• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 55
  • 43
  • 15
  • 10
  • 6
  • 6
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 160
  • 160
  • 55
  • 45
  • 41
  • 40
  • 27
  • 22
  • 20
  • 18
  • 17
  • 16
  • 16
  • 16
  • 16
  • 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.
111

Koncepce pracoviště pro měření lineárních motorů / Concept of linear motors measurement workplace

Knobloch, Jan January 2009 (has links)
Master’s thesis handles about measurement on linear motors. Acts about set of two linear machines on one rail. One is motor and second is load. Thesis paies their mathematical description, control and measurement. It’s made measurement of the linear motor load characteristic. Next measurement have to do with losses in the converter. Is chosen measuring instrument t for measurement during working cycle. During working cycle has determine power eciency of entire drive.
112

Implementace algoritmů řízení elektrických motorů v systémech CompactRIO / Implementation of Electric Motor Control Algoritms in CompactRIO systems

Gléba, Gergely January 2013 (has links)
This master’s thesis deals with the implementation of existing algorithms of electric AC motor control in Matlab Simulink to LabVIEW Control Design and Simulation. The first part of the thesis treats with the deduction of a mathematical model of an asynchronous motor, permanent magnet synchronous motor and with the theory of vector control of AC motors. In the next part there is a brief guide to create simulation algorithms in LabVIEW environment and to create the model of a motor with EMI functions in language C. The last part contains the comparison of Matlab Simulink and LabVIEW simulation tools.
113

Modelování a simulace vektorového řízení EC motorů v prostředí Simulink / Modeling and simulation of EC motor vector control in Simulink environment

Hořava, Jan January 2011 (has links)
The main goal of my work is the electrically commutated motor with the vector control’s application in the environment of Matlab – Simulink. The theoretical preamble of this document is dedicated to the physical construction of the EC motors. The most common methods are described in the following text – namely it is scalar control, direct torque control and vector control. The conclusion of this work includes the description and analyse of the single parts of a created model of concrete EC motor with the vector control, and simulations results’ evaluation.
114

Odhad polohy rotoru PMSM pomocí VF signálu / High frequency signal injection method for PMSM position estimation

Moravec, Vojtěch January 2016 (has links)
This thesis is focused on the design of vector control of interior permanent magnet synchronous motors. The first part of this work deals with vector control transformations and mathematical modelling of synchronous motors. Furthermore, algorithms of sensorless control are discussed, especially HF injection sensorless methods. One of these methods was used for torque and speed control. Problem of phase delay caused by filters and it’s compensation is also discused. One of the HF injection sensorless method was implemented on both motors. The results of simulations in MATLAB/Simulink and tests of real motors on dSpace are included.
115

