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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.
391

Hodnocení fragmentace krajiny ve vztahu k dálkovým migracím / Assessment of landscape fragmentation in relation to long-distance migration

Šťovíčková, Kateřina January 2014 (has links)
This thesis deals with the fragmentation of the landscape as a result of highway infrastructure and human settlement. The aim is to analyze the current level of fragmentation and permeability of the landscape for large mammals in the region of Moravska Brana, which is a significant migration area between the West Carpathian and Hercynian sub-provinces. The results confirm the increased degree of fragmentation in this area due to the accumulation of several line barriers from the Northeast to the Southwest, and it particularly shows the negative impact of Highway D1. By comparing the degree of fragmentation with supra- regional corridors, this thesis evaluates the Territorial system of ecological stability (TSES) and the habitat model of large carnivores. This thesis shows that the current migration corridors provide only a fragmented landscape with unsuitable habitat. While making a comprehensive analysis of the permeability of the D1 motorway, the effectiveness of the migration corridor between Klimkovice and Dolni Ujezd was evaluated with an emphasis on monitoring the ecoduct of Suchdol nad Odrou, which is used primarily by medium-sized mammals. The results show that large mammals in this area have found the most appropriate migration corridor a long elevated road through the river valleys. Key...
392

Fragmentace krajiny ČR dopravními stavbami - vývoj, současný stav a priority územní ochrany / Landscape fragmentation by line barriers in the Czech Republic - development, state of the art and priorities of territorial protection

Zýka, Vladimír January 2014 (has links)
Landscape fragmentation by line barriers in the Czech Republic - development, state of the art and priorities of territorial protection Abstract This paper deals with the problem of landscape fragmentation by linear structures and changes in land cover printed in Europe and the Czech Republic. The development of the fragmentation geometry consisting of transport infrastructure and urban areas is described in detail in the years 1920-2020. In this time boundary the development of measure of landscape fragmentation in the Czech Republic is evaluated. This paper examines also the quality of the current unfragmented landscape. The degree of landscape fragmentation refills the value of ecological integrity (according to Burkhard et al., 2009). The results of gap analysis define the most valuable areas of the Czech countryside, which are not covered by existing special protection area (NP, CHKO, Natura 2000). The resulting areas are also compared to the territorial system of ecological stability and migration important area for the large mammals. Keywords landscape fragmentation - landscape connectivity - ecological integrity - gap analysis of landscape protection
393

Prostupnost krajiny v kontextu její fragmentace dopravní infrastrukturou a sub/urbánní výstavbou / Landscape permeability in context of it's fragmentation by traffic and suburbanization

Štambergová, Barbora January 2015 (has links)
Landscape permeability is currently significantly decreasing mainly due to anthropogenic barriers - transportation infrastructure and sub/urban development. The construction of these barriers has various environmental impacts on animals that differ among taxa. Ensuring a certain degree of permeability of the landscape is crucial for the survival of many species of organisms. Effective tools for the planning protection and restoration of the permeability of the landscape are series of models, whose theoretical framework and practical use are described in this thesis. The practical part deals with the modeling of changes in landscape permeability in the southern hinterlands of Prague. The effectiveness of the implemeted mitigation measures is also evaluated. Keywords: landscape fragmentation, landscape permeability, ecoducts, mitigation measures, suburbanization
394

Forest fragmentation in the Brazilian Amazon: evidence from land reform settlements along the Transamazon Highway and in Southern Pará

Wang, Chuyuan January 1900 (has links)
Master of Arts / Department of Geography / Marcellus M. Caldas / The democratization of Brazil in 1985 brought hope and impetus for agrarian reform, especially after the proposal of a series of new settlement projects by many Presidents to expropriate and redistribute lands to the Brazil’s landless. The landless poor, however, took this new state-sanctioned program into their own hands and started occupying lands to build land reform settlements. Social Movement Organizations (SMOs) that were established and working illegally gradually emerged and invaded large private landholdings near urban areas with a specific political agenda, while far rural landless people targeted unclaimed open public forest for land occupation to build spontaneous land reform settlements. Both types of land occupation actions constituted the Direct Action Land Reform (DALR). Recent literature has outlined the socio-economic circumstance that affected DALR, DALR settlement formation process and its implication to deforestation; however, no research considers forest fragmentation in these land reform settlements and its relationship with demographic factors. In order to fill this gap in the literature, this thesis first compared the temporal and spatial dynamics of deforestation fragment patterns in spontaneous DALR settlements around the municipality of Uruará along the Transamazon Highway, and in SMO-led DALR settlements in Southern Pará region using satellite imagery from 1986 to 2010 and three landscape metrics (patch mean area, area-weighted mean shape index and patch cohesion index). Metrics results were then respectively analyzed with selected field survey data to discover the impacts of demographic factors on forest fragmentation in DALR settlements. Results showed that SMO-led DALR settlements in Southern Pará primarily exhibited larger, more irregularly shaped and more physically connected deforestation fragments than spontaneous DALR settlements in the Uruará region over the whole study period. Demographic factors that influenced forest fragmentation in DALR settlements included the number of people and children per household, family lot size, percentage of families receiving credit and the distance between the family lot and the nearest city. At last, constructive policy recommendations were provided based on research findings.
395

