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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Traveling wakefield tube: THz source powered by nonrelativistic electron beam

High peak power, tunable, narrowband terahertz emitters are becoming sought after given their portability, efficiency, and ability to be deployed in the field for industrial, medical, and military applications. The use of accelerator systems producing THz frequencies via Cherenkov radiation, generated by passing an electron beam through a slow-wave wakefield structure, is a promising method to meet future THz requirements. To date, efforts have been dedicated to analysis and design of sources utilizing laser seeded bunched electron beam drivers with relativistic energies beyond 5 MeV. Presented here is a wakefield THz generation scheme based on passing a long quasi-dc nonrelativistic beam (200 keV) through a dielectric loaded travelling wave structure. Reduced energy allows for compactness and portability of the accelerator as the size and weight of the dielectric slow wave structure is vanishingly small compared to the accelerator unit. The presented scheme can serve as a tunable high peak power THz source operated between 0.4-1.6 THz and produces power gain by a factor of five with an average efficiency of 6.8%

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Facile synthesis of epoxide-co-propylene sulphide polymers with compositional and architectural control

Here, we present a facile method to produce propylene sulphide (PS) homopolymers up to 100 kg mol -1 and PS-epoxide statistical, block, and ABA copolymers using inexpensive and versatile thio-aluminium (SAl) based initiators. Homopolymerizations of PS with SAl initiators are living and controlled, with number averaged molecular weights ($\bar M$ n ) up to 100 kg mol -1 while maintaining narrow polydispersity (Ð < 1.4). Statistical and block copolymers of PS and epichlorohydrin (ECH) or propylene oxide (PO) are synthesized and characterized by size-exclusion chromatography (SEC), differential scanning calorimetry (DSC), 1 H and 13 C NMR spectroscopy, diffusion ordered spectroscopy (DOSY), and small-angle X-ray scattering (SAXS). This work represents the first statistical copolymerization of PS and epoxides with similar reactivity ratios, allowing fine control over composition. Block-copolymers of PS and epoxides are synthesized by sequential addition, without intermediate preparative steps. Polymer architecture is controlled through modification of the initiator; we synthesized a di-functional (d-H) SAl initiator to produce ABA tri-block-copolymers. Finally, poly(ethylene glycol) (PEG) was used as a macroinitiator to create PEG-b-PPS block copolymers and characterized by 1 H, 13 C NMR spectroscopy, DOSY, DSC, and SEC.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Model-based real-time surface heat flux and temperature estimation for the DIII-D tokamak

A control-oriented model for monitoring of wall power flux densities on the DIII-D tokamak has been successfully implemented and validated experimentally. Future reactors will have to withstand severe steady state high heat flux loads on plasma-facing components (PFCs). Due to the difficulty of directly-measuring local heat fluxes on these components, monitoring and protection of PFCs during the plasma discharge can benefit from simplified physics-based real-time (RT) functional models to estimate and guide heat load control. As a first step into the development, a control-oriented model for monitoring of wall power flux densities and temperatures on DIII-D tokamak has been successfully implemented. The paper discusses the experimental demonstration and comparison of the 2-D model-based wall heat flux algorithm on the DIII-Dinner wall limiter (IWL) against infra-red camera heat flux measurements for limited plasma configurations. The paper also reports on the benchmarking of the field line tracing environment, SMITER, developed at ITER organization on DIII-D tokamak against experimental IR diagnostic data and the derivation of the component shaping weighting factors for the 2-D model-based approach. Here, the extension of the model-based approach for surface temperature estimation on the DIII-D IWL is also presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Comparing field and lab quantitative stable isotope probing for nitrogen assimilation in soil microbes

