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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Spatially-correlated Site Occupancy in the Nonstoichiometric Meta-stable ε -Al 60 Sm 11 Phase during Devitrification of Al-10.2 at.% Sm Glasses

A metastable ε-Al 60 Sm 11 phase appears during the initial devitrification of as-quenched Al-10.2 at.% Sm glasses. The ε phase is nonstoichiometric in nature since Al occupation is observed on the 16 f Sm lattice sites. Scanning transmission electron microscopic images reveal profound spatial correlation of Sm content on these sites, which cannot be explained by the “average crystal” description from Rietveld analysis of diffraction data. Thermodynamically favorable configurations, established by Monte Carlo (MC) simulations based on a cluster-expansion model, also give qualitatively different correlation functions from experimental observations. On the other hand, molecular dynamics simulations of the growth of ε-Al 60 Sm 11 in undercooled liquid show that when the diffusion range of Sm is limited to ~4 Å, the correlation function of the as-grown crystal structure agrees well with that of the scanning transmission electronic microscopy (STEM) images. Furthermore, our results show that kinetic effects, especially the limited diffusivity of Sm atoms plays the fundamental role in determining the nonstoichiometric site occupancies of the ε-Al 60 Sm 11 phase during the crystallization process.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Protecting building occupants against the inhalation of outdoor-origin aerosols

During normal operations, buildings can protect their occupants from outdoor airborne particle hazards of all types, including airborne pollutants. A long-term international research effort has advanced our knowledge of building protection physics. Recently we have developed an operationally efficient, regional-scale methodology - Regional Shelter Analysis - to account for both building protection effects and the typical distribution of people in and among buildings. To provide input to this capability, we estimate here the degree of protection afforded by the currently existing US building stock. Here, we first assemble and summarize the published literature relevant to indoor particle losses including (a) deposition to indoor surfaces, (b) losses that occur when particles penetrate through the building envelope, and (c) heating, ventilation and air conditioning (HVAC) system filtration efficiencies as well as general building operating conditions. Building protection against inhaling particulate hazards varies strongly, by orders of magnitude, according to particle size, airborne particle loss rate, and to a lesser extent building use (occupancy). Protection increases modestly as particle size increases from 0.1 to 1 μm and significantly as particle size increases from 1 to 10 μm. Model results are placed in context with previously reported measurements. Suggestions for future work, including enhanced validation datasets are provided.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2014

Delocalization and occupancy effects of 5f orbitals in plutonium intermetallics using L3-edge resonant X-ray emission spectroscopy

Although actinide (An) L3 -edge X-ray absorption near-edge structure (XANES) spectroscopy has been very effective in determining An oxidation states in insulating, ionically bonded materials, such as in certain coordination compounds and mineral systems, the technique fails in systems featuring more delocalized 5f orbitals, especially in metals. Recently, actinide L3-edge resonant X-ray emission spec- troscopy (RXES) has been shown to be an effective alternative. This technique is further demonstrated here using a parameterized partial unoccupied density of states method to quantify both occupancy and delocalization of the 5f orbital in ?-Pu, ?-Pu, PuCoGa5 , PuCoIn5 , and PuSb2. These new results, supported by FEFF calculations, highlight the effects of strong correlations on RXES spectra and the technique?s ability to differentiate between f-orbital occupation and delocalization.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A window into occupant-driven energy outcomes: Leveraging sub-metering infrastructure to examine psychosocial factors driving long-term outcomes of short-term competition-based energy interventions

Competition-based “energy saving” interventions are increasingly promoted as an effective strategy for reducing energy consumption in buildings with large occupant controlled electrical loads. However, the factors that drive energy savings in such interventions are not well understood, nor are the impacts of short-term competitions on long-term energy performance. A total of 39 8-occupant suites in a freshman residence hall were instrumented with “smart” electric meters, which recorded circuit-level electricity consumption at 15-minute intervals. During a three-week Fall 2014 competition, suites competed to reduce their overall electricity demand and achieved a 6.4% reduction in whole-building demand overall and a 12% reduction during hours of peak demand (from 12:00 to 19:00), despite peak seasonal temperatures and all-time record electricity demand. Analysis incorporating weather-normalized HVAC demand after the competition showed a significant “rebound” for a large portion of the suites (19), however 12 suites made further reductions, and the remainder maintained demand at the competition level. As a result, we compared energy data with self-reported survey data and identified self-efficacy beliefs, pro-environmental behaviors, and sense of affiliation with other residents of the hall as key factors distinguishing the suites with the greatest and most persistent reductions in demand from suites that maintained or increased demand.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2018

