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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

On the Role of Fermi Energy in Determining Properties of Superconductors: a Detailed Comparative Study of Two Elemental Superconductors (Sn and Pb), a Non-cuprate (MgB{sub 2}) and Three Cuprates (YBCO, Bi-2212 and Tl-2212)

Fermi energies (E{sub F}s) of high- T{sub c} superconductors (SCs) have of late been evincing considerable interest because they are believed to be the cause of their high T{sub c}s and gap structures. Since Bardeen-Cooper-Schrieffer (BCS) equations for elemental and generalized-BCS equations for non-elemental SCs are derived under the blanket of the assumption E{sub F}/ kθ > > 1 (k = Boltzmann constant, θ = Debye temperature), they cannot shed light on the E{sub F}s of these SCs. This fact leads us to address the gaps (Δ{sub 0}s) and T{sub c}s of both types of SCs via recently derived equations which incorporate E{sub F} as a variable. For the specification of the E{sub F} of any SC, we now need another of its properties. Choosing j{sub 0}, the critical current density of the SC at T = 0, and following an idea due to Pines, we present for both types of SCs new equations for j{sub 0} that depend solely on the following properties of the SC: E{sub F}, θ, gram-atomic volume, electronic specific heat constant and a dimensionless construct y=kθ√(2m∗)/P{sub 0}√(E{sub F}), where m* is the effective mass of superconducting electrons and P{sub 0} their critical momentum. Appeal to the experimental values of Δ{sub 0}, T{sub c} and j{sub 0} of any SC then not only leads to values of E{sub F}, m* and P{sub 0} but also provides plausible clues about how its j{sub 0}—and therefore T{sub c}—may be increased.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Compressed H{sub 3}S, Superfluid Density and the Quest for Room-Temperature Superconductivity

The discovery of superconductivity at 203 K in highly compressed sulphur hydride validates the ideas put forward by Ashcroft 50 years ago and galvanises the quest for room-temperature superconductivity. But at such temperatures, thermal fluctuations might be expected to break up Cooper pairs. For example, in the cuprates, fluctuations reduce T{sub c} by 30% or more below the mean-field value. Similar effects are found in iron pnictides. Here, we ask: how does superconductivity survive in sulphur hydride at such high temperatures? To answer this, we examine the superfluid density which is the key parameter for quantifying fluctuations in both amplitude and phase. We show that dimensionality plays a key role in suppressing or enhancing thermal fluctuations to the benefit of hydrogen sulphide and the detriment of its more layered 2D competitors. We find that the temperature scale for phase fluctuations, T{sub φ}, in superconducting H{sub 3}S exceeds 1200 K, and therefore, these are irrelevant at 200 K. But the amplitude fluctuation temperature scale, T{sub amp}, at around 300 K is much lower and this has important implications for the ongoing quest for room temperature superconductivity. Appealing to the way in which superfluid density, T{sub φ}, T{sub amp} and T{sub c} scale with each other it seems that room temperature superconductivity is nearly ruled out, but perhaps not quite. It will require 3D systems with a large Fermi velocity to achieve this goal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

The Theoretical Investigation of Electronic, Magnetic, and Thermoelectric Behavior of LiZ{sub 2}O{sub 4} (Z = Mn, Fe, Co, and Ni) by Modified Becke and Johnson Approach

Magnetic spinel oxides LiZ{sub 2}O{sub 4} (Z = Mn, Fe, Co, and Ni) have recently appealed the scientific community due to their interesting magnetic and thermoelectric applications. In the current article, the electronic, magnetic, and thermoelectric properties of LZO have been elaborated using density functional theory-based Wien2k code. The band structures and total density of states ensure the half metallic ferromagnetic (HMF) nature of the studied compounds. Furthermore, the magnetism is discussed in detail using crystal field, John-Teller, and exchange energies involved in the system and spin density. Finally, electrical conductivity, thermal conductivity, power factor, Seebeck coefficient, and thermal efficiency computed by using BoltztraP code suggest these compounds for thermoelectric device fabrications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Multi-segment Winding Application for Axial Short Circuit Force Reduction Under Tap Changer Operation in HTS Transformers

