• Journal of The Korean Society of Integrative Medicine
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• v.4 no.4
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• pp.101-108
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• 2016

Purpose : The purpose of this study was to determine the effect of selective thoracic extensor strengthening exercises in the sitting position using a foam-roller by investigating the electromyographic(EMG) activities of the thoracic and lumbar extensors. Methods : Eighteen healthy subjects with no medical history of back pain were recruited. EMG activity was recorded from thoracic extensor(TE) and lumbar extensor(LE) while subjects performed three thoracic extension exercises: prone thoracic extension(PTE), prone thoracic extension with abdominal draw-in maneuver(PTE-ADIM), and sitting thoracic extension using a foam-roller(STE). TE and LE EMG activity, and TE/LE EMG activity ratio were analyzed by one-way repeated-measures analysis of variance(ANOVA). Where a significant difference was identified, a Bonferroni correction was performed(p<.017, .05/3). Results : TE and LE EMG activity, and TE/LE EMG activity ratio differed significantly among the three exercises(p<.05). Post hoc pair-wise comparison with Bonferroni correction showed that TE muscle activity in the STE exercise was significantly different from PTE and PTE-ADIM exercises(p<.017). There was no significant difference between TE muscle activity for PTE and PTE-ADIM exercises(p>.017). LE muscle activity and TE/LE ratios were significantly different among the three exercises p<.017). Conclusion : TE/LE ratio showed superior selective thoracic extensor strengthening for the STE exercise than PTE and PTE-ADIM exercises. Therefore, we recommend STE exercise for selective thoracic extensor strengthening.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.399-404
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• 2002

This paper presents the results cf research on improved flexural performance cf reinforced concrete beams strengthened with bonded carbon fiber reinforced polymer plate. Recently, strengthening technique with CFRP plate were almost carried out by external bonding. But current external bonding technique cf CFRP plates may result in debonding CFRP plate. Therefore, this study proposes a strengthening method that prevents or delays debonding between CFRP plates and concrete and at the same time improves the strength. For this test, there were only 14 test beams manufactured and failure load, deflection, strains and modes cf failure have been examined Test variables included the type cf strengthening, steel ratio and strengthening length, and the effects according to each test variables were analyzed. The experimental results show that the strength and stiffness cf the beam significantly increased between 34.55 and 116.51% and the increase cf the more lead-carrying capacity than the control beams.

• Journal of the Korean Institute of Rural Architecture
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• v.7 no.1
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• pp.121-128
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• 2005

This experimental study was conducted to investigate beam strengthening of RC buildings with expended steel plate(ESP) in rural area. Nine test specimens were manufactured, whose variables were tensile steel ratio and the amount and the shape of expanded steel plate. The test results indicated that strengthened beams with ESP showed the improvement of flexural strength of 50%~90%, and the beam strengthening of U type was excellent for shear reinforcement as well as flexural reinforcement, more over, the honeycomb shape of ESP and anchor bolts for development of ESP were very effective.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.775-780
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• 2000

This paper was aimed to investigate the shear strengthening effect of the pre-loaded reinforced concrete beams strengthened by carbon fiber sheet (CFS) & steel plate. Main test parameters were the magnitude of pre-loading at the time of the retrofit, the strengthening methods of carbon fiber sheet and aid ratio. A series of seventeen specimens was tested to evaluate the corresponding effect of each parameters such as maximum load capacity, load-deflection relationship, load-strain relationship and failure mode. As a result, using the steel plate can increase the capacity of not only shear but also bending moment.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.609-614
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• 1997

Recently, many researchers have performed R&D about strengthening of R/C with steel plates, carbon fiber sheets. aramid fiber sheets and glass fiber sheets, and so on. However most of research were limited in study of flexural strengthening of R/C beams. This paper shows the results of an experimental study on shear reinforcement of deep beams using Glass Fiber Sheet in relation to shear-span ratio. strengthening orientation and anchorage. The results prove that shear failure is governed by reinforced orientation. adherence and anchorage. Additional anchorage of fibers does not only cause the improvement in the internal resistance, but also control the brittle shear failure of specimen after reaching the maximum load.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.517-520
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• 1999

In this study, the problem of strengthening of reinforced concrete (RC) columns by a central steel section with minimum amount is taken up. For this purpose, RC columns with central reinforcing elements such as a steel bar, a steel H section and a steel pipe were taken up. To certify the effect of this way of reinforcing, experimental study using specimens of RC columns of shear span ratio of 2.5 was carried out. The variables which are considered to affect the behavior of RC columns subjected to axial load and cyclic shear load are the magnitude of axial load, tie ratio and main bar ratio. As the results of this study, the effect of a central reinforcing element for making higher the earthquake resistant properties of RC columns were observed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.295-300
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• 2003

