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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.
401

The perception between the pro-Islamic and pro-Kurdish political streams in Turkey, 1980-2011

Dag, Rahman January 2014 (has links)
Official state ideology (Kemalism) whose core principles are Turkish nationalism and secularism excluded Kurds and Islamists from the newly formed social and political structure of modern Turkey. By insisting on a Kemalist modernization project in which assimilation of Kurdish ethnic identity within Turkish nationalism, and a top down imposition of secular policies on public and state affairs, Turkey has had to deal with two profound issues—the Kurdish question, and political Islam. As these social and political rivals of official state ideology present an alternative way of modernization projects, the Kemalist state apparatus has until recently considered their existence and development within Turkish society as a menace to their core existence. That is why the nearly century-long Kurdish question and Islamism (reactionism-gericilik) have occupied the agenda. The striking point of this reality of Turkey is that while Kurdish nationalist and Islamist social and political groups, whether they are legal or illegal, have sought to supersede the official state ideology with their understandings, they have never united or operated joint activities against their, roughly speaking, enemy. The research, because of this focuses on the reasons why these two social and political groups in Turkey did not work together to eliminate their common rival. Regarding pro-Kurdish and pro-Islamic groups, ideological distinctiveness and rigidity led them to consider each other as a part of or as an extension of official state ideology which tries to eliminate its rivals. Despite the fact that they both ideologically and practically confirmed the existence of repression towards Kurds and religious people, the leftist-oriented pro-Kurdish political stream considered religion as a component of denial and assimilationist policy of official state ideology, so that they did not differentiate between Islamist groups and the established state structure, whereas the pro-Islamic political stream refused to co-operate with any member of the leftist-oriented pro-Kurdish stream because of its secular characteristic. The reaction of these groups towards assimilation of Kurdish ethnic origin, and repression over religion, initially embodied itself in several uprisings and revolts in the Kurdish populated eastern areas of Turkey, and religiously sensitive cities, respectively. Thanks to the multi-party system, these groups have found a way in which they can express themselves through political parties, labour unions, associations and foundations so that they have become social movements forcing the Kemalism dominated state to meet their demands. As long as these demands are not met, the interaction between these two social movements and the official state ideology has been hostile. Within this process, the hostile approach to their common enemy reflected in each other’s activities and understandings as they see each other as a part of official state ideology. In the next phase in which their transformation from social movements to a legal political stream competed, the inherited ideological rigidity between pro-Kurdish and pro-Islamic political streams preserved itself. Overall, the research will indicate that since the mid-20th century, ideological barriers between pro-Kurdish and pro-Islamic streams have become the fundamental determinant of how they perceive each other.
402

Confluências idiomáticas: processos de transterritorialidade em Roda dos Trinos

Gonçalves, Celso Marques 20 October 2011 (has links)
O trabalho consiste na reflexão sobre a produção composicional estruturada em processos de hibridação, e a aplicação deste conceito à elaboração de uma peça para a formação instrumental de banda sinfônica, onde se promove a confluência entre gêneros e técnicas de linguagens distintas. Partindo sobre os princípios que emolduraram o conceito Third Stream de fusão entre o jazz com a música erudita, verificamos as possibilidades de ampliação dessa proposta agregando também elementos da música popular brasileira, e de acordo com os rumos tomados, conferimos alguns trabalhos que se assemelham ao dessa dissertação, no que concerne ao procedimento de hibridismo, mostrando fortes relações com as características da produção musical pós-moderna. / The work consists of the reflection about the compositional production structured on hybrid processes, and the use of this concept to the development of a piece for instrumental concert band, which promotes the confluence between genres and techniques of distinct languages. Starting with the principles that framed the Third Stream concept of the fusion between jazz and classical music, we verify the possibilities of the enlargement of this proposal aggregating elements of Brazilian music, and in accordance with the direction taken, we found some works that resemble the piece of this dissertation, in relation to hybrid procedures, showing strong relationships with the characteristics of post-modern musical production.
403

