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ASEAN Journal on Science and Technology for Development

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Published by Universitas Gadjah Mada

ISSN : 22249028 EISSN : 22249028 DOI : -

Core Subject : Science, Education, Engineering,

Biochemistry, Genetics & Molecular Biology Chemical Engineering, Chemistry & Bioengineering Computer Science & IT Mathematics

The coverage is focused on, but not limited to, the main areas of activity of ASEAN COST, namely: Biotechnology, Non-Conventional Energy Research, Materials Science and Technology, Marine Sciences, Meteorology and Geophysics, Food Science and Technology, Microelectronics and Information Technology, Space Applications, and Science and Technology Policy, Infrastructure and Resources Development.

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Articles 8 Documents

Search results for , issue "Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)" : 8 Documents clear

DIRECT SYNTHESIS OF LADDER WAVE DIGITAL FILTERS WITH TUNABLE PARAMETERS S.A. Samad
ASEAN Journal on Science and Technology for Development Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

This paper proposes a method for the synthesis of ladder wave digital filters (WDFs) directly from the digital domain. This method avoids the need for the synthesis of analog reference filters conventionally required in WDF design. This direct method allows for the determination of the WDF coefficients from the digital domain transfer function. This is similar to conventional infinite impulse response (IIR) filter coefficient determination but the WDF will give a more efficient realization. Due to the WDFs power complementary properties, a first-order ladder WDF can simultaneously realize both lowpass and highpass responses using the same structure, while a second-order WDF can realize both the bandpass and bandstop responses simultaneously. By appropriately choosing the WDF adaptor configuration and structure, tunable parameters can be determined from the digital domain transfer function that controls the 3dB cut-off frequency of the lowpass and highpass filters, and the centre frequency and 3-dB bandwidth of the bandpass and bandstop filters. This results in the WDFs requiring a minimum number of multipliers for realization.

ELECTROCHEMICAL BEHAVIOR OF POLYCRYSTALLINE COPPER DURING THE ADSORPTION OF CO ABSTRACT J. Salimon; M. Kalaji
ASEAN Journal on Science and Technology for Development Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The electrochemical properties of electrode copper in carbon monoxide-saturated phosphate buffered solution were investigated. The electrochemistry of copper surface was sufficiently changed after the supporting electrolyte solution was saturated with CO. The hydrogen evolution region was depressed and shifted cathodically due to the adsorption process of CO on the copper surface in a linear or terminally bonded manner, Cu-CO . The oxidation and the reduction peaks of copper were significantly changed with two couple of redox peaks. This is due to the subsequent formation and the corresponding reduction of copper(I) and the copper carbon monoxides species. Further changed in electrochemical properties occurred when the electrode surface was polarized at high cathodic potential (-1.4 V) for a period of time (15 min). The hydrogen evolution region was further depressed due to the adsorption of CO process in multiple bonding sites as adsorbed bridge bonded CO, Cu-CO B L that occurred predominantly.

CHEMICAL DESULPHURISATION OF SUB-BITUMINOUS HIGH SULPHUR INDONESIAN COAL VIA PEROXYACETIC ACID TREATMENT M.A.M. Ishak; K. Ismail; M.A.M. Nawi; A.F. Ismail
ASEAN Journal on Science and Technology for Development Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The chemical desulphurisation from an Indonesian high sulphur sub-bituminous Banjarmasin Haji Ali-Aliansar coal was investigated using the peroxyacetic acid (PAA), a mild oxidising agent. A mixture of hydrogen peroxide:acetic acid (i.e. 30:70 by volume ratio with 6% of hydrogen peroxide concentration) at 50°C of reaction temperature is capable of reducing the total sulphur content in the coal from 3.46% to 1.29% by weight, corresponding to the removal of up to ca. 72% of the total sulphur; both the inorganic (mainly pyrite) and organic sulphur forms, and approximately 10 to 44% of ashes in the coal. The simultaneous removal of both inorganic and organic sulphur forms was measured with respect to reagent volume mixed ratio, reaction temperature and hydrogen peroxide concentrations. The success of desulphurisation was measured by the reduction of the total sulphur content of the desulphurised product, its S/ C atomic ratios and ash yields of the treated coal. In general, all inorganic and some of the organic sulphur could be removed from the coal using mild conditions without severely affecting the coal microstructure as observed via the Scanning Electron Microscope with Energy Dispersive X-ray (SEM-EDX) which supplied the coal sample.

