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)

한국어 Matrix 문장 검사 도구 평가: 목록 간 동질성과 단어 위치의 영향에 대한 검증

김경현,이재희 한국청각언어재활학회 2018 Audiology and Speech Research Vol.14 No.2

Purpose: Multilingual Matrix Sentence Tests have been developed for reliable, precise, and internationally comparable sentence-innoise tests. The lists of the Korean Matrix Sentence Test have been constructed and optimized in the previous study. The sentences are generated by a base matrix of 50 Korean words (10 names, 10 adjectives, 10 objects, 10 numerals, and 10 verbs). As suggested by International Collegium of Rehabilitative Audiology working group, this study conducted evaluation tests to verify the list equivalence and the effect of word position at a fixed signal-to-noise ratio (SNR). Methods: For experiment I, fifteen normal-hearing (NH) listeners participated. As a material, the Korean Matrix sentences optimized and level-adjusted were used. Twelve test lists of ten sentences were combined to six test lists of twenty sentences (double lists) such that each listener was tested with six double-lists in an open-set format. The percentage of correct responses was measured based on word scoring at fixed SNRs of -10, -8, -6, -4 dB SNRs, with a constant noise level of 65 dB sound pressure level. List-specific intelligibility functions for each list were derived by fitting the percent-correct scores to the logistic regression function, yielding speech reception threshold (SRT) at which 50% intelligibility and also the slope at the SRT across listeners. For experiment II, thirty hearing-impaired (HI) subjects participated and all of them have used hearing aids bilaterally. The aided puretone threshold average of HI listeners was 35.9 dB HL. The materials of the Korean Matrix sentences were presented through loudspeakers while wearing listener’s hearing aids. Based on word scoring, the listeners’ recognition score was measured in four listening conditions (quiet, 6, 3, 0 dB SNRs). Results: In experiment 1, the mean SRT and mean slope across the six test lists were -9.56 dB SNR and 14.03 %/dB, respectively. Across the fixed SNRs, mean difference of SRT was within 1 dB across lists. Based on word scoring, the NH listeners were found to poorly recognize the word at the first position than words at other positions. The mean SRT and slope of the Korean Matrix test were comparable to results of other multilingual Matrix tests. In experiment 2, the results of HI listeners depended on the listening condition (quiet, 6, 3, 0 dB SNR). Regardless of condition, HI listeners poorly recognized words at the first position than words at other positions. The recognition score obtained from the closed-set format was greater than from the open-set test format. Conclusion: The equivalence in intelligibility was confirmed by the results of the Korean Matrix sentence recognition at the fixed SNRs. The results obtained from Korean Matrix test were comparable to the results of other multilingual Matrix tests. The optimized and evaluated Korean Matrix Sentence Test can be used for accurate and reliable speech intelligibility in noise measurements.

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.

