• Journal of The Korean Association For Science Education
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• v.16 no.2
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• pp.164-174
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• 1996

본연구는 자유낙하 운동에 대학 학생의 개념을 이 개념의 역사적 변천 과정과 비교하여 분석하였다. 네 연령층(ll세,13세, 15세, 17세)으로부터 총 737명이 설문조사에 참여하였으며,설문에서 주어전 문항들은 자유낙하 운동과 관련하여 과거의 과학자(예를 들어, 아리스토텔레스, 임페루스 이론가, 갈릴레오)들이 고민하였던 핵심 문제를 반영하는 것이었다. 설문에는 세 문항이 포함되었으며,각 문항은 자유낙하 운동에 관한 세 가지 측면(즉,운동의 원인,낙하높이와 낙하속력의 관계,낙하 체의 무게와 낙하속력의 관계)에 각각 관련된 것이었다. 낙하운동의 원인에 대혜서, 전체 학생의 4.3%, 25.5%. 62.7%가 아리스토텔레스,임페루스스,갈릴레오적 관점을 각각 지닌 것으로 나타났다. 낙하높이와 낙하속력의 관계에 대혜서는,20.0% 와 29.0%의 학생들이 각각 아리스토텔레스와 갈릴레오적 관점을 지닌 것으로 냐타났다. 그리고 낙하체와 무게와 낙하속력의 관계에 대혜서는,19.0%,34.8%,42.2%의 학생들이 아리스토텔레스,임페루스,갈리레오적 관점을 지닌 것으로 나타났다. 개별 문항에서 부분적으로 임페루스적 관점으로부터 갈릴레오적 관점으로의 변화가 나타났으나,전체적으로 연령이 증가함에 따라 학생의 개념이 현대적 관점으로 변화한다고 판단 하기는 어려웠다. 그리고 본 연구로부터 학생의 개념과 그 개념의 역사적 변천 과정에 사이에 상당한 유사성과 함께 차이점이 존제함을 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1330-1341
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• 1993

The kinematic synthesis deals with the systematic design of mechanisms for a given performance. The area of synthesis may be grouped into two categories to determine the type and to size the dimensions of a mechanism for a specified task. In this paper, using a database of mechanisms a designer can determine the type of mechanism conveniently and design equations are automatically generated for a given input performance. The solving method of design equations utilizes an optimization routine to obtain roots effectively. The linkages of 4, 6, and 8bars with revolute joints are considered in this study but may be extended to linkages of more bars.

• Journal of Chest Surgery
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• v.36 no.12
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• pp.928-928
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• 2003

승모판성형술 직후에 시행한 재수술에 대한 연구보고는 많지 않다. 저자들은 승모판성형술 직후 성형술 실패로 판단되는 환자에서 즉시 시행한 재수술 결과에 대해 알아보았다. 대상 및 방법: 1995년 4월부터 2001년 7월까지 세종병원에서 승모판성형술을 받은 환자 중 체외순환 이탈 직후 시행한 경식도초음파 검사에서 승모판막폐쇄부전 혹은 협착이 의미있게 잔존하거나 다른 이유로 재수술이 즉시 필요하였던 18명을 대상으로 후향적으로 조사하였다. 남녀비는 5 : 13이었고 평균 연령은 44세였다. 승모판막 질환은 폐쇄부전 12명, 협착 3명, 그리고 혼합형이 3명이었다. 원인은 류머치스성 9명, 퇴행성 8명, 그리고 심내막염이 1명이었다. 재수술의 원인은 잔존 승모판폐쇄부전 13명, 협착 4명, 그리고 좌심실천공이 1명이었다. 14명(77.8%)에서 재성형술을, 4명에서는 인공기계판막치환술이 시행되었다. 결과: 조기사망은 없었다. 조기결과는 승모판막치환을 한 4명을 제외한 14명 중 13명(92.9%)에서 0-I도의 폐쇄부전을 보였고 협착은 14명 모두 경도 이하 상태였다. 평균 33개월을 추적조사 한 결과 1명이 술 후 4개월 후 심기능부전으로 사망하였다. 승모판폐쇄부전은 9명(64.3%)에서 0-I도를, 승모판협착은 11명(78.6%)에서 경도 이하였고 재수술은 1명에서 시행되었다. 6년 생존율과 재수술로부터의 자유도는 각각 94%와 90%였다. 4년 후 승모판폐쇄부전 및 협착 재발로부터의 자유도는 각각 56%와44%였다. 결론: 승모판막성형술 직후 재수술은 양호한 조기 및 중기 생존율을 보이며 일차성형술 실패 후에도 높은 빈도에서 재성형술이 가능하다. 하지만 재성형술 시 특히 류머치스성 판막질환에서는 판막 기능부전 발생률이 높기 때문에 성형술 후 판막부전의 재발을 줄이기 위해서는 성형술의 적절한 적용 및 적응증 선별이 중요할 것으로 생각된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.899-904
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• 2014

