• 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.

• ETRI Journal
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• v.37 no.3
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• pp.491-501
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• 2015

Spectrum sensing is an elementary function in cognitive radio designed to monitor the existence of a primary user (PU). To achieve a high rate of detection, most techniques rely on knowledge of prior spectrum patterns, with a trade-off between high computational complexity and long sensing time. On the other hand, blind techniques ignore pattern matching processes to reduce processing time, but their accuracy degrades greatly at low signal-to-noise ratios. To achieve both a high rate of detection and short sensing time, we propose fast spectrum sensing with coordinate system (FSC) - a novel technique that decomposes a spectrum with high complexity into a new coordinate system of salient features and that uses these features in its PU detection process. Not only is the space of a buffer that is used to store information about a PU reduced, but also the sensing process is fast. The performance of FSC is evaluated according to its accuracy and sensing time against six other well-known conventional techniques through a wireless microphone signal based on the IEEE 802.22 standard. FSC gives the best performance overall.

• Journal of Communications and Networks
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• v.18 no.4
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• pp.610-618
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• 2016

A green cognitive radio network (CRN), characterized by base stations (BSs) that conserve energy during sleep periods, is a promising candidate for realizing more efficient spectrum allocation. To improve the spectrum efficiency and achieve greener communication in wireless applications, we consider CRNs with an long term evolution advanced (LTE-A) structure and propose a novel energy-saving strategy. By establishing a type of preemptive priority queueing model with a single vacation, we capture the stochastic behavior of the proposed strategy. Using the method of matrix geometric solutions, we derive the performance measures in terms of the average latency of secondary user (SU) packets and the energy-saving degree of BSs. Furthermore, we provide numerical results to demonstrate the influence of the sleeping parameter on the system performance. Finally, we compare the Nash equilibrium behavior and social optimization behavior of the proposed strategy to present a pricing policy for SU packets.

• International Journal of Computer Science & Network Security
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• v.21 no.8
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• pp.79-86
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• 2021

Alzheimer's is a chronic progressive disease which exhibits varied symptoms and behavioural traits from person to person. The deterioration in cognitive abilities is more noticeable through their Activities and Instrumental Activities of Daily Living rather than biological markers. This information discussed in social media communities was collected and features were extracted by using the proposed fuzzy logic based algorithm to address the uncertainties and imprecision in the data reported. The data thus obtained is used to train machine learning models in order to predict the longevity of the patients. Models built on features extracted using the proposed algorithm performs better than models trained on full set of features. Important findings are discussed and Support Vector Regressor with RBF kernel is identified as the best performing model in predicting the longevity of Alzheimer's patients. The results would prove to be of high value for healthcare practitioners and palliative care providers to design interventions that can alleviate the trauma faced by patients and caregivers due to chronic diseases.

• Journal of Yeungnam Medical Science
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• v.38 no.3
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• pp.194-201
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• 2021

Amputation changes the lives of patients and their families. Consequently, the patient must adapt to altered body function and image. During this adaptation process, psychological problems, such as depression, anxiety, and posttraumatic stress disorder, can occur. The psychological difficulties of patients with amputation are often accepted as normal responses that are often poorly recognized by patients, family members, and their primary physicians. Psychological problems can interfere with rehabilitation and cause additional psychosocial problems. Therefore, their early detection and treatment are important. A multidisciplinary team approach, including mental health professionals, is ideal for comprehensive and biopsychosocial management. Mental health professionals could help patients set realistic goals and use adaptive coping styles. Psychiatric approaches should consider the physical, cognitive, psychological, social, and spiritual functions and social support systems before and after amputation. The abilities and limitations of physical, cognitive, psychological, and social functions should also be considered. To improve the patient's adaptation, psychological interventions such as short-term psychotherapy, cognitive behavioral therapy, mindfulness meditation, biofeedback, and group psychotherapy can be helpful.

