• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1620-1625
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• 2015

In this study, a variety of industrial gears, shafts, chains, rollers, mold, etc. are widely used inautomotive steel carbon steel for machine structural SM45C typical material used for the experiments. In order to cure the surface of the test piece after the rough grinding and fine grinding was performed in order polishing. Perform the surface hardening of SM45C lacal area by using a diode laser. The output of the laser diode and the feed rate to the process variable. Micro-hardness testing, microstructure testing, scanning electron microscope testing(SEM), the heat input to the analysis. After analyzing the experiment to compare the mechanical properties of the material. When using a diode laser to assess the soundness of the surface hardening. Accordingly, the process for deriving the optimum demonstrate the feasibility.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.769-772
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• 2011

We propose a sweeping machine is equipped with a polyester filter to retain small particles of dust. The filter is washable and can be easily removed for maintenance purpose or eventual replacement. Research continues into key areas such as making the structure of machine as ship' s floor grinder as possible, and designing algorithms and systems for efficiency-related system technologies.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.40.1-40.1
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• 2009

생체용 금속 임플란트의 표면개질은 생체활성화를위하여 오래 전 부터 관심을 가지고 연구해오고 있다. 최근에 표면개질을위하여 화학적 에칭, 샌드 블래스팅, 또는 나노튜브형성등 표면에 임의의 요철을 만들어서 사용하는방법이 가장 일반적으로 적용되어 상용화되고있다. 그러나 샌드블래스팅이나 화학적 에칭은 가공은 쉽지만 가공표면에 인체에 해로운 잔류물의존재로 생체적합성에 해로운 영향을 미칠 수 있다. 이러한 문제점들을 해결하기위하여 레이저를 사용하여 임플란트 표면을 개질한 예가 보고 되었다. 레이저를 사용한 표면처리 방법의큰 장점은 잔류물이 남지 않고 비교적 표면 거칠기의 제어가 용이하다. 금속합금의 표면개질에사용되는 레이저는 주로 Nd:YAG 레이저의 파장을 반으로 줄인 녹색레이저 ($\lambda$=532nm)를 사용하거나, 자외선파장영역의레이저를 사용하는 경우가 일반적으로 가장 보 편화된 가공방법으로 연구되었다. 표면의 거칠기는 수마이크로의크기와 수십나노의 크기를 갖는 표면을 생체적합적인 측면에서 요구하고 있다. 따라서 이러한 표면의 거칠기를조절할 수 있는 펨토레이저를 사용하여 표면에 균질한 표면의 텍스춰링을 통하여 그 특성을 개선할 수 있는지를 확인하는 것이 본 과제이다. 본 실험에서는 Ti합금을 진공 아크로를 이용하여 3원계합금을 제조하고 $1000^{\circ}C$에서 24시간 열처리 후 급냉(water quenching)하였다. 열처리 후 시편은 두께 2mm로 절단 하여 #2000까지 연마 후 하여 펨토 초(10-15 second) 펄스폭 대역을 갖는 레이저를 이용하여 수마이크로 크기의 미세 요철을 표면에 형성한 후, 표면의 특성을 조사해 보았다.(NRF-2009-0074672)

• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.555-560
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• 2002

치근부 민감성 (hypersensitivity)은 부분적으로 치근면에서의 개방된 상아세관이 존재하는 것에 기인한다고 생각되며 이러한 치근부의 개방된 상아세관은 치경부 병소 (cervical lesion)에 주로 존재하는데 이는 칫솔질에 의한 마모(toothbrush abrasion), 화학적 침식 (chemical erosion), 또는 abfraction 등의 결과로 나타난다고 한다. 이미 Nd-YAG 레이저를 이용한 실험에서 레이저를 조사한 상아질 표면의 상아 세관 구경이 감소되고 상아세관의 폐쇄가 많이 증가되는 양상을 관찰한 바 있다. 이 실험의 목적은 고출력레이저인 Nd-YAC 레이저를 이용한 상아질 표면처치의 임상사용가능성을 좀 더 상세히 평가하기 위해 상아질에 레이저를 처리한 후 기계적으로 마모시킨 경우 상아질 표면의 변화를 관찰하는 것이다. 50개의 발치된 치아의 상아질을 노출시켜 표면을 연마한 후 대조군에서는 37% 인산으로 산부식하여 상아 세관을 노출시킨 후 레이저를 조사하였고, 실험군에서는 대조군과 같은 조건으로 산과 레이저로 처리된 상아질 표면을 15, 45, 90 그리고 180분 동안 전동 칫솔로 기계적으로 마모시켜 그 표면을 주사전자현미경으로 관찰한 결과, 대조군, 칫솔질을 15, 45분간 시행한 실험군에서는 상아 세관 입구가 10% 이내에서 노출되었고 50 그리고 180분간 칫솔질을 시행한 실험군에서는 45 그리고 48%의 상아세관 입구의 노출이 관찰되었다. 그러므로 Nd-YAC레이저의 조사는 상아질 표면에서 축적 시간이 45분 이상에서 90분 이하인 기계적 마모에 의한 상아 세관 입구의 노출을 억제할 수 있을 것이라 사료된다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.136-141
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• 2015

