• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.168-169
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• 2002

일반적인 광섬유가 실리카로 만들어진 클래딩과 이보다 약간 굴절률이 높은 코어로 구성되어 있는 것과는 달리 광자결정 광섬유(photonic crystal fiber 또는 다공성 광섬유(holey fiber))는 코아와 클래딩이 순수 실리카로 구성되어 있다 클래딩의 효과를 주기 위해 광섬유 축을 따라서 규칙적인 공기구멍 다발을 형성하여 준다. 광자결정 광섬유는 특이한 광학적 특성 때문에 최근에 활발히 연구되어 지고 있다. 공기구멍의 구조를 조절함으로써 넓은 파장 영역에서 단일 모드로 진행하고(1), 아주 큰 분산을 갖게 할 수 lT고, hem 반경을 조절 할 수 있으며, 특이한 분산 특성과 이의 조절이 가능하다. (중략)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.926-931
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• 2002

Although ceramic plates with many micro-hales are used as MCP (Micro-channel plate) for electron amplification, catalytic converters, filters, electrical insulators and thermal conductors in integrated circuits, the drilling of micro-hales in the ceramics is difficult because of their low thermal conductivity, high hardness and brittleness. Therefore, in this work, the machining of ceramic green body fellowed by sintering of green body was employed fur fabricating ceramic plates with many micro-holes. The micro-drilling of alumina green body was performed with diamond abrasive WC drills, and the cutting force w.r.t. drilling times was measured for the determination of toot life. From the investigation of the wear of micro-drill tip w.r.t. drilling times, the wear mechanism of tip during micro-drilling of ceramic green body was suggested.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.275-280
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• 2001

Recently, the trends of industrial products grow more miniaturization, variety and mass production. Micro drilling which take high precision in cutting work is requested more micro hole and high speed working. Especially, Micro deep hole drilling is becoming more important in a wide spectrum of precision production industries, ranging from the production of automotive fuel injection nozzle, watch and camera parts, medical needles, and thick multi-layered Printed Circuit Boards(PCB) that are demanded for very high density electric circuitry. This paper shows the tool monitoring results of micro drill with tool dynamometer. And additionally, microscope with built-in monitor inspection show the relationship between burr in workpiece and chip form of micro drill machining.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.505-506
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• 2006

Size reduction of micro-aperture using additional deposition is presented in this study. PECVD process was used for additional deposition. Rate of deposition is different with deposition direction because corners of shadowmask membrane have a taper. Deposition into backside showed better than deposition into frontside with size reduction. Shadowmask membrane with two materials has stress because of the difference of a coefficient of thermal expansion The cantilever of membrane bend to opposite direction of deposition. Deposition to both frontside and backside could reduce inside stress.

• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.96-101
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• 2011

Operational and thermal characteristics of a thin disk Yb:YAG crystal with a thickness of 0.8 mm were studied using as a pumping source a fiber-coupled 930 nm laser diode. The heat generated in the crystal was dissipated by placing both surfaces in contact with copper plates with central hole, and the dependence of the temperature change in the illuminated spot on hole size was investigated by measuring the spectral change of the lasing peaks. The slope efficiency and optical-to-optical efficiency with respect to the LD pump power were as high as 42.2% and 34.8%, respectively. The temperature at the illuminated spot increased with diode current and with increasing hole size of the copper plate. When the hole size considerably exceeded the crystal thickness, the temperature rise deviated from the linear increase at high pump power.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.570-575
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• 2015

The green algae have cellulose as a main structural component of their cell wall and the cellulose content in green algae is much higher than other marine algae such as brown algae and red algae. Furthermore, green algae do not contain lignin in their cell wall and store starch as food in their plastids. Thus, it was investigated that the effect of hydrothermal pretreatment process utilizing microwave irradiation for Ulva pertusa Kjellman, a division of green algae, which is expected to be utilized for bioenergy production, on the enzymatic hydrolysis. The hydrothermal temperature have an effect on the pretreatment of Ulva pertusa Kjellman, but the effect of power of microwave irradiation is negligible. The rate of enzymatic hydrolysis was increased as the hydrothermal temperature increased until $140^{\circ}C$. The enzymatic hydrolysis of pretreated Ulva pertusa Kjellman under the optimum pretreatment conditions (50 W of microwave irradiation power and $150^{\circ}C$ of hydrothermal temperature) with cellulase, ${\alpha}$-amylase, and Novozyme 188 having ${\beta}$-glucosidase acitivity resulted in the saccharification of 96 wt% of total carbohydrate in Ulva pertusa Kjellman during 3 hrs, while it took 24 hrs for the enzymatic hydrolysis of untreated Ulva pertusa Kjellman. It confirmed that the hydrothermal pretreatment was effective on Ulva pertusa Kjellman for the enzymatic hydrolysis.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.9
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• pp.48-53
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• 1998

