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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.
221

Capacity development of small-scale farmers in developing countries: Analysis of preferences and the role of information and communication technologies

Landmann, Dirk Hauke 29 June 2018 (has links)
No description available.
222

Zahlungsbereitschaftsanalysen in der umweltökonomischen Bewertung von öffentlichen Gütern des Waldes / Willingness to pay analyses for environmental valuation of public goods provided by forests

Weller, Priska Johanna 18 October 2018 (has links)
No description available.
223

Função da probabilidade da seleção do recurso (RSPF) na seleção de habitat usando modelos de escolha discreta / Resource of selection probability function (RSPF ) the habitat selection using discrete choice models (DCM)

Sandra Vergara Cardozo 16 February 2009 (has links)
Em ecologia, o comportamento dos animais é freqüentemente estudado para entender melhor suas preferências por diferentes tipos de alimento e habitat. O presente trabalho esta relacionado a este tópico, dividindo-se em três capítulos. O primeiro capitulo refere-se à estimação da função da probabilidade da seleção de recurso (RSPF) comparado com um modelo de escolha discreta (DCM) com uma escolha, usando as estatísticas qui-quadrado para obter as estimativas. As melhores estimativas foram obtidas pelo método DCM com uma escolha. No entanto, os animais não fazem a sua seleção baseados apenas em uma escolha. Com RSPF, as estimativas de máxima verossimilhança, usadas pela regressão logística ainda não atingiram os objetivos, já que os animais têm mais de uma escolha. R e o software Minitab e a linguagem de programação Fortran foram usados para obter os resultados deste capítulo. No segundo capítulo discutimos mais a verossimilhança do primeiro capítulo. Uma nova verossimilhança para a RSPF é apresentada, a qual considera as unidades usadas e não usadas, e métodos de bootstrapping paramétrico e não paramétrico são usados para estudar o viés e a variância dos estimadores dos parâmetros, usando o programa FORTRAN para obter os resultados. No terceiro capítulo, a nova verossimilhança apresentada no capítulo 2 é usada com um modelo de escolha discreta, para resolver parte do problema apresentado no primeiro capítulo. A estrutura de encaixe é proposta para modelar a seleção de habitat de 28 corujas manchadas (Strix occidentalis), assim como a uma generalização do modelo logit encaixado, usando a maximização da utilidade aleatória e a RSPF aleatória. Métodos de otimização numérica, e o sistema computacional SAS, são usados para estimar os parâmetros de estrutura de encaixe. / In ecology, the behavior of animals is often studied to better understand their preferences for different types of habitat and food. The present work is concerned with this topic. It is divided into three chapters. The first concerns the estimation of a resource selection probability function (RSPF) compared with a discrete choice model (DCM) using chi-squared to obtain estimates. The best estimates were obtained by the DCM method. Nevertheless, animals were not selected based on choice alone. With RSPF, the maximum likelihood estimates used with the logistic regression still did not reach the objectives, since the animals have more than one choice. R and Minitab software and the FORTRAN programming language were used for the computations in this chapter. The second chapter discusses further the likelihood presented in the first chapter. A new likelihood for a RSPF is presented, which takes into account the units used and not used, and parametric and non-parametric bootstrapping are employed to study the bias and variance of parameter estimators, using a FORTRAN program for the calculations. In the third chapter, the new likelihood presented in chapter 2, with a discrete choice model is used to resolve a part of the problem presented in the first chapter. A nested structure is proposed for modelling selection by 28 spotted owls (Strix occidentalis) as well as a generalized nested logit model using random utility maximization and a random RSPF. Numerical optimization methods and the SAS system were employed to estimate the nested structural parameters.
224

L'évaluation économique des services écosystémiques marins et côtiers et son utilisation dans la prise de décision : cas d'étude en Nouvelle-Calédonie et en Australie / Quantifying economic values of coastal and marine ecosystem services and assessing their use in decision-making : applications in New-Caledonia and Australia

