ERU - 1997
Permanent URI for this collectionhttp://192.248.9.226/handle/123/19485
Browse
Recent Submissions
- item: Conference-Full-textProceedings of Symposium on Research for Industry 1997 - Pre Text(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Hettiarachchci, P
- item: Conference-Full-textSelf-aligning antenna(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Kumara, GTDM; Liyanage, CNH; Welikada, WSP; Dias, D; Hettiarachchci, PThis paper describes an automated antenna rotating system which will find and rotate to the direction of maximum received signal strength for a selected TV channel. The antenna system is implemented using a microprocessor based control system. When a channel is selected, the microprocessor, tunes a field-strength measurement system to this channel. The antenna is fixed on to a stepper motor which rotates through 360° while the field strength measuring unit takes measurements at every’ step position. At the completion of one revolution, the microprocessor examines the measured field strengths and finds the direction corresponding to the maximum. It then issues a signal to the motor controller to rotate the stepper motor to this direction. The application of this system is particularly suitable for TV reception in Sri L anka, where the unique problems that exist, render conventional antennas unsuitable. The overall operation of this system, as well as its individual blocks and .he associated software are described in this paper.
- item: Conference-Full-textHazardous waste management in Sri Lanka(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) de Alwis, AAP; Hettiarachchci, PThe country is currently looking towards development through industrialization. The industries will inevitably generate hazardous wastes which will need special handling and disposal methods. This important aspect has not received due attention of the policy planners. However, with Sri Lanka signing the BASEL convention attention has been focused on the movement of hazardous waste from outside sources to Sri Lanka. A recent study initiated by the Ministry of Policy Planning and Implementation indicated that generation of hazardous waste in Sri Lanka to be about 40,000 MT per annum. As there is neither a proper disposal facility in Sri Lanka nor sound disposal practices by the generators themselves, the potential difficulties that may have to be face in future can be enormous. It is important to realise the potential difficulties, the decisions that need to be taken now and the Responsible Care attitudes required of the generators. The paper discusses the present position of hazardous waste generation in Sri Lanka, disposal practices and their limitations and the steps needed to ensure clean industrialisation.
- item: Conference-Full-textHydraulic performance of porous vertical coastal Structures(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Hettiarachchi, SSL; Hettiarachchci, PPorous vertical structures have been used for coast protection and for harbour structures. In the case of harbours these structures have been used as the principal breakwaters and as internal structures. The ability to predict the level of reflection and transmission plays an important role in the assessment of their hydraulic performance. This paper identifies the relative advantages of using porous vertical structures in practice and focuses attention on the hydraulic performance of a range of such structures with specific reference to energy dissipation characteristics in relation to their hydraulic design.
- item: Conference-Full-textA 12v dc/230v ac inverter/charger with advanced Protection features(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Ranaweera, A; Seneviratne, BKCC; Kalyanapala, M; Hettiarachchci, PThe inverter can be used as a source of ac power in the absence of grid power. The battery can also be charged by alternative sources of energy if grid power is not available at all. The unit described works as a batter}' charger when the ac mains power is available and automatically starts working as an inverter when the mains power fails. Regulation of the square wave output voltage is achieved by variation of the pulse width of the waveform. A manual switch is also provided to boost the voltage at higher loads. Protection is provided against overloading of the inverter as well as against improper or incomplete connections during charging, thereby protecting the user as well as the unit. The charging current of the battery as well as the voltage level of the battery are indicated on the front panel of the unit. The unit has worked satisfactorily on many types of loads regardless of the high harmonic content of the square wave output voltage.
- item: Conference-Full-textA secure database accessible through the worldwide Web(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) de Silva, GC; Hettiarachchci, PDatabase access through the World Wide Web can combine the advantages in using each of them It permits people to work away from their offices, and to carry out money transfers over the Internet There have been, however, some limitations to this. First, many of the database management systems do not provide support to put their data onto the Web. Then, the Hyper Text Transfer Protocol (HTTP) did not provide sufficient support to ensure the type of security needed by particular database management systems and real world problems using databases. The need of the ability to access any database without using proprietary tools was another limitation Open DataBase Connectivity (ODBC) drivers were used to access a database with standard calls World Wide Web Servers have been developed to support ODBC, so that database access through the Web is possible to a limited extent. The issue of security is handled by different methods in applications. Very expensive proprietary software is available from a few vendors. This research was carried out to develop a method to solve the limitations identified and to develop an example database. The main security issues when a web browser accesses a database, are to handle login names and passwords when people move from one web page to another, and to prevent accessing a site without logging in, using a bookmark put during a previous session. Microsoft Internet Information Server , running on Windows NT Server version 4 0 was used as the WWW server which presents the data to the Web A Microsoft Access database was used with ODBC drivers to maintain the data .Although an Access database is not secure on its own, security features were added programmatically. The system consisted of several Web pages, each depicting the functions that can be carried out. A database of customer information in a company was used as an analogy These include logging into the database, insertion of new data, querying the database, deleting records etc The system was able to handle login/password security, and to identify bookmarking Thus the security of data is ensured. There were some limitations which prevented specific Web page formats, but as a whole the system was fully functional.
