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Performance of Compressor XJ-41-V Turbojet Engine I - Preliminary Investigation at Equivalent Compressor Speed of 8000 RPM

Description: At the request of the Air Material Command, Arm Air Forces, an investigation was conducted at the NACA Cleveland laboratory to determine the performance characteristics of the XJ-41-V turbojet-engine compressor. The complete compressor was mounted on a collecting chamber having an annular air-flow passage simulating the burner annulus of the engine and was driven by an electric motor. The compressor was extensively instrumented to determine the overall performance of the compressor, the characteristic performance of each of the compressor components, the state of the air stream in the simulated burner annulus, and the operation of the compressor bearings. An initial investigation at an equivalent compressor speed of 8000 rpm was made to determine the performance of the compressor and the collecting chamber and to determine the similarity of the air stream at the entrance to the simulated burner annulus. The mechanical performance of the compressor over a range of actual compressors speeds from 3300 to 8000 rpm is reported.
Date: January 1, 1948
Creator: Ginsburg, Ambrose & Creagh, John W.R.
Partner: UNT Libraries Government Documents Department

Performance of Compressor of XJ-41-V Turbojet Engine II - Static-Pressure Ratios and Limitation of Maximum Flow at Equivalent Compressor Speed of 8000 rpm

Description: At the request of the Air Material Command, Army Air Forces, an investigation was conducted by the NACA Cleveland laboratory to determine the performance characteristics of the compressor of the XJ-41-V turbojet engine. This report is the second in a series presenting the compressor performance and analysis of flow conditions in the compressor. The static-pressure variation in the direction of flow through the compressor and the location and the cause of the maximum flow restriction at an equivalent speed of 8000 rpm are presented. After the initial runs were reported, the leading edges of the impeller blades and the diffuser surfaces were found to have been roughened by steel particles from a minor failure of auxiliary equipment. The leading edges of the impeller blades were refinished and all high spots resulting from scratches in the diffuser and the accessible parts of the vaned collector passages were removed. The initial overall performance and that obtained with the refinished blades are presented.
Date: January 1, 1948
Creator: Dildine, Dean M. & Arthur, W. Lewis
Partner: UNT Libraries Government Documents Department

An Analysis of the Full-Floating Journal Bearing

Description: An analysis of the operating characteristics of a full-floating bearing - a bearing in which a floating sleeve is located between the journal and bearing surfaces - is presented together with charts - from which the performance of such bearings may be predicted. Examples are presented to illustrate the use of these charts and a limited number of experiments conducted upon a glass full-floating bearing to verify some results of the analysis are reported. The floating sleeve can operate over a wide range of speeds for a given shaft speed, the exact value depending principally upon the ratio of clearances and upon the ratio of radii of the bearing. Lower operating temperatures at high rotative speeds are to be expected by using a full-floating bearing. This lower operating temperature would be obtained at the expense of the load-carrying capacity of the bearing if, for comparison, the clearances remain the same in both bearings. A full-floating bearing having the same load capacity as a conventional journal bearing may be designed if decreased clearances are allowable.
Date: January 28, 1947
Creator: Shaw, M.C. & Nussdorfer, T.J.
Partner: UNT Libraries Government Documents Department

Long Term Oxidation of Model and Engineering TiAl Alloys

Description: The purpose of this research was to characterize the oxidation behavior of several model (TiAl, TiAl-Nb, TiAl-Cr, TiAl-Cr-Nb) and engineering alloys (XD, K5, Alloy 7, WMS) after long-term isothermal exposure ({approx}7000 h) at 704 C, and after shorter time exposure ({approx}1000 h) at 800 C in air. High-resolution field emission and microprobe scanning electron microscopy were used to characterize the scales formed on these alloys. Similarities and differences observed in the scales are correlated with the various ternary and quaternary microalloying additions.
Date: August 24, 2001
Creator: Locci, IE
Partner: UNT Libraries Government Documents Department

Real-Time Risk and Fault Management in the Mission Evaluation Room for the International Space Station

