scholarly journals Single-block rockfall dynamics inferred from seismic signal analysis

2017 ◽  
Author(s):  
Clément Hibert ◽  
Jean-Philippe Malet ◽  
Franck Bourrier ◽  
Floriane Provost ◽  
Frédéric Berger ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Scaling Laws ◽  
Scaling Law ◽  
Soft Rock ◽  
Signal Amplitude ◽  
Seismic Signal ◽  
Seismic Signals ◽  
Video Cameras ◽  
The Impact

Abstract. We conducted controlled releases of single blocks within a soft-rock (black marls) gully of the Rioux Bourdoux torrent (French Alps). 28 blocks, with masses ranging from 76 kg to 472 kg, were used for the experiment. An instrumentation combining video cameras and seismometers was deployed along the traveled path. The video cameras allow to reconstruct the trajectories of the blocks and to estimate their velocities at the time of the different impacts with the slope. These data are compared to the recorded seismic signals. As the distance between the falling block and the seismic sensors at the time of each impact is known, we were able to determine the associated seismic signal amplitude corrected from propagation and attenuation effects. We compared the velocity, the loss of potential energy, the kinetic energy and the momentum of the block at each impact to the true amplitude and the energy of the corresponding part of the seismic signal. Our results suggest that the amplitude of the seismic signal scales with the momentum of the block at the impact. We also found a scaling law between the potential energy lost, the kinetic energy and the energy of the seismic radiation generated by the impacts. By combining these scaling laws, we inferred the mass and the velocity before impact of each block directly from the seismic signal. Despite high uncertainties, the values found are close to the true values of the mass and the velocities of the blocks. These relationships also provide new insights to understand the source of high-frequency seismic signals generated by rockfalls.

scholarly journals Single-block rockfall dynamics inferred from seismic signal analysis

2017 ◽  
Vol 5 (2) ◽  
pp. 283-292 ◽  
Author(s):  
Clément Hibert ◽  
Jean-Philippe Malet ◽  
Franck Bourrier ◽  
Floriane Provost ◽  
Frédéric Berger ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Soft Rock ◽  
Seismic Energy ◽  
Signal Amplitude ◽  
Seismic Signal ◽  
Seismic Signals ◽  
Video Cameras ◽  
Radiated Seismic Energy ◽  
The Impact

Abstract. Seismic monitoring of mass movements can significantly help to mitigate the associated hazards; however, the link between event dynamics and the seismic signals generated is not completely understood. To better understand these relationships, we conducted controlled releases of single blocks within a soft-rock (black marls) gully of the Rioux-Bourdoux torrent (French Alps). A total of 28 blocks, with masses ranging from 76 to 472 kg, were used for the experiment. An instrumentation combining video cameras and seismometers was deployed along the travelled path. The video cameras allow reconstructing the trajectories of the blocks and estimating their velocities at the time of the different impacts with the slope. These data are compared to the recorded seismic signals. As the distance between the falling block and the seismic sensors at the time of each impact is known, we were able to determine the associated seismic signal amplitude corrected for propagation and attenuation effects. We compared the velocity, the potential energy lost, the kinetic energy and the momentum of the block at each impact to the true amplitude and the radiated seismic energy. Our results suggest that the amplitude of the seismic signal is correlated to the momentum of the block at the impact. We also found relationships between the potential energy lost, the kinetic energy and the seismic energy radiated by the impacts. Thanks to these relationships, we were able to retrieve the mass and the velocity before impact of each block directly from the seismic signal. Despite high uncertainties, the values found are close to the true values of the masses and the velocities of the blocks. These relationships allow for gaining a better understanding of the physical processes that control the source of high-frequency seismic signals generated by rockfalls.

scholarly journals Scaling Laws and Regime Transitions of Macroturbulence in Dry Atmospheres

