• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.924-944
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• 2014

This paper investigates the power allocation and outage performance of MIMO full-duplex relaying (MFDR), based on orthogonal space-time block codes (OSTBC), in cognitive radio systems. OSTBC transmission is used as a simple means to achieve multi-antenna diversity gain. Cognitive MFDR systems not only have the advantage of increasing spectral efficiency through spectrum sharing, but they can also extend coverage through the use of relays. In cognitive MFDR systems, the primary user experiences interference from the secondary source and relay simultaneously, owing to full duplexing. It is therefore necessary to optimize the transmission powers at the secondary source and relay. In this paper, we propose an optimal power allocation (OPA) scheme based on minimizing the outage probability in cognitive MFDR systems. We also analyse the outage probability of the secondary user in noise-limited and interference-limited environments in Nakagami-m fading channels. Simulation results show that the proposed schemes achieve performance improvements in terms of reducing outage probability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.371-388
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• 2014

Cognitive Radio (CR) has been recently proposed as a promising technology to remedy the problems of spectrum scarcity and spectrum underutilization by enabling unlicensed users to opportunistically utilize temporally unused licensed spectrums in a cautious manner. In Cognitive Radio Ad Hoc Networks (CRAHNs), data routing is one of the most challenging tasks since the channel availability and node mobility are unpredictable. Moreover, the network performance is severely degraded due to large numbers of path failures. In this paper, we propose the Fault-Tolerant Cognitive Ad-hoc Routing Protocol (FTCARP) to provide fast and efficient route recovery in presence of path failures during data delivery in CRAHNs. The protocol exploits the joint path and spectrum diversity to offer reliable communication and efficient spectrum usage over the networks. In the proposed protocol, a backup path is utilized in case a failure occurs over a primary transmission route. Different cause of a path failure will be handled by different route recovery mechanism. The protocol performance is compared with that of the Dual Diversity Cognitive Ad-hoc Routing Protocol (D2CARP). The simulation results obviously prove that FTCARP outperforms D2CARP in terms of throughput, packet loss, end-to-end delay and jitter in the high path-failure rate CRAHNs.

• Journal of Preventive Medicine and Public Health
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• v.37 no.2
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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 Information Technology Services
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• v.12 no.3
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• pp.39-54
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• 2013

IT consulting is becoming a norm rather than exception in this age of smart work and information revolution. As IT consulting is one of the knowledge intensive services requiring high credence on both sides, maintaining a good trustful relationship is critical in sustenance of strategic partnership between business firms and IT service firms. Trust is known to be one of the salient constructs in service relationships. In this study, building from the social psychology literature, trust is conceptualized as two dimensions : cognitive and affective trust. Using two dimensions of trust as mediators, a research model is constructed for IT consulting specific context : relationship continuance intention as the dependent construct while expertise, service performance, reputation, relationship satisfaction and value similarity as antecedents of cognitive and affective trust. 145 data points were collected through a survey of IT service client project managers retrospectively asking their experience with IT consultants. Findings suggest that cognitive trust is associated with perceived level of expertise and service performance while affective trust with relationship satisfaction and value similarity, respectively. Interestingly, the paths from reputation are found to be statistically insignificant towards both dimensions of trust, indicating IT service context would be more practically outcome oriented than any other professional service context. Also, cognitive trust seems to maintain stronger influence on relationship continuance intention as anticipated. Implications and limitations are discussed at the end.

• Science of Emotion and Sensibility
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• v.22 no.4
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• pp.65-74
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• 2019

Extant research has proposed that the Object-Spatial-Verbal cognitive style can elucidate individual differences in the preference for modality-specific information. However, no studies have yet ascertained whether this type of information processing evinces structural correlations in the brain. Therefore, the current study used voxel-based morphometry (VBM) analyses to investigate individual differences in gray matter volumes based on the Object-Spatial-Verbal cognitive style. For this purpose, ninety healthy young adults were recruited to participate in the study. They were administered the Korean version of the Object-Spatial-Verbal cognitive style questionnaire, and their anatomical brain images were scanned. The VBM results demonstrated that the participants' verbal scores were positively correlated with regional gray matter volumes (rGMVs) in the right superior temporal sulcus/superior temporal gyrus, the bilateral parahippocampal gyrus/fusiform gyrus, and the left inferior temporal gyrus. In addition, the rGMVs in these regions were negatively correlated with the relative spatial preference scores obtained by individual participants. The findings of the investigation provide anatomical evidence that the verbal cognitive style could be decidedly relevant to higher-level language processing, but not to basic language processing.

