• Laser Solutions
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• v.18 no.4
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• pp.17-22
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• 2015

In this paper, ablation rate of $Al_2O_3$ ceramics by femtosecond laser fluence is derived with experimental method. The automatic three axis linear stage makes laser optics to move with high spatial resolution. With 10 times objective lens, minimal pattern width of $Al_2O_3$ is measured in the focal plane. Ablated surface area is shown as linear tendency increasing number of machining times with various laser power conditions. Machining times is most sensitive condition to control $Al_2O_3$ pattern width. Also, the linear increment of pattern width with laser power change is investigated. In high machining speed, the ablation volume rate is more linear with fluence because pulse overlap is minimized in this condition. Thermal effect to surrounding medium can be minimized and clean laser process without melting zone is possible in high machining speed. Ablation volume rate decelerates as increasing machining times and multiple machining times should be considered to achieve proper ablation width and depth.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.3
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• pp.68-76
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• 1985

A charge-coupled device (CCD) area image sensor has been demonstrated with an experi-mental 16$\times$16 prototype. The prototype is a vertical frame transfer charge.coupled imager using two-phase gate electrode structures. In this device, ion-implanted barriers are used for two -phase CCD, and NMOS process has been adopted. The total imaging setup consisting of optical lens, clock generators, clock drivels, staircase signal generators, and oscilloscope is easily achieved with the aid of PROM . English alphabets are displayed on the oscilloscope screen using the total imaging set-up. We measure charge transfer inefficiency and dark current for the fabricated devices.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2005.11a
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• pp.37-41
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• 2005

When screen size of the Flat Panel Display (FPD) becomes larger, the traditional photo-lithography using photomasks and UV lamps might not be possible to make patterns on Photo Resist (PR) material due to limitation of the mask size. Though the maskless photo-lithography using UV lasers and scanners had been developed to implement large screen display, it was very slow to apply the process for mass-production systems. The laser exposure system using 405 nm semi-conductor lasers and Digital Micromirror Devices (DMD) has been developed to overcome above-mentioned problems and make more than 100 inches FPD devices. It makes very fine patterns for full HD display and exposes them very fast. The optical engines which contain DMD, Micro Lens Array (MLA) and projection lenses are designed for 10 to 50 ${\mu}m$ bitmap pattern resolutions. The test patterns for LCD and PDP displays are exposed on PR and Dry Film Resists (DFR) which are coated or laminated on some specific substrates and developed. The fabricated edges of the sample patterns are well-defined and the results are satisfied with tight manufacturing requirements.

• Journal of Welding and Joining
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• v.16 no.2
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• pp.100-110
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• 1998

In this paper, the laser weldability of thin gage steels for automobile application is discussed. Welding was carried out with a high power carbon dioxide laser system, and the laser energy was concentrated through a plano-convex lens. Test results showed that the joint gap in the butt welding proved to be one of the critical conditions for an acceptable weld. In the case where the ratio of the gap clearance to the material thickness was slightly bigger than optimal value, the weld strength was reduced showing weld metal fracture. It was possible to obtained a weld penetration ratio of 0.91 when the vertical offset ratio was controlled to be 0.4 or smaller. Results also demonstrated that the weld strength of the lap joint was influenced by travel speed. At the travel speeds lower than 37 mm/s, the weld strength indicated higher value than that of class A recommendation strength of a resistance spot weld based on the KS code. It was clear that the complicated effect of specimen alignment should be considered so as to make a sound weld with high integrity when the laser process was applied to the long weld line.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.266-270
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• 2007

Small injection molded articles such as lens and mobile product's parts are usually molded in multi-cavity mold. The problems occurred in multi-cavity molding are flow imbalance among the cavities. The flow imbalance affects on the dimensions and physical properties of molded articles. First of all, the origin of flow imbalance is geometrical imbalance of delivery system. However, even the geometry of delivery system is balanced well the cavity imbalance is being developed. This comes from the unsuitable operational conditions of injection molding. Among the operational conditions, injection speed is the most significant process variable affecting the filling imbalances in multi-cavity injection molding. In this study, experimental study of flow imbalance has been conducted for various injection speeds and materials. Also, the filling Imbalances were compared with CAE results. The dimensions and physical state of multi-cavity molded parts were examined. The results showed that the filling imbalances vary according to the injection speed and flow property of resins. Subsequently, the imbalanced filling and pressure distribution in the multi-cavity affect on the dimensions and physical states of molded parts.

