This thesis deals with logistics of the satellite-based Global Positioning System (GPS) surveys. Heuristic techniques, within the field of Operational Research (OR), for hard Combinatorial Optimization Problems (COPs), have been applied to the design of GPS surveying networks. The aim of a COP is to search and determine the most suitable solution for optimizing (minimizing or maximizing) an objective function (cost, accuracy time, distance etc) over a discrete set of feasible solutions. The designing of a GPS network as a COP consists of set of feasible schedules and the goal is to determine the cheapest schedule. When related to GPS, a network can be defined as a set of stations which are co-ordinated by placing receivers on them to determine sessions between them. A session can be defined as a period of time during which two or more receivers are simultaneously recording satellite signals. The required minimum number of receivers is two, and the problem of network designing becomes crucial as this number increases. The problem addressed is to search for the best order in which these sessions can be organised to give the best schedule (minimal cost) to complete all sessions. In practice this means determining how each GPS receiver should be moved between the stations to be surveyed in an efficient manner taking into consideration some important factors such as time, cost etc. Exact methods can solve only small networks and are not practical as the size of the network increases. Hence, it is important to have approximate techniques (heuristic techniques) which can provide an optimal or near-optimal schedule for large networks in a reasonable amount of computational time. In this thesis, new techniques of research based on effective computer based heuristic optimization techniques for the above mentioned problem have been researched, designed, developed, implemented and analysed theoretically and empirically. These heuristics, which are based on ideas from Artificial Intelligence (AI), are the most recent and powerful development techniques applicable to a wide range of important problems which occur in a variety of disciplines, such as, statistics, engineering, mathematical programming and operational research. A heuristic technique starts with an initial starting solution (within this context, an initial schedule). It iteratively attempts to improve upon the current schedule by a series of local improving changes (swapping sessions) generated by a suitably defined mechanism until a stopping criterion is met. The heuristics that have been implemented in this research are Local Descent Search(LDS), Simulated Annealing (SA) and Tabu Search (TS). The LDS method accepts only a schedule that generates a reduction in the objective function value. On the other hand, both SA and TS techniques combine different operational and organizational strategies based on robustness and computer models in order to obtain high-quality schedules. Computational results for several case studies are presented for these techniques. Within the GPS surveying and OR literature, this is the first attempt of its kind to have been carried out. The main contribution of this thesis is the development of the above heuristics for solving the GPS network logistics design problem. Their performance was investigated, evaluated and compared with networks with known optimal schedule with respect to schedule quality and the computational effort. The new concept of a sessions-interchange mechanism was developed and implemented. To assist in the evaluation, tests were carried out using two large and different types of networks observed in Malta and the Seychelles. For both networks, the developed SA and TS techniques yielded high-quality schedules than those actually observed. The main limitation with the SA method is the amount of computational time required. This is considerably improved by the use of the sequential sessions structure. The use of a new cooling optimization scheme is developed and implemented to remedy the most time consuming part of process, but the design of a network still needs higher computation times. It is concluded that the SA approach of finding the cheapest schedule for large networks is time consuming. The superiority of TS has been proven both with respect to the GPS schedule quality and computational effort on large GPS networks. For the GPS surveyor, it has been shown that the techniques developed can reduce significantly the cost of carrying out a GPS survey. As these techniques have both theoretical and practical interest, not only the best results have been reported, but some variants of these techniques have been proposed. This provides a strong motivation and fertile opportunity for innovation in adapting heuristics for solving other practical surveying optimization problems where feasibility and good solutions are difficult to obtain.

