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Full-Text Articles in Engineering

Liquid Crystal Devices For Optical Communications And Sensing Applications, Sunish Mathews Nov 2011

Liquid Crystal Devices For Optical Communications And Sensing Applications, Sunish Mathews

Doctoral

This thesis is focussed on the design and development of liquid crystal based tunable photonic devices for applications in optical communications and optical sensing, with an emphasis on all-fiber device configuration. The infiltration of liquid crystals into photonic crystal fiber provides a suitable common platform to design and fabricate simple and compact all-fiber tunable photonic devices which can be easily integrated with optical fiber networks and sensing systems. Based on the infiltration of liquid crystals – materials with high dielectric anisotropy, into photonic crystal fibers a common platform is developed to address the need for electronically tunable photonic devices with …


Active Learning For Text Classification, Rong Hu Oct 2011

Active Learning For Text Classification, Rong Hu

Doctoral

Text classification approaches are used extensively to solve real-world challenges. The success or failure of text classification systems hangs on the datasets used to train them, without a good dataset it is impossible to build a quality system. This thesis examines the applicability of active learning in text classification for the rapid and economical creation of labelled training data. Four main contributions are made in this thesis. First, we present two novel selection strategies to choose the most informative examples for manually labelling. One is an approach using an advanced aggregated confidence measurement instead of the direct output of classifiers …


Novel Approaches To The Analysis Of Localised Stress Concentrations In Deformed Elastomers, John Mcnamara Sep 2011

Novel Approaches To The Analysis Of Localised Stress Concentrations In Deformed Elastomers, John Mcnamara

Doctoral

The research described here is concerned with improving finite element analysis (FEA) of rubber components subjected to dynamic loading, particularly in respect of accurate modelling of stress softening using standard software codes and phenomenological material models. The research required the design and implementation of a user subroutine capable of inclusion in standard highly nonlinear codes. Experimental methods were employed to corroborate the FEA simulations and so validate the subroutine. This was also achieved using 3D image correlation photogrammetry (ICP) and other novel experimental procedures. From this experimentation and modelling, the results for different rubber specimens and load cases were presented. …


Performance And Policy Evaluation Of Solar Energy Technologies For Domestic Application In Ireland, Lacour Ayompe May 2011

Performance And Policy Evaluation Of Solar Energy Technologies For Domestic Application In Ireland, Lacour Ayompe

Doctoral

The aim of this research is to investigate the techno-economic and environmental performance of domestic scale grid-connected photovoltaic (PV) and forced circulation solar water heating (SWH) systems in Ireland; and propose a new feed-in tariff designed using a large sample of high resolution electricity demand data in order to provide credible information for informed policy formulation. Detailed field trials of experimental installations of a 1.72 kWp grid-connected PV and two SWH systems (with 4 m2 flat plate and 3 m2 heat pipe evacuated tube collectors) were undertaken to collect data. The energy, economic and environmental performances of the systems was …


Numerical Prediction Of The Haemodynamic Impact Of Coronary Stent Implantation, Jonathan Murphy Apr 2011

Numerical Prediction Of The Haemodynamic Impact Of Coronary Stent Implantation, Jonathan Murphy

Doctoral

Arterial restenosis limits the effectiveness of coronary stenting. Restenosis is caused by excessive tissue growth which is stimulated by arterial injury and alterations to the arterial WSS. The altered WSS results from stent-induced disturbances to the natural haelnodynamics of the artery. Recent numerical studies have predcted only minor digerences in altered WSS between different stent designs using a commonly employed threshold assessment technique. While it is possible that there are only minor differences, it is more likely that the assessment technique is incapable of fully elucidating the altered WSS created by stent implantation. This thesis proposes a methodology that involves …


Arterial Tissue Perforation Using Ultrasonically Vibrating Wire Waveguides, Mark Wylie Jan 2011

Arterial Tissue Perforation Using Ultrasonically Vibrating Wire Waveguides, Mark Wylie

Doctoral

Chronic Total Occlusions (CTOs) are fibrous and calcified atherosclerotic lesions which completely occlude the artery. They are difficult to treat with standard dilation procedures as they cannot be traversed easily. Their treatment is also associated with a high risk of arterial perforation. Low frequency ultrasonic vibrations delivered via wire waveguides represent a minimally invasive treatment for CTOs and other tissue ablation applications. These devices typically operate at 20–50 kHz delivering wire waveguide distal tip amplitudes of vibration of 0-60 μm. The diseased tissue is ablated or disrupted by repetitive direct mechanical contact and cavitation. This research assesses the susceptibility of …


A Methodology Towards Comprehensive Evaluation Of Shape Memory Alloy Actuators For Prosthetic Finger Design, Kevin O'Toole Jan 2011

A Methodology Towards Comprehensive Evaluation Of Shape Memory Alloy Actuators For Prosthetic Finger Design, Kevin O'Toole

Doctoral

Presently, DC motors are the actuator of choice within intelligent upper limb prostheses. However, the weight and dimensions associated with suitable DC motors are not always compatible with the geometric restrictions of a prosthetic hand; reducing available degrees of freedom and ultimately rendering the prosthesis uncomfortable for the end-user. As a result, the search is on-going to find a more appropriate actuation solution that is lightweight, noiseless, strong and cheap. Shape memory alloy (SMA) actuators offer the potential to meet these requirements. To date, no viable upper limb prosthesis using SMA actuators has been developed. The primary reasons lie in …


Investigation To Improve The Control And Operation Of A Three-Phase Photovoltaic Grid-Tie Inverter, Mohamed Moin Hanif Jan 2011

Investigation To Improve The Control And Operation Of A Three-Phase Photovoltaic Grid-Tie Inverter, Mohamed Moin Hanif

Doctoral

Solar Energy or more precisely photovoltaic energy is one of the most promising sources of electricity for the future and it can be used as a distributed generator (DG) to play its role in ‘smart grids of the future’. Distributed PV (photovoltaic) generators can provide numerous potential benefits such as augmenting the capacity of distribution systems, deferring capital investments on distribution and transmission (T&D) systems and improving power quality and system reliability. The PV energy which possesses very special I-V and P-V characteristics has to be conditioned by a PV inverter before it can be consumed by an ac load …