Considering the South China Sea dispute as a flashpoint of regional stability and power balance within the Southeast Asian region, the first failure in ASEAN history to reach a consensus in 2012 and the deadlock in 2016 on this issue brought up uncertainty towards the ability of ASEAN member states to reach a consensus on the South China Sea issue. This thesis seeks to analyze this issue based on neo-classical realism and the two-level games theory to what extent, if any, do the ASEAN member states’ domestic factors and external relations influence their decision towards the South China Sea dispute. The theoretical framework of neoclassical realism provides three indicators for analysis, which are national interests, domestic politics, and the role and perception of political leaders. The two-level games theory addresses on the preferences and coalitions within states, political institutions, and the role of chief negotiators as the three indicators to determine the win-sets of the ASEAN member states. The conclusions show the different win-sets size of ASEAN member states vary accordingly from a larger win-sets size of an authoritarian state to a smaller win-sets size of a more democratic state.

Electrical vehicles have become more popular during recent years due to their reduced greenhouse gas emissions. The research within Li-ion batteries is therefore moving fast. Presently, two-level converters transforming the current from DC to AC. However, an alternative method of power conversion is by utilizing modular multilevel converters, which can perform better harmonics than the two-level converter. This study aims to research the impact of these converters on battery cell heat generation. In doing so, developing a digital twin of the Li-ion battery cell, which in this case is a Samsung 28 Ah nickel, manganese, and cobalt prismatic battery cell, focusing on the thermal aspects such as heat generation, heat capacity, and thermal conductivity. The modular multilevel converter may also cause significant overtones, harmonics. Therefore, this study investigates the thermal impact of these frequencies. The results show that it is possible to, via experiments and simulations, determine the heat capacity and thermal conductivity of a Li-ion cell. Furthermore, the frequencies caused by the modular multilevel converter cause a temperature rise in the cell, compared to the two-level converter. Although, if the same root mean square for the modular multilevel converter current is used, the temperature rise is lower compared to DC. During the load cycles, the results show that there are slightly higher temperatures at the positive current collector side compared to the negative. It is, however, the jelly roll core that has the highest temperatures.

This thesis addresses the military capabilities gap between the US and European member states of NATO. It seeks to answer the question, why does the US-European capabilities gap persist despite apparent agreement between Allies on strategic capabilities objectives and cooperative solutions? The paper first establishes the need for a strong, independent European Security and Defense Identity within the Alliance, particularly since NATO's operations in Libya. It then defines and explicates the military capabilities gap within the Alliance, including its scope, history, and attempts to find cooperative solutions. This analysis demonstrates that there is broad agreement both on what the Alliance requires for military capabilities and for how best to obtain them (cooperatively), yet the gap has persisted and grown for two decades. In an attempt to solve this empirical puzzle, the paper employs a two-level games framework to analyze the NATO defense planning process, which links supranational capabilities planning for the Alliance to national-level execution, dependent upon funding from state parliaments. Faced with the general answer that fiscal constraints preclude states from following through on their commitments, the paper delves deeper to determine factors that may influence differences in defense...

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Reduced-order models are frequently used in the simulation of complex flows to overcome the high computational cost of direct numerical simulations, especially for three-dimensional nonlinear problems. Proper orthogonal decomposition, as one of the most commonly used tools to generate reduced-order models, has been utilized in many engineering and scientific applications. Its original promise of computationally efficient, yet accurate approximation of coherent structures in high Reynolds number turbulent flows, however, still remains to be fulfilled. To balance the low computational cost required by reduced-order modeling and the complexity of the targeted flows, appropriate closure modeling strategies need to be employed. In this dissertation, we put forth two new closure models for the proper orthogonal decomposition reduced-order modeling of structurally dominated turbulent flows: the dynamic subgrid-scale model and the variational multiscale model. These models, which are considered state-of-the-art in large eddy simulation, are carefully derived and numerically investigated. Since modern closure models for turbulent flows generally have non-polynomial nonlinearities, their efficient numerical discretization within a proper orthogonal decomposition framework is challenging. This dissertation proposes a two-level method for an efficient and accurate numerical discretization of general nonlinear proper orthogonal decomposition closure models. This method computes the nonlinear terms of the reduced-order model on a coarse mesh. Compared with a brute force computational approach in which the nonlinear terms are evaluated on the fine mesh at each time step, the two-level method attains the same level of accuracy while dramatically reducing the computational cost. We numerically illustrate these improvements in the two-level method by using it in three settings: the one-dimensional Burgers equation with a small diffusion parameter, a two-dimensional flow past a cylinder at Reynolds number Re = 200, and a three-dimensional flow past a cylinder at Reynolds number Re = 1000. With the help of the two-level algorithm, the new nonlinear proper orthogonal decomposition closure models (i.e., the dynamic subgrid-scale model and the variational multiscale model), together with the mixing length and the Smagorinsky closure models, are tested in the numerical simulation of a three-dimensional turbulent flow past a cylinder at Re = 1000. Five criteria are used to judge the performance of the proper orthogonal decomposition reduced-order models: the kinetic energy spectrum, the mean velocity, the Reynolds stresses, the root mean square values of the velocity fluctuations, and the time evolution of the proper orthogonal decomposition basis coefficients. All the numerical results are benchmarked against a direct numerical simulation. Based on these numerical results, we conclude that the dynamic subgrid-scale and the variational multiscale models are the most accurate. We present a rigorous numerical analysis for the discretization of the new models. As a first step, we derive an error estimate for the time discretization of the Smagorinsky proper orthogonal decomposition reduced-order model for the Burgers equation with a small diffusion parameter. The theoretical analysis is numerically verified by two tests on problems displaying shock-like phenomena. We then present a thorough numerical analysis for the finite element discretization of the variational multiscale proper orthogonal decomposition reduced-order model for convection-dominated convection-diffusion-reaction equations. Numerical tests show the increased numerical accuracy over the standard reduced-order model and illustrate the theoretical convergence rates. We also discuss the use of the new reduced-order models in realistic applications such as airflow simulation in energy efficient building design and control problems as well as numerical simulation of large-scale ocean motions in climate modeling. Several research directions that we plan to pursue in the future are outlined. / Ph. D.

