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In this paper, a three-dimensional time-dependent Riesz space-fractional diffusion equation is considered, and an alternating direction implicit (ADI) difference scheme is proposed, in which a weighted and shifted Grunwald difference scheme (see Tian et al. (2015) [33] ) is utilized for the discretizations of space-fractional derivatives, and a fractional-Douglas-Gunn type ADI method is utilized for the discretization of time derivative. The method is proved to be unconditionally stable and convergent with second-order accuracy both in time and space with respect to a weighted discrete energy norm. Efficient implementation of the method is carefully discussed, and then based on fast matrix-vector multiplications, a fast conjugate gradient (FCG) solver for the resulting symmetric positive definite linear algebraic system is developed. Numerical experiments support the theoretical analysis and show strong effectiveness and efficiency of the method for large-scale modeling and simulations. Finally, a linearized ADI scheme based on second-order extrapolation method is developed and tested for the nonlinear Riesz space-fractional diffusion equation.

The study on fluid-solid interaction in heterogeneous suspensions is essential for theoretical research and engineering practice. In this paper, a three-dimensional fully resolved SPH-DEM method is presented to model suspensions with non-Newtonian fluids and solid particles of arbitrary shape. The fluid phase is modelled using SPH with a regularized Bingham model, whereas aggregates with irregular shapes is modelled using a DEM method based on surface mesh representation. A simple unified hybrid contact method is proposed to model the SPH-boundary, SPH-DEM, DEM-DEM, and DEM-boundary interactions in a generalized fashion. Furthermore, GPU parallelization is employed to increase the numerical efficiency. The coupling method is validated using numerical examples including: (1) water-entry of a sphere, (2) Poiseuille flow of a Bingham material, (3) collapse of columns of irregular particles, and (4) gravity-driven heterogeneous flows with irregular particle shape. The simulation results indicate that the presented method is suitable for heterogeneous flows with irregular solid particles.

A surface mesh represented discrete element method (SMR-DEM) for granular systems with arbitrarily shaped particles is presented. The particle surfaces are approximated using contact nodes obtained from surface mesh. A hybrid contact method which combines the benefits of the sphere-to-sphere and sphere-to-surface approaches is proposed for contact detection and force computation. The simple formulation and implementation render SMR-DEM suitable for three-dimensional simulations. Furthermore, GPU parallelization is employed to achieve higher efficiency. Several numerical examples are presented to show the performance of SMR-DEM. It is found that on the particle level the method is accurate and convergent, while on the system level SMR-DEM can effectively model particle assemblies of various regular and complex irregular shapes.

A stabilized coupled total-Lagrangian and conventional Euler kernel based smoothed particle hydrodynamics (TL-CE SPH) method is presented to model three-dimensional granular flow-structure interaction with rigid and deformable structures. In the coupled TL-CE SPH, the granular material is simulated using CESPH with the Dracker-Prager model, while the structure solver is based on TLSPH. The stabilized TLSPH with corrected kernel gradient, Lagrangian kernel function and hourglass control technique overcomes the common deficiencies of inconsistency, tensile instability and hourglass mode in structure modeling. Based on the Adami boundary condition (Adami et al., 2012), a unified framework for modeling solid boundaries and the granular media-structure interfaces is presented. Furthermore, the advanced GPU-acceleration is employed to achieve high efficiency. The coupled method is employed to simulate problems of granular collapse, granular material-structure interaction at quasi-static regime and granular flows impact on rigid and deformable structures. The presented method can simulate granular flows, the flow-structure interactions, and the deformation and stress of the structures correctly. Furthermore, the GPU-acceleration gives hundreds times of speed-up over serial CPU implementation. The presented method can be applied to large scale three-dimensional cases.

A coupled total Lagrangian (TL) and weakly compressible (WC) smoothed particle hydrodynamics (SPH) method is presented to model three-dimensional fluid–structure interactions (FSI) with deformable structures. In the coupled TL–WC SPH, the fluid phase is simulated using WCSPH, while the structure solver is based on TLSPH. The three main deficiencies of solid simulation using conventional SPH, i.e. inconsistency, tensile instability and hourglass mode are circumvented in the stabilized TLSPH by means of corrected kernel gradient, Lagrangian kernel function and hourglass control technique, respectively. The resulted stabilized TLSPH is stable, accurate and has almost quadratic convergence rate in solid modeling. To increase the accuracy in FSI modeling, the δ − SPH technique is employed to improve the pressure results in the fluid phase. Based on the Adami boundary condition (Adami et al., 2012), a unified framework for modeling solid boundaries and the fluid–structure interfaces is presented. Furthermore, the GPU parallelization is employed to accelerate the proposed TL–WC SPH method for higher efficiency. The coupled method is employed to simulate problems of pure fluid flow, elastic solids with large deformation and fluid–structure interaction with deformable structures. The numerical results are compared with analytical solutions and results from literature. The GPU efficiency and speed-up compared with CPU implementations are analyzed. The novelty of this work consists: (1) three-dimensional SPH modeling of FSI problems with deformable structures, (2) stabilized structure simulation free of hourglass mode, (3) a unified framework for FSI problems taking advantages of δ -SPH, TLSPH, hourglass control, and GPU acceleration. Importantly, with the hourglass control technique proposed by Ganzenmuller (2015), stresses can be captured accurately in the TL–WC SPH-based FSI simulations.

