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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Fuel Cell Buses in U.S. Transit Fleets: Current Status 2016

This report, published annually, summarizes the progress of fuel cell electric bus development in the United States and discusses the achievements and challenges of introducing fuel cell propulsion in transit. The report provides a summary of results from evaluations performed by the National Renewable Energy Laboratory. Funding for this effort is provided by the U.S. Department of Energy's Fuel Cell Technologies Office within the Office of Energy Efficiency and Renewable Energy and by the U.S. Department of Transportation's Federal Transit Administration. The 2016 summary results primarily focus on the most recent year for each demonstration, from August 2015 through July 2016. The results for these buses account for more than 550,000 miles traveled and 59,500 hours of fuel cell power system operation. The primary results presented in the report are from three demonstrations of two different fuel-cell-dominant bus designs: Zero Emission Bay Area Demonstration Group led by Alameda-Contra Costa Transit District (AC Transit) in California; American Fuel Cell Bus Project at SunLine Transit Agency in California; and American Fuel Cell Bus Project at the University of California at Irvine.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2017

Fuel Cell Buses in U.S. Transit Fleets: Current Status 2017

This report, published annually, summarizes the progress of fuel cell electric bus (FCEB) development in the United States and discusses the achievements and challenges of introducing fuel cell propulsion in transit. The report provides a summary of results from evaluations performed by the National Renewable Energy Laboratory. This annual status report combines results from all FCEB demonstrations, tracks the progress of the FCEB industry toward meeting technical targets, documents the lessons learned, and discusses the path forward for commercial viability of fuel cell technology for transit buses. These data and analyses help provide needed information to guide future early-stage research and development. The 2017 summary results primarily focus on the most recent year for each demonstration, from August 2016 through July 2017. The primary results presented in the report are from five demonstrations of two different fuel-cell-dominant bus designs: Zero Emission Bay Area Demonstration Group led by Alameda-Contra Costa Transit District (AC Transit) in California; American Fuel Cell Bus (AFCB) Project at SunLine Transit Agency in California; AFCB Project at the University of California at Irvine; AFCB Project at Orange County Transportation Authority; and AFCB Project at Massachusetts Bay Transportation Authority.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2022

Effects of plasma on physical properties of water: nanocrystalline-to-amorphous phase transition and improving produce washing

Recently is was discovered in various applications that many physical and chemical properties of water change their temperature dependence between about 35 and 60 degrees Celsius. In particular, heat conductance, light absorption, and surface tension all change their temperature dependence. These drastic changes were associated with water gradually changing its mesoscopic structure: while at the higher temperatures water is a uniform media (amorphous state), at the temperatures below transition it consists of many nano-to-micro-scale clusters (crystalline state). This transition is similar to the second order phase transition. In the present paper we show that treating water with non-thermal plasma (adding plasma-created active compounds) can lower the temperature of the transition and thus cause a significant change in such physical quantities as surface tension, viscosity, freezing rate, and wettability and washability. We present analytical estimates of the transition temperature shift based on the Debye-Hückel theory. We discuss the produce-washing experiments that illustrate the predicted effects.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Hydrogen Fuel Cell Electric Bus (FCEB) Evaluations in US Public Transit Service

The National Renewable Energy Laboratory (NREL) is a Department of Energy (DOE) national laboratory focused on renewable energy and energy efficiency. NREL has evaluated alternative fuel and advanced propulsion transit buses for DOE and the U.S. Department of Transportation's Federal Transit Administration (FTA). These evaluations are focused on determining the status of fuel cell systems and the corresponding infrastructure in transit applications to help DOE and FTA assess the progress toward technology readiness. For the last 19 years NREL has evaluated FCEBs in service around the United States and in Canada. The results of these evaluations have been published in numerous reports that compare FCEB performance to conventional technology as well as document the implementation experience and lessons learned by the transit agencies and their demonstration teams. Currently, 70 fuel cell buses are in active service in the US and 66 FCEBs are in development. NREL is evaluating a subset of the active FCEBs that includes three transit agencies demonstrating 25 fuel cell electric buses in California. One bus has exceeded 35,000 hours in service and 12 have exceeded 25,000 hours. Fuel economy for the current generation of FCEBs has improved 35% over the previous generation and is double that of conventional buses. Maintenance cost for FCEBs is equivalent to diesel and BEBs. The most up-to-date performance results will be presented, including fuel economy, availability, reliability, and operational costs.