Um estudo investigativo de algoritmos de regressão para data streams

Nunes, André Luís 28 March 2017 (has links)
Submitted by JOSIANE SANTOS DE OLIVEIRA (josianeso) on 2017-06-13T14:22:04Z No. of bitstreams: 1 André Luís Nunes_.pdf: 2523682 bytes, checksum: 5e3899cfac6d76db6b2c6ac16b7f5325 (MD5) / Made available in DSpace on 2017-06-13T14:22:04Z (GMT). No. of bitstreams: 1 André Luís Nunes_.pdf: 2523682 bytes, checksum: 5e3899cfac6d76db6b2c6ac16b7f5325 (MD5) Previous issue date: 2017-03-28 / Nenhuma / A explosão no volume de dados e a sua velocidade de expansão tornam as tarefas de descoberta do conhecimento e a análise de dados desafiantes, ainda mais quando consideradas bases não-estacionárias. Embora a predição de valores futuros exerça papel fundamental em áreas como: o clima, problemas de roteamentos e economia, entre outros, a classificação ainda parece ser a tarefa mais explorada. Recentemente, alguns algoritmos voltados à regressão de valores foram lançados, como por exemplo: FIMT-DD, AMRules, IBLStreams e SFNRegressor, entretanto seus estudos investigativos exploraram mais aspectos de inovação e análise do erro de predição, do que explorar suas capacidades mediante critérios apontados como fundamentais para data stream, como tempo de execução e memória. Dessa forma, o objetivo deste trabalho é apresentar um estudo investigativo sobre estes algoritmos que tratam regressão, considerando ambientes dinâmicos, utilizando bases de dados massivas, além de explorar a capacidade de adaptação dos algoritmos com a presença de concept drift. Para isto três bases de dados foram analisadas e estendidas para explorar os principais critérios de avaliação adotados, sendo realizada uma ampla experimentação que produziu uma comparação dos resultados obtidos frente aos algoritmos escolhidos, possibilitando gerar indicativos do comportamento de cada um mediante os diferentes cenários a que foram expostos. Assim, como principais contribuições deste trabalho são destacadas: a avaliação de critérios fundamentais: memória, tempo de execução e poder de generalização, relacionados a regressão para data stream; produção de uma análise crítica dos algoritmos investigados; e a possibilidade de reprodução e extensão dos estudos realizados pela disponibilização das parametrizações empregadas / The explosion of data volume and its expansion speed make tasks of finding knowledge and analyzing data challenging, even more so when non-stationary bases are considered. Although the future values prediction plays a fundamental role in areas such as climate, routing problems and economics, among others, classification seems to be still the most exploited task. Recently, some value-regression algorithms have been launched, for example: FIMT-DD, AMRules, IBLStreams and SFNRegressor; however, their investigative studies have explored more aspects of innovation and analysis of error prediction than exploring their capabilities through criteria that are considered fundamental to data stream, such as elapsed time and memory. In this way, the objective of this work is to present an investigative study about these algorithms that treat regression considering dynamic environments, using massive databases, and also explore the algorithm's adaptability capacity with the presence of concept drift. In order to do this, three databases were analyzed and extended to explore the main evaluation criteria adopted. A wide experiment was carried out, which produced a comparison of the results obtained with the chosen algorithms, allowing to generate behavior indication of each one through the different scenarios to which were exposed. Thus, the main contributions of this work are: evaluation of fundamental criteria: memory, execution time and power of generalization, related to regression to data stream; production of a critical analysis of the algorithms investigated; and the possibility of reproducing and extending the studies carried out by making available the parametrizations applyed.
404

Classificação de rios e sua relação com a comunidade de macroinvertebrados em riachos

