Ketamine이 돼지 관상동맥의 Ca(2+)Channel과 K(+)Channel에 미치는 영향

김경현,김교상,서정국,유희구,염종훈,신우중,김경현 대한마취과학회 1997 Korean Journal of Anesthesiology Vol.32 No.4

Background: Ketamine produces increasing in heart rate and arterial blood pressure, in vivo. However, the direct effects of ketamine itself on the porcine coronary arteries are not well determined. In this study, the direct effects of ketamine on the porcine coronary artery responses to vasoactive agents that operate through Ca2+ channel, K+ channels and endothelium related mechanisms were investigated, in vitro. Methods: Adult porcine hearts(n=12) were obtained from a slaughter house. Coronary arteries were perfused and dissected with 4oC Krebs solution, and were cut into vessel rings and prepared with and without the endothelium(3∼4mm in length). The ring segments were suspended in tissue bath(5ml) filled with Krebs solution at 37oC and bubbled with 95% O2-5% CO2 gas mixture. The effect of ketamine(5 10 5, 10 4, 2 10 4M) on vascular smooth muscle tone caused by Ca2+[voltage operated channel(VOC), receptor operated channel(ROC)] and K+channels(Ca2+activated K+ currents, ATP-sensitive K+ currents) regulationwere studied with Ca2+ free solution and K+channel blocker. Results: Ketamine induced vasorelaxation of porcine coronary rings that were precontracted by KCl(50 mM) or acetylcholine(3 10 7M). The changes of vascular tone in endothelium intact and removed group did not show statistical significance. In ketamine pretreated group(Ca2+ free solution), after ketamine pretreatment, the last vascular tone was same as that relaxed by ketamine. The other group that without pretreatment of ketamine, the last vascular tone was same as that precontracted with KCl or acetylcholine. In the TEA pretreated group, the porcine coronary artery relaxation was reversed. However, pretreatment with glybenclamide, the porcine coronary artery relaxation was not reversed. Conclusions: Ketamine induced vasorelaxation of the porcine coronary artery as concentration relating manner, in vitro. The vasorelaxation induced by ketamine was not associated with endothelium. Furthermore, an antagonism of Ca2+ channels(VOC, ROC) and activation of Ca2+ activated K+ channels may be responsible for the porcine coronary arterial relaxing effect of ketamine. (Korean J Anesthesiol 1997; 32: 504∼509)

Al-Cu 계 합금에서 Pb 및 Bi 첨가가 피삭특성에 미치는 영향

김경현,정인상 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.3

The machinability of Al alloys can be improved by addition of selected elements such as Pb, Bi, Sn, Cd and In. However, these elements have not only different melting points and densities but also form miscibility gap with Aluminium. This kind of phenomenon induces severe gravity segregation. The aim of this study is to observe the effect of several additives such as Pb, Bi on the machinability of Al-Cu alloys. Pb, Bi particles were finer with increasing of cooling rate and Ar bubbling pressure, and were coarsened with longer holding time after stirring. Due to the coarseness of particles with descending by gravitation, the more addition of Pb and Bi, the particle size becomes coarser. As the contents of additional elements increased, cutting properties were remarkably enhanced such as smaller cutting force and lower bite temperature without degradation of tensile properties. It is also found that the Al alloy is the optimum for free-cutting when 0.4% of Pb and Bi are added to Al-Cu alloys.

