• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.131-131
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• 2008

Silicon carbide (SiC) has attracted significant attention for high frequency, high temperature and high power devices due to its superior properties such as the large band gap, high breakdown electric field, high saturation velocity and high thermal conductivity. We performed Al ion implantation processes on n-type 4H-SiC substrate using a SILVACO ATHENA numerical simulator. The ion implantation model used a Monte-Carlo method. We studied the effect of channeling by Al implantation simulation in both 0 off-axis and 8 off-axis n-type 4H-SiC substrate. We have investigated the Al distribution in 4H-SiC through the variation of the implantation energies and the corresponding ratio of the doses. The implantation energies controlled 40, 60, 80, 100 and 120 keV and the implantation doses varied from $2\times10^{14}$ to $1\times10^{15}cm^{-2}$. In the simulation results, the Al ion distribution was deeper as increasing implantation energy and the doping level increased as increasing implantation doses. After the post-implantation annealing, the electrical properties of Al-implanted p-n junction diode were investigated by SILV ACO ATLAS numerical simulator.

• Journal of Oral Medicine and Pain
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• 제39권3호
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• pp.100-106
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• 2014

Purpose: This study was performed to investigate the relationship between temporomandibular disorders (TMDs) and the asymmetry of the mandibular height. Methods: We compared 100 randomly selected TMD patients diagnosed by the research diagnostic criteria for TMD (RDC/TMD) Axis I with 100 non-TMD control subjects matched with the TMD patients in age and gender. The mandibular heights were measured on an orthopantomogram and the asymmetry index (AI) was calculated as previously described. Results: The absolute AI value of 4.37% turned out to be the least cut-off value defining asymmetry, which showed a significant difference in asymmetry incidence (p<0.01) between the TMD and control groups. The risk of TMD increased in the asymmetry group by 4.57 (odds ratio). The incidence of asymmetry was not related to age and gender in both of the TMD and control groups. When dividing the TMD group according to the RDC/TMD Axis I diagnosis, neither the incidence of muscle disorder nor disk displacement was related to the incidence of asymmetry. However, a higher incidence of asymmetry was observed in the subjects classified into the arthrosis/arthritis groups (p<0.01). Conclusions: Although it does not imply a direct cause-and-effect relationship, asymmetry resulting in more than 4.37% difference between mandibular heights may increase the risk of TMD and correlates positively to the incidence of arthritic change in the temporomandibular joint of TMD patients.

• 한국전기전자재료학회논문지
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• 제29권3호
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• pp.175-180
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• 2016

In this study, we proposed an optical compensation method to improve the symmetricity of contrast ratio for wide viewing angle IPS (in-plane switching) LCD. First, the phase retardation depending on the thickness of compensation film is calculated, and then the phase change is presented at the $Poincar{\acute{e}}$ sphere. The phase retardation and the polarization state of the light passing through the optical elements are caculated by using the EJMM (extended Jones matrix method). In addition, the transmittance and the contrast countour are also calculated by using the Berremann's $4{\times}4$ matrix method. The simulation is carried out for a IPS LC cell with positive A/C/A compensation film. From the standard deviation of the contrast ratio, we confirmed the symmetricity at each viewing angle is inversely proportional to the standard deviation and calculated the optimum design condition of the uniaxial compensation film for the IPS LCD.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.53-54
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• 2006

We have studied the viewing angle control of a twist nematic liquid crystal display (TN-LCD). The TN-LCD exhibits a bad image quality along vertical direction, due to characteristics such as low contrast ratio and grey scale inversion. The proposed new TN-LCD has the function of switching between the wide viewing mode and narrow viewing angle mode using two tilted LC layers at both sides of a TN-cell Tilt angles of the two LC layers, $14^{\circ}$ and $60^{\circ}$ were required in both wide viewing angle and narrow viewing angle modes, respectively.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.302-304
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• 2002

In linac-based stereotactic radiosurgery, assuring the quality of the planning and delivery of external photon beam requires accurate evaluation of beam parameters, usually including output factors, tissue-phantom ratio and off-axis ratios, and measurement of actual dose distributions from simulated treatment. We're going to test the use of calibrated radio chromic film (Gafchromic film; type MD-55, Nuclear associate) using a Lumiscan 75 digitizer to measure absolute dose and relative dose distributions for linac-based radiosurgery unit Relative dose distribution of a human-style spherical acryl phantom were measured using radiochromic film and calculated by treatment planning system. The absolute dose at the sphere center was measured by radiochromic film and micro chamber (Exradin A-14, 0.009cc). What we want to demonstrate in this work, the 'well selected' radiochromic films when external photon beam are used in linac-based stereotactic radiosurgery are very accurate detector for dosimetry.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.403-406
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• 2007

A New S-PVA which is named as charge-shared super PVA (CS S-PVA) LCD mode is proposed. CS SPVA controls the voltage ratio of low pixel by sharing system between low pixel and control cap, resulting in improved off-axis image quality and transmittance increase without any side effects. Moreover, the new S-PVA LCD mode is free of image-sticking. Operating schemes and display performance of CS S-PVA are presented.

