Solar domestic hot water (SDHW) systems collect energy with a solar collector, transfer the energy to the water through a heat exchanger, and store it in a storage tank. The water in the tank should be thermally stratified to the highest possible degree to maximize system efficiency because a stratified tank has higher availability than a mixed tank temperature. The objective of this research is to develop a manifold that will enhance thermal stratification in the SDHW tank. In this work a new immersion shell-and-coil heat exchanger with a perforated manifold that extends from the heat exchanger to the top of the tank was used to enhance the thermal stratification. The purpose of the perforated manifold is to deliver the water heated by the heat exchanger to the tank at the level where the temperature of the water in the tank matches the temperature of the heated water, thereby enhancing stratification. The effectiveness of the perforated manifold was determined experimentally. An experimental set-up was designed and constructed. The experimental results were analyzed for each manifold design then compared to determine the most effective manifold. The experimental work included testing and comparing different manifold designs. To simulate an actual system, experiments were conducted on three initial tank conditions, namely cold, hot, and mixed tank conditions. The thermal performance of the system in terms of tank availability and entropy, maximum tank temperature, and thermal stratification were studied. A method to determine and design a perforated manifold that works with the standard Canadian SDHW system was established and evaluated experimentally. An availability analysis approach was developed to evaluate the thermal performance of manifolds, which have been operated at different times of the year. Theoretically, gradually increasing the diameter of the holes in the manifold from the bottom into the top should reduce the unwanted flow of cold water from the bottom of the tank to the manifold and enhance the thermal performance of the manifold. However, the experimental did not confirm this.

Climate change will affect all freshwater ecosystems via both direct physiological and indirect, biologically-mediated effects. Small lakes (< 10 ha) numerically dominate the Boreal Shield and represent an important habitat for aquatic biota. Small, shallow lakes are particularly responsive to climate-induced changes in thermal structure. Furthermore, biological interactions may be particularly important in small lakes where space, habitat heterogeneity, and thermal refugia are limited. Therefore, it is critical to understand and predict the consequences of climate change for community dynamics in small Boreal Shield lakes. Using 10 years of monitoring data and a field experiment I tested for differences in crustacean zooplankton community structure between warm and cool lake habitats. I classified years from a small, shallow Boreal Shield lake as ‘warm’ or ‘cool’ based on several characteristics of lake thermal structure. Since macroinvertebrates are often the main predators in small, shallow lakes, I further tested for potential interactions between lake thermal structure and spatially-dependent macroinvertebrate predation using in situ mesocosms. Body sizes of two ubiquitous crustacean zooplankton taxa, Leptodiaptomus minutus and Bosmina spp., were reduced in warm years, but no differences in abundance or diversity were detected at the annual scale. In contrast, in 15d enclosure experiments, crustacean zooplankton abundance and calanoid copepodid body size were reduced by the vertically-migrating predator Chaoborus punctipennis, but only in warm isothermal conditions. Zooplankton lowered their daytime depth distribution to avoid the surface-orienting notonectid predator, Buenoa macrotibialis, regardless of thermal habitat. No predation effect was detected in a hot (25ºC) isothermal habitat where both Chaoborus and notonectids were likely heat-stressed. Differences in abundance effects between the enclosure and monitoring data are likely due to the scales at which the analyses were conducted. Over short timescales predator-prey dynamics depended on lake thermal structure. However, over annual timescales zooplankton response was averaged across periods of seasonal change in thermal structure and biological processes, which may dampen the short-term effects associated with strong predation in isothermal conditions. Therefore, the importance of macroinvertebrate predators in regulating crustacean zooplankton community structure may increase if small lakes become progressively more isothermal with future climate change. / Thesis (Master, Biology) -- Queen's University, 2009-03-31 13:29:35.975

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No description available.

No description available.

