Various aspects of population ecology of Daubenton?s bat (Myotis daubentonii) were analyzed based on long-term data (1968?1984 and 1999?2009) gathered in a single model study area (ca. 10 km2) in South Bohemia, Czech Republic. Among others, population structure, roosting dynamics, movements between roosts and long-term trends in numbers of bats were described. Results of the study on patterns in reuse of tree cavities suggest that tree cavities may be reused for many consecutive seasons and that this has to be taken into consideration by conservation practices. The results of the study on microclimate of one maternity and one male colony roosting in man-made structures revealed that microclimatic differences may be one of the key factors in roosting preference between the two sexes. Further, a profound effect of changing energetic demands in females during different phases of the reproductive cycle may greatly influence their activity rhytms. In further two studies, the effect of climate on reproductive parameters of bats and abundance of ectoparasitic mites was analyzed. The results suggest that climatic variation greatly influenced reproductive parameters and parasitation of Daubenton?s bats. Last but not least, the seasonal dynamics of parasitation by ectoparasitic mites and the possible effect on bats? condition was analyzed. It was found out that seasonal dynamics in abundance of parasites is adjusted to the reproductive cycle and roosting dynamics of its host.

La compression, nécessaire à la transmission des images numériques diffusées sur les télévisions, est responsable de dégradations appelées artefacts. Pour obtenir des images de meilleure qualité, la correction des artefacts doit être efficace, robuste au large panel dimages diffusées, et simple pour que ces images soient traitées en temps réel avant leur diffusion. Pour obtenir ce compromis, notre étude se divise en 3 axes : l'estimation, la mesure et la correction.<br />En estimant quels sont les artefacts les plus gênants et les risques encourus à les corriger, nous définissons la problématique de ce travail : comment corriger les effets de bloc et de ringing qui sont des artefacts de compression sans risquer de faire apparaître un artefact de correction tel que le flou ?<br />Les métriques objectives, validées par des tests subjectifs, permettent de mesurer ces artefacts. L'étude de l'état de l'art, associée à la modélisation de notre manière de percevoir ces artefacts, nous permet d'aboutir au développement du BLE (Block Level Estimator) et du BluM (Blur Metric), métriques objectives destinées à estimer respectivement leffet de bloc et le flou sur une image. <br />La correction de l'effet de bloc et de l'effet de ringing peut ensuite être guidée et validée par ces métriques. Nous proposons des modules permettant d'améliorer, de rendre plus robustes et d'implémenter facilement les corrections existantes. Puis, pour résoudre la problématique, nous intégrons ces modules dans une solution générale appelée SQDSE (Studio Quality Digital Source Enhancement) destinée à supprimer les effets de bloc et de ringing. La structure du SQDSE et sa validation par des tests visuels et par les résultats du BLE et du BluM montrent que le compromis entre l'efficacité, la robustesse et la simplicité est atteint.

L'évaluation de la qualité d'image est un élément critique dans de nombreuses applications multimédias et en particulier lorsque l'observateur est le juge ultime. En général, le contrôle de la qualité des systèmes d'acquisitions de données est réalisé à partir de l'évaluation de la qualité d'image subjective. Cependant, les méthodes d'évaluation psycho-visuelle sont complexes, non reproductibles et dépendent de nombreux facteurs. Ces contraintes ont conduit alors à l'élaboration de nouvelles approches objectives basées sur des techniques d'analyse du signal image. Ainsi, au cours des deux dernières décennies, de nombreuses méthodes d'évaluation de la qualité d'image ont été proposées. Cependant, il n'existe pas actuellement de métrique de qualité d'image standard. L'objectif de ce travail de thèse est de proposer une approche multidimensionnelle de l'évaluation de la qualité d'image. Nous avons ainsi développé un nouveau système d'estimation de la qualité d'image (avec et sans référence) basée sur l'identification et la classification des artefacts. Cette connaissance a priori est ensuite utilisée pour sélectionner la métrique la plus appropriée. Les résultats obtenus sont très encourageants et invitent à progresser selon la démarche proposée en enrichissant le système développé par l'étude d'autres distorsions.

