• Aerospace Industry
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• v.83
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• pp.45-45
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• 2004

이륙을 준비하는 비행기의 프로펠러가 점차 빠른 속도로 회전한다. 물론 매우 빠른 속도로 회전하고 있기 때문에 또렷하게 보이지는 않지만, 어찌된 일인지 프로펠러는 갑자기 반대방향으로 천천히 돌기 시작한다. 누구나 한번쯤은 TV나 영화에서 이러한 광경을 보고 의문을 가져보았을 것이다. 확언하건대, 프로펠러가 역회전을 하는 것은 절대로 아니다. 그렇다면 잔상과 같은 눈의착각일까? 상황에 따라서 차이가 있겠지만 이 경우에는 눈의 착각이 정답은 아니다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1127-1132
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• 2007

Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.277-278
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• 2009

본 논문에서는 스테핑모터의 정 역회전 시간에 따른 속도제어 구동드라이버를 제안하였다. 모터의 속도와 위치를 단순연산으로 처리하여 가격 절감 효과를 가지고 왔으며, 각상의 제어 펄스폭을 측정하여 구동드라이버의 특성을 분석하였다.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.227-233
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• 2010

This paper treats the method to build up Motor drive-circuit using semi-conduct control part like power transistor, MOSEFT and refers to the operation theory, forward, reverse rotation control and speed control method which is changed by PWM. And also, this paper mention to the basic principle of DC Motor and various Motor control method using micro-processor.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.27-33
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• 2004

In this paper, we present a carrier recovery circuit using the polarity-decision algorithm that recovers a phase and a frequency error simultaneously. The proposed algorithm catches a frequency error based on a differential of an angular velocity of the signal constellations. Using the differential of a phase error may compensate the frequency error. The symbol prediction method in the proposed algorithm accumulates the symbols, which makes easy to calculate a phase differential. The hardware size of the algerian is small since we use Q data or I only to get phase information. As a result, the algerian shows a pull-in range of normalized frequency error 0.5 under AWGN 15dB.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.45-50
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• 1998

In recent year, inverters and cycloconverters system are widely used for fed induction motor drives. Motor drives by cycloconverter is possible to frequency have been directly changed without AC/DC converter, so that circuits is simpler than inverter. A aims of this paper is the control strategy and hardware design for vector control system by cycloconverter fed induction motor drives. In this paper, Algorithm of vector control is derivlid from the model of controlled current source-fed induction motor. Vector control system is implemented using these algorithm and a pulse width controled cycloconverter using a SCR. Cycloconverter of vector control system is controlled by pulse width of SCR's trigger signal. pulse width is controlled primary command current $li_1l$ and frequency TEX>$\omega_1$..

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.198-203
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• 2019

An adhesive wireless bookbinding machine was designed with optimal motor control and automatic cover insertion for bookbinding. The noise level was improved by modifying the thrust of the machine and changing from a compressor method to an AC induction motor control method. The automatic cover insertion function was added to improve the task speed. Motor and decelerator damage can be caused by sudden braking and acceleration of the motor rotation (clockwise and counter-clockwise), so a buffer-type locational control system was developed to secure stable movement and durability. The complicated internal design was also simplified, and the volume and weight were decreased. The results show that the noise was decreased by 57% from 135 dB to 71.7 dB, and the task speed was decreased by 57% from 18 s to 9.58 s. The automatic cover insertion was designed to supply a maximum of 130 sheets per supply.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.07a
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• pp.195-201
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• 2002

