• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.499-500
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• 2009

• Transactions of the Society of Information Storage Systems
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• v.1 no.2
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• pp.127-131
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• 2005

We report a nanometer scale mark formation using a $PtO_x$ thin film or a TbFeCo rare-earth transition metal film and the mechanism. The multi-layer samples($ZnS-SiO_2/PtOx/ZNS-SiO_2,\;ZnS-SiO_2/TbFeCo/ZnS-SiO_2$) were prepared with a magnetron sputtering method on a polycarbonate or a glass substrate. By laser irradiation of approximately a few nanoseconds, nanometer scale marks were fabricated. During the fabrication process, the thin films were thermally reacted or inter-diffused during the laser irradiation. 75 nm bubble marks in the PtOx multi-layer sample by an approximately 4-ns laser irradiation. Inside the bubble mark, Pt particles with a few nanometer sizes are distributed. The $50{\sim}100$ nm bubble marks in the TbFeCo multi-layer sample by a few nanosecond laser irradiations. We will report the detail structure of the samples, the bubble mark formation process and the mechanism.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.11
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• pp.1044-1049
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• 2015

This paper proposes an autonomous navigation system of mobile robots for indoor corridor environment. The system uses a laser scanner but does not use reflectors. The laser scanner measures the distance between robot and structures such as wall, pillar, and fixtures. Adaptive breakpoint detector and modified IEPF (iterative endpoint fit) are developed to find mark points from the distance data. The robot path for corridor is then generated using the angle histogram of the mark points. The experimental results are finally presented to show the effectiveness of the proposed method.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1069-1075
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• 2012

Laser is high density heat source, so it can make high speed welding with minimum heat input possible. Especially the high power fiber laser is recently commercialized and has high beam quality and the smallest system size compared with conventional laser due to it's unique oscillating mechanism. Because of these advantages it's thought that the most suitable heat source for LNG cargo tank welding precess which has to be conducted inside of ships. In this study fiber laser was used for welding of stainless steel for LNG carrier to applicate laser welding technique for shipbuilding industry. 1.2mmt STS304L of austenite stainless steel which apply to cargo tank was used for fiber laser welding. Butt and lap welding was conducted changing laser power, welding speed, then penetration characteristic was analyzed and optimal parameters for each materials. Consequently, we found that same or better mechanical properties were obtained in weld compared to base metal.

• Design & Manufacturing
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• v.14 no.2
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• pp.14-20
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• 2020

In OLED panel production process, it is necessary to cut a part of protective film as a preprocess for lighting inspection. The current method is to recognize only the fiducial mark of the cut-out panel. Bare Glass Cutting does not compensate for machining cumulative tolerances. Even though process defects still occur, it is necessary to develop technology to solve this problem because only the Align Mark of the panel that has already been cut is used as the reference point for alignment. There is a lot of defective lighting during panel lighting test because the correct protective film is not cut on the panel power and signal application pad position. In laser cutting process to remove the polarizing film / protective film / TSP film of OLED panel, laser processing is not performed immediately after the panel alignment based on the alignment mark only. Therefore, in this paper, we performed real time inspection which minimizes the mechanism tolerance by correcting the laser cutting path of the protective film in real time using Machine Vision. We have studied calibration algorithm of Vision Software coordinate system and real image coordinate system to minimize inspection resolution and position detection error and edge detection algorithm to accurately measure edge of panel.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2006.11a
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• pp.53-81
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• 2006

A COG(Chip on Glass) bonding process that is one of display packaging technology and bonds between driver IC chip and a glass panel using ACF(Anisotropic Conductive Film)has been investigated by using diode laser. This method is possible to raise cure temperature of ACF within one second and can reduce the total process time for COG bonding by a conventional method such as a hot plate. Also we can get good pressure mark on the surface of electrodes and higher bonding strength than that by convention method. Results show that laser COG bonding can give low pressure bonding and decrease a warpage of panel. We believe that it can be applied to fine pitch module.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.1
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• pp.31-42
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• 1997

