• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.33-36
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• 2000

In this paper, the performance of the W-CDMA system with smart antenna is investigated. The channel is assumed as wideband realistic channel mode, JTC(Joint Technique Committee), which has clustered multipaths. The beamforming-RAKE receiver structure is proposed, whose performance is analyzed on the assumption of the perfect channel estimation. In a simulation, the probability density function(pdf) of SINR(Signal to Interference and Noise Ratio) according to the number of antennas and users is presented. And based on the pdf of SINR, the BER(Bit Error Rate) is presented. According to the result of a simulation, the performance of the W-CDMA system with smart antenna over the realistic JTC channel model has been considerably improved.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.455-462
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• 1991

This paper present an analysis method of crankshaft of four cylinder internal combustion engine for studying dynamic characteristics of the shaft. For simple analysis, uniform sections of journal, pin and arm parts were assumed. Transfer Matrix Method was used, considering branched part and coordinate transformation part. Natural frequencies, natural modes and transfer functions of crank shaft were investigated based upon the Timosenko beam theory: It was shown that the calculated natural frequencies, modeshapes agree well with the experimental results.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.543-550
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• 2002

This work is concerned with the estimation of output derivatives and their use for the design of robust controller for linear systems with systems uncertainties due to modeling errors and disturbance. It is assumed that a nominal transfer function model and Quantitative bounds for system uncertainties are known. The developed control schemes are shown to achieve regulation of the system output and ensures boundedness of the system states without imposing any structural conditions on system uncertainties and disturbances. Output derivative estimation is first conducted trough restructuring of the plant in a specific parameterization. They are utilized for constructing robust nonlinear high-gain feedback controller of a SMC(Sliding Mode Controller) Type. The performances of the developed controller are evaluated and shown to be effective and useful through simulation study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.356-359
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• 2007

In this paper, the stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influences of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived using the Euler beam theory and the Lagrange's equation. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the angular velocity and the depth of crack. Also, the critical flow velocity and stability maps of the rotating pipe system as a function of mass ratio for the changing each parameter are obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.253-258
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• 2002

This work is concerned with the estimation of output derivatives and their use for the design of robust controller for linear systems with systems uncertainties due to modeling errors and disturbance. It is assumed that a nominal transfer function model and quantitative bounds for system uncertainties are known The developed control schemes are shown to achieve regulation of the system output and ensures boundedness of the system states without imposing any structural conditions on system uncertainties and disturbances. Output derivative estimation is first conducted trough restructuring of the plant in a specific parameterization. They are utilized for constructing robust nonlinear high-gain feedback controller of a SMC(Sliding Mode Controller)Type. The performances of the developed controller are evaluated and shown to be effective and useful through simulation study.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.10
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• pp.751-759
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• 2003

The theoretical method is developed to investigate the vibration characteristics of the sloshing and bulging mode for the circular cylindrical storage tank with an annular plate on free surface. The cylindrical tank is filled with an inviscid and incompressible liquid. The liquid domain is limited by a rigid cylindrical surface and a rigid flat bottom. As the effect of free surface waves Is taken into account in the analysis, the bulging and sloshing modes are studied. The solution for the velocity potential of liquid movement is assumed as a suitable harmonic function that satisfies Laplace equation and the relevant boundary conditions. The Rayleigh-Ritz method is used to derive the frequency equation of the cylindrical tank. The effect of Inner-to-outer radius ratio and thickness of annular plate and liquid volume on vibration characteristics of storage tank is studied. The finite element analysis is performed to demonstrate the validity of present theoretical method.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.56-62
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• 1994

Far-zone electric fields radiated by a coaxial cable through an aperture in a perfectly conducting ground plane are calculated utilizing the dyadic Green's function and vector wave functions. In this paper the outer radius $\alpha$ is assumed to be less than 0.02 so that the aperture fields is well approximated by the dominant TEM mode in the coaxial cable. The result of present approach is compared with the readily obtained solution. The present solution is valid outside of the spherical regions with radius `$\alpha$' from the center of coaxial cable.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3159-3162
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• 2008

A sensitivity analysis of the liquid rocket engine has been made. A mode analysis program is used to predict the performance change due to the variation of rocket engine operating environment. The propellant supply pressure and density are the major variables of the operating condition. The material properties of the turbine driving gas is assumed as the function of mixture ratio. The discrepancies of performance change between constant turbine driving gas properties and variable properties are greater for the case of fuel pump inlet pressure change than the oxidizer pump inlet pressure change.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.2
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• pp.273-282
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• 1996

This work is conceded with the estimation of output derivatives and their use for the design of robust controller for linear systems with system uncertainties due to modeling errors and disturbances. It is assumed that a nominal transfer function model and quantitative bounds for system uncertainties and known. The developed control schemes are shown to achieve regulation of the system output and ensures boundedness of the system states without imposing any structural conditions on system uncertainties and disturbances. Output derivative estimation is first conducted through restructuring of the plant in a specific parameterization. They are utilized for constructing robust nonlinear high-gain feedback controller of a SMC(Sliding Mode Control)type. The performances of the developed controller are evaluated and shown to be effective and useful through simulation study.

• The korean journal of orthodontics
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• v.26 no.6
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• pp.647-655
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• 1996

In discussing the effects of adenoids on the development of the face and dentition, it is important to note their influence on the mode of breathing and to relate this to specific facial types and dentition. This study, therefore, assumed that the ability to adapt to individual's neuromuscular complex is various. And tried to investigate the effects of reduced nasal respiratory function on the development of dentition by facial type. This paper is based on children patients with enlarged adenoids and comparing them to data taken from a control group with normal respiratory function. Among the three facial types, the most statistical significant difference was observed from dolichofacial type between experimental and control group. In dolichofacial type, the experimental group showed labioversion of upper incisor, decrease in the width of upper arch, increase in overjet, increase in the rate of cross-bite, and increase in the height of palatal vault. No significant difference was observed between the two groups in the inclination of upper and lower incisors in mesofacial type, but the experimental group was observed to show decrease in the width of upper arch and increase in the height of palatal vault. On the other hand, in brachyfacial type, no significant difference was observed between the two groups in dentition variables except showing linguoversion of upper incisor. The results, which were observed in dolichofacial type, consist with Nordlund's theory of Compression.