Graph searching problems are described as games played on graphs, between a set of searchers and a fugitive. Variants of the game restrict the abilities of the searchers and the fugitive and the corresponding search number (the least number of searchers that have a winning strategy) is related to several well-known parameters in graph theory. One popular variant is called the Cops and Robber game, where the searchers (cops) and the fugitive (robber) move in rounds, and in each round they move to an adjacent vertex. This game, defined in late 1970's, has been studied intensively. The most famous open problem is Meyniel's conjecture, which states that the cop number (the minimum number of cops that can always capture the robber) of a connected graph on n vertices is O(sqrt n). We consider a version of the Cops and Robber game, where the robber is faster than the cops, but is not allowed to jump over the cops. This version was first studied in 2008. We show that when the robber has speed s, the cop number of a connected n-vertex graph can be as large as Omega(n^(s/s+1)). This improves the Omega(n^(s-3/s-2)) lower bound of Frieze, Krivelevich, and Loh (Variations on Cops and Robbers, J. Graph Theory, to appear). We also conjecture a general upper bound O(n^(s/s+1)) for the cop number, generalizing Meyniel's conjecture. Then we focus on the version where the robber is infinitely fast, but is again not allowed to jump over the cops. We give a mathematical characterization for graphs with cop number one. For a graph with treewidth tw and maximum degree Delta, we prove the cop number is between (tw+1)/(Delta+1) and tw+1. Using this we show that the cop number of the m-dimensional hypercube is between c1 n / m sqrt(m) and c2 n / m for some constants c1 and c2. If G is a connected interval graph on n vertices, then we give a polynomial time 3-approximation algorithm for finding the cop number of G, and prove that the cop number is O(sqrt(n)). We prove that given n, there exists a connected chordal graph on n vertices with cop number Omega(n/log n). We show a lower bound for the cop numbers of expander graphs, and use this to prove that the random G(n,p) that is not very sparse, asymptotically almost surely has cop number between d1 / p and d2 log (np) / p for suitable constants d1 and d2. Moreover, we prove that a fixed-degree regular random graph with n vertices asymptotically almost surely has cop number Theta(n).

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2007. / Härtill 3 uppsatser.

Thèses (M.Sc.A.)--Université de Sherbrooke (Canada), 1997. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Submitted by Everaldo Pereira (pereira.evera@gmail.com) on 2017-02-18T18:42:32Z No. of bitstreams: 1 Tese_Tereza_Nossa_2011.pdf: 32393636 bytes, checksum: 32369543b04f84e55e4b1a1351186a73 (MD5) / Made available in DSpace on 2017-02-18T18:42:32Z (GMT). No. of bitstreams: 1 Tese_Tereza_Nossa_2011.pdf: 32393636 bytes, checksum: 32369543b04f84e55e4b1a1351186a73 (MD5) / O aquífero cárstico Salitre localiza-se na microrregião da Bacia de Irecê, situada na região centro-norte do estado da Bahia, compreendendo parte dos municípios de Irecê e Lapão, perfazendo uma área de 250km². Constituído por espessas sequências de calcarenitos, calcilutitos, calcissiltitos e dolomitos intercalados, por vezes, com sequências terrígenas subordinadas, constituídas por silexitos, arenitos, siltitos, laminitos e margas, com uma espessura máxima de 530m. As feições cársticas que ocorrem na área, como dolinas e sumidouros, equivalem a 4,7% da superfície da área de pesquisa, sendo mapeadas 177 feições cársticas no total, equivalendo a uma área de 11,73km². Com esta configuração cárstica a recarga efetiva média calculada foi de 35,49mm/ano, em função dos baixos índices pluviométricos da área, perfazendo 5,44% da precipitação total de 653mm/ano, com uma reserva reguladora média de aproximadamente, 8,9 x 106m³/ano. Nas 36 amostras de águas subterrâneas coletadas foram analisados 40 parâmetros