Marre, Jean-Baptiste 30 September 2014 (has links)
No abstract. / Coastal and marine ecosystems are some of the most heavily exploited with increasing degradation. This alarming situation appeals for urgent and effective actions. The optimal balance between use and conservation of ecosystems theoretically requires all costs and benefits to be considered in decision-making, including intangible costs and benefits such as non-market use and non-use values. The broad aim of this PhD is to examine how these economic values associated with coastal and marine ecosystem services can be measured, and how the economic valuation exercise may be considered and influence management decision- making.The first analytical part of the thesis focuses on assessing non-market use and non-use values, through econometric methods. The characterization and estimation of non-use values are complex and controversial, especially when the valuation exercise is focusing on individuals who are users of the ecosystem services being considered. An original approach based on a stated preference method, namely choice experiments, is developed then empirically applied in quantifying non-market values for marine and coastal ecosystems in two areas in New Caledonia. It allows the estimation of non-use values for populations of users in an implicit way. An in-depth analysis of the individuals’ choice heuristics during the valuation exercise is also conducted, with a focus on payment non-attendance. This issue is dealt with by comparing multiple modelling approaches in terms of: (1) inferred attendance, in relation to stated attendance; (2) attendance distribution according to several socio-economic variables; and (3) welfare estimates.After noting that the potential influence of economic valuation in decision making is unclear and largely unexplored in the literature, the second major component of this PhD aims to examine if, how and to what extent the economic valuation of ecosystem services, including measures of non-market values, influence decision-making regarding coastal and marine ecosystems management in Australia. Based on two nation-wide surveys, the perceived usefulness of the economic valuation of ecosystem services by the general public and decision-makers is studied, and the reasons why decision-makers may or may not fully consider economic values are elicited. Using a multi-criteria analysis, a part of the surveys also aims at examining the relative importance of different evaluation criteria (ecological, social and economic) when assessing the consequences of a hypothetical coastal development project on commercial activities, recreational activities and marine biodiversity.
225

Economic analysis of wireless sensor-based services in the framework of the Internet of Things. A game-theoretical approach

