• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 94
  • 82
  • 17
  • 13
  • 1
  • 1
  • Tagged with
  • 208
  • 124
  • 20
  • 18
  • 16
  • 16
  • 14
  • 12
  • 12
  • 11
  • 11
  • 11
  • 11
  • 10
  • 10
  • 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.
171

Diseño de un controlador avanzado basado en redes neuronales para la gestión de la mezcla aire-gasolina en un motor alternativo

Nevot Cercós, Javier 17 March 2000 (has links)
En la presente tesis se desarrolla un sistema de control de la mezcla de aire y gasolina en un motor alternativo de cuatro tiempos, basado en redes neuronales. Para que el catalizador logre un grado de depuración aceptable con todos los gases contaminantes simultáneamente, debe mantenerse la proporción de aire y combustible, dentro de una banda muy estrecha. En estado estacionario, este objetivo se cumple sin demasiados problemas, pero el funcionamiento habitual de un vehículo es en régimen muy transitorio, donde los sistemas convencionales no logran evitar desviaciones importantes del punto de consigna. Estos se basan además en una gran cantidad de tablas estáticas, que deben calibrarse de forma experimental, lo cual es bastante costoso tanto en tiempo como en dinero.Para evitar estos problemas se ha diseñado un modelo matemático de un motor, que comprende todo el proceso de formación de la mezcla, sensores, la generación del par motor y la dinámica del vehículo. La realización final se ha realizado en el lenguaje de simulación MatLab/Simulink®. Los datos requeridos son fácilmente obtenibles bien por metrología, bien de forma experimental. Se ha validado con un motor SEAT de 1,6 l y 74 kW.Como primer paso se ha aplicado una estrategia de control convencional bastante simple, consistente en un controlador feedforward estático, más un controlador feedback de tipo PI ó PID. Esto ha permitido el estudio de las principales características del motor desde el punto de vista de control. Con los resultados obtenidos se ha diseñado un observador basado en una red neuronal, que elimine los retardos puros del sistema y que pueda ser utilizado para cerrar el lazo de control. Primero se ha usado una red feedforward, pero vistos los malos resultados, se ha desarrollado una red neuronal recurrente a partir de la red de Elman, que se ha modificado convenientemente para adaptarla a las dificultades propias del problema. El algoritmo de entrenamiento utilizado se basa en el de retropropagación clásico, y modifica no sólo los pesos entre capas, sino también los correspondientes a las neuronas de contexto, las cuales permiten memorizar estados internos. La principal mejora consiste en separar las neuronas de contexto en tantos grupos como entradas tiene la red, y entrenarlos por separado, de modo que cada grupo se adapte a la dinámica particular de la entrada a la que va asociado. Se muestra mediante simulación el comportamiento del conjunto motor más observador en lazo cerrado, y se compara con el esquema convencional. Se prueba asimismo la robustez del sistema frente a distintas consignas, ruido en la planta y defectos de sintonía. / In the present thesis a control system for the air-fuel mixture in a reciprocating four-stroke engine is developed, based on neural networks. The air-fuel ratio has to be kept within a very narrow window so that the catalyst achieves an acceptable degree of purification simultaneously with all the polluting gases. In steady state, this goal can be fulfilled without difficulties, but the usual operation of a vehicle is in a very transient state, where the conventional systems are not able to avoid important excursions from the set point. They also rely on a great number of look-up tables, which have to be tuned experimentally, thus with an enormous investment of money and time.To avoid those problems a mathematical model of an engine has been designed, in such a way that it comprises of the whole mixture formation process, sensors, the torque generation and the vehicle dynamics. Finally it has been implemented in the simulation language MatLab/Simulink®. The required data is easily available both from metrology, and experimental work. It has been validated with a 1,6 litre 74 kW SEAT engine.As a first step, a quite simple conventional control strategy has been applied, consisting of a static feedforward controller, and a PI or PID feedback controller. This has permitted studying the main features of the engine from the control point of view.With the obtained results an observer based on a neural network has been designed, which eliminates the delays of the system and that can be used to close the control loop. First a feedforward network has been used, but due to the bad results, a recurrent neural network has been developed starting from the Elman network, which has been properly modified in order to adapt it to the characteristic difficulties of the problem. The training algorithm used is based on that of classical backpropagation, and it modifies not only the weights interconnecting different layers, but also those corresponding to the context neurons, which allow the memorising of internal states. The main improvement consists in separating the context neurons in as many groups as the network has inputs, and to train them separately, so that each group adapts to the particular dynamics of the input with which it is associated. The behaviour of the engine plus the observer in closed loop is shown by means of simulation, and is compared with the conventional scheme. It is proven the robustness of system response to different set points, noise in the plant and tuning defects.
172

