Doctor of Philosophy (Ph.D.)

Permanent URI for this collectionhttp://192.248.9.226/handle/123/8871

Browse

Now showing 1 - 20 of 21

item: Thesis-Abstract
A Framework for providing a lifelong social security system for the operational workforce in the construction Industry in Sri Lanka
Wijewickreme, SP; Ekanayaka, LL; Pathirage, CP; Egbu, C
Construction is a projectised industry. One of the important resource requirements for construction projects is the availability of an operational workforce for its physical production. Hence, the operational workforce is a critical deciding factor in the success and failure of construction projects. The construction sector in Sri Lanka is suffering from a shortage of a required operational workforce for its physical operations even though the unemployment rate in Sri Lanka is about 5.2%. Research has further highlighted that “work” and “pay” are only the surface factors, hiding underneath them (similar to an iceberg) are a multitude of different problems and the psychological needs of the workers. In addition to the shortage, there is a lack of an organised structure for human resources, which delivers time, cost and quality related behavioural constraints within the construction industry of Sri Lanka since circa the 1980’s. The aim of the research is to develop a sustainable framework for a lifelong social security system for the operational workforce of the construction industry in Sri Lanka without increasing the prevailing construction costs. The hypothesis is the minimising of resource wastages and behavioural impacts of current practices and the introduction a secured future life through a new system of lifelong social security [PR/SS] for the operational workforce. It is anticipated that the finances required for providing a social security system can be salvaged from the recovery values of material and time wastages and the demand and supply impacts generated as repercussions from the behavioural practices of the current operational workforce. The research instruments used for gathering primary and secondary data for evaluating the financial impacts of behavioural constraints were a questionnaire survey and audited financial statements. About 400 questionnaires (That were premeditated to calculate the monetary impacts of the social behaviors of the construction operatives via ‘degree of importance’ and ‘relative important index’) were distributed to higher management of contracting organisations in Sri Lanka. A further request was made to the contracting organisations to provide audited statements for the past five years. From the research, it was identified that the unavailability of a human resources structure is a major constraint for the construction industry in Sri Lanka. Salvaged finances that could derive from the removal of the transitional layers of risk multiplication and the removal of the behavioural constraints of the construction operatives are sufficient to finance a lifelong social security system for themselves. Based on the research findings, framework for the Building Forces of Sri Lanka [BFSL] was developed to overcome from the interim thinking pattern of the current construction operatives. In the current system, contracting organisations are not capable of providing the required training for the operatives. With the implementation of BFSL alongside the strong intervention from statutory organisations, a trained operational workforce can be developed to face any situation within the construction arena in Sri Lanka.
item: Thesis-Abstract
High-density high-rise vertical living : an approprate housing solution for low-income people in Colombo, Sri Lanka?
Samarathunga, TC; O’Hear, D
A house is a basic and fundamental human need. In a literal sense, a house provides warmth, shelter and security. Beyond its physical nature, the concept of ‘house5 is deeply ingrained in human civilisation as the space where the institution of family is nurtured. It is a place that reflects a person’s identity, living condition, human values, aspirations, future expectations and one’s social and cultural identity. However, despite the global recognition of its importance, many millions of people in the world live either without safe habitable housing or without any housing at all. This situation is common in developing counties, especially in urban areas. The thesis is motivated by a sincere effort to practically address the problems of housing in the city of Colombo, in particular the scarcity ofsustainable habitable housing for low-income people. The Colombo City Development Plan (UDA 2008) revealed that there were 66,000 households within the city of Colombo living in under-served settlements considered unfit for human habitation. This figure represents 51 per cent of the city’s population (UDA 2008). Since gaining independence in 1948, the Sri Lankan Government has devoted much attention to finding a solution to this situation and has introduced a number of policies, programs and projects to address the issue of under-served settlements with varying degrees ofsuccess. High-rise housing for low-income people is one option that has been chosen by the current Sri Lankan government in the hope of re-housing those who currently live in under-served settlements in Colombo in sustainable, safe and affordable housing. At the time of writing this thesis (2012), the construction of nearly 12,000 high rise housing units has commenced with the aim of constructing 35,000 high rise dwellings within the next three years (UDA 2011). However, the appropriateness of high-rise housing for low-income people is a very controversial topic. Some countries have rejected high-rises as an option for low-income housing due to significant failures in the past while other countries have been very successful IV using high-rise housing for low-income people as a way to upgrade the living conditions of the people who live in slums and shanties. Very little research has been done in this sector, especially in Sri Lanka, and this thesis attempts to fill the knowledge gap about the lowincome housing sector in Colombo, discussing the research contribution of the theory, the contribution to the Sri Lankan research and the contribution to the profession. A qualitative research approach was chosen as the most appropriate method for investigating the research problem in depth. This research uses both secondary and primary data collection methods to enhance the quality of the research. Literature review, documentary research, Internet references, case study analysis, observation and key informant interviews are the main data collection strategies which have been used throughout the research. Twelve key informant interviews were conducted with officials in various government ministries, private-sector investors and professionals who are engaged in the housing sector in Colombo city. All participants are senior critical decision-makers and well-known government and private sector experts in the housing field in Sri Lanka. The data and information collected from the key informant interviews, case studies and other sources were scrutinised, edited, coded and analysed using qualitative data-analysing methods. The quality standards of this study take into account construct validity, internal validity, external validity and the study’s reliability. Finally, this research makes recommendations to the professionals and policy-makers who work with high-rise low-income housing on how to minimise the risk associated with highrise low-income housing in Colombo and open a way ofthinking about high-rise low-income housing.
