• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.967-972
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• 2009

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector also were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flowrate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• Korean Journal of Optics and Photonics
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• v.27 no.5
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• pp.181-187
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• 2016

We report on the parameter-dependent optical characteristics of the unidirectional single-mode lasing square ring cavities. Using the taper-step section in the square cavities, the resonant direction can be selected and we characterize the optical losses by changing the taper lengths. Various kinds of square ring cavities are fabricated, based on InGaAsP/InGaAs multiple quantum well semiconductor materials. From the experimental results we obtain the optimized taper length for a given device structure, while maintaining unidirectional single-mode lasing.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.81-88
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• 2014

As the industrial technology has been developed, a dissimilar welding has been received huge attention in various engineering fields. To understand the mechanical properties and possibility of applications of dissimilar metals joining, the laser welding of Cu and Ni dissimilar metals was studied in this paper. Cu and Ni have differences in materials properties, and Cu and Ni make no intermetallic compounds according to typical binary phase of Cu and Ni system. In this study, lap welds of Cu and Ni dissimilar metals using single-mode fiber laser with high welding speed were tried, and mechanical properties of the welds zone were evaluated using a Vickers hardness test and a tensile shear test. To recognize the relation between hardness and tensile shear load, weld fusion zone of interface weld area were observed. And it was confirmed that the ultra-high welding speed could make good weld beads and higher hardness parts had higher tensile shear load under the all conditions.

• Journal of Advanced Navigation Technology
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• v.19 no.4
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• pp.323-329
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• 2015

The compensation characteristics of the distorted WDM channels compensated for by dispersion management (DM) and optical phase conjugation in the long-haul ($50\;fiber\;spans{\times}80km$) transmission link with the randomly distributed single mode fiber (SMF) length and residual dispersion per spans (RDPS) for implementing of the flexible link configuration are investigated. It is confirmed that the compensation effect in the link with the randomly distributed SMF length and RDPS is similar with that in the link with the uniform distribution, when the launch power of WDM channels are restricted within 0 dBm. This result means that the proposed link configuration is useful for designing and deploying the long-haul WDM transmission link.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.6
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• pp.865-870
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• 2012

CFRP of the advanced composite materials as structure materials for vehicles has a widely application in lightweight structural materials of air planes, ships and automobiles because of high strength and stiffness compared with conventional materials. This study is to investigate the energy absorption characteristics and collapse mode of CFRP single and double hat shaped structural member under the axial static collapse test. The CFRP single and double hat shaped structural members stacked at different angles (${\pm}15^{\circ}$, ${\pm}45^{\circ}$, ${\pm}90^{\circ}$, $90^{\circ}/0^{\circ}$ and $0^{\circ}/90^{\circ}$ where the direction on $0^{\circ}$ coincides with the axis of the member). The axial static collapse tests were carried out for each member. Collapse mode and energy absorption characteristics of the each member were analyzed.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.64-70
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• 2013

The joining of Ti and SUS304 dissimilar metals is one of the effective measures to save rare metal. But Ti and SUS304 have differences in materials properties, and Ti and Fe intermetallic compounds such as TiFe and $TiFe_2$ are easily formed in weld fusion zone between Ti and SUS304. Nevertheless, in this study, full penetration lap dissimilar welding of Ti and SUS304 using single-mode fiber laser with ultra-high welding speed was tried, and it was found out that ultra-high welding speed could control the generation of intermetallic compound. To recognize the formation of intermetallic phase in the weld fusion zone and the compound zone of interface weld area were observed and analyzed using energy dispersive X-ray spectroscopy (EDX). And it was confirmed that the ultra-high welding speed could reduce amount of intermetallic compounds, but the intermetallic compounds were existed in the weld fusion zone under the all conditions.

• Korean Journal of Optics and Photonics
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• v.9 no.6
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• pp.403-407
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• 1998

The polarizatin properties of an internal-mirror 543 nm He-Ne laser with and without a transverse magnetic field were investigated for single-mode operation. Two orthogonal eigenpolarizations field to the natural tube axes of laser were observed when the emitted laser output was linearly polarized. Polarization unstability between these polarizations occurred when the applying a 500 gauss transverse magnetic field at 35$^{\circ}$ with respect to the natural tube axes of laser. Under such conditions stable single-mode operation which is useful for the frequency stabilization of a 543 He-Ne laser to $I_2$-saturated absorptions was obtained in the tuning range of 880 MHz.

• Korean Journal of Optics and Photonics
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• v.18 no.1
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• pp.14-18
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• 2007

Photonic crystal fibers(PCFs) with silica cores within an away of air holes have unique properties. Broad band single-mode and the octave-spanning supercontinuum generation, impossible to achieve in classical fibers, can be realized. The design of PCFs is very flexible. There are two parameters to manipulate: air hole diameter, and lattice pitch. We introduced a fabrication process for control of the parameters to obtain endlessly single mode PCF, which is single mode in a large wavelength range, and highly nonlinear PCF. The numerical analysis and experiments are included.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.2
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• pp.78-85
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• 2010

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flow rate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• Journal of Power Electronics
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• v.18 no.1
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• pp.11-22
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• 2018

This paper presents a single switch, high step-up, non-isolated dc-dc converter suitable for renewable energy applications. The proposed converter is composed of a coupled inductor, a passive clamp circuit, a switched capacitor and voltage lift circuits. The passive clamp recovers the leakage inductance energy of the coupled inductor and limits the voltage spike on the switch. The configuration of the passive clamp and switched capacitor circuit increases the voltage gain. A wide continuous conduction mode (CCM) operation range, a low turn ratio for the coupled inductor, low voltage stress on the switch, switch turn on under almost zero current switching (ZCS), low voltage stress on the diodes, leakage inductance energy recovery, high efficiency and a high voltage gain without a large duty cycle are the benefits of this converter. The steady state operation of the converter in the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is discussed and analyzed. A 200W prototype converter with a 28V input and a 380V output voltage is implemented and tested to verify the theoretical analysis.