• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.559-568
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• 2014

Induction motors are critical components in industrial processes since their failure usually lead to an unexpected interruption at the industrial plant. The studies of induction motor behavior during abnormal conditions and the possibility to diagnose different types of faults have been a challenging topic for many electrical machine researchers. In this regard, an efficient and new method to detect the induction motor-fault may be the application of the Time Synchronous Averaging (TSA) to the stator current Park's Vector. The aim of this paper is to present a methodology by which defects in a three-phase wound rotor induction motor can be diagnosed. By exploiting the cyclostationarity characteristics of electrical signals, the TSA method is applied to the stator current Park's Vector, allowing the monitoring of the induction motor operation. Simulation and experimental results are presented in order to show the effectiveness of the proposed method. The obtained results are largely satisfactory, indicating a promising industrial application of the hybrid Park's Vector-TSA approach.

• The Journal of the Acoustical Society of Korea
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• 제24권4E호
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• pp.128-131
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• 2005

A new algorithm for speech signal segmentation is proposed. This algorithm is based on finding successive similar frames belonging to a segment and represents it by an average spectrum. The speech signal is a slowly time varying signal in the sense that, when examined over a sufficiently short period of time (between 10 and 100 ms), its characteristics are fairly stationary. Generally this approach is based on finding these fairly stationary periods. Advantages of the. algorithm are accurate border decision of segments and simple computation. The automatic segmentations using frame averaging show as much as $82.20\%$ coincided with manually verified segmentation of CMU ARCTIC corpus within time range 16 ms. More than $90\%$ segment boundaries are coincided within a range of 32 ms. Also it can be combined with many types of automatic segmentations (HMM based, acoustic cues or feature based etc.).

• 대한전자공학회논문지SP
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• 제46권4호
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• pp.132-138
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• 2009

본 논문에서는 기존의 Minima Controlled Recursive Averaging (MCRA)에 2차 조건 사후 최대 확률기법을 적용한 음성 향상 기법을 제안한다. 기존의 MCRA 방법은 현제 프레임의 음성 신호 존재 확률로 잡음 추정을 조정하기 때문에 음성 활동의 프레임간의 상호 연관성을 배제 하였다. 본 논문에서 제안한 알고리즘은 직전 2 프레임에서의 음성의 존재와 부재에 대한 조건을 부여해 주어 현제 프레임의 음성 신호 존재 확률을 수정하는 음성향상 기법을 적용한다. 제안된 2차 조건 사후 최대 확률기법을 적용한 MCRA 방법이 기존의 MCRA 방법보다 향상된 음성향상 결과를 나타내었다.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2288-2296
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• 2015

This paper proposes a novel systematic modeling approach for an integrated single-stage power converter in order to predict its dynamic characteristics. The basic strategy of the proposed modeling is substituting the internal converters with an equivalent current source, and then deriving the dynamic equations under a standalone operation using the state-space averaging technique. The proposed approach provides an intuitive modeling solution and simplified mathematical process with accurate dynamic prediction. The simulation and experimental results by using an integrated boost-flyback converter prototype provide verification consistent with theoretical expectations.

• Computers and Concrete
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• 제22권1호
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• pp.1-10
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• 2018

In this study an implicit algorithm for modeling of propagation of macrocracks in 3D concrete structures suffering from alkali-silica reaction has been developed and implemented. The formulation of the problem prior to the onset of localized deformation is based on a chemo-elasticity approach. The localized deformation mode, involving the formation of macrocracks, is described using a simplified form of the strong discontinuity approach (SDA) that employs a volume averaging technique enhanced by a numerical procedure for tracing the propagation path in 3D space. The latter incorporates a non-local smoothening algorithm. The formulation is illustrated by a number of numerical examples that examine the crack propagation pattern in both plain and reinforced concrete under different loading scenarios.

