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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.

Arjuna Subject : -

Articles 477 Documents

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CVD PREPARED Mn-DOPED ZnO NANOWIRES T.L. Phan; R. Vincent; D. Cherns; N.X. Nghia
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

Mn-doped ZnO nanowires prepared by chemical vapor deposition (CVD) were obtained in the temperature range of 450–500°C. X-ray diffraction patterns, SEM and TEM images indicate that crystals with a hexagonal structure grow along the c axis. At low Mn-doped concentrations, photoluminescence (PL) and Raman scattering (RS) spectra are almost independent of the Mn doping. However, the increase in concentration of Mn above 1.6 at% weakens significantly the PL signal and the RS-lines intensity in the low wavenumber range of 300–480 cm-1, and concurrently increases the RS-lines intensity in the higher wavenumber range of 480-700 cm-1.. Magnetic measurements determined the Curie temperature of Mn-doped ZnO nanowire to be about 37 K.

PHOTOLUMINESCENCE OF ZnO NANOSTRUCTURE PREPARED BY CATALYST - ASSISTED VAPOR - LIQUID - SOLID TECHNIQUE Tran Thi Quynh Hoa; Ta Dinh Canh; Nguyen Ngoc Long; Nguyen Viet Tuyen; Nguyen Duy Phuong
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

ZnO semiconductor nanostructures have been synthesized by thermal evaporation of mixture of ZnO and graphite powders. The thin layer of gold coated on Si substrates was used as a catalyst. The structure analysis shows high crystallinity of ZnO, their preferred orientation along the (0 02) plane of the wurtzite phase and their chemical purity. The scanning electron microscopy (SEM) images of products indicate that ZnO nanowires have a diameter of about 40 - 150 nm and a length of up to tens of micrometers. The morphology and structure of ZnO nanowires and nanorods depend on the thicknesses of the Au layers. The fact that Au nanoparticles are located at the tips of the nanowires represents a strong evidence for a growth process dominated by the vapor - liquid - solid mechanism. The low temperature photoluminescence spectra of the ZnO nanowires indicate a group of the ultraviolet narrow peaks and a blue - green very broad peak at 500 nm.

RESEARCH AND DEVELOPMENT OF DIODE-PUMPED PASSIVELY Q-SWITCHED Nd:YVO4 LASERS USING Cr4+:YAG CRYSTAL AS SATURABLE ABSORBER Nguyen Trong Nghia; Trinh Dinh Huy; Le Thi Thanh Nga; Nguyen Dai Hung
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 results in research and development of diode-pumped passively Q-switched Nd:YVO4 lasers are presented with Cr4+:YAG crystal used as an intra-cavity saturable absorber. Using a-cut Nd:YVO4 laser crystals, the passively Q-switched lasers have been successfully developed and provided stable single shortest pulses of 40 ns at the repetition rate of 18.5 kHz, the maximal average output power of 180 mW was achieved corresponding to the optical efficiency of 9% and the slope efficiency of 16%. The dependences of average output power, repetition rate, pulse width and peak power on pump diode power for different transmissions of output mirror are also investigated.

Spectrophotometric method for hg(ii) determination in aqueous environment using zinc-dithizonate complex Musa Ahmad Ahmad,; Elya Sufliza Marsom; Harun Hamzah
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 described the use of zinc-dithizonate for spectrophotometric determination of Hg(II) in aqueous environment. Zinc dithizonate was found to react selectively with Hg(II) to give a reddish yellow complex with optimum absorbance at pH 1.0. This complex was found to be useful for spectrophotometric determination of aqueous Hg(II) in the concentration range of 1.0 - 12.0 ppm. This method was also found to be reproducible with calculated relative standard deviation, RSD of 1.08%. At 1:1 mole ratio, interfering ions such as CH COO·, Pb2+ and Ag+ were found to interfere at degree 3 of interference of more than 10.0%.

EUROPIUM SILICATE THIN FILMS FABRICATED BY RF MAGNETRON SPUTTERING AND THERMAL TREATMENT Young Chul Shin; Eun Hong Kim; Tae Geun Kim
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 report the fabrication and optical characteristics of europium silicate thin films. Layer structures of Eu2O3/SiOX/Si (100) were deposited by an rf-sputtering method and annealed at 1100°C by rapid thermal annealing (RTA). Two methods were used for the deposition of SiOX layer: One was deposited by sputtering using SiO2 target (Ar gas at a rate of 50 sccm) and the other was deposited by reactive sputtering using Si target (Ar gas at a rate of 45 sccm, with an O2 gas at a rate of 5 sccm). Photoluminescence peak at 430 nm was observed in the sample composed of SiOx interlayer sputtered from SiO2 target. In comparison, PL peak at 570 nm was observed in the other sample, the SiOx layer of which was deposited by reactive sputtering from Si target. The compositional distributions of these samples were analyzed by X-ray photoelectron spectroscopy (XPS).

