• 전기학회논문지
• /
• 제64권12호
• /
• pp.1756-1760
• /
• 2015

This paper focuses on a priori signal to noise ratio (SNR) estimation method for the speech enhancement. There are many researches for speech enhancement with several ambient noise cancellation methods. The method based on spectral subtraction (SS) which is widely used in noise reduction has a trade-off between the performance and the distortion of the signals. So the need of adaptive method like an estimated a priori SNR being able to making a high performance and low distortion is increasing. The decision directed (DD) approach is used to determine a priori SNR in noisy speech signals. A priori SNR is estimated by using only the magnitude components and consequently follows a posteriori SNR with one frame delay. We propose a modified a priori SNR estimator and the weighted rational transfer function for speech enhancement with wind noises. The experimental result shows the performance of our proposed estimator is better Perceptual Evaluation of Speech Quality scores (PESQ, ITU-T P.862) compare to the conventional DD approach-based systems and different noise reduction methods.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1996년도 춘계학술대회
• /
• pp.283-287
• /
• 1996

This paper described the estimator and eliminator far three kinds of artifacts in electrocardiogram. The most efficient estimation of baseline drift could be obtain in the cubic spline interpolation method with the PQ and TP segment which are considered to be isoelectric, from the experimental results obtained from the applied 4 types of algorithms. The time loss and distortion could be avoided with the aid of detection criteria by checking if baseline drifts exist or not. The AIEF proposed in this paper was verified as having the best removal performance with less distortion in the QRS complex through the comparison of 5 proposed algorithms. furthermore, the AIEF are most suitable far the ECG analyzer which was only needed relatively short time data due to the fast conversion into the stable state. The proposed parabolic filter with 11 points width was identified as having the best performance for the elimination of muscle artifacts. Also we could obtain 99.7% detection accuracy of spike component and minimize the error identifying QRS complex as spike.

• 전기전자학회논문지
• /
• 제26권4호
• /
• pp.710-713
• /
• 2022

본 논문에서는 전기자동차 충전시 발생하는 고조파 성분을 매우 높은 차수까지 추정하여 전력량을 계산하되 낮은 연산능력을 가지는 저가의 보급형 전력량계에서도 구동 가능하도록 Goertzel 기반 알고리즘을 제안하였다. 제안된 알고리즘을 사용하여 전력량 계량시 큰 차수의 고조파까지 충분히 고려할 수 있음을 간단한 예제 신호에 대해 시뮬레이션을 통해 검증하였다.

• 전기학회논문지
• /
• 제56권1호
• /
• pp.1-7
• /
• 2007

Generally, an electric railroad feeding system has many problems due to the different characteristics in contrast with a load of general three-phase AC electric power system. One of them is harmonics problem caused by the switching device existing in the feeding system, and moreover, the time-varying dynamic loads of rail way is inherently another cause to increase this harmonics problem. In Korea power systems, the electric railroad feeding system is directly supplied from the substation of KEPCO. Therefore, if voltages fluctuation or unbalanced voltages are created by the voltage and current distortion or voltage drop during operation, it affects directly the source of supply. The trainloads of electric railway system have non-periodic but iterative harmonic characteristics as operating condition, because the electric characteristic of the electric railroad feeding system is changed by physical conditions of the each trainload. According to the traditional study, the estimation of harmonics has been performed by deterministic way using the steady state data at the specific time. This method is easy to analyze harmonics, but it has limits in some cases which needs an assessment of dynamic load and reliability. Therefore, this paper proposes the probabilistic estimation method, moments matching method(MW) in order to overcome the drawback of deterministic method. In this paper, distributions for each harmonics are convolved to obtain the moments and cumulants of TDD(Total Demand Distortion), and this can be generalized for any number of trains. For the case study, the electric railway system of LAT(Intra Airport Transit) in Incheon International Airport is modeled using PSCAD/EMTDC dynamic simulator. The raw data of harmonics for the moments matching method is acquired from simulation of the LAT model.

• 한국음향학회지
• /
• 제16권2호
• /
• pp.107-113
• /
• 1997

본 논문에서는 채널왜곡과 부가잡음에 강한 한국어 단어 인식기 구현을 위해 사후확률추정법에 의한 환경적응화법을 제안하고 이 방법의 인식성능 향상에 대한 유효성을 확인하였다. 이를 위해 1)채널왜곡이 발생한 경우, 2)부가잡음이 첨가된 경우, 3)채널왜곡과 부가잡음이 동시에 존재하는 각각의 경우에 대해서 제안한 환경적응화법을 이용하여 인식실험을 수행하였다. 이때 회귀계수, 지속시간 정보와 같은 부가정보의 환경적응화에 대한 유효성도 검토하였다. 100단어에 대한 환경독립, 화자독립 인식실험을 수행한 결과, 1)의 경우에 대해서는 9.0%, 2)의 경우에 대해서는 75%이상, 3)의 경우에 대해서는 11%~61.4%의 인식률 향상을 보여 사후확률추정법에 의한 환경적응화 방법이 채널왜곡 및 부가잡음이 동시에 존재하는 음성에 대하여서도 유효함을 알수 있었다. 그러나 지속시간 정보의 인식에 대한 기여는 찾아볼 수 없었다.