박한상 사건 TV 다큐멘터리를 본 한 미국유학생의 긴급반론 : 홍정욱과 박한상은 얼마나 다른가 - 신세대 미국유학생들을 위한 변명

김경현 사회평론 1994 사회평론 길 Vol.94 No.9

pragmatike historia와 tyche -폴리비오스의 역사이론과 서술의 실제-

김경현 한국사학사학회 2009 韓國史學史學報 Vol.0 No.20

This paper discusses the question of consistency between theoretical premises and narrative practice in Histories of Polybius, the Greek historian who has been numbered together with his predecessor Thucydides in the top class of ancient historiography. For, while modelling Thucydides in setting the purpose of historical research and writing for providing practical lessons for future men of state-affairs (pragmata), he advanced further in formulating the methodological principles and the requirements for would-be historian. Thus, he was the first to conceptualize the pragmatike historia, and has been duly acknowledged as such. The second chapter of this paper attempts to exhibit the cardinal aspects of the pragmatike historia. According to the historian, the genre of history he chose to write is different from that of the so-called genealogike historia: while Polybius himself does record mostly what he has seen and heard in person, thus likelier to be more faithful to the historical truth, the latter, usually tracing back to the remote past far beyond historian's ken, thus unavoidably dependent upon what has been transmitted through the writings of predecessors, by and large regardless of the truth. And Polybius tries to expound the methodology of research to the readers, as occasions are given throughout Histories. apodeiksis and aitiologia are its key-words: the former signifies the principle of analytically demonstrating facts by means of various evidences and testimony, the latter the causative explanation of historical events. The famous analysis of the Roman constitution and the military system as the secrets of Rome's success Polybius presents in the book VI of Histories epitomizes his rationalistic approach to history. And the confidence in human knowledge's continuous expansion his contemporaries are witnessing particularly in the field of ecumenical geography, reflects the historian's rationalism in a way very much reminiscent of the 18th century's European intellectual optimism. Yet, does the narrative of Histories abide by the methodological principles? The third chapter answers to this question by testing one of the most prominent features of Polybius' narrative, namely the use of the term tyche. (the total appearance is 137 times) That the historian makes frequent recourses to it prima facie contradicts diametrically the conclusion just drawn in the previous chapter, for usual connotations of the term (chance, fortune, and fate) seemingly do replace, rather than supplement, the rational causation of events. The author of this paper firstly proposes classify the usage of tyche in Histories into three categories: etiological tyche, moral (or punitive) tyche, and teleological (or providential) tyche. As for the etiological tyche, there is no need to further our discussion, for the historian himself concedes its indispensability due to human perception's limitation in cases where natural elements affect or multiple factors converge to produce historical circumstance beyond the expectation of historical agents. In the meantime, the remaining two categories are a different matter, if they are meant to be significant as of more than a conventional way of expression. For their premise is that a transcendental power intervenes in human affairs to punish the moral deviant or, to speak tyche operating on a far grander scale, to lead the entire oikumene according to a predestined plan (for example, a cycle of rise and fall). However, the final analysis of the concrete ways the historian refers to tyche, whether moral or providential, shows that the reference of tyche are nothing but a rhetorical and convenient way of expression. That moral tyche can't be by any means an objective force affecting human actions is revealed by its inconsistent nature. That is, the historian applies the operation of moral tyche solely to the figures alleged to be villains, while representing as outstanding exceptions to the rule ... This paper discusses the question of consistency between theoretical premises and narrative practice in Histories of Polybius, the Greek historian who has been numbered together with his predecessor Thucydides in the top class of ancient historiography. For, while modelling Thucydides in setting the purpose of historical research and writing for providing practical lessons for future men of state-affairs (pragmata), he advanced further in formulating the methodological principles and the requirements for would-be historian. Thus, he was the first to conceptualize the pragmatike historia, and has been duly acknowledged as such. The second chapter of this paper attempts to exhibit the cardinal aspects of the pragmatike historia. According to the historian, the genre of history he chose to write is different from that of the so-called genealogike historia: while Polybius himself does record mostly what he has seen and heard in person, thus likelier to be more faithful to the historical truth, the latter, usually tracing back to the remote past far beyond historian's ken, thus unavoidably dependent upon what has been transmitted through the writings of predecessors, by and large regardless of the truth. And Polybius tries to expound the methodology of research to the readers, as occasions are given throughout Histories. apodeiksis and aitiologia are its key-words: the former signifies the principle of analytically demonstrating facts by means of various evidences and testimony, the latter the causative explanation of historical events. The famous analysis of the Roman constitution and the military system as the secrets of Rome's success Polybius presents in the book VI of Histories epitomizes his rationalistic approach to history. And the confidence in human knowledge's continuous expansion his contemporaries are witnessing particularly in the field of ecumenical geography, reflects the historian's rationalism in a way very much reminiscent of the 18th century's European intellectual optimism. Yet, does the narrative of Histories abide by the methodological principles? The third chapter answers to this question by testing one of the most prominent features of Polybius' narrative, namely the use of the term tyche. (the total appearance is 137 times) That the historian makes frequent recourses to it prima facie contradicts diametrically the conclusion just drawn in the previous chapter, for usual connotations of the term (chance, fortune, and fate) seemingly do replace, rather than supplement, the rational causation of events. The author of this paper firstly proposes classify the usage of tyche in Histories into three categories: etiological tyche, moral (or punitive) tyche, and teleological (or providential) tyche. As for the etiological tyche, there is no need to further our discussion, for the historian himself concedes its indispensability due to human perception's limitation in cases where natural elements affect or multiple factors converge to produce historical circumstance beyond the expectation of historical agents. In the meantime, the remaining two categories are a different matter, if they are meant to be significant as of more than a conventional way of expression. For their premise is that a transcendental power intervenes in human affairs to punish the moral deviant or, to speak tyche operating on a far grander scale, to lead the entire oikumene according to a predestined plan (for example, a cycle of rise and fall). However, the final analysis of the concrete ways the historian refers to tyche, whether moral or providential, shows that the reference of tyche are nothing but a rhetorical and convenient way of expression. That moral tyche can't be by any means an objective force affecting human actions is revealed by its inconsistent nature. That is, the historian applies the operation of moral tyche solely to the figures alleged to be villains, while representing as outstanding exceptions to the rule his...

