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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Soil carbon cycling proxies: Understanding their critical role in predicting climate change feedbacks

The complexity of processes and interactions that drive soil C dynamics necessitate the use of proxy variables to represent soil characteristics that cannot be directly measured (correlative proxies), or that aggregate information about multiple soil characteristics into one variable (integrative proxies). These proxies have proven useful for understanding the soil C cycle, which is highly variable in both space and time, and are now being used to make predictions of the C fate and persistence under future climate scenarios. As these proxies are used at increasingly larger scales, the C pools and processes that proxies represent must be thoughtfully considered in order to minimize uncertainties in empirical understanding, as well as in model parameters and in model outcomes. The importance of these uncertainties is further amplified by the current need to make predictions of the C cycle for the non steady state environmental conditions resulting from global climate change. To clarify the appropriate uses of proxy variables, we provide specific examples of proxy variables that could improve decision making, adaptation choices, and modeling skill, while not foreclosing on – and also encouraging – continued work on their mechanistic underpinnings. We explore the use of three common soil proxies used to study soil organic matter: metabolic quotient, clay content, and physical fractionation. We also consider emerging data types, specifically genome-sequence data, and how these serve as proxies for microbial community activities. We opine that the demand for increasing mechanistic detail, and the flood of data from new imaging and genetic techniques, does not replace the value of correlative and integrative proxies--variables that are simpler, easier, or cheaper to measure. By closely examining the current knowledge gaps and broad assumptions in soil C cycling with the proxies already in use, we can develop new hypotheses and specify criteria for new and needed proxies.

Bailey, Vanessa L.↗
DOE OSTI2024

Aerogel-derived nickel-iron oxide catalysts for oxygen evolution reaction in alkaline media

Anion exchange membrane water electrolyzers (AEMWEs) can generate hydrogen with a pure water feed using noble metal-free catalysts. Here, the development of highly active and stable catalysts for oxygen evolution reaction (OER) is required for improving performance of AEMWEs systems. Ni-Fe (oxy)hydroxides show high OER catalytic activity in alkaline media, but typically have low surface area. In this work, we investigate a series of Ni-Fe oxides with high surface area and disordered morphology, obtained using an aerogel synthesis method. We evaluate the impact of different synthesis variables on the OER activity and demonstrate that heat treatment at high temperatures generates more ordered structure, resulting in a decrease in OER activity. Advanced characterization reveals that maintaining highly disordered and porous structure of the aerogel is essential to achieving high OER activity, as it enables the formation of highly OER-active lamellar structures of the catalyst.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A velocity/stress mixed stabilized nodal finite element for elastodynamics: Analysis and computations with strongly and weakly enforced boundary conditions

A new nodal mixed finite element is proposed for the simulation of linear elastodynamics and wave propagation problems in time domain. Our method is based on equal-order interpolation discrete spaces for both the velocity (or displacement) and stress (or strain) tensor variables. The mixed form is derived using either the velocity/stress or velocity/strain pair of unknowns, the latter being instrumental in extensions of the method to nonlinear mechanics. The proposed approach works equally well on hexahedral or tetrahedral grids and, for this reason, it is suitable for time-domain engineering applications in complex geometry. The peculiarity of the proposed approach is the use of the rate form of the stress update equation, which yields a set of governing equations with the structure of a non-dissipative space/time Friedrichs’ system. We complement standard traction boundary conditions for the stress with strongly and weakly enforced boundary conditions for the velocity (or displacement). Weakly enforced boundary conditions are particularly suitable when considering complex geometrical shapes, because they do not require dedicated data structures for the imposition of the boundary degrees of freedom, but, rather, they utilize the structure of the variational formulation. Here we also show how the framework of weakly enforced boundary conditions can be used to develop variational forms for multi-domain simulations of heterogeneous media. A complete analysis including stability and convergence proofs is included, in the case of a space–time variational approach. A series of computational tests are used to demonstrate and verify the performance of the proposed approach.

