• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 2
  • 1
  • 1
  • Tagged with
  • 9
  • 4
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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.
1

Symtomförekomst och noceboeffekter hos individer med byggnadsrelaterad ohälsa

Gabriella, Öström, Lina, Högström January 2018 (has links)
Byggnadsrelaterad ohälsa (BRO) är en av flera miljökänsligheter. De två konstrukten modern hälsooro (MHO) och somatosensorisk förstärkning (SSA) har båda visat sig kopplade till nocebo och de uppvisas ofta hos personer med miljökänsligheter. Det första syftet med uppsatsen var att öka förståelsen för vilka symtom som kännetecknar BRO, vilket undersöktes via 20 items utvalda från The Idiopathic Enviromental Intolerance Symtom Inventory (IEISI) vilka överensstämmer med WHOs lista över BRO-symtom. Det andra syftet var att öka kunskapen om vilken roll nocebo har i BRO, vilket undersöktes via Modern Health Worries (MHWS) och Somatosensory Amplification Scale (SSAS). Data inhämtades från en pågående studie vid Umeå Universitet. Urvalsgruppen utgjordes av 79 individer som uppgett att de upplevde BRO-symtom varje vecka. Data analyserades via korrelationsanalyser. Gruppen uppvisade variation i vilka och hur många symtom individerna rapporterade. Resultatet från korrelationsanalyserna visade sammantaget på att nocebo inte hade en betydande roll i rapporterandet av BRO-symtom i urvalsgruppen. Studien visade att gruppen med BROpatienter varken oroade sig mer än norm eller var särskilt känsliga för sensoriska intryck. / Building Related Illness (BRI) is one of several environmental sensitivities. The two constructs Modern Health Worries (MHW) and Somatosensory Amplification (SSA) have both been shown to be linked to nocebo and are often reported by people with environmental sensitivities. The first purpose of this paper was to increase the understanding of symptoms that characterize BRI, which was investigated via 20 items selected from The Idiopathic Enviromental Intolerance Symptom Inventory (IEISI) that complies with WHO's list of BRI symptoms. The second purpose was to increase knowledge about the role of nocebo in BRI, which was investigated via Modern Health Worries Scale (MHWS) and Somatosensory Amplification Scale (SSAS). Data was obtained from an ongoing study at Umeå University. The sample consisted of 79 individuals who reported that they experienced BRI symptoms each week. Data was analyzed via correlation analyzes. The group showed variability concerning which and how many symptoms the individuals reported. The results from the correlation analyzes showed that nocebo did not play a significant role in the reporting of BRI symptoms in the selection group. The study showed that the group of BRI patients neither worry more than the norm nor was particularly sensitive to sensory impressions.
2

Résolution numérique d'équations aux dérivées partielles à coefficients variables / Numerical resolution of partial differential equations with variable coefficients

Aghili, Joubine 02 December 2016 (has links)
Cette thèse aborde différents aspects de la résolution numérique des Equations aux Dérivées Partielles.Le premier chapitre est consacré à l'étude de la méthode Mixed High-Order (MHO). Il s'agit d'une méthode mixte de dernière génération permettant d'obtenir des approximations d'ordre arbitraire sur maillages généraux. Le principal résultat obtenu est l'équivalence entre la méthode MHO et une méthode primale de type Hybrid High-Order (HHO).Dans le deuxième chapitre, nous appliquons la méthode MHO/HHO à des problèmes issus de la mécanique des fluides. Nous considérons d'abord le problème de Stokes, pour lequel nous obtenons une discrétisation d'ordre arbitraire inf-sup stable sur maillages généraux. Des estimations d'erreur optimales en normes d'énergie et L2 sont proposées. Ensuite, nous étudions l'extension au problème d'Oseen, pour lequel on propose une estimation d'erreur en norme d'énergie où on trace explicitement la dépendance du nombre de Péclet local.Dans le troisième chapitre, nous analysons la version hp de la méthode HHO pour le problème de Darcy. Le schéma proposé permet de traiter des maillages généraux ainsi que de faire varier le degré polynomial d'un élément à l'autre. La dépendance de l'anisotropie locale du coefficient de diffusion est tracée explicitement dans l'analyse d'erreur en normes d'énergie et L2.La thèse se clôture par une ouverture sur la réduction de problèmes de diffusion à coefficients variables. L'objectif consiste à comprendre l'impact du choix de la formulation (mixte ou primale) utilisée pour la projection sur l'espace réduit sur la qualité du modèle réduit. / This Ph.D. thesis deals with different aspects of the numerical resolution of Partial Differential Equations.The first chapter focuses on the Mixed High-Order method (MHO). It is a last generation mixed scheme capable of arbitrary order approximations on general meshes. The main result of this chapter is the equivalence between the MHO method and a Hybrid High-Order (HHO) primal method.In the second chapter, we apply the MHO/HHO method to problems in fluid mechanics. We first address the Stokes problem, for which a novel inf-sup stable, arbitrary-order discretization on general meshes is obtained. Optimal error estimates in both energy- and L2-norms are proved. Next, an extension to the Oseen problem is considered, for which we prove an error estimate in the energy norm where the dependence on the local Péclet number is explicitly tracked.In the third chapter, we analyse a hp version of the HHO method applied to the Darcy problem. The resulting scheme enables the use of general meshes, as well as varying polynomial orders on each face.The dependence with respect to the local anisotropy of the diffusion coefficient is explicitly tracked in both the energy- and L2-norms error estimates.In the fourth and last chapter, we address a perspective topic linked to model order reduction of diffusion problems with a parametric dependence. Our goal is in this case to understand the impact of the choice of the variational formulation (primal or mixed) used for the projection on the reduced space on the quality of the reduced model.
3

