• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권6호
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• pp.1379-1397
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• 2013

We consider a system where a licensed radio spectrum is shared by multiple primary users(PUs) and secondary users(SUs). As the spectrum of interest is licensed to primary network, power and channel allocation must be carried out within the cognitive radio network so that no excessive interference is caused to PUs. For this system, we study the joint beamforming and power allocation problem via game theory in this paper. The problem is formulated as a non-cooperative beamforming and power allocation game, subject to the interference constraints of PUs as well as the peak transmission power constraints of SUs. We design a joint beamforming and power allocation algorithm for maximizing the total throughput of SUs, which is implemented by alternating iteration of minimum mean square error based decision feedback beamforming and a best response based iterative power allocation algorithm. Simulation results show that the algorithm has better performance than an existing algorithm and can converge to a locally optimal sum utility.

• Journal of Preventive Medicine and Public Health
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• 제37권2호
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• pp.174-181
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• 2004

Objective : To examine the association between dietary factors and cognitive impairment in older Korean women living in the community. Methods : Wave 2 data, from the Suwon Longitudinal Aging Study (SLAS), of 365 women aged 65 years or over, were used. The Korean version of the 30-point Mini-Mental State Examination (MMSE-K) was used to assess cognitive impairment (score$\geq$19). Dietary habits and frequencies of food group consumption were also examined. Results : A total of 67 women (18.4%) were found to be cognitively impaired. In bivariate analyses, nondietary factors, such as age, marital status, education, income, self-rated health, depression, emotional support, social activity, exercise, and dietary factors, such as self-rated nutritional status, frequency of beans and bean products and milk and dairy products consumption were associated with cognitive impairment. In the multivariate analysis, a higher frequency ($\geq$1 vs. <1 time/day) of beans and bean products (OR=0.48, 95% CI: 0.23-0.99) and milk and dairy products (OR=0.25, 95% CI: 0.10-0.61) consumption was inversely associated with cognitive impairment, after adjustment for non-dietary factors. Conclusion : These results suggest that dietary factors may play a significant role in cognitive impairment of older Korean women.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• 제23권2호
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• pp.49-56
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• 2012

Methylphenidate is a widely used stimulant for treatment of attention-deficit hyperactivity disorder (ADHD). In addition to core symptoms of attention and behavioral symptoms, methylphenidate is even effective for executive functions. However, abuse and misuse of stimulants, including methylphenidate, for the purpose of cognitive enhancement is an issue of concern worldwide. Some prejudices and misunderstandings against methylphenidate are popular ; however, little attention has been given to the neuropsychiatric evidence of methylphenidate for enhancement of cognitive function among healthy populations. In this article, our aim was to conduct a review of previous studies investigating the effect of methylphenidate in healthy populations. Findings from several recent studies have demonstrated the effectiveness of methylphenidate for enhancement of cognitive function in healthy populations. The mechanisms of cognitive enhancement are thought to be associated with motivation and the reward circuit in the brain. However, when considering the risk to benefit, an official discussion of the use of methylphenidate among healthy members of the population would be premature. Instead, investigation of epidemiological studies of the prevalence of misuse of stimulants among healthy members of the population, particularly adolescents and college students, is needed. In addition, based on achievements reported in previous studies, investigation of the effect of an approach using non-pharmacological enhancing motivation, which will in turn result in increased cognitive function would be helpful.

• 한국인터넷방송통신학회논문지
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• 제9권4호
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• pp.123-127
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• 2009

Cognitive Radio 환경에서 서비스영역 밖에 있는 사용자는 통신을 하지 못하도록 규정을 하고 있다. 그 이유는 주사용자가 서비스를 제공받는데 피해나 간섭의 영향을 대비하기 위해서이다. 이와 같은 규정이 보장된다면, CR 사용자는 서비스 영역 밖에서도 충분히 서비스를 제공받을 수 있게 된다. 본 논문에서는 주 사용자에게 과도한 간섭을 발생시키지 않는 실용적 시스템에 대한 논의, 즉, 제안된 기법을 통해 부사용자를 위한 가능한 이득이 주사용자에게 비간섭이 되는 사항에 중점을 둔다. 본 논문에서는 그 방법을 BBA(Bi-directional Beamforming Antenna), 즉 지향성 양방향 안테나를 이용하여 제시한다.

• 정보관리학회지
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• 제18권3호
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• pp.265-284
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• 2001

본 연구의 목적은 이용자의 인지유형과 그에 따른 웹기반 OPAC시스템 평가에 대한 상관관계를 알아보기 위한 것이다. 이용자들의 인지유형은 (1)Verbaliser/Imager와 (2) Wholist/Analytic으로 나누었고 웹기반 OPAC시스템의 (1)기능적인 측면과 (2)학습용이성 측면에 초점을 맞추어 평가를 하였다. 연구방법으로는 (1)사전조사를 위한 인터뷰, (2)주된 데이터 수집을 위한 질문지, 그리고 (3) 이용자의 인지형태 결정을 위해서 심리측정학(psychometric)방법을 사용하였다. 사전조사결과와 문헌의 리뷰에 근거하여 온라인 조사방법으로 (1)웹기반 온라인 질문지와 (2) Riding의 CSA(Cognitive Style Assessment)을 Sheffield 대학 캠퍼스 네트워크에 연결된 모든 PC에서 접속할 수 있게 온라인 테스트 환경을 구성하였다. 이 환경을 통하여 44명의 석.박사 학생들이 자발적으로 본 실험에 참가를 했으며, 이들로부터 수집된 데이터는 SPSS(Statistical Package for Social Science)를 이용하여 분석하였다. 통계분석에서 각 평가항목 변수들간의 상관관계분석을 위해서 피어슨(Pearson)의 상관계수 (Coefficient, f)를 사용하였다. 연구결과 개인의 인지형태와 웹기반 OPAC시스템 평가간에는 비교적 낮은 통계학적인 상관관계를 보였다.

