5,180 research outputs found

    Future techniques for tracking of synchronous satellites

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    A tracking system error analysis computer program is reported to study the feasibility of using range sum and range-rate sum measurements through a synchronous satellite to a user satellite, and range sum and range-rate sum measurements through a synchronous satellite to a ground based transponder for tracking of synchronous satellites. Error analysis transformed noise, bias, ground station location and orbit uncertainties into expected uncertainties in each of the orbits after tracking. Results show that both of the proposed measurement methods are feasible for determining and refining the orbits of future synchronous satellites

    Nonlinear techniques for forecasting solar activity directly from its time series

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    This paper presents numerical techniques for constructing nonlinear predictive models to forecast solar flux directly from its time series. This approach makes it possible to extract dynamical in variants of our system without reference to any underlying solar physics. We consider the dynamical evolution of solar activity in a reconstructed phase space that captures the attractor (strange), give a procedure for constructing a predictor of future solar activity, and discuss extraction of dynamical invariants such as Lyapunov exponents and attractor dimension

    Integrated command, control, communications and computation system functional architecture

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    The functional architecture for an integrated command, control, communications, and computation system applicable to the command and control portion of the NASA End-to-End Data. System is described including the downlink data processing and analysis functions required to support the uplink processes. The functional architecture is composed of four elements: (1) the functional hierarchy which provides the decomposition and allocation of the command and control functions to the system elements; (2) the key system features which summarize the major system capabilities; (3) the operational activity threads which illustrate the interrelationahip between the system elements; and (4) the interfaces which illustrate those elements that originate or generate data and those elements that use the data. The interfaces also provide a description of the data and the data utilization and access techniques

    Role of internal gases and creep of Ag in controlling the critical current density of Ag-sheathed Bi2Sr2CaCu2Ox wires

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    High engineering critical current density JE of >500 A/mm2 at 20 T and 4.2 K can be regularly achieved in Ag-sheathed multifilamentary Bi2Sr2CaCu2Ox (Bi-2212) round wire when the sample length is several centimeters. However, JE(20 T) in Bi-2212 wires of several meters length, as well as longer pieces wound in coils, rarely exceeds 200 A/mm2. Moreover, long-length wires often exhibit signs of Bi-2212 leakage after melt processing that are rarely found in short, open-end samples. We studied the length dependence of JE of state-of-the-art powder-in-tube (PIT) Bi-2212 wires and gases released by them during melt processing using mass spectroscopy, confirming that JE degradation with length is due to wire swelling produced by high internal gas pressures at elevated temperatures [1,2]. We further modeled the gas transport in Bi-2212 wires and examined the wire expansion at critical stages of the melt processing of as-drawn PIT wires and the wires that received a degassing treatment or a cold-densification treatment before melt processing. These investigations showed that internal gas pressure in long-length wires drives creep of the Ag sheath during the heat treatment, causing wire to expand, lowering the density of Bi-2212 filaments, and therefore degrading the wire JE; the creep rupture of silver sheath naturally leads to the leakage of Bi-2212 liquid. Our work shows that proper control of such creep is the key to preventing Bi-2212 leakage and achieving high JE in long-length Bi-2212 conductors and coils

    A ground track control algorithm for the Topographic Mapping Laser Altimeter (TMLA)

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    The results of an analysis of an algorithm that will provide autonomous onboard orbit control using orbits determined with Global Positioning System (GPS) data. The algorithm uses the GPS data to (1) compute the ground track error relative to a fixed longitude grid, and (2) determine the altitude adjustment required to correct the longitude error. A program was written on a personal computer (PC) to test the concept for numerous altitudes and values of solar flux using a simplified orbit model including only the J sub 2 zonal harmonic and simple orbit decay computations. The algorithm was then implemented in a precision orbit propagation program having a full range of perturbations. The analysis showed that, even with all perturbations (including actual time histories of solar flux variation), the algorithm could effectively control the spacecraft ground track and yield more than 99 percent Earth coverage in the time required to complete one coverage cycle on the fixed grid (220 to 230 days depending on altitude and overlap allowance)

