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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,693 records · Page 94
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Aircraft Interior Noise Control Using Distributed Piezoelectric Actuators

Developing a control system that can reduce the noise and structural vibration at the same time is an important task. This talk presents one possible technical approach for accomplishing this task. The target application of the research is for aircraft interior noise control. The emphasis of the present approach is not on control strategies, but rather on the design of actuators for the control system. In the talk, a theory of distributed piezoelectric actuators is introduced. A uniform cylindrical shell is taken as a simplified model of fuselage structures to illustrate the effectiveness of the design theory. The actuators developed are such that they can reduce the tonal structural vibration and interior noise in a wide range of frequencies. Extensive computer simulations have been done to study various aspects of the design theory. Experiments have also been conducted and the test results strongly support the theoretical development.

Sun, Jian Q.↗
NASA NTRS2003

Numerical Simulations of Non-Newtonian Convection in Ice: Application to Europa

Numerical simulations of solid state convection in Europa's ice shell have so far been limited to consideration of Newtonian flow laws, where the viscosity of ice is strongly dependent upon temperature, predicting that a stagnant lid should form at the top (10-40%) of a convecting ice shell. Such large thicknesses seem to contradict estimates of the effective elastic thickness of Europa s ice shell during its geologically active period. Recent laboratory experiments characterize the rheology of ice as the sum of contributions from several temperature and strain rate-dependent creep mechanisms. We present the results of numerical simulations of convection within Europa s ice shell using the finite-element model Citcom, applying the non-Newtonian rheology of grain boundry sliding. Our calculations suggest a shallower brittle/ductile transition and larger interior convective velocities compared to Newtonian rheology. The flow field is time-dependent, with small, localized upwellings and downwellings at the thermal boundary layers that have minimal topographic expression at the surface.

Barr, A. C.↗
NASA NTRS2003

Automated Finite Element Analysis of Elastically-Tailored Plates

A procedure for analyzing and designing elastically tailored composite laminates using the STAGS finite element solver has been presented. The methodology used to produce the elastic tailoring, namely computer-controlled steering of unidirectionally reinforced composite material tows, has been reduced to a handful of design parameters along with a selection of construction methods. The generality of the tow-steered ply definition provides the user a wide variety of options for laminate design, which can be automatically incorporated with any finite element model that is composed of STAGS shell elements. Furthermore, the variable stiffness parameterization is formulated so that manufacturability can be assessed during the design process, plus new ideas using tow steering concepts can be easily integrated within the general framework of the elastic tailoring definitions. Details for the necessary implementation of the tow-steering definitions within the STAGS hierarchy is provided, and the format of the ply definitions is discussed in detail to provide easy access to the elastic tailoring choices. Integration of the automated STAGS solver with laminate design software has been demonstrated, so that the large design space generated by the tow-steering options can be traversed effectively. Several design problems are presented which confirm the usefulness of the design tool as well as further establish the potential of tow-steered plies for laminate design.

Jegley, Dawn C.↗
NASA NTRS2005

Patched Off-Axis Bending/Twisting Actuators for Thin Mirrors

Two documents present updates on thin-shell, adjustable, curved mirrors now being developed for use in spaceborne imaging systems. These mirrors at an earlier stage of development were reported in Nanolaminate Mirrors With Integral Figure-Control Actuators (NPO-30221), NASA Tech Briefs, Vol. 26, No. 5 (May 2002), page 80. To recapitulate: These mirrors comprise metallic film reflectors on nanolaminate substrates that contain "in-plane" actuators for controlling surface figures with micron-level precision. The actuators are integral parts of the mirror structures, typically fabricated as patches that are bonded onto the rear (nonreflective) surfaces of the mirror shells. The current documents discuss mathematical modeling of mirror deflections caused by actuators arranged in unit cells distributed across the rear mirror surfaces. One of the documents emphasizes an actuator configuration in which a mirror surface is divided into hexagonal unit cells. Each unit cell contains four rectangular actuator patches in an off-axis cruciform pattern to induce a combination of bending and twisting. For deflections to reduce certain optical aberrations, it is found that, relative to other configurations, this configuration involves a smaller areal density of actuators.

