• Macromolecular Research
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• v.9 no.3
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• pp.171-178
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• 2001

We report the diffraction behavior of the functionalized sol-gel film composed of two different silanes. One silane (SGDR1) contains disperse red 1 (DR1) that is composed of an azobenzene unit. The other silane (SGCHC) bears a chalcone derivative that is photocrosslinkable under UV irradiation. Two-beam coupling method was employed for fabricating the diffraction gratings. The dynamics of formation and erasure of the gratings was studied in term of the variation of the diffraction efficiency. The decaying behavior of the polarization efficiency was also observed after turning off the two pump beams. For complete erasure of the diffraction gratings, we irradiated the linearly polarized single beam. During two-beam coupling, we irradiated UV light on the film surface. The effects of the photocrosslink between the double bonds in chalcone units on the value and dynamic properties of diffraction efficiency are mainly studied in this work.

• Korean Journal of Optics and Photonics
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• v.20 no.1
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• pp.1-5
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• 2009

Recently, much research has been done for to realizeing nano-scale photonic circuits based on photonic crystal, plasmonics and silicon photonics in order to overcome fundamental limits of electronic circuits. These limits include such as bottleneck of speed, and size that cannot be reduced. Even though several kinds of coupling schemes have been reported, coupling structures are still large when it is compared with the nano-scale optical circuit. In this paper, we proposed using a very thin Fresnel lens while shortening the focal length of the Fresnel lens as much as possible. We proposed, for the first time, to utilize metal slits that are able to use the optical coupling system between a nano-scale optical circuit and the standard single mode optical fiber for overcoming the limitation of focal length shortening of the Fresnel lens. Comparative study has been carried out with a FDTD simulation between normal and metal slit assisted Fresnel lens. From the result of simulation, we can achieve 65% coupling efficiency for the metal-slit Fresnel lens when the focal length of metal-slit Fresnel lens is just $4{\mu}m$. On the other hand, the coupling efficiency of the normal Fresnel lens is about 43%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1798-1804
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• 2014

A novel inductive resonator for the implementation of wireless power transfer using resonant inductive coupling is presented. The proposed inductive resonator is much smaller than the helix shape resonator suggested by MIT research team but operates the same resonant frequency with comparable wireless power transfer efficiency. The proposed inductive resonator is a spiral shape ($1,696cm^3$), which is 97 % smaller than the helix shape ($59,376cm^3$). The wireless power transfer efficiency is less than 9 % when compared to the helix shape resonator. With the reduce size and comparable efficiency, this novel inductive resonator can be used in practical application of wireless power transfer.

• Bulletin of the Korean Chemical Society
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• v.22 no.1
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• pp.63-67
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• 2001

The photophysical properties and the singlet oxygen generation efficiency of tetrathiarubyrin have been investigated to elucidate the possibility of its use as a photodynamic therapy (PDT) photosensitizer by steady-state and time-resolved spectroscopic methods. The observed photophysical properties were affected by various molecular aspects, such as extended ${\pi}conjugation$, structural distortion, and internal heavy atom. The steady-state electronic absorption spectrum was red-shifted due to the extended $\pi-conjugation$, and the spin orbital coupling was enhanced by the structural distortion and the internal heavy atom effect. As a result of the enhanced spin orbital coupling, the triplet quantum yield increased to 0.90 $\pm$ 0.10 and the triplet state lifetime was shortened to 7.0 $\pm$ 1.2 ${\mu}s$. Since the triplet state decays at a relatively faster rate, the efficiency of the oxygen quenching of the triplet state decreases. The singlet oxygen quantum yield was estimated to be 0.52 $\pm$ 0.02, which is somewhat lower than expected. On the other hand, the efficiency of singlet oxygen generation during the oxygen quenching of triplet state, $f{\Delta}^T$, is near unity. Such high efficiency of singlet oxygen generation can be explained by the following two possible factors: The hydrogen bonding of ethanol which impedes the deactivation pathway of the charge transfer complex with oxygen to the ground state, the less probability of the aggregation formation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.12
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• pp.923-929
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• 2003

