• 한국운동역학회지
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• 제14권3호
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• pp.191-202
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• 2004

The batting performance in baseball is a repetitive movement. In order to make the stabilization of posture and the efficient shift of body weight, both the range of stance and stride are important. The previous studies explained that the consistent stride which included the amount of time, stance, and direction were needed. However, the batting performance is frequently changed according to the several speed of ball. Therefore, this study was to analyze the reaction time, the range of stance, the change of stride, and the change of GRF during the batting movement in three kinds of ball speed (120km/h, 130km/h, & 140km/h). Seven elite players are participated in this study. 1. The reaction time of the stride phase was short whereas the time of the swing phase was long according to the increasing ball speed. 2. The range of the stance was wide and the mediolateral direction of the stride was decreased according to the increasing ball speed. 3. In the three kinds of ball speed, the change of body weight was transferred to the center, the rear foot, and the front foot directions. The ball speed of 130km/h showed the high frequency of the suitable batting. At this ball speed, the movement of the body weight was shifted smoothly and the value of the Ground Reaction Force was large enough.

• 한국세라믹학회지
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• 제25권5호
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• pp.561-569
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• 1988

Mixtures of very small amounts of additive, carbon and silica(about 0.46${\mu}{\textrm}{m}$) which synthesized by the hydrolysis of ethyl silicate, the molar ratio of SiO2/C was fixed to 1/10, was nitrided at 145$0^{\circ}C$. It was considered that the optimum amount of additive to promote the nitridation reaction was below 2.0wt%. By the addition of additive, the nitridation reaction was promoted and formation of $\beta$-Si3N4 was promoted at 145$0^{\circ}C$ for 1hour, but, the nitridation reaction was decreased and the ratio of $\alpha$/$\beta$ of Si3N4, was increased at 145$0^{\circ}C$ for 5 hours. The crystal phase was $\alpha$ phase and the nitridation reaction was promoted and the particle size of silicon nitride was become smaller by the addition of $\alpha$-Si3N4, but silicon nitride of whisker-like form was produced by the addition of transition elements. There was a difference in the lattice constants of $\alpha$-Si3N4, but no difference in its of $\beta$-Si3N4 according to kinds of added substance and reaction time.

• 한국세라믹학회지
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• 제33권5호
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• pp.536-546
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• 1996

The TiC-Ni/Al reaction-bonding composites were prepared by the infiltration of Ni/Al melt into the TiC preforms. The microstructure the reaction composition crystalline phase and the mechanical properties of the composites were investigated. During the reaction-bonding Ni/Al mixture had a good wettability and per-meability with TiC preform and pore-free and fully dense sintered bodies were produced. In the case of the Ni/Al atomic ratio of 0.3 and 0.5 TiC raw particle shape was changed to irregular particles because of the decomposition in the liquid matrix and its phenomena was more distinguished in the Al-rich liquid matrix. With increasing more than 1 of the Ni/Al atomic ratio the sample of TiC grain shape was changed from spherical to palatelet particles. Also with increasing the atomic ratio of Ni/Al bending strength and fracture spherical to palatelet particles. Also with increasing the atomic ratio of Ni/Al bending strength and fracture toughness were increased and its maximum value was 1073 MPa and 11 MPa.m1/2 respectively.

• Bulletin of the Korean Chemical Society
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• 제25권8호
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• pp.1217-1224
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• 2004

We have calculated the probability of HBr formation and energy disposal of the reaction exothermicity in HBr produced from the reaction of gas-phase bromine with highly covered chemisorbed hydrogen atoms on a Si (001)-(2 ${\times}$1) surface. The reaction probability is about 0.20 at gas temperature 1500 K and surface temperature 300 K. Raising the initial vibrational state of the adsorbate(H)-surface(Si) bond from the ground to v = 1, 2 and 3 states causes the vibrational, translational and rotational energies of the product HBr to increase equally. However, the vibrational and translational motions of product HBr share most of the reaction energy. Vibrational population of the HBr molecules produced from the ground state adsorbate-surface bond ($v_{HSi}$ =0) follows the Boltzmann distribution, but it deviates seriously from the Boltzmann distribution when the initial vibrational energy of the adsorbate-surface bond increases. When the vibration of the adsorbate-surface bond is in the ground state, the amount of energy dissipated into the surface is negative, while it becomes positive as vHSi increases. The energy distributions among the various modes weakly depends on surface temperature in the range of 0-600 K, regardless of the initial vibrational state of H(ad)-Si(s) bond.

• 대한금속재료학회지
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• 제47권2호
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• pp.107-113
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• 2009

Molten iron with 2 mass % carbon content was decarbonized at 1823 K~1923 K by bubbling $Ar+O_2$ gas through a submerged nozzle. The reaction rate was significantly influenced by the oxygen partial pressure and the gas flow rate. Little evolution of CO gas was observed in the initial 5 seconds of the oxidation; however, this was followed by a period of high evolution rate of CO gas. The partial pressure of CO gas decreased with further progress of the decarbonization. The overall reaction is decomposed to two elementary reactions: the decarbonization and the dissolution rate of oxygen. The assumptions were made that these reactions are at equilibrium and that the reaction rates are controlled by mass transfer rates within and around the gas bubble. The time variations of carbon and oxygen contents in the melt and the CO partial pressure in the off-gas under various bubbling conditions were well explained by the mathematical model. Based on the present model, it was explained that the decarbonization rate of molten iron was controlled by gas-phase mass transfer at the first stage of reaction, but the rate controlling step was transferred to liquid-phase mass transfer from one third of reaction time.

