ERU - 2001

Permanent URI for this collectionhttp://192.248.9.226/handle/123/14678

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Proceedings of the 7th Annual Symposium 2001 (Per Text)
(The Engineering Research Unit University of Moratuwa, 2001) Kumarage, A
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Water scheduling for better yield in paddy cultivation - a study from Mahaweli system h of Sri Lanka
(2001) Wickramaarachchi, TN; Wijesekera, NTS; Gamage, NPD
Agricultural production has given the highest priority in the Dry Zone of Sri Lanka and has become the main livelihood of people living in the area. It has been found that almost all the cultivation in the area totally depends on the irrigation water and hence proper management of irrigation water is needed in order to achieve increased crop production. The aim of this study is to analyze the present water management issues of the Distributory canal Dl at Block 406 in Mahaweli system H and come out with possible improvements to the existing system in order to optimize the water usage in achieving better paddy yield. A questionnaire survey was carried out among the farmers in the Block in order to collect information about the present water issue system. Hence the strengths and weaknesses of the existing water management system were identified. By the survey it was found that the present rotational water issue system does not concern very much on sensitivity of paddy to water stress, resulting low yield. Since paddy has some sensitivity to water stress, all the possible efforts should be put in order to avoid a water deficit during the entire season. Considering the varieties of paddy grown and their sensitivity to water shortage at different plant growth stages, an improved water management for paddy cultivation is presented in this study for the Block 406.
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Ultrasonic investigation of physical mechanical properties of steels
(2001) Sivahar, V
Ultrasonic techniques are primarily used in engineering for the purpose of flaw detection in materials and components. Such techniques can also be used for measuring the ultrasonic parameters such as wave velocity and wave attenuation in a material. These parameters are predominantly affected by the structure of the material through which the ultrasonic wave passes. Structure, in turn, affects the properties of the material. The aim of this research is to investigate such effects and to determine any correlation between the ultrasonic parameters mentioned, and the mechanical properties of metals. Usually material properties such as elastic modulus, strength, hardness, fracture toughness, grain size etc. are determined by destructive tests. Such tests not only result in the destruction of materials, but also have other disadvantages such as, increased cost and inability to give reproducible results. On the other hand non-destructive techniques such as ultrasonic inspection can be used for the determination of properties even after the manufacture of the product/component as well as in service, if a successful method is developed. This research concentrates on steels subjected to different heat treatment processes. The initial work was carried out on 0.36 percent carbon steel (AISI designation 4340). The results obtained and the correlation found, between ultrasonic measurements and destructive tests are presented.
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Thermal performance of free-running three- storey houses: an assessment through computer simulations
(2001) Jayasinghe, MTR; Attalage, RA; Jayawardena, AI
Sri Lanka is presently facing a serious energy crisis due to continuous increase in energy demand annually. One of the solutions for this is energy conservation for which houses are a good candidate. The need for using active means such as fans and air-conditioning can be minimized by planning the houses with desirable passive features. In order to determine the passive performance, computer simulations were carried out for two houses with and without passive elements. A comparison of similar volumes in these two houses indicated that it is possible for the indoor temperature of certain type of volumes to rise about 5°C above the maximum outdoor temperature when passive elements are ignored.
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The European yield model applied to bolted joints of Ginisapu timber
(2001) Hettiarachchi, MTP; Nawagamuwa, AD
The European Yield Model provides a set of equations, which are derived analytically to predict the lateral load capacity of dowel type joints and is the basis for recent revisions to structural timber design codes. The paper discusses the applicability of this method for local species of timber, based on an experimental investigation on different configurations of three member bolted timber joints of Ginisapu.
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Suitability of coir fibre as a raw material for geotextiles.
(2001) Nawarathna, NS; De Silva, N
Geotextiles are used in many geotechnical works as support in reinforcement structures. In practice geotextiles made of synthetic polymers such as polyester, polyamide and polypropylene are used. The synthetics are preferred because of their strength, extensibility and resistance to microorganisms when used in various applications usually in contact with soil particles. The natural geotextiles are expected to be less strong and less in durable while resistance to microorganisms is expected to be less than in synthetics. The suitability of jute in short-term functionality is fairly well established. The paper examines the feasibility of using coir geotextiles manufactured as a local cottage industry in geotechnical applications. The strength and extensibility parameters are comparable with those of synthetic polymers although the type of textile made of synthetic fibres differ significantly from the woven mat made of coir ropes. The moisture absorption character adds to the stability of using coir in geotechnical operations.
