Theses

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  • Subspace predictive control: stability and performance enhancement
    Subspace predictive control: stability and performance enhancement
    In the absence of prior knowledge of a system, control design relies heavily on the system identifi- cation procedure. In real applications, there is an increasing demand to combine the usually time consuming system identification and modeling step with the control design procedure. Motivated by this demand, data-driven control approaches attempt to use the input-output data to design the controller directly. Subspace Predictive Control (SPC) is one popular example of these algorithms that combines Model Predictive Control (MPC) and Subspace Identification Methods (SIM). SPC instability and performance deterioration in closed-loop implementations are majorly caused by either poor tuning of SPC horizons or changes in the dynamics of the system. Stability and performance analysis of the SPC are the focus of this dissertation. We first provide the necessary and sufficient condition for SPC closed-loop stability. The results introduce SPC stability graphs that can provide the feasible prediction horizon range. Consequently, these stability constraints are included in SPC cost function optimization to provide a new method for determining the SPC horizons. The novel SPC horizon selection enhances the closed-loop performance effectively. Note that time-delay estimation and order selection in system modeling have been a challenging step in applications and industry. Here, we propose a new approach denoted by RE-based TDE that simultaneously and fficiently estimates the time-delay for the SIM framework. In addition, we use the recently developed MSEE approach for estimating the system order. Moreover, we propose an arti- ficial intelligence approach denoted by Particle Swarm Optimization Based Fuzzy Gain-Scheduled SPC (PSO-based FGS-SPC). The method overcomes the issue of on-line adaptation of SPC gains for systems with variable dynamics in the presence of the noisy data. The approach eliminates existing tuning problem of controller gain ranges in FGS and updates the SPC gains with no need to apply any external persistently excitation signals. As a result, PSO-based FGS-SPC provides a time efficient control strategy with fast and robust tracking performance compared to conventional and state of the art methods.
    Substrate Dependent Regulation of the Human Equilibrative Nucleoside Transporter 1 (hENT1) in HEK293 Cells
    Substrate Dependent Regulation of the Human Equilibrative Nucleoside Transporter 1 (hENT1) in HEK293 Cells
    Nucleosides and nucleoside analog drugs enter cells through nucleoside transporters, such as the human equilibrative nucleoside transporter 1 (hENT1). The regulation of nucleoside transporters is poorly understood. In this study, through fluorescence-activated cell sorting (FACS) analyses, confocal microscopy and radio-ligand binding assays, I show a decrease in hENT1 abundance at the plasma membrane (PM) in HEK cells treated in the presence of a bolus amount of cytidine (40μM) for 6 hours. Kinetic and transport assays indicate that the remaining hENT1 population at the PM has a higher Vmax and Km but there is no change in overall substrate uptake compared to untreated cells. I also show that cytidine pre-treatment leads to an increased cytotoxicity from gemcitabine (a nucleoside analog drug). These are the first data that show direct substrate dependent regulation of a nucleoside transporter by a mechanism that may involve increased recycling/internalization of the transporter.
    Subthreshold Frequency Synthesis For Implantable Medical Devices
    Subthreshold Frequency Synthesis For Implantable Medical Devices
    In this thesis, several novel circuits for use in an ultra-low power integer-n frequency synthesizer operating in the 402 MHz to 405 MHz Medical Implant Communication Service spectrum have been proposed. The proposed designs include a current-reuse quadrature voltage-controlled oscillator, a novel subthreshold source-coupled logic D-latch with clear and preset functionality, a programmable frequency divider and phase/frequency detector based on the aforementioned D-latch, and a modified current-steering charge pump. A design methodology for low-power CMOS oscillators was proposed based on the MOS EKV model and gm/id design methodology. The proposed designs were implemented using IBM CMRF8SF 130 nm CMOS technology and simulated using Cadence Spectre. Simulation results for the proposed current-reuse quadrature voltage-controlled oscillator and programmable frequency divider consume 420 μW and 200 μW respectively from 0.7 V supply, a significant improvement compared to existing designs. The simulated phase noise of the proposed oscillator is -127.2 dBc/Hz at a 1 MHz offset. Measurement results from a fabricated prototype of the current-reuse quadrature verify the simulation results and serve as a proof-of-concept for the proposed design. The proposed designs were used to implement an integer-n frequency synthesizer and were submitted for fabrication. Simulation results show that the synthesizer consumes 635 μW from a 0.7 V supply and has a locking time of 250 μs.
    Suburban / urban grafting: towards an architectural and urban hybrid
    Suburban / urban grafting: towards an architectural and urban hybrid
    Land is a finite resource which does not support the low density suburban model on a large scale. The alternative, the urban condition, does not satisfy the needs of families. The goal is to define a middle ground, to create a hybrid, by taking the best qualities of the suburbs and urb to develop a new vision for the city. Is it possible to combine the typological characteristics and spatial qualities of the suburbs in an urban format where the disadvantages of the suburbs are mitigated by the multiplicity of urbanity? For the purpose of this thesis the design proposal is tested on Ijburg, Amsterdam, the Netherlands. The resultant hybrid is manifested through the mixing of different housing typologies both suburban and urban in conjunction with and elevated street which provides private access to individual units and public access to recreational and leisure facilities.