Fragmentation in stream networks: quantification, consequences, and implications to decline of native fish fauna

Perkin, Joshuah Shantee January 1900 (has links)
Doctor of Philosophy / Department of Biology / Keith B. Gido / Habitat fragmentation and loss threaten global biodiversity, but organism responses to changing habitat availability are mediated by structural properties of their habitats. In particular, organisms inhabiting dendritic landscapes with hierarchically arranged branches of habitat tend to have limited access to some patches even in the absence of fragmentation. Consequently, organisms inhabiting dendritic landscapes such as streams respond strongly to fragmentation. Using a combination of meta-analysis, field observations, and ecological network modeling I show that stream fishes respond to fragmentation in predictable ways. First, I addressed how dams and stream dewatering have created a mosaic of large river fragments throughout the Great Plains. Using a geographic information system and literature accounts of population status (i.e., stable, declining, extirpated) for eight “pelagic-spawning” fishes, I found stream fragment length predicted population status (ANOVA, F2,21 = 30.14, P < 0.01) and explained 71% of reported extirpations. In a second study, I applied a new measure of habitat connectivity (the Dendritic Connectivity Index; DCI) to 12 stream networks in Kansas to test the DCI as a predictor of fish response to fragmentation by road crossings. Results indicated fish communities in stream segments isolated by road crossings had reduced species richness (alpha diversity) and greater dissimilarity (beta diversity) to segments that maintained connectivity with the network, and the DCI predicted patterns in community similarity among networks (n = 12; F1,10 = 19.05, r2 = 0.66, P < 0.01). Finally, I modeled fish distributions in theoretical riverscapes to test for mechanistic linkages between fragmentation and local extirpations. Results suggested the number of small fragments predicted declines in patch occupancy, and the magnitude of change in occupancy varied with dispersal ability (“high” dispersers responded more strongly than “low” dispersers). Taken together, these works show context-dependencies in fish responses to fragmentation, but a unifying theme is that small fragments contribute to attenuated biodiversity. Moreover, the predictable manner in which stream fish react to fragmentation will aid in biodiversity conservation by revealing potential responses to future scenarios regarding changes to habitat connectivity.
396

Definition of areas with high conservation priority in Southern Ecuador – An approach combining spatial and temporal patterns of deforestation and human impact with endemic plant diversity / Deforestation and forest fragmentation in South Ecuador since the 1970s – losing a hotspot of biodiversity / Spatio-temporal analysis of the human footprint in South Ecuador: influence of human pressure on ecosystems and effectiveness of protected areas / Is alpha diversity enough to prioritize areas for conservation in Tropical regions? – A case study in Continental Ecuador / Synthesis

