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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.
21

Determining the best location for a nature-like fishway in Gavle River, Sweden

Buck, Sine January 2013 (has links)
The construction of dams and hydro-power stations are some of the most common anthropogenic changes of watercourses and rivers. While being important to humans and society by providing electricity, these obstructions of watercourses can have severe consequences for the aquatic ecosystems. One consequence is that dams often hinder the important movement of migrating fish species between habitats. This can lead to decline and even extinction of important fish populations. To prevent these negative effects, a number of different fish passage systems, including nature-like fishways, have been developed. Nature-like fishways mimic natural streams in order to function as a natural corridor for a wide range of species. Planning and construction of a nature-like fishway is a complex task that often involves many different interests. In the present study a combination of multi-criteria decision analysis and least-cost path analysis is used for determining the best location for a nature-like fishway past Strömdalen dam in Gavleån, Sweden. An anisotropic least-cost path algorithm is applied on a friction-layer and a digital elevation model, and the least-cost path for a nature-like fishway is determined. The results show that the method is useful in areas of varying topography and steep slopes. However, because low slope is a very important factor when constructing a nature-like fishway, slope becomes the dominating factor in this analysis at the expense of e.g. distance to roads. Combining the methods with results from biological studies of fish behavior and detailed hydrological modelling would provide a very strong tool for the planning of nature-like fishways.
22

Connecting the dots : Network analysis, landscape ecology, and practical application

Zetterberg, Andreas January 2011 (has links)
Humans have a profound impact on ecosystems, and land-use change constitutes a primary driving force in the loss of biodiversity. Habitat loss and fragmentation are key factors in this process by seriously impeding the habitat availability and movement of species, leading to a significant decrease in population viability. Landscape connectivity management able of crossing administrative and ecological spatial and temporal scales has been identified as one of the most important measures to counteract these negative impacts. The use of graph-theory and network-based landscape-ecological tools has become established as a promising way forward to address these issues. Despite urgent needs to adapt and implement such tools in planning, assessment and decision-making, surprisingly little attention has been paid to developing approaches for their effective practical application. This thesis presents the development of a toolbox with network-based, landscape-ecological methods and graph-theoretic indicators, which can be effectively implemented by practitioners within environmental assessment, physical planning and design, to analyze landscape connectivity. Recent advances in network analysis and landscape ecology are brought together and adapted for practical application, bridging the gap between science and practice. The use of participatory approaches was identified as key to successful development, and several workshops, meetings, interviews, as well as prototype testing of the developed software were conducted throughout the study. Input data and selection of species were based on the experience gained through seven real-world cases, commissioned by different governmental organizations within Stockholm County. The practitioners’ perspectives on effective practical application of the proposed toolbox were then assessed through an interview-study. The respondents anticipated improved communication with other actors in addition to being able to better assess critical ecological structures within the landscape. The toolbox was finally tested in a large-scale network analysis of impacts of the regional development plan (RUFS 2010), leading to important insights on the planning of connectivity in an urbanizing region. / <p>QC 20111125</p>
23

Optimization Of Water Distribution Networks Using Genetic Algorithm

Guc, Gercek 01 April 2006 (has links) (PDF)
This study gives a description about the development of a computer model, RealPipe, which relates genetic algorithm (GA) to the well known problem of least-cost design of water distribution network. GA methodology is an evolutionary process, basically imitating evolution process of nature. GA is essentially an efficient search method basically for nonlinear optimization cases. The genetic operations take place within the population of chromosomes. By means of various operators, the genetic knowledge in chromosomes change continuously and the success of the population progressively increases as a result of these operations. GA optimization is also well suited for optimization of water distribution systems, especially large and complex systems. The primary objective of this study is optimization of a water distribution network by GA. GA operations are realized on a special program developed by the author called RealPipe. RealPipe optimizes given water network distribution systems by considering capital cost of pipes only. Five operators are involved in the program algorithm. These operators are generation, selection, elitism, crossover and mutation. Optimum population size is found to be between 30-70 depending on the size of the network (i.e. pipe number) and number of commercially available pipe size. Elitism rate should be around 10 percent. Mutation rate should be selected around 1-5 percent depending again on the size of the network. Multipoint crossover and higher rates are advisable. Also pressure penalty parameters are found to be much important than velocity parameters. Below pressure penalty parameter is the most important one and should be roughly 100 times higher than the other. Two known networks of the literature are examined using RealPipe and expected results are achieved. N8.3 network which is located in the northern side of Ankara is the case study. Total cost achieved by RealPipe is 16.74 percent lower than the cost of the existing network / it should be noted that the solution provided by RealPipe is hydraulically improved.
24