42 ENGINEERING↗
DOE OSTI2019

A review of smart building sensing system for better indoor environment control

Here this paper aims to provide a systemic review of how indoor sensors influence in managing optimal energy saving, thermal comfort, visual comfort, and indoor air quality in the built environment. The optimal management of energy saving and occupant comfort plays a vital role in the built environment because the occupant's productivity and health are highly influenced by indoor environmental quality. In order to do this, there must be a functional sensing system that connects the environment variables (e.g., temperature) with building environmental control systems such as the heating, ventilation, and air-conditioning system. This paper starts with an overview of the importance of energy saving and occupant comfort in the built environment. It then discusses sensors and their importance in the built environment and reviews the different types of sensors, which explains them in terms of how they influence the indoor built environment and occupant productivity. The paper further explores the application of sensors in the built environment and analyzes this in terms of energy saving, thermal comfort, visual comfort, and indoor air quality. Following this, the data analysis is discussed in terms of data, information, and knowledge accrued from the sensors. Lastly, the paper discusses the future challenges for the improvement of building indoor environmental quality and energy saving by the application of sensors.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Scalar conservation and boundedness in simulations of compressible flow

With the proper combination of high-order, low-dissipation numerical methods, physics-based subgrid-scale models, and boundary conditions it is becoming possible to simulate many combustion flows at relevant conditions. However, non-premixed flows are a particular challenge because the thickness of the fuel/oxidizer interface scales inversely with Reynolds number. Sharp interfaces can also be present in the initial or boundary conditions. When higher-order numerical methods are used, there are often aphysical undershoots and overshoots in the scalar variables (e.g.passive scalars, species mass fractions or progress variable). These numerical issues are especially prominent when low-dissipation methods are used, since sharp jumps in flow variables are not always coincident with regions of strong variation in the scalar fields: consequently, special detection mechanisms and dissipative fluxes are needed. Most numerical methods diffuse the interface, resulting in artificial mixing and spurious reactions. In this paper, we propose a numerical method that mitigates this issue. As a result, we present methods for passive and active scalars, and demonstrate their effectiveness with several examples.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Estimated capital costs of fish exclusion technologies for hydropower facilities

Hydropower is a reliable source of renewable energy, and its future expansion is likely to be in the form of either smaller new stream development (NSD) projects or powering existing non-powered dams. Thresholds for entrainment risk to fish and the requirements for fish exclusion at hydropower facilities often differ depending on the species involved, the characteristics of the facility, and the goals of stakeholders, but little quantitative information is present within the literature regarding the specific costs of fish exclusion measures. Cost data associated with protection, mitigation, and enhancement (PM&E) measures related to positive barrier screening were identified using keyword searches of an existing environmental mitigation cost data set and manual extraction from regulatory licensing documents available in the Federal Energy Regulatory Commission (FERC) eLibrary. This approach yielded a total of 50 p.m.&E mitigation measures with estimated capital construction costs pertaining to positive barrier screens and represented <10% of the 171 total FERC project dockets available in the data set. These data were highly skewed toward conventional relicensing projects, as <7% were associated with NSD projects. Results indicate highly variable costs are associated with fish screening, with flow-normalized costs one to two orders of magnitude higher for screening with the highest exclusion capability (≤0.09 in. spacing) compared with coarser screening (1–2 in.). These data provide an initial baseline for estimating exclusion costs for hydropower development and may help developers consider options for more fish-friendly generation technologies, though gaps remain relating to a lack of data, particularly for NSD projects.

13 HYDRO ENERGY↗
DOE OSTI2020

An a priori evaluation of a principal component and artificial neural network based combustion model in diesel engine conditions

A principal component analysis (PCA) and artificial neural network (ANN) based chemistry tabulation approach is presented. ANNs are used to map the thermochemical state onto a low-dimensional manifold consisting of five control variables that have been identified using PCA. Three canonical configurations are considered to train the PCA-ANN model: a series of homogeneous reactors, a nonpremixed flamelet, and a two-dimensional lifted flame. The performance of the model in predicting the thermochemical manifold of a spatially-developing turbulent jet flame in diesel engine thermochemical conditions is a priori evaluated using direct numerical simulation (DNS) data. The PCA-ANN approach is compared with a conventional tabulation approach (tabulation using ad hoc defined control variables and linear interpolation). The PCA-ANN model provides higher accuracy and requires several orders of magnitude less memory. Here, these observations indicate that the PCA-ANN model is superior for chemistry tabulation, especially for modelling complex chemistries that present multiple combustion modes as observed in diesel combustion. The performance of the PCA-ANN model is then compared to the optimal estimator, i.e. the conditional mean from the DNS. The results indicate that the PCA-ANN model gives high prediction accuracy, comparable to the optimal estimator, especially for major species and the thermophysical properties. Higher errors are observed for the minor species and reaction rate predictions when compared to the optimal estimator. It is shown that the prediction of minor species and reaction rates can be improved by using training data that exhibits a variation of parameters as observed in the turbulent flame. The output of the ANN is analysed to assess mass conservation. It is observed that the ANN incurs a mean absolute error of 0.05% in mass conservation. Furthermore, it is demonstrated that this error can be reduced by modifying the cost function of the ANN to penalise for deviation from mass conservation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Discrete and continuous variables for measurement-device-independent quantum cryptography

