• Applied Chemistry for Engineering
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• v.3 no.2
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• pp.312-317
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• 1992

The interaction of dioxouranium(VI) (uranyl) ion with nitrate ion has been studied by $^{17}O$ NMR spectroscopy. The $^{17}O$ resonance of uranyl oxygen atoms(uranyl oxygens hereafter) of $UO_2NO_3{^+}$ was at lower field than that of uranyl ion. The stability constants of $UO_2NO_3{^+}$ were obtained from the variation of $^{17}O$ chemical shifts with nitrate-ion concentration at 5, 15, 25, $35^{\circ}C$ and depend on the ionic strength. Thermodynamic parameters calculated from temperature dependence of the stability constants were as follows : ${\Delta}H=-(27.2{\pm}1.7)kJ\;mol^{-1}$ and ${\Delta}S=-(110{\pm}7)JK^{-1}mol^{-1}$. There was a linear relationship between the enthalpy and entropy for 1:1 complex formation of the uranyl ion with a variety of anionic ligands.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.4
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• pp.337-340
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• 1987

This experiment was conducted on relatively acid sandy loam soil at Choong-ju campus, Kon-kuk University aimed at clarifying the influence of urea and ammonium nitrate on the effect of potassium to Chinese cabbage in soils either limed or unlimed with calcium silicate. The results are summarized as follows: a. Calcium silicate application enhanced cabbage growth and under this condition, the difference in effect of urea and ammonium nitrate can hardly be observed. b. Without calcium silicate application, the response of Chinese cabbage to ammonium nitrate was more distinctive than that to urea. This was partially attributable to the greater use of soil born potassium at ammonium nitrate treatment. c. Added potassium was not only affective in increasing cabbage yield but also contributed in improving quality of cabbage by producing greater edible portion of the cabbage. Such K effect was particularly pronounced on the acid soil where calcium silicate application was neglected. d. Potassium was easily translocated from outer leaves to inner leaves and thus, the concentration of K content in outer leaves played as a limiting factor of cabbage yield. Less than 20 me/100gr of K content in harvested dried outer leaves resulted in a linear reduction of cabbage yield.

• Journal of Sensor Science and Technology
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• v.10 no.2
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• pp.134-141
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• 2001

This paper describes a method to steer an autonomous electric vehicle using magnetic fields. Magnets are embeded along the center of the road and a magneto-resistive sensor is mounted beneath the front bumper of the vehicle. As the vehicle moves along the road neural network controller controls the vehicle using measured magnetic field variation. Based on a single magnets modeling equation, we analyzed three dimensional magnetic field distributions of embeded magnets in series on the center of the road and performed a computer simulation using this results. In simulation study, straight and curved road was configured. The steering controller for the vehicle was designed using neural network and experiment was performed on the real embeded magnets using real autonomous electric vehicle. At the experiment we compensated the earth's magnetic fields and showed a good result driving an autonomous vehicle using proposed method.

• Analytical Science and Technology
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• v.11 no.6
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• pp.436-439
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• 1998

Ginseng saponins were analysed using reversed-phase high performance liquid chromatography with several columns. The optimum conditions were as following : reverse phase column; Novapak $C_{18}$ ODS column ($3.9mm{\times}150mm$, $5{\mu}m$), acetonitrile/water binary mobile phase gradient controller system, solvent flow rate; 1.5 mL/min, and UV (203 nm) detector. The complete separation of ginsenoside $Rb_1$, $Rb_2$, Rc, Rd, Re, Rf and $Rg_1$ was achieved within 50 min. The regression coefficients of the calibration curves for seven ginsenosides were 0.98~0.99.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2005.10a
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• pp.196-203
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• 2005

축산식품 고기내의 잔류항생물질을 신속하고 간편하고 정확하게 분석하기 위한 시험법 개발 을 목적으로 하였다. 축산식품내의 일반적인 잔류항생물질에 대한 지금까지의 분석법으로는 Bioassay법, TLC법, ELISA법, GC법 및 HPLC법 등이 있지만 Streptomycin/Dihydro streptomycin, Neomycin에 대한 HPLC법은 거의 확립되어 있지 않은 실정이다. 우리나라의 공인 검사법으로는 Bioassay법 및 HPLC법 등이 있지만 그러나 지금까지의 방법으로는 검출감도가 낮은 것이 큰 문제점으로 되어 왔다. 본 연구에서는 DST에 대한 HPLC법에 대한 보고한 P. Edder 방법 중에 clean-up과정 및 이동상 조건을 대폭 수정하여 DST의 분리 및 검출감도를 낮추려고 시도하였다. 본 연구에 사용된 유도체화 장치 Post-Column Derivatization Instrument PCX 5100 (Pickering Laboratories, Inc.)의 컬럼온도는 $40^{\circ}C$, 오븐온도 $55^{\circ}C$, reagent 유속 0.6ml/min mobile phase 유속 0.8ml/min으로 검출기는 형광검출기를 이용하여 DST 검출에 대해 만족할 만한 결과를 얻었다. 이때의 분석소요시간은 약 15분이었다. 표준시료 DST의 검량선은 넓은 농도범위(0.02${\sim}$1.0ppm)에서 양호한 직선성을 나타냈다. 본 시험법에 의한 검출한계는 limit of detection (LOD)은 0.02ppm이었으며, 적어도 고기에서의 MRL이 0.6ppm임을 감안하면 DST를 정량적으로 정도 좋게 측정할 수 있다는 것을 확인했다. 상기의 조건하에서 실제시료인 고기에 표준 DST를 1ppm을 spiking한 후 SPE상에서 SCX(Strong cation exchange column)을 통한 clean-up과정을 거친 후의 DST의 limit of quantification(LOQ)는 약 0.47ppm이었으며, 이에 대한 회수율은 97.7%(n= 8)를 나타냈다. 실제 codex에서 권장한 고기의 MRL이 0.6ppm인 점을 감안하면 codex 권고치에 도달할 수 있는 것으로 판단되었다. 따라서 본 연구에서 개발된 시험법은 지금까지 국내적으로 DST에 대한 시험법이 확립되어 있지 않은 것으로 이와 아울러 간편한 parallux와 병용해 DST에 대한 정량 및 정성 분석을 유도체화 장치 및 형광검출기를 이용해 잔류항생물질 DST에 대한 분석시험법의 개발이 가능하다고 여겨진다.

• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.496-503
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• 1989

The chemical behavior of trivalent lanthanide (Pr(III) and Yb(III)) and 2, 2, 6, 6-tetramethyl-3, 5-heptanedione(dipivaloylmethane) complexes was investigated by the use of direct current, differential pulse polarography and cyclic voltammetry. In this study, it was founded that the reduction of trivalent lanthanide complexes was observed by one electron transfer process at Epc = -0. 13 V and -0.80 V of Pr(III), and -0.02 V of Yb(III) vs. Ag-AgCl electrode. Also, it was founded that the treatment of DP and CV to the case of a first-order chemical equilibrium reaction preceding a reversible and irreversible one electron transfer reaction, (a >0. 5) the socalled ErCr electrode process. The equilibrium constant (lnK) obtained, of various solvents, these constant were founded to be increases with decreasing dielectric constant of the solvents. Plots of lnK for these reaction against ln(l/D) for the solvents was fairly straight lines, and the behavior of the heavier lanthanides was decreased equilibrium constant with increasing atomic number.

• Journal of the Korean Chemical Society
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• v.37 no.8
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• pp.735-743
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• 1993

The electrocatalytic reduction of oxygen is investigated by cyclic voltammetry and chronoamperometry at glassy carbon electrode and carbon microelectrode coated with a variety of cobalt phenylprophyrins in various pH solutions. Oxygen reduction catalyzed by the monomeric porphyrin Co(Ⅱ)-TPP mainly occurs through the 2e$^-$ reduction pathway resulting in the formation of hydrogen peroxide whereas electrocatalytic process carried out 4e$^-$ reduction pathway of oxygen to H$_2$O at the electrodes coated with cofacial bis-cobalt phenylporphyrins in acidic solution. The electrocatalytic reduction of oxygen is irreversible and diffusion controlled. The reduction potentials of oxygen in various pH solutions have a straight line from pH 4 to pH 13, but level off in strong acidic solution. The reduction potentials of oxygen shift to positive potential more 400 mV at the electrode coated with monomer Co-TPP compound than bare glassy carbon electrode while 750 mV at the electrode coated with dimer Co-TPP compound.

• Clean Technology
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• v.17 no.4
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• pp.363-369
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• 2011

To evaluate the feasibility of electrodialysis for ammonia nitrogen removal from wastewater, the effects of operating parameters such as diluate concentration, applied voltage and flow rate on the removal of ammonia nitrogen were experimentally estimated. The removal rate was evaluated by measuring the elapsed time for ammonia nitrogen concentration of diluate to reach 20 mg/L. Limiting current density (LCD) linearly increased with ammonia nitrogen concentration and flow rate. The elapsed time was linearly proportional to initial concentration of diluate. Due to relatively large equivalent ion conductivity and ion mobility of ammonia nitrogen, the removal rate increased consistently with flow rate. Increase in the applied voltage gave positive effect to removal rate. From the operation of the electrodialysis module used in this research, the flow rate of 3.2 L/min and 80~90% of applied voltage for LCD are recommended as the optimum operating condition for the removal from high concentrate ammonia nitrogen solution.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.457-464
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• 2009

The now velocity distribution at inlet of diesel Particulate filter (DPF) which is connected to each curved duct was simulated using $STAR-CD^{(R)}$. Three kinds of models which describe the shapes of the curved duct ware used for the CFD simulation. The simulation results were compared with the experimental data of velocity distribution which was obtained using a Pitot tube and 2-D positioning machine. At the $90^{\circ}$ curved connecting condition, the CFD simulation results of flow velocity distribution at inlet of the DPF showed a horse hoop shape shifted from the axial center line of the DPF. The CFD simulation results agree reasonably with those of the experiments.

• Journal of the Korean Chemical Society
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• v.19 no.1
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• pp.53-64
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• 1975

The polymerization of methyl methacrylate initiated by cobalt(II) chloride in tetrahydrofuran has been studied. The conversion was increased liearly with polymerization time at initial stage of 6${\sim}$7% conversion and then the rate of polymerization was slightly reduced, and after that the autoacceleration was observed. The rate of polymerization was increased with the concentration of cobalt(Ⅱ) chloride, but at the concentration of cobalt(II) chloride higher than $3.4{\times}10^{-4}$ mole/l the rate of polymerization was decreased. The rate of polymerization was dependent on the 1.38 power of the concentration of methyl methacrylate. The effect of the radical inhibitor DPPH was observed and the inhibition time was increased with the concentration of DPPH. The apparent overall activation energy was calculated to be 13.2 kcal/mole. In the copolymerization of methyl methacrylate ($M_1$) and styrene ($M_2$), the monomer reactivity ratio was found to be $r_1$ = 2.35, $r_2$ = 0.78. From the above results. the initiation mechanism of polymerization was discussed and it was considered that the polymerization proceeds mainly via diradical mechaism.