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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Stray loss analysis of AC machines using time-stepped finite elements

Zhan, Yang Unknown Date
No description available.
12

A Spatiotemporal And Geochemical Evaluation Of Groundwater Quality Adjacent To Natural Gas Drilling And Hydraulic Fracturing In Dimock Township, Susquehanna County, Pennsylvania

Hottenstein, Aaron 12 August 2014 (has links)
In the Marcellus shale region, elevated concentrations of dissolved methane in private water wells has been shown to be linked to natural gas extraction, but little is known of the connections between methane, gas production, and water chemistry. This study evaluates the relationships of methane to the major chemical constituents of groundwater by comparing analytical data obtained from a stray gas investigation by the Pennsylvania Department of Environmental Protection (PADEP). Furthermore, spatiotemporal relationships of dissolved methane to gas well production and total iron (Fe) concentrations of groundwater to adjacent gas wellheads are examined. The objectives of this study were to identify essential pre- and post-drill test parameters that are sensitive to methane, and to determine what water types are associated with stray gas. It was discovered that total Fe concentrations in groundwater increased and sulfate (SO4) concentrations decreased likely as the result of redox reactions by anaerobic microbes in the presence of stray gas. Therefore, total Fe and SO4 should be mandated pre- and post-drill test parameters for baseline water quality assessments.
13

Monitoramento da população de cães errantes na Cidade Universitária Armando de Salles Oliveira / Monitoring of the stray dog population in the University of São Paulo Campus Armando Salles de Oliveira

