• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.9
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• pp.2101-2119
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• 2013

The spectrum allocation is an attractive issue for mobile cognitive radio (CR) network. However, the time-varying characteristic of the spectrum allocation is not fully investigated. Thus, this paper originally deduces the probabilities of spectrum availability and interference constrain in theory under the mobile environment. Then, we propose a prediction mechanism of the time-varying available spectrum lists and the dynamic interference topologies. By considering the node mobility and primary users' (PUs') activity, the mechanism is capable of overcoming the static shortcomings of traditional model. Based on the mechanism, two prediction-based spectrum allocation algorithms, prediction greedy algorithm (PGA) and prediction fairness algorithm (PFA), are presented to enhance the spectrum utilization and improve the fairness. Moreover, new utility functions are redefined to measure the effectiveness of different schemes in the mobile CR network. Simulation results show that PGA gets more average effective spectrums than the traditional schemes, when the mean idle time of PUs is high. And PFA could achieve good system fairness performance, especially when the speeds of cognitive nodes are high.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.217-226
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• 2014

In this research, we study the problem of opportunistic spectrum access (OSA) in a time-varying environment with fading channels, where the channel state is characterized by both channel quality and the occupancy of primary users (PUs). First, a finite-state Markov channel model is introduced to represent a fading channel. Second, by probing channel quality and exploring the activities of PUs jointly, a two-dimensional partially observable Markov decision process framework is proposed for OSA. In addition, a greedy strategy is designed, where a secondary user selects a channel that has the best-expected data transmission rate to maximize the instantaneous reward in the current slot. Compared with the optimal strategy that considers future reward, the greedy strategy brings low complexity and relatively ideal performance. Meanwhile, the spectrum sensing error that causes the collision between a PU and a secondary user (SU) is also discussed. Furthermore, we analyze the multiuser situation in which the proposed single-user strategy is adopted by every SU compared with the previous one. By observing the simulation results, the proposed strategy attains a larger throughput than the previous works under various parameter configurations.

• Journal of the Semiconductor & Display Technology
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• v.11 no.4
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• pp.49-55
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• 2012

This paper proposes an efficient method of object identification and localization for image recognition. The new proposed algorithm utilizes correlogram back-projection in the YCbCr chromaticity components to handle the problem of sub-region querying. Utilizing similar spatial color information enables users to detect and locate primary location and candidate regions accurately, without the need for additional information about the number of objects. Comparing this proposed algorithm to existing methods, experimental results show that improvement of 21% was observed. These results reveal that color correlogram is markedly more effective than color histogram for this task. Main contribution of this paper is that a different way of treating color spaces and a histogram measure, which involves information on spatial color, are applied in object localization. This approach opens up new opportunities for object detection for the use in the area of interactive image and 2-D based augmented reality.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.4
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• pp.81-87
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• 2015

Recently, with the development of the ICT environment, the use of the software is growing rapidly. And the number of the web server software used with a variety of users is also growing. However, There are also various damage cases increased due to a software security vulnerability as software usage is increasing. Especially web shell hacking which abuses software vulnerabilities accounts for a very high percentage. These web server environment damage can induce primary damage such like homepage modification for malware spreading and secondary damage such like privacy. Source code weaknesses checking system is needed during software development stage and operation stage in real-time to prevent software vulnerabilities. Also the system which can detect and determine web shell from checked code in real time is needed. Therefore, in this paper, we propose the system improving security for web server by detecting web shell attacks which are invisible to existing detection method such as Firewall, IDS/IPS, Web Firewall, Anti-Virus, etc. while satisfying existing secure coding guidelines from development stage to operation stage.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2002.06a
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• pp.21-31
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• 2002

The quality of education cannot be defined easily. Similarly, the quality problem of remote-education is defined, and suggests various success factors, from each different angle, according to definer's view and interest. As the Internet is being expanded gradually, the remote-education systems are being focused on as an important strategic factor. Also, many studies are being conducted concerning the remote-education system in this county. However, most studies focus on the technological side, and the actual condition is that the quality and the quantity of the studies on success factors for successful remote-education system are insufficient yet. This study tried to examine major success factors in order to realize more efficient web-based remote education system, and to maximize users'acquirement obtained from the remote education system.

