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The frequency of the applied electric field and the epitaxial strain can affect the microstructure and the overall properties of ferroelectric thin films. In this study, the ferroelectric characteristics of BaTiO3 nano single crystal thin films were investigated via phase field simulation under the epitaxial strain of -0. 1% and -0. 7%, respectively, in the frequency range of 0. 1 ~100 kHz. It is found that, with the increase in frequency, the square-shaped hysteresis loop gradually changes to an elliptic loop and the butterfly loop changes to a kidney-shaped loop. When the applied frequency is below 50 kHz, the coercive field increases rapidly with the increase in frequency, but the change in remnant polarization is not significant. When the frequency is over 50 kHz, the coercive field only increases slightly, and the remnant polarization exhibits a downward trend. It is observed that the frequency dependence of ferroelectric properties is more significantly affected by the epitaxial strain while the frequency is low. The frequency dependence is not very sensitive to the epitaxial strain while the frequency is high. Meanwhile, the compressive epitaxial strain causes significant rise in both the remnant polarization and coercive field, and the tensile epitaxial strain leads to opposite effects. By analysis, it is found that the underlying mechanism of the frequency-dependent hysteresis is due to the competition between the speed of microstructure evolution and the frequency of the applied electric field. The findings of this study serve as theoretical basis for the experiment and design of ferroelectric functional thin films, and they provide knowledge-based support for the application of high-frequency electronic devices. [ABSTRACT FROM AUTHOR]

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper establishes a microchannel model based on the pore scale distribution characteristics of natural cores from Daqing Oilfield. It considers the deformation and flow characteristics of the dispersed and continuous phases in the heterogeneous system， builds a flow model by the phase field method， and solves it by the finite element method. The paper also simulates the generation of dispersed phase particles in the microchannel， realizes particle sorting， and studies the effect of the matching coefficient and pore-throat ratio on the plugging performance of particles in the microscopic pore-throat structure. The results show that when the particles are elastically plugged in the microscopic pore-throat structure， the pressure at the entrance of the pore throat changes periodically with the migration of the particles through the pore throat. The optimal matching coefficient between the particles and the pore throat is ［1.0， 1.4）. In this interval， the particles can be temporarily plugged at the entrance of the pore throat and recover their original shape after deformation and migration through the pore throat. When the pore diameter is the same， a larger matching coefficient and pore-throat ratio indicate greater pressure of particles through the pore throat， and larger particle size reflects a smaller critical value of particles through the pore throat.

Copyright of Petroleum Geology & Recovery Efficiency is the property of Petroleum Geology & Recovery Efficiency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To provide reference for controlling the generation of uniform high frequency of droplets, aimed at droplet generation in confined microchannels, considering the influence of fluid physical properties and flow conditions, numerical simulation of droplet formation in a T-confined microchannel was carried out. Using COMSOL software, droplet generation process simulation model was established, and the phase field method was adopted to explore the capillary number, two-phase flow ratio, viscosity ratio and wall wettability effects on droplet generation. Results showed that when the continuous phase viscosity is 0.01 Pa·s, and the dispersed phase velocity and viscosity are 0.005 m/s and 0.001 Pa·s, respectively, as the continuous phase capillary number increases from 0.001 5 to 0.007 5, the continuous phase capillary number increased from 0.001 5 to 0.007 5, the dimensionless droplet length decreased from 2.8 power index to 1.5, the dimensionless liquid column length increased linearly from 2.6 to 7.6, the droplet generation frequency increased from 30 power exponents per second to 52; when the continuous phase viscosity is 0.01 Pa·s, the dispersed phase viscosity is 0.001 Pa·s, and the flow ratio increased from 0.1 to 0.9, the dimensionless droplet length increased linearly from 1.05 to 2.55, the dimensionless liquid column length decreased from 6.49 power index to 2.51, the droplet generation frequency decreased from 170 power index per second to 65, when the continuous phase velocity is 0.01 m/s, the dispersed phase velocity is 0.005 m/s, and the viscosity ratio increased from 0.025 to 0.5, and the dimensionless droplet length increased from 1.72 to 2.1 The length of the dimensionless liquid column increased from 3.11 to 3.9, and the droplet generation frequency decreased from 31 functions per second to 24. Wall wettability affects the morphology of droplets, but there is no obvious functional relationship. The physical properties and flow conditions of fluid have significant influence on droplet formation. [ABSTRACT FROM AUTHOR]

