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Article
Publication date: 11 November 2013

Andrea G. Chiariello, Carlo Forestiere, Giovanni Miano and Antonio Maffucci

Nowadays, nano-antennas or nanoscale absorbers made by innovative materials such as carbon nanotubes are gaining more and more interest, because of their outstanding features. The…

1204

Abstract

Purpose

Nowadays, nano-antennas or nanoscale absorbers made by innovative materials such as carbon nanotubes are gaining more and more interest, because of their outstanding features. The purpose of this paper is to investigate the scattering properties of carbon nanotubes, either isolated or arranged in arrays. The peculiar behaviour of such innovative materials is studied, taking also into account the finite length of the structure and the dependence of the scattering field from the operating temperature.

Design/methodology/approach

First a model is presented for the electrical transport along the carbon nanotubes, based on Boltzmann quasi-classical transport theory. The model includes quantistic and inertial phenomena observed in the carbon nanotube electrodynamics. The model also includes the effects of temperature. Using this electrodynamical model, the electromagnetic formulation of the scattering problem is cast in terms of a Pocklington-like equation. The numerical solution is obtained by means of the Galerkin method, with special care in handling the logarithmic singularity of the kernel. Case studies are carried out, either referred to isolated single-wall carbon nanotubes (SWCNTs) and array of SWCNTs.

Findings

The scattering properties of SWCNT are strongly influenced by the temperature and by the distance between the tubes. As temperature increases, the amplitude of the resonance peaks decreases, at a rate which is double the rate of changes of temperature. The resonance frequencies are insensitive to temperature. As for the distance between the tubes in an array, it influence the scattering resonance introducing a shift in the resonance frequencies which is appreciable for distances lower than the semi-length of the CNT. For higher distances the CNT scattered field may be regarded as the sum of the fields emitted by each CNT, as if they were isolated.

Research limitations/implications

As far as now only SWCNTs have been studied. The multi-wall carbon nanotubes would show a richer behaviour with temperature, due to the joint effect of reduction of the mean free path and increase of the number of conducting channels, as temperature increases.

Practical implications

Possible use of carbon nanotubes as absorbing material or scatterers.

Originality/value

The model presented here is based on a self-consistent and physically meaningful description of the CNT electrodynamics, which takes rigorously into account the effect of temperature, size and chirality of each CNT.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 32 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 5 January 2015

Andrea Gaetano Chiariello, Alessandro Formisano and Raffaele Martone

Inductances of complex coils, in the presence of linear materials only, can be computed by discretizing coils into simpler elements, whose magnetic behavior is analytically…

128

Abstract

Purpose

Inductances of complex coils, in the presence of linear materials only, can be computed by discretizing coils into simpler elements, whose magnetic behavior is analytically expressible, and suitably combining elementary contributions. Reliable results require high numbers of elements. In such cases, advantages can be taken from Graphic Processor Unit (GPU) capabilities of dealing efficiently with high numbers of repeated simple computational tasks. The purpose of this paper is to set up a fast and prompt numerical procedure to cope with the above described task.

Design/methodology/approach

The coils are first decomposed into current segments, taking into account accuracy, relative position and shape of coils to determine the number of segments. An analytical formula is then used to compute elementary contributions using GPUs to speed up the process, and finally superposition is used to recover the result.

Findings

The main advantages of the proposed approach are first demonstrated using simple examples, with analytical solutions, to validate the method accuracy and promptness, then more complex cases are taken to demonstrate its generality.

Research limitations/implications

The method is intrinsically limited by the linearity assumption, excluding the presence of magnetic materials. The adopted formulas require in addition that coils must lie in free space.

Practical implications

The proposed method can help in the design of complex coils or coils systems, where the performance depends on total magnetic energy or magnetic forces among coils.

Originality/value

The paper presents an original implementation in GPU-based computational environment of a procedure to compute inductances, based on the superposition of a high number of current segments. The procedure includes an original method to self-adaptively define number and position of current segments used in the coils discretization.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 7 September 2015

Alessandro Bonito Oliva, Andrea Gaetano Chiariello, Alessandro Formisano, Raffaele Martone, Alfredo Portone and Pietro Testoni

The purpose of this paper is to analyze the impact of different current representation models in the high field magnets characterization. Inverse source methodology used for…

94

Abstract

Purpose

The purpose of this paper is to analyze the impact of different current representation models in the high field magnets characterization. Inverse source methodology used for current reconstruction is discussed. The regularizing effect of successive field map computation in different regions is also assessed.

Design/methodology/approach

Under suitable hypotheses, the resulting inverse source problem is linear, and different current representation bases are used to assemble different matrices. Properties of matrices are then assesses using SVD. The following field computation problem is also formulated using a projection matrix, and the properties of combined matrix operators are analyzed and compared to the inversion matrix.

Findings

The characteristics of the inverse matrix depend on the choice of the current representation basis, but in any case the application of the further projection matrix has a relevant regularizing effect.

Research limitations/implications

The method is intrinsically tied to the linearity assumption, and the regularizing effect of the projection operator is stronger for further field regions.

Practical implications

The accuracy in the current reconstruction procedure can be reduced if data will be used only to compute field in distant regions.

Originality/value

The paper casts the problem of field computation in distant regions from magnetic measurements in the language of direct and inverse operators, allowing to assess its properties and fine tune the procedure parameters to achieve satisfactory results with minimum effort.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 19 June 2007

Andrea Gaetano Chiariello, Giovanni Miano, Antonio Maffucci, Fabio Villone and Walter Zamboni

To investigate the possible application of carbon nanotubes (CNTs) as interconnects and antennas.

1402

Abstract

Purpose

To investigate the possible application of carbon nanotubes (CNTs) as interconnects and antennas.

Design/methodology/approach

An electromagnetic macroscopic modelling of CNT is derived. The conduction electrons of the nanotube are considered as a 2D fluid moving on the surface representing the positive ion lattice. The linearized Euler's equation describing the fluid motion is used as a macroscopic constitutive relationship to be coupled to Maxwell's equation. A surface integral formulation coupled to the fluid model is solved numerically using a finite element method. For peculiar configurations, transmission line‐like parameters of CNTs are derived.

Findings

Single wall CNT interconnects, due to the high resistance and characteristic impedance with respect to ideally scaled silicon technology, should be used in arrays and bundles.

Research limitations/implications

Only single wall CNTs are considered.

Originality/value

The paper present a novel approach to CNTs and provides a comparison among the behaviour of CNTs with respect to ideally‐scaled silicon technology.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 26 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

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