Cvd Prepared Mn-Doped Zno Nanowires,
2017
Universiti Brunei Darussalam
Cvd Prepared Mn-Doped Zno Nanowires, Phan T.L., Vincent R., Cherns D., Nghia N.X.
ASEAN Journal on Science and Technology for Development
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 …
Study On The Osmotic Pre-Treatment And Infrared Radiation On Drying Kinetics And Colour Changes During Drying Of Agricultural Products,
2017
Universiti Brunei Darussalam
Study On The Osmotic Pre-Treatment And Infrared Radiation On Drying Kinetics And Colour Changes During Drying Of Agricultural Products, Chou, S. K., Chua, K. J., Mujumdar A. S., Tan And, M., Tan S. L.
ASEAN Journal on Science and Technology for Development
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 …
Whispering Gallery Mode Lasers In Erbium/Ytterbium Codoped Phosphate Glasses,
2017
Universiti Brunei Darussalam
Whispering Gallery Mode Lasers In Erbium/Ytterbium Codoped Phosphate Glasses, Tam Tran Thi, Trung Dang Quoc, Minh Le Huu, Vu Tran Anh, Chung Do Ngoc, Feron Patrice
ASEAN Journal on Science and Technology for Development
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.
Fermentation Of Oil Palm Trunk Acid Hydrolysate To Ethanol,
2017
Universiti Brunei Darussalam
Fermentation Of Oil Palm Trunk Acid Hydrolysate To Ethanol, Yeoh H. H., Lim K. O., Mashitah M. D.
ASEAN Journal on Science and Technology for Development
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%.
Spectrophotometric Method For Hg(Ii) Determination In Aqueous Environment Using Zinc-Dithizonate Complex,
2017
Universiti Brunei Darussalam
Spectrophotometric Method For Hg(Ii) Determination In Aqueous Environment Using Zinc-Dithizonate Complex, Ahmad, Musa Ahmad, Marsom Elya Sufliza, Hamzah Harun
ASEAN Journal on Science and Technology for Development
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%.
Preparation Of The Single Mode Planar Optical Splitter Modules And Their Characterizations,
2017
Universiti Brunei Darussalam
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
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),
2017
Universiti Brunei Darussalam
Magneto-Optic Properties And Oxidation/Reduction Of Ultrathin Magnetic Films: Fe Films On Pt(111), Nahm T.-U.
ASEAN Journal on Science and Technology for Development
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 …
Research And Development Of Diode-Pumped Passively Q-Switched Nd:Yvo4 Lasers Using Cr4+:Yag Crystal As Saturable Absorber,
2017
Universiti Brunei Darussalam
Research And Development Of Diode-Pumped Passively Q-Switched Nd:Yvo4 Lasers Using Cr4+:Yag Crystal As Saturable Absorber, Nghia Nguyen Trong, Huy Trinh Dinh, Nga Le Thi Thanh, Hung Nguyen Dai
ASEAN Journal on Science and Technology for Development
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 …
Experimental Study Of 3d Self-Assembled Photonic Crystals And Colloidal Core-Shell Semiconductor Quantum Dots,
2017
Universiti Brunei Darussalam
Experimental Study Of 3d Self-Assembled Photonic Crystals And Colloidal Core-Shell Semiconductor Quantum Dots, Nga Pham Thu, Chinh Vu Duc, Nghia Nguyen Xuan, Huy Nguyen Viet, Thuan Dao Nguyen, Cuong Pham Thai, Ha Chu Viet, Chi Do Do, Dat Nguyen Nhu, Anh Le A Lan, Barthou C., Benalloul P., Romanelli M., Maã®Tre A.
ASEAN Journal on Science and Technology for Development
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 …
Investigation Of Zno Nano Structures Fabricated On Al2o3 Substractes By Mocvd,
2017
Universiti Brunei Darussalam
Investigation Of Zno Nano Structures Fabricated On Al2o3 Substractes By Mocvd, Binh Nguyen Thanh, Bich Vu Thi, Segawa Y.