Hill-Fort Sites and Tumuli in the Shkodra Plain Region of Northern Albania: A Geospatial Perspective

Lambert, Dora Jane 09 December 2016 (has links)
The objective of this research was to determine the environmental and social factors that led to the shift of settlement patterning from agro-pastoral in the late Neolithic to hillort sites at the turn of the Early Bronze Age and why burial mounds (tumuli) were erected further than anticipated from corresponding hillort sites in the Shkodra Plain region in Northern Albania. Geospatial techniques were used to examine 168 tumuli and seven hillort sites. These were mapped to examine visibility, viewshed, slope, and potential prehistoric networks. Based on the landscape visibility GIS results, it was found that hillort sites and tumuli were part of an social landscape that thrived on trade. It was determinable that the shift of the social landscape was related to Northern trade routes and probable changes in paleo-lake levels. This new evidence provides insight to Albanian prehistoric culture and has implications to related studies in the Balkans.
25

Empirical evidence of utility sponsored conservation programs

Shay, Colin Gerald 23 December 2009 (has links)
Utility sponsored conservation programs encourage participants to consume less energy. One of the most popular methods used to achieve this is to offer monetary rebates to purchasers of high-efficiency appliances. The costs of these conservation programs are then passed-on to all customers as increased energy prices. Economic theory predicts that the income and substitution affects should decrease the consumption of non-participants in the programs and may increase the consumption of participants. Recent claims in the literature argue that the standard net benefit tests used to evaluate these programs fail to incorporate the full impact of the income and substitution affects. Relying on these theoretical arguments, new evaluation techniques, referred to as Net Economic Benefits (NEB) tests, are being introduced as solutions to this problem. Using the actual experience of a natural gas utility, this thesis analyzed the need for NEB evaluations. The results show that the price of gas is not a significant factor in determining household gas consumption. Therefore, empirical evidence cannot support the NEB claims. The evidence does show that, on an average annual basis, participants are consuming less than non-participants. / Master of Arts
26

Un cadre de mise en oeuvre du routage mulitcritères de services IP multimédia

MUSHTAQ, Sajjad Ali 16 January 2012 (has links) (PDF)
A dynamic decision making framework implementing multi criteria routing of multimedia services at private-public network border with access technology convergence is presented. The ingredients of the framework include information model, semantics capturing via ontology, information sharing and dissemination mechanisms and rule/policy specifications methodology. The control and management over the infrastructure is carried out by revamping the sole signaling protocols (SIP, diameter and SNMP). DEN-ng is enhanced and tagged in accordance with the requirements over the underlying framework. A dedicated language for the platform is proposed that has its deep roots inside the framework to avoid conflicts and overlapping. A dynamic decision engine is developed for routing the requests/sessions at private-public network border over the underlying multi-homed environment. Multi Criteria Decision Making (MCDM) theory is used for decision computation/calculation and the adapted methods are exploited according to the scenario and decision computation mode while keeping in view the corresponding enforcement mode. A test bed is developed to validate the proposed framework. The proposed system offers higher throughput and lowers call-dropping probability with an add-on susceptible delay.
27

The ecology of dispersal in lions (Panthera leo)

