• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.5
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• pp.7-14
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• 2012

The quantized beamforming systems always need the channel state information, which must be quantized into a finite set of vectors (named codebook), and feedback only sends the index representing the desired vector. Thereby it minimized the impact of feedback errors, caused by feedback overhead and delay. In this regard, index assignment (IA) methods, an exhaustive-search and group-based schemes, have been presented for minimizes the performance degradation without additional feedback bits. In this paper, we proposed enhanced group-based IA method, which used the optimal codebook design with chordal distance, having the adaptive properties in application of the existing IA methods. When the number of transmit antennas is 4 and LTE codebook is used, Monte-Carlo simulations verify that the proposed scheme has a power advantage of 0.5~1dB to obtain the same bit error rate than methods without IA, and it has 0.1~0.2 dB better performance compared with the existing IA methods over same environment.

• The Journal of Korean Physical Therapy
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• v.31 no.4
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• pp.216-221
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• 2019

Purpose: This study examined the effect of visual feedback squat on the core muscle thickness of young adults experiencing back pain. Methods: Thirty adult men and women who experienced back pain were assigned randomly to 15 members of the visual feedback squat group (VSG) and 15 of the normal squat group (NSG) to train three times a week for a total of eight weeks. The core muscle thickness was compared prior to the test for four weeks and eight weeks after the test by dividing it into warm-up exercise, main exercise, and 10 minutes finishing exercise. Before, and four weeks and eight weeks later, the thickness of the core muscle was compared using an ultrasonic imaging system. Repeated measured ANOVA was performed to compare the groups, and a Bonferroni test was performed as a post-hoc test to assess the significance of the timing of the measurements in each group according to the periods. An independent t-test was conducted to test the significance between the groups according to the measurement points. Results: A significant change in the main effects of time and interactions of the time difference in muscle thickness of transvers abdominis were observed between the visual feedback squat and control groups according to the measurement point (p<0.05). No significant difference in the muscle thickness of both muscles was observed between the groups with the exception of the right abdominis (p>0.05). Conclusion: These findings suggest that visual feedback squat exercise is expected to have positive effects on the development of transverse abdominis in core muscles.

• PNF and Movement
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• v.18 no.1
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• pp.55-64
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• 2020

Purpose: The purpose of this study was to compare the strength and walking ability of chronic stroke patients following either proprioceptive neuromuscular facilitation (PNF) pattern training with pressure biofeedback units (feedback group) or PNF pattern training without pressure biofeedback units (control group). Methods: Eighteen participants with chronic stroke were recruited from a rehabilitation hospital. They were divided into two groups: a feedback group (n = 8) and a control group (n = 10). They all received 30 minutes of neurodevelopmental therapy and PNF training for 15 minutes five times a week for three weeks. Muscle strength and spatiotemporal gait parameters were measured. Muscle strength was measured by hand-held dynamometer; gait parameters were measured by the Biodex Gait trainer treadmill system. Results: After the training periods, the feedback group showed a significant improvement in hip abductor muscle strength, hip extensor muscle strength, step length of the unaffected limb, and step time of the affected limb (p<0.05). Conclusion: The results of this study showed that proprioceptive neuromuscular facilitation pattern training with pressure biofeedback units was more effective in improving hip muscle strength and walking ability than the proprioceptive neuromuscular facilitation pattern training without pressure biofeedback units. Therefore, to strengthen hip muscles and improve the walking ability of stroke patients, using pressure biofeedback units to improve trunk stability should be considered.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.677-684
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• 2020

Our country is already in the aging corner and fall down is the elderly personal, social and economic problems are causing. therefore, executed this study for inquiring into an athletic effect for the balance ability increase that was a main variable of an fall down. The purpose of this study, to find the effect of balance training using visual feedback and somatosensory. Experimental group divided the three groups, objects measured balance ability of each experimental groups before experiment, the balance exercise group used visual feedback by Nintendo Wii(company - model), the balance exercise group used visual and TOGU, the balance exercise group used blind and TOGU. 4 experimental of each groups measured MFT and EMG value after training. having rest time, 4 experimental of each groups measured MFT and EMG value after training used balance pad. MFT - visual feedback with somatosensory training is most efficient but, indifferent both balance training with visual feedback and balance training with somatosensory. EMG - training with somatosensory is more efficient than training with visual feedback. Conclusion : in the process of improving equilibrium ability of patient who is lack of balance ability, somatosensory training is effective to correct different of left, right and frequency of left, right. visual feedback is the most effective way to improve dynamic balance sensory, so parallel of these two practice is thought to be the most effective.

• Communications of Mathematical Education
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• v.31 no.4
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• pp.409-432
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• 2017

The purpose of this study is to find out the importance of process - based evaluation and to find a way to set up and operate the formative assessment which is getting attention. As one of the ways, we investigated the effect of formative assessment through student's interactive feedback on mathematics achievement and attitude of fourth grade students in elementary school. In order to conduct the study, two groups of homogeneous grades were selected. In the experimental group, formative assessment was conducted through student's interactive feedback. In comparison group, formative assessment was conducted through self - confirmation feedback. Statistical analysis of the results after the experiment showed that the formative assessment through student's interactive feedback was found to have a positive effect on the improvement of mathematics achievement. In addition, the formative assessment through student's interactive feedback positively changed the mathematics attitude. Therefore, this suggests that applicability of formative assessment through student's interactive feedback in elementary school classroom instruction, as well as implications for follow - up study for effective implementation of formative assessment.