This thesis provides a detailed explanation of the complex interrelations between national political dynamics and policy-making processes within the European Union, with a particular emphasis on Germany's involvement in the negotiation of the Corporate Sustainability Due Diligence Directive. The central research question is as follows: What factors influenced Germany's decision to block the CSDD adoption despite agreeing to the proposal just a month earlier? The theoretical approach for this research integrates normative institutionalism and a new model of foreign policy analysis within the framework of two-level game theory. These theoretical constructs are leveraged to dissect the dual-level negotiation processes, facilitating an analysis of how Germany navigates between internal pressures and broader EU policy mandates. This theoretical exploration extends to assess the overarching dynamics of EU legislative processes, especially in relation to the alignment and conflict between economic imperatives and normative policy objectives such as sustainability. Methodologically, this thesis utilises in-depth theory- building process-tracing to identify causal-mechanisms that led from the proposal of the CSDD draft to Germanys decision to hinder the adoption of the agreed upon draft. The results underscore a nuanced landscape of negotiation and adjustment, wherein Germany's economic imperatives frequently conflict with the EU's sustainability ambitions. The analysis demonstrates that Germany's external commitments to EU sustainability policies are significantly conditioned by domestic economic considerations, which in turn influence Germany's tactical approaches within EU policy negotiations.

The Landau-Zener-Stückelberg-Majorana (LZSM) problem models diabatic transitions between energy levels in quantum two-level systems with an avoided level-crossing. The diabatic transition is a consequence of quantum tunneling in energy space when the system's Hamiltonian is perturbed with a fast-acting bias. The probability of transition between the energy states for a linear bias is known as the LZSM transition probability. The objective of this work is to investigate the LZSM problem through analytical and numerical lenses. The LZSM transition probability is derived in two ways. The first approach is based on Majorana's solution using contour integrals. The second derivation follows Landau's quasi-classical treatment. The derivations demonstrate methods for transitions in the presence of time-dependent perturbations. The ubiquity of the two-level system is discussed and an application on qubits concerning LSZM interferometry is presented, with the latter arising after considering periodic biases. Lastly, a simulation of the two-level system is conducted using Trotter-decomposed time-evolution operators, perturbation theory, and vectorization. The simulated transition probabilities for linear and periodic biases are obtained for varied parameters. The results show that the simulation achieves an accurate and efficient emulation of the LZSM problem.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第25099号 / 理博第5006号 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)講師 PETERSRobert, 教授 柳瀬 陽一, 教授 田中 耕一郎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Un préconditionneur à deux niveaux, reposant sur la technique d’accélération d’Aitken d’une suite de q vecteurs solutions de l’interface d’un pro- cessus itératif de Schwarz Additif Restreint, est conçu. Cette nouvelle technique, dénomée ARAS(q), utilise une approximation grossière de la solution sur l’interface. Différentes méthodes sont proposées, aboutissant au développement d’une tech- nique d’approximation par Décomposition en Valeures Singulières de la suite de vecteurs. Des implémentations parallèles des méthodes d’Aitken-Schwarz sont pro- posées et l’étude conduit à l’implémentation d’un code totalement algébrique, sur un ou deux niveaux de parallélisation MPI, écrit dans l’environnement de la biblio- thèque PETSc. Cette implémentation pleinement parallèle et algébrique procure un outil flexible pour la résolution de systèmes linéaires tels que ceux issus de la dif- férentiation automatique des solutions de Navier-Stokes dépendant des paramètres de la simulation / A two level preconditioner, based on the Aitken acceleration technique of a sequence of q interface’s solution vectors of the Restricted Additive Schwarz iterative process, is designed. This new technique, called ARAS(q), uses a coarse approximation of the solution on the interface. Different methods are discussed, leading to the development of an approximation technique by Singular Value De- composition of the sequence of vectors. Parallel implementations of Aitken-Schwarz methods are proposed, and the study leads to a fully algebraic one-level and two- level MPI implementation of ARAS(q) written into the PETSc library framework. This fully parallel and algebraic code gives an adaptive tool to solve linear systems such as those arising from automatic differentiation of compressible Navier-Stokes solution with respect to the simulation’s parameters