• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1999년도 제29회 춘계학술대회
• /
• pp.225-231
• /
• 1999

A lubrication model on a two dimensional Reynolds equation is presented in this paper. And also this paper gives mathematical models of primary and secondary motion of piston skirt.

• 한국군사과학기술학회지
• /
• 제3권2호
• /
• pp.231-243
• /
• 2000

This paper describes a simulation of secondary motion of piston assemblies using PISDYN by Ricardo. Motions of the piston, pin, rod and skirt are separately calculated, by integrating equations of motion for individual components and dynamic degrees of freedom. The effects of engine speed at full load and pin offsets on the piston assembly secondary motions, forces and friction were investigated in parametric study for 4-cylinder gasoline engine. Results show that lateral displacement and friction loss of the piston increase as a function of engine speed. The lateral motion of the piston is affected by the change in pin offset. The minimum friction loss for the condition of 4800rpm WOT occurs at a pin offset of 1.6mm.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
• /
• pp.385-396
• /
• 2000

The secondary motion of piston occurs due to the transient forces and moments in the clearances between piston skirt and cylinder liner The motions are very related to the skirt profile and the magnitude of piston-pin offset. Above all, the elastic deformation is another major effect on the piston secondary motion that has not been considered in the previous researches. In this work, the effects of elastic deformation of the piston skirt on the secondary piston motion are studied for the frictional power loss by using commercial softares, PISDYN and ANSYS.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2000년도 제31회 춘계학술대회
• /
• pp.227-236
• /
• 2000

The secondary motion of piston greatly influences the dynamic and frictional performances of an engine. The motion is very related to the clearance, sliding velocity and skirt profile, etc. In our work, piston dynamics is analyzed with the commercial analysis software, PISDYN by Ricardo Consultant Engineers, Inc. The effects of profiles with piston pin offsets are studied regarding the secondary motion of piston and several results are compared.

• 대한기계학회논문집B
• /
• 제26권7호
• /
• pp.1014-1021
• /
• 2002

Analysis of two-dimensional secondary flows given by an oscillatory motion of a liquid with a free surface in a rectangular container subject to a linear reciprocating force is performed by numerical and experimental methods. FVM is used for the numerical computation of the two-dimensional flows. We considered the effects of the free-surface properties such as the surface tension and the dilatational viscosity. The boundary-layer analysis as well as an experiment is used in establishing the free surface properties. The secondary flow patterns are visualized by a laser sheet. It is shown that the secondary flow patterns predicted by the numerical methods are in good agreement with the experimental results.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
• /
• pp.401-404
• /
• 1991

In this paper, the controllers for the motion of the 2-joint manipulator design two stages: (1) a primary controller that under ideal conditions makes the end-effector track the desired trajectory: (2) a secondary controller that compensates for undesirable deviations of the motion from the disired trajectory caused by external and/or internal disturbances. The secondary contoller is applied to PID control algorithm. and the controllers is actually designed using IBM-PC/AT and 8096 single chip microprocessor.

• 한국과학교육학회지
• /
• 제24권6호
• /
• pp.1049-1062
• /
• 2004

이 연구에서는 물체의 운동에 대한 과학사적 변천을 아리스토텔레스 시대부터 뉴턴의 관점까지 다양하게 구분하고, 이를 토대로 설문지를 개발하였다. 설문지는 운동의 원인, 운동의 형태, 운동에서 보존되는 양의 개념을 포함하며, 이를 예비 중등 과학 교사들에게 투입하여 이들의 응답을 과학사적 관점으로 분석하였다. 연구 대상은 물리 교육을 전공하는 대학교 2학년생 20명과 다른 과학관련 교육을 전공하는 대학교 2학년생 34명이었다. 연구 결과, 물리교육을 전공하는 중등 예비교사들은 다른 과학관련 교육을 전공하는 예비교사들보다 운동의 원인이나 운동의 형태에 관련된 개념에서는 관성과 뉴턴의 힘 개념을 가지고 있는 비율이 높았다. 그러나 이들은 전공에 상관없이 운동에서 보존되는 양에 대한 개념을 알아보는 설문지에서 운동량을 속력에 비례하는 것으로 이해한 데카르트의 관점이나 운동 에너지가 보존된다는 호이겐스의 관점을 가지는 비율이 매우 높았으며, 상대적으로 운동량을 속도에 비례하는 것으로 이해하는 뉴턴의 관점을 가지고 있지 못하였다.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
• /
• pp.411-412
• /
• 2002

Piston-cylinder system are widely used in power engineering applications. In reciprocating refrigeration compressors, where extremely low friction losses are required, ringless pistons are being used to diminish the friction between piston rings and cylinder wall. Since the ringless piston has the freedom of lateral motion there is a potential danger that it will occasionally hit the cylinder wall while moving up and down along it's axis. A good design must therefore provide a smooth and stable reciprocating motion of the piston and ensure that the fluid film separating the piston from the cylinder wall is maintained all times. And the compromise between refrigerant gas leakage through the piston-cylinder clearance and the friction losses is required utilizing a dynamic analysis of the secondary motion for the high efficiency compressor. To this end, the computer program is developed for calculating the entire piston trajectory and the lubrication characteristics as functions of crank angle under compressor running conditions. The results explored the effects of some design parameters and operating conditions on the stability of the piston, the oil leakage, and friction losses.

• Archives of Reconstructive Microsurgery
• /
• 제9권1호
• /
• pp.80-87
• /
• 2000

Acute high speed accidents that results in full thickness skin defect and exposure of tendon, nerve, vessel and periosteum over denuded bone demands soft tissue coverage. Exposed bone often ensues chronic infection and requires free flap transplantation which surely covers defects in one stage operation and enhances transport of oxygen-rich blood and converts a non-osteogenic or partially osteogenic site into a highly osteogenic site, but exposed bone which had performed free flap transplantation sometimes necroses and needs secondary bone procedure. Scar contracture limits joint motion should be excised and covered with normal soft tissue to restore normal range of motion. Authors have performed the large latissimus dorsi myocutaneous free flap in 8 cases of extensive soft tissue defect and exposed bone lesion in the leg and 1 case of the flap was failed. The secondary ilizarov bone procedure was performed in 3 of 8 cases. 2 cases of large burn scar contracture and 1 case of posttraumatic scar contracture in lower extremity were restored with the large latissimus dorsi myocutaneous free flap. Authors concluded that large latissimus dorsi myocutaneous free flap is the most acceptable microvascular procedure in large soft tissue defect combined with exposed periosteum and bone requiring secondary bone procedure and in large burn scar contracture limiting knee joint motion.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제19권1호
• /
• pp.57-68
• /
• 2015

When a straight channel formed by two parallel porous plates, through which two immiscible liquids occupying different heights are flowing a secondary motion is set up. The motion is caused by moving the upper plate with a uniform velocity about an axis perpendicular to the plates. The solutions are exact solutions. Here we discuss the effect of suction parameter and the position of interface on the flow phenomena in case of Couette flow. The velocity distributions for the primary and secondary flows have been discussed and presented graphically. The skin-friction amplitude at the upper and lower plates has been discussed for various physical parameters.