Search

Friction stir welding (FSW) and aluminium alloy 2139-T8 are currently being considered for use in future military vehicles. However, stringent regulations on weld integrity under extreme loading conditions limit the adoption of new technologies. Moreover, current finite element (FE) based methods do not give reliable predictions of strain distribution in welds, which makes it difficult to assess the performance of structures. Therefore, an extensive research program was carried out to develop a generalised finite element (FE) based methodology to predict the response of welded structures under complex loading configurations. The methodology enables the complex distribution of mechanical properties arising from welding, which is linked to microstructural variation, to be incorporated into a macro scale structural model. The method is general, and is applicable for any heat treatable aluminium alloy under a range of joining processes. To achieve this, the microstructure of 2139-T8 alloy was characterised at a range of length scales, with particular emphasis on the size and distribution of strengthening Omega precipitates. 2139-T8 was subjected to bead on plate FSW to enable characterisation of the effects of processing on the local microstructure. In addition, kinetic data for 2139-T8 was generated, allowing a simple softening model to be developed; this allowed the post-weld strength distribution to be predicted. The model was also used to recreate bulk specimens of 2139-T8 with equivalent local weld microstructure, which was verified by transmission electron microscopy. Material with equivalent microstructure was used to estimate the local mechanical property distributions across the weld, including the initial yield stress and plastic response; the mechanical properties of 2139-T8 are known to be representative of 2139-T84. From observations of this combined data, a methodology was developed to enable the estimation of the complex mechanical property distributions arising during welding. Furthermore, an automated computer program was written to implement the property distributions into FE based models. The methodology was verified using data generated for 2139-T8 and was used to simulate the response of FSW 2139-T8 loaded in uniaxial tension. The simulations were verified experimentally using digital image correlation (DIC) and the methodology was shown to demonstrate increased accuracy and reliability over existing FE methods, with respect to strain predictions. In addition, the method eliminates the need to calibrate the structural model to a particular loading configuration. Theoretically, the models are insensitive to loading and this property was tested by extending the model to simulate the strain distribution of large scale welded panels subject to explosive blast loading. The simulations were verified against blast tests where FSW 2139-T84 panels were subjected to blast loading from the detonation of plastic explosive. The results indicate that the modelling methodology developed is capable of producing accurate and reliable predictions of strain distribution in welded structures under complex loading configurations.

The aim of the research reported in this thesis was to enhance our understanding of why individuals differ in their so-called social value orientation (SVO), i.e., their preferences for allocating resources equally or unequally between themselves and another person. By comparison with 'proself' individuals, 'prosocials' prefer to allocate resources equally. This has been linked to their greater sympathy with or empathy for other people. In the current research I propose that the anticipation of cooperative or competitive emotions may underlie these different preferences. To measure anticipated emotions about allocating resources fairly or unfairly, I developed a reliable and valid measure, as reported in Chapter 2. This measure was used to investigate whether anticipated emotions mediate the relation between SVO and allocation behaviour. I found that anticipated emotions did account (at least in part) for the relationship between SVO and allocation behaviour. This pattern of mediation was consistent in two cultural settings: Western European (UK, reported in Chapter 3) and Asian (Malaysia, reported in Chapter 4). I also examined whether participants' allocation behaviour would differ as a function of whether the receiver was a member of the allocator's ingroup or outgroup. Surprisingly, no such differences were found. Nevertheless, there was some evidence that individual differences in social dominance orientation are related to participants' allocation behaviour, with anticipated emotion again mediating the relation. In Chapter 5, I experimentally manipulated anticipated emotion in an effort to show that this proposed mediator has a causal impact on allocation behaviour. Two experimental studies yielded evidence that manipulating anticipated emotion had a significant impact on allocation behaviour, and that the normally observed relation between SVO and allocation behaviour was eliminated by this manipulation. Overall, this thesis provides compelling evidence that anticipated emotion is a key psychological mechanism that helps to explain individual differences in allocation behaviour.

This research evaluates the similarities and differences between lecturers’ intentions in providing performance feedback and how low and high achievers interpret this feedback. The research examines the discussions with the lecturers and students as to the sources of misinterpretations and the solutions which they agree on. In this mixed method case study, both quantitative and qualitative data were collected. For the quantitative data, a population of 246 final year medical students were selected to answer a questionnaire to identify their expectations of their assessment lecturers’ feedback in the mini-Clinical Evaluation Exercise (Mini-CEX). 33 mini-CEX feedback sessions given by 14 Family Physician lecturers involving the selected students were audio recorded and analysed, both quantitatively and qualitatively, to determine feedback strategies. Three further sets of qualitative data were collected: the 14 Family Physician lecturers who gave the feedback to the students were interviewed. Also interviewed were 16 low achievers and 17 high achievers who were selected using stratified purposive sampling. Semi-structured telephone interviews identified the students’ interpretations of their lecturers’ feedback. Quantitative analyses showed that more than 90% of the students had high expectations towards all questionnaire statements related to the feedback except the statement about praise. Six themes emerged from the lecturers’ intentions and the low and high achievers’ interpretations. These are feedback as promoting self-regulated learning, feedback as increasing student motivation, feedback for positive reinforcement, feedback improves power sharing, feedback preserves fairness, and feedback as an opportunity. Each of the feedback strategies used by the lecturers may have more than one intention and interpretation. There are misinterpretations which were evident among the low and high achievers towards the lecturers’ feedback. For example, although the intention of adopting self-assessment is to promote self- iii regulated learning, several low and high achievers interpreted it as perceiving fairness in feedback. Low self-efficacy, test anxiety, lack of clarity of the assessment criteria, and learning culture are the four reasons that made the students disagree with the feedback. Discussions between lecturers and students highlighted seven sources and solutions of misinterpretations. This empirical study assists in creating understandings about the similarities and the differences of students’ interpretations of performance feedback. In practise, it also contributes new findings regarding sources and solutions to eliminate misinterpretations. Implications are offered for future research involving other populations of students in different years, faculties, institutions and learning cultures.

Technology-Based Industries continue to be at the forefront of a nation's sustainable economic development. These account for the largest share of employment, business activity and labour income in most primary sectors. Technology-Based Industries contribute to multi-lateral development of a nation's economy through innovation, new technologies and use of new knowledge. The government of Brunei Darussalam sought in the past decade to diversify the economy with limited success. Oil and gas and government spending still account for most of Brunei's economic activity. The small size of the domestic market discourages foreign direct investment in Brunei Darussalam. Brunei's government encourages foreign investment especially when it involves emerging new technologies and technology transfers. The research question is: how to transfer new technologies into Brunei Darussalam industry and to quantify the impact of these Technology-Based Industries; can a resource based-economy offer a solution to tackle the difficulties in industrial advancement that Brunei Darussalam is currently struggling with. This research aims to study factors for the successful transfer of technology-based industries and identify the key issues in technology transfers that significantly affect the rate of technological integration and evaluate the concept of technology transfers and its contribution to the sustainable economic development of a small state economy. It adopts multiple techniques both inductive and deductive approaches through SWOT-analysis and case studies to explore and later analyze the importance of the visionary drive underlying the technology-based industrial strategy that contributes to policy improvement, via awareness of alternatives and discovery of latent policy constraints and opportunities from investigation of others' experience. The bottom line of this research is to provide the basis for government policies on how the technology transfer can be achieved in the Brunei Darussalam industrial context.

