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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 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

In-Package Common-Mode Filter for GaN Power Module with Improved Radiated EMI Performance

This paper discusses the impact of parasitic inductances on the electromagnetic interference (EMI) performance at radiated frequency and provides a new concept for high-frequency wide bandgap (WBG) power module package design with integrated π-type common mode filter (π-CMF). The connection parasitic-inductances of a π-type CMF model are analyzed, and the parasitic inductances from the CMF to the CM noise source and to the heatsink are minimized to improve the CMF's EMI performance in the radiated frequency range. Therefore, placing the π-CMF closer to the power module (i.e. in-package CMF) provides a larger noise attenuation compared to placing it outside the module (i.e. external CMF). To verify the theoretical analysis, a half-bridge GaN power module with an in-package π-CMF is designed, and experiments are conducted by comparing the attenuated noise spectrums of a 70-V/1.75-A hard-switching buck converter built by the designed module with an external CMF and the power-module integrated CMF. According to the experiment results, up to 10 dBμV more attenuation is achieved by the in-package CMF than the external CMF, validating the analytical conclusion.

Xue, Lincoln↗
DOE OSTI2021

Comparative Virulence and Genomic Analysis of Streptococcus suis Isolates

Streptococcus suis is a zoonotic bacterial swine pathogen causing substantial economic and health burdens to the pork industry. Mechanisms used by S. suis to colonize and cause disease remain unknown and vaccines and/or intervention strategies currently do not exist. Studies addressing virulence mechanisms used by S. suis have been complicated because different isolates can cause a spectrum of disease outcomes ranging from lethal systemic disease to asymptomatic carriage. The objectives of this study were to evaluate the virulence capacity of nine United States S. suis isolates following intranasal challenge in swine and then perform comparative genomic analyses to identify genomic attributes associated with swine-virulent phenotypes. No correlation was found between the capacity to cause disease in swine and the functional characteristics of genome size, serotype, sequence type (ST), or in vitro virulence-associated phenotypes. A search for orthologs found in highly virulent isolates and not found in non-virulent isolates revealed numerous predicted protein coding sequences specific to each category. While none of these predicted protein coding sequences have been previously characterized as potential virulence factors, this analysis does provide a reliable one-to-one assignment of specific genes of interest that could prove useful in future allelic replacement and/or functional genomic studies. Collectively, this report provides a framework for future allelic replacement and/or functional genomic studies investigating genetic characteristics underlying the spectrum of disease outcomes caused by S. suis isolates.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

COHERENT EVENTS AND SPECTRAL SHAPE AT ION KINETIC SCALES IN THE FAST SOLAR WIND TURBULENCE

In this paper we investigate spectral and phase coherence properties of magnetic fluctuations in the vicinity of the spectral transition from large, magnetohydrodynamic to sub-ion scales using in situ measurements of the Wind spacecraft in a fast stream. For the time interval investigated by Leamon et al. (1998) the phase coherence analysis shows the presence of sporadic quasi-parallel Alfvén ion cyclotron (AIC) waves as well as coherent structures in the form of large-amplitude, quasi-perpendicular Alfvén vortex-like structures and current sheets. These waves and structures importantly contribute to the observed power spectrum of magnetic fluctuations around ion scales; AIC waves contribute to the spectrum in a narrow frequency range whereas the coherent structures contribute to the spectrum over a wide frequency band from the inertial range to the sub-ion frequency range. We conclude that a particular combination of waves and coherent structures determines the spectral shape of the magnetic field spectrum around ion scales. This phenomenon provides a possible explanation for a high variability of the magnetic power spectra around ion scales observed in the solar wind.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Total absorption spectroscopy of fission fragments relevant for reactor antineutrino spectra

Here, the accurate determination of reactor antineutrino spectra remains a very active research topic for which new methods of study have emerged in recent years. Indeed, following the long-recognized reactor anomaly (measured antineutrino deficit in short baseline reactor experiments when compared with spectral predictions), the three international reactor neutrino experiments Double Chooz, Daya Bay and Reno have recently demonstrated the existence of spectral distortions in their measurements with respect to the same predictions. These spectral predictions were obtained through the conversion of integral beta-energy spectra obtained at the ILL research reactor. Several studies have shown that the underlying nuclear physics required for the conversion of these spectra into antineutrino spectra is not totally understood. An alternative to such converted spectra is a complementary approach that consists of determining the antineutrino spectrum by means of the measurement and processing of nuclear data. The beta properties of some key fission products suffer from the pandemonium effect which can be circumvented by the use of the Total Absorption Gamma-ray Spectroscopy technique (TAGS). The two main contributors to the Pressurized Water Reactor antineutrino spectrum in the region where the spectral distortion has been observed are 92 Rb and 142 Cs, which have been measured at the radioactive beam facility of the University of Jyvaskyla in two TAGS experiments. We present the results of the analysis of the TAGS measurements of the β-decay properties of 92 Rb along with preliminary results on 142 Cs and report on the measurements already performed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Mass Spectrum of Mesons and Their Leptonic Decay Widths within the Relativistic Quasipotential Approach

