• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.1-6
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• 2011

Machine tool errors have to be characterized and predicted to improve machine tool accuracy. Therefore, it is very important to assess errors in machine tools. Volumetric error analysis has been developed by many researchers. This paper presents a useful technique for analyzing the volumetric errors in machine tools using the ball bar. The volumetric error model is proposed in specific vertical machining center and the program is developed for generating NC code, acquiring the ball bar data, and analyzing the volumetric errors. The developed system assesses the volumetric errors such as positional, straightness, squareness, and back lash. Also this system analyzes the dynamic performance such as servo gain mismatch. The radial data acquired by ball bar on 3D space is used for analyzing these errors. It is convenient to test the volumetric errors on 3D space because all errors are calculated at once. The developed system has been tested using an actual vertical machining center.

• International Journal of Control, Automation, and Systems
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• v.3 no.3
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• pp.453-460
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• 2005

In this paper, a prototype Cartesian Parallel Manipulator (CPM) is demonstrated, in which a moving platform is connected to a fixed frame by three PRRR limbs. Due to the orthogonal arrangement of the three prismatic joints, it behaves like a conventional X-Y-Z Cartesian robot. However, because all the linear actuators are mounted at the fixed frame, the manipulator may be suitable for applications requiring high speed and accuracy. Using a geometric method and the practical assumption that three revolute joint axes in each limb are parallel to one another, a simple forward kinematics for an actual model is derived, which is expressed in terms of a set of linear equations. Based on the error model, two calibration methods using full position and length measurements are developed. It is shown that for a full position measurement, the solution for the calibration can be obtained analytically. However, since a ball-bar is less expensive and sufficiently accurate for calibration, the kinematic calibration experiment on the prototype machine is performed by using a ball-bar. The effectiveness of the kinematic calibration method with a ball-bar is verified through the well­known circular test.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.29 no.2
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• pp.59-67
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• 2023

Background: The purpose of this study is to analyze the effect of shoulder and neck stabilization exercise using a gym ball for healthy women in their 20s with round shoulder and forward head posture, it is intended to try and find improvement for posture. Methods: The subjects of the study were 25 women who understood the purpose of the research and voluntarily agreed to participate in the experiment. They carried out the shoulder and neck stabilization exercise program using a gym ball, which was conducted for 35 minutes, 3 times a week for 4 weeks. The position of the round shoulder and shoulder bones was measured using an tape measurement and were recorded in both at pre, 2 weeks, and post intervention. The craniovertebral angle (CVA) and craniorotational angle (CRA) was measured using an image J. Results: The round shoulder posture left was statistically significantly different within group (p<.05); however, the round shoulder posture right wasn't statistically significantly different (p>.05). As a result of this contrast, test were significant different in both at pre, 2 weeks and post. The scapular position on the left and right were statistically significantly different within the group (p<.05). As a result of the contrast, test were significant different in both at pre, 2 weeks and post (p<.05). The CVA and CRA on the left and right were statistically significantly different within the group (p<.05). As a result of the contrast, test were significant different in both at pre, 2 weeks and post (p<.05). Conclusion: The gym ball exercises improved the posture of women in their 20s. Therefore, gym ball exercises can help improve the quality of life of those with shoulder and neck pain.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.40-45
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• 2005

Techniques used for throcket motors are mainly classified as fixed nozzles with mechanical exhaust jet interferences on the expansion region (such as jet tabs and jet vanes) and movable nozzles(such as ball&socket md flexible seal). Using the numerical analysis and the cold-flow test, this paper evaluates the performance of supersonic nozzle for asymmetric entrance shape at tilted position of ball&socket nozzle. Numerical results show that the asymmetric effects in the flow fields are gradually diminished up to the nozzle throat and are not noticeable downstream of the nozzle throat. Although the calculated thrust and the lateral force are less than those of cold-flow test, two results show a flirty good agreement.

• Physical Therapy Rehabilitation Science
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• v.5 no.4
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• pp.170-176
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• 2016

Objective: The purpose of this study was to compare the effect of ball kicking dual task gait training with the addition of a cognitive task with general treadmill gait training (TGT) on gait speed, gait endurance, functional gait, balance and balance confidence in patients with chronic hemiparetic stroke. Design: Randomized controlled trial. Methods: Fourteen stroke patients who volunteered to participate in this study were randomly divided into two groups with seven patients in each group: ball kicking dual task training (DTT) group and TGT group. The DTT group received ball kicking DTT with cognitive tasks consisted of three stages and the TGT group received TGT using normal walking speed, respectively, for 30 minutes per day 3 days per week for 4 weeks. Outcome assessments were made with the 10-meter walking test (10MWT), 6-minute walking test (6MWT), functional gait assessment (FGA), Berg balance scale (BBS), timed up and go test (TUG), and the activities-specific balance confidence (ABC) scale. Results: The DTT group showed more significant improvement in the 10MWT, 6MWT, FGA, BBS, TUG, and ABC than the TGT group (p<0.05). In addition, within groups comparison showed significant improvement in all variables (p<0.05). Conclusions: The findings suggest that both ball kicking dual task gait training and TGT improve gait performance and balance in patients with chronic hemiparetic stroke. However, ball kicking dual task gait training results showed more favorable outcomes than TGT for chronic hemiparetic stoke patients.