In today’s distributed applications, replica placement is essential since moving the data in the vicinity of an application will provide many benefits. The increasing requirements of data for scientific applications and collaborative access to these data make data placement even more important. Until now, replication is one of the main mechanisms used in distributed data whereby identical copies of data are generated and stored at various distributed sites to improve data access performance and data availability. Most work considers file’s popularity as one of the important parameters taken into consideration when designing replica placement strategies. However, this thesis argues that a combination of popularity and affinity files are the most important parameters which can be used in decision making whilst improving data access performance and data availability in distributed environments. A replica placement mechanism called Affinity Replica Placement Mechanism (ARPM) is proposed focusing on popular files and affinity files. The idea of ARPM is to improve data availability and accessibility in peer-to-peer (P2P) replica placement strategy. A P2P simulator, PeerSim, was used to evaluate the performance of this dynamic replica placement strategy. The simulation results demonstrated the effectiveness of ARPM hence provided a proof that ARPM has contributed towards a new dimension of replica placement strategy that incorporates the affinity and popularity of files replicas in P2P systems.

Malaysia’s rapid economic and demographic development has put pressures on its water supplies and consequently on the quality of its river water. The Selangor River, close to the nation’s capital, is now a major source of water and there are fears that its water quality will deteriorate. The Malaysian Government in its Vision for Water 2025 states that rivers should achieve Class II as measured by Malaysia’s Water Quality Index (WQI) (Class I is cleanest). The objectives of this thesis are to investigate the effects of flow through the 10 major tidal control gates (TCGs) which regulate run-off from the oil-palm plantations into the river, and to predict the water quality for the river in 2015, 2020 and 2030. In order to achieve these objectives it was necessary to set-up, calibrate and validate a commercial one-dimensional numerical model, InfoWorks, which includes both the hydrodynamics and water quality of the river-estuary network. It was concluded that there was insufficient hydrodynamic (stage and current) and water quality data to fully calibrate and validate the InfoWorks model but it performed well when compared with measured salinity transects. The model was found to be relatively insensitive to the choice of diffusion parameters but needed a high value for the oxygen transfer velocity, 0.3 m h-1, to get reasonable values for the dissolved oxygen (DO) along the river. The effect of run-off through the TCGs was less than expected and attributed to the high oxygen transfer velocity and needs to be addressed before the model can properly represent run-off through the TCGs. The model shows the WQI of the lower reaches of the river to be Class III in both wet and dry seasons except close to the estuary where it is Class II due to tidal flushing. The dissertation identifies several deficiencies in the model; the lack of an operational ramp function at the estuary boundary, the use of a single value of the oxygen transfer velocity throughout, and the exclusion of water extraction. Land-use changes above Rantau Panjang, the upper boundary of the InfoWorks model, and water quality data were used to estimate the water quality and its uncertainties at Rantau Panjang in 2015, 2020 and 2030 due to predicted development in the upper catchment for both wet and dry seasons. InfoWorks models of water quality along the river in 2015, 2020 and 2030, which included extraction at the Batang Berjuntai barrage, predict little change in the WQ (Class II/III boundary) below the barrage during the dry season but a rapid deterioration in the wet season (down to Class III/IV by 2030) showing the importance of water extraction to the water quality of the river. Overall, because of its relative simplicity and ease of operation, InfoWorks is considered to be a useful tool for river management in Malaysia.

Geometric semigroup theory means different things to different people, but it is agreed that it involves associating a geometric structure to a semigroup and deducing properties of the semigroup based on that structure. One such property is finite presentability. In geometric group theory, the geometric structure of choice is the Cayley graph of the group. It is known that in group theory finite presentability is an invariant under quasi-isometry of Cayley graphs. We choose to associate a metric space to a semigroup based on a Cayley graph of that semigroup. This metric space is constructed by removing directions, multiple edges and loops from the Cayley graph. We call this a skeleton of the semigroup. We show that finite presentability of certain types of direct products, completely (0-)simple, and Clifford semigroups is preserved under isomorphism of skeletons. A major tool employed in this is the Švarc-Milnor Lemma. We present an example that shows that in general, finite presentability is not an invariant property under isomorphism of skeletons of semigroups, and in fact is not an invariant property under quasi-isometry of Cayley graphs for semigroups. We give several skeletons and describe fully the semigroups that can be associated to these.

IL-33 and IL-17 family cytokines (IL-17A – IL-17F) have been shown to play roles in the pathogenesis of chronic inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease. However knowledge of their role in periodontal disease pathogenesis is limited. The aim of this study was therefore to determine clinical associations between IL-33 and IL-17 family cytokines and chronic periodontitis. In addition, to begin to investigate the biological significance of these associations using in vitro model systems. 97 patients with chronic periodontitis and 77 healthy volunteers were recruited in Glasgow and Newcastle. Serum, gingival crevicular fluid (GCF) and saliva were analysed for levels of IL-33 and IL-17 family cytokines by ELISA. Periodontal tissues from 17 chronic periodontitis patients and 10 healthy subjects from Glasgow were also investigated for IL-33 and IL-17 family cytokines mRNA expression by real time PCR. Immunohistochemical analysis was also performed on tissue to investigate expression of IL-33 and IL-17E at the protein level. In vitro experiments were performed using the OKF6/TERT-2 oral keratinocyte cell line and primary human gingival epithelial (PHGE) cells. The cells were stimulated with either a live Porphyromonas gingivalis monospecies biofilm or recombinant cytokines and changes in expression of cytokines, chemokines and their receptors evaluated by real-time PCR, immunocytochemical analysis or ELISA. In addition, transcriptional activity was monitored by analysis of changes in the phosphorylation (activation) of the NF-κB p65 subunit transcription factor using serum, GCF and saliva. IL-17A and IL-17A/F levels were higher in chronic periodontitis patients, but serum IL-17E was lower. IL-17A, IL-17A/F and the serum IL-17A:IL-17E ratio correlated positively with clinical parameters. IL-33, and IL-17 family cytokine (except IL-17B) gene transcripts were higher in tissue of chronic periodontitis patients. In addition, IL-33, ST2, IL-17E and IL-17RB proteins are expressed in periodontal tissues. Furthermore, IL-33 protein expression is upregulated in tissue of chronic periodontitis patients. In vitro models showed that IL-33 and its receptors (ST2 and ST2L) are expressed by oral keratinocytes (OKF6/TERT-2 cells and PHGE cells) and IL-33 expression up-regulated in response to P. gingivalis. However, IL-33 failed to induce expression of a range of inflammatory mediators and receptors in OKF6/TERT-2 cells. In vitro, IL-17E inhibited P. gingivalis monospecies biofilm and IL-17A induced expression of chemokines (IL-8 and/or CXCL5) by OKF6/TERT-2 cells at the transcriptional level by blocking the phosphorylation (activation) of the NF-κB p65 subunit. This study demonstrates clinical associations between IL-33 and IL-17 family cytokines and chronic periodontitis. The expression of IL-33 by oral keratinocytes and its up regulation upon exposure to P. gingivalis suggest it plays a role in the innate immune response to pathogens within the periodontium. However, the role of IL-33 in the periodontal inflammatory response remains to be elucidated. The negative correlations between serum levels of IL-17A and IL-17E and correlations with disease parameters, combined with their differing effects on the induction of expression of key neutrophil chemoattractants (CXCL5 and CXCL8), suggest opposing roles in periodontal immunity. Indeed, it can be hypothesised that the differential regulation of chemokine expression is due to IL-17A having pro- and IL-17E having anti-inflammatory properties. Indeed, as neutrophils play a key role in the early events associated with periodontal disease progression, the data suggests IL-17E is a rational target for therapeutic intervention.