Aline Gil Alves Guilloux 06 May 2016 (has links)
O ProMAC surgiu dentro da USP como resposta à demanda da comunidade, de abordar alguns problemas ambientais, inclusive a presença de cães errantes no campus. O presente trabalho teve como objetivo atender este programa no tocante à avaliação da dinâmica e da saúde da população de cães mantidos soltos na CUASO e dos cães recolhidos ao ATA. Utilizando a técnica de captura e recaptura fotográfica, a população de cães foi estimada em nove oportunidades ao longo de dois anos. No segundo ano, os cães dóceis foram individualmente identificados e, em quatro oportunidades, tiveram amostras biológicas coletadas (sangue, fezes e ectoparasitos). Os cães alojados no ATA foram identificados e as amostras coletadas em um único esforço contínuo ao longo de três meses. A estimativa da população errante variou entre 14 e 55 cães, com tendencia de queda não significativa ao longo do tempo. A população foi, em sua maioria composta de indivíduos machos (58,4%), adultos (77,8%) e dóceis (55,7%). A população errante apresentou alterações nos parâmetros hematológicos ao longo do ano, compatíveis com infecção subclínica, possivelmente causada por Hepatozoon canis, que teve aumento significativo de sua prevalência. Todos os cães foram negativos para Leishmania sp., Ricketsia sp., Erlichia sp. Não houve diferença significativa tanto para a SAM (Leptospira sp.,entre 14 e 50% - CUASO e 52,4% - ATA) quanto para a eliminação de ovos de Ancylostoma sp. nas fezes (entre 21 e 55% - CUASO e 27% - ATA) entre os cães da CUASO e do ATA, sendo o risco de infecção na comunidade universitária considerado baixo. A análise ambiental permitiu estabelecer que a fonte principal de alimento dos cães é a mesma dos humanos, fornecida próximo aos pontos de venda de alimentos, o que se torna preocupante ao sabermos que mais da metade destes cães são positivos para Toxoplasma sp. (entre 54 e 60%), sendo indicadores do risco ao ser humano. Os cães da população aversiva apresentam sinais reprodutivos (8,7% das fêmeas ao ano), mas os filhotes não foram encontrados possivelmente devido à baixa sobrevivência. Os adultos, tanto da população dócil como da população aversiva possuiam boa condição corporal, baixa mortalidade, sendo que os dóceis deixaram o campus mais frequentemente devido à adoção. O conjunto dos dados indicaram que o status sanitário dos cães alojados no abrigo foi semelhante àquela dos cães soltos, sendo que o bem-estar destes últimos foi maior, devido à condição precária em que o ATA era mantido, com a capacidade de alojamento de cães acima do limite máximo do abrigo. Como os cães da CUASO se distribuiam modulados pelo fornecimento de alimento e abrigo pelos usuários do campus, o manejo adequado destes cães deveria incluir o envolvimento da comunidade, além de sua responsabilização. A reprodução dos cães aversivos precisa ser eliminada, buscando métodos alternativos, devido à dificuldade de captura destes cães. O uso da área de mata destinada a pesquisa por estes cães representa um risco sanitário à comunidade universitária. / The ProMAC emerged within the University of São Paulo in response to a community demand, to address environmental problems, including the presence of stray dogs in its campus. This study aimed to address this program regarding the dynamics and health of the population of stray dogs in the campus and the dogs kept in the campus shelter. Using the technique of photographic mark and recapture, the dog population was estimated in nine occasions in a two years period. In the second year the docile dogs were individually identified and, on four occasions, had biological samples collected (blood, feces and ectoparasites). Dogs housed in the shelter were identified and biological samples were collected in a single effort over three months. The population estimates varied between 14 and 55 dogs, with a non-significant decrease trend over time. The population was mostly composed of males (58.4%), adults (77.8%) and docile individuals (55.7%). The stray population showed changes in hematological parameters throughout the year, consistent with subclinical infection, possibly caused by Hepatozoon canis, which had a significant increase in its prevalence. All dogs were negative for Leishmania sp., Rickettsia sp., Ehrlichia sp. There was no significant difference between either the MAT (Leptospira sp, between 14 and 50% -. campus and 52.4% - shelter) or the elimination of Ancylostoma sp. eggs in feces (between 21 and 55% - campus and 27% - shelter), between dogs from campus and shelter, and the risk of infection in the university community was considered low. Environmental analysis established that the stray dogs main food source are the human food given to them close to food selling points, which is a concern given that more than half of these dogs are positive for Toxoplasma sp. (from 54 to 60%) and would be risk indicators to humans. The aversive stray dogspopulation showed reproductive signs (8.7% of females per year), but the puppies were not found possibly due to low survival rate. Adults, both from docile and the aversive population, had good body condition, low mortality and the docile dogs left the campus more often due to adoption. The data indicated that the health of dogs housed in the shelter were similar to the stray population, and the welfare of the latter is higher due to the precarious condition that the shelter was maintained and the number of dogs kept being over the maximum capacity. As stray dogs were distributed and maintained by the food and shelter supplied by the campus users, the proper management of these dogs would include community involvement and responsibility. The reproduction of aversive dogs must be eliminated, seeking alternative methods, because of the difficulty of catching these dogs. Use of research forest area by these dogs poses a risk to the university community.
14

Beglobių gyvūnų apsauga Europos Sąjungoje ir Lietuvoje / Protection of stray animals in European Union and Lithuania

