• Analytical Science and Technology
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• v.37 no.4
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• pp.220-229
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• 2024

This study aims to developing a method for estimating pharmaceutical compounds within a monolith column using high-performance liquid chromatography (HPLC). The monolithic column was prepared using copolymerization of glycidyl methacrylate, co-ethylene dimethacrylate, and co-acrylic acid inside a borosilicate tube of specific dimensions a 60 mm borosilicate tube length with 1.5 mm and 3.5 mm inner and outer diameters, respectively. A UV Ultra violet source with a wavelength of 365 nm was used, and the polymerization process involved mixing glycidyl methacrylate, acrylic acid, ethylene dimethacrylate as a binder, and 2,2-dimethoxy-2-phenyl acetate phenone as an initiator in suitable solvents consisting of ethanol and 1-hexanol. The polymerization process formed the monolith column after 4 minutes, and subsequently, the epoxy groups were altered to diol groups using 0.2 M hydrochloric acid HCl, which were pumped through the column for 3 hours at a flow rate of 10 µL·min^-1. Various techniques, such as Scanning Electron Microscope SEM, Brunauer-Emmett-Teller BET, Fourier-transform infrared spectroscopy FT-IR and HNMR, were utilized to characterize and confirm the structure of the monolith. The prepared monolith was employed to estimate and identify the pharmaceutical compound of warfarin using high-performance liquid chromatography HPLC. The analytical curve of warfarin was linear in the range of 3 to 100 ㎍·mL^-1 with an r² value of 0.999. The detection and quantification limits were 0.932 and 2.788 ㎍·mL^-1, respectively. The molar absorptivity and Sandells sensitivity were 2.99138 × 10⁶ L·mol^-1·cm^-1 and 103.1 × 10^-3 ㎍·cm^-2, respectively.

• Journal of Practical Agriculture & Fisheries Research
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• v.17 no.1
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• pp.57-71
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• 2015

This study was conducted to develop the fertigation system with a peristaltic hose pump and brushless DC motor. The fertigation system was consisted of sensor, main controller, motor control unit, peristaltic pump, water supply pump, control panel, and filter. The peristaltic pump discharges liquid by squeezing the tube with rollers. Rollers attached to the external circumference of the rotor compresses the flexible tube. The fluid is contained within a flexible tube fitted inside a circular pump casing. The developed fertigation system has no mixing tank but instead injects directly a concentrated nutrient solution into a water supply pipe. The revolution speed of the peristaltic pump is controlled by PWM (Pulse width modulation) method. When the revolution speed of the peristaltic pump was 300rpm, the flow rate of the 3.2, 4.8, 6.3mm diameter tube was 202, 530, 857mL/min, respectively. As increasing revolution speed, the flow rate of the peristaltic pump linearly increased. As the inner diameter of a tube larger, a slope of graph is more steep. Flow rate of three roller was more than that of four roller. Flow rate of a norprene tube with good restoring force was more than that of a pharmed tube. As EC sensor probe was installed in direct piping in comparison with bypass piping showed good performance. After starting the system, it took 16~17 seconds to stabilize EC. The maximum value of EC was 1.44~1.7dS/m at a setting value of 1.4dS/m. The developed fertigation system showed ±0.06dS/m deviation from the setting value of EC. In field test, Cucumber plants generally showed good growth. From these findings, this fertigation system can be appropriately suitable for fertigation culture for crops.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.7
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• pp.459-466
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• 2012

In order to improved treatment performance of dielectric barrier discharge (DBD) plasma, plasm + UV process and gas-liquid mixing method has been investigated. This study investigated the degradation of N, N-Dimethyl-4-nitrosoaniline (RNO, indicator of the generation of OH radical). The basic DBD plasma reactor of this study consisted of a plasma reactor (consist of quartz dielectric tube, titanium discharge (inner) and ground (outer) electrode), air and power supply system. Improvement of plasma reactor was done by the combined basic plasma reactor with the UV process, adapt of gas-liquid mixer. The effect of UV power of plasma + UV process (0~10 W), gas-liquid mixing existence and type of mixer, air flow rate (1~6 L/min), range of diffuser pore size (16~$160{\mu}m$), water circulation rate (2.8~9.4 L/min) and UV power of improved plasma + UV process (0~10 W) were evaluated. The experimental results showed that RNO degradation of optimum plasma + UV process was 7.36% higher than that of the basic plasma reactor. It was observed that the RNO decomposition of gas-liquid mixing method was higher than that of the plasma + UV process. Performance for RNO degradation with gas-liquid mixing method lie in: gas-liquid mixing type > pump type > basic reactor. RNO degradation of improved reactor which is adapted gas-liquid mixer of diffuser type showed increase of 17.42% removal efficiency. The optimum air flow rate, range of diffuser pore size and water circulation rate for the RNO degradation at improved reactor system were 4 L/min, 40~$100{\mu}m$ and 6.9 L/min, respectively. Synergistic effect of gas-liquid mixing plasma + UV process was found to be insignificant.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.115-122
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• 1997

The powder preparation by using emulsion drying method, one of the chemical powder fabrication methods has the advantages; easy to control the chemical stoichiometry and to fabricate homogeneously fine particles. In the present study, the initial morphology and size distribution of the powder fabricated by using emulsion dry-ing method were controlled and were improved the homogeneity. By carefully controlling the mixing ratio of oil phase and aqueous solution and surfactant of preventing emulsion separation, the Bi(Pb)-Sr-Ca-Cu-O su-perconducting powders were prepared. The properties of the superconducting powder fabricated by this method and the microstructures and superconducting properties of the pelletized samples were investigated. The microstructures and electric properties of the tapes prepared by oxide powder-in-tube method were in-vestigated. The fabricated powder was spherical with less than 1$\mu$m but most of them was agglomerated with 2~5$\mu$m in size. The critical temperature of the pelletized sample annealed at 84$0^{\circ}C$ for 72 hours in oxygen par-tial pressure of 1/13atm in Ar atmosphere was 108K. And the critical current of the first and second annealed tapes in air prepared by oxide powder-in-tube process were 0.4A and 1.5A, respectively.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1981-1987
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• 2010

