• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.99-103
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• 2002

일반적인 통신 시스템의 소스 부호화기는 채널 잡음을 고려하지 않고 설계되며, 채널 부호화기는 소스 신호의 특성과 무관하게 채널 환경의 극복에만 중점을 두고 설계된다. 그러나 대역폭 제한적인 통신 환경에서 보다 효율적인 대역폭 사용을 위해서는 채널 환경에 따라 소스 부호율과 채널 부호율을 가변적으로 운용하여야 한다. 본 연구에서는 랜덤잡음 환경에서 동영상 신호를 전송함에 있어 채널 환경에 따라 한정된 채널 자원을 최적으로 할당하는 조인트 소스/채널 부호화 기법에 관하여 기술하였다. 소스 부호화로는 에러내성 기법을 적용한 MPEG-4 비디오 부호화기를 사용하였고, 채널 부호화는 RCPC 부호화기를 적용하였다. 본 논문에서는 여러 가지 채널상태(Es/No)에 따른 율-왜곡특성에 대해 분석하여 소스부호율과 채널부호율 간에 최적의 상충점(Trade-off point)을 결정하였고, 주어진 채널 상태에 대한 목표부호율과 평균제곱오차(Mean Squared Error)의 관계에 대해서 기술하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.25-25
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• 2004

이 논문에서 다루는 주제는 수동 기구부에 의해 자동으로 지면 적응이 가능한 이중 트랙 구조를 가진 ROBHAZ-DT3에 대한 설계 및 구성이다. 이 로봇은 기본적으로 군사용과 민간용으로 동시에 사용 가능하게 설계되어 있다. 이 로봇에 사용된 이중 트랙 구조는 앞쪽과 뒤쪽 트랙 사이에 수동적인 회전 조인트를 설치한 것으로 이 구조에 의해서 로봇의 트랙은 주행을 하면서 지면에 중력방향으로 순응하면서 형상이 변형되어 계단과 같은 험한 비평탄 지형에서도 높은 지형적응력을 보여주어 주행성능을 높여준다.(중략)

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.179-194
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• 2017

The segment lining design for shield tunnel is generally carried out by using the beam-spring model and the induced member forces from the model are strongly influenced by the components of the model such as imposed load, coefficient of subgrade reaction, location of segment joint and its stiffness. The structural models and stiffness of its connection part found used in abroad design cases is usually obtained as it is for the domestic design of segment of shield tunnel. Those models and stiffness in existing design cases are conventionally applied to a new tunnel design without any suitability review for the project. In this study, the application method of base components of the model such as the coefficient of subgrade reaction and modelling method to the segment lining design was suggested by carrying out the comparative study of the base elements for the member forces estimation of segment lining of shield tunnel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.107-114
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• 2017

A turbocharger is an engine supercharger that is driven by exhaust gas. It improves the output and fuel efficiency by increasing the charging efficiency of the mixture gas, which is achieved by changing the rotatory power of the turbine connected to the exhaust passage. It is important to control the supercharging for this purpose. A nozzle slide joint is one of the core parts. Austenitic stainless steel is currently used as the material for this part, and its excellent mechanical properties include high heat resistance and corrosion resistance. However, because of its poor machinability, there are many difficulties in producing products with complicated shapes. Machining is used in the production of nozzle slide joints for high dimensional accuracy after metal powder injection molding. As design variables in this study, we investigated the sintering temperature, product stress, deformation rate, radius of curvature of the punch, and angle of the chamfer punch, which are related to the strain and shapes. The goal is to suggest a forming process using Nitronic 60 that does not require machining to manufacture a nozzle slide joint for a turbocharger. Accordingly, we determined the best process environment using finite-element analysis, the signal-noise ratio, and the Taguchi method for experiment design. The relative density and hydrostatic pressure of the final product were in accordance with the results of the finite element analysis. Therefore, we conclude that the Taguchi method can be applied to the design process of metal powder injection molding.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.963-969
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• 2015

Bicycle is one of the most popular mode of transport due to the increase of interest in the well-being and environment pollution. Before fabricating a continuously variable transmission that is applied to the actual bicycle, for reducing the problems in the early stage, the reliable simulation program has been applied and the financial problem can be solved. In this paper, in order to confirm the design factor, the stress analysis has been applied. In all models, each link and the joint portion are assumed to be a major design factors, and impact of each link and joints received stress during the operation and it is confirmed by using the CAE. Also, for the analysis region, the special code has been developed to calculate pulsation phenomenon through appropriate mathematical modeling.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.1
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• pp.33-41
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• 2010