Vasconcelos, Márlon de Castro January 2012 (has links)
Nesta tese avaliei a relação entre a classificação de riachos em tipos de rios baseados nas suas características abióticas com a comunidade de macroinvertebrados. Especificamente, avaliei as seguintes questões: 1) Como as escalas de trecho de rio (local) e de bacia hidrográfica (regional) influenciam as comunidades? 2) As classificações de rios baseadas em variáveis abióticas são concordantes com aquelas baseadas em macroinvertebrados? 3) As respostas das comunidades de macroinvertebrados são similares quando diferentes abordagens de classificação são usadas? Por fim, 4) De que forma a resolução taxonômica e o tratamento dos dados influenciam as perguntas 2 e 3? Este estudo foi realizado em 38 riachos, numa área de 282 mil km2 no Rio Grande do Sul. As distâncias entre os riachos variaram entre 15 a 670 km. As variáveis físicas e químicas dos rios foram obtidas em trechos de 50 metros de extensão. A bacia hidrográfica de cada trecho foi delimitada e o uso da terra, tipo de solo e o relevo foram obtidos por meio de SIG. A tese traz uma “Apresentação geral” como Introdução. O capítulo 1 cobre a revisão da literatura e foi publicado na revista Ciência e Ambiente. O capítulo 2 apresenta a relação das variáveis ambientais e do espaço (distância geográfica) com a comunidade de macroinvertebrados. Como principal resultado, observou-se que o ambiente explica a maior parte da variação da distribuição na comunidade de macroinvertebrados, sendo que o efeito do ambiente é dependente da resolução taxonômica utilizada. No capítulo 3 avaliei a concordância entre classificações bióticas e abióticas. Avaliamos concomitantemente o efeito da resolução taxonômica, tipo de dado e da escala (trecho de rio x bacia hidrográfica). Tanto o tipo de dado quanto a resolução taxonômica influenciaram os resultados, sendo a classificação baseada nos dados no nível de família o único concordante com a classificação baseada em dados abióticos (duas escalas juntas). Outro importante resultado obtido foi a observação de que em uso de diferentes escalas, separadamente, verifica-se que a concordância se deu apenas para a escala de bacia hidrográfica, desde que para abundância no nível de gênero e presença/ausência no nível de família. No capítulo 4 verifiquei a relação da comunidade de macroinvertebrados com cinco sistemas de classificações de rios. As duas primeiras são baseadas em hidrorregiões, a terceira, em ecorregiões aquáticas da FEOW, a quarta deriva das ordens dos rios e a quinta é resultado do agrupamento de variáveis ambientais medidas localmente e regionalmente. Os resultados demonstram que a classificação baseada em variáveis ambientais se apresentou como o melhor sistema de classificação dos rios amostrados. Também avaliamos o tipo de dado e resolução taxonômica. Novamente a resolução taxonômica foi importante para os resultados obtidos e os dados de gênero obtiveram os melhores resultados. Por fim, na última parte da tese são apresentadas as considerações finais. / This thesis evaluated the relationships between stream classifications according to their abiotic characteristics and macroinvertebrate stream assemblages. Specifically, I asked the following questions: 1) How the macroinvertebrate communities are related with stream reach and catchment scales ? 2) Are the streams classifications with biotic and abiotic approach congruent? 3) Are there similar responses of macroinvertebrate assemblages when different classification approaches are used? 4) Can the taxonomic resolution and data type (abundance and presence/absence) to influence the results? This study was conducted in 38 streams, with distances among streams ranged from 15 to 670 km at an area of 282.000 km2 in Rio Grande do Sul state. The chemical and physical variables were obtained at a 50 m reach in each stream. The catchment was delimited and land use, soil coverage and relief were obtained using GIS tools. The thesis includes an “overview” as introduction. Chapter 1 covers the literature review and was published on Ciência e Ambiente. The Chapter 2 shows the relationship of environmental variables and space (distance among streams) with macroinvertebrate assemblages. The main result was that the environment accounted for most of the variation on the distribution of macroinvertebrate assemblages and this effect was dependent of the taxonomic resolution. In chapter 3 I evaluated the concordance between the abiotic and biotic classifications as well as the effect of the numerical and taxonomic resolution and the scale (stream reach x catchment). The results are dependent of the taxonomic resolution and dada type. The most important result was the effect of taxonomic resolution on the concordance between biotic and abiotic classifications. The classification based on macroinvertebrate family data was the only biotic classification concordant with the classification based on abiotic data. Another important result is that different scales, when used separately, only catchment classification was concordant with biotic one, and this result was dependent of both taxonomic and dada type. In chapter 4 we assessed the relationship of macroinvertebrate assemblages with five stream classifications. The first two is based on catchments grouped in hydrologic units, the third is based in freshwater ecoregions of FEOW, the fourth is based on stream orders and the fifth is result by cluster of environmental variables get on stream reach and catchment scales. That classification based on environmental variables had the higher scores than others classification by Classification Strength approach. The taxonomic and numeric resolutions were also evaluated. The taxonomic resolution was important to the results obtained, and genera data show the best scores. In the last part of the thesis are presented the conclusion remarks.
405

