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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 523 records · Page 29

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DOE OSTI2023

Causal interaction in high frequency turbulence at the biosphere–atmosphere interface: Structure–function coupling

At the biosphere–atmosphere interface, nonlinear interdependencies among components of an ecohydrological complex system can be inferred using multivariate high frequency time series observations. Information flow among these interacting variables allows us to represent the causal dependencies in the form of a directed acyclic graph (DAG). Here, we use high frequency multivariate data at 10 Hz from an eddy covariance instrument located at 25 m above agricultural land in the Midwestern US to quantify the evolutionary dynamics of this complex system using a sequence of DAGs by examining the structural dependency of information flow and the associated functional response. We investigate whether functional differences correspond to structural differences or if there are no functional variations despite the structural differences. We base our analysis on the hypothesis that causal dependencies are instigated through information flow, and the resulting interactions sustain the dynamics and its functionality. To test our hypothesis, we build upon causal structure analysis in the companion paper to characterize the information flow in similarly clustered DAGs from 3-min non-overlapping contiguous windows in the observational data. We characterize functionality as the nature of interactions as discerned through redundant, unique, and synergistic components of information flow. Through this analysis, we find that in turbulence at the biosphere–atmosphere interface, the variables that control the dynamic character of the atmosphere as well as the thermodynamics are driven by non-local conditions, while the scalar transport associated with CO and H 2 O is mainly driven by short-term local conditions.

58 GEOSCIENCES↗

DOE OSTI2020

Structure-based enzyme engineering improves donor-substrate recognition of Arabidopsis thaliana glycosyltransferases

Glycosylation of secondary metabolites involves plant UDP-dependent glycosyltransferases (UGTs). UGTs have shown promise as catalysts in the synthesis of glycosides for medical treatment. However, limited understanding at the molecular level due to insufficient biochemical and structural information has hindered potential applications of most of these UGTs. In the absence of experimental crystal structures, we employed advanced molecular modeling and simulations in conjunction with biochemical characterization to design a workflow to study five Group H Arabidopsis thaliana (76E1, 76E2, 76E4, 76E5, 76D1) UGTs. Based on our rational structural manipulation and analysis, we identified key amino acids (P129 in 76D1; D374 in 76E2; K275 in 76E4), which when mutated improved donor substrate recognition than wildtype UGTs. Molecular dynamics simulations and deep learning analysis identified structural differences, which drive substrate preferences. The design of these UGTs with broader substrate specificity may play important role in biotechnological and industrial applications. These findings can also serve as basis to study other plant UGTs and thereby advancing UGT enzyme engineering.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2024

Accelerating uncertainty quantification in incremental dynamic analysis using dimension reduction-based surrogate modeling

We propose a surrogate modeling framework based on dimension reduction to facilitate the quantification of seismic risk of structural systems in performance-based earthquake engineering. The framework adopts incremental dynamic analysis (IDA) for addressing hazard variability, and promotes significant computational efficiency improvement for propagating epistemic uncertainties associated with the structural models. It utilizes both linear and nonlinear dimension reduction approaches, equipped with inverse mappings, to learn a functional between the input parameter space (e.g., the epistemic uncertainties of the structure) to the high-dimensional output space created through the IDA implementation across different ground motions and seismic intensity levels. Polynomial chaos expansion is adopted as the surrogate model to learn this functional in the reduced space. A nine-story steel moment-resisting frame with uncertain structural properties is used as a testbed. Furthermore, we select the seismic fragility curves as a measure of the structure’s seismic performance, since it provides an estimate of the probability of entering specified damage states for given levels of ground shaking.

42 ENGINEERING↗

NASA NTRS1993

Analysis of passive damping in thick composite structures

Computational mechanics for the prediction of damping and other dynamic characteristics in composite structures of general thicknesses and laminations are presented. Discrete layer damping mechanics that account for the representation of interlaminar shear effects in the material are summarized. Finite element based structural mechanics for the analysis of damping are described, and a specialty finite element is developed. Applications illustrate the quality of the discrete layer damping mechanics in predicting the damped dynamic characteristics of composite structures with thicker sections and/or laminate configurations that induce interlaminar shear. The results also illustrate and quantify the significance of interlaminar shear damping in such composite structures.

