• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.362.2-362.2
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• 2016

본 실험은 CW (Continuous wave) 주파수를 가진 교류 자기장을 발생시켜 자성나노입자를 가열시키는 것이 목적이다. 이를 위해 CW 주파수 및 SMPS (Switching Mode Power Supply)를 이용해 코일에서 교류 자기장을 발생시키는 평판형 자기장 발생 장치를 자체적으로 개발하였다. 이를 이용하여 인가전압을 변화시키면서 자기장 세기의 변화를 주었다. 평판형 코일 위에는 유리 등의 원형 평판 절연체를 덮고 그 절연체 표면에 웰(Well plate)를 위치시켰고 그 안에 자성나노입자가 포함된 수용액을 넣어 교류 자기장에 노출시켰다. 자기장 측정센서(Magnetic pick up coil, Gauss Meter)를 이용하여 자기장의 세기를 측정하였고, 자성나노입자의 농도, 크기 및 자기장 세기에 따른 자성나노입자의 온도상승효과를 접촉식 온도계를 이용하여 정량적으로 측정하였다.

• Journal of Welding and Joining
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• v.13 no.1
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• pp.145-155
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• 1995

Continuous wave C $O_{2}$ laser beam welding and formability of zinc coated steel plates were investigated. First, the optimal welding condition could be obtained in lap configuration by using the data for heat input, gap size and fracture behaviour. The gap size for fully-penetrated bead could be predicted by the gap model by Akhter et al. AIso, it was found that the joining efficiency was constant. Secondly, the butt welding of dissimilar materials (zinc coated steel plate and cold rolled steel plate) with different thicknesses was investigated. In the thickness range of 0.8-2.0 mm, the maximum welding speed of 10m/min was obtained. In the butt welding of two plates with thickness 2.0 mm and l.6mm, the maximum, welding speed of 6m/min was obtained, Finally. the forming results of butt-welded plates showed that the joining design was important to apply the laser welded blank in the automotive production.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.3
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• pp.211-216
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• 1986

This paper presents theoretical analysis and experimental results on an improved interference rejection circuit in the presence of continuous wave interference at center frequency, particularly in a wide-band communication systems. This circuit is based upon a phase locked loop for estimating the CW interference phase and the MSE technique to minimize the estimation error. Therefore, the introduced rejection circuit that minimized the estimated phase error outperforms the rejection circuit with phase estimation only. As a result of experiment, we confirm that this proposed rejection circuit gives a high degree of interference rejection performances when the input J/S is large.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.119-126
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• 2004

The welding characteristics of Inconel 600 Alloy using a continuous wave Nd:YAG laser are experimentally investigated. The major process parameters studied in the present laser welding experiment were the positions of focus, laser power and travel speed of laser bean We measured the fusion zone size and its shape using an optical microscope for the observation of cross-sectional area. We performed two tests regarding the tension and the micro hardness for welding quality estimation. Then we measured residual stress in welds by electronic speckle pattern interferometry(ESPI). In conclusion the optimum butt welding process parameters were 0.5mm focus position, 1.6kW laser power, 1m/min travel speed and 5.5$\ell$/min assist gas discharge.

• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.464-469
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• 2016

All-optical non-return-to-zero (NRZ) -to- return-to-zero (RZ) data-format conversion has been successfully demonstrated using a semiconductor optical amplifier in a fiber-loop mirror (so-called SOA-loop mirror) with a continuous-wave (CW) holding beam. The converted RZ signal after pulse compression has been used to create a 40 Gb/s OTDM (Optical Time Division Multiplexing) signal. Here is proposed an NRZ-to-RZ conversion method without any additional optical clocks, unlike conventional methods based on optical AND logic. In addition, it has the merit of operating at various bit-rate speeds without any controlling device. Moreover, it has a simple structure, and it can be used for all-optical bit-rate-flexible clock recovery.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.2
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• pp.125-133
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• 1993

Electronic Speckle Pattern Interferometry(ESPI) using a CW laser, a video system and image processor was applied to the rotating displacement of rigid body. ESPI require no special surface preparation or attachments and displacements between any two arbitrary points on the surface can be measured. The characteristic speckle pattern formed when imaging a scattering surface illuminated by laser light retains phase information, which can be used for interferometric measurement of surface displacement. The application of this principle to measuring in-plane displacement resolved in one direction is described, together with the novel use of television equipment to detect and process the information contained in the speckle pattern. This is faster, and more convenient and versatile than customary photographic methods.

• Korean Journal of Optics and Photonics
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• v.29 no.1
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• pp.32-39
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• 2018

The impact of the amplified spontaneous emission (ASE) on the gain recovery time of a bulk semiconductor optical amplifier (SOA) is investigated. The gain-recovery time is obtained by determining the time evolution of the gain, carrier density, and ASE in an SOA, after the propagation of a short pump pulse and continuous-wave (CW) probe of gain dynamics. In the simulation, a wide-band-semiconductor model, which can be characterized by the material gain coefficient over a wide wavelength range, is used, because the gain bandwidth of a practical SOA is very wide. The pump pulse and counterpropagating CW probe field are considered in the simulation, with the ASE noise spectrum equally divided.

• Current Optics and Photonics
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• v.3 no.1
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• pp.33-39
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• 2019

We report development of a frequency-stabilized mid-infrared continuous-wave (cw) optical parametric oscillator (OPO) based on a fan-out grating MgO:PPLN crystal pumped at 1064 nm. The OPO resonator was designed as a pump-enhanced standing-wave cavity that resonates to the pump and signal beams. To realize stable operation of the OPO, we applied a modified Pound-Drever-Hall technique, which is a well-known method for powerful laser frequency stabilization. Tuning a poling period of the fan-out grating of the crystal allows wavelength-tunable OPO outputs from 1510 nm to 1852 nm and from 2500 nm to 3600 nm for signal and idler beams, respectively. At the idler wavelengths of 2500 nm, 3000 nm and 3500 nm, we achieved more than 50 mW of output powers at a pumping power of 1.1 W. The long-term stability of the OPO was confirmed by recording the power and wavelength variations of the idler for an hour.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.222.2-222.2
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• 2005

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.69-70
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• 2006