• Title/Summary/Keyword: Ball Head

Search Result 101, Processing Time 0.029 seconds

Changes of Various Balls Velocity under the Different Surface Conditions after Impact (충돌 후 지면 조건에 따른 다양한 볼의 속도변화에 관한 연구)

  • Park, Jin
    • Korean Journal of Applied Biomechanics
    • /
    • v.17 no.1
    • /
    • pp.91-97
    • /
    • 2007
  • The purpose of this study was to investigate the changes of various balls velocity under the different surface conditions after impact. For this study, four different balls were used which are golf ball, tang-tang ball, table tennis ball, and iron ball. And two different types of ground conditions were used which are artificial grass green and glass green. Movements of putter head and ball were recorded with 2 HD video cameras(60 Hz, 1/500s shutter speed). Small size control object($18.5cm{\times}18.5cm{\times}78.5cm$) was used in this study. To transfer the same amount of kinetic energy to the ball, pendulum putting machine was used. Analyzing the process of impact and the ball movement, a putter was digitized the whole movement but the ball was digizited within the 50cm movement. Velocities were calculated by the first central difference method(Hamill & Knutzen, 1995). Putter head velocities were about 112.2cm/s-116.2cm/s at impact. Maximum ball velocities were appeared 0.08s-0.10s after impact no matter what the ground conditions are. Table tennis ball recorded higher ball velocities than the other ball velocities and iron ball recorded the lowest ball velocity in this group. But Table tennis ball was influenced with the frictional force and immediately was decreased at the artificial grass green condition. If an object is received the kinetic energy under the static condition(v=0cm/s), the object recorded the maximum velocity shortly after the impact and then decreased the velocity because of the frictional force. The ball distance from the start position to the peak velocity position is about 6cm-10cm under the 112.2cm/s-116.2cm/s putting velocity with putter. 0.25 seconds later after impact balls were placed 40cm distance from the original position except iron ball. In this study, ball moving distances were too short therefore it was not possible to investigate the reactions after the translational force is disappeared. Rotational force would play a major role at the end of the ball movement. Future study must accept two things. One is long distance movement of ball and the other is balanced ground. Three-piece ball is a good item to investigate the golf ball movement on the different surface conditions.

Lateral Load Test for Various Aseismatic Methods of Pile Heads of Pier Type Quay Walls (잔교식 안벽의 말뚝 두부 내진 보강기법에 따른 수평재하실험)

  • 이용재;한진태;장인성;김명모
    • Proceedings of the Earthquake Engineering Society of Korea Conference
    • /
    • 2003.09a
    • /
    • pp.98-106
    • /
    • 2003
  • To construct pile-supported wharf structures that must support heavy horizontal loads, both vertical piles and batter piles are used. Batter piles are used to secure the bearing capacity against the horizontal loads. However, past case histories have shown that the heads of batter piles are vulnerable because these heads are subjected to excessive axial loads during earthquakes. Therefore, the aseismatic reinforcement method must be developed to prevent batter pile heads from breaking due to excessive seismic loads. Two different connecting methods of either inserting rubber or ball-bearing between batter pile head and upper plate were proposed to improve the aseismatic efficiency. Three large-scale pile head models(rubber type model, ball-bearing type model, and fixed type model) were manufactured and horizontal loading tests were peformed for these models. The results showed that the force-displacement relationship of the fixed type model was linear, but that of the rubber type model and the ball-bearing type model was bilinear. The increase in the horizontal displacement led to the increase in the horizontal stiffness of the rubber type models and the decrease in that of the ball-bearing type model. Compared with the values for fixed type model, the damping ratios of the rubber type model and the ball-bearing type model increased about 33~185% and 263~269%, respectively.

  • PDF

Kinematic Analysis of Drag Flick Shooting Motion for Training Shooters Specializing in Penalty Corners in Women's Field Hockey: A Case Study (여자 필드하키 페널티코너 전문 슈터 양성을 위한 Drag Flick 슈팅 동작의 운동학적 분석: 사례 연구)