Statistical methods that integrate between-individual (IA) and within-family (FA) genetic association analyses can increase statistical power to identify disease susceptibility genes, however combining IA and FA is valid only when the IA are free of population stratification bias (PSB). Existing methods initially test for PSB by comparing IA and FA results using an arbitrary testing level αPSB, typically 5%. Combined analyses are performed if no significant PSB is detected, otherwise analyses are restricted to FA. As a novel alternative, we propose a weighted (WGT) framework that combines the estimate from the most powerful analysis subject to PSB with the most powerful robust FA estimate, using weights based on the p-value from the PSB test. The WGT approach generalizes existing methods by using a continuous weighting function that depends only on the observed PSB p-value instead of a binary one that also depends on specification of an arbitrary PSB testing level αPSB. Simulations of quantitative trait and case-control data show that in comparison to existing methods, the WGT approach has 5% type I error closer to the nominal level, increased (decreased) accuracy for larger (smaller) PSB levels, and overall increased positive predictive value. The resulting PSB correction is SNP-specific and provides a good compromise between type I error control and power in candidate gene or confirmation studies limited to few loci, when PSB is likely and there are no additional empirical data available to correct PSB. We applied the WGT approach to a case-control study of childhood leukemia and a study of diabetes complications with time-to-event outcomes derived from repeated measurements obtained over 17 years of follow-up. To directly analyze the longitudinal measurements without specification of event thresholds, we developed fully Bayesian latent change-point time (LCPT) models for IA and FA. In analogy with the WGT approach, we also considered an extended LCPT model incorporating PSB evidence in analyses combining IA and FA.

Statistical methods that integrate between-individual (IA) and within-family (FA) genetic association analyses can increase statistical power to identify disease susceptibility genes, however combining IA and FA is valid only when the IA are free of population stratification bias (PSB). Existing methods initially test for PSB by comparing IA and FA results using an arbitrary testing level αPSB, typically 5%. Combined analyses are performed if no significant PSB is detected, otherwise analyses are restricted to FA. As a novel alternative, we propose a weighted (WGT) framework that combines the estimate from the most powerful analysis subject to PSB with the most powerful robust FA estimate, using weights based on the p-value from the PSB test. The WGT approach generalizes existing methods by using a continuous weighting function that depends only on the observed PSB p-value instead of a binary one that also depends on specification of an arbitrary PSB testing level αPSB. Simulations of quantitative trait and case-control data show that in comparison to existing methods, the WGT approach has 5% type I error closer to the nominal level, increased (decreased) accuracy for larger (smaller) PSB levels, and overall increased positive predictive value. The resulting PSB correction is SNP-specific and provides a good compromise between type I error control and power in candidate gene or confirmation studies limited to few loci, when PSB is likely and there are no additional empirical data available to correct PSB. We applied the WGT approach to a case-control study of childhood leukemia and a study of diabetes complications with time-to-event outcomes derived from repeated measurements obtained over 17 years of follow-up. To directly analyze the longitudinal measurements without specification of event thresholds, we developed fully Bayesian latent change-point time (LCPT) models for IA and FA. In analogy with the WGT approach, we also considered an extended LCPT model incorporating PSB evidence in analyses combining IA and FA.

Conventional concrete is a poor insulating material but has good thermal mass, while lightweight concrete provides good insulation at the price of thermal mass. Precast concrete wall systems have not been widely used in residential homes due to poor thermal and acoustic performance, despite being high quality products that are easy to construct. The variable density concrete panel was designed to combine good thermal storage, insulation and high quality precast concrete. It is produced from a single concrete mix which is vibrated to get a lightweight top layer and a normal/heavyweight bottom layer. The lightweight layer is the wall exterior, having low thermal conductivity providing good thermal insulation while the normal/heavyweight layer is the dense wall interior, having high specific heat to provide good thermal mass and sufficient strength for construction handling and to withstand service loads. The intention of this research was to estimate the hardened performance; that is the structural, serviceability and durability performance of the variable density concrete panel. Further developments to the mix design were made where the fresh properties were measured and thermal performance estimated on hardened specimens. Most of the major technical concerns were proved not being as severe as first thought, making the production of variable density concrete panels promising. To ensure that the variable density concrete would stratify, the concrete mix had to have defined fresh properties. Defined rheological ranges gave a good indication of the stratification potential, but the degree of stratification was also found to be dependent on the intensity and time of vibration. Slump flow had to be within a certain range to achieve good stratification but this alone did not guarantee stratification. Variable density concrete was found to have adequate strength capacity both in axial compression and in tension for likely service loads but the strength required to withstand handling loads at early ages was not assessed. The strength of the variable density concrete was found to be affected by several factors such as; degree of stratification, relative strength and thickness of the layers, curing environment and amount of defects. As the stratification of the concrete increased the thermal insulation improved whereas the strength decreased. Warping was found not to significantly affect the serviceability of panels despite differential shrinkage within the element. The amount of warping was mainly related to the degree of stratification. Warping decreased with better stratification as more stress and strain was relieved in the lightweight layer. The lightweight concrete was significantly weaker as well as being less stiff than the structural concrete and therefore creeps to follow the structural concrete. The thermal properties aimed for were generally not reached, but these mixes were not designed to optimise the thermal performance and were tested before the concrete was fully dried. This increased thermal conductivity and therefore reduced the measured R-values. Stratified concrete had good absorption resistance, poor permeability properties and was highly porous. If the concrete was over-vibrated it tended to have a rough surface finish that would require a coating. Delamination of the panels was not assessed in this research but is a likely mode of failure.

