identifier: Saint-Martin, Anna  (2021) How do Mothers Encourage Their Children to Take Responsibility for Protecting Themselves in Conversations about Being Harmed by a Peer? Exploring Links to Psychosocial Outcomes.  Masters thesis, Concordia University.

abstract:
The goal of this study was to explore the ways in which mothers discuss their children’s responsibility for protecting themselves in situations when they are harmed by the words or actions of a peer. Specifically, this study addressed the following research questions: 1. What are the descriptive features of mothers’ statements regarding their children’s responsibility for self-protection in the context of conversations about peer conflict? 2. Are these descriptive features differentially related to various negative psychosocial outcomes (guilt and shame proneness, self-blaming tendencies, and depressive symptomology)? The study was based on a sample of 105 mother-child dyads, divided into three groups based on the child’s age (i.e., 6-7, 10-11, 15-16). Each dyad discussed two peer conflict experiences nominated by the child. Mothers’ statements about children’s responsibility for protecting themselves from harm were coded along several dimensions; specifically, with respect to tone/evaluation, as well as types of attributions, time orientations, mindsets, and coping strategies. All of these dimensions were theorized to be differentially related to psychosocial outcomes based on the literature. Children also completed a series of psychosocial measures (guilt- and shame-proneness, self-blaming tendencies, depressive symptomology). Results indicated that overall, mothers tended to employ strategies, which are considered more adaptive for children, but that mothers’ self-protective statements were not differentially related to psychosocial outcomes in children. These findings shed light on the socialization processes related to children’s responsibility for self-protection used by mothers in the context of conversations about harm.
Keywords: mother-child relationships, conversation, peer conflict, psychosocial outcomes, responsibility, self-blame


identifier: Arora, Parteek  (2021) Stress Analysis of Rotating Annular Uniform-Thickness and Thickness-Tapered Discs made of Orthotropic and Laminated Composite Materials.  Masters thesis, Concordia University.

type: Thesis NonPeerReviewed

abstract:
Favorable mechanical properties such as high strength-to-weight ratio, high stiffness-to-weight ratio, low specific weight and high fatigue strength, and stiffness tailoring capabilities have enabled the use of composite materials in turbomachinery, automotive and aviation industries. Recent developments on the applications to rotating tapered structures such as thickness-tapered flywheels and rotors in gas turbines and airplane engines have shown increasing use of continuous fiber-reinforced composite materials. Rotating annular thickness-tapered discs made of orthotropic and fiber-reinforced composite materials have preferential stress state as compared to the uniform-thickness discs made of isotropic materials rotating at the same speed. Therefore, due to their distinct characteristics from uniform-thickness discs and wide range of applications, the design of thickness-tapered rotating discs requires comprehensive research to understand their elastic behavior under different loading and boundary conditions.
In the present work, the in-plane stress and displacement analyses of rotating annular uniform-thickness and thickness-tapered discs made of orthotropic and fiber-reinforced composite materials are conducted considering different boundary conditions. A computational solution based on the Rayleigh-Ritz method with finite-element-like modification is developed to evaluate the elastic response of rotating annular thickness-tapered discs made of orthotropic materials. Linear taper and Stodola taper profiles are considered in the elastic analysis of thickness-tapered orthotropic discs with the free-free and the clamped-free boundary conditions. The accuracy of the developed formulation for the elastic response of thickness-tapered orthotropic discs is established based on the convergence of the results obtained for the elastic response using the sub-domain-wise application of Rayleigh-Ritz method in terms of the number of divisions of the thickness-tapered disc, to the results obtained using closed-form analytical solutions available in the literature. For rotating annular uniform-thickness and thickness-tapered fiber-reinforced composite discs with the clamped-free boundary condition, the Rayleigh-Ritz method in conjunction with the Classical Laminate Theory in cylindrical coordinate system is used to evaluate the elastic response. The finite element analysis tool ANSYS is used to model the various three-dimensional internal taper configurations of rotating annular thickness-tapered fiber-reinforced composite discs. The results obtained for the elastic response of uniform-thickness and thickness-tapered fiber-reinforced composite discs using the SOLID185 and SHELL181 elements in ANSYS® are used to verify the results obtained for the same using the Rayleigh-Ritz method based on the Classical Laminate Theory in cylindrical coordinate system. Numerical and symbolic calculations to solve the boundary value problem using the Rayleigh-Ritz method are performed using the technical computing language MATLAB®. The effects of degree of orthotropy, taper profile and taper parameter values on the in-plane stress distributions and radial displacement distribution in the rotating annular thickness-tapered discs made of orthotropic materials are observed for the free-free and clamped-free boundary conditions through extensive parametric studies. The influences of fiber orientation, radius ratio, rotational velocity, laminate configuration, ply reduction and internal taper configuration on the elastic response of rotating annular thickness-tapered fiber-reinforced composite discs are thoroughly examined considering the clamped-free boundary condition. For the parametric studies, a wide range of orthotropic materials are chosen and also, the NCT-301 graphite-epoxy prepreg is chosen as a fiber-reinforced composite material. Important design aspects are systematically brought out.


identifier: Lu, Lingfeng  (2021) An Exposition of Discrete Morse Theory and Applications.  Masters thesis, Concordia University.

abstract: The classical Morse theory is a powerful tool to study topological properties of a smooth manifold by examining critical points of some differentiable functions on that manifold. Robin Forman developed a discrete variant of Morse theory by adapting it on abstract simplicial complexes that resulted in a new theory with wide applications in other fields of mathematics, computer science, data science, and others. In this thesis, we present Forman’s construction of discrete Morse theory, as well as its main theorems such as the Collapse theorem, discrete Morse inequalities, the theorem for cancelling critical simplices, and some additional topics. We also discuss some applications of discrete Morse theory with a major focus on the concept of persistence in topological data analysis. While many results exist in the literature, we wrote our own proofs, added more details and explanations, and adapted it to our own settings with a strong topological flavor whenever possible.


identifier: Moazzeni, Faridoddin  (2021) Resilient Digital Supply Chain Twins Modelling: Simulation-based Analysis on the COVID-19 Pandemic Outbreak.  Masters thesis, Concordia University.

abstract:
Over the past few years, Supply Chains (SC) have expanded rapidly in terms of dimensions and complexity (e.g., globalization, outsourcing, etc.). Besides, numerous practitioners and researchers proposed models mainly focused on minimizing SC’s total cost. Consequently, the potential financial advantages of reduced stock levels and inventory buffers have made SCs more vulnerable to local and global Low-Frequency High-Impact disruption risks which have long-term destructive effects. For instance, the COVID-19 pandemic outbreak has severely disturbed SCs, especially for essential products, by a sharp increase in demand and raw material supply failure. During this challenging situation, the focus should be shifted from cost minimization to SC’s survival, maximizing demand satisfaction, and minimizing delivery time. Consequently, these emerging issues have put forth the need for greater emphasis to develop resilient supply chains.
This study presents a methodological SC simulation modelling framework that enables visualizing the SC and making quick decisions by SC managers in near real-time to ensure resiliency during the disruption. The solution approach is applied as a case study in Luxxeen Co., a Canadian manufacturer of green disposable products, i.e. Toilet Tissues, which is considered an essential product.
First, we develop SC’s structural and behavioral conceptual model by customizing the SCOR reference model. Afterwards, we translate it to Discrete Event Simulation formalist and implement it using the “Arena simulation software” platform. Next, we design three COVID-19 pandemic outbreak disruption scenarios in suppliers, transportation networks, and retailers. Finally, three risk mitigation strategies (i.e., Multiple Sourcing, Changing Inventory Control Policy and Buffering) are suggested to ensure SC resiliency in terms of reliability and responsiveness performance metrics. Moreover, by conducting a comparison analysis using “Process Analyzer” and “Optquest” between these scenarios, the best set of actions are proposed for each disruption scenario.


identifier: Golchin, Elena  (2021) Fleet Management and Energy Management of Shared Autonomous Electric Vehicles.  Masters thesis, Concordia University.

abstract: Nowadays, many cities are supplied with one or several fleets of shared vehicles as an alternative method for daily transportation. These fleets could be improved in many aspects if they employ autonomous or electric autonomous vehicles. Zero greenhouse gas (GHG) emission, fewer personnel requirements, automatic self-charge evaluation and process, and smooth driving are some of these improvements. This essay models a fleet comprised of shared electric autonomous vehicles (SEAV), giving one-way transportation service for short-distance travels. The case study of the area around Montreal Olympic Park is suggested to test the model's validity. In this regard, five stations are introduced on the streets surrounding the park. Different combinations of the fleet parameters are considered to generate 105 various scenarios. A multi-agent model is developed in the NetLog toolkit to simulate such a fleet under each scenario. The results show that a fleet of 20 vehicles of a 50km range with 30 parking spots can meet the demand under all considered customer arrivals frequencies with 90% or above performance rates. Another finding from the results suggests that the impact of different ranges on the fleet's performance compared to the fleet size and demand probability is almost negligible. The last part investigates the number of parking spots on fleet performance. The results suggest that the fewer the number of parking spots, the fewer rejected customers but at the same time, the higher empty travels.


identifier: Trempe, Alexandra  (2021) The Effect of Triplet States on Non-Photochemical Hole Burning in Cytochrome b6f and Modified LH2 Complex.  Masters thesis, Concordia University.

abstract:
The Effect of Triplet States on Non-Photochemical Hole Burning in Cytochrome b6f and Modified LH2 Complex
Alexandra Trempe

Photosynthesis is an extraordinary process responsible for all life on Earth. In better understanding how photosynthetic complexes interact with light, we open up opportunities for advancement in environment research. While at times functionally and structurally similar, it has been shown that oxygenic photosynthetic complexes and anoxygenic photosynthetic complexes in purple bacteria possess differences. For example, oxygenic photosynthetic complexes utilise chlorophyll pigment molecules, which absorb in the red and blue regions of visible light. Purple bacteria host bacteriochlorophyll pigment molecules, absorbing at wavelengths greater than 800 nm. Important information about the functioning of photosynthetic complexes can be obtained from zero-phonon lines and phonon sidebands of the pigments. These can be observed through spectral techniques such as non-photochemical hole burning (NPHB), a type of spectral hole burning. NPHB can be explained using a two-level system, or a double-well potential, which is the simplest manner to describe the protein/pigment energy landscape.