Delamination has been recognised as the primary defect in composite structures, which can lead to rapid deterioration of the structure. This is because delamination is barely visible damage, and the presence of delamination crack growth between the fibre-matrix layered structure can severely reduce the load bearing capability without being noticed. The present work investigates the matrix toughening approach via the addition of a second phase copolymer and rigid silica nanoparticles in an attempt to enhance the delamination resistance in Glass Fibre (GF) composites. This investigation includes the analysis of the structure/property relationships of toughened epoxy matrices and their corresponding GF composites under quasi-static and fatigue loading conditions. The toughness performance and the toughening mechanisms of the modified epoxies and their corresponding composites are the main theme of this thesis. This investigation revealed a positive correlation between the interlaminar fracture toughness of GF composites and the toughness of the matrix phase. A large toughness increase was observed when using rubber-modified and core-shell rubber (CSR)-modified epoxy matrices. The use of a silica nanoparticle-modified matrix only showed a marginal toughness increase, and in some epoxy systems, the addition of silica nanoparticles was detrimental to the composite toughness. In the hybrid-modified matrix, the largest toughness increase was observed, indicating the presence of a synergistic effect between the rubber particles and silica nanoparticles. The toughening mechanisms in the rubber-modified epoxy were rubber particle cavitation and plastic void growth, whereas in the CSR-modified epoxy the toughening mechanisms were cavitation of the rubbery core and shear deformation in the polymer matrix. In the silica nanoparticle-modified epoxy, debonding of the nanoparticles and subsequent void growth were evident, but the energy dissipation was small and not sufficient to contribute to the large toughness increase. In addition, the silica nanoparticles increased the matrix stiffness and caused the matrix to be less adhered to the fibre surface, thus promoting a fibre-matrix interfacial failure. The fatigue performance of the GF composites with toughened matrices was analysed in terms of fatigue crack growth and fatigue threshold. The addition of rubber particles and silica nanoparticles reduced the fatigue crack growth rate and increased the fatigue threshold values. The fatigue threshold was further increased when using the hybrid-modified matrix suggesting a synergistic toughening effect in the threshold region. Microscopy analysis revealed there were no appreciable difference in the toughening mechanisms between the fatigue and quasi-static fracture behaviour.

Terahertz CTHz) radiation has much potential in biomedical and agricultural imaging, security screening and pharmacology applications. One source of THz radiation that is potentially well-suited to applications is the quantum cascade laser (QCL). However, the majority of THz QCL-based systems developed to date rely on incoherent detection, whereas coherent detection could enable much higher detection sensitivities, as well as providing phase information on samples under interrogation. The aim of this work is to progress towards the development of a coherent detection system for continuous wave (CW) THz QCLs employing CW semiconductor laser diodes The proposed scheme aims to take advantage of the compact nature of THz QCL sources coupled with their high optical power, which gives rise to THz field strengths that are 2 to 3 orders of magnitude greater than for continuous wave-photomixed sources. The narrowband nature of THz QCls (about 50 kHz) will also expected to allow a high degree of phase coherence. The free-space electro-optic sampling (FSEOS) detection method is proposed for this scheme. Chapter 2 presents the characterisation of a range of THz QCL sources in order to assess their suitability to operate in CW mode with a relatively high output power which will be used as the THz source of radiation in this coherent system. Then chapter 3 of the thesis discusses the development, implementation and optimisation of an optical phase-Jocked loop scheme for synchronising two CW external cavity diode lasers (ECDLs), which are ultimately intended for use as the probe beam for FSEOS of THz QCLs. Following that, the development of the optical sampling detection scheme employing an electro-optic crystal is presented. When using an electro-optic crystal with high power THz radiation, a second detection mechanism is observed and determined to be from thermo-optic (TO) origin. This is the main contribution in this work, analysis and the developed new model shows an agreement with the measured data for the first time. It is shown that this mechanism enables detection of the THz intensity, rather than the electric field. The thermo-optic response is quantified in terms of THz QCL power and not polarisation and the anisotropic model strongly influenced the magnitude of thermo-optic response. This can be found in chapter 4 and has been published in three conferences. Finally, a system to enable the coherent detection of THz QCLs using FSEOS with CW ECDLs as the probe beam is designed and setup, and initial measurements to observe the coherent interaction between THz QCL radiation and the probe beam are carried out

This research explores the concept of positive and negative behaviour in a Malaysian context and strategies used by secondary school teachers to promote positive behaviour. It also examines strategies that are perceived to be effective and possible factors that have influenced professionals’ attitudes towards positive behaviour. Mixed-method research design was used to complete three different stages. Stage 1 analysed 91 government circulars using content analysis; Stage 2 involved administering a survey to a total of 319 professionals including principals, counsellors and teachers and 494 pupils aged 16 years from 15 selected national secondary schools; Stage 3 focused on two case studies in two selected schools where classroom observations, individual interviews with professionals, and focus groups with pupils were the focal point. Statistical analysis included descriptive and inferential analysis (a chi squared test), while narrative data was analysed by using a thematic approach. Observational data was analysed manually by focusing on the frequency of target behaviour. This study proposes a Socio-ecological Model suggesting that interaction within and between ecological layers constructs the concept of positive and negative behaviour. This study also suggests that bonding and bridging social capital would improve pupil behaviour and develop school community. Findings also suggest that socio-cultural factors and professional experience have influenced professionals’ attitudes towards positive behaviour enhancement strategies. Implications for policy making, practitioners, and future research are also discussed. The research also offers recommendations which could inform policy formulation and further longitudinal research activity.

