탄성지반 위 비선형 박판의 안정 해석

김치경 한국리스크관리학회 2008 리스크 管理硏究 Vol.19 No.2

하천수에서 Campylobacter jejuni 의 오염도와 그 생존율에 관한 연구

김치경,오학식,염곤,조민기 ( Chi Kyung Kim,Hak Shik Oh,Kon Ryeom,Min Ki Cho ) 한국하천호수학회 1986 생태와 환경 Vol.19 No.3·4

Campylobacter jejuni isolated from river and lake waters and chicken samples were examined for their contamination and survival in surface waters and for inactivation by chlorination. The isolation rates of C. jejuni from chicken samples were 50 to 100%, while only one out of 48 studies was positive from the surface water. When the organisms suspended in sterile river water were incubated at 4℃, they survived upto 20 days, but they died off after 1 day incubation at 30℃ or above. The in situ survival studies of C. jejuni in the waters of Dsecheong Dam and Han-river (1st bridge) revealed that they survived upto 14 days in winter, but for shorter period of time in spring and summer. The survival rates of the organism in the deeper water were a little longer than in the surface water, but the rates were not different between the both water environments. When the organisms were treated with 0. 5, 1. 0 and 2. 0 ㎎/ℓ chlorine solution at pH 7. 0 and 15℃ for 60 minutes, they were inactivated by about 1, 4, and 6 logs, respectively, The inactivation rate was increasingly affected by lowering the reaction pH and by increasing the reaction temperature.

Non-linear analysis of skew thin plate by finite difference method

김치경,황명환 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.4

This paper deals with a discrete analysis capability for predicting the geometrically nonlinear behavior of skew thin plate subjected to uniform pressure. The differential equations are discretized by means of the finite difference method which are used to determine the deflections and the in-plane stress functions of plates and reduced to several sets of linear algebraic simultaneous equations. For the geometrically non-linear, large deflection behavior of the plate, the non-linear plate theory is used for the analysis. An iterative scheme is employed to solve these quasi-linear algebraic equations. Several problems are solved which illustrate the potential of the method for predicting the finite deflection and stress. For increasing lateral pressures, the maximum principal tensile stress occurs at the center of the plate and migrates toward the corners as the load increases. It was deemed important to describe the locations of the maximum principal tensile stress as it occurs. The load-deflection relations and the maximum bending and membrane stresses for each case are presented and discussed.

중저층건물 구조설계 통합시스템

김치경,Kim, Chi-Gyeong 한국건축구조기술사회 2006 건축구조 Vol.13 No.3

고온 및 저온처리와 자외선조사에 의한 campylobacterjejuni의 살균효과

김치경,임선희,윤만석,오학식,조민기 한국미생물학회 1989 미생물학회지 Vol.27 No.3

Campylobacter jejuni was studied for its disinfection by heat-and cold-treatment and UV-irradiation. When C. jejuni was treated by heat, no viable cell was found after 10 min treatment at $55^{\circ}C$, whereas small fraction of cell population was survived after 60 min treatment at $45^{\circ}C$ and $50^{\circ}C$. When they were treated by cold temperature for 30 days, no cell was survived at -$23^{\circ}C$ but about 4 log of the cells were survived at both temperature of $4^{\circ}C$ and -$40^{\circ}C$. When the organisms were UV-irradiated, thier survival rates were proportionally varied to the distance of irradiation. The scanning electron microscopic studies of C. jejuni cells treated by the disinfecting agents revealed that shapes of thecells were deformed from spiral rod into spherical form. The heat-treated cells showed rough and damaged surface on the scanning electron micrographs. In the heat-treated cells, some proteins of high molecular weight appeared to become accumulated in the electrophoretic analysis. The DNAs extracted from the cells treated with the physical agents showed some differences in agarose gel electrophoresis, comparing those of normal cells.

하천수의 오염도와 Escherichia coli 의 생존율과의 상관성에 관한 원위치 실험연구

김치경,정만희,김근식 ( Chi Kyung Kim,Man Hee Chung,Keun Sik Kim ) 한국하천호수학회 1984 생태와 환경 Vol.17 No.1·2

The survival of enteric bacteria in river water has been extensively studied under laboratory conditions or by jug method in river, but the correlations between the survival rate and the level of water pollution have not been reported. In this study, the survival of two strains of Escherichia coli (ATCC #25922 and a fresh isolate from polluted water) was comparatively studied in gradually polluted river waters by in situ method using dialysis sac. In all cases which the dialysis sacs containing sterile or non-sterile river water inoculated with E. coli were examined in the river waters, the survival rates were proportionally increased by the level of water pollution. The higher survival rate of E. coli in the more polluted rivers seems to be attributed to the higher growth rate of the organism on the organic pollutants in spite of the higher number of predators. Therefore, the high number of E. coli found in the more polluted river is thought to be due to the growth of the existing bacteria, not due to the influx of the bacteria including in domestic sewage. This means that the organic pollutants in river could be not only the primary problem as itself, but also the secondary problems promoting growth of the enteric bacteria in river waters, maintaining them in high number, and increasing the chances for the enteric pathogens to spread to outbreak waterborne diseases.

