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The development of portable equipments, wireless sensors networks and self-powered devices in a general manner generates a strong demand for micro-energy harvesting devices. One of the most challenging ways to self power devices is the development of systems that recycle ambient energy and continually replenish the energy consumed by the system. Apart from electromechanical energy harvesting, it is also interesting to convert thermal energy, which is "available" everywhere, into suitable electrical energy. In this thesis, the thermal to electrical energy conversion from temperature fluctuations was developed and improved, and the feasibility of this technique was also confirmed by implementing the experimental experiment. Among different ferroelectric materials, PZN-4.5PT single crystal and P(VDF-TrFE-CFE) 61.3/29.7/9 mol% were chosen as active materials due to their outstanding properties under electric field. By means of some intelligent thermodynamic cycles, e.g., Ericsson or Stirling cycle, which has been presented in previous research, the efficiency of energy conversion could be improved greatly. In the first part, pyroelectric energy harvesting on PZN-4.5PT single crystals with an Ericsson cycle was mainly investigated from two aspects: frequency effect and phase transitions. It was shown that the harvested energy demonstrated a nonlinear decrease with an increase of frequency, and the optimal use of the phase transitions during the Ericsson cycle could greatly improve the harvested energy by choosing the appropriate working temperature range. Based on it, two asymmetric Ericsson models (L-H and H-L cycles) were attempted successfully, and it was confirmed that the H-L cycle is the most effective thermal energy harvesting cycle for this material. The second part concentrated on electrostatic energy harvesting by nonlinear capacitance variation on P(VDF-TrFE-CFE) 61.3/29.7/9 mol% terpolymer. Ericsson cycle was tested experimentally between 25 and 0°C and compared with the simulation from dielectric constant values obtained under DC electric field. The identical result between simulation and experiment proved the reliability of our theoretical evaluation. It was found, from simulation, that the harvested energy increased up to 240 mJ/cm3 when raising the electric field at 80 kV/mm. The further study on Ericsson and Stirling cycle was also made under different temperature and electric field conditions for evaluation. The harvested energy increases with the rising of temperature variation and electric field in both cycles, but in contrast to Ericsson cycle, Stirling cycle can harvest more energy for the same injected energy.

