• 설비공학논문집
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• 제14권5호
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• pp.365-376
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• 2002

An experimental study has been conducted to measure the local film-cooling effectiveness and the heat transfer coefficient for a single row of rectangular-shaped holes. four different cooling hole shapes such ai a straight rectangular hole, a rectangular hole with laterally expanded exit, a circular hole and a two-dimensional slot are tested. A technique using thermochromic liquid crystals determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. Both film cooling effectiveness and heat transfer coefficient are measured for various blowing rates and compared with the results of the cylindrical ho1es and the two-dimensional slot. The flow patterns downstream of holes are calculated numerically using a cummercial package. The results show that the rectangular hopes provide better peformance than the cylindrical holes. For the rectangular holes with expanded exit, the penetration is reduced significantly, and the higher and more uniform cooling Peformance is obtained even at relatively high blowing rates.

• 대한치과교정학회지
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• 제23권2호
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• pp.217-227
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• 1993

치아이동시 생역학을 고려한 frictionless system이 공간폐쇄를 위해 이상적이지만, 이는 숙달된 wire bending이 필요하며 잘못 계산된 교정장치를 사용하였을때 부작용이 매우 클 수 있다. 최근 Straight Wire Appliance가 도입 됨에 따라 복잡한 wire bending없이 "Elastic tie back"을 이용한 공간폐쇄가 가능하지만 alignment와 leveling을 위한 치료기간이 길고 friction과 binding으로 인해 이상적인 교정력을 적용시키는데 어려움이 있다. 그러나 교정환자 수가 많아지고 짧은 치료 기간이 요구되어지는 요즈음에 선택적으로 "Elastic tie back"을 이용하는 공간폐쇄는 부작용을 최소화 하면서 손쉽게 이용할 수 있는 교정장치라고 사료된다.

• 대한기계학회논문집A
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• 제24권7호
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• pp.1795-1800
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• 2000

One of the principal sources of vibration and noise in permanent magnetic machines is cogging torque, which is induced by interaction between the rotor poles and the stator teeth. For its analysis, using finite element analysis is very time consuming and the calculation of performance factors is extremely sensitive to the discretization. Especially, Maxwell stress tensor method is sensitive to the location of integral path. In this paper, a cogging permeance fuction is defined and replaced by the straight line. And it is assumed that the flux density acting on the stator's tooth side is the euqal to the flux density of the slot area. Using this definition and assumption, analytical calculation of cogging torque is presented and validated. And several reduction method is introduced.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권4호
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• pp.299-305
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• 2005

The work described in this paper is to investigate the additional iron losses and consequent temperatures in core ends of a turbo-generator wound with high voltage cables. Electromagnetic calculations are made with 3D FE models, which include the lamination material with anisotropic properties both in magnetic permeability and electric conductivity. The models also include the geometry of the stator teeth and eventually the axial steps designated to reduce the core end losses. The 3D model of the rotor consists of field windings with straight in-slot parts and end windings. The thermal models are simplified into two dimensions and include the heat sources dumped from the 3D electromagnetic solutions. The influences of power factor on additional iron losses are studied for this cable wound machine and conventional machines. The calculation results show that the additional iron losses can be reduced to about $15\%$ by introducing some small steps around the airgap corner of core ends.

• 대한치과교정학회지
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• 제28권5호
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• pp.731-740
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• 1998

