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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.
1

Intensification de procédés par chauffage micro-ondes pour la chimie verte / Microwave process intensification applied to green chemistry

Benamara, Nassima 07 December 2017 (has links)
L'objet de cette thèse est la conception, le développement et la caractérisation d'un réacteur micro-ondes en continu pour mener tout type de réactions chimiques à températures élevées de manière fiable et dans des conditions optimisées. Le développement de ce réacteur a tout d'abord nécessité la caractérisation diélectrique et magnétique des matériaux et milieux utilisés. La simulation numérique a ensuite été utilisée afin de prédire les distributions de champ et température au sein des matériaux. L'interaction entre les ondes et les différents milieux a été finement étudiée. Elle démontre non seulement l'influence de la nature diélectrique du milieu réactionnel et du ratio volumique du fluide dans le réacteur sur le chauffage micro-ondes, mais aussi celle des dimensions de l'applicateur et de la disposition du réacteur dans ce dernier. L'hydrodynamique a également été introduite dans la simulation permettant de prédire les profils de température dans le réacteur en fonctionnement continu. L'ensemble des résultats numériques a fait l'objet de validations expérimentales qui ont aussi permis d'affiner le modèle thermique de l'ensemble conçu. Au final, une réaction de diestérification a été mise en œuvre et démontre l'efficacité thermique et chimique du réacteur. Au-delà de ce prototype, cette thèse établit un schéma général de conception d'un procédé chimique continu sous micro-ondes en ordonnant les étapes, respectant les règles clés de l'électromagnétisme, optimisant la propagation des ondes et les performances thermiques du système. / The aim of this thesis is the development and characterisation of an intensified continuous microwave reactor for green chemistry. The development of this reactor required, at first, the characterisation of the dielectric and magnetic properties of the used materials. A numerical simulation was then used to predict the field and temperature profiles within the materials. The influence of different parameters on the microwave heating was also studied, such as the influence of the dielectric nature of the reaction medium, the ratio of the fluid in the reactor, the arrangement of the reactor in the applicator and the size and shape of the latter. Hydrodynamics were also taken into account in the simulation to predict the temperature profiles in the reactor. All the numerical results were validated experimentally. Experimental results also made it possible to refine the thermal model of the reactor. In the end, an esterification reaction was carried out and it proved the thermal and chemical efficiency of the designed reactor. Beyond this prototype, this thesis establishes a general scheme for the design of a continuous chemical process under microwaves whilst following the key rules of electromagnetism and optimising the wave propagation and the thermal performance of the reactor.
2

The Importance of Synoptic-Scale Processes in Diagnosing Tropical Cyclone Rapid Intensification in the Atlantic Basin

Grimes, Alexandria Danielle 17 May 2014 (has links)
This research identifies large-scale synoptic controls that are relevant for rapid intensification (RI) in the Atlantic basin. Spatial statistical analysis techniques were performed on NASA MERRA data from 1979–2009. Rotated principal component analysis (RPCA) was performed, looking for common patterns in the datasets. The RPC’s were grouped using hierarchical clustering techniques, allowing for finding events similar in synoptic structure. The clustered events, representing the total RI and non-RI composites, were averaged yielding composite maps for different scenarios. To verify the results, a permutation test was done to show which variables are good distinguishers of RI and non-RI cases. These variables were used as input in two prediction schemes: logistic regression and support vector machine classification. The prediction scheme was a slight improvement in forecasting RI when using the synoptic variables mid-level vorticity, vertical velocity, low-level potential temperature and specific humidity, as the most significant in predicting RI.
3

Flow induced phase inversion emulsification

Kazeem, Akintunde January 1999 (has links)
No description available.
4

A preliminary study to quantify the suitable substratum of marine sessile invertebrates.

