• KSTLE International Journal
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• 제2권2호
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• pp.85-92
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• 2001

The variation of contact traction induced by different contact shapes is studied experimentally and theoretically. Considerations fer the contact shape are rounded, truncated and truncated with rounding punches. A fretting wear experiment is conducted with the contact configuration of the strip on the tube specimens. The strip specimen is pressed to form the end profile of a rounded and truncated with rounding punches shape. Wear on the tube is investigated, which is regarded as the slip region of the contact surface. Taken into consideration is the general solution of the normal traction in the case of the indentation by a punch with its end profile of the combination of parabolas. Then, partial slip solution is obtained numerically, which is compared with the wear on the tube. The radius of the rounding and the obliquity of the edge truncation affect the tractions considerably. It is found that the proper choice of the end profile can restrain the contact-induced failure such aswear.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.144-150
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• 2001

Considered is non-symmetric contact traction induced by the tilting of a contact body and/or by a far field bulk tensile load to the other body. The problem is under the regime of plane strain. General profile of the contact end is incorporated and partial slip condition is supposed. As an example contact configuration, an indentation of a punch with rounded corners onto a half plane is studied. The variation of the internal stress field due to the tilting and the bulk tension is investigated. An edge crack problem is analyzed to examine the influence of the non-symmetric traction. It is shown that the tilting of a punch does not influence the behaviour of the crack. Rather, the effect of the bulk tension on the cracking behaviour is found considerable.

• 한국생산제조학회지
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• 제24권2호
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• pp.231-237
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• 2015

The pin-gear drive is a special form of fixed-axle gear mechanism. A large wheel with cylindrical pin teeth is called a pinwheel. As pinwheels are rounded, they have a simple structure, easy processing, low cost, and easy overhaul compared with general gears. They are also suitable for low-speed, heavy-duty mechanical transmission and for occasions with more dust, poor lubrication, etc. This paper introduces a novel slewing ring bearing with an external pinwheel gear set (e-PGS). First, we consider the exact cam pinion profile of the e-PGS with the introduction of a profile shift. Then, the contact stresses are investigated to determine the characteristics of the surface fatigue by varying the shape design parameters. The results show that the contact stresses of the e-PGS can be lowered significantly by increasing the profile shift coefficient.

• 한국철도학회논문집
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• 제9권5호
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• pp.618-623
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• 2006

Understanding the contact between wheel and rail is a starting point in railway vehicle dynamic research area and especially analysis for the contact geometry between wheel and rail is important. On the one hand, the critical speed as the natural characteristics of rolling-stock is generally tested on the roller rig. The geometrical characteristics of the wheel/roller contact on the roller rig are different from these of the general wheel/rail contact because the longitudinal radius of roller is not infinite compared with rail. Thus, in this paper we developed the algorithm to analyze the wheel/roller contact geometry of our roller rig which is constructed now and analyzed the difference between whee/roller contact and wheel/rail contact. In conclusion, we found that the yaw motion of wheelset and the roller radius influence the geometrical contact parameters in wheel flange contact area.

• Tribology and Lubricants
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• 제31권5호
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• pp.189-194
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• 2015

This paper focuses on the conformal contact problem. A typical example of conformal contact is the contact between a pin and hole. In particular, this paper focuses on the condition for assuming a contact stress field to be a Hertzian pressure profile by using well-known classical solutions associated with Hertzian contact. Persson first developed the conformal contact analysis method around half a century ago, but there have been no significant improvements since then. The present research also adopted this method, but developed new solutions from the viewpoint of application to structural design. The analysis began with a comparison between Persson°Øs conformal contact stress and the Hertzian stress fields. The next step was to check the differences in the normalized stress values of both. This study used the tolerance for the difference in the peak stresses of Persson°Øs solution and the Hertz solution to validate the Hertzian assumption. This gave the range for the difference in radii of the pin and hole when the contact force and mechanical properties of the material are specified. The results showed that, at a tolerance of 5%, the Hertzian assumption is valid if half of the contact angle is less than 35°ý. In addition, the Hertzian assumption holds even for a relatively long contact length, in contrast to the general incomplete contact problem. This paper discusses these results along with other aspects of the application to the design.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.389-390
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• 2006

The cycloidal reducer is one of the velocity controlling equipments in machinery. It has advantages of the higher reduction ratio, the higher accuracy, the easier adjustment of the transmission ratio and the smaller workspace than any other kinds of the reducers. This paper proposes a simple and exact approach for the lobe profile design of the two teeth difference cycloidal plate gear, which is different from the standard cycloidal reducer, by means of the principle of the instant velocity center in the general contact mechanism and the homogeneous coordinate transformation.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.177-180
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• 2004