ABSTRACT Soil microbial communities play crucial roles in nutrient cycling and can help retain nitrogen in agricultural soils. Quantitative stable isotope probing (qSIP) is a useful method for investigating taxon-specific microbial growth and utilization of specific nutrients, such as nitrogen (N). Typically, qSIP is performed in a highly controlled lab setting, so the field relevance of lab qSIP studies remains unknown. We conducted and compared tandem lab and field qSIP to quantify the assimilation of 15 N by maize-associated soil prokaryotic communities at two agricultural sites. Here, we show that field qSIP with 15 N can be used to measure taxon-specific microbial N assimilation. Relative 15 N assimilation rates were generally lower in the field, and the magnitude of this difference varied by site. Rates differed by method (lab vs field) for 19% of the top N assimilating genera. The field and lab measures were more comparable when relative assimilation rates were weighted by relative abundance to estimate the proportion of N assimilated by each genus with only ~10% of taxa differing by method. Of those that differed, the taxa consistently higher in the lab were inclined to have opportunistic lifestyle strategies, whereas those higher in the field had niches reliant on plant roots or in-tact soil structure (biofilms, mycelia). This study demonstrates that 15 N-qSIP can be successfully performed using field-incubated soils to identify microbial allies in N retention and highlights the strengths and limitations of field and lab qSIP approaches. IMPORTANCE Soil microbes are responsible for critical biogeochemical processes in natural and agricultural ecosystems. Despite their importance, the functional traits of most soil organisms remain woefully under-characterized, limiting our ability to understand how microbial populations influence the transformation of elements such as nitrogen (N) in soil. Quantitative stable isotope probing (qSIP) is a powerful tool to measure the traits of individual taxa. This method has rarely been applied in the field or with 15 N to measure nitrogen assimilation. In this study, we measured genus-specific microbial nitrogen assimilation in two agricultural soils and compared field and lab 15 N qSIP methods. Our results identify taxa important for nitrogen assimilation in agricultural soils, shed light on the field relevance of lab qSIP studies, and provide guidance for the future application of qSIP to measure microbial traits in the field.

Reed, Kinsey (ORCID:0000000155178664)↗
DOE OSTI2022

Subsurface hydrocarbon degradation strategies in low- and high-sulfate coal seam communities identified with activity-based metagenomics

Environmentally relevant metagenomes and BONCAT-FACS derived translationally active metagenomes from Powder River Basin coal seams were investigated to elucidate potential genes and functional groups involved in hydrocarbon degradation to methane in coal seams with high- and low-sulfate levels. An advanced subsurface environmental sampler allowed the establishment of coal-associated microbial communities under in situ conditions for metagenomic analyses from environmental and translationally active populations. Metagenomic sequencing demonstrated that biosurfactants, aerobic dioxygenases, and anaerobic phenol degradation pathways were present in active populations across the sampled coal seams. In particular, results suggested the importance of anaerobic degradation pathways under high-sulfate conditions with an emphasis on fumarate addition. Under low-sulfate conditions, a mixture of both aerobic and anaerobic pathways was observed but with a predominance of aerobic dioxygenases. The putative low-molecular-weight biosurfactant, lichysein, appeared to play a more important role compared to rhamnolipids. The methods used in this study—subsurface environmental samplers in combination with metagenomic sequencing of both total and translationally active metagenomes—offer a deeper and environmentally relevant perspective on community genetic potential from coal seams poised at different redox conditions broadening the understanding of degradation strategies for subsurface carbon.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Proof that Combining the Forced-collision and DXTRAN Monte Carlo Variance-reduction Techniques is Fair

This report provides mathematical proof that the MCNP DXTRAN (also known in other codes as forced-flight) and forced-collision variance-reduction techniques do not bias the expected value of Monte Carlo simulation estimates when combined. Proof is also provided that the techniques are unbiased when used independently. To prove that the techniques are unbiased, this report derives the first History Score Moment Equation (HSME) for non-multiplying media employing only forced collisions, only DXTRAN, and then both the variance-reduction techniques combined, as defined next. The HSMEs are found by forming the History Score Probability Density Functions (HSPDFs) and then taking the first score moment. Following its derivation, each HSME with a variance-reduction technique employed is reduced to the HSME for an analog simulation. Because the HSME represents the expected contribution to estimators in the simulation, reducing the HSME with variance reduction to the analog HSME shows that the simulation is unbiased despite the variance-reduction technique considered in the HSME. Analysis regarding higher-score moments of each technique is the subject of prior work and is not addressed herein. Throughout this work, the phase space p is defined to be the particle position x, direction-of-flight unit vector $\hat{Ω}$, energy E, and statistical weight w, $$p ≡ (x; \hat{Ω}; E; w).$$ A reduced phase-space excluding the statistical weight of the particle, $$r ≡ (x; \hat{Ω}; E),$$ is also used.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

