• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1336-1356
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• 2017

The spectrum scarcity crisis has resulted in a shortage of resources for many emerging wireless services, and research on dynamic spectrum management has been used to solve this problem. Game theory can allocate resources to users in an economic way through market competition. In this paper, we propose a bidding game-based spectrum allocation mechanism in cognitive radio network. In our framework, primary networks provide heterogeneous wireless service and different numbers of channels, while secondary users have diverse bandwidth demands for transmission. Considering the features of traffic and QoS demands, we design a weighted interference graph-based grouping algorithm to divide users into several groups and construct the non-interference user-set in the first step. In the second step, we propose the dynamic bidding game-based spectrum allocation strategy; we analyze both buyer's and seller's revenue and determine the best allocation strategy. We also prove that our mechanism can achieve balanced pricing schema in competition. Theoretical and simulation results show that our strategy provides a feasible solution to improve spectrum utilization, can maximize overall utility and guarantee users' individual rationality.

• 한국지능시스템학회논문지
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• 제14권4호
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• pp.487-492
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• 2004

본 논문은 Crisp Discrete Event System(CDES)에서 다룰 수 없는 특성을 가지는 의료진단이나 교통제어와 같이 애매하거나 불확실한 판단 그리고 관련성이 모호한 판단의 근거들에 의해 결정되어지는 사건들로 이루어진 Fuzzy Discrete Event System(FDES)의 모델링 방법과 그 응용에 대하여 연구하였다. 일반적인 CDES는 모델링 방법이 많이 연구되어져 왔으나, FDES는 발생되어지는 사건들의 정성적인 특성과 적용되어지는 경우가 드문 이유로 거의 연구되어져 있지 않다. 본 논문에서는 Fuzzy Timed Transition Petri Net(FTTPN)으로 FDES인 교통 시스템을 모델링하고 교통 신호제어기를 설계하였다.

• 한국인터넷방송통신학회논문지
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• 제10권2호
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• pp.151-157
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• 2010

MEMS(Micro Electro-Mechanical Systems) 분야의 급격한 발전은 저비용의 정보 처리 센싱 능력을 갖춘 센서의 발전에 박차를 가했다. 이러한 기술의 흐름은 강력하고 높은 확장성을 가지는 WSNs(Wireless Sensor Networks)을 위하여 더 많은 센서 간 연결을 위한 연구가 진행되고 있는 실정이다. WSNs의 자원부족, Ad-hoc 배치방법, 보다 광대해지는 규모는 센서 간 통신에서 안전성을 보다 중요한 문제로 인식하게 하고 있다. 센서 네트워크의 주요 고려사항은 에너지 효율이기 때문에, 보안 기술은 통신에서의 보안 특징과 그것을 수행하기 위해 계산해야하는 오버헤드 간 균형을 맞춰야한다. 본 논문에서는 새로운 보안 인식 다중경로 위치기반 라우팅 프로토콜을 개발하기 위하여 위치정보와 전송확률을 결합한다. 네트워크 시뮬레이터(ns-2)를 실행한 결과 보다 나은 성능을 얻을 수 있음을 알 수 있다.

• 아동학회지
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• 제22권4호
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• pp.299-313
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• 2001

This study examines the current state of English education in private kindergartens in Korea. Among 1700 kindergarten teachers surveyed for this research, 680 replied that their institutions provided English lessons for children. Analyses of the data collected from these 680 teachers showed : 1) They started to teach English not because of educational considerations but because of pressure from children's parents or kindergarten principals; 2) Most of the English teachers were part-time instructors specially recruited for English lessons. Generally, English lessons were given two or three times a week, with one session lasting for about 20 minutes. A variety of teaching methods and materials were used for the lessons given to children aged three to five. Focus of the lessons was given to listening and speaking words and sentences; 3) Most of the teachers considered the scarcity of qualified English instructors as the most serious problem for providing English education in kindergartens, and they did not want to teach English themselves. They evaluated positively the performance and role of Korean part-time English instructors. The evaluations were generally poor as to native speakers serving as kindergarten English teachers.

• 가정과삶의질연구
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• 제26권5호
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• pp.109-127
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• 2008

There are few studies on the characteristics of debtors in individual rehabilitation procedures, though research in this field is needed. The scarcity of research means that public policy and perception are being made with inadequate information and, to a certain extent, based on personal prejudices and misconceptions. The purpose of this study was to find out demographic, economic and psychological characteristics of debtors in individual rehabilitation procedures. For this study, an in-depth interview was used. The major findings were as follows : The focus of this study is debtors in individual rehabilitation procedures. They were all under 40 and received relatively high educations. Interestingly, they showed a high tendency to use debt and an inability to manage their money. They had short time horizons and imperfect self-control in consumption and borrowing decisions. Monthly income, expenditures, asset and debt of the debtors, and monthly payment to creditors were reported. There were a lot of reasons for their bankruptcy : business failure, job loss, the cost of raising children, and expenditures for entertainment causing them to file for individual rehabilitation procedures. One of the major conclusions of this study was the discovery that their psychological characteristics were nearly the same. The implications of the study suggest that financial education and counseling must consider psychological characteristics.