Elliot, Nicholas Bryant January 2014 (has links)
As ecosystems become increasingly fragmented, there has been a proliferation of research into fields such as resource use, movement ecology and habitat connectivity. To understand how species may adapt to threats associated with habitat fragmentation it is necessary to study these processes in dispersing individuals. However, this is seldom done. Dispersal is one of the most important life-history traits involved in species persistence and evolution, but the consequences of dispersal are determined primarily by those that survive to reproduce. Although dispersal is most effectively studied as a three-stage process (departure, transience and settlement), empirical studies rarely do so and an investigation into the entire process has probably never been carried out on any one species. Here I investigate the survival, resource use, movement ecology and connectivity of African lions (Panthera leo) in all three dispersal phases in addition to adulthood. I make use of a longterm dataset incorporating radio-telemetry and observational data from lions in Hwange National Park, Zimbabwe. Dispersal is inherently risky and my results show that male lions that disperse while young suffer high mortality, young dispersal being brought about by high off-take of territorial males. Dispersing males may be aware of risks associated with territorial adults as they position themselves far from them and utilise habitats and resources differently. However, dispersers, compared to adult males and females, are far less averse of risky, anthropogenic landscapes, suggesting they are the demographic most prone to human-lion conflict. The ontogenetic movement behaviour of lions reflects a transition from directional movement during transience, suggestive of sequential search strategies, to random or periodic use of a fixed territory after settlement. In terms of habitat connectivity, I show that radically different conclusions emerge depending on which demographic is used to parameterise connectivity models. Understanding the shifting mechanisms that species adopt throughout ontogeny is critical to their conservation in an increasingly fragmented world.
28

Villages and valleys: connectivity and land use in Northern Messenia during Middle and Late Helladic periods. / Byar och dalgångar : Interaktion och markanvändning i norra Messenien under den mellan- och senhelladiska perioden.

Tsoumari, Vasiliki January 2019 (has links)
The use of past archaeological survey data for examination of landscape dynamics became very popular during the last decades of the 20th century, when Geographical Information Systems analysis were introduced in archaeology. In the present thesis, past survey data from Northern Messenia’s Middle and Late Helladic periods are combined to the topography and the environment of the region. These data are examined under the GIS prism, which attempts to update our knowledge on this geographical area.             The main scope of this thesis is to examine potential settlement patterns and land use, connectivity between sites and sites’ hierarchies. In the first query, the Kernel Density analysis has been used for estimating settlements’ patterns, and to consequently estimate preference of specific topographical features for land use, such as slope. Based on the patterns formed as a result of the analysis conducted in the first query, connectivity and hierarchy between sites is being tested with the use of cost connectivity and visibility tools.             The outcome of this analysis shows that the inhabitants of the past were significantly interacting with the landscape, since they preferred to nest around the protective slopes of the Soulima and the Kyparissian valleys. The area around their settlements reveals that these inhabitants opted to cultivate in flat or marginal land, while visibility from the sites seems to be an important factor for monitoring the region. However, it has been proved that a good number of collaborating sites were required to supervise the entire territory, which disproves any hierarchical ranking between them. On the other hand, connectivity depicts potential movement over Northern Messenia’s terrain and indicates that a few sites in the heart of the study area were to be considered as panoptic meeting grounds of the eastern and the western side. In conclusion, the overall analysis reveals a potential spatial bond between sites rather than a relationship based on rivalry.
29

Validation de la fonctionnalité des continuités écologiques en milieu urbain : approches plurispécifiques et multi-sites / Validation of the green infrastructure functionnality in urban landscape : multi-species and multi-sites approaches

