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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.
41

Damage stability of ships as a safety criterion for optimisation tools

Saydan, Deniz January 2006 (has links)
A literature overview of past optimisation studies revealed that whilst satisfaction of intact stability requirements has been built into existing alternative hull form optimisation packages, seeking improved hydrodynamic hull forms in terms of seakeeping, calm water resistance and added resistance, damage stability is not an automated feature. Within the context of the hydrodynamic hull form optimisation techniques their application to novel hull forms would only permit use of deterministic damage stability analysis and as this is not straight-forward damage is applied after the hull is optimised. The damage must be relevant to ship type and applied in appropriate locations with sensible extents of damage. To fulfil this need both the Marine Accident Investigation Branch (MAIB) damage data base and a damage data base generated by Lutzen (2002) are interrogated and findings are reported. The hydrodynamic analysis of the optimised hull and basis hull for the intact and damage cases is thereafter carried out using a three-dimensional singularity distribution method. The relative vertical motion responses of both intact and damaged hull forms are determined with greater structural cross-coupling than is usually applied in the solution of the equations of ship motions. This has necessitated the development of a novel approach to implement the calculation of the pure and product moment of inertias for the intact and damaged hull forms to facilitate meaningful comparison of intact and damaged ship motions. The processes are equally applicable to any kind of ship.
42

Hygrothermal ageing and its effects on the flexural properties and failure modes of plant oil based composites for maritime applications

Valgma, Mari January 2014 (has links)
This research looks at moisture uptake and its effects on the flexural properties of glass reinforced epoxy, linseed oil and castor oil composites. Water uptake damages the material through chemical, physical and mechanical ageing. At the same time there is a need to reduce the environmental effects of the maritime industry and using composites from renewable resources could be a viable solution. While the conventional composites like glass/epoxy are trusted as a structural material in harsh humid conditions, there is very little known about more sustainable composite materials. As resins have a greater environmental impact when manufactured, and no information on their long term performance is available, this research looks at the flexural performance of glass reinforced castor and linseed oil resins over 2 years of ageing in comparison with glass/epoxy. As a result of accelerated ageing it has been shown that the degradation of all three composites is significant, ranging between 18{87% over the 2 year testing period. The moisture equilibrium content in glass/epoxy was 2.11%, glass/castor oil 3.62% and glass/linseed oil 2.87%. While the moisture uptake of glass/epoxy follows an expected trend, the moisture uptake of plant oil based resin composites does not and differs from conventional models. After 2 years of ageing the properties of glass/castor oil are comparable with glass/epoxy. The degradation of properties in glass/linseed oil is the greatest. MicroCT and AE techniques were used to look at the failure modes in glass/epoxy and glass/linseed oil specimens showing changes in the failure mode of glass/linseed oil only after 3 days of ageing. The failure modes of glass/epoxy were found to be mainly fibre dominated and most of the damage occurred on the tensile side of the specimens while the failure in glass/linseed oil was largely dominated by compressive damage. For the first time the failure mechanisms of glass/linseed oil have been proposed.
43

Life extension of composite structures with application to all weather lifeboats

Roberton, D. M. V. January 2015 (has links)
With world shipping and other maritime based industries tending to operate assets requiring a large capital investment representing over half the total operating cost of the vessel, considering life extension at the end of a structure’s design life can postpone further capital investment and reduce the yearly operating costs of a particular asset for the owner. Despite this experience the concept of asset life extension for continued use once design life is exceeded is one which has been covered in very limited detail in the academic community. In more recent years the concept of asset life extension has become important to a growing number of maritime industries and as such has become an industry lead area for investigation, with the lead being taken by the Health and Safety Executive in the UK and other regulatory bodies abroad. The work presented here describes the investigations into life extension assessment of assets, with a special focus on the Severn class lifeboat fleet owned by the RNLI, who wish to assess the potential for life extension of this fleet to enable the continued use of a successful asset and offset a £120 million replacement program. The vessels themselves are a monolithic stiffened composite construction with a design life of 25 years. A methodology is devised which uses material static and fatigue data, environmental conditions and structural response data to determine the expected useful life of a composite structure. This methodology is then applied to the Severn class fleet by conducting experiments to determine the fatigue life of the materials through coupon tests, understanding the environmental conditions and the errors involved in predicting them and carrying out measurements of the structural response of a Severn class lifeboat whilst in service. Combining these variables using Monte Carlo simulations and the Miner’s rule allows an estimate of the useful life of the asset to be made.
44

