<p> There are significant challenges involved in regulating the growing commercial human spaceflight industry. The safety of the crew and passengers should be protected; however, care should be taken not to overburden the industry with too many or too stringent, or perhaps inapplicable, regulations. </p><p> An improvement in launch success would improve the safety of the crew and passengers. This study explores the effectiveness of Mission Assurance policies to guide regulations and standards. There is a severe lack of data regarding commercial human space flights. This means that a direct test of effectiveness by looking at historical commercial human space flight data is not possible. Historical data on current expendable commercial launchers have been used in this study. The National Aeronautics and Space Administration (NASA) has strong Mission Assurance policies for its launch of civil payloads. The Office of Commercial Space Transportation at the Federal Aviation Administration (FAA/AST) regulations of commercial launches are more safety oriented. </p><p> A comparison of launches between NASA and the FAA/AST is used to gauge the effectiveness of Mission Assurance policies on launch success. Variables between the two agencies are reduced so that Mission Assurance policies are isolated as the main difference between launches. Scenarios pertinent to commercial human space flight are used so results can be applicable.</p>

Details of research into the automated generation of a digital database of hydrographic charts is presented. Low level processing of digital images of hydrographic charts provides image line feature segments which serve as input to a semi-automated feature extraction system, (SAFE). This system is able to perform a great deal of the building of chart features from the image segments simply on the basis of proximity of the segments. The system solicits user interaction when ambiguities arise. IThe creation of an intelligent knowledge based system (IKBS) implemented in the form of a backward chained production rule based system, which cooperates with the SAFE system, is described. The 1KBS attempts to resolve ambiguities using domain knowledge coded in the form of production rules. The two systems communicate by the passing of goals from SAFE to the IKBS and the return of a certainty factor by the IKBS for each goal submitted. The SAFE system can make additional feature building decisions on the basis of collected sets of certainty factors, thus reducing the need for user interaction. This thesis establishes that the cooperating IKBS approach to image interpretation offers an effective route to automated image understanding.

High quality silicon nitride ceramics have shown some advantages for rolling element bearing applications. In particular hybrid bearings (silicon nitride rolling elements and steel races) have the ability to withstand high loads, severe environments and high speeds. However, the difficulties of both sintering and machining the material may result in surfacedefects,such as surface ring cracks. It is difficult to detect surface ring cracks during high volume production processes and hence it is crucially important to understand their influence and the fundamental mechanism of the failures they cause. The purpose of this study is to examine the contact fatigue failure modes of silicon nitride rolling elements with surface ring crack defects. In this study, new experimental and computational techniques are developed to measure and model the interaction of the surface with pre-existing crack defects. A rolling contact fatigue test method is devised for positioning the ring crack in the contact path. Rolling contact fatigue tests are conducted using a modified four-ball machine in a hybrid ceramic/steel combination. A three-dimensional boundary element model is used to determine the stress intensity factors and to carry out the crack face contact analysis. Research shows that the RCF life performance of silicon nitride bearing elements is dependent upon the crack location and fatigue spall happens only at a few crack orientations. The spalling fatigue failure is not only influenced by the original ring crack propagation but also strongly influenced by the subsequent crack face contact. Secondary surface cracks play an important role in the forination of a fatigue spall. The crack gap and crack face friction coefficients significantly affect the formation of secondary surface cracks. Numerical calculation results are consistent with the experimental observations. A quantitative three-dimensional boundary element model has been developed, which can be used to determine the geometry of acceptable surfacering cracks.

<p> Presented here is a detailed study of electron transport in highly disordered insulating materials (HDIM). Since HDIMs do not lend themselves to a lattice construct, the question arises: How can we describe their electron transport behavior in a consistent theoretical framework? In this work, a large group of experiments, theories, and physical models are coalesced into a single formalism to better address this difficult question. We find that a simple set of macroscopic transport equations--cast in a new formalism--provides an excellent framework in which to consider a wide array of experimentally observed behaviors. It is shown that carrier transport in HDIMs is governed by the transport equations that relate the density of localized states (DOS) within the band gap and the occupation of these states through thermal and quantum interactions. The discussion is facilitated by considering a small set of simple DOS models. This microscopic picture gives rise to a clear understanding of the macroscopic carrier transport in HDIMs. We conclude with a discussion of the application of this theoretical formalism to four specific types of experimental measurements employed by the Utah State University space environments effects Materials Physics Group.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7574. Adviser: Bruce Hajek. Includes bibliographical references (leaves 107-110) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7596. Adviser: Steve Granick. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Lehigh University, 2008.

Over the last couple of decades, there has been increased interest in environmentally friendly technologies. One of the renewable energy sources that has experienced huge growth over the years is wind power with the introduction of new wind farms all over the world, and advances in wind power technology that have made this source more efficient. This recognition, together with an increased drive towards ensuring the sustainability of wind energy systems, has led many to forecast the drivers for future performance. This study aims to identify the most sustainable wind turbine design option for future grid electricity within the context of sustainable development. As such, a methodology for sustainability assessment of different wind turbine design options has been developed taking into account environmental, data uncertainty propagation and economic aspects. The environmental impacts have been estimated using life cycle assessment, data uncertainty has been quantified using a hybrid DQI-statistical method, and the economic assessment considered payback times. The methodology has been applied to a 1.5 MW wind turbine for an assessment of the current situation and potential technology improvement opportunities. The results of this research show that overall, the design option with the single-stage/permanent magnet generator is the most sustainable. More specifically, the baseline turbine performs best in terms of embodied carbon and embodied energy savings. On the other hand, the design option with the single-stage/permanent magnet generator performs best in terms of wind farm life cycle environmental impacts and payback time compared to the baseline turbine. With respect to the design options with increased tower height, it is estimated that both designs are the least preferred options given their payback times. Therefore, the choice of the most sustainable design option depends crucially on the importance placed on different sustainability indicators which should be acknowledged in decision making and policy.

