• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.189-199
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• 2016

Many implantable hearing aids are being developed as alternatives to conventional hearing aids which has inconveniences for use and social stigma that make hearing-impaired people avoid to wear it. Particularly, the fully-implantable middle ear hearing devices (F-IMEHD) are being actively studied for mixed or sensorineural hearing impaired people. In development of F-IMEHD, the most difficult problem is improving the performance of implantable microphone. Recently, Cho et al. have studied the tympanic membrane installed microphone which has better sensitivity and is easier to operate on patient than the microphone implanted under the skin. But, it may cause howling problem due to the feedback signal via oval window and ossicle chain from the transducer on round window in the middle ear cavity, therefore, a feedback canceller is necessary. In this paper, we designed NLMS (normalized least mean square) adaptive feedback canceller for F-IMEHD with tympanic membrane installed microphone and a transducer implemented at round window, and computer simulation was performed to verify its operation. The designed adaptive feedback canceller has a delay filter, a 64 point FIR fixed filter and a 8-tap adaptive FIR filter. Computer simulation of the feedback path is modeled by using the data obtained through human cadaver experiment.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.438-443
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• 2003

In this paper, we propose a control algorithm for two-wheel mobile robot that can move the rider to his or her command and autonomously keep its balance. The control algorithm is based on a mixed $H_2/H_{\infty}$ control scheme. In this control problem the main issue is to move the rider while keeping its balance in the presence of disturbances and parameter uncertainties. The disturbance force caused by uneven road surfaces and the uncertainty due to different rider's heights are considered. To this end we first consider a state feedback controller as a basic framework. Secondly, we obtain the state feedback gain $K_2$ minimizing the $H_2$ norm and the state feedback gain $K_{\infty}$ minimizing the $H_{\infty}$ norm over the whole range of parameter uncertainty. Finally, we select mixed $H_2$/$H_{\infty}$ state feedback controller K as the geometric mean of $K_2$ and $K_{\infty}$. Simulation results show that the mixed $H_2/H_{\infty}$ state feedback controller combines the effects of the optimal $H_2$ state feedback controller and robust $H_{\infty}$ controller state feedback controller efficiently in the presence of disturbance and parameter uncertainty.

• Physical Therapy Korea
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• v.4 no.2
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• pp.59-65
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• 1997

To improve the effect of balance training, visual feedback is usually used. During the training process there are some factors which decrease the effect. Neurophysiologically, the main negative factor is thought to be synaptic fatigue which decreases the sensitivity of synapses. The purpose of this study was to find a more effective balance training method. In this study, a total of 60 normal subjects-19~30 years old young males and females(M=30, F=30)-participated, and they were randomized as A, B, and C group, each group containing 20 subjects. First, all groups had a pre-test of sway balance. One minute later, A group was trained in sway balance by continuous visual feedback for 2 minutes, B group by intermittent visual feedback which had 4 sessions of 30 seconds each and a one minute rest break. C group was not trained at all. All groups had a post-test. Only B group had improved balance compared with C group by ANOVA. On the other hand, intermittent visual feedback was more effective than continuous visual feedback in sway balance training with normal subjects.

• Korean Journal of Health Education and Promotion
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• v.23 no.2
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• pp.47-61
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• 2006

Object: This research has been conducted in order to conduct obesity prevention education providing feedback which is currently taught to the second grade students of middle school, understanding how this method of education affects the knowledge and of behavior towards obesity prevention, and that could be actually applied to classrooms. Method: A questionnaire was supplemented questionnaire whose content validity and reliability was verified in the preliminary research was used. The reliability of the research tool was Cronbach' ${\alpha}=0.70$ for obesity knowledge tool, and Cronbach' ${\alpha}=0.84$ for obesity prevention behavior tool. Result: 1) It turned out that feedback was significantly effective in improving the knowledge. 2) It turned out that the education method providing feedback was effective in improving the behavior. Conclusion: From the results of this research, it can be said that the obesity prevention education providing feedback was the most effective method in improving the obesity knowledge and prevention behavior of middle school students. Therefore, it is advisable that the obesity prevention education methods providing feedback should be developed and applied continuously.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.24 no.4
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• pp.91-98
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• 2013

The purpose of this study is to examine the effect of force feedback on video gamers' performance with two different types of game controllers, and to verify users' consistency on their perceptions of force feedback effect and their actual performances in video games. 42 qualified players' records on a driving video game were analyzed in this study. This study shows 1) the force feedback effect in video games depends on the type of game controllers, 2) there is inconsistency between gamers' perception on the force feedback effect and their actual performances with the force feedback effect, and 3) emotional pleasure (fun factor) plays a big role in gamers' performances.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.787-793
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• 2015