Tapia Armijos, María Fernanda 29 October 2015 (has links)
Los bosques del Sur del Ecuador tienen un alto valor para la conservación puesto que están muy amenazados pero también poseen altos niveles de biodiversidad y endemismo. Sin embargo, como el proceso de conservación es inherentemente espacial, la baja disponibilidad de información espacial acerca de los factores que promueven la vulnerabilidad de estos bosques y acerca de la distribución espacial de los objetivos de conservación ha provocado varios obstáculos para la conservación de los mismos. El objetivo principal de esta tesis fue generar información espacial acerca de las amenazas y los valores biológicos que ocurren en esta región para priorizar áreas de conservación. El segundo capítulo analizó los patrones de deforestación y fragmentación en la región desde 1976 usando fotografías aéreas e imágenes satelitales para identificar las áreas de bosque remanente, los frentes de deforestación, las tasas anuales de deforestación y las dinámicas de la composición y configuración del paisaje del Sur del Ecuador. Se registraron tasas anuales de deforestación de 0.75% (1976 – 1989) y 2.86% para dos periodos consecutivos. Se encontró también que el Sur del Ecuador está bajo un creciente proceso de fragmentación debido al incremento en el número de parches, el decremento en el tamaño promedio de los parches y el incremento en el aislamiento de los parches. Este estudió también contribuyó al mejor entendimiento de las dinámicas de cambio de los bosques tropicales. Se registró que la mayor superficie de bosque natural fue degradado o convertido a pastizales y que los principales frentes de deforestación están localizados en las zonas de bajas altitudes en los bosques siempreverdes premontanos. El tercer capítulo describe los patrones espaciales y temporales de la presión humana, debido a que este es uno de los principales factores que influencian la efectividad de las estrategias de conservación. Para esto se adaptó el Índice de Impacto Humano (HF) generado por Sanderson et al. (2002) y así evaluar los cambios espaciales en el HF durante 26 años a nivel de paisaje y de ecosistema. Esta información permitió identificar algunos “hotspots de cambio” y las áreas con menor influencia para de esta forma evaluar como los diferentes factores humanos contribuyen al HF y demostrar cuan efectiva ha sido el área protegida más importante de la región para reducir la presión humana al interior y exterior de sus límites. Los resultados muestran un notable incremento en los niveles de presión humana en el Sur del Ecuador y un decremento en el número de áreas sin influencia. Se identificó también que uno de los más importantes “hotspots de cambio” está localizado en la región occidental del área de estudio y en la cuenca baja del Río Zamora. Los tipos de vegetación con mayor influencia humana fueron los bosques secos estacionales y los matorrales en donde la densidad de la población fue el principal factor humano que contribuyó a los niveles de presión humana observados. Finalmente, se encontró que el Parque Nacional Podocarpus ha sido parcialmente efectivo para reducir la presión humana en su interior y exterior, puesto que los niveles de HF se incrementaron al interior del área protegida y en el área buffer pero fueron menores a los observados en las áreas circundantes. El cuarto capítulo analizó los patrones de diversidad alfa y beta de plantas endémicas para evaluar la congruencia entre ambos patrones e identificar áreas con prioridad para ser conservadas. Se encontró que el “hotspot” de diversidad alfa para las plantas endémicas está localizado en los Andes y que es poco congruente con las zonas que muestran los más altos niveles de diversidad beta, los cuales están concentrados mayormente en las estribaciones orientales y occidentales de los Andes y en las cordilleras costeras y amazónicas. También se encontró que aproximadamente 40% de la superficie con altos niveles de diversidad alfa y beta ha desaparecido debido a la deforestación y que solo el 30% remanente está bajo alguna categoría de conservación. De esta forma se proponen 12 áreas potenciales con alta prioridad para la conservación, las cuales mayormente esta localizadas en el Sur del Ecuador, para de esta forma mejorar la representatividad y complementariedad de la actual red de reservas. Finalmente, el quinto capítulo analiza los principales hallazgos de esta investigación remarcando las implicaciones para la conservación y sugiriendo áreas potenciales para ser conservadas con base a los niveles de presión humana, vegetación remanente y patrones de diversidad alfa y beta de plantas endémicas en la región Sur del Ecuador.
397

Application of Numerical Methods to Study Arrangement and Fracture of Lithium-Ion Microstructure

