scholarly journals Technique of Informative Features Selection in Geoacoustic Emission Signals

2019 ◽  
Vol 18 (5) ◽  
pp. 1066-1092 ◽  
Author(s):  
Yuri Senkevich ◽  
Yuri Marapulets ◽  
Olga Lukovenkova ◽  
Alexandra Solodchuk
Keyword(s):  
Dynamic Properties ◽  
Large Data ◽  
Signal Amplitude ◽  
Iterative Refinement ◽  
Approximation Schemes ◽  
Generation Process ◽  
Features Selection ◽  
Emission Pulse ◽  
Emission Analysis ◽  
Geoacoustic Emission

Studies of geoacoustic emission in a seismically active region in Kamchatka show that geoacoustic signals produce pronounced pulse anomalies during the earthquake preparation and post-seismic relaxation of the local stresses field at the observation point. The qualitative selection of such anomalies is complicated by a strong distortion and weakening of the signal amplitude. A review of existing acoustic emission analysis methods shows that most often researchers turn to the analysis of more accessible to study statistical properties and energy of signals. The distinctive features of the approach proposed by the authors are the extraction of informative features based on the analysis of time and frequency-time structures of geoacoustic signals and the description of various forms of recognizable pulses by a limited pattern set. This study opens up new ideas to develop methods for detecting anomalous behavior of geoacoustic signals, including anomalies before earthquakes. The paper describes a technique of information extraction from geoacoustic emission pulse streams of sound frequency range. A geoacoustic pulse mathematical model, reflecting the signal generation process from a variety of elementary sources, is presented. A solution to the problem of detection of geoacoustic signal informative features is presented by the means of description of signal fragments by the matrixes of local extrema amplitude ratios and of interval ratios between them. The result of applying the developed algorithm to describe automatically the structure of the detected pulses and to form a pattern set is shown. The patterns characterize the features of geoacoustic emission signals observed at IKIR FEB RAS field stations. A technique of reduction of the detected pulse set dimensions is presented. It allows us to find patterns similar in structure. A solution to the problem of processing of a large data flow by unifying pulses description and their systematization is proposed. A method to identify a geoacoustic emission pulse model using sparse approximation schemes is suggested. An algorithmic solution of the problem of reducing the computational complexity of the matching pursuit method is described. It is to include an iterative refinement algorithm for the solution at each step in the method. The results of the research allowed the authors to create a tool to investigate the dynamic properties of geoacoustic emission signal in order to develop earthquake prediction detectors.

Acoustic Emission Analysis of Nanoindentation-Induced Fracture Events

2004 ◽  
Vol 841 ◽  
Author(s):  
Pawel Dyjak ◽  
Raman P. Singh
Keyword(s):  
Acoustic Emission ◽  
Brittle Materials ◽  
Signal Amplitude ◽  
Crack Arrest ◽  
Quantitative Information ◽  
Local Failure ◽  
Emission Analysis ◽  
Specimen Holder ◽  
Cube Corner ◽  
Ae Signal

ABSTRACTMonitoring of acoustic emission (AE) activity was employed to characterize the initiation and progression of local failure processes during nanoindentation-induced fracture. Specimens of various brittle materials were loaded with a cube-corner indenter and AE activity was monitored during the entire loading and unloading event using an AE transducer mounted inside the specimen holder. As observed from the nanoindentation and AE response, there were fundamental differences in the fracture behavior of the various materials. Post-failure observations were used to identify particular features in the AE signal (amplitude, frequency, rise-time) that correspond to specific types of fracture events. Furthermore, analysis of the parametric and transient AE data was used to establish the crack-initiation threshold, crack-arrest threshold, and energy dissipation during failure. It was demonstrated that the monitoring of AE signals yields both qualitative and quantitative information regarding highly local failure events in brittle materials.

Dynamics of immigrant assimilation: lessons from immigrants’ trust

2019 ◽  
Vol 46 (3) ◽  
pp. 518-532
Author(s):  
Sokchea Lim ◽  
A.K.M. Mahbub Morshed
Keyword(s):  
Dynamic Properties ◽  
Country Of Origin ◽  
General Social Survey ◽  
Large Data ◽  
Fourth Generation ◽  
Data Sets ◽  
World Value Survey ◽  
Content Type ◽  
Empirical Estimates ◽  
The Usa

