• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.316-319
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• 1998

RPWM(Random Pulse Width Modulation) is a switching technique to spread the voltage and current harmonics on the wide frequency area. Using randomly changed switching frequency of the inverter, the power spectrum of the electromagnetic acoustic noise cab be spread to the wide-band area. The wide-band noise is much more comfortable and less annoying than the narrow-band one. So RPWM have been attracting an interest as an excellent method for the reduction of acoustic noise on the inverter drive system. In this paper a new RPPWM (Random Position PWM) is proposed and implemented. Each of three pulses is located randomly in each switching interval. Along with the randomization of PWM pulses, the space vector modulation is executed in the C167 microcontroller also. The experimental results show that the voltage and current harmonics were spread to wide band area and that the audible switching noise was reduced by proposed RPPWM method.

• 한국음향학회지
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• 제35권2호
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• pp.102-109
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• 2016

본 논문은 밀접한 간격의 두 개의 마이크 배열 환경에서 SNR(Signal-to-Noise Ratio) 추정을 통한 잡음 억제 방법을 제안한다. 기존의 방법은 전 밴드에서 간섭 함수 기반의 SNR 추정을 통해 이득 함수를 얻는 잡음 억제 방법을 사용한다. 그러나 이 방법은 잡음으로 인한 손상이 모든 특징 벡터 성분에 영향을 미쳐 성능을 저하시키는 문제점을 가지고 있다. 따라서 주파수 영역의 신호를 N개의 다중 주파수 밴드로 구분하고 각 밴드별로 간섭 함수 기반의 SNR 추정을 통한 이득 함수를 얻는 잡음 억제 방법을 제안한다. 제안하는 방법의 성능평가는 ITU-T(International Telecommunications Union Telecommunication)에서 제공되는 객관적인 품질 평가 방법인 PESQ(Perceptual Evaluation of Speech Quality)로 비교하여 나타내었다.

• 한국전자파학회논문지
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• 제23권5호
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• pp.640-645
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• 2012

하이브리드 전기 차량 내에 존재하는 DC-DC 컨버터 또는 DC-AC 인버터에 의해 스위칭 잡음이 발생된다. 이 스위칭 잡음은 컨버터 또는 인버터의 스위칭 회로 내에 존재하는 전력 다이오드의 역 회복 동작에 의해 발생된다. 다이오드의 반전 시간과 역 회복 시간이 역 회복 구간의 모양을 결정한다. 본 논문은 스위칭 잡음의 주파수 스펙트럼을 다이오드 역 회복 구간의 모양을 통해 예측하고, 측정 결과와 비교하여 주요 주파수 구간이 다이오드의 반전 시간과 직접적인 연관이 있다는 것을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.465-467
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• 1999

The data transmission system in MAGLEV is required a high quality and high speed for a train safety and reliability driving. In the transmission channel between a vehicle and a ground-site, Gaussian noise is negligible, but impulse noise from the chopper controlled propulsoin unit and the Power supplying device is very severe. The transmission channel must be protected from these noise. In this paper, we propose a DSSS (direct-sequence spread spectrum) modulation as a new data transmission technique in the railway and analyze this data transmission characteristics.

• 한국음향학회지
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• 제28권7호
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• pp.680-685
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• 2009

본 논문에서는 주파수 영역에서 음향학적 반향 및 잡음 제거의 통합 시스템을 위한 효과적인 잡음전력 추정 기법을 제안한다. 제안된 방법은 잡음 제거 (NS, noise suppression)가 음향학적 반향 억제 (AES, acoustic echo suppression)의 후처리단으로 결합하여 사용되는 구조에서 발생하는 잡음전력 추정오차를 줄이기 위해 마이크로폰 입력신호의 음성부재확률 (SAP, speech absence probability)을 잡음전력 갱신을 위한 스무딩 (smoothing) 파라미터로 적용한다. 따라서 제안된 기법에서는 반향 억제 후 신호에서 잡음전력 갱신을 위한 SAP를 추출하는 대신 입력신호에 대한 SAP를 NS 알고리즘에 적용함으로서 잡음 제거기가 반향 억제 후 왜곡된 잡음 스펙트럼 구간에서는 잡음전력을 갱신하지 않도록 한다. 제안된 알고리즘은 기존의 방법과 객관적인 실험을 통해 비교 평가한 결과 다양한 배경잡음 환경에서 우수한 성능을 보였다.

