39,352 research outputs found
Issues in Evaluating Health Department Web-Based Data Query Systems: Working Papers
Compiles papers on conceptual and methodological topics to consider in evaluating state health department systems that provide aggregate data online, such as taxonomy, logic models, indicators, and design. Includes surveys and examples of evaluations
Temperature and flow measurements on near-freezing aviation fuels in a wing-tank model
Freezing behavior, pumpability, and temperature profiles for aviation turbine fuels were measured in a 190-liter tank chilled to simulate internal temperature gradients encountered in commercial airplane wing tanks. When the bulk of the fuel was above the specification freezing point, pumpout of the fuel removed all fuel except a layer adhering to the bottom chilled surfaces, and the unpumpable fraction depended on the fuel temperature near these surfaces. When the bulk of the fuel was at or below the freezing point, pumpout ceased when solids blocked the pump inlet, and the unpumpable fraction depended on the overall average temperature
Experiments on fuel heating for commercial aircraft
An experimental jet fuel with a -33 C freezing point was chilled in a wing tank simulator with superimposed fuel heating to improve low temperature flowability. Heating consisted of circulating a portion of the fuel to an external heat exchanger and returning the heated fuel to the tank. Flowability was determined by the mass percent of unpumpable fuel (holdup) left in the simulator upon withdrawal of fuel at the conclusion of testing. The study demonstrated that fuel heating is feasible and improves flowability as compared to that of baseline, unheated tests. Delayed heating with initiation when the fuel reaches a prescribed low temperature limit, showed promise of being more efficient than continuous heating. Regardless of the mode or rate of heating, complete flowability (zero holdup) could not be restored by fuel heating. The severe, extreme-day environment imposed by the test caused a very small amount of subfreezing fuel to be retained near the tank surfaces even at high rates of heating. Correlations of flowability established for unheated fuel tests also could be applied to the heated test results if based on boundary-layer temperature or a solid index (subfreezing point) characteristic of the fuel
A study to determine the flight characteristics and handling qualitites of variable geometry spacecraft. Volume 3: Low L/D concept with fold-down wings
A study was conducted to determine the flight characteristics and wing deployment transients for a variable geometry spacecraft concept having a hypersonic lift-to-drag ratio near 1.0, and employing fold-down wings. Unpowered flight conditions were considered throughout the study. The body of the spacecraft uses a trapezoidal cross section. The variable geometry wings, stowed in the sides of the vehicle, are deployed at transonic speeds
Role of geometrical symmetry in thermally activated processes in clusters of interacting dipolar moments
Thermally activated magnetization decay is studied in ensembles of clusters
of interacting dipolar moments by applying the master-equation formalism, as a
model of thermal relaxation in systems of interacting single-domain
ferromagnetic particles. Solving the associated master-equation reveals a
breakdown of the energy barrier picture depending on the geometrical symmetry
of structures. Deviations are most pronounced for reduced symmetry and result
in a strong interaction dependence of relaxation rates on the memory of system
initialization. A simple two-state system description of an ensemble of
clusters is developed which accounts for the observed anomalies. These results
follow from a semi-analytical treatment, and are fully supported by kinetic
Monte-Carlo simulations.Comment: 9 pages, 6 figure
Thirring Solitons in the presence of dispersion
The effect of dispersion or diffraction on zero-velocity solitons is studied
for the generalized massive Thirring model describing a nonlinear optical fiber
with grating or parallel-coupled planar waveguides with misaligned axes. The
Thirring solitons existing at zero dispersion/diffraction are shown numerically
to be separated by a finite gap from three isolated soliton branches. Inside
the gap, there is an infinity of multi-soliton branches. Thus, the Thirring
solitons are structurally unstable. In another parameter region (far from the
Thirring limit), solitons exist everywhere.Comment: 12 pages, Latex. To appear in Phys. Rev. Let
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55-year-old Male with Exertional Dyspnea
Introduction: Dyspnea is a common presenting complaint for many patients in the emergency department.Case Presentation: A 55-year-old man with type I diabetes presented to the emergency department with one month of intermittent palpitations and dyspnea. His lungs were clear to auscultation, and his chest radiograph was normal.Discussion: This case takes the reader through the differential diagnosis and systematic work-up of dyspnea with discussion of the diagnostic study, which ultimately led to this patient’s diagnosis and successful treatment
Noise data from tests of a 1.83 meter (6-ft-) diameter variable-pitch 1.2-pressure-ratio fan (QF-9)
Acoustic and aerodynamic data for a 1.83-meter (6-ft.) diameter fan suitable for a quiet engine for short-takeoff-and-landing (STOL) aircraft are documented. The QF-9 rotor blades had an adjustable pitch feature which provided a means for testing at several rotor blade setting angles, including one for reverse thrust. The fan stage incorporated features for low noise. Far-field noise around the fan was measured without acoustic suppression over a range of operating conditions for six different rotor blade setting angles in the forward thrust configuration, and for one in the reverse configuration. Complete results of one-third-octave band analysis of the data are presented in tabular form. Also included are power spectra, data referred to the source, and sideline perceived noise levels
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