Kalinauskaitė, Milda 25 June 2013 (has links)
Magistro baigiamajame darbe išanalizuoti gyvūnų teisių apsaugos ES teoriniai aspektai, atlikta beglobių šunų apsaugos keturiose ES šalyse (Lietuvoje, Švedijoje, Olandijoje ir Slovėnijoje) palyginamoji analizė, pristatytos Lietuvos beglobių šunų teisių gerinimo ir jų skaičiaus mažinimo galimybės. Pirmojoje darbo dalyje aptariant beglobių gyvūnų apsaugos teorinį aspektą atliktas beglobių gyvūnų apsaugos ES padėties vertinimas (pateikta beglobių gyvūnų samprata, beglobių gyvūnų skaičiaus ES statistinė analizė, gyvūnų atsakymo ES priežastys), aptarti pagrindiniai beglobių gyvūnų apsaugos ir kontrolės ES pagrindiniai bruožai (gyvūnų apsaugos ES teisiniai aspektai, beglobių gyvūnų apsaugos ir kontrolės administracinė struktūra, beglobių gyvūnų skaičiaus mažinimo priemonės). Antrojoje darbo dalyje atlikta beglobių šunų apsaugos įgyvendinimo keturiose ES šalyse (Lietuvoje, Švedijoje, Olandijoje ir Slovėnijoje) palyginamoji analizė: atlikta šių šalių beglobių šunų populiacijos, gyvūnų gerovės teisinio reglamentavimo ir beglobių šunų skaičiaus kontrolės (beglobių šunų registracijos, prieglaudų skaičiaus, požiūrio į eutanaziją, sterilizacijos, šunų šeimininkų švietimo) palyginamosios analizės. Antrojoje darbo dalyje išanalizavus Švedijos, Olandijos ir Slovėnijos beglobių gyvūnų teisių ir jų populiacijos kontrolės sistemų pagrindinius bruožus ir palyginus juos su Lietuvos situacija, trečiojoje darbo dalyje minėtų sistemų pagrindu pateikti pasiūlymai Lietuvos beglobių šunų teisių apsaugos... [toliau žr. visą tekstą] / In the master‘s work there are analysed theoretical aspects of animal rights protection in EU, comparative analysis of the protection of stray dogs in four ES countries had been conducted (Lithuania, Sweden, the Netherlands and Slovenia), the possibilities of improvement of Lithuanian stray dogs‘ rights and reduction of their number have been presented. In the first part of the work evaluation of homeless animal‘s rights in the EU has been conducted (providing the notion of homeless animals, statistical analysis of the number of homeless animals in EU, the causes of the refusing of animals), discussing on the theoretical aspect of homeless animals‘ protection, the main features of the protection and control of homeless animals in EU (legal aspects of animal rights in EU, the administrative structure of homeless animals‘ protection and control, the means of reducing the number of homeless animals). In the second part of the work there is conducted comparative analysis of homeless dogs‘ protection in four EU countries (Lithuania, Sweden, the Netherlands, and Slovenia), which consists of: comparative analysis of these homeless dogs‘ population, animal welfare legal regulation and control of the number of homeless dogs (registration of homeless dogs, the number of shelters, attitudes towards euthanasia, sterilisation, dog owner education). Having analysed the main features of Sweden, the Netherlands and Slovenia‘s homeless animal rights and population control systems and... [to full text]
15

Design of Resonant Converters using Silicon Carbide Power

Moozhikkal, Rahul January 2016 (has links)
The design of series-loaded resonant converters using the state of the art SiC power transistorsis investigated in the thesis. SiC devices are chosen as they offer lower switching losses comparedto conventional Si based devices A very detailed study about the working and differentmodes of operation of the resonant converter is carried out. The thesis further explains how thehigh speed switching capabilities of the SiC devices remain untapped owing to the presence ofstray inductances in the switch-snubber layout. A comparison of all the commercially availableSiC devices are carried out to find the most suitable switch for the resonant converter. Thethesis also carries out a very detailed step by step design of the circuit and the PCB layout forthe resonant converter. Two different layouts are proposed and then compared for their strayinductance and power losses. Finally, based on the experiments the thesis validates the suitabilityof using discrete SiC power transistors in place of power modules. / Utformningen av serie-belastade resonansomvandlare med hjälp av toppmoderna SiC högeffekttransistorernaundersöks i denna avhandlingen. SiC-enheter väljs eftersom de erbjuderlägre switch-förluster jämfört med konventionella Si-baserade enheter.En mycket detaljeradstudie om funktionen och de olika operationella tillstånden hos resonansomvandlare utförs.Avhandlingen förklarar vidare hur förmågan till högfrekvent switchning hos SiC-enheterförblir ofullständigt utnyttjad på grund av förekomsten av ströinduktanser i switch-snubberlayouten.En jämförelse av alla kommersiellt tillgängliga SiC-enheter genomförs för att hittaden mest lämpliga switchen för resonansomvandlaren. Avhandlingen utförs också en mycketdetaljerad steg-för-steg-utformning av resonansomvandlaren kretsschema och kretskortlayout.Två olika layouter föreslås och jämförs därefter utifrån deras ströinduktanser ocheffektförluster. Slutligen, baserat på experimentella resultat bekräftar avhandlingen.Lämpligheten att använda diskreta SiC-effekttransistorer istället för effektmoduler medintegrerade drivarsteg för styrelektroderna.
16