    Succession of the image
    Succession of the image
    As technology evolves and spheres of information dissemination begin to converge, now is a crucial point to become critical with how these factors are beginning to influence architecture. It is important to understand the ways in which we consume architecture is affecting the architecture we produce. Is architecture a handful of money-shot renderings creating idealised moments captioned with generic copy and paste, or buried in books on shelves? Or have we as architects decided that mechanical reproduction is unable to capture the essence of architecture and that it can only be experienced? The succession of the image is the challenging of conventional methods of communication utilized by the architectural artifact. In focusing on the possibilities afforded via technological advances emerges a variety of mediums for the creation of spatial narratives. The image has progressed and disseminated architecture to this point and it is important to continuously ask what is next.
    Supersonic Windtunnel Noise Attenuation
    Supersonic Windtunnel Noise Attenuation
    The aerodynamic generated noise in the supersonic wind tunnel during operation at Ryerson University has exceeded the threshold of hearing damage. An acoustic silencer was to be designed and added to the wind tunnel to reduce the noise level.The main sources of noise generated from the wind tunnel with the silencer were identified to be located at the convergent divergent nozzle and the turbulent region downstream of the shock wave at the diffuser with the maximum acoustic power level of the entire wind tunnel at 161.09 dB. The designed silencer provided an overall sound pressure level reduction of 21.41 db which was considered as acceptable.Refinement to the mesh size and changes to the geometry of the mixing chamber was suggested for a more accurate result in noise output as well as flow conditions would match up to the physical flow. Additional acoustic treatment should be applied to the wind tunnel to further reduce sound pressure level since the noise level still exceeded the threshold of hearing loss.
    Supply chain coordination with trade credit and price discount with/without environmental considerations
    Supply chain coordination with trade credit and price discount with/without environmental considerations
    For a supply chain coordination to be effective and profitable, it requires a working mechanism among its members to entice some players to join a partnership. Two of the well-known trade credits that are widely used by businesses are the permissible delay in payments and price discounts. This thesis presents models for coordinating supply chains with both trade credits. The first model investigates the effect of utilizing delay in payments in a two-level (manufacturer-retailer) supply chain. It modifies and analyzes three known models of different production and shipping policies to account for delays in payments; it then compares them and highlights the production policy that performed the best with the total system cost being the performance measure. The second model analyzes the coordination of a three-level (supplier-manufacturer- retailer) supply chain with the delay in payments. It analyzes nine different scenarios of permissible delay among the three players. A simulation study was performed and a thorough analysis of the results was used to identify the limitations of all scenarios and to draw some managerial insights and findings. The third model investigates the effect of coupling permissible delay in payments and price discounts for coordinating a three-level. The analysis considers nine different cases of delay-in-payments along with eight cases of price discounts among the three players in the supply chain, totaling seventy-two cases. The numerical examples and the sensitivity analyses show that the coupling of delay-in- payments and price discounts maximizes the supply chain profit more than when using a single mechanism at a time. The fourth model investigates a two-level supply chain by studying the effects of various scenarios for delay-in-payments when including some environmental costs such as fuel and emissions from manufacturing and transportation. The objective of the model is to optimize the environmental and the economic performance of the supply chain. The results show that delay-in-payments improves the economic and the environmental performance of a supply chain.
    Supply chain models with consignment stock agreement, payment schemes and delay-in-payments
    Supply chain models with consignment stock agreement, payment schemes and delay-in-payments
    Supply chain management (SCM) has shown to be a successful strategy to manage the flow of goods, materials, information and services between multiple entities in one organization or multiple businesses working together to provide final customers with final products or services with the objective of improving and enhancing the performance of the chain and maximizing its profit. Inventory management (IM) is one element of the SCM that has shown researchers’ interests as it plays a major role in increasing supply chain profits and satisfying customers. Different coordination mechanisms have been developed to improve the collaboration and the integration of supply chain players. Consignment stock (CS) is one of the coordination mechanisms that is extensively studied by researchers to reflect its benefits, drawbacks, and the proper techniques of implementing it between two or more players in the chain. The studies of the CS still have some gaps that can be covered by researchers such as studying its effect in a three-level supply chain or when a delay-in-payment exists. Optimizing the number of payments or studying a three-level supply chain system with multiple suppliers and multiple buyers has not been developed. This thesis covers these gaps and considers different scenarios where a CS, a traditional policy (TP) or a combination between both of them might exist in case a system consists of three players. The main findings are optimizing the number of payments and incorporating a delay-in-payment increase the profit of the chain. In addition, a combination of a TP between the upstream players and a CS between the downstream players has shown to be better than adopting the same policy between all players. Some results of adopting a CS by all players have shown to be very close to the best scenario which could be the best option when demands highly fluctuate.
