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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.
171

Evaluating the environmental impacts of bus priority strategies at traffic signals

Zhang, Jing January 2011 (has links)
Buses, the main form of public transport in many urban areas, are considered as an efficient and environmentally friendly transport mode because of their high passenger capacity. The concept of bus priority was originally proposed to protect buses from urban traffic congestion so that buses can be perceived as a faster mode than private cars. One such measure which is expanding in extent and sophistication is bus priority at traffic signals – or Bus Signal Priority (BSP) Strategies. The previous research on BSP has mostly focused on its effectiveness on improving bus efficiency and bus regularity/punctuality, as well as the impacts on general traffic. However the potential environmental impacts that could be caused by BSP have not been studied, particularly on emissions - despite this being an increasingly important criterion in transport assessments. For bus priority implementations this could be particularly important, if the small disbenefits to a large number of the nonpriority vehicles outweigh the benefits to buses. This lack of knowledge and potential concern has been the main motivation for this research. The thesis sets out a comprehensive review on the state-of-the-art BSP systems and evaluation approaches. It revealed that microscopic traffic simulation models are the most appropriate approach for this study with the ability to model different BSP strategies in various user-defined scenarios. The Aimsun model was selected after review and comparison. From the review on the measurement and modelling approaches for transport related emissions, instantaneous emission models were found to be able to estimate emission behaviour by relating emission rates to vehicle operation during a series of short time intervals (often one second) and for a small scale. This was required by this study as at junction areas emissions could be dominated by vehicle operational modes where the traditionally ‘average speed’ models were unable to accurately capture the emission variations. The dynamic and individual-oriented features of microsimulation models and instantaneous emission models enabled their integration at various spatial and temporal levels and at different levels of vehicle aggregation. After calibration and validation to some critical parameters in Aimsun, a signalised junction under VA control was set up, and two BSP strategies were modelled, - one including green extension and early green recall facilities and the other one including additional compensation and inhibition facilities. These strategies were applied to 18 typical scenarios, involving variables of ‘degree of saturation’, traffic flows and bus flows. The results illustrated the importance of strategy optimising in the more challenging conditions of junctions operating under high degrees of saturation and /or high bus flows. The worst-case scenario was in heavy traffic conditions with high bus flows and BSP on the minor road only, when emissions could increase by about 10%. Under a free flow condition implementing BSP on the main road is an environmentally friendly measure with emissions reductions of up to 6%.The thesis also describes a method to value emissions in monetary terms, so that operational and emissions impacts can be compared in common units. Application of this method indicated that the impact of emissions is much smaller than that for delay/journey time impacts, though some under-estimation in emissions valuation is suspected.
172

From user behaviours to collective semantics

Au Yeung, Ching Man January 2009 (has links)
The World Wide Web has developed into an important platform for social interactions with the rise of social networking applications of dierent kinds. Collaborative tagging systems, as prominent examples of these applications, allow users to share their resources and to interact with each other. By assigning tags to resources on the Web in a collaborative manner, users contribute to the emergence of complex networks now commonly known as folksonomies, in which users, documents and tags are interconnected with each other. To reveal the implicit semantics of entities involved in a folksonomy, one requires an understanding of the characteristics of the collective behaviours that create these interconnections. This thesis studies how user behaviours in collaborative tagging systems can be analysed to acquire a better understanding of the collective semantics of entities in folksonomies. We approach this problem from three different but closely related perspectives. Firstly, we study how tags are used by users and how their different intended meanings can be identified. Secondly, we develop a method for assessing the expertise of users and quality of documents in folksonomies by introducing the notion of implicit endorsement. Finally, we study the relations between documents induced from collaborative tagging and compare them with existing hyperlinks between Web documents. We show that, in each of these scenarios, it is crucial to consider the collective behaviours of the users and the social contexts in order to understand the characteristics of the entities. This project can be considered as a case study of the Social Web, the research outcomes of which can be easily generalised to many other social networking applications. It also fits into the larger framework for understanding the Web set out by the emerging interdisciplinary field of Web Science, as the work involves analyses of the interactions and behaviour of Web users in order to understand how we can improve existing systems and facilitate information sharing and retrieval on the Web.
173

