Water quality in streams around the world continues to be degraded by a series of human activities that feed pollutants into the vulnerable stream ecosystem via surface and subsurface runoff. This continues to accelerate global biodiversity and habitat losses within the stream environments and across entire watersheds with net adverse effects on public health and the ability of communities and ecosystems to adapt or become resilient to the prevalent impacts of climate change. One commonly used approach for protecting stream water from pollution is the use of vegetated riparian buffer zones to mitigate pollutants in surface and subsurface runoff prior to runoff entry into the stream channel. The optimal success of this approach requires land and water resource managers to understand the mechanisms by which riparian buffer zones function and the full range of factors that influence the effectiveness of riparian buffer vegetation in abating stream water pollution. Despite this need, resource managers in different geographical locations around the world still struggle to understand the linkages between riparian vegetation and stream chemical quality. This literature review therefore sought to synthesize findings from various scientific articles on the ways in which the major attributes of riparian vegetation [type, age, width, restoration and shading effect] influence the effectiveness of riparian vegetation in protecting the chemical quality of water in streams. This was aimed at generating conclusions and perspectives that could improve academic knowledge and natural resource managers’ understanding of the intricate linkage between riparian vegetation and changes in water chemistry. The study finds that the factors of riparian vegetation type, age, width, restoration and shading effects require due consideration in the development of riparian buffer zone and stream water chemical quality management interventions. I find that these factors require a high degree of integration, triangulation and context-specificity to achieve the objectives of riparian management intervention. I further find that stream water quality decision-making processes need to combine riparian vegetation-based approaches with other measures for mitigating and containing the spillage of pollutants at the source. / <p>Presentation was conducted via Skype</p>

Le maintien des tissus péri-implantaires sains à un niveau le plus coronaire possible conditionne le succès à long terme des réhabilitations implanto-portées. Dès lors, la mise en place d'une barrière muqueuse protectrice et la préservation de l'os marginal au cours des premières semaines de cicatrisation est indispensable. Le design implantaire influence les remodelages tissulaires intervenant au niveau du col de l'implant lors des phases initiales de cicatrisation. L'objet de ce travail est d'analyser histologiquement chez le Beagle l'influence de deux systèmes implantaires innovants sur les caractéristiques de la muqueuse et la position de l'os marginal après 3 et 12 semaines de cicatrisation. Les résultats de cette étude, mis en relation avec les données de la littérature indiquent que les implants « deux-parts » présentant une connectique cône morse pourraient favoriser la mise en place d'un espace biologique court et limiter la perte osseuse marginale péri-implantaire. Les implants « une part » à col transmuqueux concave seraient quant à eux associés à des valeurs réduites d'espace biologique et autoriseraient une apposition osseuse sur l'épaule de l'implant. Dans la première partie de ce mémoire, nous établissons une synthèse des données histologiques actuelles concernant les caractéristiques et les processus de cicatrisation des tissus péri-implantaires, et l'influence de la conception implantaire sur les remodelages tissulaires marginaux intervenant au cours de la cicatrisation. Nous avons rédigé deux publications internationales que nous présentons en deuxième partie. Une réflexion analytique autour de ce travail est présentée dans la troisième partie / Aesthetic and functional long-term success of implant-supported rehabilitations relies on the preservation of peri-implant tissue levels in the most coronal position. Therefore, the achievement of an efficient protective mucosal seal, and the preservation of the peri-implant marginal bone during the first weeks of healing are essential to prevent long term implant failures. The characteristics of an implant transmucosal design (connections, platforms, surface properties) are related to biological width dimensions, marginal peri-implant bone levels, and the amount of inflammation within the peri-implant soft tissues. The aim of the research work presented in this manuscript was to investigate the effect of two innovative implant systems on peri-implant mucosa maturation, dimensions, collagen fiber organization, and marginal bone levels after 3 and 12 weeks of healing in the beagle dog. The results, compared with previous data, show that platform-switched twopiece implants exhibit reduced values of biological width and marginal bone loss, and that a concave transmucosal design in one-piece implants is associated with a short vertical value of biological width, and promote a mechanical interlocking of the implant body at the connective tissue and marginal bone levels. In the first part of this report, an overview of the current knowledge concerning the characteristics and healing patterns of peri-implant tissues, and the influence of implant design on the early peri-implant tissue remodeling is established. We have written two international publications which are presented in the second part. An analytical reflection about this work is presented in the third part

