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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.
31

Analyse de l'effet des lacs sur le bilan d'énergie de surface régionale dans le nord du Canada avec l'apport d'images satellites / Use of satellite data to estimate regional surface energy budget and analysis of lake cover impact over Northern Canada

Ikani, Vahid January 2009 (has links)
Résumé: Les lacs occupent environ 30% du territoire dans le nord du Canada. Ils peuvent avoir d’importants impacts sur le climat qui ont un effet par la suite sur les propriétés thermiques des lacs. L’étude d’un lac doit généralement débuter avec un bilan calorifique de la surface. La différentiation précise que l’énergie disponible en flux de chaleur sensible ou latent est un élément crucial pour la compréhension des interactions entre les processus climatiques à une échelle régionale. Dans cette étude, le flux de chaleur sensible et le ratio de Bowen sont obtenus à partir des données de la télédétection. La méthodologie se base sur l’utilisation de données microondes (SMM/I) afin de calculer la température de la surface du sol avec la méthode de Fily et al. (2003) et Mialon et al. (2007). La caractérisation de la surface du sol est effectuée à partir de données satellitaires optiques (capteurs SPOT & VGT). Les paramètres météorologiques utilisés pour estimer les flux proviennent de la base de données du North American Regional Reanalysis (NARR). Les résultats présentent un portrait quotidien, mensuel et saisonnier de l’énergie sensible à l’interface sol-air par rapport à la fraction de la surface de plan d’eau (FWS). Nous comparons ensuite nos résultats avec les flux du modèle NARR et quelques mesures in situ. Quatre sites couvrants différents types de surfaces à travers le Canada ont été étudiés pendant les étés 1998 et 2000 (de juin à septembre) : le nord du Québec (toundra), les Territoires du Nord-Ouest (le Grand lac des Esclaves [ou, en anglais, Great Slave Lake. GSLJ et le bassin de la rivière Mackenzie), le Manitoba (zone humide) et le Labrador (taïga). Les résultats montrent que les flux d’énergie sensible satellitaires sont semblables aux flux estimés par le NARR lorsque la FWS est petit (sans lac) ou pour des zones avec de larges surfaces d’eau (Mackenzie Great Slave Lake), mais diffèrent lorsque la FWS augmente à l’intérieur d’un pixel. Ceci signifie que les modèles climatiques régionaux devraient considérer la proposition du territoire occupée par des étendues d’eau. Nous déduisons que les effets de la taille des lacs sont reliés aux conditions environnementales du milieu. Les résultats de la comparaison avec des mesures in situ pour le GSL et la zone humide sont encourageants. Le ratio de Bowen sur le site du bassin de la rivière Mackenzie montre qu’il y a une augmentation de la chaleur sensible durant la deuxième moitié de l’été en comparaison à la première moitié. Il y a ainsi un plus grand stress hydrique pendant la deuxième moitié de l’été. Cependant, il n’y a pas de patrons clairs en comparaison avec le site GSL. La comparaison entre les différents sites indique une variation énergétique annuelle minimale pour la zone humide. || Abstract: Lakes occupy roughly 30% of Canada's northern landscape. They can have important impacts on the climate, and climate modification will affect lake thermal properties. Study of a lake most generally begins with heat budget at its surface. Accurate partitioning of the available energy at the surface into sensible and latent heat flux is crucial to the understanding of interactions between climate processes on a regional scale. In this study, sensible heat flux and the Bowen ratio for the summer period are retrieved using reanalysis and remote sensing data. The methodology is based on the use of microwave data for retrieving land surface temperature (SSM/I) with the method of Fily et al. (2003) and Mialon et al. (2007). The land cover characterization is derived from remotely sensed optical data (SPOT VGT sensor). Some meteorological parameters used for retrieving flux are derived from the North American Regional Reanalysis (NARR) database. The results from this study present a picture of the daily, monthly and seasonally sensible energy over summer period at the land-air interface versus the Fraction of Water Surface (FWS). We compare our results with the NARR model's flux in addition to few in situ measurements. Four sites covering different land cover types across Canada were investigated during the 1998 and 2000 summers (June to September): Northern Quebec (tundra), Northwest Territories (Great Slave Lake, or GSL, and Mackenzie River Basin), Manitoba (wetlands) and Labrador (taiga). The results show that the satellite-derived sensible flux is close to the NARR flux estimate when the fraction of water surface is small (no lakes) and over large open water areas (Mackenzie Great Slave Lake), but differs when the FWS increases within the pixel. This means that regional climate models should take into account lake cover fraction. We infer that effects of the lake-size are closely related to surrounding environmental conditions. The results of the comparison with in situ measurements for Great Slave Lake (1998) and the Wetland site are encouraging. For the Mackenzie River Basin site, the results of the Bowen ratio show that there is an increase of sensible heat partition during the second half of the summer in comparison with the first half, meaning that there is more water stress over the second half of the summer than the first. But for the Wetland site, there is no clear pattern, and in comparison with GSL, temporal variation is less significant. Comparisons between different sites indicate minimum year to year energy variation for the Wetland area.
32

