• The Journal of Engineering Geology
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• v.20 no.3
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• pp.319-327
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• 2010

Surface roughness profiles were measured from 19 joint samples using a laser scanner, and Joint Roughness Coefficient (JRC) values were calculated from 30 sections in each sample. Although JRC values varied with the location of the section, the average JRC values from any three sections provides an adequate representation of the average JRC value for the entire surface well. Direct shear tests were performed on nine joints reproduced using molds of real joints in samples of gypsum. The peak friction angles (${\phi}_p$) showed a linear relationship with the average JRC values, yielding the following relationship: ${\phi}_p=41.037+1.046JRC$. However, the shear strengths measured by direct shear tests differed from those calculated using Barton's criterion. The relationship between calculated from direct shear tests and JRC measured from joint surfaces is defined as $JRC_R=f{\cdot}JRC$, and the correction coefficient f is was calculated as $f=3.15JRC^{-0.5}$, as calculated by regression. A modified shear-strength criterion, is proposed using the correction coefficient, ${\tau}={\sigma}_n{\cdot}tan(3.15JRC^{0.5}{\bullet}{\log}_{10}\frac{JCS}{{\sigma}_n}+{\phi}_b)$. This criterion may be effective in calculating the shear strength of moderately weathered rock joints and highly weathered rock joints with low strength and ductile behavior.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.2
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• pp.93-106
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• 2021

In general, segment lining tunnel refers to a tunnel formed by connecting precast concrete segments as a ring and connecting such rings to each other in the longitudinal direction of the tunnel. As the structural properties of the segment lining is highly dependent on the behavior of the segment joints, thus correct modelling of joint behavior is crucial to understand and design the segment tunnel lining. When the tunnel is subjected to ground loads, the segment joint behaves like a hinge that resists rotation, and when the induced moment exceeds a certain limit of the rotation then it may enter into non-linear field. In understanding the effect of the segment joint on the lining behavior, a moment-rotation relationship of the segment joint was explored based on the Japanese practice and Janssen's approach commonly used in the actual design. This study also presents a method to determine the rotational stiffness of joint refer to the bearing strength. The rotation of the segment joint was estimated in virtual design conditions based on the existing models and the proposed method. And the sectional force of the segment lining and joint were calculated along with the estimated rotation. As the rotation at the segment joint increases, the joint contact area decreases, so the designer have to verify the segment joint for bearing strength as well. This paper suggests a consistent method to determine the rotational stiffness and bearing strength of joints.

• Korean Journal of Community Nutrition
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• v.25 no.3
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• pp.226-235
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• 2020

Objectives: Decreasing muscle strength in old age has become a significant health problem because it increases the risk of falls or fractures and transfers to other diseases. The precise role of dietary protein intake in preventing or reducing muscle weakness is unclear. This study examined the relationship between handgrip strength and protein intake in Korean female elderly. Methods: This was a cross-sectional study that used data from the Seventh Korean National Health and Nutrition Examination Surveys (KNHANES) on female subjects aged 65 years and older. Low handgrip strength (LHGS) was defined as a handgrip strength below than 18 kg. Dietary intake data were obtained using the 1-day 24-hour recall method. Multiple regression was performed to test whether there is an independent relationship between the grip strength and protein intake, and the association between protein intake and LHGS was confirmed through multiple logistic regression. Results: The mean age of the 2,083 elderly females was 73.3 ± 0.1 years, and the prevalence of LHGS was 35% (n=734). Elderly women with an LHGS consumed less energy, total protein, and animal-based protein than those in the normal group. A multiple regression analysis after adjusting for covariate revealed a significant positive association between the handgrip strength and energy, protein, and animal-based protein intake. Multiple logistic regression analysis showed that the odds ratio (OR) of LHGS in female elderly with the highest quartiles of consumption of energy [OR, 0.65; 95% confidence interval (CI), 0.43-0.82; P for trend=0.004], and animal-based protein [OR, 0.59; CI, 0.40-0.87; P for trend=0.037] were significantly lower than those in the lowest quartiles. Conclusions: The energy intake and animal-based protein intake were negatively associated with the LHGS. These results suggest that adequate energy intake and protein intake, particularly those from animal-based sources, for elderly women in Korea are beneficial in lowering the risk of LHGS.

