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To analyze the system development, manufacturing practices and system evaluation procedures of representative PPES manufacturers, two companies (i.e., one "small", referred to here as "simple manufacturer (SM)", and one "large", referred here as "complex manufacturer (CM)" — in terms of workforce, market presence, and capital) that develop first responder PPES, which voluntarily agreed to participate in the research were chosen. The complex PPES is an Air-Pak, a self contained breathing apparatus (SCBA) used by first responders for artificial breathing in life-threatening scenarios and the simple PPES is the Fire-Eye device, a thermal sensor that attaches to the visor of the firefighter in order to convey the visual warning of the ambient thermal environment. In order to differentiate the two distinct methodological approaches, the dissertation has been split into two different parts. The first methodology is a "case study" type of empirical investigation which follows a triangulation approach utilizing surveys, structured interviews, process and system observations, and examination of archival records. The second type of methodology is an experimental empirical research one, which involves laboratory-scale and full-scale real-life fire scenarios to conduct product evaluation. The research goals of the case study research were to identify the problems faced by the manufacturers of PPES and to formulate guidelines with regards to manufacturing, compliance, design and development processes, etc., for the PPES manufacturers. The investigation sought answer to the following key questions: a) How do PPES manufacturers currently approach the systems design and development process and what best practices in manufacturing and quality control have they adopted? b) What human factors and ergonomic measures are adopted by these companies while designing their products and what human testing is conducted by companies? c)What safety measures are considered by the safety designer while designing the product? The recommendations also include modifications to the product design process taking into account the market trends in the product design processes, involvement of ergonomics and safety aspects. The research goals for the experimental part of this dissertation were to identify appropriate evaluation methods and conduct the PPES evaluation in simulated fire environments. The Fire-Eye device primarily functions in hot environments and warns the firefighters of the ambient temperature. Therefore, the laboratory-scale evaluation was conducted using test methods such as the Static Oven, Fire Equipment Evaluator, and Radiant Panel, methods which represent controlled environment test conditions. The Fire-Eye device was also evaluated in realistic fire environment created in an ISO burn room by conducting several tests using different types of fuels such as Heptane, Natural Gas, and Living-room set-up (i.e., furniture as fuel). The Fire-Eye device was tested for repeatability and reproducibility of its performance in both of the experimental settings. Statistical data analysis was conducted to determine any differences in performance of the Fire-Eye device among each laboratory-scale methods as well as to compare the performance of the device between laboratory-scale and full-scale fire environments in identical heat locations. The results suggest that a dual approach (laboratory-scale and full-scale fire environment) for evaluating the performance of PPES is more effective than is testing the device in either one of the methods. / Ph. D.

No / The Internet of Things (IoT) has brought significant advancements in various domains, providing innovative and efficient solutions. However, ensuring the safe design and operation of IoT devices is crucial, as the consequences of component failure can range from system downtime to dangerous operating states. Several methods have been proposed to evaluate the failure behaviours of IoT-based systems, including Fault Tree Analysis (FTA), a methodology adopted from other safetycritical domains. This study integrated FTA and Bayesian Network (BN) models to assess IoT system reliability based on components’ reliability data and other statistical information. The integrated model achieved efficient predictive failure analysis, considering combinations of 12 basic events to quantify the overall system’s reliability. The model also enables criticality analysis, ranking basic events based on their contributions to system failure and providing a guide for design modification in order to enhance IoT safety. By comparing failure data in FTA and criticality indices obtained using the BN model, the proposed integration offers a probabilistic estimation of IoT system failure and a viable safety guide for designing IoT systems.

While many organizations claim to "put safety first," safety is rarely considered early in the design process when system-level architectural decisions are made. Instead, system design follows an abstraction-to-detail process to first meet functional and then performance requirements. Following this process, safety assurance occurs in the later stages of design through a rigorous expert review process. The significant cost of safety-based redesign and the growing complexity of engineered systems motivates a need for early design-stage fault analysis. This research presents a novel method of including safety into the model-based design and analysis of complex systems using low-fidelity behavior simulations. Specifically, this research demonstrates the adaption of the functional design process to explicitly include the system property of safety in the system representation. Next, early design fault analysis is extended to connect component failure behavior to system-level hazards. Finally, this research develops three methods of results clustering to provide different evaluation metrics of the system design. In summary, this research demonstrates a framework for incorporating safety into early design decision making. This research addresses safety and failure in the design of complex systems incorporating diverse technology domains as found in energy, transportation, and aerospace systems. / Graduation date: 2012