Dysfunkce gastrointestinálního traktu u kriticky nemocných / Gastrointestinal tract dysfunction in critical ill patients

Balihar, Karel January 2015 (has links)
Multiorgan dysfunction syndrom is the major driving pathophysiological mechanism of morbidity and mortality in critically ill patients. Gastrointestinal dysfunction usually develops as a result critical illness and it is believed to play a key role in the development and progression of multiple organ dysfunction. Moreover, any primary disorder of the gastrointestinal tract, if severe enough, can lead to a critical state and secondary multiorgan dyfunction. Despite intensive experimental and clinical research, reliable tools for monitoring and evaluation of the severity of gastrointestinal dysfunction remain unknown. In the same line, therapy of this complex pathology remains largely supportive. The aim of this thesis was first to explain the severity of the most common and most serious nosocomial infection of the digestive tract, second to elucidate the safety and effectiveness of the endoscopic dual enteral probe insertion in ventilated critically ill patients, and, third to evaluate new diagnostic tools of the gastrointestinal dysfunction. Finally, we present an ongoing project aimed at investigating esophageal dysfunction in mechanically ventilated critically ill patients.
173

Avaliação da esterilidade dos instrumentais laparoscópicos de uso único reprocessados após contaminação artificial / Sterility evaluation of single use laparoscopic devices reprocessed after artificial contamination