GHOST IMAGE ANALYSIS FOR OPTICAL SYSTEMS

Abd El-Maksoud, Rania Hassan January 2009 (has links)
Ghost images are caused by the inter-reflections of light from optical surfaces that have transmittances less than unity. Ghosts can reduce contrast, provide misleading information, and if severe can veil parts of the nominal image. This dissertation develops several methodologies to simulate ghost effects arising from an even number of light reflections between the surfaces of multi-element lens systems. We present an algorithm to generate the ghost layout that is generated by two, four and up to N (even) reflections. For each possible ghost layout, paraxial ray tracing is performed to calculate the locations of the Gaussian cardinal points, the locations and diameters of the ghost entrance and exit pupils, the locations and diameters of the ghost entrance and exit windows, and the ghost chief and marginal ray heights and angles at each surface in the ghost layout. The paraxial ray trace data is used to estimate the fourth order ghost aberration coefficients. Petzval, tangential, and sagittal ghost image surfaces are introduced. Potential ghosts are formed at the intersection points between the ghost image surfaces and the Gaussian nominal image plane. Paraxial radiometric methodology is developed to estimate the ghost irradiance point spread function at the nominal image plane. Contrast reduction by ghosts can cause a reduction in the depth of field, and a simulation model and experimental technique that can be used to measure the depth of field is presented. Finally, ghost simulation examples are provided and discussed.
17

Population dynamics and management strategies of stray and free-ranging dogs in Bor, Serbia

Skrijelj, Lejla January 2019 (has links)
Dogs are one of the most widespread carnivore and the third most invasive mammal, after cats and rodents. Stray dogs affect wildlife negatively by predation, disturbance, disease spreading, competition and hybridization with other wild canids. Even in urban environments stray dogs cause problems such as disturbance, pollution, traffic accidents, bites and risk of disease spreading. Serbia is one of many countries in the Balkan region that has a problem with overpopulation of stray dogs. The aim of this study is to investigate the population dynamics of stray dogs in Bor, Serbia and discuss different dog population management strategies. A total of 361 stray dogs were registered, 111 male dogs, 85 female dogs and 165 dogs with undetermined sex. 55 dogs (15.23%) were estimated to be older than 7 years old, 262 dogs (72.57%) were estimated to be between 3-7 years old, 30 dogs (8.31%) were estimated to be between 6-24 months old and 14 dogs (3.87) were estimated to be between 0-6 months old. No dogs showed any signs of rabies or CDV (canine distemper virus) and 241 stray dogs (66.75%) seemed healthy. 120 stray dogs (33.25%) did however have some kind of impaired health. To achieve a stop in the population increase,70% sterilisation rate is required and to teach responsible dog ownership. The stray dogs showed different reactions towards people, 164 dogs (45.42%) were neutral and 100 dogs (27.70%) showed no fear or aggression towards humans and gladly interacted. Since the dogs are highly accessible, they would be acceptable for a TNR (trap-neuter-release) program and male dogs need to be prioritised considering their dispersal patterns. / Hundar är en av de mest spridda karnivorerna och det tredje mest invasiva däggdjuret, efter katter och gnagare. Gatuhundar påverkar vilda djur negativt genom predation, störning, spridning av sjukdomar, konkurrens och hybridisering med andra vilda hunddjur. Även i urbana miljöer har gatuhundar en negativ påverkan, genom störning, förorening, trafikolyckor, bett och sjukdomsrisk. Serbien är ett av många länder i Balkanregionen som har för stora populationer av gatuhundar. I detta arbete undersöks populationsdynamiken hos gatuhundar i Bor, Serbien och diskuterar olika metoder för att hantera gatuhundpopulationen. Totalt inventerades 361 gatuhundar, 111 hanar, 85 honor och 165 med obestämt kön. 55 hundar (15.23%) uppskattades vara äldre än 7 år, 262 hundar (72.57%) uppskattades vara mellan 3-7 år, 30 hundar (8.31%) uppskattades vara mellan 6-24 månader gamla och 14 hundar (3.87) uppskattades vara mellan 0-6 månader gamla. Inga hundar visade tecken på rabies eller CDV (canine distemper virus) och 241 gatuhundar (66.75%) föreföll friska. Däremot visade 120 hundar (33.25%) någon typ av nedsatt hälsa. För att uppnå ett stopp i populationsökningen krävs minst 70% steriliseringstakt samt att man lär ut ansvarsfullt hundägande. Gatuhundarna visade olika reaktioner mot människor, 164 hundar (45.42%) var neutrala och 100 hundar (27.70%) visade ingen rädsla eller aggression för människor och interagerade gärna. Eftersom gatuhundarna är lättillgängliga, skulle de kunna ingå i populationshanteringar som TNR (trap-neuter-release) och hanhundar bör prioriteras med tanke på deras spridningsmönster.
18

