Determination of the difference between the arrival times of a chaotic radio pulse at two receivers based on the cross-correlation of of the pulse envelopes

2011 ◽  
Vol 56 (6) ◽  
pp. 663-669
Author(s):  
Yu. A. Dmitriev ◽  
A. V. Klevtsov
Keyword(s):  
Cross Correlation ◽  
Radio Pulse ◽  
Arrival Times ◽  
The Cross ◽  
The Difference

Seismic analysis of the 7 January 1998 Chemical plant explosion at Kean Canyon, Nevada

1999 ◽  
Vol 89 (4) ◽  
pp. 938-945 ◽  
Author(s):  
Gene A. Ichinose ◽  
Kenneth D. Smith ◽  
John G. Anderson
Keyword(s):  
Seismic Analysis ◽  
Correlation Method ◽  
Chemical Safety ◽  
P Waves ◽  
Arrival Times ◽  
Chemical Company ◽  
Optimal Separation ◽  
The Difference ◽  
Possible Cause

Abstract An accident at the Sierra Chemical Company Kean Canyon plant, 16 km east of Reno, Nevada, resulted in two explosions 3.52 sec apart that devastated the facility. An investigation into a possible cause for the accident required the determination of the chronological order of the explosions. We resolved the high-precision relative locations and chronology of the explosions using a cross-correlation method applied to both seismic and air waves. The difference in relative arrival times of air waves between the explosions indicated that the first explosion occurred at the northern site. We then determined two station centroid separations between explosions, which average about 73 m with uncertainties ranging from ± 17 to 41 m depending on the alignment of station pairs. We estimated a centroid separation of 80 m using P waves with a larger uncertainty of ± 340 m. We performed a grid search for an optimal separation and the azimuth by combining air-wave arrivals from three station pairs. The best solution for the relative location of the second explosion is 73.2 m S35°E from the first explosion. This estimate is well within the uncertainties of the survey by the U.S. Chemical Safety and Hazard Investigation Board (CSB). The CSB reported a separation of approximately 76.2 m S33°E. The spectral amplitudes of P waves are 3 to 4 times higher for the second explosion relative to the first explosion, but the air waves have similar spectral amplitudes. We suggest that this difference is due to the partitioning of energy between the ground and air caused by downward directivity at the southern explosion, and upward directivity at the northern explosion. This is consistent with the absence of a crater for the first explosion and a 1.8-m-deep crater for the second explosion.

Further results on Kendall's autoregressive series

1975 ◽  
Vol 12 (1) ◽  
pp. 180-182
Author(s):  
Jay C. Hardin ◽  
Thomas J. Brown
Keyword(s):  
Fourier Transform ◽  
Difference Equation ◽  
Fast Fourier Transform ◽  
Cross Correlation ◽  
Input And Output ◽  
The Cross ◽  
The Difference ◽  
Autoregressive Series

Theoretical expressions for the cross correlation and cross spectra of the input and output variables in the difference equation Xt=aXt−1 + bXt−2+ Yt are derived. These expressions are compared with estimates of these expectations obtained by employing a Fast Fourier Transform technique on digitally generated series.

scholarly journals Simultaneous determination of the cosmic birefringence and miscalibrated polarization angles from CMB experiments

2019 ◽  
Vol 2019 (8) ◽  
Author(s):  
Yuto Minami ◽  
Hiroki Ochi ◽  
Kiyotomo Ichiki ◽  
Nobuhiko Katayama ◽  
Eiichiro Komatsu ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Power Spectra ◽  
Microwave Background ◽  
Polarization Data ◽  
Satellite Mission ◽  
Cmb Polarization ◽  
Angle Alpha ◽  
The Difference ◽  
Polarization Spectra

Abstract We show that the cosmic birefringence and miscalibrated polarization angles can be determined simultaneously by cosmic microwave background (CMB) experiments using the cross-correlation between $E$- and $B$-mode polarization data. This is possible because the polarization angles of the CMB are rotated by both the cosmic birefringence and miscalibration effects, whereas those of the Galactic foreground emission are rotated only by the latter. Our method does not require prior knowledge of the $E$- and $B$-mode power spectra of the foreground emission, but uses only the knowledge of the CMB polarization spectra. Specifically, we relate the observed $EB$ correlation to the difference between the observed$E$- and $B$-mode spectra in the sky, and use different multipole dependences of the CMB (given by theory) and foreground spectra (given by data) to derive the likelihood for the miscalibration angle $\alpha$ and the birefringence angle $\beta$. We show that a future satellite mission similar to LiteBIRD can determine $\beta$ with a precision of 10 arcmin.

