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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Prony Ringdown GUI (CERTS Prony Ringdown, part of the DSI Tool Box)

The PNNL Prony Ringdown graphical user interface is one analysis tool included in the Dynamic System Identification toolbox (DSI Toolbox). The Dynamic System Identification toolbox is a MATLAB-based collection of tools for parsing and analyzing phasor measurement unit data, especially in regards to small signal stability. It includes tools to read the data, preprocess it, and perform small signal analysis. 5. Method of Solution: The Dynamic System Identification Toolbox (DSI Toolbox) is designed to provide a research environment for examining phasor measurement unit data and performing small signal stability analysis. The software uses a series of text-driven menus to help guide users and organize the toolbox features. Methods for reading in populate phasor measurement unit data are provided, with appropriate preprocessing options for small-signal-stability analysis. The toolbox includes the Prony Ringdown GUI and basic algorithms to estimate information on oscillatory modes of the system, such as modal frequency and damping ratio.

Tuffner, Francis↗
NASA NTRS1989

Optimizing Locations Of Nodes To Reduce Vibrations

Distribution of mass modified to move nodes to desired locations. Modal shaping proposed as method to reduce structural vibration. Current optimization technique deals with placement of nodal points, related to modal shaping and consists of modifying distribution of mass of structure to place node of mode at desired location. Key to procedure; analysis of sensitivity of locations of nodes, provides straightforward expressions for derivatives of locations of nodes.

Adelman, Howard M.↗
NASA NTRS2002

Major Element Analysis of the Target Rocks at Meteor Crater, Arizona

We collected approximately 400 rock chips in continuous vertical profile at Meteor Crater, Arizona, representing, from bottom to top, the Coconino, Toroweap, Kaibab, and Moenkopi Formations to support ongoing compositional analyses of the impact melts and their stratigraphic source depth(s) and other studies at Meteor Crater that depend on the composition of the target rocks. These rock chips were subsequently pooled into 23 samples for compositional analysis by XRF (x ray fluorescence) methods, each sample reflecting a specific stratigraphic "subsection" approximately 5-10 in thick. We determined the modal abundance of quartz, dolomite, and calcite for the entire Kaibab Formation at vertical resolutions of 1-2 meters. The Coconino Formation composes the lower half of the crater cavity. It is an exceptionally pure sandstone. The Toroweap is only two inches thick and compositionally similar to Coconino, therefore, it is not a good compositional marker horizon. The Kaibab Formation is approximately 80 in thick. XRD (x ray diffraction) studies show that the Kaibab Formation is dominated by dolomite and quartz, albeit in highly variable proportions; calcite is a minor phase at best. The Kaibab at Meteor Crater is therefore a sandy dolomite rather than a limestone, consistent with pronounced facies changes in the Permian of SE Arizona over short vertical and horizontal distances. The Moenkopi forms the 12 in thick cap rock and has the highest Al2O3 and FeO concentrations of all target rocks. With several examples, we illustrate how this systematic compositional and modal characterization of the target ideologies may contribute to an understanding of Meteor Crater, such as the depth of its melt zone, and to impact cratering in general, such as the liberation of CO2 from shocked carbonates.

See, Thomas H.↗
DOE OSTI2020

System and method for automated extraction of high resolution structural dynamics from video

A method for extracting vibrational modes of a structure includes: receiving a plurality of video frames, each of the video frames including a plurality of pixels; decomposing each of the video frames on a plurality of spatial scales in accordance with complex steerable pyramid filters to obtain a filter response for each of the spatial scales; computing a plurality of local phases of the pixels of each frame; removing a temporal mean from each frame to obtain a plurality of factored vibration motion functions; performing principal component analysis on the factored vibration motion functions to obtain principal components; blind source separating the principal components to compute a plurality of modal coordinates; computing frequency and damping ratios in accordance with the modal coordinates; and outputting the computed frequency and damping ratios.