A chart display and navigation information system for integrated bridge

Fawcett, Stephen P. M. January 1992 (has links)
No description available.
45

Cost modelling for inland waterway transport systems

Kader, Ab Saman Abd January 1997 (has links)
Inland waterways have proven to be a significant mode of infrastructure for the carriage of freight. Examples of this can be seen in many developed regions such as Continental Europe, the United States of America and to a lesser extent, the United Kingdom. The benefit resulting from the existence of waterways are enormous in both transportational and non-transportational benefits. Hence there are considerable benefits which will result from a sustained development of waterways. This study identifies all relevant parameters associated with the waterways system. They include the waterway route, the barge provision to carry the cargo and terminal facilities as an interface point for cargo handling operations. Methods have been determined to enable various costs to be estimated. This estimating procedure can be very useful for a preliminary evaluation of development proposals pending a more detailed cost analysis. Estimated benefits can also be quantified at this preliminary stage. Data has been collected from a number of reliable sources. Models have successfully been generated and each model has been validated to an acceptable level of accuracy. The analysis has been applied to a proposed development of an inland waterway transportation system in the Klang Valley region of Malaysia. The results indicate viability for the scheme and, moreover, show the degree to which designers and planners can benefit from the use of the models.
46

Quantitative human reliability assessment in marine engineering operations

Abujaafar, Khalifa Mohamed January 2012 (has links)
Marine engineering operations rely substantially on high degrees of automation and supervisory control. This brings new opportunities as well as the threat of erroneous human actions, which account for 80-90% of marine incidents and accidents. In this respect, shipping environments are extremely vulnerable. As a result, decision makers and stakeholders have zero tolerance for accidents and environmental damage, and require high transparency on safety issues. The aim of this research is to develop a novel quantitative Human Reliability Assessment (HRA) methodology using the Cognitive Reliability and Error Analysis Method (CREAM) in the maritime industry. This work will facilitate risk assessment of human action and its applications in marine engineering operations. The CREAM model demonstrates the dynamic impact of a context on human performance reliability through Contextual Control Model controlling modes (COCOM-CMs). CREAM human action analysis can be carried out through the core functionality of a method, a classification scheme and a cognitive model. However, CREAM has exposed certain practical limitations in its applications especially in the maritime industry, including the large interval presentation of Human Failure Probability (HFP) values and the lack of organisational factors in its classification scheme. All of these limitations stimulate the development of advanced techniques in CREAM as well as illustrate the significant gap between industrial needs and academic research. To address the above need, four phases of research study are proposed. In the first phase, the adequacy of organisation, one of the key Common Performance Conditions (CPCs) in CREAM, is expanded by identifying the associated Performance Influencing Factors (PIFs) and sub-PIFs in a Bayesian Network (BN) for realising the rational quantification of its assessment. In the second phase, the uncertainty treatment methods' BN, Fuzzy Rule Base (FRB) , Fuzzy Set (FS) theory are used to develop new models and techniques' that enable users to quantify HFP and facilitate the identification of possible initiating events or root causes of erroneous human action in marine engineering operations. In the third phase, the uncertainty treatment method's Evidential Reasoning (ER) is used in correlation with the second phase's developed new models and techniques to produce the solutions to conducting quantitative HRA in conditions in which data is unavailable, incomplete or ill-defined. In the fourth phase, the CREAM's prospective assessment and retrospective analysis models are integrated by using the established Multiple Criteria Decision Making (MCDM) method based on, the combination of Analytical Hierarchical Process (AHP), entropy analysis and Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS). These enable Decision Makers (DMs) to select the best developed Risk Control Option (RCO) in reducing HFP values. The developed methodology addresses human actions in marine engineering operations with the significant potential of reducing HFP, promoting safety culture and facilitating the current Safety Management System (SMS) and maritime regulative frameworks. Consequently, the resilience of marine engineering operations can be further strengthened and appreciated by industrial stakeholders through addressing the requirements of more safety management attention at all levels. Finally, several real case studies are investigated to show end users tangible benefits of the developed models, such as the reduction of the HFPs and optimisation of risk control resources, while validating the algorithms, models, and methods developed in this thesis.
47

