Weekly Petroleum Status Report
Gasoline and Diesel Fuel Update (EIA)
Table 12. Spot Prices of Ultra-Low Sulfur Diesel Fuel, Kerosene-Type Jet Fuel, and Propane... 1.549 1.389 1.395 1.391 1.326 1.082 Propane Mont Belvieu ......
Chambers County, Texas: Energy Resources | Open Energy Information
County, Texas Reliant Baytown Biomass Facility Places in Chambers County, Texas Anahuac, Texas Baytown, Texas Beach City, Texas Cove, Texas Mont Belvieu, Texas Old...
STATEMENT OF MELANIE KENDERDINE DIRECTOR OF THE OFFICE OF ENERGY...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
2.97gal above the price at Mont Belvieu. This differential sent a strong signal to producers and distributors, and market participants responded by moving additional supplies...
Vilim, R.B.
1985-08-01
The principle methods for performing reactor hot spot analysis are reviewed and examined for potential use in the Applied Physics Division. The semistatistical horizontal method is recommended for future work and is now available as an option in the SE2-ANL core thermal hydraulic code. The semistatistical horizontal method is applied to a small LMR to illustrate the calculation of cladding midwall and fuel centerline hot spot temperatures. The example includes a listing of uncertainties, estimates for their magnitudes, computation of hot spot subfactor values and calculation of two sigma temperatures. A review of the uncertainties that affect liquid metal fast reactors is also presented. It was found that hot spot subfactor magnitudes are strongly dependent on the reactor design and therefore reactor specific details must be carefully studied. 13 refs., 1 fig., 5 tabs.
Energy Science and Technology Software Center (OSTI)
2010-10-20
The "Monte Carlo Benchmark" (MCB) is intended to model the computatiional performance of Monte Carlo algorithms on parallel architectures. It models the solution of a simple heuristic transport equation using a Monte Carlo technique. The MCB employs typical features of Monte Carlo algorithms such as particle creation, particle tracking, tallying particle information, and particle destruction. Particles are also traded among processors using MPI calls.
Energy Science and Technology Software Center (OSTI)
2014-01-01
In automotive industry, destructive inspection of spot welds is still the mandatory quality assurance method due to the lack of efficient non-destructive evaluation (NDE) tools. However, it is costly and time-consuming. Recently at ORNL, a new NDE prototype system for spot weld inspection using infrared (IR) thermography has been developed to address this problem. This software contains all the key functions that ensure the NDE system to work properly: system input/output control, image acquisition, datamore » analysis, weld quality database generation and weld quality prediction, etc.« less
Plasmonic electromagnetic hot spots temporally addressed by photoinduced molecular displacement.
Juan, M. L.; Plain, J.; Bachelot, R.; Vial, A.; Royer, P.; Gray, S. K.; Montgomery, J. M.; Wiederrecht, G. P.; Univ. de Technologie de Troyes
2009-04-23
We report the observation of temporally varying electromagnetic hot spots in plasmonic nanostructures. Changes in the field amplitude, position, and spatial features are induced by embedding plasmonic silver nanorods in the photoresponsive azo-polymer. This polymer undergoes cis?trans isomerization and wormlike transport within resonant optical fields, producing a time-varying local dielectric environment that alters the locations where electromagnetic hot spots are produced. Finite-difference time-domain and Monte Carlo simulations that model the induced field and corresponding material response are presented to aid in the interpretation of the experimental results. Evidence for propagating plasmons induced at the ends of the rods is also presented.
ARM - Datastreams - aosaeth2spot
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
carbon concentration for spot 2 uncorrected for loading factors ngm3 equivalentblackcarbonspot2uncorrected ( time, wavelength ) Aethalometer instrument flags unitless...
Sensor Placement + Optimization Software (SPOT) | Open Energy...
modeling tools User Interface: Spreadsheet Website: www.archenergy.comSPOT Cost: Free Language: English References: http:www.archenergy.comSPOT SPOT(tm) is intended to...
Energy Science and Technology Software Center (OSTI)
2006-05-09
The Monte Carlo example programs VARHATOM and DMCATOM are two small, simple FORTRAN programs that illustrate the use of the Monte Carlo Mathematical technique for calculating the ground state energy of the hydrogen atom.
U.S. Energy Information Administration (EIA)
Annual Energy Outlook [U.S. Energy Information Administration (EIA)]
recent price increase may be due to the nearing phase 1 completion of the Targa Galena Park Terminal on the Houston Ship Channel near Mont Belvieu. The terminal's nameplate export...
New construction era reflected in East Texas LPG pipeline
Mittler, T.J. )
1990-04-02
Installation of 240 miles of 6, 10, and 12-in. LPG pipelines from Mont Belvieu to Tyler, Tex., has provided greater feedstock-supply flexibility to a petrochemical plant in Longview, Tex. The project, which took place over 18 months, included tie-ins with metering at four Mont Belvieu suppliers. The new 10 and 12-in. pipelines now transport propane while the new and existing parts of a 6-in. pipeline transport propylene.
Hot Spot | Open Energy Information
definitions:Wikipedia Reegle Tectonic Settings List of tectonic settings known to host modern geothermal systems: Extensional Tectonics Subduction Zone Rift Zone Hot Spot...
SPOT Suite Transforms Beamline Science
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
SPOT Suite Transforms Beamline Science SPOT Suite Transforms Beamline Science SPOT Suite brings advanced algorithms, high performance computing and data management to the masses August 18, 2014 Contact: Linda Vu, +1 510 495 2402, lvu@lbl.gov als.jpg Advanced Light Source (ALS) at Berkeley Lab (Photo by Roy Kaltschmidt) Some mysteries of science can only be explained on a nanometer scale -even smaller than a single strand of human DNA, which is about 2.5 nanometers wide. At this scale, scientists
ClearSpot Energy | Open Energy Information
ClearSpot Energy Jump to: navigation, search Name: ClearSpot Energy Sector: Solar Product: US-based solar project developer for rooftop commercial installations. References:...
HotSpot | Department of Energy
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
HotSpot HotSpot Current Central Registry Toolbox Version(s): 2.07.1 Code Owner: Department of Energy, Office of Emergency Operations and Lawrence Livermore National Laboratory (LLNL) Description: The HotSpot Health Physics Code is used for safety-analysis of DOE facilities handling nuclear material. Additionally, HotSpot provides emergency response personnel and emergency planners with a fast, field-portable set of software tools for evaluating incidents involving radioactive material. HotSpot
A procedure to determine the planar integral spot dose values of proton pencil beam spots
Anand, Aman; Sahoo, Narayan; Zhu, X. Ronald; Sawakuchi, Gabriel O.; Poenisch, Falk; Amos, Richard A.; Ciangaru, George; Titt, Uwe; Suzuki, Kazumichi; Mohan, Radhe; Gillin, Michael T.
2012-02-15
found to have angular anisotropy. This anisotropy in PPBS dose distribution could be accounted in a reasonable approximate manner by taking the average of PISD values obtained using the in-line and cross-line profiles. The PISD{sub RBPC} values fall within 3.5% of those measured by BPC. Due to inherent dosimetry challenges associated with PPBS dosimetry, which can lead to large experimental uncertainties, such an agreement is considered to be satisfactory for validation purposes. The PISD{sub full} values show differences ranging from 1 to 11% from BPC measured values, which are mainly due to the size limitation of the BPC to account for the dose in the long tail regions of the spots extending beyond its 4.08 cm radius. The dose in long tail regions occur both for high energy beams such as 221.8 MeV PPBS due to the contributions of nuclear interactions products in the medium, and for low energy PPBS because of their larger spot sizes. The calculated LTDCF values agree within 1% with those determined by the Monte Carlo (MC) simulations. Conclusions: The area integration method to compute the PISD from PPBS lateral dose profiles is found to be useful both to determine the correction factors for the values measured by the BPC and to validate the results from MC simulations.
McIlhany, K.; Whitehouse, D.; Smith, D.; Eisner, A.M.; Wang, Y.X.
1994-12-31
A Monte Carlo program describing the response of the Liquid Scintillation Neutrino Detector (LSND) at the Los Alamos Meson Physics Facility (LAMPF) was written using the GEANT geometry and simulation package. Neutrino interactions were simulated in the detector through the production of Cerenkov and scintillation light in the range of 2-3 eV. Since GEANT does not normally track photons to electron-volt energies, the tracking program (TRAK) was modified to produce both Cerenkov and scintillator light, the latter being simulated using the Birks equation. The LSND Monte Carlo program was used to predict the quantity of scintillator (b-PBD) used in the mineral oil to provide a ratio of roughly 4:1 light output resulting from scintillation and Cerenkov light respectively.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Quantum Monte Carlo for the Electronic Structure of Atoms and Molecules Brian Austin Lester Group, U.C. Berkeley BES Requirements Workshop Rockville, MD February 9, 2010 Outline Applying QMC to diverse chemical systems Select systems with high interest and impact Phenol: bond dissociation energy Retinal: excitation energy Algorithmic details Parallel Strategy Wave function evaluation O-H Bond Dissociation Energy of Phenol Ph-OH Ph-O * + H * (36 valence electrons)
Marcus, Ryan C.
2012-07-25
MCMini is a proof of concept that demonstrates the possibility for Monte Carlo neutron transport using OpenCL with a focus on performance. This implementation, written in C, shows that tracing particles and calculating reactions on a 3D mesh can be done in a highly scalable fashion. These results demonstrate a potential path forward for MCNP or other Monte Carlo codes.
HotSpot Software Configuration Management Plan
Walker, H; Homann, S G
2009-03-12
This Software Configuration Management Plan (SCMP) describes the software configuration management procedures used to ensure that the HotSpot dispersion model meets the requirements of its user base, which includes: (1) Users of the PC version of HotSpot for consequence assessment, hazard assessment and safety analysis calculations; and (2) Users of the NARAC Web and iClient software tools, which allow users to run HotSpot for consequence assessment modeling These users and sponsors of the HotSpot software and the organizations they represent constitute the intended audience for this document. This plan is intended to meet Critical Recommendations 1 and 3 from the Software Evaluation of HotSpot and DOE Safety Software Toolbox Recommendation for inclusion of HotSpot in the Department of Energy (DOE) Safety Software Toolbox. HotSpot software is maintained for the Department of Energy Office of Emergency Operations by the National Atmospheric Release Advisory Center (NARAC) at Lawrence Livermore National Laboratory (LLNL). An overview of HotSpot and NARAC are provided.
Hot Spot Removal System: System description
1997-09-01
Hazardous wastes contaminated with radionuclides, chemicals, and explosives exist across the Department of Energy complex and need to be remediated due to environmental concerns. Currently, an opportunity is being developed to dramatically reduce remediation costs and to assist in the acceleration of schedules associated with these wastes by deploying a Hot Spot Removal System. Removing the hot spot from the waste site will remove risk driver(s) and enable another, more cost effective process/option/remedial alternative (i.e., capping) to be applied to the remainder of the site. The Hot Spot Removal System consists of a suite of technologies that will be utilized to locate and remove source terms. Components of the system can also be used in a variety of other cleanup activities. This Hot Spot Removal System Description document presents technologies that were considered for possible inclusion in the Hot Spot Removal System, technologies made available to the Hot Spot Removal System, industrial interest in the Hot Spot Removal System`s subsystems, the schedule required for the Hot Spot Removal System, the evaluation of the relevant technologies, and the recommendations for equipment and technologies as stated in the Plan section.
Energy Science and Technology Software Center (OSTI)
2007-07-26
The TEVA-SPOT Toolkit (SPOT) supports the design of contaminant warning systems (CWSs) that use real-time sensors to detect contaminants in municipal water distribution networks. Specifically, SPOT provides the capability to select the locations for installing sensors in order to maximize the utility and effectiveness of the CWS. SPOT models the sensor placement process as an optimization problem, and the user can specify a wide range of performance objectives for contaminant warning system design, including populationmore » health effects, time to detection, extent of contamination, volume consumed and number of failed detections. For example, a SPOT user can integrate expert knowledge during the design process by specigying required sensor placements or designating network locations as forbidden. Further, cost considerations can be integrated by limiting the design with user-specified installation costs at each location.« less
Eolica Montes de Cierzo | Open Energy Information
Montes de Cierzo Jump to: navigation, search Name: Eolica Montes de Cierzo Place: Navarra, Spain Sector: Wind energy Product: Spanish wind farm developer in the region of Navarra....
Isotropic Monte Carlo Grain Growth
Energy Science and Technology Software Center (OSTI)
2013-04-25
IMCGG performs Monte Carlo simulations of normal grain growth in metals on a hexagonal grid in two dimensions with periodic boundary conditions. This may be performed with either an isotropic or a misorientation - and incliantion-dependent grain boundary energy.
Volume higher; spot price ranges widen
1994-11-01
This article is the October 1994 uranium market summary. During this reporting period, volume on the spot concentrates market doubled. Twelve deals took place: three in the spot concentrates market, one in the medium and long-term market, four in the conversion market, and four in the enrichment market. The restricted price range widened due to higher prices at the top end of the range, while the unrestricted price range widened because of lower prices at the bottom end. Spot conversion prices were higher, and enrichment prices were unchanged.
,"Weekly Henry Hub Natural Gas Spot Price (Dollars per Million...
U.S. Energy Information Administration (EIA) Indexed Site
Henry Hub Natural Gas Spot Price (Dollars per Million Btu)" ,"Click worksheet name or tab ... Data for" ,"Data 1","Weekly Henry Hub Natural Gas Spot Price (Dollars per ...
Investigations of initiation spot size effects
Clarke, Steven A; Akinci, Adrian A; Leichty, Gary; Schaffer, Timothy; Murphy, Michael J; Munger, Alan; Thomas, Keith A
2010-01-01
As explosive components become smaller, a greater understanding of the effect of initiation spot size on detonation becomes increasingly critical. A series of tests of the effect of initiation spot size will be described. A series of DOI (direct optical initiation) detonators with initiation spots sizes from {approx}50 um to 1000um have been tested to determine laser parameters for threshold firing of low density PETN pressings. Results will be compared with theoretical predictions. Outputs of the initiation source (DOI ablation) have been characterized by a suite of diagnostics including PDV and schlieren imaging. Outputs of complete detonators have been characterized using PDV, streak, and/or schlieren imaging. At present, we have not found the expected change in the threshold energy to spot size relationship for DOI type detonators found in similar earlier for projectiles, slappers and EBWs. New detonators designs (Type C) are currently being tested that will allow the determination of the threshold for spot sizes from 250 um to 105um, where we hope to see change in the threshold vs. spot size relationship. Also, one test of an extremely small diameter spot size (50um) has resulted in preliminary NoGo only results even at energy densities as much as 8 times the energy density of the threshold results presented here. This gives preliminary evidence that 50um spot may be beyond the critical initiation diameter. The constant threshold energy to spot size relationship in the data to date does however still give some insight into the initiation mechanism of DOI detonators. If the DOI initiation mechanism were a 1D mechanism similar to a slapper or a flyer impact, the expected inflection point in the graph would have been between 300um and 500um diameter spot size, within the range of the data presented here. The lack of that inflection point indicates that the DOI initiation mechanism is more likely a 2D mechanism similar to a sphere or rod projectile. We expect to
Energy Science and Technology Software Center (OSTI)
2010-03-02
The HotSpot Health Physics Codes were created to provide emergency response personnel and emergency planners with a fast, field-portable set of software tools for evaluating incidents involving radioactive material. The software is also used for safety-analysis of facilities handling nuclear material. HotSpot provides a fast and usually conservative means for estimation the radiation effects associated with the short-term (less than 24 hours) atmospheric release of radioactive materials.
Energy Science and Technology Software Center (OSTI)
2013-04-18
The HotSpot Health Physics Codes were created to provide emergency response personnel and emergency planners with a fast, field-portable set of software tools for evaluating insidents involving redioactive material. The software is also used for safety-analysis of facilities handling nuclear material. HotSpot provides a fast and usually conservative means for estimation the radiation effects associated with the short-term (less than 24 hours) atmospheric release of radioactive materials.
Optimized nested Markov chain Monte Carlo sampling: theory (Conference...
Office of Scientific and Technical Information (OSTI)
Optimized nested Markov chain Monte Carlo sampling: theory Citation Details In-Document Search Title: Optimized nested Markov chain Monte Carlo sampling: theory Metropolis Monte ...
Exact Monte Carlo for molecules
Lester, W.A. Jr.; Reynolds, P.J.
1985-03-01
A brief summary of the fixed-node quantum Monte Carlo method is presented. Results obtained for binding energies, the classical barrier height for H + H2, and the singlet-triplet splitting in methylene are presented and discussed. 17 refs.
ATS Spotted MSI Analysis with Matlab
Energy Science and Technology Software Center (OSTI)
2012-02-09
Samples are placed on a surface using an acoustic transfer system (ATS). This results in one ore more small droplets on a surface. Typically there are hundreds to thousands of these droplets arrayed in a regular coordinate system. The surface is analyzed using mass spectrometry imaging (MSI) and at each position, one or more mass spectra are recorded. The purpose of the software is to help the user assign locations to the spots and buildmore » a report for each spot.« less
Mont Vista Capital LLC | Open Energy Information
Vista Capital LLC Jump to: navigation, search Name: Mont Vista Capital LLC Place: New York, New York Zip: 10167 Sector: Services Product: Mont Vista Capital is a leading global...
Monte Carlo Simulations of APEX
Xu, G.
1995-10-01
Monte Carlo simulationsof the APEX apparatus, a spectrometer designed to meausre positron-electron pairs produced in heavy-ion collisions, carried out using GEANT are reported. The results of these simulations are compared with data from measurements of conversion electron, positron and part emitting sources as well as with the results of in-beam measurements of positrons and electrons. The overall description of the performance of the apparatus is excellent.
Friction Stir Spot Welding of Advanced High Strength Steels II...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
Friction Stir Spot Welding of Advanced High Strength Steels II Friction Stir Spot Welding of Advanced High Strength Steels II 2011 DOE Hydrogen and Fuel Cells Program, and Vehicle ...
Solar Renewable Energy Credits (SRECs) Spot Market Program
Broader source: Energy.gov [DOE]
NOTE: While interested parties can still trade DE SRECs in the spot market, the spot market in itself is limited since most of the SRECs produced are part of the SREC Purchase Program, or the SREC...
Fermi surface topology and hot spot distribution in the Kondo...
Office of Scientific and Technical Information (OSTI)
Fermi surface topology and hot spot distribution in the Kondo lattice system CeB 6 ... September 17, 2016 Title: Fermi surface topology and hot spot distribution in the Kondo ...
,"Henry Hub Natural Gas Spot Price (Dollars per Million Btu)...
U.S. Energy Information Administration (EIA) Indexed Site
12:23:06 PM" "Back to Contents","Data 1: Henry Hub Natural Gas Spot Price (Dollars per Million Btu)" "Sourcekey","RNGWHHD" "Date","Henry Hub Natural Gas Spot Price (Dollars per ...
,"Henry Hub Natural Gas Spot Price (Dollars per Million Btu)...
U.S. Energy Information Administration (EIA) Indexed Site
12:23:08 PM" "Back to Contents","Data 1: Henry Hub Natural Gas Spot Price (Dollars per Million Btu)" "Sourcekey","RNGWHHD" "Date","Henry Hub Natural Gas Spot Price (Dollars per ...
,"Henry Hub Natural Gas Spot Price (Dollars per Million Btu)...
U.S. Energy Information Administration (EIA) Indexed Site
12:23:12 PM" "Back to Contents","Data 1: Henry Hub Natural Gas Spot Price (Dollars per Million Btu)" "Sourcekey","RNGWHHD" "Date","Henry Hub Natural Gas Spot Price (Dollars per ...
Sweet Spot Supersymmetry and Composite Messengers
Ibe, Masahiro; Kitano, Ryuichiro
2007-10-30
Sweet spot supersymmetry is a phenomenologically and cosmologically perfect framework to realize a supersymmetric world at short distance. We discuss a class of dynamical models of supersymmetry breaking and its mediation whose low-energy effective description falls into this framework. Hadron fields in the dynamical models play a role of the messengers of the supersymmetry breaking. As is always true in the models of the sweet spot supersymmetry, the messenger scale is predicted to be 10{sup 5} GeV {approx}< M{sub mess} {approx}< 10{sup 10} GeV. Various values of the effective number of messenger fields N{sub mess} are possible depending on the choice of the gauge group.
Friction Stir Spot Welding of Advanced High Strength Steels
Hovanski, Yuri; Grant, Glenn J.; Santella, M. L.
2009-11-13
Friction stir spot welding techniques were developed to successfully join several advanced high strength steels. Two distinct tool materials were evaluated to determine the effect of tool materials on the process parameters and joint properties. Welds were characterized primarily via lap shear, microhardness, and optical microscopy. Friction stir spot welds were compared to the resistance spot welds in similar strength alloys by using the AWS standard for resistance spot welding high strength steels. As further comparison, a primitive cost comparison between the two joining processes was developed, which included an evaluation of the future cost prospects of friction stir spot welding in advanced high strength steels.
Energy Monte Carlo (EMCEE) | Open Energy Information
with a specific set of distributions. Both programs run as spreadsheet workbooks in Microsoft Excel. EMCEE and Emc2 require Crystal Ball, a commercially available Monte Carlo...
Spot market volume sluggish in October
1995-11-01
This article is the October 1995 uranium market summary. Spot market volume reached a meager 116,000 lbs of U3O8 and equivalent. The restricted price range increased from September`s high end of $11.75 to $12.00. The unrestricted range also increased with September`s high end of $9.65 as October`s low end and a high of $9.80. Conversion prices have held steady the past few months. However, the SWU price range increased this month to a high of $97.00.
Monte%20Carlo.jpg | OSTI, US Dept of Energy Office of Scientific and
Office of Scientific and Technical Information (OSTI)
Technical Information Monte%20Carlo
Optimal sampling efficiency in Monte Carlo sampling with an approximat...
Office of Scientific and Technical Information (OSTI)
Journal Article: Optimal sampling efficiency in Monte Carlo sampling with an approximate potential Citation Details In-Document Search Title: Optimal sampling efficiency in Monte ...
A hybrid Monte Carlo method for equilibrium equation of state...
Office of Scientific and Technical Information (OSTI)
MONTE CARLO SIMULATION METHODS Benchmark for perturbation theory methods NPT, NVT - single ... EXPLOSIVES; MIXTURES; MONTE CARLO METHOD; PERTURBATION THEORY; SHOCK WAVES; SIMULATION
Jefferson Lab finds its man Mont (Inside Business) | Jefferson...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
https:www.jlab.orgnewsarticlesjefferson-lab-finds-its-man-mont-inside-business Jefferson Lab finds its man Mont Hugh Montgomery Hugh Montgomery, a British nuclear physicist...
Monte-Carlo particle dynamics in a variable specific impulse...
Office of Scientific and Technical Information (OSTI)
Monte-Carlo particle dynamics in a variable specific impulse magnetoplasma rocket Citation Details In-Document Search Title: Monte-Carlo particle dynamics in a variable specific ...
Applications of FLUKA Monte Carlo Code for Nuclear and Accelerator...
Office of Scientific and Technical Information (OSTI)
Applications of FLUKA Monte Carlo Code for Nuclear and Accelerator Physics Citation Details In-Document Search Title: Applications of FLUKA Monte Carlo Code for Nuclear and ...
Fundamentals of Monte Carlo (Technical Report) | SciTech Connect
Office of Scientific and Technical Information (OSTI)
Fundamentals of Monte Carlo Citation Details In-Document Search Title: Fundamentals of Monte Carlo Authors: Wollaber, Allan Benton 1 + Show Author Affiliations Los Alamos ...
Monte Carlo Ion Transport Analysis Code.
Energy Science and Technology Software Center (OSTI)
2009-04-15
Version: 00 TRIPOS is a versatile Monte Carlo ion transport analysis code. It has been applied to the treatment of both surface and bulk radiation effects. The media considered is composed of multilayer polyatomic materials.
Improved Monte Carlo Renormalization Group Method
DOE R&D Accomplishments [OSTI]
Gupta, R.; Wilson, K. G.; Umrigar, C.
1985-01-01
An extensive program to analyze critical systems using an Improved Monte Carlo Renormalization Group Method (IMCRG) being undertaken at LANL and Cornell is described. Here we first briefly review the method and then list some of the topics being investigated.
Friction Stir Spot Welding of DP780 Carbon Steel
Santella, M. L.; Hovanski, Yuri; Frederick, Alan; Grant, Glenn J.; Dahl, Michael E.
2009-09-15
Friction stir spot welds were made in uncoated and galvannneled DP780 sheets using polycrystalline boron nitride stir tools. The tools were plunged at either a single continuous rate or in two segments consisting of a relatively high rate followed by a slower rate of shorter depth. Welding times ranged from 1-10 s. Increasing tool rotation speed from 800 to 1600 rpm increased strength values. The 2-segment welding procedures also produced higher strength joints. Average lap-shear strengths exceeding 10.3 kN were consistently obtained in 4 s on both the uncoated and the galvannealed DP780. The likelihood of diffusion and mechanical interlocking contributing to bond formation was supported by metallographic examinations. A cost analysis based on spot welding in automobile assembly showed that for friction stir spot welding to be economically competitive with resistance spot welding the cost of stir tools must approach that of resistance spot welding electrode tips.
Finite Cosmology and a CMB Cold Spot
Adler, R.J.; Bjorken, J.D.; Overduin, J.M.; /Stanford U., HEPL
2006-03-20
The standard cosmological model posits a spatially flat universe of infinite extent. However, no observation, even in principle, could verify that the matter extends to infinity. In this work we model the universe as a finite spherical ball of dust and dark energy, and obtain a lower limit estimate of its mass and present size: the mass is at least 5 x 10{sup 23}M{sub {circle_dot}} and the present radius is at least 50 Gly. If we are not too far from the dust-ball edge we might expect to see a cold spot in the cosmic microwave background, and there might be suppression of the low multipoles in the angular power spectrum. Thus the model may be testable, at least in principle. We also obtain and discuss the geometry exterior to the dust ball; it is Schwarzschild-de Sitter with a naked singularity, and provides an interesting picture of cosmogenesis. Finally we briefly sketch how radiation and inflation eras may be incorporated into the model.
