• The Journal of Korean Physical Therapy
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• v.3 no.1
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• pp.123-149
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• 1991

This study has been attempted to be helpful for the back rehabilization of Korean workers by analyzing the general, occupational, social aspects of low back pain and to identify possible risk factors for back pain in White and Blue collar workers. The primary data were collected from 380 workers in Seoul city by means of a Questionnaire with random which was distributed from March 10 to 31, 1990. For the test of statistical significance, chi-square analysis was used to compare the back pain characteristics between above two groups. The results were as follows : 1. The incidence of low back pain in all walkers studied was $79.7\%$. The incidence of Blue collar with low back pain $(87.2\%)$ was higher than that of White collars $(75.0\%)$. 2. With regard to the relationship of back pain to the occupational characteristics, statistically significant differences were observed between workers with and without back pain concerning the job factors on work-time, job satisfaction, mental stress, chair fittness, work posture, work rotation, weight lifting, monotonous repetitive movements, vibration, and heavy noise (p<0.05). 3. With regard to the relationship of back pain to the social characteristics, there were no differences with respect to having car, personality types, drinking habits, and leisure-time activities. However, significant differences were showed between no pain and pain groups for the using bed, sleeping posture, traffic time amount, walking health state, smoking habits, and physical exercise (p<0.05). 4. The comparative analysis of back pain related to work factors showed highly significant differences with respect to mental stress, chair fittness, work posture, trunk rotation, weight lifting, monotonous repetitive work in White collar group (p<0.01) ; and job satisfaction, mental stress, trunk rotation, weight lifting, monotonus repetitive work, exposure to vibration and heavy noise in Blue collar group(p<0.01). 5. The comparative analysis of social factors in two groups showed differences with respect to the using bed, sleeping posture, walking amount, health state, physical exercise, smoking habits in White cellar group (p<0.05) ; and walking amount, traffic time amount, health state, smoking habits, physical exercise in Blue cellar group (p<0.05). 6. In regard to the general aspects of back pain between two groups, there were differences concerning etiolgy of back pain, counselling partners, treatment types, and sick-leaves(p<0.05), except pain duration, and awareness of back pain.

• PNF and Movement
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• v.15 no.2
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• pp.185-194
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• 2017

Purpose: The purpose of this study was to prove the effects of the PNF patterns combined with whole-body vibration (PWBV) training on muscle strength, balance, walking speed, and endurance in stroke patients. Methods: Sixteen subjects were randomly assigned to the PWBV group (n=8) and the whole-body vibration (WBV) group (n=8). The PWBV group performed PNF pattern exercises using sprinter combined with WBV, while the WBV group performed using squatting for 30 minutes. Both groups performed therapeutic interventions five days per week over a period of four weeks. The manual muscle test, timed up and go test (TUG), 10-meter walk test (10MWT), and six-minute walk test (6MWT) were used to assess the muscle strength, balance, and gait of the participants. The SPSS Ver. 19.0 statistical program was used for data processing. Statistical analysis included a pared t-test to compare the pre- and post-intervention, and an independent t-test was used to compare groups. The significance level was set as 0.05. Results: The PWBV group and WBV group showed significant improvements in the TUG, 10MWT, and 6MWT (P<0.05). Significant differences between the PWBV and WBV groups were found (P<0.05). Conclusion: The PWBV improved muscle strength, balance, gait speed, and endurance in stroke patients. Thus, PWBV may be suggested as a therapeutic intervention in patients with stroke hemiplegia.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1167-1172
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• 2007

This study investigates human floor impact sounds; not only the children's jumping and running represented by heavy-weight impact source such as bang machine and impact ball but also the high-heel walking and the light weight object dropping represented by tapping machine in the standard measurements. However, due to reliability problems as a standard impactor, bang machine has not been included in the new draft of ISO 10140 Part 3: Measurement of impact sound insulation. Therefore, the procedure to convert the floor impact sound level of the bang machine into that of the impact ball has been demanded because the bang machine has been only the standard heavy-weight standard impact source and much of its data has been collected, This study indicates that the use of impact ball is reliable and that the bang machine data can be successfully converted into the impact ball data in case of box-frame type reinforced concrete structures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.262-265
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• 2006

In order to investigate characteristics of floor impact sound generated in the apartment buildings, questionnaire survey was conducted for respondents living in apartments in 200t. Questions in the surrey were on the characteristics of real impact sounds, subjective annoyance and satisfaction on the heavy and light impact sources. From the survey results, it was found that most annoying time of a day and the space were 8 p.m. to midnight at living room. It was also revealed that the main source of the floor impact sound from the upper floor is a child's jumping and running at from six to nine. More than half of people were not satisfied on the floor impact isolation performance of their own apartments. The percentage of residents who were annoyed by the heavy-weight impact sound such as children's jumping and adult's walking was $5{\sim}10%$ lower than by light-weight impact sound. In addition, females being responded more annoyed by floor impact sound than males.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.6
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• pp.568-572
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• 2006

