• Particle and aerosol research
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• v.14 no.1
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• pp.9-16
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• 2018

We have developed an electrostatic precipitation (ESP) type air cleaner for indoor air quality and investigated its performances regarding CADR (Clean air delivery rate), single-pass efficiency and gas removal efficiency. The ESP air cleaner used an ACF (Activated carbon fiber) filter for gas removal and the ACF as a high voltage electrode for particle removal. The ESP air cleaner was tested in a chamber with the volume of $1m^3$ regarding CADR and gas removal efficiency. The applied CADR area of the ESP was $1.8m^2$. Gas removal efficiency was tested with 3 gases (Acetaldehyde, Acetic acid, Ammonia). As the results of the gas removal efficiency, the ESP air cleaner shows the removal efficiencies of 90, 98 and 85% for acetaldehyde, acetic acid and ammonia, respectively.

• Journal of the Korea Convergence Society
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• v.8 no.8
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• pp.33-40
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• 2017

In this paper, we propose a text extraction method by pattern analysis on contour for effective text detection in image. Text extraction algorithms using edge based methods show good performance in images with simple backgrounds, The images of complex background has a poor performance shortcomings. The proposed method simplifies the color of the image by using K-means clustering in the preprocessing process to detect the character region in the image. Enhance the boundaries of the object through the High pass filter to improve the inaccuracy of the boundary of the object in the color simplification process. Then, by using the difference between the expansion and erosion of the morphology technique, the edges of the object is detected, and the character candidate region is discriminated by analyzing the pattern of the contour portion of the acquired region to remove the unnecessary region (picture, background). As a final result, we have shown that the characters included in the candidate character region are extracted by removing unnecessary regions.

• Korean Journal of Optics and Photonics
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• v.23 no.4
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• pp.159-166
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• 2012

We have developed a daytime measuring rotational Raman LIDAR system for temperature measurement. To decrease the background signal from sunlight, we have designed and installed narrow band (0.5 nm) and high rejection ($10^{-6}$) rate band pass filter system using a grating and an interference filter. We calibrated our system by comparing our horizontal temperature profile and KMA (Korea Meteorological Administration) data. We have found that our temperature profile has a good correlation with KMA data within our theoretically expected variance. And we have used these calibration values in obtaining a vertical temperature distribution. To check our system, we also have compared our vertical temperature data with US standard atmospheric temperature profile. We also have compared our temperature profile with sonde data.

• 전자공학회논문지 IE
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• v.47 no.4
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• pp.1-9
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• 2010

This paper describes a ultrasonic signal processing front-end IC for distance range meter and body detector. The burst shaped ultrasonic signal is generated by a self oscillator and its frequency range is about 40[kHz]-300[kHz]. The generated ultrasonic signal transmit through piezo resonator. The another piezo device transduce from received ultrasonic signal to electrical signals. This front-end IC contained low noise amplifier, band pass filter, busrt detector and time pulse generator and so on. This IC has two type of new idea for improve function and performance, which are self frequency control (SFC) and Variable Gain Control amplifier (VGC) scheme. The dimensions and number of external parts are minimized in order to get a smaller hardware size. This device has been fabricated in a O.6[um] double poly, double metal 40[V] High Voltage CMOS process.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.83-91
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• 1996

The SPICE circuit analysis program has a limited math capability and, in general, cannot be used for RF and microwave simulation because a complex arithmetic is required to compute S-parameters from node voltages. This paper presents two test bench models that can be used to obtain node voltages proportional to incident, reflected, and transmitted signals. From SPICE computed node voltages, S-parameters are computed using the math capability of the PSPICE post processor, PROBE, as an example for a low-pass filter consisting of transmission line sections. The results of this example are compared with another high frequency circuit analysis program, TOUCHSTONE. The difference between the results of these two programs in magnitude was less than 0.003 and in phase was a few tenths of a degree. By using these test benchs to simulate a filter, RF and microwave analysis can be made with the SPICE, which can be a cost-effective and readily available computational tool for educators and practicing engineers.