• Tribology and Lubricants
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• v.13 no.3
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• pp.48-55
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• 1997

The ball bearing with thin-section raceways which is much lighter than other conventional bearings used in most modem passenger cars and small tracks. The important design parameters of this bearing is the groove radius of raceways, the diametral clearance, the free contact angle and so on. The optimal value of these parameters were determined by considering the dynamic load capacity, the contact angle and the calculated fatigue life. The contact angle between a ball and raceways was calculated by considering the local contact deformation and the structural deformation of thin-section raceways which was estimated by FEM. The raceways were made by means of the press-forming process. The fatigue life tester was designed and manufactured. The fatigue life test was executed and the reliability of this bearing was confirmed.

• Journal of The Korean Society of Integrative Medicine
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• v.1 no.3
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• pp.111-118
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• 2013

Purpose : The purpose of this study was to investigate the effect of horse riding exercise for pain and body flexibility in the patient with chronic low back pain. Method : 26 subjects in H-equestrian were randomly divided two group, ball exercise(BE) group and horse-riding exercise(HE) group. Each group carried out 40 minutes exercise three times a week for 8 weeks. VAS were measured for pain, and evaluation of body flexibility in position with forward and backward. Result : The results were as follows, the pain scales of VAS(visual analog scale) between ball exercise and horse-riding exercise groups in post-test, were significantly different in measures(p<.05). And there were significant in two group after exercise(p<.05). The flexibility scales of body between ball exercise and horse-riding exercise groups in post-test, were significantly different in measures(p<.05). And there were significant in two group after exercise(p<.05). Conclusion : These finding revealed that horse-riding exercise was effective on pain and body flexibility of patient with chronic low back pain so that these exercise can be new altematives exercise for pain and body flexibility in the patient with chronic low back pain.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.299-302
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• 2011

[ $WO_3$ ]powders were ball-milled with an alumina ball for 0-72 hours. $In_2O_3$ doped $WO_3$ was prepared by soaking ball-milled $WO_3$ in an $InCl_3$ solution. The mixed powder was annealed at $700^{\circ}C$ for 30 min in an air atmosphere. A paste for screen-printing the thick film was prepared by mixing the $WO_3$:In2O3 powders with ${\alpha}$-terpinol and glycerol. $In_2O_3$ doped $WO_3$ thick films were fabricated into a gas sensor by a screen-printing method on alumina substrates. The structural properties of the $WO_3$:$InO_3$ thick films were a monoclinic phase with a (002) dominant orientation. The particle size of the $WO_3$:$InO_3$ decreased with the ball-milling time. The sensing characteristics of the $In_2O_3$ doped $WO_3$ were investigated by measuring the electrical resistance of each sensor in the test-box. The highest sensitivity to 5 ppm $CH_4$ gas and 5 ppm $CH_3CH_2CH_3$ gas was observed in the ball-milled $WO_3$:$InO_3$ gas sensors at 48 hours. The response time of $WO_3$:$In_2O_3$ gas sensors was 7 seconds and recovery time was 9 seconds for the methane gas.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.97-103
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• 2013

This study proposes a path generation technique for simultaneous five-axis driving for ball bar measurement, which is equivalent to cone frustum machining as mentioned in the NAS979 standard. The technique is generalized for a 3D circular path, and it is applicable to all machine tools regardless of their structural configurations. A mathematical machine input model that consists of a five-axis machine tool, ball-bar measurement and conical path information as inputs is presented for easy NC code generation, simulation for various test conditions, and a measurement test. The movement range of rotary axes, which depends on various conditions, is mathematically analyzed based on the proposed conical path model. Moreover, the effect of the movement range on various conditions (apex angle and inclination angle, ball bar tilting acceptance angle, offset position of workpiece ball, etc.) is analyzed.

• Physical Therapy Korea
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• v.10 no.3
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• pp.109-126
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• 2003

This study was designed 10 investigate the effects of therapeutic gymnastic ball exercise on pain, flexibility, lumbar disability level and daily activity levels in male patients of the armed forces medical hospital who complain of chronic low back pain. Twenty-three males were placed in the experimental group and twenty-nine males were placed in the control group. All of the subjects were chosen on the basis of availability among in-patients who were diagnosed with low back pain. The control patients were matched to the experimental group and they were selected considering gender, pain duration and age. Gymnastic ball exercise therapy was developed by the author with the assistance of a rehabilitation specialist. Gymnastic ball exercise therapy includes muscle relaxation, flexibility, muscle strength and posture development exercises. The gymnastic ball exercise therapy was carried out by the experimental group three times a week for eight weeks. Before and after the experiments, the intensity of pain, the lumbar joint mobility (flexibility), the lumbar disability levels, and the daily activity levels of the subjects were measured, respectively. The intensity of pain and the lumbar disability levels were measured by the Visual Analogue Scale, the level of flexibility by a measurement ruler, and the level of disability by the Oswestry Low Back Pain Disability Scale. Data were analysed using a t-test, a paired t-test and an unpaired t-test. The results were as follows: 1. The intensity of pain in the lumbar spine in the experimental group was significantly decreased compared with that of the control group during the 4th week and 8th week. 2. The flexibility of the lumbar spine in the experimental group was significantly increased compared with that of the control group during the 4th week and 8 week. 3. The level of pain caused by anterior, posterior, left lateral and right lateral bending and by rotation in experimental group was significantly decreased compared with that of the control group. 4. The Oswestry Disability score of the experimental group was significantly increased compared with that of control group. These findings indicate that gymnastic ball exercise therapy could be effective in decreasing pain and lumbar disability, and increasing the daily activity levels and lumbar flexibility in patients with chronic low back pain. The study also suggests that gymnastic ball exercise therapy could be an essential factor for effective nursing intervention for patients suffering from chronic low back pain.