• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4367-4386
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• 2015

The concept of Internet of Things (IoT) has shed new light on WSN technologies. MAC protocol issues improving the network performance are important in WSNs because of the increase in demand for various applications to secure spectrum resources. Cognitive radio (CR) technology is regarded as a solution to the problems in this future wireless network. In recent years, energy efficiency has become an issue in CR networks. However, few relevant studies have been conducted. In this paper, an energy-efficient non-overlapping channel MAC (ENC-MAC) for CR-enabled sensor networks (CRSNs) is proposed. Applying the dedicated control channel approach, ENC-MAC allows the SUs to utilize channels in a non-overlapping manner, and thus spectrum efficiency is improved. Moreover, the cooperative spectrum sensing that allows an SU to use only two minislots in the sensing phase is addressed to en-hance energy efficiency. In addition, an analytical model for evaluating the performance, such as saturation throughput, average packet delay, and network lifetime, is developed. It is shown in our results that ENC-MAC remarkably outperforms existing MAC protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1532-1553
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• 2014

Radio spectrum is a precious resource and characterized by fixed allocation policy. However, a large portion of the allocated radio spectrum is underutilized. Conversely, the rapid development of ubiquitous wireless technologies increases the demand for radio spectrum. Cognitive Radio (CR) methodologies have been introduced as a promising approach in detecting the white spaces, allowing the unlicensed users to use the licensed spectrum thus realizing Dynamic Spectrum Access (DSA) in an effective manner. This paper proposes a generalized framework for DSA between the licensed (primary) and unlicensed (secondary) users based on Continuous Time Markov Chain (CTMC) model. We present a spectrum access scheme in the presence of sensing errors based on CTMC which aims to attain optimum spectrum access probabilities for the secondary users. The primary user occupancy is identified by spectrum sensing algorithms and the sensing errors are captured in the form of false alarm and mis-detection. Simulation results show the effectiveness of the proposed spectrum access scheme in terms of the throughput attained by the secondary users, throughput optimization using optimum access probabilities, probability of interference with increasing number of secondary users. The efficacy of the algorithm is analyzed for both imperfect spectrum sensing and perfect spectrum sensing.

• Industrial Engineering and Management Systems
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• v.13 no.2
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• pp.185-192
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• 2014

This study stems from the work of Lehman et al. (Ergonomics, 2001) which concluded that standing yields better work performance, and from the growing health trend of recommending the reduction of the amount of time spent in sitting (Owen et al., Exercise and Sport Science Reviews, 2010). Lajoie et al. (Experimental Brain Research, 1993) provided an initial significant contribution to a theory that standing requires a person to control balance, equating to demand higher productive output from the cognitive system than when a person is sitting. An assumption was formulated that standing position during class is feasible and can be adopted on the belief that it might contribute positive results to students' performance. The purpose of this study is to identify whether a body position during exams tested along with exposure durations has a significant effect on college students' performance. Mathematical analysis and reading comprehension exam was used to measure the cognitive performance of the students. Two factors, position and duration, were tested for significance with two levels each subjected to six replicates. Twenty-four students from the College of Engineering and Agro-Industrial Technology, University of the Philippines Los Ba$\tilde{n}$os were randomly selected. The experiment showed that the body position during exams is a significant factor for the Math exam, but insignificant for the Reading Comprehension exam.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3810-3830
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• 2015

In this paper, we investigate the differential game theoretic approach for distributed dynamic cooperative power control in cognitive radio ad hoc networks (CRANETs). First, a payoff function is defined by taking into consideration the tradeoff between the stock of accumulated power interference to the primary networks and the dynamic regulation of the transmit power of secondary users (SUs). Specifically, the payoff function not only reflects the tradeoff between the requirement for quickly finding the stable available spectrum opportunities and the need for better channel conditions, but also reveals the impact of the differentiated types of data traffic on the demand of transmission quality. Then the dynamic power control problem is modeled as a differential game model. Moreover, we convert the differential game model into a dynamic programming problem to obtain a set of optimal strategies of SUs under the condition of the grand coalition. A distributed dynamic cooperative power control algorithm is developed to dynamically adjust the transmit power of SUs under grand coalition. Finally, numerical results are presented to demonstrate the effectiveness of the proposed algorithm for efficient power control in CRANETs.

• Proceedings of the Korean Society for Cognitive Science Conference
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• 2006.06a
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• pp.59-60
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• 2006

To date, there has been minimal researchregarding the cerebral activation of Korean language. There need the database for Korean language that is quite different from alphabetic system. This study examined the brain activation of picture naming, word reading, picture-word matching, and semantic categorization in Korean language. Moreover, we investigated the cortical activation pattern according to semantic demand for the above tasks.

