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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1961

Methods for Determining Blood Flow Through Intact Vessels of Experimental Animals Under Conditions of Gravitational Stress and in Extraterrestrial Space Capsules

Work during the initial six months of this program has proceeded along three lines: (1) technical development of blood flowmeter instrumentation: (2) surgical considerations related to special problems of chronic implantation of flowmeter probes: (3) study of the relationship between levels of blood flow and organ activity. Principal engineering effort has been focused on the fundamental phenomena operative in the flowmeter probe and on probe design. Two probes have been constructed and a third is nearing completion. A previously unrecognized source of zero drift has been discovered and corrected. has been designed, assembled, tested and successfully employed in work on the several probes. A significant innovation which has been introduced is the use of a transformer coupled input for suppression of unwanted common mode signals. New low noise transistor amplifiers with characteristics suitable for space vehicle packaging are being developed. Linearity of the present apparatus has been found to extend at least into the near turbulent flow region. Attention has been directed to the two vascular beds of physiologic interest that present particular problems with regard to chronic implantation of flowmeter probes, the myocardium and the liver. Surgical techniques have been perfected that will permit myocardial and liver blood flow measurement. Two groups of animals have successfully undergone surgery and await the implantation of probes. Studies of the relationship between organ blood flow and levels of physiologic activity have been initiated. The first organ system studied was the heart, For the first time autoregulatory mechanisms have been demonstrated within the myocardial vascular bed which rapidly and precisely maintain coronary blood flow at a level i n keeping with the magnitude of cardiac work, Following a summary statement of the status of the program, the work performed is described, A financial review of expenditures incurred and a proposal for future funding are appended,

Shaw, R. F.↗
DOE OSTI2025

Efficient analysis of magnetic field line behavior in toroidal plasmas

The confinement of plasmas in tokamaks and stellarators depends on magnetic field lines lying in nested toroidal surfaces. The transition near the plasma edge away from the lines lying in magnetic surfaces defines properties of divertors. The transition in time defines properties of disruptions. Divertor design and disruption analyses require a detailed understanding of these transitions. The use of a Fourier transform coupled with a Gaussian window function allows far more information to be extracted about these transitions using far shorter field line integrations than can be obtained using traditional methods based on Poincaré plots. The physics of divertors and disruptions is reviewed to clarify why the type of information that can be gained from more efficient methods of analysis is of central importance to the fusion program based on magnetic confinement.

Boozer, Allen H. [Columbia Univ., New York, NY (Un↗
NASA NTRS1973

An iterative approach to the feature selection problem

The B-average divergence for m-distinct classes, resulting from the linear transformation y = Bx, is proposed as a feature selection criterion, where B is a k by n matrix of rank k not greater than n. It is shown that if the B-average divergence resulting from B is large enough, then the probability of misclassification, considered as a function f the class of all k by n matrices, is essentially minimized by B. A computer program, utilizing a gradient procedure, is developed to numerically maximize the B-average divergence and results are presented for the Cl flight line. For this example, corresponding to 9-distinct classes, most of the discriminatory information is found to lie in a 3-dimensional subspace, defined by an appropriately chosen 3 by 12 matrix B.

Decell, H. P., Jr.↗
NASA NTRS1978

Identification of the stability parameters of an aeroelastic airplane

Phase variable transformations are used to construct the mathematical model of an aeroelastic aircraft in a form that is amenable to partial or piecemeal acceptance of parameters estimated from flight data. The problem is one of parameter identification of large scale dynamic systems involving a system matrix characterized by about 200 elements. A mathematical model of the USAF Total In-Flight Simulator was computed using the FLEXSTAB program. As data became available during the progress of the flight test program, it was processed and substituted in the mathematical model for parameters obtained from the FLEXSTAB program. Results tend to show a progressive and orderly transition from an analytically defined mathematical model to one obtained from the flight tests of the actual aircraft.

Rynaski, E. G.↗
NASA NTRS1978

Computer quantitation of coronary angiograms

A computer technique is being developed at the Jet Propulsion Laboratory to automate the measurement of coronary stenosis. A Vanguard 35mm film transport is optically coupled to a Spatial Data System vidicon/digitizer which in turn is controlled by a DEC PDP 11/55 computer. Programs have been developed to track the edges of the arterial shadow, to locate normal and atherosclerotic vessel sections and to measure percent stenosis. Multiple frame analysis techniques are being investigated that involve on the one hand, averaging stenosis measurements from adjacent frames, and on the other hand, averaging adjacent frame images directly and then measuring stenosis from the averaged image. For the latter case, geometric transformations are used to force registration of vessel images whose spatial orientation changes.