• Korean Journal of Health Education and Promotion
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• v.16 no.1
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• pp.83-100
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• 1999

Modern technology has lessened the physical demand of every activities. Thus, physical inactivity has led to a rise in ‘Hypokinetic diseases’. The prefix, hypo, means lack of and kinetic refers to movement. Individuals who do not exercise regularly are at greater risk of developing hypokinetic diseases such as coronary heart disease, hypertension, hyperlipidemia, obesity, musculoskeletal disease. Systematic exercise program defenses development of hypokinetic diseases. Exercise program bases on basic physical fitness test. The physical fitness evaluation is used to degree of Wellness of the individuals. It includes the evaluation of Health-Related Physical Fitness -musclular strength, muscular endurance, flexibility, cardiorespiratory endurance, body composition - and skill or sports related fitness -agility, balance, coordination, reaction time, speed. In present study, the authors investigated health-related physical fitness test result and questionnaire for 133 male and 71 female from Jannuary 16 to March 15, 1997. The purpose of this study is to observe relationship health related physical fitness and self-perceived health status. The results are as follows. 1. There were statistically significant differences in BMI, grip strength, back strength, muscular endurance, cardiorespiratory endurance, and flexibility between male and female subjects. Flexibility is higher in female than male subject, but Others are higher in male than female subjects. 2. There were statistically significant differences in grip strength, muscular endurance between 30s, 40s, and 50s group In both gender subjects, and In cardiorespiratoryendurance between the groups especially in Female subjects. 3. For male subjects, flexibilitywas measured lower in group who classified low level in self-perceived health status than group of others. Also, for female, subjects, Muscular endurance ＆ flexibility were measured. 4. It was shown that grip strength, back strength, and muscular endurance were significantly lower in group who have chronic diseases than normal group for Male subjects. But, For female subjects, all the component were statistically insignificant results between normal and disease group. 5. Both male and female subjects, there were Positive correlation among grip strength, back strength, muscular endurance, cardiorespiratory endurance, and flexibility but, negative correlation for age. Therefore, health-related physical fitness is very important component for Heath Promotion ＆ Wellness. Physical Fitness test is valuable test in health evaluation, health management and health promotion, so available for hospital, sports center, community health center, industrial field, school etc.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.506-514
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• 2018

This study was conducted to investigate the relationship between hand grip strength and cardiopulmonary fitness in patients with myocardial infarction. In this retrospective study, 67 patients who experienced myocardial infarction for 10 months were analyzed. Hand grip strength was measured using a handheld dynamometer. Dynapenia was diagnosed based on a dominant hand grip strength of less than 30 kg for males and 20 kg for females. A cardiopulmonary exercise test was performed using a treadmill. Physical activity status was also evaluated. Cardiorespiratory fitness parameters were analyzed using a t-test and a Mann-Whitney test. VO2max, METmax, and exercise time significantly decreased in the dynapenia group compared with the non-dynapenia group. Correlation analysis revealed that dominant handgrip strength was significantly related to cardiorespiratory fitness parameters. Moreover, VO2max, METmax, and exercise time were significantly increased in patients with vigorous activity compared with the sedentary group. These findings indicate that handgrip strength could potentially be used as a marker of cardiorespiratory functions. Accordingly, patients with myocardial infarction should be evaluated for grip strength and physical activity, and we can encourage patients to participate actively in cardiac rehabilitation.

• Journal of the Korean Data and Information Science Society
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• v.28 no.1
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• pp.49-56
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• 2017

Among the techniques for analyzing big data, the association rule mining is a technique for searching for relationship between some items using various relevance evaluation criteria. This associative rule scheme is based on the direction of rule creation, and there are positive, negative, and inverse association rules. The purpose of this paper is to investigate the applicability of various types of relatively causal strength measures to the types of association rules from the point of view of interestingness measure. We also clarify the relationship between various types of confidence measures. As a result, if the rate of occurrence of the posterior item is more than 0.5, the first measure ($RCS_{IJ1}$) proposed by Good (1961) is more preferable to the first measure ($RCS_{LR1}$) proposed by Lewis (1986) because the variation of the value is larger than that of $RCS_{LR1}$, and if the ratio is less than 0.5, $RCS_{LR1}$ is more preferable to $RCS_{IJ1}$.

