Thesis (Ph. D.)--Lehigh University, 2004. / Includes vita. Includes bibliographical references.

Thesis (Ph.D.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 174-181.

This thesis is based on an industry project with Teekay Shipping Co ., which is an international transportation service provider for oil companies, refiners and traders. Teekay is interested in knowing which factors contribute most to its operating incidents and accidents. Based on available data, namely vessel name, team, type, hull, and age, as well as incident and accident records, we quantified in this thesis the effects of these factors on the incident and accident frequency. The thesis presented the technical details of the Poisson regression analysis, which we used for quantifying the risk factors. Teekay is also interested in having a consistent method to present Teekay's overall risk picture, and to indicate best investment areas for its risk reducing purpose. Teekay has already implemented an Online Root Cause Analyses (ORCA) system, which collects the direct cause and root cause soon after an incident happens. We reviewed the ORCA system and made suggestions about certain parts of the system which were subsequently revised. Furthermore, we designed a bubble chart tool to present the overall risk faced by Teekay. The bubble chart tool has the capacity to indicate best investment areas clearly, and it is consistent over time, thereby enabling Teekay to evaluate easily the risk mitigation effect of its earlier investment in risk management. Finally, we designed a continuous monitoring tool, which allows Teekay managers to interactively explore the relationships among near misses, incidents and accidents, and to compare event frequencies of various vessel groups, such as vessel team, age, type and hull structure. The powerful continuous monitoring tool provides Teekay managers a full- range view of the risks the company faces. The design and the sample usage of this continuous monitoring tool are discussed in this thesis. / Business, Sauder School of / Graduate

Gasification of biomass has become an area of key interest as it is a reasonably quick and direct way of converting material into a fuel source that works in many industrial systems. The purpose of the present work is to explore biomass gasification and in particular pyrolysis behavior of corn kernels, oat hulls, and paper sludge. For the materials, low temperature gasification behavior was studied. Here, tests were performed with pyrolysis temperatures from 400 - 800°C, at 1 atm and a rapid heating rate. A small concentration of O2 was added to the gasification agent (N2) to enhance CO yields, similar to modern industrial gasifiers. The evolution of CO, CO2, CH4, H2, and O2 were measured throughout the pyrolysis process. Results show a direct correlation between temperature and the composition of the gas byproduct for all biomasses. CO production increases with an increase in temperature while CO2 shows no temperature correlation. O2 depletion mimics the CO evolution and increases with an increase in temperature. CH4 production was observed, however the results were rarely repeatable due to the sensor's sensitivity to moisture and tar in the gas byproduct. No hydrogen was observed, as would be expected for the short experimental residence time (0.2 seconds).

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Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (p. 67-69). / This work investigates the fundamental relationships of wave loading on cross deck structures for trimaran vessels. In contrast with a monohull ship, trimaran vessels experience several possible structural loading cases including: longitudinal bending, transverse bending, torsional bending, spreading and squeezing of hulls, inner and outer hull slam pressures, wet deck slam pressures, loading from ship's motions, and whipping of slender hulls. This work investigates wave loading cases that result in transverse and torsional bending of the cross deck structure. The wave loading cases investigated include: side hull troughing and cresting in longitudinal waves, side hull torsion in longitudinal waves, and transverse hogging and sagging. For each of these load cases, a design load using a fully statistical sea state was derived using an analytical model of a trimaran represented by rigidly connected box barges. The design loadings with a reliability index of 5 for almost 500 trimaran configurations were calculated varying main hull length, side hull length, side hull transverse placement, and side hull longitudinal placement. The design loadings were curve fit to a fourth order polynomial in the three independent variables. / (cont.) The load predictions of the analytical box model of a trimaran were applied to a trimaran vessel with a realistic hull form using the finite element ship structural analysis program MAESTRO. Given the number of approximations and assumptions in the analytical model, the forces predicted by analytical model agreed closely with the finite element model's results. The fitted curve of design loadings allows an initial design stage loading estimate for cross deck structural loading, given general characteristics of length and spacing of a trimaran's hulls. This estimate of structural loading combined with other characteristics of good trimaran design including stability, roll, and resistance characteristics will aid in optimizing an overall trimaran ship design. / by Jason L. Rhoads. / S.M. / Nav.E.

