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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 OSTI2014

Verification of maximum radial power peaking factor due to insertion of FPM-LEU target in the core of RSG-GAS reactor

Verification of Maximum Radial Power Peaking Factor due to insertion of FPM-LEU target in the core of RSG-GAS Reactor. Radial Power Peaking Factor in RSG-GAS Reactor is a very important parameter for the safety of RSG-GAS reactor during operation. Data of radial power peaking factor due to the insertion of Fission Product Molybdenum with Low Enriched Uranium (FPM-LEU) was reported by PRSG to BAPETEN through the Safety Analysis Report RSG-GAS for FPM-LEU target irradiation. In order to support the evaluation of the Safety Analysis Report incorporated in the submission, the assessment unit of BAPETEN is carrying out independent assessment in order to verify safety related parameters in the SAR including neutronic aspect. The work includes verification to the maximum radial power peaking factor change due to the insertion of FPM-LEU target in RSG-GAS Reactor by computational method using MCNP5and ORIGEN2. From the results of calculations, the new maximum value of the radial power peaking factor due to the insertion of FPM-LEU target is 1.27. The results of calculations in this study showed a smaller value than 1.4 the limit allowed in the SAR.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

Tuning of in-plane optical anisotropy by inserting ultra-thin InAs layer at interfaces in (001)-grown GaAs/AlGaAs quantum wells

The in-plane optical anisotropy (IPOA) in (001)-grown GaAs/AlGaAs quantum wells (QWs) with different well widths varying from 2 nm to 8 nm has been studied by reflectance difference spectroscopy. Ultra-thin InAs layers with thickness ranging from 0.5 monolayer (ML) to 1.5 ML have been inserted at GaAs/AlGaAs interfaces to tune the asymmetry in the QWs. It is demonstrated that the IPOA can be accurately tailored by the thickness of the inserted ultra-thin InAs layer at the interfaces. Strain-induced IPOA has also been extracted by using a stress apparatus. We find that the intensity of the strain-induced IPOA decreases with the thickness of the inserted InAs layer, while that of the interface-induced IPOA increases with the thickness of the InAs layer. Theoretical calculations based on 6 band k ⋅ p theory have been carried out, and good agreements with experimental results are obtained. Our results demonstrate that, the IPOA of the QWs can be greatly and effectively tuned by inserting an ultra-thin InAs layer with different thicknesses at the interfaces of QWs, which does not significantly influence the transition energies and the transition probability of QWs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Effects of lithium insertion on thermal conductivity of silicon nanowires

Recently, silicon nanowires (SiNWs) have been applied as high-performance Li battery anodes, since they can overcome the pulverization and mechanical fracture during lithiation. Although thermal stability is one of the most important parameters that determine safety of Li batteries, thermal conductivity of SiNWs with Li insertion remains unclear. In this letter, using molecular dynamics simulations, we study room temperature thermal conductivity of SiNWs with Li insertion. It is found that compared with the pristine SiNW, there is as much as 60% reduction in thermal conductivity with 10% concentration of inserted Li atoms, while under the same impurity concentration the reduction in thermal conductivity of the mass-disordered SiNW is only 30%. With lattice dynamics calculations and normal mode decomposition, it is revealed that the phonon lifetimes in SiNWs decrease greatly due to strong scattering of phonons by vibrational modes of Li atoms, especially for those high frequency phonons. The observed strong phonon scattering phenomenon in Li-inserted SiNWs is similar to the phonon rattling effect. Our study serves as an exploration of thermal properties of SiNWs as Li battery anodes or weakly coupled with impurity atoms.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Folding and insertion thermodynamics of the transmembrane WALP peptide

The anchor of most integral membrane proteins consists of one or several helices spanning the lipid bilayer. The WALP peptide, GWW(LA){sub n} (L)WWA, is a common model helix to study the fundamentals of protein insertion and folding, as well as helix-helix association in the membrane. Its structural properties have been illuminated in a large number of experimental and simulation studies. In this combined coarse-grained and atomistic simulation study, we probe the thermodynamics of a single WALP peptide, focusing on both the insertion across the water-membrane interface, as well as folding in both water and a membrane. The potential of mean force characterizing the peptide’s insertion into the membrane shows qualitatively similar behavior across peptides and three force fields. However, the Martini force field exhibits a pronounced secondary minimum for an adsorbed interfacial state, which may even become the global minimum—in contrast to both atomistic simulations and the alternative PLUM force field. Even though the two coarse-grained models reproduce the free energy of insertion of individual amino acids side chains, they both underestimate its corresponding value for the full peptide (as compared with atomistic simulations), hinting at cooperative physics beyond the residue level. Folding of WALP in the two environments indicates the helix as the most stable structure, though with different relative stabilities and chain-length dependence.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Enhancement of magnetoresistance by inserting thin NiAl layers at the interfaces in Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5}/Ag/Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5} current-perpendicular-to-plane pseudo spin valves