Saravanos, D. A.↗

DOE OSTI2022

Molecular determinants of pH sensing in the proton-activated chloride channel

In response to acidic pH, the widely expressed proton-activated chloride (PAC) channel opens and conducts anions across cellular membranes. By doing so, PAC plays an important role in both cellular physiology (endosome acidification) and diseases associated with tissue acidosis (acid-induced cell death). Despite the available structural information, how proton binding in the extracellular domain (ECD) leads to PAC channel opening remains largely unknown. Here, through comprehensive mutagenesis and electrophysiological studies, we identified several critical titratable residues, including two histidine residues (H130 and H131) and an aspartic acid residue (D269) at the distal end of the ECD, together with the previously characterized H98 at the transmembrane domain–ECD interface, as potential pH sensors for human PAC. Mutations of these residues resulted in significant changes in pH sensitivity. Some combined mutants also exhibited large basal PAC channel activities at neutral pH. By combining molecular dynamics simulations with structural and functional analysis, we further found that the β12 strand at the intersubunit interface and the associated “joint region” connecting the upper and lower ECDs allosterically regulate the proton-dependent PAC activation. Our studies suggest a distinct pH-sensing and gating mechanism of this new family of ion channels sensitive to acidic environment.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1975

Analytical displacements and vibrations of cantilevered unsymmetric fiber composite laminates

A fiber composite flat cantilever plate that has symmetric and nonsymmetric laminate configurations is theoretically investigated to determine its static and dynamic structural response. The finite element analysis method used includes a unique triangular finite element developed at Lewis for the analysis of fiber composite airfoils. The various responses investigated include tip displacements, natural frequencies, and fundamental mode shapes. The results show that the displacements and the natural frequencies can be in considerable error for nonsymmetric laminate configurations if the membrane-bending coupling is not taken into account. Structural response results obtained from ten laminate configurations are presented in tabular forms and may be used as an aid in selecting laminate configurations for composite airfoils.

Minich, M. D.↗

NASA NTRS1975

Analytical displacements and vibrations of cantilevered unsymmetric fiber composite laminates

A fiber composite flat cantilever plate that has symmetric and nonsymmetric laminate configurations is theoretically investigated to determine its static and dynamic structural response. The finite element analysis method used includes a unique triangular finite element developed at Lewis for the analysis of fiber composite airfoils. The various responses investigated include tip displacements, natural frequencies, and fundamental mode shapes. The results show that laminate configurations may be selected for a cantilever such that when the tip at the leading edge is loaded normal to the plane of the plate, the tip at the trailing edge can (1) deflect in the opposite direction, (2) deflect about the same, or (3) deflect more than the tip at the leading edge. This variation in response can be utilized to provide built-in structural damping to resist flutter.

Minich, M. D.↗

NASA NTRS1976

Advances in engineering science, volume 2

Papers are presented dealing with structural dynamics; structural synthesis; and the nonlinear analysis of structures, structural members, and composite structures and materials. Applications of mathematics and computer science are included.

Source record↗

NASA NTRS1989

Infrared imaging of the coma of Comet Wilson

The brightness of the nuclear condensation noted in March 13-15, 1987 thermal IR images of Comet Wilson did not vary, in contrast to Comet Halley's behavior; a dynamical analysis of the dust coma/tail structure establishes that the particle size distribution in this comet, while different from that of Comet Giacobini-Zinner, is nevertheless more similar to that in Comet Halley. The nonisotropic character of the dust ejection is taken to be evidence for prograde rotation of the nucleus, and it is speculated that Comet Wilson is too young to have developed a dust mantle; this would account for the lack of short time scale variability.