Hot spot-ridge crest convergence in the northeast Pacific
Karsten, J.L.; Delaney, J.R. )
1989-01-10
Evolution of the Juan de Fuca Ridge during the past 7 m.y. has been reconstructed taking into account both the propagating rift history and migration of the spreading center in the 'absolute' (fixed hot spot) reference frame. Northwestward migration of the spreading center (at a rate of 30 km/m.y.) has resulted in progressive encroachment of the ridge axis on the Cobb Hot Spot and westward jumping of the central third of the ridge axis more recently than 0.5 Ma. Seamounts in the Cobb-Eickelberg chain are predicted to display systematic variations in morphology and petrology, and a reduction in the age contrast between the edifice and underlying crust, as a result of the ridge axis approach. Relative seamount volumes also indicate that magmatic output of the hot spot varied during this interval, with a reduction in activity between 2.5 and 4.5 Ma, compared with relatively more robust activity before and after this period. Spatial relationships determined in this reconstruction allow hypotheses relating hot spot activity and rift propagation to be evaluated. In most cases, rift propagation has been directed away from the hot spot during the time period considered. Individual propagators show some reduction in propagation rate as separation between the propagating rift tip and hot spot increases, but cross comparison of multiple propagators does not uniformly display the same relationship. No obvious correlation exists between propagation rate and increasing proximity of the hot spot to the ridge axis or increasing hot spot output. Taken together, these observations do not offer compelling support for the concept of hot spot driven rift propagation. However, short-term reversals in propagation direction at the Cobb Offset coincide with activity of the Heckle melting anomaly, suggesting that local propagation effects may be related to excess magma supply at the ridge axis.
Wall and laser spot motion in cylindrical hohlraums
Huser, G.; Courtois, C.; Monteil, M.-C.
2009-03-15
Wall and laser spot motion measurements in empty, propane-filled and plastic (CH)-lined gold coated cylindrical hohlraums were performed on the Omega laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Wall motion was measured using axial two-dimensional (2D) x-ray imaging and laser spot motion was perpendicularly observed through a thinned wall using streaked hard x-ray imaging. Experimental results and 2D hydrodynamic simulations show that while empty targets exhibit on-axis plasma collision, CH-lined and propane-filled targets inhibit wall expansion, corroborated with perpendicular streaked imaging showing a slower motion of laser spots.
Forecasting Crude Oil Spot Price Using OECD Petroleum Inventory Levels
Reports and Publications (EIA)
2003-01-01
This paper presents a short-term monthly forecasting model of West Texas Intermediate crude oil spot price using Organization for Economic Cooperation and Development (OECD) petroleum inventory levels.
Unique Bioreactor Finds Algae's Sweet Spot - News Feature | NREL
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Unique Bioreactor Finds Algae's Sweet Spot February 18, 2014 Close-up photo of a vial of green algae. Enlarge image Aeration helps algae grow and helps replicate real-life ...
Portsmouth Training Exercise Helps Radiological Trainees Spot Mistakes
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
Safely | Department of Energy Portsmouth Training Exercise Helps Radiological Trainees Spot Mistakes Safely Portsmouth Training Exercise Helps Radiological Trainees Spot Mistakes Safely February 11, 2016 - 12:10pm Addthis Connie Martin performs work inside the Error Lab while trainees observe her actions for mistakes. Connie Martin performs work inside the Error Lab while trainees observe her actions for mistakes. Lorrie Graham (left) talks with trainees in a classroom setting before
On the burn topology of hot-spot-initiated reactions
Hill, Larry G; Zimmermann, Bjorn; Nichols, Albert L
2009-01-01
We determine the reaction progress function for an ideal hot spot model problem. The considered problem has an exact analytic solution that can derived from a reduction of Nichols statistical hot spot model. We perform numerical calculations to verify the analytic solution and to illustrate the error realized in real, finite systems. We show how the baseline problem, which does not distinguish between the reactant and product densities, can be scaled to handle general cases for which the two densities differ.
Jefferson Lab Medical Imager Spots Breast Cancer | Jefferson Lab
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Medical Imager Spots Breast Cancer PEM This PEM image shows two cancerous lesions. The one on the right was depicted by conventional mammography, but the one on the left was only identified by the PEM unit. Image courtesy: Eric Rosen, Duke University Medical Center Jefferson Lab Medical Imager Spots Breast Cancer March 3, 2005 Newport News, VA - A study published in the February issue of the journal Radiology shows that a positron emission mammography (PEM) device designed and built by Jefferson
Imager Spots and Samples Tiny Tumors | Jefferson Lab
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Imager Spots and Samples Tiny Tumors Imager Spots and Samples Tiny Tumors NEWPORT NEWS, Va. Feb. 8, 2008 -- The positron emission mammography/tomography breast imaging and biopsy system was designed and constructed by scientists at Jefferson Lab, West Virginia University and the University of Maryland School of Medicine. The PEM/PET system is designed for detecting and guiding the biopsies of suspicious breast cancer lesions. "This is the most-important and most-difficult imager we've
Wang, Dongxu Dirksen, Blake; Hyer, Daniel E.; Buatti, John M.; Sheybani, Arshin; Dinges, Eric; Felderman, Nicole; TenNapel, Mindi; Bayouth, John E.; Flynn, Ryan T.
2014-12-15
Purpose: To determine the plan quality of proton spot scanning (SS) radiosurgery as a function of spot size (in-air sigma) in comparison to x-ray radiosurgery for treating peripheral brain lesions. Methods: Single-field optimized (SFO) proton SS plans with sigma ranging from 1 to 8 mm, cone-based x-ray radiosurgery (Cone), and x-ray volumetric modulated arc therapy (VMAT) plans were generated for 11 patients. Plans were evaluated using secondary cancer risk and brain necrosis normal tissue complication probability (NTCP). Results: For all patients, secondary cancer is a negligible risk compared to brain necrosis NTCP. Secondary cancer risk was lower in proton SS plans than in photon plans regardless of spot size (p = 0.001). Brain necrosis NTCP increased monotonically from an average of 2.34/100 (range 0.42/100–4.49/100) to 6.05/100 (range 1.38/100–11.6/100) as sigma increased from 1 to 8 mm, compared to the average of 6.01/100 (range 0.82/100–11.5/100) for Cone and 5.22/100 (range 1.37/100–8.00/100) for VMAT. An in-air sigma less than 4.3 mm was required for proton SS plans to reduce NTCP over photon techniques for the cohort of patients studied with statistical significance (p = 0.0186). Proton SS plans with in-air sigma larger than 7.1 mm had significantly greater brain necrosis NTCP than photon techniques (p = 0.0322). Conclusions: For treating peripheral brain lesions—where proton therapy would be expected to have the greatest depth-dose advantage over photon therapy—the lateral penumbra strongly impacts the SS plan quality relative to photon techniques: proton beamlet sigma at patient surface must be small (<7.1 mm for three-beam single-field optimized SS plans) in order to achieve comparable or smaller brain necrosis NTCP relative to photon radiosurgery techniques. Achieving such small in-air sigma values at low energy (<70 MeV) is a major technological challenge in commercially available proton therapy systems.
Friction Stir Spot Welding of DP780 Carbon Steel
Santella, Michael L [ORNL; Hovanski, Yuri [ORNL; Frederick, David Alan [ORNL; Grant, Glenn J [ORNL; Dahl, Michael E [ORNL
2010-01-01
Friction stir spot welds were made in uncoated and galvannealed DP780 sheets using polycrystalline boron nitride stir tools. The tools were plunged at either a single continuous rate or in two segments consisting of a relatively high rate followed by a slower rate of shorter depth. Welding times ranged from 1 to 10 s. Increasing tool rotation speed from 800 to 1600 rev min{sup -1} increased strength values. The 2-segment welding procedures also produced higher strength joints. Average lap shear strengths exceeding 10 {center_dot} 3 kN were consistently obtained in 4 s on both the uncoated and the galvannealed DP780. The likelihood of diffusion and mechanical interlocking contributing to bond formation was supported by metallographic examinations. A cost analysis based on spot welding in automobile assembly showed that for friction stir spot welding to be economically competitive with resistance spot welding the cost of stir tools must approach that of resistance spot welding electrode tips.
Quantum Monte Carlo by message passing
Bonca, J.; Gubernatis, J.E.
1993-01-01
We summarize results of quantum Monte Carlo simulations of the degenerate single-impurity Anderson model using the impurity algorithm of Hirsch and Fye. Using methods of Bayesian statistical inference, coupled with the principle of maximum entropy, we extracted the single-particle spectral density from the imaginary-time Green's function. The variations of resulting spectral densities with model parameters agree qualitatively with the spectral densities predicted by NCA calculations. All the simulations were performed on a cluster of 16 IBM R6000/560 workstations under the control of the message-passing software PVM. We described the trivial parallelization of our quantum Monte Carlo code both for the cluster and the CM-5 computer. Other issues for effective parallelization of the impurity algorithm are also discussed.
Quantum Monte Carlo by message passing
Bonca, J.; Gubernatis, J.E.
1993-05-01
We summarize results of quantum Monte Carlo simulations of the degenerate single-impurity Anderson model using the impurity algorithm of Hirsch and Fye. Using methods of Bayesian statistical inference, coupled with the principle of maximum entropy, we extracted the single-particle spectral density from the imaginary-time Green`s function. The variations of resulting spectral densities with model parameters agree qualitatively with the spectral densities predicted by NCA calculations. All the simulations were performed on a cluster of 16 IBM R6000/560 workstations under the control of the message-passing software PVM. We described the trivial parallelization of our quantum Monte Carlo code both for the cluster and the CM-5 computer. Other issues for effective parallelization of the impurity algorithm are also discussed.
FRICTION STIR SPOT WELDING OF 6016 ALUMINUM ALLOY
Mishra, Rajiv S.; Webb, S.; Freeney, T. A.; Chen, Y. L.; Gayden, X.; Grant, Glenn J.; Herling, Darrell R.
2007-01-08
Friction stir spot welding (FSSW) of 6016 aluminum alloy was evaluated with conventional pin tool and new off-center feature tools. The off-center feature tool provides significant control over the joint area. The tool rotation rate was varied between 1000 and 2500 rpm. Maximum failure strength was observed in the tool rotation range of 1200-1500 rpm. The results are interpreted in the context of material flow in the joint and influence of thermal input on microstructural changes. The off-center feature tool concept opens up new possibilities for plunge-type friction stir spot welding.
Four decades of implicit Monte Carlo
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Wollaber, Allan B.
2016-04-25
In 1971, Fleck and Cummings derived a system of equations to enable robust Monte Carlo simulations of time-dependent, thermal radiative transfer problems. Denoted the “Implicit Monte Carlo” (IMC) equations, their solution remains the de facto standard of high-fidelity radiative transfer simulations. Over the course of 44 years, their numerical properties have become better understood, and accuracy enhancements, novel acceleration methods, and variance reduction techniques have been suggested. In this review, we rederive the IMC equations—explicitly highlighting assumptions as they are made—and outfit the equations with a Monte Carlo interpretation. We put the IMC equations in context with other approximate formsmore » of the radiative transfer equations and present a new demonstration of their equivalence to another well-used linearization solved with deterministic transport methods for frequency-independent problems. We discuss physical and numerical limitations of the IMC equations for asymptotically small time steps, stability characteristics and the potential of maximum principle violations for large time steps, and solution behaviors in an asymptotically thick diffusive limit. We provide a new stability analysis for opacities with general monomial dependence on temperature. Here, we consider spatial accuracy limitations of the IMC equations and discussion acceleration and variance reduction techniques.« less
REAL TIME ULTRASONIC ALUMINUM SPOT WELD MONITORING SYSTEM
Regalado, W. Perez; Chertov, A. M.; Maev, R. Gr.
2010-02-22
Aluminum alloys pose several properties that make them one of the most popular engineering materials: they have excellent corrosion resistance, and high weight-to-strength ratio. Resistance spot welding of aluminum alloys is widely used today but oxide film and aluminum thermal and electrical properties make spot welding a difficult task. Electrode degradation due to pitting, alloying and mushrooming decreases the weld quality and adjustment of parameters like current and force is required. To realize these adjustments and ensure weld quality, a tool to measure weld quality in real time is required. In this paper, a real time ultrasonic non-destructive evaluation system for aluminum spot welds is presented. The system is able to monitor nugget growth while the spot weld is being made. This is achieved by interpreting the echoes of an ultrasound transducer located in one of the welding electrodes. The transducer receives and transmits an ultrasound signal at different times during the welding cycle. Valuable information of the weld quality is embedded in this signal. The system is able to determine the weld nugget diameter by measuring the delays of the ultrasound signals received during the complete welding cycle. The article presents the system performance on aluminum alloy AA6022.
Status of Monte-Carlo Event Generators
Hoeche, Stefan; /SLAC
2011-08-11
Recent progress on general-purpose Monte-Carlo event generators is reviewed with emphasis on the simulation of hard QCD processes and subsequent parton cascades. Describing full final states of high-energy particle collisions in contemporary experiments is an intricate task. Hundreds of particles are typically produced, and the reactions involve both large and small momentum transfer. The high-dimensional phase space makes an exact solution of the problem impossible. Instead, one typically resorts to regarding events as factorized into different steps, ordered descending in the mass scales or invariant momentum transfers which are involved. In this picture, a hard interaction, described through fixed-order perturbation theory, is followed by multiple Bremsstrahlung emissions off initial- and final-state and, finally, by the hadronization process, which binds QCD partons into color-neutral hadrons. Each of these steps can be treated independently, which is the basic concept inherent to general-purpose event generators. Their development is nowadays often focused on an improved description of radiative corrections to hard processes through perturbative QCD. In this context, the concept of jets is introduced, which allows to relate sprays of hadronic particles in detectors to the partons in perturbation theory. In this talk, we briefly review recent progress on perturbative QCD in event generation. The main focus lies on the general-purpose Monte-Carlo programs HERWIG, PYTHIA and SHERPA, which will be the workhorses for LHC phenomenology. A detailed description of the physics models included in these generators can be found in [8]. We also discuss matrix-element generators, which provide the parton-level input for general-purpose Monte Carlo.
Monte Carlo simulation for the transport beamline
Romano, F.; Cuttone, G.; Jia, S. B.; Varisano, A.; Attili, A.; Marchetto, F.; Russo, G.; Cirrone, G. A. P.; Schillaci, F.; Scuderi, V.; Carpinelli, M.
2013-07-26
In the framework of the ELIMED project, Monte Carlo (MC) simulations are widely used to study the physical transport of charged particles generated by laser-target interactions and to preliminarily evaluate fluence and dose distributions. An energy selection system and the experimental setup for the TARANIS laser facility in Belfast (UK) have been already simulated with the GEANT4 (GEometry ANd Tracking) MC toolkit. Preliminary results are reported here. Future developments are planned to implement a MC based 3D treatment planning in order to optimize shots number and dose delivery.
A Monte Carlo algorithm for degenerate plasmas
Turrell, A.E. Sherlock, M.; Rose, S.J.
2013-09-15
A procedure for performing Monte Carlo calculations of plasmas with an arbitrary level of degeneracy is outlined. It has possible applications in inertial confinement fusion and astrophysics. Degenerate particles are initialised according to the FermiDirac distribution function, and scattering is via a Pauli blocked binary collision approximation. The algorithm is tested against degenerate electronion equilibration, and the degenerate resistivity transport coefficient from unmagnetised first order transport theory. The code is applied to the cold fuel shell and alpha particle equilibration problem of inertial confinement fusion.
Avoiding Carbon Bed Hot Spots in Thermal Process Off-Gas Systems...
Office of Scientific and Technical Information (OSTI)
Avoiding Carbon Bed Hot Spots in Thermal Process Off-Gas Systems Citation Details In-Document Search Title: Avoiding Carbon Bed Hot Spots in Thermal Process Off-Gas Systems You ...
Avoiding Carbon Bed Hot Spots in Thermal Process Off-Gas Systems...
Office of Scientific and Technical Information (OSTI)
Conference: Avoiding Carbon Bed Hot Spots in Thermal Process Off-Gas Systems Citation Details In-Document Search Title: Avoiding Carbon Bed Hot Spots in Thermal Process Off-Gas ...
Cluster expansion modeling and Monte Carlo simulation of alnico...
Office of Scientific and Technical Information (OSTI)
Accepted Manuscript: Cluster expansion modeling and Monte Carlo simulation of alnico 5-7 permanent magnets This content will become publicly available on March 5, 2016 Prev Next...
Mont Vernon, New Hampshire: Energy Resources | Open Energy Information
Mont Vernon, New Hampshire: Energy Resources Jump to: navigation, search Equivalent URI DBpedia Coordinates 42.8945294, -71.6742393 Show Map Loading map......
Evaluation of Monte Carlo Electron-Transport Algorithms in the...
Office of Scientific and Technical Information (OSTI)
Series Codes for Stochastic-Media Simulations. Citation Details In-Document Search Title: Evaluation of Monte Carlo Electron-Transport Algorithms in the Integrated Tiger Series ...
Quantum Monte Carlo Calculations of Light Nuclei Using Chiral...
Office of Scientific and Technical Information (OSTI)
Title: Quantum Monte Carlo Calculations of Light Nuclei Using Chiral Potentials Authors: Lynn, J. E. ; Carlson, J. ; Epelbaum, E. ; Gandolfi, S. ; Gezerlis, A. ; Schwenk, A. ...
South El Monte, California: Energy Resources | Open Energy Information
El Monte, California: Energy Resources Jump to: navigation, search Equivalent URI DBpedia Coordinates 34.0519548, -118.0467339 Show Map Loading map... "minzoom":false,"mapping...
North El Monte, California: Energy Resources | Open Energy Information
El Monte, California: Energy Resources Jump to: navigation, search Equivalent URI DBpedia Coordinates 34.1027861, -118.0242333 Show Map Loading map... "minzoom":false,"mapping...
Molecular Monte Carlo Simulations Using Graphics Processing Units...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
allocation of the GPU hardware resources. We make comparisons between the GPU and the serial CPU Monte Carlo implementations to assess speedup over conventional microprocessors....
HILO: Quasi Diffusion Accelerated Monte Carlo on Hybrid Architectures
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
fidelity simulation of a diverse range of kinetic systems. Available for thumbnail of Feynman Center (505) 665-9090 Email HILO: Quasi Diffusion Accelerated Monte Carlo on Hybrid...
Quantum Monte Carlo methods for nuclear physics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Carlson, Joseph A.; Gandolfi, Stefano; Pederiva, Francesco; Pieper, Steven C.; Schiavilla, Rocco; Schmidt, K. E,; Wiringa, Robert B.
2014-10-19
Quantum Monte Carlo methods have proved very valuable to study the structure and reactions of light nuclei and nucleonic matter starting from realistic nuclear interactions and currents. These ab-initio calculations reproduce many low-lying states, moments and transitions in light nuclei, and simultaneously predict many properties of light nuclei and neutron matter over a rather wide range of energy and momenta. We review the nuclear interactions and currents, and describe the continuum Quantum Monte Carlo methods used in nuclear physics. These methods are similar to those used in condensed matter and electronic structure but naturally include spin-isospin, tensor, spin-orbit, and three-bodymore » interactions. We present a variety of results including the low-lying spectra of light nuclei, nuclear form factors, and transition matrix elements. We also describe low-energy scattering techniques, studies of the electroweak response of nuclei relevant in electron and neutrino scattering, and the properties of dense nucleonic matter as found in neutron stars. A coherent picture of nuclear structure and dynamics emerges based upon rather simple but realistic interactions and currents.« less
Quantum Monte Carlo methods for nuclear physics
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Carlson, J.; Gandolfi, S.; Pederiva, F.; Pieper, Steven C.; Schiavilla, R.; Schmidt, K. E.; Wiringa, R. B.
2015-09-09
Quantum Monte Carlo methods have proved valuable to study the structure and reactions of light nuclei and nucleonic matter starting from realistic nuclear interactions and currents. These ab-initio calculations reproduce many low-lying states, moments, and transitions in light nuclei, and simultaneously predict many properties of light nuclei and neutron matter over a rather wide range of energy and momenta. The nuclear interactions and currents are reviewed along with a description of the continuum quantum Monte Carlo methods used in nuclear physics. These methods are similar to those used in condensed matter and electronic structure but naturally include spin-isospin, tensor, spin-orbit,more » and three-body interactions. A variety of results are presented, including the low-lying spectra of light nuclei, nuclear form factors, and transition matrix elements. Low-energy scattering techniques, studies of the electroweak response of nuclei relevant in electron and neutrino scattering, and the properties of dense nucleonic matter as found in neutron stars are also described. Furthermore, a coherent picture of nuclear structure and dynamics emerges based upon rather simple but realistic interactions and currents.« less
Quantum Monte Carlo methods for nuclear physics
Carlson, J.; Gandolfi, S.; Pederiva, F.; Pieper, Steven C.; Schiavilla, R.; Schmidt, K. E.; Wiringa, R. B.
2015-09-09
Quantum Monte Carlo methods have proved valuable to study the structure and reactions of light nuclei and nucleonic matter starting from realistic nuclear interactions and currents. These ab-initio calculations reproduce many low-lying states, moments, and transitions in light nuclei, and simultaneously predict many properties of light nuclei and neutron matter over a rather wide range of energy and momenta. The nuclear interactions and currents are reviewed along with a description of the continuum quantum Monte Carlo methods used in nuclear physics. These methods are similar to those used in condensed matter and electronic structure but naturally include spin-isospin, tensor, spin-orbit, and three-body interactions. A variety of results are presented, including the low-lying spectra of light nuclei, nuclear form factors, and transition matrix elements. Low-energy scattering techniques, studies of the electroweak response of nuclei relevant in electron and neutrino scattering, and the properties of dense nucleonic matter as found in neutron stars are also described. Furthermore, a coherent picture of nuclear structure and dynamics emerges based upon rather simple but realistic interactions and currents.
Quantum Monte Carlo methods for nuclear physics
Carlson, Joseph A.; Gandolfi, Stefano; Pederiva, Francesco; Pieper, Steven C.; Schiavilla, Rocco; Schmidt, K. E,; Wiringa, Robert B.
2014-10-19
Quantum Monte Carlo methods have proved very valuable to study the structure and reactions of light nuclei and nucleonic matter starting from realistic nuclear interactions and currents. These ab-initio calculations reproduce many low-lying states, moments and transitions in light nuclei, and simultaneously predict many properties of light nuclei and neutron matter over a rather wide range of energy and momenta. We review the nuclear interactions and currents, and describe the continuum Quantum Monte Carlo methods used in nuclear physics. These methods are similar to those used in condensed matter and electronic structure but naturally include spin-isospin, tensor, spin-orbit, and three-body interactions. We present a variety of results including the low-lying spectra of light nuclei, nuclear form factors, and transition matrix elements. We also describe low-energy scattering techniques, studies of the electroweak response of nuclei relevant in electron and neutrino scattering, and the properties of dense nucleonic matter as found in neutron stars. A coherent picture of nuclear structure and dynamics emerges based upon rather simple but realistic interactions and currents.
THE MCNPX MONTE CARLO RADIATION TRANSPORT CODE
WATERS, LAURIE S.; MCKINNEY, GREGG W.; DURKEE, JOE W.; FENSIN, MICHAEL L.; JAMES, MICHAEL R.; JOHNS, RUSSELL C.; PELOWITZ, DENISE B.
2007-01-10
MCNPX (Monte Carlo N-Particle eXtended) is a general-purpose Monte Carlo radiation transport code with three-dimensional geometry and continuous-energy transport of 34 particles and light ions. It contains flexible source and tally options, interactive graphics, and support for both sequential and multi-processing computer platforms. MCNPX is based on MCNP4B, and has been upgraded to most MCNP5 capabilities. MCNP is a highly stable code tracking neutrons, photons and electrons, and using evaluated nuclear data libraries for low-energy interaction probabilities. MCNPX has extended this base to a comprehensive set of particles and light ions, with heavy ion transport in development. Models have been included to calculate interaction probabilities when libraries are not available. Recent additions focus on the time evolution of residual nuclei decay, allowing calculation of transmutation and delayed particle emission. MCNPX is now a code of great dynamic range, and the excellent neutronics capabilities allow new opportunities to simulate devices of interest to experimental particle physics; particularly calorimetry. This paper describes the capabilities of the current MCNPX version 2.6.C, and also discusses ongoing code development.
Multilevel Monte Carlo simulation of Coulomb collisions
Rosin, M.S.; Ricketson, L.F.; Dimits, A.M.; Caflisch, R.E.; Cohen, B.I.
2014-10-01
We present a new, for plasma physics, highly efficient multilevel Monte Carlo numerical method for simulating Coulomb collisions. The method separates and optimally minimizes the finite-timestep and finite-sampling errors inherent in the Langevin representation of the Landau–Fokker–Planck equation. It does so by combining multiple solutions to the underlying equations with varying numbers of timesteps. For a desired level of accuracy ε, the computational cost of the method is O(ε{sup −2}) or O(ε{sup −2}(lnε){sup 2}), depending on the underlying discretization, Milstein or Euler–Maruyama respectively. This is to be contrasted with a cost of O(ε{sup −3}) for direct simulation Monte Carlo or binary collision methods. We successfully demonstrate the method with a classic beam diffusion test case in 2D, making use of the Lévy area approximation for the correlated Milstein cross terms, and generating a computational saving of a factor of 100 for ε=10{sup −5}. We discuss the importance of the method for problems in which collisions constitute the computational rate limiting step, and its limitations.