Analysis of the propulsion and manoeuvring characteristics of survey-style AUVs and the development of a multi-purpose AUV

Palmer, Alistair Robin January 2009 (has links)
Autonomous Underwater Vehicles (AUVs) are a developing technology with multiple applications including oceanographic research, military missions and commercial activities such as oil and gas field exploration. The reported research covers two main areas, namely, the assessment of the survey performance of AUVs and the development of the next generation of multi-purpose AUVs. The performance characteristics of long range survey-style AUVs are examined and improvements in performance are sought through the use of hybrid devices. Hybrid devices are defined as those that provide both propulsion and manoeuvring forces. Two devices were chosen for detailed investigation; a vectored thruster and a collective and cyclic pitch propeller. The manoeuvring performance of both devices was found to be insufficient to justify the additional engineering complexity associated with them. The aim of the next generation of AUVs is to be able to combine long range survey capabilities with low speed investigation of the environment encountered. An assessment of a likely mission profile and a review of the available design options demonstrate that maintaining the survey efficiency of the AUV is of principal importance. Therefore the investigation focuses on approaches to the addition of low speed control to an existing survey-style AUV design using propeller based thrusters. Externally mounted thrusters and through-body tunnel thrusters are reviewed and new experimental investigations are reported to provide insight into the performance characteristics on a survey-style AUV hull form. The main body of the experimental programme characterises forward and aft mounted tunnel thruster performance over a range of forward speeds and small yaw angles. The results are used to develop a new, simple modelling procedure representing the performance of tunnel thrusters on an AUV which facilitates the incorporation of the characteristics of tunnel thrusters into numerical simulations of AUV performance. Such a simulation is used to examine approaches to undertaking the transition phase between high speed survey and low speed manoeuvring operation. The results demonstrate the advantageous nature of undertaking a smooth interchange between control approaches considering both the vehicle performance and the energy demands.
48

Cost-efficient resource management for scientific workflows on the cloud

Pietri, Ilia January 2016 (has links)
Scientific workflows are used in many scientific fields to abstract complex computations (tasks) and data or flow dependencies between them. High performance computing (HPC) systems have been widely used for the execution of scientific workflows. Cloud computing has gained popularity by offering users on-demand provisioning of resources and providing the ability to choose from a wide range of possible configurations. To do so, resources are made available in the form of virtual machines (VMs), described as a set of resource characteristics, e.g. amount of CPU and memory. The notion of VMs enables the use of different resource combinations which facilitates the deployment of the applications and the management of the resources. A problem that arises is determining the configuration, such as the number and type of resources, that leads to efficient resource provisioning. For example, allocating a large amount of resources may reduce application execution time however at the expense of increased costs. This thesis investigates the challenges that arise on resource provisioning and task scheduling of scientific workflows and explores ways to address them, developing approaches to improve energy efficiency for scientific workflows and meet the user's objectives, e.g. makespan and monetary cost. The motivation stems from the wide range of options that enable to select cost-efficient configurations and improve resource utilisation. The contributions of this thesis are the following. (i) A survey of the issues arising in resource management in cloud computing; The survey focuses on VM management, cost efficiency and the deployment of scientific workflows. (ii) A performance model to estimate the workflow execution time for a different number of resources based on the workflow structure; The model can be used to estimate the respective user and energy costs in order to determine configurations that lead to efficient resource provisioning and achieve a balance between various conflicting goals. (iii) Two energy-aware scheduling algorithms that maximise the number of completed workflows from an ensemble under energy and budget or deadline constraints; The algorithms address the problem of energy-aware resource provisioning and scheduling for scientific workflow ensembles. (iv) An energy-aware algorithm that selects the frequency to be used for each workflow task in order to achieve energy savings without exceeding the workflow deadline; The algorithm takes into account the different requirements and constraints that arise depending on the workflow and system characteristics. (v) Two cost-based frequency selection algorithms that choose the CPU frequency for each provisioned resource in order to achieve cost-efficient resource configurations for the user and complete the workflow within the deadline; Decision making is based on both the workflow characteristics and the pricing model of the provider.
49

