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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Measurement and modeling of dispersive pulse propagation in draw wire waveguides

An analytical model of dispersive pulse propagation in semi-infinite cylinders due to transient axially symmetric end conditions has been experimentally investigated. Specifically, the dispersive propagation of the first axially symmetric longitudinal mode in thin wire waveguides, which have ends in butt contact with longitudinal piezoelectric ultrasonic transducers, is examined. The method allows for prediction of a propagated waveform given a measured source waveform, together with the material properties of the cylinder. Alternatively, the source waveform can be extracted from measurement of the propagated waveform. The material properties required for implementation of the pulse propagation model are determined using guided wave phase velocity measurements. Hard tempered aluminum 1100 and 304 stainless steel wires, with 127, 305, and 406 micron diam., were examined. In general, the drawn wires were found to behave as transversely isotropic media.

Madaras, Eric I.↗
NASA NTRS1996

Planet-B: Technical notes and drawings

The design of the transformer designated as T101 (061-0351) in the Filament/Bias module (061-0119) in the Planet-B NMS instrument was verified because of the differences from the GCMS and INMS instrument designs. A breadboard of a representation of the Hybrid 2301065, Bias Drive A driving a 2N3700 NPN transistor, with dual 75V secondaries, with loads, was used to test the circuit. The initial transformer design that was wound with bifilar secondaries was too unstable to test. The second 1408 transformer with a split bobbin and the feedback winding below the primary was also found to be unstable. (It was nearly impossible to keep the circuit from squeeging). The third transformer tested has the feedback on the outside of the resonant winding. The primary goal of the design was to have as tight a magnetic coupling as possible to the resonant winding, and as loose a coupling as possible to the primary. Further, the circuit AC ground is connected to the winding at the feedback end of the secondary winding. This transformer proved to be very stable - it is virtually impossible to make this design squeg. An emitter resistor (Rl29A) was added to this circuit, as referenced to the GCMS design, to protect Q102 from thermal runaway in the event of a turn on with a non- resonate circuit or load short. This was verified to protect Q102 for at least 30 seconds in the event of a short. Approximately 1% of the 4lmW input power is lost in this protection resistor under normal operation. The circuit was verified to operate normally when a radiated Q102 (2N3700), (low Beta) transistor was substituted for the normal 2N3700. It should be noted that the monitored drive voltage went to approximately 2.7V with this low gain transistor.

Carignan, George R.↗
NASA NTRS2004

Quick Draw

A NASA spacecraft set for launch Nov. 17 is designed to help scientists determine the origin of gamma-ray bursts by pinpointing their sources in the sky and quickly focusing optical/ultraviolet and X-ray telescopes on them.

Morring, Frank, Jr.↗
NASA NTRSDate not supplied

Constructing a Knowledge Graph & Applying Graph Algorithms to Draw Insights about GES-DISC Jira Tickets

In order to assess the complexities of Jira tickets created by NASA Goddard Earth Sciences Data and Information Services Center (GES-DISC), it was beneficial to create a knowledge graph. The knowledge graph receives ticket data through the Jira API. The creation of a knowledge graph will help to answer high-level questions about internal structure, knowledge gaps, and team organization within GES-DISC. To work towards this goal, the knowledge graph was constructed in adockerizedNeo4j graph database. Once the graph had been created, graph algorithms were applied to answer high-level questions, such as exploring the role of staff in relation to projects, which qualities of a ticket contribute to the formation of communities within the graph, etc. To answer these questions, centrality and community detection algorithms were applied using Cypher querying language. The analysis of the results of the algorithms indicated that, as expected, certain individuals were more connected to some projects, while others were serving as hub nodes between two or more projects. Similarly, specific keywords are more likely to increase a Jira ticket’s centrality in the graph. In terms of community detection, when tickets in a community have certain qualities, it is more probable for them to be grouped together. To best visualize which nodes had higher centrality scores or were grouped into certain communities, interactive graphs were created in Python using Plotly and Matplotlib. Ultimately, the project was successful in creating and deploying a knowledge graph to better understand the relationships between data in GES-DISC Jira tickets

Rebecca Lipton↗
DOE OSTI2016

Development of Switchable Polarity Solvent Draw Solutes

Results of a computational fluid dynamic (CFD) study of flow and heat transfer in a printed circuit heat exchanger (PCHE) geometry are presented. CFD results obtained from a two-plate model are compared to corresponding experimental results for the validation. This process provides the basis for further application of the CFD code to PCHE design and performance analysis in a variety of internal flow geometries. As a part of the code verification and validation (V&V) process, CFD simulation of a single semicircular straight channel under laminar isothermal conditions was also performed and compared to theoretical results. This comparison yielded excellent agreement with the theoretical values. The two-plate CFD model based on the experimental PCHE design overestimated the effectiveness and underestimated the pressure drop. However, it is found that the discrepancy between the CFD result and experimental data was mainly caused by the uncertainty in the geometry of heat exchanger during the fabrication. The CFD results obtained using a slightly smaller channel diameter yielded good agreement with the experimental data. A separate investigation revealed that the average channel diameter of the OSU PCHE after the diffusion-bonding was 1.93 mm on the cold fluid side and 1.90 mm on the hot fluid side which are both smaller than the nominal design value. Consequently, the CFD code was shown to have sufficient capability to evaluate the heat exchanger thermal-hydraulic performance.

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