This paper presents the device of recognizing image of the studded paving blocks, transmitting, the information by vibration to a visually handicapped person. Usually the blind uses the walking stick to recognize the studded paving block. This research uses a PCA (Principal Component Analysis) based image processing approach for recognizing the paving blocks. We classify the studded paving blocks into 5 classes, that is, vertical line block, right-declined line block, left-declined line block, dotted block and flat block. The 8 images for each of 5 classes are captured for each block by 112*120 pixels, then the eigenvectors are obtained in magnitude order of eigenvectors by using principal component analysis. The principal components for images can be calculated using projection of transformation matrix composed of eigenvectors. The classification has been executed using Euclidean's distance, so the block having minimum distance with a image is chosen as matched one. The result of classification is transmitted to the blind by electric vibration signals with different magnitudes and frequencies.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.276-280
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• 2020

A linear piezoelectric actuator that utilizes the elliptical motion of the two tips of the actuator is proposed. This device is easy to fabricate owing to its simple structure, consisting of three piezo ceramic benders and is suitable for use in micro robotic applications. A π-shaped structure, which was composed of four piezo ceramic benders, was constructed. Two of the benders were positioned on the center of the actuator, and the joints were attached at the ends of the cantilever. The other two benders were positioned on the side of the actuator and were attached between the joint and the tips. The actuator structure was designed to obtain the first bending mode of the horizontal vibration and the vertical vibration at the same frequency, resulting in elliptical motions at the tips. When two sinusoidal wave voltages with a 90-degree phase difference were applied to the two pairs of the actuator benders, elliptical motions were obtained at the tips. The driving characteristics of the prototype actuator were then measured using a laser doppler vibrometer.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.4
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• pp.62-69
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• 2010

In this study, the serviceability performance of Waffle Shaped(WAS) and Double-Tee(DT) precast concrete slabs were evaluated and compared based on the vertical acceleration magnitude induced by walking and heel drop loads. Tests were conducted for practical building structures of which floor systems used WAS and DT slabs. Natural frequencies of the slabs were similar to those obtained by using analytical models. The measured acceleration level was evaluated by vertical floor acceleration criteria presented by ISO-2631, AIJ(1991, Japan) and a previous study regarding floor vibration limit. Test results showed that both WAS and DT slabs satisfied all the criteria and Peak acceleration level of WA slabs was lower than that of DT slabs.

• Journal of International Academy of Physical Therapy Research
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• v.11 no.4
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• pp.2253-2260
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• 2020

Background: Patients with low back pain (LBP) experience misalignments in the center of pressure (COP) and muscle imbalances due to frequent onesided posture adjustments to avoid pain. Objectives: To identify the effects of Squat Exercises with Vertical Whole-Body Vibration on the Center of Pressure and Trunk Muscle Activity. Design: Randomized controlled trial. Methods: Thirty LBP patients with an imbalance in the COP were sampled and randomly assigned to an experimental group of 15 patients who under went an intervention involving squat exercises with vertical WBV and a control group of 15 patients who were treated via a walking intervention. As pretests before the interventions, the subjects' COP was identified by measuring their stability index (ST), and erector spinae, rectus abdominis, transverse abdominis, gluteus medius muscle activity was analyzed by determining the % reference voluntary contraction (%RVC) value using surface electromyography while sit to stand. After four weeks, a post test was conducted to remeasure the same variables using the same methods. Results: Statistically significant differences were found in the ST (P<.01) and trunk muscle (P<.05, P<.001) in the experimental group before and after the intervention. In terms of the differences between the left- and right-side (RL) muscle activity, only the transverse abdominis (TrA) and gluteus medius (GM) exhibited statistically significant increase (P<.05). A comparison of the groups showed statistically significant differences in the TrA with respect to muscle activity (P<.05) and in the RLTrA and RLGM in terms ofthe difference between left- and right-side muscle activity (P<.01). Conclusion: Squat exercises with vertical WBV produced effective changes in the COP of patients with LBP by reducing muscle imbalances through the delivery of a uniform force. In particular, strengthening the TrA and reducing an imbalance in the GM were determined to be important factors in improving the COP.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.565-568
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• 1998

In this paper, we implemented the electornic moving aid system for safe walking of the blind. An obstacle detecting of each sector used ultrasound and a distance measurement used time of flight. The alarm is designed to have a sound and a tactile function that can be selected on an user's convenience. This system can detect and obstacle of upward, forward, downward and optimally warn to the blind with vibration, beep sound by appling warning algorithm on object detection. Experimental testing and performance evaluation have been successfully carried out with a prototype cane, and the experiment shows the capability of the function to detect unknown objects within an assigned distance, under knees, over head height, and crushed puddles.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.110-123
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• 1994

The development of automatic production systems have required inteligent diagnostic and monitoring function to repair system failure and reduce production loss by the failure. In order to perform accurate functions of intelligent system, inferencing about total system failure and fault analysis due to each mechanical component failures are required. Also the solution about repair and maintenance can be suggested from these analysis results. As an essential component of mechanical system, a bearing system is investigated to define the failure behavior. The bearing failure is caused by lubricant system failure, metallurgical defficiency, mechanical condition(vibration, overloading, misalignment) and environmental effect. This study described roller bearing fault train due to stress variation and metallurgical defficiency from lubricant failure by using FTA.