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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

State of the Art of Molecular Visualization in Immersive Virtual Environments

Abstract Visualization plays a crucial role in molecular and structural biology. It has been successfully applied to a variety of tasks, including structural analysis and interactive drug design. While some of the challenges in this area can be overcome with more advanced visualization and interaction techniques, others are challenging primarily due to the limitations of the hardware devices used to interact with the visualized content. Consequently, visualization researchers are increasingly trying to take advantage of new technologies to facilitate the work of domain scientists. Some typical problems associated with classic 2D interfaces, such as regular desktop computers, are a lack of natural spatial understanding and interaction, and a limited field of view. These problems could be solved by immersive virtual environments and corresponding hardware, such as virtual reality head‐mounted displays. Thus, researchers are investigating the potential of immersive virtual environments in the field of molecular visualization. There is already a body of work ranging from educational approaches to protein visualization to applications for collaborative drug design. This review focuses on molecular visualization in immersive virtual environments as a whole, aiming to cover this area comprehensively. We divide the existing papers into different groups based on their application areas, and types of tasks performed. Furthermore, we also include a list of available software tools. We conclude the report with a discussion of potential future research on molecular visualization in immersive environments.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2021

Scalable FBP decomposition for cone-beam CT reconstruction

Filtered Back-Projection (FBP) is a fundamental compute intense algorithm used in tomographic image reconstruction. Cone-Beam Computed Tomography (CBCT) devices use a cone-shaped X-ray beam, in comparison to the parallel beam used in older CT generations. Distributed image reconstruction of cone-beam datasets typically relies on dividing batches of images into different nodes. This simple input decomposition, however, introduces limits on input/output sizes and scalability.We propose a novel decomposition scheme and reconstruction algorithm for distributed FPB. This scheme enables arbitrarily large input/output sizes, eliminates the redundancy arising in the end-to-end pipeline and improves the scalability by replacing two communication collectives with only one segmented reduction. Finally, we implement the proposed decomposition scheme in a framework that is useful for all current-generation CT devices (7th gen). In our experiments using up to 1024 GPUs, our framework can construct 40963 volumes, for real-world datasets, in under 16 seconds (including I/O).

Chen, Peng↗
DOE OSTI2024

Analysis of twelve genomes of the bacterium Kerstersia gyiorum from brown-throated sloths ( Bradypus variegatus ), the first from a non-human host

Kerstersia gyiorum is a Gram-negative bacterium found in various animals, including humans, where it has been associated with various infections. Knowledge of the basic biology of K. gyiorum is essential to understand the evolutionary strategies of niche adaptation and how this organism contributes to infectious diseases; however, genomic data about K. gyiorum is very limited, especially from non-human hosts. In this work, we sequenced 12 K. gyiorum genomes isolated from healthy free-living brown-throated sloths (Bradypus variegatus) in the Parque Estadual das Fontes do Ipiranga (São Paulo, Brazil), and compared them with genomes from isolates of human origin, in order to gain insights into genomic diversity, phylogeny, and host specialization of this species. Phylogenetic analysis revealed that these K. gyiorum strains are structured according to host. Despite the fact that sloth isolates were sampled from a single geographic location, the intra-sloth K. gyiorum diversity was divided into three clusters, with differences of more than 1,000 single nucleotide polymorphisms between them, suggesting the circulation of various K. gyiorum lineages in sloths. Genes involved in mobilome and defense mechanisms against mobile genetic elements were the main source of gene content variation between isolates from different hosts. Sloth-specific K. gyiorum genome features include an IncN2 plasmid, a phage sequence, and a CRISPR-Cas system. The broad diversity of defense elements in K. gyiorum (14 systems) may prevent further mobile element flow and explain the low amount of mobile genetic elements in K. gyiorum genomes. Gene content variation may be important for the adaptation of K. gyiorum to different host niches. This study furthers our understanding of diversity, host adaptation, and evolution of K. gyiorum, by presenting and analyzing the first genomes of non-human isolates.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1982