As the complexity of systems increases, so does what can go wrong with them. For example, the United States Air Force selected McDonnell Douglas’ design for the F-15 Eagle fighter aircraft in 1967 and the aircraft’s first test flight was in 1972, 5 years later. In contrast, the US military selected Lockheed Martin as one of two companies to develop the F-35 Lightning II in 1997 and its first flight was in 2006, 9 years later, and the first production aircraft had its first flight in 2011, 14 years after the selection. This complex program’s problems have been well-documented by the U.S. Government Accountability Office (GAO) and have contributed to the project’s long lead time and skyrocketing budget. GAO reports on other military projects reveal that problems the F-35 project has experienced are shared among all of these projects. In this dissertation I posit that similar problems plague all complex systems engineering projects and that a combination of these problems may lead to negative consequences, such as budget and schedule exceedances, quality concerns, not achieving mission objectives, as well as accidents resulting in loss of human life.<div><br></div><div>Accidents, or unexpected events resulting in loss, have been well-studied over time and we currently have sophisticated theories that help explain how they occur. The leading theory is that most accidents are a result of an accumulation of “mundane” errors at an organization, and that these errors are similar across industries. However, these mundane errors, such as failing to follow procedures and poorly training personnel, occur in all companies, such as companies that design and manufacture military aircraft. My theory is that these mundane errors accumulate in all organizations and result in many different kinds of systems engineering failures, including failures traditionally referred to as “accidents” that result in loss of life, as well as other types of failures which I refer to as “project failures”.<br></div><div><br></div><div>What can be learned from these systems engineering failures? In this dissertation, I begin by mining publicly-available reports to determine whether seemingly dissimilar failures, accidents and project failures, share common causes. I then explain the similarities and dissimilarities between these causes and provide examples from the failures I studied. To help provide systems engineers with actionable advice on these common causes, I describe how I linked the causes to recommendations from accident reports in a cause-recommendation network. I then discuss the results of interviews I held with systems engineers to determine whether the problems I identified in past failures occur in similar ways to the problems they have encountered on their projects. I also discuss the criticisms these systems engineers have about systems engineering education based on the tasks their newly-hired systems engineers struggle with. I explain how I used what I learned about problems in systems engineering that lead to failures to develop survey questions designed to gauge whether systems engineering education at Purdue prepares students to identify and fix these problems. Then, to help systems engineers learn from the data I collected and solve the problems they encounter on their projects, I describe how I built an interactive, web-based tool that presents expert advice on systems engineering failures. I finally explain the results from feedback I received from experts and novices in systems engineering to determine whether this tool could be useful for engineers in this context.<br></div>

Silicon carbide, SiC, is a semiconductor material which has many diverse uses in many of today's leading technologies. The wide band-gap aspect of the material has been utilized to create power and high frequency electronics, its physical hardness enables its use for MEMS devices, and the biological compatibility make perfect for utilization in medical applications. SiC is not a chemical compound normally found in nature and must be artificially generated. One of the methods used for the creation of single crystal, high quality SiC material is provided through the use of a chemical vapor deposition reactor. The University of South Florida currently has a horizontal hot-wallLPCVD reactor used by Dr. S. E. Saddow and his group to grow epitaxial SiC material for research grants by ONR and ARL.These agencies have commissioned the construction of a second LPCVD reactor for the primary purpose of growing 3C-SiC, a specific SiC crystal polytype, and this work describes the fabrication of the new reactor, MF2. This reactor was designed using the first reactor, MF1, as a template, but the design was modified to better facilitate single crystalline growth. The environment of the reactor is a very important consideration for crystal growth, and slight variations can cause critical defect incorporation into the crystal lattice. Many conditioning runs were required to facilitate the epitaxial growth of the different polytypes of SiC, and constant switching of the primary hot-zone required for the growth of hexagonal 4H-SiC and 6H-SiC to the hot zone required for 3C-SiC consumed precious resources and time. The new reactor uses a single primary control to monitor the three most important environmental concerns; hot-zone temperature, gaseous flow, and chamber pressure. The new reactor has been designed to use 100 mm Si substrates instead of the 50mm Si substrate size currently in use by MF1. The construction, testing, and 3C-SiC epitaxial growth on Si substrate capability of a 200 mm 3C-SiC hot-wall LPCVD reactor are demonstrated through this work.

Die Welt wird beherrscht durch Veränderung. Von den kleinsten Elementarteilchen bis zu den größten Galaxien kann man ein Entstehen und Vergehen beobachten. Diese Regel schließt auch die lebende Materie mit ein. Wir sehen Bäume wachsen oder das Getreide auf den Feldern reifen und wir müssen erkennen, daß auch wir, die Menschen, diesem Gesetz der Veränderung, dieser Vergänglichkeit unterliegen....

