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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

International Collaborations Activities on Disposal in Argillite R&D: Characterization Studies and Modeling Investigations

This interim report is an update of ongoing experimental and modeling work on bentonite material described in Jové Colón et al. (2019, 2020) from past international collaboration activities. As noted in Jové Colón et al. (2020), work on international repository science activities such as FEBEX-DP and DECOVALEX19 is either no longer continuing by the international partners. Nevertheless, research activities on the collected sample materials and field data are still ongoing. Descriptions of these underground research laboratory (URL) R&D activities are described elsewhere (Birkholzer et al. 2019; Jové Colón et al. 2020) but will be explained here when needed. The current reports recent reactive-transport modeling on the leaching of sedimentary rock.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Case Studies and Model Guidance for Establishing Solar Cybersecurity Working Groups

This tool outlines actions that states can take to establish state-level working groups, which can be a critical first step to establishing state cybersecurity programs and efforts to support cybersecurity in distributed energy resources. Specifically, these working groups can lead the development of cybersecurity task forces focused around distributed energy resources, formal recommendations for policy makers and regulators, and the creation of a response strategies and plans for cybersecurity impacts or incidents in solar photovoltaic systems.

14 SOLAR ENERGY↗
DOE OSTI2023

Tensor renormalization group study of 3D principal chiral model

We study the three-dimensional SU(2) principal chiral model using different tensor renormalization group methods based on the triad and anisotropic decomposition of the tensor. The tensor network representation is formulated based on the character expansion of the Boltzmann weight. We compare the average action obtained using these two tensor network algorithms and confirm that the resulting critical coupling and exponent are comparable with the recent estimations from the Monte Carlo methods.

Unmuth-Yockey, Judah↗
DOE OSTI2023

Tensor renormalization group study of 3D principal chiral model

We study the three-dimensional $SU(2)$ principal chiral model (PCM) using different tensor renormalization group methods based on the triad and anisotropic decomposition of the tensor. The tensor network representation is formulated based on the character expansion of the Boltzmann weight. We compare the average action obtained using these two tensor network algorithms and confirm that the resulting critical coupling and exponent are comparable with the recent estimations from the Monte Carlo methods.

Akiyama, Shinichiro↗
DOE OSTI2021

Superconductivity of incoherent electrons in the Yukawa Sachdev-Ye-Kitaev model

We study a model of N fermions in a quantum dot, coupled to M bosons by a disorder-induced complex Yukawa coupling [Yukawa Sachdev-Ye-Kitaev (SYK) model], in order to explore the interplay between non-Fermi liquid and superconductivity in a strongly coupled, (quantum-)critical environment. We analyze the phase diagram of the model for an arbitrary complex interaction and arbitrary ratio of N/M, with special focus on the two regimes of non-Fermi-liquid behavior: an SYK-like behavior with a power-law frequency dependence of the fermionic self-energy and an impuritylike behavior with frequency independent self-energy. We show that the crossover between the two can be reached by varying either the strength of the fermion-boson coupling or the ratio M/N. We next argue that in both regimes the system is unstable to superconductivity if the strength of time-reversal-symmetry-breaking disorder is below a certain threshold. We show how the corresponding onset temperatures vary between the two regimes. We argue that the superconducting state is highly unconventional with an infinite set of minima of the condensation energy at T = 0, corresponding to topologically different gap functions. We discuss in detail similarities and differences between this model and the model of dispersion-full fermions tuned to a metallic quantum-critical point, with an effective singular dynamical interaction V(Ω) ∝ 1/|Ω| γ (the γ model).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Predicting wind farm operations with machine learning and the P2D‐RANS model: A case study for an AWAKEN site

Abstract The power performance and the wind velocity field of an onshore wind farm are predicted with machine learning models and the pseudo‐2D RANS model, then assessed against SCADA data. The wind farm under investigation is one of the sites involved with the American WAKE experimeNt (AWAKEN). The performed simulations enable predictions of the power capture at the farm and turbine levels while providing insights into the effects on power capture associated with wake interactions that operating upstream turbines induce, as well as the variability caused by atmospheric stability. The machine learning models show improved accuracy compared to the pseudo‐2D RANS model in the predictions of turbine power capture and farm power capture with roughly half the normalized error. The machine learning models also entail lower computational costs upon training. Further, the machine learning models provide predictions of the wind turbulence intensity at the turbine level for different wind and atmospheric conditions with very good accuracy, which is difficult to achieve through RANS modeling. Additionally, farm‐to‐farm interactions are noted, with adverse impacts on power predictions from both models.

