• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.46-53
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• 1996

Adaptive LMS algorithm has been used in many application areas due to its low complexity. In this paper input signal is transformed into the subbands with arbitrary bandwidth. In each subbands the dynamic range can be reduced, so that the independent filtering in each subbands has faster convergence rate than the full band system. The DCT transform domain LMS adaptive filtering has the whitening effect of input signal at each bands. This leads the convergence rate to very high speed owing to the decrease of eigen value spread Finally, the filtered signals in each subbands are synthesized for the output signal to have full frequency components. In this procedure wavelet filter bank guarantees the perfect reconstruction of signal without any interspectra interference. In simulation for the case of speech signal added additive white gaussian noise, the suggested algorithm shows better performance than that of conventional NLMS algorithm at high SNR.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.5
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• pp.543-548
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• 2006

This paper is to be researched into ozone generation character of Bi-Ti-Si type high dielectric ceramic catalyst discharge tube. And conditions of basic experiment are the outside diameter of discharge tube : 52 mm, the length of discharge tube : 350 mm, the frequence : 900 Hz, the temperature of cooling water : $25^{\circ}C$, quantity of flow : 5, 10, 20 L/min, pressure : 1.2, 1.4, 1.6 atm, and distance of discharge gap : 0.4, 0.6, 0.8 mm. Ozone generation characteristics were measured to consumption power. At quantity of flow : 20 L/min, discharge gap : 0.6 mm, pressure : 1.6, and consumption power : 150 W, Maximum ozone generation efficiency of 175 g/kWh was obtained. And a range of maximum ozone generation efficiency was measured below the flow quantity of 20 L/min at below pressure of 1.6 atm. However, Maximum ozone generation efficiency was measured over the flow quantity of 20 L/min at over pressure of 1.6 atm.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.1-7
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• 2003

Mode superposition method(MSM) is the most commonly used for solving linear response problems of structural dynamics. The major advantage of MSM is that usually a small number of lower mode is sufficient to analysis the response. However, the convergence is slow and many modes would be needed to give an accurate MSM in large structure with many degrees of freedom. The inaccuracies of MSM are caused by mode truncation in the solution. These demerits can be overcome by use of the mode acceleration method(MAM). Example analyses are carried out in simple beam subjected to harmonic loadings and compared the convergence of the joint displacements by the two methods. For relatively low frequency loadings, a good results was obtained by the lowest one mode in MAM, so the method is more economic in numerical analysis on an accurate solution.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.8
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• pp.1-8
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• 2000

We have achieved a high aspect ratio track-following microactuator (TFMA) which is capable of driving 0.3 ${\mu}m$ magnetic head for hard disk drive (HDD). it was fabricated on silicon on insulator (SOI) wafer with 20 ${\mu}m$ trick active silicon and 2 ${\mu}m$ thick thermally grown oxide and piggyback electrostatic principle was used for driving TFMA. The first vibration mode frequency of TFMA was 18.5 kHz which is enough for a recording density of higher than 10 Gb/in$^2$. Its displacement was 1.4 ${\mu}m$ when 15 V dc bias plus 15 V ac sinusoidal driving input was applied and its electrostatic force was 50 N. The fabricated actuator shows 7.51 dB of gain margin and 50.98$^{\circ}$ of phase margin for 2.21 kHz servo-bandwidth.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.10
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• pp.74-79
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• 2010

In this paper, a high gain W-band amplifier is presented using 70 run mHEMT MMIC technology. The length of source feedback line of common-source FET is carefully determined to maximize the gain at a design frequency. Simulation shows that MAG can be increased by 0.8 dB by optimizing the length of this line. In addition, this feedback line changes the input impedance of the common-source FET in a way that the input match can be made easier. In this work, 4-stage amplifier is designed on CPW using the source feedback. The measurement shows the excellent gain performance higher than 22.0 dB across 70~103 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.12
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• pp.1075-1083
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• 2016

Nowadays, the use of wireless input devices has been increasing on the basis of high convenience and portability. In particular the most widely used wireless keyboard and the mouse to use the 2.4 GHz frequency band, but due to the third party receives the electromagnetic wave from leaking when the radio equipment it is easy to obtain the personal information and the vulnerability is also being reported consistently. In this paper, implement a system to analyze and manipulate the packets of 2.4 GHz wireless keyboard and mouse using USRP device and GNU Radio package for verify the vulnerability of 2.4 GHz wireless keyboard and mouse. Using the construction system has attained a equipment specific address and key information by analyzing the communication protocol and the packet structure of the device was proved that a user can operate the PC to send the random key from long distance.