A method able to analyze and optimize subsystems could be useful to reduce project cost, increase subsystem reliability, improve overall aircraft safety and reduce subsystem weight. The earlier the optimization of development of an aircraft in the design phase can be performed, the better the yield of the optimization becomes. This master thesis was formed in order to construct an automatic analysis method, implementing a Matlab script, evaluating devices forming aircraft subsystems using a Genetic Algorithm. In addition to aircraft subsystems, the method constructed in the work is compatible with systems of various industries with minor modifications of the script.

Neste trabalho, é proposta a utilização de múltiplas antenas de transmissão juntamente com o embaralhamento de pacotes para aumentar a segurança de uma rede composta por dois nós legítimos (Alice e Bob) e um espião passivo, todos eles providos com múltiplas antenas. Levando em consideração o denominado intervalo de segurança (Security Gap) como métrica de desempenho e assumindo um cenário com desvanecimento quase-estático, foi então analisado (analítica e numericamente) o intervalo de segurança em termos de probabilidade de outage e de taxa de erro de pacotes (usando códigos convolucionais), mostrando que em ambas as situações é possível atingir níveis negativos de intervalo de segurança com um número praticável de antenas transmissoras. Além disso, mostra-se que usando uma aproximação para o intervalo de segurança baseado na probabilidade de outage, é possível estimar com precisão o número de antenas em Alice para se atingir um determinado nível de segurança. Também é mostrado que utilizando o esquema de seleção de antena de transmissão juntamente com o método de combinação de razão máxima na recepção (TAS/MRC) com o embaralhamento de pacote, é possível ter os mesmos resultados, ou muito similares, para um caso real utilizando a FER quando comparado com o caso ideal da probabilidade de outage. / In this work, the use of multiple transmitting antennas with frame scrambling is proposed to increase the security of a network composed by two legitimate nodes (Alice and Bob) and a passive eavesdropper, all of them provided with multiple antennas. Considering the so-called security gap as the performance metric and assuming a quasi-static fading scenario, it was evaluated (analytically and through numerical results) the security gap based on both the outage probability and the frame error rate (using convolutional codes), showing that, in both situations, it is possible to achieve negative values of security gap with a feasible number of transmitting antennas. Moreover, it is showed that using an approximation to security gap based on outage probability, one can accurately estimate the number of antennas in Alice needed to achieve a given level of security. It is also showed that using TAS/MRC with frame scrambling, it is possible to get the same results, or almost the same, in a real case using FER when it is compared to an ideal case with outage probability.

Neste trabalho, é proposta a utilização de múltiplas antenas de transmissão juntamente com o embaralhamento de pacotes para aumentar a segurança de uma rede composta por dois nós legítimos (Alice e Bob) e um espião passivo, todos eles providos com múltiplas antenas. Levando em consideração o denominado intervalo de segurança (Security Gap) como métrica de desempenho e assumindo um cenário com desvanecimento quase-estático, foi então analisado (analítica e numericamente) o intervalo de segurança em termos de probabilidade de outage e de taxa de erro de pacotes (usando códigos convolucionais), mostrando que em ambas as situações é possível atingir níveis negativos de intervalo de segurança com um número praticável de antenas transmissoras. Além disso, mostra-se que usando uma aproximação para o intervalo de segurança baseado na probabilidade de outage, é possível estimar com precisão o número de antenas em Alice para se atingir um determinado nível de segurança. Também é mostrado que utilizando o esquema de seleção de antena de transmissão juntamente com o método de combinação de razão máxima na recepção (TAS/MRC) com o embaralhamento de pacote, é possível ter os mesmos resultados, ou muito similares, para um caso real utilizando a FER quando comparado com o caso ideal da probabilidade de outage. / In this work, the use of multiple transmitting antennas with frame scrambling is proposed to increase the security of a network composed by two legitimate nodes (Alice and Bob) and a passive eavesdropper, all of them provided with multiple antennas. Considering the so-called security gap as the performance metric and assuming a quasi-static fading scenario, it was evaluated (analytically and through numerical results) the security gap based on both the outage probability and the frame error rate (using convolutional codes), showing that, in both situations, it is possible to achieve negative values of security gap with a feasible number of transmitting antennas. Moreover, it is showed that using an approximation to security gap based on outage probability, one can accurately estimate the number of antennas in Alice needed to achieve a given level of security. It is also showed that using TAS/MRC with frame scrambling, it is possible to get the same results, or almost the same, in a real case using FER when it is compared to an ideal case with outage probability.