• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.380-390
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• 2003

This paper addresses the problem of the modeling and vibration control of tapered rotating blade modeled as thin-walled beams and incorporating damping capabilities. The blade model incorporates non-classical features such as anisotropy, transverse shear, secondary warping and includes the centrifugal and Coriolis force fields. For the rotating blade system, a thorough validation and assessment. of a number of non-classical features including the taper characteristics is accomplished. The damping capabilities are provided by a system of piezoactuators bonded or embedded into the structure and spread over the entire span of the beam. Based on the converse piezoelectric effect, the piezoactuators produce a localized strain field in response to a voltage and consequently, a change of the dynamic response characteristics is induced. A velocity feedback control law relating the piezoelectrically induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and thebeneficial effects upon the closed-loop dynamic characteristics of the blade are highlighted.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.691-697
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• 2003

Extensive researches have been carried out on machine tool chatter to obtain assessment procedure and improvement measures. In this study, chatter limit is predicted on a newly fabricated universal machining center by the combination of structural dynamic characteristics and cutting mechanics. We showed the unstable cutting conditions, and from them we could plot the unstable borderlines. From the chatter simulations we could say that the newly built universal machining center can be well used in the finishing machining of steel as other common machine tools.

• Asian Journal of Business Environment
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• v.5 no.4
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• pp.67-72
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• 2015

Purpose - This aim of this study is to examine how conglomerates in Korea have evolved from the perspective of institutional economics. The growth of the economy, dominated by large conglomerates, is projected in light of the dynamic equilibrium between government and capitalists. Research design, data, and methodology - The historical formation of big business groups is examined in chronological order. For the analysis, we divide the assessment into three different eras: Japanese colonial rule, liberation up to the civil war, and the fast growing period since the military coup. Each period is viewed as a dynamic equilibrium that is shaped by economic agents. Results and Conclusion - Despite the rise of modern commerce during the colonial era, contemporary conglomerates came into being with the "enemy property" allotted by the government. Around the civil war, the government coexisted with prototype conglomerates through foreign aid. As the external aid decreased, the system could not be sustained anymore, thus the military coup took place. The reinstated strong bond between government and the conglomerates has shaped the forms of the modern conglomerates thereafter.

• The Journal of Korean Physical Therapy
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• v.13 no.3
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• pp.495-507
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• 2001

The purpose of this study was to find the effects of the dynamic lumbar stabilization exercise on functional recovery of low back pain patients. The subjects were consisted of sixty patients who had nonspecific subacute low back pain. All subjects randomly assigned to dynamic lumbar stabilization exercise group. Williams exercise group and modalities treatment group. The dynamic lumbar stabilization exercise group received modalities treatment with dynamic lumbar stabilization exercise. Williams exercise group received modalities treatment with Williams flexion exercise and modalities treatment group received modalities treatment without exercise. The Oswestry low back pain disability questionnaire was used to measure disability of low back pain. Assessment was carried out before treatment fur obtain baseline measurement of low back pain and reassessment were carried out at after 20 and 40 treatment sessions. The results of this study were as following: 1. The Oswestry low back pain disability questionnaire scores were significantly decreased after 20th and 40th treatment in dynamic lumber stabilization exercise group(p<.05). 2. The Oswestry low back pain disability questionnaire scores were significantly decreased after 20th and 40th treatment in Williams exercise group(p<.05). 3. The Oswestry low back pain disability questionnaire scores were significantly decreased after 20th and 40th treatment in modalities treatment group(<.05). 4. There were no statistical difference between the 3 groups at pre-treatment with Oswestry low back pain disability questionnaire scores(p>.05). 5. There were no statistical difference between the 3 groups after 20th treatment with Oswestry low back pain disability questionnaire scores(p>.05). 6. There were statistical difference between the 3 groups after 40th treatment with Oswestry low back pain disability questionnaire scores(p<.05). 7. The Oswestry low back pain disability questionnaire scores were significantly decreased after 40th treatment in all 3 groups and the decrement were greater in order of dynamic lumbar stabilization exercise group. Williams exercise group and modalities treatment group.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.29 no.3
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• pp.43-53
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• 2023

