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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Active turbulence control in wallbounded flow using direct numerical simulations

An exploratory study of concepts for active control of turbulent boundary layers using the direct numerical simulation technique was performed. Significant drag reduction was achieved when the surface boundary condition was modified such that it could suppress the large-scale structures present in the wall region. This was achieved by prescribing the normal component of velocity at the wall to be 180 deg out of phase with the normal velocity slightly above the wall at each instant. The drag reduction was accompanied with significant reduction in the intensity of the wall-layer structures and reductions in the magnitude of Reynolds stresses throughout the flow. Suitability of wall-pressure and shear-stress fluctuations for detection of flow structures above the wall was examined. A preliminary result obtained by applying the present control strategy to a transitional flow is also briefly described, from which one can infer a possible linkage between the control strategy and flow stability.

Kim, J.↗
NASA NTRS1991

Coordination strategies of crew management

An exploratory study that describes and contrasts two three-person flight crews performing in a B-727 simulator is presented. This study specifically attempts to delineate crew communication patterns accounting for measured differences in performance across routine and nonroutine flight patterns. The communication patterns in the two crews evaluated indicated different modes of coordination, i.e., standardization in the less effective crew and planning/mutual adjustment in the more effective crew.

Conley, Sharon↗
NASA NTRS1992

Multivariate statistical analysis software technologies for astrophysical research involving large data bases

The existing and forthcoming data bases from NASA missions contain an abundance of information whose complexity cannot be efficiently tapped with simple statistical techniques. Powerful multivariate statistical methods already exist which can be used to harness much of the richness of these data. Automatic classification techniques have been developed to solve the problem of identifying known types of objects in multi parameter data sets, in addition to leading to the discovery of new physical phenomena and classes of objects. We propose an exploratory study and integration of promising techniques in the development of a general and modular classification/analysis system for very large data bases, which would enhance and optimize data management and the use of human research resources.

Djorgovski, Stanislav↗
NASA NTRS1993

Transition on a sharp cone at high enthalpy - New measurements in the shock tunnel T5 at GALCIT

An exploratory study of the laminar, transitional and turbulent boundary layer on a slender cone in hypervelocity flow was conducted in the high-enthalpy shock tunnel T5. A novel flow visualization technique using sodium seeding to increase the sensitivity of conventional interferometric techniques by resonant enhancement of the refractivity of the medium was developed to study its structure. The experiments were designed to cover a large range of specific reservoir enthalpy, ranging from the perfect-gas region to the range where significant oxygen and some nitrogen dissociation and recombination effects may be expected in the boundary layer. Surface heat flux measurements indicate that the transition Reynolds number is approximately the same as that observed in cold hypersonic flow in conventional continuous flow facilities, but significantly lower than that observed in 'quiet' tunnels. No significant effect of reservoir specific enthalpy on transition was observed. The heat flux distribution showed differences between the air and the nitrogen experiments in the laminar regime. These are consistent with the presence of recombination of oxygen at the wall. This view is supported by the fact that this effect is absent in the low-enthalpy region, where the heat flux distribution agrees with the similarity theory.

Germain, P.↗
NASA NTRS1993

Effect of impact damage on the compression fatigue behavior of composite tubes

Experimental results are presented from an exploratory study to assess the effect of barely visible impact damage on the fatigue behavior of thin walled composite tubes. Undamaged composite tubes and tubes containing barely visible impact damage were tested in compression-compression fatigue. All tubes were inspected ultrasonically prior to testing. Tubes were outfitted with strain gages both in the damaged and far-field regions and an extensometer was utilized to measure axial displacements across the damaged region. Periodically, testing was halted and tubes were inspected ultrasonically and statically tested. In general, the impact damaged tubes exhibited a significantly shorter life than the undamaged tubes; however, there were considerable differences in the lives of the individual impact damaged tubes. No damage growth or stiffness loss was observed prior to failure. Failure of the impact damaged tubes was observed to occur in a combination of delamination buckling and shear crippling modes.