High-temperature superconducting (HTS) transformers have remarkable appealing advantages over conventional ones. But higher brittleness of HTS windings with respect to copper windings makes HTS transformers more vulnerable in short circuit and inrush current situations. During tap changer operation, appreciable asymmetry and non-uniform distribution of ampere-turn along the windings causes high axial component of short circuit forces and makes the situation more severe. In this paper, multi-segment winding method is employed for reduction of axial short circuit forces. An analytical method is presented for calculation of axial component of short circuit forces under tap changer operation. Analytical method shows that with utilizing HLHLHLH asymmetrical multi-segment windings, during tap changer operation, the axial component of short circuit forces reduces significantly. The results of the analytical method are compared with the results of finite element method (FEM) model simulations, and the consistency is demonstrated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis and characterization of intrinsically radiolabeled lanthanide phosphate nanoparticles toward biomedical and environmental applications

Lanthanide phosphate nanomaterials are appealing as multifunctional platforms for biomedical applications because of their low toxicity, radiation resistance, and unique luminescence and magnetic properties. Lanthanide phosphate nanoparticles (NPs) radiolabeled with 156 Eu were synthesized by an aqueous route using sodium tripolyphosphate as a phosphate source and complexing agent. GdPO 4 was used as a host matrix, while synthetic concentrations of Ce 3+ /Tb 3+ and Eu 3+ were varied between 5–40% and 10–30%, respectively, and yielded spherical NPs with hexagonal crystal system and particle size < 5 nm. Luminescence emission and magnetic susceptibility were influenced by lanthanide concentrations where characteristic 5 D 0 - 7 F J and 5 D 4 - 7 F J transitions were observed for Eu 3+ - and Tb 3+ -doped NPs, respectively. Chemical yield of > 90% was achieved for GdPO 4 and Gd 0.6 Ce 0.3 Tb 0.1 PO 4 NPs intrinsically radiolabeled with 156 Eu. Lastly, in vitro retention of 156 Eu within LnPO 4 NPs was > 97% over 3 weeks. Intrinsically radiolabeled LnPO 4 NPs have the potential to combine the luminescence and magnetic properties of Ln 3+ ions with lanthanide radioisotopes for biomedical and environmental applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Exploring the interoperability of remote GPGPU virtualization using rCUDA and directive-based programming models

Directive-based programming models, such as OpenMP, OpenACC, and OmpSs, enable users to accelerate applications by using coprocessors with little effort. These devices offer significant computing power, but their use can introduce two problems: an increase in the total cost of ownership and their underutilization because not all codes match their architecture. Remote accelerator virtualization frameworks address those problems. In particular, rCUDA provides transparent access to any graphic processor unit installed in a cluster, reducing the number of accelerators and increasing their utilization ratio. Joining these two technologies, directive-based programming models and rCUDA, is thus highly appealing. In this work, we study the integration of OmpSs and OpenACC with rCUDA, describing and analyzing several applications over three different hardware configurations that include two InfiniBand interconnections and three NVIDIA accelerators. Our evaluation reveals favorable performance results, showing low overhead and similar scaling factors when using remote accelerators instead of local devices.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Basic Oxygen Furnace: Assessment of Recent Physicochemical Models

Modeling of the basic oxygen furnace (BOF) process, both for online monitoring and fundamental research, has gained importance in steelmaking industry over the past few decades. Especially models integrating fundamental physicochemical relations are appealing. Even though a vast amount of these kind of models and submodels can be found in the literature, no recent review paper is available which thoroughly discusses the most up-to-date BOF modeling methods. This study aims to do so. In the introductory chapters, an overview is given on the assumptions and models for underlying BOF phenomena, which are frequently used in the BOF models and submodels. Focus was put on six models with emphasis on the chemical aspect of the BOF process. For each model, its assumptions are given and subsequently evaluated, highlighting both their strengths and limitations. The six different models are also compared with each other. Finally, opportunities for future research are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Comparative Study of Zinc Cold-Spray Coating and Pre-treatments for Magnesium Alloys

