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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

DEGAS: Dynamic Exascale Global Address Space Programming Environments

The Dynamic, Exascale Global Address Space programming environment (DEGAS) project will develop the next generation of programming models and runtime systems to meet the challenges of Exascale computing. The Berkeley part of the project concentrated on communication-optimal code generation to optimize speed and energy efficiency by reducing data movement. Our work developed communication lower bounds, and/or communication avoiding algorithms (that either meet the lower bound, or do much less communication than their conventional counterparts) for a variety of algorithms, including linear algebra, machine learning and genomics. The Berkeley part of the project concentrated on communication-optimal code generation to optimize speed and energy efficiency by reducing data movement. Our work developed communication lower bounds, and/or communication avoiding algorithms (that either meet the lower bound, or do much less communication than their conventional counterparts) for a variety of algorithms, including linear algebra, machine learning and genomics.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Buried Ducts: A Cost-Effective Technical Solution to High Performance Homes

Traditionally, attics have been insulated at the flat ceiling with deliberate venting to manage heat and moisture. Having all the duct air distribution system in the conditioned space is the best building science approach, however this is not always the preferable solution for builders that like to use the roof space for air distribution. Ducts in attics are exposed to very intense heating and cooling conditions. Not only do we have thermal conduction, convection and radiation exchanges occurring but important duct leakage losses that create significant energy balance losses. In the recent IECC 2018 code, deeply buried attics have been credited for reducing the energy losses. Due to the complex thermal performance in each zone adjacent to the buried ductwork these credits seem to be not consistent with the benefits achieve by buring the ductwork in insulation. The thermal performance of buried ducts was examined in both 2-D and 3-D to determine the actual improvement as a function of duct size, duct insulation and attic insulation. In this paper we will describe the field/laboratory and modeling effort undertaken by to quantify the performances of duct systems. Climate zone 2A is included in the field testing, that encompass both hot/dry climates and hot and humid climates. Attics with deeply buried ducts and low air duct leakage had excellent thermal performance and exhibited the best overall thermal performances. Indeed, based on the thermal simulation analysis of deep buried ducts the thermal performance is better than the credit given to them by IRC 2018 code.

Salonvaara, Mikael↗
DOE OSTI2012

Beam-wave interaction analysis of a magnetically insulated line oscillator

Magnetically insulated line oscillator (MILO) using a metal disc-loaded coaxial cylindrical waveguide as its RF interaction structure is field analyzed for the beam-wave interaction using the linearized Vlasov equation. The beam present dispersion relation of the device is obtained applying the modal matching technique which is further used to estimate the oscillation frequency, temporal growth rate, output energy, and other device parameters. Further, MILO is simulated using commercial pic code 'magic,' and the electron momentum and energy plots are found to be in agreement with those obtained through the present analysis within 5%. Furthermore, the device temporal growth rate reported in the literature for the experimental MILO device is also compared with the present analytical theory and found in agreement {approx}5%.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

LDES-Sizing-and-siting-model (Power grid test cases for long-duration energy storage (LDES) siting) [SWR-25-75]

This repository contains code and data for performing a siting analysis of long-duration energy storage (LDES) in the 5-bus and RTS systems using the Sienna suite developed by the National Renewable Energy Laboratory for production cost modeling (PCM). This analysis involves moving the LDES component to different buses in the system, running a simulation, and considering the production cost of the simulation. Different system configurations are also analyzed with these scripts (such as moving load or renewable dispatch generators to different buses) to observe the impacts the system configuration has on optimal siting. This repository contains three sub directories discussed below. Both the 5-bus and RTS systems have two different initial configurations for the renewable energy components in them, one that is predominantly PV-driven and one that is predominantly wind-driven. Sienna suite can be found here: https://github.com/NREL-Sienna

Cole, David [University of Wisconsin]↗
DOE OSTI2020

NWPEsSe: an Adaptive-Learning Global Optimization Algorithm for Nanosized Cluster Systems

Global optimization constitutes an important and fundamental problem in theoretical studies in many chemical fields, such as catalysis, materials or separations problems. In this paper, a novel algorithm has been developed for the global optimization of large systems including neat and ligated clusters in gas phase, and supported clusters in periodic boundary conditions. The method is based on an updated artificial bee colony (ABC) algorithm method, that allows for adaptive-learning during the search process. The new algorithm is tested against four classes of systems of diverse chemical nature: gas phase Au_55, ligated Au_8^(2+), Au_8 supported on graphene oxide and defected rutile, and a large cluster assembly ?[Co?_6 Te_8 (PEt_3 )_6][C_60 ]_n, with sizes ranging between 1 to 3 nm and containing up to 1300 atoms. Reliable global minima (GMs) are obtained for all cases, either confirming published data or reporting new lower energy structures. The algorithm and interface to other codes in the form of an independent program, Northwest Potential Energy Search Engine (NWPEsSe), is freely available and it provides a powerful and efficient approach for global optimization of nanosized cluster systems. The work described in this publication was performed at Pacific Northwest National Laboratory (PNNL), which is operated by Battelle for the United States Department of Energy (DOE) under Contract DE-AC05-76RL0180. J. Z. and V.-A. G. acknowledge support from DOE, Office of Science, Office of Basic Energy Sci-ences, Chemical, Geological and Biological Sciences Division and computing resources from PNNL’s Research Computing Facility and the National Energy Research Scientific Computing Center.

