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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 325 records · Page 18

BETO 2021 Peer Review - Inverse Bioproduct Design Through Machine Learning and Molecular Simulation

This work aims to identify performance advantaged bioproducts (PABPs) through property prediction, which will guide experimental synthesis. The impact of this work will be faster market adoption of bioproducts with greater performance relative to incumbent products. We have identified >106 bioproduct candidates, but only some will have superior performance to create a market pull. High-throughput property prediction, enabled by machine learning, and elucidation of structure-function relationships, enabled by molecular simulation, provide a hypothesis driven approach for down selection of candidate biomolecules to pursue experimentally. To enable machine learning and molecular simulation for bioproduct discovery, automated structure generation and embedding must capture relevant features for prediction, databases must cover domains applicable to biobased products, and best practices for simulation of polymer systems must be developed. To address these challenges, we have established bioproduct relevant datasets, developed high-throughput polymer structure generation, and built end-to-end neural networks that have predicted 8 properties for >1.4 x 106 biopolymers. A molecular simulation pipeline for building, running, and analyzing polymers and polymer additives is being used to predict performance and develop design principles of biobased products. In collaboration with the PABP synthesis project, these computational tools are guiding synthesis and informing design of PABPs.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Applications of Artificial Neural Networks in Structural Engineering with Emphasis on Continuum Models

The use of continuum models for the analysis of discrete built-up complex aerospace structures is an attractive idea especially at the conceptual and preliminary design stages. But the diversity of available continuum models and hard-to-use qualities of these models have prevented them from finding wide applications. In this regard, Artificial Neural Networks (ANN or NN) may have a great potential as these networks are universal approximators that can realize any continuous mapping, and can provide general mechanisms for building models from data whose input-output relationship can be highly nonlinear. The ultimate aim of the present work is to be able to build high fidelity continuum models for complex aerospace structures using the ANN. As a first step, the concepts and features of ANN are familiarized through the MATLAB NN Toolbox by simulating some representative mapping examples, including some problems in structural engineering. Then some further aspects and lessons learned about the NN training are discussed, including the performances of Feed-Forward and Radial Basis Function NN when dealing with noise-polluted data and the technique of cross-validation. Finally, as an example of using NN in continuum models, a lattice structure with repeating cells is represented by a continuum beam whose properties are provided by neural networks.

Kapania, Rakesh K.↗

Design and Construction of Large Size Micromegas Chambers for the ATLAS Upgrade of the Muon Spectrometer

Large area Micromegas detectors will be employed for the first time in high-energy physics experiments. A total surface of about 150 m{sup 2} of the forward regions of the Muon Spectrometer of the ATLAS detector at LHC will be equipped with 8-layer Micromegas modules. Each module extends over a surface from 2 to 3 m{sup 2} for a total active area of 1200 m{sup 2}. Together with the small strip Thin Gap Chambers they will compose the two New Small Wheels, which will replace the innermost stations of the ATLAS end-cap muon tracking system in the 2018/19 shutdown. In order to achieve a 15% transverse momentum resolution for 1 TeV muons, in addition to an excellent intrinsic resolution, the mechanical precision of each plane of the assembled module must be as good as 30 μm along the precision coordinate and 80 μm perpendicular to the chamber. In the prototyping towards the final configuration two similar quadruplets with dimensions 1.2 x 0.5 m{sup 2} have been built with the same structure as foreseen for the NSW upgrade. It represents the first example of a Micromegas quadruplet ever built, realized using the resistive-strip technology and decoupling the amplification mesh from the readout structure. All readout planes are segmented into strips with a pitch of 400 μm for a total of 4096 strips. In two of the four planes the strips are inclined by 1.5 deg. and provide a measurement of the second coordinate. The design and construction procedure of the Micromegas modules will be presented, as well as the design for the assembly of modules onto the New Small Wheel. Emphasis will be given on the methods developed to achieve the challenging mechanical precision. Measurements of deformation on chamber prototypes as a function of thermal gradients, gas over-pressure and internal stress (mesh tension and module fixation on supports) will be also shown in comparison to simulation. These tests were essential in the development of the final design in order to minimize the effects of deformations. During installation and operation all deformations and relative misalignments will be monitored through an optical alignment system and compensated in the tracking software. The optical alignment concept will also be outlined. 2 (authors)