Magnesium (Mg) alloys are appealing for automotive lightweighting owing to their high specific strength. However, their susceptibility to corrosion in harsh environments remains a major challenge. Conventional industrial pre-treatment coatings, including zinc phosphate, chromate conversion, and non-chromate conversion, often exhibit discontinuities and microcracks, leading to localized corrosion near fasteners and parting lines. Here, this study investigates cold-sprayed zinc (Zn) coatings as a novel pre-treatment alternative for high-pressure die cast (HPDC) AZ91 Mg alloys, demonstrating significant improvements in wear and corrosion performance. Cold spray produces uniform and robust coatings, reducing wear rate by over 50% and reducing corrosion rate by over 99.3%, as measured by evolved hydrogen release, compared to traditional pre-treatments. Multimodal corrosion testing reveals that Zn cold-spray coatings form a protective layer during exposure, minimizing general and filiform corrosion, and exhibiting corrosion potential (E corr ) that is nobler by ~ 400 mV than the surfaces of both pre-treated and uncoated AZ91. Scalability of cold spray for selective application around multimaterial joints further strengthens their industrial viability. This work establishes Zn cold-spray coatings as highly effective pre-treatment solutions for the advancement of corrosion resistant Mg alloy components in automotive applications.

multimodal corrosion↗
DOE OSTI2019

Non-invasive Risk Stratification for Coronary Artery Disease: Is It Time for Subclassifications?

Purpose of Review: Coronary artery disease (CAD) is the leading contributor to cardiovascular disease; it is the most prevalent non-communicable disease globally and has high morbidity, mortality and health care cost. Risk stratification is defined as prevention or containment of disease prior to it occurring or progressing, and non-invasive surrogates include history, examination, biomarkers and non-invasive imaging. This review aims to highlight advancement in current diagnostic strategies and explores gaps for CAD secondary to atherosclerosis and non-obstructive vascular diseases. Recent Findings: Cardiac risk scores have largely proven inadequate in risk stratifying heterogeneous patient populations. Greater emphasis should also be provided to posttest risk stratification. Non-invasive imaging with MRI is the most accurate but least cost efficacious presently due to availability and expertise. Echocardiography and nuclear imaging have good accuracy, but radiation limits the latter. Novel echocardiographic technologies may increase its appeal. Cardiac CT angiography is increasingly promising. Summary: Non-invasive and minimally invasive imaging has significantly influenced the cost-efficacy trajectory of coronary artery disease diagnosis and management. Recent studies suggest that future guidelines will incorporate more subclassifications from the findings of these novel technologies and for more diverse patient demographics.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Fluorescence in situ hybridization in 1 mL of selective urine for the detection of upper tract urothelial carcinoma: a feasibility study

Kidney-sparing surgery of upper tract urothelial carcinoma (UTUC) requires a stringent follow-up with frequent ureteroscopies. Triage testing could reduce the number of follow-up ureteroscopies and hence minimize the invasiveness of follow-up. The use of urine-based markers for triage seems appealing but should be feasible with selective urine from outpatient cystoscopy to maximize the reduction of invasiveness. In this study, the feasibility of UroVysion{sup ®} fluorescence in situ hybridization (FISH) for the detection of UTUC in 1 mL of selective urine is investigated. Ten consecutive patients with biopsy-proven UTUC and five patients with negative diagnostic ureteroscopy findings were included in this case-control study. During ureteroscopy, 1 mL of selective urine was collected passively with a ureteral splint for Urovysion® FISH. The FISH rater was blinded to any clinical information. The results of FISH were compared to the findings of concomitantly collected selective urine cytology and the patients’ UTUC status. FISH was feasible in all samples with a sensitivity of 90% and a specificity of 80% for UTUC. In comparison, selective cytology resulted in a diagnostic yield of 87% with a sensitivity of 80% and a specificity of 67%. In conclusion, UTUC detection is feasible with FISH in 1 mL of passively collected selective urine. Thus from a technical point of view, FISH could be used as an outpatient triage test to decide if follow-up ureteroscopy is necessary after kidney-sparing surgery of UTUC. Evaluation of the diagnostic accuracy of FISH for the suggested pathway deserves further attention.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