42 ENGINEERING↗
DOE OSTI2018

Nano-structural analysis of engrafted human induced pluripotent stem cell-derived cardiomyocytes in mouse hearts using a genetic-probe APEX2

Many studies have shown the feasibility of in vivo cardiac transplantation of human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) in animal experiments. However, nano-structural confirmation of the successful incorporation of the engrafted iPSC-CMs including electron microscopy (EM) has not been accomplished, partly because identification of graft cells in EM has proven to be difficult. Using APEX2, an engineered ascorbate peroxidase imaging tag, we successfully localized and analyzed the fine structure of sarcomeres and the excitation contraction machinery of iPSC-CMs 6 months after their engraftment in infarcted mouse hearts. APEX2 made iPSC-CMs visible in multiple imaging modalities including light microscopy, X-ray microscopic tomography, transmission EM, and scanning EM. EM tomography allowed assessment of the differentiation state of APEX2-positive iPSC-CMs and analysis of the fine structure of the sarcomeres including T-tubules and dyads.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Reachability analysis of linear dynamic systems with constant, arbitrary, and Lipschitz continuous inputs

This paper sets forth a method for reachability analysis of linear dynamic systems in continuous time that can be used to compute time-domain bounds of states and outputs with floating-point precision. The focus is on the particular initial conditions and inputs that cause state or output trajectories to attain their extreme values in time. Inputs can be constant, arbitrary, or Lipschitz continuous waveforms. Uncertainties in initial conditions and inputs are modeled using zonotopes. The calculations exploit the definition of zonotopes and the modal information of the linear system dynamics.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2017

In Situ Chemical Imaging of Solid-Electrolyte Interphase Layer Evolution in Li–S Batteries

Parasitic reactions of electrolyte and polysulfide with the Li-anode in lithium sulfur (Li-S) batteries lead to the for-mation of solid electrolyte interphase (SEI) layers, which are the major reason behind severe capacity fading in these systems. Despite numerous studies, the evolution mechanism of the SEI layer and specific roles of polysulfides and oth-er electrolyte components are still unclear. We report an in-situ X-ray photoelectron spectroscopy (XPS) and chemical imaging analysis combined with ab initio molecular dynamics (AIMD) computational modeling to gain fundamental understanding regarding the evolution of SEI layers on Li-anodes within Li-S batteries. A multi-modal approach in-volving AIMD modeling and in-situ XPS characterization uniquely reveals the chemical identity and distribution of active participants in parasitic reactions as well as the SEI layer evolution mechanism. The SEI layer evolution has three major stages: the formation of a primary composite mixture phase involving stable lithium compounds (Li2S, LiF, Li2O etc); and formation of a secondary matrix type phase due to cross interaction between reaction products and elec-trolyte components, which is followed by a highly dynamic mono-anionic polysulfide (i.e. LiS5) fouling process. These new molecular-level insights into the SEI layer evolution on Li- anodes are crucial for delineating effective strategies for the development of Li–S batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

A call to standardize metrics for monitoring baleen whales near marine construction activities

Effective monitoring is necessary to protect marine mammal species during the construction of offshore infrastructure. The tools for detecting or monitoring marine mammals span traditional (e.g., visual observers, optical cameras), to newer (e.g., passive acoustic monitoring, infrared cameras, tags), and emerging (e.g., satellite imagery, environmental DNA, dimethyl sulfide concentration) technologies. Some are better suited for use during offshore development; however, peer-reviewed literature does not typically evaluate and report on the performance of these various technologies. We define a minimum set of metrics related to efficacy (i.e., confusion matrix, precision and recall, probability of missed mitigation), detection range (i.e., maximum and reliable detection range, spatial resolution), and data delivery (i.e., detection latency, system reliability, temporal resolution) that we recommend are needed to assess the utility of monitoring technologies for this purpose. Following a literature review of relevant studies, we highlight which publications reported these metrics and used multiple technologies to compare relative performance. We also emphasize the benefits of multi-modal approaches and recommend performance assessments through modeling or large-scale collaborative field testing. These metrics will standardize data collection, reporting, and analysis; promote consistent and comparable results; and foster collaboration among developers, regulatory agencies, and scientists. This may lead to the co-development of technology that achieves multiple goals, has greater application, and can answer research questions while collecting data to fulfill permitting requirements. These metrics may also inform decisions on what systems regulatory agencies might consider using and reduce monitoring costs, which is critical to support the marine sector's rapid growth alongside marine mammal conservation.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1975