This study was performed to investigate the surface roughness of the Cerec Vita Mark II polished by various polishing techniques, compare with that of the Vintage enamel porcelain glazed by high temperature glazing technique. All of the Cerec specimen were finished with sequential use of high speed diamond burs(grit 45, 30 and $15{\mu}m$). The groups were divided into 5 groups : Group I : Cerec Vita Mark II block specimens polished with Sof-lex discs. Group II : Cerce Vita Mark II block specimens polished with Two Striper MPS. Group III : Cerce Vita Mark II block specimens polished with Enhance. Group IV : Cerce Vita Mark II block specimens polished with Porcelain laminate polishing FG kit. Group V : Vintage enamel porcelain glazed by high temperature glazing Technique. Each group was consisted of 10 specimens. The surfaces produced were examined quantitatively using a laser specular reflectance machine(Perthen RM600-s, Feinpruf Perthen GmbH., Germany) and qualitatively under SEM(JSM-5400, JEOL, Japan). The Results were as follows : 1. The arithmetic mean roughness value(Ra) in groups 1, 2, 3 and 4 was higher than that of group5. There was statistically significant difference(P<0.05). 2. The arithmetic mean roughness value(Ra) decreased in the following orders : group 1, group 2, group 4, group 3 and there was no statistically significant difference between group 1 and group 2, group 3, and group 4. There was statistically significant difference among group 1, 2, and group 3, 4 and group 5(P<0.05). 3. The maximum individual peak-to-valley-height(Rmax) decreased in the following orders : group 2, group 1, group 4, group 3, group 5 and there was no statistically significant difference between group 1 and 2, group 1 and group 4, group 3 and group 5. There was statistically significant difference among group 1, 2, and group 1, 4 and group 3, 5(P<0.05). 4. The treated surfaces of group 5 had smoother surface than that of groups 1, 2, 3, 4 with SEM.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.11
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• pp.1379-1389
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• 1999

A new technique for control of size and shape of flame-made particles is Introduced. The characteristic sintering time can be controlled Independently of collision time by heating the particles with irradiation of laser because the sintering time strongly depends on temperature. A coflow oxy-hydrogen diffusion flame burner was used for $SiCl_4$ conversion to silica particle. Nanometer sized aggregates irradiated by a high power CW $CO_2$ laser beam were rapidly heated up to high temperatures and then were sintered to approach volume-equivalent spheres. The sphere collides much slower than the aggregate, which results in reduction of sizes of particles maintaining spherical shape. Light scattering of Ar ion laser and TEM observation using a local sampling device were used to confirm the above effects. When the $CO_2$ laser was irradiated at low position from the burner surface, particle generation due to gas absorption of laser beam occurred and thus scattering intensity increased with $CO_2$ laser power. At high irradiation position, scattering intensity decreased with $CO_2$ laser power and TEM image showed a clear mark of evaporation and recondensation of particles for high $CO_2$ laser power. When the laser was irradiated between the above two positions where small aggregates exist, average size of spherical particles obviously decreased to 58% of those without $CO_2$ laser irradiation with the spherical shape. Even for increased carrier gas flow rate by a factor of three, TEM photograph also revealed considerable reduction of particle size.

• Journal of Periodontal and Implant Science
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• v.52 no.1
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• pp.77-87
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• 2022

Purpose: This pilot study assessed the immediate in vivo effect of high peak pulse power neodymium-doped yttrium aluminum garnet (Nd:YAG) laser monotherapy on selected red/orange complex periodontal pathogens in deep human periodontal pockets. Methods: Twelve adults with severe periodontitis were treated with the Laser-Assisted New Attachment Procedure (LANAP®) surgical protocol, wherein a free-running, digitally pulsed, Nd:YAG dental laser was used as the initial therapeutic step before mechanical root debridement. Using a flexible optical fiber in a handpiece, Nd:YAG laser energy, at a density of 196 J/cm² and a high peak pulse power of 1,333 W/pulse, was directed parallel to untreated tooth root surfaces in sequential coronal-apical passes to clinical periodontal probing depths, for a total applied energy dose of approximately 8-12 joules per millimeter of periodontal probing depth at each periodontal site. Subgingival biofilm specimens were collected from each patient before and immediately after Nd:YAG laser monotherapy from periodontal pockets exhibiting ≥6 mm probing depths and bleeding on probing. Selected red/orange complex periodontal pathogens (Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia/nigrescens, Fusobacterium nucleatum, Parvimonas micra, and Campylobacter species) were quantified in the subgingival samples using established anaerobic culture techniques. Results: All immediate post-treatment subgingival biofilm specimens continued to yield microbial growth after Nd:YAG laser monotherapy. The mean levels of total cultivable red/orange complex periodontal pathogens per patient significantly decreased from 12.0% pretreatment to 4.9% (a 59.2% decrease) immediately after Nd:YAG laser monotherapy, with 3 (25%) patients rendered culture-negative for all evaluated red/orange complex periodontal pathogens. Conclusions: High peak pulse power Nd:YAG laser monotherapy, used as the initial step in the LANAP® surgical protocol on mature subgingival biofilms, immediately induced significant reductions of nearly 60% in the mean total cultivable red/orange complex periodontal pathogen proportions per patient prior to mechanical root instrumentation and the rest of the LANAP® surgical protocol.