Rubidium and cesium frequency standards status and performance on the GPS program

The on-oribt operational performance of the frequency standards on the Global Positioning System (GPS) 1 to 10 NAVSTAR satellites are discussed. The history of the Rb frequency standards showing the improvements incorporated at various stages of the program and the corresponding results are presented. Also presented is the operational history of the NAVSTAR cesium frequency standards. The frequency standards configuration data presented covers the chronology of events from the concept validation satellites, NAVSTAR 1 to 10, starting in 1978 to the present, including the configurations of clocks to be used on the GPS Production Program. Data are presented showing the results of long-term laboratory testing of a production Rb frequency standard with the necessary data taken to calculate Delta F, drift, time error, and Allan variance

College Students Experiencing Homelessness: The Consequence of Failed Macro Policies

Homelessness among college students is a growing trend, yet the problem is difficult to document due to the stigma associated with the circumstance. Flaws in policies related to jobs and wages, affordable housing, and affordable education interact to increase the risks faced by economically vulnerable students who enter college without secure housing, or who lose it during the course of their studies. A concerted institutional response is needed to mitigate both the risks and the consequences of homelessness, and to reduce the numbers of U.S. college students whose educational attainment is compromised by housing insecurity

Innovative Sexually Transmitted Infection Prevention-Intervention for African-American Adolescent Girls

The purpose of this study is to determine whether implementation of an innovative STI prevention intervention design affects participants’ knowledge of sexually transmitted infections and sexual self-efficacy. The population this research focuses on is African-American adolescent girls. The participants included in this study are aged 13-19. This particular population is disproportionately infected by sexually transmitted diseases, so it is vital that intervention programs be tailored to fit their culture and gender-specific needs in order to achieve maximum results. However, current interventions for African-American girls could be improved. The researcher has designed an innovative STI prevention intervention that draws from current, best evidence interventions. The researcher has hypothesized that: (1) participants that complete the intervention will have increased STI knowledge; and, (2) upon completion of the intervention, participants will have greater sexual self-efficacy

Production of gaseous fuel by pyrolysis of municipal solid waste

Pilot plant tests were conducted on a simulated solid waste which was a mixture of shredded newspaper, wood waste, polyethylene plastics, crushed glass, steel turnings, and water. Tests were conducted at 1400 F in a lead-bath pyrolyser. Cold feed was deaerated by compression and was dropped onto a moving hearth of molten lead before being transported to a sealed storage container. About 80 percent of the feed's organic content was converted to gaseous products which contain over 90 percent of the potential waste energy; 12 percent was converted to water; and 8 percent remained as partially pyrolyzed char and tars. Nearly half of the carbon in the feed is converted to benzene, toluene and medium-quality fuel gas, a potential credit of over $25 per ton of solid waste. The system was shown to require minimal preprocessing and less sorting then other methods

Contractor point of view for system development and test program

Industry's practice of testing space qualified hardware is examined. An overview of the Global Positioning System (GPS) Test Program is discussed from the component level to the sub-system compatibility tests with the space vehicle and finally to the launch site tests, all related to the Rubidium clock

QCD resummation in hadron production

We present calculations of next-to-leading order and resummed QCD corrections for semi-inclusive deep-inelastic scattering and single-inclusive e+e− annihilation. The resummation is performed to next-to-leading logarithmic accuracy. Knowing these QCD corrections is important in order to extract parton distribution functions and fragmentation functions from present and future data for these reactions. We present phenomenological results relevant for the COMPASS, HERMES, and BELLE experiments

Solving the primitive equations on a spherical geodesic grid: a technical report to a new class of dynamical cores

November 1998.Includes bibliographical references.This report documents the development and testing of a new type of dynamical core. Toe· model uses the invariant form of the primitive equations, solving the vorticity and divergence equations in place of the momentum equation. In the horizontal directions the model is discretized on a geodesic grid which is nearly uniform over the entire globe. In the vertical direction the model can use a variety of coordinate systems, including the generalized sigma coordinate of Suarez et al. (1983) and the Phillips (1957) sigma coordinate. By integrating the vorticity and divergence equations, terms related to gravity wave propagation are isolated and an efficient semi-implicit time stepping scheme is implemented. The model is tested using the idealized forcing proposed by Held and Suarez (1994). Results are presented for a variety of vertical coordinate systems with horizontal resolutions using 2562 polygons (approximately 4.5° x 4.5°) and using 10242 polygons (approximately 2.25° x 2.25° ). The results are compared to standard spectral model simulations truncated at T30 and T63. In terms of averages and variances of state variables, e geodesic grid model results using 2562 polygons are comparable to those of a spectral model truncated at slightly less than TIO, while a simulation with 10242 polygons is comparable to a spectral model simulation truncated at slightly less than T63. In terms of computational efficiency, further development of this geodesic grid model is required. Model timings completed on an SGI Origin 2000 indicate that the geodesic grid model with 10242 polygons is 2.7 times slower than the spectral model truncated at T63. At these resolutions, the MFlop rate of the geodesic grid model is 15% faster than the spectral model, so the differences in model speed are due to differences in the number of floating point operations required per day of simulation. The geodesic grid model is more competitive at higher resolution than at lower resolution, so further optimization and future trends toward higher resolution should benefit the geodesic grid model.Sponsored by the U.S. Department of Energy DE-FG03-98ER62611 and DE-FG03-94ER61929