• Land and Housing Review
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• v.9 no.3
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• pp.9-18
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• 2018

Administrative city has been developed step by step aiming to being a public transport-oriented new city. In spite of its primary goal, administrative city is dominated by car-oriented tansportaion system because the supply of public transportation has not been adequately and timely performed. In this study, we investigate the current situation related to (public) transportation use in administrative city. Also, we examine the issues of traffic system through a survey on residents' consciousness about public transportation use. Additionally, the analysis of demand elasticity according to the change of the conditions of using public transportation and passenger car is conducted for passenger car users. As a result, it is analyzed that as the neighborhood is more stabilized after the completion of development the resistance to the abandonment of passenger car is higher when the tide demand control method is introduced. Therefore, it is concluded that pre-emptive public transportation supply and the management of car demand management are necessary for the activation of public transportation in Administrative city.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.10
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• pp.687-696
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• 2020

Accounting policies are principles and practices by which an entity uses to recognize, measure and report economic transactions. Improper application of accounting policies can lead to misrepresentation of firms' financial position and performance which consequently results in incorrect accounting information to the users. This paper aims to investigate the factors influencing the choices of accounting policies in small and medium enterprises (SMEs) in Vietnam by reviewing relevant literature to build a research model. The research model comprises of one dependent variable that is income-decreasing accounting procedures and six independent variables namely the firm size, financial leverage, incentives, auditor, accountants, and tax policies. After this, the authors collected primary data from more than 200 questionnaires sent to directors and chief accountants of the SMEs for the period 2018 to 2019. We then used Ordinary Least Squares regression method (OLS) to analyze the data. The results showed that four factors influenced selection of accounting policies in which auditors are associated with income-increasing accounting policies; and there are three factors associated with income-decreasing accounting policies which are, company size, tax and accountant. Especially, the research results indicate that company size has a significant influence on the selection of accounting policies in the SMEs. Based on the results, we propose instructive suggestions for regulators and lawmakers improve choices of accounting policies in the SMEs.

• ETRI Journal
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• v.40 no.5
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• pp.613-623
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• 2018

The instability of operational channels on cognitive radio networks (CRNs), which is due to the stochastic behavior of primary users (PUs), has increased the complexity of the design of the optimal routing criterion (ORC) in CRNs. The exploitation of available opportunities in CRNs, such as the channel diversity, as well as alternative routes provided by the intermediate nodes belonging to routes (internal backup routes) in the route-cost (or weight) determination, complicate the ORC design. In this paper, to cover the channel diversity, the CRN is modeled as a multigraph in which the weight of each edge is determined according to the behavior of PU senders and the protection of PU receivers. Then, an ORC for CRNs, which is referred to as the stability probability of communication between the source node and the destination node (SPC_SD), is proposed. SPC_SD, which is based on the obtained model, internal backup routes, and probability theory, calculates the precise probability of communication stability between the source and destination. The performance evaluation is conducted using simulations, and the results show that the end-to-end performance improved significantly.

• Publications of The Korean Astronomical Society
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• v.26 no.1
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• pp.1-24
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• 2011

Korea Astronomy and Space Science Institute (KASI) has constructed online database of the Korean Astronomical Almanac as a part of the 'Knowledge and Information Business Project 2009' supported by the Ministry of Knowledge Economy. Throughout this project, KASI provides both digitized images and extracted text from the almanac covering approximately 240 years. The primary purpose of this paper is to serve as a reference for users of the almanac database. Hence, we introduce the calendar history and kinds of the astronomical almanac used in Korea, and explain the contents of the almanacs according to its appearance time. We also briefly mention the steps employed in constructing the database system and Web site. Since ancient times, astronomical almanacs have been an essential part of daily life. We, therefore, believe that the astronomical almanac database constructed by KASI will prove its usefulness in various fields, and particularly in the study of historical astronomy.

• ETRI Journal
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• v.37 no.3
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• pp.471-479
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• 2015

Traditional designs of cognitive radio (CR) focus on maximizing system throughput. In this paper, we study the joint overlay and underlay power allocation problem for orthogonal frequency-division multiple access-based CR. Instead of maximizing system throughput, we aim to maximize system energy efficiency (EE), measured by a "bit per Joule" metric, while maintaining the minimal rate requirement of a given CR system, under the total power constraint of a secondary user and interference constraints of primary users. The formulated energy-efficient power allocation (EEPA) problem is nonconvex; to make it solvable, we first transform the original problem into a convex optimization problem via fractional programming, and then the Lagrange dual decomposition method is used to solve the equivalent convex optimization problem. Finally, an optimal EEPA allocation scheme is proposed. Numerical results show that the proposed method can achieve better EE performance.