A high-gain omnidirectional satellite antenna technique Final report

High gain omnidirectional satellite system design, using planar and circular multiple beam arrays and solid state switchin

Application of an Electronic Analog Computer for the Simulation of Hydrologic Events on a Southwest Watershed

The hydrologic characteristics of watersheds in semiarid regions are dependent upon many variable and often interrelated factors. A quantitative knowledge of these factors and of their relative influence upon the system as a whole is needed in order to improve the efficiency of watershed management in these areas. In an attempt to develop a comprehensive simulation model of a semiarid watershed, research workers in the Agricultural Research Service considered the electronic quently signed with Utah State University. Analog modeling concepts are based upon the development of basic relationships which describe the various processes which occur within the surface hydrologic system of a semiarid watershed. Once established, the model is applicable to any particular geographic unit by determining the appropriate constants of the hydrologic equations. The analog computer is ideally suited to the many time-dependent differential equations which are encountered in hydrologic systems. To test individual equations and to verify the model, a subbasin of Walnut Gulch watershed in southern Arizona was simulated. In preliminary tests, close agreement was achieved between the observed and computed runoff hydrographs for a single storm. Some progress is also reported in the development of an analog technique to plot isohyetal lines corresponding to selected time intervals during the course of a storm

DETERMINATION OF THE COEFFICIENT OF DRAG OF THREE DIFFERENT TENNIS BALLS USING A WIND TUNNEL

INTRODUCTION: The constant improvement of tennis rackets and coaching has changed the current game to such an extent that critics complain it is dominated by the serve. Tennis balls are being served at higher velocities with each improvement. There may soon be a point at which the receiver may not be able to react quickly enough. Before any changes can be suggested, it is necessary to have a complete understanding of the game of tennis in terms of the ball mechanics and flight. This paper documents preliminary study of the aerodynamics of tennis balls. METHODS: The investigation considered three different tennis balls, differing both in construction and quality of nap. The three ball types used are as follows: an unspoiled pressurized ball fresh from its container; an unspoiled ‘permanent’ pressure ball fresh from its container; and a well worn pressurized ball showing significant visual reduction in quality and overall bulk of nap. By using the above set of tennis balls, the effects of both construction and surface quality on a balls flight through the air were analyzed. Initial testing involved an investigation of the velocity profile of the wind tunnel. It was found that the velocity was constant across the working section up to the maximum velocity of 26ms-1. This result meant that the complete viewing area of 230mm could be used for collection of data. Three different tennis balls were dropped through the working section of the wind tunnel using an electronically activated ball drop apparatus. The wind velocity was increased in equal increments of 3ms-1, from zero to 26.3ms-1, dropping all three balls at each setting. The motion of the ball during flight was captured digitally using a KODAK Motioncorder at a frame rate of 100fs-1 and a shutter speed of 1/1000 second. The frames containing the flight of the ball were transferred from the Motioncorder and captured digitally on a computer, creating a store of several images over the duration of the flight. Data was collected from individual images using OPTIMAS 6 which exported the data to Microsoft Excel 5. The analysis used three points on the circumference of the ball, producing chords to find the its center. The resulting trajectory of the ball was viewed in the form of a graph of displacement versus time. A second order polynomial which explained the data set was fitted to the chart. The differentiation of this gave the acceleration of the ball during flight. RESULTS: The results obtained from the tests were plotted on a graph of coefficient of drag (CD) versus the Reynolds number. This chart showed that the ball with the significant removal of nap had a lower CD when compared to the balls with a brand new nap. A computational model was developed to predict the trajectory of a tennis ball. Using the results from these tests on a ball hit horizontally with an initial velocity of 26.3ms-1 and zero spin, it was estimated that the ball with the significant removal of nap would travel 1m further than the balls with unspoiled nap

Application of an Electronic Analog Computer to the Problems of River Basin Hydrology

As demands upon available water supplies increase, there is an accompanying increase in the need to assess the downstream consequences resulting from chances at specific locations within a hydrologic system. This problem was approached by electronic analog simulation of the hydrologic system. The complexity of a hydrologic model depends to a large extent upon the magnitude of the time and spatial increments utilized in the model. The increment size selected depends upon the types of problems to be solved. Three models are described, and in each succeeding model the definition in terms of time and/or space is improved. While the problems as its predecessor, it is also capable of solving many additional problems which require a higher degree of definition. Preliminary verification studies for both the second and third models have shown close agreement between observed and computed discharge hydrographs from prototype basins

