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Showing papers by "Universiti Teknologi Malaysia published in 1995"


Journal Article
TL;DR: In this paper, the authors highlight the potential use of palm oil fuel ash (POFA) as partial cement replacement material in mortar and concrete in housing construction and demonstrate that up to 20% replacement level is possible without causing adverse effect on strength characteristic.
Abstract: This paper is an attempt to highlight the potential use of palm oil fuel ash (POFA) as partial cement replacement material in mortar and concrete in housing construction. The ash tested satisfies the chemical and physical requirements for a reactive pozzolanic ash as specified by ASTM C618-84 and hence classified into class F fly ash. Mortar cube samples of OPC/POFA containing 10% to 40% ash replacement level were analysed and tested for strength characteristics in accordance with the procedures outlined in the BS 12 part 2 :1971. The mortar samples were also tested for the ash reactivity and pozzolanicity using thermogravimetry apparatus as well as the water permeability and porosity using water permeability apparatus and mercury intrusion porosimeter respectively. The results indicate that both engineering and chemical and microstructural characteristics are very promising. POFA replacement level up to 20% is possible without causing adverse effect on strength characteristic. This is enhanced by the TG test results which indicate that POFA is positively reacting to produce more gel hence offsetting the loss of strength due to the OPC replaced. The hydrating products are found to be more dense as shown by the mercuryporosimetry test results. Water permeability and construction material durability shows at least a comparable performance to the OPC control results.

37 citations


Journal ArticleDOI
TL;DR: In this paper, the specific heat capacity of some triglycerides commonly found in palm oil were determined with a heat-flux differential scanning calorimeter, and the experimental specific heat capacities are within ± 1% precision with a 95% confidence level.
Abstract: The specific heat capacities of some triglycerides commonly found in palm oil were determined with a heat-flux differential scanning calorimeter. The specific heat capacity measurements were made under the optimum operating conditions determined earlier: scan rate 17 deg·min−1, sample mass 21 mg and purge gas (nitrogen) flow rate 50 ml/min. Pure triglycerides (four simple and four mixed) were used in the experiments. The four simple triglycerides were trilaurin, trimyristin, tripalmitin and tristearin, and the mixed triglycerides were 1,2-dimyristoyl-3-oleoyl, 1,2-dimyristoyl-3-palmitoyl, 1,2-dipalmitoyl-3-oleoyl and 1,2-dioleoyl-3-palmitoyl. The results of this study are compared with literature values and also with values obtained by using estimation methods. The experimental specific heat capacities are within ±1% precision with a 95% confidence level.

27 citations


Journal ArticleDOI
TL;DR: In this paper, the essential oil isolated by hydrodistillation from the fresh rhizomes of Alpinia conchigera Griff was analyzed by capillary GC and GC/MS.
Abstract: The essential oil isolated by hydrodistillation from the fresh rhizomes of Alpinia conchigera Griff was analyzed by capillary GC and GC/MS. More than 40 constituents were present in the oil, from which 34 components could be identified. The major components include β-sesquiphellandrene (20.5%), β-bisabolene (12.1%) and 1,8-cineole (11.6%).

25 citations


Proceedings ArticleDOI
22 Oct 1995
TL;DR: A method using neural networks to tune the PID gains such that human operators tune the gains adaptively according to the environmental condition and systems specification is proposed.
Abstract: The authors consider stabilization of an inverted pendulum which can be controlled by moving a cart in an intelligent way. Here, the authors adopt a PID(proportional plus integral plus derivative) control method to stabilize the pendulum since the PID controller has been extensively used in the industrial world. This controller requires the determination of PID control gains, but it is difficult to select the best gains theoretically. Thus, there have been many approaches to determine them empirically. Most of them are based on experience of operators and knowledge. Here, the authors propose a method using neural networks to tune the PID gains such that human operators tune the gains adaptively according to the environmental condition and systems specification. The tuning method is based on the error backpropagation method (BP method) and hence, it may be trapped in a local minimum. In order to avoid the local minimum problem, the authors use the genetic algorithm to find the initial values of the connection weights of the neural network and initial values of PID gains. The experimental results show the effectiveness of the present approach.

