1,730 research outputs found

    Estimation of fan pressure ratio requirements and operating performance for the National Transonic Facility

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    The National Transonic Facility (NTF), a fan-driven, transonic, pressurized, cryogenic wind tunnel, will operate over the Mach number range of 0.10 to 1.20 with stagnation pressures varying from 1.00 to about 8.8 atm and stagnation temperatures varying from 77 to 340 K. The NTF is cooled to cryogenic temperatures by the injection of liquid nitrogen into the tunnel stream with gaseous nitrogen as the test gas. The NTF can also operate at ambient temperatures using a conventional chilled water heat exchanger with air on nitrogen as the test gas. The methods used in estimating the fan pressure ratio requirements are described. The estimated NTF operating envelopes at Mach numbers from 0.10 to 1.20 are presented

    Orbiter thermal pressure drop characteristics for shuttle orbiter thermal protection system components: High density tile, low density tile, densified low density tile, and strain isolation pad

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    Pressure drop tests were conducted on available samples of low and high density tile, densified low density tile, and strain isolation pads. The results are presented in terms of pressure drop, material thickness and volume flow rate. Although the test apparatus was only capable of a small part of the range of conditions to be encountered in a Shuttle Orbiter flight, the data serve to determine the type of flow characteristics to be expected for each material type tested; the measured quantities also should serve as input for initial venting and flow through analysis

    Guide for users of the National Transonic Facility

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    The National Transonic Facility (NTF) is a fan-driven, closed-circuit, continuous flow, pressurized wind tunnel. The test section is 2.5 m x 2.5 m and 7.62 m long with a slotted-wall configuration. The NTF will have a Mach number range from 0.2 to 1.2, with Reynolds number up to 120 10 to the sixth power at Mach 1 (based on a reference length of 0.25 m). The pressure range for the facility will be from 1 to about 9 bars (1 ban = 100 kPa), and the temperature can be varied from 340 to 78 K. This report provides potential users of the NTF with the information required for preliminary planning to test programs and for preliminary layout of models and model supports which may be used in such programs

    Beta-delayed-neutron studies of 135,136^{135,136}Sb and 140^{140}I performed with trapped ions

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    Beta-delayed-neutron (β\betan) spectroscopy was performed using the Beta-decay Paul Trap and an array of radiation detectors. The β\betan branching ratios and energy spectra for 135,136^{135,136}Sb and 140^{140}I were obtained by measuring the time of flight of recoil ions emerging from the trapped ion cloud. These nuclei are located at the edge of an isotopic region identified as having β\betan branching ratios that impact the r-process abundance pattern around the A~130 peak. For 135,136^{135,136}Sb and 140^{140}I, β\betan branching ratios of 14.6(11)%, 17.6(28)%, and 7.6(28)% were determined, respectively. The β\betan energy spectra obtained for 135^{135}Sb and 140^{140}I are compared with results from direct neutron measurements, and the β\betan energy spectrum for 136^{136}Sb has been measured for the first time

    Regulation of the fibrosis and angiogenesis promoter SPARC/osteonectin in human adipose tissue by weight change, leptin, insulin, and glucose

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    This is the final version of the article. Available from the publisher via the DOI in this record.OBJECTIVE: Matricellular Secreted Protein, Acidic and Rich in Cysteine (SPARC), originally discovered in bone as osteonectin, is a mediator of collagen deposition and promotes fibrosis. Adipose tissue collagen has recently been found to be linked with metabolic dysregulation. Therefore, we tested the hypothesis that SPARC in human adipose tissue is influenced by glucose metabolism and adipokines. RESEARCH DESIGN AND METHODS: Serum and adipose tissue biopsies were obtained from morbidly obese nondiabetic subjects undergoing bariatric surgery and lean control subjects for analysis of metabolic markers, SPARC, and various cytokines (RT-PCR). Additionally, 24 obese subjects underwent a very-low-calorie diet of 1,883 kJ (450 kcal)/day for 16 weeks and serial subcutaneous-abdominal-adipose tissue (SCAT) biopsies (weight loss: 28 +/- 3.7 kg). Another six lean subjects underwent fast-food-based hyperalimentation for 4 weeks (weight gain: 7.2 +/- 1.6 kg). Finally, visceral adipose tissue explants were cultured with recombinant leptin, insulin, and glucose, and SPARC mRNA and protein expression determined by Western blot analyses. RESULTS: SPARC expression in human adipose tissue correlated with fat mass and was higher in SCAT. Weight loss induced by very-low-calorie diet lowered SPARC expression by 33% and increased by 30% in adipose tissue of subjects gaining weight after a fast-food diet. SPARC expression was correlated with leptin independent of fat mass and correlated with homeostasis model assessment-insulin resistance. In vitro experiments showed that leptin and insulin potently increased SPARC production dose dependently in visceral adipose tissue explants, while glucose decreased SPARC protein. CONCLUSIONS: Our data suggest that SPARC expression is predominant in subcutaneous fat and its expression and secretion in adipose tissue are influenced by fat mass, leptin, insulin, and glucose. The profibrotic effects of SPARC may contribute to metabolic dysregulation in obesity.This work was supported by Diabetes UK, Swedish Research Council (11285), University Hospital of Linkoping Research Funds; Diabetes Research Centre of Linkoping University; and the Gamla Tjaenarinnor Foundation. No potential conflicts of interest relevant to this article were reported. Parts of this study were presented in abstract form at the 69th Scientific Sessions of the American Diabetes Association, New Orleans, Louisiana, 5–9 June 2009

