• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.7
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• pp.620-624
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• 2016

In this paper we designed a current mode logic frequency divider to transmit a baseband amplitude modulated signal. From simulation result, we studied input and output waveforms according to the variation of input bias voltage. For the purpose of the verification of the study, we designed a current mode logic frequency divider at 1,400 MHz. The designed frequency divider operates between 100 MHz and 3,000 MHz, for -33 dBm input power. The circuit draws $I_{total}=30mA$ from $V_{DD}=3V$ supply, and the simulation result shows that an amplitude modulated signal at 1,400 MHz with the modulation index of 0.5 was successfully downconverted to 700 MHz.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1146-1149
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• 2014

To discriminate polarities of stator windings for 3 phase induction motors terminal tags of which are not readable, it is possible to utilize the residual magnetic flux present at their rotors as well as to use the way based on external exciting current. The induced voltages are basically decided by parameters such as the quantity of residual flux, the rotator speed by hand force and the phase properties between stator windings. To adopt induced voltages by residual flux for polarity discrimination at sites, the measured voltages by multi-testers need to be readable in magnitude enough to discriminate winding condition with reasonable phase characteristics. This study focuses on the analysis of various connection cases in the expectation that the summing voltages induced by residual flux shall show zero in case of normal connections while the sum becomes greater indication if the connection is in wrong condition. The proposed method is applied to actual motors to disclose how effective it is for polarity discrimination at sites through comparison of output signals between normal and fault connections.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.2
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• pp.332-338
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• 2010

Annually, electrical fires caused by arcing phenomena in power system rapidly increase as the use of more electric appliances, but there is no established method for the prevention of the accidents. With this background, this paper dealt with the experimental results on a series arc detection technique and a device for air conditioners. Series arcing phenomena that is generated in incomplete connection of air conditioners was simulated, and the frequency spectrum was analyzed. The Fast Fourier Transform (FFT) of the arc pulse showed that the dominant frequency components exist in ranges of 190 kHz~250 kHz and 900 kHz~1.6 MHz. An arc detection circuit with low cut off frequency of 170 kHz to attenuate 60 Hz by 170 dB and a signal discriminator were designed. Also, an algorithm which separate series arc signal from unwanted noises produced by switching operation, inverter, and surge was proposed. Application experiment was carried out on several types of air-conditioners by using the arc generator specified in UL1699, and the results showed the over 99 % accuracy.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.1
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• pp.71-81
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• 2009

Die steel for plastic molding were used as mold material of automobile parts and electronic component industry. The material of this paper has superior to mechanical properties, such as repair weldability, corrosion resistance and high temperature strength, required mold parts for semitransparent. Laser-induced surface hardening technology is widely adopted to improver fatigue life and wear resistance via localized hardening at the surface of mold parts. The objective of this research work is to investigate on the characteristics of surface hardening of the laser process parameters, such as beam travel speed, laser power and defocsued spot position, for the case of die steel for plastic molding. Lens for surface hardening of large area is plano-convex type with elliptical profile to maintain uniform laser irradiation. According to the experimental results, large size of hardened layer at the surface of die steel for plastic molding was achieved, and microstructure of this layer was lath martensite. Optimal surface status and mechanical property of hardened layer could be obtained at 1095Watt, $0.25{\sim}0.3m/min$, 0mm (focal length: 232mm) for laser power, beam travel speed, and focal position. Where, heat input was $0.793{\times}10^{3}J/cm^2$, and width of hardened layer was 27.58mm.

• Journal of the Korean Geophysical Society
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• v.5 no.3
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• pp.165-174
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• 2002

Seismic velocity and attenuation coefficient of the rocks under the broad-band earthquake observatories of the Korea Meteorological Administration have been measured in the laboratory by using very high frequency seismic waves. Estimated P velocities of the rocks range from 3.2 km/s to 5.6 km/s, depending on the rock type, mineral, and weathering, while, the attenuation coefficients vary from 0.06 to 4.3 db/kHz-m. It seems that P velocities is inversely proportional to the attenuation coefficients of the rocks. Average travel-time delays of the broad-band stations seem to be related with the measured P velocities in the laboratory.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.225-231
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• 2006

