• 정보저장시스템학회논문집
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• 제1권1호
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• pp.34-41
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• 2005

We report some recent results in the rewritable Blu-ray Disc with enhanced overwrite cyclability by using the growth dominant eutectic based Ge(Sb70Te30)+Sb recording layer, GeN interface layer and write strategy optimization. We have developed phase-change optical media with appropriate write strategy for 36(i.e., 1X)-72Mbps(i.e., 2X) dual speed Blu-ray Disc system and fur the future high speed optical data storage. For recording layer, eutectic-based Ge(Sb70Te30)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so called Time-Shifted Multipulse (TSMP) write strategy where starting position of multipulse parts are shined from reference clock. With this write strategy, the jitter characteristics of the disc was improved and we found that leading edge jitter was improved much more than trailing edge jitter in 1X-2X speed recording. Finally, we investigated the higher speed feasibility of 144Mbps(i.e., 4X) by adopting some elemental doping to the eutectic based Ag-In-Sb-Te recording layer and structural optimization of constitution layers in Blu-ray Disc. In the paper, we report the effect of Sn addition for the feasibility of higher speed recording. The addition of Sn shows increases of the crystallization speed of phase change recording layer.

• 한국유체기계학회 논문집
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• 제14권1호
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• pp.11-17
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• 2011

The numerical study was conducted to investigate the pump performance due to impeller related parameters change in centrifugal pump of very low specific speed by using CFD code. A small centrifugal pump whose specific speed is $N_s=76.2$ was used, and the performance characteristics were discussed for different number of vanes, rotational speed, and the length and height of vane. The numerical results at a very low specific speed show that the increase of the number of vanes has little effect on improvement of output pressure but results in the reduction of pressure fluctuation, and that the head increases with the increase in the rotational speed. The decreasing the length of vane has a considerable reduction of the capacity coefficient in comparison with decreasing the height of vane.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권10호
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• pp.634-640
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• 2004

In this paper, the control strategy for high speed operation in light rail transit system is proposed. Recently, the vector control strategy is used to get high capacity control characteristic in low speed area. But Six step mode that is one pulse mode is used in high speed region to use DC link voltage to the maximum. Therefore, in high speed area, the vector control can not be used but scalar control method is used. To get a driving performance to be stabilized, the method of smooth mode change between the low speed and high speed area and PWM control is desired. So this paper proposes the control strategy using vector control include the one pulse mode. And also proposes overmodulation method that makes to change in one pulse mode softly. The performance of traction system will be verified by simulation results using MATLAB and experimental results.

• Journal of the Korean Data and Information Science Society
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• 제20권5호
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• pp.797-807
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• 2009

후미추돌사고가 발생하면 사고의 규모인 차량손상정도와 승차자 상해는 속도변화에 영향을 받는다. 본 연구는 서울, 인천 지역에서 발생한 실제 사고사례자료로부터 사진판독에 의해 손상깊이를 측정하고 사고개황 및 속도에 관한 진술 자료로부터 속도변화를 산출하였으며, 진단기간, 입원일 등 상해발생관련 자료를 수집하였다. 손상깊이와 승차자의 상해.무상해의 유무 및 증상기간의 예측평가를 위한 손상깊이와 입원치료기간에 대한 관계영역도표를 구하여 실증적인 자료와 비교하였다. 또한, 수집한 실제 사고자료의 진단기간 및 입원일 등 상해정도는 통계분석결과 객관적 충격정도인 피추돌차의 손상깊이 및 속도변화와 전혀 상관관계가 없는 것으로 나타났는데, 이는 선행연구와 본 연구의 통계분석결과를 종합하여 설정한 상해역치에 미달하는 대인사고 사례가 약 78.1%로 거짓 또는 과장된 상해주장이 많은 것으로 나타났다. 향후 상해주장에 대한 인정은 사고 규모에 대한 객관적 정보의 제공 및 본 연구에서 제시한 상해역치 수준의 적용은 유용할 것으로 사료된다.

• 한국정밀공학회지
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• 제21권1호
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• pp.133-139
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• 2004

High speed machining (HSM) can reduce machining time with the high metal removal rate by high speed spindle and feedrate. This paper supports HSM technology using the small size tool with the optimal tool path generation and modification of tool change. The optimum tool path is generated to reduce cutting length of cavity pattern and change the cutting tool for preventing the tool breakage by wear. The tool path is modified with the experiment data of tool wear and breakage to support tool change on reasonable time. The result can contribute to HSM technology of high hardness materials using the small size end-mill.

• 대한기계학회논문집B
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• 제28권9호
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• pp.1042-1050
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• 2004

Theoretical study has been conducted to clarify pressure characteristics of KTX(Korea Train eXpress) in tunnel. The severe pressure change in tunnel may give rise to the ear-discomfort for passenger and fatigue for car body. The external and internal pressure of rolling stock have been measured by using the running test with atmospheric pressure sensors and portable data acquisition system in high speed train. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. We found that there are similar patterns of external pressure change for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity. And, the patterns of pressure wave in tunnel are classified into eight groups.

• 유공압시스템학회논문집
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• 제8권1호
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• pp.1-9
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• 2011

The main design factors which effect on operating speed of linear actuator for valve operation are mass of plunger, electromagnetic motive force, inductance, and return spring, and these factors are not independent but related with each other in view point of design and electromagnetic theory. It is impossible to increase the operating speed by only change the value of any one design factor. The change of any one value results in change of any value related it in various design factors. This paper presents a speed increasing method of linear actuator using a solenoid design method by some governing equations which are composed of electromagnetic theory and empirical knowledge and permanent magnets as assistant material, and proved the propriety by experiments.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1655-1660
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• 2004

Theoretical study has been conducted to clarify pressure characteristics of KTX(Korea Train eXpress) in tunnel. The external and internal pressure of rolling stock have been measured by using the atmospheric pressure sensors and portable data acquisition system on Seoul-Busan high speed railroad line. These pressure change may give rise to the ear-discomfort for passenger and fatigue for car body. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. From the results of experiment, the pattern of pressure change generally agrees to RTRI's experimental result for Shinkansen. We found that there are similar patterns of external pressure variation for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity.

• 동력기계공학회지
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• 제10권4호
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• pp.181-186
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• 2006

In this paper, a noncontact type torque meter using silicone rubber to measure the exact torque value and reduce a vibration and a noise, was developed. When planetary gear speed reducer runs, torque, RPM etc.. of motor change according to load or speed change. So, it needs a device to detect load's change or to diagnose the state of thewhole drive department by monitoring these result values. The noncontact type torque meter using silicone rubber that we're trying to develop this time is low-cost and can measure RPM and torque value simply. Also, it caculate a power using this value and indicate them on screen.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.799-804
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• 2005

In this work, the characteristics of train performance of Korean rubber-tired AGT system(K-AGT) are evaluated by using TPS(Train Performance Simulation) and these results are compared to those of other LRT(Light Rail Transit) systems. The performance characteristics of K-AGT was analyzed by comparing the scheduled speed and the energy consumption in case of station interval change and rail track condition change in, the scheduled construction line. In the scheduled construction line, scheduled speed of K-AGT was no difference with other systems and energy consumption was less than other LRT's. In case station intervals are increased, scheduled speed of K-AGT shows similar increasing rate and in curved and graded track conditions K-AGT has no difference in scheduled speed with other systems. As a simulation result by track condition change, when the track which is smaller than curved line of 250m dominates more than $50\%$ in whole track, K-AGT is similar to other systems to the point of scheduled speed and there is advantage in energy consumption.