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Reactivity of poly(dimethylsiloxane) toward acidic permanganate
Trung-Dung Dang,주상우,Marcos A. Cheney,스즈첸,민봉기 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.6
Poly(dimethylsiloxane) (PDMS) has been widely used in various microfluidic devices because it is considered to be one of the most inert materials available. A PDMS-based microfluidic system for the synthesis of manganese oxide (MO) nanoparticles is developed and tested. However, synthesis of MO nanoparticles in the PDMS-based microfluidic system is unsuccessful due to an unexpected reaction between acidic permanganate and PDMS. PDMS is pitted and coated with MnO2 and opalized silica,which are confirmed by SEM and EDX. The products of the reaction between PDMS and acidic permanganate are mainly MnO2, Cl2, SiO2 and CO2, respectively. Here we report for the first time the reactivity of PDMS toward acidic permangante resulting in a new process to coat the channel walls with MnO2.
Fabrication of Microfluidic Hemicylindrical Lenses for Light Scanning of Laser Sheet
Trung-Dung Dang,김규만,김영호,박철우 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.10
A light scanning device with two microfluidic hemicylindrical lenses was demonstrated for adjustable laser sheet beam scanning applications. An elastomeric hemicylindrical lens, whose focal length can be adjusted by control of the applied fluidic pressure, was fabricated by application of the pressurized casting process on polydimethylsiloxane (PDMS) obtained from a prepared microsized mold. The hemicylindrical lens consisted of a thin membrane, a liquid chamber and a microchannel. The applied fluidic pressure deformed the lens membrane and changed the lens shape. The change of the lens shape allowed beam shape transformation or beam scanning according to the relative size of the beam to the lens. By orthogonally placing two microfluidic lenses of different sizes, 1 mm × 5 mm and 3 mm × 15 mm, respectively, a spot laser beam from a 200μm-large pinhole was transformed into laser sheet, and then the laser sheet was scanned. The relationship between the lens properties, including lens curvature and laser beam shaping according to different applied pressures on the lens, were systematically investigated. Laser beam scanning properties of the microfluidic light scanning device were also characterized for various applied pressures and offset distances.
Dang, Trung-Dung,Cheney, Marcos A.,Qian, Shizhi,Joo, Sang Woo,Min, Bong-Ki American Chemical Society 2013 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.52 No.7
<P>We report for the first time a novel rapid synthesis method for manganese oxide (MO) nanoparticles by a reaction between acidic permanganate and poly(dimethylsiloxane) (PDMS). In contrast to the existing traditional methods for synthesis of MO nanoparticles, the new method has the advantage of shorter reaction time (∼2 h) at room temperature (∼25 °C). The produced MO nanoparticles are characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM, HRTEM). The material produced is semicrystalline silicon-doped MnO<SUB>2</SUB> with homogeneous size and morphology with an average particle size around 300 nm. Other products of the reactions include Cl<SUB>2</SUB>, silicon dioxide sheets on PDMS, and CO<SUB>2</SUB>. A mechanism for this reaction is proposed. The prepared MO was successfully used as a catalyst for the rapid and highly efficient degradation of a water pollutantRhodamine B (RhB).</P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ie302971g'>ACS Electronic Supporting Info</A></P>
Preparation of monodisperse PEG hydrogel microparticles using a microfluidic flow-focusing device
Trung-Dung Dang,Young Ho Kim,Hwan Gon Kim,김규만 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.4
A microfluidic assisted preparation method of nearly monosized poly(ethylene glycol) (PEG)microparticles has been described. Three types of microfluidic flow-focusing devices with different geometries were fabricated using polydimethylsiloxane (PDMS). Microdroplets of PEG hydrogel were successfully prepared in the microfluidic flow-focusing devices by adjusting the flow rates of the continuous phase, namely, mineral oil, and the dispersed phase, viz., hydrogel solution. Then, the microdroplets of PEG hydrogel were cured by UV irradiation. Various experimental conditions pertaining to the geometry of the microfluidic flow-focusing device, flow rates of the dispersed and continuous phases, and concentration of PEG hydrogel solution were investigated and optimized to fabricate monosized PEG hydrogel microparticles. The prepared PEG microparticles were nearly monosized in the range of 40 mm to 200 mm in diameter according to the above experimental conditions. Then, PEG hydrogel particles laden with microbeads of 6 mm diameter were fabricated using the microfluidic flowfocusing devices with the optimized conditions.