A Random Forest Approach to Identifying Young Stellar Object Candidates in the Lupus Star-forming Region

The identification and characterization of stellar members within a star-forming region are critical to many aspects of star formation, including formalization of the initial mass function, circumstellar disk evolution, and star formation history. Previous surveys of the Lupus star-forming region have identified members through infrared excess and accretion signatures. We use machine learning to identify new candidate members of Lupus based on surveys from two space-based observatories: ESA’s Gaia and NASA’s Spitzer. Astrometric measurements from Gaia's Data Release 2 and astrometric and photometric data from the Infrared Array Camera on the Spitzer Space Telescope, as well as from other surveys, are compiled into a catalog for the random forest (RF) classifier. The RF classifiers are tested to find the best features, membership list, non-membership identification scheme, imputation method, training set class weighting, and method of dealing with class imbalance within the data. We list 27 candidate members of the Lupus star-forming region for spectroscopic follow-up. Most of the candidates lie in Clouds V and VI, where only one confirmed member of Lupus was previously known. These clouds likely represent a slightly older population of star formation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Investigation of the ordered and disordered corrosion morphologies on Ni-based alloy in the passive state

We report an order and disorder combined corrosion morphology of dual-phase Ni-based alloy in the passive state. After galvanostatic polarization in the passive region, the surface of the γ(Ni) phase presents amorphous feature while that of the γ′(Ni 3 Al) phase maintains crystalline. The variations in weight percentages of Ni (50.19% → 3.80%), Co (19.24% → 0.65%), Ta (0.85% → 21.19%), and W (5.73% → 43.79%) of γ surface are evident, whereas the composition of γ′ surface is nearly unchanged. The passive film comprises $W^{6+}_{ox}$, $Ta^{5+}_{ox}$, $Cr^{3+}_{ox}$, $Co^{8/3+}_{ox}$, $Ni^{2+}_{hy}$, and $Co^{2+}_{hy}$, and it shows stronger protection effect on the γ phase.

Density functional theory↗
DOE OSTI2020

Photoemission and dynamical mean field theory study of electronic correlations in a t 2 g 5 metal SrRhO 3 thin film

Perovskite rhodates are characterized by intermediate strengths of both electronic correlation as well as spin-orbit coupling (SOC) and usually behave as moderately correlated metals. A recent publication on epitaxial SrRhO 3 thin films reported a bad-metallic behavior and suggested the occurrence of antiferromagnetism below 100 K. In this work, we have further studied this SrRhO 3 thin film by hard x-ray photoemission spectroscopy and found a very small density of states (DOS) at the Fermi level $(E_F)$, which is consistent with the previously reported bad-metallic behavior. However, the absence of DOS persists up to room temperature, which contradicts the explanation of antiferromagnetic transition at ~100 K. We also employed electronic structure calculations within the framework of density functional theory and dynamical mean-field theory. In contrast to the photoemission results, our calculations indicate metallic behaviors of both bulk SrRhO 3 and the SrRhO 3 thin film, and a stronger correlation effect was observed in the thin film than that in the bulk. The calculated uniform magnetic susceptibility is substantially larger in the thin film than that in the bulk. We also investigated the role of SOC and found only a moderate modulation of the band structure. Hence SOC is not expected to significantly affect the electronic correlation in SrRhO 3 . Extrinsic effects of finite-thickness effects beyond our calculations and localization effects may play important roles to induce the negligible spectral weight at $(E_F)$.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Isoscalar and Isovector Giant Resonances in Closed Shells Nuclei and Bulk Properties of Nuclear Matter