When describing NPHB, the model normally considers both a singlet ground state and a singlet excited state of the pigment. In this thesis, we will explore the limitations of only considering these two electronic state for cytochrome b6f and a modified purple bacteria light-harvesting complex II (LH2) containing chlorophylls. In particular, we originally set out to observe the illumination-intensity dependence (previously seen in cytochrome b6f) in our modified LH2 in an attempt to validate the presence of local heating of the protein by the laser beam causing the NPHB. Unfortunately, we were unable to see local heating. This brought the introduction of a triplet state to explain hole burn depth discrepancies between hole growth kinetic curves and post-burn hole spectra. Our modelling allowed us to see that transient holes caused by triplet states contributed to slower burning of persistent holes with increased intensity, as we had observed. We also examined the case of increased triplet lifetime expected when cytochrome b6f and modified LH2 were placed in a deuterated solvent. An expected triplet lifetime for both complexes in a deuterated solution is around 2 ms, while we examined triplet lifetimes ranging from 1 ms up to 5 ms. Even with a five-fold increase of the simulated triplet lifetime, it did not quite match the experimental difference between protonated and deuterated samples. Likely local heating along with triplet states explain the difference.

Finally, we introduce preliminary data relating to pigment participation in the two-level system. Thermocycling hole recovery results revealed a similar recovery rate for chlorophylls placed in either B800 bacteriochlorophyll pockets or somewhere else in modified LH2. However, in both cases, the holes recovered more quickly than in the regular, bacteriochlorophyll-containing LH2. Given that the two-level system is usually expected to represent the protein environment, chlorophylls in the same location as bacteriochlorophylls were expected to recover similarly. Instead, chlorophylls in different environments recovered similarly, leading to the potential assumption that pigments also contribute to the generalised coordinate of the two-level system.


identifier: Hu, Juqi  (2021) Tire-Road Friction Coefficient Estimation and Control of Autonomous Vehicles.  PhD thesis, Concordia University.

abstract:
This thesis aims to design and develop trajectory planning and tracking strategies integrating with the estimated tire-road friction coefficient (TRFC) so as to enhance the safety and reliability of the autonomous vehicles (AVs) under varying road friction conditions. A two-stage hierarchical framework is firstly developed for estimating TRFC in a computationally efficient manner considering vehicle’s lateral dynamic responses to double (DLC) and single (SLC) lane-change maneuvers.
An alternate two-stage TRFC estimation framework is developed further on the basis of the longitudinal dynamics of the vehicle. A sequence of braking pressure pulses is designed in the first stage to identify desired minimal pulse pressure needed for reliable estimation of TRFC with minimal interference with the vehicle motion. In the second stage, a constrained unscented Kalman filter (CUKF) algorithm is subsequently proposed to identify the precise TRFC for achieving rapid convergence and enhanced estimation accuracy.
A trajectory planning scheme integrating the estimated TRFC is subsequently developed for path-change maneuvers considering both the maneuver safety and the occupant’s comfort. For this purpose, a 7th-order polynomial function is constructed to ensure continuity up to the derivative of the acceleration (jerk). The friction-adaptive acceleration and speed-adaptive jerk limits are further defined and integrated in the framework to enhance occupant’s comfort and acceptance. Both numerical simulation and Quanser self-driving car (QCar) experimental results have revealed the effectiveness and practicability of the proposed lane change trajectory planning scheme.
An adaptive model predictive control (MPC) tracking scheme is proposed for tracking the desired lane-change path considering wide variations in vehicle speed and TRFC. With integrated consideration of output weights in the cost function together with constraints on the magnitude of the outputs, the proposed MPC scheme required only lateral position for tracking the planned path. An interesting way of integrating adaptive control gains with consideration of steering saturation by using the backstepping technique is also designed for low-speed AVs to enhance trajectory tracking, while respecting to the input boundaries. The effectiveness of the proposed tracking control scheme is verified experimentally using the QCar test platform.


identifier: Aoun, Alain ORCID: https://orcid.org/0000-0001-9038-5335 <https://orcid.org/0000-0001-9038-5335>  (2021) On the Improving of Approximate Computing Quality Assurance.  Masters thesis, Concordia University.

abstract:
Approximate computing (AC) has been predominantly recommended for implementation in error-tolerant applications as it offers a reduced resource usage, e.g.,~area and power, for a trade-off in output quality. However, AC implementation has not been adopted in commercial designs yet as it is still falling short in providing a good enough quality. Thus, continued research in the field in the field of improving quality of AC designs is indispensable. In this direction, a recent study exploited the use of machine learning (ML) to improve output quality. Nonetheless, the idea of quality assurance in AC designs could be improved in many aspects.

In the work we present in this thesis, we propose a few practical methods to improve an ML-based quality assurance methodology, which consist of an ML-model that select the most suitable design from a library of AC circuits. For instance, we extend the library of AC designs used for the ML-based approach with larger data path circuits. Larger designs, however, result in an exponential growth of complexity. Thus we propose the use of data pre-processing in order to reduce this hurdle by prioritizing designs based on their physical properties.

Another direction of improving AC circuits designs in general, and the ML-based model in particular is design space exploration (DSE). We therefore propose a novel DSE that drastically reduces the design space based on the aimed targets for area, latency and power of the AC circuit. Moreover, even with a narrowed design space, the number of AC designs to be assessed for their quality could be enormous. Thus, as part of this thesis, we propose a DSE that uses an intricate mathematical modeling for designs to assess their quality.

In another effort in improving quality assurance for AC design, we introduce a highly reliable model that uses a minimal overhead. This work is achieved by using redundant AC modules to form an approximate quadruple modular redundancy (AQMR) design. The proposed AQMR is superior to the exact triple modular redundancy (TMR) by offering a better reliability on top of the resource savings resulting from the implementation of AC.


identifier: Chausseau, Nicolas  (2021) Comparison of Sequence-to-Sequence and Retrieval Approaches on the Code Summarization and Code Generation Tasks.  Masters thesis, Concordia University.

abstract:
In this study, we evaluate and compare state-of-the-art models on the code generation and code summarization tasks (English-to-code and code-to-English). We compare the performance of neural seq2seq BiLSTM [Yin et al. 2018] and attentional-GRU architectures [LeClair et al. 2019], along with that of a semantic code search model reproduced from [Sachdev et al. 2018]. We compare these three models' BLEU scores (1) on their original study datasets as well as (2) on additional benchmark datasets [Yin et al. 2018, Sennrich et al. 2018, LeClair et al. 2019], each time for translation and back-translation (i.e. English-to-code and code-to-English). We observe that, surprisingly, semantic code search performs best overall, surpassing the seq2seq models on 5 task-dataset combinations out of 8. We find that the seq2seq BiLSTM always outperforms the attentional-GRU, including on the relatively large (2M pairs) Javadoc-based dataset from the original attentional-GRU study, setting a new high score on that dataset, higher than four previous published studies.
However, we also observe that model scores remain low on several datasets. Some test-set questions are harder to answer due to a lack of relevant examples in the training-set. We introduce a new procedure for estimating the degree of novelty, and difficulty of any given test-set question. We use the BLEU score of the highest-scoring training-set entry as reference point for model scores on the question, a procedure which we call BLEU Optimal Search, or BOS. The BOS score (i) allows us to generate an information retrieval ceiling for model scores for each test-set question, (ii) can help to shed light on the seq2seq models' capacity to generalize to novel, unseen questions on any dataset, and (iii) helps to identify dataset-artifacts, by inspecting the rare model answers that score above it. We observe that the BOS is not reliably surpassed by the seq2seq models, except in the presence of dataset-artifacts (such as when the first words of the question contains the answer), and call for further empirical investigation.


identifier: Yeganehdoust, Firoozeh  (2021) A Comparative Study on the Performance of Bio-inspired Slippery Lubricant Impregnated and Superhydrophobic surfaces in Droplet Impact and Shedding.  PhD thesis, Concordia University.

abstract:
The development of robust surfaces that repel liquid droplets has a broad impact on enhancing surfaces in several applications of anti-icing/fogging, anti-biofouling, and anti-dewing.
Despite high repellency features in superhydrophobic surfaces, these surfaces may be ineffective when they are used in harsh environments.
Inspiration from the natural non-wetting behavior of slippery surfaces of the pitcher plant has led to the development of slippery lubricant impregnated surfaces (SLIPS/LIS). They are designed by creating micro/nano-structured surfaces that are infused with a low surface tension lubricant which can enhance droplet mobility for a wide range of liquids with low surface tension properties.
Designing slippery lubricant impregnated surfaces is still ongoing research as it involves several parameters.
The physics of the impact and shedding of the liquid droplet on slippery surfaces remains elusive.
In this regard, both experimental and numerical tools have been used in this work to explore the associated physics in slippery surfaces and their advantages and disadvantages compared to superhydrophobic surfaces.

The first goal was to evaluate the effect of an immiscible lubricant with different thicknesses on the impact of a millimeter-sized water droplet for different impact velocities.
A three-phase flow numerical simulation based on a finite volume solution coupled with a volume of fluid method has been implemented. The numerical model showed that the droplet spontaneous bouncing occurred due to the air entrapment because of the deformation in both droplet and liquid film surface in which the details of the gas layer thickness and dynamics of fluid motions were illustrated. It is observed that liquid film surfaces can enhance the probability of droplet spontaneous bouncing.

