• Tribology and Lubricants
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• v.27 no.1
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• pp.25-33
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• 2011

Rolling contact ball bearings are utilized almost exclusively for liquid propellant rocket engine turbopump. Turbopump ball bearings are required to endure high speed and high load for a poor lubricated condition in cryogenic environment. To evaluate bearing heat generation performance, friction torque is investigated as a function of rotation speed, bearing load and cooling flow rate through an experimental study using water coolants. Radial and axial loads are simultaneously applied to the test bearing by gas pressurized cylinder rod. Endurance performance of bearing has been also verified under the bearing required load for operating condition during total accumulated test time 2,100 sec.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.57-60
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• 2005

This study discusses spalling and fire enduring performance of high performance concrete (HPC) RC column subjected to loading under heating for 3 hours. According to the test, both the plain concrete and the concrete attached with fire enduring PC panel exceed allowable temperature after 60 minutes due to the exposure of steel bar and falling off of concrete resulting from severe spalling failure. It leads to buckling of main bar and at the same time, occurrence of collapse of plain HPC column member is observed after 2 hours and 1 hour 40 minutes's exposure to fire, respectively. On the other hand, HPC applying both PP fiber of 0.1$\%$ by mass of concrete and PP fiber+lateral confinement by metal lath maintains their original cross section, which is satisfied with the 3 hours fire endurance criteria, by discharging internal vapour pressure and enhanced lateral confinement force.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.481-484
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• 2006

This study investigates the engineering and fire endurance properties of ultra high strength concrete. The mixture proportions with water to binder ratios (W/B) of 0.15 and 0.25 consist of various adding ratios, such as 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 percent respectively, of polypropylene (PP) fiber. As for the parameters of specimens, fluidity, compressive strength and unloading fire test were carried out. Test showed that an increase of fiber contents had the favorable properties in fire endurance performance; specimens in W/B 15% required 0.3vol% of PP fiber and specimens in W/B 25% needed only 0.1vol% to prevent spalling.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.55-59
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• 2011

Folding endurance, bending fatigue and monotonic tensile tests of 4 kinds of Cu foil on flexible substrate was performed to investigate the relationship between folding or bending endurances and tensile characteristics. The repeated 5.3 or 2.0% strain was applied to Cu foil in folding endurance test or bending fatigue test while monitoring the electrical resistance. Elastic modulus, yield strength, ultimate tensile strength, ductility, and toughness were obtained by monotonic tensile test on the same samples. The Cu foil with higher toughness and ductility showed higher reliabilities in folding or bending fatigue. However, elastic modulus and yield strength did not show any relationship with folding and bending reliability. This is because the failures of Cu foil by folding or bending fatigue were closely related to the fracture energy of metal.

• Journal of the Korean Society of Physical Medicine
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• v.11 no.4
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• pp.33-39
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• 2016

PURPOSE: The purpose of this study was to investigate whether a circuit aerobic exercise program positively affects pulmonary function and gait endurance in chronic stroke patients. METHODS: Twenty-four chronic stroke patients were allocated equally and randomly to an experimental group (n=12) or a control group (n=12). All participants received 60 minutes of comprehensive rehabilitation treatment, the experimental group additionally performed a circuit aerobic exercise for 30 minutes, while the control group additionally performed a general aerobic exercise, i.e., gait training on the treadmill for 30 minutes. These 30-minute exercise sessions were held three times per week for six weeks. Pulmonary function was assessed using forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and maximal voluntary ventilation (MVV), and gait endurance was assessed using the 6-minute walk test (6MWT). RESULTS: In the both groups, FVC, FEV1, MVV, and 6MWT were significantly increased after training. Members of the experimental group showed significant improvements in FVC, FEV1, and MVV, and significantly greater improvements than controls (p<.05). However, 6MWT improvements were not significantly different in the two groups (p>.05). CONCLUSION: The devised circuit aerobic exercise program offers an effective rehabilitation aerobic exercise for improving pulmonary function and gait endurance in patients after chronic stroke.

• Korean Journal of Adult Nursing
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• v.13 no.1
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• pp.5-14
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• 2001

The purpose of this study was to explore the change of muscle strength, muscle endurance, flexibility and activities of daily living to develop a rehabilitational program. The subjects were selected randomly among the patients who underwent kidney transplantations at one major transplantation hospital in Seoul, Korea. This study was carried out between November 23, 1999 and February 15, 2000. The subjects in this study consisted of 16 patients who had kidney transplantations between 1 month and 12 months ago prior to this study. They were all on steroids and did not take any physical exercise regularly. The muscle strength, muscle endurance, flexibility and activities of daily living were evaluated at 1st week and after 12 weeks. The data were analyzed with numbers, percentiles, mean, standard deviation and t-test. The results were as follows: 1. After 12 weeks, the grip strength was significantly decreased than 1st week (p=.0002). 2. After 12 weeks, the back lift strength was significantly decreased than 1st week (p=.0002). 3. After 12 weeks, the muscle endurance was increased than 1st week, but it was not significant(p=.5487). 4. After 12 weeks, the flexibility was significantly decreased than 1st week (p=.0002). 5. After 12 weeks, the activities of daily living was significantly decreased than 1st week (p=.0006). Like the above result, the kidney transplant receipients' muscle strength, flexibility and activities of daily living were reduced. In order to solve this problem, the writer has found that program development to prevent the defects should be extremely required. Since now on the number of patients should expand. After the kidney transplantation, the periods of 4, 8, 12 and 16 weeks are extended. The writer proposes to examine the different phase of change in each periods.

