Silicon photonics has witnessed rapid development in recent years for its fabrication compatibility with the cost-effective CMOS technology. The advancement of relevant simulation tools, however, is at a relatively slow pace. The high index contrast of the usual silicon waveguide that has imposed new challenges to the convergence and accuracy of the solution technique, the growing intricacy in solitary component design, and the increased complexity of their integration, are the impelling factors that motivate us to improve the computer-aided design, modeling, simulation, and optimization methods. The theme of the thesis is on the frequency domain simulation methods supported by the complex mode theory. The complex mode theory is introduced to the simulation domain truncated by the perfectly matching layers (PMLs) enclosed in the perfectly reflected boundaries (PRBs), wherein the discrete complex modes as eigen solutions can represent the continuous radiation fields, thus yields a unified approach for handling both guided (discrete) and radiation (continuous) waves. In this thesis, theoretical investigations have been conducted along a few different lines aiming at improving the efficiency and accuracy in complex mode expansion. Properties of high-order complex Berenger modes are firstly addressed through asymptotic solutions, and it is found that as the mode order increases, the symmetry of the cladding and substrate in the simulation domain, instead of the guiding schemes, plays a more and more decisive role regarding mode classification and modal field distribution. A weighed optical path method is then proposed to unify the high-order Berenger modes, and to enhance the symmetry of high order modes’ field distributions in the asymmetric structures, leading to the improvement in convergence speed and stability in the mode expansion. Next, an improved mode-matching method (MMM) is proposed based on an error-minimizing method instead of the conventional approach relying on the unreliable modal orthogonal property. The newly proposed method is significantly more robust as numerical errors usually jeopardize the modal orthogonality. This claim is exemplified by simulation results on silicon channel waveguide facet, bending waveguide, and silicon-germanium photo-detector waveguide. As a direct application of the improved complex mode theory, a hybrid plasmonic-photonic nano-ribbon waveguide is proposed, standing as a combination of the silicon slot and surface plasmon polariton (SPP) waveguides, is proposed and analyzed. We have found that the fundamental mode is featured at low loss as in optical waveguide as well as high confinement as in plasmonic structure. Simulations have shown that millimeter range propagation can be sustained with strong confinement. We have further studied such waveguide with an extra layer of phase changing material incorporated, attempting to realize the efficient electro-optical phase and/or loss modulation. Finally, an optical switch design is proposed by taking the full advantage of the aforementioned structure. / Thesis / Doctor of Philosophy (PhD)

Renewable energy is a critical component in combating climate change. Ocean wave energy is a source of renewable energy that can be harvested using Wave Energy Converters (WECs). One such WEC is the floating Oscillating Water Column (OWC), which has been successfully field tested and warrants further exploration. This research implements a publicly accessible code in MatLab and SimuLink to simulate the dynamics of a floating OWC in the time domain. This code, known as the Floating OWC Iterative Time Series Solver (FlOWCITSS), uses the pressure distribution model paired with state space realization to capture the internal water column dynamics of the WEC and estimate pneumatic power generation. Published experimental results of floating moored structures are then used to validate FlOWCITSS. While FlOWCITSS seemed to capture the period and general nature of the heave, surge, and internal water column dynamics, the magnitude of the response sometimes had errors ranging from 1.5% −37%. This error could be caused by the modeling techniques used, or it could be due to uncertainties in the experiments. The presence of smaller error values shows potential for FlOWCITSS to achieve consistently higher fidelity results as the code undergoes further developments. To demonstrate the use of FlOWCITSS, geometry variations of a Backward Bent Duct Buoy (BBDB) are explored for a wave environment and mooring configuration. The reference model from Sandia National Labs, RM6, performed significantly better than a BBDB with an altered stern geometry for a 3 second wave period, indicating that stern geometry can have a significant impact on pneumatic power performance. / Master of Science / Renewable energy is a critical component in combating climate change. Ocean wave energy is a source of renewable energy that can be converted into electricity using Wave Energy Converters (WECs). One such WEC is the floating Oscillating Water Column (OWC), which has been successfully field tested and warrants further exploration. Floating OWCs are partially submerged floating structures that have an internal chamber which water oscillates in. The motions of the water displace air inside this chamber, causing the air to be forced through a high speed turbine, which generates electricity. This research develops a publicly accessible code using MatLab and SimuLink to evaluate the motions and power generation capabilities of floating OWCs. This code is then validated against physical experiments to verify its effectiveness in predicting the device's motions. This publicly accessible code, known as the Floating OWC Iterative Time Series Solver (FlOWCITSS), showed error ranging from 1.5 % - 37% for the most important motions that are relevant to energy harvesting and power generation. These errors could be caused by the numerical models used, or uncertainties in experimental data. The presence of smaller error values shows potential for FlOWCITSS to achieve consistently higher fidelity results as the code undergoes further developments. To demonstrate the use of FlOWCITSS, geometry variations of floating OWCs are explored.

