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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
441

Foraging strategies of Southern Royal Albatrosses, Diomedea epomophora, Campbell Island during incubation

Troup, Christina January 2004 (has links)
Among the species of Diomedea albatrosses, diverse foraging strategies during breeding have been described, indicating species differences in foraging ecology and behaviour. Foraging strategies of Southern Royal Albatrosses, Diomedea epomophora (SRA) breeding on Campbell Island were studied in January – early February 1999 during the latter half of incubation. Movements and activity of ten birds were monitored using satellite transmitters and wet-dry activity recorders. Three birds from a pilot tracking study in February 1997 were also included in some analyses. Foraging strategies, zones used, factors influencing the duration of foraging trips, and the influence of wind conditions were investigated. Foraging activity took place at sites with bathymetric characteristics associated with high productivity: outer shelf and shelf-break zones, with a concentration of activity on a shelf contour south of the Snares Islands. This is in contrast to Wandering (D. exulans) and Gibson’s (D. gibsoni) albatrosses, typically deep oceanic foragers, but is similar to Northern Royal Albatross (D. sanfordi). The maximum distance of foraging trips from the colony was 1250 kilometres (mean 584 +351(SD)). This was closer than for incubating Wandering and Gibson’s Albatrosses but more distant than for Northern Royal Albatross from the Otago Peninsula. The mean duration of 77 foraging trips from 52 nests was 10.11 days for females and 8.76 for males (ns). Foraging trips became shorter as incubation progressed. Foraging trips were shorter, but not significantly so, when the median wind speed throughout the foraging trip was higher. No significant relationship was found between bird mass and duration of foraging trips. The mean cumulative distance flown by the ten birds tracked in 1999 was 4262 km + 1318 (SD). Eight of the ten SRA employed a ‘commute, forage, commute’ foraging strategy, and the other two alternated short bouts of commuting and foraging. Commuting phases were characterised by rapid directional flight with a straight-line distance (range) of 180 km to 800 km between positions 24 hours apart. Foraging phases were characterised by a range of less than 180 km per 24 hour interval and frequent tight turns. Displacement rate between successive uplinks was significantly higher during commuting phases (28.6 kph + 1.93 SE) than foraging phases (15.1 kph + 1.4 SE). Wind strength and direction influenced the timing of the return commute to the colony. SRA covered greater distances at more favourable wind angles relative to flight track (broad reach and close reach) than in head, tail or direct side winds. Birds of low mass (< 8kg) made fewer landings in winds above 40 kph than in lighter winds, whereas heavier birds had a similar level of landing activity across all wind speed bands. One bird was delayed for several days by light winds, and another flew off course during strong winds. Two birds exploited the same window of wind conditions to return to the colony, each flying a similar course in both timing and route. These results define the foraging strategies of SRA during incubation, and demonstrate the influence of wind conditions and other factors on the overall duration of foraging trips and on the timing of commuting and foraging phases.
442

Effective Spatial Mapping for Coupled Code Analysis of Thermal–Hydraulics/Neutron–Kinetics of Boiling Water Reactors