An analytical solution to heat conduction with a moving heat source

김치경 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.4

This paper deals with an analytical solution to heat conduction in the medium subjected to a moving heat source. It evaluates the temperature distribution around a rectangular shape source moving at a constant speed along the axis of a bar. The transient temperature field from a moving heat source was analyzed using a Fourier series procedure. The most interesting result of the theory, is the derivation of a single formula capable of predicting the cooling time and cooling rate with a fairly good accuracy for ranges of temperature. Because of the passage of the heat source, the rise of temperature produced at a given near the source, tends to rapidly become constant. Several sample problems are discussed and illustrated, and comparisons with numerical approaches where these can also be used made. The results show that these solutions are in good agreement with the numerical results.

A Safety Analysis on the Structural Rupture of Cylindrical Shell by Finite Difference Method

김치경,박화용 대한안전경영과학회 2011 대한안전경영과학회지 Vol.13 No.3

본 연구에서는 실린더 형 쉘 구조물의 구조적 안정성에 대하여 해석 하였다. 임계하중은 하중을 점차적으로 증가하여 구조물이 파괴가 발생 할 때의 상태에서 가장 작은 하중을 의미한다. 셸 구조의 안정성을 임계하중의 크기로 기초를 두고 해석 하였다. 실린더 형 쉘의 차분해석은 일차적 원통형 판구조와 같으므로 최근에 많은 연구의 대상이 되어왔다. 차분법은 복잡한 구조물에서도 물론, 다양한 경계조건을 포함하는 문제에 이르기까지 효과적인 수치방법이다. 본 연구에서는 기본 쉘의 지배방정식을 유도하고 차분화 하여 직접적으로 접근하였다. 등분포 하중의 내압을 받고 있는 갇힌 실린더 형 쉘의 처짐 및 응력을 해석 하였다. 수치해석 결과를 해석해와 비교 검토하였으며 안정성에 대하여 임계 하중강도의 범위를 산출하였다

Spontaneous Carotid Cavernous Fistula in a Case with Protein S Deficiency that Newly Developed Ophthalmoplegia after Embolization

김치경,신제영,장준영,이승훈 대한신경과학회 2011 Journal of Clinical Neurology Vol.7 No.3

Background Carotid cavernous fistula (CCF) is an abnormal communication between the carotid artery and the cavernous sinus. The pathogenesis of spontaneous CCF remains unclear,although sinus thrombosis is known to be a predisposing factor for dural arteriovenous fistula. Because spontaneous CCFs are mainly of the dural type, we considered that thrombogenic conditions, such as, protein S deficiency might be associated with CCF. Case Report A 42-year-old woman complained of conjunctival injection and retro-orbital pain that first appeared 1-month before visiting our hospital. She had no history of head trauma or intracranial surgery. Exophthalmos and chemosis were observed in her left eye, which also had lower visual acuity and higher intraocular pressure than the right eye. Magnetic resonance images and cerebral angiography revealed a left dural CCF. Her protein S was low, at 41%(normal range: 70-140%), but other hematologic values related to coagulation were normal. Her symptoms were relieved after initial transvenous coil embolization. However, a newly developed sixth-nerve palsy was detected 4 days after initial embolization. Follow-up angiography revealed a minimal shunt, and thus transvenous coil embolization was repeated. Two days later, the ophthalmoplegia started reducing, and 1-month later it had almost disappeared. Conclusions To the best of our knowledge, this is the first report of spontaneous dural CCF in a Korean patient with concurrent protein S deficiency. Interestingly, transient sixth-nerve palsy developed after transvenous coil embolization in this patient. This additional symptom caused by the residual fistula was relieved after additional transarterial embolization.

Pseudomonas spp . 에 의한 4 - chlorobiphenyl 의 분해 및 Plasmid 와의 연관성

김치경,이익근 ( Chi Kyung Kim,Ik Keun Lee ) 생화학분자생물학회 1990 BMB Reports Vol.23 No.3

Including the Pseudomonas strains reported in the previous works, two bacterial strains which are able to degrade 4-chlorobiphenyl(4CB) were isolated from natural environments. They were investigated for their ability to degrade 4CB and for growth on 4CB as a sole source of carbon and energy. It was found by UV-scanning spectrophotometry that both strains of DJ-12 and DJ-26 degraded 4CB to produce the meta-cleavage compound and then to 4-chlorobenzoic acid (4CBA) through the meta-cleavage pathway without dechlorination step. The DJ-12 strain was also turned out to degrade 4CB to produce 4CBA as assayed by HPLC. Through conjugation with Pseudomonas putida KT2440, the genes responsible for degradation of 4CB in the strain DJ-12 were found to be associated with a plasmid of about 65kb in size.