Krafchak, T. M.↗
NASA NTRS1992

Effects of refrigerating preinoculated Vitek cards on microbial physiology and antibiotic susceptibility

Reference cultures of 16 microorganisms obtained from the American Type Culture Collection and four clinical isolates were used in standardized solutions to inoculate 60 cards for each test strain. A set of three ID and three susceptibility cards was processed in the Vitek AutoMicrobic System (AMS) immediately after inoculation. The remaining cards were refrigerated at 4 C, and sets of six cards were removed and processed periodically for up to 17 days. The preinoculated AMS cards were evaluated for microorganism identification, percent probability of correct identification, length of time required for final result, individual substrate reactions, and antibiotic minimal inhibitory/concentration (MIC) values. Results indicate that 11 of the 20 microbes tested withstood refrigerated storage up to 17 days without detectable changes in delineating characteristics. MIC results appear variable, but certain antibiotics proved to be more stable than others. The results of these exploratory studies will be used to plan a microgravity experiment designed to study the effect of microgravity on microbial physiology and antibiotic sensitivity.

Skweres, Joyce A.↗
NASA NTRS1994

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 36: Technical uncertainty as a correlate of information use by US industry-affiliated aerospace engineers and scientists

This paper reports the results of an exploratory study that investigated the influence of technical uncertainty on the use of information and information sources by U.S. industry-affiliated aerospace engineers and scientists in completing or solving a project, task, or problem. Data were collected through a self-administered questionnaire. Survey participants were U.S. aerospace engineers and scientists whose names appeared on the Society of Automotive Engineers (SAE) mailing list. The results support the findings of previous research and the following study assumptions. Information and information-source use differ for projects, problems, and tasks with high and low technical uncertainty. As technical uncertainty increases, information-source use changes from internal to external and from informal to formal sources. As technical uncertainty increases, so too does the use of federally funded aerospace research and development (R&D). The use of formal information sources to learn about federally funded aerospace R&D differs for projects, problems, and tasks with high and low technical uncertainty.

Pinelli, Thomas E.↗
NASA NTRS1993

NASA/DOD Aerospace Knowledge Diffusion Research Project. Report 15: Technical uncertainty and project complexity as correlates of information use by US industry-affiliated aerospace engineers and scientists: Results of an exploratory investigation

An exploratory study was conducted that investigated the influence of technical uncertainty and project complexity on information use by U.S. industry-affiliated aerospace engineers and scientists. The study utilized survey research in the form of a self-administered mail questionnaire. U.S. aerospace engineers and scientists on the Society of Automotive Engineers (SAE) mailing list served as the study population. The adjusted response rate was 67 percent. The survey instrument is appendix C to this report. Statistically significant relationships were found to exist between technical uncertainty, project complexity, and information use. Statistically significant relationships were found to exist between technical uncertainty, project complexity, and the use of federally funded aerospace R&D. The results of this investigation are relevant to researchers investigating information-seeking behavior of aerospace engineers. They are also relevant to R&D managers and policy planners concerned with transferring the results of federally funded aerospace R&D to the U.S. aerospace industry.

Pinelli, Thomas E.↗
NASA NTRS1993

Multivariate statistical analysis software technologies for astrophysical research involving large data bases

The existing and forthcoming data bases from NASA missions contain an abundance of information whose complexity cannot be efficiently tapped with simple statistical techniques. Powerful multivariate statistical methods already exist which can be used to harness much of the richness of these data. Automatic classification techniques have been developed to solve the problem of identifying known types of objects in multiparameter data sets, in addition to leading to the discovery of new physical phenomena and classes of objects. We propose an exploratory study and integration of promising techniques in the development of a general and modular classification/analysis system for very large data bases, which would enhance and optimize data management and the use of human research resource.

Djorgovski, George↗
NASA NTRS1995

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 54: The technical communications practices of engineering technology students: Results of the NASA/DOD Aerospace Knowledge Diffusion Research Project phase 3 student surveys

Engineering technology programs are characterized by their focus on application and practice, and by their approximately 50/50 mix of theory and laboratory experience. Engineering technology graduates are employed across the technological spectrum and are often found in areas that deal with application, implementation, and production. Yet we know very little about the communications practices and information-use skills of engineering technology students. In this paper, we report selected results of an exploratory study of engineering technology students enrolled in three U.S. institutions of higher education. Data are presented for the following topics: career goals and aspirations; the importance of, receipt of, and helpfulness of communications and information-use skills instruction; collaborative writing; use of libraries; and the use of electronic (computer) networks.