X-ray focal spot locating apparatus and method
Gilbert, Hubert W.
1985-07-30
An X-ray beam finder for locating a focal spot of an X-ray tube includes a mass of X-ray opaque material having first and second axially-aligned, parallel-opposed faces connected by a plurality of substantially identical parallel holes perpendicular to the faces and a film holder for holding X-ray sensitive film tightly against one face while the other face is placed in contact with the window of an X-ray head.
Texas students win regional National Science Bowl competition, secure spot
National Nuclear Security Administration (NNSA)
in finals in nation's capital | National Nuclear Security Administration | (NNSA) Texas students win regional National Science Bowl competition, secure spot in finals in nation's capital Monday, March 21, 2016 - 10:22am NPO's Mark Padilla congratulates the winning Amarillo High School Team Black with their victory at the Pantex Science Bowl 2016. More than 200 students from 37 from High schools across the Texas Panhandle gathered together with a few hundred volunteers for a meeting and
The Information Role of Spot Prices and Inventories
U.S. Energy Information Administration (EIA) Indexed Site
Information Role of Spot Prices and Inventories James L. Smith, Rex Thompson, and Thomas Lee June 24, 2014 Independent Statistics & Analysis www.eia.gov U.S. Energy Information Administration Washington, DC 20585 This paper is released to encourage discussion and critical comment. The analysis and conclusions expressed here are those of the authors and not necessarily those of the U.S. Energy Information Administration. WORKING PAPER SERIES June 2014 James L. Smith, Rex Thomas, and Thomas K.
Price convergence in North America natural gas spot markets
King, M.; Cuc, M.
1996-12-01
Government policy changes and subsequent regulatory actions in Canada and the United States (US) in the mid-1980s led to effective deregulation of the commodity market for natural gas. This was done by price deregulation, unbundling of pipeline services, and the fostering of a competitive market through equal and open access to pipeline transportation capacity by all suppliers and users. This paper attempts to measure the degree of price convergence in the North American natural gas spot markets. 38 refs.
Exploring theory space with Monte Carlo reweighting
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Gainer, James S.; Lykken, Joseph; Matchev, Konstantin T.; Mrenna, Stephen; Park, Myeonghun
2014-10-13
Theories of new physics often involve a large number of unknown parameters which need to be scanned. Additionally, a putative signal in a particular channel may be due to a variety of distinct models of new physics. This makes experimental attempts to constrain the parameter space of motivated new physics models with a high degree of generality quite challenging. We describe how the reweighting of events may allow this challenge to be met, as fully simulated Monte Carlo samples generated for arbitrary benchmark models can be effectively re-used. Specifically, we suggest procedures that allow more efficient collaboration between theorists andmore » experimentalists in exploring large theory parameter spaces in a rigorous way at the LHC.« less
Exploring theory space with Monte Carlo reweighting
Gainer, James S.; Lykken, Joseph; Matchev, Konstantin T.; Mrenna, Stephen; Park, Myeonghun
2014-10-13
Theories of new physics often involve a large number of unknown parameters which need to be scanned. Additionally, a putative signal in a particular channel may be due to a variety of distinct models of new physics. This makes experimental attempts to constrain the parameter space of motivated new physics models with a high degree of generality quite challenging. We describe how the reweighting of events may allow this challenge to be met, as fully simulated Monte Carlo samples generated for arbitrary benchmark models can be effectively re-used. Specifically, we suggest procedures that allow more efficient collaboration between theorists and experimentalists in exploring large theory parameter spaces in a rigorous way at the LHC.
Exploring theory space with Monte Carlo reweighting
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Gainer, James S.; Lykken, Joseph; Matchev, Konstantin T.; Mrenna, Stephen; Park, Myeonghun
2014-10-13
Theories of new physics often involve a large number of unknown parameters which need to be scanned. Additionally, a putative signal in a particular channel may be due to a variety of distinct models of new physics. This makes experimental attempts to constrain the parameter space of motivated new physics models with a high degree of generality quite challenging. We describe how the reweighting of events may allow this challenge to be met, as fully simulated Monte Carlo samples generated for arbitrary benchmark models can be effectively re-used. In particular, we suggest procedures that allow more efficient collaboration between theoristsmoreand experimentalists in exploring large theory parameter spaces in a rigorous way at the LHC.less
SU-E-T-239: Monte Carlo Modelling of SMC Proton Nozzles Using TOPAS
Chung, K; Kim, J; Shin, J; Han, Y; Ju, S; Hong, C; Kim, D; Kim, H; Shin, E; Ahn, S; Chung, S; Choi, D
2014-06-01
Purpose: To expedite and cross-check the commissioning of the proton therapy nozzles at Samsung Medical Center using TOPAS. Methods: We have two different types of nozzles at Samsung Medical Center (SMC), a multi-purpose nozzle and a pencil beam scanning dedicated nozzle. Both nozzles have been modelled in Monte Carlo simulation by using TOPAS based on the vendor-provided geometry. The multi-purpose nozzle is mainly composed of wobbling magnets, scatterers, ridge filters and multi-leaf collimators (MLC). Including patient specific apertures and compensators, all the parts of the nozzle have been implemented in TOPAS following the geometry information from the vendor.The dedicated scanning nozzle has a simpler structure than the multi-purpose nozzle with a vacuum pipe at the down stream of the nozzle.A simple water tank volume has been implemented to measure the dosimetric characteristics of proton beams from the nozzles. Results: We have simulated the two proton beam nozzles at SMC. Two different ridge filters have been tested for the spread-out Bragg peak (SOBP) generation of wobbling mode in the multi-purpose nozzle. The spot sizes and lateral penumbra in two nozzles have been simulated and analyzed using a double Gaussian model. Using parallel geometry, both the depth dose curve and dose profile have been measured simultaneously. Conclusion: The proton therapy nozzles at SMC have been successfully modelled in Monte Carlo simulation using TOPAS. We will perform a validation with measured base data and then use the MC simulation to interpolate/extrapolate the measured data. We believe it will expedite the commissioning process of the proton therapy nozzles at SMC.
Friction Stir Spot Welding of Advanced High Strength Steels
Hovanski, Yuri; Santella, M. L.; Grant, Glenn J.
2009-12-28
Friction stir spot welding was used to join two advanced high-strength steels using polycrystalline cubic boron nitride tooling. Numerous tool designs were employed to study the influence of tool geometry on weld joints produced in both DP780 and a hot-stamp boron steel. Tool designs included conventional, concave shouldered pin tools with several pin configurations; a number of shoulderless designs; and a convex, scrolled shoulder tool. Weld quality was assessed based on lap shear strength, microstructure, microhardness, and bonded area. Mechanical properties were functionally related to bonded area and joint microstructure, demonstrating the necessity to characterize processing windows based on tool geometry.
Algorithms for a spot price responding residential load controller
Schweppe, F.C.; Daryanian, B.; Tabors, R.D.
1989-05-01
Increased unbundling of electric utility services has become a major interest in the industry. This paper presents a description of the logic and structure for a set of spot price based algorithms designed for use in residential load control systems. The paper presents the functions to be fulfilled by such a price responding device and describes the end use devices available in residences and the control logics applicable to each. The paper concludes that there is a need to understand customer attitudes and acceptance in the design of the response strategies and in the design of the man machine interface.
Monte Carlo Implementation Of Up- Or Down-Scattering Due To Collisions...
Office of Scientific and Technical Information (OSTI)
Monte Carlo Implementation Of Up- Or Down-Scattering Due To Collisions With Material At Finite Temperature Citation Details In-Document Search Title: Monte Carlo Implementation Of ...
Recent advances and future prospects for Monte Carlo
Brown, Forrest B
2010-01-01
The history of Monte Carlo methods is closely linked to that of computers: The first known Monte Carlo program was written in 1947 for the ENIAC; a pre-release of the first Fortran compiler was used for Monte Carlo In 1957; Monte Carlo codes were adapted to vector computers in the 1980s, clusters and parallel computers in the 1990s, and teraflop systems in the 2000s. Recent advances include hierarchical parallelism, combining threaded calculations on multicore processors with message-passing among different nodes. With the advances In computmg, Monte Carlo codes have evolved with new capabilities and new ways of use. Production codes such as MCNP, MVP, MONK, TRIPOLI and SCALE are now 20-30 years old (or more) and are very rich in advanced featUres. The former 'method of last resort' has now become the first choice for many applications. Calculations are now routinely performed on office computers, not just on supercomputers. Current research and development efforts are investigating the use of Monte Carlo methods on FPGAs. GPUs, and many-core processors. Other far-reaching research is exploring ways to adapt Monte Carlo methods to future exaflop systems that may have 1M or more concurrent computational processes.
Hot spot-derived shock initiation phenomena in heterogeneous nitromethane
Dattelbaum, Dana M; Sheffield, Stephen A; Stahl, David B; Dattelbaum, Andrew M
2009-01-01
The addition of solid silica particles to gelled nitromethane offers a tractable model system for interrogating the role of impedance mismatches as one type of hot spot 'seed' on the initiation behaviors of explosive formulations. Gas gun-driven plate impact experiments are used to produce well-defined shock inputs into nitromethane-silica mixtures containing size-selected silica beads at 6 wt%. The Pop-plots or relationships between shock input pressure and rundistance (or time)-to-detonation for mixtures containing small (1-4 {micro}m) and large (40 {micro}m) beads are presented. Overall, the addition of beads was found to influence the shock sensitivity of the mixtures, with the smaller beads being more sensitizing than the larger beads, lowering the shock initiation threshold for the same run distance to detonation compared with neat nitromethane. In addition, the use of embedded electromagnetic gauges provides detailed information pertaining to the mechanism of the build-up to detonation and associated reactive flow. Of note, an initiation mechanism characteristic of homogeneous liquid explosives, such as nitromethane, was observed in the nitromethane-40 {micro}m diameter silica samples at high shock input pressures, indicating that the influence of hot spots on the initiation process was minimal under these conditions.
March market review. [Spot market prices for uranium (1993)
Not Available
1993-04-01
The spot market price for uranium in unrestricted markets weakened further during March, and at month end, the NUEXCO Exchange Value had fallen $0.15, to $7.45 per pound U3O8. The Restricted American Market Penalty (RAMP) for concentrates increased $0.15, to $2.55 per pound U3O8. Ample UF6 supplies and limited demand led to a $0.50 decrease in the UF6 Value, to $25.00 per kgU as UF6, while the RAMP for UF6 increased $0.75, to $5.25 per kgU. Nine near-term uranium transactions were reported, totalling almost 3.3 million pounds equivalent U3O8. This is the largest monthly spot market volume since October 1992, and is double the volume reported in January and February. The March 31 Conversion Value was $4.25 per kgU as UF6. Beginning with the March 31 Value, NUEXCO now reports its Conversion Value in US dollars per kilogram of uranium (US$/kgU), reflecting current industry practice. The March loan market was inactive with no transactions reported. The Loan Rate remained unchanged at 3.0 percent per annum. Low demand and increased competition among sellers led to a one-dollar decrease in the SWU Value, to $65 per SWU, and the RAMP for SWU declined one dollar, to $9 per SWU.
Diode magnetic-field influence on radiographic spot size
Ekdahl, Carl A. Jr.
2012-09-04
Flash radiography of hydrodynamic experiments driven by high explosives is a well-known diagnostic technique in use at many laboratories. The Dual-Axis Radiography for Hydrodynamic Testing (DARHT) facility at Los Alamos was developed for flash radiography of large hydrodynamic experiments. Two linear induction accelerators (LIAs) produce the bremsstrahlung radiographic source spots for orthogonal views of each experiment ('hydrotest'). The 2-kA, 20-MeV Axis-I LIA creates a single 60-ns radiography pulse. For time resolution of the hydrotest dynamics, the 1.7-kA, 16.5-MeV Axis-II LIA creates up to four radiography pulses by slicing them out of a longer pulse that has a 1.6-{micro}s flattop. Both axes now routinely produce radiographic source spot sizes having full-width at half-maximum (FWHM) less than 1 mm. To further improve on the radiographic resolution, one must consider the major factors influencing the spot size: (1) Beam convergence at the final focus; (2) Beam emittance; (3) Beam canonical angular momentum; (4) Beam-motion blur; and (5) Beam-target interactions. Beam emittance growth and motion in the accelerators have been addressed by careful tuning. Defocusing by beam-target interactions has been minimized through tuning of the final focus solenoid for optimum convergence and other means. Finally, the beam canonical angular momentum is minimized by using a 'shielded source' of electrons. An ideal shielded source creates the beam in a region where the axial magnetic field is zero, thus the canonical momentum zero, since the beam is born with no mechanical angular momentum. It then follows from Busch's conservation theorem that the canonical angular momentum is minimized at the target, at least in principal. In the DARHT accelerators, the axial magnetic field at the cathode is minmized by using a 'bucking coil' solenoid with reverse polarity to cancel out whatever solenoidal beam transport field exists there. This is imperfect in practice, because of
Seven federally protected Mexican spotted owl chicks hatch on Los Alamos
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
National Laboratory property Federally protected Mexican spotted owl chicks hatch on LANL property Seven federally protected Mexican spotted owl chicks hatch on Los Alamos National Laboratory property Biologists located a record seven federally threatened Mexican spotted owl chicks on Los Alamos National Laboratory property during nest surveys last month. July 13, 2015 A parent owl sits with two chicks. A parent owl sits with two chicks. Contact Los Alamos National Laboratory Lorrie
Monte Carlo Hauser-Feshbach Calculations of Prompt Fission Neutrons...
Office of Scientific and Technical Information (OSTI)
Technical Report: Monte Carlo Hauser-Feshbach Calculations of Prompt Fission Neutrons and Gamma Rays: Application to Thermal Neutron-Induced Fission Reactions on U-235 and Pu-239 ...
Generalizing the self-healing diffusion Monte Carlo approach...
Office of Scientific and Technical Information (OSTI)
Generalizing the self-healing diffusion Monte Carlo approach to finite temperature: A path for the optimization of low-energy many-body bases Citation Details In-Document Search ...
Efficient Monte Carlo Simulations of Gas Molecules Inside Porous...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Efficient Monte Carlo Simulations of Gas Molecules Inside Porous Materials Previous Next List J. Kim and B. Smit, J. Chem. Theory Comput. 8 (7), 2336 (2012) DOI: 10.1021ct3003699 ...
Fast Monte Carlo for radiation therapy: the PEREGRINE Project (Conference)
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
| SciTech Connect Fast Monte Carlo for radiation therapy: the PEREGRINE Project Citation Details In-Document Search Title: Fast Monte Carlo for radiation therapy: the PEREGRINE Project × You are accessing a document from the Department of Energy's (DOE) SciTech Connect. This site is a product of DOE's Office of Scientific and Technical Information (OSTI) and is provided as a public service. Visit OSTI to utilize additional information resources in energy science and technology. A paper copy
Monte Carlo Hybrid Applied to Binary Stochastic Mixtures
Energy Science and Technology Software Center (OSTI)
2008-08-11
The purpose of this set of codes isto use an inexpensive, approximate deterministic flux distribution to generate weight windows, wihich will then be used to bound particle weights for the Monte Carlo code run. The process is not automated; the user must run the deterministic code and use the output file as a command-line argument for the Monte Carlo code. Two sets of text input files are included as test problems/templates.
Multiscale MonteCarlo equilibration: Pure Yang-Mills theory
Endres, Michael G.; Brower, Richard C.; Orginos, Kostas; Detmold, William; Pochinsky, Andrew V.
2015-12-29
In this study, we present a multiscale thermalization algorithm for lattice gauge theory, which enables efficient parallel generation of uncorrelated gauge field configurations. The algorithm combines standard Monte Carlo techniques with ideas drawn from real space renormalization group and multigrid methods. We demonstrate the viability of the algorithm for pure Yang-Mills gauge theory for both heat bath and hybrid Monte Carlo evolution, and show that it ameliorates the problem of topological freezing up to controllable lattice spacing artifacts.
Effects of High Shock Pressures and Pore Morphology on Hot Spot...
Office of Scientific and Technical Information (OSTI)
Effects of High Shock Pressures and Pore Morphology on Hot Spot Mechanisms in HMX Citation ... Sponsoring Org: USDOE Country of Publication: United States Language: English Subject: 75 ...
Modeling Hot-Spot Contributions in Shocked High Explosives at the Mesoscale
Harrier, Danielle
2015-08-12
When looking at performance of high explosives, the defects within the explosive become very important. Plastic bonded explosives, or PBXs, contain voids of air and bonder between the particles of explosive material that aid in the ignition of the explosive. These voids collapse in high pressure shock conditions, which leads to the formation of hot spots. Hot spots are localized high temperature and high pressure regions that cause significant changes in the way the explosive material detonates. Previously hot spots have been overlooked with modeling, but now scientists are realizing their importance and new modeling systems that can accurately model hot spots are underway.
Spot Prices for Crude Oil and Petroleum Products
U.S. Energy Information Administration (EIA) Indexed Site
Spot Prices (Crude Oil in Dollars per Barrel, Products in Dollars per Gallon) Period: Daily Weekly Monthly Annual Download Series History Download Series History Definitions, Sources & Notes Definitions, Sources & Notes Product by Area 08/30/16 08/31/16 09/01/16 09/02/16 09/05/16 09/06/16 View History Crude Oil WTI - Cushing, Oklahoma 46.32 44.68 43.17 44.39 44.39 44.85 1986-2016 Brent - Europe 47.94 47.94 45.05 45.96 46.72 46.21 1987-2016 Conventional Gasoline New York Harbor, Regular
Mechanism of cathode spot splitting in vacuum arcs in an oblique magnetic field
Beilis, I. I.
2015-10-15
Experiments in the last decade showed that for cathode spots in a magnetic field that obliquely intercepts the cathode surface, the current per spot increased with the transverse component of the magnetic field and decreased with the normal component. The present work analyzes the nature of cathode spot splitting in an oblique magnetic field. A physical model for cathode spot current splitting was developed, which considered the relation between the plasma kinetic pressure, self-magnetic pressure, and applied magnetic pressure in a current carrying cathode plasma jet. The current per spot was calculated, and it was found to increase with the tangential component of the magnetic field and to decrease with the normal component, which agrees well with the experimental dependence.
Morphological changes in ultrafast laser ablation plumes with varying spot size
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Harilal, S. S.; Diwakar, P. K.; Polek, M. P.; Phillips, M. C.
2015-06-04
We investigated the role of spot size on plume morphology during ultrafast laser ablation of metal targets. Our results show that the spatial features of fs LA plumes are strongly dependent on the focal spot size. Two-dimensional self-emission images showed that the shape of the ultrafast laser ablation plumes changes from spherical to cylindrical with an increasing spot size from 100 to 600 ?m. The changes in plume morphology and internal structures are related to ion emission dynamics from the plasma, where broader angular ion distribution and faster ions are noticed for the smallest spot size used. The present resultsmoreclearly show that the morphological changes in the plume with spot size are independent of laser pulse width.less
SU-E-J-72: Geant4 Simulations of Spot-Scanned Proton Beam Treatment Plans
Kanehira, T; Sutherland, K; Matsuura, T; Umegaki, K; Shirato, H
2014-06-01
Purpose: To evaluate density inhomogeneities which can effect dose distributions for real-time image gated spot-scanning proton therapy (RGPT), a dose calculation system, using treatment planning system VQA (Hitachi Ltd., Tokyo) spot position data, was developed based on Geant4. Methods: A Geant4 application was developed to simulate spot-scanned proton beams at Hokkaido University Hospital. A CT scan (0.98 × 0.98 × 1.25 mm) was performed for prostate cancer treatment with three or four inserted gold markers (diameter 1.5 mm, volume 1.77 mm3) in or near the target tumor. The CT data was read into VQA. A spot scanning plan was generated and exported to text files, specifying the beam energy and position of each spot. The text files were converted and read into our Geant4-based software. The spot position was converted into steering magnet field strength (in Tesla) for our beam nozzle. Individual protons were tracked from the vacuum chamber, through the helium chamber, steering magnets, dose monitors, etc., in a straight, horizontal line. The patient CT data was converted into materials with variable density and placed in a parametrized volume at the isocenter. Gold fiducial markers were represented in the CT data by two adjacent voxels (volume 2.38 mm3). 600,000 proton histories were tracked for each target spot. As one beam contained about 1,000 spots, approximately 600 million histories were recorded for each beam on a blade server. Two plans were considered: two beam horizontal opposed (90 and 270 degree) and three beam (0, 90 and 270 degree). Results: We are able to convert spot scanning plans from VQA and simulate them with our Geant4-based code. Our system can be used to evaluate the effect of dose reduction caused by gold markers used for RGPT. Conclusion: Our Geant4 application is able to calculate dose distributions for spot scanned proton therapy.
May market review. [Spot market prices for uranium (1993)
Not Available
1993-06-01
Seven uranium transactions totalling nearly three million pounds equivalent U3O8 were reported during May, but only two, totalling less than 200 thousand pounds equivalent U3O8, involved concentrates. As no discretionary buying occurred during the month, and as near-term supply and demand were in relative balance, prices were steady, while both buyers and sellers appeared to be awaiting some new market development to signal the direction of future spot-market prices. The May 31, 1993, Exchange Value and the Restricted American market Penalty (RAMP) for concentrates were both unchanged at $7.10, and $2.95 per pound U3O8, respectively. NUEXCO's judgement was that transactions for significant quantities of uranium concentrates that were both deliverable in and intended for consumption in the USA could have been concluded on May 31 at $10.05 per pound U3O8. Two near-term concentrate transactions were reported in which one US utility purchased less than 200 thousand pounds equivalent U3O8 from two separate sellers. These sales occurred at price levels at or near the May 31 Exchange Value plus RAMP. No long-term uranium transactions were reported during May. Consequently, the UF6 Value decreased $0.20 to $24.30 per kgU as UF6, reflecting some weakening of the UF6 market outside the USA.
DRAMATIC CHANGE IN JUPITER'S GREAT RED SPOT FROM SPACECRAFT OBSERVATIONS
Simon, Amy A.; Wong, Michael H.; De Pater, Imke; Rogers, John H.; Orton, Glenn S.; Carlson, Robert W.; Asay-Davis, Xylar; Marcus, Philip S.
2014-12-20
Jupiter's Great Red Spot (GRS) is one of its most distinct and enduring features. Since the advent of modern telescopes, keen observers have noted its appearance and documented a change in shape from very oblong to oval, confirmed in measurements from spacecraft data. It currently spans the smallest latitude and longitude size ever recorded. Here we show that this change has been accompanied by an increase in cloud/haze reflectance as sensed in methane gas absorption bands, increased absorption at wavelengths shorter than 500nm, and increased spectral slope between 500 and 630nm. These changes occurred between 2012 and 2014, without a significant change in internal tangential wind speeds; the decreased size results in a 3.2day horizontal cloud circulation period, shorter than previously observed. As the GRS has narrowed in latitude, it interacts less with the jets flanking its north and south edges, perhaps allowing for less cloud mixing and longer UV irradiation of cloud and aerosol particles. Given its long life and observational record, we expect that future modeling of the GRS's changes, in concert with laboratory flow experiments, will drive our understanding of vortex evolution and stability in a confined flow field crucial for comparison with other planetary atmospheres.
Duo at Santa Fe's Monte del Sol Charter
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Duo at Santa Fe's Monte del Sol Charter School takes top award in 25th New Mexico Supercomputing Challenge April 21, 2015 Using nanotechnology robots to kill cancer cells LOS ALAMOS, N.M., April 21, 2015-Meghan Hill and Katelynn James of Santa Fe's Monte del Sol Charter Sol took the top prize in the 25 th New Mexico Supercomputing Challenge Tuesday at Los Alamos National Laboratory for their research project, "Using Concentrated Heat Systems to Shock the P53 Protein to Direct Cancer into
Electrophoretic extraction of proteins from two-dimensional electrophoresis gel spots
Zhang, Jian-Shi; Giometti, C.S.; Tollaksen, S.L.
1987-09-04
After two-dimensional electrophoresis of proteins or the like, resulting in a polyacrylamide gel slab having a pattern of protein gel spots thereon, an individual protein gel spot is cored out from the slab, to form a gel spot core which is placed in an extraction tube, with a dialysis membrane across the lower end of the tube. Replicate gel spots can be cored out from replicate gel slabs and placed in the extraction tube. Molten agarose gel is poured into the extraction tube where the agarose gel hardens to form an immobilizing gel, covering the gel spot cores. The upper end portion of the extraction tube is filled with a volume of buffer solution, and the upper end is closed by another dialysis membrane. Upper and lower bodies of a buffer solution are brought into contact with the upper and lower membranes and are provided with electrodes connected to the positive and negative terminals of a dc power supply, thereby producing an electrical current which flows through the upper membrane, the volume of buffer solution, the agarose, the gel spot cores and the lower membrane. The current causes the proteins to be extracted electrophoretically from the gel spot cores, so that the extracted proteins accumulate and are contained in the space between the agarose gel and the upper membrane. 8 figs.
