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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.
101

Monitoring railway track condition using inertial sensors on an in-service vehicle

Yeo, Graeme James January 2017 (has links)
Effective maintenance of railway track is critical for the safe operation of any railway network. Efficient maintenance may also result in economic benefits for rail operators. The work in this thesis looks into how an inexpensive measurement system could be fitted to in-service railway vehicles such as commuter trains, to provide a relatively high frequency of measurement on their routes of operation, when compared to dedicated measurement vehicles. This thesis describes how a prototype inertial measurement system was designed and built, and fitted to a commuter train operating in the region south of London, UK. Inertial data is processed to provide a vertical profile of the track. A novel use of a modified Bryson-Frazier filter is used to produce vertical profile datasets which are repeatable to within 0.2 mm. Profiles calculated from multiple passes of the same areas of track are compared to show track degradation. Methods of estimating track stiffness are developed using vertical geometry data from repeated passes of the same track sections at differing speeds. Some correlation to stiffness is shown through the results, but exact measurements were not possible. Finally, two case studies are presented which show findings at a bridge approach, and through two level crossings.
102

An investigation of the slipstreams and wakes of trains and the associated effects on trackside people and objects

Jordan, Sarah Catherine January 2008 (has links)
A mathematical model is developed which predicts if a person or a pushchair is destabilised by a train's slipstream. The model simulates the mean slipstream velocity time history using the theories of potential flow, boundary layer growth and wake decay. The turbulence-induced fluctuations are reproduced with an autoregressive model. A randomised person is generated and subjected to the simulated slipstream, and their response is modelled by a simple solid object and a mass-spring-damper system. If the slipstream forces cause the person to be displaced by a critical distance the person is destabilised. A randomised pushchair is also generated and positioned so as to be capable of being destabilised by either toppling over or moving along the ground on its wheels. A toppling pushchair is modelled as a simple solid object in a similar manner to that of a person, and a pushchair will move along the ground on its wheels if the slipstream force is greater than the frictional force. Greater numbers of destabilised people and pushchairs are associated with the slipstream of a freightliner than that of a passenger train, increasing train speed and decreasing distance from the train side.
103

Railway traffic flow optimisation with differing control systems

Zhao, Ning January 2013 (has links)
This thesis describes the development of a multi-train simulator in which different train control systems are simulated on a common section of high-speed line operating with four trains. The simulator is used to estimate and compare train knock-on delay performance with different signalling systems. This thesis further demonstrates a train trajectory optimisation work. Four searching approach have been implemented to find, for a specific train, the most appropriate target speed in different areas in order to minimise energy usage and delays. A West Coast Main Line case study is presented in order to assess the operational impact of using optimised train trajectory and different practical train control system configurations combined with three different operating priorities. The result shows that, by using more advanced signalling systems or optimal train trajectories, interactions between trains can be reduced, thereby improving performance. This also has the effect of reducing the energy required to make a particular journey. Simple control systems when coupled with the optimisation process have been shown to have similar performance to the more advanced signalling systems. The use of a dynamic programming allows an objective function to be minimised with the best results and an acceptable computation time.
104

Experimental investigation of the aerodynamics of a class 43 high speed train

Gallagher, Martin January 2017 (has links)
This study aims to investigate the aerodynamic phenomena of passenger trains by undertaking a series of experimental investigations into the aerodynamics of a Class 43 high speed train (HST). A contextual research background is presented with regards to two significant aerodynamic phenomena - slipstreams and crosswinds. Model-scale experiments were undetaken on a l/25th scale HST model at the TRAIN rig moving model rig facility in order to measure slipstreams at a range of trackside positions and with different ballast heights. Crosswind effects were investigated through two model-scale tests and an extensive campaign of innovative train-based surface pressure measurements onboard an operational HST. A wind tunnel test investigated the flow field and pressure distribution around an HST power car and calculation of aerodynamic loads. A symmetrical pair of pressure taps at the train nose enabled yaw angle to be calculated at full scale. A scale-model test using a crosswind generator was undertaken and the magnitudes of aerodynamic loads compared very favorably with the wind tunnel data. The novel full scale it has been possible it isolate open-air data and gusts, and estimate the overturning forces due to crosswinds by a considered approach to surface pressure measurements.
105

Improved railway vehicle inspection and monitoring through the integration of multiple monitoring technologies

Zhang, Zhenhe January 2017 (has links)
The effectiveness and efficiency of railway vehicle condition monitoring is increasingly critical to railway operations as it directly affects safety, reliability, maintenance efficiency, and overall system performance. Although there are a vast number of railway vehicle condition monitoring technologies, wayside systems are becoming increasingly popular because of the reduced cost of a single monitoring point, and because they do not interfere with the existing railway line. Acoustic sensing and visual imaging are two wayside monitoring technologies that can be applied to monitor the condition of vehicle components such as roller bearing, gearboxes, couplers, and pantographs, etc. The central hypothesis of this thesis is that it is possible to integrate acoustic sensing and visual imaging technologies to achieve enhancement in condition monitoring of railway vehicles. So this thesis presents improvements in railway vehicle condition monitoring through the integration of acoustic sensing and visual imaging technologies.
106

En demokratibestämmelse i mediestödet – hindrande åtgärd i TF:s mening? / “Democracy criterion” in Swedish state aid to the press – preventive action in violation of Freedom of the Press Act?

