SEARCH · Search NASA

Results for “structured model reduction”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56

All sources NASA NTRS DOE OSTI

NASA NTRS1982

AgRISTARS. Supporting research: Algorithms for scene modelling

The requirements for a comprehensive analysis of LANDSAT or other visual data scenes are defined. The development of a general model of a scene and a computer algorithm for finding the particular model for a given scene is discussed. The modelling system includes a boundary analysis subsystem, which detects all the boundaries and lines in the image and builds a boundary graph; a continuous variation analysis subsystem, which finds gradual variations not well approximated by a boundary structure; and a miscellaneous features analysis, which includes texture, line parallelism, etc. The noise reduction capabilities of this method and its use in image rectification and registration are discussed.

Rassbach, M. E.↗

NASA NTRSDate not supplied

Effect of Micrometeoroid and Orbital Debris Impact on Modal Response of Persistent Assets

Protecting the infrastructure and payload components of persistent assets (PAs) from damage caused by MicroMeteoroid and/or Orbital Debris (MMOD) impacts is a significant design consideration. The impact resistance to MMOD will need to be provided by the robustness of the structural configuration such that the asset does not suffer loss of function or catastrophic failure. Finite element modelling (FEM) can be used to investigate the effects of MMOD impact on the overall structural behavior of the PA. The models are being used here to investigate the structural response to ‘missing’ truss members, and parametric studies are being performed to identify the worst-case scenario of an impact catastrophically damaging a truss element. These models will be used to determine which truss members are the most critical to the structural performance, and thus, which may require a higher degree of protection or robustness to ensure they can withstand an MMOD impact without causing catastrophic effects on the entire structure. Initial results have been generated indicating a reduction in the global frequency due to missing truss members as a result of MMOD impact.

in-space assembly (ISA)↗

DOE OSTI2020

Utilization of protein film electrochemistry to characterize the mechanisms imparting aerotolerance and bidirectionality in soluble, multimeric [NiFe]-hydrogenases (Final Report for Grant No. DE-SC0008074)

The overall goal of this project was to better understand how structural features control functional aspects of enzymes involved in catalysis in which a substrate is oxidized or reduced. Two types of model enzymes were explored: the soluble [NiFe]-hydrogenase from Pyrococcus furiousus and the thiosulfate reductase from Pyrobaculum aerophilum. Both are models for complex, multielectron transformations such as nitrogen and carbon dioxide reduction, and parts of important biogeochemical cycles. In this project, electrochemical methods were used to define the activities of these enzymes and targeted variants designed to modulate activity. We showed that the catalytic activity of the soluble hydrogenase from Pyrococcus furiosus can be modulated by removing large parts of the enzyme far from the active site. This surprising result suggests that interactions between functional centers far apart within the enzyme may be essential for controlling and tuning activity. We also showed that the catalytic activity of thiosulfate reductase from Pyrobaculum aerophilum can be modulated by changing the metal at the active site to be either molybdenum or tungsten. These results contribute to our understanding of how the protein environment can tune the reactivity of an embedded metal, catalytic center. The results were and are being published in peer-reviewed, scientific publications.

08 HYDROGEN↗

DOE OSTI2021

Employing Fracture Statistics to Track Cell Reliability Through Module Fabrication

In this work we demonstrate how fracture statistics may be employed to track cell reliability through module fabrication steps. We were able to detect how cell cutting equipment could reduce cell fracture strain by 25 % as well as increase its variability. A smaller reduction was found to result from the ribbon soldering operation, and all cells measured were weaker when strained in an orientation perpendicular to the gridlines. Cell fracture measurements were found to be consistent with the number of cracked cells experienced in full sized modules exposed to mechanical loading. A structural mechanics model was created to elucidate how the requisite fracture strain is developed in a cell encapsulated within a PV module and demonstrates that this strain decreases more than 50 % from its center to edge when placed within the inner loading span of four-point flexure. The associated implications on the apparent cell strength is examined with an effective volume treatment.