Ledbetter, D. C.↗
NASA NTRS1993

Proposed data compression schemes for the Galileo S-band contingency mission

The Galileo spacecraft is currently on its way to Jupiter and its moons. In April 1991, the high gain antenna (HGA) failed to deploy as commanded. In case the current efforts to deploy the HGA fails, communications during the Jupiter encounters will be through one of two low gain antenna (LGA) on an S-band (2.3 GHz) carrier. A lot of effort has been and will be conducted to attempt to open the HGA. Also various options for improving Galileo's telemetry downlink performance are being evaluated in the event that the HGA will not open at Jupiter arrival. Among all viable options the most promising and powerful one is to perform image and non-image data compression in software onboard the spacecraft. This involves in-flight re-programming of the existing flight software of Galileo's Command and Data Subsystem processors and Attitude and Articulation Control System (AACS) processor, which have very limited computational and memory resources. In this article we describe the proposed data compression algorithms and give their respective compression performance. The planned image compression algorithm is a 4 x 4 or an 8 x 8 multiplication-free integer cosine transform (ICT) scheme, which can be viewed as an integer approximation of the popular discrete cosine transform (DCT) scheme. The implementation complexity of the ICT schemes is much lower than the DCT-based schemes, yet the performances of the two algorithms are indistinguishable. The proposed non-image compression algorith is a Lempel-Ziv-Welch (LZW) variant, which is a lossless universal compression algorithm based on a dynamic dictionary lookup table. We developed a simple and efficient hashing function to perform the string search.

Cheung, Kar-Ming↗
NASA NTRS2004

HSCT Sector Combustor Evaluations for Demonstration Engine

In LET Task 10, critical development issues of the HSCT lean-burn low emissions combustor were addressed with a range of engineering tools. Laser diagnostics and CFD analysis were applied to develop a clearer understanding of the fuel-air premixing process and premixed combustion. Subcomponent tests evaluated the emissions and operability performance of the fuel-air premixers. Sector combustor tests evaluated the performance of the integrated combustor system. A 3-cup sector was designed and procured for laser diagnostics studies at NASA Glenn. The results of these efforts supported the earlier selection of the Cyclone Swirler as the pilot stage premixer and the IMFH (Integrated Mixer Flame Holder) tube as the main stage premixer of the LPP combustor. In the combustor system preliminary design subtask, initial efforts to transform the sector combustor design into a practical subscale engine combustor met with significant challenges. Concerns about the durability of a stepped combustor dome and the need for a removable fuel injection system resulted in the invention and refinement of the MRA (Multistage Radial Axial) combustor system in 1994. The MRA combustor was selected for the HSR Phase II LPP subscale combustor testing in the CPC Program.

Greenfield, Stuart↗
NASA NTRS2006

SI: The Stellar Imager

The ultra-sharp images of the Stellar Imager (SI) will revolutionize our view of many dynamic astrophysical processes: The 0.1 milliarcsec resolution of this deep-space telescope will transform point sources into extended sources, and simple snapshots into spellbinding evolving views. SI s science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI s prime goal is to enable long-term forecasting of solar activity and the space weather that it drives in support of the Living With a Star program in the Exploration Era by imaging a sample of magnetically active stars with enough resolution to map their evolving dynamo patterns and their internal flows. By exploring the Universe at ultra-high resolution, SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled structures and processes in the Universe.

Carpenter, Kenneth G.↗
NASA NTRS2007

XML Flight/Ground Data Dictionary Management

A computer program generates Extensible Markup Language (XML) files that effect coupling between the command- and telemetry-handling software running aboard a spacecraft and the corresponding software running in ground support systems. The XML files are produced by use of information from the flight software and from flight-system engineering. The XML files are converted to legacy ground-system data formats for command and telemetry, transformed into Web-based and printed documentation, and used in developing new ground-system data-handling software. Previously, the information about telemetry and command was scattered in various paper documents that were not synchronized. The process of searching and reading the documents was time-consuming and introduced errors. In contrast, the XML files contain all of the information in one place. XML structures can evolve in such a manner as to enable the addition, to the XML files, of the metadata necessary to track the changes and the associated documentation. The use of this software has reduced the extent of manual operations in developing a ground data system, thereby saving considerable time and removing errors that previously arose in the translation and transcription of software information from the flight to the ground system.