• Physical Therapy Korea
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• v.27 no.4
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• pp.257-263
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• 2020

Background: The hip muscle plays various roles. Several types of functional performance tests are used for the assessment of patients with various lower extremity injuries. Hip muscle functions are important to test the performance of maintaining the spine, pelvic, and leg during bridging exercise. We designed a novel functional performance test tool, which we named close kinetic chain dynamic lower extremity stability (CKCLE) test to assess hip muscle functions. Objects: The purpose of this study was to determine the relationship between CKCLE test and hip extensor, external rotator, and abductor strengths. Methods: Twenty-two subjects were recruited in the present study (13 males and 9 females). The hip extensor, external rotator, and abductor muscle strengths were measured using a Smart KEMA strength sensor. When the examiner said "Go", the subject performed the CKCLE test by moving one leg from the floor and touching the opposite knee and then return to the floor while maintaining the bridging position. The subjects attempted as many "touches" as possible in the allotted time (20 seconds) during the maximal tests. The correlation between the hip muscle (extensor, external rotator, and abductor) strength of the supporting leg and the number of CKCLE tests performed in 20 seconds was determined using the Pearson correlation. Results: Hip extensor (r = 0.626, p < 0.05), hip external rotator (r = 0.616, p < 0.05), and hip abductor muscle strengths (r = 0.475, p < 0.05) positively correlated with the number of CKCLE tests performed. Conclusion: We designed a CKCLE test and found that performance in the test correlated with hip extensor, external rotator, and abductor muscle strengths. The result suggests that the CKCLE test can be applied as a performance test to assess the functions of the hip extensor, external rotator, and hip abductor muscles.

• Computers and Concrete
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• v.19 no.4
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• pp.395-404
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• 2017

In this paper, the mechanical property of CFRP, BFRP, GFRP and their hybrid FRP was experimentally studied. The elastic modulus and tensile strength of CFRP, BFRP, GFRP and their hybrid FRP were tested. The experimental results showed that the elastic modulus of hybrid FRP agreed well with the theoretical rule of mixture, which means the property of hybrid composites are linear with the volumes of the corresponding components while the tensile strength did not. The bearing capacity, peak strain, stress-strain relationship of circular concrete columns confined by CFRP, BFRP, GFRP and hybrid FRP subjected to axial compression were recorded. And the confinement effect of hybrid FRP on concrete columns was analyzed. The test results showed that the bearing capacity and ductility of concrete columns were efficiently improved through hybrid FRP confinement. A strength model and a stress-strain relationship model of hybrid FRP confined concrete columns were proposed. The proposed stress-strain model was shown to be capable of providing accurate prediction of the axial compressive strength of hybrid FRP confined concrete compared with Teng et al. (2002) model, Karbhari and Gao (1997) model and Miyachi et al. (1999) model. The modified stress-strain model was also suitable for single FRP confinement cases and it was so concise in form and didn't have piecewise fitting, which would be easy for use in structural design.

• Composites Research
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• v.24 no.5
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• pp.34-38
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• 2011

Carbon nanotubes (CNTs) have been widely investigated as reinforcements of CNT/polymer nanocomposites to enhance mechanical and electrical properties of polymer matrices since their discovery in the early 90's. Furthermore, the number of studies about incorporating CNTs into carbon fiber reinforced plastics (CFRP) to reinforce their polymer matrices is increasing recently. In this study, single-walled carbon nanotubes (SWNT) were dispersed in epoxy with 0.2 wt.% and 0.5 wt.%. Then, the SWNT/epoxy mixtures were processed to carbon fiber composites by a vacuum assisted resin transfer molding (VARTM) and a wet lay up method. The processed composite samples were tested for the interlaminar shear strength (ILSS). The relationship between the interlaminar shear strengths and processing, and the reinforcement mechanism of carbon nanotubes were investigated. CNT/epoxy nanocomposite specimens showed the increased tensile properties. However, the ILSS of carbon fiber composites was not enhanced by reinforcing the matrix with CNTs because of processing issues caused by increased viscosity of the matrix due to addition of CNTs particularly for a VARTM method.

• KIEE International Transactions on Electrophysics and Applications
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• v.2C no.6
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• pp.281-286
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• 2002

The temperature accelerated dielectric breakdown strength of on-wafer low-k dielectric polymer films with thicknesses ranging from 94 nm to 1141 nm is investigated by using the current-voltage characteristic measurements with MIS structures. The temperature dependence of dielectric strength is demonstrated to be Arrhenious for all thicknesses. However, the activation energy is found to be strongly thickness dependent. It follows an exponential relationship rather than being a single value, i.e., the activation energy increase significantly as film thickness increases for the thickness below 500 nm, but it is almost constant for the thickness above 500 nm. This relationship suggests that the change of the activation energy corresponding to different film thickness is closely related to the temperature dependence of the electron trapping/detrapping process in polymer thin films, and is determined by both the trapping rate and the detrapping rate. Thinner films need less energy to form a conduction path compared to thicker films. Hence, it leads to smaller activation energy in thinner films, and the activation energy increases with the increase in film thickness. However, a nearly constant value of the activation energy is achieved above a certain range of film thickness, indicating that the trapping rate and detrapping rate is almost equal and eventually the activation energy approaches the value of bulk material.