Packaging Design of IGBT Power Module Using Novel Switching Cells

Li, Shengnan 01 December 2011 (has links)
Parasitic inductance in power modules generates voltage spikes and current ringing during switching which cause extra stress in power electronic devices, increase electromagnetic interference (EMI), and degrade the performance of the power converter system. As newer power devices have faster switching speeds and higher power ratings, the effect of the parasitic inductance of the power module is more pronounced. This dissertation proposes a novel packaging method for power electronics modules based on the concepts of novel switching cells: P-cell and N-cell. It can reduce the stray inductance in the current commutation path in a phase-leg module and hence improve the switching behavior. Taking an insulated gate bipolar transistor (IGBT) as an example, two phase-leg modules, specifically a conventional module and a P-cell and N-cell based module were designed. Using Ansoft Q3D Extractor, electromagnetic simulation was carried out to extract the stray inductance from the two modules. An ABB 1200 V / 75 A IGBT model and a diode model were built for simulation study. Circuit parasitics were extracted and modeled. Switching behavior with different package parasitics was studied based on the Saber simulation. Two prototype phase-leg modules were fabricated. The parasitics were measured using a precision impedance analyzer. The measurement results agree with the simulation very well. A double pulse tester was built in laboratory. Several approaches were used to reduce the circuit and measuring parasitics. From the switching characteristics of the two modules, it was verified that the larger stray inductance in the layout causes higher voltage overshoot during turn off, which in turn increases the turn off losses. Multichip (two in parallel) IGBT modules applying novel switching cells was also designed. The parasitics were extracted and compared to a conventional design. The overall loop inductance was reduced in the proposed module. However, the mismatch of the paralleled branches was larger.
19

Bidirectional Non-Isolated Fast Charger Integrated in the Electric Vehicle Traction Drivetrain

