Volume 11(1) (1999)

Table of Contents

No. Article


1. Simulation of the Flow Pattern Around Spur Dykes Using FLUENTS
Othman A. Karim & K.H.M. AliAbstract
The ultimate objective of this study is the prediction of flow pattern associated with spur dykes. Prediction of velocity fields and bed shear stresses were obtained using the FLUENT package. The RNG k-eformulation in FLUENT has been validated against selected benchmark solutions of flow in the vicinity of spur dykes. Extensive testing procedures have been implemented to ensure that the equations and solution algorithms used by FLUENT would provide an accurate simulation of flow. Experiments carried out by Mayerle et al. (1995) and Zaghloul and McCorquodale (1975) were selected as benchmark for verification purposes. FLUENT predicted reasonably Iwell the attachment point downstream of the dyke in the flat-bed case. Calculated bed shear stresses can then be used in appropriate sediment continuity equations for the prediction of scour hole geometries.

download buttonPage 3-19

2. Performance Enhancement of Cellular Topologies Employing Dynamic Cell Sectoring and Base Station Antenna Beam
Steering Using Time Division Multiple Access
Mahamod Ismail, IL.Doumi & l.G.GardinerAbstract
This paper discusses the performance of cellular radio topologies employing dynamic cell sectoring and beam steering. Interference analysis and a teletraffic simulation study based on a TDMA cellular system employing dynamic cell sectoring and base station antenna beam steering technique has been carried out. Results in term of calls dropped, handovers per call, channel utilisation and mean value of C/I at the mobiles are compared with those obtained when omni-directional and uni-directional antenna patterns are used in base stations. Simulation results have shown that dynamic cell sectoring system improved teletraffic performances over omni-system but not over sectorisation in some cases.

download buttonPage 21-34

3. Development of a Long-Term Fetal Heart Rate Recorder using an Ambulatory Approach
Firoz Ahmed, Zahari Mohamed Darus & Mohd Alauddin Mohd AliAbstract
Ambulatory recorders have been widely used in the acquisition of adult electrocardiogram (ECG). Such an ambulatory system will also be beneficial for the recording of both the fetal and maternal ECG from the abdomen of pregnant women. This paper describes a device with the possibility of producing a fetal and maternal heart rate recorder system employing an ambulatory approach by using three electrodes for recording the abdominal signal. The signal is amplified and digitized by an amplifier and an analog to digital converter. The digitized signal is stored into static RAM (SRAM) and then downloaded to a personal computer (PC) through a serial interface circuit. Both the fetal and maternal heart rates can be measured from the downloaded signal. This paper also presents real data acquired by the constructed ambulatory recorder. The performance of the constructed recorder was found to be acceptable acquiring signal with system noise kept below 3mV peak to peak. Such signals are suitable for the measurement and analysis of both fetal and maternal heart rates.

download buttonPage 35-41

4. Mode II Interlarninar Failure Mechanisms in Carbon Fibre / PEEK and Carbon Fibre / Epoxy Composites
RozZi Zulkijli, Wesley l. Cantwell & Matt BlytonAbstract
The mode II interlaminar fracture properties of two high performance composites have been examined in detail. The failure mechanisms occurring in these materials are investigated using the double end-notched flexure (DENF) geometry. Tests have been undertaken at crosshead displacement rates between 0.1 mm/minute and 3m/s and the failure mechanisms investigated in the scanning electron microscope. Detail studies of the crack tip regions in the DENF specimens showed that the amount and nature of damage depended strongly on the rate at which the specimen was deformed. At low loading rates, the crack tip damage zone in carbon fibre reinforced PEEK was very large extending on planes above and below that of the starter defect. At high rates of loading, damage was confined to the resin-rich region immediate to the crack tip. Similar observations were made in the carbon fibre/epoxy composite where large shear cracks were evident at low – rates of loading and an array of microcracks at high rates.

download buttonPage 43-51

5. A Top-Down Approach in Fuzzy Controller Design with VHDL
Khandaker Abul Kalam Azad, Zahari Mohamed Darus & Mohd Alauddin Mohd AliAbstract
With the rapid increase in size and complexity of digital systems, hardware description languages, such as VHDL, are quickly becoming the main integral part of the tools used for advanced digital system design. Although many of the HDL-based design practices follow bottom-up fashion, the real strength of VHDL is that it facilitates the top-down design process where high level design concepts can be described and verified without delving into implementation details. The top-down design approach is described in this paper for designing a multi-level fuzzy controller.

download buttonPage 53-60

6. Effect of Pre-Chamber Charge Temperature on Engine Performances and Emissions of a Dual Chamber Spark Ignition Engine
Chalilullah RangkutiAbstract
The performances, fuel economy and emissions from a dual chamber; stratified charge, spark ignition engine with heated pre-chamber charge temperature were investigated. The total hydrocarbon emissions from the engine, when tested at Leeds, proved considerably lower than in the early British Leyland study. The vaporizer system used at Leeds would probably have led to increased pre-chamber mixture temperature. It was therefore decided to investigate the effects of this mixture chamber temperature, by raising its value from 30°C used in the reference test to 45°C in a comparative test series. The good specific fuel economy and NOx emissions noted in the Leyland study were confirmed in the current work,’ however the (reduced) UHC emissions found in the current tests were still excess of those expected from a conventional single chamber engine.
   download buttonPage 61-70
7. Jerapan Sianida pada Permukaan Tanah Baki Granit dan Lempung (Cyanide Absorption on the Granite and Clay Soil Surface Balance)
Mohd Raihan Taha, Debnath Depankar & Shamala PeramayahAbstract
Soil pollution is a widespread problem in developing countries due to uncontrolled disposal of waste. Thus a study related to soil-pollutant interaction is necessary to study contaminant behaviour and its migration to surrounding areas. It will also help to plan necessary mitigation and clean-up measures for contaminated land. One study which will provide significant input to this cause is the soil- contaminant adsorption kinetics, as conducted in this research program Two types of soil were used, i.e. granite residual soil and kaolinite. The adsorption interaction between these two on cyanide were then compared. Data obtained showed that the granite. residual soil adsorbed more cyanide than that of kaolinite. The Kd value of 0.64 and 0.022 for granite residual soils and kaolinite, respectively, obtained from laboratory tests proved this point. Moreover, other adsorption parameters showed significant differences between the two soils. This is possibly because the granite residual soil have a higher organic content and clay fraction than kaolinite. Also the residual soil is less negatively charged than kaolinite as shown by its more acidic pH. The results also reveal that residual soils may be an option to kaolinite for use as landfill liners.
download buttonPage 71-81