Purpose The purpose of this paper is to examine the dynamics and persistence of interpersonal trust among immigrants in the USA. More specifically, the authors investigate the association between the levels of trust of US immigrants and the levels of trust in their home countries across different cohorts and generations of immigrants. Design/methodology/approach In order to quantify the extent of this relationship, the authors use two large sets of survey data, the General Social Survey and the World Value Survey, to construct the trust of immigrants in the USA and their levels of trust in their country of origin. The final sample size for the immigrants’ trust is 27,531 observations. Findings The examination of the two trust variables at different levels and for different cohorts show that there is an association between the levels of US immigrants’ trust and the levels of trust in the country of origin, suggesting that immigrants bring their culture with them and transmit it to the next generation. However, this association differs across various cohorts and generations of immigrants. The transmission of trust is strong in the second generation but becomes weaker in the third generation and seems to disappear in the fourth generation. Social implications Empirical estimates of how long the cultural traits embodied in a new immigrant are sustained in the newly adopted country are essential to the appraisal of the current apparent segregation of immigrants in the USA. Originality/value This paper focuses on the under-researched area of the dynamic properties of immigrants’ trust by using large data sets from social surveys. The authors examine this cultural assimilation across different cohorts and generations.

scholarly journals Forecasting Principles from Experience with Forecasting Competitions

Forecasting ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 138-165
Author(s):  
Jennifer L. Castle ◽  
Jurgen A. Doornik ◽  
David F. Hendry
Keyword(s):  
Large Data ◽  
Large Data Sets ◽  
Annual Data ◽  
Data Sets ◽  
Generation Process ◽  
Data Generation ◽  
Data Set ◽  
Economic Forecasting ◽  
The Many ◽  
Many Sources

Economic forecasting is difficult, largely because of the many sources of nonstationarity influencing observational time series. Forecasting competitions aim to improve the practice of economic forecasting by providing very large data sets on which the efficacy of forecasting methods can be evaluated. We consider the general principles that seem to be the foundation for successful forecasting, and show how these are relevant for methods that did well in the M4 competition. We establish some general properties of the M4 data set, which we use to improve the basic benchmark methods, as well as the Card method that we created for our submission to that competition. A data generation process is proposed that captures the salient features of the annual data in M4.

FRACTAL ASPECTS OF PROTEIN STRUCTURE AND DYNAMICS

Fractals ◽  
1993 ◽  
Vol 01 (02) ◽  
pp. 179-189 ◽  
Author(s):  
T. GREGORY DEWEY
Keyword(s):  
Dynamic Properties ◽  
Linear Chain ◽  
Protein Structures ◽  
Three Dimensional ◽  
Alpha Helix ◽  
Large Data ◽  
Thermal Fluctuations ◽  
Radius Of Gyration ◽  
Data Set ◽  
Long Range Correlations

Proteins have well-defined three dimensional structures which are dictated by their amino acid sequence. Despite this great specificity, general structural and dynamic properties exist. Scaling relationships for the radius of gyration and surface area of a large data set of proteins are demonstrated in this work. These results show that proteins scale as collapsed polymers. Thermal fluctuations are examined for two different proteins by an analysis of the Debye-Waller factors derived from X-ray crystallographic data. Long-range correlations exist between fluctuations along the backbone. A disordered Ising model is presented which gives similar correlations. To further examine the role of multiple connectivity in protein structures, the vibrational spectrum for an alpha helix (linear chain with H-bonds) is analyzed from recursive relationships derived using a decimation technique.

An archive of data from resonant column and cyclic torsional shear tests performed on Italian clays

2020 ◽  
pp. 875529302093669
Author(s):  
Johann Facciorusso
Keyword(s):  
Earthquake Engineering ◽  
Multiple Testing ◽  
Laboratory Tests ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Large Data ◽  
Dynamic Parameters ◽  
Data Set ◽  
Geotechnical Earthquake Engineering ◽  
Geotechnical Tests

Measurement of soil properties under cyclic and dynamic loading conditions is a critical task in the solution of most geotechnical earthquake engineering problems. The main dynamic properties of soils are usually expressed in terms of shear modulus, G, and damping ratio, D, and they are generally obtained from laboratory tests at different strain levels. Dynamic geotechnical problems often require a site-level or territorial approach involving a considerable number of dynamic laboratory tests that might be too expensive and time-consuming. Thus, it is a common practice to use empirical relationships between dynamic parameters and measurements from routine geotechnical tests. Therefore, the availability of a large and reliable archive of multiple testing results constitutes a fundamental step for geotechnical earthquake engineers and researchers. To this aim, a large data-set of the index and dynamic parameters measured from 170 undisturbed clay samples obtained from 90 sites in Central and Northern Italy is made available, and its use and application are further described and discussed.

scholarly journals Recent Advances in the Calculation of Dynamical Correlation Functions