A specific columnar crystal structure is obtained using the directional solidification technique, which has a substantial effect on the optimization of the axial mechanical properties of the alloy. Additionally, the convection phenomenon in the melt changes the temperature field and concentration field at the front of the solid–liquid interface, affecting the shape of this interface. Thus, the influence on alloy properties cannot be ignored. Although the phase field method has more research on the microdendrite growth morphology, the results of coupling the flow field into the phase field and exploring the microdendrite morphology of directional solidification are still scarce. In this paper, the phase field model of a coupled flow field is used to simulate dendritic growth during directional solidification. The effects of the anisotropy coefficient and interfacial energy on the growth of directionally solidified dendrites and the growth behavior of dendrites under forced convection were studied. For the numerical solution procedure, a uniform grid of the finite difference method was used to discretize the governing equations. A combined solution of the MAC algorithm and a phase field discrete calculation was realized. When addressing the coupling of the microvelocity and pressure fields, the MAC algorithm was used to solve the Navier–Stokes equation and pressure Poisson equation, and the interlocked grid method was applied to handle the complex free interface. The results show that the growth rate of the dendrite tip increases, and the radius of curvature and the solute concentration at the root of the dendrite decrease with an increasing anisotropy coefficient. When the anisotropy coefficient is a maximum of 0.065, the wall of the dendrite tends to develop toward a secondary dendrite because of the influence of the anisotropy coefficient; with increasing interfacial energy, the radius of curvature of the dendrite tip increases. When the interfacial energy is a maximum of 0.6 J·m−2, the solidification shows a flat interface advancing mode; forced convection has a great influence on the growth direction of directional solidification dendrites. The directional solidification of dendrites in the upstream direction is coarse and grows faster with increasing flow rate. Additionally, the dendrite growth morphology observed using an optical microscope agrees well with the experimental results.

To explore the demulsification mechanism of emulsion under electric fields, the movement process of dispersed phase droplets in water-in-oil emulsion was simulated with the finite element method. Herein, the oil-water distribution was represented with the phase field method, and the accuracy and efficiency of calculation on fluid flow process was improved with the structured quadrilateral grid. Besides, the influence laws of electric field parameters, as well as the physical parameters of emulsion, on the droplet deformation and coalescence were systematically studied to provide theoretical basis for the efficient application of electric demulsification technology. According to the results, the higher the electric field intensity, root mean square(RMS) of electric field waveform and droplet size, the greater the deformability and coalescence ability of droplets are. The droplet deformation is independent of frequency under the high-frequency conditions, and the frequency has little effect on the coalescence rate of droplets. Meanwhile, the droplet deformation and coalescence rate can been improved by decreasing the continuous phase viscosity and oil-water interfacial tension. In addition, the microcosmic mechanism of droplet deformation and coalescence was also discussed. It is found that the maximum droplet deformation is in strong linear relationship with the electric Weber number in the case of small deformation, and the electric field intensity,droplet size and interfacial tension affect the coalescence efficiency of droplets by influencing the evolution of liquid bridge between droplets.

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: In order to explore the effect of an external electrostatic field on the growth of ice crystals during food freezing. Methods: Based on the classic Kobayashi model of phase field method, the free energy density of electric field was introduced into the phase field model. Used the five-point difference scheme in the finite difference method to discretize the partial differential equation, the simulation and visualization of ice crystal growth were realized by programming. Results: The results showed that the simulation results were consistent with other simulation results and experimental results, and the ice crystal morphology had a typical sixfold symmetry; With the increase of electric field intensity, the growth rate of main branches and nucleation growth of ice crystals were inhibited. Conclusion: In the process of quick-frozen food preservation, adding a certain electric field strength will reduce the formation of ice crystals, and retain the quality and flavor of food as much as possible.