Peltonen, Joanna January 2013 (has links)
Analyses of nuclear reactor safety have increasingly required coupling of full three dimensional neutron kinetics (NK) core models with system transient thermal–hydraulics (TH) codes.  In order to produce results within a reasonable computing time, the coupled codes use two different spatial description of the reactor core.  The TH code uses few, typically 5 to 20 TH channels, which represent the core.  The NK code uses explicit one node for each fuel assembly.  Therefore, a spatial mapping of a coarse grid TH and a fine grid NK domain is necessary.  However, improper mappings may result in loss of valuable information, thus causing inaccurate prediction of safety parameters. The purpose of this thesis is to study the effectiveness of spatial coupling (channel refinement and spatial mapping) and develop recommendations for NK/TH mapping in simulation of safety transients.  Additionally, sensitivity of stability (measured by Decay Ratio and Frequency) to the different types of mapping schemes, is analyzed against OECD/NEA Ringhals–1 Stability Benchmark data. The research methodology consists of spatial coupling convergence study, by increasing the number of TH channels and varying mapping approaches, up to and including the reference case.  The reference case consists of one-to-one mapping: one TH channel per one fuel assembly.  The comparisons of the results are done for steady–state and transient results.  In this thesis mapping (spatial coupling) definition is formed and all the existing mapping approaches were gathered, analyzed and presented.  Additionally, to increase the efficiency and applicability of spatial mapping convergence, a new mapping methodology has been proposed.  The new mapping approach is based on hierarchical clustering method; the method of unsupervised learning that is adopted by many researchers in many different scientific fields, thanks to its flexibility and robustness.  The proposed new mapping method turns out to be very successful for spatial coupling problem and can be fully automatized allowing for significant time reduction in mapping convergence study. The steady–state results obtained from three different plant models for all the investigated cases are presented.  All models achieved well converged steady–state and local parameters were compared and it was concluded that solid basis for further transient analysis was found.  Analyzing the mapping performance, the best predictions for steady–state conditions are the mappings that include the power peaking factor feature alone or with any combination of other features.  Additionally it is of value to keep the core symmetry (symmetry feature).  The big part of this research is devoted to transient analysis.  The selection of transients was done such that it covers a wide range of transients and gathered knowledge may be used for other types of transients.  As a representative of a local perturbation, Control Rod Drop Accident was chosen.  A specially prepared Feedwater Transient was investigated as a regional perturbation and a Turbine Trip is an example of a global one.  In the case of local perturbation, it has been found that a number of TH channels is less important than the type of mapping, so a high number of TH channels does not guarantee improved results.  To avoid unnecessary averaging and to obtain the best prediction, hot channel and core zone where accident happens should be always separated from the rest.  The best performance is achieved with mapping according power peaking factors, and therefore this one is recommended for such type of perturbation. The regional perturbation has been found to be more challenging than the others.  This kind of perturbation is strongly dependent on mapping type that affects the power increase rate, SCRAM time, onset of instability, development of limit cycle, etc.  It has been also concluded that a special effort is needed for input model preparation.   In contrast to the regional perturbation, the global perturbation is found to be the least demanding transient.  Here, the number of TH channels and type of mapping do not have significant impact on average plant behaviour – general plant response is always well recreated.  A special effort has also been paid to investigate the core stability performance, in both global and regional mode.  It has been found that in case of unstable cores, a low number of TH channels significantly suppresses the instability.  For these cases number of TH channels is very important and therefore at least half of the core has to be modeled to have a confidence in predicted DR and FR.  In case of regional instability in order to get correct performance of out-of-phase oscillations, it is recommended to use full-scale model.  If this is not possible, the mapping which is a mixture of 1st power mode and power peaking factors, should be used. The general conclusions and recommendations are summarized at the end of this thesis.  Development of these recommendations was one of the purposes of this investigation and they should be taken into consideration while designing new coupled TH/NK models and choosing mapping strategy for a new transient analysis. / <p>QC 20130516</p>
443

Raumstrukturelle Einflüsse auf das Verkehrsverhalten - Nutzbarkeit der Ergebnisse großräumiger und lokaler Haushaltsbefragungen für makroskopische Verkehrsplanungsmodelle

