• Journal of ILASS-Korea
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• v.13 no.2
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• pp.79-84
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• 2008

The correlations for cross-flow have not been well established, because of the complexity of breakup and atomization mechanism. A study was performed to investigate the characteristics of spray behaviour of liquid jet in the bag breakup regime injected into low-speed cross-flow with the pressure single-hole nozzle. The shadow-graphy method was used for the cross-flow jet visualization. The experimental variables of liquid jet were nozzle diameter $(0.3mm{\sim}1.0mm)$, injection pressure $(50kPa{\sim}150kPa)$, and the velocity of cross-flow $(27m/s{\sim}42m/s)$. The highest penetration trajectories of liquid jet are governed by the momentum ratio $({\rho}_{\iota}U_{\iota}^2/{\rho}_aU_{cross}^2)$ rather than the Weber number and the new empirical equations of the highest penetration trajectory and breakup point at low-speed corss-flow are established.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.5
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• pp.56-62
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• 2000

In this paper, an automatic extraction of the blood flow contour from cardiac MRI is proposed. By using the GVF snake which has wider capture range than the conventional snake, and by automatically generating the initial points along the outside of the contour of the zero GVF field in the edge image of the cardiac MRI, the blood flow contour can be automatically extracted, even when the contours have boundary concavities due to the papillary muscles, without any manual initialization of the experts. Experiments are conducted on the various real cardiac MRIs including noise and papillary muscles, and the proposed method is proved to be efficient in automatic extraction of the blood contours even if they have the boundary concavities.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.5
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• pp.9-17
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• 2008

Pseudo-3D spatial distribution of spray droplets is investigated by using Dual-mode Phase Doppler Anemometry (DPDA) in order to examine the disintegration and spreading behavior of spray exiting from liquid-propellant thruster injector. Spray injected from nozzle orifice with length-to-diameter ratio ($L/d_o$) of 1.67 and under the injection pressure of 27.6 bar is aligned to the vertical. Vertical and horizontal mean velocities of droplets, Sauter Mean Diameter (SMD), and volumetric flux decrease as droplets travel from center/upstream toward outer region/downstream of spray. Although the distribution of spray characteristic parameters is symmetric against the geometric axis of nozzle orifice, their absolute values are asymmetric.

• Journal of Power System Engineering
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• v.13 no.3
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• pp.20-26
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• 2009

디젤기관에서 배출되는 유해배출성분인 NOx(Nitrogen oxides)와 PM(Particulate matter)은 기관 실린더내의 혼합기 분포에 의해 그 생성이 지배된다. 이 때문에 그 유해배출물들을 저감하기 위해서는 연소의 전단계인 혼합기 분포 및 그 생성과정의 해석은 매우 중요하다. 디젤기관에서 노즐로부터 분사된 연료는 주위기체와 혼합기를 형성하는 과정에서 액체에서 기체로 상변화를 동반한다. 따라서 분무의 혼합기형성과정을 해석하기 위해서는 액상과 기상을 동시에 분리하여 계측하는 것이 필요하다. 그러므로 본 연구에서는 디젤분무를 대상으로 Melton 등이 제안한 엑시플렉스(Exciplex) 형광법을 이용하여, 분무의 액상과 기상을 동시에 2차원분리해서 가시화촬영을 행하였다. 그 엑시플렉스 형광법을 이용하여 획득한 이미지에 화상 응용해석을 실시하여 비정상증발디젤분무의 혼합기형성과정에 대한 정보를 얻고자 하였다. 엑시플렉스 형광법을 이용해서 증발분무의 거동측성을 해석한 결과 프랙틸해석을 이용한 분무 흐트러짐(Disturbance)의 평가에서 플랙틸차원은 분사압력의 변화에 관계없이 하나의 값, 약 1.1로 정리 할 수 있고, 그 결과 각 분사압력에 대한 분무 기상외곽곡선(외주)은 거의 동일한 정도의 요철형상을 갖는다.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.16-22
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• 2012

Performance of a liquid rocket thrust chamber with regenerative cooling scheme has been numerically analyzed using in-house CFD code which can predict combustion/cooling performance and provide nozzle design parameters. This paper investigates trade-offs between combustion and cooling performance with varying amount of fuel directly injected into the chamber wall to form cooling films and mixture ratios for the peripheral injectors. Further efforts to verify/improve the simulation methodology including comparison with the firing test results are planned to make it a reliable tool to optimize the film cooling and other major design parameters.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.38 no.1
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• pp.19-25
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• 2001

A novel approach for the feature extraction of handwritten characters is proposed by using spatial filtering neural networks with 4 layers. The proposed system first removes rough pixels which are easy to occur in handwritten characters. The system then extracts and removes the boundary information which have no influence on characters recognition. Finally, The system extracts feature information and removes the noises from feature information. The spatial filters adapted in the system correspond to the receptive fields of ganglion cells in retina and simple cells in visual cortex. With PE2 Hangul database, we perform experiments extracting features of handwritten characters recognition. It will be shown that the network can extract feature informations from handwritten characters successfully.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.19-24
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• 2001

The Pilot-Tube is the device that measures velocity and altitude of high speed vehicle. Accurate measurements of speed and altitude are essential to the safe and efficient operation of aircraft. For the purpose of determining optimal design parameters of Pilot-Tube such as nose inlet configuration, nose shape, static hole configuration, and static hole location, subsonic flow field was calculated numerically and analyzed. A Pilot-Tube was manufactured based on numerical flow field analysis, and pressure and air velocity was measured experimentally in the wind tunnel. As a result manufacturing and design technologies of the Pilot-Tube were acquired to make flight-device.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.4
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• pp.10-16
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• 2011

A cabinet is an outer frame of a TV, which is usually made of poly-carbonate. Cabinets are apt to be deformed because of applied heat during injection molding process and UV joining process. Severely deformed cabinets cause a falling-off in quality of the final product. Therefore cabinets should be inspected and only the good ones should be delivered to the following process. We implemented an experimental system for shape recognition of a cabinet and proposed several indices to characterize the shape of a cabinet. We also proposed algorithms to eliminate the possible bias present in measured data and to check the goodness of a cabinet. Experimental results show the feasibility of the propose algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.75-79
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• 2004

In this paper, a single plane wide band microstrip antenna for integrated circuit as MMIC and LTCC is designed and fabricated. A new configuration for a wide band microstrip antenna with omni-directional pattern is proposed. This antenna consists of two rectangular folded dipoles, which are fed by a coplanar waveguide(CPW). It was effected stabilization ground that a signal plane of CPW feed have been limited ground plane. Therefore, a ground plane of folded structure should be extended outside folded antenna in this research. The characteristics of the proposed antenna were analyzed by using an FDTD methods. The return loss and radiation patterns were simulated and measured. The proposed antenna is get 120MHz bandwidth of PCS band and 250MHz bandwidth of IMT2000 band, used ISM band.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.191-199
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• 1997

This paper develops the piece creation of Hull-structure using PC(Personal Computer) which is from CADRA of graphic program. Large-sized shipbuilding yard was carried out on the development of CNC(Computer Numerical Control) auto cutting system used in super S/W such as AUTODEF, TRIBON. But this system needs lots of expenses and high technician, and only used in large-sized shipbuilding yard, not medium-sized and small-sized shipbuilding yard. To bring up the small and medium-sized ship building yard lacking a little competitive power. Small and medium-sized shipbuilding yard need the piece creation of Hull Structure S/W which is joined with the CADRA. Therefore the piece creation of Hull-Structure S/W is developed to joined with the CADRA of graphic S/W to create the piece to be needed on as auto cutting process using PC.