Hickey, Gregory↗
DOE OSTI2020

Accelerating Hanford Site Cleanup through Operations Research Modeling - 20238

The Hanford Site cleanup effort will require the integration of dozens of unique facilities and processes, many of which will be first-of-a-kind in implementation and design. Each facility will be governed by its own set of operating logic, configured with a unique array of unit operations, and subject to a set of constraints that will affect its behavior. The collection of facilities have multiple points of interface, making the operations of any one facility potentially significant to the operations of other up- or downstream processes. It is therefore highly desirable to accurately predict these operations, as it allows for Site officials to identify and preempt bottlenecks and vulnerabilities before they unexpectedly inhibit the cleanup mission. With the quantity and complexity of the processes that will be on Site, building a pen-and-paper or even a spreadsheet-assisted model of the cleanup mission quickly becomes overwhelming in scope and inaccurate in execution. The Engineering organization for the Site's Tank Operations Contract (TOC) has therefore implemented the use of operations research (OR) modeling to simulate and predict future operations of Site facilities. These models are created using a discrete event simulation tool that allows for the development of detailed, versatile, and robust models. Not only can these models account for complex logical behaviors, but they can also simulate process details down to the level of vessel sizing, labor utilization, equipment reliability, and resource availability. To date, the TOC has developed OR models for several facilities on Site, including for single-shell tank (SST) farms, double-shell tank (DST) farms, the Effluent Treatment Facility (ETF), and the waste transfer system. These models have focused on identifying bottlenecks and operational constraints, and have been used to quantify the effects of implementing process changes. This latter point is particularly valuable, as it allows for several alternatives to be studied in a virtual setting before committing resources to making a change in the field. The decision to develop OR models has gained tremendous support from the Site's stakeholders and the U.S. Department of Energy (DOE) management, and has prompted the use of the tool to support additional internal and external initiatives. Recently, an initiative was proposed to use the models to help identify and provide quantitative backing for risks and opportunities for the TOC. This application of OR could not only help inform how the TOC manages its risks (e.g. quantities and types of spare parts), but could also help drive process improvements whose benefits might otherwise be hard to quantify. The models have also been used to drive the TOC's cloud computing, artificial intelligence (AI), and machine learning (ML) initiatives. These initiatives will not only improve the ability of the TOC to more rapidly respond to the needs of its customers, but it will also aid in the ability of the TOC to analyze and improve the processes it studies. Partnership with two external software development and consulting companies (Lanner and Ynformed) has furthered not only the application of AI and ML within the TOC, but has also spurred the development of new/improved software tools and platforms used by the companies. These partnerships have proven to be mutually beneficial and productive, and have set a precedent for the types of gains that can be made by exploring such options. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1987

Analysis of shell-type structures subjected to time-dependent mechanical and thermal loading

A general mathematical model and solution methodologies are being developed for analyzing structural response of thin, metallic shell-type structures under large transient, cyclic, or static thermomechanical loads. Among the system responses, which were associated with these load conditions, were thermal buckling, creep buckling, and ratcheting. Thus, geometric as well as material-type nonlinearities (of high order) can be anticipated and must be considered in the development of the mathematical model. Furthermore, this must also be accommodated in the solution process.

Simitses, G. J.↗
DOE OSTI2016

Distribution of Iron Oxide Core-Titanium Dioxide Shell Nanoparticles in VX2 Tumor Bearing Rabbits Introduced by Two Different Delivery Modalities

This work compares intravenous (IV) versus fluoroscopy-guided transarterial intra-catheter (IC) delivery of iron oxide core-titanium dioxide shell nanoparticles (NPs) in vivo in VX2 model of liver cancer in rabbits. NPs coated with glucose and decorated with a peptide sequence from cortactin were administered to animals with developed VX2 liver cancer. Two hours after NPs delivery tumors, normal liver, kidney, lung and spleen tissues were harvested and used for a series on histological and elemental analysis tests. Quantification of NPs in tissues was done both by bulk inductively coupled plasma mass spectrometry (ICP-MS) analysis and by hard X-ray fluorescence microscopy. Both IV and IC NPs injection are feasible modalities for delivering NPs to VX2 liver tumors with comparable tumor accumulation. It is possible that this is an outcome of the fact that VX2 tumors are highly vascularized and hemorrhagic, and therefore enhanced permeability and retention (EPR) plays the most significant role in accumulation of nanoparticles in tumor tissue. It is, however, interesting to note that IV delivery led to increased sequestration of NPs by spleen and normal liver tissue, while IC delivery lead to more NP positive Kupffer cells. This difference is most likely a direct outcome of blood flow dynamics. Armed with this knowledge about nanoparticle delivery, we plan to test them as radiosensitizers in the future.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Selective molecular transport through the protein shell of a bacterial microcompartment organelle