Calculation of the flow field including boundary layer effects for supersonic mixed compression inlets at angles of attack

The flow field in supersonic mixed compression aircraft inlets at angle of attack is calculated. A zonal modeling technique is employed to obtain the solution which divides the flow field into different computational regions. The computational regions consist of a supersonic core flow, boundary layer flows adjacent to both the forebody/centerbody and cowl contours, and flow in the shock wave boundary layer interaction regions. The zonal modeling analysis is described and some computational results are presented. The governing equations for the supersonic core flow form a hyperbolic system of partial differential equations. The equations for the characteristic surfaces and the compatibility equations applicable along these surfaces are derived. The characteristic surfaces are the stream surfaces, which are surfaces composed of streamlines, and the wave surfaces, which are surfaces tangent to a Mach conoid. The compatibility equations are expressed as directional derivatives along streamlines and bicharacteristics, which are the lines of tangency between a wave surface and a Mach conoid.

Vadyak, J.↗
NASA NTRS1988

Aeropropulsive characteristics of isolated combined turbojet/ramjet nozzles at Mach numbers from 0 to 1.20

An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine the aeropropulsive performance characteristics (the aerodynamic quantities affected by propulsion) of 13 isolated combined turbojet/ramjet nozzle configurations. These configurations simulated the variable-geometry features of two nozzle designs designated as the multiple-expansion ramp nozzle (MERN) and the composite contour nozzle (CCN). Test data were obtained at static conditions and at Mach numbers of 0.60, 0.90, and 1.20 with jet exhaust simulated by high-pressure air. The results showed that the CCN had the higher performance over the Mach number range than the MERN, as indicated by the difference of thrust minus drag divided by ideal thrust. Increasing the ramjet throat area for the MERN resulted in an increase in performance that increased with Mach number. For the CCN at Mach numbers less than 1.20, increasing the ramjet throat area resulted in a loss in performance.

Carson, George T., Jr.↗
NASA NTRS1992

Microstrip Reflectarray Antenna

Proposed microstrip reflectarray antenna provides two or more beams in different directions, without power-dividing circuitry. Because antenna flat, mass and cost of fabrication less than paraboloidal reflector with aperture of equal size, and mounted easier with less supporting structure. Designed to be mounted on ground or surfaces of ships, land vehicles, and buildings.

Huang, John↗
NASA NTRS1992

Middle atmosphere of Venus and its clouds: Latitude and solar time variations

The structure of the middle atmosphere of Venus and its upper clouds, derived from infrared spectrometry (from 250 to 1650 cm(exp -1)) on Venera 15 are discussed. Poleward increasing of temperature, monotonous on the average, at altitudes h greater than 70 km changes to poleward decreasing at h less than 60 km. Temperature inversion at 85-95 km at low latitudes was observed as a half-day wave with two minima near 9:00 a.m. and 9:00 p.m, with a more pronounced morning feature. At high latitudes the inversion with temperature minimum near 64 km exists. There are several minima depending on solar time, but the most pronounced is one on the dayside, where the depth of inversion may reach more than 40 K (near 10:00 a.m.; we have no observations closer to noon). Another minimum is situated symmetrically on the nightside. Usually in the polar region the temperature inversion is situated deeper in the atmosphere (near 62 km). A jet at latitudes 50-55 deg N divides Venus into two drastically different latitude zones: pretty homogeneous at 56-95 km zone less than 50 deg N with diffuse clouds and daily temperature variations near cloud tops about several degrees, and zones greater than 55 deg N (where such dynamic structures as cold collar and hot dipole were observed) with dense low clouds (with the exceptions of the regions at 55-80 deg N outside the cold collar). We separate Venus into four latitudinal zones with approximate latitude boundaries, where the different IR-features were observed.

