scholarly journals Study on the characteristic mechanisms of infrasonic precursors during the damage process of impending earthquake sources

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0257345
Author(s):  
Wei Wang ◽  
Xiaorong Xue ◽  
Weisheng Chen ◽  
Xiaoyan Xue
Keyword(s):  
Low Frequency ◽  
Pulse Number ◽  
Fracture Site ◽  
Theoretical Research ◽  
Theoretical Simulation ◽  
Earthquake Sources ◽  
Fracture Formation ◽  
Initiation And Propagation ◽  
Damage Process ◽  
Complex Forms

Infrasonic signals measured before an earthquake carry information about the size and development speed of the source fracture, the stress at the fracture site and the elastic properties of the geologic medium. The infrasonic signal has a stable time scale, and compared with other precursors, infrasound has a unique sensitivity to earthquake disasters. However, to date, there has been no relevant theoretical research on the mechanism of infrasonic anomalies, and information on the development of fracture sources cannot be obtained from these characteristics, which makes the application of this anomaly in earthquake prediction challenging. In this study, we obtained the characteristics of short-term and impending infrasonic anomalies based on the infrasound data of more than 100 strong earthquakes. With a range of elastic medium models with a large number of fractures, we completed the theoretical simulation of the formation process of infrasonic precursors during the formation of the main fractures, analyzed the physical evolution of acoustic signals when cracks are generated, and quantitatively described the stages of large fracture formation caused by the initiation and propagation of seismic cracks. Specifically, this study revealed the causes of various and complex forms of infrasonic precursors near the critical point and the causes of the time- and space-dependent characteristics of these precursors, such as a noticeable attenuation of the pulse number, a low frequency and a large amplitude, which verified the effectiveness of infrasonic anomalies as strong earthquake precursors.

Das Werk als Entgrenzung. : Werkkomplex und Dynamik des Gesamtwerks

2021 ◽  
Vol 31 (1) ◽  
pp. 139-154
Author(s):  
Svetlana Efimova
Keyword(s):  
Dynamic Structure ◽  
Intermediate Stage ◽  
Literary Work ◽  
Theoretical Research ◽  
Semantic Composition ◽  
Complex Forms ◽  
Special Relevance ◽  
Reception Side

Abstract Im Kontext des neu aufgekommenen theoretischen Interesses für die Werkkategorie wird überwiegend das ,Einzelwerk‘ fokussiert. Im vorliegenden Aufsatz wird das heuristische Potenzial des Konzepts ,Gesamtwerk‘ als ein anderer Teil der Werkkategorie herausgearbeitet. Neben dem üblichen Aspekt eines ,Lebenswerks‘ schließt das Gesamtwerk vielfältige Werkkomplexe und Werkgruppierungen ein, die auf Produktions- oder Rezeptionsseite entstehen. Analysiert werden feste und variable Anordnungen, Ab- und Entgrenzungen zwischen Einzelwerken eines Autors, die das Gesamtwerk zu einem dynamischen Gefüge machen. Ein Werkkomplex bildet eine Zwischenstufe und ein Bindeglied zwischen ,Einzelwerk‘ und ,Gesamtwerk‘. Daher besitzt er eine besondere Relevanz für die semantische Zusammensetzung der Werkkategorie als Trias, deren Teile sich aufeinander beziehen: Opus – Werkkomplex – Œuvre.The newly arisen theoretical research on the literary work category focuses mainly on the ,single work‘. This paper argues for the heuristic potential of the ,oeuvre‘ as another part of the work category. In addition to the usual aspect of a ,life’s work‘, the oeuvre includes diverse work complexes and work groupings that emerge on the production or reception side. The paper analyzes a dynamic structure of the oeuvre: fixed and variable arrangements, boundaries and dissolution of borders between single works by the same author. A work complex forms an intermediate stage and a link between ,single work‘ and ,oeuvre‘. It therefore has a special relevance for the semantic composition of the work category as a triad, the parts of which refer to each other: single work – work complex – oeuvre.