• 한국결정성장학회지
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• 제10권1호
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• pp.5-12
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• 2000

Silicon carbide(SiC)는 뛰어난 전기적, 열적, 물리적 특성 때문에 내환경 전자소자용 반도체 재료로 널리 연구되고 있다. 본 연구에서는 화학기상증착법으로 단결정 6H-SiC 동종박막을 성장시키고 이의 성장 특성을 조사하였다. 특히, 몰리브덴 (Mo)-plate를 이용하여 SiC를 코팅하지 않은 graphite susceptor를 사용한 6H-SiC 동종박막 성장조건을 성공적으로 얻었다. 대기압 상태의 RF-유도가열식 챔버에서 CVD성장을 수행하였고, <1120> 방향으로 $3.5^{\circ}$off-axis된 기판을 사용하였다. 성장 박막의 결정성을 평가하기 위하여 Nomarski 관찰, 투과율 측정 , 라만 분광, XRD, 광발광(PL) 분광, 투과전자현미경(TEM) 측 정 등의 방법을 이용하였다. 이상과 같은 실험을 통하여, 본 연구에서는 성장온도 $1500^{\circ}C$, C/Si flow ratio ($C_3H_8$ 0.2 sccm, $SiH_4$ 0.3 sccm)인 성장조건에서 결정성이 가장 좋은 6H-SiC 동종박막을 얻을 수 있었다.

• 한국유체기계학회 논문집
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• 제17권6호
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• pp.64-68
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• 2014

This paper is intended to provide experimental data for the design of the small VAWT(vertical axis wind turbine). Three types(lift, drag, and hybrid) of the blade of VAWT are tested with digital wind tunnel in this study. From the test, the relation of power coefficient and tip speed ratio for the blades are evaluated and compared each other depending on the blade type. Especially, the characteristics of hybrid blade which is shown to be expanded in the market without any logical data is proposed in the relation of power coefficient and tip speed ratio. It is shown that the hybrid blade can be used to make higher starting torque with trade off of degradation of power coefficient.

• 한국태양에너지학회 논문집
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• 제25권2호
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• pp.27-33
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• 2005

To improve the performance of the top-positioning space in buildings, we suggested the environment-friendly system integrating various design techniques in the previous paper. This work discussed to calculate the length of PV considering a part of metallic radiators for radiative cooling, an critical element of the whole system, for shading not to prevent the PV on roof from generating electricity. In the process of calculating the shading area, we used the geometrical relationship between the sun-rays and the variable roof. For general applications, we utilized DL, the ratio of the length of PV and that of metallic radiator on roof, as a design factor, and then used the maximum insolation and the specific insolation($200W/m^2$) to decide the distance off the axis of rotation. As a result, for DL, we found out the reasonable value of 1.0 with full covering, 1.2 with 90%, and 2.0 with 70% in PV covering.

• 한국의학물리학회지:의학물리
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• 제11권2호
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• pp.117-122
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• 2000

해상도가 뛰어나며 디지털영상으로 저장하므로 공간에 제약을 받지 않으며 재사용이 가능하다는 장점으로 현재 국내 병원에서는 Imaging Plate(IP)가 필름을 대체해가고 있는 추세에 있다. 본 연구는 진단용으로 사용되는 If를 이용하여 치료영역에서 선량측정용도로의 가능성 여부를 알아보고자 하였다. 실험을 하는데 사용되었던 IP는 Fuji사의 ST-V$_{A}$라는 모델이고 가속기는 Varian 2100C의 6 MV 광자선을 사용하였다. 먼저 전리함으로 측정한 심부선량을 기준으로 If로 측정한 값과 비교를 하였다. 조사문 선량(portal dose)을 측정하기 위하여 SSD=100 cm 위치에 두께 14 cm 되는 폴리스틸렌 팬텀을 놓고 그 밑에 전자포탈영상기구(Electronic Portal Imaging Device: EPID)가 위치한 지점에서 상대적 흡수선량(Off Axis Ratio: OAR)을 측정 그리고 계산하였다. 이때 전리함, 필름(Kodak X-Omat V) 및 IP를 전자포탈영상기구와 같은 위치에 놓고 측정을 하였고 이에 더하여 EGS4 몬테칼로전산모사를 통하여 조사문 선량을 계산하였다. 심부선량(PDD)을 측정한 결과 IP는 BaFBr:Eu$^{2+}$의 인광물질로 이루어져 있기 때문에 물보다 전자밀도가 높아 산란선에 매우 민감함을 알 수 있었다. 따라서 현재 진단영역에서 사용되고있는 IP는 심부선량측정계로는 적합하지 않다. 그러나 IP는 반음영외부부분(outside penumbra)을 제외한 조사문 선량측정에 비교적 정확한 것으로 밝혀졌다 또한 IP를 치료위치 확인용으로 사용할 수 있을 것으로 기대된다.