22 citations


Journal ArticleDOI
TL;DR: Extraction of the stems and leaves of Piper ridleyi with ether afforded N - iso butyl-15-(3′,4′-methylenedioxyphenyl)-2 E,4 E,12 E -pentadecatrienamide (ridleyamide), as well as the known amide, retrofractamide, and sterols was described in this paper.

18 citations


Journal ArticleDOI
TL;DR: In this paper, the specific heat capacity of triglyeerides was obtained by using heat-flux DSC under improved operating conditions, such as the scanning rate, the sample mass and the atmosphere within the DSC chamber.
Abstract: Reproducible specific heat capacities (Cp) of triglyeerides can be obtained by using heat-flux DSC under improved operating conditions. The improved operating parameters, such as the scanning rate, the sample mass and the atmosphere within the DSC chamber, were established via statistical analysis of the experimental data with trilaurin as a sample. The specific heat capacity results on trilaurin were compared with the values calculated by using estimation methods. The precision of the specific heat capacity measured for trilaurin under these conditions was within +1%.

17 citations


Proceedings ArticleDOI
27 Sep 1995
TL;DR: Simulation results for throughput and delays for a distributed radio LAN for different values of inter frame spacing periods, transmission speeds and number of nodes suggest that proper inter frame space values have to be chosen for optimal network performance.
Abstract: Carrier sense multiple access with collision avoidance (CSMA-CA) will be used as the basic medium access control (MAC) protocol for wireless LANs. Wireless LAN will be supporting two types of services, time bounded and asynchronous data transmission. In this paper we present simulation results for throughput and delays for a distributed radio LAN for different values of inter frame spacing periods, transmission speeds and number of nodes. Depending on the application, the results obtained suggest that proper inter frame space values have to be chosen for optimal network performance.

16 citations


Journal ArticleDOI
TL;DR: In this paper, a two-level hierarchical control concept for robot manipulators is proposed based on a deterministic approach, which is capable of withstanding the expected variations and uncertainties in the system, and will render the robot manipulator able to track a prescribed trajectory to within a small ultimate boundedness set.
Abstract: This paper deals with the hierarchical control of a class of robot manipulators. A two-level hierarchical control concept for robot manipulators is proposed. The controller is formulated based on a deterministic approach. In synthesizing the controller, it is assumed that the upper bounds on the nonlinearities, couplings and uncertainties present in the system are available. It is shown through computer simulations that the proposed control strategy is capable of withstanding the expected variations and uncertainties in the system, and will render the robot manipulator able to track a prescribed trajectory to within a small ultimate boundedness set.

8 citations


Journal ArticleDOI
TL;DR: In this article, a study on the evaluation of pollution trends in marine core sediments taken in the vicinity of an industrial zone was attempted by analyzing trace elements such as As, Ce, Cr, Dy, Eu, La, Lu, Mn, Sb, Sc, Sm, Th, U, V and Yb using neutron activation analysis.
Abstract: A study on the evaluation of pollution trends in marine core sediments taken in the vicinity of an industrial zone was attempted by analyzing trace elements such as As, Ce, Cr, Dy, Eu, La, Lu, Mn, Sb, Sc, Sm, Th, U, V and Yb using neutron activation analysis. The elemental concentrations were expressed in terms of enrichment factors (EF) obtained by the elemental ratioing technique using scandium as the reference element. The quantitative distribution and assessment on the extent of pollution by some of the elements were done by comparing their EFs to those found in reference materials. The general elemental distribution was presented on maps and any abnormalities in the distribution pattern found were deduced with reference to their point sources.

