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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.
361

The importance of edge effects in determining fish distributions in patchy seagrass habitats

Smith, Timothy Malcolm January 2009 (has links)
Boundaries between adjacent habitats can create unique biotic and abiotic conditions, varying species compositions and abundances between the edge and interior of habitats. As habitats become fragmented, the relative amount of edge increases. Understanding the role that habitat edges have in determining species compositions and abundances is fundamental for conservation and management of habitats, particularly those under threat from fragmentation. Seagrass habitats are common nearshore habitats that harbour a rich and diverse faunal assemblage that are under threat worldwide from human disturbance. Human induced fragmentation, and the propensity of seagrass to form naturally patchy landscapes, makes it an ideal system to study the effects of edges on fauna. / Evidence of fish displaying edge effects in seagrass habitats is equivocal. Assessment of fish edge effects was done by sampling seven positions within seagrass habitats at fine spatial scales. Strong, consistent patterns in fish distributions demonstrated clear edge effects both within and alongside seagrass at these sites. The total number of fish sampled was greater at the seaward seagrass edge than the seagrass middle, but there was little difference between the seagrass middle and the shoreward seagrass edge. Four individual fish species showed preferences for the seagrass edges. Further investigation revealed that patch size could influence the magnitude of edge effects in seagrass beds. Fish were sampled in ten variously sized seagrass patches in three positions within each patch. Two species showed variations in edge effects across patches which could be attributed to the area of the patch. Changes in patch size can influence the magnitude of edge effects that species display, suggesting that patch area effects (fish density varying with patch size) could be caused by edge effects. / Food availability and predation are mechanisms commonly used to explain edge effect patterns. Gut analysis was done on Stigmatopora nigra sampled at the edge and middle of patches to determine if prey consumption varied between positions, and explain S. nigra distribution. There was little difference in prey consumed by S. nigra at the edge and middle of patches, suggesting that food was unlikely to be causing S. nigra edge effects, or that the influence of prey distribution was being masked by other factors such as seagrass structure. Predator abundances and foraging efficiency may vary at the edge and middle of patches, and consequently influence the distribution of prey fish within patches. Underwater videos were placed at four positions within seagrass habitats to assess predator distributions. Predatory Australian salmon, Arripis spp., spend more time over adjacent sand than other positions, while small potential prey species (King George whiting, Sillaginodes punctata, recruits) appear to prefer the middle of seagrass patches, possibly to avoid encounters with salmon. To test if the predator-prey distributions reflected actual predation pressure, a tethering experiment was done to determine if predation was causing edge effects in small fishes. / King George whiting recruits and pipefish (Stigmatopora spp.) were tethered at each of the four positions at different depths. Survival time of whiting recruits was greater in the middle of shallow seagrass patches than other positions. Few pipefish were preyed upon, and survival time was lower over sand adjacent to seagrass than at the seagrass edge or middle. Video footage revealed that salmon was the dominant predator of both whiting recruits and pipefish. The distribution of predators and associated predation can explain edge effects for some species (whiting) but other mechanisms, or a combination of mechanisms, are determining edge effects for other species (pipefish). / Edge effects were common amongst fish species in seagrass habitats, and included permanent, temporary and predatory species. Patch size was found to influence the extent of the edge effect. There was little evidence to support prey consumption as an underlying mechanism causing higher fish abundances at the interior or edge of patches, however there was evidence that predation could be causing edge effects. Changes in fish distributions within seagrass patches due to patch size and predation when seagrass undergoes fragmentation need to be considered by not only ecologists, but also by managers in the development of plans for seagrass conservation. Future studies should investigate the relative contribution of different edge characteristics in determining the degree of seagrass edge effects.
362

