Papers by Keyword: Effective Permittivity

Abstract: The simplified model of biochar-bearing iron ore with binder was studied. It was considered a mixture of two types of core-shell particles, ‘iron ore – binder’ particles and ‘biochar – binder’ particles. The expressions to calculate complex effective permittivity and permeability was derived by effective medium approximation (EMA). The corresponding dependencies on volume fraction of iron ore in the mixture are provided.

Abstract: With the increasing of resonant frequency and integration of film bulk acoustic resonator (FBAR), the electromagnetic interference (EMI) of FBAR devices appears to be extremely important. The electric fields of the common electrical model and finite element model are assumed to be quasi-static and cannot simulate the electromagnetic (EM) property. A 3-D EM model of FBAR is achieved by means of high frequency EM simulation software HFSS. A real-time simulation of EM distributed effects, EM coupling and piezoelectric effects is achieved by employing an effective permittivity in the EM model. The effects of the high frequency EM distributed effects and the EM coupling on resonant characteristics are analyzed. By optimizing the distance between FBAR and components, introducing substrate materials with different permittivity, the EM coupling is effectively reduced.

Abstract: To investigate the effective permittivity of composites composed of ellipsoidal inclusions, three-dimension numerical models for ellipsoidal inclusions distributed randomly are built with the finite-element modeling software Comsol Multiphysics. After calculating the effective permittivity for different cases and comparing the results with analytical results from the Maxwell-Garnett mixing rule, we find that the finite-element method has an advantage in detecting details of the interaction among inclusions, which have some impacts on the effective permittivity and could not be accurately taken into account in the analytical model. The finite-element method is expected to solve more complex problems on electromagnetic computation.

Abstract: A structural simulation strategy was developed for characterizing the thin films of ferromagnetic - ferroelectric nanocomposites consisting of a spinel and a perovskite. The (1-y) Ni_0.5Zn_0.5Fe₂O₄ - y BaTiO₃ magnetoelectric ceramic, with (1-y) = 0.5 - 0.9 obtained by ferrite grains embedding into the BaTiO₃ matrix has found multiple applications for magnetoelectric sensors, four-state memories, anti-electro-magnetic interference (EMI) devices, etc. The tunability of the electromagnetic properties, considered until now as a matter of chemistry, strictly depending on the synthesizing process of the nanocomposite, can be reached by the 3D simulation methods, which reproduce the structure and simulate the interactions between constituents and with external fields. The thin film samples were simulated in the field of a horn antenna (4 ÷ 18 GHz), above the ferromagnetic resonance of the pure ferrite. The effective permittivity, respectively permeability were determined and their evolutions with different internal and external parameters (relative volume fractions, substitution ion radii in the ferrite, polarizing fields) were linked on the intrinsic characteristics of the constituent phases. The obtained surface plots indicates us the sets of optimal control parameters which have to be correlated in practice in order to obtain the desired value of an effective parameter, in a considered frequency subdomain. It appears that the system behaves optimal at a frequency around 8.9 GHz, where the values of the correlated control parameters is convenient for applications at microwave devices. A ferromagnetic - ferroelectric system tunability ranging from 13 to 37% was achieved, depending upon each structure characteristics.

Abstract: Dependences of distribution, penetration, reflection and absorption of microwaves in the layers of conductive micro-particles on the frequency of the incident radiation and size of particles are obtained and investigated. Layers of conductive spherical particles as the shell, and without it are accepted in our work as the most common model of powder metals. So, this study allows to describe and classify features of electromagnetic wave heating of various metal powders and to predict the performance, in which it will be effective heating of metal powders by electromagnetic radiation.

Abstract: It is known from experimental data that bulk metallic samples reflect microwaves while powdered samples can absorb such radiation and be heated efficiently. In the present paper we investigate theoretically the mechanisms of penetration of microwave radiation through a layer of metallic powder and microwave heating of such system.

Abstract: . It is known that bulk metallic samples reflect microwaves (MWs) while metallic powdered samples can absorb such radiation and be heated efficiently. The present paper shows a direct evidence of penetration of MW radiation into and through a layer of metallic powder and contains theoretical explanation of such behavior.

Abstract: In the paper, firstly self-consistent model (SCM) is used for establishing the predicted formula which can predict the effective permittivity of the composite materials with core-shell type inclusions. Then the factors on the effective permittivity of this kind of composite are investigated on the base of this predicted formula. The researching results indicate the effective permittivity of composite depends on not only the volume fraction of inclusions, but also the permittivity of matrix and inclusions (core and shell). According to our works, the optimal design of composite with core-shell type inclusion must be done if we want to make this composite get better effect of absorbing wave.