• Journal of the Korean Magnetics Society
• /
• v.15 no.6
• /
• pp.320-324
• /
• 2005

The core loss of $3\%$ SiFe is strongly dependent on silicon content, impurities, permeability, and domain structure of the SiFe. Domain refining has been proved to be very good method for reduction of core loss in high permeability grain oriented SiFe, and laser scribing is well-blown as an effective and industrially important method of domain refinement. In this work, magnetic domain refinement has been carried out by using a pulsed Nd : YAG laser, and the core losses have been measured and analyzed to and optimal parameters of the laser treatment. The laser hem was focused with a spot size of $100{\mu}m$ and pulse energy of 10${\~}$35mJ and the lines were scribed with a period of ${\~}$5mm. The core loss was improved up to $17\%$ with 30 ns-Nd : YAG laser beam in $3\%$ SiFe.

• Journal of Periodontal and Implant Science
• /
• v.27 no.4
• /
• pp.829-844
• /
• 1997

Dentin hypersensitivity must be one of the most frequent postoperative complaints in periodontal patients. Obliterating the open dentinal tubules or decreasing the diameter of their orifices would, therefore, be an objective of treatment for hypersensitive teeth. The purpose of this study was to evaluate the effect of a pulsed Nd:YAG laser irradiation on obliteration of dentinal tubules and to determine any difference according to irradiation methods. The 45 posterior teeth that had been extracted due to periodontal disease were initially treated with tetracycline HCI(100 mg/ml, 4 min.) to remove the smear layer after root planing. The root surfaces were then irradiated by a pulsed Nd:YAG laser(EL.EN.EN060, Italy) by different laser beam spot size and different exposure condition: ${\cdot}$ group 1: irradiated group by small spot(beam diameter=1mm, lW, 2 sec) ${\cdot}$ group 2: irradiated group by large spot(beam diameter=10mm, 1W, 200 sec) ${\cdot}$ group 3: irradiated group by gradual increase of watt (from 0.3W to 1.0W), beam diameter=4mm ${\cdot}$ group 4: irradiated group by fixed watt(1.0 W), beam diameter=4mm ${\cdot}$ control group: no irradiation but root planing and tetracycline HCI conditioning only. Additionally, the specimens were retreated with tetracycline HCI(100mg/ml, 4min.) to evaluate the stability of obliteration effect by Nd:YAG laser. Specimens were examined under the scanning electron microscope(JEOL, JSM-840A, Japan). Photomicrographs were taken at ${\times}4,000$ magnification and were analyzed statistically. The results were as follows: l. Scanning electron micrographs of root surface treated by tetracycline HCI alone(control group) showed widened, funnel-shaped dentinal tubules, while those of the root surface irradiated by various methods showed partially or completely obliterated dentinal tubules and various surface alterations, eg, flat, multiple pitted, melted and resolidified surface at the same energy density. 2. There was no significant difference in the obliteration effect of dentinal tubules between group 1 and group 2, and between group 3 and group 4(p>0.05). 3. The obliteration effect of dentinal tubules by a Nd:YAG laser irradiation was relatively stable to tetracycline HCI. The results demonstrate that a pulsed Nd:YAG laser irradiation within 1.0W, regardless of irradiation methods, can obliterate dentinal tubules effectively.

• Journal of Welding and Joining
• /
• v.29 no.3
• /
• pp.82-88
• /
• 2011

With a tendency for the application of thin magnesium alloy plates in portable electronic equipment such as cell phone and notebook PC, there is a requirement to develop a welding technology for the lap welding of these thin magnesium alloy. This paper presents the single pulsed laser welding of AZ31B magnesium alloy. The effects of fiber types and parameters such as peak power and pulse width on laser weldability were investigated. The results show that weld defects, especially solidification crack, were always generated in the weld. These defects couldn't be controlled by the simple square pulse, but could be improved through the application of variable pulse. It is because that variable pulse has effect of solidification delay by dropping peak power gradually.

• Laser Solutions
• /
• v.3 no.1
• /
• pp.12-20
• /
• 2000

The nuclear steam generators are subjected to corrosion environmental condition during operation that can result in stress corrosion in the tube wall. If any tube wall degradation is recognized, the tube must be repaired by plugging or sleeving. For the sleeving repair, Nd : YAG laser welded sleeving technology is one of the most promising when considering radioactive working conditions in the nuclear power plant. In this paper, the laser welding characteristics of steam generator tube and sleeve materials are investigated. The effects of average laser power, laser energy, welding speed, pulse duration and frequency are evaluated. Based on these results, Nd : YAG laser welded sleeving repair was applied to the degraded steam generator tubes in real environment.

