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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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A review on energy efficiency standards and labels: present status and implementation possibilities in malaysia T.M.I. Mahlia,; H.H. Masjuki,; I.A. Choudhury; and R. Saidur R. Saidur
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

This article is a review on energy efficiency standards and labels for household electrical appliances around the world. Through the review of other country experiences on energy efficiency standards and labels, we attempt to identify savings possibilities in Malaysian households. The implementation possibilities of standards and labels for various household electrical appliances in Malaysia are also examined. It is found that various household appliances in Malaysia offer some potential in reducing electricity consumption. Finally, it is concluded that there are many advantages for Malaysia to implement the standards and labels for household electrical appliances as soon as possible in order to reduce electricity bills and energy consumption in Malaysian households.

EXPERIMENTAL STUDY OF 3D SELF-ASSEMBLED PHOTONIC CRYSTALS AND COLLOIDAL CORE-SHELL SEMICONDUCTOR QUANTUM DOTS Pham Thu Nga; Vu Duc Chinh; Nguyen Xuan Nghia; Nguyen Viet Huy; Dao Nguyen Thuan; Pham Thai Cuong; Chu Viet Ha; Do Thuy Chi; Nguyen Nhu Dat; Le A Lan Anh; C. Barthou; P. Benalloul; M. Romanelli; A. Maître
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

In this contribution we present an experimental study of 3D opal photonic crystals. The samples are opals constituted by colloidal silica spheres, realized with self-assembly technique. The sphere diameter is selected in order to obtain coupling of the photonic band gap with the emission from CdSe/ZnS colloidal quantum dots. The quantum dots infiltrated in the opals is expected to be enhanced or suppressed depending on the detection angle from the photonic crystal. The structural and optical characterization of the SiO2 opal photonic crystals are performed by field-emission scanning electron microscopy and reflectivity spectroscopy. Measurements performed on samples permits to put into evidence the influence of the different preparation methods on the optical properties. Study of self-activated luminescence of the pure opals is also presented. It is shown that the luminescence of the sample with QDs have original QD emission and not due to the photonic crystal structure. The optical properties of colloidal core-shell semiconductor quantum dots of CdSe/ZnS which are prepared in our lab will be mention.

Concentrations of lead (pb) in road dust in bandar seri begawan, brunei darussalam Shahrizal Emran,; K. Rodney Fernando,; and Miroslav Radojevic Radojevic
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 first-ever survey oflead (Pb) in road dust in Bandar Seri Begawan (B.S.B.), the capital of Brunei Darussalam, was carried out in 1996, three years after the introduction of unleaded petrol. The concentration of Pb at 114 sites varied between 12 and 544 µg/g (mean: 125 µg/g; standard deviation: 103 µg/g). There was a significant correlation (r=0.546) between lead in road dust and traffic volume at 17 sites for which traffic counts were available. An assessment of the potential hazard posed to children was made. It is concluded that concentration levels of Pb in road dust in B.S.B. are considerably lower than levels found in London and Hong Kong, and they do not pose a major public health hazard.

INVESTIGATION OF ZnO NANO STRUCTURES FABRICATED ON AL2O3 SUBSTRACTES BY MOCVD Nguyen Thanh Binh; Vu Thi Bich; Y. Segawa
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

High quality ZnO nanostructures were grown directly on sapphire subtracts by metal organic vapor deposition. By changing the growth conditions, the different nano structures (nanorods,nanotubes, nanowalls, nanonetworks) can be selectively. These nanostructures were all epitaxially grown and had the same epitaxial relationship with respect to the substrate. Mechanisms corresponding to different nanostructures were discussed. The nanostructures exhibited stable excitonic states at room temperature, and the emission due to exciton-exciton scattering was observed

DURATION LIMIT OF LASER PULSES EMITTED FROM A Ce-DOPED CRYSTAL SHORT CAVITY Le Hoang Hai; Nguyen Dai Hung; Hoang Huu Hoa; Alex V. V. Quema; Nobuhiko Sarukura
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

Based on the rate equation set for broadband cavities, the dependence of pulse duration on cavity and pumping parameters is analyzed. The cavity uses a Ce-doped crystal as a gain medium. Computation results show the variation of the pulse width with the change of cavity length, mirror reflectivity, pumping energy and pumping pulse duration. A significant influence of multiple-pulse operation in limiting pulse duration is realized and a pulse-width of the order 200 ps is found to be the limit for the direct generation of ultraviolet single picosecond pulses from a Ce:LLF short cavity.

SYNTHESIS AND CHARACTERISTICS OF POLY(PARA-PHENYLENEVINYLENE) Pham Thi Minh Chau; Jung Il Jin
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

Poly(para-phenylenevinylene) [PPV] films and nanotubes were prepared via chemical vapor deposition polymerization (CVDP) by vapor phase pyrolysis of ?, ?'-dichloro p-xylene on the quartz plate, silicon wafers and Al2O3 membrane substrate with the pore size f = 100 nm. We prepared graphitic carbon films and carbon nanotubes by carbonizing the poly(para-phenylenevinylene) [PPV] films and nano parterns under thermal treatment range from 500°C to 900°C. When the PPV films on quartz plate were treated at 900°C highly oriented graphitic carbon films were obtained. The characterization of the PPV nanotube and nanotube carbon has been investigated by means of IR, SEM, AFM and Raman scattering study.