Bacterial microcompartments are widespread prokaryotic organelles that have important and diverse roles ranging from carbon fixation to enteric pathogenesis. Current models for microcompartment function propose that their outer protein shell is selectively permeable to small molecules, but whether a protein shell can mediate selective permeability and how this occurs are unresolved questions. In this paper, biochemical and physiological studies of structure-guided mutants are used to show that the hexameric PduA shell protein of the 1,2-propanediol utilization (Pdu) microcompartment forms a selectively permeable pore tailored for the influx of 1,2-propanediol (the substrate of the Pdu microcompartment) while restricting the efflux of propionaldehyde, a toxic intermediate of 1,2-propanediol catabolism. Crystal structures of various PduA mutants provide a foundation for interpreting the observed biochemical and phenotypic data in terms of molecular diffusion across the shell. Finally and overall, these studies provide a basis for understanding a class of selectively permeable channels formed by nonmembrane proteins.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Properties of isoscalar giant multipole resonances in medium-heavy closed-shell nuclei: A semimicroscopic description

The semimicroscopic particle-hole dispersive optical model (PHDOM) is implemented to describe main properties of Isoscalar Giant Multipole Resonances (up to L=3) in medium-heavy closed-shell nuclei. Here, the main properties are characterized by the strength distribution, transition density, partial and total probabilities of direct one-nucleon decay. Calculation results obtained for the 208 Pb nucleus are compared with available experimental data.

190 ≤ A ≤ 219↗
DOE OSTI2019

Achieving Highly Durable Random Alloy Nanocatalysts through Intermetallic Cores

Pt catalysts are widely studied for the oxygen reduction reaction, but their cost and susceptibility to poisoning limit their use. A strategy to address both problems is to incorporate a second transition metal to form a bimetallic alloy; however, the durability of such catalysts can be hampered by leaching of non-noble metal components. Here, we show that random alloyed surfaces can be stabilized to achieve high durability by depositing the alloyed phase on top of intermetallic seeds using a model system with PdCu cores and PtCu shells. Specifically, random alloyed PtCu shells were deposited on PdCu seeds that were either the atomically random face-centered cubic phase (FCC A1, Fm$\bar{3}$m) or the atomically ordered CsCl-like phase (B2, Pm$\bar{3}$m). Precise control over crystallite size, particle shape, and composition allowed for comparison of these two core@shell PdCu@PtCu catalysts and the effects of the core phase on electrocatalytic durability. Indeed, the nanocatalyst with the intermetallic core saw only an 18% decrease in activity after stability testing (and minimal Cu leaching), whereas the nanocatalyst with the random alloy core saw a 58% decrease (and greater Cu leaching). The origin of this enhanced durability was probed by classical molecular dynamics simulations of model catalysts, with good agreement between model and experiment. Although many random alloy and intermetallic nanocatalysts have been evaluated, this study directly compares random alloy and intermetallic cores for electrocatalysis with the enhanced durability achieved with the intermetallic cores likely general to other core@shell nanocatalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Assessment of the accuracy of coupled cluster perturbation theory for open-shell systems. I. Triples expansions

The accuracy at which total energies of open-shell atoms and organic radicals may be calculated is assessed for selected coupled cluster perturbative triples expansions, all of which augment the coupled cluster singles and doubles (CCSD) energy by a non-iterative correction for the effect of triple excitations. Namely, the second- through sixth-order models of the recently proposed CCSD(T–n) triples series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)] are compared to the acclaimed CCSD(T) model for both unrestricted as well as restricted open-shell Hartree-Fock (UHF/ROHF) reference determinants. By comparing UHF- and ROHF-based statistical results for a test set of 18 modest-sized open-shell species with comparable RHF-based results, no behavioral differences are observed for the higher-order models of the CCSD(T–n) series in their correlated descriptions of closed- and open-shell species. In particular, we find that the convergence rate throughout the series towards the coupled cluster singles, doubles, and triples (CCSDT) solution is identical for the two cases. For the CCSD(T) model, on the other hand, not only its numerical consistency, but also its established, yet fortuitous cancellation of errors breaks down in the transition from closed- to open-shell systems. The higher-order CCSD(T–n) models (orders n > 3) thus offer a consistent and significant improvement in accuracy relative to CCSDT over the CCSD(T) model, equally for RHF, UHF, and ROHF reference determinants, albeit at an increased computational cost.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Vanadium fine-structure K-shell electron impact ionization cross sections for fast-electron diagnostic in laser–solid experiments

