Static and dynamic behavior of multiphase porous media: Governing equations and finite element implementation.

The mechanical behavior of porous media such as geomaterials is largely governed by the interactions of the solid skeleton (or grains) with the fluids existing in the pores. These interactions occur through the interfaces between bulk components. Traditional analysis procedures of porous media, based on the principle of effective stress and Darcy's law, commonly fail to account for these interactions. In this dissertation, a continuum theory of multiphase porous media is developed, capable of rigorously characterizing the interactions among bulk components. Central to the theory is the implementation of the dynamic compatibility conditions that microscopically represent the constraints on the pressure jumps through interfaces. It is shown that Terzaghi's effective stress and capillary pressure can be characterized within a common framework. Within this context, a theoretical framework for poroelastoplasticity is developed, allowing the hysteresis in capillary pressure and plastic deformation of skeleton to be simulated in a hierarchical way. It is found that the mixture theory-based models of porous media can be linked with Biot's poroelasticity theory. A linear model based on the proposed theory is developed and used to analyze the propagation of acoustic waves in unsaturated soils and favorable comparisons to experimental results are obtained. A finite element procedure is developed and implemented into a computer code (called U_DYSAC2) for elastoplastic static and dynamic analyses of saturated and unsaturated porous media. Numerical examples including wave propagation, two-phase flow, consolidation, and seismic behavior of an embankment are presented. These examples show the capability of the theory for modeling a wide variety of behaviors of porous media

Strength Theory Model of Unsaturated Soils with Suction Stress Concept

A theoretical model is developed for describing the strength property of unsaturated soils. The model is able to predict conveniently the strength changes of unsaturated soils undergoing repeated changes of water content. Suction stress is adopted in the new model in order to get the sound form of effective stress for unsaturated soils. The shear strength of unsaturated soils is dependent on its soil-moisture state based on the results of shear experiments. Hence, the parameters of this model are related tightly to hydraulic properties of unsaturated soils and the strength parameters of saturated soils. The predictive curves by the new model are coincident with experimental data that underwent single drying and drying/wetting cycle paths. Hence, hysteretic effect in the strength analysis is necessary to be considered to predict the change of shear strength of unsaturated soils that underwent drying/wetting cycles. Once the new model is used to predict the change of shear strength, lots of time could be saved due to avoiding heavy and complicated strength tests of unsaturated soils. Especially, the model can be suitable to evaluate the shear strength change of unsaturated soils and the stability of slopes experienced the drying/wetting cycles

Electrochemical Model-Based Fast Charging: Physical Constraint-Triggered PI Control

This paper proposes a new fast charging strategy for lithium-ion (Li-ion) batteries. The approach relies on an experimentally validated high-fidelity model describing battery electrochemical and thermal dynamics that determine the fast charging capability. Such a high-dimensional nonlinear dynamic model can be intractable to compute in real-time if it is fused with the extended Kalman filter or the unscented Kalman filter that is commonly used in the community of battery management. To significantly save computational efforts and achieve rapid convergence, the ensemble transform Kalman filter (ETKF) is selected and tailored to estimate the nonuniform Li-ion battery states. Then, a health- and safety-aware charging protocol is proposed based on successively applied proportional-integral (PI) control actions. The controller regulates charging rates using online battery state information and the imposed constraints, in which each PI control action automatically comes into play when its corresponding constraint is triggered. The proposed physical constraint-triggered PI charging control strategy with the ETKF is evaluated and compared with several prevalent alternatives. It shows that the derived controller can achieve close to the optimal solution in terms of charging time and trajectory, as determined by a nonlinear model predictive controller, but at a drastically reduced computational cost

An integrated chromatin accessibility and transcriptome landscape of human pre-implantation embryos

Early human embryonic development involves extensive changes in chromatin structure and transcriptional activity. Here the authors present LiCAT-seq, a method enabling simultaneous profiling of chromatin accessibility and gene expression with ultra-low input of cells and map chromatin accessibility and transcriptome landscapes for human pre-implantation embryos

Corrigendum to: The TianQin project: current progress on science and technology

In the originally published version, this manuscript included an error related to indicating the corresponding author within the author list. This has now been corrected online to reflect the fact that author Jun Luo is the corresponding author of the article

Constitutive Model for Gas Hydrate–Bearing Soils Considering Hydrate Occurrence Habits

To exploit the resource of methane hydrate, it is crucial to understand the mechanical behavior of hydrate-bearing sediments. In this paper an elastoplastic constitutive model is developed for describing the mechanical behavior of gas hydrate–bearing soils (GHBS). To address the effect of the hydrate occurrence habits, the concept of the effective degree of saturation of the gas hydrate is introduced, and the effective stress stresses are redefined for describing the mechanical response of the GHBS. Within this context, a yield or loading function is developed while considering the bonding effect of gas hydrate; thus, the yield function can expand or shrink as gas hydrate forms or dissociates. To describe more realistically the mechanical behavior of the GHBS, a nonassociative flow rule is proposed by assuming the dilatancy to be a function of bonding stresses, suction stress, and stress ratio. The proposed model is applied to analyze the mechanical responses of the GHBS with different hydrate occurrence habits under different environmental loadings. It is demonstrated that the proposed model can well capture the main features of the mechanical behavior of GHBS, including the hydrate-induced enhancements of stiffness, strength and dilatancy, the unsaturation-related characteristics, and the hydrate occurrence habits dependency, showing that the proposed model is capable of describing the mechanical behavior of GHBS due to hydrate dissociation or under other environmental loadings