físico-químicos constantes nas legislações aplicáveis, considerados orientativos para consumo humano. Foram obtidos valores mais elevados que os valores máximos permitidos para os seguintes elementos: cálcio, magnésio, dureza total, sólidos totais dissolvidos, sulfato, fluoreto, nitrato, nitrito, cloreto e arsênio. Dessa forma, as águas subterrâneas analisadas se enquadram como águas de “Classe 3”, em função da detecção de valores mais elevados que os valores máximos permitidos, sobretudo para nitrato, nitrito, cloreto e arsênio. Foram selecionados 32 compostos semivoláteis, constantes nas legislações aplicáveis, para consumo humano, sendo constatado nas análises a não detecção dos compostos pesquisados. Das amostras analisadas referentes às campanhas de 2009 e 2010, 51,62% são caracterizadas como águas Bicarbonatadas Cálcicas e Mistas e 48,38% apresentam características de águas Cloretadas Cálcicas e Mistas. Dessa forma, foi constatado um certo equilíbrio entre a qualidade das águas analisadas. As análises isotópicas das águas subterrâneas coletadas em poços tubulares localizados no setor leste da área, à montante do fluxo, apresentam-se mais empobrecidas em isótopos pesados do que aquelas obtidas de poços localizados no setor norte-noroeste, à jusante do fluxo, com valores enriquecidos para oxigênio e deutério (δ18O) e (δD), demonstrando que são águas mais evaporadas. Os valores crescentes de carbono inorgânico dissolvido (δ13CCID), evidenciam as interações com as rochas calcárias, corroborados pelo fato de que o enriquecimento isotópico ocorre preferencialmente no sentido (E-W), concordante com as direções preferenciais de fluxo obtidas na área. A análise granulométrica dos solos coletados em 17 pontos de amostragem permitiu a caracterização textural dos solos na área como: silto-arenoso (41,18%), silto-argiloso (35,29%) e siltoso (23,53%). Foram selecionados 07 pontos para análise de metais no solo: Cu+2, Zn+2, Pb+2, Fe+2 e Ni+2 e foi constatado, de acordo com os valores orientadores das legislações aplicáveis, valores elevados de chumbo de 242,8mg/kg na amostra S-16, coletada na área de disposição de rejeitos da mineração Galvani. A elaboração do Mapa de Uso e Ocupação dos Solos possibilitou a delimitação de classes de uso e ocupação dos solos da seguinte maneira: Agropecuária (75,70%); Cobertura Vegetal Nativa (17,41%); Área Urbanizada (4,36%), Áreas da Mineração Galvani (2,48%) e Lixões (0,05%), com predomínio das atividades de agropecuária, sobretudo das atividades agrícolas. A análise do Mapa de Vulnerabilidade Intrínseca à Contaminação permitiu a delimitação de três classes de vulnerabilidade na área: Moderada (53%), Baixa (40%) e Muito Alta (7%), obtidas com base na análise dos atributos discriminados pela metodologia COP e nos mapas temáticos gerados: Mapa Hidrogeológico, Mapa de Dolinas e Fraturas, Mapa de Declividade e Mapa de Uso e Ocupação dos Solos. Os fatores que mais influenciaram nos índices COP gerados na área foram: o fator “C”, nas áreas de influência das feições cársticas (dolinas e sumidouros), que equivale às classes de vulnerabilidade Muito Alta e Moderada e o fator “O” tanto nestas classes, como no restante da área, delimitada como classe de vulnerabilidade Baixa. O fator “P” não contribui de forma direta para o zoneamento de vulnerabilidade no aquífero Salitre. O Mapa de Vulnerabilidade Intrínseca à Contaminação, pode ser validado, sobretudo, em função da delimitação de feições cársticas, como dolinas e sumidouros, mapeadas no Mapa de Dolinas e Fraturas, uma vez que não foi constatada de fato, contaminação de origem comprovadamente antrópica, que venha comprometer a qualidade da água do aquífero Salitre na área. / ABSTRACT - The karst aquifer Salitre is located in the Irecê Basin micro region, located in north-central Bahia state, comprising areas of Irecê and Lapão municipalities, covering an area of 250km². Consisting of thick sequences of calcarenites, calcilutites, calcisiltites and dolomites, interspersed sometimes with subordinate