• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.6
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• pp.855-859
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• 2014

Quality criteria for interaction between a pantograph and overhead contact wire is a most important requirement to assess of the performance for the current collection system. Interaction performance between pantograph and catenary system is subject to approval by the infrastructure manager when a new design and contraction of overhead contact line and pantograph are installed. Among the various performance, percentage of arcing at maximum line speed is a simple test method compared with contact force of pantograph due to direct sensing of pantagraph, calibrations, installations of train, and etc. On the other hand, percentage of arcing is need to reliable arcing detector and general requirements with accordance with EN 50317. In this paper, percentage of arcing are investigated on the function of duration of arc and proposed which is satiable of percentage of arcing. As a results, we proposed which duration of arcs are unsuitable from infrastructures point of view as performance testing for quality of current collection.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.17 no.1
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• pp.249-258
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• 1987

The purpose of this article was to determine the amount of cranio-facial asymmetry in normal subject before the analysis of the cranio-facial asymmetry as the result of internal derangement in T.M.J. dysfunction. The author has conducted analysis using Cephalometric P-A reviews of 54 males and 51 females. Following the Grayson's method of measurement, the standard value of cranio-facial asymmetry in normal subject was obtained. The following results were obtained: 1. Compared with right and left width, asymmetry could be identified in normal subject, although the degree of the difference appears to be small. 2. In male, asymmetric value of contact point of the upper central incisors is 0.76±0.84㎜ that of the lower central incisors is 0.86±0.86㎜, and that of center of genial tubercle is 0.87±1.06㎜. In female, asymmetric value of contact point of the upper central incisors is 1.03±1.29㎜, that of lower incisors is 1.11 ±1.18㎜, and that of center of genial tubercle is 1.45±2.15㎜. 3. Cranio-facial saymmetry in female is somewhat greater than that of male.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.293-298
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• 2001

In this paper, film thickness and temperature distribution are measured in EHL point contact at high roll/slip ratios. Infrared temperature mapping with two band pass filters, proposed by Ausherman (1976), is used to measure temperature distribution. And the optical interferometric method with two filters (red and green filters) is used to measure film thickness. Result of experiment showed that temperature rising at film and ball surface occurred very dramatically in Dimple zone. As slip velocity, roll/slip ratio and load increased, size of Dimple and temperature rising became more large. In addition, position and shape of Dimple were changed by roll/slip ratios, and increasing of Dimple size decreased traction coefficient. In short, it is appointed that the Dimple phenomenon be developed by the effect of viscosity wedge.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.129-136
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• 2004

Anisotropic characteristics of deformation are important to understand the particular behavior in the pre-failure state of soils. Recent experiments shows that cross-anisotropic moduli of granular soils can be expressed by functions of normal stresses in the corresponding directions, which is closely linked to micromechanical characteristics of particles. Granular soils are composed of a number of particles so that the force-displacement relationship at each contact point governs the macroscopic stress-strain relationship. Therefore, the micromechanical approach in which the deformation of granular soils is regarded as a mutual interaction between particle contacts is one of the best ways to investigate the anisotropic deformation of soils. In this study, a numerical program based on the theory of micromechanics is developed. Modified Hertz-Mindlin model is adopted to represent the force-displacement relationship in each contact point for the realistic prediction of anisotropic moduli. To evaluate the model parameters, a set of analytical solutions of anisotropic moduli is derived in the isotropic stress condition. By comparing the analytical solutions with exact values, we confirm that the analytical solutions can be utilized to evaluate model parameters within the acceptable range of error of 10%.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.7
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• pp.653-658
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• 2016

As this paper is related to the relay and its driving control method, it explains about the relay which connects or interrupts the DC high voltage battery's power to drive the electric car's inverter. The paper suggests a sub-relay which prevents strong sparks from relay's contact point when the relay connects to the DC high voltage battery and also compensates for the increasing internal resistance value that is caused by deterioration at contact point. The relay's rated power is approximately 10KW and the relay's electric property has been verified through electrical instantaneous power short test, etc.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.479-484
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• 1996

This paper describes a method of measuring tilt motion. This method measures the tilt motion of drilling machines using a laser interferometer, a simple sliding linear bearing, measurement of the probe and the LSC(least square center) method. The next order of business is discussing the procedure of measurement. First, The measured position is considered to be the point of contact between the drill shank and the probe. The revolution of the drill axis delivers the point of contact to the probe. Second, because the laser interferometer is attached on the sliding linear bearing, any movement of probe influences laser reflector. Thus, the laser program displays the moving factor of laser reflector. Namely, this is tilt factor. Third. the points of measurement are a full circle which has 8 points (each are 45$^{\circ}$), After it is finished measuring the 8 points, let the spindle of the drilling machine move down about 5 cm. Repeating this procedure three times, we can get tilt motion's values which are calculated by LSC method. Many error factors affect the accurate measurement of tilt motion. However in this paper we ignore some error factors because they are less significant than tilt motion.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.47-55
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• 2009