This study was aimed at the design of the dies for the unified pipe joint of the intermediate shaft using the computer simulation to shorten the period of production, on the basis of the process planning which was designed by the field experts. In the computer simulation, 'Deform-3d' and 'eesy-DieOpt' have been used, which are the commercial process analysis and die design program. Through the process analysis, we could know the propriety of the forming process, the inner pressure of the die and the suitable fitting pressure between the insert and the sleeve which was not showing any positive tangential stresses in the insert. Through the simulation of die design, we could know the number of the stress ring, the diameter ratios, the stresses of the die, the shrink fitting tolerance and temperature in the condition of the already determined maximum outer die diameter of the multi-stage former. The validity of the die design using the computer simulation was analyzed by the experiments and the results were satisfactory. As the results of this study, the new and easy die design system for multi-forging has been developed.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.3
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• pp.123-137
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• 1998

The finite deformation with self contact problem of C. V. joint boots is analysed by using the implicit finite element code ABAQUS/Standard. It is shown that analysis results have a good agreement with experimental ones to the degree of maximum rotation angle. As an application of design modification, the effects of thickness change of the rounded part of boot model on the bending and the contact situation of deformed geometry are investigated. In this paper, the effect of the design modification in the end on the leakage is examined using 2-D finite element simulation. To solve the leakage problem of grease, the length of the small end is enlarged. From this study, it is confirmed that we can save the cost and time by applying FEM techniques to analyze and design the boot model.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.582-588
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• 2011

This study was aimed at the design of the dies for the unified shaft joint using the computer simulation to shorten the period of production, on the basis of the process planning which was designed by the field experts. In the computer simulation, 'Deform-3d' and 'Eesy-DieOpt' have been used, which are the commercial process analysis and die design program. Through the process analysis, we could know the propriety of the forming process, the inner pressure of the die and the suitable fitting pressure between the insert and the sleeve which was not showing any positive tangential stresses in the insert. Through the simulation of die design, we could know the number of the stress ring, the diameter ratios, the stresses of the die, the shrink fitting tolerance and temperature in the condition of the already determined maximum outer die diameter of the multi-stage former. The validity of the die design using the computer simulation was analyzed by the experiments and the results were satisfactory. As the results of this study, the new and easy die design system for multi-forging has been developed.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.523-528
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• 2008

An open frame structure is fastened by bolt joints for strength and shock attenuation. Therefore the full finite element model of an open frame structure should be properly modeled including bolt joints for strength analysis of the frames and joint assemblies which are operated under multi-loading conditions such as driving, drop, inertia and torsional loads. Then the joints and frames must satisfy the specified allowable strength constraints. Because the full finite element model has a large number of elements to perform strength analysis, a detailed fine bolt analysis seems to be very expensive. Therefore bolts of the full finite element model are approximately modeled by constraints equations to constrain degree of freedoms between adjacent nodes. However, the constraints equation method can exaggerate stress results at the constrained nodes. Thus a detailed bolt analysis and a theoretical/experiential formula of bolts for a worst bolt joint are performed using reaction force applied both bolt and bolt joint. Finally, the results from the two methods are compared and discussed to verify the safety of the open frame structure.

• Journal of the KSME
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• v.28 no.2
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• pp.138-145
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• 1988

본 글에서는 로봇의 운동학적 및 동력학적 문제를 풀기 위한 기본적 이론과 그 적용례를 들었다. 운동학적 고찰은 로봇 링크의 위치와 방향을 설정하기 위한 동차변환에 근거하여 이루어졌고, 기준좌표계와 조인트 좌표계사이의 정변환과 역변환이 정운동학과 역운동학적 과정에서 고찰되 었다. 동력학적 과정에서는 로봇은 능동기구로 간주하여 운동방정식이 유도되었으며 이 유도 과정에서 운동학적 분석결과가 어떻게 사용되는가를 살펴보았다. 한편 유도된 운동방정식이 어떻게 활용되는가를 정동력학과 역동력학적 과정을 통하여 살펴보았으며 이러한 과정들은 로 봇의 설계, 모델링(simulation), 제어 등 연구에 기초이론으로 사용됨을 적용례를 통하여 보였고 일반적으로 정운동학, 역운동학, 역동력학, 정동력학의 순으로 전개됨이 합리적이라는 것을 인 지하였다.