• Journal of Photoscience
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• 제3권3호
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• pp.141-145
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• 1996

The heat generated by nonradiative decay dynamics induces thermal lens effect. From such an effect, photodynamic properties of solutions can be investigated with two-color pulsed thermal lens experiments which have the time resolution of down to nanoseconds. In this study, using nanosecond two-color thermal lens method, we investigated the triplet state of benzophenone and the singlet oxygen state dynamics in various oxygen concentration solvents. The measured triplet state lifetimes, singlet oxygen relaxation times and singlet oxygen formation quantum yields are in good agreement with the reference values. From these parameters the existence of the triplet exciplex formation between benzophenone and benzene is proved, and it is also suggested that the relaxations of triplet states of benzophenone undergo coupled dynamics with some of singlet oxygens in oxygen-rich conditions.

• 한국생산제조학회지
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• 제21권5호
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• pp.773-777
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• 2012

Recently UV laser micromachining processes is widely introduced to meet the needs of advanced components of IT, BT and ET industries. Due to the characteristics of non-contact and high-speed laser processing, UV laser micromachining is applied to manufacture very thin substrate such as polymer, metals and composite. These minimum line width obtained by UV laser micromachining is generally determined from laser wavelength, optical lens and its numerical aperture. In this paper we will show the lens effect of water droplet on the surface of workpiece to reduce the line width when UV laser light is irradiated and focused through the water droplet. Because of the refraction effect generated by the semi-spherical or spherical shape of water droplet, we can find smaller line width. And water droplet could not only protect thermal deformation, but also carry away burr around micro dent. Firstly fundamental theory of minimum line width was derived from relationship between the geometry of water droplet and laser light trace, and then experimental and simulation results will be finally compared to verify the effectiveness of water droplet lens effect of UV laser micromachining process.

• 한국광학회지
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• 제18권3호
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• pp.208-215
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• 2007

광섬유 연결 반도체레이저 여기 세라믹 Nd:YAG 레이저의 열렌즈를 보상하기 위한 공진기를 구성하였다. 초점거리 30 mm, 유효직경 22 mm인 보상렌즈를 레이저 매질의 단면으로부터 25 mm 떨어진 곳에 위치시켜 열렌즈 효과를 보상하였다. 보상렌즈가 없는 경우 레이저 출력은 열렌즈 효과에 의해 여기파워 6 W 이상에서 급격히 감소하기 시작하였으며, 12 W에 이르러서는 레이저가 거의 발진되지 않았다. 열렌즈 효과가 보상되었을 경우 레이저 출력은 선형적으로 증가하였으며, 여기파워 12 W에서 $M^{2}$값은 2.4로 좋은 빔질을 나타내었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.95-98
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• 2006

LCD-BLU (Back Light Unit) is one of kernel parts of LCD unit. The fabrication method of a 3-D micro mold patterned with micro-lenses for the LGP (Light Guiding Plate), one of the most important parts of LCD-BLU, was presented. Instead of dot pattern made by etching, 3-D optical pattern design with $50{\mu}m$ micro-lens was applied in the present study. The micro-lens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP. The positive micro-lens patterned injection mold with different aspect ratios (i.e. 0.3 and 0.4) was fabricated with modified LiGA with thermal reflow process. The brightness of LCD-BLU increased as aspect ratio of micro-lens increased.

• Tribology and Lubricants
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• 제25권2호
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• pp.86-95
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• 2009

Adhesion tests were carried out in order to investigate the effect of temperature on the adhesion behavior between a PMMA film and a fused silica lens in the micro scale. For the tests, a microtribometer system was specially designed and constructed. The pull-off forces on the PMMA film were measured under atmospheric condition as the temperature of the PMMA film was increased from 300 K to 443 K and decreased to 300 K. The contact area between the PMMA film and the lens was observed during the test. The adhesion behavior was changed with the change of the PMMA surface state as the temperature increased. In glassy state below 363 K, the pull-off force did not change with the increase of temperature. In rubbery state from 383 K to 413 K, the pull-off force increased greatly as the temperature increased. In addition, the area of contact was enlarged. In viscous state above 423 K, the fingering instability was observed in the area of contact when the PMMA film contacted with the lens. It was also found that the adhesion behavior can be varied with the thermal history of the PMMA film. The residual solvent in the PMMA film could emerge to the PMMA surface due to the heating and reduced the pull-off force.

• 한국컴퓨터정보학회논문지
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• 제21권12호
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• pp.19-26
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• 2016

In this paper, we propose an efficient design method for a thermal camera with continuous zoom based on the research and manufacturing experience of the thermal camera. In addition, it is divided into system design method, optical design method, mechanical design method, and electronic design method. First, we propose an effective NUC compensation method and a lens-specific sensitivity design method in terms of system. Second, we propose a zoom trajectory design method considering the temperature effect on the optical aspect. Third, it suggests the minimization of optical axis shaking between magnification conversion in terms of mechanism. Finally, we propose a lens-specific temperature compensation method and a speed conversion algorithm according to the zoom interval as an electronic aspect.

