Intrinsic and scattering attenuations of the Sichuan-Yunnan region in China from S coda waves

Seismic attenuation is a fundamental property of the Earth's media.Attenuation structure for the complicated geological structures with strong seismicity in the Sichuan-Yunnan region is poorly studied.In this study,we collected 108,399 waveforms of 11,517 local small earthquakes with magnitudes between 1.5 and 3.5 from January 2014 to September 2021 in the Sichuan-Yunnan region and its adjacent areas.We employed an envelope inversion technique for separating the intrinsic and scattering attenuations of the S coda wave,and obtained the intrinsic and scattering attenuation structures for frequencies between 0.25 and 8.00 Hz.The attenuation structures correlate well with the geological units,and some major faults mark the attenuation variations where historic large earthquakes have occurred.The regional average attenuation shows a negative frequency dependence.The average scattering attenuation has a faster descending rate than the average intrinsic attenuation,and is dominant at low frequencies,while at high frequencies the average intrinsic attenuation is stronger.The lateral variation in the intrinsic attenuation is consistent with the variation in heat flow,the scattering attenuation may be related to the scatter distribution and size.The total attenuation is consistent with the previous studies in this region,and the separate intrinsic and scattering attenuation may be useful in understanding regional tectonics and important in earthquake prevention and disaster reduction.

A seismic elastic moduli module for the measurements of low-frequency wave dispersion and attenuation of fluid-saturated rocks under different pressures

Knowledge about the seismic elastic modulus dispersion,and associated attenuation,in fluid-saturated rocks is essential for better interpretation of seismic observations taken as part of hydrocarbon identification and time-lapse seismic surveillance of both conventional and unconventional reservoir and overburden performances.A Seismic Elastic Moduli Module has been developed,based on the forced-oscillations method,to experimentally investigate the frequency dependence of Young's modulus and Poisson's ratio,as well as the inferred attenuation,of cylindrical samples under different confining pressure conditions.Calibration with three standard samples showed that the measured elastic moduli were consistent with the published data,indicating that the new apparatus can operate reliably over a wide frequency range of f∈[1-2000,10^(6)]Hz.The Young's modulus and Poisson's ratio of the shale and the tight sandstone samples were measured under axial stress oscillations to assess the frequency-and pressure-dependent effects.Under dry condition,both samples appear to be nearly frequency independent,with weak pressure dependence for the shale and significant pressure dependence for the sandstone.In particular,it was found that the tight sandstone with complex pore microstructure exhibited apparent dispersion and attenuation under brine or glycerin saturation conditions,the levels of which were strongly influenced by the increased effective pressure.In addition,the measured Young's moduli results were compared with the theoretical predictions from a scaled poroelastic model with a reasonably good agreement,revealing that the combined fluid flow mechanisms at both mesoscopic and microscopic scales possibly responsible for the measured dispersion.

Layered metastructure containing freely-designed local resonators for wave attenuation

Combining periodic layered structure with three-dimensional cylindrical local resonators,a hybrid metastructure with improved wave isolation ability was designed and investigated through theoretical and numerical approaches.The metastructure is composed of periodic rubber layers and concrete layers embedded with three-dimensional resonators,which can be freely designed with multi local resonant frequencies to attenuate vibrations at required frequencies and widen the attenuation bandgap.The metastructure can also effectively attenuate seismic responses.Compared with layered rubber-based structures,the metastructure has more excellent wave attenuation effects with greater attenuation and wider bandgap.

P-and SV-wave dispersion and attenuation in saturated microcracked porous rock with aligned penny-shaped fractures

P-and SV-wave dispersion and attenuation have been extensively investigated in saturated poroelastic media with aligned fractures.However,there are few existing models that incorporate the multiple wave attenuation mechanisms from the microscopic scale to the macroscopic scale.Hence,in this work,we developed a unified model to incorporate the wave attenuation mechanisms at different scales,which includes the microscopic squirt flow between the microcracks and pores,the mesoscopic wave-induced fluid flow between fractures and background(FB-WIFF),and the macroscopic Biot's global flow and elastic scattering(ES)from the fractures.Using Tang's modified Biot's theory and the mixed-boundary conditions,we derived the exact frequency-dependent solutions of the scattering problem for a single penny-shaped fracture with oblique incident P-and SV-waves.We then developed theoretical models for a set of aligned fractures and randomly oriented fractures using the Foldy approximation.The results indicated that microcrack squirt flow considerably influences the dispersion and attenuation of P-and SV-wave velocities.The coupling effects of microcrack squirt flow with the FB-WIFF and ES of fractures cause much higher velocity dispersion and attenuation for P waves than for SV waves.Randomly oriented fractures substantially reduce the attenuation caused by the FB-WIFF and ES,particularly for the ES attenuation of SV waves.Through a comparison with existing models in the limiting cases and previous experimental measurements,we validated our model.

