Eine einfache Methode zur Ermittlung aller Querspannungen in Faserverbundplatten als Voraussetzung einer verbesserten Versagensanalyse

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Implementing U.S. Foreign Policy: A Framework for Applying American Foreign Policy

The following thesis portfolio addresses the overarching research question of “How should U.S. foreign policy be implemented?” To answer this question, the thesis examines three areas of study: (1) how policy is sold, (2) how it should be crafted, and (3) finally, how it could be implemented. Chapter one examines how U.S. presidents sell foreign policy to the American public, focusing on the tool that religion and religious speech play in the process. While a powerful political force, the chapter sought to determine how religion can drive policy. Examining presidential speeches and decisions pertaining to foreign policy in two case studies, the research determined that religion can play a number of roles in any given presidency, and that it can be used to secure political capital for momentous policy initiatives or significant shifts in policy. Chapter two asked “What should be the fundamental/theoretical underpinnings of American foreign policy?” This chapter addressed this question in the hope of learning what core considerations should always be contemplated when devising policy. After analyzing various geopolitical theories, we set out how to describe the utility conservative geopolitical thought brings to current foreign policy issues and why certain hard-truths to include culture, geography and history must always be consulted in formulating policy. Chapter three was dedicated to completing the foreign policy process, exploring the topic of application or implementation. Having explored how policy can be sold and how it should be crafted, it was natural to examine how it would successfully be put into action. Specifically, the research goal in this chapter was to determine the most critical component required to successfully implement U.S. foreign policy and then construct a prospective policy to demonstrate implementation of a policy aimed at preserving a vital national interest. To demonstrate this, a threat analysis was conducted on the possibility of a chemical, biological, radiological or nuclear (CBRN) terror attack on the American homeland

Optimization-based calibration of hydrodynamic drag coefficients for a semisubmersible platform using experimental data of an irregular sea state

For the simulation of the coupled dynamic response of floating offshore wind turbines, it is crucial to calibrate the hydrodynamic damping with experimental data. The aim of this work is to find a set of hydrodynamic drag coefficients for the semisubmersible platform of the Offshore Code Comparison Collaboration, Continuation, with Correlation and unCertainity (OC6) project which provides suitable results for an irregular sea state. Due to the complex interaction of several degrees of freedom (DOF), it is common to calibrate drag coefficients with the time series of decay tests. However, applying these drag coefficients for the simulation of an irregular sea state results in misprediction of the motions. By using numerical optimization, it is possible to calibrate multiple drag coefficients simultaneously and effectively, while also considering several DOF. This work considers time series of structural displacements from wave tank tests of the OC6 project and from simulations of the same load cases in OpenFAST. Results are transferred into the frequency domain and the deviation between power spectral densities of surge, pitch and heave from experiment and numerical simulation is used as an objective function to obtain the best fitting drag coefficients. This novel numerical optimization approach enables finding one set of drag coefficients for different load cases, which is a major improvement compared to decay-test-tuned drag coefficients. © Published under licence by IOP Publishing Ltd

A comparison study on jacket substructures for offshore wind turbines based on optimization

The structural optimization problem of jacket substructures for offshore wind turbines is commonly regarded as a pure tube dimensioning problem, minimizing the entire mass of the structure. However, this approach goes along with the assumption that the given topology is fixed in any case. The present work contributes to the improvement of the state of the art by utilizing more detailed models for geometry, costs, and structural design code checks. They are assembled in an optimization scheme, in order to consider the jacket optimization problem from a different point of view that is closer to practical applications. The conventional mass objective function is replaced by a sum of various terms related to the cost of the structure. To address the issue of high demand of numerical capacity, a machine learning approach based on Gaussian process regression is applied to reduce numerical expenses and enhance the number of considered design load cases. The proposed approach is meant to provide decision guidance in the first phase of wind farm planning. A numerical example for a National Renewable Energy Laboratory (NREL) 5&thinsp;MW turbine under FINO3 environmental conditions is computed by two effective optimization methods (sequential quadratic programming and an interior-point method), allowing for the estimation of characteristic design variables of a jacket substructure. In order to resolve the mixed-integer problem formulation, multiple subproblems with fixed-integer design variables are solved. The results show that three-legged jackets may be preferable to four-legged ones under the boundaries of this study. In addition, it is shown that mass-dependent cost functions can be easily improved by just considering the number of jacket legs to yield more reliable results.</p

Mechanical Properties of Boehmite Evaluated by Atomic Force Microscopy Experiments and Molecular Dynamic Finite Element Simulations

Boehmite nanoparticles show great potential in improving mechanical properties of fiber reinforced polymers. In order to predict the properties of nanocomposites, knowledge about the material parameters of the constituent phases, including the boehmite particles, is crucial. In this study, the mechanical behavior of boehmite is investigated using Atomic Force Microscopy (AFM) experiments and Molecular Dynamic Finite Element Method (MDFEM) simulations. Young's modulus of the perfect crystalline boehmite nanoparticles is derived from numerical AFM simulations. Results of AFM experiments on boehmite nanoparticles deviate significantly. Possible causes are identified by experiments on complementary types of boehmite, that is, geological and hydrothermally synthesized samples, and further simulations of imperfect crystals and combined boehmite/epoxymodels. Under certain circumstances, the mechanical behavior of boehmite was found to be dominated by inelastic effects that are discussed in detail in the present work. The studies are substantiated with accompanying X-ray diffraction and Raman experiments.DFG/FOR/202

Hyperfine Magnetic Field Measurement in Heusler Alloys by TDPAC Technique

This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit