• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2430-2432
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• 2005

최근 다이오드 레이저의 파워가 높아짐에 따라 다이오드 레이저를 이용한 레이저 가공 공정이 많은 분야에서 응용되고 있다. 그러나 고출력 다이오드 레이저의 출력은 타원형의 빔이므로 정밀 공정이 어려워 원형의 빔으로 변환하여야 한다. 본 논문에서는 여러 가지 렌즈를 사용하여 설계를 시도하였으며 최적의 설계로서 anamorphic prism pair를 이용하여 타원형의 빔을 원형의 빔으로 바꾸는 광학계를 설계하였으며 원형빔의 크기를 축소하기 위해 beam size reducer를 설계하였다.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.91-101
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• 2017

In this study, we conducted the preliminary research for high speed laser cutting of LED module. In particular, the feasibility of ultra-high speed laser cutting of 100 mm/s which exceeds the cutting speed of conventional dicing saw was examined. For this, copper/ceramic and silicone/ceramic hybrid substrates, which are the components of the LED module, were fabricated, and the surface morphology, surface roughness and flexural strength of the laser-cut samples were investigate and compared with the dicing-cut samples. To investigate optimal laser cutting conditions for hybrid substrates, the effects of various laser cutting conditions on cutting surface characteristics were studied using single ceramic and copper substrate. Optimal laser cutting conditions of the hybrid substrates were the use of Ar assist gas, high laser power and high assist gas pressure. Comparing the cutting surface of the hybrid substrates, the surface characteristics of the laser-cut samples are slightly inferior to those of the dicing-cut samples. The average surface roughness of the laser-cut samples was about $9{\mu}m$, and that of the dicing-cut samples was about $4{\mu}m$. However, considering very low cutting speed (3 mm/s) of the dicing saw, the surface morphology of the laser-cut sample was relatively uniform, and the surface roughness was not much different from that of the dicing-cut sample. The flexural strength of the laser-cut samples was equivalent to or slightly inferior to the flexural strength of dicing-cut samples. However, if the laser processing conditions are sufficiently optimized, the ultra-high speed laser cutting of the LED module will be possible.

• Korean Journal of Optics and Photonics
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• v.32 no.2
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• pp.55-61
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• 2021

The lateral-mode characteristics of 850-nm GaAs/(Al,Ga)As multiple-quantum-well laser diodes and their influence on the kinks in output optical power are investigated. For the investigation, self-consistent electro-thermal-optical simulation and measurement of fabricated devices are used. From this investigation, the optimal P-cladding thickness that provides single-lateral-mode operation is determined, so that high beam quality can be achieved even at high output powers.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.589-595
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• 2001

The present study conducted heat transfer analysis in multi-layer of CD-R. It is necessary to analyze heat transfer during the recording process to find optimum power and write strategy in CD-R. This study investigated effects of several parameters such as recording speed, laser power, layer thickness and thermal property. The calculated results presented temperature distribution in the multi-layer and detailed information of recording characteristics. Optimum laser power was estimated, comparing an optimum mark length with the calculated mark lengths. The results showed that the optimum laser power was influenced significantly by the layer thickness and the thermal properties of the dye.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.154-160
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• 1990

System modeling for Heterodyne/Coherent Optical BFSK receiver is described and its receiver performance is evaluated. Receiver performance is deteriorated due to both shot noise and laser phase nois. Therefore, to minimize these noise impacts PLL loop natural frequency is selected optimally. For different power penalty due to phase error, required phase error variance to achieve $BER=10^{-9}$, nomalized loop power, and laser linewidth/bit rate(${\Delta\nu}s/Rb$) are derived. For 0.5dB power penalty, phase error variance=0.035(${rad^2}$), photon numbers=20.0, nomalized loop power = $3.8{\times}10^{-3}$(electron/s per herz), and ${\Delta\nu}s/Rb=5.24{\times}10^{-3}$ are obtained.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.108-108
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• 2009

Precipitation hardening nickel base alloys strengthened by intermetallic compounds are extensively used to manufacture on the components of the hot section of gas turbine engines. To ensure structural stability and maintenance of strength properties for a long time, nickel alloys are normally subjected to complex alloying with elements to form ${\gamma}'$(gamma prime). Such alloys have a limited weldability, are normally welded in high temperature. However, laser welding have a merit that applies in room temperature as easy control of welding parameter and heat input. In this study, $CO_2$ laser welding is applied on STS304 plate with good ductility and precipitation hardening nickel base alloy (GTD111DS) used blade material. Also, several welding parameters are applied on powder, power and travel speed. There are no cracks in Rene 80 and IN 625 powder when STS304 plate is used. But IN 625 powder has no cracks and Rene 80 have some cracks in welds with GTD111DS substrate. Adjusting of welding parameter is tried to apply Rene 80 having a good strength compare to IN 625. In the result of adjusted welding parameter, optimized welding parameters are set with low power, low feed rate and high welding speed. Tensile strength of GTD111DS substrate with Rene 80 powder is same and over than the one of base metal in room temp and high temp($760^{\circ}C$).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.217-221
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• 2018

Selective laser melting (SLM) technique is one of the additive manufacturing processes, in which functional, complex parts can be directly manufactured by selective melting layers of powder. SLM technique has received great attention due to offering a facile part-manufacturing route and utilizing a hard-to-manufacturing material (e.g. Ti6Al4V). The SLM process allows the accurate fabrication of near-net shaped parts and the significant reduction in the consumption of raw materials when compared to the traditional manufacturing processes such as casting and/or forging. In this study, we focus the high-speed additive manufacturing of Ti6Al4V parts in the aspect of manufacturing time, controlling various process parameters.

• Archives of design research
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• v.18 no.2 s.60
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• pp.303-314
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• 2005

This study is intended to promote local woodcraft industry with revitalization of local festival in Inje-county. To do so, we propose the travel souvenir design with local identity and the plan for production and marketing based on the management of 'Design Hospital' and the building of production method through 'laser wood inlaying technique like puzzle style'. Research method is benchmarking analysis of successful cases of travel souvenir which is developed for cultural contents of local festival. The result of this study is the following. First, design outsourcing is done one of support in industry focused on old boy network, Through it, Special brain of design can be supplied without compensation. Also the difficulty of manpower problem is lessened and the ability of product development in short term can be guaranteed. On the basis of this, we are able to apply Mass Customization production by up to date digital production method. This enables us to maintain the production flexibility of cultural goods fit for the traits of local festival. This study is intended to present the best model guananteeing both profit of wood technological industry and the possibility of local cultural.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.7
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• pp.7-14
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• 2009

In this paper, the effects of annealing conditions on the structural ((002) intensity, FWHM, d-spacing, grain size, (002) peak position), optical (UV peak, UV peak position) and electrical properties (carrier concentrations, resistivity, mobility) of ZnO films were investigated. ZnO films were deposited onto SiO$_2$/si substrates by RF magnetron sputtering from a ZnO target. The substrate was not heated during deposition. ZnO films were annealed in temperature ranges of $500\sim650^{\circ}C$ in the O$_2$ flow for 5$\sim$20 min. The film average thicknesses were in the range of 291 nm. The surface morphologies and structures of the samples were characterize by SEM and XRD, respectively. The optical properties were evaluated by photoluminescence (PL) measurement at room temperature (RT) using a He-Cd 325 nm laser. As the annealing temperature and time vary, the following relations were also observed: (1) proportional relationships among UV intensity (002) intensity, and grain size exist, (2) UV intensity is inversely proportional to FWHM, (3) there is no special relationship between UV intensity and electron carrier concentrations, (4) d-spacing is inversely proportional to (002) peak position, (5) UV peak position in the range of 3.20$\sim$3.24 eV means that ZnO films have a n-type conductivity which was consistent with that obtained from the electrical property, (6) the optimal conditions for the best optical and structural characteristics were found to be oxygen fraction, (O$_2$/(O$_2$+Ar)) of 0.2, RF power of 240W, substrate temperature of RT, annealing condition of 600$^{\circ}C$ for 20 min, and sputtering pressure of 20 mTorr.