• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2696
  • 1013
  • 375
  • 255
  • 157
  • 139
  • 73
  • 62
  • 27
  • 11
  • 9
  • 6
  • 6
  • 5
  • 4
  • Tagged with
  • 5269
  • 1584
  • 1297
  • 1271
  • 684
  • 606
  • 604
  • 527
  • 428
  • 359
  • 355
  • 352
  • 343
  • 332
  • 329
  • 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.
251

Návrh a ověření cyklotras v okolí Blanského lesa\\ / Suggestion and homologation of cycling routes in the area of Blanský les\\

BRABEC, Daniel January 2010 (has links)
My thesis focuses on verification and projecting of cycle tracks in the Protected Landscape Area of Blansky Forest. It also considers current state of the tracks its description and suggestions how to improve and increase attraction of the tracks. Further my thesis deals with new draughts of the tracks whose goal should be recognition of the landscape combined with physical activity and at the same time the newly proposed tracks should only sensitively trench the enviroment of the area.Each of the track will be visualized and drawn into the map or eventually designed for using GPS navigation including kilometrage, crossfalls and KPČ suggestions.
252

Investigação da camada limite planetária noturna na região metropolitana de São Paulo utilizando o modelo LES / Investigation of the nocturnal boundary layer in the Metropolitan Region of São Paulo

