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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.
71

Connecting Landscapes to People: Assessing the Distribution of Ecosystem Service Flows Using the SPAN Approach

Johnson, Gary Wayne 01 January 2014 (has links)
The Service Path Attribution Network (SPAN) framework provides a novel, user-centric, connectivity-based approach to ecosystem service assessment and valuation (ESAV). Ecosystem services are delivered to users through the simulated flow of some service medium (i.e., matter, energy, or information) from the ecosystems in which it originates (sources) to the people or assets which it affects (users). Along the way, the service medium may be absorbed by intervening landscape features (sinks) or captured by rival users. Crucially, the service medium is not itself an ecosystem service or benefit but rather an agnostic transport mechanism which establishes connectivity between sources, sinks, rival users, and nonrival users within a delimited study region. Each user then receives benefits or harm from the encountered service medium depending on their specific relationship with it. For example, if surface water is the simulated service medium, it may increase productivity at a hydropower plant but damage farmers in floodplains by drowning their crops. In the SPAN terminology, sources provide provisioning ecosystem services to users with a beneficial relationship with the service medium. Similarly, sinks provide preventive ecosystem services to users with a detrimental relationship with the service medium by reducing the amount flowing to their locations. Notably, within a single SPAN analysis, both sources and sinks may provide ecosystem services given a sufficiently heterogeneous pool of users. The results of a SPAN ESAV analysis are myriad, totalling up to 30 output maps for some services. Taken together, these maps tell the story of which sources provide services to which users, which sinks protect users from harm, which users compete for the same resources (and who wins), and how all of the sources, sinks, rival users, and nonrival users affect one another. Additionally, a SPAN simulation produces maps of the flow paths taken by the service medium from sources to users as well as where and by how much the flow strength is reduced by sinks. Studying these flow paths can help decision makers identify those locations at which management actions would be maximized or minimized depending on their specific development goals. A crowning achievement of this work is that for most ecosystem services the SPAN algorithm's complexity is guaranteed to be linear O(n) in both time and space with respect to the number of discrete locations analyzed. This makes it a viable option for high resolution landscape level ESAV studies using no more than commodity hardware. This dissertation explores the SPAN framework in depth, from its novel conceptual terminology and computational algorithms through to the intended interpretation of its results. In addition to describing the conceptual and mathematical components of this system in detail, this work also provides a complete Literate Program demonstrating the application of the SPAN framework to an assessment of the scenic beauty ecosystem service in Chittenden County, Vermont.
72

Optimisation basée sur l'étude des trajectoires dans un environnement aléatoire : application au pilotage de systèmes de production / Optimization based on the study of trajectories in a random environment : application to the control of production systems

