• 한국정밀공학회지
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• 제30권7호
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• pp.694-701
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• 2013

The gear-reduction units of Korean high-speed trains consist of a motor reduction unit, an axle gear box reduction unit, and a tripod joint shaft. A reduction gear unit is a gearbox used to reduce the rotational speed of the input shaft to a slower rotational speed on the output shaft. This reduction in output speed helps to increase torque. Defective reduction gear units in high-speed trains are caused by damage to the gear or by gear fatigue. To diagnose potential problems, it is important to know the vibration characteristics of the reduction gear units. In this study, we analyzed the vibration characteristics of reduction gears under various conditions. The test setup included a full-scale test rig to evaluate reduction gear under both normal and extreme operating conditions.

• 전기학회논문지
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• 제65권4호
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• pp.533-538
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• 2016

In a power grid that has a high penetration of wind power, the highly-fluctuating output power of wind turbine generators (WTGs) adversely impacts the power quality in terms of the system frequency. This paper proposes a power smoothing scheme of a variable-speed WTG that can smooth its fluctuating output power caused by varying wind speeds, thereby improving system frequency regulation. To achieve this, an additional loop relying on the frequency deviation that operates in association with the maximum power point tracking control loop, is proposed; its control gain is modified with the rotor speed. For a low rotor speed, to ensure the stable operation of a WTG, the gain is set to be proportional to the square of the rotor speed. For a high rotor speed, to improve the power smoothing capability, the control gain is set to be proportional to the cube of the rotor speed. The performance of the proposed scheme is investigated under varying wind speeds for the IEEE 14-bus system using an EMTP-RV simulator. The simulation results indicate that the proposed scheme can mitigate the output power fluctuation of WTGs caused by varying wind speeds by adjusting the control gain depending on the rotor speed, thereby supporting system frequency regulation.

• 반도체디스플레이기술학회지
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• 제16권2호
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• pp.49-54
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• 2017

In this paper, recent researches on new and renewable energy have been conducted due to problems such as energy exhaustion and environmental pollution, and new researches on high efficiency and high speed switching are needed. Therefore, we compared the efficiency by using high speed switching devices instead of IGBT which can't be used in high speed switching. The experiment was performed theoretically by applying the same parameters of the high speed switching devices which are the Cool MOS of Infineon Co., SiC C3M of Cree, and GaN FET device of Transform, by implementing the DC-DC boost converter and measuring the actual efficiency for output power and frequency. As a result, the GaN FET showed good efficiency at all switching frequency and output power.

• 인터넷정보학회논문지
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• 제9권2호
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• pp.15-23
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• 2008

본 논문에서는 고효율을 유지하며 QoS를 보장하는 새로운 구조의 다중 입출력 버퍼링 방식의 스위치와 이 스위치에서 사용되는 새로운 중재 알고리즘인 Anti-Empty 알고리즘을 제안한다. 새로운 스위치 구조는 MIQ와 MOQ를 기본으로 하여 외부회선 속도와 동일한 속도를 가지는 버퍼를 사용하는 구조로 설계되었으며 기존 방식의 단점을 제거하고 QoS를 지원하기 위해 MOQ의 동작 방법에 새로운 방식을 도입하였다. 이로서 스위치 전체의 수율과 지연 등의 성능이 고 효율의 출력 버퍼형 스위치와 동일하면서 셀 손실이 없는 QoS를 지원하는 고속 스위칭을 보장한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.883-884
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• 2004

High-speed IC for time-division multiplexing (TDM) optical transmission systems have been designed and fabricated by using InP heterojunction-bipolar-transistor (HBT) technology. The driver IC was developed for driving external modulators, featuring differential outputs and the operation speed up to 10 Gbps with an output voltage swing of 1.3 Vpp at each output which was the limit of the measurement. Because -3 dB frequency was 20GHz, this circuit will be operated up to 20Gbps. 1.3Vpp differential output was achieved by switching 50 mA into a 50 $\Omega$ load. The power dissipation of the driver IC was 1W using a single supply voltage of -3.5Y. Input md output return loss of the IC were better than 10 dB and 15 dB, respectively, from DC to 20GHz. The chip size of fabricated IC was $1.7{\Box}1.2 mm^{2}$.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1271-1278
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• 2010

