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This project examined absenteeism as a surrogate for ill health and itsusefulness in the context of the different survival problem. The data came from an occupational cohort study of arsenic (7440382) and lung cancer. The cohort c...
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This project examined absenteeism as a surrogate for ill health and itsusefulness in the context of the different survival problem. The data came from an occupational cohort study of arsenic (7440382) and lung cancer. The cohort consisted of all white male workers employed for 1 year or more between 1940 and 1964 at a copper smelter in Tacoma, Washington. After controlling for the level of current exposure, age at hire and year at hire, the risk of having a 30 day or longer absence was generally higher with increased level of cumulative exposure. In contrast, current exposure level shows an inverse relationship with absence. The mortality analysis suggests that a recent absence of more than 30 days was associated with a higher risk of death from respiratory cancer among employees exposed to arsenic. The authors caution that information on absenteeism without knowledge of the reasons for the absence is not in and of itself in such studies.
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In the first phase of this study, software packages for routing and schedulingdemand actuated transit systems were compared. The software package selected was then installed in the Barry County (Michigan) Transit system. This phas...
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In the first phase of this study, software packages for routing and schedulingdemand actuated transit systems were compared. The software package selected was then installed in the Barry County (Michigan) Transit system. This phase of this study was an evaluation of the selected system. The software package was considered to be successful based on a comparison of operating parameters, user satisfaction as expressed in a survey, and comments from the dispatcher. Measures of performance (M.O.E.) included passengers per vehicle hour, passenger per bus mile and vehicle-hour of service per available vehicle hour. Each of these three measures showed an increase between the before and after period. A questionnaire was distributed to bus passengers to assess their satisfaction with system. The response ranged from 53 percent who rated the transfer process as positive to over 90 percent who rated the ability to make reservations as good or very good. The response to all the questions were answered by a majority of the respondents as positive. Finally, the dispatcher noted that the algorithm assisted in reducing data entries, responding more rapidly to inquiries and fewer lost or misplaced repeat trip cards.
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The mesoscale vertical velocity induced by stress changes in the surface layer isevaluated as a function of the size of the rough patch in relation to environmental parameters. The nature of the flow perturbation strongly depends ...
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The mesoscale vertical velocity induced by stress changes in the surface layer isevaluated as a function of the size of the rough patch in relation to environmental parameters. The nature of the flow perturbation strongly depends on the relation between the width of the rough patch and the two natural scales of the flow, i.e. the inverse inertia wave number and the inverse of the Scorer parameter. When the width of the rough patch is comparable to the inverse inertia wave number or larger, the atmospheric perturbation is trapped, the vertical scale equals the depth of the stress surface layer, and the horizontal scale equals the Rossby radius. When the width of the rough patch is larger than the inverse of the Scorer parameter, but smaller than the inverse inertia wave number, the atmospheric perturbation is a hydrostatic gravity wave with a vertical wave number equal to the Scorer parameter. When the width of the rough patch is comparable to the inverse of the Scorer parameter, the atmospheric perturbation is a propagating lee wave with a vertical wave number equal to the Scorer parameter. When the ambient flow is strong over a small rough patch, the flow is irrotational. The same limitations, inherent to the linear gravity waves excited by the forcing in the atmosphere (e.g. mountain waves, gravity waves initiated by convection, etc.), apply to the mesoscale perturbation induced by a rough patch.
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A video image analysis technique for concentration measurements and flow visualization was developed for the study of diffusion in building wakes and other wind tunnel flows. Smoke injected into the flow was photographed from abov...
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A video image analysis technique for concentration measurements and flow visualization was developed for the study of diffusion in building wakes and other wind tunnel flows. Smoke injected into the flow was photographed from above with a video camera, and the video signal was digitized in real time during the experiment and during playback with a video image analysis system. The relation between the digitized smoke intensity and the vertically integrated concentration of smoke particles was obtained from calibration experiments in which the smoke was replaced by a mixture of ethane and air. The time-averaged vertically-integrated concentration of the ethane tracer was measured at discrete points throughout the flow field and correlated with the time-averaged smoke intensity data. After the system was calibrated, the instantaneous and time-averaged fields of vertically integrated concentration were obtained by simply photographing the smoke plume. Color-contoured images of the plume were created and displayed in real time thus creating a pseudo-color movie that was very useful for flow visualization. The technique was used to study the effects of building geometry and source location on the concentration and flow patterns in building wakes. (Copyright (c) 1991 Pergamon Press plc.)
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As air traffic density increases, effective use of airspace must include consideration of weather. Accurate identification of turbulent volumes is of paramount importance to flight safety. The advent of Doppler radar has made it p...