Species’ ranges arise from the interplay between environmental preferences, biotic and abiotic environmental conditions, and accessibility. Understanding of – and predictive models on – species distributions often build from the assumption that these factors apply homogenously within each species, but there is growing evidence for individual variation. Here, I use movement data to investigate individual-level decisions and compromises regarding the different costs and benefits influencing individuals’ geographic locations, and the species-level spatial patterns that emerge from these. I first developed a new method that uses tracking data to quantify individual specialisation in geographic space (site fidelity) or in environmental space (environmental specialisation). Applying it to two species of albatrosses, I found evidence of site fidelity but weak environmental specialisation. My results have implications for how limited research efforts are best-targeted: if animals are generalists, effort are best spent by understanding in depth individual patterns, i.e., better to track fewer individuals for long periods of time; whereas if animals tend to be specialists, efforts should be dedicated to tracking as many individuals as possible, even if for shorter periods. I then investigated individual migratory strategies and their drivers in nine North American bird species, using ringing/recovery data. I found latitudinal redistribution of individuals within the breeding and non-breeding ranges that generally did not follow textbook patterns (‘chain migration’ or ‘leapfrog migration’). Migratory individuals tend to trade off the benefits of migration (better tracking of climatic niche; better access to resources) and its costs (increasing with migratory distance). I found that birds are more likely to remain as residents in areas with warmer winter temperatures, higher summer resource surpluses and higher human population densities (presumably because of a buffering effect of urban areas). Overall, my results highlight the importance of considering individual variation to understanding the ecological processes underpinning species’ spatial patterns.

This work deals with high power pulse converters (tens of kW) using new semiconductor devices of silicon carbide (SiC). Firstly the current state of the issue is analyzed. A research in a specific area of high power buck converters with pulse transformer follows. There was a strong emphasis on minimizing size and weight. The design process was focused also on reliability and robustness. To achieve the defined objectives, it was necessary to use the latest available switching transistors and diodes, and an unusually high switching frequency (100 kHz at a power of about 16 kW). Due to the high switching frequency, we achieved small size of pulse transformers and output chokes. An optimization of high-frequency pulse transformer with demand on minimum volume and weight of core and windings represents a separate theoretical part of the thesis. There have been proposed several analytical solutions of optimization problems, the results of which could overlap with the implementation in practice of switching power supplies. The combination of high switching frequency, fast semiconductors and the high power brings various parasitic effects to the power circuit. In the thesis, these parasitic effects are analyzed. Solutions which minimize or completely remove those effects were theoretically designed and successfully implemented, tested and finalized in experimental part of the work. Detailed description of the implementation of functional sample and series of validation measurements are included in the final part.

Solar Bora AB is a Linköping based company that provides end to end solution for clean and reliable energy. System developed by them generates high power 230V AC to run electrical appliances. The system consist of string of batteries which are charged by rooftop solar cells and the energy stored in the batteries is converted to AC to provide a grid voltage like experience even though the system is not connected to a grid. Energy stored in the batteries need to be converted from DC to AC efficiently. Inverter used for conversion should be efficient enough to reduce losses. This master thesis deals with optimization and Up-gradation of Half-Bridge inverter board so that switching loss can be minimized to increase efficiency. Initial part of the thesis involves investigation of different parameters which contribute to losses in inverter. Based on that some improvements were suggested in existing design of half-bridge board. Another task involved in the thesis was complete re-design of half-bridge. More efficient and robust components were selected for complete re-design. Based on new components and its specifications a new circuit and PCB was designed in Altium Designer. Lab testing was performed to verify the functionality of new Half-bridge.

