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Migration images guided high-resolution velocity modeling based on fully convolutional neural network
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作者 DU Meng MAO Weijian +1 位作者 YANG Maoxin ZHAO Jianzhi 《Global Geology》 2024年第3期145-153,共9页
Current data-driven deep learning(DL)methods typically reconstruct subsurface velocity models directly from pre-stack seismic records.However,these purely data-driven methods are often less robust and produce results ... Current data-driven deep learning(DL)methods typically reconstruct subsurface velocity models directly from pre-stack seismic records.However,these purely data-driven methods are often less robust and produce results that are less physically interpretative.Here,the authors propose a new method that uses migration images as input,combined with convolutional neural networks to construct high-resolution velocity models.Compared to directly using pre-stack seismic records as input,the nonlinearity between migration images and velocity models is significantly reduced.Additionally,the advantage of using migration images lies in its ability to more comprehensively capture the reflective properties of the subsurface medium,including amplitude and phase information,thereby to provide richer physical information in guiding the reconstruction of the velocity model.This approach not only improves the accuracy and resolution of the reconstructed velocity models,but also enhances the physical interpretability and robustness.Numerical experiments on synthetic data show that the proposed method has superior reconstruction performance and strong generalization capability when dealing with complex geological structures,and shows great potential in providing efficient solutions for the task of reconstructing high-wavenumber components. 展开更多
关键词 deep learning seismic inversion migration imaging velocity modeling
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用Velocity Verlet积分器改进HMC抽样方法
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作者 李婉荧 唐亚勇 《四川大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第1期25-34,共10页
Hamilton Monte Carlo (HMC)方法是一种常用的快速抽样方法.在对哈密顿方程进行抽样时,HMC方法使用Leapfrog积分器,这可能造成方程的位置及动量的迭代值在时间上不同步,其产生的误差会降低抽样效率及抽样结果的稳定性.为此,本文提出了IH... Hamilton Monte Carlo (HMC)方法是一种常用的快速抽样方法.在对哈密顿方程进行抽样时,HMC方法使用Leapfrog积分器,这可能造成方程的位置及动量的迭代值在时间上不同步,其产生的误差会降低抽样效率及抽样结果的稳定性.为此,本文提出了IHMC(Improved HMC)方法,该方法用Velocity Verlet积分器替代Leapfrog积分器,每次迭代时都计算两变量在同一时刻的值.为验证方法的效果,本文进行了两个实验,一个是将该方法应用于非对称随机波动率模型(RASV模型)的参数估计,另一个是将方法应用于方差伽马分布的抽样,结果显示:IHMC方法比HMC方法的效率更高、结果更稳定. 展开更多
关键词 HMC方法 velocity Verlet积分器 RASV模型 方差伽马分布
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GLOBAL SOLUTIONS TO A HYDRODYNAMIC MODEL FOR SEMICONDUCTORS WITH VELOCITY RELAXATION
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作者 王先婷 陆云光 +1 位作者 Richard De la cruz 尤国桥 《Acta Mathematica Scientia》 SCIE CSCD 2023年第2期975-980,共6页
In this paper,we apply the method given in the paper“Zero relaxation time limits to a hydrodynamic model of two carrier types for semiconductors”(Mathematische Annalen,2022,382:1031–1046)to study the Cauchy problem... In this paper,we apply the method given in the paper“Zero relaxation time limits to a hydrodynamic model of two carrier types for semiconductors”(Mathematische Annalen,2022,382:1031–1046)to study the Cauchy problem for a one dimensional inhomogeneous hydrodynamic model of two-carrier types for semiconductors with the velocity relaxation. 展开更多
关键词 global L solution hydrodynamic model two-carrier types velocity relaxation
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FeatureMatching Combining Variable Velocity Model with Reverse Optical Flow
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作者 Chang Zhao Wei Sun +3 位作者 Xiaorui Zhang Xiaozheng He Jun Zuo Wei Zhao 《Computer Systems Science & Engineering》 SCIE EI 2023年第5期1083-1094,共12页
