3D and 2D topographic correction to estimated geothermal gradient from the base of gas hydrate stability zone in the Andaman Forearc Basin

Methane gas hydrate related bottom-simulating reflectors(BSRs)are imaged based on the in-line and cross-line multi-channel seismic(MCS)data from the Andaman Forearc Basin.The depth of the BSR depends on pressure and temperature and pore water salinity.With these assumptions,the BSR depth can be used to estimate the geothermal gradient(GTG)based on the availability of in-situ temperature measurements.This calculation is done assuming a 1D conductive model based on available in-situ temperature measurement at site NGHP-01-17 in the study area.However,in the presence of seafloor topography,the conductive temperature field in the subsurface is affected by lateral refraction of heat,which focuses heat in topographic lows and away from topographic highs.The 1D estimate of GTG in the Andaman Forearc Basin has been validated by drilling results from the NGHP-01 expedition.2D analytic modeling to estimate the effects of topography is performed earlier along selected seismic profiles in the study area.The study extended to estimate the effect of topography in 3D using a numerical model.The corrected GTG data allow us to determine GTG values free of topographic effect.The difference between the estimated GTG and values corrected for the 3D topographic effect varies up to~5℃/km.These conclude that the topographic correction is relatively small compared to other uncertainties in the 1D model and that apparent GTG determined with the 1D model captures the major features,although the correction is needed prior to interpreting subtle features of the derived GTG maps.

Origins of three-dimensional charge and two-dimensional phonon transports in Pnma phase PbSnSe_(2)thermoelectric crystal

Recently,PbSnSe_(2)alloy was found to exhibit a large hysteresis effect on transport properties,demonstrating its significant potential for thermoelectric applications.Using ab initio approaches,we studied the carrier transport properties of PbSnSe_(2)crystal,which is a special case of the alloy with the shortest-range order.A peak power factor of 134.2μW cm^(-1)K^(-2)was found along the crossplane direction in the n-type PbSnSe_(2)at a doping concentration of 7×10^(20)cm^(-3)at 700 K.This high power factor originates from delocalized p electrons between intra-plane Pb-Se pairs and between cross-plane Sn-Se pairs that can build up transport channels for conducting electrons,leading to a high electrical conductivity of 5.9×10^(5)S m^(-1).Introducing Pb atoms into Pnma phase SnSe can decrease the phonon group velocities and enhance the phonon-phonon scatterings,leading to a low thermal conductivity of 0.53 W m^(-1)K^(-1)at 700 K along the cross-plane direction.The calculated peak ZT of~3 along the cross-plane direction at an n-type doping concentration of around 5×10^(19)cm^(-3),which represents a theoretical upper limit for an idealized PbSnSe_(2)crystal.This work interprets the origins of three-dimensional charge and two-dimensional phonon transport behavior in PbSnSe_(2)and demonstrates that such crystals are promising high-performance thermoelectric semiconductors.

A new three-dimensional elastography using phase based shifted Fourier transform

Elastography is an imaging technique with the ability to determine low quantities of some of the mechanical properties of tissues.The aim of our research is to design a new 3D algorithm using the Shifted Fourier Transform(SFT)to perform a quasi-static elastography.Our innovative idea is implementation of a 3D convolution instead of using three 2D convulsions.At first,we collected the raw data from Abaqus engineering software in the form of breast tissue with a coefficient of elasticity of healthy tissue and tumor tissue with a coefficient of elasticity of tumor tissue.The primary raw data consists of a number of points with x,y and z specified for tumor and healthy breast tissue.At this step,we simulated the displacements in directions of x,y and z at each point of the prescribed tissues for 15 mm displacement of probe in–Y direction then we collected 1831 points for tumor and 4186 points for breast before and after pressure.After applying a novel reconstruction algorithm,we convolved all images with the 3D Gabor filters to obtain phases,represented displacements of the breast and tumor images for before and after pressure.To reach this goal,we designed a Gabor filter bank based on the dimensions of the input images in different scales,directions,and deviations.Using the 3D SFT,we calculated the displacements of the breast and tumor tissues followed by 3D elastogram representation of the images.Finally,we implemented a 2D analysis of SFT in order to investigate validation of the 3D SFT.In 2D algorithm,we used three two-dimensional convulsions in XY,YZ and XZ planes.The results obtained from the small displacements marked by circles,confirmed the accuracy of the 3D SFT algorithm.These areas of interest are the tumor areas in the 2D analysis.