• Tunnel and Underground Space
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• v.14 no.3
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• pp.167-174
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• 2004

This paper is to introduce an article published in Rock Mechanics and Rock Engineering, 2003. In this research, a fracture mechanics model is developed to illustrate the importance of time-dependence far brittle fractured rock. In particular a model is developed fer the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value that results in slope instability. A second example is given where variations in some of the material parameters are assumed. A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability of failure is found to increase with time, from an initial value of 5% to a value at 100 years of over 40%. These examples show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for relatively short-term rock structures.

• Journal of muscle and joint health
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• v.19 no.3
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• pp.319-328
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• 2012

Purpose: The purpose of this study was to explore effects of a Cancer-overcome BeHaS exercise program that consists of exercise, education, and cognitive supports to improve shoulder external rotation, cancer coping, group cohesion in mastectomy patients. Methods: A one group pre-post test design was used. Thirty mastectomy patients from C Hospital participated in the supervised exercise program once a week for 8 weeks. Data were collected from May to July 2011 using self-administered questionnaires and physical measurement. SPSS/WIN 19.0 was used for the data analysis. Results: The mean age of participants was 53.7 and the mean postoperative period after the surgery was 12.93 months. There were significant differences in the shoulder external rotation, cancer coping, group cohesion between pre and post program. Conclusion: The results showed that cancer-overcome BeHaS exercise program was an effective nursing intervention for improving breast cancer patient's shoulder external rotation, cancer coping and group cohesion.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.499-502
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• 2003

The purpose of this study is to understand the sliding characteristics of the infilling-joint surface using the new devised shear test apparatus with changeable slope for the original infilling materials and the infilling materials experienced cyclic freezing-thawing processes. Three types of the mother rock classified as the igneous rock, the metamorphic rock and the sedimentary rock and the infilling materials were collected for laboratory test. The cohesion according to the slope change of the rock joint shows large variation within ${\pm}$5 degrees but the internal friction angle shows appears the linear decreasing tendency. It is confirmed that the affecting factor of slope change of rock joint at the behavior of rock mass is larger than that of the infilling thickness. Test results show that the cohesion and the internal friction angle in 100 times of cyclic freezing-thawing processes are decreased about 50 percent compared with original one. A further study using various infillings materials would lead to a better understanding of the failure mechanism of rock mass by slope change of rock joint.

• Journal of muscle and joint health
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• v.10 no.1
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• pp.19-31
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• 2003

Purpose : The purpose of this study was to examine the effect of the self- efficacy, group cohesion and family support on adherence of aquatic exercise in arthritis patients. Method : The Subjects were 30 patients with arthritis who had participated in the 6-week aquatic exercise programs of Korean Rheumatology Health Professionals Society. All subjects were interviewed from November to December, 2001(1st) and Feburary, 2002(2nd) using a structured questionnaire which was composed of 42 items. SPSS Win 10.0 was used for data analysis. Results : Ten out of thirty were adherer who were keeping aquatic exercise for three months since they completed 6-week aquatic exercise program. The major reasons of adherence were affectional reasons and general condition improvement on the first month. The reasons of 3-month adherence were improvement of arthritis symptoms, affectional improvement, expectations, general condition improvement and group activity. The major reasons of drop out were environment factors and physical factors. The environmental reason were time shortage, economic problem and long distance. And the physical factor were cold, pain and other health problem. The scores of self-efficacy were decreased from 528.00 to 476.00 within 3 months after compeleting aquatic exercise program and that was statistically significant(p=.029). But there were no statistically differences in group cohesion and family support. There was a significant positive correlation between exercise adherence and self-efficacy. Factors influencing the exercise adherence was self-efficacy which accounted for 23% of the variance in the exercise adherence. Conclusion : In conclusion, self-efficacy is a significant variable in the exercise adherence and changes within 3 month after completing aquatic exercise program. The results of this study suggested that the strategy for maintaining self-efficacy should be developed.

• Journal of muscle and joint health
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• v.8 no.1
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• pp.5-26
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• 2001