item: Thesis-Abstract
An advanced trajectory planner for industrial robot manipulators
(2014-08-22) Munasinghe, SR
This thesis focuses on trajectory planning for industrial robot manipulators. It describes the existing problem of trajectory planning and proposes an appropriate solution. The proposed solution has been devised, implemented and verified for effective functionality. Trajectory planning in this context is the process of planning time-based joint position trajectories for a desired end-effector motion. It needs to consider all relevant constraints of the manipulator and given task specifications; because the final end-effector performance totally depends on the way the joint trajectories are planned. However, most trajectory planners in industrial robotics, even today, have adapted the technique of direct sampling of the desired end-effector motion, and transform such Cartesian positions to joint space using inverse kinematics. Then, the planned joint trajectories are simulated to check if they are realizable within the constraints. It is also inspected if the given task specifications are fulfilled sufficiently. Planned end-effector trajectory is iteratively adjusted by trial-and-error, until an optimum trajectory is obtained. This process has many demerits and it is therefore necessary to develop an appropriate trajectory planning algorithm which has provisions to consider constraints and task specifications in planning end-effector trajectories. It should also be generally applicable to industrial manipulators. Through constant collaboration with Yaskawa Robotics Inc., the major considerations of trajectory planning were identified as being : 1. trajectory allowance, 2. sharp corners, 3. joint acceleration limit, 4. assigned end-effector velocity, 5. Jerk reduction, and 6. delay dynamics. They were considered one-by-one, and techniques were developed to incorporate them into a single trajectory planner. Usually, desired end-effector trajectory is not the optimal trajectory. Therefore, the trajectory planner plans a realizable trajectory with the mentioned considerations above. Realizable trajectory is the optimal trajectory within the given trajectory allowance. At sharp corners, a circular arc is introduced within the trajectory allowance. Joint acceleration limit refers to the power amplifier current rating of the servo controller, and assigned end-effector velocity is the speed specification. End-effector trajectory can be planned using maximum joint acceleration as long as the end-effector remains below the assigned velocity. However, as the end-effector reaches assigned velocity, joint accelerations should be reduced and the speed should be uniformly maintained. Jerk can be reduced by fitting a spline approximation to the planned joint trajectories. Delay dynamics can be compensated by way of pole placement techniques and optimizing the pole by considering servo control input. The proposed trajectory planner was devised and implemented to control an industrial robot manipulator (Performer MK3s) so that a significant improvement of end-effector performance could be demonstrated. The same trajectory planner was rearranged into an autonomous module and incorporated with real-time control. This new implementation was proposed and implemented for supervisory controlled telerobotics applications. It was also applied for welfare robotics applications. Proposed trajectory planner is an off-line process, and it does not require hardware alterations. Thus, it could be conveniently implemented with existing robot manipulator systems.
item: Thesis-Abstract
A systems approach to earthquake vulnerability assessment
(2014-07-07) Sanchez-Silva, M
The ability to take decisions about the expected response of existing projects (i.e. buildings, lifelines, cities) to an earthquake is difficult and complex. The behaviour of a few selected parameters of the main structural system (e.g. inter-storey drift) are commonly used to make judgements. The behaviour of a project clearly depends upon the structure but it also depends upon many other factors which often are not considered. These include, safety culture, management, condition, use, construction, materials and so forth. The modelling and measurement of these factors vary in quality since they are very different in nature. A model which enables these factors to be put together to assess the proneness to failure of a particular project is proposed. The model follows a systems approach and concentrates on the modelling and management of information. The management of the uncertainty, which is classified into fuzzincss, incompleteness and randomness, is an important part of the model. Hierarchically arranged holons describe the processes making up the project and capture inherent fuzziness of the problem. The model includes tests (such as audits) which a project must pass in order to be declared dependably safe. Dependability is a measure of the degree to which an engineering theory has been tested in practical problems. The proposed methodology combines existing numerical models as well as ways of processing vague information and expert judgement. It is also a very flexible tool which allows the handling of various types of projects and situations which are slightly different from past experience. Experts will use linguistic assessments to measure the evidence about the dependability of processes to sustain their function during an earthquake. Linguistic assessments are matched to interval probability numbers. An interval number is used to capture, in a practical manner, features of fuzziness and incompleteness. Interval probability theory is used to combine evidential support values throughout the hierarchy. A computer implementation of the model (i.e. EVAS) was developed to show its potential for practical use. The software developed was used to apply the methodology to the Hospital Regional de Buenaventura in Colombia. Further testing of the proposed model and EVAS in practical applications should be carried out to ensure their dependability.