Effect of occupant behavior and air-conditioner controls on humidity in typical and high-efficiency homes

Increasing insulation levels and improved windows are reducing sensible cooling loads in high-efficiency homes. This trend raises concerns that the resulting shift in the balance of sensible and latent cooling loads may result in higher indoor humidity, occupant discomfort, and stunted adoption of high-efficiency homes. This study utilizes established moisture-buffering and air-conditioner latent degradation models in conjunction with an approach to stochastically model internal gains. Building loads and indoor humidity levels are compared for simulations of typical new construction homes and high-efficiency homes in 10 US cities. The sensitivity of indoor humidity to changes in cooling set point, air-conditioner capacity, and blower control parameters are evaluated. The results show that high-efficiency homes in humid climates have cooling loads with a higher fraction of latent loads than the typical new construction home, resulting in higher indoor humidity. Reducing the cooling set point is the easiest method to reduce indoor humidity, but it is not energy efficient, and overcooling may lead to occupant discomfort. Eliminating the blower operation at the end of cooling cycles and reducing the cooling airflow rate also reduce indoor humidity and with a smaller impact on energy use and comfort.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Residential Demand Flexibility: Modeling Occupant Behavior using Sociodemographic Predictors

Demand flexibility (DF) has the potential to increase the saturation of renewables in the grid and reduce operating costs for both utilities and customers. However, less than 8% of U.S. residential electric customers are enrolled in DF programs. A major research gap on this topic is an uneven understanding of behavioral drivers of electricity use and DF program participation at the household level. In this study, we employ machine learning models to predict residential occupant behavior in activities relevant to DF. We model occupants' extensive decisions (i.e., choice of action) and intensive behaviors (i.e., amount of time spent) during peak and off-peak time periods using the publicly available American Time Use Survey, which includes activities data for approximately 200,000 respondents. In our machine learning models, predictions for both extensive and intensive behavior fell within a +/-20% error margin at the aggregate level. We identify 13 key sociodemographic predictors of DF-related intensive behavior using LASSO inference and beta coefficient ranking. However, these top predictors differ by activity, suggesting potential scope for differential user targeting for DF events and technologies during program design. This work also contributes to understanding when and who might adopt these DF technologies based on their daily routine activities.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Post-occupancy evaluation of indoor environmental quality in ten nonresidential buildings in Chongqing, China

Indoor environmental quality (IEQ) is an essential element of sustainable building performance. To advance knowledge of indoor environmental quality in Chinese nonresidential buildings, this study conducted post-occupancy evaluation (POE) in varied use areas within schools, hospitals, offices, hotels and shopping malls through environmental measurements and occupant surveys in 10 buildings over four seasons in Chongqing, China. Measured thermal conditions were more frequently within comfort standards in winter than in summer according to the predicted mean vote – predicted percentage dissatisfied model; but the model did not reliably predict thermal satisfaction. There was insufficient illuminance in 28% of studied areas and high illuminance in shopping malls led to complaints about glare. Sound pressure exceeded the Chinese guideline in all buildings with shopping malls having significantly higher levels than other buildings. CO 2 was generally below the Chinese national guideline of 1000 ppm; the two percent of measurements that exceeded the guideline occurred in classrooms, hospital wards and underground supermarkets. Formaldehyde did not exceed the limit level of 0.1 mg/m3 in any space. Most of the buildings did not provide effective protection from outdoor fine particulate matter (PM2.5), and infiltration from outdoors was the main factor for exceeding health-based guidelines indoors. Shopping malls had lower IEQ satisfaction than offices, schools and hospitals. Sound was the factor with the lowest satisfaction level among the four principal environmental factors. Overall, this study demonstrates value of POE on identifying deficiencies in indoor environment and provides a reference for assessment of IEQ in nonresidential buildings.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2013

Conspicuous variation of the lattice unit cell in the pavonite homologous series and its relation with cation/anion occupational modulations