Eduardo Wilde Bárbaro 23 August 2010 (has links)
O presente trabalho tem como objetivo investigar a evolução temporal e espacial da camada limite planetária (CLP) na cidade de São Paulo durante o período noturno, utilizando o modelo LES. Foram simulados os campos tridimensionais das três componentes da velocidade do vento, temperatura potencial e concentração de monóxido de carbono (CO). Três propriedades da CLP noturna em São Paulo foram analisadas: a) Altura da CLP estável (CLE); b) Jatos de baixos níveis (JBN); c) Dispersão turbulenta de CO. Foi analisado também o ciclo diurno dos fluxos turbulentos de calor sensível e de CO na superfície. Inicialmente foi desenvolvido um procedimento de validação para avaliar o desempenho do modelo LES na simulação das propriedades da CLP convectiva, neutra e estável, utilizando como referência os resultados de simulações consagrados na literatura. A validação foi realizada comparando os perfis verticais médios de velocidade horizontal, temperatura potencial, variância das componentes da velocidade e as componentes da equação do balanço de energia cinética turbulenta (ECT). Os resultados dessa comparação indicam que o modelo LES atual é capaz de reproduzir todas as características dos processos turbulentos destes escoamentos. Foram realizados quatro experimentos numéricos com o intuito de investigar a evolução diurna da CLP para a situação de inverno em São Paulo, usando como condições de contorno, valores horários médios mensais de temperatura potencial e concentração de monóxido de carbono observados em superfície durante o mês de junho em São Paulo. Esses experimentos utilizaram também como condição de contorno a situação média nos dias de céu claro (sem nuvem) no mês de junho em São Paulo. O impacto da intensidade do vento também foi analisado especificando-se como forçante externa o vento geostrófico igual a 5 m/s e 10 m/s de oeste. Os dados utilizados neste trabalho foram medidos na plataforma micrometeorológica do IAG-USP (temperatura do ar e fluxo turbulento de calor sensível) e na estação Lapa da CETESB (concentração de monóxido de carbono e velocidade do vento). Os resultados destas 4 simulações indicam que a altura da CLE foi simulada pelo modelo LES de forma consistente com as forçantes e condições de contorno usadas, indicando que durante o mês de junho em São Paulo a altura da CLE varia entre 100 m e 275 m (médias) e 62 m e 203 m (dias de céu claro). Verificou-se também que a turbulência da CLE é mantida pela produção mecânica de ECT e dissipada majoritariamente pela destruição térmica. A dissipação molecular tem um papel secundário e o transporte turbulento não afeta as propriedades da CLE. Os resultados indicam que as formulações empíricas utilizadas neste trabalho são capazes de reproduzir de forma equivalente a ordem de magnitude da altura da CLE simulada para São Paulo. O melhor resultado foi obtido com h = 700 u*. As simulações do JBN indicaram que para São Paulo o mecanismo de ajuste inercial gera máximos da ordem de 7,1 m/s em torno de 210 m as 05:30 HL (forçante de 5 m/s) e de 14,5 m/s em torno de 420 m e as 05:30 HL (forçante de 10 m/s). Foi observada uma intensificação da turbulência acima do topo da camada estável. A evolução espacial e temporal da concentração de CO simulado pelo modelo LES apresenta um padrão de dispersão turbulento compatível com o esperado para o inverno em São Paulo. Finalmente, o modelo LES é capaz de reproduzir as principais características da evolução diurna do fluxo de calor sensível e de monóxido de carbono da superfície observados no mês de junho na cidade de São Paulo. / The main objective of this work is to investigate the temporal and spatial evolutions of the planetary boundary layer (PBL) in the city of São Paulo during the nighttime period, using a large-eddy simulation (LES) model. It was simulated the 3-dimensional fields of the three components of the wind speed, potential temperature and carbon monoxide concentration. Three properties of nocturnal PBL were investigated: a) PBL depth; b) Low level jet (LLJ) and c) Turbulent dispersion of CO. The diurnal evolution of the turbulent fluxes of sensible heat and CO was also analyzed. Initially, a validation procedure was carried considering the performance of LES model in to simulate the behavior of the PBL for convective, neutral and stable conditions using as reference simulation results available in the literature. The validation was performed by comparing the mean vertical profiles of horizontal wind, potential temperature, variance of wind speed components and the turbulent kinetic energy (TKE) equation components. They indicated that the actual version of LES model is capable to simulate the entire cycle of the PBL diurnal evolution over a homogeneous and flat surface. Once validated, the LES model was applied to simulate the PBL for a complete diurnal cycle over a flat and homogeneous surface with aerodynamic roughness length representative of a typical urban area of São Paulo. Four simulations were designed to investigate the nighttime PBL evolution for winter conditions in São Paulo, using as input, monthly average hourly values of potential temperature and monoxide carbon observed at the surface during June in São Paulo. The mean condition for clear sky days observed in June in São Paulo was also considered as input in these simulations. The impact of wind intensity was also analyzed by considering as the external forcing in these simulations a constant background geostrophic wind of $5$ and $10 ms^{-1}$ from West. The dataset used in this work was observed in the micrometeorological platform of IAG (air temperature and sensible heat flux) and at the surface station of environmental agency of the state of São Paulo (CETESB) locate at Lapa (CO and wind speed). The results indicate that the height of stable PBL was simulated consistently with the boundary conditions and external forcing, indicating that during June the in São Paulo the PBL height may vary from 100m (mean condition) and 62m (clear days condition) at the beginning of the night to 275m (mean condition) and 203m (clear sky conditions) at the end of nighttime. It was verified that the turbulence in the Stable PBL is maintained by the mechanical production of TKE and dissipated, mainly, by the negative thermal production. Molecular dissipation has a secondary role and turbulent transport of TKE does not affect the stable PBL. All the empirical formulations used here reproduced the order of magnitude of the stable PBL height. The best performance was obtained by $h = 700 u_*$ and $h = 0.5 \\sqrt{\\frac{u_* L}{\\left|fight|}}$. The simulated nocturnal LLJ indicated that for São Paulo the inertial oscillation yields a maximum intensity is $7.1 ms^{-1}$ at $210m$ and 05:30LT (forcing of $5 ms^{-1}$) and $14.5 ms^{-1}$ at $420m$ at 05:30LT (forcing of $10 ms^{-1}$). In both cases the LLJ intensified the turbulence at the top of the stable PBL. The simulated spatial and temporal evolution of the carbon monoxide concentration shows a pattern of turbulent dispersion consistent with the expected one for winter time in the city of São Paulo. Finally, LES model is able to reproduce the main features of the diurnal evolution of turbulent sensible heat and carbon monoxide fluxes at the surface for São Paulo during the winter.
253