The performance of superhydrophobic surfaces might fail their functions for micro-scale droplets as both the micro-structured surfaces and droplets are on the same scale.
Thus, the anti-wetting performance of slippery lubricant impregnated surfaces compared to superhydrophobic surfaces for different surface morphologies have been numerically investigated during droplet impingement.
The effect of the surface structure has been studied by considering different series of square-pillar arrays.
A three-phase flow solver in conjunction with an accurate contact angle method has been implemented.
It was observed that slippery surfaces with low--density micro-textured surfaces enhanced droplet mobility and repellency compared to superhydrophobic surfaces.
Additionally, the quantitative results indicated that the droplet pinning decreased significantly compared to superhydrophobic surfaces.

In order to assess the mobility of droplets under the effect of air shear flow on slippery surfaces and superhydrophobic surfaces, an experimental study in conjunction with a numerical model has been conducted.
It is observed that the hydrodynamics of droplet motion is completely different on superhydrophobic compared to slippery surfaces.
The wetting length and position of a droplet on all surfaces have been measured. Although similar trends are observed in quantitative measurements for slippery surfaces, the speed of droplets is greatly affected by the lubricant properties. A numerical simulation based on the VOF method coupled with the Large Eddy Simulation turbulent model in conjunction with the dynamic contact angle method has been used.
A developed boundary condition is also implemented to consider the effect of lubricant on slippery surfaces. The numerical simulations are compared with the experimental study to provide further information on the experimental results.


identifier: Churchill, L. Logan  (2021) Behind New Eyes: The Expression of Dual Loyalties Among Young Canadians & Newcomers.  Masters thesis, Concordia University.

abstract:
Using survey data drawn from the 2014 Provincial Diversity Project, this thesis provides a look at how the 1982 Constitution Act and the Charter of Rights and Freedoms shaped the political identities of Canadians and their understanding of the federation. More specifically, it examines how native-born Canadians and first-generation immigrants balance provincial and federal identities. My findings show that those introduced to Canada following the enactment of the 1982 Constitution have a stronger pro-Canada balancing of identity and weaker feelings of regional alienation relative to those introduced before 1982.

Additionally, this thesis explores the limits of institutional learning theory by examining how the strength of Canadian identity may predict the levels of support for national policies: multiculturalism, bilingualism, the equalization payments program, and feelings of regional alienation. My findings show that generally, the relationship between strength of Canadian identity and support for national policies is of equal strength among pre-, peri-, and post-Charter generations. Ultimately this thesis concludes that while it cannot demonstrate a clear generational break in the political behaviour of native-born Canadians and first-generation immigrants, the observed differences between Charter relative generations can be attributed to the enactment of the 1982 Constitution.


identifier: Matiuzzi Kunzler, Luccas ORCID: https://orcid.org/0000-0003-2586-7586 <https://orcid.org/0000-0003-2586-7586>  (2021) An Investigation of Series and Parallel Configurations for Hybrid Power Amplifiers.  PhD thesis, Concordia University.

abstract:
Power Hardware-in-the-Loop (PHIL) is becoming increasingly popular for compartmentalized testing of electric power equipment in several areas such as in electric drive systems and distributed power generation systems. The fundamental idea of PHIL is to create flexible conditions for Devices under Test (DUT) to be properly assessed in real time and dynamic conditions with their rated power levels. Connected to the DUT is the Power Amplifier (PA), which is responsible for increasing the voltage and current levels, given from the Real-Time Simulator (RTS). The DUT is a physical equipment and high-complexity models are used to control the PAs to emulate necessary conditions for the DUT to be evaluated. One of the main benefits of PHIL is that it can provide a platform for conducting a number of severe tests without risking damaging the equipment that is being emulated, while testing the actual response of the DUT. It can also help with the preliminary design and performance assessment of new types of machines, drivers and controllers, thus significantly reducing the time to market of new equipment. The flexibility of PHIL is also one of its main assets, since the combination of the RTS and the PA can be used for various applications only by changing the model and/or parameters of the emulated element.
This thesis will evaluate the main architectures, control strategies and PHIL applications of PAs. Linear Power Amplifiers (LPA) provide an overall great performance due to its high bandwidth but are expensive, mostly at increased power ratings. For high PAs with fast dynamic response and reduced waveform distortion, the Hybrid Power Amplifier (HPA) configuration provides a good cost-performance compromise. HPAs are built essentially with the association of a low-cost Switch Mode Power Amplifier (SMPA) and an LPA.
 The first configuration to be investigated is the series connected HPA intended for high voltage systems. The SMPA consists of a Cascaded H-Bridge Multilevel (CHBM) converter for increased modularity. A single-pulse per H-bridge modulation technique called Nearest Level of Control (NLC) is used for minimizing the switching losses. However, this leads to unbalanced power consumption by the H-bridges when the SMPA provides relatively low output voltages, thus compromising the reliability and power quality of the SMPA.  A new modulation technique called Split-Voltage Fist-In First-Out (SV-FIFO) that mitigates this issue is proposed. Its implementation requires the use of a supplemental, but simple, control loop based on the magnitude and frequency of the reference output voltage. Experimental results are presented to validate the design approach and demonstrate the high performance achieved with SV-FIFO.
The parallel connected HPA is also evaluated in this thesis. In a similar way to the series connected HPA, the LPA provides high bandwidth (BW) and active power filtering while the bulk of the power is provided by the SMPA. The SMPA is realized with a three-phase Voltage Source Converter (VSC) and three single-phase LPAs. The contribution relies on proposing a new topology and current control strategy that aims to reduce the size of the required LPA, which is costly. This is achieved by using the reference current of the HPA for the current control loop of the LPA, and the actual HPA current as the reference for the SMPA current loop. By making the bandwidth of the current loop of the LPA higher than that the SMPA one, the first provides the fast transient components and harmonic filtering while the second, the bulk of the HPA current.
Additionally, this thesis also covers the evaluation of techniques for Amplitude, Phase Angle and Frequency (APAF) detection for single-phase systems. Amplitude, phase and frequency detection is a key feature for the control of the series HPA, but it is also useful for other important applications, such as the synchronization of renewable sources to Alternate Current (AC) grids, which is a largely growing practice.  APAF for single-phase systems are more challenging since they require additional and more complex techniques to determine the phase angle. Usually, both single and three-phase systems are designed for a single and known frequency, usually the grid’s frequency. However, a wider range of frequencies is necessary for other applications such as HPAs. This thesis will examine two proposed techniques for APAF. The first is based on the combination of the integral and derivative actions and the second is based on the modification of a zero-crossing detection system. Both systems are discussed in detail and validated experimentally.


identifier: Gawande, Nilesh  (2021) Characterization of the Heterotrimeric G Protein Gene Families in Triticum aestivum and the Caleosins CLO3 and CLO7 in Brachypodium distachyon.  PhD thesis, Concordia University.

abstract:
In the last few decades global food security has been an important issue due to continuously growing population. The common bread wheat, Triticum aestivum, belongs to the tribe Triticeae and serves globally as one of the most important staple foods. The minimization of the losses in the crop yield caused by biotic and abiotic factors will be a beneficial approach to increase the crop production. The identification of the genes that change gene expression in response to stresses has been an important avenue to identify candidate genes that may contribute to stress tolerance.  Whole genome and transcriptomic analysis has accelerated the discovery and characterization of genes related to stress responses and tolerance. Several gene families in T. aestivum that respond to abiotic stress conditions have been identified and their characterization is in progress. Heterotrimeric G protein gene families have been long known to be involved in the regulation of plant growth and development under control and stress conditions and these gene family members are also found to play regulatory roles through interaction with other proteins. Here we have characterised the heterotrimeric G protein gene families in the T. aestivum. The heterotrimeric G protein α subunit (Gα) has been shown to interact with caleosins, a class of calcium binding proteins, and regulate stress responses through abscisic acid signalling. T. aestivum Gα is known to interact physically with Caleosin 3. However, the facility for genetic studies in T. aestivum is somewhat limited due to the lack of a readily available set of mutants, it’s polyploid nature and difficulty for transformation.  Brachypodium distachyon has been developed as a model experimental species for monocotyledons with the particular relevance to the crop species in the Triticeae.  It is important to know if the caleosins in Brachypodium also interact with its Gα subunit and the interaction is conserved among the species. In addition, Brachypodium lines with mutations for two caleosin genes are available and in this study have been characterized for their effects on root growth in response to abiotic stresses.
The first study (Chapter 2) of this thesis characterises the heterotrimeric G protein gene families in T. aestivum. Two of the Gγ’ were validated through in vivo protein-protein interaction by bimolecular fluorescence complementation. The differential expression analysis using RNA-Seq and microarray analysis showed that at least one homeologous gene copy of these members responded to abiotic stress conditions such as drought, heat, or cold, whereas only the Gγ1 paralog was found to be induced after inoculation of spore suspension of the fungus Fusarium graminearum in the resistant line NIL38 compared to the F. graminearum susceptible line NIL 51. This study will create a rationale to elucidate the possible role of heterotrimeric G protein gene family members in wheat under these stress conditions, which can be further investigated through mutant analysis.
The second study (Chapter 3) of this thesis report the physical interaction of B. distachyon heterotrimeric G protein subunit Gα with its CALEOSIN 7 (Bd-CLO7) and the role of CLO7 in regulation of root growth. We investigated the effect of Brachypodium CLO7 mutation on the regulation of primary, coleoptile node and lateral root growth under ABA and osmotic stress. Brachypodium CLO7 has found to regulate the lateral root growth under osmotic stress through ABA independent signalling.
The third study (Chapter 4) of this thesis determines the physical interaction of Brachypodium CALEOSIN 3 (Bd-CLO3) and, its N and C terminal truncations with Bd-Gα. We investigated the role of Brachypodium Caleosin 3 in the regulation of primary, coleoptile node and lateral root growth under ABA and osmotic stress by mutant analysis. Bd-CLO3 has been found to affect the primary root growth under ABA and osmotic stress and negatively regulate the coleoptile node root growth under non stress and osmotic stress conditions. In addition, Brachypodium CLO3 negatively regulates the lateral root growth through ABA signalling, whereas under osmotic stress it affects lateral root growth through both ABA dependent and independent pathways.


identifier: Racicot, Jesse  (2021) Domination : Offline, Online, Any Time.  Masters thesis, Concordia University.

title: Domination : Offline, Online, Any Time

abstract:
Given a \emph{graph} $G = (V, E)$, a subset $D \subseteq V$ is called a \emph{dominating set} if each vertex $v \in V$ either belongs to $D$ or is adjacent to some vertex in $D$. The typical objective is to find a dominating set of minimum size.  Depending on the context, the problem may be viewed from an algorithmic perspective or a purely mathematical one.  The following thesis explores the topic of domination from these two different perspectives, where the former is split further into two settings.  In particular, we study the topic as a computational problem within an \emph{offline setting} where an algorithm is given an input graph in its entirety and alternatively, in an \emph{online setting} where an algorithm is forced to make irrevocable decisions with limited information about an input graph. We also approach the topic as a purely mathematical problem as we study the domination number of a well-known family of graphs known as the \emph{Kn{\"o}del} graphs.

