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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Use of multiscale zirconium alloy deformation models in nuclear fuel behavior analysis

Accurate prediction of cladding mechanical behavior is a key aspect of modeling nuclear fuel behavior, especially for conditions of pellet-cladding interaction (PCI), reactivity-initiated accidents (RIA), and loss of coolant accidents (LOCA). Current approaches to fuel performance modeling rely on empirical constitutive models for cladding creep, growth and plastic deformation, which are limited to the materials and conditions for which the models were developed. To improve upon this approach, a microstructurally-based zirconium alloy mechanical deformation analysis capability is being developed within the United States Department of Energy Consortium for Advanced Simulation of Light Water Reactors (CASL). Specifically, the viscoplastic self-consistent (VPSC) polycrystal plasticity modeling approach, developed by Lebensohn and Tomé [1], has been coupled with the BISON engineering scale fuel performance code to represent the mechanistic material processes controlling the deformation behavior of light water reactor (LWR) cladding. A critical component of VPSC is the representation of the crystallographic nature (defect and dislocation movement) and orientation of the grains within the matrix material and the ability to account for the role of texture on deformation. A future goal is for VPSC to obtain information on reaction rate kinetics from atomistic calculations to inform the defect and dislocation behavior models described in VPSC. The multiscale modeling of cladding deformation mechanisms allowed by VPSC far exceed the functionality of typical semi-empirical constitutive models employed in nuclear fuel behavior codes to model irradiation growth and creep, thermal creep, or plasticity. This paper describes the implementation of an interface between VPSC and BISON and provides initial results utilizing the coupled functionality.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Behavior of the maximum likelihood in quantum state tomography

Quantum state tomography on a d-dimensional system demands resources that grow rapidly with d. They may be reduced by using model selection to tailor the number of parameters in the model (i.e., the size of the density matrix). Most model selection methods typically rely on a test statistic and a null theory that describes its behavior when two models are equally good. Here, we consider the loglikelihood ratio. Because of the positivity constraint ρ ≥ 0, quantum state space does not generally satisfy local asymptotic normality (LAN), meaning the classical null theory for the loglikelihood ratio (the Wilks theorem) should not be used. Thus, understanding and quantifying how positivity affects the null behavior of this test statistic is necessary for its use in model selection for state tomography. We define a new generalization of LAN, metric-projected LAN, show that quantum state space satisfies it, and derive a replacement for the Wilks theorem. In addition to enabling reliable model selection, our results shed more light on the qualitative effects of the positivity constraint on state tomography.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Leaching Behavior of Rare Earth Elements in Fort Union Lignite Coals of North America

Rare earth elements are crucial materials in an incredible array of consumer goods, energy system components and military defense applications. However, the global production and entire value chain for rare earth elements is dominated by China, with the U.S. currently 100% import reliant for these critical materials. Traditional mineral ores including those previously mined in the U.S., however, have several challenges. Chief among these is that the content of the most critical and valuable of the rare earths are deficient, making mining uneconomical. Further, the supply of these most critical rare earths is nearly 100% produced in China from a single resource that is only projected to last another 10 to 20 years. The U.S. currently considers the rare earths market an issue of national security. It is imperative that alternative domestic sources of rare earths be identified and methods developed to produce them. Recently, coal and coal byproducts have been identified as one of these promising alternative resources. This paper details the results of a study on characterization of North Dakota lignite and lignite-related feedstocks as an assessment of their feasibility for rare earth element recovery. The abundance, distribution and modes of occurrence of the rare earth elements in the samples collected were determined in this initial study to inform the selection of appropriate extraction and concentration methods to recover the rare earth elements. Materials investigated include the lignite coals, clay-rich sediments associated with the coal seams, and materials associated with a lignite beneficiation system and power plant. The results show that high rare earth element levels exist both in lignite coals and associated sediments. The form of the rare earth elements in the clay materials is primarily as ultra-fine mineral grains. In the lignite coals, approximately 80-95% of the rare earths content is organically associated, primarily as coordination complexes.