Wright, Jesse↗
NASA NTRSDate not supplied

Transformation of the NASA Life Sciences Portal to a FAIR Data Point

The FAIR principles emphasize optimizing metadata, the vast majority of which are textual in nature, and often organized into attribute name-value pairs. This uniformity has led to the development of guidelines and best practices for providing programmatic access to scientific data through their metadata, yielding the first iteration of the FAIR Data Point Specifications (FDPS). A key feature of the FDPS is its support for automated agents seeking and fetching data without first needing to learn a plethora of different application programming interfaces. These software agents can interrogate metadata catalogs that adhere to FDPS in a uniform manner because each catalog describes itself and its metadata schema consistently. This approach enhances the sustainability of data retrieval support, allowing systems to refine and update their metadata schemas as needed and without requiring data-seeking software agents to change how they interrogate FDPS catalogs. An essential aspect of the FDPS is the standardization of data catalog semantics, which formalizes concepts such as “metadata” and “metadata service” and links them to other concepts specifications including the Data Catalog Vocabulary (DCAT), a W3C standard that is also the basis of NASA-STD-2831 “Metadata Standard for Data Discoverability,” authored by NASA’s Office of the Chief Information Officer. The FDPS references DCAT (version 2) elements which focus on the distribution of datasets and support the goal of stream-lined catalog integration across repositories for improved data discovery. Additionally, the FDPS also prescribe the use of Linked Data Platform elements for data catalog-metadata record containment descriptions, allowing users to ascertain which data and metadata belong to which catalogs. NASA’s Life Sciences Portal is implementing the FDPS while formalizing its metadata schema to support the accelerated synthesis of knowledge from space life sciences investigations.

platform↗
DOE OSTI2024

CRISPR Tools for Engineering Prokaryotic Systems: Recent Advances and New Applications

In the past decades, the broad selection of CRISPR-Cas systems has revolutionized biotechnology by enabling multimodal genetic manipulation in diverse organisms. Rooted in a molecular engineering perspective, we recapitulate the different CRISPR components and how they can be designed for specific genetic engineering applications. We first introduce the repertoire of Cas proteins and tethered effectors used to program new biological functions through gene editing and gene regulation. We review current guide RNA (gRNA) design strategies and computational tools and how CRISPR-based genetic circuits can be constructed through regulated gRNA expression. Then, we present recent advances in CRISPR-based biosensing, bioproduction, and biotherapeutics across in vitro and in vivo prokaryotic systems. Finally, we discuss forthcoming applications in prokaryotic CRISPR technology that will transform synthetic biology principles in the near future.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1973

Evaluation of LRC Spectral Analyses of Simulated Gust Velocity Data

The NASA Langley Research Center (LRC) has been computing power spectra of simulated atmospheric turbulence data by various techniques, in preparation for the B-57 gust velocity data analysis program. The results of these studies have confirmed earlier suspicions that conventional first-difference pre-whitening of gust velocity data can produce serious distortions in the spectral densities at very low frequencies (below the frequency of the gust velocity spectral "knee"). The results also indicate that the frequency averaging procedures have certain merits over ensemble averaging procedures in the computation of spectra by direct Fourier transform operations. Finally, the results do not reveal any significant difference in the spectral estimates obtained using Hann versus Parzen smoothing procedures.

Piersol, Allan G.↗
NASA NTRS1982

Required developments in structural dynamics

The finite element method, modal component synthesis, and the use of fast Fourier transformation were key developments in structural dynamics in the past 15 to 20 years. Current areas requiring additional effort include: (1) the correct calculation of modal shape and natural frequencies for complex structures; (2) the correlation of math models with test data; (3) the establishment of a criteria for "goodness" of the correlation between analysis and test; (4) the selection of the correct displacement functions when using computer programs for modal synthesis; (5) accuracy of response calculations; and (6) the inverse problem of determining the force problem from the response data. Trends identified include the use of distributed computing, greater reliance on analysis, and the possible use of artificial intelligence techniques, or some way of feeding back information, to provide solution guidance to engineers.