Pinelli, Thomas E.↗
NASA NTRS1998

Rating the Relevance of QUORUM-Selected ASRS Incident Narratives to a "Controlled Flight into Terrain" Accident

An exploratory study was conducted to identify commercial aviation incidents that are relevant to a "controlled flight into terrain" (CFIT) accident using a NASA-developed text processing method. The QUORUM method was used to rate 67820 incident narratives, virtually all of the narratives in the Aviation Safety Reporting System (ASRS) database, according to their relevance to two official reports on the crash of American Airlines Flight 965 near Cali, Colombia in December 1995. For comparison with QUORUM's ratings, three experienced ASRS analysts read the reports of the crash and independently rated the relevance of the 100 narratives that were most highly rated by QUORUM, as well as 100 narratives randomly selected from the database. Eighty-four of 100 QUORUM-selected narratives were rated as relevant to the Cali accident by one or more of the analysts. The relevant incidents involved a variety of factors, including, over-reliance on automation, confusion and changes during descent/approach, terrain avoidance, and operations in foreign airspace. In addition, the QUORUM collection of incidents was found to be significantly more relevant than the random collection.

McGreevy, Michael W.↗
NASA NTRS1998

Parallel and Distributed System Simulation

This exploratory study initiated our research into the software infrastructure necessary to support the modeling and simulation techniques that are most appropriate for the Information Power Grid. Such computational power grids will use high-performance networking to connect hardware, software, instruments, databases, and people into a seamless web that supports a new generation of computation-rich problem solving environments for scientists and engineers. In this context we looked at evaluating the NetSolve software environment for network computing that leverages the potential of such systems while addressing their complexities. NetSolve's main purpose is to enable the creation of complex applications that harness the immense power of the grid, yet are simple to use and easy to deploy. NetSolve uses a modular, client-agent-server architecture to create a system that is very easy to use. Moreover, it is designed to be highly composable in that it readily permits new resources to be added by anyone willing to do so. In these respects NetSolve is to the Grid what the World Wide Web is to the Internet. But like the Web, the design that makes these wonderful features possible can also impose significant limitations on the performance and robustness of a NetSolve system. This project explored the design innovations that push the performance and robustness of the NetSolve paradigm as far as possible without sacrificing the Web-like ease of use and composability that make it so powerful.

Dongarra, Jack↗
NASA NTRS1998

Developing Information Power Grid Based Algorithms and Software

This was an exploratory study to enhance our understanding of problems involved in developing large scale applications in a heterogeneous distributed environment. It is likely that the large scale applications of the future will be built by coupling specialized computational modules together. For example, efforts now exist to couple ocean and atmospheric prediction codes to simulate a more complete climate system. These two applications differ in many respects. They have different grids, the data is in different unit systems and the algorithms for inte,-rating in time are different. In addition the code for each application is likely to have been developed on different architectures and tend to have poor performance when run on an architecture for which the code was not designed, if it runs at all. Architectural differences may also induce differences in data representation which effect precision and convergence criteria as well as data transfer issues. In order to couple such dissimilar codes some form of translation must be present. This translation should be able to handle interpolation from one grid to another as well as construction of the correct data field in the correct units from available data. Even if a code is to be developed from scratch, a modular approach will likely be followed in that standard scientific packages will be used to do the more mundane tasks such as linear algebra or Fourier transform operations. This approach allows the developers to concentrate on their science rather than becoming experts in linear algebra or signal processing. Problems associated with this development approach include difficulties associated with data extraction and translation from one module to another, module performance on different nodal architectures, and others. In addition to these data and software issues there exists operational issues such as platform stability and resource management.