The issue of deflagration to detonation transition (DDT) is one of the key factors influencing safety standards, risk assessment and risk managements in the petrochemical industries. It is also one of the most outstanding problems in combustion theory. Despite the efforts from a number of scientists around the world, numerical predictions of DDT is still an un-resolved problem due to the high level of complexities involved. Although there have been relatively more experimental efforts, a comprehensive database to assist model validation and development is still lacking. The present thesis includes numerical analysis of a wide range of combustion regimes to establish the critical conditions under which transition from deflagration to detonation occurs. In order to facilitate the study, new correlations for hydrogen burning velocity are derived from curve-fitting to experimental data from literature and implemented in the code for simulation of initial stages of flame acceleration and deflagration propagation. DetoFOAM, a code for solving transient and fully compressible Euler equations, has been developed within the framework of the OpenFOAM toolbox for numerical simulations of gaseous detonation. The detonation solver uses the total variation diminishing (TVD) numerical schemes which are suitable for shock capturing. A one step reaction mechanism has been developed following first principle and tuned for both small and large scale simulations. Since the numerical solver for DDT simulations must be capable of handling both deflagration and detonation as well as the transition, a new solver, DDTFOAM, which is based on solving fully compressible and transient Navier-Stokes equations has also been developed. DDTFOAM also uses the TVD numerical schemes for shock capturing and uses the Implicit Large Eddy Simulation (ILES) approach as a compromise for accuracy and computational efficiency [131]. Implementing an adequate chemical reaction mechanism in the DDTFOAM has been challenging to ensure that the right amount of chemical energy release is supplied in the right place and at the right time. Incorrect models for chemical energy release can significantly modify the flow behaviour. The available reactions in the literature are very limited and valid for limited range of conditions, e.g. for laminar flames only. A single step Arrhenius type reaction has been designed, tuned and implemented in DDTFOAM. The reaction mechanism has been carefully designed to reproduce flame properties e.g. laminar flame speed and thickness as well as detonation properties such as detonation thickness, propagation velocity, etc. The main difference between DetoFOAM and DDTFOAM that the former is designed for supersonic combustions (detonations) only; therefore it neglects the diffusive effects and solves reactive Euler Equations, whereas in DDTFOAM full Navier Stokes Equations are solved. The detonation solver is mainly designed for large scale detonation simulations therefore the derived reaction mechanism for this solver is obtained trough slightly different procedure compared to the DDT solver. Obtaining the reaction mechanism for DDTFOAM is more challenging as it has to reproduce properties of deflagrations as well as detonations correctly. The computational power which is required to carry out the simulations is extremely high. Different techniques have been employed to reduce the computational cost without compromising accuracy. These include using the ILES approach in cooperation with adaptive mesh refinement and multiple meshes. Numerical predictions have been conducted for different combustion regimes including laminar flames, turbulent flames and detonations as well as the actually DDT processes. The predictions of deflagrations waves are found to be In reasonably good agreement with some published experiment data. In case of detonations, detailed studies have been conducted on the detonation front structure, cellular structures as well as large industrial scenarios. This work involved contributions to Buncefield explosion investigations [109-110]. Finally, numerical simulations of some standard DDT tests have been carried out. The predictions have again achieved reasonable agreement with published experimental data and previous simulations. Successful simulations of large scale detonation in the present work represent the capability of the present study to address the increasing demands from the industries to study real scale accidental scenarios. Furthermore the obtained results for DDT simulations compare well with the medium scale experimental works and provide a step forward towards large scale and unconfined DDT studies.

Global climate change is one of the greatest challenges of the 21st century. Rising ambient temperatures and deterioration of weather patterns are anticipated to result from increased atmospheric concentrations of greenhouse gases caused in part by the use of fossil fuels for electricity generation and domestic heating purposes. The possibility of a global temperature rise of between 1 degree C and 4.5 degree Celsius has led to considerable research efforts into the effects of changes in temperature and other climatic variables. The increasing use of private capital in the energy industry has altered the focus from the provision of a service to the need to make profits from the production and sale of a commodity. Additionally, with respect to Luxembourg, the dependency on imported energy is an important risk factor. This thesis presents biomass as an essential alternative to substitute for some of the fossil fuels in the domain of heat, cooling and power generation. The results presented show an increase in energy utilisation and thus energy efficiency and reduction in emissions when used in combined generation modes as opposed to single generation. These results are gathered through meticulous analytical models, computational fluid dynamics (CFD), and laboratory testing of real life biomass systems. The technologies and analysis investigated here are targeted at those involved in climate change research, providing them with valuable data on the energy analysis of biomass and its associated emissions, highlighting the potential for reduction in pollutions when biomass is used instead of fossil fuels; in energy policy making; investors; engineers; and all others involved in the biomass design and operation of combined generation of biomass applications.