Nous étudions la stratification de Newton des variétés de Shimura de type PEL aux places de bonne réduction. Nous considérons la strate basique de certaines variétés de Shimura simples de type PEL modulo une place de bonne réduction. Sous des hypothèses simplificatrices nous prouvons une relation entre la cohomologie l-adique de ce strate basique et la cohomologie de la variété de Shimura complexe. En particulier, nous obtenons des formules explicites pour le nombre de points dans la strate basique sur des corps finis, en termes de représentations automorphes. Nous obtenons les résultats à l'aide de la formule des traces et de la troncature de la formule de Kottwitz pour le nombre de points sur une variété de Shimura sur un corps fini. Nous montrons, en utilisant la formule des traces, que n'importe quelle strate de Newton d'une variété de Shimura de type PEL de type (A) est non vide en une place de bonne réduction. Ce résultat a déjà été établi par Viehmann-Wedhorn; nous donnons une nouvelle preuve de ce théorème. Considérons la strate basique des variétés de Shimura associées à certains groupes unitaires dans les cas où cette strate est une variété finie. Alors, nous démontrons un résultat d' équidistribution pour les opérateurs de Hecke agissant sur cette strate. Nous relions le taux de convergence avec celui de la conjecture de Ramanujan. Dans nos formules ne figurent que des représentations automorphes cuspidales sur Gl_n pour lesquelles cette conjecture est connue, et nous obtenons donc des estimations très bonnes sur la vitesse de convergence. En collaboration avec Erez Lapid nous calculons le module de Jacquet d'une représentation en échelle pour tout sous-groupe parabolique standard du groupe général linéaire sur un corps local non-archimédien.

Förevarande studie tar sin utgångspunkt i ett Stockholm satt i förändring. Som allt mer inbäddat i en global och post-industriell ordning skapas nya konfigurationer i gruppers sociala och kulturella mönster – i studien begreppsliggjort och analyserat genom livsstilar - och hur dessa sammanbinds med specifika platser. Särskilt intressant är det att få insikt i hur de i Stockholms socioekonomiskt svaga ytterstadsområden upplever, deltar i och tillägnar sig innerstaden, som en plats där processer av gentrifikation och stegrande kulturkonsumtion gradvis omförhandlar villkoren för vad ett besök kan och bör bestå i. För studiens räkning har en rad livsvärldsintervjuer skett med unga vuxna boende eller med härkomst i miljonprogramsområdena i Järva (Kista, Akalla, Rinkeby, Tensta och Rissne) i västra Stockholm, där deras berättelser ger uttryck för deras unika förhållanden till kvaliteterna i stadens socialt skiktade rum. Redan under ungdomsåren kommer innerstaden att representera något sublimt i en stadsmiljö diametralt annorlunda Järva, och genom betingelserna av den blå tunnelbanelinjen beskriver flera informanter hur ett utforskande tog vid av den nyupptäckta platsen. I vuxen ålder tonar innerstaden till stora delar upp som tydligt kopplat till selektiva nyttjanden i form av konsumtionen av varor och nöjen – där i synnerhet krog- och klubbscenen visar sig vara föremål för besök - men inbjuder för merparten av informanterna sällan till ett mer villkorslöst, icke-konsumerande fördröjande i de offentliga rummens gator, torg och parker. I själva erfarenheten av Stockholm är dikotomin förort - innerstad tydlig och genererar en diskursiv schematik mina informanter på olika sätt förhåller sig till.