• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.808-811
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• 2015

Cognitive radio 기술은 유망한 동적 주파수 스펙트럼 할당 기법으로 연구되어왔다. Cognitive radio의 주파수 스펙트럼 감지 기술은 주파수 면허대역에서 주사용자(면허대역 사용자)에게 간섭을 유발하지 않으면서 부사용자(비면허 사용자)가 면허대역을 사용할 수 있는 방법을 제공한다. 그러나 스펙트럼을 감지함에 있어서 면허대역을 주사용자가 사용하고 있는지 여부를 한 개의 부 사용자가 판단하여 결정하면 무선채널에서의 페이딩, 잡음 불확실성에 의한 새도우잉, 그리고 히든 노드 문제 등 의해 오류가 발생할 수 있다. 이를 해결하기 위해 협력 스펙트럼 감지 기술이 등장하였다. 본 논문에서는 면허대역 사용여부를 퓨전센터에서 결정하는 협력 스펙트럼 감지기술을 제안하였다. 부사용자는 세 개의 threshold를 사용하여 주사용자 존재여부를 판단하며, 판단 결과를 퓨전센터로 전송한다. 퓨전센터의 협력 스펙트럼 감지기술로 OR 기법을 사용하였고, 컴퓨터 모의실험을 통해 성능평가를 수행하였으며, 성능평가 결과에 따르면 OR 기법의 성능이 가장 우수함을 알 수 있었다.

• International Journal of Computer Science & Network Security
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• 제24권2호
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• pp.178-188
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• 2024

In the near future, it is expected that there will be billions of connected devices using fifth generation (5G) network services. The recently available base stations (BSs) need to mitigate their loads without changing and at the least monetary cost. The available spectrum resources are limited and need to be exploited in an efficient way to meet the ever-increasing demand for services. Device to Device communication (D2D) technology will likely help satisfy the rapidly increasing capacity and also effectively offload traffic from the BS by distributing the transmission between D2D users from one side and the cellular users and the BS from the other side. In this paper, we propose to apply D2D overlay communication with cognitive radio capability in 5G networks to exploit unused spectrum resources taking into account the dynamic spectrum access. The performance metrics; throughput and delay are formulated and analyzed for CSMA-based medium access control (MAC) protocol that utilizes a common control channel for device users to negotiate the data channel and address the contention between those users. Device users can exploit the cognitive radio to access the data channels concurrently in the common interference area. Estimating the achievable throughput and delay in D2D communication in 5G networks is not exploited in previous studies using cognitive radio with CSMA-based MAC protocol to address the contention. From performance analysis, applying cognitive radio capability in D2D communication and allocating a common control channel for device users effectively improve the total aggregated network throughput by more than 60% compared to the individual D2D throughput without adding harmful interference to cellular network users. This approach can also reduce the delay.

• 생물정신의학
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• 제13권2호
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• pp.82-94
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• 2006

Objectives : In order to explore effects of board-game therapy for cognitive rehabilitation in patients with schizophrenia, we investigated the change of executive cognitive function over a 2-month period of board-game therapy in patients with schizophrenia. Methods : Two groups of chronic schizophrenic inpatients were participated in this study. One group(n=21) were treated with board-game therapy for 2 months and the other control group(n=19) were not treated. For the evaluation of the executive cognitive function, a Wisconsin Card Sorting Test(WCST) was administered before and after the introduction of the board-game therapy. PANSS score change was also evaluated. Result : At the beginning of this study, there was no significant difference in performance of cognitive function tests, demographical data or clinical severity between both patient groups. After 2 months of treatment with the board-game therapy, the board-game therapy group showed significant improvements of executive cognitive function without any significant change of their schizophrenic symptoms. On the contrary, there was no change in control group. Conclusion : This study showed that a board-game therapy is effective for the enhancement of executive cognitive function in patients with chronic schizophrenia. A board-game therapy could be introduced with ease into psychiatric fields, such as inpatients' or outpatients' clinic wards and day hospital. Our result indicates that the board-game therapy is a promising tool for the enhancement of cognitive function, especially executive cognitive function and helpful for cognitive rehabilitation for schizophrenic patients.