New relativistic semiclassical conditions and leptonic decay widths are obtained within quantum chromodynamics for nonsingular confining quasipotentials and funnel-type potentials (instantoninteraction approximation). The respective analysis is performed within a fully covariant quasipotential approach in quantum field theory. This approach is formulated in the relativistic configuration representation for the case of interaction between two relativistic spinless particles of arbitrary mass.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Systematic Uncertainties and Cross-Checks for the NOvA Joint $\nu_\mu$+$\nu_e$ Analysis

The physics goals of NOvA are the constraints of neutrino oscillation parameters such as the octant of $\theta_{23}$, $\delta_{\rm{CP}}$, and the neutrino mass hierarchy via a joint fit to $\nu_{\mu}$ and $\nu_{e}$ oscillation spectrum. We do this by propagating $\nu_{\mu}$ from the world's most intense neutrino beam at Fermilab, over a baseline of 810 km to northern Minnesota, USA, and measure the $\nu_{\mu}$ to $\nu_{e}$ oscillation probability. NOvA announced its latest oscillation results, based on 8.85$\times10^{20}$ (6.9$\times10^{20}$) protons on target neutrino (antineutrino) data. Preliminary results for the allowed values of oscillation parameters are: $\Delta m^2_{32}=2.51^{+0.12}_{-0.08}\times 10^{-3} \mathrm{eV}^2$, $\mathrm{sin}^2\theta_{23} = 0.58 \pm 0.03$ (upper octant), and $\delta_{\rm{CP}}=0.17\pi$ with preference to the normal hierarchy. Reliable constraints on these oscillation parameters require a rigorous treatment of systematic uncertainties and thorough cross-checks. In this paper, we present an overview of the treatment of systematic uncertainties as well as cross-checks using muon removed simulations and cosmic muon bremsstrahlung showers.

Gandrajula, Reddy Pratap↗
DOE OSTI2015

CFD Modeling and Image Analysis of Exhaled Aerosols due to a Growing Bronchial Tumor: towards Non-Invasive Diagnosis and Treatment of Respiratory Obstructive Diseases

Diagnosis and prognosis of tumorigenesis are generally performed with CT, PET, or biopsy. Such methods are accurate, but have the limitations of high cost and posing additional health risks to patients. In this study, we introduce an alternative computer aided diagnostic tool that can locate malignant sites caused by tumorigenesis in a non-invasive and low-cost way. Our hypothesis is that exhaled aerosol distribution is unique to lung structure and is sensitive to airway structure vari-ations. With appropriate approaches, it is possible to locate the disease site, determine the disease severity, and subsequently formulate a targeted drug delivery plan to treat the disease. This study numerically evaluated the feasibility of the proposed breath test in an image-based lung model with varying pathological stages of a bronchial squamous tumor. Large eddy simulations and a Lagran-gian tracking approach were used to model respiratory airflows and aerosol dynamics. Respira-tions of tracer aerosols of 1 µm at a flow rate of 20 L/min were simulated, with the distributions of exhaled aerosols recorded on a filter at the mouth exit. Aerosol patterns were quantified with multiple analytical techniques such as concentration disparity, spatial scanning and fractal analysis. We demonstrated that a growing bronchial tumor induced notable variations in both the airflow and exhaled aerosol distribution. These variations became more apparent with increasing tumor severity. The exhaled aerosols exhibited distinctive pattern parameters such as spatial probability, fractal dimension, and multifractal spectrum. Results of this study show that morphometric measures of the exhaled aerosol pattern can be used to detect and monitor the pathological states of respiratory diseases in the upper airway. The proposed breath test also has the potential to locate the site of the disease, which is critical in developing a personalized, site-specific drug de-livery protocol.