Dynamique des sédiments fins en milieu marin et agitation portuaire

Sanchez Angulo, Martin 14 January 2000 (has links) (PDF)
Mes travaux de recherche sous la direction du Professeur A. Grovel, ont fait l'objet d'une thèse de doctorat sous le titre : "Modélisation dans un estuaire à marée. Rôle du bouchon vaseux dans la tenue des sols sous marins", soutenue à l'université de Nantes le 10 juillet 1992, devant le jury composé par : M. Bélorgey, C. Larsonneur, J. Chapon, A. Graillot, A. Grovel et P. Jouve.<br /> Depuis 1992, les recherches que je mène se situent dans le cadre de l'hydraulique maritime appliquée aux travaux maritimes. Ces recherches concernent principalement les problèmes d'aménagement portuaire et côtier, car les résultats de celles-ci apportent des éléments de réflexion aux ingénieurs en génie côtier, lesquels doivent tenir compte des contraintes environnementales propres à chaque site dans la conception des ouvrages maritimes. Il se pose alors quatre types de problèmes indissociables :<br />a) l'étude des conditions environnementales locales comprenant la mesure de la houle in situ, l'étude de la marée extrême locale et l'étude des couches sédimentaires mobilisables sous contraintes hydrodynamiques,<br />b) l'étude de l'implantation des ouvrages de protection contre la houle afin d'assurer une navigation en toute sécurité garantie par une modélisation fine de l'agitation portuaire, tenant compte de la houle incidente et des réflexions de la houle par les frontières latérales,<br />c) l'analyse de la stabilité d'ouvrages de génie civil nécessitant une connaissance approfondie de la houle de projet, de la marée, et de la tenue des sols marins,<br />d) l'examen de l'impact sédimentaire causé par les ouvrages de protection sur les problèmes d'ensablement, d'envasement et d'érosion.<br /> Les trois principaux thèmes sur lesquels je travaille actuellement à la Faculté des Sciences et des Techniques de Nantes, sont tous liés aux problèmes décrits ci-dessus ; les deux premiers ont des points communs avec ma thèse de doctorat et le troisième est un thème de recherche que j'étudie depuis 1994. Ces trois thèmes sont :<br />1) les processus sédimentaires des vases,<br />2) les problèmes hydrosédimentaires dans les estuaires et les zones côtières,<br />3) l'agitation portuaire.<br /> Ces thèmes sont développés respectivement dans les chapitres 1, 2 et 3 de ce mémoire, ensuite, les différentes activités liées à la recherche auxquelles j'ai participées depuis 1992 sont décrites au chapitre 4 et finalement les conclusions et perspectives sont présentées.
363

Sondage de Canal SIMO à l'intérieur des bâtiments et formation de faisceaux numérique utilisant des techniques de traitement de signal à haute résolution et corrélateurs cinq-ports

Braga, A. Judson 18 September 2006 (has links) (PDF)
Le développement de systèmes de communication mobile large bande demandent une connaissance des caractéristiques du canal mobile comme celles du profile de puissance, l'angle d'arrivée et la décalage Doppler des trajets multiples. Un sondeur de canal peut réaliser une caractérisation multidimensionnelle du canal à petite échelle afin de l'appliquer à la modélisation stochastique de canal où à l'évaluation des performances de systèmes de communication. Des instruments capables de réaliser un sondage de canaux de propagation SIMO à l'intérieur des bâtiments sont assemblés, notamment, le réflectomètre Cinq-port utilisé comme démodulateur homodyne de signaux RF et des techniques d'estimation à haute résolution comme MUSIC. Un système de formation de faisceaux qui peut réaliser un filtrage spatial pour de nombreuses applications est aussi implémenté utilisant la plupart de ces outils. Le réflectomètre Cinq-port réalise une conversion directe des signaux RF et utilise un troisième mixeur de redondance pour diminuer la dépendance du système au déséquilibre de phase et amplitude de l'oscillateur local. La procédure d'estimation de la réponse spatio-temporelle du canal est basée sur les algorithmes MUSIC et lissage spatial (2D-SS) sur deux dimensions. Le traitement simultané des données sur les domaines de l'espace et de la fréquence nous permet l'estimation conjointe de l'angle d'arrivée et du retard des trajets multiples même en présence des signaux corrélés. La technique de tracée de rayons est implémentée afin de comparer les paramètres du canal calculé de façon déterministe avec ceux déterminés par le sondage de canaux.
364

