• Natural Product Sciences
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• 제4권4호
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• pp.268-273
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• 1998

Two new triterpenoid saponins, named segetoside D and E, have been isolated from the seeds of Vaccaria segetalis. On the basis of chemical reactions and spectral data, structures of segetoside D and E have been established as: $28-O-[{\beta}-D-xylopyranosyl-(1{\rightarrow}4)-{\alpha}-L-rhamnopyranosyl-(1{\rightarrow}2)]-[5-O-acetyl-{\alpha}-arabinofuranosyl(1{\rightarrow}3)]-[4-O-acetyl-{\beta}-D-fucopyranosyl]-quillaic\;acid-3-O-[{\beta}-D-galactopyranosyl(1{\rightarrow}2)]6-O-methyl\;ester-{\beta}-D-glucuronopyranoside$ and $28-O-[{\beta}-D-xylopyranosyl-(1{\rightarrow}4)-{\alpha}-L-rhamnopyranosyl-(1{\rightarrow}2)]-[5-O-acetyl-{\alpha}-arabinofuranosyl(1{\rightarrow}3)]-[4-O-acetyl-{\beta}-D-fucopyranosyl]-quillaic\;acid\;-3-O-[{\beta}-D-galactopyranosyl(1{\rightarrow}2)]-6-O-n-butyl\;ester-{\beta}-D-glucuronopyranoside$, respectively.

• 한국환경과학회지
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• 제6권4호
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• pp.351-357
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• 1997

In the Atmosphere under the various physical and chemical condition different chemical reactions occur and there are a number of air pollutants which are generated by photochemical reaction by absorbing solar energy. Therefor various testing simulation was done as foundation work to develop the numerical model for the prediction of concentration of air pollutants. It was shown change of msjor air pollutants concentration In according to variation of photodissociation speed constant, Kl and Initial condition of air pollutants concentration which plays major role In photochemical reaction. The photochemical reaction model which was used In this study Is found to be useful for understanding relationship among the concentration of reacting air pollutants and the prediction of concentration of air pollutants in urban atmosphere.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1804-1814
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• 2015

In order to explore the characteristics of electrons in DC negative corona discharge, an improved plasma chemical model is presented for the simulation of bar-plate DC corona discharge in dry air. The model is based on plasma hydrodynamics and chemical models in which 12 species are considered. In addition, the photoionization and secondary electron emission effect are also incorporated within the model as well. Based on this model, electron mean energy distribution (EMED), electron density distribution (EDD), generation and dissipation rates of electron at 6 typical time points during a pulse are discussed emphatically. The obtained results show that, the maximum of electron mean energy (EME) appears in field ionization layer which moves towards the anode as time progresses, and its value decreases gradually. Within a pulse process, the electron density (ED) in cathode sheath almost keeps 0, and the maximum of ED appears in the outer layer of the cathode sheath. Among all reactions, R1 and R2 are regarded as the main process of electron proliferation, and R₂₂ plays a dominant role in the dissipation process of electron. The obtained results will provide valuable insights to the physical mechanism of negative corona discharge in air.

• 공업화학
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• 제24권6호
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• pp.567-578
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• 2013

미생물연료전지는 혐기성 조건에서 미생물의 촉매 반응을 통해 유기물질의 화학에너지를 전기에너지로 변환하는 생물전기화학 장치이다. 미생물연료전지의 전력밀도 및 쿨롱효율은 산화전극 챔버 내 미생물의 종류, 시스템 구성요소 및 운전조건에 영향을 받는다. 미생물연료전지에서 달성할 수 있는 전력은 구성요소, 물리적 및 화학적 운전조건, 바이오 촉매 선택 등의 최적화로 디자인을 변형하여 현저하게 증가시킬 수 있다. 본 총설에서는 미생물연료전지의 구성, 운전 매개변수의 최적화 및 성능과 더불어 장래 응용에 대한 최근 연구를 중점적으로 고찰하고자 한다.

• Journal of Astronomy and Space Sciences
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• 제39권4호
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• pp.169-180
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• 2022

We investigated the chemical composition of the planetary host halo star HD47536 via high-resolution spectral observations recorded using a 1.5 meter Cerro Tololo Inter-American Observatory (CTIO) telescope (Chile). Furthermore, we determined the abundances of 38 chemical elements. Both light and heavy elements were overabundant compared to the iron group elements. The abundance pattern of HD47536 was similar to that of halo-type stars, with an enrichment of heavy elements. We analyzed the relationships between the relative abundances of chemical elements and their second ionization potentials and condensation temperatures. We demonstrated that the interplay of charge-exchange reactions owing to the accretion of interstellar matter and the gas-dust separation mechanism can influence the initial abundances and can be used to qualitatively explain the abundance patterns in the atmosphere of HD47536.

