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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Real-time capable modeling of ICRF heating on NSTX and WEST via machine learning approaches

Abstract A real-time capable core Ion Cyclotron Range of Frequencies (ICRF) heating model on NSTX and WEST is developed. The model is based on two nonlinear regression algorithms, the random forest ensemble of decision trees and the multilayer perceptron neural network. The algorithms are trained on TORIC ICRF spectrum solver simulations of the expected flat-top operation scenarios in NSTX and WEST assuming Maxwellian plasmas. The surrogate models are shown to successfully capture the multi-species core ICRF power absorption predicted by the original model for the high harmonic fast wave and the ion cyclotron minority heating schemes while reducing the computational time by six orders of magnitude. Although these models can be expanded, the achieved regression scoring, computational efficiency and increased model robustness suggest these strategies can be implemented into integrated modeling frameworks for real-time control applications.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Impacts of elevated temperature on ant species, communities and ecological roles at two temperate forests in Eastern North America

Over the course of five years we have established a long-term array of warming chambers at Duke and Harvard Forest that simulate future conditions with regard to temperature. In these chambers, we have studied, ants, other animal taxa, fungi, bacteria and plants and their responses to the treatments. We have coupled these studies with lab experiments, large-scale observations, and models to contextualize our results. Finally, we have developed integrative models of the future distribution of species and their consequences as a result of warming in eastern North America and more generally.

99 GENERAL AND MISCELLANEOUS↗
NASA NTRS2012

Impact of Aerosols on Convective Clouds and Precipitation

Aerosols are a critical.factor in the atmospheric hydrological cycle and radiation budget. As a major agent for clouds to form and a significant attenuator of solar radiation, aerosols affect climate in several ways. Current research suggests that aerosols have a major impact on the dynamics, microphysics, and electrification properties of continental mixed-phase convective clouds. In addition, high aerosol concentrations in urban environments could affect precipitation variability by providing a significant source of cloud condensation nuclei (CCN). Such pollution . effects on precipitation potentially have enormous climatic consequences both in terms of feedbacks involving the land surface via rainfall as well as the surface energy budget and changes in latent heat input to the atmosphere. Basically, aerosol concentrations can influence cloud droplet size distributions, the warm-rain process, the cold-rain process, cloud-top heights, the depth of the mixed-phase region, and the occurrence of lightning. Recently, many cloud resolution models (CRMs) have been used to examine the role of aerosols on mixed-phase convective clouds. These modeling studies have many differences in terms of model configuration (two- or three-dimensional), domain size, grid spacing (150-3000 m), microphysics (two-moment bulk, simple or sophisticated spectral-bin), turbulence (1st or 1.5 order turbulent kinetic energy (TKE)), radiation, lateral boundary conditions (i.e., closed, radiative open or cyclic), cases (isolated convection, tropical or midlatitude squall lines) and model integration time (e.g., 2.5 to 48 hours). Among these modeling studies, the most striking difference is that cumulative precipitation can either increase or decrease in response to higher concentrations of CCN. In this presentation, we review past efforts and summarize our current understanding of the effect of aerosols on convective precipitation processes. Specifically, this paper addresses the following topics: observational evidence of the effect of aerosols on precipitation processes, and results from (CRM) simulations. Note that this presentation is mainly based on a recent paper published in Geophy. Rev. (Tao et al. 2012).