14 SOLAR ENERGY↗

DOE OSTI2021

Kinetically Controlled Linker Binding in Rare Earth-2,5-Dihydroxyterepthalic Acid Metal–Organic Frameworks and Its Predicted Effects on Acid Gas Adsorption

In the pursuit of highly stable and selective metal–organic frameworks (MOFs) for the adsorption of caustic acid gas species, an entire series of rare earth MOFs have been explored. Each of the MOFs in this series (RE-DOBDC; RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; DOBDC = 2,5-dihydroxyterepthalic acid) was synthesized in the tetragonal space group I4/m. Crystallized MOF samples, specifically Eu-DOBDC, were seen to have a combination of monodentate and bidentate binding when synthesized under typical reaction conditions, resulting in a contortion of the structure. However, extended crystallization times determined that this binding is kinetically controlled and that the monodentate binding option was crystallographically eliminated by extended reaction times at higher temperatures. Furthermore, this series allows for the direct study of the effect of the metal center on the structure of the of the MOF; herein, the lanthanide metal ionic radii contraction across the periodic table results in a reduction of the MOF pore size and lattice parameters. Scanning electron microscopy–energy-dispersive spectroscopy was used to investigate the stages of crystal growth for these RE-DOBDC MOFs. All MOFs, except Er-DOBDC had a minimum of two stages of growth. These analogues were demonstrated by analysis of neutron diffraction (PND) to exhibit a cooperative rotational distortion of the secondary building unit, resulting in two crystallographically distinct linker sublattices. Computational modeling efforts were used to show distinct differences on acid gas (NO 2 and SO 2 ) binding energies for RE-DOBDC MOFs when comparing the monodentate/bidentate combined linker with the bidentate-only linker crystal structures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

A Pore‐Scale Investigation of Mineral Precipitation Driven Diffusivity Change at the Column‐Scale

Abstract Mineral precipitation affects the pore structure and thus transport properties of porous media. In this study, we investigated the pore‐scale dynamics of precipitation in diffusion controlled systems and the resulting impacts on the effective diffusivity, using a micro‐continuum reactive transport model. Forty two‐dimensional pore structures representing both idealized and realistic geometries were simulated with consideration of different precipitation scenarios and rates. A homogeneous nucleation scenario reproduced patterns observed in previous experimental study showing mixing‐induced precipitation, and a surface growth scenario captured the pattern for mineral precipitation on a substrate with the same or similar mineral structures. In all cases, local precipitation resulted in the reduction in the average porosity of the domain ( Φ ) until the cessation of diffusive transport and the termination of precipitation. The minimum porosity reached was referred to as the critical porosity ( Φ c ). The effective diffusivity ( D eff ) decreased with Φ and dropped sharply to effectively zero, that is, the critical effective diffusivity ( D eff c ), as Φ c was reached. These pore‐scale dynamics can be captured by a revised relationship that explicitly considers the critical porosity and the corresponding effective diffusivity, and the pre‐exponential coefficient and the exponent of the relationship varied with initial pore structure and the precipitation kinetics. Overall, the homogeneous nucleation scenario results in systematically larger Φ c and coefficients that give rise to a sharper decrease in diffusivity as Φ c is approached, compared to the surface growth scenario. The revised relationship was also implemented at continuum scale and used to examine column scale diffusivity change and reactions.

58 GEOSCIENCES↗

DOE OSTI2014

Hard X-ray photoelectron spectroscopy of Li{sub x}Ni{sub 1−x}O epitaxial thin films with a high lithium content

The core-level and valence-band electronic structures of Li{sub x}Ni{sub 1−x}O epitaxial thin films with x = 0, 0.27, and 0.48 were studied by hard X-ray photoelectron spectroscopy. A double peak structure, consisting of a main peak and a shoulder peak, and a satellite structure were observed in the Ni 2p{sub 3/2} core-level spectra. The intensity ratio of the shoulder to main peak in this double peak structure increased with increasing lithium content in Li{sub x}Ni{sub 1−x}O. This lithium doping dependence of the Ni 2p{sub 3/2} core-level spectra was investigated using an extended cluster model, which included the Zhang–Rice (ZR) doublet bound states arising from a competition between O 2p – Ni 3d hybridization and the Ni on-site Coulomb interaction. The results indicated that the change in the intensity ratio in the main peak is because of a reduction in the ZR doublet bound states from lithium substitutions. This strongly suggests that holes compensating Li doping in Li{sub x}Ni{sub 1−x}O are of primarily ZR character.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Impact of nonadiabatic charge transfer on the rate of redox chemistry of carbon oxides on rutile TiO2 (110) surface

