• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.599-601
• /
• 2015

The short time scale X-ray variability associated with the accretion disk around compact objects is complex and is vaguely understood. The study of the cross correlation function gives an insight into the energy dependent behavior of the variations and hence connected processes. Using high resolution RXTE data, we investigate the dynamical cross correlation function of an observation of a black hole source XTE J1550-564 in the steep power law state. The cross correlation between soft and hard X- ray energy bands revealed both correlated and anti-correlated delays (${\leq}{\pm}15s$) on a correlation time scale of 50 s. It was noticed that the observed delays were similar to the delays between X-ray and optical/IR bands in other black hole and neutron star sources. We discuss the possible mechanisms/processes to explain the observed delays in the dynamical CCF.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.10 s.352
• /
• pp.18-26
• /
• 2006

In this paper, we propose new beamforming algorithm which overcomes signal cancellation effect even high cross correlation existing between target and interfering signal. Using the proposed method, we show that direction of arrival (DOA) of interfering signal can be estimated using correlation matrix and the cross-correlation can be eliminated in the correlation matrix of input signal. The proposed method gives high performance enhancement compared with the spatial averaging method in our computer simulation results.

• Journal of the Institute of Convergence Signal Processing
• /
• v.9 no.4
• /
• pp.304-312
• /
• 2008

Orthogonal codes like Walsh and Golay codes may have large correlation value when they are not synchronized, hence they are seldom used in asynchronous CDMA systems. Wysocki[1] showed that by multiplying the original Walsh-Hadamard matrix with an orthogonal transformation matrix the resultant matrix sustains orthogonality between row vectors and their cross-correlation can be reduced. Soberly and Wysocki[2] proposed similar scheme on Golay codes. This implies that using the proper orthogonal transformation cross-correlation of Walsh and Golay codes can be reduced, and the transformed codes can be used for user separation in the CDAM reverse link. In this paper we discuss cross-correlation related parameters which affect the performance of an asynchronous CDMA link, and we investigate the correlation properties of the transformed codes. When we designed orthogonal transformation matrices for Walsh and Golay codes, we minimized the maximum value of aperiodic cross-correlation of the codes ($ACC_{max}$) or the mean square value of the aperiodic cross-correlation($R_{cc}$) with preserving the orthogonality of the modified codes. We also evaluate the asynchronous CDMA system that uses the transformed Walsh and Golay codes.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.3
• /
• pp.264-273
• /
• 2002

Adaptive filters cannot exactly estimate the echo path of the receiving room because of the cross-correlation of stereo signals. In this paper, a new pre-processing method reducing the cross-correlation without degradation of stereophony is proposed to enhance the performance of stereophonic acoustic echo canceller. To reduce the cross-correlation, absolutes of two orthogonal signals derived from each channel signals are added to original channel signals. Assuming that the power of each channel signal is larger than that of the cross-correlation, the computation of pre-processing can be reduced. As results of simulations, it is shown that the performance of stereo acoustic echo canceller with the proposed pre-processing method is better than that of conventional ones.

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

• Proceedings of the IEEK Conference
• /
• 2000.09a
• /
• pp.193-196
• /
• 2000

An stereophonic acoustic echo canceller cannot exactly estimate the echo path in the receiving room, because of the cross-correlation between stereo signals. In this paper, the new preprocessing filter is proposed to reduce the cross-correlation between the signals without influence on stereophonic sound. Two channel signals are linearly decorrelated by using orthogonality principles and the attenuated absolute values of the decorrelated signals are added to each channel input signals. Assuming that the power of each channel signal is larger than that of the cross-correlation, computational burden is reduced.

• Journal of Biomedical Engineering Research
• /
• v.12 no.4
• /
• pp.261-266
• /
• 1991

As the ensemble averaged dz/dt signal during exercise gets smoothed, it is difficult to find the distinctive marks for estimation of stroke volume. The cross correlation function was made use of estimating these marks for automatic calculation by computer from the ensemble averaged dz/dt signal. LVET( Left Ventricular Ejection Time) and stroke volume were estimated based on the calculated parameters from the characteristic points. LVET, stroke volume calculated by hand, by the ensemble average and the cross correlation were compared for accuracy validation.

• The Journal of Churna Manual Medicine for Spine and Nerves
• /
• v.8 no.2
• /
• pp.39-46
• /
• 2013

Objectives : To identify the association between cross-sectional area of lumbar regional muscle and stability(ST), center of pressure(COP) assessed by tetrax. Methods : Patients(n=55) who had taken L-SPINE MRI and Tetrax(Sunlight, Israel) were analyzed retrospectively. To evaluate the cross-sectional area of lumbar regional muscle, L-SPINE MRI was used. Data of ST, COP were accumulated by using dynamic equilibrium analysis by Tetrax. Of the lumbar regional muscles, the Psoas muscles and the Paraspinalis muscles were examined. Using Pearson correlation, we analyzed COP, ST and the difference between the cross-sectional area of lumbar regional muscles. Results : The variance of cross-sectional area of both sides of Psoas muscle and COP had moderate positive correlation(r=0.621). Between variance of cross-sectional area of both sides of Paraspinalis and lumbar regional muscle and COP there was low positive correlation(r=0.287, r=0.329) ST also had low correlation with variance of cross-sectional area of both sides of Psoas muscle. Conclusion : The variance of cross-sectional area between both sides of Psoas muscle had moderate correlation with COP.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37A no.12
• /
• pp.1140-1144
• /
• 2012

In this paper, we propose a timing offset estimation scheme for initial ranging of IEEE 802.16e systems. The conventional scheme estimates the timing offset by using the cross-correlation between the local and received signals only. On the other hand, this paper proposes a timing offset estimation scheme with additional cross-correlations accumulated on the conventional cross-correlation. The additional cross-correlations are obtained by using the ranging signal with a repetitive structure. Numerical results show that the proposed scheme provides the better timing offset estimation performance compared with that of the conventional scheme.

• Korean Journal of Remote Sensing
• /
• v.24 no.5
• /
• pp.445-452
• /
• 2008

Preliminary results are reported on ship detection using coherence images computed from cross-correlating images of multi-look-processed dual-polarization data (HH and HV) of ENVISAT ASAR. The traditional techniques of ship detection by radars such as CFAR (Constant False Alarm Rate) rely on the amplitude data, and therefore the detection tends to become difficult when the amplitudes of ships images are at similar level as the mean amplitude of surrounding sea clutter. The proposed method utilizes the property that the multi-look images of ships are correlated with each other. Because the inter-look images of sea surface are covered by uncorrelated speckle, cross-correlation of multi-look images yields the different degrees of coherence between the images and water. In this paper, the polarimetric information of ships, land and intertidal zone are first compared based on the cross-correlation between HH and HV images, In the next step, we examine the technique when the dual-polarization data are split into two multi-look images, It was shown that the inter-look cross-correlation method could be applicable in the performance improvement of small ship detection and the land masking, It was also found that a simple combination of coherence images from each co-polarised (HH) inter-look and cross-polarised (HV) inter-look data can provide much higher target-detection possibilities.