Campins, Humberto↗

NASA NTRS2004

Fluid Structure Interaction in a Turbine Blade

An unsteady, three dimensional Navier-Stokes solution in rotating frame formulation for turbomachinery applications is presented. Casting the governing equations in a rotating frame enabled the freezing of grid motion and resulted in substantial savings in computer time. The turbine blade was computationally simulated and probabilistically evaluated in view of several uncertainties in the aerodynamic, structural, material and thermal variables that govern the turbine blade. The interconnection between the computational fluid dynamics code and finite element structural analysis code was necessary to couple the thermal profiles with the structural design. The stresses and their variations were evaluated at critical points on the Turbine blade. Cumulative distribution functions and sensitivity factors were computed for stress responses due to aerodynamic, geometric, mechanical and thermal random variables.

Gorla, Rama S. R.↗

NASA NTRS2006

Microthruster Propulsion for the Space Technology 7 (ST7) Technology Demonstration Mission

For future applications to precision formation flying missions, NASA's New Millennium Program is scheduled to test colloid micro-Newton thrusters (CMNTs) on the ST7 technology demonstration mission. These CMNTs are part of a disturbance reduction system (DRS) on the ESA SMART-2 Spacecraft or LISA Pathfinder. The goal of the ST7 DRS is to demonstrate technologies necessary to meet the nanometer precision positioning control requirements of the LISA mission. In order to achieve these goals, the CMNTs are required to demonstrate a thrust resolution of less than 0.1 micro-N and a thrust noise of less than 0.1 micro-N/[square root]Hz for thrust levels between 5 and 30 micro-N. Developed by Busek Co. with support from JPL in testing an design, the CMNT has been developed over the last four years into a flight-ready microthrust system. The development, validation testing, and flight unit production of the CMNTs are described. Development tests and analysis include preliminary wear tests, propellant loading process verification, flow testing, and performance verification. Validation and flight unit verification includes thermal and structural analysis, life testing, thermal and dynamic load testing, and performance verification. Final delivery of the units is planned in 2007 with and planned launch and flight demonstration 2009.

microthruster↗

NASA NTRS2010

Investigation of Alternative Return Strategies for Orion Trans-earth Injection Design Options

The purpose of this study is to investigate alternative return strategies for the Orion trans-Earth injection (TEI) phase. A dynamical systems analysis approach considers the structure of the stable and unstable Sun perturbed Earth-Moon manifolds near the Earth-Moon interface region. A hybrid approach, then, combines the results from this analysis with classical two-body methods in a targeting process that seeks to expand the window of return opportunities in a precision entry scenario. The resulting startup arcs can be used, for instance, to enhance the block set of solutions available onboard during an autonomous targeting process.

Marchand, Belinda G.↗

NASA NTRS2011

Three-Dimensional Model for Preservation and Restoration of Architectural Heritage

Thc aim of the research will be to create a model, three-dimensional mathematical. implementation. consultation and assistance to "large" restoration projects that will assist the structural analysis, allowing easier display of dynamic strain. analysis and lighting noise. It could also be a valuable tool for decision support. therefore. may simulate several possible scenarios for intervention, This model appears therefore an excellent support for recovering. ordering and monitoring information about materials and data (stage of restoration. photographs. sampling points. results of diagnostic tests, etc.) collected dynamically during the "life" of the cultural heritage. allowing to document its complete history

Marchis, Elena↗

NASA NTRS2023

A Finite Element Approach for Simplified 2D Nonlinear Dynamic Contact/Impact Analysis

In this paper, a simplified numerical approach for finite element dynamic analysis of an inelastic solid structure subjected to solid object impact is presented. The approach approximates the impacting solid as the selected multiple nodes, for which mass of the impactor is distributed. The node-to-segment contact formulation with the penalty constraint technique incorporated is employed to impose contact conditions between the nodes and the surface of the receiver structure. The node-to-segment algorithm is integrated into Newton–Raphson time integration scheme and the Lagrange multiplier technique is applied to enforce the identical displacements for the selected nodes throughout the analysis process. The approach is verified using two-dimensional plane strain models considering elastic-perfectly-plastic material behavior. The results obtained using the proposed approach are in a good agreement with those simulated using a commercial finite element code, ABAQUS dynamic/implicit, in terms of displacements and stress distribution fields. The proposed approach is shown to be computationally superior to general finite element method-based contact/impact analysis without significantly sacrificing the accuracy.