Aerosol breath test↗
DOE OSTI2016

The NANOGrav nine-year data set: Limits on the isotropic stochastic gravitational wave background

We compute upper limits on the nanohertz-frequency isotropic stochastic gravitational wave background (GWB) using the 9 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration. Well-tested Bayesian techniques are used to set upper limits on the dimensionless strain amplitude (at a frequency of 1 yr{sup −1}) for a GWB from supermassive black hole binaries of A{sub gw}<1.5×10{sup −15}. We also parameterize the GWB spectrum with a broken power-law model by placing priors on the strain amplitude derived from simulations of Sesana and McWilliams et al. Using Bayesian model selection we find that the data favor a broken power law to a pure power law with odds ratios of 2.2 and 22 to one for the Sesana and McWilliams prior models, respectively. Using the broken power-law analysis we construct posterior distributions on environmental factors that drive the binary to the GW-driven regime including the stellar mass density for stellar-scattering, mass accretion rate for circumbinary disk interaction, and orbital eccentricity for eccentric binaries, marking the first time that the shape of the GWB spectrum has been used to make astrophysical inferences. Returning to a power-law model, we place stringent limits on the energy density of relic GWs, Ω{sub gw}(f)h{sup 2}<4.2 × 10{sup −10}. Our limit on the cosmic string GWB, Ω{sub gw}(f)h{sup 2}<2.2 × 10{sup −10}, translates to a conservative limit on the cosmic string tension with Gμ<3.3×10{sup −8}, a factor of four better than the joint Planck and high-l cosmic microwave background data from other experiments.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Reaction intermediates during operando electrocatalysis identified from full solvent quantum mechanics molecular dynamics

Electrocatalysis provides a powerful means to selectively transform molecules, but a serious impediment in making rapid progress is the lack of a molecular-based understanding of the reactive mechanisms or intermediates at the electrode–electrolyte interface (EEI). Recent experimental techniques have been developed for operando identification of reaction intermediates using surface infrared (IR) and Raman spectroscopy. However, large noises in the experimental spectrum pose great challenges in resolving the atomistic structures of reactive intermediates. To provide an interpretation of these experimental studies and target for additional studies, we report the results from quantum mechanics molecular dynamics (QM-MD) with explicit consideration of solvent, electrode–electrolyte interface, and applied potential at 298 K, which conceptually resemble the operando experimental condition, leading to a prototype of operando QM-MD (o-QM-MD). With o-QM-MD, we characterize 22 possible reactive intermediates in carbon dioxide reduction reactions ( C O 2 RRs). Furthermore, we report the vibrational density of states (v-DoSs) of these intermediates from two-phase thermodynamic (2PT) analysis. Accordingly, we identify important intermediates such as chemisorbed C O 2 ( b - C O 2 ), *HOC-COH, *C-CH, and *C-COH in our o-QM-MD likely to explain the experimental spectrum. Indeed, we assign the experimental peak at 1,191 cm −1 to the mode of C-O stretch in *HOC-COH predicted at 1,189 cm −1 and the experimental peak at 1,584 cm −1 to the mode of C-C stretch in *C-COD predicted at 1,581 cm −1 . Interestingly, we find that surface ketene (*C=C=O), arising from *HOC-COH dehydration, also shows signals at around 1,584 cm −1 , which indicates a nonelectrochemical pathway of hydrocarbon formation at low overpotential and high pH conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Toward wide-spectrum antivirals against coronaviruses: Molecular characterization of SARS-CoV-2 NSP13 helicase inhibitors

To date, effective therapeutic treatments that confer strong attenuation against coronaviruses (CoVs) remain elusive. Among potential drug targets, the helicase of CoVs is attractive due to its sequence conservation and indispensability. We rely on atomistic molecular dynamics simulations to explore the structural coordination and dynamics associated with the SARS-CoV-2 Nsp13 apo enzyme, as well as their complexes with natural ligands. A complex communication network is revealed among the five domains of Nsp13, which is differentially activated because of the presence of the ligands, as shown by shear strain analysis, principal components analysis, dynamical cross-correlation matrix analysis, and water transport analysis. The binding free energy and the corresponding mechanism of action are presented for three small molecules that were shown to be efficient inhibitors of the previous SARS-CoV Nsp13 enzyme. Together, our findings provide critical fresh insights for rational design of broad-spectrum antivirals against CoVs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

SCALE/AMPX multigroup libraries for sodium-cooled fast reactor systems

New multigroup cross section libraries and associated covariance files that are optimized for the analysis of sodium-cooled fast reactors were generated with the AMPX tools distributed with the SCALE code system. These new libraries account for the fast neutron flux spectrum with sufficient resolution of resonances in the higher energy range to reproduce continuous-energy reference results and to provide the basis for sensitivity and uncertainty analyses of fast spectrum systems with the SCALE code system. The performance of the new libraries was investigated in terms of the eigenvalue, the neutron flux and reaction rates in criticality calculations, and the generation of group constants. A library using 302 energy groups and a fast neutron flux spectrum as the weighting function led to very good agreement with reference continuous-energy results. As a result, the performance of the new library was demonstrated in calculations of experiments from the International Criticality Safety Benchmark Evaluation Project handbook.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