Centroid energies, E CEN , of the isoscalar (T = 0) and isovector (T = 1) giant resonances of multipolarities L = 0 – 3 in 40,48 Ca, 68 Ni, 90 Zr, 116 Sn, 144 Sm and 208 Pb, were calculated within the fully self-consistent spherical Hartree-Fock (HF)-based random phase approximation (RPA) theory, using 33 different energy density functionals associated with Skyrme-type effective nucleon-nucleon interactions of the standard form commonly employed in the literature. Here, we also calculate the Pearson linear correlation coefficients between each E CEN and each bulk property of nuclear matter (NM), associated with the Skyrme interactions used in the calculations, and determine the sensitivity of E CEN to bulk properties of NM. By comparing the calculated values of E CEN to the experimental data, we constrain the values of the bulk NM properties. We find that interactions associated with the values of the NM effective mass, m* / m = 0.70 to 0.90, incompressibility coefficient, K NM = 210 to 240 MeV, and the enhancement coefficient of the energy weighted sum rule of the isovector giant dipole resonance, κ = 0.25 to 0.70, best reproduce the experimental data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Graph network heterogeneity predicts interplant wake losses

Wind plants generate large-scale wakes, which can affect the performance of neighboring installations. Such wakes are challenging to estimate due to the inherent complexity in modeling wake interactions between large quantities of turbines at various distances. Weighted directed graph networks can inform complex models by linking turbine pairs into chains of upstream and downstream neighbors for a given wind direction. A novel interpretation of the graph network adjacency matrix is proposed where each element of the matrix represents the cumulative impact of upstream turbines on an individual. In this study, wake losses were estimated with an engineering wake model across a range of inflow conditions for nine parametric variations of a system containing two neighboring wind plants. The parametric nature of the study isolates turbine spacing within the plant, separation distance between plants, and wind direction as the main drivers of wake losses. Spatial heterogeneity is computed from the weighted average adjacency matrix of each plant arrangement. The proposed method is orders of magnitude faster than wake modeling and does not require detailed turbine information or atmospheric conditions. Furthermore, the weighted average adjacency matrix provides insight on the spatial organization of wake losses at various scales. Plant heterogeneity is correlated with wake losses within and among plants. Framing wind plant wake interaction in terms of graph network spatial heterogeneity provides an efficient approach for predicting wake losses within and among neighboring wind plants with applications to other complex systems where wake interactions are key factor.

17 WIND ENERGY↗
DOE OSTI2023

Deletion of Carboxypeptidase E in β-Cells Disrupts Proinsulin Processing but Does Not Lead to Spontaneous Development of Diabetes in Mice

Carboxypeptidase E (CPE) facilitates the conversion of prohormones into mature hormones and is highly expressed in multiple neuroendocrine tissues. Carriers of CPE mutations have elevated plasma proinsulin and develop severe obesity and hyperglycemia. We aimed to determine whether loss of Cpe in pancreatic β-cells disrupts proinsulin processing and accelerates development of diabetes and obesity in mice. Pancreatic β-cell–specific Cpe knockout mice (βCpeKO; Cpe fl/fl x Ins1 Cre/+ ) lack mature insulin granules and have elevated proinsulin in plasma; however, glucose-and KCl-stimulated insulin secretion in βCpeKO islets remained intact. High-fat diet–fed βCpeKO mice showed weight gain and glucose tolerance comparable with those of Wt littermates. Notably, β-cell area was increased in chow-fed βCpeKO mice and β-cell replication was elevated in βCpeKO islets. Transcriptomic analysis of βCpeKO β-cells revealed elevated glycolysis and Hif1α-target gene expression. On high glucose challenge, β-cells from βCpeKO mice showed reduced mitochondrial membrane potential, increased reactive oxygen species, reduced MafA, and elevated Aldh1a3 transcript levels. Following multiple low-dose streptozotocin injections, βCpeKO mice had accelerated development of hyperglycemia with reduced β-cell insulin and Glut2 expression. In conclusion, these findings suggest that Cpe and proper proinsulin processing are critical in maintaining β-cell function during the development of hyperglycemia.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Electronic Bottleneck Suppression in Next‐Generation Networks with Integrated Photonic Digital‐to‐Analog Converters

