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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Coupled nonlinear elasticity, plastic slip, twinning, and phase transformation in single crystal titanium for plate impact loading

High purity single crystal titanium (Ti) under shockwave loading in plate impact experiment is modelled and simulated, with help of the finite element. A thermodynamically consistent system of equations is formulated in the frame of large deformation to consider material anisotropy, rate dependence, and multi-physics including nonlinear elasticity, dislocation based plastic slip, deformation twinning, and phase transformation. A novel kinematics is proposed to consider phase transformation in the α twin variants and also to consider the dislocation based slip in all of components of parent material, primary twins and the ω phase. The thermodynamically consistent driving forces for plastic slip, twinning, and phase transformation are developed based upon the second law of thermodynamics. For nonlinear elasticity, the stiffness matrix is dependent on the volume fractions of all components, and the volumetric part of Cauchy stress is obtained from the nonlinear equation of state. Dislocation based plastic slip in multi-variant and multiphase heterogeneous materials is developed and interactions of dislocations among all slip modes are taken into account. A mechanism for dislocation density evolution during twinning and phase transformation is proposed. The shock loading along the [0001] and [10$\bar{1}1$ directions of single crystal high purity Ti is investigated computationally. Very good correspondence between simulation and experiment is obtained, which includes pole figures, volume fractions of components, free surface velocity, peak pressure, and phase transformation pressure. Multiple experimental phenomena are interpreted based upon the progression of dislocation slip, deformation twinning, and phase transformation. In compression with the [10$\bar{1}1$ crystal, a higher volume fraction in the primary twins but a lower secondary twin volume fraction in the [0001] crystal in experiment was observed. Finally, the higher propensity for phase transformation occurs in the [0001] crystal is reproduced. In addition to material texture, distributions of temperature, stresses, and plastic strains dependent on the impact loading directions are revealed.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Accelerated aging test of new plastic scintillators

Fogging in plastic scintillators is a degradation mechanism that reduces light collection efficiency. In an effort to reduce maintenance costs, multiple groups have attempted to understand and prevent this problem by changing plastic compositions and system level designs. New formulations have been produced that are promising with respect to fogging resistance. In this paper, we study a variety of new compositions by subjecting them to an accelerated aging experiment with varying temperature and humidity profiles. Compositions are analyzed for their resistance to degradation after saturation periods, with those containing polymethyl methacrylate and divinyl benzene being the most promising. Pulse height spectra revealed that after environmental aging, many of the samples suffered a reduction in light yield to different degrees, a result that could be due to heating of the samples and may be prevented by further production optimization.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Optimal placement of data concentrators for expansion of the smart grid communications network

Evolving power systems with increasing renewables penetration, along with the development of the smart grid, calls for improved communication networks to support these distributed generation sources. Automatic and optimal placement of communication resources within the advanced metering infrastructure is critical to provide a high‐performing, reliable, and resilient power system. Three network design formulations based on mixed‐integer linear and non‐linear programming approaches are proposed to minimise network congestion by optimising residual buffer capacity through the placement of data concentrators and network routeing. Results on a case study show that the proposed models improve network connectivity and robustness, and increase average residual buffer capacity. Maximising average residual capacity alone, however, results in both oversaturated and underutilised nodes, while maximising either minimum residual capacity or total reciprocal residual capacity can yield much‐improved network load allocation. Consideration of connection redundancy improves network reliability further by ensuring quality‐of‐service in the event of an outage. Analysis of multi‐period network expansion shows that the models do not deviate significantly from optimal when used progressively (within 5% deviation), and are effective for utility planners to use for smart grid expansion.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2014

Current density partitioning in time-dependent current density functional theory

We adapt time-dependent current density functional theory to allow for a fragment-based solution of the many-electron problem of molecules in the presence of time-dependent electric and magnetic fields. Regarding a molecule as a set of non-interacting subsystems that individually evolve under the influence of an auxiliary external electromagnetic vector-scalar potential pair, the partition 4-potential, we show that there are one-to-one mappings between this auxiliary potential, a sharply-defined set of fragment current densities, and the total current density of the system. The partition electromagnetic (EM) 4-potential is expressed in terms of the real EM 4-potential of the system and a gluing EM 4-potential that accounts for exchange-correlation effects and mutual interaction forces between fragments that are required to yield the correct electron dynamics. We prove the zero-force theorem for the fragmented system, establish a variational formulation in terms of action functionals, and provide a simple illustration for a charged particle in a ring.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

MHD effects and heat transfer for the UCM fluid along with Joule heating and thermal radiation using Cattaneo-Christov heat flux model