WE-E-BRE-04: Dual Focal Spot Dose Painting for Precision Preclinical Radiobiological Investigations
Stewart, J; Lindsay, P; Jaffray, D
2014-06-15
Purpose: Recent progress in small animal radiotherapy systems has provided the foundation for delivering the heterogeneous, millimeter scale dose distributions demanded by preclinical radiobiology investigations. Despite advances in preclinical dose planning, delivery of highly heterogeneous dose distributions is constrained by the fixed collimation systems and large x-ray focal spot common in small animal radiotherapy systems. This work proposes a dual focal spot dose optimization and delivery method with a large x-ray focal spot used to deliver homogeneous dose regions and a small focal spot to paint spatially heterogeneous dose regions. Methods: Two-dimensional dose kernels were measured for a 1 mm circular collimator with radiochromic film at 10 mm depth in a solid water phantom for the small and large x-ray focal spots on a recently developed small animal microirradiator. These kernels were used in an optimization framework which segmented a desired dose distribution into low- and high-spatial frequency regions for delivery by the large and small focal spot, respectively. For each region, the method determined an optimal set of stage positions and beam-on times. The method was demonstrated by optimizing a bullseye pattern consisting of 0.75 mm radius circular target and 0.5 and 1.0 mm wide rings alternating between 0 and 2 Gy. Results: Compared to a large focal spot technique, the dual focal spot technique improved the optimized dose distribution: 69.2% of the optimized dose was within 0.5 Gy of the intended dose for the large focal spot, compared to 80.6% for the dual focal spot method. The dual focal spot design required 14.0 minutes of optimization, and will require 178.3 minutes for automated delivery. Conclusion: The dual focal spot optimization and delivery framework is a novel option for delivering conformal and heterogeneous dose distributions at the preclinical level and provides a new experimental option for unique radiobiological investigations
April market review. [Spot market prices for uranium (1993)
Not Available
1993-05-01
The spot market price for uranium outside the USA weakened further during April, and at month end, the NUEXCO Exchange Value had fallen $0.35, to $7.10 per pound U3O8. This is the lowest Exchange Value observed in nearly twenty years, comparable to Values recorded during the low price levels of the early 1970s. The Restricted American Market Penalty (RAMP) for concentrates increased $0.40, to $2.95 per pound U3O8. Transactions for significant quantities of uranium concentrates that are both deliverable in and intended for consumption in the USA could have been concluded on April 30 at $10.05 per pound U3O8, up $0.05 from the sum of corresponding March Values. Four near-term concentrates transactions were reported, totalling nearly 1.5 million pounds equivalent U3O8. One long-term sale was reported. The UF6 Value also declined, as increased competition among sellers led to a $0.50 decrease, to $24.50 per kgU as UF6. However, the RAMP for UF6 increased $0.65, to $5.90 per kgU as UF6, reflecting an effective US market level of $30.40 per kgU. Two near term transactions were reported totalling approximately 1.1 million pounds equivalent U3O8. In total, eight uranium transactions totalling 28 million pounds equivalent U3O8 were reported, which is about average for April market activity.
Bayesian Monte Carlo Method for Nuclear Data Evaluation
Koning, A.J.
2015-01-15
A Bayesian Monte Carlo method is outlined which allows a systematic evaluation of nuclear reactions using TALYS. The result will be either an EXFOR-weighted covariance matrix or a collection of random files, each accompanied by an experiment based weight.
Monte Carlo event generators for hadron-hadron collisions
Knowles, I.G.; Protopopescu, S.D.
1993-06-01
A brief review of Monte Carlo event generators for simulating hadron-hadron collisions is presented. Particular emphasis is placed on comparisons of the approaches used to describe physics elements and identifying their relative merits and weaknesses. This review summarizes a more detailed report.
Monte-Carlo simulation of noise in hard X-ray Transmission Crystal...
Office of Scientific and Technical Information (OSTI)
Monte-Carlo simulation of noise in hard X-ray Transmission Crystal Spectrometers: ... Title: Monte-Carlo simulation of noise in hard X-ray Transmission Crystal Spectrometers: ...
Soci t d exploitation du parc olien de Mont d H z cques SARL...
Soci t d exploitation du parc olien de Mont d H z cques SARL Jump to: navigation, search Name: Socit d'exploitation du parc olien de Mont d'Hzcques SARL Place:...
Assessment of Prices of Natural Gas Futures Contracts As A Predictor of Realized Spot Prices, An
Reports and Publications (EIA)
2005-01-01
This article compares realized Henry Hub spot market prices for natural gas during the three most recent winters with futures prices as they evolve from April through the following February, when trading for the March contract ends.
Calculation of the fast ion tail distribution for a spherically symmetric hot spot
McDevitt, C. J.; Tang, X.-Z.; Guo, Z.; Berk, H. L.
2014-10-15
The fast ion tail for a spherically symmetric hot spot is computed via the solution of a simplified Fokker-Planck collision operator. Emphasis is placed on describing the energy scaling of the fast ion distribution function in the hot spot as well as the surrounding cold plasma throughout a broad range of collisionalities and temperatures. It is found that while the fast ion tail inside the hot spot is significantly depleted, leading to a reduction of the fusion yield in this region, a surplus of fast ions is observed in the neighboring cold plasma region. The presence of this surplus of fast ions in the neighboring cold region is shown to result in a partial recovery of the fusion yield lost in the hot spot.
DOE Science Showcase - Monte Carlo Methods | OSTI, US Dept of Energy Office
Office of Scientific and Technical Information (OSTI)
of Scientific and Technical Information Monte Carlo Methods Monte Carlo calculation methods are algorithms for solving various kinds of computational problems by using (pseudo)random numbers. Developed in the 1940s during the Manhattan Project, the Monte Carlo method signified a radical change in how scientists solved problems. Learn about the ways these methods are used in DOE's research endeavors today in "Monte Carlo Methods" by Dr. William Watson, Physicist, OSTI staff. Image
Electrophoretic extraction of proteins from two-dimensional electrophoresis gel spots
Zhang, Jian-Shi; Giometti, Carol S.; Tollaksen, Sandra L.
1989-01-01
After two-dimensional electrophoresis of proteins or the like, resulting in a polyacrylamide gel slab having a pattern of protein gel spots thereon, an individual protein gel spot is cored out from the slab, to form a gel spot core which is placed in an extraction tube, with a dialysis membrane across the lower end of the tube. Replicate gel spots can be cored out from replicate gel slabs and placed in the extraction tube. Molten agarose gel is poured into the extraction tube where the agarose gel hardens to form an immobilizing gel, covering the gel spot cores. The upper end portion of the extraction tube is filled with a volume of buffer solution, and the upper end is closed by another dialysis membrane. Upper and lower bodies of a buffer solution are brought into contact with the upper and lower membranes and are provided with electrodes connected to the positive and negative terminals of a DC power supply, thereby producing an electrical current which flows through the upper membrane, the volume of buffer solution, the agarose, the gel spot cores and the lower membrane. The current causes the proteins to be extracted electrophoretically from the gel spot cores, so that the extracted proteins accumulate and are contained in the space between the agarose gel and the upper membrane. A high percentage extraction of proteins is achieved. The extracted proteins can be removed and subjected to partial digestion by trypsin or the like, followed by two-dimensional electrophoresis, resulting in a gel slab having a pattern of peptide gel spots which can be cored out and subjected to electrophoretic extraction to extract individual peptides.
Spot size dependence of laser accelerated protons in thin multi-ion foils
Liu, Tung-Chang Shao, Xi; Liu, Chuan-Sheng; Eliasson, Bengt; Wang, Jyhpyng; Chen, Shih-Hung
2014-06-15
We present a numerical study of the effect of the laser spot size of a circularly polarized laser beam on the energy of quasi-monoenergetic protons in laser proton acceleration using a thin carbon-hydrogen foil. The used proton acceleration scheme is a combination of laser radiation pressure and shielded Coulomb repulsion due to the carbon ions. We observe that the spot size plays a crucial role in determining the net charge of the electron-shielded carbon ion foil and consequently the efficiency of proton acceleration. Using a laser pulse with fixed input energy and pulse length impinging on a carbon-hydrogen foil, a laser beam with smaller spot sizes can generate higher energy but fewer quasi-monoenergetic protons. We studied the scaling of the proton energy with respect to the laser spot size and obtained an optimal spot size for maximum proton energy flux. Using the optimal spot size, we can generate an 80 MeV quasi-monoenergetic proton beam containing more than 10{sup 8} protons using a laser beam with power 250 TW and energy 10 J and a target of thickness 0.15 wavelength and 49 critical density made of 90% carbon and 10% hydrogen.
Wang, Z; Gao, M
2014-06-01
Purpose: Monte Carlo simulation plays an important role for proton Pencil Beam Scanning (PBS) technique. However, MC simulation demands high computing power and is limited to few large proton centers that can afford a computer cluster. We study the feasibility of utilizing cloud computing in the MC simulation of PBS beams. Methods: A GATE/GEANT4 based MC simulation software was installed on a commercial cloud computing virtual machine (Linux 64-bits, Amazon EC2). Single spot Integral Depth Dose (IDD) curves and in-air transverse profiles were used to tune the source parameters to simulate an IBA machine. With the use of StarCluster software developed at MIT, a Linux cluster with 2100 nodes can be conveniently launched in the cloud. A proton PBS plan was then exported to the cloud where the MC simulation was run. Results: The simulated PBS plan has a field size of 1010cm{sup 2}, 20cm range, 10cm modulation, and contains over 10,000 beam spots. EC2 instance type m1.medium was selected considering the CPU/memory requirement and 40 instances were used to form a Linux cluster. To minimize cost, master node was created with on-demand instance and worker nodes were created with spot-instance. The hourly cost for the 40-node cluster was $0.63 and the projected cost for a 100-node cluster was $1.41. Ten million events were simulated to plot PDD and profile, with each job containing 500k events. The simulation completed within 1 hour and an overall statistical uncertainty of < 2% was achieved. Good agreement between MC simulation and measurement was observed. Conclusion: Cloud computing is a cost-effective and easy to maintain platform to run proton PBS MC simulation. When proton MC packages such as GATE and TOPAS are combined with cloud computing, it will greatly facilitate the pursuing of PBS MC studies, especially for newly established proton centers or individual researchers.
Monte Carlo calculations for r-process nucleosynthesis
Mumpower, Matthew Ryan
2015-11-12
A Monte Carlo framework is developed for exploring the impact of nuclear model uncertainties on the formation of the heavy elements. Mass measurements tightly constrain the macroscopic sector of FRDM2012. For r-process nucleosynthesis, it is necessary to understand the microscopic physics of the nuclear model employed. A combined approach of measurements and a deeper understanding of the microphysics is thus warranted to elucidate the site of the r-process.
The Monte Carlo Independent Column Approximation Model Intercomparison
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Project (McMIP) 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
Quantum Monte Carlo Calculations in Nuclear Theory | Argonne Leadership
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Computing Facility Blue Gene/Q scaling This figure shows Blue Gene/Q scaling with respect to increasing number of nodes for calculations of the first isospin-1 state of $^{12}$C. The good multinode scaling is a result of the ADLB library. Quantum Monte Carlo Calculations in Nuclear Theory PI Name: Steven Pieper PI Email: spieper@anl.gov Institution: Argonne National Laboratory Allocation Program: ESP Year: 2015 Research Domain: Physics Tier 2 Code Development Project Numerical
Calculations of pair production by Monte Carlo methods
Bottcher, C.; Strayer, M.R.
1991-01-01
We describe some of the technical design issues associated with the production of particle-antiparticle pairs in very large accelerators. To answer these questions requires extensive calculation of Feynman diagrams, in effect multi-dimensional integrals, which we evaluate by Monte Carlo methods on a variety of supercomputers. We present some portable algorithms for generating random numbers on vector and parallel architecture machines. 12 refs., 14 figs.
Olson, R. E.; Leeper, R. J.
2013-09-15
The baseline DT ice layer inertial confinement fusion (ICF) ignition capsule design requires a hot spot convergence ratio of ∼34 with a hot spot that is formed from DT mass originally residing in a very thin layer at the inner DT ice surface. In the present paper, we propose alternative ICF capsule designs in which the hot spot is formed mostly or entirely from mass originating within a spherical volume of DT vapor. Simulations of the implosion and hot spot formation in two DT liquid layer ICF capsule concepts—the DT wetted hydrocarbon (CH) foam concept and the “fast formed liquid” (FFL) concept—are described and compared to simulations of standard DT ice layer capsules. 1D simulations are used to compare the drive requirements, the optimal shock timing, the radial dependence of hot spot specific energy gain, and the hot spot convergence ratio in low vapor pressure (DT ice) and high vapor pressure (DT liquid) capsules. 2D simulations are used to compare the relative sensitivities to low-mode x-ray flux asymmetries in the DT ice and DT liquid capsules. It is found that the overall thermonuclear yields predicted for DT liquid layer capsules are less than yields predicted for DT ice layer capsules in simulations using comparable capsule size and absorbed energy. However, the wetted foam and FFL designs allow for flexibility in hot spot convergence ratio through the adjustment of the initial cryogenic capsule temperature and, hence, DT vapor density, with a potentially improved robustness to low-mode x-ray flux asymmetry.
An investigation of the dynamic separation of spot welds under plane tensile pulses
Ma, Bohan; Fan, Chunlei; Chen, Danian Wang, Huanran; Zhou, Fenghua
2014-08-07
We performed ultra-high-speed tests for purely opening spot welds using plane tensile pulses. A gun system generated a parallel impact of a projectile plate onto a welded plate. Induced by the interactions of the release waves, the welded plate opened purely under the plane tensile pulses. We used the laser velocity interferometer system for any reflector to measure the velocity histories of the free surfaces of the free part and the spot weld of the welded plate. We then used a scanning electron microscope to investigate the recovered welded plates. We found that the interfacial failure mode was mainly a brittle fracture and the cracks propagated through the spot nugget, while the partial interfacial failure mode was a mixed fracture comprised ductile fracture and brittle fracture. We used the measured velocity histories to evaluate the tension stresses in the free part and the spot weld of the welded plate by applying the characteristic theory. We also discussed the different constitutive behaviors of the metals under plane shock loading and under uniaxial split Hopkinson pressure bar tests. We then compared the numerically simulated velocity histories of the free surfaces of the free part and the spot weld of the welded plate with the measured results. The numerical simulations made use of the fracture stress criteria, and then the computed fracture modes of the tests were compared with the recovered results.
Real-time spot size camera for pulsed high-energy radiographic machines
Watson, S.A.
1993-06-01
The focal spot size of an x-ray source is a critical parameter which degrades resolution in a flash radiograph. For best results, a small round focal spot is required. Therefore, a fast and accurate measurement of the spot size is highly desirable to facilitate machine tuning. This paper describes two systems developed for Los Alamos National Laboratory`s Pulsed High-Energy Radiographic Machine Emitting X-rays (PHERMEX) facility. The first uses a CCD camera combined with high-brightness floors, while the second utilizes phosphor storage screens. Other techniques typically record only the line spread function on radiographic film, while systems in this paper measure the more general two-dimensional point-spread function and associated modulation transfer function in real time for shot-to-shot comparison.
Real-time spot size camera for pulsed high-energy radiographic machines
Watson, S.A.
1993-01-01
The focal spot size of an x-ray source is a critical parameter which degrades resolution in a flash radiograph. For best results, a small round focal spot is required. Therefore, a fast and accurate measurement of the spot size is highly desirable to facilitate machine tuning. This paper describes two systems developed for Los Alamos National Laboratory's Pulsed High-Energy Radiographic Machine Emitting X-rays (PHERMEX) facility. The first uses a CCD camera combined with high-brightness floors, while the second utilizes phosphor storage screens. Other techniques typically record only the line spread function on radiographic film, while systems in this paper measure the more general two-dimensional point-spread function and associated modulation transfer function in real time for shot-to-shot comparison.
Electron depletion via cathode spot dispersion of dielectric powder into an overhead plasma
Gillman, Eric D.; Foster, John E.
2013-11-15
The effectiveness of cathode spot delivered dielectric particles for the purpose of plasma depletion is investigated. Here, cathode spot flows kinetically entrain and accelerate dielectric particles originally at rest into a background plasma. The time variation of the background plasma density is tracked using a cylindrical Langmuir probe biased approximately at electron saturation. As inferred from changes in the electron saturation current, depletion fractions of up to 95% are observed. This method could be exploited as a means of communications blackout mitigation for manned and unmanned reentering spacecraft as well as any high speed vehicle enveloped by a dense plasma layer.
Six years of monitoring annual changes in a freshwater marsh with SPOT HRV data
Mackey, H.E. Jr.
1992-12-01
Fifteen dates of spring-time SPOT HRV data along with near-concurrent vertical aerial photographic and phenological data from spring 1987 through spring 1992 were analyzed to monitor annual changes in a 150-hectare, southeastern floodplain marsh. The marsh underwent rapid changes during the six years from a swamp dominated by non-persistent, thermally tolerant macrophytes to persistent macrophyte and shrub-scrub communities as reactor discharges declined to Pen Branch. Savannah River flooding was also important in the timing of the shift of these wetland communities. SPOT HRV data proved to be an efficient and effective method to monitor trends in these wetland community changes.
Six years of monitoring annual changes in a freshwater marsh with SPOT HRV data
Mackey, H.E. Jr.
1992-01-01
Fifteen dates of spring-time SPOT HRV data along with near-concurrent vertical aerial photographic and phenological data from spring 1987 through spring 1992 were analyzed to monitor annual changes in a 150-hectare, southeastern floodplain marsh. The marsh underwent rapid changes during the six years from a swamp dominated by non-persistent, thermally tolerant macrophytes to persistent macrophyte and shrub-scrub communities as reactor discharges declined to Pen Branch. Savannah River flooding was also important in the timing of the shift of these wetland communities. SPOT HRV data proved to be an efficient and effective method to monitor trends in these wetland community changes.
Effects of minimum monitor unit threshold on spot scanning proton plan quality
Howard, Michelle Beltran, Chris; Mayo, Charles S.; Herman, Michael G.
2014-09-15
Purpose: To investigate the influence of the minimum monitor unit (MU) on the quality of clinical treatment plans for scanned proton therapy. Methods: Delivery system characteristics limit the minimum number of protons that can be delivered per spot, resulting in a min-MU limit. Plan quality can be impacted by the min-MU limit. Two sites were used to investigate the impact of min-MU on treatment plans: pediatric brain tumor at a depth of 5–10 cm; a head and neck tumor at a depth of 1–20 cm. Three-field, intensity modulated spot scanning proton plans were created for each site with the following parameter variations: min-MU limit range of 0.0000–0.0060; and spot spacing range of 2–8 mm. Comparisons were based on target homogeneity and normal tissue sparing. For the pediatric brain, two versions of the treatment planning system were also compared to judge the effects of the min-MU limit based on when it is accounted for in the optimization process (Eclipse v.10 and v.13, Varian Medical Systems, Palo Alto, CA). Results: The increase of the min-MU limit with a fixed spot spacing decreases plan quality both in homogeneous target coverage and in the avoidance of critical structures. Both head and neck and pediatric brain plans show a 20% increase in relative dose for the hot spot in the CTV and 10% increase in key critical structures when comparing min-MU limits of 0.0000 and 0.0060 with a fixed spot spacing of 4 mm. The DVHs of CTVs show min-MU limits of 0.0000 and 0.0010 produce similar plan quality and quality decreases as the min-MU limit increases beyond 0.0020. As spot spacing approaches 8 mm, degradation in plan quality is observed when no min-MU limit is imposed. Conclusions: Given a fixed spot spacing of ≤4 mm, plan quality decreases as min-MU increased beyond 0.0020. The effect of min-MU needs to be taken into consideration while planning proton therapy treatments.
Properties of reactive oxygen species by quantum Monte Carlo
Zen, Andrea; Trout, Bernhardt L.; Guidoni, Leonardo
2014-07-07
The electronic properties of the oxygen molecule, in its singlet and triplet states, and of many small oxygen-containing radicals and anions have important roles in different fields of chemistry, biology, and atmospheric science. Nevertheless, the electronic structure of such species is a challenge for ab initio computational approaches because of the difficulties to correctly describe the statical and dynamical correlation effects in presence of one or more unpaired electrons. Only the highest-level quantum chemical approaches can yield reliable characterizations of their molecular properties, such as binding energies, equilibrium structures, molecular vibrations, charge distribution, and polarizabilities. In this work we use the variational Monte Carlo (VMC) and the lattice regularized Monte Carlo (LRDMC) methods to investigate the equilibrium geometries and molecular properties of oxygen and oxygen reactive species. Quantum Monte Carlo methods are used in combination with the Jastrow Antisymmetrized Geminal Power (JAGP) wave function ansatz, which has been recently shown to effectively describe the statical and dynamical correlation of different molecular systems. In particular, we have studied the oxygen molecule, the superoxide anion, the nitric oxide radical and anion, the hydroxyl and hydroperoxyl radicals and their corresponding anions, and the hydrotrioxyl radical. Overall, the methodology was able to correctly describe the geometrical and electronic properties of these systems, through compact but fully-optimised basis sets and with a computational cost which scales as N{sup 3} ? N{sup 4}, where N is the number of electrons. This work is therefore opening the way to the accurate study of the energetics and of the reactivity of large and complex oxygen species by first principles.
Coupled Monte Carlo neutronics and thermal hydraulics for power reactors
Bernnat, W.; Buck, M.; Mattes, M.; Zwermann, W.; Pasichnyk, I.; Velkov, K.
2012-07-01
The availability of high performance computing resources enables more and more the use of detailed Monte Carlo models even for full core power reactors. The detailed structure of the core can be described by lattices, modeled by so-called repeated structures e.g. in Monte Carlo codes such as MCNP5 or MCNPX. For cores with mainly uniform material compositions, fuel and moderator temperatures, there is no problem in constructing core models. However, when the material composition and the temperatures vary strongly a huge number of different material cells must be described which complicate the input and in many cases exceed code or memory limits. The second problem arises with the preparation of corresponding temperature dependent cross sections and thermal scattering laws. Only if these problems can be solved, a realistic coupling of Monte Carlo neutronics with an appropriate thermal-hydraulics model is possible. In this paper a method for the treatment of detailed material and temperature distributions in MCNP5 is described based on user-specified internal functions which assign distinct elements of the core cells to material specifications (e.g. water density) and temperatures from a thermal-hydraulics code. The core grid itself can be described with a uniform material specification. The temperature dependency of cross sections and thermal neutron scattering laws is taken into account by interpolation, requiring only a limited number of data sets generated for different temperatures. Applications will be shown for the stationary part of the Purdue PWR benchmark using ATHLET for thermal- hydraulics and for a generic Modular High Temperature reactor using THERMIX for thermal- hydraulics. (authors)
Optimization of Gutzwiller wave functions in quantum Monte Carlo
Koch, E.; Gunnarsson, O.; Martin, R.M.
1999-06-01
Gutzwiller functions are popular variational wave functions for correlated electrons in Hubbard models. Following the variational principle, we are interested in the Gutzwiller parameters that minimize, e.g., the expectation value of the energy. Rewriting the expectation value as a rational function in the Gutzwiller parameters, we find a very efficient way for performing that minimization. The method can be used to optimize general Gutzwiller-type wave functions both in variational and in fixed-node diffusion Monte Carlo. {copyright} {ital 1999} {ital The American Physical Society}
Quantum Monte Carlo Simulation of Overpressurized Liquid {sup 4}He
Vranjes, L.; Boronat, J.; Casulleras, J.; Cazorla, C.
2005-09-30
A diffusion Monte Carlo simulation of superfluid {sup 4}He at zero temperature and pressures up to 275 bar is presented. Increasing the pressure beyond freezing ({approx}25 bar), the liquid enters the overpressurized phase in a metastable state. In this regime, we report results of the equation of state and the pressure dependence of the static structure factor, the condensate fraction, and the excited-state energy corresponding to the roton. Along this large pressure range, both the condensate fraction and the roton energy decrease but do not become zero. The roton energies obtained are compared with recent experimental data in the overpressurized regime.
Communication: Water on hexagonal boron nitride from diffusion Monte Carlo
Al-Hamdani, Yasmine S.; Ma, Ming; Michaelides, Angelos; Alf, Dario; Lilienfeld, O. Anatole von
2015-05-14
Despite a recent flurry of experimental and simulation studies, an accurate estimate of the interaction strength of water molecules with hexagonal boron nitride is lacking. Here, we report quantum Monte Carlo results for the adsorption of a water monomer on a periodic hexagonal boron nitride sheet, which yield a water monomer interaction energy of ?84 5 meV. We use the results to evaluate the performance of several widely used density functional theory (DFT) exchange correlation functionals and find that they all deviate substantially. Differences in interaction energies between different adsorption sites are however better reproduced by DFT.
Cluster Monte Carlo simulations of the nematic-isotropic transition
Priezjev, N. V.; Pelcovits, Robert A.
2001-06-01
We report the results of simulations of the three-dimensional Lebwohl-Lasher model of the nematic-isotropic transition using a single cluster Monte Carlo algorithm. The algorithm, first introduced by Kunz and Zumbach to study two-dimensional nematics, is a modification of the Wolff algorithm for spin systems, and greatly reduces critical slowing down. We calculate the free energy in the neighborhood of the transition for systems up to linear size 70. We find a double well structure with a barrier that grows with increasing system size. We thus obtain an upper estimate of the value of the transition temperature in the thermodynamic limit.
A Post-Monte-Carlo Sensitivity Analysis Code
Energy Science and Technology Software Center (OSTI)
2000-04-04
SATOOL (Sensitivity Analysis TOOL) is a code for sensitivity analysis, following an uncertainity analysis with Monte Carlo simulations. Sensitivity analysis identifies those input variables, whose variance contributes dominatly to the variance in the output. This analysis can be used to reduce the variance in the output variables by redefining the "sensitive" variables with greater precision, i.e. with lower variance. The code identifies a group of sensitive variables, ranks them in the order of importance andmore » also quantifies the relative importance among the sensitive variables.« less
Element Agglomeration Algebraic Multilevel Monte-Carlo Library
Energy Science and Technology Software Center (OSTI)
2015-02-19
ElagMC is a parallel C++ library for Multilevel Monte Carlo simulations with algebraically constructed coarse spaces. ElagMC enables Multilevel variance reduction techniques in the context of general unstructured meshes by using the specialized element-based agglomeration techniques implemented in ELAG (the Element-Agglomeration Algebraic Multigrid and Upscaling Library developed by U. Villa and P. Vassilevski and currently under review for public release). The ElabMC library can support different type of deterministic problems, including mixed finite element discretizationsmore » of subsurface flow problems.« less
Monte Carlo Bayesian search for the plausible source of the Telescope...
