The purpose of this research was to investigate the fit of men's dress shirt collars among men 18 years and older and sized small to large. Fit was evaluated by the subject's response to a comfort scale based on physical comfort. Static fit (ease) was determined by subtracting the neck measurement from the collar measurement. Dynamic fit was determined by subtracting the ease for movement from the ease in the collar. Men from Virginia Tech and the vicinity of Blacksburg, Virginia were asked to participate. One hundred men volunteered for this study. The data analysis was conducted on 90 of the 100 surveys. Some surveys were eliminated due to incomplete information. Pearson Correlation Coefficient was used to determine if there was a positive correlation between ease and comfort. The data were analyzed with Analysis of Variance to determine if there were significant differences between age groups for perceived comfort or for ease. Analysis of Variance was used to determine if there were significant differences between size groups for perceived comfort, for ease for movement or for ease. Analysis of variance was also used to determine whether there were significant differences between age groups and size groups for comfort or for ease. The results of the study showed that 2.2% of the subjects did not have ease in static fit and 4.4% of the subjects did not have ease for movement in dynamic fit. There was a significant positive correlation between ease and comfort. There were significant differences between age groups for perceived comfort but not for ease; there were significant differences between size groups for ease but not for ease for movement or perceived comfort; and there were no significant differences between age groups and size groups for perceived comfort or for ease. Although the median value for ease for movement was 1/4 of an inch, 16 of the 90 men (17.8% ) had greater than 1 14 of an inch ease for movement. The results of the present study and Langan's study (1984) indicated that the tie may be the major contributor to neckwear tightness. / Master of Science

A little-known approach to toxicity testing--based on negative phototaxis of larval <u>Aedes aegypti</u>--was investigated as a contribution to the search for rapid methods applicable to the field of water pollution control. Zinc and copper were the toxicants tested. All tests were conducted with a standard "synthetic" dilution water. A mosquito colony was established to provide a uniform supply of test larvae. Preliminary tests were performed on the acute toxicity of zinc and copper against <u>A. aegypti</u> larvae, as well as tests on larval growth and development at various concentrations of the metals. For the photomigration toxicity tests, two juxtaposed troughs were used, one containing the test solution, the other a control. Third instar larvae migrated away from a six-watt fluorescent light for two minutes per run. This was repeated at intervals until 50% were unable to migrate 50 cm in 120 sec. Photographs were taken of the larval migrations. From the pictures an empirical criterion was derived (the 40-cm, 60-sec ET₅₀) through a series of graphical interpolations. All inactivation analyses were based on this criterion. From time-inactivation regression lines, exponential toxicity curves were obtained by interpolation. The curves were of an unusual shape, depicting the characteristic nature of the dosage-response. The sensitivity of the inactivation technique was comparable to that of the acute toxicity tests. However, inactivation was far quicker; depending on concentration, it occurred within one to five hours. By all methods used in this study, zinc and copper were judged to be slow-acting and of low overall toxicity. Copper was, however, consistently more toxic than zinc by at least one order of magnitude. The ET₅₀ in 10 ppm Cu⁺⁺ was 147 min.; in 10 ppm Zn⁺⁺, it was 209 min. Some possible improvements in technique were discussed. It was suggested that the photornigration approach to toxicity testing can be of definite practical use to biologists in water pollution control. / Master of Science

Globally, Atlantic salmon aquaculture is faced with a critical challenge: How best to deliver long-term sustainable growth, whilst optimising the opportunity for the expansion of the industry presented by an increasing global seafood demand? The thesis presents a novel framework of complementary decision support approaches to enable decision-makers to better understand the factors influencing aquaculture development, and examine alternative production (growout) technologies that more effectively address the challenges associated with intensification and expansion. The framework was developed through a combination of fieldwork (international data-gathering), key stakeholder discussions, and the application of targeted qualitative and quantitative analytical approaches; using the Tasmanian industry as a Case Study. The initial research focused on shorter-term (tactical) decision support. A situational analysis defined the business environment, and appraised viable expansion options (offshore, closed-containment and extractive bio-remediation). An economic analysis of selected options then provided a comparison of financial performance and risk. The outputs of this initial component next informed strategic decision-making approaches; employing scenario analysis to explore plausible strategies for the adoption of land-based recirculating aquaculture systems; and qualitative modelling to understand the causal dynamics driving and regulating the industry, and their impact on technology selection. Whilst it was clear that business economic viability is paramount, the results suggested that societal acceptance (the Social License to operate) is playing an increasingly important role in influencing business decisions. There is no single ‘right' technological solution; social acceptance, in particular considerations regarding human wellbeing, trust, and animal welfare concerns, will shape the business environment and therefore technology selection. The research emphasised the importance of employing a balance of tactical and strategic decision-making techniques, and of engaging with a broad range of industry stakeholders. It also highlighted the complexity and dynamic nature of the industry and that key variances (economic, regional, strategic, technological, and temporal) must be included in decision-making.