The ORB-SLAM2 based on the constant velocity model is difficult to determine the search window of the reprojection of map points when the objects are in variable velocity motion,which leads to a false matching,with an... The ORB-SLAM2 based on the constant velocity model is difficult to determine the search window of the reprojection of map points when the objects are in variable velocity motion,which leads to a false matching,with an inaccurate pose estimation or failed tracking.To address the challenge above,a new method of feature point matching is proposed in this paper,which combines the variable velocity model with the reverse optical flow method.First,the constant velocity model is extended to a new variable velocity model,and the expanded variable velocity model is used to provide the initial pixel shifting for the reverse optical flow method.Then the search range of feature points is accurately determined according to the results of the reverse optical flow method,thereby improving the accuracy and reliability of feature matching,with strengthened interframe tracking effects.Finally,we tested on TUM data set based on the RGB-D camera.Experimental results show that this method can reduce the probability of tracking failure and improve localization accuracy on SLAM(Simultaneous Localization and Mapping)systems.Compared with the traditional ORB-SLAM2,the test error of this method on each sequence in the TUM data set is significantly reduced,and the root mean square error is only 63.8%of the original system under the optimal condition. 展开更多
关键词 Visual SLAM feature point matching variable velocity model reverse optical flow
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Modeling continuous traffic flow with the average velocity effect of multiple vehicles ahead on gyroidal roads
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作者 Cong Zhai Weitiao Wu Yingping Xiao 《Digital Transportation and Safety》 2023年第2期124-138,共15页
In the future connected vehicle environment,the information of multiple vehicles ahead can be readily collected in real-time,such as the velocity or headway,which provides more opportunities for information exchange a... In the future connected vehicle environment,the information of multiple vehicles ahead can be readily collected in real-time,such as the velocity or headway,which provides more opportunities for information exchange and cooperative control.Meanwhile,gyroidal roads are one of the fundamental road patterns prevalent in mountainous areas.To effectively control the system,it is therefore significant to explore the evolution mechanism of traffic flow on gyroidal roads under a connected vehicle environment.In this paper,we present a new continuum model with the average velocity of multiple vehicles ahead on gyroidal roads.The stability criterion and KdV-Burger equation are deduced via linear and nonlinear stability analysis,respectively.Solving the above KdV-Burger equation yields the density wave solution,which explores the formation and propagation property of traffic jams near the neutral stability curve.Simulation examples verify that the model can reproduce complex phenomena,such as shock waves and rarefaction waves.The analysis of the local cluster effect shows that the number of vehicles ahead and the radius information,and the slope information of gyroidal roads can exert a great influence on traffic jams.The effect of the first and second terms are positive,while the last term is negative. 展开更多
关键词 Average velocity of multiple vehicles ahead Gyroidal roads Continuum model Stability KdV-Burger equation
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Near-surface velocity model construction based on a Monte-Carlo scheme 被引量:2
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作者 杨锴 李辉 刘玉柱 《Applied Geophysics》 SCIE CSCD 2012年第4期475-482,497,共9页
In tomographic statics seismic data processing, it 1s crucial to cletermme an optimum base for a near-surface model. In this paper, we consider near-surface model base determination as a global optimum problem. Given ... In tomographic statics seismic data processing, it 1s crucial to cletermme an optimum base for a near-surface model. In this paper, we consider near-surface model base determination as a global optimum problem. Given information from uphole shooting and the first-arrival times from a surface seismic survey, we present a near-surface velocity model construction method based on a Monte-Carlo sampling scheme using a layered equivalent medium assumption. Compared with traditional least-squares first-arrival tomography, this scheme can delineate a clearer, weathering-layer base, resulting in a better implementation of damming correction. Examples using synthetic and field data are used to demonstrate the effectiveness of the proposed scheme. 展开更多
