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Structural vibration transmission in ships using statistical energy analysisConnelly, Terence January 1999 (has links)
This thesis presents the results of an investigation into the application of statistical energy analysis (SEA) to predict structure-borne noise transmission in ship structures. The first three chapters introduce the problems of noise and vibration in ships; the previous research on the application of SEA to ships; the basic theory of SEA and the experimental measurement techniques and procedures used to gather data The main body of this thesis presents a wave transmission model for the hull frame joint which is commonly encountered on the hull, bulkheads and deck plates of ship structures. The wave model allows the transmission coefficients to be calculated for hull frame joints which can be used in the coupling loss factor equations of SEA models. The joint model has been verified against measured data taken on a simple two subsystem single joint laboratory structures and a large complex 38 plate test structure with multiple joints intended to represent a 1/10' scale model of a hull section. In addition to the laboratory structures, the SEA modelling of sections of a ship is presented for a large ribbed deck plate, a section of the ship superstructure and a section of the ships hull. The results from the SEA models are compared with measured attenuation data taken on the respective ship sections. A large amount of damping data has been gathered on the test and ship structures and an equation for the internal steel based on data gathered by other researchers has been verified. It has been shown in this thesis that SEA can be applied to ships. Better agreement is found with real structures in contrast to the poor results presented for SEA when applied to simple one dimensional structures. The level of detail of the model is important as a coarse model yields better predictions of vibration level. As with all models the results are sensitive to the damping level and it is necessary to include bending, longitudinal and transverse wave types in any SEA model to obtain the best prediction. It was also found that the flange plates can be neglected from the frame joint model without compromising the accuracy.
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Proposed llfe prediction model for an automotive wheelMcGrath, PJ 01 January 2004 (has links)
Summary
Historicully, stress analysis used for component design
assames "ideal" materials, i.e. with isotropic,
homogeneous and uniform metallurgical properties.
We know that this is untrue, no matter how good
the design. As design cannot provide fo, defect-free
materials or components, ok appropriute defect tolerance
should be the aim of the designer. Hence the
concept of fuil-safe components has been introduced
fo, safety-critical purts. Automotive wheels, howeveF,
ure not considered fail-safe and fatigue lW
prediction techniques fo, these components need to
be improved in an endeavour to provide light-weight,
attractive, but still safe und durable wheels. This
applied approuch, where the proposed lW prediction
model employs relutionships given by Gerber und a
proposed lW prediction model derived from combining
aspects of lW prediction models according to
Collins und Juvinall & Marshek. The results show
good coruelation with that of uctual wheel
fatigue
data.
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The production of a language in dialogue : A computational modelHoughton, G. January 1986 (has links)
This thesis presents a computational model of some of the knowledge and processing capabilities required by a speaker to produce fluent, coherent discourse in a natural language. The main purpose of the work is to study the representation of linguistic knowledge and the way in which this knowledge is used to produce utterances which achieve a communicative task in a given discourse situation. The model defines a simple world in which two actors communicate with each other in the course of attempting to achieve practical goals. The actors' behaviour is organised at three levels the level of non-linguistic planning and action, the level of the organisation of self-other interactions (turn-taking), and the level of the construction of individual utterances. Actions at lower levels gain functional relevance by their contribution to the achievement of goals defined at higher levels. At all levels, the model performs principled computations based on explicitly represented knowledge, thus embodying an account of how a non-linguistic goal might give rise to a particular form of words under appropriate circumstances
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Skyrmion interactions and vibrationsFeist, Dankrad Tjark Joseph January 2013 (has links)
No description available.