Investigating the development and delivery of integrated product-service systems

Clayton, Richard J. January 2011 (has links)
Driven by the highly cyclical nature of their increasingly commoditised product offerings, many capital goods manufacturers are seeing the benefits of delivering services integrated with their core product offerings. Whilst existing research is almost unanimous in advocating the value of a servitization strategy, understanding how these product-service systems (PSSs) can be developed and delivered remains a significant challenge. The closely related PSS field, which has its heritage in the environmental and social science disciplines, is more mature in this area and a number of models have been proposed. The research reported within this thesis contributes to knowledge by investigating whether the approaches to PSS development, reported within the PSS literature, reflects the PSS development practice of servitized manufacturers. More specifically, soft systems methodology was used to explore the delivery of PSSs within the UK railway industry in order to gain an understanding of the implications for developing new PSSs. With this understanding, the existing approaches to PSS development were evaluated with respect to one servitized manufacturer through an in-depth single case study. The findings highlighted a number of significant differences between the practice of the servitized manufacturer and the literature. A survey was used to investigate whether the differences were generalisable to a larger sample of servitized manufacturers. The findings point towards the simplification of the reported phases within PSS development and the inclusion of a number of previously unreported processes and activities. Based on these results a new model of PSS development is proposed to better reflect the practice of servitized manufacturers. The model, consisting of four phases and seventeen processes, was operationalised in the form of a workbook and tested through application. Applying the workbook resulted in the successful creation of a number of new PSS concepts.
33

Semi-Solid Slurry Formation Via Liquid Metal Mixing

Findon, Matthew M. 21 July 2003 (has links)
"New, economical semi-solid metal (SSM) processes rely on forced convection during solidification to influence non-dendritic growth. The fundamental mechanisms that produce SSM microstructures in the presence of forced convection (due to fluid flow) are not fully understood. The objective of this work is to elucidate these mechanisms through the use of a new semi-solid slurry-making technique. Employing an apparatus developed at WPI, two alloy melts are mixed within a static reactor that induces convection and rapid cooling. Experiments carried out with this apparatus, named the “Continuous Rheoconversion Process” (CRP), result in globular semi-solid microstructures throughout a wide range of processing conditions. These conditions include the superheat in the melts before mixing, cooling rate of the slurry through the SSM range, and the presence or absence of inoculants in the melts. The results comprise repeatable sets of semi-solid microstructures having fine particle size and shape factors approaching unity. Even in the absence of melt inoculants, uniform distributions of α-Al particle sizes of about 60µm are attainable. Entrapped liquid is not present in the majority of the samples obtained with the CRP, and irregular particles that form in the process are of a limited distribution. Variation of slurry analysis methods indicates that these structures can be obtained consistently for both thixocasting and rheocasting applications. The design of the mixing reactor leads to turbulent fluid flow just as solidification commences. The results suggest that the following factors must be considered in identifying the mechanisms operating under the above conditions: copious nucleation of the primary phase; dispersion of nuclei throughout the bulk liquid; and inhibited remelting of nuclei due to temperature uniformity. In the CRP, these factors consistently lead to suppression of dendritic growth, significant grain refinement, and globular slurries. The exact fundamental mechanism leading to this effect is yet to be uncovered; however it is clear that temperature gradients ahead of the liquid are such that a cellular, non-dendritic morphology is the most stable growth form. Through further exploration of the process and identification of the operating mechanisms, future development of economical, continuous rheocasting methods will be facilitated."
34

Optimization of the Heat Treatment of Semi Solid Processed A356 Aluminum Alloy

Dewhirst, Brian A 17 November 2005 (has links)
"This research investigated the relationship between T5 heat treatment and elongation in thixocast and rheocast SSM components as a means to reduce the energy, time, and cost associated with T6 treatments while still producing improved properties over the as-cast condition. Temperature and time were varied as a part of work to optimize aging conditions for SSM materials. Both conventional furnace and fluidized bed heat treatments were employed. Tensile bars were fabricated from the heat treated A356 components and were pulled. Extensive SEM and stereo microscopy were performed to examine the factors which produced favorable results in the T5 condition. Data generated for T6 and as-cast components were also collected for purposes of comparison. Quality index calculations were employed to help evaluate the results. Optimized procedures and aging parameters have been presented"
35

Managing Urban Sprawls in Cities of the Developing South : The Case of Slum Dwellers International

