Doctor of Philosophy (PhD)
Man, Zakaria (2003)
Thesis
PhD
Man, Zakaria
Institute of Science and Technology
2003
University of Manchester
Formation and Properties of Epoxy Resins Containing PES Copolymer Modifiers
Two epoxy network-forming systems based either on a diglycidyl ether of bisphenol A (Epikote 828) or a triglycidyl p-amino phenol (MY051 0), were crosslinked using stoichiometric amounts of 4,4'-diaminodiphenyl sulfone (DDS). Both epoxy systems were modified with random copolymers, polyethersulfone-poly( ether-ethersulfone) (PES:PEES), with either amine- (NHz-) or chlorine- (CI-) end-groups, at I 0 and 20wt %. The Epikote 828/DDS (ED) and MY051 0/DDS (MD) systems were reacted at 190 and 180 ?øC, respectively, and all the unmodified and modified epoxy systems were prepared without the use of solvent. Real-time analytical techniques were used to study network structure development through investigations of polymerisation kinetics using DSC and FTIR spectroscopy and of gel times and power-law behaviour using rheometry. DSC has limitations for the measurement of chemical conversion, particularly as crosslinking reactions approached completion. As an alternative, FTIR spectroscopy in the near-infrared frequency region was refined and improved to provide more accurate conversiontime data. Overall, the reaction mechanisms were autocatalytic in nature independent of the PES:PEES concentration. Gel-point conversions, PgeJ, were determined from combined DSC and rheology data. Values of Pgei for unmodified ED and MD systems were 0.61 ?ñ 0.01 and 0.50 ?ñ 0.02, respectively, compared with 0.58 and 0.41, as predicted by Flory-Stockmayer statistics, for the corresponding ideal networkforming systems. The gel times, lgeJ, in the epoxy network-forn1ing systems were delayed by incorporating PES:PEES, which acts as a diluent. although gel conversions were unaffected. In addition, a posteriori characterisation of the fully-reacted network materials was carried out using TMDSC, DMA and tensile tests, SAXS. SEM and TEM to evaluate the thermal and mechanical properties in relation to morphological structures. The modified ED systems were miscible at the molecular level as shown by SAXS analysis. In contrast the modified MD systems were phase-separated. Co-continuous and phase-inverted morphologies were generated in MD systems containing. respectively, 20 wt % of amine-and chlorine-terminated PES:PEES. Differences in the morphologies between modified ED and MD systems were related to differences in crosslink densities of the epoxy networks. In the phase-separated systems, the Tg of PES:PEES-rich phases shifted to higher temperatures, and the Tg of the epoxy-rich phases shifted to lower temperatures, as shown by TMDSC and DMA. In the rubbery state, the presence of PES:PEES in the epoxy systems was shown to increase the molecular weight between crosslinks, Me. so decreasing the crosslink density. The increase in Me with increasing modifier content was attributed to a swelling effect in the epoxy network by molten PES:PEES. Incorporating PES:PEES in the epoxy network systems increased the ductility of the unmodified epoxy systems. This was shown by SEM on epoxy fracture surfaces carried out after tensile testing. Modified epoxy systems increased tensile properties such as strain at break, strength and toughness with only slight reductions in the Young's modulus. The tensile toughness of the modified ED and MD systems containing 20 wt% NH2-PES:PEES were increased by 130 and 300 %, respectively.
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Saad, Nordin (2003)
Thesis
PhD
Saad, Nordin
Department of Automatic Control and Systems Engineering
2003-05
The University of Sheffield
Modelling, Simulation, and Analysis of Supply Chain Systems Using Discrete-Event Simulation
Many approaches have been developed which support the construction of detailed supply chain models useful for analysis and simulation. However, most of these approaches lack the ability to model the supply chain in a single model, and usually produce solutions that lead to conflicting strategies between the companies. Simulation using a discrete-event simulation (DES) is an effective tool for the dynamically changing supply chain variables, thus allowing the system to be modelled more realistically. Considering the complexities of the supply chain system and the interrelations between its various systems, the task of developing such a model is challenging. The aim of this thesis is to develop a simulation model of a fast moving consumer goods (FMCG) supply chain with a DES tool. This model would be utilised as a decision-support system (DSS) for the investigation of the effectiveness of several inventory policies towards effective coordination and control of productioninventory system, in various situations. This thesis discusses fundamental issues in the development of a simulation model for a supply chain using the DES tool, ARENA. A modelling procedure for the development of a supply chain simulation model is presented. The overall structure of the model is constructed by incorporating the well documented concept of modelling materials flowing downstream with an approach of modelling orders flowing upstream (modelling of feedback information). The model has an easily adaptable structure where rules (inventory policies) and model variables can be modified. The flexibility in the model's structure allows devising appropriate experimental designs, for several tests to be performed to imitate some realistic situations or scenarios (including the presence of disturbances). A new control theory oriented inventory policy, called the pseudo PID, is proposed. Detailed evaluations of five inventory policies for a production-inventory control under dynamic and stochastic conditions is presented. The findings demonstrate the ability of the approach to provide a wealth of potential solutions to the decision-maker, and confirm the qualitative behaviour of a supply chain in response to the different policies.
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Abdul-Karim, Zainal Ambri (2004)
Thesis
PhD
Abdul-Karim, Zainal Ambri
Aeronautical & Automotive Engineering
2004-06
Loughborough University
Direct Injection Diesel Engine Combustion Diagnostics
The demand for the protection of the environment from air pollution and reduction of carbon dioxide has resulted in worldwide exhaust emissions regulations imposed on the diesel engines. Fortunately, diesel engine offers the best fuel economy and low emissions of carbon dioxide of most engines currently available. However, the engine's inherent drawbacks are that the engine is heavy, noisy, and expensive, in addition to producing significant level of particulates and nitrogen oxides emissions. The present research attempts to understand the combustion characteristics and emissions trade-off by experimental investigations of the diesel engine using a production Lister Petter 2.97 liters, four-cylinder, high-speed, direct injection diesel engine. The investigation involved the analysis of the in-cylinder pressure data, heat release rate calculation and exhaust gas measurements of various injectors having different nozzle geometry. The engine experiments cover both the investigation of the fuel injection and the engine operating parameters such as injection rate, nozzle geometry, the engine load and speed. The effects of each parameter on ignition delay, heat release rate, nitrogen oxides emissions, smoke density, and total hydrocarbon levels were investigated. Two complementary diagnostic techniques were employed in order to assist in understanding the injection characteristics. The first technique involved the imaging of the fuel sprays from the different injectors in a constant volume spray chamber using a CCD camera. The images were than process using a dedicated image processing software. The second technique involved the measurements of the fuel injection rates from the injectors using the Bosch Tube meter. A three-zone model was developed to determine the heat release rate of combustion. The cylinder pressure data was used to validate the model written in MATLAB computer program. The model is based on the principles of the First Law of Thermodynamics applied to the three zones, formed due to the fuel injection into the combustion chamber. The heat release rate profiles produced by the model were used to analyze the formation of pollutants that were measured in the exhaust gas. The results showed that injectors with large nozzle hole diameters produced high smoke levels, especially at high engine load conditions with small increase in NOx. These injectors also caused the sprays to impinged on the combustion chamber walls at high load conditions. On the other hand, injectors having small nozzle hole diameters produced high levels of NOx while the smoke emission levels were low. The effect of nozzle geometry has little significant on the emissions of THC.
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Awang Rambli, Dayang Rohaya (2004)
Thesis
PhD
Awang Rambli, Dayang Rohaya
Department of Computer Science
2004-12
Loughborough University, The United Kingdom
Factors Affecting Spatial Awareness in Non-Stereo Visual Representations of Virtual, Real and Digital Image Environments
The increasing number of applications employing virtual environment (VE) technologies as a tool, particularly those that use VE as surrogates, makes it important to examine the ability of VE to provide realistic simulations to users. Accurate space and distance perceptions have been suggested as essential preconditions for the reliable use of VE technologies in various applications. However, space and distance perception in the VE has been reported by some investigators as being perceived differently from the real world. Thus, the overall aim of this thesis is to improve our understanding of factors affecting spatial awareness in the VE. The general approach is based on a strategy of conducting empirical investigations comparing tasks performed in the VE to similar tasks performed in the real world. This research has examined the effect of display related factors on users' spatial task performance in the context of static, dynamic and interactive presentations. Three sets of experiments in these respective contexts were conducted to explore the influence of image type, display size, viewing distance, physiological cues, interface device and travel modes on distance estimate and spatial memory tasks. For distance perception, results revealed that the effect of image type depends on the context of presentations, the type of asymmetrical distances and image resolution. The effect of display size in static and dynamic presentations is consistent with the results of previous investigations. However, results from evaluations conducted by the author have indicated that other factors such as viewing distance and physiological cues were also accountable. In interactive presentations, results indicated that display size had different effects on different users whereby familiarity with display size may influence user's performance. Similarly, it was shown that a commonly used interface device is more useful and beneficial for user's spatial memory performance in the VE than the less familiar ones. In terms of travel mode, the natural method of movement available in the real world may not necessary be better than the unnatural movement which is possible in the VE. The results of investigations reported in this thesis contribute towards knowledge and understanding on factors affecting spatial awareness in the real and VE. In particular, they highlight the influence of these factors in space and distance perception in different contexts of VE presentations which will serve as important scientifically based guidelines for designers and users of VE applications.
