• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.6
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• pp.568-576
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• 2010

It is widely known that the leak locating of underground plastic pipelines is much more difficult than that of cast iron pipelines. The precision of the leak locating depends upon the speed of leak signal and the time delay estimation between the two sensors on the pipeline. In this paper, six different windowing filters are considered to improve the time delay estimation especially for the plastic pipelines. The time delay is usually estimated from the peak time of cross-correlation functions. The filtering windows including rectangle, Roth, Wiener, SCOT, PHAT and maximum likelihood are applied to derive the generalized cross-correlation function and compared each other. Experimental results for the actual plastic underground water supply pipeline show that the introduction of the filtering windows improved the precision of time delay estimation. Some window functions provide excellent leak locating capability for the plastic pipe of 98 m long, which is less than 1 % of the pipe lengths. Also a new probabilistic approach that the combinations of all results from each filtering window is suggested for the better leak locating.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.2
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• pp.122-129
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• 2014

Identification of the whipping response out of the combined wave-vibration response of a flexible sea going vessel is one of the most interesting research topic from ship designer's point of view. In order to achieve this goal, a novel methodology based on the wavelet cross-correlation technique was proposed in this paper. The cross-correlation of the wavelet power spectrum averaged across the frequency axis was introduced to check the similarity between the combined wave-vibration response and impulse response. The calculated cross-correlation of the wavelet power spectrum was normalized by the auto-correlation of the each spectrum with zero time lag, eventually providing the cross-correlation coefficient that stays between 0 and 1, precisely indicating the existence of the impulse response buried in the combined wave-vibration response. Additionally, the weight function was introduced while calculating the cross-correlation of the two spectrums in order to filter out the signal of lower frequency so that the accuracy of the similarity check becomes as high as possible. The validity of the proposed methodology was checked through the application to the artificially generated ideal combined wave-vibration signal, together with the more realistic signal obtained by running 3D hydroelasticity program WISH-Flex. The correspondence of the identified whipping instances between the results, one from the proposed method and the other from the calculated slamming modal force, was excellent.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.268-275
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• 2008

In this paper, we introduce a new method for detecting and estimating faults on a power line using the time-frequency domain reflectometry system. The system rests upon time-frequency signal analysis and uses a chirp signal which is multiplied by Gaussian envelope. The chirp signal is used as a reference signal, and we can get the reflected signal from a fault on a wire. To detect and estimate faults, we analyze the reflected signal by Wigner time-frequency distribution function and normalized time-frequency cross correlation function. In this paper we design an optimal reference signal for power line and implement a system for estimating fault distance on a power line with the TFDR implemented by PXI equipments. This approach is verified by some experiments with HIV 2.25mm power lines.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9C
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• pp.669-675
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• 2008

For an odd prime p, n=4k and $d=((p^2k+1)/2)^2$, there are $(p^{2k}+1)/2$ distinct decimated sequences, s(dt+1), $0{\leq}l<(p^{2k}+1)/2$, of a p-ary m-sequence, s(t) of period $p^n-1$. In this paper, it is shown that the cross-correlation function between s(t) and s(dt+l) takes the values in $\{-1,-1{\pm}\sqrt{p^n},-1+2\sqrt{p^n}\}$ and their, cross-correlation distribution is also derived.

• Journal of information and communication convergence engineering
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• v.8 no.2
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• pp.163-167
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• 2010

In underwater acoustic communication, acoustic signals from transducers or hydrophones are used. And the underwater acoustic communication channels are very complicated, because of vertical distribution of acoustic velocity according depths, and reflections from boundaries like as surface or bottom. For the implementation of the underwater acoustic communication channel, the image method or ray tracing method have been used. In this paper, we introduce a new approach for implementation of underwater acoustic communication channel using the simulation of the Transmission Line Matrix Modeling and cross-correlations from the input and output signals.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.827-832
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• 2012

In this paper, we present a new decimated Gold-like m-sequence with a binary m-sequence of period $2^n-1$. And we show that the cross-correlation function of the proposed sequence is four-valued.

• International Journal of Railway
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• v.6 no.3
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• pp.120-124
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• 2013

The aim of this study was to clarify the characteristics of interior noise in Japanese, Korean, and Chinese subways. The octave-band noise levels, A-weighted equivalent continuous sound pressure level ($L_{Aeq}$) and parameters extracted from interaural cross-correlation/autocorrelation functions (ACF/IACFs) were analyzed to evaluate the noise inside running train cars quantitatively and qualitatively. The average $L_{Aeq}$ was 72-83 dBA. The IACF/ACF parameters of the noise showed variations in their values, suggesting they are affected by the characteristics of the trains running, wheel-rail interaction, and cross-section of the tunnels.

• The Mathematical Education
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• v.45 no.3 s.114
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• pp.315-318
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• 2006

In this paper we present the simple updating formulas for a sum of product and a sum of cross product when a new value is added on or a specific value is eliminated from the original data. The sample variance and correlation for the new data set are derived by new computing formulas. Any statistic which is a function of the sum of product and a sum of cross product also can be updated by proposed method even though the original data is not available.

• Physical Therapy Rehabilitation Science
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• v.10 no.4
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• pp.398-405
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• 2021

Objective: The interest of clinicians is increasing due to the newly established medical insurance for pulmonary rehabilitation. Improvement of respiratory muscle strength and pulmonary function is an important factor in pulmonary rehabilitation, and this study aims to investigate the correlation between changes in respiratory muscle contraction thickness that can affect respiratory muscle strength and pulmonary function. Design: Cross-sectional observational study. Methods: Thirty-one subjects (male=13, female=18) participated in this study. The respiratory muscle strength was measured by dividing it into inspiratory/forced expiratory muscles, and the pulmonary function was measured by forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC. To evaluate the respiratory muscle length increase, in resting and concentric contraction thickness of diaphragm, external/internal oblique, transverse abdominis, and rectus abdominis were measured by using ultrasonography. Results: Inspiratory muscle strength showed a significant correlation with the length increase of the inspiratory muscle (r=0.368~0.521, p<0.05), and forced expiratory muscle strength showed a significant correlation with length increase of forced expiratory muscle (r=0.356~0.455, p<0.05). However, pulmonary function was not correlated with the length increase of the respiratory muscle. Conclusions: In this study, a correlation between respiratory muscle strength and respiratory muscle length increase was confirmed, but no correlation with the pulmonary function was found. It is considered that the respiratory muscle strength can be improved by increasing the respiratory muscle thickness through appropriate respiratory muscle training.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.747-752
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• 2011

The position detection of overlapping area in the interframe for image stitching using auto and cross correlation function (ACCF) and compounding one image with the stitching algorithm is presented in this paper. ACCF is used by autocorrelation to the featured area to extract the filter mask in the reference (previous) image and the comparing (current) image is used by crosscorrelation. The stitching is detected by the position of high correlation, and aligns and stitches the image in shifting the current image based on the moving vector. The ACCF technique results in a few computations and simplicity because the filter mask is given by the featuring block, and the position is enabled to detect a bit movement. Input image captured from CMOS is used to be compared with the performance between the ACCF and the window correlation. The results of ACCF show that there is no seam and distortion at the joint parts in the stitched image, and the detection performance of the moving vector is improved to 12% in comparison with the window correlation method.