Bilinguisme : Une diversité linguistique – une ressource

Johansson, Jenny January 2012 (has links)
Les familles bilingues sont de plus en plus nombreuses dans notre société, et dans les écoles aujourd’hui il y a beaucoup plus d’étudiants qui parlent couramment plus d’une langue qu’il y a quelques années. Un nouveau système d’apprentissage où les langues étrangères seront plus utilisées dans les matières comme les maths, l’histoire, la géographie, la biologie, etc. pourrait avoir un impact positif sur l’apprentissage des langues étrangères mais aussi sur les autres matières et aussi un impact favorable sur les élèves qui seront plus en confiance en eux même et plus préparer en sortant des écoles pour affronter la nouvelle société multilingue.  Le bilinguisme est une ressource très précieuse tant pour l’individu que pour la société. La langue porte la culture et elle est nécessaire pour communiquer, penser, rêver ainsi pour se développer en tant qu’êtres humains.   L’homme est un être social et la nécessité de communiquer nous motive à apprendre des langues. Il y a une différence importante entre être capable de communiquer dans une langue et d’utiliser une langue comme un outil de réflexion, une personne parfaitement bilingue doit savoir faire les deux.  Les langues se ressemblent de structures et une des conséquences de ce fait est que dans les sociétés plurilingues, les enfant exposés à diverses langues sont habitués à comparer plus ou moins inconsciemment et ils deviennent plus facilement multilingues. Les écoles d’aujourd’hui ont besoin de faire quelques changements pour s’adapter à une enseignement bilingue car le bilinguisme est une ressource qu’il faut commencer d’utiliser dans notre société multilinguistique. On pourrait avoir le même effet  dans les écoles si on introduirait les langues étrangères plus tôt dans l’enseignement.
254

Détection moléculaire des eucaryotes dans les selles de primates : étude exploratoire / Molecular exploring of eukaryotes in human and non- human primate guts : exploratory study

Hamad, Ibrahim 30 October 2015 (has links)
Chez les mammifères, les Eucaryotes représentent une composante importante des micro-organismes peuplant le tractus digestif. Au total, 16 champignons et 2 autres micro-eucaryotes ont été identifiés dans l’échantillon provenant de la personne saine. Par contre, peu d’espèces fongiques ont été identifiées via l’échantillon provenant du patient atteint de tuberculose.D'autre part, la diversité des eucaryotes qui peuplent les primates non humains tels que les grands singes demeure relativement inexploré .Pour ces raisons, nous avons entrepris une analyse moléculaire dans le but de détecter ces micro-organismes eucaryotes, dont certains demeurent pathogènes pour l’homme, en utilisant un seul échantillon fécal prélevé chez un gorille sauvage en provenance de l’ouest du Caméroun. Ces analyses ont été suivies d’une détection moléculaire spécifique du potentiel pathogène de ces eucaryotes du tractus gastro-intestinal des gorilles sauvages. En conséquence, ils ont permis d’identifier 87 espèces eucaryotes. Nous avons également signalé la présence de champignons pathogènes, et de parasites. Afin d’examiner d’une manière plus approfondie si ces gorilles abritaient d’autres parasites, nous avons analysé 91 échantillons fécaux à la recherche d’agents pathogènes comme la leishmaniose. Les résultats ont montré que 12 échantillons contenaient des parasites du genre Leishmania et 4 phlébotomes comme vecteurs. L’analyse moléculaire a été effectuée par enchaînement de 3 différentes réactions de polymérase en chaine (PCR) spécifiques aux agents de la leishmaniose. / Eukaryotes represent significant component of the mammalian intestinal tract. Their occurrence might have either beneficial or virulent parasitic effects on the host.A total of 16 fungal species and 2 other micro-eukaryotes were identified in healthy fecal sample. Contrary, a very few fungi were detected in the fecal sample from patient with resistant tuberculosis. On another hand , The diversity of eukaryotes inhabiting non-human primates such as great apes remains relatively unexplored .For these reasons we undertook an extensive molecular analysis for detecting eukaryotic microbiota including some human eukaryotic pathogens in a single fecal sample from a wild western lowland gorilla from Cameroon, and then followed by specific molecular detection of potential human eukaryotic pathogen in gastrointestinal tracts of wild population of gorillas. Our effort resulted in retrieving 87 eukaryotic species. We also reported the occurrence of pathogenic fungi, parasites. To further examine whether these gorillas harbor other sever parasites, we screened 91 of their fecal samples for the presence of blood borne pathogen such as Leishmania. The results showed that, 12 fecal samples contained Leishmania parasites, and 4 contained phlebotomine sand fly vectors. The molecular identity was determined by running 3 different polymerase chain reaction tests for detection of Leishmania major.
255

