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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Design and an automated parametric study of geodesic domes

Jones, Cecil Allen January 1978 (has links)
An automated parametric investigation of geodesic domes is conducted in this study. A brief description of the stiffness method of matrix structural analysis is included in addition to a discussion of the fully-stressed design procedure via the stress-ratio method. Automated solution algorithms based on the stiffness method are utilized in the development of WATFIV/FORTRAN computer codes to analyze space trusses and space frames. Several geodesic dome demonstration problems are formulated and subjected to axisymmetric and asymmetric loads to ascertain the three-dimensional load distribution characteristics of these structures. Shallowness effects are investigated and a demonstration problem is modified to determine the load distribution characteristics in a geodesic dome evenly supported about its base perimeter. Analysis results are recorded and presented along with commentary and conclusions. Several suggestions for further study are also provided. The WATFIV/FORTRAN computer code for space truss analysis is modified to include a stress-ratio algorithm for an automated fully-stressed design procedure. Numerical results obtained from a computer-aided design of a geodesic dome demonstration problem are provided in the appendix. / Master of Science
142

A model of the aluminum industry in the United States

Kelly, Miguel A. January 1978 (has links)
The energy crisis, the high capital requirements and the high price of the raw materials are critically affecting the short and long run decisions of the aluminum industry in the United States. To study the effect of these and other factors in the optimal development of the industry, a time dynamic linear model was developed. The model represents the industry in the United States interacting with the raw materials supplying countries. To demonstrate the capability of the model, nine case studies were run representing nine probable scenarios. The results, which should be approached from both a qualitative and a quantitative point of view, are discussed and some limited conclusions are derived. / Master of Science
143

Development of floral primordia and prediction of flowering in white oak (Quercus alba L.)

Merkle, Scott Arthur January 1978 (has links)
A two-part study was undertaken to gain a better understanding of oak floral development and flower crop variability as they relate to acorn crop variability. The first part traced the ontogeny of staminate and pistillate primordia of white oak (Quercus alba L.). It was found that staminate inflorescences are initiated in late spring and staminate flowers are structurally mature before the onset of dormancy in October. Pistillate inflorescences are not initiated until late summer, and pistillate flowers complete almost all of their development during the three weeks prior to anthesis. The second part of the study attempted to formulate predictive models for mature staminate and pistillate flower crop frequency distributions and densities by comparing the established phenology of floral differentiation with that of bud samples collected up to one month prior to flowering. It was found that the densities of staminate inflorescences (catkins), pistillate inflorescences (stalks) and total inflorescences are sufficiently predictable to make practical the use of linear models. However, because the pistillate inflorescence is so difficult to distinguish from the developing lateral bud, a large amount of error is generated in stalk counts completed one month before flowering. Also, the rapidity with which individual pistillate flowers are initiated just prior to pollination makes anticipation of their final number very difficult. The data suggests that although the year to year production of mature flower crops by a particular white oak may be consistent, it is not necessarily innate. / Master of Science
144

Economic strategies for forest regeneration

Thomson, Thomas Alfred January 1978 (has links)
This study derives a theoretical basis for planning forest regeneration operations and forest regeneration research projects. The purpose of such planning, is to facilitate effective implementation and monitoring of projects so that the forest investment goals of the finn may most easily be met. After discussing three approaches to problem solving, a production economic theory model is developed to derive the optimum production relationships. Regeneration strategies are defined as plans aimed at achieving these optimum results. A concept of regeneration research strategies is limited by the perfect certainty assumption of the model. Due to the uncertain nature of future events and the long period of forest production, the perfect certainty restriction is abandoned. Several methods for dealing with risk are discussed, including expected value, risk-adjusted discount rates, certainty equivalents, and risk measurement. A Markowitz efficient risk-return investment frontier is illustrated. Optimal investment strategies are those which maximize the firms risk-return utility preference subject to the efficient investments frontier. The scope of regeneration and regeneration research strategies is expanded and illustrated through use of the risk-return model. Regeneration strategies are plans aimed at making the highest return from forest production subject to the firms risk-return preferences. Regeneration research strategies are employed to select the optimum methods of research and optimum project selection. Regeneration research should be aimed at increasing the forest production function, learning more about the production relationships, and reducing the risks of production. / Master of Science
145