An experiment with spiral wound reverse osmosis membranes for the Desalination of seawater M.N.A. Hawlader Hawlader,; J.C. Ho Ho, and; K.T. Chua
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

In the research, the performance characteristics of Reverse Osmosis (RO) Spiral Wound (SW) membrane are evaluated. The effects of feed water concentration, temperature, pressure and flow rate on the performance of this membrane are investigated. The product recovery (<I>) of SW membrane is found to increase with feed water temperature and pressure, but decrease with increasing feed water concentration and flow rate. Salt passage (SP) increases with feed water temperature and concentration, but decreases with increasing feed pressure and flow rate. Under the tested feed water conditions, <I> of SW varies from 6% - 18% and permeate salinity is approximately 130ppm. In addition, validity of the Complete Mixing Model is verified and successfully extended to the derivation of water and salt transport parameters of SW membrane. Plots of I/SR' versus l/Jw display linear relationships, as predicted in the model.

Seasonal orientation of solar collectors for the philippines Saiful Bari
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

In this paper, a method to determine the slope angle for seasonal applications of flat plate collectors is described for the Philippines territory. For seasonal applications, where the collectors are used only for a fraction of the year, the slope angles need to be different from those for year-round operations. For year-round operations, most flat collectors are usually fixed, and mounted at an angle equal to the latitude tilt angle. The method described here utilized both direct and diffuse components of solar radiation, and air mass using average atmosphere. For seasonal applications of solar energy such as crop drying, the optimum slope angle can be found conveniently and accurately by this method

Thermal diffusivity measurements using open photoacoustic cell technique W. Mahmood Mat Yunus; C. Y. J. Fanny,; I. V. Grozescu,; S. A. Halim and,; M. M. Moksin
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

The application of open photoacoustic cell (OPC) technique is demonstrated for measuring thermal diffusivity of solid samples. It is based upon the measurement of the photoacoustic signal in the modulation frequency region where the thermal diffusion length equals to the sample thickness. The measurements were carried out at room temperature for gold alloys (Au0 75Ag0.and Au. Ag. ); epoxidised natural rubbers 25 0 50 0 50 [ENR 25 (75%C ) and ENR 50 (75%C)]; and supercond ucti ng ceramics (Bi2Pb0 .6 Sr2Ca1.94Ba 0. Cu 0 , and Bi Pb . Sr Ca1. Zn. Cu 0 ) . The thermal 06 3 8 2 0 6 2 93 0 07 3 8 diffusivity values obtained in this measurement were in the range of 0.97 for Al down to 1.61 x 10-3 cm2/s for polymer sample.

Effects of thinning on the incidence of damage and severity of decay in bagras (eucalyptus deglupta blume) plantations Emelio 0. Anino 0. Anino
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

Thinning of intermediate and suppressed trees has been implemented on 3- to 4-year-old bagras (E. deglupta) plantations in Surigao de! Sur, Philippines. The objective is to remove unwanted competition and to gain some form of revenue by selling the felled trees as banana props. However, the falling trees caused damage to other plantation trees. Bagras is susceptible to heart rot. A study was, therefore, conducted to determine the extent of decay in bagras due to thinning. Data showed that injured bagras developed extensive decay in the sapwood and heartwood. Six percent of the injured trees died. Retained-trees, which were already exposed to sunlight, developed an average of eight epicormic branches on the lower stems. Thinning methods must, therefore, be improved to reduce sapwood injury aud ensuing decay aud to prevent the development of unwanted epicormic branches on the commercially useful portion of the stem.

OPTICAL AND STRUCTURAL PROPERTIES OF OPTICAL THIN FILMS WITH VARIOUS COLUMNAR MICROSTRUCTURES Seouk-Hoon Woo; Yong Jun Park; Chang Kwon Hwangbo
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 study, optical and structural properties of the thin films prepared using glancing angle deposition (GLAD) are investigated. Various glancing angles and substrate rotations are employed to control the columnar microstructure of the films. The results show that as the glancing angle increases, the column angle and the porosity of TiO2 films increase and the refractive index decreases, due to shadow effects. The optical anisotropy of tilted and zigzag microstructure TiO2 films have a large anisotropy and reaches a maximum at a glancing angle of 60°, while that of helical microstructure TiO2 film deposited at 60° with substrate rotation shows a very small anisotropy due to the symmetric structure. It is found that the optical anisotropy of TiO2 films deposited by GLAD can be controlled by modification of microstructure.

Page 17 of 48 | Total Record : 477

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