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1

Interaction between an edge dislocation and a rigid hypotrochoidal inhomogeneity

Wang X., Schiavone P.

Archives of Mechanics

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2024

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Vol. 76, nr 1-2

143--153

EN

We study the plane elasticity problem associated with a rigid hypotrochoidal inhomogeneity embedded in an infinite isotropic elastic matrix subjected to an edge dislocation located at an arbitrary position. A closed-form solution to the problem is derived primarily with the aid of conformal mapping and analytic continuation. All of the unknown complex constants appearing in the pair of analytic functions characterizing the elastic field in the matrix are determined in an analytical manner. In addition, a simple method distinct from that by Santare and Keer (1986) is proposed to determine the rigid body rotation of the rigid inhomogeneity.

2

Piezoelectric effect on thermoelastic Lamb waves in functionally graded plates

Wang X., Ren X., Yu J., Zhou H., Zhang X., Leng J

Archives of Mechanics

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2023

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Vol. 75, nr 1-2

3--26

EN

Based on the Lord–Shulman thermoelectric elasticity theory, the piezoelectric effect on the thermoelastic Lamb wave propagation in the functionally graded material (FGM) plate is investigated. The coupled wave equations are solved by employing the Legendre polynomial series approach (LSPA), which poses the advantages of small scale of eigenvalues matrix and a convenient solution. It can directly obtain the complex wave number solutions without iteration. The obtained complex solutions, which represent the wave propagation and attenuation, are compared with those available data. Numerical examples show that the influence of gradient is profound. Results indicate that the piezoelectric effects on attenuation with the open and closed circuit condition are consistent for the S0 and S1 modes, but are inconsistent for the A0 and A1 modes. Although the piezoelectric effect is weak on the dispersion and attenuation of thermal waves, it is notable for their physical field distributions. In addition, the relaxation time is critical to electric displacements of a thermal wave mode, but is not essential for those of Lamb-like modes. The results can be used for the optimization of thermo-electric-elastic coupling structures.

3

Uniformity of electroelastic field within a three-phase anisotropic piezoelectric elliptical inhomogeneity in anti-plane shear

Wang X., Schiavone P.

Archives of Mechanics

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2022

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Vol. 74, nr 2-3

143--156

EN

Using the Stroh quartic formalism, we prove that the internal electroelastic field is unconditionally uniform inside a three-phase anisotropic piezoelectric elliptical inhomogeneity with two confocal elliptical interfaces when the surrounding matrix is subjected to uniform remote anti-plane mechanical and in-plane electrical loading. The inhomogeneity and the matrix comprise monoclinic piezoelectric materials with symmetry plane at x3 = 0 and with poling in the x3-direction; the intermediate interphase layer is a transversely isotropic piezoelectric material with poling in the x3-direction. Moreover, we obtain the internal uniform electroelastic field inside the elliptical inhomogeneity and the non-uniform electroelastic field in the interphase layer in real-form in terms of the fundamental piezoelectricity matrices for both the inhomogeneity and the matrix and the generalized Barnett–Lothe tensors for both the interphase layer and the matrix.

4

Peridynamic analysis of 2-dimensional deformation and fracture based on an improved technique of exerting traction on boundary surface

Zhou Z., Yu M., Wang X., Huang Z.

Archives of Mechanics

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2022

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Vol. 74, nr 6

441--461

EN

For 2-dimensional problems in peridynamics, the transfer functions of boundary traction are constructed. The peridynamic motion equation introducing the boundary traction is improved and used to solve some typical 2-dimensional deformation and fracture problems, including the uniaxial tension and pure bending of plate, and fracture of a plate with the small circular hole or central crack. The acquired numerical solutions are close to the analytical solutions of elasticity and numerical solutions given by the finite element method. The results show that the improved technique of exerting traction on a boundary surface is valid for calculating the deformation and failure of solid. It provides a new method and path for the analysis of traction boundary value problems in peridynamics.