The lithium-sulfur (Li-S) battery has received widespread attention because of the high theoretical energy density and inexpensive raw material. However, some issues still restrict its commercialization, including the shuttle effect, the lithium dendrite growth and low safety, etc. In this work, a PMMA-LLZO/PP/AB multifunctional separator was designed and facilely prepared to overcome these problems. A composite dense layer of the PMMA and LLZO sheets with excellent interface stability was coated on one side of the PP separator to face lithium metal anode, which can inhibit the lithium dendrites growth and increase the safety. Meanwhile, this composite coating possesses high affinity with the liquid electrolyte and the soluble polysulfides, which can improve the ionic conductivity, effectively adsorb the polysulfides. An acetylene black (AB) layer was further coated on the other side of the PP separator to not only act as an electron conductor but also adsorb and hinder the migration of lithium polysulfides. The co-modified PMMA-LLZO/PP/AB separator displays remarkable electrochemical performances and an excellent thermal stability. The cell with the co-modified separator exhibits high specific capacities of 1456 mAh g−1 at 0.1 C and 969 mAh g−1 at 1.0 C, and retains a capacity of 413 mAh g−1 after 500 cycles, corresponding to a retention of 42.6% as well as a low decay of 0.114%/cycle. Especially, the cell with the multifunctional separator also displays a high capacity and a low decay even for a high sulfur mass loading cathode of 2.5–3.0 mg cm−2 or at a high temperature of 60 °C. The co-modified multifunctional separator has great application potential in the high-performance Li-S battery.

Traixial test is a common method for the study of the mechanical behaviors of granular materials. And, the interaction between the membrane and particles will greatly influence the test results. In this paper, computational contact mechanics method is developed for the simulation of sphere-sphere and sphere-membrane contacts in triaxial test. In both algorithms, the contact state and distance functions are determined according to the geometric information of the spheres instead of the finite element mesh. Two benchmarks have been used to validate the proposed algorithms, and the results showed that the sphere-sphere and sphere-membrane interactions were accurately and stably simulated. Furthermore, the size of the spherical particle elements has minor influence on the numerical results and therefore, it can be used for the study of the granular mechanics with larger number of particles. Finally, the consolidation process of a triaxial test is studied and compared with the laboratory tests, which also shows that the algorithm can not only better simulate the membrane penetration process but also the meso mechanics of the granular materials.

Extrusion damage in the concrete face was widely observed in high concrete-faced rockfill dams in the last two decades. However, the accurate estimation of the concrete stress remains a great challenge. In this paper, a thermo-mechanical coupling method is presented to numerically evaluate the solar radiation effect on the concrete stress within the dual mortar finite element framework. The heat conduction is modelled as a transient time-dependent equation and hence the heat flow can be determined by meteorological data. The thermo-mechanical coupling is conducted in a weak way such that the linear system can be split into two subsystems friendly to the linear solver. The present method based on using nonconforming meshes is validated by the comparisons with node-to-segment method, conforming mesh and analytical solution. The application to a concrete-faced rockfill dam indicates that the phase lag and amplitude damping effects are apparent in the thermal analysis, confirming the importance of using transient heat conduction theory. The observed slab-slab separations emphasis the importance of using dual mortar contact method. The thermal stress is found to be larger than 10 MPa and therefore needs to be considered in the design and safety assessment.

In the construction of high concrete-faced rockfill dams (CFRDs), soft filler is used in the longitudinal joints in order to avoid extrusion damage to the concrete face slab. In this paper, we consider the soft joint contact as an equivalent contact interface to avoid introducing conventional elements. Based on the introduction of a general transformation to obtain fully decoupled contact constraints, a new generalized node-to-segment formulation is developed to solve the multi-body contact problem in CFRDs. The high CFRD of Tianshengqiao-1 in China is numerically analyzed; the results show that soft joints can significantly reduce the axial stress of face slabs.