정밀도로지도 경량화 정보 기반 전역경로 생성 가속화 방법론

김경현,홍석진,유진우 한국자동차공학회 2024 한국 자동차공학회논문집 Vol.32 No.5

A global route is an essential technical element in implementing an SAE Level 4 fully autonomous driving system without driver intervention. Under this requirement, research on creating a high-definition, map-based global path and developing a preprocessing algorithm is being actively conducted. In this paper, the BFS (Breadth-First Search) technique was applied by clustering driving route nodes in a precise road map. Later, it was confirmed that the proposed method improved performance after comparing the computational amount and execution time of the Dijkstra algorithm-based global path.

문화는 무엇을 할 수 있는가 3 미국에서 성장한 한 문화학도의 자유주의 문화 담론에 대한 문제제기 - 서태지와 미국 언더그라운드 , 그리고 문화평론가 이재현

김경현 사회평론 1996 사회평론 길 Vol.96 No.8

N/A

The Influences of Different Ratios of Biphasic Calcium Phosphate and Collagen Augmentation on Posterior Lumbar Spinal Fusion in Rat Model

김경현,구성욱,박정윤,박효숙,김근수,진동규,조용은 연세대학교의과대학 2017 Yonsei medical journal Vol.58 No.2

Purpose: To determine the influence of different ratios of hydroxyapatite (HA)/beta tricalcium phosphate (β-TCP) and collagen augmentation for posterior lumbar fusion in a rat model. Materials and Methods: We generated a posterior lumbar fusion model in 50 rats and divided it into five groups of equal number as follows; 1) autologous bone graft as group A, 2) 70% HA+30% β-TCP as group B, 3) 70% HA+30% β-TCP+collagen as group C, 4) 30% HA+70% β-TCP as group D, and 5) 30% HA+70% β-TCP+collagen as group E. Rats were euthanized at 12 weeks after surgery and fusion was assessed by manual palpation, quantitative analysis using microCT and histology. Results: The score of manual palpation was significantly higher in group C than group E (3.1±1.1 vs. 1.8±0.8, p=0.033). However, in terms of microCT analysis, group D showed significantly higher scores than group B (5.5±0.8 vs. 3.1±1.1, p=0.021). According to quantitative volumetric analysis, 30% HA+70% β-TCP groups (group D and E) showed significantly reduced fusion mass at 12 weeks after surgery (123±14.2, 117±46.3 vs. 151±27.3, p=0.008, 0.003, respectively). Collagen augmentation groups revealed superiorresults in terms of both microCT score and histologic grade. Conclusion: A 7:3 HA/β-TCP ratio with collagen augmentation rather than a 3:7 HA/β-TCP ratio could be a more favorable graft substitute for lumbar spinal fusion. There was positive role of collagen as an adjunct for spinal bone fusion process.

고온용 마그네슘합금의 개발 현황 및 응용

김경현,손근용,Kim, Gyeong-Hyeon,Son, Geun-Yong 재료연구소 2004 機械와 材料 Vol.16 No.2

이종 영계수 영역의 위치 추정용 변형 영상 합성곱 신경망의 최적 커널 크기

김경현,이두용 제어로봇시스템학회 2022 제어로봇시스템학회 국내학술대회 논문집 Vol.2022 No.6