    A Comparative Study of Linear and Nonlinear Estimate at Completion Methods

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    Controlling costs in the acquisition of new defense systems is a major challenge in today\u27s environment of declining budgets and rapidly changing technology. One of the challenges faced by program managers and cost analysts is selecting the most appropriate Estimate at Completion (EAC) method for their program. This study compares the performance of the popular index-based EAC methods with several newer nonlinear, regression based EAC methods to determine whether the complex nonlinear methods perform better than the simpler index-based methods. In addition, the sensitivity of the results to stage of contract completion, system type, program phase, contract type, Department of Defense service component, and inflation effects are also investigated. Eighty-eight contracts were examined in this study and it was found that overall the index-based EAC methods performed significantly better than the nonlinear regression based methods as measured by two criteria, the accuracy and stability of the EACs. In addition, the top performing method overall was determined to be the index-based method using the Composite Index. The best performing method was, however, sensitive to all of the factors investigated in the sensitivity analysis

    Low-lying level structure of 56^{56}Cu and its implications on the rp process

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    The low-lying energy levels of proton-rich 56^{56}Cu have been extracted using in-beam γ\gamma-ray spectroscopy with the state-of-the-art γ\gamma-ray tracking array GRETINA in conjunction with the S800 spectrograph at the National Superconducting Cyclotron Laboratory at Michigan State University. Excited states in 56^{56}Cu serve as resonances in the 55^{55}Ni(p,γ\gamma)56^{56}Cu reaction, which is a part of the rp-process in type I x-ray bursts. To resolve existing ambiguities in the reaction Q-value, a more localized IMME mass fit is used resulting in Q=639±82Q=639\pm82~keV. We derive the first experimentally-constrained thermonuclear reaction rate for 55^{55}Ni(p,γ\gamma)56^{56}Cu. We find that, with this new rate, the rp-process may bypass the 56^{56}Ni waiting point via the 55^{55}Ni(p,γ\gamma) reaction for typical x-ray burst conditions with a branching of up to \sim40%\%. We also identify additional nuclear physics uncertainties that need to be addressed before drawing final conclusions about the rp-process reaction flow in the 56^{56}Ni region.Comment: 8 pages, accepted for Phys. Rev.

    Thermodynamic theory of epitaxial ferroelectric thin films with dense domain structures

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    A Landau-Ginsburg-Devonshire-type nonlinear phenomenological theory is presented, which enables the thermodynamic description of dense laminar polydomain states in epitaxial ferroelectric thin films. The theory explicitly takes into account the mechanical substrate effect on the polarizations and lattice strains in dissimilar elastic domains (twins). Numerical calculations are performed for PbTiO3 and BaTiO3 films grown on (001)-oriented cubic substrates. The "misfit strain-temperature" phase diagrams are developed for these films, showing stability ranges of various possible polydomain and single-domain states. Three types of polarization instabilities are revealed for polydomain epitaxial ferroelectric films, which may lead to the formation of new polydomain states forbidden in bulk crystals. The total dielectric and piezoelectric small-signal responses of polydomain films are calculated, resulting from both the volume and domain-wall contributions. For BaTiO3 films, strong dielectric anomalies are predicted at room temperature near special values of the misfit strain.Comment: 19 pages, 8 figure
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