We present the results of a density functional theory (DFT) within the LDA+U approximation on large models of partially reduced TiO2 (110) rutile surface to investigate the nature of charge transfer and the role of non-adiabatic effects on three prototypical redox reactions: (i) O2 adsorption (ii) CO oxidation and (iii) CO2 reduction. Charge-constrained DFT (cDFT) is used to estimate kinetic parameters for a Marcus theory rate law that accounts for adiabatic coupling effects on reaction rates. We find that for O2 adsorption, the coupling between adiabatic states is strong, leading to fast charge transfer rates. The lowest energy structures at high coverage consist of two chemisorbed O2-, one adsorbed at a VO site and the other adsorbed at an adjacent Ti5C site. For CO oxidation, however, all reactions are kinetically hindered on the ground state due to the weak adiabatic coupling at the state crossing, such that one has to overcome two kinetically unfavorable charge transfer events to drive the process (non-adiabatically) on the thermal ground state. The process can be driven by photochemical means but would result in an adsorbed radical [OCOO-] intermediate species. Similarly, CO2 reduction also proceeds via a non-adiabatic charge transfer to form an adsorbed CO2- species followed by a second non-adiabatic charge transfer to produce CO. Our analysis provides important computational guidelines for modeling these types of processes. We thank Z. Dohnalek, M. Hendersen, G. Kimmel, H. Metieu, and N. Petrik for invaluable discussions. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences and performed at the Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated for DOE by Battelle. Computational resources were provided at W. R. Wiley Environmental Molecular Science Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at PNNL and the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.

charge transfer↗

DOE OSTI2023

Compressing the Cosmological Information in One-dimensional Correlations of the Lyman-$\alpha$ Forest

Observations of the Lyman-α forest from spectroscopic surveys such as the Baryon Oscillation Spectroscopic Survey or its extension, eBOSS, or the ongoing Dark Energy Spectroscopic Instrument (DESI) survey offer a unique window to study the growth of structure on megaparsec scales. Interpretation of these measurements is a complicated task, requiring hydrodynamical simulations to model and marginalize over the thermal and ionization state of the intergalactic medium. This complexity has limited the use of Lyα clustering measurements in joint cosmological analyses. In this work we show that the cosmological information content of the one-dimensional power spectrum (P 1D ) of the Lyman-α forest can be compressed into a simple two-parameter likelihood without any significant loss of constraining power. We simulate P 1D measurements from DESI using hydrodynamical simulations and show that the compressed likelihood is model independent and lossless, recovering unbiased results even in the presence of massive neutrinos or running of the primordial power spectrum.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2019

Network Modeling of the U.S. Petrochemical Industry under Raw Material and Hurricane Harvey Disruptions

A geographically resolved network model of the U.S. chemical industry in 2017 is designed, and optimal chemical flows between units are calculated using linear programming. A baseline solution and three disruption scenarios (primary raw material disruptions, reported Hurricane Harvey ethylene cracker disruptions, and assumed capacity disruptions based on the Hurricane Harvey geographic storm track) are reported on to determine how the structure of the industry is modified to adapt to widespread and geographically specific disruptions. The calculated impacts of the assumed Hurricane Harvey disruption include 170 chemical units in 26 states that change production level as a result of supply chain disruptions during the storm. The systemic impact for the assumed Hurricane Harvey disruption is 19.3 million tonnes of gross chemical production. The day with the largest impact on gross chemical production shows a reduction from baseline operations of 1.3 million tonnes (42% of baseline). This model can be utilized for analysis of future disruption scenarios and to test resilience strategies, including impacts of new manufacturing configurations or technologies.

02 PETROLEUM↗

DOE OSTI2021

Insights into the thermal decomposition of plutonium(IV) oxalate – a DFT study of the intermediate structures

The thermal decomposition of plutonium oxalate to oxide is one of the most studied reactions in actinide chemistry but the intermediates have been the subject of debate for decades. Recent experimental data suggest that the decomposition of Pu(IV) oxalate in air undergoes dehydration first, then reduction to Pu(III) oxalate. The precise structural modifications that take place are unknown as experiments have not been able to fully characterize the intermediates at the microscopic level. To rectify this, we employed solid state density functional theory calculations at the PBE-D3 level with a Hubbard U correction to model the structures and energetics of potential dehydrated Pu(IV) and Pu(III) oxalate intermediate compounds. Based on the theoretical study presented here, the anhydrous analogues of the known hydrated Pu(IV) and Pu(III) oxalates are the preferred crystal structures formed through an overall exothermic reaction process. However, decomposition could proceed through the formation of a higher energy, more complicated 3D lattice structure with frustrated oxalate binding. It is expected that the intermediates presented here could be identified using spectroscopic techniques to enable further insight into the reaction mechanism.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2019

Vehicle energy consumption estimation using large scale simulations and machine learning methods