<p>Simulation of the planing hull in waves has been addressed during the last 25 years and basically been approached by strip methods. This work follows that tradition and describes a time-domain strip model for simulation of the planing hull in waves. The actual fluid mechanical problem is simplified through the strip approach. The load distribution acting on the hull is approximated by determining the section load at a number of hull sections, strips. The section-wise 2-dimensional calculations are expressed in terms of added mass coefficients and used in the formulations of both inertia and excitation forces in the equations of motions. The modeling approach starts from the hypothetic assumption that the transient conditions can be modeled based on those section-wise calculations. The equation of motion is solved in the time-domain. The equation is up-dated at each time step and every iteration step with respect to the momentary distribution of section draught and relative incident velocity between the hull and water and catches the characteristic non-linear behavior of the planing craft in waves.</p><p>The model follows the principles of the pioneering work of E. E. Zarnick differing on model structure and in details such as the modeling of the lift in the transom area. A major part of the work is concerned with experiments and evaluation of simulations with respect to performed model tests and to published experiment data. Simulations of model tests have been performed and comparisons have been made between measured and simulated time series. The link between simulation and experiment is a wave model which is based on a wave height measurement signal. It is developed and evaluated in the thesis.</p><p>The conclusions are in favor of the 2-dimensional approach to modeling the conditions for the planing hull in waves and among further studies is evaluation of simulated loads and motions to full-scale trial measurement data.</p>

La nécessité de simuler des systèmes complexes et multi-physiques est de plus en plus courante dans l’industrie, en particulier avec l’avènement de la conception mécatronique. Ce phénomène couplé à la pression économique poussant les industriels dans la voie de l’optimisation de leurs produits conduit à une augmentation forte des temps de simulation que les progrès techniques ne parviennent pas à compenser. Les travaux menés lors de cette thèse ont permis de proposer une approche hybride analytique/éléments finis pour la simulation temporelle de la dynamique des transmissions par engrenages en présence de non-linéarités de contact. Couplée à une réduction des modèles éléments finis, cette approche permet la résolution rapide de la dynamique d’un réducteur et offre ainsi la possibilité d’intégrer le réducteur comme composant d’un système complexe tel qu’un système mécatronique. La résolution de la dynamique du réducteur peut être menée en parallèle des autres physiques en prenant en compte des couplages forts. L’optimisation d’un tel système est abordée sur un exemple pour clore cette étude. / The need to simulate complex and multi-physics systems is increasingly common in the industry, especially with the advent of mechatronic design. This coupled with economic pressure pushing the industry towards optimizing their products led to a strong increase in simulation time that technological advances can not compensate. An hybrid method analytical/finite element has been developed for the time domain simulation of gear transmissions involving contact non-linearities. Coupled with a reduction of finite element models, this approach allows fast resolution of the dynamics of a gearbox. Consequently, it is possible to integrate a gearbox as a part of a more complex mechatronic system. All physical phenomena involved in such a complex product are solved at the same time allowing strong coupling to be considered. The optimization of such a system is discussed with an example to conclude this study.

Simulation of the planing hull in waves has been addressed during the last 25 years and basically been approached by strip methods. This work follows that tradition and describes a time-domain strip model for simulation of the planing hull in waves. The actual fluid mechanical problem is simplified through the strip approach. The load distribution acting on the hull is approximated by determining the section load at a number of hull sections, strips. The section-wise 2-dimensional calculations are expressed in terms of added mass coefficients and used in the formulations of both inertia and excitation forces in the equations of motions. The modeling approach starts from the hypothetic assumption that the transient conditions can be modeled based on those section-wise calculations. The equation of motion is solved in the time-domain. The equation is up-dated at each time step and every iteration step with respect to the momentary distribution of section draught and relative incident velocity between the hull and water and catches the characteristic non-linear behavior of the planing craft in waves. The model follows the principles of the pioneering work of E. E. Zarnick differing on model structure and in details such as the modeling of the lift in the transom area. A major part of the work is concerned with experiments and evaluation of simulations with respect to performed model tests and to published experiment data. Simulations of model tests have been performed and comparisons have been made between measured and simulated time series. The link between simulation and experiment is a wave model which is based on a wave height measurement signal. It is developed and evaluated in the thesis. The conclusions are in favor of the 2-dimensional approach to modeling the conditions for the planing hull in waves and among further studies is evaluation of simulated loads and motions to full-scale trial measurement data.