Sanchis Cano, Ángel 25 May 2018 (has links)
El mundo de las telecomunicaciones está cambiando de un escenario donde únicamente las personas estaban conectadas a un modelo donde prácticamente todos los dispositivos y sensores se encuentran conectados, también conocido como Internet de las cosas (IoT), donde miles de millones de dispositivos se conectarán a Internet a través de conexiones móviles y redes fijas. En este contexto, hay muchos retos que superar, desde el desarrollo de nuevos estándares de comunicación al estudio de la viabilidad económica de los posibles escenarios futuros. En esta tesis nos hemos centrado en el estudio de la viabilidad económica de diferentes escenarios mediante el uso de conceptos de microeconomía, teoría de juegos, optimización no lineal, economía de redes y redes inalámbricas. La tesis analiza la transición desde redes centradas en el servicio de tráfico HTC a redes centradas en tráfico MTC desde un punto de vista económico. El primer escenario ha sido diseñado para centrarse en las primeras etapas de la transición, en la que ambos tipos de tráfico son servidos bajo la misma infraestructura de red. En el segundo escenario analizamos la siguiente etapa, en la que el servicio a los usuarios MTC se realiza mediante una infraestructura dedicada. Finalmente, el tercer escenario analiza la provisión de servicios basados en MTC a usuarios finales, mediante la infraestructura analizada en el escenario anterior. Gracias al análisis de todos los escenarios, hemos observado que la transición de redes centradas en usuarios HTC a redes MTC es posible y que la provisión de servicios en tales escenarios es viable. Además, hemos observado que el comportamiento de los usuarios es esencial para determinar la viabilidad de los diferentes modelos de negocio, y por tanto, es necesario estudiar el comportamiento y las preferencias de los usuarios en profundidad en estudios futuros. Específicamente, los factores más relevantes son la sensibilidad de los usuarios al retardo en los datos recopilados por los sensores y la cantidad de los mismos. También hemos observado que la diferenciación del tráfico en categorías mejora el uso de las redes y permite crear nuevos servicios empleando datos que, de otro modo, no se aprovecharían, lo cual nos permite mejorar la monetización de la infraestructura. También hemos demostrado que la provisión de capacidad es un mecanismo válido, alternativo a la fijación de precios, para la optimización de los beneficios de los proveedores de servicio. Finalmente, se ha demostrado que es posible crear roles específicos para ofrecer servicios IoT en el mercado de las telecomunicaciones, específicamente, los IoT-SPs, que proporcionan servicios basados en sensores inalámbricos utilizando infraestructuras de acceso de terceros y sus propias redes de sensores. En resumen, en esta tesis hemos intentado demostrar la viabilidad económica de modelos de negocio basados en redes futuras IoT, así como la aparición de nuevas oportunidades y roles de negocio, lo cual nos permite justificar económicamente el desarrollo y la implementación de las tecnologías necesarias para ofrecer servicios de acceso inalámbrico masivo a dispositivos MTC. / The communications world is moving from a standalone devices scenario to a all-connected scenario known as Internet of Things (IoT), where billions of devices will be connected to the Internet through mobile and fixed networks. In this context, there are several challenges to face, from the development of new standards to the study of the economical viability of the different future scenarios. In this dissertation we have focused on the study of the economic viability of different scenarios using concepts of microeconomics, game theory, non-linear optimization, network economics and wireless networks. The dissertation analyzes the transition from a Human Type Communications (HTC) to a Machine Type Communications (MTC) centered network from an economic point of view. The first scenario is designed to focus on the first stages of the transition, where HTC and MTC traffic are served on a common network infrastructure. The second scenario analyzes the provision of connectivity service to MTC users using a dedicated network infrastructure, while the third stage is centered in the analysis of the provision of services based on the MTC data over the infrastructure studied in the previous scenario. Thanks to the analysis of all the scenarios we have observed that the transition from HTC users-centered networks to MTC networks is possible and that the provision of services in such scenarios is viable. In addition, we have observed that the behavior of the users is essential in order to determine the viability of a business model, and therefore, it is needed to study their behavior and preferences in depth in future studios. Specifically, the most relevant factors are the sensitivity of the users to the delay and to the amount of data gathered by the sensors. We also have observed that the differentiation of the traffic in categories improves the usage of the networks and allows to create new services thanks to the data that otherwise would not be used, improving the monetization of the infrastructure and the data. In addition, we have shown that the capacity provision is a valid mechanism for providers' profit optimization, as an alternative to the pricing mechanisms. Finally, it has been demonstrated that it is possible to create dedicated roles to offer IoT services in the telecommunications market, specifically, the IoT-SPs, which provide wireless-sensor-based services to the final users using a third party infrastructure. Summarizing, this dissertation tries to demonstrate the economic viability of the future IoT networks business models as well as the emergence of new business opportunities and roles in order to justify economically the development and implementation of the new technologies required to offer massive wireless access to machine devices. / El món de les telecomunicacions està canviant d'un escenari on únicament les persones estaven connectades a un model on pràcticament tots els dispositius i sensors es troben connectats, també conegut com a Internet de les Coses (IoT) , on milers de milions de dispositius es connectaran a Internet a través de connexions mòbils i xarxes fixes. En aquest context, hi ha molts reptes que superar, des del desenrotllament de nous estàndards de comunicació a l'estudi de la viabilitat econòmica dels possibles escenaris futurs. En aquesta tesi ens hem centrat en l'estudi de la viabilitat econòmica de diferents escenaris per mitjà de l'ús de conceptes de microeconomia, teoria de jocs, optimització no lineal, economia de xarxes i xarxes inalàmbriques. La tesi analitza la transició des de xarxes centrades en el servici de tràfic HTC a xarxes centrades en tràfic MTC des d'un punt de vista econòmic. El primer escenari ha sigut dissenyat per a centrar-se en les primeres etapes de la transició, en la que ambdós tipus de tràfic són servits davall la mateixa infraestructura de xarxa. En el segon escenari analitzem la següent etapa, en la que el servici als usuaris MTC es realitza per mitjà d'una infraestructura dedicada. Finalment, el tercer escenari analitza la provisió de servicis basats en MTC a usuaris finals, per mitjà de la infraestructura analitzada en l'escenari anterior. Als paràgrafs següents es descriu amb més detall cada escenari. Gràcies a l'anàlisi de tots els escenaris, hem observat que la transició de xarxes centrades en usuaris HTC a xarxes MTC és possible i que la provisió de servicis en tals escenaris és viable. A més a més, hem observat que el comportament dels usuaris és essencial per a determinar la viabilitat dels diferents models de negoci, i per tant, és necessari estudiar el comportament i les preferències dels usuaris en profunditat en estudis futurs. Específicament, els factors més rellevants són la sensibilitat dels usuaris al retard en les dades recopilats pels sensors i la quantitat dels mateixos. També hem observat que la diferenciació del tràfic en categories millora l'ús de les xarxes i permet crear nous servicis emprant dades que, d'una altra manera, no s'aprofitarien, la qual cosa ens permet millorar la monetització de la infraestructura. També hem demostrat que la provisió de capacitat és un mecanisme vàlid, alternatiu a la fixació de preus, per a l'optimització dels beneficis dels proveïdors de servici. Finalment, s'ha demostrat que és possible crear rols específics per a oferir servicis IoT en el mercat de les telecomunicacions, específicament, els IoT-SPs, que proporcionen servicis basats en sensors inalàmbrics utilitzant infraestructures d'accés de tercers i les seues pròpies xarxes de sensors. En resum, en aquesta tesi hem intentat demostrar la viabilitat econòmica de models de negoci basats en xarxes futures IoT, així com l'aparició de noves oportunitats i rols de negoci, la qual cosa ens permet justificar econòmicament el desenrotllament i la implementació de les tecnologies necessàries per a oferir servicis d'accés inalàmbric massiu a dispositius MTC. / Sanchis Cano, Á. (2018). Economic analysis of wireless sensor-based services in the framework of the Internet of Things. A game-theoretical approach [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/102642 / TESIS
226