대안형 아트페어의 특성 연구

김경현,김선영 한국상품문화디자인학회 2022 상품문화디자인학연구 Vol.70 No.-

Recently, many alternative art fairs have been created one after another, but most of them are disappearing without being able to endure for long due to the limitations of their operational structure, lack of financial resources, and competition with similar art fairs. Therefore, this study tried to suggest the development plan of the alternative art fair by analyzing the characteristics of the alternative art fair and pointing out the problems pointed out in the operation process. As the research method, multi-case analysis and in-depth interviews were adopted. ‘Eulji Art Fair’ was selected as a domestic example, and ‘Independent Art Fair’ and ‘Spring Break Art Show’ were selected as overseas art fairs. As a result of the study, the characteristics of the alternative art fair are that, first, it serves as a new space and a place of information exchange for up-and-coming artists. Second, it provides opportunities for up-and-coming artists and new spaces, and broadens the spectrum of artists and media to form a diversity of works. Third, although it focuses on enhancing the credibility of the event management through collaboration with institutions and communication between galleries, it is insufficient to evaluate the credibility of the work value. Fourth, the openness is increased by increasing the participation of the audience through SNS PR, field events, and side events. Fifth, a network is formed naturally when new spaces and emerging artists with similar situations and interests gather. In addition, as problems of the alternative art fair, publicity focused on SNS, lack of budget, inexperienced operation, and monotonous profit structure were derived. As a development plan, a plan for profit improvement was prepared for expanding various PR channels and stable finance, securing sufficient labor and thorough preparation in advance were suggested. 최근 많은 대안형 아트페어들이 속속 생겨나고 있지만 대부분 운영 구조의 한계, 재원의 부족, 유사 아트페어와의 경쟁 등으로 인해 오래 버티지 못하고 사라지고 있다. 이에 본 연구는 대안형 아트페어의 특징을 분석하고, 운영 과정에서 지적되는 문제점을 짚어봄으로써 대안형 아트페어의 발전 방안을 제시하고자 하였다. 연구 방법은 다중사례 분석 및 심층 면접을채택하였다. 국내 사례로는 ‘을지아트페어’를, 해외 아트페어로는 ‘인디펜던트 아트페어’, ‘스프링 브레이크 아트쇼’를 각각선정하였다. 연구 결과, 대안형 아트페어의 특성은 첫째, 신생공간과 신진작가들의 정보 교환의 장으로서의 역할을 한다. 둘째, 신진작가와 신생공간에 기회를 제공하고 작가와 매체에 스펙트럼을 넓혀 작품의 다양성을 형성한다. 셋째, 기관과의협업과 갤러리들 간의 소통을 통해 행사 운영에 대한 신뢰도를 높이는데 집중하지만, 작품 가치에 관한 신뢰성 면에서는평가하기 부족한 면이 있다. 넷째, SNS 홍보와 현장이벤트, 부대행사를 활용하여 관객의 참여를 높여 개방성을 높이고 있다. 다섯째, 비슷한 상황과 관심사가 비슷한 신생공간과 신진작가들이 모이기에 자연스럽게 네트워크가 형성된다. 한편 대안형 아트페어의 문제점으로는 SNS에 치중된 홍보, 예산 부족, 운영 미숙, 단조로운 수익구조 등이 도출되었다. 발전 방안으로는 다양한 홍보 채널을 확대, 안정적 재정을 위해 수익개선을 위한 방안 마련, 충분한 인력 확보와 철저한 사전 준비등을 제시하였다.

구결막에 발생한 신경초종 1예

김경현,심재형,서성욱 대한안과학회 2009 대한안과학회지 Vol.50 No.6

Purpose: To report one case of neurilemoma of the bulbar conjunctiva with a review of the relevant literature. Case summary: A 15-year-old girl presented with a bulbar conjunctival mass in the right eye. There were no other medical or ophthalmologic problems. The patient wanted to remove the mass for cosmetic reasons. We performed an excisional biopsy and simple wound closure. The mass was composed of bipolar spindle shaped cells that were arranged in bundles and fascicles in dense fibrous tissue. Immunohistochemical staining for the S-100 protein was positive. Two months after mass excision, there was no evidence of recurrence. Conclusions: We successfully treated a case of bulbar conjunctival neuriliemoma by simple excision. 서론: 드문 질환으로 알려진 구결막에 발생한 신경초종 1예를 보고하고자 한다. 증례요약: 15세 여자환자가 3~4년 전 발견 후 지속된 우안 구결막의 종괴를 주소로 내원하였다. 환자는 전신질환의 과거력은 없었으 며, 안질환의 병력도 없었다. 미용상의 이유로 수술적인 치료를 원하였으며 양성 종양 의심 하에 구결막 종괴 제거술을 시행하였다. 결막 종양은 공막으로의 침범은 관찰되지 않았으며 정상 결막을 포함하여 쉽게 제거가 가능하였다. 조직검사상 양극성 방추형 세포가 조밀하게 분포되어 있었으며 비정형세포는 관찰되지 않았다. S-100 면역검사상 양성 반응으로 나타나 신경초종으로 진단되었다. 수술 후 2달째 창상부위는 치유된 상태로 재발 소견은 관찰되지 않고 있다. 결론: 신경초종은 결막에는 매우 드물게 발생하는 양성 종양이며 단순절제만으로 좋은 결과를 경험하였기에 증례보고 하는 바이다.

하천 내 유사와 인 이동에 관한 모델링

김경현 한국물환경학회 2010 한국물환경학회지 Vol.26 No.2

A model has been developed to investigate in-river sediment and phosphorus dynamics. This advective-dispersive model is coupled with hydrodynamics and sediment transport submodels to simulate suspended sediment, total dissolved phosphorus, total phosphorus, and particulate phosphorus concentrations under unsteady flow conditions. It emphasizes sediment and phosphorus dynamics in unsteady flow conditions, in which the study differs from many previous solute transport studies, conducted in relatively steady flow conditions. The diffusion wave approaximation was employed for unsteady flow simulations. The first-order adsorption and linear adsorption isotherm model was used on the basis of the three-layered riverbed submodel with riverbed sediment exchange and erosion/deposition processes. Various numerical methods were tested to select a method that had minimal numerical dispersion under unsteady flow conditions. The responses of the model to the change of model parameter values were tested as well.

티베리우스·그라쿠스와 개혁의 정치

김경현 韓國西洋古典學會 1991 西洋古典學硏究 Vol.5 No.-

로봇활용교육의 교육적 유용성에 대한 교사의 인식

김경현 사단법인 인문사회과학기술융합학회 2017 예술인문사회융합멀티미디어논문지 Vol.7 No.1

This paper is to explore the teachers' perception on the educational usability of RBE(Robot Based Education). I carry out a survey consisting of five factors about the educational usability of RBE, targeting 116 teachers who had have experiences about RBE. The results has shown the following three findings: 1) The teachers have perceived that RBE can improve creativity and problem solving ability of the students. 2) It can efficiently facilitate the interaction of them as well. 3) The teachers express their own opinion that RBE can apply to various subjects, therefore if robot media are introduced in their classes, they will use it continuously. However on the question that whether RBE is a convenient method for teaching, the results show lower score than other items. For the reason that RBE is a national project to be called for big budget comparing to other projects, when it is used in school classes overall, we need to collect extensive opinions from the teachers who are positioned at the advance of applying it, in addition, elaborately examine the teachers' ability on carrying it out. 본 연구는 로봇활용교육의 교육적 유용성에 대한 교사의 인식을 살펴보는 것이다. 이를 위해 로봇활용교육 경험이 있는 현직 교사 116명을 대상으로 로봇활용교육의 유용성에 대해 다섯 요인으로 구성된 설문을 수행하였다. 본 연구의 결과, 그들은 로봇활용교육이 학생의 창의력과 문제해결능력을 향상시키는 것으로 인식하였으며 상호작용을 촉진시킬 수 있는 효과적인 교육 방법으로 생각하였다. 뿐만 아니라, 로봇활용교육이 여러 교과에서도 적용 가능하며 로봇매체가 학교에 도입된다면 지속적으로 활용할 것이라는 의견을 피력하였다. 그러나 로봇활용교육이 학생들의 학습을 지도하는 데 편리한가에 대해서 대체로 긍정적이었으나 다른 문항에 비해서는 상대적으로 낮은 점수를 나타냈다. 로봇활용교육은 다른 매체에 비해 많은 예산이 요청되는 국가적인 사업이므로, 이를 확대 적용함에 있어서 수행의 선두적인 위치에 있는 교원들을 대상으로 한 보다 광범위한 의견 수렴의 과정과 이를 수행할 수 있는 교원의 능력에 대해 면밀히 검토할 필요가 있다.

