• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.134-135
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• 2000

LCD의 전력소모중 약 70%를 차지하는 부분이 백라이트 유닛이다. 전세계적으로 저전력, 고화질, 대면적의 LCD 디스플레이를 개발하기 위한 연구가 활발히 진행중이다. 주로 백라이트 유닛을 구성하는 입사광학계와 도광체 및 프리즘 필름 등을 기존 제작공정 내에서 개선하는 것에 연구 개발의 초점이 맞추어져 있다. 본 연구는 기존의 개선 방법에서 벗어나 도광판의 형태와 산란입자의 크기에 따른 산란정도를 조절하여 기존의 도광판보다 더 나은 산란효율을 얻고자 한다. 이를 위해 투명도와 경도가 우수한 PMMA(polymethyl methacrylate)에 다양한 산란자를 투입하여 도광판을 제작한다. 도광판의 실제 제작 이전에 고효율 도광판속에서의 정확한 산란전산모사를 필수적으로 선행하여야 한다. 따라서 광산란 측정장치를 제작하여 산란자의 종류에 따른 원통형 도광체에서 측정한 산란강도와 산란전산모사에서의 결과를 비교 분석하여 저전력, 고화질, 대면적의 백라이트 유닛을 개발하기 위한 기초 자료로 사용하고자 한다. (중략)

• Laser Solutions
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• v.10 no.1
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• pp.19-27
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• 2007

Previous studies demonstrated that laser ablation under transparent liquid can result in ablation enhancement and particle removal from the surface. Although the ablation enhancement by liquid is already known for semiconductor and metal, the phenomena of polymer ablation have not been studied. In this work, tile liquid-assisted excimer laser ablation process is examined for polymer materials, such as polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) with emphasis on ablation enhancement and surface topography. In the case of PET and PMMA, the effect of liquid is analyzed both for thin water film and bulk water. The results show that application of liquid increases the ablation rate of PMMA while that of PET remains unchanged even in the liquid-assisted process. However, the surface roughness is generally deteriorated in the liquid-assisted process. The surface topography is found to be strongly dependent on the method of liquid application, i.e., thin film or bulk liquid.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.777-779
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• 2002

We report the performance of pentacene-based organic thin film transistors (OTFT) with PMMA (polymethyl methacrylate) as the gate insulator which was spin-coated on the ITO (indium tin oxide) glass substrate which was used as the gate contact. The pentacene thin film was deposited on the PMMA film and then Au source/drain contacts were deposited through shadow mask. The pentacene film shows better molecular ordering on PMMA compared with $SiO_2$ of Si wafer. The devices exhibited the field effect mobility of ${\sim}0.004cm^2$/Vs and on/off current ratio of ${\sim}10^3$.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2006.06a
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• pp.60-65
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• 2006

Previous studies demonstrated that laser ablation under transparent liquid can result in ablation enhacement and particle removal from the surface. In this work, the liquid-assisted excimer laser ablation process is examined fer polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), Si, and alumina with emphasis on ablation enhacement, surface topography, and debris formation. In the case of PET and PMMA, the effect of liquid is analyzed both fer thin water film and bulk water. As the ablation enhanement by liquid is already known for Si and alumina, the analysis focuses on surface topography and debris formation resulting from the liquid-assisted laser ablation process. The results show that application of liquid increases the ablation rate of PMMA while that of PET remains unchanged even in the liquid-assisted process. It is also revealed that the liquid can significantly improve the surface quality by reducing the debris deposition. However, the surface roughness is generally deteriorated in the liquid-assisted process. The surface toporaphy is found to be strongly dependent on the method of liquid application, i.e., thin film or bulk liquid.

• Journal of the Korean Ceramic Society
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• v.54 no.2
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• pp.102-107
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• 2017

The dependence of the IR optical properties of PMMA/$Al_2O_3$ nanocomposite on the alumina content was investigated in the wavelength range of $3500-2800cm^{-1}$. The samples were prepared via emulsion polymerization technique using oleic acid as a coupling agent. Grafting density calculations were carried out by means of elemental analysis CHN to yield the best coupling agent content. FTIR analysis confirmed the existence of a chemical bond between aluminum oxide and oleic acid. The outcomes of XRD analyses showed the presence of cubic gamma aluminum oxide in the nanocomposite, in contrast to the amorphous nature of PMMA. TEM images showed the core-shell morphology of the particles other than pristine PMMA. Optical constants of the nanocomposite were calculated based on FTIR spectra and the Kramers-Kronig equations. The presence of nano alumina modified some of the optical indexes in IR region.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.475-476
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• 2006

Using microwave synthesized HAp nano powder and polymethyl methacrylate (PMMA) as a pore-forming agent, the porous biphasic calcium phosphate (BCP) ceramics were fabricated depending on the sintering temperature. The synthesized HAp powders was about 70-90 nm in diameter. In the porous sintered bodies, the pores having $150-180\;{\mu}m$ were homogeneously dispersed in the BCP matrix. Some amounts of pores interconnected due the necking of PMMA powders which will increase the osteoconductivity and ingrowth of bone-tissues while using as a bone substrate. As the sintering temperature increased, the relative density increased and showed the maximum value of 79.6%. From the SBF experiment, the maximum resorption of $Ca^{2+}$ ion was observed in the sample sintered at $1000^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.349-349
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• 2005

