• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.1
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• pp.17-21
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• 2005

Shielded laser ablation system composed of laser system, image analyser, XYZ translator with motion controller, ablation chamber, manipulator and various optics was designed. Nd:YAG laser which can be tunable from 1064 nm to 266 m was selected as light source. CCD camera(< $\pm$200) was chosen to analyze a crater less than 50 un in diameter. XYZ translator was composed of three linear stage which can travel 50 w with a minimum movement of 1 um and motion controller. Before the performance test, each part of system was optically aligned. To perform the ablation test, the specimen was ablated by 50 um interval and observed by image analyser The shape of crater was almost round, indicating laser beam has homogeneous energy distribution. The resolution and magnification of image system were compatible with the design.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.214-217
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• 2011

A fresnoite glass-ceramics has been investigating considerably because of the second order nonlinearity as well as its permanent optical nonlinearity. However, the chemical compositions of transparent glass-ceramics examined in the previous studies have been limited to adjust the composition close to fresnoite stoichiometrically. In this study, to investigate the effect of strontium ions in glass-ceramics on second order nonlinearity, $K_2O-TiO_2-SiO_2$ (KTS) glasses soaked in molten $Sr(NO_3)_2$ were prepared. Crystalline phases of the soaked glasses were measured by X-ray diffraction (XRD) as soaking times and additional heat treatment. The exchange of strontium ions into the glass was verified by Field Emission Scanning Electron Microscope (FE-SEM). And the phenomena of second order harmonic generation (SHG) was observed using Nd-YAG laser.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.665-672
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• 2013

With the development of advanced processing technology, laser processing systems, which require high-quality precision processing, have attracted considerable attention. Although laser equipment is expensive, it enables quick processing and less deformation of materials. This technology is often applied to secondary batteries, which has thus farinvolved the use of argon tungsten inert gas (TIG) welding. However, the welding characteristics of argon TIG welding are not yet good, and a laser is used for welding to address this problem. In this study, lap-joint welding was conducted, and the desired welding characteristics were obtained when the laser power was 1800W and the laser beam travel speed was 1.8 m/min. Lap-joint welding was conducted on Ni-coated SS41. Two cases were compared. No pores were observed in the Ni-coated SS41 lap-joint welding part, and cracks appeared from the lap-joints. Moreover, the pole rod and tap were welded together in a T-joint form to improve the output of the secondary battery. T-joint laser welding showed better welding characteristics than TIG welding.

• Laser Solutions
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• v.7 no.2
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• pp.1-10
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• 2004

This work was attempted to join SCP sheet and STS304 sheet by using Nd:YAC laser beam. SCP sheet has good formability and low cost, while STS304 has excellent corrosion resistance and mechanical properties in high temp. In this experiment, butt joint type was used to develop the tailored blank welding for dissimilar steel. Sheets which have different thermal properties. Computer simulation was conducted to obtain the off-set position for efficient welding by considering laser power, scanning speed, focal length and basic properties. The result showed that the optimum thermal distribution was obtained when the laser beam was irradiated at $0.05{\sim}0.1$ mm off-set toward the SCP sheet side. The experiment was conducted based on the result of computer simulation to show the same optimum conditions. Optimum conditions were 3KW in laser beam power, 6m/min in scanning speed, -0.5mm in focal position, 0.1mm off-set toward SCP. Microhardness test, tensile test, bulge test, optical microscopy, EDS, and XRD were performed to observe the microstructure around fusion zone and to evaluate the mechanical properties of optimum conditions, The weld zone had high microhardness values by the formation of the martensitic structure. Tensile test measured the strength of welded region by vertical to strain direction and the elongation of welded region by parallel to strain direction. Bulge test showed $52\%$ formability of the original materials. Bead shape, grain size, and martensitic structure were observed by the optical microscopy in the weld zone. Detailed results of EDS, XRD confirmed that the welded region was connected of martensitic structure.

