NiO-ZnO-Fe_2O_3 System의 물성에 관한 연구

최재시,김규홍,전종호,박광하 연세대학교 자연과학연구소 1984 學術論文集 Vol.13 No.-

NiO-Z_nO-Fe_2O_3계에 대하여, Solid Solution 을 이루는 적합한 조성관계와 여러가지 비율로 혼합한 페라이트에 대하여 자성, 전도성을 측정하였다. 각 시료의 비저항은 3×10^-6Ωcm이었고, α-Fe_2O_3, NiO, ZnO의 조성비가 50, 15, 35mol %인 페라이트가 가장 높은 μ와 Q값을 갖는다. physical-chemical properties and the best composition of the solid solution of the NiO-ZnO-Fe_2O_3 system were checked by Q-meter and electrometer. The resistivity of each sample is 3×10^-6Ωcm, and the best composition of nickel ferrite for radio frequency use is α-Fe_2O_3:NiO:ZnO=50:15:35(mol%).

지역관광개발 영향인식과 지역주민 태도의 상관성에 관한 연구

최병길,송재호,김시영 제주대학교 관광과경영경제연구소 2004 産經論集 Vol.20 No.-

중 란탄족 산화물의 결합구조와 전기전도성

강영환,최재시,윤기현 연세대학교 대학원 1980 延世論叢 Vol.16 No.2

The electrical conductivity of highly pure polycrystalline Gd₂O₃, Ho₂O₃ and Yb₂O₃ has been measured from 650 to 1050℃ under oxygen pressure range of 10^(-6) to 10² torr. Plots of logσ vs. T at constant oxygen pressure are found to be linear. and the conductivity dependence of oxygen pressure in the high temperature region (750-1050℃) is approximated by σ α po₂1/5.3. This shows that the conduction mechanism is associated with doubly ionized metal vacancies. Fairly low activation energy and the lack of oxygen pressure dependence are found over the temperature range of 650 to 750℃. The conduction mechanism is explained by not metal vacancies, but hopping oxygen ions in the oxides. The sesquioxides exhibit mixed conduction with some ionic conduction and major electronic conduction carriers.

카드뮴 첨가된 α형 산화철에 의한 일산화탄소의 촉매산화 반응연구

이성한,김용록,김돈,정원양,김규홍,최재시 연세대학교 자연과학연구소 1983 學術論文集 Vol.11 No.-

α형 산화철에 카드뮴을 4mol%, 8mol% 및 12mol%로 각각 첨가시켜 외성영역의 특성을 갖는 산화물들을 제조하였다. 이 산화물들을 촉매로한 일산화탄소의 산화반응 속도론적 연구를 통하여 본산화물의 결함구조, CO 산화반응에 대한 촉매성 및 불순물 첨가효과등을 조사하였다. 또한 450℃에서 O_2 및 CO를 여러압력으로 도입시켜 Cd-doped α-Fe_2O_3의 전기전도도를 측정하고 이를 반응속도론적 데이타와 결부시켜 본산화물상에서 CO 의 산화반응 메카니즘과 율속단계를 제안하였다. 반응온도범위 350~460℃에서 산출된 활성화에너지는 10.1~11.3kcal.mol^-1이었다. CO_2흡착에 의한 CO산화반응의 억제효과는 본실험의 반응온도 영역인 350~460℃에서는 나타나지 않았으며 CO 산화반응의 전반응속도 차수는 1.5차로서 일산화탄소에 대해서는 1차, 산소에 대해서는 0.5차임이 밝혀졌다. 반응속도론적 데이타와 전기전도도 데이타에 의해 본촉매의 활성은 카드뮴도프로 인해 생성된 산소공위(Vo"-2e^-)에 기인한 것이었다. 카드뮴의 첨가량이 증가할수록 반응속도는 증가하였으나 12mol% 이상의 카드뮴이 첨가된 산화철상에서는 반응속도가 크게 증가하지 않는 것으로 나타났다. CO와 O_2는 근본적으로 화학흡착하며 CO의 흡착자리는 격자산소(O^-2_(latt))와 기흡착원산소 (O^-_(ads)), 그리고 O_2의 흡착자리는 산소공위(Vo"-2e^-)로 밝혀졌다. The α-Ferric oxide containing 4, 8, and 12mol% with cadmium were prepared. The oxidation rates of carbon monoxide in the presence of these oxide systems were measured to investigate the defect structure, the catalytic activity for the oxidation of carbon monoxide, and the impurity effect. The conductivity was also measured at 450℃ under the various pressures of oxygen and carbon monoxide. From the agreement between the kinetic and conductivity data, the oxidation mechanism of carbon monoxide and the rate determining step on this oxide catalyst were suggested. In the temperature range from 350 to 460℃, the calculated activation energy for the CO oxidation over Cd-doped α-Fe_2O_3 systems were 10.1∼11.3kcal·mol^-1. The inhibition by an adsorbed CO_2 during the CO oxidation was not observed in the above temperature range. The overall reaction order for the CO oxidation is 1.5; the first order with respect to CO and the one-half order with respect to O_2. The catalytic activity of this oxide system is due to oxygen vacancies induced by Cd-doping. The oxidation rates increase with increasing the amount of dopant and above 12mol%, however, don't highly increased. CO and O_2 are essentially chemisorbed as ions and the adsorption sites for CO are the lattice oxygens (O^2-_(latt)) and prechemisorbed oxygens (O^-_(ads)), the adsorption site for O_2 is the oxygen vacancies (Vo¨-2e^-).

