• Journal of information and communication convergence engineering
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• v.1 no.4
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• pp.194-198
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• 2003

Recently, the use of TCP/IP protocols over wireless LANs poses significant problems. In this paper, we have analyzed transmission control protocol (TCP) packet transmission time for mobile IP over wireless local area networks (LANs) using a proposed a new random backoff scheme. We call it as a proxy backoff scheme. It is considered the transmission time of TCP packet on the orthogonal frequency division multiplexing (OFDM) in additive white gaussian noise (AWGN) channel. From the results, a proposed proxy backoff scheme produces a better performance than an original random backoff in mobile IP over wireless LANs environment. Also, in OFDM/quadrature phase shift keying (QPSK) medium access control (MAC), we have obtained that the transmission time in wireless channel decreases as the TCP packet size increases.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.1-8
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• 2016

The characteristics of Korean power systems are large capacity of generation sites and concentrated load in Seoul metropolitan area. According to the national generation facility plan, more generation facilities are needed to be constructed as the electrical demands are forecasted to increase. Moreover, the size of generation sites are expected to increase, too. Therefore transient stability problems become worse and worse. Recently, the necessity of HVDC has been raised to overcome the difficulty of constructing HVAC transmission lines. This paper shows the analysis of transient stability when HVDC transmission system is added to the power system consisting of large generation sites.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.61-65
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• 2002

It becomes difficult and high in cost to construct new ducts and/or tunnels for power cables in metropolitan areas. This paper presents possible applications of an HTS superconducting power cables for transmitting electric power in metropolitan areas. Reflected were its important distinction such as compactness for installation in underground ducts and considerably high efficiency compared with present underground cables. In this paper, system modeling, transmission capacity and voltage class of compact HTS cables which should be applied to existing ducts were reviewed. Based on this, the following items on urban transmission system are examined. (1) A method of constructing a model system to introduce high temperature superconducting cables to metropolitan areas is presented. (2)The maximum outer diameter of HTS cables to be accommodated in exiting ducts is calculated based on the design standards for current cable ducts. (3)The voltage level that can be accommodated by existing ducts is examined.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.348-354
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• 2003

An analysis of the dynamic behavior between disk and roller has been performed when the torque is transmitted to toroidal IVT (Infinitely Variable Transmission). The contact area, shape and pressure with elliptical shapes between disk and roller are computed as the transmission ratios are changed. This study will give the information of contact shapes between roller-input dist and roller-output disk which are working under the most severe condition. The computed results are expected to guide the design criteria for the enhanced endurance li(e. Furthermore, the investigation of contact behaviors is very crucial to develop the traction oil that the efficiency of IVT system is most dependent on.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.7
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• pp.2862-2878
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• 2020

Data Security is the most challenging area in Internet communication, where most of the secret sharing schemes are proposed for binary images. But still it lacks in providing security for data communication, especially in image transmission. Traditional visual cryptography scheme generate meaningless diwies and the reconstruction phase leads to quality degradation over the secret image. In this work, an intelligent two dimensional secret share construction scheme is proposed. A secret image is expanded into n diwies with the choice of scheme selection. By Stacking all the qualified diwies to revert the secret image without content loss and less than s^* - 1 shares could not reveal any information about the secret image. The experimental results emphasize that the proposed secret share scheme is highly secured for image transmission.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.9
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• pp.2213-2231
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• 2013

Compressed sensing is a novel technology used in the field of wireless communication and sensor networks for channel estimation, signal detection, data gathering, network monitoring, and other applications. It plays a significant role in highly secure, real-time, well organized, and cost-effective data communication in smart-grid (SG) systems, which consist of multi-tier network standards that make it challenging to synchronize in power management communication. In this paper, we present a multi-layer communication model for SG systems and propose compressed-sensing based data transmission at every layer of the SG system to improve data transmission performance. Our approach is to utilize the compressed-sensing procedure at every layer in a controlled manner. Simulation results demonstrate that the proposed monitoring devices need less transmission power than conventional systems. Additionally, secure, reliable, and real-time data transmission is possible with the compressed-sensing technique.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.34-37
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• 2001

This paper evaluate reliability indices of a part of transmission network of KEPCO system. Quantitative evaluation of transmission system reliability is very important because successful operation of an electric power system in the deregulated electricity market depends on transmission system reliability management. Monte Carlo methods are often preferable, when complex operating conditions are involved and/or the number of sever events is relatively large. Monte Carlo simulation methods and CMELDC(CoMposite power system Effective Load Duration Curve) were used in this paper.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.613-615
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• 1995

KEPCO is now going on upgrading the highest system voltage from 345kV to 765kV since 1992. The main reason of this 765kV project is the bulk power transmission from the power generation sites at the East and West coasts to the Kyeong-in area. The first 765kV transmission lines will be constructed by 1998 and operated as 345kV level until 2001. This system needs a detailed evaluation of the 2nd arc in case of 765kV transmission line outages and the countermeasures for the fast arc reduction for the successful high speed reclosing. So, this paper deals with the simulation results of the 2nd arc characteristics using EMTP and comparison of Sh.R and HSGS for the reduction methods.

• Journal of Korean Port Research
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• v.14 no.2
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• pp.133-142
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• 2000

In order to streamline the procedure of data transmission in port and logistics industries, MOMAF introduced EDI systems as the method of data transmission of 19 documents 5 years ago. While operating EDI system, MOMAF has found the inconvenience and the inefficiency of using EDI systems in the field of requesting fast response. This thesis focuses on finding the possible fields of on-line processing system. The result of the paper presents that if data transmission area such as 'application for pilot'is changed to on-line processing method, the processing cost and time will be reduced compared with EDI processing method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.425-428
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• 2004

65% of the Korean peninsula is composed of mountainous area, 97% of which is composed of forest. Therefore, there is high possibility of mountain fire because a lot of potential inflammables such as fallen leaves are stacked on the ground. Moreover, most of the overhead transmission lines in Korea are operated on the mountain. However, there has been very little study for the effect of mountain fire on polymeric insulator for transmission line, though the study is significantly required Therefore, in this study the authors observed the deformation of the housing of the insulator under fire with respect to the ignition time, using artificial ignition testing equipment, and investigated electrical and mechanical characteristics of the insulator by dry withstand voltage test, impulse flashover test and tensile load test.