended Search)

TEMPO-based Catholyte for High Energy Density Nonaqueous Redox Flow Batteries. TEMPO-based Catholyte for High Energy Density Nonaqueous Redox Flow Batteries. Abstract: We will...

484

Engineering Density of States of Earth Abundant Semiconductors...  

Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site

Density of States of Earth Abundant Semiconductors for Enhanced Thermoelectric Power Factor Engineering Density of States of Earth Abundant Semiconductors for Enhanced...

485

High Energy Density Laboratory Plasmas Program | National Nuclear...  

National Nuclear Security Administration (NNSA)

Photo Gallery Jobs Apply for Our Jobs Our Jobs Working at NNSA Blog Home High Energy Density Laboratory Plasmas Program High Energy Density Laboratory Plasmas Program...

486

Density Functional Theory Approach to Nuclear Fission  

E-Print Network (OSTI)

The Skyrme nuclear energy density functional theory (DFT) is used to model neutron-induced fission in actinides. This paper focuses on the numerical implementation of the theory. In particular, it reports recent advances in DFT code development on leadership class computers, and presents a detailed analysis of the numerical accuracy of DFT solvers for near-scission calculations.

N. Schunck

2013-01-20T23:59:59.000Z

487

Modern applications of covariant density functional theory  

E-Print Network (OSTI)

Modern applications of Covariant Density Functional Theory (CDFT) are discussed. First we show a systematic investigation of fission barriers in actinide nuclei within constraint relativistic mean field theory allowing for triaxial deformations. In the second part we discuss a microscopic theory of quantum phase transitions (QPT) based on the relativistic generator coordinate method.

P. Ring; H. Abusara; A. V. Afanasjev; G. A. Lalazissis; T. Niksic; D. Vretenar

2011-09-19T23:59:59.000Z

488

Thermal conductivity of low density carbon aerogels  

Science Journals Connector (OSTI)

Carbon aerogels with densities ranging from 0.182 to 0.052g/cm3, pore sizes ranging from 88 to 227nm, and particle diameters ranging from 20 to 13nm were prepared. Thermal conductivity measurements by laser fl...

Junzong Feng; Jian Feng; Changrui Zhang

2012-10-01T23:59:59.000Z

489

Estimating density of Florida Key deer  

E-Print Network (OSTI)

for this species since 1968; however, a need to evaluate the precision of existing and alternative survey methods (i.e., road counts, mark-recapture, infrared-triggered cameras [ITC]) was desired by USFWS. I evaluated density estimates from unbaited ITCs and road...

Roberts, Clay Walton

2006-08-16T23:59:59.000Z

490

Density Perturbations for Running Cosmological Constant  

E-Print Network (OSTI)

The dynamics of density and metric perturbations is investigated for the previously developed model where the decay of the vacuum energy into matter (or vice versa) is due to the renormalization group (RG) running of the cosmological constant (CC) term. The evolution of the CC depends on the single parameter \

Julio C. Fabris; Ilya L. Shapiro; Joan Sola

2007-01-26T23:59:59.000Z

491

Drawing Electron Density Maps Tutorial : J. Reibenspies  

E-Print Network (OSTI)

file Choose the difference map #12;Step 2 · If necessary generate full molecule in XSEED or XP shift key to pan) #12;Step 4 · All ball and stick plot to spice it up ZOOMED #12;Step 5 · Save screen the electron density in the macocyclic void in order to understand the disorder #12;Step one · In the INS

Meagher, Mary

492

Master's Thesis Density Functional Theory for  

E-Print Network (OSTI)

of the information found during my work. v #12;vi #12;Contents Abstract #12;Abstract This thesis presents a number of results for basic quantum mechanical models intended to be used in the development of density functional theory for systems with edges. Following previous work

Armiento, Rickard

493

Self-interaction corrections in density functional theory  

SciTech Connect

Self-interaction corrections for Kohn-Sham density functional theory are reviewed for their physical meanings, formulations, and applications. The self-interaction corrections get rid of the self-interaction error, which is the sum of the Coulomb and exchange self-interactions that remains because of the use of an approximate exchange functional. The most frequently used self-interaction correction is the Perdew-Zunger correction. However, this correction leads to instabilities in the electronic state calculations of molecules. To avoid these instabilities, several self-interaction corrections have been developed on the basis of the characteristic behaviors of self-interacting electrons, which have no two-electron interactions. These include the von Weizscker kinetic energy and long-range (far-from-nucleus) asymptotic correction. Applications of self-interaction corrections have shown that the self-interaction error has a serious effect on the states of core electrons, but it has a smaller than expected effect on valence electrons. This finding is supported by the fact that the distribution of self-interacting electrons indicates that they are near atomic nuclei rather than in chemical bonds.

