• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.1
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• pp.22-27
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• 2012

This paper presents a ball screw-driven robotic gripper mechanism which is possible to grasp an object and analyzes its kinematic feature for grasping by simulation. For the purpose of identifying the feature of the robot gripper, we try to confirm the kinematics relating the joint space of the driving actuator to the gripper's tip space. To be specific, the proposed robot gripper employs one actuator and a symmetrical closed-chain structure. As a result, the specified robot gripper has an advantage of robustness to external forces structurally, and it is easy to implement simple grasping operations. Also the gripper has a useful squeezing effect for power grasping.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.703-707
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• 2000

Machine tool errors have to be characterized and predicted to improve machine tool accuracy. A real-time error compensation system has been developed based on volumetric error synthesis model which is composed of machine tool errors. This paper deals with new algorithm about verification of machine tool errors. This new algorithm uses a simplified volumetric error synthesis model. This simplified model is constructed with only main components among the error components of the machines. This main error components are analyzed by three-dimensional helical ball bar test. By substituting result of helical ball bar test fer simplified model, we could find that obtained error components are closed to real error components.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.209-214
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• 2003

We developed a new type of human-sized BWR (biped walking robot), named KUBIR1 which is driven by the closed-chain type of actuator. A new type of the closed-chain actuator for the robot is developed, which is composed of the four-bar-link mechanism driven by the ball screw which has high strength and high gear ratio. Each leg of the robot is composed of 6 D.O.F joints. For front walking, three pitch joints and one roll joint at the ankle. In addition to this, one yaw joint for direction change, and another roll joint for balancing the body are attached. Also, the robot has two D.O.F joints of each hand and three D.O.F. for eye motion. There are three actuating motors for stereo cameras for eyes. In all, a 18 degree-of-freedom robot was developed. KUBIR1 was designed to walk autonomously by adapting small 90W DC motors as the robot actuators and batteries and controllers are on-boarded. The whole weight for Kubir1 is over 90Kg, and height is 167Cm. In the paper, the performance test of KUBIR1 will be shown.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.3
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• pp.107-117
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• 2000

Ball poppet valve type high pressure hydrogen injection valve actuated by solenoid has been developed for the feasibility of practical use of hydrogen fueled engine with direct injection and the precise control of fuel injection ratio in hydrogen fueled engine with dual injection. The gas-tightness of ball poppet injection valve is improved by the introduction of ball-shaped valve face, valve end typed spherical pair, and valve stem with rotating blade. Ball poppet valve is mainly closed by differential pressure due to the area difference between valve fillet and pressure piston. So, it can be operated by solenoid actuator with small driving force. From the evaluation of ball poppet injection valve, it was found that the gastightness and controlment of this injection valve are better than those of injection valve had been developed before.

• Journal of the Korean Mathematical Society
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• v.60 no.1
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• pp.213-225
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• 2023

For every n ≥ 2, let ℝⁿ_‖·‖ be Rn with a norm ‖·‖ such that its unit ball has finitely many extreme points more than 2n. We devote to the description of the sets of extreme and exposed points of the closed unit balls of 𝓛(²ℝⁿ_‖·‖) and 𝓛_𝒮(²ℝⁿ_‖·‖), where 𝓛(²ℝⁿ_‖·‖) is the space of bilinear forms on ℝⁿ_‖·‖, and 𝓛_𝒮(²ℝⁿ_‖·‖) is the subspace of 𝓛(²ℝⁿ_‖·‖) consisting of symmetric bilinear forms. Let 𝓕 = 𝓛(²ℝⁿ_‖·‖) or 𝓛_𝒮(²ℝⁿ_‖·‖). First we classify the extreme and exposed points of the closed unit ball of 𝓕. We also show that every extreme point of the closed unit ball of 𝓕 is exposed. It is shown that ext B_{𝓛𝒮(²ℝⁿ‖·‖)} = ext B_{𝓛(²ℝⁿ‖·‖)} ∩ 𝓛_𝒮(²ℝⁿ_‖·‖) and exp B_{𝓛𝒮(²ℝⁿ‖·‖)} = exp B_{𝓛(²ℝⁿ‖·‖)} ∩ 𝓛_𝒮(²ℝⁿ_‖·‖), which expand some results of [18, 23, 28, 29, 35, 38, 40, 41, 43].