ZDES simulations of propulsive jets : physical analysis and influence of upstream turbulence / Simulations ZDES de jets propulsifs : analyse physique et influence de la turbulence amont

Verrière, Jonas 23 September 2016 (has links)
Ce travail porte sur l’évaluation de la méthode ZDES pour la simulation de jets propulsifs. L’analyse se concentre sur le positionnement des cellules de chocs et le développement des couches de mélange d’une tuyère double-flux avec plug externe, typique des moteurs d’avions modernes. Les champs statistiques sont comparés aux résultats expérimentaux et discutés en termes de grandeurs moyennes, fluctuantes et dans le domaine fréquentiel. L’intérêt d’utiliser un schéma spatial peu dissipatif ainsi qu’une échelle de longueur sous-maille basée sur la vorticité locale est mis en évidence, notamment pour le dévelopement de la couche de mélange interne, et le mode 2 ("automatique") de la ZDES a démontré un comportement similaire au mode 1 ("manuel") dans les couches de mélange. Par ailleurs, la technique Random Flow Generation (RFG) mise en oeuvre afin de reproduire la turbulence amont existant au coeur des jets primaire et secondaire a permis d’accélérer la transition RANS-LES dans les deux couches de mélanges, plus conformément à l’expérience. La transition est d’autant plus rapide que le taux de turbulence est élevé et l’échelle de la turbulence injectée est petite. Le positionnement des cellules de choc est également amélioré, soulignant l’importance de prendre en compte la turbulence amont dans les simulations de jets. / In this thesis, the ZDES method is assessed for the simulation of propulsive jets. This work focuses on the shock-cell positioning and the mixing layer development of a dual-stream nozzle configuration with an external plug, typical of modern aircraft engines. Reynolds averaged data are discussed in terms of mean and fluctuating quantities as well as in the frequency domain and compared with experimental data. First, the advantage of using a low dissipative spatial scheme as well as a subgrid length scale based on the local vorticity is demonstrated, especially for the development of the core mixing layer. Besides, the "automatic" mode of ZDES (mode 2) is found to provide similar mixing layers as the user defined mode.Then, the use of the Random Flow Generation (RFG) technique at the inlet boundaries of the core and fan channels in order to reproduce the turbulence rate at the center of the nozzle ducts is shown to accelerate the RANS-to-LES transition in both external and internal mixing layers, which is in better agreement with the experimental results. The transition length is further reduced when the injected turbulent ratio is higher, but also when the injected turbulent length scale is smaller. Of interest, the shock-cell positioning in the fan jet is also improved using RFG, which emphasizes the importance of accounting for upstream turbulence for this type of simulations.
256

Combustion dynamics of premixed swirling flames with different injectors / Dynamique de la combustion des flammes de prémélange swirlées avec des différentes injecteurs

