• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.1
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• pp.60-69
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• 2014

Footstep detection using seismic sensors for security is a very meaningful task, but readings can easily fluctuate due to noise in outdoor environment. We propose NSSC method based on nonlinear spectral subtraction and cross-correlation using prime footstep model signal as a footstep signal refining process that enhances the signal-to-noise ratio (SNR) and attenuates noise. After de-noising, a detection event classification method is presented as further refining process to ensure that the detection result is a footstep. To validate the proposed algorithm, representative experiments including sunny and rainy-day cases are demonstrated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.993-998
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• 2002

At Power amplifier, distortion of output is appeared because of non-linearlity, so we must study method of compensation for non-linearity. In this paper, it was studied about the characteristic of predistorter using serial schottky diode for an amplifier. As a result, we confirmed that power amplifier was able to linearize when we put predistorter using non-linearity of schottky diode before power amplifier. When input carrier level was low, input carrier was delivered directly into power amplifier but input carrier level was high, input carrier was delivered into power amplifier through predistorter with suppressed level. As a result power amplifier always was at saturation region. Through simulation using serenade 8.0, we have concluded that efficiency was improved about 3%, and predistorter got best linearity at 1.8㎓ between 800㎒∼2.2㎓.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.739-747
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• 2007

Dual-mode bandpass filter was designed by using periodic stepped impedance ring resonator with step perturbation. The periodic stepped impedance ring resonator has the effects of size reduction and $2^{nd}$ harmonic suppression by changing characteristic impedance ratio. The perturbation for dual-mode generation was also easily controlled by characteristic impedance ratio, and the variation of dual-mode resonant frequencies and attenuation pole frequencies were analyzed by the effect of step perturbation. Chip capacitors were used for input/output coupling, and the variation of center frequency by the coupling capacitance and step perturbation was also considered. From the results, two types of 2 GHz dual-mode bandpass filter were fabricated in size of $14{\times}14mm^2$, those have different attenuation poles and bandwidths. The measured results of proposed bandpass filters showed a good agreement with the calculated estimations, and those have insertion loss of 2.52, 0.52 dB and 3 dB bandwidth of 4.03, 15.02 %, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.2
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• pp.43-54
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• 1989

In this paper, measured and calculated responses are compared in order to give how the static and dynamic responses occurred in steel railway bridges due to train loads could be calculated appropriately. From this, it is investigated how the impact factors are varied by changing the train speed above 100km/h Field measurement is carried out by the steel strain gages and displacement transducers at the main design points, and then the static and dynamic response, fundamental frequencies, damping ratios and impact factors of the bridges are obtained. Static analysis is done using the computer program developed according to three dimensional matrix structural analysis in which the trains and bridges are modelled as 1,2 and 3 dimensions. Dynamic analysis is done according to 2 approaches, the moving force and mass problem. In moving force problem, the solutions are obtained by the modesuperposition-method and in moving mass problem by the direct integration method. From this study, it is known that in order to obtain the static response in the railway bridges, the bridge could be modelled by 1 or 2 dimension as in the highway bridge, however the response ratio(measured/calculaled) is high comparing to the highway bridges. By the way, the dynamic response should be obtained by the moving mass problem. And by comparing the measured and code specified impact factors, it is known that the factors specified in the present railway bridge code are very safe under the present service speed below 100km/h. However, because the factors become very high under the speed above 100km/h, especially in the simple plate girder bridge, it is thought that the code specification on impact factor should be discussed enough under the rapid transit system.

• The Journal of the Korea Contents Association
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• v.9 no.1
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• pp.139-146
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• 2009

This paper addresses a modified spectral subtraction schemes which is suitable to speech recognition under low signal-to-noise ratio (SNR) noisy environment such as the automatic speech recognition (ASR) system in car. The conventional spectral subtraction schemes rely on the SNR such that attenuation is imposed on that part of the spectrum that appears to have low SNR, and accentuation is made on that part of high SNR. However, such postulation is adequate for high SNR environment, it is grossly inadequate for low SNR scenarios such as that of car environment. Proposed methods focused specifically to low SNR noisy environment by using weighting function for enhancing speech dominant region in speech spectrum. Experimental results by using voice commands for car show the superior performance of the proposed method over conventional methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.189-197
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• 2011