关键词 Monte Carlo sampling scheme construction of near-surface velocity model priorinformation poster probability distribution simulate annealing algorithm
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Submerged flexible vegetation impact on open channel flow velocity distribution: An analytical modelling study on drag and friction 被引量:6
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作者 Jaan H. Pu Awesar Hussain +3 位作者 Ya-kun Guo Nikolaos Vardakastanis Prashanth R. Hanmaiahgari Dennis Lam 《Water Science and Engineering》 EI CAS CSCD 2019年第2期121-128,共8页
In this paper,an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied.In the present vegetated flow modelling,the whole flow field h... In this paper,an analytical model that represents the streamwise velocity distribution for open channel flow with submerged flexible vegetation is studied.In the present vegetated flow modelling,the whole flow field has been separated into two layers vertically: a vegetated layer and a non-vegetated free-water layer.Within the vegetated layer,an analysis of the mechanisms affecting water flow through flexible vegetation has been conducted.In the non-vegetated layer,a modified log-law equation that represents the velocity profile varying with vegetation height has been investigated.Based on the studied analytical model,a sensitivity analysis has been conducted to assess the influences of the drag (CD) and friction (Cf ) coefficients on the flow velocity.The investigated ranges of CD and Cf have also been compared to published values.The findings suggest that the CD and Cf values are non-constant at different depths and vegetation densities,unlike the constant values commonly suggested in literature.This phenomenon is particularly clear for flows with flexible vegetation,which is characterised by large deflection. 展开更多
关键词 ANALYTICAL model FLEXIBLE VEGETATION Flow velocity FRICTION Drag SUBMERGED VEGETATION
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Which velocity model is more suitable for the 2017 M_S7.0 Jiuzhaigou earthquake? 被引量:5
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作者 LiSheng Xu Xu Zhang ChunLai Li 《Earth and Planetary Physics》 2018年第2期163-169,共7页
On Aug.8, 2017, an M_S 7.0 earthquake struck Jiuzhaigou, a county of Sichuan province, China. A number of investigations and studies have been conducted, some of which involved local velocity models. However, the suit... On Aug.8, 2017, an M_S 7.0 earthquake struck Jiuzhaigou, a county of Sichuan province, China. A number of investigations and studies have been conducted, some of which involved local velocity models. However, the suitability of these models has not been properly addressed. Here we collect 11 already-existing models, including those used in studies of the 2017 M_S 7.0 Jiuzhaigou earthquake,choose 10 local stations surrounding the earthquake, and employ the same technique(TRIT) to relocate the hypocenter. And furthermore, we choose a more suitable model from the 11 already-existed models by analyzing the relocation process and the relocated results for reasonability. Finally, our conclusion is that the model Fang 2018 is more suitable and the hypocenter parameters, 103.801°E,33.192°N and 15.8 km for longitude, latitude and depth, respectively, and 2017-08-08 13:19:46.66 for its origin time, based on this model should be recommended for the 2017 M_S7.0 Jiuzhaigou earthquake. 展开更多
关键词 the 2017 MS7.0 Jiuzhaigou EARTHQUAKE the MORE suitable velocity model the RELOCATION of the mainshock
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Effect of Relative Velocity on the Optimal Velocity Model 被引量:3
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作者 董力耘 孟庆勋 《Journal of Shanghai University(English Edition)》 CAS 2005年第4期283-285,共3页
In this letter, an improved optimal velocity model was proposed that assumes the effect of relative velocity deceases with the increment of gap between successive cars. Numerical simuation was carried out to test whet... In this letter, an improved optimal velocity model was proposed that assumes the effect of relative velocity deceases with the increment of gap between successive cars. Numerical simuation was carried out to test whether this model could depict the braking process correctly. The simuation results show good agreement with observed data. 展开更多
关键词 traffic flow car-following model optimal velocity model.
