보조 동력 장치 연료 공급용 서보밸브의 토크모터 전자기 해석

장세명,장강원,정헌술,이동호,Chang, Se-Myong,Jang, Gang-Won,Jeong, Heon-Sul,Rhee, Dong-Ho 항공우주시스템공학회 2007 항공우주시스템공학회지 Vol.1 No.3

As a main part of an utility helicopter, the APU(Auxiliary Power Unit) has a solenoid valve system operated with a torque motor, which controls the flow rate in the fuel supply system. In this paper, we solved the Maxwell potential equations to analyze the electromagnetic force in the torque motor, and some additional analytic methods are used to compute the quantity of torque produced by the torque motor for the given circuit current. For the convenience, small displacement is assumed, and only magneto-static problem is considered for the two-dimensional cross section. The result will be compared with the three-dimensional analysis that will be studied in the near future.

앞이 무딘 물체에서 반사되는 약한 충격파

장세명,장근식,Chang, Se-Myong,Chang, Keun-Shik 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.7

Investigated In this paper is the shock reflection from a blunt body, In particular, a circular cylinder of 20 mm diameter, for the weak shock impinging in the range 1<$M_s$ <2. Pressure and shock speed are measured for various shock strengths. Double-pulse holographic interferograms are taken to study the unsteady flow field at $M_s=1.34$. These experimental results are, in overall, well compared with the unstructured adaptive finite volume computation of the Euler equations performed in this study. Correlation of incident and reflected shocks and shock-shock locus obtained by experiment, computation, and theory are presented in parallel.

농작물을 위한 드론 분무 농약 살포의 3차원 분석에 관한 연구

문인식(In Sik Moon),권현진(Hyun Jin Kown),김미현(Mi Hyeon Kim),장세명(Se Myong Chang),나인호(In Ho Ra),김흥태(Heung Tae Kim) 한국스마트미디어학회 2020 스마트미디어저널 Vol.9 No.4

농작물들의 크기와 형태는 매우 다양하며 생육 환경도 각기 다르다. 따라서 드론을 활용하여 농약을 살포할 때에는 각 농작물에 대한 재배 환경과 특성이 고려되어야 하며, 이에 따라 드론의 비행고도, 전진속도 등 비행 조건이 달라져야 한다. 실제로 비행 조건에 따라 농약의 액적 유동이 크게 영향을 받게 되며, 살포 영역에 큰 변화가 발생하고 이로 인해 불균일한 액적 분포가 후류에 형성되어 농약의 전달 효율성이 떨어질 수 있을 뿐만 아니라 비산에 대한 위험성이 존재하게 된다. 본 논문에서는 농업용 드론을 사용하여 특성이 다른 3가지 농작물을 선정하고 드론의 비행 조건을 각각 다르게 하여 농약을 살포했을 때 후류에서의 노즐 유동을 수치해석을 통하여 분석하였으며, 전달되는 액체의 비율을 확률 밀도 함수의 평균 제곱근을 나눈 새로운 성능지수를 이용하여 비교함으로써 작물의 특성에 따른 드론의 농약 살포 가이드라인을 구축하고자 한다. The size and shape of crops are diverse, and the growing environment is also different. Therefore, when one uses a drone to spray pesticides, the characteristics of each crop must be considered, and flight conditions such as the flight height and forwarding velocity of the drone should be changed. The droplet flow of pesticides is affected by various flight conditions, and a large change occurs in the sprayed area. As a result, an uneven distribution of liquid may be formed at the wake, and the transport efficiency will be decreased as well as there would be a risk of toxic scatter. Therefore, this paper analyzes the degree of distribution of pesticides to the crops through numerical analysis when pesticide is sprayed onto the selected three crops with different characteristics by using agricultural drones with different flight conditions. On the purpose of establishing a guideline for spraying pesticides using a drone in accordance with the characteristics of crops, this paper compares the amount of pesticides distributed in the crops at the wake of nozzle flow using the figure of merit, and the sum of transported liquid rate divided by the root mean square of the probability density function.

뼈 나이 진단을 위한 관심 영역 인식 심층 합성곱 신경망

김민정(Min-Jeong Kim),손창환(Chang-Hwan Son),추현승(Hyun-seung Choo) 한국정보기술학회 2019 Proceedings of KIIT Conference Vol.2019 No.11

뼈 나이는 성장기 아동에게 발육 상태와 관련한 유용한 정보를 제공한다. 하지만 기존의 뼈 나이 추정은 수작업으로 진단되기 때문에 번거롭고 많은 시간이 소요된다. 따라서 본 논문에서는 뼈 나이 진단을 위한 관심 영역 인식 심층 합성곱 신경망을 제안하고자 한다. 핵심 아이디어는 X선 영상에서 뼈 나이에 대한 정보를 담고 있는 영역은 손과 손목 부분이고 반면에 배경 영역에서는 아무런 정보가 없다는 것이다. 이러한 아이디어를 딥러닝 프레임워크에 반영하기 위해, 제안한 심층 학습모델은 두 종류의 심층 합성곱 신경망으로 구성된 두 개의 스트림을 형성한다. 하나의 스트림에서는 관심 영역과 배경 영역을 입력으로 받아 영역별로 특징의 중요도를 판별하고 다른 스트림에서는 대비가 강화된 X선 영상으로부터 특징을 추출하는 역할을 한다. 실험 결과를 통해 제안한 기법의 평균 절대 오차가 약 8.0236개월로, 기존의 전이 학습 기법보다 성능이 우수함을 확인할 수 있었다. Bone age provides useful information about developmental status for growing children. Traditional bone age prediction, however, can be cumbersome and time consuming because it is manually diagnosed. Therefore, this paper proposes a region-of-interest-aware deep convolutional neural network (ROI-aware DCNN) for bone age diagnosis. The key idea is that the area containing bone age in the X-ray image is the hand and wrist, while there is no information in the background. To reflect this idea in the deep learning framework, the proposed deep learning model forms two streams composed of two types of DCNNs. In one stream, the region of interest and the background region are received as inputs to determine the importance of the feature for each region, and in the other stream, the feature is extracted from the contrast-enhanced X-ray image. The experimental results show that the mean absolute error of the proposed method is about 8.0236 months, which is superior to the previous transfer learning method.