Les changements environnementaux à l’échelle globale peuvent se traduire par une modification des conditions abiotiques et de la diversité biologique. La fonction de production des écosystèmes forestiers a la particularité d'être à la fois soumise à, et régulatrice de ces changements environnementaux. Il apparaît alors primordial de comprendre la manière dont la diversité en essences et les facteurs abiotiques exercent le contrôle de cette fonction. Au cours de mes travaux j’ai étudié la variation de l'effet du mélange d’essences sur leur productivité dans un contexte climatique et édaphique changeant. Grâce à une double approche, basée sur des données locales et des données de l'Inventaire forestier national, je me suis concentrée sur cinq espèces forestières européennes majeures en peuplements purs et bispécifiques : Quercus petraea, Pinus sylvestris, Fagus sylvatica, Abies alba et Picea abies. En plaine je montre que l'effet du mélange d’essences varie peu avec les facteurs abiotiques. De plus cet effet est déterminé par la tolérance à l'ombrage de l'espèce accompagnatrice. En montagne l’effet du mélange d’essences sur leur productivité est plus fort et positif lorsque les facteurs abiotiques sont les plus limitants pour la croissance. Ces résultats illustrent l’intérêt d'intégrer les facteurs abiotiques et les caractéristiques fonctionnelles des espèces comme déterminants de l'effet de la diversité biologique sur les fonctions de l'écosystème. / Global environmental changes may lead to a modification of abiotic factors and biological diversity. The production function in forest ecosystems has the particularity to be both subjected to, and a regulator of, these environmental changes. Understanding how forest productivity is driven by species diversity and environmental factors is therefore a critical issue. This PhD thesis studies how tree species mixture affects their productivity along edaphic and climatic gradients. Based on an approach using both an original dataset and the national forest inventory dataset, I focused on five major species of European forests in pure and two-species forests: Quercus petraea, Pinus sylvestris, Fagus sylvatica, Abies alba and Picea abies. In lowlands, abiotic factors had little impacts on the outcome of tree species mixture on productivity. In addition, the effect of tree species mixture was determined by the shade tolerance of companion species. In highlands, the positive effects of tree species mixture were strongest when the abiotic factors were the most limiting for growth. These results highlight the importance of considering abiotic factors and the functional characteristics of species as drivers of the effect of biological diversity on ecosystem functions.

MU LT I L E V E L inverters are becoming the preferred choice for medium voltage high power applications. Multilevel inverters have a number of inherent advantages over conventional two level inverters. The output voltage has multiple steps or levels, resulting in reduced dV/dt, which leads to lower electromagnetic interference, making it easier to meet electromagnetic compatibility (EMC) regulations. Multilevel inverters have a much lower effective switching frequency, which leads to a reduction in switching losses. The output voltage of multilevel inverters has a much lower harmonic content. In applications such as power conversion or grid-connection, filters need to be much smaller, or can be eliminated. In motor drive applications, the low harmonic content results in smoother, ripple-free shaft torque. The neutral-point clamped (NPC), cascaded H-bridge (CHB) and flying capacitor (FC) topologies were among the earliest multilevel topologies. NPC topologies require additional clamping diodes to clamp the output to the DC bus midpoint. CHB topologies use a number of isolated DC suplies to generate multilevel output. FC topologies work with a single DC link but use additional floating capacitors. Since then, a number derivatives and improvements to these topologies have been proposed. Topologies with low switch counts are desirable because of the corresponding reduction in system size and cost. A low total component count is also desirable since it results in better reliability. Induction motors in high power applications are often operated in the open-end configuration. Here, the start terminals of the motor phase windings are connected to one three phase inverter, while