• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.26-31
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• 2015

This paper describes the characteristics of voltage drop and thermal for poor connection on electrical connector of circuit breaker in control box of small size pulverizer. In order monitor, we did the changes of RMS in voltage and temperature value with video and made normal state over $2.5N{\cdot}m$ and poor connections state below $0.2N{\cdot}m$ by screw gage. In case of voltage signal, the voltage drop was increased when the current was increased due to poor connections. In case of temperature signal, the temperature difference indicates ten times at 5A and fourteen times at 15A in the normal state. According to increase thermal energy, the insulation of electrical wiring and connector of circuit breaker can be carbonized. The results of this study will be useful to the development of preventive devices and system for electric fire by poor connection at small size pulverizer.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.359-364
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• 2006

Interference can seriously degrade the performance of GPS receiver because GPS signal has extremely low power at earth surface. This paper presents a Narrowband Interference Excision Filter (NIEF) in frequency domain that removes narrowband interferences with small signal loss. A NIEF transforms the received GPS signals with interferences into the frequency domain with FFT and then compute statistics such as mean and standard deviation to determine an excision threshold. All spectrums exceeding the threshold are removed and the remaining spectrums are restored by IFFT. A NIEF effectively can remove various and strong interferences with a simple structure. However, the signal power loss is unavoidable during FFT and IFFT. Besides the hamming window and overlap technique, a threshold-whitening technique and an adaptive detection threshold are adopted to effectively reduce the signal power loss. The performance of implemented NIEF is evaluated using real signals obtained by 12 bit GPS signal acquisition board. The output of NIEF is fed into the Software Defined Receiver to evaluate the acquisition and tracking performance. Experimental results shows that many types of interference such as single-tone CWI, AM, FM, swept CWI and multi-tones CWI are effectively mitigated with small signal power loss.

• Korean Journal of Optics and Photonics
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• v.33 no.3
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• pp.99-105
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• 2022

We have evaluated the performance of an all-optical automatic gain-controlled (AGC) erbium-doped fiber amplifier (EDFA) to suppress the optical signal fluctuation induced by atmospheric turbulence in terrestrial free-space optical communication systems. In our measurements, the input power into the EDFA was set to be -30 dBm and -10 dBm to operate the amplifier in the small-signal and saturation regions, respectively. The fluctuations in the optical signal were emulated with an acousto-optic modulator driven with a sinusoidal voltage. From the measured results, we have found that an all-optical AGC EDFA could suppress the optical signal fluctuation effectively, as long as the EDFA operated in the small-signal region with a high feedback amplified spontaneous emission (ASE) power.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.42-47
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• 2001

Analyzing the ECG signal, we can find heart disease, for example, arrhythmia and myocardial infarction, etc. Particularly, detecting arrhythmia is more important, because serious arrhythmia can take away the life from patients within ten minutes. In this paper, we would like to introduce the signal processing for ECG analysis and the device made for wireless communication of ECG data. In the signal processing, the wavelet transform decomposes the ECG signal into high and low frequency components using wavelet function. Recomposing the high frequency bands including QRS complex, we can detect QRS complex and eliminate the noise from the original ECG signal. To recognize the ECG signal pattern, we adopted the polynomial approximation partially and statistical method. The ECG signal is divided into small parts based on QRS complex, and then, each part is approximated to the polynomials. Comparing the approximated ECG pattern with the database, we can detect and classify the heart disease. The ECG detection device consists of amplifier, filters, A/D converter and RF module. After amplification and filtering, the ECG signal is fed through the A/D converter to be digitalized. The digital ECG data is transmitted to the personal computer through the RF transceiver module and serial port.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1130-1141
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• 2015

Conventionally, a pulse radar is used for middle-sized or large-sized ships to detect other ships or obstacles located at a long distance. However, it is hardly equipped for most of the small-sized ships due to mounting and maintenance costs. Therefore, FMCW(frequency modulated continuous wave) radar is suggested as an alternative for the small-sized ships. Since it operates with low power and has good range resolution for relatively close objects, it is eligible for the small-sized ships. In previously proposed FMCW radar system, it only estimates distance and velocity of a target ship placed in the direction of main beam and is hard to detect several ships simultaneously. Thus, we suggest the method for detecting several ships at the same time by applying MUSIC(multiple signal classification) algorithm to FMCW radar signal received by a phased array antenna. In addition, by combining digital beam forming with the MUSIC algorithm, better angle resolution is achievable.