Electromagnetic Property of La0.7Sr0.3MnO3/Ag Composite at High Frequency

2015 ◽  
Vol 655 ◽  
pp. 182-185
Author(s):  
Ke Lan Yan ◽  
Run Hua Fan ◽  
Min Chen ◽  
Kai Sun ◽  
Xu Ai Wang ◽  
...  
Keyword(s):  
High Frequency ◽  
Single Phase ◽  
Low Frequency ◽  
Electromagnetic Property ◽  
High Frequency Range ◽  
Frequency Range ◽  
Free Electron Concentration ◽  
Theoretical Simulation ◽  
Electrical And Magnetic Properties ◽  
Three Phase

The phase structure, and electrical and magnetic properties of La0.7Sr0.3MnO3(LSMO)-xAg (xis the mole ratio,x=0, 0.3, 0.5) composite were investigated. It is found that the sample withx=0 is single phase; the samples withx=0.3 and 0.5 present three phase composite structure of the manganese oxide and Ag. With the increasing of Ag content, the grain size of the samples increases and the grain boundaries transition from fully faceted to partially faceted. The permittivity of spectrum (10 MHz - 1 GHz) and the theoretical simulation reveal that the plasma frequencyfpincrease with Ag content, due to the increasing of free electron concentration, which is further supported by the enhancement of conductivity. While for the permeability (μr'), theμr'decrease with the increasing of Ag content at low frequency range (f< 20 MHz), while at the relative high frequency range (f> 300 MHz), theμr'increased with Ag content. Therefore, the introduction of elemental Ag resulted in a higherμr'at the relative high frequency range.

scholarly journals Observation of Flaking Process in Rolling Contact Fatigue by Laminography Using Ultra-bright Synchrotron Radiation

2018 ◽  
Vol 165 ◽  
pp. 11002
Author(s):  
Yoshikazu Nakai ◽  
Daiki Shiozawa ◽  
Shoichi Kikuch ◽  
Hitoshi Saito ◽  
Takashi Nishina ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Crack Initiation ◽  
Rolling Contact Fatigue ◽  
Rolling Direction ◽  
Contact Fatigue ◽  
Critical Length ◽  
Rolling Contact ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Damage Process

The flaking failure in rolling contact fatigue (RCF) results from crack initiation and propagation has been believed to originate from non-metallic inclusions located beneath the surface. With conventional microscopies, however, damage process in the internal region of materials could not be observed, then RCF crack initiation and propagation behaviours were observed by using synchrotron radiation computed laminography (SRCL) in the brightest synchrotron facility in Japan, and the effect of the inclusion orientation on the RCF property was examined. In our previous studies, crack initiation and propagation behaviours caused by extended MnS inclusions distributed in depth or transverse (width) direction was observed by the SRCL. In the present study, the fracture mechanism under RCF was discussed on specimens with MnS inclusions distributed in the rolling direction. As a result, vertical cracks were initiated on the surface, parallel to the ball-rolling direction in specimens. The crack propagation direction was then changed perpendicular to the rolling direction. Thereafter, similar with our previous studies, vertical cracks caused the horizontal cracks beneath the surface, when the vertical cracks reached to a critical length. The ratio of the vertical crack initiation life to the flaking life was higher than specimens with other inclusion orientation.

Microstructure Evolution During Alternating-Current-Induced Fatigue

Materials ◽  
2004 ◽  
Author(s):  
R. R. Keller ◽  
R. H. Geiss ◽  
Y.-W. Cheng ◽  
D. T. Read
Keyword(s):  
Electron Backscatter Diffraction ◽  
Failure Process ◽  
Low Frequency ◽  
Surface Damage ◽  
Alternating Current ◽  
Fiber Texture ◽  
Electrical Failure ◽  
Damage Process ◽  
Current Densities ◽  
Interconnect Lines

Subjecting electronic interconnect lines to high-density, low-frequency alternating current creates cyclic thermomechanical stresses that eventually cause electrical failure. A detailed understanding of the failure process could contribute to both prevention and diagnostics. We tested unpassivated Al-1Si traces on the NIST-2 test chip; these are 3.5 μm wide by 0.5 μm thick by 800 μm long, with a strong (111) as-deposited fiber texture and an initial average grain diameter of approximately 1 μm. We applied rms current densities of 11.7 to 13.2 MA/cm2 at 100 Hz. Resistance changes in the lines indicated that such current densities produce temperature cycles at 200 Hz with amplitude exceeding 100 K. Open circuits occurred in under 10 minutes, with substantial surface damage seen after only one minute. A few failures initiated at lithography defects initially present in the lines, but most were produced by the current alone. In one detailed example presented in this paper, we monitored the damage process by interrupting the current at 10, 20, 40, 80, 160, and 320 s in order to characterize an entire line by scanning electron microscopy and automated electron backscatter diffraction (EBSD); failure took place after 697 s. Results are described in terms of deformation, grain growth, and orientation changes.

