• Journal of Information Processing Systems
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• v.4 no.2
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• pp.77-86
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• 2008

This research proposes a new neural network for text categorization which uses alternative representations of documents to numerical vectors. Since the proposed neural network is intended originally only for text categorization, it is called NTC (Neural Text Categorizer) in this research. Numerical vectors representing documents for tasks of text mining have inherently two main problems: huge dimensionality and sparse distribution. Although many various feature selection methods are developed to address the first problem, the reduced dimension remains still large. If the dimension is reduced excessively by a feature selection method, robustness of text categorization is degraded. Even if SVM (Support Vector Machine) is tolerable to huge dimensionality, it is not so to the second problem. The goal of this research is to address the two problems at same time by proposing a new representation of documents and a new neural network using the representation for its input vector.

• Journal of Korean Institute of Industrial Engineers
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• v.31 no.1
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• pp.10-19
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• 2005

The minimum spanning tree (MST) problem is one of the traditional optimization problems. Unlike the MST, the degree constrained minimum spanning tree (DCMST) of a graph cannot, in general, be found using a polynomial time algorithm. So, finding the DCMST of a graph is a well-known NP-hard problem of importance in communications network design, road network design and other network-related problems. So, it seems to be natural to use evolutionary algorithms for solving DCMST. Especially, when applying an evolutionary algorithm to spanning tree problems, a representation and search operators should be considered simultaneously. This paper introduces a new tree representation scheme and a genetic operator for solving combinatorial tree problem using evolutionary algorithms. We performed empirical comparisons with other tree representations on several test instances and could confirm that the proposed method is superior to other tree representations. Even it is superior to edge set representation which is known as the best algorithm.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.27-32
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• 2010

In this paper, we research a virtual card generation system to secure e-commerce. Network security has increased the need to meet rapidly growing trend. And the amount and quality of e-commerce expansion due to the need for secure commerce transactions has increased even more. Instead of exposing the actual credit card number, we expose a virtual card number on the network. It can prevent the risk of hacking. We proved that through various experiments.

• 한국전산유체공학회:학술대회논문집
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• 2001.05a
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• pp.149-154
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• 2001

Parallel performance of a Myrinet based PC-cluster was tested and compared with a conventional Fast-Ethernet system. A preconditioned Navier-Stokes code was parallelized with domain decomposition technique, and used for the parallel performance test. Speed-up ratio was examined as a major performance parameter depending on the number of processor and the network topology. As was expected, Myrinet system shows a superior parallel performance to the Fast-Ethernet system even with a single network adpater for a dual processor SMP machine. A test for the dependency on problem size also shows that network communication speed is a crucial factor for parallelized computational fluid dynamics analysis and the Myrinet system is a plausible candidate for high performance parallel computing system.

• Journal of the Korean Operations Research and Management Science Society
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• v.35 no.3
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• pp.45-58
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• 2010

Due to rapid developments of IT technologies, convergence services like IPTV (Internet protocol television) are shown up. Even though expert and customer had great expectations for this innovative service, commercialization was delayed for years by the legal dispute between industry players. One of the biggest problems was that whether internet backbone providers have to share their internet network backbone with IPTV service providers (which don't have network backbone) or not. As other countries, Korean government set the rules that ISP have to offer indiscriminate access to other IPTV service provider. At the same time, internet backbone providers can charge access charge based on cost by way of compensation. Thus access charge is very critical to the IPTV industry players. The objective of this paper is to provide model that can calculate the reasonable access charge by system dynamics, based upon real data in Korean telecommunication industry.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.12 no.2
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• pp.119-131
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• 2008

The paper considers the computation method in the performance evaluation of cellular network in the phase-type distribution assumptions that the channel holding times induced from mobility are modeled by well-fitted distributions to reflect an actual situation. When ww consider a phase-type distribution model instead of exponential distribution, the complexity of the computation increase exponential even though the accuracy is improved. We consider an efficient numerical algorithm to compute the performance evaluations in cellular networks such as a handoff call dropping probability, new call blocking probability, and handoff arrival rate. Numerical experiment shows that numerical analysis results are well approximated to the results of simulation.

• Korean Management Science Review
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• v.19 no.2
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• pp.169-178
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• 2002

The growth of Internet usage even accelerated by the spread of high-speed Internet access network such as ADSI is affecting our socioeconomic activities and culture in a great way. Korea is recently reported to be the number one high-speed Internet network subscription per 100 people in the world. In a way to reflect this situation, we collect a moderate size of sample proportional to the population of each region across country and investigate what factors might explain the level of user's dissatisfaction with respect to Internet service they have been receiving. The results indicate that the set of gender, age, Internet usage, service kinds, incoming e-mails, and e-shopping is significantly influencing user's dissatisfaction, in that dissatisfaction is measured in 11 perspectives. In particular, user's age, gender, and e-shopping experiences are considered to be mostly explainable.

• Journal of information and communication convergence engineering
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• v.10 no.4
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• pp.359-364
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• 2012

Harvesting energy from the environment is essential for many applications to slow down the deterioration of energy of the devices in sensor networks and in general, the network itself. Energy from the environment is an inexhaustible supply which, if properly managed and harvested from the sources, can allow the system to last for a longer period - more than the expected lifetime at the time of deployment, or even last indefinitely. The goal of this study is to develop a simple algorithm for ns-2 to simulate energy harvesting in wireless sensor network simulations. The algorithm is implemented in the energy module of the simulator. Energy harvesting algorithms have not yet been developed for ns-2. This study will greatly contribute to the existing knowledge of simulating wireless sensor networks with energy harvesting capabilities in ns-2. This paper will also serve as a basis for future research papers that make use of energy harvesting.

• Journal of Information Display
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• v.5 no.3
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• pp.35-40
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• 2004

In this study, we collected data used to formulate the relationship between quantitative metrological parameters in CRT display and the perceived focus quality. Human perception of the focusing quality was evaluated in terms of user feedback scores regarding the character legibility from four highly trained inspectors. Thirteen CRT monitors from five different manufacturers were compared relatively with respect to the norm monitor. The profile of electron beam such as spot size and the shape of distribution made by electron beam, contrast, convergence of RGB beams, and luminance characteristics were measured using a precision measurement system. Linear regression analysis and artificial neural network models were used to formulate the relationship between human perception and the quantitative measurements. The accuracy of the formulated linear regression model ($R^2$=0.515) was not satisfactory but the nonlinear neural network model ($R^2$=0.716) was fairly convincing and robust even the utilized data included subjective differences.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.461-471
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• 2004

The primary objective of this paper is to investigate the corridor of Eurasia High-Speed Railway Network from the governmental view of the Republic of Korea, whose High-Speed Train has been recently operated. The country is also expected to figure out the changes of Eurasia infrastructure system under the assumption that Trans-Korean Railway is connected to the Continent. As a result of research, the corridor connecting the TKR to TSR seems to be more attractive to the Republic of Korea than that of the TKR-TCR under the current economic and operational environments. However, even in a case, the railway linkage through the TSR between Europe and Asia should remain a supplementary means of the sea transportation route. Lastly, TSR may need a program of structural reforms, in order to continuously provide preferable services like the Pan-European Transport Network (PETN) which is currently initiated by the European Union, such as to improve outdated infrastructure (railway, bridges, signal systems, etc.), to simplify and to standardize the process of custom clearance and internal tariffs, and ultimately to construct a uniform management system for the corridor linking the TKR to TSR.