Instrument responses of digital seismographs at Borovoye, Kazakhstan, by inversion of transient calibration pulses

1996 ◽  
Vol 86 (1A) ◽  
pp. 191-203 ◽  
Author(s):  
Won-Young Kim ◽  
Göran Ekström
Keyword(s):  
Pulse Shape ◽  
Waveform Analysis ◽  
Northern Caucasus ◽  
Linear Filters ◽  
Small Perturbations ◽  
Cutoff Frequencies ◽  
Digital Seismograms ◽  
Transient Calibration ◽  
The Time Domain ◽  
Good Agreement

Abstract A method is developed to determine the response of digital seismographs from transient calibration pulses. Based on linear system theory, the digital seismograph is represented by a set of first- and higher-order linear filters characterized by their cutoff frequencies and damping coefficients. The transient calibration pulse is parameterized by a set of instrument constants, and the problem is linearized for small perturbations of the constants with respect to their nominal values. The observed calibration pulse shape is matched in the time domain using an iterative linearized inverse technique. The method is used to derive complete instrument responses for digital seismographs operating at the Borovoye Observatory (BRVK) in Kazakhstan, for which previously only the amplitude responses have been determined. To test this method, we apply it to calibration pulses from a modern digital seismograph system at Kislovodsk (KIV) in northern Caucasus, Russia, and obtain good agreement between known and derived instrument constants. The results of the calibration pulse shape inversion for these seismographs indicate that the method is efficient and that the results are reliable even when microseismic noise is present in the recorded transient calibration pulse. The derived parameters make possible improved quantitative waveform analysis of digital seismograms recorded at BRVK.

High Amplitude Sound Propagation at Low Frequencies in a Flow Duct Lined With Resonators: A Time Domain Solution

1988 ◽  
Vol 110 (4) ◽  
pp. 545-551 ◽  
Author(s):  
A. Cummings ◽  
I.-J. Chang
Keyword(s):  
Time Domain ◽  
Internal Combustion Engines ◽  
Sound Propagation ◽  
Sound Field ◽  
High Amplitude ◽  
Combustion Engines ◽  
Low Frequencies ◽  
The Time Domain ◽  
Flow Duct ◽  
Good Agreement

A quasi one-dimensional analysis of sound transmission in a flow duct lined with an array of nonlinear resonators is described. The solution to the equations describing the sound field and the hydrodynamic flow in the neighborhood of the resonator orifices is performed numerically in the time domain, with the object of properly accounting for the nonlinear interaction between the acoustic field and the resonators. Experimental data are compared to numerical computations in the time domain and generally very good agreement is noted. The method described here may readily be extended for use in the design of exhaust mufflers for internal combustion engines.

scholarly journals Numerical and Experimental Investigation on a Moonpool-Buoy Wave Energy Converter

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2364 ◽  
Author(s):  
Hengxu Liu ◽  
Feng Yan ◽  
Fengmei Jing ◽  
Jingtao Ao ◽  
Zhaoliang Han ◽  
...  
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Scale Model ◽  
Energy Converter ◽  
Point Absorber ◽  
Motion Responses ◽  
Computational Fluid Dynamics Cfd ◽  
The Time Domain ◽  
Good Agreement

This paper introduces a new point-absorber wave energy converter (WEC) with a moonpool buoy—the moonpool platform wave energy converter (MPWEC). The MPWEC structure includes a cylinder buoy and a moonpool buoy and a Power Take-off (PTO) system, where the relative movement between the cylindrical buoy and the moonpool buoy is exploited by the PTO system to generate energy. A 1:10 scale model was physically tested to validate the numerical model and further prove the feasibility of the proposed system. The motion responses of and the power absorbed by the MPWEC studied in the wave tank experiments were also numerically analyzed, with a potential approach in the frequency domain, and a computational fluid dynamics (CFD) code in the time domain. The good agreement between the experimental and the numerical results showed that the present numerical model is accurate enough, and therefore considering only the heave degree of freedom is acceptable to estimate the motion responses and power absorption. The study shows that the MPWEC optimum power extractions is realized over a range of wave frequencies between 1.7 and 2.5 rad/s.

Numerical Simulation of Broadband Combustion Noise With the RPM-CN Approach

2009 ◽  
Author(s):  
B. Mu¨hlbauer ◽  
R. Ewert ◽  
O. Kornow ◽  
B. Noll ◽  
M. Aigner
Keyword(s):  
High Efficiency ◽  
Numerical Approach ◽  
Combustion Noise ◽  
Acoustic Measurements ◽  
Noise Sources ◽  
Computational Costs ◽  
Acoustic Perturbation ◽  
Simulation Results ◽  
The Time Domain ◽  
Good Agreement

A new numerical approach called RPM-CN approach is applied to predict broadband combustion noise. This highly efficient hybrid CFD/CAA approach can rely on a reactive RANS simulation. The RPM method is used to reconstruct stochastic broadband combustion noise sources in the time domain based on statistical turbulence quantities. Subsequently, the propagation of the combustion noise is computed by solving the acoustic perturbation equations (APE-4). The accuracy of the RPM-CN approach will be demonstrated by a good agreement of the simulation results with acoustic measurements of the DLR-A flame. The high efficiency and therefore low computational costs enable the usage of this numerical approach in the design process.