Office of Scientific and Technical Information (OSTI)
Title: Monte Carlo Bayesian search for the plausible source of the Telescope Array hotspot Authors: He, Hao-Ning ; Kusenko, Alexander ; Nagataki, Shigehiro ; Zhang, Bin-Bin ; Yang, ...
Monte Carlo Fundamentals E B. BROWN and T M. S N
Office of Scientific and Technical Information (OSTI)
or reflect those of the United States Government or any ... Monte Carlo approach: Generate a sequence of states, (pol ... partide from birth to death During the particle ...
OSTIblog Articles in the Monte Carlo Topic | OSTI, US Dept of Energy Office
Office of Scientific and Technical Information (OSTI)
of Scientific and Technical Information Monte Carlo Topic The Unbelievable Accuracy of the Monte Carlo Method by Kathy Chambers 18 Jan, 2013 in Science Communications 4680 Monte%20Carlo.jpg The Unbelievable Accuracy of the Monte Carlo Method Read more about 4680 The year was 1945, the year I was born. That in itself is of great significance to me. However, it was a momentous year in history. World War II came to its merciful end and the development of the first electronic computer - the
Application of Monte Carlo Methods in Molecular Targeted Radionuclide Therapy
Hartmann Siantar, C; Descalle, M-A; DeNardo, G L; Nigg, D W
2002-02-19
Targeted radionuclide therapy promises to expand the role of radiation beyond the treatment of localized tumors. This novel form of therapy targets metastatic cancers by combining radioactive isotopes with tumor-seeking molecules such as monoclonal antibodies and custom-designed synthetic agents. Ultimately, like conventional radiotherapy, the effectiveness of targeted radionuclide therapy is limited by the maximum dose that can be given to a critical, normal tissue, such as bone marrow, kidneys, and lungs. Because radionuclide therapy relies on biological delivery of radiation, its optimization and characterization are necessarily different than for conventional radiation therapy. We have initiated the development of a new, Monte Carlo transport-based treatment planning system for molecular targeted radiation therapy as part of the MINERVA treatment planning system. This system calculates patient-specific radiation dose estimates using a set of computed tomography scans to describe the 3D patient anatomy, combined with 2D (planar image) and 3D (SPECT, or single photon emission computed tomography) to describe the time-dependent radiation source. The accuracy of such a dose calculation is limited primarily by the accuracy of the initial radiation source distribution, overlaid on the patient's anatomy. This presentation provides an overview of MINERVA functionality for molecular targeted radiation therapy, and describes early validation and implementation results of Monte Carlo simulations.
Friction Stir Spot Welding of DP780 and Hot-Stamp Boron Steels
Santella, Michael L.; Frederick, Alan; Hovanski, Yuri; Grant, Glenn J.
2008-05-16
Friction stir spot welds were made in two high-strength steels: DP780, and a hot-stamp-boron steel with tensile strength of 1500 MPa. The spot welds were made at either 800 or 1600 rpm using either of two polycrystalline boron nitride tools. One stir tool, BN77, had the relatively common pin-tool shape. The second tool, BN46, had a convex rather than a concave shoulder profile and a much wider and shorter pin. The tools were plunged to preprogrammed depths either at a continuous rate (1-step schedule) or in two segments consisting of a relatively high rate followed by a slower rate. In all cases, the welds were completed in 4s. The range of lap-shear values were compared to values required for resistance spot welds on the same steels. The minimum value of 10.3 kN was exceeded for friction stir spot welding of DP780 using a 2-step schedule and either the BN77- or the BN46-type stir tool. The respective minimum value of 12 kN was also exceeded for the HSB steel using the 2-step process and the BN46 stir tool.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Casper, Katya M.; Beresh, Steven J.; Schneider, Steven P.
2014-09-09
To investigate the pressure-fluctuation field beneath turbulent spots in a hypersonic boundary layer, a study was conducted on the nozzle wall of the Boeing/AFOSR Mach-6 Quiet Tunnel. Controlled disturbances were created by pulsed-glow perturbations based on the electrical breakdown of air. Under quiet-flow conditions, the nozzle-wall boundary layer remains laminar and grows very thick over the long nozzle length. This allows the development of large disturbances that can be well-resolved with high-frequency pressure transducers. A disturbance first grows into a second-mode instability wavepacket that is concentrated near its own centreline. Weaker disturbances are seen spreading from the centre. The wavesmore » grow and become nonlinear before breaking down to turbulence. The breakdown begins in the core of the packets where the wave amplitudes are largest. Second-mode waves are still evident in front of and behind the breakdown point and can be seen propagating in the spanwise direction. The turbulent core grows downstream, resulting in a spot with a classical arrowhead shape. Behind the spot, a low-pressure calmed region develops. However, the spot is not merely a localized patch of turbulence; instability waves remain an integral part. Limited measurements of naturally occurring disturbances show many similar characteristics. From the controlled disturbance measurements, the convection velocity, spanwise spreading angle, and typical pressure-fluctuation field were obtained.« less
On the mechanism of operation of a cathode spot cell in a vacuum arc
Mesyats, G. A.; Petrov, A. A.; Bochkarev, M. B.; Barengolts, S. A.
2014-05-05
The erosive structures formed on a tungsten cathode as a result of the motion of the cathode spot of a vacuum arc over the cathode surface have been examined. It has been found that the average mass of a cathode microprotrusion having the shape of a solidified jet is approximately equal to the mass of ions removed from the cathode within the lifetime of a cathode spot cell carrying a current of several amperes. The time of formation of a new liquid-metal jet under the action of the reactive force of the plasma ejected by the cathode spot is about 10?ns, which is comparable to the lifetime of a cell. The growth rate of a liquid-metal jet is ?10{sup 4}?cm/s. The geometric shape and size of a solidified jet are such that a new explosive emission center (spot cell) can be initiated within several nanoseconds during the interaction of the jet with the dense cathode plasma. This is the underlying mechanism of the self-sustained operation of a vacuum arc.
Casper, Katya M.; Beresh, Steven J.; Schneider, Steven P.
2014-09-09
To investigate the pressure-fluctuation field beneath turbulent spots in a hypersonic boundary layer, a study was conducted on the nozzle wall of the Boeing/AFOSR Mach-6 Quiet Tunnel. Controlled disturbances were created by pulsed-glow perturbations based on the electrical breakdown of air. Under quiet-flow conditions, the nozzle-wall boundary layer remains laminar and grows very thick over the long nozzle length. This allows the development of large disturbances that can be well-resolved with high-frequency pressure transducers. A disturbance first grows into a second-mode instability wavepacket that is concentrated near its own centreline. Weaker disturbances are seen spreading from the centre. The waves grow and become nonlinear before breaking down to turbulence. The breakdown begins in the core of the packets where the wave amplitudes are largest. Second-mode waves are still evident in front of and behind the breakdown point and can be seen propagating in the spanwise direction. The turbulent core grows downstream, resulting in a spot with a classical arrowhead shape. Behind the spot, a low-pressure calmed region develops. However, the spot is not merely a localized patch of turbulence; instability waves remain an integral part. Limited measurements of naturally occurring disturbances show many similar characteristics. From the controlled disturbance measurements, the convection velocity, spanwise spreading angle, and typical pressure-fluctuation field were obtained.
Jacobi, Rober
2007-03-28
This Topical Report (#6 of 9) consists of the figures 3.6-13 to (and including) 3.6-18 (and appropriate figure captions) that accompany the Final Technical Progress Report entitled: “Innovative Methodology for Detection of Fracture-Controlled Sweet Spots in the Northern Appalachian Basin” for DOE/NETL Award DE-AC26-00NT40698.
Jacobi, Rober
2007-03-31
This Topical Report (#6 of 9) consists of the figures 3.6-13 to (and including) 3.6-18 (and appropriate figure captions) that accompany the Final Technical Progress Report entitled: "Fracture-Controlled Sweet Spots in the Northern Appalachian Basin” for DOE/NETL Award DE-AC26-00NT40698.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Hybrid Deterministic/Monte Carlo Solutions to the Neutron Transport k-Eigenvalue Problem with a Comparison to Pure Monte Carlo Solutions Jeffrey A. Willert Los Alamos National Laboratory September 16, 2013 Joint work with: Dana Knoll (LANL), Ryosuke Park (LANL), and C. T. Kelley (NCSU) Jeffrey A. Willert Hybrid k-Eigenvalue Methods September 16, 2013 1 / 25 CASL-U-2013-0309-000 1 Introduction 2 Nonlinear Diffusion Acceleration for k-Eigenvalue Problems 3 Hybrid Methods 4 Classic Monte Carlo
Hot-spot mix in ignition-scale implosions on the NIF
Regan, S. P.; Epstein, R.; McCrory, R. L.; Meyerhofer, D. D.; Sangster, T. C.; Hammel, B. A.; Suter, L. J.; Ralph, J.; Scott, H.; Barrios, M. A.; Bradley, D. K.; Callahan, D. A.; Cerjan, C.; Collins, G. W.; Dixit, S. N.; Doeppner, T.; Edwards, M. J.; Farley, D. R.; Glenn, S.; Glenzer, S. H.; and others
2012-05-15
Ignition of an inertial confinement fusion (ICF) target depends on the formation of a central hot spot with sufficient temperature and areal density. Radiative and conductive losses from the hot spot can be enhanced by hydrodynamic instabilities. The concentric spherical layers of current National Ignition Facility (NIF) ignition targets consist of a plastic ablator surrounding a thin shell of cryogenic thermonuclear fuel (i.e., hydrogen isotopes), with fuel vapor filling the interior volume [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. The Rev. 5 ablator is doped with Ge to minimize preheat of the ablator closest to the DT ice caused by Au M-band emission from the hohlraum x-ray drive [D. S. Clark et al., Phys. Plasmas 17, 052703 (2010)]. Richtmyer-Meshkov and Rayleigh-Taylor hydrodynamic instabilities seeded by high-mode () ablator-surface perturbations can cause Ge-doped ablator to mix into the interior of the shell at the end of the acceleration phase [B. A. Hammel et al., Phys. Plasmas 18, 056310 (2011)]. As the shell decelerates, it compresses the fuel vapor, forming a hot spot. K-shell line emission from the ionized Ge that has penetrated into the hot spot provides an experimental signature of hot-spot mix. The Ge emission from tritium-hydrogen-deuterium (THD) and deuterium-tritium (DT) cryogenic targets and gas-filled plastic-shell capsules, which replace the THD layer with a mass-equivalent CH layer, was examined. The inferred amount of hot-spot-mix mass, estimated from the Ge K-shell line brightness using a detailed atomic physics code [J. J. MacFarlane et al., High Energy Density Phys. 3, 181 (2006)], is typically below the 75-ng allowance for hot-spot mix [S. W. Haan et al., Phys. Plasmas 18, 051001 (2011)]. Predictions of a simple mix model, based on linear growth of the measured surface-mass modulations, are consistent with the experimental results.
Srinivasan, Bhuvana; Tang, Xian-Zhu
2014-10-15
In an inertial confinement fusion target, energy loss due to thermal conduction from the hot-spot will inevitably ablate fuel ice into the hot-spot, resulting in a more massive but cooler hot-spot, which negatively impacts fusion yield. Hydrodynamic mix due to Rayleigh-Taylor instability at the gas-ice interface can aggravate the problem via an increased gas-ice interfacial area across which energy transfer from the hot-spot and ice can be enhanced. Here, this mix-enhanced transport effect on hot-spot fusion-performance degradation is quantified using contrasting 1D and 2D hydrodynamic simulations, and its dependence on effective acceleration, Atwood number, and ablation speed is identified.
Barrios, M. A.; Suter, L. J.; Glenn, S.; Benedetti, L. R.; Bradley, D. K.; Collins, G. W.; Hammel, B. A.; Izumi, N.; Ma, T.; Scott, H.; Smalyuk, V. A.; Regan, S. P.; Epstein, R.; Kyrala, G. A.
2013-07-15
Bright spots in the hot spot intensity profile of gated x-ray images of ignition-scale implosions at the National Ignition Facility [G. H. Miller et al., Opt. Eng. 443, (2004)] are observed. X-ray images of cryogenically layered deuterium-tritium (DT) and tritium-hydrogen-deuterium (THD) ice capsules, and gas filled plastic shell capsules (Symcap) were recorded along the hohlraum symmetry axis. Heterogeneous mixing of ablator material and fuel into the hot spot (i.e., hot-spot mix) by hydrodynamic instabilities causes the bright spots. Hot-spot mix increases the radiative cooling of the hot spot. Fourier analysis of the x-ray images is used to quantify the evolution of bright spots in both x- and k-space. Bright spot images were azimuthally binned to characterize bright spot location relative to known isolated defects on the capsule surface. A strong correlation is observed between bright spot location and the fill tube for both Symcap and cryogenically layered DT and THD ice targets, indicating the fill tube is a significant seed for the ablation front instability causing hot-spot mix. The fill tube is the predominant seed for Symcaps, while other capsule non-uniformities are dominant seeds for the cryogenically layered DT and THD ice targets. A comparison of the bright spot power observed for Si- and Ge-doped ablator targets shows heterogeneous mix in Symcap targets is mostly material from the doped ablator layer.
Brachytherapy structural shielding calculations using Monte Carlo generated, monoenergetic data
Zourari, K.; Peppa, V.; Papagiannis, P.; Ballester, Facundo; Siebert, Frank-Andr
2014-04-15
Purpose: To provide a method for calculating the transmission of any broad photon beam with a known energy spectrum in the range of 201090 keV, through concrete and lead, based on the superposition of corresponding monoenergetic data obtained from Monte Carlo simulation. Methods: MCNP5 was used to calculate broad photon beam transmission data through varying thickness of lead and concrete, for monoenergetic point sources of energy in the range pertinent to brachytherapy (201090 keV, in 10 keV intervals). The three parameter empirical model introduced byArcher et al. [Diagnostic x-ray shielding design based on an empirical model of photon attenuation, Health Phys. 44, 507517 (1983)] was used to describe the transmission curve for each of the 216 energy-material combinations. These three parameters, and hence the transmission curve, for any polyenergetic spectrum can then be obtained by superposition along the lines of Kharrati et al. [Monte Carlo simulation of x-ray buildup factors of lead and its applications in shielding of diagnostic x-ray facilities, Med. Phys. 34, 13981404 (2007)]. A simple program, incorporating a graphical user interface, was developed to facilitate the superposition of monoenergetic data, the graphical and tabular display of broad photon beam transmission curves, and the calculation of material thickness required for a given transmission from these curves. Results: Polyenergetic broad photon beam transmission curves of this work, calculated from the superposition of monoenergetic data, are compared to corresponding results in the literature. A good agreement is observed with results in the literature obtained from Monte Carlo simulations for the photon spectra emitted from bare point sources of various radionuclides. Differences are observed with corresponding results in the literature for x-ray spectra at various tube potentials, mainly due to the different broad beam conditions or x-ray spectra assumed. Conclusions: The data of
Monte Carlo prompt dose calculations for the National Ingition Facility
Latkowski, J.F.; Phillips, T.W.
1997-01-01
During peak operation, the National Ignition Facility (NIF) will conduct as many as 600 experiments per year and attain deuterium- tritium fusion yields as high as 1200 MJ/yr. The radiation effective dose equivalent (EDE) to workers is limited to an average of 03 mSv/yr (30 mrem/yr) in occupied areas of the facility. Laboratory personnel determined located outside the facility will receive EDEs <= 0.5 mSv/yr (<= 50 mrem/yr). The total annual occupational EDE for the facility will be maintained at <= 0.1 person-Sv/yr (<= 10 person- rem/yr). To ensure that prompt EDEs meet these limits, three- dimensional Monte Carlo calculations have been completed.
Quantum Monte Carlo simulation of spin-polarized H
Markic, L. Vranjes; Boronat, J.; Casulleras, J.
2007-02-01
The ground-state properties of spin polarized hydrogen H{down_arrow} are obtained by means of diffusion Monte Carlo calculations. Using the most accurate to date ab initio H{down_arrow}-H{down_arrow} interatomic potential we have studied its gas phase, from the very dilute regime until densities above its freezing point. At very small densities, the equation of state of the gas is very well described in terms of the gas parameter {rho}a{sup 3}, with a the s-wave scattering length. The solid phase has also been studied up to high pressures. The gas-solid phase transition occurs at a pressure of 173 bar, a much higher value than suggested by previous approximate descriptions.
Peelle's pertinent puzzle using the Monte Carlo technique
Kawano, Toshihiko; Talou, Patrick; Burr, Thomas; Pan, Feng
2009-01-01
We try to understand the long-standing problem of the Peelle's Pertinent Puzzle (PPP) using the Monte Carlo technique. We allow the probability density functions to be any kind of form to assume the impact of distribution, and obtain the least-squares solution directly from numerical simulations. We found that the standard least squares method gives the correct answer if a weighting function is properly provided. Results from numerical simulations show that the correct answer of PPP is 1.1 {+-} 0.25 if the common error is multiplicative. The thought-provoking answer of 0.88 is also correct, if the common error is additive, and if the error is proportional to the measured values. The least squares method correctly gives us the most probable case, where the additive component has a negative value. Finally, the standard method fails for PPP due to a distorted (non Gaussian) joint distribution.
Optimization of Monte Carlo transport simulations in stochastic media
Liang, C.; Ji, W.
2012-07-01
This paper presents an accurate and efficient approach to optimize radiation transport simulations in a stochastic medium of high heterogeneity, like the Very High Temperature Gas-cooled Reactor (VHTR) configurations packed with TRISO fuel particles. Based on a fast nearest neighbor search algorithm, a modified fast Random Sequential Addition (RSA) method is first developed to speed up the generation of the stochastic media systems packed with both mono-sized and poly-sized spheres. A fast neutron tracking method is then developed to optimize the next sphere boundary search in the radiation transport procedure. In order to investigate their accuracy and efficiency, the developed sphere packing and neutron tracking methods are implemented into an in-house continuous energy Monte Carlo code to solve an eigenvalue problem in VHTR unit cells. Comparison with the MCNP benchmark calculations for the same problem indicates that the new methods show considerably higher computational efficiency. (authors)
A study of Monte Carlo radiative transfer through fractal clouds
Gautier, C.; Lavallec, D.; O`Hirok, W.; Ricchiazzi, P.
1996-04-01
An understanding of radiation transport (RT) through clouds is fundamental to studies of the earth`s radiation budget and climate dynamics. The transmission through horizontally homogeneous clouds has been studied thoroughly using accurate, discreet ordinates radiative transfer models. However, the applicability of these results to general problems of global radiation budget is limited by the plane parallel assumption and the fact that real clouds fields show variability, both vertically and horizontally, on all size scales. To understand how radiation interacts with realistic clouds, we have used a Monte Carlo radiative transfer model to compute the details of the photon-cloud interaction on synthetic cloud fields. Synthetic cloud fields, generated by a cascade model, reproduce the scaling behavior, as well as the cloud variability observed and estimated from cloud satellite data.
Quantitative Monte Carlo-based holmium-166 SPECT reconstruction
Elschot, Mattijs; Smits, Maarten L. J.; Nijsen, Johannes F. W.; Lam, Marnix G. E. H.; Zonnenberg, Bernard A.; Bosch, Maurice A. A. J. van den; Jong, Hugo W. A. M. de; Viergever, Max A.
2013-11-15
Purpose: Quantitative imaging of the radionuclide distribution is of increasing interest for microsphere radioembolization (RE) of liver malignancies, to aid treatment planning and dosimetry. For this purpose, holmium-166 ({sup 166}Ho) microspheres have been developed, which can be visualized with a gamma camera. The objective of this work is to develop and evaluate a new reconstruction method for quantitative {sup 166}Ho SPECT, including Monte Carlo-based modeling of photon contributions from the full energy spectrum.Methods: A fast Monte Carlo (MC) simulator was developed for simulation of {sup 166}Ho projection images and incorporated in a statistical reconstruction algorithm (SPECT-fMC). Photon scatter and attenuation for all photons sampled from the full {sup 166}Ho energy spectrum were modeled during reconstruction by Monte Carlo simulations. The energy- and distance-dependent collimator-detector response was modeled using precalculated convolution kernels. Phantom experiments were performed to quantitatively evaluate image contrast, image noise, count errors, and activity recovery coefficients (ARCs) of SPECT-fMC in comparison with those of an energy window-based method for correction of down-scattered high-energy photons (SPECT-DSW) and a previously presented hybrid method that combines MC simulation of photopeak scatter with energy window-based estimation of down-scattered high-energy contributions (SPECT-ppMC+DSW). Additionally, the impact of SPECT-fMC on whole-body recovered activities (A{sup est}) and estimated radiation absorbed doses was evaluated using clinical SPECT data of six {sup 166}Ho RE patients.Results: At the same noise level, SPECT-fMC images showed substantially higher contrast than SPECT-DSW and SPECT-ppMC+DSW in spheres ≥17 mm in diameter. The count error was reduced from 29% (SPECT-DSW) and 25% (SPECT-ppMC+DSW) to 12% (SPECT-fMC). ARCs in five spherical volumes of 1.96–106.21 ml were improved from 32%–63% (SPECT-DSW) and 50%–80
Fuel temperature reactivity coefficient calculation by Monte Carlo perturbation techniques
Shim, H. J.; Kim, C. H.
2013-07-01
We present an efficient method to estimate the fuel temperature reactivity coefficient (FTC) by the Monte Carlo adjoint-weighted correlated sampling method. In this method, a fuel temperature change is regarded as variations of the microscopic cross sections and the temperature in the free gas model which is adopted to correct the asymptotic double differential scattering kernel. The effectiveness of the new method is examined through the continuous energy MC neutronics calculations for PWR pin cell problems. The isotope-wise and reaction-type-wise contributions to the FTCs are investigated for two free gas models - the constant scattering cross section model and the exact model. It is shown that the proposed method can efficiently predict the reactivity change due to the fuel temperature variation. (authors)
Monte-Carlo Continuous Energy Burnup Code System.
Energy Science and Technology Software Center (OSTI)
2007-08-31
Version 00 MCB is a Monte Carlo Continuous Energy Burnup Code for a general-purpose use to calculate a nuclide density time evolution with burnup or decay. It includes eigenvalue calculations of critical and subcritical systems as well as neutron transport calculations in fixed source mode or k-code mode to obtain reaction rates and energy deposition that are necessary for burnup calculations. The MCB-1C patch file and data packages as distributed by the NEADB are verymore » well organized and are being made available through RSICC as received. The RSICC package includes the MCB-1C patch and MCB data libraries. Installation of MCB requires MCNP4C source code and utility programs, which are not included in this MCB distribution. They were provided with the now obsolete CCC-700/MCNP-4C package.« less
Optimized nested Markov chain Monte Carlo sampling: theory
Coe, Joshua D; Shaw, M Sam; Sewell, Thomas D
2009-01-01
Metropolis Monte Carlo sampling of a reference potential is used to build a Markov chain in the isothermal-isobaric ensemble. At the endpoints of the chain, the energy is reevaluated at a different level of approximation (the 'full' energy) and a composite move encompassing all of the intervening steps is accepted on the basis of a modified Metropolis criterion. By manipulating the thermodynamic variables characterizing the reference system we maximize the average acceptance probability of composite moves, lengthening significantly the random walk made between consecutive evaluations of the full energy at a fixed acceptance probability. This provides maximally decorrelated samples of the full potential, thereby lowering the total number required to build ensemble averages of a given variance. The efficiency of the method is illustrated using model potentials appropriate to molecular fluids at high pressure. Implications for ab initio or density functional theory (DFT) treatment are discussed.
Monte Carlo Simulation Tool Installation and Operation Guide
Aguayo Navarrete, Estanislao; Ankney, Austin S.; Berguson, Timothy J.; Kouzes, Richard T.; Orrell, John L.; Troy, Meredith D.; Wiseman, Clinton G.
2013-09-02
This document provides information on software and procedures for Monte Carlo simulations based on the Geant4 toolkit, the ROOT data analysis software and the CRY cosmic ray library. These tools have been chosen for its application to shield design and activation studies as part of the simulation task for the Majorana Collaboration. This document includes instructions for installation, operation and modification of the simulation code in a high cyber-security computing environment, such as the Pacific Northwest National Laboratory network. It is intended as a living document, and will be periodically updated. It is a starting point for information collection by an experimenter, and is not the definitive source. Users should consult with one of the authors for guidance on how to find the most current information for their needs.
Improved version of the PHOBOS Glauber Monte Carlo
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Loizides, C.; Nagle, J.; Steinberg, P.
2015-09-01
“Glauber” models are used to calculate geometric quantities in the initial state of heavy ion collisions, such as impact parameter, number of participating nucleons and initial eccentricity. Experimental heavy-ion collaborations, in particular at RHIC and LHC, use Glauber Model calculations for various geometric observables for determination of the collision centrality. In this document, we describe the assumptions inherent to the approach, and provide an updated implementation (v2) of the Monte Carlo based Glauber Model calculation, which originally was used by the PHOBOS collaboration. The main improvement w.r.t. the earlier version (v1) (Alver et al. 2008) is the inclusion of Tritium,more » Helium-3, and Uranium, as well as the treatment of deformed nuclei and Glauber–Gribov fluctuations of the proton in p +A collisions. A users’ guide (updated to reflect changes in v2) is provided for running various calculations.« less
MONTE-CARLO BURNUP CALCULATION UNCERTAINTY QUANTIFICATION AND PROPAGATION DETERMINATION
Nichols, T.; Sternat, M.; Charlton, W.