Ramírez Restrepo, Laura María 26 September 2016 (has links)
Dans le contexte international actuel, les entreprises doivent être capables de développer des stratégies leur permettant d’augmenter leurs performances et d'être plus compétitives. Cet environnement très évolutif introduit de nombreuses incertitudes et contraintes qui rendent beaucoup plus difficile la détermination de la meilleure stratégie à adopter selon les objectifs fixés. Le travail développé dans cette thèse, s’inscrit dans ce cadre et nous nous intéressons plus précisément à l'optimisation du pilotage de systèmes de production soumis à aléas (comme les pannes des machines) de façon à minimiser les coûts globaux. Pour la modélisation, le modèle à flux continus est choisi afin de représenter le flux de matières transitant dans le système. Ce modèle, nous permet également d'intégrer les délais de transfert et de transport entre les différents éléments qui composent le système.La méthode de résolution analytique utilisée est issue des méthodes d’analyse de sensibilité et correspond à la méthode d’analyse des perturbations infinitésimales (IPA). Cette méthode nous permet de déduire à partir d'une étude de trajectoires, un gradient du coût global pour chacune des études menées. Nous prouvons alors que ces gradients ne sont pas biaisés. Cela nous permet de les utiliser dans des simulations numériques. Ces simulations nous permettent de déterminer les variables de décision des stratégies de pilotage du système considéré. Le pilotage intègre la maintenance à la production. Pour le pilotage des systèmes considérés, nous considérons également des contraintes liées aux trois piliers du développement durable. Ces contraintes sont intégrées à nos modèles sous forme de coûts. Ainsi, les coûts globaux peuvent comporter en plus de coûts purement économiques, des coûts environnementaux et sociaux. Nous montrons donc que l'approche de résolution proposée peut être utilisée pour optimiser d'autres objectifs dans un cadre de durabilité / In the current international context, companies need to be able to develop strategies to increase their performance and become more competitive. This rapidly changing environment introduces many uncertainties and constraints, making much more difficult to determine the best strategy according to the objectives set. The work developed in this thesis falls within this context and, more precisely, we are interested in the optimization of the control of production systems subject to uncertainties (such as machine failures) in order to minimize the overall costs. For modeling, the continuous-flow model is chosen to represent the material flow moving through the system. This model allows us to integrate transfer and transportation delays between the different components of the system. The analytical resolution method used is based on the sensitivity analysis methods and corresponds to the infinitesimal perturbation analysis method (IPA). This method allows us to deduce, based on learning from sample-paths, a gradient of the overall cost for each of the studies conducted. We prove that these gradients are unbiased, which allows us to use them in numerical simulations. The simulations allow us to determine the decision variables of control strategies of the studied systems. The control integrates the maintenance to the production. For the control of the considered systems, we also take into account constraints linked to the three pillars of sustainable development. These constraints are integrated into our models in terms of costs. Thus, the overall costs may not only include purely economic costs, but also environmental and social costs. We show that the proposed resolution approach may be used to optimize other objectives within a sustainability framework
73

Modelo conceitual de fluxo do Aquitarde Serra Geral e do Sistema Aquífero Guarani na região de Ribeirão Preto, SP / Conceptual flow model for the Serra Geral aquitard and the Guarani Aquifer system in Ribeirão Preto, SP

