• Composites Research
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• 제36권3호
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• pp.162-166
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• 2023

복합재료는 일반적인 고강도 구조체에 활용성이 증가하고 있지만 최신의 복합적인 전자기기 내부 소자 등과 같은 multifunctional 재료들의 성능 특성 요구가 증가하고 있다. 기기의 방열 특성의 경우 대표적으로 요구되는 물성인 반면 복합재료의 경우 적층 공정으로 인해 수직 방향의 열적 특성 제어는 해결해야 될 문제 중 하나이다. 본 연구에서는 vacuum filtration 방법을 이용하여 Carbon fiber reinforced polymer를 제작하였다. 복합재료 제작 공정에서는 섬유들의 분산에 활용성이 가장 뛰어난 세 가지 solvent들을 사용하여 solvent의 영향을 살펴보았다. 또한 세가지의 aspect ratio를 가지는 단섬유 carbon fiber들의 수직 방향의 배열성을 확인하기 위해 현미경을 통한 morphology를 관찰하였고 제작된 시편의 열전도도 측정을 통해 배열성을 검토하였다. 시편의 열전도도 측정 결과 단섬유 carbon fiber의 aspect ratio가 낮을수록 높은 열전도도를 보였으며 through-plane 방향의 열전도도는 DMF, NMP, Acetone 순으로 각각 8.69 W/m·K, 10.32 W/m·K, 13.01 W/m·K의 증가되는 값을 보였다.

• 한국인터넷방송통신학회논문지
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• 제14권4호
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• pp.165-172
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• 2014

자동차가 도로를 주행하는데 있어, 도로설계기준에 미흡한 노면의 상태와 도로환경은 운전자에게 큰 영향을 미친다. 특히, 과거에는 도로설계를 경험적이고 관념적인 판단으로 설계하고 수행하였으나, 최근에는 3, 4차원의 요소들을 동시에 검토하고 조정하는 새로운 기술개발이 시도되고 있다. 본 연구에서는 교통사고 재현을 위한 PC-crash 프로그램을 이용하여 빙판도로의 최고점에서 제동시 주행속도와 종단경사 변화에 따른 차량의 거동특성을 분석하였다. 그 결과로, 교차로 종단경사에 대한 차량거동특성에 노면상태에 따른 마찰계수와 차량속도가 영향을 미친다는 사실을 확인하였으며, 도로설계에 대한 문제점을 사전에 해결하기 위한 시뮬레이션을 통하여 검증의 적합성을 보여주었다.

• 구강회복응용과학지
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• 제30권4호
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• pp.329-338
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• 2014

치주질환이나 우식으로 인해 구치부 치아가 상실된 환자들은 잔존하고 있는 전치부 및 소구치부 치아로 안정된 교합고경을 유지하기 어렵다. 구치의 상실로 대합치의 정출이나 인접치의 경사가 발생되는 경우 교합평면이 붕괴되거나 부적절한 교합간섭을 야기하게 된다. 만약 치아 상실 상태가 지속된 경우에는 하악의 전방이동으로 인해 상악 전치의 동요와 순측 이개를 초래하게 되며 치주질환이 동반된 경우에는 더욱 심각한 상황으로 변화한다. 이와 같이 치아의 병적 이동이 일어난 환자의 치료는 보존 및 치주치료, 교정 치료를 통한 재배열, 그리고 상실된 치아의 보철수복을 통한 교합 고경의 재설정 및 유지와 같은 다과간 협력 진료가 매우 중요하다.

• Journal of the Optical Society of Korea
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• 제5권2호
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• pp.55-59
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• 2001

Results of an experimental study of possible ways to extend the capabilities of a big size transmission type holographic screen are presented. Different approaches to the problem of making a big size screen have been considered and tested experimentally. Up to 60$\times$80 $\textrm{cm}^2$ screens have been recorded on a single photographic plate VRP-M. By attaching a mirror behind the screen, the reflection mode of operation has been obtained. In this arrangement some additional peculiarities appear in the screen, which can be used to extend the screen capabilities. The first possibility is to increase the screen size by mosaicking the subscreens in the reflection mode of operation. Screens of 120$\times$80 $\textrm{cm}^2$ and 180$\times$40 $\textrm{cm}^2$ have been obtained by proper alignment of 60$\times$40 $\textrm{cm}^2$ subscreens. The second possibility is to move the viewing Bone by rotation of the screen together with the mirror and thereby realize by the eye-tracking capability. Methods of increasing vertical size of the viewing zone have been considered. Along with the multi-exposure method, which was considered in previous papers, addition of the vertical diffuser with the optimized scattering angle has been tested experimentally. The vertical size of the viewing zone has been increased by up to 10-15 cm. Another method consists of usage of a diffraction grating with vertical dispersion to solve the same problem.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.699-704
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• 2018