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Mahinder Singh, Balbir Singh (2004)
Thesis
PhD
Mahinder Singh, Balbir Singh
IRC
2004-06-01
Universiti Sains Malaysia (USM)
A Study of an Optimum Parabolic Through Concentrator Design for Possible Power Generation in Malaysia
The aim of this research work is to design an optimum parabolic trough concentrator, where the optimum design parameters are identified by using simulation method. A new parabolic trough concentrator model was proposed. The new model, based on a standard model of a parabolic trough concentrator, has back copper tubes attached to the parabolic concentrator. The back copper tubes are expected to pick up the surplus heat on the iron concentrator due to incoming solar radiation that is not reflected. Simulations were carried out by using software programmed specifically for this research work and by using the outcomes from simulation, an experimental new model was fabricated based on optimum design parameters. The optimisers that were identified by simulations are the rim angle, concentration ratio, acceptance half-angle and receiver's absorber tube size. The optimum value for rim angle is 90° and concentration ratio is 10. The acceptance half-angles falls in the range between 1.55° and 1.72°, where the optimum diameter for the receiver's absorber tube range between 27 mm and 30 mm. A rim angle of 90° can be obtained when the parabolic depth becomes equal to the focus point. The receiver's absorber tube diameter size was 30 mm, where for the concentration ratio to be 10, the width was calculated as 1.0 m and depth and focus point was set at 0.25 m. The length of the concentrator at 1.83 m was determined by using the thermal module simulation and was also subjected to the budget availability.
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Nayan, Mohd Yunus (2004)
Thesis
PhD
Nayan, Mohd Yunus
Department of Computer Science
2004-12
Loughborough University
A Family of Stereoscopic Image Compression Algorithms Using Wavelet Transforms
With the standardization of JPEG-2000, wavelet-based image and video compression technologies are gradually replacing the popular DCT-based methods. In parallel to this, recent developments in autostereoscopic display technology is now threatening to revolutionize the way in which consumers are used to enjoying the traditional 2D display based electronic media such as television, computer and movies. However, due to the two-fold bandwidth/storage space requirement of stereoscopic imaging, an essential requirement of a stereo imaging system is efficient data compression. In this thesis, seven wavelet-based stereo image compression algorithms are proposed, to take advantage of the higher data compaction capability and better flexibility of wavelets. In the proposed CODEC I, block-based disparity estimation/compensation (DE/DC) is performed in pixel domain. However, this results in an inefficiency when DWT is applied on the whole predictive error image that results from the DE process. This is because of the existence of artificial block boundaries between error blocks in the predictive error image. To overcome this problem, in the remaining proposed CODECs, DE/DC is performed in the wavelet domain. Due to the multiresolution nature of the wavelet domain, two methods of disparity estimation and compensation have been proposed. The first method is performing DEJDC in each subband of the lowest/coarsest resolution level and then propagating the disparity vectors obtained to the corresponding subbands of higher/finer resolution. Note that DE is not performed in every subband due to the high overhead bits that could be required for the coding of disparity vectors of all subbands. This method is being used in CODEC II. In the second method, DEJDC is performed m the wavelet-block domain. This enables disparity estimation to be performed m all subbands simultaneously without increasing the overhead bits required for the coding disparity vectors. This method is used by CODEC III. However, performing disparity estimation/compensation in all subbands would result in a significant improvement of CODEC III. To further improve the performance of CODEC ill, pioneering wavelet-block search technique is implemented in CODEC IV. The pioneering wavelet-block search technique enables the right/predicted image to be reconstructed at the decoder end without the need of transmitting the disparity vectors. In proposed CODEC V, pioneering block search is performed in all subbands of DWT decomposition which results in an improvement of its performance. Further, the CODEC IV and V are able to perform at very low bit rates(< 0.15 bpp). In CODEC VI and CODEC VII, Overlapped Block Disparity Compensation (OBDC) is used with & without the need of coding disparity vector. Our experiment results showed that no significant coding gains could be obtained for these CODECs over CODEC IV & V. All proposed CODECs m this thesis are wavelet-based stereo image coding algorithms that maximize the flexibility and benefits offered by wavelet transform technology when applied to stereo imaging. In addition the use of a baseline-JPEG coding architecture would enable the easy adaptation of the proposed algorithms within systems originally built for DCT-based coding. This is an important feature that would be useful during an era where DCT-based technology is only slowly being phased out to give way for DWT based compression technology. In addition, this thesis proposed a stereo image coding algorithm that uses JPEG-2000 technology as the basic compression engine. The proposed CODEC, named RASTER is a rate scalable stereo image CODEC that has a unique ability to preserve the image quality at binocular depth boundaries, which is an important requirement in the design of stereo image CODEC. The experimental results have shown that the proposed CODEC is able to achieve PSNR gains of up to 3.7 dB as compared to directly transmitting the right frame using JPEG-2000.
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Wan Ahmad, Wan Fatimah (2004)
Thesis
PhD
Wan Ahmad, Wan Fatimah
Fakulti Teknologi dan Sains Maklumat
2004
Universiti Kebangsaan Malaysia
Pembangunan dan Keberkesanan Perisian Multimedia dalam Pendidikan Matematik untuk Visualisasi Corak Geometrik (V-MATHS)
Perkembangan Teknologi Maklumat dan Komunikasi (ICT) yang pesat pada masa kini, terutama sekali perkembangan teknologi multimedia, telah memberikan nafas baru kepada penggunaan komputer dalam pendidikan. Melalui teknologi multimedia, pelbagai perisian kursus multimedia dapat dibangunkan dengan penyepaduan pelbagai media seperti teks, grafik, audio dan animasi serta keupayaan interaktiviti dalam proses pengajaran dan pembelajaran. Penggunaan perisian kursus multimedia dalam pendidikan untuk pengajaran dan pembelajaran dilihat sebagai suatu alat yang lebih berkesan berbanding media pembelajaran tradisional seperti buku teks, carta dan realia. Ini bermakna, pembangunan perisian multimedia dalam pendidikan tempatan yang berkualiti dan sesuai perlu dihasilkan supaya dapat melaksanakan proses pengajaran dan pembelajaran dengan lebihberkesan. Penyelidikanini melibatkan dua objektif utama iaitu: Pembangunan perisian multimedia bagipembelajaran Matematik Tingkatan Lima untuk menarik minat dan juga mempertingkatkan kebolehan visualisasi bentuk geometrik di kalangan para pelajar sekolah menengah; dan satu kajian kes kebolehgunaan perisian multimedia dalam pembelajaran berasaskan pengajaran menggunakan perisian V-Maths berbanding dengan kaedah pengajaran konvensyenal. Pembangunan perisian multimedia V-Maths ini mengambil kira komponen seperti pedagogi, teori-teori pembelajaran dan kognitif, interaktiviti dan penyepaduan elemen-elemenmultimedia seperti grafik, audio, animasi dan teks dalam satu persekitaran digital bagi membolehkan para pelajar mendapat gambaran tentang gabungan penjelmaan bagi bentuk geometrik. Perisian multimedia V-Maths ini dibangunkan menggunakan alat pengarangan Director 8.5 dan terdiri daripada lima modul: Modul Pengenalan, Modul Bimbingan, Modul Pengukuhan, Modul Pengayaan dan Modul Ujian. Bagi menguji kepenggunaan pakej perisian multimedia, kaedah pemerhatian etnografi dan eksperimen separa telah digunakan. Seramai 61 orang pelajar Tingkatan Lima dari sekolah Menengah Teknik di Perak terlibat dalam eksperimen tersebut yang mana 30 orang pelajar diajar menggunakan kaedah konvensyenal manakala 31 orang pelajar diajar menggunakan perisian multimedia. Data yang diperoleh dianalisis dengan menggunakan kaedah berparameter. Alat/instrumen kajian seperti set kertas Pra ujian dan Pasca Ujian, senarai semakan, skedul temu bual telah dibangunkan bagi mengukur keberkesanan dan kebolehgunaan perisian multimedia berbanding kaedah konvensyenal. Data telah dianalisis dengan menggunakan persian SPSS versi 11.5. Hasil kajian yang didapati menunjukkan bahawa penggunaan perisian multimedia adalah lebih berkesan dalam mempertingkatkan visualisasi gabungan bentuk geometrik di kalangan pelajar berbanding dengan kaedah konvensyenal. Penyelidikan initelah berjaya menyumbang ke arah penghasilan: (i) metodologi pembangunan perisian multimedia dalam pendidikan, (ii) model ID bagi visualisasi bentuk geometrik, (iii) prototaip V-Maths, (iv) modul-modul seperti Pengenalan, Bimbingan, Pengukuhan, Pengayaan dan Ujian, (v) senarai semakan bagi menguji pencapaian dankebolehgunaan perisian multimedia dan (iv) hasil kajian eksperimen kebolehgunaanmultimedia V-Maths.
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Wilfred, Cecilia Devi (2004)
Thesis
PhD
Wilfred, Cecilia Devi
Department of Chemistry
2004-06
The University of York
Tandem Oxidation Processes Using Manganese Dioxide
This thesis is concerned with new applications of tandem oxidation processes (TOP) involving manganese dioxide. Chapter I reviews the background to the in situ manganese dioxide-oxidation and TOP, and outlines the objectives of this research. Chapter 2 describes the application of TOP methodology to a formal synthesis of a bioactive natural product, podoscyphic acid (96), which has an unusual y,o-dioxoacrylate moiety.
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Baharudin, Baharum (2005)
Thesis
PhD
Baharudin, Baharum
Department of Electronic Imaging and Media Communications
2005
University of Bradford
Image Indexing and Retrieval based on Hybrid Feature Extraction and Classification Using Image Processing and Machine Learning Algorithms
Everyday more images are being created, stored and transmitted. However these three acts themselves do not really pose serious problems. The problem becomes apparent when the stored images need to be retrieved. Query using the traditional text-based approaches, though simple and easy to implement, are no longer sufficient when considering the large volume of images that have to be manually labelled. A logical solution to this problem is to search for images based on its content. Thus ContentBased Image Retrieval (CBIR) was born. Since then, many systems have been developed either commercially or in the form of research prototypes. The heart of any CBIR system is feature extraction. In other words features extracted from the images (usually in the form of a vector representation) becomes the index by which the images will be searched. In terms of the number of features used to represent images, it is generally accepted that the use of multiple image features is more desirable than using a single feature. This is evident judging from the major CBIR systems that have been developed. In this thesis, a hybrid feature extraction scheme is proposed based on a combination of features derived from the compressed as well as the pixel domain. By using two well-known classifiers; the Backpropagation Neural Network and Support Vector Machines, the performance of the proposed hybrid feature approach is compared with that of the other feature based approaches which serve as benchmarks. From the results obtained it has been shown that the hybrid feature extraction approach outperforms all the other feature based methods used in the experiments.
