• Journal of the Korean Ceramic Society
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• v.36 no.10
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• pp.1062-1068
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• 1999

The flexural strength distribution of alumina ceramics was observed using ball-on-3 ball test after thermal shock into the distilled water of 25$^{\circ}C$ Crack distribution was also observed by dye-penetration after thermal shock test. Fracture probability of alumina ceramics by ball-on-3 ball test was studied and compared with that by 3-point bending test. The crack distance from the center of thespecimen showed the stronger effect on the flexural strength by ball-on-3 ball test than the crack density.

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.225-230
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• 1999

Ball-on-3-ball 시험에서 이축 강도를 결정하기 위한 방법에 대해 고찰하였다. 알루미나 시편을 이용하여 ball-on-3-ball 시험과 poston-on-3-ball 시험을 하여 이축 강도를 측정하였다. piston-on-3-ball 시험에서의 강도 식과 등가 반지름을 이용하여 계산한 ball-on-3-ball 시험에서의 이축 강도와, piston-on-3-ball 시험에서의 이축 강도를 분산 분석(ANOVA)한 결과, 두 평균이 동일하다고 할 수 있었다. 따라서, ball-on-3-ball 시험에서의 이축 강도는 piston-on-3-ball 시험에서의 강도 식과 등가 반지름을 이용하여 계산할 수 있다. 또한, 유한 요소법을 이용하여 ball-on-3-ball 시험시 시편에 인가되는 응력 분포를 고찰해 보았다.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.713-720
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• 2000

The biaxial fracture behavior of alumina ceramics was studied using ball-on-3-ball test. The polished surfaces of alumina specimens were indented at 0mm, 1mm, 2mm, 3mm apart from the center of the specimen along path A, passing between the two supporting balls from the center of the specimen, and along path B, passing above the three supporting balls from the center of the specimen. The fracture strength of the indented specimens was measured using the ball-on-3-ball test, a kind of biaxial strength test. The fracture strength increased with increasing the distance from the center to indented position. The fracture strength of the specimen indented along path B was higher than that of the specimens indented along path A. It was presented that the fracture caused by tangential stress rather than radial stress when the indented positions are 1mm and 2mm from the center of the specimen. This phenomenon was in good agreement with FEM analysis.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.711-717
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• 1999

Biaxial fracture behavior of alumina specimens with the diameter of 20mm and four kinds of thickness of 1.9, 2.3, 2.6 and 2.8mm was studied by the ball-on-3-ball test and the fracture results were analyzed by he analysis of variance (ANOCA), The strength measured with the down speed prescribed in ASTM showed that the measured strength was not dependent on the thickness of the specimens. Equivalent radius and crack-braching number were observed to increase lineraly with the thickness of the specimens. The jog direction was observed to study the effect of grinding direction on surface flaws. It is though that the surface finishing with #600 grit diamond wheel did not affect the surface flaws of the specimens.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.180-184
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• 2012

3-way ball valves have been mostly used for high temperature/high pressure valves using in petrochemical carriers and oil tankers, which requires high quality products with confidentiality and durability. As a larger disaster may be generated by leakage of oil or gas from valves, thus the present research applied a numerical analysis method with thermal-structural coupled field analysis and the performance test. The Max stress by parts was confirmed through thermal-structural coupled field analysis and develop the 3-way ball valve design, which is safe on operating condition. And its performance was verified by carrying out pressure test, leakage test and durability test for the manufactured 3-way ball valves with satisfying it's regulations.

• PNF and Movement
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• v.9 no.2
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• pp.55-63
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• 2011

Purpose : The Purpose of this study was performed to find out back flexibility and strength by Swiss ball and sling exercise. Methods : Subjects were randomly assigned to 3 groups; Swiss ball(n=9), Sling(n=8) and Swiss ball and Sling(n=8). Each groups had the exercise 30 minute per week for 4 weeks. The case of Swiss ball-sling group had 15 minutes for ball exercise and 15 minute for sling exercise. Results : First, sling group among groups significantly increased in flexibility test 1. Second, ball group among groups significantly increased in flexibility test 2. Third, ball-sling group among groups significantly increased in strength test 1 and 2. Fourth, follow-up study after 2 weeks was revealed that flexibility and strength were decreased in all groups. Conclusion : The effect were not consistent with exercise methods. Accordingly, it should be selected for purpose and effect you want.

• Journal of International Academy of Physical Therapy Research
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• v.3 no.2
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• pp.435-439
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• 2012

This study was conducted to evaluate the effect of the exercise on elderly balance ability by using hippotherapy and therapeutic ball exercise. 10 patients were assigned to the hippotherapy group and they got with 30 minutes of hippotherapy. Another 10 elderly were assigned to the therapeutic ball group and they got with 30 minutes of therapeutic ball exercise. All procedures were repeated 5 times a week for the total of four weeks. To investigate the participants balancing abilities, the Time" Up & Go"(TUG) and One Leg Stand Test(OLST) were evaluated. The results of study were significant differences between pre-test and post-test of TUG and OLST(p<.05), and there were no significant differences between hippotherapy and therapeutic ball exercise(p>.05). The conclusion showed that both the hippotherapy and the therapeutic ball exercises were effective on elderly balancing ability. Consequently, it would be better to practice therapeutic ball than hippotherapy for elderly exercise because the more economical and there is less restriction of space than the hippotherapy.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.3
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• pp.289-296
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• 1997

In this paper, a method has been proposed for error measurement/diagnosis of CNC machine tools using the ball link bar on three dimensional space. For the circular motion error measurement, deviation between the desired and actual test path has been measured and analysed using a new type of ball link which incorporates ideal three point contact between reference balls and sockets. Computer program for the error evaluation has been developed and implemented under PC environment. Using the developed program, the circular test data on a CNC machine tool have been analysed, and thus, machine tool errors were effectively evaluated.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.7 no.1
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• pp.35-42
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• 2009

Purpose : The purpose of this study was to investigate the effects of Swiss ball lumbar stabilization exercise on the strength and flexibility, balance for the subjects. 30 university students who aged an average $23.21{\pm}4.41$ years. Methods : The exercise program lasted for 4 weeks with a frequency of 3 times per week within 12 to RPE. The result was analyzed by case study were measured by sit-up for strength, and back muscle strength, and trunk flexion test and trunk extension lifting for flexibility, and also measured by balance test before and during, and after the Swiss ball exercise program. Statistical analysis was performed using SPSS/Win(15.0) version and t-test. Results : By the result of this study, we found that the number of performing sit-up strength was increased, and back muscle strength was increase, and trunk flexion test and trunk extension lifting was increased after the 4 weeks Swiss ball exercise program. Conclusion : These finding indicate that Swiss ball lumbar stabilization exercise using Swiss ball could be beneficial to the subjects. The effect of increasing strength and flexibility, balance was flexibility.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.173-179
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• 1998

The processing conditions for the synthesis of platelet WS$_2$ lubricant powder through the solid-gas reaction were optimized. The tungsten and sulfur powders were sealed in a vacuum of 10$^{-6}$ torr, prior to heat-treating at 850$\circ$C for 8 days. The react~on product showed the well-developed platelet WS$_2$ powder with an average size of 3.8 $\mu$m. The synthesized WS$_2$ powder was coated on the commercial deep grooved ball bearing (No. 6203) to examine the effects of WS$_2$ coating layer on the noise and endurance of the ball bearing. The level of noise obtained from WS$_2$ coated-ball bearing was higher (56 dB) than the value occurred in the case of greece (37 dB). The life-time of the ball-bearing assembled after coating WS$_2$ powder increased 50 times compared to the non-coated bali-bearing.