Theoretical Modeling of the N-H and N-D Stretching Bands of Hydrogen-Bonded 1-Methylthymine Crystal and Its Deuterated Form

2006 ◽  
Vol 2 (4) ◽  
pp. 205-219
Author(s):  
Marek Boczar ◽  
Łukasz Boda ◽  
Marek J. Wójcik
Keyword(s):  
Hydrogen Bonds ◽  
High Frequency ◽  
Molecular Crystals ◽  
Low Frequency ◽  
Unit Cell ◽  
Fermi Resonance ◽  
Bending Vibrations ◽  
Theoretical Simulation ◽  
Stretching Vibrations ◽  
Centrosymmetric Dimers

Theoretical model for vibrational interactions in the hydrogen bonds in molecular crystals with four molecules forming two centrosymmetric dimers in the unit cell is presented. The model takes into account anharmonic-type couplings between the high-frequency N-H(D) and the low-frequency N•••O stretching vibrations in each hydrogen bond, resonance interactions (Davydov coupling) between equivalent hydrogen bonds in each dimer, resonance interdimer interactions within an unit cell and Fermi resonance between the N-H(D) stretching fundamental and the first overtone of the N-H(D) in-plane bending vibrations. The vibrational Hamiltonian, selection rules, and expressions for the integral properties of an absorption spectrum are derived. The model is used for theoretical simulation of the νs stretching bands of 1-methylthymine and its ND derivative at 300 K. The effect of deuteration is successfully reproduced by our model.

Computational Modelling of Ring-Shaped Magnetic Domains

1998 ◽  
Vol 529 ◽  
Author(s):  
A.F. Gal'tsev ◽  
V.G. Pokazan'ev ◽  
Y.I. Yalishev
Keyword(s):  
Local Density ◽  
Computational Modelling ◽  
Low Frequency ◽  
Magnetic Domain ◽  
Magnetic Film ◽  
Static Stability ◽  
Film Plane ◽  
Theoretical Research ◽  
Magnetization Distribution ◽  
Domain Structures

AbstractA theoretical research of static stability of peculiar localized domain structures (LDS) in a thin magnetic film with the perpendicular anisotropy is presented. The model describes a system consisting of cylindrical magnetic domain (CMD) and several concentric ring-shaped domains. Such structures arise under influence of the external low frequency (100–1000 Hz) magnetic field applied perpendicular to the film plane and were observed experimentally in 1992. Non-linear singular integro-differential equation for a magnetization distribution is provided by a minimization condition for the system's complete energy local density. Energy dependencies on geometry parameters are calculated numerically. The conditions of magnetostatic stabilization of the simplest CMD-ring system, as well as some of its dynamical properties, are discussed in detail on this basis.

Determination of Damage Criteria in Medial Collateral Ligaments

2010 ◽  
Author(s):  
Zheying Guo ◽  
Raffaella De Vita ◽  
Jennifer G. Barrett ◽  
Joseph G. Freeman
Keyword(s):  
Tensile Tests ◽  
Collateral Ligaments ◽  
Sprague Dawley ◽  
Threshold Strain ◽  
Sprague Dawley Rats ◽  
Initiation And Propagation ◽  
Damage Process ◽  
Complete Failure ◽  
Damage Criteria

The effect of consecutive and gradually increasing strain on the mechanical behavior of rat medial collateral ligaments (MCLs) was studied to characterize and understand the damage evolution process. Displacement-controlled tensile tests were conducted on femur-MCL-tibia complexes (FMTCs) harvested from 9 Sprague Dawley rats. Each FMTC was loaded to a given displacement, unloaded, and re-loaded to another increasing displacement several times until complete failure occurred. From the recorded tensile stress-strain data, two different phenomena indicative of initiation and propagation of damage were observed: an elongation of the toe region and a decrease in stiffness of the linear region. The threshold strain at which the elongation of the toe region first appeared was found to be (2.59±1.37)% while the threshold strain at which the decrease in stiffness first occurred was determined to be (5.11 ± 1.25)%. These results suggest that there are two different mechanisms that control the damage process in ligaments and further investigation is needed to elucidate their micro-structural origin.