Prior to this thesis, research on the dominating set problem in an online setting was sparse.  We consider an online setting where a vertex is revealed to an algorithm and the choice to add this vertex or not is a finality.  In this setting, an adversary must reveal the entire neighborhood of a vertex to an algorithm while keeping the revealed portion of the graph connected at all times.  We present  algorithms that achieve 2-competitiveness on trees, 2.5-competitiveness on cactus graphs, $(t-1)$ on $K_{1,t}$-free graphs, and  $\Theta(\sqrt{\Delta})$ for maximum degree $\Delta$ graphs.  Moreover, we show that all of those competitive ratios are tight.  Then, we study several more general classes of graphs, such as threshold, bipartite  planar, and series-parallel graphs, and show that they do not admit competitive algorithms (that is, when competitive ratio is independent of the input size). Our results are compared with earlier results in a different input model, where a vertex is revealed  alongside its restricted neighborhood: those neighbors that are among already  revealed vertices. Thus, conceptually, our results quantify the value of knowing the entire neighborhood at the time a vertex is revealed as compared to the restricted neighborhood.

The family of graphs known as the Kn{\"o}del graphs are studied extensively with an emphasis on determining closed form expressions for certain graph parameters.  Our main contribution is the novel use of techniques from elementary number theory to establish an upper bound on the \emph{domination number} of the Kn{\"o}del graph on $n$ vertices.  In particular, we show that whenever we find a prime $p$ dividing $n$ with $p \leq  \lceil \log n \rceil$ such that $2$ is a \emph{primitive root} modulo $p$ then there is a dominating set of size $\frac{n}{p}$.  Moreover, if we suppose that $2$ is a primitive root modulo $p^k$, where $p^k$ divides $n$ and $\phi(p^k) < \lceil \log n \rceil$ then we can construct a dominating set of size $\frac{2n}{p^k}$.


identifier: Hagi-Yusuf, Jama  (2021) Development of a high-throughput assay for fatty acid decarboxylases.  Masters thesis, Concordia University.

abstract:
Biorenewables have the potential to move society’s dependence away from petrol-based industrial products, towards cleaner and more sustainable sources. The technology has moved from focussing on low energy density ethanol- or butanol-based fuel sources to more complex,
energy rich hydrocarbons. Recently, a heme-dependent P450 decarboxylase enzyme, OleTJE, was discovered in the bacterium Jeotgalicoccus sp 8456. This enzyme catalyzes the decarboxylation
of a broad-range of long-chain fatty acids producing terminal alkenes that are key energy-rich hydrocarbons valuable for biofuels. Here, we developed an absorbance-based high-throughput assay that facilitated the determination of the activity and Michaelis-Menten kinetics of OleTJE. We screened OleTJE decarboxylation by detecting CO2, a product of decarboxylation. In this assay, CO2 was converted to bicarbonate and then catalyzed by phosphoenolpyruvate carboxylase and malate dehydrogenase to malate, leading to a decrease in NADH, the detecting
molecule. This assay was then used to screen a mutant OleTJE and a non-P450 decarboxylase, to showcase its versatility to screen mutant variants and other decarboxylases.


identifier: Quach, Sophia  (2021) Studying the Use of SZZ with Non-functional bugs.  Masters thesis, Concordia University.

abstract:
Non-functional bugs bear a heavy cost on both software developers and end-users. Tools to reduce the occurrence, impact, and repair time of non-functional bugs can therefore provide key assistance for software developers racing to fix these issues.
Classification models that focus on identifying defect-prone commits, referred to as \emph{Just-In-Time (JIT) Quality Assurance} are known to be useful in allowing developers to review risky commits. JIT models, however, leverage the SZZ approach to identify whether or not a past change is bug-inducing.
However, the due to the nature of non-functional bugs, their fixes may be scattered and separate from their bug-inducing locations in the source code. Yet, prior studies that leverage or evaluate the SZZ approach do not consider non-functional bugs, leading to potential bias on the results.

In this thesis, we conduct an empirical study on the results of the SZZ approach on the non-functional bugs in the NFBugs dataset, and the performance bugs in Cassandra, and Hadoop. We manually examine whether each identified bug-inducing change is indeed the correct bug-inducing change. Our manual study shows that a large portion of non-functional bugs cannot be properly identified by the SZZ approach. We uncover root causes for false detection that have not been previously found. We evaluate the identified bug-inducing changes based on criteria from prior research. Our results may be used to assist in future research on non-functional bugs, and highlight the need to complement SZZ to accommodate the unique characteristics of non-functional bugs.
Furthermore, we conduct an empirical study to evaluate model performance for JIT models by using them to identify bug-inducing code commits for performance related bugs.
Our findings show that JIT defect prediction classifies non-performance bug-inducing commits better than performance bug-inducing commits. However, we find that manually correcting errors in the training data only slightly improves the models. In the absence of a large number of correctly labelled performance bug-inducing commits, our findings show that combining all available training data yields the best classification results.


identifier: Zarei Chamgordani, Raheleh  (2021) Comparative Study of Speed-Up Routing Algorithms in Road Networks.  Masters thesis, Concordia University.

abstract:
We study the problem of finding the shortest distance and the shortest path from one node to another in graphs modeling large road networks. Classical algorithms like Dijkstra and Astar do not have good performance in such networks. In recent years, two new approaches called Contraction Hierarchy and Hub Labeling which use preprocessing to generate auxiliary data to improve the query time
performance were proposed, and many variants have followed. These algorithms are very efficient on large networks when a large number of queries is expected. In the literature, these algorithms are called speed-up algorithms. More recently, dynamic routing algorithms have been proposed, such as Customizable Contraction Hierarchy and Dynamic Hierarchical Hub Labeling. These are designed to
respond efficiently to edge weight changes resulting from changes in traffic.
In this thesis, we present an experimental study of the performance of the above static and dynamic routing algorithms on two different road networks, in terms of travel time and query processing time. Our results show that Customizable Contraction Hierarchy is the best for shortest path query in both the static and dynamic settings, while Hub Labeling is the most efficient in answering shortest distance queries
in the static setting. We also show that Dynamic Hub Labeling’s edge weight update operations are inefficient in practice.


identifier: Gao, Xiang  (2021) Stochastic control, numerical methods, and machine learning in finance and insurance.  PhD thesis, Concordia University.

abstract: We consider three problems motivated by mathematical and computational finance which utilize forward-backward stochastic differential equations (FBSDEs) and other techniques from stochastic control. Firstly, we review the case of post-retirement annuitization with labor income in framework of optimal stochastic control and optimal stopping. We apply the martingale approach to a Cobb–Douglas type utility maximization problem. We have proved the theoretical existence and uniqueness of an optimal solution. Several analyses are made based on the simulations for the optimal stopping choice and strategies. Secondly, We review the convolution method in backward stochastic differential equations (BSDEs) framework and study the application of convolution method to Heston model. We provide an easy representation of the Heston characteristic function that avoids the discontinuities caused by branch rotations in the logarithm of complex functions and is able to be applied in calibration. We proposed two convolution schemes to the Heston model and provide the error analysis that shows the error orders of discretization and truncation. We review two error control methods and improve the accuracy on the boundaries. Numerical results comparing to a Fourier method and an integration method is provided. Thirdly, we review the forecasting problem in bond markets. Our data include both U.S. Treasuries and coupon bonds from twelve corporate issuers. We apply the arbitrage-free model in predicting the yields and the prices of coupon bonds in a sequential model with the Kalman filter, the extended Kalman filter and the particle filter. We implement the arbitrage penalty and obtain the optimal dynamic parameterization using deep neural networks. The purpose of the prediction is to examine the effect of arbitrage penalty and the forecasting performance on different time horizons. Our result shows that the arbitrage-free penalty has improving performance on short time period but downgrading performance on long time period. We provide analysis on the prediction errors, the distribution of errors, and the average excess return. The predicted bond prices shows the prediction errors have non-Gaussian distribution, excess kurtosis, and fat tails. Future works will be from two aspects, refine the importance sampling by non-parametric distribution and refine the term structure model with jump process and credit risk.


identifier: Smith, Audrey  (2021) Thickening of Brewery Sludge to be used as Animal Feed through the Addition of Biopolymers.  Masters thesis, Concordia University.

