Sri Lanka's participation rates in higher education are low and have risen only slightly in the last few decades; the number of places for higher education in the state university system only caters for around 3% of the university entrant age cohort. The literature reveals that the highly competitive global knowledge economy increasingly favours workers with high levels of education who are also lifelong learners. This lack of access to higher education for a sizable proportion of the labour force is identified as a severe impediment to Sri Lanka‟s competitiveness in the global knowledge economy. The literature also suggests that Information and Communication Technologies are increasingly relied upon in many contexts in order to deliver flexible learning, to cater especially for the needs of lifelong learners in today‟s higher educational landscape. The government of Sri Lanka invested heavily in ICTs for distance education during the period 2003-2009 in a bid to increase access to higher education; but there has been little research into the impact of this. To address this lack, this study investigated the impact of ICTs on distance education in Sri Lanka with respect to increasing access to higher education. In order to achieve this aim, the research focused on Sri Lanka‟s effort from three perspectives: policy perspective, implementation perspective and user perspective. A multiple case study research using an ethnographic approach was conducted to observe Orange Valley University‟s and Yellow Fields University‟s (pseudonymous) implementation of distance education programmes using questionnaires, qualitative interviewing and document analysis. In total, data for the analysis was collected from 129 questionnaires, 33 individual interviews and 2 group interviews. The research revealed that ICTs have indeed increased opportunities for higher education; but mainly for people of affluent families from the Western Province. Issues identified were categorized under the themes: quality assurance, location, language, digital literacies and access to resources. Recommendations were offered to tackle the identified issues in accordance with the study findings. The study also revealed the strong presence of a multifaceted digital divide in the country. In conclusion, this research has shown that iii although ICT-enabled distance education has the potential to increase access to higher education the present implementation of the system in Sri Lanka has been less than successful.

The interest in use of SMAs in vibrational systems is stimulated by their ability to dissipate energy and consequently their potential to control the dynamic behaviour of the system. In this thesis nonlinear dynamics of an impact oscillator with one sided motion constraint made of a shape memory alloy (SMA) is investigated. The pseudoelastic behaviour of SMAs is characterized by high non-linear recovery deformations and energy dissipation due to the occurrence of hysteresis. The thermo-mechanical description of the SMA element follows the formulation proposed by Bernardini et al. [1,2]. Extensive numerical investigations into the influence of the forcing parameters, which characterize the intensity of the load acting on the SMA has been carried out. They suggest that the system can exhibit complex dynamic responses, which if appropriately controlled can be used for vibration reduction. The comparison with the equivalent elastic oscillator response has shown that the use of the SMA can significantly change the dynamic response of the system. Whereas low amplitude regimes are not affected by the SMA element, at resonances when the response amplitudes are large, a significant vibration reduction is achieved due to the phase transformation hysteresis loop. Two types of periodic response co-existence is also revealed in these regions. At the same time, in other frequency ranges the existence of additional modes of motion in the pseudoelastic oscillator can cause new large amplitude responses (both periodic and chaotic) to be generated, as well as eliminate some of the co-existing responses. Various bifurcation scenarios are constructed and the influence of the SMA element is discussed. To verify the obtained theoretical predictions, an experimental rig was designed and limited experimental studies have been conducted. The substantial response amplitude reduction at resonances has been captured, as well as the jumps to higher amplitude responses due to the softening behaviour of SMA. The numerical results appeared to be in a good agreement with the experimental data.

This thesis describes a form of non-contact measurement using two dimensional hall effect sensing to resolve the location of a moving magnet which is part of a ‘magnetic spring’ type suspension system. This work was inspired by the field of Space Robotics, which currently relies on solid link suspension techniques for rover stability. This thesis details the design, development and testing of a novel magnetic suspension system with a possible application in space and terrestrial based robotics, especially when the robot needs to traverse rough terrain. A number of algorithms were developed, to utilize experimental data from testing, that can approximate the separation between magnets in the suspension module through observation of the magnetic fields. Experimental hardware was also developed to demonstrate how two dimensional hall effect sensor arrays could provide accurate feedback, with respects to the magnetic suspension modules operation, so that future work can include the sensor array in a real-time control system to produce dynamic ride control for space robots. The research performed has proven that two dimensional hall effect sensing with respects to magnetic suspension is accurate, effective and suitable for future testing.

