scholarly journals Checking the adequacy of the method for generating a random process of disturbance of oscillations of rail carriages according to the impulse response of the forming filter

2021 ◽  
Vol 79 (6) ◽  
pp. 327-336
Author(s):  
A. N. Savos’kin ◽  
N. S. Lavlinskaya
Keyword(s):  
Random Process ◽  
Numerical Integration ◽  
Cross Correlation ◽  
Random Disturbance ◽  
Frequency Method ◽  
Verification Method ◽  
Operation Speed ◽  
Stable Frequency ◽  
The Time Domain ◽  
The Given

Usually, to study the vibrations of rail carriages, the equivalent geometric unevenness of the track obtained as a result of processing the records of the track measuring car is taken as a disturbance. Such a record contains a certain set of irregularity wavelengths, for example, 50, 25 and 12.5 m. However, when it is used to simulate disturbances at different operation speeds, these wavelengths will correspond to frequencies depending on the given speed of motion, which is not permissible, since a stable frequency range from 0.2 to 10 Hz is required to excite the vibrations of all the bodies included in the carriage. To eliminate this drawback, in the previously performed works it was proposed to generate a random process of geometric irregularities for a given operation speed by changing the set of wavelengths included in the irregularities. In this paper, based on the study of random oscillations of a simplified model of a rail carriage, as a system with one degree of freedom, the adequacy of the method for generating a random disturbance process is verified in two ways. In the first method, it was found that the characteristics of random oscillations of such a model, obtained in the time domain on the basis of numerical integration of the equation of motion when specifying the generated disturbance, have satisfactory convergence with similar characteristics found by the frequency method using Shannon's formula. In the second verification method, the cross-correlation function and the mutual spectral density between the disturbance and the bouncing oscillations were determined from the generated disturbance realization and obtained by numerical integration of the vibration process realization. Then, using the method of identifying the dynamic system, experimental amplitude and phase frequency characteristics were found, which showed satisfactory convergence with the corresponding calculated characteristics obtained by numerically solving the equation of oscillations of the model under study. On the basis of the results obtained, it was concluded that the considered method of generating a random process of disturbance is sufficiently adequate and that it can be applied to solve problems of the dynamics of rail carriages.

scholarly journals Note on the Application of Compound Poisson Processes to Sickness and Accident Statistics

1960 ◽  
Vol 1 (4) ◽  
pp. 224-237 ◽  
Author(s):  
Carl Philipson
Keyword(s):  
Random Process ◽  
Conditional Probability ◽  
Compound Poisson Process ◽  
Compound Poisson ◽  
Continuous Parameter ◽  
Absolute Probability ◽  
Image Position ◽  
The Given ◽  
Accident Statistics ◽  
Uniformly Bounded

In order to fix our ideas an illustration of the theory for (a) a general elementary random process, (b) a compound Poisson process and (c) a Polya process shall be given here below following Ove Lundberg (On Random Processes and Their Application to Accident and Sickness Statistics, Inaug. Diss., Uppsala 1940).Let the continuous parameter t* be measured on an absolute scale from a given point of zero and consider the random function N* (t*) which takes only non-negative and integer values with N* (o) = o. This function constitutes a general elementary random process for which the conditional probability that N* (t*) = n relative to the hypothesis that shall be denoted , while the absolute probability that N* (t) = n i.e. shall be written If quantities of lower order than dt* are neglected, we may write for the conditional probability that N* (t* + dt*) = n + 1 relative to thehyp othesis that N* (t*) = n, i.e. is the intensity function of the process which is assumed to be a continuous function of t* (the condition of existence for the integral over the given interval of t* for every n > m may be substituted for the condition of continuity). The expectations for an arbitrary but fix value of t* of N* (t*) and p* (t*) will be denoted by the corresponding symbol with a bar so thatIf is uniformly bounded for all n in the interval o ≤ t* < T*, where T* is an arbitrary but fix value of t*, we have i.a. that

The Role of Phase-locking to the Temporal Envelope of Speech in Auditory Perception and Speech Intelligibility

