• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.2
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• pp.528-544
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• 2015

Base Station Cooperation (BSC) has been a promising technique for combating the Inter-Cell Interference (ICI) by exchanging information through a high-speed optical fiber back-haul to increase the diversity gain. In this paper, we propose a novel pilot symbol assisted data fusion scheme for distributed Uplink BSC (UBSC) based on Differential Evolution (DE) algorithm. Furthermore, the proposed scheme exploits the pre-defined pilot symbols as the sample of transmitted symbols to constitute a sub-optimal Weight Calculation (WC) model. To circumvent the non-linear programming problem of the proposed sub-optimal model, DE algorithm is employed for searching the proper fusion weights. Compared with the existing equal weights based soft combining scheme, the proposed scheme can adaptively adjust the fusion weights according to the accuracy of cooperative information, which remains the relatively low computational complexity and back-haul traffic. Performance analysis and simulation results show that, the proposed scheme can significantly improve the system performance with the pilot settings of the existing standards.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1257-1263
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• 1998

To realize a highly reliable satellite-base data distribution system efficiently, a hierarchical distributed control network which utilizers a sub control station(SCS) in addition to a hub and a user station(US) is proposed and evaluated. The results show that there exists an optimum number of sub control stations that minimizes the polling processing time as a parameter of the processing time ratio between US-SCS and SCS-CS links. From a viewpoint of the control network cost, it is shown that the cost can be less compared to the conventional one, when the communication cost between the US and SCS is slightly reduced.

• The Journal of Information Technology
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• v.12 no.2
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• pp.1-12
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• 2009

China first started its mobile phone services in 1987, and the number of users has exponentially increased so that it reached 700 millions in January 2009. Currently China's 2G(GSM) users is 650 millions. These 2G (GSM) services have an advantage of the capability to use the mobile phone with a SIM (Subscriber Identity Modul) card, one kind of smart cards, inserted into it. However, due to the security vulnerability of SIM cards being used within China's 2G (GSM) services, SIM cards cloning. Problems concerning mobile phone surveillance towards a designated person by illegal cloning ESN and IMSI have recently risen to be a massive social issue within Korea as well. These studies have experimented the possibility of SIM cards clone in various mobile communication corporations using 2G (GSM) in China, and hence discovered the security vulnerability such as the incoming outgoing, SMS service and additional services on mobile phones using clone SIM cards.

• Proceedings of the Korea Contents Association Conference
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• 2005.11a
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• pp.596-600
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• 2005

In High-speed Portable Internet system to improve performance of whole system, adaptive modulation and coding technology is used, this technology changes modulation and encoding techniques depending on wireless channel environment. Modulation technology that is used in High-speed Portable Internet system is BPSK, QPSK, 16QAMs and 64QAMs. If terminal is distant from base station transceiver system, BPSK or QPSK technology Is used and 16QAMs or 64QAM technology is used if is near in the base station transceiver system. In this paper, number of sub-channel in each modulation technology minimized total transmitting number of PDU is analyzed for efficient radio resources usage. For this, simulation is conducted and the results are presented at High-speed Portable Internet system environments.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.643-644
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• 2006

In this paper, WiBro system which is one of the mobile wireless metropolitan area network systems is presented. WiBro is an OFDMA system which has a sub-channelization process unlike conventional OFDM systems. The sub-channelization is the time consuming processing, so a time-efficient hardware architecture is needed. WiBro RAS(Radio Access Station) demodulator is designed with Verilog HDL, and the gate count is 81k using the $0.18{\mu}m$ processing.

• International Journal of Railway
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• v.2 no.1
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• pp.18-21
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• 2009

The basis of modem risk-based safety management is to focus on what might happen and ensure it is designed out of the system by robust hazard identification and risk analysis. However, in the real world things go wrong and it is essential to be prepared for the worst so that the response can minimise harm and loss of property and damage to the environment. Whilst some hazard mitigation measures are aimed at preventing incidents, others are venting escalation. The results of the tests concluded that the most effective means by the control room, both with and without, local station staff assistance using directive public address announcements and CCTV surveillance.

• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.62-67
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• 2022

Liquid hydrogen (LH₂) has a higher density than gaseous hydrogen, so it has high transport efficiency and can be stored at relatively low pressure. In order to use efficient bulk hydrogen in the industry, research for the LH₂ supply system is needed. In the high-pressure hydrogen station based on LH₂ currently being developed in Korea, a heat exchanger is used to heat up supercritical hydrogen at 700 bar and 60 K, which is pressurized by a cryogenic high-pressure pump, to gas hydrogen at 700 bar and 300 K. Accordingly, the heat exchanger used in the hydrogen station should consider the design of high-pressure tubes, miniaturization, and freezing prevention. A helical heat exchanger generates secondary flow due to the curvature characteristics of a curved tube and can be miniaturized compared to a straight one on the same heat transfer length. This paper evaluates the heat transfer performance through parametric study on the distance between coils, guide effect, and anti-icing design of helical heat exchanger. The helical heat exchanger has better heat transfer performance than the straight tube exchanger due to the influence of the secondary flow. When the distance between the coils is uniform, the heat transfer is enhanced. The guide between coils increases the heat transfer performance by increasing the heat transfer length of the shell side fluid. The freezing is observed around the inlet of distribution tube wall, and to solve this problem, an anti-icing structure and a modified operating condition are suggested.

• Economic and Environmental Geology
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• v.56 no.3
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• pp.277-291
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• 2023

To analyze the crustal velocity structures beneath 21 broadband seismic stations in Gangwon Province, South Korea, we first applied the H-κ stacking method to 139 teleseismic event data (Mw ≥ 5.8 and the epicentral distance of 30° - 90°) occurring between March 18, 2019 and December 31, 2022 to estimate the Moho depths and V_p/V_s ratios beneath each station. The Moho depths and V_p/V_s ratios from the H-κ stacking method range from 24.9 to 33.2 km depth and 1.695 - 1.760, respectively, and the estimated V_p/V_s ratios were applied to the joint inversion of receiver functions and surface wave dispersion to obtain 1-D crustal velocity models beneath each station. The resulting Moho depths range from 25.9 to 33.7 km depth, similar to the results from the H-κ stacking method. Moho depth results from the both methods are generally consistent with Airy's isostasy. The 1-D crustal velocity models confirm that the existence of 2 km thick low-velocity layers with P-wave velocities of 5 km/s or less at some stations in the Taebaeksan basin, and at the stations CHNB and GAPB in northern Gangwon Province, which are located above the Cenozoic sedimentary layer. The station SH2B, although not overlying a sedimentary layer, has a low P-wave velocity near the surface, which is probably due to various factors such as weathering of the bedrock. We also observe a velocity inversion with decreasing velocity with depth at all stations within 4 - 12 km depths, and mid-crustal discontinuities possibly due to density differences in the rocks at around 10 km depth below some stations.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.5
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• pp.341-347
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• 2009

Soil microbial community has been changed after the treatment of anaerobic fermentation using wheat bran or rice bran was applied to the soil. In the dilution plate technique, the number of anaerobic bacteria and fungi was higher in rice bran-treated soil than in non and wheat bran-treated soil, but of yeast was higher in wheat bran-treated soil than in non and rice bran-treated soil. Specially, the fungi were not detected in the wheat bran-treated soil. Identified by 16S rDNA sequencing, the number of aerobic bacteria was similar in all treatments, the dominant bacteria was the genus Bacillus. In the phospholipid fatty acid (PLFA) technique, both Gram-positive and Gram-negative bacteria change slightly in all treatments for 20 days of fermentation process but, after 20day, increased rapidly in wheat or rice bran-treated soil. In conclusion, the microbial communities structure was dramatically changed after the treatment of wheat or rice bran to soil.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1551-1559
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• 2007

Seoul Metro has been constructing the screen doors on the platforms to provide safe and comfort environments. The screen doors of each station are configured so that they can be operated in automatic mode in connection with ATC/ATO through the integrated control panel in the station control room and in manual mode through the control panel of the station control room and crew control panel. These systems have been implemented with different data communication protocols between systems, HMI configuration, and so on due to ordering processes, implementation time and diverse suppliers, and manufactured to be operated within single station. Seoul Metro has been planning to implement the integrated control system to secure seamless train operation and safety and to have a fast response system against emergency situations such as PSD failure and fire, by implementing the system that is able to collectively manage, monitor and control the operation status and equipment conditions of PSD on to the integrated control center. This paper has studied a scheme to reduce the budget for the future facility constructions by standardizing the data format for data communication with the integrated station control panel and using the open standard protocols, in order to secure consistency of operation, system expansion and maintenance with unified and standardized control items.