• Language and Information
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• v.8 no.1
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• pp.163-182
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• 2004

Since metaphor was proposed to be a matter of thought instead of language over two decades ago, the research in this area has made most of its progress by the cognitivists. For the cognitivists represented by Lakoff, metaphor is not a mere poetic or rhetoric device, but is central to our everyday language. Furthermore, according to them, we categorize the world and break it into concepts mainly through metaphors, and truth conditions simply cannot account for metaphor. However, this cognitivists' view has been severely counterattacked by the truth-conditional semanticists. Their main criticism is that the cognitivists do not provide a way to go from our internal representations to the outside world. It is also criticized that the cognitive theory of metaphor as cross-conceptual domain mappings is too broad and general, and that they do not explain why a particular metaphorical expression should be subsumed under one mapping rather than another mapping, i.e., their schemes and structural relations are not predictive. In this context, the purpose of this paper is to propose a model for metaphor interpretation that combines the virtues of the two opposite views of metaphor. Truth-conditional semantics cannot ignore cognitive aspects of language, so-called states of affairs or mental representations, while cognitive theories cannot neglect vigorous representation of meaning with objective reality. This paper will try to present a preliminary outline of this combining model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.1
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• pp.1-19
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• 2020

In an underlay cognitive simultaneous wireless information and power transfer (SWIPT) network, communication from secondary user (SU) to secondary destination (SD) is accomplished with decode-and-forward (DF) relays. Multiple energy-constrained relays are assumed to harvest energy from SU via power splitting (PS) protocol and complete SU secure information transmission with beamforming. Hence, physical layer security (PLS) is investigated in cognitive SWIPT network. In order to interfere with eavesdropper and improve relay's energy efficiency, a destination-assisted jamming scheme is proposed. Namely, SD transmits artificial noise (AN) to interfere with eavesdropping, while jamming signal can also provide harvested energy to relays. Beamforming vector and power splitting ratio are jointly optimized with the objective of SU secrecy capacity maximization. We solve this non-convex optimization problem via a general two-stage procedure. Firstly, we obtain the optimal beamforming vector through semi-definite relaxation (SDR) method with a fixed power splitting ratio. Secondly, the best power splitting ratio can be obtained by one-dimensional search. We provide simulation results to verify the proposed solution. Simulation results show that the scheme achieves the maximum SD secrecy rate with appropriate selection of power splitting ratio, and the proposed scheme guarantees security in cognitive SWIPT networks.

• Journal of the Ergonomics Society of Korea
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• v.18 no.3
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• pp.41-53
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• 1999

More than twenty HRA (Human Reliability Analysis) methodologies have been developed and used for the safety analysis in nuclear field during the past two decades. However, no methodology appears to have universally been accepted, as various limitations have been raised for more widely used ones. One of the most important limitations of conventional HRA is insufficient analysis of the task structure and problem space. To resolve this problem, we suggest a framework of informational analysis for HRA. The proposed informational analysis consists of three parts. The first part is the scenario analysis that investigates the contextual information related to the given task on the basis of selected scenarios. The second is the goals-means analysis to define the relations between the cognitive goal and task steps. The third is the cognitive function analysis that identifies the cognitive patterns and information flows involved in the task. Through the three-part analysis. systematic investigation is made possible from the macroscopic information on the tasks to the microscopic information on the specific cognitive processes. It is expected that analysts can attain a structured set of information that helps to predict the types and possibility of human error in the given task.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.1
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• pp.34-49
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• 2015

Market means of spectrum trading have been utilized as a vital method of spectrum sharing and access in future cognitive radio system. In this paper, we consider the spectrum trading with multiple primary carrier providers (PCP) leasing the spectrum to multiple secondary carrier providers (SCP) for a short period of time. Several factors including the price of the resource, duration of leasing, and the spectrum quality guides the proposed model. We formulate three trading policies based on the game theory for dynamic spectrum access in a LTE based cognitive radio system (CRS). In the first, we consider utility function based resource sharing (UFRS) without any knowledge of past transaction. In the second policy, each SCP deals with PCP using a non-cooperative resource sharing (NCRS) method which employs optimal strategy based on reinforcement learning. In variation of second policy, third policy adopts a Nash bargaining while incorporating a recommendation entity in resource sharing (RERS). The simulation results suggest overall increase in throughput while maintaining higher spectrum efficiency and fairness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.35-41
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• 2017

To solve the shortage of radio spectrum and utilize spectrum resource more efficiently, cognitive radio technologies are proposed, and many studies on cognitive radio have been conducted. Multi-hop routing is one of the important technologies to enable the nodes to transmit data further with lower power in ad-hoc cognitive radio networks. In a multi-channel cognitive radio networks, each channel should be allocated to minimize interference to primary users. In the multi-hop routing, channel allocation should consider the inter-channel interference to maximize network throughput. In this paper, we propose multi-channel scheduling scheme which minimizes inter-channel interferences and avoids collision with primary users for the multi-hop multi-channel cognitive radio networks. The proposed scheduling is designed to determine both of routing path and channel selection. The performance of proposed channel allocation scheme is evaluated by the computer simulation in the aspect of capacity and collision rate.