• Journal of Navigation and Port Research
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• v.27 no.2
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• pp.217-221
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• 2003

In this work, we used a novel RF-CSP to develop a broadband amplifier MMIC, including all the matching and biasing components, for Ku and K band applications. By utilizing an ACF for the RF-CSP, the fabrication process for the packaged amplifier MMIC could be simplified and made cost effective. STO (SrTiO$_3$) capacitors were employed to integrate the DC biasing components on the MMIC. A pre-matching technique was used for the gate input and drain output of the FETs to achieve a broadband design for the amplifier MMIC. The amplifier CSP MMIC exhibited good RF performance (Gain of 12.5$\pm$1.5 dB, return loss less than -6 dB, PldB of 18.5$\pm$1.5 dBm) over a wide frequency range. This work is the first report of a fully integrated CSP amplifier MMIC successfully operating in the Ku/K band.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.27-37
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• 1998

The sloshing is very important in a safe transport of the liquid cargo by a ship. With the increasing number of supertanker and LNG carriers, this problem has become increasingly more important. In order to study the magnitude and characteristics of impact pressures due to sloshing, experiments ware performed with a rectangular tank and compared with numerical results. Structural responses of tank wall under impulsive pressures were measured. Structural vibrations induced by the sloshing load were analysed by including hydroelastic erects in terms of added mass and damping. To check the validity of the numerical model, the natural frequencies of plate in air and water were compared with measurements, and a good agreement was found. In the case that a plate vibrates under impulsive loads, the pressure on the flexible plate is larger than that on the rigid plate without hydroelastic effects, which was confirmed experimentally. The frequency of oscillatory pressure as well as accel%pion coincides with the natural frequency of plate in water.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.18-26
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• 2001

In this paper, the resonant characteristics and modes of the film bulk acoustic wave resonator (FBAR) used in 1~2 GHz frequency region are analyzed by it's input impedance which was calculated by three dimensional finite element method formulated as eigenvalue problem using electro-mechanical wave equation and boundary condition. It was extracted that the resonant and the spurious characteristics considering the effects of electrode area and shape variation and unsymmetry of upper and lower electrode. Those effects couldn't be analyzed by on dimensional analysis, e.g. Mason equivalent model. The simulation result was confirmed by comparing with the simulation data from Mason model analysis and the measured data of the ZnO FBAR fabricated using micro-machining technique. Also, through the simulation of the area variations of FBAR, it was obtained that the optimum ratio of length and thickness is 20:1 and the minimum ratio is 5:1 to operate thickness vibration mode.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.4
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• pp.333-336
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• 2017

A speaker diaphragm generates a divided vibration. The influence of the break-up mode is sufficient to cause a shape change in the diaphragm. In this paper, is widely used in ultra-thin multi-media devices, including smart phones is the advance guard of the IT sector, the micro-speakers and its target. Micro-speakers are different from general speakers. The plate has structural form and space constraints. In particular, they utilize a closed-type drive space. It is difficult to provide cooling for the auxiliary suspension structure because of the heat generated in the moving coil. The present study considered the relationship between the break-up mode and the heat transfer of the diaphragm. An experiment was conducted in two stages to compare the embodiment of the break-up mode and heat transfer in a certain frequency range. The changes in the heat were determined through measurements and thermal imaging of the break-up mode. The break-up mode tendency of the diaphragm could be rapidly predicted based on the imaging results using the thermal imaging camera. This will help in the optimal design of micro-speakers.