Transient elastography with controlled attenuation parameter for the diagnosis of colorectal polyps in patients with nonalcoholic fatty liver disease

BACKGROUND The severity of nonalcoholic fatty liver disease(NAFLD)and lipid metabolism are related to the occurrence of colorectal polyps.Liver-controlled attenuation parameters(liver-CAPs)have been established to predict the prognosis of hepatic steatosis patients.AIM To explore the risk factors associated with colorectal polyps in patients with NAFLD by analyzing liver-CAPs and establishing a diagnostic model.METHODS Patients who were diagnosed with colorectal polyps in the Department of Gastroenterology of our hospital between June 2021 and April 2022 composed the case group,and those with no important abnormalities composed the control group.The area under the receiver operating characteristic curve was used to predict the diagnostic efficiency.Differences were considered statistically significant when P<0.05.RESULTS The median triglyceride(TG)and liver-CAP in the case group were significantly greater than those in the control group(mmol/L,1.74 vs 1.05;dB/m,282 vs 254,P<0.05).TG and liver-CAP were found to be independent risk factors for colorectal polyps,with ORs of 2.338(95%CI:1.154–4.733)and 1.019(95%CI:1.006–1.033),respectively(P<0.05).And there was no difference in the diagnostic efficacy between liver-CAP and TG combined with liver-CAP(TG+CAP)(P>0.05).When the liver-CAP was greater than 291 dB/m,colorectal polyps were more likely to occur.CONCLUSION The levels of TG and liver-CAP in patients with colorectal polyps are significantly greater than those patients without polyps.Liver-CAP alone can be used to diagnose NAFLD with colorectal polyps.

Sensitivity of seismic attenuation and dispersion to dynamic elastic interactions of connected fractures: Quasi-static finite element modeling study

Prediction of seismic attenuation and dispersion that are inherently sensitive to hydraulic and elastic properties of the medium of interest in the presence of mesoscopic fractures and pores,is of great interest in the characterization of fractured formations.This has been very difficult,however,considering that stress interactions between fractures and pores,related to their spatial distributions,tend to play a crucial role on affecting overall dynamic elastic properties that are largely unexplored.We thus choose to quantitatively investigate frequency-dependent P-wave characteristics in fractured porous rocks at the scale of a representative sample using a numerical scale-up procedure via performing finite element modelling.Based on 2-D numerical quasi-static experiments,effects of fracture and fluid properties on energy dissipation in response to wave-induced fluid flow at the mesoscopic scale are quantified via solving Biot's equations of consolidation.We show that numerical results are sensitive to some key characteristics of probed synthetic rocks containing unconnected and connected fractures,demonstrating that connectivity,aperture and inclination of fractures as well as fracture infills exhibit strong impacts on the two manifestations of WIFF mechanisms in the connected scenario,and on resulting total wave attenuation and phase velocity.This,in turn,illustrates the importance of these two WIFF mechanisms in fractured rocks and thus,a deeper understanding of them may eventually allow for a better characterization of fracture systems using seismic methods.Moreover,this presented work combines rock physics predictions with seismic numerical simulations in frequency domain to illustrate the sensitivity of seismic signatures on the monitoring of an idealized geologic CO_(2) sequestration in fractured reservoirs.The simulation demonstrates that these two WIFF mechanisms can strongly modify seismic records and hence,indicating that incorporating the two energy dissipation mechanisms in the geophysical interpretation can potentially improving the monitoring and surveying of fluid variations in fractured formations.

Oxidative Molecular Layer Deposition Tailoring Eco-Mimetic Nanoarchitecture to Manipulate Electromagnetic Attenuation and Self-Powered Energy Conversion

Advanced electromagnetic devices,as the pillars of the intelligent age,are setting off a grand transformation,redefining the structure of society to present pluralism and diversity.However,the bombardment of electromagnetic radiation on society is also increasingly serious along with the growing popularity of"Big Data".Herein,drawing wisdom and inspiration from nature,an eco-mimetic nanoarchitecture is constructed for the first time,highly integrating the advantages of multiple components and structures to exhibit excellent electromagnetic response.Its electromagnetic properties and internal energy conversion can be flexibly regulated by tailoring microstructure with oxidative molecular layer deposition(oMLD),providing a new cognition to frequency-selective microwave absorption.The optimal reflection loss reaches≈−58 dB,and the absorption frequency can be shifted from high frequency to low frequency by increasing the number of oMLD cycles.Meanwhile,a novel electromagnetic absorption surface is designed to enable ultra-wideband absorption,covering almost the entire K and Ka bands.More importantly,an ingenious self-powered device is constructed using the eco-mimetic nanoarchitecture,which can convert electromagnetic radiation into electric energy for recycling.This work offers a new insight into electromagnetic protection and waste energy recycling,presenting a broad application prospect in radar stealth,information communication,aerospace engineering,etc.