당중덩(Trung-Dung Dang),김영호(Young Ho Kim),최진호(Jin-Ho Choi),김환곤(Hwan-Gon Kim),이상학(Sang Hak Lee),김규만(Gyu-Man Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
A microfluidic synthetic device using polydimethylsiloxane (PDMS) has been devised to fabricate microsized hydrogel particles. In the microfluidic synthetic device, micro-droplets of poly(ethylene glycol) (PEG) hydrogle were successfully prepared by adjusting flow rate ratios between hydrogel liquid flow and mineral oil flow as a sheath flow. By UV irradiation, the prepared micro-droplets were cured and produced microsphere in the range of 40 ㎛ to 200 ㎛ in diameter according to the flow rates. Especially the size variation of the fabricated hydrogel microspheres was very low such as monosized particles. Various experimental parameters that influence on the preparation of hydrogel microspheres including microfluidic channel geometry with various channel diameters, flow rate of hydrogel solution or mineral oil and surfactant concentration were investigated and optimized. Then silver nanoparticle laden hydrogel microspheres had been fabricated by the microfluidic synthetic method.
Preparation of hydrogel microsphere by microfluidic flow focusing device
당중덩(Trung Dung Dang),김영호(Young Ho Kim),최진호(Jin Ho Choi),김규만(Gyu Man Kim) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
A microfluidic synthetic device using polydimethylsiloxane (PDMS) has been devised to fabricate microsized hydrogel particles. In the microfluidic synthetic device, micro-droplets of poly(ethylene glycol) (PEG) hydrogle were successfully prepared by adjusting flow rate ratios between hydrogel liquid flow and mineral oil flow as a sheath flow. By UV irradiation, the prepared micro-droplets were cured and produced microsphere in the range of 40 ㎛ to 200 ㎛ in diameter according to the flow rates.
Trung-Sinh Dang,Anh-Dung Tran,이범선,윤상웅 한국전자통신연구원 2013 ETRI Journal Vol.35 No.3
This letter presents a power amplifier (PA) with an on-chip power detector for 2.4-GHz wireless local area network application. The power detector consists of a clamp circuit, a diode detector, and a coupled line directional coupler. A series inductor for an output matching network in the PA is combined with a through line of the coupler, which reduces the coupling level. Therefore, the coupler employs a metamaterial-based transformer configuration to increase coupling. The amount of coupling is increased by 2.5 dB in the 1:1 symmetric transformer structure and by 4.5 dB from two metamaterial units along the coupled line.
The Impact of Human Resource Management Activities on the Compatibility and Work Results
NGUYEN, Duc Trung,HA, Van Dung,DANG, Truong Thanh Nhan Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.9
This research focuses on determining the impact of human resource management activities on the compatibility and work results of employees of Ho Chi Minh Stock Exchange (HOSE) listed companies. The paper includes five parts: introduction, literature review, research methodology, research results, and conclusion and policy implications. The data are collected from the survey of 350 listed companies in HOSE, in which 315 survey notes filled with sufficient information are used for analysis. The paper employs both qualitative method and quantitative method. Group discussion of 10 experts is for qualitative research. Quantitative method performs analysis of Statistics, Cronbach's Alpha, EFA analysis, CFA analysis and SEM model. The results of the research clearly indicate that human resource management (HRM) activities are measured through improving the ability, improving the motivation and improving the opportunity. While compatibility is measured through suitability, connection and sacrifice; whereby HRM activities of ability improvement have a positive effect on the job suitability and connection; HRM activities of motivation improvement have a positive effect on the job suitability, connection and sacrifice; and HRM activities of opportunity improvement have a positive effect on the job suitability, sacrifice and connection; Finally, the job suitability, sacrifice and connection positively affect the work results of employees.
Bui, Huyen T.T.,Dang, Trung-Dung,Le, Hang T.T.,Hoang, Thuy T.B. The Korean Electrochemical Society 2019 Journal of electrochemical science and technology Vol.10 No.1
The corrosion inhibiting mechanism of Vietnam orange peel essential oil (OPEO) for mild steel in 1 N HCl solution was investigated elaborately. Corrosion inhibition ability of OPEO was characterized by electrochemical polarization, electrochemical impedance spectroscopy (EIS), and weight loss method. In the corrosive solution, OPEO worked as a mixed inhibitor and the inhibition efficiency of OPEO increased with the increase of its concentration. High inhibition efficiencies over 90% were achieved for the concentration of 3 - 4 g/L OPEO, comparable to that of 3.5 g/L urotropine (URO), a commercial corrosion inhibitor for acid media used in industry. By using adsorption isotherm models (Langmuir, Temkin and Frumkin), thermodynamic parameters of adsorption were calculated. The obtained results indicated physical adsorption mechanism of OPEO on the steel surface. The components responsible for the corrosion inhibition activity of OPEO were not only D-limonene, but also other compounds, which contain C=O, C=C, O-H, C-O-C, -C=CH and C-H bonding groups in the molecules.