Nonlinear resonances in a class of multi-degree-of-freedom systems

An analysis is presented of the superharmonic, subharmonic, and combination resonances in a multi-degree-of-freedom system which has cubic nonlinearity and modal viscous damping and is subject to harmonic excitation. It is shown that, in the absence of internal resonances, the steady-state response contains only the modes which are directly excited. It is shown that, in the presence of internal resonances, modes other than those that are directly excited can appear in the response. The strong influence of internal resonances is exhibited in numerical examples involving hinged-clamped beams. It is shown that when a multimode solution exists the lowest mode can dominate the response, even when it is not directly excited.

Sridhar, S.↗
NASA NTRS1987

Self-consistent analysis of gain saturation in channeled-substrate-planar double-heterojunction lasers

A self-consistent model for semiconductor lasers (using the channeled-substrate-planar (CSP) double-heterojunction (DH) laser as an example) which does not assume constant optical power along the laser axis is developed. This approach allows for the analysis of high-power lasers with low facet reflectivities which produce nonuniform photon densities along the propagation direction. Analytical equations for the modal gain coefficient, the threshold current density, and the radiated power for a specific CSP laser structure are obtained.

Butler, Jerome K.↗
NASA NTRS1994

Active magnetic bearing control loop modeling for a finite element rotordynamics code

A mathematical model of an active electromagnetic bearing which includes the actuator, the sensor and the control system is developed and implemented in a specialized finite element code for rotordynamic analysis. The element formulation and its incorporation in the model of the machine are described in detail. A solution procedure, based on a modal approach in which the number of retained modes is controlled by the user, is then shown together with other procedures for computing the steady-state response to both static and unbalance forces. An example of application shows the numerical results obtained on a model of an electric motor suspended on a five active-axis magnetic suspension. The comparison of some of these results with the experimental characteristics of the actual system shows the ability of the present model to predict its performance.

Genta, Giancarlo↗
NASA NTRS2002

Contrast and harmonic imaging improves accuracy and efficiency of novice readers for dobutamine stress echocardiography

BACKGROUND: Newer contrast agents as well as tissue harmonic imaging enhance left ventricular (LV) endocardial border delineation, and therefore, improve LV wall-motion analysis. Interpretation of dobutamine stress echocardiography is observer-dependent and requires experience. This study was performed to evaluate whether these new imaging modalities would improve endocardial visualization and enhance accuracy and efficiency of the inexperienced reader interpreting dobutamine stress echocardiography. METHODS AND RESULTS: Twenty-nine consecutive patients with known or suspected coronary artery disease underwent dobutamine stress echocardiography. Both fundamental (2.5 MHZ) and harmonic (1.7 and 3.5 MHZ) mode images were obtained in four standard views at rest and at peak stress during a standard dobutamine infusion stress protocol. Following the noncontrast images, Optison was administered intravenously in bolus (0.5-3.0 ml), and fundamental and harmonic images were obtained. The dobutamine echocardiography studies were reviewed by one experienced and one inexperienced echocardiographer. LV segments were graded for image quality and function. Time for interpretation also was recorded. Contrast with harmonic imaging improved the diagnostic concordance of the novice reader to the expert reader by 7.1%, 7.5%, and 12.6% (P < 0.001) as compared with harmonic imaging, fundamental imaging, and fundamental imaging with contrast, respectively. For the novice reader, reading time was reduced by 47%, 55%, and 58% (P < 0.005) as compared with the time needed for fundamental, fundamental contrast, and harmonic modes, respectively. With harmonic imaging, the image quality score was 4.6% higher (P < 0.001) than for fundamental imaging. Image quality scores were not significantly different for noncontrast and contrast images. CONCLUSION: Harmonic imaging with contrast significantly improves the accuracy and efficiency of the novice dobutamine stress echocardiography reader. The use of harmonic imaging reduces the frequency of nondiagnostic wall segments.

