• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.21-40
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• 2018

In this paper, we propose the distributed robust beamforming design scheme in cognitive two-way amplify-and-forward (AF) relay networks with imperfect channel state information (CSI). Assuming the CSI errors follow a complex Gaussian distribution, the objective of this paper is to design the robust beamformer which minimizes the total transmit power of the collaborative relays. This design will guarantee the outage probability of signal-to-interference-plus-noise ratio (SINR) beyond a target level at each secondary user (SU), and satisfies the outage probability of interference generated on the primary user (PU) above the predetermined maximum tolerable interference power. Due to the multiple CSI uncertainties in the two-way transmission, the probabilistic constrained optimization problem is intractable and difficult to obtain a closed-form solution. To deal with this, we reformulate the problem to the standard form through a series of matrix transformations. We then accomplish the problem by using the probabilistic approach based on two sorts of Bernstein-type inequalities and the worst-case approach based on S-Procedure. The simulation results indicate that the robust beamforming designs based on the probabilistic method and the worst-case method are both robust to the CSI errors. Meanwhile, the probabilistic method can provide higher feasibility rate and consumes less power.

• Journal of the Korean Society of Safety
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• v.29 no.1
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• pp.47-53
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• 2014

The application of advanced Main Control Room(MCR) is accompanied with lots of changes and different forms and features through the virtue of new digital technologies. The characteristics of these digital technologies and devices give many opportunities to the interface management, and can be integrated into a compact single workstation in advanced MCR so that workers can operate the plant with minimum physical burden under any operation conditions. However, these devices may introduce new types of human errors and thus a means to evaluate and prevent such errors is needed, especially those related to characteristics of digital devices. This paper reviewed the new type of human error hazards of tasks based on digital devices and surveyed researches on physiological assessment related to human error. An experiment was performed to verify human error hazards by physiological responses such as EEG which was measured to evaluate the cognitive workload of operators. And also, the performances of four tasks which are representative in human error hazard tasks based on digital devices were compared. Response time, ${\beta}$ power spectrum rate of each task by EEG, and mental workload by NASA-TLX were evaluated. In the results of the experiment, the rate of the ${\beta}$ power was increased in the task 1 and task 4 which are searching and navigating task and memory task of hierarchical information, respectively. In case of the mental workload, in most of evaluation items, task 1 and 4 were highly rated comparatively. In this paper, human error hazards might be identified by highly cognitive workload. Conclusively, it was concluded that the predictive method which is utilized in this paper and an experimental verification can be used to ensure the safety when applying the digital devices in Nuclear Power Plants (NPPs).

• Journal of the Korean Society of Safety
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• v.37 no.2
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• pp.35-42
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• 2022

When an accident occurs, the associated human activity is typically regarded as a "human error," or a temporal deviation. On the other hand, if the accident results in a serious loss or if it evokes a social issue, the person determined to be responsible may be punished with a "violation" of related laws or regulations. However, as Heinrich stated, it is neither appropriate nor reasonable in terms of probability theory and cognitive science to distinguish whether it is a "human error" or a "violation" with a criterion of resultant accident severity. Nonetheless, some in society get on the social climate to strengthen regulations on workers who have caused accidents, especially violations. This response can present a social issue due to the lack of systematic judgment procedure which distinguishes violations from human errors. The purpose of this study was to develop an objective and systematic procedure to assess whether workers' activities which induced industrial accidents should be categorized as violations rather than human errors. Various analysis techniques for the determination of violation procedure were investigated and compared using an analysis approach method. An appropriate technique was not found, however, for judging the culpability of intentional violations. As an alternative, this study developed the process of creating violations, based on cognitive procedure, as well as the criteria to determine and categorize an activity as a violation. In addition, the developed procedure was applied to cases of industrial accidents and nuclear power plant issues to test its practical applicability. The study demonstrated that the proposed model could be used to determine the existence of a violation even in the case of multiple workers who work simultaneously.

• Korean Journal of Cognitive Science
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• v.18 no.2
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• pp.193-221
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• 2007

This study explored the efficient hierarchical data structure of mobile interfaces. The first experiment demonstrated the effects of grouping(clear/unclear), depth level(2/3/5), and the number of items(32/64/128) on the search time and the number of errors. The results indicated that participants spent less time and made fewer errors to perform the task when the clear mobile interfaces, low depth level, and fewer items were provided. In addition, the results indicated that there were no effects of the depth level and the number of items on the search time and number of errors in clear mobile interfaces conditions. As depth level and the number of items changed, on the other hand, participants spent longer time to complete the task and made more mistakes in unclear mobile interfaces conditions. The second experiment investigated the effects of grouping(clear/unclear), the number of items(32/64/128), and spacial cues(colors/ windows/ number of cues) on search time and the number of errors in hierarchical data structures which had five depth levels. The results indicated that participants spent less time to complete the task and made less errors in a mobile interface when grouping is clear and the number of items are fewer. The results were identical with the first experiments. In addition, the main effect of spacial cues indicated that providing spacial cues via pictures and numbers can be helpful to reduce errors in search behaviors.