Description: Effective anomaly resolution in the Mission Evaluation Room (MER) of the International Space Station (ISS) requires consideration of risk in the process of identifying faults and developing corrective actions. Risk models such as fault trees from the ISS Probabilistic Risk Assessment (PRA) can be used to support anomaly resolution, but the functionality required goes significantly beyond what the PRA could provide. Methods and tools are needed that can systematically guide the identification of root causes for on-orbit anomalies, and to develop effective corrective actions that address the event and its consequences without undue risk to the crew or the mission. In addition, an overall information management framework is needed so that risk can be systematically incorporated in the process, and effectively communicated across all the disciplines and levels of management within the space station program. The commercial nuclear power industry developed such a decision making framework, known as the critical safety function approach, to guide emergency response following the accident at Three Mile Island in 1979. This report identifies new methods, tools, and decision processes that can be used to enhance anomaly resolution in the ISS Mission Evaluation Room. Current anomaly resolution processes were reviewed to identify requirements for effective real-time risk and fault management. Experience gained in other domains, especially the commercial nuclear power industry, was reviewed to identify applicable methods and tools. Recommendations were developed for next-generation tools to support MER anomaly resolution, and a plan for implementing the recommendations was formulated. The foundation of the proposed tool set will be a ''Mission Success Framework'' designed to integrate and guide the anomaly resolution process, and to facilitate consistent communication across disciplines while focusing on the overriding importance of mission success.
Date: May 30, 2003
Creator: Nelson, W.R. & Novack, S.D.
Partner: UNT Libraries Government Documents Department

Proton radiation damage in high-resistivity n-type silicon CCDs

Description: A new type of p-channel CCD constructed on high-resistivity n-type silicon was exposed to 12 MeV protons at doses up to 1x1011 protons/cm2. The charge transfer efficiency was measured as a function of radiation dose and temperature. We previously reported that these CCDs are significantly more tolerant to radiation damage than conventional n-channel devices. In the work reported here, we used pocket pumping techniques and charge transfer efficiency measurements to determine the identity and concentrations of radiation induced traps present in the damaged devices.
Date: December 20, 2001
Creator: Bebek, C.J.; Groom, D.E.; Holland, S.E.; Karcher, A.; Kolbe, W.F.; Lee, J. et al.
Partner: UNT Libraries Government Documents Department

Proton radiation damage in P-channel CCDs fabricated on high-resistivity silicon

Description: P-channel, backside illuminated silicon CCDs were developed and fabricated on high-resistivity n-type silicon. Devices have been exposed up to 1x1011 protons/cm2 at 12 MeV. The charge transfer efficiency and dark current were measured as a function of radiation dose. These CCDs were found to be significantly more radiation tolerant than conventional n-channel devices. This could prove to be a major benefit for long duration space missions.
Date: July 28, 2002
Creator: Bebek, C.; Groom, D.; Holland, S.; Karcher, A.; Kolbe, W.; Lee, J. et al.
Partner: UNT Libraries Government Documents Department

An evaluation of the 1997 JPL Summer Teacher Enhancement Program

Description: There were two major components in the Jet Propulsion Laboratory (JPL) Summer Teacher Enhancement Project (STEP). First, the Summer Institute was structured as a four-week, 4-credit-unit University course for middle school science teachers, and consisted of workshops, lectures, labs, and tours as activities. The second component consists of follow-up activities related to the summer institute's contents, and again is structured as a University credit-bearing course for participants to reinforce their summer training. Considerable information from the comments and course ratings as given by the participants is included.
Date: October 20, 1997
Creator: Slovacek, Simeon P. & Doyle-Nichols, Adelaide R.
Partner: UNT Libraries Government Documents Department

Effect of CH4 and O2 variations on rates of CH4 oxidation and stable isotope fractionation in tropical rain forest soils

