• The Journal of Information Systems
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• v.24 no.2
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• pp.53-72
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• 2015

Purpose The purpose of this study was to investigate the factors affecting the users' stress and using reluctant intention to use social network service(SNS). This study especially focused on stress of SNSs' user. Because SNS has led to negative effects such as invasion of privacy, addiction and social overload recently. In addition, adverse effects of SNS had caused SNSs' user to feel stress and fatigue. Design/methodology/approach This study developed hypotheses to empirically examine the factors that affect SNS users' stress and using reluctant intention. In order to verify research hypotheses, this study collected data from 362 users who currently use the SNS in Korea. Further, we used the smartPLS analysis. Findings The results of this study are as follows; First, reputation perception, unwanted relation burden, privacy concern, information overload and interaction overload had a significant positive effect on SNS users' stress. But international influence had no significant positive effect on SNS users' stress. Second, SNS users' stress had a significant positive effect on using reluctant intention. The results of this study provides theoretical foundations on the research for dark side of SNS and implies that SNS providers are in need of exerting an effort to minimize the negative aspects.

• Smart Structures and Systems
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• v.15 no.2
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• pp.395-408
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• 2015

This study aims to propose a Bayesian approach to consider changes in temperature and vehicle weight as environmental and operational factors for vibration-based long-term bridge health monitoring. The Bayesian approach consists of three steps: step 1 is to identify damage-sensitive features from coefficients of the auto-regressive model utilizing bridge accelerations; step 2 is to perform a regression analysis of the damage-sensitive features to consider environmental and operational changes by means of the Bayesian regression; and step 3 is to make a decision on the bridge health condition based on residuals, differences between the observed and predicted damage-sensitive features, utilizing 95% confidence interval and the Bayesian hypothesis testing. Feasibility of the proposed approach is examined utilizing monitoring data on an in-service bridge recorded over a one-year period. Observations through the study demonstrated that the Bayesian regression considering environmental and operational changes led to more accurate results than that without considering environmental and operational changes. The Bayesian hypothesis testing utilizing data from the healthy bridge, the damage probability of the bridge was judged as no damage.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.3
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• pp.872-885
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• 2015

The rapid increase of smart mobile devices and mobile applications has led to explosive growth of data traffic in cellular network. Offloading data traffic becomes one of the most urgent technical problems. Recent work has proposed to exploit opportunistic communications to offload cellular traffic for mobile data dissemination services, especially for accepting large delayed data. The basic idea is to deliver the data to only part of subscribers (called target-nodes) via the cellular network, and allow target-nodes to disseminate the data through opportunistic communications. Human mobility shows temporal and spatial characteristics and predictability, which can be used as effective guidance efficient opportunistic communication. Therefore, based on the regularity of human mobility we propose NodeRank algorithm which uses the encounter characteristics between nodes to choose target nodes. Different from the existing work which only using encounter frequency, NodeRank algorithm combined the contact time and inter-contact time meanwhile to ensure integrity and availability of message delivery. The simulation results based on real-world mobility traces show the performance advantages of NodeRank in offloading efficiency and network redundant copies.

• Human Ecology Research
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• v.52 no.4
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• pp.429-441
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• 2014

The use of smartphones has grown rapidly over a short period of time, particularly for commuting news search, smart banking, and social networking services, and has had a significant impact on the pattern of contemporary life. Further, a wide range of applications are downloaded on to smartphones. This has also led a considerable number of complaints regarding these applications. In this study, we focus on the levels of dissatisfaction that users experience with smartphone applications and their effects on consumer complaint behavior along with the moderating effects of the complaint handling process and attribution. The aim of this study is to verify whether the following hypothesis--2 (low/high dissatisfaction level of smartphone applications)${\times}2$ (poor/excellent complaint handling process)${\times}2$ (internal/external consumer attribution)--is in accordance with the betweengroup design to build a factorial design experiment. The results of this study are as follows. First, the consumer's tendency to complain significantly influenced their dissatisfaction level. Second, consumer complaint behavior is modulated by the complaint handling process. Third, the external-attribution tendency of consumers was found to lead to more dissatisfaction than the tendency for internal attribution.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.834-848
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• 2013

To effectively use these functions many kinds of human-phone interface are used such as touch, voice, and gesture. However, the most important touch interface cannot be used in case of hand disabled person or busy both hands. Although eye tracking is a superb human-computer interface method, it has not been applied to smartphones because of the small screen size, the frequently changing geometric position between the user's face and phone screen, and the low resolution of the frontal cameras. In this paper, a new eye tracking method is proposed to act as a smartphone user interface. To maximize eye image resolution, a zoom lens and three infrared LEDs are adopted. Our proposed method has following novelties. Firstly, appropriate camera specification and image resolution are analyzed in order to smartphone based gaze tracking method. Secondly, facial movement is allowable in case of one eye region is included in image. Thirdly, the proposed method can be operated in case of both landscape and portrait screen modes. Fourthly, only two LED reflective positions are used in order to calculate gaze position on the basis of 2D geometric relation between reflective rectangle and screen. Fifthly, a prototype mock-up design module is made in order to confirm feasibility for applying to actual smart-phone. Experimental results showed that the gaze estimation error was about 31 pixels at a screen resolution of $480{\times}800$ and the average hit ratio of a $5{\times}4$ icon grid was 94.6%.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.377-389
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• 2014