일차원 나노구조물은 양자 갇힘 효과 및 나노와이어가 갖는 체적 대비 높은 표면적 비에 기인하는 독특한 전기적, 광학적, 광전기적, 전기화학적 특성으로 인하여 많은 주목을 받아왔다. 특히 수직으로 성장된 나노와이어는 체적 대비 높은 표면적 비의 특성을 나타낸다. VLS(Vapor-Liquid-Soild) 공정은 나노구조물의 성장 과정에서 자기정렬 효과 때문에 더욱 주목을 받는다. 본 연구에서는 두 영역 열화학 기상증착법을 이용하여 Si\$SiO_2$(300 nm)\Pt 기판 위에 수직으로 정렬된 실리콘 옥사이드 나노기둥을 VLS 공정으로 성장시켰다. 성장된 실리콘 옥사이드 나노기둥의 형상과 결정학적 특성을 주사전자현미경 및 투과전자현미경으로 분석하였다. 그 결과 성장된 실리콘 옥사이드 나노기둥의 지름과 길이는 촉매 박막의 두께에 따라 변하였다. 실리콘 옥사이드 나노 기둥의 몸체는 비정질 상을 나타내었으며, Si과 O로 구성되어 있었다. 또한 성장된 실리콘 옥사이드 나노 기둥의 머리는 결정성을 나타내었으며, Si, O, Pt 및 Ti으로 구성되어 있었다. 실리콘 옥사이드 나노 기둥의 수직 정렬은 촉매물질인 Pt/Ti 합금의 결정성 정렬 선호에 기인하는 것으로 판단되며, 수직 성장된 실리콘 옥사이드 나노기둥은 기능성 나노소재로 활용이 가능할 것으로 기대된다.

• 전기학회논문지
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• 제56권1호
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• pp.132-138
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• 2007

Carbon nanotubes (CNTs) arc grown on Ni catalysts employing an inductively-coupled plasma chemical vapor deposition (ICP-CVD) method. The structural and field-emissive properties of the CNTs grown are characterized in terms of the substrate-bias applied. Characterization using the various techniques, such as field-omission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Auger spectroscopy (AES), and Raman spectroscopy, shows that the structural properties of the CNTs, including their physical dimensions and crystal qualities, as well as the nature of vertical growth, are strongly dependent upon the application of substrate bias during CNT growth. It is for the first time observed that the provailing growth mechanism of CNTs, which is either due to tip-driven growth or based-on-catalyst growth, may be influenced by substrate biasing. It is also seen that negatively substrate-biasing would promote the vertical-alignment of the CNTs grown, compared to positively substrate-biasing. However, the CNTs grown under the positively-biased condition display a higher electron-emission capability than those grown under the negatively-biased condition or without any bias applied.

• 한국전기전자재료학회논문지
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• 제15권4호
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• pp.367-372
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• 2002

The vertically well-aligned carbon nanotubes(CNTs) were successfully grown on Ni coated silicon wafer substrate by DC bias-assisted PECVD(Plasma Enhanced Chemical Vapor Deposition). As a catalyst, Ni thin film of thickness ranging from 15~30nm was prepared by electron beam evaporator method. In order to find the optimum growth condition, the type of gas mixture such as $C_2H_2-NH_3$ was systematically investigated by adjusting the gas mixing ratio at $570^{\circ}C$ under 0.4Torr. The diameter of the grown CNTs was 40~200nm and the diameter of the CNTs increased with increasing the Ni particles size. TEM images clearly showed carbon nanotubes to be multiwalled. The measured turn-on field was $3.9V/\mu\textrm{m}$ and an emission current of $1.4{\times}10^4A/\textrm{cm}^2$ was $7V/\mu\textrm{m}$. The CNTs grown by bias-assisted PECVD was able to demonstrate high quality in terms of vertical alignment, crystallization of graphite and the processing technique at low temperature of $570^{\circ}C$ and this can be applied for the emitter tip of FEDs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.108-109
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• 2006

