• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.3862-3888
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• 2017

In high diversity node situation, single-channel MAC protocols suffer from many collisions. To solve this problem, the research of multichannel MAC protocol has become a hotspot. And the cyclic quorum-based multichannel (CQM) MAC protocol outperformed others owing to its high frequency utilization. In addition, it can avoid the bottleneck that others suffered from and can be easily realized with only one transceiver. To obtain the accurate performance of CQM MAC protocol, a Markov chain model, which combines the channel hopping strategy of CQM protocol and IEEE 802.11 distributed coordination function (DCF), is proposed. The metrics (throughput and average packet transmission delay) are calculated in performance analysis, with respect to node number, packet rate, channel slot length and channel number. The results of numerical analysis show that the optimal performance of CQM protocol can be obtained in saturation bound situation. And then we obtain the saturation bound of CQM system by bird swarm algorithm (BSA). Finally, the Markov chain model and saturation bound are verified by Qualnet platform. And the simulation results show that the analytic and simulation results match very well.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.11
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• pp.256-264
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• 2020

Industrial Wireless Sensor Networks (IWSNs) is exploited to achieve various objectives such as improving productivity and reducing cost in the diversity of industrial application, and it has requirements such as low-delay and high reliability packet transmission. To accomplish the requirement, the network manager performs graph construction and resource allocation about network topology, and determines the transmission cycle and path of each node in advance. However, this network management scheme cannot treat mobile devices that cause continuous topology changes because graph reconstruction and resource reallocation should be performed as network topology changes. That is, despite the growing need of mobile devices in many industries, existing scheme cannot adequately respond to path failure caused by movement of mobile device and packet loss in the process of path recovery. To solve this problem, a network management scheme is required to prevent packet loss caused by mobile devices. Thus, we analyse the location and movement cycle of mobile devices over time using machine learning for predicting the mobility pattern. In the proposed scheme, the network manager could prevent the problems caused by mobile devices through performing graph construction and resource allocation for the predicted network topology based on the movement pattern. Performance evaluation results show a prediction rate of about 86% compared with actual movement pattern, and a higher packet delivery ratio and a lower resource share compared to existing scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.2
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• pp.151-160
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• 1997

In this paper, we have carried out the DS/CDMA with a suppressed pilot channel, which is used in receiving coherently with Rake diversity and in synchronizing the chip timing, in the mobile satellite communication. Also, we have investigated the envelope variation of a shadowed Rician fading simulator, and analyzed the error performences of DS/CDMA in the mobile satellite communication. The results showed that the error performance in the Heavy shadowing environment might be degraded more than in the Rayleigh fading environment since the fading envelopes in the former environment are varied randomly compared with those in the latter environment. And the performence of DS/CDMA system could be improved about 10 dB compared with that of narrowband QPSK system. In conclusion, DS/CDMA with a suppressed pilot channel had the best performance in the case of the suppressed pilot channel to transmission power ratio $\beta$=-8 dB, the number of complex delay profiles $N_{profile}$=32, and using these values, the error performance of DS/CDMA in Light shadowing environment was identical to the ideal QPSK error performance.

• Korean Journal of Medicinal Crop Science
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• v.11 no.2
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• pp.102-108
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• 2003

This experiment was conducted to evaluate the diversity and purity of the Korean ginseng (Panax gjnseng) lines developed by the pure line selection using RAPD markers. Four primer (OPA 19, OPM 11, URP 3 and UBC 98) out of the 48 primer tested produced band which showed within-line polymorphisms at least in one line. Within-line polymorphisms were detected in six lines by OPA 19, in four lines by URP 03, in five lines by OPM 11, and in one line by UBC 98 respectively. Five plants obtained from the commercial cultivar 'Cheonpung' were differentiated using the primers OPA 19 and OPM 11. Five plants obtained from the 'Yeonpung were differentiated using the primer OPM 11. Detection of within-line RAPD polymorphisms might be attributed to the fact that cross pollination appear in P. gjnseng and a long period of three to four years required to reach the reproductive stage thereby delay the process to homozygosity.

• Membrane Journal
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• v.32 no.6
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• pp.367-382
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• 2022

Numerous metal-organic frameworks (MOFs) produced by periodic combinations of organic ligands and metal ions or metal-oxo clusters have led the way for the creation of energy-efficient membrane-based separations that may serve as viable replacements for traditional thermal counterparts. Although tremendous progress has been made over the past decade in the synthesis of polycrystalline MOF membranes, only a small number of MOFs have been exploited in the relevant research. Intercrystalline defects, or nonselective diffusion routes in polycrystalline membranes, are likely the reason behind the delay. Postsynthetic modifications (PSMs) are newly emerging strategies for providing polycrystalline MOF membrane diversity by leveraging advanced membranes as a platform and improving their separation capabilities via physical and/or chemical treatments; therefore, neither designing and developing MOFs nor tailoring membrane synthesis techniques for focused MOFs is necessary. In this minireview, seven subclasses of PSM techniques that have recently been adapted to polycrystalline MOF membranes are outlined, along with obstacles and future directions.