• Safety and Health at Work
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• v.9 no.2
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• pp.203-209
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• 2018

Background: Night shift work is associated with many problems such as sleep deprivation, sleepiness, decreased cognitive performance, increased human errors, and fatigue. This study set out to measure cognitive performance, melatonin rhythms, and sleep after different consecutive night shifts (7 vs. 4) among control room operators (CORs). Methods: The participants included 60 CORs with a mean age of 30.2 years (standard deviation, 2.0) from a petrochemical complex located in Southern Iran. Cognitive performance was assessed using the n-back task and continuous performance test. To evaluate melatonin, saliva was collected and tested by enzyme-linked immunosorbent assay. To assess sleep and sleepiness, the Pittsburgh Sleep Quality Index and Karolinska Sleepiness Scale were used, respectively. Results: Individuals who worked 7 consecutive night shifts had a significantly better cognitive performance and sleep quality than those who worked 4 consecutive night shifts. However, salivary melatonin profile and sleepiness trend were not affected by shift type. Conclusion: The main duty of CORs working night shifts at the studied industry included managing safety-critical processes through complex displays; a responsibility that demands good cognitive performance and alertness. It is suggested that an appropriate number of consecutive night shifts in a rotating shift system should be planned with the ultimate aim of improving CROs performance/alertness and enhancing safety.

• Journal of Digital Convergence
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• v.10 no.11
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• pp.323-329
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• 2012

This study examines the anchoring effect and the adjustment process of two variables(verbal information, cognition load) with snack products. In the results of this study, 1) we found the anchoring effect because the respondents predicted more the number of real units(goraebap) on the packaging painted 25 units than 5 ones. 2) We confirmed the moderating effect of verbal information. The difference of the number of real units predicted between the two packaging was decreased when the visual information was in company with verbal information. And 3) the moderating effect of cognitive load appeared because the more cognitive load was, the less the difference of the number of real units predicted was. This study has shown that we can reduce the errors and biases by adjusting the information frame or the cognitive load. This research provides a theoretical-practical implications to the marketing staffs like packaging designers as well as scholars to study consumer psychology.

• Journal of the Korea Society of Computer and Information
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• v.11 no.2 s.40
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• pp.319-327
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• 2006

Higher grade elementary school students who have superior cognitive abilities need education of basic principles of computer or programming rather than computer in education. In this study, all the errors occurring while elementary school students wrote and executed programs were collected. in the method of predicting and dealing with possible-to-occur problems on programming education of the higher grades (4th, 5th and 6th grades) during their optional special activities or during talent aptitude activities after school, classified by type and analyzed. If the errors analyzed are put to practical use, optimal programming curriculums could be written and such curriculums could be a great contribution to induction of learning effect and interest on teaching learning. It was found by analyzing the errors collected for this study that the most of elementary school students during programming felt difficulties in simple errors by poor use of software and in simple coding by poor use of reserved words in English. In the next, students occurred errors by difficulties in understanding grammar. It was exposed that these error types were the opposite phenomena to those analyzed by commercial software developing companies, however, it is predicted that if teaching learning is setting improved, the same phenomena could be found desirably.

• Korean Journal of Cognitive Science
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• v.3 no.1
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• pp.25-39
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• 1991

When an ending which begins with 'a/a'combines to a stem,'a/a'can be deleted.Especially when ot combines to an h-irregular verb,it is represented as a variant like '-a-','-e-','-ia-',or'-ie-'.In order to analyze the variants of 'a/a',we suggest the format of a grammatical morpheme dictionary which is represented as a binary tree and several procedures which process the variants so that the unexpected errors can be removed which occur frequently when we analyze Korean worl phrase.

• ETRI Journal
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• v.36 no.4
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• pp.545-553
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• 2014

This paper proposes an algorithm to sense orthogonal frequency-division multiplexing (OFDM) signals in cognitive radio (CR) systems. The basic idea behind this study is when a primary user is occupying a wireless channel, the covariance matrix is non-diagonal because of the time domain cross-correlation of the cyclic prefix (CP). In light of this property, a new decision metric that measures the power of the data found on two minor diagonals in the covariance matrix related to the CP is introduced. The impact of synchronization errors on the signal detection is analyzed. Besides this, a likelihood-ratio test is proposed according to the Neyman-Pearson criterion after deriving probability distribution functions of the decision metric under hypotheses of signal presence and absence. A threshold, subject to the requirement of probability of false alarm, is derived; also the probabilities of detection and false alarm are computed accordingly. Finally, numerical simulations are conducted to demonstrate the effectiveness of the proposed algorithm.

• Industrial Engineering and Management Systems
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• v.10 no.4
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• pp.288-291
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• 2011

Recommendations for older driver-friendly automobile interior design have been determined by taking into account older people's physical and cognitive characteristics. Twenty three older people (aged from 54 to 78) and five younger people (from 20 to 29) performed several tasks in actual driving conditions, in which their reaction times and performance errors were recorded. Some design factors were found to be related to older drivers' visibility and controllability. Several design recommendations were proposed in terms of cluster color and font, display location, and HVAC control type. Proposed recommendations are expected to satisfy a wider range of older drivers as these will facilitate automobile interior designs which are fitter to older drivers' visual, cognitive, and manual capabilities.