• 한국통신학회논문지
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• 제34권11A호
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• pp.822-830
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• 2009

The spectrum efficiency of mobile communication networks can be improved dramatically adopting multiple antennas technologies. In order to guarantee the licensed rights of primary user (PU), the cognitive radio system should perform in a relatively low interference manner when it gets access to the spectrum of licensed networks. In this paper, we explore a uniformly distributed circular antenna array to implement beamforming algorithm that is accomplished by optimization method at the base station of cognitive radio networks, and therefore we can suppress the interference to PU by steering quite low transmission power toward PU and constructing a narrow beam toward cognitive user (CU). By reducing the constraint number of the optimization problem, we also propose a null steering algorithm that steers rather low radiation power toward PU, while the other areas in the same cell are covered by radiation power except the local area around PU. It is pursued to reduce the computation load and enlarge the capacity of cognitive radio networks extremely. The simulation results demonstrate that the proposed algorithms process superior performance.

• Journal of Information Processing Systems
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• 제10권1호
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• pp.119-131
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• 2014

In recent literature on traffic scheduling, the combination of the two-dimensional discrete-time Markov chain (DTMC) and the Markov modulated Poisson process (MMPP) is used to analyze the capacity of VoIP traffic in the cognitive radio system. The performance of the cognitive radio system solely depends on the accuracy of spectrum sensing techniques, the minimization of false alarms, and the scheduling of traffic channels. In this paper, we only emphasize the scheduling of traffic channels (i.e., traffic handling techniques for the primary user [PU] and the secondary user [SU]). We consider the following three different traffic models: the cross-layer analytical model, M/G/1(m) traffic, and the IEEE 802.16e/m scheduling approach to evaluate the performance of the VoIP services of the cognitive radio system from the context of blocking probability and throughput.

• 의학교육논단
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• 제22권2호
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• pp.77-84
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• 2020

This study introduces cognitive constructivism in reference to its emergence in the development of medical education. The main concepts of cognitive constructivism as they relate to knowledge construction and the learner's process were described, and cognitive constructivism as a learning theory was examined in its capacity to help interpret the phenomenon of medical education. Piaget's theory of cognitive constructivism and Ausubel's meaningful learning theory were applied in an attempt to explore the role of students and educators, curriculum, and teaching and learning in medical education from a cognitive constructivist perspective. When faced with new information, learners compare it with the existing schema to understand, and in order to resolve conflicts caused by inconsistencies in the information, learners incorporate assimilation and accommodation to help maintain equilibration. Therefore, instructors must meaningfully connect new content to the learner's existing schema and make endless efforts to satisfy learners' intellectual curiosity. The basic premises of medical education content is a suitable subject of meaningful learning. A learner who already possesses well-structured knowledge is likely to experience meaningful learning and a richer intellectual experience. Therefore, it is necessary to organize the curriculum strategically and elaborately so that learners can have an improved and effective learning experience.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권6호
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• pp.2128-2147
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• 2021

Cognitive radio systems are being implemented recently to tackle spectrum underutilization problems and aid efficient data traffic. Spectrum sensing is the crucial step in cognitive applications in which cognitive user detects the presence of primary user (PU) in a particular channel thereby switching to another channel for continuous transmission. In cognitive radio systems, the capacity to precisely identify the primary user's signal is essential to secondary user so as to use idle licensed spectrum. Based on the inherent capability, a new spectrum sensing technique is proposed in this paper to identify all types of primary user signals in a cognitive radio condition. Hence, a spectrum sensing algorithm using improved convolutional neural network and long short-term memory (CNN-LSTM) is presented. The principle used in our approach is simulated annealing that discovers reasonable number of neurons for each layer of a completely associated deep neural network to tackle the streamlining issue. The probability of detection is considered as the determining parameter to find the efficiency of the proposed algorithm. Experiments are carried under different signal to noise ratio to indicate better performance of the proposed algorithm. The PU signal will have an associated modulation format and hence identifying the presence of a modulation format itself establishes the presence of PU signal.