Wallin, Karin January 2019 (has links)
Swedish state aid to the press (presstödet) aims to ensure diversity in news publishing and advocacy and is considered to fill an important democratic function. However, the technical development has left the aid system obsolete, and plans are under way to replace the system in its current form with a technology neutral aid (mediestöd), addressing news media of all content forms and means of dissemination. A recurring debate in this context has been whether the new aid system is to include a so called “democracy criterion”, requiring publishing companies that receive aid to display “democratic values”. A corresponding rule already exists in the Swedish Radio and Television Act. The legal conditions surrounding such a rule targeting the press are, however, fundamentally different. Above all, it can be questioned whether a democracy criterion would cause the state aid to be considered a preventive action in violation of the Freedom of the Press Act, which forms part of the Swedish constitution. In this thesis, it is argued that so, in fact, would be the case. It is also maintained that arguments relating to the democracy promoting objective of the criterion are of no relevance to the legal analysis.
107

Development of an upgrade selection process for railway renewal projects

Chen, Xindi January 2017 (has links)
Currently, many railway systems need to be upgraded to meet the demand for rapidly increasing railway capability, environmental concerns and customer satisfaction, while there is a lack of the right models and tools required to support the early decision making stage of railway renewal projects. In this thesis, a new railway selection upgrade process is proposed, which aims to support early stage decision-making in railway renewal projects by finding the most appropriate solutions to take forward for more detailed consideration. The railway selection upgrade process consists of modelling, simulation, split into macros-assessment and micro-simulation, and evaluation. A high-level feasibility analysis model is developed for the macro-assessment, to help engineers efficiently select the most promising upgrade options for further detailed consideration using microscopic simulation. This process provides a quick and efficient way to quantify evaluation functions, based on the 4Cs (capacity, carbon, customer satisfaction and cost) framework, to give a final suggestion on the most appropriate upgrade options. Two case studies, based on the East Coast Main Lines and the Northern Ireland railway network, are presented in order to demonstrate the application and verify the feasibility of the high-level feasibility analysis model and the railway upgrade selection process.
108

Improving railway operations through the integration of macroscopic and microscopic modelling with optimisation

Umiliacchi, Silvia January 2016 (has links)
Britain's railway industry is implementing the vision of the system in the next thirty years, as outlined in the Rail Technical Strategy (2012); the main objectives to achieve are: carbon and cost reduction, capacity increase and customer satisfaction. The timetable design process is identified as a key enabler of the strategy's implementation. The current method in use is considered as a lengthy process with little computer support and optimisation. This study tries to overcome the outlined weaknesses of the existing method by proposing a more automated process in which the optimisation of a timetable is a properly design stage. The method has been applied to minimise the total energy consumption of five trains on the Aberdeen-Inverness line, while meeting operational and safety constraints. The results showed a reduction in the total energy consumption of 7%, while the average train total journey time is increased by 1% in comparison with the initial schedule.
109

Improving railway safety : risk assessment study

Chen, Yao January 2013 (has links)
Railway safety is very important, as it concerns human lives. Therefore identifying risks from possible failures is vital to maintain the safety of railways. Currently, many mature tools, such as fault tree analysis and event tree analysis, are applied to investigate possible risks to railway safety. However, in many circumstances, the applications of these tools are unable to provide satisfactory results when the risk data is incomplete or there is a high level of uncertainty involved in the risk dataThus it is essential to develop new methods to overcome the weakness of current assessment tools. This thesis introduces an improved intelligent system for risk analysis usingfuzzy reasoning approach (FRA) and improved fuzzy analytical hierarchy decision making process (Fuzzy-AHP), which is specially designed and developed for the railways, and able to deal with the uncertainty in risk assessment.
110

A Framework for Evaluating Recommender Systems

Bean, Michael Gabriel 01 December 2016 (has links)
Prior research on text collections of religious documents has demonstrated that viable recommender systems in the area are lacking, if not non-existent, for some datasets. For example, both www.LDS.org and scriptures.byu.edu are websites designed for religious use. Although they provide users with the ability to search for documents based on keywords, they do not provide the ability to discover documents based on similarity. Consequently, these systems would greatly benefit from a recommender system. This work provides a framework for evaluating recommender systems and is flexible enough for use with either website. Such a framework would identify the best recommender system that provides users another way to explore and discover documents related to their current interests, given a starting document. The framework created for this thesis, RelRec, is attractive because it compares two different recommender systems. Documents are considered relevant if they are among the nearest neighbors, where "nearest" is defined by a particular system's similarity formula. We use RelRec to compare output of two particular recommender systems on our selected data collection. RelRec shows that LDA recommeder outperforms the TF-IDF recommender in terms of coverage, making it preferable for LDS-based document collections.

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