• The Pure and Applied Mathematics
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• v.25 no.1
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• pp.49-57
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• 2018

We have introduced two new notions of convexity and closedness in functional analysis. Let X be a real normed space, then $C({\subseteq}X)$ is functionally convex (briefly, F-convex), if $T(C){\subseteq}{\mathbb{R}}$ is convex for all bounded linear transformations $T{\in}B$(X, R); and $K({\subseteq}X)$ is functionally closed (briefly, F-closed), if $T(K){\subseteq}{\mathbb{R}}$ is closed for all bounded linear transformations $T{\in}B$(X, R). By using these new notions, the Alaoglu-Bourbaki-Eberlein-${\check{S}}muljan$ theorem has been generalized. Moreover, we show that X is reflexive if and only if the closed unit ball of X is F-closed. James showed that for every closed convex subset C of a Banach space X, C is weakly compact if and only if every $f{\in}X^{\ast}$ attains its supremum over C at some point of C. Now, we show that if A is an F-convex subset of a Banach space X, then A is bounded and F-closed if and only if every element of $X^{\ast}$ attains its supremum over A at some point of A.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.1
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• pp.106-112
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• 2017

The present study describes flow induced noise generated from a ball valve used for a gas pipeline. Noise generation from a ball valve mainly induces by interference between unstable(or fluctuating) leakage flow and pipe wall when the ball valve is working closed or opened. To measure the positions of the noise source and the amplitude of noise with respect to measuring frequencies, a commercial acoustic camera is introduced. Noise characteristics generated by the ball valve have been performed by four valve opening rates: 30, 50, 70 and 100 percents. It is noted that 100 percent opening rate means that the valve is fully opened. Throughout the experimental measurements using the acoustic camera, the location of the noise source and the noise amplitude with respect to the frequencies for the test ball valve are clearly evaluated. It is found that the dominant frequencies come from the fluctuating flow at the downstream of the ball valve for four opening rates are observed between 3,000Hz and 3,200Hz. Maximum noise amplitude comes from the ball valve reaches 75dB at the valve opening rate of 50 percent.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.540-543
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• 2002

Conventional robot manipulators actuated by motors with the speed reducer such as the harmonic drive have weakness in the load capacity, since the speed reducer does not have enough strength. To overcome this, we proposed and constructed a new type of the robot actuator which is four-bar-link mechanism driven by the ball screw. We developed a new type of a revolute-jointed robot manipulator composed of four axes. The base axis is actuated with conventional speed reducer, but the others are actuated by the proposed actuators. We analyzed the mechanism of the actuators of the robot joints, and developed the dynamics model. The dynamics are expressed in the joint coordinates, and then they are mapped into the sliding coordinates of the ball screw. The structure specifications of the manipulator shown.

• Communications of the Korean Mathematical Society
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• v.12 no.4
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• pp.1023-1032
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• 1997

This paper deals with certain conditions under which irreducibility of a 3-manifold is preserved under attaching a 2-handle along a simple closed curve (and then, if necessary, capping off a 2-sphere boundary component by a 3-ball).

• Journal of the Korean Society of Physical Medicine
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• v.7 no.1
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• pp.49-58
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• 2012

Purpose : The purpose of this study was to investigate the effects of trunk stabilization exercise using swiss ball and core stabilization exercise on balance and gait in elderly women. Methods : Subjects 19 elderly women were randomly divided by the swiss ball exercise group (n=10) and the core stabilization exercise group (n=9). In a period of 4 weeks, they took trunk stabilization exercise using swiss ball and core stabilization exercise for 60 minutes 3 times a week. Balance and gait were measured by Functional Reach Test (FRT), One Leg Stand Test with Open Eye (OLSTOE), One Leg Stand Test with Closed Eye (OLSTCE), Timed Up and Go Test (TUG) and 6 m Walking Test (6MWT). These tests were measured at before exercise, 4 weeks after exercise and after the follow-up period of 2 weeks. Results : As a result, in all measurement values there was no significant difference in two groups (p>.05). In FRT, TUG, OLSTOE and 6MWT before exercise and 4 weeks after exercise, there was significant difference in both of two groups (p<.05). Moreover, according to results from 4 weeks after exercise and after the follow-up period of 2 weeks, without any particular exercise, in FRT and 6MWT there was no significant difference (p>.05). Conclusion : These finding indicate that trunk stabilization exercise using swiss ball could improve balance and gait in elderly women. Accordingly, In this study trunk stabilization exercise using swiss ball and core stabilization exercise is judged to be used for elderly people with gait and balance problems to prevent hurts from fall.