scholarly journals Modeling of orientational polarization within the framework of extended micropolar theory

2021 ◽  
Author(s):  
Elena N. Vilchevskaya ◽  
Wolfgang H. Müller
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Dielectric Material ◽  
Traditional Approach ◽  
Relaxation Times ◽  
Thermal Motion ◽  
Effective Length ◽  
Micropolar Theory ◽  
Production Term ◽  
The Impact

AbstractIn this paper the process of polarization of transversally polarizable matter is investigated based on concepts from micropolar theory. The process is modeled as a structural change of a dielectric material. On the microscale it is assumed that it consists of rigid dipoles subjected to an external electric field, which leads to a certain degree of ordering. The ordering is limited, because it is counteracted by thermal motion, which favors stochastic orientation of the dipoles. An extended balance equation for the microinertia tensor is used to model these effects. This balance contains a production term. The constitutive equations for this term are split into two parts, one , which accounts for the orienting effect of the applied external electric field, and another one, which is used to represent chaotic thermal motion. Two relaxation times are used to characterize the impact of each term on the temporal development. In addition homogenization techniques are applied in order to determine the final state of polarization. The traditional homogenization is based on calculating the average effective length of polarized dipoles. In a non-traditional approach the inertia tensor of the rigid rods is homogenized. Both methods lead to similar results. The final states of polarization are then compared with the transient simulation. By doing so it becomes possible to link the relaxation times to the finally observed state of order, which in terms of the finally obtained polarization is a measurable quantity.

scholarly journals Квазистационарные процессы диэлектрической релаксации в тонких поликристаллических пленках PZT

2020 ◽  
Vol 62 (10) ◽  
pp. 1665
Author(s):  
В.В. Иванов ◽  
Е.Н. Голубева ◽  
О.Н. Сергеева ◽  
Г.М. Некрасова ◽  
И.П. Пронин ◽  
...  
Keyword(s):  
Electric Field ◽  
Dielectric Relaxation ◽  
External Electric Field ◽  
Annealing Temperature ◽  
Relaxation Times ◽  
Polarization Vector ◽  
Silicon Substrates ◽  
Relaxation Processes ◽  
Pzt Films

In this work, relaxation processes in polycrystalline PZT films formed on silicon substrates with a quasistatic change in the external electric field are studied. It is shown that dielectric relaxation is characterized by at least three relaxation times, which depend on the direction of self-polarization vector in the film, the magnitude of the polarizing field, and also on the annealing temperature of the PZT films.

scholarly journals Heavy Metals Nanofiltration Using Nanotube and Electric Field by Molecular Dynamics

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Tiago da Silva Arouche ◽  
Rosely Maria dos Santos Cavaleiro ◽  
Phelipe Seiichi Martins Tanoue ◽  
Tais Sousa de Sa Pereira ◽  
Tarciso Andrade Filho ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Boron Nitride ◽  
Electric Field ◽  
Metal Ions ◽  
External Electric Field ◽  
Ion Selectivity ◽  
Intermolecular Forces ◽  
Water Molecules ◽  
The Impact

Heavy metal contamination in the world is increasing the impact on the environment and human life. Currently, carbon nanotubes and boron are some possible ideals for the nanofiltration of heavy metals due to the property of ion selectivity, optimized by the applications of the surface and the application of an external electric field. In this work, molecular dynamic was used to transport water with heavy metals under the force exerted by the electric field action inside nanotubes. This external electric field generates a propelling electrical force to expel only water molecules and retain ions. These metal ions were retained to pass through only water molecules, under constant temperature and pressure, for a time of 100 ps under the action of electric fields with values from 10-8 to 10-1 au. Each of the metallic contaminants evaluated (Pb2+, Cd2+, Fe2+, Zn2+, Hg2+) was subjected to molecular test simulations in the water. It was found that the measurement of the intensity of the electric field increased or the percentage of filtered water reduced (in both nanotubes), in which the intramolecular and intermolecular forces intensified by the action of the electric field contribute to retain the heavy metal ions due to the evanescent effect. The best results for nanofiltration in carbon and boron nanotubes occur under the field 10-8 au. Since the filtration in the boron nitride nanotubes, a small difference in the percentage of filtered water for the boron nitride nanotube was the most effective (90 to 98%) in relation to the carbon nanotube (80 to 90%). The greater hydrophobicity and thermal stability of boron nanotubes are some of the factors that contributed to this result.

