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1 – 10 of 294
Article
Publication date: 1 December 2004

S. Guenneau, A. Nicolet, C. Geuzaine, F. Zolla and A.B. Movchan

This paper investigates new technological devices to be utilised in future optical communications, by means of variational method (FEM) and multipole scattering approach…

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Abstract

This paper investigates new technological devices to be utilised in future optical communications, by means of variational method (FEM) and multipole scattering approach (Rayleigh method). This last one provides interesting asymptotic results in the long‐wavelength limit. The so‐called photonic crystal fibres (PCF) possess radically different guiding properties due to photonic band gap guidance: removing a hole within a macro‐cell leads to a defect state within the gap. In the case of multi‐core PCF, the localised modes start talking to each other which possibly leads to a new generation of multiplexer/demultiplexers.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 23 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 2 October 2017

Miguel Castillo Acero

The purpose of this paper is to present the studies to develop structural highly orthotropic panels. These types of panels provide the capabilities required for structural…

Abstract

Purpose

The purpose of this paper is to present the studies to develop structural highly orthotropic panels. These types of panels provide the capabilities required for structural morphing. They are highly deformable in one given direction; and in the perpendicular direction, one must be compliant to sustain the internal loads per certification stiffness and strength requirements.

Design/methodology/approach

Neither classic orthotropic panels nor regular cellular solids Bloch wave theories are strictly applicable on their study. A combination of computational method, MATLAB-coded, to analyze stability and classic structural beam theory is studied. Then, non-linear finite element method models are developed for an aerospace control surface application; their results are compared with reported Bloch wave sequences on periodic cellular solid panels.

Findings

The stability along stiffer direction is a requirement to obtain a continuous deformation and plasticization sequence of the cell rows in the perpendicular direction. A sample panel is sized and 3D modeled, and then produced using additive layer manufacturing process to demonstrate the initial stages of a validation and verification campaign.

Originality/value

This paper provides a new method to mechanical characterize highly orthotropic panels.

Details

International Journal of Structural Integrity, vol. 8 no. 5
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 8 March 2011

Mehmet Canturk, Erol Kurt and Iman N. Askerzade

The purpose of this paper is to employ an alternative numerical approach to analyze the characteristics of superconducting charge qubit based on a single Cooper pair box…

Abstract

Purpose

The purpose of this paper is to employ an alternative numerical approach to analyze the characteristics of superconducting charge qubit based on a single Cooper pair box (SCB), also to study the influence of the bias current.

Design/methodology/approach

The paper starts with the circuit model of a charge qubit system based on Josephson junction using Hamiltonian formalism. Corresponding Schrodinger eigenvalue problem with periodic boundary condition is converted to the Mathieu type eigenvalue problem. By applying finite difference technique, energy spectrum of charge qubit is obtained and the solutions in the lowest band are obtained in the form of Bloch waves whose superposition provides a wave packet to investigate the effect of bias current to the Coulomb blockade.

Findings

The paper identifies a periodic tridiagonal Hermitian matrix form of the eigenvalue problem that is believed to be a special eigenvalue problem. The paper emphasizes that Schrodinger formalism is very useful to model superconducting qubits systems. The investigations indicate that the bias current strongly influences the Coulomb blockade and expectation value of supercurrent (as well as number of Cooper pairs) are affected by gate voltage and energy scale.

Research limitations/implications

In the present study, Schrodinger eigenvalue problem is time independent, therefore, current‐voltage characteristics of the charge qubit system could not be considered. The solution technique applied here can also be used to apply other type of Josephson junction based qubits and circuits.

Practical implications

The paper includes theoretical findings for the development of superconducting qubit that can be valuable for experimentalist. The result obtained in this study is useful for the comparison of experimental study with the expectation value of number of Cooper pairs as function of gate voltage. Working parameters of a SCB can be determined from the findings.

Originality/value

This paper fulfils the contribution of the numerical study of Schrodinger equation for the investigation of superconducting qubits under the influence of bias current.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 9 March 2015

Tae-Bong Lee and Min-Nyeon Kim

– The purpose of this paper is to analyze far and near field emitted field patterns through more exact calculation of the modes formed in finite periodic dielectric gratings.

Abstract

Purpose

The purpose of this paper is to analyze far and near field emitted field patterns through more exact calculation of the modes formed in finite periodic dielectric gratings.

Design/methodology/approach

For the mode calculation, equations are newly defined by applying vertical boundary condition on the assumption that transverse electric modes are generated in the structure. After finding modes, near field patterns are calculated using the wave number and coefficient of the mode.

Findings

Additionally, the results from these calculations are compared with that of the rigorous-coupled method. Finally, far field patterns are derived by applying fast Fourier transform to near field patterns and also compared with the results of rigorous-coupled method.