Seungwook Seok↗

NASA NTRS1987

Recent advances in structural dynamics of large space structures

Recent progress in the area of structural dynamics of large space structures is reviewed. Topics include system identification, large angle slewing of flexible structures, definition of scaling limitations in structural models, and recent results on a tension-stabilized antenna concept known as the hoop-column. Increasingly complex laboratory experiments guide most of the activities leading to realistic technological developments. Theoretical progress in system identification based on system realization theory resulting in unification of several methods is reviewed. Experimental results from implementation of a theoretical large-angle slewing control approach are shown. Status and results of the development of a research computer program for analysis of the transient dynamics of large angle motion of flexible structures are presented. Correlation of results from analysis and vibration tests of the hoop-column antenna concepts are summarized.

Pinson, Larry D.↗

NASA NTRS1987

Recent advances in structural dynamics of large space structures

Pinson, Larry D.↗

NASA NTRS1987

Coherent structures: Comments on mechanisms

There is now overwhelming evidence that in most turbulent flows there exist regions moving with the flow where the velocity and vorticity have a characteristic structure. These regions are called coherent structures because within them the large-scale distributions of velocity and/or vorticity remain coherent even as these structures move through the flow and interact with other structures. Since the flow enters and leaves the bounding surfaces of these structures, a useful definition for coherent structures is that they are open volumes with distinctive large-scale vorticity distributions. Possible fruitful directions for the study of the dynamics of coherent structures are suggested. Most coherent structures research to data was concentrated on measurement and kinematical analysis; there is now a welcome move to examine the dynamics of coherent structures, by a variety of different methods. A few of them will be described.

Hunt, J. C. R.↗

NASA NTRS2000

Probabilistic Multi-Scale, Multi-Level, Multi-Disciplinary Analysis and Optimization of Engine Structures

Aircraft engines are assemblies of dynamically interacting components. Engine updates to keep present aircraft flying safely and engines for new aircraft are progressively required to operate in more demanding technological and environmental requirements. Designs to effectively meet those requirements are necessarily collections of multi-scale, multi-level, multi-disciplinary analysis and optimization methods and probabilistic methods are necessary to quantify respective uncertainties. These types of methods are the only ones that can formally evaluate advanced composite designs which satisfy those progressively demanding requirements while assuring minimum cost, maximum reliability and maximum durability. Recent research activities at NASA Glenn Research Center have focused on developing multi-scale, multi-level, multidisciplinary analysis and optimization methods. Multi-scale refers to formal methods which describe complex material behavior metal or composite; multi-level refers to integration of participating disciplines to describe a structural response at the scale of interest; multidisciplinary refers to open-ended for various existing and yet to be developed discipline constructs required to formally predict/describe a structural response in engine operating environments. For example, these include but are not limited to: multi-factor models for material behavior, multi-scale composite mechanics, general purpose structural analysis, progressive structural fracture for evaluating durability and integrity, noise and acoustic fatigue, emission requirements, hot fluid mechanics, heat-transfer and probabilistic simulations. Many of these, as well as others, are encompassed in an integrated computer code identified as Engine Structures Technology Benefits Estimator (EST/BEST) or Multi-faceted/Engine Structures Optimization (MP/ESTOP). The discipline modules integrated in MP/ESTOP include: engine cycle (thermodynamics), engine weights, internal fluid mechanics, cost, mission and coupled structural/thermal, various composite property simulators and probabilistic methods to evaluate uncertainty effects (scatter ranges) in all the design parameters. The objective of the proposed paper is to briefly describe a multi-faceted design analysis and optimization capability for coupled multi-discipline engine structures optimization. Results are presented for engine and aircraft type metrics to illustrate the versatility of that capability. Results are also presented for reliability, noise and fatigue to illustrate its inclusiveness. For example, replacing metal rotors with composites reduces the engine weight by 20 percent, 15 percent noise reduction, and an order of magnitude improvement in reliability. Composite designs exist to increase fatigue life by at least two orders of magnitude compared to state-of-the-art metals.

Chamis, Christos C.↗