Laser surface polishing is a polishing method for improving surface roughness using an integrated laser beam. Using a laser for surface polishing can improve the surface condition without physical contact or chemical action. Laser polishing has mainly been used to polish the surface of diamond or optical articles, such as lenses and glasses. Recently, diverse studies on laser polishing for metals have been conducted. The analytic study of laser surface polishing has been conducted with experimental trials for comparison, so that the proper conditions for laser polishing can be recommended. In this study, laser surface polishing was simulated in order to predict the heat-affected zone on the die steel depending on the power of the pulsed laser. The simulated results were verified by comparing them to those of the experimental trials. Through this study, therefore, the application of FEM to the selection of appropriate laser conditions could be possible.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5460-5466
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• 2014

In this study, mainly for kitchen knives and small swords, cutlery, etc. STS420J2 used material used for the experiments. In order to cure the surface of the test piece after the rough grinding and fine grinding was performed in order polishing. Perform the surface hardening of STS420J2 local area by using a diode laser. The output of the laser diode and the feed rate to the process variable. Micro-hardness testing, microstructure testing, scanning electron microscope testing(SEM), the heat input to the analysis. After analyzing the experiment to compare the mechanical properties of the material. When using a diode laser to assess the soundness of the surface hardening. Accordingly, the process for deriving the optimum demonstrate the feasibility.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.173-179
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• 1999

The effect of the surface activation treatment on the crystallization of the amorphous silicon film was investigated. The amorphous silicon film was deposited on the silica substrate with LPCVD technique. Wet blasting with silica slurry or exposure with Nd:YAG laser beam was applied on the amorphous silicon film before annealing for the crystallization. For the analysis of the crystallinity, XRD, Raman, and SEM were employed. In this investigation, the prior surface activation treatment like silica wet blasting or Nd:YAG laser beam exposure before annealing for the crystallization were found to be effective in the enhancement of the crystallization. It is believed that these treatment lower the activation energy required for the crystallization of the amorphous silicon film.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1105-1111
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• 2011

The objective of this study is to investigate the influence of surface roughness on the morphology of aluminum 6061-T6 alloy after irradiation with a Nd:YAG pulsed laser. The test specimen was prepared by a polishing process using a diamond paste ($1{\mu}m$) and emery polishing papers (#100, #220, #600, #2400) to obtain different initial surface roughness. After irradiation with ten pulsed-laser shots, the surface morphology was examined by using scanning electron microscopy (SEM), optical microscopy (OM), and atomic force microscopy (AFM). The diameter of the melted zone increased with the surface roughness because the multiple reflections and absorption of the laser beam occurred on the surface because of the surface roughness, so that the absorptance of the laser beam changed. This result was verified using the relative absorptance calculated from the diameter of the melted zone with the surface roughness and the diameter increased with the average surface roughness.

• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.1-8
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• 2008

The purpose of this study was to evaluate the effect of a new resin monomer, filler size and polishing technique on the surface roughness of composite resin restorations using confocal laser scanning microscopy. By adding new methoxylated Bis-GMA (Bis-M-GMA, 2,2-bis[4-(2-methoxy-3-methacryloyloxy propoxy) phenyl] propane) having low viscosity, the content of TEGDMA might be decreased. Three experimental composite resins were made: EX1 (Bis-M-GMA/TEGDMA = 95/5 wt%, 40 nm nanofillers); EX2 (Bis-M-GMA/TEGDMA = 95/5 wt%, 20 nm nanofillers); EX3 (Bis-GMA/TEGDMA = 70/30 wt%, 40 nm nanofillers). Filtek Z250 was used as a reference. Nine specimens (6 mm in diameter and 2 mm in thickness) for each experimental composite resin and Filtek Z250 were fabricated in a teflon mold and assigned to three groups. In Mylar strip group, specimens were left undisturbed. In Sof-lex group, specimens were ground with #1000 SiC paper and polished with Sof-lex discs. In DiaPolisher group, specimens were ground with #1000 SiC paper and polished with DiaPolisher polishing points. The Ra (Average roughness), Rq (Root mean square roughness), Rv (Valley roughness), Rp (Peak roughness), Rc (2D roughness) and Sc (3D roughness) values were determined using confocal laser scanning microscopy. The data were statistically analyzed by Two-way ANOVA and Tukey multiple comparisons test (p = 0.05). The type of composite resin and polishing technique significantly affected the surface roughness of the composite resin restorations (p < 0.001). EX3 showed the smoothest surface compared to the other composite resins (p < 0.05). Mylar strip resulted in smoother surface than other polishing techniques (p < 0.05). Bis-M-GMA. a new resin monomer having low viscosity, might reduce the amount of diluent, but showed adverse effect on the surface roughness of composite resin restorations.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.41-46
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• 2003

In order to evaluate the sufficient etching time for successful bonding and also minimizing unnecessary mineral loss, the enamel surface roughness analysis was performed using confocal laser scanning microscopy. Sixty extracted sound human molar teeth were imbedded in the center of acrylic cylinder using self-curing clear resin exposing buccal surface, and then polished with series of SiC paper(220, 500, 800, 1000, 2000, 4000 grit). Each specimen was randomly assigned to six groups(N=10). 37% phosphoric acid was applied to the polished tooth surface for 10, 20, 30, 40, 50, 60 seconds respectively and washed with copious water. After the surface roughness analysis, five roughness parameters(Sa, Sq, Sz, Sdr, Ra) were statistically analysed by ANOVA and Duncan post hoc test. We found that the all five parameters had higher roughness value in 30 seconds etching time, especially parameter Sz showed the lowest value in 10 seconds etching time and the highest value in 30 seconds etching time compared with the other etching times(p<0.05).