Design and implementation of ANN based phase comparators applied to transmission line protection

Chawla, Gaganpreet 24 February 2010
There has been significant development in the area of neural network based power system protection in the previous decade. Neural network technology has been applied for various protective relaying functions including distance protection. The reliability and efficiency of ANN based distance relays is improving with the developing digital technologies. There are, however, some inherent deficiencies that still exist in the way these relays are designed. This research addresses some of these issues and proposes an improved protective relaying scheme.<p> The traditional ANN distance relay designs use parameter estimation algorithms to determine the phasors of currents and voltages. These phasors are used as inputs to determine the distance of a fault from relay location. The relays are trained and tested on this criterion; however, no specific relay characteristic has been defined. There is a need for development of a new methodology that will enable designing of an ANN that works as a generic distance relay with clearly defined operating boundary.<p> This research work presents a modified distance relaying algorithm that has been combined with a neural network approach to eliminate the use of phasors. The neural network is trained to recognize faults on basis of a specific relay characteristic. The algorithm is flexible and has been extended for the design of other relays. The neural network has been trained using pure sinusoidal values and has been tested on a 17-bus power system simulated in PSCAD. The training and testing of the neural network on different systems ensures that the relay is generic in nature. The proposed relay can be used on any transmission line without re-training the neural network.<p> The design has been tested for different fault conditions including different fault resistances and fault inception angles. The test results show that the relay is able to detect faults in lesser time as compared to conventional relay algorithms while maintaining the integrity of relay boundaries.
4

Design and implementation of ANN based phase comparators applied to transmission line protection

Chawla, Gaganpreet 24 February 2010 (has links)
There has been significant development in the area of neural network based power system protection in the previous decade. Neural network technology has been applied for various protective relaying functions including distance protection. The reliability and efficiency of ANN based distance relays is improving with the developing digital technologies. There are, however, some inherent deficiencies that still exist in the way these relays are designed. This research addresses some of these issues and proposes an improved protective relaying scheme.<p> The traditional ANN distance relay designs use parameter estimation algorithms to determine the phasors of currents and voltages. These phasors are used as inputs to determine the distance of a fault from relay location. The relays are trained and tested on this criterion; however, no specific relay characteristic has been defined. There is a need for development of a new methodology that will enable designing of an ANN that works as a generic distance relay with clearly defined operating boundary.<p> This research work presents a modified distance relaying algorithm that has been combined with a neural network approach to eliminate the use of phasors. The neural network is trained to recognize faults on basis of a specific relay characteristic. The algorithm is flexible and has been extended for the design of other relays. The neural network has been trained using pure sinusoidal values and has been tested on a 17-bus power system simulated in PSCAD. The training and testing of the neural network on different systems ensures that the relay is generic in nature. The proposed relay can be used on any transmission line without re-training the neural network.<p> The design has been tested for different fault conditions including different fault resistances and fault inception angles. The test results show that the relay is able to detect faults in lesser time as compared to conventional relay algorithms while maintaining the integrity of relay boundaries.
5

