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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 477 Documents

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Cathodic Electrodeposition and Characterization of ni3se2 thin Films K Anuar; Z Zainal; N Saravanan; A.R Kartini
ASEAN Journal on Science and Technology for Development Vol. 21 No. 1 (2004): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Nickel selenide thin films have been potentiostatically electrodeposited on titanium substrate at room temperature from aqueous solution containing Ni-EDTA and Na2SeO3. Various deposition potentials were attempted in order to determine the optimum electrodeposition potential. The films were characterised using x-ray diffraction analysis (XRD) and the photoactivity of the electrosynthesised films were studied using linear sweep voltammetry (LSV). The band-gap energy was determined using UV-visible spectroscopy. The XRD analysis indicated the formationof polycrystalline Ni3Se2. The film exhibited p-type semiconductor behaviour with good photosensitivity. The bandgap energy (Eg) was about 1.4eV.

Optical Response of Poly (1,4-Phenylene-1,2-Di (P-Phenoxyphenyl) Vinylene) Towards Oxygen Gas F.S Mehamod; R Daik; M Ahmad
ASEAN Journal on Science and Technology for Development Vol. 21 No. 1 (2004): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

This research involved the synthesis of poly (1,4-phenylene-1,2-di (p-phenoxyphenyl) vinylene), dpop-PDV from di (p-phenoxybenzoyl) benzene compound as the monomer. The potential of the produced polymer as sensing reagent for O2 detection based on fluorescence quenching was studied. Di (p-phenoxybenzoyl) benzene was synthesised via the Friedel-Crafts benzoylationwith terephthaloydichloride and biphenylether as starting materials and anhydrous AlCl3 as the catalyst, while the dpop-PDV was synthesized via the McMurry coupling reaction. The polymerization was carried out in THF with TiCl4 and Zn as the catalyst and reducing agent respectively. Characterization on monomer and polymer had been carried out by using FTIR, GCMS, DSC, TGA, GPC and melting point measurement. Response of the polymer towards oxygen gas was described in terms of fluorescence spectra, repeatability, reproducibility and the response curve. Results obtained showed that the fluorescence intensity decreased upon exposure to O2 gas, indicating that the polymer was responsive to the presence of the O2 gas and the sample was found regenerable by flushing the polymer solution with N2 gas.

Mesoporous Inorganic Membrane Reactor for Oxidative Coupling of Methane N.C May; A.R Mohamed; S Bhatia
ASEAN Journal on Science and Technology for Development Vol. 21 No. 1 (2004): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The mesoporous inorganic membrane has been developed and characterized for oxidative coupling of methane reactions. In this research, g-alumina membrane was modified with Lanthanum. The membrane has shown thermal stability in prolonged exposure to the high-temperature application of 600-900°C. The results were confirmed by TGA and OCM experimentations. TGA results showed only 2-3% loss from an initial weight that is mainly due to evaporation of water and release of the nitrate compound. The membrane was also found stable for at least a month of operationwhile the catalyst was being regenerated to regain its activity. The SEM cross-sections show successful deposition of Lanthanum in spite of its non-uniform deposition layer and crack formation.

Associations of Common ?-Thalassemia Mutations With ?-Globin Gene Frameworks in Northern Thailand P Sanguansermsri; D Shimbu; R Wongvilairat; T Sanguansermsri
ASEAN Journal on Science and Technology for Development Vol. 21 No. 1 (2004): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

This study aimed to characterize polymorphism of the b-globin gene (framework) among common b-thalassemia mutations found in northern Thailand. Thirty-one homozygous b-thalassemia major patients admitted to Chiang Mai University Hospital were identified using direct DNA sequencing method. Among 15 patients with homozygous of codon 41/42 (-TCTT), eight were homozygous of framework 1 (FW1), one was homozygous of FW3A, and the remainders were heterozygousof FW1 and FW3A. The gene frequencies of FW1 and FW3A in the patients were 0.733 (22/ 30) and 0.267 (8/30), respectively. All 11 patients with homozygous of codon 17 (A-T) were homozygous of FW3A, while three patients with homozygous of intron 1 nt 1 (G-T) were homozygous of FW1. Both patients with homozygous of codon 71/72 (+A) were FW3A. In this report, the numbers of b-globin gene frameworks were restricted in each b-thalassemia mutation. This investigation may provide further information for the study of the evolution of common mutations causing b-thalassemia major in northern Thailand.

Characterization of Lignin Precipitated From The Soda Black Liquor of Oil Palm Empty Fruit Bunch Fibers by Various Mineral Acids M.N Mohamad Ibrahim; S.B Chuah; W.D. Wan Rosli
ASEAN Journal on Science and Technology for Development Vol. 21 No. 1 (2004): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Soda lignin from oil palm empty fruit bunch was directly isolated by various mineral acids i.e. sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid at three levels of concentration (20% v/v, 60%v/v and concentrated). A comparison study was performed through physicochemical properties and structural features using FT-IR, UV, 13C-NMR and nitrobenzene oxidation. The FT-IR results showed that there is no significant difference between the main structures of the lignin isolated by various acids. However, low concentration of phosphoric acid is preferable because of its highest yield. The S: V: H ratio of 7-15:6-11:1 as evaluated by the nitrobenzene oxidation procedure suggests that soda lignin can be classified as belonging to either the cereal straw on grass type. The UV results indicate that phosphoric acid consistently gave the highest absorbance value among the four acids tested in this study regardless of its concentration level. The C13-FTNMR spectra, suggest that the lignin structure is independent of the type of acid used for precipitation.