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Simple analytical model for depth-averaged velocity in meandering compound channels 被引量:3
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作者 Yuqi SHAN Chao LIU Maokang LUO 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2015年第6期707-718,共12页
A simple but applicable analytical model is presented to predict the lat- eral distribution of the depth-averaged velocity in meandering compound channels. The governing equation with curvilinear coordinates is derive... A simple but applicable analytical model is presented to predict the lat- eral distribution of the depth-averaged velocity in meandering compound channels. The governing equation with curvilinear coordinates is derived from the momentum equation and the flow continuity equation under the condition of quasi-uniform flow. A series of experiments are conducted in a large-scale meandering compound channel. Based on the experimental data, a magnitude analysis is carried out for the governing equation, and two lower-order shear stress terms are ignored. Four groups of experimental data from different sources are used to verify the predictive capability of this model, and good predictions are obtained. Finally, the determination of the velocity parameter and the limitation of this model are discussed. 展开更多
关键词 meandering compound channel simple analytical model lateral distribu-tion method physical experiment depth-averaged velocity
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Modeling of softsphere normal collisions with characteristic of coefficient of restitution dependent on impact velocity 被引量:3
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作者 Youhe Zhou 《Theoretical & Applied Mechanics Letters》 CAS 2013年第2期16-20,共5页
This letter presents a theoretical model of the normal (head-on) collisions between two soft spheres for predicting the experimental characteristic of the coefficient of restitution dependent on impact velocity. Aft... This letter presents a theoretical model of the normal (head-on) collisions between two soft spheres for predicting the experimental characteristic of the coefficient of restitution dependent on impact velocity. After the contact force law between the contacted spheres during a collision is phenomenologically formulated in terms of the compression or overlap displacement under considera- tion of an elastic-plastic loading and a plastic unloading subprocesses, the coefficient of restitution is gained by the dynamic equation of the contact process once an initial impact velocity is input. It is found that the theoretical predictions of the coefficient of restitution varying with the impact velocity are well in agreement with the existing experimental characteristics which are fitted by the explicit formula. 展开更多
关键词 soft spheres normal collisions coefficient of restitution impact velocity theoretical model
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Model for seawater fouling and effects of temperature,flow velocity and surface free energy on seawater fouling 被引量:3
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作者 Dazhang Yang Jianhua Liu +1 位作者 Xiaoxue E Linlin Jiang 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2016年第5期658-664,共7页
A kinetic model was proposed to predict the seawater fouling process in the seawater heat exchangers.The new model adopted an expression combining depositional and removal behaviors for seawater fouling based on the K... A kinetic model was proposed to predict the seawater fouling process in the seawater heat exchangers.The new model adopted an expression combining depositional and removal behaviors for seawater fouling based on the Kern–Seaton model.The present model parameters include the integrated kinetic rate of deposition(k d)and the integrated kinetic rate of removal(k r),which have clear physical signi ficance.A seawater-fouling monitoring device was established to validate the model.The experimental data were well fitted to the model,and the parameters were obtained in different conditions.SEM and EDX analyses were performed after the experiments,and the results show that the main components of seawater fouling are magnesium hydroxide and aluminum hydroxide.The effects of surface temperature,flow velocity and surface free energy were assessed by the model and the experimental data.The results indicate that the seawater fouling becomes aggravated as the surface temperature increased in a certain range,and the seawater fouling resistance reduced as the flow velocity of seawater increased.Furthermore,the effect of the surface free energy of metals was analyzed,showing that the lower surface free energy mitigates the seawater fouling accumulation. 展开更多
关键词 FOULING Seawater model Surface temperature Flow velocity Surface free energy
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Improvements in seismic event locations in a deep western U.S. coal mine using tomographic velocity models and an evolutionary search algorithm 被引量:7
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作者 LURKA Adam SWANSON Peter 《Mining Science and Technology》 EI CAS 2009年第5期599-603,共5页