A novel composite (Ag-CNT/$TiO_2$) of silver treated carbon nanotubes (Ag-CNT) and $TiO_2$ was synthesized via wet chemistry followed by a heat treatment. The dispersion and structure of the silver in the synthesized composites determined by X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy(TEM). XRD patterns of the composites showed that the composites contained a mixing anatase and rutile phase. The EDX spectra showed the presence of C, O, Ti and Ag peaks. The $TiO_2$ particles were distributed uniformly in the CNT network, and silver particles were virtually fixed on the surface of the tube. The photocatalysis degraded behaviors of the Ag-CNT/$TiO_2$ composites of the methylene blue, which increased with an increase of the silver component. The Ag-CNT/$TiO_2$ composites have excellent antibacterial activities against Escherichia coli (E. Coli), Pseudomonas aeruginosa (P. Aeru) and Bacillus subtilis (B. Sub) under visible light.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1061-1070
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• 2003

A triple flame in a mixing layer was studied experimentally with concentration gradient and mean velocity by using a multi-slot burner, which can stabilize the lift-off flame. Flame stabilization condition, lift-off heights, and some other characteristics were examined for methane and propane flame within a range of very low concentration gradient. Pitot-tube and LDV(Laser Doppler Velocimetry) were used for velocity. Mass spectroscopy and Rayleigh scattering signal were used for concentration gradients. Thermo-couples and SiC TFP(Thin Filament Pyrometer) were used for temperature. It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity and this means that the propagation velocity has a maximum value. The scales of flame to the burner nozzle and intensity variation of the diffusion flame were suspected as the cause.

• Journal of the Korean Society of Combustion
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• v.4 no.2
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• pp.23-33
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• 1999

A turbulent non-premixed ethylene flame, which was set up in a vertical wind tunnel, was examined to understand the effect of turbulent mixing on formations of soot and gaseous species in the flames. Temperature and velocity profiles were measured using uncoated thermocouples and LDV system. Gaseous samples were withdrawn by using a water cooled stainless iso-kinetic gas sampling probe. The samples for inorganic compounds and light hydrocarbons were collected with sampling bottles and were analyzed by a gas chromatography. The samples for aromatic hydrocarbons were collected on a sorbent tube and were analyzed on a GC/MS system. Some of main results were followed. CO and $CO_2$ were measured relatively in early part of flame and the concentration of CO was greater than that of $CO_2$ all over the early flame region due to the scavenging of the oxidizing species OH by soot particles. Aromatic hydrocarbons were measured at x/D=122 along the radial direction and main important species were benzene, xylene, toluene, styrene, indene, naphthalene. The peak points of these compounds occurred at r/D=0.8 apart from the center of flame, around in which the concentration of $C_2H_2$ decayed relatively rapidly from the maximum value.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1997.12a
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• pp.255-262
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• 1997

A low-cost and precise metering device, which is suitable to automatic mixing of nutrient-solution for hydroponic culture, was developed for small-scale growers. The metering device was composed of three parts those were supply pumps, metering cylinders and venturi tube. Those parts were controlled by personal computer with time-based odoff control method. To verify the performance of the developed metering device, the relationship between operating time and discharge was examined and the accuracy of the developed metering device was compared with commercial metering pumps. The results of this study are as follows. 1. The correlation coefficient between the flow rate and operating time was 0.9999, and the linear regression equation computed was y=21.759x, where y is the discharge(g) and x is the operating time(s). 2. The developed device has greater accuracy than commercial metering pumps in terms of the full-scale error. Calculated errors for the developed metering device and two commercial pump were $\pm$0.3 %, $\pm$2.45 % and $\pm$1.38 % respectively. 3. Above results show developed metering device is a useful tool for nutrient-solution control system.

• Progress in Superconductivity and Cryogenics
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• v.7 no.4
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• pp.1-3
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• 2005

Superconducting $MgB_2$ fibers are in-situ grown by a diffusion method. The fibers are prepared by exposing B filaments to Mg vapor inside a folded Ta foil over a wide range of temperature and growth time. The materials are sealed inside a quartz tube by gas welding. The as - grown fibers are characterized by scanning electron microscopy and energy dispersive x - ray analysis. The fibers have a diameter of about $110{\mu}m$. Surface morphology of the fibers looks dependent on growth temperature and mixing ratio of Mg and B. Radial distribution of Mg ions into B is observed and analyzed over the cross - sectional area. Transport properties of the $MgB_2$ fibers are examined by a physical property measurement system. The $MgB_2$ fibers grown at $900^{\circ}C$ for 2 hours show a superconducting transition at 39.8K with ${\Delta}T_c<$ 2.0 K. Resistance at room temperature $MgB_2$ is 3.745 $\Omega$ and residual resistivity ratio (RRR) is estimated as 4.723.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.335-339
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• 2014

The studies on the characteristics of composite of silica aerogel and pulps were carried out. The composite was manufactured by mixing the paste of silica aerogel and pulps and analyzed by SEM. Using the impedence tube, the sound absorption measurement was investigated. The maximum value of sound absorption coefficient of this composite was obtained in the range of 900 Hz. It was found that the composite of silica aerogel and pulps could be a new sound absorbent because of high absorption capacity and durability which was due to hydrophobic effect on the surface of the composite.