• Journal of The Korean Association For Science Education
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• v.27 no.1
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• pp.18-27
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• 2007

This study examined the influences of cognitive conflict and non-cognitive variables induced by a discrepant event on process of conceptual change, and the processes that a discrepant event lead to situational interest. Seventh graders participated in this study. A preconception test was administered to select students possessing misconceptions about density. The tests of cognitive response and situational interest to a discrepant event were administered. After learning with a CAl program, the tests assessing attention and effort allocated to the CAl, and conceptual understanding were also administered. A path analysis revealed that cognitive conflict induced by a discrepant event caused situational interest, which in turn increased attention and/or effort and thus, resulted in conceptual change. The results of the path analysis on the processes in which a discrepant event led to situational interest suggested that novelty may be a primary source of situational interest. Novelty influenced situational interest directly as well as through attention demand, exploration intention, and instant enjoyment. Moreover, novelty exerted a direct effect on challenge, which in turn had negative effects on instant enjoyment directly as well as through cognitive conflict, and thus, decreased situational interest. However, the path coefficients of the latter were relatively smaller than those of the former. Educational implications are discussed.

• The Korean Journal of Health Service Management
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• v.12 no.1
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• pp.81-93
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• 2018

Objectives : This cross-sectional study aims to investigate the differences in general health status (GHS) and physical care burdens (PCB) of inpatient groups in long-term care hospitals (LTCH). Methods : The data of 228 patients were analyzed by integrating the electronic medical record (EMR) data of 2016, recorded by the nurses of hospitalized patients in the hospital. Results : There was a statistically significant difference in the GHS between the high-medical demand group and the other groups, but there was no difference in the GHS among other groups. The overall PCB was higher in the high-medical demand group than in the middle-medical demand, and cognitive impairment groups, but not in the problem behavioral group. Conclusions : The current classification of patient groups has shown limitations in terms of the basis of differential benefits of the groups. In particular, the PCB of the problem behavior group was not different from that of any group; hence, it should be adjusted through further study. To control the surge of medical care costs, it is necessary to improve the irrationality of the LTCH pay system in terms of the integration and continuity for elderly care.

• KIISE Transactions on Computing Practices
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• v.20 no.12
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• pp.688-693
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• 2014

With the advent of ubiquitous environments, the smart phone has come into wide use and the demand for various content increases. Thus, in order to efficiently utilize limited resources cognitive radio technology is regarded as a possible solution. Besides spectrum sensing or access schemes, the provision of VoIP traffic service for secondary users with limited spectrum resources is a very important issue. In this paper, a resource allocation and control system for VoIP QoS provision in cognitive radio networks is proposed. Firstly, as the system model, the time structure of the network is addressed and, according to the structure, a bandwidth broker is proposed. In addition, based on available bandwidth estimated by the bandwidth broker, a connection admission control for secondary users is developed. It is demonstrated that the provision of VoIP QoS is greatly affected by channel utilization, the number of channels, and the length of timeslot.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.6
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• pp.2709-2734
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• 2020

The growing demand to make wireless data services 5G compatible has necessitated the development of an energy-efficient approach for an effective new wireless environment. In this paper, we first propose a cognitive sensor node (CSN) based game theory for deriving energy via a primary user-transmitted radio frequency signal. Cognitive users' time was segmented into three phases based on a time switching protocol: energy harvest, spectrum sensing and data transmission. The proposed model chooses the optimal energy-harvesting phase as the effected factor. We further propose a distributed energy-harvesting model as a utility function via pricing techniques. The model is a non-cooperative game where players can increase their net benefit in a selfish manner. Here, the price is described as a function pertaining to transmit power, which proves that the proposed energy harvest game includes Nash Equilibrium and is also unique. The best response algorithm is used to achieve the green connection between players. As a result, the results obtained from the proposed model and algorithm show the advantages as well as the effectiveness of the proposed study. Moreover, energy consumption was reduced significantly (12%) compared to the benchmark algorithm because the proposed algorithm succeeded in delivering energy in micro which is much better compared to previous studies. Considering the reduction and improvement in power consumption, we could say the proposed model is suitable for the next wireless environment represented in 5G.

• Journal of the Korean Society of Food Culture
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• v.35 no.2
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• pp.156-166
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• 2020

In this study, 594 questionnaires administered to men and women residing in the capital metropolitan area who work night shifts were analyzed in order to study the effect of health information cognition on healing needs in accordance with the type of food selection criteria of the night worker. The results of confirmatory factor analysis in deriving food selection type identified four categories, a safety seeking type, a food exploratory type, a habitual seeking type, and a rational type, and the cognition types on health information were classified into physical cognition and psychological cognition. The need for healing, which was the investigated factor, was found to have a high correlation between questionnaire items with high reliable consistency. The results of this study were as follows. First, the food selection types of safety seeking type and habitual food seeking type had significant positive effects on the cognitive level of physical health information, and food exploratory type and habitual seeking type had significant positive effects on the cognitive level of psychological health information. In addition, it was shown that food exploratory type and rational type had significant positive effects on healing needs. As a result of this study, it was found that the cognition level of physical and psychological information was different according to food selection type, and the higher the cognitive level, the higher the healing needs. In particular, the result that the level of psychological health information significantly affected healing needs signifies that there is a demand to develop programs and menus that satisfy various needs related to healing and recovery from fatigue. In addition, further interest and study on the health and healing of night workers are required.