IMMOBILIZATION OF INVERTASE ON CARBOXYMETHYLCELLULOSE PREPARED FROM NATA DE COCO FOR THE INVERSION OF SUCROSE Fundador, E.O.V.; Fundador, V.C. Sabularse; Revilleza, M.A.J.R.
ASEAN Journal on Science and Technology for Development Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Nata de coco, the cellulose produced by Acetobacter aceti with coconut water as substrate, was used as starting material in the synthesis of carboxymethylcellulose after treatment with NaOH and monochloroacetic acid. The product, referred to as carboxymethyl-“nata” (CMN), had a degree of substitution of 0.76, a higher value than those previously reported. This was used in the immobilization of invertase via ionic interaction and adsorptive forces, which produced a viscous colloidal suspension. Agar was incorporated to facilitate pellet formation. Interactions between the agar and the CMN-invertase may have resulted from ionic interactions as well as H-bonding. The immobilized enzyme retained 71% of its initial activity and exhibited optimum pH of 4.5 and an optimum temperature of 55°C. It was more sensitive to pH and temperature changes. The Michaelis constant, Km, was 107.43 mM for the immobilized enzyme, and 71.42 mM for the free enzyme. The Vmax values were 89.28 µmole min-1 and 82.64 µmole min for the free and immobilized enzyme, respectively. Statistical analyses showed that V values did not vary significantly. The higher K of the immobilized enzyme may be attributed to diffusional effects, steric hindrance and conformational modifications of the enzyme. The immobilized enzyme has potential for further applications because of its stability with storage, repeated and continuous use.

REMOVAL OF SULFUR DIOXIDE FROM FLUE GAS USING ABSORBENT PREPARED BY WATER AND STEAM HYDRATION Teong, Lee Keat; Mohamed, Abdul Rahman; Bhatia, Subhash
ASEAN Journal on Science and Technology for Development Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Active absorbent for flue gas desulfurization was prepared from coal fly ash, calcium oxide (CaO) and calcium sulfate (CaSO4 ) by hydro-thermal process; steam and water hydration. The absorbents were examined and compared for its micro-structural properties. The experiments were conducted based on Design of Experiments (DOE) according to 24 factorial design. The effect of various absorbent preparation variables such as hydration period (Factor A), ratio of CaO to fly ash (Factor B), amount of calcium sulfate used (Factor C) and drying temperature (Factor D) towards the BET surface area of the absorbent were studied. The BET surface area of the absorbent was in the range of 12.9-169.3 m2/g. Fisher’s test showed that there is a strong influence of factor A, B and D towards the absorbent surface area, while its dependence on factor C is negligible. Comparison between absorbents prepared from water and steam hydration showed that the BET surface area of absorbents prepared from water hydration gives a higher surface area, but at a lower rate. The optimum BET surface area for the prepared absorbent 169.3 m 2 /g, was obtained at the following absorbent preparation variables using water hydration; hydration period of 24 hours, ratio of CaO to fly ash of 1:2, CaSO4 amount of 3 g and drying temperature of 200°C.

STABILITY AND STABILIZATION OF NONLINEAR DYNAMICAL SYSTEMS Sattayatham, P.; Saelim, R.; Sujitjorn, S.
ASEAN Journal on Science and Technology for Development Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Exponential and asymptotic stability for a class of nonlinear dynamical systems with uncertainties is investigated. Based on the stability of the nominal system, a class of bounded continuous feedback controllers is constructed. By such a class of controllers, the results guarantee exponential and asymptotic stability of uncertain nonlinear dynamical system. A numerical example is also given to demonstrate the use of the main result.

APPLICATION OF BACK PROPAGATION NEURAL NETWORK IN PREDICTING PALM OIL MILL EMISSION I.A. Azid; A.R. Yusoff; K.N. Seetharamu; A.L. Ahmad
ASEAN Journal on Science and Technology for Development Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The paper presents an approach to investigate and monitor the air pollution caused by the palm oil mill. A concept of dealing with the problem from its causes is used where the sources of pollution from the stack gases were examined. The main causes were from the combustion of shell fibre and of the palm oil. However, in the boiler itself, several parameters like steam load and pressure, fuel capacity and temperature also contribute to the pollution. The study uses Neural Network (NN) to simulate the process of combustion and stack gases. This neural network was trained by using the data on emission and combustion bed taken from local palm oil plant in Perak, Malaysia. The trained data by NN agrees well with the measured data, i.e. almost within 8% error for pollutants like CO, SO2, NO and particulate matters.

INTEGRATING ABC AND EVA TO EVALUATE INVESTMENT DECISIONS N. Chiadamrong
ASEAN Journal on Science and Technology for Development Vol. 20 No. 1 (2003): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The significance of investment is transparent in the world of competitive business. Traditional costing systems in which their emphasizes are for short term savings rather than long term benefits have shown some lacking in providing accurate and reliable cost data for the investment decisions. Activity-based Costing (ABC), which is developed to satisfy some of the weaknesses of the traditional costing systems, can provide valuable insights into the operating processes and come up with more accurate cost data. In this paper, ABC is used to provide significant information for investment decisions. Although, the ABC method provides accurate operating product costs, it does not identify which products are economic valued added creators and so contribute to companies’ wealth. This drawback can be overcome by applying Economic Value Added (EVA). The adoption of ABC and EVA can represent a considerable change in the managerial thinking and to corporate strategies and business performance.

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