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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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R unning Head: Novel Recombinant Phytate - d egrading Enzyme Production Statistical Optimization of the Induction of Phytase Production by Arabinose in a recombinant E. coli using Response Surface Methodology Abd - ElAziem Farouk; Anis Shobirin Meor Hussin; Ralf Greiner; Shareef Mohideen Ismail; Mohamed Faizal Batcha; Hamadah Mohd Nur Lubis
ASEAN Journal on Science and Technology for Development Vol. 27 No. 1 (2010): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The production of phytase in a recombinant E.coliusing thepBAD expression system wasoptimized using response surface methodology with full-factorial faced centered central composite design. The ampicilin and arabinose concentrationin the cultivation media and the incubation temperature were optimized in order to maximize phytase productionusing 23 central composite experimental design. With this design the number of actual experiment performed could be reduced while allowing eludidation of possible interactions among thesefactors. The most significant parameter was shown to be the linear and quadratic effect of the incubation temperature. OPtim al conditionsfor phytase production were determinedto be100 ?g/ml ampicilin, 0.2 % arabinose and an incubation temperature of37ºC.The production of phytase in the recombinant E. coliwas scaledup to 100ml and 1000ml.

Adaptive Backstepping Control of Electrical Transmission Drives with Elastic, Unknown Backlash and Coulomb Friction Nonlinearity Huỳnh Văn Đông; Trần Xuân Kiên; Nguyễn Công Định
ASEAN Journal on Science and Technology for Development Vol. 27 No. 1 (2010): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

In this paper, we present a new scheme to design an adaptive controller for uncertain nonlinear systems with unknown backlash, Coulomb friction nonlinearity. The control design is achieved by introducing a smooth approximate backlash model and certain well defined functions and by using backstepping technique. Itis shown that the proposed controller can guarantee that the system is global asymptotic stable.

PECULIAR OPTICAL PROPERTIES OF Co2MnGa ALLOYS Joo Yull Rhee; Y.V. Kudryavtsev; K.W. Kim; Y.P. Lee
ASEAN Journal on Science and Technology for Development Vol. 24 No. 1-2 (2007): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Co2MnGa alloy was prepared by the conventional arc-melting method. The optical conductivity (OC) spectrum of the alloy was measured by a rotating-analyzer spectroscopic ellipsometer. The OC spectrum was also calculated based on the electronic structure by using the full-potential linearized-augmented-plane-wave method within the local-spin-density approximation to the density-functional theory. The calculated OC spectrum does not agree well with the experimental one. Since the Co2MnGa alloy could be a strongly-correlated material, the so-called 'LDA+U' method was applied with U = 5.4 eV. The calculated OC spectrum using the 'LDA+U' method agrees very well with the experimental one. The inclusion of the onsite Coulombpotential during the self-consistent calculation significantly modifies the minorityspin Co and Mn 3d bands, resulting in a contraction of the energy gaps between states which are strongly involved in interband absorption peaks.

Fermentation of Oil Palm Trunk Acid Hydrolysate to Ethanol H. H. Yeoh; K. O. Lim; M. D. Mashitah
ASEAN Journal on Science and Technology for Development Vol. 18 No. 1 (2001): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Studies on the feasibility of using oil palm trunk acid hyd10lysates as a substrate for ethanol p10duction using the yeast Saccha10myces cerevisiae were carried out in shake flask culture. The effect of pH and fermentation time on the rate of ethanol p10duction were investigated. Results showed that with 3 hours fermentation period, the highest ethanol yield was obtained at pH 4.75. This yield was about 14% of the dry weight of the sample used; thus giving a fermentation efficiency of 94.7%.

SPIN-POLARIZED PHOTOCURRENT THROUGH QUANTUM DOT PHOTODETECTOR Hieu, Nguyen Van; Ha, Nguyen Bich
ASEAN Journal on Science and Technology for Development Vol. 24 No. 1-2 (2007): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The theory of the photocurrent through the photodetector based on a two-level semiconductor quantum dot (QD) is presented. The analytical expressions of the matrix elements of the electronic transitions generated by the absorption of the circularly polarized photons are derived in the lowest order of the perturbation theory with respect to the electron tunneling interaction as well as the electron-photon interaction. From these expressions the mechanism of the generation of the spin-polarized of electrons in the photocurrent is evident. It follows that the photodetector based on the two-level semiconductor QD can be used as the model of a source of highly spinpolarized electrons.

