• 대한의용생체공학회:의공학회지
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• 제27권6호
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• pp.323-331
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• 2006

The purpose of this study was to investigate the effect of performing a cognitive task during treadmill walking on the stride rate variability. Ten university students(age $24.0{\pm}0.25$, height $172{\pm}3.1cm$, weight $66{\pm}5.3kg$) were participated in dual task experiments which consist of both walking alone and walking with a cognitive task. Two-back task was selected for the cognitive task since it did not have learning effect during the experimental procedure.3D motion analysis system was used to measure subject's position data by changing walking speed with 4.8, 5.6, 6.4, 6.8, and 7.2 km/hr. Stride rate was calculated by the time between heel contact and heel contact. Accuracy rate of a cognitive task during walking, coefficient of variance, allometric scaling methods and Fano factor were used to estimated the stride rate variability. As the walking speed increased, accuracy rate decreased and the logarithmic value of Fano factor increased which showed the statistical difference. Thus it can be concluded that the gait control mechanism is distracted by the secondary attention focus which is the cognitive task ie. two-back task. Further study is needed to clarify this by increasing the number of subject and experiment time.

• 아동학회지
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• 제8권1호
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• pp.65-82
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• 1987

The purpose of the present research was to study mothers' perceptions about their children' cognitive abilities and the relations between such perceptions and the children's cognitive level. The subjects of this study were 60 children (mean age: 6 years 1 month: age range = 5;8 to 6;7) and their mothers. Each child responded to 18 tasks drawn from the Kodae-Binet IQ test. Subsequently, the mothers were asked 4 questions: an estimate of her child's success or failure on the tasks, a rating of the certainty of her judgment, an estimate of the age of mastery on each task both for her owr child and children in general. The data of the present study were analyzed with the 3-way ANOVA (sex x birth order x mother's education level), t-test, and Pearson correlation coefficient. Significant differences were found in (1) mothers' accuracy of their children's cognitive abilities according to children's birth order, (2) mothers' accuracy, overestimation, and certainty according to the level of difficulty of each task, and (3) mothers' estimate of age at mastery according to the level of each task. Furthermore, there were positive correlations between accurate predictions by the mother and correct answers by the child and between overestimations by the mother and correct answers by the child.

• Journal of information and communication convergence engineering
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• 제14권1호
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• pp.1-8
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• 2016

Spectrum sensing in cognitive radio networks allows secondary users to sense the unused spectrum without causing interference to primary users. Cognitive radio requires more accurate sensing results from unused portions of the spectrum. Accurate spectrum sensing techniques can reduce the probability of false alarms and misdetection. In this paper, a two-stage spectrum sensing scheme is proposed for cooperative spectrum sensing in cognitive radio networks. In the first stage, spectrum sensing is executed for each secondary user using energy detection based on double adaptive thresholds to determine the spectrum condition. If the energy value lies between two thresholds, a fuzzy logic scheme is applied to determine the channel conditions more accurately. In the second stage, a fusion center combines the results of each secondary user and uses a fuzzy logic scheme for combining all decisions. The simulation results show that the proposed scheme provides increased sensing accuracy by about 20% in some cases.

• 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.

• International journal of advanced smart convergence
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• 제12권2호
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• pp.17-24
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• 2023

Given the surge in the elderly population, and increasing in dementia cases, there is a growing interest in digital therapies that facilitate steady remote treatment. However, in the cognitive assessment of digital therapies through clinical trials, the absence of log data as an essential evaluation factor is a significant issue. To address this, we propose a solution of utilizing weighted derived variables based on high-importance variables' accuracy in log data utilization as an indirect cognitive assessment factor for digital therapies. We have validated the effectiveness of this approach using machine learning techniques such as XGBoost, LGBM, and CatBoost. Thus, we suggest the use of log data as a rapid and indirect cognitive evaluation factor for digital therapy users.

• 한국어교육
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• 제28권4호
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• pp.1-38
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• 2017

This longitudinal study analyzed syntactic development (Complexity, Accuracy, and Fluency; CAF) of six L2 Korean learners in a natural learning context. The learners recalled the stories of a short animated video through speaking and writing every 3 months, from month 0 to 15. The learners' responses were analyzed for a series of CAF measures and their cognitive, psychological, and social variables were investigated. The results showed that (i) L2 Korean learners' speaking and writing in various time periods showed significant differences in spoken and written accuracy, and complexity; (ii) the correlation between spoken and written complexity, spoken and written accuracy, as well as spoken and written fluency were significant, and (iii) the regression analysis showed that learners' cognitive, social, and psychological variables have significant effect on the L2 Korean syntactic development. The current study reports that L2 Korean learners engaged in self-learning in a natural learning environment without formal instruction made significant syntactic development.

• International Journal of Internet, Broadcasting and Communication
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• 제14권3호
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• pp.230-242
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• 2022

The purpose of this study was to verify the effectiveness of the computerized cognitive rehabilitation program in which areas and to suggest effective ways to utilize the program in the future, being conducted for 20 college students. We lasted this study from May 3 to 23, 2021. As a result of analyzing the groups using the Computer-based Cognitive Rehabilitation Program (CoTras), in terms of the difference in accuracy for the case of visual perception group B was statistically significantly improved than group C(p<0.05). In the case of attention, memory, and orientation, there was no significant difference between groups(p>0.05). In the case of reaction time difference, there was no significant difference between groups in visual perception, concentration, memory, and orientation(p>0.05). And in order to improve attention and visual perception, it is recommended to conduct the program three times with a duration of 20 minutes, and in order to improve orientation and memory, it can be said that it is helpful to conduct one experiment for at least 30 minutes rather than conducting short and frequent experiments. Through this study, we found that it is effective to apply different times according to each area to improve cognitive function. In other words, depending on the purpose of which cognitive function is to be improved, the duration of the program should be applied differently.