Highlights: ► Strong non-uniform variation of unit cell parameters in the pavonite homologous series. ► Conspicuous unit cell variation due to an underlying sub-lattice with cation/anion occupation. ► A modulated model common to the whole series using the superspace formalism proposed. ► Model successfully applied to the {sup 7}P pavonite Ag{sub 3}(Bi,Pb){sub 7}S{sub 12}. ► The model can be applied in a predictive way to other members of the family. - Abstract: The pavonites is a homologous series of sulfosalts with galena-like modules of variable size. A survey of their unit cells reveals that they are severely constrained by the metrics of an underlying common average sublattice. The unit cell of any compound of the series accommodates with high precision an integer number of approximately equal subcells. This explains a peculiar non-uniform variation of the unit cell parameters within the series and evidences that the interface between the galena-like modules, despite having a very different topology, approximately maintains the subperiodicity of the modules, and must therefore be subject to strong steric restrictions. It also implies that cations and anions occupy the nodes of the observed common underlying average sublattice according to a striking alternate cation/anion occupational modulation. This is the starting point for a description of these materials as modulated structures, which can make a proficient use of the approximate atomic positional non-crystallographic correlations caused by their modular character. Under this approach only four parameters suffice to define a realistic approximate model of any member of the series. A full structural characterization of any of the compounds only requires the determination of additional small/smooth modulations. As an example, the case of the {sup 7}P pavonite Ag{sub 3}Bi{sub 6.2}Pb{sub 0.8}S{sub 12}, is analyzed.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Identification of serum biomarkers for occupational medicamentosa-like dermatitis induced by trichloroethylene using mass spectrometry

Occupational medicamentosa-like dermatitis induced by trichloroethylene (OMLDT) is an autoimmune disease and it has become a serious occupational health hazard. In the present study, we collected fasting blood samples from patients with OMLDT (n = 18) and healthy volunteers (n = 33) to explore serum peptidome patterns. Peptides in sera were purified using weak cation exchange magnetic beads (MB-WCX), and analyzed by matrix-assisted laser desorption ionization time-of-flight-mass spectrometry (MALDI-TOF-MS) and ClinProTools bioinformatics software. The intensities of thirty protein/peptide peaks were significantly different between the healthy control and OMLDT patients. A pattern of three peaks (m/z 2106.3, 2134.5, and 3263.67) was selected for supervised neural network (SNN) model building to separate the OMLDT patients from the healthy controls with a sensitivity of 95.5% and a specificity of 73.8%. Furthermore, two peptide peaks of m/z 4091.61 and 4281.69 were identified as fragments of ATP-binding cassette transporter family A member 12 (ABCA12), and cationic trypsinogen (PRRS1), respectively. Our findings not only show that specific proteomic fingerprints in the sera of OMLDT patients can be served as a differentiated tool of OMLDT patients with high sensitivity and high specificity, but also reveal the novel correlation between OMLDT with ABC transports and PRRS1, which will be of potential value for clinical and mechanistic studies of OMLDT. - Highlights: • Identify 30 differential protein/peptide peaks between OMLDT and healthy control • The test sensitivity and test specificity were 95.5% and 73.8%, respectively. • ABCA12 and PRSS1 were identified as potential biomarkers in OMLDT patients.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Quaternary Pavonites A 1+ x S 2– x Bi 5+ x S 10 (A + = Li + , Na + ): Site Occupancy Disorder Defines Electronic Structure

The field of mineralogy represents an area of untapped potential for the synthetic chemist, as there are numerous structure types that can be utilized to form analogues of mineral structures with useful optoelectronic properties. In this work, we describe the synthesis and characterization of two novel quaternary sulfides A 1+x Sn 2–x Bi 5+x S 10 (A = Li + , Na + ). Though not natural minerals themselves, both compounds adopt the pavonite structure, which crystallizes in the C2/m space group and consists of two connected, alternating defect rock-salt slabs of varying thicknesses to create a three-dimensional lattice. Despite their commonalities in structure, their crystallography is noticeably different, as both structures have a heavy degree of site occupancy disorder that affects the actual positions of the atoms. The differences in site occupancy alter their electronic structures, with band gap values of 0.31(2) eV and 0.07(2) eV for the lithium and sodium analogues, respectively. LiSn 2 Bi 5 S 10 exhibits ultralow thermal conductivity of 0.62 W m –1 K –1 at 723 K, and this result is corroborated by phonon dispersion calculations. Here, this structure type is a promising host candidate for future thermoelectric materials investigation, as these materials have narrow band gaps and intrinsically low thermal conductivities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Linear scaling pseudo Fermi-operator expansion for fractional occupation

Recursive Fermi-operator expansion methods for the calculation of the idempotent density matrix are valid only at zero electronic temperature with integer occupation numbers. We show how such methods can be modified to include fractional occupation numbers of an approximate or pseudo Fermi-Dirac distribution and how the corresponding entropy term of the free energy is calculated. The proposed methodology is demonstrated and evaluated for different electronic structure methods including density functional tight-binding theory, Kohn-Sham density functional theory using numerical orbitals, and quantum chemistry Hartree-Fock theory using Gaussian basis functions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Development of Nontargeted Workflow of Occupational Exposure by Infrared Ion Spectroscopy and Silicone Wristbands’ Passive Sampling

