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(This thesis consists of two parts.) Part I Comparison of Traveling Wave and Gain-Clamped Semiconductor Optical Amplifiers. Today's Wavelength Division Multiplexing (WDM) optical networks are getting dynamic light-path reconfigurable and optical transparent. Optical amplification without optoelectronic conversion is a key technology in all-optical networks. semiconductor optical amplifier (SOA) is a very potential device in this field. Besides the linear amplification, the nonlinear features of SOA make it has a broad application in wavelength conversion, tunable wavelength filter, optical switching and optical logic. The simple structure and very compact size of SOA indicate the essential low-cost and compatibility of integration. Resonant cavity is the basic structure of conventional SOAs, while gain-clamped SOAs (GC-SOAs) provide a constant gain which raises a lot of interests in applications. SOA with Distributed Bragg Reflectors (DBR) is one of the structures to realize the clamped gain. In this thesis the performances of traveling wave SOA (TW-SOA) and DBR-SOA are compared through a dynamic model. This model consists of a distributed feedback wave equation, a carrier rate equation and a material gain model, thereby can be used to simulate both of the two SOAs. To balance the time cost of simulation and the accuracy of the result, three important non-physical parameters, simulated bandwidth, cavity discritization and frequency discretizaiton, are investigated. The simulation results show that DBR-SOA has a very stable device gain which is independent on input optical power. From a noise level point of view DBR-SOA and TW-SOA have different characteristics. These comparison is conducted with both large signal input and small signal input. In addition, a desirable application, SOA in a multi-channel WDM system, is also simulated with GC-SOA and TW-SOA. The Bit Error Rate (BER) of TW-SOA increases greatly due to inter-channel cross talk, while the BER of GC-SOA is virtually constant with the variation of WDM channel number. Another application, wavelength converter, shows TW-SOA is very useful in non-linear application. Part II Impact of Dispersion on Hybrid of Frequency-Hopped Optical CDMA and WDMA Networks. A new analytical formula for analysis of the system performance of the Hybrid of Wavelength Division Multiple Access (WDMA) and Code Division Multiple Access (CDMA) is developed and presented. The effects of fiber dispersion and inter-channel crosstalk are considered and their impact on system performance is analyzed in terms of power penalty. Finally, methods to overcome the effects of the fiber dispersion are discussed. / Thesis / Master of Applied Science (MASc)

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The L2 gain of a nonlinear time-dependent system measures the maximal gain in the transfer of energy from admissible input signals to the output signals, in which both the input and output signals are measured with the L2 norm. For general nonlinear systems, obtaining a sharp estimate of the L2 gain is challenging both theoretically and numerically. In this thesis, we explore a computationally efficient way to obtain numerical estimations of L2 gains for systems with quadratic nonlinearity. The approach utilizes a recently developed method that solves a class of Hamilton-Jacobi-Bellman equations via a Taylor series-based approximation, which is scalable to high-dimensional problems given the utilization of linear tensor systems. The ideas are demonstrated through a few concrete examples that include a one-dimensional problem with an explicit energy function and several Galerkin approximations of the viscous Burgers equation. / Master of Science / With nonlinear systems that are of the form of input-output models, questions often arise as to how to measure the energy that passes through such systems and determine strategies to look for specific signals that allow the designer freedom to explore certain system behaviors. The energy comes in the form of a signal. For general nonlinear systems, obtaining a sharp estimate of such energy gain is challenging both theoretically and numerically. In this thesis, we explore a computationally efficient way to obtain numerical estimations of these gains for systems with quadratic nonlinearity. The approach combines fundamental theoretical understandings established in the literature with scalable software recently developed in approximating the solution of the underlying partial differential equation, called the Hamilton-Jacobi-Bellman (HJB) equation. In this approach, the energy gain is linked to a single scalar parameter in the HJB equation. Roughly speaking, the energy gain is the lower bound of this scalar parameter above which the HJB equation always admits a non-negative solution. Thus, it boils down to approximating the HJB solution using the software while changing this scalar parameter. We will present the theoretical foundation of the approach and illustrate the foundation through several academic examples ranging from low to relatively high dimensions.