Methods of improving seismic event locations were investigated as part of a research study aimed at reducing ground control safety hazards. Seismic event waveforms collected with a 23-station three-dimensional sensor ... Methods of improving seismic event locations were investigated as part of a research study aimed at reducing ground control safety hazards. Seismic event waveforms collected with a 23-station three-dimensional sensor array during longwall coal mining provide the data set used in the analyses. A spatially variable seismic velocity model is constructed using seismic event sources in a passive tomographic method. The resulting three-dimensional velocity model is used to relocate seismic event positions. An evolutionary optimization algorithm is implemented and used in both the velocity model development and in seeking improved event location solutions. Results obtained using the different velocity models are compared. The combination of the tomographic velocity model development and evolutionary search algorithm provides improvement to the event locations. 展开更多
关键词 seismic event location tomographic velocity model an evolutionary search algorithm
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A Kinematic Thermal Model for Descending Slabs with Velocity Boundary Layers:A Case Study for the Tonga Subducting Slab 被引量:2
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作者 ZHANG Keliang WEI Dongping 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2011年第1期211-222,共12页
For the purpose of investigating the influence of metastable olivine(MO) phase transformations on both deep seismicity and stagnation of slabs,we constructed a 2-dimensional finite element thermal model for a 120 Ma... For the purpose of investigating the influence of metastable olivine(MO) phase transformations on both deep seismicity and stagnation of slabs,we constructed a 2-dimensional finite element thermal model for a 120 Ma-old 50°dipping oceanic lithosphere descending at 10 cm/yr with velocity boundary layers,which would mitigate the interference of constant velocity field for the slab. The resulting temperatures show that most of intermediate and deep earthquakes occurring within the Tonga slab are occurring inside the 800℃and 1200℃isotherm,respectively.The elevation of olivine transformation near~410 km and respective persistence of metastable olivine and spinel within the transition zone and beneath 660 km would thus result in bimodal positive,zonal,negative density anomalies,respectively.These results together with the resulting pressure anomalies may reflect the stress pattern of the Tonga slab:(i) slab pull force exerts above a depth of~230 km;(ii) MO existence changes the buoyancy force within the transition zone and facilitates slab stagnation at a depth of 660 km;(iii) as the subducting materials accumulated over 660 km,deepest earthquakes occur due to MO transformation;(iv) a flattened‘slab’ may penetrate into the lower mantle due to the density increment of Sp transformation. 展开更多
关键词 kinematic thermal model subduction zone velocity boundary layer metastable olivine double seismic zone finite element method
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The failure propagation of weakly stable sediment:A reason for the formation of high-velocity turbidity currents in submarine canyons
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作者 Yupeng REN Yi ZHANG +3 位作者 Guohui XU Xingbei XU Houjie WANG Zhiyuan CHEN 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2023年第1期100-117,共18页
The long-distance movement of turbidity currents in submarine canyons can transport large amounts of sediment to deep-sea plains.Previous studies show obvious differences in the turbidity current velocities derived fr... The long-distance movement of turbidity currents in submarine canyons can transport large amounts of sediment to deep-sea plains.Previous studies show obvious differences in the turbidity current velocities derived from the multiple cables damage events ranging from 5.9 to 28.0 m/s and those of field observations between 0.15 and 7.2 m/s.Therefore,questions remain regarding whether a turbid fluid in an undersea environment can flow through a submarine canyon for a long distance at a high speed.A new model based on weakly stable sediment is proposed(proposed failure propagation model for weakly stable sediments,WS S-PFP model for short)to explain the high-speed and long-range motion of turbidity currents in submarine canyons through the combination of laboratory tests and numerical analogs.The model is based on two mechanisms:1)the original turbidity current triggers the destabilization of the weakly stable sediment bed and promotes the destabilization and transport of the soft sediment in the downstream direction and 2)the excitation wave that forms when the original turbidity current moves into the canyon leads to the destabilization and transport of the weakly stable sediment in the downstream direction.The proposed model will provide dynamic process interpretation for the study of deep-sea deposition,pollutant transport,and optical cable damage. 展开更多