17 WIND ENERGY↗
DOE OSTI2024

Modeling the Effects of Artificial Drainage on Agriculture-dominated Watersheds using a Fully Distributed Integrated Hydrology Model: Datasets, code, models files

This model-data archive is for a modeling study focused on the effects of artificial drainage on agriculture-dominated watersheds using a fully distributed integrated hydrology model. This study introduced a novel strategy to represent the effects of tile drains and agricultural ditches in a fully distributed basin-scale integrated hydrology model. The numerical experiments in this study reveal the effects of surface and subsurface drainage on various hydrological states and fluxes. The details about the datasets can be found in the "readme" document attached with the dataset.

Agricultural Watersheds↗
DOE OSTI2021

Tropical Cyclone Precipitation Response to Surface Warming in Aquaplanet Simulations With Uniform Thermal Forcing

While many modeling studies have attempted to estimate how tropical cyclone (TC) precipitation is impacted by climate change, the multitude of analysis techniques and methodologies have resulted in varying conclusions. Simplified models may be able to help overcome this problem. Radiative-convective equilibrium (RCE) model simulations have been used in various configurations to study fundamental aspects of Earth's climate. While many RCE modeling studies have focused on TC genesis, intensification, and size, limited work has been done using RCE to study TC precipitation. Here, in this study, the response of TC precipitation to sea surface temperature (SST) change is analyzed in global Community Atmosphere Model (CAM) aquaplanet simulations run with Radiative-Convective Equilibrium Model Intercomparison Project protocols, with the addition of planetary rotation. We expect that the insight gained about how TC precipitation responds to SST warming will help predict how TCs in the real world respond to climate change. In the CAM RCE simulations, the warmer SST simulations have less TCs on average, but the TCs tend to be larger in outer size and more intense. As simulation SST increases, more extreme precipitation rates occur within TCs, and more of the TC precipitation comes from these extreme rates. For extreme (99th percentile) TC precipitation, SST, and TC intensity increases dominate the 8.6% per K increase, while TC outer size changes have little impact. For accumulated TC precipitation, SST, and TC intensity contributions are still the majority, but TC outer size changes also contribute to the 6.6% per K increase.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Modeling the role of lateral surface flow in low‐relief polygonal tundra

Abstract Ice‐wedge polygon troughs play an important role in controlling the hydrology of low‐relief polygonal tundra regions. Lateral surface flow is confined to troughs only, but it is often neglected in model projections of permafrost thermal hydrology. Recent field and modeling studies have shown that, after rain events, increases in trough water levels are significantly more than the observed precipitation, highlighting the role of lateral surface flow in the polygonal tundra. Therefore, understanding how trough lateral surface flow can influence polygonal tundra thermal hydrology is important, especially under projected changes in temperatures and rainfall in the Arctic regions. Using an integrated cryohydrology model, this study presents plot‐scale end‐of‐century projections of ice‐wedge polygon water budget components and active layer thickness with and without trough lateral surface flow under the Representative Concentration Pathway 8.5 scenario. Trough lateral surface flow is incorporated through a newly developed empirical model, evaluated against field measurements. The numerical scenario that includes trough lateral surface flow simulates discharge (outflow from a polygon) and recharge (rain‐induced inflow to a polygon trough from upslope areas), while the scenario that does not include trough lateral surface flow ignores recharge. The results show considerable reduction (about 100–150%) in evapotranspiration and discharge in rainy years in the scenarios ignoring trough lateral surface flow, but less effect on soil water storage, in comparison with the scenario with trough lateral surface flow. In addition, the results demonstrate long‐term changes (~10–15 cm increase) in active layer thickness when trough lateral surface flow is modeled. This study highlights the importance of including lateral surface flow processes to better understand the long‐term thermal and hydrological changes in low‐relief polygonal tundra regions under a changing climate.