Resistance mechanisms of Port-Orford-cedar to Phytophthora lateralis

Oh, Eunsung 30 November 2004 (has links)
Breeding Port-Orford-cedar for resistance to Phytophthora lateralis, a causal agent of root disease, begins by screening, through artificial inoculation, phenotypically resistant trees selected from natural stands. The successful program selected tolerant or resistant POC parent trees for the purpose of disease management. Candidate resistant POCs were used in my dissertation to: 1. validate screening methods such as stem- and root-dip inoculation; 2. test for increased virulence of P. lateralis; and 3. evaluate detection techniques. The results showed that the established screening methods were appropriate, and no evidence of changed virulence was found. A PCR technique was more reliable than other techniques for detection of P. lateralis in seedlings. An additional test for foliar infection showed that initial penetration through wounds and natural openings was possible. POC seedlings and rooted cuttings from resistant and susceptible families were used to demonstrate resistance mechanisms. In order to explain the mechanisms at the cellular level, the susceptible response of POC seedlings to P. lateralis was first observed with light microscopy. Zoospores encysted on lateral roots, germinated, and penetrated by means of appressoria. Direct penetration between epidermal cells was common but penetration through epidermal cell walls was also observed. The hyphae colonized the root cortex inter- and intracellularly. Wound inoculation on stems resulted in inter- and intra cellular hyphal growth in cambial, sieve, and parenchyma cells in the secondary phloem. Several resistance mechanisms were observed: 1) there was a difference in zoospore attraction between susceptible and certain resistant POCs revealed by microscopic observation, direct count of encysted zoospores, and quantitative real-time PCR; 2) the frequency of encystment, penetration, and colonization of resistant seedlings was much lower than susceptible seedlings, but no differences in infection pathway were observed by means of light or electron microscopy; 3) collapsed cell walls were present in resistant POCs showing increased cell wall thickness, wall appositions, and electron dense materials. / Graduation date: 2005
365

Geoarchaeology at Tseriadun (35CU7), Curry County, Oregon /

Anderson, Frederick C. January 1900 (has links)
Thesis (M.A.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 113-120). Also available on the World Wide Web.
366

The Group Areas Act and Port Elizabeth's heritage: a study of memorial recollection in the South End Museum.

Kadi, Palesa. January 2007 (has links)
<p>The second half of the 1990's was marked by a significant reworking of memory and history in South Africa. WHilst the Truth and Reconciliation Commission (TRC) was involved in its hearings on amnesty applications and gross human rights violations, new museums were emerging and older ones began reshaping their displays. This thesis interrogated the changing representations of history, culture, identity and heritage in one South African city, Port Elizabeth, which in 2005 was re-named the Nelson Mandela Bay Municipal area. This discussion examined, at times, the historical era prior to South Africa's democracy and the period after the first democratic elections of 27 April 1994.</p>
367

A Study of ¡§the Merger of Kaohsiung City & Kaohsiung Port¡¨ & the Development of ¡§Maritime Capital¡¨

Huang, Shu-mei 01 August 2007 (has links)
Taiwan is a typical country of island which locates at the shipping center of northeast & southeast Asia. The economic circle constituted by its relevant ocean shipping routes reveals its importance of sea transportation and trade location. With the natural condition, the advantageous Taiwanese coastal line lasts for around 1500 kilometers, the island currently has international ports such as Keelung, Taichung, Kaohsiung, Hualien, etc; in addition, there are also supplementary ports such as Taipei, Anping and Suao. The export economic trade from the port is the main economic lifeblood in Taiwan as the large overseas trade relies heavily on sea transportation. Kaohsiung city is a province as Port of Kaohsiung is the largest one in the country which plays a decisive role of the throughput in the world. The research starts from the marine capital ¡V Kaohsiung. The integrated plan and construction of port and city, development of economy & trade and cultural tourism, relevant regulation and the advancement of strategic direction and other factors all influence the change of greater economic environment in the country, which also exhibits the crucial role of the marine capital. The port-city integration and the transformation of container port organization of the marine capital have become the public focus of the society; President Chen Shui-bian declared the thorough implementation of the policy and concept of port-city integration dated 5th of Aug. 2000, which indicated the mutual participation of municipal works and plan, construction, management and operation of commercial port of the government and local administration. In the aspect of concrete action, Ministry of Transportation and Communications, R.O.C. will establish shipping administration bureau, set branches in each port and reform Maritime Administration into special public incorporated administration. The task of port-city integration of Kaohsiung city was transferred and consigned to Management Committee of Port of Kaohsiung for advancement and management from the 19th of May 2001, which is a big step forward of the management of port-city integration. Kaohsiung city government and Maritime Administration had substantial interaction in the aspects of transportation, tourism, culture and many constructions during the period of time, in addition, the 13th Kaohsiung Military Port was transferred to Kaohsiung city government dated 30th of Oct. 2005 and now has become one of the tourist scenic spot, which is an indication of the expected port-city integration. For further advancement of marine capital, heading to port-city integration, future perspective of the plan for municipal works and international competitiveness, the research will collect and organize relevant construction, plan and literature of Port of Kaohsiung and discuss the current condition and current implementation condition of Kaohsiung city and the geographical environment of the port area. The following discussion is made at the relevant problems between 4 major international ports in Taiwan and the international area, as the further synthesized analysis is carried out for the discussion of the operation strategy and development of Kaohsiung port-city integration in the hope to achieve the ideal of marine capital as soon as possible.
368

