This dissertation describes a methodology for assessing the software process (both development and maintenance) used by an organization. The assessment methodology integrates the principles of Total Quality Management and the work of the Software Engineering Institute. The integrated assessment methodology results in a well understood, well-documented, quantitatively evaluated software process. The methodology utilizes four steps: investigation, modeling, data collection, and analysis of both process content and process output. The integrated assessment methodology was implemented at a large commercial software organization over a two year period. Implementation results are presented and significant conclusions are discussed. Four areas for further research are also presented. / Ph. D.

The initial forecasting of logistical support for new types of military aircraft is a perplexing problem. The objective of this research was to investigate the feasibility of using data generated by the accelerated flight tests as a basis for forecasting the logistical field requirements. The data used in the study were obtained from the U.S. Army Aviation Board, Fort Rucker, Alabama, where performance tests are conducted on all new aircraft to determine their suitability for Army use. It was statistically shown that the use of these data could provide more realistic logistical forecasts earlier in the introductory phase of the aircraft. This concept would increase the operational availability of the aircraft and reduce the cost of maintaining the aircraft during its introductory phase.

This research presents a framework system dynamics (simulation) model that evaluates the effect of maintenance policies on system performance and life-cycle cost. The model highlights factors such as learning, aging and the technological upgrades that occur during the life-cycle of a system. The metrics used to measure the effectiveness of maintenance policies are the system life-cycle cost and cumulative breakdowns. In this research, a varying maintenance policy has been modeled using system dynamics methodology to determine the future performance of the system that is dependent upon its past performance when breakdowns occur randomly. The main objective of this modeling approach is to balance the cost of preventive maintenance actions with the opportunity losses due to system breakdowns. The approach used in this research primarily involves forecasting future breakdowns using an average of accumulated opportunity losses. This research effort was mainly aimed at developing a (framework) model to determine effective maintenance policy for a system and evaluating the effect on the life-cycle cost for various scenarios. This model could further form the basis of a decision support system for maintenance modeling. / Master of Science

Today's technological systems are expected to perform at very high standards throughout their operational phase. The cost associated with unavailability of these systems is very high and especially with the defense systems or medical equipment which can directly affect human lives. The maintenance system plays an important role in achieving higher performance targets. In order to manage maintenance activities in more informed and rational manner, it is very important to understand the inherently complex and dynamic structure of the system. Traditionally maintenance policies are derived from reliability characteristics of individual components or sub-systems. This research makes an attempt to understand the system from the forest level and suggest better maintenance policies for achieving higher availability and lower system degradation. The leverage is gained from System Dynamics framework's ability to model complex systems and capture various feedback loops. The simulation results reveal that with the limited preventive maintenance capacity and within the given assumptions of the model, there exists and optimal preventive maintenance interval which is not the minimum. The simulation results also reflect that frequent preventive maintenance is required at higher load factors. / Master of Science

The problem of this study was to determine the best methods in relation to caring for materials that compose football equipment by studying the recommendations suggested by those who manufacture the materials; and also to report the results on information received as to how to care for and maintain the materials commonly found in football equipment. Further, the problem was to write a handbook of instructions for the care and maintenance of football equipment.

Yes / Maintenance planning for busy railway systems is challenging because there is growing pressure on increasing operation time, which reduces the infrastructure-accessible time for maintenance. This paper proposes an optimization model that is aimed at finding the best maintenance schedule for multiple components in a railway track to minimize the total cost in the planning horizon. One distinct and practical feature of the model is that the track accessible time for maintenance is limited. We formulate all relevant costs in the component's life cycle, including maintenance cost, fixed track-closure (possession) cost, social-economic cost related to the effects of maintenance time on the train operation, and service-life shortening cost due to the shifting of activities. Generally, it is beneficial to cluster and maintain several components in a single possession because this helps reduce the cost by occupying the track only once. However, the decision must depend on the available possession time. A sensitivity analysis is performed to highlight the effects of available possession time on the number of required possessions as well as the total cost incurred.

This thesis presents a decision support system, MAINTAIN, that was developed to assist maintenance and logistics planners in the evaluation of alternative strategies that might be used in the maintenance of a finite population of end items. The modeled population must consist of a finite number of identical end items, each at age zero at the beginning of the analysis. End items are modeled at their component level, with the lifetime of each component described by a probability distribution. These components are assumed to fail independently of each other and to cause end item failure if any one component should fail. Several component-level preventive maintenance policies are integrated into the modeling system and include age-based replacement, opportunistic lookahead replacement, or no replacement until failure. Also incorporated into the model is the use of two repair facilities, which function as constraints on the resources available to perform maintenance tasks. One repair facility is used under normal conditions, while the second can be used when the first facility is operating beyond its capacity. MAINTAIN is a simulation-based modeling system, in that a proposed or actual maintenance system is captured as an input data set and its operation is simulated over the specified planning horizon. Time-series output statistics are produced by the model to allow the analysis of time dependent parameters such as population availability, maintenance costs, spares requirements and repair facility utilization. Output data are available in several forms for use in external analyses. / M.S.

Maintenance costs in deregulated power systems play an important role. This mainly includes direct costs associated with material and labor costs; and indirect costs associated with spare parts inventory, shipment, test equipment cost, indirect labor, and opportunity costs. The cost function is used as the sole or main component of the objective function in maintenance scheduling and planning activities. The cost has been modeled in literature with several representations for centralized power systems. With deregulation of power industries in many countries the costs representation to be used within the maintenance model in the decentralized power systems has become an important research question. This paper presents modeling of different components of maintenance costs that can be used within the main objective function of the maintenance scheduling and planning problem for the deregulated environment.

Maintainability must be integrated into software as early in the development life cycle as possible to avoid overwhelming maintenance costs at later stages. This research describes a methodology which assists in the development of maintainable systems and does so without disrupting industry standard development techniques. The process uses software metrics and iterative enhancement concepts to reduce the complexity of high-level language code, making it less error-prone and more maintainable. The experiment uses large-scale system software from a major software producer. / Master of Science

The primary object of this research was to develop a two-phase strategy for preventive maintenance and the critical number of units. Maintenance is done if the number of failures is equal to or greater than the critical number of units. The system under consideration had q components. The system failed when k (k < q) components or more failed. This system when subjected to preventive maintenance can be described by a Markov Process. The transition probabilities of the Markov Process were obtained from the distributions qf the strength and stress of the components. The underlying distributions were assumed to be double exponential. Various combinations of the inspection period and the critical number of units were used to obtain the global minimum. The criteria were that the system should not fail and minimum cost. / Master of Science