High-speed traction has voltage source variation because the electric power of tractions is supplied by difference traction power system according to operating section. This paper proposes the robust control maintaining constant output performance against voltage source variation for PWM converters of the high speed traction. The proposed scheme consists of feed-forward compensation for current controller by on-line calculating the rms voltage of voltage source. Total dynamic performance of high speed traction can be improved by the reduction of the output voltage ripple which is resulted from voltage source sag and variation. The superior performance and validity of the proposed scheme is proved through the simulation.

• Journal of Electrical Engineering and Technology
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• 제6권5호
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• pp.640-646
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• 2011

The current study presents the design and performance of a novel 4/2 switched reluctance motor (SRM) for a high-speed air blower. With a comparative study of some rotor structures for a high-speed drive, a stepper-type rotor is optimized to produce a continuous torque and a low torque ripple. Rotor pole arc is modified to have a wide continuous output torque region, and air gap is determined to develop less torque ripple. The rotor radius is determined to reduce torque ripple with a reiterative FEM analysis. The designed rotor has three regions: short uniform, long uniform, and nonuniform air-gap region. The positive torque region is wider than a conventional 4/2 SRM without any torque dead zone. A prototype is tested and the efficiency is up to 72[%] at 30,000[rpm], 600[w] output.

• 한국레이저가공학회지
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• 제2권2호
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• pp.42-51
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• 1999

This study has been performed to investigate into some effects of the output power and traverse speed of laser beam on the microstructures, hardness and fatigue resistance of the ductile iron surface-hardened by $CO_2$ laser defocussed beam. Optical micrographs have shown that with increasing the output power and decreasing the traverse speed, the martensite was coarsened and some retained austenite were appeared in ductile iron. The microstructures of hardening zone were composed of bull's eye and some nodular graphite dissolved structures by the effect of self quenching. Fatigue fracture characteristics of ductile iron have appeared in the high stress and low stress ranges. The fracture initiated at nodular graphites in the surface hardened layer due to the stress concentration caused by a notch effect. The interior graphite nodules were broken away or popped out during crack propagation. Fatigue test has shown that values of fatigue strength considerably increased with increasing output power at a given traverse speed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.328-330
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• 1994

The Ultrasonic motor(USM) has many good characteristics such as high torque at low speed range, large holding torque based upon frictional force, high speed response, flexible free ferns, compactness in size, low magnetic noise and silentness in motion. Because of having low speed rotation, USM is good as an actuator of a small size direct drive (DD) manipulator. The acturators for the DD manipulators must have good controllability on the speed and torque from zero to maximum value continuously. New method was developed for speed and torque control by the phase difference control of the two-phase driving signals of the motor. Then rule adjustable compliant and dumped motion was realized on the output shaft of the motor by PD control of the output shaft angle.

• International Journal of Advanced Culture Technology
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• 제10권3호
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• pp.332-338
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• 2022

The article presents a concept of designing a Multiplexer circuit which acts as a "Selector" and that becomes capable to select different speed created at different TTL Gate configurations; Standard TTL(Normal Speed), High Speed TTL(High Speed), Schottky TTL(Super High Speed) and further connect the selected Gate speed to the CAR shape created using C-Programming at Computer Graphics and finally CAR shape display at different speed to the color TV. The Multiplexer supporting efficient and more reliable selection criteria using "Logical based selection criteria" and further the output from multiplexer is provided to CAR shape created using c-programming and finally CAR shape is display to color TV system. Basic purposes and assumptions regarding the design and development of this system as well as a description of its operation have been presented.