Research on the Static and Dynamics Characteristics of Soft Yoke Mooring System Based on Multi-Rigid Body Interaction

2020 ◽  
Author(s):  
Hongwei Wang ◽  
Zizhao Zhang ◽  
Gang Ma ◽  
Rongtai Ma ◽  
Jie Yang
Keyword(s):  
Time Domain ◽  
Rigid Bodies ◽  
Coupled Analysis ◽  
Mooring System ◽  
Accurate Analysis ◽  
Restoring Force ◽  
Stiffness Characteristics ◽  
The Time Domain ◽  
Multi Body ◽  
Good Agreement

Abstract Select the common mooring system-soft yoke mooring system as the research object. The soft yoke mooring system is regarded as a structure composed of multiple rigid bodies, and the theoretical analysis of multi-body dynamics is used to discuss the interaction of multi-rigid bodies. The classical HYSY113 FPSO is selected as an example, for the soft yoke mooring system, the stiffness characteristics and static restoring force curved compared with those of software OrcaFlex, and they are in good agreement, which verify the reliability of the formula derived, and it is a prerequisite for the accurate simulations in further steps. Coupled analysis to the whole system in time domain is also carried out both in OrcaFlex and AQWA, and the representative response of the FPSO under different environmental conditions is compared, the results are consistent well with each other. It is a good reference for the future study in this field. Good static characteristics are a prerequisite for accurate analysis of time-domain motion. By comparing the results in the time domain, it is found that under the same working conditions, the analysis results calculated by different commercial software (AQWA and OrcaFlex) may be different. We need to perform design analysis based on the characteristics of the software.

scholarly journals Temporal characterization of femtosecond laser pulses using tunneling ionization in the UV, visible, and mid-IR ranges

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Wosik Cho ◽  
Sung In Hwang ◽  
Chang Hee Nam ◽  
Mina R. Bionta ◽  
Philippe Lassonde ◽  
...  
Keyword(s):  
Wavelength Range ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Tunneling Ionization ◽  
Optical Gating ◽  
Dispersion Data ◽  
Materials Used ◽  
The Time Domain ◽  
Good Agreement

Abstract To generalize the applicability of the temporal characterization technique called “tunneling ionization with a perturbation for the time-domain observation of an electric field” (TIPTOE), the technique is examined in the multicycle regime over a broad wavelength range, from the UV to the IR range. The technique is rigorously analyzed first by solving the time-dependent Schrödinger equation. Then, experimental verification is demonstrated over an almost 5-octave wavelength range at 266, 1800, 4000 and 8000 nm by utilizing the same nonlinear medium – air. The experimentally obtained dispersion values of the materials used for the dispersion control show very good agreement with the ones calculated using the material dispersion data and the pulse duration results obtained for 1800 and 4000 nm agree well with the frequency-resolved optical gating measurements. The universality of TIPTOE arises from its phase-matching-free nature and its unprecedented broadband operation range.

Coherent backscattering of a picosecond pulse from a disordered medium: Analysis of the pulse shape in the time domain

1989 ◽  
Vol 39 (7) ◽  
pp. 3728-3731 ◽  
Author(s):  
K. M. Yoo ◽  
K. Arya ◽  
G. C. Tang ◽  
Joseph L. Birman ◽  
R. R. Alfano
Keyword(s):  
Time Domain ◽  
Pulse Shape ◽  
Picosecond Pulse ◽  
Coherent Backscattering ◽  
The Time Domain ◽  
Disordered Medium

Reflection of circumferential modes in a choked nozzle

2002 ◽  
Vol 467 ◽  
pp. 215-239 ◽  
Author(s):  
S. R. STOW ◽  
A. P. DOWLING ◽  
T. P. HYNES
Keyword(s):  
Acoustic Wave ◽  
Low Frequency ◽  
Effective Length ◽  
Mean Flow ◽  
Small Perturbations ◽  
Choked Flow ◽  
First Case ◽  
Propagating Waves ◽  
Flow Through ◽  
Good Agreement