OFDM systems are much studied for the recent high speed wireless optical communication system. OFDM system has basically high PAPR and ICI easily generated because of non-linearity and RF impairments. In the wireless optical communication system, optical output power driven by current of LED is not linear so that transmission signals are distorted. Therefore, research about reception performance of this nonlinear optical output emitted by non-linear LED transfer function and OFDM signal has been conducted. Nonlinear effect of LED is different from nonlinear effect of OFDM system in the conventional radio communication system, which degrades the BER performance. In this paper, we apply non-linear transfer function of recently studied LED into OFDM system. So, for reducing the PAPR and suppressing the ICI in frequency domain of receiver, we suggest a new PAPR reduction technique to reduce non-linear distortion of LED and an adaptive ICI suppression algorithm so that BER performance may be improved. Also, the proposed method is verified through simulation results.

• Economic and Environmental Geology
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• v.39 no.4 s.179
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• pp.473-483
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• 2006

Although application of electrical methods in Korea began with observation of self potentials before World War II, the methods were developed slowly by the beginning of 1980's when a major burst of development activity took place. DC resistivity methods are applied in Korea more to geotechnical problems rather than to environmental ones unlike other developed countries. As with every other branch of technology, the evolving speed of the silicon chip and of streaming data to hard disk has revolutionized data collection and noise reduction processing. The last two decades saw major advances in data collection, processing, and interpretation of electrical data. Development of smooth-model two-dimensional (2D) resistivity inversion is one of the most visible changes to geophysical interpretation of the last 40 years and is now routinely applied to apparent resistivity data. The ability to represent resistivities in section rather than pseudosection view has revolutionized interpretation. Although calculation of sensitivities for general electromagnetic problems require numerous forward modelings, DC resistivity methods can enjoy computational efficiencies if sources and receivers occupy the same position, and previously intractable 3D inversion is now becoming available.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.257-258
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• 2008

지능형 로봇에서 환경인식과 이러한 환경에 따른 행동 결정 능력은 로봇이 필수적으로 갖추어야 할 기능이다. 특히 상체의 움직임이 많은 휴머노이드 로봇에서 비전기반의 높은 환경에 대한 인식 기능을 위해서는 전처리 단계로 로봇 자체의 움직임을 감쇄 시켜주는 기능이 필수적이다. 본 논문에서는 Gaussian 모델과 Wavelet을 사용하여 추적하고자 하는 영역을 추출하고 PCA와 FNCC를 이용하여 움직임을 상쇄시키는 방법을 제안한다. 본 방법은 기존의 픽셀 단위로 움직임을 분석하는 방법에 비하여 간단하면서도 우수한 성능을 보인다. 본 시스템을 제작한 로봇에 적용한 결과 보다 높은 인식 성능을 얻을 수 있었다.

• Proceedings of the Speleological Society Conference
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• 2005.11a
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• pp.69-77
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• 2005

비 직선적 정(+) 저항온도계수 특성을 갖은 PTC thermistor눈 전이온도(큐리점) 부근에서 온도변화에 대하여 극히 큰 저항 값의 변화를 나타내는 산화물계반도체 저항기(또는 발열체)로써, 일반적으로 반도체의 온도-저항 특성과 같이 상온영역에서 온도의 상승과 함께 부성저항 특성을 나타내어 감소하다가, 온도가 점점 증가하여 큐리점 부근에 도달하면 저항이 급격히 증가하는 독특한 특성을 갖는다. Perovskite 구조의 BaTiO$_3$를 주성분으로 미량의 Dopant를 첨가하여 도전성을 갖게 한 N형 반도체의 일종으로, 저항-온도 특성, 전류-전압 특성, 전류감쇄 특성 등을 이용하여 과전류 보호회로, 히터, TV 소자회로(degausser) 모터기동회로, 온도센서, 정온발열기기 등으로 널리 사용된다. 본 연구는 큐리점 부근의 급격한 저항변화 현상과 결정입계의 전위장벽 형성 및 그에 따른 정온발열 기능의 상관성으로부터 정온발열 탐사기능 온열부츠 제작 용 PTC 부픔소재의 응용성을 조사하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.28-33
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• 2004

We developed a fiber-optic CT for large current monitoring in power systems. We used a FRG fiber sensor coil to suppress CT output degradation caused by linear birefringence, and different optical sources were used to compare their noise characteristics. From the experiments, we obtained output variation less than $\pm$0.4(%) when the sensor coil suffered mechanical perturbations, and the ASE source showed -23(㏈) less noise in the output than singlemode laser diode.