Tao, Wei-Kuo↗
DOE OSTI2016

Drivers of Change in Managed Water Resources: Modeling the Impacts of Climate and Socioeconomic Changes Using the US Midwest as a Case Study

A global integrated assessment model including a water-demand model driven by socio-economics, is coupled in a one-way fashion with a land surface hydrology – routing – water resources management model. The integrated modeling framework is applied to the U.S. Upper Midwest (Missouri, Upper Mississippi, and Ohio) to advance understanding of the regional impacts of climate and socio-economic changes on integrated water resources. Implications for future flow regulation, water supply, and supply deficit are investigated using climate change projections with the B1 and A2 emission scenarios, which affect both natural flow and water demand. Changes in water demand are driven by socio-economic factors, energy and food demands, global markets and prices. The framework identifies the multiple spatial scales of interactions between the drivers of changes (natural flow and water demand) and the managed water resources (regulated flow, supply and supply deficit). The contribution of the different drivers of change are quantified regionally, and also evaluated locally, using covariances. The integrated framework shows that water supply deficit is more predictable over the Missouri than the other regions in the Midwest. The predictability of the supply deficit mostly comes from long term changes in water demand although changes in runoff has a greater contribution, comparable to the contribution of changes in demand, over shorter time periods. The integrated framework also shows that spatially, water demand drives local supply deficit. Using elasticity, the sensitivity of supply deficit to drivers of change is established. The supply deficit is found to be more sensitive to changes in runoff than to changes in demand regionally. It contrasts with the covariance analysis that shows that water demand is the dominant driver of supply deficit over the analysed periods. The elasticity indicates the level of mitigation needed to control the demand in order to reduce the vulnerability of the integrated system in future periods. The elasticity analyses also emphasize the need to address uncertainty with respect to changes in natural flow in integrated assessment.

climate change, water resources management, socio-↗
DOE OSTI2021

Modeling airborne pathogen transport and transmission risks of SARS-CoV-2

An integrated modeling approach has been developed to better understand the relative impacts of different expiratory and environmental factors on airborne pathogen transport and transmission, motivated by the recent COVID-19 pandemic. Computational fluid dynamics (CFD) modeling was used to simulate spatial-temporal aerosol concentrations and quantified risks of exposure as a function of separation distance, exposure duration, environmental conditions (e.g., airflow/ventilation), and face coverings. The CFD results were combined with infectivity models to determine probability of infection, which is a function of the spatial-temporal aerosol concentrations, viral load, infectivity rate, viral viability, lung-deposition probability, and inhalation rate. Uncertainty distributions were determined for these parameters from the literature. Probabilistic analyses were performed to determine cumulative distributions of infection probabilities and to determine the most important parameters impacting transmission. This modeling approach has relevance to both pathogen and pollutant dispersion from expelled aerosol plumes.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Dynamic urban land extensification is projected to lead to imbalances in the global land-carbon equilibrium

Abstract Human-Earth System Models and Integrated Assessment Models used to explore the land-atmosphere implications of future land-use transitions generally lack dynamic representation of urban lands. Here, we conduct an experiment incorporating dynamic urbanization in a multisector model framework. We integrate projected dynamic non-urban lands from a multisector model with projected dynamic urban lands from 2015 to 2100 at 1-km resolution to examine 1 st -order implications to the land system, crop production, and net primary production that can arise from the competition over land resources. By 2100, future urban extensification could displace 0.1 to 1.4 million km 2 of agriculture lands, leading to 22 to 310 Mt of compromised corn, rice, soybean, and wheat production. When considering increased corn production required to meet demands by 2100, urban extensification could cut increases in yields by half. Losses in net primary production from displaced forest, grassland, and croplands ranged from 0.24 to 2.24 Gt C yr −1 , potentially increasing land emissions by 1.19 to 6.59 Gt CO 2 yr −1 . Although these estimates do not consider adaptive responses, 1 st -order experiments can elucidate the individual role of sub-sectors that would otherwise be masked by model complexity.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1988

Developing integrated parametric planning models for budgeting and managing complex projects

The applicability of integrated parametric models for the budgeting and management of complex projects is investigated. Methods for building a very flexible, interactive prototype for a project planning system, and software resources available for this purpose, are discussed and evaluated. The prototype is required to be sensitive to changing objectives, changing target dates, changing costs relationships, and changing budget constraints. To achieve the integration of costs and project and task durations, parametric cost functions are defined by a process of trapezoidal segmentation, where the total cost for the project is the sum of the various project cost segments, and each project cost segment is the integral of a linearly segmented cost loading function over a specific interval. The cost can thus be expressed algebraically. The prototype was designed using Lotus-123 as the primary software tool. This prototype implements a methodology for interactive project scheduling that provides a model of a system that meets most of the goals for the first phase of the study and some of the goals for the second phase.