Study on Fluorine Pollution in a Slag Yard

This paper suggests a large-scale three-dimensional numerical simulation method to investigate the fluorine pollution near a slag yard. The large-scale three-dimensional numerical simulation method included an experimental investigation, laboratory studies of solute transport during absorption of water by soil, and large-scale three-dimensional numerical simulations of solute transport. The experimental results showed that the concentrations of fluorine from smelting slag and construction waste soil were well over the discharge limit of 0.1 kg/m3 recommended by Chinese guidelines. The key parameters of the materials used for large-scale three-dimensional numerical simulations were determined based on an experimental investigation, laboratory studies, and soil saturation of survey results and back analyses. A large-scale three-dimensional numerical simulation of solute transport was performed, and its results were compared to the experiment results. The simulation results showed that the clay near the slag had a high saturation of approximately 0.9, consistent with the survey results. Comparison of the results showed that the results of the numerical simulation of solute transport and the test results were nearly identical, and that the numerical simulation results could be used as the basis for groundwater environmental evaluation

A new theory for membrane efficiency coefficient of compacted clay

A new method for calculation the membrane efficiency coefficient w of compacted clay is proposed in this paper. The influence of fixed negative charge on the surface of clay minerals is considered. What’s more, the change of porosity during deformation is considered. Based on the chemical potential of specimens, the true ion concentration in pore-water is obtained. Based on the true ion concentration in pore water, the disjoining pressure considering fixed negative charge inside soils and the change of void ratio is proposed. A new calculation method for the membrane efficiency coefficient of compacted clay is established. The test data of w considering different porosity are calculated and the calculated results are compared with the traditional calculation methods. The new calculation methods of w provide a more physical-based theory for environmental geotechnical engineering

Splošna analitična rešitev enodimenzionalne konsolidacije za nezasičene zemljine pri različnih obtežnih pogojih

A general analytical solution is developed for the onedimensional consolidation problem of unsaturated soil under various time-dependent loading conditions based on a differential transformation method (DTM). In particular, analytical solutions are obtained for different relationships between the coefficients in the governing equations for unsaturated soil consolidation. The Fourier series expansion technique is adopted to account for both the continuous differentiable loading and the periodic piecewise loading. A comparison between the results of the current solution and the existing theoretical solution indicates that the proposed solution yields excellent results, while it is straightforward to obtain the analytical solution of the unsaturated consolidation problems. It was also found that the variations in the coefficients in the governing equations can significantly influence the dissipation of both the excess pore-air pressure and the excess pore-water pressure, though the magnitudes of their variations are different.V članku je predstavljena splošna analitična rešitev za enodimenzionalno konsolidacijo nezasičene zemljine v različnih časovno odvisnih obtežnih pogojih, ki temelji na metodi diferencialne transformacije (DTM). Zlasti so dobljene analitične rešitve za različna razmerja med koeficienti v vodilnih enačbah za konsolidacijo nezasičenih zemljin. Tehnika razširitve Fourierjeve vrste je spremenjena tako, da upošteva tako kontinuirano diferencialno obtežbo, kot tudi periodično posamično obtežbo. Primerjava med rezultati predlagane rešitve in obstoječe teoretične rešitve kaže, da predlagana rešitev daje odlične rezultate, medtem ko je enostavno dobiti analitično rešitev konsolidacije nezasičenih zemljin. Ugotovljeno je bilo tudi, da lahko razlike v koeficientih v vodilnih enačbah znatno vplivajo na disipacijo tako pornega zračnega nadtlaka kot tudi pornega vodnega nadtlaka, čeprav so velikosti njihovih variacij različne

Electrothermal dynamics-conscious lithium-ion battery cell-level charging management via state-monitored predictive control

Lithium-ion battery charging management has become an enabling technology towards a paradigm shift of electrified mobility. Fast charging is desired for convenience improvements but may excessively degrade battery\u27s health or even cause safety issues. This paper proposes a novel algorithm to manage battery charging operations using a model-based control approach. Based on a fully coupled electrothermal model, the fast charging strategy is formulated as a linear-time-varying model predictive control problem, for the first time. Constraints are explicitly imposed to protect the battery from overcharging and overheating. To enable the state-feedback control, unmeasurable battery internal states including state-of-charge and core temperature are estimated via a nonlinear observer using noisy measurements of current, voltage, and surface temperature. Illustrative results demonstrate that the proposed approach is able to optimally balance time and temperature increase. In addition, it is shown from simulations that the model predictive control based charging algorithm appears promising for real-time implementation