• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.1-13
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• 2004

A scanning stereo-PIV system was developed to measure the three-dimensional distribution of three-component velocity in a turbulent round jet. A laser light beam produced by a high repetition rate YLF pulse laser was expanded vertically by a cylindrical lens to form a laser light sheet. The light sheet is scanned in a direction normal to the sheet by a flat mirror mounted on an optical scanner, which is controlled by a programmable scanner controller. Two high-speed mega-pixel resolution C-MOS cameras captured the particle images illuminated by the light sheet, and stereoscopic PIV method was adopted to acquire the 3D-3C-velocity distribution of turbulent round jet in an octagonal tank filled with water. The jet Reynolds number was set at Re=1000 and the streamwise location of the measurement was fixed at approximately x = 40D. Time evolution of three-dimensional vortical structure, which is identified by vorticity, is visualized. It revealed that the existence of a group of hairpin-like vortex structures was quite evident around the rim of the shear layer of the jet. Turbulence statistics shows good agreement with the previous data, and divergence of a filtered (unfiltered) velocity vector field was $7\%\;(22\%)$ of root-me an-squared vorticity value.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.95-95
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• 2012

스터퍼링 기술이 1852년 Grove에 의해서 최초 발견되어 1979년 Chapin에 의해서 planar magnetron cathode 개발로 진공코팅기술의 새로운 영역을 열게 되어 현재까지 디스플레이, 반도체, 태양전지, 광학산업 및 전자부품 등 나노 산업에 필수적으로 적용되고 있다. 스퍼터링 입자는 운동량 전달에 의한 것으로 운동량을 갖는 나노 스퍼터링 입자는 기판에 대한 박막의 부착력이 우수하고 대면적에 균일하고 재현성 있게 성막되는 특징을 갖고 있다. 마그네트론 스퍼터링 기술이 산업에 응용되면서 주로 4분야에서 많은 연구, 개발이 되어져 왔다. 첫째는 타겟의 고순도 및 고밀도화와 더불어 가격이 고가로 됨에 따라 타겟 사용효율의 향상이다. 플라즈마를 발생시키는 캐소드의 자기회로를 1차원, 2차원 및 회전운동을 통해서 사용효율을 향상시키고 있다. 둘째는 기판에 대해서 박막특성이 균일하도록 코팅하는 것이다. 디스플레이에서는 글래스 기판이 대면적으로 됨에 따라서 핸들링이 어려워져 여러 개의 캐소드 자기회로를 선형적으로 이동시켜 박막두께분포를 최적화하며 반응성 가스를 사용해서 균일한 특성의 박막을 제작하는 경우에는 가스분사관과 배기펌프계의 기하학적 위치 및 가스 유동학적 해석이 필요하다. 셋째는 스퍼터링 입자의 이온화로 의한 박막의 특성향상과 반도체 trench의 높은 aspect ratio hole을 채우는 것이다. 이온화 방법으로는 inductively coupled plasma (ICP), microwave amplified (MA), high power impulse (HIPI), hollow cathode magnetron (HCM), self-sustained sputtering 등이 사용되어져 왔으며 최근에는(neutral beam-assisted sputtering (NBAS)에 의한 박막특성향상 방법이 발표되고 있다. 넷째는 플라즈마 및 박막두께 시뮬레이션에 대해서 많은 발표가 되고 있다. 본 발표에서는 상기의 4 분야를 포함한 향후 개발방향에 대해서 소개할 예정이다.

• Journal of Korea Foundry Society
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• v.15 no.5
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• pp.514-522
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• 1995

The microstructural evolution with isothermal stirring during semi-solid state processing of hypoeutectic Al-6.2wt%Si alloy was studied. Substructure of the individual primary solid particle in the slurry was investigated through transmission electron microscopy(TEM). Formation of subgrain boundaries on the rheocast Al-6.2wt%Si alloy is observed and the misorientation between the grains is shown typically under 2 degrees by analyzing selected area diffraction (SAD) and convergent beam electron diffraction (CBED) patterns. The existence of high angle grain boundaries are also observed in the alloy. Based upon these observations, mechanisms for the primary particles fragmentation are considered. With isothermal stirring, the dislocation density increases, and the evolution of dislocation cell structure takes place, which is interpreted as a process of achieving uniform deformation by dynamic recovery under applied shear stress.

• 연구논문집
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• s.30
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• pp.147-157
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• 2000

The filtered vacuum arc source (FVAS), which is adopted by magnetic filtering methode to remove the macro-particle in vacuum arc plasma, was composed of a torus structure with bending angle of 60 degree. The radius of torus was 266 mm, the radius of plasma duct was 80 mm and the total length was 600 mm. The magnet parts were consisted of one permanent magnet, one magnetic yoke and five solenoid magnets. The plasma duct was electrically isolated from the ground so that a bias voltage could be applied. The baffles inside plasma duct were installed in order to prevent the recoil effect of macro-particles. Graphite was used as the cathode material to coat the amorphic diamond film and its diameter was 80 mm. The amorphic diamond film attracts much attention due to its excellent mechanical, optical and tribological properties suitable for wide range of applications. The effects of solenoid magnet in plasma extraction were studied by computer simulation and experiment using Taguchi's method. The source and extraction magnet affected the arc stabilization. The extraction beam current was maximized with low value of the source magnet current and high value of the filtering magnet current. Optimum deposition condition was obtained when the currents of arc discharge, source, extraction, bending, deflection and outlet magnet were 30 A, 1 A, 3 A, 5 A, and 5 A, respectively.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.605-610
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• 2014

Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements because there is no Doppler effect if the clouds move in the perpendicular direction to the laser beam path of Doppler lidar. In this paper, we present a method for the measurement of cloud velocity using lidar's range detection and DIC (Digital Image Correlation) system to overcome the disadvantage of Doppler lidar. The lidar system acquires the distance to the cloud, and the cloud images are tracked using the developed fast correlation algorithm of DIC. We acquired the velocities of clouds using the calculated distance and DIC algorithm. The measurement values had a linear distribution.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.149-149
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• 2013

반도체 공정 및 디스플레이 공정에서 발생하는 오염입자는 공정 불량을 일으키는 가장 큰 인 중의 하나이며, 수십 나노에서 수 백 나노의 크기를 갖는다. 최근 반도체 산업이 발전함에 따라 회로의 선폭이 점차 감소하고 있으며 오염입자의 임계 직경(critical diameter) 또한 작아지고 있다. 또한 디스플레이 산업에서는 패널이 대형화되고 공정이 발달함에 따라 입자에 의한 패널 오염이 이슈가 되고 있는 실정이다. 현재 반도체 및 디스플레이 산업에서 사용되는 측정방법으로는 레이저를 이용하여 공정 후 표면에 남아있는 오염입자를 측정하는 ex-situ 방법이 주를 이루고 있다. Ex-situ 방법을 이용한 오염입자의 제어는 웨이퍼 전체를 측정할 수 없을 뿐만 아니라 실시간 측정이 불가능하기 때문에 공정 모니터링 장비로 사용이 어려우며 오염입자와 공정 간의 상관관계 파악에도 많은 제약이 따르게 된다. 이에 따라 저압에서 in-situ 방법을 이용한 실시간 오염입자 측정 기술 개발이 요구되고 있다. 또한 입자의 크기 뿐 아니라 성분과 형상까지 측정할 수 있는 장치의 개발 요구가 높아지고 있는 실정이다. 이를 위해 입자의 크기 및 분포를 측정할 수 있는 Particle Beam Mass Spectrometer (PBMS)와 형상을 측정할 수 있는 Scanning Electron Microscope (SEM)의 기능을 통합하여 실시간으로 나노입자의 복합특성(크기, 성분, 형상)을 측정할 수 있는 장치를 개발하였다. 또한 기존 장치들의 문제점 중 하나가 실시간으로 교정이 불가능하다는 것이었는데 이 장치의 경우 실시간으로 측정되는 결과의 조합으로 실시간 교정까지도 가능한 장점을 가지고 있다.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.103-110
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• 2004

The major trend in global automotive market is changing drastically in the way that a vehicle FECPS(Front End Cooling Pack System) is designed and manufactured as an assembly part. The system can encompass many functions, be assembled into a vehicle as a module, and reduce the production cost as well as time. The FECPS consists of an impact beam, an aluminum condenser and a radiator, a carrier and a cooling fan with a BLDC motor. In order to predict the performance of a FECPS accurately, it is essential to properly model the air flow field through various heat exchangers, such as a condenser or a radiator. In this study, the flow field of the system is measured by a PIV(Particle Image Velocimetry) system. The result is compared with that measured with multi-channel anemometer.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.8-15
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• 1998

The spray characteristics of emulsified fuel of W/O type has been experimentally investigated. The mixture of light oil and water by using ultrasonic energy adding system is used as the emulsified fuel. The SMD of sprayed droplet of emulsified fuel is measured by using the particle size analyzer. Major parameters of the present experimental study are the volume fraction of water in emulsified fuel, $0\sim30%$ by 5%, injection pressure, $10kg_f/cm^2\sim18kg_f/cm^2$ by $2kg_f/cm^2$, and the measurement distance, $10\sim100mm$, between injection nozzle tip and analyzer beam. Compared with light oil, the SMD of emulsified fuel is larger gradually by increasing the volume fraction of water in emulsified fuel, heightening injection pressure and increasing the spray distance. Also, In considering the fact that the pattern of drop size distribution of emulsified fuel is alike that of light oil, the real time spray in coincidence with making emulsified fuel by adding ultrasonic energy can stabilize spray pattern without modificating the injection system used by now.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.446-451
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• 2001

We made a laser induced grating spectrometer(LIGS) and measured the thermal grating signal generated in a $C_3$ $H_{8}$ flame. The thermal grating was formed in the C7Ha flame with two second-harmonic Nd:YAG pulse laser beams, and an LIGS signal was generated by Bragg scattering of a probe laser beam A $r^+.laser(488 nm). We found the modulation period of the signal depends linearly on the spacing of the grating set in the flame. We determined flame temperature by fitting the modulated signal and soot concentration with signal strength. Using this technique, we also obtained temperature profile and soot-particle distribution in a $C_3$ $H_{8}$ flame .e .

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.138-144
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• 2008

Micro-machining of a brittle material such as glass, silicon, etc., is important in micro fabrication. Particularly, micro-abrasive jet machining (${\mu}-AJM$) has become a useful technique for micro-machining of such materials. The ${\mu}-AJM$ process is mainly based on the erosion of a mask which protects brittle substrate against high velocity of micro-particle. Therefore, fabrication of an adequate mask is very important. Generally, for the fabrication of a mask in the ${\mu}-AJM$ process, a photomask based on the semi-conductor fabrication process was used. In this research a rapid mask fabrication technology has been developed for the ${\mu}-AJM$. By scanning the focused UV laser beam, a micro-mask pattern was fabricated directly without photolithography process and photomask. Two kinds of mask patterns were fabricated using SU-8 and photopolymer (Watershed 11110). Using fabricated mask patterns, abrasive-jet machining of Si wafer were conducted successfully.