The primary objective of the presented research is to develop a class of integrated compact silicon diffractive sensors (CSDS) based on in-plane diffraction gratings. This class of sensors uses a silicon-on-insulator (SOI) substrate to limit costs, exploit established fabrication processes, enable integration of supporting electronics, and use the well-understood telecommunications wavelength of 1.55µm. Sensing is achieved by combining constant-diffraction-efficiency and highly-angularly-selective in-plane resonance-domain diffraction gratings. Detection is based on the diffraction efficiency of the highly angularly selective grating. In this research, the design processes for the constant-diffraction-efficiency and the highly angularly selective gratings are detailed. Grating designs are optimized with rigorous coupled-wave analysis (RCWA) and simulated with finite-difference time-domain (FDTD) analysis. Fabrication results are presented for the CSDS gratings. An inductively coupled plasma (ICP) Bosch etch process enables grating fabrication to within one percent of designed values with nearly vertical sidewalls. Experimental results are presented for individual CSDS gratings, the prototype sensor, and a prototype linear sensor array. The results agree well with simulation. The linear sensor array prototype demonstrates the intrinsic splitting mechanism and forms the basis of a 2-D sensor array. Finally, a toluene sensor was functionally demonstrated. The proof-of-concept device includes a polymer immobilization layer and microfluidic delivery of toluene. Toluene concentrations as low as 100ppm are measured, corresponding to a refractive index change of 3x10⁻⁴ RIU.

Small open-deck roll-on/roll-off passenger ferries in Indonesia have a poor safety record. The Indonesian Government is interested in means by which the safety of these vessels can be improved, and this was the main catalyst for commencing research in this area. Any solution should be capable of being retrofitted to both existing vessels and new designs to improve their stability and, hence, their safety. The research therefore focused on the intact stability of the bare hulls, and with addition of side casings, for the vessels for which data was made available by the Indonesian Government. The research covered both quasi-static analysis, based on the objective of meeting the IMO intact stability criteria, and a dynamic approach using time-domain simulation in regular beam waves. A parametric study of the stability parameters of the twenty vessels demonstrated that, without the presence of side casings, the vessels had difficulties in complying with the IMO intact stability criteria. The problems were solved by introducing side casings (watertight spaces above the vehicle deck) either inboard of the vessel’s side-shell plating, or partially inboard and partially outboard of the side shell. The minimum extent (breadth) of side casings required was determined by iteration on each of the twenty vessels, incorporating variations in the height of the centre of gravity and loading conditions. The implementation of the minimum side casings showed that each vessel then met the IMO intact stability criteria. However, the assessment of the vessels’ dynamic stability characteristics using time-domain simulation provided inconsistent results for these vessels with side casings which met the IMO intact stability criteria. For some particular conditions, the existence and the different forms of side casings could decrease vessel survivability by increasing the roll motion amplitudes for both inside and outside casings and could lead the vessel to capsize. The results of the dynamic stability analysis also confirmed the vulnerability of small vessels with small stability parameters to large waves, and the different roll seakeeping behavior of the different vessel stability parameters.

Small open-deck roll-on/roll-off passenger ferries in Indonesia have a poor safety record. The Indonesian Government is interested in means by which the safety of these vessels can be improved, and this was the main catalyst for commencing research in this area. Any solution should be capable of being retrofitted to both existing vessels and new designs to improve their stability and, hence, their safety. The research therefore focused on the intact stability of the bare hulls, and with addition of side casings, for the vessels for which data was made available by the Indonesian Government. The research covered both quasi-static analysis, based on the objective of meeting the IMO intact stability criteria, and a dynamic approach using time-domain simulation in regular beam waves. A parametric study of the stability parameters of the twenty vessels demonstrated that, without the presence of side casings, the vessels had difficulties in complying with the IMO intact stability criteria. The problems were solved by introducing side casings (watertight spaces above the vehicle deck) either inboard of the vessel’s side-shell plating, or partially inboard and partially outboard of the side shell. The minimum extent (breadth) of side casings required was determined by iteration on each of the twenty vessels, incorporating variations in the height of the centre of gravity and loading conditions. The implementation of the minimum side casings showed that each vessel then met the IMO intact stability criteria. However, the assessment of the vessels’ dynamic stability characteristics using time-domain simulation provided inconsistent results for these vessels with side casings which met the IMO intact stability criteria. For some particular conditions, the existence and the different forms of side casings could decrease vessel survivability by increasing the roll motion amplitudes for both inside and outside casings and could lead the vessel to capsize. The results of the dynamic stability analysis also confirmed the vulnerability of small vessels with small stability parameters to large waves, and the different roll seakeeping behavior of the different vessel stability parameters.

