An important characteristic of all systems is availability. Availability is the probability that a system or piece of equipment will operate in a prescribed manner when used under specified conditions. It is primarily a design dependent parameter. Availability derives from a systems reliability and maintainability. Reliability is the probability that a system will operate for a specified time under specified operating conditions. It is commonly measured by the mean-time-between-failure (MTBF). Maintainability is the ability of a system to be maintained. For this report, maintainability is measured by the mean maintenance down time (MDT). The MDT is a function of several variables, including the mean-time-to-repair (MTIR) and Logistics Delay Time (LDT). MTIR is the time that active maintenance is being performed. The LDT is the time delay due to spare part availability, transportation, repair facility availability, traveling to the location of the malfunction, etc. LDT is a major portion of the MDT. In order to meet a requirement of improved system availability, the MTBF and/or the MDT must be improved. Decreasing the distance between the repair organization and the location of the failure may have a significant impact on LDT, assuming that the system's LDT is positively correlated to the distance traveled. An improvement in the LDT corresponds to an improvement in the MDT, hence the availability. For a situation where the repair function (referred to as the repair unit) travels to the location of the failed component, the deployment location may have a critical impact on a system's availability. In a system where the operating components are located over a wide area and the repair organization must travel to the component to effect a repair, there are numerous ways to deploy the servicing units. The systems maintenance concept addresses this issue. The deployment of the repair units is the central focus of this report. / Master of Science

Master of Science

Master of Science

<p>The deletion of the Centralized HPAS from DDG 51 Class Flight IIA, and the development of improved, more cost effective, dedicated subsystems via ECP 51-1216 was a considerable effort which required a structured design approach. The approach taken and described in this paper closely resembled the systems develo~t process prescribed by reference (a); deviations taken (1. e. fonnal preparation of functional flow diagrams and detailed R&M calculations/allocation), were carefully considered and balanced against Program schedule and cost constraints, as well as overall Program objectives for development of detailed specificat10n requirements. Further, Program direction to utilized existing, proven, and supported hardware, coupled with limited prototype testing, reduced the risks associated with such deviations. Moreover, this paper demonstrated the significant influences of human factors in the design of each new replacement subsystem; it was shown that conslderation of such human factors attributes as functional effectiveness, operator safety, accessibility, and operability are fundamental to proper system design throughout the system development process. To this end, the objectives cited in Section 1.1 of this paper were met.</p> / Master of Science

Although the use of nuclear power has several advantages over the burning of fossil fuels, it has several disadvantages also. The inherent danger of a nuclear accident at a power plant is one of these disadvantages. Although the probability of an accident is very low in comparison to other risks we normally encounter, the consequences are significant. Thousands of local citizens could be exposed to radiation levels more than the normal background levels. It is the responsibility of the State to make the necessary decisions regarding the evacuation of its citizens. To make the best decision possible, it is necessary to obtain a large amount of information regarding the concentration of radionuclides being released and to quickly make projections of the exposure to ionizing radiation of the neighbors of the plant. / Master of Science

see document / Master of Science

Master of Science

In the past, tool life tests have been performed using a conventional Taylor testing technique. This methodology is expensive and time-consuming. It requires wearing a number of tools until the tool failure criterion has been reached. A number of short-term tests designed to replace the Taylor test have been proposed but they suffer from a number of drawbacks. Many of these tests are performed under non- standard cutting conditions or require special workpiece preparation or equipment. As a result, tool life models developed from these tests are of limited usefulness in predicting tool failure times for conventional machining operations. A methodology is required which combines the time and cost advantages of non-conventional tests with statistical validity and robustness. In this research, two short-term tests are presented which are based on the Taylor test. Response surface models are used to develop the parameters of Taylor's tool life equation. The tests are shortened by using regression equations of flank wear data to predict the tool failure time without wearing the tool to failure. The two methods, abbreviated conventional testing and sequential composite testing, are statistically validated and compared with the Hill Taylor test. The results show that these tests can accurately predict tool life and the resulting Taylor models are not significantly different from those estimated by conventional means. / Master of Engineering

The purpose of this project was to develop the preliminary design of a public transportation system (PTS) that would support a theme park. Disney's America, a theme park originally planned for Northern Virginia, was used as the basis for this project. The problem was that the primary interstate that serves the park site was already overcrowded; this project was intended to expand the realm of possible transportation solutions to include public-transit solutions. The following report identifies five feasible transit mode alternatives for the PTS. It shows calculations that were performed to determine various aspects of each transit system design, including headway, operating time, cycle time, number of vehicles, total number of vehicles required, and frequency of service. This report also describes evaluation criteria that were used in the decision making process. It presents the results of a life-cycle cost analysis that was performed as part of the evaluation of alternatives. From the alternative systems that were considered, the bus transit system was selected for the PTS. / Master of Science

Master of Science