• 한국컴퓨터정보학회논문지
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• 제14권9호
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• pp.195-204
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• 2009

본 연구에서는 DMB 휴대폰 마케팅에서 인지정보와 감정정보의 초점에 따라 소비자의 태도와 구매의도가 어떻게 달라지는지를 알아보고자 하였다. 이를 위해서 실험설계에 따라 인지초점집단, 감정초점집단의 태도와 구매의도를 측정하여, 무조작집단과 비교하였다. 실험결과에서 인지초점집단은 인지적 태도에서 높은 수준을 보였고, 감정초점집단은 감정적 태도에서 높은 수준을 보였다. 구매의도에서는 감정초점집단의 구매의도가 가장 높았고, 인지초점집단의 구매의도가 중간수준, 무조작집단의 구매의도가 가장 낮았다. 일정 기간후의 기억에서는 인지초점집단은 인지정보를 많이 기억하였고 감정초점집단은 감정정보를 많이 기억했으나, 유의적 차이는 아니었다. 결론적으로 제시된 제품정보의 초점에 따라 소비자들은 태도와 구매의도를 형성한다고 할 수 있으며, 감정정보의 영향이 인지정보보다 크다는 점을 알 수 있었다. 그리고 초점효과는 시간의 경과에 따라 약화되지만 지속적으로 소비자의 구매행동에 영향을 미친다고 할 수 있다.

• ETRI Journal
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• 제42권1호
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• pp.36-45
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• 2020

A priority-based data communication approach, developed by employing cognitive radio capacity for sensor nodes in a wireless terrestrial sensor network (TSN), has been proposed. Data sensed by a sensor node-an unlicensed user-were prioritized, taking sensed data importance into account. For data of equal priority, a first come first serve algorithm was used. Non-preemptive priority scheduling was adopted, in order not to interrupt any ongoing transmissions. Licensed users used a nonpersistent, slotted, carrier sense multiple access (CSMA) technique, while unlicensed sensor nodes used a nonpersistent CSMA technique for lossless data transmission, in an energy-restricted, TSN environment. Depending on the analytical model, the proposed wireless TSN environment was simulated using Riverbed software, and to analyze sensor network performance, delay, energy, and throughput parameters were examined. Evaluating the proposed approach showed that the average delay for sensed, high priority data was significantly reduced, indicating that maximum throughput had been achieved using wireless sensor nodes with cognitive radio capacity.

• 아동학회지
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• 제37권3호
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• pp.135-146
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• 2016

Objective: This study explored the creative thinking styles of children according to cluster analyses and examined group differences in language ability, cognitive ability, and peer relationships. Methods: The study used the data from the 2012 Panel Study of Korean Children by the Korea Institute of Child Care and Education. The participants comprised 1,681 4-year-olds. Data were analyzed via cluster analyses, ${\chi}^2$ distributions, and ANOVA tests. Results and Conclusion: The results from the cluster analyses based on percentiles of the subfactors of K-FCTYC (Korean Figural Creativity Test for Young Children) indicated four clusters: "divergent creative with openness," "non-creative," "divergent creative," and "multiple creative." Additionally, the four clusters differed by gender, language ability, cognitive ability, and peer relationships.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.3003-3017
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• 2013

In this paper, we investigate the outage performance of a cognitive relay network. We consider mutual interference in an independent, non-identically distributed Nakagmai-m fading environment. We first derive the close-form outage probability expression, which provides an efficient means to evaluate the effects of several parameters. This allows us to study the impact of several parameters on the network's performance. We then derive the asymptotic expression and reveal that the diversity order is strictly determined by the fading severity of the cognitive system. It is not affected by the primary network. Moreover, the primary network only affects the coding gain of the cognitive system. Finally, Monte Carlo simulations are provided, which corroborate the analytical results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.1998-2016
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• 2012

Reliable spectrum sensing algorithm is a fundamental component in cognitive radio. In this paper, a non-cooperative spectrum sensing algorithm which needs only one cognitive radio node named CORDIC (Coordinate Rotation Digital Computer) Jacobi based method is proposed. The algorithm computes the eigenvalues of the sampled covariance of received signal mainly by shift and additional operations, which is suitable for hardware implementation. Based the latest random matrix theory (RMT) about the distribution of the limiting maximum and minimum eigenvalue ratio, the relationship between the probability of false alarm and the decision threshold is derived. Simulations and discussions show the method is effective. Real captured digital television (DTV) signals and Universal Software Radio Peripheral (USRP) are also employed to evaluate the performance of the algorithm, which prove the proposed algorithm can be applied in practical spectrum sensing applications.