Non-NASA Center↗
NASA NTRS1978

Stability analysis of a liquid fuel annular combustion chamber

High frequency combustion instability problems in a liquid fuel annular combustion chamber are examined. A modified Galerkin method was used to produce a set of modal amplitude equations from the general nonlinear partial differential acoustic wave equation in order to analyze the problem of instability. From these modal amplitude equations, the two variable perturbation method was used to develop a set of approximate equations of a given order of magnitude. These equations were modeled to show the effects of velocity sensitive combustion instabilities by evaluating the effects of certain parameters in the given set of equations.

Mcdonald, G. H.↗
NASA NTRS2019

Nonmodal Growth of TravelingWaves on Blunt Cones at Hypersonic Speeds

The existing database of transition measurements in hypersonic ground facilities has established that, as the nosetip bluntness is increased, the onset of boundary layer transition over a circular cone at zero angle of attack shifts downstream. However, this trend is reversed at sufficiently large values of the nose Reynolds number, so that the transition onset location eventually moves upstream with a further increase in nose-tip bluntness. Because modal amplification is too weak to initiate transition at moderate-to-large bluntness values, nonmodal growth has been investigated as the potential basis for a physics-based model for the frustum transition. The present analysis investigates the nonmodal growth of traveling disturbances initiated within the nose-tip vicinity that peak within the entropy layer. Results show that, with increasing nose bluntness, both planar and oblique traveling disturbances experience appreciable energy amplification up to successively higher frequencies. For moderately blunt cones, the initial nonmmodal growth is followed by a partial decay that is more than overcome by an eventual, modal growth as Mack-mode waves. For larger bluntness values, the Mack-mode waves are not amplified anywhere upstream of the experimentally measured transition location, but the traveling modes still undergo a significant amount of nonmodal growth. This finding does not provide a definitive link between optimal growth and the onset of transition, but it is qualitatively consistent with the experimental observations that frustum transition in the absence of sufficient Mack-mode amplification implies a double peak in disturbance amplification and the appearance of transitional events above the boundary-layer edge.

Hypersonic speed↗
NASA NTRS1992

Middeck zero-gravity dynamics experiment - Comparison of ground and flight test data

An analytic and experimental study of the changes in the modal parameters of space structural test articles from one- to zero-gravity is presented. Deployable, erectable, and rotary modules was assembled to form three one- and two-dimensional structures, in which variations in bracing wire and rotary joint preload could be introduced. The structures were modeled as if hanging from a suspension system in one gravity, and unconstrained, as if free floating in zero-gravity. The analysis is compared with ground experimental measurements, made on a spring/wire suspension system with a nominal plunge frequency of one Hertz, and with measurements made on the Shuttle middeck. The degree of change in linear modal parameters as well as the change in nonlinear nature of the response is examined. Trends in modal parameters are presented as a function of force amplitude, joint preload, and ambient gravity level.

Crawley, Edward F.↗
DOE OSTI2013

Chaotic dynamics of flexible Euler-Bernoulli beams

Mathematical modeling and analysis of spatio-temporal chaotic dynamics of flexible simple and curved Euler-Bernoulli beams are carried out. The Kármán-type geometric non-linearity is considered. Algorithms reducing partial differential equations which govern the dynamics of studied objects and associated boundary value problems are reduced to the Cauchy problem through both Finite Difference Method with the approximation of O(c{sup 2}) and Finite Element Method. The obtained Cauchy problem is solved via the fourth and sixth-order Runge-Kutta methods. Validity and reliability of the results are rigorously discussed. Analysis of the chaotic dynamics of flexible Euler-Bernoulli beams for a series of boundary conditions is carried out with the help of the qualitative theory of differential equations. We analyze time histories, phase and modal portraits, autocorrelation functions, the Poincaré and pseudo-Poincaré maps, signs of the first four Lyapunov exponents, as well as the compression factor of the phase volume of an attractor. A novel scenario of transition from periodicity to chaos is obtained, and a transition from chaos to hyper-chaos is illustrated. In particular, we study and explain the phenomenon of transition from symmetric to asymmetric vibrations. Vibration-type charts are given regarding two control parameters: amplitude q{sub 0} and frequency ω{sub p} of the uniformly distributed periodic excitation. Furthermore, we detected and illustrated how the so called temporal-space chaos is developed following the transition from regular to chaotic system dynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Merkel Cell Carcinoma: 27-Year Experience at the Peter MacCallum Cancer Centre