5

Uniform stress field inside a non-parabolic open inhomogeneity interacting with a mode III crack

Wang X., Schiavone P.

Archives of Mechanics

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2021

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Vol. 73, nr 1

67--81

EN

Using conformal mapping techniques, analytic continuation and the theory of Cauchy singular integral equations, we prove that a non-parabolic open inhomogeneity embedded in an elastic matrix subjected to a uniform remote anti-plane stress nevertheless admits an internal uniform stress field despite the presence of a finite mode III crack in its vicinity. Our analysis indicates that: (i) the internal uniform stress field is independent of the specific shape of the inhomogeneity and the presence of the finite crack; (ii) the existence of the finite crack plays a key role in the non-parabolic open shape of the inhomogeneity and in the non-uniform stresses in the surrounding matrix; (iii) the two-term asymptotic expansion at infinity of the stress field in the matrix is independent of the presence of the finite crack. Detailed numerical results are presented to demonstrate the proposed theory.

6

Uniform field within a non-elliptical inhomogeneity in the vicinity of a nearby non-circular Eshelby inclusion

Wang X., Schiavone P.

Archives of Mechanics

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2021

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Vol. 73, nr 5-6

541--555

EN

We rigorously prove that a non-elliptical inhomogeneity continues to permit an internal uniform stress field despite the presence of a nearby non-circular Eshelby inclusion undergoing uniform anti-plane eigenstrains when the surrounding matrix is subjected to uniform remote anti-plane stresses. Here, we adopt a specific representation of the non-circular Eshelby inclusion as a Booth’s lemniscate inclusion. Our analysis indicates that the internal uniform stress field inside the non-elliptical inhomogeneity is independent of the existence of the Booth’s lemniscate inclusion whereas the non-elliptical shape of the inhomogeneity is attributed entirely to its presence. Representative numerical examples are presented to demonstrate the feasibility of the proposed method of general solution.

7

A screw dislocation located outside, inside or on the interface of a parabolic elastic inhomogeneity

Wang X., Schiavone P.

Archives of Mechanics

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2021

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Vol. 73, nr 3

219--235

EN

Using conformal mapping techniques, superposition and analytic continuation, we derive analytic solutions to the problem of a screw dislocation interacting with a parabolic elastic inhomogeneity. The screw dislocation can be located anywhere either in the surrounding matrix or in the parabolic inhomogeneity or simply on the parabolic interface itself. We obtain explicit expressions for the two analytic functions in the image plane characterizing the elastic fields describing displacement and stresses in the two-phase composite. Using the Peach-Koehler formula, we also obtain the image force acting on the screw dislocation. The analytic function defined in the parabolic inhomogeneity in the physical plane can be interpreted in terms of real and image screw dislocations for any location of the real screw dislocation.

8

The Machine Learning Method of PIDVCA

Li L., Wang X., Chen G.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2020

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Vol. 14. no. 3

533--540

EN

Building a dynamic collision knowledge base of self-learning is one of the core contents of implementing "personified intelligence" in Personifying Intelligent Decision-making for Vessel Collision Avoidance (short for PIDVCA). In the paper, the machine learning method of PIDVCA combined with offline artificial learning and online machine learning is proposed. The static collision avoidance knowledge is acquired through offline artificial learning, and the isomeric knowledge representation integration method with process knowledge as the carrier is established, and the Dynamic collision avoidance knowledge is acquired through online machine learning guided by inference engine. A large number of simulation results show that the dynamic collision avoidance knowledge base constructed by machine learning can achieve the effect of anthropomorphic intelligent collision avoidance. It is verified by examples that the machine learning method of PIDVCA can realize target perception, target cognition and finally obtain an effective collision avoidance decision-making.

9

Three-phase parabolic inhomogeneities with internal uniform stresses in plane and anti-plane elasticity

Wang X., Schiavone P.