This PhD attempts to study and learn about issues that influence Information Systems research development in Malaysia. An Action Case was conducted to learn about how to improve research in the author's institution in Malaysia. The action case included participatory activities to promote qualitative research in the author's institution and collecting information from qualitative interviews and discussions. This thesis is presented as a story from a first-person perspective and narrative of the researcher. The first person perspective was chosen because the author wanted to present his work from the his own perspective and for the reader to follow the research experience itself. The narrative also fits into many of the discussions in the thesis for action-based methods placing the researcher as the research tool and that the researcher is the 'hero' of the research story. This also ties into one of the main aspects of the thesis which is actuality. To improve IS research in Malaysia, those who conduct and administer research need to understand each other's actuality. The thesis suggests due to Malaysia's academic culture there are misunderstandings that cause IS research to be left behind in terms of research support. Despite the contextual difference of views among researchers and administrators, there are patterns of similarities that can be taken from government policies and university policies. The thesis proposes that by increasing understanding using these patterns and actuality, Malaysian IS research can be improved and developed further. The thesis proposes more Action Research in the future to improve this understanding. This thesis contributes by proposing theoretical aspects that discuss the issues related to IS research improvement. This thesis proposes the action case method as an approach for Malaysian-based IS research. And this thesis along with the author attempts to make a positive difference in improving IS research in the author's institution specifically, and Malaysia in general.

This thesis comprises three essays on convergence issues in selected Asian countries, focusing on both macro and micro perspectives. These papers encompass issues on convergence testing from time series and panel perspectives, with in-depth coverage on convergence in aggregate and structural ( inter sectors and sub sectors convergence) of the Asian economies. The first essay examines the convergence hypothesis using both time series and panel frameworks, from a macro perspective. Utilizing the concepts of stochastic convergence, the study tests the income convergence hypothesis by using both linear and nonlinear unit root tests. The present study emphasizes the usefulness of the nonlinear unit root tests due to Kapetanios, Shin and Snell (2003) and extended by Chong, Hinich, Liew and Lim (2008) to permit the test of long-run convergence and catching-up hypothesis. Next, the study utilized the recent panel unit root test for the nonlinear heterogeneous panel model proposed by Ucar and Omay (2009). In the present study, despite using the univariate and panel nonlinear tests for convergence, the results suggest strong evidence of divergence among the Asian countries with Japan. Further analysis was undertaken using tests for convergence with two robust tests that do not require stationarity in the data generating process suggested by Nahar and Inder (2002) and recently proposed by Phillips and Sul (2007a). On the one hand, the Nahar-Inder test indicates divergence between the Asian economies with Japan (except for Singapore), however, on the other hand, the Phillips-Sul test suggests that, all the other Asian economies converge towards Japan. The study suggests that since the Asian economies are in iii various stages of development, the Phillips-Sul test for convergence is more appropriate for such transition economies. Thus, testing for convergence using the unit root and cointegration test for transitional dynamics in the data may not be appropriate. Bernard and Durlauf (1996: p.172) have cautioned that “the (time-series) test may therefore be invalid if the data are largely driven by transition dynamics” and in this study, this found support. The second paper tries to bridge the gap between the macroeconomic issue of productivity convergence at the aggregate level and the microeconomic issues of convergence at the industry level. The study investigates structural convergence in selected Asian countries over the period of 1970-2005 using the non-linear time-varying coefficients factor model proposed by Phillips and Sul (2007a). This model has the flexibility to model a large number of transition paths to convergence, and allows for convergence clubs as well. Structural convergence exists if the convergence progress in income is accompanied by convergence at a sectoral or disaggregated level. The study finds strong divergence in income convergence at the aggregate level, and the clustering shows four clubs. To be robust, the study presents three measures of structural convergence, namely productivity, labour shares and value added. Convergence tests on productivity and value added shares indicate divergence in all sectors that leads to possible creation of club convergence. On the other hand, the labour share shows convergence in aggregate in three sectors (manufacturing,mining and construction). Also, the paper reveals that there is strong sectoral club convergence within the manufacturing sector in Asian whereas the evidence of convergence club for services, agriculture, and construction as well as for mining is rather weak. While the integration process is actively geared in Asian, the question of candidates’ suitability for the AEC (Asian Economic Community), as proposed in this study JAKITH (Japan, Korea, India, Taiwan, Hong Kong, and ASEAN) is still a debatable issue. Utilizing the concept of sub-sectoral convergence, the third study tests the convergence in competitiveness for 13 Asian countries for medium/high technology manufacturing sub-industries in three decades. This paper focuses on the issue of competitiveness measured in terms of productivity and labour input efficiency at the industry level within the manufacturing sector of Asian countries. The study applies the non-linear time-varying coefficients factor model that allows for large transition path to converge and also convergence clubs (Phillips and Sul, 2007a). The results indicate that in general Asian countries have a constant increase in its competitiveness yet no aggregate convergence is achieved. Club convergence indicates that labour productivity is likely to iv be driven by high income countries, as opposed to labor input efficiency. However, the low income countries show significant increase of productivity and high labour input efficiency as compared to richer countries. The high labour input efficiency indicates low wages paid to workers, significantly correlated with high density population countries as India and Indonesia. Based on comparative advantage theory, focusing on the industry level, the study also utilized the Krugman specialized index to show the clustering of concentrated industries among countries in Asia. The study found no trace of close to convergence situation, which indicates that the economic activity of Asia is focused or concentrated in specific activities, explaining the divergence in the sub-industries. The growing similarity of Asian economies in terms of overall productivity masks a continued high degree of specialization in particular industries. These findings should help policy makers for both target groups in designing appropriate growth-oriented programme as well as in setting priorities in their implementation

A high critical current density Jc is crucial for the application of HTS YBa2Cu3O7-δ (YBCO) in the fabrication of energy efficient power devices and wires. We have prepared and studied YBCO films with nanoinclusions for increasing the current-carrying capability. All films were prepared by pulsed laser deposition (PLD) on single crystal SrTiO3 (STO) substrates at optimised condition parameters. We found that the substrate temperature Ts of 780° C, laser energy E ~ 218 mJ/pulses, distance between target and substrate Dt of about 55 mm, annealing oxygen pressure Oap 450 Torr and cooling rate Ct 8°/min were the optimum conditions for making good films with Tc = 91 K. We have used a method for introducing artificial pinning centers which has been shown to be successful in the nanotechnology of pinning centres: distributing a secondary phase, YBCO with 1% Gd2Ba4CuWOy (2411W) nano-inclusions, YBCO with 2% wt BaZrO3 (BZO) and YBCO with 4% wt BZO nano-crystalline particles in the film. The superconducting properties were determined by AC susceptibility, magnetisation loops and transport measurements using a Quantum Design Magnetic property measurement system (MPMS) and a Physical properties measurement system (PPMS). Scanning and transmission electron microscopy (SEM) and (TEM), Atomic force microscopy (AFM) and X-ray were also used to characterise the micro-structure of the films. Both 2411W and BZO nano-inclusions led to increased Jc in applied fields and self-field. Scaling of the flux pinning force based on the Dew-Hughes model has been used in this work for investigating the flux pinning mechanism.