수동소자를 PCB(Printed Circuit Board) 안으로 집적하기 위한 방법의 일환으로 polymer-metal, polymer-ceramic composite에 연구가 국내외 연구 국내외 연구기관에서 광범위하게 진행되고 있다. 본 연구에서는 polymer-metal-ceramic composite 에서 PZT-coated Ni의 volume fraction에 따른 유전율 변화에 대하여 조사하였다. 원료로는 PZT(52/48) solution. 니켈금속분말, PMMA(polymethyl methacrylate)를 사용하였다. 전기적 특성은 임피던스분석기를 이용하여 측정하였으며 mixing rule과 percolation theory를 이용하여 결과를 해석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.206.1-206.1
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• 2013

유기 혼합물을 사용한 비휘발성 메모리 소자는 간단히 공정 할 수 있고 생산성이 높기 때문에 많은 연구가 진행 중이다. 하지만 종류가 많은 유기 혼합물 중에서, [6,6]- phenyl-C85 butyric acid methyl ester (PCBM) 나노 입자가 고분자 박막에 분산되어 있는 유기 혼합물을 사용하여 제작한 메모리 소자에 대한 연구는 아직 미미하다. 본 연구에서는 PCBM 나노 입자를 포함한 polymethyl methacrylate (PMMA) 박막을 활성층으로 사용하는 비휘발성 메모리 소자를 제작하고 활성층의 두께를 변화하며 전기적 특성과 안정성에 대한 실험을 통해 성능을 평가했다. 소자는 PCBM 나노 입자와 PMMA를 클로로벤젠으로 용해시킨 후에 초음파 교반기를 사용하여 PCBM 나노 입자가 PMMA용액에 고르게 섞이도록 해서 제작하였다. Indium tin oxide (ITO)가 증착한 유리기판 위에 PCBM/PMMA 형성된 고분자 용액을 여러가지 rpm 속도로 스핀 코팅하였다. 용매를 가열해서 제거하여, PCBM 나노 입자가 PMMA에 분산된 두께가 다른 박막을 형성 하였다. 상부 전극은 분산된 PMMA 박막 위에 열 진공 증착기를 이용하여 제작하였다. 본 연구에서 전류-전압 (I-V) 측정을 사용하여 메모리 소자의 기억층의 두께 변화에 따른 전기적 성질을 관찰 하였다. I-V 측정 결과는 특정 두께의 박막에서 큰 ON/OFF 전류 비율을 보였다. 기억층의 두께가 최적화된 소자로 형성된 박막에서 전류-시간 유지 특성을 측정하여 소자의 ON/OFF 비율이 $1{\times}104$ 초까지 유지되는 것을 확인 할 수 있었다. 나노 입자가 포함된 박막의 특정 두께에서 성능이 향상된 메모리 특성을 보이는 것을 확인하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.5
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• pp.109-116
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• 2016

Polymethyl methacrylate is commonly used in the outer lens of automotive rear lamps. However, if the lens warps above the allowable limit, it may lead to faulty connection with the housing, and failure of the assembly. This study investigated the effects of gate diameter and cooling line distance in the mold design for automotive outer lens. The optimal gate diameter and cooling line distance to minimize the warp of the outer lens were derived as 3.0 mm and 50-60 mm respectively, and the cooling temperature to minimize warp was shown to be $60-80^{\circ}C$ (mold surface temperature $48-67^{\circ}C$). A higher cooling temperature may somewhat mitigate the warp, but is undesirable because it may cause injection molding problems, such as sinks. A mold was constructed matching the optimal design and the produced lens properties, particularly the degree of warp, were comparable with the CAE predictions.

• Journal of the Korean Society of Radiology
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• v.11 no.6
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• pp.453-458
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• 2017

Computed Tomography (CT) provides information on the Diagnostic Reference Level Computed Tomography Dose Index (CTDI) and Dose Length Product (DLP) for accurate diagnosis of patients. However, it does not provide a dose change according to the table height for the diagnostic reference level provided by the CT equipment. The purpose of this study was to evaluate the image and dose according to the table height change using phantom (PMMA: Polymethyl Methacrylate) in order to find the optimal image and the minimum dose during computed tomography examination. When examining using a 32 cm PMMA phantom with the same thickness as the abdomen of an adult, there was little change in dose with table height. However, the noise evaluation of the image caused a high fluctuation of noise depending on the table height. and in the case of the 16 cm PMMA phantom, the change of the noise was small, but the dose change was about 30%. In conclusion, the location of the patient and the center of the detector are important during computed tomography (CT) examinations. In addition, table height setting is considered to be important for examinations with optimized image and minimum dose.