7 Search Results

In this study, we have extended the detector response function toolkit (DRiFT) to provide modeling capabilities of semiconductor sensors. DRiFT provides realistic nuclear instrumentation response by post-processing Monte-Carlo N-particle (MCNP®) radiation transport outputs. MCNP® is capable of modeling radiation transport in complex environments, but has limited detector physics and readout electronics modeling capabilities. Semiconductor detector response can be calculated with a high-fidelity for a flexible range of environments by utilizing MCNP® to simulate radiation interactions inside of detector volumes, and then using DRiFT to model charge transport and signal formation in the semiconductor, as well as the readout electronics. DRiFTmore » models charge transport in the semiconductor, the preamplifier, shaping amplifier, pulse pile-up, and electronic noise to generate detector response. The semiconductor application in DRiFT can model a range of semiconductor materials, shapes, and sizes; and is demonstrated here for a large volume coaxial high-purity germanium (HPGe) detector. Here, we compare detector response functions of a coaxial HPGe detector with measurement of ⁶⁰Co, ¹³³Ba, and ¹³⁷Cs at varying count rates, and we conduct a parameter study to demonstrate the effect of changing parameters in the DRiFT simulation. The HPGe detector response function shows excellent agreement with measurements of difference sources with varying dead times and count rates.« less

This paper describes the analysis of a wind turbine and support structure subject to simulated hurricane wind fields. The hurricane wind fields, which result from a large eddy simulation of a hurricane, exhibit features such as very high gust factors (>1.7), rapid direction changes (30° in 30 s), and substantial veer. Wind fields including these features have not previously been used in an analysis of a wind turbine, and their effect on structural loads may be an important driver of enhanced design considerations. With a focus on blade root loads and tower base loads, the simulations show that these features ofmore » hurricane wind fields can lead to loads that are substantially in excess of those that would be predicted if wind fields with equally high mean wind speeds but without the associated direction change and veer were used in the analysis. This result, if further verified for a range of hurricane and tropical storm simulations, should provide an impetus for revisiting design standards.« less

Trade-offs in resource selection by central-place foragers are driven by the need to balance the benefits of selecting resources against the costs of travel from the central place. For group-territorial central-place foraging birds, trade-offs in resource selection are likely to be complicated by a competitive advantage for larger groups at high group density that may limit accessibility of high-quality distant resources to small groups. We used the group-territorial, central-place foraging Red-cockaded Woodpecker Leuconotopicus borealis (RCW) as a case study to test predictions that increases in group density lead to differences in foraging distances and resource selection for groups of differentmore » sizes. We used GPS tracking and LiDAR-derived habitat data to model effects of group size on foraging distances and selection for high-quality pines (≥ 35.6 cm diameter at breast height (dbh)) and lower quality pines (25.4–35.6 cm dbh) by RCW groups across low (n = 14), moderate (n = 10) and high group density (n = 10) conditions. At low and moderate group density, all RCW groups selected distant high-quality pines in addition to those near the central place because competition for resources was low. In contrast, at high group density, larger groups travelled further to select high-quality pines, whereas smaller groups selected high-quality pines only when they were close to the central place and, conversely, were more likely to select lower quality pines at greater distances from the central place. Selection for high-quality pines only when close to the cavity tree cluster at high group density is important to long-term fitness of small RCW groups because it allows them to maximize benefits from both territorial defence and selecting high-quality resources while minimizing costs of competition. Furthermore these relationships suggest that intraspecific competition at high group density entails substantive costs to smaller groups of territorial central-place foragers by limiting accessibility of distant high-quality foraging resources.« less

The electrical characteristics of 1.2-kV-rated 4H-SiC accumulation (Acc) and inversion (Inv) channel MOSFETs with linear, square, hexagonal, and octagonal cell topologies fabricated using the same design rules and process flow in a 6-in foundry are compared for the first time. TCAD numerical simulations have been conducted to analyze the structures. For all the cell topologies, it was found that the Acc MOSFETs have lower specific ON-resistance (RON,sp) than the Inv counterparts due to higher channel mobility resulting in 1.3-2.0× smaller high-frequency figure-of-merit (HF-FOM[RON × Qgd]), where Qgd is the gate-to-drain charge. It is observed that the square and hexagonal cellmore » topologies with the same structural dimensions show similar electrical performance. Here, when compared with the standard linear cell topology: 1) the hexagonal cell topology has 1.15× better specific ON-resistance and 1.12× worse HF-FOM[RON × Qgd] and 2) the octagonal cell topology has 1.5× worse specific ON-resistance and 1.4× better HF-FOM[RON × Qgd]. In addition, the octagonal cell topology has a much superior figure-of-merit (FOM[Ciss/Crss]), where Ciss is the input capacitance and Cgd is the reverse transfer capacitance.« less

We welcome the comments provided by Dargent et al. (2018) and appreciate the effort they have made to evaluate our recently reported data on the stability of uranyl(VI) chloride complexes as function of temperature (Migdisov et al., 2018). We also appreciate the opportunity provided by the editor to clarify issues in our paper that were not clearly articulated or in error.

The shock response of polymers is important for a number of commercial and defense–related applications, but it is difficult to obtain empirical shock response data over the wide range of preparations and aging conditions typically found in such applications. Ultrafast compression is useful to characterize polymer shock response over a wide range of polymer initial conditions due to the high throughput of this method. To establish greater confidence in ultrafast compression experiments and to characterize the detailed shock response of several variations in a single base polymer, the results of sub–nanosecond shock compression experiments in ~5 μm thick layers ofmore » the polydimethylsiloxane (PDMS)–based elastomeric rubbers Sylgard–184, SE1700, and an unfilled, end–linked model PDMS network are presented. The results of conventional ultrafast shock etalon measurements to time–of–flight measurements for similar thickness layers of irradiated and unirradiated SE1700 are compared. Here, good agreement between the shock response measured by these two ultrafast shock methods, as well as consistency between ultrafast data and long time scale gas gun data is found.« less

In this work, we present the Kinetic-j code, a computational kernel for evaluating the linearized Vlasov equation with application to calculating the kinetic plasma response (current) to an applied time harmonic wave electric field. This code addresses the need for a configuration space evaluation of the plasma current to enable kinetic full-wave solvers for waves in hot plasmas to move beyond the limitations of the traditional Fourier spectral methods. Furthermore, we benchmark the kernel via comparison with the standard k-space forms of the hot plasma conductivity tensor.