abstract: The waste crisis has become a global issue, forcing many industries to reconsider their disposal methods and environmental practices. When examining the brewery industry, it produces a significant amount of sludge with a high water content. To avoid landfilling, this waste can be thickened to recover valuable materials. This process typically involves the addition of metal based coagulants. In this case, the desired outcome of the brewery sludge would be to produce animal feed. The use of biopolymers like chitosan which act as a coagulant can safely thicken the sludge without leaving toxic residuals. Chitosan is a by-product from the shellfish processing industry and therefore reduces its environmental imprint by using the waste from one industry to treat the waste from another. The objective of this research is to study the effect of using chitosan with coagulation-flocculation on brewery sludge, specifically its mechanisms relating to settling, turbidity and solids removal while applying different dosages and molecular weight biopolymers. It was found that the bridging and charge neutralization mechanisms allowed the high molecular weight chitosan to remove 97% of turbidity within 30 minutes of sedimentation with a dosage of 420mg/L. Its solids classification also produced an overall greater solids removal. The low molecular weight chitosan yielded lower contaminant removal, but settled faster. These results are linked to the Sludge Volume Index as increasing the molecular weight of the chitosan results in a higher index. Overall, the use of chitosan could be a safe and effective way to thicken the brewery sludge.


identifier: Troop, Dylan  (2021) Bias-Corrected Peaks-Over-Threshold Estimation of theCVaR and Application to Multi-Armed Bandits.  Masters thesis, Concordia University.

abstract: The conditional value-at-risk (CVaR) is a useful risk measure in fields such as machine learning, finance, insurance, energy, etc. When measuring very extreme risk, the commonly used CVaR estimation method of sample averaging does not work well due to limited data above the value-at-risk (VaR), the quantile corresponding to the CVaR level. To mitigate this problem, the CVaR can be estimated by extrapolating above a lower threshold than the VaR using a generalized Pareto distribution (GPD), which is often referred to as the peaks-over-threshold (POT) approach. This method often requires a very high threshold to fit well, leading to high variance in estimation, and can induce significant bias if the threshold is chosen too low. We address this bias-variance tradeoff by developing a novel CVaR estimator based on the POT approach that is proven to be asymptotically unbiased and less sensitive to lower thresholds being used. It is then shown empirically that the new estimator provides a significant reduction in error compared with competing CVaR estimators in finite samples from heavy-tailed distributions. To demonstrate the use of the estimator in sequential decision-making, it is applied in a best arm identification multi-armed bandit problem under a fixed budget, and a significant performance improvement is shown when compared with other estimators.


identifier: LI, JUNJIE  (2021) Tracking the Evolution of Static Code Warnings: the State-of-the-Art and a Better Approach.  Masters thesis, Concordia University.

abstract:
Static bug detection tools help developers detect problems in the code, including bad programming practices and potential defects. However, it is known that static bug detectors remain underutilized due to various reasons. Recent advances to incorporate static bug detectors in modern software development workflows, such as in code review and continuous integration, are shown capable of better motivating developers to fix the reported warnings on the fly. A proper mechanism to track the evolution of the reported warnings can better support such integration. Moreover, tracking the static code warnings will benefit many downstream software engineering tasks, such as learning the fix patterns for automated program repair and learning which warnings are of more interest, so they can be prioritized automatically. Hence, precisely tracking the warnings by static bug detectors is critical to improve the utilization of static bug detectors further.
In this thesis, we study the effectiveness of the state-of-the-art (SOA) solution in tracking the warnings by static bug detectors and propose a better solution based on our analysis of the insufficiencies of the SOA solution. In particular, we examined over 2000 commits in four large-scale open-source systems (i.e., JClouds, Kafka, Spring-boot, and Guava) and crafted a dataset of 3,452 static code warnings by two static bug detectors (i.e., Spotbugs and PMD). We manually uncover the ground-truth evolution status of the static warnings: persistent, resolved, or newly-introduced. Moreover, upon manual analysis, we identified the main reasons behind the insufficiencies of the SOA solution. Finally, we propose a better approach to improve the tracking of static warnings over software development history. Our evaluation shows that our proposed approach provides a significant improvement in terms of the precision of the tracking, i.e., from 66.9% to 90.0%.


identifier: Leone, Frédéric  (2021) Using the 13C/12C Ratio of Bacteria-Specific Fatty Acids to Determine the Lability of Terrestrial and Marine Organic Matter in Coastal Sediments.  Masters thesis, Concordia University.

abstract: The bottom waters of the St. Lawrence Estuary and Gulf are currently characterized by low dissolved oxygen levels (hypoxia), which influence the health of this ecosystem. The progression of hypoxia since the beginning of the century is due in part to an increase in the flux of organic matter (OM) and inorganic nutrients discharged in this aquatic system by the St. Lawrence River. The increase in nutrient abundance leads to higher primary productivity and concentrations of dissolved and particulate OM in the water column, which in turn results in a higher consumption rate of oxygen during the degradation of OM by microorganisms. To further our understanding of the carbon cycle in the St. Lawrence system, the biological lability of terrestrially-derived and marine OM was indirectly estimated through the analysis of the 13C/12C ratio of bacteria-specific fatty acid (iso C15:0 and anteiso C15:0) using gas chromatography coupled to an isotope ratio mass-spectrometer (GC-IRMS). Ubiquitous bacteria strains responsible for the degradation of OM were cultivated in marine broth enriched in 13C with 13C-sodium acetate to assess the relationship and isotopic fractionation between the 13C signature of the food source and that of the bacteria. Using this calibration and the isotopic signature of the terrestrial and marine OM end-members, it was possible to determine the proportions of each type of OM being degraded at the different sampling stations along the St. Lawrence Estuary and Gulf continuum. Better constraining of the role of bacteria in terrestrial and marine OM degradation within the St. Lawrence Estuary and Gulf allows for better understanding of the causes driving deep water hypoxia and, eventually, will allow better remediation efforts to improve the health of this important ecosystem. Finally, as part of a small side project, the method used to decarbonate samples with HCl vapour in preparation for elemental analysis (EA) was investigated using a 13C-labelled short-chain organic acid to assess the extent to which the acid is lost through volatilization upon its protonation.


identifier: Abdelrahman, Osama  (2021) Performance of Green Smart-Heat Cured Cementitious Materials.  Masters thesis, Concordia University.

abstract: During the cold winter season, all in-situ construction activities are halted, leading to economic losses. Hence, shifting to precast elements represents an optimum solution. However, the high energy intensity heat curing process for precast elements represents a challenge. On the other hand, microencapsulated phase change materials (MPCMs) was used to improve cementitious material thermal storage capacity. However, a reduction in mechanical properties and losing thermal efficiency were reported due to MPCMs breakage during the construction process. Hence, this dissertation proposed two solutions: 1) Modifying cementitious mixtures design to reduce MPCMs fracturing risk while maintaining adequate performance and 2) Novel smart external curing sheets. Results reveal that incorporating limestone filler in mixtures was a promising green sustainable solution. Moreover, maintain adequate MPCMs in the mixtures was found to improve the later thermal performance for elements, which is considered additional benefits. The external use of MPCMs in the curing process had resulted in shorting the required curing period to achieve targeted strength. Optimizing thermal capacity and heat curing process for precast elements will increase work efficiency and economic benefits for the precast industry. It will also reduce the energy demand and cut down the precast industry's carbon footprint, leading to a higher level of sustainability.


identifier: Macairan, Jun-Ray ORCID: https://orcid.org/0000-0003-2173-7768 <https://orcid.org/0000-0003-2173-7768>  (2021) Development of Multisensing Imaging Probes Using Carbon Dots.  PhD thesis, Concordia University.

abstract:
Imaging probes serve as unique diagnostic tools in biomedical applications offering high sensitivity particularly in their ability to image cells and tissues. These tools are crucial for early detection and disease diagnostics especially with an increase in numbers of an aging population and the requirement for more efficient health care. Recent advancements in the field of nanomaterials have propelled research groups into investigating these nanoparticles for various biological applications including drug delivery, biosensing and bioimaging, among others. Recently, carbon dots have garnered significant attention because they can be prepared from simple synthetic routes using inexpensive precursors, offering tunable optical properties, low cytotoxicity and good biocompatibility. Their inherent fluorescent nature not only allows for fluorescence imaging, but also for sensing environmental changes, which can provide additional insights for the development of novel diagnostic applications.
Herein, carbon dots are synthesized using a one-step microwave- and solvothermal-assisted reaction. The prepared dots fluoresce simultaneously in both the blue and the red regions of the electromagnetic spectrum. The dots’ physico-optical properties are thoroughly studied to shed light on their fluorescence mechanism, which remains of topic of debate in the literature. It is demonstrated that the fluorescence of the nanoparticles is tailored through manipulation of key synthesis parameters to determine the underlying effect on the observed optical signature. The dots’ unique optical properties are believed to derive from the carbon core- and molecular-states fluorescence mechanism. In brief, the blue fluorescence stems from the core, while the red counterpart originates from the molecular states that are typically localized on the surface of the dot.
With their unique fluorescence properties and our understanding of this phenomenon, these dots offer the possibility of sensing changes in temperature and pH, using ratiometric approaches. Both temperature- and pH-sensing measurements translate well from the cuvette to the cellular model. The change in physiological parameters are in agreement with the change in emission using epifluorescence and confocal microscopy. The ability to glean such information renders these nanoparticles into versatile diagnostic nanotools with the ability to shed new insights on disease mechanisms and can be foreseen as future tools for in vivo sensing applications.


identifier: Saied, Amamer  (2021) Resource Allocation Management of D2D Communications in Cellular Networks.  PhD thesis, Concordia University.