    Analysis of reentry into the White Sands Missile Range (WSMR) for the LifeSat mission

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    This study investigates the reentry of the LifeSat vehicles into the WSMR. The LifeSat mission consists of two reusable reentry satellites, each carrying a removable payload module, which scientists will use to study long-term effects of microgravity, Van Allen belt radiation, and galactic cosmic rays on living organisms. A series of missions is planned for both low-Earth circular orbits and highly elliptic orbits. To recover the payload module with the specimens intact, a soft parachute landing and recovery at the WSMR is planned. This analysis examines operational issues surrounding the reentry scenario to assess the feasibility of the reentry

    Impact of Corporate Social Responsibility and Sustainability Practices on Brand Trust and Purchase Intention in the Wine Industry

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    The wine industry continues to grow and is expected to reach 429 billion U.S. dollars by 2023 (Oloruntoba, 2020) and is a major contributor to environmental degradation. The wine industry plays a role in soil degradation, water pollution, waste disposal, and land/vegetation damage. The wine-making process creates emissions and depletes oxygen in the environment, which is linked with increased death rates of aquatic organisms. The wine industry impacts crop growth, the solubility of metals in soil, increases toxicity of water, and generates destructive algal bloom. The industry has been slow to adopt sustainable practices and has been subject to less scrutiny than other industries. Although consumer preference studies have shown that customers care about sustainability and corporate social responsibility, little research existed on consumer preferences in the wine industry. To better understand if more companies in the wine industry should adopt higher sustainability and socially responsible behaviors, this body of research explored the impact of corporate social responsibility and sustainability on brand trust and purchase intention in the wine industry. The research was conducted with participants who drink or purchase wine, and the results indicate that both corporate social responsibility and sustainability impact consumers\u27 brand trust and purchase intention in the wine industry. This study is important for business leaders to better understand their consumers’ preferences and accordingly make critical changes in their business strategies. It is also important for academia to further research on developing topics in the industry and for consumers to help expand awareness on socially responsible and sustainable companies

    Peer Victimization and Reactive and Proactive Aggression in Childhood: The Protective Roles of Physical Activity and Sleep

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    A growing body of literature indicates that the link between peer victimization and aggressive behavior may vary according to specific aggression subtypes; however, research has yet to identify factors that moderate these associations. The purposes of the present study were to further examine the links between peer victimization and reactive and proactive aggression and evaluate whether physical activity and sleep moderated these relations. Participants included 294 predominantly Caucasian children (50.7% male) between 7 and 11 years of age (M = 8.71, SD = 1.17), and their homeroom teacher. Peer victimization was assessed using self- and teacher-reports, and teachers provided ratings of children's aggressive behavior. Children also completed self-report measures assessing physical activity and sleep duration. Consistent with previous research, peer victimization was uniquely associated with reactive, but not proactive, aggression. Findings failed to provide support for the hypothesis that physical activity and sleep would serve as protective factors against the reactive aggression associated with experiences of victimization. Directions for future research are discussed

    Results from the CDMS II Experiment

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    I report recent results and the status of the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory in Minnesota, USA. A blind analysis of data taken by 30 detectors between October 2006 and July 2007 found zero events consistent with WIMPs elastically scattering in our Ge detectors. This resulted in an upper limit on the spin-independent, WIMP-nucleon cross section of 6.6 x 10^-44 cm^2 (4.6 x 10^-44 cm^2 when combined with our previous results) at the 90% C.L. for a WIMP of mass 60 GeV/c^2. In March 2009 data taking with CDMS II stopped in order to install the first of 5 SuperTowers of detectors for the SuperCDMS Soudan project. Analysis of data taken between August 2007 and March 2009 is ongoing.Comment: 5 pages, 4 figures, to appear in the proceedings of the TAUP09 conference (Rome, July 1st-5th 2009
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