ASEAN Journal on Science and Technology for Development
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
Co Cluster Formation In Tio2 Dms And A Method Of Estimation,
2017
Universiti Brunei Darussalam
Co Cluster Formation In Tio2 Dms And A Method Of Estimation, Hong Le Van, Thuan Nguyen Chi, Dai Nguyen Van, Phuc Nguyen Xuan
ASEAN Journal on Science and Technology for Development
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 …
Synthesis And Photoluminescence Studies On Zinc Oxide Nanowires,
2017
Universiti Brunei Darussalam
Synthesis And Photoluminescence Studies On Zinc Oxide Nanowires, Long Nguyen Ngoc, Dai Ngo Xuan, Hien Nguyen Thi Thuc
ASEAN Journal on Science and Technology for Development
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 …
Spin-Polarized Photocurrent Through Quantum Dot Photodetector,
2017
Universiti Brunei Darussalam
Spin-Polarized Photocurrent Through Quantum Dot Photodetector, Hieu Nguyen Van, Ha Nguyen Bich
ASEAN Journal on Science and Technology for Development
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 …
Photoluminescence Of Zno Nanostructure Prepared By Catalyst - Assisted Vapor - Liquid - Solid Technique,
2017
Universiti Brunei Darussalam
Photoluminescence Of Zno Nanostructure Prepared By Catalyst - Assisted Vapor - Liquid - Solid Technique, Hoa Tran Thi Quynh, Canh Ta Dinh, Long Nguyen Ngoc, Tuyen Nguyen Viet, Phuong Nguyen Duy
ASEAN Journal on Science and Technology for Development
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 …
Synthesis And Characteristics Of Poly(Para-Phenylenevinylene),
2017
Universiti Brunei Darussalam
Synthesis And Characteristics Of Poly(Para-Phenylenevinylene), Chau Pham Thi Minh, Jin Jung Il
ASEAN Journal on Science and Technology for Development
Poly(para-phenylenevinylene) [PPV] films and nanotubes were prepared via chemical vapor deposition polymerization (CVDP) by vapor phase pyrolysis of α, α'-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 …
Concentrations Of Lead (Pb) In Road Dust In Bandar Seri Begawan, Brunei Darussalam,
2017
Universiti Brunei Darussalam
Concentrations Of Lead (Pb) In Road Dust In Bandar Seri Begawan, Brunei Darussalam, Emran, Shahrizal, Fernando, K. Rodney, Radojevic And Miroslav Radojevic
ASEAN Journal on Science and Technology for Development
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 …
Optical And Structural Properties Of Optical Thin Films With Various Columnar Microstructures,
2017
Universiti Brunei Darussalam
Optical And Structural Properties Of Optical Thin Films With Various Columnar Microstructures, Woo Seouk-Hoon, Park Yong Jun, Hwangbo Chang Kwon
ASEAN Journal on Science and Technology for Development
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 …
Duration Limit Of Laser Pulses Emitted From A Ce-Doped Crystal Short Cavity,
2017
Universiti Brunei Darussalam
Duration Limit Of Laser Pulses Emitted From A Ce-Doped Crystal Short Cavity, Hai Le Hoang, Hung Nguyen Dai, Hoa Hoang Huu, Quema Alex V. V., Sarukura Nobuhiko
ASEAN Journal on Science and Technology for Development
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.
Peculiar Optical Properties Of Co2mnga Alloys,
2017
Universiti Brunei Darussalam
Peculiar Optical Properties Of Co2mnga Alloys, Rhee Joo Yull, Kudryavtsev Y.V., Kim K.W., Lee Y.P.
ASEAN Journal on Science and Technology for Development
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 …
Mixed - Mode Operating System For Real - Time Performance,
2017
Universiti Brunei Darussalam
Mixed - Mode Operating System For Real - Time Performance, M. Hasan M., S. Sultana, C.K. Foo
ASEAN Journal on Science and Technology for Development
The purpose of the mixed-mode system research is to handle devices with the accuracy of real-time systems and at the same time, having all the benefits and facilities of a matured Graphic User Interface(GUI)operating system which is typicallynon-real-time. This mixed-mode operating system comprising of a real-time portion and a non-real-time portion was studied and implemented to identify the feasibilities and performances in practical applications (in the context of scheduled the real-time events). In this research an i8751 microcontroller-based hardware was used to measure the performance of the system in real-time-only as well as non-real-time-only configurations. The real-time portion is an …