2020 ◽  
Vol 8 ◽  
Author(s):  
J. Florencio ◽  
O. F. de Alcantara Bonfim
Keyword(s):  
Correlation Functions ◽  
Relaxation Function ◽  
Heisenberg Model ◽  
Recurrence Relations ◽  
Dynamic Properties ◽  
Approximation Schemes ◽  
Xy Model ◽  
Many Body ◽  
Dynamical Correlation ◽  
Numerical Work

We review various theoretical methods that have been used in recent years to calculate dynamical correlation functions of many-body systems. Time-dependent correlation functions and their associated frequency spectral densities are the quantities of interest, for they play a central role in both the theoretical and experimental understanding of dynamic properties. In particular, dynamic correlation functions appear in the fluctuation-dissipation theorem, where the response of a many-body system to an external perturbation is given in terms of the relaxation function of the unperturbed system, provided the disturbance is small. The calculation of the relaxation function is rather difficult in most cases of interest, except for a few examples where exact analytic expressions are allowed. For most of systems of interest approximation schemes must be used. The method of recurrence relation has, at its foundation, the solution of Heisenberg equation of motion of an operator in a many-body interacting system. Insights have been gained from theorems that were discovered with that method. For instance, the absence of pure exponential behavior for the relaxation functions of any Hamiltonian system. The method of recurrence relations was used in quantum systems such as dense electron gas, transverse Ising model, Heisenberg model, XY model, Heisenberg model with Dzyaloshinskii-Moriya interactions, as well as classical harmonic oscillator chains. Effects of disorder were considered in some of those systems. In the cases where analytical solutions were not feasible, approximation schemes were used, but are highly model-dependent. Another important approach is the numericallly exact diagonalizaton method. It is used in finite-sized systems, which sometimes provides very reliable information of the dynamics at the infinite-size limit. In this work, we discuss the most relevant applications of the method of recurrence relations and numerical calculations based on exact diagonalizations. The method of recurrence relations relies on the solution to the coefficients of a continued fraction for the Laplace transformed relaxation function. The calculation of those coefficients becomes very involved and, only a few cases offer exact solution. We shall concentrate our efforts on the cases where extrapolation schemes must be used to obtain solutions for long times (or low frequency) regimes. We also cover numerical work based on the exact diagonalization of finite sized systems. The numerical work provides some thermodynamically exact results and identifies some difficulties intrinsic to the method of recurrence relations.

scholarly journals Adaptive Threshold Scheme for Pulse Detection under Condition of Background Nonstationary Noise

2021 ◽  
Vol 2096 (1) ◽  
pp. 012019
Author(s):  
A O Shcherbina ◽  
O O Lukovenkova ◽  
A A Solodchuk
Keyword(s):  
High Frequency ◽  
Background Noise ◽  
Signal Amplitude ◽  
Threshold Value ◽  
Adaptive Threshold ◽  
Threshold Scheme ◽  
Pulse Detection ◽  
Geoacoustic Emission ◽  
Time Parameters ◽  
Frequency Pulse

Abstract The paper describes a new adaptive threshold scheme for detecting pulses in high-frequency signals against a background of non-stationary noise. The result of the scheme operation is to determine the pulse boundaries by comparing the signal amplitude-time parameters with the threshold. The threshold value is calculated in non-overlapping windows of fixed length and depends only on the background noise level. The detected pulses undergo additional shape checking, taking into account their characteristics. The parameters of the algorithms for detecting pulses and checking their shape can be adjusted for any type of high-frequency pulse signals. This threshold scheme is tuned to detect pulses in high frequency geoacoustic emission signals. The results of the scheme operation on an artificial signal and on fragments of a geoacoustic signal are given, a comparison is made between the proposed scheme and the previously used (outdated) one. The new threshold scheme proposed by the authors is less sensitive to the choice of the initial threshold value and it is more stable in operation. When processing 15-minute fragments of a geoacoustic signal, the new scheme correctly detects, on average, 5 times more pulses.