Bell states and entanglement dynamics on two coupled quantum molecules

This work provides a complete description of entanglement properties between electrons inside coupled quantum molecules, nanoestructures which consist of two quantum dots. Each electron can tunnel between the two quantum dots inside the molecule, being also coupled by Coulomb interaction. First, it is shown that Bell states act as a natural basis for the description of this physical system, defining the characteristics of the energy spectrum and the eigenstates. Then, the entanglement properties of the eigenstates are discussed, shedding light on the roles of each physical parameters on experimental setup. Finally, a detailed analysis of the dynamics shows the path to generate states with a high degree of entanglement, as well as physical conditions associated with coherent oscillations between separable and Bell states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

FIB-ToF-SIMS characterization of irradiated U-10Zr

Post-irradiation examination (PIE) is critical for the performance assessment and qualification of nuclear fuels. Secondary ion mass spectrometry (SIMS) is a powerful materials characterization technique that allows for elemental and isotopic mapping with a depth resolution greater than EDS and EPMA. However, it has not yet been applied to PIE of metallic nuclear fuel. Here, in this work, we characterize an fast neutron spectrum irradiated U-10Zr fuel sample using a time-of-flight SIMS (ToF-SIMS) system connected to a FIB/SEM system, which allows for flexible sample analysis compared to a dedicated ToF-SIMS instrument. Analysis of the resulting hyperspectral micrograph data was aided by the development of an unsupervised machine learning (ML) algorithm that iterates on existing methods to segment the 3D micrographic datasets based on the similarity of mass spectra. The results showed that the FIB-ToF-SIMS instrument was potentially capable of spatially resolving closed fission gas bubbles in 3D by continued ion sputtering of the analyzed volume. Additionally, the ML algorithm proved useful in revealing the chemical segregation of light fission products (those with an atomic mass between approximately 85–105 amu, such as ruthenium and rhodium) plus matrix zirconium, heavy fission products (those with an atomic mass between approximately 135–150 amu, such as the lanthanides) and uranium. Future studies are planned to conduct FIB-ToF-SIMS analysis on more irradiated U-Zr samples to study the constituent redistribution.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

A novel blue-greenish emitting phosphor Ba{sub 3}LaK(PO{sub 4}){sub 3}F:Tb{sup 3+} with high thermal stability

Highlights: • The Ba{sub 3}LaK(PO{sub 4}){sub 3}F:Tb{sup 3+} phosphors exhibit a broad excitation band. • The Ba{sub 3}LaK(PO{sub 4}){sub 3}F:Tb{sup 3+} emission color adjust from blue to green. • The Ba{sub 3}LaK(PO{sub 4}){sub 3}F:Tb{sup 3+} show superior thermal stability. - Abstract: Ba{sub 3}La{sub 1−m}K(PO{sub 4}){sub 3}F:mTb{sup 3+}(m = 0.01–0.50) phosphors have been prepared by a traditional high temperature solid-state reaction. XRD analysis verified the apatite-type phase structure of the as-prepared samples, and the morphology has been checked by the Scanning electron microscope (SEM). The emission spectrum of Ba{sub 3}LaK(PO{sub 4}){sub 3}F:Tb{sup 3+} phosphor consists of two regions, blue emission band from 380 to 470 nm and green emission band from 470 to 650 nm. With increasing Tb{sup 3+} ions doped concentration (m), the color hue of Ba{sub 3}La{sub 1−m}K(PO{sub 4}){sub 3}F:mTb{sup 3+}adjusts from blue to green. On the basis of concentration quenching method, the critical distance between Tb{sup 3+} ions is calculated to be 7.98 Å, suggesting that multipolar interaction predominate in quenching process. In addition, the temperature-dependence PL spectra of Ba{sub 3}LaK(PO{sub 4}){sub 3}F:0.01Tb{sup 3+} and Ba{sub 3}LaK(PO{sub 4}){sub 3}F:0.40Tb{sup 3+} phosphor are given,which exhibit superior thermal stability.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Radio frequency abnormal dielectric response of manganese chromite (MnCr{sub 2}O{sub 4}) nanoparticles synthesized by coprecipitation method

