• Design & Manufacturing
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• v.2 no.1
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• pp.33-38
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• 2008

As consumer in optics, electronics, aerospace and electronics industry grow, the demand for ultra precision aspherical surface lens increases higher. Precision turning with single-diamond tools has a long history of development for fabrication of optical quality surfaces since the advent of aerostatic rotary spindles and precise linear motion guide ways. To enhance the precision and productivity of ultra precision aspherical surface micro lens, the following specification of ultra precision grinding system is required: the highest rotational speed of the grinder is 100,000rpm and its turning accuracy is $0.1{\mu}m$, positioning accuracy is $0.1{\mu}m$. The development process of the grinding system for the ultra precision aspherical surface micro lens for optoelectronics industry is introduced. In the work reported in this paper, an intelligent grinding system for ultra precision aspherical surface machining was designed by considering the factors affecting the surface roughness and profiles accuracy. An aerostatic form was adopted to build the spindle of the workpiece and the spindle of grinder and ultra precision LM guide way was adopted in this system. And this paper deals with mirror grinding of an aspheric surface micro lens by resin bonded diamond wheel and spherical lens of BK7. It results was that a form accuracy of $0.6{\mu}m$ P-V and a surface roughness of $0.006{\mu}m$ Rmax.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1211-1222
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• 2011

It is necessary to use prestressed modal analysis to calculate the modal frequencies and mode shapes of a prestressed structure such as a spinning blade, a preloaded structure, or a thermally deformed pipe, because the prestress effect sometimes causes significant changes in the frequencies and mode shapes. When the finite element model under consideration has a very large number of degrees of freedom, repeated prestressed modal analyses for investigating the prestress effects might become too computationally expensive to finish within a reasonable design-process time. To alleviate these computational difficulties, a Krylov subspace-based model order reduction, which reduces the number of degrees of freedom of the original finite element model and speeds up the necessary prestressed modal analysis with the reduced order models (ROMs), is presented. The numerical process for the moment-matching model reduction is performed directly on the full order models (FOMs) (modeled in ANSYS) by the Arnoldi process. To demonstrate the advantages of this approach for performing prestressed modal analysis, the prestressed wheel and the compressor impeller under their high-speed rotation are considered as examples.

• Journal of the Korean Society for Nondestructive Testing
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• v.37 no.1
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• pp.29-36
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• 2017

Recently, KTX (Korean Train Express) train stoppage accidents were mainly caused by malfunctioning equipment, aging and cracking of railway vehicles, crack breakages of brake disks, and breakages of brake disks. Breakage of brake disk can cause large-scale casualties such as high-speed collision and concern about derailment by hitting lower axle and wheel. Therefore, in this study, a brake disk with solid and ventilation type, which is the brake disk of a KTX train was modeled, and a dynamometer system was constructed to operate the disk. A Rayleigh wave was used to inspect the surface of the brake disk. An ultrasonic inspection module was developed for the brake disk by using a local immersion method due to the difficulty involved in ultrasonic inspection using an existing immersion method. In addition, the surface defects of the brake disk were evaluated using a dynamometer mock-up system and an ultrasonic inspection module of the brake disk.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.19-23
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• 2009

This paper focuses on vehicle fuel economy improvement using D-Range neutral control of automatic transmission. The system objected to reducing of fuel consumption during idle. Usually, turbine of conventional auto transmission is mechanically linked to wheel during idling condition. Therefore speed ratio of torque converter is zero for that period. This causes needless power loss by the torque converter slip. To improve this inefficiency automobile makers develops electronically-controlled D-range neutral control system. The D-range neutral control system minimizes slip on the torque converter by shifting gear to a neutral position during vehicle stoped with D-range gear position. However there's insufficient study about the effect of D-range neutral control system on vehicle fuel economy. In this paper, researches are performed on effect of D-range neutral control system on vehicle fuel economy by experiment with two different vehicle. And it is also estimated the effect on vehicle fuel economy using computer simulation. As a result, 1.8% of LA-4 mode fuel economy improvement can be achieved in a vehicle by D-range neutral control system.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.223-233
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• 2017

The railway turnout system is one of the most important systems that set train routes. Turnout system integrity should be guaranteed for robust train operation. To diagnose the turnout system status, LVDT and accelerometers are installed on a turnout system in a high speed line. The LVDT and accelerometers produce signals containing physical meaning of the turnout systems. The LVDT produces the displacement of the rail gauge and vibration when point moving or a train passes on turnout systems and the accelerometer produces impact forces induced by wheel sets. We performed data extraction from the measured signals and parameterized the extracted signals into meaningful quantities. The parameters are used for classifying whether the turnout status is normal. We proposed two methods for the classification, one uses probabilistic distribution and the other artificial neuron networks. The probabilistic distribution is used for the parameter being classified by the quantities and the artificial neuron networks for the form classification. Finally, we show how to learn the normal status of a turnout system.