Digital‐to‐analog converters (DAC) are indispensable functional units in signal processing instrumentation and wide‐band telecommunication links for both civil and military applications. As photonic systems are capable of high data throughput and low latency, an increasingly found system limitation stems from the required domain crossing such as digital to analog and electronic to optical. A photonic DAC implementation, in contrast, enables a seamless signal conversion with respect to both energy efficiency and short signal delay, often requiring bulky discrete optical components and electric–optic transformation, hence introducing inefficiencies. Herein, a novel coherent parallel photonic DAC concept along with a 4‐bit experimental prototype capable of performing this DAC without optic–electric–optic domain crossing is introduced. This new paradigm guarantees a linear intensity weighting among bits when operating at high sampling rates (50 GHz), featuring an exceptional sampling efficiency (> 100 GS ) and small footprint (≈1 mm 2 ) in an 8‐bit implementation. Importantly, this photonic DAC enables seamless interfaces of next‐generation data processing hardware with high relevance in data centers, task‐specific compute accelerators such as neuromorphic engines, and network edge processing applications.

Meng, Jiawei↗
DOE OSTI2023

Thermoresponsive antifouling ultrafiltration membranes from mesophase templating

Nanostructured polymers synthesized by lyotropic liquid crystal (LLC) templates with normal hexagonal (H 1 ) structure exhibit a 3D-continuous transport path, which makes them ideal for membrane separation application. Incorporating additional functionality, especially stimuli-responsiveness, in such an ordered structure provides even more application opportunities. Here, in this work, we present the first successful synthesis of H 1 -structured thermoresponsive ultrafiltration (UF) membranes via LLC templating. The membrane contains thermoresponsive Pluronic P84 diacrylate (P84DA) which not only acts as the monomer and structure-directing amphiphile, but also enables the pore size change with temperature. Experimental studies reveal that the swelling capacity of H 1 -templated polymer as well as permeability and selectivity of the obtained membrane can be altered by changing the temperature. Increasing the temperature from 25 to 45 °C increases the normalized flux from 28 to 68 L m -2 h -1 μm and molecular weight cut-off (MWCO) from 2200 to 3900 Da. Furthermore, the membrane shows an outstanding fouling resistance against different solutes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Recycling of natural fiber composites: Challenges and opportunities

Natural fibers have been widely used for reinforcing polymers attributed to their sustainable nature, excellent stiffness to weight ratio, biodegradability, and low cost compared with synthetic fibers like carbon or glass fibers. Thermoplastic composites offer an advantage of recyclability after their service life, but challenges and opportunities remain in the recycling of natural fiber reinforced polymer composites (NFRPCs). This article summarized the effects of reprocessing/recycling on the material properties of NFRPCs. The material properties considered include mechanical performance, thermal properties, hygroscopic behavior, viscoelasticity, degradation, and durability. NFRPCs can generally be recycled approximately 4–6 times until their thermomechanical properties change. After recycling 7 times, the tensile strength of NFRPCs can decrease by 17%, and the tensile modulus can decrease by 28%. The mitigation approaches to overcome degradation of material properties of NFRPCs such as adding functional additives and virgin plastics are also discussed. The main challenges in these approaches such as degradation and incompatibility are discussed, and an effort is made to provide a rationale for reprocessing/recyclability assessment. Finally, future applications of NFRPCs such as additive manufacturing and automotive part use are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Metasurface-based ultra-lightweight high-gain off-axis flat parabolic reflectarray for microwave beam collimation/focusing

