• 지구물리와물리탐사
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• 제7권1호
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• pp.7-13
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• 2004

In this paper, we demonstrate that Common Mid-Point (CMP) cross-correlation gathers of multi-channel and multi-shot surface waves give accurate phase-velocity curves, and enable us to reconstruct two-dimensional (2D) velocity structures with high resolution. Data acquisition for CMP cross-correlation analysis is similar to acquisition for a 2D seismic reflection survey. Data processing seems similar to Common Depth-Point (CDP) analysis of 2D seismic reflection survey data, but differs in that the cross-correlation of the original waveform is calculated before making CMP gathers. Data processing in CMP cross-correlation analysis consists of the following four steps: First, cross-correlations are calculated for every pair of traces in each shot gather. Second, correlation traces having a common mid-point are gathered, and those traces that have equal spacing are stacked in the time domain. The resultant cross-correlation gathers resemble shot gathers and are referred to as CMP cross-correlation gathers. Third, a multi-channel analysis is applied to the CMP cross-correlation gathers for calculating phase velocities of surface waves. Finally, a 2D S-wave velocity profile is reconstructed through non-linear least squares inversion. Analyses of waveform data from numerical modelling and field observations indicate that the new method could greatly improve the accuracy and resolution of subsurface S-velocity structure, compared with conventional surface-wave methods.

• Journal of Information Technology Applications and Management
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• 제22권3호
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• pp.105-114
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• 2015

This paper presents a fast Time Difference of Arrival (TDOA) estimation for sound source localization. TDOA is the time difference between the arrival times of a signal at two sensors. We propose a partial cross correlation method to increase the speed of TDOA estimation for sound source localization. We do this by predicting which part of the cross correlation function contains the required TDOA value with the help of the signal energies, and then we compute the cross correlation function in that direction only. Experiments show approximately 50% reduction in the cross correlation computation time thereby increasing the speed of TDOA computation. This makes it very relevant for real world surveillance.

• 전기학회논문지
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• 제59권12호
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• pp.2324-2328
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• 2010

In this paper we proposed a new algorithm that can reduce the open-loop pitch estimation time of G.723.1. The time domain cross-correlation method is simple but has long processing time by recursive multiplication. For reduction of processing time, we use the method that compute the cross-correlation by multiplying the Fourier value of speech by it's complex conjugate. Also, we can reduce the processing time by omitting the bit-reversing of FFT and IFFT for time-frequency domain transform. As a result, the processing time of improved hybrid domain cross-correlation algorithm is reduced by 67.37% of conventional time domain cross-correlation.

• 대한의용생체공학회:의공학회지
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• 제12권1호
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• pp.19-22
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• 1991

Cross correlation method was newly applied for the calculation of latency of evoked otoacoustic emission. The latency was calculated froth the main peak of cross correlation function, which is one of Possible definition of latency. The output was also compared with those of conventional autocorrelation method. The results show that cross correlation method has better Performance than that of conventional method.

• ETRI Journal
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• 제33권3호
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• pp.401-406
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• 2011

This paper presents a fast block-matching algorithm based on the normalized cross-correlation, where the elimination order is determined based on the gradient magnitudes of subblocks in the current macroblock. Multilevel Cauchy-Schwartz inequality is derived to skip unnecessary block-matching calculations in the proposed algorithm. Also, additional complexity reduction is achieved re-using the normalized cross correlation values for the spatially neighboring macroblock because the search areas of adjacent macroblocks are overlapped. Simulation results show that the proposed algorithm can improve the speed-up ratio up to about 3 times in comparison with the existing algorithm.