와동에 입사하는 충격파의 반사 및 투과 (Ⅰ)-실험적 모델-

장세명(Se-Myong Chang),장근식(Keun-Shik Chang) 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.9

An experimental model is investigated in this paper using the experimental method with a shock tube and the numerical technique. The shock-vortex interaction generated by this model is visualized with<br/> various methods: holographic interferometry, shodowgraphy, and numerical computation. In tenns of shock dynamics, there are two meaningful physics in the present problem. They are reflective wave from the slip layer at the vortex edge and transmitted slwck penetrating the vortex core. The discussion in this study is mainly focused on the two kinds of waves contributing to the quadrupolar pressure distribution around the vortex center during the interaction.<br/> <br/>

비정상 압축성 유동 해석을 위한 고차 정확도 적응 격자 기법의 연구

장세명(S.M. Chang),Philip J. Morris 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.3

The high-order numerical method based on the adaptive mesh refinement(AMR) on the quadrilateral unstructured grids has been developed in this paper. This adaptive-grid method, originally developed with MUSCL-TVD scheme, is now extended to the WENO (weighted essentially no-oscillatory) scheme with the Runge-Kutta time integration of fifth order in spatial and temporal accuracy. The multidimensional interpolation was studied in the preliminary research, which allows us to maintain the same order of accuracy for the computation oj numerical flux between two adjacent cells of different levels. Some standard benchmark tests are done to validate this method for checking the overall capacity and efficiency of the present adaptive-grid technique.

샤딘 문제에서의 충격파 - 와동 상호 간섭에 대하여

장세명(S. M. Chang),장근식(K. S. Chang) 한국항공우주학회 1998 韓國航空宇宙學會誌 Vol.26 No.7

초음파 조사를 이용한 압축성 평행 제트의 활성화

장세명(Se-Myong Chang),신성룡(Seong-Ryong Shin),이수갑(Soogab Lee) 한국전산유체공학회 2001 한국전산유체공학회 학술대회논문집 Vol.2001 No.-

An experimental model to enhance the mixing of parallel supersonic-subsonic jet (M₁=1.78 and M₂=0.30) is simulated with a numerical technique by modeling the wall-mounted cavity to a boundary condition of oscillating pressure. The computed pitot pressure distributions along three representative cross sections show a good agreement with the equivalent experimental data. The irradiation of acoustic wave in the ultrasonic range causes the mixing augmentation of jet and wake due to the transfer of vibration energy between fluid particles.

Standard Procedure for the Aerodynamic Design of Small Wind Turbine Blades

장세명(Chang, Se-Myong),정수윤(Jeong, Su-Yun),서현수(Seo, Hyun-Soo),경남호(Kyong, Nam-Ho) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.11

There have been many academic researches on the aerodynamic design of wind turbine based on blade element method (BEM) and momentum theory (MT, or actuating disk theory). However, in the real world, the turbine blade design requires many additional constraints more than theoretical analysis. The standard procedure is studied in the present paper to design new blades for the wind turbine system ranged from the small size from 1 to 10 kW. From the experience of full design of a 10 kW blade, the authors tried to set up a standard procedure for the aerodynamic design based on IEC 61400-2. Wind-turbine scale, rotating speed, and geometrical chord/twist distribution at the segmented span positions are calculated with a suitable BEM/MT code, and the geometrical shape of tip and root should be modified after considering various parameters: wing-tip vortex, aerodynamic noise, turbine efficiency, structural safety, convenience of fabrication, and even economic factor likes price, etc. The evaluated data is passed to the next procedure of structural design, but some of them should still be corresponded with each other: the fluid-structure interaction is one of those problems not yet solved, for example. Consequently, the design procedure of small wind-turbine blades is set up for the mass production of commercial products in this research.

자동차용 PCV 밸브의 특성 측정에 대한 연구

장세명(Se-Myong Chang) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.9

Positive Crankcase Ventilation(PCV) is a plumbing system installed at the intake of internal combustion engines for the feed-back control of blow-by gas from the leakage of piston-cylinder system. The blow-by gas must be regulated in a short time, so the PCV valve should be opened in a certain range of the pressure difference between intake manifold and crank room. For the high pressure difference at the idling and deceleration, the PCV valve is controlled proportional to the production of blow-by gas. However, for the low pressure difference at the full stroke, the ventilation should be closed because the excess blow-by flow can enter the combustion chamber directly through the breather hose. The PCV valve controls the area of throat by using the elasticity of a spring. In this paper, the author constructed a measurement system con cering the characteristics of two types of commercial PCV valves for automobiles. The measured flow rates are plotted to make a new speculation of proper test for products, and compared with theoretical prediction based on compressible fluid dynamics.