Bayesian Rayleigh wave inversion with an unknown number of layers

Surface wave methods have received much attention due to their efficient, flexible and convenient characteristics. However, there are still critical issues regarding a key step in surface wave inversion. In most existing methods, the number of layers is assumed to be known prior to the process of inversion. However, improper assignment of this parameter leads to erroneous inversion results. A Bayesian nonparametric method for Rayleigh wave inversion is proposed herein to address this problem. In this method, each model class represents a particular number of layers with unknown S-wave velocity and thickness of each layer. As a result, determination of the number of layers is equivalent to selection of the most applicable model class. Regarding each model class, the optimization search of S-wave velocity and thickness of each layer is implemented by using a genetic algorithm. Then, each model class is assessed in view of its efficiency under the Bayesian framework and the most efficient class is selected. Simulated and actual examples verify that the proposed Bayesian nonparametric approach is reliable and efficient for Rayleigh wave inversion, especially for its capability to determine the number of layers.

Effect of the number of layers on the bond strength for multi-layer brittle coating-substrate system

Finite element method(FEM) was used to investigate the effect of the number of layers on the bond strength for the brittle coating/substrate materials at contact load condition,which has not been addressed previously.The maximum shear stress was used to act as the criterion of the bonded strength.This paper discussed the relationship between the number of coating layers and the maximum shear stress of the layer/substrate interface.Firstly,the results of the FEM and the Hertz analytical method were compared to verify the accuracy of the FEM model.It was found that with the increase in the number of coating layers,the position of the suddenly changed stress along the z axis is transformed from the interface to the external surface of the coating.Finally,the increase in the number of layers contributes to the decrement of the stress along the x axis.

Numerical Study of the Efficiency of Multi-Layer Membrane Filtration in Desalination Processes

Multi-layer membrane filtration is a widely used technology for separating and purifying different components ofa liquid mixture. This technique involves passing the liquid mixture through a series of membranes with decreasing pore sizes, which allows for the separation of different components according to their molecular size. Thisstudy investigates the filtration process of a fluid through a two-dimensional porous medium designed forseawater desalination. The focus is on understanding the impact of various parameters such as the coefficientof friction, velocity, and the number of layers on filtration efficiency. The results reveal that the number of layersplays a crucial role in desalination, with an increase in layers leading to enhanced filtration quality, following apower law relationship. The study explores the influence of the coefficient of friction on filtration performance,emphasizing its significant effect on the number of particles filtered over time. Additionally, the role of the initialvelocity in filtration efficiency is examined, showing distinct effects at both high and low velocities. Biofouling isidentified as a factor influencing filtration, with an initial increase in filtered particles followed by a decline due toparticle accumulation in pores.

The effect of the density difference between supercritical CO_(2) and supercritical CH_(4) on their adsorption capacities: An experimental study on anthracite in the Qinshui Basin

Deep unmineable coals are considered as economic and effective geological media for CO_(2) storage and CO_(2) enhanced coalbed methane(CO_(2)-ECBM) recovery is the key technology to realize CO_(2) geological sequestration in coals. Anthracite samples were collected from the Qinshui Basin and subjected to mercury intrusion porosimetry, low-pressure CO_(2) adsorption, and high-pressure CH_(4)/CO_(2) isothermal adsorption experiments. The average number of layers of adsorbed molecules(ANLAM) and the CH_(4)/CO_(2) absolute adsorption amounts and their ratio at experimental temperatures and pressures were calculated. Based on a comparison of the density of supercritical CO_(2) and supercritical CH_(4), it is proposed that the higher adsorption capacity of supercritical CO_(2) over supercritical CH_(4) is the result of their density differences at the same temperature. Lastly, the optimal depth for CO_(2)-ECBM in the Qinshui Basin is recommended. The results show that:(1) the adsorption capacity and the ANLAM of CO_(2) are about twice that of CH_(4) on SH-3 anthracite. The effect of pressure on the CO_(2)/CH_(4) absolute adsorption ratio decreases with the increase of pressure and tends to be consistent.(2) A parameter(the density ratio between gas free and adsorbed phase(DRFA)) is proposed to assess the absolute adsorption amount according to the supercritical CO_(2)/CH_(4) attributes. The DRFA of CO_(2) and CH_(4) both show a highly positive correlation with their absolute adsorption amounts, and therefore, the higher DRFA of CO_(2) is the significant cause of its higher adsorption capacity over CH_(4) under the same temperature and pressure.(3) CO_(2) adsorption on coal shows micropore filling with multilayer adsorption in the macro-mesopore, while methane exhibits monolayer surface coverage.(4) Based on the ideal CO_(2)/CH_(4) competitive adsorption ratio, CO_(2) storage capacity, and permeability variation with depth, it is recommended that the optimal depth for CO_(2)-ECBM in the Qinshui Basin ranges from 1000 m to 1500 m.