• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.1477-1479
• /
• 2004

Increasing numbers of photovoltaic arrays are being connected to the power utility through the power conditioning systems (PCS). This has raised potential problems of network protection. If, due to the action of the PCS, the local network voltage and frequency remain within regulatory limits when the utility is disconnected, then islanding is said to occur. In this paper, the representative methods to prevent the islanding are described and a PSIM-based model and analysis of the reactive power variation (RPV) method are presented. A novel phase detector using the all-pass filter and digital phase locked loop (DPLL) is proposed especially for the single-phase PCS. Finally, this paper provides the simulation and experimental results with a single-phase 3kW prototype PCS. Islanding test method of IEEE Std. 929-2000 was performed for verification.

• Journal of Digital Convergence
• /
• v.17 no.9
• /
• pp.471-477
• /
• 2019

The purpose of this study is to analyse the attacking pattern of the key player through plenty of passes on field hockey between the winning games and losing ones through the preliminary game and the tournament. It has shown that the Korean women national team on field hockey is analysed all the passes through the sportscode for the 6 games of the World-League Final, and is investigated the centrality through the social network analysis using the R analytic software. The result is followed : First, It has shown three tendencies on the preliminary games that it has shown a lower Degree-Centrality, a same with Closeness, and a higher Betweenness than the tournament. Second, It has also described on winning games that it has explained a lower Degree-Centrality, a same with Closeness, and a higher Betweenness than losing games. On the conclusion, it has revealed that Korean women national team on field hockey showed a tendency that prefer to use a counter-attacking. Based on these study, expect to be used as a way to analyze performance in the field.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.1
• /
• pp.81-86
• /
• 2009

Almost all network systems provide an authentication mechanism based on user ID and password. In such system, it is easy to obtain the user password using a sniffer program with illegal eavesdropping. The one-time password and challenge-response method are useful authentication schemes that protect the user passwords against eavesdropping. In client/server environments, the one-time password scheme using time is especially useful because it solves the synchronization problem. In this paper, we propose a new identification scheme One Pass Identification. The security of Password base System is based on the square root problem, and Password base System is secure against the well known attacks including pre-play attack, off-line dictionary attack and server comprise. A number of pass of Password base System is one, and Password base System processes the password and does not need the key. We think that Password base System is excellent for the consuming time to verify the prover.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.12
• /
• pp.120-127
• /
• 2008

HMIPv6 draws lots of attentions in recent years for providing an efficient handover and reducing the signaling overhead. HMIPv6 employs MAP(Mobility Anchor Point) in order to minimize a signaling overhead and a local mobility management. MAP completes an efficient mobility management in HMIPv6 network environment with frequent handover. However, HMIPv6 causes load concentration at a paricular MAP and may have unnecessary latency between HN(Mobile Node) and CN(Correspondent Node) within the same network. A MAP may also disturb the route optimization in HMIPv6 network because all packets must be transmitted through a MAP. In this paper, we propose a scheme to optimize the route in HMIPv6 networks according to MAP load. We configure a threshold in order to support the better service into MAP domain. The packets do not pass through MAP and are directly transmitted to AR(Access Router) if the number of current MNs attached to the MAP exceed the desired threshold. We simulate the performance of the proposed scheme and compare with HMIPv6. Resultly, the proposed scheme reduces signaling costs and mitigates concentration of a paticular MAP as well.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.26 no.4
• /
• pp.133-141
• /
• 2001

Rapid development in computer and network technology these days has created in environment in which decisions for manufacturing companies can be made in a much broader perspective. Especially, better decisions on production and distribution planning(PDP) problems can be made laking advantage of real time information from all the parties concerned. However, since the PDP problem-a core part of the supply chain management- is known to be the so-called NP-hard problem, so heuristic methods are dominantly used to find out solutions in a reasonable time. As one of those heuristic techniques, many previous studios considered genetic a1gorithms. A standard genetic a1gorithm applies rules of reproduction, gene crossover, and mutation to the pseudo-organisms so the organisms can pass along beneficial and survival-enhancing trails to a new generation. When it comes to representing a chromosome on the problem, it is hard to guarantee an evolution of solutions through classic a1gorithm operations alone, for there exists a strong epitasis among genes. To resolve this problem, we propose a hybrid genetic a1gorithm based on Silver-Meal heuristic. Using IMS-TB(Intelligent Manufacturing System Test-bed) problem sets. the good performance of the proposed a1gorithm is demonstrated.