• 한국신뢰성학회지:신뢰성응용연구
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• 제6권2호
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• pp.173-186
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• 2006

This paper presents a study on the failure mechanism for optical engine of Projection TV. The lenses of which optical engine composes are failed by various environmental conditions, that is, thermal effect, moisture effect, mechanical shock or chemical effect. By surveying on actual TV working condition, the major factor of failure was turned out the thermal effect. Because the actual surface temperature of optical engine rose at max. $51^{\circ}C$ during it worked, the relative humidity around optical engine was kept at less than 20% that is difficult to do chemical reaction with humidity. Therefore we can make a conclusion that the major failure of optical engine resulted from thermal effect.

• 새물리
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• 제68권11호
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• pp.1167-1172
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• 2018

탄소 나노 튜브는 탄소 원자들이 육각형의 벌집모양으로 서로 연결된 고분자 탄소동소체로 다중벽일 경우 $3000W{\cdot}m^{-1}{\cdot}K^{-1}$, 단일벽일 경우 $6000W{\cdot}m^{-1}{\cdot}K^{-1}$ 정도로 매우 높은 열전도도를 보인다. 본 연구에서는 단일 빔과 이중 빔 방법으로 열렌즈 효과를 이용하여, 1.5 M 다중벽 탄소 나노튜브 분산액의 투과율과 열확산도를 측정하였다. 단일 레이저 빔의 진행방향으로 시료를 움직이는 z-scan 방법을 통해 비선형 광학계수들을 구하고, 이중 레이저 빔을 이용하여 열확산도를 측정하였다. 펌프 빔으로는 파장 532 nm이고 세기가 100 mW인 DPSS (Diode-pumped solid state, DPSS) 레이저를 사용하였고, 프로브빔으로는 파장이 633 nm이며 세기가 5 mW인 He-Ne 레이저를 사용하였다. 실험 결과 농도가 9.99, 11.10, 16.65, 19.98 mM일 때 비선형 흡수계수는 각각 0.046, 0.051, 0.136, 0.169 m/W였다. 또한 비선형 굴절률은 0.20, 0.51, 1.25, $1.32{\times}10^{-11}m^2/W$였고, 열확산도 평균치는 $1.33{\times}10^{-6}m^2/s$이었다.

• 한국재료학회지
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• 제28권8호
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• pp.452-458
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• 2018

This research is conducted to create a functional hydrogel ophthalmic lens containing nanoparticles. Carbon nanoparticles and PEGMEMA are used as additives for the basic combination of HEMA, MA, and MMA, and the materials are copolymerized with EGDMA as the cross-linking agent and AIBN as the thermal initiator. The hydrogel lens is produced using a cast-mold method, and the materials are thermally polymerized at $100^{\circ}C$ for an hour. The polymerized lens sample is hydrated in a 0.9 % saline solution for 24 hours before the optical and physical characteristics of the lens are measured. The refractive index, water content, contact angle, light transmittance, and tensile strength are measured to evaluate the physical and optical characteristics of the hydrogel lens. The refractive index, water content, contact angle, UV-B light transmittance, UV-A light transmittance, visible light transmittance, tensile strength and breaking strength of the hydrogel lens polymer are 1.4019~1.4281, 43.05~51.18 %, $31.95{\sim}68.61^{\circ}$, 21.69~58.11 %, 35.59~84.26 %, 45.85~88.06 %, 0.1075~0.1649 kgf and 0.1520~0.2250 kgf, respectively. The results demonstrate an increase in refractive index, tensile strength and breaking strength and a decrease in contact angle and light transmittance. Furthermore, the visible light transmissibility is significantly increased at PEG 10 %. It is clear that this material can be used for high-performance ophthalmic lenses with wettability, ultraviolet ray blocking effect, and tensile strength.

• 통합자연과학논문집
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• 제11권1호
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• pp.1-8
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• 2018

HEMA, AA, MMA, and EGDMA as crosslinking agent and AIBN as an initiator, and 2,4-dihydroxybenzophenone, 2-ethylhexyl-trans-4-methoxy-cinnamate, 2-hydroxy-4-(methacryloyloxy)benzophenone as additives at 0.1-1.0% ratios were used to manufacture hydrophilic ophthalmic lenses through thermal polymerization before their physical properties were measured. The results showed that the samples containing of 2,4-dihydroxybenzophenone and 2-ethylhexyl-trans-4-methoxy-cinnamate resulted in a decrease of the UV blocking performance after high-pressure sterilization whereas the sample containing 2-hydroxy-4-(methacryloyloxy)benzophenone showed no change in the UV blocking performance. It is judged that this is induced by presence or absence of an acyl functional group in benzophenone.