We have investigated the effects of insertion of a thin NiAl layer (≤0.63 nm) into a Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5} (CFGG)/Ag interface on the magnetoresistive properties in CFGG/Ag/CFGG current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo spin valves (PSVs). First-principles calculations of ballistic transmittance clarified that the interfacial band matching at the (001)-oriented NiAl/CFGG interface is better than that at the (001)-Ag/CFGG interface. The insertion of 0.21-nm-thick NiAl layers at the Co{sub 2}FeGa{sub 0.5}Ge{sub 0.5}/Ag interfaces effectively improved the magnetoresistance (MR) output; the observed average and the highest MR ratio (ΔRA) are 62% (25 mΩ μm{sup 2}) and 77% (31 mΩ μm{sup 2}) at room temperature, respectively, which are much higher than those without NiAl insertion. Microstructural analysis using scanning transmission electron microscopy confirmed the existence of thin NiAl layers at the Ag interfaces with only modest interdiffusion even after annealing at 550 °C. The improvement of the interfacial spin-dependent scattering by very thin NiAl insertion can be a predominant reason for the enhancement of the MR output.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Crystallographic snapshots of sulfur insertion by lipoyl synthase

Lipoyl synthase (LipA) catalyzes the insertion of two sulfur atoms at the unactivated C6 and C8 positions of a protein-bound octanoyl chain to produce the lipoyl cofactor. To activate its substrate for sulfur insertion, LipA uses a [4Fe-4S] cluster and S-adenosylmethionine (AdoMet) radical chemistry; the remainder of the reaction mechanism, especially the source of the sulfur, has been less clear. One controversial proposal involves the removal of sulfur from a second (auxiliary) [4Fe-4S] cluster on the enzyme, resulting in destruction of the cluster during each round of catalysis. Here, we present two high-resolution crystal structures of LipA from Mycobacterium tuberculosis: one in its resting state and one at an intermediate state during turnover. In the resting state, an auxiliary [4Fe-4S] cluster has an unusual serine ligation to one of the irons. After reaction with an octanoyllysine-containing 8-mer peptide substrate and 1 eq AdoMet, conditions that allow for the first sulfur insertion but not the second insertion, the serine ligand dissociates from the cluster, the iron ion is lost, and a sulfur atom that is still part of the cluster becomes covalently attached to C6 of the octanoyl substrate. Here, this intermediate structure provides a clear picture of iron–sulfur cluster destruction in action, supporting the role of the auxiliary cluster as the sulfur source in the LipA reaction and describing a radical strategy for sulfur incorporation into completely unactivated substrates.

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

Insertion products in the reaction of carbonyl oxide Criegee intermediates with acids: Chloro(hydroperoxy)methane formation from reaction of CH 2 OO with HCl and DCl

The reactions of carbonyl oxides (“Criegee intermediates”) with organic and inorganic acids have been postulated to proceed predominantly by an insertion mechanism, and the hydroperoxy-substituted ester products from reactions with organic acids have been spectroscopically observed. Here this work characterizes the products from one of the simplest reactions of carbonyl oxides with inorganic acids, that of formaldehyde oxide, CH 2 OO, with hydrogen chloride, which occurs via a 1,2-insertion in the H–Cl bond. Reactions of both HCl and DCl isotopologues yield product signal at the mass of the insertion product chloro(hydroperoxy)methane and a dissociative ionisation peak at the mass of the protonated (or deuteronated) Criegee intermediate. The isotopic composition of the insertion product has been measured for reaction mixtures where both HCl isotopologues are present, and the H/D ratio of the product is consistently higher (by a factor of 1.6 ± 0.3) than that of the reactants. This isotope selectivity in the products has smaller uncertainty than the ratio of measured rate coefficients and suggests a normal (k H > k D ) kinetic isotope effect in the reaction. Theoretical kinetics calculations predict a small normal kinetic isotope effect for the overall reaction (k H / k D = 1.35 at 20 Torr N 2 and k H / k D = 1.2 for 1 atm N 2 ) but predict a substantial inverse kinetic isotope effect (k D > k H ) for the stabilisation fraction, in disagreement with the experimental observation.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2025

Simulations of Heat Transfer Using Tight-Fitting Twisted Tape Inserts for First Wall Cooling in Molten Salt Breeder Blankets