Vehicle energy consumption and powertrain operations for future vehicle powertrain technologies are predicted through full-vehicle simulations using Autonomie, a simulation tool developed at Argonne National Laboratory. Over 1 million vehicles, with different powertrain types (conventional and numerous electrified powertrains) and component technologies (advanced engines, batteries, electrical machines, light weighting) are simulated for outputs including vehicle fuel economy and cost. Despite the ability of Autonomic to predict fuel economy given various combination of vehicle inputs, the full-vehicle simulation is very time-consuming. It takes approximately 84 h to simulate for 33,060 vehicles even using distributed computing on a cluster of 128 worker nodes. Moreover, Autonomic is unable to populate a continuous output space through simulation since it only yields outputs with discrete values instead of an input-output relation. This paper proposes a novel large-scale learning and prediction process (LSLPP) via machine learning approaches to answer the need for a continuous space of vehicle fuel economy and a more efficient simulation process. By learning in a supervised fashion to discover structures in data, the machine learning approaches seek to train a model that can explain the data with which we can perform prediction over unseen data. As such, we are able to accomplish analytic continuation on the current discrete space of simulation results. In addition, we present a random sampling -based numerosity reduction algorithm incorporated in LSLPP that reduces simulation runs and improves efficiency of data procurement. We analytically derive a theoretical bound in order to guarantee the effectiveness of our algorithm. We also compare random sampling to stratified sampling and suggest sampling strategies. A user-friendly tool is developed to support the process. Our experimental results confirm that the proposed LSLPP is able to greatly accelerate prediction and analysis of vehicle fuel economy. The output of this study is used by the US government to evaluate the impact of its R&D funding on energy security and CO 2 emission as well as for the setting of Corporate Average Fuel Economy (CAFE) standards.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2025

Bayesian calibration of irradiated graphite property models under high temperatures

Graphite under high temperatures and irradiation is central to advanced reactors. We develop a Bayesian calibration framework for graphite property models that explicitly represents model-data mismatch via a Gaussian-process discrepancy. The approach propagates uncertainty from parameters, experimental noise, and model form, with a hierarchical variance structure to capture group and cross-group noise. Using two predictive models across five grades (IG-110, NBG-18, PCEA, NBG-17, 2114) and four properties-irradiation-induced dimension change, creep, Young’s modulus change ratio, and coefficient of thermal expansion change ratio-we obtain average predictive-error reductions of 54%, 65%, 17%, and 17% when discrepancy is included. We illustrate engineering impact with a multiphysics model of a very-high-temperature reactor prismatic reflector brick, analyzing stresses under high fluence and temperature. Accounting for model discrepancy markedly improves predictive accuracy and provides a robust basis for reliable graphite component design in advanced reactors.

36 - MATERIALS SCIENCE↗

DOE OSTI2017

ISO 50001 and SEP Faster and Cheaper - Exploring the Enterprise-Wide Approach

ISO 50001 and other management systems (e.g., ISO 9001 and ISO 14001) allow for implementation and certification at the enterprise level. The "Central Office" concept, which allows a small group of employees to manage and facilitate the organization’s energy management system (EnMS) at the enterprise level, was introduced within the ISO 50003 standard to provide guidance to ISO 50001 certification bodies. Four industrial companies have partnered with the United States Department of Energy to pilot the enterprise-wide ISO 50001/SEP concept under the Better Buildings Superior Energy Performance (SEP) Enterprise-wide Accelerator. Each organization developed a Central Office to host their EnMS while implementing ISO 50001/SEP at multiple physically separated sites. The four corporate partners tailored their Central Office implementation model to meet their own specific circumstances and needs. This paper reviews the commonalities, differences, and benefits of each of these enterprise-wide implementation models, including organizational structures, Central Office staff responsibilities, and key strategies. The cost savings and benefits of using the enterprise-wide approach were assessed, including the cost per site compared with that of a conventional, single-site ISO 50001/SEP implementation approach. This paper also discusses the drivers for the cost reductions realized through these enterprise-wide approaches. The four partner companies worked with 30 total sites. On average, these 30 sites improved energy performance by 5% annually over their SEP achievement periods, saved more than $600,000 annually in energy costs and reduced implementation cost for ISO 50001 and SEP by $19,000 and 0.8 Full Time Equivalent × years (FTE-yr) of staff time per site. The results can inform other organizations seeking to implement enterprise-wide ISO 50001/SEP, as well as energy efficiency organizations seeking to promote wider adoption of ISO 50001 implementation.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2024

