• Physical Therapy Rehabilitation Science
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• v.10 no.4
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• pp.414-420
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• 2021

Objective: The purpose of this study was to investigate the effects of coordinative locomotor training(CLT) using elastic bands on dynamic balance and grip strength for Elementary school baseball players and to provide correct posture guidance and reference on the prevention and rehabilitation program of sports damage and injury in the future. Design: Two groups pre-post randomized controlled design. Methods: Forty-six subjects were randomly divided in two groups;1) CLT using Elastic Band group(Experimental group, n=23), 2) Routine baseball training group(Control group, n=23). The intervention was conducted total 16 times for sixty minutes a day, 2 times a week, for 8 weeks. Evaluations of dynamic balance ability and grip strength were performed with all subjects before the commencement of training and 8 weeks after training. Results: Compared to the control group after training, the dynamic balance ability and dominant handgrip strength of the experimental group were significantly more improved(p<0.05). Conclusions: We confirmed that the effects of CLT using elastic bands on dynamic balance ability and grip strength in Elementary school baseball player. This study should be used for improving the quality of the Elementary school baseball player's training and would be contributed prevention and rehabilitation program of sports damage and injury.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1215-1225
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• 2014

Volcanic rocks formed from magma near the earth surface commonly show vesicular structures due to exsolution of gaseous phases in magma. The distinction and the amount of vesicles are greatly various, but there are few researches on the effect of volume percentage of vesicles on the mechanical properties. In this study, mechanical characteristics of volcanic rocks in relation to the porosity are investigated through experimental tests with Jeju basalt. Two methods (the buoyancy method and the caliper method) are adopted for measuring porosity. And unconfined compressive strength, elastic modulus, tensile strength, and elastic wave velocity are plotted against porosity in order to propose the empirical relations after the regression analysis. Also, unconfined compressive strength and the elastic modulus in relation to the elastic wave velocity are proposed with the analysis. In the case of vesicular rocks with more than 5% porosity, it is found that the buoyancy method provides more accurate estimation of porosity than the caliper method. The unconfined compressive strength, the elastic modulus, and the elastic wave velocity decrease curvilinearly with increasing in porosity. Also, the unconfined compressive strength and the elastic modulus increase linearly with increasing in elastic wave velocity.

• Computers and Concrete
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• v.31 no.4
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• pp.359-370
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• 2023

Slime is produced by excavation during the installation of embedded piles, and it tends to mix with the cement paste injected into the pile shafts. The objective of this study is to investigate the strength and stiffness characteristics of cement pasteslime mixtures. Mixtures with different slime ratios are prepared and cured for 28 days. Uniaxial compression tests and elastic wave measurements are conducted to obtain the static and dynamic properties, respectively. The uniaxial compressive strengths and static elastic moduli of the mixtures are evaluated according to the curing period, slime ratio, and water-cement ratio. In addition, dynamic properties, e.g., the constrained, shear, and elastic moduli, are estimated from the compressional and shear wave velocities. The experimental results show that the static and dynamic properties increase under an increase in the curing period but decrease under an increase in the slime and water-cement ratios. The cement paste-slime mixtures show several exponential relationships between their static and dynamic properties, depending on the slime ratio. The bearing mechanisms of embedded piles can be better understood by examining the strength and stiffness characteristics of cement paste-slime mixtures.

• Journal of the Society of Disaster Information
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• v.15 no.2
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• pp.249-258
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• 2019

Purpose: The purpose of this study is to attain the correlation analysis and thereby to deduce the uniaxial compressive strength of rock specimens through the elastic wave velocity and the elastic modulus among the physical characteristics measured from the rock specimens collected during drilling investigations in Seoul and Gyeonggi region. Method: Experiments were conducted in the laboratory with 119 granite specimens in order to derive the correlation between the compressive strength of the rocks and elastic wave velocity and elastic modulus. Results: In the case of granite, the results of the analysis of the interaction between the compressive strength of a rock and the elastic wave velocity and elastic modulus were found to be less reliable in the relation equation as a whole. And it is believed that the estimation of the compressive strength by the elastic wave velocity and elastic modulus is less used because of the composition of non-homogeneous particles of granite. Conclusion: In this study, the analysis of correlation between the compressive strength of a rock and the elastic wave velocity and elastic modulus was performed with simple regression analysis and multiple regression analysis. The coefficient determination ($R^2$) of simple regression analysis was shown between 0.61 and 0.67. Multiple regression analysis was 0.71. Thus, using multiple regression analysis when estimating compressive strength can increase the reliability of the correlation. Also, in the future, a variety of statistical analysis techniques such as recovery analysis, and artificial neural network analysis, and big data analysis can lead to more reliable results when estimating the compressive sterength of a rock based on the elastic wave velocity and elastic modulus.