Cristiane de Lion Botero Couto Lopes 20 December 2006 (has links)
Os materiais de uso único (MUU) são utilizados há décadas na assistência à saúde. Inicialmente produzidos com a finalidade de prontamente disponibilizar os materiais para uso na assistência a saúde e ao mesmo tempo diminuir a sobrecarga com o trabalho inerente ao reprocessamento dos materiais. Com o passar do tempo, principalmente por questões financeiras, estes passaram a ser reutilizados. A partir de então diversos questionamentos têm sido suscitados a respeito do risco de transmissão de infecção pelo reuso destes artigos em decorrência da dificuldade para de limpeza, desinfecção e esterilização seguras destes. Os materiais utilizados para as cirurgias vídeo-laparoscópicas encontram-se entre os MUU de preço considerável e complexidade importante em relação às dificuldades para limpeza, devido à sua conformação com espaços internos inacessíveis e impossibilidade de desmonte. Isto posto, as pinças grasper, dissector, tesoura, agulha de Veress, sistema de sonda de eletrocirurgia (ou aspirador e irrigador) e sua respectiva haste, instrumentais básicos nos procedimentos de vídeo-cirurgia-laparoscópica, foram o objeto desta investigação com o propósito de avaliar a eficácia da esterilidade destes acessórios de uso único após contaminação artificial desafio e comparar os resultados dos testes de esterilidade dos MUU com os dos materiais equivalentes reprocessáveis – denominados neste estudo como grupo controle. Tratou-se de uma pesquisa experimental, laboratorial e comparativa. O inóculo utilizado para a contaminação artificial dos instrumentais de uso único constituiu-se de suspensão de esporos bacterianos do Bacillus atrophaeus var. niger e de sangue de carneiro desfibrinado esterilizado. Para o grupo controle o microrganismo eleito foi o Geobacillus stearothermophilus acrescido também de sangue de carneiro desfibrinado. Antes de proceder aos experimentos validou-se a metodologia analítica em duas fases: fase 1 - realizada a contagem de U.F.C. em três unidades de cada um dos materiais dos grupos experimental e controle após a contaminação artificial antecedendo a limpeza; fase 2 - realizada a contagem de U.F.C. em três unidades de cada um dos materiais dos grupos experimental e controle após a contaminação artificial e procedimento de limpeza. Desta forma, assegurada a recuperação dos contaminantes em todas as amostras da primeira fase e a diminuição do bioburden inicial após a limpeza dos instrumentais na 2ª fase, deu-se prosseguimento aos experimentos. Os materiais laparoscópicos foram intencionalmente contaminados com o inóculo desafio e submetidos após ao protocolo teste para validação que consistiu da seguinte seqüência: limpeza automatizada em lavadora ultra-sônica com retrofluxo com auxílio do detergente enzimático, limpeza manual complementar com serpilhos e irrigação dos lumens dos instrumentais com água sob pressão. Por fim, foi realizado o enxágüe com água destilada esterilizada, secagem com ar comprimido medicinal, acondicionamento em embalagem de papel grau cirúrgico e filme e submetidos a esterilização em Óxido de Etileno 12/88 (materiais de uso único) e em autoclave (materiais de aço inoxidável). Os materiais esterilizados foram inoculados diretamente nos meios de cultura de caseína soja e incubados por 20 dias quando foi feita a leitura final dos resultados das culturas. Os resultados encontrados foram 100% negativos para a recuperação dos microrganismos contaminantes nos 2 grupos - experimental e controle. Estes achados permitiram concluir que o reprocessamento dos materiais de uso único foi validado em relação à esterilidade permitindo chegar a um protocolo de reprocessamento / Single use devices (SUD) have been used in healthcare for decades. They were initially produced for making them readily available for use in healthcare and at the same time lower the inherent workload for device reprocessing. After time, mainly for financial reasons, they became reused. Since then, several questioning has been raised regarding to the risk of infection transmission by reusing these devices due to their difficulty of safe cleaning, disinfection and sterilization. Devices used for videosurgeries are among the SUD of considerable price and important complexity due to cleaning difficulties, because of their adjustments in inaccessible inner spaces and impossibility of taking them out into pieces. Thus, grasper calipers, dissecting forceps, scissors, Veress insuflation needle, electrosurgery probe system (or suction and irrigation tubes) and its respective dissector cannula, basic devices in videosurgery laparoscopic procedures were all the subject of investigation aimed to evaluate the effectiveness of sterility of these single use products after challenged artificial contamination and comparing the results of sterility tests of SUD to their equivalent reprocessed devices – named in this study as control group. It’s a comparative, laboratory experimental research. The inoculum used for artificial contamination of single use devices was the suspension of Bacillus atrophaeus var. niger bacteria spores and sterilized defibrinated sheep blood. For the control group, the elected strain was Geobacillus stearothermophilus adding also the defibrinated sheep blood. Before carrying out the experiments, the analytical methodology was validated in two phases: phase 1 – counting the colony formation units in three units of each one of the devices from the experimental and control groups after the artificial contamination and cleaning procedures. This way, assured the contaminant recovery in all samples of the 1st phase and the reduction of initial bioburden after device cleaning in the 2nd phase, it was carried on the experiments. The laparoscopic devices were intentionally contaminated with challenged inoculum and submitted after the trial test to validation that was consisted of the following sequence: cleaning in automated narrow-lumen cleaner with enzymatic detergent, complementary manual cleaning with brush and lumen washing of devices with water under pressure. At last, it was made rinsing with sterile distillated water, drying with medical compressed air, packing in surgical paper and film wrapping and submitted to sterilization in ethylene oxide 12/88 (single use devices) and in autoclave (stainless steel devices). The sterilized devices were contaminated directly in the casein soy media and incubated for 20 days when it was made the final reading of media results. The outcomes found were 100% negative for recovering of contamination strains in the 2 groups – the experimental and the control. These findings permitted us to conclude that single use device reprocessing was validated regarding to sterility allowing us to get a reprocessing guideline
174

Desenvolvimento de uma sonda TDR helicoidal para uso em conjunto com o ensaio CPT / Developing a coil TDR probe to use together with the CPT test

