• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.160-167
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• 2005

The gain-clamped EDFA has been developed to eliminate the output power change of WDM surviving channels to occur with added or dropped channels, which degrades the performance of WDM optical network. It maintains the constant gain of surviving channels when WDM channels are added or dropped in a network amplifying node. In this paper, the hi-directionally pumped gain-clamped EDFA is implemented to compensate the change of the input power by a lasing. The results show that the lasing of a short wavelength and backward propagation is the optimal condition to minimize the transient response of surviving channels in terms of the overshoot and gain saturation due to the inhomogeneous broadening effect.

• Journal of the Korean Chemical Society
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• v.34 no.3
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• pp.304-306
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• 1990

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.157-163
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• 2006

Our research dealt with micro fabrication using micro forming process. The goal of the research was to establish the limit of forming process concerning the size of forming material and formed shape. Flat-rolled ultra thin metallic foils of pure copper(3.0 and $1.0{\mu}m$ in thickness)and stainless steel($2.5{\mu}m$ in thickness) were used for forming material. We obtained the various shapes of micro channels as using designed forming process. $12-14{\mu}m$ wide and $9{\mu}m$ deep channels were made on $3.0{\mu}m$ thick foil and $6{\mu}m$ wide and $3{\mu}m$deep channels were made on $1.0{\mu}m$ thick foil. Si wafer die for forming was fabricated by using etching technique. And the relation of etching time and die dimension was investigated for fabricating precisely die groove. For the forming, die and metal foil were vacuum packed and the forming was conducted with a cold isostatic press. The formed channels were examined in terms of their dimension, surface qualities and potential for defects. Base on the examinations, formability of ultra thin metallic foil was also discussed. Finally, we compared the forming result with simulation. The result of research showed that metal forming technology is promising to produce micro parts.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6A
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• pp.547-555
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• 2006

We implemented DPU(Double-Pass Gain-Clamped) L-band EDFA for highly efficient amplification. A lasing signal generated within the linear cavity, can minimize the fluctuation of surviving channels when several WDM(Wavelength Division Multiplexing) channels are added or dropped. The new method measuring the characteristics of transient response of surviving channels quantitatively is suggested. It is to measure the ratio of lasing output before add or drop to that after add or drop. We investigated dynamic characteristics by using this method according to lasing wavelengths and propagation directions within the cavity. Experimental measurements show that the short lasing wavelength and backward propagation direction is the best condition for small fluctuation of surviving channels.

• The Journal of Engineering Research
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• v.7 no.1
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• pp.5-16
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• 2005

We implemented DPGC(Double-Pass Gain-Clamped) L-band EDFA for highly efficient amplification. A lasing signal generated within the linear cavity, can minimize the fluctuation of surviving channels when several WDM(Wavelength Division Multiplexing) channels are added or dropped. The new method describing the characteristics of transient response of surviving channels quantitatively is suggested. It is to measure the ratio of lasing output before add or drop to that after add or drop. We investigated dynamic characteristics by using this method according to lasing wavelengths and propagation directions within the cavity. The experimental measurements show that the short lasing wavelength and backward propagation direction is the best condition for small fluctuation of surviving channels.

• Journal of Distribution Science
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• v.19 no.1
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• pp.5-15
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• 2021

Purpose: This study explores the types of relational benefits that generate loyalty to room-sharing services among Chinese customers based on the relationship marketing literature. The study also examines the moderating effect of alternative attractiveness on this relationship. Research design, data and methodology: Based on research hypotheses, questionnaires with items measuring the proposed constructs in three dimensions, including relational benefits, alternative attractiveness, and customer loyalty, were designed to test the hypotheses. Data were collected via an online questionnaire of 220 room-sharing service customers in China. Results: Results verify the effects of relational benefits on customers' loyalty to room-sharing services and the mediating effect of alternative attractiveness. More specifically, confidence, social, and safety benefits positively affect customer loyalty to room-sharing services, and alternative attractiveness moderates only the effect of social benefits. Conclusions: The results suggest that room-sharing service providers should concentrate on providing confidence, social, and safety benefits to maintain long-term relationships with customers. This study also provides practical implication for building relationships between channel members in service distribution channels. The study concludes that without customer relationships marketing for managing collaborative and social communication channels, the entire distribution channel might lose out eventually.

• Journal of Broadcast Engineering
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• v.10 no.1 s.26
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• pp.4-13
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• 2005

An equalization algorithm is proposed to guarantee a stable performance in fast fading channels for digital television (DTV) systems from the advanced television system committee (ATSC) standard. In channels with high Doppler shifts, the conventional equalization algorithm shows severe performance degradation. Although the conventional equalizer compensates poor channel conditions to some degree, long filter taps required to overcome long delay profiles are not suitable for fast fading channels. The Proposed sparse equalization algorithm is robust to the multipaths with long delay Profiles as well as fast fading by utilizing channel estimation and equalizer initialization. It can compensate fast fading channels with high Doppler shifts using a filter tap selection technique as well as variable step-sizes. Under the ATSC test channels, the proposed algorithm is analyzed and compared with the conventional equalizer. Although the proposed algorithm uses small number of filter taps compared to the conventional equalizer, it is stable and has the advantages of fast convergence and channel tracking.

• Bulletin of the Korean Chemical Society
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• v.12 no.6
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• pp.658-661
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• 1991

The gas-phase nucleophilic substitution reaction of pentafluoroanisole with $OH^-$ and ${NH_2}^-$ nucleophiles have been studied theoretically using the AM1 method. Three reaction channels, $S_N2$, IPSO and $S_NAr$ (scheme 1), are all very exothermic so that all are accessible despite the varying central energy barriers which are much lower than the reactants level. In the IPSO and $S_NAr$ channels, the reactants form directly a stable ,${\sigma}$-anion complex which proceeds to form a proton transfer complex via a transition barrier corresponding to a loose ${\pi}$-type complex with the F-(or ${OCH_3}^-$) leaving group. Due to a greater number of probable reaction sites available for $S_NAr$ compared to the other two processes, the $S_NAr$ channel is favored as experimentally observed.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.228-228
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• 2004

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.102-108
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• 2010

In this paper, we analyse the frequency diversity of BICM-OFDM with extended interleaving. The extended interleaving is an interleaving which is added to the existing BICM-OFDM system to extends the interleaving depth by times to the previous interleaving depth. Using the extended interleaving, the diversity order of the proposed system over -tap frequency selective channels is increased from min($d_{free}$, L) to min($d_{free}$, KL), where $d_{free}$ is minimum Hamming distance of the convolutional code. Simulation is also performed to show that the performance of the proposed system is better than that of the existing system even if the channel is an on-off channel in which the number of multi-paths is varying.