• 대한인간공학회지
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• 제29권6호
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• pp.907-914
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• 2010

Cognitive model, that is cognitive architecture, is the model expressed with computer program to show the process how human solve a certain problem and it is continuously under investigation through various fields of study such as cognitive engineering, computer engineering, and cognitive psychology. In addition, the much extensive applicability of cognitive model usually helps it to be used for quantitative prediction of human Behavior or Natural programming of human performance in many HCI areas including User Interface Usability, artificial intelligence, natural programming language and also Robot engineering. Meanwhile, when a system designed, an usability test about conceptual design of interface is needed and in this case, analysis evaluation using cognitive model like GOMS or ACT-R is much more effective than empirical evaluation which naturally needs products and subjects. In particular, if we consider the recent trend of very short-end term between a previous technology development and the next new one, it would take time and much efforts to choose subjects and train them in order to conduct usability test which is repeatedly followed in the process of a system development and this finally would bring delays of development of a new system. In this study, we predicted quantitatively the human behavior processes which contains cognitive processes for menu selection in touch screen interface through ACT-R, one of the common method of usability test. Throughout the study, it was shown that the result using cognitive model was equal with the result using existing empirical evaluation. And it is expected that cognitive model has a possibility not only to be used as an effective methodology for evaluation of HCI products or system but also to contribute the activation of HCI cognitive modeling in Korea.

• 대한통합의학회지
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• 제9권4호
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• pp.201-210
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• 2021

Purpose : There is a lack of research on this field in the Republic of Korea, especially those that have seen the effect of interaction between transcranial direct current stimulation and computerized cognitive rehabilitation therapy. This study divided 30 dementia patients into a treatment group, which received transcranial direct current stimulation and computerized cognitive rehabilitation, and a control group, which received pseudo-transcranial direct current stimulation and pseudo-computerized cognitive rehabilitation. This study evaluated the effects of these treatments on the visual perception, cognition functions, and daily activities of dementia patients. Methods : Fifteen subjects were allocated to the treatment group and the other 15 subjects were allocated to the control group. Treatments were given at intervals of five sessions per week (30 minutes per session) for six weeks (30 times in total). This study used the Neurobehavioral Cognitive Status Examination (NCSE) to examine cognitive functions, MVPT to evaluate visual perception, and FIM to test daily living activities before and after applying the treatments. Results : The results of this study showed that cognitive functions, visual perception, and daily living activities significantly (p<.05) improved after the intervention in the treatment group and the control group. The changes in cognitive functions, visual perception, and daily living activities due to the treatments were significantly different between the groups (p<.05). Conclusion : The results indicated that transcranial direct current stimulation and computerized cognitive rehabilitation therapy improved visual perception and daily living activities by increasing cognitive functions. Consequently, it was found that the simultaneous application of transcranial direct current stimulation in conjunction with a computerized cognitive rehabilitation program was an intervention method that could positively affect the visual perception, cognitive function, and daily living activities of dementia patients. Based on the results of this study, the study of arbitration protocols for demential will have to be more active.

• Physical Therapy Rehabilitation Science
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• 제13권1호
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• pp.43-52
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• 2024

Objective: This study aimed to investigate the impact of a 12-week combined cognitive and physical exercise program on cognitive and physical functions in older adults diagnosed with mild cognitive impairment (MCI). Design: A one-group pretest-posttest study. Methods: Twelve participants with MCI engaged in a weekly 60-minute session of combined cognitive and physical exercise program. Cognitive function was assessed using the Montreal Cognitive Assessment (MoCA), while physical function was evaluated through measures of muscle strength, postural balance, and walking capabilities. Muscle strength assessments included the arm curl test, handgrip strength, and the 5 sit-to-stand test. Postural balance was evaluated using the one-leg stance test, timed up-and-go test, functional reach test, and four square step test. Walking function was analyzed through a gait analysis device. Pre- and post-intervention measurements were compared to determine the effects of the exercise program. Results: The results demonstrated significant improvements in MoCA, arm curl test, timed up-and-go test, walking speed, and cadence following the 12-week intervention (p<0.05). MoCA scores revealed enhanced cognitive performance, while measures of muscle strength, including the arm curl test, exhibited significant changes. Improvements in timed up-and-go test scores indicated enhanced mobility, accompanied by increased walking speed and cadence, as evidenced by gait analysis. Conclusions: This study suggests that a structured 12-week program incorporating both cognitive and physical exercises can lead to meaningful improvements in cognitive and physical functions among older adults with MCI.