Wittwer, Rico 23 January 2008 (has links) (PDF)
Für die Verkehrsnachfragemodellierung stehen dem Planer sehr differenzierte Modellansätze zur Verfügung. Ein wesentliches Unterscheidungskriterium stellt dabei der Modellierungsgegenstand dar. Der Fokus der vorliegenden Arbeit ist auf makroskopische Verkehrsplanungsmodelle gerichtet. Es wird der Frage nachgegangen, in welcher Form die Ergebnisse großräumiger und lokaler Haushaltsbefragungen effizient bzw. sich gegenseitig ergänzend in Modellierungsaufgaben Einsatz finden können. Im Mittelpunkt der empirischen Datenanalyse steht die Frage, ob ein Unterschied in der Ausprägung zentraler modellierungsrelevanter Kenngrößen differenziert nach Raumtypen statistisch belegbar und planungspraktisch bedeutsam ist. Vor diesem Hintergrund wird auch die Auswirkung der komplexen Stichprobenpläne von MiD 2002 und SrV 2003 auf die Varianz der Parameterschätzung berücksichtigt. Ein in dieser Arbeit entwickelter, mehrstufiger Bewertungsalgorithmus, der dem Signifikanz-Relevanz-Problem hinreichend Rechnung trägt, bildet die Grundlage der Hypothesenprüfung. Er verbindet das Standardvorgehen (Signifikanztest) mit normativ gesetzten Effektgrößen und dem schätzerbasierten Vorgehen (Konfidenzintervalle). Eine besonders hohe Transparenz und Entscheidungskonsistenz erlangt der Ansatz dadurch, dass die Hypothesenprüfung auf Basis zweier voneinander unabhängig erhobener Untersuchungsgruppen (MiD, SrV) erfolgt. Die intensive Arbeit mit den Datengrundlagen MiD und SrV liefert eine Vielzahl von Erkenntnissen zur weiteren Qualifizierung des Erhebungsinstrumentes „Mobilität in Städten – SrV“. In Vorbereitung der im Jahre 2008 anstehenden Neuauflage der Erhebungsreihe wird nach Ansicht des Autors mit der Arbeit ein wesentlicher Impuls zur Weiterentwicklung der Methodik gegeben.
444

Dynamische Modellierung des Gaspfades eines Gesamt-IGCC-Kraftwerkes auf Basis des SFG-Verfahrens

Bauersfeld, Sindy 08 August 2014 (has links) (PDF)
Im Rahmen der vorliegenden Arbeit werden dynamische Modelle eines IGCC-Kraftwerkes mit CO2-Abtrennung unter Verwendung des Modellierungstools Modelica/Dymola entwickelt. Dabei liegt der Schwerpunkt auf dem Gaspfad der Gasreinigung. Es ist vorteilhaft, für verschiedene Aufgaben, Modelle mit unterschiedlicher Tiefe zu verwenden. Mit den detaillierten Modellen werden Simulationen der Teilprozesse durchgeführt. Für den Aufbau eines Gesamtsystems werden vereinfachte Modelle verwendet. Anhand des Gesamtsystems werden drei Regelkonzepte (Gleitdruckregelung, Leistungsregelung der Gasturbine, Leistungsregelung des Vergasers) untersucht und bewertet. Des Weiteren werden drei Störfallszenarien (Ausfall des Sättigers im Brennstoffsystem, Betriebsstörung in der Vergaserinsel, Unterbrechung der Stickstoffzumischung im Brennstoffsystem) getestet.
445

Contrôle actif de la transition laminaire-turbulent en écoulement hypersonique / Active control of laminar-turbulent transition in a hypersonic flow