Background: Patients with neck pain develop instability due to muscle imbalance, decreased proprioception, and balance disorders. Studies have examined various exercise methods as treatment methods, but few studies have compared the effects of cervical stabilization exercise and dynamic balance exercise. The purpose of this study was to investigate the effects of dynamic balance exercise on pain, functional level, and psychosocial level in patients with non-specific chronic neck pain. Methods: Thirty-four non-specific chronic neck pain patients were randomly assigned to the experimental group (EG, n=17) and control group (CG, n=17); the cervical stabilization exercise and dynamic balance exercise program were applied to the EG; and only the cervical stabilization exercise program was applied to the CG. The intervention was conducted twice a week, for six weeks. Assessment items evaluated pain, dysfunction (Korean version neck disability index), range of motion, craniocervical flexion test, cervical deep flexor endurance test, and psychosocial level. Data analysis was performed using intention-to-treat analysis as assigned. To analyze differences in the items assessed in the two groups, we used a repeated measures analysis of variance with an interaction between group (EG, CG) and time point (baseline, 6 weeks, 12 weeks). Results: The endurance of the cervical flexor muscles between the group and the measurement point after intervention (p<.05). Both groups showed significantly improved endurance between time points after the intervention (p<.05), with the EG showing a greater change than the CG. None of the other measurement items differed in the pattern of change between measurement points. Conclusion: In conclusion, the EG applying a cervical stabilization exercise and a dynamic balance exercise experienced a significant difference in muscle endurance improvement compared to the CG. We propose an exercise intervention program that includes stabilization exercises and dynamic balance exercises for patients with chronic cervical pain who lack muscle endurance.

• Journal of the Korean Society of Physical Medicine
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• v.2 no.1
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• pp.73-84
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• 2007

Purpose : The purpose of this study was to determine risk factors and methods in balance assessment associated with fall in older adults. Methods : This article describes many of the tools that can be used to evaluate the physical parameters associated with fall risk in older adults. Results : Composite ratings of performance(Tinetti balance assessment, Guralnik test battery, Berg balance scale, modified-physical performance test) measures the score compounding the balance measure to determine fall risk. Static balance instruments are composed of FICSIT-4 that measures the ability of maintaining foot positions and CTSIB that measures postural stability. Dynamic balance instrument is composed of functional reach test. To measure walking velocity and mobility, 8-foot up-and-go test and walking around two cones are used. We can use 1-RM and to measure muscular strength, isokinetic dynamometery, and 30-second chair stand to measure lower extremity muscle strength. Conclusion : The described instruments are easy to use and widespread. To select and use these tool kits carefully is considered to be helpful in identifying those who are most likely to fall. The final part of the article includes a brief discussion of the potential role of exercise training interventions to improve these physical parameters and prevent falls.

• Earthquakes and Structures
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• v.15 no.5
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• pp.487-498
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• 2018

Buckling-restrained braces are passive control devices with high level of energy dissipation ability. However, they suffer from low post-yield stiffness which makes them vulnerable to severe ground motions, especially near-field earthquakes. Among the several methods proposed to improve resistance of BRB frames, mega-brace configuration can be a solution to increase frame lateral strength and stiffness and improve distribution of forces to prevent large displacement in braces. Due to the limited number of research regarding the performance of such systems, the current paper aims to assess seismic performance of BRB frames with mega-bracing arrangement under near-field earthquakes via a detailed probabilistic framework. For this purpose, a group of multi-story mega-BRB frames were modelled by OpenSEES software platform. In the first part of the paper, simplified procedures including nonlinear pushover and Incremental Dynamic Analysis were conducted for performance evaluation. Two groups of near-fault seismic ground motions (Non-pulse and Pulse-like records) were considered for analyses to take into account the effects of record-to-record uncertainties, as well as forward directivity on the results. In the second part, seismic reliability analyses are conducted in the context of performance based earthquake engineering. Two widely-known EDP-based and IM-based probabilistic frameworks are employed to estimate collapse potential of the structures. Results show that all the structures can successfully tolerate near-field earthquakes with a high level of confidence level. Therefore, mega-bracing configuration can be an effective alternative to conventional BRB bracing to withstand near-field earthquakes.