Gatti, Marco 18 October 2019 (has links)
Les systèmes de combustion à prémélange pauvre (PP) sont l’une des technologies les mieux adaptées pour la réduction des émissions de polluants, mais ils sont très sensibles aux phénomènes d’extinction, aux retours de flamme (flashback) dans l’injecteur et aux instabilités de combustion. La plupart des chambres de combustion des turbines à gaz utilisent de swirleurs pour stabiliser des flammes compactes et permettre une combustion efficace et propre avec des densités de puissance élevée. Une meilleure connaissance des mécanismes de la dynamique de la combustion d’écoulements swirlés PP présente un intérêt aussi bien pratique que fondamental. Ce travail est une contribution pour atteindre ce but. Le brûleur Noisedyn, avec une geometrie modifiable, a été spécialement conçu pour répondre à cet objectif. Une analyse expérimentale a etait conduite pour examiner les paramètres qui reduisent la sensibilité des systèmes PP aux phénomènes dynamiques. Mesures de fonction de transfert de flamme (FTF), diagnostiques laser (LDV et PIV) et imagerie des flammes sont les principaux techniques utilisé dans ce travail. Large eddy simulation sont aussi utilisé pour expliquer les mécanismes derrière les observations experimentaux. / Lean premixed (LPM) combustion systems achieve low pollutant emission levels, with compact flames and high power densities, but are highly sensitive to dynamic phenomena, e.g, flashback, blowout and thermoacoustic instabilities, that hinder their practical application. Most LPM gas turbine combustors use swirling flows to stabilize compact flames for efficient and clean combustion. A better knowledge of the mechanisms of steady and unsteady combustion of lean premixed swirled mixtures is then of practical, as well as fundamental interest. This thesis is a contribute towards the achievement of this goal. A burner, made of several components with variable geometry, was specifically designed for this scope. An experimental analysis was conducted to investigate the main parameters leading to a reduction of the sensitivity of LPM systems to dynamic phenomena. The diagnostics applied include flame transfer function (FTF) measurements, laser diagnostics (LDV and PIV) and flame imaging. Large eddy simulations were also exploited to elucidate the mechanisms behind the experimental observations.
257

A Filtered-Laminar-Flame PDF subgrid scale closure for LES of Premixed Turbulent Flames : Application to a Stratified Bluff-body burner with Differential Diffusion / Modélisation LES de la combustion turbulente prémélangée et stratifiée basée sur une PDF construite sur des flammes laminaires filtrées : Application à un brûleur stratifié avec diffusion différentielle.

Nambully, Suresh Kumar 18 March 2013 (has links)
Un modèle de sous-maille pour la simulation aux grandes échelles de la combustion turbulente, basé sur le filtrage de flammes laminaires est présenté. Le formalisme repose sur une fonction de densité de probabilité (PDF) présumée construite à partir du filtrage de flammes laminaires 1D et sur une chimie tabulée. La taille de filtre LES appliqué à la combustion n'est pas fixée dans cette nouvelle approche mais est déterminée en fonction du niveau local de fluctuations de sous-maille. Le modèle a été validé sur des flammes laminaires 1D filtrées, sur des flammes de bec Bunsen et sur une configuration 3D turbulente avec la LES d'un brûleur à swirl. La comparaison de la simulation avec l'expérience en prémélangé et en stratifié est pleinement satisfaisante confirmant l'intérêt du nouveau modèle. Les échelles spatiales associées à la stratification sont trouvées grandes devant celles associées à la flamme (épaisseurs de zone de réaction et thermique) dont la propagation reste quasi-homogène. / A sub-grid scale closure for Large Eddy Simulation (LES) of turbulent combustion, based on physical space filtering of laminar flames is presented. The proposed formalism relies on a presumed probability density function (PDF) derived from the filtered laminar flames and flamelet tabulated chemistry. The combustion LES filter size is not fixed in this novel approach when sub-grid scale wrinkling occurs, but calibrated depending on the local level of unresolved scalar fluctuations. The model was validated by simulating 1D filtered laminar flames and 2D Bunsen flames. Subsequently, the model was tested on a 3D turbulent scenario by performing LES of the premixed and stratified configurations of the Cambridge swirl burner, experimentally studied by Sweeney and co-workers. Comparison of simulation and experiments for both the premixed and stratified configurations showed good agreement emphasizing the model characteristiscs. Instantaneous and time averaged LES data were analyzed to extract
258