the end terminals are connected to a second three-phase inverter. The two inverters are typically powered by isolated supplies to prevent the flow of common mode currents through the motor. The open end configuration has a number of advantages It can be used with nearly all high power motors with no need for electrical or mechanical modification, since all six winding terminal are available externally. The two inverters driving the open-end motor are effectively cascaded. As a result, two inverters of lower voltage and power rating can replace a single inverter with higher voltage and power rating. In addition, if one of the inverter fails, it can be bypassed and the system can be operated at reduced power. In many applications such as heating, ventilation and air conditioning (HVAC), the load power is proportional to the cube of the shaft speed, so a 50% reduction in power translates to only 20% reduction in speed, thereby improving overall system reliability. The cascading of inverters also enables multilevel operation, which is exploited for the topologies proposed in this thesis. In the open-end configuration it is important to ensure that both the DC supplies deliver power to the load. Otherwise, power can circulate through the motor windings. In addition, if the two inverters are powered by rectifier supplies, the DC bus of one inverter can charge uncontrollably, resulting in distortion of phase voltages and currents. If DC bus overcharging continues unchecked the DC bus voltage can even exceed the system rating, resulting in permanent damage. This thesis proposes two novel topologies for open-end induction motor drives with low switch counts. Both topologies are powered by two unequal, isolated DC sources having DC voltages in a 3:1 ratio. Multiple levels in the output voltage are obtained using a number of floating capacitors in each phase. Modulation and control schemes are also proposed for both topologies to ensure that DC bus overcharging never occurs, while all the capacitor voltages are kept balanced at their nominal values. The first of these two topologies is a nine level inverter for open end induction motor drives. It consists of two three-level flying capacitor inverters connected to the induction motor in the open end configuration. The two inverters are powered by DC sources of voltage 6VDC/8 and 2VDC/8, which generates an effective phase voltage having nine levels in steps of VDC/8. This topology has only eight switches and two floating capacitors per phase. The space vector structure for this topology is hexagonal, and has 217 space vector locations. A space-vector based formulation is used to determine the pole voltage of the inverter such that DC bus over charging is prevented. In addition, selection of switching states is used to balance the voltages of all floating capacitors. This scheme allows the floating capacitors to be charged up during system startup, thereby eliminating the need for separate pre-charging circuitry. A level-shifted carrier PWM based modulation scheme has been developed, which can be used with both scalar and vector control schemes. The gating signal for switches turning on must be delayed by a small amount (to allow the complementary switch to turn of), failing which current shoot through can occur. This delay is called dead time, during which gate signals to both complementary devices are turned of. Under certain conditions in the flying capacitor topology, the pole voltage can contain large undesirable transients during the dead time which result in phase current distortion, and electromagnetic noise. A novel scheme to eliminate this problem is proposed using a digital state machine approach. The switching state for each subsequent switching interval is determined based on the present switching state such that the pole voltage does not contain a transient, without affecting the phase voltage of the inverter, and irrespective of the current magnitude or direction. The state machine was implemented using an FPGA, and required an additional computation time of just 20ns, which is much smaller than the inverter dead time duration of typically 2.5µs. The second novel topology proposed in this thesis is a seventeen level inverter for an open end induction motor drive. Here, one three-level inverter and one seven-level inverter are connected to the two ends of the induction machine. The three-level inverter is a flying capacitor inverter. The seven-level inverter is a hybrid topology – it consists of an H-bridge cascaded to each phase of a three level flying capacitor inverter. This scheme is also powered by two isolated DC sources in 3:1 ratio with magnitudes 12VDC/16 and 4VDC/16. The effective phase voltage has seventeen levels in steps of VDC/16. This topology has a total of twelve switches and three floating capacitors per phase. The space vector structure for this topology is hexagonal, and has 817 space-vector locations. Space vector analysis was used to determine the pole voltages, and the switching states such that DC bus overcharging is prevented