  • Park, Jongchul;Byun, Kyungseok;Kim, Eonho
    • Korean Journal of Applied Biomechanics
    • /
    • v.29 no.2
    • /
    • pp.43-51
    • /
    • 2019
  • Objective: This study aims to propose an efficient technical model through a kinematic analysis of field hockey drag flick shooting motion in laboratory situations and game situations and to build up the basic data on drag flick shooting technique through a comparative analysis of a Korean specialized shooter and specialized shooters of competing Asian countries. Method: This study selected one Korean female national specialized shooter and seven specialized shooters of competing countries, China, Japan, India, and Malaysia, who participated in the 2018 Asian Hockey Champions Trophy as research subjects. In exercise situations, a 3-D motion analysis utilizing an infrared camera was conducted, while in game situations, an image-based 3-D motion analysis utilizing a digital camera was conducted. Results: The Korean specialized shooter had smaller changes in the angles of the trunk and the stick in game situations than in exercise situations. She had a high angular velocity of the trunk and the stick head, and the maximum speed of the ball was high. The Korean specialized shooter had the maximum angular velocity of the trunk higher than the specialized shooters of the competing countries did, and the angular velocity of the stick head and the maximum speed of the ball were in the average level. Conclusion: As for drag flick shooting in game situations, changes in the angle of the trunk and the stick were small, and the angular velocity was high due to the pressure that the shooters should perform the motion fast with the defenders' interruptions, and this high angular velocity of the trunk and the stick head affected the movement of the ball. Thus, the maximum speed of the ball was higher in game situations than in exercise situations. The Korean specialized shooter had the maximum angular velocity higher than the specialized shooters of the competing countries did; however, the maximum speed of the ball was average, and it turned out that the maximum speed of the ball was associated with the angular velocity of the stick head in P3. Therefore, Korean specialized shooters need complementary training for a change to the torque of the stick head, using the strong torque of the trunk.

Effects of the Cranio-cervical Static Stabilization Exercises among the Using Small Tools

  • Bae, Won-Sik;Lee, Keon-Cheol;Lee, Hyun-Ok
    • Journal of the Korean Society of Physical Medicine
    • /
    • v.11 no.3
    • /
    • pp.65-72
    • /
    • 2016
  • PURPOSE: The purpose of this study is to determine the differences between the muscle activity of cranio-cervical flexion and extension muscles according to the types of tools used through a short-term intervention of cranio-cervical static stabilization exercises using small tools. METHODS: A total of fifteen male and female adults in their 20s who showed forward head posture in the overall body posture measurement system participated in this study. Each subject performed cranio-cervical static stabilization exercises about flexion and extension while using a sling, a foam roller, a TOGU ball, and without tools separately, and the muscle activity of the sternocleidomastoid muscle, scalenus anterior and splenius capitis was measured. Each value was measured for 10 seconds a total of three times. The maximum voluntary isometric contraction value was computed using the average during the middle four seconds. RESULTS: Cranio-cervical flexion exercises using various tool types, the average activity of the sternocleidomastoid and scalenus anterior muscles was significantly higher when applying the TOGU ball (p<.05). According to the results of implementing cranio-cervical flexion exercise using various tools, the maximum muscle activity of the sternocleidomastoid muscle was significantly higher for the TOGU ball (p<.05). CONCLUSION: Based on these results, the provision of an unstable surface using small tools rather than a stable surface is recommended as an exercise scheme for proprioceptive stimulation in a forward head posture. Particularly, we recommend using the TOGU ball for the provision of an unstable surface to increase the muscle activity of the sternocleidomastoid muscle and scalenus anterior.

Effects of Neck and Pelvic Exercise Using Swiss Ball on Spinal Curve in Adults with Forward Head Posture (전방머리자세 대상자에 대한 목운동과 골반운동이 척추 굽이에 미치는 효과)

  • Bae, Won-Sik;Jang, Chel
    • Journal of The Korean Society of Integrative Medicine
    • /
    • v.9 no.3
    • /
    • pp.193-201
    • /
    • 2021
  • Purpose : The purpose of this study was to compare the effect of pelvic exercise on the CVA and spinal curve in adults with forward head posture compared to the group using only neck exercise when pelvic exercise was performed in parallel with conventional neck exercise. Methods : GPS 400 and Formetric were used to identify craniovertebral angle (CVA), thoracic kyphosis, lumbar lordosis, and pelvic torsion and were measured by an experienced research manager. Forward head posture (FHP) was selected for people whose angle between the line connecting the ear ball and the seventh cervical spine and the horizontal line is 50 degrees or less. The 30 selected students were randomly divided into 15 experimental groups and 15 control groups. Mackenzie exercise and sling exercise were performed for neck exercise in both the experimental group and the control group, and pelvic exercise using a Swiss ball was additionally performed in the experimental group. All data collected in this study were analyzed using SPSS statistics 21.0. Cervical vetebral angle (CVA), thoracic kyphosis, lumbar lordosis, and pelvic torsion were compared at 0 weeks, 3 weeks, and 6 weeks for each measurement factor using ANOVA with repeated measures. For the statistical significance test, the significance level of α was set to .05. Results : The changes of pelvic torsion, thoracic kyphosis and CVA due to pelvic exercise using Swiss Ball and neck exercise were changed over time, but lumbar lordosis were not changed. And there were no significant differences among the groups. Conclusion : In conclusion, the pelvic correction exercise is considered to be an effective exercise for correcting the FHP and requires regular pelvic correction exercises. We expect the results to be used in clinical trials.