Evenemangsturism : - En studie om besökarupplevelser

Ulstrup, Kim, Utter, Henrik, Waldubo, Martin January 2008 (has links)
<p>Ett evenemang är en isolerad händelse i tid och rum där en eller flera speciella aktiviteter äger rum. Besökarna på ett evenemang blir utsatta för en mängd olika upplevelser, både positiva och negativa. Syftet med denna avhandling var att undersöka vilka upplevelser som påverkade besökarna starkast på Skidskytte-VM i Östersund 2008 samt att jämföra resultatet med en tidigare forskningsrapport från Alpina VM i Åre 2007. Deltagande observationer gjorda av studenter på Mittuniversitetet i Östersund utgjorde grunden för studien. Där listades de bästa och sämsta upplevelserna av varje respondent under två dagars besök på evenemangen. Därefter sammanställdes de vanligast förekommande faktorerna för positiva respektive negativa upplevelser. Dessa studerades sen gentemot fyra olika teorier; kedjeteorin, kaosteorin, Maslows behovshierarki och Pine och Gilmores teori om besökarengagemang. Resultatet av studien visar ett antal gemensamma upplevelsefaktorer mellan de båda evenemangen. Efter att de grundläggande behoven var tillfredsställda utmärkte sig stämningen och aktivitetsutbudet som de viktigaste upplevelsefaktorerna. Framträdande kaosfaktorer identifierades under båda mästerskapen; kylan som överskuggade många andra upplevelser under VM i Östersund och de sportsliga framgångarna för Sverige under VM i Åre som skapande positiva upplevelser trots kyla och dåligt väder.</p><p>Nyckelord: Alpina VM, besökarbehov, evenemang, evenemangsturism, Skidskytte-VM, upplevelsefaktorer.</p> / ETOUR
50

Evenemangsturism : - En studie om besökarupplevelser

Ulstrup, Kim, Utter, Henrik, Waldubo, Martin January 2008 (has links)
Ett evenemang är en isolerad händelse i tid och rum där en eller flera speciella aktiviteter äger rum. Besökarna på ett evenemang blir utsatta för en mängd olika upplevelser, både positiva och negativa. Syftet med denna avhandling var att undersöka vilka upplevelser som påverkade besökarna starkast på Skidskytte-VM i Östersund 2008 samt att jämföra resultatet med en tidigare forskningsrapport från Alpina VM i Åre 2007. Deltagande observationer gjorda av studenter på Mittuniversitetet i Östersund utgjorde grunden för studien. Där listades de bästa och sämsta upplevelserna av varje respondent under två dagars besök på evenemangen. Därefter sammanställdes de vanligast förekommande faktorerna för positiva respektive negativa upplevelser. Dessa studerades sen gentemot fyra olika teorier; kedjeteorin, kaosteorin, Maslows behovshierarki och Pine och Gilmores teori om besökarengagemang. Resultatet av studien visar ett antal gemensamma upplevelsefaktorer mellan de båda evenemangen. Efter att de grundläggande behoven var tillfredsställda utmärkte sig stämningen och aktivitetsutbudet som de viktigaste upplevelsefaktorerna. Framträdande kaosfaktorer identifierades under båda mästerskapen; kylan som överskuggade många andra upplevelser under VM i Östersund och de sportsliga framgångarna för Sverige under VM i Åre som skapande positiva upplevelser trots kyla och dåligt väder. Nyckelord: Alpina VM, besökarbehov, evenemang, evenemangsturism, Skidskytte-VM, upplevelsefaktorer. / ETOUR

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