- item: Conference-Full-textManagement of unaccounted -for-water in the greater colombo water supply Distribution system.(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Ratnayake, N; Chandrasekera, HJVC; Hettiarachchci, PWater losses in the water distribution system is a common phenomenon experienced by water supply facilities all over the world. Unaccounted-for-Water (UFW) is the difference between the quantity of water produced and the total quantity of water consumed in the water supply system. UFW cannot be eradicated from a water supply system, as some components of it cannot be avoided, but it could be minimized and maintained at a low level, by proper management of operations and controls in the system. Non-Revenue-Water (NRW) is the difference between the quantity of water produced and the quantity which brings in revenue to the water authority. Sometimes NRW is used instead of UFW, but they are not identical, as there are some components which are not common to both these terms. In this study, the problem of UFW and NRW in this Greater Colombo Water Distribution System was investigated with respect to the various components. Having identified the most significant components theoretical and field studies were carried out to develop management techniques to effectively reduce these significant components of UFW. The Study concluded that the throttling of standposts to a limit that did not produce a noticeable reduction of pressure at the consumer’s tap was one of the most effective means of reducing NRW. Replacement of defective and unreliable water meters, particularly the turbine type meters, and the introduction of a caretaker system for the distribution system were also shown to be effective management techniques. The Minimum Night Flow Test, which was carried out for a section of the distribution system in this study is recommended as a suitable monitoring tool for UFW. Further study is needed to develop an action plan for the successful control of illegal consumption.
- item: Conference-Full-textDesign of high strength concrete mixes(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Jayanandana, ADC; Jayasinghe, MTR; Hewagama, CI; Hettiarachchci, PHigh strength concrete offers many advantages in the construction of high-rise buildings and bridges. In many countries, concrete strengths higher than 40 MPa are widely produced on commercial basis using normal aggregates and cement. Use of chemical and mineral admixtures has become an integral part of producing high strength concretes. At present, normal strength concrete is used in reinforced concrete construction in Sri Lanka. As the current trend for high rise buildings and the use of precast concrete is expected to increase, there wall be a greater demand in Sri Lanka for high strength concrete. A study was undertaken at the University7 of Moratuwa to examine various approaches for developing high strength concrete and to achieve concrete strengths higher than 40 MPa using only locally available materials. A high range water reducing admixture presently available in the market was used to reduce water/cement ratio of the concrete mixes while achieving sufficient workability. Compressive strengths up to 65 MPa w7ere achieved using locally available cement, sand and coarse aggregates with moderate dosages of water reducing admixture.
- item: Conference-Full-textApplications of high strength concrete in highrise buildings(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Jayasinghe, MTR; Jayanandana, ADC; Alwis, KGNC; Hettiarachchci, PHigh strength concrete can be used in high-rise buildings to minimise the size of columns, especially in the lower floors. High strength concrete has the added advantage of a higher elastic modulus that can reduce the deflection. It also has a lower specific creep that makes it possible to use higher stresses associated with high strength concrete. It is shown by a case study that the use of high strength concrete can reduce the cost of construction in Sri Lanka with the currently prevailing prices of concrete and steel. There is also the added advantage to the owners of the building in getting a higher rentable area resulting from reduced member sizes. The use of slender members can make the structure more flexible. However, it is shown that the use of high strength concrete in columns will not adversely increase the wind induced accelerations of the building since the reduction in column size is compensated by the higher modulus of elasticity.
- item: Conference-Full-textWind loads for high-rise buildings constructed in Sri Lanka(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Jayasinghe, MTR; Jayathilake, SAVSW; Perera, KAAA; Wickramasinghe, P; Hettiarachchci, PIn the design of high-rise buildings, it is of paramount importance to control the wind induced accelerations of the buildings to acceptable limits so that the majority of occupants will not feel the wind induced movements of the building. In this respect, it is necessary for the structural designer to evaluate the dynamic behaviour of the building at a very early stage of the design, on the basis of appropriate wind velocities. It is shown here that the 3 second gust wind velocities used for zone 3 of Sri Lanka could be too low for high-rise buildings. The use of low velocities may not control the drift index sufficiently so that the designers may come up with flexible structural forms that would have a dynamic behaviour unacceptable to the occupants. In order to control the drift index adequately, it is suggested adopting an average basic design velocity of 30 m/s for the high-rise buildings constructed in zone 3 and 2 of Sri Lanka. It is also shown that when higher design velocities are used, it would be appropriate to use gust factor method which takes account of the dynamic behaviour of the building for the evaluation of wind loads for structural design purposes.
