• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.231-234
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• 2002

Ultrasonic machining technology has been developed over recent years for the manufacture of cost-effective and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile. Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. The process is non-thermal, non-chemical and non-electric and hardly creates changes to the mechanical properties of the brittle materials machined. This paper describes the characteristics of the micro-hole of $\textrm{Al}_2\textrm{O}_3$ by ultrasonic machining with tungsten carbide tool. The effects of various parameters of ultrasonic machining, including abrasives, machining force and pressure, on the material removal rate, hole quality, and tool wear presented and discussed. The ultrasonic Machining of micro-holes in ceramics has been under taken and the machining mechanism in the ultrasonic machining of ceramics based on the fracture-mechanics concept has been analyzed.

• Tribology and Lubricants
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• v.15 no.2
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• pp.193-198
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• 1999

Applying design methodology, new type friction tester has been developed. Functional analysis has been executed and functional structure were constructed during the conceptual design. Optimal solution has been selected and a proto model has been manufactured according to the conceptual design. Using the tester developed in the laboratory, frictional characteristics of natural rubbers have been experimentally analyzed. Friction coefficient has been calculated from the measured normal force and friction force under various speeds, loads, and temperatures. The corelations between the various operating conditions and friction coefficients have been verified. Especially, drag friction due to the visco-elastic behavior of the rubber has been observed in this analysis.

• Journal of Korea Society of Digital Industry and Information Management
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• v.4 no.2
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• pp.101-108
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• 2008

In this paper, we develop system to backup automatically personal data by real time based on ECA model. This system backups data that is changed in user PC using CDP technology based on ECA model. Proposed ECA model defines file's change such as file creation, update, remove etc. in user PC to event for synchronization between server and user PC. If event is detected about file, proposed system examines condition that is defined and backup the file to server. Backup data that is stored to server can recovery on point of time that user wants. The proposed system can be applied to data management system for business, personal data management system, high-capacity contents management system etc.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1535-1540
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• 2008

This paper are using a test apparatus developed in the laboratory, friction and wear characteristics of various rubbers have been analyzed by experimental study. Friction coefficient has been calculated from the measured normal force and friction force under various speed operating conditions, such as, loads and temperatures. The tire are used in a automobile, the relations between the various operating conditions and friction characteristics have been verified.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.29-36
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• 2000

This investigation has been studied about friction and wear properties which were important problem, when carbon fiber reinforced plastic(CFRP) was used practically. Unidirection carbon fiber reinforced composites was fabricated with epoxy resin matrix and carbon fiber as a reinforced, and its surface was modified by the ion-assisted reaction. And then we tested the their friction and wear properties according to the ion-irradiation. when the amount of ion-irradiation was 1${\times}$10l6$\^$16/ ions/$\textrm{cm}^2$, the friction coefficient values were about 0.1, where as, the friction coefficient values of non-treatment composites were about 0.16. The former was the stablest in wear mode. We know that ion-irradiation was not proportioned to the friction coefficient, so we found the optimal conditions of the friction and wear according to the ion-irradiation.

• Tribology and Lubricants
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• v.17 no.4
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• pp.335-340
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• 2001

It was reviewed that the kinds of lubricating oil, viscosity, temperature and strength of materials affected the wear of the surface heat treatment. When lubricants is used under severe running conditions, their tribological characteristics are very important. We have studied the lubricating oil viscosity, kinds of additives and their amounts, and lubricating oil temperatures were changed. In order to study the effect of oil temperature on the wear of the surface, the temperature of the oil was changed for the same sample. It was shown from the test results that wear is not greatly affected by the amount of ZnDTP (Zinc dialkyl dithio phosphate) antiwear agent, but EP (Extreme pressure) additives are less effective against wear than ZnDTP additives. The viscosity of lubricating oil and its temperature greatly affect the wear of the surface. Combining all the wear data with those of the surface strength, it was observed that the higher the load, the lower the scratch of wear, and also in the case of the same running load, the lower the wear, the longer the life of the surface strength.

• Tribology and Lubricants
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• v.14 no.2
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• pp.57-62
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• 1998

When lubricants is used under severe running conditions, their tribological characteristics are very important. We have studied the lubricating oil viscosity, kinds of additives and their amounts, and lubricating oil temperatures were changed. In order to study the effect of oil temperature on the wear of the surface, the temperature of the oil was changed for the same sample. Moreover, the temperatures of three kinds of oils which have very different viscosities at room temperature, were varied between 6$0^{\circ}C$ and 115$^{\circ}C$ while the oil viscosity was unchanged. It was shown from the test results that surface wear is not greatly affected by the amount of ZnDTP (Zinc dialkyl dithio phosphate) antiwear agent, but EP (Extreme pressure) additives are less effective against wear than ZnDTP additives. The viscosity of lubricating oil and its temperature greatly affect the wear of the surface. Combining all the wear data with those of the surface strength, it was observed that the higher the load, the wider the scratching of wear, and also in the case of the same running load, the lower the wear, the longer the life of the surface strength.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.1865-1870
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• 2014

Torque converter is a complex turbomachine used to transfer power smoothly from an engine to a transmission by lock-up clutch. A torque converter consists of the hydrodynamic clutch device and the lock-up clutch device. The retaining plate and driven plate are part of the lock-up clutch. The lock-up clutch connects directly to achieve the improvement of efficiency and fuel consumption. In this paper, using structure analysis of stress distribution on the shape of the mechanical stopper on retaining plate. The shape of mechanical stopper has effect on the stress distribution of lock-up clutch.

• Journal of Information Technology Services
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• v.12 no.4
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• pp.109-124
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• 2013

Recently domestic companies have struggled to deal with different kinds of crisis accrued from various sources. However, their perception on the crisis and crisis management system are extremely vulnerable. In particular, although almost all companies have had many business related crisis, they have tended to ignore the crisis with simply considering it as unlucky and not to approach it provocatively in preparing some preventive measures and turning it into an opportunity due to the lack of recognizing the importance of risk management. In other words, domestic companies have not systematically prepared detailed plans for potential crisis, rather have tended to recognize the importance of having crisis management system after experiencing a detrimental crisis or accident. Furthermore research on the issue has conducted sparsely in the academic world. The purpose of this study was to investigate the differences among types of businesses in terms of the degree of crisis experienced previously, the perception on the importance of crisis management system, the level of crisis management implementation, and the areas of crisis management being focused in the future. Usable data was collected from 201 companies using an on-site survey. Data was analyzed with SPSS 21.0 using some descriptive statistics and a series of ANOVA (One-way Analysis of Variance). Results and implications were provided, along with some future research directions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.8-14
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• 2016

Medical bed head consoles (BHC) are generally used to increase the efficiency of medical equipment and speed the medical treatment response time. The BHC design has been consistently improved including a movable shelf unit that is embedded to mount stably medical instruments on the lower part of the main console. The cost of a BHC can be reduced through design optimization to limit the overall weight. However, as the size of a head console might decrease due to design optimization, the BHC deflection could be increased. In this study, multi-objective optimal design was adopted to consider this BHC design problem. In order to reduce the cost of optimization planning, an approximate model was applied for the design optimization. In the context of approximate optimization, we used the response surface method and non-dominant sorting genetic algorithm developed from various fields. Multi-objective optimal solutions were also compared with a single objective optimal design.