• Journal of Platform Technology
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• v.9 no.1
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• pp.3-14
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• 2021

Cognitive Radio network (CR) is a promising paradigm that helps the unlicensed user (Secondary User) to analyse the spectrum and coordinate the spectrum access to support the creation of common control channel (CCC). The cooperation of secondary users and broadcasting between them is done through transmitting messages in CCC. In case, if the control channels may get jammed and it may directly degrade the network's performance and under such scenario jammers will devastate the control channels. Hopping sequences may be one of the predominant approaches and it may be used to fight against this problem to confront jammer. The jamming attack can be alleviated using one of the game modelling approach and in this proposed scheme stochastic games has been analysed with more single users to provide the flexible control channels against intrusive attacks by mentioning the states of each player, strategies ,actions and players reward. The proposed work uses a modern player action and better strategic view on game theoretic modelling is stochastic game theory has been taken in to consideration and applied to prevent the jamming attack in CR network. The selection of decision is based on Q learning approach to mitigate the jamming nodes using the optimal MDP decision process

• Journal of Yeungnam Medical Science
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• v.38 no.1
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• pp.65-69
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• 2021

Donepezil is a cholinesterase inhibitor used extensively to treat Alzheimer disease. The increased cholinergic activity is associated with adverse effects, therefore gastrointestinal symptoms, including nausea, vomiting, and diarrhea, are common. Hypokalemia is a rare adverse event that occurs in less than 1% of donepezil-treated patients. Although hypokalemia of mild and moderate grade does not present serious signs and symptoms, severe hypokalemia often results in prolonged hospitalization and mortality. Herein, we report a case of hypokalemia developed after the initiation of donepezil therapy for cognitive impairment.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.3
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• pp.1-9
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• 2022

In this study we conducted a research regarding the effect on learning immersion and perception of the learning environment by learning presence of students in the Department of aeronautical science and flight operation in the context of non-face-to-face lectures caused by COVID-19. The relationship between learning presence (cognitive presence, emotional presence, and social presence) and learning commitment showed a high correlation. The learning immersion was also found to increase when cognitive presence, emotional presence, and social presence increased in multiple regression analysis to find out the effects of cognitive presence, emotional presence, and social presence, which are sub-factors of learning presence. The advantage of non-face-to-face classes was to be the ease of learning, and the disadvantage of non-face-to-face classes was the most difficulty of the learning process in the content analysis of the non-face-to-face class environment.

• Korean Journal of Cognitive Science
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• v.26 no.2
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• pp.209-239
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• 2015

Previous studies on the effect of incidental semantic priming on judgment, have focused mainly on mutually exclusive hypotheses. However, the present study explored whether incidental semantic activation affects diagnostic inference depending on the type of the hypothesis: mutually exclusive hypotheses vs compatible hypotheses. In Experiment 1, in case of mutually exclusive hypotheses, the final hypothesis was selected according to the incidental semantic priming, but there was no difference in the number of generated hypothesis in comparison with the control. However, for compatible hypotheses (i.e., both hypotheses can be true), the semantic priming affected the number of generated hypotheses, but not the selection of the final hypothesis. The same pattern of results was observed even when the cognitive load was increased. In Experiment 2, we found a boundary condition of incidental semantic activation on diagnostic inference. When cues related to each of the hypotheses were presented simultaneously, the incidental semantic effect disappeared. These results suggest that people consider all possible cues when making diagnostic inference in daily life. In light of these findings, further research on hypothesis generation/evaluation should take the type of hypothesis into account.

• Journal of the Korea Convergence Society
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• v.10 no.12
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• pp.387-397
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• 2019

The purpose of this study is to analyze the relationship between health related physical fitness, cognitive function, depression and quality of life variables of elderly people in a comprehensive way based on quantitative evaluation. The subjects of this study were 385 people who voluntarily participated in the elderly welfare center in Gyeonggi and Seoul the elderly people. As for the data collection methods, were measured the characteristics, depression and quality of life, cognitive function questionnaires along with measures of lower and upper body strength, dynamic equilibrium and agility, total endurance and grip strength. As a result, the first was a statistically significant correlation between integrated health of the elderly, cognitive function, quality of life and depression. Second, the analysis of cognitive function, elderly integrated health, quality of life, and depression revealed statistical significance among all variables. Third, there was the partial intervention effect of function in the quality of life and depression of the elderly.