item: Thesis-Abstract
The Development of a structure for the design of hazard audits
(2014-07-07) Dester, WS
Hazard auditing, which is a formal, systematic, critical examination of a situation or set of circumstances to identify hazards, is fundamental to hazard management. Auditing is facilitated by "an audit" that details activities, procedures, systems and artefacts, where hazards might be identified. This thesis describes the development of a structure, in the form of a hierarchy, that can be used in the design of hazard audits. An examination of systems such as manufacturing and process plants, for hazards, is usually undertaken by examining the subsystems, (i.e. activities, systems, and procedures). Existing audits therefore, tend to be specific, as for example, audits of unsafe acts, unsafe conditions, technical functioning of materials and machinery, management. This type of audit restricts the examination to a closed system within observable and well described physical and organisational boundaries. It is argued in this thesis that examinations for hazards should go beyond this closed system and also look for hazards within the larger systems of society and industry. An examination of hazards can be seen as a search for evidence of proneness to failure. The hierarchy developed in this research focuses on hazard auditing for a construction project. Construction, which is associated with the construction industry, is only one phase in a larger system, the project, which encompasses development, use, and withdrawal from use. It is argued that evidence of proneness to failure of a construction project may be found in these systems, (project and industry), in the larger system of a social environment, and in the subsystems that are part of a construction project. These hazards are described in terms cf concepts, and presented in the form of a hierarchy that indicates inter-dependencies between concepts. This hierarchy is a basic structure to be used in the design of hazard audits. The concepts incorporated into the hierarchy are discussed and described in terms of their potential to provide evidence of proneness to failure. Sections of hierarchy are built up and presented at appropriate positions in the thesis. It is proposed that this approach to hazard auditing will allow for flexibility in dealing with specific situations, yet provide for the identification of hazards that can exist and develop outside of those situations. It is suggested that such an approach should be regarded as a specialist activity of hazard management. Further, it is argued that the activity of hazard engineering should be recognized as a separate discipline within its own right.
item: Thesis-Abstract
Optical properties of likely constituents of interstellar dust
(2014-07-01) Dayawansa, IJ
Optical properties of polyoxymethelene (POM) at room temperature have been measured from the near ultra-violet to infra-red as an initial stage of a line between interstellar dust and organic matter, and we report our results which are particularly relevant to interstellar extinction. There is a strong possibility of a more complex organic component which could significantly contribute to the interstellar extinction. Measurements have also been made of the effect of fast neutron bombardment on the optical properties of quartz (SiO). At a high total flux of neutrons the crystalline quartz will change to its amorphous form which has extinction properties that resemble the interstellar extinction. Extinction due to small particles of several forms of SiO.2 have been measured and among them the hydrated mineral, opal, behaved like an amorphous silica. Neutron irradiated olivine showed a stronger and a broader lOym band in addition to weaker bands towards the longer wavelengths which indicated that atomic damage has been produced. At high fluxes more atomic damage is expected to change the crystalline structure and there by cause changes in the infra-red absorption properties. Extinction measurements were also made for smoke particles of MgO in the infra-red. When the measurements Were made with the particles deposited on substrates, in addition to a very broad surface mode absorption feature around 20ym an extinction maximum was observed typical of the bulk mode at 25ym. Extinction measurements for MgO smoke particles in air also showed similar results. However when the particles were dispersed in a non-absorbing medium, the bulk absorption mode was not observed. This implies that the appearance of the bulk mode is due to clumping. It was also observed that the width of the band reduced significantly with decreasing powder density f in the medium. Hence it is concluded that considerable broadening is due to interactions which is not properly accounted for in the single particle theory.
item: Thesis-Abstract
An Investigation of some factors influencing the use of colliery discards as a fill material for reinforced earth construction
(2014-06-06) Fernando, DA
This thesis is concerned with an investigation of some factors influencing the use of coarse colliery discards as a fill material for reinforced earth construction. The work carried out in this study is primarily a laboratory study, investigating the properties of the fill materials, reinforcements and the soil-reinforcement interaction coefficients. Test were carried out on Cardown colliery discards to establish the geotecnical properties and to establish weather the discards satisfied the criteria set out by BE3/78(revised) and the DTp specification for Highway works(1986). Instruments ranging fro free field strain coils were used to measure strains in the soils. All methods utilised are reported. But, the success of the methods considered varied due to the nature of the fill materials.A through investigation was carried out to establish the shear strength envelope. The shear strength envelopes were established, they are as follows: i0 Particle sizes pertaining to the whole grading curve; ii)Specific particles size ranges; These tests indicate that the envelope can e segregated into two sections, one for the low stress region and another for the high stress region. The results of the former indicate tht the shear strength is stress dependent and can be accurately fitted by curvilinear regression analyses. The interaction tests carried out in this study and the data reviewed fro the other sources when represented non-dimentionally indicates that the RMS strips and the Tenser SR2 grinds yield the highest alpha values and hence the coefficients of friction. The result of shales tested with RMS strips yeild the highest coefficients of interaction. Envelopes have been formulated, subsequent to the collection of data for all the materials considered in this study. The results indicates that the alpha values as presented in BE3/78(re viced) are conservative, in the case of the RMS strips. The pull-out tests carried out in this study indicates that the RMS strips are the most efficient of all the conventional strips. The grid tests yielded the highest pull-out forces and they were most efficient of all the reinforcements tested. The field pull-out test data as reported by we indicated that the friction coefficients were lower with respect to the laboratory Data. This can be attributed to the difference in compaction. Comparison of the coefficient of friction indicates that the skin friction tests as measured in the shearbox are lower with respect to the pull-out test data. An equation was formulated using the results of the established Mohr envelopes with respect to particle size, skin friction tests and the spacing of the ribs in a RMS strip. The predicted values are accurate to within 10% of the measured values. The assessments of the cost benefits of using collier discards as the fill materials indicate that the benefit of colliery discard utilization is dependent on the cost of the fill and the haulage costs. With the benefits being over 30% with respect to conventional structures. The results of this study indicate that colliery discards when carefully selected and tested can be used as a fill material in reinforced earth constructions.