abstract:
To improve the system capacity, spectral performance, and energy efficiency, stringent requirements for increasing reliability, and decreasing delays have been intended for next-generation wireless networks. Device-to-device (D2D) communication is a promising technique in the fifth-generation (5G) wireless communications to enhance spectral efficiency, reduce latency and energy efficiency. In D2D communication, two wireless devices in close proximity can communicate with each other directly without pass through the Base Station (BS) or Core Network (CN). In this proposal, we identify compromises and challenges of integrating D2D communications into cellular networks and propose potential solutions. To maximize gains from such integration, resource management, and interference avoidance are key factors. Thus, it is important to properly allocate resources to guarantee reliability, data rate, and increase the capacity in cellular networks.
In this thesis, we address the problem of resource allocation in D2D communication underlaying cellular networks. We provide a detailed review of the resource allocation problem of D2D communications. My Ph.D research will tackle several issues in order to alleviate the interference caused by a D2D user-equipment (DUE) and cellular-userequipment (CUE) in uplink multi-cell networks, the intra-cell and inter-cell interference are considered in this work to improve performance for D2D communication underlaying cellular networks. The thesis consists of four main results. First, the preliminary research proposes a resource allocation scheme to formulate the resource allocation problem through optimization of the utility function, which eventually reflects the system performance concerning network throughput. The formulated optimization problem of maximizing network throughput while guaranteeing predefined service levels to cellular users is non-convex and hence intractable. Thus, the original problem is broken down into two stages. The first stage is the admission control of D2D users while the second one is the power control for each admissible D2D pair and its reuse partner.
Second, we proposed a spectrum allocation framework based on Reinforcement Learning (RL) for joint mode selection, channel assignment, and power control in D2D communication. The objective is to maximize the overall throughput of the network while ensuring the quality of transmission and guaranteeing low latency requirements of D2D communications. The proposed algorithm uses reinforcement learning (RL) based on Markov Decision Process (MDP) with a proposed new reward function to learn the policy by interacting with the D2D environment. An Actor-Critic Reinforcement Learning (AC-RL) approach is then used to solve the resource management problem. The simulation results show that our learning method performs well, can greatly improve the sum rate of D2D links, and converges quickly, compared with the algorithms in the literature.
Third, a joint channel assignment, power allocation and resource allocation algorithm is proposed. The algorithm designed to allow multiple DUEs to reuse the same CUE channel for D2D communications underlaying multi-cell cellular networks with the consideration of the inter-cell and intra-cell interferences. Obviously, under satisfying the QoS requirements of both DUEs and CUEs, the more the number of the allowed accessing DUEs on a single CUE channel is, the higher the spectrum efficiency is, and the higher the network throughput can be achieved. Meanwhile, implementing resource allocation strategies at D2D communications allows to effectively mitigate the interference caused by the D2D communications at both cellular and D2D users. In this part, the formulated optimization problem of maximizing network throughput while guaranteeing predefined service levels to cellular users. Therefore, we propose an algorithm that solves this nonlinear mixed-integer problem in three steps wherein the first step, subchannel assignment is carried out, the second one is the power allocation, while the third step of the proposed algorithm is the resource allocation for multiple D2D pairs based on genetic algorithm. The simulation results verify the effectiveness of our proposed algorithm.
Fourth, integrating D2D communications and Femtocells in Heterogeneous Networks (HetNets) is a promising technology for future cellular networks. Which have attracted a lot of attention since it can significantly improve the capacity, energy efficiency and spectral performance of next-generation wireless networks (5G). D2D communication and femtocell are introduced as underlays to the cellular systems by reusing the cellular channels to maximize the overall throughput in the network. In this part, the problem is formulated to maximize the network throughput under the QoS constraints for CUEs, DUEs and FUEs. This problem is a mixed-integer non-linear problem that is difficult to be solved directly. To solve this problem, we propose a joint channel selection, power control, and resource allocation scheme to maximize the sum rate of the cellular network system. The simulation results show that the proposed scheme can effectively reduce the computational complexity and improve the overall system throughput compared with existing well-known methods.


identifier: Racherache, Badis  (2021) Insider Threat Detection using Profiling and Cyber-persona Identification.  Masters thesis, Concordia University.

abstract:
Nowadays, insider threats represent a significant concern for government and business organizations alike. Over the last couple of years, the number of insider threat incidents increased by 47%, while the associated cost increased by 31%. In 2019, Desjardins, a Canadian bank, was a victim of a data breach caused by a malicious insider who exfiltrated confidential data of 4.2 million clients. During the same year, Capital One was also a victim of a data breach caused by an insider who stole the data of approximately 140 thousand credit cards. Thus, there is a pressing need for highly-effective and fully-automatic insider threat detection techniques to counter these rapidly increasing threats. Also, after detecting an insider threat security event, it is essential to get the full details on the entities causing it and to gain relevant insights into how to mitigate and prevent such events in the
future. In this thesis, we propose an elaborated insider threat detection system leveraging user profiling and cyber-persona identification. We design and implement the system as a framework that employs a combination of supervised and unsupervised machine learning and deep learning techniques, which allow modelling the normal behaviour of the insiders passively by analyzing their network traffic. We can deploy the framework as part of online traffic monitoring solutions for insider profiling and cyber-persona identification as well as for detecting anomalous network behaviours. The different models employed are assessed
using specific metrics such as Accuracy, F1 score, Recall and Precision. The conducted experimental evaluation indicates that the proposed framework is efficient, scalable, and suitable for near-real-time deployment scenarios.


identifier: Childerhouse, Mariah  (2021) Educators’ Perspectives on Executive Function and the Role of Pretend Play.  Masters thesis, Concordia University.

abstract: This qualitative study examines educators’ perspectives on the role of pretend play in the development of executive function (EF) in preschool-aged children. Five educators, aged 24-62, were recruited from three different early childcare centers in Montreal, Quebec. Data were collected online through semi-structured interviews and demographic and classroom environment questionnaires. Findings suggest that pretend play serves as a medium in which children can develop, practice and integrate skills associated with EF, such as working memory, inhibition and cognitive flexibility. It was also found that child-directed play and teacher-directed play are meaningful experiences that help to engage children’s EF abilities. The study concludes that educators and the classroom environment are both moderating factors that scaffold and support children in the attainment of EF.


identifier: Pimentel, Erica  (2021) Making the Best of It: Three Essays on Overcoming Challenges in the Public Accounting Profession.  PhD thesis, Concordia University.

abstract: This dissertation reports on three essays relating to challenges public accountants face in exercising their profession. These essays explore how public accountants sensemake about these challenges and reframe (or not) their vision of the value their occupation provides. The first chapter draws on Alasdair MacIntyre’s virtue ethics framework and narrative interviews with twenty Tunisian auditors to understand how they make sense of ethical challenges in a context where transnational norms for the profession are at odds with the local customs. In this context, auditors adapt their purpose within the profession to serve a telos that is congruent with their moral tradition. The second article leverages a qualitative field study into the blockchain specialty practice of a large accounting firm to study the practices auditors deploy when expanding into the blockchain field. This chapter explores the role of Bourdieu’s master concept of habitus in guiding auditors’ approach to and understanding of the terrain they seek to conquer. Without shared habitus, auditors and blockchainers fail to agree on which types of assurance are needed in the blockchain ecosystem, how assurance should be communicated, and who should be providing it. Ultimately, this study sheds light on how auditors can establish a lasting presence in settings where technological innovation is prevalent. The final chapter draws on 31 semi-structured interviews with public accountants carried out during the height of the first wave of the COVID-19 pandemic. It suggests that accountants can experience a sense of freedom when they are given choices that appeal to their value set, which, in this case, is their desire to make rational choices that maximize their human capital value. Choice itself becomes a technique of governmentality because employers control the array of available choices, or the choice architecture, and the information used to evaluate those choices. Altogether, these three studies dig into settings where practicing the profession is difficult – and shed light on how accountants as a profession and as individuals can overcome these obstacles.


identifier: Ali, Samr ORCID: https://orcid.org/0000-0003-4068-709X <https://orcid.org/0000-0003-4068-709X>  (2021) Hidden Markov Models and their Extensions for Proportional Sequential Data.  PhD thesis, Concordia University.

abstract:
We are facing an all-time high in the worldwide generation of data. Machine learning techniques have proven successful in unveiling patterns within data to further human knowledge. This includes building systems with overall better prediction and accuracy levels. Nonetheless, many areas have yet to be studied which warrants further exploitation of these techniques. Hence, data modeling is one of the topics at the forefront of scientific research. A particularly interesting field of research is the appropriate choice of distribution that corresponds to the nature of the data.
In this thesis, we focus on tackling challenges in the approximation of proportional Hidden Markov Models (HMM). We review the main concepts behind HMM; one of the cornerstone probabilistic graphical models for time series or sequential data. We also discuss various modern challenges that exist when training or using HMMs. Nonetheless, we primarily focus on the notorious model estimation process of HMMs as well as the appropriate choice of emission distribution based on the nature of the data. We have tackled these problems using variational inference and Maximum A Posteriori (MAP) approximation with the Dirichlet, the Generalized Dirichlet, and the Beta-Liouville (BL) distributions-based HMMs for proportional data. In this thesis, we develop frameworks for learning these proportional HMMs that have been proposed recently as an efficient way for modeling sequential proportional data. In contrast to the conventional Baum Welch algorithm, commonly used for learning HMMs, the proposed algorithms place priors for the learning of the desired parameters; hence, regularizing the estimation process. We also extend these models into infinity for a data-driven dynamically chosen structure of HMMs. Such a setup enables flexibility in the model structure with a lower computational cost for model selection. We also investigate the fusion of the trained classifiers and witness a consequent improved performance. Moreover, we incorporate a simultaneous feature selection paradigm as well as investigate online deployment. We present our recently proposed methodologies that address the aforementioned problems and discuss the achieved results across a variety of computer vision applications. We also present how a simple novel experimental setup can drastically improve the performance of HMMs in occupancy detection, and estimation by extension, in a smart building for an applied research contribution. Finally, we conclude and recommend potential future work.


identifier: Ahmed, warda Mansour  (2021) Characteristics of siphon flow under submerged discharge conditions.  PhD thesis, Concordia University.