Laudal, Daniel A.↗
DOE OSTI2018

Aqueous aggregation behavior of citric acid coated magnetite nanoparticles: Effects of pH, cations, anions, and humic acid

Highlights: • Citric acid (CA) coatings greatly enhanced the stability of MNPs at pH = 5–9. • Stability of CA-MNPs increased with pH increase due to CA deprotonation. • The valence and adsorption of ions affected the surface charge of CA-MNPs. • The aggregation behaviors of CA-MNPs agreed with DLVO predictions. Improving the colloidal stability of magnetite nanoparticles (MNPs) is essential for their successful applications. In this study, the surface zeta potential and particle size evolutions of citric acid coated magnetite nanoparticles (CA-MNPs) were measured under varied aqueous conditions using dynamic light scattering (DLS). The effects of pH (5.0–9.0), ionic strength (IS), cations (Na{sup +} and Ca{sup 2+}), anions (phosphate, sulfate, and chloride) and humic acid on the aggregation behaviors of CA-MNPs were explored. Compared with bare MNPs, the stability of CA-MNPs were greatly improved over the typical pH range of natural aquatic environments (pH = 5.0–9.0), as the coated CA-MNPs were highly negatively charged over the pH range due to the low pK{sub a1} value (3.13) of citrate acid. CA-MNPs were more stable in the presence of monovalent cation (Na{sup +}) compared with divalent cation (Ca{sup 2+}), as Ca{sup 2+} could neutralize the surface charge of MNPs more significantly than Na{sup +}. In the presence of anions, the surface charges of CA-MNPs became more negative, and the stability of CA-MNPs followed the order: in phosphate > sulfate > chloride. The observed aggregation trend could be explained by the differences in the valences of the anions and their adsorption behaviors onto CA-MNPs, which altered the surface charges of CA-MNPs. The measured critical coagulation concentrations (CCC) values of CA-MNPs in these electrolyte solutions agreed well with Derjaguin–Landau–Verwey–Overbeek (DLVO) calculations. With the addition of Humic acid (HA), the aggregation of CA-MNPs was inhibited in all electrolyte solutions even with the critical coagulation concentrations. This is due to the adsorption of HA onto CA-MNPs, which enhanced the electrostatic and steric repulsive forces between CA-MNPs. Considering the good stability of CA-MNPs in solutions with varied pH and electrolyte compositions, as well as with the easy synthesis of CA-MNPs and their non-toxicity, this study suggested CA coating as a good strategy to increase the stability of MNPs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Persistence of collective behavior at high spin in the N = 88 nucleus Tb 153

Excited states in the N = 88 nucleus 153 Tb were observed up to spin ~40 in an experiment utilizing the Gammasphere array. The 153 Tb states were populated in a weak α4n evaporation channel of the 37 Cl + 124 Sn reaction. Two previously known sequences were extended to higher spins, and a new decoupled structure was identified. The πh 11/2 band was observed in the spin region where other N = 88 isotopes exhibit effects of prolate to oblate shape changes leading to band termination along the yrast line, whereas 153 Tb displays a persistent collective behavior. Furthermore, minor perturbations of the very highest state in both signatures of this h 11/2 band are observed, which perhaps signal the start of the transition towards band termination.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Incubation temperature influences the behavioral traits of a young precocial bird

Abstract The environment in which animals develop can have important consequences for their phenotype. In reptiles, incubation temperature is a critical aspect of the early developmental environment. Incubation temperature influences morphology, physiology, and behavior of non‐avian reptiles, however, little is known about how incubation temperature influences offspring phenotype and behaviors important to avian survival. To investigate whether incubation temperature influences avian behaviors, we collected wood duck ( Aix sponsa ) eggs from the field and incubated them at three naturally occurring incubation temperatures (35.0, 35.8, and 37.0°C). We conducted multiple repeated behavioral trials on individual ducklings between 5 and 15 days post‐hatch to assess activity, exploratory, and boldness behaviors, classified along a proactive‐reactive continuum. We measured growth rates and circulating levels of baseline and stress‐induced corticosterone levels to investigate possible physiological correlates of behavior. Ducklings incubated at the lowest temperature displayed more proactive behaviors than those incubated at the two higher temperatures. We also found that younger ducklings exhibited more proactive behavior than older ducklings and males exhibited more proactive behavior than females. Further, duckling behaviors were repeatable across time and contexts, indicative of a proactive–reactive continuum of behavioral tendencies. However, neither corticosterone levels nor growth rates were related to behavior. This provides some of the first evidence that incubation temperature, a critical parental effect, influences avian offspring behaviors that may be important for survival. Our results identify incubation temperature as a mechanism that contributes to the development of behavioral traits and, in part, explains how multiple behavioral types may be maintained within populations.

Hope, Sydney F.↗
DOE OSTI2018

Understanding scale-dependent soft-error behavior of scientific applications

Analyzing application fault behavior on large-scale systems is time-consuming and resource-demanding. Currently, researchers need to perform fault injection campaigns at full scale to understand the effects of soft errors on applications and whether these faults result in silent data corruption. Both time and resource requirements greatly limit the scope of the resilience studies that can be currently performed. In this work, we propose a methodology to model application fault behavior at large scale based on a reduced set of experiments performed at small scale. We employ machine learning techniques to accurately model application fault behavior using a set of experiments that can be executed in parallel at small scale. Our methodology drastically reduces the set and the scale of the fault injection experiments to be performed and provides a validated methodology to study application fault behavior at large scale. We show that our methodology can accurately model application fault behavior at large scale by using only small scale experiments. In some cases, we can model the fault behavior of a parallel application running on 4,096 cores with about 90% accuracy based on experiments on a single core.