Stershic, Andrew Joseph January 2016 (has links)
<p>The focus of this work is to develop and employ numerical methods that provide characterization of granular microstructures, dynamic fragmentation of brittle materials, and dynamic fracture of three-dimensional bodies.</p><p>We first propose the fabric tensor formalism to describe the structure and evolution of lithium-ion electrode microstructure during the calendaring process. Fabric tensors are directional measures of particulate assemblies based on inter-particle connectivity, relating to the structural and transport properties of the electrode. Applying this technique to X-ray computed tomography of cathode microstructure, we show that fabric tensors capture the evolution of the inter-particle contact distribution and are therefore good measures for the internal state of and electronic transport within the electrode. </p><p>We then shift focus to the development and analysis of fracture models within finite element simulations. A difficult problem to characterize in the realm of fracture modeling is that of fragmentation, wherein brittle materials subjected to a uniform tensile loading break apart into a large number of smaller pieces. We explore the effect of numerical precision in the results of dynamic fragmentation simulations using the cohesive element approach on a one-dimensional domain. By introducing random and non-random field variations, we discern that round-off error plays a significant role in establishing a mesh-convergent solution for uniform fragmentation problems. Further, by using differing magnitudes of randomized material properties and mesh discretizations, we find that employing randomness can improve convergence behavior and provide a computational savings.</p><p>The Thick Level-Set model is implemented to describe brittle media undergoing dynamic fragmentation as an alternative to the cohesive element approach. This non-local damage model features a level-set function that defines the extent and severity of degradation and uses a length scale to limit the damage gradient. In terms of energy dissipated by fracture and mean fragment size, we find that the proposed model reproduces the rate-dependent observations of analytical approaches, cohesive element simulations, and experimental studies.</p><p>Lastly, the Thick Level-Set model is implemented in three dimensions to describe the dynamic failure of brittle media, such as the active material particles in the battery cathode during manufacturing. The proposed model matches expected behavior from physical experiments, analytical approaches, and numerical models, and mesh convergence is established. We find that the use of an asymmetrical damage model to represent tensile damage is important to producing the expected results for brittle fracture problems.</p><p>The impact of this work is that designers of lithium-ion battery components can employ the numerical methods presented herein to analyze the evolving electrode microstructure during manufacturing, operational, and extraordinary loadings. This allows for enhanced designs and manufacturing methods that advance the state of battery technology. Further, these numerical tools have applicability in a broad range of fields, from geotechnical analysis to ice-sheet modeling to armor design to hydraulic fracturing.</p> / Dissertation
398

Improvement of blast-induced fragmentation and crusher efficiency by means of optimized drilling and blasting in Aitik

H. Beyglou, Ali January 2012 (has links)
Rock blasting is one of the most dominating operations in open pit mining efficiency. As many downstream processes depend on the blast-induced fragmentation, an optimized blasting strategy can influence the total revenue of a mine to a large extent.Boliden Aitik mine in northern Sweden is one of the largest copper mines in Europe. The annual production of the mine is expected to reach 36 million tonnes of ore in 2014; so continuous efforts are being made to boost the production. Highly automated equipment and new processing plant, in addition to new crushers, have sufficient capacity to reach the production goals; the current obstacle in the process of production increase is a bottleneck in crushers caused by oversize boulders. Boulders require extra efforts for secondary blasting or hammer breakage and if entered the crushers, they cause downtimes. Therefore a more evenly distributed fragmentation with less oversize material can be advantageous. Furthermore, a better fragmentation can cause a reduction in energy costs by demanding less amounts of crushing energy.In order to achieve a more favorable fragmentation, two alternative blast designs in addition to a reference design were tested and the results were evaluated and compared to the current design in Aitik. A comparatively large bench was divided to three sections with three different drill plans, which led to different specific charges in each section. The sections were drilled in patterns of 6x9 m, 7x9 m and 7x10 m of burden and spacing; planned specific charges of the sections were 1.17 kg/m3, 1.02 kg/m3, and 0.91 kg/m3 respectively. Similar to the current drill plan in Aitik, the section with 7x9 m (1.02 kg/m3 specific charge) was used as the reference for results comparison. The drilling and charging processes were monitored carefully and the post-blast parameters were measured accordingly. Laser scanning was used to measure the swelling of the sections and two different methods of image analysis were utilized to evaluate the fragmentation of the rock for each section. Drilling log data (MWD) were analyzed to evaluate the hardness of the rock; energy consumption log of the crusher was also analyzed and all the data was collected in a single database. VBA (Visual Basic for Applications) programming language was embedded within data spreadsheets to correlate the mentioned data to the coordinates of the rock by means of Minestar logs, which include both timestamps and coordinates of all machinery e.g. shovels and trucks.The results of the test show significant improvements in fragmentation and oversize material percentage in the section with 6x9 m drill plan (1.17 kg/m3). The advantage of 6x9 m plan was confirmed by 52% higher swelling, 66% lower oversize material and 26% lower crushing energy compared to the reference section. The section with 7x10 m drill plan (0.91 kg/m3) also showed theoretically acceptable results; however, the deviations from reference were not as large as formerly mentioned section. The swelling had a decrease of 8% compared to the reference section and the percentage of oversize material and crushing energy were increased by 16% and 2% respectively.Presented results are based only on technical aspects and do not include the costs of drilling and charging. Thus, in order to evaluate the drill plans in practice an economical evaluation of the sections should be conducted. Also a confirmation test with more accurate geology explorations is recommended.Finally, upon the request of Boliden Mines, a short report on the usage of Air-decking technique in Aitik is enclosed as an appendix. The report includes a brief introduction to air-decking and discusses practical solutions to apply this technique in Aitik. / Validerat; 20121001 (anonymous)
399