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Speed reduction as a road safety measure
(2001) Ranaweera, RPKS; Jayasinghe, C; Ratnayake, LL
The growing number of road accidents is a major national problem in Sri Lanka. By analyzing the police database of past accident records, the causes for the road accidents have been identified as a prominent cause for road traffic accidents. According to the past accident records from the year 1992 to 1999, there were about 17507 fatal accidents, and 29526 grievous accidents occurred out of the total of 613785 accidents over the last eight years. The annual loss due to road traffic accidents has been evaluated as Rs. 12.9 billion in year 1999. The research was focused on high speeds at intersections since a higher percentage of accidents occurred close to or at intersections. A feasibility study has been conducted for a speed reduction measure which uses transverse bar markings. The results before the study and after the study indicated that there is a marginal drop in the speeds due to the presence of transverse strips. Thus, the use of a combination of transverse strips and other measures is suggested at intersections.
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Simulation of deep excavations using finite element method
(2001) Jayakody, NJ; Peiris, TA
Finite Element calculations arc frequently utilized for the design of deep excavations because a prediction of ground movements and wail deformation is not possible with classical limit equilibrium methods. To solve such Geotechnical boundary value problems, appropriate constitutive laws are necessary for the description of mechanical behaviours of soils. The possible combinations of these behaviours are divided into two groups; those with a constitutive law based on plasticity and those without. The latter group contains linear elasticity and variable elasticity. A key distinction between the plasticity and the elasticity group is that in latter, strains are recoverable upon decreases in stresses, where as elastoplastic models strains are only partly recoverable. A crucial point in determining the choice of a suitable soil constitutive model is the ease with, which values can be assigned to the constants defining it. With considering those pointed above, this paper summarizes the application of simplest linear elasticity analysis for convenience for modeling 15m deep base excavation supported with bored pile wall. Finite element software GEO SLOPE/SIGMAW DEFINE is applied for 2-D plain strain analysis. The mechanical behaviour of the soil is modeled with linear elastic constitutive model using reasonable soil parameters. Excavation was carried out in 4 steps, pre-stressed anchors were used as additional supports, just before each excavation step. The FEM simulation was carried out to compare the computed and observed pattern.
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Simplified biomedical system for artificial defibrillation
(2001) Balasuriya, JC; Jayasinghe, JAKS; De Silva, GTF
Sudden deaths due to various forms of heart failures are very common at present, especially in Sri Lanka. Whatever the causes and types of ailments are, the final stage known as fibrillation causes the patient to die within minutes. Fibrillation is the complete disorder of the heart beat pattern as shown in the Electro-cardiogram (ECG). In order to overcome this condition, it is attempted to give a strong electrical pulse to the heart of the patient, this is done by the use of an equipment called the defibrillator. It is seen that only a few hospitals are equipped with this instrument in Sri Lanka, mainly due to its high cost. This paper presents a design of low cost defibrillator, which will work on a new concept with advanced features and hardware system satisfying the safety standards found in commercial equipment.
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Rehabilitation of steel bridges in Sri Lanka
(2001) Chandrasiri, BVDN; Jayasinghe, MTR
Nearly one half of the approximately 3700 highway bridges on A and B class roads of Sri Lanka are more than 50 years old. About 60% of the total bridges have a width of less than 8.0 m; out of these 689 are steel bridges. Most of these steel bridges would need upgrading in future to cater for present day traffic needs. The upgrading option can be either replacement or rehabilitation. Rehabilitation can be quite attractive if it can have cost savings and fewer disturbances to traffic. In this paper, various options available for rehabilitation of steel bridges arc reviewed. The methods better suited for Sri Lanka arc identified. The criteria to determine the economic feasibility arc highlighted. The anticipated cost of replacement is determined to indicate the importance of adopting rehabilitation whenever cost effective.
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Regionalization of catchments in Sri Lanka for regional flood frequency analysis
(2001) Gamage, NPD
In flood frequency analysis the objective is to estimate flood quantile magnitudes for different return periods at a station or at a number of stations in a river system. An understanding of the hydrologic characteristics of a catchment is essential in order to obtain a reliable estimate of the relationship between extreme flood quantiles and the associated return periods. An approach to catchment regionalization is presented, in which an agglomerative hierarchical clustering algorithm is used to define homogeneous regions that can be used for regional flood frequency analysis. Catchment similarity is expressed using seasonality measures derived from the mean date of occurrence of the annual maximum flood and its associated dispersion. Regions that are largely geographically contiguous are obtained by incorporating gauge latitude and gauge longitude to the clustering algorithm. The initial regions formed using the clustering algorithm are subsequently modified in an attempt to enhance the overall regional homogeneity. The approach is demonstrated through an application to a set of catchments in Sri Lanka.