• ETRI Journal
• /
• v.29 no.4
• /
• pp.421-429
• /
• 2007

This paper presents a direct-conversion CMOS transceiver for fully digital DS-UWB systems. The transceiver includes all of the radio building blocks, such as a T/R switch, a low noise amplifier, an I/Q demodulator, a low pass filter, a variable gain amplifier as a receiver, the same receiver blocks as a transmitter including a phase-locked loop (PLL), and a voltage controlled oscillator (VCO). A single-ended-to-differential converter is implemented in the down-conversion mixer and a differential-to-single-ended converter is implemented in the driver amplifier stage. The chip is fabricated on a 9.0 $mm^2$ die using standard 0.18 ${\mu}m$ CMOS technology and a 64-pin MicroLead Frame package. Experimental results show the total current consumption is 143 mA including the PLL and VCO. The chip has a 3.5 dB receiver gain flatness at the 660 MHz bandwidth. These results indicate that the architecture and circuits are adaptable to the implementation of a wideband, low-power, and high-speed wireless personal area network.

• Journal of Korea Multimedia Society
• /
• v.17 no.11
• /
• pp.1307-1312
• /
• 2014

Online games are virtual space where it connects individual users through network connection to offer enjoyment of play games and game developer who service online games have to develop new contents and provide them to users to extend life of their service. Typically, in order to update new contents, all service companies have maintenance schedule to stop the game service for a while to update both server and client applications. Usually this process takes quite amount of time and users do not have any other choice but disconnected from server and wait until it is over. The purpose of this thesis is to describe the advantages of new design system which will allows users to continue to play the game even during the update. The main focus of this design is to make users feel more convenience in online gaming experience by move client from previous server to new server while users are still playing. If they can to connect current client with new server without any certificate validation process while users information from the client can automatically pass through to the new server, users may not need to experience maintenance for new contents update.

• Journal of KIISE:Information Networking
• /
• v.30 no.5
• /
• pp.641-648
• /
• 2003

In this paper, we propose a general analysis tool that derives guaranteed delay bounds for real-time sessions when those sessions pass through heterogeneous schedulers in general packet networks. This tool characterizes each different scheduler by a homogeneous service curve server. We show that service curve servers can characterize a strictly larger class of schedulers than LR servers. That is, we can characterize not only all LR servers but also RC-EDF and SC scheduler by service curve servers. Even with such advantage over LR servers, service curve servers provide accurate analysis results. We prove mathematically that if we analyze a network that can be analyzed by both LR servers and service curve servers,,both cases yield the same delay bound.

• KIISE Transactions on Computing Practices
• /
• v.22 no.7
• /
• pp.315-319
• /
• 2016

Recurrent neural network based language models (RNN LM) have shown improved results in language model researches. The RNN LMs are limited to post processing sessions, such as the N-best rescoring step of the wFST based speech recognition. However, it has considerable vocabulary problems that require large computing powers for the LM training. In this paper, we try to find the 1st pass N-gram model using word embedding, which is the simplified deep neural network. The class based language model (LM) can be a way to approach to this issue. We have built class based vocabulary through word embedding, by combining the class LM with word N-gram LM to evaluate the performance of LMs. In addition, we propose that part-of-speech (POS) tagging based LM shows an improvement of perplexity in all types of the LM tests.

• Journal of the Korean Data and Information Science Society
• /
• v.22 no.6
• /
• pp.1053-1063
• /
• 2011

Social network analysis is the social statistical analysis of any social structure involving a stream of mutual information between observations. In this study we used the results of passes between players in a soccer game. The analysis contents are as follows. (1) Players with important or leading roles are identified. (2) Players are assessed by pass frequency and the success rate of passes. The purpose of this study is for use as basic data for future team strategy, and achieves this by evaluating the role of each individual player within a team. In this study, social network analysis without separating positions is conducted, and is also performed for defensive and attacking positions respectively. The results of this study are as follows: First, when complete team data were available, the players performing leadership roles were Jung-woo Kim, Sung-yeung Ki and Chung-young Lee, whereas Jeong-su Lee acted as a sub-leader. In case of data for defensive positions Jeong-su Lee was a leading player, and in terms of attacking positions, all of the players excelled in the game and could be evaluated as playing lead roles.