关键词 turbidity current excitation wave dense basal layer velocity WSS-PFP model
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Velocity and Structural Modeling of Mesozoic Chiltan Limestone and Goru Formation for Hydrocarbon Evaluation in the Bitrisim Area, Lower Indus Basin, Pakistan 被引量:1
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作者 Sarfraz KHAN Zahid LATIF +2 位作者 Muhammad HANIF Irfan U. JAN Shahid IQBAL 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2016年第1期258-275,共18页
The present study focuses on building a workflow for structural interpretation and velocity modeling and implementing to Jurassic-Cretaceous succession (Chiltan Limestone and Massive sand of the Lower Goru Formation... The present study focuses on building a workflow for structural interpretation and velocity modeling and implementing to Jurassic-Cretaceous succession (Chiltan Limestone and Massive sand of the Lower Goru Formation). 2D-Migrated seismic sections of the area are used as data set and in order to confirm the presence of hydrocarbons in the study area, P and S-wave seismic velocities are estimated from single-component seismic data. Some specific issues in the use of seismic data for modeling and hydrocarbon evaluation need to deal with including distinguishing the reservoir and cap rocks, and the effects of faults, folds and presence of hydrocarbons on these rocks. This study has carried out the structural interpretation and modeling of the seismic data for the identification of traps. The results demonstrate existence of appropriate structural traps in the form of horst and grabens in the area. 2D and 3D velocity modeling of the horizons indicates the presence of high velocity zones in the eastern half of the study while relatively low velocity zones are encountered in the western half of the area. Two wells were drilled in the study area (i.e. Fateh-01 and Ichhri-01) and both are dry. Immature hydrocarbons migration is considered as a failure reason for Fateh-01 and Ichhri-01 well. 展开更多
关键词 2D and 3D Time-Depth models velocity modeling structural modeling Chiltan limestone Goru Formation
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Effects of the Reynolds number on a scale-similarity model of Lagrangian velocity correlations in isotropic turbulent flows 被引量:1
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作者 Zhaoyu SHI Jincai CHEN Guodong JIN 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第11期1605-1616,共12页
A scale-similarity model of a two-point two-time Lagrangian velocity correlation(LVC) was originally developed for the relative dispersion of tracer particles in isotropic turbulent flows(HE, G. W., JIN, G. D., and ZH... A scale-similarity model of a two-point two-time Lagrangian velocity correlation(LVC) was originally developed for the relative dispersion of tracer particles in isotropic turbulent flows(HE, G. W., JIN, G. D., and ZHAO, X. Scale-similarity model for Lagrangian velocity correlations in isotropic and stationary turbulence. Physical Review E, 80, 066313(2009)). The model can be expressed as a two-point Eulerian space correlation and the dispersion velocity V. The dispersion velocity denotes the rate at which one moving particle departs from another fixed particle. This paper numerically validates the robustness of the scale-similarity model at high Taylor micro-scale Reynolds numbers up to 373, which are much higher than the original values(R_λ = 66, 102). The effect of the Reynolds number on the dispersion velocity in the scale-similarity model is carefully investigated. The results show that the scale-similarity model is more accurate at higher Reynolds numbers because the two-point Lagrangian velocity correlations with different initial spatial separations collapse into a universal form compared with a combination of the initial separation and the temporal separation via the dispersion velocity.Moreover, the dispersion velocity V normalized by the Kolmogorov velocity V_η ≡ η/τ_η in which η and τ_η are the Kolmogorov space and time scales, respectively, scales with the Reynolds number R_λ as V/V_η ∝ R_λ^(1.39) obtained from the numerical data. 展开更多
关键词 turbulent mixing relative dispersion Lagrangian velocity correlation scalesimilarity model dispersion velocity Reynolds number effect
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Theoretical modeling of the effects of temperature and moisture content on the acoustic velocity of Pinus resinosa wood 被引量:1
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作者 Shan Gao Xinmin Tao +1 位作者 Xiping Wang Lihai Wang 《Journal of Forestry Research》 SCIE CAS CSCD 2018年第2期532-539,共8页