Present study examines the numerical analysis of MHD flow of Maxwell fluid with thermal radiation and Joule heating by considering the recently developed Cattaneo-Christov heat flux model which explains the time relaxation characteristics for the heat flux. The objective is to analyze the governing parameters such as viscoelastic fluid parameter, Magnetic parameter, Eckert and Prandtl number’s impact on the velocity and temperature profiles through graphs and tables. Suitable similarity transformations have been used to reduce the formulated PDEs into a system of coupled non-linear ODEs. Shooting technique has been invoked for finding the numerical solutions of the dimensionless velocity and temperature profiles. Additionally, the MATLAB built-in routine bvp4c has also been used to verify and strengthen the results obtained by shooting method. From some special cases of the present work, a comparison with the previously published results has been presented.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Sub-system quantum dynamics using coupled cluster downfolding techniques

In this paper, we discuss extending the sub-system embedding sub-algebra coupled cluster (SES-CC) formalism and the double unitary coupled cluster (DUCC) ansatz to the time domain. As we demonstrated in earlier studies, it is possible, using these formalisms, to calculate the energy of the entire system as an eigenvalue of downfolded/effective Hamiltonian in the active space, that is identifiable with the sub-system of the composite system. In these studies, we demonstrated that downfolded Hamiltonians integrate out Fermionic degrees of freedom that do not correspond to the physics encapsulated by the active space. We extend these results to the time-dependent Schrödinger equation, showing that a similar construct is possible to partition a system into a sub-system that varies slowly in time and a remaining subsystem that corresponds to fast oscillations. This time dependent formalism allows coupled cluster quantum dynamics to be extended to larger systems and for the formulation of novel quantum algorithms based on the quantum Lanczos approach, which have recently been considered in the literature.

coupled cluster, Electron correlation, quantum dyn↗
DOE OSTI2015

Impacts of Time Delays on Distributed Algorithms for Economic Dispatch

Economic dispatch problem (EDP) is an important problem in power systems. It can be formulated as an optimization problem with the objective to minimize the total generation cost subject to the power balance constraint and generator capacity limits. Recently, several consensus-based algorithms have been proposed to solve EDP in a distributed manner. However, impacts of communication time delays on these distributed algorithms are not fully understood, especially for the case where the communication network is directed, i.e., the information exchange is unidirectional. This paper investigates communication time delay effects on a distributed algorithm for directed communication networks. The algorithm has been tested by applying time delays to different types of information exchange. Several case studies are carried out to evaluate the effectiveness and performance of the algorithm in the presence of time delays in communication networks. It is found that time delay effects have negative effects on the convergence rate, and can even result in an incorrect converge value or fail the algorithm to converge.

Yang, Tao↗
DOE OSTI2013

Resonant excitation of intense acoustic waves in crystals

The resonant excitation of an intense elastic wave through nonspecular reflection of a special pump wave in a crystal is described. The choice of the plane and angle of incidence is dictated by the requirement that the excited reflected wave be close to the bulk eigenmode with its energy flow along a free boundary. The resonance parameters have been found for a medium with an arbitrary anisotropy. General relations are concretized for monoclinic, rhombic, and hexagonal systems. A criterion is formulated for an optimal selection of crystals in which the resonant reflection is close to the conversion one, when almost all of the energy from the incident beam of the pump wave falls into the near-surface narrow high-intensity reflected beam. Estimates and illustrations are given for such crystals as an example. The intensity of the reflected beam increases with its narrowing, but its diffraction divergence also increases with this narrowing. Nevertheless, the intensity of the beam can be increased by a factor of 5-10 at sufficiently high frequencies while keeping its divergence at an acceptable level. Amplification by two orders of magnitude can be achieved by compressing the beam in two dimensions through its double reflection.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Design Progress for the 22 GeV CEBAF Energy Upgrade

Extending the energy reach of CEBAF up to 22 GeV within the existing tunnel is being explored. Proposed energy upgrade can be achieved by increasing the number of recirculations, while using the existing CEBAF SRF cavity system. A proposal was formulated to raise CEBAF energy by replacing the highest-energy arcs with FFA arcs. The new pair of arcs configured with FFA (Fixed Field Alternating Gradient) lattice would support simultaneous transport of additional 6 passes with energies spanning a factor of two, using the non-scaling FFA principle implemented with Halbach-derived permanent magnets - a novel magnet technology that significantly saves energy and lowers operating costs. The design involves new optics for the linacs and remaining electromagnetic arcs, as well as new electromagnetic switchyard. These feed into the permanent magnet FFA arcs. We also report on ongoing beam dynamics studies and mitigating measures to alleviate energy loss and emittance dilution due to synchrotron radiation.