Zero-Emissions Roadmap for Oakland County

This document outlines a strategic pathway for Oakland County, Michigan to achieve zero emissions by 2050 under the Clean Energy to Communities (C2C) Program. The report encompasses analyses and high-level modeling to guide Oakland County in its emission reduction goals. Key methods include establishing an emissions inventory baseline with ongoing evaluation of future projects’ emissions impacts. Core elements include decommissioning old infrastructure, enhancing energy efficiency, deploying hybrid and ground-source heat pumps, and transitioning to electric fleets. It is proposed to structure the planning process into 5-year strategic plans to make the decarbonization process manageable. The document also emphasizes the need for reassessment of goals and periodic updates to remain adaptive to technological advancements and funding considerations. A matrixed approach for evaluating projects by cost and emissions savings is suggested to optimize decision-making given finite resources.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

NASA NTRS1971

Static and Dynamic Analysis, F-14A Boron Horizontal Stabilizer

A static stress analysis and a dynamic modal analysis of the horizontal stabilizer of the F-14A aircraft has been conducted at the Naval Air Development Center employing the NASTRAN program. The structural model contains 1518 elements including bars, rods, shear panels and orthotropic and isotropic membrane elements with 1357 degrees of freedom. Static deflection and stresses, including thermal stresses, under maximum load at room and at elevated temperatures are calculated and results are in good agreement with experimental data. Through application of "Guyan Reduction" the number of degrees of freedom used in the dynamic analysis is reduced to 137 . The frequencies and mode shapes for the first two modes are obtained .

S. L. Huang↗

NASA NTRS2014

Hybrid-Wing-Body Vehicle Composite Fuselage Analysis and Case Study

Recent progress in the structural analysis of a Hybrid Wing-Body (HWB) fuselage concept is presented with the objective of structural weight reduction under a set of critical design loads. This pressurized efficient HWB fuselage design is presently being investigated by the NASA Environmentally Responsible Aviation (ERA) project in collaboration with the Boeing Company, Huntington Beach. The Pultruded Rod-Stiffened Efficient Unitized Structure (PRSEUS) composite concept, developed at the Boeing Company, is approximately modeled for an analytical study and finite element analysis. Stiffened plate linear theories are employed for a parametric case study. Maximum deflection and stress levels are obtained with appropriate assumptions for a set of feasible stiffened panel configurations. An analytical parametric case study is presented to examine the effects of discrete stiffener spacing and skin thickness on structural weight, deflection and stress. A finite-element model (FEM) of an integrated fuselage section with bulkhead is developed for an independent assessment. Stress analysis and scenario based case studies are conducted for design improvement. The FEM model specific weight of the improved fuselage concept is computed and compared to previous studies, in order to assess the relative weight/strength advantages of this advanced composite airframe technology

Mukhopadhyay, Vivek↗

DOE OSTI2018

Friction Stir Scribe Joining of Carbon Fiber Reinforced Polymer (CFRP) to Aluminum

The purpose of this project was to develop the critical process technology, models, and tools necessary to advance the Friction Stir Scribe, FSS, joining method through experimentation, validation at the laboratory scale, and integration into a production-like robotic environment. Implementation of FSS technology for joining polymer composites to metals will enable greater use of lightweight materials by providing technology capable of joining linear configurations without the use of adhesives or other third-body fasteners by creating an in-situ joint from the parent materials. As FSS technology provides the capability to join multi-material structures on robotic platforms using linear configurations, the development of this technology for use on the BIW will impact a great diversity of CFRP joints within the vehicle; thus, allowing a greater reduction in vehicle mass through more specifically designed structures. The FSS process has been developed to include integration of the FSS tool with a stationary shoulder, which has been shown to be required to achieve the desired surface quality (i.e., crown flash level). However, the targeted joint strength has not been achieved because the resulting stirred CFRP microstructure does not provide similar performance as the as-molded composite leading to low fracture strengths despite our efforts investigating various unique alternative approaches. In support of the experimental work, a process-structure model was developed and validated for the FSS joining (FSSJ) process using surrogate materials (steel and Al). The cyclic corrosion testing of the FSS joints and self-piercing riveted (SPR) joints revealed different modes of galvanic corrosion in the two types of joints. The SPR samples exhibited a greater amount of corrosion on the external surfaces. The presence of steel rivets in these joints exacerbated the situation, with the rivets getting preferentially corroded. The FSSJ samples despite exhibiting less surface corrosion, exhibited severe corrosion under the joint overlap area.

36 MATERIALS SCIENCE↗