43 PARTICLE ACCELERATORS↗

Temperature evolution of interferometer visibility in a small radius fibre coil current sensor

We have experimentally demonstrated periodic oscillations of interferometer visibility in a current sensor in response to changes in the temperature of a small-radius spun fibre sensing coil. The observed effect has been shown to depend on the magnitude of the bend-induced linear birefringence in the spun fibre in the magnetically sensitive coil and the temperature behaviour of the built-in linear birefringence in the fibre. Using a model that considers a helical structure of the built-in linear birefringence axes in spun fibre, we have shown that the above factors result in periodic oscillations of the ellipticity of polarised light at the ends of the sensing coil and that this underlies the temperature oscillations of interferometer visibility in the current sensor. The effect may cause errors in the response of a fibre-optic current sensor with a small sensing coil. (fibre-optic sensors)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Test stand for Titan 34D SRM static firing

An existing liquid engine test stand at the AF Astronautics Laboratory was refurbished and extensively modified to accommodate the static firing of the Titan 34D solid rocket motor (SRM) in the vertical nozzle down orientation. The main load restraint structure was designed and built to secure the SRM from lifting off during the firing. In addition, the structure provided weather protection, temperature conditioning of the SRM, and positioning of the measurement and recording equipment. The structure was also used for stacking/de-stacking of SRM segments and other technological processes. The existing stand, its foundation and anchorage were thoroughly examined and reanalyzed. Necessary stand modifications were carried out to comply with the requirements of the Titan 34D SRM static firing.

Glozman, Vladimir↗

Structural optimization and recent large ground antenna installations

Within the past several years, the Jet Propulsion Laboratory has designed and built major ground antenna structures in Spain, Australia, and California. One of the antennas at each location is a 70 meter-diameter structure that is a retrofit of the existing 64 meter antenna. The 64 meter existing antennas were first stripped back to a 34 meter interior and then completely new construction with deeper trusses was added to extend the interior to 70 meters. The 70 meter project included the rare opportunity to collect field data to compare with predictions of the finite-element analytical models. The new quadripod design was tested for its lower mode natural frequencies and the main reflector was measured by theodolite to determine deflections of subsets of the backup-structure deformations under load. The emphasis here is to examine measurement results and possibly provide some appreciation of the relationship of predictions made from the design model to actual measurements.

Levy, Roy↗

Materials for Energy Conversion: Materials for Energy Conversion and Storage

The main objective of this collaborative research project was to identify a formulation and develop a catalyst for electro-oxidation of ethanol. Ethanol is one of the most mass-produced biofuels, and such catalysts will enable the development of Direct Ethanol Fuel Cell technology and through it, will interconnect fuel cells with biofuels. Several catalysts for direct electrochemical oxidation of ethanol have been selected on the principles of rational desig from the knowledge build in studying aqueous oxidation of ethanol. The program involved fundamental study of ethanol oxidation in liquid media, and particularly in alakine solutions. The lessons learned from the heterogeneous catalysis of ethanol thermal oxidation have been applied to the design of an electrocatalyst for direct ethanol fuel cells. The successful chemical compositions are based on PdZn and NiZn allows. The studies reveled the role of the transition metal oxide phase as a co-catalyst and the role of the active support material. To complete the set of materials for ethanol fuel cell, this program also invested n the development of ctalysts for oxygen reduction that are selective against alcohol oxidation. Non-platinum ctalysts based on pyrolyzed macrocycles or similar composites have been studied. This program included also the development of stuctured supports as an integral part of the catalyst development. A new family of materials has been designed based on mesoporous silica templating with synthetic carbon resulting in hierarchicaly porous structure. Structure-to-property relationship of catalysis and catalysts has been the center of this program. This have been engaged in both surface and bulk level and pursued with the tools avialble at the academic institutions and at LANSCE at LANL. The structural studies have been built in interaction with a computational effort on the basis of DFT approach to materials structure and reactivity.