Etnyre, Vance A.↗
DOE OSTI2014

Workshop on Modeling and Simulation of Systems and Applications, August 13-14, 2014, University of Washington, Seattle

In our efforts to continue the momentum toward quantitative understanding of the performance, power, and reliability of systems and applications, the modeling and simulation (hereafter ModSim) community gathered for its annual Workshop on Modeling & Simulation of Systems and Applications, held August 13-14, 2014 in Seattle. The 2014 Workshop on Modeling & Simulation of Systems and Applications, or ModSim 2014, focused on three critical technological areas: 1. Integrated Modeling and Simulation of Performance, Power, and Reliability; 2. Standards, Integration, and Interoperability of ModSim Methodologies and Tools; and 3. Advances in Core Modeling and Simulation Methods and Tools. The two-day meeting featured 21 presentations (based on peer-reviewed submissions) delivered over six parallel sessions, and there were six invited talks. Discussions aimed toward consolidating and directing this diverse technical community were especially beneficial as we continue to map out the future and form of ModSim research and development. This report presents a summary of the presentations, discussions, and findings culled from ModSim 2014. Each of the three critical technology areas are presented, structured as major research directions, gaps, cross-pollination, and path forward.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2010

Expert Elicitation Method Selection Process and Method Comparison

Research on integrative modeling has gained considerable attention in recent years and expert opinion has been increasingly recognized as an important data source and modeling contributor. However, little research has systematically compared and evaluated expert elicitation methods in terms of their ability to link to computational models that capture human behavior and social phenomena. In this paper, we describe a decision-making process we used for evaluating and selecting a task specific elicitation method within the framework of integrative computational social-behavioral modeling. From the existing literature, we identified the characteristics of problems that each candidate method is well suited to address. A small-scale expert elicitation was also conducted to evaluate the comparative strength and weaknesses of the methods against a number of consensus-based decision criteria. By developing a set of explicit method evaluation criteria and a description characterizing decision problems for the candidate methods, we seek to gain a better understanding of the feasibility and cost-effectiveness of integrating elicitation methods with computational modeling techniques. This serves an important first step toward expanding our research effort and trajectory toward greater interdisciplinary modeling research of human behavior.

99 GENERAL AND MISCELLANEOUS↗
NASA NTRS1981

Neutral winds and electric fields in the dust auroral oval. II - Theory and model

A two-dimensional numerical model of the thermosphere is applied to the auroral zone neutral wind, electric field, and plasma density data set, presented in an earlier paper. The model shows that the action of the Lorentz force can be responsible to a great extent for the large zonal velocities near the 150-km altitude. Model equations are described, an explanation of the use of the geophysical conditions is given, and model integrations are compared to the wind measurements. However, for the two-dimensional model to be effective, the atmosphere must not cross too many meridians of local time during the integration period, so that the background state should remain fairly uniform. It is concluded that the two-dimensional model cannot accurately explain the details of the wind profiles because of the three-dimensional character of the physical situation. Thus it is noted that the observed winds were part of a large-scale three-dimensional flow which is only weakly coupled to short-term variations in magnetospheric conditions.

