9,606 research outputs found

    Media Use and Performance in Air Force Organizations: Testing the Value of Media Richness Theory

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    Communication is a critical factor in any organization. The choices Air Force members make when communicating have a direct impact on mission accomplishment. Media Richness Theory (MRT) recognizes that communication needs, and the ability of various media to support them, are influenced by a number of factors involving the message content, situational elements, and its symbolic aspects. The theory predicts employees who use more appropriate communication media face to face conversation, telephone, e-mail, and written correspondence as predicted by the theory, will be more effective performers. The ability of MRT to explain supervisory performance ratings for a group of junior enlisted Air Force members (n=48) and another group of senior enlisted Air Force members (n=33) was tested. Results showed that junior enlisted members who made media choices more consistent with MRT were rated as more effective performers by their supervisors. This is consistent with the findings of previous studies. However, the results for senior enlisted members were not consistent with the theory. For senior enlisted members, agreement with their supervisor\u27s media choices was a better predictor of performance than agreement with MRT\u27s predictions. This suggests that MRT may be more applicable for some types of employees than others

    Development of a new laser Doppler velocimeter for the Ames High Reynolds Channel No. 2

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    A new two-channel laser Doppler velocimeter developed for the Ames High Reynolds Channel No. 2 is described. Design features required for the satisfactory operation of the optical system in the channel environment are discussed. Fiber optics are used to transmit the megahertz Doppler signal to the photodetectors located outside the channel pressure vessel, and provision is made to isolate the optical system from pressure and thermal strain effects. Computer-controlled scanning mirrors are used to position the laser beams in the channel flow. Techniques used to seed the flow with 0.5-micron-diam polystyrene spheres avoiding deposition on the test-section windows and porous boundary-layer removal panels are described. Preliminary results are presented with a discussion of several of the factors affecting accuracy

    Predictor Equations for Beach Processes and Responses

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    A stepwise (linear) multiple regression procedure is applied to 11 environmental variables (or predictors) in the beach-ocean-atmosphersey stema t Virginia Beach, Virginia, for the following five predictands: mean longshore current velocity, mean bottom slope in the shoaling-wave zone, average mean grain size in the shoaling-wave zone, and beach deposition and beach erosion on the lower foreshore. Predictors consist of variables related to beach geometry, local water properties, local wind conditions, tidal fluctuations, and wave characteristics The resultant equations are tested against a set of independent data and, with one exception, agree reasonably. It is believed that if the data set were increased to include at least one year\u27s continuous measurements the procedure outlined would yield valid equations for all but stormy-weather conditions.It is presupposed that some provision will have to be made for preconditioning the data, as \u27storm\u27 and \u27nonstorm\u27 data will probably have to be analyzed separately

    Critical components for novel direct cardiac compression device

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    According to the American Heart Association, there are currently 5 million Americans diagnosed with congestive heart failure and that number is steadily increasing (AHA, 2003). The alarming problem of congestive heart failure and other related medical complications has created a need for devices that not only assist the heart but also help the heart to grow and remodel back to its normal configuration. Currently, there are several direct cardiac compression devices (DCCDs) that do assist the heart, however, they do not help the heart to grow and remodel correctly. Dr. John C. Criscione of Texas A&M University has proposed a novel DCCD, in which the compression of the device reinforces the natural curvature of the heart, helping it to grow and remodel correctly. It is hypothesized that with the support of the device, the cells of the heart will be stimulated to grow and remodel back to their normal size and return to their proper function. Two key components necessary to the novel DCCD were designed and constructed for this study. The first component was an adjustable outer shell which enabled the device to become smaller as the failing heart returned to normal size. The second component was an inflatable inner membrane that applies direct pressure to the outer wall of the heart in a way that promotes physiological stress and strain patterns

    Development and marketing of a prosthetic urinary control valve system

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    An implantable prosthetic for the control of urinary incontinence was developed and marketed. Three phases are presented: bench development studies, animal trials, and human clinical trials. This work was performed under the direction of a Research Team at Rochester General Hospital (RGH). Bench trials were completed on prototype hardware and provided early verification of the device's ability to withstand repeated cyclic testing. Configurational variants were evaluated and a preferred design concept was established. Silicone rubber (medical grade) was selected as the preferred material for the prosthesis