CO CLUSTER FORMATION IN TiO2 DMS AND A METHOD OF ESTIMATION Le Van Hong; Nguyen Chi Thuan; Nguyen Van Dai; Nguyen Xuan Phuc
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 paper presents experimental observations of the Co cluster formation in TiO2/Co powder samples prepared by the Sol-Gel method. The obtained X-ray diffraction patterns and Raman scattering show that the anatase phase of TiO2 was successfully synthesized at an annealing temperature of 450°C. Comprehensive studies by means of X-ray diffraction, Raman scattering, thermal magnetization in a temperature range of 300–1000 K and magnetic hysteresis at room temperature confirm that a part of Co did not substitute for Ti in TiO2 structure, otherwise it has reasonably formed cluster of Co in samples. Based on the thermal magnetization curves a method to estimate the magnetic moment per one Co ion substituted for Ti in TiO2 structure was proposed. By means of this method the volume of Co substituted for Ti has been estimated for samples annealed at various temperatures around 450°C. The obtained results show that the volume of Co cluster rises when the annealing temperature increases. This obtained result persuasively explains the large divergence in the magnetic moment per one Co ion reported in the most published papers.

SYNTHESIS AND PHOTOLUMINESCENCE STUDIES ON ZINC OXIDE NANOWIRES Nguyen Ngoc Long; Ngo Xuan Dai; Nguyen Thi Thuc Hien
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

Semiconductor single crystal ZnO nanowires have been successfully synthesized by a simple method based on thermal evaporation of ZnO powders mixed with graphite. Metallic catalysts, carrying gases, and vacuum conditions are not necessary. The x-ray diffraction (XRD) analysis shows that the ZnO nanowires are highly crystallized and have a typical wurtzite hexagonal structure with lattice constants a = 0.3246 nm and c = 0.5203 nm. The scanning electron microscopy (SEM) images of nanowires indicate that diameters of the ZnO nanowires normally range from 100 to 300 nm and their lengths are several tens of micrometers. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the nanowires were measured in the range of temperature from 15 K to the room temperature. Photoluminescence spectra at low temperatures exhibit a group of ultraviolet (UV) narrow peaks in the region 368 nm ~ 390 nm, and a blue-green very broad peak at 500 nm. Origin of the emission lines in PL spectra and the lines in PLE spectra is discussed.

SIMULATED-DATA ADAPTATION BASED PIECEWISE LINEAR TRANSFORMATION FOR ROBUST SPEECH RECOGNITION Nattanun Thatphithakkul; Boontee Kruatrachue; Chai Wutiwiwatchai; Sanparith Marukatat; Vataya Boonpiam
ASEAN Journal on Science and Technology for Development Vol. 24 No. 4 (2007): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

This paper proposes an efficient method of simulated-data adaptation for robust speech recognition. The method is applied to tree-structured piecewise linear transformation (PLT). The original PLT selects an acoustic model using tree-structured HMMs and the acoustic model is adapted by input speech in an unsupervised scheme. This adaptation can degrade the acoustic model if the input speech is incorrectly transcribed during the adaptation process. Moreover, adaptation may not be effective if only the input speech is used. Our proposed method increases the size of adaptation data by adding noise portions from the input speech to a set of prerecorded clean speech, of which correct transcriptions are known. We investigate various configurations of the proposed method. Evaluations are performed with both additive and real noisy speech. The experimental results show that the proposed system reaches higher recognition rate than MLLR, HMM-based model selection and PLT.

THE SYNTHESIS OF A NOVEL BIBENZOPYRAN RELIED ON ELECTROOXYDATION OF MALLOAPELTA B BY CYCLIC VOLTAMMETRY Phan Thi Binh; Bui Hai Ninh; Chau Van Minh; Nguyen Hoai Nam; Le Mai Huong; Phan Van Kiem
ASEAN Journal on Science and Technology for Development Vol. 24 No. 4 (2007): ASEAN Journal on Science and Technology for Development (AJSTD)
Publisher : Universitas Gadjah Mada

A novel bibenzopyran named bimalloapelta (1) was synthesized relying on electrooxydation of malloapelta B by cyclic voltammetry in acetonitril adding LiClO4 0.1 M as supporting electrolyte. Its structure determination based on extensive NMR studies and ESI mass spectral measurements. The new compound showed significant cytotoxicity againsts two cancer cell lines as human hepatocellular carcinoma (Hep-2; IC50: 0.46 µg/m) and rhabdosarcoma (RD; IC50: 0.33 µg/m). These results were the same that of malloapelta B (Hep-2, IC50: 0.49 µg/ml and KB, IC50: 0.54 µg/ml).

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