In this study, a robot foot having toes for firm stepping on uneven surface is proposed. The toes are connected to the lower leg by parallel links so that the lower leg can rotate in the rolling and pitching directions during stance phase without ankle joint. The landing performance of the foot on uneven surface was evaluated by relative comparison with that of the most common foot making point contact with the walking surface, since the test conditions considering real uneven surface could be hardly defined for its objective evaluation. Anti-slip margin(ASM) was defined in this study to express the slip resistance of a robot foot when it lands on a projection with half circular-, triangular- or rectangular cross section, assuming that uneven surface consists of projections having these kind of cross sections in different sizes. Based on the ASM analysis, the slip conditions for the two feet were experimentally confirmed. The results showed that the slip resistance of the new foot is not only higher than that of the conventional point contact type foot but also less sensitive to the surface friction coefficient.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.252-252
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• 2011

최근 주목받고 있는 amorphous gallium-indium-zinc-oxide (a-GIZO) thin film transistors (TFTs)는 수소가 첨가된 비정질 실리콘 TFT에 비해 높은 이동도와 뛰어난 전기적, 광학적 특성에 의해 큰 주목을 받고 있다. 또한 넓은 밴드갭을 가지므로 가시광 영역에서 투명한 특성을 보이고, 플라스틱 기판 위에서 구부러지는 성질에 의해 플랫 패널 디스플레이나 능동 유기 발광소자 (AM-OLED), 투명 디스플레이에 응용되고 있다. 뿐만 아니라, 일반적인 Poly-Si TFT는 자체적으로 가지는 결정성에 의해 대면적화 시 균일성이 좋지 못하지만 GIZO는 비정질상 이기 때문에 백플레인의 대면적화에 유리하다는 장점이 있다. 이러한 TFT를 제작하기 전, 전기적 특성에 대한 정보를 얻거나 예측하는 것이 중요한데, 이에 따라 고안된 구조가 바로 metal point contact FET (pseudo FET)이다. pseudo FET은 소스/드레인 전극을 따로 증착할 필요 없이 채널을 증착한 후, 프로브 탐침을 채널의 표면에 적당한 압력으로 접촉시켜 전하를 공급하는 소스와 드레인처럼 동작시킬 수 있다. 따라서 소스/드레인을 증착하거나 lithography와 같은 추가적인 공정을 요구하지 않아 소자의 특성을 보다 간단하고 수월하게 분석할 수 있다는 장점이 있다. 본 연구에서는 p-type 기판위에 100nm의 oxidation SiO2를 게이트 절연막으로 사용하는 a-GIZO pseudo FET를 제작하였다. 소자 제작 후, 열처리 온도에 따른 전기적 특성을 분석하였고, 열처리 조건은 30분간 N2 분위기에서 실시하였다. 열처리 후 전기적 특성 분성 결과, 450oC에서 가장 낮은 subthreshold swing 값과 게이트 전압의 더블 스윕 후 문턱 전압의 변화가 거의 없음을 확인하였다.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.222-227
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• 2001

This paper introduces the spring-mounted odometer system which maintains the correct contact with the pipe wall and measures the distance along the pipe. The odometer wheel is designed to keep contact to the pipelines inner wall and to generate fifty rectangular pulses per one turn(l59.5681mm) during pigging. The pipeline has the defects in various types such as buckles, winkles, cracks, dents, welding point and so on. Specially, girth welding points which exist each 12m of the pipeline, much affects the operational environment of the odometer. The measurement error of the distance along the pipe is accumulated, for the measurement error of wheel's circumference and the pipeline inner environment. So, this paper proposes the method for the error compensation based on the analysis of the odometer's behavior around the girth welding point of pipe. The experimental results show that developed odometer system can be used for the intelligent pig with good performances.

• Journal of Sensor Science and Technology
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• v.18 no.3
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• pp.185-189
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• 2009

In this paper, we present design and analysis of the omni-directional linear piezoelectric actuator which was consisted of one actuator using the half-wave vibrator. Through calculating vibration speeds on each sector of the actuator, the displacement of contact point of the actuator is theoretically confirmed to be about 33 nm. To confirm an applicable possibility of omni-directional linear piezoelectric actuator, elliptical motion for linear movement, displacement of the tip, changing directions and admittance characteristics are simulated by ATILA. Compared with theoretical result, we obtained similar data with displacement of 32.5 nm at contact point. And then the actuator is simulated elliptical trajectories for linear motions and changing directions according to combination of input signal.