2015 ◽  
Vol 27 (3) ◽  
pp. 533-545 ◽  
Author(s):  
Rebecca E. Millman ◽  
Sam R. Johnson ◽  
Garreth Prendergast
Keyword(s):  
Speech Intelligibility ◽  
Cross Correlation ◽  
Phase Locking ◽  
A Priori ◽  
Whole Brain ◽  
Temporal Envelope ◽  
Speech Stimuli ◽  
Intelligible Speech ◽  
The Time Domain ◽  
Physically Identical

The temporal envelope of speech is important for speech intelligibility. Entrainment of cortical oscillations to the speech temporal envelope is a putative mechanism underlying speech intelligibility. Here we used magnetoencephalography (MEG) to test the hypothesis that phase-locking to the speech temporal envelope is enhanced for intelligible compared with unintelligible speech sentences. Perceptual “pop-out” was used to change the percept of physically identical tone-vocoded speech sentences from unintelligible to intelligible. The use of pop-out dissociates changes in phase-locking to the speech temporal envelope arising from acoustical differences between un/intelligible speech from changes in speech intelligibility itself. Novel and bespoke whole-head beamforming analyses, based on significant cross-correlation between the temporal envelopes of the speech stimuli and phase-locked neural activity, were used to localize neural sources that track the speech temporal envelope of both intelligible and unintelligible speech. Location-of-interest analyses were carried out in a priori defined locations to measure the representation of the speech temporal envelope for both un/intelligible speech in both the time domain (cross-correlation) and frequency domain (coherence). Whole-brain beamforming analyses identified neural sources phase-locked to the temporal envelopes of both unintelligible and intelligible speech sentences. Crucially there was no difference in phase-locking to the temporal envelope of speech in the pop-out condition in either the whole-brain or location-of-interest analyses, demonstrating that phase-locking to the speech temporal envelope is not enhanced by linguistic information.

The Research on Cable Force Measurement Based on Degenerated Element with Frequency Method

2013 ◽  
Vol 405-408 ◽  
pp. 1709-1715
Author(s):  
Xin Cui ◽  
Yong Jiang ◽  
Li Wen Fu ◽  
Jin Feng Wang
Keyword(s):  
Numerical Method ◽  
Theoretical Basis ◽  
Force Measurement ◽  
Beam Element ◽  
Testing System ◽  
Frequency Method ◽  
Operation Procedure ◽  
Cable Force ◽  
Cable Force Measurement ◽  
The Given

At present, among the methods of cable force measurement, the frequency method is applied extensively for its mature theory and rapid and repeated operation procedure. Based on the theory of frequency method measurement, it generally uses the numerical method with beam element to analysis the parameters of cables under the given conditions. However, the conventional beam element is not able to simulate the bending stiffness in beams section. Therefore, it turns to degenerated beam element to simulate cables and the results agree well with the results based on beam element and formulas calculation, and it provides theoretical basis for the later cable force testing system.

scholarly journals Quantification of time delay between damages caused by windstorms and by Ips typographus

2015 ◽  
Vol 61 (4) ◽  
pp. 221-231 ◽  
Author(s):  
Roman Modlinger ◽  
Petr Novotný
Keyword(s):  
Bark Beetle ◽  
Cross Correlation ◽  
Static Stability ◽  
Stochastic Delay ◽  
Salvage Logging ◽  
Spruce Bark ◽  
Future Consequences ◽  
Near Future ◽  
The Given ◽  
Disturbed Stand

AbstractDamages by wind and by European spruce bark beetle (I. typographusL.) were compared on the basis of the reports about the occurrence of harmful forest agents for the period 1964−1991 across former regional state forest directorates. In the given period, the quantity of salvage logging (70 million m3) was more than five times that of sanitation felling (13 million m3). Damage intensity increased over the decades. Using a cross-correlation function between the time series, an increase in the abundance ofI. typographusdue to windfall was demonstrated with a delay of 1–3 years. Wind damage was also shown to arise as a result of disturbed stand stability after sanitation felling with a stochastic delay of 1−5 years. Thus, disturbance of static stability of forest stands may be considered as one of the main harmful consequences of bark beetle outbreaks for the near future. Consequences for forest management are discussed.

scholarly journals Optimized Operator-Splitting Methods in Numerical Integration of Maxwell's Equations