We have fabricated electrostatic lens with novel structure by mixing surface- and bulk-micromachining technology. Polysilicon was used for both the structure and sacrificial layer, and the structure layer was passivated with thermal oxide in order not to be attacked during the silicon wet etching. Compared with conventional electrostatic lens used in microcolumn, this device has the advantages in ; 1) hole alignment, throughput, reliability, damage of lens, 2) the possibility of arrayed lithography through the integration of microcolumn.

• Journal of the KSME
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• v.30 no.3
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• pp.246-251
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• 1990

마이크로폴라 탄성이론은 다른 마이크로연속체(microcontinuum) 이론에 비해 적용이 간단하며, 실제 많은 물리적인 현상을 규명하는 데 다양하게 이용할 수 있다. 특히 고전 탄성이론에 의해 적절하게 해결될 수 없는 덤벨(dumbell) 분자로 이루어진 물체, 액체 결정체(liquid crystals), 과립상(granular)의 분자로 구성된 물체와 복합 섬유재료(composite fibrous materials) 등은 마 이크로폴라 탄성이론에 의해 잘 해결될 수 있다. 또한 마이크로폴라 탄성이론은 고체 내에서의 파의 전파(propagation)와 분산(dispersion), 구멍 주위의 응력집중과 외부 하중을 받는 물체에 있어 균열끝에서의 응력 분포 등의 고체역학 문제들은 물론이고, 경계층(boundary layer), 난 류(turbulence), 유체 유동의 불안정(instability)과 표면장력 현상 등의 유체역학에서의 복잡한 문제들을 해결하는 데에도 이용할 수 있다. 마이크로폴라 탄성이론은 고전 탄성이론에 비해 상 대적으로 새롭고 미개척 분야이긴 하지만 이론의 기반이 확고하기 때문에 앞으로의 회전응력 측정장치의 개발을 통해 미소구조의 영향을 고려해야 하는 많은 문제들을 해결하는데 큰 기여를 할 것으로 전망된다.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.4
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• pp.67-72
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• 2001

An Effort has been made to more accurately analyze the flow in the chip cavity, particularly to model the flow through the openings in the leadframe and correctly treat the thermal boundary condition at the leadframe. The theoretical analysis of the flow has been done by using the Hele-Shaw approximation in each cavity separated by a leadframe. The cross-flow through the openings in the leadframe has been incorporated into the Hele-Shaw formulation as a mass source term. The optimization program based on the complex method integrated with flow analysis program has been successfully used to obtain the optimal filling conditions to avoid short shot.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.231-238
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• 2002

미세 절삭에 의한 마이크로 형상가공 및 이를 이용한 미세금형 가공기술개발을 위하여 절삭 공구를 이용한 기계적 미세 가공법에 대한 고찰과 더불어 shaping, end-milling, drilling 등의 가공이 가능한 기계적 미세 가공시스템을 구성하고 이를 이용한 미세 치형 그루브와 미세 격벽 등 미세 형상 구조의 금형 개발을 위한 가공실험을 수행하였다. 본 실험에서는 먼저 shaping 방식으로 세 종류의 다이아몬드 바이트를 사용하여 알루미늄, PMMA, Nickel, 황동 등의 소재에 pitch $150{\mu}m$, 높이 $8{\mu}m$ 내외의 미세 치형의 금형 코어를 가공하였고, 다음으로 Z축에 air spindle을 설치하여 $\phi0.2mm$의 end-mill(WC)을 사용하여 황동 소재에 깊이 $200{\mu}m$, 폭 $200{\mu}m,\;100{\mu}m,\;50{\mu}m,\;30{\mu}m$의 두께 변화를 주어 미세 격벽에 대한 가공실험을 하였다. 미세 구멍가공실험으로는 drilling 전용장비를 구성하여 $\phi0.6\~0.15mm$의 drill공구로 SM45C와 세라믹$(Si_3N_4-BN)$ 소재에 스텝이송방식에 의한 미세 구멍 가공 실험을 실시하였다.