item: Thesis-Abstract
Hyperbolic paraboloid shell roofs
(2014-04-10) Mathai, AC
Of recent years,hyperbolic paraboloid doubly curved surface, has been used extensively in construction. It makes efficient ur.e of materials by relying on form or shape for strength rather than on mass. The simplicity of its structural action and its inherent beauty make it possible to achieve aesthetically pleasing structures of imposing proportions. One of the features of the hyperbolic paraboloid form, which appeals to the architect, is the many ways in which this warped surface can be combined to achieve completely dissimilar striking effects. The groined vault, the inverted umbrella and the saddle shape vault are all popular examples of the different appearances which can be achieved with basically the same
item: Thesis-Abstract
Use of rice hull ash in water treatment
(2014-04-08) Mampitiyaarachchi, TR
Rice hulls, the largest milling byproduct of rice, constitute one fifth of the paddy by weight. The hulls which can be obtained at relatively low cost, are in abundant supply in most developing countries, particularly in the Asian region. Hull contains approximately 20% silica by weight and, on combustion, yields a porous ash having a silica content of approximately 90 percent. This thesis investigates the following two possible applications of rice hull ash in water treatment processes: (i) the use of rice hull ash as a filter medium; (ii) the use of rice hull ash as a coagulant aid. Rice hull ash comprising amorphous silica was produced from locally available rice hulls, using a specially constructed incinerator. Scanning electron microscopic studies were conducted to evaluate the microstructure of this ash as well as diatomaceous earth and filter sand. The laboratory filtration experiments were conducted at slow to semi-rapid filtration rates in order to investigate the effectiveness of rice hull ash medium in removing turbidity, bacteria and colour from water, and to compare its performance with a conventional sand filter. Synthetic water was made by adding suitable amounts of kaolin clay, Escherichia coli suspension, coffee/leaf extract, to laboratory tap water. Filtrate quality and head loss were considered as the major parameters in assessing the performance of these filters. A number of thin layer filter experiments were conducted to obtain the variation of turbidity with depth in rice hull ash filters, under selected operating conditions. Solubility studies of rice hull ash at various strengths of sodium hydroxide and for various steeping periods were made to evaluate the optimum conditions for silica solubilisation. A dilution procedure including partial neutralization and Subsequent aging prior to further dilution was adopted to convert alkali soluble rice hull ash into activated silica. Coagulation of dilute clay suspensions (£ 40 m g / L ) , using alum, activated silica and selected polyelectrolytes were conducted with the aid of a jar test apparatus. The filtrate turbidity for approximately 750 mm depth of rice hull ash medium was equal to or less than that of a sand medium, at rates of filtration 0.25 to 2.0 m 3 / m 2h and a turbidity range of 20 to 60 FTU. The rate of head loss in the sand medium was 1.5 to 5 times more than in an ash filter. The optimum rate of filtration for the ash filter occurred at 1.0 m 3 / m 2 h , with a rate of head loss of 52 mm/d. At filtration rates of 0.5 and 1.0 m 3 / m 2 h , for an influent Escherichia coli concentration of 100 - 2000 no/mL, approximately 70% to 90% reductions in bacterial numbers were achieved by 750 mm depths of rice hull ash media. Colour removal of at least 30% was achieved by shallow depths (< 320 mm) of ash media, at slow rates of filtration (< 0.25 m 3 / m 2 h ). The results obtained from thin layer filtration experiments were analysed using a statistical filtration model known as the chi-square distribution analogy. This technique was successful in predicting the performance of rice hull ash filters at specific operating conditions. The optimum removal of silica from rice hull ash occurred when ash was steeped in 5% NaOH solution for a period of 24 h. A procedure for the preparation of activated silica from rice hull ash was developed. The addition of 5 mg/L of activated silica as a coagulant aid during the coagulation of turbid water (4 0 mg/L of kaolin clay) with 50 mg/L of alum at pH value of 6, was sufficient to achieve a residual turbidity of 1.2 FTU. The coagulation of the same water with alum or alum-polyelectrolyte at similar conditions led to higher residual turbidity.