Wahnfried, Ingo Daniel 23 June 2010 (has links)
O presente trabalho teve como principais objetivos testar a existência de drenança através do aquífero fraturado Serra Geral (ASG) para o Sistema Aquífero Guarani (SAG), estabelecer o modelo conceitual de fluxo destes aquíferos, e determinar seus parâmetros hidráulicos, em local onde o ASG possui ao redor de 100 m de espessura. O local escolhido fica aproximadamente 9 km a sul da cidade de Ribeirão Preto, SP. O estudo fez parte de um projeto de pesquisa mais amplo denominado FRATASG, do Instituto Geológico (Secretaria do Meio Ambiente do Estado de São Paulo). Os métodos geofísicos de superfície caminhamento elétrico (CE), sondagem elétrica vertical (SEV) e levantamento áudio-magnetotelúrico de fonte controlada (CSAMT) foram usados com o intuito de localizar zonas hidraulicamente ativas no basalto, e determinar a espessura e profundidade das camadas geológicas, para a locação de três poços perfurados no ASG. Ao lado de um poço de produção já existente no SAG (Poço Esmeralda - PE), foram construídos dois piezômetros com aberturas no ASG e SAG. Descontinuidades planares verticais no basalto, associados a lineamentos, foram detectadas em metade dos CEs e das seções realizadas com o método CSAMT, sendo que uma destas seções indicou continuidade de duas fraturas entre SAG e ASG. Para realizar testes hidráulicos e coletar amostras em profundidades discretas no ASG, foram construídos obturadores pneumáticos, baseados em modelos produzidos pelo Serviço Geológico Americano (USGS), que foram adaptados a equipamentos existentes no Brasil. Neste trabalho é feita descrição dos equipamentos, de suas aplicações, dos levantamentos prévios necessários para seu uso, os procedimentos de campo e as interpretações de alguns tipos de ensaio e coletas de amostras. Com o intuito de calcular os parâmetros hidráulicos do SAG e do ASG, foram realizados um teste de bombeamento de 171 horas no poço de produção do SAG, com monitoramento nos piezômetros, e testes hidráulicos em intervalos discretos em um poço do ASG (Poço Limeira - PL), isolados com os obturadores pneumáticos. Durante todos os ensaios de bombeamento, e em mais dois poços já existentes, abertos no ASG, foram coletadas amostras para análise hidroquímicas e, em amostras selecionadas, dos isótopos ³H, ²H, \'ANTPOT.18 O\', \'ANTPOT.13 C\' e \'ANTPOT.14 C\'. No SAG, o rebaixamento registrado nos dois piezômetros permitiu identificar a existência de anisotropia neste aquífero, com relação entre transmissividade máxima (\'T IND.máx\' = \'T IND.x\' =160 m²/d) e mínima (\'T IND.mín.\' = \'T IND.y\' = 103 m²/d) é de 1,55, sua condutividade hidráulica (K = 4,6x\'10 POT.-1\' m/d e 7,0x\'10 POR.-1\' m/d), e armazenamento (S = 1,6x\'10 POT.-3\' e 8,4x\'10 POT.-4\', sempre para os piezômetros PPE-1G e PPE-2G respectivamente, localizados em direções distintas em relação ao PE). A anisotropia provavelmente é causada pelos planos de sedimentação das dunas eólicas da Formação Botucatu. Também foram realizados dois testes com traçadores no PE, com injeção no SAG e no ASG e coleta no SAG, que permitiu a obtenção da porosidade efetiva do SAG no local, entre 18,8 e 20,3%. No ASG, os testes hidráulicos permitiram a identificação das zonas mais transmissivas, sempre formadas por fraturas sub-horizontais. A transmissividade (T) de intervalos reduzidos variou entre 5x\'10 POT.-2\' a 3x\'10 POT.-1\' m2/d, e a existência de comportamento análogo ao de dupla porosidade no basalto, causado pela presença de vesículas e fraturas sub-verticais associadas às fraturas subhorizontais. As análises químicas mostram uma evolução com a profundidade, com o aumento de Na+K. Isto permitiu uma clara diferenciação entre as amostras coletadas em profundidades rasa, de 16 m, intermediária, de 25 m, e profunda, coletada a 55 m. O mesmo agrupamento é encontrado nos isótopos estáveis, e os radioativos indicam idade maior nas águas mais profundas do ASG. As amostras do SAG se assemelham mais às águas rasas do ASG, hidroquimica- e isotopicamente. Os resultados mostram pouca ou nenhuma conectividade entre SAG e ASG, e uma circulação preferencial rasa e horizontal dentro do ASG. / The main objectives of the present thesis were to test the existence of leakage through the fractured Serra Geral Aquifer (SGA) to the Guarani Aquifer System (GAS), create a conceptual flow model for both aquifers, and obtain their hydraulic parameters, at a location where the SGA-forming basalt has 100 m thickness. The chosen area is 9 km to the south of Ribeirão Preto, São Paulo State, Brazil. The study is part of a research project called FRATASG, from the Geological Institute (São Paulo Environmental Secretariat). Surface geophysical methods (vertical electrical sounding, electric resistivity survey and controlled source audiomagnetotelluric survey - CSAMT) were used to locate fractures in the basalt that are possibly hydraulically active, and also to determine the contact depths between overburden, basalt, and the eolian sandstones that form the GAS. Vertical low electric-resistivity planar features were identified in the basalt, at locations were lineaments were described, in half of the electric resistivity and CSAMT surveys, and one of the latter showed continuity of the feature down to the GAS. This was interpreted as possible water bearing fractures, and was used to define the location of three wells in the SGA. Two piezometers were also drilled, open to both SGA and GAS, close to an existing production well in the GAS (Esmeralda Well - PE). To collect discrete depth samples in the SGA, a pneumatic packer system was built, based on models used by the USGS, adapting equipment that is available in Brazil. The system, as well as other equipment used, the procedures and interpretation of the hydraulic tests and sample collection at discrete depths, are described. A 171 hour long pumping test was executed in the GAS, where anisotropy was identified, probably caused by the sedimentary layering present in the eolic dunes in the sandstone. The highest transmissivity, \'T IND.max\' = \'T IND.x\', is 160 m²/d, and the lowest transmissivity, \'T IND.min\' = \'T IND.y\', is 103 m²/d. The correlation between Tmax / Tmin is 1,55. Hydraulic conductivity (K) is 4,6x\'10 POT.-1\' m/d and 7,0x\'10 POT.-1\' m/d, and storativity (S) is 1,6x\'10 POT.-3\' and 8,4x\'10 POT.-4\', determined respectively at piezometers PPE-1G and PPE-2G, located at different directions from PE. Dye-tracer tests were also conducted, with injection in GAS and SGA, and collection in the GAS. The effective porosity was determined, ranging from 18,8 to 20,3%. Several hydraulic tests were done in discrete depths in the SGA, in one well. The transmissivity (T) of small intervals ranges between 5x\'10 POT.-2\' and 3x\'10 POT.-1\' m²/d. The highest T of individual features is always associated to sub-horizontal fractures. The drawdown curve showed double porosity behavior in the basalt, caused by vesicules and sub-vertical fractures connected to the sub-horizontal ones. Water samples were collected during all pumping tests, in the GAS, in two open wells in the SGA and in discrete zones in this aquifer, for hydrochemical analysis. Stable and radioactive isotope analysis (³H, ²H, \' ANTPOT.18 O\', \'ANTPOT.13 C\' and \' ANTPOT.14 C\') were done with selected samples, both from GAS and ASG. The fractured aquifer shows and hydrochemical evolution with depth, with Na+K increase. Samples can thus be grouped as shallow (around 16 m depth), intermediate (around 25 m) and deep (around 55 m). The same groups are found in the stable isotope results, whereas the radioactive show an age increase with depth. Samples from GAS are isotopically and hydrochemically closer to the shallow waters from the SGA. It can thus be concluded that the connection between both aquifers is very limited, or not present, and water flow in the SGA is mostly horizontal and shallow.
74