Kestor, Gokcen G.↗
DOE OSTI2024

Individual low-carbon behaviors and influencing factors: Insights from a behavior survey study in China

Climate change is a major global concern. Greenhouse gas emissions that cause global climate change are directly or indirectly affected by human activities. Individual low-carbon behaviors are crucial in reducing CO 2 emissions and improving environmental and ecological health. To effectively promote individual low-carbon behavior, this study designed a questionnaire on the factors influencing individual low-carbon intentions and behavior based on theoretical models of environmental behavior. A total of 2430 valid questionnaires were collected in China. This study focuses on analyzing the impact of demographic characteristics, internal and external factors on individual low-carbon behaviors and their interrelationships. The research shows correlations between internal and external factors in determining low-carbon intention or behaviors. Internal factors-related low-carbon behavior is not closely linked with demographic variables, whereas the external factors-related low-carbon behavior vary significantly by age, residence, education, marital status, occupation, and income. The findings have important implications for designing effective policies to promote low-carbon behaviors, such as creating a more favorable external environment and increasing the use of policy tools for reducing CO 2 emission.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2015

An opinion-driven behavioral dynamics model for addictive behaviors

We present a model of behavioral dynamics that combines a social network-based opinion dynamics model with behavioral mapping. The behavioral component is discrete and history-dependent to represent situations in which an individual’s behavior is initially driven by opinion and later constrained by physiological or psychological conditions that serve to maintain the behavior. Additionally, individuals are modeled as nodes in a social network connected by directed edges. Parameter sweeps illustrate model behavior and the effects of individual parameters and parameter interactions on model results. Mapping a continuous opinion variable into a discrete behavioral space induces clustering on directed networks. Clusters provide targets of opportunity for influencing the network state; however, the smaller the network the greater the stochasticity and potential variability in outcomes. Furthermore, this has implications both for behaviors that are influenced by close relationships verses those influenced by societal norms and for the effectiveness of strategies for influencing those behaviors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Self-reported health behaviors, including sleep, correlate with doctor-informed medical conditions: data from the 2011 Health Related Behaviors Survey of U.S. Active Duty Military Personnel

Health behaviors and cardiometabolic disease risk factors may differ between military and civilian populations; therefore, in U.S. active duty military personnel, we assessed relationships between demographic characteristics, self-reported health behaviors, and doctor-informed medical conditions. Methods Data were self-reported by 27,034 active duty military and Coast Guard personnel who responded to the 2011 Department of Defense Health Related Behaviors Survey. Multivariate linear and logistic regressions were used to estimate cross-sectional associations between (1) demographic characteristics (age, sex, service branch, marital status, children, race/ethnicity, pay grade) and self-reported behaviors (exercise, diet, smoking, alcohol, sleep); (2) demographic characteristics and doctor-informed medical conditions (hypertension, hypercholesterolemia, low high density lipoprotein (HDL) cholesterol, hyperglycemia) and overweight/obesity; and (3) behaviors and doctor-informed medical conditions. Results Among respondents (age 29.9 ± 0.1 years, 14.7% female), females reported higher intake than men of fruit, vegetables, and dairy; those with higher education reported higher intakes of whole grains; those currently married and/or residing with children reported higher intake of starches. Older age and female sex were associated with higher odds (ORs 1.25 to 12.54 versus the youngest age group) of overweight/obesity. Older age and female sex were also associated with lower odds (ORs 0.29 to 0.65 versus male sex) of doctor-informed medical conditions, except for blood glucose, for which females had higher odds. Those currently married had higher odds of high cholesterol and overweight/obesity, and separated/divorced/widowed respondents had higher odds of high blood pressure and high cholesterol. Short sleep duration (< 5 versus 7–8 h/night) was associated with higher odds (ORs 1.36to 2.22) of any given doctor-informed medical condition. Strength training was associated with lower probability of high cholesterol, high triglycerides, and low HDL, and higher probability of overweight/obesity. Dietary factors were variably associated with doctor-informed medical conditions and overweight/obesity. Conclusions This study observed pronounced associations between health behaviors—especially sleep—and medical conditions, thus adding to evidence that sleep is a critical, potentially modifiable behavior within this population. When possible, adequate sleep should continue to be promoted as an important part of overall health and wellness throughout the military community.

60 APPLIED LIFE SCIENCES↗