cephalosporin acylase 구조로부터 자가분해 활성화기작에 대한 고찰

김경현 National Academy of Science USA 2006 Proc. Natl Acad. Sci. USA Vol.103 No.-

MBE로 성장된 Al_0.25Ga_0.75As/In_0.2Ga_0.8As pHEMT 에피구조의 RTA에 따른 전도 특성

김경현,홍성의,백문철,조경익,최상식,양전욱,심규환,Kim, Kyung-Hyun,Hong, Sung-Ui,Paek, Moon-Cheol,Cho, Kyung-Ik,Choi, Sang-Sik,Yang, Jeon-Wook,Shim, Kyu-Hwan 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.7

We have investigated $Al_{0.25}Ga_{0.75}As/In_{0.2}Ga_{0.8}As$ structures for pseudomorphic high electron mobility transistor(pHEMT), which were grown by molecular beam epitaxy(MBE) and consequently annealed by rapid thermal anneal(RTA), using Hall measurement, photoluminescence, and transmission electron microscopy (TEM). According to intensity and full-width at half maximum maintained stable at the same energy level, the quantized energy level in $Al_{0.25}Ga_{0.75}As/In_{0.2}Ga_{0.8}As$ quantum wells was independent of the RTA conditions. However, the Hall mobility was decreased from $6,326cm^2/V.s\;to\;2,790cm^2/V.s\;and\;2,078cm^2/V.s$ after heat treatment respectively at $500^{\circ}C\;and\;600^{\circ}C$. The heat treatment which is indispensable during the fabrication procedure would cause catastrophic degradation in electrical transport properties. TEM observation revealed atomically non-uniform interfaces, but no dislocations were generated or propagated. From theoretical consideration about the mobility changes owing to inter-diffusion, the degraded mobility could be directly correlated to the interface scattering as long as samples were annealed below $600^{\circ}C$ lot 1 min.

중형 저상전기버스 도입에 따른 지불용의액 추정 연구

김경현,박상민,박성호,윤일수 한국ITS학회 2018 한국ITS학회논문지 Vol.17 No.1

현재 지구촌 기후변화 대응 패러다임은 선진국 중심이 아닌 모든 국가가 참여하는 보편적대응체제로 전환되었으며, 우리나라 또한 2030년까지 수송분야 온실가스 감축목표를 25.9백만톤으로 설정하였다. 한국 사회는 고령화 사회에 진입하였으며, 2026년 초 고령화 사회로진입할 전망이다. 이에 본 연구에서는 대중교통부문 온실가스 저감 및 교통약자 이동편의 증진을 위해서 기존 마을버스를 중형 전기저상버스로 교체할 경우를 가정하여 지불용의액 및사회적 편익을 추정하였다. 수도권 마을버스 이용자를 대상으로 설문조사를 수행하였으며, 비시장가치 평가방법 중 하나인 조건부 가치측정법을 이용하여 지불용의액을 추정하였다. 지불의사금액 모형 추정결과 평균 WTP는 51.4(원/회․인)이며, 2014년 기준 경기도 마을버스이용자의 경제적 편익 추정 결과 평일 약 5천만 원, 주말 약 4천만 원으로 분석되었다. Currently, the global climate change response paradigm has been changed to a universal response system in which all nations, not the developed countries, participate. Korea has also set a target of 25.9 million tons of transportation greenhouse gas reduction targets by 2030. Korean society is expected to enter the super aging society in 2026. In this study, to reduce the greenhouse gas emissions in public transport and to improve the convenience of transportation vulnerable, we estimate the willingness to pay(WTP) and social benefits assuming that the existing feeder buses are replaced with medium-sized low floor electric buses. To this end, survey was conducted on bus users in the metropolitan area and WTP was estimated by using contingent valuation method(CVM), which is one of the non-market value evaluation methods. As a result of estimation of WTP, the average WTP is 51.4 (won / time·person), estimated the economic benefits were 50 million won on weekdays and 40 million won on weekends in Gyeonggi Province in 2014.