Tesot, Longinus January 2013 (has links)
This thesis seeks to review Urban Sustainability in cities of the Developing South within the broader spectrum of Sustainable Development. Notably, the Developing South has for many years struggled to embrace Sustainability in its general terms: in part, because of the fragile institutions that cannot be counted on to uphold sustainability in the truest sense of the word; and in part because of the numerous challenges that often distract any attempt to prioritize Sustainable Development. Sustainability then becomes an option in the midst of other options, rather than an option that should affect all other options. Narrowing it down further to matters urban makes it even stranger in a host of cities across the Developing South. It is against this backdrop that this study seeks to examine in depth the contextual challenges that have invariably stood in the way of Sustainable Development across the Developing South. While it may not be practically possible in a four-month study to offer outright solutions or recommendations that could address these challenges in entirety, this study nevertheless has endeavoured to stay true to the realities that are often ignored whenever challenges of Sustainable Development are mentioned on global platforms. Among these realities is the reality of slum presence in most cities of the Developing South that existentially complicates any equation for urban sustainability ever formulated to provide a way out or forward for these cities. State governments understand this too well, and so do Civil Society Organizations (CSOs) and international organizations alike involved in the crusade for improved living conditions for city resident, and in particular slum residents. Yet the State governments have never been as resolute in their quest for slum free cities. The question then remains: exactly what are the sustainable approaches for this noble cause? While the State governments have over the years insisted on enforcing conventional approaches (that include forced evictions, relocations and/ or redevelopment); one international network, however, thinks and responds differently to slum situations. The network is Shack/Slum Dwellers International (SDI). It is considerably this network of slum dwellers and their undeniably innovative approach to urban sustainability and inclusivity that largely frames the direction and general content of this study. Specifically, the methodology adopted in the study is one of a Case study - which in this case is SDI; and two separate Cases, namely Railway Relocation Action Plan (RAP) in Nairobi, Kenya and slum Re-blocking project in Joe Slovo, Cape Town, South Africa, respectively - as typical cases that captures in large part the enormous contribution that SDI is making towards inclusive and sustainable cities in the Developing South. In the discussion part, however, the study introduces Soft Systems Methodology (SSM) as a comparative methodology to SDI’s approach. SSM particularly benefits from LUMAS model and Social Learning – both key components that potentially reserve a dynamic capacity to enriching SDI’s approach as a future reference methodology for urban sustainability and inclusivity.
36

Applying Systems Approach to Educational-Organizational Change : Improvement of an Interdisciplinary Program, Masters in Sustainable Development

Karim, Sanaz January 2009 (has links)
After the introduction of the term,  sustainable development, a variety of  academicians from different disciplines tried to conceptualize it in their own way, drawing on these views, many different degrees but with similar titles have been established in many universities all around the world. Masters  program in  Sustainable Development  (MSD) at Uppsala University and the Swedish University of Agricultural Sciences (SLU) is one the most recent ones. Before starting this study, it was investigated that the expectations of the different actors in this program are not fulfilled completely. Presence of many different ideas and perspectives in addition to the high number of actors involved in the situation made the situation too complex to be fixed easily. Therefore, the Soft Systems Methodology (SSM), as an appropriate approach for improving complex problematic situations,  is  used to reform the organization of  the  MSD in coming years. The process of identifying the  challenges of this program and then  improving some of them in  practice  are described in this thesis. Alongside the  action phase, the applications of Systems Approach in transformation of Education for Sustainable Development (ESD) are explored.  It is investigated that three levels of learning, i.e. basic, meta-  and epistemic learning, and accordingly three levels of organizational change, i.e. the first, second and third order, need to be recognized, if an ESD program is to be different from the unsustainable trends of education.
37

Etude de la multifragmentation du systeme Au+Au entre 40 et 100 MeV/A: expansion et flot radial

Lavaud, Franck 28 September 2001 (has links)
Mon travail de thèse, concernant les collisions centrales Au+Au entre 40 et 100 MeV/A, se place dans le cadre d'une analyse comprenant le dépouillement et l'interprétation des résultats de la 4ème campagne de mesure du multidétecteur INDRA. La première phase de cette étude, dite de "dépouillement", a permis de reconstruire, à partir des données brutes des deux premiers étages de détection d'INDRA (chambre d'ionisation, Silicium), les énergies cinétiques et la charge des fragments détectés. Pour la première fois, il a été possible de mettre en évidence et de corriger les effets de non-linéarité dans la chaîne d'acquisition <br />d'INDRA. A l'issue de ce travail, je me suis attaché à selectionner les collisions centrales. <br />Pour ce faire, et dans le souci de ne pas biaiser les interprétations physiques résultantes, j'ai mis en oeuvre deux méthodes distinctes: sélection en paramètre d'impact ainsi qu'une analyse en composante principale. Une étude comparative de ces deux outils mathématiques a été entreprise donnant lieu à des résultats très instructifs.<br /><br /><br />L'interprétation des résultats a fait appel à plusieurs types de modèles lesquels impliquant la validité de certaines hypothèses (équilibre thermodynamique, existence d'un volume de "freeze-out"). L'emploi de modèles statistiques (SMM, MMMC) a permis <br />d'extraire la taille du système émetteur, dit "source unique", ainsi que son énergie d'excitation. L'anisotropie des distributions en énergie cinétiques des fragments, a permis de <br />mettre en évidence, en fonction de l'énergie incidente de la collision, une déformation de la source, mais également de reconstruire les énergies thermique et collective entrant en jeu. Une nouvelle comparaison des données à l'aide de modèles dits "dynamique" (QMD,CMD) a été également entreprise. A l'issu de cette étude, des critiques portant sur la validité d'une approche telles SMM ou MMMC ont pu être émises remettant en jeu le fondement de l'interprétation physique du flot collectif couramment employé.
38