The Pennsylvania Department of Transportation is conducting a study focusing on risk assessment associated with movement of hazardous materials, and determination of corresponding vulnerable areas in the state. A goal of this research is to make the hazardous material risk assessment an integral part of accident analysis find risk management functions in transportation agencies. To achieve these objectives, the authors developed an interactive, user friendly microcomputer package. The risk assessment model behind this package relies on the notion that data can be obtained easily and updated over time. This package, therefore, employs existing data on accident reports, traffic information, and geometric parameters that is transferred from a mainframe database to the microcomputer. The modelling framework consists of several modules: LEVEL, EDIT, INFO, ZOOM, ANALYZE, MITIGATE, PRINT, HELP, RESET, and QUIT Module. It employs a color coding of streets, municipalities, counties, and states for easy and clear interpretation. To enhance graphic display capabilities of the model, shape points are digitized for each network link. In the LEVEL module three different scales are defined ranging from a small scale county level to a large scale street level, namely, 1)County, 2)Municipality, and 3)Street Any scale may be selected for analysis at any time in the procedure. All other modules are, then, performed on the basis of chosen scale. The EDIT module can be used for data input or investigating hypothetical changes in order to determine the best strategies for problem alleviation. Creating or deleting techniques are included to avoid redigitizing the whole map provided link geometries will be changed over time. Edited data can either be saved on diskette files or be used temporarily in memory without altering original flies. The INFO module employs dialogue boxes with bar graphs or color shadow maps to facilitate depicting numeric values of input and output statistics. The ZOOM module allows user to see the area in question in more detail. The ANALYZE module comprises the main part of this package. Two primary features include : 1) vulnerability and risk assessment at the macro level which provides a ranking of the most affected counties, municipalities and streets (Macro analysis), and 2) risk analysis at the micro level (i.e. street level) which determines corridors of least risk between fixed origins and destinations (Micro analysis). The MITIGATION module is provided for evaluation of mitigating measures. The HELP module uses pop-window techniques to provide quick information with minimal program disruption. The RESET module exits ZOOM module and resets screen. Finally, QUIT module shells out to DOS or exits the package. / Ph. D.

Developing real-time traffic diversion strategies is a major issue of Advanced Traffic Management Systems (ATMS), a component of Intelligent Vehicle Highway Systems (IVHS). Traffic diversion utilizes available capacity in the urban network during a congestion-causing event. If an alternative route selected for diversion is not congested at the current time, a certain part of the route may become congested by the time the diverted drivers reach that part of the network. Thus the ability to forecast future traffic variables on each link along various routes in a prompt and accurate fashion may be necessary to ensure the success of a diversion strategy. Forecasting future traffic variables would also be helpful for urban traffic control. In addition, the forecasting model may help assign the vehicles onto the alternate roads, if the information on driver destinations and the routes between a diversion point and the destinations are available. This dissertation is aimed at developing and evaluating two prediction models: link-based model and network-based model. The link-based prediction model has two components. One component is an Auto Regressive Integrated Moving Average (ARIMA) time series model based on the latest (current) traffic data. The other component is the smoothed historical traffic volume (historical average) for that period as obtained from previous days. These two components are combined to represent the dynamic fluctuations in the traffic flow behavior. The combined model is designed to produce the predicted traffic volumes for a look-ahead period of 30 minutes, divided into 6-minute time intervals. The results show that the combined model is promising for light to medium congested traffic conditions. The network-based prediction model combines current traffic, historical average, and upstream traffic. It is presumed that traffic volume on the upstream can be used to predict the downstream traffic in a specific time period. Three prediction models are developed for traffic prediction: a combination of historical average and upstream traffic, a combination of current traffic and upstream traffic, and a combination of all three variables. The three models are evaluated through regression analysis. The third model is found to be the most applicable while the first model was the least. In order to consider current traffic conditions, a heuristic adaptive weighting system is devised based on the relationships between the origin of prediction and the previous periods. The developed models are applied to real freeway data in 15-minute time interval measured by regular induction loop detectors. The prediction models are shown to be capable of producing reliable and accurate forecasts under congested traffic condition. The prediction systems perform better in the 15-minute range than in the ranges of 30-minute or 45-minute. It is noted that the combined models usually produce more consistent forecasts than the historical average. / Ph. D.

