Showing papers by "Universiti Teknologi Malaysia published in 1998"

Consider this: The role of imperatives in scholarly writing

Abstract: There have been numerous investigations in recent years into the linguistic and rhetorical features of research articles, but none, to our knowledge, has examined the 'fringe phenomenon' of imperatives This study investigates the use of imperatives in research articles from ten disciplines Five articles in each field, all five from one journal, were scanned for imperative uses in both main text and notes, and instances were collated and analysed In fields where imperatives were present in the main text (five out of ten), we recorded interviews with the authors of one of the articles Results show that main-text imperatives tend to congregate in sections where the principal argumentation occurs, but are very unevenly distributed across fields The interview data also reveals that, despite the potentially face-threatening nature of imperatives, authors use them for vanous strategic purposes such as engaging the reader, achieving text economy, or manifesting personal style Finally, there appear to be a number of field-specific expectations and conventions Given these subtleties, a case can be made for rather more sophisticated materials for NNS researchers and students than currently available.

Changing Attitudes to University Mathematics Through Problem Solving

Abstract: University mathematics is often presented in a formal way that causes many students to cope by memorising what they perceive as a fixed body of knowledge rather than learning to think for themselves. This research studies the effects on students' attitudes of a course encouraging co-operative problem-solving and reflection on the thinking activities involved. The attitudinal questionnaire was shown to the students' teachers who were asked to specify the attitudes they expect from their students and the attitudes they prefer. This was used to give a ‘desired direction of change’ from expected to preferred. Before the course, half the students responded that university mathematics did not make sense. A majority declared negative attitudes such as anxiety, fear of new problems and lack of confidence. During the problem-solving course the changes were almost all in the desired direction. During the following six months of standard mathematics lecturing, almost all changes were in the opposite direction.

Genetic algorithm for optimal reactive power dispatch

Abstract: Scheduling of reactive power in an optimum manner reduces circulating VAr promoting flatter voltage profile which lead to appreciable MW saving on account of reduced power system losses. Hence, the optimal reactive power dispatch assumes extremely important functioning both in the planning stage as well as in day to day operation of the power system. This paper presents an alternative approach to optimal reactive power dispatch based on genetic algorithm techniques (GAs). The technique is used to search for transformer tap settings and the value of shunt capacitors of a given power system such that the total system power loss is minimised. The proposed method is tested on IEEE 14 and 30 bus test systems and their results are compared with those obtained using load flow calculation.

Essential oil of Curcuma aeruginosa Roxb. from Malaysia

Abstract: The essential oil of Curcuma aeruginosa Roxb. from Malaysia obtained by hydrodistillation of the rhizomes was analyzed by a combination of GC and GC/MS. Twenty-six components have been identified, of which the major constituents were found to be curzerenone (24.6%), 1,8-cineole (11.0%), camphor (10.6%), zedoarol (6.3%), isocurcumenol (5.8%), curcumenol (5.6%) and furanogermenone (5.5%). The structure elucidation of the sesquiterpenes were confirmed by IR, 1H- and 13C-NMR spectroscopies.

Multiprocessor scheduling using mean-field annealing

Abstract: This paper presents our work on the static task scheduling model using the mean-field annealing (MFA) technique. Mean-field annealing is a technique of thermostatic annealing that takes the statistical properties of particles as its learning paradigm. It combines good features from the Hopfield neural network and simulated annealing, to overcome their weaknesses and improve on their performances. Our MFA model for task scheduling is derived from its prototype, namely, the graph partitioning problem. MFA is deterministic in nature and this gives the advantage of faster convergence to the equilibrium temperature, compared to simulated annealing. Our experimental work verifies this finding on various network and task graph sizes. Our work also includes the simulation of the MFA model on several network topologies and parameters.

Adaptive Neuro-fuzzy Control System by RBF and GRNN Neural Networks

Abstract: Recently, adaptive control systems utilizing artificial intelligent techniques are being actively investigated in many applications. Neural networks with their powerful learning capability are being sought as the basis for many adaptive control systems where on-line adaptation can be implemented. Fuzzy logic, on the other hand, has proved to be rather popular in many control system applications due to providing a rule-base like structure. In this paper, an adaptive neuro-fuzzy control system is proposed in which the Radial Basis Function neural network (RBF) is implemented as a neuro-fuzzy controller (NFC) and the General Regression neural network (GRNN) as a predictor. The adaptation of the system involves the following three procedures: (1) tuning of the control actions or rules, (2) trimming of the control actions, and (3) adjustment of the controller output gain. The tuning method is a non-gradient descent method based on the predicted system response which is able to self-organize the control actions from the initial stage. The trimming scheme can help to reduce the aggressiveness of the particular control rules such that the response is stabilized to the set-points more effectively, while the controller gain adjustment scheme can be applied in the cases where the appropriate controller output gain is difficult to determine heuristically. To show the effectiveness of this methodology, its performance is compared with the well known Generalized Predictive Control (GPC) technique which is a combination of both adaptive and predictive control schemes. Comparisons are made with respect to the transient response, disturbance rejection and changes in plant dynamics. The proposed control system is also applied in controlling a single link manipulator. The results show that it exhibits robustness and good adaptation capability which can be practically implemented.