scholarly journals Theoretical and numerical analysis of nano-actuators based on grafted polyelectrolytes in an electric field

2017 ◽  
Vol 199 ◽  
pp. 487-510 ◽  
Author(s):  
N. V. Brilliantov ◽  
Yu. A. Budkov ◽  
C. Seidel
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Md Simulations ◽  
Friction Model ◽  
Nano Particle ◽  
Variational Theory ◽  
Vibration Direction ◽  
Theoretical And Numerical Analysis ◽  
The Impact ◽  
Bulk Part

We analyze, theoretically and by means of molecular dynamics (MD) simulations, the generation of mechanical force by a polyelectrolyte (PE) chain grafted to a plane and exposed to an external electric field; the free end of the chain is linked to a deformable target body. Varying the field, one can alter the length of the non-adsorbed (bulk) part of the chain and hence the deformation of the target body and the arising force. We focus on the impact of added salt on the magnitude of the generated force, which is especially important for applications. In particular, we develop a simple variational theory for the double layer formed near electrodes to compute the electric field acting on the bulk part of the chain. Our theoretical predictions agree well with the MD simulations. Next, we study the effectiveness of possible PE-based nano-vices, comprised of two clenching planes connected by PEs exposed to an external electric field. We analyze a novel phenomenon – two-dimensional diffusion of a nano-particle, clenched between two planes, and introduce a quantitative criterion for clenching efficiency, the clenching coefficient. It is defined as a logarithm of the ratio of the diffusion coefficients of a free and clenched particle. Using first a microscopic counterpart of the Coulomb friction model, and then a novel microscopic model based on surface phonons, with the vibration direction normal to the surface, we calculate the clenching coefficient as a function of the external electric field. Our results demonstrate a dramatic decrease of the diffusion coefficient of a clenched nano-particle for the range of parameters relevant for applications; this proves the effectiveness of the PE-based nano-vices.

Refractive index changes in constant total effective length GaN/AlN multiple quantum well systems under external electric field

2014 ◽  
Vol 28 (29) ◽  
pp. 1450204 ◽  
Author(s):  
M. Solaimani
Keyword(s):  
Refractive Index ◽  
Electric Field ◽  
Quantum Well ◽  
External Electric Field ◽  
Energy Levels ◽  
Multiple Quantum Well ◽  
Oscillatory Behavior ◽  
Effective Length ◽  
Multiple Quantum ◽  
Index Changes

In this work we have investigated the effect of external electric field on the electronic structure and refractive index changes of a GaN/AlN constant total effective length multiple quantum well. A decreasing oscillatory behavior for energy levels was seen when the electric field increased and in some energy values the energy levels intersected. By increasing the number of wells, oscillator strength dropped suddenly and moved to higher electric field in a critical electric field. By using the number of wells and the total length of the structure as two tuning tools, we were able to select our previously determined critical electric field.

