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Articles 31 - 45 of 45

Full-Text Articles in Engineering Science and Materials

Characterisation, Modelling And Simulation Of Flexible Polyurethane Foam, Conor Briody, Barry Duignan, Stephen Jerrams Jun 2011

Characterisation, Modelling And Simulation Of Flexible Polyurethane Foam, Conor Briody, Barry Duignan, Stephen Jerrams

Conference Papers

Flexible polyurethane foam is an open-celled polymeric material that exhibits strain rate and temperature effects. It has found various applications in areas including the packaging, medical, sports, aerospace and aeronautical industries. Polyurethane foam is ubiquitous in seating applications and finds particular use in specialised wheelchair seating where customised seating solutions are required which can provide proper comfort and support without the risk of developing pressure ulcers. Proper seating design is critical for users if this problem is to be avoided, but a lack of quantitative knowledge of this material’s behaviour has limited its effectiveness. The objectives of the work presented …

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Review Of The Maxus 8 Sounding Rocket Experiment To Investigate Solidification In A Ti-Al-Nb Alloy, Robin Mooney, David Browne, Olga Budenkova, Yves R. Fautrelle, Ludo Froyen, Andrey Kartavykh, Stephan Rex, Burkhard Schmitz, Daniella Voss, Shaun Mcfadden May 2011

Review Of The Maxus 8 Sounding Rocket Experiment To Investigate Solidification In A Ti-Al-Nb Alloy, Robin Mooney, David Browne, Olga Budenkova, Yves R. Fautrelle, Ludo Froyen, Andrey Kartavykh, Stephan Rex, Burkhard Schmitz, Daniella Voss, Shaun Mcfadden

Conference Papers

A review of the MAXUS 8 sounding rocket microgravity experiment to investigate solidification structures in a Ti-Al-Nb intermetallic alloy is presented. The experiment was part of the Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS) EU FP6 project. Key objectives were to investigate columnar and equiaxed solidification, and to achieve Columnar-to-Equiaxed Transition (CET) in the alloy. A microgravity experiment was designed to achieve this using a controlled power-down method. Two alloys were tested: one inoculated with a grain refiner and the other without grain refinement. Unrefined samples displayed axial and radial columnar growth. Boride inoculated samples displayed …

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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 …

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Phase Change Materials For Thermal Regulation Of Building Integrated Photovoltaics, Ahmad Hassan Jan 2010

Phase Change Materials For Thermal Regulation Of Building Integrated Photovoltaics, Ahmad Hassan

Doctoral

In outdoor deployed photovoltaics (PV), standard test conditions (STC) of 25 °C PV temperature, 1000 Wm-2 solar radiation intensity and 1.5 air-mass rarely prevail. PV temperature can rise 40-100 °C above STC inducing a power drop in crystalline silicon PV with a coefficient of -0.4 to -0.65 %/K above STC. Increased operating temperature also results in accelerated PV degradation due to cell delamination allowing moisture ingress. vConventional building integrated photovoltaics (BIPV) cooling techniques using passive
or active heat removal by air or water flow are limited by (i) very low heat transfer or (ii) large capital as well as maintenance …

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A Study Of Demoulding Force Prediction Applied To Periodic Mould Surface Profiles, Kevin Delaney, Giuliano Bissacco, David Kennedy Jan 2010

A Study Of Demoulding Force Prediction Applied To Periodic Mould Surface Profiles, Kevin Delaney, Giuliano Bissacco, David Kennedy

Conference Papers

Demoulding components without damage to either the components or tool is critical to successful replication processes. Accurate demoulding force prediction prior to tool fabrication helps designers optimize replication tools to minimize the demoulding force and resultant stress on replicated parts. Various models have been proposed to predict demoulding forces. One such model, the stair-step model, was developed by Colton et al for stereolithographic moulding tools. This paper investigates applying the model to other periodic surfaces with validation using published experimental data. In addition validity of the model for application to micro mould surfaces produced by micro milling is discussed.