2008 ◽  
Vol 65 (7) ◽  
pp. 2153-2173 ◽  
Author(s):  
Tapio Schneider ◽  
Christopher C. Walker
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Surface Potential ◽  
Scaling Laws ◽  
Potential Temperature ◽  
Eddy Kinetic Energy ◽  
Eddy Flux ◽  
Available Potential Energy ◽  
Mean Fields ◽  
The Mean

Abstract In simulations of a wide range of circulations with an idealized general circulation model, clear scaling laws of dry atmospheric macroturbulence emerge that are consistent with nonlinear eddy–eddy interactions being weak. The simulations span several decades of eddy energies and include Earth-like circulations and circulations with multiple jets and belts of surface westerlies in each hemisphere. In the simulations, the eddy available potential energy and the barotropic and baroclinic eddy kinetic energy scale linearly with each other, with the ratio of the baroclinic eddy kinetic energy to the barotropic eddy kinetic energy and eddy available potential energy decreasing with increasing planetary radius and rotation rate. Mean values of the meridional eddy flux of surface potential temperature and of the vertically integrated convergence of the meridional eddy flux of zonal momentum generally scale with functions of the eddy energies and the energy-containing eddy length scale, with a few exceptions in simulations with statically near-neutral or neutral extratropical thermal stratifications. Eddy energies scale with the mean available potential energy and with a function of the supercriticality, a measure of the near-surface slope of isentropes. Strongly baroclinic circulations form an extended regime in which eddy energies scale linearly with the mean available potential energy. Mean values of the eddy flux of surface potential temperature and of the vertically integrated eddy momentum flux convergence scale similarly with the mean available potential energy and other mean fields. The scaling laws for the dependence of eddy fields on mean fields exhibit a regime transition between a regime in which the extratropical thermal stratification and tropopause height are controlled by radiation and convection and a regime in which baroclinic entropy fluxes modify the extratropical thermal stratification and tropopause height. At the regime transition, for example, the dependence of the eddy flux of surface potential temperature and the dependence of the vertically integrated eddy momentum flux convergence on mean fields changes—a result with implications for climate stability and for the general circulation of an atmosphere, including its tropical Hadley circulation.

scholarly journals Implementing and testing theoretical fission fragment yields in a Hauser-Feshbach statistical decay framework

2018 ◽  
Vol 169 ◽  
pp. 00006 ◽  
Author(s):  
Patrick Jaffke ◽  
Peter Möller ◽  
Ionel Stetcu ◽  
Patrick Talou ◽  
Christelle Schmitt
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Fission Fragment ◽  
Energy Surface ◽  
Prompt Neutron ◽  
Fission Fragments ◽  
Statistical Decay ◽  
Γ Ray ◽  
The Impact

We implement fission fragment yields, calculated using Brownian shape-motion on a macroscopic-microscopic potential energy surface in six dimensions, into the Hauser-Feshbach statistical decay code CGMF. This combination allows us to test the impact of utilizing theoretically-calculated fission fragment yields on the subsequent prompt neutron and γ-ray emission. We draw connections between the fragment yields and the total kinetic energy TKE of the fission fragments and demonstrate that the use of calculated yields can introduce a difference in the 〈TKE〉 and, thus, the prompt neutron multiplicity v, as compared with experimental fragment yields. We deduce the uncertainty on the 〈TKE〉 and v from this procedure and identify possible applications.

Nonlinear Dynamic Modeling and Vibration Analysis of Faulty Rolling Bearing Based on Collision Impact

2021 ◽  
Vol 16 (6) ◽  
Author(s):  
Longkui Zheng ◽  
Yang Xiang ◽  
Chenxing Sheng
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Dynamic Model ◽  
Nonlinear Dynamic ◽  
Rolling Bearing ◽  
Hertzian Contact ◽  
Nonlinear Dynamic Model ◽  
Impact System ◽  
Rolling Element ◽  
The Impact

