• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.315-318
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• 2005

Lots of researches have been focusing on ubiquitous computing which means wherever, whenever, whatever the required information must be accessible. In ubiquitous computing environment, ubiquitous sensor network (USN) is the basis technology for gathering and transferring the required information. However sensor network characteristically has more severe vulnerability than the existing networks do. The paper presents operation of secure protocols for delivering information in secure in ubiquitous computing environment and show improvement of the secure transferring protocol.

• Journal of Mechanical Science and Technology
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• v.14 no.3
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• pp.331-337
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• 2000

A numerical procedure for contact analysis and calculating subsurface stress was developed. The procedure takes the advantage of signal processing technique in frequency domain to achieve shorter computing time. Boussinesq's equation was adopted as a response function in contact analysis. The validity of this procedure was proved by comparing the numerical results with the exact solutions. The fastness of this procedure was also compared with other algorithm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.994-999
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• 2002

The Pendulum Automatic Dynamic Balancer is a device to reduce the unbalanced mass of rotors. For the analysis of dynamic stability and behavior, the nonlinear equations of motion for a system including the Pendulum Balancer are derived with respect to polar coordinate by Lagrange's equations. And the perturbation method is applied to find the equilibrium positions and to obtain the linear variation equations. Based on the linearized equations, the dynamic stability of the system around the equilibrium positions is investigated by the eigenvalue problem. Furthermore, in order to confirm the stability, the time responses for the system are computed from the nonlinear equations of motion.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.593-598
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• 2002

Coupling adjacent steel frame using elastic dampers for control of response to low and moderate dynamic event is investigated in this paper. The complex modal superposition method is first used to determine dynamic characteristic, mainly modal damping ratio and modal frequency, of damper linked linear adjacent steel frame for fractical use. Dynamic response of steel frame linked by hydraulic-excitation method. This combined method can efectively and accurately determine dynamic response of non-clasically damped systems in the frequency domain. Parametric studties are finally performed to identify optimal parameters of elastic dampers for achieving the maximum modal damping ratio or the maximum response reduction of steel frame. It is demonstrated that using discrete elasatic dampers of proper parameters to link steel frame can reduce dynamic response significantly.

• Journal of the Korean Magnetic Resonance Society
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• v.5 no.1
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• pp.13-18
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• 2001

Natural alpha radiation produced a stable defect center to certain minerals. Electron Paramagnetic Resonance(EPR) spectroscopy is a powerful tool f3r quantifying this defect center. EPR method has been applied to trace alpha-radiation effect around the uranium ore deposit. The results show that EPR technique can be used to measure rapidly and nondestructively the defect center produced by natural alpha radiation. In general, a good correlation was achieved between defect center concentration and actinide elements(U, Th). These results imply that the concentration of defect center is dependent on the alpha radiation dose over long time scale.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.468-472
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• 2007

For small capacity rectifier circuits such as these for consumer electronics and appliances, capacitor input type rectifier circuits are generally used. Consequently, various harmonics generated within the power system become a serious problem. Various studies of this effect have been presented previously. The absence of switching devices makes systems more tolerant to over-load, and brings low radio noise benefits. We propose a power factor correction scheme using a LC resonant in commercial frequency without switching devices. In this method, It makes a sinusoidal wave by widening conduction period using the current resonance in commercial frequency, Hence, the harmonic characteristics can be significantly improved, where the lower order harmonics, such as the fifth and seventh orders are much reduced. The result are confirmed by the theoretical and expermental implementations

• Journal of the Korea Safety Management & Science
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• v.10 no.3
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• pp.267-274
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• 2008

This paper reports generating creative ideas based on customer needs using Kano Model and Importance-Differentiation Matrix (I-D Matrix). Nowadays, every customer demands creative ideas on product innovations in order to be satisfied her needs. However, most existing methods are limited to get creative ideas that reflect customer needs. Any creative ideas that do not fully reflect customer needs are obviously more difficult to succeed in the market than those that reflect customer needs. This paper distinguishes each quality elements the customer needs in terms of Kano Model. And it presents the effective ways of generating creative ideas by I-D Matrix in order to overcome current uppermost limits.

• Nuclear Engineering and Technology
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• v.29 no.5
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• pp.393-398
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• 1997

Batch sorption experiments were carried out to investigate the sorption characteristics of $^{90}$ Sr onto domestic granite(HG) and tuff(TF) samples. The effect of three independent variables ([Sr], Vo1/Wt], [pH]) on the sorption was investigated. (Sr) played as the most significant variable for the $^{90}$ S $r^{2+}$ sorption onto HG, whereas [pH] had the greatest effect among three variables onto TF. Tuff shooed much greater sorption than granite, which ues accounted for their differences in mineralogical properties. The selectivity of $^{90}$ Sr was much lower than that of $^{l37}$Cs.s.s.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.140-146
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• 2001

Seals in a universal joint bearing are important components reinforcing lubrication performance by holding lubricant and preventing infiltration of dust, moisture, etc.. There is a great difference in seal performance according to seal shape and bonding position. Therefore, in this study, as for both the lip type seal and the O-ring type seal, FE analysis is conducted using Mooned-Rivlin Model. The results show that O-ring type seal does not have any effect of misalignment angle compared with lib type seal, which is more profitable.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.357-358
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• 2010

This study was performed an evaluation of chloride attack resistance properties of marine concrete by accelerated deterioration test of artificial seawater. As the results of study, when considering the compressive strength and chloride ion penetration of concrete, the proper type to improvement of chloride attack resistance is thought to marine cement.