• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5223-5242
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• 2017

In the last decade, the 2.4 GHz band of IEEE 802.11 WLANs has become heavily congested due to the explosive increase in demand of Wi-Fi connectivity. With the current deployment of enterprise WLANs, channel switching mechanism continues to exhibit inefficiencies because it cannot adapt to real-time channel condition and the inability to support seamless channel switching. Software Defined Networking (SDN) as an emerging architecture is promising to introduce flexibility and programmability for wireless network management. Leveraging SDN to existing enterprise WLANs, channel switching method can be improved significantly. This paper presents a software-defined enterprise WLAN framework with a load aware automatic channel switching solution, which utilizes AP load and channel interference factor (CIF) to provide seamless channel switching. Two automatic channel switching algorithms named Single Switch (SS) and Double Switch (DS) are proposed to improve the overall user experience and the experience of users with highest traffic load respectively. Experiment results demonstrate that our solution can efficiently improve user experience in terms of jitter, transmission delay and network throughout when compared to the conventional channel switching mechanism.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.1
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• pp.68-82
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• 2011

Wireless mesh networks (WMNs) provide high-speed backbone networks without any wired cable. Many researchers have tried to increase network throughput by using multi-channel and multi-radio interfaces. A multi-radio multi-channel WMN requires channel assignment algorithm to decide the number of channels needed for each link. Since the channel assignment affects routing and interference directly, it is a critical component for enhancing network performance. However, the optimal channel assignment is known as a NP complete problem. For high performance, most of previous works assign channels in a centralized manner but they are limited in being applied for dynamic network environments. In this paper, we propose a simple flow estimation algorithm and a hybrid channel assignment algorithm. Our flow estimation algorithm obtains aggregated flow rate information between routers by packet sampling, thereby achieving high scalability. Our hybrid channel assignment algorithm initially assigns channels in a centralized manner first, and runs in a distributed manner to adjust channel assignment when notable traffic changes are detected. This approach provides high scalability and high performance compared with existing algorithms, and they are confirmed through extensive performance evaluations.

• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.343-351
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• 2017

T1, T2 relaxation time and relaxation rates were measured and analyzed according to the change of RF coil channel number of MAGiC sequence. T1, T2, R1 and R2 maps were obtained by using MAGiC sequence with phantom (1.0, 0.6, 0.2, 0 mM) on the RF coil with channel number of 1, 8, 16 and 32 respectively. T1, T2, R1, R2 values and relaxation rates were measured for each channel number and concentration, and Relaxivity was calculated according to each concentration. T1, T2, R1, and R2 values were measured in each coil. There was no significant difference between T1 and R1 values (p> 0.05). However, T2 and R2 values were significantly different (p <0.05). In the post-analysis results, T2 value was significantly different from that measured on 1, 8, 16, and 32 channel coils (p <0.05) and There was no difference between 8, 16, and 32 channel coils (p> 0.05). The R2 value was significantly different from that measured on the 8, 16, and 32 channel coils in the 1 channel coil, and the results on the 8 channel coils and the 16 channel coils showed a significant difference (P <0.05). In conclusion, T1 and R1 values were not significantly different according to the number of channels in the coil, but T2 and R2 values were significantly different. Therefore, when quantitative measurement of T2 and R2 values using the MAGiC sequence, the same number of coils should be used for reproducibility.

• Journal of Haehwa Medicine
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• v.12 no.2
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• pp.199-225
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• 2004

For the purpose of experimental and clinical studies on the 14 channels and collaterals, we performed an inquiry on the anatomical mapping of neronal, circulatory and muscular networks in the human body which possibly correspond to the major pathway of Du channel and Ren channel known to be critical for overall controlling and mediating 12 regular channel connections. The theoretical background of this analysis was based on the oriental medicinal treatises which described acu-points and related anatomical informations. We suggest that rearrangement methodology for the 12 regular channels as described here may be applied to other 12 regular channels and to develop the new concept on the elucidation of the medical efficacy based on precise anatomical localization of channels and collaterals as well as the meridian points. It is proposed that interdisciplinary studies between oriental and western medicine are critical for more efficient achievement.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.5
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• pp.393-400
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• 2009

NO released by myenteric neurons controls the off contraction induced by electrical field stimulation (EFS) in distal esophageal smooth muscle, but in the presence of nitric oxide synthase (NOS) inhibitor, L-NAME, contraction by EFS occurs at the same time. The authors investigated the intracellular signaling pathways related with G protein and ionic channel EFS-induced contraction using cat esophageal muscles. EFS-induced contractions were significantly suppressed by tetrodotoxin ($1\;{\mu}M$) and atropine ($1\;{\mu}M$). Furthermore, nimodipine inhibited both on and off contractions by EFS in a concentration dependent meaner. The characteristics of 'on' and 'off contraction and the effects of G-proteins, phospholipase, and $K^+$ channel on EFS-induced contraction in smooth muscle were also investigated. Pertussis toxin (PTX, a $G_i$ inactivator) attenuated both EFS-induced contractions. Cholera toxin (CTX, $G_s$ inactivator) also decreased the amplitudes of EFS-induced off and on contractions. However, phospholipase inhibitors did not affect these contractions. Pinacidil (a $K^+$ channel opener) decreased these contractions, and tetraethylammonium (TEA, ${K^+}_{Ca}$ channel blocker) increased them. These results suggest that EFS-induced on and off contractions can be mediated by the activations Gi or Gs proteins, and that L-type $Ca^{2+}$ channel may be activated by G-protein ${\alpha}$ subunits. Furthermore, ${K^+}_{Ca^-}$ channel involve in the depolarization of esophageal smooth muscle. Further studies are required to characterize the physiological regulation of $Ca^{2+}$ channel and to investigate the effects of other $K^+$ channels on EFS-induced on and off contractions.