Chou, Ya-Lan 08 August 2003 (has links)
Seasonal reproduction of marine sessile organisms may be an adaptation of seasonal variation in suitable substratum availability. This research is focused on how to quantfy the suitable substratum of marine sessile organisms. Then the potential seasonal change of suitable substrate availability can be assessed. We tested 1-1.5 meters scale is a population closed spatial scale. At this scale we try to find ¡§intensification phenomenon¡¨ using different-size panels. If intensification phenomenon dose exist at 1-1.5 meter scale, then the amount of the suitable substratum can be estimated. We also compared three different current environments at Tiaoshi area in Nan-wan-Bay, the 3rd Nuclear Power Plant Inlet and the Hobihu Yacht Wharf to find out if the intensification phenomenon exists at this different situations. Lastly, sand and reef area were compared. Since reef areas has more suitable natural substratum than sand areas. The intensification phenomenon at 1-meter scale was not found. The larval density in water column might be highly heterogeneous even in very small scale. On the other hand, we consistently found higher settlement density in sand areas than in reef areas. This phenomenon may well have been caused by the intensification phenomenon.
5

Coffee and landscape change in the Colombian countryside 1970-2002

Guhl, Andrés. January 2004 (has links)
Thesis (Ph. D.)--University of Florida, 2004. / Title from title page of source document. Document formatted into pages; contains 343 pages. Includes vita. Includes bibliographical references.
6

Den lilla kemifabriken : En studie för att undersöka om nyttan av skogsrester kan ökas i norra Sveriges inland

Häggkvist, Sofie January 2016 (has links)
The background of this work is to suggest ways to take care of branches and tops of trees that today are left out in the north of Sweden after logging because it has to low value to be worth transporting. A solution to this is to place small chemical factories in the sparsely populated areas in the inland of Norrland that can take care of the forest residues and break it into valuable chemicals directly in the forest an then transport it to a market. The aim of this work was to find out if it´s a good idea to invest in these small chemical factories in the north of Sweden. This study has been carried out using literature study and interviews of key people. The largest part of the result comes from the interviews. The results of this study show that the small chemical factory is a good idea. Forest residues contains many valuable substances that should be greater used today. The results section of the report describes various factor that are crucial for the small chemical factory and these are: the products that can be produced, what technology that is suitable, if there is an market, who should be taking care of the factory and how the inland endurance will be affected. The conclusions that can be drawn from the study is that the small chemical factory should produce high-grade-sary chemicals directed at the chemical market. It may also be noted that there is existing technology that can be used in the factories, what has been done in the laboratories today can be implemented in the factory. The market will obviously depend on which product that will be produces, but finding a suitable market should not be impossible. The inland endurance will be positively impacted, among other things, the social endurance is enhances when these small chemical factories creates job opportunities in the inland and it can lead to decreasing the emigration.
7

The effects of agriculture on swallows Hirundo rustica

Evans, K. L. January 2001 (has links)
No description available.
8

Soil erosion and suspended sediment dynamics in intensive agricultural catchments

Sherriff, Sophie C. January 2015 (has links)
Excessive delivery of fine sediment from agricultural river catchments to aquatic ecosystems can degrade chemical water quality and ecological habitats. Management of accelerated soil losses and the transmission of sediment-associated agricultural pollutants, such as phosphorus, is required to mitigate the drive towards sustainable intensification to increase global food security. Quantifying soil erosion and the pathways and fate of fine-grained sediment is presently under-researched worldwide, and particularly in Ireland. This thesis established a sediment monitoring network upon an existing catchment study programme (Agricultural Catchments Programme) in five instrumented catchments (~10 km2) across Ireland. The research used novel, high quality measurement and analysis techniques to quantify sediment export, determine controls on soil erosion and sediment transport, and identify sediment contributions from multiple sources in different agricultural systems over time to evaluate approaches to fine sediment management. Results showed suspended sediment measurement using a novel ex situ methodology was valid in two of the study catchments against in situ and direct depth-integrated cross-section methodologies. Suspended sediment yields in the five intensive agricultural catchments were relatively low compared to European catchments in the same climatic zone, attributed to regionally-specific land use patterns and land management practices expressed in terms of ‘landscape complexity’ (irregular, small field sizes partitioned by abundant hedgerows and high drainage ditch densities) resulting in low field-to-channel connectivity. Variations in suspended sediment yield between catchments were explained primarily by soil permeability and ground cover, whereby arable land use on poorly-drained soils were associated with the largest sediment yields. Storm-event sediment export and sediment fingerprinting data demonstrated that sediment connectivity fluctuations resulted from rainfall seasonality, which in turn regulated the contrasting spatial and temporal extent of surface hydrological pathways. Increased transport occurred when and where sediment sources were available as a result of hillslope land use (low groundcover) or channel characteristics. Field topsoils were most vulnerable when low groundcover coincided with surface hydrological pathways; frequently on poorly-drained soils and following extreme rainfall events on well-drained soils as storage decreased. Although well-drained soils currently demonstrate low water erosion risk, past sugar beet crops exposed freshly drilled soils during periods of greater rainfall risk and soil removal during crop harvesting. Sediment loss from grassland catchments dominated by poorly-drained soils and extensive land drainage (sub-surface and surface) primarily derived from channel banks due to the delivery of high velocity flows from up-catchment drained hillslopes. Catchment specific soil erosion and sediment loss mitigation measures are imperative to cost-effectively preserve or improve soil and freshwater ecosystem quality worldwide.
9

