A three-phase finite element model of water-infiltrated porous materials subjected to freezing

In areas of geotechnical engineering, artificial ground freezing is commonly used as an effective way to deal with various ground construction challenges such as groundwater control and temporary excavation support. For the description of the coupled thermo-hydro-mechanical behavior of soil exposed to frost action, this paper presents a three-phase Finite Element model of porous materials, consisting of solid skeleton, liquid water and crystal ice, where the liquid phase contains both weakly-bound pore water and strongly-bound water film. Within the theory of thermo-poroelasticity proposed by Coussy [1, 2], poroelastic constitutive relations are provided from an energy approach of poromechanics. In addition, the phase transition between water and ice is characterized by a purely temperature-dependent thermodynamic state function named liquid saturation degree considering the pore size distribution. The cryo-suction mechanism that induces migration of water towards the frozen sites is impelled by the chemical potential difference existing between the pre-melted water film and the adjacent pore water. By choosing solid displacement, liquid pressure and mixture temperature as principal unknowns, the model is implemented in a geometrically-linear Finite Element context base upon the governing balance equations for the soil constituents and their mixture. The validation procedure is shown by selected examples with analyses of different aspects of the model behavior

Two-phase simulation of the pressure loss in helical channel

The CFD simulations are carried out for the flows in a helical gas-liquid separator, which is installed at the inlet of the electric submersible pump (ESP) to separate gas from gas-liquid mixture and keep the efficiency of the pump. The effects of mass flux, curvature and helix angle on two-phase pressure drop have been investigated. Through theoretical analysis and numerical simulation, it is found that the mass flux of two-phase flow and the curvature of spiral passage have influence on pressure drop, while the spiral angle has little effect on pressure loss

Characterizations and perturbation analysis of a class of matrices related to core-EP inverses

[EN] Let A, B is an element of C-nxn with ind(A) = k and ind(B) = s and let L-B = (BB)-B-2(sic). A new condition (C-s,C-*): R(A(k)) boolean AND N((B-s)*) = {0} and R(B-s) boolean AND N((A(k))*) = {0}, is defined. Some new characterizations related to core-EP inverses are obtained when B satisfies condition (C-s,C-*). Explicit expressions of B(sic) and BB(sic) are also given. In addition, equivalent conditions, which guarantee that B satisfies condition (C-s,C-*), are investigated. We proved that B satisfies condition (C-s,C-*) if and only if L-B has a fixed matrix form. As an application, upper bounds for the errors parallel to B(sic) - A(sic)parallel to/parallel to A(sic)parallel to and parallel to BB(sic) - AA(sic)parallel to are studied. (c) 2021 Elsevier B.V. All rights reserved.The authors thank the Editor and Reviewers sincerely for their constructive comments and suggestions which have improved the quality of the paper. This research is supported by the National Natural Science Foundation of China (Nos. 11771076, 11871145), the Postgraduate Research and Practice Innovation Program of Jiangsu Province (No. KYCX18 -0053), the China Scholarship Council (File No. 201906090122). The third author is partially supported by Ministerio de Economia y Competitividad of Spain (grant Red de Excelencia MTM2017-90682-REDT) and partially supported by Universidad de Buenos Aires, Argentina. EXP-UBA: 13.019/2017, 20020170100350BAZhou, M.; Chen, J.; Thome, N. (2021). Characterizations and perturbation analysis of a class of matrices related to core-EP inverses. Journal of Computational and Applied Mathematics. 393:1-11. https://doi.org/10.1016/j.cam.2021.113496S11139

The W-weighted Drazin-star matrix and its dual

[EN] After decades studying extensively two generalized inverses, namely Moore--Penrose inverse and Drazin inverse, currently, we found immersed in a new generation of generalized inverses (core inverse, DMP inverse, etc.). The main aim of this paper is to introduce and investigate a matrix related to these new generalized inverses defined for rectangular matrices. We apply our results to the solution of linear systems.The authors wish to thank the editor and reviewers sincerely for their constructive comments and suggestions that have improved the quality of the paper. This research is supported by the Postgraduate Research and Practice Innovation Program of Jiangsu Province (No. KYCX18_0053), the China Scholarship Council (File No. 201906090122), the National Natural Science Foundation of China (No.11771076, 11871145). The third author is partially supported by Ministerio de Economía y Competitividad of Spain (grant Red de Excelencia MTM2017-90682-REDT) and Universitat Nacional de La Pampa, Facultad de Ingeniería (Grant Resol. No. 135/19)Zhou, M.; Chen, J.; Thome, N. (2021). The W-weighted Drazin-star matrix and its dual. The Electronic Journal of Linear Algebra. 37:72-87. https://doi.org/10.13001/ela.2021.5389S72873

Development of hybrid SVM-FA, DT-FA and MLR-FA models to predict the flexural strength (FS) of recycled concrete

Recycled concrete from construction waste used as road material is a current sustainable approach. To provide feasible suggestions for civil engineers to prepare recycled concrete with high flexural strength (FS) for the road pavement, the present study proposed three hybrid machine learning models by combining support vector machine (SVM), decision tree (DT) and multiple linear regression (MLR) with the firefly algorithm (FA) for the computational optimization, named as SVM-FA, DT-FA, and MLR-FA, respectively. Effective water-cement ratio (WC), aggregate-cement ratio (AC), recycled concrete aggregate replacement ratio (RCA), nominal maximum recycled concrete aggregate size (NMR), nominal maximum normal aggregate size (NMN), bulk density of recycled concrete aggregate (BDR), bulk density of normal aggregate (BDN), water absorption of RCA (WAR) and water absorption of NA (WAN) were employed as the input variables. To determine the predicting results of varying hybrid models, root mean square error (RMSE) and correlation coefficient (R) were used as performance indexes. The results showed that the SVM-FA demonstrated the highest R values and the lowest RMSE values, and the fitting effect of the predicted values and the actual values of the FS of recycled concrete is the best. All the above analysis proving that the SVM optimized by FA hyperparameters has the highest prediction accuracy and SVM-FA can provide engineers a more accurate and convenient tool to evaluate the FS of recycled concrete. The results of sensitivity analysis showed that WC has the most significant influence on the FS of recycled concrete, while RCA has the weakest influence on the FS, which should be noticed when engineers apply recycled concrete to road design in the future