Zasova, L. V.↗
NASA NTRS1995

International GPS (Global Positioning System) Service for Geodynamics

The International GPS (Global Positioning System) Service for Geodynamics (IGS) began formal operation on January 1, 1994. This first annual report is divided into sections, which mirror different aspects of the service. Section (1) contains general information, including the history of the IGS, its organization, and the global network of GPS tracking sites; (2) contains information on the Central Bureau Information System; (3) describes the International Earth Rotation Service (IERS); (4) details collecting and distributing IGS data in Data Center reports; (6) describes how the IGS Analysis Centers generate their products; (7) contains miscellaneous contributions from other organizations that share common interests with the IGS.

Zumberge, J. F.↗
DOE OSTI2023

Hierarchical Flexibility Offering Strategy for Integrated Hybrid Resources in Real-time Energy Markets

This paper proposes a hierarchical model for determining the energy flexibility offering strategy of integrated hybrid resources (IHRs) in power distribution systems to participate in real-time energy markets. The proposed model utilizes the scalability, fast response time, and uncertainty observation of deep reinforcement learning (DRL) to overcome the scalability issue of operating numerous flexible resources and deliverability of energy flexibility to the real-time markets in the presence of the network constraints. To that end, the power distribution system is divided into multiple IHRs, where different types of flexible loads, energy storage systems, and solar plants with controllable inverters are operated through local IHR controllers, trained by deep deterministic policy gradient (DDPG) algorithm. Active power request and reactive power capacity of IHRs are then transmitted to a central flexibility controller, where a quadratic optimization model ensures the deliverability of the energy flexibility to the real-time energy market by satisfying the distribution network constraints. The proposed model is implemented on the 123-bus test power distribution system, demonstrating the capability of DRL-based hierarchical model for scalable operation of IHRs in order to offer deliverable energy flexibility to the real-time energy market.

Majidi, Majid↗
DOE OSTI2024

Mean-Field Ring Polymer Rates Using a Population Dividing Surface

Mean-field Ring Polymer Molecular Dynamics (MF-RPMD) offers a computationally efficient method for the simulation of reaction rates in multi-level systems. Previous work has established that, to model a nonadiabatic state-to-state reaction accurately, the dividing surface must be chosen to explicitly sample kinked ring polymer configurations where at least one bead is in a different electronic state than the others. Building on this, we introduce a population difference coordinate and a kink-constrained dividing surface, and we test the accuracy of the resulting mean-field rate theory on a series of bilinear coupling model systems. Here, we demonstrate that this new MF-RPMD rate approach is efficient to implement and quantitatively accurate for models over a wide range of driving forces, coupling strengths, and temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1979

Coolant tube curvature effects on film cooling as detected by infrared imagery

Reported herein are comparative thermal film cooling footprints observed by infrared imagery from straight, curved and looped coolant tube geometries. It was hypothesized that the difference in secondary flow and turbulence structure of flow through these three tubes should influence the mixing properties between the coolant and mainstream. The coolant was injected across an adiabatic plate through a hole angled at 30 deg to the surface in line with the free stream flow. The data cover a range of blowing rates from 0.37 to 1.25 (mass flow per unit area of coolant divided by free stream). Average temperature difference between coolant and tunnel air was 25 C. Data comparisons confirmed that coolant tube curvature significantly influences film cooling effectiveness.

Papell, S. S.↗
DOE OSTI2021

Multistability of isolated and hydrogenated Ga–O divacancies in β–Ga 2 O 3

This work systematically explores 19 unique configurations of the close-associate Ga–O divacancies (V Ga V O ) in β–Ga 2 O 3 , including their complexes with H impurities, using hybrid functional calculations. Interestingly, most configurations are found to retain the negative-U behavior of V O , as they exhibit a thermodynamic (–/3–) charge-state transition level energetically located in the upper part of the band gap, where the 3– charge state is associated with the formation of a Ga–Ga dimer. The energy positions of the thermodynamic (–/3–) charge-state transition levels divide the divacancy configurations into three different groups, which can be understood from the three possible Ga–Ga dimerizations resulting from the tetrahedral and octahedral Ga sites. The relative formation energies of the different divacancy configurations, and hence the electrical activity of the divacancies, is found to depend on the Fermi-level position, and the energy barriers for transformation between different divacancy configurations are explored from nudged elastic band calculations. Hydrogenation of the divacancies is found to either passivate their negative-U charge-state transition levels or shift them down in Fermi level position, depending on whether the H resides at V O or forms an O–H bond at V Ga , respectively. Finally, the divacancy is discussed as a potential origin of the so-called E$^{*}_{2}$ center previously observed by deep-level transient spectroscopy.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Length scales and scale-free dynamics of dislocations in dense solid solutions