Modelling Bird Migration with Motus Data and Bayesian State-Space Models

Baldwin, Justin 27 October 2017 (has links)
Bird migration is a poorly-known yet important phenomenon, as understanding movement patterns of birds can inform conservation strategies and public health policy for animal-borne diseases. Recent advances in wildlife tracking technology, in particular the Motus system, have allowed researchers to track even small flying birds and insects with radio transmitters that weigh fractions of a gram. This system relies on a community-based distributed sensor network that detects tagged animals as they move through the detection nodes on journeys that range from small local movements to intercontinental migrations. The quantity of data generated by the Motus system is unprecedented, is on its way to surpass the size of all other centralized databases of animal detection and requires novel statistical methods. Building from the bsam package in R, I propose two new biologically informed Bayesian state-space models for animal movement in JAGS that include informed assumptions about songbird behavior. I evaluate the models using a simulation study in realistic conditions of data missingness. One of these models is generalized to a hierarchical version that fits population-level movement through joint estimation of movement parameters over multiple animal tracks. To apply the models, I then employ a localization routine on a Motus data set from migrating songbirds (Red-eyed Vireos - Vireo olivaceus) from the Eastern coast of North America. This allows me to apply the new hierarchical model and its predecessor to estimate unobserved locations and behaviors. Migratory flights were observed to occur mostly in the evenings along the coast and directed migratory flights were detected over water over e.g. the Bay of Fundy, the Long Island Sound and the New York Bight. Area-restricted searches were confined to coastal areas, in particular the Gulf of Maine, Long Island and Cape May.
39

Aplikace pro monitorování multicastových relací / Monitoring Application for Multicast sessions

Kopecký, Martin January 2009 (has links)
This work deals with a monitoring application for multicast sessions. The general aim is to develop the application for monitoring multicast sessions from network elements of a laboratory computer network. The first part describes possibilities of monitoring computer networks in terms of monitoring techniques and protocols. The second part contains a topology of the laboratory computer network and several basic commands for setting of the multicast in Cisco IOS. The third part is devoted to the developed application for monitoring the multicast in Java language. The last part describes the testing on an actual multicast network and an example of such testing is stated there.
40

The spin relaxation of nitrogen donors in 6H SiC crystals as studied by the electron spin echo method

Savchenko, Dariya, Shanina, Bela, Kalabukhova, E., Pöppl, Andreas, Lancok, J., Mokhov, Evgeny 23 May 2018 (has links)
We present the detailed study of the spin kinetics of the nitrogen (N) donor electrons in 6H SiC wafers grown by the Lely method and by the sublimation “sandwich method” (SSM) with a donor concentration of about 10 17cm-3 at T=10–40K. The donor electrons of the N donors substituting quasi-cubic “k1” and “k2” sites (Nk1,k2) in both types of the samples revealed the similar temperature dependence of the spin-lattice relaxation rate (T1 -1), which was described by the direct one-phonon and two-phonon processes induced by the acoustic phonons proportional to T and to T9, respectively. The character of the temperature dependence of the T1 -1 for the donor electrons of N substituting hexagonal (“h”) site (Nh) in both types of 6H SiC samples indicates that the donor electrons relax through the fast-relaxing centers by means of the cross-relaxation process. The observed enhancement of the phase memory relaxation rate (Tm -1) with the temperature increase for the Nh donors in both types of the samples, as well as for the Nk1,k2 donors in Lely grown 6H SiC, was explained by the growth of the free electron concentration with the temperature increase and their exchange scattering at the N donor centers. The observed significant shortening of the phase memory relaxation time Tm for the Nk1,k2 donors in the SSM grown sample with the temperature lowering is caused by hopping motion of the electrons between the occupied and unoccupied states of the N donors at Nh and Nk1,k2 sites. The impact of the N donor pairs, triads, distant donor pairs formed in n-type 6H SiC wafers on the spin relaxation times was discussed.

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