الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Reliability is the probability that a system will perform satisfactorily for at least a given period of time when used under stated conditions. Therefore, the probability that a system successfully performs as designed is called ”system reliability,” or the ”probability of survival.” Often, unreliability refers to the probability of failure. System reliability is a measure of how well a system meets its design objective. A system can be characterized as a group of stages or subsystems integrated to perform one or more specified operational functions. In describing the reliability of a given system, it is necessary to specify A) the failure process, B) the system configuration that describes how the system is connected and the rules of operation, and C) the state in which the system is defined to be failed. The failure process describes the probability law governing those failures. The system configuration, on the other hand, defines the manner in which the system reliability function will behave. The third consideration in developing the reliability function for a no maintainable system is to define the conditions of system failure [1]. Reliability is defined as the probability that a device will perform its intended functions satisfactorily for a specified period of time under specified operating conditions. Based on this definition, reliability is measured as a probability. Reliability is defined in terms of a device, which may be a component in a system or a system consisting of many components. Since the performance of a system usually depends on the performance of its components, the reliability of a system is a function of the reliability of its components. The intended function of the device is supposedly understood and the degree of success of the device’s performance of the intended function can be measured so that we can easily conclude if the performance is satisfactory or not. Time is an important factor in the definition of reliability. If a newly purchased device can perform its intended functions satisfactorily, what is the probability that it will last (continue to perform satisfactorily) for a specified period of time, say three years? How long will it last? In other words, what will be the life of this device? The lifetime of the device can be treated as a random variable with a statistical distribution and related properties. Further, the operating conditions, such as stress, load, temperature, pressure, and/or other environmental factors, under which the device is expected to operate, must be specified. Under Chapter 1 3 most circumstances in our discussions throughout this thesis, the operating conditions are constant and implicit. When the operating conditions of a device change over its lifetime, it is explicitly stated.