A generalized machine requirements planning algorithm for serial flow machining systems

Hayes, Glenn M. January 1978 (has links)
The machine requirements planning problem is one which is applicable throughout the manufacturing industry. The use of automation and computer technology makes the use of machine requirements modelling particularly attractive, and the vast capital investment in machining equipment offers significant opportunity for savings through optimization. The machine requirements problem must be modelled as a mixed integer linear program. However, a dynamic programming solution procedure with linear programming postoptimality techniques at each stage of the machining process is utilized to provide an efficient, flexible algorithm. The machine requirements model is capable of optimizing any type of machining system, whether of a discrete or continuous operating mode. Through discretizing the machine parameters problem, by limiting tool changes to between passes of a tool, any continuous mode system is approximated as discrete for optimization purposes and a direct interface with the machine requirements planning model is provided. The dynamic programming solution procedure is compared with a mixed integer procedure. The DP formulation is not only more efficient in both time and core but provides sensitivity information and offers a broad spectrum of further application into more complex aspects of manufacturing systems. / Master of Science
146

A comparison of visual and memory search processes within a single task

Weiss, Regina Ann January 1978 (has links)
The present information processing research provided a comparison of visual search and memory search processes with respect to search rates and search strategies. An innovative paradigm was evaluated which varied search type (i.e., visual or memory) randomly between trials of a single choice reaction time (RT) task. The following sequence of events for each of the 280 trials occurred. A ''memory" list of letters appeared, which subjects (N = 12) turned off by pulling simultaneously a left and right-hand RT trigger. After 3 sec, a warning buzzer sounded followed by a variable interval ranging from .5 to 1 sec and the "recognition" list. The subject pulled the left or right-hadn trigger as quickly as possible to indicate whether the memory and recognition lists included the same letter. A single target letter appeared as the memory list on the 140 visual search trials and as the recognition list for the 140 memory search trials. The search set (presented either as a memory list or recognition list) contained three, five, or seven letters. Memory Search was faster and less accurate than was Visual Search in the present task, The RT slope and serial position data indicated that Visual Search involved a serial, self-terminating comparison process, whereas the Memory Search data confirmed Sternberg's serial, exhaustive model. It was noted that physical characteristics of the task could have biased Visual Search toward a self-terminating strategy. Suggestions for future research in this area were discussed, as well as the author's plans to apply the paradigm to the study of information processing deficits in learning disabled children. / Master of Science
147

Some diseases and parasites affecting cottontail rabbits in Virginia

Jones, Edwin J. January 1978 (has links)
A serologic survey at Fort Pickett, Virginia was undertaken to determine if tularemia could be a factor in the continued low hunter harvest of cottontail rabbits. Between December 1976 and February 1978, ninety serum samples were collected from 11 species of mammals and 1 avian species, and tested for antibodies against Francisella tularensis. Evidence of infection was found in 5 raccoons, 3 opossums, 1 striped skunk, 1 Norway rat, 1 chipmunk, 1 white-tailed deer, and 1 bobwhite quail. This indicated that tularemia was present at Fort Pickett in a number of species and could be responsible for the low numbers of cottontails present. As the result of an epizootic of cerebrospinal nematodiasis among rabbits caused by Baylisascaris procyonis, a survey of the presence of B. procyonis in its definitive host was undertaken. Between December 1976 and February 1978, 72 raccoons from 11 counties were examined. B. procyonis was found in raccoons from Augusta, Carroll, and Montgomery Counties. It was not found in any raccoons collected from the 6 counties east of the Blue Ridge. This indicates that B. procyonis may only be a cottontail regulatory factor west of the Blue Ridge Mountains. A final phase of the study was to determine the effects of parasitism and nutritive restriction. In a 2x2 factorial design experiment 19 cottontails were placed on an ad libitum or 70 percent ad libitum diet and treated with Atgard<sup>R</sup>, an anthelmintic, or untreated control. It was found that Trichostrongylus spp. were the only parasites significantly affected by drug treatment. The animals on the 70 percent ad libitum diet had lower final body weights, carcass weights, liver weights, tibia and femur marrow fat levels, and lower abdominal fat indices. It was concluded that the parasite loads were too light to significantly affect the host. / Master of Science
148