Efterlevnad av svaveldirektiven : En studie over hur landerna i svavelkontrollomradena agerar for att sakerstalla svaveldirektivens efterlevnad

Pettersson, Niclas January 2013 (has links)
De senaste åren har utsläppsreglerna för sjöfarten blivit allt hårdare och under de kommande åren skärps de ännu mer. För att svaveldirektiven för sjöfarten ska fungera effektivt så krävs det också att de efterlevs. Syftet med den här studien var därför att undersöka hur länderna i Europeiska SECA områdena agerar och kommer att agera i framtiden för att se till att svaveldirektiven efterlevs. Studien syftar också till att undersöka hur efterlevnadskontroller genomförs, samt se om länderna har infört sanktioner mot överträdelser och vad dessa innebär. För att få svar på detta studerades lagar och förordningar, men framförallt skickades frågeformulär ut till de ansvariga myndigheterna i flera olika länder kring SECA områdena. Slutsatsen av det här arbetet är att samtliga länder anser att efterlevnadskontroll sker i tillräcklig omfattning och alla länder använder sig av samma metod. I Sverige pågår utveckling av en optisk mätmetod för att mäta svavelhalt i avgaserna ifrån luften, men än är metoden inte tillräckligt säker för att kunna användas. Det framkom också att i flera länder anses det på grund av flera faktorer vara svårt att fälla någon ifall de bryter mot gällande svavelförordningar, därför anses det också finnas en risk för överträdelser. Detta trots att det i andra länder faktiskt sker ingripande mot överträdelser och samtliga länder använder sig av samma metoder för efterlevnadskontroll. Det saknas i dagsläget även sanktioner mot överträdelser i flera länder.
369

Architecture that Binds: A Place for Weddings and Funerals for a New Society

Lam, Yvonne Y.S. January 2005 (has links)
Weddings and funerals are some of the most universally profound events of our lives. Both acts, however disparate, ultimately celebrate life. This thesis draws on themes of life and regeneration in its reading of a neglected yet historically significant site in the port lands of Toronto. The changes that have occurred at the mouth of the Don mirror the changes that have occurred in Toronto from settlement to post-modernity. It is here that the thesis proposes a place that simultaneously reclaims its roots and creates a new identity for the port lands. As a means of reinhabiting this site, the design uses the power of weddings and funerals to generate a collective point of gathering that reflects the multicultural nature of Toronto today.
370

Alphanumeric LCD infrared control via computer’s parallel port

Jaramillo Cantu, Hector January 2006 (has links)
The present work will explain a method to achieve a remote controlled (via IR LED) alphanumeric Liquid Crystal Display. In modern times, the remote access of different devices has become quite popular, therefore, the aim of this project is to provide a useful tool that will integrate common and easy to access devices. The system includes a C language based user interface, an assembly language code for the AT89C51ED2 microcontroller instructions and some digital electronic circuits needed for the driving and control of both the LCD and the infrared communication, as well as the PC with a parallel port. The interaction of all the devices provides a whole system that can be helpful in different applications, or it can be separated into each one of its different stages to take the best advantage as possible.

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