• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.257-262
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• 2008

In this paper, the key parameters of $CO_2$ laser(focus depth, air blow rate, total laser beam time, number of pulse) are experimented for thru-hole and scribing line on AIN(aluminum nitride) substrate with high thermal conductivity. And, microstrip line & spiral planar inductor are fabricated on AIN substrate using 5 um Cu-plating with self-masking technique. The microstrip line of AIN has 0.1 dB/mm attenuation at 10 GHz and 6 nH spiral planar inductor has 56 maximum quality factor at 1 GHz. Thus, the AIN substrate is promising for GHz applications of high power area.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.3
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• pp.212-216
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• 2017

Aerodynamic analysis for the airfoil, KARI-11-180 having 18% thickness ratio, was performed with CFD techniques. The boundary layer grid was generated by projecting the wall grid normally and fine grid was placed behind the trailing edge to capture the wake accurately. The distance to the far boundary is 100 chords and the flow condition is same as the wind tunnel test condition. Transition SST and DES turbulence models were utilized for accurate prediction of the transiton point. The predicted lift is higher but the drag is predicted lower than the wind tunnel test. 3-dimensional results with airfoil models of which aspect ratio were 2 and 5 were compared with 2-dimensional results.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.3
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• pp.53-61
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• 1999

Impinging jets are observed when exhaust gases from missiles or V/STOL aircrafts impinge on the ground, flame deflector, ship deck, etc. The flow shows different patterns according to the nozzle geometry, nozzle-to-plate distance, and plate angle, for example. This paper describes experimental works on the phenomena (pressure distribution, occurrence of stagnation bubble, and so on.) when underexpanded supersonic jets impinge on a perpendicular flat plate using a supersonic cold-flow system, and compares the results with those obtained using a shock tunnel. The flow characteristics for the supersonic cold-flow system were also investigated. Surface pressure distribution of supersonic cold-flow system differed from that of shock tunnel because of water and temperature in the low-pressure chamber. Surface pressure distribution as to underexpanded ratio showed similar patterns together.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.238-244
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• 1994

We numerically studied on the dark solitons propagation for initial amplitude and phase shapes in the normalized nonlinear Schr dinger equation(NLSE) which describes the propagations of optical solitons. As the propagation distance increases, odd dark solitons evolve into a black soliton and pairs of gray solitons which have a different sign of blackness, and even dark solitons evolve into pairs of gray solitons without black solitons. When there exists a black soliton and a gray soliton, even though the initial amplitude shape is same, the sign of blackness of a gray solitons determines whether they would collide or not. We could see that the energy of dark solitons evolve into a couple of solitons of different blackness since there exists a continuous range of dark solitons with arbitrary blackness parameter, and this phenomenon was more clearly seen from the change of phase shapes from that of amplitude shapes. hapes.

• Applied Chemistry for Engineering
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• v.10 no.4
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• pp.615-619
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• 1999

Polyether-clay nanocomposite was not polymerized with stearyltrimethylammonium ion exchanged montmorillonite, but it was self-polymerizable when heated with both stearyltrimethylammpmoim and m-phenylenediammonium ions intercalated montmorillonite to form polyether-clay nanocomposites. Molcular disperion of montmorillonite within the crosslinked epoxy matrix verified using X-ray diffraction and transmission electron microscopy found that the final product contains a uniform dispersion of exfoliated $10{\AA}$ thin clay layers seperated by $250{\sim}500{\AA}$of polyether polymer, thus verifying the nanocomposite structure.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.100-100
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• 1999