Pattern Exploration from Citizen Geospatial Data

Ke Liu (5930729) 17 January 2019 (has links)
Due to the advances in location-acquisition techniques, citizen geospatial data has emerged with opportunity for research, development, innovation, and business. A variety of research has been developed to study society and citizens through exploring patterns from geospatial data. In this thesis, we investigate patterns of population and human sentiments using GPS trajectory data and geo-tagged tweets. Kernel density estimation and emerging hot spot analysis are first used to demonstrate population distribution across space and time. Then a flow extraction model is proposed based on density difference for human movement detection and visualization. Case studies with volleyball game in West Lafayette and traffics in Puerto Rico verify the effectiveness of this method. Flow maps are capable of tracking clustering behaviors and direction maps drawn upon the orientation of vectors can precisely identify location of events. This thesis also analyzes patterns of human sentiments. Polarity of tweets is represented by a numeric value based on linguistics rules. Sentiments of four US college cities are analyzed according to its distribution on citizen, time, and space. The research result suggests that social media can be used to understand patterns of public sentiment and well-being.
75

Stockperformance indicators post recession : <em>- A Study of valuation tools and strategies during recovery</em>

Kazachenko, Sergey, Paz, Diana January 2009 (has links)
<p>Problem:   What are the most useful techniques to indicate the stocks that will outperform the market 12 month post the recession period?  Purpose:  The purpose is to find out which method(s): P/B, EV/EBIT, level of debt and so on, will offer investors the highest returns on the investments post the recession period based on the example of the IT crisis of 2000/2001.  Method:  Quantitative study, covering the Swedish OMX Index from 2001 until December 2002.  Conclusions:  Three variables should be reconsidered when making an investment decision post the recession period. These variables were earlier 12 months returns, dividend yield and P/E ratios. However, it is crucial to understand that these three tools should not be viewed all together.</p><p> </p>
76