Damage-Mitigating Control of Mechanical Systems: Part I—Conceptual Development and Model Formulation

1994 ◽  
Vol 116 (3) ◽  
pp. 437-447 ◽  
Author(s):  
Asok Ray ◽  
Min-Kuang Wu ◽  
Marc Carpino ◽  
Carl F. Lorenzo
Keyword(s):  
Service Life ◽  
Continuous Time ◽  
High Performance ◽  
Power Plants ◽  
Dynamic Properties ◽  
Current System ◽  
Mechanical Systems ◽  
Generation Process ◽  
Damage Mitigation ◽  
Complex Mechanical Systems

A major goal in the control of complex mechanical systems such as advanced aircraft, spacecraft, and power plants is to achieve high performance with increased reliability, availability, component durability, and maintainability. The current state-of-the-art of control systems synthesis focuses on improving performance and diagnostic capabilities under constraints that often do not adequately represent the dynamic properties of the materials. The reason is that the traditional design is based upon the assumption of conventional materials with invariant characteristics. In view of high performance requirements and availability of improved materials, the lack of appropriate knowledge about the properties of these materials will lead to either less than achievable performance due to overly conservative design, or over-straining of the structure leading to unexpected failures and drastic reduction of the service life. The key idea of the research reported in this paper is that a significant improvement in service life can be achieved by a small reduction in the system dynamic performance. This requires augmentation of the current system-theoretic techniques for synthesis of decision and control laws with governing equations and inequality constraints that would model the properties of the materials for the purpose of damage representation and failure prognosis. The major challenge in this research is to characterize the damage generation process in a continuous-time setting, and then utilize this information for synthesizing algorithms of robust control, diagnostics, and risk assessment in complex mechanical systems. Damage mitigation for control of mechanical systems is reported in the two-part paper. The concept of damage mitigation is introduced and a continuous-time model of fatigue damage dynamics is formulated in this paper which is the first part. The second part which is a companion paper presents the synthesis of the open-loop control policy and the results of simulation experiments for transient operations of a reusable rocket engine.

scholarly journals Spectrum Analysis of Signal in Wolfram Mathematica System

2021 ◽  
Vol 20 (2) ◽  
pp. 173-178
Author(s):  
M. A. Hundzina
Keyword(s):  
Spectrum Analysis ◽  
Graphical Representation ◽  
Dynamic Properties ◽  
Audio Signal ◽  
Signal Amplitude ◽  
Morlet Wavelet ◽  
Original Signal ◽  
Additional Information ◽  
Basic Wavelet ◽  
The Fourier Transform

The purpose of this paper is a spectrum analysis of signals of various nature, construction of the signal scalogram using Morlet wavelet, modification of the scalogram to obtain a more informative graphic representation of the signal. Spectral analysis of the signal is constructed by means of the Fourier transform. A modification of the graphical representation of the result of the wavelet transform has been developed with the help of  the Mathematica system. For this, a wavelet scalogram has been used as a two-dimensional representation of the original signal. A scale has been introduced on it for the value of the signal amplitude depending on the time and period of its constituent components. This graphical representation allows us to obtain additional information about the dynamic properties of the original signal.  A modification of the representation of the original signal scalogram has been developed for a more complete spectrum analysis (determination of the period of the constituent components). The paper contains an example using a modified scalogram for the analysis of a signal containing two pulses, an audio signal and white noise. The basic wavelet in this case is the Morlet wavelet. A comparison of the scalogram, obtained using the built-in function, and the modified scalogram has been made in the paper. The disadvantage of the first scalogram is the impossibility of assessing the frequency of the signal; its advantage is the ability to assess the localization of the pulse. For a modified scalogram, the advantage is the estimation of the signal periodicity, and the disadvantage is the inaccuracy in determining the range of pulse localization. For spectrum analysis in Mathematica, it is recommended to use a combination of two approaches (using a standard built-in function to determine the localization of the pulse) and a modified scalogram (to determine the periods of the constituent components).

An example of spectrum imaging used for comparison of EELS quantitative analysis techniques on Al-Li

1991 ◽  
Vol 49 ◽  
pp. 726-727
Author(s):  
John A. Hunt
Keyword(s):  
Quantitative Analysis ◽  
Large Data ◽  
Difference Spectrum ◽  
Large Data Sets ◽  
Foil Thickness ◽  
Data Sets ◽  
Analysis Techniques ◽  
Spectrum Imaging ◽  
Normal Spectrum ◽  
Electron Energy Loss

Spectrum-imaging is a useful technique for comparing different processing methods on very large data sets which are identical for each method. This paper is concerned with comparing methods of electron energy-loss spectroscopy (EELS) quantitative analysis on the Al-Li system. The spectrum-image analyzed here was obtained from an Al-10at%Li foil aged to produce δ' precipitates that can span the foil thickness. Two 1024 channel EELS spectra offset in energy by 1 eV were recorded and stored at each pixel in the 80x80 spectrum-image (25 Mbytes). An energy range of 39-89eV (20 channels/eV) are represented. During processing the spectra are either subtracted to create an artifact corrected difference spectrum, or the energy offset is numerically removed and the spectra are added to create a normal spectrum. The spectrum-images are processed into 2D floating-point images using methods and software described in [1].

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