In a recent Article in Nature Photonics, Pirandola et al.1 claim that the achievable secret key rates of discrete-variable (DV) measurementdevice- independent (MDI) quantum key distribution (QKD) (refs 2,3) are “typically very low, unsuitable for the demands of a metropolitan network” and introduce a continuous-variable (CV) MDI QKD protocol capable of providing key rates which, they claim, are “three orders of magnitude higher” than those of DV MDI QKD. We believe, however, that the claims regarding low key rates of DV MDI QKD made by Pirandola et al.1 are too pessimistic. Here in this paper, we show that the secret key rate of DV MDI QKD with commercially available high-efficiency single-photon detectors (SPDs) (for example, see http://www.photonspot.com/detectors and http://www.singlequantum.com) and good system alignment is typically rather high and thus highly suitable for not only long-distance communication but also metropolitan networks.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

An inductively heated hot cavity catcher laser ion source

An inductively heated hot cavity catcher has been constructed for the production of low-energy ion beams of exotic, neutron-deficient Ag isotopes. A proof-of-principle experiment has been realized by implanting primary {sup 107}Ag{sup 21+} ions from a heavy-ion cyclotron into a graphite catcher. A variable-thickness nickel foil was used to degrade the energy of the primary beam in order to mimic the implantation depth expected from the heavy-ion fusion-evaporation recoils of N = Z {sup 94}Ag. Following implantation, the silver atoms diffused out of the graphite and effused into the catcher cavity and transfer tube, where they were resonantly laser ionized using a three-step excitation and ionization scheme. Following mass separation, the ions were identified by scanning the frequency of the first resonant excitation step while recording the ion count rate. Ion release time profiles were measured for different implantation depths and cavity temperatures with the mean delay time varying from 10 to 600 ms. In addition, the diffusion coefficients for silver in graphite were measured for temperatures of 1470 K, 1630 K, and 1720 K, from which an activation energy of 3.2 ± 0.3 eV could be determined.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Impact of winds from intermediate-mass stars on molecular cloud structure and turbulence

Observations of nearby molecular clouds detect “shells,” which are likely caused by winds from young main sequence stars. However, the progenitors of these observed features are not well characterized and the mass-loss rates inferred from the gas kinematics are several orders of magnitude greater than those predicted by atomic line-driven stellar wind models. We use magnetohydrodynamic simulations to model winds launching within turbulent molecular clouds and explore the impact of wind properties on cloud morphology and turbulence. We find that winds do not produce clear features in turbulent statistics such as the Fourier spectra of density and momentum but do impact the Fourier velocity spectrum. The density and velocity distribution functions, especially as probed by CO spectral lines, strongly indicate the presence and influence of winds. We show that stellar mass-loss rates for individual stars must be m-dot {sub w}≳10{sup −7} M{sub ⊙} yr{sup −1}, similar to those estimated from observations, to reproduce shell properties. Consequently, we conclude that B and A-type main sequence stars have mass-loss rates several orders of magnitude larger that those predicted by models or that young stars are more variable than expected due to magnetic activity or accretion.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Influence of uniaxial single-ion anisotropy on the magnetic and thermal properties of Heisenberg antiferromagnets within unified molecular field theory