• 지구물리와물리탐사
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• 제3권2호
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• pp.61-69
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• 2000

지표 경계 조건은 유한 차분법을 이용한 탄성파 파동 방정식 모델링에서 수치해의 정확성을 떨어뜨리는 한편 포아송 비에 따른 해의 안정성을 제한하는 주 요인이 된다. 본 연구에서는 지표 경계 조건과 같은 Neumann 경계 조건의 처리에 효과적인 적분법(integration method)에 기반 하여 차분식을 유도하고, 이로부터 중간점 차분 기법을 제안하였다. 또한, 개발된 알고리즘을 Lamb의 문제에 적용하여 이론해와 비교함으로써 타당성을 검증하였다.

• 한국지반공학회논문집
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• 제23권3호
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• pp.51-59
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• 2007

다양한 불확실성을 체계적으로 반영하는 신뢰성 기반 해석기법을 사면안정 해석의 한 형식으로 제시한다. 통계오차, 공간 변동성, 그리고 공간 평균의 효과를 고려할 수 있는 지반특성 표현식이 사용되었다. 여러 가지 형식의 지반특성 표현식을 이용하여 사면안정 신뢰성 해석을 수행한 결과 통계오차, 공간적 상관성, 그리고 조건부 해석기법을 사용할 경우가 기존의 단순 확률변수 기법에 비해 상당히 작은 파괴확률을 제시한다는 사실이 밝혀졌다. 이 결과는 사면안정 해석에서 공간적 변동성과 통계오차가 합리적으로 고려되어야 한다는 점을 제시한다.

• 한국의학물리학회지:의학물리
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• 제28권4호
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• pp.171-180
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• 2017

The purpose of this study is to install a system that compensated for the respiration motion using an articulated robotic manipulator couch which enables a wide range of motions that a Stewart platform cannot provide and to evaluate the performance of various prediction algorithms including proposed algorithm. For that purpose, we built a miniature couch tracking system comprising an articulated robotic manipulator, 3D optical tracking system, a phantom that mimicked respiratory motion, and control software. We performed simulations and experiments using respiratory data of 12 patients to investigate the feasibility of the system and various prediction algorithms, namely linear extrapolation (LE) and double exponential smoothing (ES2) with averaging methods. We confirmed that prediction algorithms worked well during simulation and experiment, with the ES2-averaging algorithm showing the best results. The simulation study showed 43% average and 49% maximum improvement ratios with the ES2-averaging algorithm, and the experimental study with the $QUASAR^{TM}$ phantom showed 51% average and 56% maximum improvement ratios with this algorithm. Our results suggest that the articulated robotic manipulator couch system with the ES2-averaging prediction algorithm can be widely used in the field of radiation therapy, providing a highly efficient and utilizable technology that can enhance the therapeutic effect and improve safety through a noninvasive approach.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 가을 학술발표회 논문집
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• pp.291-292
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• 2003

Although the tensile strength of textile materials are determined by that of their components, it is well known that the tensile strength of fiber bundles and yams is not accurately predicted from that of single-fibers by simple averaging methods or mathematical calculations, because of variations in their strength. Therefore, there have been attempts to interpret the bundle strength from that of its elements by the stochastical approach. (omitted)

• Industrial Engineering and Management Systems
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• 제10권1호
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• pp.84-94
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• 2011

In this paper, we propose a method to provide the distribution of option price under local volatility model when market-provided implied volatility data are given. The local volatility model is one of the most widely used smile-consistent models. In local volatility model, the volatility is a deterministic function of the random stock price. Before estimating local volatility surface (LVS), we need to estimate implied volatility surfaces (IVS) from market data. To do this we use local polynomial smoothing method. Then we apply the Dupire formula to estimate the resulting LVS. However, the result is dependent on the bandwidth of kernel function employed in local polynomial smoothing method and to solve this problem, the proposed method in this paper makes use of model averaging approach by means of bandwidth priors, and then produces a robust local volatility surface estimation with a confidence interval. After constructing LVS, we price barrier option with the LVS estimation through Monte Carlo simulation. To show the merits of our proposed method, we have conducted experiments on simulated and market data which are relevant to KOSPI200 call equity linked warrants (ELWs.) We could show by these experiments that the results of the proposed method are quite reasonable and acceptable when compared to the previous works.