abstract:
Characteristics of siphon flow under submerged discharge conditions

Water reservoirs serve such essential purposes as water supply, irrigation, and hydroelectric power developments. Their effective and safe operations need reliable hydraulic structures for flow control. Siphon spillways are a flow control structure, with two main advantages: 1) no moving parts required and thus less susceptible to breakdown; 2) the ability to pass full discharge with a minimal increase of reservoir water level. The second advantage makes it easier to maintain target water levels as water resources while to ensure safe operations. The design of a siphon spillway uses one discharge head only, termed the design head, which is derived from statistical analysis of hydrological data for the reservoir region. However, under climate change, most existing siphons have been or are expected to be subject to actual discharge heads larger than their design heads. In other words, climate change results in submerged exit condition for siphon flow.
	Previous studies of siphons focus on their hydraulic performance under free discharge condition. How submergence affects the flow is a question, not addressed previously. The flow over the crest of a siphon is highly curved. It is a challenge to deal with the curved boundary surface of the crest in siphon analysis. Streamline curvatures, three-dimensional vorticities and other subtle characteristics of the velocity and pressure fields remain to be discovered. Existing studies limit to a qualitative description of siphon flow and oversimplify flow mechanisms. The purpose of this research is to improve our understanding of siphon flow characteristics in a range of submerged exit conditions; to reveal any changes in the hydraulic performance of siphons, compared to free discharge conditions; and ultimately to contribute to an improved design of siphons.This research took the approach of combining laboratory experiments with mathematical modelling. The experiments used a scaled model siphon. It was fabricated and tested in the Hydraulics Laboratory at Concordia University. A series of experiments were conducted to determine the discharge coefficient in a range of flow rates. A three‐dimensional computational fluid dynamics (CFD) model was established for predicting the velocity and pressure fields as well as turbulence quantities. The CFD model used mesh refinement for regions close to solid boundaries and computed two-phase flow. The free surface of reservoir was tracked using the volume-of-fluid (VOF) method. Turbulence closure was obtained using the RNG k‐ε model.
	The CFD model predicted detailed distributions of the flow field, including curvilinear flow features in the crest region. The flow characteristics corresponded to various conditions of submergence at the downstream exit of the siphon conduit, and included primary flow velocity, secondary flow velocity, turbulence kinetic energy, and pressure. The predicted discharge coefficient compared well with experimental data. The predicted mean-flow velocities were validated using estimates from the potential flow theory.
	The experimental and computational results lead to the following findings: 1) The flow in the upstream reservoir is relatively uniform, with smooth movement toward the siphon entrance. At the entrance, the flow contracts, causing the pressure to drop below the hydrostatic pressure level in the upper corner of the entrance. Under the impact of centrifugal forces, the flow at the crest is forced to move in the extrados direction, causing secondary flow and an increased velocity above the crest. 2) The velocity rapidly increases near the crest, and reaches the maximum at a very small height from the crest surface. In the zone above the boundary layer, the velocity decreases gradually before it starts to rapidly decrease near the crown surface. 3) Flow separation occurs just a short distance downstream of the crest. Eddies start to form on the crest and develop along the lower leg of the siphon. Further downstream, the flow contracts by a deflector, creating flow separation on the downstream side. 4) The pressures differ along the siphon conduit, with negative values in the crest region. The pressure decrease is proportional to the increase of velocity. Negative pressures at the crest surface may drop to water vapour pressure at the prototype scale. 5) The discharge coefficient is a parameter of practical importance. It allows one-to-one determination of siphon discharge from the head which is simple to measure. Values of the discharge coefficient range from 0.62 to 0.68 under submerged exit conditions. These values are larger than those under free discharge conditions.
This study has contributed to a better understanding of flow behaviours in a region bounded by curved boundaries. The CFD modelling strategies discussed in this research can be applied to analyse complex flows in similar hydraulic structures. The pressure data reported can possibly be used to access risks of cavitation in siphon spillways. In conclusion, the siphon flow is a complex flow, with curvatures, three dimensionality and turbulence. Through laboratory experiments and mathematical modelling, this research sheds lights on the flow characteristics such as discharge performance, velocity distribution, and pressure distribution.


identifier: Stotz, Quinton  (2021) Applying Complex Dynamic Systems Theory to Identify Dynamic Properties of Plurilingual Repertoires.  Masters thesis, Concordia University.

abstract:
Language repertoires have been traditionally construed as a set of chronologically determined compartments (i.e., L1, L2, Ln), a scheme which upholds several validity and ethical issues when operationalized in research and education (Larsen-Freeman, 2017; Ortega, 2019). Complex Dynamic Systems Theory (also Complexity theory, here CDST) has been hailed as one solution to these issues moving forward. Still, CDST has rarely been used to examine multiple languages within a repertoire and thus its applicability to plurilingual settings remains largely untested. This exploratory study contributes by examining whether the inherent properties of CDST manifest in the perceptions that plurilinguals have on their own language development as their language systems change over time.

This study used retrodictive qualitative modelling (Dörnyei, 2014) where the developmental trajectory of changing language systems was discerned by working backwards through data collected during an observation window. Over a three-month period, three plurilingual individuals assessed their language systems through weekly surveys and participated in open-ended interviews. A three-stage phenomenological analysis evaluated the data against CDST’s theoretical prism and allowed for the data-driven identification of five CDST properties (i.e., attractor states, phase shifts, co-adaptation, self-organization, and emergence) in the participants’ perceptions of how their repertoires changed over time. Results indicate that the components of plurilingual repertoires exhibit the aforementioned dynamics of CDST, although evidence for emergence was less certain. Importantly, this study shows that these dynamics are discernable in an individual’s perception of their own language development.


identifier: Deshpande, Vinayak  (2021) Model Predictive Control with Fault Detection and Diagnosis for Multivariable Systems.  Masters thesis, Concordia University.

abstract:
The feedback control system design technique of Model Predictive Control (MPC) has been vastly used in the chemical and process engineering industry, due to its ability to handle dynamics with multiple inputs and multiple outputs, which are essentially the majority of today's engineering systems. In addition, the field of Fault Detection and Diagnosis (FDD) in control systems also has been extensively researched over the past decades as it is critical for the controller to realize when and if a fault has occurred within a system. However, due to the high computational requirements, it is often challenging to implement FDD based MPC algorithms in resource limited real world systems.

This thesis addresses the development of MPC algorithms with combined state and fault estimation. Firstly, a novel Quadratic Programming (QP) formulation is developed for a recently proposed efficient MPC method along with simultaneous state and fault estimation. Another contribution is the enhancement of a standard integral action MPC algorithm (which has an implicit fault tolerance capability), to provide state and actuator fault estimation in real time. This work focuses on faults which are modeled as a Loss Of Effectiveness (LOE). The algorithm to estimate the system faults and states simultaneously is a simple observer based method which can be tuned beforehand, thus eliminating the need for on-line real time complex calculations. Lastly, a third contribution of this thesis is the application of the above methods to design MPC based flight control systems for fixed wing aircraft. Simulations are presented to demonstrate the effectiveness of the proposed methods.


identifier: Trudeau, Émilie  (2021) How to be a Settler: Using Immersive Media and Critical Pedagogies as a Means to Unsettle.  Masters thesis, Concordia University.

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abstract: This research-creation project considers the pedagogical potential of immersive media in a process of ‘unsettling’. As conceptualized by Paulette Regan, Eric Steinman and other settler colonial scholars, ‘unsettling’ can be understood as an identificatory shift on the part of White settlers as to their positions within settler colonialism. Immersive media offers filmmakers the opportunity to harness a sense of presence and embodiedness. Inquiring into alternative pedagogies in line with Indigenous pedagogies, I explore whether these assets can be mobilized to ethically work towards unsettling with settler students of high school age. To do so, I began by exploring how an artistic practice could contribute to a deeper understanding of my settler identity by creating a personal film prompted by the 2019 Amherst street’s name change to Atateken. I worked with Indigenous filmmakers to create their own 360° films, and used the above as the basis for study guides intended for high school students.


identifier: Olyaei, Farnaz  (2021) Identification of genes encoding β-ketoadipate pathway enzymes in biodegradation of aromatic compounds by Aspergillus niger.  Masters thesis, Concordia University.

abstract:
Fungi, together with bacteria, are responsible for the degradation of aromatic compounds in the environment. The β-ketoadipate pathway is a common pathway for the cleavage of dihydroxylated aromatics such as catechol but while the bacterial enzymes for this pathway have been well-characterized, those from fungi have not.
This pathway in bacteria includes two branches: one with six enzymes to convert catechol to acetyl coenzyme A and succinate, and the other with seven enzymes to catalyze the conversion of protocatechuate (3,4-dihydroxybenzoate) to the same products plus CO2. BLAST sequence comparisons identified genes in the Aspergillus niger genome that are likely to encode these enzymes.  Aspergillus niger cDNA was used to amplify 12 of these genes, which were subsequently cloned using ligation-independent cloning into the pLATE11 vector and the resulting plasmids were tested for expression in E.coli BL21. Of these, 4 proteins were successfully expressed and then purified using a combination of column chromatography techniques. Assays of two of these proteins combined with UV analysis of reaction intermediates indicated that they encode β-carboxymuconate cyclase (NRRL3_02586) and β-carboxymuconolactone hydrolase/decarboxylase (NRRL3_01409) activities from the protocatechuate branch of the pathway.   The β-carboxymuconolactone hydrolase/decarboxylase was shown to be a monomer and is the first such enzyme to which a sequence has been assigned.  The other two proteins, encoded by NRRL3_10507 and NRRL3_04788, were active in assays for muconate isomerase and 3-oxoadipate enol lactone hydrolase, respectively, from the catechol branch of the pathway. Both enzymes were found to be dimers.  In comparison, the bacterial muconate isomerase is a decameric enzyme with smaller subunits, while bacterial 3-oxoadipate enol lactone hydrolase is also dimeric.
These data have resulted in the identification of molecular functions for four genes encoding key enzymes in aromatic degradation by A. niger.