An application of neural network in power system harmonic detection

Abstract: Widely distributed power electronic loads are an increasingly important source of harmonics in power systems. The objective of the paper is to detect the components (magnitudes and phases) of harmonics in power distribution systems by means of the multilayer perceptron neural network. The detection of 3rd, 5th and 7th harmonic components is verified by means of computer simulation. This method of harmonic detection has the advantage that it can determine harmonic components in real time. It is seen that neural networks can determine the harmonic components with very low error.

Neural network approach of harmonics detection

Abstract: This paper describes a novel approach of harmonics detection in a power system which can be used as an alternative to the conventional approaches. The proposed approach uses the multilayer feed forward neural network to determine the harmonic components in a six-pulse bridge converter. In this paper the detection of 5th, 7th, and 11th harmonic components from the distorted waves has been verified by means of the computer simulation. It is found that once trained by the learning algorithm, the neural network can determine each harmonic component very effectively and efficiently.

Sesquiterpenes from Curcuma aeruginosa

Abstract: Curcuma aeruginosa Roxb. (Zingiberaceae) is widely cultivated in Malaysia and is known as temu hitam, owing to the blueish-grey internal colour of the rhizomes, as distinct from the yellow or orange colour of most species of the genus (1). The rhizome is used medicinally to treat asthma and cough (2), and is also applied externally, pounded in coconut oil for scurf (3). Previous studies of C. aeruginosa have resulted in the isolation of aerugidiol (4), difurocumenone (5) and guaiane sesquiterpene lactones (6). The chemical compositions of the essential oil of C. aeruginosa of Malaysia have been reported to comprise mainly curzerenone (7).

Numerical Conformal Mapping for Exterior Regions via the Kerzman-Stein Kernel

Abstract: A simple numerical method is described for computing a conformal map from a domain exterior to a smooth Jordan curve in the complex plane onto the exterior of the unit disk. The numerical method is based on a boundary integral equation similar to the Kerzman-Stein integral equation for interior mappings. Typical examples show that numerical results of high accuracy can be obtained provided that the boundaries are smooth

Pyrolytic recycling of agro-industrial solid wastes in Malaysia

Abstract: The agro-industrial sector of Malaysia generates a significant amount of solid waste, including those from palm-oil mills, paddy rice, and scrapped tyres and tubes. All these can be recycled to improve materials and produce energy. Among the various recycling techniques the most promising method appears to be thermochemical pyrolysis. In this study, rice husk and palm shell wastes were considered for recycling. Feed particles underwent fluidised-bed pyrolysis at moderate temperature and were converted into pyrolytic oil, solid char and gas. Oil and char were collected, and the gas was flared. The oil was characterised by FTIR, GC and GC-MS techniques, and the char was analysed for its elemental composition. The phenolic fraction in the oil was found to be quite high, and the gasoline range fraction was found to be present also; however, the components were mostly oxygenated.

Essential Oil Constituents of Alpinia mutica Roxb.

Abstract: The oil of Alpinia mutica Roxb. was produced by hydrodistillation from fresh rhizomes, collected from cultivated plants in Universiti Pertanian Malaysia. The oil was analyzed by GC/MS and 24 components were identified which constituted 87.5% of the oil. The major components of the oil were camphor (35.6%), 1,8-cineole (9.4%) and borneol (8.3%)

Probing the active sites of aluminated mesoporous molecular sieve MCM-41 by secondary synthesis in the conversion of cyclohexanol.

Abstract: The active sites of H-AI-MCM-41 aluminated by secondary synthesis have been probed by the conversion of cyclohexanol and compared with those of HAI-MCM-41 prepared by direct synthesis, purely siliceous MCM-41, AIP04-5 and H-ZSM-5. Conversion of cyclohexanol produces cyclohexene, cyclohexanone and 3-methylpentane in the presence of Bronsted, basic and Lewis acid sites respectively. Whereas cyclohexanol is converted to polyaromatic compounds in the presence of very strong acid sites as those found in H-ZSM-5. The formation of cyclohexene as the only product of conversion over H-AI-MCM-41 prepared by direct and secondary synthesis indicates the presence of Bronsted acid sites in both systems, which is not observed in the purely siliceous MCM-41 and AIP04-5 samples. The larger amount of cyclohexene formed over H-AI-MCM-41 by secondary synthesis suggests that there is a higher degree of Bronsted acidity in this system than that of H-AI-MCM-41 by direct synthesis. However, the strength of acidity in HAI-MCM-41 by secondary synthesis is weaker than that of H-ZSM-5. In addition, the results of this reaction, supported by IR spectroscopy study, do not indicate the presence of Lewis acidity in H-AI-MCM-41 prepared by secondary synthesis.

