• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1994-1999
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• 2003

This paper discusses dynamic characteristics of motion of a pair of multi-degrees of freedom robot fingers executing grasp of a rigid object and controlling its orientation with the aid of rolling contacts. In particular, the discussions are focused on a problem of gain-tuning of sensory feedback signals proposed from the viewpoint of sensorymotor coordination, which consist of a feedforward term, a feedback term for controlling rotational moment of the object, and another term for controlling its rotational angle. It is found through computer simulations of the overall fingersobject dynamics subject to rolling contact constraints that some dynamic characteristics of torque-angular velocity relation may play an important role likely as reported by experimental results in muscle physiology and therefore selection of damping gains in angular velocity feedback depending on the guess of object mass is crucial. Finally, a guidance of gain-tuning in each feedback term is suggested and its validity is discussed by various computer simulations.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.816-822
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• 2010

A comprehensive review for the selection of urban rail vehicle systems that best suit Gimpo railway line is taking place with consideration of the project area characteristics in light of line planning, passenger demand, supply of rolling stock, and railway construction and operation. Various aspects of vehicle systems including passenger demand on concerned lines, regional characteristics, vehicle types, and railway construction and operational settings should be taken into consideration. In addition, request for the introduction of customized vehicle systems reflecting the convenience of transit users such as wide and hospitable inner space, low noise, flexible operation of 2 to 4 car train-set and eye catching slim bridge piers is increasing. A study on alternatives to place an order to opt for optimum rolling stock systems considering line characteristics of Gimpo City's urban railway and future passenger demand while meeting the needs of Gimpo City has been conducted.

• Journal of the Korean Society of Clothing and Textiles
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• v.10 no.3
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• pp.27-36
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• 1986

The purpose of this study was, to estimate the detergency of commercial detergent and to examine the interrelationship between detergency and detergent characteristics, detergent concentration, fiber characteristics, and Rolling-up phenomenon which is the major removal mechanism of oily soil. A mixture of oleic acid-olive oil was used as oily soil. The detergency was estimated by analysis of oleic acid on cotton ana polyester fabrics before and after washing by means of liquid scintillation counting. The Rolling-up of oily soil from PET film was observed and change of contact angle and removal time were measured. The results were as follows ; 1. In the case of soaps and powder synthetic detergents, the optimum concentrations we-re about $0.2\~0.3\%$. And detergencies of liquid synthetic detergents were considerably low, and the detergency was continually increased up with increasing concentration to $0.5\%$, which seemed to be caused by the lower pH than that of soap and powder synthetic deter-gent solutions. 2. As the effect of external or internal fiber structure; the detergency of cotton was lower than that of polyester. 3. In the observation of Rolling-up, the contact angle increased and the Rolling-up time became shorter with increasing detergent concentrations ($0.05\~0.5\%$). And it was confirmed that detergency was increased with Rolling-up effect. In addition, the study on the actual laundry condition was studied using the questionaire. From the results, about $76\%$ of households used the concentration of detergent roughly or excessively and housewives were highly concerned on the recommended dose, but grade of practice were very low.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.971-978
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• 2016

Recent trends in miniaturization and lightness in portable electronics parts have driven developments in subminiature screws. This study aims to investigate the thread rolling process of a subminiature screw with an outer diameter and pitch of 1.0 and 0.25 mm, respectively. Finite element (FE) analyses were performed for the thread rolling process of symmetric and asymmetric screw threads. Through FE analyses, various process parameters, such as the horizontal and vertical die gap and the rolling stroke, were investigated in terms of the forming accuracy. The material flow characteristics in the thread rolling process of the symmetric and asymmetric screws were also discussed, and the relevant process parameters were determined accordingly. These simulation results were then reflected on real thread rolling processes, from which the symmetric and asymmetric screws could be formed successfully with allowable dimensional accuracy.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.376-385
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• 1991

