• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.994-1002
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• 2012

Acoustic power transmission loss(TL) is an important performance of the muffler system. TL will be affected by the velocity of the fluid in duct since acoustic pressure varies according to the fluid velocity. In this paper, two kinds of fluid model, potential flow and turbulent flow, for the fluid flowing in simple expansion chamber are considered. The effects of their two fluid models in acoustic TL are investigated for the straight and L-shaped simple expansion chamber. In higher frequency range, the characteristics of TL of the two fluid models show different results. The variation of TL according to the fluid velocity is shown more distinctly when turbulence model is used. Turbulent flow model should be used to obtain better estimation of acoustic TL in higher frequency range.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.361-364
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• 2002

The paper presents a basic study on reliability evaluation using METRIS for long term expansion planning of transmission system. The main frame of methodelogy of the reliability evaluation of a transmission system in the METRIS is based on evaluation philosophy that the reliability level of a transmission system is equal to difference between the reliability level of HLII and that of HLI. While basic general theory of probabilistic reliability evaluation of transmission system has been presented, the GUI characteristics of input/out data system of METRIS have been demonstrated by the RBTS case study on METRIS.

• Journal of KSNVE
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• v.9 no.4
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• pp.738-746
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• 1999

The performance of muffler can be improved for a frequency range of interest by moving inlet and outlet locations. And optimal location of inlet and outlet can be determined to improve the acoustic performance. The optimum design using FEM, however, may take a very long time and be very hard to take inlet and outlet locations as design variables. In this paper, the acoustic performance of reactive type single expansion chamber muffler is predicted using higher order mode theory. The sensitivity analysis of transmission loss with respect to the location of inlet and outlet is suggested. And the acoustic power transmission coefficient for a frequency of interest is used as cost function. Optimum location of inlet and outlet is determined to minimize cost function by using SUMT algorithm.

• Journal of the Korean institute of surface engineering
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• v.35 no.5
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• pp.289-294
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• 2002

ZnTe films have been grown on (100) GaAs substrate with two representative problems. The one is lattice mismatch, the other is thermal expansion coefficients mismatch of ZnTe /GaAs. It claims here, the relationship of film thickness and defects distribution with (100) ZnTe/GaAs using hot wall epitaxy (HWE) growth was investigated by transmission electron microscopy (TEM). It analyzed on the two-sort side using TEM with cross-sectional transmission electron microscopy (XTEM) and high-resolution electron microscopy (HREM). Investigation into the nature and behavior of dislocations with dependence-thickness in (100) ZnTe/ (100) GaAs hetero-structures grown by transmission electron microscopy (TEM). This defects range from interface to 0.7 $\mu\textrm{m}$ was high density, due to the large lattice mismatch and thermal expansion coefficients. The defects of low density was range 0.7$\mu\textrm{m}$~1.8$\mu\textrm{m}$. In the thicker range than 1.8$\mu\textrm{m}$ was measured hardly defects.

• Journal of KSNVE
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• v.3 no.3
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• pp.271-278
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• 1993

Acoustic characteristics of silencer system are affected by various geometric parameters such as cross sectional geometry, size of chamber, and location of inlet-outlet port. It is impossible to obtain exact solutions of the equations of acoustic wave propagation except few simple cases. So, we resort to numerical techniques to analyze performance of acoustic system. In this work, finite element formulation has been obtained to predict transmission loss of an arbitrary 3-dimensional muffler in the presence of mean flow of low mach number. The effect of the degree of the ellipticity of expansion chambers on the transmission loss has been studied using the resulting finite element equation.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.6
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• pp.412-419
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• 2000

There has been a considerable attention on Invar alloys due to its low thermal expansion property. A low thermal expansion property of Invar alloys, lower than $10^{-6}$ near the room temperature, is attractive for electric transmission lines and precision machine tools. However, the expansion property of Invar alloys is limited below about 520K, and mechanical properties are relatively low to apply to electric transmission line. In order to improve mechanical properties in this alloy, Ti alloying element was added to the $Ni_{38}-Mo_2-Cr_1-Fe$ invar alloy. The microstructure Ti added alloy showed finer than that of the unalloyed one. It was found that the (Mo, Ti), Mo carbide formed by Ti addition obstacled grain growth by pinning effect and supplyed recrystallization sites during heat-treatment. Optimum heat-treatment conditions with Ti addition were also discussed in the modified Invar alloy.

• JOURNAL OF ELECTRICAL WORLD
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• no.7 s.163
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• pp.17-22
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• 1990

• JOURNAL OF ELECTRICAL WORLD
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• no.10 s.154
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• pp.8-15
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• 1989

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.7
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• pp.358-365
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• 2005

Transmission networks play an important role which transfer generated electric power to a consumer in power system operation. In a competitive environment of electric power industry, developing the technological criterions and methodologies on transmission planning is becoming new challenge to transmission system planner. The use of a locational signal and the provision of a indicative plan to control the transmission investment reasonably is very important in the viewpoint of a regulator. The main target of this study is to develop a systematic criterion of transmission expansion planning. And system congestion cost is considered. The proposed methodology was demonstrated with several case studies.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.6
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• pp.921-928
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• 1990

A multivariable equalizer is designed which compensates transmission distortion for coaxial transmission line. The characteristic transfer function with bilateral parameter domain is approximated using the expansion method of orthonormal function and Gram Schmidt orthogonal function, but the parameter domain of approximated function is limited to unilateral. To solve that problem, Bode type transfer function is used to give bilateral variable characteristic to approximated function. The multivariable equalizer in this paper can be substituted for the current equalizer which consist of a fixed equalizer and a variable equalizer.