Mikkelsen, I. S.↗
DOE OSTI2026

Multimodal framework for the joint analysis of single-cell RNA and T cell receptor sequencing data predicts T cell response to cancer immunotherapy

T cell states are prognostic in different cancer types. Recent technologies enable joint profiling of T cell RNA and T cell receptor (TCR) sequences at single-cell resolution. Here we present the TCR-RNA Integrating Model (TRIM), a multi-modal variational autoencoder framework that integrates RNA-TCR data and predicts T cell clonality and transcriptional states. TRIM learns a shared representation of the data conditioned on patient, tissue source, and treatment timepoint. We applied TRIM to three independent datasets that included T cells collected before and after checkpoint inhibitor treatment, sourced either from blood and tumor biopsies in patients with head and neck squamous cell carcinoma and colorectal cancer, or from tumor and adjacent tissue in a pan-cancer dataset. In all settings, TRIM accurately predicted intra-tumor T cell clonal expansion and transcriptional status based on T cells from blood or normal tissue before treatment, demonstrating its utility in modeling multimodal T cell data and predicting T cell response to treatment and disease progression.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

Modeling Impacts of Climate Change Mitigation Technologies on Power Grids

This paper describes a modeling approach that simulate the impacts of different climate change mitigation technologies on power grids for power system planning purposes. Because the historical data is less credible when new technologies are being deployed to the system, it is then critical to model them to address their impacts. This paper illustrated how to integrate modeling results obtained from different modeling tools to give a reasonable forecast of the future. Building simulation tools, distribution power grid modeling tools, and power system planning tools are used to model and aggregate the impacts from the end-use to the system level. Electricity generation, production cost, emission, and transmission congestions are used to quantify the influence of different mitigation technologies. Modeling results have shown that the cross-discipline modeling approach provided the modeler with the necessary time resolution and input details to address the variables that influence the modeling results. Different modeling issues are also addressed in the paper.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2021

Edge-localized-mode simulation in CFETR steady-state scenario

We report the EPED1 model and self-consistent core-pedestal coupling in integrated modeling are used to design the pedestal structure of the China Fusion Engineering Testing Reactor (CFETR) steady-state scenario. The key parameters, such as β p and q 95 , are based on the grassy edge-localized-mode (ELM) experimental database. In this work, we use the BOUT++ six-field two-fluid code to simulate the onset of the ELM in the CFETR steady-state scenario. The ELM size is around 0.2% in nonlinear simulations, which is in the experimental range of the grassy ELM discharges, 0.1%–1% observed in multiple tokamak devices. Linear and nonlinear simulations show that the dominant high-n ballooning modes peak around n = 40. Compared to type-I ELM crashing dynamics, grassy ELM crashing has a smaller initial crash and is then followed by three phases of turbulence spreading, which are dominated by multi-modes, a high-n mode of n = 45 and low-n mode of n = 5, respectively. In contras to type-I ELM, the perturbation of the high-n mode has a narrow width around ψ = 0.95, and magnetic island formation and reconnection occur only beyond ψ = 0.95, leading to a small initial crash. Mode–mode interaction in the multi-mode coexistence stage stops the growth of individual modes and reduces the transport of particles and heat, and these are the two reasons why the ELM size is small. In–out asymmetry of transient heat flux with a ratio of E out /E in = 3.5 is found during grassy ELM crash. The rise and delay times of the heat flux match the calculation from the free-streaming model. To evaluate the erosion of the divertor target, the energy fluence at the outer divertor target is calculated, which is 0.029 MJ m -2 , 5.5 times smaller than the tungsten melting limit 0.16 MJ m -2 . The calculated energy fluency still follows the experimental scaling law from type-I ELM experiments. The fluctuation eddies in the toroidal direction show a filament structure at the outer mid-plane. Parallel heat flux patterns with a toroidal mode number n = 10 are found at the outer divertor with an amplitude of 680 MW m -2 .