One of the major components in fusion energy systems is the fusion blanket, which has a vacuum vessel to contain the plasma. As part of the fusion blanket/vacuum vessel, the first wall and plasma-facing components require sufficient cooling to prevent material degradation during operation from the superheated plasma. Most fusion blanket concepts involve first wall and divertor coolant channels with heat transfer enhancements (HTEs) that are intended to withstand the incident high heat fluxes of 1 to 5 MW/m 2 . Twisted tape inserts are a proposed HTE that have been investigated previously for first wall cooling and monoblock divertor cooling channels and in other nonfusion heat transfer components. By inserting twisted tapes into straight pipes, the amount of turbulence in the system can be increased at lower Reynolds numbers by swirling the flow. This results in better heat transfer characteristics with marginal increases in frictional pressure losses. In particular, simulations of high-Prandtl-number fluids such as the proposed molten salt FLiBe in twisted tapes, which is prototypic to liquid immersion blankets, have not been previously explored. Here, in this study, we simulate various Prandtl numbers in pipes with twisted tape inserts using large eddy simulations to determine the effects of increasing Prandtl numbers on heat transfer performance. The quantities of particular interest are the Nusselt number and the friction factor, which were recovered using data reduction techniques to determine impacts on heat transfer and pressure losses. This work serves as a starting point for determining the feasibility of twisted tape inserts for liquid immersion blanket concepts.

LES↗
DOE OSTI2019

A microfabricated, 3D-sharpened silicon shuttle for insertion of flexible electrode arrays through dura mater into brain

Electrode arrays for chronic implantation in the brain are a critical technology in both neuroscience and medicine. Recently, flexible, thin-film polymer electrode arrays have shown promise in facilitating stable, single-unit recordings spanning months in rats. While array flexibility enhances integration with neural tissue, it also requires removal of the dura mater, the tough membrane surrounding the brain, and temporary bracing to penetrate the brain parenchyma. Durotomy increases brain swelling, vascular damage, and surgical time. Insertion using a bracing shuttle results in additional vascular damage and brain compression, which increase with device diameter; while a higher-diameter shuttle will have a higher critical load and more likely penetrate dura, it will damage more brain parenchyma and vasculature. One way to penetrate the intact dura and limit tissue compression without increasing shuttle diameter is to reduce the force required for insertion by sharpening the shuttle tip. We describe a novel design and fabrication process to create silicon insertion shuttles that are sharp in three dimensions and can penetrate rat dura, for faster, easier, and less damaging implantation of polymer arrays. Sharpened profiles are obtained by reflowing patterned photoresist, then transferring its sloped profile to silicon with dry etches. We demonstrate that sharpened shuttles can reliably implant polymer probes through dura to yield high quality single unit and local field potential recordings for at least 95 days. On insertion directly through dura, tissue compression is minimal. Significance. This is the first demonstration of a rat dural-penetrating array for chronic recording. This device obviates the need for a durotomy, reducing surgical time and risk of damage to the blood-brain barrier. This is an improvement to state-of-the-art flexible polymer electrode arrays that facilitates their implantation, particularly in multi-site recording experiments. This sharpening process can also be integrated into silicon electrode array fabrication.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Suppressing Screening-Current-Induced Strain in a 72-mm-Bore REBCO Insert for a 20-T Magnet: A Numerical Study

Rare-earth barium copper oxide (REBCO) high-temperature superconducting (HTS) magnets are considered a game changer for the capability of generating magnetic fields exceeding 20 T at or above liquid helium temperature, combined with the potential for substantially reduced manufacturing and operational costs. Princeton Plasma Physics Laboratory is dedicated to developing large-bore high-field superconducting magnet systems to support forefront physics research. Here, our current project focuses on a φ72-mm cold-bore REBCO insert comprising 21 dry-wound double-pancake coils, designed to generate at least 8 T when nested within a 12-T outsert magnet. A significant challenge for high-field REBCO magnets is the time-varying-magnetic-field-induced screening currents (SC) in the REBCO conductors, which can cause localized strain and stress concentrations. This paper presents a numerical study of the SC-induced strain in the REBCO insert magnet, confirming that the SC-induced strain can be substantially suppressed by energizing the REBCO insert before the outsert magnets. We discuss and reveal the mechanism behind this reduction. By applying this strategy, we expect to unleash the potential of the REBCO insert magnet to generate up to 12 T in a 12-T background field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Collimator design for a multipinhole brain SPECT insert for MRI