Archives of Mechanics

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2020

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Vol. 72, nr 1

27--38

EN

We examine the in-plane and anti-plane stress states inside a parabolic inhomogeneity which is bonded to an infinite matrix through an intermediate coating. The interfaces of the three-phase parabolic inhomogeneity are two confocal parabolas. The corresponding boundary value problems are studied in the physical plane rather than in the image plane. A simple condition is found that ensures that the internal stress state inside the parabolic inhomogeneity is uniform and hydrostatic. Furthermore, this condition is independent of the elastic properties of the coating and the two geometric parameters of the composite: in fact, the condition depends only on the elastic constants of the inhomogeneity and the matrix and the ratio between the two remote principal stresses. Once this condition is met, the mean stress in the coating is constant and the hoop stress on the coating side is also uniform along the entire inhomogeneity-coating interface. The unconditional uniformity of stresses inside a three-phase parabolic inhomogeneity is achieved when the matrix is subjected to uniform remote anti-plane shear stresses. The internal uniform anti-plane shear stresses inside the inhomogeneity are independent of the shear modulus of the coating and the two geometric parameters of the composite.

10

Positive solutions for the one-dimensional p-Laplacian with nonlinear boundary conditions

Hai D. D., Wang X.

Opuscula Mathematica

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2019

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Vol. 39, no. 5

675--689

EN

We prove the existence of positive solutions for the p-Laplacian problem [formula] where [formula] can be nonlinear, i=1,2 , f:(0,∞)→R is p-superlinear or p-sublinear at ∞ and is allowed be singular (±∞) at 0, and λ is a positive parameter.

11

Improved dolphin swarm optimization algorithm based on information entropy

Li Y., Wang X.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2019

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Vol. 67, nr 4

679--685

EN

In order to overcome the shortcomings of the dolphin algorithm, which is prone to falling into local optimum and premature conver-gence, an improved dolphin swarm algorithm, based on the standard dolphin algorithm, was proposed. As a measure of uncertainty, information entropy was used to measure the search stage in the dolphin swarm algorithm. Adaptive step size parameters and dynamic balance factors were introduced to correlate the search step size with the number of iterations and fitness, and to perform adaptive adjustment of the algorithm. Simulation experiments show that, comparing with the basic algorithm and other algorithms, the improved dolphin swarm algorithm is feasible and effective.

12

Screw dislocations in piezoelectric laminates with four or more phases

Wang X., Chen L., Schiavone P.

Archives of Mechanics

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2019

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Vol. 71, nr 3

239--262

EN

We present an analytical solution to the problem of a screw dislocation in a four-phase piezoelectric laminate composed of two piezoelectric layers of equal thickness sandwiched between two semi-infinite piezoelectric media. A new version of the complex variable formulation is proposed such that the 2 × 2 real symmetric matrix appearing in the formulation becomes dimensionless. Using analytic continuation, the original boundary value problem is reduced to the identification of a single 2D analytic vector function which is completely determined following rigorous solution of the resulting linear recurrence relations in matrix form. An explicit expression for the image force acting on the piezoelectric screw dislocation is obtained once the single 2 × 2 real matrix function is identified. We also discuss the solution for a screw dislocation in an N-phase piezoelectric laminate composed of N − 2 piezoelectric layers of equal thickness sandwiched between two semi-infinite piezoelectric media.

13

Stability of air nucleus in liquid water and cavitation inception on marine engineering

Fu Q., Chen M., Wang X., Zhu R., Zhang G.

