• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.251-255
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• 2003

In this paper, a miniaturized directional coupler utilizing lumped element is proposed as a interdigital capacitor. The traditional miniaturization technique of transmission line realized a utilizing MIM(Metal-Insulator-Metal) capacitor on CPW(Coplanar Waveguide). However, we present a simplified design procedure without additional manufacturing process utilizing interdigital capacitor on microstrip with ease of design. The similar characteristics between the conventional directional coupler with ${\lambda}/4$ transmission line and the miniaturized directional coupler with ${\lambda}/8$ transmission line are validated through simulation and measurement results. Miniaturization rate of total size is about 25% while coupled line is about 60%. As a result, this proposed directional coupler can reduce the size of mobile communication system at 2 GHz.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.216-221
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• 2000

In this study, two mathematical models are first constructed to analyze vibration characteristics of a gear train - spindle system of an NC lathe gear box. One is a lumped parameter model which is used for calculating natural frequencies of the torsional vibration, the other is a finite element model for analyzing lateral vibration and critical speeds of the spindle system. In addition, this study examines some possible resonance conditions such as gear mesh frequencies, 1X shaft rpm frequencies over whole operating speed range, and so on. The results may be helpful to design a machine tool gear box with low noise and vibration.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.837-839
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• 2000

Capacitor-run single induction motors have the unbalanced elliptic rotating magnetic field so that it is difficult to analyze the characteristic and calculate the accurate slot leakage reactance of the rotor with the closed slot by using the lumped parameter. In this paper, the characteristic is analyzed by the symmetrical coordinate method in terms of the lumped parameter coupled with the numerical analysis. The secondary parameters are calculated by the one slot pitch boundary condition applying to Finite Element Method (FEM). The analysis results are compared with experimental ones.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.374-379
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• 2010

In this paper, we have mathematically analyzed lumped element type negative group delay circuit (NGDC) and derived general design equation. The applicability of the proposed design equation is validated with mathematical and circuit simulation as well as with experimental results for intentional mobile telecommunication 2000 (IMT-2000) downlink band. As a design example, single branch NGDC with -0.8ns of group delay (GD) for narrow bandwidth of the specific frequency is simulated and fabricated. Finally, $\pi$-network NGDC is proposed and validated to obtain wideband GD response of $-1.7{\pm}0.06$ nsec for 60 MHz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.333-338
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• 1997

A hollow crankshaft is considered as part of an effort to reduce the weight of the automobile powertrain. Since the resulting mass reduction alters both the inertia and stiffness properties of the crankshaft, the vibration characteristics of the hollow crankshaft needs to be investigated in comparison with the original solid crankshaft. The crankshafts are modeled by 38 lumped mass and stiffness elements, in which the dynamic parameters for each lumped element are obtained by the finite element calculation. The fluid-film bearings supporting the crankshaft give rise to linear spring and damping elements that can be derived from the hydrodynamic bearing model. The transfer matrix method is applied to yield the natural frequencies and mode shapes of the crankshaft vibration. The natural frequencies of the hollow crankshaft are founded to be greater than that of the solid crankshaft, and the incorporation of the bearing stiffness tends to accentuate the difference.

• Journal of Advanced Navigation Technology
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• v.17 no.1
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• pp.33-38
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• 2013

In this paper, we present the design and measured performances of an dual-band Gysel power divider based on band-stop characteristic. After the Gysel divider is designed by lumped elements at single operating frequency, and then using filter conversion technique the lumped elements were changed a band-stop characteristic with dual-band characteristics. The features of this design method are that ${\lambda}/4$ transmission line by replacing lumped elements suppressed harmonic characteristics and also can reduce the size. To validate of the proposed power divider, the divider has been designed and measured at 880 MHz and 1650 MHz dual frequencies. The measured performances of the Gysel divider agree with prediction results at two frequencies.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.54-59
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• 2009

In this paper, the effect of the position and size of a lumped mass on the structural stability of a high speed underwater vehicle is presented. For simplicity, a real vehicle was modeled as a follower force subjected beam that was resting on an elastic foundation, and the lumped mass effect was simplified as an elastic intermediate support. The stability of the simplified model was numerically analyzed based on the Finite element method (FEM). This numerical simulation revealed that flutter type instability or divergence type instability occurs, depending on the position and stiffness of the elastic intermediate support, which implies that the instability of the real model is affected by the position and size of the lumped mass.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.1
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• pp.34-42
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• 1998

This paper discribes an analysis for the sleeve monopole antenna with single sleeve. The structure of the proposed antenna is very simple. Therefore, it is very economical in terms of manufacturing and installation which makes it convenient for either portable or mobile use by making an up-and-down type antenna. In the method of analysis, instead of the complex electro- magneticapproach, we used a lumped element equivalent circuit derived from the information about the electrical dimensions and the resonance characteristics of the antenna. An error between a resonant frequency by lumped-element circuit analysis of the proposed antenna and a measured one by an experiment is below 0.9%. It is shown that the theoretical and experiment results are little different.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.205-208
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• 2001

A lumped electrical circuit is an approximate representation of the field within a curtain frequency range. The finite element modelling is a synonym of the equivalent circuit. The electric conduction field and electric potential wave field have been modelled by an admittance network and an LC low-pass filter network. Here in the present paper, the equivalent magnetic circuit representation is created for a magnetostatic field by the finite element modelling in two dimension.

• Journal of the Korean Institute of Telematics and Electronics
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• v.12 no.5
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• pp.19-24
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• 1975

The problem of realizing a driving-Point impedance, the argument, $\theta$o, of which is as constant as possible over a given frequency reange was considered. An optimal design technique was applied by varying systematically the shape of the distributed element and the parameter values of the lumped elements. As a result it was possible to make the argument over two decades of frequencies within-2.5$^{\circ}$ for $\theta$o=- 30$^{\circ}$ and -60$^{\circ}$ and very flat above a certain frequency for $\theta$o=-45$^{\circ}$.