7 citations


Journal ArticleDOI
01 Jan 1995
TL;DR: In this article, the use of ethylenediaminetetraacetic acid (EDTA) as the pH buffer was used for determining sulfasalazine, a reducible azo group, in the presence of significantly larger amounts of sulfadimidine (which is not reducible) and copper ion.
Abstract: Non-reducible organic compounds that can be accumulated at a hanging mercury drop electrode as copper(I) complexes or salts, and can then be determined indirectly by reduction of the copper(I), may interfere in the determination of reducible compounds that adsorb on the electrode and are determined directly by cathodic stripping voltammetry. This would occur if there were appreciable amounts of copper(II) in the sample or in the de-ionized water supply. The prevention of this interference by the use of ethylenediaminetetraacetic acid as the pH buffer is illustrated here in determining sulfasalazine, a sulfonamide drug which has a reducible azo group, in the presence of significantly larger amounts of sulfadimidine (which is not reducible) and copper ion. In this type of application the EDTA serves a dual purpose as the pH buffer and as a complexant to mask interfering cations, such as copper(II).

4 citations


Proceedings ArticleDOI
27 Sep 1995
TL;DR: The effects of the propagation path loss coefficient (/spl gamma/) and power control on the forward-link frequency reuse efficiency (K) of a direct sequence code division multiple access (CDMA) cellular system is investigated and the degradation in K as /spl gamma/ is increased is significantly less for CDMA than for the traditional FDMA and TDMA cellular systems.
Abstract: The effects of the propagation path loss coefficient (/spl gamma/) and power control on the forward-link frequency reuse efficiency (K) of a direct sequence code division multiple access (CDMA) cellular system is investigated. A simple analytical model is developed to express the interference received by a user in the home cell from other base stations based on the inverse power-of-distance /spl gamma/ law. Proper factors for optimum power control performance are estimated according to /spl gamma/. With these factors, K is improved to twice that without power control for /spl gamma/ between 4.5 and 2.5. The degradation in K as /spl gamma/ is increased is significantly less for CDMA than for the traditional FDMA and TDMA cellular systems.

Journal ArticleDOI
TL;DR: In this paper, an initial study conducted on an electrical contracting company. Assessments on existing management systems were conducted and recommendations provided for the next course of action to ensure successful implementation of BS 5750 in this company.
Abstract: Quality has been proven to be an important strategic weapon in order to survive in today’s highly competitive business environment. To build quality in products and services requires organizations to implement a quality management system which is accepted internationally. BS 5750 which is similar to ISO 9000 helps achieve this objective. Service industries are also striving towards excellence in service and therefore require a quality system. Shows the result of an initial study conducted on an electrical contracting company. Assessments on existing management systems were conducted and recommendations provided for the next course of action to ensure successful implementation of BS 5750 in this company. BS 5750 provides a foundation in the quest towards total quality management.

Journal ArticleDOI
01 Sep 1995
TL;DR: In this article, the authors proposed that the existing distribution network be operated in "island groups" by paralleling selected feeders into an island, where each feeder is connected to other feeders in an island.
Abstract: Distribution system loss reduction has been grossly neglected by most electricity utilities even though it contributes to no less than 75 per cent of the total system losses. Existing methods of loss reduction involve enormous capital cost and extensive rehabilitation to the existing distribution reticulation and are hence not very practical, compounded with the problem of coping with the high and dynamic load growth in most developing countries. The paper looks into techniques of selecting and operating the distribution system, with minimum or no physical change in the present distribution reticulation to reduce losses. It proposes that the existing distribution network be operated in 'island groups' by paralleling selected feeders into an island.

Book ChapterDOI
01 Jan 1995
TL;DR: In this paper, a process scheme of independently studying the pyrolysis and catalytic reforming reactions has been proposed to alleviate the constraints of the combined pyrotelysis-reforming scheme.
Abstract: The increasing amount of waste plastics which causes serious pollution problems is a cheap and abundant source of chemicals and energy. Chemical recycling method which recovers hydrocarbons is recognized as the ideal approach in recycling the waste.1 The economics and engineering constraints in the chemical method of a combined pyrolysis-reforming reactor has been discussed earlier.2 The pyrolysis-reforming reactor was found to inhibit systematic study on the effects of various reaction conditions. A proposed process scheme of independently studying the pyrolysis and catalytic reforming reactions has been shown to alleviate the constraints of the combined pyrolysis-reforming scheme.2