• 대한의용생체공학회:의공학회지
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• 제43권4호
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• pp.185-192
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• 2022

Early detection of mild cognitive impairment can help prevent the progression of dementia. The purpose of this study was to design and validate a machine learning model that automatically differential diagnosed patients with mild cognitive impairment and identified cognitive decline characteristics compared to a control group with normal cognition using resting-state quantitative electroencephalogram (qEEG) with eyes closed. In the first step, a rectified signal was obtained through a preprocessing process that receives a quantitative EEG signal as an input and removes noise through a filter and independent component analysis (ICA). Frequency analysis and non-linear features were extracted from the rectified signal, and the 3067 extracted features were used as input of a linear support vector machine (SVM), a representative algorithm among machine learning algorithms, and classified into mild cognitive impairment patients and normal cognitive adults. As a result of classification analysis of 58 normal cognitive group and 80 patients in mild cognitive impairment, the accuracy of SVM was 86.2%. In patients with mild cognitive impairment, alpha band power was decreased in the frontal lobe, and high beta band power was increased in the frontal lobe compared to the normal cognitive group. Also, the gamma band power of the occipital-parietal lobe was decreased in mild cognitive impairment. These results represented that quantitative EEG can be used as a meaningful biomarker to discriminate cognitive decline.

• 감성과학
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• 제10권4호
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• pp.583-601
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• 2007

웨어러블 컴퓨팅 환경은 대개 이동 중일 가능성이 많고 이때 눈과 손이 자유롭지 못하고 많은 주의가 필요한데 기존의 데스크탑 인터페이스 방식(WIMP)은 적합하지 않다. 또한 웨어러블 환경에서 모바일 기기의 소형화로 인하여 작은 화면에서 정보를 확인하고 처리해야 하기 때문에 기능 수행에 따른 인지부하가 늘어남과 동시에 수행 속도가 느려지고 많은 오류가 발생하는 등 어려움이 따른다. 이와 같이 변화된 환경에 적합한 입력 방식의 적정 수준을 찾는 연구가 필요하다. 본 연구는 이동 상황에서 모바일 기기를 사용할 때 동시에 여러 가지 일을 수행함으로써 걸릴 수 있는 인지부하를 줄여주기 위한 방법을 기기의 입력 방식과 사용되는 메뉴구조의 복잡성을 중심으로 분석하였다. 입력 방식을 포인팅입력 방식, 버튼입력 방식, 동작입력 방식으로 나누고, 이 방식들을 통한 메뉴탐색 과제와 화면에 제시되는 도형기억 과제를 동시에 수행했을 때 수행의 정확도와 과제수행 속도를 측정하였다. 또한 제시되는 메뉴탐색 과제의 메뉴계층의 수를 변화시켜서 입력 방식의 복잡성에 따른 과제 수행을 살펴보았다. 실험은 정지 상황과 이동 상황에서 모두 이루어졌다. 정지 상황과 이동 상황 모두에서 포인팅입력 방식이 과제 수행의 정확도가 가장 높은 반면 수행 속도에서 가장 느린 것으로 나타났다. 동작입력 방식에서는 수행의 정확도는 떨어졌으나 수행 속도는 빠르게 나타났다. 이는 이동 중에 수행되는 과제에서 정확도보다도 속도가 중요한 상황에서는 동작입력 방식이 적합하다는 것을 시사한다.

• 대한의용생체공학회:의공학회지
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• 제43권1호
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• pp.52-60
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• 2022

Purpose: For now, cognitive load is assessed based on survey-based methods, which can be difficult to track the amount of cognitive load in real-time. In this study, we investigated the difference in electrophysiological activation due to different levels of cognitive load not only at sensor-level but also at source-level using electroencephalogram that might be potentially used for quantitative cognitive load evaluation. Materials and Methods: In this study, ten healthy subjects (mean age 24.3 ± 2.1, three female) participated the experiment. All participants performed 4 sessions of n-back task in different difficulties: 0-, 1-, 2-, and 3-back during electroencephalogram recording. For sensor-level analysis, we calculated the event-related potential and event-related spectral perturbation while low resolution brain electromagnetic tomography (LORETA) to estimate the source activation. Each result was compared between different workload conditions using statistical analysis. Results: Statistical results revealed that the accuracy of the task performance was significantly different between different cognitive loads (p = 0.018). The post-hoc analysis confirmed that the accuracy of the 3-back task was significantly decreased compared to 1-back condition (p = 0.018), but not with 2-back condition (p = 0.180). ERP results showed that P300 target amplitude between 1-back and 3-back had a marginal difference in Cz (p = 0.059) and Pz(p = 0.093). A significant inhibition in Cz high-beta activation (p = 0.017) and decrease in source activation of right parahippocampal gyrus was found in 3-back condition compared to 1-back condition (p < 0.05). Conclusion: In this study, we compared the sensor- and source-level differences in electroencephalogram between different levels of cognitive load, that were found to be in line with the previous reports related to cognitive load evaluation. We expect that the outcome of the current study can be used as a feature to establish a quantitative cognitive load assessment system.