The fundamental interactions between an edge dislocation and a random solid solution are studied by analyzing dislocation line roughness profiles obtained from molecular dynamics simulations of Fe 0.70 Ni 0.11 Cr 0.19 over a range of stresses and temperatures. These roughness profiles reveal the hallmark features of a depinning transition. Namely, below a temperature-dependent critical stress, the dislocation line exhibits roughness in two different length scale regimes which are divided by a so-called correlation length. This correlation length increases with applied stress and at the critical stress (depinning transition or yield stress) formally goes to infinity. Above the critical stress, the line roughness profile converges to that of a random noise field. Motivated by these results, a physical model is developed based on the notion of coherent line bowing over all length scales below the correlation length. Above the correlation length, the solute field prohibits such coherent line bow outs. Using this model, we identify potential gaps in existing theories of solid solution strengthening and show that recent observations of length-dependent dislocation mobilities can be rationalized.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Speciation of Mercury in Sludge Solids: Unwashed Sludge

The objective of this applied research task is to study the type and concentration of mercury compounds found within the contaminated Savannah River Site Liquid Waste System (SRS LWS). A method of selective sequential extraction (SSE), originally developed by (Eurofins) Frontier Global Sciences (FGS) and adapted by the Savannah River National Laboratory (SRNL), utilizes an extraction procedure divided into seven separate tests for different species of mercury. In the SRNL’s modified procedure four of these tests were applied to an unwashed sample of high-level radioactive waste sludge.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1974

Propagation of transverse waves in a radially expanding plasma

Investigation of the properties of low-frequency transverse waves in an expanding plasma. The wave vector, the background magnetic field, and the streaming velocity of the plasma are all assumed to lie along the radial direction. Expressions are presented for the radial dependence of the amplitude and phase of left and right circularly polarized waves, correct to first order in the wave frequency divided by the proton cyclotron frequency. Differences in the phase velocities of these two circular polarizations result in a Faraday rotation that can be substantial for typical interplanetary conditions near 1 AU. The implications of these results for a realistic solar wind model with the interplanetary magnetic field along the spiral direction are also considered.

Solodyna, C. V.↗
NASA NTRS1985

General Automatic Components of Motion Sickness

A body of investigations performed in support of experiments aboard the space shuttle, and designed to counteract the symptoms of Space Adaptation Syndrome, which resemble those of motion sickness on Earth is reviewed. For these supporting studies, the automatic manifestations of earth-based motion sickness was examined. Heart rate, respiration rate, finger pulse volume and basal skin resistance were measured on 127 men and women before, during and after exposure to nauseogenic rotating chair tests. Significant changes in all autonomic responses were observed across the tests. Significant differences in autonomic responses among groups divided according to motion sickness susceptibility were also observed. Results suggest that the examination of autonomic responses as an objective indicator of motion sickness malaise is warranted and may contribute to the overall understanding of the syndrome on Earth and in Space.

Suter, S.↗
NASA NTRS1986

General autonomic components of motion sickness

This report refers to a body of investigations directed toward the examination of autonomic nervous system responses to motion sickness. Heart rate, respiration rate, finger pulse volume, and basal skin resistance were measured on 127 men and women before, during, and after exposure to a nauseogenic rotating chair test. Significant changes in all autonomic responses were observed across the tests (p less than .05). Significant differences in autonomic responses among groups divided according to motion sickness susceptibility were also observed (p less than .05). Results suggest that the examination of autonomic responses as an objective indicator of motion sickness malaise is warranted and may contribute to the overall understanding of the syndrome.

Cowings, Patricia S.↗