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Project manager to combat corruption in procurement: some issues with special reference to Sri Lanka
(2001) Kodikara, GW
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Processing of high grit ball clays
(2001) Mayooran, D; Gunasekera, HKM; Cristin, M; Fernando, WLW
In Sri Lanka high grit ball clay is not mined al all from the ball clay deposits as the process adopted in purification is Dry Processing. It involves dry grinding causing high wear and tear to the grinding mill. Hence the cut- off grade of ball clay for Mining and processing is determined by the grit content which is limited to a maximum of 2%. In this research the authors have experimented on high grit ball clay and have suggested a flow sheet for its processing Though the capital outlay is high in the method suggested . authors’ aim is to make use of this mineral deposit industrially with optimum utilization.
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Prediction of dissolved oxygen in harbours using artificial neural networks: an application to the port of Colombo
(2001) Dayanthi, WKCN; Jayaweera, MW
Maintenance of high dissolved oxygen (DO) level in harbours is highly important as it could give rise to catastrophic effects if it is depleted affecting day- to- day port functions such as dredging activities and other maintenance work. The depletion of DO results not only in toxic gases such as methane and hydrogen sulphide but also in accumulation of wastes. Frequent monitoring of DO is therefore imperative, but creates practical difficulties due to ship movements and other activities. Hence, prediction of DO with an empirical model using Artificial Neural Networks (ANNs) was done with success with an application to the Port of Colombo (PoC). This model aims to reduce the frequency of monitoring DO and to foresee the responses of the system due to environmental changes. The performances of ANNs were compared with Multiple Linear Regression (MLR). Monthly values of 14 water quality parameters at several depths for a particular period were collected. The values of weather parameters of rainfall and wind velocity for the corresponding period were also collected. The inputs of the best model were temperature, depth and five rainfall intensities (including rainfall values on four immediate previous days). A sensitivity analysis was carried out to assess the potentials of small changes in each input on the neural network output. MLR model with the same number of input variables indicated a low value for R after several transformations. The rainfall intensity of the 3rd previous day was the most influential variable among the ANN inputs affecting the output. In conclusion, it could be inferred that the ANN model is capable of predicting DO in PoC considerably well compared with MLR.
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Objective assessment of fabric defects - design of a computerised inspection system
(2001) Niles, SN; Fernando, S; De Silva, N
Inspection of fabrics is a major consideration in fabric manufacture, as well as in the manufacture of garments and other fabric-based goods. In the Sri Lankan industry almost all fabric inspection is carried out by manual methods, and is therefore subjective and prone to human error. Various automated fabric inspection systems have been developed in various parts of the world. These systems are, however, rather costly. The purpose of this research is to design a cost-effective fabric inspection system for the objective assessment of fabric defects. This system is being designed with special relevance to the Sri Lankan industry, and should be capable of giving consistent results irrespective of user. Image processing techniques are used to scan images of the test fabric, compare it with an ideal sample with which the system has been calibrated before the commencement of inspection, and identify defects, according to pre-learnt rules. The information gathered would then be used to grade the fabric, either by giving the frequency of occurrence of defects or by assigning points. A new classification method for common defects has been designed, that will facilitate easy grading according to commonly used grading systems. A coding system for defects has also been designed, which will help in the reporting of defects to the user.
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Numerical modelling of rock-socketed piles
(2001) Kodagoda, SSI; Puswewala, UGA
Axisymmctric finite element meshes are developed to model the pile tip in the rock-socket, for four different ratios of socket length to pile diameter, the values being I to 4. The pile material (concrete) and the surrounding rock material arc both considered as isotropic linear elastic materials. Analyses arc conducted to determine the shear stress distribution profile at the interface and the axial load variation within the pile along the socket length, for various socket length/pile diameter ratios and a range of Young's Moduli representing the rock material. The results indicate the variation of the percentages of load resisted by interface shear along the socket wall and end-bearing at pile tip as the pertinent parameters are varied. An interface element to model the interface shear behaviour is introduced, and its performance in the finite element analysis is discussed.