Katerin Guerrero Doria 21 August 2015 (has links)
A reflectometria no domínio do tempo permite estimar o teor de umidade de um meio através da sua correlação com a constante dielétrica. Uma sonda helicoidal TDR, que pode ser cravada em conjunto outros ensaios de penetração in situ para a estimativa do teor de umidade em diversas profundidades, tem aplicação interessante para a investigação geotécnica do subsolo. No presente trabalho, uma sonda TDR foi adaptada e utilizada em conjunto ao ensaio CPT para caracterização de um perfil de solo arenoso não saturado que ocorre na região de Bauru (SP). A calibração dessa sonda foi feita em laboratório especificamente para esse solo. As equações de calibração que mostraram os melhores resultados foram definidas correlacionando a constante dielétrica, condutividade elétrica aparente e a massa específica seca com o teor de umidade. Com o intuito de melhorar a acurácia na determinação do teor de umidade em campo e eliminar possíveis interferências no registro da onda eletromagnética, foram efetuadas modificações em algumas características do projeto original dessa sonda. Tais modificações consistiram em separar os eletrodos condutores e as partes metálicas da sonda, e eliminar o cabo coaxial de extensão, conectando a sonda diretamente a um cabo coaxial de 12 m de comprimento. Tais mudanças levaram a uma melhoria significativa na determinação do perfil de teor de umidade do local estudado. Os valores de teor de umidade de campo determinados usando o TDR ao longo de 8 m de profundidade foram comparados com os valores de referência obtidos de amostras deformadas retiradas com trado mecânico. O erro médio na estimativa do perfil de teor de umidade gravimétrico utilizando a sonda TDR helicoidal foi de 1.61%, na última campanha de ensaios realizados. Os resultados dessa pesquisa indicam que esta ferramenta é adequada para estimar do perfil de teor de umidade para uso em conjunto com o ensaio CPT. / The time domain reflectometry allows estimating the moisture content of a medium by means of its correlation with the dielectric constant. A coil TDR probe, which can be driven into the ground together with others in situ penetration tests, can be used to estimate the moisture content at different depths. It is an interesting approach for geotechnical site characterization. In this work, a coil TDR probe was adapted and used in combination with the CPT test for the site characterization of an unsaturated sandy soil profile which occurs in the region of Bauru (SP). The probe calibration was performed in laboratory specifically for that soil. The calibration equation, which presented the best results, were defined correlating the dielectric constant, electrical conductivity and dry density with the moisture content. In order to improve the accuracy for determining the water content in the field and to eliminate possible interference on the electromagnetic wave registration, modifications were made in some characteristics of the original design of this probe. Such modifications consisted in separating the conductive electrodes from the metal parts of the probe, and eliminating the coaxial extension cable, connecting the probe directly to a coaxial cable 12 m long. Such changes have led to a significant improvement in the determination of the moisture content profile of the studied site. The moisture content values determined in situ by using the TDR along 8 m depth were compared with reference values obtained from disturbed soil samples collected using mechanical augers. The root mean square error of the gravimetric water content profile using the TDR coil probe was 1.61% in the last test campaign. The results of this research indicate that this tool is suitable to estimate the gravimetric moisture content together with the CPT test.
175

Analýza dynamických interakcí těl axonů a jejich biofyzikální modelování. / Analysis of dynamical interactions of axon shafts and their biopysical modelling.

Šmít, Daniel January 2017 (has links)
in English While axon fasciculation plays a key role in the development of neural networks, very lit- tle is known about its dynamics and the underlying biophysical mechanisms. In a model system composed of neurons grown ex vivo from explants of embryonic mouse olfactory epithelia, we observed that axons dynamically interact with each other through their shafts, leading to zippering and unzippering behaviour that regulates their fasciculation. Taking advantage of this new preparation suitable for studying such interactions, we carried out a detailed biophysical analysis of zippering, occurring either spontaneously or induced by micromanipulations and pharmacological treatments. We show that zippering arises from the competition of axon-axon adhesion and me- chanical tension in the axons. This is upheld on quantitative level by conforming change of network global structure in response to various pharmacological treatments, without active involvement of growth cones. The calibrated manipulations of interacting shafts provide qualitative support for the hypothesis, and also allow us to quantify the mechan- ical tension of axons in our system. Furthermore, we introduce a biophysical model of the zippering dynamics, which efficiently serves the purpose of estimating the magnitude of remaining involved...
176

Kurz lavinové prevence pro střední školy / Avalanche prevention course for High schools

Žegklitz, Martin January 2016 (has links)
The theme of this thesis is the Avalanche prevention course for High Schools. Thesis includes both theoretical and experimental part. The theoretical part mainly includes a description of various items used in the avalanche prevention courses. It also contains various methodological procedures, rules, strategy and analysis, which are used for such courses. The research part includes the avalanche prevention course for secondary schools proposal itself under the given conditions and next specifics. In partial steps thesis is mainly focused on proposed content, time allocation, methodical layout, capacity of the course and equipment needed for the implementation of the course.
177