• Clinics in Shoulder and Elbow
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• v.1 no.1
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• pp.40-45
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• 1998

Multidirectional instability of the shoulder joint is an unusual entity which is not yet well understood. Traditionally recommended treatment is non-operative, but recently arthroscopic treatment has been performed. This is a retrospective review of 20 patients who had multidirectional instability, who had been treated with arthroscopic capsular shift(7 cases), and arthroscopic treatment using Ho:YAG laser(l3 cases) at Department of Orthopaedic Surgery, Chungnam National University Hospital from July, 1988to February, 1997. Results of this study were as follows: 1. In five patients who were treated with arthroscopic anterior capsular shift only, all cases had redislocation of the shoulder joint. But there was no redislocation in two patients who were treated with arthroscopic anterior and posterior capsular shift. 2. ln three patients who were treated with laser-assisted capsular shift only, all cases had redislocation of the shoulder joint. But there was only one redislocation in ten patients treated with laser-assisted capsular shrinkage and capsular plication. Ho: Y AG laser has been found to be a safe and efficacious adjunct to many arthroscopic shoulder procedures. We had satisfactory results by combining a transglenoid capsular shift with laser-assisted capsular shrinkage. Arthroscopic laser-assisted capsular shrinkage and capsular plication is a one of recommendable treatment options in multidirectional instability of the shoulder joint.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.1
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• pp.27-32
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• 2000

In this paper, ultrasonic wave in the thermoelastic regime was generated in a steel disk by illuminating a pulse laser (Q-switched Nd:YAG) on the surface of the sample and was detected on the other side by Michelson interferometer which was stabilized by feed back control. The experimentally detected displacement waveform of the ultrasonic wave showed good agreement with the theoretically expected one. Also it was shown that sound speeds of longitudinal and shear wave were similar to ones measured by pulse-echo method using a contact transducer. As an application of the noncontact ultrasonic measurement by using laser based ultrasonics, the sound speed in the sample was monitored while the sample was heated in a furnace, and the result showed that it decreased according to the increase of sample temperature.

• Korean Journal of Remote Sensing
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• v.29 no.5
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• pp.581-588
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• 2013

We developed the three channel lidar system to measure stratospheric aerosols at the Gwangju Institute for Science and Technology (GIST), a suburban site in Republic of Korea. The system provides backscatter coefficient (${\beta}$) at 532 and 1064 nm as well as depolarization ratios (${\delta}$) at 532 nm ($2{\beta}+1{\delta}$) using the doubled Nd:YAG laser wavelength at 532 and 1064 nm. The lidar system is optimized to measure stratospheric aerosols such as volcanic ashes. This paper describes the details of the optical setup, data acquisition system, and analysis method. This study shows an example of measuring stratospheric aerosols emitted by the volcanic eruption which occurred in Mt. Nabro ($13.37^{\circ}$ N, $41.70^{\circ}$ E).

• Korean Journal of Materials Research
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• v.24 no.12
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• pp.710-714
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• 2014

The effect of titanium dioxide ($TiO_2$) on the properties of color conversion glasses was examined for glasses based on $BaO-ZnO-B_2O_3-SiO_2$. One glass sample, containing 25 mol% of each component, was used as a reference; the other three glass samples contained 1, 3, and 5 mol% $TiO_2$, respectively. The four color conversion glass samples were prepared by sintering a mixture of glass frits and a $YAG:Ce^+$ phosphor. The characteristics of the color conversion glass samples, such as luminous efficacy, luminance, CIE (Commission International de I'Eclairage) chromaticity, CCT (Correlated Color Temperature), and CRI (Color Rendering Index) were analyzed according to the PL spectrum. The refractive index of the glass samples was found to increase with the titanium dioxide content. In conclusion, luminous efficacy of color conversion glasses increased as the content of $TiO_2$ was raised in the glass matrix.

• Korean Journal of Crystallography
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• v.3 no.1
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• pp.37-43
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• 1992

KTiOP04 is a nonlinear optical crystal which is most widely used for frequency doubling of the radiation of Nd : YAG laser. In the experiment, sin ale crystals of KTiOP04 were grown by TSSG technique using 3K2W04·P2O5 flux. Low temperature gradient furnace suitable for KTP single crystal growth was used. Seed crystal was placed at the surface of the solution for the purpose of better observation of the growing crystals and the possibility of diameter control. Solution included 66.7mol% KTiOP04 for all experiments and its saturation temperature was 1020℃. The conditions of single crystal growth were as follows: cooling rate 0.2℃/h, crystal rotation rate 50rpm, c -axis seed. Using these conditions, single crystals up to 23 ×25×25mm3 have been groan from about 100cc solution. We have also observed a change in the crystal growth habit which resulted in the formation of large (201) faces and small (100) faces. And some crystals have (101) faces.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.5
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• pp.600-607
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• 2011

Recently, high carbon steel has become essential not only for shipbuilding parts, but also mass production. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate, microstructural changes and hardness characteristics of two parts (the surface treatment part, and parental material) are observed with the change of laser beam speed and surface temperature.