• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.232-234
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• 2005

In this paper, A fuzzy logic based turn-off angle compensator for torque ripple reduction in a linear switched reluctance motor is proposed. The turn-off angle, as a complex function of motor speed and current, is automatically changed for a wide speed range to reduce torque ripple. Simulation results are presented that show ripple reduction when the turn-off angle compensator is used.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.613-615
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• 1995

KEPCO is now going on upgrading the highest system voltage from 345kV to 765kV since 1992. The main reason of this 765kV project is the bulk power transmission from the power generation sites at the East and West coasts to the Kyeong-in area. The first 765kV transmission lines will be constructed by 1998 and operated as 345kV level until 2001. This system needs a detailed evaluation of the 2nd arc in case of 765kV transmission line outages and the countermeasures for the fast arc reduction for the successful high speed reclosing. So, this paper deals with the simulation results of the 2nd arc characteristics using EMTP and comparison of Sh.R and HSGS for the reduction methods.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1616-1618
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• 2005

In this paper, A fuzzy logic based turn-off angle compensator for torque ripple reduction in a linear switched reluctance motor is proposed. The turn-off angle, as a complex function of motor speed and current, is automatically changed for a wide speed range to reduce torque ripple. Simulation results are presented that show ripple reduction when the him-off angle compensator is used.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.559-563
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• 2005

The wafer positioning robot used in the semiconductor industry is required to operate at high speed for the improvement of productivity. However, the residual vibration produced by the high speed of the wafer positioning robot makes the life of the robot shorter and the cycle time longer. In this study, the input shaping and the path of the system are designed for the reduction of the residual vibration and the optimization of the cycle time. The followings are the process for the reduction and the optimization; 1)System modeling of wafer positioning robot, 2)Verification of dynamic characteristic of wafer positioning robot, 3)Input shaping plan using impulse response reiteration, 4)Simulation test using simulink, 6)Analysis of result.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.121-129
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• 2005

In this paper, we consider a periodic preventive maintenance(PM) policy in which each PM reduces the hazard rate of amount proportional to the failure intensity, which increases since the last PM and slows down the wear-out speed to that of new one. And the proportion of reduction in hazard rate decreases with the number of PMs. Our model is similar to $ARI_1$ proposed by Doyen and Gaudoin(2004) in the sense of reduction of hazard rate. Our model has totally different wear-out pattern of hazard rate after PM's, however, and the proportion of reduction depends on the number of PM's. Assuming that the system undergoes only minimal repairs at failures between PM's, the expected cost rate per unit time is obtained. The optimal number N of PM and the optimal period x, which minimize the expected cost rate per unit time are discussed. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.471-475
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• 2001

Planetary Speed Reducer consists of a sun gear, a planetary gear and a ring gear and if one element is fixed at this Speed Reducer, another elements operate to become a drive-axis and a subordination-axis respectively. Planetary Speed Reducer is frequently used for gear Speed Reducer because it has the advantage of having the high efficiency and getting the high Speed Reducer ratio in small space. However, it is difficult to know the current transmitted torque immediately during the use of Speed Reducer and so complicated equipment is installed in addition to protect the overload of system. The object of this paper is to design the Speed Reducer of torque- meter type that can know the torque transmitted using the power transmission feature of a simple Planetary Speed Reducer fixed at ring gear.

• The Journal of the Korean dental association
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• v.47 no.7
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• pp.444-454
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• 2009

The purpose of this study was to compare the shaping abilities of LightSpeed, ProTaper-Universal, and hybrid technique using S-series of ProTaper-Universal and LigthSpeed. The 72 simulated root canals of J-shape were used and classified as flowing 3 groups according to the instrumentation methods; Group P of 24 canal blocks were prepared with ProTaper-Universal, Group L was prepared with LightSpeed, and Group H was prepared with hybrid technique (initial shaping with ProTaper-Universal SI and S2 and apical shaping with LightSpeed from #25 to #50). A second-year resident of Endodontic department prepared the resin block canals to apical size #50 (F5 in Group P). The time lapses for instrumentation and the reduction of root canal curvature after shaping were measured. The pre- and post-instrumented root canals were scanned and superimposed to evaluate and calculate the increased canal width and apical centering ratio. The results were as followings: Group Land H showed significant less instrumentation time than Group P (p < 0.05). The ProTaper system showed greater reduction of root canal curvature and working length diminishment than other methods (p < 0.05). LightSpeed system showed best canal curvature preserving characteristics. The Group P had greater instrumented widths at all levels examined (p < 0.05). Group L and Group H showed lower centering ratio (ability to preserve the canal center; the lower ratio means the better canal center preservation) than Group P (p < 0.05). Group H had the lowest centering ratio at the 1 mm level.

• International Journal of Highway Engineering
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• v.14 no.4
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• pp.103-111
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• 2012

PURPOSES : Effective speed management is necessary for preventing traffic crashes on the road. Speed hump is known as an effective tool for managing speed. Unlike existing studies which are mainly focused on humps for vehicles, this study proposed a novel method to determine design parameters for bicycle speed humps based on a multi-criteria decision making process. METHODS : Three objectives including the effectiveness of speed reduction, bicycle safety, and user's comfortability were incorporated into the proposed evaluation framework for determining design parameters. A multi-criteria value function was also derived and utilized as a part of the proposed method. RESULTS : Extensive simulations and statistical tests show that an integrated bike-box way is identified as the best in terms of operational efficiency and safety. CONCLUSIONS : It is expected that the outcomes of this study can be a valuable precursor for developing design guidelines for bicycle road and facility.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.961-964
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• 1997

In this paper, grinding characteristics of ultra high speed cylindrical plunge grinding was investigated by use of vitrified CBN wheel. From the experimental result, it was convinced that grinding power is decreased according to the increase of wheel and workpiece speed due to changing of grinding mechanism which decreases depth of cut and length of contact curve according to increment of wheel speed. And also, stock removal reduction of each gram lead to improvement of surface roughness by increasing the wheel speed.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1435-1440
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• 2008

High-speed train under development is a type of EMU(electric multiple units). Since power sources like motors and gears are distributed in the high-speed EMU, the high-speed EMU generates vibration and sound more than the articulated high-speed train. Vibration of vehicle, vibration between rails and wheels, hunting of bogie and snake motion reduce ride comfort. In this paper, to decrease the vibration of the articulated high-speed train, improvements were presented using an analytical model and a simulation model. The simulation model of the high-speed EMU was designed on the basis of the korean high-speed train and the design parameters for ride comfort were showed and the dynamic characteristics of the vehicle was understood. To consider the characteristics of the vehicle suspension, the analytical model was designed and the simulation model was verified with it.