For manufacturing trimming-free plates which have rectangular shaped edges and straight edges in as-rolled state, it is necessary to investigate rolling characteristics of overlap, bulge and width deviation etc. in a standardized plate rolling process. The present wok is for preventing edge overlap as the first approach to develop trimming-free plate rolling technique. An experimental study on overlap control was done with plasticine material in order to examine influence factors and find a control method by use of a laboratory mill scaled down to one tenth of actual production mill. It was found that edge overlapping was increased with the increase of slab thickness and of broadside rolling ratio, but decreased with the increase of chamfered amount on slab edges. In the simulated rolling experiment with edge chamfered slabs of various chamfered angles, the chamfered angle of 60.deg. was the most effective one for reducing overlapping irrespective of slab thickness and of broadside rolling ratio.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.554-570
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• 1990

he rolling contact behaviors between a smooth ball and a flat rough surface under dynamic load are intricately affected by many factors, such as the diameter of a ball, normal load and the roughness of a flat surface etc. Accordingly, the experimental study is done to find them on the base of elastic hysteresis loss as theoretical approach is very difficult. The experimental apparatus composed of damped-free vibration system is used. This paper investigates the damping characteristics on the rolling contact area through rolling friction force and logarithmic decrement versus displacement obtained in accordance with the variations of those factors, and presents a new experimental method to find out contact width using the relations of logarithmic decrement and rolling friction force with displacement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.393-397
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• 2005

Since the braking system of rolling stock is directly linked to it's safety, ensuring reliability of braking system and evaluation of performance of it are very important. To develope the performance of braking system, it is required advanced technology and gradually various factors in the field test result. This study is designed to analyze the air pressure control about braking force in rolling stock, also, by comparing braking force of high speed railway with that of high speed train. This paper suggests to establish a method of computation of braking force form the air pressure control. And The high speed train researches into patterns of braking system such as the train of speed up and introduction of electric and pneumatic braking system.

• Transactions of Materials Processing
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• v.24 no.3
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• pp.161-166
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• 2015

The finite element method has been widely used in the analysis of ring rolling. For ring rolling it requires a high computational expense due to the non-steady state material flow characteristics of the process. The high computational expense causes the finite element analysis to be impractical for industrial applications. In the current study, we aim to develop a practical implicit finite element modeling method for ring rolling. This method uses a step-wise steady state assumption and is called the “Stepped method”. The stepped method divides the whole process time of unsteady-state flow model into a finite number of steady-state models. It then solves the process at several specific time steps until convergence is reached. In order to confirm the performance and validity of the newly proposed stepped method, the result from the stepped method were compared to the results from a Lagrangian finite element method and to results from experiments reported in the literature.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.616-621
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• 2003

MIG or TIG welding has been the most popular welding process for joining aluminum alloy structures. However, porosity, hot crack and distortion were serious problems in inert gas fusion welding. Since FSW(Friction Stir Welding) was invented by TWI in 1991, it has been the powerful candidate for solving the problems of inert gas welding. In this paper, the principle and characteristics of FSW is introduced and its application to rolling stocks is presented to make basis for future development in production technology of aluminum rolling Stocks.

• Tribology and Lubricants
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• v.13 no.1
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• pp.62-69
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• 1997

Rapid increase of refrigeration and air-conditioning systems 9r & a systems) in modern industries brings attention to the urgency of research & development as a core technology in the area. And it is required to the compatibility problem of r & a systems to alternative refrigerant for the protection of environment. The, it is requested to study the lubrication characteristics of refrigerant compressor which is the core technology in the r & a systems. The study of lubrication characteristics in the critical sliding component is essential for the design of refrigerant compressor. Therefore, theoretical investigation of the lubrication characteristics of rotary compressor for r & a systems is studied. The newton-Raphson method is used for the EHL analysis between vane and rolling piston in the rotary compressor. The results show that the rotational speed of a shaft and the discharge pressure influence significantly the friction force between vane and rolling piston. This results give important basic data for the further lubrication analysis and design of a rotary compressor.