As a comparative study, the global performance of two cases for a floating harbor system are researched by numerical analysis and compared with results from experiments: one is a two-body case such that a floating quay is placed next to a fixed quay, a normal harbor, and the other is a three-body case such that a container ship is posed in the middle of the floating quay and the fixed quay. The numerical modeling is built based on the experimental cases. Mooring system used in the experiments is simplified to sets of linear springs, and gaps between adjacent bodies are remarkably narrow as 1.3m~1.6m with reference to large scales of the floating structures; a water plane of the fixed quay is 480m×160m, and the ship is 15000 TEU (twenty-foot equivalent unit) class. With the experiment-based models, numerical analysis is implemented on two domains: frequency domain using a three dimensional constant panel method, WAMIT, and time domain using a coupled dynamic analysis program of moored floating structures, CHARM3D/HARP. Following general processes of the two main tools, additional two calibrations are implemented if necessary: revision of external stiffness and estimation of damping coefficients. The revision of the external stiffness is conducted to match natural frequency of the simulation with that of the experiment; to find out natural frequencies RAO comparison is used. The next, estimation of damping coefficients is carried out on time domain to match the responses of the simulation with those of the experiment. After optimization of the numerical analysis, a set of experimental results from regular wave tests is compared with RAO on frequency domain, and results from an irregular wave test of the experiment are compared with response histories of simulation on time domain. In addition, fender forces are compared between the simulation and experiment. Based on response histories relative motions of the floating quay and container ship are compared. And the floating harbor system, the three-body case, is compared with a conventional harbor system, a fixed quay on the portside of the container ship, in terms of motions of the container ship. As an additional simulation, the three-body case is investigated on an operating sea state condition. From the present research, the experimental results are well matched with the numerical results obtained from the simulation tools optimized to the experiments. In addition, the floating harbor system show more stable motions of the container ship than the conventional harbor system, and the floating harbor system in the operating sea state condition have motions even smaller enough to operate in term of relative motions between the floating quay and the container ship.

Simuler temporellement les réseaux électriques modernes requiert d'importants moyens de calcul de par la dimension et la raideur des systèmes différentiels algébriques résultants. De plus, la fréquence d'oscillation de certains signaux simulés contraint fortement le pas d'intégration des schémas classiques, y compris en régime établi où ils sont proches de sinusoïdes oscillant à la fréquence nominale du système. L'objectif de la méthode des prédicteurs sinusoïdaux proposée dans cette thèse est donc de tirer parti de cette propriété afin d'améliorer les performances du solveur tout en contrôlant l'erreur de calcul. Elle consiste à décomposer la solution en deux parties : une sinusoïde, dont les coefficients de Fourier sont fixés pour chaque intervalle d'intégration puis mis à jour par estimation paramétrique, et un terme de correction sur lequel le système d'EDA est reformulé et résolu à l'aide d'un schéma d'intégration à pas adaptatif. Une attention particulière a été portée au choix de l'estimateur paramétrique, ce dernier ayant un impact direct sur le pas d'intégration de par sa précision et indirect de par son effet sur la stabilité globale de la méthode. L'estimateur finalement développé consiste à calculer les coefficients de Fourier qui minimisent une mesure de la stationnarité du système. Ce dernier étant convergent en régime permanent, le terme de correction est progressivement amorti, permettant ainsi d'accroître considérablement le pas d'intégration. Cette méthode, intégrée au sein du solveur SUNDIALS IDA puis interfacée avec un moteur de calcul industriel, permet d'accélérer très nettement les simulations en comparaison avec une implémentation classique / Modern power systems time-domain simulations require important computational resources due to the resulting differential algebraic systems dimension and stiffness. In addition, some simulated signals oscillation frequency dramatically limits the classical schemes step size, even in steady-state during which they are close to sinusoids oscillating at system nominal frequency. That's why the sinusoidal predictors method proposed in this thesis aims at taking this property into account in order to enhance solver performances while controlling the integration error. It consists in decomposing the solution into two parts: a sinusoid, whose Fourier coefficients are fixed for each time integration interval and then updated by parametric estimation, and a correction term on which the DAE system is rewritten and solved using an adaptive step size integration scheme. A particular focus has been given on the estimator choice, given its precision direct impact on the step size and its indirect effect on the global method stability. The finally developed estimator consists in computing Fourier coefficients minimizing a system stationarity measurement. As it converges in steady-state, the correction term is progressively damped, which enables to considerably increase the step size. This method, integrated into the reference solver SUNDIALS IDA and interfaced with an industrial simulation engine, enables to very significantly accelerate simulations in comparison with a classical implementation