Tsuneda, Takao, E-mail: ttsuneda@yamanashi.ac.jp [Fuel Cell Nanomaterials Center, University of Yamanashi, Kofu 400-0021 (Japan)] [Fuel Cell Nanomaterials Center, University of Yamanashi, Kofu 400-0021 (Japan); Hirao, Kimihiko [Computational Chemistry Unit, RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047 (Japan)] [Computational Chemistry Unit, RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047 (Japan)

2014-05-14T23:59:59.000Z

494

Hybrid Dynamic Density Functional Theory for Polymer Melts and Blends  

E-Print Network (OSTI)

We propose a high-speed and accurate hybrid dynamic density functional theory for the computer simulations of the phase separation processes of polymer melts and blends. The proposed theory is a combination of the dynamic self-consistent field (SCF) theory and a time-dependent Ginzburg-Landau type theory with the random phase approximation (GRPA). The SCF theory is known to be accurate in evaluating the free energy of the polymer systems in both weak and strong segregation regions although it has a disadvantage of the requirement of a considerable amount of computational cost. On the other hand, the GRPA theory has an advantage of much smaller amount of required computational cost than the SCF theory while its applicability is limited to the weak segregation region. To make the accuracy of the SCF theory and the high-performance of the GRPA theory compatible, we adjust the chemical potential of the GRPA theory by using the SCF theory every constant time steps in the dynamic simulations. The performance of the GRPA and the hybrid theories is tested by using several systems composed of an A/B homopolymer, an AB diblock copolymer, or an ABC triblock copolymer. Using the hybrid theory, we succeeded in reproducing the metastable complex phase-separated domain structures of an ABC triblock copolymer observed by experiments.

Takashi Honda; Toshihiro Kawakatsu

2006-09-05T23:59:59.000Z

495

Photoconductivity and density of states in microstructural amorphous silicon  

SciTech Connect

It has been reported in previous works that using of RF 55 kHz PECVD method allows to deposit microstructural inhomogeneous a-Si:H films at high deposition rate (10--20{angstrom}/c) and with high photoconductivity. The structural analysis with using of IR spectroscopy and atomic force microscopy (AFM) performed in this work have shown that these films possess a relatively regular microstructure consisting of grains with characteristic size of {approximately}300--500{angstrom}. The regular microstructure of investigated films differs from inhomogeneous a-Si:H with deteriorate electronic properties. At the same time the diffraction analysis didn't reveal the presence of microcrystals. Therefore, the authors denoted their films as microstructural a-Si:H films. In this work they performed the modeling of the photoconductivity of microstructural a-Si:H films to analyze the density-of-states (DOS) responsible for recombination kinetics. For this purpose different approaches to photoconductivity modeling have been used to simulate the experimentally measured temperature dependence of photoconductivity. The comparative analysis of results of these simulations and ESR measurements have shown that recombination in high photoconductive microstructural films is controlled by deep neutral states.

Budaguan, B.G.; Aivazov, A.A.; Radosel'sky, A.G.; Popov, A.A.

1997-07-01T23:59:59.000Z

496

Exact eigenvalues of the pairing Hamiltonian using continuum level density  

Science Journals Connector (OSTI)

The pairing Hamiltonian constitutes an important approximation in many-body systems; it is exactly soluble and quantum integrable. On the other hand, the continuum single-particle level density (CSPLD) contains information about the continuum energy spectrum. The question of whether one can use the Hamiltonian with constant pairing strength for correlations in the continuum is still unanswered. In this paper we generalize the Richardson exact solution for the pairing Hamiltonian including correlations in the continuum. The resonant and nonresonant continua are included through the CSPLD. The resonant correlations are made explicit by using the Cauchy theorem. Low-lying states with seniority 0 and 2 are calculated for the even carbon isotopes. We conclude that energy levels can indeed be calculated with constant pairing in the continuum using the CSPLD. It is found that the nucleus 24C is unbound. The real and complex energy representations of the continuum is developed and their differences are shown. The trajectory of the pair energies in the continuum for the nucleus 28C is shown.