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Mahadzir, Shuhaimi (2005)
Thesis
PhD
Mahadzir, Shuhaimi
School of Chemical Engineering and Analytical Science
2005
University of Manchester
Integrated Production for Oil Refineries and Petrochemical Plants
In an increasingly globalised commodity market and under continually changing economic scenarios, oil, gas and petrochemical plants are forced to improve their operation practices in order to remain competitive. One strategy that can be adopted is to exploit the synergy between oil refineries and petrochemical plants through the strategy of integrated production. In this work, issues of integrated production strategy with respect to profitability, implementation and flexibility are explored. Profitability is the key motivation for any plant to change its operation practices. Three options for the strategy of integrated production are considered: integration of final products, integration of intermediate products, and integration of processing units. Decisions are made on the allocation of material resources, the distribution of products and the operating conditions of process units. These decisions are optimised for maximum profit while satisfying all production constraints. In the integrated production of an oil refinery and a petrochemical plant, propylene, naphtha, gasoil and pygas are selected for integration. The benefits of the integrated production strategy are lower costs and higher profits to the integrated plants. Systematic implementation of integrated production strategy is carried out by evaluating the necessary condition and generating an interaction model to bridge information flow between the two plants. Sensitivity analysis is used to evaluate the necessary condition for integrated production. The interaction model regulates the required information !low between the two plants and screens for options of integrated production network. Flexibility of integrated production plan is studied by varying demands and prices of exchanged materials. For an integrated production plant to be flexible, it has to remain feasible even when these parameters change. Flexibility analysis allows steps to be carried out at an early stage to ensure feasibility of the integrated production plan. All integrated production planning problems are formulated as nonlinear programming problem (NLP) and solved using the modular sequential optimisation approach. Case studies are performed to demonstrate how the three issues are addressed.
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Meor Said, Mior Azman (2005)
Thesis
PhD
Meor Said, Mior Azman
Department of Mechanical and Aerospace Engineering
2005-05
Washington University
Numerical Simulation of Natural Convection heat Transfer in Nanofluids
The goal of this thesis is to model the behavior of the nanofluids so that their performances can be evaluated analytically and computationally. In this thesis, we consider analytical models that describe molecular viscosity f.!, thermal conductivity k. density p, specific heat c"" and the coefficient of thermal expansion f3 for a nanofluid in terms of volume fraction ljJ of nanoparticles, size of the nanoparticles (e.g. radius of the nanoparticle, rp), size of the base fluid molecule (e.g. radius of the liquid molecule, r1) and the temperature T. In order to validate these analytical models, we study numerically the natural convection heat transfer in a closed pipe using the commercially available CFD software FLUENT 6.0, since the experimental data is available for this configuration. In particular, we study the natural convection flow field in two configurations of L/0=0.5 and LID=l.O, where L is the length of the pipe and D is the diameter. For nanofluids, we consider the suspensions of Ab03 and CuO particles in water. Three cases with volume fraction ljJ = 0, l% and 4% for both AhOJ and CuO are considered. It is assumed that the nanoparticles of AbOJ or CuO are uniformly suspended in water; there is no aggregation of nanoparticles in the fluid medium. It is shown that the use of experimentally measured values of k. or the kinetic model of k, gives better correlation with experimental data for heat transfer compared to the Maxwell model.
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Che Ismail, Mokhtar (2005)
Thesis
PhD
Che Ismail, Mokhtar
School of Materials
2005
The University of Manchester
Prediction of CO2 Corrosion with the Presence of Acetic Acid"
The roles and effects of organic acid species in CO2 corrosion have received relatively little attention and thus have not been included in the corrosion analysis of oil and gas systems. This is potentially detrimental as most of the predictive models used for materials selection do not incorporate considerations of the effects of such species. The scope of the study is to understand and predict the effect of organic acids, acetic acid specifically, on the CO2 corrosion rate of carbon steel. The electrochemical studies consist of static test and rotating cylinder electrode (RCE) tests that focus on the effect of acetic acid species concentrations on the corrosion rate with the presence of CO2 at fixed pH and different temperatures. These studies are based on linear polarisation resistance (LPR) and potentiodynamic polarisation methods of a three-electrode system. The results are compared with the performance predicted by three openly available predictive models; NORSOK, Cassandra and de Waard Milliams models. The results of static tests showed that the corrosion rate increases almost linearly with the concentration of acetic acid under non-scaling conditions and decreases to a low value after the formation of protective film. The RCE tests at pH 5.5 show similar results, with an increased corrosion rate that varies linearly with the acetic acid concentration. In addition, the presence of more than 400 ppm acetic acid at 22?øC and 800 ppm at 50?øC reduces the corrosion rate due to inhibition. The cathodic reaction in the presence of acetic acid is diffusion controlled but changes to mixed diffusion and charge-transfer control at high acetic acid concentration. There is no significant change in the anodic reaction mechanism with the presence of acetic acid. The overall corrosion process is mainly controlled by a charge transfer process. Based on the findings, it is concluded that acetic acid species increase the corrosion rate of carbon steel in CO2 corrosion substantially from the additional cathodic reactions of acetic acid dissociation and direct reduction of acetic acid. Standard predictive models do not account for the presence of acetic acid in CO2 corrosion. Thus, new equations are proposed to predict the CO2 corrosion rate of carbon steel with the presence of acetic acid for stagnant/low-flow and turbulent flow conditions.
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Sinnathambi, Chandra Mohan (2005)
Thesis
PhD
Sinnathambi, Chandra Mohan
Department of Chemistry
2005-12
The University of Liverpool
Mo-Modified HZSM-5 Zeolite for the Dehydrooligomerisation and Aromatisation of Methane in the Absence of Oxygen
Methane dehydrogenation aromatization (MDA) has been highly pursued since 1993 as a route of converting methane to aromatics. It is believed to proceed via a by bi-functional catalyst namely Mo modified HZSM where by methane is activated by the Mo carbide by dehydrogenation process and the intermediate species are oligomerized and dehydrocyclised over the acid site of the HZSM-5 zeolite. The aim of this study is to optimise catalytic activity with high yield and selectivity to aromatics and low coke yield and selectivity. This will include basic principles behind catalyst design, activation and stabilisation. The MDA analysis was carried out on a quartz micro reactor operating at 1 atm. and 700?øC using an on-line GC and a list of catalyst characterisation equipments to explain the findings. The optimum catalytic activities were investigated using methane on Mo modified HZSM5 (Si/Al =41). Mo wt% loadings used were 3, 5 and 10 prepared by wet impregnation of ammonium heptamolybdate on HZSM-5. The preliminary micro reactor test showed that a GHSV of 1500 h-1 was the optimum flow rate for the process. Based on investigation on the hcp ~-Mo2C and fcc a-MoC 1-x , Mo loading of 10wt% is found to be the optimum catalytic loading for MDA for both. Re-dispersion of the Mo03 species over the catalyst surface and into the channels of the zeolite or pore is governed by calcination. Based on this study for the hcp ~-Mo2C catalyst 600?øC was the optimum calcination temperature while for the a-MoC 1-x it was 500?øC. Activation of the Mo03 species results in the formation of hcp ~-Mo2C and fcc a-MoC1.x. the active Mo carbide phase which is responsible for methane activation and follow different route of preparation. It was found the hcp ~-Mo2C catalyst has higher catalytic activity than the fcc aMoC1. x counterpart. This higher catalytic activity for the hcp ~-Mo2C is attributed by the higher coke deposition as compared fcc a-MoC1_x which has lower coke yield and selectivity but higher aromatic yield and selectivity at lower calcinations temperature. Catalytic activity and stability was found to be improved by co-dosing with CO onto both the hcp ~-Mo2C and MoC1-x catalysts. CO dosing was found to prevent coke build up during MDA reactions. From this investigation, it was found CO dosing is more significant towards higher Mo loading of 10wt% rather than for the lower loading of 3wt%. The most suitable CO for the !Owt% a-MoC 1-x was 4 v/v%, while for 10wt % hcp ~-Mo2C it is 12 v/v%
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Ahmad, Murni Melati (2006)
Thesis
PhD
Ahmad, Murni Melati
Department of Chemical Engineering
2006-03
Carnegie Mellon University
Design of Aqueous Two-Phase Protein Extraction Process
Aqueous Two-Phase Extraction Systems (ATPES) comprise a liquid-liquid extraction technique that exploits phase separation phenomenon to recover protein. The two-liquid-phase systems are formed when two phase forming agent,s are aclclecl together in certain proportions or conditions that exceed a critical, and cu·e under a ma.ximum concentration, temperature or pH threshold. In this water-rich system, a protein selectively partitions into one of the phases, and this selectivity can be enhanced. Other than offering high yield for protein recovery, ATPES also allows continuous steady-state operation with high capacity, easy engineering scale-up, concentration of target species, and most encouragingly, it can directly extract product from crude feedstock rnaking integration with upstream processing possible. Despite the fact that ATPES has the potential to fulfill the dynamic and evolving clernand by indus try as an efficient, huge-scale; primary downstream process to extract protein, there are still a limited number of applications at industrial scale. This is clue to the economic concerns regarding the arnount of polymer required to extract a small amount of protein as some of the polymers are expensive. Furthermore, there are limited design methods available compared to other separation techniques used in chemical process industries. In this thesis, we present a heuristic design approach to investigate ATPES as a protein extraction technique. This work involves developing a thermodynamic modeling framework that uses the Flory-Huggins model [52, 77] to calculate the liquid-liquid equilibrium behavior in aqueous polyrner mixture and polymer-salt ATPESs. This thermodynamic work, based on the minimization of the Gibbs energy of mixing, is able to represent the ATPES equilibrium behavior in the presence of a target protein, a contaminant and other phaseforming components in dilute concentrations within a design range.