2011-05-08
MONTEBURNS is a Monte-Carlo depletion routine utilizing MCNP and ORIGEN 2.2. Uncertainties exist in the MCNP transport calculation, but this information is not passed to the depletion calculation in ORIGEN or saved. To quantify this transport uncertainty and determine how it propagates between burnup steps, a statistical analysis of a multiple repeated depletion runs is performed. The reactor model chosen is the Oak Ridge Research Reactor (ORR) in a single assembly, infinite lattice configuration. This model was burned for a 25.5 day cycle broken down into three steps. The output isotopics as well as effective multiplication factor (k-effective) were tabulated and histograms were created at each burnup step using the Scott Method to determine the bin width. It was expected that the gram quantities and k-effective histograms would produce normally distributed results since they were produced from a Monte-Carlo routine, but some of results do not. The standard deviation at each burnup step was consistent between fission product isotopes as expected, while the uranium isotopes created some unique results. The variation in the quantity of uranium was small enough that, from the reaction rate MCNP tally, round off error occurred producing a set of repeated results with slight variation. Statistical analyses were performed using the {chi}{sup 2} test against a normal distribution for several isotopes and the k-effective results. While the isotopes failed to reject the null hypothesis of being normally distributed, the {chi}{sup 2} statistic grew through the steps in the k-effective test. The null hypothesis was rejected in the later steps. These results suggest, for a high accuracy solution, MCNP cell material quantities less than 100 grams and greater kcode parameters are needed to minimize uncertainty propagation and minimize round off effects.
Modeling granular phosphor screens by Monte Carlo methods
Liaparinos, Panagiotis F.; Kandarakis, Ioannis S.; Cavouras, Dionisis A.; Delis, Harry B.; Panayiotakis, George S.
2006-12-15
The intrinsic phosphor properties are of significant importance for the performance of phosphor screens used in medical imaging systems. In previous analytical-theoretical and Monte Carlo studies on granular phosphor materials, values of optical properties, and light interaction cross sections were found by fitting to experimental data. These values were then employed for the assessment of phosphor screen imaging performance. However, it was found that, depending on the experimental technique and fitting methodology, the optical parameters of a specific phosphor material varied within a wide range of values, i.e., variations of light scattering with respect to light absorption coefficients were often observed for the same phosphor material. In this study, x-ray and light transport within granular phosphor materials was studied by developing a computational model using Monte Carlo methods. The model was based on the intrinsic physical characteristics of the phosphor. Input values required to feed the model can be easily obtained from tabulated data. The complex refractive index was introduced and microscopic probabilities for light interactions were produced, using Mie scattering theory. Model validation was carried out by comparing model results on x-ray and light parameters (x-ray absorption, statistical fluctuations in the x-ray to light conversion process, number of emitted light photons, output light spatial distribution) with previous published experimental data on Gd{sub 2}O{sub 2}S:Tb phosphor material (Kodak Min-R screen). Results showed the dependence of the modulation transfer function (MTF) on phosphor grain size and material packing density. It was predicted that granular Gd{sub 2}O{sub 2}S:Tb screens of high packing density and small grain size may exhibit considerably better resolution and light emission properties than the conventional Gd{sub 2}O{sub 2}S:Tb screens, under similar conditions (x-ray incident energy, screen thickness)
SU-E-T-188: Film Dosimetry Verification of Monte Carlo Generated Electron Treatment Plans
Enright, S; Asprinio, A; Lu, L
2014-06-01
Purpose: The purpose of this study was to compare dose distributions from film measurements to Monte Carlo generated electron treatment plans. Irradiation with electrons offers the advantages of dose uniformity in the target volume and of minimizing the dose to deeper healthy tissue. Using the Monte Carlo algorithm will improve dose accuracy in regions with heterogeneities and irregular surfaces. Methods: Dose distributions from GafChromic{sup } EBT3 films were compared to dose distributions from the Electron Monte Carlo algorithm in the Eclipse{sup } radiotherapy treatment planning system. These measurements were obtained for 6MeV, 9MeV and 12MeV electrons at two depths. All phantoms studied were imported into Eclipse by CT scan. A 1 cm thick solid water template with holes for bonelike and lung-like plugs was used. Different configurations were used with the different plugs inserted into the holes. Configurations with solid-water plugs stacked on top of one another were also used to create an irregular surface. Results: The dose distributions measured from the film agreed with those from the Electron Monte Carlo treatment plan. Accuracy of Electron Monte Carlo algorithm was also compared to that of Pencil Beam. Dose distributions from Monte Carlo had much higher pass rates than distributions from Pencil Beam when compared to the film. The pass rate for Monte Carlo was in the 80%99% range, where the pass rate for Pencil Beam was as low as 10.76%. Conclusion: The dose distribution from Monte Carlo agreed with the measured dose from the film. When compared to the Pencil Beam algorithm, pass rates for Monte Carlo were much higher. Monte Carlo should be used over Pencil Beam for regions with heterogeneities and irregular surfaces.
Projectile containing metastable intermolecular composites and spot fire method of use
Asay, Blaine W.; Son, Steven F.; Sanders, V. Eric; Foley, Timothy; Novak, Alan M.; Busse, James R.
2012-07-31
A method for altering the course of a conflagration involving firing a projectile comprising a powder mixture of oxidant powder and nanosized reductant powder at velocity sufficient for a violent reaction between the oxidant powder and the nanosized reductant powder upon impact of the projectile, and causing impact of the projectile at a location chosen to draw a main fire to a spot fire at such location and thereby change the course of the conflagration, whereby the air near the chosen location is heated to a temperature sufficient to cause a spot fire at such location. The invention also includes a projectile useful for such method and said mixture preferably comprises a metastable intermolecular composite.
Vertically-tapered optical waveguide and optical spot transformer formed therefrom
Bakke, Thor; Sullivan, Charles T.
2004-07-27
An optical waveguide is disclosed in which a section of the waveguide core is vertically tapered during formation by spin coating by controlling the width of an underlying mesa structure. The optical waveguide can be formed from spin-coatable materials such as polymers, sol-gels and spin-on glasses. The vertically-tapered waveguide section can be used to provide a vertical expansion of an optical mode of light within the optical waveguide. A laterally-tapered section can be added adjacent to the vertically-tapered section to provide for a lateral expansion of the optical mode, thereby forming an optical spot-size transformer for efficient coupling of light between the optical waveguide and a single-mode optical fiber. Such a spot-size transformer can also be added to a III-V semiconductor device by post processing.
Influence of hot spot features on the initiation characteristics of heterogeneous nitromethane
Dattelbaum, Dana M; Sheffield, Stephen A; Stahl, David B; Dattelbaum, Andrew M; Engelke, Ray
2010-01-01
To gain insights into the critical hot spot features influencing energetic materials initiation characteristics, well-defined micron-scale particles have been intentionally introduced into the homogeneous explosive nitromethane (NM). Two types of potential hot spot origins have been examined - shock impedance mismatches using solid silica beads, and porosity using hollow microballoons - as well as their sizes and inter-particle separations. Here, we present the results of several series of gas gun-driven plate impact experiments on NM/particle mixtures with well-controlled shock inputs. Detailed insights into the nature of the reactive flow during the build-up to detonation have been obtained from the response of in-situ electromagnetic gauges, and the data have been used to establish Pop-plots (run-distance-to-detonation vs. shock input pressure) for the mixtures. Comparisons of sensitization effects and energy release characteristics relative to the initial shock front between the solid and hollow beads are presented.
Geometrically nonlinear behaviour of spot welded joints in tensile and compressive shear loading
Radaj, D.; Zhang, S.
1995-05-01
The geometrically nonlinear behavior of spot welded joints including buckling and gap closure and its influence on local stress parameters at the weld spot edge (structural stresses, notch stress or fatigue notch factor, stress intensity factors) are determined by a large displacement analysis of the tensile shear specimen subjected to tensile and compressive loading. The local parameters mentioned are considered decisive for fatigue crack initiation. A continuous beam model and a plate strip model are used within a simplified procedure. A more sophisticated finite element model is applied on the specimens thereafter. The nonlinear effect is small for steel plates more than 1 mm thick in the medium and high cycle fatigue range of tensile loading. It may be stronger for compressive loading but is at least partially compensated for in this case by the gap closure effect. 4 refs.
Eutectic structures in friction spot welding joint of aluminum alloy to copper
Shen, Junjun Suhuddin, Uceu F. H.; Cardillo, Maria E. B.; Santos, Jorge F. dos
2014-05-12
A dissimilar joint of AA5083 Al alloy and copper was produced by friction spot welding. The Al-MgCuAl{sub 2} eutectic in both coupled and divorced manners were found in the weld. At a relatively high temperature, mass transport of Cu due to plastic deformation, material flow, and atomic diffusion, combined with the alloy system of AA5083 are responsible for the ternary eutectic melting.
Macrophyte mapping in ten lakes of South Carolina with multispectral SPOT HRV data
Mackey, H.E. Jr.
1989-01-01
Fall and spring multispectral SPOT HRV data for 1987 and 1988 were used to evaluate the macrophyte distributions in ten freshwater reservoirs of South Carolina. The types of macrophyte and wetland communities present along the shoreline of the lakes varied depending on the age, water level fluctuations, water quality, and basin morphology. Seasonal satellite data were important for evaluation of the extent of persistent versus non-persistent macrophyte communities in the lakes. This paper contains only the view graphs of this process.
X marks the spot: Researchers confirm novel method for controlling plasma
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
rotation to improve fusion performance | Princeton Plasma Physics Lab X marks the spot: Researchers confirm novel method for controlling plasma rotation to improve fusion performance By Raphael Rosen June 23, 2015 Tweet Widget Google Plus One Share on Facebook Representative plasma geometries, with the X-point location circled in red / Reprinted from T. Stoltzfus-Dueck et al., Phys. Rev. Lett. 114, 245001 (2015). Copyright 2015 by the American Physical Society. Representative plasma
X marks the spot: Researchers confirm novel method for controlling plasma
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
rotation to improve fusion performance | Princeton Plasma Physics Lab X marks the spot: Researchers confirm novel method for controlling plasma rotation to improve fusion performance By Raphael Rosen June 23, 2015 Tweet Widget Google Plus One Share on Facebook Representative plasma geometries, with the X-point location circled in red / Reprinted from T. Stoltzfus-Dueck et al., Phys. Rev. Lett. 114, 245001 (2015). Copyright 2015 by the American Physical Society. Representative plasma
Spot test for 1,3,5-triamino-2,4,6-trinitrobenzene, TATB
Harris, Betty W.
1986-01-01
A simple, sensitive and specific spot test for 1,3,5-triamino-2,4,6-trinitrobenzene, TATB, is described. Upon the application of the composition of matter of the present invention to samples containing in excess of 0.1 mg of this explosive, a bright orange color results. Interfering species such as TNT and Tetryl can be removed by first treating the sample with a solvent which does not dissolve much of the TATB, but readily dissolves these explosives.
Spot test for 1,3,5-triamino-2,4,6-trinitrobenzene, TATB
Harris, B.W.
1984-11-29
A simple, sensitive and specific spot test for 1,3,5-triamino-2,4,6-trinitrobenzene, TATB, is described. Upon the application of the composition of matter of the subject invention to samples containing in excess of 0.1 mg of this explosive, a bright orange color results. Interfering species such as TNT and Tetryl can be removed by first treating the sample with a solvent which does not dissolve the TATB, but readily dissolves these interfering explosives.
Students do cool summer research projects in one of the hottest spots |
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Princeton Plasma Physics Lab Students do cool summer research projects in one of the hottest spots August 4, 2016 Tweet Widget Google Plus One Share on Facebook Priya Jaglal (Photo by Elle Starkman/PPPL Office of Communications) Priya Jaglal More than 40 college students pursuing careers in physics, engineering and computer science are spending their summer at the U.S. Department of Energy's Princeton Plasma Physics Laboratory working with scientists and engineers on hands-on research
SU-E-T-73: Commissioning of a Treatment Planning System for Proton Spot Scanning
Saini, J; Kang, Y; Schultz, L; Nicewonger, D; Herrera, M; Wong, T; Bowen, S; Bloch, C
2014-06-01
Purpose: A treatment planning system (TPS) was commissioned for clinical use with a fixed beam line proton delivery system. An outline of the data collection, modeling, and verification is provided. Methods: Beam data modeling for proton spot scanning in CMS Xio TPS requires the following measurements: (i) integral depth dose curves (IDDCs); (ii) absolute dose calibration; and (iii) beam spot characteristics. The IDDCs for 18 proton energies were measured using an integrating detector in a single spot field in a water phantom. Absolute scaling of the IDDCs were performed based on ion chamber measurements in mono-energetic 1010 cm{sup 2} fields in water. Beam spot shapes were measured in air using a flat panel scintillator detector at multiple planes. For beam model verification, more than 45 uniform dose phantom and patient plans were generated. These plans were used to measure range, point dose, and longitudinal and lateral profiles. Tolerances employed for verification are: point dose and longitudinal profiles, 2%; range, 1 mm; FWHM for lateral profiles, 2 mm; and patient plan dose distribution, gamma index of >90% at 3%/3 mm criteria. Results: More than 97% of the point dose measurements out of 115 were within +/-2% with maximum deviation of 3%. 98% of the ranges measured were within 1 mm with maximum deviation of 1.4mm. The normalized depth doses were within 2% at all depths. The maximum error in FWHM of lateral profiles was found to be less than 2mm. For 5 patient plans representing different anatomic sites, a total of 38 planes for 12 beams were analyzed for gamma index with average value of 99% and minimum of 94%. Conclusions: The planning system is successfully commissioned and can be safely deployed for clinical use. Measurements of IDDCs on user beam are highly recommended instead of using standard beam IDDCs.
Friction Stir Spot Welding (FSSW) of Advanced High Strength Steel (AHSS)
Santella, M. L.; Hovanski, Yuri; Pan, Tsung-Yu
2012-04-16
Friction stir spot welding (FSSW) is applied to join advanced high strength steels (AHSS): galvannealed dual phase 780 MPa steel (DP780GA), transformation induced plasticity 780 MPa steel (TRIP780), and hot-stamped boron steel (HSBS). A low-cost Si3N4 ceramic tool was developed and used for making welds in this study instead of polycrystalline cubic boron nitride (PCBN) material used in earlier studies. FSSW has the advantages of solid-state, low-temperature process, and the ability of joining dissimilar grade of steels and thicknesses. Two different tool shoulder geometries, concave with smooth surface and convex with spiral pattern, were used in the study. Welds were made by a 2-step displacement control process with weld time of 4, 6, and 10 seconds. Static tensile lap-shear strength achieved 16.4 kN for DP780GA-HSBS and 13.2kN for TRIP780-HSBS, above the spot weld strength requirements by AWS. Nugget pull-out was the failure mode of the joint. The joining mechanism was illustrated from the cross-section micrographs. Microhardness measurement showed hardening in the upper sheet steel (DP780GA or TRIP780) in the weld, but softening of HSBS in the heat-affect zone (HAZ). The study demonstrated the feasibility of making high-strength AHSS spot welds with low-cost tools.
Complete Monte Carlo Simulation of Neutron Scattering Experiments
Drosg, M.
2011-12-13
In the far past, it was not possible to accurately correct for the finite geometry and the finite sample size of a neutron scattering set-up. The limited calculation power of the ancient computers as well as the lack of powerful Monte Carlo codes and the limitation in the data base available then prevented a complete simulation of the actual experiment. Using e.g. the Monte Carlo neutron transport code MCNPX [1], neutron scattering experiments can be simulated almost completely with a high degree of precision using a modern PC, which has a computing power that is ten thousand times that of a super computer of the early 1970s. Thus, (better) corrections can also be obtained easily for previous published data provided that these experiments are sufficiently well documented. Better knowledge of reference data (e.g. atomic mass, relativistic correction, and monitor cross sections) further contributes to data improvement. Elastic neutron scattering experiments from liquid samples of the helium isotopes performed around 1970 at LANL happen to be very well documented. Considering that the cryogenic targets are expensive and complicated, it is certainly worthwhile to improve these data by correcting them using this comparatively straightforward method. As two thirds of all differential scattering cross section data of {sup 3}He(n,n){sup 3}He are connected to the LANL data, it became necessary to correct the dependent data measured in Karlsruhe, Germany, as well. A thorough simulation of both the LANL experiments and the Karlsruhe experiment is presented, starting from the neutron production, followed by the interaction in the air, the interaction with the cryostat structure, and finally the scattering medium itself. In addition, scattering from the hydrogen reference sample was simulated. For the LANL data, the multiple scattering corrections are smaller by a factor of five at least, making this work relevant. Even more important are the corrections to the Karlsruhe data
Quantum Monte Carlo Calculations Applied to Magnetic Molecules
Larry Engelhardt
2006-08-09
We have calculated the equilibrium thermodynamic properties of Heisenberg spin systems using a quantum Monte Carlo (QMC) method. We have used some of these systems as models to describe recently synthesized magnetic molecules, and-upon comparing the results of these calculations with experimental data-have obtained accurate estimates for the basic parameters of these models. We have also performed calculations for other systems that are of more general interest, being relevant both for existing experimental data and for future experiments. Utilizing the concept of importance sampling, these calculations can be carried out in an arbitrarily large quantum Hilbert space, while still avoiding any approximations that would introduce systematic errors. The only errors are statistical in nature, and as such, their magnitudes are accurately estimated during the course of a simulation. Frustrated spin systems present a major challenge to the QMC method, nevertheless, in many instances progress can be made. In this chapter, the field of magnetic molecules is introduced, paying particular attention to the characteristics that distinguish magnetic molecules from other systems that are studied in condensed matter physics. We briefly outline the typical path by which we learn about magnetic molecules, which requires a close relationship between experiments and theoretical calculations. The typical experiments are introduced here, while the theoretical methods are discussed in the next chapter. Each of these theoretical methods has a considerable limitation, also described in Chapter 2, which together serve to motivate the present work. As is shown throughout the later chapters, the present QMC method is often able to provide useful information where other methods fail. In Chapter 3, the use of Monte Carlo methods in statistical physics is reviewed, building up the fundamental ideas that are necessary in order to understand the method that has been used in this work. With these
Quantum Monte Carlo for electronic structure: Recent developments and applications
Rodriquez, M. M.S.
1995-04-01
Quantum Monte Carlo (QMC) methods have been found to give excellent results when applied to chemical systems. The main goal of the present work is to use QMC to perform electronic structure calculations. In QMC, a Monte Carlo simulation is used to solve the Schroedinger equation, taking advantage of its analogy to a classical diffusion process with branching. In the present work the author focuses on how to extend the usefulness of QMC to more meaningful molecular systems. This study is aimed at questions concerning polyatomic and large atomic number systems. The accuracy of the solution obtained is determined by the accuracy of the trial wave function`s nodal structure. Efforts in the group have given great emphasis to finding optimized wave functions for the QMC calculations. Little work had been done by systematically looking at a family of systems to see how the best wave functions evolve with system size. In this work the author presents a study of trial wave functions for C, CH, C{sub 2}H and C{sub 2}H{sub 2}. The goal is to study how to build wave functions for larger systems by accumulating knowledge from the wave functions of its fragments as well as gaining some knowledge on the usefulness of multi-reference wave functions. In a MC calculation of a heavy atom, for reasonable time steps most moves for core electrons are rejected. For this reason true equilibration is rarely achieved. A method proposed by Batrouni and Reynolds modifies the way the simulation is performed without altering the final steady-state solution. It introduces an acceleration matrix chosen so that all coordinates (i.e., of core and valence electrons) propagate at comparable speeds. A study of the results obtained using their proposed matrix suggests that it may not be the optimum choice. In this work the author has found that the desired mixing of coordinates between core and valence electrons is not achieved when using this matrix. A bibliography of 175 references is included.
Duo at Santa Fe's Monte del Sol Charter School takes top award in 25th
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
New Mexico Supercomputing Challenge 5th New Mexico Supercomputing Challenge Duo at Santa Fe's Monte del Sol Charter School takes top award in 25th New Mexico Supercomputing Challenge Meghan Hill and Katelynn James took the top prize for their research project April 21, 2015 Katelynn James, left, and Meghan Hill of Monte del Sol Charter School in Santa Fe. Katelynn James, left, and Meghan Hill of Monte del Sol Charter School in Santa Fe. Contact Los Alamos National Laboratory Steve Sandoval
Perfetti, Christopher M; Rearden, Bradley T
2014-01-01
This work introduces a new approach for calculating sensitivity coefficients for generalized neutronic responses to nuclear data uncertainties using continuous-energy Monte Carlo methods. The approach presented in this paper, known as the GEAR-MC method, allows for the calculation of generalized sensitivity coefficients for multiple responses in a single Monte Carlo calculation with no nuclear data perturbations or knowledge of nuclear covariance data. The theory behind the GEAR-MC method is presented here, and proof of principle is demonstrated by using the GEAR-MC method to calculate sensitivity coefficients for responses in several 3D, continuous-energy Monte Carlo applications.
Monte Carlo Simulations of Cosmic Rays Hadronic Interactions
Aguayo Navarrete, Estanislao; Orrell, John L.; Kouzes, Richard T.
2011-04-01
This document describes the construction and results of the MaCoR software tool, developed to model the hadronic interactions of cosmic rays with different geometries of materials. The ubiquity of cosmic radiation in the environment results in the activation of stable isotopes, referred to as cosmogenic activities. The objective is to use this application in conjunction with a model of the MAJORANA DEMONSTRATOR components, from extraction to deployment, to evaluate cosmogenic activation of such components before and after deployment. The cosmic ray showers include several types of particles with a wide range of energy (MeV to GeV). It is infeasible to compute an exact result with a deterministic algorithm for this problem; Monte Carlo simulations are a more suitable approach to model cosmic ray hadronic interactions. In order to validate the results generated by the application, a test comparing experimental muon flux measurements and those predicted by the application is presented. The experimental and simulated results have a deviation of 3%.
Pseudopotentials for quantum Monte Carlo studies of transition metal oxides
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Krogel, Jaron T.; Santana Palacio, Juan A.; Reboredo, Fernando A.
2016-02-22
Quantum Monte Carlo (QMC) calculations of transition metal oxides are partially limited by the availability of high-quality pseudopotentials that are both accurate in QMC and compatible with major plane-wave electronic structure codes. We have generated a set of neon-core pseudopotentials with small cutoff radii for the early transition metal elements Sc to Zn within the local density approximation of density functional theory. The pseudopotentials have been directly tested for accuracy within QMC by calculating the first through fourth ionization potentials of the isolated transition metal (M) atoms and the binding curve of each M-O dimer. We find the ionization potentialsmore » to be accurate to 0.16(1) eV, on average, relative to experiment. The equilibrium bond lengths of the dimers are within 0.5(1)% of experimental values, on average, and the binding energies are also typically accurate to 0.18(3) eV. The level of accuracy we find for atoms and dimers is comparable to what has recently been observed for bulk metals and oxides using the same pseudopotentials. Our QMC pseudopotential results compare well with the findings of previous QMC studies and benchmark quantum chemical calculations.« less
High order Chin actions in path integral Monte Carlo
Sakkos, K.; Casulleras, J.; Boronat, J.
2009-05-28
High order actions proposed by Chin have been used for the first time in path integral Monte Carlo simulations. Contrary to the Takahashi-Imada action, which is accurate to the fourth order only for the trace, the Chin action is fully fourth order, with the additional advantage that the leading fourth-order error coefficients are finely tunable. By optimizing two free parameters entering in the new action, we show that the time step error dependence achieved is best fitted with a sixth order law. The computational effort per bead is increased but the total number of beads is greatly reduced and the efficiency improvement with respect to the primitive approximation is approximately a factor of 10. The Chin action is tested in a one-dimensional harmonic oscillator, a H{sub 2} drop, and bulk liquid {sup 4}He. In all cases a sixth-order law is obtained with values of the number of beads that compare well with the pair action approximation in the stringent test of superfluid {sup 4}He.
Reduced Variance for Material Sources in Implicit Monte Carlo
Urbatsch, Todd J.
2012-06-25
Implicit Monte Carlo (IMC), a time-implicit method due to Fleck and Cummings, is used for simulating supernovae and inertial confinement fusion (ICF) systems where x-rays tightly and nonlinearly interact with hot material. The IMC algorithm represents absorption and emission within a timestep as an effective scatter. Similarly, the IMC time-implicitness splits off a portion of a material source directly into the radiation field. We have found that some of our variance reduction and particle management schemes will allow large variances in the presence of small, but important, material sources, as in the case of ICF hot electron preheat sources. We propose a modification of our implementation of the IMC method in the Jayenne IMC Project. Instead of battling the sampling issues associated with a small source, we bypass the IMC implicitness altogether and simply deterministically update the material state with the material source if the temperature of the spatial cell is below a user-specified cutoff. We describe the modified method and present results on a test problem that show the elimination of variance for small sources.
Random Number Generation for Petascale Quantum Monte Carlo
Ashok Srinivasan
2010-03-16
The quality of random number generators can affect the results of Monte Carlo computations, especially when a large number of random numbers are consumed. Furthermore, correlations present between different random number streams in a parallel computation can further affect the results. The SPRNG software, which the author had developed earlier, has pseudo-random number generators (PRNGs) capable of producing large numbers of streams with large periods. However, they had been empirically tested on only thousand streams earlier. In the work summarized here, we tested the SPRNG generators with over a hundred thousand streams, involving over 10^14 random numbers per test, on some tests. We also tested the popular Mersenne Twister. We believe that these are the largest tests of PRNGs, both in terms of the numbers of streams tested and the number of random numbers tested. We observed defects in some of these generators, including the Mersenne Twister, while a few generators appeared to perform well. We also corrected an error in the implementation of one of the SPRNG generators.
Improving computational efficiency of Monte Carlo simulations with variance reduction
Turner, A.