bus↗
DOE OSTI2019

Nonequilibrium vibrational population and donor-acceptor vibrations affecting rates of radiationless transitions

Here, an analytical theory is developed for radiationless transitions in molecules characterized by nonequilibrium populations of their vibrational modes. Several changes to the standard transition-state framework follow from nonequilibrium conditions: (i) non-Arrhenius kinetics, (ii) the violation of the fluctuation-dissipation theorem (FDT), and (iii) the breakdown of the detailed balance. The violation of the FDT is reflected in the breakdown of relations between the first (Stokes shift) and second (inhomogeneous band-width) spectral moments, and of similar relations between reorganization parameters for radiationless transitions. The detailed balance between the forward and backward rates is not maintained, requiring a lower effective free energy of the reaction relative to the thermodynamic limit. Lastly, the model suggests that strong control of radiationless transitions can be achieved if a nonequilibrium population of vibrations modulating the donor-acceptor distance is produced.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Investigation of experimental signatures of spin glass transition temperature

We present a series of temperature and field-dependent magnetization studies of large single-crystal spin glass samples, focusing on both field-cooled (FC) and zero-field-cooled (ZFC) magnetization studies, as well as ac susceptibility measurements. Using the above experimental techniques we aim to understand the nature of spin glass transition in presence of a field, a key factor in understanding the properties of these systems. Building on previous studies that have explored magnetic signatures indicative of spin glass transitions, our research employs a systematic approach to refine the identification of this transition temperature. Through static and dynamic measurements, we aim to shed light on the open issues regarding the key markers of spin glass transitions, enhancing our understanding of these complex systems.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Hydrostatic and Uniaxial Pressure Tuning of Iron-Based Superconductors: Insights into Superconductivity, Magnetism, Nematicity, and Collapsed Tetragonal Transitions

Iron-based superconductors are well-known for their intriguing phase diagrams, which manifest a complex interplay of electronic, magnetic and structural degrees of freedom. Among the phase transitions observed are superconducting, magnetic, and several types of structural transitions, including a tetragonal-to-orthorhombic and a collapsed-tetragonal transition. In particular, the widely-observed tetragonal-to-orthorhombic transition is believed to be a result of an electronic order that is coupled to the crystalline lattice and is, thus, referred to asnematic transition. Nematicity is therefore a prominent feature of these materials, which signals the importance of the coupling of electronic and lattice properties. Correspondingly, these systems are particularly susceptible to tuning via pressure (hydrostatic, uniaxial, or some combination). We review efforts to probe the phase diagrams of pressure-tuned iron-based superconductors, with a strong focus on our own recent insights into the phase diagrams of several members of this mate-rial class under hydrostatic pressure. These studies on FeSe, Ba(Fe 1-x Co x ) 2 As 2 , Ca(Fe 1-x Co x ) 2 As 2 and CaK(Fe 1-x Ni x ) 4 As 4 were, to a significant extent, made possible by advances of what measurements can be adapted to the use under differing pressure environments. We point out the potential impact of these tools for the study of the wider class of strongly correlated electron systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Speciation of Transition Metal Dissolution in Electrolyte from Common Cathode Materials

Abstract Significant capacity loss has been observed across extended cycling of lithium‐ion batteries cycled to high potential. One of the sources of capacity fade is transition metal dissolution from the cathode active material, ion migration through the electrolyte, and deposition on the solid‐electrolyte interphase on the anode. While much research has been conducted on the oxidation state of the transition metal in the cathode active material or deposited on the anode, there have been limited investigations of the oxidation state of the transition metal ions dissolved in the electrolyte. In this work, X‐ray absorption spectroscopy has been performed on electrolytes extracted from cells built with four different cathode active materials (LiMn 2 O 4 (LMO), LiNi 0.5 Mn 1.5 O 4 (LNMO), LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811), and (x Li 2 MnO 3 *(1‐x) LiNi a Mn b Co c O 2 , with a+b+ c =1) (LMRNMC)) that were cycled at either high or standard potentials to determine the oxidation state of Mn and Ni in solution. Inductively coupled plasma‐mass spectrometry has been performed on the anodes from these cells to determine the concentration of deposited transition metal ions. While transition metal ions were found dissolved in all electrolytes, the oxidation state(s) of Mn and Ni were determined to be dependent on the cathode material and independent of cycling potential.