Research limitations/implications

For convenience of coordinate, we use rectangular coordinate, though the shape of radome is a hemisphere.

Practical implications

In this paper, the authors derive more exact near field patterns without the assumption of infiniteness so that these results can be used practically for a making real frequency-selective structure.

Originality/value

Conventional periodic finite dielectric gratings analysis has been done using Floquet–Bloch wave theory, coupled-mode, rigorous-coupled method which is based on the assumption of infiniteness of the structure.

Details

Journal of Systems and Information Technology, vol. 17 no. 1
Type: Research Article
ISSN: 1328-7265

Keywords

Article
Publication date: 21 July 2020

Chengcheng Luo, Shaowu Ning, Zhanli Liu, Xiang Li and Zhuo Zhuang

This paper aims to propose a design method for attenuating stress waves pressure using soft matrix embedded with particles.

Abstract

Purpose

This paper aims to propose a design method for attenuating stress waves pressure using soft matrix embedded with particles.

Design/methodology/approach

Based on the phononic crystal theory, the particle composed of hard core and soft coating can form a spring oscillator structure. When the frequency of the wave is close to the resonance frequency of the spring oscillator, it can cause the resonance of the particle and absorb a lot of energy. In this paper, the resonant phononic crystal with three phases, namely, matrix, particle core and coating, is computationally designed to effectively mitigate the stress wave with aperiodic waveform.

Findings

The relationship between the center frequency and width of the bandgap and the geometric and physical parameters of particle core are discussed in detail, and the trend of influence is analyzed and explained by a spring oscillator model. Increasing the radius of hard core could effectively enhance the bandgap width, thus enhancing the effect of stress wave attenuation. In addition, it is found that when the wave is in the bandgap, adding viscosity into the matrix will not further enhance the stress attenuation effect, but will make the stress attenuation effect of the material worse because of the competition between viscous dissipation mechanism and resonance mechanism.

Research limitations/implications

This study will provide a reference for the design of stress wave protection materials with general stress waves.

Originality/value

This study proposes a design method for attenuating stress waves pressure using soft matrix embedded with particles.

Details

Engineering Computations, vol. 38 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 4 October 2021

Rolando Yera, Luisina Forzani, Carlos Gustavo Méndez and Alfredo E. Huespe

This work presents a topology optimization methodology for designing microarchitectures of phononic crystals. The objective is to get microstructures having, as a…

Abstract

Purpose

This work presents a topology optimization methodology for designing microarchitectures of phononic crystals. The objective is to get microstructures having, as a consequence of wave propagation phenomena in these media, bandgaps between two specified bands. An additional target is to enlarge the range of frequencies of these bandgaps.

Design/methodology/approach

The resulting optimization problem is solved employing an augmented Lagrangian technique based on the proximal point methods. The main primal variable of the Lagrangian function is the characteristic function determining the spatial geometrical arrangement of different phases within the unit cell of the phononic crystal. This characteristic function is defined in terms of a level-set function. Descent directions of the Lagrangian function are evaluated by using the topological derivatives of the eigenvalues obtained through the dispersion relation of the phononic crystal.

Findings

The description of the optimization algorithm is emphasized, and its intrinsic properties to attain adequate phononic crystal topologies are discussed. Particular attention is addressed to validate the analytical expressions of the topological derivative. Application examples for several cases are presented, and the numerical performance of the optimization algorithm for attaining the corresponding solutions is discussed.

Originality/value

The original contribution results in the description and numerical assessment of a topology optimization algorithm using the joint concepts of the level-set function and topological derivative to design phononic crystals.

Details

Engineering Computations, vol. 39 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 8 June 2015

Lei Li and Qing Liu

– The purpose of this paper is to propose a modal method to calculate the band gaps of one-dimensional (1D) phononic crystals.

Abstract

Purpose

The purpose of this paper is to propose a modal method to calculate the band gaps of one-dimensional (1D) phononic crystals.

Design/methodology/approach

The phononic crystals have modes with exponential form envelope in the band gaps, however, outside the band gaps the modes are of amplitude modulation periodic form. Thus the start and end frequencies of band gaps can be determined from the existence conditions of periodic modes. So, the band gaps calculation of 1D phononic crystal is transformed into the existence discussion of periodic solution of mode shapes equation. The results are verified by finite element harmonic response analysis.

Findings

At the start and end frequencies of the band gap, the mode equation have solution with period of lattice constant.

Originality/value

Compared with the traditional theoretical methods, the proposed modal method has a clearer principle and easier calculation.