Bogacz, Alex [Thomas Jefferson National Accelerato↗
DOE OSTI2013

Computational model for autophagic vesicle dynamics in single cells

Macroautophagy (autophagy) is a cellular recycling program essential for homeostasis and survival during cytotoxic stress. This process, which has an emerging role in disease etiology and treatment, is executed in four stages through the coordinated action of more than 30 proteins. An effective strategy for studying complicated cellular processes, such as autophagy, involves the construction and analysis of mathematical or computational models. When developed and refined from experimental knowledge, these models can be used to interrogate signaling pathways, formulate novel hypotheses about systems, and make predictions about cell signaling changes induced by specific interventions. Here, we present the development of a computational model describing autophagic vesicle dynamics in a mammalian system. We used time-resolved, live-cell microscopy to measure the synthesis and turnover of autophagic vesicles in single cells. The stochastically simulated model was consistent with data acquired during conditions of both basal and chemically induced autophagy. The model was tested by genetic modulation of autophagic machinery and found to accurately predict vesicle dynamics observed experimentally. Furthermore, the model generated an unforeseen prediction about vesicle size that is consistent with both published findings and our experimental observations. Taken together, this model is accurate and useful and can serve as the foundation for future efforts aimed at quantitative characterization of autophagy.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1972

Development of the Air Transport Industry

The major developments are outlined in the U.S. scheduled air transport industry both domestic and international, together with a brief history of the European air transport system. The role and formulation of the U.S. Civil Aeronautics Board, International Civil Aviation Organization, and International Air Transport Association are also covered.

Taneja, N.↗
NASA NTRS1973

Control of spin ambiguity during reorientation of an energy dissipating body

A quasi-rigid body initially spinning about its minor principal axis and experiencing energy dissipation will enter a tumbling mode and eventually reorient itself such that stable spin about its major principal axis is achieved. However, in this final state the body may be spinning in a positive or negative sense with respect to its major axis and aligned in a positive or negative sense with the inertially fixed angular momentum vector. This ambiguity can be controlled only through an active system. The associated dynamical formulations and simulations of uncontrolled reorientations are presented. Three control schemes are discussed and results offered for specific examples. These schemes include displacement of internal masses, spinning up of internal inertia, and reaction jets, all of which have demonstrated the ability to control spin ambiguity.

Kaplan, M. H.↗
NASA NTRS1974

Results from computer program for analyzing scattered light suppression systems for large space telescope

A computer program was developed which has the ability to analyze the performance of most light suppression systems so as to predict the amount of scattered light which will reach the image plane for various conditions of unwanted light input from the sun, earth, or moon. This program was used to analyze three different configurations of the large space telescope (LST): an LST with a truncated sunshield, an LST with an extended cylindrical sunshield, and an LST with a conical sunshield which is tilted upwards. The computer program gives the user detailed information as to the paths taken by the unwanted stray light to reach the image plane, and pinpoints those portions of the light suppression system which contribute most of the stray light, so that areas requiring improvements are evident. Certain design guide lines were formulated for any light suppression system selected for the LST, and one which meets these requirements (the tilted sunshade) is described in detail.

Tifft, W. G.↗
NASA NTRS1976

LANDSAT D instrument module study

Spacecraft instrument module configurations which support an earth resource data gathering mission using a thematic mapper sensor were examined. The differences in size of these two experiments necessitated the development of two different spacecraft configurations. Following the selection of the best-suited configurations, a validation phase of design, analysis and modelling was conducted to verify feasibility. The chosen designs were then used to formulate definition for a systems weight, a cost range for fabrication and interface requirements for the thematic mapper (TM).

Source record↗
NASA NTRS1977

NASTRAN hydroelastic modal studies. Volume 3: NASTRAN 3-D hydroelastic analysis and MESHGEN user's manuals

The method used to formulate the fluid/structure equations is described in the updates to the NASTRAN Theoretical Manual. The basis for defining the fluid are three dimensional finite elements connected to fluid grid points defining the Eulerian pressure at a point fixed in space. The use of a pressure single degree of freedom at each point rather than three displacements allows a finer mesh of elements with a reasonable matrix order. In the formulation of the fluid/structure system the interior fluid degrees of freedom are transformed and removed from the solution matrices. The eigenvalues of the combination are extracted from small, fully dense, symmetric mass and stiffness matrices, efficiently processed with the Givens method. The solution matrices are defined by the free surface displacements and the reduced structure coordinates.

Source record↗
NASA NTRS1983

Space Shuttle contamination measurements from flights STS-1 through STS-4

Results of contamination measurements performed on the initial four flights of the Space Shuttle Orbiter are summarized and compared with requirements contained in the Space Shuttle Flight and Ground System Specifications and those formulated by the Contamination Requirements Definition Group. In general, the results of measurements carried out with the induced environment contamination monitor indicate that molecular fluxes, deposition rates, and average counts of particulates are within the requirements and close to predicted values. Among the exceptions, were such special circumstances as water dumps, payload bay door closures, and RCS engine, APU, and flash evaporator operations which led to molecular and particulate contamination levels exceeding the limits. In cases where these circumstances would interfere with sensitive payload operations, careful mission planning to preclude a contamination source by operational limitation should be done to avoid losses.

Ehlers, H. K. F.↗