- item: Conference-Full-textEarthquake design techniques for Sri Lanka(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Jayasinghe, MTR; Kulatilake, SAS; Alwis, KGNC; Angammana, RB; Perera, GDTS; HettiarachchciTwo major factors discourage the introduction of seismic resistant design to low seismic regions like Sri Lanka. They are the cost associated with improved seismic resistance and the misconception that the area concerned is seismically inactive. On many occasions the assumption that a particular area is seismically inactive hcS been proven wrong at the cost of human life and severe destruction to the infrastructure of the area. In Sri Lanka, structural designers have not paid sufficient attention to the performance of structures in an earthquake. Hence, a number of undesirable features are found in many existing structures as highlighted. In order to adopt structures that will survive an earthquake with minimum damage at minimum extra capital cost, a detailed study has been carried out to select appropriate earthquake design techniques for Sri Lanka. The precautions that should be taken with respect to the structural form are also highlighted.
- item: Conference-Full-textPassive solar techniques for Sri Lanka(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Jayasinghe, MTR; Sujeewa, LC; Fernando, KKJS; Wijayapriya, RA; Hettiarachchci, PPassive solar architecture can be described as the utilisation of the energy of the sun together with the characteristics of the local climate to directly maintain thermally comfortable conditions in buildings while minimising energy consumption. Since Sri Lanka is a tropical country, passive solar techniques include minimisation of solar heat gain while maximising the ventilation and structural cooling. It is shown that passive solar techniques should be included at a very early stage of the design of a passive solar building. The effects of orientation, shading devices, window sizes, roofing materials, insulation, colour of the exterior and interior walls, use of courtyards to maximise natural ventilation, and arrangement of roof to maximise structural cooling is shown with suitable examples.
- item: Conference-Full-textIntegration of cost control and estimation using Spreadsheets and databases(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Kodikara, GW; Hettiarachchci, PCost control is very important for any industry, since it is the activity which monitors the actual cost against the budgeted costs and initiates corrective actions if the costs are higher than expected. The estimating activity produces the anticipated cost or the budget and it is advantageous if the cost control activity could be linked to the estimating process. Computers can be effectively used to link the two processes, maximising data sharing and forwarding. In Sri Lanka most of the construction companies do not have integrated estimating and cost control systems in order to improve their performances although there are some " off the shelf packages" available in the market for independent activities. Therefore, it is required to conduct research and development in this area. As a first step, it is advisable to use readily available general software such as spreadsheets and databases and develop low cost system to address the need. This paper presents research work undertaken at the Department of Civil Engineering of the University of Moratuwa to develop a simple cost control system (using a database) linked to an estimating system (in a spreadsheet environment). A detailed study of existing literature on estimating and cost control was carried out and the concept for integration was established. Collection of cost data at site level is tiecessary for cost control, hence cost collection data sheets were designed to gather cost information at sites daily and enter to the system weekly to produce reports. It was decided to collect the maximum amount of data with minimum paper work since personnel at work sites are generally reluctant to undertake additional paper work. A cost control system was developed using Microsoft Access® and was linked to the estimating system, which is in the Microsoft Excel® environment. A test run was successfully carried out using a two storied building as an example. The system produces four reports for variance analysis for the most recent week, variance analysis for the whole period, percentage of work completed and cost details (breakdown of cost under major cost areas) for each BOQ item under construction. This information helps to monitor the behaviour of work in a better way.
- item: Conference-Full-textDesign and construction of horizontal axis wind mill For water pumping(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Balasuriya, PD; Nimal, RP; Pathirana, CR; Sugathapala, AGT; Hettiarachchci, PThis paper presents design and construction details of a six-bladed horizontal axis wind mill suitable for small scale lift irrigation. The main outcome of the study is the improvement of the rotor performance by introduction of a hub fairing. The air flow that normally passes through the hub section, without energy been extracted, is deflected radially to pass through the rotor blades. The optimum radial variations of the blade twist and chord length are employed so that the available energy is converted to useful mechanical energy more effectively. The estimated increase in the power coefficient is approximately 16% at the design speed. The new rotor has a higher starting torque and thus starts at lower wind speeds compared with conventional rotors. The construction phase of the wind mill is nowr complete and tests are in progress to assess the field performance.