In this paper, a flow model for avalanches based on the three-dimensional yield criterion is presented in an attempt to allow the relaxation of the assumption of lateral confinement pressure that is adopted in the traditional three-dimensional Savage–Hutter model (S–H model). One of the advantages of this model is that a simplified constitutive relationship for granular flow, which could reveal the internal mechanism of avalanches, is adopted. Additionally, another advantage is that the strength parameters used in the proposed model are readily available for natural materials. The flow properties of avalanches are influenced by the generalized friction coefficient, which is a parameter that can be assessed by introducing the three-dimensional yield criterion. By comparing the results obtained by numerical simulations using the model proposed in this paper and laboratory experiments, a reasonably good agreement can be reached with regard to the prediction of the moving process of avalanches.

Conventional two-field mortar methods have master/slave bias and need special treatments for the cross corner problem. In this work, we present a three-field dual mortar method, which employs an intermediate interface to connect individual subdomains with nonconforming meshes. Using this intermediate interface as the master face, a dual mortar method can be formulated by discretizing Lagrange multipliers on the subdomain interfaces using dual basis functions. Furthermore, the computational cost is minimized by static condensation of Lagrange multipliers and elimination of displacement unknowns on subdomain interfaces. Owing to the three-field formulation, the presented method is free of master/slave bias and can handle the cross corner problem naturally. The stability condition for the intermediate interface mesh is investigated by theoretical analysing and numerical modelling. Numerical tests show that the presented method has optimal convergence rate and allows great flexibility in mesh preparation.

This study aimed to explore whether the depression of offspring caregivers can be affected by the intergenerational disagreements on preferred living arrangements for the elderly, and the extent of this influence.A total of 875 participants from five urban neighborhoods were investigated in a cross-sectional survey in Jinan, China. Depressive symptoms were assessed by the Self-rating Depression Scale (SDS). Multiple stratification was performed based on participants' characteristics, then generalized linear models (GLM) were used to adjust confounding factor and analyze the effect of the intergenerational disagreements on depressive symptoms among participants with different characteristics.The intergenerational disagreements on preferred living arrangements for the elderly greatly impact on offspring caregivers' depressive symptoms. Especially in the following two situations: (1) in the case of older adults were relatively independent and offspring caregivers had to co-reside with older adults against their own will, the max mean difference on the depression measures was up to 10.603 (p0.001), in comparison with both parties were willing to co-reside. (2) In the case of older adults were fully dependent and offspring caregivers had not to hire a maid to care older adults against their own will, the max mean difference on the depression measures was up to 8.937 (p0.001), in comparison with both parties were willing not to hire a maid.Intergenerational disagreements on preferred living arrangement for the elderly have negative effect on offspring caregivers' depressive symptoms.

In this paper, we analyze the constitutive laws of a hydraulic dynamic model, the Savage–Hutter (S–H) model, and the Hungr model. To overcome their limitations, we adopt a frictional viscoplastic constitutive law for dense granular flow and propose a new constitutive law-based dynamic model for avalanches by simplifying the internal stresses for shallow granular flow. The range of the earth pressure coefficient in each model is studied and compared. Finally, we compare the previous experimental results with those obtained from the proposed model and the S–H model, and we find that the new model can capture the flow properties of an avalanche.

This paper presents a general 3D contact smoothing method based on the meshfree radial point interpolation method to improve the numerical simulation of contact problems. In particular, a locally smooth contact surface is constructed from the scattered surface nodes by point interpolation using the combination of polynomial and radial bases. With such bases, this method reproduces smooth surfaces even for coarse meshes and the constructed surface passes exactly through the surface nodes. Results for contact problems involving deformable bodies are included to demonstrate its advantages.

Following the completion of triaxial compression tests on cement ellipsoid specimens, the particle size distribution for the specimen was analyzed after testing. It is found that neither particle strength nor confining pressure had much effect on the particle size distribution of completely broken particles. That is, the aggregates with different particle strengths have approximately the same fractal dimension. Hardin’s relative breakage was modified based on the concept of optimum distribution. Also, a relationship between relative breakage and plastic work was suggested and verified in this paper.

The mechanical behavior and constitutive modeling of interfaces between two granular materials is one of the significant concerns in design of soil structures such as earth-rock-fill dams. The simple shear tests were conducted to investigate the strength and deformation characteristics for interfaces between core material and filter material in earth core rock-fill dam. Based on the test results, the perfect-plastic model was proposed to describe the interface behavior. The model was incorporated in the finite element software to study the interface behavior, and the non-linear failure process of interfaces was captured by the proposed model.

