• Korean Journal of Materials Research
• /
• v.31 no.11
• /
• pp.601-607
• /
• 2021

Laser cladding a surface treatment process that grants superior characteristics such as toughness, hardness, and corrosion resistance to the surface, and rebuilds cracked molds; as such, it can be a strong tool to prolong service life of mold steel. Furthermore, compared with the other similar coating processes - thermal spray, etc., laser cladding provides superior bonding strength and precision coating on a local area. In this study, surface characteristics are studied after laser cladding of low carbon steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), known for its high hardness and excellent corrosion resistance. A diode laser with wavelength of 900-1070 nm is adopted as laser source under argon atmosphere; electrical power for the laser cladding process is 5, 6, and 10 kW. Fundamental surface characteristics such as crossectional microstructure and hardness profile are observed and measured, and special evaluation, such as a soldering test with molten ALDC12 alloy, is conducted to investigate the corrosion resistance characteristics. As a result of the die-soldering test by immersion of low carbon alloy steel in ALDC12 molten metal, the clad layer's soldering thickness decreases.

• Journal of Acupuncture Research
• /
• v.26 no.1
• /
• pp.49-57
• /
• 2009

Objectives : During the past three decades there has been a significant evolution of laser acupuncture application in the nature of the clinical approach and the research of traditional medicine and laser therapy field. However, there have been no standard and guideline of laser equipment can be applied as laser acupuncture. This study aims to investigate the condition of laser equipment required as a laser acupuncture method. Methods : First, we performed literature search using the Medline(from 1999 to Oct 2008) to confirm types and ranges of laser equipments that can be applied as laser acupuncture. In addition, we investigated the characters of acupoints such as sites and depths, and compared with penetrating depths of each laser. Results : A total of 37 articles for clinical studies using laser acupuncture were selected, and 41 lasers were used. GaAs laser was used three times, GaAlAs laser 14, InGaAlP 18, HeNe laser 4, and Argon laser and CO2 laser were used one time, respectively. From all 361 points of fourteen meridians, depths of 341 points(94.5%) were 1 cun(2.3-3.2cm) or less. The mean depth of all points was 0.48 cun(1.1-1.5cm). Hence, it appeared that the majority of therapeutic lasers satisfied with the condition. HeNe, InGaAlP, GaAlAs, GaAs lasers are recommended for laser acupuncture, however, it may plausible that other surgical lasers could be used as the laser acupuncture, because it have the biostimulation effect to some extent, too. Conclusions : It is suggested that to select appropriate laser type and give the adequate output power to reach the acupoints under the skin using laser acupuncture. Further evaluation and research for the condition of laser acupuncture are warranted.

• Restorative Dentistry and Endodontics
• /
• v.25 no.1
• /
• pp.109-115
• /
• 2000

This study was designed to evaluate the microhardness of restorative composite resin and dual-cured composite resin cement which were light cured through the 1.5mm thickness composite overlay. For restorative materials, Z100 and Tetric Ceram were used. For dual cured composite cements, Variolink II((VL II) of three consistency (low, high, ultra high) were used. To determine the optimal microhardness of Z100, Tetric Ceram and Variolink II, each material was packed into the 1mm thickness teflon mold without composite overlay and light cured for 60 seconds. Then the microhardnesses of each sample were measured, averaged and regarded as optimal hardness of each material. To evaluate the microhardness of restorative composite resin and dual-cured composite resin cement which were light cured through the 1.5mm thickness composite overlay, the composites were packed into 1mm thickness teflon mold, coverd with celluloid strip, and then precured composite overlay which was made of Targis(Ivoclar/Vivadent, Liechtenstein) was positioned. 2 types of visible light curing machine, the power density of one of which was 400$mW/cm^2$ and the other was 900$mW/cm^2$, and one type of argon laser were used to cure the restorative composite and dual cured cement. For each group, 10 sample were assigned. The light curing tip was positioned over the composite overlay and light cured for 1min., 2min. or 3min with visible light curing machine or 15sec, 30 sec, 45sec, and 60 sec with argon laser. The Vickers hardnesses of upper and lower surface of Z100, Tetric Ceram, and 3 types of VL II cement were measured. When the 900 $mW/cm^2$ curing light was used, 2min. was needed for optimal curing of Z100 and Tetric Ceram. Variolink II did not be cured optimally even though the curing time was extended to 3min. When 400$mW/cm^2$ curing light was used, 3min. was necessary for Z100, whereas 3min. was not enough for Tetric Ceram. Variolink II was not cured optimally even though the curing time was extended to 3min. When argon laser was used, Z100, Tetric Ceram and Variolink II were not cured optimally in 60 seconds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.473-476
• /
• 1997