Train scheduling with application to the UK rail network

Khosravi, Banafsheh January 2013 (has links)
Nowadays, transforming the railway industry for better performance and making the best usage of the current capacity are the key issues in many countries. Operational research methods and in particular scheduling techniques have a substantial potential to offer algorithmic solutions to improve railway operation and control. This thesis looks at train scheduling and rescheduling problems in a microscopic level with regard to the track topology. All of the timetable components are fixed and we aim to minimize delay by considering a tardiness objective function and only allowing changes to the order and to the starting times of trains on blocks. Various operational and safety constraints should be considered. We have achieved further developments in the �eld including generalizations to the existing models in order to obtain a generic model that includes important additional constraints. We make use of the analogy between the train scheduling problem and job shop scheduling problem. The model is customized to the UK railway network and signaling system. Introduced solution methods are inspired by the successful results of the shifting bottleneck to solve the job shop scheduling problems. Several solution methods such as mathematical programming and different variants of the shifting bottleneck are investigated. The proposed methods are implemented on a real-world case study based on London Bridge area in the South East of the UK. It is a dense network of interconnected lines and complicated with regard to stations and junctions structure. Computational experiments show the effciency and limitations of the mathematical programming model and one variant of the proposed shifting bottleneck algorithms. This study also addresses train routing and rerouting problems in a mesoscopic level regarding relaxing some of the detailed constraints. The aim is to make the best usage of routing options in the network to minimize delay propagation. In addition to train routes, train entry times and orders on track segment are defined. Hence, the routing and scheduling decisions are combined in the solutions arising from this problem. Train routing and rerouting problems areformulated as modified job shop problems to include the main safety and operational constraints. Novel shifting bottleneck algorithms are provided to solve the problem. Computational results are reported on the same case study based on London Bridge area and the results show the efficiency of one variant of the developed shifting bottleneck algorithms in terms of solution quality and runtime.
174

A paradox of privacy : unravelling the reasoning behind online location sharing

Zafeiropoulou, Aristea-Maria January 2014 (has links)
With the emergence of web applications that enabled user-generated content and social interactions, the Web became a place where people can engage in a number of new activities. With the success of smart enabled devices people now actively share their location data through various applications. However, as this thesis reveals, location plays a primal role in linking and inferring new information about people, often without their knowledge or consent. Due to this inferential power of location data new privacy concerns arise, as the actual affordances of their data are far greater than people are even aware of. Regardless of the numerous controversies around privacy, people keep on sharing their data on the Web. However, privacy systems themselves (and the ways in which individuals express their preferences) have changed very little. This thesis argues that understanding the mechanisms that people employ in their privacy decisions can provide fundamental insight for the design of privacy systems. The main focus of this thesis is to understand the underlying reasons why people share their location and whether their disclosure behaviour is paradoxical when compared with their stated attitudes towards location sharing. The first part of this thesis involves a study comprising of an online survey that addresses these two issues. The findings provide supporting evidence that people's location sharing decisions are indeed paradoxical in comparison with their stated attitudes and that privacy decision-making can be seen as a process of structuration, in the sense that people's decisions are tempered by contextual factors (external structures). The second part comprises of a series of focus groups that act as a follow-up study and aim to explore in more detail the underlying reasons behind people's sharing decisions. The findings show that people's decisions are influenced by a number of different contextual factors, grouped together into three main categories; social capital, trust in the application and functionality. Based on the outcomes of the two studies, a conceptual model was developed, called the Isorropic Model, that points out the prominent role of context in privacy decision-making and stresses the need for more dynamic privacy systems.
175

Modelling motorcycles driving cycles and emissions in Edinburgh

Kumar, Ravindra January 2009 (has links)
The level of ownership and use of motorcycling has increased rapidly in Edinburgh and the UK in the last ten years. In this study, motorcycle driving cycles (rural and urban) were developed for Edinburgh (Edinburgh Motorcycle Driving cycle-EMDC). The analysis of EMDC demonstrates that motorcycles‘ driving behaviour differs between urban and rural areas. EMDC shows a typical transient nature of speed, acceleration and deceleration, which is also different from regulatory driving cycles (Economic Commission for Europe-ECE and World Motorcycle Test Cycle-WMTC) and examples from Asia (Taiwan, Bangkok and China). This research underlines the need for detailed investigations of driving cycles in any local condition. It is not generally feasible for a driving cycle developed in one area to be applicable in another area, even with some similar characteristics. Emission factors were also estimated using onboard, laboratory and micro simulation measurements along the test corridor (Air Quality Management Area-AQMA). Laboratory measurements were carried out by applying a number of standard driving cycles (ECE and WMTC) and the derived EMDCs. Results show that the emission factors (EFs) calculated in the laboratory for carbon monoxide (CO) and Hydrocarbons (HC) are higher for the urban EMDC cycle compared to the standard regulatory factors than they are for the rural (except Nitrogen Oxide-NOx). Laboratory emission factors for CO and HC for the urban EMDC were found to be higher than the micro-simulation and onboard methods. EFs obtained from micro-simulation and onboard emissions using the National Atmospheric Emission Inventory (NAEI) emission coefficients were not very different with the exception of NOx, which were relatively higher than those of EMDC. Micro simulation models were mainly developed for private cars and therefore special care should be taken when using them for modelling other conditions (e.g. motorcycles driving characteristics). This study illustrates the extent to which micro-simulation may be utilised to accurately model emissions and discusses the refinements required to model motorcycle motion (hence emission) accurately in micro simulation. The study provides a platform for a large number of potential future applications for the evaluation of emissions and for developing various policy scenarios of pollution reduction and reducing health impacts at local levels.
176