André, Thierry 25 March 2016 (has links)
Lors d’un vol hypersonique (Mach 6, 20 km d’altitude) la couche limite se développant sur l’avant-corps d’un véhicule hypersonique est laminaire. Cet état cause un désamorçage du moteur (statoréacteur) assurant la propulsion du véhicule. Pour pallier ce problème, il faut forcer la transition de la couche limite á l’aide d’un dispositif de contrôle dont l’effet est permanent (passif) ou modulable (actif) pendant le vol. Dans ce travail, nous analysons l’efficacité d’un dispositif actif d’injection d’air á la paroi pour forcer la transition de la couche limite sur un avant-corps générique. L’interaction jet d’air/couche limite est simulée numériquement avec une approche aux grandes échelles (LES). Une étude paramétrique sur la pression d’injection permet de quantifier l’efficacité du jet á déstabiliser la couche limite. L’influence des conditions de vol (altitude, Mach) sur la transition est également étudiée. Une analyse des résultats de simulation par Décomposition en Modes Dynamiques (DMD) est menée pour comprendre quels sont les modes dynamiques responsables de la transition et les mécanismes sous-jacents. Des essais dans la soufflerie silencieuse de l’université de Purdue (BAM6QT) ont été effectués pour tester expérimentalement l’efficacité des dispositifs passifs (rugosité isolée en forme de losange) et actifs (mono-injection d’air) pour faire transitionner la couche limite. Une peinture thermo-sensible et des capteurs de pression (PCB, Kulite) ont été utilisés pour déterminer la nature de la couche limite. Les résultats de ce travail montrent qu’une injection sonique suffit pour forcer la couche limite. On observe des essais, que pour une même hauteur de pénétration, les rugosités isolées sont moins efficaces que les jets (mono injection) pour déstabiliser la couche limite. / During a hypersonic flight (Mach 6, 20 km altitude), the boundary layer developing on the forebody of a vehicle is laminar. This state may destabilize the scramjet engine propelling the vehicle. To overcome this problem during the flight, the boundary layer transition has to be forced using a control device whose effect is fixed (passive) or adjustable (active). In this work, we analyze the efficiency of a jet in crossflow in forcing the boundary layer transition on a generic forebody. The flow is computed with a Large Eddy Simulations (LES) approach. A parametric study of the injection pressure allows the efficiency of the jet in tripping the boundary layer to be quantified. The influence of flight conditions (Mach, altitude) on the transition is also studied. Dynamic Mode Decomposition (DMD) is applied to the simulation results to determine the transition leading to dynamic modes and to understand underlying transition mechanisms. Experiments in the Purdue University quiet wind tunnel (BAM6QT) were performed to quantify the efficiency of a passive transition device (diamond roughnesses) and an active transition device (single air jet) in tripping the boundary layer. A thermo-sensitive paint and pressure transducers (Kulite, PCB) were used to determine the state of the boundary layer on the generic forebody. Experimental and numerical results show a sonic injection is sufficient to induce transition. We observe from the experiments that for the same penetration height, a single roughness is less efficient than a single air jet in destabilizing the boundary layer.
446

Ici et là-bas : Représentations spatiales et pratiques touristiques en milieu scolaire (Lyon et Cracovie) / Here and there : Spatial representations and tourism practices in schools (Lyon and Cracow)