Discovering Natural Product Chemistries for Vector Control

Lide Bi (15347593) 25 April 2023 (has links)
<p>  </p> <p>Vector-borne diseases (VBDs) represent a significant health burden worldwide, threatening approximately 80% of the global population. Insecticide-based vector control is the most effective method to manage many VBDs, but its efficacy has been declining due to high levels of resistance in vector populations to the main insecticide classes which operate via limited modes of action. Therefore, the discovery of new chemistries from non-conventional chemical classes and with novel modes of action is a priority for the control of vectors and VBDs. Natural products (NPs) are diverse in chemical structures and, potentially, modes of action. They have been used as insecticides for many decades and have inspired the development of multiple synthetic insecticides, suggesting the discovery of novel NPs could lead to the development of highly effective insecticides. </p> <p><br></p> <p>In this thesis, I report two studies with a main goal to identify novel mosquito-active insecticide leads that operate via modes of action distinct from existing insecticides. First, I tested the hypothesis that new mosquito-active insecticide leads with novel chemical structures, possibly operating via novel modes of action, can be identified by high-content larval phenotypic screening against a natural product collection and using novel phenotypic endpoints in addition to mortality endpoints. Here, I performed a high-content larval phenotypic screen using first instar (L1) larvae of <em>Aedes aegypti</em> (Linnaeus, 1762) against 3,680 compounds from the AnalytiCon MEGx Natural Product Libraries and a screening platform developed by Murgia et al., (2022). Compounds were screened in a 384-well plate format using the Perkin Elmer Opera Phenix and larvae were scored for lethal and novel phenotypic endpoints. Screening revealed five chemistries that caused larval mortality, including rotenone and a new NP chemistry, NP-4. The identification of rotenone confirmed the ability of the screen to detect mosquito-active NP chemistries. NP-4 caused high levels of larval mortality in the screen, and toxicity was confirmed in a subsequent concentration-response assay against third instar (L3) larvae of <em>Ae. aegypti</em>. 140 chemistries that caused atypical larval phenotypes, including cuticular pigmentation and morphometric changes relative to negative controls, were also identified by the screen. Some of these chemistries may operate by disruption of pathways regulating melanization, growth and development, and novel targets in the insect nervous systems, thus representing potential leads for further insecticide toxicity and mode of action studies. To facilitate quantitative analyses of atypical phenotypes, an attempt was made to assess the morphometrics of the thorax in larvae exposed to test chemistry, relative to control larvae. However, assessment was limited by the number of larvae images of suitable quality for measurements. </p> <p><br></p> <p>In the second study, I tested the hypothesis that metergoline (Murgia et al., 2022) and NP-4 (this study), two chemistries identified by the HTP phenotypic screen described in this project, operate via disruption of targets in the insect nervous systems that are distinct from the current insecticidal modes of products used in mosquito control programs. Specifically, I explored the hypothesis that metergoline operates via one or more insect orthologs of the mammalian G protein-coupled serotonin and dopamine receptors. An electrophysiology study was performed using the suction electrode technique and ganglia of the German cockroach, <em>Blattella germanica </em>(Linnaeus, 1767). To facilitate the investigation of metergoline agonism/antagonism and disruption of invertebrate GPCR signaling, 5-hydroxytryptamine (5-HT; serotonin) was included as a chemical probe. Electrophysiological recordings showed 5-HT (10µM and 1mM) and metergoline (10µM) caused no significant neurological activity at the tested concentrations in comparison to the saline control. However, a consistent neuro-inhibitory trend was observed, suggesting possible agonism of a 5-HT1-like receptor ortholog and antagonism of a putative 5-HT7-like receptor ortholog in the cockroach, respectively.  NP-4 caused significant neuro-inhibition at the tested concentration of 20µM, in comparison to the negative saline control. Given the demonstration of rapid contact toxicity to <em>Ae. aegypti</em> larvae and neurological inhibition in <em>B. germanica</em>, we propose NP-4 may act at one or more conserved targets in the insect nervous systems, which remain to be elucidated. </p> <p><br></p> <p>The significance of the present study is three-fold. First, this study reports the first high-content phenotypic screen of mosquito larvae against a NP collection and identification of 145 mosquito-active chemistries associated with lethal and phenotypic endpoints. These data confirm that the screening platform provided an innovative and effective system to rapidly identify mosquito-active small molecules with potential novel modes of action. Second, metergoline and NP-4 represent potential novel chemical leads for the development of new insecticides that can be incorporated into vector control programs targeting insecticide-resistant populations. Lastly, the study describes the first electrophysiology study of 5-HT, metergoline, and NP-4 via the suction electrode technique in an insect system and contributes new knowledge to the study of the insect serotonergic system, which represents an expanding area of vector biology research given its roles in feeding regulation.  </p> <p><br></p> <p>Future studies resulting from this thesis might include: (1) development of a set of morphometric criteria for quantitative analyses of atypical larval phenotypes, (2) incorporation of new phenotypic endpoints to expand the capacity of the screen to identify novel mode of action chemistries for insecticide discovery, and (3) identification of chemistry candidates suitable for further development from the 140 chemistries associated with atypical larval phenotypes in the primary screen using chemo-informatic and toxicological studies. In addition, studies using reverse transcription-polymerase chain reaction (RT-PCR), cell-based expression systems, mutant/insecticide resistant strains, and patch clamp electrophysiology could be pursued to further investigate the molecular mode of action of metergoline and NP-4, and potential for vector control.</p>
116

Concept and design of a hall-effect thruster with integrated thrust vector control

Stark, Willy, Gondol, Norman, Tajmar, Martin 01 March 2024 (has links)
Hall-effect thrusters (HETs) are among the most commonly used propulsion systems for attitude and orbit control of satellites. As an arrangement in a cluster or individually, equipped with a mechanical suspension, thrust in all three spatial directions can be generated, but requires additional mechanisms and components. Therefore, the Technische Universität Dresden (TU Dresden) is currently working on a concept for developing a Hall-effect thruster with integrated thrust vector control, which would allow steering in all three spatial directions with just a single thruster. This new concept is intended to work solely by influencing the ion beam and should not have any additional mechanical components. The HET will come with a segmented anode to set different electrical potentials at the anode and cause an inhomogeneous distribution of the electric field within the discharge channel, which results in an inhomogeneous force vector distribution at the exit plane. It is assumed that this will generate turning moments around the center of gravity. Deliberately causing those turning moments can therefore be used for steering with just one thruster. This work presents the concept of the propulsion system, gives an outlook on the advantages of its technology and shows capabilities for space applications.
117