Rationale: Published studies have shown that immigrants undergo dietary acculturation which may have positive or negative impact on their health. Therefore, a study was conducted to investigate this critical issue of dietary acculturation and any possible influence on the health status of newly arrived international students at Virginia Tech in Fall 2010. Design: In this study weight, fasting blood glucose and blood pressure of 35 international students (age 18-36 years) were determined at three time points, 5-6 weeks apart. Participants filled out a 20-item-questionnaire addressing alteration in the native and American dietary habits. Furthermore, 24 hrs dietary recalls and frequency of consuming the most popular food items in the US was assessed. Results: Total sample population (TSP) had a significant increase in average weight by 2.79 lbs from visit 1 (V1) to visit 3 (V3) (p=0.0082), Participants who gained weight (PGW; n=10) had an average increase by 9 lbs. Country wise, Chinese had a statistically significant average increase in their weights by 4.16 lbs (p=0.0077) whereas, Indians and Germans had an average increase by 2.36 lbs and 1.28 lbs respectively. Gender wise, the average increase in weight for females was 3.99 lbs (p=0.0015) while for males 1.52 lbs from V1 to V3. There were no significant differences in total caloric consumption from V1 to V3 for both groups of international students. There were no significant changes in the fasting blood glucose and systolic blood pressure from V1 to V3. There was an increase in frequency of consuming high calorie American food items in V3 when compared with V1. Frequency of burger consumption was highly increased in the TSP group while bagels were significantly increased in PGW group. There was an overall increasing trend towards American diet, cooking and eating habits. Finally, we conclude that the international students are gradually acculturating to the American diet and have impact on their weight which may potentially have a negative impact on their health status. Future studies and orientation program catered to the needs of adjusting to acculturation process of international students are recommended. / Master of Science

Nitrogen excreted by ruminants may negatively impact the environment, and N not retained is not utilized for growth and production. Experiments were conducted to examine the effect of 48 h oscillation of two levels of low ruminally degradable dietary CP on N metabolism in lambs and performance of steers. In Exp. 1, a metabolism trial was conducted with 28 lambs (31 kg), allotted to four different diets: 8% CP, 10% CP, 12% CP, and 8% and 12% CP diets oscillated every 48 h. After adaptation, transition, and preliminary periods, feces and urine were collected for 10 d. Ruminal fluid and blood samples were taken at the end of collection and again 2 d later. In Exp. 2, 24 crossbred steers (228 kg) were allotted to four diets: 1) 7.5% CP, 2) 9% CP, 3) 10.5% CP, and 4) 7.5% and 10.5% CP diets oscillated every 48 h. Feed intake was measured during the 112 d study, and ADG and gain to feed ratio were calculated. Cattle were weighed every 14 d and blood samples were taken every 28 d. In Exp. 1, N retention was lowest (P < 0.05) for the lambs fed the 8% CP diet, with no differences among lambs fed the other diets. Differences in urinary N excretion accounted for most of the differences in total N excretion. Ruminal NH3-N and BUN levels were greater in animals fed higher amounts of CP. Ruminal pH and VFA concentrations were not affected by diet. In Exp. 2, feed intake did not differ among steers fed different diets. Average daily gain was lowest for cattle fed the 7.5% CP diet. No significant difference was evident for ADG between steers fed the 7.5/10.5% CP oscillating diet and those fed the 9% or the 10.5% CP diet. Gain to feed ratio was lower (P < 0.05) for steers fed the 7.5% CP diet compared to steers fed all other diets. Blood urea N level was higher for cattle fed the 10.5% CP diet than those fed the two lower CP levels, and differences were usually significant (P < 0.05). No consistent significant difference in BUN levels existed between steers fed the 7.5/10.5% CP oscillating diet and those fed the 9% and 10.5% CP diets continuously. Oscillating two levels of low ruminally degradable dietary CP every 48 h had no significant effect on N retention in lambs nor on the performance of steers compared to animals fed the same level of CP daily in these experiments. / Master of Science

