5,553 research outputs found

    Applicability of the control configured design approach to advanced earth orbital transportation systems

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    The applicability of the control configured design approach (CCV) to advanced earth orbital transportation systems was studied. The baseline system investigated was fully reusable vertical take-off/horizontal landing single-stage-to-orbit vehicle and had mission requirements similar to the space shuttle orbiter. Technical analyses were made to determine aerodynamic, flight control and subsystem design characteristics. Figures of merit were assessed on vehicle dry weight and orbital payload. The results indicated that the major parameters for CCV designs are hypersonic trim, aft center of gravity, and control surface heating. Optimized CCV designs can be controllable and provide substantial payload gains over conventional non-CCV design vertical take-off vehicles

    A large scale height galactic component of the diffuse 2-60 keV background

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    The diffuse 2-60 keV X-ray background has a galactic component clearly detectable by its strong variation with both galactic latitude and longitude. This galactic component is typically 10 percent of the extragalactic background toward the galactic center, half that strong toward the anticenter, and extrapolated to a few percent of the extragalactic background toward the galactic poles. It is acceptably modeled by a finite radius emission disk with a scale height of several kiloparsecs. The averaged galactic spectrum is best fitted by a thermal spectrum of kT about 9 keV, a spectrum much softer than the about 40 keV spectrum of the extragalactic component. The most likely source of this emission is low luminosity stars with large scale heights such as subdwarfs. Inverse Compton emission from GeV electrons on the microwave background contributes only a fraction of the galactic component unless the local cosmic ray electron spectrum and intensity are atypical

    Measuring Molecular, Neutral Atomic, and Warm Ionized Galactic Gas Through X-Ray Absorption

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    We study the column densities of neutral atomic, molecular, and warm ionized Galactic gas through their continuous absorption of extragalactic X-ray spectra at |b| > 25 degrees. For N(H,21cm) < 5x10^20 cm^-2 there is an extremely tight relationship between N(H,21cm) and the X-ray absorption column, N(xray), with a mean ratio along 26 lines of sight of N(xray)/N(H,21cm) = 0.972 +- 0.022. This is significantly less than the anticpated ratio of 1.23, which would occur if He were half He I and half He II in the warm ionized component. We suggest that the ionized component out of the plane is highly ionized, with He being mainly He II and He III. In the limiting case that H is entirely HI, we place an upper limit on the He abundance in the ISM of He/H <= 0.103. At column densities N(xray) > 5x10^20 cm^-2, which occurs at our lower latitudes, the X-ray absorption column N(xray) is nearly double N(H,21cm). This excess column cannot be due to the warm ionized component, even if He were entirely He I, so it must be due to a molecular component. This result implies that for lines of sight out of the plane with |b| ~ 30 degrees, molecular gas is common and with a column density comprable to N(H,21cm). This work bears upon the far infrared background, since a warm ionized component, anticorrelated with N(H,21cm), might produce such a background. Not only is such an anticorrelation absent, but if the dust is destroyed in the warm ionized gas, the far infrared background may be slightly larger than that deduced by Puget et al. (1996).Comment: 1 AASTeX file, 14 PostScript figure files which are linked within the TeX fil

    Comparison of the COBE FIRAS and DIRBE Calibrations

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    We compare the independent FIRAS and DIRBE observations from the COBE in the wavelength range 100-300 microns. This cross calibration provides checks of both data sets. The results show that the data sets are consistent within the estimated gain and offset uncertainties of the two instruments. They show the possibility of improving the gain and offset determination of DIRBE at 140 and 240 microns.Comment: Accepted for publication in the Astrophysical Journal 11 pages, plus 3 figures in separate postscript files. Figure 3 has three part

    Unequal Playing Time

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    Unequal Playing Time In his book The American College Town, Blake Gumprecht claims one of the defining features of college towns is that they are more progressive, liberal-minded, and socially-blended spaces. However, this is not the type of college town that appears in Marshall University’s collection of archives. Throughout the years, many groups of students were often overlooked due to minority population status. This presentation examines the lack of recognition for one such group, in particular, women’s athletics during the 1920’s. Student yearbooks published between 1920 and 1930 were analyzed for content featuring men versus women’s athletics. At the start of the decade in 1920, female athletes were given a one-page segment placed at the end of the athletics section which discussed the athletic classes offered to women. During that same year, there happened to be nine women and seven men on the yearbook’s editorial board. In the following years, the number of women on the editorial board decreased and despite the girl’s athletic association being the largest student organization on campus, so did the amount of recognition for the association. One could easily surmise that the men on the yearbook staff often overlooked women when it came to athletics. However, when men were the bulk of the yearbook editors, women were often most noted for their beauty and popularity, rather than their athletic achievements. Such inconsistencies directly contrast with Gumprecht’s definition of a college town being broadminded and socially incorporated

    Evidence Propagation and Consensus Formation in Noisy Environments

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    We study the effectiveness of consensus formation in multi-agent systems where there is both belief updating based on direct evidence and also belief combination between agents. In particular, we consider the scenario in which a population of agents collaborate on the best-of-n problem where the aim is to reach a consensus about which is the best (alternatively, true) state from amongst a set of states, each with a different quality value (or level of evidence). Agents' beliefs are represented within Dempster-Shafer theory by mass functions and we investigate the macro-level properties of four well-known belief combination operators for this multi-agent consensus formation problem: Dempster's rule, Yager's rule, Dubois & Prade's operator and the averaging operator. The convergence properties of the operators are considered and simulation experiments are conducted for different evidence rates and noise levels. Results show that a combination of updating on direct evidence and belief combination between agents results in better consensus to the best state than does evidence updating alone. We also find that in this framework the operators are robust to noise. Broadly, Yager's rule is shown to be the better operator under various parameter values, i.e. convergence to the best state, robustness to noise, and scalability.Comment: 13th international conference on Scalable Uncertainty Managemen

    Effect of Fibrinogen and Ca 2+ on the Thrombin-Catalyzed Proteolytic Event That Triggers Activation of Factor XIII

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75101/1/j.1749-6632.1986.tb34575.x.pd

    Are state laws granting pharmacists authority to vaccinate associated with HPV vaccination rates among adolescents?

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    We explored whether state laws allowing pharmacists to administer human papillomavirus (HPV) vaccinations to adolescents are associated with a higher likelihood of HPV vaccine uptake
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