Yhe Compression Meso-Mechanics Theoretical Model and Experimental Verification of Polyurethane-Based Warp-Knit Spacer Fabric Composites

2021 ◽  
Vol 8 (5) ◽  
pp. 30-38
Author(s):  
Si Chen
Keyword(s):  
Theoretical Model ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Beam Theory ◽  
Theoretical Research ◽  
Dimensional Structure ◽  
Static Compression ◽  
Theoretical Simulation ◽  
Winkler Elastic Foundation ◽  
Spacer Fabric

In this research, a new type of binary material, a polyurethane-based warp-knitted spacer fabric composite (PWSF), having a unique three-dimensional structure, high strength, and a variety of surface structures was prepared. The compression meso-mechanics theoretical model based on the Winkler elastic foundation beam theory and structural parameters of PWSF were used to predict the compression performance of PWSF. To verify the validity of compression model, the compression stress-strain curves of theoretical simulation were compared with the quasi-static compression test results. The deviation between these two compression moduli was less than 7%. The compression meso-mechanics model established in this study can effectively simulate the actual compression behaviors for different PWSF specimens. A regular pattern of compression properties of this novel composite from the theoretical research on meso-mechanics perspectives can be proposed.

An Improved Frequency-Shift Compression Method Based on Auto Energy Gain Compensation for Digital Hearing Aids

2015 ◽  
Vol 719-720 ◽  
pp. 1068-1073
Author(s):  
Zhi Liang Zhao ◽  
Zhao Yang Guo ◽  
Xiang Xiang Luo ◽  
Feng Jie Xue ◽  
Xin An Wang
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Low Frequency ◽  
Energy Gain ◽  
Compression Method ◽  
Subjective Test ◽  
Theoretical Simulation ◽  
Digital Hearing Aids ◽  
Gain Compensation ◽  
Speech Loudness

Sensorineural hearing impaired individuals have narrow hearing range, especially in high frequency. Due to acoustic diffusion masking, just amplifying speech can’t meet patients’ demands. Traditional methods restore the signal of high frequency in low frequency, which has two weaknesses. On the one hand high frequency covers low frequency, on the other hand the methods change the energy of speech. These two aspects severely decrease speech loudness, perception and recognition. To solve the above problems, we have proposed an improved frequency shifting compression method based on Auto Energy Gain Compensation (AEGC) which is used for hearing aids. Fully investigating the relationship of speech frequency with energy and recognition, the scheme selectively keeps the information of vital frequency band. Meanwhile, it compensates the speech loudness with AEGC module. With the proposed scheme, it has obviously improved the speech perception and recognition. Both the theoretical simulation result and subjective test in APP on android platform show the energy is compensated and the speech recognition ratios are enhanced 20%-30% in different environments, especially efficient in quiet, noisy and normal environment.

scholarly journals Design and Implementation of the Universal Servo Control Algorithm Verification System Based on High-Speed Communication Fieldbus

2021 ◽  
Vol 25 (2) ◽  
pp. 248-257
Author(s):  
Yonghua Xiong ◽  
Ke Li ◽  
Zhen-Tao Liu ◽  
Jinhua She ◽  
◽  
...  
Keyword(s):  
High Speed ◽  
Control Algorithm ◽  
Experimental System ◽  
Servo Control ◽  
Theoretical Research ◽  
Control Algorithms ◽  
Master Program ◽  
Theoretical Simulation ◽  
Industrial Sites ◽  
Algorithm Verification

In recent years, there have been several breakthroughs in the theoretical research of servo control algorithms. However most of these control algorithms remain in the simulation stage. They are difficult to be applied directly to practical platforms or complex industrial sites because of the lack of an experimental system suitable for the verification of their effectiveness. To address this problem, we designed a multi-function servo control algorithm verification experiment system (MVES) within the MATLAB/Simulink theoretical simulation model directly to communicate with the TwinCAT 3 PLC master program to perform different servo control experiments. The MVES supports various Simulink models. However, its and the operation is simple and convenient, which greatly reduces the workload of the algorithm test and has important practical value. Two sets of comparative experiments were used to verify the versatility and superiority of MVES.

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