terrigenous sequences constituted of silexites, sandstones, siltstones, marls and laminations, with a maximum thickness of 530m. There are 177 mapped karst features in the area, such as dolines and sinkholes, equivalent to 4.7% of the surface area of research, with an area of 11.73km². With this configuration karst, the effective charge average was calculated at 35.49mm/year, due to the low rainfall area, totaling 5.44% of total precipitation 653mm/year with a buffer averaging about 8.9 x 106m³/year. In 36 groundwater samples collected, were analyzed 40 physical and chemical parameters contained in the applicable legislation, considered as targeted at human consumption. Values obtained were higher than the maximum allowed for the following elements: calcium, magnesium, total hardness, total dissolved solids, sulfate, fluoride, nitrate, nitrite, chloride and arsenic. Thus, groundwater waters analyzed were classified as "Class 3", based on the detection of higher values than the maximum allowed, especially for nitrate, nitrite, chloride and arsenic. We selected 32 semi-volatile compounds contained in the applicable laws for human consumption, and revealed in the analysis did not detect the compounds studied. Of the samples related to the campaigns of 2009 and 2010, 51.62% are characterized as Bicarbonated, Calcium and Mixed water and 48.38% had features of Calcium, Chlorinated and Mixed water. Thus, we found a certain balance between the qualities of the water samples. The isotopic analysis of groundwater collected from wells located in the eastern sector of the area, the amount of flow, have become more impoverished in heavy isotopes than those obtained from wells located in the north-northwest sector, the downstream flow, with values enriched for oxygen and deuterium (δ18O) and (δD), showing that they are more water evaporated. The increasing values of dissolved inorganic carbon (δ13CCID), show the interactions with the limestone, supported by the fact that the isotopic enrichment occurs preferentially in the direction (E-W), consistent with preferential flow directions obtained in the area. The size analysis of soils collected at 17 sampling points allowed textural characterization of soils in the area as silt-sand (41.18%), silt-clay (35.29%) and silty (23.53%). Were selected 07 points for analysis of metals in the soil: Cu+2, Zn+2, Pb+2, Fe+2 and Ni+2 and was determined, in accordance with the guiding values of the applicable laws, high levels of lead 242,8mg/kg in sample S-16, collected in the area of disposal of mining tailings Galvani. The drafting of Use Map and Land use classes allowed the delimitation of use and occupation of land as follows: Agriculture (75.70%), Native Vegetation (17.41%); Urbanized Area (4,36%), Mining Areas Galvani (2.48%) and dumps (0.05%), with a predominance of agricultural activities, especially agricultural activities. The analysis of the Intrinsic Vulnerability Map of the Contamination led to the delineation of three classes of vulnerability in the area: Moderate (53%), Low (40%) and Very High (7%), obtained based on analysis of attributes discriminated against by the COP method and thematic maps generated: Hydro geological Map, Map of Sinkholes and Fractures, Slope Map and Land Use Map. The factors that most influenced the COP generated in the indices were: the factor "C" in the areas of influence of karst features (sinkholes and sinks), which equates to Very High vulnerability classes and Moderate and the factor "O" both these classes, as in the rest of the area demarcated as Low vulnerability class. The factor "P" does not contribute directly to the zoning of vulnerability in aquifer Salitre. The Map of Intrinsic Vulnerability to Contamination can be validated, mainly due to the delimitation of karst features as dolines and sinkholes mapped in the Map of Sinkholes and Fractures, as it was not detected in fact, proven contamination of anthropogenic origin, which may compromise the water quality in the aquifer Salitre in the area.