• 산업기술연구
• /
• 제28권B호
• /
• pp.167-174
• /
• 2008

In this paper, the analysis on type effect of inverter output voltage distortion on the control of an induction motor is discussed. The inverter output voltage is distorted differently from the reference voltage owing to the inverter nonlinear characteristic. The inverter nonlinear characteristic results from the voltage drop, the inherent characteristic of the power semiconductor, and the dead time for preventing the short circuit of the inverter leg. This characteristic distorts the inverter output voltage and then, causes the motor flux estimation error. Although this characteristics do not significantly effect in the general-purpose induction motor control, but significantly effect on the low-speed operation of high performance motor control such as the sensorless vector control.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2006년도 춘계 학술발표회 논문집
• /
• pp.249-256
• /
• 2006

New infrastructures and buildings are being constructed increasingly in congested urban areas, and excavation-induced ground movements often cause distortion and damage to adjacent buildings. Protection of adjacent structures occupies a major part of the cost, schedule and third-party impacts of urban development. To limit damage or mitigate their effects on nearby structures, it is highly important to understand the whole mechanism from excavation to building damage, and to estimate building damage reliably before excavation and provide appropriate measures. This paper investigates the effects of excavation-induced ground movements on nearby structures, considering soil-structure interactions for ground and structures, and a building damage criterion, which is based on the state of strain, is proposed. The criterion is compared with other existing damage estimation criteria and a procedure is finally provided for estimating building damage due to excavation-induced ground movements.

• 산업공학
• /
• 제21권2호
• /
• pp.151-160
• /
• 2008

Defect size distribution is a probability density function for the defects that occur on wafers or glasses during semiconductor/LCD fabrication. It is one of the most important information to estimate manufacturing yield using well-known statistical estimation methods. The defects are detected by automatic optical inspection (AOI) facilities. However, the data that is provided from AOI is not accurate due to resolution of AOI and its defect detection mechanism. It causes distortion of defect size distribution and results in wrong estimation of the manufacturing yield. In this paper, I suggest a size conversion method and a maximum likelihood estimator to overcome the vague defect size information of AOI. The methods are verified by the Monte Carlo simulation that is constructed as similar as real situation.

• ETRI Journal
• /
• 제29권5호
• /
• pp.607-613
• /
• 2007

Most signal-to-noise ratio (SNR) estimation techniques in digital communication channels derive the SNR estimates solely from samples of the received signal after the matched filter. They are based on symbol SNR and assume perfect synchronization and intersymbol interference (ISI)-free symbols. In severe channel distortion where ISI is significant, the performance of these estimators badly deteriorates. We propose an SNR estimator which can operate on data samples collected at the front-end of a receiver or at the input to the decision device. This will relax the restrictions over channel distortions and help extend the application of SNR estimators beyond system monitoring. The proposed estimator uses the characteristics of the second order moments of the additive white Gaussian noise digital communication channel and a linear predictor based on the modified-covariance algorithm in estimating the SNR value. The performance of the proposed technique is investigated and compared with other in-service SNR estimators in digital communication channels. The simulated performance is also compared to the Cram$\acute{e}$r-Rao bound as derived at the input of the decision circuit.

• Journal of Communications and Networks
• /
• 제4권3호
• /
• pp.189-198
• /
• 2002

Precoder has been shown to be able to provide source diversity and design flexibility. In this paper we employ precoding techniques for block transmission based on a multirate filterbank structure. To accommodate multiuser communication with variable data rates, different precoders with corresponding coefficients and up/down sampling rates are used. However, due to unknown multipath distortion, different interferences may exist in the received data, such as multiuser interference, intersymbol interference and interblock interference. To estimate channel parameters for a desired user, we employ all structured signature waveforms associated with different symbols of that user and apply subspace techniques. Therefore better performance of channel estimator can be achieved than the conventional subspace method based only on the signature of the current symbol. The delay for that user can also be jointly estimated. Channel identifiability conditions and asymptotic channel estimation error are investigated in detail. Numerical examples are provided to justify the proposed method. gest either multicode (MC) or multiple processing gain (MPG) mechanism [2], while requiring data rates to be integral multiples of some basic low-rate. In order to support variable rate transmission however, a comprehensive scheme needs to be investigated.