As for the marine propulsion shafting system using 4 stroke diesel engine, it is common to apply a reduction gear box between diesel engine and shafting to increase propulsion efficiency, which requires inevitably a certain elastic coupling to avoid chattering and hammering inside of gear box. In this study, the optimum method of rectifying propulsion shafting system in case of 750 ton fishing vessel is theoretically studied in a view of dynamic characteristics of torsion. After the replacement of diesel engine and gear box, the torsional vibration get worse and so some countermeasures are needed. The elastic coupling is modified from a present rubber coupling of block type having relatively high torsional stiffness to a rubber coupling haying two serially connected elements. Torsional vibration damper was installed at crankshaft free end additionally and moment of inertia of flywheel was adjusted. The dynamic characteristics of shafting system was improved by these modification. The theoretical analysis of torsional vibration are compared to measurement results using two laser torsion meters during the sea trial.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.575-582
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• 2002

A new coupling method of Element-Free Galerkin Method(EFGM) and Boundary Element Method(BEM) using the domain decomposition method is presented in this paper. This proposed methodology is that the problem domain is decomposed into sub-domains being modeled by the EFGM and BEM respectively and the respective EFGM and BEM domains share a partially overlapped region over an entire domain. Then, the each sub-domain is separately computed and the variables on common region are iteratively updated until converging. It is an important note that in the developed coupling method, there is no need to combine the coefficient matrices of EFGM and BEM sub-domains, in contrast with the other conventional coupling methods. In the first part of this paper, a theory of EFGM and BEM is summarized, and then a brief introduction of domain decomposition method is described. Then, a new coupling method is presented. Also, patch test and Some numerical examples are studied to verify stability, accuracy and efficiency of the proposed method, in which numerical performance of the method is compared with that of conventional method such as EFGM-BEM variational coupling method, EFGM and BEM.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.15-16
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• 2007

A design of a light coupler between a LED and a very thin light guide (0.2mm thickness) is presented. Due to the light guide's very thin thickness, conventional light couplings between LEDs and light guides do not provide enough coupling efficiency. We investigate two different coupling methods: side coupling using a complex-shaped lens and bottom coupling using a grating. This paper presents a draft design of the first approach which couples light from 0.4mm LED to 0.2mm light guide without significant losses.

• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.9-12
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• 2001

Optical aligning process to archive the maximum optical coupling is crucial in many optical device manufacturing line such as laser diode module. Due to the three-dimensional nature of housing module and the aligning process for laser diode coupler, large amount of the manufacturing time, typically ranging from tens of minutes to an hour has to be devoted to the aligning process alone. In this thesis, we propose a new optical aligning process that employee a two-pass algorithm: coarse-to-fine search. Coarse search is a kind of blind search that finds the candidate region where the maximum optical coupling might mostly occur, followed by a fine searching that finds the maximum within the candidate region. The algorithm has been tested on 50 samples of cam-type laser diode modules, and the experimental results are analyzed in terms of aligning time and coupling efficiency.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.301-304
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• 2008

This paper presented an structural efficiency of steel coupling beam jointed single plate shear connections with seat and top angle. Parameters for the test specimens were are seat and top angle, reinforcing of concrete, embedded length, section loss. Steel coupling beam with angle showed excellent strength, stiffness, energy dissipation capacity. The specimen with no reinforcement around the embedded steel plate showed slightly low deformation capacity because of early failure in the precast concrete walls. However, the specimen with reinforcement around the embedded steel plate showed good deformation capacity. Deformation capacity was not decrease despite short embedded length. The specimen with section loss showed excellent deformation capacity. Because shear strength of steel coupling beam was lesser than of connections. These results showed that for workability and cost efficiency, the proposed system is promising for one of steel coupling beam.

• Journal of the Korean Magnetics Society
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• v.21 no.6
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• pp.225-230
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• 2011

Magnetic materials has been applied to various fields due to their energy convertible properties between electrical and mechanical energy. Particularly, permanent magnets have been currently attracted much attention because they produce external magnetic field without any electrical current. For high efficiency, a demand for permanent magnets containing rare earth elements has been continuously increased, which abruptly raises the price and causes the supply difficulty of rare earth materials. Therefore, the development of permanent magnets with less or without rare earth elements become a urgent issue. In this report, the current trend and major issues on high efficiency permanent magnets, particularly exchange-coupling magnets, are discussed.