Rynearson, Leah↗
DOE OSTI2025

Millisecond Phase Transition Kinetics of Lyotropic Liquid Crystalline Nanoparticles Observed by Time‐Resolved Small Angle X‐ray Solution Scattering

This study investigates the dynamic behavior of lyotropic liquid crystal nanoparticles (LCNPs), which are widely recognized for their applications in drug delivery. By employing nanosecond near‐infrared laser pulse‐induced temperature jump (T‐jump) and time‐resolved X‐ray solution scattering, the structural dynamics of phase transitions in phytantriol‐based cubosomes and hexosomes are revealed. Both cubosome and hexosome LCNPs undergo phase transitions into noncrystalline phases at high temperatures. Their phase transition kinetics, occurring within milliseconds (ms) and involving one intermediate structure, are captured. Additionally, the reverse self‐assembly processes of LCNPs were observed, occurring on the timescale of a few hundred ms. To our knowledge, this is the first observation of LCNP T‐jump induced phase transitions on the ms timescale and their reverse self‐assembly. These findings provide valuable insights into the LCNP phase transition processes, with potential implications for drug delivery applications.

Chemistry↗
DOE OSTI2017

Non-resonant collider signatures of a singlet-driven electroweak phase transition

We analyze the collider signatures of the real singlet extension of the Standard Model in regions consistent with a strong first-order electroweak phase transition and a singlet-like scalar heavier than the Standard Model-like Higgs. A definitive correlation exists between the strength of the phase transition and the trilinear coupling of the Higgs to two singlet-like scalars, and hence between the phase transition and non-resonant scalar pair production involving the singlet at colliders. We study the prospects for observing these processes at the LHC and a future 100 TeV pp collider, focusing particularly on double singlet production. We also discuss correlations between the strength of the electroweak phase transition and other observables at hadron and future lepton colliders. Searches for non-resonant singlet-like scalar pair production at 100 TeV would provide a sensitive probe of the electroweak phase transition in this model, complementing resonant di-Higgs searches and precision measurements. Our study illustrates a strategy for systematically exploring the phenomenologically viable parameter space of this model, which we hope will be useful for future work.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Influence of the electromagnetic field on the transition of a two-level system in a Gaussian confinement potential with LO phonon and of thickness effects

In this paper, the asymmetric Gaussian confinement potential and the parabolic confinement potential (PCP) are selected to describe the along growth direction and perpendicular to growth direction confinement potential (PC) of electron in a disk quantum dot, respectively. The phonons mean number and the energies of the ground and first excited states of the electron in a quantum dot with the polarization and the thickness effect are investigated by using Lee–Low–Pines unitary transformation and the Pekar-type variational method, and on the basis of the Fermi Golden Rule, the transition of the electron caused by the electromagnetic field is discussed. Our numerical results have displayed that the electric field and the magnetic field are an indispensable condition for the induced polaron transition. The weak electric field has a strong regulatory function on the transition. The influence of the well width L and the well depth V{sub 0} of the AGFCP on the mean number of phonons, energies and transition are important and interesting; it is also found in this work that the AGFCP is better than PCP in explaining the quantum size effect of QDs and modulating electron transition properties, respectively. This quantum system can be employed as a two-level quantum qubit.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Relativistic distorted-wave collision strengths for Δn = 0 transitions in the 67 Li-like, F-like and Na-like ions with 26 ≤ Z ≤ 92