Business Valuation : How to Value Private Limited Knowledge Based Companies

Olsson, Fredrik, Persson, Martin January 2009 (has links)
Abstract Purpose The purpose of this study is to investigate the methods used for valuating private limited knowledge based companies and if a new approach is required, create or modify a foundation that will constitute as a base within the valuation process. Method This is a qualitative study using interviews to obtain primary data. People working in the valuation industry were contacted and we got eight respondents. The questions were designed to answer our purpose and research questions. Telephone interviews were chosen due to the fact that we believed the response would be higher.      Frame of References The theories used in this section is divided into three parts; the financial analysis including traditional valuating methods such as the Discounted Cash Flow model and relative valuating and multiples. The non-financial analysis focus on the underlying analysis consistent of structural- and intellectual capital and also value drivers that are creating value for the firm. In the end other theories concerning the analysis are presented, such as the risk-return trade-off, risk rating systems and analytical hierarchy process.             Empirical Findings In this section the presentations of the respondents’ answers and and Analysis a brief analysis related to each question. After this an extended analysis is presented focusing on the subject and our risk scheme and guidelines we created/modified. The extended analysis is connected to the respondents’ answers. The purpose of this section is to have a better understanding about the risk of transient intellectual capital and give recommendations how to handle it. Also, guidelines of how to weight different value driver are discussed. Conclusion We concluded that all valuations utilize more than one approach in order to estimate the most accurate value for the company. For knowledge based companies the biggest risk with a M&amp;A transaction is the probability of diminishing the intellectual capital. We constructed a model that will manage this risk based on our interviews and established theories.
77

Stockperformance indicators post recession : - A Study of valuation tools and strategies during recovery

Kazachenko, Sergey, Paz, Diana January 2009 (has links)
Problem:   What are the most useful techniques to indicate the stocks that will outperform the market 12 month post the recession period?  Purpose:  The purpose is to find out which method(s): P/B, EV/EBIT, level of debt and so on, will offer investors the highest returns on the investments post the recession period based on the example of the IT crisis of 2000/2001.  Method:  Quantitative study, covering the Swedish OMX Index from 2001 until December 2002.  Conclusions:  Three variables should be reconsidered when making an investment decision post the recession period. These variables were earlier 12 months returns, dividend yield and P/E ratios. However, it is crucial to understand that these three tools should not be viewed all together.
78

A Sleep-Scheduling-Based Cross-Layer Design Approach for Application-Specific Wireless Sensor Networks

Ha, Rick Wan Kei January 2006 (has links)
The pervasiveness and operational autonomy of mesh-based wireless sensor networks (WSNs) make them an ideal candidate in offering sustained monitoring functions at reasonable cost over a wide area. To extend the functional lifetime of battery-operated sensor nodes, stringent sleep scheduling strategies with communication duty cycles running at sub-1% range are expected to be adopted. Although ultra-low communication duty cycles can cast a detrimental impact on sensing coverage and network connectivity, its effects can be mitigated with adaptive sleep scheduling, node deployment redundancy and multipath routing within the mesh WSN topology. This work proposes a cross-layer organizational approach based on sleep scheduling, called Sense-Sleep Trees (SS-Trees), that aims to harmonize the various engineering issues and provides a method to extend monitoring capabilities and operational lifetime of mesh-based WSNs engaged in wide-area surveillance applications. Various practical considerations such as sensing coverage requirements, duty cycling, transmission range assignment, data messaging, and protocol signalling are incorporated to demonstrate and evaluate the feasibility of the proposed design approach.
79

A Study of Polycarbonate / Poly (butylene terephthalate) Compounding in a Twin Screw Extruder