• Journal of the Korea Computer Industry Society
• /
• v.2 no.4
• /
• pp.565-572
• /
• 2001

At the most recent years, laser medical instruments, laser applications and laser nuclear fusion need strong visible light and ultraviolet rays. Nonlinear optical devices, such as harmonic generators and parametric oscillators, provide a means of extending the frequency range of available laser sources. Frequency conversion is a useful technique for extending the utility of high-power lasers. It utilizes the nonlinear optical response of an optical medium in intense radiation fields to generate new frequencies. These progresses have been used to generate high-power radiation in all spectral regions, from the ultraviolet to the far infrared. Optical parametric oscillators and amplifiers generate two waves of lower frequency They are capable of generating a range of wavelengths from a single frequency source, in some cases spanning the entire visible and near infrared regions. Consequently, in order to obtain the green light, the pulsed Nd:YAG laser using multiple-mesh PFN(Pulsed Forming Network) method with Nonlinear optical device was adopted. We compared the current pulseshapes with the laser output energy, and conversion efficiency.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.1
• /
• pp.99-104
• /
• 2010

Magnesium and magnesium alloys, the lightest structural materials, have been received plenty of global attention recently. These alloys could be applied in various fields, especially the electronics industry, because of their excellent electromagnetic interference shielding. However, the welding technique of magnesium alloys has not been established. This study is related to the welding of AZ31B magnesium alloy by a short-pulsed a Nd:YAG laser. Two types of pulse waves, square pulse and variable pulse, were used to control weld defects. Results show that the crack and porosity, generated in the weld, had not been controlled by general square pulse. But through the application of variable pulse, the defects could be prevented and the good weld zone was obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.921-924
• /
• 1995

Case hardening behavior of carbon tool steel(SK5) was investigated after pulsed YAG laser irradiation. In the case od beam passes,martensite formed in the melt zone and in former pearlite regions of the austenitization zone exhibits vary high Vickers hardness values. The molten depth and width decrease as the beam power density increase. The influence of depth and width of color painted specimen was also investigated. The molten zone of the black painted specimen was the largest. The were loss of the black painted specimen was smaller than any other painted or raw material.

• Proceedings of the KIEE Conference
• /
• 1997.11a
• /
• pp.373-375
• /
• 1997

In this study, we designed multiple mesh circuit consisting of 3-6 meshes and pulse superposition one consisting of a 3 mesh, and fabricated the electrical power supply and the single elliptical resonator. We developed the two pulse superposition technique forming the step pulse shapes of pulsed Nd:YAG laser with single shot multivibrator and 2 SCRs. Laser beam generated by multiple mesh circuit and superposition one respectively irradiated target surface to analyze process state of surface with spark and vapor. And it was obtained experimental results that all superposition meshes had common points which the best efficiency was obtained at delay time 0[${\mu}s$], followed by, no superposition and obtained at delay time 250[${\mu}s$].

• The Korean Journal of Ceramics
• /
• v.6 no.3
• /
• pp.206-208
• /
• 2000

0.65 mol% MgO-doped LiNbO$_3$single crystals were grown by CZ method. The obtained single crystals were colorless and transparent. Noncritically phase-matched second harmonic generation (SHG) of 532-nm radiation from 1064-nm in MgO-doped LiNbO$_3$has been investigated by using pulsed Nd:YAG laser. The phase-matching temperature was room temperature. SHG conversion efficiencies were typically achieved higher than 50% at the phase-matching temperature with no photorefractive damage in the region of fundamental power density which was used in this experiment. The thermo-birefringence coefficient and the electro-birefringence coefficient of SHG were calculated from the temperature phase-matching profile with the electric field.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.51-52
• /
• 2005

Phosphorus doped ZnO thin films on (001) $Al_2O_3$ substrate have been prepared by a pulsed laser deposition (PLD) technique using a Nd:YAG laser. After deposition, phosphorus doped ZnO thin films have been annealed in vacuum, air, nitrogen, and oxygen ambients using pulsed Nd:YAG laser. We report the electrical properties of phosphorus doped ZnO thin films with the variation of the laser annealing conditions for the applications of optoelectronic devices.