Congestion and delay problems at airports have received much attention in recent years because of the unbalanced condition between demand and supply. Recent demand forecasts indicate that the problems are expected to increase in the next decade. Relieving congestion of the air transportation networks requires several strategies to enhance the runway capacity. Among these strategies is reducing the runway occupancy time a critical factor in affecting runway capacity. And one approach to reducing the runway occupancy time (ROT) is locating the high speed exits optimally. In addressing the reduction of the runway occupancy time, a full information on the distribution of aircraft landing distance is required. The landing performance at a specific airport may be found by observing the actual landings. However, this is costly and may not be transferable to other airports. An alternative approach is to use a simulation model. A simulation model was built at Center for Transportation Research at Virginia Tech based on point mass kinematics in the flying phase over runway and the ground roll phase on runway to predict the landing roll distance and time to a specified exit speed. Many influencing parameters were incorporated into the model, and then were calibrated using the field data obtained from real operations. The prediction of a nominal landing roll distance and time to decelerate to a specified exit speed is not sufficient for estimating ROT because the additional time to reach a designated exit should be taken into account. To compute the additional time, a braking adjustment scheme is selected from several alternative schemes. The combination of the selected braking adjustment scheme and the simulation model approximates very closely the observed ROT. An optimization model is formulated to determine the exit locations so as to minimize the weighted average ROT of the defined aircraft mix. A polynomial-time solution algorithm is developed for this model using Dynamic Programming technique. The major input parameters for the model are the distribution of the landing roll distance to the specified exit speed and the information on the aircraft mix. The model structured to address the problem of designing a new runway as well as the problem of improving an existing runway. A runway capacity model is used to convert the optimized ROT into capacity gains. Four scenarios are analyzed. Among the scenarios, one is based on the present Air Traffic Control procedures, and three are based on the future developments. The capacity analysis reveals that the ROT does not affect the runway capacity for landing operations. However, the ROT is found as a critical factor for the runway capacity for mixed operations. Hence, the ROT should be optimized for the current system and more crucially for the future developments. The capacity gains by optimizing the ROT under the current Air Traffic Control systems and standards are estimated 2 to 7 more operations per hour. These gains will increase to 20 more operations per hour in the future environment. / Ph. D.

Although there have been warnings about the decline in the U.S. transportation infrastructure for the last two decades, the infrastructure's service condition remains barely above current requirements, and is insufficient to meet future demands of growth and economic development. This deterioration and obsolescence primarily derives from a lack of investment, inappropriate management, and growing travel demands. The objective of this research is to develop a model, using a system dynamics methodology, that serves as an instrumentality for generating scenarios for facilitating highway infrastructure management -- policy-making, planning, budgeting, and programming for the Virginia highway system. The Highway Management System (H~1S) model, developed in this research, is a system dynamics model equipped with capabilities for analyzing and solving the meta-problems related to highway infrastructure planning and management. The HMS consists of five subsystems: 1) Physical Subsystem (Pavement Management System, and Bridge Management System), 2) Evaluation Subsystem, 3) Functional Subsystem, 4) Financial Subsystem, and 5) Administration Subsystem. Through steady state analysis, an understanding of the relationship between state variables and decision variables can be obtained. The nomographs corresponding to the steady state solutions of the HMS are the analytically-based, manual means of gaining understanding by tracing paths from decision variables to state variables. Simulations were performed using the HMS, based on various budget-size and allocation scenarios for the I-81 corridor. The results indicate that the service condition of the highway will be diminished and will return to its pre-expansion condition in several years, if the maintenance budget is not increased according to the expansion. The HMS is a useful tool for decision-makers and engineers attempting to analyze and solve meta-problems related to transportation infrastructure management. The HMS presents a whole picture of the highway system according to various policy options. This systems approach to highway management also can be applied to the management of other infrastructure, and eventually it should be possible to achieve an integrated infrastructure management system. / Ph. D.

In Code Division Multiple Access (CDMA) systems forward error correction (FEC) is an important factor in improving system performance. Because of the multiple access interference observed in asynchronous CDMA, FEC is required to improve system capacity. Several alternative coding techniques are available, including "trellis codes" specifically designed for CDMA, very low rate convolutional codes and conventional convolutional codes. An analytic approach is developed to compare the performance of different coding techniques for CDMA on the same basis by extending several improved analysis techniques which were developed for uncoded CDMA. Analytic results are presented for additive white Gaussian noise (AWGN) channels and frequency non-selective Rician Fading (FNRF) channels. The performance of coded CDMA systems in frequency selective Rayleigh fading channels is also analyzed using simulation techniques. Both analytic and simulation results show that by using trellis codes or very low rate convolutional codes significant performance improvement is achieved over conventional convolutional codes. Trellis codes outperform very low rate convolutional codes in AWGN and FNRF channels while both codes show similar performance in frequency selective Rayleigh fading channels. / Master of Science

A library for rare books and a reading garden, the following project emerged from an attempt to better understand the idea of an autonomous architecture. Framing architectural questions as a choice between opposing alternatives of perceived relevance (e.g., geometric construction versus geometric composition, self referential versus self governing, singular versus universal) the project, which at its beginning was a simple exercise in geometric constructive technique, evolved as it was viewed through the lenses of those dualities. / Master of Architecture

The unimodality of a function seems a simple concept. But in the Euclidean space R^m, m=3,4,..., it is not easy to define. We have an easy tool to find the minimum point of a unimodal function. The goal of this project is to formalize and support distinctive strategies that typically guarantee convergence. Support is given both by analytic arguments and simulation study. Application is envisioned in low-dimensional but non-trivial problems. The convergence of the proposed iterated grid search algorithm is presented along with the results of particular application studies. It has been recognized that the derivative methods, such as the Newton-type method, are not entirely satisfactory, so a variety of other tools are being considered as alternatives. Many other tools have been rejected because of apparent manipulative difficulties. But in our current research, we focus on the simple algorithm and the guaranteed convergence for unimodal function to avoid the possible chaotic behavior of the function. Furthermore, in case the loss function to be optimized is not unimodal, we suggest a weaker condition: almost (noisy) unimodality, under which the iterated grid search finds an estimated optimum point. / Ph. D.