• Journal of the Korean Society of Radiology
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• v.2 no.1
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• pp.23-29
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• 2008

The present study proposed a method that dissolves ultrasonographic images into multiple resolutions using wavelet conversion and a boundary detection filter and improves the quality of ultrasonographic images through boundary detection filtering. In order to reduce noises and strengthen edges, the proposed method adjusted selectivity coefficient by area step by step from a low resolution image obtained from wavelet converted images to a high resolution image and performed edge filtering in consideration of direction. Through this method, we generated a selective low pass filtering effect in areas except edges by decreasing the wavelet coefficient for pixels in spot areas, improved continuity by smoothing edges in the tangential direction, and enhanced contrast by thinning in the normal direction. Through an experiment, we compared the filtering method using a non linear anisotropic expansion model and the filtering method using wavelet contraction structure in single resolution.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.958-960
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• 2002

High Temperature Superconducting (HTS) devices make it possible to operate with no electrical loss by resistance. If, however, the applied current is over its critical current, the phase of HTS devices is changed to normal state, so called, quench. In this case, since resistance of HTS is increased abruptly, it can not be avoidable to damage the whole apparatus. In this study, quench detector to protect HTS devices was proposed. We designed the quench detecting circuit and tested the performance of the circuit. The detecting circuit was consisted of Op-Amp and low pass filter etc, to detect very low voltage around $1{\mu}V$. The circuit detected effectively the low voltage when over current is applied to HTS tapes. At the next step, we are going to apply and test the circuit to protect the prototype HTS cable.

• Publications of The Korean Astronomical Society
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• v.12 no.1
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• pp.35-45
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• 1997

SOFT($\underline{So}lar\;\underline{F}lare\;\underline{T}elescope$) installed at BOAO(Bohyunsan Optical Astronomy Observatory) is purposed for observing solar active regions using four refractors on single mount with a $400"\times300"$ field of view: Two refractors with a diameter of 15cm(f15) are observe the white light and $H\alpha$, and the other two refractors with a diameter of 20cm(f8) are observe the magnetic field distribution and Doppler shifts at the solar chromosphere. Three Lyot filters, one of the most important observational instruments, are installed on the optical rails for VMG, LMG, and $H\alpha$ that possible to very narrow pass band observation under high precision stability of temperature. From the combination of KD*P and quarter wave plate in the Lyot filter possible observe the magnetic fields strength and doppler shifts by using the characteristics of polarization components. In this paper, we introduce the basic characteristics, optical system, and monitor system of the SOFT.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.3
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• pp.102-107
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• 2006

In this paper, we propose a method of a sound synthesis of Korean plucked string instrument, gayageum, by physical modeling which use impulse responses of body and Anjok. Gayageum consists of three kinds of systems: string, body, and Anjok. These are a serial combination of linear time invariant systems. String can be modeled by digital delay line. Body and Anjok can be estimated by their impulse responses. We found three resonance frequencies in the body impulse response, and implemented resonator as body. Anjok was implemented as high pass filter in fundamental frequency band of gayageum. RMSEs of synthesized sounds are distributed from 0.01 to 0.03. It was difficult to distinguish the resulting synthesized sounds from the originals sound by ear.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.427-434
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• 2011

This paper is focused on application of recursive least squares method to estimate rail irregularities from the acceleration measurement on an axle-box or a bogie for the rail condition monitoring with in-service high-speed trains. Generally, the rail condition was monitored by a special railway inspection vehicle but the monitoring method needs an expensive measurement system. A monitoring method using accelerometers on an axle-box or a bogie was already proposed in the previous study, and the displacement was successfully estimated from the acceleration data by using Kalman and frequency selective band-pass filters. However, it was found that the displacement included not only the rail irregularities but also phase delay of the applied filters, and effect of suspension of the bogie and conicity of the wheel. To identify the rail irregularities from the estimated displacement, a compensation filter method is proposed. The compensation filters are derived by using recursive least squares method with the estimated displacement as input and the measured rail irregularity as output. The estimated rail irregularities are compared with the true rail irregularity data from the rail inspection system. From the comparison, the proposed method is a useful tool for the measurement of lateral and vertical rail irregularity.