item: Thesis-Full-text
Consolidation analysis of Sri Lankan peaty clay using elasto-viscoplastic theory
(7/16/2011) Karunawardena, WA; Kulathilaka, SAS
is necessary to take these properties into account in order to obtain better predictions from peat consolidation analyses. In the present study, the consolidation behavior of peaty clay found in Sri Lanka is extensively studied using a model based on the elasto-viscoplastic theory. The model can describe the prominent creep behavior of peaty soil as a continuous process. In addition, the model can accommodate the effect of structural degradation on the consolidation process. The analysis takes into account all the main features involved in the peat consolidation process, namely, finite strain, variable permeability, and the effect of secondary compression. Also, it considers the variable compressibility for stage constructed embankments which exert high levels of pressure on the peaty subsoil. The constitutive equations used in the model and the procedure adapted to account for the above-mentioned features of the analysis are described. The constitutive model is based on Perzyna's type viscoplastic theory and the Cambridge elasto-plastic theory combined with empirical evidence. In the finite element formulations, which are based on the finite deformation theory, an updated Lagrangian method is adopted. A description of the material parameters used in the model and the procedures applied to evaluate them, with standard laboratory and field tests, are explained. In addition,. a performance of the model incorporating the original and the modified Cam-clay theory is evaluated by simulating triaxial test results. A comparison shows that with the present definition of the parameters, the original model yields more representative results than the model based on the modified Cam-clay theory. Initially, the capability of the constitutive model to capture the consolidation behavior is verified using the consolidation model test data on peaty clay found in Sri Lanka. It is confirmed that the constitutive model is able to predict the observed creep characteristics and the effect of sample thickness on settlement predictions for the material under consideration. The performance of the model in predicting the consolidation behavior under field conditions is studied using field data on instrumented earth fill constructed on peaty clay. One-dimensional compression is assumed for the peaty clay due to the large plane area of the fill. Separate analyses are carried out by the model considering the infinitesimal strain theory, the finite strain theory, and the finite strain theory together with the effect of structural degradation in order to explore how these features describe the observed field behavior. Analyses reveal that it is necessary to consider finite deformation together with the effect of structural degradation in order to successfully simulate the resultant large strain and the stagnated pore water pressure observed in the field. The construction of road embankments over peat deposits is quite problematic, and thus, it is often done after first improving the properties of the peaty soil through the utilization of appropriate ground-improvement techniques. Understanding the field response of peaty clay during this improvement process is naturally of great importance. A constitutive model is applied to predict the field performance of embankments constructed on peaty clay using different ground-improvement techniques. The back analysis of embankments constructed with the preloading method indicates that the model can be successfully applied to predict both the deformation and the stability of structures constructed on peaty clays. The stability of the embankment during and after construction is verified by investigating the stress-strain characteristics of the subsoil. The model applications used to predict the consolidation behavior of embankments constructed by the preloading method, combined with other ground-improvement techniques, are then discussed. Embankments constructed with prefabricated vertical drains (PVDs) and sand compaction piles (SCPs) are considered, and finite element analyses are carried out in all cases by converting the actual three-dimensional conditions that exist around the drains into simplified two-dimensional plane strain conditions. The field behavior when PVDs are installed in the peaty clay is simulated using the equivalent vertical permeability for the PVD-improved subsoil. In the case of SCPs, a conversion scheme is used to transform the axisymmetric nature of sand columns into equivalent plane strain conditions. A comparison of the predicted results with the field observations shows a reasonable agreement. An analysis of the PVD-improved foundation indicates that the installation of PVDs not only accelerates the rate of consolidation, but influences the deformation pattern of the subsoil due to embankment loading. The analysis also shows that the use of PVDs can significantly increase embankment stability. The model prediction for the SCP-improved foundation reveals that the stiffness and the area replacement ratio used in the conversion scheme play vital roles in predicting the behavior of SCP-improved soft grounds. The observed improvements in the bearing capacity of the subsoil and in the stability of the embankment, brought about by the installation of SCPs, can be simulated by the model.
item: Thesis-Abstract
Representation of transformers in switching surge studies
Lucas, JR
A Transformer representation suitable for switching surge analysis is derived in terms of 'primitive' inductance and capacitance matrices. Connection matrices are used to account for all types of winding connections. Frequency dependance of elements is considered. The transmission line is formulated on a frequency basis, and the earth return path is represented by Carson's formula. Series and shunt compensation are also included with the line. The cable is similarly formulated. The problem is solved in the frequency plane using the Fourier Transform, and then transformed back into the time domain. Modal analysis is used for both transmission line and cable two port admittance matrix formulation. Energisation on both low voltage as well as high voltage sides of the source side transformer are considered for transformer feeders. A few comparisons with field test oscillograms are given to validate the formulation of the problem. Voltage non-linearities when surge divertors are present are considered using a step response of the linear system and Duhamel's integral, together with the Newton-Raphson iterative technique for both single phase and three operation. Finally, the Newton-Raphson algorithm is further extended to take into account the magnetic non-linearity of the transformer 'core. Flux coupling between phases during saturation is calculated based on the instantaneous reluctance values of the individual limbs and the leakage air path.