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Hamid, Nor Hisham (2006)
Thesis
PhD
Hamid, Nor Hisham
IRC
2006-03
The University of Edinburgh
Can Deep-Sub-Micron Device Noise Be Used As the Basis for Probabilistic Neural Computation?
This thesis explores the potential of probabilistic neural architectures for computation with future nanoscale Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs). In particular, the performance of a Continuous Restricted Boltzmann Machine {CRBM) implemented with generated noise of Random Telegraph Signal (RTS) and 1/ f form has been studied with reference to the 'typical' Gaussian implementation. In this study, a time domain RTS based noise analysis capability has been developed based upon future nanoscale MOSFETs, to represent the effect of nanoscale MOSFET noise on circuit implementation in particular the synaptic analogue multiplier which is subsequently used to implement stochastic behavior of the CRBM. The result of this thesis indicates little degradation in performance from that of the typical Gaussian CRBM. Through simulation experiments, the CRBM with nanoscale MOSFET noise shows the ability to reconstruct training data, although it takes longer to converge to equilibrium. The results in this thesis do not prove that nanoscale MOSFET noise can be exploited in all contexts and with all data, for probabilistic computation. However, the result indicates, for the first time, that nanoscale MOSFET noise has the potential to be used for probabilistic neural computation hardware implementation. This thesis thus introduces a methodology for a form of technology-down streaming and highlights the potential of probabilistic architecture for computation with future nanoscale MOSFETs.
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Johl, Satirenjit Kaur (2006)
Thesis
PhD
Johl, Satirenjit Kaur
Institute for Enterprise and Innovation
2006-01
University of Nottingham
Corporate Enterpreneurship and Corporate Governance: An Empirical Analysis
This thesis focuses on the relationship between corporate governance and corporate entrepreneurship activities in firms. Existing research examines aspects of governance and entrepreneurship without any consideration of the links that may exist between these two drivers. This study seeks to address this gap. Practicing corporate entrepreneurship has become an important element to compete successfully in today's competitive environment. However, an over emphasis of entrepreneurship could also lead towards negative implications such as high risk as the outcome is unknown and involves an element of uncertainty which could have negative implications on the company. On the other hand, organizations are also required to practice robust corporate governance in order to enhance greater transparency and accountability. Although the benefits of corporate governance are well acknowledge, there is the potential for a tension to arise between these two corporate imperatives; an organization is required to practice governance and control whilst simultaneously engaging in entrepreneurial activities. It is argued that by placing emphasis on control and accountability, an organization's entrepreneurial activities may be curbed. It is in this context that the relationship of corporate governance and entrepreneurship is examined. A mixed method approach (pragmatic) was employed for testing propositions, triangulating and elaborating upon the research findings. Two qualitative studies were undertaken to ascertain the nature of corporate entrepreneurship and corporate governance, as they are generally perceived. This, along with other evidence, enabled the development of a corporate entrepreneurship index and a corporate governance index. A quantitative analysis was then undertaken, based on the FTSE100 companies to ascertain the nature of any relationship between the two indices. Qualitative case studies were then used through an interview process to gain a deeper understanding of the issues involved. Certain aspects of corporate governance control mechanisms such as board size, frequency of board and sub-committee meetings were found to impact negatively on entrepreneurial activities whilst others, such as dominance of institutional block holders had a positive impact. Also, it was found linking annual bonuses to performance criteria exerts a positive effect on entrepreneurship. These findings indicate that whilst certain aspects of governance may have negative implications for entrepreneurship, others may impact positively. In addition, there are practices that an organization could implement that may positively stimulate entrepreneurial activity and thus serve to reduce the negative effects of governance.
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Mohd Zaid, Hasnah (2006)
Thesis
PhD
Mohd Zaid, Hasnah
School of Physics and Astronomy
2006-10
The University of Birmingham
Chemically Amplified Resists for Electron Beam Lithography
This thesis describes the development of chemically amplified resists for electron beam lithography. The techniques and concepts oflithography are discussed and the motivations for the development of chemically amplified resists are examined. The experimental techniques used in this work are then described. Two groups of resists, derivatives of fullerene and derivatives of triphenylene, were tested for chemical amplification and the results obtained from the research are presented. A systematic study of the response of several methanofullerenes and polysubstituted triphenylene derivatives before and after chemical amplification is presented. Films of the compounds were prepared by dissolving the resists in solvents such as chloroform and adding to the solution various concentrations of certain photoacid generators and crosslinkers, and spin coating the mixture on hydrogen terminated silicon wafers. The films were irradiated using 20 keY electrons. Post exposure bakes between 90 to 120 'C for 30 to 180 s were applied to the resists before development with non-polar solvents such as monochlorobenzene. Most of the chemically amplified resists showed sensitivity enhancement compared to their pure counterparts. Fullerene derivative, 3' H-cyclopropa [I, 9, 5, 6] fullerene-C60-Ih - 3', 3'- carboxylic [ 2-2-(2-hydroxyethoxy) ethoxyl ethyl] ester (a mixture of adducts) demonstrated the highest sensitivity enhancement with the incorporation of an epoxy novolac crosslinker and bis[4-di(phenylsulfonio) phenyl]sulfide bis(hexafluorophoshate) as photoacid generator with a sensitivity of -8 ~Clem' and a resolution of -24 nm. The polysubstituted triphenylene derivative, 2,6,10-trihydroxy-3,7,11- tri(pentyloxy) triphenylene, showed a sensitivity of -5 ~Clem' when the crosslinker hexamethoxymethylmelamine and the photoacid generator triphenylsulfonium triflate were added to the compound. However, fine patterning in the resist was not very successful due to acid diffusion. An alternative triphenylene derivative similar to 2,6, 1 0-trihydroxy-3,7, 11- tri(pentyloxy) triphenylene, with epoxides incorporated into the structure showed better results with the photoinitiator bis[ 4-di(pheny lsulfonio) phenyl]sulfide bis(hexa fluorophoshate). The chemically amplified C51epoxide demonstrated a sensitivity of ~9 f..!C/cm2 and a resolution of 40 nm. The etch durabilities of these chemically amplified resists for dry plasma etching with SF6 are reasonably high, comparable to a conventional high durability novolac resist.
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Sulaiman, Suziah (2006)
Thesis
PhD
Sulaiman, Suziah
Department of Computer Science
2006-10
University College London
User Haptic Experience: Transferring Real World Tactile Sensation of Drawing Tools Into Haptic Interfaces
Haptic perception is context dependent, suggesting that haptic cues in one particular domain of applications may not be suitable for another. Literature suggests that options should be given to users to aiiow customisation of feedback received to fit their needs. How these options should be presented has not been investigated. Also, little has been reported with respect to haptic cues in drawing, a fundamental domain in art. This research explores haptic sensations that artists recognise in a drawing environment and investigates design representations to support those sensations. It addresses these interrelated questions: (I) What are the haptic features involved in drawing? (2) What haptic cues are suitable for a drawing application and how to integrate them? (3) In such an application, do users prefer to interact with an interface design that has a ""fixed haptic"" sensation or its ""variable haptic"" counterpart? (4) If a variable haptic design is preferred, do users prefer to interact with haptic information represented in the system using an interface metaphor that involves a real world object-based representation whose underlying haptic sensation feels similar to its real world counterpart, or a textual description of the underlying feature that corresponds to an intuitive haptic sensation? These questions were addressed in three practical aspects of research work: a study to capture the design requirements, implementation of the haptic interfaces, and a main evaluation study. The first study resulted in a taxonomy of haptic cues for drawing. The haptic cues for a drawing application were integrated into two different types of interface. The integration was motivated by the role and reification of metaphor to make haptic information concrete. An evaluation study tested users' preferences on these design representations suggesting a preference for a variation of force feedback. The findings suggest that both designs have potential to be accepted by users.
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Sulaiman, Shaharin Anwar (2006)
Thesis
PhD
Sulaiman, Shaharin Anwar
School of Mechanical Engineering
2006-12
The University of Leeds
Burning Rates and Instabilities in the Combustion of Droplet and Vapour Mixtures
It is well established that the laminar burning rate plays an important role in turbulent combustion and previous work at Leeds has suggested that the laminar burning velocity of an aerosol mixture is little different from that of a gaseous mixture at similar conditions. However, it has been shown that flames within well defined droplet suspensions (aerosols) more readily become unstable than for gaseous ones. Flame instabilities, characterized by wrinkling and cellular surface structure, increase the burning rate due to the associated increase in surface area. For gaseous mixtures, the effect has been shown theoretically and experimentally to be a function of Markstein number and critical Peclet number, which marks the flame radius at which cellularity is first observed. In aerosol combustion, the presence of liquid droplets has been shown to influence instabilities by causing earlier onset of cellularity than for gaseous flames. Therefore it is imperative to conduct a fundamental study to understand the complex interactions between droplets and combustion. In the present work, spherically expanding flames were employed to quantify the burning rates in gaseous and aerosol flames and to determine their differences. lso-octane-air aerosols were generated by expansion of the gaseous pre-mixture, based on the Wilson cloud chamber principle of expansion cooling, to produce a homogeneously distributed suspension of fuel droplets. Flames were centrally ignited for quiescent aerosols at near atmospheric pressures, drop sizes of up to 30 ~m and overall equivalence ratios between 0.8 to 2.0. The flame progress was monitored using high-speed schlieren photography, from which burning rates were determined. In turbulent studies, measurements were made for stoichiometric aerosols at root mean square turbulence velocities of between 1.0 and 4.0 m/s. For comparison, gaseous combustion at conditions similar to those of aerosols were studied. From the laminar study, it was shown that the burning rate of lean mixtures is independent of droplet diameter. However, at higher equivalence ratios, the burning rate became a strong function of droplet diameter and equivalence ratio. This was associated with the onset of instabilities, which were, in tum, related to measured values of Markstein number and critical Peclet number for aerosol flames in a similar manner to those for gaseous flames. Heat loss from the flame due to droplet evaporation is probably the main reason for instabilities in aerosol flames. Interestingly, droplets which were assumed by previous workers to be fully evaporated at the flame front, were shown, at certain conditions in the present work, to survive behind the flame front. Thus other possible mechanisms for instabilities in aerosol flames could be important. For very rich mixtures, gaseous flames were shown to be partially smooth, slow, and were strongly affected by natural convection. Conversely, with the presence of droplets at similar mixture conditions, flames were found to be fully cellular and faster, with little sign of the effect of natural convection. This was suggested to be due to early instabilities caused by the presence of droplets, which, in tum, increased the burning rates. Oscillating flames, in which the flame speed and flame structure alternated between low and high values and smooth and cellular respectively, during flame development, were observed for some experimental conditions. These oscillations were most probably caused by aerodynamic interaction between droplets and gas motion ahead of the flame. This was examined using simultaneous laser sheet imaging and PIV analysis, with a simple model proposed by Atzler et al. (2001) which simulated aerodynamic interaction between droplets and gas phase motion ahead of the flame front. A dimensionless comparison between turbulent flames of aerosol and gaseous mixtures showed similar burning rates. The measurements were compared with existing turbulent burning velocity expressions and correlations. In general, these expressions are in quite good agreement with the present results, particularly at low stretch rate.