The aim of this research is to present indirect vector control (IVC) for a Brushless Doubly Fed Twin Induction Generator (BDFTIG) for wind energy conversion. The system is anticipated as an advanced solution to the conventional doubly fed induction generator (DFIG) to decrease the maintenance cost and increase the system reliability of the wind turbine system. The proposed BDFTIG employs two cascaded induction machine sets, which consists of two wound rotor induction machines with their rotors connected in cascade to eliminate the brushes and copper rings in the DFIG. This new machine would ideally have one common rotor, and the two stators to be integrated within one housing. For the practical purpose of this research two separate DFIG’s were coupled together to a single prime mover. The dynamic model of the BDFTIG with the two machines’ rotors electromechanically coupled in a back-to-back configuration is developed and implemented using Matlab/Simulink. Based on the model, the control scheme for flexible power flow control in the BDFTIG with a bidirectional converter is developed. Independent control of the active and reactive power flow is achieved by a four-quadrant power converter under the closed-loop stator flux oriented control scheme. In the proposed control strategy, the generator speed tracks the reference speed very well, and thus the maximum power extract. Which is the optimum speed derived from the maximum power point tracking of the wind turbine.

No description available.

The investigation was undertaken firstly to identify, classify and assess requirements and methods for in-service training in the use of computer-aided design (CAD) systems in UK building surveying practice. The second purpose was to develop, test and assess alternative instructional methods for practitioners to acquire and develop capabilities for appropriate use of CAD. Requirements, opportunities and constraints were informed through discussion with practitioners, suppliers of CAD systems or associated services, and a postal survey of 50 UK building surveying practices. Collated information was considered within Romiszowski's (1984) framework for problem solving in the organisation. Conventional methods for CAD training in the UK construction industry, and relevant instructional theory, were investigated in a literature search. Alternative instructional models and methods were identified and developed through an action research methodology based upon Cohen and Manion (1989). Proposals were assessed conceptually using the first three of Popper's (1959) four tests for theories. Prototyping core components, substantially by computer-based methods, and classroom experiments with students of building surveying, or clients of the Leicester CAD Centre, both at De Montfort University, were used in place of Popper's fourth test. The research findings contribute detailed analysis of requirements, provision and constraints to a sparse knowledge base for use of CAD in building surveying. They also provide a critical review of conventional methods for developing users of the technology in this domain. Three core principles are proposed to guide the policies and actions of building surveying practices in relation to CAD, emphasising integration of staff development within an overall CAD strategy. An alternative instructional model, synthesised from results across the research programme, is recommended for developing relevant practical capabilities with CAD. Corresponding specifications are made for a hybrid of manual, interpersonal and computer-based methods for its implementation. The model is set in the context of wider considerations for effective use of CAD technology, and is independent of particular software systems, types of workplace and trainee. Theoretically the model is capable of rapidly enabling staff in any practice to apply relevant CAD hardware and software effectively to authentic tasks, and subsequently contribute to developing application methods in the workplace. In conjunction with recommended operational principles the alternative instructional model improves significantly upon conventional methods identified for in-service training in CAD by provision for strategic integration, system independence, and responsiveness to local requirements. The investigation concluded by identifying four foci for further research and development to overcome constraints on implementing the model by the methods prototyped. A fifth focus recommends investigation of an optimal model and methods to develop capabilities of staff in building surveying practices for appraising, implementing, managing and developing the use of CAD systems.

In this work the structure and interface structure of ErSi₂₋ˣ nanostructures grown on Si(001) are investigated by aberration corrected high angle annular dark field scanning transmission electron microscopy. The initial nucleation and growth mechanism are investigated by direct observation of the structure of ultra-small nanowires and it was found that the preferred structure does not fit with the currently accepted growth model. The nanowires nucleate in the hexagonal phase with an orientation relationship with the silicon substrate of (001)_Si/(011̄0)_ErSi₂₋ˣ, [110]_Si/[0001]_ErSi₂₋ˣ which is the exact opposite of the currently accepted strained growth model. As the nanowires increase in size it was observed that the nanostructures transform their orientation relationships to reduce their strain resulting in the structure that is expected from the strained growth model. A new growth model is suggested in that the observed orientation relationship has been found by previous calculations to be lower in energy than the strained growth equivalent for ultra-small nanowires. The interfaces of the ErSi₂₋ˣ nanostructures with Si(001) are found to be highly varied and complex, containing many defects which contribute to a lowering of the intensity of the Er columns directly at the interface. A new strain reduction mechanism is observed where the silicide nanostructure drops down a single Si step on the substrate surface. A structure model of this mechanism is proposed. The nanostructures have shown a preference for the triangular projection of Er columns at the interface which is not thought to be a remnant of the new orientation relationship, but a strain reduction mechanism that competes with the double stepped interface. Some interfaces have been found to have Er columns shifted from their expected positions up into the silicide. This was attributed to an ordering of the vacancies within the ErSi₂₋ˣ silicon lattice at the interface.

No description available.

No description available.

No description available.