Abstract Ultra-lightweight deployable antennas with high-gain are pivotal communication components for small satellites, which are intrinsically constrained in size, weight, and power. In this work, we design and demonstrate metasurface-based ultra-lightweight flat off-axis reflectarrays for microwave beam collimation and focusing, similar to a parabolic dish-antenna. Our ultra-thin reflectarrays employ resonators of variable sizes to cover the full 2 π phase range, and are arranged on the metasurface to realize a two-dimensional parabolic focusing phase distribution. We demonstrate a 30° off-axis focusing reflector that exhibits a measured gain of 27.5 dB at the central operating frequency of 11.8 GHz and a 3 dB directionality < $$\pm $$ ± 1.6°. Furthermore, we carry out full-wave simulations of the reflectarray, showing high gain of the beam focusing/collimation functionality, in good agreement with measurements. The demonstrated reflectarrays will enable low-cost, lightweight, and high-gain deployable transceivers for small-satellite platforms.

42 ENGINEERING↗
DOE OSTI2024

DNA Strand Displacement Driven Molecular Additive Manufacturing (DSD-MAM)

The goal of this project was to validate two-dimensional molecular printers, initially selfassembled from DNA and then actuated by externally driven cycles of DNA strand displacement, as prototype integrated nanosystems for molecular additive manufacturing. Novel functionalities of these nanomachines were explored during this project, including the following: nanometer-precision positioning mechanisms based on DNA strand displacement with multivalent interactions for discrete stepping or else diffusive capture; integration of independently moving layers of DNA origami to achieve 2D controllable motion; integration of spatial positioning with deposition functionality. The principal importance of this project was to provide an essential step in the development of a new technology for atomically precise manufacturing. Our first generation molecular 2D printer offers several advantages over conventional DNA-origami patterning, such as faster prototyping, faster dynamic rearrangement of patterns, and the ability to respond with feedback. We anticipate that our first-generation molecular printers may inspire future generations of molecular printers with iterative improvements in robustness and throughput. Potential applications of atomically precise manufacturing include the following: photovoltaics; photosynthetic and fuel cells; thermoelectrics and anisotropic heat spreaders; solid-state lighting; molecular electronic and plasmonic circuits; selectively preamble membranes; self-repairing materials with high strength-to-weight and fracture resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Ion diffusion coefficients in poly(3-alkylthiophenes) for energy conversion and biosensing: role of side-chain length and microstructure

Conductive polymers are promising materials as active elements for energy storage and conversion devices due to mixed ion–electron conduction. The ion diffusion coefficient is a relative measure of the efficacy of ion transport, allowing for comparison between materials and electrochemical conditions. In this work, diffusion coefficients of hexafluorophosphate (PF6–) counterions in poly(3-alkylthiophene) (P3AT) materials are measured as a function of both side-chain length and microstructure using electrochemical impedance spectroscopy (EIS). For semi-crystalline films, the diffusion coefficient is found to be anomalous and nearly independent of applied electrochemical potential. Here, the anomalous behavior of diffusion indicates that spin casting yields compact films with an enthalpic barrier to ion transport, attributed to ionic trapping. Diffusion coefficient values ~10 –11 cm 2 s –1 were measured for all films, indicating interchain spacing, in the absence of strong intermolecular interactions with the electrolyte, is not a viable design strategy to control ion transport. For the prototypical system of poly(3-hexylthiophene), we observe almost no potential dependence in ion transport for regioregular and regiorandom films of comparable molecular weight, with both exhibiting anomalous diffusion. Alternatively, changing the microstructure of poly(3-hexylthiophene) to a mostly amorphous, ion-imprinted structure yields ~500× increase in the diffusion coefficient to ~2 × 10 –8 cm 2 s –1 at 0.8 V vs. Ag/Ag + with behavior closer to ordinary diffusion. Collectively, these results indicate new insight into ion transport in conductive polymers, where ionic trapping effects can be mitigated through electrodeposition protocols over post-synthesis processing (i.e. spin coating).

14 SOLAR ENERGY↗