Modelling, Analysis, and Control Aspects of a Rotating Power Electronic Brushless Doubly-Fed Induction Generator

Malik, Naveed ur Rehman January 2015 (has links)
This thesis deals with the modeling, analysis and control of a novel brushlessgenerator for wind power application. The generator is named as rotatingpower electronic brushless doubly-fed induction machine/generator (RPEBDFIM/G). A great advantage of the RPE-BDFIG is that the slip power recoveryis realized in a brushless manner. This is achieved by introducing an additionalmachine termed as exciter together with the rotating power electronicconverters, which are mounted on the shaft of a DFIG. It is shown that theexciter recovers the slip power in a mechanical manner, and delivers it backto the grid. As a result, slip rings and carbon brushes can be eliminated,increasing the robustness of the system, and reducing the maintenance costsand down-time of the turbine. To begin with, the dynamic model of the RPE-BDFIG is developed andanalyzed. Using the dynamic model, the working principle of the generatoris understood and its operation explained. The analysis is carried out atspeeds, ±20% around the synchronous speed of the generator. Moreover, thedynamics of the generator due to external load-torque disturbances are investigated.Additionally, the steady-state model is also derived and analyzed forthe machine, when operating in motor mode. As a next step, the closed-loop control of the generator is considered indetail. The power and speed control of the two machines of the generator andthe dc-link voltage control is designed using internal model control (IMC)principles. It is found that it is possible to maintain the stability of thegenerator against load-torque disturbances from the turbine and the exciter,at the same time maintain a constant dc-link voltage of the rotor converter.The closed-loop control is also implemented and the operation of the generatorwith the control theory is confirmed through experiments.In the third part of the thesis, the impact of grid faults on the behaviourof the generator is investigated. The operation of the generator and its responseis studied during symmetrical and unsymmetrical faults. An approachto successful ride through of the symmetrical faults is presented, using passiveresistive network (PRN). Moreover, in order to limit the electrical and mechanicaloscillations in the generator during unsymmetrical faults, the dualvector control (DVC) is implemented. It is found that DVC to a certain extentcan be used to safeguard the converter against large oscillations in rotorcurrents. Finally, for completeness of the thesis, a preliminary physical design ofthe rotating power electronic converter has been done in a finite elementsoftware called ANSYS. The thermal footprint and the cooling capability,with estimates of the heatsink and fan sizes, are presented. Besides, another variant of a rotating electronic induction machine whichis based on the Lindmark concept and operating in a single-fed mode is also investigated. It’s steady-state model is developed and verified through experiments. / <p>QC 20151006</p>
118

Analysis and Control Aspects of Brushless Induction Machines with Rotating Power Electronic Converters

Malik, Naveed ur Rehman January 2012 (has links)
This thesis deals with the steady-state, dynamic and control aspects of new type of brushless configuration of a doubly-fed induction machine in which the slip rings and carbon brushes are replaced by rotating power electronics and a rotating exciter. The aim is to study the stability of this novel configuration of the generator under mechanical and grid disturbances for wind power applications. The derivation, development and analysis of the steady-state model of the brushless doubly-fed induction machine with a rotating excitor and the power electronic converters mounted on the shaft and rotating with it, is studied. The study is performed at rated power of the generator between ±20% slip range. Moreover unity power factor operation between ±20% speed range is also discussed. Furthermore dynamic modeling and control aspects of the generator are also analyzed. The controllers were designed using Internal Model Control principles and vector control methods were used in order to control the generator in a closed-loop system. It is shown that through the use of proper feedback control, the generator behaves in a stable state both at super-synchronous and sub-synchronous speeds. Moreover Low Voltage Ride Through of the generator during symmetrical and unsymmetrical voltage dips is also investigated. Passive Resistive Network strategy is employed for Low Voltage Ride Through of the generator during symmetrical voltage dips. On the other hand, Extended Vector Control is used in order to control the negative sequence currents during unsymmetrical voltage dips. Suppression of negative sequence currents is important as they cause extra heating in the windings and affects the lifetime of the mechanical and electrical components of the generator and system due to oscillations in power and torque. In addition to the above studies a steady-state model of a single-fed induction machine is also developed and investigated where the rotating exciter is removed and the rotor windings are short-circuited through the two rotating power electronic converters. In this way the slip power circulates in the rotor and with the help of the two rotating electronic converters, rotor current is used to magnetize the induction machine thereby improving the power factor. The steady state model is verified through experimental results. / <p>20120914</p> / Brushless Wind Generator with Rotating Power Electronic Converters
119