The cellular phone industry in Malaysia: toward IMT-2000

Abstract: Explosive growth of the cellular phone industry in Malaysia has been witnessed in the 1990s. Eight nationwide cellular phone operators with different technology bases exist in a single market. This article provides an overview of the telecommunications industry, especially the cellular phone sector, and also the activities on IMT-2000 in Malaysia.

Voltage-current characteristics of metal oxide varistors for low voltage telephone lightning protector under the application of multiple lightning impulse

Abstract: Surges resulting from lightning strikes could propagate not only into the power line but also into a low voltage line such as the telecommunication system and could cause damage to the equipment. In order to protect this highly sensitive equipment, a telephone lightning protector (MOV) has to be installed in the telephone set. Since the natural characteristics of lightning are a multiple stroke/flash, the response of the protector under this condition has to be investigated. This paper presents the experimental studies on the voltage and current characteristic of the MOV under the application of multiple lightning impulse voltage and current.

Instrumentation and calibration of geotextiles used in centrifuge modeling of slopes

Abstract: Research on the application of geotextile strips used as reinforcement in marginally stable soft soil slopes was performed with a geotechnical centrifuge. A variety of instrumentation was used in the model studies. When centrifuge models are used, the elements being modeled must be scaled down by the level of centrifuge acceleration—that is, the g level used in the modeling process. This results in the use of very small geotextile reinforcing strips, which are difficult to instrument. In this study, small strips of nonwoven geotextile were driven into the model slope while the centrifuge was in flight. These strips were instrumented with miniature foil-type strain gauges. The following items are discussed in detail: various stages of installation of the strain gauges on nonwoven geotextiles, selection of suitable bonding techniques, use of thin coatings for gauge protection, and selection of suitable bridge excitation voltages for the gauges. The devices used in the calibration process, and the calibratio...

Defect detection and identification of sources in GIS based on laboratory and on-site experience

Abstract: The most common defects in GIS apparatus are due to the presence of metallic particles, protrusions, as well as floating shields which originate mainly from imperfect manufacturing process, operation of switches, or may become trapped during assemble. The presence of defects deteriorates the insulation strength of a compressed SF/sub 6/ GIS apparatus and causes serious limitation in its practical application. These defects can be detected by several techniques, one of which is that using acoustic sensors placed on the enclosure. This paper reports on the defect detection and identification of sources in GIS apparatus using acoustic technique, based on laboratory and on-site experience. The tests give satisfactory result.

The use of charcoal from agriculture waste in the speciation of iodine from well and river waters

Abstract: The concentrations of iodine in fresh waters are known to be within the range of 0.5 to 35 ng·ml−1, much lower than in oceanic waters. The iodine concentrations, particularly that of129I which is significant from the radiation safety aspect, in public drinking waters have to be specified in order to verify the required level before distribution for domestic use. A modified version of an established method was used in the adsorption of iodine, iodate, total inorganic iodine and charcoal-adsorbable iodine using activated carbon prepared from oil palm kernel wastes. A thorough investigation of the physical properties of the activated carbon was carried out to determine its viability as an adsorbent for volatile species such as iodine. The iodine species were preconcentrated from water samples collected from wells in villages and from water intake points along rivers. The quantitative analysis of the species adsorbed was done by irradiating the activated charcoal loaded with the respective species in a neutron flux of 5.1·1012 n·cm−2·s−1 from a TRIGA MkII, nuclear reactor. Recovery experiments using spiked samples was done to provide quality assurance controls.

Galloping Limit Cycle Amplitude and Frequency Estimation

Abstract: The amplitude, frequency, and mode shape of a single galloping conductor are estimated. A finite element model of the line and supports based upon the weighted residual method is presented. The results produced by the analysis show good agreement with results obtained elsewhere. It is demonstrated that the fundamental galloping frequency can be aerodynamically dependent. Also included in the model are compliant line supports to represent the towers.

Lightning induced surges on an unenergized test overhead telecommunication subscriber line

Abstract: Voltages induced on a test unenergized 1.8 km straight overhead telecommunication subscriber line by nearby lightning return stroke to ground is presented by solving transmission line coupling equations using time domain approach in combination with the numerical calculation of horizontal and vertical electric fields from return stroke current as inducing source. Both horizontal and vertical electric fields have a significant effect on induced voltages. The effect of the line length and line height on induced voltages is illustrated in this paper. A comparison between numerically calculated data and experimentally recorded data is also made in this paper. The ground conductivity is considered infinite and a triangular current pulse moving from ground to cloud through a 4 km upright vertical channel is taken as channel current. It is found that the calculated results are in reasonably good agreement with experimental results.