item: Thesis-Abstract
An Approach to conceptualizing the environmental image of an urban locality for planning
Munasinghe, JN
Recent trends in local level planning have emphasized the importance of enhancing place images. Hence, conceptualizing the form of a locality's image has become a need in urban planning. Having noted the limitations in available approaches, and the knowledge gaps for such conceptualizing through a literature review, this study was undertaken to evolve a conceptual model of the structure of a locality's image. For this purpose the results of an empirical investigation of the inhabitants' cognition were interpreted in the light of theoretical positions established by previous studies. The research was designed on the premises that the 'spatial extent' of the environment constitutes the substantial domain of urban planning and the planners aspire to work in its 'public realm'. Hence, the focus was on the shared spatial references in inhabitants' cognition. The empirical work included a questionnaire survey, a field reconnaissance and a cartographic survey. Referring to the 'invariant' and the 'context specific' characteristics of the findings, it was suggested that the environmental image of a place was a 'unitary' concept and its structure was configured of the 'reference points' both 'collectively' and 'individually' held by the inhabitants. Therefore, the model evolved here was named the unitary image of the place. Its 'collective' domain was shown as the potential area for the urban planners to intervene to work about a locality's image and thereby, to integrate inhabitants' cognition with the planning process. Keywords: Environmental Image, Cognition, Place, Locality, Inhabitants, Spatial Elements.
item: Thesis-Abstract
Optimising earthmoving by linear programming and computer simulation
(5/24/2011) Jayawardane, AKW
The accuracy of planning and estimating of earthmoving operations in any highway construction is important for both successful tendering and high profit margins. Mass-haul diagrams and experienced engineering judgment together with deterministic methods have been the key factors in planning and estimating earthmoving operations. Despite this, the limited use of Mass-haul diagrams and inaccuracy of deterministic estimates are well known. Although Stochastic and Linear Programming methods were developed to overcome some of these limitations, those available hitherto are relatively fundamental and are not bold enough to incorporate most real life problems. After identifying the need for a relatively quick and accurate planning and estimating procedure, a new approach was developed by combining Computer Simulation and Linear/Integer Programming. The developed model was named RESOM; an acronym for Roadwork Earthmoving System Optimisation Model and was developed in three basic stages: simulation model; LPIIP model; and network model. RESOM can be applied to any road project to obtain an optimum earthmoving plan including material distribution, plant utilisation incorporating real life problems and constraints. The main aims of the simulation model were to obtain realistic unit costs and production rates using balanced plant teams. Various cycle element times of earthmoving equipment were obtained from standard distributions fitted onto field data collected from four sites in Sri Lanka. Comprehensive LPIIP formulations were developed incorporating constraints like project duration, plant availability, sequence of operations etc. to obtain an optimum earthmoving plan using the simulated results. The third stage of RESOM involved the presentation of the selected earthmoving plan in the form of network diagrams and barcharts. RESOM was successfully validated using two actual case studies (Anamaduwa Gam Udawa, Sri Lanka, and the A42 - Measham and Ashby By-pass, UK). Application and experimentation with RESOM were explained using two other case studies (the M40 - Banbury By-pass and a hypothetical example) and proved that about 20% cost savings can be obtained. The experimentation process revealed that RESOM could be of considerable help in planning, estimating and obtaining optimum earthmoving plans.