• Journal of Distribution Science
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• v.21 no.1
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• pp.119-128
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• 2023

Purpose: Due to COVID-19, the rapidly changing untact culture from offline to online has spread rapidly, increasing the utilization of omni-channel. However, among the studies on consumers in the online market, there are not many studies that analyze Shopping Values and attitudes toward omnichannel Acceptance. Research design, data, and methodology: This study investigated through empirical analysis how Shopping Values and innovation propensity of consumers using omni channels affect omni channel Acceptance attitudes. The analysis results based on a total of 268 questionnaires using SPSS v.23 and AMOS v.23 statistical programs are as follows. Results: First, it was found that the perceived Value of omnichannel use had a positive effect on the innovation tendency, and the pleasure Value had a greater effect than the actual Value. Second, it was found that the practical and hedonic Value of the omnichannel had a positive effect on the attitude of service Acceptance. Third, it was found that Omni Channel's consumer innovation tendency had a positive effect on service Acceptance attitude. Conclusion: This study proved that Shopping Value perception and individual innovation propensity for omnichannel services have a positive effect on Acceptance attitude, and it is of academic significance in that it expanded understanding of what factors are needed to increase Acceptance attitude of Omni Channel services.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.11b
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• pp.238-241
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• 2002

본 논문에서는 워터마크가 갖추어야 할 요소 중 하나인 비가시성과 강인성을 만족하기 위하여 변환된 DFT주파수 영역에 HVS의 DPC(Decomposition Perceptual Channel)를 사용하였다. 워터마크의 삽입 위치를 실험적으로 최적 Channel을 도출하였으며, 실험을 통하여 다양한 공격에 대한 강인성을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3498-3511
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• 2016

We investigate the channel state information (CSI) in multi-input multi-output (MIMO) cooperative networks that employ the amplify-and-forward transmission scheme. Least squares and expectation conditional maximization have been proposed in the system. However, neither of these two approaches takes advantage of channel sparsity, and they cause estimation performance loss. Unlike linear channel estimation methods, several compressed channel estimation methods are proposed in this study to exploit the sparsity of the MIMO cooperative channels based on the theory of compressed sensing. First, the channel estimation problem is formulated as a compressed sensing problem by using sparse decomposition theory. Second, the lower bound is derived for the estimation, and the MIMO relay channel is reconstructed via compressive sampling matching pursuit algorithms. Finally, based on this model, we propose a novel algorithm so called sparsity adaptive expectation maximization (SAEM) by using Kalman filter and expectation maximization algorithm so that it can exploit channel sparsity alternatively and also track the true support set of time-varying channel. Kalman filter is used to provide soft information of transmitted signals to the EM-based algorithm. Various numerical simulation results indicate that the proposed sparse channel estimation technique outperforms the previous estimation schemes.

• Biomolecules & Therapeutics
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• v.15 no.3
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• pp.156-161
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• 2007

Rapid advances in pharmacogenomic research have provided important information to improve drug selection, to maximize drug efficacy, and to minimize drug adverse reaction. The SNPs that are the most abundant type of genetic variants have been proven as valid biomarkers to give information on the prediction of pharmacokinetic/pharmacodynamic properties of drugs based on genotype. In order to elucidate a correlation between SNPs of calcium channel encoding gene and adverse reactions of calcium channel blockers, we investigated SNPs in CACNA1C gene known as a binding site of calcium channel blocker. 96 patients with hypertension who had taken or are taking an antihypertensive drug, 1,4-dihydropyridine (DHP) were included for analysis. These patients were composed of 47 patients with adverse drug reactions (ADR) such as edema from calcium channel blockers and 49 patients without ADR as a control group. The exons encoding the drug binding sites were amplified by PCR using specific primers, and SNPs were analyzed by direct sequencing. We found that there was no SNP in the exons encoding DHP binding site, but four novel SNPs in the exon-intron junction region. However, four novel SNPs were not associated with the ADR of calcium channel blockers. In conclusion, this study showed that ADR from calcium channel blockers may not be caused by SNPs of the binding sites of calcium channel blockers in CACNA1C gene.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.309-318
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• 2003

This paper presents an in-depth study of a UWB indoor radio channel between 1 and 9 GHz, which was used for the subsequent development of a new statistical UWB multipath channel model, focusing on short range indoor scenarios. The channel sounding process was carried out covering different indoor environments, such as laboratories, halls or corridors. A combination of new and traditional parameters has been used to accurately model the channel impulse response in order to perform a precise temporal estimation of the received pulse shape. This model is designed specifically for UWB digital systems, where the received pulse is correlated with an estimated replica of itself. The precision of the model has been verified through the comparison with measured data from equivalent scenarios and cases, and highly satisfactory results were obtained.