Jornalismo em retração, poder em expansão: como o encolhimento das redações e o uso crescente de redes sociais por governantes podem degradar o ambiente informativo e prejudicar a democracia / Journalism in retraction, power in expansion: how shrinking newsrooms and the growing use of social networks by governments can degrade the information environment and undermine democracy

Gandour, Ricardo 25 June 2019 (has links)
O presente trabalho apresenta um mapeamento quantitativo inédito de como as redações dos jornais brasileiros diminuíram em número de jornalistas e em estrutura, na última década, em consequência da crise do modelo de negócio causada pela queda do faturamento publicitário e das transformações impostas pelos novos meios digitais. Emoldurado por revisão bibliográfica acerca de fundamentos teóricos do jornalismo, da evolução das mídias, das características da transmissão da informação e da fragmentação causada pelas forças disruptivas das tecnologias digitais, o estudo sistematiza, sumariza e analisa esse encolhimento e seus efeitos nos processos de produção da cadeia jornalística. Realizada em nível nacional, com representatividade de 80% da circulação dos jornais, a pesquisa de campo detalha a diminuição do volume de páginas impressas editadas e da produção própria de conteúdo -fenômeno que se verificou em todos os ambientes pesquisados, qualquer que seja o meio de veiculação. O presente trabalho analisa também qual foi a estratégia de conteúdo dos jornais ao atravessarem essa transição. Este estudo ainda compara, em períodos simultâneos, o volume de atividade digital de jornais com a atividade dos governadores numa rede social selecionada, o Facebook. O resultado da comparação complementa a pesquisa e mostra, de forma quantitativa e pela primeira vez, o risco potencial de que, exposta a discursos \"oficiais\" diretamente disseminados por mandatários do Poder Executivo, a sociedade perca as referências habituais geradas pelo jornalismo profissional. Assim, a presente dissertação lança um alerta: a disseminação do uso das redes sociais por parte de governantes combinada com o recuo da presença dos jornais pode indicar um risco para a qualidade informativa do debate público na democracia contemporânea. / This study presents an unprecedented quantitative mapping of how newsrooms in Brazil have diminished in number of journalists and in structure in the last decade as a consequence of the crisis of the business model caused by the fall in advertising revenues and the transformations imposed by the new digital media. Framed by a bibliographical review about the theoretical foundations of journalism, the evolution of the media, the characteristics of information transmission and the fragmentation caused by the disruptive forces of digital technologies, this study systematizes, summarizes and analyzes that shrinkage and its effects on the production processes of the journalistic chain. Held at the national level, with 80% representation of newspaper circulation, the field research details the decrease in the volume of edited printed pages and the production of original content --a phenomenon that occurred in all the environments surveyed, regardless of the medium. The present paper also analyzes the content strategy of newspapers when crossing the transition. This study also compares, in simultaneous periods, the volume of digital newspaper activity with the activity of the governors in a selected social network, Facebook. The result of the comparison complements the research and shows, in a quantitative way and for the first time, the potential risk that, when exposed to \"official\" discourses directly disseminated by representatives of the government, society loses the usual references generated by professional journalism. Thus, the present dissertation warns that the dissemination of the use of social networks by governments combined with the retreat of the presence of newspapers may indicate a risk for the informative quality of the public debate in contemporary democracy.
400

Video quality encoding characterization and comparison / Kvalificering och jämförelse av videokvaliteter

Andersson, Julia, Hultqvist, Andreas January 2019 (has links)
Adaptive streaming is a popular technique that allows quality adaption for videos based on the current playback conditions. The purpose of this thesis is to investigate how chunks in video files downloaded from YouTube correlate to each other. We investigate how the chunk size characteristics depend on the category and encoding of the video. The main focus is to analyze the chunk sizes of the video, focusing on distinctness between 360$^\circ$ and 2D videos. This is performed using the YouTube API. The videos are downloaded and analysed using youtube-dl and mkv-info. The results show that chunk sizes for adjacent qualities have higher correlation and that videos having a similarity between scenes have higher correlation. In addition, 360$^\circ$ videos differ primarily from regular 2D videos by the amount of qualities used and a generally higher correlation for all qualities.

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