Genom att studera individers upplevelse av lärande inom ett populärt lagspel online försöker denna uppsats att ge en ökad förståelse för vad som lärs in genom onlinespel och hur detta förs vidare till andra spelare genom Communities of practice's begreppsram. Detta i syfte att kunna använda sig av onlinelärande och överföringen av denna på ett bättre sätt inom onlinestudier och distansstudier. Underlaget har framkommit genom sex intervjuer i en kvalitativ forskningsanda. Uppsatsen använder sig av en induktiv ansats och meningskoncentrering för att sammanställa resultaten. Resultaten visar vikten av en lärandegrupp samt kommunikation för ett kunskapsutbyte med sina medspelare genom en gemensam chattgrupp. Denna kunskap genereras både genom praktiken och att delta i mer perifiera aktiviteter som att delta inom olika streams, forumdiskussioner samt genom chattgruppen. Resultaten visar även på hur överföringen av kunskap sker mellan olika erfarenhetsgrader. Slutsatsen är därför att kommunikation inom lärandegruppen är nödvändig för att inlärningen ska fungera optimalt trots ett fysiskt avstånd. Vilket visar relevansen av att fortsätta att studera lärandet online genom ett kvalitativt perspektiv för att kunna applicera kommande resultat inom förbättrad onlineutbildning.

Esta dissertação analisa o resultado da COP 21, que aconteceu em Paris no ano de 2015, através da capacidade que as coalizões domésticas, dentro de China e Estados Unidos, tiveram em influenciar a política climática durante o período que vai de 1992 até 2015. É através da identificação das coalizões domésticas (ambiental e pó-desenvolvimento econômico) que buscamos explicar como o processo político doméstico, nos dois países, foi moldado a partir das articulações e interações entre os grupos que compõe as coalizões. Até a COP 21, a política climática global parecia não avançar em vistas a uma solução do aquecimento global, a COP 15 é referenciada neste trabalho como o fracasso dos acordos climáticos, no entanto, 5 anos mais tarde, em 2015, juntos EUA e China, o dois maiores emissores da atualidade, anunciam suas metas de redução dos gases de efeito estufa. O que explica essa mudança de posicionamento, segundo a hipótese deste trabalho, é o amadurecimento e a articulação das coalizões doméstica dentro dos dois países, em primeiro lugar, e os acordos bilaterais que ambos promoveram entre os anos de 2009 e 2015 para trata das questões climáticas fora do sistema ONU de tomada d decisão. O resultado encontrado é que de fato, até 2009, a coalizão pró-desenvolvimento econômico conseguiu que sua influencia no processo político da condução da politica climática prevalecesse, no entanto, do período posterior a 2009 até 2015, pudemos ver que a coalizão ambiental conseguiu que sua influencia causasse, inclusive, um transbordamento para a arena internacional. / This essay analyze the COP 21 outcomes, that was held in Paris in 2015, through the domestic coalitions capacity, inside China and USA, had to influence the climate policy during the period that goes from 1992 until 2015. It is through the identification of domestic (environmental and economic development) coalitions that we seek to explain how the domestic political process, in both countries, was shaped by the articulations and interactions between the groups that make up the coalitions. Until COP 21, global climate policy did not seem to advance towards a solution to global warming, COP 15 is referred to, in this paper, as the failure of climate agreements, however, 5 years later in 2015, U.S and China together, the two largest emitters today, announce their targets for reducing greenhouse gases. What explains this change of position, according to the hypothesis of this work, is that the maturation and articulation of domestic coalitions within both countries, first, and the bilateral agreements that both promoted between the years of 2009 and 2015 to deal with the climate change issues outside of the UN system of decision-making. The result was that in fact, until 2009, the economic development coalition had its influence on the political process of climate policy prevailing, however, from the period after 2009 until 2015, we could see that the environmental coalition succeeded in its influence would even cause an overflow to the international arena.

Philosophiae Doctor - PhD / The invasion by Striga in most cereal crop fields in Africa has posed an acute threat to food security and socioeconomic integrity. Consequently, numerous technological and research developments have been made to minimize and even control the Striga impacts on crop production. So far, efforts to control Striga have primarily focused on the manipulation of the genetics of the host crops, as well as understanding the phenological and physiological traits, along with the chemical composition of the weed.