Le développement des équipements portables, des réseaux de capteurs sans fil et systèmes auto-alimentés d'une manière générale génère une forte demande pour les dispositifs de récupération de micro-énergie. Une des voies les plus intéressantes pour auto-alimenter des dispositifs consiste à développer des systèmes recyclant l'énergie ambiante afin de renouveler sans cesse l'énergie consommée par le dispositif. En dehors de la récupération d'énergie électromécanique, il est également intéressant de convertir l'énergie thermique, qui est «disponible» partout, en énergie électrique. Au cours de cette thèse, la conversion d’énergie thermique en énergie électrique fondée sur des variations temporelles de température a été développée et améliorée. Parmi les matériaux ferroélectriques, des monocristaux de PZN-4.5PT et le terpolymère P(VDF-TrFECFE) 61.3/29.7/9 mol % ont été choisis comme matériaux actifs en raison de leurs propriétés remarquables sous champ électrique. En utilisant des cycles thermodynamiques intelligents, par exemple, Ericsson ou à cycle de Stirling, l'efficacité de la conversion de l'énergie pourrait être considérablement améliorée. Dans la première partie, la récupération d'énergie pyroélectrique en utilisant des monocristaux de PZN-4.5PT a été principalement étudiée sous deux aspects: l'effet de fréquence et des transitions de phase sur les cycles d’Ericsson. Il a été montré que l'énergie récupérée diminue de façon non linéaire avec une augmentation de la fréquence. De plus, l’utilisation optimale des transitions de phase pendant le cycle d’Ericsson permet d’améliorer grandement l’énergie récupérée en choisissant une gamme de température de travail appropriée. A partir de ces résultats, deux cycles d’Ericsson asymétriques (LH et HL) ont été réalisés avec succès. Avec les monocristaux de PZN-4.5PT, le cycle HL est le cycle le plus efficace pour la conversion d’énergie thermique en énergie électrique. La deuxième partie traite de la récupération d'énergie électrostatique via la variation non linéaire de la capacité du terpolymère P(VDF-TrFE-CFE) 61.3/29.7/9 mol %. Un cycle d’Ericsson a été réalisé entre 25 et 0°C et comparé à sa simulation à partir de la valeur de la constante diélectrique sous champ électrique DC. La concordance entre la simulation et l’expérience a prouvé la fiabilité de notre évaluation théorique. A partir de la simulation, l'énergie récupérée augmente jusqu'à 240 mJ/cm3 en appliquant un champ électrique de 80 kV/mm. Des cycles de Stirling et d’Ericsson ont également été simulés sous différentes variations de température et champ électriques. L'énergie récupérée augmente avec l’accroissment de la variation de température et de la valeur du champ électrique appliqué et ceci quelque soit le cycle réalisé. Contrairement au cycle d’Ericsson, un cycle de Stirling peut récupérer plus d'énergie pour une même énergie injectée. / The development of portable equipments, wireless sensors networks and self-powered devices in a general manner generates a strong demand for micro-energy harvesting devices. One of the most challenging ways to self power devices is the development of systems that recycle ambient energy and continually replenish the energy consumed by the system. Apart from electromechanical energy harvesting, it is also interesting to convert thermal energy, which is “available” everywhere, into suitable electrical energy. In this thesis, the thermal to electrical energy conversion from temperature fluctuations was developed and improved, and the feasibility of this technique was also confirmed by implementing the experimental experiment. Among different ferroelectric materials, PZN-4.5PT single crystal and P(VDF-TrFE-CFE) 61.3/29.7/9 mol% were chosen as active materials due to their outstanding properties under electric field. By means of some intelligent thermodynamic cycles, e.g., Ericsson or Stirling cycle, which has been presented in previous research, the efficiency of energy conversion could be improved greatly. In the first part, pyroelectric energy harvesting on PZN-4.5PT single crystals with an Ericsson cycle was mainly investigated from two aspects: frequency effect and phase transitions. It was shown that the harvested energy demonstrated a nonlinear decrease with an increase of frequency, and the optimal use of the phase transitions during the Ericsson cycle could greatly improve the harvested energy by choosing the appropriate working temperature range. Based on it, two asymmetric Ericsson models (L-H and H-L cycles) were attempted successfully, and it was confirmed that the H-L cycle is the most effective thermal energy harvesting cycle for this material. The second part concentrated on electrostatic energy harvesting by nonlinear capacitance variation on P(VDF-TrFE-CFE) 61.3/29.7/9 mol% terpolymer. Ericsson cycle was tested experimentally between 25 and 0°C and compared with the simulation from dielectric constant values obtained under DC electric field. The identical result between simulation and experiment proved the reliability of our theoretical evaluation. It was found, from simulation, that the harvested energy increased up to 240 mJ/cm3 when raising the electric field at 80 kV/mm. The further study on Ericsson and Stirling cycle was also made under different temperature and electric field conditions for evaluation. The harvested energy increases with the rising of temperature variation and electric field in both cycles, but in contrast to Ericsson cycle, Stirling cycle can harvest more energy for the same injected energy.

The PhD thesis focuses on the performance assessment of permeable pavement systems incorporating ground source heat pumps (GSHP). The relatively high variability of temperature in these systems allows for the survival of pathogenic organisms within the sub‐base. Salmonella sp, Escherichia coli, Enterococci and total heterotrophic bacteria were analysed in order to assess potential risk to health. Supplementary carbon dioxide monitoring indicated relatively high microbial activity on the geotextile and within the lower parts of the sub‐base. Anaerobic processes were concentrated in the space around the geotextile, where carbon dioxide concentrations reached up to 2000 ppm. The overall water treatment potential was high, with up to 99% biochemical oxygen demand removal. Variable removal efficiencies have been calculated for nutrients such as ortho‐phosphate‐phosphorus, ammonia and nitrates/nitrites. Calculated Coefficients of Performance and Energy Efficiency Rates provided evidence on correctness of GSHP design. Collected data was analysed with non‐parametrical statistics and a self‐organizing map model was used to assess relationships between variables. Findings present correlations considered as low and insignificant between temperature fluctuations and pathogen numbers. Highly significant correlations (p<0.01) were calculated for influent‐effluent relationships. Air and water temperatures and water quality data variability within the systems provided evidence for the high level of biological processes leading to a low risk of pathogen transition to human.

