Asymptotic estimates for localized electromagnetic modes in doubly periodic structures with defects

2007 ◽  
Vol 463 (2080) ◽  
pp. 1045-1067 ◽  
Author(s):  
A.B Movchan ◽  
N.V Movchan ◽  
S Guenneau ◽  
R.C McPhedran
Keyword(s):  
Periodic Structures ◽  
Numerical Models ◽  
Electric Polarization ◽  
Silica Matrix ◽  
Effective Diameter ◽  
Localized Modes ◽  
Helmholtz Equations ◽  
Defect Modes ◽  
Electric And Magnetic Fields ◽  
Thin Bridge

The paper presents analytical and numerical models describing localized electromagnetic defect modes in a doubly periodic structure involving closely located inclusions of elliptical and circular shapes. Two types of localized modes are considered: (i) an axi-symmetric mode for the case of transverse electric polarization with an array of metallic inclusions; (ii) a dipole type localized mode that occurs in problems of waveguide modes confined in a defect region of an array of cylindrical fibres, and propagating perpendicular to the plane of the array. A thin bridge asymptotic analysis is used for case (i) to establish double-sided bounds for the frequencies of localized modes in macro-cells with thin bridges. For the case (ii), the electric and magnetic fields independently satisfy Helmholtz equations, but are coupled through the boundary conditions. We show that the model problem associated with localized vibration modes is the Dirichlet problem for the Helmholtz operator. We characterize defect modes by introducing a parameter called the ‘effective diameter’. We show that for circular inclusions in silica matrix, the effective diameter is accurately represented by a linear function of the inclusion radius.

scholarly journals Oscillatory and Localized Perturbations of Periodic Structures and the Bifurcation of Defect Modes

2015 ◽  
Vol 47 (5) ◽  
pp. 3832-3883 ◽  
Author(s):  
V. Duchêne ◽  
I. Vukićević ◽  
M. I. Weinstein
Keyword(s):  
Periodic Structures ◽  
Defect Modes

LOCAL HYDROGEN AND DEUTERIUM VIBRATIONAL MODES IN Si-DOPED GaAs

2002 ◽  
Vol 13 (05) ◽  
pp. 613-623
Author(s):  
S. D. D. ROY ◽  
P. MURUGAN ◽  
K. RAMACHANDRAN ◽  
N. KRISHNAMURTHY
Keyword(s):  
Plasma Treatment ◽  
Infrared Absorption ◽  
Isotope Shift ◽  
Molecular Model ◽  
Vibrational Modes ◽  
Deuterium Plasma ◽  
Localized Modes ◽  
Defect Modes ◽  
Theoretical Methods ◽  
Si Doped

Infrared absorption on GaAs doped with the isotopes of silicon under hydrogen or deuterium plasma treatment has shown the presence of two new localized modes, all in the range of 625–1725 cm-1. We present a simple nine-atom molecular model to compute these defect modes by assuming the hydrogen or deuterium to be bound in the antibonding position of the substituted Si atom, resulting in a defect complex of C3V symmetry. The two new vibrational modes of the paired Si are found with a small isotope shift, when H is replaced by D. Group theoretical methods are employed for the precise identification of the localized modes.

Assessment of exposure of electric and magnetic fields of industrial frequency on overhead power lines with voltage of 500 and 750 kV

2020 ◽  
Vol 60 (11) ◽  
pp. 797-800
Author(s):  
Tatyana A. Konshina
Keyword(s):  
Magnetic Fields ◽  
Numerical Models ◽  
Estimation Method ◽  
Power Lines ◽  
Work Shift ◽  
Instrumental Assessment ◽  
Electric And Magnetic Fields ◽  
Permissible Levels ◽  
Overhead Power Lines ◽  
Industrial Frequency

Introduction. Certain types of work in the vicinity of overhead power lines may be accompanied by prolonged presence of personnel during the work shift in areas where the maximum permissible levels of electric and magnetic fields of industrial frequency are exceeded. The aim of study is a comprehensive theoretical and instrumental assessment of the exposure of electric and magnetic fields of industrial frequency in places where personnel may stay when working near overhead power lines with a voltage of 500 and 750 kV. Materials and methods. The measurement points were determined using a matrix estimation method, taking into account the location of phases and sanitary protection zones of overhead power lines. The development and calculation of numerical models were carried out in the three-dimensional modeling environment SEMCAD X 14.8.6. Results. As a result of instrumental assessment of electric and magnetic fields of industrial frequency, places with exceeding the maximum permissible levels of the electric field of industrial frequency for a work shift were identified, which indicates the need to limit the time spent by personnel without the use of personal protective equipment. At the same time, no excess of the maximum permissible levels of the industrial frequency magnetic field was detected. Conclusions. The obtained numerical models of 500 and 750 kV overhead transmission lines when evaluating the levels of electric and magnetic fields of industrial frequency showed compliance with the data obtained during field measurements. This allows further research to assess the exposure of personnel performing work without removing voltage on overhead power lines of 500 and 750 kV.

scholarly journals Finite Element Approaches to Model Electromechanical, Periodic Beams

2020 ◽  
Vol 10 (6) ◽  
pp. 1992
Author(s):  
Wiktor Waszkowiak ◽  
Marek Krawczuk ◽  
Magdalena Palacz
Keyword(s):  
Finite Element ◽  
Periodic Structures ◽  
Numerical Models ◽  
Dynamic Properties ◽  
Modern Technology ◽  
Frequency Spectra ◽  
Scope Of Application ◽  
The Time Domain ◽  
Spectral Finite Element ◽  
Control Of Parameters