A case study of blasting vibration attenuation based on wave component characteristics

A typical blasting vibration wave is a composite wave,and its attenuation law is affected by the type of dominant wave component.The purpose of the present study is to establish an attenuation equation of the peak particle velocity(PPV),taking into account the attenuation characteristics of P-,S-and R-waves in the blasting vibration wave.Field blasting tests were carried out as a case to specifically apply the proposed equation.In view of the fact that the discrete properties of rock mass will inevitably cause the uncertainty of blasting vibration,we also carried out a probability analysis of PPV uncertainty,and introduced the concept of reliability to evaluate blasting vibration.The results showed that the established attenuation equation had a higher prediction accuracy,and can be considered as a promising equation implemented on more complex sites.The adopted uncertainty analysis method can comprehensively take account of the attenuation law of blasting vibration measured on site and discrete properties of rock masses.The obtained distribution of the PPV uncertainty factor can quantitatively evaluate the reliability of blasting vibration,which is a powerful and necessary supplement to the PPV attenuation equation.

Analysis on Attenuation Efficiency of Lightning Current by Lightning Interceptor

Lightning interception technology is one of the three core technical systems of regional lightning protection theory.Among them,the omni-directional multi-pulse lightning interceptor(hereinafter referred to as lightning interceptor,the same below)has the ability to attenuate lightning current≥40%and significantly reduce the intensity of the spatial electromagnetic field around the lightning point.In order to explore the attenuation mechanism and effect of lightning interceptor to lightning current,this paper analyzed a lightning stroke process at 16:00 on August 19,2022,and tried to explain the attenuation effect of lightning interceptor to lightning current with the physical parameters of lightning stroke.

Harmonics in the Squirrel Cage Induction Motor Analytic Calculation-Part Ⅰ: Differential Leakage, Attenuation, Asynchronous Parasitic Torques

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynchronous parasitic torques have been discussed in great detail in the literature, but always separately, for a long time. However, systematization of the phenomenon still awaits. Therefore, it is worth summarizing the completeness of the phenomena in a single study – with a new approach at the same time-in order to reveal the relationships between them. The role of rotor slot number is emphasized much more than before. An existing, commonly used, but still impractical basic figure has been modified to more clearly demonstrate the response of the rotor for the harmonics of the stator. The need to treat differential leakage, asynchronous parasitic torques and attenuation together will be demonstrated: new formula for asynchronous parasitic torque is derived;the long-used characteristic curves for differential leakage and attenuation used separately so far was merged into one, correct curve in order to provide a correct design guide for the engineers.

Four-stage cascaded variable optical attenuator with large attenuation range for quantum key distribution

A four-stage cascaded variable optical attenuator(VOA)with a large attenuation range is presented.The VOA is based on a Mach–Zehnder interferometer(MZI)and fabricated in a silica-based planar lightwave circuit(PLC)platform.The thermo-optic effect is used to achieve intensity modulation.The measured maximum attenuation of the four-stage cascaded VOA is 88.38 d B.The chip is also tested in a quantum key distribution(QKD)system to generate signal and decoy states.The mean photon number after attenuation of the four-stage cascaded VOA is less than 0.1,which can meet the requirement of QKD.

Vibration attenuation of meta-mortar with spring-mass resonators

Metamaterial based on local resonance has excellent vibration attenuation ability in low frequency.In this research,an attempt was performed to make meta-mortar with spring-mass resonators to attenuate vibration and shock hazards.Single-spring-mass resonators and dual-spring-mass resonators were designed and made using lead or aluminum blocks and SWPB springs encased by PMMA(polymethyl methacrylate)or aluminum frames.These resonators were placed into mortar blocks to make metamortar specimens.Vibration attenuation effect was investigated by sweeping vibration with frequency from 50 Hz to 2000 Hz.All these meta-mortar blocks exhibit excellent vibration attenuation ability in the designed band gaps.With dual-spring-mass resonators,meta-mortar blocks have two distinct vibration attenuation bands.