• Physical Therapy Korea
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• v.19 no.3
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• pp.40-50
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• 2012

The purpose of this study was to investigate the effect of visual feedback on the postural control of stroke patients, by systematically varying conditions of visual feedback [eye-open condition (EO) vs. eye-closed condition (EC)], and base-support (both-side support, affected-side support, and unaffected-side support). In this study, we allocated 41 stroke patients with no damage in the cerebellum and visual cortex who can walk at least 10 meters independently, and 35 normal adults who have no experience of stroke to the control group. Both groups were asked to perform a "sit-to-stand" task three to five times, and their postural control ability was measured and compared in terms of asymmetric dependence (AD) instead of the traditional symmetric index (SI) in the literature. The results showed that although both subject groups maintained better postural control in the EO condition than in the EC condition, the patient group appeared to be more stable in EC than in EO when they were required to perform the task of the support condition given on the affected side. These results implied that visual feedback can impair stroke patients' postural control when it is combined with a specific support condition.

• Safety and Health at Work
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• v.8 no.4
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• pp.393-397
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• 2017

Background: It has been suggested that engaging technology can empower individuals to be more proactive about their health and reduce their health risks. The aim of the present intervention was to study the effects of technology-aided testing and feedback on physical activity and biological age of employees in a middle-sized enterprise. Methods: In all, 121 employees (mean age $42{\pm}10$ years) participated in the 12-month three-arm cluster randomized trial. The fitness measurement process (Body Age) determined the participants' biological age in years. Physical activity was measured with the International Physical Activity Questionnaire Short Form. Results: Physical activity did not change during the intervention. Biological age (better fitness) improved in all groups statistically significantly (p < 0.001), but with no interaction effects. The mean changes (years) in the groups were -2.20 for the controls, e2.83 for the group receiving their biological age and feedback, and -2.31 for the group receiving their biological age, feedback, and a training computer. Conclusion: Technology-aided testing with feedback does not seem to change the amount of physical activity but may enhance physical fitness measured by biological age.

• Physical Therapy Korea
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• v.8 no.3
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• pp.27-34
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• 2001

Physical therapists have been using biofeedback training to induce improvements in various circumstances. The purpose of this study was to compare the effects of visual and tactile feedback using electrical stimulation on quadriceps strength. Nineteen women without known impairment of the neuromusculoskeletal system volunteered for this study. Subjects were randomly allocated into three groups: visual feedback, tactile feedback, and control group. The torque of isometric knee extension force was measured. Subjects were asked to exert the maximal isometric contraction force of quadriceps over a 30 second period. The resting period of 10 minutes was given after the maximal isometric contraction to avoid the muscle fatigue. In between groups comparison, significant differences of the peak torque and the torque area were found on the performance of the maximal isometric contraction of quadriceps (p<.05). The values peak of torque and torque area were significantly higher during visual feedback than tactile feedback. The results of this study suggest that visual feedback is more powerful than tactile feedback (p<.01).

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1101-1107
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• 2017

This study explored the effect of ASR-based pronunciation instruction, using a mobile platform, on EFL learners' pronunciation development. Particularly, this quasi-experimental study focused on whether using mobile ASR, which provides voice-to-text feedback, can enhance the perception and production of target English consonants minimal pairs (V-B, R-L, and G-Z) of Korean EFL learners. Three intact classes of 117 Korean university students were assigned to three groups: a) ASR Group: ASR-based pronunciation instruction providing textual feedback by the mobile ASR; b) Conventional Group: conventional face-to-face pronunciation instruction providing individual oral feedback by the instructor; and the c) Hybrid Group: ASR-based pronunciation instruction plus conventional pronunciation instruction. The ANCOVA results showed that the adjusted mean score for pronunciation production post-test on the Hybrid instruction group (M=82.71, SD =3.3) was significantly higher than the Conventional group (M=62.6, SD =4.05) (p<.05).

• The Journal of the Korea Contents Association
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• v.14 no.5
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• pp.487-497
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• 2014

The purpose of this study is to investigate the efficacy of interaction using Wiki in communication-oriented classes taught by native teachers on the incidental improvement of productive vocabulary knowledge. Eighty two university freshmen participated in the study and they were divided into two groups. Thirty eight students(Process Group) received process feedback from the teacher while forty four students(Result Group) received result feedback. They were given a short movie project working in a group of four or five people to practice interaction between peers and between students and the teacher. Data were collected from one receptive and three productive vocabulary knowledge test scores. The results showed that interaction using Wiki was conducive to the growth of productive vocabulary knowledge incidentally due to continuous opportunities to use vocabulary. The students of process feedback group made greater gains of productive vocabulary than those of result feedback group. Based on these results, pedagogical implications are discussed.