Highlights: • Uniform MnCr{sub 2}O{sub 4} nanoparticles synthesized by surfactant-free coprecipitation route. • XRD analysis confirmed the single spinel phase formation in the material. • Dielectric loss was found abnormal over certain lower frequencies. • AC conductivity proved the involvement of small polarons in conduction process. - Abstract: Radio frequency dielectric behavior of nanocrystalline MnCr{sub 2}O{sub 4} synthesized via surfactant-free controlled coprecipitation route has been studied. Keeping in view the necessity of particle size uniformity and phase purity for genuine performance, experimental conditions were optimized accordingly. The scanning electron micrographs of the synthesized product revealed the formation of monodispersed particle system. X-ray diffraction analysis confirmed monophasic spinel structure formation with 65 nm crystallite size. Two characteristic peaks observed between 700 cm{sup −1} and 400 cm{sup −1} in the FTIR spectrum also supported the spinel phase purity of compound. The dielectric constant was found normal, but loss tangent of the sample showed abnormal behavior with frequency. The observed dielectric behavior of the synthesized product has been explained on the basis of space-charge polarization according to Maxwell–Wagner’s model and mutual contribution of n-type &p-type charge carriers (Rezlescu model). The ac conductivity linearly increased with frequency highlighting the existence of polaron hopping.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A two-dimensional numerical study of ion-acoustic turbulence

We investigate the linear and nonlinear evolution of the current-driven ion-acoustic instability in a collisionless plasma via two-dimensional (2-D) Vlasov–Poisson numerical simulations. We initialise the system in a stable state and gradually drive it towards instability with an imposed, weak external electric field, thus avoiding physically unrealisable super-critical initial conditions. A comprehensive analysis of the nonlinear evolution of ion-acoustic turbulence (IAT) is presented, including the detailed characteristics of the evolution of the particles’ distribution functions, (2-D) wave spectrum and the resulting anomalous resistivity. Our findings reveal the dominance of 2-D quasi-linear effects around saturation, with nonlinear effects, such as particle trapping and nonlinear frequency shifts, becoming pronounced during the later stages of the system's nonlinear evolution. Remarkably, the Kadomtsev–Petviashvili (KP) spectrum is observed immediately after the saturation of the instability. Another crucial and noteworthy result is that no steady saturated nonlinear state is ever reached: strong ion heating suppresses the instability, which implies that the anomalous resistivity associated with IAT is transient and short-lived, challenging earlier theoretical results. Towards the conclusion of the simulation, electron-acoustic waves are triggered by the formation of a double layer and strong modifications to the particle distribution induced by IAT.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Quantification of Deformation-Induced Concentration Fluctuations in Polymeric Liquids by Small-Angle Neutron Scattering

This study demonstrates how the large concentration fluctuations of polymeric liquids under deformation and flow can be quantitatively studied by applying the spherical harmonic expansion technique to small-angle neutron scattering. Using a series of binary polymer blends, it is shown that the emergence of the so-called butterfly patterns is caused by the change of sign in the leading anisotropic component of the small-angle spectrum, when the scattering is dominated by intermolecular correlation associated with flow-induced demixing. The increasing spatial fluctuations of concentration are evidenced by the enhancement of the isotropic component of the scattering spectrum in the zero-angle limit and peak shift of the leading anisotropic coefficients toward low Q. Additionally, the spherical harmonic expansion framework permits real-space analysis of anisotropic scattering length density correlation in a convenient form. The methodology described in this work provides a concrete venue for quantitative studies of phase behavior of fluids under deformation and flow via small-angle scattering techniques, where mainly qualitative approaches were previously employed.

Chemical structure↗
DOE OSTI2021

Development of a Fast-Spectrum Self-Powered Neutron Detector for Molten Salt Experiments in the Versatile Test Reactor

The self-powered neutron detector (SPND) is a widely used flux monitor in thermal nuclear reactors. Although this is a mature technology, the current state of the art is tuned for a thermal neutron spectrum, so many of the devices currently in use lack sensitivity to fast neutrons. Because current in SPNDs is produced through nuclear reactions with the neutron flux inside a reactor, sensitivity in SPNDs is determined by the neutron cross section of the neutron-sensitive portion of the detector, termed the emitter. This neutron cross section drops by orders of magnitude between thermal and fast neutron energies for many emitters in currently used SPNDs, with a corresponding drop in current from the detector. This paper discusses efforts to develop a fast-spectrum self-powered neutron detector (FS-SPND) that is sensitive to neutrons with energies ranging from 0.025 eV up to 1 MeV. An in-depth analysis of Evaluated Nuclear Data File (ENDF)/B-VII.1 neutron-capture cross sections was performed, and four new materials were identified that are suitable emitter candidates for use in measuring fast neutrons. All four materials are stable mid-shell nuclei in the region between doubly magic 132Sn and 208Pb. Each candidate was simulated with the Geant4 Monte Carlo simulation toolkit to optimize overall detector efficiency.

Goetz, Callie↗