Adaptive degree of parallelism for the spar runtime

Vogel, Adriano Jos? 28 March 2018 (has links)
Submitted by PPG Ci?ncia da Computa??o (ppgcc@pucrs.br) on 2018-08-22T17:39:55Z No. of bitstreams: 1 ADRIANO_JOS?_VOGEL_DIS.pdf: 2344216 bytes, checksum: e0dd6229d4a98c039e793851290beab0 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-08-24T14:50:33Z (GMT) No. of bitstreams: 1 ADRIANO_JOS?_VOGEL_DIS.pdf: 2344216 bytes, checksum: e0dd6229d4a98c039e793851290beab0 (MD5) / Made available in DSpace on 2018-08-24T17:31:58Z (GMT). No. of bitstreams: 1 ADRIANO_JOS?_VOGEL_DIS.pdf: 2344216 bytes, checksum: e0dd6229d4a98c039e793851290beab0 (MD5) Previous issue date: 2018-03-28 / As aplica??es de stream se tornaram cargas de trabalho representativas nos sistemas computacionais. Diversos dom?nios de aplica??es representam stream, como v?deo, ?udio, processamento de gr?ficos e imagens. Uma parcela significativa dessas aplica??es demanda paralelismo para aumentar o desempenho. Por?m, programadores frequentemente enfrentam desafios entre produtividade de c?digo e desempenho devido ?s complexidades decorrentes do paralelismo. Buscando facilitar a paraleliza??o, a DSL SPar foi criada usando atributos (stage, input, output, and replicate) do C++-11 para representar paralelismo. O compilador reconhece os atributos da SPar e gera c?digo paralelo automaticamente. Um desafio relevante que ocorre em est?gios paralelos da SPar ? a demanda pela defini??o manual do grau de paralelismo, o que consome tempo e pode induzir a erros. O grau de paralelismo ? definido atrav?s do n?mero de r?plicas em est?gios paralelos. Por?m, a execu??o de diversas aplica??es pode ser pouco eficiente se executadas com um n?mero de r?plicas inadequado ou usando um n?mero est?tico que ignora a natureza din?mica de algumas aplica??es. Para resolver esse problema, ? introduzido o conceito de um n?mero de r?plicas transparente e adaptativo para a SPar. Al?m disso, os mecanismos implementados e as regras de transforma??o s?o descritos para possibilitar a gera??o de c?digo paralelo na SPar com um n?mero adaptativo de r?plicas. Os mecanismos adaptativos foram avaliados demonstrando a sua efic?cia. Ainda, aplica??es reais foram usadas para demonstrar que os mecanismos adaptativos propostos podem oferecer abstra??es de alto n?vel sem significativas perdas de desempenho. / In recent years, stream processing applications have become a traditional workload in computing systems. They are traditionally found in video, audio, graphic and image processing. Many of these applications demand parallelism to increase performance. However, programmers must often face the trade-off between coding productivity and performance that introducing parallelism creates. SPar Domain-Specific Language (DSL) was created to achieve the optimal balance for programmers, with the C++-11 attribute annotation mechanism to ensure that essential properties of stream parallelism could be represented (stage, input, output, and replicate). The compiler recognizes the SPar attributes and generates parallel code automatically. The need to manually define parallelism is one crucial challenge for increasing SPAR?s abstraction level, because it is time consuming and error prone. Also, executing several applications can fail to be efficient when running a non suitable number of replicas. This occurs when the defined number of replicas in a parallel region is not optimal or when a static number is used, which ignores the dynamic nature of stream processing applications. In order to solve this problem, we introduced the concept of the abstracted and adaptive number of replicas for SPar. Moreover, we described our implemented strategy as well as transformation rules that enable SPar to generate parallel code with the adaptive degree of parallelism support. We experimentally evaluated the implemented adaptive strategies regarding their effectiveness. Thus, we used real-world applications to demonstrate that our adaptive strategy implementations can provide higher abstraction levels without significant performance degradation.
406