Baseplate Design to Improve Swaging Performance of Actuator in a HDD (HDD 액추에이터의 스웨이징성능향상을 위한 베이스플레이트 최적설계)

  • Lee, Haeng-Soo;Hong, Eo-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.33 no.8
    • /
    • pp.760-766
    • /
    • 2009
  • In the manufacturing process of HDD, ball swaging method is commonly used to joint the Head Gimbal Assembly(HGA) with the arm of the actuator. The hub on the HGA is placed into the hole of the actuator arm, and the hub and arm is bonded by the pressure of steel ball. The pressure for plastic deformation on the baseplate causes the undesirable deformation on HGA, such as tilting, flying height change of head. After obtaining the key parameters that have large sensitivity on the swaging process, the optimal shape of baseplate is proposed to increase the static performance during swaging process. Contribution of the proposed design for the swaging performance is verified by contact simulation with elasto-plastic deformation.

An Atypical Case of Chronic Invasive Fungal Sinusitis with Concurrent Fungal Ball (진균구를 동반한 비정형적 만성 침습형 진균성 부비동염 1예)

  • Jung, Young Do;Kim, Bo Mun;Kang, Byung Jun;Shin, Seung Heon
    • Journal of Clinical Otolaryngology Head and Neck Surgery
    • /
    • v.29 no.2
    • /
    • pp.264-268
    • /
    • 2018
  • Chronic invasive fungal sinusitis (CIFS) is a relatively rare disease which occurs in immunocompetent or immunocompromised patients. We report a case of CIFS in ethmoid sinus with concurrent fungal ball in maxillary sinus. After surgical debridement and antifungal therapy, CIFS recurred with submucosal invasion in nasopharynx and osteomyelitis of clivus. Although CIFS encompasses a slowly progressing invasive fungal disease but potentially aggressive. It should be noted that CIFS could progress and extend through submucosal route without evidence of mucosal lesion.

Reliability computation technique for ball bearing under the stress-strength model

  • Nayak, S.;Seal, B.
    • International Journal of Reliability and Applications
    • /
    • v.17 no.1
    • /
    • pp.51-63
    • /
    • 2016
  • Stress function of ball bearing is function of multiple stochastic factors and this system is so complex that analytical expression for reliability is difficult to obtain. To address this pressing problem, in this article, we have made an attempt to approximate system reliability of this important item based on reliability bounds under the stress strength setup. This article also provides level of error of this item. Numerical analysis has been adopted to show the closeness between the upper and lower bounds of this item.

Reliability Evaluations for Shear Strength of Resistance Welded Ball Stud according to Different Cooling Methods

  • Park, In-Duck;Nam, Ki-Woo
    • Journal of Power System Engineering
    • /
    • v.22 no.6
    • /
    • pp.44-50
    • /
    • 2018
  • As a type of bolt with a spherical head, the ball stud is widely used as a part of a ball joint in steering or suspension systems in automobiles. Balls and studs are subjected to heat treatment suitable for each material; in particular, the shear strength of the ball stud must meet the specifications of the production company. This study evaluated the shear strength of joints according to the cooling method of ball studs subject to resistance welding. The shear stress of water cooling was higher than that of air cooling (as-received material). Note, however, th at oil cooling showed lower stress than that of as-received. When judged by standard deviation, mean, and coefficient of variation according to the arithmetic statistics and shape parameter as well as scale parameter, oil cooling is suitable.

Correlation between the linear impulse and ball spin rate (선 충격 량과 공의 회전 속도와의 상관관계)

  • Roh, Woo-Jin;Lee, Chong-Won
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2007.11a
    • /
    • pp.870-874
    • /
    • 2007
  • Golf ball spin rate after impact with club is created by the contact force, which is greatly influenced by ball and club mass, material, impact speed, and club loft angle. Previous studies showed that the contact force is determined as the resultant force of the reaction forces normal and tangential to the club face at the contact point. The normal force causes the compression and restitution of the ball, and the tangential force creates the spin. Especially, the tangential force takes either positive or negative values as the ball rolls and slides along the club face during impact. Although the positive and negative tangential forces are known to create and reduce the back spin rate, respectively, the mechanism of ball spin creation has not yet been discussed in detail. It is shown in this work that the linear impulse of the tangential force is directly related to generation of back spin rate of golf ball. The linear impulse can be calculated from the tangential force, which depends upon many factors such as ball and club mass, material, impact speed, and club loft angle. In this research, the influence of the contact force between golf club and ball is investigated to analyze the mechanism of impact. For this purpose, the contact force and the contact time at impact between golf club head and ball are computed using FEM.

  • PDF