My warranty has expired: I need to be retested

The concept of warranty period, the duration of time during which the patient’s risk remains low, is appealing. However, some points remain to be resolved before its translation in the clinical arena. Methodological issues should be standardized in order to compare the results of studies in different patient populations. Also, the definition of a “normal” study should always take into consideration the history of prior revascularization, the achieved level of exercise, and the stressor used. The promise of warranty can be questioned by the patient’s baseline demographic and clinical characteristics and may also be influenced by life-style modification in the course of the follow-up. The “warranty period” concept should shift from data reflecting the time to a cardiac event to the development of ischemia, given an opportunity for intervention before a cardiac event occurs. In this context, clarify the role of serial imaging can be extremely useful, in particular to evaluate if and when retesting a patient after a normal scan.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Interrogating Proton Affinities of Organophosphonate Species Via Atmospheric Flow Tube Mass Spectrometry and Computational Methods

Within trace vapor analysis in environmental monitoring, defense, and industry, atmospheric flow tube mass spectrometry (AFT-MS) can fill a role that incorporates non-contact vapor analysis with the selectivity and low detection limits of mass spectrometry. AFT-MS has been applied to quantitating certain explosives by selective clustering with nitrate and more recently applied to detecting tributyl phosphate and dimethyl methylphosphonate as protonated species. Developing AFT-MS methods for organophosphorus species is appealing, given that this class of compounds includes a range of pollutants, chemical warfare agent (CWA) simulants, and CWA degradation products. A key aspect of targeting organophosphorus analytes has included the use of dopant ion chemistry to form adducts that impart additional analytical selectivity. The assessment of potential dopant molecules suited to enhance detection of these compounds is hindered by few published ion thermochemical properties for organophosphorus species, such as proton affinity, which can be used for approximating proton-bound dimer bond strength. As a preliminary investigation for the progression of sensing methods involving AFT-MS, we have applied both the extended kinetic method and computational approaches to eight organophosphorus CWA simulants to determine their respective gas-phase proton affinities. Notable observed trends, supported by computational efforts, include an increase in proton affinity as the alkyl chain lengths on the phosphonates increased. .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Whole Body MRI: Non-oncological Musculoskeletal Applications

Purpose of the Review: Whole-body MRI is an emerging imaging technique on continuous evolution, used in many oncologic indications and introduced more recently in rheumatologic and systemic disorders. In this article, we review the recent musculoskeletal applications of this technique outside the field of cancer. Recent Findings: Whole-body MRI, with its high sensitivity to bone marrow and soft-tissue alterations, and ability of extensive body coverage, is progressively regarded as an effective and powerful imaging tool for the detection, staging, and monitoring under treatment of many rheumatic diseases and systemic pathologies affecting the musculoskeletal system. Disease specific imaging protocols have been designed. Summary: Whole-body MRI is an appealing, non-irradiating tool emerging in musculoskeletal imaging. It is becoming the imaging of choice in several non-oncologic indications, and its application field is on continuous expansion.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Compatible meshfree discretization of surface PDEs

Meshfree discretization of surface partial differential equations is appealing, due to their ability to naturally adapt to deforming motion of the underlying manifold. In this work, we consider an existing scheme proposed by Liang et al. reinterpreted in the context of generalized moving least squares (GMLS), showing that existing numerical analysis from the GMLS literature applies to their scheme. With this interpretation, their approach may then be unified with recent work developing compatible meshfree discretizations for the div-grad problem in R d . Informally, this is analogous to an extension of collocated finite differences to staggered finite difference methods, but in the manifold setting and with unstructured nodal data. In this way, we obtain a compatible meshfree discretization of elliptic problems on manifolds which is naturally stable for problems with material interfaces, without the need to introduce numerical dissipation or local enrichment near the interface. As a result, we provide convergence studies illustrating the high-order convergence and stability of the approach for manufactured solutions and for an adaptation of the classical five-strip benchmark to a cylindrical manifold.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Coupling of Adhesion and Anti-Freezing Properties in Hydrogel Electrolytes for Low-Temperature Aqueous-Based Hybrid Capacitors