Details

Multidiscipline Modeling in Materials and Structures, vol. 11 no. 1
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 14 November 2022

Yingli Li, Muhammad Zahradeen Tijjani, Xudong Jiang and Jamiu Opeyemi Ahmed

The main purpose of this paper is to investigate the vibration isolation performance of a quasi-zero stiffness (QZS) metastructure by employing the band gap (BG) mechanism.

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Abstract

Purpose

The main purpose of this paper is to investigate the vibration isolation performance of a quasi-zero stiffness (QZS) metastructure by employing the band gap (BG) mechanism.

Design/methodology/approach

The metastructure QZS characteristic was investigated through static analysis by numerical simulation. Based on that, the BG mechanism is primarily used in this article to investigate the wave propagation characteristics of this structure. The model's dispersion relation is then examined using theoretical (perturbation method) and finite element techniques. The dynamic response of the finite-size systems and experimental analysis is used to confirm the vibration mitigation property under investigation. Finally, the model's ability to absorb energy was examined and contrasted with a traditional model.

Findings

The analytical analysis reveals the dispersion curve and the effect of the nonlinear parameter on the curve shifting. The dispersion curve in the finite element method (FEM) result depicts five complete BGs within the range of 0–1,000 Hz, and the BG width accounted for 67.4% of the frequency concerned (0–1,000 Hz). Eigenmodes of the dispersion curves were analyzed to investigate the BG formation mechanisms. The dependence of BG opening and closure on structure parameters was also studied. Finally, the energy absorption property of the QZS metastructure was evaluated by comparing it with a classical model. The QZS structure absorbs 4.08 J/Kg compared to the 3.69 J/Kg absorbed by the classical model, which reveals that the QZS demonstrates better energy absorption performance. Based on the BG mechanism, it is clear that this model is an excellent vibration isolator, and the study reveals the frequencies at which complete vibration mitigation is achieved. As a result, this model could be a promising candidate for vibration mitigation engineering structures and energy absorption.

Originality/value

The tough vibration issue, which is primarily experienced in mechanical equipment, will be resolved in this study. This study provides a precise understanding of the QZS metastructure's isolation of vibration, including the frequencies at which this isolation occurs.

Details

International Journal of Structural Integrity, vol. 13 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

Open Access
Article
Publication date: 25 October 2018

Giuseppe Rocchetta and Geminiano Mancusi

Within the context of 2D square lattices, searching for the existence of band gaps assumes a great interest owing to many possible fields of application: from energy…

Abstract

Purpose

Within the context of 2D square lattices, searching for the existence of band gaps assumes a great interest owing to many possible fields of application: from energy absorption devices to noise and vibration controllers, as well as advanced strategies for the seismic isolation.

Design/methodology/approach

The underlying microstructure may influence the mechanical response of 2D square lattices according to a complex interplay between different factors. A first one is related to the so-called “size-effect”. A second one relates, instead, to the mass density distribution.

Findings

It has been observed that lumped masses may induce additional band gaps to appear and may magnify their width. Finally, an additional factor deals with the inner damping characteristics of the constituent materials, which usually are polymer-based.

Originality/value

This study focuses on the first factor from a specific perspective: to investigate the influence of the size effect on the existence and properties of frequency band gaps.

Details

PSU Research Review, vol. 2 no. 2
Type: Research Article
ISSN: 2399-1747

Keywords

Article
Publication date: 13 January 2012

Shibin Chen, Dichen Li, Xiaoyong Tian, Minjie Wang and Wei Dai

The purpose of this paper is to present a novel and effective fabricating method of 3D ceramic photonic crystals with diamond structure.

Abstract

Purpose

The purpose of this paper is to present a novel and effective fabricating method of 3D ceramic photonic crystals with diamond structure.

Design/methodology/approach

The reverse diamond‐structure resin molds are fabricated by stereolithography (SL), then ceramic slurry is prepared and injected into the molds under vacuum condition. Subsequently, ceramic photonic crystals are obtained after vacuum freeze‐drying and sintering.

Findings

The combination of SL, gel‐casting and freeze‐drying could be used to fabricate the 3D ceramic photonic crystals with diamond structure which have intact structure and minimal shrinkage. The samples have been tested and the experimental results indicate that their band gap is in the range of 10.14‐12.20 GHz, consistent with the simulation results.

Research limitations/implications

The influence of fabrication process on the photonic band gap needs further study.

Originality/value

This paper presents a novel fabricating method of 3D diamond‐structure ceramic photonic crystals based on SL, gel‐casting and freeze‐drying. The method fabricates complex ceramic photonic crystals with high accuracy and helps further research in this field.

Details

Rapid Prototyping Journal, vol. 18 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

1 – 10 of 294