As a study of efficient velocity analysis in sonic log, several preexisting techniques have been adopted to the sonic data taken from model borehole in Kangwon National University, and the results were compared. For the data taken from monopole source, Slowness-Time Coherence method which is a common technique for nondispersive wave was used. For the data taken from dipole source, conventional STC and Tang's method(Tang et al., 1995) were used. From the good matches in the P and Stoneley wave velocities, we could confirm the effectiveness of STC computation. We also could find that shear velocity obtained from Tang's method were exactly matched with shear velocity obtained from monopole source, and that the velocity were within the range of S wave velocity values obtained from conventional STC application to dispersive flexural waves.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.103-109
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• 2017

In order to apply the patient monitoring system to the hospital field, it is necessary to be able to measure and analysis data the major bio-signals that are basically covered by the existing patient monitoring system. We have implemented a wearable device and the patient monitoring system for measuring ECG and oxygen saturation. The implemented system transmits the measured bio-signal to the server on the nursing station via Bluetooth. It is represented by graph waveforms and numerical values that can be checked by the medical staff in the patient monitoring system. The validity of this system is verified by comparing the data collected through the designed system with the data obtained from the conventional equipment.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.3
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• pp.582-592
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• 1996

본 실험은 삼차신경 자극으로 발생되는 체성 감각 유발 전위에 대한 국소마취제의 효과를 관찰하였다. 나트륨 통로차단을 통하여 약리작용을 나타내는 것으로 알려져 있는 리도카인를 뇌 피질에 국소 투여한 후 삼차신경의 체성 감각유발 전위의 강도및 지연시간을 측정하였다. 케타민으로 마취된 흰쥐의 대측성 구레나룻 자극후 뇌의 체성 감각영역으로부터 기록되는 유발전위를 분석한 결과, 리도카인을 뇌 피질에 국소 투여시 유발전위의 강도 및 지연시간의 감소가 나타났으며, 필드 전위의 형태는 이상성 (양극성 및 음극성) 혹은 삼상성 (양극성, 음극성 및 양극성) 의 파형으로 나타났다. 필드 전위의 발생 부위는 뇌 피질의 중대뇌동맥의 상행지 상방영역이었다. 본 실험에서 나타난 초기 전위변동은 피질판 상층에 존재하는 신경세포의 탈분극 과청에 의하여 생성되고 후기의 전위 변동은 동일 영역의 하층 신경세포에서 과분극 혹은 재분극이 발생한 결과라고 유추된다. 따라서 삼차신경계의 체성 감각 영역에서는 피질 상층및 하층의 과립성 피라미드 세포의 순차적인 활성화에 의하여 기본적인 신경 회로망이 형성되어 있으며 생리적 자극으로 유발되는 필드 전위는 이러한 신경망를 통하여 발생될 것으로 사료된다.

• The Journal of the Acoustical Society of Korea
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• v.22 no.1
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• pp.61-68
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• 2003

The guided wave has been widely employed to characterize thin plates and layered media. The dispersion curves of phase and group velocities are essential for the quantitative application of guided waves. In the present work, a fully automated system for the measurement of backward radiation of LLW has been developed. The specimen moves in two dimensional plane as well as in angular rotation. The signals of backward radiation of LLW were measured from an elastic plate in which specific modes of Lamb wave were strongly generated. Phase velocity of the corresponding modes was determined from the incident angle. The generated Lamb waves propagated forward and backward with the leakage of energy into water. Backward radiated LLW was detected by the same transducer and its frequency components were analyzed to extract the related information to the dispersion curves. The dispersion curves of phase velocity were measured by varying the incident angle. Moving the specimen in the linear direction of LLW propagation, group velocity was determined by measuring the transit time shift in the ultrasonic waveform.

• The Journal of the Acoustical Society of Korea
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• v.19 no.3
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• pp.26-34
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• 2000

In this paper, we propose a 4kbps speech coder that combines the harmonic vector excitation coding with time-separated transition coding. The harmonic vector excitation coding uses the harmonic excitation coding in the voiced frame and uses the vector excitation coding with the structure of analysis-by-synthesis in the unvoiced frame, respectively. But two mode coding method is not effective for transition frame mixed in voiced and unvoiced signal and a new method beyond using unvoiced/voiced mode coding is needed. Thus, we designed a time-separated transition coding method for transition frame in which a voiced/unvoiced decision algorithm separates unvoiced and voiced duration in a frame, and harmonic-harmonic excitation coding and vector-harmonic excitation coding method is selectively used depending on the previous frame U/V decision. In the decoder, the voiced excitation signals are generated efficiently through the inverse FFT of harmonic magnitudes and the unvoiced excitation signals are made by the inverse vector quantization. The reconstructed speech signal are synthesized by the Overlap/Add method.