Industrial relations in the UK shipping industry since the Second World War

McConville, J. January 1982 (has links)
The shipping industry has undergone a period of rapid and fundamental change during the three decades since the end of the Second World War. While these changes have been experienced world-wide and have promoted the implementation of technological advances and the growth of the world fleet, they have occurred during a period which has also witnessed a substantial relative decline in Britain's maritime position. It is the aim of this study to analyse their effect on industrial relations in the U.K. shipping industry.
177

The effectiveness of marketing communication through social media on small to medium size enterprises (SMES) in Kuwait

Alqaoud, Faisal January 2015 (has links)
This thesis is concerned with two major areas: marketing communication via social media and small to medium size enterprise marketing for Kuwaiti SMEs. The researcher has been looking carefully at major social media sites such as Facebook, Twitter, Instagram and others by opening accounts and being involved in daily interactions in them. They have been observing and witnessing the great potential of social media and that led to five questions concerning social media marketing and its usefulness to SMEs in Kuwait. (i) Can SMEs market their products and services better through using social media rather than traditional media? (ii) Can SMEs reach their target customers through social media more easily than through traditional media? (iii) What are the benefits of marketing communication in social media? (iv) Can marketing communication be more effective by using social media rather than using traditional media? (v) Can Kuwait benefit from SMEs’ empowerment to improve its economy by reducing dependency on oil production? It was from these questions, the topic of this thesis was born, which is investigating the effectiveness of marketing communication through social media for SMEs in Kuwait. Primary data were collected through depth interviews from the owners/managers of Kuwaiti SMEs. Grounded theory as Strauss and Corbin was used. Five models are developed and recommendations made to improve the effectiveness of social media marketing communications for SMEs in Kuwait.
178

Espectroscopia de alcalinos em Hélio líquido / Spectroscopy of Alkali in Liquid Helium

Lucas Modesto da Costa 11 March 2010 (has links)
Átomos alcalinos são boas sondas para compreender as propriedades do He líquido. Considerável atenção experimental tem sido empregada para analisar as mudanças da posição e da largura da linha do espectro de absorção de átomos alcalinos imersos em um ambiente de He líquido. No lado teórico, vários estudos têm usado modelos simplificados como o modelo de bolhas e o modelo de agregado. Considerações de modelos mais realista agora são oportunas e relevantes. Neste trabalho, nós usamos a combinação da simulação de Monte Carlo (MC) e cálculos ab-initio de mecânica quântica (MQ). As configurações do líquido foram geradas para cálculos posteriores de MQ.Umimportante aspecto é a complexa interação interatômica do par He-He. Usando potenciais parametrizados, as simulações clássicas de MC foram efetuadas para sistemas alcalinos (Na, Rb, Cs e Na2) em He líquido e as condições foram T = 3 K e p = 1 atm. Estruturas estatisticamente descorrelacionadas formadas por um elemento alcalino central, envolvido pela primeira camada de solvatação completa, são amostradas e submetidas em um cálculo do espectro com DFT dependente do tempo usando diferentes funcionais híbridos e conjuntos de bases. Usando os funcionais PBE1PBE e O3LYP com conjuntos de bases extensos obtemos o deslocamento espectral em excelente concordância com os resultados experimentais para os sistemas de um único átomo alcalino. Para comparação, também usamos um modelo de agregado com 14 átomos de He em volta do átomo alcalino obtendo excelentes resultados também. O raio do modelo de agregado convergiu para perto do máximo da primeira camada de solvatação da função de distribuição radial. Um ponto adicional a ser considerado é o cálculo da largura da linha obtido com a simulação em He líquido que é discutida neste trabalho. Para o átomo de Rb, a energia de excitação em He líquido é em torno de -18,9 nm. Com a simulação em ambiente de He líquido obtivemos os melhores resultados entre -16,3 nm e -23,3 nm. O valor do deslocamento espectral usando o modelo de agregado ficou entre os -17,3 nm e - 22,3 nm. Os dois modelos apresentam o mesmo raio da bolha, por volta de 6-7Å. Para outros sistemas, como Na e Cs, encontramos a mesma convergência entre o modelo de agregado, a simulação do He líquido e os resultados experimentais. Para o sistema contendo Na2, os valores obtidos ficaram em boa concordância com os valores experimentais. / Alkali atoms are good probes for the understanding of liquid He properties. As such considerable experimental attention has been devoted to the analysis of the changes of line position and widths of the absorption spectra of alkali atoms in liquid He environment. On the theoretical side, several studies have used simplified models such as bubble and cluster models. Considerations of more realistic models are now timely and relevant. In this work, we use a combination of Monte Carlo (MC) simulation and ab initio quantum mechanical (QM) calculations. Liquid configurations are generated for subsequent QM calculations. One important aspect is the consideration of the complex interatomic interaction of the He-He pair. Using parametrized potentials, classical MC simulations are made for the alkali systems (Na, Rb, Cs and Na2) in liquid He. The conditions were T=3K and p=1 atm. Statistically uncorrelated configurations composed of a central alkaline element, surrounded by the full first solvation shell, are sampled and submitted to time-dependent DFT calculations of the spectrum using dierent hybrids functionals and dierents basis sets. Using the PBE1PBE and O3LYP functionals with large basis sets we obtained a spectral shift in excellent agreement with experiment for the systems of single alkaline atom. For comparison, we also used a cluster model and obtained 14 He atoms around the alkali atom with excellent results too. The radius of the cluster model converged to a value close to the maximum of the first solvation shell in radial distribution function. An additional point considered is the calculation of the spectral line width using the liquid simulation also discussed in this work. For Rb atom, the excitation energy in liquid He is about -18.9 nm. With the liquid He environment simulation we obtained the best results between -16.3 nm and -23.3 nm. The values of the spectral shift using the cluster model were between -17.3 nm and 22.3 nm. The two models show the same bubble radius, about 6-7Å. For the others system, like Na and Cs, we found the same convergence between the cluster model, the simulation of the He liquid and the experimental results. For Na2, the values obtained were in good agreement to the experimental values.
179