The behavior of crack initiation, propagation and coalescence in rock is the key mechanics of rock deformation, strength and stability, and it is important to predict and analyze crack growth behavior by numerical method. Phase field（PF） method overcomes the challenge of the traditional fracture mechanics theory and numerical method to explicitly track the crack surface within the framework of strict and accurate theory, and can simulate crack initiation, propagation, branching and multi-cracking. A multi-scale model that can reflect the internal microstructure of rock materials was established at the main area of crack growth. The failure progress of crack initiation, propagation and coalescence within the basalt under three-point bending test was predicted and analyzed by phase field method. The influence of the distribution of mineral inclusions and energy release rate on the crack propagation behavior was investigated and the numerical simulation results were compared and verified with the experimental data. It is shown that the proposed multi-scale PF model considering the complex internal microstructure of basalt rock is able to simulate and predict the progress of the crack behavior. The behavior of crack initiation, propagation and coalescence in rock is the key mechanics of rock deformation, strength and stability, and it is important to predict and analyze crack growth behavior by numerical method. Phase field（PF） method overcomes the challenge of the traditional fracture mechanics theory and numerical method to explicitly track the crack surface within the framework of strict and accurate theory, and can simulate crack initiation, propagation, branching and multi-cracking. A multi-scale model that can reflect the internal microstructure of rock materials was established at the main area of crack growth. The failure progress of crack initiation, propagation and coalescence within the basalt under three-point bending test was predicted and analyzed by phase field method. The influence of the distribution of mineral inclusions and energy release rate on the crack propagation behavior was investigated and the numerical simulation results were compared and verified with the experimental data. It is shown that the proposed multi-scale PF model considering the complex internal microstructure of basalt rock is able to simulate and predict the progress of the crack behavior. [ABSTRACT FROM AUTHOR]

In order to study the microcosmic mechanism of ice formation in ship structure, a numerical simulation is conducted. Based on the Wheeler phase field model, the finite difference method is used to simulate the solidification shape of seawater at different undercoolings. In the process of simulation, sea water is regarded as the binary mixture of salt and pure water, and the authenticity of ice crystal growth is ensured by setting ice physical parameters and introducing crystal nucleus. In the calculation, four nuclei are set up to simulate the ice crystal growth, and the influence of different undercoolings on the ice crystal growth is discussed. The results show that the growth rate of ice crystal increases with the increase of undercooling, and it is linear with the change of undercooling. When the dimensionless undercooling is less than 0.85, the dendrite has only a few branches which are thin. When the dimensionless undercooling is higher than 0.85, the ice crystal has more than two-stages of branches which are obviously thicker. When the dimensionless undercooling reaches 1.0, the branches are squeezed by the main branches and lessned, and the crystal cores are finally filled.

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Investigation of the influence of helium bubbles on the dynamic strength has drawn continuous attention. In this article, the phase field method (PFM) is applied to investigate the evolution of helium bubbles at an early stage in shock-loaded aluminum based on its advantage to describe the interface evolution. PFM is coupled with the crystal plasticity finite element method (CPFEM), which makes it possible to investigate the interaction between the helium bubbles and the collective behaviors of dislocation assembles. It is found that the heterogeneity of helium bubbles induces a local concentration of plastic deformation, which leads to a rarefaction wave along the propagation direction of the shock wave. From an energy perspective, it is inferred that both the growth of helium bubbles and the plastic deformation are driven by the strain energy, which indicates that these two processes may compete with each other. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai University of Engineering Science / Shanghai Gongcheng Jishu Daxue Xuebao is the property of Journal of Shanghai University of Engineering Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dynamic wetting phenomena of droplets are widely observed in nature and industrial production, the numerical research of which needs a solution of singularity and a correct model of the dynamic contact angle. Based on the phase field method (PFM) and the modified dynamic contact angle model, a 2-phase flow numerical method with dynamic wetting effects was developed, and the related program was realized on the OpenFOAM platform. The dynamic process of droplets impacting on a wall was simulated, and the comparison of the computation results of different contact angle models was conducted. The results indicate that the contact angle model influences the dynamic wetting process simulation significantly; the results of the proposed method are in good agreement with those of the experiment, which shows the proposed method is effective in the simulation of dynamic wetting phenomena. [ABSTRACT FROM AUTHOR]

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Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)