A numerical study on manoeuvrability of wind turbine installation vessel using OpenFOAM

ABSTRACTIn this study, a numerical prediction method on manoeuvrability of Wind Turbine Installation Vessel (WTIV) is presented. Planar Motion Mechanism (PMM) captive test for the bare hull of WTIV is carried out in the model basin and compared with the numerical results using RANS simulation based on Open-source Field Operation And Manipulation (OpenFOAM) calculation to validate the developed method. The manoeuvrability of WTIV with skeg and/or without skeg is investigated using the numerical approach along with the captive model test. In the numerical calculations, the dynamic stability index which indicates the course keeping ability is evaluated and compared for three different hull configurations i.e. bare hull and other two hulls with center skeg and twin skeg. This paper proves that the numerical approach using RANS simulation can be readily applied to estimate the manoeuvrability of WTIV at the initial design stage

Optimal experimental design under a new multivariate Weibull regression function

"May 2014."Dissertation Supervisor: Dr. Nancy Flournoy.Includes vita.In the manufacturing industry, it may be important to study the relationship between machine component failures under stress. Examples include failures such as integrated circuits and memory chips in electronic merchandise given various levels of electronic shock. Such studies are important for the development of new products and for the improvement of existing products. We assume two component systems for simplicity and we assume the joint probability of failures increases with stress as a cumulative bivariate Weibull function. Optimal designs have been developed for two correlated binary responses using the Gumbel model, the bivariate binary Cox model and the bivariate probit model. In all these models, the amount of damage ranges from negative to positive infinity. In the Weibull model, the amount of damage is positive which is natural for experimental factors such as voltage, tension or pressure. First, we describe locally optimal designs under bivariate Weibull assumptions. From among many optimal objective functions, we use the D-optimality criterion which minimizes the inverse of the determinant of information matrix. Since locally optimal designs with non-linear models depend on pre-determined parameter values, misspecified parameter values may lead to designs of the low efficiency. To improve the efficiency of locally optimal designs, we recommend a multi-stage procedure. We show how using a two-stage procedure substantially improves a locally optimal design with misspecified parameters. In addition to D-optimal designs, we describe c-optimal designs under the trivariate Weibull regression model. We assume that the amount of damage decreases sequentially as the stress progresses through the three components. The target stress can be expressed in terms of a linear predictor function, and we evaluate c-optimal designs for optimizing the prediction of the target stress. To compensate for the loss of efficiency of optimal designs with non-linear models, we show a two-stage procedure, and then compare the efIncludes bibliographical references (pages 118-120)

Introducing an Integrated Model of Adults’ Wearable Activity Tracker Use and Obesity Information–Seeking Behaviors From a National Quota Sample Survey

Background: Research from multiple perspectives to investigate adults’ use of wearable activity-tracking devices is limited. We offer a multiperspective model and provide empirical evidence of what leads to frequent usage of wearable health technologies from a large, nationally representative survey sample. Objective: This study aims to explore factors affecting the use of wearable activity-tracking devices among health consumers from the perspectives of individual health beliefs (perceived severity, perceived susceptibility, perceived benefits, and self-efficacy) and information-seeking behaviors. Methods: Our Integrated Model of Wearable Activity Tracker (IMWAT) use and proposed hypotheses were validated and tested with data collected from a telephone survey with a national quota sample. The data were analyzed using a variety of statistical techniques, including structural equation analysis. Results: The sample comprised 2006 participants. Our results showed that the perceived benefits of physical activity, perceived susceptibility, and self-efficacy toward obesity were significant predictors of information-seeking behaviors, which, in turn, mediated their effects on the use of wearable activity trackers. Perceptions of obesity severity directly promoted wearable device usage. Conclusions: This study provided a new and powerful theoretical model that combined the health beliefs and information-seeking behaviors behind the use of wearable activity trackers in the adult population. The findings provide meaningful implications for developers and designers of wearable health technology products and will assist health informatics practitioners and obesity prevention communicators

Minkowski Tensors in Two Dimensions - Probing the Morphology and Isotropy of the Matter and Galaxy Density Fields

We apply the Minkowski Tensor statistics to two dimensional slices of the three dimensional density field. The Minkowski Tensors are a set of functions that are sensitive to directionally dependent signals in the data, and furthermore can be used to quantify the mean shape of density peaks. We begin by introducing our algorithm for constructing bounding perimeters around subsets of a two dimensional field, and reviewing the definition of Minkowski Tensors. Focusing on the translational invariant statistic $W^{1,1}_{2}$ - a $2 \times 2$ matrix - we calculate its eigenvalues for both the entire excursion set ($\Lambda_{1},\Lambda_{2}$) and for individual connected regions and holes within the set ($\lambda_{1},\lambda_{2}$). The ratio of eigenvalues $\Lambda_{2}/\Lambda_{1}$ informs us of the presence of global anisotropies in the data, and $\langle \lambda_{2}/\lambda_{1} \rangle$ is a measure of the mean shape of peaks and troughs in the density field. We study these quantities for a Gaussian field, then consider how they are modified by the effect of gravitational collapse using the latest Horizon Run 4 cosmological simulation. We find $\Lambda_{1,2}$ are essentially independent of gravitational collapse, as the process maintains statistical isotropy. However, the mean shape of peaks is modified significantly - overdensities become relatively more circular compared to underdensities of the same area. When applying the statistic to a redshift space distorted density field, we find a significant signal in the eigenvalues $\Lambda_{1,2}$, suggesting that they can be used to probe the large-scale velocity field.Comment: 17 pages, accepted for publication in AP

Adjoint asymptotic multiplier ideal sheaves

In this paper, we initiate the study of a triple $(X,\Delta,D)$ which consists of a pair $(X,\Delta)$ and a polarizing pseudoeffective divisor $D$. The adjoint asymptotic multiplier ideal sheaf $\mathcal{J}(X,\Delta;\lVert D \rVert)$ associated to the triple gives a simultaneous generalization of the multiplier ideal sheaf $\mathcal{J}(D)$ and asymptotic multiplier ideal sheaf $\mathcal{J}(\lVert D \rVert)$. We describe the closed set defined by the ideal sheaf $\mathcal{J}(X,\Delta;\lVert D \rVert)$ in terms of the minimal model program. We also characterize the case where $\mathcal{J}(X,\Delta;\lVert D \rVert)=\mathcal{O}_X$. Lastly, we also prove a Nadel type vanishing theorem of cohomology using $\mathcal{J}(X,\Delta;\lVert D \rVert)$