R. Id Betan

2012-06-07T23:59:59.000Z

497

Comparison of Born-Oppenheimer and hyperspherical adiabatic approximations in the trinucleon problem  

Science Journals Connector (OSTI)

Ground state energies of the three-nucleon system interacting via standard S-projected potentials are studied using Born-Oppenheimer and hyperspherical adiabatic approximations. The extreme and the uncoupled hyperspherical adiabatic approximations, which are the lower and upper bounds for the exact ground state energy, are found to define a narrow band with the Born-Oppenheimer approximation lying close to it. While the hyperspherical adiabatic approximation conserves the basic symmetry requirements, the other does not. In spite of this, the Born-Oppenheimer approximation is found to be comparable to the other for potentials with a soft core repulsion.

T. K. Das; H. T. Coelho; V. P. Brito

1993-11-01T23:59:59.000Z

498

Skyrme, Peierls-Yoccoz, and statistical approximations for the inertia parameter  

Science Journals Connector (OSTI)

Angular momentum operator identities are used to show that Skyrme's expression can be written using the y component of angular momentum only. It is shown that the Gaussian approximation for the matrix element of Jy4 leads to the Peierls-Yoccoz expression. A new approximation based on the theory of probability is introduced. The numerical calculations for the 2s-1d shell nuclei show that the inverse of the inertia parameter using the statistical approximation is much closer to Skyrme's value than the one given by the Peierls-Yoccoz approximation.[NUCLEAR STRUCTURE Approximations for nuclear inertia parameter.

Nazakat Ullah

1978-02-01T23:59:59.000Z

499

Energy-Density Relation for Nuclear Matter  

Science Journals Connector (OSTI)

In most previous calculations of nuclear matter the energy has been calculated only at the equilibrium density, which density has been determined by a minimum condition. In the present paper the author's theory of nuclear matter is applied to a study of the complete energy-density relation of nuclear matter, in the neighborhood of the equilibrium density. The emphasis here is not upon duplicating the accepted value for the equilibrium binding energy, but rather upon a study of the leading (diagonal) contribution of the quasi-particle interaction term g1(k1k2|k3k4), which is the matrix element of a reaction matrix G1. It is shown that g1(k1k2|k1k2) must be evaluated partly by using observed nucleon-nucleon scattering phase shifts and partly by calculating the close-in behavior of the two-nucleon wave function, and that this second part receives a large contribution from the deuteron state. Curves are given for the dependence of g1(k1k2|k1k2) on the density and the center-of-mass momentum. It is also shown that g1(k1k2|k1k2) is sensitive to the size of the nucleon repulsive core, but not upon the character of the attraction, when agreement with scattering data has first been achieved. Finally, a comparison of g1(k1k2|k1k2) with the prediction of first-order perturbation theory is made.

Franz Mohling

1962-11-01T23:59:59.000Z

500

Cosmographic analysis of the equation of state of the universe through Pad approximations  

Science Journals Connector (OSTI)

Cosmography is used in cosmological data processing in order to constrain the kinematics of the universe in a model-independent way, providing an objective means to evaluate the agreement of a model with observations. In this paper, we extend the conventional methodology of cosmography employing Taylor expansions of observables by an alternative approach using Pad approximations. Due to the superior convergence properties of Pad expansions, it is possible to improve the fitting analysis to obtain numerical values for the parameters of the cosmographic series. From the results, we can derive the equation of state parameter of the universe and its first derivative and thus acquire information about the thermodynamic state of the universe. We carry out statistical analyses using observations of the distance modulus of type 1a supernovae, provided by the union 2.1 compilation of the supernova cosmology project, employing a Markov chain MonteCarlo approach with an implemented Metropolis algorithm. We compare the results of the original Taylor approach to the newly introduced Pad formalism. The analyses show that experimental data constrain the observable universe well, finding an accelerating universe and a positive jerk parameter. We demonstrate that the Pad convergence radii are greater than standard Taylor convergence radii, and infer a lower limit on the acceleration of the universe solely by requiring the positivity of the Pad expansion. We obtain fairly good agreement with the Planck results, confirming the ?CDM model at small redshifts, although we cannot exclude a dark energy density varying in time with negligible speed of sound.

Christine Gruber and Orlando Luongo

2014-05-05T23:59:59.000Z