Zhang, Jun↗
DOE OSTI2016

Interaction of atomic and low-energy deuterium with tungsten pre-irradiated with self-ions

Polycrystalline tungsten (W) specimens were pre-irradiated with self-ions to create identical samples with high density of defects up to ∼2.5 μm near the surface. Then, W specimens were exposed to either thermal atomic deuterium (D) beam with an incident energy of ∼0.2 eV or low energy D plasma with the incident energy varied between 5 and 200 eV at different sample temperatures. Each sample was exposed once at certain temperature and fluence. The D migration and accumulation in W were studied post-mortem by nuclear reaction method. It was shown that the rate of the D to occupy radiation-induced defects increases with increasing the incident energy, ion flux, and temperature. Experimental investigation was accompanied by modelling using the rate-equation model. Moreover, the analytical model was developed and benchmarked against numerical model. The calculations of the deuterium diffusion with trapping at radiation-induced defects in tungsten by analytical model are consistent with numerical calculations using rate-equation model. The data of reflection and penetration of atomic and low-energy D were taking from calculations using molecular dynamics (MD) with Juslin interatomic potentials and a binary collision code TRIM. MD calculations show an agreement with a binary collision code TRIM only in a very narrow range of deuterium energies between 1 and 20 eV. Incorporation of the data of reflection and penetration of deuterium in the macroscopic modelling has been done to verify the range of validity of calculations using MD and binary collision code TRIM by comparison of modelling results with experimental data. Modelling results are consistent with experiments using reflection and penetration data of D obtained from TRIM code for incident ion energy above 1 eV. Otherwise, the parameters obtained from MD should be incorporated in the rate-equation model to have a good agreement with the experiments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Utah FORGE: Composite 3D Seismic Velocity Model

This is a composite 3D seismic velocity that was constructed from compiled information from several local studies regarding seismic velocities and structural information. This seismic velocity model is provided in NonLinLoc format (slow_len), which is readily usable in NonLinLoc software. Other model formats and versions of the model can be produced using the Python script provided with this data set. Details on how the model was created and prior velocity and structural information was used is provided in the accompanying documentation.

15 GEOTHERMAL ENERGY↗
DOE OSTI2021

Explicit Modeling of Pebble Temperature in the Porous-medium Framework for Pebble-bed Reactors Applications

In this study, an explicit model for pebble temperature calculations in the framework of a porous-medium approach has been developed and implemented in the SAM code. The solid-phase energy conservation equation, including the explicit modeling of pebble temperature, is a multi-scale model, which can predict the macroscopic (pebble-bed) and microscopic (pebble) temperature distributions under both steady-state and transient conditions. Extensive and successful code verifications and demonstrations have been performed for this newly developed model. By explicitly modeling pebble temperatures, this new model addresses a major deficiency of the previously implemented model, which assumed a local solid-phase thermal equilibrium that is not appropriate for pebble-bed reactor design and safety analysis applications.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

Electron temperature measurements inside the ablating plasma of gas-filled hohlraums at the National Ignition Facility

The first measurement of the electron temperature (T{sub e}) inside a National Ignition Facility hohlraum is obtained using temporally resolved K-shell X-ray spectroscopy of a mid-Z tracer dot. Both isoelectronic- and interstage-line ratios are used to calculate the local T{sub e} via the collisional–radiative atomic physics code SCRAM [Hansen et al., High Energy Density Phys 3, 109 (2007)]. The trajectory of the mid-Z dot as it is ablated from the capsule surface and moves toward the laser entrance hole (LEH) is measured using side-on x-ray imaging, characterizing the plasma flow of the ablating capsule. Data show that the measured dot location is farther away from the LEH in comparison to the radiation-hydrodynamics simulation prediction using HYDRA [Marinak et al., Phys. Plasmas 3, 2070 (1996)]. To account for this discrepancy, the predicted simulation T{sub e} is evaluated at the measured dot trajectory. The peak T{sub e}, measured to be 4.2 keV ± 0.2 keV, is ∼0.5 keV hotter than the simulation prediction.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