Impact craters on Venus: An overview from Magellan observations

Magellan has revealed an ensemble of impact craters on Venus that is unique in many important ways. We have compiled a database describing 842 craters on 89 percent of the planet's surface mapped through orbit 2578 (the craters range in diameter from 1.5 to 280 km). We have studied the distribution, size-frequency, morphology, and geology of these craters both in aggregate and, for some craters, in more detail. We have found the following: (1) the spatial distribution of craters is highly uniform; (2) the size-density distribution of craters with diameters greater than or equal to 35 km is consistent with a 'production' population having a surprisingly young age of about 0.5 Ga (based on the estimated population of Venus-crossing asteroids); (3) the spectrum of crater modification differs greatly from that on other planets--62 percent of all craters are pristine, only 4 percent volcanically embayed, and the remainder affected by tectonism, but none are severely and progressively depleted based on size-density distribution extrapolated from larger craters; (4) large craters have a progression of morphologies generally similar to those on other planets, but small craters are typically irregular or multiple rather than bowl shaped; (5) diffuse radar-bright or -dark features surround some craters, and about 370 similar diffuse 'splotches' with no central crater are observed whose size-density distribution is similar to that of small craters; and (6) other features unique to Venus include radar-bright or -dark parabolic arcs opening westward and extensive outflows originating in crater ejecta

Who the hell was that? Stories, bodies and actions in the world

This article explores a two-way relationship between stories and the experiential actions of bodies in the world. Through an autoethnographic approach, the article presents a series of interlinked story fragments in an effort to show and evoke a feel for the ways in which stories, bodies, and actions influence and shape each other over time. It offers some reflections on the experiences the stories portray from the perspective of a social constructionist conception of narrative theory and suggest that while stories exert a powerful influence on the actions of our bodies, our bodies intrude on or ‘talk back’ to this process because bodies have an existence beyond stories

Snowmelt Simulation

The rapid growth in recent years of a variety of demands upon available water resources has lead to an increasing interest in more fundamental approaches to the science of hydrology. Accompanying this growth has been a need for an increased understanding of the snowmelt process. A completely adequate description of the entire physical process of snowmelt under all conditions is not yet available. The complex interrelated and variable nature of the snowmelt processes that occur simultaneously complicate the problem. A preliminary mathematical model of the snowmelt process has been developed in which processes such as pack settlement rates and energy flow in the pack by means of both conduction and liquid movement are considered. Factors such as an temperature, surface albedo, and degree and direction of slope are also included. A temperature criterion is applied to predict the form of precipitation input (snow or rain) to the model. Equations of the various processes are synthesized into a dynamic model of the total system by means of an electronic analog computer. This computer was utilized primarily because of its ability to (1) perform repetitive operations at very high speeds and (2) solve directly the several time-dependent partial differential equations included in the model. Field data from snow laboraties operated by the Corps of Engineers and highly instrumented watersheds of the Agricultural Research Service are being used to test and verify the model. Inital results have indicated close agreement between observed and computed results. Sensitivity studies have been conducted, and work is continuing to further test and improve the model

Application of Electronic Analog Computer to Solution of Hydrologic and River Basin Planning Problems: Utah Simulation Model II

As demands upon available water supplies increase, there is an accompanying increase in the need to assess the downstream hydrologic system. At Utah State University this problem is being approached by electronic analog simulation of the hydrologic system. Modeling concepts are based upon the development of basic relationships which describe the various hydrologic processes. Within a system, these relationships are linked by the continuity -of-mass principle which requires a hydrologic balance at all points. Once established, the model is applied to any particular geographic unit by determining the appropriate constants of the hydrologic equations. The analog computer is ideally suited to the solution of the many time-dependent differential equations which are encountered in the hydrologic systems. The complexity of a hydrologic model depends to a large extent upon the magnitude of the time and spatial increments utilized in the model. In this study the mathematical development was based on the concepts of relatively small increments of space and large time increments. The model is, therefore, applicable to in-basin probelms involving a time increment of, for example, one month. To test individual equations and to verify the model, the Circle Valley subbasin of the Servier River system in Utah was simulated. Close agreement between computed and observed outflows was achieved on both a monthly and a total annual basis

Majorana and the quasi-stationary states in Nuclear Physics

A complete theoretical model describing artificial disintegration of nuclei by bombardment with alpha-particles, developed by Majorana as early as in 1930, is discussed in detail alongside the basic experimental evidences that motivated it. By following the quantum dynamics of a state resulting from the superposition of a discrete state with a continuum one, whose interaction is described by a given potential term, Majorana obtained (among the other predictions) the explicit expression for the integrated cross section of the nuclear process, which is the direct measurable quantity of interest in the experiments. Though this is the first application of the concept of quasi-stationary states to a Nuclear Physics problem, it seems also that the unpublished Majorana's work anticipates by several years the related seminal paper by Fano on Atomic Physics.Comment: latex, amsart, 13 page