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Towards Blended Learning For Deaf Studies At Third Level In Ireland,, Brian Nolan, Lorraine Leeson, John Bosco Conama Jan 2009

Towards Blended Learning For Deaf Studies At Third Level In Ireland,, Brian Nolan, Lorraine Leeson, John Bosco Conama

Conference Papers

Irish Sign Language (ISL), an indigenous language of Ireland, is recognized by the EU as a natural language. It is a language seperate from the other languages used in Ireland, including English, Irish, and, in Northern Ireland.

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Hand-Held Flyback Driven Coaxial Dielectric Barrier Discharge: Development And Characterization, Victor J. Law, Vladimir Milosavljevic, Neil O’Connor, James F. Lalor, Steven Daniels Sep 2008

Hand-Held Flyback Driven Coaxial Dielectric Barrier Discharge: Development And Characterization, Victor J. Law, Vladimir Milosavljevic, Neil O’Connor, James F. Lalor, Steven Daniels

Articles

The development of a handheld single and triple chamber atmospheric pressure coaxial dielectric barrier discharge driven by Flyback circuitry for helium and argon discharges is described. The Flyback uses external metal-oxide-semiconductor field-effect transistor power switching technology and the transformer operates in the continuous current mode to convert a continuous dc power of 10–33 W to generate a 1.2–1.6 kV 3.5 μs pulse. An argon discharge breakdown voltage of ∼768 V is measured. With a 50 kHz, pulse repetition rate and an argon flow rate of 0.5–10 argon slm (slm denotes standard liters per minute), the electrical power density deposited in …

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Investigation Of Uv-Led Initiated Photopolymerisation Of Bio-Compatible Hema, Sharon Mcdermott Sep 2008

Investigation Of Uv-Led Initiated Photopolymerisation Of Bio-Compatible Hema, Sharon Mcdermott

Doctoral

Ultraviolet (UV) fluorescent lamps are widely used in photopolymerisation processes. However, there a number of disadvantages to these lamps, namely, their intensity varies over time and has to be constantly monitored. This thesis is concerned with the possibility of replacing these lamps with UV Light Emitting Diodes (UV-LEDs). A number of emission characteristics of both the fluorescent lamp and the UV-LEDs were measured and compared to ensure that the optical properties of the UV-LEDs were equivalent to those of the lamps. From this study it was shown that the UV-LEDs have a quicker warm up time and exhibit a more …

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Comparison Of Vacuum Glazing Thermal Performance Predicted Using Two- And Three-Dimensional Models And Their Experimental Validation, Brian Norton, Philip Eames, Yueping Fang, Trevor Hyde, Neil Hewitt Jan 2008

Comparison Of Vacuum Glazing Thermal Performance Predicted Using Two- And Three-Dimensional Models And Their Experimental Validation, Brian Norton, Philip Eames, Yueping Fang, Trevor Hyde, Neil Hewitt

Conference Papers

The thermal performance of vacuum glazing was predicted using two dimensional (2-D) finite element and three dimensional (3-D) finite volume models. In the 2-D model, the vacuum space, including the pillar arrays, was represented by a material whose effective thermal conductivity was determined from the specified vacuum space width, the heat conduction through the pillar array and the calculated radiation heat transfer between the two interior glass surfaces within the vacuum gap. In the 3-D model, the support pillar array was incorporated and modeled within the glazing unit directly. The difference in predicted overall heat transfer coefficients between the two …

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Structure Property Relationships In Electron Donating Systems For Potential Photovoltaic Applications., Jonathan Moghal Jan 2008

Structure Property Relationships In Electron Donating Systems For Potential Photovoltaic Applications., Jonathan Moghal

Doctoral

Conjugated polymers are considered to be one-dimensional semiconductors. In conjugated polymers single and double bonds alternatively bond the carbon atoms along the polymer chain. The loosely bound electrons determine the electronic properties of conjugated polymers. In order to utilise the properties of conjugated polymers in terms of a photovoltaic (PV) device application an acceptor material must be added. The acceptor material used in this study is used in buckminsterfullerence (C60). C60 was selected for this purpose due to its size and the fact that it can accept up to six additional electrons. Ultrafast charge transfers from a conducting polymer onto …