An intelligent method for the effective displacement back-analysis of earth-rockfill dams was proposed by combining artificial neural networks and evolutionary calculation. This method employs artificial neural networks, with optimal architecture trained by the evolutionary calculation and Vogl’s algorithm, instead of the time-consuming finite element analysis. In the back analysis, the soil parameters were optimized by performing evolutionary calculations on the tested neural network. The proposed method was verified by applying it to the displacement back-analysis of two projects in China, and the influence of generation number and set size on the simulation ability of neural networks was investigated.

Various measures including material experiments, centrifuge modeling tests and FEM numerical analyses were performed to study systematically the action mechanism of the geotextile-reinforced cushion under breakwater on soft ground and the effects of the strata characterization and the reinforcement condition on the stability of the breakwater-ground system. In the aspect of controlling the deformation, the geotextile-reinforced cushion under breakwater constrains the lateral displacement of both the embankment and the ground. From the viewpoint of stress, the reinforcement suppressed the range of high stress level in the system. In general, the weaker the ground is and the greater the modulus of the geotextile is, the more effective the reinforcement is. The tensile force in the geotextile is greater in the range of the main part of the embankment.

A series of parametric studies were performed to investigate the three-dimensional (3D) effect on the stability of an earth–rockfill dam, with respect to some major factors, such as geometrical characteristics of the dam and topography of the canyon. The length–height ratio of the earth–rockfill dam clearly influences the 3D safety factor. A power function suitably expresses the relationship between the increment ratio for the safety factor and the length–height ratio. The canyon shape, gradient of dam slope and height of the dam significantly influence the 3D effect. The results may be used as a blueprint by combining the two-dimensional (2D) safety factor in common use, and the relationship between 2D and 3D safety factors established in this study.

Negative temperature coefficient (NTC) thermistors based on Ni 0.9 Mn 2.1-x Mg x O 4 (0&lex&le0.3) materials with different compositions were synthesized by a rheological phase reaction with ultrasound radiation (RPR-UR) method. It was found that the as-prepared powder crystallized well with spinel structure. It presented a microstructure of well-packed grains. The resistivity, B 25/50 constant and activation energy with a wide range of values were obtained. And it can be adjusted to desired values for industrial applications by controlling the MgO content. All the results suggest that the RPR-UR method is a promising technique for the preparation of Ni 0.9 Mn 2.1-x Mg x O 4 NTC ceramic materials.

The contact behavior between concrete face slab and dam body is important to the safety of concrete-faced rockfill dams. The deficient of dam body and the separation of concrete slab from cushion layer during construction and in operation are the main concerns. This paper proposes a contact analysis method to study the effect of non-linearity and time-dependent deformation on the separation and the deficient. This contact analysis method regards dam body and concrete slab as two independent deformable bodies. These two deformable bodies follow Coulomb friction law at contact interface when they contact each other. The rockfill materials in dam body are assumed to be non-linear and time-dependent but concrete slab is elastic. As an example, a high concrete-faced rockfill dam of Tianshengqiao-I in China is numerically analyzed, and the numerical results are compared with in situ measurements. The results reveal that whether the deformation of dam body is non-linear or time-dependent, this contact analysis method can effectively simulate the separation between concrete slab and cushion layer without the drawbacks of interface element methods.

Wave-induced transient response of seabeds is numerically analyzed through a radial point interpolation meshless method (radial PIM). The Biot’s consolidation theory is employed and incorporated with virtual boundary conditions to describe this wave-induced transient response of the seabed. Displacement and pore water pressure are spatially discretized by the radial PIM with the same shape function. Compactly supported basis functions are proposed to obtain a banded system equation. Because the radial PIM passes through all nodal points within an influence domain, essential boundary conditions as well as virtual boundary conditions can be easily implemented at local level. Fully implicit integration scheme is used in time domain to avoid spurious ripple effect. The proposed algorithm is assessed through the comparison of numerical results with closed-form solution or finite element solutions.

A new analytic solution of the mild-slope long wave equation is derived for studying the effects of bottom topography on combined refraction and diffraction. The solution is essentially of a series form involving the Bessel functions of real orders but is found to be singular as the bottom tends to be parabolic. Numerical evaluation of the solution nearby the singularity requires some special considerations. The particular solution under the singular condition is also given. Study on combined refraction and diffraction for waves around a circular island on the top of a shoal, which is radially described by a power function with two independent parameters, indicates that there exist an extremely high wave zone near the top of a hyperparabolic shoal. It is also found that the intensity of wave ray focusing increases significantly as the mean slope decreases. A direct consequence of the wave ray focusing is the concentration of wave energy and an increase of the maximal wave runup height around the island.