Solid-state zinc-ion capacitors are emerging as promising candidates for large-scale energy storage owing to improved safety, mechanical and thermal stability and easy-to-direct stacking. Hydrogel electrolytes are appealing solid-state electrolytes because of eco-friendliness, high conductivity and intrinsic flexibility. However, the electrolyte/electrode interfacial contact and anti-freezing properties of current hydrogel electrolytes are still challenging for practical applications of zinc-ion capacitors. Here, we report a class of hydrogel electrolytes that couple high interfacial adhesion and anti-freezing performance. The synergy of tough hydrogel matrix and chemical anchorage enables a well-adhered interface between hydrogel electrolyte and electrode. Meanwhile, the cooperative solvation of ZnCl 2 and LiCl hybrid salts renders the hydrogel electrolyte high ionic conductivity and mechanical elasticity simultaneously at low temperatures. More significantly, the Zn||carbon nanotubes hybrid capacitor based on this hydrogel electrolyte exhibits low-temperature capacitive performance, delivering high-energy density of 39 Wh kg –1 at –60 °C with capacity retention of 98.7% over 10,000 cycles. With the benefits of the well-adhered electrolyte/electrode interface and the anti-freezing hydrogel electrolyte, the Zn/Li hybrid capacitor is able to accommodate dynamic deformations and function well under 1000 tension cycles even at –60 °C. This work provides a powerful strategy for enabling stable operation of low-temperature zinc-ion capacitors.

25 ENERGY STORAGE↗
DOE OSTI2021

Progress of Nanotechnology for Lithium-Sulfur Batteries

Lithium-Sulfur (Li-S) battery has been proposed and investigated since the 1960s as an effective energy storage device via reversible electrochemical reactions. As the fast development and commercialization of Li-ion battery (LIB) technology kept moving forward, no breakthroughs have been attained to solve critical technical issues facing Li-S batteries during the following decades. In the year 2000s, Li-S batteries reattracted significant interests in the research field owing to their low-cost advantages, high theoretical specific energy of 2600 Wh kg -1 , which is at least 3 times higher than the current LIB technology. The low-cost and high abundance of sulfur (i.e., the cathode active material), make Li-S batteries more appealing than LIBs given the fact that the latter use critical materials such as cobalt and nickel in the manufacturing of the cathodes. Moreover, the high-energy and low-cost features make the Li-S battery a promising energy storage technology in practical applications such as portable devices, electric vehicles, and grid storage when coupled with the harvesting of solar or wind renewable energies. For example, since 2007, SION Power Corporation (Tucson, USA) and Oxis Energy (UK) made progress towards the commercialization of Li-S batteries with products showing specific energies over 350 Wh kg -1 for powering electric vehicles. To be on a par with the current LIB technology, the ultimate goal of achieving 500 Wh kg -1 for Li-S battery will make it more competitive for widespread commercialization.

Li, Mengya↗
DOE OSTI2021

Deep convolutional autoencoders as generic feature extractors in seismological applications

The idea of using a deep autoencoder to encode seismic waveform features and then use them in different seismological applications is appealing. In this paper, we designed tests to evaluate this idea of using autoencoders as feature extractors for different seismological applications, such as event discrimination (i.e., earthquake vs. noise waveforms, earthquake vs. explosion waveforms), and phase picking. These tests involve training an autoencoder, either undercomplete or overcomplete, on a large amount of earthquake waveforms, and then using the trained encoder as a feature extractor with subsequent application layers (either a fully connected layer, or a convolutional layer plus a fully connected layer) to make the decision. By comparing the performance of these newly designed models against the baseline models trained from scratch, we conclude that the autoencoder feature extractor approach may only outperform the baseline under certain conditions, such as when the target problems require features that are similar to the autoencoder encoded features, when a relatively small amount of training data is available, and when certain model structures and training strategies are utilized. The model structure that works best in all these tests is an overcomplete autoencoder with a convolutional layer and a fully connected layer to make the estimation.

58 GEOSCIENCES↗