• 한국환경과학회지
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• 제14권10호
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• pp.919-928
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• 2005

This study introduces the development of new supercritical water oxidation(SCW)(multiple step oxidation) to destruct recalcitrant organic substances totally and safely by using sodium nitrate as an oxidant. This method has solved the problems of conventional SCW, such as precipitation of salt due to lowered permittivity, pressure increase following rapid rise of reaction temperature, and corrosion of reactor due to the generation of strong acid. Destruction condition and rate in the supercritical water were examined using Polyvinyl Chloride(PVC) and ion exchange resins as organic substances. The experiment was carried out at $450^{\circ}C$ for 30min, which is relatively lower than the temperature for supercritical water oxidation $(600-650^{\circ}C)$. The decomposition rates of various incombustible organic substances were very high [PVC$(87.5\%)$, Anion exchange resin$(98.6\%)$, Cationexchange resin$(98.0\%)$]. It was observed that hetero atoms existed in organic compounds and chlorine was neutralized by sodium (salt formation). However, relatively large amount of sodium nitrate (4 equivalent) was required to raise the decomposition ratio. For complete oxidation of PCB was intended, the amount of oxidizer was an important parameter.

• 대한화학회지
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• 제17권3호
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• pp.207-212
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• 1973

毛細灌法을 利用하여 여러가지 混合溶媒系(dioxane-n-butanol, dioxane-sec-butanol, dioxane-ethyleneglycol, dioxane-kerosene)중에서 polyvinylacetate의 희박용액을 機械的으로 切斷하여 그 결과로 얻어진 平均切斷速度定數(k) 및 極限重合度(g)를 moleculare dimension이 동일한 조건하에서 比較검토하였다. 그 결과 k보다는 g의 값이 사용하는 solvent의 종류에 따라 크게 영향을 받음을 알았으며 이에 關하여 考察하였다.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2263-2270
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• 2014

Solvolysis rate constants of 2-phenylethyl-(2-$PhCH_2CH_2OCOCl$, 1) and 2,2-diphenylethyl chloroformate (2,2-$Ph_2CHCH_2OCOCl$, 2), together with the previously studied solvolyses of ${\alpha}$- and ${\beta}$-substituted chloroformate ester derivatives, are reported in pure and binary solvents at $40.0^{\circ}C$. The linear free energy relationship (LFER) and sensitivities (l and m) to changes in solvent nucleophilicity ($N_T$) and solvent ionizing power ($Y_{Cl}$) of the solvolytic reactions are analyzed using the Grunwald-Winstein equation. The kinetic solvent isotope effects (KSIEs) in methanol and activation parameter values in various solvents are investigated for 1 and 2. These results support well the bimolecular pathway with same aspects. Furthermore, the small negative values of the entropies of activation of solvolysis of 1 and 2 in the highly ionizing aqueous fluoroalcohols are consistent with the ionization character of the rate-determining step, and the KSIE values of 1.78 and 2.10 in methanol-d indicate that one molecule of solvent acts as a nucleophile and the other acts as a general-base catalyst. It is found that the ${\beta}$-substituents in alkyl chloroformate are not the important factor to decide the solvolysis reaction pathway.

• 설비공학논문집
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• 제9권3호
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• pp.343-353
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• 1997

This paper presents a theoretical model for predicting transient behaviors during storage process of the cool storage system using the R141b clathrate. Introduction of the lumped capacitance method along with a brine reservoir having large thermal capacity yields a set of simplified energy equations. Based on the Arrhenius equation and the known experimental findings, the formation rate of clathrate for which the degree of subcooling is properly accounted is newly developed. An effective nondimensionalization of the model equations facilitates the closure of modeling as well as parametric study. Calculated results for a specific case not only simulate a typical pattern of temperautre variation in the tank successfully, but also agree reasonably well with available data. The effect of each characteristic parameter on the system performance is also investigated. It is revealed that the dominant among relevant parameters are the activation energy of reaction, the degree of subcoling and the initial mass fraction of refrigerant. Finally, the uncertainty associated with modeling of the shaft work variation appears to need further studies.

• 음성과학
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• 제15권2호
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• pp.145-156
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• 2008

The purpose of this study was to investigate the reason why puberphonia patients revisit hospitals after completion of its treatment and the effect of visual voice therapy on voice improvement. The subject the study included are two puberphonia patients who had been diagnosed by laryngologists. The patients who were diagnosed as puberphonia by the laryngologist and treated by the a speech pathologist, completed their treatment and revisited hospital. The study used laryngoscopy, acoustic and aerodynamic analysis before and after voice treatment to investigate what change happens and why generalization of treatment effect did not occur naturally in the daily life. Their voices of pre-therapy and post-therapy were analyzed on the aspects of acoustics, aerodynamics and laryngeal endoscopy. As a result, it was found that fundamental frequency(Fo) was significantly lowered in respect of acoustic change and maximum phonation time(MPT) was increased to some extent in respect of aerodynamic change. In addition, there was a laryngoscopic change and commissure glottic chink disappeared generally in the phonation. The reason why the generalization did not occur naturally in one’s daily routine was mainly due to the fact that high-pitched voicing was used for a long time. Other than that reason, negative reaction or attitude of surrounding people and lack of confidence were to blame for failure of generalization.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 반도체 재료 센서 박막재료 전자세라믹스
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• pp.30-33
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• 2004