Wada, B. K.↗
NASA NTRS1984

Perturbation analysis of the limit cycle of the free van der Pol equation

A power series expansion in the damping parameter, epsilon, of the limit cycle of the free van der Pol equation is constructed and analyzed. Coefficients in the expansion are computed in exact rational arithmetic using the symbolic manipulation system MACSYMA and using a FORTRAN program. The series is analyzed using Padeapproximants. The convergence of the series for the maximum amplitude of the limit cycle is limited by two pair of complex conjugate singularities in the complex epsilon-plane. A new expansion parameter is introduced which maps these singularities to infinity and leads to a new expansion for the amplitude which converges for all real values of epsilon. Amplitudes computed from this transformed series agree very well with reported numerical and asymptotic results. For the limit cycle itself, convergence of the series expansion is limited by three pair of complex conjugate branch point singularities. Two pair remain fixed throughout the cycle, and correspond to the singularities found in the maximum amplitude series, while the third pair moves in the epsilon-plane as a function of t from one of the fixed pairs to the other. The limit cycle series is transformed using a new expansion parameter, which leads to a new series that converges for larger values of epsilon.

Dadfar, M. B.↗
NASA NTRS1986

A computer code for three-dimensional incompressible flows using nonorthogonal body-fitted coordinate systems

In this report, a numerical method for solving the equations of motion of three-dimensional incompressible flows in nonorthogonal body-fitted coordinate (BFC) systems has been developed. The equations of motion are transformed to a generalized curvilinear coordinate system from which the transformed equations are discretized using finite difference approximations in the transformed domain. The hybrid scheme is used to approximate the convection terms in the governing equations. Solutions of the finite difference equations are obtained iteratively by using a pressure-velocity correction algorithm (SIMPLE-C). Numerical examples of two- and three-dimensional, laminar and turbulent flow problems are employed to evaluate the accuracy and efficiency of the present computer code. The user's guide and computer program listing of the present code are also included.

Chen, Y. S.↗
NASA NTRS1990

A patched-grid algorithm for complex aircraft configurations

A patched-grid algorithm for the analysis of complex configurations with an implicit, upwind-biased Navier-Stokes solver is presented. Through the use of a generalized coordinate transformation at the zonal interface between two or more blocks, the algorithm can be applied to highly stretched viscous grids and to arbitrarily-shaped patch boundaries. Applications are made to the SR71 reconnaissance aircraft in a high-altitude environment at a supersonic speed and to the F/A-18 forebody-strake configuration at subsonic, high-alpha conditions, in support of the NASA High-Alpha Research Program.

Walters, Robert W.↗
NASA NTRS2001

Sensor Applications at Kennedy Space Center (KSC)

Transducers used at KSC (Kennedy Space Center), in support of processing and launch of flight vehicles and payloads, are designed and tested to meet specific program requirements. Any equipment, transducer or support instrumentation in direct contact or in support to flight vehicle operations is considered ground support equipment (GSE) and required to meet strict program requirements (i.e. Space Shuttle Program, Space Station Program, Evolved Expendable Launch Vehicles, etc.) Transducers used in KSC applications are based on commercial off-the-shelf (COTS) transducers and sensors. In order to fully meet KSC requirements, these transducers evolve from standard COTS to modified COTS. The Transducer and Data Acquisition Group of the Instrumentation Branch at Kennedy Space Center is responsible for providing the technical expertise as well as qualification-testing capability to transform these COTS transducers in modified COTS suitable for use around flight hardware.

Perotti, Jose M.↗
NASA NTRS1990

Radiolysis of aqueous solutions of acetic acid in the presence of Na-montmorillonite

The gamma-irradiation of 0.8 mol dm-3 aqueous, oxygen-free acetic acid solutions was investigated in the presence or absence of Na-montmorillonite. H2, CH4, CO, CO2, and several polycarboxylic acids were formed in all systems. The primary characteristics observed in the latter system were: (1) Higher yield of the decomposition of acetic acid; (2) Lower yield of the formation of polycarboxylic acids; (3) No effect on the formation of methane; (4) Higher yield of the formation of carbon dioxide; and (5) The reduction of Fe3+ in the octahedral sites of Na-montmorillonite. A possible reaction scheme was proposed to account for the observed changes. The results are important in understanding heterogeneous processes in radiation catalysis and might be significant to prebiotic chemistry.

Non-NASA Center↗