The effects of a monetary reward and self-monitoring on reducing interdialytic weight gain (IWG) were compared for 6 hemodialysis patients in an outpatient setting. A single-subject experimental design (A-B-BC-B-BC) was used to examine each variable individually and in combination, with alternating phases to control for possible sequencing effects. Monetary reward (50 cents - $3) was administered in a titrated manner according to standardized criteria, ranging from 3 % and 4% of patients' dry weight on weekdays and weekends, respectively, to 3.5% and 4.5% for weekdays and weekends. Self-monitoring involved recording daily fluid and diet intake. Results indicated that by the end of the treatment program, the 6 participants averaged a 14% reduction in weekday IWG and a 15.45% reduction in weekend IWG; however, due to significant variability, it cannot be concluded that the reductions are treatment effects. Four out of 6 participants reduced their average IWG for both weekends and weekdays by .75 kg (1.65 lb.). The average weekend reduction for these 4 participants was .85 kg (1.87 lbs.) while the average weekday reduction was .65 kg (1.43 lb.). All 6 participants showed reductions in weekday IWG that averaged .53 kg (1.17 lb.). However, only 2 participants demonstrated IWG reductions that could be attributable to either of the 2 treatment variables. The standardized dry weight criterion for assessing fluid adherence may have posed excessively stringent demands on participants, as only 1 of the 6 participants actually met the criterion. Future research should address the role of nonspecific treatment factors, as well as patient characteristics and responsivity to particular treatment components in an effort to identify those factors responsible for behavior change in this population.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Cette thèse présente un nouveau cadre pour la conception de correcteurs à gain programmé. Une partie de ce cadre est une fusion novatrice de la théorie des systèmes et de la commande (la métrique ν-gap et sa variante fréquentiellle) et de l'analyse en grappes, technique commune en analyse de données statistiques, apprentissage automatique, fouille de données, etc. La combinaison des deux champs permet de subdiviser le domaine de fonctionnement d'un système non linéaire en secteurs afin de récupérer des informations sur le comportement en boucle fermée avant la conception de la commande. Chaque secteur représente une partie du domaine opérationnel ayant des propriétés de retour similaires, c'est-à-dire que les points de fonctionnement dans un secteur ont des comportements davantage similaires (mesurés par la mesure d'écart ponctuel) les uns des autres que les points de fonctionnement des autres secteurs. La solution de sectorisation est utilisée en vue de réaliser des correcteurs séquencés réglés à partir d'un modèle linéarisé. Par exemple, une distribution optimisée et parcimonieuse des points de synthèse pour les correcteurs LTI est sélectionnée et la distribution des secteurs est exploitée pour le mélange des correcteurs linéaires individuels en un correcteur non-linéaire couvrant l'ensemble du domaine de fonctionnement. L'avantage général de ce cadre est qu'il présente une procédure systématique qui réduit potentiellement le temps, les efforts et donc le coût global d'un projet de développement en réduisant les itérations inutiles au cours du cycle de conception. Le cadre proposé est évalué à partir d’un exemple générique de missile industriel. / This thesis presents a new framework for the design of gain-scheduled controllers. Part of this framework is a novel merging of system & control theory (the ν-gap and pointwise gap metric) and cluster analysis, a common technique in statistical data analysis, machine learning, data mining, etc. The combination of both fields allows for a subdivision of a nonlinear system's operating domain into sectors in order to retrieve information on the feedback behaviour before the actual control design. Each sector represents a part of the operating domain with similar feedback properties, i.e. operating points inside a sector are more similar (as measured by the pointwise gap metric) to each other than to operating points in other sectors. The sectoring solution is used in the proposed framework to support the design of a linearization-based gain-scheduled controller. For example, a reduced and optimized distribution of design points for the LTI controllers is selected and the sectors' distribution is exploited for the blending of the individual linear controllers into an operating domain wide nonlinear controller. The overall advantage of the framework is that it presents a systematic procedure that potentially reduces the overall time, effort, and therefore cost of a development project by preventing unnecessary iterations in the design cycle specifically associated with the control design. The proposed framework is verified at the example of a generic industrial missile benchmark.

Dans ce travail de thèse, nous avons étudié différentes approches qui devraient permettre d’obtenir l’effet laser dans le germanium. Nous avons pu montrer expérimentalement l’influence du dopage et de la déformation sur la structure de bande du germanium, et l’adéquation avec les modèles concluants à l’existence de gain. Nous avons exploré les possibilités offertes par l’hétéro-épitaxie sur III-V pour obtenir une déformation en tension du germanium. Nous avons évalué la déformation résultante par des mesures croisées de rayons X, de diffusion Raman et de photoluminescence, et étudié l’évolution de la qualité des couches épitaxiées en fonction de la déformation et de l’épaisseur. Une nouvelle méthode de déformation du germanium, s’appuyant sur le dépôt par plasma de couches contraintes de nitrure, a été introduite et étudiée. L’effet laser a été recherché par la conception de guides ridges et microdisques déformés par ces dépôts. Plusieurs voies d’application de la déformation dans ces cavités ont été explorées à travers des simulations par éléments finis et la conception de structures de test. Cette optimisation préalable nous a permis d’observer sur les microdisques une déformation biaxiale de 1.11%. En uniaxial, nous avons pu appliquer au germanium une déformation de 1.07% et montrer expérimentalement l’importance de la direction de la déformation dans l’augmentation de la luminescence. Nous avons pu observer et mesurer un gain optique net de 80 cm⁻¹ dans des structures déformées uniaxialement à 0.8%. / In this PhD work, we studied different approaches that should lead to a germanium laser. We have experimentally shown the influence of strain and doping on the germanium band structure, and the adequacy of the existing models. We explored the possibilities offered by heteroepitaxy on III-V compounds to apply stress. We investigated the resulting strain by cross-checking X-rays, Raman spectroscopy and photoluminescence measurements, and analysed the quality of the grown layers depending on strain and thickness. A new method to apply strain to the germanium, by means of plasma deposited stressed nitride layers, was introduced and studied. Lasing has been pursued by conceiving ridges and microdisks strained by this method. An optimization of the geometry was performed through finite element modeling and the production of test structures. This optimization allowed to achieve a maximum biaxial strain of 1.1%. For uniaxial strains, we observed a maximum of 1.07% and showed experimentally the importance of the crystalline orientation in the enhancement of the emission. We demonstrated a modal gain value of 80 cm⁻¹ in ridges uniaxially strained at 0.8%.