Genetic Algorithms in Stochastic Optimization and Applications in Power Electronics

Genetic Algorithms (GAs) are widely used in multiple fields, ranging from mathematics, physics, to engineering fields, computational science, bioinformatics, manufacturing, economics, etc. The stochastic optimization problems are important in power electronics and control systems, and most designs require choosing optimum parameters to ensure maximum control effect or minimum noise impact; however, they are difficult to solve using the exhaustive searching method, especially when the search domain conveys a large area or is infinite. Instead, GAs can be applied to solve those problems. And efficient computing budget allocation technique for allocating the samples in GAs is necessary because the real-life problems with noise are often difficult to evaluate and require significant computation effort. A single objective GA is proposed in which computing budget allocation techniques are integrated directly into the selection operator rather than being used during fitness evaluation. This allows fitness evaluations to be allocated towards specific individuals for whom the algorithm requires more information, and this selection-integrated method is shown to be more accurate for the same computing budget than the existing evaluation-integrated methods on several test problems. A combination of studies is performed on a multi-objective GA that compares integration of different computing budget allocation methods into either the evaluation or the environmental selection steps. These comparisons are performed on stochastic problems derived from benchmark multi-objective optimization problems and consider varying levels of noise. The algorithms are compared regarding both proximity to and coverage of the true Pareto-optimal front, and sufficient studies are performed to allow statistically significant conclusions to be drawn. Finally, the multi-objective GA with selection integrated sampling technique is applied to solve a multi-objective stochastic optimization problem in a grid connected photovoltaic inverter system with noise injected from both the solar power input and the utility grid

Nonlinear optics in thin film interference coatings

Nonlinear optical effects play a crucial role in modern optical systems. They are applied in mode-locking for the generation of ultrashort optical pulses, in the generation of otherwise unavailable wavelengths, or for new approaches in measurement techniques. However, implementing the required nonlinear optical processes mainly relies on conventional optical systems comprising separate components and free-space constructions, which limits the possibilities for miniaturization and integration of functional groups. Contrary to this, optical interference coatings offer highly developed capabilities for combining optical functions into a single, monolithic stack of transparent materials. So far, the applications of optical coatings have generally been limited to the linear optical regime. If nonlinear effects were considered, it was mostly directed at their suppression to avoid undesired effects. This thesis, therefore, investigates the combination of selected nonlinear optical effects with specially designed optical coatings to create novel components as alternatives to established optical systems. Due to the amorphous nature of thin film coating materials, the two effects chosen for investigation are based on the third-order susceptibility χ(3). The first effect is the optical Kerr effect, which is utilized to achieve all-optical switching of incident light. In the second case, optical coatings are utilized to solve phase matching issues for the third harmonic generation in frequency tripling mirrors and significantly increase conversion efficiency. The manufacturing processes and material research are presented for both approaches, together with the experimental testing of the novel components’ function. It was found that while the frequency tripling mirrors provide a greatly enhanced efficiency compared to the third harmonic generated in more typical optical coatings, the total efficiency is currently limited by free-electron effects occurring during the conversion process. The optical switches show significant modulation of 20% in transmittance and 30% in reflectance with a repeatable process which can be clearly distinguished from laser-induced damage occurring at higher intensities. Therefore, the created optical switch can present a viable alternative to established switching concepts.Nichtlineare optische Effekte spielen eine essenzielle Rolle in modernen optischen Systemen. Sie finden Anwendung in der Modenkopplung zur Erzeugung ultrakurzer Laserpulse, bei der Generation von Laserwellenlängen, die auf andere Weise nicht verfügbar wären und bei neuartigen Messverfahren. Die Implementierung der benötigten nichtlinearen optischen Prozesse basiert dabei auf konventionellen optischen Aufbauten aus einzelnen Komponenten in Freistrahlkonfigurationen, was die Möglichkeiten für Miniaturisierung und Integration von Funktionsgruppen limitiert. Im Gegensatz dazu sind optische Interferenzbeschichtungen ein hochentwickeltes Verfahren für die Kombination von optischen Funktionen in einzelne, monolithische Schichtsysteme aus transparenten Materialien. Bisher waren die Anwendungen von optischen Beschichtungen dabei auf den linearen Bereich der optischen Wechselwirkung beschränkt. Wenn nichtlineare optische Effekt berücksichtigt wurden, dann üblicherweise nur, um diese als unerwünschte Effekte zu unterdrücken. Diese Arbeit untersucht daher die Kombination von ausgewählten nichtlinearen optischen Effekten mit speziell entworfenen optischen Beschichtungen. Ziel hierbei ist die Schaffung von neuartigen Komponenten, die als Alternative zu etablierten optischen Systemen fungieren können. Wegen der amorphen Struktur der Beschichtungsmaterialien, basieren die zwei betrachteten nichtlinearen Effekte auf der Suszeptibilität der dritten Ordnung χ(3). Der erste Effekt ist der optische Kerr-Effekt, welcher genutzt wird, um einfallendes Licht ausschließlich optisch zu schalten. Im zweiten Fall werden optische Beschichtungen genutzt, um das Problem der Phasenanpassung bei Erzeugung der dritten Harmonischen in frequenzverdreifachenden Spiegeln zu lösen und so die Konversionseffizienz deutlich zu erhöhen. Für beide dieser Anwendungen werden die Herstellungsverfahren, die Untersuchung der benötigten optischen Materialien, sowie die experimentelle Überprüfung der hergestellten Komponenten präsentiert. Die Untersuchungen haben gezeigt, dass die frequenzverdreifachenden Spiegel zwar die Konversionseffizienz deutlich steigern können, aktuell aber noch durch die Generation freier Elektronen sowie die daraus resultierenden Effekte limitiert werden. Die optischen Schalter zeigen eine deutliche Modulation ihrer optischen Eigenschaften mit Änderungen der Transmission und Reflexion um etwa 20% beziehungsweise 30%. Der Modulationsprozess ist dabei ein reproduzierbarer Prozess, der klar von der laserinduzierten Zerstörung bei höheren Intensitäten unterschieden werden kann. Der geschaffene optische Schalter kann daher eine funktionale Alternative zu etablierten Schaltkonzepten darstellen