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

U-10Mo/Zr Interface Modeling using a Microstructure-Based FEM Approach

The U-10Mo in low enrichments (LEU) has been identified as the most promising alternative to the current highly enriched uranium (HEU) used in the United States’ fleet of high performance research reactors (USHPRRs). The nominal configuration of the new LEU U-10Mo plate fuel comprises a U-10Mo fuel foil enriched to slightly less than 20% U-235 (0.08” to 0.02” thick), a thin Zr interlayer/diffusion barrier (25 m thick) and a relatively thick outer can of 6061 aluminum. Currently, the Zr interlayer is clad by hot roll bonding. Previous studies and observations revealed a thinning of the zirconium (Zr) layer during this fuel fabrication process, which is not desirable from the fuel performance perspective. Coarse UMo grains, dendritic structures, Mo concentration segregation, carbides, and porosity are present in the as-cast material and can lead to a nonuniform UMo/Zr interface. The purpose of the current work is to investigate the effects of these microstructural parameters on the Zr coating variation. A microstructure-based finite-element method model was used in this work, and a study on the effect of homogenization on the interface between U-10Mo and Zr was conducted. The model uses actual backscattered electron–scanning electron microscopy microstructures, Mo concentrations, and mechanical properties to predict the behavior of a representative volume element under compressive loading during the rolling process. The model successfully predicted the experimentally observed thinning of the Zr layer in the as-cast material. The model also uses results from a homogenization model as an input, and a study on the effect of different levels of homogenization on the interface indicated that homogenization helps decrease this thinning. This model can be considered a predictive tool representing a first step for model integration and an input into a larger fuel fabrication performance model.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Powered By reV [Slides]

The reV model empowers users to calculate energy capacity, generation, and cost based on geospatial intersection with grid infrastructure and land-use characteristics. The tool can model a single site up to an entire continent at temporal resolutions ranging from five minutes to hourly, spanning a single year or multiple decades. By automating access to resource data at unprecedented scale, fidelity, and flexibility, the reV model integrates formerly disparate analysis frameworks in the fields of resource modeling, technical potential, and energy cost supply curves.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
NASA NTRS1987

Execution environment for intelligent real-time control systems

Modern telerobot control technology requires the integration of symbolic and non-symbolic programming techniques, different models of parallel computations, and various programming paradigms. The Multigraph Architecture, which has been developed for the implementation of intelligent real-time control systems is described. The layered architecture includes specific computational models, integrated execution environment and various high-level tools. A special feature of the architecture is the tight coupling between the symbolic and non-symbolic computations. It supports not only a data interface, but also the integration of the control structures in a parallel computing environment.

Sztipanovits, Janos↗
NASA NTRS2007

Planetary Moon Cycler Trajectories

Free-return cycler trajectories repeatedly shuttle a spacecraft between two bodies using little or no fuel. Here, the cycler architecture is proposed as a complementary and alternative method for designing planetary moon tours. Previously applied enumerative cycler search and optimization techniques are generalized and specifically implemented in the Jovian and Saturnian moon systems. In addition, the algorithms are tested for general use to find non-Earth heliocentric cyclers. Overall, hundreds of ideal model ballistic cycler geometries are found and several representative cases are documented and discussed. Many of the ideal model solutions are found to remain ballistic in a zero radius sphere of influence patched conic ephemeris model, and preliminary work in a high-fidelity fully integrated model demonstrates near-ballistic cycles for several example cases.

trajectory↗
NASA NTRSDate not supplied

Low-G Slosh Workshop Results From 2023: State of the Art, Gaps and Forward Work

The NASA Engineering and Safety Center (NESC) sponsored a workshop to dis-cuss low-g slosh. Over a dozen different NASA centers and industry partners participated in this workshop. The main topics were to identify the state of the art regarding test data, Computational Fluid Dynamics (CFD) analysis resources, and GN&C models that are available for this problem. The primary intent was to determine deficiencies in the collective knowledge base and to identify priorities that should be established for proactive work in the areas of model development, validation, and model integration. Recommendations from workshop participants include establishing an online slosh modeling resource, conducting ground/flight testing, developing surrogate models, and establishing co-simulation techniques. This paper summarizes the workshop findings and recommendations for the larger community.

Lattice-Boltzmann↗