while also balancing the voltages of the floating capacitors. A non-iterative algorithm was developed for determining the switching states, suitable for implementation in digital logic using an FPGA. The scheme is able to charge the all capacitors at startup as well, eliminating the need for separate pre-charging circuits. Hardware prototypes were built for both the topologies described above for experimental verification, and used to drive a three phase 50Hz, 1.5kW, four pole induction motor in V/f control mode. The inverters topologies were built using 1200V, 75A IGBT half-bridge modules (Semikron SKM75GB12T4) with hybrid opto-isolated gate drivers (Mitsubishi M57962). Three phase rectifiers were used to create the asymmetric DC supplies Hall effect sensors were used to sense the DC link and floating capacitor voltages and phase currents (LEM LV20P voltage sensors and LA55 current sensors). Signal conditioning circuitry was built using discrete components. The PWM signals and V/f controller were implemented using a digital signal processor (Texas Instruments TMS320F28335). Synchronous PWM with was used to eliminate sub-harmonics from the phase voltage, and to ensure three-phase and half-wave symmetry. The internal ADC of the DSP was used for sampling all voltages and currents. The remaining digital logic for switch state selection was implemented on a FPGA (Xilinx Spartan3 XC3S200). Dead time functionality was also implemented within the FPGA, eliminating the need for separate dead time hardware. Both topologies were first tested for steady state operation over the full modulation range, and the pole voltages, phase voltages and phase currents were recorded. System startup, and the ability of the controllers to balance all the capacitors at startup was tested next. The capacitor voltages were also observed during sudden loading, by quickly accelerating the motor. Finally, the phenomenon of DC bus overcharging was also demonstrated. These results demonstrate the suitability of the proposed topology for a number of applications, including industrial drives, alternate energy systems, power conversion and electric traction.

Doppler radar wind profilers are already widely used to measure atmospheric winds throughout the free troposphere and stratosphere. Several methods have been developed to quantify atmospheric turbulence with such radars, but to date they have remained largely un-tested; this thesis presents the first comprehensive validation of one such method. Conventional in-situ measurements of turbulence have been concentrated in the surface layer, with some aircraft and balloon platforms measuring at higher altitudes on a case study basis. Radars offer the opportunity to measure turbulence near continuously, and at a range of altitudes, to provide the first long term observations of atmospheric turbulence above the surface layer. Two radars were used in this study, a Mesosphere-Stratosphere-Troposphere (MST) radar, at Capel Dewi, West Wales, and the Facility for Ground Based Atmospheric Measurements (FGAM) mobile boundary layer profiler. In-situ measurements were made using aircraft and tethered-balloon borne turbulence probes. The spectral width method was chosen for detailed testing, which uses the width of a radar's Doppler spectrum as a measure of atmospheric velocity variance. Broader Doppler spectra indicate stronger turbulence. To obtain Gaussian Doppler spectra (a requirement of the spectral width method), combination of between five and seven consecutive spectra was required. Individual MST spectra were particularly non-Gaussian, because of the sparse nature of turbulence at its observation altitudes. The width of Gaussian fits to the Doppler spectrum were compared to those from the `raw' spectrum, to ensure that non-atmospheric signals were not measured. Corrections for non-turbulent broadening, such as beam broadening, and signal processing, were investigated. Shear broadening was found to be small, and the errors in its calculation large, so no corrections for wind shear were applied. Beam broadening was found to be the dominant broadening contribution, and also contributed the largest uncertainty to spectral widths. Corrected spectral widths were found to correlate with aircraft measurements for both radars. Observing spectral widths over time periods of 40 and 60 minutes for the boundary layer profiler and MST radar respectively, gave the best measure of turbulence intensity and variability. Median spectral widths gave the best average over that period, with two-sigma limits (where sigma is the standard deviation of spectral widths) giving the best representation of the variability in turbulence. Turbulent kinetic energies were derived from spectral widths; typical boundary layer values were 0.13 m 2.s (-2) with a two-sigma range of 0.04-0.25 m 2.s (-2), and peaked at 0.21 m 2.s (-2) with a two-sigma range of 0.08-0.61 m 2.s (-2). Turbulent kinetic energy dissipation rates were also calculated from spectral widths, requiring radiosonde measurements of atmospheric stability. Dissipation rates compared well width aircraft measurements, reaching peaks of 1x10 (-3) m 2.s (-3) within 200 m of the ground, and decreasing to 1-2x10 (-5) m 2.s (-3) near the boundary layer capping inversion. Typical boundary layer values were between 1-3x10 (-4) m 2.s (-3). Those values are in close agreement with dissipation rates from previous studies.