• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.235-240
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• 2002

In micro-EBM, it is well blown that RC circuit is suitable for discharge circuit because of its low pulse width and relatively high peak current. To increase machining speed without changing unit discharge energy, charge resistance should be decreased. But, if very low, continuous (or normal) arc discharge occurs, then increases electrode wear and reduces machining speed remarkably. In this paper, RC circuit with transistor is used to micro-EDM. Experimental results show that RC circuit with transistor can cut off continuous (or normal) arc discharge effectively if duty factor and switching period of transistor are set up optimally. Through experiments with varying charge resistance, it can be known that RC circuit with transistor has about two times faster machining speed than that of RC circuit. Especially, it has prominent rise-effect of machining speed in low unit discharge energy, so that a high-quality and high-speed micro-EDM can be realized through RC circuit with transistor.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.44-51
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• 2004

In a micro-EDM, it is well known that an RC circuit is suitable as a discharge circuit because of its low pulse width and relatively high peak current. To increase machining speed without changing unit discharge energy, charge resistance should be decreased. But, when the resistance is very low, continuous (or normal) arc discharge occurs, electrode wear increases and machining speed is reduced remarkably. In this paper, an RC circuit with transistors is used in a micro-EDM. Experimental results show that the RC circuit with transistors can cut off a continuous (o. normal) arc discharge effectively if the duty factor and switching period of the transistor are set up optimally. Through experiments with varying charge resistances, it is shown that the RC circuit with transistors has about two times faster machining speed than that of an RC circuit.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.235-238
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• 2009

To study the relationship between spark ignition and the gap in the nano-scale region, the electric potential was applied to between a Pt-Ir tip and a gold substrate. The tip was sharpened by electro-chemical etching process in the solution of $CaCl_2;H_2O$ and acetone. The radius of tip was measured to be around 200nm and attached to the scanning probe microscope to control the gap between the tip and the substrate. The electric potential of 10V to 80V was applied to initialize the spark. The gaps and the current profile were measured to analyze the characteristics of spark ignition. A spark sustaining time was measured to be between 50ns and 200ns depending on the applied electric potential and the gap between the electrodes. The continuous electric discharge was successfully sustained up to 1 second of spark or arc time. The developed process can be applicable to the micro-scale fabrication of automotive sensors as a similar concept of GTAW.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.227-230
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• 2003

Silicone rubber has very excellent chemical stability and hydrophobicity. A hydrophobic surface can prevent the formation of continuous water films on the surface in wet and heavily contaminated conditions. This phenomenon contributes to the suppression of leakage current and partial discharges on insulator surfaces. Silicone rubber has been used much for housing materials of polymer insulators. ATH is added to the silicone rubber for improvement of its resistance against surface discharge. In this paper, ATH with different particle size and content was added to the silicone rubber during compounding. Silicone rubber was deteriorated by a corona treatment. Hydrophobicity recovery rate after corona treatment and arc resistance of silicone rubber were investigated. Hydrophobicity recovery rate of silicone rubber was evaluated by the measurement of contact angle. Arc resistance was evaluated by measuring weight loss of silicone rubber after arc resistance test. It was observed that the hydrophobicity recovery rate and arc resistance of silicone rubber were different when different particle size and content of ATH were added.

• The Korean Journal of Health Service Management
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• v.1 no.1
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• pp.59-74
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• 2007

Considering the characteristics of the Korean family which maintain a close connection with their patients from the moment of their falling sick to hospitalization to discharge, the family is the most important environmental factor of the social supporting system, and is the important object of the client as well as activity system. The medical social work intends to meet the practical needs of aged chronic patients, providing them and their family with a professional human service. The end of this study is to find out the hardships of both the aged chronic patients and their family as well as their needs for the social welfare service, and to search out the way of comprehensive social work service. The summary of the analysis of the survey is as follows: 1. The needs of aged chronic patients are divided into those of the solution of the problems of falling ill, social welfare program and discharge. Those needs arc affected by the various factors of the types of hospitals, the patients' age, the kinds of insurance, and the supporting systems, etc. Accordingly, the assessment of the needs of the patients are asked to be done comprehensively in accordance with the kinds of diseases and social environments. 2. The importance of the family to the aged chronic patients is evident. The family plays a decisive role in the patients' hospitalization and discharge, the family being an important supporting system and making it necessary to take an approach to client system. The family has difficulty in getting connection of community resources, in adapting to social life after the patient's discharge, and in paying the treatment. The family suffers the secondary hardships more than the burden of the treatment expenses. 3. For this reason various interventions are needed to reduce the stress caused by supporting and nursing patients. Thus the social welfare service for the aged chronic patients and their family needs the following prepositions: 1. It is the characteristics of the aged chronic patients that they need continuous care and that the strengths of the patients and their family cannot be too much emphasized, and that comprehensive assessment based on the connection 'with the community and the mutual interchange 'with the environment, is much emphasized. 2. The family of the aged chronic patient is a resources system as well as a client one. 3. Another characteristic of the aged chronic patients is that with the resources connection in mind, it needs an active intervention of social workers in the community. With these prepositions considered, the development of practical social work service for the aged chronic patients is thought urgently needed.