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Abdullah, Azrai (2007)
Thesis
PhD
Abdullah, Azrai
Business Management
2007-07
The University of Hull
From Natural Economy to Capitalism: The State and Economic Transformation in Perak, Malaysia
The thesis provides the first description and analysis of long-term economic change and development in the Peninsular Malaysian State of Perak from about 1800 to 2000. Although a considerable number of studies have been undertaken on the colonial economy of Perak focusing on tin and rubber production, given the vital importance of these commodities and of Perak's position in the British imperial enterprise, very little research has been done in relating the state's pre-colonial status and its colonial development to post-independence transformations. The thesis coordinates and re-evaluates the material on colonial period concentrating particularly on the available statistical data and the relations between tin, rubber and rice. It then links colonial developments with contemporary change by examining the three key economic elements of land, labor and capital, and utilizes a considerable amount of government economic data on the recent period. It also considers the relations between the policies and practices of the colonial and post-colonial state and processes of economic development. It argues that the role of the state, though different and changing, has been vitally important in promoting and underpinning economic transformations from British intervention in 1874 until the present. The major change can be characterized as the transition from a primarily 'natural' economy to a 'state capitalist' one.
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Burhanudin, Zainal Arif (2007)
Thesis
PhD
Burhanudin, Zainal Arif
Electronic Science and Technology
2007-08
Shizuoka University
Single-Charge Detection Using Ultrathin Si Single-Hole-Tunneling Transistors
Single-charge-tunneling devices can be considered as one of the most sensitive charge sensors. My group has previously fabricated single-hole tunneling transistors (SHT) using Si-on-insulator (SOl) wafer with ultrathin Si layer(< 10 nm) and demonstrated that they can be utilized as single-photon detectors or single-charge detectors. However, there are two problems remaining, i.e., thermal instability of the thin Si layer and low quantum efficiency (QE) due to thin photon absorbing layer. Thus, the purposes of this work are to study the thermal instability of the ultrathin Si layer and to improve the QE by fabricating SHT with an additional photon absorption layer in the SOl substrate. In the study of the thermal instability of ultrathin Si layer, the experiments for three crystalline orientations revealed that the Si agglomerations occur due to high temperature annealing in ultrahigh vacuum. More interestingly, it was also found that low surface free-energy facets in certain crystalline orientations determine the shape and the alignment of the agglomerated Si, e.g., islands for (1 00) and (11 0}, and wires for (111) oriented Si. Concerning the QE improvement, the ionization of single-acceptor atoms within the additional photon absorption layer was successfully detected. This is the basis of the detection of photo-generated single-charges and higher QE. As a summary, this work has been performed for the purposes of clarifying the thermal instability of ultrathin si layer and QE-improvement of photon-sensitive SHT transistors. As a result, the ionization of single-dopant has been detected successfully. This will be the first step towards high QE photon detectors.
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Hassan, Mohd Fadzil (2007)
Thesis
PhD
Hassan, Mohd Fadzil
School of Informatics
2007
The University of Edinburgh
Coordinated Constraint Relaxation Using a Distributed Agent Protocol
The interactions among agents in a multi -agent system for coordinating a distributed, problem solving task can be complex, as the distinct sub-problems of the individual agents are interdependent. A distributed protocol provides the necessary framework for specifying these interactions. In a model of interactions where the agents' social norms are expressed as the message passing behaviours associated with roles, the dependencies among agents can be specified as constraints. The constraints are associated with roles to be adopted by agents as dictated by the protocol. These constraints are commonly handled using a conventional constraint solving system that only allows two satisfactory states to be achieved - completely satisfied or failed. Agent interactions then become brittle as the occurrence of an over-constrained state can cause the interaction between agents to break prematurely, even though the interacting agents could, in principle, reach an agreement. Assuming that the agents are capable of relaxing their individual constraints to reach a common goal, the main issue addressed by this thesis is how the agents could communicate and coordinate the constraint relaxation process. The interaction mechanism for this is obtained by reinterpreting a technique borrowed from the constraint satisfaction field, deployed and computed at the protocol level. The foundations of this work are the Lightweight Coordination Calculus (LCC) and the distributed partial Constraint Satisfaction Problem (CSP). LCC is a distributed interaction protocol language, based on process calculus, for specifying and executing agents' social norms in a multi-agent system. Distributed partial CSP is an extension of partial CSP, a means for managing the relaxation of distributed, over-constrained, CSPs. The research presented in this thesis concerns how distributed partial CSP technique, used to address over-constrained problems in the constraint satisfaction field, could be adopted and integrated within the LCC to obtain a more flexible means for constraint handling during agent interactions. The approach is evaluated against a set of over constrained Multi-agent Agreement Problems (MAPs) with different levels of hardness. Not only does this thesis explore a flexible and novel approach for handling constraints during the interactions of heterogeneous and autonomous agents participating m a problem solving task, but it is also grounded in a practical implementation.
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Ismail, Lukman (2007)
Thesis
PhD
Ismail, Lukman
Department of Mechanical and Chemical Engineering
2007-07
Heriot-Watt University
An Experimental Investigation of Paraffin Wax Deposition in a Batch Oscillatory Baffled Column
Problems related to crystallization and deposition of paraffin waxes on oil pipelines during production and transportation of crude oil caused huge operational and financial losses to petroleum industry. This study is focused on the fundamental understanding of the mechanisms of wax deposition and investigates the effect of several major parameters on such deposition in a batch oscillatory baffled column (OBC). The OBC is a relatively new mixing technology and offers more uniform mixing and particle suspension than traditional reactors. It is the intention of this work to characterize the effect of oscillatory mixing on the wax deposition process perhaps as an alternative way for mitigation of wax deposition problems. Experiments have been carried out to examine the effects of OBC's operational parameters, wax-oil volume, paraffin wax content, carbon number of the solvents, baffles materials and structure on the wax deposition. Analyses conducted to evaluate and characterize the wax deposition are: the percentage of wax deposition (0, wt.%); the Avram exponent (n) which corresponds to the type of wax crystals; and the half time of deposition (tll2) which is associated with the rate of deposition. On the study of the effect of OBC' s parameters, it was found that increasing the oscillation frequency and amplitude reduced the overall deposition; baffles oscillation altered the type of wax crystal formed from needle type to clustered plate-like shapes; and accelerated the rates of deposition. On the effect of wax-oil volume, it was observed that increasing the volume reduced the deposition, increased n values and t112 hence reduced the deposition rates. The study on the effect of paraffin wax content revealed that increasing the wax content increased the deposition, reduced n values and caused higher crystallization rates. On the effect of solvent carbon numbers, it was found that the higher the carbon numbers, the more the deposition, lower the turn. Lastly on the study of baffles materials and structure, it can be deduced that using different baffle materials had no significant impact on the deposition in the OBC. In summary, oscillatory baffled flow can be an effective means of mitigation of wax deposition problems. This work may also lead to a screening test for wax deposition inhibitors. Since the deposition of viscous materials is common to other sectors of the process industries, the results of this study will provide essential information for understanding and perhaps later implementation of the OBC technology in the related fields.
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Karuppanan, Saravanan (2007)
Thesis
PhD
Karuppanan, Saravanan
Department of Engineering Science
2007
Oxford University
Analysis of Incomplete and Complete Contacts in Sliding and Partial Slip
Fretting fatigue is a type of contact fatigue which causes premature failure in a number of engineering assemblies subjected to vibration or other forms of cyclic loading. It is concerned with the nucleation of cracks due to oscillatory micro slip between contacting bodies. Therefore, a detailed knowledge of the interface conditions and the means of quantifying crack nucleation are very important, and will be the ultimate goal of this thesis. The analysis of an incomplete contact (Herzian contact) is considered first followed by various complete contacts. Fretting fatigue tests employing a Hertzian contact are analyzed accurately by introducing several modifications needed to the classical formulation. With the total state of stress in a strip established, the crack tip stress intensity factor for a crack growing inward from the trailing edge of the contact is determined by the distributed dislocation technique. The results are then correlated with local solutions for the contact stress field which enable an estimate of the crack nucleation life, and hence a characteristic material property quantifying initiation, to be found. The interfacial contact pressure distribution beneath a complete sliding contact between elastically similar components, in the presence of friction, has been studied in detail, with particular reference to contacts whose edge angles are 60?ø, 90?ø and 120?ø. The possible types of behavior at the edge of contacts, namely power order singularity, power order bounded and square root bounded, are discussed. A full understanding of the behavior requires a detailed study of a characteristic equation, and this shows the kinds of pressure distribution to be anticipated, which can vary very markedly. The transition from power order behavior to local separation and bounded behavior is examined, and an appropriate asymptotic form developed. The problem of trapezium shaped punches pressed into a frictional, elastically similar half-plane, and subject to sequential normal and shear loading, under partial slip, is studied. Detailed considerations have again been given to the specific cases of 60?ø, 90?ø and 120?ø punches, and maps have been developed showing the initial mix of stick, slip and separation regions, together with the steady state response when the shearing force is cycled. Conditions for full stick are established.