Focused Ar ion laser beam can be utilized to fabricate microstructures on silicon substrate as well as other materials(e.g. such as ceramic). The laser using in this study is an argon ion laser with maximum power of 6 W, wavelength of 514 nm. This laser beam is focused by objectives with a high numerical aperture, a long working distance. We have achieved line width about 1 ${\mu}{\textrm}{m}$ with high scan speed. The resolution for Si machining is determined by the selectivity of the chemical reaction rather than the laser spot size. In this study, we have obtained the maximum etch rate of 434.7 ${\mu}{\textrm}{m}$/sec with high aspect ratio. The characteristics of etched groove was investigated by scanning electron microscope(SEM) and auger electron spectroscopy(AES). It is assumed that the technique using arson ion laser is applicab1e to fabricate microstructures.

• Proceedings of the KIEE Conference
• /
• 1998.07d
• /
• pp.1444-1446
• /
• 1998

Direct writing of copper lines has been achieved by pyrolytic decomposition of copper formate films using a focused argon ion laser beam($\lambda$ =514.5nm) on a glass. The thickness and linewidth of the deposited copper films were considered as a function of laser power and scan speed. As the result from AES, there are no other elements except for copper after decomposition in the atmospheric ambient.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1120-1125
• /
• 2004

Welding characteristics of STS304 stainless steel and Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. Alloy 600 being used in steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion environment, stress corrosion cracking can occur on this material. Presented here are the results from a series of experiments in which dissimilar metal welds were made using the gas tungsten arc welding process with pure argon shielding gas. But It is well known that solidification cracking susceptibility of austenitic alloys depends on the solidification temperature range and amount/distribution of solute rich liquid that exists at the terminal stages of solidification. An experimental study was conducted to determine effects of welding parameters and to optimize those parameters that have the most influence on eliminating or reducing the extent welding zone formation at dissimilar metal welds.

• Korean Journal of Acupuncture
• /
• v.28 no.3
• /
• pp.1-12
• /
• 2011

Objectives : The purpose of this study is to review laser acupuncture studies to find possibility for applying high intensity laser to acupuncture and moxibustion treatment. Methods : Searching papers was performed using search engines of five electronic databases, including Pubmed, Thomson ISI, EMBASE, Sciencedirect, and EBSCO, from inception to May 2011 without language limitation. Inclusion criteria were clinical studies with human, randomized controlled trials (RCTs), case-control studies, and case reports. Selecting papers was performed with titles and abstracts in first step, scrutinize full text in second step, and then the extrated data was analyzed by two authors independently. The methodological quality for RCTs was evaluated using Jadad's scale. Results : Total 8 papers, (3 RCTs, 5 controlld studies, and 1 case reports), were finally selected. The study dealt with surgical laser, argon and $CO_2$ laser was one for each, with GaAs laser was two, and with new semiconductor laser, GaN, were four. The output range was from 110 mW to 15 W. The study diseases were alcohol addiction, knee osteoarthritis, bronchopneumonia and asthma for children, and circulation. All studies reported positive effect. The methodological quality in all RCTs was low because of below 3 points and all studies had few subject numbers. Conclusions : We suggest that high intensity laser can be applied to acupuncture and moxibustion. Further rigorous and well-designed study will be needed for various disease. The oriental medical society needs to take active measures to study and clinical application of acupuncture and moxibustion treatment with high intensity laser.