AN ANALOG SEISMlC CORRELATOR

Geophysics ◽  
1961 ◽  
Vol 26 (3) ◽  
pp. 298-308 ◽  
Author(s):  
F. N. Tullos ◽  
L. C. Cummings
Keyword(s):  
Seismic Data ◽  
Cross Correlation ◽  
Correlation Coefficients ◽  
Analog Computer ◽  
Signal Power ◽  
Arrival Times ◽  
Data Points ◽  
The Cross ◽  
Correlation Process ◽  
Total Average

An analog computer has been built to compute the cross‐correlation coefficients of multi‐trace seismograms. The evaluation program has shown that the computer has greater accuracy than is normally required to compute the cross‐correlation functions of short samples of data. Points on the correlation curves are computed and plotted at the rate of approximately 50 points per minute. Scanning is in difference of arrival times (Δt) across the record, with increments of [Formula: see text] to 16 millisecond. The correlation process is completely automatic with the exception of normalization, which is approximated by holding the total average signal power constant with a ganged attenuator. Analysis of synthetic and actual seismic data indicates that the correlation will be an interpretational aid in areas where the data are poor.

scholarly journals DETERMINATION OF EARTHQUAKE FOCUS COORDINATES USING THE CASSINI OVAL METHOD WITH SECOND- AND FOURTH-ORDER HYPERBOLA FIGURES

2020 ◽  
Vol 46 (4) ◽  
pp. 134-142
Author(s):  
B. I. Shakhtarin ◽  
T. G. Aslanov ◽  
U. R. Tetakaev
Keyword(s):  
Comparative Analysis ◽  
Fourth Order ◽  
Relative Position ◽  
Seismic Waves ◽  
Arrival Times ◽  
Earthquake Focus ◽  
Seismic Sensors ◽  
Calculation Results ◽  
The Difference

Objectives. To study the dependencies obtained when determining the coordinates of an earthquake hypocentre using the figures of fourth and second orders.Method. A comparative analysis of determining the coordinates of the earthquake focus using the Cassini oval method, both taking errors in the readings of seismic sensors into account the and ignoring them, is presented.Result. A new method is proposed for determining the coordinates of the earthquake hypocentre, which uses the fourth-order figure, the Cassini oval, in the calculations. A graph is obtained for the distribution of errors in determining the coordinates of the earthquake focus (using the Cassini oval) depending on the relative position of two seismic sensors with different values of their errors in determining the difference in travel times of seismic waves.Conclusion. Since the calculation results are independent of the error sign in determining the difference in the arrival times of seismic waves, the method is suitable for the initial determination of the coordinates of the earthquake hypocentre as well as for comparison with the results of other methods for identifying the error sign. 

scholarly journals CCID: Cross-Correlation Identity Distinction Method for Detecting Shrew DDoS

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Cheng Huang ◽  
Ping Yi ◽  
Futai Zou ◽  
Yao Yao ◽  
Wei Wang ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Transmission Control Protocol ◽  
Denial Of Service ◽  
Gaussian White Noise ◽  
Normal Flow ◽  
Flow Properties ◽  
Data Packets ◽  
Lower Maximum ◽  
The Cross ◽  
The Difference

This study presents a new method for detecting Shrew DDoS (Distributed Denial of Service) attacks and analyzes the characteristics of the Shrew DDoS attack. Shrew DDoS is periodic to be suitable for the server’s TCP (Transmission Control Protocol) timer. It has lower maximum to bypass peak detection. This periodicity makes it distinguishable from normal data packets. By proposing the CCID (Cross-Correlation Identity Distinction) method to distinguish the flow properties, it quantifies the difference between a normal flow and an attack flow. Simultaneously, we calculated the cross-correlation between the attack flow and the normal flow in three different situations. The server can use its own TCP flow timer to construct a periodic attack flow. The cross-correlation between Gaussian white noise and simulated attack flow is less than 0.3. The cross-correlation between single-door function and simulated attack flow is 0.28. The cross-correlation between actual attack flow and simulated attack flow is more than 0.8. This shows that we can quantitatively distinguish the attack effects of different signals. By testing 4 million data, we can prove that it has a certain effect in practice.

scholarly journals A novel method for quantifying periodicity and time delay in dynamic neural networks using unstable subaction potential threshold depolarizations

2020 ◽  
Vol 123 (3) ◽  
pp. 1236-1246
Author(s):  
Julian Sorensen ◽  
Nick J. Spencer
Keyword(s):  
Neural Networks ◽  
Correlation Function ◽  
Time Delay ◽  
Action Potentials ◽  
Cross Correlation ◽  
Time Lag ◽  
Cross Correlation Function ◽  
Electrical Signals ◽  
The Cross