2013-07-01
CCFE perform Monte-Carlo transport simulations on large and complex tokamak models such as ITER. Such simulations are challenging since streaming and deep penetration effects are equally important. In order to make such simulations tractable, both variance reduction (VR) techniques and parallel computing are used. It has been found that the application of VR techniques in such models significantly reduces the efficiency of parallel computation due to 'long histories'. VR in MCNP can be accomplished using energy-dependent weight windows. The weight window represents an 'average behaviour' of particles, and large deviations in the arriving weight of a particle give rise to extreme amounts of splitting being performed and a long history. When running on parallel clusters, a long history can have a detrimental effect on the parallel efficiency - if one process is computing the long history, the other CPUs complete their batch of histories and wait idle. Furthermore some long histories have been found to be effectively intractable. To combat this effect, CCFE has developed an adaptation of MCNP which dynamically adjusts the WW where a large weight deviation is encountered. The method effectively 'de-optimises' the WW, reducing the VR performance but this is offset by a significant increase in parallel efficiency. Testing with a simple geometry has shown the method does not bias the result. This 'long history method' has enabled CCFE to significantly improve the performance of MCNP calculations for ITER on parallel clusters, and will be beneficial for any geometry combining streaming and deep penetration effects. (authors)
Cohesion Energetics of Carbon Allotropes: Quantum Monte Carlo Study
Shin, Hyeondeok; Kang, Sinabro; Koo, Jahyun; Lee, Hoonkyung; Kim, Jeongnim; Kwon, Yongkyung
2014-01-01
We have performed quantum Monte Carlo calculations to study the cohesion energetics of carbon allotropes, including sp3-bonded diamond, sp2-bonded graphene, sp-sp2 hybridized graphynes, and sp-bonded carbyne. The comput- ed cohesive energies of diamond and graphene are found to be in excellent agreement with the corresponding values de- termined experimentally for diamond and graphite, respectively, when the zero-point energies, along with the interlayer binding in the case of graphite, are included. We have also found that the cohesive energy of graphyne decreases system- atically as the ratio of sp-bonded carbon atoms increases. The cohesive energy of -graphyne, the most energetically- stable graphyne, turns out to be 6.766(6) eV/atom, which is smaller than that of graphene by 0.698(12) eV/atom. Experi- mental difficulty in synthesizing graphynes could be explained by their significantly smaller cohesive energies. Finally we conclude that the cohesive energy of a newly-proposed two-dimensional carbon network can be accurately estimated with the carbon-carbon bond energies determined from the cohesive energies of graphene and three different graphynes.
Status of the MORSE multigroup Monte Carlo radiation transport code
Emmett, M.B.
1993-06-01
There are two versions of the MORSE multigroup Monte Carlo radiation transport computer code system at Oak Ridge National Laboratory. MORSE-CGA is the most well-known and has undergone extensive use for many years. MORSE-SGC was originally developed in about 1980 in order to restructure the cross-section handling and thereby save storage. However, with the advent of new computer systems having much larger storage capacity, that aspect of SGC has become unnecessary. Both versions use data from multigroup cross-section libraries, although in somewhat different formats. MORSE-SGC is the version of MORSE that is part of the SCALE system, but it can also be run stand-alone. Both CGA and SGC use the Multiple Array System (MARS) geometry package. In the last six months the main focus of the work on these two versions has been on making them operational on workstations, in particular, the IBM RISC 6000 family. A new version of SCALE for workstations is being released to the Radiation Shielding Information Center (RSIC). MORSE-CGA, Version 2.0, is also being released to RSIC. Both SGC and CGA have undergone other revisions recently. This paper reports on the current status of the MORSE code system.
Monte Carlo analysis of localization errors in magnetoencephalography
Medvick, P.A.; Lewis, P.S.; Aine, C.; Flynn, E.R.
1989-01-01
In magnetoencephalography (MEG), the magnetic fields created by electrical activity in the brain are measured on the surface of the skull. To determine the location of the activity, the measured field is fit to an assumed source generator model, such as a current dipole, by minimizing chi-square. For current dipoles and other nonlinear source models, the fit is performed by an iterative least squares procedure such as the Levenberg-Marquardt algorithm. Once the fit has been computed, analysis of the resulting value of chi-square can determine whether the assumed source model is adequate to account for the measurements. If the source model is adequate, then the effect of measurement error on the fitted model parameters must be analyzed. Although these kinds of simulation studies can provide a rough idea of the effect that measurement error can be expected to have on source localization, they cannot provide detailed enough information to determine the effects that the errors in a particular measurement situation will produce. In this work, we introduce and describe the use of Monte Carlo-based techniques to analyze model fitting errors for real data. Given the details of the measurement setup and a statistical description of the measurement errors, these techniques determine the effects the errors have on the fitted model parameters. The effects can then be summarized in various ways such as parameter variances/covariances or multidimensional confidence regions. 8 refs., 3 figs.
Ensemble bayesian model averaging using markov chain Monte Carlo sampling
Vrugt, Jasper A; Diks, Cees G H; Clark, Martyn P
2008-01-01
Bayesian model averaging (BMA) has recently been proposed as a statistical method to calibrate forecast ensembles from numerical weather models. Successful implementation of BMA however, requires accurate estimates of the weights and variances of the individual competing models in the ensemble. In their seminal paper (Raftery etal. Mon Weather Rev 133: 1155-1174, 2(05)) has recommended the Expectation-Maximization (EM) algorithm for BMA model training, even though global convergence of this algorithm cannot be guaranteed. In this paper, we compare the performance of the EM algorithm and the recently developed Differential Evolution Adaptive Metropolis (DREAM) Markov Chain Monte Carlo (MCMC) algorithm for estimating the BMA weights and variances. Simulation experiments using 48-hour ensemble data of surface temperature and multi-model stream-flow forecasts show that both methods produce similar results, and that their performance is unaffected by the length of the training data set. However, MCMC simulation with DREAM is capable of efficiently handling a wide variety of BMA predictive distributions, and provides useful information about the uncertainty associated with the estimated BMA weights and variances.
Non-adiabatic molecular dynamics by accelerated semiclassical Monte Carlo
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
White, Alexander J.; Gorshkov, Vyacheslav N.; Tretiak, Sergei; Mozyrsky, Dmitry
2015-07-07
Non-adiabatic dynamics, where systems non-radiatively transition between electronic states, plays a crucial role in many photo-physical processes, such as fluorescence, phosphorescence, and photoisomerization. Methods for the simulation of non-adiabatic dynamics are typically either numerically impractical, highly complex, or based on approximations which can result in failure for even simple systems. Recently, the Semiclassical Monte Carlo (SCMC) approach was developed in an attempt to combine the accuracy of rigorous semiclassical methods with the efficiency and simplicity of widely used surface hopping methods. However, while SCMC was found to be more efficient than other semiclassical methods, it is not yet as efficientmore » as is needed to be used for large molecular systems. Here, we have developed two new methods: the accelerated-SCMC and the accelerated-SCMC with re-Gaussianization, which reduce the cost of the SCMC algorithm up to two orders of magnitude for certain systems. In many cases shown here, the new procedures are nearly as efficient as the commonly used surface hopping schemes, with little to no loss of accuracy. This implies that these modified SCMC algorithms will be of practical numerical solutions for simulating non-adiabatic dynamics in realistic molecular systems.« less
Non-adiabatic molecular dynamics by accelerated semiclassical Monte Carlo
White, Alexander J.; Gorshkov, Vyacheslav N.; Tretiak, Sergei; Mozyrsky, Dmitry
2015-07-07
Non-adiabatic dynamics, where systems non-radiatively transition between electronic states, plays a crucial role in many photo-physical processes, such as fluorescence, phosphorescence, and photoisomerization. Methods for the simulation of non-adiabatic dynamics are typically either numerically impractical, highly complex, or based on approximations which can result in failure for even simple systems. Recently, the Semiclassical Monte Carlo (SCMC) approach was developed in an attempt to combine the accuracy of rigorous semiclassical methods with the efficiency and simplicity of widely used surface hopping methods. However, while SCMC was found to be more efficient than other semiclassical methods, it is not yet as efficient as is needed to be used for large molecular systems. Here, we have developed two new methods: the accelerated-SCMC and the accelerated-SCMC with re-Gaussianization, which reduce the cost of the SCMC algorithm up to two orders of magnitude for certain systems. In many cases shown here, the new procedures are nearly as efficient as the commonly used surface hopping schemes, with little to no loss of accuracy. This implies that these modified SCMC algorithms will be of practical numerical solutions for simulating non-adiabatic dynamics in realistic molecular systems.
MARKOV CHAIN MONTE CARLO POSTERIOR SAMPLING WITH THE HAMILTONIAN METHOD
K. HANSON
2001-02-01
The Markov Chain Monte Carlo technique provides a means for drawing random samples from a target probability density function (pdf). MCMC allows one to assess the uncertainties in a Bayesian analysis described by a numerically calculated posterior distribution. This paper describes the Hamiltonian MCMC technique in which a momentum variable is introduced for each parameter of the target pdf. In analogy to a physical system, a Hamiltonian H is defined as a kinetic energy involving the momenta plus a potential energy {var_phi}, where {var_phi} is minus the logarithm of the target pdf. Hamiltonian dynamics allows one to move along trajectories of constant H, taking large jumps in the parameter space with relatively few evaluations of {var_phi} and its gradient. The Hamiltonian algorithm alternates between picking a new momentum vector and following such trajectories. The efficiency of the Hamiltonian method for multidimensional isotropic Gaussian pdfs is shown to remain constant at around 7% for up to several hundred dimensions. The Hamiltonian method handles correlations among the variables much better than the standard Metropolis algorithm. A new test, based on the gradient of {var_phi}, is proposed to measure the convergence of the MCMC sequence.
The effect of laser spot shapes on polar-direct-drive implosions on the National Ignition Facility
Weilacher, F.; Radha, P. B. Collins, T. J. B.; Marozas, J. A.
2015-03-15
Ongoing polar-direct-drive (PDD) implosions on the National Ignition Facility (NIF) [J. D. Lindl and E. I. Moses, Phys. Plasmas 18, 050901 (2011)] use existing NIF hardware, including indirect-drive phase plates. This limits the performance achievable in these implosions. Spot shapes are identified that significantly improve the uniformity of PDD NIF implosions; outer surface deviation is reduced by a factor of 7 at the end of the laser pulse and hot-spot distortion is reduced by a factor of 2 when the shell has converged by a factor of ?10. As a result, the neutron yield increases by approximately a factor of 2. This set of laser spot shapes is a combination of circular and elliptical spots, along with elliptical spot shapes modulated by an additional higher-intensity ellipse offset from the center of the beam. This combination is motivated in this paper. It is also found that this improved implosion uniformity is obtained independent of the heat conduction model. This work indicates that significant improvement in performance can be obtained robustly with the proposed spot shapes.
On-the-fly nuclear data processing methods for Monte Carlo simulations of fast spectrum systems
Walsh, Jon
2015-08-31
The presentation summarizes work performed over summer 2015 related to Monte Carlo simulations. A flexible probability table interpolation scheme has been implemented and tested with results comparing favorably to the continuous phase-space on-the-fly approach.
APR1400 LBLOCA uncertainty quantification by Monte Carlo method and comparison with Wilks' formula
Hwang, M.; Bae, S.; Chung, B. D.
2012-07-01
An analysis of the uncertainty quantification for the PWR LBLOCA by the Monte Carlo calculation has been performed and compared with the tolerance level determined by Wilks' formula. The uncertainty range and distribution of each input parameter associated with the LBLOCA accident were determined by the PIRT results from the BEMUSE project. The Monte-Carlo method shows that the 95. percentile PCT value can be obtained reliably with a 95% confidence level using the Wilks' formula. The extra margin by the Wilks' formula over the true 95. percentile PCT by the Monte-Carlo method was rather large. Even using the 3 rd order formula, the calculated value using the Wilks' formula is nearly 100 K over the true value. It is shown that, with the ever increasing computational capability, the Monte-Carlo method is accessible for the nuclear power plant safety analysis within a realistic time frame. (authors)
On-the-Fly Doppler Broadening for Monte Carlo Codes (Journal...
Office of Scientific and Technical Information (OSTI)
Title: On-the-Fly Doppler Broadening for Monte Carlo Codes Authors: Yesilyurt, G. ; Martin, W. ; Brown, F. 1 ; Univ. of Michigan) 2 ; Los Alamos National Laboratory) 2 + Show ...
Multiscale Monte Carlo equilibration: Pure Yang-Mills theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Endres, Michael G.; Brower, Richard C.; Orginos, Kostas; Detmold, William; Pochinsky, Andrew V.
2015-12-29
In this study, we present a multiscale thermalization algorithm for lattice gauge theory, which enables efficient parallel generation of uncorrelated gauge field configurations. The algorithm combines standard Monte Carlo techniques with ideas drawn from real space renormalization group and multigrid methods. We demonstrate the viability of the algorithm for pure Yang-Mills gauge theory for both heat bath and hybrid Monte Carlo evolution, and show that it ameliorates the problem of topological freezing up to controllable lattice spacing artifacts.
MODELING OF HIGH SPEED FRICTION STIR SPOT WELDING USING A LAGRANGIAN FINITE ELEMENT APPROACH
Miles, Michael; Karki, U.; Woodward, C.; Hovanski, Yuri
2013-09-03
Friction stir spot welding (FSSW) has been shown to be capable of joining steels of very high strength, while also being very flexible in terms of controlling the heat of welding and the resulting microstructure of the joint. This makes FSSW a potential alternative to resistance spot welding (RSW) if tool life is sufficiently high, and if machine spindle loads are sufficiently low so that the process can be implemented on an industrial robot. Robots for spot welding can typically sustain vertical loads of about 8kN, but FSSW at tool speeds of less than 3000 rpm cause loads that are too high, in the range of 11-14 kN. Therefore, in the current work tool speeds of 3000 rpm and higher were employed, in order to generate heat more quickly and to reduce welding loads to acceptable levels. The FSSW process was modeled using a finite element approach with the Forge® software package. An updated Lagrangian scheme with explicit time integration was employed to model the flow of the sheet material, subjected to boundary conditions of a rotating tool and a fixed backing plate [3]. The modeling approach can be described as two-dimensional, axisymmetric, but with an aspect of three dimensions in terms of thermal boundary conditions. Material flow was calculated from a velocity field which was two dimensional, but heat generated by friction was computed using a virtual rotational velocity component from the tool surface. An isotropic, viscoplastic Norton-Hoff law was used to model the evolution of material flow stress as a function of strain, strain rate, and temperature. The model predicted welding temperatures and the movement of the joint interface with reasonable accuracy for the welding of a dual phase 980 steel.
Numerical studies of third-harmonic generation in laser filament in air perturbed by plasma spot
Feng Liubin; Lu Xin; Liu Xiaolong; Li Yutong; Chen Liming; Ma Jinglong; Dong Quanli; Wang Weimin; Xi Tingting; Sheng Zhengming; Zhang Jie; He Duanwei
2012-07-15
Third-harmonic emission from laser filament intercepted by plasma spot is studied by numerical simulations. Significant enhancement of the third-harmonic generation is obtained due to the disturbance of the additional plasma. The contribution of the pure plasma effect and the possible plasma-enhanced third-order susceptibility on the third-harmonic generation enhancement are compared. It is shown that the plasma induced cancellation of destructive interference [Y. Liu et al., Opt. Commun. 284, 4706 (2011)] of two-colored filament is the dominant mechanism of the enhancement of third-harmonic generation.
Quantum Monte Carlo methods and lithium cluster properties. [Atomic clusters
Owen, R.K.
1990-12-01
Properties of small lithium clusters with sizes ranging from n = 1 to 5 atoms were investigated using quantum Monte Carlo (QMC) methods. Cluster geometries were found from complete active space self consistent field (CASSCF) calculations. A detailed development of the QMC method leading to the variational QMC (V-QMC) and diffusion QMC (D-QMC) methods is shown. The many-body aspect of electron correlation is introduced into the QMC importance sampling electron-electron correlation functions by using density dependent parameters, and are shown to increase the amount of correlation energy obtained in V-QMC calculations. A detailed analysis of D-QMC time-step bias is made and is found to be at least linear with respect to the time-step. The D-QMC calculations determined the lithium cluster ionization potentials to be 0.1982(14) (0.1981), 0.1895(9) (0.1874(4)), 0.1530(34) (0.1599(73)), 0.1664(37) (0.1724(110)), 0.1613(43) (0.1675(110)) Hartrees for lithium clusters n = 1 through 5, respectively; in good agreement with experimental results shown in the brackets. Also, the binding energies per atom was computed to be 0.0177(8) (0.0203(12)), 0.0188(10) (0.0220(21)), 0.0247(8) (0.0310(12)), 0.0253(8) (0.0351(8)) Hartrees for lithium clusters n = 2 through 5, respectively. The lithium cluster one-electron density is shown to have charge concentrations corresponding to nonnuclear attractors. The overall shape of the electronic charge density also bears a remarkable similarity with the anisotropic harmonic oscillator model shape for the given number of valence electrons.
Quantum Monte Carlo methods and lithium cluster properties
Owen, R.K.
1990-12-01
Properties of small lithium clusters with sizes ranging from n = 1 to 5 atoms were investigated using quantum Monte Carlo (QMC) methods. Cluster geometries were found from complete active space self consistent field (CASSCF) calculations. A detailed development of the QMC method leading to the variational QMC (V-QMC) and diffusion QMC (D-QMC) methods is shown. The many-body aspect of electron correlation is introduced into the QMC importance sampling electron-electron correlation functions by using density dependent parameters, and are shown to increase the amount of correlation energy obtained in V-QMC calculations. A detailed analysis of D-QMC time-step bias is made and is found to be at least linear with respect to the time-step. The D-QMC calculations determined the lithium cluster ionization potentials to be 0.1982(14) [0.1981], 0.1895(9) [0.1874(4)], 0.1530(34) [0.1599(73)], 0.1664(37) [0.1724(110)], 0.1613(43) [0.1675(110)] Hartrees for lithium clusters n = 1 through 5, respectively; in good agreement with experimental results shown in the brackets. Also, the binding energies per atom was computed to be 0.0177(8) [0.0203(12)], 0.0188(10) [0.0220(21)], 0.0247(8) [0.0310(12)], 0.0253(8) [0.0351(8)] Hartrees for lithium clusters n = 2 through 5, respectively. The lithium cluster one-electron density is shown to have charge concentrations corresponding to nonnuclear attractors. The overall shape of the electronic charge density also bears a remarkable similarity with the anisotropic harmonic oscillator model shape for the given number of valence electrons.
Utility of Monte Carlo Modelling for Holdup Measurements.
Belian, Anthony P.; Russo, P. A.; Weier, Dennis R. ,
2005-01-01
Non-destructive assay (NDA) measurements performed to locate and quantify holdup in the Oak Ridge K25 enrichment cascade used neutron totals counting and low-resolution gamma-ray spectroscopy. This facility housed the gaseous diffusion process for enrichment of uranium, in the form of UF{sub 6} gas, from {approx} 20% to 93%. Inventory of {sup 235}U inventory in K-25 is all holdup. These buildings have been slated for decontaminatino and decommissioning. The NDA measurements establish the inventory quantities and will be used to assure criticality safety and meet criteria for waste analysis and transportation. The tendency to err on the side of conservatism for the sake of criticality safety in specifying total NDA uncertainty argues, in the interests of safety and costs, for obtaining the best possible value of uncertainty at the conservative confidence level for each item of process equipment. Variable deposit distribution is a complex systematic effect (i.e., determined by multiple independent variables) on the portable NDA results for very large and bulk converters that contributes greatly to total uncertainty for holdup in converters measured by gamma or neutron NDA methods. Because the magnitudes of complex systematic effects are difficult to estimate, computational tools are important for evaluating those that are large. Motivated by very large discrepancies between gamma and neutron measurements of high-mass converters with gamma results tending to dominate, the Monte Carlo code MCNP has been used to determine the systematic effects of deposit distribution on gamma and neutron results for {sup 235}U holdup mass in converters. This paper details the numerical methodology used to evaluate large systematic effects unique to each measurement type, validates the methodology by comparison with measurements, and discusses how modeling tools can supplement the calibration of instruments used for holdup measurements by providing realistic values at well
MONTE CARLO SIMULATION OF METASTABLE OXYGEN PHOTOCHEMISTRY IN COMETARY ATMOSPHERES
Bisikalo, D. V.; Shematovich, V. I. [Institute of Astronomy of the Russian Academy of Sciences, Moscow (Russian Federation); Grard, J.-C.; Hubert, B. [Laboratory for Planetary and Atmospheric Physics (LPAP), University of Lige, Lige (Belgium); Jehin, E.; Decock, A. [Origines Cosmologiques et Astrophysiques (ORCA), University of Lige (Belgium); Hutsemkers, D. [Extragalactic Astrophysics and Space Observations (EASO), University of Lige (Belgium); Manfroid, J., E-mail: B.Hubert@ulg.ac.be [High Energy Astrophysics Group (GAPHE), University of Lige (Belgium)
2015-01-01
Cometary atmospheres are produced by the outgassing of material, mainly H{sub 2}O, CO, and CO{sub 2} from the nucleus of the comet under the energy input from the Sun. Subsequent photochemical processes lead to the production of other species generally absent from the nucleus, such as OH. Although all comets are different, they all have a highly rarefied atmosphere, which is an ideal environment for nonthermal photochemical processes to take place and influence the detailed state of the atmosphere. We develop a Monte Carlo model of the coma photochemistry. We compute the energy distribution functions (EDF) of the metastable O({sup 1}D) and O({sup 1}S) species and obtain the red (630nm) and green (557.7nm) spectral line shapes of the full coma, consistent with the computed EDFs and the expansion velocity. We show that both species have a severely non-Maxwellian EDF, that results in broad spectral lines and the suprathermal broadening dominates due to the expansion motion. We apply our model to the atmosphere of comet C/1996 B2 (Hyakutake) and 103P/Hartley 2. The computed width of the green line, expressed in terms of speed, is lower than that of the red line. This result is comparable to previous theoretical analyses, but in disagreement with observations. We explain that the spectral line shape does not only depend on the exothermicity of the photochemical production mechanisms, but also on thermalization, due to elastic collisions, reducing the width of the emission line coming from the O({sup 1}D) level, which has a longer lifetime.
PyMercury: Interactive Python for the Mercury Monte Carlo Particle Transport Code
Iandola, F N; O'Brien, M J; Procassini, R J
2010-11-29
Monte Carlo particle transport applications are often written in low-level languages (C/C++) for optimal performance on clusters and supercomputers. However, this development approach often sacrifices straightforward usability and testing in the interest of fast application performance. To improve usability, some high-performance computing applications employ mixed-language programming with high-level and low-level languages. In this study, we consider the benefits of incorporating an interactive Python interface into a Monte Carlo application. With PyMercury, a new Python extension to the Mercury general-purpose Monte Carlo particle transport code, we improve application usability without diminishing performance. In two case studies, we illustrate how PyMercury improves usability and simplifies testing and validation in a Monte Carlo application. In short, PyMercury demonstrates the value of interactive Python for Monte Carlo particle transport applications. In the future, we expect interactive Python to play an increasingly significant role in Monte Carlo usage and testing.
Khodabakhshi, F.; Kazeminezhad, M., E-mail: mkazemi@sharif.edu; Kokabi, A.H.
2012-07-15
Constrained groove pressing as a severe plastic deformation method is utilized to produce ultra-fine grained low carbon steel sheets. The ultra-fine grained sheets are joined via resistance spot welding process and the characteristics of spot welds are investigated. Resistance spot welding process is optimized for welding of the sheets with different severe deformations and their results are compared with those of as-received samples. The effects of failure mode and expulsion on the performance of ultra-fine grained sheet spot welds have been investigated in the present paper and the welding current and time of resistance spot welding process according to these subjects are optimized. Failure mode and failure load obtained in tensile-shear test, microhardness, X-ray diffraction, transmission electron microscope and scanning electron microscope images have been used to describe the performance of spot welds. The region between interfacial to pullout mode transition and expulsion limit is defined as the optimum welding condition. The results show that optimum welding parameters (welding current and welding time) for ultra-fine grained sheets are shifted to lower values with respect to those for as-received specimens. In ultra-fine grained sheets, one new region is formed named recrystallized zone in addition to fusion zone, heat affected zone and base metal. It is shown that microstructures of different zones in ultra-fine grained sheets are finer than those of as-received sheets. - Highlights: Black-Right-Pointing-Pointer Resistance spot welding process is optimized for joining of UFG steel sheets. Black-Right-Pointing-Pointer Optimum welding current and time are decreased with increasing the CGP pass number. Black-Right-Pointing-Pointer Microhardness at BM, HAZ, FZ and recrystallized zone is enhanced due to CGP.
SMART II : the spot market agent research tool version 2.0.
North, M. J. N.
2000-12-14
Argonne National Laboratory (ANL) has worked closely with Western Area Power Administration (Western) over many years to develop a variety of electric power marketing and transmission system models that are being used for ongoing system planning and operation as well as analytic studies. Western markets and delivers reliable, cost-based electric power from 56 power plants to millions of consumers in 15 states. The Spot Market Agent Research Tool Version 2.0 (SMART II) is an investigative system that partially implements some important components of several existing ANL linear programming models, including some used by Western. SMART II does not implement a complete model of the Western utility system but it does include several salient features of this network for exploratory purposes. SMART II uses a Swarm agent-based framework. SMART II agents model bulk electric power transaction dynamics with recognition for marginal costs as well as transmission and generation constraints. SMART II uses a sparse graph of nodes and links to model the electric power spot market. The nodes represent power generators and consumers with distinct marginal decision curves and varying investment capital as well individual learning parameters. The links represent transmission lines with individual capacities taken from a range of central distribution, outlying distribution and feeder line types. The application of SMART II to electric power systems studies has produced useful results different from those often found using more traditional techniques. Use of the advanced features offered by the Swarm modeling environment simplified the creation of the SMART II model.
