Cross-correlation Analysis Techniques Research Articles

On-site pilot testing of maturity sensors in conjunction with ambient condition monitoring device to get an insight into the concrete strength gain process

The article demonstrates the performance of newly developed concrete maturity sensors on the construction site of residential complex “New Line” in Nur-Sultan. The sensors were mounted on the rebar of reinforced concrete structures to monitor the curing temperature of poured concrete grade M350 during 7 days. Additionally, the sensor device monitoring ambient temperature and relative humidity was set nearby. 14 cubic specimens were molded for compression test to determine the concrete strength. To get an idea on the degrees of influence of considered factors on concrete strength gain, the correlation analysis was conducted. As expected, the curing temperature showed a significant correlation with compressive strength, and its degree of influence amounted 58%. The ambient temperature with influence degree of 36% seemed to affect the concrete strength vividly. The relative humidity affected insignificantly with 6%. Based on conducted investigations the well-enough performance of maturity sensors is concluded. Moreover, there was set plans on the extension of their software solution with colored cross-correlation analysis technique.

High-resolution surface acoustic wave (SAW) strain sensor based on acoustic Fabry-Pérot resonance

A surface acoustic wave (SAW) strain sensor based on measuring acoustic Fabry-Pérot resonance peaks from a 2-port SAW resonator is demonstrated. A theoretical analysis is proposed to estimate the frequency sensitivity to strain of IDT and cavity resonances and to predict strain distributions in both the cavity and IDT regions of a 2-port SAW resonator bonded to a tapered cantilever beam. The frequency stability of cavity resonance peaks for fabricated 2-port SAW resonators of different cavity length are measured and analyzed to determine the cavity length which exhibits maximum frequency stability. A cross-correlation analysis technique is then introduced to improve the detection of the frequency shift of SAW resonances and enable multimode frequency shift detection. The measured frequency sensitivity to strain of the cavity resonances of a resonator 10 mm in length (operating frequency = 97.7 MHz) was found to be − 103.2 ± 0.2 Hz/με while demonstrating excellent linearity (R2 = 0.9999). By considering a minimum signal to noise ratio (SNR) of 3 dB, the device exhibits a minimum strain resolution of only 234 nε.

Towards Operational Detection of Forest Ecosystem Changes in Protected Areas

This paper discusses the application of the Cross-Correlation Analysis (CCA) technique to multi-spatial resolution Earth Observation (EO) data for detecting and quantifying changes in forest ecosystems in two different protected areas, located in Southern Italy and Southern India. The input data for CCA investigation were elaborated from the forest layer extracted from an existing Land Cover/Land Use (LC/LU) map (time T1) and a more recent (T2, with T2 > T1) single date image. The latter consist of a High Resolution (HR) Landsat 8 OLI image and a Very High Resolution (VHR) Worldview-2 image, which were analysed separately. For the Italian site, the forest layer (1:5000) was first compared to the HR Landsat 8 OLI image and then to the VHR Worldview-2 image. For the Indian site, the forest layer (1:50,000) was compared to the Landsat 8 OLI image then the changes were interpreted using Worldview-2. The changes detected through CCA, at HR only, were compared against those detected by applying a traditional NDVI image differencing technique of two Landsat scenes at T1 and T2. The accuracy assessment, concerning the change maps of the multi-spatial resolution outputs, was based on stratified random sampling. The CCA technique allowed an increase in the value of the overall accuracy: from 52% to 68% for the Italian site and from 63% to 82% for the Indian site. In addition, a significant reduction of the error affecting the stratified changed area estimation for both sites was obtained. For the Italian site, the error reduction became significant at VHR (±2 ha) in respect to HR (±32 ha) even though both techniques had comparable overall accuracy (82%) and stratified changed area estimation. The findings obtained support the conclusions that CCA technique can be a useful tool to detect and quantify changes in forest areas due to both legal and illegal interventions, including relatively inaccessible sites (e.g., tropical forest) with costs remaining rather low. The data obtained through CCA intervention could not only support the commitments undertaken by the European Habitats Directive (92/43/EEC) and the Convention of Biological Diversity (CBD) but also satisfy UN Sustainable Development Goals (SDG).