Techniques to identify and correlate the propagation of electrical signals (like action potentials) along neural networks are well described, using multisite recordings. In these cases, the waveform of action potentials is usually relatively stable and discriminating relevant electrical signals straightforward. However, problems can arise when attempting to identify and correlate the propagation of signals when their waveforms are unstable (e.g., fluctuations in amplitude or time course). This makes correlation of the degree of synchronization and time lag between propagating electrical events across two or more recording sites problematic. Here, we present novel techniques for the determination of the periodicity of electrical signals at individual sites. When recording from two independent sites, we present novel analytical techniques for joint determination of periodicity and time delay. The techniques presented exploit properties of the cross-correlation function, rather than utilizing the time lag at which the cross-correlation function is maximized. The approach allows determination of directionality of the spread of excitation along a neural network based on measurements of the time delay between recording sites. This new method is particularly applicable to analysis of signals in other biological systems that have unstable characteristics in waveform that show dynamic variability. NEW & NOTEWORTHY The determination of frequency(s) at which two sources are synchronized, and relative time delay between them, is a fundamental problem for a wide a range of signal-processing applications. In this methodology paper, we present novel procedures for periodicity estimation for single time series and joint periodicity and time delay estimation for two time series. The methods use properties of the cross-correlation function rather than the cross-correlation function explicitly.

scholarly journals A semi-automatic approach to identify first arrival time: the Cross-Correlation Technique

2015 ◽  
Vol 18 (2) ◽  
pp. 107-113 ◽  
Author(s):  
Mustafa Senkaya ◽  
Hakan Karslı
Keyword(s):  
Cross Correlation ◽  
Seismic Refraction ◽  
Correlation Technique ◽  
Arrival Times ◽  
Refraction Tomography ◽  
First Arrival ◽  
The Cross ◽  
Seismic Refraction Data ◽  
Cross Correlation Technique ◽  
Refraction Data

<p class="MsoNormal" style="line-height: 200%;">The high-quality interpretation of seismic refraction data depends on the accurate and reliable identification of the first arrival times. First arrivals can be identified on a graphic or image by conventional picking, but this process depends on external factors, such as the scale and quality of the imaging data, amplitude ratio, sensitivity of the picking cursor and user experience. Under these considerations, identifying first arrivals in noisy data becomes more complex and unstable. In this study, the Cross-Correlation Technique (CCT), which is widely used in the process of analyzing reflection data, has been used to pick the first arrival times in noisy or noiseless seismic refraction data by a semi-automatic process. The CCT has reduced the dependence on user and decreased incorrect picking caused by environmental noise, displaying characteristics and scaling factors. The CCT has been tested with synthetic models with different noise contents and various field data. The Chi-square error criterion was used to assess the performance of the pickings. In addition, effects of small-time differences between the conventional picking process and the CCT have been demonstrated on a refraction tomography velocity section. Therefore, we believe that our proposed method is a useful contribution to the existing methods of first arrival picking.</p><p class="MsoNormal" style="line-height: 200%;"> </p><p class="MsoNormal" style="line-height: 200%;"><strong>Resumen</strong></p><p class="MsoNormal" style="line-height: 200%;">La buena interpretación de datos estadísticos de refracción sísmica depende de la identificación acertada y confiable de los tiempos de llegada. Los primeros tiempos de llegada se pueden identificar en un gráfico o imagen por picado convencional, pero este proceso depende de factores externos como la escala y la calidad de información de la imagen, el índice de amplitud, la sensibilidad del cursor de recolección y la experiencia del usuario. Bajo estas consideraciones, la identificación de los tiempos de llegada bajo información ruidosa se vuelve más compleja e inestable. En este estudio, la técnica de Correlación Cruzada (CCT, en inglés), que es ampliamente trabajada en el proceso de análisis de datos de reflexión, se utilizó para seleccionar los primeros tiempos de llegada en información sísmica ruidosa o no ruidosa con un proceso semiautomático. La CCT redujo la dependencia en el usuario y bajó el nivel de selección incorrecta causada por el ruido ambiental al desplegar características y factores de escala. La CCT se ha probado en modelos sintéticos con diferentes contenidos de ruidos y diversa información de campo. El error de la norma Chi-cuadrado se utilizó para evaluar el desempeño de las selecciones. En adición, los efectos de las pequeñas diferencias de tiempo entre el proceso convencional de selección y la CCT se han demostrado en una tomografía reflexiva de velocidad. Además, se estima que el método propuesto es una contribución útil a los métodos existentes de la recolección de los primeros tiempos de llegada.</p>

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