In order to support reliable medium access control (MAC) layer multicast services in Broadband Wireless Access (BWA) networks, we here propose spreading codes (Cumulative ACK (CA) code and ARQ Feedback Request (AFR) code) based reliable multicast feedback scheme. The status indications based on the automatic repeat request (ARQ) mechanism are needed in some multicast services. In accordance with various wireless channel environments, we demonstrate the performance excellency of our proposed scheme with respect to required uplink resources compared with the original feedback scheme based on unicast ARQ feedback messages. In addition, we analyze packet error rate (PER) against the various wireless channel environments.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.2
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• pp.53-69
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• 2007

Internet shopping websites have offered comfort to consumers in shopping and built trust relationships with them by providing electronic agents for recommendation, escrow services, and customer centers etc. But as there is little big difference among the shopping websites in terms of technical competence, website design, operational policy, they recognize online feedback (reviews or recommendation of consumers or experts) and online feedback mechanism as important marketing tools. Based on online feedback related studies, this study explores antecedents (consensus, vividness of reviews, interactions in review boards) of the perceived effectiveness of review boards which are text-based feedback mechanisms and its consequences such as trust, satisfaction, and intention to use. The results show that the perceived effectiveness of review boards is significantly affected by vividness of reviews and interactions in review boards, and the impact of interaction in review boards on the perceived effectiveness of review boards is stronger than that of vividness of reviews. The results also show that the perceived effectiveness of review boards has a significant influence on trust and satisfaction with the shopping websites, and intention to use is influenced by both trust and satisfaction.

• Journal of the Korean Society of Physical Medicine
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• v.5 no.3
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• pp.313-322
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• 2010

Purpose : This study was to evaluate the effects of cognitive rehabilitation training on the cognitive decline of dementia patients. Therefore the purpose of this study was to examine the influence of brain activation according to bio-feedback training in dementia. Methods : Ten dementia patients were recruited this study. Experiment was performed for 30min per session, five times a week through 4 week and two measurements before and after bio-feedback training. Brain activity was measured by Korea Electroencephalogram(EEG) system. Statistical analysis was used Wilcoxon signed rank test to know difference of EEG between pre and post-test in each group and Mann-Whitney U test was to know difference between experimental and control group. Results : Significant improvement of slow-alpha wave was observed following bio-feedback in experiment group. There was no significant change in experiment and control group. Conclusion : In this study, the bio-feedback training was effective in improving slow-alpha wave in dementia patients. It is suggested that bio-feedback training with dementia patients can be useful to ameliorate the cognitive decline. And it will be effective for prevention of cognitive function decline.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.20-28
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• 2014

This paper presents static output feedback LQ and $H_{\infty}$ controllers for rollover prevention. Linear quadratic static output feedback controllers have been proposed for rollover prevention in such a way to minimize the lateral acceleration and the roll angle. Rollover prevention capability can be enhanced if $H_{\infty}$ controller is designed. To avoid full-state measurement for feedback requirement or sensitiveness of an observer to nonlinear model error, static output feedback is adopted. To design static output feedback controllers, Kosut's method is adopted because it is simple to calculate. Differential braking and active anti-roll bar are adopted as actuators that generate yaw and roll moments, respectively. The proposed method is shown to be effective in preventing rollover through the simulations on nonlinear multi-body dynamic simulation software, CarSim.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.7
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• pp.1-14
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• 1996

Effects of the external optical feedback on the optical transmission characteristics were evaluated for 3 kinds of commercialized DFB-LD modules for 2.5Gbps optical communication systems. As a result, intensity noise induced by external optical feedback via generating the external cavity modes deteriorated the transmission performances of sthe DFB-LD modules as much as 1.5dB, 1.2dB, and 1.0dB for the maximum feedback ratio of -8.8dB which corresponds to the worst reflection along the fiber transmission line. Additional penalty of 0.5dB was occurrred when state of polarization of feedback light was adjusted. From the experiments evaluating the isolation ratio of the single polarization optical isolator, decrease of the polarization dependent isolation ratio as much as 10dB from that of specification and the effective isolation ratio as much as 20dB from that of specification was mjor cause of high sensitivity of DFB-LD modules to external feedback. It was suggested that polarization independent optical isolator or single polarization optical isolator with isolation ratio specification of more than 40dB is required for 2.5Gbps DFB-LD modules with complete suppression of external feedback effects.