    Support vector machines for environmental informatics : application to biological nitrogen removal in wastewater treatment plants
    Support vector machines for environmental informatics : application to biological nitrogen removal in wastewater treatment plants
    In order to meet the more stringent environmental regulations, the adaptive and optimal control strategies should be investigated for the biological nitrogen removal (BNR) processes in wastewater treatment plants. Because of the complex nature of the microbial metabolism involved, the conventional mechanistic models for nitrogen removal are difficult to formulate and the existing ones are still uncertain to some extent. Alternatively, the machine learning methods have been investigated as black-box modelling techniques. A new approach, Support Vector Machine (SVM) was proposed to be used to model the biological nitrogen removal processes in this thesis. Specifically, LS-SVM, a simplified formulation of SVM, was applied to predict the concentration of nitrate & nitrite (NO). The simulation results indicate that the proposed method has better generalization performance in comparison with generalized regression neural network, especially under weather conditions that are quite different from the training weather conditions.
    Supportive Housing For Those Dealing With Mental Health And Addiction Issues In Toronto : An Interview Study To Consider System Level Characeristics and Service Planning Issues
    Supportive Housing For Those Dealing With Mental Health And Addiction Issues In Toronto : An Interview Study To Consider System Level Characeristics and Service Planning Issues
    This paper reports on an interview study that was conducted by the author with executive directors representing 10 agencies in Toronto which provide supportive housing for those dealing with mental health and/or addiction issues. It provides a review of the literature and evidence with respect to such housing, and describes its origin, evolution and general characteristic in Toronto. It then focuses on discussing themes identified over the course of the interviews, in relation to overall system planning...and lack thereof. Alongside of expected but important themes, such as the desperate shortage of housing stock, a number of more subtle trends are uncovered. For example, the increasing imposition of concepts and practices from the hospital and private data management sectors, are proving troublesome for some supportive housing providers as they threaten their community and client centered values, beliefs, principles and practices.
    Supramolecular Bodipy Dye Architectures for Advanced Light Harvesting and Energy Transfer Applications
    Supramolecular Bodipy Dye Architectures for Advanced Light Harvesting and Energy Transfer Applications
    Shape-persistent phenylacetylene macrocycles have been explored in a number of optoelectronic and light-harvesting applications, including two-photon absorption. Likewise, BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes) dyes have also been extensively used in material applications, owing to their tunable, intense absorption and sharp emission spectra exhibiting high quantum yields. Combining these two architectures, this thesis presents a derivative where a BODIPY is contained orthogonally within the phenylacetylene-macrocycle. This structure was inspired by photosystem II antennae complexes where energy is obsorbed by antennae complexes and funneled down to a reaction centre. Specifically, this family of molecules uses the phenylacetylene macrocycle to harvest the light and transfer it to the BODIPY core, and this has been observed by examining the fluorescence emission from the BODIPY (Figure 1). This novel dye design if coupled to a donor (D) and acceptor (A) capable of anchoring to TiO2 could be modified to become a π-spacer (i.e. D-π-A motif) for dye-sensitized solar cells resulting in panchromatic absorption, and ultimately more efficient devices.
    Surface Modification of Polyethylene Film by Catalytic Ozonation
    Surface Modification of Polyethylene Film by Catalytic Ozonation
    The hydrophobicity of polymer surfaces limits their applications in many areas such as for use as biomaterials and in membrane filtration. One solution to this problem is to modify the polymer surface by ozonation. Ozonation introduces peroxide groups on polymer surface, which can initiate graft polymerization of monomers with hydrophilic groups, and thus improves the hydrophilicity of the polymer surfaces. The concentration of peroxide groups formed can be used to indicate the effectiveness of ozonation process. In this study, the low cost polyethylene film was selected as a model polymer film to conduct the investigation. Ozonation treatment was carried out in both gaseous and aqueous phases, to study the contribution of hydroxyl radical in the generation of peroxide group. Results revealed that aqueous ozonation generated slightly less peroxide than gaseous ozonation. However, the addition of soluble catalyst, copper (II) sulfate, to the aqueous ozonation resulted in 18% more peroxide concentration than that yielded by gaseous ozonation. Further investigation indicated that 0.05 g/L copper (II) sulfate was the optimal catalyst dose, and the optimal pH was approximately 5.60. A 19% reduction in tensile strength of the film was observed after 120 minutes of catalytic ozonation. Upon addition of a radical scavenger, tert-butyl alcohol (TBA), a decrease of 12% in the peroxide concentration was observed for catalytic ozonation with 0.1 mol/L TBA. This decrease indicated that both ozone and hydroxyl radical contributed to the peroxide generation in catalytic ozonation. A reaction mechanism for aqueous ozonation of polyethylene was proposed in this study by combining the reaction mechanism for gaseous ozonation of polyethylene and the decomposition mechanism of ozone in water. The experimental data found in this study verified the exponential function obtained for peroxide concentration. This verification was obtained for various ozonation time and dose ranging from 15 – 120 minutes and 1.0 – 3.0 wt%, respectively.