The underlying resistance mechanisms to cocoa pod borer (CPB) in cocoa were investigated. Experiments performed under field conditions in Malaysia showed that female CPB preferred to lay eggs on pods of clones with a rough pod surface compared to clones with a smooth pod surface. This appeared to be related to a higher density of trichomes on rough pods. The production of volatile compounds by cocoa pod trichomes is thought to stimulate females CPB to lay more eggs. Cocoa pods develop a lignified sclerotic layer and the thickness of this sclerotic layer determines the hardness of the pod, but pod hardness also depends on the composition of sclereid cells in the sclerotic layer. The sclerotic layers are soft in young pods and gradually increase in thickness and hardness as the pod grows. The quality of the pod as a food source affected the life-history traits of the CPB. However, the concentration of nitrogen and polyphenols in the pod walls did not appear to be a factor limiting the growth and development of CPB larvae. Therefore, the importance of other food quality components such as lipids, proteins, amino acids and carbohydrates (including water) warrants further investigation. The variation in CPB attack between clones under natural field conditions appeared to be influenced by plant and insect variables, and modified by environmental conditions. Any changes in the plant variables affect the spatial and temporal distribution of CPB and then, subsequently influence the expression of resistance. Clones with good resistant traits also face severe infestation in the absence of favourable pod size, particularly during low pod production or the presence of non-bearing cocoa trees within rows or blocks. The basis for characterising resistant clones was proposed. A resistance index based on eight variables, low number of CPB eggs recorded on the surface of the pod, low number of entry holes observed on the pod, harder sclerotic layer, smoother pod surface, high larval mortality in the pre-sclerotic layer, low larval penetration through the sclerotic layer, low number of exit holes, and low pod damage index was derived and is proposed as a basis for screening and selecting resistant clones to CPB. The lowest average rank for these variables reflects the highest overall resistance level to CPB. Among the eight variables, the percentage larval penetration appeared to be a prominent key to the damage severity of the cocoa pod.

Due to the ever increasing demand for new services and applications, wireless broadband communications is becoming even more popular since users have been provided with an "anywhere any time" type of service. Mobile worldwide interoperability for microwave access (WiMAX) provides mobile broadband connectivity and some essential applications, including location and positioning (L&P) for mobile users. In this thesis, we have utilised some of the features offered by WiMAX, including multiple input multiple output (MIMO) and beamforming, to improve the location estimation accuracy of location services. In a MIMO system, the number of links is increased, not only for the spatial multiplexing of data to be transmitted or received, but also for simultaneous distance measurement between a base station (BS) and a mobile station (MS). Utilising MIMO will both significantly improve the capacity and throughput of a wireless link and facilitate improvement of the location accuracy of a MS. We have proposed a geometrical approach using a multiple linear lines of position (MLLOP) technique for MIMO antenna mode configurations in WiMAX networks with range measurements from only three BSs in non-line of sight (NLOS) environments. Going beyond MIMO systems, an innovative location estimation algorithm, involving virtual BSs in MIMO systems (called VirBSs), is proposed and investigated, offering the reduction in NLOS error effects. We also explored existing beamforming features for improving accuracy of location estimation. A hybrid positioning method is proposed that utilises the time of arrival (TOA) and direction of arrival (DOA)-based beamforming in MIMO systems. More specifically, two hybrid L&P techniques are presented. The first of these hybrid techniques expands the fundamental principle of using an MLLOP scheme by utilizing multiple LOP instead of circular LOP to determine new lower and upper bounds of DOA The second proposed technique utilises only one MIMO SS, with range and angle measurements from two or more multi-paths, thus extending the virtual BS concept to enhance estimation accuracy with no extra network infrastructure required. We have shown that all the developed techniques provide L&P accuracy improvement with lower implementation complexity and are compatible with the existing WiMAX specifications.

This study addresses the issue of the nature of contemporary kinship relationships among the Cham Muslim community of migrants from Cambodia, now settled in Malaysia. The study was conducted in 2006 in Pulau Keladi Village, a Cham settlement on the East Coast of peninsula Malaysia, and employed an ethnographic research approach combining traditional participant observation with simple survey techniques. The study is primarily concerned with how modernization has affected kinship relations among the Cham. Modernization is used here to designate the processes of involvement in the commercial relations of a market-based society. In the case of the Cham, the transition to such relations was intertwined with the process of movement from their country of origin, i.e. Cambodia, to another country. With the process of movement and resettlement, this community confronted real challenges and had to develop new ways of life in a new milieu. From traditional forms of farming and fishing, which had been their main sources of economic support in Cambodia, these people utilized a similar physical environment to develop commercially-oriented economic activities in their new settlement. The degree of cooperation in the village helps producers to produce and market larger quantities than if everyone operated as an isolated unit. The spirit of mutual help which pervades this community, and which is interrelated with kinship, is an important aspect of this study. Through the way in which they responded to their new milieu and the cultural challenges which it provided, the Cham managed to re-establish strong kinship networks and to assemble a large group of kin in a single place. Through examining the kinship structure and ideology of the Cham, their marriage patterns, relations between parents, adult children and adult siblings, the role of kinship in life course transitions and ceremonies, the utilisation of kinship in economic activities and the interplay of migration, ethnic identity and kinship, the study identifies the significance of kinship to Cham social organisation and explores the elements of continuity and change. Over the last three decades, these people have undergone significant transformation due to the modernization process and resettlement. The data of this study suggests that changes have taken place in some aspects of their lives. However, compared to western communities, the resilience of kinship ties is clearly transparent. While there are more elements of freedom for the younger generation in many areas of life, they still accept considerable guidance from older family members, and the range of kin who are recognised and who meet regularly to celebrate family events, the preference for working with kin, the patterns of financial and emotional assistance, the relatively high levels of arranged marriages and of cousin marriage, the exceptionally low rates of divorce and remarriage, and the close relations between parents and adult children and between adult siblings, all illustrate the importance that the Cham attach to the bonds of kinship and their efforts to protect kinship from the eroding influence of modernisation. Finally, the study suggests that important contributing factors to the continuing strength of kinship are the historical and contemporary efforts of a minority group to maintain their identity, persecution under the Khmer Rouge and the subsequent migration and resettlement, which have all both accentuated the importance of kinship as protection and resource, and deepened the attachment of the Chain to a collective identity - now in the form of Orang Kemboja - which kinship plays an important role in maintaining.