완전 방실차단을 동반한 급성 심근염

이유선,정진옥,박용규,박형서,노상필,정승현,김정희,이재환,최시완,성인환 충남대학교 의학연구소 2003 충남의대잡지 Vol.30 No.2

급성 심근염환자에서 발행한 완전 방실차단을 영구 심장박동 조율기로 치료한 1예를 경험하였기에 문헌고찰과 함께 보고하는 바이다. Myocarditis, an inflammatory process involving the myocardal wall, may be caused by most infectious agents. Irrespective of its etiology, it presents commonly with evidence of heart failure, hypotension, and various electrocardiographic abnormalities. Patient with myocarditis may be asymptomatic or may have a rapidly progressive fatal disease. Medical management of patients with myocarditis includes specific therapy for underlying infection and control of the complication of myocarditis such as congestive heart failure and arrhythmia. Recently we had experienced myocarditis with complete atrioventricular block in 37-year-old man. Although he had shown complete recovery of heart failure, he had shown complete atrioventricular block, so we inserted permanent pacemaker. We report it with review of the literature.

Saponins, Especially Platyconic Acid A, from <i>Platycodon grandiflorum</i> Reduce Airway Inflammation in Ovalbumin-Induced Mice and PMA-Exposed A549 Cells

Choi, Jae Ho,Jin, Sun Woo,Kim, Hyung Gyun,Choi, Chul Yung,Lee, Hyun Sun,Ryu, Shi Yong,Chung, Young Chul,Hwang, Young Jung,Um, Yeon Ji,Jeong, Tae Cheon,Jeong, Hye Gwang American Chemical Society 2015 Journal of agricultural and food chemistry Vol.63 No.5

<P>We investigated the inhibitory effects of <I>Platycodon grandiflorum</I> root-derived saponins (Changkil saponins: CKS) on ovalbumin-induced airway inflammation in mice. CKS suppressed leukocytes number, IgE, Th1/Th2 cytokines, and MCP-1 chemokine secretion in bronchoalveolar lavage fluid. Also, ovalbumin-increased MUC5AC, MMP-2/9, and TIMP-1/-2 mRNA expression, NF-κB activation, leukocytes recruitment, and mucus secretion were inhibited by CKS treatment. Moreover, the active component of CKS, platyconic acid A (PA), suppressed PMA-induced MUC5AC mRNA expression (from 2.1 ± 0.2 to 1.1 ± 0.1) by inhibiting NF-κB activation (from 2.3 ± 0.2 to 1.2 ± 0.1) via Akt (from 3.7 ± 0.3 to 2.1 ± 0.2) (<I>p</I> < 0.01) in A549 cells. Therefore, we demonstrate that CKS or PA suppressed the development of respiratory inflammation, hyperresponsiveness, and remodeling by reducing allergic responses, and they may be potential herbal drugs for allergen-induced respiratory disease prevention.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jafcau/2015/jafcau.2015.63.issue-5/jf5043954/production/images/medium/jf-2014-043954_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jf5043954'>ACS Electronic Supporting Info</A></P>