Stable attenuation-compensated reverse time migration and its application to land seismic data

Intrinsic attenuation of the earth causes energy loss and phase distortion in seismic wave propagation.To obtain high-resolution imaging results,these negative effects must be considered during reverse time migration(RTM).We can easily implement attenuation-compensated RTM using the constant Q viscoacoustic wave equation with decoupled amplitude attenuation and phase dispersion terms.However,the nonphysical amplitude-compensation process will inevitably amplify the high-frequency noise in the wavefield in an exponential form,causing the numerical simulation to become unstable.This is due to the fact that the amplitude of the compensation grows exponentially with frequency.In order to achieve stable attenuation-compensated RTM,we modify the analytic expression of the attenuation compensation extrapolation operator and make it only compensate for amplitude loss within the effective frequency band.Based on this modified analytic formula,we then derive an explicit time-space domain attenuation compensation extrapolation operator.Finally,the implementation procedure of stable attenuation-compensated RTM is presented.In addition to being simple to implement,the newly proposed attenuation-compensated extrapolation operator is superior to the conventional low-pass filter in suppressing random noise,which will further improve the imaging resolution.We use two synthetic and one land seismic datasets to verify the stability and effectiveness of the proposed attenuationcompensated RTM in improving imaging resolution in viscous media.

Two-Way ANOVA for Comparison of Remedial Nutrient Solution and Enhanced Natural Attenuation Using SPSS for Treating Petroleum Contaminated Soils

Statistical comparison of two remediation methods: Remedial nutrient solution and enhanced natural attenuation were analyzed in terms of TPH of different soil samples collected from Khana Local Government Area of Rivers State, Nigeria at different locations and placed inside sample bottles labelled A to D and replicated into two, one for each of the above treatment technique. The TPH of the soil was determined using GC analyzer after solvent extraction was carried out using hexane/dichloromethane mixture. Three batches of treatment were performed on the samples at every interval of eight weeks for a duration of six months. The result obtained was analyzed using a two-way ANOVA factorial experimental design to test the significance of the various sources of variation. From the result obtained, source of variation for sample and interactions were non-significantly different from each other which means that irrespective of the number of samples analyzed or the combination of both samples and batches of treatment, they will still not be significantly different from each other. The source of variation for batch and replications were significantly different from each other and this means that irrespective of the batches of treatment applied or the number of replications (methods of treatment used), they will always be significantly different from each other. The individual comparison of each sample showed that the efficiency of the Remedial Nutrient Solution method was better than Enhanced Natural Attenuation method.

Measuring stellar populations,dust attenuation and ionized gas at kpc scales in 10010 nearby galaxies using the integral field spectroscopy from MaNGA

As one of the three major experiments of the fourth-generation Sloan Digital Sky Survey(SDSS-IV),the Mapping Nearby Galaxies at Apatch Point Observatory(MaNGA)survey has obtained high-quality integral field spectroscopy(IFS)with a resolution of 1–2 kpc for104galaxies in the local universe during its six-year operation from July 2014 through August 2020.It is crucial to reliably measure the physical properties of the different components in each spectrum before one can use the data for any scientific study.In the past years we have made lots of efforts to develop a novel technique of full spectral fitting,which estimates a model-independent dust attenuation curve from each spectrum,thus allowing us to break the degeneracy between dust attenuation and stellar population properties when fitting the spectrum with stellar population synthesis models.We have applied our technique to the final data release of Ma NGA,and obtained measurements of stellar population properties and emission line parameters,as well as the kinematics and dust attenuation of both stellar and ionized gas components.In this paper we describe our technique and the content and format of our data products.The whole dataset is publicly available in Science Data Bank with the link https://doi.org/10.57760/sciencedb.j00113.00088.

Vegetation scattering attenuation characteristics of terahertz wave

A terahertz(THz)wave transmitted through vegetation experiences both absorption and scattering caused by the air molecules and leaves.This paper presents the scattering attenuation characteristics of vegetation in a THz range.The theoretical path loss model near the vegetation yields the average attenuation of THz waves in a mixed channel composed of air and vegetation leaves.Furthermore,a simplified model of the vegetation structure is obtained for generic vegetation types based on a variety of parameters,such as leaf size,distribution,and moisture content.Finally,based on specific vegetation species and different levels of air humidity,the attenuation characteristics under different conditions are calculated,and the influence of different model parameters on the attenuation characteristics is obtained.