Dongarra, Jack↗
NASA NTRS1998

Algorithms and Libraries

This exploratory study initiated our inquiry into algorithms and applications that would benefit by latency tolerant approach to algorithm building, including the construction of new algorithms where appropriate. In a multithreaded execution, when a processor reaches a point where remote memory access is necessary, the request is sent out on the network and a context--switch occurs to a new thread of computation. This effectively masks a long and unpredictable latency due to remote loads, thereby providing tolerance to remote access latency. We began to develop standards to profile various algorithm and application parameters, such as the degree of parallelism, granularity, precision, instruction set mix, interprocessor communication, latency etc. These tools will continue to develop and evolve as the Information Power Grid environment matures. To provide a richer context for this research, the project also focused on issues of fault-tolerance and computation migration of numerical algorithms and software. During the initial phase we tried to increase our understanding of the bottlenecks in single processor performance. Our work began by developing an approach for the automatic generation and optimization of numerical software for processors with deep memory hierarchies and pipelined functional units. Based on the results we achieved in this study we are planning to study other architectures of interest, including development of cost models, and developing code generators appropriate to these architectures.

Dongarra, Jack↗
NASA NTRS1998

Developing Information Power Grid Based Algorithms and Software

This exploratory study initiated our effort to understand performance modeling on parallel systems. The basic goal of performance modeling is to understand and predict the performance of a computer program or set of programs on a computer system. Performance modeling has numerous applications, including evaluation of algorithms, optimization of code implementations, parallel library development, comparison of system architectures, parallel system design, and procurement of new systems. Our work lays the basis for the construction of parallel libraries that allow for the reconstruction of application codes on several distinct architectures so as to assure performance portability. Following our strategy, once the requirements of applications are well understood, one can then construct a library in a layered fashion. The top level of this library will consist of architecture-independent geometric, numerical, and symbolic algorithms that are needed by the sample of applications. These routines should be written in a language that is portable across the targeted architectures.

Dongarra, Jack↗
NASA NTRS1999

Applications of Constituent Data Assimilation Systems

Organizations in Europe, Australia, and the United States have recently broadened constituent assimilation activities beyond that water vapor, which has been assimilated for years in the numerical weather prediction community. Many of these activities have focused on ozone, with some efforts focused on the entire suite of reactive constituents that control the ozone distribution. This talk will draw from results from the near real-time ozone data assimilation system being run by NASA's Data Assimilation Office. This system utilizes ozone observations from both the TOMS and the SBUV instrument to generate global synoptic maps of ozone. The initial application of this product is to provide ozone fields to assist in the atmospheric corrections' that are necessary for the retrieval of information from other NASA instruments. The validation of the ozone assimilation system shows that the assimilated product agrees well with independent HALOE and ozonesonde observations. This suggests that the product is of sufficient quality to be extended to other applications. This talk will enumerate these other applications and present initial results from exploratory research. The applications being considered include estimates of tropospheric ozone, provision of ozone fields for interactive retrievals, use of analysis increments from the assimilation to evaluate model performance, and development of long-term consistent three-dimensional global ozone fields. The results from the exploratory studies are promising, and help demonstrate how assumptions made in the p development of the ozone assimilation impact the other applications. For instance, RMS errors in the current product are large near the tropopause, which is sensitive to the specification of vertical correlation functions, which in turns impacts the amount of ozone analyzed to be in the troposphere. How these sensitivities impact the different applications will also be discussed.

Rood, Richard B.↗
NASA NTRS1999

TLNS3D/CDISC Multipoint Design of the TCA Concept

This paper presents the work done to date by the authors on developing an efficient approach to multipoint design and applying it to the design of the HSR TCA (High Speed Research Technology Concept Aircraft) configuration. While the title indicates that this exploratory study has been performed using the TLNS3DMB flow solver and the CDISC (Constrained Direct Iterative Surface Curvature) design method, the CDISC method could have been used with any flow solver, and the multipoint design approach does not require the use of CDISC. The goal of the study was to develop a multipoint design method that could achieve a design in about the same time as 10 analysis runs.

Campbell, Richard L.↗
NASA NTRS1999

TLNS3D/CDISC Multipoint Design of the TCA Concept

This paper presents the work done to date by the authors on developing an efficient approach to multipoint design and applying it to the design of the HSR TCA configuration. While the title indicates that this exploratory study has been performed using the TLNS3DMB flow solver and the CDISC design method, the CDISC method could have been used with any flow solver, and the multipoint design approach does not require the use of CDISC. The goal of the study was to develop a multipoint design method that could achieve a design in about the same time as 10 analysis runs.

Campbell, Richard L.↗