<p> The speed of a squirrel-cage induction motor is controlled by varying the supply frequency. The design of an SCH controlled inverter, using gating from a logic unit to give a variable-frequency power-level output, is described.</p> / Thesis / Master of Engineering (MEngr)

The growing demand for compact and compliant mobility assistive devices has driven interest in low-profile actuating technologies. With the increasing mobility needs of an aging population, such devices could meet this growing market if they can provide low power capabilities, high strength, and compatibility with standard industrial fabrication processes. As a result, researchers have been investigating smart materials, such as carbon nanotube (CNT) and their higher-order structures, as potential components for soft actuator systems. However, reported works using this material within actuators have remained limited due to the material's prohibitive cost and fabrication complexity. Furthermore, presented actuator designs are difficult to compare due to custom fabrication procedures and inconsistent characterizations. The recent availability of commercial higher-order CNT products and the superior material consistency they provide present an opportunity to comprehensively analyze these materials in actuators without the challenges faced in previous work. This thesis addressed this opportunity by evaluating a stiffness-variable actuator design leveraging a commercially available CNT fibre. The evaluation focused on the effects on the mechanical and electrical properties in addition to its electrothermal and electromechanical responses when changing selected actuator design and operational parameters. The findings highlight the importance of optimal coating and embedded pre-stretch to achieve optimal contractile stress and contractile strain performance, while increased fibre diameter diminishes these properties. Furthermore, the usage of commercial CNT yarn ensured consistent mechanical and electrical properties during the fabrication and testing of actuator prototypes. This in-depth understanding of this actuator design's strengths, weaknesses, and the influence of selected operational and design parameters on performance establishes a foundation for future CNT-based actuator research within a repeatable framework.

This thesis is a collection of three articles in applied economics that explore food security and social cohesion among population affected by violence and forced displacement. Chapter II aims at quantifying the effect of violent conflict on food security and dietary quality in Iraq. Specifically, I estimate the effect of physical insecurity on caloric availability and household dietary diversity by using an instrumental variable (IV) approach. Results show that conflict has a positive (negative) effect of on per capita caloric availability (household dietary diversity). The direction of this relationship, although seemingly counterintuitive, is unsurprising given Iraq’s relatively high-income levels and large public food distribution system. Overall, the results suggest that, for countries transitioning to diets high in calories and fat, violent conflict may drive the population towards an unhealthier diet and may thus contribute to the nation’s growing prevalence of nutrition-related non-communicable diseases. In the third Chapter, I use a household dietary diversity score and a food consumption score to measure the effect of structural and physical Israeli settler violence on Palestinian food security in the occupied West Bank. In doing so, I employ a novel instrumental variable which correlates with settlement proximity while remaining exogenous to other confounders. According to the main results, both the presence of settlements and the insecurity they generate have a statistically significant negative effect on food security via continuous violence against Palestinians and their properties. This finding is further supported by a supplemental analysis of two potential underlying mechanisms: access to water and commuting time to the closest food market. The last empirical article in Chapter IV assesses the impact of the Education Program for Syrian Refugees and Host Communities (BILSY) implemented in Turkey. BILSY relied on positive contact to enhance trust and reciprocity among Syrian and Turkish children. Exploiting a unique primary data on Syrian and Turkish children, we1 investigate whether the BILSY program was effective in promoting social cohesion (altruism and trust) among them by running both dictator and trust games. The sample for the study is drawn from the BILSY program participants and it comprises 685 individuals of Turkish and Syrian background aged between 6 and 11 years old. Since all the participants received the treatment at some point, we randomized the time of interview, namely before or after receiving the treatment. We relied on the short length of the activities implemented to mimic a randomized control trial. Our results show that the program does not significantly affect the participants’ decisions during the games, neither towards children of different nationality, nor toward other fellow citizens.

Sex-dependent differences in the prevalence of diabetes and cardiovascular diseases are well established. The objective of this project is to investigate the molecular mechanisms by which estrogen modulates chronic disease progression. Our lab, and others, have previously implicated endoplasmic reticulum (ER) stress in the development and progression of diabetes and cardiometabolic disease. We hypothesize that estrogens protect pancreatic beta cell health, and slow the progression of cardiometabolic disease, by modulating the unfolded protein response (UPR) in response to ER stress. Two distinct mouse models were used in these studies. The ApoE-/-Ins2+/Akita mouse model of hyperglycemia-induced atherosclerosis, in which females are significantly protected from hyperglycemia and atherosclerosis relative to males, and the TALLYHO/JngJ mouse model, in which females are protected from chronic hyperglycemia relative to males. We found that ovariectomy of female ApoE-/-Ins2+/Akita or TALLYHO/JngJ mice promoted chronic hyperglycemia. Supplementation with exogenous 17-beta estradiol significantly lowered blood glucose levels in ovariectomized ApoE-/-Ins2+/Akita mice and reduced atherosclerotic lesion development in both male and ovariectomized female mice. Pancreatic islets from sham operated ApoE-/-Ins2+/Akita female mice showed a significant increase in the expression of protective UPR factors and a decrease in pro-apoptotic factors, compared to males or ovariectomized females. To determine if alleviating ER stress could moderate hyperglycemia, male and ovariectomized female TALLYHO/JngJ mice were treated with the chemical chaperone 4-phenylbutryic acid (4-PBA). We showed that 4-PBA treatment significantly lowered fasting blood glucose levels and improved glucose tolerance. The results of this thesis suggest that estrogens play a protective role in the maintenance of beta cell health and blood glucose regulation by activating the adaptive UPR. This mechanism may explain the protection observed in premenopausal women and may lead to the development of targeted therapies to treat diabetes and cardiometabolic diseases. / Thesis / Doctor of Philosophy (PhD) / People who suffer from diabetes mellitus have a higher risk of developing heart attack and stroke compared to those who do not have diabetes. Moreover, the risk of heart attack and stroke is higher in men than in women. We still do not understand the underlying reasons for these differences. This thesis project has used unique mouse models that display many of the same sex differences in disease progression that we see in humans to study the pathways and mechanisms that promote diabetes development. Specifically, we examined the protective effects of estrogen towards the development of diabetes and cardiovascular disease and how this hormone affected specific cells and tissues. The results of these studies are important because they will provide more information regarding the effects of menopause and aging on chronic disease progression in women.

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