• International journal of advanced smart convergence
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• v.8 no.1
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• pp.106-112
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• 2019

Pulsation variance technique is blended the bumpy popple-sonance status of the brilliant-disparity understanding level (BDUL) on pulsation understanding gestalt. The understanding level condition by the pulsation understanding gestalt system is composed with the popple-sonance system. As to look for a two-node white-small dot of the brilliant situation, we are to take of the pulsation value with two-node white-small dot by the output signal. The concept of understanding level is composed the reference of brilliant-disparity level for variance signal by the pulsation sonance gestalt. Moreover indicating a bumpy variance of the BDUL of the maximum-minimum in terms of the popple-sonance gestalt, and pulsation two-node white-small dot sonance that was the a pulsation value of the far variance of the Pul-ug-FA-${\pi}_{MAX}$-MIN with $23.24{\pm}3.36units$, that was the a pulsation value of the convenient variance of the Pul-ug-CO-${\pi}_{MAX}$-MIN with $7.97{\pm}1.60units$, that was the a pulsation value of the flank variance of the Pul-ug-FL-${\pi}_{MAX}$-MIN with $3.02{\pm}0.47units$, that was the a pulsation value of the vicinage variance of the Pul-ug-VI-${\pi}_{MAX}$-MIN with $0.50{\pm}(-0.01)units$. The popple sonance will be to evaluate at the bumpy ability of the popple-sonance gestalt with two-node white-small dot by the pulsation understanding level on the BDUL that is indicated the brilliant-disparity gestalt by the understanding level system. We will be possible to suppress of a gestalt by the special signal and to utilize a pulsation data of popple sonance level by the popple understanding system.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.183-186
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• 1998

In this article, an algorithm for improving the performance of the convolutional decoder for a COFDM receiver using the subchannel information is introduced. The proposed algorithm defines the average amplitude of the received signal at each subchannel as a certainty of the received signal at that subchannel. If the certainty of a subchannel is low, then the received signal of that subchannel is mitigated, and the brach matric of the convolutional decoder is affected by that signal in a relatively small degree. However if the certainty of a subchannel is high, then the signal is enlarged and the branch matric is affected in a relatively large degree. simulations will show the improved BER performance of a COFDM system when the proposed method has been applied.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.4
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• pp.81-89
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• 2006

In this paper, a watermark technique for identifying friendly and foe is proposed during communication. The speech signal is processed in several stages. First, speech signal is partitioned into small time frames and the frames are transformed into frequency domain using DFT(Discrete Frequency Transform). The DFT coefficients are quantized and the watermark signal is embedded into the quantized DFT coefficients. At the destination channel quantization errors of received signal are regarded as the watermark signal. Identification of friendly and foe are done by correlating the detected watermark and the original watermark. As in most other watermark techniques, this method has a trade off between noise robustness and quality. However, this is solved by a partial quantization and a noise level dependent quantization step. Simulation results in the various noisy environments show that the proposed method is reliable for identification between friendly and foe.

• KIEE International Transactions on Electrophysics and Applications
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• v.2C no.5
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• pp.273-278
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• 2002

Even though the modulating signal frequency of the light is too high to detect directly, the signal can be extracted by frequency conversion at the same time as the detection by means of the non-linearity of the APD. An analysis is presented for super-high-speed optical demodulation by an APD with electronic mixing. A normalized gain is defined to evaluate the performance of the frequency conversion demodulation. The nonlinear effect of the internal capacitance was included in the small signal circuit analysis. We showed theoretically and experimentally that the normalized gain is dependent on the down converted difference frequency component. In the experiment, the down converted different frequency outputs became larger than the directly detected original signal for the applied local signal of 20㏈m.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1429-1434
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• 2003

A number of dust particles are intruded into ODD(Optical disk drive) due to the flow caused by disk rotation and are adhered to a lens or disk surface. The space between the disk and the lens is being reduced. Someone indicates the problems of this drive that are relatively small data storing capacity and slow access time. In recent, the problems of this optical disk drive mentioned above are being solved by adding the speed of the disk's revolution, making the actuator high-speed or light, and making the beam spot size smaller than making the space narrow between disk and lens. These particle contamination affects seriously RF Signal, readout signal in an ODD. Especially, the affected parts by a particle contamination in an ODD's readout signal are objective lens and media.