• 한국과학교육학회지
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• 제21권3호
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• pp.497-505
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• 2001

본 연구에서는 고등학생 165명을 대상으로 학생들의 분자 구조에 대한 개념 이해도와 인지 변인들 사이의 관계를 조사하였다. 학생들이 두 학기 동안 '고등학교 화학 II 과목을 학습한 후, 분자 구조에 대한 개념, 공간 지각 능력, 논리적 사고력, 기억 용량, 학습 접근 방식 검사를 실시하였다. 연구 결과, 분자 구조 개념에 대한 학생들의 이해는 불완전하였으며, 몇 가지 오개념이 발견되었다. 개념 검사 점수는 모든 인지 변인 검사 점수들과 유의미한 상관이 있었다. 개념 이해에 대한 인지 변인들의 예언력을 조사하기 위해 중다 회귀 분석을 실시하였다. 유의미 학습 접근 방식이 가장 큰 예언력을 나타내었고, 논리적 사고력, 기계적 학습 접근 방식, 기억 용량의 순으로 예언력이 컸다. 그러나 공간 지각 능력은 예언력이 없었다.

• 한국콘텐츠학회논문지
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• 제18권11호
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• pp.527-539
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• 2018

노화로 인한 인지의 변화는 정상 노인들의 통사처리에 부정적 영향을 끼치는데 작업기억용량이 중요한 인지기능을 한다고 알려져 있다. 본 연구는 명사구 연결 전치사구의 이해에 도움이 되는 문맥을 제시할 때와 그렇지 않을 때 정상 노인과 젊은 성인이 어떻게 명사구 연결 전치사구를 처리하는지 단어별 자율조절읽기 방법을 통해 알아보았다. 또한, 이 때 어떤 인지기능이 문맥 이용을 통한 명사구 연결 전치사구의 처리능력과 관련이 있는지도 살펴보았다. 정상 노인은 읽기과제에서 문맥유무에 상관없이 젊은 성인보다 읽기속도가 느렸다. 그러나 두 그룹 모두 문맥이 존재할 때 명사구 연결 전치사구의 처리 속도가 빨랐다. 즉, 노인들의 노화로 인한 인지의 저하는 처리 속도만 느리게 했을 뿐 질적인 면에서 차이는 없었다. 문맥을 이용한 명사구 연결 전치사구 처리 시 관련된 인지기능은 교대주의력으로 나타났으며 본 연구에서는 작업기억용량의 역할은 발견되지 않았다. 이를 통해 노화가 통사처리에 끼치는 영향은 반드시 부정적인 것이 아니라 통사구조에 따라 다를 수 있으며, 통사 구문의 종류에 따라 관련된 인지기능이 다를 수 있음을 시사한다.

• 대한약침학회지
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• 제27권2호
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• pp.70-81
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• 2024

Objectives: Cognitive impairments, ranging from mild to severe, adversely affect daily functioning, quality of life, and work capacity. Despite significant efforts in the past decade, more than 200 promising drug candidates have failed in clinical trials. Herbal remedies are gaining interest as potential treatments for dementia due to their long history and safety, making them valuable for drug development. This review aimed to examine the mechanisms behind the effect of Polygonum multiflorum on cognitive function. Methods: This study focused primarily on the effects of Polygonum multiflorum and its chemical constituents on cognitive behavioral outcomes including the Morris water maze, the passive avoidance test, and the Y maze, as well as pathogenic targets of cognitive impairment and Alzheimer's disease (AD) like amyloid deposition, amyloid precursor protein, tau hyperphosphorylation, and cognitive decline. Additionally, a thorough evaluation of the mechanisms behind Polygonum multiflorum's impact on cognitive function was conducted. We reviewed the most recent data from preclinical research done on experimental models, particularly looking at Polygonum multiflorum's effects on cognitive decline and AD. Results: According to recent research, Poligonum multiflorum and its bioactive components, stilbene, and emodin, influence cognitive behavioral results and regulate the pathological target of cognitive impairment and AD. Their mechanisms of action include reducing oxidative and mitochondrial damage, regulating neuroinflammation, halting apoptosis, and promoting increased neurogenesis and synaptogenesis. Conclusion: This review serves as a comprehensive compilation of current experiments on AD and other cognitive impairment models related to the therapeutic effects of Polygonum multiflorum. We believe that these findings can serve as a basis for future clinical trials and have potential applications in the treatment of human neurological disorders.

