• Nuclear Engineering and Technology
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• 제39권2호
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• pp.133-142
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• 2007

The Electric Power Research Institute (EPRI) demonstrated a method for monitoring the performance of instrument channels in Topical Report (TR) 104965, 'On-Line Monitoring of Instrument Channel Performance.' This paper presents the results of several models originally developed by EPRI to monitor three nuclear plant sensor sets: Pressurizer Level, Reactor Protection System (RPS) Loop A, and Reactor Coolant System (RCS) Loop A Steam Generator (SG) Level. The sensor sets investigated include one redundant sensor model and two non-redundant sensor models. Each model employs an Auto-Associative Kernel Regression (AAKR) model architecture to predict correct sensor behavior. Performance of each of the developed models is evaluated using four metrics: accuracy, auto-sensitivity, cross-sensitivity, and newly developed Error Uncertainty Limit Monitoring (EULM) detectability. The uncertainty estimate for each model is also calculated through two methods: analytic formulas and Monte Carlo estimation. The uncertainty estimates are verified by calculating confidence interval coverages to assure that 95% of the measured data fall within the confidence intervals. The model performance evaluation identified the Pressurizer Level model as acceptable for on-line monitoring (OLM) implementation. The other two models, RPS Loop A and RCS Loop A SG Level, highlight two common problems that occur in model development and evaluation, namely faulty data and poor signal selection

• 한국소음진동공학회논문집
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• 제14권4호
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• pp.310-318
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• 2004

For many industrial problems originating from aerodynamic noise, noise prediction techniques, reliable and easy to apply, would be of great value to engineers and manufacturers. General algorithm is presented for the prediction of internal flow-induced noise from quick opening throttle valve in an automotive engine. This algorithm is based on the integral formula derived by using the General Green Function, Lighthill's acoustic analogy and Curle's extension of Lighthill's. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve show good agreement with actual measurements. The results show that the dipole noise is dominant in this phenomena and the origin of noise sources is attributed to the anti-vortex lines formed in the down-stream from a throttle valve. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• 한국진공학회지
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• 제16권6호
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• pp.458-462
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• 2007

타원편광분석법은 반도체 물질의 광 특성과 전이점 연구에 유용하게 쓰이는 기술이다. 측정된 유전율 함수로부터 전이점을 구하기 위해서 전통적으로 이차 미분스펙트럼을 이용하여 분석하는데, 이 방법은 high frequency 의 잡음을 크게 증폭시키는 단점이 있다. 본 연구에서는 역 공간 푸리에 변환 (Fourier transform)을 이용하여 low-, medium-, high-index 의 푸리에 계수로부터 baseline, 정보, high frequency 잡음을 분리하는 방법을 소개하고자 한다. 이 방법을 이용하여 광전자소자에 폭넓게 사용되는 ZnCdSe 화합물 반도체의 $E_1,\;E_1+{\Delta}_1$ 전이점에 대한 연구를 하여 전통적인 이차 미분법과 비교해 보았다.

• 한국지구과학회지
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• 제36권5호
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• pp.437-446
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• 2015

Many edge detection methods, based on horizontal and vertical derivatives, have been introduced to provide us with intuitive information about the horizontal distribution of a subsurface anomalous body. Understanding the characteristics of each edge detection method is important for selecting an optimized method. In order to compare the characteristics of the individual methods, this study applied each method to synthetic magnetic data created using homogeneous prisms with different sizes, the numbers of bodies, and spacings between them. Seven edge detection methods were comprehensively and quantitatively analyzed: the total horizontal derivative (HD), the vertical derivative (VD), the 3D analytic signal (AS), the title derivative (TD), the theta map (TM), the horizontal derivative of tilt angle (HTD), and the normalized total horizontal derivative (NHD). HD and VD showed average good performance for a single-body model, but failed to detect multiple bodies. AS traced the edge for a single-body model comparatively well, but it was unable to detect an angulated corner and multiple bodies at the same time. TD and TM performed well in delineating the edges of shallower and larger bodies, but they showed relatively poor performance for deeper and smaller bodies. In contrast, they had a significant advantage in detecting the edges of multiple bodies. HTD showed poor performance in tracing close bodies since it was sensitive to an interference effect. NHD showed great performance under an appropriate window.