Balbi, Manon 30 November 2017 (has links)
Le maintien de la connectivité à travers les paysages urbains, par nature très fragmentés, est un enjeu majeur de conservation de la biodiversité urbaine. On observe une prise en compte croissante de la connectivité dans les politiques d’aménagement du territoire, notamment avec l’établissement de la trame verte et bleue. De multiples outils cartographiques permettent de mettre en évidence les continuités écologiques (zones de forte connectivité), mais leur validation fonctionnelle fait souvent défaut. L’objectif de cette thèse est de valider les prédictions d’un modèle de chemin de moindre coût, sur plusieurs villes et avec différents modèles biologiques. Les espèces étudiées présentent différents modes et capacités de dispersion (vol, marche, reptation) et des exigences écologiques spécifiques (préférences pour les milieux herbacés ou boisés). Des protocoles de validation basés sur l’écologie du mouvement et la génétique du paysage sont appliqués, dans un souci de réplication (au sein de plusieurs villes) et de contrôle de la variabilité inter-individuelle. Nos résultats montrent des mouvements accrus au sein des continuités écologiques comparés à ceux observés en contextes paysagers prédits comme non connectés : les hérissons transloqués s’y déplacent sur des distances plus longues, plusieurs passereaux répondent à la repasse de chant sur de plus longues distances et les papillons de nuit montrent des taux de recapture beaucoup plus élevés. Par ailleurs, les analyses indirectes réalisées sur l’escargot petit-gris montrent une relation assez faible entre la différenciation génétique des populations et les modèles de connectivité. Ce travail fournit des arguments scientifiques pour soutenir la mise en place de continuités écologiques en milieu urbain. / Maintaining connectivity across urban landscape, intrinsically fragmented, is a major issue of urban biodiversity conservation. Connectivity is increasingly taken into account by policy and stakeholders, especially through the establishment of the blue-green infrastructure. Multiple mapping tools allow to detect ecological networks (highly connected areas), however their functionnal validation is often lacking. The objective of this study is to validate least cost path analysis predictions in several cities with different biological models. Studied species vary in terms of dispersal means and capacities (flight, walk, crawling) and habitat requirement (e.g. herbaceous or forested habitats). Several protocols based on movement ecology and landscape genetic are applied, focusing on replication (within and among cities) and control of inter-individual variability. Our results indicate that movement is increased in predicted ecological networks when compared with areas predicted as poorly connected: the translocated hedgehogs travelled longer distances, several passerine responded to song playback over longer distances, and moths showed increased recapture rates. Indirect analysis on the garden snail showed a weak relation between population genetic differentiation and connectivity models. This work provides scientific support for the establishment of ecological networks in urban landscapes.
30

First peopling of the Americas : modelling the palaeo-landscape and potential Upper Palaeolithic human migration routes

Igrejas Lopes Martins Costa, Catharina 05 1900 (has links)
Le peuplement des Amériques fut le dernier grand événement migratoire de Homo sapiens et nous méconnaissons toujours les détails à son sujet. Des débats surgissent concernant l’environnement, les populations concernées, ainsi que les cultures impliquées. Malheureusement, des biais scientifiques persistent quant à la chronologie de cet événement et il peut donc être difficile de proposer quelque chose de nouveau. Avec ArcMap 10.7.1, nous présentons de nouveaux modèles de migrations terrestres basés sur les sentiers de moindre effort, retraçant les routes potentielles que les humains ont pu utiliser afin d’arriver en Amérique au cours du Pléistocène; nous surlignons les facteurs environnementaux, génétiques et archéologiques spécifiques qui doivent être considérés pour les modèles futurs, et nous présentons deux trajets de migration qui auraient pu avoir été utilisé pendant le Paléolithique Supérieur, élucidant par conséquent comment les humains sont arrivés pour la première fois dans le continent américain. / The peopling of the Americas was the last great dispersal event of our species, Homo sapiens, and there is still so much we do not know about it. Debates arise concerning the environment, the populations involved, as well as the cultural or physical markers they might have left behind. Unfortunately, the debate concerning the First Peopling of North America is marked by scientific biases and it can thus be difficult to propose something new. Through ArcMap 10.7.1, we present a Least Cost model of terrestrial migrations from Asia to America, we highlight the specific environmental, genetic and archaeological factors that need to be considered in future models, and present two migration paths that could have been used during the Late Pleistocene, thus shedding light onto how humans first arrived in the American continent.

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