Shallow p+-n junctions were formed by low-energy ion implantation and dual-step annealing processes The dopant implantation was performed into the crystalline substrates using $BF_2$ ions. The annealing was performed with a rapid thermal processor and a furnace. FA+RTA annealing sequence exhibited better junction characteristics than RTA+FA thermal cycle from the viewpoint of junction depth. A new simulator is designed to model boron diffusion in silicon, which is especially useful for analyzing the annealing process subsequent to ion implantation. The model which is used in this simulator takes into account nonequilibrium diffusion, reactions of point defects, and defect-dopant pairs considering their charge states, and the dopant inactivation by introducing a boron clustering reaction. Using a resonable parameter values, the simulator covers not only the equilibrium diffusion conditions but also the nonequilibrium post-implantation diffusion. Using initial conditions and boundary conditions, coupled diffusion equation is solved successfully. The simulator reproduced experimental data successfully.

• Journal of Astronomy and Space Sciences
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• 제14권2호
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• pp.386-394
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• 1997

본 연구에서는 유연모드를 고려한 위성체 모델링 방법들을 소개하고, 이에 따라 3축 안정화 위성의 유연모드를 모델링하였다. 이 모델을 강체에 대해 설계되었던 반작용휠을 이용한 자세제어루프에 적용하였다. 본 연구에서는 유한요소모델이 완성되기 전 단계에서 집합모드모델 중 전역모드모델을 이용하는 것을 제안하였고, 이를 유한요소법을 이용하여 계산된 모델과 제어기 필터 설계의 관점에서 비교하였다. 새로운 유연모드가 적용됨에 따라 제어기 요구조건을 만족시키기 위한 필터가 필요하여 반작용휠의 모터제어기 루프와 축제어기 루프에 각각 1차 필터를 설계하여 추가하였다. 제어루프 설계 및 시뮬레이션을 위해 MATLAB/Simulink를 사용하였다.

• 동력기계공학회지
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• 제9권4호
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• pp.130-136
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• 2005

The effects of additional Mg content, the size and volume fraction of reinforcement phase on the mechanical properties of ceramic particle reinforced aluminium matrix composites fabricated by pressureless metal infiltration process were investigated. The hardness of $SiC_p/AC8A$ composites increased gradually with an increase in the additive Mg content, while the bending strength of $SiC_p/AC8A$ composites increased with an increase in additive Mg content up to 5%. However, this decreased when the level of additive Mg content was greater than 5% due to the formation of coarse precipitates by excessive Mg reaction and an increase in the porosity level. The hardness and strength of the composites increased with decreasing the size of SiC particle. It was found that the composites with smaller particles enhanced the interfacial bonding than those with bigger particles from fractography of the composites. The hardness of $Al_2O_{3p}/AC8A$ composites increased gradually with an increase in the volume fraction, however, the bending strength of $Al_2O_{3p}/AC8A$ composites decreased when the volume fraction of alumina particle was greater than 40% owing to the high porosity level.

• 한국정밀공학회지
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• 제18권5호
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• pp.137-146
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• 2001

A robust controller with the sliding mode is proposed for stable dynamic walking of the biped robot in this paper. For the robot system to be controlled, which is modeled as 14 DOF rigid bodies by the method of multi-body dynamics, the joint angle trajectories are determined by the velocity transformation matrix. Also Hertz force model and Hysteresis damping element are utilized for the ground reaction and impact forces during the contact with the ground. The biped robot system becomes unstable since those forces contain highly confused noise components and some discontinuity, and modeling uncertainties such as parameter inaccuracies. The sliding mode control is applied to solve above problems. Under the assumption of the bounded estimation errors on the unknown parameters, the proposed controller provides a successful way to achieve the stability and good performance in spite of the presence of modeling imprecisions of uncertainties.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.554-554
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• 2012

Controlling the size distribution of gold nanoparticles (NPs) is of great importance due to the fact that their properties are strongly dependent upon the size distribution as well as the size itself. In the citrate reduction method for gold NP synthesis, the citrate works as (1) a reducing agent, (2) a surfactant, and also (3) a weak base: it raises the pH of the whole reaction mixture. Here, we have extensively studied the all three roles of the citrate, by adding other reagents separately (NaBH4, CTAB, and NaOH) for the independent control of the three roles of the citrate. Among the roles of the citrate, that as a weak base was found to be the most critical parameter affecting the size distribution of gold NPs and the size distribution became much more improved with the increase of the solution pH, while adding a supplementary surfactant or reducing agent resulted in the formation of less homogeneous NPs.