• PNF and Movement
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• v.8 no.1
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• pp.67-77
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• 2010

Purpose : The purpose of this study was to investigate the usefulness of clinical balance tests through the correlation of balance evaluation using by forceplate in elderly. Methods : Thirty nine healthy elderly subjects (14 males, 25 females) participated in the study. The subjects were evaluated with clinical balance tests [(Berg balance scale (BBS), Functional reach test (FRT), Tinetti's performance oriented mobility assessment (POMA), and one leg standing (OLS)]. Static balance evaluation was assessed by using forceplate. Center of pressure (COP) parameters were obtained using it as total path distance, total sway area, X mean frequency and Y mean frequency for 20 seconds in the following conditions: (1) comfortable standing with eyes opened and closed, (2) uncomfortable standing with eyes opened and closed. After static balance evaluation tested, dynamic balance evaluation was assessed. COP parameters were error distance and area during sine curve trace. COP parameters were movement time, error distance, and maintained time in the circle during COP movement task. Results : Clinical balance tests showed statistically significant correlation between static and dynamic balance evaluations. Among the clinical balance tests, the BBS, POMA, and OLS showed significant correlation with to assess the balance ability of elderly in clinical setting both evaluations. Conclusion : Clinical balance tests can be recommended in clinical setting because of low costs and simplicity.

• Science of Emotion and Sensibility
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• v.16 no.3
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• pp.373-386
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• 2013

In this research, we specify the image consumers' preferred image quality ranges based on objective image quality evaluation factors and follow a method which measures preference of the natural image scenes. In other words, according to No-Reference, we select dynamic range, color, and contrast as factors of image quality measurements. For collecting sample images, we choose the preferred 200 landscapes which have over 30 recommendations by image consumers on the internet photo gallery. According to the scores of three objective factors of image quality measurements, the final expected score which means the image quality preference is measured and its total score is 100 points. In the main test, the actual image sample shows dynamic range 10 stop, LAB mean value L:54.7, A:2.96, B:-15.84, and RSC contrast 376.9. Total 200 image samples' normal distribution z value represents in dynamic range 0.21, LAB mean value L:0.15, A:0.38, B:0.13, and RSC contrast 0.08. In the standard normal distribution table, we can convert the z value as a percentage; dynamic range is 8.32%, LAB mean value is L:5.96%, A:14.8%, B:5.17%, and RSC contrast is 3.19%. And then, we convert the percentage values into the scores of 100; dynamic range is 91.68, LAB mean value is 91.36, and RSC contrast is 96.81. Therefore, we can conclude that the sample image's total mean score is 94.99 based on three objective image quality factors. Throughout our proposed image quality assessment model, we can measure the preference value of natural scenes. Also, we can specify the preferred image quality representation ranges and measure the expected image quality preference.

• The Journal of Korean Physical Therapy
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• v.24 no.5
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• pp.325-333
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• 2012

Purpose: The purpose of this study was to determine the concurrent validity between Figure-of-8 Walking Test (F8W), Berg Balance Scale (BBS), Four Squared Step Test (FSST), and Timed UP and GO Test (TUG) in patients with stroke. Methods: Forty two participants (26 men, 16 women, $55.0{\pm}11.72$) with at least three months post stroke who were able to walk at least 10 m without walking aid participated in this study. Assessment of concurrent validity between the F8W (time and steps) and BBS was performed using Spearman rank order correlation and between the F8W (time and steps), FSST and TUG assessed using Pearson correlation. Results: The time of the F8W showed correlation with BBS (r=-0.46, p<0.01), FSST (r=0.64, p<0.01), and TUG (r=0.81, p<0.01), and steps of the F8W showed correlation with BBS (r=-0.43, p<0.01), FSST (r=0.47, p<0.01), and TUG (r=0.51, p<0.01). Conclusion: The F8W is a valid measure of balance and walking skill among patients with stroke and may provide complementary information with regard to dynamic balance and functional walking for the real life of stroke patients.