• Structural Engineering and Mechanics
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• v.55 no.5
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• pp.1015-1035
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• 2015

A three-dimensional (3D) numerical analysis for the train-bridge interaction (TBI) system is actively developed in this study in order to investigate the vibration characteristics of rigid-frame reinforced concrete (RC) viaducts in both vertical and lateral directions respectively induced by running high-speed trains. An analytical model of the TBI system is established, in which the high-speed train is described by multi-DOFs vibration system and the rigid-frame RC viaduct is modeled with 3D beam elements. The simulated track irregularities are taken as system excitations. The numerical analytical algorithm is established based on the coupled vibration equations of the TBI system and verified through the detailed comparative study between the computation and testing. The vibration responses of the viaducts such as accelerations, displacements, reaction forces of pier bottoms as well as their amplitudes with train speeds are calculated in detail for both vertical and lateral directions, respectively. The frequency characteristics are further clarified through Fourier spectral analysis and 1/3 octave band spectral analysis. This study is intended to provide not only a simulation approach and evaluation tool for the train-induced vibrations upon the rigid-frame RC viaducts, but also instructive information on the vibration mitigation of the high-speed railway.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.9
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• pp.417-422
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• 2002

ZnO thin films were deposited on various substrates, such as Si-(111), SiO$_2$(5000 $\AA$ by thermal CVD)/Si-(100), and SiO$_2$(2000 $\AA$ by RF sputtering)/Si-(100). The (002)-orientation, surface morphology and roughness, and electrical resistivity of deposited films were measured and compared in terms of substrate. Surface acoustic wave(SAW) filters with a multilayered configuration of IDT/ZnO/SiO$_2$/Si were also fabricated and the IDT was obtained using a lift-off method. From the frequency-response characteristics of fabricated devices, the insertion loss and side-lobe rejection were estimated. The experimental results showed that the (002)-oriented growth nature of ZnO films, which played a crucial role of determining the characteristic of SAW device, was strong1y dependent upon the SiO$_2$buffer.

• Journal of the Korean Institute of Rural Architecture
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• v.3 no.2
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• pp.71-78
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• 2001

The purpose of this study was to analyze the space composition and utilization characteristics of cultural facilities in city which was surrounded by rural area. For this study, it was surveyed 18 cultural facilities including PyungTaek-city in our country. The below was analyzed : The first, the present conditions of space program and functions of central cultural facilities in small city. The second, a frequency and peculiarity in utilization of it. And the third is about system of management. A data of design which can be directly applied by above process is like the below. The function of cultural facilities in city can be fixed from space composition with regional specifics and similarity. The space composition of cultural facilities is diversified by art performance and assembly space, by exhibitional space and reading space, and by the fact whether there is public or not. We know hall of cultural facilities has multi-purpose. Management system needs some changes throughout participation of citizen or experts for more active usage.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_1
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• pp.377-385
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• 2021

High voltage direct current(HVDC) systems has been an alternative method of a power transmission to replace high voltage alternate current(HVAC), which is a traditional AC transmission method. Due to technical limitations, Line commutate converter HVDC(LCC-HVDC) was mainly used. However, result from many structural problems of LCC-HVDC, the voltage source converter HVDC(VSC-HVDC) are studied and applied recently. In this paper, after analyzing the reactive power and output voltage ripple, which are the main problems of LCC-HVDC, the characteristics of each HVDC are summarized. Based on this result, a new LCC-HVDC structure is proposed by combining LCC-HVDC with the MMC structure, which is a representative VSC-HVDC topology. The proposed structure generates lower reactive power than the conventional method, and greatly reduces the 12th harmonic, a major component of output voltage ripple. In addition, it can be easily applied to the already installed LCC-HVDC. When the proposed method is applied, the control of the reactive power compensator becomes unnecessary, and there is an advantage that the cut-off frequency of the output DC filter can be designed smaller. The validity of the proposed LCC-HVDC is verified through simulation and experiments.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.645-657
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• 2015

In this study floor impact noise and structure acceleration response of bare concrete slabs were predicted by using Finite Element Analysis(FEA). Prediction results were compared with experimental results to prove the accuracy of numerical model. Acoustic absorption were addressed by using panel impedance coefficients with frequency characteristics and structural modal damping of numerical model were applied by modal testing results and analysis of prediction and test results. By using frequency response function, the floor acceleration and acoustic pressure responses for various impact sources were calculated at the same time. In the FEA, the natural frequencies and the shapes of vibration and acoustic modes can be estimated through the eigen-value analysis, and it can be visually seen the vibration and sound pressure field and the contribution of major modes.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.1
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• pp.84-93
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• 2001