• 연구논문집
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• s.30
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• pp.101-110
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• 2000

Weft insertion mechanism is for completing the structure of yarn and weft yarn and its driving method is screw type. In the high speed rapier loom, weft yarn is thrown by insert rapier and carrier rapier into the shed which make divide two parts of upper part ant lower part for warp yarn. It is possible for this mechannism to reduce the size of rapier and wheel, and directly connected to the main shaft without gear belt. Therefore, exact rapier motion through realization of arbitrary acceleration diagram requested rapier and optimal design for high speedization and operating rate increasing are necessary. In this study, with a view to exact system analysis for understanding of overall trace and high speedization of rapier loom through computer simulation. we report not only deduction of displacement, velocity, and acceleration components of rapier for analysis theory establishment, of weft insertion mechanism and exact motion induction according to screw rotation, but also development of simulation program for realization these on the monitor.

• Journal of Korean Society for Geospatial Information Science
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• v.3 no.2 s.6
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• pp.213-220
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• 1995

Map Matching is the method for correcting the current position from dead reckoning in Car Navigation System. In this paper, we proposed the new map matching algorithm that can correct the positioning error caused by sensors and digital map data around the cross road area. To do this, first we set the error boundary of the cross road area by combining the relative error of moving distance and the absolute error of road length, second, we find out the starting point of turning within the determined error boundary of the cross point area, third, we compare the turning angle of the car to the angle of each possible road, and the last, we decide the matched road. We used wheel sensor as a speed sensor and used optical fiber gyro as a directional sensor, and assembled the sensors to the notebook computer. We testified our algorithm by driving the Daejeon area-which is a part of south Korea-as a test area. And we proved the efficiency by doing that.

• Bulletin of the Society of Naval Architects of Korea
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• v.9 no.2
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• pp.43-48
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• 1972

Inertia friction welding, a relatively recent innovation in the art of joining materials, is a forge-welding process that releases kinetic energy stored in the flywheel as frictional heat when two parts are rubbed together under the right conditions. In a comparatively short time, the process has become a reliable method for joining ferrous, and dissimilar metals. The process is based on thrusting one part, attached to a flywheel and rotating at a relatively high speed, against a stationary part. The contacting surfaces, heated to plastic temperatures, are forged together to produce a reliable, high-strength weld. Welds are made with little or no workpiece preparation and without filler metal or fluxes. However, In order to obtain a good weld, the determination of the optimum weld parameters is an important problem. Especially, because the amount of the flywheel mass will be determined according to the initial rotating velocity values at the constant thrust load, the initial rotating velocity is an important factor to affect a weld character of the inertia-welded IN713C-SAE8630, which is used for the wheel-shafts of turbine rotors or turbochargers, exhausting valves, etc. In this paper, the effects of initial rotational velocity on a weld character of inertia-welded IN713C-SAE8630 was studied through considerations of weld parameters determination, micro-structural observations and tensile tests. The results are as the following: 1) As initial rotating velocity was reduced to 267 FPM, cracks and carbide stringers were completely eliminated in the micro-structure of welded zone. 2) As initial rotating velocity was reduced and flywheel mass was increased correspondingly, the maximum welding temperatures were decreased and the plastic working in the weld zone was increased. 3) As initial rotating velocity was progressively decreased and carbides were decreased, the tensile strengths were increased. 4) And also the fracture location moved out of the weld zone and the tensile tests produced, the failures only in the cast superalloy IN713C which do not extend into the weld area. 5) The proper initial rotating velocity could be determined as about 250 thru 350 FPM for the better weld character.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1716-1721
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• 2005

Conventionally, 2WS is used for vehicle sleeting, which can only steering front wheel. In case of trying to high speed slalom or emergency through this kind of vehicle equipped 2WS, it may occur much of side slip angle. On the other hand, 4WS makes decreasing of side slip angle, outstandingly, so it is possible to support vehicle movement stable. And conventional ABS and TCS can only possible control the longitudinal movement of braking equipment and drive which can only availab to control of longitudinal direction. There after new braking system ESP was developed, which controls both of longitudinal and lateral, with adding of the function of controlling Active Yaw Moment. On this paper, we show about not only designing of improed braking and steering system through establishing of the integrated control system design of 4WS and ESP but also designing of the system contribute to precautious for advanced vehicle stability problem.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.87-94
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• 2006

Estimating moving vehicle loads is important in modeling design loads for bridge design and construction. The paper proposes a moving force identification algorithm using moment influence lines measured at multi-axes. Density estimation function was applied to estimate more than two wheel loads when estimated load values fluctuated severely. The algorithm has been examined through simulation studies on a simple-span plate-girder bridge. Influences of measurement noise and error in velocity on the identification results were investigated in the simulation study. Also, laboratory experiments were carried out to examine the algorithm. The load identification capability was dependent on the type and speed of moving loads, but the developed algorithm could identify loads within 10% error in maximum.