Abstract This study proposes a new nonlinear dynamic model of rolling bearing faults based on a collision impact system. The dynamic model accounts for the collision impact system consisting of the rolling elements and localized faults according to the nonlinear Hertzian contact. First, considering the impact of the rolling element and fault structure, the collision impact system between rolling element and localized fault is established, and the vibration responses of the collision impact system can be obtained. Second, the overall rolling bearing is treated as a mass-spring model, and the contact between the rolling element and raceway is treated as a nonlinear spring that conforms to the Hertzian contact deformation theory. Third, according to the Lagrange equation, overall potential energy, overall kinetic energy, elastic potential energy, and kinetic energy of the collision impact system are used to describe the vibration characteristics. Considering the impact of collision impact systems, a nonlinear dynamic model of rolling bearing faults is established. The simulated acceleration results based on the nonlinear dynamic model are compared to experimental results. The comparison indicates that the numerical model can be used to predict the vibration characteristics of rolling bearings faults effectively.

scholarly journals Soft projectile impact forces measurement using Hopkinson bars: application to ice, artificial bird and rubber

2021 ◽  
Vol 250 ◽  
pp. 01008
Author(s):  
Ramón del Cuvillo ◽  
Jose Alfonso Artero-Guerrero ◽  
Jesús Pernas-Sánchez ◽  
Jorge López Puente
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Soft Materials ◽  
Peak Force ◽  
Video Cameras ◽  
Impact Forces ◽  
Compression Strain ◽  
Experimental Campaign ◽  
The Impact ◽  
Semiconductor Strain

This work presents an experimental campaign of impacts of soft projectiles to measure the induced force during the impact. Three different materials acting as soft impactors that could strike against a aeronautical structural component: ice, artificial bird and rubber have been impacted at several velocities against an aluminium Hopkinson bar. This device has been instrumented with semiconductor strain gauges that allow to obtain the induced compression strain. Additionally, all the impacts were recorded using high-speed video cameras, allowing the kinematic analysis of the projectile during the impact. After the results study, it has been concluded that there is a linear dependency between the kinetic energy and the peak force for all three materials. Added to that, it has been proved that the higher peak force corresponds to ice, despite the kinetic energy, followed by rubber and finally the artificial bird. In addition, while ice and artificial bird projectiles get radially dispersed after the impact, rubber spheres rebound due to its different behaviour. The obtained data is of great interest to design structures which could be subjected to impacts of soft materials such as aeronautic structures

High-resolution seismic signals from band-limited data using scaling laws of wavelet transforms

Geophysics ◽  
2009 ◽  
Vol 74 (2) ◽  
pp. WA143-WA152 ◽  
Author(s):  
K. R. Devi ◽  
Herb Schwab
Keyword(s):  
High Resolution ◽  
Power Law ◽  
Seismic Data ◽  
Wavelet Transforms ◽  
Scaling Laws ◽  
Scaling Law ◽  
Well Log ◽  
Seismic Signals ◽  
Local Scaling ◽  
Seismic Wavelet

Time-scale spectra, obtained from seismic data wavelet transforms, are useful in analyzing local scaling properties of seismic signals. In particular, the wavelet transform modulus maxima (WTMM) spectra, obtained by following the local extrema of wavelet transforms along a constant phase line, describe characteristics of discontinuities such as interfaces. They also show a smooth behavior as a function of scale and thus allow us to derive local scaling laws. We use scaling behavior of WTMM spectra to enhance the bandwidth of seismic data. An analysis of well-log scaling behaviors and the seismic data shows that, whereas the WTMM spectrum of well logs at each interface exhibits a power-law behavior as a function of scale, the corresponding seismic signal spectrum shows a more complicated behavior, arising from seismic wavelet effects. Under the assumption that local well-log power-law behavior holds in general, a scaling law for seismic signals can be derived in terms of parameters that describe subsurface scaling effects and the seismic wavelet. A stable estimation of these parameters can be carried out simultaneously, as a function of time and over the seismic bandwidth, using the modified scaling law. No well-log information is needed to derive the seismic wavelet. Then wavelet transforms can be corrected for seismic wavelet effects and a high-resolution signal reconstructed. This reconstructed high-resolution signal can be used to map features that might not be obvious in the original seismic data, such as small faults, fractures, and fine-scale variations within channel margins.

