• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.369-370
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• 2002

To clarify the tribological properties of biodegradable lubricating oils, the four-ball tests were carried out under dip-feed lubrication using a Soda-type four-ball machine. The test balls were lubricated with soybean oil, rapeseed oil, corn oil and turbine oil. From the tests, the coefficient of friction for all the test balls lubricated with biodegradable lubricating oils was lower than that for the test ball lubricated with turbine oil. Further, from the calculation of the pV value, it was clear that the seizure resistance for all the test balls lubricated with biodegradable lubricating oils was higher than that for the test ball lubricated with turbine oil.

• 대한기계학회논문집A
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• 제29권9호
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• pp.1253-1261
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• 2005

Cast stainless steel (CSS) is thermally aged by a long term exposure in the range of nuclear power plant operating temperature. The thermal aging is a cause of concern for the continued safe and reliable operation of CSS nuclear components. Therefore, an assessment of degradation in material properties of these components has been importantly considered. In this study the ball indentation tests were performed on four cast stainless steels aged at $400^{\circ}C$ for 3600 hours, to investigate the applicability of ball indentation test to the assessment of aging degradation of cast stainless steels. Thus, the reliability of ball indentation test for aged CSS was analyzed by evaluating the scattering of data tested from each material and by comparing tensile properties obtained from ball indentation test and standard tensile test. Also, the tensile properties of aged CSS obtained from ball indentation test were compared with those predicted by the evaluation procedure developed on the basis of material database for aged CSS.

• 한국세라믹학회지
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• 제36권7호
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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.

• Tribology and Lubricants
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• 제11권5호
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• pp.184-189
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• 1995

The antiwear performance of dialkyl 3, 5-di-t-butyl 4-hydroxy benzyl phosphonates was investigated using a four ball wear test machine. Diethyl 3, 5-di-t-butyl 4-hydroxy benzyl phosphonate (DEP) and dibutyl 3,5-di-t-butyl 4-hydroxy benzyl phosponate (DBP) among them showed excellent antiwear performances compared with conventional additives, ZDDP and TCP as the bulk oil temperature and the sliding velocity increased. The surface analysis through an optical microscopy was conducted for tribological studies.

• 국제물리치료학회지
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• 제3권2호
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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.

• Nuclear Engineering and Technology
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• 제36권3호
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• pp.237-247
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• 2004

To investigate the applicability of automated ball indentation (ABI) tests in the evaluation of the tensile properties of cast stainless steel (CSS), ABI tests were performed on four types of unaged CSS and on 316 stainless steel, all of which had a different microstructure and strength. The reliability of ABI test data was analyzed by evaluating the data scattering of the ABI test and by comparing tensile properties obtained from the ABI test and the tensile test. The results show that the degree of scattering of the ABI test data is reasonably acceptable in comparison with that of standard tensile data, when two points data that exhibit out-of-trend are excluded from five to seven points data tested on a specimen. In addition, the scattering decreases slightly as the content of ${\delta}-ferrite$ in CSS increases. Moreover, the ABI test can directly measure the flow parameters of CSS with error bounds of about ${\pm}10\%$ for the ultimate tensile stress and the strength coefficient, and about ${\pm}15\%$ for the yield stress and the strain hardening exponent. The accuracy of the ABI test data is independent of the amount of ${\delta}-ferrite$ in the CSS.

• 제어로봇시스템학회논문지
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• 제8권6호
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• pp.484-491
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• 2002

We developed a new type of human-sized BWR (biped walking robot) driven by a new actuator based on the ball screw which has high strength and high gear ratio. Each leg of the robot is composed of three pitch joints and one roll joint. In all, a 10 degree-of-freedom robot with two balancing joints was developed. A new type of actuator for the robot is proposed, which is composed of four bar link mechanism driven by the ball screw. The robot overcomes the limit of the driving torque of conventional BWRs. The BWR was designed to walk autonomously by adapting small DC motors for the robot actuators and has a space to board DC battery and controllers. In the performance test, the BWR performed sitting-up and down motion, and walking motion. Through the test, we found the possibility of a high performance biped-walking.

• 대한물리의학회지
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• 제7권4호
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• pp.541-550
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• 2012

PURPOSE: The purpose of this study was compare quadriceps femoris muscle activity while performing wall slide squats of four methods. METHODS: Forty subjects, with no history of patellofemoral pain, quadriceps injury, or other knee injury volunteered for this study. Muscle activation of the vastus medialis obliquus, rectus femoris, vastus lateralis muscles were recorded while subjects performed 10 consecutive wall slide squats. Subjects performed the wall slide squats during four different methods: (1) basic wall slide squat, (2) keep back upright against fitness ball, (3) standing of unstable surface, (4) squeezing ball between both knees. Statistical analysis were accomplished by utilizing the one-way ANOVA(Bonferroni's post-hoc test) by SPSS 20.0 program. Significance level was set at p<.05. RESULTS: Muscle activations induced wall slide squats of four methods compared and results showed that there was significant difference only in vastus medialis obliquus and rectus femoris but there was no significant difference in vastus lateralis. The vastus medialis obliquus was significantly different only keep back upright against fitness ball at post-hoc test. The rectus femoris was significantly different keep back upright against fitness ball and standing of unstable surface at post-hoc test. CONCLUSION: Based on these results, we conclude that quadriceps femoris muscle activations are differenced by performing wall slide squats of four different methods in healthy subjects. These data suggest that for quadriceps muscle strengthening, exercise professionals can perform the wall slide squats by altering several task variables. Further research is needed to determine the exact mechanism by which quadriceps function is altered.

• Tribology and Lubricants
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• 제21권6호
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• pp.278-282
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• 2005

Deep groove ball bearing is installed in a control element of an integral nuclear reactor, where water is used as coolant and lubricant. This bearing is made of STS440C stainless steel for the raceways and the balls to use in radioactive environment and water. It is known that the retainer design affects ball bearing operability and endurance life, however there is no verified retainer design and material for water lubricated ball bearing. Four kinds of retainers are manufactured for the endurance test of water lubricated deep groove ball bearing. Three of them are commercially developed types and the other is designed for this research. It is verified that ball bearings with steel pressed and general plastic retainer can not survive to required life in the water, however bearings with machined type and cylinder type retainer can survive. This proves that one of the major design parameters for water lubricated ball bearing is retainer type and material. In this paper, experimental research of endurance test for water-lubricated ball bearing are reported.

• 대한통합의학회지
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• 제4권2호
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• pp.13-22
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• 2016

Purpose: The purpose of this study was to determine the effects of the swissball exercise in combination with core muscle in beginner golfer. In general, the swiss ball exercise was related in the core muscle ability. Methods: The experiment was conducted with a total of 10 beginner golfer, and they were dicide into two groups: comparison group(n=5) and experimental group(n=5). In this research, the subjects of the comparison group performed the general matte exercise three times a week, for four weeks. The subjects of the experimental group performed the swiss ball exercise in combination with core muscle three times a week, for four weeks. Use the 7-iron and driver were measured head speed and distance of the comparison group and the experimental group, respectively. The collected data were analyzed by using the paired t-test and ANCOVA Results: The results of this study were as follows: 1) Swiss ball exercise in combination with core muscle revealed the significant improvements after corresponding exercise in golf performance capability. 2) Mat exercise was seen less better than the swiss ball exercises. Conclusion: This results suggested that it was improved the golfer shot performance of beginner proposes to see the Swiss combined movement.