DEFINING THE 'BLIND SPOT' OF HINODE EIS AND XRT TEMPERATURE MEASUREMENTS
Winebarger, Amy R.; Cirtain, Jonathan; Mulu-Moore, Fana [NASA Marshall Space Flight Center, VP 62, Huntsville, AL 35812 (United States); Warren, Harry P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Schmelz, Joan T. [Physics Department, University of Memphis, Memphis, TN 38152 (United States); Golub, Leon [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Kobayashi, Ken, E-mail: amy.r.winebarger@nasa.gov [Center for Space Plasma and Aeronomic Research, 320 Sparkman Dr, Huntsville, AL 35805 (United States)
2012-02-20
Observing high-temperature, low emission measure plasma is key to unlocking the coronal heating problem. With current instrumentation, a combination of EUV spectral data from Hinode Extreme-ultraviolet Imaging Spectrometer (EIS; sensitive to temperatures up to 4 MK) and broadband filter data from Hinode X-ray Telescope (XRT; sensitive to higher temperatures) is typically used to diagnose the temperature structure of the observed plasma. In this Letter, we demonstrate that a 'blind spot' exists in temperature-emission measure space for combined Hinode EIS and XRT observations. For a typical active region core with significant emission at 3-4 MK, Hinode EIS and XRT are insensitive to plasma with temperatures greater than {approx}6 MK and emission measures less than {approx}10{sup 27} cm{sup -5}. We then demonstrate that the temperature and emission measure limits of this blind spot depend upon the temperature distribution of the plasma along the line of sight by considering a hypothetical emission measure distribution sharply peaked at 1 MK. For this emission measure distribution, we find that EIS and XRT are insensitive to plasma with emission measures less than {approx}10{sup 26} cm{sup -5}. We suggest that a spatially and spectrally resolved 6-24 Angstrom-Sign spectrum would improve the sensitivity to these high-temperature, low emission measure plasma.
Monitoring seasonal and annual wetland changes in a freshwater marsh with SPOT HRV data
Mackey, H.E. Jr.
1989-12-31
Eleven dates of SPOT HRV data along with near-concurrent vertical aerial photographic and phenological data for 1987, 1988, and 1989 were evaluated to determine seasonal and annual changes in a 400-hectare, southeastern freshwater marsh. Early April through mid-May was the best time to discriminate among the cypress (Taxodium distichum)/water tupelo (Nyssa acquatica) swamp forest and the non-persistent (Ludwigia spp.) and persistent (Typha spp.) stands in this wetlands. Furthermore, a ten-fold decrease in flow rate from 11 cubic meters per sec (cms) in 1987 to one cms in 1988 was recorded in the marsh followed by a shift to drier wetland communities. The Savannah River Site (SRS), maintained by the US Department of Energy, is a 777 km{sup 2} area located in south central South Carolina. Five tributaries of the Savannah River run southwest through the SRS and into the floodplain swamp of the Savannah River. This paper describes the use of SPOT HRV data to monitor seasonal and annual trends in one of these swamp deltas, Pen Branch Delta, during a three-year period, 1987--1989.
Monitoring seasonal and annual wetland changes in a freshwater marsh with SPOT HRV data
Mackey, H.E. Jr.
1989-01-01
Eleven dates of SPOT HRV data along with near-concurrent vertical aerial photographic and phenological data for 1987, 1988, and 1989 were evaluated to determine seasonal and annual changes in a 400-hectare, southeastern freshwater marsh. Early April through mid-May was the best time to discriminate among the cypress (Taxodium distichum)/water tupelo (Nyssa acquatica) swamp forest and the non-persistent (Ludwigia spp.) and persistent (Typha spp.) stands in this wetlands. Furthermore, a ten-fold decrease in flow rate from 11 cubic meters per sec (cms) in 1987 to one cms in 1988 was recorded in the marsh followed by a shift to drier wetland communities. The Savannah River Site (SRS), maintained by the US Department of Energy, is a 777 km{sup 2} area located in south central South Carolina. Five tributaries of the Savannah River run southwest through the SRS and into the floodplain swamp of the Savannah River. This paper describes the use of SPOT HRV data to monitor seasonal and annual trends in one of these swamp deltas, Pen Branch Delta, during a three-year period, 1987--1989.
Sensitivity of inertial confinement fusion hot spot properties to the deuterium-tritium fuel adiabat
Melvin, J.; Lim, H.; Rana, V.; Glimm, J.; Cheng, B.; Sharp, D. H.; Wilson, D. C.
2015-02-15
We determine the dependence of key Inertial Confinement Fusion (ICF) hot spot simulation properties on the deuterium-tritium fuel adiabat, here modified by addition of energy to the cold shell. Variation of this parameter reduces the simulation to experiment discrepancy in some, but not all, experimentally inferred quantities. Using simulations with radiation drives tuned to match experimental shots N120321 and N120405 from the National Ignition Campaign (NIC), we carry out sets of simulations with varying amounts of added entropy and examine the sensitivities of important experimental quantities. Neutron yields, burn widths, hot spot densities, and pressures follow a trend approaching their experimentally inferred quantities. Ion temperatures and areal densities are sensitive to the adiabat changes, but do not necessarily converge to their experimental quantities with the added entropy. This suggests that a modification to the simulation adiabat is one of, but not the only explanation of the observed simulation to experiment discrepancies. In addition, we use a theoretical model to predict 3D mix and observe a slight trend toward less mixing as the entropy is enhanced. Instantaneous quantities are assessed at the time of maximum neutron production, determined dynamically within each simulation. These trends contribute to ICF science, as an effort to understand the NIC simulation to experiment discrepancy, and in their relation to the high foot experiments, which features a higher adiabat in the experimental design and an improved neutron yield in the experimental results.
Joint strength in high speed friction stir spot welded DP 980 steel
Saunders, Nathan; Miles, Michael; Hartman, Trent; Hovanski, Yuri; Hong, Sung Tae; Steel, Russell
2014-05-01
High speed friction stir spot welding was applied to 1.2 mm thick DP 980 steel sheets under different welding conditions, using PCBN tools. The range of vertical feed rates used during welding was 2.5 mm 102 mm per minute, while the range of spindle speeds was 2500 6000 rpm. Extended testing was carried out for five different sets of welding conditions, until tool failure. These welding conditions resulted in vertical welding loads of 3.6 8.2 kN and lap shear tension failure loads of 8.9 11.1 kN. PCBN tools were shown, in the best case, to provide lap shear tension fracture loads at or above 9 kN for 900 spot welds, after which tool failure caused a rapid drop in joint strength. Joint strength was shown to be strongly correlated to bond area, which was measured from weld cross sections. Failure modes of the tested joints were a function of bond area and softening that occurred in the heat-affected zone.
Wear testing of friction stir spot welding tools for joining of DP 980 Steel
Ridges, Chris; Miles, Michael; Hovanski, Yuri; Peterson, Jeremy; Steel, Russell
2011-06-06
Friction stir spot welding has been shown to be a viable method of joining ultra high strength steel (UHSS), both in terms of joint strength and process cycle time. However, the cost of tooling must be reasonable in order for this method to be adopted as an industrial process. Several tooling materials have been evaluated in prior studies, including silicon nitride and polycrystalline cubic boron nitride (PCBN). Recently a new tool alloy has been developed, where a blend of PCBN and tungsten rhenium (W-Re) was used in order to improve the toughness of the tool. Wear testing results are presented for two of these alloys: one with a composition of 60% PCBN and 40% W-Re (designated as Q60), and one with 70% PCBN and 30% W-Re (designated at Q70). The sheet material used for all wear testing was DP 980. Tool profiles were measured periodically during the testing process in order to show the progression of wear as a function of the number of spots produced. Lap shear testing was done each time a tool profile was taken in order to show the relationship between tool wear and joint strength. For the welding parameters chosen for this study the Q70 tool provided the best combination of wear resistance and joint strength.
Sun, Xin; Stephens, Elizabeth V.; Khaleel, Mohammad A.
2006-04-28
This paper examines the effects of fusion zone size on failure modes, static strength and energy absorption of resistance spot welds (RSW) of advanced high strength steels (AHSS). DP800 and TRIP800 spot welds are considered. The main failure modes for spot welds are nugget pullout and interfacial fracture. Partial interfacial fracture is also observed. The critical fusion zone sizes to ensure nugget pull-out failure mode are developed for both DP800 and TRIP800 using the limit load based analytical model and the micro-hardness measurements of the weld cross sections. Static weld strength tests using cross tension samples were performed on the joint populations with controlled fusion zone sizes. The resulted peak load and energy absorption levels associated with each failure mode were studied using statistical data analysis tools. The results in this study show that the conventional weld size of 4 t can not produce nugget pullout mode for both the DP800 and TRIP800 materials. The results also suggest that performance based spot weld acceptance criteria should be developed for different AHSS spot welds.
Multiparticle Monte Carlo Code System for Shielding and Criticality Use.
Energy Science and Technology Software Center (OSTI)
2015-06-01
Version 00 COG is a modern, full-featured Monte Carlo radiation transport code that provides accurate answers to complex shielding, criticality, and activation problems.COG was written to be state-of-the-art and free of physics approximations and compromises found in earlier codes. COG is fully 3-D, uses point-wise cross sections and exact angular scattering, and allows a full range of biasing options to speed up solutions for deep penetration problems. Additionally, a criticality option is available for computingmore » Keff for assemblies of fissile materials. ENDL or ENDFB cross section libraries may be used. COG home page: http://cog.llnl.gov. Cross section libraries are included in the package. COG can use either the LLNL ENDL-90 cross section set or the ENDFB/VI set. Analytic surfaces are used to describe geometric boundaries. Parts (volumes) are described by a method of Constructive Solid Geometry. Surface types include surfaces of up to fourth order, and pseudo-surfaces such as boxes, finite cylinders, and figures of revolution. Repeated assemblies need be defined only once. Parts are visualized in cross-section and perspective picture views. A lattice feature simplifies the specification of regular arrays of parts. Parallel processing under MPI is supported for multi-CPU systems. Source and random-walk biasing techniques may be selected to improve solution statistics. These include source angular biasing, importance weighting, particle splitting and Russian roulette, pathlength stretching, point detectors, scattered direction biasing, and forced collisions. Criticality For a fissioning system, COG will compute Keff by transporting batches of neutrons through the system. Activation COG can compute gamma-ray doses due to neutron-activated materials, starting with just a neutron source. Coupled Problems COG can solve coupled problems involving neutrons, photons, and electrons. COG 11.1 is an updated version of COG11.1 BETA 2 (RSICC C00777MNYCP02
Cranmer-Sargison, G.; Weston, S.; Evans, J. A.; Sidhu, N. P.; Thwaites, D. I.
2011-12-15
Purpose: The goal of this work was to implement a recently proposed small field dosimetry formalism [Alfonso et al., Med. Phys. 35(12), 5179-5186 (2008)] for a comprehensive set of diode detectors and provide the required Monte Carlo generated factors to correct measurement. Methods: Jaw collimated square small field sizes of side 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, and 3.0 cm normalized to a reference field of 5.0 cm x 5.0 cm were used throughout this study. Initial linac modeling was performed with electron source parameters at 6.0, 6.1, and 6.2 MeV with the Gaussian FWHM decreased in steps of 0.010 cm from 0.150 to 0.100 cm. DOSRZnrc was used to develop models of the IBA stereotactic field diode (SFD) as well as the PTW T60008, T60012, T60016, and T60017 field diodes. Simulations were run and isocentric, detector specific, output ratios (OR{sub det}) calculated at depths of 1.5, 5.0, and 10.0 cm. This was performed using the following source parameter subset: 6.1 and 6.2 MeV with a FWHM = 0.100, 0.110, and 0.120 cm. The source parameters were finalized by comparing experimental detector specific output ratios with simulation. Simulations were then run with the active volume and surrounding materials set to water and the replacement correction factors calculated according to the newly proposed formalism. Results: In all cases, the experimental field size widths (at the 50% level) were found to be smaller than the nominal, and therefore, the simulated field sizes were adjusted accordingly. At a FWHM = 0.150 cm simulation produced penumbral widths that were too broad. The fit improved as the FWHM was decreased, yet for all but the smallest field size worsened again at a FWHM = 0.100 cm. The simulated OR{sub det} were found to be greater than, equivalent to and less than experiment for spot size FWHM = 0.100, 0.110, and 0.120 cm, respectively. This is due to the change in source occlusion as a function of FWHM and field size. The corrections required for the 0.5 cm field
Nguyen, Vanthan; Yan, Lihe Si, Jinhai; Hou, Xun
2015-02-28
Photoluminescent carbon nanodots (C-dots) with size tunability and uniformity were fabricated in polyethylene glycol (PEG{sub 200N}) solution using femtosecond laser ablation method. The size distributions and photoluminescence (PL) properties of C-dots are well controlled by adjusting the combined parameters of laser fluence, spot size, and irradiation time. The size reduction efficiency of the C-dots progressively increases with decreasing laser fluence and spot size. The optimal PL spectra are red-shifted and the quantum yields decrease with the increase in C-dots size, which could be attributed to the more complex surface functional groups attached on C-dots induced at higher laser fluence and larger spot size. Moreover, an increase in irradiation time leads to a decrease in size of C-dots, but long-time irradiation will result in the generation of complex functional groups on C-dots, subsequently the PL spectra are red-shifted.
Hyer, Daniel E. Hill, Patrick M.; Wang, Dongxu; Smith, Blake R.; Flynn, Ryan T.
2014-09-15
Purpose: In the absence of a collimation system the lateral penumbra of spot scanning (SS) dose distributions delivered by low energy proton beams is highly dependent on the spot size. For current commercial equipment, spot size increases with decreasing proton energy thereby reducing the benefit of the SS technique. This paper presents a dynamic collimation system (DCS) for sharpening the lateral penumbra of proton therapy dose distributions delivered by SS. Methods: The collimation system presented here exploits the property that a proton pencil beam used for SS requires collimation only when it is near the target edge, enabling the use of trimmers that are in motion at times when the pencil beam is away from the target edge. The device consists of two pairs of parallel nickel trimmer blades of 2 cm thickness and dimensions of 2 cm × 18 cm in the beam's eye view. The two pairs of trimmer blades are rotated 90° relative to each other to form a rectangular shape. Each trimmer blade is capable of rapid motion in the direction perpendicular to the central beam axis by means of a linear motor, with maximum velocity and acceleration of 2.5 m/s and 19.6 m/s{sup 2}, respectively. The blades travel on curved tracks to match the divergence of the proton source. An algorithm for selecting blade positions is developed to minimize the dose delivered outside of the target, and treatment plans are created both with and without the DCS. Results: The snout of the DCS has outer dimensions of 22.6 × 22.6 cm{sup 2} and is capable of delivering a minimum treatment field size of 15 × 15 cm{sup 2}. Using currently available components, the constructed system would weigh less than 20 kg. For irregularly shaped fields, the use of the DCS reduces the mean dose outside of a 2D target of 46.6 cm{sup 2} by approximately 40% as compared to an identical plan without collimation. The use of the DCS increased treatment time by 1–3 s per energy layer. Conclusions: The spread of the
Accuracy of Monte Carlo simulations compared to in-vivo MDCT dosimetry
Bostani, Maryam McMillan, Kyle; Cagnon, Chris H.; McNitt-Gray, Michael F.; Mueller, Jonathon W.; Cody, Dianna D.; DeMarco, John J.
2015-02-15
Purpose: The purpose of this study was to assess the accuracy of a Monte Carlo simulation-based method for estimating radiation dose from multidetector computed tomography (MDCT) by comparing simulated doses in ten patients to in-vivo dose measurements. Methods: MD Anderson Cancer Center Institutional Review Board approved the acquisition of in-vivo rectal dose measurements in a pilot study of ten patients undergoing virtual colonoscopy. The dose measurements were obtained by affixing TLD capsules to the inner lumen of rectal catheters. Voxelized patient models were generated from the MDCT images of the ten patients, and the dose to the TLD for all exposures was estimated using Monte Carlo based simulations. The Monte Carlo simulation results were compared to the in-vivo dose measurements to determine accuracy. Results: The calculated mean percent difference between TLD measurements and Monte Carlo simulations was −4.9% with standard deviation of 8.7% and a range of −22.7% to 5.7%. Conclusions: The results of this study demonstrate very good agreement between simulated and measured doses in-vivo. Taken together with previous validation efforts, this work demonstrates that the Monte Carlo simulation methods can provide accurate estimates of radiation dose in patients undergoing CT examinations.
Fission matrix-based Monte Carlo criticality analysis of fuel storage pools
Farlotti, M.; Larsen, E. W.
2013-07-01
Standard Monte Carlo transport procedures experience difficulties in solving criticality problems in fuel storage pools. Because of the strong neutron absorption between fuel assemblies, source convergence can be very slow, leading to incorrect estimates of the eigenvalue and the eigenfunction. This study examines an alternative fission matrix-based Monte Carlo transport method that takes advantage of the geometry of a storage pool to overcome this difficulty. The method uses Monte Carlo transport to build (essentially) a fission matrix, which is then used to calculate the criticality and the critical flux. This method was tested using a test code on a simple problem containing 8 assemblies in a square pool. The standard Monte Carlo method gave the expected eigenfunction in 5 cases out of 10, while the fission matrix method gave the expected eigenfunction in all 10 cases. In addition, the fission matrix method provides an estimate of the error in the eigenvalue and the eigenfunction, and it allows the user to control this error by running an adequate number of cycles. Because of these advantages, the fission matrix method yields a higher confidence in the results than standard Monte Carlo. We also discuss potential improvements of the method, including the potential for variance reduction techniques. (authors)
Komarov, V M; Charukhchev, A V; Andreev, A A; Platonov, K Yu
2014-12-31
We have investigated the effect of the laser spot shape on the spatial distribution of accelerated ions on the front and back sides of a thin target irradiated by a picosecond laser pulse having the intensity of (3 – 4) × 10{sup 18} W cm{sup -2}. Experimental data are compared with numerical calculations. It is shown that the spatial structure of the ion bunch on the front side of the target resembles the laser spot structure rotated by 90°. (interaction of laser radiation with matter. laser plasma)
Electric rate that shifts hourly may foretell spot-market kWh
Springer, N.
1985-11-25
Four California industrial plants have cut their electricity bills up to 16% by shifting from the traditional time-of-use rates to an experimental real-time program (RTP) that varies prices hourly. The users receive a price schedule reflecting changing generating costs one day in advance to encourage them to increase power consumption during the cheapest time periods. Savings during the pilot program range between $11,000 and $32,000 per customer. The hourly cost breakdown encourages consumption during the night and early morning. The signalling system could be expanded to cogenerators and independent small power producers. If an electricity spot market develops, forecasters think a place on the stock exchanges for future-delivery contracts could develop in the future.
Reciprocal space mapping by spot profile analyzing low energy electron diffraction
Meyer zu Heringdorf, Frank-J.; Horn-von Hoegen, Michael
2005-08-15
We present an experimental approach for the recording of two-dimensional reciprocal space maps using spot profile analyzing low energy electron diffraction (SPA-LEED). A specialized alignment procedure eliminates the shifting of LEED patterns on the screen which is commonly observed upon variation of the electron energy. After the alignment, a set of one-dimensional sections through the diffraction pattern is recorded at different energies. A freely available software tool is used to assemble the sections into a reciprocal space map. The necessary modifications of the Burr-Brown computer interface of the two Leybold and Omicron type SPA-LEED instruments are discussed and step-by-step instructions are given to adapt the SPA 4.1d software to the changed hardware. Au induced faceting of 4 deg. vicinal Si(001) is used as an example to demonstrate the technique.
Kury, P.; Zahl, P.; Horn-von Hoegen, M.; Voges, C.; Frischat, H.; Guenter, H.-L.; Pfnuer, H.; Henzler, M.
2004-11-01
Spot profile analysis low energy electron diffraction (SPA-LEED) is one of the most versatile and powerful methods for the determination of the structure and morphology of surfaces even at elevated temperatures. In setups where the sample is heated directly by an electric current, the resolution of the diffraction images at higher temperatures can be heavily degraded due to the inhomogeneous electric and magnetic fields around the sample. Here we present an easily applicable modification of the common data acquisition hardware of the SPA-LEED, which enables the system to work in a pulsed heating mode: Instead of heating the sample with a constant current, a square wave is used and electron counting is only performed when the current through the sample vanishes. Thus, undistorted diffration images can be acquired at high temperatures.
On the development of nugget growth model for resistance spot welding
Zhou, Kang, E-mail: zhoukang326@126.com, E-mail: melcai@ust.hk; Cai, Lilong, E-mail: zhoukang326@126.com, E-mail: melcai@ust.hk [Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)
2014-04-28
In this paper, we developed a general mathematical model to estimate the nugget growth process based on the heat energy delivered into the welds by the resistance spot welding. According to the principles of thermodynamics and heat transfer, and the effect of electrode force during the welding process, the shape of the nugget can be estimated. Then, a mathematical model between heat energy absorbed and nugget diameter can be obtained theoretically. It is shown in this paper that the nugget diameter can be precisely described by piecewise fractal polynomial functions. Experiments were conducted with different welding operation conditions, such as welding currents, workpiece thickness, and widths, to validate the model and the theoretical analysis. All the experiments confirmed that the proposed model can predict the nugget diameters with high accuracy based on the input heat energy to the welds.
Impact of tool wear on joint strength in friction stir spot welding of DP 980 steel
Miles, Michael; Ridges, Chris; Hovanski, Yuri; Peterson, Jeremy; Santella, M. L.; Steel, Russel
2011-09-14
Friction stir spot welding has been shown to be a viable method of joining ultra high strength steel (UHSS), both in terms of joint strength and process cycle time. However, the cost of tooling must be reasonable in order for this method to be adopted as an industrial process. Recently a new tool alloy has been developed, using a blend of PCBN and tungsten rhenium (W-Re) in order to improve the toughness of the tool. Wear testing results are presented for two of these alloys: one with a composition of 60% PCBN and 40% W-Re, and one with 70% PCBN and 30% W-Re. The sheet material used for all wear testing was 1.4 mm DP 980. Lap shear testing was used to show the relationship between tool wear and joint strength. The Q70 tool provided the best combination of wear resistance and joint strength.
Crystal structure of Spot 14, a modulator of fatty acid synthesis
Colbert, Christopher L.; Kim, Chai-Wan; Moon, Young-Ah; Henry, Lisa; Palnitkar, Maya; McKean, William B.; Fitzgerald, Kevin; Deisenhofer, Johann; Horton, Jay D.; Kwon, Hyock Joo
2011-09-06
Spot 14 (S14) is a protein that is abundantly expressed in lipogenic tissues and is regulated in a manner similar to other enzymes involved in fatty acid synthesis. Deletion of S14 in mice decreased lipid synthesis in lactating mammary tissue, but the mechanism of S14's action is unknown. Here we present the crystal structure of S14 to 2.65 {angstrom} and biochemical data showing that S14 can form heterodimers with MIG12. MIG12 modulates fatty acid synthesis by inducing the polymerization and activity of acetyl-CoA carboxylase, the first committed enzymatic reaction in the fatty acid synthesis pathway. Coexpression of S14 and MIG12 leads to heterodimers and reduced acetyl-CoA carboxylase polymerization and activity. The structure of S14 suggests a mechanism whereby heterodimer formation with MIG12 attenuates the ability of MIG12 to activate ACC.
Ultrasonic Spot Welding of AZ31B to Galvanized Mild Steel
Pan, Dr. Tsung-Yu; Franklin, Teresa; Pan, Professor Jwo; Brown, Elliot; Santella, Michael L
2010-01-01
Ultrasonic spot welds were made between sheets of 0.8-mm-thick hot-dip-galvanized mild steel and 1.6-mm-thick AZ31B-H24. Lap-shear strengths of 3.0-4.2 kN were achieved with weld times of 0.3-1.2 s. Failure to achieve strong bonding of joints where the Zn coating was removed from the steel surface indicate that Zn is essential to the bonding mechanism. Microstructure characterization and microchemical analysis indicated temperatures at the AZ31-steel interfaces reached at least 344 C in less than 0.3 s. The elevated temperature conditions promoted annealing of the AZ31-H24 metal and chemical reactions between it and the Zn coating.
Landsat and SPOT data for oil exploration in North-Western China
Nishidai, Takashi
1996-07-01
Satellite remote sensing technology has been employed by Japex to provide information related to oil exploration programs for many years. Since the beginning of the 1980`s, regional geological interpretation through to advanced studies using satellite imagery with high spectral and spatial resolutions (such as Landsat TM and SPOT HRV), have been carried out, for both exploration programs and for scientific research. Advanced techniques (including analysis of airborne hyper-multispectral imaging sensor data) as well as conventional photogeological techniques were used throughout these programs. The first program using remote sensing technology in China focused on the Tarim Basin, Xinjiang Uygur Autonomous Region, and was carried out using Landsat MSS data. Landsat MSS imagery allows us to gain useful preliminary geological information about an area of interest, prior to field studies. About 90 Landsat scenes cover the entire Xinjiang Uygru Autonomous Region, this allowed us to give comprehensive overviews of 3 hydrocarbon-bearing basins (Tarim, Junggar, and Turpan-Hami) in NW China. The overviews were based on the interpretations and assessments of the satellite imagery and on a synthesis of the most up-to-date accessible geological and geophysical data as well as some field works. Pairs of stereoscopic SPOT HRV images were used to generate digital elevation data with a 40 in grid cover for part of the Tarim Basin. Topographic contour maps, created from this digital elevation data, at scales of 1:250,000 and 1:100,000 with contour intervals of 100 m and 50 m, allowed us to make precise geological interpretation, and to carry out swift and efficient geological field work. Satellite imagery was also utilized to make medium scale to large scale image maps, not only to interpret geological features but also to support field workers and seismic survey field operations.