item: Thesis-Abstract
Porting a distributed operating system to a shared memory parallel computer
Atukorala, GS
This thesis describes the porting of a distributed operating system, Helios, to a bus based, shared memory, parallel processing computer. Helios design was originally based on a distributed memory, transputer network, connected via serial links. After examining the design of distributed operating systems in general, the design issues and the implementation of porting Helios to a Motorola MC68020jMC68881 based, shared memory, parallel computer, are described. Performance measurements that were taken on the new version of the operating system are then described. The results are compared with that of the original version and also with that of the Tripos operating system. Running a parallel programming application to test the efficiency in utilizing the available parallel processing power is also described. Finally, future work is suggested, particularly in the areas of inter-processor communication, the use of shared memory and porting Helios to other processors
item: Thesis-Full-text
Some factors influencing the engineering properties of Hawkesbury Sandstone
De Silva, MDK
The Hawkesbury Sandstone is a major rock unit within the Permian-Triassic sediments which form the Sydney Basin, Australia. It covers an area of about 12,5000 square kilometers and has a thickness of about 300 meters. As a result of its widespread occurrence in the region, particularly in the metropolitan area, it is of considerable importance to both the civil engineer and the geologist. This thesis examines the factors causing variations in the engineering properties of Hawkesbury Sandstone. An investigation has also been included to determine the suitability of crushed sandstone as a concrete and road aggregate. The determination of the mechanical properties of fresh Hawkesbury Sandstone was carried out in the laboratory on small specimens of intact rock, free from obvious macroscopic discontinuities, sampled at different locations in accordance with the standard test procedures. A number of sandstone exposures, in the form of quarries and roadside cuttings, were examined to understand the natural processes of weathering occurring in the field. Samples of weathered rock, representing all stages of weathering, were also tested in the laboratory to determine the effects of weathering on the properties of this sandstone. Thin section studies were made on all fresh and weathered samples to study the mineralogy and the texture of the rock. The clay fraction of the rock was analysed using X-ray diffraction and differential thermal analysis techniques. Samples of fresh Hawkesbury Sandstone were also collected in the field to produce crushed aggregates having a nominal particle size of 19 mm. Two trial mixes of concrete were made in the laboratory using crushed sandstone as the coarse aggregate. After curing, the strength and the deformation measurements of concrete were made. The stress-strain relationship of Hawkesbury Sandstone subject to uniaxial compression exhibits strong non-linearity at low stress levels. The results obtained in the measurement of mechanical properties of sandstone showed wide variations. The analysis of these results based on statistical techniques, revealed that the material characteristics of the rock, such as density, porosity, moisture content, mineralogy and texture, significantly influence the strength properties and the modulus of elasticity of the rock. The physical processes of weathering appears to be more widespread than the chemical process and cover a number of changes. These changes include opening of discontinuities and formation of new discontinuities in the rock mass; opening of grain boundaries and grain fracturing in the rock material. Alternate wetting and drying was found to be the most significant single process of weathering which contributes largely towards the degradation of the rock. The strength and modulus of elasticity of the weathered rock were appreciably lower than those of fresh rock. The failure of certain properties of the sandstone aggregate to satisfy the limits set by the currently available specifications has proved it to be an unsatisfactory material in the upper courses of a road-pavement. The success of its use in the lower courses, mainly in the sub-base, depends on its grading, durability and stability to environmental and traffic variations. The performances of crushed sandstone as a concrete aggregate where much poorer than those of conventional types of aggregates.
item: Thesis-Abstract
Degenerating Orr-Sommerfeld Eigenmodes and Development of Three-dimensional Perturbations
(5/24/2011) Shanthini, R
Degeneracies of temporally damped Orr-Sommerfeld eigenmodes are studied primarily for plane Poiseuille flow. The discrete spectrum of the eigenmodes is shown to possess infinitely much degeneracy, each appearing at a certain combination of k (the modulus of resultant wavenumber) and αR (the streamwise wavenumber times the Reynolds number). The streamwise phase velocities of the degeneracies are close to about 2/3of the centreline velocity, and their damping rates decrease with increasing Reynolds number. Interestingly, several degeneracies are operative even at sub-transitional Reynolds number. Degeneracies are found also in water table flow and some of these degeneracies are shown to have the same characteristics and modal structures as those in plane Poiseuille flow. The responses of the degeneracies in plane Poiseuille flow are investigated through the initial-value problem. The initial perturbation field is chosen to be free of normal vorticity, and its velocity component normal to the walls is described by the generalized Orr-Sommerfeld eigenfunction in the normal direction. The subsequent temporal development of this normal velocity is shown to be that of monotonical decay, in the linear regime. Notable initial growth is exhibited by the streamwise velocity of the two-dimensional perturbation flow in case of the least damped degeneracy. Nevertheless, in all cases of the degeneracies investigated, the two-dimensional perturbation flow looses its kinetic energy with increasing time. In the case of a three-dimensional perturbation flow, the span wise variations in the normal velocity induce normal vorticity. The amplitude of the induced vorticity and, hence, that of the streamwise perturbation velocity are shown to grow to significant peak values, before the exponential decay predicted by the linear theory sets in. The amplitude of the induced vorticity is shown to increase also with increasing Reynolds number. The presence of normal vorticity causes the perturbation flow to gain kinetic energy from the basic Poiseuille flow. This gain is so great in cases of the least damped symmetric and anti symmetric degeneracies, that the perturbation flow overcomes its energy loss due to viscous dissipation and exhibits significant initial growth of its kinetic energy, at crucial Reynolds numbers such as the transitional one. These growths, according to the linear theory, do not influence the normal velocity that is monotonically decaying with time. It is shown, however, that these growths are to be followed by nonlinear equations at about the transitional Reynolds number. It is also shown that describing the solution of the nonlinear system as waves travelling in one single oblique direction does not change the monotonous behaviour of the normal velocity. Key words: degeneracy, double eigenvalue, Orr-Sornmerfeld equation, direct resonance, stability, plane Poiseuille flow, water table flow, initial-value problem, three-dimensionality, vortex stretching, induced vorticity, nonlinearity, Reynolds stress, perturbation energy.
item: Thesis-Abstract
Studies in pressure .filtration on upward facing surfaces from a structural point of view
(5/24/2011) Herath Banda, SM
A direct technique to obtain information about the structure of a filter cake is described. Cakes formed from two different materials are consolidated and the porosity and pore size distribution in polished sections of these cakes are measured directly by using an image analyser. Two methods of impregnating filter cakes have been developed and are discussed in the paper. They are also suitable for consolidation of cakes formed from sub-sieve size material (<38μm).