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.1
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• pp.57-66
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• 2020

Purpose : This study aimed to identify whether resistance exercise using elastic bands for six weeks can improve muscle strength, muscle tone, balance, and gait in patients with stroke. Methods : In total, 35 patients with stroke were randomly divided into three groups: resistance exercise using elastic band training combined with less affected side training group, more affected side training group, and both sides training group. Muscle strength, muscle tone, balance, and gait were assessed using a hand-held dynamometer, the modified Ashworth scale, the Berg Balance scale (BBS), and wireless 3-axis accelerometer, before and after training. Results : All three groups showed a significant increase in muscle strength of the lower extremity after training, and there was a significant difference among the groups. There was no change in muscle tone in all three groups. BBS scores increased significantly in all three groups after training, but these scores were not significantly different. The gait speed increased significantly in all three groups after the training, but the difference was not significant. The cadence increased significantly in Group 2 after training; however, there was no significant difference between Groups 1 and 3. There were no significant differences between the groups before and after the training. Step length increased significantly in Groups 2 and 3 after the training, but it was not significantly different in Group 1. After training, Groups 2 and 3 were significantly greater than Group 1 in the change in step length. Conclusion : The results show that resistance exercise using elastic bands can improve strength, balance, and gait in patients with chronic stroke. Especially, more affected side training was more effective in improving muscle strength than less affected side training. More affected side and both sides training are thought to be more effective than less affected side training to improve step length.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.4
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• pp.425-431
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• 2007

[ $Al_2O_3/SiC$ ]composite ceramics were sintered to evaluate the bending strength and elastic wave characteristics. The three-point bending test was carried out under room temperature. The elastic wave was detected by fracture wave detector. The crack healing behavior was investigated from 1373 K to 1723 K. The bending strength of $Al_2O_3/SiC$ composite by nanocomposite is higher than that of $Al_2O_3$ monolithic. Crack-healing behavior depended on an amount of additive powder $Y_2O_3$. In $Al_2O_3/SiC$ composite ceramics with 3 wt. % $Y_2O_3$ for additive powder, the bending strength at 1573 K is about 100% increase than that of the smooth specimens. From the result of wavelet analysis of elastic wave signal, the smooth specimen and heat treated specimen of $Al_2O_3$ monolithic and $Al_2O_3/SiC$ composite ceramics showed characteristics of frequency about 58 kHz. The strength of $Al_2O_3/SiC$ composite ceramics was a little higher than those of $Al_2O_3$ monolithic. The dominant frequencies were high with increasing of $Y_2O_3$ for additive powder. The dominant frequencies had direct connection with the bending strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.422-425
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• 2006

AISC-LRFD, ACI 318 and Korean design specifications for concrete filled circular steel tube columns do not consider the increasing of axial stiffness such as the elastic modulus and the yield strength due to the confinement effect. AISC-LRFD and ACI 318, however, shows different basic philosophy and equations for computing the elastic modulus and the strength of CFT columns. Through this experimental study, 9 circular CFT column specimens were made by varying thickness steel tube and concrete strength, the axial stiffness were compared. The comparison between the design specifications and the test results shows different values on the elastic modulus and yield strength of the CFT columns. Even though, yield strength of the CFT columns are very similar between AISC-LRFD and Korean design specifications.

• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.343-348
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• 2018

This paper reports mechanical behavior of recycled fine aggregate concretes after high temperatures. It is found that compressive strength of recycled fine aggregate concretes decline significantly as the temperature rises. The elastic modulus of recycled fine aggregate concretes decreases with the increase in temperature, and the decrease is much quicker than the decrease in compressive strength. The split tensile strength of recycled fine aggregate concrete decrease as the temperature rises. Through the regression analysis, the relationship of the mechanical behavior with temperature are proposed, including the compressive behavior, elastic modulus and split tensile strength, which are fitting the test data.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.245-250
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• 1996

The aim of this study is to suggest the new elastic modulus equation that suits to a domestic situation to coincide the improved mechanical properties of high-strength concrete and ultra-high-strength concrete. For thish purpose, this study collected the laboratory data more than 400 connceted with the the modulus of elasticity that performed in this country and also analyzed it statistically. The compressive strength of investigated concrete ranged from 400 to 1,400kg/$\textrm{cm}^2$. As a result, a practical and useful elastic modulus equation is proposed, it can be considered as most suitable equation in domestic situation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.456-464
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• 2016

Increasing the strength of structural materials allows their self-weight to be reduced and this, in turn, enables the structures to satisfy esthetic requirements. The yield strength of high-performance steel is almost 480 MPa, which is approximately 50% higher than that of general structural steel. The use of high strength materials, however, makes the sections more slender, which can potentially result in significant local stability problems. The strength of slender element sections might be governed by their elastic buckling behavior, and the elastic buckling strength is very sensitive to the boundary conditions. Because the web provides the boundary conditions of the compressive thin-flange, the stiffness of the web can affect the elastic buckling strength of the flange. In this study, therefore, the effects of the flange and web slenderness ratios on the elastic flange local buckling of I-girders subjected to a pure bending moment were evaluated by finite element analysis (FEA). The analysis results show that the elastic local buckling strength and buckling modes were affected not only by the web support conditions, but also by the flange and web slenderness ratios.