가시광선 영역에서 높은 광학적 투과성과 함께 우수한 전기 전도성을 갖는 ITO 박막은 디스플레이 소자나 투명전극재료 등 다양한 분야에서 응용성이 더욱 증대되고 있다. 증착기판으로서 유리를 사용할 때 생기는 활용범위 제한을 극복하고자 최근 유기물 위에 증착이 가능한 저온 증착방법에 대한 연구가 활발히 이루어지고 있다. 그 가운데 이온빔과 같은 energetic한 beam을 이용한 박막의 제조는 기판을 플라즈마 발생지역으로부터 분리시켜 이온빔의 flux 및 에너지, 입사각 등의 자유로운 조절을 통해 상온에서도 우수한 성질의 박막 형성 가능성이 제시되어 왔다. 본 연구에서는 ion beam assisted evaporation방법을 이용하여 ITO 박막을 성장시켰으며, ion-surface interaction 효과가 박막 성장주에 미치는 영향을 이해하기 위하여 먼저 반응성 산소 이온빔에 비 반응성 아르곤 이온빔을 다양하게 변화시켜가며 증착하였으며, 이와 더불어 산소 분위기에서 아르곤 이온빔에 의한 ITO 박막의 특성 변화를 각각 관찰하였다. 증착전 후의 열처리 없이 상온에서 비저항이 ~10-4$\Omega$cm 이하로 낮고 80% 이상의 투과율을 갖는 ITO 박막을 성장시켰다. 실험에서 이용된 e-beam evaporation 물질은 In2O3-SnO2(1-wt%)였으며, 이온빔 source는 산소에 의한 filament의 산화를 막기 위해 filament cathodes type이 아닌 rf(radio-frequency)를 사용하였다. 중요 증착변수인 이온빔의 flux 변화는 산소와 Ar의 flow rate를 MFC로 조절하고 rf power를 변화시켜 얻었으며, 이온빔 에너지는 가속 grid의 가속전압 변화와 ion gun과 기판사이의 거리 조절을 통해 최적화하였다. 이온빔의 에너지와 flux는 Faraday cup으로 측정하였으며, 성박된 박막의 특성은 UV-spectrometer, 4-point probe, Hall measurement. $\alpha$-step, XRD, XPS 등을 이용하여 광학적, 전기적, 구조적 특성을 분석하였다.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.72.4-73
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• 2018

북극 스발바르의 사면 지형에는 걸리가 발달되어 있다. 이러한 걸리는, 그 성인에는 여러 의견이 있으나, 화성에도 중고위도를 중심으로 다수 분포한다. 화성의 걸리는 2000년대에 들어 비로소 본격적으로 규명되고 있으나, 지형적 특성으로 인한 탐사의 한계로 지구에 분포하는 유사지형을 통한 비교 연구가 일반적이다(Costard, et al. 2007 등). 이 연구에서는 스발바르의 주도 롱이어비엔에서 UAV을 이용하여 획득한 DEM으로 스발바르 걸리를 측량하고, 이를 화성 중위도의 테라 사이메리아, 테라 시레넘, 노아 키스 테라에 분포하는 걸리와 비교하였다. Longyearbreen 빙하 전방에 위치한 사면을 UAV로 촬영하고, 이를 SfM-MVS(Structure from Motion & MultiView Stereo) 기법으로 3차원 점군 모델과 고해상도 DEM을 제작하여 분석하였다. 화성의 경우 MRO궤도 탐사선이 촬영한 HiRise DTM을 이용하여 분석하였다. 두 걸리는 기후와 지질 조건에 차이가 있음에도 불구하고 유사한 패턴을 보였다. 특히 테라 사이메리아에 위치한 걸리와 롱이어비엔 북사면의 걸리는 기준거리, 단면적, 폭, 경사, 제방 두께 등에서 상당한 정량적 유사관계가 있었다. 이는 두 행성의 걸리가 유사한 성인 및 형성 프로세스를 거쳤을 가능성을 시사한다. 측량 기법과 UAV 의 안정성을 개선시키면 지형 모델의 품질 향상 및 극지에서의 UAV 운용이 용이해질 것으로 기대된다. 또한 스발바르의 기후 요소 및 물리량 적용은 향후 화성 지형연구에도 응용할 수 있을 것으로 사료된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.114-117
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• 1992

This paper presents the design and calibration methods of self-integrated magnetic sensor. Also the distance response measurement of magnetic field produced a transient large current and the frequency response measurement are carried out As the integrating resistance increases. the sensitivity of the sensor is improved, but the decay time constant of response decreases, Also the experimental results are well agreed with the theoretical analysis of the equivalent circuit.

• Journal of The Korean Association of Information Education
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• v.7 no.2
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• pp.239-246
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• 2003

In field of school, parents can't attend to education activities of school really because of the time and spacial reason, economical reason and the sense of distance for school, although they are very concerned about a school education. In this paper, I suggested the e-Home system that is an organic system to can confirm the communication channel between parents and school or teacher by using infrastructure of educational information based on established Home-page of each school. It should bring a qualitative promotion for public education. Of couse, it will be increasing a relationship of student, teacher and parents furthermore, it make a desirable relation between teacher and parents via participation of parents for school education in elementary school.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.754-757
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• 2003

In Oriental medicine, the shape of collarette that formed with position in iris of patients often used by health diagnotcian to grasp health condition. In this paper, we present method that effectively extract collarette that exist in Iris image. After proposed method detert iris area using circular edge detector, derides boundary candidate point through radial line search and threshold value establishment. And boundary candidate line is treated to use nearest neighbor calculation at each boundary candidate point, finally extracts collarette through linear interpolation. As a result of experimenting about iris images, We Confirmed that can be used as assistant tool of diagnostic system that can presume state of ventriculus of human body.