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Nadeem, Muhammad (2007)
Thesis
PhD
Nadeem, Muhammad
Department of Chemistry
2007-12
University of Agriculture
A Study on Enhanced Oil Recovery by Surfactants for a Malaysian Sandstone Reservoir
A laboratory scale investigation into the utilization of conventional and nonconventional surfactants for Enhanced Oil Recovery (EOR) was conducted using an inhouse imbibition cell flooded with formation water in the presence of polymers and alkaline mixtures. The success of chemical enhanced recovery treatment hinges on many factors; firstly there is a need for the selected chemical mixture to be sufficiently benign towards the aggressive components of the formation water. Secondly there is a need for the components of the chemical flooding mixture to possess certain desirable properties namely, stability, viscosity, extend of IFT reduction, partition coefficient, adsorption and wettability alteration. Formation water from Angsi field was analyzed for mineral contents using volumetric analyses and Atomic Absorption Spectroscopy (AAS). Surfactants and polymers have been examined for temperature stability using Thermo Gravimetric Analyses (TGA). The viscosities of the polymers have been determined using a rotary viscometer. The presence of alkali, surfactants and a raise in temperature led to a decrease in the viscosity of the polymers. Reduction in IFT at the oil/water interface has been recorded using an interfacial tensiometer. Partition coefficients of the surfactants in oil and water phases have been calculated. Emulsification and wettability alterations have been evaluated by an Atomic Force Microscopy (AFM) and contact angle measurements respectively. BET surface and micropore areas of the cores have been measured. Sandstone cores possessing suitable porosity and permeability have been characterized and used for the imbibition studies. The internal structure and mineral profiles of the sandstones have been illustrated and analyzed using a Scanning Electron Microscopy (SEM) and an Energy Dispersive X-ray (EDX) respectively. Molecular interactions between the various components have been elaborated by Fourier-Transform-Infra red (FTIR) spectroscopy. It was concluded that oil recovery can be significantly enhanced, when an appropriate mixture of non-conventional anionic surfactants (Aerosol OT & TR) has been utilized along with alkali and polymer. The preliminary screening results obtained by an in-house imbibition cell have also been adequately verified by industry accepted coreflooding experiments. Adsorption mechanism of the surfactants on sandstone cores is well elaborated by the Langmuir isotherm instead of the Freundlich isotherm. Adsorption kinetics obeys the Pseudo-second-order kinetics. It can be concluded that the polymer is responsible to increase the macroscopic displacement efficiency, whereas the synergistic effect of the surfactants and alkali are responsible to produce an ultra-low IFT (10"" dyne/cm) resulting in a pronounced microscopic displacement efficiency. Nonconventional surfactants can produce an ultra-low IFT even in minuscule amounts of alkali and polymer. It was concluded that Low-Alkaline-Surfactant-Polymer (LASP) is not only an economical technology but it can also enhance oil productiondrastically.
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Zakaria, Mohamed Nordin (2007)
Thesis
PhD
Zakaria, Mohamed Nordin
School of Physics
2007-01-04
Universiti Sains Malaysia (USM)
Multiresolution Ray Tracing for Pointbased Geometry
The primary concern in this thesis is with the incorporation of multiresolutionbased optimization into ray tracing algorithms specially tailored for point-based geometry. In recent years, increasing demand for model complexity has led to an increasing use of 3D scanning technologies capable of digitizing a complex physical model into a dense, massive and unstructured point cloud. Despite the dense amount of information contained in this data set, work in human perception study has shown that not all of it will be perceptible by a human viewer. Hence multiresolution technique offers an opportunity to reduce the computational workload involved in ray tracing such data set. In this respect, the first contribution in this thesis is the adaptation and enhancement of a Bounding Volume Hierarchy data structure in order to allow for faster ray tracing. The resulting data structure incorporates an efficient Level-of-Detail control and backface-culling optimization, and uses a mixture of bounding spheres and boxes to enable faster ray tracing. The second contribution in this thesis is an approach for incorporating multiresolution-based optimization into a point-based geometry ray tracer that is already optimized by use of a cost-optimized kd-tree. The resulting data structure incorporates an efficient Level of Detail control and a new variant of ray-surface intersection scheme that improves the ray tracing performance. Both the image quality and the ray tracing performance obtained point to the effectiveness of the multiresolution techniques introduced in this thesis.
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Baharom, Masri (2008)
Thesis
PhD
Baharom, Masri
School of Engineering, Design and Technology
2008-0
University of Bradford
Design of A Semi-Active Steering System for A Passenger Car
This thesis presents research into an improved active steering system technology for a passenger car road vehicle, based on the concept of steer-by-wire (SBW) but possessing additional safety features and advanced control algorithms to enable active steering intervention. An innovative active steering system has been developed as 'Semi-Active Steering' (SAS) in which the rigid steering shaft is replaced with a low stiffness resilient shaft (LSRS). This allows active steer to be performed by producing more or less steer angle to the front steered road wheels relative to the steering wheel input angle. The system could switch to either being 'active' or 'conventional' depending on the running conditions of the vehicle; e.g. during normal driving conditions, the steering system behaves similarly to a power-assisted steering system, but under extreme conditions the control system may intervene in the vehicle driving control. The driver control input at the steering wheel is transmitted to the steered wheels via a controlled steering motor and in the event of motor failure, the LSRS provides a basic steering function. During operation of the SAS, a reaction motor applies counter torque to the steering wheel which simulates the steering 'feel' experienced in a conventional steering system and also applies equal and opposite counter torque to eliminate disturbance force from being felt at the steering wheel during active control operation. The thesis starts with the development of a mathematical model for a cornering road vehicle fitted with hydraulic power-assisted steering, in order to understand the relationships between steering characteristics such as steering feel, steering wheel torque and power boost characteristic. The mathematical model is then used to predict the behaviour of a vehicle fitted with the LSRS to represent the SAS system in the event of system failure. The theoretical minimum range of stiffness values of the flexible shaft to maintain safe driving was predicted. Experiments on a real vehicle fitted with an LSRS steering shaft simulator have been conducted in order to validate the mathematical model. It was found that a vehicle fitted with a suitable range of steering shaft stiffness was stable and safe to be driven. The mathematical model was also used to predict vehicle characteristics under different driving conditions which were impossible to conduct safely as experiments. Novel control algorithms for the SAS system were developed to include two main criteria, viz. power-assistance and active steer. An ideal power boost characteristic curve for a hydraulic power-assisted steering was selected and modified and a control strategy similar to Steer-by-Wire (SBW) was implemented on the SAS system. A full-vehicle computer model of a selected passenger car was generated using ADAMS/car software in order to demonstrate the implementation of the proposed SAS system. The power-assistance characteristics were optimized and parameters were determined by using an iteration technique inside the ADAMS/car software. An example of an open-loop control system was selected to demonstrate how the vehicle could display either under-steer or over-steer depending on the vehicle motion. The simulation results showed that a vehicle fitted with the SAS system could have a much better performance in terms of safety and vehicle control as compared to a conventional vehicle. The characteristics of the SAS system met all the requirements of a robust steering system. It is concluded that the SAS has advantages which could lead to its being safely fitted to passenger cars in the future. Keywords: steer-by-wire, active steering, innovative, power-assisted steering, steering control, flexible shaft, steering intervention, system failure, safety features.