Polish Maritime Research

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2018

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S 3

111--119

EN

The micro air nucleus widely distributed in the ocean is a necessary condition for the cavitation of hydraulic machinery in seawater. In order to study the stability of air nucleus in seawater and cavitation inception, the computational domain of water molecules with air nucleus was studied using the method of molecular dynamics simulation, and the transient characteristics of air nucleus in liquid water were obtained. The key factors influencing nuclei stability were analyzed. The results showed that air nucleus with a certain mass could maintain the dynamic equilibrium in liquid water. The internal density of air nuclei had a critical value that allowed the nuclei to stably exist in water. The air nuclei mass was the decisive factor in its equilibrium volume in water, and the two were positively correlated. The internal density of air nuclei was negatively correlated with the nuclei radius when the nuclei was stable in water. Liquid surface tension was an important factor affecting the stability of the air nuclei. The larger the initial radius of nuclei, the smaller the water pressure, and the more likely the cavitation occurs.

14

Modelling of ship’s trajectory planning in collision situations by hybrid genetic algorithm

Ni S., Liu Z., Cai Y., Wang X.

Polish Maritime Research

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2018

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nr 3

14--25

EN

Ship collision-avoidance trajectory planning aims at searching for a theoretical safe-critical trajectory in accordance with COLREGs and good seamanship. In this paper, a novel optimal trajectory planning based on hybrid genetic algorithm is presented for ship collision avoidance in the open sea. The proposed formulation is established based on the theory of the Multiple Genetic Algorithm (MPGA) and Nonlinear Programming, which not only overcomes the inherent deficiency of the Genetic Algorithm (GA) for premature convergence, but also guarantees the practicality and consistency of the optimal trajectory. Meanwhile, the encounter type as well as the obligation of collision avoidance is determined according to COLREGs, which is then considered as the restricted condition for the operation of population initialization. Finally, this trajectory planning model is evaluated with a set of test cases simulating various traffic scenarios to demonstrate the feasibility and superiority of the optimal trajectory.

15

Effects of processing parameters on the properties of amphiphilic block copolymer micelles prepared by supercritical carbon dioxide evaporation method

Jiao Z., Wang Z., Wang X., Fan W.

Polish Journal of Chemical Technology

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2018

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Vol. 20, nr 1

81--86

EN

The operation parameters for the supercritical carbon dioxide (ScCO2 ) evaporation method greatly affect the properties of the prepared drug-loaded micelles. In this study, the effects of those key parameters on the drug-loading content (LC) and drug entrapment efficiency (EE) are discussed. It is observed that EE and LC of the micelles are slightly increased with the enhancing temperature and the copolymer molecular ratio of hydrophilic/hydrophobic segment, while decreased with the enhancing ScCO2 evaporation rate. The pressure and volume ratio of ScCO2 to H2 O are observed the optimum condition. In addition, the verification experiment is carried out under the obtained optimizing parameters. The prepared micelles exhibit relatively regular spherical shape and narrow size distribution with the EE and LC value of 70.7% and 14.1%, respectively.

16

Adsorption efficiency of pentafluorobenzene on ionic liquids-based silicas

Wang X., Lin L., Xie J., Yan X., Xiao W., Tian P.

Polish Journal of Chemical Technology

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2018

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Vol. 20, nr 3

47--52

EN

The adsorption of pentafl uorobenzene on nine ionic liquid-based silicas was investigated using solid phase extraction. The effects of several variables such as the type of ionic liquid groups, adsorption time, temperatures and water ratio in the solution system were experimentally evaluated. The imidazole-chloride ionic liquid group based silica exhibited the highest adsorption efficiency under the optimized conditions of 5 min adsorption at 30°C in water/methanol (30:70, vol%) solution. In addition, the effects of pH, as well as type and concentrations of chloride salts were investigated. At pH values other than neutral and high salt concentration, the adsorption efficiency was reduced. Finally, the relative standard deviation of less than 5.8% over a 5-day period showed a high precision for the nine tested sorbents.