A Platform for Practical Nanophotonic Systems Nitrides and Oxides for Integrated Plasmonic Devices

The fields of nanophotonics and metamaterials have revolutionized the way we think of optical space (ε,µ), enabling us to engineer the refractive index almost at will, to confine light to the smallest of volumes, as well as to manipulate optical signals with extremely small foot prints and energy requirements. Throughout the past, this field of research has largely been limited to the use of noble metals as plasmonic materials, largely due to the high conductivity (low loss) and wide availability in research institutions. However, the research which follows focuses on the development of two alternative material platforms for nanophotonics: namely the transition metal nitrides and the transparent conducting oxides. Through this research, we have explored the nonlinear optical properties of thin films, demonstrating unique and ultrafast dynamic response, and have designed and realized high performance integrated plasmonic devices. Ultimately, this work aims to demonstrate the impact and potential of alternative plasmonic materials for numerous nanophotonic applications

Machine learning assisted optimization with applications to diesel engine optimization with the particle swarm optimization algorithm

A novel approach to incorporating Machine Learning into optimization routines is presented. An approach which combines the benefits of ML, optimization, and meta-model searching is developed and tested on a multi-modal test problem; a modified Rastragin\u27s function. An enhanced Particle Swarm Optimization method was derived from the initial testing. Optimization of a diesel engine was carried out using the modified algorithm demonstrating an improvement of 83% compared with the unmodified PSO algorithm. Additionally, an approach to enhancing the training of ML models by leveraging Virtual Sensing as an alternative to standard multi-layer neural networks is presented. Substantial gains were made in the prediction of Particulate matter, reducing the MMSE by 50% and improving the correlation R^2 from 0.84 to 0.98. Improvements were made in models of PM, NOx, HC, CO, and Fuel Consumption using the method, while training times and convergence reliability were simultaneously improved over the traditional approach