identifier: Desmarais, Kim  (2021) Leaving ‘Em High and Dry: An Examination of Mothers’ Experiences Accessing Services for their Children with Autism Spectrum Disorder.  PhD thesis, Concordia University.

abstract:
This dissertation reports on the results of a qualitative investigation of the experiences of mothers whose children with autism spectrum disorder were experiencing transitions into and out of adolescence. A Constructivist Grounded Theory methodology was implemented in this study. Semi-structured interviews were conducted with 78 mothers who had children between the ages of 12 and 22. Mothers’ experiences were influenced by several factors, arranged in four core categories: parent stressors (67%), services (4%), professionals (24%), and parent solutions (5%). The constructivist grounded theory process culminated with the Parents’ Perceptions Theory (PPT) emerging from the data. The PPT theory explains that maternal stress is elevated when services or clinical practices are perceived to be unhelpful. Specifically, when services or practices were perceived as not addressing the needs of the parents or child from the mothers’ perspectives, mothers reported higher stress. The PPT provides a new account grounded in mothers’ own experiences for the observation that mothers’ who actively receive services still report significant stress.
	In Study 2, the author sought to explore whether the PPT would also be evident in the daily accounts of parenting stress in parents of younger children with ASD (ages 3-11). Semi-structured interviews about daily parenting stress conducted with 20 parents (18 mothers; 2 fathers) were analyzed for the presence of the coding scheme and the PPT that emerged from Study 1. Three of the core categories were present in the data: Parent stressors (88%), services (2%), and professionals (10%). The Parents’ Perceptions Theory was also reflected. Parents’ perceptions of the usefulness of services or clinical practices were found to influence their reported stress.
     The application of Constructivist Grounded Theory across two samples of parents of children with autism spectrum disorder provided important insight into how the disconnect between parents’ perceptions of whether services are meeting their caregiving needs and the receipt of services contributes to parenting stress. The PPT suggests that delivery of services should be informed by regular assessment of parental perceptions of whether their needs are being met in order to provide better support to these families throughout the child’s lifespan.


identifier: Esmaeeli, Hamed ORCID: https://orcid.org/0000-0003-3141-6028 <https://orcid.org/0000-0003-3141-6028>  (2021) Advisory Safety System for Autonomous Vehicles under Sun-glare.  PhD thesis, Concordia University.

abstract:
Autonomous Vehicles (AVs) are expected to provide a large number of benefits such as improving comfort, vehicle safety and traffic flow. AVs use various sensors and control systems to empower driver’s decision-making under uncertainties as well as, assist the driving task under adverse conditions such as vision impairment. Excessive sunlight has been recognized as the primary source of the reduction in vision performance during daytime. Sun glare oftentimes leads to an impaired visibility for drivers and has been studied from different aspects on roadways. However, there is a lack of knowledge regarding the potential detrimental effects of natural light brightness differential, particularly sun glare on driving behavior and its possible risks.
This dissertation addresses this issue by developing an integrated vehicle safety methodology as an advisory system for safe driving under sun glare. The main contribution of this research is to establish a real-time detection of the vision impairment area on roadways. This study also proposes a Collision Avoidance System Under Sun-glare (CASUS) in which upcoming possible vision impairment is detected, a warning message is sent, and the speed of vehicle is adjusted accordingly.
In this context, real-world data is used to calibrate a psychophysical car-following model within VISSIM, a traffic microscopic simulation tool. Traffic safety impacts are explored through the number of conflicts extracted from the microsimulation tool and assessed by the time-to-collision indicator. Conventional/human-driven vehicles and different type of AVs are modeled for a straight segment of the TransCanada highway under various AVs penetration rates.
The findings revealed a significant reduction in potential collisions due to adjustment of travel speed of AVs under the sun glare. The results also indicated that applying CASUS to the AVs with a failing sensory system improves traffic safety by providing optimal-safe speeds. Furthermore, the CASUS algorithm has the potential to be integrated into driving simulators or real vehicles to further evaluate and examine its benefits under different vision impairment scenarios.


identifier: Liu, Yisi  (2021) Prediction of Hardness and Residual Stress in Orthogonal Cutting of Inconel 718.  Masters thesis, Concordia University.

abstract: Due to its high strength in high temperatures, Inconel 718 is widely used in the aerospace industry.  However, Inconel 718 is a difficult-to-cut alloy with poor machinability.  For instance, the cutting force is high in cutting Inconel 718, resulting in work-hardening of the machined surface and high residual stress in the machined surface.  When residual stress releases, the part deforms and scrapes with error beyond tolerance.  Therefore, it is necessary to predict the residual stress in the machined surface under a set of machining conditions.  By modifying the machining conditions, the residual stress in the machined surface is under control, and the part deformation is limited.  In this research, an analytical approach to the hardness and the residual stress in the machined surface in orthogonal cutting is proposed.   This research has advantages over the experiment, the conventional approach and the FEA methods.  With this approach, the cutting parameters can be optimized to minimize the residual stress in the machined surface and improve the surface integrity.


identifier: Tabakow, Elizabeth  (2021) Idealized Spaces, Internationalized Selves: Japanese Migration to Montreal, Canada, 1990-Present.  PhD thesis, Concordia University.

abstract:
This thesis explores the intersections of race, class, gender, and mobility in the lifeworlds of Japanese migrants to Montreal, Canada in the 1990s and 2000s. Following the dramatic burst of Japan’s bubble economy of the late 1980s, Japanese politicians advanced a series of large-scale changes drawing on the popularity of market deregulation and neo-liberalism. During what has become known as the post-bubble period or lost decades, successive Japanese governments rapidly dismantled Japan’s postwar social contract in the name of privatization and cost-cutting. These measures unraveled the state apparatus that had sustained decades of male single breadwinner households supported by housewives in charge of home finances, household management, and childrearing. Social and political commentators examining this period have imagined a multiplicity of bleak Japans; while some critics point to employment precarity or the postponement of marriage as the primary concerns of the present, others scour the population looking for scapegoats. Against this backdrop, young Japanese people, and especially young women, have turned to alternative life-paths both inside and outside of the archipelago to temper the social and economic pressures felt at home.

Drawing on oral histories conducted with thirty Japanese people who migrated to Montreal in the 1990s and first decades of the 2000s, as well as Japanese language media sources including widely circulated non-fiction paperbacks, television dramas, and travel writing, I argue that migration is central to Japanese youth’s ability to create idealized “neo-liberal” selves. By turning their gaze abroad, these migrants seek more flexible lifestyles free from overwork and societal expectations. Yet, in Canada they continue to struggle with the social and economic realities of late capitalism, including precarious work, racism, and isolation from the host society they had hoped to fully participate in. As such, this thesis interrogates Canadian multicultural mythology and the emancipatory power of being “on-the-move” in the contemporary world. As they navigate post-bubble Japan’s mounting pressures and the limits of Montreal’s socioeconomic racialized landscape, the stories of Japanese lifestyle migrants exemplify the constant tension between optimism and disillusionment, and agency and oppression, that characterize the search for happiness in the contemporary world.


identifier: Richard, Christopher  (2019) The Relationship Between Lattice Structure Topology and Rapid Investment Casting Performance.  Masters thesis, Concordia University.

abstract: To leverage the unprecedented design freedom of additive manufacturing (AM), this work aims to develop a design methodology for lattice structures fabricated by rapid investment casting (RIC). What lattice topological properties have the most significant impact on the overall performance in RIC, and how to improve them? The hypothesis is that the relative strut size, number of joints, joint valence, and strut angle significantly affect the performance. There is no overarching analysis of the effect that lattice topology has on casting performance. To remedy this, various lattice topologies underwent mold flow simulation, finite element analysis, casting experiments, and grain structure analysis. From the results, a set of design guidelines for RIC is created, and new lattice structures are designed. The design recommendations by importance are as follows. A relative strut size, number of joints, and joint valence should be below 0.20, 9, and 8, respectively. For mechanical performance, the strut angle distribution should include vertical, diagonal, and horizontal struts. The two proposed topologies: proposed cell and hourglass, meet all these criteria and achieve good casting and mechanical performance.


identifier: Lajevardi, Setareh Sadat  (2021) Stochastic Integrated Physician and Patient Scheduling in Multidisciplinary Clinics.  Masters thesis, Concordia University.

abstract:
In this research, we study a stochastic integrated physician and patient scheduling problem with uncertainty in demand, service times, and patients’ pathways in the context of a multidisciplinary clinic. These uncertainties were implemented in order to make our scheduling model more reflective of the real world. We propose a two-stage integer stochastic programming model where physicians’ shifts are set in the first stage while taking into account their preferences and fair distributions of workloads. In the second stage, the demand of patients from different health categories realizes and we admit a portion of them and postpone the rest to the next scheduling horizon. Then, we also allocate appointment times to admitted patients. In this stage, we also may need to reschedule patients due to either the uncertainty in service times of physicians or patients’ pathways caused by the referral of a patient by one physician to another. The second-stage objective function is to minimize the total patients’ waiting, rescheduling, and postponement costs, and physicians’ idle cost. A literature review is presented to study possible approaches toward various definitions of this scheduling problem. We solve the proposed two-stage stochastic programing model in the framework of a sample average approximation algorithm to find statistical upper and lower bounds.
Extensive computational experiments were carried out and a total of 541 instances were solved to evaluate the efficiency of the proposed solution approach and to perform sensitivity analyses. The instances were solved deterministically for the second time, considering only an average scenario for the uncertain parameters. The results show that the solutions obtained from the stochastic approach reduce the objective function value by 25% on average compared to a deterministic approach.