PREPARATION OF THE SINGLE MODE PLANAR OPTICAL SPLITTER MODULES AND THEIR CHARACTERIZATIONS Mien, Vu Doan; Nghiem, Vu Thi; Truong, Pham Van
ASEAN Journal on Science and Technology for Development Vol. 24 No. 1-2 (2007): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

Optical splitter modules have been prepared based on 1x8 single mode silica planar waveguide optical splitter chips with 250 µm spacing and v-groove fiber arrays for applications in fiber optic communications. We report the technology of precise optical coupling and packaging of the splitter modules and the measurements of the insertion loss (< 11 dB), uniformity (< 0.80 dB) and polarization dependence loss (PLD < 0.10 dB) as well as the lateral profile and the image of the input and output lights for the wavelengths of 1310 nm and 1550 nm. The main characteristics of the prepared splitter modules are about the same for the commercial available products. The prepared modules have been tested for operation in the conditions of wide temperature range (5–80°C) and humidity range (50–98%) and no changes in the main characteristics were observed.

MAGNETO-OPTIC PROPERTIES AND OXIDATION/REDUCTION OF ULTRATHIN MAGNETIC FILMS: FE FILMS ON Pt(111) T.-U. Nahm
ASEAN Journal on Science and Technology for Development Vol. 24 No. 1-2 (2007): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

We have investigated magneto-optic properties of ultrathin Fe films grown on Pt(111) surfaces by using the in situ surface magneto-optic Kerr effect (SMOKE) and X-ray photoelectron spectroscopy (XPS). SMOKE measurements show that the Fe layers are not ferromagnetic when the film is thinner than approximately 4.5 MLs (monolayers), but the in-plane magnetization is present for a 4.1 ML Fe film on Pt(111) annealed at 550 K. Upon post-annealing at 770 K, a 9.2 ML Fe film does not show any Kerr signal, while a 6.3 ML Fe film has the in-plane Kerr signal with increased coercivity. The oxidation and reduction of ultrathin Fe films have also been studied by using XPS. Upon an oxygen exposure of 300 Langmuir at a film temperature of 873 K, the Fe layers were mostly oxidized as Fe3O4. When the Fe films were exposed to the same amount of oxygen at room temperature, a partial oxidation as Fe3O4 was observed for a 3 ML Fe film, while there was no oxidation for a 2 ML Fe film. On heating the 873 K oxidized films, Fe3O4O was reduced to FeO, and even the decomposition was observed. Underlying reasons for these chemical changes of Fe and iron-oxide films are discussed.

WHISPERING GALLERY MODE LASERS IN ERBIUM/YTTERBIUM CODOPED PHOSPHATE GLASSES Tran Thi Tam; Dang Quoc Trung; Le Huu Minh; Tran Anh Vu; Do Ngoc Chung; Patrice Feron
ASEAN Journal on Science and Technology for Development Vol. 24 No. 1-2 (2007): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

The study of whispering gallery mode laser in Er3+/Yb3+ co-doped phosphate glass microsphere has been reported. The coupling was carried out by fiber half taper technique. The microsphere lasers have been studied under pumping at 980 nm, to take full advantage of energy transfer effect from ion Ytterbium to ion Erbium. The observed lasing range extends from 1533 nm to 1612 nm.

The Mobilization and Utilization of Scientific and Technological Human Resources in Developing Countries Michel J Moravscik
ASEAN Journal on Science and Technology for Development Vol. 3 No. 1 (1986): Vol. 3 No. 1 (1986)
Publisher : Universitas Gadjah Mada

Human resources (henceforth abbreviated as "manpower") in the development and the functioning of science and technology in developing countries is the most crucial ingredient, and forms, most often, the bottleneck in evolution. This is so because it takes an extended period of time (decades) to establish an indigenous scientific and technological manpower of sufficient quality and quantity, and because it is a much more difficult and uncertain undertaking to do so than to asquire sufficient financial resources. For this reason problems related to the generation and utilization of scientific and technological manpower are at the very centre of attantion when it comes to managing science and technology in developing countries.

Study on the osmotic pre-treatment and infrared radiation on drying kinetics and colour changes during drying of agricultural products S. K. Chou,; K. J. Chua,; A. S. Mujumdar; M. Tan, and; S. L. Tan
ASEAN Journal on Science and Technology for Development Vol. 18 No. 1 (2001): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

A combination of intermittent infrared and continuous convection heating was used to dehydrate various osmotically pretreated sample of potato (in solutions of 10%, 20% and 30% NaCl) and pineapple (in solutions of 30%, 50%, 70% Brix). In one set of runs, the infrared source was turned on and off sequentially according to a predetermined time schedule. In the other set, a thermocouple located on the surface of the drying slice exposed to the radiant heat flux measured the temperature continuously and cut off the infrared source automatically when the surface temperature reached 36 to 45°C. The effect of osmotic-IR conditions on colour changes of potato, pineapple and apple was investigated. With appropriate choice of infrared intermittency as well as osmotic pretreatment, it is possible to reduce the overall colour change while maintaining high drying rates. Results from the temperature feedback system indicated no measurable colour degradation occurred despite faster drying kinetics, reduction in drying times and minimisation in product shrinkage.

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