« Il n'y a rien de plus contagieux que la psychologie » : Les familles troublées dans La vie devant soi et L'Amant / "There Is Nothing More Contagious Than Psychology" : Troubled Families in La Vie Devant Soi and L’Amant

Bohman, Malin January 2020 (has links)
Two French novels, La vie devant soi by Romain Gary and L’Amant by Marguerite Duras, are used to examine how mental illness in the parent, in this case the mother figures, influences the development of the children, Momo and “je.” As its points of departure, this paper employs attachment theory, developed by Bowlby and Ainsworth et al., as well as family systems theory by Murray Bowen and Michael Kerr. The impact of the mother figures’ behavior toward their children is analyzed based on three factors: the parent-child relationship, the child’s desire for closeness with the parent, and the child’s desire to distance him/herself from the parent. A comparison is made between La vie devant soi and L’Amant to identify the differences and similarities in how the mother figures’ conduct influence Momo and “je.”
259

Vietnamští imigranti v Praze před rokem 1989 a poté v transgenerační a transnacionální perspektivě / Vietnamese immigrants in Prague before and after 1989 in transgenerational and transnational perspective

Horáčková, Tereza January 2015 (has links)
This thesis presents the results of a historical investigation of the arrival and presence of Vietnamese immigrants in Prague between 1974 and 1993. Methodologically, the research is based on interviews with witnesses of the program of socialist internationalism and on the study of the Czechoslovak government administrative documents from the period between 1974, ie. the year the signing of the Agreement between the Government Czechoslovak Socialist Republic and the Socialist Republic of Vietnam about employing Vietnamese citizens in Czechoslovak organizations1 , with a milestone in 1989 as the collapse of the communist regime, and the year 1993, as the separation of Slovakia and the establishment of an independent Czechoslovak Republic This work is not only based on the assumption that this program influenced the integration of the first generation in Czechoslovak society, but it also shows an indirect influence on the second generation coming after the Velvet Revolution, due to the program's effect on the emergence of Vietnamese social networks. The research aims to uncover the factors that influence the adaptation of the first and second generations in the majority environment and to indicate the effect that the normative framework of the program had on the formation of ethnic social networks. It...
260

Srovnání diverzity vybraných skupin epigeických členovců v hospodářském nížinném lese s různou věkovou strukturou a typem managementu

Staněk, Luboš January 2019 (has links)
The aim of this thesis is to investigate the species richness and abundance of epigeic arthropods (spiders, ground beetles, centipedes, millipedes, woodlice) in relation to different age structure and types of forest management. The arthropods were sampled from four different age classes (clearings, young, middle-aged and old forest stands), while within two of them (clearings and old forest stands) the influence of management was also evaluated. According to comparison of stages of forest succession most species were found in clearings without any mechanical soil preparation. On the other hand younger age classes hosted the least amount of arthropod species. The highest abundances of species were detected within young forest stands whereas the lowest in middle-aged stands. The results of forest management impacts indicate that soil milling is not suitable for any investigated group of organisms. The response to management of the old stands varied for different arthropod groups. The results reveal high importance of diversified silviculture in form of various age classes, a regulation is also necessary to restrict large area milling of clearings and for both managed and unmanaged forest stands the continuity must be maintained.

Page generated in 0.0441 seconds