• 대한화학회지
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• 제37권8호
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• pp.717-722
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• 1993

물에서 [PtCl$_4$]^{2-}$의 백금(II)에 결합된 클로로리간드를 디티오카바메이트로 치환시켜 [Pt(A)], [Pt(B)$_2$]Cl$_2$, [Pt(C)$_2$] 및 [Pt(D)(CH$_2$=CH$_2$)Cl]Cl를 합성하였다. 백금 착물은 원소분석, 적외선 및 자외선-가시광선 스펙트럼과 전도도 측정을 하여 이들의 성질을 조사하였따. 이들 백금(II)의 디티오카바메이트류 착물은 물, 알코올, 디메틸술폭시드 및 티메틸포름아미드와 같은 극성용매에 잘 녹았다. 이들 백금(II) 착물의 원소분석과 물리적 측정결과에서부터 그 가능한 구조를 제시하였다.

• Journal of the Korean Wood Science and Technology
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• 제41권2호
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• pp.111-122
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• 2013

The steam explosion-chemical pretreatment is a more effective wood pretreatment technique than the conventional physical pretreatment by accelerating reactions during the pretreatment process. In this paper, two-stage pretreatment processes of hardwood were investigated for its enzymatic hydrolysis and the succinic acid yield from the pretreated solid. The first stage pretreatment was performed under conditions of low severity to optimize the amount of solid recovery. In the second stage pretreatment washed solid material from the first stage pretreatment step was impregnated again with chemical (alkaline or chlorine-based chemicals) to remove a portion of the lignin, and to make the cellulose more accessible to enzymatic attack. The effects of pretreatment were assessed by enzymatic hydrolysis and fermentation, after the two stage pretreatments. Maximum succinic acid yield (16.1 g $L^{-1}$ and 77.5%) was obtained when the two stage pretreatments were performed at steam explosion -3% KOH.

• 공업화학
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• 제3권1호
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• pp.148-155
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• 1992

콘크리트의 내구성을 향상시키는 기존의 공법과는 다르게, 시멘트 입자 표면에 아스팔트 막(膜)을 부분적으로 형성시킨 후 카본블랙을 처리(處理)하여 콘크리트의 전반적인 내구성(耐久性)을 현격히 향상시킨 고내구성(高耐久性) 포틀랜드시멘트(ACTPC)의 수화반응(水和反應) 특성(特性)을 X-Ray, SEM, 전도열량계 등을 사용하여 조사한 결과는 다음과 같다. ACTPC가 물과 접촉하면 발수성을 나타내는 아스팔트 막(膜)은 시멘트 입자(粒子)와 물의 접촉 및 시멘트 입자(粒子)로부터 각종 이온들의 용출(溶出)을 방해하여 초기(初期) 수화반응(水和反應)이 억제되지만, 카본블랙은 결정핵 역할을 하므로 일정기간이후의 수화반응(水和反應)을 촉진한다.

• Current Photovoltaic Research
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• 제3권4호
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• pp.112-115
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• 2015

In this study, the surface of ITO films was modified using $N_2-O_2$ molecular plasma, and the effects of oxygen concentration in the plasma on the ITO surface properties were investigated. Upon plasma treatment of ITO films, the surface roughness of ITO films seldom changed up to the oxygen concentration in the range of 0% to 40%, while the roughness of the films slightly changed at or above the oxygen concentration of 60%. The contact angle of water droplet on ITO films dramatically changed with varying oxygen concentration in the plasma, and the minimum value was found to be at the oxygen concentration of 20%. The plasma resistance at this condition exhibited a maximum value, and the change of resistance showed an inverse relationship compared to that of contact angle. From these results, it was conjectured that the chemical reactions in the sheath of the molecular plasma dominated more than the physical actions due to energetic ion bombardment, and also the plasma resistance could be used as an indirect indicator to qualitatively diagnosis the state of plasma during the plasma treatment.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1639-1645
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• 1991

Because of the important role LD converters play in the production of high quality steel, various dynamic models have been attempted in the past by many researchers not only to understand the complex chemical reactions that take place in the converter process but also to assist the converter operation itself using computers. And yet no single dynamic model was found to be completely satisfactory because of the complexity involved with the process. The process indeed involves dynamic energy and mass balances at high temperatures accompanied by complex chemical reactions and transport phenomena in the molten state. In the present study, a mathematical model describing the dynamic behavior of LD converter process has been developed. The dynamic model describes the time behavior of the temperature and the concentrations of chemical species in the hot metal bath and slag. The analysis was greatly facilitated by dividing the entire process into three zones according to the physical boundaries and reaction mechanisms. These three zones were hot metal (zone 1), slag (zone 2) and emulsion (zone 3) zones. The removal rate of Si, C, Mn and P and the rate of Fe oxidation in the hot metal bath, and the change of composition in the slag were obtained as functions of time, operating conditions and kinetic parameters. The temperature behavior in the metal bath and the slag was also obtained by considering the heat transfer between the mixing and the slag zones and the heat generated from chemical reactions involving oxygen blowing. To identify the unknown parameters in the equations and simulate the dynamic model, Hooke and Jeeves parttern search and Runge-Kutta integration algorithm were used. By testing and fitting the model with the data obtained from the operation of POSCO #2 steelmaking plant, the dynamic model was able to predict the characteristics of the main components in the LD converter. It was possible to predict the optimum CO gas recovery by computer simulation