• Geomechanics and Engineering
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• v.16 no.6
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• pp.609-618
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• 2018

A new mechanical model for predicting the vibration of a pipe pile embedded in longitudinally layered visco-elastic media with radial inhomogeneity is proposed by extending Novak's plain-strain model and complex stiffness method to consider viscous-type damping. The analytical solutions for the dynamic impedance, the velocity admittance and the reflected signal of wave velocity at the pile head are also derived and subsequently verified by comparison with existing solutions. An extensive parametric analysis is further performed to examine the effects of shear modulus, viscous damping coefficient, coefficient of disturbance degree, weakening or strengthening range of surrounding soil and longitudinal soft or hard interbedded layer on the velocity admittance and the reflected signal of wave velocity at the pile head. It is demonstrated that the proposed model and the obtained solutions provide extensive possibilities for practical application compared with previous related studies.

• Journal of the Semiconductor & Display Technology
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• v.19 no.4
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• pp.126-129
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• 2020

We introduce a lifetime assessment technique using deep learning algorithm with complex electrical parameters such as resistivity, permittivity, impedance parameters as integrated indicators for predicting the degradation of the organic molecules. The evaluation system consists of fully automated in-situ measurement system and multiple layer perceptron learning system with five hidden layers and 1011 perceptra in each layer. Prediction accuracies are calculated and compared depending on the physical feature, learning hyperparameters. 62.5% of full time-series data are used for training and its prediction accuracy is estimated as r-square value of 0.99. Remaining 37.5% of the data are used for testing with prediction accuracy of 0.95. With k-fold cross-validation, the stability to the instantaneous changes in the measured data is also improved.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.170-178
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• 2010

In this paper, we propose the modeling of the power/ground plane which includes complex dielectric permittivity and loss tangent for the power/ground coupled noise. In order to estimate the effects of the dielectric substrate for the coupled noise, we used full-wave simulators, HFSS(High Frequency Structure Simulation) and MWS(MicroWave Studio). The simulated results for the commercial substrates are compared with the measured values. TLM(Transmission Line Method) was used for the calculation of power plane impedance using Debye model which depicts the dielectric loss of PCB. Finally, impedance from proposed circuit model showed very good coincidence to the measured data.

• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.655-659
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• 2007

Zirconia polycrystals co-doped with x mol% CaO and (10-x) mol% $Y_2O_3$ were prepared by solid state reaction method. The compositions were chosen for nominally the same oxygen vacancy concentration of 5 mol%. X-ray diffraction patterns indicated the formation of cubic zirconia by heat treatment at $1600^{\circ}C$. Impedance spectroscopy was applied to deconvolute the bulk and grain boundary response. Electrical conductivity was measured using the complex impedance technique from 516 to 874 K in air. Maximum conductivity was exhibited by the composition with equal amounts of CaO and $Y_2O_3$, which may be ascribed to the smaller degree of defect-interactions in that composition due to the competition of different ordering schemes between the two systems. When compared to the composition containing $Y_2O_3$ only, co-doping of CaO increases the grain boundary resistance considerably. The activation energy of grain and grain boundary conductivity was 1.1 eV and 1.2 eV, respectively, with no appreciable dependence on dopant compositions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.789-796
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• 2012

Radiated noise analysis from a ship structure is a challenging topic owing to difficulties in the accurate calculation of the fluid-structure interaction as well as owing to a massive degree of freedom of the problem. To reduce the severity of the problem, a new fluid-structure interaction formulation is proposed in this paper. The complex frequency-dependent added mass and damping matrices are calculated using the high-order Burton-Miller boundary integral equation formulation to obtain accurate values over all frequency bands. The calculated fluid-structure interaction effects are added to the structural matrices calculated by commercial finite element software, MSC/NASTRAN. Then, the impedance and underwater radiation noise due to an excitation of structure are calculated. The present formulation is applied to a ship to calculate the underwater radiated noise.