The K-shell electron impact ionization (EII) cross section, along with the K-shell fluorescence yield, is one of the key atomic parameters for fast-electron diagnostic in laser–solid experiments through the K-shell emission cross section. In addition, in a campaign dedicated to the modeling of the K lines of astrophysical interest (Palmeri et al. (2012)), the K-shell fluorescence yields for the K-vacancy fine-structure atomic levels of all the vanadium isonuclear ions have been calculated. In this study, the K-shell EII cross sections connecting the ground and the metastable levels of the parent vanadium ions to the daughter ions K-vacancy levels considered in Palmeri et al. (2012) have been determined. The relativistic distorted-wave (DW) approximation implemented in the FAC atomic code has been used for the incident electron kinetic energies up to 20 times the K-shell threshold energies. Moreover, the resulting DW cross sections have been extrapolated at higher energies using the asymptotic behavior of the modified relativistic binary encounter Bethe model (MRBEB) of Guerra et al. (2012) with the density-effect correction proposed by Davies et al. (2013)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Similarity and differences between the radion and Higgs boson production and decay processes involving off-shell fermions

The radion is a scalar particle that occurs in brane world models and interacts with the trace of the energy–momentum tensor of the Standard Model (SM). The radion–SM fermion interaction Lagrangian differs from the Higgs boson–fermion interaction Lagrangian for off-shell fermions. It is shown that all additional, as compared to the Higgs boson, contributions to the amplitudes of radion production and decay processes involving off-shell fermions are canceled out for both massless and massive fermions. Thus, additional terms in the interaction Lagrangian do not change properties of these processes for the radion and the Higgs boson, except for the general normalization factors. This similarity is a consequence of gauge invariance for the processes with production of gauge bosons. When an additional scalar particle is produced, there are no apparent reasons for the above cancellation, as confirmed, for example, by the process with production of two scalar particles, which features an additional contribution of the radion in comparison with the Higgs boson.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Axionlike particles and sterile neutrinos solve the 𝐵 → 𝐾⁢$𝜈⁢\bar{𝜈}$ and 𝐵 → 𝜋⁢𝐾 puzzles

The recent measurement of the branching ratio of 𝐵 + → 𝐾 + +inv (where “inv” denotes invisible states) by the Belle II Collaboration is enhanced relative to the standard model expectation by 2.7⁢𝜎. An older puzzle persists in measurements of the branching ratios and 𝐶⁢𝑃 asymmetries of 𝐵 → 𝜋⁢𝐾 decays. We address these two anomalies in flavor-changing neutral current 𝐵 decays, with a short-lived axionlike particle (ALP) with mass close to that of the 𝜋 0 . In the model with the minimum number of new couplings, the ALP has couplings to the photon, top quark and a heavy sterile neutrino. The ALP contributes to the 𝐵 → 𝜋 0 ⁢𝐾 decays by mixing with the 𝜋 0 . It contributes to 𝐵 + → 𝐾 + + inv by its off-shell coupling to sterile neutrino pairs. The model can explain the excess in the total rate, but not the observed distribution of signal events. We make predictions for all 𝐵 → 𝐾 (*) + inv modes and for the rare kaon decays, 𝐾 + → 𝜋 + + inv and 𝐾 𝐿 → 𝜋 0 + inv. We find an appreciable contribution to the magnetic moment of the muon, and negligible contributions to the magnetic moment of the electron and 𝑏 → 𝑠⁢𝑒 + ⁢𝑒 − .

axion-like particles↗
DOE OSTI2025

Molecular Modeling and Molecular Dynamics Simulation of a Packed and Intact Bacterial Microcompartment