입고ㆍ예냉ㆍ출고까지 전 공정을 자동화하고 진공압력을 작물의 품온에 따라 능동적으로 제어할 수 있고 진공챔버내에 콜드트랩을 설치하여 냉각효율을 향상시킨 진공예냉장치를 개발하여 고랭지 배추와 느타리버섯, 상추를 대상으로 예냉성능을 평가하고 예냉이 이들 작물에 미치는 영향을 분석하였다. 가. 새로 개발된 진공식 예냉장치는 공급컨베이어, 좌우 자동 슬라이딩 문, 이송컨베이어, 진공챔버, 진공펌프 콜드트랩, 냉동기로 구성되어 있다. 팔레트를 공급컨베이어에 올려놓고 작동을 시작하면, 입구문이 열리고 팔레트가 진공챔버내로 이송되면, 진공펌프에 의해 진공챔버내의 압력을 떨어뜨리고, 콜드트랩과 냉동기가 작동되어 예냉이 시작된다. 예냉이 완료되면 출구문이 열리고 이송컨베이어가 역회전하여 밖으로 배출되도록 되어있다. 나. 제작된 예냉장치의 예냉성능을 평가하기 위하여 느타리버섯, 고랭지 배추, 상추를 대상으로 냉각속도, 냉각균일도, 예냉후 저장중 품질변화시험을 실시하였다. 다. 시험결과 냉각소요시간은 느타리버섯의 경우 초기품온 15.2$^{\circ}C$에서 $1.5^{\circ}C$까지 냉각시키는데 24분, 고랭지배추는 13.5$^{\circ}C$에서 3.7$^{\circ}C$까지 냉각시키는데 18분, 상추는 13.4$^{\circ}C$에서 2.$0^{\circ}C$까지 냉각시키는데 24분 소요되었다. 평균냉각속도는 느타리버섯이 34.3$^{\circ}C$/h, 고랭지배추 32.6$^{\circ}C$/h, 상추 28.5$^{\circ}C$/h로 나타났다. 라. 또한 각층간의 냉각균일도를 알아보기 위하여 포장상자내에서 표면 품온과 내부품온변화를 조사한 결과 차이가 거의 없어 균일한 냉각이 가능하였다.생기 양단의 온도차는 높게 나타났고, 재생기 양단의 압력 차는 낮게 나타났다. 재생기 축열재로서 철망-철선을 사용할 경우 철선-철망 ø1.2-150이 전열 표면적은 작으나 재생기 양단의 온도차가 가장 큰 것으로 나타났으며 재생기 양단의 압력 차는 가장 낮게 나타나 공시 철망- 철선 혼합 축열재중 가장 우수함을 알 수 있다. 4. 철망사이에 철선을 삽입한 축열재의 경우, 철망사이에 삽입한 철선의 직경이 큰 것이 철선의 직경이 작은 것보다 재생기의 양단의 온도차가 높게 나타났고 재생기 양단의 압력차는 작게 나타났다. 그러므로 철망사이에 철선을 삽입한 것 중 성능이 우수한 것은 150-ø2. 0-150으로 나타났다. 5. 실험한 재생기 축열재들 중에서 성능이 우수한 것들을 비교한 결과, 복합 철선 ø1.2-1 50이 가장 성능이 좋은 것으로 나타났다.적외선.열풍 복합건조방법이 높게 나타나 이것은 곡물 표면에 원적외선 방사에의한 복사열이 전달되어 열장해를 받았기 때문으로 판단되며, 금후 더 연구하여 적정 열풍온도 및 방사체 크기를 구명해야 할 것이다.으로 보여진다 따라서 옻나무 유래 F는 포유동물의 생식기능에 중요하게 작용하는 것으로 사료된다.된다.정량 분석한 결과이다. 시편의 조성은 33.6 at% U, 66.4 at% O의 결과를 얻었다. 산화물 핵연료의 표면 관찰 및 정량 분석 시험시 시편 표면을 전도성 물질로 증착시키지 않고, Silver Paint 에 시편을 접착하는 방법으로도 만족한 시험 결과를 얻을 수 있었다.째, 회복기 중에 일어나는 입자들의 유입은 자기폭풍의 지속시간을 연장시키는 경향을 보이며 큰 자기폭풍일수록 현저했다. 주상에서 관측된 이러한 특성은 서브스톰 확장기 활동이 자기폭풍의 발달과 밀접한 관계가 있음을 시사한다.se that were all low in two aspects, named "the Nonsignificant group". And th

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.77-87
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• 2008

This study is to formulate strategy for subject who are selected as national team in horizontal bars event in apparatus gymnastics. For this, skill training program was applied to players for 8 weeks. Then it was analyzed by using 3D motion Analysis system to seek the difference between before and after using the program. There were decisive demerit element K's first try for Tkatchev stretched movement from low elevation and crooked body while elevating. Not only, the location of his center of mass is far and low and there was some concern in his landing due to bended his hip-joint, but also, it exposed weak point in retro-action followed technique. Thus, to overcome that weak point, the subject repeated practices on following; when preparing for Tkatchev stretched movement at downward for big spin, make sure extend shoulder angle faster, make sure Tap movement is short and concise using hip-joint angular while delaying Tap timing for folding the body, and moreover, while backlashing the body, used shoulder joint angle wide to pull up the body. As a result, the speed of vertical upward did rut increase when separation from the bar. However, height of elevation increased that the leg would rut hit the horizontal bar even straight up the hip-joint. Therefore, the movement itself provided magnificent motion and even helped decrease the demerits.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.1
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• pp.57-66
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• 2012

The purpose of this study was to evaluate the relation between intentionally induced internal stress and cyclic fatigue failure of ProTaper Universal. ProTaper Universal (Dentsply Maillefer) S1, S2, F1, F2, F3, F4 and F5 (25 mm length) were used in this study. To give the internal stress, the ProTaper Universal were put into the .02 taper Endo-Training-Bloc (Dentsply Maillefer) until auto-stop by torque controlled motor. The rotation speed was 300 rpm and torque value was 1.0 Ncm. ProTaper Universal were grouped by the induced number of internal stress and randomly distributed among one control group and three experimental groups (n=10). The four groups were Stress 0 (control), Stress 1, Stress 2 and Stress 3. These instruments were rotated until separation. For cyclic fatigue measurement, inclined plane was used and time for separation was recorded. It was statistically analyzed using two-way ANOVA and Duncan post-hoc test at 95% confidential level. In all ProTaper Universal, there was statistically significant decrease on time for separation in Stress 3. In F2 and F3, there were statistically significant difference between control group and all experimental groups. And in F4 and F5, Stress 2 and 3 groups showed significantly lower cyclic fatigue resistance from Stress 0 group. In the limitation of this study, cyclic fatigue failure of ProTaper Universal is influenced by accumulated internal stress.