• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1903-1908
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• 2008

This paper presents a characteristics of linear induction motor considering airgap variation for railway transit in order to achieve high performance of the vehicle. The operating principle of a LIM(Linear induction motor) is identical to a rotary induction motor. Space-time variant magnetic fields are generated by the primary part across the airgap and induce the electro-motive force(EMF) in the secondary part, a conducting sheet. This EMF generates the eddy currents, which interact with the airgap flux and so produce the thrust force known as Loren's force. Even though the operating principal is exactly same as a rotary motor, the linear motor has a finite length of the primary or secondary parts and it causes static and dynamic end-effect which is the discontinuous airgap flux phenomenon. This end-effect causes the deterioration of the system performance, especially in high-speed operation. Another problem is that construction tolerance restricts the minimum airgap in order to prevent a collision between the primary part and the secondary reaction plate. More over, as the airgap length is getting smaller, the attraction force between the primary part and secondary parts is getting larger dramatically and the attraction force would be another friction against propulsion. Therefore, it is necessary to figure out the characteristics of linear induction motor considering airgap variation in order to achieve high performance of the vehicle. The dynamic model of LIM taking into account end-effects is derived. Then the modified mechanical load equation considering the effect of the attraction and thrust force according to the airgap variation is analyzed. The simulation results are presented to show the effect of the LIM according to the airgap variation.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.279-282
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• 2008

The vertical forces in rail fasteners at areas of bridge transitions near the embankment and on the pier will occur due to different deformations of adjoining bridges caused by the trainloads. The up-lifting forces is not large problem in the blast track because the elasticity of blast and rail pad buffs up-lifting effect. But, it is likely to be difficult to ensure the serviceability of the railway and the safety of the fastener in the end in that concrete slab track consist of rail, fastener, and track in a single body, delivering directly the up-lifting force to the fastener if the deck is bended because of the end rotation of the overhang due to the vertical load. When the up-lifting force exceeds the clamp force of the fastener clip, the rail pad is out of fastener, which makes decrease the serviceability of the railway, such as noise and vibration. Furthermore, it is possible to reduce the safety of the track as the longitudinal resistance. This study is focused on guideline suggestion to decrease up-lifting force in the fastener adjacent to the civil joint of slab track of bridge throughout the parametric analysis between the vertical spring stiffness of the fastener as the material approach, the space of fastener adjacent to bridge transition, the rigidity of the girder as the geometrical approach and up-lifting force under the train load.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2001년도 가을 학술발표논문집 Vol.28 No.2 (3)
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• pp.754-756
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• 2001

현재 인터넷 사용자의 증가와 더불어 사용자들이 원하는 서비스가 다양해짐에 따라 기존의 Best effort 서비스로는 사용자들이 요구하는 응용 서비스들을 제대로 지원할 수가 없게되었고, 이에 IETF(Internet Engineering Task Force)애서는 사용들의 QoS 제공을 위해 Integrated service model과 Differential service model이 제안되었다. 그러나 소규모 망에서 적용 가능한 Intserv와 대규모 망에서 사용적절한 Diffserv망의 service 방식이 다르기 때문에 End-to-End간에 QoS 제공을 위해서는 이에 대한 망의 연동이 필요하다. 본 논문에서는 두 망간의 연동을 위한 Framework을 제안하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.23-27
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• 1990

This paper proposes the calculation method of the needed thrust force and the input current which are considered the end effect and the normal force effect of SLIM for the propulsion vehicles. To estaninate theperformance of SLIM, the thrust force, the normal force, the efficiency and the power factor are comput ed according to the variation of frequency and pole pitch.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.833-837
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• 2000

The purpose of this study is an evaluation of end mills to develop appropriate tools for the high speed machining. First of all, several flat end mills which are produced by different makers are selected to analyze the performances of the tools. Experimental works are also executed to measure cutting force, tool wear and surface roughness for different cutting conditions. And then the results are compared and analyzed for developing optimal cutting tool in the high speed condition. Especially, analysis about tool wear is introduced in this research.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.125-128
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• 1997

They use a Ball End-mill in order to manufacturing sculptured surface when making metal mold, mold, cars and aircraft. In the work of a Ball End-mill case, customers do not often satisfied with manufacturing precision. Eventually, they have to re-work for the purpose of meeting manufacturing precision. There are resulted in lots of loss, whereby, in terms of both time and costs. The reasons of tolerance reducing manufacturing precision are thermal strain, the surface is damaged because of increasing cutting force and tool wear, tool deflection etc.. We focus on, however, manufacturing precision caused due to deflection of tool.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.347-350
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• 2003

Many researches on the prediction of cutting forces of ball-end mil is have been achieved since before several decades ago. These kinds of researches have been concentrated on the study on how to make the prediction equations for the cutting forces based on 2-D cutting experimentation. The results of them were really good and impressive. But it's not proper to practical uses for industrial fields, because if sculptured surface were to be machined, then it would be very difficult to understand the complicated kinematical interaction between the sculptured surface and the flutes of a ball-end mill. So, we propose the method for solving these kind of problems using existed commercial CAD/CAM software; Unigraphics. Furthermore, the modification of tool path which is done off line is offered to increase the precision of cutting.

• 한국안전학회지
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• 제13권1호
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• pp.3-12
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• 1998

On the stability of the cantilever beam subjected to a follower force at the free end, the influences of the translational spring and the moment of inertia of a tip mass at the free end have been studied by numerical methods. The centroid of a tip mass is offset from the free end of a Beam and is located along its extended axis to vary the value of moment of inertia of a tip mass. It is proved that as the constants of a spring supporting the free end are augmented, the critical flutter loads of the above system decrease, whereas they increase without a tip mass.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.422-427
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• 2004

The tool geometry parameters and cutting process have complex relationships. Until now, various cutting test were needed to acquire optimal design of end mill for the purpose of high speed machining, due to the insufficient knowledge about cutting process in high speed machining. Using various tools with different geometry, relationships between tool geometry parameter (rake angle, clearance angle, length of cutter) and cutting process (cutting force, surface accuracy, surface roughness) have been studied. Acquired data can be used to design optimal tool for high speed machining and to develop a software for design of end mill geometry.

• 한국정밀공학회지
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• 제12권10호
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• pp.149-156
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• 1995

This paper presents a method of detecting chatter vibration in end-mill process. The detecting system consists of an adaptive signal processing scheme which uses an autore- gressive time-series model and a neural network is proposed and is verified its effectiveness by using acceleration and cutting force signals recorded during slotting in end-mill operations. Expeerimental results indicate that the proposed system provides excellent detection when chatter is occured within the ranges of cutting conditions considered in this study and an effectiveness of the integration of signals is confirmed.