Knowledge management is a response to the growing realization of knowledge as the deliverer of organizational success. Because much attention has been given to the private sector, knowledge management initiatives in educational settings seem to be lacking. Considering that knowledge activities – capturing, creating, sharing, applying and storing – are important activities in education, particularly schools, the failure to fully appreciate the potential of managing knowledge within education is surprising. A review of the literature suggests that factors such as management, technology and culture contribute differently to managing knowledge in many organizations. The management factor, for example, was a catalyst in providing a conducive work environment, whereas technology provides the mechanism as an enabler for knowledge management initiatives. Culture was important for the knowledge context and could play a significant role in the uptake of managing knowledge. The purpose of this study was to explore the relationship between these contextual factors – management, technology and culture – and the knowledge activities. The study took place in Malaysian secondary schools and highlighted the Smart School Project as one of the seven flagships of Malaysia Multimedia Super Corridor. A mixed method approach was used as a strategy of inquiry in order to explore the knowledge management contextual factors in relation to knowledge activities. The quantitative method focused on collecting data based on a survey instrument. There were 1313 respondents and Smart Schools and non Smart Schools participated in responding to the questionnaire. As for the interview method, the study focused on 21 individuals who were purposely selected based on their special implementation roles in the schools – school principals, information technology coordinators and teachers. The survey data were analysed by using the Statistical Package for the Social Sciences (SPSS) software. There were three types of statistical application used, namely the descriptive statistics, the t-test and regression, whereas the interview data were analysed manually by looking and searching for noticeable patterns to be connected to the research framework. The findings suggest that although there is no explicit knowledge management system used in managing knowledge in the educational sector, there are a lot of elements and positive practices of knowledge management already in place that could help schools to develop and encourage activities such as knowledge sharing. As far as the contribution of the contextual factors to knowledge activities, technology was an important instrument in all of the knowledge activities, but it was certainly not the only or the most prominent one. The culture factor played a more significant role in all knowledge activities particularly when knowledge sharing was considered as a social and spiritual obligation in the communities of practice. Despite this, there were also barriers in the uptake of knowledge management initiatives in schools which seemed to limit knowledge activities due to time constraints and teacher workload.

This thesis is about exploring the business environments which influence the construction industry in Brunei Darussalam. It aims to analyse the existing business environments after the crippling effect of the 1997 financial crisis. It also aims to identify the business conditions for public-private partnerships, privatisation and private finance initiatives to flourish in Brunei and the corresponding critical success factors and failure reducing criteria. Relevant literature for public-private partnerships, privatisation and private finance initiatives were used to identify the critiques on these models. Relevant literature on business environments in which these models have been successfully implemented were also studied. The research questions look at the business conditions of successful public-private partnerships, privatisation and private finance initiatives and try to emulate them in the existing business environments by identifying the critical success factors and failure reducing criteria. The difficulties in collecting data in this type of research led to the selection of the Delphi technique. The Delphi technique was carried out in four rounds and six critical success factors and fourteen failure reducing criteria were identified and ranked according to their importance. Retrospective interviews were also conducted to validate the factors and give further insights on the potential implementation of these models in Brunei. Four practitioners validated the interpretations of this research. The results from the synthesis found four layers of business enviroments in which government influence exist in all levels. The private sector and private support services are only present in the fourth layer and are not the critical success factors in the business environments. The thesis concludes by discussing methods to improve the business environments in which public-private partnerships, privatisation and private finance initiatives could flourish in Brunei, and the direction of future research to improve the business environinents for private sector activities in general.

The research involves devising new control and compensation methods for DC power distribution systems containing power electronics loads with constant power characteristic. A compensation method called an active damping network is examined, which utilises capacitor and inductor energy storage elements and high frequency switching devices. This network is controlled to behave as a small-signal resistor so that any instabilities in the power distribution system due to the interaction between interconnected sub-systems will be damped and eliminated successfully. This method is studied and analysed in detail. The system was designed and simulated, and was verified by experimental results. The results show that stable operation is achieved of a small-scale power distribution system that contains power electronic loads with constant power characteristics such as DC-DC converters and electrical drives.

This is an exploratory study, which aims to examine the factors affecting the research publication productivity of academic engineers and scientists from the National University of Malaysia (UKM) and University of Malaya (UM). This study aims to identify problems, as well as increase the understanding of factors conducive for a productive academic research environment.

In this study the use of seeded microfiltration (MF) with modified powdered carbon focussed on the removal of copper ions from an aqueous solution. The aim of the study was to look into the possibility of utilisation of suitable modified activated carbons combined with membrane filtration (microfiltration) as an alternative technique for the treatment and recovery of copper ions from liquid wastes, to give high removal efficiency with low energy consumption. To enhance the filtration process, the particle size of modified activated carbon used was small because it provides a larger surface area and a shorter diffusional distance for base metals to be adsorbed. Furthermore, in order to minimise the fouling effect, a surface filter (nickel membrane) which had pores, or slots, that passed directly from one side of the filter to the other with no tortuosity was used.

This thesis is a study of the traditional Islamic educational institution (ipondok) in Malaysia. The aim of this thesis is to analyse the existing pondok educational system and to suggest changes which need to be introduced in order to make it relevant to the modern needs without thereby compromising the traditional values. The study starts with a brief discussion about the nature of knowledge in Islam. This is followed by a discussion about the origins of the methodology of teaching with an analysis of the terms used in Islamic education, the methodologies of Gabriel and the Prophet. In Chapter Two, discussion pertaining to the theories and practices of the methodology of teaching is presented through examining the various aspects of teaching which could be discerned from the Qur'an and relating them to the practical and customary spheres. Chapter Three presents the influence of traditional Islamic education on the Malays, giving considerable attention to the manners in which the Malays pursued their religious study. Chapter Four attempts to examine the pondok system by studying the daily and educational life of the institution. In Chapter Five a critical analysis of the methodology of the teaching at the pondok is presented along with the recommended changes of which the pondok system as a whole stands in need for its future survival. This is followed by a conclusion, a bibliography and appendices.

