• Journal for History of Mathematics
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• v.18 no.1
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• pp.103-110
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• 2005

This paper is aimed at studying a historical background of graph theory and we deal with the computer representation of graph through a simple example. Graph is represented by adjacency matrix, edge table, adjacency lists and we study the matrix representation by Euler circuit. The effect of the matrix representation by Euler circuit economize the storage capacity of computer. The economy of a storage capacity has meaning on a mobile system.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.4
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• pp.233-239
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• 2000

There are many difficult problems in analyzing the gas flow in puffer type circuit breaker such as complex geometry, moving boundary, shock wave and so on. To predict the interruption performance accurately, these should be considered in the simulation. In this paper, the analysis procedure of the cold gas flow in the circuit breaker is presented. Euler equation is solved by FVFLIC method which is an explicit time difference scheme for an unsteady flow computation. Moving boundaries are treated with a cell elimination-addition technique. The pressure and density in front of piston are calculated from the rate of the cell volume change. The presented method is applied to the real circuit breaker model and the pressure in front of the piston is good agreement with the experimental one.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.4
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• pp.121-128
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• 2001

Numerical schemes for the simulation of the cold gas flow in the SF6 puffer type circuit breaker is presented. The governing equation is axisymmetric compressible Euler Equation and FVM is used to analyze the behavior of flow. The upwind scheme is used to avoid numerical instability and MUSCL is used to obtain high order accuracy. For the efficient calculation, AF-ADI scheme is used. The simulation result shows good agreement with the experimental data.

• Smart Structures and Systems
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• v.7 no.5
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• pp.417-432
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• 2011

The present paper is devoted to vibration canceling and shape control of piezoelastic slender beams. Taking into account the presence of electric networks, an extended electromechanically coupled Bernoulli-Euler beam theory for passive piezoelectric composite structures is shortly introduced in the first part of our contribution. The second part of the paper deals with the concept of passive shape control of beams using shaped piezoelectric layers and tuned inductive networks. It is shown that an impedance matching and a shaping condition must be fulfilled in order to perfectly cancel vibrations due to an arbitrary harmonic load for a specific frequency. As a main result of the present paper, the correctness of the theory of passive shape control is demonstrated for a harmonically excited piezoelelastic cantilever by a finite element calculation based on one-dimensional Bernoulli-Euler beam elements, as well as by the commercial finite element code of ANSYS using three-dimensional solid elements. Finally, an outlook for the practical importance of the passive shape control concept is given: It is shown that harmonic vibrations of a beam with properly shaped layers according to the presented passive shape control theory, which are attached to an resistor-inductive circuit (RL-circuit), can be significantly reduced over a large frequency range compared to a beam with uniformly distributed piezoelectric layers.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.882-884
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• 2002

The transient voltage characteristics of capacitor self-exited induction generator are analyzed by the state equation which is obtained from the d-q axis equivalent circuit of stationary reference frame and torque equation. The d-q equivalent circuit is composed using the condition of stationary reference frame. The mutual inductance is only considered as a function of magnetizing current in the equivalent circuit. The characteristics are analyzed and discussed by the backward Euler method for various load conditions under specified initial conditions and input.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.106-109
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• 2008

Piecewise linear diode models are widely used for large-signal circuit analyses, especially power electronic circuit simulations. When using a piecewise linear diode model for simulation, a switching method to select a proper one among linear models is needed. The conventional switching method keeps the previous ON, OFF state information, and applies different switching conditions according to the state. However, this method has difficulties especially in extending to multi-piecewise linear models. This paper presents a switching method which appropriately divides the v-i plane into regions and select a linear model according to the region where the operating point(the voltage and the current of the diode) belongs. This switching method is easily extended to multi-Piecewise linear models. An example using the tableau analysis and the backward Euler integration is presented for verification.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.3
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• pp.115-121
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• 2003

This paper proposes a radiation model, which considers radiation transport as an important component in hot gas analysis. This radiation model is derived from combining the method of partial characteristics (MPC) with net emission coefficient (NEC), and it covers the drawbacks of existing models. Subsequently, using this proposed model, the arc-flow interaction in an arcing chamber can be efficiently computed. The arc is represented as an energy source term composed of ohmic heating and the radiation transport in the energy conservation equation. Ohmic heating term was computed by the electric field analysis within the conducting plasma region. Radiation transport was calculated by the proposed radiation model. Also, in this paper, radiation models were introduced and applied to the gas circuit breaker (GCB) model. Through simulation results, the efficiency of the proposed model was confirmed.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.306-308
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• 1997

In this paper, We present the transient analysis method of induction motor by TDFE(Time Domain Finite Element) method. For simulation of transient performance, Maxwell's equations are solved using 2-Dimensional TDFE method, and the circuit equations from the stator and rotor are solved simultaneously. The time derivatives are discretized with Euler scheme and the Newton-Raphson iteration method is applied to a large system of equations which are representing the whole magnetic and feeding circuit equations because of the magnetic nonlinearity of the stator and rotor core. The presented method is applied to three phase induction motor. And we obtained the phase currents, torque and rotor position until the steady state.

• Journal of IKEEE
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• v.23 no.4
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• pp.1321-1327
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• 2019

This paper describes an efficient hardware implementation of modular square root (MSQR) computation over GF(p), which is the operation needed to map plaintext messages to points on elliptic curves for elliptic curve (EC)-ElGamal public-key encryption. Our method supports five sizes of elliptic curves over GF(p) defined by the National Institute of Standards and Technology (NIST) standard. For the Koblitz curves and the pseudorandom curves with 192-bit, 256-bit, 384-bit and 521-bit, the Euler's Criterion based on the characteristic of the modulo values was applied. For the elliptic curves with 224-bit, the Tonelli-Shanks algorithm was simplified and applied to compute MSQR. The proposed method was implemented using the finite field arithmetic circuit with 32-bit datapath and memory block of elliptic curve cryptography (ECC) processor, and its hardware operation was verified by implementing it on the Virtex-5 field programmable gate array (FPGA) device. When the implemented circuit operates with a 50 MHz clock, the computation of MSQR takes about 18 ms for 224-bit pseudorandom curves and about 4 ms for 256-bit Koblitz curves.

• Smart Structures and Systems
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• v.19 no.5
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• pp.567-576
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• 2017

Design of piezoelectric energy harvester for a wide operating frequency range is a challenging problem and is currently being investigated by many researchers. Widening the operating frequency is required, as the energy is harvested from ambient source of vibration which consists of spectrum of frequency. This paper presents a new technique to increase the operating frequency range which is achieved by designing a harvester featured by a propped cantilever beam with variable over hang length. The proposed piezoelectric energy harvester is modeled analytically using Euler Bernoulli beam theory and the effectiveness of the harvester is demonstrated through experimentation. The results from analytical model and from experimentation reveal that the proposed energy harvester generates an open circuit output voltage ranging from 36.43 V to 11.94 V for the frequency range of 27.24 Hz to 48.47 Hz. The proposed harvester produces continuously varying output voltage and power in the broadened operating frequency range.