• Korean Journal of Pharmacognosy
• /
• v.21 no.3
• /
• pp.239-241
• /
• 1990

A new method for quantitative determination of byakangelicin in Angelicae dahuricae Radix by high performance liquid chromatography was established. A reversed-phase system with a ${\mu}Bondapak$ $C_{18}$ column using THF : dioxane : MeOH : HAc : 5% $H_3PO_4$ : $H_2O$=72.5 : 62.5 : 25 : 10 : 1 : 329 as a mobile phase was developed. Byakangelicin together with ter-O-byakangelicin and oxypeucedanin methanolate, and isooxypeucedanin as an internal reference were detected at 350 nm and the analysis was successfully carried out within 30 min.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.494-497
• /
• 2002

The influence of isomeric state of doped azo dye on the $B_7$ phase of bent-shaped liquid crystal (LC) is studied. It was found that modulating the isomeric trans-cis state of azo dye can change the molecular arrangement of the bent-shaped LCs. To identify these phenomena the observations of microscopic texture, electro-optic response, second harmonic wave generation (SHG) and switching current were carried out..

• Korean Journal of Pharmacognosy
• /
• v.30 no.3
• /
• pp.328-331
• /
• 1999

A new method for quantitative determination of p-methoxycinnamic acid in Scrophulariae radix by high performance liquid chromatography was established. A reversed-phase system with SPHERI-5 RP-18 5 micron $(250\;{\times}\;4.6\;mm)$ column using TFA (0.05%) and acetonitrile as a mobile phase was developed. p-Methoxycinnamic acid and N-(p-methoxycinnamoyl)-p-aminophenol as an internal reference were detected at 310 nm and the analysis was successfully carried out within 50 min.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2005.04a
• /
• pp.195-198
• /
• 2005

A solid-phase microextraction and gas chromatography-mass spectrometry for the extraction and analysis of methyl-tert-butyl ether has been described. methyl-tert-butyl ether was extracted from aqueous solution using SPME fiber coated polydimethylsiloxane and analysed by GC-MS with capillary column. Extraction parameters and chromatographic separation conditions were optimized. The applied method represented good analytical performance in terms of precision (3-8%, RSD) and accuracy(93-102%, mean recovery) with a method detection limit of 0.03 ppb.

• Journal of the Korean Society of Industry Convergence
• /
• v.7 no.1
• /
• pp.97-105
• /
• 2004

The Vapor-liquid equilibrium data for the binary system of 2-methyl-2-propanol-2-butanone are measured at subatmospheric pressure of 100, 200, 300, 400, 500, 600, 700 and 760 torr. This study shows that the relations between logarithmic values of relative valatility(log ${\alpha}$)and liquid phase composition(${\chi}$) in the above binary systems are expressed as a linear function. When the linear relationships of between logarithmic values of relative volatilities and liquid phase compositions in the binary systems of various pressure intersect at a point, this empirical equation can be applied to the systems of this kind. From these relations the vapor-liquid equilibrium data are estimated and compared with the measured values to be in a good agreement with in accuracy ${\pm}0.0021$ for the various pressure.

• Proceedings of the KOSOMBE Conference
• /
• v.1995 no.05
• /
• pp.167-170
• /
• 1995

A quadrature-channel MODEM using amplitude modulation was constructed. To test the MODEM, 6.4 MHz sinusoidal wave 1 KHz triangular wave were modulated, then the modulated signal was fed into the demodulator, to reconstruct the triangular wave.

• Proceedings of the KIEE Conference
• /
• 2000.07b
• /
• pp.1143-1145
• /
• 2000

In this paper, it presents the design and implementation of a Microstep control IC using Programmable Logic Device(PLD). A Microstep driver is implemented with a 5-phase hybrid stepping motor, which has a Pentagon winding, power MOSFETs, and some devices to improve the system characteristics. The Microstep driving method is used for high performance motion control, low vibration and low noise in motor control system. The improvement of the electrical and mechanical driving characteristic of a step motor is achieved by applying microstep driver.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.12
• /
• pp.1807-1811
• /
• 2004

Supercritical fluid chromatography (SFC) was considered for separating racemic ibuprofen. The chromatographic column (3.9 ${\times}$ 150 mm) was packed with Kromasil$^{\circledR}$ CHI-TBB, and the mobile phase was supercritical carbon dioxide with modifier of IPA. The experimental variables were the content of IPA, and temperature and pressure of supercritical mobile phase. To determine the separation condition, the empirical equation of retention factor and resolution was proposed. In the case of retention factor, the empirical equation was in the form, $k\;=\;a{\rho}\;+b/F\;+\;c\;({\rho}/F)\;+\;d$. The empirical equation for resolution was proposed as a linear form, $R\;=\;a{\rho}\;+\;bF\;+\;c$.

• Journal of computational fluids engineering
• /
• v.14 no.4
• /
• pp.1-6
• /
• 2009

In the present study, numerical simulations were performed in a stirred solid/liquid system by using Eulerian multi-phase model. The transient flow field of liquid and distribution of solid particles were predicted in the stirred tank with pitched paddle impeller and baffles. The Frozen rotor method is adopted to consider the rotating motion of the impeller. The effects of number and width of baffles on the mixing time and the quality of solid suspension in the stirred tank are presented numerically. The result shows that the mixing time decreases as the width and number of baffles increase. The present numerical methodology can be applied to optimizing mixing condition of industrial mixer.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2720-2724
• /
• 2007

Field measurements have revealed that the pressure drop over a borehole during drilling of a slim oil well or a well with a long reach can depend significantly on the rotation speed of the drill pipe. An accurate prediction of the annular frictional pressure drop is therefore important for conditions where the annular clearance is small. An experimental study was carried out to study solid-liquid two phase flow in a slim hole annulus. Annular velocities of carrier fluids varied from 0.2 m/s to 1.5 m/s. The carrier fluids which were utilized included tap water and CMC water solutions. Pressure drops and average flow rates were measured for the parameters such as inner-pipe rotary speed, carrier fluid velocity, hole inclination and particle injection rate. For both water and CMC solutions, the higher the concentration of the solid particles is, the larger the pressure gradients become.