Many studies have reported that regular aquatic exercise can lead to improvement of health for patients suffering from arthritis. In spite of these benefits, the adherence rate has shown as few as 26% of patients with arthritis who had completed the aquatic exercise education program. Moreover, when patients with arthritis begin an aquatic exercise, 47% withdraw within the first 6 month. No study has been found that constructs model to explain aquatic exercise adherence of patients with arthritis. The purpose of this study were to identify the factors influencing exercise adherence and to construct and test a structural model to explain aquatic exercise adherence of patients with arthritis. Hypothesized model was constructed on the basis of Bandura's social cognitive theory and literature review. Exogenous latent variables included in this model are group cohesion and barrier, endogenous latent variables are self-efficacy, outcome expectancy and self-evaluation. Empirical data used was collected through individual interviews with the structural questionnaire on 249 patients with arthritis who had completed the 6-week aquatic exercise education program of Korean Rheumatology Health Professionals Academy. The interviews were performed from September 6, 1999 through October 8, 1999. A model tested by the covariance structural analysis with LISREL 8.12a program and by descriptive statistics and correlation with SAS 6.12 program. The results are summarized as follows: First, hypothesized model showed a good fit to the empirical data. In the modified model added one new path showed a much better fit. Second, group cohesion had a direct, indirect positive effects, self-efficacy and self evaluation had a direct positive effects on exercise adherence. Barrier had a direct, indirect negative effects on exercise adherence. Outcome expectancy had a direct negative effect, indirect positive effects through self-evaluation on exercise adherence, but total effects was not significant. Total effect size of the variables were group cohesion, self-efficacy, barrier and self evaluation in order. All variables accounted for 54% of the total variance of exercise adherence in the model. In conclusion, this model confirmed to be proper in explaining of aquatic exercise adherence. Group cohesion, self-efficacy, outcome expectancy, self-evaluation, barrier contributed to the aquatic exercise adherence of patients with arthritis. The results of this study suggested that improvement of group cohesion, self-efficacy and self-evaluation, motivation of outcome expectancy through self-evaluation, and reduction of the barrier should be included in the strategy of nursing intervention for the aquatic exercise adherence of patients with arthritis.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.203-211
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• 2013

Shear behavior of joint plane has been investigated considering the magnitude of normal stresses and initial surface roughness. Shear strength of joint plane has been measured by performing the multi-stage shear test in which applied normal stress level has been increased stepwise. Multi-stage shear test within the specified normal stress range has been repeated and two types of strength parameter variation have been observed: type 1 - both cohesion and friction angle decrease, type 2 - cohesion decrease and friction angle increase. Trends of strength parameter variation for the three rock types, gneiss, granite and shale, have been investigated and the influence of initial roughness of joint plane on the sequential shear strength change for the repeated multi-stage shear tests also has been analyzed.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1133-1138
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• 2000

The interface necessarily exists in joints using cement mortar, UP(Unsaturated Polyester : UP) mortar and SBR(SBR-latex) mortar. Characteristics of shear transfer in joint interface consisting of different materials are studied with experimental and analytical methods. The uniaxial compressive shear experiments are accomplished with various angle of inclination (35, 45, 55, 65, 75°), materials of old and new-cast mortar. In this study, The results are as follows ① Mohr-coulomb's slip theory be applied to the interface consisting different materials ② The cohesion of UP mortar is superior to that f cement mortar, SBR mortar.

• Tunnel and Underground Space
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• v.10 no.2
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• pp.180-195
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• 2000

Grouting has been practiced as a reliable technique to improve the mechanical properties of rock mass. But, the study of ground improvement by greeting is rare especially in jointed rock mass. In this study, joint compression test and direct shear test were performed on pure rock joint and cement milk grouted rock joint to examine the grouting effect on the property of rock joint. In the pure rock joint compression test, joint closure varied non-linearly with normal stress. But after cement milk grouting, the normal deformation characteristics of the joint was linear at the low normal stress level. As normal stress increased. deformation of the sample rapidly increased due to the stress concentration at the joint asperities. Peak shear strength of the grouted joint in low normal stress was higher than that of non-grouted joint due to the cohesion, decreased exponetially as the grout thickness increased. Thus after cement milk grouting, the failure envelope modified to a curve that has cohesion due to grout material hydration with decreased friction angle. Shear stiffness and peak dilation angle of the grouted joint decreased as the grout thickness increased. The peak shear strength from the direct shear test on grouted rock joint was represented by an empirical equation as a fuction of grout thickness and roughness mean amplitude.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.63-64
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• 2014

In this study, we has a purpose to estimate the joint movement responsiveness performance for the domestic products of one-component structural silicon sealants. For this purpose, we make a comparative study for the four domestic products focused on tensile properties after allowed the cyclic-movements for three days at initial step of curing phase. A joint movement range ±10% and the rate of compression and extension 3.2mm/h were assumed in those tests. As a result, the large space were induced inside the sealant by rupture, and then adhesion and cohesion failures were caused by stress concentration. The tensile properties were reduced by 15~60% in comparison with physical properties. In this case, the generating defect was caused and the service-life was decreased. Thus, further researches as relationship of test condition and products properties on this behavior would be studied.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.86-94
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• 2009

A three dimensional rock joint element was developed considering fracture mechanics and subcritical crack growth to simulate non-linear behavior and the progressive failure of rock joints. Using this 3-D joint element, joint shear tests of rock discontinuities were simulated by a numerical method. The asperities on the joint surface began to fail at stress levels lower than the rock fracture toughness and continued progressively due to subcritical crack growth. As a result of progressive failing in each and every asperity, the joint showed non-linear stress-time behavior including stress hardening/softening and the reaching of a residual stress.