Wakes from arrays of buildings

Experiments were carried out in a small wind tunnel in which atmospheric flow around buildings was simulated. Arrays of one, two, three, and four model buildings were tested, and wake profiles of velocity and turbulence were measured. The data indicate the effect of the buildings on the wind environment encountered by aircraft during landing or takeoff operations. It was possible to use the results to locate the boundaries of the air regions affected by the obstacles and to recommend preferred arrangements of buildings to maximize light safety

Wind tunnel measurements of three-dimensional wakes of buildings

Measurements relevant to the effect of buildings on the low level atmospheric boundary layer are presented. A wind tunnel experiment was undertaken to determine the nature of the flow downstream from a gap between two transversely aligned, equal sized models of rectangular cross section. These building models were immersed in an equilibrium turbulent boundary layer which was developed on a smooth floor in a zero longitudinal pressure gradient. Measurements with an inclined (45 degree) hot-wire were made at key positions downstream of models arranged with a large, small, and no gap between them. Hot-wire theory is presented which enables computation of the three mean velocity components, U, V and W, as well as Reynolds stresses. These measurements permit understanding of the character of the wake downstream of laterally spaced buildings. Surface streamline patterns obtained by the oil film method were used to delineate the separation region to the rear of the buildings for a variety of spacings

Rough-to-smooth transition of an equilibrium neutral constant stress layer

Purpose of research on rough-to-smooth transition of an equilibrium neutral constant stress layer is to develop a model for low-level atmospheric flow over terrains of abruptly changing roughness, such as those occurring near the windward end of a landing strip, and to use the model to derive functions which define the extent of the region affected by the roughness change and allow adequate prediction of wind and shear stress profiles at all points within the region. A model consisting of two bounding logarithmic layers and an intermediate velocity defect layer is assumed, and dimensionless velocity and stress distribution functions which meet all boundary and matching conditions are hypothesized. The functions are used in an asymptotic form of the equation of motion to derive a relation which governs the growth of the internal boundary layer. The growth relation is used to predict variation of surface shear stress

A comparison of wake characteristics of model and prototype buildings in transverse winds

Previously measured mean velocity and turbulence intensity profiles in the wake of a 26.8-m long building 3.2 m high and transverse to the wind direction in an atmospheric boundary layer several hundred meters thick were compared with profiles at corresponding stations downstream of a 1/50-scale model on the floor of a large meteorological wind tunnel in a boundary layer 0.61 m in thickness. The validity of using model wake data to predict full scale data was determined. Preliminary results are presented which indicate that disparities result from differences in relative depth of logarithmic layers, surface roughness, and the proximity of upstream obstacles

Effect of laser frequency noise on fiber-optic frequency reference distribution

The effect of the linewidth of a single longitude-mode laser on the frequency stability of a frequency reference transmitted over a single-mode optical fiber is analyzed. The interaction of the random laser frequency deviations with the dispersion of the optical fiber is considered to determine theoretically the effect on the Allan deviation (square root of the Allan variance) of the transmitted frequency reference. It is shown that the magnitude of this effect may determine the limit of the ultimate stability possible for frequency reference transmission on optical fiber, but is not a serious limitation to present system performance

The Influence of Prior Performance, Slack, and Top Management Turnover on Divestiture and Subsequent Firm Performance.

This research is an investigation of the influence of contextual factors on a multidivisional firm\u27s decision to divest an entire business unit, and the effects of that divestiture on firm operating performance, market performance, and organizational slack generation and usage. Contextual influences and outcomes are assessed for a sample of 102 U.S. based firms representing 43 different industries, as defined by primary four-digit Standard Industry Classification (SIC). This research drew on prior research in strategic management, finance, and organizational theory to develop an integrated model of firm-level influences on divestiture and determine if those influences can be used to predict divestiture. Four important contextual influences on divestiture are examined: (1) The influences of prior operating performance, (2) prior organizational slack generation and usage patterns, (3) prior market performance, and (4) top manager turnover are examined to determine the combined effect of these influences on divestiture. Additionally, the ex-post divestiture effect on these variables is examined to determine the strategic effects of a unit divestiture. The study\u27s overall results tend to demonstrate that the firm-level factors investigated are not significantly related to divestiture, and these factors could not usefully discriminate between divesting and non-divesting firms. Additionally, the proposed model of the effect of a divestiture on subsequent firm operating performance, market performance, and absorbed and unabsorbed organizational slack was generally not supported. The overall results showed no significant relationship between divestiture and subsequent firm performance and organizational slack relationships. This investigation supports the view that divestiture of a unit in a multidivisional firm is influenced by factors other than the primary contextual variables investigated in this study. Furthermore, the ex-post effect of a divestiture on a divesting firm is generally weak and may not be evident from commonly-used variables measured in a conventional manner

The one dimensional Black college football player : a mixed methods approach to understanding racial and athletic identity

The complex relationship between sports, representation and power is constantly being documented through modern omnipresent media. Daily inundation of various media images permeates social understanding to the point of realistic expectations. These expectations are often substituted for genuine physical interaction, as is the case for many Black male collegiate football players. Media often scripts Black males as successful by way of their athletic achievements, often misrepresenting their multifaceted potential. As result of that portrayal, many Black males single-mindedly purse athletic careers at the degradation of the many other facets and gifts they possess. Thus, the purpose of this study is to examine the effects of media consumption and character portrayals on the identity negotiation of Black male collegiate football players. This study employed mixed-methods framework by surveying 226 Black college football players and conducting 16 interviews with Black collegiate football players and athletic administrators. The study found that media portrayal can negatively influence the negotiation of identities priming Black collegiate football players for athletic one-dimensionalism. The data generated five themes; Media Influence, Black College Football Player Politics, Athletic Industrial Complex and Football Culture, One Dimensional versus Multi-Dimensional, and What Schools Can do Better. Quantitatively, Cross Racial identity Scale (CRIS) and the Athletic Identity Measurement Scale (AIMS) were used to gauge identity participant attitudes. Quantitatively, the study affirmed Black college football players have elevated athletic identity and a suppressed racial identity. There was a negative relationship between athletic identity and athletic classification. There was a correlation represented between a racial identity attitude and athletic classification. The implications of this study are to promote multidimensional beings and help elucidate the effects of media portrayals and consumption. The study also contextualizes Black athletes’ experiences at the juncture of sport and social justice. Furthermore, the study is contributing to current and future literature through a nuanced investigation of the experiences and identity negotiation of Black collegiate athletes.Curriculum and Instructio

Design of a fiber-optic transmitter for microwave analog transmission with high phase stability

The principal considerations in the design of fiber-optic transmitters for highly phase-stable radio frequency and microwave analog transmission are discussed. Criteria for a fiber-optic transmitter design with improved amplitude and phase-noise performance are developed through consideration of factors affecting the phase noise, including low-frequency laser-bias supply noise, the magnitude and proximity of external reflections into the laser, and temperature excursions of the laser-transmitter package