An electromagnetic micro x-y stage for probe-based data storage (PDS) has been fabricated. The x-y stage consists of a silicon body inside which planar copper coils are embedded, a glass substrate bonded to the silicon body, and eight permanent magnets. The dimensions of flexures and copper coils were determined to yield $100{\;}\mu\textrm{m}$ in x and y directions under 50 mA of supplied current and to have 440 Hz of natural frequency. For the application to PDS devices, electromagnetic stage should have flat top surface for the prevention of its interference with multi-probe array, and have coils with low resistance for low power consumption. In order to satisfy these design criteria, conducting planar copper coils have been electroplated within silicon trenches which have high aspect ratio ($5{\;}\mu\textrm{m}$in width and $30{\;}\mu\textrm{m}$in depth). Silicon flexures with a height of $250{\;}\mu\textrm{m}$ were fabricated by using inductively coupled plasma reactive ion etching (ICP-RIE). The characteristics of a fabricated electromagnetic stage were measured by using laser doppler vibrometer (LDV) and dynamic signal analyzer (DSA). The DC gain was $0.16{\;}\mu\textrm{m}/mA$ and the maximum displacement was $42{\;}\mu\textrm{m}$ at a current of 180 mA. The measured natural frequency of the lowest mode was 325 Hz. Compared with the designed values, the lower natural frequency and DC gain of the fabricated device are due to the reverse-tapered ICP-RIE process and the incomplete assembly of the upper-sided permanent magnets for LDV measurements.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.6
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• pp.1149-1154
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• 2017

To obtain good recognition performance of speech recognition system under background noise, it is very important to select appropriate feature parameters of speech. The feature parameter used in this paper is Mel frequency cepstral coefficient (MFCC) with the human auditory characteristics applied to Wiener filter method. That is, the feature parameter proposed in this paper is a new method to extract the parameter of clean speech signal after removing background noise. The proposed method implements the speaker recognition by inputting the proposed modified MFCC feature parameter into a multi-layer perceptron network. In this experiments, the speaker independent recognition experiments were performed using the MFCC feature parameter of the 14th order. The average recognition rates of the speaker independent in the case of the noisy speech added white noise are 94.48%, which is an effective result. Comparing the proposed method with the existing methods, the performance of the proposed speaker recognition is improved by using the modified MFCC feature parameter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2264-2270
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• 2006

This paper describes fast-hewing frequency synthesizers for multi-band OFDM(MB-OFDM) ultra-wide band(UWB) systems. Three different structures in generating 3 center frequencies(3432MHz, 3960MHz, 4488MHz) are designed and compared. The first structure generates 3 center frequencies using only one PLL operating at 4224MHz, and the second uses three PLLs operating at corresponding center frequencies. The proposed third structure employes two PLLs operating at 3960MHz and 528MHz. Simulation results using 0.18um RF CMOS process parameters show that the third structure exhibits boner characteristics in spur, area and current consumption than the other structures. The band switching time of the proposed synthesizer is less than 1.In and the spur is less than -36dBc. The synthesizer consumes 22mA from a 1.8V supply.

• Journal of Astronomy and Space Sciences
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• v.20 no.3
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• pp.185-196
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• 2003

In this paper, we make a design study for a local oscillator system of the 100 ㎓ band cosmic radio receiving system. We use the YIG oscillator with digital driver which is the main oscillator. This oscillator has a good frequency and phase stability at some temperature variation, and the easy computer aided control characteristics. This total system designed to two subsystem, first is the oscillator system include YIG oscillator, tripler, harmonic mixer and triplexer etc., second is the PLL system to supply the precise and stable local oscillator frequency to mixer. The proposed local oscillator system in this paper can be used in a single or multi pixel receiver because this system can be lock the local oscillator frequency automatically using PC.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.9
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• pp.427-433
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• 2001

A linear ultrasonic motor was designed by a combination of the first longitudinal and fourth bending mode, and the motor consisted of a straight aluminum alloys bar bonded with a piezoelectric ceramic element as a driving element. That is,$L_1-B_4$ linear ultrasonic motor can be constructed by a multi-mode vibrator of longitudinal and bending modes. Linear ultrasonic motors are based on an elliptical motion on the surface elastic body, such as bar or plates. In general, the natural resonance frequency of the stator is used as a driving frequency of the motor which provides a large elliptical motion. The corresponding eigenmode of one resonance frequency can be excited twice at the same time with a Phase shift of 90 degrees in space and time. And the rotation can be reversed by changing the phase between the two signals from sin$\omega$t to cos$\omega$t. Moreover, the tangential force pushes the slider(rotor) and, therefore, determines the thrust and speed of the motor. The experimental results of fabrication motors, bimorph-tyPe motor showed more excellent than unimorph-type. The maximum speed of TBL-200, TBL-300, TBL-400, TBL -220, TBL-310 and TBL-420 motors were 0.12, 0.37, 0.39, 0.14, 0.55 and $0.60ms6{-1}$, respectively. And the efficiency were reported 1.15, 7.9, 6.6, 2.36, 10.1 and 16.5%, respectively. That time, output thrust of the motor was a strong(1~2N) and the weight of stator was a lightness(5~7g).