• Journal of the Korean Ceramic Society
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• v.45 no.4
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• pp.208-213
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• 2008

In this study, helical antenna with microwave ZST ceramics was designed using finite element method and developed. Studied parameters are relative dielectric constant of the dielectric core and the width of the conduction metal band of the antenna. As shown in the results, the center frequency of the antenna was decreased as the dielectric constant increased. Also beam width of the antenna increased as both the dielectric constant and the conduction band width increased. Based on the designed optimal shape, the manufactured antenna has the good beam width at center frequency 1.58 GHz.

• Journal of Information Processing Systems
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• v.15 no.1
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• pp.189-202
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• 2019

During thermal power coal-fired boiler operation, it is very important to detect the pulverized coal concentration in the air pipeline for the boiler combustion stability and economic security. Because the current measurement methods used by power plants are often involved with large measurement errors and unable to monitor the pulverized coal concentration in real-time, a new method is needed. In this paper, a new method based on microwave circular waveguide is presented. High Frequency Electromagnetic Simulation (HFSS) software was used to construct a simulation model for measuring pulverized coal concentration in power plant pipeline. Theoretical analysis and simulation experiments were done to find the effective microwave emission frequency, installation angle, the type of antenna probe, antenna installation distance and other important parameters. Finally, field experiment in Jilin Thermal Power Plant proved that with selected parameters, the measuring device accurately reflected the changes in the concentration of pulverized coal.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.531-537
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• 2009

Lightning has a broad frequency spectrum from DC to a few MHz. Consequently, the high frequency performance of grounding systems for protection against lightning should be evaluated, with the distributed parameter circuit model in a uniform soil being used to simulate grounding impedances. This paper proposes a simulation method which applies the distributed parameter circuit model for the frequency-dependent impedance of vertically driven ground rods by considering multi-layered soil structures where ground rods are buried. The Matlab program was used to calculate the frequency-dependent ground impedances for two ground rods of different lengths. As a result, an increase of the length of ground rod is not always followed by a decrease of grounding impedance, at least at a high frequency. The results obtained using the newly proposed simulation method considering multi-layered soil structures are in good agreement with the measured results.

• Journal of information and communication convergence engineering
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• v.6 no.3
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• pp.275-278
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• 2008

In this paper, I propose the full CMOS FLL(frequency locked loop) circuit. The proposed FLL circuit has a simple structure which contains a FVC(frequency-to-voltage converter), an operational amplifier and a VCO(voltage controlled oscillator). The operation of FLL circuit is based on frequency comparison by the two FVC circuit blocks. The locking time of FLL is short compared to PLL(phase locked loop) circuit because the output signal of FLL is synchronized only in frequency. The circuit is designed by 0.35${\mu}m$ process and simulation carried out with HSPICE. Simulation results are shown to illustrate the performance of the proposed FLL circuit.

• Journal of the Semiconductor & Display Technology
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• v.4 no.2 s.11
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• pp.11-14
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• 2005

In plasma processing reactors, it is common practice to control plasma density and ion bombardment energy by manipulating excitation voltage and frequency. In this paper, a dually excited capacitively coupled rf plasma reactor is self-consistently simulated with a three moment model. Effects of phase differences between primary and secondary voltage waves, simultaneously modulated at various combinations of commensurate frequencies, on plasma properties are investigated. The simulation results show that plasma potential and density as well as primary self-dc bias are nearly unaffected by the phase lag between the primary and the secondary voltage waves. The results also show that, with the secondary frequency substantially lower than the primary frequency, secondary self·do bias remains constant regardless of the phase lag. As the secondary frequency approaches to the primary frequency, however, the secondary self-dc bias becomes greatly altered by the phase lag, and so does the ion bombardment energy at the secondary electrode. These results demonstrate that ion bombardment energy can be more carefully controlled through plasma simulation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.845-851
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• 1986

This Paper presents micro-computer simulation programs for a pneumatic control system. The simulation programs have been written in BASIC language which is suitable for 6502CPU with 48KB memory and consist of 11 programs which describe the time response and frequency response of the pneumatic actuation system. This simulation package is stored in 51/4 inch floppy diskette. The user requires no simulation expertise on the part of designer. As the result of using this simulation programs for the pneumatic control system with stabilizing tank, it has shown that the response time of the system using air as working medium takes more time to be settled but relatively stable rather than the system using helium.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.505-506
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• 2012

• Earthquakes and Structures
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• v.8 no.6
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• pp.1463-1480
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• 2015

This research aims to develop an empirical model for simulation of time-varying frequency in earthquake ground motion so as to be used easily in engineering applications. Briefly, 10545 recordings of the Next Generation Attenuation (NGA) global database of accelerograms from shallow crustal earthquakes are selected and binned by magnitude, distance and site condition. Then the wavelet spectrum of each acceleration record is calculated by using one-dimensional continuous wavelet transform, and the frequencies corresponding to the maximum values of the wavelet spectrum at a series of sampling time, named predominant frequencies, are extracted to analyze the variation of frequency content of seismic ground motions in time. And the time-variation of the predominant frequencies of 178 magnitude-distance-site bins for different directions are obtained by calculating the mean square root of predominant frequencies within a bin. The exponential trigonometric function is then use to fit the data, which describes the predominant frequency of ground-motion as a function of time with model parameters given in tables for different magnitude, distance, site conditions and direction. Finally, a practical frequency-dependent amplitude envelope function is developed based on the time-varying frequency derived in this paper, which has clear statistical parameters and can emphasize the effect of low-frequency components on later seismic action. The results illustrate that the time-varying predominant frequency can preferably reflect the non-stationarity of the frequency content in earthquake ground motions and that empirical models given in this paper facilitates the simulation of ground motions.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.173-176
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• 1999

Frequency responses of the surface acoustic wave(SAW) filters are simulated by using the impulse modeling. The simulation technique of the SAW filters is to use the Fourier transformation to make a correspondence between the impulse response of the filter and the taps in the delay line. Since the Fourier series must be truncated after a finite number of terms, window functions are often used to weight the coefficients to obtain the desirable side-lobe level and bandwidth. The filter design is operated through the iterative simulation procedures. The design process is capable of yielding filters with optimized frequency response characteristics.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.77-84
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• 2003

For stochastic strong ground motion simulation, frequency-dependent Q model (= $Q_{o}$ $f^{η}$) were evaluated for major geographical blocks according to the epicentral distance ranges by using a lateral Q tomography technique. The inversed Q results were used to qualitatively identify seismic albedos of each Q blocks and were compared with the previous Q studies. In addition, a functional Q model calibrated to the low frequency spectra of local earthquakes were suggested especially for use in analysing large and distant regional earthquake events.s.