• Journal of Information Technology Applications and Management
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• 제23권2호
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• pp.177-194
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• 2016

This study analyzed President Park's speeches and the government's industry policy in the field of information security using cognitive map. The relationship analysis between policy tool variables and policy goal variables was employed to derive revitalization strategy of information security. This paper found that entrepreneurship revitalization has very strong causality with expansion of domestic market and global market. But, on the other hand, HR development has very weak causality with job creation and future growth driver because the labor market in the information security industry is poor and its transfer rate to other industry is very high. This study showed that this cognitive map could be characterized by a scarcity of feedback loops and a strong emphasis on the positive loops in the structure of virtuous circle. In this paper, we also constructed a comprehensive cognitive map on the policy vision of information security, showing that there are a risk of cyber threat, an opportunity of new fusion security market, information security reinforcing circle, global economic circle, and domestic market circle.

• IEIE Transactions on Smart Processing and Computing
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• 제5권2호
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• pp.100-106
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• 2016

Spectrum sensing is an integral part of cognitive radio, which seeks to address the perceived spectrum scarcity that is caused by inefficient utilization of the available spectrum. In this paper, a spectrum sensing system using energy detection for analog TV and FM broadcast transmitters as well as modified Integrated Services Digital Broadcasting Terrestrial (ISDB-T) signals is implemented on a software-defined radio platform using GNU' Not Unix (GNU) radio and the N200 Universal Software Radio Peripheral (USRP). Real-time implementation and experimental tests were conducted in Metro Cebu, a highly urbanized area in the southern part of the Philippines. Extensive tests and measurements were necessary to determine spectrum availability, particularly in the TV band. This is in support of the Philippine government' efforts to provide internet connectivity to rural areas. Experimental results have so far met IEEE 802.22 requirements for energy detection spectrum sensing. The designed system detected signals at -114 dBm within a sensing time of 100 ms. Furthermore, the required $P_d({\geq}90)$ and $P_{fa}({\leq}10)$ of the standard were also achieved with different thresholds for various signal sources representing primary users.

• IEIE Transactions on Smart Processing and Computing
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• 제6권4호
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• pp.299-304
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• 2017

A wireless passive sensor network is a network consisting of sink nodes, sensor nodes, and radio frequency (RF) sources, where an RF source transfers energy to sensor nodes by radiating RF waves, and a sensor node transmits data by consuming the received energy. Against theoretical expectations, a wireless passive sensor network suffers from many practical difficulties: scarcity of energy, non-simultaneity of energy reception and data transmission, and inefficiency in allocating time resources. Perceiving such difficulties, we propose a simple contending-type medium access control (MAC) scheme for many sensor nodes to deliver packets to a sink node. Then, we derive an approximate expression for the network-wide throughput attained by the proposed MAC scheme. Also, we present an approximate expression for the optimal partition, which maximizes the saturated network-wide throughput. Numerical examples confirm that each of the approximate expressions yields a highly precise value for network-wide throughput and finds an exactly optimal partition.

• 한국의상디자인학회지
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• 제14권2호
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• pp.49-62
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• 2012

The purpose of this study was to investigate the relationship between well-being lifestyles and herbal cosmetics benefits sought of female consumers. The data were collected from 301 women living in Seoul, Gyeonggi, Gwangju, Busan, and Gyeongnam province in June, 2011. Statistical methods including frequency, F-test, t-test, Duncan test, factor analysis, Cronbach's ${\alpha}$, correlation coefficient, and multiple regression were used for this study. The results of this study were as follows.: The well-being lifestyles were composed of five factors, 'health pursuit activity', 'eco-friendly product interest', 'eco-friendly dietary', 'eco-friendly clothing', and 'eco-friendly housing'. The herbal cosmetics benefits sought were composed of seven factors, 'special function pursuit', 'skin 'fitness pursuit', 'brand pursuit', 'nutritional reinforcement pursuit', 'economy pursuit', 'fragrance pursuit', and 'scarcity pursuit'. The well-being lifestyles and herbal cosmetics benefits sought according to female consumers's demographic characteristics showed a difference. Female consumers's well-being lifestyles showed that correlation with the herbal cosmetics benefits sought. Female consumers's well-being lifestyles had a influence on their herbal cosmetics benefits sought. The study results are highly expected to be used as valuable sources in marketing strategies for herbal cosmetic industries.

• Advances in concrete construction
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• 제5권2호
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• pp.145-154
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• 2017

In the present day scenario, concrete construction is rapidly becoming uneconomical and non sustainable practice, due to the scarcity of raw materials and environmental pollution caused by the manufacturing of cement. In this study an attempt has been made to propose recycled aggregates from demolition wastes as coarse aggregate in geopolymer concrete (GPC). Experimental investigations have been conducted to find optimum percentage of recycled aggregates (RA) in GPC by replacing 20%, 30%, 40%, 50% and 60% of coarse aggregates by RA to produce recycled aggregate geopolymer concrete (RGPC). From the study it has been found that the optimum replacement percentage of recycled aggregates was 40% based on mechanical properties and workability. In order to study and compare the flexural behaviour of RGPC and GPC four beams of size $175mm{\times}150mm{\times}1200mm$ were prepared and tested under two point loading. Test results were evaluated with respect to first crack load, ultimate load, load-deflection characteristics, ductility and energy absorption characteristics. Form the experimental study it can be concluded that the addition of recycled aggregate in GPC causes slight reduction in its strength and ductility. Since the percentage reduction in strength and behaviour of RGPC is meager compared to GPC it can be recommended as a sustainable and environment friendly construction material.