Property size preferences and the value of private and public outdoor spaces amid a shift to high-density residential development: A case study of Kitchener-Waterloo, Ontario

DeFields, Emma January 2013 (has links)
Planning policies in Ontario, such as the Provincial Policy Statement and the Growth Plan for the Greater Golden Horseshoe, enforce urban growth boundaries to preserve natural and agricultural lands while improving neighbourhood and city vibrancy. Consequently, urban areas must be intensified through high-density development, which will limit the land available for public green spaces and large private yards. As a result, homebuyers looking for spacious properties will have to rely mainly on the turnover of older homes. Therefore, this thesis explores how residents currently living in homes with private yards value private and public outdoor space, and whether they have interest in upsizing or downsizing their homes in the future. Neighbourhood and property attributes that may be influential in homebuyer decision-making are also investigated. The cities of Kitchener and Waterloo (“Kitchener-Waterloo”) were chosen as the study location, as both cities are affected by the Growth Plan and are currently being intensified. From March to August, 2012, a random sample of 1272 households living in homes with private yards were invited to participate in a survey on yard landscaping and maintenance practices and property preferences, after which a total of 206 surveys were analyzed. Most respondents were living in medium-sized homes with medium-sized yards, and results indicated that homes and yards of medium size would be the most commonly preferred options if residents were to move (considering their household size, health, finances, etc.). On the whole, the target market for high-density homes (i.e. condominiums, small houses, and small yards) came mainly from the aging population. Nevertheless, when asked if they would ever live with less yard space in the future (when their household conditions could differ from what they were at the time of the survey), 58% of all respondents indicated that they may live in a home with a small yard and 41% indicated that they may live with no yard. Such a finding further indicated that residents may find high-density dwellings more appealing as they age. Based on findings, ways of increasing the appeal of compact dwellings are discussed, such as including a small yard or balcony, providing privacy, ensuring access to public green spaces, and being located in a safe neighbourhood. Landscapes neat in appearance and designed with grass, colourful vegetation, trees, and natural gardens are also expected to increase property appeal. Overall, if development is to remain restricted to built-up areas, developers and planners will have to create desirable high-density homes located in communities that accommodate the lifestyles of potential residents. This thesis addresses such a challenge by delineating target market groups with the potential to move to high-density homes, and by providing insight into the variables that may increase the appeal of properties as landscapes are intensified.
10

Super GTA: Urban Implications of Ontario's Greenbelt

Martin, Edward Johnson January 2006 (has links)
In early 2005, increasing social and infrastructural costs associated with the rapidly expanding Greater Toronto Area [GTA] pressed the Province of Ontario to initiate a growth management strategy for the region. The Provincial <em>Growth Plan</em>, coupled with its <em>Greenbelt Plan</em>, effectively legislates a minimum of 40 per cent infill development by 2015 and limits land supply until 2031. This book explores the extents and implications of this legislation, with a particular focus on the Town of Milton, a key community west of downtown Toronto, where city and Greenbelt meet. <br>    The structure of suburban communities can and should be modified to improve their sense of identity, and reduce their environmental impact and dependency on automobiles. The thesis aims to reflect the policies inherent in the Provincial Growth Plan, which advocates placing walkable infill development in close proximity to public transit. A design proposal links natural corridors and recreational spaces with a public thoroughfare along the existing railway line in Milton, Ontario. A dense new community flanks this public armature which connects the public realm network of this rapidly developing town to the larger network of the Metropolitan Greenbelt. <br>    The Town of Milton becomes a test case for scenarios which are common within the GTA, and examines the human impact on environmental systems moving towards symbiosis. The context of this city-building predicts a fundamental conceptual shift in the priorities of urban living, where residents understand the value of the natural environment and their relationship to it. That is to say, its context is one in which nature matters.

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