• 한국미생물·생명공학회지
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• 제20권1호
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• pp.61-67
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• 1992

유기용매 이상계에서의 thermolysin을 사용하여 아스파탐 전구체 합성시 pH, 온도, 기질농도, 그리고 유기용매상에 대한 수용액상의 부비피 ($\alpha$)등의 변화에 따른 기질의 분해 반응, 효소의 안정성, 그리고 Z-APM 합성에 미치는 복합적인 영향을 조사함으로써 반응조건의 최적화를 도모하였다. 유기용매 이상계에서의 L-PM.HCL의 자연분해는 수용액에서보다 훨씬 느리게 일어나며, 또한 $\alpha$가 증가할 수록 분해속도가 감소하는 것을 알 수 있었다.

• 멤브레인
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• 제14권4호
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• pp.275-288
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• 2004

본 연구에서는 준 회분식 교반조를 사용하여 polybutene (PB)와 polyisobutylene (PIB)고분자를 용해한 벤젠 용액을 연속상, 물을 불연속상으로 구성한 w/o 에멀션액막에 $CO_2$을 흡수시켜 흡수속도를 측정하였다. 점탄성을 나타내는 Deborah 수를 사용하여 점탄성 비뉴튼액체에서 구한 부피물질전달계수 ($k_La$)를 고찰하고, 수용액에 첨가한 2-amino-2-methyl-1-propanol(AMP)와 $CO_2$의 반응 메카니즘을 해석하였다.

• 대한기계학회논문집B
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• 제23권8호
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• pp.1022-1030
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• 1999

A numerical study was carried out to analyze the effect of flow distribution of stirred part and plug flow part on combustion efficiency at the coal gasification process in an entrained bed coal reactor. The model of computation was based on gas phase eulerian balance equations of mass and momentum. The solid phase was described by lagrangian equations of motion. The $k-{\varepsilon}$ model was used to calculate the turbulence flow and eddy dissipation model was used to describe the gas phase reaction rate. The radiation was solved using a Monte-Carlo method. One-step parallel two reaction model was employed for the devolatilization process of a high volatile bituminous Kideco coal. The computations agreed well with the experiments, but the flame front was closer to the burner than the measured one. The flow distribution of a stirred part and a plug flow part in a reactor was a function of the magnitude of recirculation zone resulted from the swirl. The combustion efficiency was enhanced with decreasing stirred part and the maximum value was found around S=1.2, having the minimum stirred part. The combustion efficiency resulted from not only the flow distribution but also the particle residence time through the hot reaction zone of the stirred part, in particular for the weak swirl without IRZ(internal recirculation zone) and the long lifted flame.

• 대한예방한의학회지
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• 제12권1호
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• pp.73-87
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• 2008

In recent years, there has been a globally increasing application of herbal medicines and dietary supplements to treat various chronic diseases and to promote health. However, there are increasing clinical reports on the organ toxicities associated with consumption of herbal medicines. In general, most xenobiotics are metabolized by Phase I reaction(the main enzyme : cytochrome P450) and Phase II reaction. However, reactive oxygen species, free radicals and electrophils are produced inevitably during xenobiotics metabolism. These toxic species and metabolites are increased whenever the endogenous substances and enzymes for Phase II reaction not available. In addition, herbal-drug interactions are pharmacokinetic, with most actually or theoretically affecting the metabolism of the affected product by way of the cytochrome P450 enzymes. This review updated the knowledge on metabolic activation of herbal components and its clinical and toxicological implications. Also, the possible way for preventing the side-effects by herbal-medicine use was suggested.

• The Korean Journal of Ceramics
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• 제2권1호
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• pp.25-32
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• 1996

Solid electroyte nasion was synthesized by the optimized solid state reaction minimizing the volume fraction of secondary $ZrO_2$ and glassy phases. To compensate for the evaporation of Na and P during heat-treatment, excess Na and P were added to the starting composition $Na_{1+x} Zr_2 Si_x P_{d-x} O_{12}$ (x=2.1). Phases pure nasicon comparable in volume fraction to the one obtaied from sol-gel process were synthesized after the reaction at $1100~1150^{\circ}C$,$ P_{O2}>=0.1-0.15 $$ZrO_2$ increased with the heat-treatment time due to the decomposition of nasicon phase and that of glassy phase increased as partial oxygen pressure decreased. The synthesized nasion showed a good electrical conductivity of $-1{\times}10^{-2}({\omega}{\cdot}cm)^{-1}$ at $350^{\circ}C$.