- item: Conference-Full-textWind resource assessment for designing of Wind farms in Sri Lanka(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Nanayakkara, DPN; Udawatta, UKDLP; Pulasinghe, KN; Hettiarachchci, PWind energy conversion at potential sites would be an alternative solution for the existing energy crisis. In recen: years, there has been growing interest in utilizing wind electric power conversion systems to provide some of the electricity demand on large scale. This study is carried out to investigate the feasibility of wind energy extraction systems for electric power generation in Sri Lanka. Wind data collected by Ceylon Electricity Board(CEB), at eight sites of southern Sri Lanka are analyzed. One of the objectives is to carry out an analysis on the available wind speed data at measured heights to evaluate surface roughness exponent and thereby estimate the probable speec at a height of 30m, which is the selected hub height of the wind turbine and the parameter Mean Annual Wind Speed. Annual energy extraction and plant factors at selected eight sites are calculated for a 300kW horizontal axis stall regulated wind turbine.
- item: Conference-Full-textThe importance of humphreys spiral in heavy mineral Separation(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Fernando, WLW; Hettiarachchci, PThe Humphreys Spiral Concentrator which was developed in 1943 is now being used extensively for the concentration and the recovery of heavy minerals. In Sri Lanka, this device is very effectively used by the mineral sand industry and in the beneficiation of glass sands. The advantage of this over the Wilfley Table is that the capacity of Spirals are high and the running costs are very low. The study conducted by the author has shown that this method can be profitably used in the upgrading of Gold bearing sands. In this study, samples of river sands collected from Welioya, Kaltota area were subjected to gravity separation using the Spiral followed by the Wilfley Table. The concentrates obtained by this research showed Gold values ranging from zero to 0.0019%. The discovery of Cyanide heap leaching followed by activated Carbon Adsorption now makes it possible for samples containing considerably less than 0.0003% to be considered an ore. Thus, the beneficiated samples have economically recoverable Gold values.
- item: Conference-Full-textTargeting and design of heat fiecovery network Considering different heat transfer conditions(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Rathnasiri, PG; Hettiarachchci, PTo date supertargeting which is the industrial software available for targeting, designing and simulation of heat recovery network has only been able to trade off energy and capital ahead of designing and to give optimum minimum driving force (Atj^jn opt). The new targeting method suggested in this work identifies different heat transfer conditions such as boiling, condensation and sensible heat transfer in the heat recovery network and explores all the feasible stream shifting schemes to identify an alternative optimum for the given energy consumption. As an outcome, new graphical tools to screen and scope the design options at the targeting stage are introduced. It identifies ±e different optima for the different process heat recovery levels instead of identifying single optima for the entire heat recovery network. This leads to the new range targeting procedure. New insight can then be used to utilise the capital cost of the process in an economical manner. If the energy requirement is a constraint, new method suggests the range of area that can be best utilised to achieve the given energy consumption. The newly developed tools are built on the combined thermodynamic and mathematical programming approaches. Following the judgement on the optimal individual stream contributions and minimum capital at the targeting stage, the initial network structure obtained from the mathematical optimisation is next subjected to non linear cost optimisation which gives the optimum design parameters for final design. The effectiveness of the new method has been demonstrated by the case study solved.
- item: Conference-Full-textFree space optical links(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Punchihewa, AG; Hettiarachchci, PThis paper describes a future scenario where optical links are used for interlinking data super highways. Conventionally, optical carriers are used in guided form where it travels within an optical fibre. However, in space applications guided data channels are not possible. This will open up a new form of emission carrier having a very large bandwidth from the upper end of the electromagnetic spectrum.
- item: Conference-Full-textOptimisation of energy consumption and productivity Of a garment factory(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Wickramasinghe, GLD; Hettiarachchci, PIn most Garment factories the energy cost represents a considerable portion of the total production cost. The aim of this project is to build a computer model for a garment factory so as to analyse the various conditions that affect the energy. Most of the Garment factories use air-conditioners. Since 40- 60% of the total energy cost of a garment factory is due to the air-condit. oners, it is proposed to first make a computer model to control the Temperature, Humidity level, and Oxygen level for given conditions so as to optimise the total energy cost.
- item: Conference-Full-textMathematical modelling and extrapolation of Streamflow for hydro-power development(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 1997-11) Wijesekera, NTS; Hettiarachchci, PHydro-power development is important for Sri Lanka not simply because it is a means of energy generation but also because it utilizes a resource which does not create environmental hazards in the process of energy conversion. The viability of Hydro-power develpment projects mostly depend on the extractable energy from such projects, and hence on the streamflow available for tapping. Knowledge of available streamflow also enables the developer to assess the degree of incorporating requisite environmental impact mitigatory measures in situations where such impact assessments involve significant subjectivity. The work presented contain the estimation of streamflow at Bopath Ella extrapolating streamflow data in an adjacent watershed. Data checking and filling based on the comparison of daily and monthly, rainfall and streamflow characteristics was carried out in cases where the missing data duration was of short length. The instances where data were missing for significant continuous durations, filling was carriedout using a conceptual mathematical model developed for the particular catchment. Catchment information such as topography, land use and rainfall quantity were used to carryout the data extrapolation and subsequent computations of available energy.