• 한국통신학회논문지
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• 제35권8A호
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• pp.768-776
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• 2010

본 논문에서는 다중 안테나를 사용하는 인지무선 시스템과 허가된 사용자(주사용자)가 공존하는 환경을 고려한다. 여기에서 부사용자 송신기는 직교 시공간 부호(OSTBC)를 사용하고 수신기는 Maximum Likelihood(ML) 검출 방식을 사용한다. Flat 페이딩 채널에서 ML 검출기를 사용할 경우, 최적의 precoder는 고유 빔포밍 방법이다. 본 논문에서는 벡터의 유사성에 기반한 가중치를 적용하여 간섭을 최소화하는 선형 precoding 알고리즘을 제안한다. 시뮬레이션 결과를 통해 제안된 알고리즘이 기존의 ZF(Zero-forcing) 빔포밍보다 최소 2~8dB 우수한 간섭억압 능력을 보여 우수한 SER 성능과 최대 8bps/Hz의 Capacity 증가를 보이는 것으로 나타났다.

• 한국과학교육학회지
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• 제16권3호
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• pp.278-285
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• 1996

High school students' achievements in algorithmic problems, and figure-formatted and textual-formatted conceptual problems concerning stoichiometry, gaseous state, and solution, were measured by the Chemistry Problem Solving Ability Test. The relationships among the achievement scores in the three types of problems and cognitive variables such as logical thinking ability, mental capacity, and field dependence/field independence were examined. The portion of variance of explanation for each achievement score was also studied by a multiple regression analysis. The results showed that logical thinking ability was significantly correlated with the achievement score in the algorithmic problems, and accounted for the significant portion of the variance of the score. Mental capacity accounted for the significant portion of the variance of the score in the figure-formatted conceptual problems. Although field dependence/field independence was significantly correlated with all the achievement scores, it did not significantly account for any scores in multiple regression analyses. However, the magnitudes of correlation coefficients among the achievement scores were higher than those between the achievement scores and cognitive variables. The best predictor for each score was also found to be one of the other achievement scores. Educational implications are discussed.

• Journal of electromagnetic engineering and science
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• 제11권2호
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• pp.128-132
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• 2011

In interference tolerance based spectrum sharing systems, primary receivers (PRs) are protected by a predefined peak or average interference power constraint. To implement such systems, cognitive radio (CR) transmitters are required to adjust their transmit power so that the interference power received at the PR receivers is kept below the threshold value. Hence, a CR-transmitter requires knowledge of its channel and the primary receiver in order to allocate the transmit power. In practice, it is impossible or very difficult for a CR transmitter to have perfect knowledge of this channel state information (CSI). In this paper, we investigate the impact of imperfect knowledge of this CSI on the performances of both a primary and cognitive radio network. For fixed transmit power, average interference power (AIP) constraint can be maintained through knowledge of the channel distribution information. To maintain the peak interference power (PIP) constraint, on the other hand, the CR-transmitter requires the instantaneous CSI of its channel with the primary receiver. First, we show that, compared to the PIP constraint with perfect CSI, the AIP constraint is advantageous for primary users but not for CR users. Then, we consider a PIP constraint with imperfect CSI at the CR-transmitter. We show that inaccuracy in CSI reduces the interference at the PR-receivers that is caused by the CR-transmitter. Consequently the proposed schemes improve the capacity of the primary links. Contrarily, the capacities of the CR links significantly degrade due to the inaccuracy in CSI.