Periodic structures have some interesting properties, of which the most evident is the presence of band gaps in their frequency spectra. Nowadays, modern technology allows to design dedicated structures of specific features. From the literature arises that it is possible to construct active periodic structures of desired dynamic properties. It can be considered that this may extend the scope of application of such structures. Therefore, numerical research on a beam element built of periodically arranged elementary cells, with active piezoelectric elements, has been performed. The control of parameters of this structure enables one for active damping of vibrations in a specific band in the beam spectrum. For this analysis the authors propose numerical models based on the finite element method (FEM) and the spectral finite element methods defined in the frequency domain (FDSFEM) and the time domain (TDSFEM).

scholarly journals MODELING ELECTROMAGNETIC NANOSTRUCTURES AND EXPERIMENTING WITH NANOELECTRIC ELEMENTS TO FORM PERIODIC STRUCTURES

2020 ◽  
Vol 10 (4) ◽  
pp. 4-14
Author(s):  
Miloslav Steinbauer ◽  
Roman Pernica ◽  
Jiri Zukal ◽  
Radim Kadlec ◽  
Tibor Bachorec ◽  
...  
Keyword(s):  
Periodic Structures ◽  
Numerical Models ◽  
Harmonic Signal ◽  
Plasma Generator ◽  
Signal Propagation ◽  
Random Motion ◽  
Carbon Structure ◽  
Fundamental Dimension ◽  
Spurious Signals ◽  
High Repeatability

We discuss the numerical modeling of electromagnetic, carbon-based periodic structures, including graphene, graphane, graphite, and graphyne. The materials are suitable for sub-micron sensors, electric lines, and other applications, such as those within biomedicine, photonics, nano- and optoelectronics; in addition to these domains and branches, the applicability extends into, for example, microscopic solutions for modern SMART elements. The proposed classic and hybrid numerical models are based on analyzing a periodic structure with a high repeatability, and they exploit the concept of a carbon structure having its fundamental dimension in nanometers. The models can simulate harmonic and transient processes; are capable of evaluating the actual random motion of an electric charge as a source of spurious signals; and consider the parameters of harmonic signal propagation along the structure. The results obtained from the analysis are utilizable for the design of sensing devices based on carbon periodic structures and were employed in experiments with a plasma generator. The aim is to provide a broader overview of specialized nanostructural modeling, or, more concretely, to outline a model utilizable in evaluating the propagation of a signal along a structure’s surface.

scholarly journals Homogenized description of defect modes in periodic structures with localized defects

2015 ◽  
Vol 13 (3) ◽  
pp. 777-823 ◽  
Author(s):  
Vincent Duchêne ◽  
Iva Vukićević ◽  
Michael I. Weinstein
Keyword(s):  
Periodic Structures ◽  
Defect Modes ◽  
Localized Defects

Waves in lattices with imperfect junctions and localized defect modes

2008 ◽  
Vol 464 (2096) ◽  
pp. 2037-2054 ◽  
Author(s):  
V.V Zalipaev ◽  
A.B Movchan ◽  
I.S Jones
Keyword(s):  
Vibration Mode ◽  
Periodic Structures ◽  
Lattice Models ◽  
Theory Of Elasticity ◽  
Defect Modes ◽  
Thin Walled Structures ◽  
Discrete Lattices ◽  
Thin Walled ◽  
Type Boundary ◽  
Type Boundary Condition

A correspondence between continuum periodic structures and discrete lattices is well known in the theory of elasticity. Frequently, lattice models are the result of the discretization of continuous mechanical problems. In this paper, we discuss the discretization of two-dimensional square thin-walled structures. We consider the case when thin-walled bridges have defects in the vicinity of junctions. At these points, the displacement satisfies an effective Robin-type boundary condition. We study a defect vibration mode localized in the neighbourhood of the damaged junction. We analyse dispersion diagrams that show the existence of standing waves in a structure with periodically distributed defects.

scholarly journals Numerical Methods in Studies of Liquid Crystal Elastomers

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1650
Author(s):  
Madjid Soltani ◽  
Kaamran Raahemifar ◽  
Arman Nokhosteen ◽  
Farshad Moradi Kashkooli ◽  
Elham L. Zoudani
Keyword(s):  
Liquid Crystal ◽  
Numerical Models ◽  
Future Research ◽  
Artificial Muscles ◽  
Suitable Candidate ◽  
Numerical Studies ◽  
Wide Range ◽  
Electric And Magnetic Fields ◽  
Liquid Crystal Elastomers ◽  
External Stimuli

Liquid crystal elastomers (LCEs) are a type of material with specific features of polymers and of liquid crystals. They exhibit interesting behaviors, i.e., they are able to change their physical properties when met with external stimuli, including heat, light, electric, and magnetic fields. This behavior makes LCEs a suitable candidate for a variety of applications, including, but not limited to, artificial muscles, optical devices, microscopy and imaging systems, biosensor devices, and optimization of solar energy collectors. Due to the wide range of applicability, numerical models are needed not only to further our understanding of the underlining mechanics governing LCE behavior, but also to enable the predictive modeling of their behavior under different circumstances for different applications. Given that several mainstream methods are used for LCE modeling, viz. finite element method, Monte Carlo and molecular dynamics, and the growing interest and reliance on computer modeling for predicting the opto-mechanical behavior of complex structures in real world applications, there is a need to gain a better understanding regarding their strengths and weaknesses so that the best method can be utilized for the specific application at hand. Therefore, this investigation aims to not only to present a multitude of examples on numerical studies conducted on LCEs, but also attempts at offering a concise categorization of different methods based on the desired application to act as a guide for current and future research in this field.

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