An inverse analysis of fluid flow through granular media using differentiable lattice Boltzmann method

This study presents a method for the inverse analysis of fluid flow problems.The focus is put on accurately determining boundary conditions and characterizing the physical properties of granular media,such as permeability,and fluid components,like viscosity.The primary aim is to deduce either constant pressure head or pressure profiles,given the known velocity field at a steady-state flow through a conduit containing obstacles,including walls,spheres,and grains.The lattice Boltzmann method(LBM)combined with automatic differentiation(AD)(AD-LBM)is employed,with the help of the GPU-capable Taichi programming language.A lightweight tape is used to generate gradients for the entire LBM simulation,enabling end-to-end backpropagation.Our AD-LBM approach accurately estimates the boundary conditions for complex flow paths in porous media,leading to observed steady-state velocity fields and deriving macro-scale permeability and fluid viscosity.The method demonstrates significant advantages in terms of prediction accuracy and computational efficiency,making it a powerful tool for solving inverse fluid flow problems in various applications.

Predicting bathymetry based on vertical gravity gradient anomaly and analyses for various influential factors

The prediction of bathymetry has advanced significantly with the development of satellite altimetry.However,the majority of its data originate from marine gravity anomaly.In this study,based on the expression of vertical gravity gradient(VGG)of a rectangular prism,the governing equations for determining sea depths to invert bathymetry.The governing equation is solved by linearization through an iterative process,and numerical simulations verify its algorithm and its stability.We also study the processing methods of different interference errors.The regularization method improves the stability of the inversion process for errors.A piecewise bilinear interpolation function roughly replaces the low-frequency error,and numerical simulations show that the accuracy can be improved by 41.2%after this treatment.For variable ocean crust density,simulation simulations verify that the root-mean-square(RMS)error of prediction is approximately 5 m for the sea depth of 6 km if density is chosen as the average one.Finally,two test regions in the South China Sea are predicted and compared with ship soundings data,RMS errors of predictions are 71.1 m and 91.4 m,respectively.

Spatial distribution characteristics and mechanism of nonhydrological time-variable gravity in China's Mainland

The purpose of this study is to explore nonhydrological mass transfer in China's Mainland.For this purpose,gravity recovery and climate experiment(GRACE)data were obtained to study the spatial distribution of time variant gravity signals in China's Mainland.Then,from auxiliary hydrological data processed according to the current hydrological model,a new more comprehensive hydrological model of China's Mainland was constructed.Finally,the time variant signals of this new hydrological model were removed from the time variant gravity field computed from GRACE data,thus obtaining a description of the nonhydrological mass transfer of China's Mainland.The physical sources and mechanisms of the resulting mass transfer are then discussed.The improved,more realistic,hydrological model used here was created by selecting the hydrological components with the best correlations in existing hydrological models,by use of correlation calculation,analysis,and comparison.This improved model includes water in soils and deeper strata,in the vegetation canopy,in lakes,snow,and glaciers,and in other water components(mainly reservoir storage,swamps,and rivers).The spatial distribution of the transfer signals due to nonhydrological mass in China's Mainland was obtained by subtracting the combined hydrological model from the GRACE time-variable gravity field.The results show that the nonhydrological signals in China's Mainland collected in GRACE data were mainly positive signals,and were distributed in the Bohai Rim and the northern and eastern parts of the Tibetan Plateau.The above nonhydrological mass transfer signals have been studied further and are discussed.The results show that the nonhydrological mass migration signals in the Bohai Rim region originate primarily from sea level change and marine sediment accumulation.The mass accumulation from Indian plate collision in the Tibetan Plateau appears to be the main reason for the increase in the residual gravity field in that region.

Different Decaying Wood Effects on Bacterial Diversity:Insights from Molecular Methods

Decaying wood is a novel key factor required for biodiversity and function of a forest,as it provides a good account of substrate and habitats for various organisms.Herein,the bacterial diversity in decaying wood of Betula platyphylla was discussed through high throughput sequencing.Our results showed that most of the obtained sequences belonged to the phyla Firmicutes,Proteobacteria,Bacteroidetes,Actinobacteria,Acidobacteria and Verrucomicrobia.Bacterial community compositions in samples with higher moisture content were obviously different than that with lower content,which could be reflected by richness estimators,diversity indices,and cluster and heatmap analysis.All three networks were non-random and possessed topological features of complex systems such as small-world and modularity features.However,these networks exhibited distinct topological features,indicating the potential ability of extensive cooperative and competitive interactions in the decayed wood microenvironments.Redundant analysis showed that most bacterial phyla were mainly distributed in highermoisture trunks.The obtained data will increase the knowledge of the complex bacterial diversity associated with dead wood,and lay a foundation for the bioconversion technology of plant cell walls using bacteria.

From Coarse to Fine:Two-Stage Indoor Localization with Multisensor Fusion

Increasing attention has been paid to high-precision indoor localization in dense urban and indoor environments.Previous studies have shown single indoor localization methods based on WiFi fingerprints,surveillance cameras or Pedestrian Dead Reckoning(PDR)are restricted by low accuracy,limited tracking region,and accumulative error,etc.,and some defects can be resolved with more labor costs or special scenes.However,requesting more additional information and extra user constraints is costly and rarely applicable.In this paper,a two-stage indoor localization system is presented,integrating WiFi fingerprints,the vision of surveillance cameras,and PDR(the system abbreviated as iWVP).A coarse location using WiFi fingerprints is done advanced,and then an accurate location by fusing data from surveillance cameras and the IMU sensors is obtained.iWVP uses a matching algorithm based on motion sequences to confirm the identity of pedestrians,enhancing output accuracy and avoiding corresponding drawbacks of each subsystem.The experimental results show that the iWVP achieves high accuracy with an average position error of 4.61 cm,which can effectively track pedestrians in multiple regions in complex and dynamic indoor environments.

Research advance in rosacea

Rosacea is a common disease,but its pathogenesis is still poorly understood.For instance,there is a hypothesis in which subtypes develop in an array or another where subtypes are likely to present separately as part of a syndrome.On the other hand,with the improvement in healthcare and diagnosis techniques,more designed studies have been conducted to investigate associated factors of rosacea such as the effect of sunlight,climate and other risk factors.In this study,updates have

Comparison between topical tacrolimus and potent topical steroids in treatment of childhood vitiligo

Objective To assess which of topical tacrolimus and topical highly potent steroids,is more effective and safer in the treatment of pediatric vitiligo.Methods The PubMed,Cochrane library,Scopus and CINAHL plus databases were retrieved.The search was confined to English language articles.The randomized controlled trial(RCT)articles were included in our study.The quality of the identified articles was examined by using the CASP Randomised Controlled Trials Checklist.Results As a result,there were only a few studies related to the comparison.However,there were only two RCTs regarding a comparison of topical tacrolimus 0.1%and clobetasol propionate 0.05%in childhood vitiligo.Conclusion When the body surface area(BSA)involved in the child is<20%,and the disease is not rapidly spreading,topical therapy is the first choice.Topical tacrolimus may be considered as an alternative therapy for childhood vitiligo,especially for acrofacial and segmental types,before considering other modalities,but still need to observe long-term side effects.