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Identification of a Novel Virulence Factor in Campylobacter jejuni: Characterization, Pathogenesis and Immunity of Cj1534cTheoret, James January 2009 (has links)
Infection with Campylobacter jejuni is one of the leading causes of bacterial gastroenteritis, causing an estimated 2.1 million cases annually. Although infections with C. jejuni resolve naturally, over 13,000 hospitalizations and 100 deaths are attributed to this organism. Despite these alarming numbers, relatively little is known about C. jejuni pathogenesis, when compared to other enteric pathogens. This dissertation outlines the identification and characterization of a novel virulence factor in C. jejuni, the protein expressed by the Cj1534c gene. Using microarray and RT real time PCR, Cj1534c was found to be greater than 10 fold over expressed in both swine and poultry. Employing immunoelectron microscopy, we determined that at least a subset of the protein is surface localized. Based on the surface localization and up regulation in poultry, colonization studies were performed. Results demonstrate a significant reduction in colonization by a Cj1534c deficient mutant as compared to wild type. In vitro binding assays using both biotic and abiotic surfaces indicate this protein is involved with attachment to surfaces, as well as the invasion of cultured epithelial cells. In vitro findings were confirmed in vivo using swine, with the Cj1534c mutant being highly attenuated as compared to wild type strains. Additionally, the Cj1534c protein was tested for its potential as a vaccine in poultry. Studies demonstrated that Cj1534c recombinantly expressed in a Salmonella expression vector partially protected chickens, reducing cecal colonization three logs as compared to wild type. Taken together, this data demonstrates a major role of Cj1534c in both chicken cecal colonization and infection of swine.
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Model Structure Estimation and Correction Through Data AssimilationBulygina, Nataliya January 2007 (has links)
The main philosophy underlying this research is that a model should constitute a representation of both what we know and what we do not know about the structure and behavior of a system. In other words it should summarize, as far as possible, both our degree of certainty and degree of uncertainty, so that it facilitates statements about prediction uncertainty arising from model structural uncertainty. Based on this philosophy, the following issues were explored in the dissertation: Identification of a hydrologic system model based on assumption about perceptual and conceptual models structure only, without strong additional assumptions about its mathematical structure Development of a novel data assimilation method for extraction of mathematical relationships between modeled variables using a Bayesian probabilistic framework as an alternative to up-scaling of governing equations Evaluation of the uncertainty in predicted system response arising from three uncertainty types: o uncertainty caused by initial conditions, o uncertainty caused by inputs, o uncertainty caused by mathematical structure Merging of theory and data to identify a system as an alternative to parameter calibration and state-updating approaches Possibility of correcting existing models and including descriptions of uncertainty about their mapping relationships using the proposed method Investigation of a simple hydrological conceptual mass balance model with two-dimensional input, one-dimensional state and two-dimensional output at watershed scale and different temporal scales using the method
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Determining price differences among different classes of wool from the U.S. and AustraliaHager, Shayla Desha 30 September 2004 (has links)
The U.S. wool industry has long received lower prices for comparable wool types than those of Australia. In order to better understand such price differences, economic evaluations of both the U.S. and Australian wool markets were conducted. This research focused on two primary objectives. The first objective was to determine what price differences existed between the Australian and U.S. wool markets and measure that difference. The second objective was to calculate price differences attributable to wool characteristics, as well as those resulting from regional, seasonal, and yearly differences. In order to accomplish the objectives, the study was set up into three different hedonic pricing models: U.S., Australian, and combined. In the U.S. model, there were significant price differences in season, year, region, level of preparation, and wool description. In addition, average fiber diameter (AFD) had a negative nonlinear relationship with price and lot weight had a positive linear relationship with price. The Australian model was notably different than the U.S. model in that there were only three variables. The yearly variable follows the same general pattern as the U.S. data but with a smaller span of difference. The seasonal price differences were distinctly different than the U.S. because of the difference in seasonal patterns. In addition, the AFD had a similar negative nonlinear relationship with price. The final model combines both the U.S. data and the Australian data. The combined model had only three variables: season, year, AFD and country. As in the case of the previous two models, AFD had the same negative nonlinear relationship and similar price elasticity. Overall, there was a -30.5 percent discount for U.S. wool when compared to Australian wool. This can be attributed to several different factors. One of which is that the Australian wool industry has a more extensive marketing scheme when compared to the U.S wool market as a whole. However, this is only a beginning to future research that needs to be conducted. Continuing this study for future years, having more descriptive categories, and additional countries would further add explanation to wool prices.
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Conditional nonlinear asset pricing kernels and the size and book-to-market effectsBurke, Stephen Dean 05 1900 (has links)
We develop and test asset pricing model formulations that are simultaneously conditional
and nonlinear. Formulations based upon five popular asset pricing models are tested against
the widely studied Fama and French (1993) twenty-five size and book-to-market sorted portfolios.
