• 한국소음진동공학회논문집
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• 제25권11호
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• pp.771-778
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• 2015

In this work, vibration characteristics of high speed rotary bell cup for paint atomizer are numerically investigated. New type of bell cup model is proposed and additional corresponding models with design parameter variations for length and diameter are constructed. Dynamic characteristics, such as natural frequencies and corresponding mode shapes, are studied for each model as a first step. To investigate operation stability, critical speed of rotary bell cup is numerically analyzed based on Campbell diagram and separation margin between operating speed and critical speed is identified. Unbalance vibration responses are also investigated with respect to design parameter variation, operating speed and balancing quality grade of G. Then the proper design guideline for stable operation of high speed rotary bell cup for paint atomizer is suggested.

• 한국소음진동공학회논문집
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• 제26권7호
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• pp.857-864
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• 2016

In the present work, vibration analysis of high speed rotary bell cup model for paint atomizer application is carried out through numerical simulation. At first, eight bell cup models, considering four different cup shapes and two different cup diameters, are proposed and corresponding dynamic characteristics are investigated. To evaluate the operating stability, critical speed analysis is conducted using Campbell diagram and separation margin between operating speed and critical speed is identified. Unbalance vibration responses are also studied according to operating speed and balancing quality grade of G. Finally, the stability and adequacy of the proposed bell cup models are discussed for field application.

• 대한수학회보
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• 제51권4호
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• pp.1127-1133
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• 2014

Let S be a nonempty subset of a ring R. A map $f:R{\rightarrow}R$ is called strong commutativity preserving on S if [f(x), f(y)] = [x, y] for all $x,y{\in}S$, where the symbol [x, y] denotes xy - yx. Bell and Daif proved that if a derivation D of a semiprime ring R is strong commutativity preserving on a nonzero right ideal ${\rho}$ of R, then ${\rho}{\subseteq}Z$, the center of R. Also they proved that if an endomorphism T of a semiprime ring R is strong commutativity preserving on a nonzero two-sided ideal I of R and not identity on the ideal $I{\cup}T^{-1}(I)$, then R contains a nonzero central ideal. This short note shows that the conclusions of Bell and Daif are also true without the additivity of the derivation D and the endomorphism T.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.212-217
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• 1993

In this paper, characteristics of the motions of a human arm are investigated experimentally. When the conditions of the target point are restricted, human adjusts its trajectory and velocity pattern of the arm to fit the conditions skillfully. The purpose of this work is to examine the characteristics of the trajectory, velocity pattern, and the size of the duration in the following cases. First, we examine the case of point-to-point motion. The results are consistent with the minimum jerk theory. However, individual differences in the length of the duration can be observed in the experiment. Second, we examine the case which requires accuracy of positioning at the target point. It is found that the velocity pattern differs from the bell shaped pattern explained by the minimum jerk theory, and has its peak in the first half of the duration. When higher accuracy of the positioning is required, learning effects can be observed. Finally, to examine the case which requires constraint of the arm posture at the target point, we conduct experiments of a human trying to grasp a cup. It is considered that this motion consists of two steps : one is the positioning motion of the person in order to start the grasping motion, the other is the grasping motion of the human's hand approaching toward the cup and grasping it. In addition, two representative velocity patterns are observed : one is the similar velocity pattern explained in the above experiment, the other is the velocity pattern which has its relative maximum in the latter half of the duration.