이전의 preadjusted appliance 개발을 위한 치관경사도의 계측에 있어서는 교합평면을 계측기준으로 사용했는데, 교합평면은 Spee 만곡으로 인해 브라켓 부착점들을 연결하는 선(Andrews' plane)에 평행하지 않은 문제점이 있었다. 따라서 본 연구에서는 Spee 만곡에 영향받지 않으며, Andrews' plane에 보다 평행한 계측기준으로 각각의 구치의 근, 원심측 변연융선을 잇는 가상선을 설정하고, 이를 변연융선평면으로 명명하였다. 교합평면과 변연융선평면으로부터 각각 정상교합자의 구치부 치관경사도를 계측하여 비교한 결과 교합평면을 기준으로 한 치관경사도가 특히 상, 하악 제 1소구치(P<0.05) 및 제 2대구치(P<0.01)에서 Spee 만곡의 영향을 받음을 발견하였다. 구치부 치아들의 치관경사도는 Spee 만곡의 양에 따라 변해야만 인접치간 변연융선의 불일치가 생기지 않는다. 이전의 연구들에서는 다소의 Spee만곡을 갖는 정상교합자 표본에서 교합평면을 기준으로 계측한 치관경사도를 Spee 만곡이 없는 교합평면이 치료 목표의 일부인 bracket system에 적용하는 오류가 있었다. 이러한 치관경사도와 Spee 만곡 사이의 부조화는 Spee만곡이 straight wire에 의해 완전히 leveling되었을 때 변연융선 불일치를 초래할 수 있다. 이를 해결하기 위해서는 구치부 브라켓 slot이 변연융선평면에 평행하도록 브라켓 경사도를 결정하는 것이 추천된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.553-558
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• 2001

To find the effective combinations of blowing ratio and injection angle for a straight slot film cooling, film cooling characteristics was investigated using both flow visualization experiment and numerical simulation. Injection angles from $15^{\circ}\;to\;50^{\circ}$ and blowing ratios from 0.2 to 3.0 were selected for the simulation. Comparison between experimental and numerical results shows a good agreement, for the case of the injection angle of $30^{\circ}$ and blowing ratio ranging from 0.55 to 2.0. Film cooling effectiveness was found to be an increasing function of blowing ratio. The effects of injection angle became prominent as the blowing ratio increases. An interesting phenomenon was found for the injection angle of $15^{\circ}$ : the lowest film cooling effectiveness for the blowing ratio smaller than 1.0, but the highest film cooling effectiveness for the blowing ratio greater than 2.0 within wide range of downstream region. There exist optimum injection angles corresponding to maximum film cooling effectiveness : injection angle of $25^{\circ}$ for the blowing ratio from 0.2 to 2.0, and injection angle of $15^{\circ}$ for the blowing ratio of 3.0. Present study provides a design combination among film cooling effectiveness, blowing ratio, and injection angle.

• ETRI Journal
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• 제37권6호
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• pp.1220-1230
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• 2015

An autonomous valet parking (AVP) system is designed to locate a vacant parking space and park the vehicle in which it resides on behalf of the driver, once the driver has left the vehicle. In addition, the AVP is able to direct the vehicle to a location desired by the driver when requested. In this paper, for an AVP system, we introduce technology to recognize a parking space using image sensors. The proposed technology is mainly divided into three parts. First, spatial analysis is carried out using a height map that is based on dense motion stereo. Second, modelling of road markings is conducted using a probability map with a new salient-line feature extractor. Finally, parking space recognition is based on a Bayesian classifier. The experimental results show an execution time of up to 10 ms and a recognition rate of over 99%. Also, the performance and properties of the proposed technology were evaluated with a variety of data. Our algorithms, which are part of the proposed technology, are expected to apply to various research areas regarding autonomous vehicles, such as map generation, road marking recognition, localization, and environment recognition.

• 한국항공우주학회지
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• 제30권3호
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• pp.17-26
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• 2002

훈련기의 1/12 축소 날개반쪽 모델 및 1/16 축소 완제기 전체모델에 날개끝 불어내기 방향이 다른 3가지 슬롯(전방 35도 방향, 날개방향, 후방35도 방향)을 장착하고, 또한 3가지 불어내기 운동량 계수 (0. 004, 0.009, 0.017)의 변화를 받음각의 증가에 따라 양력과 항력의 공력특성의 변화를 비교하였고, 반쪽모델에서는 전체모델과 같은 방법으로 날개 윗면의 압력을 측정하여 기본형과 비교하였다. 실험결과 날개방향으로 불어내기를 하였을 경우와 불어내기 운동량 계수가 0.017인 경우가 가장 큰 항력감소와 양항비의 증가를 나타냈으며, 받음각 8도에서 가장 큰 항력감소율과 양항비 증가율이 있었음을 알 수 있었다.