Measuring, analysing and explaining the value of travel time savings for autonomous driving

Kolarova, Viktoriya 29 October 2021 (has links)
Autonomes Fahren (AF) wird potenziell die Präferenzen für die im Auto verbrachte Zeit stark beeinflussen und dementsprechend den Wert der Reisezeit, der ein Schlüsselelement von Kosten-Nutzen-Analysen im Verkehr ist. Die Untersuchung dieses Aspekts des AF ist daher entscheidend für die Analyse potenzieller Auswirkungen der Technik auf die zukünftige Verkehrsnachfrage. Trotz der steigenden Anzahl an Studien zu diesem Thema, gibt es noch erhebliche Forschungslücken. Der Fokus der Dissertation ist die potenziellen Änderungen des Reisezeitwerts, die durch das AF entstehen, zu messen sowie ihre Determinanten zu analysieren. Es wurden sowohl qualitative Ansätze als auch quantitative Methoden verwendet. Dabei wurden zwei Konzepte von AF betrachtet: privates und geteiltes autnomes Fahrzeug. Die Ergebnisse der Analysen zeigen einen niedrigeren Wert der Reisezeitersparnis beim AF im Vergleich zum manuellen Fahren, allerdings nur auf Pendelwegen. Das private Fahrzeug wird als eine attraktivere Option als ein geteiltes Fahrzeug wahrgenommen, jedoch unterscheiden sich die Nutzerpräferenzen für geteilte Fahrzeug stark zwischen den durchgeführten Studien. Individuelle Charakteristiken, wie Erfahrung mit Fahrassistenzsystemen, beeinflussen stark die Wahrnehmung der Zeit im AF; andere sozio-demographischen Faktoren, wie Alter und Geschlecht haben vor allem einen indirekten Effekt auf den Reisezeitwert indem sie Einstellungen potenzieller Nutzer beeinflussen. Die Verbesserung des Fahrterlebnisses durch das AF und das Vertrauen in die Technik sind wichtige Determinanten der Reisezeitwahrnehmung. Fahrvergnügen und andere wahrgenommene Vorteile vom manuellen Fahren gleichen in einem gewissen Ausmaß den Nutzen vom AF aus. Es wurden Reisezeitwerte für unterschiedliche potenzielle Nutzersegmente berechnet. Abschließend wurden politische Implikationen, Empfehlungen für die Entwicklung von AF sowie Empfehlungen für künftige Studien und potenziellen Forschungsgebiete abgeleitet. / Autonomous driving will potentially strongly affect preferences for time spent in a vehicle and, consequently, the value of travel time savings (VTTS). As VTTS is a key element of cost-benefit analysis for transport, these interrelations are crucial for analysing the potential impact of the technology on future travel demand. Despite the increasing number of studies dedicated to this topic there are still many unanswered questions. The focus of the thesis is to measure potential changes in the VTTS resulting from the introduction of autonomous driving and analyse their determinants. Qualitative approaches and quantitative methods were used. Two concepts of AVs were considered: a privately-owned AV (PAV) and a shared AV (SAV). The analysis results suggest lower VTTS for autonomous driving compared to manual driving, but only on commuting trips. A PAV is perceived as a more attractive option than an SAV, but user preferences for SAVs vary between the conducted studies. Individual characteristics, such as experience with advanced driver assistance systems, strongly affect the perception of time in an AV; other socio-demographic factors, such as age and gender, affect mode choices and the VTTS mainly indirectly by influencing the attitudes of potential users. The improvement in travel experiences due to autonomous driving and trust in the technology are important determinants of the perception of travel time. Enjoyment of driving and other perceived benefits of manual driving partially counterbalance the utility of riding autonomously. VTTS for different potential user segments were calculated. In conclusion, several policy implications, development recommendations for AVs as well as recommendations for future studies and potential research avenues are derived from the findings.
227