Inundações e enxurradas, município de Esteio - RS

Brubacher, João Paulo January 2016 (has links)
As inundações se constituem como um dos principais desastres que acometem frequentemente diversas cidades no mundo. Embora sejam ocasionadas por meio da dinâmica natural dos cursos de água, as cidades que tiveram o seu desenvolvimento às margens de rios e arroios e apresentam como característica crescimento irregular, principalmente em áreas da planície de inundação, sofrem com os danos causados. O município de Esteio/RS é cortado por dois arroios, afluentes do rio dos Sinos, e são recorrentes os casos em que esses arroios causam inundações. Esse estudo tem como objetivo principal analisar as ocorrências de inundações no município de Esteio/RS, considerando o contexto da dinâmica local e as recentes obras viárias realizadas no município. Para tanto, o primeira etapa realizada foi a aquisição de dados de precipitação do período entre 1984 e 2015, assim como a aquisição de imagens LANDSAT. Posteriormente, foi realizada a organização das séries históricas de precipitação e o pré-processamento das imagens LANDSAT e matemática de bandas, visando a análise das inundações no município de Esteio por meio de índice de água por diferença normalizada modificada (MNDWI) e índice de diferença normalizada para lagos (NDPI); elaboração dos mapas de distribuição espacial das maiores inundações; a última etapa, contou com o estudo do contexto das obras viárias nas inundações do município. Entre os principais resultados, destaca-se a análise da série histórica de precipitação, por meio da qual é possível afirmar que a dinâmica das inundações e eventos extremos não é novidade no município, no entanto, os eventos referentes a agosto, outubro e novembro de 2013, além do evento de julho de 2015 foram, de fato, acima da média histórica. As áreas do município afetadas pelas inundações praticamente se repetem a cada evento extremos. A construção da BR 448 e da Avenida Brasil, coincidiu com o aumento das inundações no município, o que não se explica simplesmente pelo aumento da precipitação. A falta de mecanismos para evitar o efeito de remanso das águas dos arroios próximos a BR 448, bem como as alterações na várzea do rio dos Sinos, pode ter contribuído com os últimos eventos. Questionar a eficácia da Avenida Brasil enquanto dique de contenção de inundações, nesse momento, seria precipitado, principalmente se for levado em conta a necessidade das obras das bacias de contenção - a serem construídas. No entanto, medidas estruturais nem sempre são garantias de resolução desse tipo de desastre. / Floods constitute one of the main disasters that often affect several cities in the world. Although caused by natural dynamics of rivers, cities that had the development on the banks of rivers and streams and have a characteristic irregular growth, especially in areas of the floodplain, suffer the damage. The municipality of Esteio/RS is cut by two streams, tributaries of the Sinos river, and are recurring cases where these streams cause flooding. This study aims to analyze the occurrence of flooding in the city of Esteio/RS, considering the context of the local dynamics and the recent road works carried out in the municipality. Therefore, the first step was carried out the acquisition period of the precipitation data between 1984 and 2015, as well as the acquisition of LANDSAT images. It was subsequently set up the organization of the historical series of precipitation and pre-processing of Landsat and math bands images, aimed at analysis of floods in Esteio municipality through a modified normalized difference water index (MNDWI) and normal difference pound index (NDPI); preparation of spatial distribution maps of the largest floods; the last stage, had the study of the context of road works in the city's flooding. Among the main results, there is the analysis of time series of precipitation, by which it can be said that the dynamics of floods and extreme events is not new in the city, however, the events related to August, October and November 2013 beyond the July 2015 event were, in fact, above the historical average. The municipal areas affected by floods almost repeat every extreme event. The construction of the BR 448 and Brazil Avenue, coincided with increased flooding in the city, which cannot be explained simply by the increase in precipitation. The lack of mechanisms to prevent backwater effect of the waters of the streams near BR 448, as well as changes in the floodplain of the Sinos river, may have contributed to the latest events. Questioning the effectiveness of the avenue Brazil as dike containment flooding at this point would be premature, especially if one takes into account the need of the works of containment basins - to be built. However, structural measures are not guarantees of resolution this type of disaster.
407