• 대한인간공학회지
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• 제21권3호
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• pp.47-58
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• 2002

The similarity of shape of shape of interface between human cognitive map and real product is the important factor to determine the human performance. Nevertheless, the degree of similarity between these has not been defined quantitatively in recent studies. Therefore, in this study, the cognitive map and the mental workload were measured by SMM(Sketch Map Method) and RNASA-TLX(Revision of NASA-Task Load Index). And the numerical expression of the accuracy point was suggested for the quantitative calculation of relative positional similarity between cognitive map and real product. In the experiment, nine subjects were participated and two kinds of vehicles were used. Mental workload was mental workload was measured immediately after the road test. The result of analysis on the relationship between accuracy and mental workload shows that the negative correlation exists on each vehicle, and the lower score of mental workloads id measured on the vehicle that has the higher score of accuracy between two vehicles.

• Journal of Communications and Networks
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• 제16권2호
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• pp.146-154
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• 2014

This paper proposes a bandwidth-aware localized-routing algorithm that is capable of sensing the available spectrum bands within a two-hop neighboring for choosing the highly opportunistic routes. A mixed-integer linear programming (MILP) is utilized to formulate the optimization problem. Then, the proposed algorithm is used to determine the maximum bandwidth possible of link pairs via a bandwidth approximation process of relaxed variables. Thereby, the proposed algorithm can allow selected routes corresponding to maximum bandwidth possible between cognitive radio (CR) users through link pairs in cognitive radio networks. By comparing the solution values to previous works, simulation results demonstrate that the proposed algorithm can offer a closed-optimal solution for routing performance in cognitive radio networks. The contribution of this paper is achieved through approximately 50% throughput utilized in the network.

• IEIE Transactions on Smart Processing and Computing
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• 제3권4호
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• pp.173-180
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• 2014

Random access protocols feature inherent sensing functionality and distributed coordination, making them suitable for cognitive radio communication environments, where secondary users must detect the white space of the primary spectrum and utilize the idle primary spectrum efficiently without centralized control. These characteristics have led to the adoption of carrier-sensing-multiple-access/collision-avoidance (CSMA/CA) in cognitive radio. This paper proposes a new analytical framework for evaluating the performance of a CSMA/CA protocol that considers the characteristics of idle periods based on the primary traffic behavior in cognitive radio systems. In particular, the CSMA/CA-based secondary network was analyzed in the terms of idle period utilization, which is the average effective data transmission time portion in an idle period. The use of the idle period was maximized by taking its statistical features into consideration.

• Journal of information and communication convergence engineering
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• 제13권4호
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• pp.221-227
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• 2015

Spectrum sensing plays an essential role in a cognitive radio network, which enables opportunistic access to an underutilized licensed spectrum. In conventional cooperative spectrum sensing (CSS), all cognitive users (CUs) in the network spend the same amount of time on spectrum sensing and waste time in remaining silent when other CUs report their sensing results to the fusion center. This problem is solved by the superposition cooperative spectrum sensing (SPCSS) scheme, where the sensing time of a CU is extended to the reporting time of the other CUs. Subsequently, SPCSS assigns the CUs different sensing times and thus affects both the sensing performance and the throughput of the system. In this paper, we propose an algorithm to determine the optimal sensing time of each CU for SPCSS that maximizes the achieved system throughput. The simulation results prove that the proposed scheme can significantly improve the throughput of the cognitive radio network compared with the conventional CSS.