Was zieht uns an? Empirische Grundlagen für eine verbesserte Abbildung der Einkaufszielwahl in Verkehrsnachfragemodellen / Variabilität, Motive und räumliche Muster der Geschäftswahl

Cyganski, Rita 23 November 2020 (has links)
Eine große Herausforderung für Verkehrsmodelle stellt die korrekte Abbildung der Entscheidungsmuster bei der Zielwahl dar. Diese bestimmt die räumlichen Strukturen der Nachfrage und steht in engem Zusammenhang mit zentralen Ergebnissen der Nachfragemodellierung. Rund ein Drittel der Alltagswege in Deutschland sind Einkaufs- und Erledigungwege. Zahlreiche Arbeiten zeigen die Bedeutung von habitualisierten Verhaltensmustern bei der Wahl eines Einkaufsortes. Die Motive der Geschäftswahl gelten als sehr vielfältig. Besondere Bedeutung wird zudem den Primäraktivitätenorten zugeschrieben. Gleichwohl erfolgt die Abbildung der Zielwahl in der Nachfragemodellierung zumeist sehr vereinfachend. Gewöhnlich wird von einem Versorgungseinkauf mit der Geschäftsgröße und der Anreisezeit ausgegangen. Diese Arbeit zeigt anhand empirischer Auswertungen Möglichkeiten einer verhaltensorientierten Abbildung der Einkaufszielwahl in mikroskopischen Personenverkehrsmodellen auf. Im Fokus stehen die Variabilität der Geschäftswahl, die ausschlaggebenden Motive sowie die räumlichen Bezugspunkte der Suche. Am Beispiel des Erwerbs von Nahrungs- und Genussmitteln, von Textilien sowie von Unterhaltungselektronik werden Unterschiede zwischen Einkaufswaren verschiedener Fristigkeit, aber auch zwischen verschiedenen Personengruppen herausgearbeitet. Simulationsrechnungen mit dem Nachfragemodell TAPAS zeigen, dass eine Differenzierung der Einkaufsart sowie die Nutzung eines motivgestützen Erreichbarkeitsmaßes die Modellierungsergebnisse stark verbessern. Die Arbeit stellt erweiterte Indikatoren für eine Berücksichtigung der räumlichen Bezugspunkte bei der Beurteilung der Modellierungsergebnisse bereit. Auch stehen mit den Analysen der Aktivitätenräume, der Umwegfaktoren, der Lage der Einkaufsorte sowie der kumulierten Reiseweiten Informationen zur Verfügung, die generell für die Definition adäquater Suchräume und Bezugspunkte für die Modellierung städtischer Untersuchungsgebiete genutzt werden können. / A major challenge in travel demand modelling is the correct representation of decision patterns underlying the choice of destinations. This choice determines the spatial structures of demand and is closely related to central modelling results. Around one third of everyday trips in Germany are for shopping and errands. Numerous studies show the importance of habitualised behavioral patterns when choosing a shopping location. The motives for choosing a shop are considered to be very diverse. Particular importance is attributed to primary activity locations. Nevertheless, the representation of the target choice in demand modelling is usually very simplified. Usually, a supply purchase is implicitly assumed, with the size of the shop and travel time from the previous location being the most important choice criteria. Using empirical analyses, this dissertation shows possibilities for a behavior-oriented depiction of shopping location choice in microscopic passenger transport models. These are discussed in terms of their usability for modeling. The analyses focus on the variability of destinations, the decisive motives and the spatial reference points of the location search. Using the example of the purchase of food and beverages, textiles and consumer electronics, differences between shopping goods of different periodicity and also different groups of people are presented. Simulation calculations with the demand model TAPAS show that a differentiation of the type of purchase and the use of a motive-based accessibility measure greatly improves the modelling results. The dissertation provides extended indicators for a consideration of spatial reference points in the evaluation of the modelling results. Furthermore, the analyses of activity areas, diversion factors, the location of shopping locations and cumulative travel distances provide information that can be generally used to define adequate search areas and reference points for the modelling of urban study areas.Einkaufsverhalten

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