• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.203-208
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• 2005

Electronic components for space launch vehicles are exposed to a severe vibrational environment at launch and flight. The structural reliability of each component can be verified using mathematical approaches. In order to verify the structural reliability, an important parameter is the natural frequency of PCB(Printed Circuit Board) assembly mounted electronic components on and housing mounted PCB assembly in. In this paper, in order to find natural frequencies of PCB assemblies and the housing of hydrazine TCU(Thruster Control Unit), FEM(Finite Element Method) is adapted. The analytical result of FEM is verified by experimental method.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.96-99
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• 2000

We presents a BGA(Ball Grid Array) package for RF circuit modules and extracted its electrical parameters. We constructed a BGA package of ITS(Intelligent Transportation System) RF module and examined electrical parameters with a HP5475A TDR(Time Domain Reflectometry) equipment and compared its electrical parasitic parameters with PCB RF circuits. With a BGA substrate of 3 $\times$ 3 input and output terminals, we have found that self capacitance of BGA solder ball is 68.6fF, self inductance 146pH, mutual capacitance 10.9fF and mutual inductance 16.9pH. S parameter measurement with a HP4396B Network Analyzer showed the resonance frequency of 1.55㎓ and the loss of 0.26dB. Thus, we may improve electrical performance when we use BGA package structures in the design of RF circuit modules.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.230-235
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• 2017

When the characteristics of a linear induction motor (LIM) are analyzed using finite element analysis (FEA), it is desirable to set the voltage source as an input. If the voltage source is set as an input in FEA, the leakage inductance and primary resistance of the equivalent circuit must be entered by direct calculation, and the magnetizing inductance and secondary reaction effects are directly considered in FEA. Exact calculation is necessary because the primary winding resistance and leakage inductance directly entered will have a significant effect on the LIM output. Therefore, in this study, we accurately calculated the primary leakage inductance and analyzed the resulting LIM characteristics. We calculated the leakage inductance using an analytical equation and FEA, and we confirmed the accuracy by comparing the results with the value experimentally calculated using a manufactured model. We also analyzed the instrument performance and thrust of the LIM as a function of the difference in the leakage inductance. Finally, we present the conclusions on the precise analysis based on the calculation of the leakage inductance.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.6
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• pp.500-504
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• 2001

The present approach based on the genetic algorithm with improved selections of bonds was adopted to extract a bridged T equivalent circuit elements of $\times10\mu m^2$InGaP/GaAs HBT. the small-signal model parameters were extracted using the genetic algorithm from S-parameters measured at different frequencies under multiple forward-active biases, which demonstrate physically meaningful values and consistency. The agreement between the measured and modeled S-parameters is excellent over the frequency range of 2 to 26.5GHz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.100-103
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• 2003

In this paper, the characteristics of an inverted-F antenna for the 2.4GHz local wireless communication system have been analysed in terms of the variation of design parameters. The antenna can be integrated on printed circuit board, and the characteristics in terms of the variation of the gap between feed line and shorting stub, gap between antenna's leg and ground plane, antenna leg's width, substrate's height and dielectric constant are analysed. By using these characterization plot of design parameter, the tuning techniques are proposed to design optimum antenna. The designed antenna has 6.4% frequency bandwidth for VSWR under 1.5 and 3dB gain.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.2
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• pp.276-283
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• 2003

In this paper, a 2-stage power amplifier(PA) for IMT-2000 handset has been designed and fabricated using SiGe HBT, which has excellent frequency characteristics and linearity, to reduce size and weight instead of existing linearization techniques. DC I-V characteristics and S-parameter of SiGe HBT were simulated by Agilent circuit simulator(ADS), with large signal Gummel-Poon nonlinear circuit model. Then the output and interstage matching circuits were designed to satisfy the high power condition and the high gain condition, respectively. The experimental results showed output power of 27.1dBm and ACLR of 20dB, PAE of 34%, and linear power gain of 18.9dB over frequency ranges from 1920MHz to 1980MHz.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.700_701
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• 2009

In comparison with conventional motors, Superconducting Homopolar Synchronous Motors (SHSMs) have advantages that it generates high magnetic field by superconducting winding. Therefore, superconducting coil used in SHSM can reduce the motor size and enhance the motor efficiency for high torque applications under the space constraints for propulsion system. During the design process of SHSM, it is required to evaluate the performance of initial design model, that is accurately analyzed using 3D magnetic field modeling large air-gap and flux distribution of axial direction is properly taken into account. In this paper, we analyze magnetic field of a homopolar motor with a 4-pole homopolar rotor and a stator of 3 phase windings. The field analysis is done using 3D finite element analysis which can reflect the end effect and overhang winding. And we extract mutual inductances between a rotor wind and the 3 stator windings. The extracted inductances are used for evaluation of overall motor performances that are calculated with generalized circuit theory of electrical machines.

• Journal of Electrical Engineering and Technology
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• v.3 no.1
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• pp.88-93
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• 2008

The electromagnetic parameters of a permanent magnet synchronous motor (PMSM) such as the open load permanent magnet flux, d axis reactance $X_d$, and q axis reactance $X_q$, are most essential to the performance analysis and optimization design of the motor. Based on the numerical analysis of the 3D electromagnetic field, the three electromagnetic parameters of permanent magnet synchronous motors with U form interior rotor structures are calculated by FEA. The rules of the leakage coefficient and reactance parameters changing with the air gap length, permanent magnet magnetism length, and isolation magnetic bridge dimensions in the rotor are given. The calculated values agree well with the measured values. The FEA results are integrated with the self compiled electromagnetic design program to optimize the prototype motor. The tested performances of the prototype motor prove that the method is suitable for the optimization of motor structure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.11
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• pp.5616-5630
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• 2019

Fully homomorphic encryption allows a third-party to perform arbitrary computation over encrypted data and is especially suitable for secure outsourced computation. This paper investigates secure outsourced computation of multiple matrix multiplication based on fully homomorphic encryption. Our work significantly improves the latest Mishra et al.'s work. We improve Mishra et al.'s matrix encoding method by introducing a column-order matrix encoding method which requires smaller parameter. This enables us to develop a binary multiplication method for multiple matrix multiplication, which multiplies pairwise two adjacent matrices in the tree structure instead of Mishra et al.'s sequential matrix multiplication from left to right. The binary multiplication method results in a logarithmic-depth circuit, thus is much more efficient than the sequential matrix multiplication method with linear-depth circuit. Experimental results show that for the product of ten 32×32 (64×64) square matrices our method takes only several thousand seconds while Mishra et al.'s method will take about tens of thousands of years which is astonishingly impractical. In addition, we further generalize our result from square matrix to non-square matrix. Experimental results show that the binary multiplication method and the classical dynamic programming method have a similar performance for ten non-square matrices multiplication.

• Journal of the Korea Computer Industry Society
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• v.2 no.10
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• pp.1253-1260
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• 2001

In this paper, a new voltage-controlled tunable analog active element for low-voltage applications and information protection is proposed. The proposed active element is composed of the CMOS complementary cascode circuit which can extend transconductance of an element. Therefore, the unity gain frequency which is determined transconductance is increased than that of the conventional element. And then these results are verified by the $0.25\mutextrm{m}$ CMOS n-well parameter HSPICE simulation. As a result, the gain and the unity gain frequency are 42㏈ and 200MHz respectively in the element on 2V supply voltage. And power dissipation of the designed circuit is 0.32mW.