Use of Semi-Analytical Solutions to Examine Parameter Sensitivity and the Role of Spatially Variable Stream Hydraulics in Transient Storage Modeling

Schmadel, Noah M. 01 May 2014 (has links)
Anticipating how stream water quality will respond to change, such as increased pollution or water diversions, requires knowledge of the main mechanisms controlling water and chemical constituent movement and a reasonable representation of those mechanisms. By deriving mathematical models to represent a stream system and collecting supporting field-based measurements, water quality response can be predicted. However, because each stream is unique and the movement of water and constituents is spatially and temporally complex, assessing whether the stream is appropriately represented and whether predictions are trustworthy is still a challenge within the scientific and management communities. Building on decades of stream research, this dissertation provides a step towards better representing some of the complexities found within streams and rivers to better predict water quality responses over long stream distances. First, a method is presented to assess which mechanisms are considered most important in chemical constituent predictions. Next, the number of measurements necessary to represent the general complexities of water, mass, and heat movement in streams was determined. The advancements developed in this dissertation provide a foundation to more efficiently and accurately inform water resource management.
408

Effects of stream restoration on macroinvertebrate communities in an Oregon Coast Range system

Christensen, M. Jo 09 February 1996 (has links)
Stream-restoration projects are usually designed to improve habitat quality for fishes. These projects manipulate flow patterns, substrate distribution, and amount and placement of large woody debris. Consequently, they also affect the size and composition of the aquatic macroinvertebrate community. This research evaluates two types of fish habitat restoration: off-channel structures (alcoves) and in-channel structures (log weirs). I compared macroinvertebrate habitats and communities in natural and artificial alcoves in Upper and South Fork Lobster Creeks, Lane Co., and examined the effects of log weirs on in-channel habitat diversity, community composition, drift patterns, and fish consumption of macroinvertebrates. Macroinvertebrate samples were collected from artificial and natural alcoves using hand pumps and D-nets. Within the channel, macroinvertebrates were collected from restored and unrestored reaches with a Hess sampler and using a stratified random sampling scheme. Forty-eight hour invertebrate drift samples were obtained at outlets of log-weir pools. Stomach contents were obtained from coho salmon (Oncorhynchus kisutch) and cutthroat trout (O. clarki) in restored reaches. Although natural alcoves differed from artificial in location within the floodplain, morphology, permanence, and degree of interaction with the stream channel, both alcovetypes provided similar habitats and contained similar macroinvertebrate communities. Average densities and diversity within the alcoves depended on habitat and time of year. Average densities were higher in artificial than in natural. Alcoves contained 29% of species richness within Upper Lobster Creek. Within the stream channel, the diversity of macroinvertebrate habitat was lower in restored than in unrestored sections. Log weirs were associated with reduced taxonomic and functional feeding-group diversity. Composition of drift was not significantly different in restored and unrestored areas; however, drift densities were significantly lower in restored reaches. Diets of fishes in restored areas were composed primarily of organisms produced from outside restored areas. Although in-channel structures may enhance physical habitat for fishes, they may alter or reduce the availability of food for fishes feeding on drifting invertebrates. Recommendations are given for improving the design of stream restoration projects with respect to macroinvertebrates; however stream restoration should focus on restoring whole-system integrity and function, instead of targeting just one or two types of organisms. / Graduation date: 1996
409