This is a study of constitutional and political development in Brunei Darussalam between 1944 and 1962. Responding to new forces unleashed by World War II, British planners in the Colonial Office embarked on a policy of promoting political progress in Brunei Darussalam with the aim of eventually introducing self-government, with the widest possible participation of the people of all communities. The thesis traces the origins of the Colonial Office's plan to introduce constitutional government in Brunei Darussalam, examines the evolution of the plan taking particular account of the obstructive intrusion of certain post-war developments which inevitably delayed the fruition of a full political advancement; and analyses the interaction between the local ruling elite, the British Colonial administration, and the Partai Rakyat Brunei (People's Party of Brunei). In the event the Brunei Darussalam Constitution, promulgated on 29 September 1959, failed to give full satisfaction to a large section of the people, causing in the end a rebellion which broke out on 8 December 1962. It also analyses the British plan to bring Brunei Darussalam in closer association with its neighbours in a loose federation. When this plan failed, the British put pressure on Brunei Darussalam to enter the Malaysia Federation, which inevitably gave impetus to the rebellion. In the end, Brunei Darussalam not only did not join the Malaysia Federation, it also chose not to adopt a democratic form of government. Instead, when it resumed its full independence on 1 January 1984, Brunei chose to be governed by a Sultan under the concept of Malay Islamic Monarchy.

The interest in one dimensional (1D) magnetism has been strongly renewed with the synthesis of many magnetic compounds which exhibit a quasi one dimensional magnetic behaviour. One of the peculiarities of this 1D system is the absence of a long range magnetic ordered phase at any finite temperature for the ideal 1D system with short range interaction. Tetramethylammonium manganese chloride (CH3)4NMnCl3(TMMC) exhibits the properties of an ideal one dimensional antiferromagnets for temperature above 1 K, the transition to a three dimensional (3D) long range ordered state only occurs at 0.84K. In addition to its magnetic transition, TMMC exhibits structural phase transition due to the ordering of the tetramethylammonium (TMA) ions which makes also this compound very attractive from a lattice dynamical point of view. Structural phase transitions of tetramethylammonium manganese chloride (TMMC), tetramethylammonium manganese bromide (TMMB) and tetramethylammonium manganese chloride doped with 8% Cu (TMMC:Cu) of the hexagonal type compounds are investigated using the Brillouin scattering method. These crystals show pronounced acoustic anomalies in the region of the structural phase transition. The acoustic anomalies were observed by measuring sound velocity and hence the elastic constant can be deduced. The phase transition temperatures were observed at 129.6K and 388.6K (TMMC), 114.6K and 377.6K (TMMB) and at 108.6K and 359.6K (TMMC:Cu). The elastic constant at room temperature were C11 = 2.10 (TMMC) and C11 = 1.59 (TMMB) in units of 1010 Nm-2. The phase transition of these compounds were further investigated macroscopically using the Differential Scanning Calorimetry (DSC) method. Activation energies of TMMC, TMMC:Cu, TMMB and deuterated TMMB at the phase transition were determined using this method. The values are 70.612 kJ/mol (TMMC), 49.224 kJ/mol (TMMC:Cu), 51.747 kJ/mol (TMMB) and 69.909 kJ/mol (d12-TMMB). The elastic constant of the linear chain antiferromagnet CsNiCl3 and RbNiCl3 was also determined using the Brillouin scattering method. The room temperature measurements give C11 = 3.77 (3.71) and C33 = 5.62 (5.42) in units of 1010 Nm·2 for CsNiCl3 and RbNiCl3 respectively. The phonon dispersion curves at room temperature in the hexagonal CsFeBr3 have been studied using the inelastic neutron scattering technique. From the initial slope of the dispersion curve, the sound velocity was deduced which enable us to calculate the elastic constant of CsFeBr3 at room temperature. The values obtained are C11 = 7.33, C66 = 1.01, C33 = 2.58 and C44 = 0.56 in units of 1010 Nm·2.

This thesis describes a study of the potential contribution of industrial design to the adaptation of agricultural machinery for use in Malaysia. The study identifies the nature of agricultural machinery and equipment design which uses mainly adaptation concepts as a means of getting a 'quick' design. The nature of industrial design with regard to agricultural machinery and equipment design in Malaysia and the UK was also studied. This research has established the potential of industrial designers to contribute in this area of design activity. This researchu tilised a combinedm ethodologyo f'triangulation' where quantitative surveysa nd qualitative studies were used. Literature surveys, a groundwork study, questionnaire surveys, case studies, interviews, and observations were carried out. Case studies and interviews were the main methods of data collection while questionnaire surveys helped to provide information, support, and validate findings from the former methods. Case studies and interviews involved five establishmentsin Malaysia and four companiesi n the UK. Adaptation designw as confirmed as'a successfulc oncept, however, the processesin volved in the designo f machinesa nd equipmentn eedt o be developeda nd improved. There were generally no specific design processes or procedures adhered to while carrying adaptation design work. They were determinedb y the samef actors i. e. the types of projects, aims/objectiveso f project, duration and date-line, funding and level of adaptation design. From the quantitative survey and qualitatives tudyr esults,i t was establishedth at industrial design should be incorporated into the adaptation design concept. The role of industrial designers in adaptation design can be that of assisting and advising the engineers and working collectively as a team. The potential contributionso f industriald esignersw ould be to improve 'appearance('a esthetics),q uality, and overall design. Industrial design knowledge in human-factors- ergonomics/anthropometricswere also sort for in order to satisfy factors such as safety and ease of use. Industrial designers were also needed to achieve designs which could reduce costs and to increase sales of machinery/equipmenpt roducts. The thesis concludes that the diverse nature of agricultural machinery and equipment design, especiallyfo cusingo n the adaptationd esignc oncept,r equiresa synthesisa pproachr equiring the participation and consideration of such factors as: inter-disciplinary relationships, agricultural policy, designp olicy, designe ducation,a nd public awarenessA. ll thesef actors coupled with the contributions made by industrial designers would bring improvements to the success rates of adaptation design. V

This study concerns mainly with the status and position of dhimmi in various aspects of Islamic law. It is an attempt to survey the legal status of dhimmi in the scattered writings of Muslim jurists, and tie them up systematically in a one work. The Introduction deals with the purpose of the inquiry, the scope, and the relevant literature of the " thesis. In Chapter One the Muslim conception of the world, or Islamic law of nations; viz. dar al-Isläm, d8r alh" arb. dgr al-'ahd. is analysed as is the nature of the relationship among those states, and category of non- Muslims. Chapter Two is devoted to the dimmr's obligations pertaining to the fundamental concepts of lizyah kharä_i. 'ushr, and their need to observe some aspects of Islamic law. Chapter Three is concerned with the principles and aspects of the Islamic conception of tolerance towards non-Muslims as well as some archetypes of Muslim tolerance. Chapter Four gives a detailed discussion of the dhimmi's judicial status in Islamic criminal and family laws, and the law of contracts.Chapter Five is concerned mainly with the analysis of dhimmf's religio-socio-political status. The question of religious autonomy, political rights, economic, education, welfare etc. will be discussed. Finally, Chapter Six outlines the result of this study.