Asinchroninės bejutiklės pavaros modeliavimas / Modelling of sensorless induction drive

Trinkūnaitė, Ingrida 21 June 2011 (has links)
Baigiamajame darbe sudarytas uždarosios asinchroninės bejutiklės vektoriškai valdomos pavaros imitacinis modelis ir ištirtos charakteristikos. Teorinėje darbo dalyje yra aptariami asinchroninių elektros pavarų privalumai bei šiose pavarose naudojami greičio jutikliai. Aprašomi stebiklių privalumai bei trūkumai, pagrindžiamas jų naudojimas asinchroninėse pavarose. Nagrinėjami bejutiklių elektros pavarų ypatumai, aprašomi vektorinio valdymo bendrieji principai bei aprašomi bejutiklėse vektoriškai valdomose pavarose naudojamų stebiklių modeliai. Pateikiami du skirtingi asinchroninių variklių matematiniai modeliai. Tiriamojoje dalyje parenkamas asinchroninio variklio modelis, tiriant abiejų imitacinių modelių dinamines greičio charakteristikas. Sudaromas stebiklio imitacinis modelis. Tiriamos stebiklio greičio dinaminės charakteristikos, sudaroma uždaroji greičio reguliavimo sistema su stebikliu. Analizuojamos uždarosios greičio reguliavimo sistemos greičio charakteristikos be apkrovos, su šuoline apkrova ir harmoniškai kintančia apkrova. Nagrinėjama sistemos stiprinimo koeficiento įtaka uždarosios greičio reguliavimo sistemos greičio charakteristikų pereinamiesiams procesams. Magistro darbas baigiamas tyrimo išvadomis, kuriose aptariamas darbo rezultatų realaus pritaikymo galimybės. Darbą sudaro 8 dalys: įvadas, žymėjimai, literatūros šaltinių analizė, tyrimo tikslas ir uždaviniai, teorinė dalis, tiriamoji dalis išvados ir pasiūlymai, literatūros šaltiniai. / The final master degree thesis presents sensorless vector controlled induction motor drive simulation model and characteristics. In the analytic part of master thesis advantages of induction motor drives and speed sensors are described. Advantages and disadvantages of speed estimators are presented and purpose of using them are proved. Peculiarities of sensorless motor drives, principles of vector control and models of speed estimators are analyzed. Two simulation models of induction motor are proposed. In the research part characteristics of induction motors are compared and motor model is chosen. Characteristics of open loop induction motor drive are investigated and simulation model of closed loop induction motor drive with speed estimator is designed. Characteristics of closed loop control system at no load, constant load and harmonic load are analyzed and influence of speed controller gain is considered. Thesis is closed with conclusions about designed system application in real projects. Structure: introduction, list of symbols, literature review, the study aims and objectives, the theoretical part, research part, conclusions and proposals, references.
120

Vigilância entomológica de vetores de arbovírus na cidade de São Paulo: análise espaço temporal de criadouros, de acordo com fatores sazonais e socioeconômicos, no período de 2012 a 2016 / Entomological surveillance of arbovirus vectors in the city of São Paulo: analysis of breeding sites, according to seasonal and socioeconomic factors, between 2012 and 2016

