• Restorative Dentistry and Endodontics
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• v.30 no.2
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• pp.112-120
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• 2005

This study was done to evaluate whether there were any differences in microleakage of class V composite restorations according to restoration site and cavity size. Total sixty-four restorations were made in molar teeth using Esthet-X. Small ($2\;{\times}\;2\;{\times}\;1.5\;mm$) and large ($4{\times}2{\times}1.5\;mm$) restorations were made at the buccal/lingual surface and the proximal surface each. After 1,000 times of thermocycling ($5^{\circ}\;-\;55^{\circ}C$), resin replica was made and the percentage of marginal gap to the whole periphery of the restoration was estimated from SEM evaluation. Thermocycled tooth was dye penetrated with $50\%$ silver nitrate solution. After imbedding in an auto-curing resin, it was serially ground with a thickness of 0.25 mm. Volumetric microleakage was estimated after reconstructing three dimensionally. Two-way ANOVA and independent T-test for dye volume, Mann-Whitney U test for the percentage of marginal gap, Spearman's rho test for the relationship between two techniques were used, The results were as follows : 1. The site and size of the restoration affected on the microleakage of restoration. Namely, much more leakage was seen in the proximal and the large restorations rather than the buccal/lingual and the small restorations. 2. Close relationship was found between two techniques (Correlation coefficient = 0.614/ P = 0.000). Within the limits of this study, it was noted that proximal and the large restorations leaked more than buccal/lingual and the small restorations. Therefore, it should be strictly recommended large exposure of margins should be avoided by reducing unnecessary tooth reduction.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2438-2443
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• 2007

In order to guarantee the performance of electronic products. It is needed to improve the cooling performance of heat sink. So this paper has been made to investigate the cooling performance for the aluminum heat sink using pulsating heat pipe(PHP). The pulsating heat pipe was used as a heat spreader. Working fluid was R-22. Heater (50 mm ${\times}$ 50 mm ${\times}$ 3mm) was attached to heat sink and it generated 30W, 60W, 80W, 100W. Heat sink was tested for forced convection with 1${\sim}$4m/s of inlet air velocity. And both type heat sinks were carried out by using CFD simulation. This study showed that pulsating heat pipe can be a good tool to improve cooling performance of heat sink.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1129-1132
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• 1995

Recently, the concept of automation is widely in shipping and unloading materials using the overhead crane for the enhanced productivity. In this regards, we designed an overhead crane that can be operated by operated by computer control system and installed this system at KAERI. In this paper, we introduce algorithms to find the 3D position, diameter, width, and rotated angle of objects such as drum, coil, and container. And the performance of the presented algorithms is tested using drum and container. The result will be useful for positoning grapple device such as spreader to objects in order to automatically grasp them.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.437-442
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• 2004

In this paper, design specifications for a new generation container crane in year 2013 is investigated. After analyzing the trend of the development of container cranes from the 1950s to date, a prospective size for targeting year 2013 is proposed. Introductory specifications of the frame, trolley, hoist and spreader for the proposed new crane are discussed. Considering that the mega-ships will load and unload more than 15000 boxes at one stop, rough dimensions of the crane including outreach, rail gage, lift, backreach, etc. are also suggested. Although the sheer size of the cranes already present some challenges, the biggest challenge is to improve productivity by maximizing the moves per hour. For this, the speeds of trolleys and hoists, rail loads, stability, etc. are discussed.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.410-415
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• 2018

Expanded graphite (EG)/Ag nanoparticle composites were synthesized by the chemical reduction of Ag ions, followed by the addition of expanded graphite into an Ag reducing solution. The prepared composites showed uniform dispersion of Ag nanoparticles on the surface of expanded graphite and exhibited relatively higher thermal conductivities than those of pure expanded graphite. In the case of 10% Ag content in the composite, the thermal conductivity in the thickness direction was 78% higher than the pure expanded graphite. We suggest that EG/Ag nanoparticle composites are a strong candidate for advanced heat spreading material.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.166.4-166
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• 2001

The oscillation of a crane system is divided into the oscillation of container in respect of its trolley and the oscillation of trolley in relation to the whole crane system. We introduce a new type of crane system that avoids to the irreducible sway of crane system caused by hanging cables. The cables suspending the spreader are replaced by using an "anti-sway system". The proposed system is composed of mechanical arms with function of anti-sway based on conventional line system. The effectiveness of the proposed new type crane system and the controller is shown through the simulation results.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.8
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• pp.727-734
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• 2010

This paper deals with an anti-sway control for a ship-mounted container crane which is disturbed by the wave-induced motions of the ship. We derive a simple dynamics of the ship-mounted container crane with an active anti-sway control system and transform it into a dynamic function for a horizontal variable on the absolute coordinate. Then we propose an control method to reduce pendulation of the spreader and compare its performance with well-known feedback linearization control in computer simulation.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.353-358
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• 2000

This paper presents the experimental investigation about miniature heat pipe for notebook PC. The focus of analysis is the operating temperature not to exceed $65^{\circ}C$ maximum allowable CPU surface temperature. Copper is used to heat pipe material and brass is wick material, and working fluid is selected to water. This cooling system is heat spreader method using a aluminum plate, since this method is most commonly used. According to the present study, heat for 3mm heat pipe, 8W, and for 4mm heat pipe, 10W, is found to power dissipation limit respectively, Soon after this investigation, sufficient long term life test should be followed.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.165-172
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• 1999

Crane operation for transporting heavy loads causes swinging motion at the loads. This sway causes the suspension ropes to leave their grooves and leads to possibility of serious damages. Generally crane is operated by expert's knowledge. Therefore, a satisfactory control method to supress object sway during transport is indispensible. The dynamic behavior of the crane shows nonlinear characteristics. when the length of the rope is changed the crane is time varying system and the design of anti-sway controller is very difficult. In this paper, the nonlinear dynamic model for the industrial overhead crane is derived. and the feedback gain matrix based on the pole-placement method is proposed to supress the swing motion and control the position of the crane. The performance of the controller for the crane model is simulated on the personal computer.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.613-619
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• 1997

The present study has an objetive to define the characteristic of the Porous Concrete to be used in the resistant layers of the pavement. Up to the moment there is no material which is capable which is capable of satisfying the mechanical resistances and drainability, two characterstics which interves, and a detailled study has been carried out on the same order to obtain the porous concrete of this study. such as: Mode and time of compaction. type of cement, water/cement ratio, maxium size of aggregates, sieve test. incorporation of some additives and additions etc., among them emphasizing the use of a method of compaction vibro-compression in the laboratory with which an optimum compacting was reached, and can be obtanied on the site with a spreader rated with double tamper. With this porous concrete for this study whose dominating characteristics is the drainability jointly with a high mechanical resistance. a safe and silence firm is obtained, with can be a great diffusion in the near future, for its application on the pavements. Based on these works carried out, there was the first experience in the world of field application with 25cm of resistance layer of Porous Concrete Pavement in Salamanca, Spain.