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Microstrip vehicular antenna for mobile-satellite communications
(2001) Senavirathna, HMSB; Dayawansa, IJ
Circularly polarized antennas are used in mobile-satellite or MSAT communication systems. This reduces the polarization mismatch due to the rotational orientation between the transmitter and the receiver and it also minimizes the interference from multipath reflections. Circularly polarized microstrip antennas are commonly used in these systems because of compactness, the light-weight and the low-profile. It eases the installation on a vehicular body or on the surface ofa satellite. This paper presents a circularly polarized microstrip circular patch antenna designed for vehicular use for MSAT communications at a frequency of around I.6GHz. It has right-hand circular polarization (RHCP) and near hemispherical coverage needed by the user. The antenna was first simulated using MatLab software for TM110 resonance mode and fabricated on a substrate of epoxy glass fiber. The antenna was tested on a curved ground plane, which was similar to the surface of a vehicle. This low profile microstrip antenna is suitable for vehicle rooftop mounting. A combination of the resonance cavity model and the transmission-line model was used to analyze the antenna, which consists of a single circular patch as the driven clement. In order to obtain circular polarization, perturbation segments to the perimeter of the patch were inserted with a single probe feed on the 45° axis with respect to the perturbation segments, known as mode-de- tuning. As such no external phasing network is required to obtain the 90° time phase difference required for circular polarization. It was fed with a 50Ω coaxial feed line which was soldered to the inset probe. By adjusting the area of the perturbation segments circular polarization and a good axial ratio was obtained. Half power beam widths of the antenna are 115° in the H plane and 105° in the E plane. The antenna has a gain of 5.7dBi and a bandwidth of 286MHz which is approximately 17% of the centre frequency. The design criteria and performance of the circularly polarized microstrip antenna, which is suitable for MSAT communications, are presented.
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Matric suction characteristics of unsaturated residual soils at the Naketiya landslide site
(2013-11-27) Ratnajothy, T; Puswewala, UGA; Kulathilaka, SAS
This paper discusses the experimental determination of some matric suction characteristics of residual soils from Naketiya landslide site, Badulla District, Sri Lanka. The test programme required the modification of the triaxial test apparatus using high air entry disks so that pore-air and pore-water pressures of a soil sample could be maintained at required magnitudes. Samples were made from soil obtained from the Naketiya landslide site, and these were tested in triaxial conditions under different matric suction values. The shear strength function and the soil-moisture characteristic curve for the soil are developed. These results are of importance in interpreting the variation of shear strength with the moisture content for the residual soil at Naketiya, which will have a direct bearing on stability of the slopes there.
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Is anaerobic digestion of municipal garbage to produce biogas economically feasible ?
(2001) Perera, SAS
The problem of collecting, transporting and disposal of market and domestic garbage is probably the greatest problem confronted by many municipalities and local authorities. The dumping of garbage in solid waste dumps without proper evaluation of the environmental and health hazards of such dumps has lead to protests by the public and many environmentalists. Moreover, such dumps, while causing major environmental and health problems to the people living within close proximity, have ruined the landscape and the aesthetic beauty of the land. They have become the breeding grounds for cats, dogs, rats, reptiles, insects, mosquitoes and flies, too. Safe and efficient collection, transport and disposal of garbage has been the subject of many seminars, conferences and workshops. There are many diverse views on what process is the best, to dispose garbage. Anaerobic digestion of municipal garbage to produce biogas, has been mooted as the solution to the municipal garbage problem in Sri Lanka, by many engineers and scientists. However, the technical and economical feasibility of biogas manufacture from municipal garbage, has yet to be properly established, by those who have done research and development work in this area. This paper critically evaluates the NHRDC (National Engineering Research and Development Centre) Dry Batch Biogas Syatem, which has been described by the NERDC as a better system for biogas production than the Chinese and Indian biogas systems. The paper also presents data and appropriate scientific calculations, which leads to the conclusion that anaerobic digestion of garbage to produce biogas by dry batch technology, is not economically feasible, and recommends that further capital investment should not be made, either by the government sector or by the private sector to establish new biogas plants, using this system.
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Interfacing field device substitutes to central control terminals through interface cards
(2001) Thimirachandra, RS; Jayasinghe, JAKS; Samarasiri, BS
In an integrated plant environment, it is not feasible to replace an existing field device with a different model unless the protocols are properly matched. The system complexity is a deterrent to a software modification in order to tackle the problem. A microcontroller based interface card would be an elegant solution. This card takes information from the new device and manipulates it dynamically so that the central controller can understand and vice versa. Due to the new features of microcontrollers, design and development of such cards are not intricate.

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