Diniz, Patricia Placoná 13 June 2018 (has links)
Introdução: Conhecer e monitorar fatores associados a transmissão de arboviroses são um grande desafio para os gestores de saúde pública e também uma necessidade para regiões onde há registro da circulação de arbovírus e a presença de vetores. Objetivos: Identificar os principais grupos de recipientes que podem se tornar ou são criadouros de mosquitos vetores no Município de São Paulo e verificar se os mesmos sofrem influências de fatores sazonais e socioeconômicos em sua distribuição. Método: Foram levantados dados das inspeções realizadas nas atividades de vigilância e controle de Aedes aegypti no período de 2012-2016, por Supervisão Técnica de Saúde e para o município. Em seguida foram construídos grupos de recipientes para avaliar predominância nas diferentes condições de encontro (existente, com água, com larva). Os indicadores gerados foram utilizados para testar diferenças significativas das frequências entre as estações do ano e analisar correspondência entre incidência de casos dengue e predominância de grupos de criadouros. Posteriormente, foi realizada análise de agrupamento por fatores socioeconômicos para identificar diferenças na distribuição dos grupos de recipientes. Para as análises de variância foi utilizado o teste não paramétrico de Kruskal-Wallis. Resultados: O grupo de recipientes móveis foi o potencial criadouro mais frequente em todos os anos, seguido dos grupos planta e pneus. Móvel e planta foram os criadouros mais frequentes para o município. O grupo móveis, apesar de numeroso, não foi o mais colonizado. Por outro lado, os depósitos para armazenamento de água tiveram baixa frequência, porém alta proporção de colonização. A sazonalidade influenciou na distribuição de recipientes com água e com larva, sendo que as maiores frequências ocorreram no verão e outono. A proporção de imóveis tendo recipientes com água aumentou de acordo com o tempo, principalmente em 2015. O grupo que teve maior incremento do índice nesse período foi o de depósito não ligado à rede. Foram gerados cinco grupos de STS por condições socioeconômicas, nos quais houve diferenças no padrão de distribuição de potenciais criadouros e criadouros. Regiões com melhor condição socioeconômica apresentaram menor frequência dos indicadores, mas não necessariamente menor risco de transmissão de dengue no período avaliado. Conclusões: Os principais grupos de criadouros mais frequentes no Município de São Paulo dentro do período analisado foram os de menor tamanho, principalmente os do tipo móvel. Reservatórios de maior tamanho e destinados ao armazenamento de água demonstraram importância na proporção de colonização e tiveram sua frequência aumentada no período da crise hídrica do abastecimento. Fatores sazonais e condições socioeconômicas influenciaram a distribuição de criadouros em São Paulo. Para melhor direcionamento das ações de prevenção e controle de vetores, analises sistemáticas e continuas por regiões devem ser realizadas. / Introduction: Knowing and controlling factors associated with arbovirus transmission is a major challenge for public health managers, but it is necessary for regions where arbovirus circulation and the presence of vectors are present. Objectives: To identify the main groups of containers that can become or are breeding sites of mosquito vectors in the São Paulo Municipality and verify if their distribution are influenced by seasonal and socioeconomic factors. Method: Data were collected from the inspections carried out in the surveillance and control activities of Ae. aegypti in the period 2012-2016, by Health Technical Supervision and county. Groups of containers were then created to evaluate predominance in the different checked conditions (existing, with water, with larvae). The generated indicators were used to test significant differences of the frequencies between the seasons of the year and to analyze correspondence between incidence of dengue cases and predominance of breeding sites groups. After, a socioeconomic grouping analysis was performed to identify differences in the distribution of groups of recipients. The Kruskal-Wallis non-parametric test was used for the variance analysis. Results: The group of mobile containers was the most frequent potential breeding site in all the years, followed by container plants and tires groups. Mobile and plant were the most frequent breeding sites for the county. The mobile group, although numerous, was not the most colonized. On the other hand, deposits for water storage had a low frequency, but a high proportion of colonization. Seasonality influenced the distribution of water and larvae containers, with the highest frequencies occurring in summer and fall. The proportion of buildings having containers with water increased over time, especially in 2015. The group that had the largest increase in the index in this period was the deposit not connected to the water supply network. Five Health Technical Supervision groups were generated by socioeconomic conditions, in which there were differences in the pattern of distribution of potential breeding sites and breeding sites for mosquitoes. Regions with better socioeconomic status had lower frequency of indicators, but not necessarily a lower risk of dengue transmission in the period evaluated. Conclusions: The main breeding sites groups most frequent in the city of São Paulo during the analyzed period were the smaller groups, mainly those of the mobile type. Larger reservoirs destined to water storage showed importance in the proportion of colonization and had their frequency increased in the period of the water supply crisis. Seasonal factors and socioeconomic conditions influenced the distribution of breeding sites in. To better target vector prevention and control actions, systematic and continuous analyzes by regions should be performed.

Page generated in 0.0745 seconds