We calculated relativistic distorted-wave collision strength for all possible Δn=0 transitions, where n denotes the valence shell of the ground level, in the 67 Li-like, F-like and Na-like ions with Z in the range 26 ≤ Z ≤92. This choice produces 3 transitions with n=2 in the Li-like and F-like ions, and 10 transitions with n=3 in the Na-like ions. Moreover, for the Li-like and F-like ions, the calculations were made for the six final, or scattered, electron energies E'=0.008,0.04,0.10,0.21,0.41, and 0.75, where E' is in units of Z$2\atop{eff}$ Ry with Z eff = Z- 1.66 for Li-like ions and Z eff = Z- 6.667 for F-like ions. For the Na-like ions, the calculations were made for the six final electron energies E'=0.0025,0.015,0.04,0.10,0.21, and 0.40, with Z eff = Z- 8.34. In the present calculations, an improved “top-up” method, which employs relativistic plane waves, was used to obtain the high partial-wave contribution for each transition, in contrast to the partial-relativistic Coulomb–Bethe approximation used in previous works by Zhang, Sampson and Fontes [H.L. Zhang, D.H. Sampson, C.J. Fontes, At. Data Nucl. Data Tables 44 (1990) 31; H.L. Zhang, D.H. Sampson, C.J. Fontes, At. Data Nucl. Data Tables 48 (1991) 25; D.H. Sampson, H.L. Zhang, C.J. Fontes, At. Data Nucl. Data Tables 44 (1990) 209]. In those previous works, collision strengths were also provided for Li-, F- and Na-like ions, but for a more comprehensive set of transitions. Finally, the collision strengths covered in the present work should be more accurate than the corresponding data given in those previous works and are presented here to replace those earlier results.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Ovate family protein1 interaction with BLH3 regulates transition timing from vegetative to reproductive phase in Arabidopsis

We study the Three-Amino-acid-Loop-Extension(TALE) homeodomain transcription factor BLH3 that regulates timing of transition from vegetative to reproductive phase. Previous preliminary results obtained using large-scale yeast two-hybrids indicate that BLH3 protein possibly interact with Ovate Family Proteins(OFPs) transcription co-regulators. Nevertheless, it is uncertain whether OFP1–BLH3 complex is involved in regulation of timing of transition from vegetative to reproductive phase in Arabidopsis. The interaction between BLH3 and OFP1 was re-tested and verified by a yeast two-hybrid system. We found that the BLH3–OFP1 interaction was mainly mediated through the BLH3 homeodomain. Meanwhile, this interaction was further confirmed by bimolecular fluorescence complementation (BiFC) in vivo . In addition, by establishing protoplast transient expression, we discovered that BLH3 acts as a transcriptional activator, whereas OFP1 functioned as a repressor. The interactions between OFP1 and BLH3 can reduce BLH3 transcriptional activity. The ofp1 mutant lines and blh3 mutant lines, OFP1 overexpress lines and BLH3 overexpress lines can both influence timing of transition from vegetative to reproductive phase. Furthermore, 35s:OFP1/blh3 plants exhibited flowering and leaf quantity similar to that of the wild-type controls. 35s:BLH3/ofp1 plants flowered earlier and had less leaves than wild-type controls, indicating that OFP1 protein might depend partially on BLH3 in its function to regulate the timing of transition from vegetative to reproductive phase. In conclusion, these results support our assumption that, by interacting with OFP1, BLH3 forms a functional protein complex that controls timing of progression from vegetative to reproductive phase, and OFP1 might negatively regulate BLH3 or the BLH-KNOX complex, an important interaction for sustaining the normal transition from vegetative to reproductive phase.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

SPATULA regulates floral transition and photomorphogenesis in a PHYTOCHROME B-dependent manner in Arabidopsis

Highlights: • SPT promotes floral transition in Arabidopsis. • SPT promotes flowering via FLC, SVP, FT and SOC1. • SPT regulates photomorphogenesis in a PHYB-dependent manner. Light is the most important exogenous stimulus regulating plant growth and various developmental processes. Phytochromes, especially PHYTOCHROME B (PHYB) mediates the various light-mediated processes in Arabidopsis. SPATULA (SPT) is an important transcription factor, which has been reported previously to participate in temperature-mediated transition from seed dormancy to germination. Here we investigate the function of SPT in the floral transition under long day conditions and photomorphogenesis in Arabidopsis. In this study, spt-2 shows significantly delayed flowering time. But mutation of SPT in the background of phyb-1 rescues the phenotype of spt-2. The flowering time of double mutant of spt-2/phyb-1 is similar with the wild type. These results indicate that SPT promotes the transition from vegetative stage to floral stage and it regulates this transition in a PHYB-dependent manner. With qRT-PCR analysis, it is found that SPT regulates flowering time via FLC, SVP, FT and SOC1. Furthermore, SPT also controls photomorphogenesis. spt-2 displays shortened hypocotyls and increased chlorophylls contents compared with the wild type. These phenotypes are also rescued in the double mutant of spt-2/phyb-1. These results indicate that SPT is also involved in photomorphogenic development in Arabidopsis and SPT regulates photomorphogenesis in a PHYB-dependent manner. Collectively, SPT is not only a temperature responder but it is also an important light regulator during plant growth and development.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Estimating the health benefits of planned public transit investments in Montreal