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-11T12:39:13Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação Mestrado M276 - Gilberto.pdf: 3559945 bytes, checksum: e0e92cec09c72c5a7b8b98260c3b9a8e (MD5) / Made available in DSpace on 2017-07-11T12:39:13Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação Mestrado M276 - Gilberto.pdf: 3559945 bytes, checksum: e0e92cec09c72c5a7b8b98260c3b9a8e (MD5) Previous issue date: 2016-03-22 / Este trabalho apresenta um estudo comparativo de conversores monofásicos aplicados a sistemas fotovoltaicos sem transformador. Topologias de inversores sem transformador têm menores custos, tamanho e peso. Contudo, a não utilização do transformador pode ser responsável por consideráveis valores de correntes de fuga. A associação em série de vários módulos fotovoltaicos se faz necessária para alcançar o nível de tensão desejado no barramento c.c.. Com o intuito de reduzir o número de módulos fotovoltaicos em série, topologias com característica de elevação de tensão (boost) podem ser utilizadas. Portanto, topologias que possuem estas características e que possam apresentar baixos valores de correntes de fuga devem ser escolhidas para o estudo. As topologias presentes neste trabalho são: o conversor de dois estágios, o inversor fonte Z monofásico com diodo adicional, e o inversor fonte Z de três estados. / This work presents a comparative study of single-phase converters applied to transformerless photovoltaic systems. Topologies of transformerless inverters have lower costs, size and weight. However, not using it may cause considerable amounts of leakage currents. The association in series of several PV modules is needed to achieve the voltage level desired in d.c. bus. In order to reduce the number of photovoltaic modules in series, topologies with voltage boost characteristic can be used. Therefore, topologies that have voltage boost characteristic and can have low leakage current values are chosen for the study. Topologies present in this work are: the two stages single-phase converter, the single-phase Z-source inverter with additional diode, and the single-phase three switch three state Z-source inverter.

Work chair is considered as an important element for the users to improve comfort in work environment. An ergonomic chair design and engineering is therefore considered very important for its usability and comfort view of point for the users. The aim of the thesis is to improve the mobility and ergonomics of the existing chair in all aspects. Ergonomically designed chairs are important for long time seated workers to increase their productivity and also to reduce low back injuries which arise due to the poor design chairs in ergonomic aspects. In addition, ergonomically designed chairs help to increase the seating comfortability of the chair users. QFD and waterfall model was followed for the work execution. In this paper, we discuss a design of an ergonomically efficient chair with simple adjustments which gives more comfortability. This will give us a better likelihood to stay in a neutral position. The Ergonomics of the chair is improved in various steps. This thesis focuses on many ideas in which some of them are implemented and evaluated.

This master´s thesis describes switch mode power supply. The aim of this master´s thesis is the design and the construction of the switch mode power supply, which will be used as a laboratory tool.

The aim of the diploma thesis is to create conditions for safe and continuous transit through the local road II / 368 Moravská Třebová. The thesis deals with the new design of the broad layout of the communication, the creation of a safe transfer of cyclists, the modification of all existing crossroads and the creation of new platforms for bus stops. Additionally, existing paved surfaces in the associated space of the local road are modified.

This thesis deals with the effect of frequency inverter on the lifetime of roller bearings. The measurement has been carried out on the frequency inverter and induction motor by Siemens in the Switchgear laboratory of Fakulty of elektrical engineering and communication. Data has been recorded and processed on Adash VA4 Pro analyzer. Methods of measuring RMS values and frequency analysis of vibration and current were used for the analysis. Based on the mutual similarity of frequency spectrum, the presence of the high frequency capacitive current in the bearings has been proven. To prevent this, possible solutions have been presented. In the second part of the experiment an effect of changing pulse width modulation (PWM) on vibration was examined. The goal was to make a basic analysis and to provide background material for further research.