Test results indicate that the conditional nonlinear specification of the Fama and
French (1993) three state variable model (FF3) is the only specification not rejected by the
data and thus capable of pricing the "size" and "book-to-market" effects simultaneously.
The pricing performance of the FF3 conditional nonlinear pricing kernel is corifirmed by
robustness tests on out-of-sample data as well as tests with alternative instrumental and
conditioning variables. While Bansal and Viswanathan (1993) and Chapman (1997) find
unconditional nonlinear pricing kernels sufficient to capture the size effect alone, our results
indicate that similar unconditional nonlinear pricing kernels considered here do not price the
size and book-to-market effects simultaneously. However, nested model tests indicate that,
in isolation, both conditioning information and nonlinearity significantly improve the pricing
kernel performance for all five asset pricing models. The success of the conditional nonlinear
FF3 model also suggests that the combination of conditioning and nonlinearity is critical
to pricing kernel design. Implications for both academic researchers and practitioners are
considered.
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Essays in empirical asset pricingSmith, Daniel Robert 11 1900 (has links)
This thesis consists of two essays which contribute to different but related aspects of
the empirical asset pricing literature. The common theme is that incorrect restrictions
can lead to inaccurate decisions. The first essay demonstrates that failure to account
for the Federal Reserve experiment can lead to incorrect assumptions about the explosiveness
of short-term interest rate volatility, while the second essay demonstrates
that we need to incorporate skewness to develop models that adequately account for
the cross-section of equity returns.
Essay 1 empirically compares the Markov-switching and stochastic volatility diffusion
models of the short rate. The evidence supports the Markov-switching diffusion
model. Estimates of the elasticity of volatility parameter for single-regime models
unanimously indicate an explosive volatility process, whereas the Markov-switching
models estimates are reasonable. We find that either Markov-switching or stochastic
volatility, but not both, is needed to adequately fit the data. A robust conclusion is
that volatility depends on the level of the short rate. Finally, the Markov-switching
model is the best for forecasting. A technical contribution of this paper is a presentation
of quasi-maximum likelihood estimation techniques for the Markov-switching
stochastic-volatility model.
Essay 2 proposes a new approach to estimating and testing nonlinear pricing models
using GMM. The methodology extends the GMM based conditional mean-variance
asset pricing tests of Harvey (1989) and He et al (1996) to include preferences over
moments higher than variance. In particular we explore the empirical usefulness of
the conditional coskewness of an assets return with the market return in explaining
the cross-section of equity returns. The methodology is both flexible and parsimonious.
We avoid modelling any asset specific parameters and avoid making restrictive
assumptions on the dynamics of co-moments. By using GMM to estimate the models'
parameters we also avoid making any assumptions about the distribution of the data.
The empirical results indicate that coskewness is useful in explaining the cross-section
of equity returns, and that both covariance and coskewness are time varying. We also
find that the usefulness of coskewness is robust to the inclusion of Fama and French's
(1993) SMB and HML factor returns.
There is an interesting debate raging in the empirical asset pricing literature comparing
the SDF versus beta methodologies. This paper's technique is a conditional
version of the beta methodology, which turns out to be directly comparable with
the SDF methodology with only minor modifications. Our SDF version imposes the
CAPM's restrictions that the coefficients in the pricing kernel are known functions of
the moments of market returns, which are modelled using macro-variables. We find
that the SDF implied by the three-moment CAPM provides a better fit in this data
set than current practice of parameterizing the coefficients on market returns in the
SDF. This has an interesting application to the current SDF versus beta methodology
debate.
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Using age of infection models to derive an explicit expression for RoYang, Christine K. 05 1900 (has links)
Using a multiple stage age of infection model, we derive an expression for the basic reproduction number, Ro. We apply this method to find Ro in analogous treatment models. We find, in the model without treatment, Ro depends only on the mean infective period, and not on the infective distribution. In treatment models, Ro depends on the mean infective and mean treatment period, as well as the distribution of the infective period, but not on the distribution of the treatment period. With an explicit formula for Ro and the final size relation, we provide a practical alternative to evaluating the effect of treatment and other control measures. We compare our models to previous models of SARS and TB.
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