Interaction of H2O and H2S with Cu(111) and the impact of the electric field: the rotating & translating adsorbate, and the rippled surface

2015 ◽  
Vol 17 (1) ◽  
pp. 588-598 ◽  
Author(s):  
Jin Hyun Chang ◽  
Ahmed Huzayyin ◽  
Keryn Lian ◽  
Francis Dawson
Keyword(s):  
Density Functional Theory ◽  
Electric Field ◽  
External Electric Field ◽  
Density Functional ◽  
Functional Theory ◽  
The Impact

The interactions of H2O and H2S monomers with Cu(111) in the absence and presence of an external electric field are studied using density functional theory.

scholarly journals The influence of external electrostatic field on the combustion of hexamine

2020 ◽  
pp. 42-49
Author(s):  
Ilya A. Zur ◽  
Alexander S. Fedotov
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Electric Fields ◽  
Spatial Configuration ◽  
Scientific Work ◽  
Threshold Value ◽  
Degree Of Ionization ◽  
Fire Extinguishing ◽  
Electrode Space ◽  
The Impact

In scientific work investigates the impact of electric fields on combustion of hexamine. The experimental setup has been developed to study the interaction of an electric field with a low-temperature flame. The optimal spatial configuration of the electrodes for extinguishing the flame was established; the dynamics of airflows caused by the ion wind was studied; the threshold value of the electric field leading to flame extinguishing was determined. An expression is proposed based on the equation of motion that connects the speed of motion of partially ionized gas particles, the viscosity and degree of ionization of the gas, and the intensity of the external electric field. It is shown that the strength of the external electric field, leading to extinguishing of hexamine combustion, increases with decreasing inter-electrode space. The values of corresponding electric field strength lied in range from 80 to 135 kV/m at interelectrode distances of 0.4 and 0.1 m, respectively. The results of the study can be used for effective fire extinguishing in compact devices running on dry fuel.

scholarly journals On relaxation processes in a completely ionized plasma

2020 ◽  
Keyword(s):  
Distribution Function ◽  
Electric Field ◽  
External Electric Field ◽  
Electron Distribution ◽  
Electron Distribution Function ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Energy And Momentum ◽  
Energy And Momentum Densities ◽  
Relaxation Coefficients

Relaxation of the electron energy and momentum densities is investigated in spatially uniform states of completely ionized plasma in the presence of small constant and spatially homogeneous external electric field. The plasma is considered in a generalized Lorentz model which contrary to standard one assumes that ions form an equilibrium system. Following to Lorentz it is neglected by electron-electron and ion-ion interactions. The investigation is based on linear kinetic equation obtained by us early from the Landau kinetic equation. Therefore long-range electron-ion Coulomb interaction is consequentially described. The research of the model is based on spectral theory of the collision integral operator. This operator is symmetric and positively defined one. Its eigenvectors are chosen in the form of symmetric irreducible tensors which describe kinetic modes of the system. The corresponding eigenvalues are relaxation coefficients and define the relaxation times of the system. It is established that scalar and vector eigenfunctions describe evolution of electron energy and momentum densities (vector and scalar system modes). By this way in the present paper exact close set of equations for the densities valid for all times is obtained. Further, it is assumed that their relaxation times are much more than relaxation times of all other modes. In this case there exists a characteristic time such that at corresponding larger times the evolution of the system is reduced described by asymptotic values of the densities. At the reduced description electron distribution function depends on time only through asymptotic densities and they satisfy a closed set of equations. In our previous paper this result was proved in the absence of an external electric field and exact nonequilibrium distribution function was found. Here it is proved that this reduced description takes also place for small homogeneous external electric field. This can be considered as a justification of the Bogolyubov idea of the functional hypothesis for the relaxation processes in the plasma. The proof is done in the first approximation of the perturbation theory in the field. However, its idea is true in all orders in the field. Electron mobility in the plasma, its conductivity and phenomenon of equilibrium temperature difference of electrons and ions are discussed in exact theory and approximately analyzed. With this end in view, following our previous paper, approximate solution of the spectral problem is discussed by the method of truncated expansion of the eigenfunctions in series of the Sonine polynomials. In one-polynomial approximation it is shown that nonequilibrium electron distribution function at the end of relaxation processes can be approximated by the Maxwell distribution function. This result is a justification of Lorentz–Landau assumption in their theory of nonequilibrium processes in plasma. The temperature and velocity relaxation coefficients were calculated by us early in one- and two-polynomial approximation.

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