NOISE AND TARGET SIGNALS SIMULATION IN PASSIVE SEISMIC LOCATION SYSTEMS

2018 ◽  
pp. 73-78
Author(s):  
Yu. V. Morozov ◽  
M. A. Rajfeld ◽  
A. A. Spektor
Keyword(s):  
Pulse Sequence ◽  
Signal To Noise Ratio ◽  
Seismic Signal ◽  
Seismic Signals ◽  
Simulation Procedure ◽  
Proposed Model ◽  
Seismic Location ◽  
Passive Seismic ◽  
System Characteristics ◽  
Primary Pulse

The paper proposes the model of a person seismic signal with noise for the investigation of passive seismic location system characteristics. The known models based on Gabor and Berlage pulses have been analyzed. These models are not able wholly to consider statistical properties of seismic signals. The proposed model is based on almost cyclic character of seismic signals, Gauss character of fluctuations inside a pulse, random amplitude change from pulse to pulse and relatively small fluctuation of separate pulses positions. The simulation procedure consists of passing the white noise through a linear generating filter with characteristics formed by real steps of a person, and the primary pulse sequence modulation by Gauss functions. The model permits to control the signal-to-noise ratio after its reduction to unity and to vary pulse shifts with respect to person steps irregularity. It has been shown that the model of a person seismic signal with noise agrees with experimental data.

scholarly journals A New Method to Determine the Impact of Individual Field Quantities on Cycle-to-Cycle Variations in a Spark-Ignited Gas Engine

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4136
Author(s):  
Clemens Gößnitzer ◽  
Shawn Givler
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Negative Impact ◽  
Operating Conditions ◽  
Engine Operation ◽  
Gas Engine ◽  
Cycle Simulation ◽  
Simulation Results ◽  
The Impact

Cycle-to-cycle variations (CCV) in spark-ignited (SI) engines impose performance limitations and in the extreme limit can lead to very strong, potentially damaging cycles. Thus, CCV force sub-optimal engine operating conditions. A deeper understanding of CCV is key to enabling control strategies, improving engine design and reducing the negative impact of CCV on engine operation. This paper presents a new simulation strategy which allows investigation of the impact of individual physical quantities (e.g., flow field or turbulence quantities) on CCV separately. As a first step, multi-cycle unsteady Reynolds-averaged Navier–Stokes (uRANS) computational fluid dynamics (CFD) simulations of a spark-ignited natural gas engine are performed. For each cycle, simulation results just prior to each spark timing are taken. Next, simulation results from different cycles are combined: one quantity, e.g., the flow field, is extracted from a snapshot of one given cycle, and all other quantities are taken from a snapshot from a different cycle. Such a combination yields a new snapshot. With the combined snapshot, the simulation is continued until the end of combustion. The results obtained with combined snapshots show that the velocity field seems to have the highest impact on CCV. Turbulence intensity, quantified by the turbulent kinetic energy and turbulent kinetic energy dissipation rate, has a similar value for all snapshots. Thus, their impact on CCV is small compared to the flow field. This novel methodology is very flexible and allows investigation of the sources of CCV which have been difficult to investigate in the past.

scholarly journals On the Impact and Mitigation of Signal Crosstalk in Ground-Based and Low Altitude Airborne GNSS-R

2021 ◽  
Vol 13 (6) ◽  
pp. 1085
Author(s):  
Corentin Lubeigt ◽  
Lorenzo Ortega ◽  
Jordi Vilà-Valls ◽  
Laurent Lestarquit ◽  
Eric Chaumette
Keyword(s):  
Specular Reflection ◽  
Signal Amplitude ◽  
Satellite System ◽  
Mitigation Strategies ◽  
Variance Estimator ◽  
Single Source ◽  
Dual Source ◽  
Reflected Signal ◽  
The Impact ◽  
Signal Crosstalk