Proteção contra perda de excitação em geradores síncronos: uma nova proposta utilizando o método do cálculo contínuo da impedância aparente / Loss of excitation protection in synchonous generators: a new approach using the continuous apparent impedance calculation method

Gazen, Yuri Neves 16 October 2015 (has links)
This work presents a new Loss-of-Excitation in synchronous generators protection scheme based on the Continuous Apparent Impedance Calculation. This methodology aiming to improve security and dependability to the ANSI 40 function in order to distinguish cases of loss of excitation from other external disturbances such as stable power swings caused by the elimination of short circuits, for instance. Traditional loss of excitation protection methods may operate incorrectly in the occurrence of this kind of disturbance. Since the proposed methodology have settings related to the reactance parameters of the protected generator (Xd e X d), tests have been carried out considering two different machines with distinct parameters of the WSCC 9-bus system. Aiming to test the proposed technique and compare it with other widely used methods Mason, Berdy and Positive Offset, three kinds of events were simulated, namely, total loss of excitation, partial loss of excitation and stable power swing, for different initial generator loading. The computer simulation results demonstrate that the proposed method correctly identifies the occurrence of loss-of-excitation and does not operate in situations of stable power swings, regardless of the parameters of generators and their operating condition. Its alarm function allows taking the underexcited machine out faster by using manual intervention, which is especially useful when the initial loading is light or when it‟s a partial loss of excitation case. Another highlight is the ease adjustment of the method, which is related only with the generator‟s reactances data. / Este trabalho apresenta um novo método de proteção contra perda de excitação de geradores síncronos fundamentado no Cálculo Contínuo da Impedância Aparente. Este novo conceito visa garantir segurança e disponibilidade para a função de proteção ANSI 40 através da distinção de casos de perda de excitação e outros distúrbios externos ao gerador, tais quais as oscilações estáveis de potência ocorridas após a eliminação de curto-circuitos. As técnicas tradicionais de proteção contra perda de excitação podem apresentar operações indevidas quando da ocorrência de tais distúrbios. Considerando que a metodologia desenvolvida possui ajustes em função dos parâmetros das reatâncias do gerador protegido (Xd e X d), são feitos testes com duas máquinas de parâmetros distintos do sistema WSCC 9-barras. Visando testar a técnica proposta e compará-la com métodos amplamente utilizados Mason, Berdy e Offset Positivo, foram simulados três tipos de eventos, ou seja, perda de excitação total, perda de excitação parcial e oscilação estável de potência, para diferentes pontos operacionais do gerador. Os resultados das simulações computacionais demonstraram que o método proposto identifica corretamente a ocorrência de perda de excitação e não opera em situações de oscilação estável de potência, independentemente dos parâmetros do gerador e de sua condição de operação. A função de alarme permite desligar a máquina subexcitada mais rapidamente através de intervenção manual, o que é especialmente útil quando o carregamento inicial é baixo ou a perda de excitação é parcial. Destaca-se ainda a facilidade de ajuste do método, o qual depende apenas dos dados das reatâncias do gerador.
6

Avaliação do desempenho dos métodos de proteção contra a perda de excitação em geradores síncronos: uma contribuição utilizando a teoria dos conjuntos nebulosos / Performance evaluation of the loss of excitation protection methods in synchronous generator: a contribution using fuzzy set theory