Here, the influence of uniaxial single-ion anisotropy –DS 2 z on the magnetic and thermal properties of Heisenberg antiferromagnets (AFMs) is investigated. The uniaxial anisotropy is treated exactly and the Heisenberg interactions are treated within unified molecular field theory (MFT), where thermodynamic variables are expressed in terms of directly measurable parameters. The properties of collinear AFMs with ordering along the z axis (D>0) in applied field H z = 0 are calculated versus D and temperature T, including the ordered moment μ, the Néel temperature T N , the magnetic entropy, internal energy, heat capacity, and the anisotropic magnetic susceptibilities χ ∥ and χ ⊥ in the paramagnetic (PM) and AFM states. The high-field average magnetization per spin μ z (H z ,D,T) is found, and the critical field H c (D,T) is derived at which the second-order AFM to PM phase transition occurs. The magnetic properties of the spin-flop (SF) phase are calculated, including the zero-field properties T N (D) and μ(D,T). The high-field μ z (H z ,D,T) is determined, together with the associated spin-flop field H SF (D,T) at which a second-order SF to PM phase transition occurs. The free energies of the AFM, SF, and PM phases are derived from which H z –T phase diagrams are constructed. For f J =–1 and –0.75, where f J = θ pJ /T NJ and θ pJ and T NJ are the Weiss temperature in the Curie-Weiss law and the Néel temperature due to exchange interactions alone, respectively, phase diagrams in the H z –T plane similar to previous results are obtained. However, for f J = 0 we find a topologically different phase diagram where a spin-flop bubble with PM and AFM boundaries occurs at finite H z and T. Also calculated are properties arising from a perpendicular magnetic field, including the perpendicular susceptibility χ ⊥ (D,T), the associated effective torque at low fields arising from the –DS 2 z term in the Hamiltonian, the high-field perpendicular magnetization μ ⊥ , and the perpendicular critical field H c⊥ at which the second-order AFM to PM phase transition occurs. In addition to the above results for D > 0, the T N (D) and ordered moment μ(T,D) for collinear AFM ordering along the x axis with D < 0 are determined. In order to compare the properties of the above spin systems with those of noninteracting systems with –DS 2 z uniaxial anisotropy with either sign of D, Supplemental Material is provided in which results for the thermal and magnetic properties of such noninteracting spin systems are given.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Secondary-Side Active Rectifier Synchronization and Control in LCC-LC Compensated Inductive Power Transfer Systems

This paper proposes a communication-less synchronization and output power control strategy for LCC-LC compensated inductive power transfer systems with a secondaryside active rectifier. By replacing the passive rectifier with an active bridge, the proposed architecture eliminates the need for a separate secondary-side DC-DC converter and enables direct regulation of battery power. The key challenge in such a system is achieving robust synchronization of the secondary active bridge with the primary inverter without access to primary-side signals. To address this issue, the secondary-side variables are analyzed and the current through the secondary series inductor is identified as a load-independent synchronization variable with a fixed phase relationship to the primary excitation. A fixed-frequency second order generalized (SOGI)-based phase locked loop (PLL) is used to estimate the switching phase and frequency, and a phase-shift-based output power controller is developed using a phasor-transformer model of the active bridges. A modified control formulation is further introduced to remove phase-dependent loop-gain variation and simplify controller design. Simulation results validate the proposed method under both fixed and varying switching-frequency conditions, demonstrating successful frequency tracking from 82 kHz to 88 kHz and accurate output power regulation over a wide operating range. The proposed method offers a compact and effective solution for high-power IPT systems by enabling secondary-side synchronization and control without wireless communication or an additional DC-DC conversion stage.

Fernandes, Arnold Anthony [ORNL] (ORCID:0009000631↗
DOE OSTI2013

Correlation properties of entangled multiphoton states and Bernstein's paradox

A normally ordered characteristic function (NOCF) of Bose operators is calculated for a number of discrete-variable entangled states (Greenberger-Horne-Zeilinger (GHZ) and Werner (W) qubit states and a cluster state). It is shown that such NOCFs contain visual information on two types of correlations: pseudoclassical and quantum correlations. The latter manifest themselves in the interference terms of the NOCFs and lead to quantum paradoxes, whereas the pseudoclassical correlations of photons and their cumulants satisfy the relations for classical random variables. Three- and four-qubit states are analyzed in detail. An implementation of an analog of Bernstein's paradox on discrete quantum variables is discussed. A measure of quantumness of an entangled state is introduced that is not related to the entropy approach. It is established that the maximum of the degree of quantumness substantiates the numerical values of the coefficients in multiqubit vector states derived from intuitive considerations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Sequential Linearization Method for Bound-Constrained Mathematical Programs with Complementarity Constraints

Here, we propose an algorithm for solving bound-constrained mathematical programs with complementarity constraints on the variables. Each iteration of the algorithm involves solving a linear program with complementarity constraints in order to obtain an estimate of the active set. The algorithm enforces descent on the objective function to promote global convergence to B-stationary points. We provide a convergence analysis and preliminary numerical results on a range of test problems. We also study the effect of fixing the active constraints in a bound-constrained quadratic program that can be solved on each iteration in order to obtain fast convergence.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Los Alamos National Laboratory Fall Avian Migration Monitoring Report 2010-2018