item: Thesis-Abstract
Molecular and ultrafine structure of cotton fibres
(5/24/2011) Fernando, LD
Differences among native cottons which have been recognized the textile industry for many years, and have formed the basis for Cotton classification in commerce and ultimate utilization, include Factors such as fiber length, fineness and spinnability. Recent, detailed investigations have established that, in addition, cotton types wary in their fundamental mechanical properties. The object of the present work has been to ascertain whether the variation in fiber properties are due to differences which exist at the ultrafine and molecular levels of the structure. Furthermore, with the advent of man-made fibers, modifications of the properties of natural fibers has become a compelling requirement, for their survival in the competitive world markets; and for this reason a detailed study of the structure of the cotton fiber has particular relevance. The ultrafine and molecular structure of several varieties of cottons have been examined by means of transmission electron micro-scope and X-ray and electron diffraction techniques. It has been possible to establish that there are no significant differences in: (i) the size of the particles (obtained after hydrolysis) whose dimensions may be taken to represent the combined crystalline and Para-crystalline regions, and (ii) the crystal structure (cellulose I), between different cotton types. X-ray studies have shown that differences in the orientation of the 'crystallites' I have an effect on the mechanical properties of the fiber. Thus, the evidence leads to the conclusion that variation in fiber properties are due to differences at higher (fibrillar) levels of structural organization. Electron diffraction results have conclusively shown the inadequacies of the widely accepted model for the fundamental structural unit of crystalline cellulose I (unit cell), proposed by Meyer and Misch on the basis of X-ray diffraction studies. A possible unit cell to fit the observed data, from electron (and X-ray) diffraction, has been postulated, even though a detailed elaboration of a unit cell for cellulose I was outside the scope of this work. The present study has laid the foundations for further |investigations into the structure of cotton fibres at the fibrillar level and a more rigorous study of the unit cell of native cellulose means of electron diffraction.
item:
Long waves on water of variable depth
(5/24/2011) Gunasekara, MM
This dissertation is mainly a review of some of the work done by various authors on the long wave (shallow water) approximation and its applications to different problems. Shallow water wave equations are derived which are identical with Stoker's equations but the method of derivation is slightly different. The method of characteristics is used in solving the differential equations governing the shallow water wave theory. The climbing and breaking of waves on sloping beaches is discussed. After the derivation of the transport equations for the discontinuities that can exist across a characteristic an equation is obtained for the time and hence the distance of breaking. A simple explanation of the formation of a bore in a sloping stream is given here. The climb of a bore on a beach of uniform and non-uniform slope is also discussed briefly because of its close resemblance to non-uniform shock propagation in gas dynamics. The notion of tsunami waves and the use of shallow water wave theory in the study of the numerical simulation of realistic tsunamis is also discussed briefly.
item: Thesis-Abstract
The growth of buddhist monastic institutions in Sri Lanka from Brahmi inscriptions :
(2001) Dias M; Reynolds CHB
The propagation of Buddhism in Sri Lanka in the third century B.C. as witnessed by the lithic records and the chronicles was due to the efforts of the Buddhist monks who spread Theravada or the orthodox tradition of the religion in the first few centuries. Its spread went parallel wtith the growth of monastic institutions in the island. At first the patronage extended by the kings and the people towards the Buddhist monks was to safe-guard the religion. They were endowed with dwellings and requisites for their maintenance. To make them self-sufficient the monks were endowed with permanent and valuable gifts consisting of land, tanks, revenue from taxes and so forth. When these endowments were made, the monks became landholders and gained a role of leadership in society. On the one hand, the relationship with the masses made thc Saitgha an institution which dominated society in its own way. On the other, it became a major factor to check the royal power. The monks generally regarded themselves as having a two-fold task; striving for their own salvation and preaching the Dhamma to lead others to find their salvation. It was the scholar and the preacher in them that were useful to society. Buddhism was flourishing in.the entire island by the second century A.D. Even before that dissensions among members of the Sattgha were visible in the premiere establishments such as Mahavihara and Abhayagirivihara. Some individuals struggled for power and tried to gain favours from the kings. By about the third century A.D. new trends of thought in Buddhism, coming from the subcontinent of India, were making headway in the island. By contact with these new movements, the monks of the Abhayagirivihara were becoming liberal in their views. The new schools of thought such as Vaitulyavada, described as heresies in the chronicles, divided them into sects. These schools of new thought had the backing of some kings though the Mahavihara vehemently opposed them. By about the fourth century, there were three fraternities, namely, Mahavihara, Abhayagiri and Jetavana. The inscriptions and the chronicles bear clear evidence to the manifestation of Mahayana ideals such as the Bodhisattva worship. The sixth and seventh century inscriptions attach great importance to the merit-making rituals that accompanied them. Here we find the Safigha in the role of the priest invoking blessings on the masses and becoming an indispensable figure in society.