9,666 research outputs found

    Volunteers and the Economic Downturn

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    The recent economic crisis has subjected America's nonprofit organizations to considerable fiscal stress. To find out more about the response of nonprofits to the recent economic climate, the Corporation for National and Community Service partnered with the Johns Hopkins Nonprofit Listening Post Project on a national survey of nonprofits and AmeriCorps sponsor organizations.The survey revealed that 80 percent of responding organizations experienced some level of fiscal stress between September 2008 through March 2009, when the downturn intensified, and that for close to 40 percent of them the stress was considered "severe" or "very severe." In response, nearly a quarter (23%) of nonprofits reported decreasing staff hours, a third reported eliminating staff positions, and 40 percent reported postponing the filling of new positions. At the same time, nearly three-fourths of the organizations reported they had maintained or increased the number of people their organizations served, and even among those reporting "severe" or "very severe" fiscal stress and resulting cutbacks in staff, 60 percent reported they had been able to maintain or increase the number of people their organizations served

    User's manual for the Langley boundary layer noise propagation program (MRS-BLP)

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    A computer program, McAninch-Rawls-Spence Boundary Layer Propagation (MRS-BLP), is described. This program models the refractive and scattering effects on acoustic pressure waves propagating through a boundary layer encompassing an aircraft's fuselage. The noise source is assumed known and generated by a propeller. The fuselage is represented by an infinitely long cylinder embedded in a longitudinal flow. By matching a numerical solution inside the boundary layer with an analytical solution outside the boundary layer, the program calculates the acoustic pressure at the surface of the cylinder given the incident field at the top of the boundary layer. The boundary layer flow velocity and sound speed profiles, as well as the boundary layer thickness may be specified by the user. A detailed description of the input parameters and how to execute the program is given. Example executions of MRS-BLP showing results are also included

    Observations of discrete, global magnetospheric oscillations directly driven by solar wind density variations

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    Communiqué No. 16: Escalating Pension Benefit Costs -- Another Threat to Nonprofit Survival?

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    Provides findings from a national survey of nonprofits that examines the benefits of nonprofit retirement programs, explores the financial stress the plans are under, and describes the coping strategies developed by organizations

    Communiqué No. 15: Health Care and Nonprofits: The Hidden Dimension of America's Health Care Crisis

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    Providings findings from a national survey that examines how nonprofits and their employees are affected by rising health care costs

    Application of intersatellite links to domestic satellite systems

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    The results of a study on intersatellite link (ISL) applications for domestic satellite communications are presented. It was determined if any technical, economic, or performance benefits could be gained by introducing intersatellite links into a domestic satellite communication network. Several key systems issues of domestic ISL's are addressed. These include the effect of a skewed traffic distribution on the selection of ISL satellite orbit locations, tolerable satellite spacing, and crosslink traffic-handling requirements. An ISL technology assessment is made by performing a parametric link analysis for several microwave and optical implementations. The impact of the crosslink on the end-to-end link performance is investigated for both regenerative and nonregenerative ISL architectures. A comparison is made between single satellite systems operating at C-, and Ku-bands and the corresponding ISL systems in terms of ground segment cost, space segment cost, and net link performance. Results indicate that ISL's can effectively expand the CONUS orbital arc, with a 60 GHz ISL implementation being the most attractive

    Complementary satellite sound broadcasting systems: A NASA assessment for the Voice of America

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    Satellite concepts are examined which offer potentially significant sound broadcast coverage of audio as a complement to VOA's existing and planned terrestrial sound broadcasting system. HF bands are emphasized but additional discussion is included for systems using higher frequencies. Low altitude satellites, shuttle altitude (275 km) and sun synchronous (about 1600 to 1800 km), would not be practical for international broadcasting since many satellites would be required for reliable and widespread coverage. Two concepts are discussed which would offer significant and practical broadcast coverage at HF. One, an 8-hr posigrade equatorial orbit, would offer about 1 hr of widespread, twice daily, coverage to three areas of the globe. The time of coverage is even greater when confined to densely populated areas only (2 to 3 hrs). Another orbit, the Apogee at Constant Time/Equatorial (ACE), provides the same coverage, but only once daily to each area. The latter orbit is highly elliptical, allowing insertion of a greater payload (more broadcast channels) with the existing launch capability. The ACE and 8-hr orbit concepts led to systems of about equal costs, with the ACE being slightly better

    Relative occurrence rates and connection of discrete frequency oscillations in the solar wind density and dayside magnetosphere

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    [1] We present an analysis of the occurrence distributions of statistically significant apparent frequencies of periodic solar wind number density structures and dayside magnetospheric oscillations in the f = 0.5–5.0 mHz range. Using 11 years (1995–2005) of solar wind data, we identified all spectral peaks that passed both an amplitude test and a harmonic F test at the 95% confidence level in 6-hour data segments. We find that certain discrete frequencies, specifically f = 0.7, 1.4, 2.0, and 4.8 mHz, occur more often than do other frequencies over those 11 years. We repeat the analysis on discrete oscillations observed in 10 years (1996–2005) of dayside magnetospheric data. We find that certain frequencies, specifically f = 1.0, 1.5, 1.9, 2.8, 3.3, and 4.4 mHz, occur more often than do other frequencies over those 10 years. Many of the enhancements found in the magnetospheric occurrence distributions are similar to those found in the solar wind. Lastly, we counted the number of times the same discrete frequencies were identified as statistically significant using our two spectral tests on corresponding solar wind and magnetospheric 6-hour time series. We find that in 54% of the solar wind data segments in which we identified a spectral peak, at least one of the same discrete frequencies was statistically significant in the corresponding magnetospheric data segment. Our results argue for the existence of inherent apparent frequencies in the solar wind number density that directly drive global magnetospheric oscillations at the same discrete frequencies, although the magnetosphere also oscillates through other physical mechanisms

    ULF waves in the solar wind as direct drivers of magnetospheric pulsations

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    [1] Global magnetospheric ULF pulsations with frequencies in the Pc 5 range (f = 1.7–6.7 mHz) and below have been observed for decades in space and on the Earth. Recent work has shown that in some cases these pulsations appear at discrete frequencies. Global cavity and waveguide modes have been offered as possible sources of such waves. In these models the magnetosphere is presumed to resonate globally at frequencies determined solely by its internal properties such as size, shape, field topology, mass density distribution, etc. We show in this work that upstream solar wind number density and dynamic pressure variations precede and drive compressional magnetic field variations at geosynchronous orbit. Furthermore, spectral analysis shows that wave power spectra in both the solar wind and magnetosphere contain peaks at the same discrete frequencies. Therefore, in contrast to the cavity mode hypothesis, we suggest that discrete ULF pulsations observed within the magnetosphere are at least sometimes directly driven by density oscillations present in the ambient solar wind. Finally, we comment on possible sources for such pulsations observed in the solar wind
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