Bogacz, Katarzyna 07 December 2012 (has links)
Cette recherche comparative – terrains français et polonais – a été menée à Lyon et à Cracovie. L’objet du travail concerne le tourisme social destiné aux enfants, et ce dans le cadre des classes de découvertes en France et écoles vertes en Pologne, ces voyages scolaires constituant à la fois un temps de vie collective et un temps d’éducation. Le cadre scolaire de la recherche concerne l’école primaire. Le travail s’inscrit dans la vaste problématique de l’acquisition de savoirs géographiques. Le sujet de la recherche mobilise le champ du tourisme dans la mesure où les pratiques qui en relèvent constituent des moyens et modalités d’appropriation de l’espace que les individus mettent en œuvre dans l’élaboration de leurs représentations spatiales. A travers ses expériences, l’individu construit un modèle intériorisé de son environnement. Cette recherche questionne les modalités de l’apprentissage spatial chez les jeunes enfants, questionnement dont l’objectif essentiel est de valider l’hypothèse selon laquelle l’expérience du voyage scolaire est susceptible de modifier leurs représentations spatiales. Pour vérifier si tous les enfants ont des chances égales pour se construire leur propre capital spatial, la recherche examine aussi l’influence sur leurs représentations de la mobilité spatiale antérieure. Afin d’approcher les représentations spatiales des écoliers, sont mobilisés à la fois les données discursives (questionnaires) et graphiques (cartes mentales). L’enquête, menée auprès de 192 élèves de Lyon et de Cracovie, explore donc finalement l’interface entre deux champs scientifiques, ceux de la géographie et ceux de la psychologie, en s’appuyant sur le postulat de représentations spatiales intrinsèques au paradigme qui conçoit l’espace comme un construit. Le travail s’inscrit dans l’approche d’une géographie mettant l’espace vécu au centre de ses préoccupations. / This comparative research - in France and Poland - was conducted in Lyon and Cracow. The purpose of the work is social tourism for children, more specifically the “discovery classes” in France and the “green schools” in Poland, the school trips constituting both a life experience and a time of collective education. The object of the research is primary schools.The work is part of a broader problem of the acquisition of geographical knowledge. The subject of the research mobilizes the field of tourism since the practices that stem from it are ways and means of appropriation of space that individuals implement in the construction of representations of space. Through experience, the individual constructs an interior model of his or her environment. This research project studies the modalities of spatial learning. The objective is to understand if the experience of school trips modifies children’s spatial representations. To ensure that all children have an equal opportunity to build their own spatial capital, research also examines the influence on their representations of previous spatial mobility. In order to examine the children’s spatial representations, both discursive (questionnaires) and graphics data (mental maps) are mobilized. The research, carried out with 192 pupils in Lyon and Cracow, is related to two disciplines, geography and psychology. It is supported by the postulate of spatial representations within the framework of the paradigm of spatial production. The work is part of an approach to geography, in which the “espace vécu” is the central preoccupation.
447

Optimalizace predikce pozice v síti / Optimization of network position prediction

Pospíšil, Petr January 2008 (has links)
This work is about position prediction in network, it is focused to find Landmark closest to the Host in the network (with lowest distance vector). The algorithm is based on GNP system. In terms of GNP system simulation was selected method for mathematical part of position prediction. The method was Simplex Downhill. The designed algorithm was implemented in Java. In the first step chose Host continent by meassuring the distance vector. In next step is selected nearest part in the continent. In conclusion estimate Host its position and then closest Landmark. Results from this work is important for designing TTP protocol. The verdict is that the GNP can be used for TTP, but Landmarks must be located in uniform density.
448

Dynamische Modellierung des Gaspfades eines Gesamt-IGCC-Kraftwerkes auf Basis des SFG-Verfahrens

Bauersfeld, Sindy 17 June 2014 (has links)
Im Rahmen der vorliegenden Arbeit werden dynamische Modelle eines IGCC-Kraftwerkes mit CO2-Abtrennung unter Verwendung des Modellierungstools Modelica/Dymola entwickelt. Dabei liegt der Schwerpunkt auf dem Gaspfad der Gasreinigung. Es ist vorteilhaft, für verschiedene Aufgaben, Modelle mit unterschiedlicher Tiefe zu verwenden. Mit den detaillierten Modellen werden Simulationen der Teilprozesse durchgeführt. Für den Aufbau eines Gesamtsystems werden vereinfachte Modelle verwendet. Anhand des Gesamtsystems werden drei Regelkonzepte (Gleitdruckregelung, Leistungsregelung der Gasturbine, Leistungsregelung des Vergasers) untersucht und bewertet. Des Weiteren werden drei Störfallszenarien (Ausfall des Sättigers im Brennstoffsystem, Betriebsstörung in der Vergaserinsel, Unterbrechung der Stickstoffzumischung im Brennstoffsystem) getestet.
449