Jan, Ahmad↗
DOE OSTI2023

Blind photovoltaic modeling intercomparison: A multidimensional data analysis and lessons learned

The Photovoltaic (PV) Performance Modeling Collaborative (PVPMC) organized a blind PV performance modeling intercomparison to allow PV modelers to blindly test their models and modeling ability against real system data. Measured weather and irradiance data were provided along with detailed descriptions of PV systems from two locations (Albuquerque, New Mexico, USA, and Roskilde, Denmark). Participants were asked to simulate the plane-of-array irradiance, module temperature, and DC power output from six systems and submit their results to Sandia for processing. The results showed overall median mean bias (i.e., the average error per participant) of 0.6% in annual irradiation and –3.3% in annual energy yield. While most PV performance modeling results seem to exhibit higher precision and accuracy as compared to an earlier blind PV modeling study in 2010, human errors, modeling skills, and derates were found to still cause significant errors in the estimates.

14 SOLAR ENERGY↗
DOE OSTI2020

The Long-term Storage of ILW: Building Stores with the Appropriate Environmental Controls - 20294

In the UK, containers for the storage and disposal of intermediate level radioactive waste (ILW) typically use stainless steel due to its excellent mechanical properties and corrosion resistance. The period of interim storage before a disposal facility is available, however, is longer than available engineering experience with stainless steels in relevant environmental conditions. Additionally, after disposal the ability of ILW containers to withstand further periods of exposure to the environment is expected to provide substantial benefits to the operation of a disposal facility and the safety case underpinning its closure. For these reasons, although there have been no instances of failure of stainless steels in indoor storage conditions, a focused R and D programme has been carried out to identify the environmental envelope over which the material does not significantly degrade. In this study we summarise experimental and modelling studies carried out over the last decade to build a solid mechanistic understanding of the corrosion behaviour of stainless steels in indoor atmospheric conditions. We then identify suitable environmental regimes to minimise the risk of degradation processes and explore approaches to monitoring the storage conditions to gain confidence in the long-term performance of the system. (authors)

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DOE OSTI2023

Practical Understanding of Cancer Model Identifiability in Clinical Applications

Mathematical models are a core component in the foundation of cancer theory and have been developed as clinical tools in precision medicine. Modeling studies for clinical applications often assume an individual’s characteristics can be represented as parameters in a model and are used to explain, predict, and optimize treatment outcomes. However, this approach relies on the identifiability of the underlying mathematical models. In this study, we build on the framework of an observing-system simulation experiment to study the identifiability of several models of cancer growth, focusing on the prognostic parameters of each model. Our results demonstrate that the frequency of data collection, the types of data, such as cancer proxy, and the accuracy of measurements all play crucial roles in determining the identifiability of the model. We also found that highly accurate data can allow for reasonably accurate estimates of some parameters, which may be the key to achieving model identifiability in practice. As more complex models required more data for identification, our results support the idea of using models with a clear mechanism that tracks disease progression in clinical settings. For such a model, the subset of model parameters associated with disease progression naturally minimizes the required data for model identifiability.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Thermodynamic modeling of double azeotropy systems

Azeotropes are boiling liquid mixtures which have identical vapor and liquid compositions. Known as polyazeotropy, azeotropic mixtures may exhibit more than one azeotrope at a given temperature or pressure. While the thermodynamic condition for azeotrope formation in vapor-liquid equilibrium is well established, thermodynamic modeling of mixtures exhibiting polyazeotropy remains challenging and prior modeling studies often failed to satisfactorily correlate the polyazeotropic behavior of associating systems. Based on the association NRTL model, this study presents successful correlation and analysis of double azeotrope formation for three diverse systems: strongly associating methanol + diethylamine binary, weakly associating ammonia + pentafluoroethane binary, and non-associating benzene + hexafluorobenzene binary systems. Furthermore, these systems exhibit polyazeotropic behavior as the temperature increases and approaches their Bancroft points.

42 ENGINEERING↗