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As air traffic density increases, effective use of airspace must include consideration of weather. Accurate identification of turbulent volumes is of paramount importance to flight safety. The advent of Doppler radar has made it possible to observe wind motion in connective clouds. Over a number of years, research has lead to the spectral width (standard deviation) of the Doppler velocity measurements as an indicator of turbulence. In this paper we address the hypotheses that turbulence is essentially isotropic in convective systems, and therefore, observations of turbulence are independent of viewing angle. Radar observations made during the months of April, May, and June in 1980-1985 were scanned to locate storms amendable to analysis. A number of cases are presented in which a dual-Doppler network provided the essential data. Each case is in a different quadrant with respect to the Norman Doppler. Forty-four horizontal planes were studied from six different storms. The results of four of these storms are presented. Maximum reflectivity of these storms range from 51 to 58 dBZ. Altitudes include in this study range from near surface to 7 km. At these altitudes the maximum spectral width was 12 ms-1. For these cases, involving nearly 30,000 data points, 70% of the spectral width observations from CIM and NRO were within 1 ms-1 or less. These results indicate that the use of Doppler radar to detect turbulent regions within thunderstorms has a high probability of success, and the turbulent regions can be detected independent of the direction from which they are viewed. (KR)
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A series of flow visualization experiments was conducted in the large towing tank of the EPA Fluid Modeling Facility. The objective of the experiments was to define the flow over a simple cosine-shaped ridge and within a valley fo...
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A series of flow visualization experiments was conducted in the large towing tank of the EPA Fluid Modeling Facility. The objective of the experiments was to define the flow over a simple cosine-shaped ridge and within a valley formed by a pair of such ridges when there is a stable ambient flow normal to the ridge. Three experimental parameters were varied during the study: the Froude number, the steepness of the ridge, and the separation distance between the ridges. The flow over single ridges was found to be similar to previously published results for isolated hills. The flow within the valley formed by a pair of ridges was dependent upon the steepness of the ridge. For the most gentle ridge, there appeared to be little aerodynamic interaction between the two ridges even at the minimum separation of S/W = 1. The separation tended to be unstable with the flow switching from an attached to a separated condition during the tow.
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A surface panel method suitable for the analysis of marine propellers is developed and applied to various geometries to demonstrate its effectiveness. A reliable pressure distribution around a marine propeller, especially near the...
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A surface panel method suitable for the analysis of marine propellers is developed and applied to various geometries to demonstrate its effectiveness. A reliable pressure distribution around a marine propeller, especially near the leading edge of the blade, is obtained. Hub effects are naturally included by distributing panels on the hub surface. Detailed study of the flows at the trailing edge near the tip suggests a pressure Kutta condition, which requires the pressures of the last panels at the trailing edge be equal. Due to the nonlinear aspect of the pressure Kutta condition, an iterative process is employed. An efficient approximation of the ultimate wake is achieved by replacing it with a sink disk a the beginning of the ultimate wake. The sample geometries include an ellipsoid at zero angle of attack, a circular planform wing, a rectangular planform wing with varying sweep angles, a wing-body configuration, a long axisymmetric duct, and a marine propeller. Calculated pressure distributions around the wing-body configuration are in excellent agreement with the experimental data. Calculated thrust and torque for the propeller agree well experimental results.
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The development of a panel method suitable for the analysis of ducted propellers is presented. The method is first applied to the problem of the two-dimensional hydrofoil, the propeller with hub and the axisymmetric duct in unifor...
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The development of a panel method suitable for the analysis of ducted propellers is presented. The method is first applied to the problem of the two-dimensional hydrofoil, the propeller with hub and the axisymmetric duct in uniform flow. Some comparisons are made with exact solutions and with other panel codes. The difficulties associated with the modeling of ducted propeller flows are discussed. Convergence of the method for a typical ducted propeller is shown. The results include overall forces on the propeller and the duct, circulation distributions, and chordwise pressure distributions on the duct at different positions between blades.
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In laboratory experiments it is not possible to simulate all of the phenomena which affect the flow within a valley. It is especially difficult to simulate Coriolis effects which may be important for large valleys and thermal effe...
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In laboratory experiments it is not possible to simulate all of the phenomena which affect the flow within a valley. It is especially difficult to simulate Coriolis effects which may be important for large valleys and thermal effects associated with diurn
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As a part of the NASA Storm Hazards Program, the wind velocity in several thunderstorms was measured by an F-106B instrumented airplane and a ground-based Doppler radar. The results of five airplane penetrations of two storms in 1...
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As a part of the NASA Storm Hazards Program, the wind velocity in several thunderstorms was measured by an F-106B instrumented airplane and a ground-based Doppler radar. The results of five airplane penetrations of two storms in 1980 and six penetrations of one storm in 1981 are given. Comparisons were made between the radial wind velocity components measured by the radar and the airplane. The correlation coefficients for the 1980 data and part of the 1981 data were 0.88 and 0.78, respectively. It is suggested that larger values for these coefficients may be obtained by improving the experimental technique and in particular by slaving the radar to track the airplane during such tests.
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