This master thesis presents an analogue peak holder circuit design aimed at facilitating the non-invasive inspection of the ageing process in electric drives. The ageing process of electric drives is a crucial aspect that demands accurate monitoring to ensure their long-term performance and reliability. The proposed peak holder circuit is specifically designed to detect fast and narrow-width pulses of ringing current present in the PWM drive current. By capturing and measuring the peak values of these pulses, the circuit provides valuable insights into the ageing characteristics of electric drives. Experimental results demonstrate the remarkable efficiency of the peak holder circuit in accurately detecting and quantifying the peak values of the ringing current pulses. The circuit exhibits a stable output swing within a specified effective input swing range, with low mean-squared error (MSE) values. This signifies a strong linear correlation between the input and output signals, enhancing the reliability of the ageing detection process. The ability of the peak holder circuit to effectively detect and analyze the ageing process of electric drives offers numerous advantages. By focusing on peak detection, which captures the highest values of the ringing current, the circuit provides a more efficient and targeted approach to inspecting the ageing process. This enables engineers and maintenance personnel to gain crucial insights into the degradation and performance of electric drives, allowing for timely interventions and proactive maintenance. / Detta examensarbete presenterar en nyutvecklad kretslösning för toppvärdesdetektering hos elektriska drivsystem, med målet att underlätta ickeinvasiv övervakning av åldrandesprocessen hos eldrivsystem. Åldrandet hos eldrivsystem är en avgörande faktor som kräver noggrann övervakning för att säkerställa deras långsiktiga prestanda och tillförlitlighet. Den föreslagna kretsen för att detektera toppvärden är specifikt utformad för att detektera snabba och kortvariga ringningar i PWM-modulerade strömmar. Genom att mäta toppvärdena ger kretsen värdefull information om åldrandekaraktären hos eldrivsystemen. Experimentella resultat visar på den enastående effektiviteten hos spetsdetekteringskretsen för att noggrant detektera och kvantifiera toppvärdena hos ringningarna i strömmen. Kretsen uppvisar en stabil utsignal inom ett specificerat ingångsintervall, med låga medelkvadratiska felvärden (MSE). Detta indikerar en stark linjär korrelation mellan ingångs- och utgångssignalerna, vilket förbättrar tillförlitligheten hos åldersdetektionsprocessen. Krestsens förmåga att effektivt detektera och analysera åldrandeprocessen hos eldrivsystem erbjuder flera fördelar. Genom att fokusera på toppvärdesdetektering, som fångar de högsta värdena av ringströmmen, ger kretsen ett mer effektivt och riktat tillvägagångssätt för att inspektera åldrandet. Det möjliggör för ingenjörer och underhållspersonal att få viktig information om nedbrytning och prestanda hos eldrivsystem, vilket möjliggör tidiga insatser och proaktivt underhåll.

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Wound Field Synchronous Generators provide more than 95% of the electricity need worldwide. Their primacy in electricity production is due to ease of voltage regulation, performed by simply adjusting the direct current intensity in their rotor winding. Nevertheless, the rapid progress of power electronics devices enables new possibilities for alternating current add-ins in a more than a century long DC dominated technology. Damping the rotor oscillations with less energy loss than before, reducing the wear of the bearings by actively compensating for the mechanic unbalance of the rotating parts, speeding up the generator with no need for additional means, these are just few of the new applications which imply partial or total alternated current supplying of the rotor winding. This thesis explores what happens in a winding traditionally designed for the direct current supply when an alternated current is injected into it by an inverter. The research focuses on wound field salient pole synchronous machines and investigates the changes in the field winding parameters under AC conditions. Particular attention is dedicated to the potentially harmful voltage surges and voltage gradients triggered by voltage-edges with large slew rate. For this study a wide frequency band simplified electromagnetic model of the field winding has been carried out, experimentally determined and validated. Within the specific application of the fast field current control, the research provides some references for the design of the rotor magnetic circuit and of the field winding. Finally the coordination between the power electronics and the field winding properties is addressed, when the current control is done by means of a long cable or busbars, in order to prevent or reduce the ringing.