Description: Methane-oxidizing bacteria are the primary sink for CH{sub 4} in reduced soils, and account for as much as 90 percent of all CH{sub 4} produced. Methanotrophic bacteria strongly discriminate against the heavy isotopes of carbon, resulting in CH{sub 4} emissions that are significantly more enriched in {sup 13}C than the original source material. Previous studies have used an isotope mass balance approach to quantify CH{sub 4} sources and sinks in the field, based on the assumption that the fractionation factor for CH{sub 4} oxidation is a constant. This study quantifies the effect of systematic variations in CH{sub 4} and O{sub 2} concentrations on rates of CH{sub 4} oxidation and stable isotope fractionation in tropical rain forest soils. Soils were collected from the 0-15 cm depth, and incubated with varying concentrations of CH{sub 4} (100 ppmv, 500 ppmv, 1000 ppmv, and 5000 ppmv) or O{sub 2} (3 percent, 5 percent, 10 percent, and 21 percent). The isotope fractionation factor for CH{sub 4} oxidation was calculated for each incubation using a Rayleigh fractionation model. Rates of CH{sub 4} oxidation varied significantly between CH{sub 4} treatments, with the 100 ppmv CH{sub 4} treatment showing the lowest rate of CH{sub 4} uptake, and the other 3 treatments showing similar rates of CH{sub 4} uptake. Rates of CH{sub 4} oxidation did not vary significantly between the different O{sub 2} treatments. The fractionation factor for CH{sub 4} oxidation varied significantly between the different CH{sub 4} treatments, with the 5000 ppmv CH{sub 4} treatment showing the largest {sup 13}C-enrichment of residual CH{sub 4}. In treatments where CH{sub 4} concentration was not rate-limiting (> 500 ppmv CH{sub 4}), the fractionation factor for CH{sub 4} oxidation was negatively correlated with CH{sub 4} oxidation rate (P < 0.003, r{sup 2} = 0.86). A multiple regression model that included initial CH{sub ...
Date: October 1, 2003
Creator: Teh, Yit Arn; Conrad, Mark; Silver, Whendee L. & Carlson, Charlotte M.
Partner: UNT Libraries Government Documents Department

Dose-dependent misrejoining of radiation-induced DNA double-strand breaks in human fibroblasts: Experimental and theoretical study for high and low LET radiation

Description: Misrejoining of DNA double-strand breaks (DSBs) was measured in human primary fibroblasts after exposure to X-rays and high LET particles (He, N and Fe) in the dose range 10-80 Gy. To measure joining of wrong DNA ends, the integrity of a 3.2 Mbp restriction fragment was analyzed directly after exposure and after 16 hr of repair incubation. It was found that the misrejoining frequency for X-rays was non-linearly related to dose, with less probability of misrejoining at low doses than at high doses. The dose dependence for the high LET particles, on the other hand, was closer to being linear, with misrejoining frequencies higher than for X-rays particularly at the lower doses. These experimental results were simulated with a Monte-Carlo approach that includes a cell nucleus model with all 46 chromosomes present, combined with realistic track structure simulations to calculate the geometrical positions of all DSBs induced for each dose. The model assumes that the main determinant for misrejoining probability is the distance between two simultaneously present DSBs. With a Gaussian interaction probability function with distance, it was found that both the low and high LET data could be fitted with an interaction distance (sigma of the Gaussian curve) of 0.25 {micro}m. This is half the distance previously found to best fit chromosomal aberration data in human lymphocytes using the same methods (Holley et al. Radiat. Res . 158, 568-580 (2002)). The discrepancy may indicate inadequacies in the chromosome model, for example insufficient chromosomal overlap, but may also partly be due to differences between fibroblasts and lymphocytes. Although the experimental data was obtained at high doses, the Monte Carlo calculations could be extended to lower doses. It was found that a linear component of misrejoining versus dose dominated for doses below 1 Gy for all radiations, including X-rays. The calculated ...
Date: November 18, 2004
Creator: Rydberg, Bjorn; Cooper, Brian; Cooper, Priscilla K.; Holley, William & Chatterjee, Aloke
Partner: UNT Libraries Government Documents Department

A U.S. Carbon Cycle Science Plan

Description: This reassessment of the U.S. carbon cycle science priorities was initiated by the U.S. Carbon Cycle Interagency Working Group (CCIWG) and Carbon Cycle Science Steering Group (CCSSG) in 2008. This planning process has culminated in the publication of the new U.S. Carbon Cycle Science Plan. The new Plan is intended to provide guidance for U.S. research efforts on the global carbon cycle for the next decade.
Date: August 2011
Creator: Michalak, Anna M.; Jackson, Robert B.; Marland, Gregg; Sabine, Christopher L. & Carbon Cycle Science Working Group
Partner: UNT Libraries