Developing novel nonlinear materials for metaphotonics device applications

Recent advancements in flat-optics, metamaterials research, and integrated optical devices have established the need for more efficient, spectrally tunable, and Si-compatible optical media and nanostructures with designed linear/nonlinear responses that can enable high-density integration of ultrafast photonic-plasmonic functionalities on the chip. Traditional methodologies for nanoscale photon manipulation utilize lossy materials, such as noble metals, which lack significant optical tunablility and compatibility with complementary metal-oxide-semiconductor technologies. In this dissertation, we propose, develop, and characterize alternative plasmonic materials that overcome these limitations while providing novel opportunities for significant optical nonlinear enhancement. Specifically, we investigate the plasmonic resonant regime and the nonlinear optical responses of Si- and O2- doped titanium nitride, SiO2- doped indium oxide, and Sn-doped indium oxide with engineered structural and optical dispersion behavior. We study a number of novel passive metaphotonic devices that leverage refractive index control in low-loss materials for near-field engineering and nanoscale nonlinear optical enhancement. Moreover, we integrate the developed alternative plasmonic materials into active metaphotonic surfaces for electro-optical modulation, enhanced light absorption, and ultrafast photon detection. Furthermore, utilizing the double-beam accurate Z-scan technique, we characterize the intrinsic nonlinear susceptibility χ(3) of optical nanolayers with epsilon-near-zero behavior as a function of their microstructural properties that we largely control by post-deposition annealing. A main objective of this work is to establish robust structure-property relationships for the control of optical dispersion, Kerr nonlinearity, and near-field resonances that extend from the visible to the infrared. This work substantially expands and diversifies the reach of plasmonics, flat-optics, and nonlinear optics across multiple spectral regions within scalable and Si-compatible novel material platforms

A Comprehensive Survey on Particle Swarm Optimization Algorithm and Its Applications

Particle swarm optimization (PSO) is a heuristic global optimization method, proposed originally by Kennedy and Eberhart in 1995. It is now one of the most commonly used optimization techniques. This survey presented a comprehensive investigation of PSO. On one hand, we provided advances with PSO, including its modifications (including quantum-behaved PSO, bare-bones PSO, chaotic PSO, and fuzzy PSO), population topology (as fully connected, von Neumann, ring, star, random, etc.), hybridization (with genetic algorithm, simulated annealing, Tabu search, artificial immune system, ant colony algorithm, artificial bee colony, differential evolution, harmonic search, and biogeography-based optimization), extensions (to multiobjective, constrained, discrete, and binary optimization), theoretical analysis (parameter selection and tuning, and convergence analysis), and parallel implementation (in multicore, multiprocessor, GPU, and cloud computing forms). On the other hand, we offered a survey on applications of PSO to the following eight fields: electrical and electronic engineering, automation control systems, communication theory, operations research, mechanical engineering, fuel and energy, medicine, chemistry, and biology. It is hoped that this survey would be beneficial for the researchers studying PSO algorithms

Plasmonic devices based on transparent conducting oxides for near infrared applications

In the past decade, there have been many breakthroughs in the field of plasmonics and nanophotonics that have enabled optical devices with unprecedented functionalities. Even though remarkable demonstration of at photonic devices has been reported, constituent materials are limited to the noble metals such as gold (Au) and silver (Ag) due to their abundance of free electrons which enable the support of plasmon resonances in the visible range. With the strong demand for extension of the optical range of plasmonic applications, it is now a necessity to explore and develop alternative materials which can overcome intrinsic issues of noble metals such as integration challenges, considerable optical losses, and lack of tunability of their optical properties. As most promising alternative to noble metals, transparent conducting oxides (TCOs) have been proposed as a promising new class of plasmonic materials for the IR applications. The main objective of the thesis is to explore the various plasmonic devices based on TCOs in order to evaluate the capabilities of TCOs as alternative metallic component for plasmonic applications. By beginning with a discussion of the general (optical, electrical and morphological) properties of TCOs, we describe the demonstration of devices such as plasmonic resonator for bio-sensing and waveplate metasurfaces. In addition, we study the impact of TCOs to local antenna as epsilon-near-zero (ENZ) substrate. The technological importance of the IR range is apparent and growing, and as plasmonics develops a niche at these frequencies, I believe this study represents a scientific directive toward the quest to bring plasmonics into the IR

Texture and Colour in Image Analysis

Research in colour and texture has experienced major changes in the last few years. This book presents some recent advances in the field, specifically in the theory and applications of colour texture analysis. This volume also features benchmarks, comparative evaluations and reviews