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Total dose simulation for high reliability electronics

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New technologies enable the exploration of space, high-fidelity defense systems, lighting fast intercontinental communication systems as well as medical technologies that extend and improve patient lives. The basis for these technologies is high reliability electronics devised to meet stringent design

New technologies enable the exploration of space, high-fidelity defense systems, lighting fast intercontinental communication systems as well as medical technologies that extend and improve patient lives. The basis for these technologies is high reliability electronics devised to meet stringent design goals and to operate consistently for many years deployed in the field. An on-going concern for engineers is the consequences of ionizing radiation exposure, specifically total dose effects. For many of the different applications, there is a likelihood of exposure to radiation, which can result in device degradation and potentially failure. While the total dose effects and the resulting degradation are a well-studied field and methodologies to help mitigate degradation have been developed, there is still a need for simulation techniques to help designers understand total dose effects within their design. To that end, the work presented here details simulation techniques to analyze as well as predict the total dose response of a circuit. In this dissertation the total dose effects are broken into two sub-categories, intra-device and inter-device effects in CMOS technology. Intra-device effects degrade the performance of both n-channel and p-channel transistors, while inter-device effects result in loss of device isolation. In this work, multiple case studies are presented for which total dose degradation is of concern. Through the simulation techniques, the individual device and circuit responses are modeled post-irradiation. The use of these simulation techniques by circuit designers allow predictive simulation of total dose effects, allowing focused design changes to be implemented to increase radiation tolerance of high reliability electronics.

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Date Created
2014

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Development of high reliability construction work systems: lessons from production practices of high performance work crews

Description

The construction industry faces important performance problems such as low productivity, poor quality of work, and work-related accidents and injuries. Creating a high reliability work system that is simultaneously highly productive and exceptionally safe has become a challenge for construction

The construction industry faces important performance problems such as low productivity, poor quality of work, and work-related accidents and injuries. Creating a high reliability work system that is simultaneously highly productive and exceptionally safe has become a challenge for construction practitioners and scholars. The main goal of this dissertation was to create an understanding of high reliability construction work systems based on lessons from the production practices of high performance work crews. High performance work crews are defined as the work crews that constantly reach and maintain a high level of productivity and exceptional safety record while delivering high quality of work. This study was conceptualized on findings from High Reliability Organizations and with a primary focus on lean construction, human factors, safety, and error management. Toward the research objective, this dissertation answered two major questions. First, it explored the task factors and project attributes that shape and increase workers' task demands and consequently affect workers' safety, production, and quality performance. Second, it explored and investigated the production practices of construction field supervisors (foremen) to understand how successful supervisors regulate task and project demands to create a highly reliable work process. Employing case study methodology, this study explored and analyzed the work practices of six work crews and crew supervisors in different trades including concrete, masonry, and hot asphalt roofing construction. The case studies included one exceptional and one average performing crew from each trade. Four major factors were considered in the selection of exceptional crew supervisors: (1) safety performance, (2) production performance, (3) quality performance, and (4) the level of project difficulty they supervised. The data collection was carried out in three phases including: (1) interview with field supervisors to understand their production practices, (2) survey and interview with workers to understand their perception and to identify the major sources of task demands, and (3) several close field observations. Each trade's specific findings including task demands, project attributes, and production practices used by crew supervisors are presented in a separate chapter. At the end the production practices that converged to create high reliability work systems are summarized and presented in nine major categories.

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Date Created
2012