In recent years, Smart Water Grid (SWG) concept has globally emerged over the last decade and also gained significant recognition in South Korea. Especially, there has been growing interest in water demand forecast and this has led to various studies regarding energy saving and improvement of water supply reliability. In this regard, this study aims to develop a nonlinear ensemble model for hourly water demand forecasting which allow us to estimate uncertainties across different model classes. The concepts was demonstrated through application to observed from water plant (A) in the South Korea. Various statistics (e.g. the efficiency coefficient, the correlation coefficient, the root mean square error, and a maximum error rate) were evaluated to investigate model efficiency. The ensemble based model with an cross-validate prediction procedure showed better predictability for water demand forecasting at different temporal resolutions. In particular, the performance of the ensemble model on hourly water demand data showed promising results against other individual prediction schemes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.12
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• pp.54-62
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• 2013

In this study, a mock powder room was installed with variable LED lighting environments in order to conduct the experiments. The experimental conditions include luminaire type, illuminance ratio, vertical illuminance and color temperatures. The evaluation methods used were the Semantic Differential Method and a subjective evaluation on activities through observation. The SD evaluation result factor analysis categorizes ideas into three factors: brightness, emotion, and glare. The vertical bracket or the combined luminaire (luminous panel+ Vertical bracket) has better brightness than luminous panel. A vertical illuminance of 500lx is not significantly difference as compared to 600lx, allowing 500lx to be considered standard. The emotional atmosphere is evaluated as being better at lower color temperature. The luminous panel is the best for reducing glare while the vertical bracket is the worst. The best conditions differ according to the illuminance ratio of the luminous panel and vertical bracket. In the subjective evaluation (satisfaction with lighting environment, suitability to activity) the combined luminaire and 4000K received the best evaluation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2B
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• pp.225-231
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• 2010

In this paper, a sensor network system for providing u-health services is suggested and is implemented. It steadily collects biological data of resident people and automatically detects emergency situations. LEID (Lighting Embedded Information Device) nodes are the most essential component of the sensor network. They embed sensor network technology into lightening devices which are indispensable to most living spaces. To verify practicality of the proposed u-health system, a prototypical system is realized in the Smart Home Industrialization Support Center at Kookmin University, and is tested within many practical circumstances. The proposed u-health system can be used at various places where many patients are continuously cared.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.4
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• pp.269-275
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• 2017

Automatic vehicle detection is a very important function for autonomous vehicles. Conventional vehicle detection approaches are based on visible-light images obtained from cameras mounted on a vehicle in the daytime. However, unlike daytime, a visible-light image is generally dark at night, and the contrast is low, which makes it difficult to recognize a vehicle. As a feature point that can be used even in the low light conditions of nighttime, the rear lamp is virtually unique. However, conventional rear lamp-based detection methods seldom cope with atypical lamps, such as LED lamps, or flashing turn signals. In this paper, we detect atypical lamps by blurring the lamp area with a low pass filter (LPF) to make out the lamp shape. We also propose to detect flickering of the turn signal lamp in a manner such that the lamp area is vertically projected, and the maximum difference of two paired lamps is examined. Experimental results show that the proposed algorithm has a higher F-measure value of 0.24 than the conventional lamp pairing-based detection methods, on average. In addition, the proposed algorithm shows a fast processing time of 6.4 ms per frame, which verifies real-time performance of the proposed algorithm.

• Journal of the Korean Society of Costume
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• v.64 no.6
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• pp.120-130
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• 2014

The present study aimed to find out the most effective instructional method for illustration to aid the $21^{st}$-century post digital generation learners in their education. Although the literature discusses government-led enactment and revision of educational policy and curriculums and research reports by the Ministry of Education and other government agencies as well as many other research articles deal with futuristic instructional methods, the instructional methods in practice have not fully changed yet. Illustration is a means of visual communication and a subject that best represent 'expressionism' and 'speed' of the post digital generation. The present study exemplifies instructional methods to establish the need for lesson plans that best suit individuality of students and for re-training instructors. Also, the feedback process with students proved that the post digital generation learned Photoshop quickly and improved creativity via image synthesis even in short-term instructions. The present findings can be possibly used as reference data for instructional methods for illustration using digital media that best suits learners of the post digital generation. This being said, further studies should delve into specific instructional methods.