• Korean Management Science Review
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• v.30 no.2
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• pp.11-30
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• 2013

Small and medium-sized enterprises (SMEs) constitute an important part of current industrial economies. Information technologies can be useful strategic weapons for SMEs by enhancing their competitiveness. Categorized as one kind of cloud computing, SaaS is a computing resource and software sharing model which can be accessed via the Internet. Based on virtualization technology, SaaS is expected to improve the efficiency and quality of the IT service level in SMEs. This study attempts to identify the determinants of SaaS adoption intention among Korean SMEs. Through the lens of the theory of planned behavior, this study adopts technological, organizational, environmental factors to explore the determinants of cloud computing adoption intention. The research population is the SMEs that have been funded by the Korean government. Partial least square method was used for empirical analysis of 190 samples collected through on-line survey. The results show that the positive attitude is influenced by business process improvements. Vender support and top management support are positively associated with subjective norm. Vendor support, top management support can relieve perceived behavior control factors. Government support directly influences adoption intention of cloud computing. These findings can provide useful strategy for both SMEs and vendors of SaaS.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.75-79
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• 2009

A four beam interference optical system for laser micro structuring using a pulse laser was demonstrated. The four beam interference optical system using a pulse laser(picosecond laser) can fabricate micro structure on mold material(NAK80) directly. Micro structure on the polymer can be reproduced economically by injection molding of the micro structure on the mold material. The four beam interference optical system was composed by the DOE(Diffractive Optical Element) and two lenses. The laser intensity distribution of four beam interference was explained by an interference optics point of view and by the image optics point of view. We revealed that both views showed the same result. The laser power distribution of a $1{\mu}m$ peak pattern was made by the four beam interference optical system and measured by the objective lens and CCD. A $1{\mu}m$ pitch dot pattern on the mold material was fabricated and measured by SEM(Scanning Electron Microscopy).

• Journal of the Korea Society of Computer and Information
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• v.4 no.3
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• pp.60-66
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• 1999

The purpose of this study is to design and materialize the simulated courseware which is based on new educational environments and student-based education. The scope of this study is reflection and refraction of in the physics of high school. This paper introduce the theoretical background of courseware and investigate the structure and process of the teaching-theory by visualized computer simulation. We applied the basic concept about the reflection and refraction of light and explained the simulated images of spherical mirror and lens with the principles expressions and relative image forms. The last we simulated the various kinds of the images, shapes and distance of the images by changing the distance of object and focus which are made by computer simulation.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_2
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• pp.693-699
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• 2020

355nm UV pulse laser is irradiated on the surface of polyimide (PI) by LDW (Laser Direct Writing) method to produce a high sensitivity flexible humidity sensor using a simple one-step process. The LDW method continuously investigates 2-D CAD data using a galvano scanner and an F-lens. This method is non-contact, so it minimizes physical strain on the PI. Laser-induced graphene (LIG) produced by lasers has a high surface area due to its high flexibility and numerous pores and oxidizers compared to conductors. For this reason, it is highly useful as a flexible humidity sensor. The humidity sensor produced in this study was attached to the inside of a mask filter, which has become a hot topic recently, and its applicability was confirmed.The measurement of humidity measured the sensitivity, reactivity, stability and recovery behavior of the sensor by measuring changes in capacitance and resistance.

• Food Science and Biotechnology
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• v.14 no.3
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• pp.344-349
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• 2005

Aldose reductase catalyzes the conversion of glucose into sorbitol. Inhibiting this enzyme in diabetes mellitus can delay or prevent pathogenic process. Aldose reductase inhibitor was screened from Korean fermented soybean pastes (Doen-jang) and purified via sequential processes of ethanol extraction, HP-20 column chromatography, ethyl acetate extraction, silica gel column chromatography, and crystallization. Aldose reductase inhibitor was identified as genistein with molecular weight of 270 Da and molecular formula of $C_{15}H_{10}O_5$ based on UV spectrometry, $^1H$ and $^{13}C\;NMRs$, and mass spectrometry. Genistein inhibited aldose reductase of pig lens with $IC_{50}$ level of $20\;{\mu}M$. Because genistein was effective against aldose reductase of animal source, it may be a potential therapeutic agent for diabetic complications.