The development of a tilting train with construction of electric line on the conventional railway is required for speed-up on the conventional railway with many curving sections. For development of tilting train, the study and development of the tilting system and tilting bogie having the different mechanism with a general high speed train will play a main role for improving the technology in the field of Korean railway The study and development of the pantograph tilting mechanism in order to keep a good contact behavior between a pantograph and a contact wire by tilting a pantograph on the opposite direction of the vehicle tilting direction. In this study, we analyzed the aerodynamic characteristic of a developing pantograph on the tilting train and obtained the contact force with catenary by aerodynamic lift force by the aerodynamic analysis. We also performed the numerical analysis for design the device controlling lift force on a pantograph. From the aerodynamic simulation and parameter study for a device to control the lift force, we will suggest the various shape and the optimal shape of it corresponding to a developing tilting pantograph. The Fluent software is used for the calculation of flow profile in this study.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.467-471
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• 2004

The development of a tilting train with construction of electric line on the conventional railway is required for speed-up on the conventional railway with many curving sections. For development of tilting train, the study and development of the tilting system and tilting bogie having the different mechanism with a general high speed train will play a main role for improving the technology in the field of Korean railway. The study and development of the pantograph tilting mechanism in order to keep a good contact behavior between a pantograph and a contact wire by tilting a pantograph on the opposite direction of the vehicle tilting direction. In this study, we analyzed the aerodynamic characteristic of a developing pantograph on the tilting train and obtained the contact force with catenary by aerodynamic lift force by the aerodynamic analysis. We also performed the numerical analysis for design the device controlling lift force on a pantograph. From the aerodynamic simulation and parameter study for a device to control the lift force, we will suggest the various shape and the optimal shape of it corresponding to a developing tilting pantograph. The Fluent software is used for the calculation of flow profile in this study.

• 대한수의학회지
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• 제35권4호
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• pp.843-851
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• 1995

To observe the effect of Demodex canis infection on the cellular immune response and hematological profile, 8 Doberman pinschers experimentally infected with D cains and 4 uninfected control dogs were sensitized with 2, 4-dinitro-chlorobenzene(DNCB) on the skin and were challenged with DNCB 14 days after the initial sensitization to elicit allergic contact dermatitis. Histological and hematological changes of these dogs were then observed. Macroscopic changes of skin challenged with DNCB in D canis-infected dogs included significantly reduced area of allergic reaction(p<0.05) than in uninfected control group. Infiltration of inflammatory cells in the D canis-infected group was also significantly reduced(p<0.05) than in the uninfected control group. These changes indicated that the cell-mediated immune response of the animals was suppressed by the infection with D canis. Total white blood cell count in dogs infected with D canis was increased when dogs were sensitized with DNCB (p<0.01). The result appeared to be caused by stress due to D canis infection, secondary bacterial infection and decreased efficacy of general body defense system. Blood eosionophils were increased in D canis-infected dogs which appreared to be caused by the allergic contact dermatitis. Blood chemistry analysis revealed that total protein and globulin were increased(p<0.05), while albumin level was decreased. This result appeared to be caused by secondary bacterial infection.

• 한국산학기술학회논문지
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• 제22권3호
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• pp.339-351
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• 2021

본 연구에서는 초, 중, 고 학생의 부모-자녀 간 대화 빈도에 대한 인식 차이에 따른 차별적인 특징을 갖는 유형을 탐색하고, 탐색된 유형에 따라 초, 중, 고 학생의 진로개발역량과 학업적 특성에 차이가 있는지 검증하였다. 이를 위해 초·중등 진로 교육 현황조사(2018) 자료를 활용하였으며, 잠재프로파일분석 방법을 사용하였다. 분석 결과, 초, 중, 고 학생의 부모-자녀 간 대화 빈도에 대한 인식 차이는 초등학생 6개 잠재계층(자녀 학교생활 대화 상, 자녀 상-부모 학교 생활 대화 상, 자녀 하-부모 하, 자녀 상-부모 상, 자녀-부모 학교생활 대화 상, 자녀 하-부모 중), 중학생 6개 잠재계층(자녀 하-부모 하, 자녀 중-부모 중, 자녀 상-부모 하, 자녀 상-부모 중상, 자녀 하-부모 상, 자녀 최상-부모 최상), 고등학생 7개 잠재계층(자녀-부모 학교생활 대화 상, 자녀 상-부모 하, 자녀 중-부모 중, 자녀 중-부모 상, 자녀 하-부모 하, 자녀 상-부모 중상, 자녀 최상-부모 최상)이 존재하는 것으로 확인되었다. 그리고 초, 중, 고 모두 잠재계층에 따라 진로개발역량(자기이해와 사회성, 직업이해, 진로탐색, 진로설계와준비도)과 학업적 특성(자율적 학습 동기, 자기주도학습)에 차이가 있는 것으로 나타났으며, 대체로 부모-자녀 모두 대화 빈도가 높다고 인식한 집단과 부모보다 자녀가 인식한 대화 빈도 수준이 높은 집단의 진로개발역량과 학업적 특성 점수가 높은 것으로 확인되었다. 본 연구는 초, 중, 고 학생은 부모와의 대화 빈도를 부모와 다르게 인식할 수 있으며, 이와 같은 인식의 차이가 진로개발역량과 학업적 특성에 영향을 미칠 수 있음을 시사한다.