In discontinuous composite mechanics, shear lag theory is one of the most popular model because of its simplicity and accuracy. However, it does not provide sufficiently accurate strengthening predictions in elastic regime when the fiber aspect ratio is small. This is due to its neglect of stress transfer across the fiber ends and the stress concentrations that exist in the matrix regions near the fiber ends. To overcome this shortcoming, a more simplified shear lag model introducing the stress concentration factor which is a major function of modulus ratio is proposed. It is found that the proposed model gives a good agreement with finite element results and has the capability to correctly predict the values of intefacial shear stresses and local stress variations in the small fiber aspect ratio regime.

• PNF and Movement
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• v.17 no.3
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• pp.441-450
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• 2019

Purpose: This study identified the co-activation of quadriceps and hamstring muscles during hamstring strengthening exercises in healthy adults. Methods: Twenty-one participants were required for the present study design to achieve 80% power, 0.8 effect size (η2), and an alpha level of 0.05. Thus, this study recruited 21 healthy adults. All participants performed Nordic exercises, bridge exercises, and one-leg deadlifts randomly. The activity of the rectus femoris, vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (SM) were measured. In addition, the ratios of VM/VL and hamstring/quadriceps (HQ) were measured during the three hamstring strengthening exercises using electromyography. One-way ANOVA was used to compare the co-activation of quadriceps and hamstring muscles in the three exercises. Results: The activity of VM and VL during the performance of one-leg deadlifts was significantly higher than the other two exercises. The BF had significantly higher activity during the Nordic exercises compared to the other two exercises. In addition, the SM activation was significantly greater during Nordic exercises than one-leg deadlifts. Additionally, there was significant difference in HQ ratio among hamstring strengthening exercises. In specific, the one-leg deadlifts yielded a significantly lower HQ ratio. Conclusion: This study revealed that one-leg deadlifts are effective in rehabilitation for anterior cruciate ligament injury. In addition, Nordic exercises can be recommended to facilitate hamstring muscle activation.

• Journal of Industrial Convergence
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• v.19 no.6
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• pp.81-91
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• 2021

This study was conducted to investigate the effect of ankle muscle strengthening exercise using BOSU ball and taping on static and dynamic plantar pressure in patients with hallux valgus. Subjects were 26 men and women in their twenties with hallux valgus, and they were randomly assigned to a taping group (TG; n=13) and an ankle strengthening group (ASG; n=13). Each group received the appropriate intervention over a total of 4 weeks, and static and dynamic plantar pressure were measured before and after the intervention. Independent T-test was performed to examine the difference in the amount of change between groups, and paired-sample T-test was performed to determine whether the difference between the pre-post values within the group was significant. The statistical significance level was set as α=.05. As for the ratio of the total body weight of the foot (Foot), the amount of change in the ASG of the left foot was significantly decreased compared to the TG within the group (p<.05). Significantly increased (p<.05). As for the degree of pronation of the foot (MP/change ratio), the amount of change in the TG of the right foot was significantly decreased compared to the ASG (p<.05), and in the force of the foot, the TG of the left foot was the amount of change within the group compared to the ASG. was significantly increased (p<.05), and in the group-to-group change, the amount of change in TG was significantly different than that of ASG (p<.05). Therefore, it can be considered that ankle strengthening exercise using bosu ball and taping are insufficient to give effective change to patients with hallux valgus.

• International journal of steel structures
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• v.18 no.5
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• pp.1577-1588
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• 2018

As the excellent mechanical performance and easy construction of concrete filled steel tubes (CFST) composite structure, it has the potential to be used to strengthen RC pier columns. Therefore, tests were conducted on 2 reinforcement concrete (RC) stub columns and 9 RC columns strengthened with circular CFST under axial loading. The test results show that the circular CFST strengthening method is effective since the mean bearing capacity of the RC columns is increased at least 3.69 times and the ductility index is significantly improved more than 30%. One of the reasons for enhancement is obvious confinement provided by steel tube besides the additional bearing capacity supplied by the strengthening materials. From the analysis of the enhancement ratio, the strengthening structure has at least an extra 20% amplification except for taking full advantage of the strength of the strengthening material. Through the analysis of confining stress provided by steel tube and the stress-strain relationship of confined concrete, it is found that the strength of the core concrete can be increased by 21-33% and the ultimate strain can be enhanced to beyond $15,000{\mu}{\varepsilon}$.