During the fall of 2018, biologists at Los Alamos National Laboratory completed the ninth year of monitoring fall migration passerines (songbirds). Songbirds were captured at a mist-netting station located in a wetland/riparian complex in Technical Area 36 on the north side of Pajarito Road in Los Alamos County. Captured birds were identified, measured, and banded with a United States Fish and Wildlife Service (USFWS) migratory bird band. Banding operations took place between August and October, with the completion of a total of 10 mist-netting sessions annually. This project was conducted as part of the implementation of the Biological Resources Management Plan and is in compliance with the 2013 Memorandum of Understanding between the USFWS and the United States Department of Energy/National Nuclear Security Administration and Executive Order 13186. Between 2010 and 2018 the overall number of birds and species captured was variable. We saw significant differences in the bird community composition when we compared earlier years to later years. Although environmental variables including a drought severity index, were not shown to influence the community composition, insectivorous birds and the percentage of hatch year birds were influenced by drought severity. Additionally, Audubon’s Warbler and Virginia’s Warbler numbers decreased from 2010 and showed declining trends in their abundances. The variability in bird populations is likely driven by regional climatic factors, but more data are needed for robust assessments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

GR 290 (ROMANO’S STAR). II. LIGHT HISTORY AND EVOLUTIONARY STATE

We have investigated the past light history of the luminous variable star GR 290 (M33/V532, Romano’s Star) in the M33 galaxy, and collected new spectrophotometric observations in order to analyze links between this object, the LBV category, and the Wolf–Rayet stars of the nitrogen sequence. We have built the historical light curve of GR 290 back to 1901, from old observations of the star found in several archival plates of M33. These old recordings together with published and new data on the star allowed us to infer that for at least half a century the star was in a low luminosity state, with B ≃ 18–19, most likely without brighter luminosity phases. After 1960, five large variability cycles of visual luminosity were recorded. The amplitude of the oscillations was seen increasing toward the 1992–1994 maximum, then decreasing during the last maxima. The recent light curve indicates that the photometric variations have been quite similar in all the bands and that the B – V color index has been constant within ±0.1{sup m} despite the 1.5{sup m} change of the visual luminosity. The spectrum of GR 290 at the large maximum of 1992–94 was equivalent to late-B-type, while, during 2002–2014, it varied between WN10h-11h near the visual maxima to WN8h-9h at the luminosity minima. We have detected, during this same period, a clear anti-correlation between the visual luminosity, the strength of the He ii 4686 Å emission line, the strength of the 4600–4700 Å lines’ blend, and the spectral type. From a model analysis of the spectra collected during the whole 2002–2014 period, we find that the Rosseland radius R {sub 2/3}, changed between the minimum and maximum luminosity phases by a factor of three while T {sub eff} varied between about 33,000 and 23,000 K. We confirm that the bolometric luminosity of the star has not been constant, but has increased by a factor of ∼1.5 between minimum and maximum luminosity, in phase with the apparent luminosity variations. Presently, GR 290 falls in the H–R diagram close to WN8h stars and is probably younger than them. In the light of current evolutionary models of very massive stars, we find that GR 290 has evolved from an ∼60 M {sub ☉} progenitor star and should have an age of about four million years. From its physical charcteristics, we argue that GR 290 has left the LBV stage and is presently moving from the LBV stage to a Wolf–Rayet stage of a late nitrogen spectral type.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Data management strategy to improve global use of ocean acidification data and information

Ocean acidification (OA) refers to the general decrease in pH of the global ocean as a result of absorbing anthropogenic CO 2 emitted in the atmosphere since preindustrial times (sabine et al., 2004). There is, however, considerable variability in ocean acidification, and many careful measurements need to be made and compared in order to obtain scientifically valid information for the assessment of patterns, trends, and impacts over a range of spatial and temporal scales, and to understand the process involved. A single country or institution cannot undertaken measurements of worldwide coastal and open ocean OA changes; therefore, international cooperation is needed to achieve that goal. Here, the OA data that have been, and are being, collected represent a significant public investment. To this end, it is critically important that researchers (and others) around the world are easily able to find and use reliable OA information that range from observing data (from time-series moorings, process studies, and research cruises), to biological response experiments (e.g., mesocosm), data products, and model output.

54 ENVIRONMENTAL SCIENCES↗