Thickness profiled blank is designed using optimization techniques for maximizing the bulged heights during the free bulging of Inconel 718. The thickness of the blank was described by the Bezier curve and the locations of the control points were used as the design variables for optimization. The maximization of the bulged heights within the limited strain range served as the objective function and constraints for optimization. The equivalent static loads method for non-linear static response structural optimization (ESLSO) was used and the result of the optimization revealed 22 increased bulged heights. A free bulging test using a blank with an optimized profile was conducted to verify the optimization process. The results were compared with those of numerical analysis in terms of bulged height and deformed shape.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.791-797
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• 2017

Today, we are using computer simulations in various engineering disciplines to reduce the time and cost of product development. The scope of simulations is increasingly complex and diverse for different fields such as mechanical, electrical, thermal, and fluid. Thus, it is necessary to use integrated simulations. In order to overcome these problems, a language has been developed to effectively describe and implement simulations is Modelica. To model and simulate a system, physical models can be broadly divided into causal and acausal models. The most important feature of Modelica is acausal programming. In this study, we will introduce simple concepts and explain about the usage of Modelica. Furthermore, we will explain the vibration analysis of a two degree-of-freedom system and the design of appropriate parameters by using Modelica.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.5
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• pp.418-425
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• 1991

This study was designed to observe the effects of the fish oil and some seed oils on the improvement of the fatty acid compositions of liver and brain tissue in rats. In order to induce the hypertriglyceridemia in the rats of the Sprague-Dawley, 12% coconut oil and 3% each of olive oil, lard, fish oil, perilla oil, corn oil, red pepper seed oil and evening primrose oil were administered to the rats for 4 weeks. In the fatty acid composition of liver lipid, n-3 PUFA contents were most in the fish oil and perilla oil groups of phospholipid fraction, and n-6 PUFA contents were most in the corn oil, red pepper seed oil and evening primrose oil groups of triglyceride fractions. Fatty acid composition of liver lipid fractions were influenced from the fatty acid composition of the test lipids. In the fatty acid composition of brain phospholipid, n-3 PUFA contents (8.8~17.2%) were most in the fish oil group, and n-6 PUFA (34.6~38.2%), though it contains high percentage, showed little difference between groups.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2D
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• pp.105-111
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• 2010

Operating speed is one of key elements in the design and operation of freeway. Few studies have been carried out macroscopically to find characteristics of free-flow speed (FFS) using small sample size and not considering the conditions of traffic volume and the effects of hour periods. As an attempt to find out the characteristics of FFS, this study microscopically analysed both the distributions of freeway FFS and percentile speeds according to traffic volume and daily hour periods using huge sample size. It was found out that speed distributions are changed and showed different behaviors under the conditions of traffic volumes(1-5 veh/30sec) and daily hour periods(0-5, 6-8, 9-11, 12-19, 20-23). V85(85th percentile speed) at morning, night, and midnight period decreases according to increase in traffic volume respectively, whereas V85 at day time does not show considerable differences. So the behaviors of V85 according to hour periods dramatically changed according to the increase in traffic volume.

• Journal of Chest Surgery
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• v.37 no.10
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• pp.839-844
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• 2004

Background: The Y-composite graft of internal thoracic artery and radial artery is commonly used in coronary bypass surgery. The aim of this study is to look for a way to raise the free flow of the internal thoracic graft and to see flow dynamics of the Y-graft. Material and Method: In 15 patients undergoing coronary bypass surgery, free flow of the in-situ internal thoracic artery graft was measured using two different papaverine application methods; extraluminal papaverine spray in 7 patients and intraluminal papaverine injection in 8. In 18 other patients for whom the Y-graft was used, total free flow and flow changes from the two ends were measured. Result: The free flow of the in-situ internal thoracic artery graft almost doubled with internal papaverine injection than with external papaverine spray $(47.7\pm9.6$ mL/min $vs.100.8\pm26.3$ mL/min, p<0.001). Total flow of the Y-composite graft was significantly more than either flow of the internal thoracic artery end or radial artery graft end $(173.3\pm45.3$ mL/min vs. $121.1\pm34.3$ mL/min or $117.5\pm42.8$ mL/min). When both ends of the Y-composite graft were opened, free flows from the two ends were similar $(85.4\pm27.8$ mL/min vs: $87.9\pm42.4$ mL/min, p=0.772). The flow of one end of the Y-composite graft was increased significantly by clamping of the other-end than when both ends were opened. Conclusion: Intraluminal papaverine injection is very effective in raising free flow of the internal thoracic artery graft, and the free flow of the Y-composite graft of in-situ internal thoracic artery and free radial artery graft is more than that of the in-situ internal thoracic artery graft. The flow of one end flow of the Y-graft may be altered by the flow change of the other end.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.06a
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• pp.146-147
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• 2004

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.12
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• pp.1041-1047
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• 2002

It is known that parallel-type mechanisms have many singularities than serial-type mechanisms. In haptic application, these singularities deteriorate the system performance when the haptic system displays the reflecting force. Moreover, different from general manipulators, haptic systems can't avoid the singular point because they are operated by user's random motion command. Although many singularity-free algorithms for serial mechanisms have been proposed and studied. singularity-free algorithms for parallel haptic application have not been deeply discussed. In this paper, various singularity-free algorithms, which are appropriate to parallel haptic system, will be discussedand evaluated.