• 한국음향학회지
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• 제15권5호
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• pp.90-98
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• 1996

본 논문에서는 잡음 환경에서의 음성 인식을 위한 전처리기로서 청각 모델을 제안하였다. 제안된 청각 모델은 와우각 대역 통과 필터와 비선형단으로 구성되어 있으며, 잡음 환경에서도 신호의 주파수 정보와 강도 정보를 효과적으로 표현할 수 있다. 주파수 정보는 신호의 영교차 간격에 의해서, 또 강도 정보는 피크 검출기와 포화 비선형 함수에 의해서 구해진다. 영교차 간격이 교란되는 양의 분산을 교차 레벨 값의 함수로 표현함으로써 영교차 간격을 사용하는 것이 레벨 교차간격에 비해 잡음에 둔감한 특성이 있음을 보였다. 제안된 청각 모델은 다른 청각 모델에 비해 계산량이 적고, 미리 많은 파라미터를 정해줄 필요가 없다. 화자 독립 격리단어 인식 실험 결과 제안된 방법은 잡음 환경에서 우수한 성능을 보였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.230-233
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• 2003

In this paper, it is shown that, in DS/CDMA mobile systems, halving or doubling the spreading factor (HSF or DSE) when retransmission is requested possibly improves the throughput. Given transmit power, DSF essentially decreases probability of packet error (PPE) by increasing the signal energy per information bit. It, however, doubles the time duration needed for transmitting the original packet. On the other hand, HSF increases PPE. It, however halves the time duration required to carry the original packet. Thus, the efficiency of HSF or DSF as a retransmission strategy depends on the amount of increased or reduced PPE after HSF or DSF is selected. With achieving given residual error probability (REP) in CDMA systems, the effective throughput is evaluated in this paper to find conditions with which HSF or DSF achieves better performance than using the original one. Analytic results show that HSF or DSF performs better when relatively small or big changes in their PPE's are present, respectively.

• 한국산학기술학회논문지
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• 제13권5호
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• pp.1990-1995
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• 2012

본 연구에서는 다구찌 방법을 이용하고 유한요소해석을 통해 알루미늄 피스톤 제조에 큰 영향을 미치는 설계변수의 적합한 조건을 도출하였다. 단조 최대 성형하중을 목적함수로 하고 설계변수로서 예비성형체, 소재온도 및 빼기구배를 선정하였으며 마찰을 잡음인자로 하는 직교배열표를 작성하고 시뮬레이션별 유한요소해석을 통해 하중을 평가하였다. 이를 통해 설계 변수들이 미치는 영향을 분석한 결과를 바탕으로 설계변수의 최적조합조건은 제안하였다. 이러한 방법은 여러 가지 금속성형공정에서 최종 단조품 전단계에서 여러 예비성형체에서 적합한 예비성형체를 결정할 때 도움을 줄 수 있으며 특히, 최적의 설계조합을 결정할 때 쉽게 적용할 수 있을 것이다.

• The Journal of the Acoustical Society of Korea
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• 제22권4E호
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• pp.183-196
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• 2003

General algorithm is developed for the prediction of internal flow-induced noise. This algorithm is based on the integral formula derived by using the General Green Function, Lighthill's acoustic analogy and Curl's extension of Lighthill's. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve are compared with actual measurements. This illustrative computation shows that the current method penn its generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• 음성과학
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• 제12권4호
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• pp.53-70
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• 2005

A Vowel of speech signals are multicomponent signals composed of AM-FM components whose instantaneous frequency and instantaneous amplitude are time-varying. The changes of emotion states cause the variation of the instantaneous frequencies and the instantaneous amplitudes of AM-FM components. Therefore, it is important to estimate exactly the instantaneous frequencies and the instantaneous amplitudes of AM-FM components for the extraction of key information representing emotion states and changes in speech signals. In tills paper, firstly a method decomposing speech signals into AM - FM components is addressed. Secondly, the fundamental frequency of vowel sound is estimated by the simple method based on the spectrogram. The estimate of the fundamental frequency is used for decomposing speech signals into AM-FM components. Thirdly, an estimation method is suggested for separation of the instantaneous frequencies and the instantaneous amplitudes of the decomposed AM - FM components, based on Hilbert transform and the demodulation property of the extended Fourier transform. The estimates of the instantaneous frequencies and the instantaneous amplitudes can be used for modification of the spectral distribution and smooth connection of two words in the speech synthesis systems based on a corpus.

• 대한기계학회논문집A
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• 제21권6호
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• pp.942-950
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• 1997

Far field acoustic pressure from the evolution and interaction of three-dimensional vortex filament is calculated numerically. A vortex ring is a typical example of the three-dimensional vortex filament. An elliptic vortex ring emits a strong sound signal due to significant distortion and stretching of the vortec filament. The far field acoustic pressure is linearly dependent on the third time derivatives of the vortex positions. A numerical scheme of high resolution is employed to describe in detail the elliptic vortex ring motions which ar highly nonlinear. Descretized vortex filaments are interpolated by using a parametric blending function to remove a possible numerical instability. The distorted vortex filament, owing to the self-induced and the induced velocity from the other vortex segments, is redistributed at each time step. The accuracy and efficiency of the scheme are validated by comparisons with the analytic solution of circular vortex ring interaction.