Purpose: Brain single photon emission computed tomography (SPECT) imaging is an important clinical tool, with unique tracers for studying neurological diseases. Nowadays, most commercial SPECT systems are combined with x-ray computed tomography (CT) in so-called SPECT/CT systems to obtain an anatomical background for the functional information. However, while CT images have a high spatial resolution, they have a low soft-tissue contrast, which is an important disadvantage for brain imaging. Magnetic resonance imaging (MRI), on the other hand, has a very high soft-tissue contrast and does not involve extra ionizing radiation. Therefore, the authors designed a brain SPECT insert that can operate inside a clinical MRI. Methods: The authors designed and simulated a compact stationary multipinhole SPECT insert based on digital silicon photomultiplier detector modules, which have shown to be MR-compatible and have an excellent intrinsic resolution (0.5 mm) when combined with a monolithic 2 mm thick LYSO crystal. First, the authors optimized the different parameters of the SPECT system to maximize sensitivity for a given target resolution of 7.2 mm in the center of the field-of-view, given the spatial constraints of the MR system. Second, the authors performed noiseless simulations of two multipinhole configurations to evaluate sampling and reconstructed resolution. Finally, the authors performed Monte Carlo simulations and compared the SPECT insert with a clinical system with ultrahigh-resolution (UHR) fan beam collimators, based on contrast-to-noise ratio and a visual comparison of a Hoffman phantom with a 9 mm cold lesion. Results: The optimization resulted in a stationary multipinhole system with a collimator radius of 150.2 mm and a detector radius of 172.67 mm, which corresponds to four rings of 34 diSPM detector modules. This allows the authors to include eight rings of 24 pinholes, which results in a system volume sensitivity of 395 cps/MBq. Noiseless simulations show sufficient axial sampling (in a Defrise phantom) and a reconstructed resolution of 5.0 mm (in a cold-rod phantom). The authors compared the 24-pinhole setup with a 34-pinhole system (with the same detector radius but a collimator radius of 156.63 mm) and found that 34 pinholes result in better uniformity but a worse reconstruction of the cold-rod phantom. The authors also compared the 24-pinhole system with a clinical triple-head UHR fan beam system based on contrast-to-noise ratio and found that the 24-pinhole setup performs better for the 6 mm hot and the 16 mm cold lesions and worse for the 8 and 10 mm hot lesions. Finally, the authors reconstructed noisy projection data of a Hoffman phantom with a 9 mm cold lesion and found that the lesion was slightly better visible on the multipinhole image compared to the fan beam image. Conclusions: The authors have optimized a stationary multipinhole SPECT insert for MRI and showed the feasibility of doing brain SPECT imaging inside a MRI with an image quality similar to the best clinical SPECT systems available.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Structural and electrophysical properties of In{sub 0.52}Al{sub 0.48}As/In{sub 0.53}Ga{sub 0.47}As/In{sub 0.52}Al{sub 0.48}As/InP HEMT nanoheterostructures with different combinations of InAs and GaAs inserts in quantum well

A complex investigation of structural and electrical properties of In{sub 0.52}Al{sub 0.48}As/In{sub y}Ga{sub 1−y}As/In{sub 0.52}Al{sub 0.48}As nanoheterostructures on InP substrates containing thin InAs and GaAs inserts in a quantum well (QW) has been performed. The GaAs nanolayers are grown at the QW boundaries between InGaAs and InAlAs layers, while the double InAs inserts are grown in InGaAs layers symmetrically with respect to the QW center. The layer and interface structures have been studied by transmission electron microscopy. It is shown that, when using the proposed epitaxial growth conditions, the introduction of ∼1.2-nm-thick InAs nanoinserts into the InGaAs QW and a ∼1-nm-thick GaAs nanobarrier at the QW boundaries does not induce structural defects. The diffusion of the InAlAs/InGaAs interface (2–3 monolayers) and InAs/InGaAs nanoinsert interface (1–2 monolayers) has been estimated. Measured Hall mobilities and electron concentrations in structures with different combinations of InAs and GaAs inserts have been analyzed using calculated energy band diagrams and electron density distributions. It is found that the photoluminescence spectra of the structures under study have differences caused by specific structural features of coupled QWs (specifically, the change in the In molar fraction due to InAs inserts and the change in the QW thickness due to GaAs transition barriers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Final technical report for: Insertional Mutagenesis of Brachypodium distachyon DE-AI02-07ER64452