Tests were conducted for 71 pesticides in weekly bulk (wet + dry) deposition samples collected from May 25 to September 21 over two years at two sites in the City of Winnipeg, Canada. Twenty-one pesticides and their metabolites were detected in this study and 99% of samples collected contained mixtures of two or more pesticides. Malathion and glyphosate were the largest contributors to bulk deposition in 2010 and 2011, respectively. A second study examined the mineralization of 2,4-D and 17β-estradiol using a novel in-field soil microcosm study and a series of laboratory experiments under different temperature incubations. Results indicated that temperature fluctuations do not greatly affect the amount or rate of mineralization relative to the traditionally constant laboratory incubations of 20°C; however long-term freezing of soil reduced potential mineralization over time. This research advances scientific knowledge of agri-chemical fate and provides data for strengthening current environmental policy analysis in Canada.

There are 12 species of bats that occur in Illinois; 5 of these species can be found hibernating in abandoned mines and caves in southern Illinois. Due to the destruction of their natural hibernacula, caves, many species of bats have found abandoned mines to be suitable replacement habitat. A complex of abandoned underground microcrystalline silica mines in southern Illinois owned by Unimin Specialty Minerals Corporation now provides hibernacula for 5 species of cavernicolous bats: the federally endangered Indiana bat (Myotis sodalis), little brown bat (M. lucifugus), eastern pipistrelle (Perimyotis subflavus), big brown bat (Eptesicus fuscus), and the northern long-eared bat (M. septentrionalis). Within the last 10 years the number of bats using these mines has increased dramatically, especially the Indiana bat which has increased from just over 9,000 to 43,000 hibernating in Magazine Mine. One concern of having so many endangered bats hibernating in one mine is stability. Mines were created relatively recently and are still in the process of settling. Thus, these mines might act as a potential sink, drawing in hibernating bats but potentially collapsing and killing them. Thirteen mines were surveyed for bats and for the amount of spalling that occurred over the 16-month study period from September 2006 to December 2007. Factors that could increase the amount of spalling were quantified, including temperature, moisture, and moisture variability in the material of the walls in the mines, and temperature variability. Number of hibernating bats in the mines was also documented. Data were analyzed with logistic regression. Temperature was a significant predictor of spalling (W2 = 12.76, p = 0.0004) when considered as a univariate variable, as was temperature variation (W2 = 21.89, p = <0.0001). Considering multiple logistic regression analyses, moisture was the best predictor. For the 13 mines surveyed, number of hibernating bats ranged from 0 to 3,755. Whereas all three variables were important at predicting the presence of bats, temperature variation (W2 = 35.98, p =<0.0001) was a better predictor than temperature or moisture. In a multiple logistic regression, temperature (W2 = 46.75, p = < 0.0001) and temperature variation (W2 = 20.56, p = < 0.0001) were better at predicting presence of bats then was moisture. The less variation in temperature the more likely that bats will be present. Because bats prefer stable temperatures and spalling occurs more often at high variability of temperatures and very low temperatures, bats were usually in areas that exhibited little or no spalling.

Yes / Polymer extrusion is an energy intensive production process and process energy e ciency has become a key concern in the current industry with the pressure of reducing the global carbon footprint. Here, knowledge of the pattern of energy usage and losses of each component in the plant is highly useful in the process energy optimization. Moreover, it is essential to maintain the melt quality while improving the energy e ciency in polymer processing. In this work, an investigation was made on the total energy consumption, drive motor energy consumption, power factor and the melt temperature profile across the die melt flow (as an indication of the melt thermal quality) of an industrial scale extruder with three di erent screw geometries, three polymer types and wide range of processing conditions (altogether 135 di erent processing situations were observed). This aims to widen the knowledge on process energy and thermal behaviors while exploring possible correlation/s between energy demand and melt quality (in terms of melt temperature fluctuations across the melt flow). The results showed that the level and fluctuations of the extruder’s power factor is particularly dependent upon the material being processed. Moreover, it seems that there is a relation between the level of energy demand of the heaters and the level of melt temperature fluctuations. While the extruder specific energy consumption decreases with increasing screw speed, specific energy consumption of the drive motor may have either increasing or decreasing behavior. Overall, this study provides new insights in a wide range on process energy demand and melt thermal quality in polymer extrusion. Moreover, further research is recommended to establish strong correlation/s between process energy consumption and melt thermal quality which should help to enhance process control and hence the product quality in single screw polymer extrusion.