TH-E-BRE-06: Challenges in the Dosimetry of Flattening Filter Free Beams

Purpose: In current dosimetry protocols [AAPM TG51, IAEA TRS-389] the beam quality correction factor kQ and the water-to-air restricted mass collision stopping-power ratio SPR are related to beam quality specifiers %dd(10){sub x} respectively TPR{sub 20,10} Determining kQ and SPR using these regular beam quality specifiers for conventional accelerators (WFF) and flattening filter free accelerators (FFF) similarly could lead to systemic bias.The influence of the flattening filter on the relationship between various beam quality specifiers and SPR respectively k{sub Q} was studied using Monte Carlo simulations with realistic beam sources. Methods: All Monte Carlo simulations were performed using the BEAMnrc/EGSnrc code system. Radiation transport through nine linear accelerator heads modeled according to technical drawings given by the manufactures and a {sup 60} Co therapy source was simulated with BEAMnrc and then used as a radiation source for further simulations. FFF beam sources were implemented by removing the fattening filter from the WFF model. SPR was calculated applying the user code SPRRZnrc. The mean photon energy below the accelerator head and the mean energies of photons and electrons at the measuring point within the water phantom were calculated using FLURZnrc. Dose calculations within a small water voxel and the thimble ionization chamber PTW-31010 in a water depth of 10 cm were made using the egs-chamber code. Results: SPR and k{sub Q} as a function of fluence spectra based beam quality specifiers as well as conventional beam quality specifiers differ systematically between FFF and WFF beams. According to the results the specifier %dd(10){sub x} revealed the smallest deviation (max. 0.4%) between FFF and WFF beams. Conclusion: The results show that %dd(10){sub x} is an acceptable beam quality specifier for FFF beams. Nevertheless the results confirm the expected bias between FFF and WFF beams which must by further investigated.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2024

AdvEP

AdvEP is a code repository which contains PyTorch implementations of various adversarial attacks on a deep neural network trained with Equilibrium Propagation (EP), which is a neuromorphic learning framework. AdvEP allows for the training, testing, and conducting white/black-box attacks of EP models on a wide variety of applications and datasets. AdvEP is based on the open-source code https://github.com/Laborieux-Axel/Equilibrium-Propagation which was developed to train energy models. AdvEP was created by modifying the original code to perform and test against adversarial attacks. AdvEP was developed in Python, a high-level programming language that takes advantage of the Python ecosystem of high-quality open-source packages for machine learning. AdvEP interfaces heavily with the open-source PyTorch Python package as well as the open-source Adversarial Robustness Toolbox (ART) package.

Mansingh, Siddarth↗
DOE OSTI2010

Large Hospital 50% Energy Savings: Technical Support Document

This Technical Support Document documents the technical analysis and design guidance for large hospitals to achieve whole-building energy savings of at least 50% over ANSI/ASHRAE/IESNA Standard 90.1-2004 and represents a step toward determining how to provide design guidance for aggressive energy savings targets. This report documents the modeling methods used to demonstrate that the designrecommendations meet or exceed the 50% goal. EnergyPlus was used to model the predicted energy performance of the baseline and low-energy buildings to verify that 50% energy savings are achievable. Percent energy savings are based on a nominal minimally code-compliant building and whole-building, net site energy use intensity. The report defines architectural-program characteristics for typicallarge hospitals, thereby defining a prototype model; creates baseline energy models for each climate zone that are elaborations of the prototype models and are minimally compliant with Standard 90.1-2004; creates a list of energy design measures that can be applied to the prototype model to create low-energy models; uses industry feedback to strengthen inputs for baseline energy models andenergy design measures; and simulates low-energy models for each climate zone to show that when the energy design measures are applied to the prototype model, 50% energy savings (or more) are achieved.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1989

Preliminary analyses of space radiation protection for lunar base surface systems

Radiation shielding analyses are performed for candidate lunar base habitation modules. The study primarily addresses potential hazards due to contributions from the galactic cosmic rays. The NASA Langley Research Center's high energy nucleon and heavy ion transport codes are used to compute propagation of radiation through conventional and regolith shield materials. Computed values of linear energy transfer are converted to biological dose-equivalent using quality factors established by the International Commision of Radiological Protection. Special fluxes of heavy charged particles and corresponding dosimetric quantities are computed for a series of thicknesses in various shield media and are used as an input data base for algorithms pertaining to specific shielded geometries. Dosimetric results are presented as isodose contour maps of shielded configuration interiors. The dose predictions indicate that shielding requirements are substantial, and an abbreviated uncertainty analysis shows that better definition of the space radiation environment as well as improvement in nuclear interaction cross-section data can greatly increase the accuracy of shield requirement predictions.