Several bioenergy grasses are poised to become a major source of energy in the United States. Despite their increasing importance, we know little about the basic biology underlying the traits that control the utility of grasses as energy crops. Better knowledge of grass biology (e.g. identification of the genes that control cell wall composition, plant architecture, cell size, cell division, reproduction, nutrient uptake, carbon flux, etc.) could be used to design rational strategies for crop improvement and shorten the time required to domesticate these species. The use of an appropriate model system is an efficient way to gain this knowledge. Brachypodium distachyon is a small annual grass with all the attributes needed to be a modern model organism including simple growth requirements, fast generation time, small stature, small genome size and self-fertility. These attributes led to the recommendation in the DOE’s “Breaking the Biological Barriers to Cellulosic Ethanol: A Joint Research Agenda” report to propose developing and using B. distachyon as a model for energy crops to accelerate their domestication. Strategic investments (e.g. genome sequencing) in B. distachyon by the DOE are now bearing fruit and B. distachyon is being used as a model grass by hundreds of laboratories worldwide. Sequence indexed insertional mutants are an extremely powerful tool for both forward and reverse genetics. They allow researchers to order mutants in any gene tagged in the collection by simply emailing a request. The goal of this project was to create a collection of sequence indexed insertional mutants (T-DNA lines) for the model grass Brachypodium distachyon in order to facilitate research by the scientific community. During the course of this grant we created a collection of 23,649 B. distachyon T-DNA lines and identified 26,112 unique insertion sites. The collection can be queried through the project website (http://jgi.doe.gov/our-science/science-programs/plant-genomics/brachypodium/brachypodium-t-dna-collection/) and through the Phytozome genome browser (http://phytozome.jgi.doe.gov/pz/portal.html). The collection has been heavily utilized by the research community and, as of October 23, 2015, 223 orders for 12,069 seeds packets have been filled. In addition to creating this resource, we also optimized methods for transformation and sequencing DNA flanking insertion sites.

09 BIOMASS FUELS↗
DOE OSTI2018

Strength Ranking of Hard-Alloy Cutting Inserts of Different Shape

The stress–strain state of replaceable polyhedral inserts in composite tools is calculated by the finite-element method. The influence of the insert’s design parameter, the basing and attachment configuration, and the load on the stress and strain is established. Besides the strength of the inserts, attention is paid to the positional accuracy in the tool housing. Cutting inserts of maximum strength have been developed and patented.

42 ENGINEERING↗
NASA NTRS1975

Interfacial insert for electrical connectors

The development of interfacial inserts for improved electric connectors is discussed. The inserts were manufactured from epoxy resins. The design features of the inserts and the manufacturing equipment are described. The reliability test program is reported. Drawings of the interfacial inserts are provided.

Macavay, D.↗
NASA NTRS1981

Wind tunnel supplementary Mach number minimum section insert

A device is described which changes the Mach number capability of a wind tunnel without permanently altering the existing nozzle of the tunnel. An insert is removably attached to the wall of the existing nozzle expansion area thereby creating a second minimum section upstream of the model test section. The added insert may be removed without complicated and expensive changes to the basic wind tunnel. In one embodiment, a removable insert is disposed within wind tunnel nozzle walls with a portion of the flow boundary layer being bled off from the tunnel via passageway and tunnel exit to reduce the extent of separated flow normally occuring upstream of the insert contraction section.

Couch, L. M.↗
NASA NTRS1984

Laboratory tests on an aircraft fuselage to determine the insertion loss of various acoustic add-on treatments

This paper describes a laboratory study of add-on acoustic treatments for a propeller-driven light aircraft fuselage. The treatments included: no treatment (i.e., baseline fuselage); a production-type double-wall interior; and various amounts of high density fiberglass added to the baseline fuselage. The sound source was a pneumatic-driver with attached exponential horn, supplied with a broadband signal. Data were acquired at the approximate head positions of the six passenger seats. The results were analyzed on space-averaged narrowband, one-third octave band and overall insertion loss basis. In addition, insertion loss results for the different configurations at specific frequencies representing propeller tone spectra are presented. The propeller tone data includes not only the space-averaged insertion loss, but also the variation of insertion loss at these particular frequencies across the six microphone positions.

Heitman, K. E.↗
NASA NTRS1986

Thrust improvement with ablative insert nozzle extension

Aspects are examined of an investigation by the Marshall Space Flight Center into the conceptual feasibility of increasing the thrust performance of the Space Shuttle Main Engine (SSME) by using a conical nozzle extension fitted with an ablative insert in order to achieve a low-cost, near-term gain in payload. The ablating insert would provide a controlled increase in nozzle expansion ratio during launch and early climbout (first 30-60 seconds) so as to reduce thrust loss from nozzle over-expansion in the lower atmosphere. Summaries are given of JPL studies in the area of: defining the near-wall flow environment in the extended nozzle insert region; selecting potential insert materials; conceptualizing an extension/insert geometrical configuration; and identifying future experimental efforts necessary to verify the feasibility of the concepts.

Clayton, R. M.↗