Global Navigation Satellite System Reflectometry (GNSS-R) is a powerful way to retrieve information from a reflecting surface by exploiting GNSS as signals of opportunity. In dual antenna conventional GNSS-R architectures, the reflected signal is correlated with a clean replica to obtain the specular reflection point delay and Doppler estimates, which are further processed to obtain the GNSS-R product of interest. An important problem that may appear for low elevation satellites is signal crosstalk, that is the direct line-of-sight signal leaks into the antenna dedicated to the reflected signal. Such crosstalk may degrade the overall system performance if both signals are very close in time, similar to multipath in standard GNSS receivers, the reason why mitigation strategies must be accounted for. In this article: (i) we first provide a geometrical analysis to justify that the estimation performance is only affected for low height receivers; (ii) then, we analyze the impact of crosstalk if not taken into account, by comparing the single source conditional maximum likelihood estimator (CMLE) performance in a dual source context with the corresponding Cramér–Rao bound (CRB); (iii) we discuss dual source estimators as a possible mitigation strategy; and (iv) we investigate the performance of the so-called variance estimator, which is designed to eliminate the coherent signal part, compared to both the CRB and non-coherent dual source estimators. Simulation results are provided for representative GNSS signals to support the discussion. From this analysis, it is found that: (i) for low enough reflected-to-direct signal amplitude ratios (RDR), the crosstalk has no impact on standard single source CMLEs; (ii) for high enough signal-to-noise ratios (SNR), the dual source estimators are efficient irrespective of the RDR, then being a promising solution for any reflected signal scenario; (iii) non-coherent dual source estimators are also efficient at high SNR; and (iv) the variance estimator is efficient as long as the non-coherent part of the signal is dominant.

scholarly journals Asymmetric Unimodal Maps with Non-universal Period-Doubling Scaling Laws

2020 ◽  
Vol 379 (1) ◽  
pp. 103-143
Author(s):  
Oleg Kozlovski ◽  
Sebastian van Strien
Keyword(s):  
Scaling Laws ◽  
Scaling Law ◽  
Period Doubling ◽  
Cantor Sets ◽  
Unimodal Maps ◽  
Renormalization Theory

Abstract We consider a family of strongly-asymmetric unimodal maps $$\{f_t\}_{t\in [0,1]}$$ { f t } t ∈ [ 0 , 1 ] of the form $$f_t=t\cdot f$$ f t = t · f where $$f:[0,1]\rightarrow [0,1]$$ f : [ 0 , 1 ] → [ 0 , 1 ] is unimodal, $$f(0)=f(1)=0$$ f ( 0 ) = f ( 1 ) = 0 , $$f(c)=1$$ f ( c ) = 1 is of the form and $$\begin{aligned} f(x)=\left\{ \begin{array}{ll} 1-K_-|x-c|+o(|x-c|)&{} \text{ for } x<c, \\ 1-K_+|x-c|^\beta + o(|x-c|^\beta ) &{} \text{ for } x>c, \end{array}\right. \end{aligned}$$ f ( x ) = 1 - K - | x - c | + o ( | x - c | ) for x < c , 1 - K + | x - c | β + o ( | x - c | β ) for x > c , where we assume that $$\beta >1$$ β > 1 . We show that such a family contains a Feigenbaum–Coullet–Tresser $$2^\infty $$ 2 ∞ map, and develop a renormalization theory for these maps. The scalings of the renormalization intervals of the $$2^\infty $$ 2 ∞ map turn out to be super-exponential and non-universal (i.e. to depend on the map) and the scaling-law is different for odd and even steps of the renormalization. The conjugacy between the attracting Cantor sets of two such maps is smooth if and only if some invariant is satisfied. We also show that the Feigenbaum–Coullet–Tresser map does not have wandering intervals, but surprisingly we were only able to prove this using our rather detailed scaling results.

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