Throughout this work, conditional failure rates for discrete positive integer-valued random variables and some of their applications are considered in some detail. Conditional failure rates are of fundamental importance in the study of lifetime distributions and many of their properties. All the notions introduced and the results derived here can be used in reliability theory, operations research, inventory theory, biometry, etc. Chapter 1 begins with the concept of conditional failure rate of a discrete random variable. Then, it is shown how to obtain explicit expressions for probability densities and survival distributions in terms of this notion. Next, extensions of the univariate results are discussed for bivariate discrete random vectors. Finally, some multivariate concepts and results are outlined. One of the fundamental applications of conditional failure rates is the mathematical representation of ageing. In Chapter 2, several univariate notions of ageing are given for discrete random variables. Such notions constitute the starting point for the classification and study of lifetime distributions that have significant importance in reliability theory, biometry, and several other areas. In Chapter 3, three important ordering relations, and a chain of implications among them, are discussed; the likelihood ratio ordering, the failure rate ordering, and the stochastic ordering. These orderings are useful in applied probability, stochastic processes, statistics, etc. In particular, they are an essential tool in the study and analysis of systems with dependent components, specially when the components are associated. No attempt is made, however, to consider specific applications of these orderings here. Finally, Chapter 4 contains an application of conditional failure rates in the analysis of repairable systems. A random mechanism of repair of failed units, called imperfect repair, is introduced and some simplified models are considered in some extent. These models can be used in the analysis and design of maintenance policies.

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Concentrated solar power systems are expected to be sited in desert locations where the direct normal irradiation is above 1800 kWh/m2.year. These systems include large solar collector assemblies, which account for a significant share of the investment cost. Solarreflectors are the main components of these solar collector assemblies and dust/sand storms may affect their reflectance properties, either by soiling or by surface abrasion. While soiling can be reverted by cleaning, surface abrasion is a non reversible degradation.The aim of this project was to study the accelerated aging of second surface silvered thickglass solar reflectors under simulated sandstorm conditions and develop a multi-parametric model which relates the specular reflectance loss to dust/sand storm parameters: wind velocity, dust concentration and time of exposure. This project focused on the degradation caused by surface abrasion.Sandstorm conditions were simulated in a prototype environmental test chamber. Material samples (6cm x 6cm) were exposed to Arizona coarse test dust. The dust stream impactedthese material samples at a perpendicular angle. Both wind velocity and dust concentrationwere maintained at a stable level for each accelerated aging test. The total exposure time in the test chamber was limited to 1 hour. Each accelerated aging test was interrupted every 4 minutes to measure the specular reflectance of the material sample after cleaning.The accelerated aging test campaign had to be aborted prematurely due to a contamination of the dust concentration sensor. A robust multi-parametric degradation model could thus not be derived. The experimental data showed that the specular reflectance loss decreasedeither linearly or exponentially with exposure time, so that a degradation rate could be defined as a single modeling parameter. A correlation should be derived to relate this degradation rate to control parameters such as wind velocity and dust/sand concentration.The sandstorm chamber design would have to be updated before performing further accelerated aging test campaigns. The design upgrade should improve both the reliability of the test equipment and the repeatability of accelerated aging tests. An outdoor exposure test campaign should be launched in deserts to learn more about the intensity, frequencyand duration of dust/sand storms. This campaign would also serve to correlate the results of outdoor exposure tests with accelerated exposure tests in order to develop a robust service lifetime prediction model for different types of solar reflector materials.

Knowledge of the implementation practices of successful elementary schools will be beneficial to other elementary principals who seek to improve student success in reading. This study examined perceptions of principals from elementary schools in Texas whose schools received the Gold Performance Acknowledgement (GPA) from the Texas Education Agency (TEA) for Continuous Improvement in Reading (CIR) on the Texas Assessment of Academic Skills (TAAS) in 2002. The study had two purposes: (1) to identify the principal??s perception of the levels of implementation and impact of selected reading strategies used by selected elementary schools in Texas to improve student success in reading and (2) to determine the principal??s perception of the extent to which Accelerated Reader (AR) and AR-like recommend practices were used in selected elementary schools in Texas. The research design for this study was descriptive. Parameters, which are descriptive measures of a population, were used since all 721 members of the population were mailed questionnaires. Research was conducted during the winter of2004. Two hundred fifty-two principals responded. A questionnaire using a Likerttype scale for the principals?? responses was used to collect the data. Principals?? perceptions were measured to determine the degree of implementation and impact of AR and other selected reading strategies. Data were analyzed for all 252 respondents for selected reading strategies and by the categories of AR and non-AR schools for AR recommended reading strategies and AR-like recommended reading strategies, respectively. This study identified the characteristics of a successful reading program in Texas elementary schools. To maximize their budgets while improving student success in reading, principals should provide their teachers with professional development, implement student/teacher conferences to direct reading practice, allow students to self-select books on their independent reading level for independent reading practice, consider use of literature circles, classroom libraries and reading textbooks, review the use of rewards and posting of goals to determine if these practices increase students?? success in reading, assess computer reading programs to determine if there are less costly options available, and in schools using the AR program, review implementation practices for greater impact.