Multifractal cross-correlation effects in two-variable time series of complex network vertex observables.

We investigate the scaling of the cross-correlations calculated for two-variable time series containing vertex properties in the context of complex networks. Time series of such observables are obtained by means of stationary, unbiased random walks. We consider three vertex properties that provide, respectively, short-, medium-, and long-range information regarding the topological role of vertices in a given network. In order to reveal the relation between these quantities, we applied the multifractal cross-correlation analysis technique, which provides information about the nonlinear effects in coupling of time series. We show that the considered network models are characterized by unique multifractal properties of the cross-correlation. In particular, it is possible to distinguish between Erdös-Rényi, Barabási-Albert, and Watts-Strogatz networks on the basis of fractal cross-correlation. Moreover, the analysis of protein contact networks reveals characteristics shared with both scale-free and small-world models.

Analysis of Sunspot Time Series During the Ascending Phase of Solar Cycle 24 Using the Wavelet Transform

The sunspots are widely used to measure the rotational rate of solar surface. We are interested in analysis of the temporal evaluation of the short-term period present in sunspot time series (i.e. sunspot number and area) during the ascending phase of Solar Cycle 24. For the better understanding of variation in solar activity originated at different layers of the solar atmosphere with respect to sunspot cycles, we study the phase relation between sunspot numbers and sunspot areas using cross correlation analysis techniques based on extended wavelet based approaches such as continuous wavelet transform, cross-wavelet transform, and wavelet coherence. In this study we found the short-term periodicity “27 days-rotational rate of Sun” for current solar cycle 24 (January2008-May2013), which suggested that the Solar Cycle24 has minimum solar activity. We have also investigated the correlation between both parameters and identify the unusual conditions in space weather.

Periodicities of solar activity and the surface temperature variation of the Earth and their correlations

Based on the well-calibrated systematiCmeasurements of sunspot numbers, the reconstructed data of the total solar irradiance (TSI), and the observed anomalies of the Earth’s averaged surface temperature (global, ocean, land), this paper investigates the periodicities of both solar activity and the Earth’s temperature variation as well as their correlations on the time scale of centuries using the wavelet and cross correlation analysis techniques. The main results are as follows. (1) Solar activities (including sunspot number and TSI) have four major periodic components higher than the 95% significance level of white noise during the period of interest, i.e. 11-year period, 50-year period, 100-year period, and 200-year period. The global temperature anomalies of the Earth have only one major periodic component of 64.3-year period, which is close to the 50-year cycle of solar activity. (2) Significant resonant periodicities between solar activity and the Earth’s temperature are focused on the 22- and 50-year period. (3) Correlations between solar activity and the surface temperature of the Earth on the long time scales are higher than those on the short time scales. As far as the sunspot number is concerned, its correlation coefficients to the Earth temperature are 0.31-0.35 on the yearly scale, 0.58-0.70 on the 11-year running mean scale, and 0.64-0.78 on the 22-year running mean scale. TSI has stronger correlations to the Earth temperature than sunspot number. (4) During the past 100 years, solar activities display a clear increasing tendency that corresponds to the global warming of the Earth (including land and ocean) very well. Particularly, the ocean temperature has a slightly higher correlation to solar activity than the land temperature. All these demonstrate that solar activity has a non-negligible forcing on the temperature change of the Earth on the time scale of centuries.