An interactive data reduction system for real-time millimeter wave experiments

Kauffman, Steve R. January 1978 (has links)
The nature of data acquisition in a realtime millimeter wave experiment is discussed. Goals for a data reduction system are presented and the available processing environment analyzed. Some currently popular software design methodologies are then reviewed and selectively applied to a complete system design based on modern database methods. / Master of Science
149

The effects of temperature on the sensitivity of Daphnia pulex to two simulated industrial effluents

McGinniss, Matthew Jerome January 1978 (has links)
The purpose of this study was to assess the effect of temperature on the sensitivity of mixed age adult Daphnia pulex to a simulated cooling tower blowdown and a simulated refinery effluent. In addition, the metabolic rate compensation capability of Daphnia exposed to temperature was determined. An artificial refinery mixture (ARM) simulated the 1977 guidelines promulgated by EPA. Components of the ARM in mg were: ammonia (10), chromium (0.25), oil (10), phenol (0.1), sulfide (0.17) and suspended solids (20). Components of the simulated blowdown mixture (SBM) in mg 𝓁⁻¹ were: zinc (2), phosphate (25), chromate (15), sulfate (824) and boron (0.5). After 72 hours at 20 C and 120 hours at 10 C, the median apparent threshold LC50s of the SBM were 0.045 at 10 C and 0.026 at 20 C. Similarly, threshold LC50s of the ARM were 0.106 at 10 C and 0.016 at 20 C. Mixed age adult Daphnia were pre-exposed to sublethal levels (LC10) of the SBM and the ARM at both 10 and 20 C and then subjected to t's above ambient of 5.4, 8 and 12 C for one hour. One other group received sublethal exposure only and the controls were maintained only in dilution water. After exposure survival and the number of viable and nonviable young were assessed. Daphnia pre-exposed to both simulated effluents and short-term thermal shock had significantly more nonviable eggs and young. Survival of 20 C Daphnia pre-exposed to both simulated effluents and subjected to a 12 C thermal shock was significantly reduced. Reproductively immature Daphnia showed a noncompensatory temperature acclimation pattern. Several hypotheses were presented to explain the adaptive nature of the noncompensatory pattern observed. / Master of Science
150

Assessment of the effects of impingement and entrainment on the fish community of the New River, Virginia

Potter, Wayne January 1978 (has links)
The loss of organisms to cooling water intakes has been identified as having an impact on aquatic biota. Impingement and entrainment of organisms are unavoidable if natural waters are to be used by utilities for cooling water purposes. This study was initiated to determine the effects of operation of the intake of the Glen Lyn Power Station on the fish community of the New River, Glen Lyn, Virginia. Estimates of the numbers of fishes impinged by the Glen Lyn Power Station were made for the period mid-May 1976 through May 1977. The estimated total impingement was 6219 fish of 22 species. The alewife (Alosa pseudoharengus) accounted for 86.6% of the fish; most of these were impinged during the winter probably as a result of cold induced mortality in an upstream reservoir population. The estimated numbers of other species impinged ranged from 6 to 182. Most of the fish were dead prior to impingement. An estimated 30,200,000 larval fish of an estimated 172,000,000 that drifted by the Glen Lyn Power Station during June 1976 through May 1977 were entrained by the power station. Larvae of the carp (Cyprinus carpio) accounted for 94.8% of the ichthyoplankton drift. Estimates of 14.5 to 21.7% of the larvae of selected representative species that drifted by the power station were entrained. The criteria listed by the United States Environmental Protection Agency for assessing the impact of intake operation on aquatic communities were used in conjunction with collected data and information on the fish community of the New River available in the literature. It was concluded that the losses to the intake of the Glen Lyn Power Station were not significant enough to affect the fish community structure of the New River near Glen Lyn, Virginia in its present condition. / Master of Science

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