Dynamic Mechanical Thermal Analysis (DMTA) of Thermoplastic Natural Rubber (TPNR) Barium Ferrite (bafe12o19) Composites S Hamdan; D.M.A Hasihim; M Yusop
ASEAN Journal on Science and Technology for Development Vol. 21 No. 1 (2004): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

filled with 0-6 volume percentage of barium ferrite was performed using a Polymer Laboratory- Dynamic Mechanical Thermal Analyser (PL-DMTA) over a range of temperature from -100 to 100°C at 10hz. The results showed that the storage modulus (E') of the composites below the transition temperature increase with filler content up to ~3-4 volume percentage. Incorporation of the filler does not change the matrix glass transition that occurs around -40°C but the damping curve becomes broader with increasing filler content. The addition of filler in the compositedoes not affect the glass transition and melting temperature. The blend of TPNR and barium ferrite powder is only a physical mixture that does not act chemically.

Effect of the reciprocating mass of slider-crank mechanism on torsional vibrations of diesel engine systems M.S. Pasricha Pasricha; F.M. Hashim
ASEAN Journal on Science and Technology for Development Vol. 23 No. 1-2 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The torsional vibration phenomenon in the running gear of reciprocating engine systems isusually dealt with by considering a series of constant inertias connected by sections of massless shafting. However in reality, a slider crank mechanism is a vibrating system with varying inertia because the effective inertia of the total oscillating mass of each crank assembly varies twice per revolution of the crankshaft. Large variations in inertia torques can give rise to the phenomenonof secondary resonance in torsional vibration of modern marine diesel engines which can not be explained by conventional theory incorporating only the mean values of the varying inertias. In the past associated secondary resonances and regions of instability tended to be dismissed by most engineers as interesting but of no importance. The situation changed in recent years since there is evidence of the existence of thesecondary resonance effects which could have contributed to a number of otherwise inexplicable crankshaft failures in large slow speed marine engines. The cyclic variation of the polar moment of inertia of the reciprocating parts during each revolution causes a periodic variation of frequency and corres ponding amplitude of vibration of reciprocating engine systems. It also causes an increase in the speed range over which resonance effects are experienced and only a partial explanation of the behaviour of the systems has been worked out. It is impossible to avoid these instabilities by changes in thedesign , unless of course the variations in mass and spring constant can be made zero. In the present paper a critical appraisal of the regions of instability as determined from the equation of motion which takes into account variation of inertia is given. The motion in the form of complex waveforms is studied at different speeds of engine rotation. A comparison of theoretical results with Goldsbrough’s experimental resultsand Gregory’s analysis is included.

Creep analysis of bimaterial microcantilever beam for sensing device using artificial neural network (ANN) WaiChi Wong; HingWah Lee; Ishak A. Azid; K.N. Seetharamu
ASEAN Journal on Science and Technology for Development Vol. 23 No. 1-2 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

In this study, a feed-forward back-propagation Artificial Neural Network (ANN) is used to predict the stress relaxation and behavior of creep for bimaterial microcantilever beam for sensing device. Results obtained from ANSYS® 8.1 finite element (FE) simulations, which show good agreement with experimental work [1], is used to train the neural network. Parametric studies are carried out to analyze the effects of creep on the microcantilever beam in term of curvature and stress deve loped with time. It is shown that ANN accurately predicts the stress level for the microcantilever beam using the trained ANSYS® simulation results due to the fact that there is no scattered data in the FE simulation results. ANN takes a small fraction of time and effort compar ed to FE prediction.

Characterisation of multicrystalline solar cells A.Q. Malik; Chong Chew Hah; Chan Siang Khwang; Lim Chee Ming; Tan Kha Sheng
ASEAN Journal on Science and Technology for Development Vol. 23 No. 1-2 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The evaluation and assessment of the performance of photovoltaic (PV) cells in terms of measurable parameters requires the measurement of the current as a function of voltage, temperature, intensity, wind speed and spectrum. Mo st noticeable of all these parameters is the PV conversion efficiency ?, defined as the maximum electrical power Pmax produced by the PV cell divided by the incident photon power P in which is measured with respect to standard test conditions (STC). These conditions refer to the spectrum (AM 1.5), solar radiation intensity (1000 Wm-2), cell temperature (25 ±2oC) and wind speed (2 mph). Tests under STC are carried out in the laboratory at a controlled environment. There have been several studies that analyze uncertainties in the laboratory measurement of solar cell efficiencies using different solar simulators and their transference to operational situations. Our preliminary results demonstratethat the short circuit current (ISC) of the solar cell decreases when irradiance is less than 1000 Wm-2 irrespective of the working temperature of the cell.

On a solution to improve the object detection ability of radars by dynamic polarization method Nguyen Quoc An
ASEAN Journal on Science and Technology for Development Vol. 23 No. 1-2 (2006): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

One of the most importan problems of modern radar is increasing object detection, object distinction ability. In the last years, the used traditional radar signal processing methods are seem to use up. For solving this question, specialists are interested in analyzing the fine structure of radar signal, and the first is po larization structure. The use of polarization information allows to raise the information ability of radar systems and provides high probability of radar objects detection, high contrast of small-scale man-made objects on the radar map and radar objects classification.The article deals with the detection of radar objects by exploiting the information on polarization based on the scattering matrix (SM) of the object. A solution to improve the object detection ability of radars by dynamic polarization method (to modify the polarization of radiative wave) is introduced.

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