• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6B
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• pp.483-488
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• 2012

With the fast growing data traffic, the performance of the convergent overlay network environment under the cognitive networking environment is crucial for the implementation of the efficient network structure. In order to achieve high capacity and reliable link quality in wireless communication of the overlay convergent networks with the cognitive networking based on the advanced capability of the mobile terminal, a Distributed Wireless Communication System (DWCS) can provide the capability of ambient-aware dual cell system's operation. This paper has considered virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on DWCS network. One is the Active Virtual Cell which exists for user's actual data traffic and the other is the Candidate Virtual Cell which contains a set of candidate antennas to protect user's link quality from performance degradation or interruption. The considered system constructs DVC by using cognitive ability of finding useful virtual signals. Also, for multi-user high-rate data transmission, the DWCS system exploits Space-Time Trellis Codes. The effects of changing environments on the system performance has been investigated thereafter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8C
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• pp.767-774
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• 2007

A new transmit antenna selection and shuffling($AS^2$) method for spatially correlated double space time transmit diversity(DSTTD) systems is proposed. The proposed method allows dumb antennas and the superposition of multiple signals at the same transmit antenna, whereas the conventional methods consider the antenna shuffling(AS) only. According to the simulation result, the proposed method provides a 1.8 dB signal-to-noise ratio(SNR) gain over the conventional methods for spatially correlated transmit antennas. Although the number of candidates for $AS^2$ is much higher than that of AS, it is found that the number of candidates for $AS^2$ can be reduced to 36 by using the characteristics and properties of preprocessing matrices, and among them, only 6 candidates are almost always chosen. Next, we empirically compare the bit-error-rate (BER) performance of the proposed method with the conventional spatial multiplexing(SM) technique with antenna selection. Simulation results show that the proposed method outperforms the SM technique.

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.28-35
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• 2003

A numerical analysis of electrochemical reaction and dynamics of the fluid flow in the channels of a DMFC separator was carried out by using a commercial Computational Fluid Dynamics(CFD) code fluent(ver.6.0). From the simulation work, many valuable informations were obtained in terms of distributions of velocity, pressure, temperature, concentration and current density over the flow field. And it was possible to optimize the flow field structure by using the simulation results. The simulation work using the Cm code was found very helpful in analysing the phenomena occurring in the fuel cell and optimizing the structures of electrodes and flow field.

• Journal of the Korean Society for information Management
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• v.25 no.3
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• pp.143-158
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• 2008

This study was conducted under the premise of providing the model for the construction of the library and the digital library in PUST, the joint construction from South and North Korea. First, we determined the problems in the construction of digital libraries as well as possible issues that may rise from the construction of the digital library in PUST. The results of the research showed that there were imminent problems from the operation of a digital library with the inadequate progress in the Held of copyright. In addition, the difference in the language system and the knowledge foundations of the two countries will produce problems in the homepage access, database construction, and information retrieval. In order to overcome these predictable problems, this research proposes the following: (1) parallel operation of both digital and high-drive libraries; (2) duplexing the homepage through the application of unicode concerning the digital library; (3) development and application of converted letter codes through the establishment of NCHAR data type; and (4) construction of an authority database.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.110-116
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• 2003

With the growth of aircraft performance and needs for light aircraft, the problems associated with hail impacts on aircraft during flights and grounding become and important issue. These hail encounters can cause severe damages to aircraft and result in major concerns in safety and cost. Since nearly all external components of the commercial and military aircraft-in particular, the nose section and the leading edge of the wing and tail-are subject to damages, much effort has been put into understanding of this problem. However, most of the previous studies have focused on the composite components and few results have been reported for the metallic components. In this paper, we study the ice impacts on the aluminum component with the finite element analysis method utilizing commercial non-linear dynamics solver LS-DYNA. The results are compared with the experimental data and a simple measure of the ice impact effects is proposed.

• Communications of Mathematical Education
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• v.26 no.4
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• pp.351-362
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• 2012

Until the 1950s, linear algebra was considered only as one of abstract and advanced mathematics subject among in graduate mathematics courses, mainly dealing with module in algebra. Since the 1960s, it has been a main subject in undergraduate mathematics education because matrices has been used all over. In Korea, it was considered as a course only for mathematics major students until 1980s. However, now it is a subject for all undergraduate students including natural science, engineering, social science since 1990s. In this paper, we investigate the early history of linear algebra and its development from a historical perspective and mathematicians who made contributions. Secondly, we explain why linear algebra became so popular in college mathematics education in the late 20th century. Contributions of Chinese and H. Grassmann will be extensively examined with many newly discovered facts.

• Communications of Mathematical Education
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• v.34 no.2
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• pp.119-134
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• 2020

Korea, where the national curriculum is run, can change school education by specifying basic competence in the common curriculum of elementary and middle schools for students to pursue school learning and real life. The numeracy as a basic competence should not be limited to mathematics, so it needs to be specified in the national curriculum covering several subjects and guided through various subject curriculums. To this end, the study proposed concepts, components, and levels of numeracy and proposed ways to reflect them in the national curriculum and other subjects' curricula. To ensure its validity, the UK, Canada and Australia curriculum are analyzed, and the results of the survey are proposed for various education experts. This study proposed two ways to briefly state the numeracy in the national curriculum and to imply the contents related to the numeracy in each subject curriculum, and to present the concepts, components and levels of numeracy in the national curriculum in detail and to describe numeracy code in each subject curriculum. These suggestions obtained high consent from experts.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.4
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• pp.336-343
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• 2014

Modern advanced-turboprop propellers are required to have high structural strength to cope with the thrust requirement at high speed. The high stiffness and strength carbon/epoxy composite material is used for the major structure and skin-spar-foam sandwich structural type is adopted for advantage in terms of the blade weight. As a design procedure for the present study, the structural design load is estimated through investigation on aerodynamic load and then flanges of spars from major bending loads and the skin from shear loads are sized using the netting rule and Rule of Mixture. In order to investigate the structural safety and stability, stress analysis is performed by finite element analysis code MSC. NASTRAN. It is found that current methodology of composite structure design is a valid method through the static structural test of prototype blade.

• Journal of Information Management
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• v.42 no.3
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• pp.117-145
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• 2011

This research tries to develop standards of library goods and managerial guidance. It is developed to make buying and managing library goods efficient in promoting environmental and digital-friendly library, and to set a standard guidance of library goods. The research divides 117 library goods into 6 categories, and develops a table of recommended standard and managerial guidance of library goods. The table has 11 indicators of information, which includes the name of each library goods, classification code, identification number of 'Narajangteo', definitions of the goods, purpose and usage, type and size, structure, place to install, goods management, and note. The research hopes to be reflected in library related laws, standards, and manuals, and finally to standardize library goods in the national level.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.3
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• pp.35-46
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• 2016

Social network services (SNS) that help to build relationship network and share a particular interest or activity freely according to their interests by posting comments, photos, videos,${\ldots}$ on online communities such as blogs have adopted and developed widely as a social phenomenon. Several researches have been done to explore the pattern and valuable information in social networks data via text mining such as opinion mining and semantic analysis. For improving the efficiency of text mining, keyword-based approach have been applied but most of researchers argued the limitations of the rules of Korean orthography. This research aims to construct a database of non-standard Korean words which are difficulty in data mining such abbreviations, slangs, strange expressions, emoticons in order to improve the limitations in keyword-based text mining techniques. Based on the study of subjective opinions about specific topics on blogs, this research extracted non-standard words that were found useful in text mining process.