Morais, Adriano Peres de 28 July 2008 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work aims to evaluate the performance of the loss of field protection methods in synchronous generators. The methods are introduced to make available in a single text the various ways to protect the synchronous generator against the loss of field. The conventional methods have some problems, and the main of them is the improper operation caused by the power stable oscillations. In order to solve or minimize the relay algorithm malfunction, two new methods of loss of field protection are proposed. The first is designed to increase the operational area of the generator on steady state conditions, bounded by the conventional loss of field protection. It was accomplished by modifying the operational characteristic of the mho relay, which is better coordinated with the generator capability curve. The second makes use of loss of field conception in a fuzzy set theory. With the objective to identify the performance of each one, the methods were evaluated through computational simulations of loss of field and stable power oscillation. The methods were set and evaluated according to the generator parameters (Xd and X'd). Since, tests in three machines with different parameters were carried out. So it was possible to conclude that the methods do not behave the same way for different generators parameters. On the other hand, the proposed technique, which is based on the fuzzy set theory was more efficient and not have been affected by the generator parameters and system considered. / Este trabalho visa avaliar o desempenho dos métodos de proteção contra a perda de excitação em geradores síncronos. Os métodos são apresentados de forma a tornar disponível em um único texto as diversas maneiras de se proteger o gerador síncrono contra a perda do seu sistema de excitação. Os métodos convencionais abordados apresentam alguns problemas, sendo o principal, a operação indevida causada por oscilações estáveis de potência. Visando solucionar ou minimizar estes problemas, dois novos métodos de proteção contra a perda de excitação são propostos. O primeiro, objetivando aumentar a área operacional do gerador em regime permanente, restringida pela proteção contra a perda de excitação convencional, por meio de uma característica operacional modificada, melhor coordenada com a curva de capacidade do gerador. O segundo introduz os fundamentos clássicos da proteção contra a perda de excitação na teoria dos conjuntos nebulosos. Com o objetivo de se identificar o desempenho de cada um, os métodos existentes e os propostos foram avaliados por meio de simulações computacionais de perda de excitação e oscilação estável de potência. Como os métodos possuem ajustes em função dos parâmetros do gerador protegido (Xd e X d), realizaram-se testes com três máquinas de parâmetros distintos. Deste modo, foi possível concluir que os métodos não se comportam da mesma maneira para geradores de diferente porte. Por outro lado, a técnica proposta, que tem como base a teoria dos conjuntos nebulosos se mostrou eficiente e não teve seu desempenho afetado pelos parâmetros do gerador e do sistema considerado.
7

Hepatic Hedgehog Signaling Participates in the Crosstalk between Liver and Adipose Tissue in Mice by Regulating FGF21

Ott, Fritzi, Körner, Christiane, Werner, Kim, Gericke, Martin, Liebscher, Ines, Lobsien, Donald, Radrezza, Silvia, Shevchenko, Andrej, Hofmann, Ute, Kratzsch, Jürgen, Gebhardt, Rolf, Berg, Thomas, Matz-Soja, Madlen 09 October 2023 (has links)
The Hedgehog signaling pathway regulates many processes during embryogenesis and the homeostasis of adult organs. Recent data suggest that central metabolic processes and signaling cascades in the liver are controlled by the Hedgehog pathway and that changes in hepatic Hedgehog activity also affect peripheral tissues, such as the reproductive organs in females. Here, we show that hepatocyte-specific deletion of the Hedgehog pathway is associated with the dramatic expansion of adipose tissue in mice, the overall phenotype of which does not correspond to the classical outcome of insulin resistance-associated diabetes type 2 obesity. Rather, we show that alterations in the Hedgehog signaling pathway in the liver lead to a metabolic phenotype that is resembling metabolically healthy obesity. Mechanistically, we identified an indirect influence on the hepatic secretion of the fibroblast growth factor 21, which is regulated by a series of signaling cascades that are directly transcriptionally linked to the activity of the Hedgehog transcription factor GLI1. The results of this study impressively show that the metabolic balance of the entire organism is maintained via the activity of morphogenic signaling pathways, such as the Hedgehog cascade. Obviously, several pathways are orchestrated to facilitate liver metabolic status to peripheral organs, such as adipose tissue.
8

Évaluation de la relation entre la fibrose des tissus adipeux et la résistance à l’insuline chez l’humain obèse, avant et après chirurgie bariatrique