Footwear can affect postural stability in individuals, particularly in elderly people. Aging-related decline in postural stability, particularly in the mediolateral (ML) direction, is a risk factor for falls and fall-related injuries among older adults. This study aimed to investigate the effects of high cushioned and minimal shoes on dynamic postural stability in ML during obstacle crossing in defined older and younger adults. Six healthy older adults (50–60 years old, body weight: 74.8 kg, body height: 168.0 cm) and six healthy younger adults (18–32 years old, body weight: 73.8 kg, body height: 174.8 cm) participated in the study. A Vicon motion analysis system with 10 optical cameras was used to capture the obstacle (20 cm height) crossing motion of the participants at 200 Hz, and ground reaction forces of obstacle crossing were collected at 1000 Hz. Motion data of obstacle crossing were collected at three shoe conditions, namely, minimal shoe, high cushioned shoe and barefoot (control). Data from five trials of obstacle crossing for each shoe condition were processed using Vicon Nexus software 2.11.0 and Matlab R2013b. Displacement and velocity of centre of mass (COM) in the ML direction, COM–centre of pressure (COP) ML separation, step length, step velocity, toe clearance, pre-horizontal distance, hip flexion angle and hip abduction angle during obstacle crossing were examined. One-way ANOVA with pairwise analysis showed that toe clearance was significantly larger in the high cushioned shoe conditions than in the minimal shoe and barefoot conditions in older adults (high cushioned shoes vs. barefoot: p = 0.019; cushioned shoes vs. minimal shoes: p = 0.031) and younger adults (high cushioned shoes vs. barefoot: p = 0.016; high cushioned shoes vs. minimal shoes: p = 0.000). No significant difference in the measures was found between the minimal shoe and barefoot conditions in each group. Compared with older adults, younger adults showed significantly larger step length in barefoot condition (p = 0.000) and minimal shoe (p = 0.016). Independent t-test for examination of the significant difference of the means of each measure when the shoe condition was changed showed that only step length and step velocity were significantly different between older and younger adults. When the shoe condition was changed from minimal shoe or barefoot to high cushioned shoe, older adults showed significantly bigger change in step velocity (10.04 ± 4.39 cm/s for older; 1.87 ± 0.81 cm/s for younger; p = 0.034) and step length (14.26 ± 6.99 cm for older; 2.086 ± 1.13 cm for younger; p = 0.041) than younger adults. This result indicates that older adults had 23% greater total range of step length and 12% greater total range of step velocity compared with younger adults when shoe condition changed. Moreover, older adults showed 16% smaller total range in their maximal COM-COP ML separations than younger adults when shoe condition changed. It is concluded that high cushioned shoes can influence dynamic postural stability in the ML direction during obstacle crossing in younger and older adults. The minimal shoe and barefoot conditions did not show significant influence on postural stability in the ML direction during obstacle crossing in older and younger adults. The minimal shoe on dynamic postural stability in the ML direction is not significant. Age differences in dynamic postural stability in the ML direction during obstacle crossing were found at the same shoe conditions. Moreover, when shoe condition was changed, shoe cushioning conditions affected postural stability to a larger extent in older adults compared with younger adults. The high cushioned shoe led to a more challenged postural stability in adults aged 50 to 60 than younger adults aged 18 to 32.

In recent years a growing interest in Borehole Heat Exchangers (BHEs) has been shown in Europe thanks to the increase of installations in systems connected to Ground Source Heat Pumps (GSHPs) used for heating and cooling needs. Different geometries and technical solutions have been de- veloped in order to improve heat exchange with the ground, accompanied by several descriptive models. Recently, innovative technologies as optical fiber for a new Distributed Thermal Response Test (DTRT) have been proposed. This method allows the quantification of the BHE local perfor- mances, so that a more accurate punctual analysis of thermal phenomena is allowed. The aim of this thesis is to locate an analytical model thanks to the most recent data, to achieve the definition of overall efficiency of a single BHE in terms of thermal resistance and of a BHE-GSHP system in terms of evaluation of the Coefficient of Performance. This model accuracy will be verified with new measures in a real installation. A particular attention will be given to the thermal-fluid-dynamics aspects, defining semi-empirical correlation for free and forced convection within the BHE groundwater filling.