Bacterial microcompartments (BMCs) are protein-bound organelles found in some bacteria which encapsulate enzymes for enhanced catalytic activity. These compartments spatially sequester enzymes within semipermeable shell proteins and are packed full of enzyme cargoes and metabolites as they fulfill their function. Coupling together recent SAXS and proteomics work, it is possible to develop molecular models for these microcompartments and interrogate enzyme and metabolite dynamics within. Our primary goal of this study is to quantify the permeability of metabolite glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP) across the BMC shell through classical molecular dynamics simulation. The Haliangium ochraceum model of BMC shell (PDB: 6MZX) was used to model an intact BMC of approximately 10 million atoms. Working at this scale presented its own challenges in managing large data sets, with multiple challenges and hardware advances discussed that facilitated this work. Over approximately 750 ns of aggregate simulation, we see multiple permeation events for these metabolites that were added at high concentration through the pores present within BMC shell tiles. When compared to independent permeability estimates for the same metabolites determined through replica exchange umbrella sampling simulations, the permeabilities varied by approximately 3 orders of magnitude. Regardless, the permeability coefficients for both G3P and DHAP are highly similar and very high, such that only very small concentration gradients can be maintained across the BMC shell between the cytosol and BMC interior. The large simulation systems also facilitated comparisons for molecular diffusivity in the crowded environment within the BMC shell. By our estimates, the viscosity within a packed BMC shell is at least 10-fold higher than it would be in neat solution and is the real driver for varying permeability estimates we obtained through simulation. These findings will be used as design inputs for future bioengineering efforts to make products from BMCs, highlighting how permeable BMC shells can be.

Diffusion↗
DOE OSTI2019

Self-Evolving Machine: A Continuously Improving Model for Molecular Thermochemistry

Because collecting precise and accurate chemistry data is often challenging, chemistry data sets usually only span a small region of chemical space, which limits the performance and the scope of applicability of data-driven models. To address this issue, we integrated an active learning machine with automatic ab initio calculations to form a self-evolving model that can continuously adapt to new species appointed by the users. In the present work, we demonstrate the self-evolving concept by modeling the formation enthalpies of stable closed-shell polycyclic species calculated at the B3LYP/6-31G(2df,p) level of theory. By combining a molecular graph convolutional neural network with a dropout training strategy, the model we developed can predict density functional theory (DFT) enthalpies for a broad range of polycyclic species and assess the quality of each predicted value. For the species which the current model is uncertain about, the automatic ab initio calculations provide additional training data to improve the performance of the model. For a test set composed of 2858 cyclic and polycyclic hydrocarbons and oxygenates, the enthalpies predicted by the model agree with the reference DFT values with a root-mean-square error of 2.62 kcal/mol. Finally, we found that a model originally trained on hydrocarbons and oxygenates can broaden its prediction coverage to nitrogen-containing species via an active learning process, suggesting that the continuous learning strategy is not only able to improve the model accuracy but is also capable of expanding the predictive capacity of a model to unseen species domains.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Designing Janus Ligand Shells on PbS Quantum Dots using Ligand–Ligand Cooperativity

We present a combined experimental and theoretical study of ligand ligand cooperativity during X-type carboxylate-to-carboxylate ligand exchange reactions on PbS quantum dot surfaces. We find that the ligand dipole moment (varied through changing the substituents on the benzene ring of cinnamic acid derivatives) impacts the ligand-exchange isotherms; in particular, ligands with large electron withdrawing character result in a sharper transition from an oleate-dominated ligand shell to a cinnamate-dominated ligand shell. We developed a two-dimensional lattice model to simulate the ligand-exchange isotherms that accounts for the difference in ligand binding energy as well as ligand ligand cooperativity. Our model shows that ligands with larger ligand ligand coupling energy exhibit sharper isotherms indicating an order disorder phase transition. Lastly, we developed an anisotropic Janus ligand shell by taking advantage of the ligand ligand cooperative ligand exchanges. We monitored the Janus ligand shell using 19 F nuclear magnetic resonance, showing that when the ligand ligand coupling energy falls within the order region of the phase diagram, Janus ligand shells can be constructed.

36 MATERIALS SCIENCE↗
NASA NTRS1983

Thermally driven flow in a rotating spherical shell Axisymmetic states

A spherical analogue of the rotating annulus experiments modeling atmospheric motion, in which a liquid is contained between two rigid, corotating and concentric hemispheres upon both of which thermal gradients are imposed, is presently studied by means of numerical models. Temperatures are lower on the inner than on the outer sphere, and decrease towards the pole. Using Navier-Stokes equations which assume symmetry about the polar axis, finite difference numerical models yield steady-state solutions to the equations. Hydrostatic and nonhydrostatic solutions are compared for cylindrical and spherical cases, and it is found in the case of the spherical shell that the differences between hydrostatic and nonhydrostatic solutions are small and largely confined to the regions near the pole and equator. It is suggested that nonhydrostatic effects on the axisymmetric state will not affect the flow's baroclinic stability.

Miller, T. L.↗