A nonparametric spectrum estimation method for dispersion and attenuation analysis of borehole acoustic measurements

Dispersion and attenuation analysis can be used to determine formation anisotropy induced by fractures,or stresses.In this paper,we propose a nonparametric spectrum estimation method to get phase dispersion characteristics and attenuation coefficient.By designing an appropriate vector filter,phase velocity,attenuation coefficient and amplitude can be inverted from the waveform recorded by the receiver array.Performance analysis of this algorithm is compared with Extended Prony Method(EPM)and Forward and Backward Matrix Pencil(FBMP)method.Based on the analysis results,the proposed method is capable of achieving high resolution and precision as the parametric spectrum estimation methods.At the meantime,it also keeps high stability as the other nonparametric spectrum estimation methods.At last,applications to synthetic waveforms modeled using finite difference method and real data show its efficiency.The real data processing results show that the P-wave attenuation log is more sensitive to oil formation compared to S-wave;and the S-wave attenuation log is more sensitive to shale formation compared to P-wave.

Modeling wave attenuation by vegetation with accompanying currents in SWAN

Coastal wetlands such as salt marshes and mangroves provide important protection against stormy waves.Accurate assessments of wetlands’capacity in wave attenuation are required to safely utilize their protection services.Recent studies have shown that tidal currents have a significant impact on wetlands’wave attenuation capacity,but such impact has been rarely considered in numerical models,which may lead to overestimation of wave attenuation in wetlands.This study modified the SWAN(Simulating Waves Nearshore)model to account for the effect of accompanying currents on vegetation-induced wave dissipation.Furthermore,this model was extended to include automatically derived vegetation drag coefficients,spatially varying vegetation height,and Doppler Effect in combined current-wave flows.Model evaluation against an analytical model and flume data shows that the modified model can accurately simulate wave height change in combined current-wave flows.Subsequently,we applied the new model to a mangrove wetland on Hailing Island in China with a special focus on the effect of currents on wave dissipation.It is found that the currents can either increase or decrease wave attenuation depending on the ratio of current velocity to the amplitude of the horizontal wave orbital velocity,which is in good agreement with field observations.Lastly,we used Hailing Island site as an example to simulate wave attenuation by vegetation under hypothetical storm surge conditions.Model results indicate that when currents are 0.08–0.15 m/s and the incident wave height is 0.75–0.90 m,wetlands’wave attenuation capacity can be reduced by nearly 10%compared with pure wave conditions,which provides implications for critical design conditions for coastal safety.The obtained results and the developed model are valuable for the design and implementation of wetland-based coastal defense.The code of the developed model has been made open source,in the hope to assist further research and coastal management.

Experimental Study on the Attenuation Law of Vibration Wave Propagation in Natural Gas Wells in Coal-Gas Cross-Mining Area

Aiming at the safety distance between coal mining working face and natural gas wells in the cross-mining area of multiple mineral resources, the cross- mining area of gas and coal resources in the Ordos Basin is taken as the engineering background. An anti-collision early warning technology method based on vibration wave propagation attenuation monitoring is proposed to prevent collision accidents between road headers and natural gas wells. Through the steel pipe and steel pipe concrete knocking vibration test and underground digging vibration test, the research results show that: The exponential decay coefficients of the vibration wave in steel pipe, steel pipe concrete and coal rock respectively are 0.1, 0.1140 and 0.03, which are all in accordance with the exponential decay law, and the vibration wave firstly decays sharply and then decays slowly;the formula for the distance from the road header to the natural gas well was derived based on the vibration attenuation formula, to provide a new method for realizing the problem of precise and coordinated extraction by surface monitoring of the distance from down hole road headers to gas wells, collision prevention prediction and warning and prevention of collision of extraction equipment with gas wells.

Layered power scheduling optimization of PV hydrogen production system considering performance attenuation of PEMEL

To analyze the additional cost caused by the performance attenuation of a proton exchange membrane electrolyzer(PEMEL)under the fluctuating input of renewable energy,this study proposes an optimization method for power scheduling in hydrogen production systems under the scenario of photovoltaic(PV)electrolysis of water.First,voltage and performance attenuation models of the PEMEL are proposed,and the degradation cost of the electrolyzer under a fluctuating input is considered.Then,the calculation of the investment and operating costs of the hydrogen production system for a typical day is based on the life cycle cost.Finally,a layered power scheduling optimization method is proposed to reasonably distribute the power of the electrolyzer and energy storage system in a hydrogen production system.In the up-layer optimization,the PV power absorbed by the hydrogen production system was optimized using MALTAB+Gurobi.In low-layer optimization,the power allocation between the PEMEL and battery energy storage system(BESS)is optimized using a non-dominated sorting genetic algorithm(NSGA-Ⅱ)combined with the firefly algorithm(FA).A better optimization result,characterized by lower degradation and total costs,was obtained using the method proposed in this study.The improved algorithm can search for a better population and obtain optimization results in fewer iterations.As a calculation example,data from a PV power station in northwest China were used for optimization,and the effectiveness and rationality of the proposed optimization method were verified.