• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.1931-1938
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• 2012

A by-pass path in wireless sensor networks is the alternative path which be able to forward data when a routing path is being broken. One reason of depleting energy is occurred by the path. The method for solving prior to addressed the problem is proposed. However, this method may deplete radio resource. The best path has advantage that network lifetime of sensor nodes is prolonged; on the contrary, in order to maintain the best path it have to share their information between the entire nodes. In this paper, we propose the best path searching algorithm in the distributed three dimensional sensor networks. Through the neighboring informations sharing in the proposed method, the proposed algorithm can decide the best k-path as well as the extension of network lifetime.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.203-209
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• 2010

A compact ANSI/EIA 709.1 protocol analyzer system suited for maintenance of LonWorks network for safety management of underground facilities was developed and tested. The hardware is based on the TMS320LF2406A embedded system, and the software was designed using Visual C++6.0 under Windows XP environment. Connected to the LonWorks network the developed protocol analyzer decodes the raw packets and pass them to the master PC through USB port. Then on the PC the packets are processed and analyzed in various aspects and the key features that are essential to the maintenance of LonWorks network installed at underground facilities are displayed in a user-friendly format. Performance of the developed protocol analyzer was evaluated through a series of experiments, by measuring the speed of packet analysis and the error rate. The protocol analyzer proved to work reliably even under the increased bandwidth. However, more comprehensive tests under various underground environmental conditions are desired.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.120-127
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• 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 Communications and Networks
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• v.10 no.4
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• pp.455-464
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• 2008

To provide network services consistently under various network failures, enterprise networks increasingly utilize path diversity through multi-homing. As a result, multi-homed non-transit autonomous systems become to surpass single-homed networks in number. In this paper, we address an inevitable problem that occurs when networks with multiple entry points deploy firewalls in their borders. The majority of today's firewalls use stateful inspection that exploits connection state for fine-grained control. However, stateful inspection has a topological restriction such that outgoing and incoming traffic of a connection should pass through a single firewall to execute desired packet filtering operation. Multi-homed networking environments suffer from this restriction and BGP policies provide only coarse control over communication paths. Due to these features and the characteristics of datagram routing, there exists a real possibility of asymmetric routing. This mismatch between the exit and entry firewalls for a connection causes connection establishment failures. In this paper, we formulate this phenomenon into a state-sharing problem among multiple fire walls under asymmetric routing condition. To solve this problem, we propose a stateful inspection protocol that requires very low processing and messaging overhead. Our protocol consists of the following two phases: 1) Generation of a TCP SYN cookie marked with the firewall identification number upon a SYN packet arrival, and 2) state sharing triggered by a SYN/ACK packet arrival in the absence of the trail of its initial SYN packet. We demonstrate that our protocol is scalable, robust, and simple enough to be deployed for high speed networks. It also transparently works under any client-server configurations. Last but not least, we present experimental results through a prototype implementation.

• Journal of Korea Spatial Information System Society
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• v.11 no.1
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• pp.127-136
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• 2009

This paper proposes an on-line mining algorithm of moving trajectory patterns in RFID data streams considering changing characteristics over time and constraints of single-pass data scan. Since RFID, sensor, and mobile network technology have been rapidly developed, many researchers have been recently focused on the study of real-time data gathering from real-world and mining the useful patterns from them. Previous researches for sequential patterns or moving trajectory patterns based on stream data have an extremely time-consum ing problem because of multi-pass database scan and tree traversal, and they also did not consider the time-changing characteristics of stream data. The proposed method preserves the sequential strength of 2-lengths frequent patterns in binary relationship table using the time-evolving graph to exactly reflect changes of RFID data stream from time to time. In addition, in order to solve the problem of the repetitive data scans, the proposed algorithm infers candidate k-lengths moving trajectory patterns beforehand at a time point t, and then extracts the patterns after screening the candidate patterns by only one-pass at a time point t+1. Through the experiment, the proposed method shows the superior performance in respect of time and space complexity than the Apriori-like method according as the reduction ratio of candidate sets is about 7 percent.

• Progress in Medical Physics
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• v.15 no.1
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• pp.54-58
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• 2004

The aim of this study was to develop special birdcage resonators for small objects including the human wrist, hand and small animals, using 3T MRI/MRS. Before substantial development, different types of parameters were arranged, based on theoretical analysis, through lumped element transmission line theory. The primary analysis was peformed with a network analyzer (HP 4195A) and the final experimental analysis was carried out with 3T MRI (Medinus, Korea). The manufactured birdcage resonator is typically composed of 12-element structures to which a low-pass filter is fundamentally applied. The diameter and length of each element of the birdcage resonator were as follows: (1) diameter 12 cm, length of element 22 cm, (2) diameter 15 cm, length of element 22 cm, and (2) diameter 17 cm, length of element 25 cm. Copper tape with a width of 1 cm was used for the coils. MRI acquisition parameters were TR=500 ms, TE=17 ms, and Ave=2 for T1-WT images, and TR=4,000 ms, TE=96 ms, and Ave=2 for T2-WT images. The ratio of the samples diameter to the birdcage resonators diameter was approximately 55%, 63% and 70%, respectively, for the three elements. This study determined that the best image quality and S/N ratio were obtained when the ratio of the object's diameter was approximately 50∼80%. A general theoretical analysis of the birdcage coil differs in many respects from the experimental results which were influenced by many factors that were not considering when the general theoretical analysis of the birdcage coil was peformed. The induced resistance may be considered as part of the resistive loss if the quantitative value can be determined using a radiation resistance approach.

• Journal of the Korean Data and Information Science Society
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• v.26 no.3
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• pp.619-630
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• 2015

The purpose of this study is to provide basic information to develop a game strategy plan of a team in a future by identifying the patterns of attack and pass of national men's professional volleyball teams and extracting core key words related with volleyball game performance to evaluate game performance using 'social network analysis' and 'text mining'. As for the analysis result of 'social network analysis' with the whole data, group '0' (6 players) and group '1' (11 players) were partitioned. A point of view the degree centrality and betweenness centrality in 'social network analysis' results, we can know that the group '1' more active game performance than the group '0'. The significant result for two group (win and loss) obtained by 'text mining' according to two groups ('0' and '1') obtained by 'social network analysis' showed significant difference (p-value: 0.001). As for clustering of each network, group '0' had the tendency to score points through set player D and E. In group '1', the player K had the tendency to fail if he attack through 'dig'; players C and D have a good performance through 'set' play.

• Journal of Korean Society of Transportation
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• v.33 no.1
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• pp.50-60
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• 2015

Pedestrians not only walk along roads, but also pass through buildings or across open spaces. This study defines these unusual walk routes as social path. Social path is an informal pedestrian route that is not considered in a pedestrian network, even though it should be regarded as pedestrian route considering the fact that many people actually use this path. In response, current study related to travel behavior cannot evaluate properly due to lack of consideration for realistic travel behavior such as social path. In order to deal with this situation, this study analyzes the effect of social path at two complex centers in Seoul. Evaluation indices are service area analysis and urban network analysis which is one of the spatial network analysis. In particular, we subdivide the network into three steps by the level of network building and analyze each step. As a result, it is revealed that step three which includes social path shows the greatest improvement in pedestrian accessibility. In this regard, we confirm that social path should be considered when evaluating pedestrian accessibility in further studies. Furthermore, a lot of undervalued facilities will be re-appraised in the field of travel behavior.

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

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