18,139 research outputs found

    Surface interactions relevant to space station contamination problems

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    The physical and chemical processes at solid surfaces which can contribute to Space Station contamination problems are reviewed. Suggested areas for experimental studies to provide data to improve contamination modeling efforts are presented

    Rotary antenna attenuator

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    Radio frequency attenuator, having negligible insertion loss at minimum attenuation, can be used for making precise antenna gain measurements. It is small in size compared to a rotary-vane attenuator

    Optimal Flood Control

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    A mathematical model for optimal control of the water levels in a chain of reservoirs is studied. Some remarks regarding sensitivity with respect to the time horizon, terminal cost and forecast of inflow are made

    Operational cost drivers

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    To be economically viable, the operations cost of launch vehicles must be reduced by an order of magnitude as compared to the Space Transportation System (STS). A summary of propulsion-related operations cost drivers derived from a two-year study of Shuttle ground operations is presented. Examples are given of the inordinate time and cost of launch operations caused by propulsion systems designs that did not adequately consider impacts on prelaunching processing. Typical of these cost drivers are those caused by central hydraulic systems, storable propellants, gimballed engines, multiple propellants, He and N2 systems and purges, hard starts, high maintenance turbopumps, accessibility problems, and most significantly, the use of multiple, nonintegrated RCS, OMS, and main propulsion systems. Recovery and refurbishment of SRBs have resulted in expensive crash and salvage operations. Vehicle system designers are encouraged to be acutely aware of these cost drivers and to incorporate solutions (beginning with the design concepts) to avoid business as usual and costs as usual

    CIRCA 2000 operations criteria

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    The current Shuttle Program was used as a working model and certified data source in the identification of Space Transportation System (STS) operational cost drivers. Changes to flight hardware, processing methodologies, and identification of automation applications that would reduce costs were derived by reference to that data. The CIRCA 2000 Criteria were developed using these critical analyses of the on-going Shuttle Program. Several innovative suggestions are reviewed

    A computer vision approach to classification of birds in flight from video sequences

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    Bird populations are an important bio-indicator; so collecting reliable data is useful for ecologists helping conserve and manage fragile ecosystems. However, existing manual monitoring methods are labour-intensive, time-consuming, and error-prone. The aim of our work is to develop a reliable system, capable of automatically classifying individual bird species in flight from videos. This is challenging, but appropriate for use in the field, since there is often a requirement to identify in flight, rather than when stationary. We present our work in progress, which uses combined appearance and motion features to classify and present experimental results across seven species using Normal Bayes classifier with majority voting and achieving a classification rate of 86%

    Cognitive Dissonance, Pessimism, and Behavioral Spillover Effects

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    This paper reports results from a unique two-stage experiment designed to examine the spillover effects of optimism and pessimism. In stage 1, we induce optimism or pessimism onto subjects by randomly assigning a high or low piece rate for performing a cognitive task. We find that participants receiving the low piece rate are significantly more pessimistic with respect to performance on this task. In stage 2 individuals participate in an ultimatum game. We find that minimum acceptable offers are significantly lower for pessimistic subjects, though this pessimism was generated in a completely unrelated environment. These results highlight the existence of important spillover effects that can be behaviorally and economically important - for example, pessimism regarding one’s initial conditions (e.g., living in poverty) may have spillover effects on one’s future labor market outcomes.

    Breast feeding practices and views among diabetic women: a retrospective cohort study

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    Objective: to explore the pattern and experiences of breast-feeding practices among diabetic women. Design: retrospective cohort study using maternal records and postal questionnaires in a Baby-Friendly hospital. Participants: diabetic mothers including women with gestational diabetes, and type 1 and 2 diabetes mellitus. Findings: from the total group of respondents, 81.9% intended to breast feed. The actual breast feeding rates were 81.9% at birth, 68.1% at 2 weeks and 28.7% at 6 months postpartum. Major themes that were identified from women's experiences included information and advice, support vs. pressure, classification and labelling, and expectations. Conclusions: more than two-thirds of the diabetic women intended to breast feed and actually did breast feed in this study. For both the total study population and the type 1 and 2 diabetics alone, more than half were still breast feeding at 2 weeks postpartum, and approximately one-third were still breast feeding at 6 months postpartum. Implications for practice: structured support, provided for women through Baby-Friendly initiatives, was appreciated by the diabetic women in this study. The extent to which this support influenced the highly successful breast feeding practices in this group of women needs focused investigation. The need for a delicate balancing act between pressure and advice in order to prevent coercion was noted.</p

    The z=0.8596 Damped Lyman Alpha Absorbing Galaxy Toward PKS 0454+039

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    We present {\it Hubble Space Telescope} and ground--based data on the zabs=0.8596z_{abs}=0.8596 metal line absorption system along the line of sight to PKS 0454+0356. The system is a moderate redshift damped Lyman alpha system, with N(HI)=(5.7±0.3)×1020{\rm N(HI)}=(5.7\pm0.3)\times10^{20}~cm2^{-2} as measured from the {\it Faint Object Spectrograph} spectrum. We also present ground--based images which we use to identify the galaxy which most probably gives rise to the damped system; the most likely candidate is relatively underluminous by QSO absorber standards (MB19.0M_B \sim -19.0 for q0=0.5q_0=0.5 and H0=50H_0=50 \kms Mpc1^{-1}), and lies 8.5h1\sim 8.5h^{-1} kpc in projection from the QSO sightline. Ground--based measurements of Zn~II, Cr~II, and Fe~II absorption lines from this system allow us to infer abundances of [Zn/H]=1.1-1.1, [Cr/H]=1.2-1.2, and [Fe/H]=1.2-1.2, indicating overall metallicity similar to damped systems at z>2z >2, and that the depletion of Cr and Fe onto dust grains may be even {\it less} important than in many of the high redshift systems of comparable metallicity. Limits previously placed on the 21-cm optical depth in the z=0.8596z=0.8596 system, together with our new N(H~I) measurement, suggest a very high spin temperature for the H~I, TS>>580T_S >> 580 K.Comment: changed uuencode header to produce .Z file so that unix uncompress command will work without modifying file nam
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