• Journal of Navigation and Port Research
• /
• v.31 no.10
• /
• pp.865-868
• /
• 2007

Recently, wireless LANs are often applied in home or office because of its various of convenience. Frequency range of wireless LANs specified by IEEE 802.11b is at 2.4 GHz. The bluetooth, the microwave oven, and the PDA(Personal Digital Assistants) uses, however, the same frequency band. So problems will be produced in these environments, such as multi-pass interference and system-to-system interference. These problems can be eliminated by using EM wave absorber. In this paper, we designed and fabricated EM wave absorber using MnZn-Ferrite, Sendust, and CPE( Chlorinated Polyethylene). The EM wave absorber with the ratio of material (MnZn-Ferrite : Sendust : CPE = 64 : 16 : 20 wt.%) has thickness of 3.7 mm and absorption ability more than 17 dB at 2.4 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.3
• /
• pp.482-488
• /
• 2009

Mobile Ad-hoc Networks provide communication without a centralized infrastructure, which makes them suitable for communication in disaster areas or when quick deployment is needed. On the other hand, they are susceptible to malicious exploitation and have to face different challenges at different layers due to its open Ad-hoc network structure which lacks previous security measures. Denial of service (DoS) attack is one that interferes with the radio transmission channel causing a jamming attack. In this kind of attack, an attacker emits a signal that interrupts the energy of the packets causing many errors in the packet currently being transmitted. In harsh environments where there is constant traffic, a jamming attack causes serious problems; therefore measures to prevent these types of attacks are required. The objective of this paper is to carry out the simulation of the jamming attack on the nodes and determine the DoS attacks in OPNET so as to obtain better results. We have used effective anomaly detection system to detect the malicious behaviour of the jammer node and analyzed the results that deny channel access by jamming in the mobile Ad-hoc networks.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.16 no.6
• /
• pp.1175-1182
• /
• 2021

The receiver of each radio telescope of KVN, has a sampler that converts astronomical radio signal to digital data. The ability of this sampler (the bandwidth, sampling frequency, and sampling bits) is improved by sqrt(n), if the bandwidth is increased by n times, and the number of observable objects increases exponentially in the case of continum spectrum radio sources. As the bandwidth increases, there are the more spectrum lines that can be simultaneously monitored in the radio source. This will greatly expand the research area in astronomical radio observation. For this reason, we are trying to independently develop the technology of the fast digital sampler. Therefore, based on the research experience and technology accumulated so far, An ability of sampling up to 3.5 GHz, that can vary the sampling frequency and can observe in a wider band, was designed and made for proto-type. In this study, we introduce the development details and test results for new sampling system.

• KNOM Review
• /
• v.23 no.1
• /
• pp.26-33
• /
• 2020

Bitcoin is an electronic money that does not rely on centralized institutions such as banks and financial institutions, unlike the world's paper currencies such as dollar, won, euro and yen. In Bitcoin network, a block with transaction details is generated by mining, and the message that the block has been created is broadcast to all participating nodes in a broadcasting method to secure reliability through verification. Likewise, the mining and block propagation methods in the Bitcoin network are greatly affected by the performance of the P2P network. For example, in the case of mining, the node receiving the reward for mining varies depending on whether the block is first mined in the network and the proof of mining is propagated faster. In this paper, we applied local characteristics and Round-to-Trip(RTT) measurement to solve the problems of the existing neighbor connection method and block propagation method performed in Bitcoin network. An algorithm to improve block propagation speed is presented. Through experiments, we compare the performance of the improved algorithm with the existing algorithm to verify that the overall block propagation time is reduced.

• Journal of the International Relations & Interdisciplinary Education
• /
• v.3 no.1
• /
• pp.87-103
• /
• 2023

In the era of self-media, short videos are developing strongly. In addition to its rapid development, it has brought new development opportunities for the dissemination of Chinese traditional culture through innovative cultural expressions. In this environment, the video blogger Li ziqi has rapidly become popular among many other types of self-media, which provides good material for us to analyze the reshaping and dissemination of Chinese traditional culture in the age of self-media. This paper discusses the reshaping and dissemination of Chinese traditional culture in the age of self-media by combining the case of the famous short video blogger "Li ziqi", reveals the problems of the current traditional culture dissemination through the content analysis of the reshaping and dissemination of traditional culture in the age of self-media, and puts forward the optimization strategies.

• Korea Trade Review
• /
• v.42 no.4
• /
• pp.49-68
• /
• 2017

This paper investigates the spillover effect of the U.S. Interest on Korea's interest rate as well as the role of exchange rate in the spillover effects, by utilizing a open macro model on the determinants of long-term interest rates. According to the cointegration estimation and the Impulse response function, it is found that, across both long-term and short-term, there exist the spillover effect of the U.S. Interest on Korea's interest rate. The fiscal deficit and expected exchange rate have significantly positive relationship with the Koreas's long-term interest rate. Further, foreign exchange market intervention in Korea did not have significant effect on the spillover effect. Thus, this study suggests that exchange rate flexibility would not be enough to restrain the spillover effects of the U.S. interest rate.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5A
• /
• pp.917-925
• /
• 2006

Experimental tests were performed to estimate velocities of the acoustic signals through prestressed concrete beam and source locations using acoustic emission (AE) techniques. Seven AE sensors are mounted on the surface of 5m length test beam with equal spacing and using Schmidt Hammer AE events are made at 18 locations. The velocities of AE signals are estimated using the time differences of arrival times and the distances between the source locations and the AE sensor locations. In addition, using the Least Square Method, the AE source locations are re-evaluated reversely using both of the arrival times and the velocities of AE signals. Test results show the average velocity of the AE signals is about 4,000 m/sec and the velocity decreased with the increase of the distance from source locations to AE sensors due to the effect of attenuation. Based on the estimation of the source locations, it is observed that the errors of source locations are decreased when the velocities of each AE sensor are used rather than the average velocity.

• The Magazine of the IEIE
• /
• v.19 no.9
• /
• pp.71-86
• /
• 1992

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.10 no.1
• /
• pp.69-76
• /
• 1999

• 정보통신주요정책설명회
• /
• s.2007
• /
• pp.102-123
• /
• 2007