Purpose: To retrospectively evaluate the treatment outcome of patients with Merkel cell carcinoma after local and/or regional treatment. Methods and Materials: Patients presenting to our center between January 1980 and July 2006 with Merkel cell carcinoma and without distant metastases were reviewed. The primary endpoint was locoregional control. Secondary endpoints were distant recurrence, survival and treatment toxicity. Results: A total of 176 patients were identified. The median age was 79 years. The median follow-up was 2.2 years for all patients and 3.9 years for those alive at the last follow-up visit. The most common primary site was the head and neck (56%), and 62 patients(35%) had regional disease at presentation. The initial surgery to the primary tumor involved (wide) local excision in 140 patients and biopsy only in 28 patients (8 patients had no identifiable primary tumor); 33 patients underwent nodal surgery. Of the 176 patients, 165 (94%) underwent radiotherapy (RT) and 29 of them also underwent concurrent chemotherapy. The median radiation dose was 50 Gy (range, 18-60). Locoregional recurrence developed in 33 patients(19%), with a median interval to recurrence of 8 months. Distant metastases developed in 43 patients(24%). Age, primary tumor size, and RT (no RT vs. <45 Gy vs. {>=}45 Gy) were predictive of locoregional control on univariate analysis. However, only RT remained significant on multivariate analysis. The estimated 5-year actuarial rate for locoregional control, progression-free survival, and overall survival was 76%, 60%, and 45%, respectively. Conclusion: The locoregional control rate for Merkel cell carcinoma in our study was comparable to those from other series using combined modality treatment with RT an integral part of treatment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

Radiation Therapy for Primary Cutaneous Anaplastic Large Cell Lymphoma: An International Lymphoma Radiation Oncology Group Multi-institutional Experience

Purpose: To collect response rates of primary cutaneous anaplastic large cell lymphoma, a rare cutaneous T-cell lymphoma, to radiation therapy (RT), and to determine potential prognostic factors predictive of outcome. Methods and Materials: The study was a retrospective analysis of patients with primary cutaneous anaplastic large cell lymphoma who received RT as primary therapy or after surgical excision. Data collected include initial stage of disease, RT modality (electron/photon), total dose, fractionation, response to treatment, and local recurrence. Radiation therapy was delivered at 8 participating International Lymphoma Radiation Oncology Group institutions worldwide. Results: Fifty-six patients met the eligibility criteria, and 63 tumors were treated: head and neck (27%), trunk (14%), upper extremities (27%), and lower extremities (32%). Median tumor size was 2.25 cm (range, 0.6-12 cm). T classification included T1, 40 patients (71%); T2, 12 patients (21%); and T3, 4 patients (7%). The median radiation dose was 35 Gy (range, 6-45 Gy). Complete clinical response (CCR) was achieved in 60 of 63 tumors (95%) and partial response in 3 tumors (5%). After CCR, 1 tumor recurred locally (1.7%) after 36 Gy and 7 months after RT. This was the only patient to die of disease. Conclusions: Primary cutaneous anaplastic large cell lymphoma is a rare, indolent cutaneous lymphoma with a low death rate. This analysis, which was restricted to patients selected for treatment with radiation, indicates that achieving CCR was independent of radiation dose. Because there were too few failures (<2%) for statistical analysis on dose response, 30 Gy seems to be adequate for local control, and even lower doses may suffice.

62 RADIOLOGY AND NUCLEAR MEDICINE↗