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Hasbullah, Halabi (2008)
Thesis
PhD
Hasbullah, Halabi
Fakulti Kejuruteraan
2008
Universiti Kebangsaan Malaysia
Peroutan Kualiti Perkhidmatan Berasaskan Corak trafik dalam Rangkaian Tanpa Wayar Adhoc Bluetooth
Peroulan kualiti perkhidmatan (Quality of Service, QoS) adalah suatu kaedah penghantaran yang membolehkan maklumat dihantar dan diterima dengan suatu tahap kepuasan pengguna. Bagaimanapun, peroutan QoS di dalam rangkaian tanpa wayar ad hoc Bluetooth menghadapi cabaran-cabaran teknikal yang sukar kerana ia bersekutu dengan beberapa kekangan yang terbit daripada rekabentuknya sendiri, contohnya kuasa penghantaran rendah, hubungan jarak dekat, dan komunikasi dipacu-induk. Tambahan pula, kebanyakan trafik multimedia dan masa nyata yang wujud hari ini adalah berletusan, yang tidak lagi boleh dimodelkan dengan taburan Poisson, sebaliknya berekor-berat menuruti hukum kuasa dengan taburan Pareto. Trafik berletusan memerlukan kaedah pengendaliannya yang khusus kerana ia bersekutu dengan gelagat serupa-diri yang berkebolehubahan tinggi. Trafik jenis ini telah dikenalpasti memberi kesan langsung ke atas prestasi sistem rangkaian dan protokolprotokol sokongannya. Objektif kerja kajian ini adalah untuk membangunkan satu skim kawalan peroutan QoS yang boleh mengendalikan trafik berletusan, sehinggakan suatu nod penghantar boleh membuat keputusan-keputusan peroutan yang cekap dan boleh percaya demi mengoptimumkan penggunaan sumber rangkaian Bluetooth yang terbatas. Fungsi kawalan peroutan QoS dilakukan secara bersama oleh pengatur Token Bucket dan Pengawal Penghantaran. Suatu model sistem kawalan peroutan QoS berasaskan corak trafik telah dibangunkan, yang mana melaluinya suatu model matematik digunakan untuk mencirikan trafik punca dan membuat keputusankeputusan peroutan pacta suatu nod penghantar. Untuk mengukur prestasi skim, satu set larian simulasi peristiwa-diskret menggunakan Matlab telah digunakan. Didapati bahawa dengan mencirikan trafik punca serta mengambilkira kecekapan jenis paket dan kualiti semasa saluran penghantaran, kecekapan dan kebolehpercayaan ke atas peroutan QoS telah dapat ditingkatkan. Dengan surih video digunakan sebagai trafik punca, simulasi telah menghasilkan kebarangkalian kehilangan paket kurang dari 10%, Iengah penghantaran di dalam julat 5 hingga 20 ms, penggunaan rangkaian mencapai sehingga 99%, dan celusan stabil telah dicapai. Semua nilai ini memberikan ukuran prestasi boleh terima bagi suatu aplikasi video
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Hussin, Fawnizu Azmadi (2008)
Thesis
PhD
Hussin, Fawnizu Azmadi
Department of Information Processing
2008-09-18
Nara Institute of Science and Technology
Studies on Core-Based Testing of System-on-Chips Using Functional Bus and Network-on-Chip Interconnects
The tests of a complex system such as a microprocessor-based system-on-chip (SoC) or a network-on-chip (NoC) are difficult and expensive. In this thesis, we propose three core-based test methods that reuse the existing functional interconnects-a flat bus, hierarchical buses of multiprocessor SoC's (MPSoC), and a NoC in order to avoid the silicon area cost of a dedicated test access mechanism (TAM). However, the use of functional interconnects as functional TAM's introduces several new problems. During tests, the interconnects-including the bus arbitrator, the bus bridges, and the NoC routers-operate in the functional mode to transport the test stimuli and responses, while the core under tests (CUT) operate in the test mode. Second, the test data is transported to the CUT through the functional bus, and not directly to the test port. Therefore, special core test wrappers that can provide the necessary control signals required by the different functional interconnect are proposed. We developed two types of wrappers, one buffer-based wrapper for the bus-based systems and another pair of complementary wrappers for the NoC based systems. Using the core test wrappers, we propose test scheduling schemes for the three functionally different types of interconnects. The test scheduling scheme for a flat bus is developed based on an efficient packet scheduling scheme that minimizes both the buffer sizes and the test time under a power constraint. The scheduling scheme is then extended to take advantage of the hierarchical bus architecture of the MPSoC systems. The third test scheduling scheme based on the bandwidth sharing is developed specifically for the NoC-based systems. The test scheduling is performed under the objective of co-optimizing the wrapper area cost and the resulting test application time using the two complementary NoC wrappers. For each of the proposed methodology for the three types of SoC architecture, we conducted a thorough experimental evaluation in order to verify their effectiveness compared to other methods.
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Ahmad, Rohiza (2009)
Thesis
PhD
Ahmad, Rohiza
Faculty of Computer Science and Information Technology
2009-05
University of Malaya
A Generic Database Querying System for Wap-Enabled Mobile Phone
The introduction of mobile phones into the market has opened up a new platform for database access. With the ever increasing number of mobile phone users and mobile workers, the potential of providing such capability to mobile phones would be invaluable. However, at the moment, very few reported works which specifically addressed mobile phones as clients for remote database querying can be found in the literature. Thus, currently, the majority of mobile, database-related querying application systems are for ""thicker"" clients such as the notebooks and the PDAs; and, even for these devices, the systems are mostly appiication-specific. Furthermore, these applications are only capable of supporting limited numbers and types of possible queries which are mostly being predetermined by the application developers. Hence, in this thesis, the researcher advocates that the method used for formulating database queries on mobile phones, in particular, for querying relational databases, should be generic. In other words, the querying method is not designed for one specific database application in mind, but, the same method can also be applied to query other database applications as well. For achieving so, the method should cater for a complete range of query types and also handle unplanned queries. Therefore, a method that involves the construction of a novel query language was developed. This language is free-formed. It adopts the concept used by the universal relation in which query terms are treated as if they are a part of one big relation. Using this concept, there will be no requirement for specifying any intermediate joins. Moreover, the language also conforms to the relational completeness theory. Thus, it supports projection, selection, Cartesian product (including join), union, and set difference operations. Using multiple research methodologies, several qualitative types of data collection activities were conducted throughout the research. The results from these data collections were used for defining as well as constructing the query formulation method. In order to evaluate the method, a prototype of a generic database querying system, named as MobileQ, which implements the method, was developed. This prototype which was developed in J2ME is for usage on W AP-enabled mobile phones. The prototype was tested for functionality and usability. Hence, after the completion of functionality tests, the prototype was verified to be performing as expected and therefore, ready for real user evaluation. Usability evaluation by users, on the other hand, produced results which show that the query formulation method introduced, is indeed effective, efficient and user satisfying for performing queries on mobile phones. Thus, this research is able to successfully achieve the stated objectives and contributes the following: (i) a generic database querying method that includes a novel database querying language, i.e., MobileQ language, along with the process involved in developing it, (ii) a generic database querying system prototype, i.e., MobileQ, along with the process involved in developing it, (iii) a method for conducting functionality tests for generic database querying systems on mobile phones, and (iv) a method as well as the results of conducting usability tests for generic database querying systems on mobile phones.
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Jaafar A, Jafreezal (2009)
Thesis
PhD
Jaafar A, Jafreezal
School of Informatics
2009
University of Edinburgh
A Reactive Architecture for Autonomous Virtual Agents Using Fuzzy Logic
One of the fundamental aspect of a virtual environment is a virtual agents that inhabit them. In many applications, virtual agents are required to perceive input information from their environment and make decisions appropriate to their task based on their programmed reaction to those inputs. The research presented in this thesis focuses on the reactive behaviours of the agents. We propose a new control of architecture to allow agents to behave autonomously in navigation tasks in an unknown environments.
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Jaafar, Azuraien (2009)
Thesis
PhD
Jaafar, Azuraien
Humanities
2009
University of Liverpool
Duct Flow of Polymer Solutions
The drag-reducing ability of a rigid ""rod-like"" polymer solution. scleroglucan. in a circular-pipe geometry together with the drag-reducing behaviour of a semi-rigid polymer, xanthan gum. in a concentric annular pipe have been investigated experimentally via pressure-drop measurements and using laser Doppler anemometry. The laminar and transitional flow in the annular pipe, with particular attention placed on the transitional regime, of two different polymers -a xanthan guns and a polymer known to exhibit a yield stress, carhopol - are also investigated in this work and compared to that ofa Nemonian fluid, a glycerine-water mixture. Complete nccological characterization ofthe diflerent polymer solutions investigated showed that sclerogluean. xanthan gum and carbopol, exhibited increased shear-thinning \w ith increasing Solution collcentratioll. Wall slip occurred in the carbopol solutions and was minimized using a roughened parallel-plate geometry I'or the steady-shear viscosity measurements producing a very high first Newtonian region at cry low shear stresses. typical ol'a ""yiel(l stress- fluid. Capillary break-up extensional viscosity measurements conducted for scleroglucan and xanthan guns showed Nemonian-like linear filament-thinning behaviour mth a Trouton ratio (?¯)) confirnlin`g the non-Nemonian nature of these polymers in extensional flow. The drag-rccluctloll study t??r scleroglucan was carried 0111 in a glass pipc-flom facility. A concentric annular-flow hicility (radius ratio A-=0.506) as utilized for the drab, -rccluction and transitional flow study of zanthan gum and carhopol. For all fluids. pressure-drop and detailed mean l1ow and turbulence characteristics were obtained at axial distances from the inlet sufficient for the Ncwonian and non-Newtonian flows to reach fully-developed conditions
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Basri, Shuib (2010)
Thesis
PhD
Basri, Shuib
Department of Sciences and Information Technology
2010
Dublin City University
Software Process Improvement in Very Small Entities: An investigation of Software Development Knowledge Management and Team issues in maintaining and evolving software process and process improvement.
The focus of this thesis is on how software process and Software Process Improvement (SPI) is practiced within the Very Small Entities (VSEs) among Irish software development companies. In particular the research is concerned with the process of software development knowledge management and team issues in supporting the software process and process improvement. In addition the study has put an emphasize on the issue of software quality standards to understand the reasons and factors that contributes to their low acceptance and implementation in VSEs. Using a mixed method research methodology which is dominated by the qualitative approach, this study has utilized in depth the interview technique at both management and team level in software development VSEs. These methods assisted the researchers in examining the attitude and perceptions of practitioners towards the research issues. The researchers also made use of survey questionnaires in VSEs in order to gain more input and to validate the qualitative data. The findings from the first stage analysis (qualitative analysis), in which the content analysis and grounded theory coding approaches were used, show the pattern and detailed categories that influence and are related with the software process and process improvement in VSEs. These categories are related to each other and adjoin the researchers to produce and validate the studies theoretical model. Likewise the second stage analysis (quantitative analysis) assisted the researchers in conforming and enhancing the first stage findings. This investigation shows that SPI programs in VSEs are being undertaken in a very informal manner and also in indirect ways. The primary reasons identified for the informal nature of VSE SPI are due to cost, time, customer and company size, which give a higher priority to the product rather than process. In relation to teams, the small team size coupled with the working and management style have lead VSEs to be more informal in their knowledge management process and team organization. Moreover VSEs are largely ignoring the best practice SPI models. The reasons and acceptance criteria for this are discussed. This research also confirmed that SPI does not solely depend on technology but also the contributions of human aspects have a strong emphasize, especially in YSEs. Therefore a contribution of this research is to provide an extended knowledge and understanding of SPI research area in general and within VSEs domain in particular.