Small perturbations of a choked flow through a thin annular nozzle are investigated. Two cases are considered, corresponding to a ‘choked outlet’ and a ‘choked inlet’ respectively. For the first case, either an acoustic or entropy or vorticity wave is assumed to be travelling downstream towards the nozzle contraction. An asymptotic analysis for low frequency is used to find the reflected acoustic wave that is created. The boundary condition found by Marble & Candel (1977) for a compact choked nozzle is shown to apply to first order, even for circumferentially varying waves. The next-order correction can be expressed as an ‘effective length’ dependent on the mean flow (and hence the particular geometry of the nozzle) in a quantifiable way.For the second case, an acoustic wave propagates upstream and is reflected from a convergent–divergent nozzle. A normal shock is assumed to be present. By considering the interaction of the shock's position and flow perturbations, the reflected propagating waves are found for a compact nozzle. It is shown that a significant entropy disturbance is produced even when the shock is weak, and that for circumferential modes a vorticity wave is also present. Numerical calculations are conducted using a sample geometry and good agreement with the analysis is found at low frequency in both cases, and the range of validity of the asymptotic theory is determined.

scholarly journals Time-domain observation and synthesis of split spheroidal and torsional free oscillations of the 1960 chilean earthquake: Preliminary results

1978 ◽  
Vol 68 (2) ◽  
pp. 325-332 ◽  
Author(s):  
Seth Stein ◽  
Robert J. Geller
Keyword(s):  
Time Domain ◽  
Normal Modes ◽  
Wave Form ◽  
Central Frequency ◽  
Complex Wave ◽  
Location Depth ◽  
The Time Domain ◽  
Theoretical Results ◽  
Good Agreement ◽  
Chilean Earthquake

Abstract The rotationally and elliptically split normal modes of the earth are observed for the 1960 Chilean earthquake by analysis in the time domain. One hundred and fifty hours of the Isabella, California, strain record are narrow band filtered about the central frequency of each split multiplet to isolate the complex wave form resulting from the interference of the different singlets. We compute synthetic seismograms using our previous theoretical results, which show the dependence of the amplitude and phase of the singlets on source location, depth, mechanism, and the position of the receiver. By comparing these synthetics to the filtered record, we conclusively demonstrate the splitting of modes whose splitting had not been definitely resolved: torsional modes (0T3, 0T4) and spheroidal modes (0S4, 0S5). The splitting of 0S2 and 0S3 is reconfirmed. We obtain good agreement between the synthetics and the filtered data for a source mechanism (previously determined from long-period surface waves) of thrust motion on a shallow dipping fault.

scholarly journals Numerical modeling of plasma oscillations with consideration of electron thermal motion

2018 ◽  
pp. 194-206
Author(s):  
А.А. Фролов ◽  
Е.В. Чижонков
Keyword(s):  
Traveling Wave ◽  
Numerical Experiments ◽  
Plasma Temperature ◽  
Thermal Motion ◽  
Initial Region ◽  
Small Perturbations ◽  
Plasma Oscillations ◽  
Lagrangian Variables ◽  
Increasing Temperature ◽  
Good Agreement

Исследовано влияние теплового движения электронов на плоские нерелятивистские нелинейные плазменные колебания. Численно и аналитически показано, что при учете теплового движения колебания трансформируются в бегущую волну. При этом амплитуда волны растет с ростом температуры, что способствует выносу энергии из первоначальной области локализации колебаний. Для численного моделирования построена схема метода конечных разностей на основе эйлеровых переменных. При использовании лагранжевых переменных для приближения малых возмущений получены распределения максимумов электронной плотности в зависимости от температуры плазмы. Аналитические результаты находятся в хорошем соответствии с численными экспериментами. The effect of electron thermal motion on plane nonrelativistic nonlinear plasma oscillations is studied. It is shown numerically and analytically that when the thermal motion is taken into account, the oscillations are transformed to a traveling wave. At the same time, the wave amplitude grows with increasing temperature, which promotes the removal of energy from the initial region of oscillation localization. A finite-difference scheme is proposed for the numerical simulation on the basis of Eulerian variables. When using the Lagrangian variables to approximate small perturbations, the distributions of electron density maxima are obtained depending on the plasma temperature. The obtained analytical results are in good agreement with numerical experiments.

Analytical solution of higher order modes of a dielectric-lined eccentric coaxial cable

2020 ◽  
pp. 1-8
Author(s):  
Mehdi Gholizadeh ◽  
Farrokh Hojjat Kashani
Keyword(s):  
Spectral Response ◽  
Coaxial Cable ◽  
Analytic Method ◽  
Coordinate Systems ◽  
Dielectric Parameters ◽  
Cutoff Frequencies ◽  
Full Wave ◽  
Higher Order Modes ◽  
Validity Range ◽  
Good Agreement

Abstract This study provides an analytic method for the calculation of the cutoff frequencies and waveguide modes of a partially filled eccentric coaxial cable. The method is based on the expressions of the involved electromagnetic fields in bipolar coordinate systems and the validity range of the solution is discussed. It is shown how the waveguide geometry and dielectric parameters may be selected to engineer the lined waveguide's spectral response. Numerical results are included which show good agreement with the corresponding results from full-wave simulations by commercial software.

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