17

Water film structure during rupture as revealed by MDS image analysis

Truong N. T., Dang L. X., Lin C.-L., Wang X., Miller J. D.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 4

1060--1069

EN

The structure of thin water films during the rupture process was investigated by a new approach, which combines molecular dynamics simulation (MDS) with image processing analysis. The analysis procedure was developed to convert MDS trajectories to readable 3D images. The water films were studied at different thicknesses by MDS to determine the critical thickness at which the film ruptures. The potential energy of each specific film thickness during the simulation time was analyzed, and the results showed that the potential energy of stable films remained unchanged while the potential energy kept decreasing for films which ruptured during the simulation time. By applying the new procedure, the molecular porosity, which is defined as the void fraction between the volume of molecular pores in the water film and the total volume of the water film, was calculated. The results of molecular porosity for different film thicknesses during the simulation time suggested a critical molecular porosity as 49%. In other words, stable films have a molecular porosity of less than 49%. If a water film has a molecular porosity greater than 49%, rupture occurs during the simulation.

18

Influence of fenugreek-gum and particle size on performance of talc flotation

Gu G., Mo C., Zhao K., Chen Z., Wang X.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 3

1026--1033

EN

Talc usually exists as a gangue mineral in copper-nickel sulfide, molybdenite etc. In order to separate precious metals, naturally hydrophobic talc should be depressed effectively in flotation process. The effect of fenugreek-gum (FG) on the flotation performance of talc with different particle sizes was studied. The depression mechanism was investigated extensively through tests of flotation, adsorption and zeta potential, as well as infrared spectroscopy and laser particle size analysis. Flotation results indicated that the FG had a strong depression ability for talc with the particle size of -0.074 + 0.037 mm, -0.037 mm and -0.010 mm when proper dosage of FG was added. The coarse talc was completely depressed by 2.5 mg/ dm3 FG. When the particle size decreased, more FG was required to obtain the maximum depressing effect, which was verified by adsorption tests. FG reduced the electronegativity on the talc surface by chemical adsorption, and flocculation of talc powders caused a high efficient depressing effect.

19

Effect of oxidation on the wetting of coal surfaces by water: experimental and molecular dynamics simulation studies

Li E., Lu Y., Cheng F., Wang X., Miller J. D.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 4

1039--1051

EN

The wettability of coal surfaces by water continues to be one of the key factors which determines the success of coal flotation. Consequently, oxidation of coal surfaces is a fundamental issue of interest. In this work, the effect of oxidation on the wetting of coal surfaces and the interaction between water molecules and oxygen-containing sites at the coal surface was investigated based on advancing/receding contact angle measurements and molecular dynamics simulations. For the simulation studies, a flat coal surface was constructed with the assistance of the molecular repulsion between graphite surfaces and the assembly of Wiser coal molecules. Our results indicated that the simulated advancing and receding contact angles were very similar, and both of them decreased, as expected, with an increase of hydroxyl sites at the coal surface. The good agreement between the simulated advancing/receding contact angles and the experimental receding contact angle values suggested that the configuration of the systems and the set of parameters for the simulation were appropriate. The spreading of water is mainly due to the hydrogen bonds formed between the interfacial water molecules and the hydroxyl sites at the coal surface. The hydroxyl groups show stronger hydration capacity than other oxygen-containing groups according to the calculated hydrogen bonds and interaction energies.

20

Dodecyl amine adsorption at different interfaces during bubble attachment/detachment at a silica surface

Wang X., Miller J. D.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 1

81--88

EN

The reverse flotation of quartz and other gangue silicate minerals with alkyl amines is an important and well known strategy for the processing of iron ore, low grade bauxite ore, and phosphate rock. Some details of amine adsorption by quartz have been described in the literature, but little is known about the disposition of amine during bubble attachment. Now, a new experimental procedure involving vibrational sum frequency spectroscopy (VSFS) has been developed to provide, for the first time, a more detailed analysis of the state of dodecyl amine (DDA) adsorption at different interfaces during bubble attachment/detachment at a silica surface. The results show that the hydrophobic surface state at the silica surface is created by the transfer of a well-organized monolayer of DDA from the bubble surface to the silica surface during bubble contact and attachment.