Noeei Ancheh, Vahid January 2008 (has links)
Blends of poly butylene terephthalate (PBT) and polycarbonate (PC) form a very important class of commercial blends in numerous applications requiring materials with good chemical resistance, impact resistance even at low temperatures, and aesthetic and flow characteristics. PC and PBT are usually blended in a twin screw extruder (TSE). Product melt volume flow rate (MVR) is a property used to monitor product quality while blending the PC/PBT in a twin screw extruder. It is usually measured off line in a quality control laboratory using extrusion plastometer on samples collected discretely during the compounding operation. Typically a target value representing the desired value of the quality characteristics for an in-control process, along with upper and lower control limits are specified. As long as the MVR measurement is within the control limits, the sample is approved and the whole compounded blend is assumed to meet the specification. Otherwise, the blend is rejected. Because of infrequent discrete sampling, corrective actions are usually applied with delay, thus resulting in wasted material. It is important that the produced PC/PBT blend pellets have consistent properties. Variability and fault usually arise from three sources: human errors, feed material variability, and machine operation (i.e. steady state variation). Among these, the latter two are the major ones affecting product quality. The resulting variation in resin properties contributes to increased waste products, larger production cost and dissatisfied customers. Motivated by this, the objective of this project was to study the compounding operation of PC/PBT blend in a twin screw extruder and to develop a feasible methodology that can be applied on-line for monitoring properties of blends on industrial compounding operations employing available extruder input and output variables such as screw speed, material flow rate, die pressure and torque. To achieve this objective, a physics-based model for a twin screw extruder along with a MVR model were developed, examined and adapted for this study, and verified through designed experiments. This dynamic model for a TSE captures the important dynamics, and relates measurable process variables (screw speed, torque, feed rates, pressure etc.) to ones that are not being measured (material holdups and compositions at the partially and filled section along a TSE barrel). This model also provides product quality sensors or inferential estimation techniques for prediction of viscosity and accordingly MVR. The usefulness of the model for inferential MVR sensing and fault diagnosis was demonstrated on experiments performed on a 58 mm co-rotating twin-screw extruder for an industrial compounding operation at a SABIC Innovative Plastics plant involving polycarbonate – poly butylene terephthalate blends. The results showed that the model has the capability of identifying faults (i.e., process deviation from the nominal conditions) in polymer compounding operations with the twin screw extruder. For instance, the die pressure exhibited a change as a function of changes in raw materials and feed composition of PC and PBT. In the presence of deviations from nominal conditions, the die pressure parameters are updated. These die pressure model parameters were identified and updated using the recursive parameter estimation method. The recursive identification of the die pressure parameters was able to capture very well the effects of changes in raw material and/or composition on the die pressure. In addition, the developed MVR model showed a good ability in monitoring product MVR on-line and inferentially from output process variables such as die pressure which enables quick quality control to maintain products within specification limits and to minimize waste production.
80

A Sleep-Scheduling-Based Cross-Layer Design Approach for Application-Specific Wireless Sensor Networks

Ha, Rick Wan Kei January 2006 (has links)
The pervasiveness and operational autonomy of mesh-based wireless sensor networks (WSNs) make them an ideal candidate in offering sustained monitoring functions at reasonable cost over a wide area. To extend the functional lifetime of battery-operated sensor nodes, stringent sleep scheduling strategies with communication duty cycles running at sub-1% range are expected to be adopted. Although ultra-low communication duty cycles can cast a detrimental impact on sensing coverage and network connectivity, its effects can be mitigated with adaptive sleep scheduling, node deployment redundancy and multipath routing within the mesh WSN topology. This work proposes a cross-layer organizational approach based on sleep scheduling, called Sense-Sleep Trees (SS-Trees), that aims to harmonize the various engineering issues and provides a method to extend monitoring capabilities and operational lifetime of mesh-based WSNs engaged in wide-area surveillance applications. Various practical considerations such as sensing coverage requirements, duty cycling, transmission range assignment, data messaging, and protocol signalling are incorporated to demonstrate and evaluate the feasibility of the proposed design approach.

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