Visegrad Group Facing The Nord Stream And South Stream Gas Pipeline Projects

Senterzi, Zahide Tugba 01 August 2012 (has links) (PDF)
This thesis analyzes the Visegrad Group&rsquo / s stance toward the Russian-German Nord Stream and Russian-Italian South Stream gas pipeline projects, which aimed to circumvent the traditional energy routes situated in Central Europe and Eastern Europe. The level of the Visegrad Group&rsquo / s dependency on inherited Soviet gas pipeline routes is examined alongside the Visegrad Group&rsquo / s policy setting ability within the group itself and in the European Union. The thesis also traces the evolution of energy relations between Europe and Russia and Visegrad Group&rsquo / s adaptation to the new state of affairs after the collapse of the Soviet Union, particularly with respect to energy issues. It is argued that despite all differences, Visegrad Group members are able to set a cooperation platform at times of crisis and develop common energy strategies. However, the thesis shows that the Visegrad Group&rsquo / s endeavor has encountered some setbacks at the national level and serious challenges at the European level, largely owing to the lack of a common European energy policy. The thesis concludes that the Visegrad Group&rsquo / s energy policy is both dependent on the stances of Russia and larger EU actors.
410

Insect community composition and physico-chemical processes in summer-dry streams of Western Oregon

Dieterich, Martin 07 December 1992 (has links)
Seven streams, one of them permanent, were studied in western Oregon, USA. The research was designed to assess the value of summer-dry headwaters for conservation oriented landscape management. Streams were categorized primarily according to exposure (forest versus meadow sites) and secondarily according to flow duration (ephemeral = short-flow versus temporary = long-flow sites). Ephemeral streams have discontinuous flow and last less than three months annually. Temporary streams have continuous flow for more than five months each season. Ephemeral forest streams were highly efficient at filtering road-generated sediment. Uptake lengths for suspended sediment were short (36 m-105 m) at moderately elevated input concentrations. As a result of the filtration mechanism, filtration efficiency is expected to increase as annual flow duration decreases. Injection experiments yielded nitrate uptake rates of almost 1% per m of temporary stream channel. Exchange with subsurface flow was the most important route for nitrate removal from the water column. Biological uptake was insignificant in a light-limited forest stream, whereas a considerable amount of nitrate was retained by the biota a nutrient-limited meadow channel. At least 207 insect species were collected from the summer-dry streams. Species richness recorded from temporary forest streams exceeded that in an adjacent permanent headwater and there was high overlap between the fauna of the permanent and the temporary streams. Species richness in ephemeral channels was only 1/4 to 1/3 of that in long-flow forest streams. Multivariate analysis of community structure revealed flow duration and microhabitat pattern (riffle-pool) as the most important environmental factors determining faunal composition in temporary forest streams. Summer drought conditions at the sample sites also were important. By providing habitat and contributing to water quality in permanent downstream reaches, summer-dry streams have the potential to serve multiple purposes in conservation management. Their value from a conservation perspective is unexpectedly high. Landscape management therefore should be directed toward the preservation and protection of ephemeral and temporary streams. / Graduation date: 1993

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