Architektura virtuálna / The Architecture of the Virtual

Halinár, Matej January 2017 (has links)
Architecture Jail Escape It is a specific device for futuroptimist people based on the philosophy of posthumanism and transhumanism, a version of their own faith in endless life on the net. It is a belief in the possibility of technological transformation of humanity that will allow us to overcome our physical and biological limits. Clause 2.0 is architecture for pioneers - the protagonist of this transformation - enabling the longest and most complete stay in virtual reality. This avant-garde is anxious 2.0. Escapist personalities of digital age soldiers are looking for a haven and their own version of the world in the cyberspace. They create a vision of paradise and colonize (cyber) space without the political consequences of the finiteness of the physical world and the exhaustion of natural resources. They live on the frontier of the being, and they want to unburden themselves and merge with the world they understand more. They fight with their own brain and body that cannot break away from the world. The endlessness of the virtual space has the limits of body and senses. Long-term stay in a cyberspace is a loss of sense of time and space. This monastic life in clause 2.0 is able to keep them in shape, by observing the ritual, the physical performance of walking that they must undergo so that they can exist every day in their version of the digital monastery. These versions are infinite, and they can be ritually traced among them. Clause geometry isolates them from one another. The clause is a monastic concept that allows the people to live hermetically, as well as the physical world. The gateway to the virtual space is a "zero architecture" - a room, a cell, a cube on a 4x4 meter plan, rid of any visual architectural site. It provides only a flat floor as the reflection point for an endless virtual world and four walls and a ceiling with a corresponding thickness for a sufficient separation from the outside world. The world of infinite freedom opens behind this "zero architecture". It seems that not through "architectural innovation and political subversion" a modern architect's dream of architecture will be realized as machines for the liberation of man but through the abandonment of physical architecture as such. The prospect of "zero architecture" opens up a space where the new architecture will no longer be "luxuries and good homes, not the architecture of separation and imprisonment, but it will ultimately be the architecture of freedom.
450

Raumstrukturelle Einflüsse auf das Verkehrsverhalten - Nutzbarkeit der Ergebnisse großräumiger und lokaler Haushaltsbefragungen für makroskopische Verkehrsplanungsmodelle

Wittwer, Rico 18 January 2008 (has links)
Für die Verkehrsnachfragemodellierung stehen dem Planer sehr differenzierte Modellansätze zur Verfügung. Ein wesentliches Unterscheidungskriterium stellt dabei der Modellierungsgegenstand dar. Der Fokus der vorliegenden Arbeit ist auf makroskopische Verkehrsplanungsmodelle gerichtet. Es wird der Frage nachgegangen, in welcher Form die Ergebnisse großräumiger und lokaler Haushaltsbefragungen effizient bzw. sich gegenseitig ergänzend in Modellierungsaufgaben Einsatz finden können. Im Mittelpunkt der empirischen Datenanalyse steht die Frage, ob ein Unterschied in der Ausprägung zentraler modellierungsrelevanter Kenngrößen differenziert nach Raumtypen statistisch belegbar und planungspraktisch bedeutsam ist. Vor diesem Hintergrund wird auch die Auswirkung der komplexen Stichprobenpläne von MiD 2002 und SrV 2003 auf die Varianz der Parameterschätzung berücksichtigt. Ein in dieser Arbeit entwickelter, mehrstufiger Bewertungsalgorithmus, der dem Signifikanz-Relevanz-Problem hinreichend Rechnung trägt, bildet die Grundlage der Hypothesenprüfung. Er verbindet das Standardvorgehen (Signifikanztest) mit normativ gesetzten Effektgrößen und dem schätzerbasierten Vorgehen (Konfidenzintervalle). Eine besonders hohe Transparenz und Entscheidungskonsistenz erlangt der Ansatz dadurch, dass die Hypothesenprüfung auf Basis zweier voneinander unabhängig erhobener Untersuchungsgruppen (MiD, SrV) erfolgt. Die intensive Arbeit mit den Datengrundlagen MiD und SrV liefert eine Vielzahl von Erkenntnissen zur weiteren Qualifizierung des Erhebungsinstrumentes „Mobilität in Städten – SrV“. In Vorbereitung der im Jahre 2008 anstehenden Neuauflage der Erhebungsreihe wird nach Ansicht des Autors mit der Arbeit ein wesentlicher Impuls zur Weiterentwicklung der Methodik gegeben.

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