Highlights: • An integrated burden of transportation in association with planned modifications of the public transit infrastructure. • Based on our results planned public transit projects in Montreal will not reduce significantly the burden of transportation. • Future work needs to address land use and public transit projects needed to further reduce the burden of transportation. Since public transit infrastructure affects road traffic volumes and influences transportation mode choice, which in turn impacts health, it is important to estimate the alteration of the health burden linked with transit policies.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Thermophysical properties and reversible phase transitions in yttrium hydride

In this study, the thermophysical properties of yttrium hydrides were investigated as a function of temperature (room temperature [RT] to 700°C) and hydrogen concentration (H/Y ratio ranges from 1.52 to 1.93). The results indicate that at the temperatures below 300°C, the hydrogen content did not have a significant influence on the thermal expansion, while the specific heat capacity, the thermal diffusivity, and the calculated thermal conductivity were slightly higher for the larger H/Y ratio. Between 300°C and 700°C, a reversible second-order endothermic transition in all measured thermal properties was observed. It was also found that the onset temperatures of the observed transition varied, with the composition having inverse dependence on the hydrogen content. The phase transition from ( α - Y + δ -YH x ) mixed phase to the δ -YH x single phase was excluded from the main contributors to the observed transition. An attempt was made to explain the behavior of the thermophysical properties at higher temperatures by considering the order–disorder transition as a result of hydrogen redistribution.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A melting-like process and the local structures during the anatase-to-rutile transition

Highlights: • The maximum size of anatase crystallites is more useful to describe the phase stability than the traditional critical size. • The melting-like process accelerates the phase transition from anatase to rutile. • The cis-coordinated anatase is transformed to trans-coordinated rutile by torsion & rotation of TiO{sub 6} octahedra in anatase. Phase transition of titanium oxide from anatase to rutile was investigated by using transmitted electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction (XRD), in combination with the atomic pair distribution function (PDF) technique. The transition range is about 528–805 °C and the critical size is ~73 nm for the sol-gel samples calcined for 6 h. A melting-like process was evidently observed in the transition samples by SEM and it will speed up the phase transition. PDF reveals that anatase crystallites are packed by neighbouring TiO{sub 6} octahedra in a cis-coordinated way. Anatase crystallites larger than the critical size will be unstable and transform into rutile in a trans-coordinated way by torsion and rotation of part of octahedra and it will rapidly spread the entire crystallites driven by a melting-like process. We suggest the maximum size of anatase will be more technically useful for the description of the phase stability from anatase to rutile because unstable small anatase crystals are consumed during longer calcination process to grow the larger anatase crystals.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Suppression of magnetostructural transition on GdSiGe thin film after thermal cyclings

The influence of thermal cycling on the microstructure, magnetic phase transition and magnetic entropy change of a Gd 5 Si 1.3 Ge 2.7 thin film up to 1000 cycles is investigated. The authors found that after 1000 cycles a strong reduction of the crystallographic phase responsible for the magnetostructural transition (Orthorhombic II phase) occurs. We attribute this to the chemical disorder, caused by the large number of expansion/compression cycles that the Orthorhombic II phase undergoes across the magnetostructural transition. The suppression of the magnetostructural transition corresponds to a drastic decrease of the thin film magnetic entropy change. Our results reveal the importance of studying the thermal/magnetic cycles influence on magnetostructural transitions as they can damage a real-life device.

36 MATERIALS SCIENCE↗