• ETRI Journal
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• 제39권1호
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• pp.87-96
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• 2017

Ultrasonic surgical devices are routinely used for surgical procedures. The incision and coagulation of tissue generate a temperature of $40^{\circ}C-150^{\circ}C$ and depend on the controllable output power level of the surgical device. Recently, research on the classification of grasped tissues to automatically control the power level was published. However, this research did not consider the specific characteristics of the surgical device, tissue denaturalization, and so on. Therefore, this research proposes a robust algorithm that simulates noise to resemble real situations and classifies tissue using conventional classifier algorithms. In this research, the bioimpedance spectrum for six tissues (liver, large intestine, kidney, lung, muscle, and fat) is measured, and five classifier algorithms are used. A signal-to-noise ratio of additive white Gaussian noise diversifies the testing sets, and as a result, each classifier's performance exhibits a difference. The k-nearest neighbors algorithm shows the highest classification rate of 92.09% (p < 0.01) and a standard deviation of 1.92%, which confirms high reproducibility.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.175-179
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• 2007

수중 천이 신호를 탐지하기 위한 기존의 기법은 에너지 변화와 스펙트럼 변이를 이용한 것으로 백색잡음 환경에서 탐지가 잘 되지만 유색잡은 환경에서는 탐지가 잘 되지 않는다. 본 논문에서는 백색잡은 환경과 유색잡음 환경에서 수중 천이 신호의 탐지성능을 높이기 위해 Double-Density 이산 웨이블렛 변환과 CFAR Power-Law기법을 이용한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.308-312
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• 2003

The objective of this paper is to investigate the power spectrum of a three-phase and a two-phase RCD (Random Pulse Centered Displacement) PWM scheme. The two-phase or three-phase pulses of RCD-PWM scheme are mutually center-aligned as in SVM(Space Vector Modulation), but the common pulse center is displaced randomly from the middle of the period. To verify the validity of the proposed two-phase RCD-PWM scheme, the power spectra of the output voltage, the d.c link current in the inverter drives and the radiated acoustic noise are experimentally investigated. And, the performance of the proposed two-phase RCD-PWM scheme was compared and discussed with the conventional three-phase RCD-PWM scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.841-845
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• 1991

There are Carrier Current Communication or Power line Carrier (PLC) Communication conducted data exchange using power line Which is installed existing indoor. Power line is possible to construct data link economically, on the other hand, have an inferior transmission environment such as irregular noise and severe level variation. The purpose of this paper is to present transmission possibility for PLC using spread spectrum technique. In the initial synchronization, established computer simulation for the S/N in relation to PN code generator. By using this result, construct the prototype SS system and then experiment the transmission characteristics.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1489-1503
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• 2018

Spectrum reuse has attracted much concern of researchers and scientists, however, the dynamic spectrum access is challenging, since an individual secondary user usually just has limited sensing abilities. One key insight is that spectrum usage forecasting among secondary users, this inspiration enables users to obtain more informed spectrum opportunities. Therefore, spectrum usage forecasting is vital to cognitive radio networks (CRNs). With this insight, a spectrum usage forecasting model for the occurrence of primary users prediction is derived in this paper. The proposed model is based on auto regressive enhanced primary user emergence reasoning (AR-PUER), which combines linear prediction and primary user emergence reasoning. Historical samples are selected to train the spectrum usage forecasting model in order to capture the current distinction pattern of primary users. The proposed scheme does not require the knowledge of signal or of noise power. To verify the performance of proposed spectrum usage forecasting model, we apply it to the data during the past two months, and then compare it with some other sensing techniques. The simulation results demonstrate that the spectrum usage forecasting model is effective and generates the most accurate prediction of primary users occasion in several cases.