Chabot, Katherine 07 1900 (has links)
L’obésité est associée au développement de plusieurs complications métaboliques, dont la résistance à l’insuline (RI). Or, certains sujets obèses ne développent pas de RI. Ces obèses sensibles à l’insuline (ISO) représentent un modèle humain unique pour étudier les facteurs impliqués dans le développement de la RI. La fibrose du tissu adipeux a été directement associée au développement de la RI chez le rongeur. Nous avons donc évalué la fibrose dans les tissus adipeux sous-cutané (TASC) et viscéral (TAV) d’individus obèses ISO, résistants à l’insuline (IRO) et diabétiques de type 2 (DT2), avant et six mois après leur chirurgie bariatrique. Malgré un âge, IMC et pourcentage de masse grasse semblables, les ISO présentaient une RI inférieure à celle des IRO avant la chirurgie (p < 0,05). Aucune différence n’a été observée entre les sujets ISO, IRO et DT2 en ce qui concerne la fibrose totale et les niveaux d’expression de gènes associés à la fibrose, ni dans le TASC ni dans le TAV. Toutefois, le log du pourcentage de fibrose dans le TASC était positivement corrélé avec le log de HOMA-IR (r = 0,3847, p = 0,0476) avant la chirurgie. Six mois plus tard, les niveaux de fibrose demeurent inchangés dans le TASC, mais la RI est significativement réduite dans tous les groupes, particulièrement chez les DT2. Aucune corrélation n’a été observée entre la fibrose du TASC et l’HOMA-IR après la chirurgie. Ces résultats montrent une association significative, mais éphémère entre la fibrose du TASC et la RI chez l’humain obèse. / Obesity is associated to the development of metabolic complications, including insulin resistance. Yet, a distinctive subset of obese patients seems protected from insulin resistance. Such insulin-sensitive obese subpopulation (ISO) offers a unique opportunity to investigate factors underlying the development of insulin resistance in humans without the confounding effect of major differences in adiposity. Adipose tissue fibrosis has been directly linked to the development of obesity-associated insulin resistance in rodents. Therefore, we quantified total fibrosis and examined the expression of fibrosis-related genes in subcutaneous (SAT) and visceral (VAT) adipose tissue biopsies of diabetic (T2D) and non diabetic obese patients stratified into ISO or insulin-resistant obese (IRO) based on the OGTT-derived ISIMatsuda index, before and six months after bariatric surgery. Despite similar age, BMI, and percent fat mass, ISO had lower insulin resistance than IRO subjects (p<0.05) at baseline. No difference was found between ISO, IRO and T2D, neither in terms of total fibrosis, nor in the expression of fibrosis-related genes in the adipose tissues before surgery. However, log SAT fibrosis positively correlated with log HOMA-IR at baseline (r = 0.3847, p < 0.05). Six months after surgery, fibrosis levels remained unchanged in SAT, but insulin resistance was significantly reduced in all groups, especially in T2D patients. No correlation was found between SAT fibrosis and HOMA-IR after surgery. These results show a significant, yet ephemeral association between SAT fibrosis and insulin resistance in obese humans.
9

Aspects of modern health worries as predictors of development of anxiety and depression symptoms

Edberg, Arvid, Ahlzén, Emil January 2018 (has links)
Worries about the negative health effects of modern life (Modern health worries, MHW) have increased during the last decades, but the phenomenon is not fully understood. The present study investigated the associative and predictive relationship between different types of MHW and symptoms of anxiety and depression in a large sample from Västerbotten county, Sweden (n=2223). The four subscales of the Modern Health Worries Scale (MHWS) were used to assess different types of MHW, while symptoms of depression and anxiety were assessed by using the Hospital Anxiety and Depression Scale. Spearman's correlation analysis and hierarchical multiple regression analysis were used to assess the degrees of association and prediction, respectively. It was shown that the subscales were associated with symptoms of both anxiety and depression to varying degrees, however MHW did not significantly predict symptoms of neither anxiety nor depression. This suggests that when using the MHWS in clinical settings, examining the subscales rather than the global score of MHWS provides a more nuanced understanding of an individual's experience. It also suggests that experiencing MHW does not cause an increase in neither anxiety nor depression. / Oro kopplad till de negativa hälsoaspekterna av ett modernt liv (Modern hälsooro, MHO) har ökat under de senaste årtiondena, men fenomenet är inte helt klarlagt. Den här studien undersökte associativa och prediktiva samband mellan olika typer av modern hälsooro och symtom av ångesttillstånd samt depression i ett urval i Västerbottens län (n=2223). De fyra subskalorna av Modern Health Worries Scale (MHWS) användes för att undersöka de olika typerna av MHO medan Hospital Anxiety and Depression Scale användes för att mäta symtom av ångesttillstånd och depression. Korrelationsanalyser baserat på Spearmans korrelationskoefficient samt hierarkiska, multipla regressionsanalyser användes för att mäta graden av association respektive prediktion.  Resultatet visar att de olika subskalorna var associerade med symtom av både depression och ångesttillstånd i olika hög grad. Dock predicerade inte MHO en signifikant förändring av varken ångest- eller depressionssymtom. Detta tyder på att ett enskilt beaktande av subskalorna ger en mer nyanserad bild av en individs upplevelse av MHO jämfört med om endast totalpoängen på MHWS beaktas. Resultatet föreslår vidare att en upplevelse av MHO inte orsakar en ökning av varken ångest eller depressionssymtom.

Page generated in 0.0252 seconds