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Ibrisam, Akbar (2010)
Thesis
PhD
Ibrisam, Akbar
Department of Environmental and Mining Engineering
2010
University of Adelaide
Debonding Mechanisms of Fibre Reinforced Polymer Strengthen Steel Member
Applying Fibre Reinforce Polymer (FRP) to steel structures has been proved to be an-effective method of strengthening. Experimentally, ageing steel structures such as bridge decks and composite beams which have been strengthened with FRP have shown lifetime extension and enhanced strength. Numerically, different approaches have been carried out to quantify the relationship between FRP and steel members in regard to the observance of the experimental works. This thesis contributes in term of quantifying the debonding mechanism of FRP strengthened steel members. First, a procedure in the derivation of the bond-slip (x-<j) relationship is presented by combining the results of the experimental work with a numerical method developed specifically for this purpose. Secondly, the debonding mechanisms of FRP strengthened steel plates due to the yielding of steel is established by experimental and numerical works. Finally, a numerical method was developed to quantify the plate end debonding of a simply supported steel beam. A total of seventeen pull tests with different types of FRP lengths and adhesives were tested to quantify the (x-o) relationship. Another four steel plate tests were carried out to study the debonding mechanism of FRP allowing for the steel to yield. Three different numerical methods were developed to analyse the results obtained experimentally.
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Md Khir, Mohd Haris (2010)
Thesis
PhD
Md Khir, Mohd Haris
Department of Mechanical Engineering
2010
Oakland University Rochester, Michigan
Design and Microfabrication of a CMOS-MEMS Piezoresistive Accelerometer and a Nano-Newton Force Sensor
A low-cost, high-sensitivity CMOS-MEMS piezoresistive accelerometer with large proof mass has been fabricated. Inherent CMOS polysilicon thin film was utilized as piezoresistive material and full Wheatstone bridge was constructed through easy wiring allowed by three metal layers in CMOS thin films. The device fabrication process consists of a standard CMOS process for sensor configuration and a deep reactive ion etching (DRIE) based post-CMOS microfabrication for MEMS structure release. Bulk single-crystal silicon (SCS) substrate was included in the proof mass to increase sensor sensitivity. Using a low operating power of 1.67 m W, the sensitivity was measured as 30.7 mV/g after amplification and 0.077 mV/g prior to amplification. With a total noise floor of 1.03 mg!-!Hz, the minimum detectable acceleration is found to be 32.0 mg for a bandwidth of I kHz which is sufficient for many applications. The second device investigated in this thesis work is a CMOS-MEMS capacitive force sensor capable of Nano-Newton out-of-plane force measurement. Sidewall and fringe capacitance formed by the multiple CMOS metal layers were utilized and fully differential sensing was enabled by common-centroid wiring of the sensing capacitors. Single-crystal silicon (SCS) is incorporated in the entire sensing element for robust structures and reliable sensor deployment in force measurement. A sensitivity of 8 m V /g prior to amplification was observed. With a total noise floor of 0.63 mgl-IHz, the minimum detection acceleration is found to be 19.8 mg, which is equivalent to a sensing force of 449 nN. This work also addresses the design and simulation of an observer-based nonlinear controller employed in a CMOS-MEMS nano-Newton force sensor actuator system. Measurement errors occur when there are in-plane movements of the probe tip; these errors can be controlled by the actuators incorporated within the sensor. Observer based controller is necessitated in real-world control applications where not all the state variables are accessible for on-line measurements
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Lai, Fong Woon (2011)
Thesis
PhD
Lai, Fong Woon
Business and Accountancy
2011
University of Malaya
An Examination of Value Enhancing Enterprise Risk Management Implementation Framework for Malaysian Public Listed Companies
Enterprise risk management or ERM is fast ascending the corporate agenda globally. Its relevancy and popularity as a management technique are abetted by the changing business practices and burgeoning regulatory requirements on risk management. ERM is defined as the process of identifying and analyzing risk from an integrated, company-wide perspective in a structured and disciplined approach in aligmng strategy, processes, people, technology and knowledge with a purpose of evaluating and managing the uncertainties facing the enterprise as it creates value. ERM essentially lays concern for managing the firm's specific risk apart from the systematic risks. However, the neo-classical finance theory (NCFT) postulates that managing firm-specific risk is irrelevant. Nonetheless, this notion is in stark contrast to the phenomenon of increased acceptance of ERM by industry practitioners. As such, this thesis attempts to propose an ERM implementation framework to theorize a model that captures the causal relationships of the risks that are strategically associated with the firms' business performance and the cost of capital, e.g. risk premium. This thesis highlights the notion of managing firms' unsystematic (specific) risk via an ERM implementation framework that leads to the enhancement of shareholders' value. The mechanism through which the firms' value enhancement takes place is theorized by a strategic conceptualization of risk premium model. The model cites managing the firm's three classes of unsystematic risk, namely tactical risk, strategic risk, and normative risk. The specific aims of this thesis are fourfold: (i) to examine the depth of penetration of ERM practices among the public listed companies in Malaysia; (ii) to examine how an effective impiementation process of ERM will bring about value-enhancing outcome to Malaysia public listed companies (PLCs); (iii) to analyze the value proposition hypotheses of corporate risk management as the determinants for ERM practices; and (iv) to investigate the validity of the theorized value creation transmission mechanism of the proposed ERM framework via the strategic conceptualization of risk premium model. The data is collected through questionnaires survey from 128 PLCs on the Malaysian stock exchange. Variables in the questionnaire are measured in 5-point Likert's scale. The analyses encompass factor analysis and structural equation modeling (SEM). Outcomes of the factor analysis provide inputs (the measurement model) for the SEM analysis. The SEM validates the theorized causal relationships among the three constructs, i.e. ERM implementation challenge, ERM implementation intensity, andperceivedERM benefitmeasures: The modified model incorporates a second-order factor model which presents improved overall goodness-of-fit values than the proposed model. Apart from that, the analytic also comprises bivariate correlation analysis of hypotheses testing in relation to the various aspects of: (i) the value maximization theory of ERM practices; and (ii) the value creation transmission mechanism of the proposed ERM implementation framework. The analysis results conclude the following: (i) that all causal relationships (structural model) under SEM examination indicate significant parameters; (ii) that ERM implementation has significant positive associations with value maximization theories of risk management; (iii) that ERM implementation has significant positive effects in reducing the firm's tactical and strategic risks with the consequence of lowering the firm's risk premium.
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Hee, Min Teh (2012)
Thesis
PhD
Hee, Min Teh
IRC
2012
The University of Edinburgh
Hydrodynamic Performance of Free Surface Semicircular Breakwaters
Different types of breakwaters have been developed in the past for the protection of valuable coastal property, commercial activity and beach morphology. Among these, gravity-type breakwaters are the most common and provide good surface wave attenuation. However, these breakwaters are not always suitable due to their adverse impact on the coastal environment. To alleviate the problem, free surface breakwaters with a variety of caisson designs have been proposed and developed. The main advantages of such breakwaters are low capital cost, freedom from silting and scouring, short construction period, circulation of water beneath the breakwater and exertion of relatively low hydrodynamic forces on the structure as compared to conventional breakwaters. However, complete tranquility on the lee side is not likely to occur due to wave energy transfer through the permeable pans of the breakwater. The degree of wave attenuation primarily depends on the configuration of the breakwater, the water depth and the incident wave conditions. The hydrodynamic performance of such free surface breakwaters is the subject of this thesis. Semicircular breakwaters mounted on a low-crested rubble mound structure were successfully built for harbor protection in Japan and China. However, the concept of having semicircular structures as free surface breakwaters has not yet been explored by the research community. As a result, this research is initiated with the aim of developing a free surface semicircular breakwater (SCB) that would serve as an anti-reflection barrier and provide reasonably good wave protection to coastal and marine infrastructures. To meet this research goal, a free surface SCB models were constructed and tested in a wave flume under various wave conditions. The experiments were conducted in three stages. For the first stage, the SCB model was initially tested without any perforations on the curved surface (i.e. a solid SCB) for different depths of immersion from the still water level in the wave flume. For the second stage, the front curved wall of the model was subsequently perforated with rectangular openings of different dimensions, producing front wall porosity of 9, 18 and 27%. Following this, two rows of rectangular openings near the crest of the rear curved wall were provided so as to facilitate water infiltration and escape of the run-up waves. For the third stage, additional effort was made to extend the draft of the breakwater by adding a wave screen at the front or/and rear. The screen porosity was 25, 40 and 50%. The hydrodynamic characteristics of the SCB models were investigated in both regular and irregular seas through a series of systematic experimental program. The water surface elevations were measured at different locations upstream and downstream of the models to determine the coefficients of wave transmission (C7), reflection (C.) and energy dissipation (CL) as well as the wave climate coefficients in front and inside the breakwater chamber. The horizontal wave forces exerted on the SCB models and the wave screen(s) were also measured and subsequently normalized to yield the force coefficients in the analysis. These hydrodynamic coefficients for the respective test cases are presented and discussed in this thesis. The experimental results revealed that even though the solid SCB was a better wave attenuator than the perforated ones, it produced a considerable amount of wave reflection. The perforated SCB with 9% porosity of the front wall (denoted as SCB9) outperformed the other perforated breakwater models; however, it produced high wave transmission when the draft was limited and subjected to longer period waves. Hence, wave screens were added to further enhance the performance of the SCB9. The SCB9 with double screens of 25% porosity was found to provide the highest hydraulic performance. Empirical equations were developed using a multiple regression technique to provide design formulae for wave transmission, wave reflection and horizontal wave forces. The proposed empirical equations showed good agreement with the experimental data. These equations are intended to be of direct use to engineers in predicting the hydrodynamic performance of free surface SCBs. However, sensible engineering judgement must be taken while using these equations as they are based on small scale laboratory tests.
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