Pavement performance prediction in terms of fatigue cracking and surface rutting are essential for any mechanistically-based pavement design method. Traditionally, the estimation of the expected fatigue field performance has been based on the laboratory bending beam test. Full-scale Accelerated Pavement Testing (APT) is an alternative to laboratory testing leading to advances in practice and economic savings for the evaluation of new pavement configurations, stress level related factors, new materials and design improvements. This type of testing closely simulates field conditions; however, it does not capture actual performance because of the limited ability to address long-term phenomena. The same pavement structure may exhibit different response and performance under APT than when in-service. Actual field performance is better captured by experiments such as Federal Highway Administration's Long-Term Pavement Performance (LTPP) studies. Therefore, to fully utilize the benefits of APT, there is a need for a methodology to predict the long-term performance of in-service pavement structures from the results of APT tests that will account for such differences. Three models are generally suggested to account for the difference: shift factors, statistical and mechanistic approaches. A reliability based methodology for fatigue cracking prediction is proposed in this research, through which the three models suggested previously are combined into one general approach that builds on their individual strengths to overcome some of the shortcomings when the models are applied individually. The Bias Correction Factor (BCF) should account for all quantifiable differences between the fatigue life of the pavement site under APT and in-service conditions. In addition to the Bias Correction Factor, a marginal shift factor, M, should be included to account for the unquantifiable differences when predicting the in-service pavement fatigue life from APT. The Bias Correction Factor represents an improvement of the currently used "shift factors" since they are more general and based on laboratory testing or computer simulation. By applying the proposed methodology, APT performance results from a structure similar to an in-service structure can be used to perform four-point bending beam tests and structural analysis to obtain an accurate estimate of the necessary Bias Correction Factor to estimate in-service performance.

The purpose of the present study was to investigate the effects of Accelerated Reader on the reading motivation and achievement of fourth grade students. The participants were 68 fourth grade students who attended an elementary school in a suburban location north of a large Midwestern city. Quantitative and qualitative methods were employed in the investigation to understand and analyze the effects of the program.Quantitative methods utilized a pre/post-test design using the Motivation to Read Profile (Gambrell, Palmer, Codling, & Mazzzoni, 1996) to assess motivation and the STAR Reading Diagnostic Test (Renaissance Learning, 2002) to measure achievement through instructional reading levels. Participants were divided into three groups based upon the total number of Accelerated Reader points they had accumulated during a continuous 14 week period. Analyses compared the differences in gains in motivation and reading achievement among the groups. The only significant effect noted was that the higher the number of Accelerated Reader points accumulated, the smaller the decrease in motivational scores. A comparison of the number of books read among the groups revealed the group obtaining the highest number of points read significantly more books than the group with lowest.Qualitative measures consisted of the administration of the Conversational Interview portion of the Motivation to Read Profile (Gambrell, et al., 1996) to nine students, three randomly selected from each of the previously established groups. Interviews were conducted to gain information concerning students' motivation for reading through the construction of theories based upon consistencies and differences among and between groups' responses. The categories within which all themes were grouped included motivations for book selections, reasons for reading, and the amount of knowledge retained through reading. Very little mention of Accelerated Reader was made in any portion of the interview sessions. / Department of Elementary Education

Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Industrial and Systems Engineering." Includes bibliographical references (p. 171-179).

Thesis (Ph.D.)--McMaster University, 2002. / Adviser: N. Balakrishnan. Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph.D.)--McMaster University, 2002. / Adviser: N. Balakrishnan. Includes bibliographical references. Also available via World Wide Web.