• 한국수자원학회논문집
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• 제38권10호
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• pp.851-859
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• 2005

정규 상호 상관 (상관계수)은 입자영상유속계(PIV) 분석에서 형태 분석을 위한 가장 정확하고 적합한 척도이다. 그러나 상관계수는 주파수 영역에서 그에 상당하는 간단한 수식 표현이 없기 때문에, 빠르지만 부정확한 척도들이 종종 이용된다. 이러한 척도 중에서 선정된 세 가지 방법과 상관계수법을 상호 비교하였다. 그 결과 상관계수법을 제외한 나머지 척도들은 모두 종종 부정확한 결과를 도출함을 알 수 있었다. 그러나 상관계수법은 계산 시간이 많이 걸린다는 단점을 지니고 있다. 이 문제를 해결하기 위해, 상관계수법을 계산하는 빠르고 정확한 방법을 제시하였다. 이 방법은 상관계수의 분산을 계산하는 Fn 알고리듬과 분모를 계산하는 순차가감법을 결합한 것이다. 시험 결과 이 방법은 상관계수를 빠르고 정확하게 계산할 수 있음을 보였다.

• 한국정보통신학회논문지
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• 제17권12호
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• pp.2875-2882
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• 2013

여러 가지 디지털통신 시스템에서 많이 사용되고 있는 의사 난수열을 설계하는데 있어 가장 중요한 문제는 생성된 수열들 사이의 상호상관관계가 낮은 수열을 생성하는 것이다. 또한 설계된 이진수열의 상호상관관계의 빈도분석은 많은 연구자에 의해 연구되어왔다. 본 논문에서는 n=2m, $d=2^{n-1}(3{\cdot}2^m-1)$일 때 5-값 상호상관관계를 갖는 비선형 이진수열군 $S^r=\{Tr^m_1\{[Tr^n_m(a{\alpha}^t+{\alpha}^{dt}]^r\}{\mid}a{\in}GF(2^m),0{\leq}t < 2^n-1\}$에 대한 상호상관관계에 대한 빈도 분석과 여러 가지 상호상관관계 성질을 분석한다. 여기서 $gcd(r,2^m-1)=1$이다.

• Journal of applied mathematics & informatics
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• 제31권5_6호
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• pp.869-876
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• 2013

The design of large family size with the optimal cross-correlation property is important in spread spectrum and code division multiple access communication systems. In this paper we present the sequences with the decimation $d=2{\cdot}2^m-1$, calculate the cross-correlation spectrum for $0{\leq}t{\leq}2^n-2$ and count the number of the value $2^m-1$ occurring for $0{\leq}{\tau}2^n-2$. The sequences have the optimal cross-correlation property. The work on this paper can make it easier to count the number of the whole value occurring for $0{\leq}{\tau}2^n-2$.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.447-450
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• 2004

This study was conducted to characterize groundwater and river-water fluctuations at a riverbank filtration site in Daesan-myeon adjacent to the Nakdong River, using time series analysis. Water levels from six observation wells from January 2003 to October 2003 were measured. The autocorrelation analysis indicates that the wells are divided into three groups: group 1 represents strong linearity and memory, group 2 intermediate linearity and memory, and group 3 weak linearity and memory. The analysis indicates that groundwater levels in different monitoring wells vary in response to river-water levels, groundwater withdrawal and seasonal rainfall. Cross-correlation was also divided into three groups. Group 1 shows the highest cross-correlation function (0.49 - 0.54) for a lag time of 0 hours, group 2 intermediate cross-correlation function (0.34 - 0.45), and group 3 the lowest cross-correlation function (0.23 - 0.25). Different cross-correlation functions among the 3 groups are interpreted as an effect of tile distance from the river to the pumping wells.

• Nuclear Engineering and Technology
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• 제44권8호
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• pp.977-984
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• 2012

The cross-correlation technique has been widely used for leakage detection of buried pipes, and this technique can be successfully applied when the leakage signal has a high signal-to-noise ratio. In the case of a power plant, the measured leakage signals obtained from the sensors may contain background noise and mechanical noise generated by adjacent machinery. In such a case, the conventional method using the cross-correlation function may fail to estimate the leakage point. In order to enhance the leakage estimation capability of a buried pipe in a noisy environment, an improved cross-correlation technique is proposed. It uses a noise rejection technique in the frequency domain to effectively eliminate the tonal noise due to rotating machinery. Experiments were carried out to verify the validity of the proposed method. The results show that even in a tonal noisy environment, the proposed method can provide more reliable means for estimating the time delay of the leakage signals.