To investigate the effects of temperature and moisture content(MC) on acoustic wave velocity(AWV)in wood,the relationships between wood temperature,MC,and AWV were theoretically analyzed.According to the theoretical p... To investigate the effects of temperature and moisture content(MC) on acoustic wave velocity(AWV)in wood,the relationships between wood temperature,MC,and AWV were theoretically analyzed.According to the theoretical propagation characteristics of the acoustic waves in the wood mixture and the differences in velocity among various media(including ice,water,pure wood or oven-dried wood),theoretical relationships of temperature,MC,and AWV were established,assuming that the samples in question were composed of a simple mixture of wood and water or of wood and ice.Using the theoretical model,the phase transition of AWV in green wood near the freezing point(as derived from previous experimental results) was plausibly described.By comparative analysis between theoretical and experimental models for American red pine(Pinus resinosa) samples,it was established that the theoretically predicted AWV values matched the experiment results when the temperature of the wood was below the freezing point of water,with an averageprediction error of 1.66%.The theoretically predicted AWV increased quickly in green wood as temperature decreased and changed suddenly near 0 °C,consistent with the experimental observations.The prediction error of the model was relatively large when the temperature of the wood was above the freezing point,probably due to an overestimation of the effect of the liquid water content on the acoustic velocity and the limited variables of the model.The high correlation between the predicted and measured acoustic velocity values in frozen wood samples revealed the mechanisms of temperature,MC,and water status and how these affected the wood(particularly its acoustic velocity below freezing point of water).This result also verified the reliability of a previous experimental model used to adjust for the effect of temperature during field testing of trees. 展开更多
关键词 Acoustic velocity WOOD TEMPERATURE Moisture content Theoretical model
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An improved multidirectional velocity model for micro-seismic monitoring in rock engineering 被引量:3
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作者 李健 吴顺川 +2 位作者 高永涛 李莉洁 周喻 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第6期2348-2358,共11页
An improved multidirectional velocity model was proposed for more accurately locating micro-seismic events in rock engineering. It was assumed that the stress wave propagation velocities from a micro-seismic source to... An improved multidirectional velocity model was proposed for more accurately locating micro-seismic events in rock engineering. It was assumed that the stress wave propagation velocities from a micro-seismic source to three nearest monitoring sensors in a sensor's array arrangement were the same. Since the defined objective function does not require pre-measurement of the stress wave propagation velocity in the field, errors from the velocity measurement can be avoided in comparison to three traditional velocity models. By analyzing 24 different cases, the proposed multidirectional velocity model iterated by the Simplex method is found to be the best option no matter the source is within the region of the sensor's array or not. The proposed model and the adopted iterative algorithm are verified by field data and it is concluded that it can significantly reduce the error of the estimated source location. 展开更多
关键词 multidirectional velocity model micro-seismic event Simplex method rock engineering field measurement error estimation
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Evaluating Two-Layer Models for Velocity Profiles in Open-Channels with Submerged Vegetation 被引量:3
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作者 Xiaonan Tang 《Journal of Geoscience and Environment Protection》 2019年第1期68-80,共13页
For submerged vegetated flow, the velocity profile has two distinctive distributions in the vegetation layer in the lower region and the surface layer in the upper non-vegetated region. Based on a mixing-layer analogy... For submerged vegetated flow, the velocity profile has two distinctive distributions in the vegetation layer in the lower region and the surface layer in the upper non-vegetated region. Based on a mixing-layer analogy, different analytical models have been proposed for the velocity profile in the two layers. This paper evaluates the four analytical models of Klopstra et al., Defina & Bixio, Yang et al. and Nepf against a wide range of independent experimental data available in the literature. To test the applicability and robust of the models, the author used the 19 datasets with various relative depths of submergence, different vegetation densities and bed slopes (1.8 × 10?6 - 4.0 × 10?3). This study shows that none of the models can predict the velocity profiles well for all datasets. The three models except Yang’s model performed reasonably well in certain cases, but Yang’s model failed in most the cases studied. It was also found that the Defina model is almost the same as the Klopstra model, if the same mixing length scale of eddies (λ) is used. Finally, close examination of the mixing length scale of eddies (λ) in the Defina model showed that when λ/h = 1/40(H/h)1/2, this model can predict velocity profiles well for all the datasets used. 展开更多
关键词 AQUATIC VEGETATION velocity Profile Vegetated FLOW ANALYTICAL model RIGID VEGETATION Open-Channel FLOW
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