• Korean Journal of Materials Research
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• v.10 no.6
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• pp.430-436
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• 2000

In this paper, we have studied the effect of constituent ratio NiO, CuO and doped with B-Bi-Zn on proper-ties(microstructure, density, shrinkage, permeability as a function of frequency, etc.) of hexagonal-ferrite for high fre- quency chip-inductor material about several GHz. The permeability were analyzed by impedance analyzer(100 kHz∼ 40 MHz) and network analyzed(30 MHz∼3 GHz). As a result of the characteristics. the B-Bi-Zn glass ceramic was used to lower the sintering temperature for additive as function of frequency from 100kHz to 1.8 GHz showed con-stant tends. The maximum imaginary value of complex permeability was observed near the resonance frequency of 2 GHz.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.75-85
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• 2016

A pyrotechnic system consisting of donor/acceptor pair separated by a gap relies on shock attenuation characteristics of the gap material and shock sensitivity of the donor and acceptor charges. Despite of its common use, numerical study of such pyrotechnic train configuration is seldom reported because proper modeling of the full process requires precise capturing of the shock wave attenuation in the gap prior to triggering a full detonation of high explosive and accurate description of the high strain rate dynamics of the explosively loaded inert confinements. We apply a Eulerian level-set based multimaterial hydrocode with reactive flow models for pentolite donor and heavily aluminized RDX as acceptor charge. The complex shock interaction, critical gap thickness, acoustic impedance, and go/no-go characteristics of the gap test are quantitatively investigated.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.1
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• pp.61-69
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• 2013

Polymer exchange membrane (PEM) fuel cells have multifunctional properties, and bipolar plates are one of the key components in these fuel cells. Generally, a bipolar plate has a gas flow path for hydrogen and oxygen liberated at the anode and cathode, respectively. In this study, the influence of iodine applied to a bipolar plate was investigated. Accordingly, we compared bipolar plates with and without iodine coating, and the performances of these plates were evaluated under operating conditions of $75^{\circ}C$ and 100% relative humidity. The membrane and platinum-carbon layer were affected by the iodine-coated bipolar plate. Bipolar plates coated with iodine and a membrane-electrode assembly (MEA) were investigated by electron probe microanalyzer (EPMA) and energy-dispersive x-ray spectroscopy (EDS) analysis. Polarization curves showed that the performance of a coated bipolar plate is approximately 19% higher than that of a plate without coating. Moreover, electrochemical impedance spectroscopy (EIS) analysis revealed that charge transfer resistance and membrane resistance decreased with the influence of the iodine charge transfer complex for fuel cells on the performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.361-366
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• 2002

Spinel $LiMn_{2-y}M_yO_4$ and $LiMn_{2-y}M_yO_4$ (M=Mg, Zn) powders were synthesized by solid-state method at $800^{\circ}C$ for 37h. Crystal structure and electrochemical properties were analyzed by X-ray diffraction, charge-discharge test, cyclic voltammetry and ac impedance to $LiMn_{2-y}M_yO_4$. All cathode material showed spinel structure in X-ray diffraction. Ununiform distortion which calculated by (111) face and (222) face was almost constant in spite of the change of the kind and the substituting ratio of the metal cation in $LiMn_{2-y}M_yO_4$ (M=Mg, Zn). $LiMn_{1.9}Mg_{0.05}Zn_{0.05}O_4/Li$ cell substituted $Mg^{+2}$ and $Zn^{+2}$ showed excellent discharge capacities than other cells, which it presented about 120mAh/g at the 1st cycle and about 73mAh/g at the 250th cycle, respectively. AC impedance of $LiMn_{2-y}M_yO_4/Li$ cells showed the similar resistance of about 65~110$\Omega$ before cycling.

• Journal of Navigation and Port Research
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• v.32 no.10
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• pp.805-811
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• 2008

This paper presents a design of RFID(Radio Frequency Identification) tag antenna which is available for a vehicle's side mirror and directivity characteristics by mr body. The proposed Tag antenna is designed symmetrical structure to improve the broad bandwidth characteristic and the readable range. A proposed tag antenna($30\;mm{\times}24\;mm{\times}1\;mm$) has resonant frequency at 910 MHz and bandwidth is 780 MHz ($540\;MHz{\sim}1320\;MHz$). The chip impedance is the 16 - $j131\;{\Omega}$ and the complex conjugate impedance of commercial chip has been used for tag antenna design. In order to evaluate effects of tag antenna for side view mirror's permittivity as well as car body(conductor), radiation pattern characteristics and readable range have been calculated and measured. The optimized position for a vehicle's RFID system has been observed in the inside of a side mirror and the calculated results show good agreement with the measured results.