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Microstructures And Viscoelastic Properties Of Anisotropic Magnetorheological Elastomers, Lin Chen Jan 2007

Microstructures And Viscoelastic Properties Of Anisotropic Magnetorheological Elastomers, Lin Chen

Articles

The microstructures and viscoelastic properties of anisotropic magnetorheological elastomers were investigated in this paper. The measurement results show that their mechanical properties are greatly dependent on the magnetic flux density applied in preparation. A finite-column model was proposed to describe the relations between the microstructures and the viscoelastic properties. The simulation results agree well with the experimental results.

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Investigation On Magnetorheological Elastomers Based On Natural Rubber, Lin Chen Jan 2007

Investigation On Magnetorheological Elastomers Based On Natural Rubber, Lin Chen

Articles

Magnetorheological Elastomers (MR Elastomers or MREs) are a kind of novel smart material, whose mechanical, electrical, magnetic properties are controllable under applied magnetic fields. They have attracted increasing attentions and broad application prospects. But conventional MREs are limited to wide applications because their MR effects and mechanical performances are not high enough. This paper aims to optimize the fabrication method and to fabricate good natural rubber based MREs with high modulus by investigating the influences of a variety of fabrication conditions on the MREs performances, such as matrix type, external magnetic flux density, and temperature, plasticizer and iron particles. Among …

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A Novel Processing Route For The Production Of Nanoparticulate Zinc Oxide, Declan Mccormack, Grainne Duffy, Suresh Pillai Jan 2007

A Novel Processing Route For The Production Of Nanoparticulate Zinc Oxide, Declan Mccormack, Grainne Duffy, Suresh Pillai

Articles

Zinc oxide nanoparticles have been processed from a novel isophthalate
precursor. In contrast to those processed from an oxalate precursor, this
material exhibits three-dimensional, non-directional aggregation behaviour.
Such non-directional aggregation of uniaxial crystallites may allow for the
production of structures with a higher proportion of catalytically active
surfaces than can be prepared through conventional sol–gel methods. XRD,
FTIR, TEM and SEM were used to characterize the synthesized materials.
Zinc oxide particles synthesized by using isophthalic acid
(C6H4-1,3-(COOH)2) are found to be slightly smaller than the previously
reported materials prepared through chelation with oxalic acid
(H2C2O2·2H2O).

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Thermal Sprayed Surface Coatings And Optical Characterisation, Yueqiang Xue Jan 2006

Thermal Sprayed Surface Coatings And Optical Characterisation, Yueqiang Xue

Masters

This research work aims to establish the potential of defect detection of thermal sprayed surface coatings by using a newly developed optical non-destructive interferometric technique – Electronic Speckle Pattern Shearing Interferometry (ESPSI), rather than using mechanical destructive testing methods and other non-destructive methods. This technique has been used in many industries for non-destructive testing (NDT). However, it is innovative to use this technique for NDT of thermal sprayed metal alloy coatings, especially those that are produced by flame powder spraying process. Investigations were carried out by the SUPERJET spray process, which was the flame powder spray process utilised in this …

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Adaptive Voip Playout Scheduling: Assessing User Satisfaction, Miroslaw Narbutt, Andrew Kelly, Liam Murphy, Philip Perry Jan 2005

Adaptive Voip Playout Scheduling: Assessing User Satisfaction, Miroslaw Narbutt, Andrew Kelly, Liam Murphy, Philip Perry

Articles

Delay and packet loss dramatically affect the quality of a voice-over-IP (VoIP) call and depend on the playout buffer scheme implemented at the receiver. The choice of playout algorithm can’t be based on statistical metrics without considering the perceived end-to-end conversational speech quality. The authors present a method for evaluating various playout algorithms that extends the Emodel concept by estimating user satisfaction from time-varying transmission impairments. This article evaluates several playout algorithms and shows a correspondence between their results and those obtained via statistical loss and delay metrics.

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