08 HYDROGEN↗

Synthesis, structure and optical properties of two isotypic crystals, Na{sub 3}MO{sub 4}Cl (M=W, Mo)

Two isotypic compounds, Na{sub 3}MO{sub 4}Cl (M = W, Mo) have been obtained from the high temperature solution, and their structures were determined by single-crystal X-ray diffraction. Both of them crystallize in the space group P4/nmm of tetragonal system with the unit cells: a=7.5181(15), c=5.360(2) for Na{sub 3}WO{sub 4}Cl and a=7.4942(12), c=5.3409(18) for Na{sub 3}MoO{sub 4}Cl. The structure exhibits a 3D network built up by the ClNa{sub 6} groups, and the MO{sub 4} groups reside in the tunnels of the 3D network. The structural similarities and differences between Na{sub 3}MO{sub 4}Cl (M=W, Mo) and Sr{sub 3}MO{sub 4}F (M=Al, Ga) have been discussed. Meanwhile, detailed structure comparison analyses between Na{sub 3}MO{sub 4}Cl (M=W, Mo) and Na{sub 3}MO{sub 4}F (M=W, Mo) indicate that the different connection modes of ClNa{sub 6} and FNa{sub 6} make Na{sub 3}MO{sub 4}Cl and Na{sub 3}MO{sub 4}F crystallize in different structures. The IR spectra were used to verify the validity of the structure. The diffuse reflectance spectra show that the UV absorption edges are about 249 nm (4.99 eV) and 265 nm (4.69 eV) for Na{sub 3}WO{sub 4}Cl and Na{sub 3}MoO{sub 4}Cl, respectively. In addition, the first-principles theoretical studies are also carried out to aid the understanding of electronic structures and linear optical properties. - Graphical abstract: Two isotypic compounds, Na{sub 3}MO{sub 4}Cl (M=W, Mo) have been obtained from the high temperature solution. Both of them crystallize in the space group P4/nmm of tetragonal system. The structure exhibits a 3D network built up by the ClNa{sub 6} groups, and the MO{sub 4} groups reside in the tunnels of the 3D network. - Highlights: • Structure and properties of Na{sub 3}MO{sub 4}Cl (M=W, Mo) are reported for the first time. • They show a 3D network built by ClNa{sub 6}, and WO{sub 4} lies in the tunnels of the network. • IR spectra were used to verify the validity of the structure. • Band structures and density of states have been calculated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Reduced complexity structural modeling for automated airframe synthesis

A procedure is developed for the optimum sizing of wing structures based on representing the built-up finite element assembly of the structure by equivalent beam models. The reduced-order beam models are computationally less demanding in an optimum design environment which dictates repetitive analysis of several trial designs. The design procedure is implemented in a computer program requiring geometry and loading information to create the wing finite element model and its equivalent beam model, and providing a rapid estimate of the optimum weight obtained from a fully stressed design approach applied to the beam. The synthesis procedure is demonstrated for representative conventional-cantilever and joined wing configurations.

Hajela, Prabhat↗

Querying Proofs

We motivate and introduce a query language PrQL designed for inspecting machine representations of proofs. PrQL natively supports hiproofs which express proof structure using hierarchical nested labelled trees. The core language presented in this paper is locally structured (first-order), with queries built using recursion and patterns over proof structure and rule names. We define the syntax and semantics of locally structured queries, demonstrate their power, and sketch some implementation experiments.

Aspinall, David↗

Tests of beaded and tubular structural panels

Two efficient concepts built from curved elements were identified, and a data base for tubular panels was developed. The tubular panel failure modes were understood, and the data base for these panels indicated that their performance can be predicted. The concepts are currently being tested in a realistic builtup structure; 157 room temperature tests and 67 hot tests were made with no structural failures, although all of these tests were not at the design load of the structure.