Monitoring chemical exposure has well-established protocols and procedures for occupational health and industrial hygiene across various career fields and in a variety of occupational and environmental conditions. Iterative analytical development has led to validated methods to provide employers and employees with safe working conditions in terms of industrial hygiene. These validated methods are commonly supported by commercial laboratories. Here, this workflow is explicitly a targeted approach in which sampling media, sample preparation, chemical separation, quantitative target detection, and post processing are well established. This workflow also relies on commercially available chemical surrogates, isotopically labeled internal standards, and certified/standard reference materials from reputable vendors. An untargeted workflow lacks many key ingredients of validated analytical methods to include the known chemical target.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Single-cell quantification of ribosome occupancy in early mouse development

Translation regulation is critical for early mammalian embryonic development. However, previous studies had been restricted to bulk measurements, precluding precise determination of translation regulation including allele-specific analyses. Here, to address this challenge, we developed a novel microfluidic isotachophoresis (ITP) approach, named RIBOsome profiling via ITP (Ribo-ITP), and characterized translation in single oocytes and embryos during early mouse development. We identified differential translation efficiency as a key mechanism regulating genes involved in centrosome organization and N 6 -methyladenosine modification of RNAs. Our high-coverage measurements enabled, to our knowledge, the first analysis of allele-specific ribosome engagement in early development. These led to the discovery of stage-specific differential engagement of zygotic RNAs with ribosomes and reduced translation efficiency of transcripts exhibiting allele-biased expression. By integrating our measurements with proteomics data, we discovered that ribosome occupancy in germinal vesicle-stage oocytes is the predominant determinant of protein abundance in the zygote. The Ribo-ITP approach will enable numerous applications by providing high-coverage and high-resolution ribosome occupancy measurements from ultra-low input samples including single cells.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Single occupancy spectroelectrochemistry of freely diffusing flavin mononucleotide in zero-dimensional nanophotonic structures

Zero-mode waveguides (ZMW) have the potential to be powerful confinement tools for studying electron transfer dynamics at single molecule occupancy conditions. Flavin mononucleotide contains an isoalloxazine chromophore, which is fluorescent in the oxidized state (FMN) while the reduced state (FMNH 2 ) exhibits dramatically lower light emission, i.e. a dark-state. This allows fluorescence emission to report the redox state of single FMN molecules, an observation that has been used previously to study single electron transfer events in surface-immobilized flavins and flavoenzymes, e.g. sarcosine oxidase, by direct wide-field imaging of ZMW arrays. Single molecule electron transfer dynamics have now been extended to the study of freely diffusing molecules using fluorescence measurements of Au ZMWs under single occupancy conditions. The Au in the ZMW serves both as an optical cladding layer and as the working electrode for potential control, thereby accessing single molecule electron transfer dynamics at μM concentrations. Consistent with expectations, the probability of observing single reduced molecules increases as the potential is scanned negative, E appl < E eq , and the probability of observing emitting oxidized molecules increases at E appl > E eq . Different single molecules exhibit different electron transfer properties as reflected in the position of E eq and the distribution of E eq among a population of FMN molecules. Two types of actively-controlled electroluminescence experiments were used: chronofluorometry experiments, in which the potential is alternately stepped between oxidizing and reducing potentials, and cyclic potential sweep fluorescence experiments, analogous to cyclic voltammetry, these latter experiments exhibiting a dramatic scan rate dependence with the slowest scan rates showing distinct intermediate states that are stable over a range of potentials. These states are assigned to flavosemiquinone species that are stabilized in the special environment of the ZMW nanopore.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Anisotropic orbital occupation and Jahn-Teller distortion of orthorhombic YMnO{sub 3} epitaxial films: A combined experimental and theoretical study on polarization-dependent x-ray absorption spectroscopy