ZnO semiconductor has a wide band gap of 3.37 eV and a large exciton binding energy of 60 meV, and displays excellent sensing and optical properties. In particular, ZnO based 1D nanowires and nanorods have received intensive attention because of their potential applications in various fields. We grew ZnO buffer layers prior to the growth of ZnO nanorods for the fabrication of the vertically well-aligned ZnO nanorods without any catalysts. The ZnO nanorods were grown on Si (111) substrates by vertical MOCVD. The ZnO buffer layers were grown with various thicknesses at $400^{\circ}C$ and their effect on the formation of ZnO nanorods at $300^{\circ}C$ was evaluated by FESEM, XRD, and PL. The synthesized ZnO nanorods on the ZnO film show a high quality, a large-scale uniformity, and a vertical alignment along the [0001]ZnO compared to those on the Si substrates showing the randomly inclined ZnO nanorods. For sample using ZnO buffer layer, 1D ZnO nanorods with diameters of 150-200 nm were successively fabricated at very low growth temperature, while for sample without ZnO buffer the ZnO films with rough surface were grown.

• 대한전자공학회논문지
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• 제23권6호
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• pp.758-765
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• 1986

The design, fabrication and performance of vertical double diffused power MOSFET (VDMOS) were described. On the antimony (Sb) doped (~7x10**17 cm**-3) silicon substrate (N+), epitaxial layer(N-) was grown. The thickness and the resistivity of this layer were 32\ulcorner and about 12\ulcorner-cm, respectively. The P- channel length which was controlled by sequential P-/N+ double diffuison method was about 1~2 \ulcorner, and was processed with the self alignment of 21 \ulcorner width poly silicon. To improve the breakdown voltage with constant on-resistance (Ron) about 1\ulcorner, three P+ guard rings were laid out around main pattern. With chip size of 4800\ulcorner x4840 \ulcorner, the VDMOS has shown breakdown voltage of 410~440V, on-resistance within 1.0~1.2\ulcornerand the current capablity of more than 5A.

• 대한치과보철학회지
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• 제32권2호
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• pp.327-353
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• 1994

This study was performed to evaluate the effects of number and alignment of implant fixture and various bar designs on the retention of denture and the stress distribution. Six kinds of photoelastic mandibular models and nine kinds of overdenture specimens were designed. A unilateral vertical load was gradually applied on the right first molar to calculate the maximal dislodgement load of each specimen. A unilateral vertical load of 17 Kgf was applied on the right first molar and a vertical load of 10 Kgf was applied on the interincisal edge region. The stress pattern which developed in each photoelastic model was analyzed by the reflection polariscope. The results obtained were as follows: 1. The maximal dislodgement load reversely increased with the distance from the loading point to the implant fixture, while it linearly increased with that from the most posterior implant fixture to the mesial clip. The maximal dislodgement load also increased with the use of a cantilever bar. 2. Under the posterior vertical load, the stress to the supporting tissue of the denture base increased with the distance from the loading point to the implant future. The stress concentration on the apical area of the implant future reversely increased with the distance from the loading point to the implant future. 3. In the overdentures supported by two implant fixtures under the posterior vertical load. the specimen implanted on lateral incisor areas with a cantilever bar exhibited more favorable stress distribution than that without a cantilever bar. The specimen implanted on the canine areas without a cantilever bar, however, exhibited more favorable stress distribution. 4. In the overdentures supported by three implant fixtures. the specimen implanted ell the midline and canine areas exhibited more favorable stress distribution than that implanted oil the midline and the first premolar areas. 5. In the overdentures supported by four implant fixtures. the specimen implanted with two adjacent implant fixtures exhibited more favorable stress distribution than that implanted at equal distance under the posterior vertical load. 6. Under the anterior vertical load, the overdentures supported by three implant fixtures exhibited stress concentration on the supporting structure of the middle implant future. In overdentures supported by two or four implant futures, no significant difference was noted in stress distribution between the types of bars. These results indicate that the greater the number of implant fixtures, the better the stress distribution is. A favorable stress distribution may be obtained in the overdentures supported by two or three implant fixtures, if the location and the design of the bar are appropriate.