Book ChapterDOI
01 Jan 1995
TL;DR: In this paper, an attempt is made to control vibration at the point of vibration generation to the substructure to reduce the transmission of vibrational power flow to remote areas. But this method is not suitable for the case where the substructures are located in areas where structure-borne noise radiation occurs.
Abstract: Machines inevitably generate unwanted vibration which are then transmitted into the substructures via their mountings. The resulting vibration subsequently transmits via various propagation waves to adjoining structures or regions where structure-borne noise radiation occurs. It is usually necessary to control excessive vibration such as to avoid potential fatigue failure to structures. Attempts can been made to control vibration at the point of vibration generation to the substructure to reduce the transmission of vibrational power flow to remote areas.

Proceedings ArticleDOI
21 Nov 1995
TL;DR: The results of the study show that substantial savings in consumer outage costs are obtained by devising and implementing emergency actions strategy in situations of capacity outages, and suggest the importance of emergency action strategy for electric utilities in reducing the consumer economic losses arising from unreliable electric service.
Abstract: This paper presents the results of a study carried out to assess the savings in consumer outage costs that can be accrued as a result of implementing emergency actions strategy. The use of emergency actions strategy plays a significant role in curtailing the consumer outage costs ensuing from unreliable electric service. In order to calculate the savings in outage costs, the probabilistic framework of the frequency and duration method has been used in conjunction with emergency actions. At first, the outage costs of various consumer sectors are estimated without considering the emergency actions. Secondly, the consumer outage costs are calculated by combining the frequency and duration method, and unserved energy with the emergency actions invoked. The results of the savings in consumer outage costs that can be accrued by utilising emergency actions strategy are presented for a synthetic system. The results of the study show that substantial savings in consumer outage costs are obtained by devising and implementing emergency actions strategy in situations of capacity outages. The results are of particular relevance and utility to the underdeveloped and developing countries where capacity shortages occur quite frequently. These results also suggest the importance of emergency actions strategy for electric utilities in reducing the consumer economic losses arising from unreliable electric service.

Book ChapterDOI
01 Jan 1995
TL;DR: P. diminuta isolated from a mining environment was adapted to grow in 50µM Ag+. The silver-resistant strain was then incubated with different amounts of silver and its uptake profile studied as discussed by the authors.
Abstract: P. diminuta isolated from a mining environment was adapted to grow in 50µM Ag+. The silver-resistant strain was then incubated with different amounts of silver and its uptake profile studied. It was found that the total amount of silver accumulated in the acid wash fraction (denoting surface bound silver) and the pellet digest (denoting intracellularly bound silver) was quite similar at pH 6.5 and 10.0. The double reciprocal plots for the 2 fractions at both pH’s showed a straight line with a clear break which seems to suggest that there are 2 types of binding sites for Ag+. The Langmuir isotherms which were further plotted seemed to indicate single layer adsorption of Ag+, however, it was interesting to note that the acid wash fraction at pH 6.5 did not obey the Langmuir isotherms, probably suggesting a more complex adsorption pattern. This was confirmed by applying the BET plot which as expected yielded a straight line.

Book ChapterDOI
01 Jan 1995
TL;DR: In this article, the potential use of composite materials in marine structures is realized with its various applications, which ranges from hull structure of displacement vessels, fishing vessels, small crafts, high performance craft (surface effect ships and hovercrafts) to other applications such as deck houses to submersibles.
Abstract: The potential use of composite materials in marine structures is been realized with its various applications. It ranges from hull structure of displacement vessels, fishing vessels, small crafts, high performance craft (surface effect ships and hovercrafts) to other applications such as deck houses to submersibles. The advantages of Fibre Reinforced Plastic (FRP) are well documented1. It includes in particular relatively low density and good resistance to fatigue and to the harsh marine environment. In addition, the low stiffness property of the material compared to metals may be an advantage in some applications. By varying the lay-ups and the constituent matrix and fibers, many specific properties are obtained against non structural requirements such as reflectivity and acoustic damping.