Application of mean-shift clustering to Blood oxygen level dependent functional MRI activation detection

BackgroundFunctional magnetic resonance imaging (fMRI) analysis is commonly done with cross-correlation analysis (CCA) and the General Linear Model (GLM). Both CCA and GLM techniques, however, typically perform calculations on a per-voxel basis and do not consider relationships neighboring voxels may have. Clustered voxel analyses have then been developed to improve fMRI signal detections by taking advantages of relationships of neighboring voxels. Mean-shift clustering (MSC) is another technique which takes into account properties of neighboring voxels and can be considered for enhancing fMRI activation detection.MethodsThis study examines the adoption of MSC to fMRI analysis. MSC was applied to a Statistical Parameter Image generated with the CCA technique on both simulated and real fMRI data. The MSC technique was then compared with CCA and CCA plus cluster analysis. A range of kernel sizes were used to examine how the technique behaves.ResultsReceiver Operating Characteristic curves shows an improvement over CCA and Cluster analysis. False positive rates are lower with the proposed technique. MSC allows the use of a low intensity threshold and also does not require the use of a cluster size threshold, which improves detection of weak activations and highly focused activations.ConclusionThe proposed technique shows improved activation detection for both simulated and real Blood Oxygen Level Dependent fMRI data. More detailed studies are required to further develop the proposed technique.

Variable Time-Delay Estimation for Anesthesia Control During Intensive Care

The presence of artifacts plays a crucial role in automatic sedation systems and may introduce variable time delays (TDs) in the closed-loop-control structures. This paper presents a successful procedure to estimate the varying TD of the bispectral index (BIS) monitor used in closed-loop control during intensive care. The TD estimation (TDE) is based on the cross-correlation analysis technique and the method is validated with real measured signals of propofol and BIS. Extended prediction self-adaptive control is used in combination with a Smith predictor to reduce the computational burden imposed by the variable TD. The conclusion is that an online TDE of the BIS monitor improves the performance of the closed-loop system for reference tracking, disturbance rejection, and overall stability.

Time-series PIV measurements in a very large rotating tank

We describe a non-intrusive PIV system developed for performing high-resolution measurements in a field of view of 2 m×3 m, as required on the LEGI-Coriolis 13 m diameter rotating platform. Particle preparation, laser illumination, photographic digitization, and cross-correlation analysis techniques are explained. Some results on the wake behind a cylinder illustrate the possibilities of this PIV system.

Determination of the Si(111)-(√3x√3) Au surface structure using UHV TEM

For the past few decades the Si(111)-(√3×√3) Au surface (denoted hereafter as √3-Au) has received considerable attention in the literature as one of the prototypical Si(111)-(√3×√3) Metal systems. The √3 -Au system appears for gold coverages from roughly 0.5 ML to 1.0 ML after annealing of the substrate over 280°C. Several authors have noted the small surface domains of this structure and several possible diffraction spot features associated with different coverages and annealing temperatures. The two dominant models which have been proposed for this surface are the missing top layer twisted trimer (MTLTT) and the conjugate honeycomb chained trimer (CHCT) models.The √3-Au surface was prepared on bulk Si(111) TEM samples thinned by mechanical polishing and HNO3/HF solution chemical etching. Under UHV conditions the samples were cleaned by cycles of Ar+ ion milling and electron beam annealing until well defined Si(111)-(7×7) diffraction patterns were visible. On these surfaces roughly 0.7 ML of gold was evaporated followed by light electron beam annealing to produce the √3-Au surface. Through exposure electron diffraction patterns from three different sample locations and crystal tilts were collected and the negatives quantified using a cross correlation analysis technique.

Interaction between neurons displaying tonic response to sound and other cells of the feline auditory cortex

Interaction between neurons with a tonic response pattern and either nearby or further removed (by about 400–500 µm) cortical neurons was investigated during acute experiments on 15 immobilized cats using cross-correlation analysis techniques. Synchronizing excitatory input common to the nerve cells was found in cross-correlation histograms (CCH) in 26 out of 36 test pairs of neurons (72%). Both positive and negative cross-correlation (five pairs in each case) were discovered, pointing to mono- or polysynaptic excitatory and inhibitory effects of the tonic neuron on spike activity in the other cell from CCH of 10 pairs of neurons. The functional diversity of neurons f distinguished by a tonic pattern of response to sound was deduced on the basis of findings from this research. The theory that some tonic type cells act as excitatory neurons and others fulfil the function of inhibitory interneurons is examined.

