• 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.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.

• Nuclear Engineering and Technology
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• v.26 no.2
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• pp.190-196
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• 1994

In order to investigate the ball-milling effect on the property changes of UO$_2$ ex-AUC powder, the sinterability of ball -milled powder was studied in terms of the ball -milling time. Spherical shape was found to be kept for ball-milled UO$_2$ powder and the particle size showed a bimodal distribution, which seems to have a higher packing ratio compared with those having monomodal gaussian distribution. The increase of sintered density of the ball -milled UO$_2$ powder is assumed to be mainly affected by the packing ratio, which increase with longer ball -milling time. It is confirmed that the sinterability of UO$_2$ ex-AUC powder is improved by the ball-milling process.

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.183-188
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• 2006

This research is to know differentiation of CP(center of pressure) pattern among four pitching sort(straight ball, raise ball, change up ball, drop ball). Subject are three national or junior athletes. We use the one camera, Novel Win pressure measurement system. Conclusions are as follows : 1. When we throw the straight ball, CP of left foot is effective to end movement at middle of foot in body balance on arm angular motion and enhanced speed. 2. When we throw the raise ball, to change CP from middle to post is more effective in order to raise the ball. 3.In drop ball pitching, in order to fall down the ball in front of hitter, CP of left foot move from post foot to interior part of forefoot 4. In change up ball pitching, if CP of left foot move into forefoot, it is a cause of high ball and hitter can recognize the change up ball because of late arm rotation motion.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.237-242
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• 2001

In this paper, we theoretically analyzed the NRRO(the non-repeatable run-out) of a ball bearing with ball geometric imperfection. The quasi-static and dynamic analysis of a ball bearing was performed to calculate the displacement of shaft center caused by the ball form errors while the shaft is rotating. From consideration of the generating mechanism of NRRO, it is found that the size and form errors of ball generate vibrations with (equation omitted)$\_$c/ and n(equation omitted)$\_$b/${\pm}$(equation omitted)$\_$c/(where n is even) components, respectively. The ball form errors of a ball bearing were precisely measured and NRRO of a ball bearing was calculated using the measured data. A statistical approach was peformed to analyze NRRO of ball bearings with radial errors.

• Journal of Bio-Environment Control
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• v.10 no.2
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• pp.88-94
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• 2001

Physical and chemical properties, the salt accumulation and leaching of salt by water of coal fly ash ball (ash ball) were evaluated in comparison with perlite and granule rockwool (rockwool). Bulk density, particle density, solid phase, and porosity of ash ball were 0.93 g.cm$^{-3}$ , 2.29 g.cm$^{-3}$ , 40.6%, 59.4%, respectively. The bulk density of ash ball was greater, while porosity was smaller, than that of perlite and rockwool. Saturation moisture capacity was 52% in ash ball, 71% in perlite, and 90% in rockwool. Water contents after drainage for 1 hr of ash ball, perlite, and rockwool were 21%, 27%, and 80%, respectively. Water content of small granules (3-5 mm) of ash ball was 5% greater than that of large (7-15 mm) grannules. The ash ball was a weak alkali substrate with pH 7.6, but not electric conductivity (EC), of the nutrient solution supplied to ash ball slightly increased. When the absorption of mineral ions to substrates were analyzed, ash ball and RW absorbed mainly PO￣$_4$. On tomato culture, salt accumulation in ash ball substrate was similar to that in perlite. Most of the salts in the ash balls were removed by submerging the substrate eight times in distilled water. It is concluded that water holding capacity of ash ball substrate was lo as compared to other substrates, but air permeability, and water diffusion was excellent, making control of medium water content easy.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.50-56
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• 2011

Injection molding process is one of the popular manufacturing methods to produce plastic parts with high efficiency and low cost. Ball seat for automobile suspension is made by an injection molding process as a part to support pivot function of ball joint consisted of ball stud and housing. It is necessary for a ball seat to have a dimensional stability in the three dimensional inner area to be contacted with ball stud. In this paper, the dimensional stability of inner surface is indirectly analyzed by checking the difference of inner diameter around the circumferential direction and the thickness variation at the top part of ball seat. Measurement was performed by using the coordinate measuring machine and the fixture to hold ball seat. Optimization of injection molding processes such as injection time, cooling time and temperatures of cylinder barrel was derived to reduce the difference of inner diameter and the thickness variation at the top part of ball seat based on the Taguchi method.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.11
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• pp.1136-1141
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• 2014

This paper proposes a new contact type ball tracking sensor to improve the control performance of a low cost ball-and-beam system. It is well-known that the impulsive measurement noise contained in ball position measurement is one of the factors which severely degrades the ball-and-beam control performance. The impulsive ball position measurement noises often appear under the sporadical ball floating on the beam. This fact motivates us to devise a simple analog preprocessing circuit to determine whether the ball loses the contact or not. Once the abnormal ball position measurement is detected, the design problem of the ball tracking sensor can be cast into the typical state estimation problem with missing data. In order to tackle the real-time implementation issue, a steady-state Kalman filter is applied to the problem. Through the experimental results, the usefulness of the proposed scheme is demonstrated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.540-545
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• 2016

Many golf balls have wrong rotation axis owing to bad production and scratch. A flying golf ball makes sliced or curved motion mainly to owing the wrong rotation axis of golf ball. Dimples of golf ball make a golf ball higher and more straight flying. When we hit a golf ball by driver or iron club, the dimpled ball flies straight and rotates as well. While the ball flying, the rotating axis of the ball convergence. And this makes the ball motion curved. If we hit a golf ball in direction of the rotation axis, the flying ball makes straight motion. In this paper, we develop a control system to detect convergence axis and time of flying golf ball based on vision system. To show validity of the developed system, We experimented several case for dimpled golf balls.

• Journal of Sport and Applied Science
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• v.3 no.2
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• pp.11-16
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• 2019

Purpose: New sports is a modified physical activity which is developed for participants to easily learn and play. This study is to analyze distribution channels and related strategies of Korea new sports and to discuss strategies for promoting Korea new sports, especially for two-two ball. Research design, data, and methodology: The study reviewed literatures including documents of Dae-Han two-two-ball association and new sports related research articles. Results: First, Dae-Han two-two-ball association has introduced two two ball to consumers via educational organizations such as schools and youth education sectors. Second, Dae-Han two-two-ball association has introducted two two ball to school teachers by teacher training sessions. Third, Dae-Han two-two-ball association has educated future instructors and provided certificates to them. Fourth, Dae-Han two two ball association has applied governmental projects and sought to promote domestic new sports. Finally, Dae-Han two two ball association has hosted national events every year for facilitating Korea new sports across nation. Conclusions: In conclusion, Korea new sports shoud be spread out by school teachers and educational organizations. Two-two ball association needs to develop a systematic educational and managerial process for training instructors. Finally, Two-two ball association needs to make opportunities of teacher training sessions. Future directions were discussed.