• Journal of Nutrition and Health
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• v.35 no.8
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• pp.825-833
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• 2002

The effects of dietary supplementation of Eleutherococcus senticosus, taurine and carnitine on maximal endurance exercise performance along with other related parameters were evaluated in rats that underwent aerobic exercise training for 6 weeks. Thirty-two male rats (4 weeks old) were randomly divided into 4 groups, and fed experimental diets and/or aerobic exercise trained according to the protocol: SC (sedentary control group), EC (exercise-trained control group), EE (exercise-trained Eleutherococcus senticosus-supplemented group), and EETC (exercise-trained Eleutherococcus senticosus, taurine and carnitine-supplemented group). The food efficiency ratio of EC rats was significantly lower than the value for SC rats (p < 0.01). Exercise-trained control animals (92 $\pm$ 8.8 min) could run significantly longer until exhausted on the treadmill than sedentary control rats (11 $\pm$ 0.8 min) (p < 0.001). Animals fed an Eleutherococcus senticosus-supplemented diet, and an Eleuthherococcus sonticosus, taurine and carnitine- supplemented diet while undergoing aerobic exercise training for 6 weeks exhibited, respectively, 8 and 5 minutes longer running performance until exhausted than the rats fed the control diet. The gastrocnemius muscle glycogen concentration of the rats, measured at 48 hours post maximal exercise performance test, was 43% higher in EC rats than the value for SC rats (p < 0.05), but was not different among EC, EE, and EETC rats. The mitochondrial citrate synthase activity of the soleus muscle was significantly higher in EC rats compared to the value for SC rats (p < 0.01), and showed a tendency to increase, without statistical significance, in EE or EETC rats compared to the value for EC rats. These results indicate that aerobic exercise training for 6 weeks significantly improved maximal exercise performance, muscle glycogen content along with citrate synthase activity, which are important in the energy metabolism of muscle under aerobic exercise. Dietary supplementation of Eleutherococcus senticosus in rats while undergoing aerobic exercise training improved maximal endurance exercise performance without significantly affecting muscle glycogen content and enzyme activities involved in energy metabolism during exercise. Taurine and carnitine supplementation failed to show an additive effect on maximal endurance exercise performance when consumed along with Eleutherococcus senticosus.

• Physical Therapy Rehabilitation Science
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• v.9 no.3
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• pp.149-154
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• 2020

Objective: This study aimed to evaluate the effects of the Kaltenborn-Evjenth concept of nerve mobilization combined with intermittent cervical segment traction (ICST) on pain, Neck Disability Index (NDI) scores, range of motion (ROM) and endurance in persons with cervical radiculopathy (CR). Design: Two-group pretest-posttest design. Methods: Thirty subjects participated in this study and were randomly assigned to two groups. The ICST group (n=15) was performed simultaneously with nerve mobilization and cervical traction for the segment with cervical pain at the same time. The intermittent cervical total traction (ICTT) group (n=15) performed nerve mobilization and cervical traction for the whole cervical area at the same time. In this study, outcome measures such as the Visual Analog Scale (VAS), NDI, ROM, endurance (cranio-cervical flexion test), and passive intervertebral motion performed before and 4 weeks after the experiment were compared to investigate the effects of each intervention. Results: In both groups, there were significant differences in the VAS, NDI scores, and endurance, and there were significant differences between the two groups except for endurance (p<0.05). In the ICST group, significant differences were found in all ROM, and in the ICTT group, significant differences were found in only extension, and there were significant differences between the two groups (p<0.05). Conclusions: The ICST group showed more improvement than the ICTT group in pain, NDI scores and ROM. Moreover, our findings show that the ICST could be used as a new strategy for manual therapy in persons with CR.

• International Journal of Advanced Culture Technology
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• v.8 no.3
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• pp.334-341
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• 2020

Through a investigation of the physical activity status of 1794 undergraduates who were non-sports majors from freshman to senior in Jiangxi Normal University, to analyze physical fitness status of college students with different physical activity levels. The results showed that in physical activity, high-intensity physical activity of male was higher than female, while medium-intensity and low-intensity (insufficient) physical activity of female was higher than male. College students' high-intensity physical activity group's physical test scores were better than the medium-intensity physical activity group, and the medium-intensity physical activity group was superior to the low physical activity group. In terms of physical fitness, among the test indicators of body shape and physiological function, the vital capacity and body mass index of male and female were ranked at a pass level. In the physical fitness test indicators, the performance of college students' endurance qualities was better while the overall performance of strength qualities was lower. The overall fitness of college students was ranked at a pass level, and the physical test scores of female were better than male.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.104-109
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• 2018

Generally, the durability of the parking lock gear is evaluated through an endurance test for the entire transmission but no test standard exists for the durability test of one part of a parking lock gear. Therefore, in this study, the durability test standards of the parking lock gear were determined autonomously, and the durability performance test was conducted. A static fracture test was carried out to determine the yield strength of the parking lock gear, and a durability test condition was set to 60 % of the yield strength. The durability test of 1,000,000 times was conducted under the given conditions using a dedicated test jig manufactured for the test. Because the jig fractured during the static fracture test, finite element analysis for the jig was carried out and the jig was re-designed. The modified jig was manufactured and the durability test was carried out based on the test standard of autonomously. The basic data on the performance and endurance limit of the parking lock gear were obtained using these tests and analyses, and the basic data will be used as fundamental materials for the design and the development of the parking lock gear.