As climate change exacerbates heat stress during the summer season, it becomes increasingly critical to develop effective strategies to safeguard the productivity of tomato plants (Solanum Lycopersicon L.). This research delves into the tools and techniques aimed at enhancing the cultivation of summer tomatoes in the coastal region of Virginia. The study explores the optimization of transplant dates, the implementation of reflective mulches, and the application of kaolin clay particle films. Field trials spanning two seasons were carried out, comparing different planting dates in May, June, and July, as well as the use of reflective, black, and white plastic mulches, both with and without foliar kaolin sprays. The findings of this study underscore the impact of transplanting tomatoes in May, demonstrating a substantial increase in yields when compared to transplanting in June and July. Reflective mulches enhanced plant height and fruit production relative to the conventional black plastic mulch. The combination of kaolin clay sprays with standard black mulch, resulting in yield increases of over 35%, rivaling the outcomes achieved with reflective and white mulch treatments. The application of kaolin did not significantly affect leaf-level physiological processes. These results highlight the significant potential of strategic early planting and the adoption of emerging heat mitigation technologies, such as kaolin clay films, in sustaining and enhancing the productivity of summer tomatoes. This becomes particularly relevant as growing conditions continue to evolve due to rising temperatures and the increasing extremity of weather events resulting from climate change. / Master of Science in Life Sciences / With the challenge of hotter summers due to climate change, finding effective ways to grow tomatoes is more crucial than ever. In our two-season study in Virginia's coastal region, we experimented with various methods to improve tomato growth in these warmer conditions. What we discovered was quite promising. Planting tomatoes in early May resulted in significantly better yields than later planting times. Using reflective mulch was beneficial too; it helped the plants grow taller and produce more fruit compared to traditional black mulch. However, the most impressive result came from combining kaolin clay spray with black mulch. This approach led to a matching of the performance of black plastic plus the combination of kaolin clay against reflective and white mulches. It's interesting to note that the kaolin spray didn't alter the basic functioning of the plants at the leaf level. These findings are encouraging. They suggest that early planting and innovative approaches like kaolin clay sprays can effectively boost tomato production, even as we contend with rising temperatures and evolving climate patterns. Embracing these strategies could be key to successful tomato farming in an era of climate change

In this article a Novikov engine with fluctuating hot heat bath temperature is presented. Based on this model, the performance measure maximum expected power as well as the corresponding efficiency and entropy production rate is investigated for four different stationary distributions: continuous uniform, normal, triangle, quadratic, and Pareto. It is found that the performance measures increase monotonously with increasing expectation value and increasing standard deviation of the distributions. Additionally, we show that the distribution has only little influence on the performance measures for small standard deviations. For larger values of the standard deviation, the performance measures in the case of the Pareto distribution are significantly different compared to the other distributions. These observations are explained by a comparison of the Taylor expansions in terms of the distributions’ standard deviations. For the considered symmetric distributions, an extension of the well known Curzon–Ahlborn efficiency to a stochastic Novikov engine is given.

Tato práce popisuje výzkum zaměřený na studium vertikálních teplotních profilů a fluktuací v turbulentní Rayleighově-Bénardově konvekci. Experiment byl proveden v "Barrel of Ilmenau" obsahující válcovou experimentální celu s průměrem 7,15 m a výškou 4,7 m ("the aspect ratio" = 1,5) naplněnou suchým vzduchem. Teplotní profily a fluktuace byly studovány podél vertikální osy cely mezi horní a spodní deskou spodní deskou v rozmezí Rayleighova čísla (Ra) 1E11 4E12. Teplotní profily byly změřeny novou metodou využívající systém s optickým vláknem Luna ODiSI-B, který byl pořízen týmem z Ilmenau. Systém umožňuje měřit teplotní profil ve všech bodech podél celého vlákna současně s prostorovým rozlišením 5 mm.