Neuronal interaction in the cat cerebellar cortex: A cross correlation analysis

Neuronal interaction in the cat cerebellum was investigated by cross correlation analysis techniques. Excitatory connections of varying effectiveness were found between neurons of 13 out of 90 pairs investigated (or 14%). Inhibitory interaction was observed in 38 pairs, or 42%. Neurons of 26 pairs (40%) had shared inputs. Effectiveness of connections between cerebellar cortex neurons was demonstrated by changing stimulus parameters. Findings obtained agree with existing data on the functional organization of the cerebellar cortex. Possible reasons for the large numbers of inhibitory connections discovered are discussed.

A Study of Planetary Waves in the Southern Winter Troposphere and Stratosphere. Part I: Wave Structure and Vertical Propagation

Abstract Planetary wave propagation in the southern winter troposphere and stratosphere is studied in an attempt to trace the origins of upward propagating disturbance. Daily geopotential girds from 1000 to 1 mb are analyzed for two 120-day winter seasons. A cross-correlation analysis technique is developed which allows coherent wave structure to be traced in time. Significant correlations are observed between the troposphere and stratosphere at finite time lags, indicative of vertically propagating waves. The observed vertical propagation time scales between the middle troposphere and middle stratosphere are on the order of 4 days for zonal wavenumber 1 (k=1), 1–2 days for k=2, and 1 day for k=3. The cross-correlation analysis also delineates the meridional and vertical structures of the transient (in time) planetary waves. Zonal wavenumber 1 fluctuations exhibit a vertical out-of-phase relationship between the midlatitude troposphere and atmosphere. Three out-of-phase maxima in latitude are observed in ...

Teleconnections of rainfall anomalies and of the Southern Oscillation over the entire tropics and their seasonal dependence

The teleconnections between rainfall anomalies of selected areas within the tropics to each other are investigated with respect to their seasonal dependence, employing a cross correlation analysis technique. They are related to the Southern Oscillation. The magnitude and phase of these rainfall anomalies are computed for a typical El Nino event using a so-called composite analysis. Rainfall anomalies persist for almost an entire year over the islands of the equatorial Central Pacific, whereas over most areas in and around the tropical Indian and Pacific Ocean, they only tend to persist for a season or two. Seasons during which rainfall anomalies are most persistent (in a particular region) are also seasons, during which teleconnections between rainfall anomalies of these regions to each other are strongest. The Southern Oscillation is negative-correlated with the majority of the rainfall anomalies except for those from India, Indonesia, Hawaii and the Northcoast of Venezuela. The rainfall anomalies calculated for a typical El Nino event fit into this general scheme of teleconnections. DOI: 10.1111/j.1600-0870.1987.tb00295.x

Auto and cross-correlation analysis techniques on-board spacecraft

An efficient method of producing spectrograms of signals recorded on spacecraft is to compute on board the correlation function and, after telemetering this to ground, subjecting it to aFft(Fast Fourier Transform). This is the procedure adopted onGeos 1and 2. Results are presented of whistlers, chorus, hiss and electrostatic waves illustrating that high quality spectrograms can be obtained by this method. Correlators to be flown on the InterKosmos spacecraftMagik,despite having a very low allocated telemetry rate still yield spectrograms on which one may distinguish chorus,hiss and whistlers.

The effect of an air flow on a single side branch helmholtz resonator in a circular duct

A single side branch Helmholtz resonator has been tested in a circular duct in which both sound and an air flow could be passed in the same direction. The sound input was broad band and the transfer function across the resonator was determined by using two microphones and a cross-correlation analysis technique in which the broad band sound input was cross-correlated with each microphone signal in turn. The fundamental resonant frequency, as obtained from the transfer function of the resonator, was found to increase with increasing flow velocities in the duct. It was possible for the entire mass end correction of the orifice of the resonator to be eliminated by the flow. The higher natural frequencies of the resonator were not affected as much by the air flow.