Shideler, J. L.↗

GADB: A database facility for modelling naturally occurring geophysical fields

In certain kinds of geophysical surveys, the fields are continua, but measured at discrete points referenced by their position or time of measurement. Systems of this kind are better modelled by databases built from basic data structures attuned to representing traverses across continua that are not of pre-defined fixed length. The general Array DataBase is built on arrays (ordered sequencies of data) with each array holding data elements of one type. The arrays each occupy their own physical data set, in turn inter-related by a hierarchy to other arrays over the same space/time reference points. The GADB illustrates the principle that a data facility should reflect the fundamental properties of its data, and support retrieval based on the application's view. The GADB is being tested by its use in NASA's project MAGSAT.

Dampney, C. N. G.↗

GIS Supported Optimal Site Selection for Coastal Structure Integrated Wave Energy Converters: Preprint

There is an urgent need for adaptative engineering towards more resilient coastal communities, and Coastal Structure Integrated Wave Energy Converters (CSI-WECs) are a promising solution. CSI-WECs are wave energy converters (WECs) that are built into coastal protection structures, such as breakwaters. These devices provide the dual benefits of coastal protection and local energy production, and unlike other WECs, maximizing energy production is not always the main objective. CSI-WECs are located near the shore, where the wave resource is lower, thus site selection for these devices differs from the typical offshore WECs. Other attributes of a site that may be more important than wave power include existing coastal structures, port proximity, electric transmission line proximity, and location of disadvantaged communities. Geospatial information systems (GIS) interfaces can be used to easily visualize geospatial data that represents these difference kinds of criteria important for the determination of optimal marine energy sites. Multi-Criteria Decision Analysis (MCDA) is a geospatial analysis method that allows for the evaluation of multiple, usually overlapping, criteria. This project applies GIS-based MCDA methods to two distinct case studies in Puerto Rico and California for CSI-WEC site selection. The two study sites contrast in terms of wave resource, coastal hazards, and local energy needs. This research demonstrates the utility of applying an MCDA framework within GIS to facilitate efficient site selection for devices with unique characteristics in different use cases.

coastal protection↗

A mechanism for agonist activation of the glucagon-like peptide-1 (GLP-1) receptor through modelling & molecular dynamics

Highlights: • Two structures for active-state GLP-1R have been published in 2017. • There are aspects of these structures which are incompatible with each other. • We built a hybrid model using both structures and subjected it to molecular dynamics. • We propose a mechanism for agonist-mediated receptor activation. The receptor for glucagon-like peptide 1 (GLP-1R) is a validated drug target for the treatment of type 2 diabetes and obesity. Recently the first three structures of GLP-1R were published – an X-ray structure of the apo transmembrane domain in the inactive conformation; an X-ray structure of the full-length receptor bound to a truncated peptide agonist; and a cryo-EM structure of the full-length receptor bound with GLP-1 and coupled to the G protein G{sub s}. Since the inactive structure was incomplete, and the two active-state structures shared significant differences, we utilised all available knowledge to build hybrid models of the full length active and inactive state receptors. The two models were simulated using molecular dynamics and the output trajectories analysed and compared to reveal insights into the mechanism for agonist-mediated receptor activation. His-7, Glu-9 and Asp-15 of GLP-1 act together to destabilise transmembrane helix 6 and extracellular loop 3 in order to generate an active conformation of GLP-1R.

60 APPLIED LIFE SCIENCES↗

Vibration suppression for precision segmented reflector backup structure

An ongoing effort at the JPL on vibration suppression for the Precision Segmented Reflector backup structure is centered on the vibration damping augmentation through a system consisting of active and passive damping members. An active member is a structural member with built-in piezoelectric actuator and sensors. An efficient method was developed for optimal placement of active and passive damping members in the truss-type backup structure. A simple synergistic model between the active and passive damping was proposed based on a weighted energy dissipation criterion. A baseline passive member design with constrained viscoelastic material treatment was used as the source of passive damping.