• Restorative Dentistry and Endodontics
• /
• v.21 no.2
• /
• pp.652-663
• /
• 1996

The purpose of this study was to evaluate the tensile bond strength to tooth structure of composite resin and glass ionomer cement according to filling methods and light curing units. In this study, two class V cavities were prepared on the buccal surface of each tooth of 140 extracted human molars, and they were randomly assigned into 3 experimental groups with 40 teeth and control group with 20 teeth. And then, each experimental groups subdivided into 2 groups(A,B) according to light curing units. The cavities of each group were filled with the CLEARFIL FII self curing resin(Control Group), Z-100 light curing resin(Group 1), Vitremer$^{TM}$ light curing glass ionomer cement(Group 2) and Z-100 light curing resin over the Vitrebond$^{TM}$ liner(Group 3). And subdivided A Group used Argon Laser(SPECTRUM$^{TM}$, U.S.A.), B Group used XL 1,000 curing light (3M, U.S.A.). The specimens underwent temperature changed from $5^{\circ}C$ to $55^{\circ}C$ five hundred times. After thermocycling, specimens were stored in 100% relative humidity at $37^{\circ}C$ for 24 hours. And then, the tensile bond strength of specimens were calculated with Universal Testing Machine(AGS-100A, Japan). The results were as follows : 1. Among the experimental groups, the group 2-B showed the highest tensile bond strength ($18.89{\pm}7.80$) and the group 1-A showed the lowest tensile bond strength ($11.68{\pm}2.28$). There was significant difference between group 2-B and group 1-A(p<0.01). 2. Between the light curing units, the XL 1,000 unit showed higher tensile bond strength ($16.63{\pm}3.20$) than that of the Argon Laser unit ($13.73{\pm}2.30$). There was significant difference between XL 1,000 and Argon Laser(p<0.01). 3. About filling methods and materials, the group 2 showed the highest tensile bond strength ($17.56{\pm}1.89$) and the group 1 showed the lowest tensile bond strength($13.03{\pm}1.90$). There was significant difference between group 2 and group 1,3(p<0.01). In conclusion, the results showed that the glass-ionomer cement that cured by XL 1,000 light curing unit demonstrated significantly higher tensile bond strength than other curing unit and filling methods.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.7
• /
• pp.106-115
• /
• 2002

Growth characteristics of micro carbon structures fabricated by laser-assisted chemical vapor deposition are studied. Argon ion laser and ethylene were used as the energy source and reaction gas, respectively, to grow micro carbon rod through pyrolytic decomposition of the reaction gas. Experiments were performed at various conditions to investigate the influence of process parameters on growth characteristics such as the diameter or growth rate of the micro carbon rod with respect to reaction gas pressure and incident laser power. Reaction gas pressure in experiments ranges from 200 to 600Torr and the incident laser power from 0.3 to 3.8W. For these conditions, the diameter of the rod increases linearly with respect to the laser power but is almost independent of the reaction gas pressure. Growth rate of the rod changes little with gas pressure when the laser power remains below IW. For a constant reaction gas pressure, the growth rate increase with Increasing laser power, but the rate of increase decreases gradually, implying that the chemical vapor deposition condition changes from a kinetically-limited regime to a mass-transport-limited regime. When the carbon rod was grown at near threshold laser power, a very smooth surface is obtained on the rod. By continuously moving the focusing lens in the direction of growth, a micro carbon rod with a diameter of 287${\mu}{\textrm}{m}$ and aspect ratio of 100 was fabricated..

• Journal of the Korean Vacuum Society
• /
• v.13 no.1
• /
• pp.29-33
• /
• 2004

In this paper, we investigated the ultra-low temperature(<$150^{\circ}C$) polycrystalline silicon film on plastic substrate application using RF-magnetron sputtering and excimer laser annealing. Amorphous silicon films were deposited using Ar/He mixture gas at $120^{\circ}C$ and in-film argon concentration was less than 2%, which was measured to Rutherford Backscattering Spectrometry. At energy density 320mJ/$\textrm{cm}^2$, RMS roughness was 267$\AA$ and UV crystallinity was 62%. The grain size varies from 50nm to 100nm after excimer laser irradiation.