    Impact of Land Model Calibration on Coupled Land-Atmosphere Prediction

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    Land-atmosphere (L-A) interactions play a critical role in determining the diurnal evolution of both planetary boundary layer (PBL) and land surface heat and moisture budgets, as well as controlling feedbacks with clouds and precipitation that lead to the persistence of dry and wet regimes. Recent efforts to quantify the strength of L-A coupling in prediction models have produced diagnostics that integrate across both the land and PBL components of the system. In this study, we examine the impact of improved specification of land surface states, anomalies, and fluxes on coupled WRF forecasts during the summers of extreme dry and wet land surface conditions in the U.S. Southern Great Plains. The improved land initialization and surface flux parameterizations are obtained through calibration of the Noah land surface model using the new optimization and uncertainty estimation subsystem in NASA's Land Information System (LIS-OPT/UE). The impact of the calibration on the a) spinup of the land surface used as initial conditions, and b) the simulated heat and moisture states and fluxes of the coupled WRF simulations is then assessed. Changes in ambient weather and land-atmosphere coupling are evaluated along with measures of uncertainty propagation into the forecasts. In addition, the sensitivity of this approach to the period of calibration (dry, wet, average) is investigated. Results indicate that the offline calibration leads to systematic improvements in land-PBL fluxes and near-surface temperature and humidity, and in the process provide guidance on the questions of what, how, and when to calibrate land surface models for coupled model prediction

    Impact of Calibrated Land Surface Model Parameters on the Accuracy and Uncertainty of Land-Atmosphere Coupling in WRF Simulations

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    Land-atmosphere (L-A) interactions play a critical role in determining the diurnal evolution of both planetary boundary layer (PBL) and land surface temperature and moisture budgets, as well as controlling feedbacks with clouds and precipitation that lead to the persistence of dry and wet regimes. Recent efforts to quantify the strength of L-A coupling in prediction models have produced diagnostics that integrate across both the land and PBL components of the system. In this study, we examine the impact of improved specification of land surface states, anomalies, and fluxes on coupled WRF forecasts during the summers of extreme dry (2006) and wet (2007) land surface conditions in the U.S. Southern Great Plains. The improved land initialization and surface flux parameterizations are obtained through the use of a new optimization and uncertainty estimation module in NASA's Land Information System (LIS-OPT/UE), whereby parameter sets are calibrated in the Noah land surface model and classified according to a land cover and soil type mapping of the observation sites to the full model domain. The impact of calibrated parameters on the a) spinup of the land surface used as initial conditions, and b) heat and moisture states and fluxes of the coupled WRF simulations are then assessed in terms of ambient weather and land-atmosphere coupling along with measures of uncertainty propagation into the forecasts. In addition, the sensitivity of this approach to the period of calibration (dry, wet, average) is investigated. Finally, tradeoffs of computational tractability and scientific validity, and the potential for combining this approach with satellite remote sensing data are also discussed

    Dynamics of monatomic liquids

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    We present a theory of the dynamics of monatomic liquids built on two basic ideas: (1) The potential surface of the liquid contains three classes of intersecting nearly-harmonic valleys, one of which (the ``random'' class) vastly outnumbers the others and all whose members have the same depth and normal mode spectrum; and (2) the motion of particles in the liquid can be decomposed into oscillations in a single many-body valley, and nearly instantaneous inter-valley transitions called transits. We review the thermodynamic data which led to the theory, and we discuss the results of molecular dynamics (MD) simulations of sodium and Lennard-Jones argon which support the theory in more detail. Then we apply the theory to problems in equilibrium and nonequilibrium statistical mechanics, and we compare the results to experimental data and MD simulations. We also discuss our work in comparison with the QNM and INM research programs and suggest directions for future research.Comment: 53 pages, 16 figures. Differs from published version in using American English spelling and grammar (published version uses British English
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