The b-axis oriented orthorhombic YMnO{sub 3} (o-YMnO{sub 3}) epitaxial films on a YAlO{sub 3} (010) substrate were fabricated with pulsed-laser deposition. The anisotropic orbital occupation and Jahn-Teller (JT) distortion of an o-YMnO{sub 3} film were investigated with polarization-dependent x-ray absorption spectra and configuration-interaction multiplet-cluster calculations. A significant energy difference, ∼3.8 eV, for the main white line along E//b and E//a in polarization-dependent Mn K-edge spectra of o-YMnO{sub 3} indicates an extraordinary JT distortion and significant anisotropic Mn–O bonding within the ab plane in the o-YMnO{sub 3} film. Most importantly, although the orbital occupation of 3d electrons in o-YMnO{sub 3} films is almost the same as that in single crystalline o-DyMnO{sub 3}, the JT distortion of o-YMnO{sub 3} films is larger than that of single crystalline o-DyMnO{sub 3}, deduced from the multiplet calculations. We speculate that this JT distortion predominantly contributes to the origin of the cycloidal spin deformation in bulk o-YMnO{sub 3}, because of a suppressed nearest-neighbor superexchange interaction and an enhanced next-nearest-neighbor superexchange interaction. These complementary results provide insight into the origin of the E-type magnetic configuration of o-YMnO{sub 3}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Prediction of variation in d-orbital occupancy in strain induced tetragonal phase of BiFeO{sub 3} thin film

A theoretical study of the possible variation of d-orbital occupancy while going from the rhombohedral bulk phase to the strain induced tetragonal phase of BiFeO{sub 3} thin film has been carried out. A possible existence of an intermediate spin (IS) state, S=3/2 and a low spin (LS) state, S=1/2 in the tetragonal phase has been predicted, thereby clearly establishing the role of strain behind the d-orbital occupancy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Quasi-chemical theory of F - (aq): The “no split occupancies rule” revisited

We use ab initio molecular dynamics (AIMD) calculations and quasi-chemical theory (QCT) to study the inner-shell structure of F-(aq) and to evaluate that single-ion free energy under standard conditions. Following the “no split occupancies” rule, QCT calculations yield a free energy value of -101 kcal/mol under these conditions, in encouraging agreement with tabulated values (-111 kcal/mol). The AIMD calculations served only to guide the definition of an effective inner-shell constraint. QCT naturally includes quantum mechanical effects that can be concerning in more primitive calculations, including electronic polarizability and induction, electron density transfer, electron correlation, molecular/atomic cooperative interactions generally, molecular flexibility, and zero-point motion. No direct assessment of the contribution of dispersion contributions to the internal energies has been attempted here, however. We anticipate that other aqueous halide ions might be treated successfully with QCT, provided that the structure of the underlying statistical mechanical theory is absorbed, i.e., that the “no split occupancies” rule is recognized.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

THE GALAXY-HALO/SUBHALO CONNECTION: MASS RELATIONS AND IMPLICATIONS FOR SOME SATELLITE OCCUPATIONAL DISTRIBUTIONS

We infer the local stellar-to-halo/subhalo mass relations (MRs) for central and satellite galaxies separately. Our statistical method is an extension of the abundance matching, halo occupation distribution, and conditional stellar mass function formalisms. We constrain the model using several combinations of observational data, consisting of the total galaxy stellar mass function (GSMF), its decomposition into centrals and satellites, and the projected two-point correlation functions (2PCFs) measured in different stellar mass (M{sub *}) bins. In addition, we use the {Lambda}CDM halo and subhalo mass functions. The differences among the resulting MRs are within the model-fit uncertainties (which are very small, smaller than the intrinsic scatter between galaxy and halo mass), no matter what combination of data are used. This shows that matching abundances or occupational numbers is equivalent, and that the GSMFs and 2PCFs are tightly connected. We also constrain the values of the intrinsic scatter around the central-halo (CH) and satellite-subhalo (SS) MRs assuming them to be constant: {sigma}{sub c} = 0.168 {+-} 0.051 dex and {sigma}{sub s} = 0.172 {+-} 0.057 dex, respectively. The CH and SS MRs are actually different, in particular when we take the subhalo mass at the present-day epoch instead of at their accretion time. When using the MRs for studying the satellite population (e.g., in the Milky Way, MW), the SS MR should be chosen instead of the average one. Our model allows one to calculate several population statistics. We find that the central galaxy M{sub *} is not on average within the mass distribution of the most massive satellite, even for cluster-sized halos, i.e., centrals are not a mere realization of the high end of the satellite mass function; however for >3 Multiplication-Sign 10{sup 13} M{sub Sun} halos, {approx}15% of centrals could be. We also find that the probabilities of MW-sized halos of having N Magellanic Cloud (MC) sized satellites agree well with observational measures; for a halo mass of 2 Multiplication-Sign 10{sup 12} M{sub Sun }, the probability to have two MCs is 5.4%, but if we exclude those systems with satellites larger than the MCs, then the probability decreases to <2.2%.

79 ASTRONOMY AND ASTROPHYSICS↗