Análisis del estatuto jurídico de compras públicas en Chile

Ayala Castro, Jaime Antonio January 2016 (has links)
Memoria (licenciado en ciencias jurídicas y sociales) / Con ocasión de los múltiples casos conocidos por el Tribunal de Defensa de la Libre Competencia en Chile en materia de contratación pública, este trabajo se centra, en primer lugar, en el análisis de las interacciones que existen entre ambos sectores de nuestro ordenamiento jurídico tanto a nivel dogmático –por la vía de los principios consagrados por la Constitución Política de la República de Chile– como a nivel legal y reglamentario –las que, como demostraremos, son escasas– a fin de escudriñar cómo los entes legislativos han dado reconocimiento expreso o tácito a tal vinculación. En segundo lugar, y a efectos de demostrar la necesidad de que ambos estatutos jurídicos se relacionen de forma más íntima y expresa, señalamos algunos pronunciamientos judiciales y doctrinales que explican cómo hacer aplicable, por la vía del principio de juridicidad administrativa, la obligación de observar por parte de todos los órganos de la Administración del Estado, en todas sus actuaciones, las normas contenidas en el DL 211. En tercer lugar, identificamos los casos en que el H. Tribunal de Defensa de la Libre Competencia ha emitido pronunciamientos respecto de conductas anticompetitivas en el marco de procesos de licitación regidos por la Ley N° 19.886, conociendo y resolviendo demandas incoadas por particulares y requerimientos interpuestos por la Fiscalía Nacional Económica en contra de diversos órganos administrativos licitantes, a fin de extraer de ellos los criterios que dicho Tribunal ha aplicado. Enseguida, expondremos algunas directrices que el ente persecutor de infracciones a la libre competencia en Chile, la FNE, ha recomendado a la Administración para, preventivamente, evitar conductas anticompetitivas y también ciertos lineamientos que la Organización para la Cooperación y el Desarrollo Económico (OCDE) ha aconsejado para resguardar la competencia en procesos licitatorios. Por último, hemos escogido un caso de cierta relevancia mediática y relativamente reciente para ser analizado a la luz de todos los planteamientos que se expusieron a lo largo del trabajo, cual es el de Sonda con Registro Civil, en el marco de la licitación para la provisión de servicios de identificación personal
178

Základy právního vědomí u žáků jako východisko pro výuku výchovy k občanství / Legal awareness among pupils as a starting point for civic education

Dousková, Pavla January 2021 (has links)
The diploma thesis is focused on the basics of legal awareness of pupils. Its aim is to examine children's conceptions of responsibility and the processes associated with it in pupils at the beginning of the secondary school, to identify gaps and misconceptions with which pupils come to teaching and to propose recommendations for teaching. The theoretical part introduces the concept of responsibility, especially from the point of view of law, the psychological foundations of children's concepts and research devoted to children's concepts in the field of law. The practical part consists of a probe into children's conceptions of responsibility. The probe is implemented on pupils before the transition to the secondary school and on pupils in the 6th grade. The probe is based on two situations, which pupils can meet in their daily lives. The situations take place in two familiar environments - school and park. We focused on these situations in semi-structured interviews, which were then qualitatively evaluated. Based on the probe, it was found that students at the beginning of the 2nd grade understand responsibility, but have difficulty identifying the rules according to which it is attributed and do not understand the relationships and powers of the institutions associated with responsibility. Also...
179

Aplikace rychlostní sondy se žhavenými drátky při měření rychlostního pole za automobilovou vyústkou / Application of an anemometric hot-wire probe to the measurement of a velocity field downstream of an automotive ventilation outlet

Šíp, Jan January 2018 (has links)
This diploma thesis deals with the research of the flow in front of the benchmark automotive vent. Using thermoanemometry, the velocity field in the area in front of the vent was measured in detail and the intensity of the turbulence was calculated. Computational fluid dynamics of the air flow from the vent was also performed using the STAR-CCM + program. In addition, the influence of the surrounding surfaces simulating the real environment of the automobile on the air flow from the vent was investigated. The diploma thesis contains the calculation of measurement uncertainty. The purpose of this thesis is to obtain complex data on the velocity field and to use them for validation of Computational fluid dynamics.
180

Stavební průzkum a diagnostika konstrukce / Survey and Diagnostics of Building Construction

Pernová, Jana January 2019 (has links)
The object of the theoretical part of this diploma thesis is overview of the historical development of reinforced concrete and concrete reinforcements, including the elaboration of a detailed methodology for the assessment of the state of bridge structures. It is applied in practical parts of two bridges independent on each other. There are used the most modern technologies like device Hilti PS1000, profometer PM-630 to diagnose objects and they are completed by chopped probe. It also includes a structural analysis of the load capacity, that concurrently evaluates the quality of the construction.

Page generated in 0.0417 seconds