Chen, G.-S.↗

Three-Dimensional Reconstruction of Defects and Structures in Additively Manufactured Parts with Automated Serial Sectioning

Metal additive manufacturing (AM) processes have been demonstrated to be effective at reducing costs and lead times associated with complex components for space flight applications. Laser powderbed fusion (L-PBF) is a commonly used AM technology due to the ability to produce complex parts with fine feature resolution in a wide variety of alloys and applications. L-PBF, like many other manufacturing processes, can produce minor flaws in parts when in nominal operation as well as process-escape defects when process abnormalities occur. The effects of the flaws and methods of detecting the flaws are a subject of interest to understand the difficulties in detecting these flaws with current technology and how much risk the flaws or defects pose to potential flight parts. Using a RoboMet.3D automated serial sectioning system, seeded defects as well as minor process flaws can be imaged and reconstructed in three dimensions to compare to non-destructive evaluation (NDE) techniques, such as x-ray computed tomography (CT), neutron CT, and in-situ monitoring. The RoboMet automates the metallography process by automatically grinding, polishing, and imaging samples in a single system and providing the control data for NDE comparisons to know the real size of defects built into coupons. These comparisons provide an understanding behind the technological limitations of the NDE techniques for different alloys. The same serial sectioning methods have also been utilized to characterize the surfaces of parts to reconstruct the surfaces and take measurements of internal features not easily examined with non-destructive methods. Using the RoboMet, fine lattice structures built with L-PBF have been characterized to determine the actual thicknesses of struts and density of the lattice structures. These structures have been used as finer build supports for the L-PBF process, designs for fine catalysts, and other design considerations for small components. The RoboMet data helps to inform the modeling and design efforts around these fine components.

additive manufacturing↗

Structural features of ISG borosilicate nuclear waste glasses revealed from high-energy X-ray diffraction and molecular dynamics simulations

Vitrification is a widely accepted method to immobilize nuclear waste. Detailed structural information is critical to understand the physical and chemical behaviors, including the long-term chemical durability of these glasses that are to be stored in geological storage sites. High-energy X-ray diffraction studies are used to obtain accurate structural information of the International Simple Glass (ISG), a six-component borosilicate model nuclear waste glass with a composition (mol%) of 60.2SiO 2 -16.0B 2 O 3 -12.6Na 2 O-3.8Al 2 O 3 -5.7CaO-1.7ZrO 2 . Classical molecular dynamics (MD) simulations with recently developed effective potentials are utilized to generate structural models of the ISG glasses to provide interpretation of the high-energy X-ray structural data and additional short and medium range structural details. The atomic structure model generated from MD simulations shows an excellent agreement with high-energy X-ray diffraction, measured for the first time for ISG, with an R x value of 5.5%. Systematic investigations of the medium-range structural features of ISG are performed, built upon recent study of the short-range structure. In particular, the glass former cation oxygen polyhedral analysis show that [SiO 4 ]-[SiO 4 ] and [BO 4 ]-[SiO 4 ] connections are the most abundant while [ZrO 6 ] octohedra having higher probability to connect to another [SiO 4 ], [BO 4 ] and [BO 3 ]. Moreover, we have studied the ISG surface structure using MD simulations. Noticeable differences in terms of both chemical compositions and structural features between the bulk and surface are observed. There exist increased small-sized rings, under coordinated Si species, high 3-coordinated boron content (86.5%) on the surface. Very importantly, sodium ions are found to be enriched on the glass surface, consistent with recent experimental results. Furthermore, both bulk and surface structural information are discussed in terms of the dissolution and corrosion mechanisms of ISG and related nuclear waste glasses.

36 MATERIALS SCIENCE↗

Some design constraints required for the use of generic software in embedded systems: Packages which manage abstract dynamic structures without the need for garbage collection

The embedded systems running real-time applications, for which Ada was designed, require their own mechanisms for the management of dynamically allocated storage. There is a need for packages which manage their own internalo structures to control their deallocation as well, due to the performance implications of garbage collection by the KAPSE. This places a requirement upon the design of generic packages which manage generically structured private types built-up from application-defined input types. These kinds of generic packages should figure greatly in the development of lower-level software such as operating systems, schedulers, controllers, and device driver; and will manage structures such as queues, stacks, link-lists, files, and binary multary (hierarchical) trees. Controlled to prevent inadvertent de-designation of dynamic elements, which is implicit in the assignment operation A study was made of the use of limited private type, in solving the problems of controlling the accumulation of anonymous, detached objects in running systems. The use of deallocator prodecures for run-down of application-defined input types during deallocation operations during satellites.

Johnson, Charles S.↗