Eull, William-Michael January 2021 (has links)
Electric vehicles present an opportunity to reduce the substantial global footprint of road transportation. Cost and range anxiety issues, however, remain major roadblocks to their widespread adoption. One of the simplest ways to reduce cost is to remove components from the vehicle via novel topologies, estimation and control; to reduce range anxiety, charging infrastructure needs to be simplified and the power electronics in the vehicle made more efficient. This thesis proposes a bidirectional non-isolated fast charger integrated in the traction drivetrain of an electric vehicle that is enabled by a modular power electronic converter topology called the autoconverter module. The autoconverter module is an evolution of previous modular power electronic concepts with the goal of a highly integrated, high performance converter capable of being used in a number of applications through simple parallelization. By simplifying system design through the use of one base power conversion block, overall system cost can be reduced. Key to the realization of the power module is state estimation. To enable high performance operation of the system, low noise state information must be provided to the controller. State estimation is capable of filtering measurement noise to achieve this goal. However, conventional estimation techniques typically have low bandwidth and a convergence time associated with them, limiting the overall control system's performance. Higher performance techniques, such as receding horizon estimation, offer near-instantaneous estimation with noise rejection capabilities, which makes it an attractive solution. State estimators can also realize a cost reduction through the removal of sensors with little to no performance degradation. Using high performance state estimation and three autoconverter modules in parallel, a novel three-phase inverter/rectifier topology is conceived. Using this topology, a bidirectional non-isolated integrated fast charger capable of universal, i.e. single- and three-phase AC and DC, electric vehicle charging is realized. To interface with the AC power grid and AC traction motor, a novel three-phase common mode voltage controller is developed. By controlling the common mode voltage, leakage currents, which are generated by the fluctuation of the common mode voltage across a parasitic capacitance, can be attenuated and the transformer safely removed from the system. The removal of the transformer presents a significant cost and efficiency gain for both on-board chargers and dedicated charging units. With no transformer, the need for a dedicated on-board charger is obviated; instead, the existing high power traction inverter can be used as the primary charging interface, significantly reducing the cost, size and weight of on-board charging. High efficiency in charging mode is demonstrated, with a peak efficiency of 99.4% and an efficiency at rated power of 11kW of 98.4% shown. Traction mode efficiency with the proposed integrated charger is increased by 0.6% relative to a standard drive at the motor's rated power of 5kW. Damaging leakage currents and shaft voltages are reduced by over 90% because of the common mode voltage control, which will increase drive reliability and lifetime. The topology can be applied to motor drive applications outside automotive to increase efficiency and reliability. State estimation theory for permanent magnet synchronous machine drives is expanded upon and guarantees for estimatability and stability of the estimators are provided. Two estimation schemes, a Luenberger observer and a receding horizon estimator, are studied for sensor removal and the development of a failsafe operating mode involving one phase current sensor. Both estimators function equivalently in the steady state with the receding horizon estimator having slightly better transient performance. The Luenberger observer has conditions on estimatability, whereas the receding horizon estimator has none. Both estimators permit the removal of one current sensor for cost reduction. In regular operation, there is no performance degradation.
20

Is there hope beyond fear? Effects of social rehabilitation on unsocialized stray dogs

Casaca, Miriam January 2021 (has links)
Unsocialized stray dogs live unrestrained in urban areas, having limited to no direct contact with humans. Aggressive behaviour towards humans leads to their apprehension to shelters, where they tend to stay permanently. This study aimed to determine if unsocialized stray dogs could be rehabilitated and develop the social skills needed for adoption. Six unsocialized stray dogs (Group Stray) and 12 socialized dogs (C1: Control Group 1, n=6; C2: Control Group 2, n=6) housed in a shelter were selected. Stray and C2 dogs went through two training phases: social rehabilitation towards humans and leash training. Sociability towards humans and behaviour on a leash were tested in all groups following Valsecchi et al. (2011). Sociability Tests (ST) and Leash Tests (LT) were conducted before any intervention (ST1), after sociability training (ST2, LT1) and after leash training (ST3, LT2). Training sessions and tests were video recorded and posteriorly analysed by four observers. Results showed that for Stray, but not for C1 and C2, there was a significant increase in sociability from ST1 to ST3. Moreover, for Stray Group there was a significant decrease in the frequency of fear-related behaviours between ST1 and ST3. For leash behaviour, no significant changes were found from LT1 to LT2 for neither group. However, there was considerable individual variation, as not all strays overcame their extreme fear towards humans. These findings suggest that dog­–human interactions can be improved through training for dogs who do not show extreme fear and/or aggression towards humans.

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