The present study is an attempt to provide an explicit account of Malay relative clause formation using the transformational approach. It aims at providing an analysis which can characterize Malay relative clauses in the most adequate manner. Various analyses which have been proposed for English are examined and their problem as applied to Malay discussed. It is found that there is no justification for assuming that yang, introducing relative clauses is a relative pronoun and I propose that this element be analyzed as a complementizer. The standard analysis of relative clause formation, ie the wh-movement analysis, is found to be inadequate for describing Malay relatives and as an alternative a deletion rule is proposed. It is shown, however, that only nominals in the left-most position of the embedded clause may be relativized (deleted) and it is argued that whenever the relativized element does not occupy this position, other rules such as Passives, Topicalization, Tough Movement and Left-Dislocation have to apply prior to relativization process. The proposed analysis is found to be capable of accounting not only for restrictive relatives but also for free relatives as well as non-restrictive relatives.

The primary objective of this thesis was to examine the major factors affecting the sorptive separation of simple water soluble organics, eg alcohols, aldehydes, ketones, carboxylic acids, with hydrophobic adsorbents. The model system considered is the separation of aqueous ethanol with an adsorbent formed by pelletizing micron sized hydrophobic silicalite crystals. The structural characteristics of the bi-dispersed silicalite pellets are examined in Chapter 2. The size distribution of the crystals was measured by various techniques and fitted a log-normal distribution with a median size of 3.78 um. The macropore size distribution of the pellets was determined by mercury porosimetry and showed a unimodal distribution with a mean macropore diameter of 0.6 um. The pellets had a macropore volume of 0.202 cm[3]/g, a macropore voidage of 0.26 and a density of 1.285 g/cm[3] . The sorption equilibria for the system {ethanol-water}/silicalite crystals is considered in Chapter 3. The basic difference between vapour and liquid phase sorption and the fundamental constraint caused by the inaccessibility of the adsorbed phase to direct measurement are considered first. This is followed by the development of a novel technique which for the first time enables the direct measurement of the individual adsorption isotherms for microporous solids. Comparison of the measured data with the predictions based on the available theories of adsorption from solution show considerable discrepancy. This is traced to the inherent assumption of no volume change of mixing common to all the proposed theories. For the system {ethanol-water}/silicalite the adsorbed phase exhibits as much as 30% volume change of mixing. The packing density and the total number of molecules adsorbed is therefore a very strong function of composition. Chapter 4 is devoted to a rigorous thermodynamic analysis of the adsorption equilibria for the system {ethanol-waterl/silicalite. The relevant thermodynamic relationships are derived first without any a priori assumption other than the existence of a distinct adsorbed phase. The major significance of the analysis presented is that for the very first time it is based on measured rather than predicted adsorbed phase composition. For the {ethanol-water }/silicalite system, the behaviour of the adsorbed phase is shown to be radically different from that of the bulk solution. The bulk liquid exhibits strong positive deviation from Raoult's law indicating that water-water and ethanol-ethanol molecular interactions dominate over that between unlike species. The adsorbed phase activity coefficients, however, show strong negative deviation from Raoult's law; indicating that ethanol-water interactions overshadow that between the like molecules. The major practical consequence of this observation is that surface modification of the hydrophobic crystals is unlikely to alter the selectivity significantly. The analysis presented also enables a direct thermodynamic consistency test of the adsorption data which has not been previously reported. The models proposed to describe intraparticle mass transfer are critically reviewed in Chapter 5 and the macropore-micropore diffusion model is identified as the most realistic for silicalite pellets. The intracrystalline diffusion rates were measured directly and their analysis reveals fundamental differences between uptake of pure ethanol and pure water consistent with the observed equilibrium behaviour. This information is used to determine the controlling mechanism for mass transfer between a flowing fluid and silicalite pellets. The time constants for external film mass transfer, macropore diffusion and micropore diffusion are estimated at 2.72, 82.32 and 0.07 seconds respectively. The controlling mechanism is therefore macropore diffusion with intracrystalline diffusion playing an insignificant role. This a direct consequence of the small crystal size and the relatively rapid intracrystalline diffusivity of water and ethanol in silicalite. The above information is pulled together in a mathematical model to describe the dynamics of adsorption of ethanol-water mixtures onto a fixed-bed of silicalite pellets. The model allows for axial dispersion, external film mass transfer and describes the intraparticle mass transfer in terms of a macropore diffusion model. The model partial differential equations are solved by the orthogonal collocation technique. A detailed sensitivity analysis is conducted which confirms axial dispersion and external film mass transfer coefficients can be confidently predicted from the available literature correlations. The isotherm is measured independently which leaves only the effective macropore diffusivity to be obtained by matching with experimental breakthrough curve. Such curves were obtained on a carefully designed small pilot adsorption unit with considerable attention to the distortions caused by the entrance and exit effects and the sampling procedures. The effective macropore diffusivity recovered is 4.0x10[-6] cm[2]/s which suggests a tortuosity of 3.2 for the silicalite pellets. This model and the parameter values determined independently provides a valuable tool for future scale-up and design studies.

Recently, friction stir spot welding (FSSW), a variant of “linear” friction stir welding (FSW) has received considerable attention from automobile industries to replace electric resistance spot welding with aluminum frames. Thus far, the FSSW process has been successfully developed and applied in various cases, but the physics behind the process is not yet fully understood. Effective and reliable computational models of the FSSW process would greatly enhance the study of friction phenomena during the process as well as energy dissipation. Approaches for the computational modeling of the FSSW process, however, are still under development and much work is still needed, particularly the application of explicit finite element codes for a verifiable simulation. The main objective of this dissertation research is aimed at describing the friction phenomena and heat generation during FSSW process. To achieve this objective, a three-dimensional fully coupled thermal-stress finite element (FE) model has been developed in Abaqus/Explicit code. The simulation model utilizes the advantages offered by the arbitrary Lagrangian Eulerian (ALE) formulation in simulating severe element distortion using an adaptive mesh scheme. Rate dependent Johnson-Cook material model is used for elastic plastic work deformations. Since friction in FSSW cannot be effectively treated by a simple “friction coefficient”, a friction coefficient, which is dependant on pressure, temperature and slip rate is used with sliding Coulomb friction at the interface between the workpiece and the welding tool. The simulation results include temperature, stress and strain distributions as well as frictional dissipation energy, which are presented at the end of this dissertation. The peak temperature at the tip of the pin and frictional dissipation energy are in close agreement with the experimental work done by Gerlich et al. [1], which is about 5.1% different.