Electrical Conductivity of Samarium Sesquioxide

Choi, Jae Shi,Won, Hui Jun 연세대학교 자연과학연구소 1983 學術論文集 Vol.12 No.-

다결정성 삼산화사마륨의 전기전도도가 10^-5~10^-1기압의 산소압력 범위와 300~1000℃ 온도 범위에서 축적되었다. 전기전도도의 온도 의존성과 산소 압력의존성을 측정함으로써 결함 구조와 반도체의 형을 조사하였다. 활성화 에너지는 고온 영역과 저온 영역에서 각각 1.18과 0.39_eV이다. 전기전도도의 산소압력 의존성은 650℃를 기준으로 아래 온도에서는 σα po_2^(1/5.5)이고 위의 온도에서는 σα po_2^(1/5.3)이다. Sm_2O_3는 두 온도영역에서 O_i"+V_M"'과 V_M"'의 두 종류를 결함구조를 가진 전자구멍 전도를 나타낸다. 전지전도 메카니즘을 본 논문에 제시하였다. The electrical conductivity of polycrystalline samarium sesquioxide was measured from 300 to 1000℃ under the oxygen pressures 10^-5 to 10^-1 atm. The defect structures, type of semiconductor, and electrical conduction mechanism are investigated by measuring the temperature and oxygen pressure dependences of the electrical conductivity. The activation energies are 1.18 and 0.39eV at high-and low-temperature regions, respectively. The oxygen pressure dependences of electrical conductivity are characterized by σα po_2^(1/5.5) and σα po_2^(1/5.3) at low-and high-temperature regions below and above 650℃, respectively. Sm_2O_3 exhibits electronic hole conduction with two different defects, i.e., O_i"+V_M"' mixture and V_M"'at two temperature regions. The conduction mechanism has been suggested.

Medicinal Chemistry : Article ; Saponins, Especially Platyconic Acid A, from Platycodon grandiflorum Reduce Airway Inflammation in Ovalbumin-Induced Mice and PMA-Exposed A549 Cells

( Jae Ho Choi ),( Sun Woo Jin ),( Hyung Gyun Kim ),( Chul Yung Choi ),( Hyun Sun Lee ),( Shi Yong Ryun ),( Young Chul Chung ),( Young Jung Hwang ),( Yeon Ji Um ),( Tae Cheon Jeong ),( Hye Gwang Jeong 영남대학교 약품개발연구소 2015 영남대학교 약품개발연구소 연구업적집 Vol.25 No.-

We investigated the inhibitory effects of platycodon grandiflorum root-derived saponins (Cfangkil saponins;CKS) on ovalbumin-induced airway inflammation in mice. CKS suppressed leukocytes number,IgE,Th1/Th2 cytokines, and MPC-1 chemokine secretion in bronchoalveolar lavage fluid. Also,ovalbumin-increased MUC5AC,MMP-2/9,and TLMP-1/-2 mRNA expression,NF-kB activation,leukocyes recruitment,and mucus secretion were inhibited by CKS treatment. Moreover,the active component of CKS,platyconic acid A (PA),suppressed PMA-induced MUC5AC mRNA expression(from2.1±0.2to1.1±0.1)by inhibiting NF-kB activation(from 2.3±0.2 to 1.2±0.1)via Akt(from3.7±0.3 to 2.1±0.2)(P<0.01) in A549 cells. Therefore,we demonstrate that CKS or PA suppressed the development of respiratory inflammation, hyperresponsiveness,and remodeling by reducing allergic responses,and they may be potential herbal drugs for allergen-induced respiratory disease prevention.

이속압연에의해제조된AA1100판재의소성변형비예측

최시훈 ( Shi Hoon Choi ),김형욱 ( Hyoung Wook Kim ),조재형 ( Jae Hyung Cho ),강석봉 ( Seok Bong Kang ),최재권 ( Jae Kwon Choi ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.7

Conventional rolling (symmetric) and differential speed rolling (DSR) were both applied to AA1050 sheets at various velocity ratios, from 1 to 2 between the top and bottom rolls. An electron backscatter diffraction (EBSD) technique was used to measure texture inhomogeneity through the thickness direction. After the annealing process, the annealing texture of the DSR processed sheets was different from that of conventionally rolled sheets. The velocity ratio between the top and bottom rolls affected the texture inhomogeneity and macroscopic plastic strain ratio of the AA1050 sheets. A prediction for the macroscopic plastic strain ratio of AA1050 sheets was carried out using a visco-plastic self-consistent (VPSC) polycrystal model. The strain ratio directionality that was predicted using the VPSC polycrystal model was in good agreement with experimental results.

Kinetics of the Oxidation of Carbon Monoxide on NiO at Low Temperature

최재시(Jae Shi Choi),김규홍(Keu Hong Kim) 대한화학회 1974 대한화학회지 Vol.18 No.2