Stepped hull forms are hulls with a vertical step in the hull bottom to improve performance at top speed. Stepped hulls are well documented anecdotally and scientifically to improve calm water performance at high speeds, but commonly demonstrate dangerous and unexpected dynamic instabilities during initial trials. These hulls also operate practically in waves, but their performance characteristics in waves are not well understood and rarely evaluated prior to full scale trials. To expand the scientific understanding of stepped hull performance, a systematic set of experiments and Reynolds Averaged Navier Stokes (RANS) computational fluid dynamics (CFD) simulations are used to evaluate the calm water performance, dynamic stability, and regular head wave response of two stepped hull models. Calm water experiments on two stepped hull models at varying displacement, longitudinal center of gravity location and forward speed offer data which can be used in the design to interpolate hull performance throughout expected operating conditions. CFD simulations in calm water are validated using the experimental results and numerical modeling approaches for stepped hull simulations are recommended. The calm water dynamic stability of both stepped hulls is investigated experimentally and numerically and procedures to evaluate the dynamic stability using both approaches are recommended. The performance of both stepped hulls in regular head waves is studied through experiments, which are used to validate CFD simulations of the hull in regular waves. System identification is used on five calm water CFD simulations to identify a reduced order model for the prediction of stepped hull response in waves. / Doctor of Philosophy / Boats designed specifically for high-speed operations, like military patrol craft, can often achieve higher top speeds when small vertical steps are added to the bottom of the hull. When a step is introduced, the back portion of the hull bottom is raised above the forward portion of the hull bottom to allow air underneath the hull at high speeds. When designed properly, a stepped hull can be safely operated by experienced and unexperienced users at higher speeds than conventional hulls. However, when the steps are not designed well a boat can be dangerous to operate, suffering from unexpected phenomena like end swapping (where the boat violently rotates from bow to stern) when beginning a turn. Unfortunately, it is currently difficult to predict how a stepped hull will behave during the early stages of the design. Builders often rely on full-scale prototype trials to assess the performance and safety of their designs, which is an expensive process. In this work, experimental tests (on small scale models) and computer simulations were performed on two stepped hull models in calm water and in waves to establish techniques to predict performance and safety without a full-scale prototype. The experiments were used to compare the performance of two geometries and assess the accuracy of computer simulation predictions. The computer simulations were found to predict the stepped hull performance accurately enough to be used in design prior to prototyping. Procedures are recommended to evaluate the safety of a stepped hull through experiments and computer simulations. Evaluation of hull safety through computer simulations or experiments offers the opportunity to reduce danger to test personnel during full scale trials and minimize the need for expensive design modifications after construction of the first prototype. The performance of the two hull designs in waves were studied experimentally, through computer simulation, and through a simplified method informed by computer simulations. The development of a simplified method to evaluate stepped hull performance in waves offers the opportunity for designers to consider performance in waves earlier in the design for a lower cost than previously available.

Optimization techniques are used to investigate changes in structural design which increase the energy absorbing capabilities of a marine vessel in a collision. The structural model of the vessel includes the stiffened shell, web frame supports, and rigid bulkheads. The failure criterion used is hull rupture, appropriate for tanker design. The collision scenario is a right angle strike by a rigid vertical bow midway between two rigid bulkheads. The stiffened shell is modelled as a series of longitudinal beams in plastic bending and plastic membrane tension. Optimization parameters included both the number and dimensions of the transverse web frames and longitudinal beams. The technique was applied to the redesign of a large oil tanker. Minimizing the weight with a constraint on the energy was superior to maximizing the energy with a weight constraint in both computation time and performance. Optimization increased the volume of the shell beams while decreasing their moment-of-inertia. In addition the volume and strength of the frame were decreased precipitating early development of membrane tension in the shell and spreading of damage throughout the compartment. An reduced the number of web frames from optimum design six to two and increased the energy absorbed before rupture by 130%. Lesser collisions energies were found for more conservative designs which included a set number of web frames and restrictions of other design parameters. The use of high strength steel was also investigated. / M.S.