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Z. X. Huang ◽  
X. L. Wu ◽  
W. E. I. Sha ◽  
B. Wu
Keyword(s):  
Numerical Integration ◽  
Time Domain ◽  
Maxwell’S Equations ◽  
Maxwell's Equations ◽  
Operator Splitting ◽  
Splitting Methods ◽  
High Order ◽  
Numerical Results ◽  
Operator Splitting Methods ◽  
The Time Domain

Optimized operator splitting methods for numerical integration of the time domain Maxwell's equations in computational electromagnetics (CEM) are proposed for the first time. The methods are based on splitting the time domain evolution operator of Maxwell's equations into suboperators, and corresponding time coefficients are obtained by reducing the norm of truncation terms to a minimum. The general high-order staggered finite difference is introduced for discretizing the three-dimensional curl operator in the spatial domain. The detail of the schemes and explicit iterated formulas are also included. Furthermore, new high-order Padé approximations are adopted to improve the efficiency of the proposed methods. Theoretical proof of the stability is also included. Numerical results are presented to demonstrate the effectiveness and efficiency of the schemes. It is found that the optimized schemes with coarse discretized grid and large Courant-Friedrichs-Lewy (CFL) number can obtain satisfactory numerical results, which in turn proves to be a promising method, with advantages of high accuracy, low computational resources and facility of large domain and long-time simulation. In addition, due to the generality, our optimized schemes can be extended to other science and engineering areas directly.

A COMPARISON OF THE VARIOUS PARAMETERS EMPLOYED IN THE VARIABLE‐FREQUENCY INDUCED‐POLARIZATION METHOD

Geophysics ◽  
1964 ◽  
Vol 29 (3) ◽  
pp. 425-433 ◽  
Author(s):  
Philip G. Hallof
Keyword(s):  
Induced Polarization ◽  
Frequency Effect ◽  
Variable Frequency ◽  
Transient Method ◽  
Polarization Method ◽  
Applied Current ◽  
Frequency Method ◽  
Pulse Transient Method ◽  
Factor Data ◽  
The Time Domain

The increased use of the induced‐polarization method in recent years has resulted in two methods of measurement. The measurements in the frequency domain (variable‐frequency method) rely on changes in the apparent resistivities measured as the frequency of the applied current is varied. The measurement in the time domain (pulse‐transient method) detects transients in the measured potentials when the applied current is interrupted. The “chargeability” is the parameter used in the pulse‐transient method, while both the “frequency effect” and the normalized parameter “metal factor” are used in the variable‐frequency method. The most useful parameter would be the one which best indicates the amount of metallic mineralization present. Eight sets of field results from variable‐frequency field surveys are shown. The cases are shown in pairs; in each pair, the geometry of the source is much the same. By comparing the resistivity, the frequency effect (chargeability), and metal‐factor data with the amount of mineralization indicated by the drilling results, the usefulness of these parameters can be evaluated.

scholarly journals Cross-Correlation of THz Pulses from the Electron Storage Ring BESSY II

2020 ◽  
Vol 5 (2) ◽  
pp. 24
Author(s):  
Ulrich Schade ◽  
Peter Kuske ◽  
Jongseok Lee ◽  
Barbara Marchetti ◽  
Michele Ortolani
Keyword(s):  
Synchrotron Radiation ◽  
Storage Ring ◽  
Time Domain ◽  
Cross Correlation ◽  
Bunch Length ◽  
Pump Probe ◽  
Electron Storage ◽  
Coherent Synchrotron Radiation ◽  
Longitudinal Length ◽  
The Time Domain

Coherent synchrotron radiation from an electron storage ring is observed in the THz spectral range when the bunch length is shortened down to the sub-mm-range. With increasing stored current, the bunch becomes longitudinally unstable and modulates the THz emission in the time domain. These micro-instabilities are investigated at the electron storage ring BESSY II by means of cross-correlation of the THz fields from successive bunches. The investigations allow deriving the longitudinal length scale of the micro bunch fluctuations and show that it grows faster than the current-dependent bunch length. Our findings will help to set the limits for the possible time resolution for pump-probe experiments achieved with coherent THz synchrotron radiation from a storage ring.

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