Nealy, John E.↗
NASA NTRS2007

The Use of the BAT Instrument on SWIFT for the Detection of Prompt Gamma-Ray Emission from Novae

Gamma-rays are expected to be emitted during and immediately following a nova explosion due to the annihilation of positrons emitted by freshly produced short-lived radioactive isotopes. The expected gammaray emission is relatively short-lived and as nova explosions are unpredictable, the best chance of detecting the gamma-rays is with n wide field instrument. At the time when the flux is expected to rcach its peak, most of the gamma-ray production is at depths such that the photons suffer several Compton scatterings before escaping, degrading their energy down to the hard X-ray band (10s of keV). SWIFT/BAT is a very wide field coded mask instrument working in the energy band 14-190 keV and so is very well suited to the search for such gamma-rays. A retrospective search is being made in the BAT data for evidence for gamma-ray emission from the direction of novae at around the time of their explosion. So far the only positive detection is of RS Ophiuchi and in this case the emission is probably due to shock heating.

Skinner, Gerry↗
DOE OSTI2014

Achieving 50% Energy Savings in New Schools, Advanced Energy Design Guides: K-12 Schools (Brochure)

This fact sheet summarizes recommendations for designing elementary, middle, and high school buildings that will result in 50% less energy use than conventional new schools built to minimum code requirements. The recommendations are drawn from the Advanced Energy Design Guide for K-12 School Buildings, an ASHRAE publication that provides comprehensive recommendations for designing low-energy-use school buildings (see sidebar). Designed as a stand-alone document, this fact sheet provides key principles and a set of prescriptive design recommendations appropriate for smaller schools with insufficient budgets to fully implement best practices for integrated design and optimized performance. The recommendations have undergone a thorough analysis and review process through ASHRAE, and have been deemed the best combination of measures to achieve 50% savings in the greatest number of schools.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2011

A Guide to Building Commissioning

Commissioning is the process of verifying that a building's heating, ventilation, and air conditioning (HVAC) and lighting systems perform correctly and efficiently. Without commissioning, system and equipment problems can result in higher than necessary utility bills and unexpected and costly equipment repairs. This report reviews the benefits of commissioning, why it is a requirement for Leadership in Energy and Environmental Design (LEED) certification, and why building codes are gradually adopting commissioning activities into code.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2014

Plasma heating in solar flares and their soft and hard X-ray emissions

In this paper, the energy budgets of two single-loop-like flares observed in X-ray are analyzed under the assumption that nonthermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 February 20 and June 2, respectively. Using a one-dimensional (1D) hydrodynamic code for both flares, the energy deposited in the chromosphere was derived applying RHESSI observational data. The use of the Fokker-Planck formalism permits the calculation of distributions of the NTEs in flaring loops and thus spatial distributions of the X-ray nonthermal emissions and integral fluxes for the selected energy ranges that were compared with the observed ones. Additionally, a comparative analysis of the spatial distributions of the signals in the RHESSI images was conducted for the footpoints and for all the flare loops in selected energy ranges with these quantities' fluxes obtained from the models. The best compatibility of the model and observations was obtained for the 2002 June 2 event in the 0.5-4 Å GOES range and total fluxes in the 6-12 keV, 12-25 keV, 20-25 keV, and 50-100 keV energy bands. Results of photometry of the individual flaring structures in a high energy range show that the best compliance occurred for the 2002 June 2 flare, where the synthesized emissions were at least 30% higher than the observed emissions. For the 2002 February 20 flare, synthesized emission is about four times lower than the observed one. However, in the low energy range the best conformity was obtained for the 2002 February 20 flare, where emission from the model is about 11% lower than the observed one. The larger inconsistency occurs for the 2002 June 2 solar flare, where synthesized emission is about 12 times greater or even more than the observed emission. Some part of these differences may be caused by inevitable flaws of the applied methodology, like by an assumption that the model of the flare is symmetric and there are no differences in the emissions originating from the feet of the flares loop and by relative simplicity of the applied numerical 1D code and procedures. No doubt a significant refinement of the applied numerical models and more sophisticated implementation of the various physical mechanisms involved are required to achieve a better agreement. Despite these problems, a collation of modeled results with observations shows that soft and hard X-ray emissions observed for analyzed single-loop-like events may be fully explained by electron-beam-driven evaporation only.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Proton-induced fission of actinides at energies 26.5 and 62.9 MeV--Theoretical interpretation

Fission properties of proton-induced fission on {sup 232}Th, {sup 237}Np, {sup 238}U, {sup 239}Pu and {sup 241}Am targets, measured at the Louvain-la-Neuve cyclotron facility at proton energies of 26.5 and 62.9 MeV, are compared with the predictions of the state-of-the-art nuclear reaction code TALYS. The sensitivity of the calculations to the input parameters of the code and possible improvements are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