Late Eocene Uplift of the Al Hajar Mountains, Oman, Supported by Stratigraphy and Low-Temperature Thermochronology

Hansman, Reuben J., Ring, Uwe, Thomson, Stuart N., den Brok, Bas, Stübner, Konstanze 12 1900 (has links)
Uplift of the Al Hajar Mountains in Oman has been related to either Late Cretaceous ophiolite obduction or the Neogene Zagros collision. To test these hypotheses, the cooling of the central Al Hajar Mountains is constrained by 10 apatite (U-Th)/He (AHe), 15 fission track (AFT), and four zircon (U-Th)/He (ZHe) sample ages. These data show differential cooling between the two major structural culminations of the mountains. In the 3km high Jabal Akhdar culmination AHe single-grain ages range between 392 Ma and 101 Ma (2 sigma errors), AFT ages range from 518 Ma to 324 Ma, and ZHe single-grain ages range from 62 +/- 3Ma to 39 +/- 2 Ma. In the 2 km high Saih Hatat culmination AHe ages range from 26 +/- 4 to 12 +/- 4 Ma, AFT ages from 73 +/- 19Ma to 57 +/- 8 Ma, and ZHe single-grain ages from 81 +/- 4 Ma to 58 +/- 3 Ma. Thermal modeling demonstrates that cooling associated with uplift and erosion initiated at 40 Ma, indicating that uplift occurred 30 Myr after ophiolite obduction and at least 10 Myr before the Zagros collision. Therefore, this uplift cannot be related to either event. We propose that crustal thickening supporting the topography of the Al Hajar Mountains was caused by a slowdown of Makran subduction and that north Oman took up the residual fraction of N-S convergence between Arabia and Eurasia.
180

Dyscalculia in higher education

Drew, Simon January 2016 (has links)
This research study provides an insight into the experiences of dyscalculic students in higher education (HE). It explores the nature of dyscalculia from the student perspective, adopting a theoretical framework of the social model of disability combined with socio-cultural theory. This study was not aimed at understanding the neurological reasons for dyscalculia, but focussed on the social effects of being dyscalculic and how society can help support dyscalculic students within an HE context. The study s primary data collection method was 14 semi-structured interviews with officially identified dyscalculic students who were currently, or had been recently, studying in higher education in the UK. A participant selection method was utilised using a network of national learning support practitioners due to the limited number of participants available. A secondary data collection method involved reflective learning support sessions with two students. Data were collected across four research areas: the identification process, HE mathematics, learning support and categorisations of dyscalculia. A fifth area of fitness to practise could not be examined in any depth due to the lack of relevant participants, but the emerging data clearly pinpointed this as a significant area of political importance and identified a need for further research. A framework of five categories of dyscalculic HE student was used for data analysis. Participants who aligned with these categories tended to describe differing experiences or coping behaviours within each of the research areas. The main findings of the study were the importance of learning support practitioners in tackling mathematical anxiety, the categorisations of dyscalculic higher education students, the differing learning styles of dyscalculic and dyslexic students, and the emergence of four under-researched dyscalculic characteristics: iconicity, time perception, comprehension of the existence of numbers that are not whole and dyscalculic students understanding of non-cardinal numbers.

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