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Article
Publication date: 4 June 2021

Junning Qin and Hongzhi Zhong

Various time integration methods and time finite element methods have been developed to obtain the responses of structural dynamic problems, but the accuracy and computational…

Abstract

Purpose

Various time integration methods and time finite element methods have been developed to obtain the responses of structural dynamic problems, but the accuracy and computational efficiency of them are sometimes not satisfactory. The purpose of this paper is to present a more accurate and efficient formulation on the basis of the weak form quadrature element method to solve linear structural dynamic problems.

Design/methodology/approach

A variational principle for linear structural dynamics, which is inspired by Noble's work, is proposed to develop the weak form temporal quadrature element formulation. With Lobatto quadrature rule and the differential quadrature analog, a system of linear equations is obtained to solve the responses at sampling time points simultaneously. Computation for multi-elements can be carried out by a time-marching technique, using the end point results of the last element as the initial conditions for the next.

Findings

The weak form temporal quadrature element formulation is conditionally stable. The relation between the normalized length of element and the suggested number of integration points in one element is given by a simple formula. Results show that the present formulation is much more accurate than other time integration methods and its dissipative property is also illustrated.

Originality/value

The weak form temporal quadrature element formulation provides a choice with high accuracy and efficiency for solution of linear structural dynamic problems.

Details

Engineering Computations, vol. 38 no. 10
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 7 March 2016

Minmao Liao and Hongzhi Zhong

The purpose of this paper is to highlight the implementation of a recently developed weak form quadrature element method for nonlinear free vibrations of Timoshenko beams…

Abstract

Purpose

The purpose of this paper is to highlight the implementation of a recently developed weak form quadrature element method for nonlinear free vibrations of Timoshenko beams subjected to three different boundary conditions.

Design/methodology/approach

The design of the paper is based on considering the geometrically nonlinear effects of axial strain, bending curvature, and shear strain. Then the quadrature element formulation of the beam is introduced.

Findings

The efficiency of the method is demonstrated by a convergence study. Ratios of the nonlinear fundamental frequencies to the corresponding linear frequencies are extracted. Their variations with the ratio of amplitude to radius of gyration and the slenderness ratio are examined. The effects of the nonlinearity on higher order frequencies and mode shapes are also investigated.

Originality/value

The computed results show fast convergence and compare well with available literature results.

Details

Engineering Computations, vol. 33 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 6 April 2022

Sinan Maraş and Mustafa Yaman

This study aims to demonstrate the numerical application of differential quadrature (DQ) methods and show the experimental application of free vibration analysis of fiber-metal…

Abstract

Purpose

This study aims to demonstrate the numerical application of differential quadrature (DQ) methods and show the experimental application of free vibration analysis of fiber-metal laminated composite (FML) plates with various boundary conditions.

Design/methodology/approach

The FMLs are hybrid structures consisting of fiber-reinforced polymer matrix composites such as carbon, glass, aramid and different metal sheets, and are currently widely used in the automobile, aircraft and aerospace industries. Thus, free vibration analysis of these hybrid materials is necessary for the design process. The governing equations of motion are derived based on the classical plate theory. The DQ, generalized DQ (GDQ) and harmonic DQ (HDQ) differential quadrature methods have been used to solve the governing equations of an FML composite plate numerically. The accuracy and convergence of the numerical model have been verified by comparing the results available in the published literature with the results obtained from these methods. Moreover, an experimental procedure has been performed in order to compare the results against those of the numerical methods.

Findings

It is noteworthy that a high degree of similarity and accuracy was observed between the numerical results obtained by the DQ methods and the experimental results. Thus, the present study validates the applicability of the DQ methods for designing the FML composite plates.

Originality/value

In this study, the advantages of the DQ methods have been demonstrated differently from previous studies on the vibration analysis of the FML plates.

Details

Engineering Computations, vol. 39 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 27 February 2024

Feng Qian, Yongsheng Tu, Chenyu Hou and Bin Cao

Automatic modulation recognition (AMR) is a challenging problem in intelligent communication systems and has wide application prospects. At present, although many AMR methods…

Abstract

Purpose

Automatic modulation recognition (AMR) is a challenging problem in intelligent communication systems and has wide application prospects. At present, although many AMR methods based on deep learning have been proposed, the methods proposed by these works cannot be directly applied to the actual wireless communication scenario, because there are usually two kinds of dilemmas when recognizing the real modulated signal, namely, long sequence and noise. This paper aims to effectively process in-phase quadrature (IQ) sequences of very long signals interfered by noise.

Design/methodology/approach

This paper proposes a general model for a modulation classifier based on a two-layer nested structure of long short-term memory (LSTM) networks, called a two-layer nested structure (TLN)-LSTM, which exploits the time sensitivity of LSTM and the ability of the nested network structure to extract more features, and can achieve effective processing of ultra-long signal IQ sequences collected from real wireless communication scenarios that are interfered by noise.

Findings

Experimental results show that our proposed model has higher recognition accuracy for five types of modulation signals, including amplitude modulation, frequency modulation, gaussian minimum shift keying, quadrature phase shift keying and differential quadrature phase shift keying, collected from real wireless communication scenarios. The overall classification accuracy of the proposed model for these signals can reach 73.11%, compared with 40.84% for the baseline model. Moreover, this model can also achieve high classification performance for analog signals with the same modulation method in the public data set HKDD_AMC36.

Originality/value

At present, although many AMR methods based on deep learning have been proposed, these works are based on the model’s classification results of various modulated signals in the AMR public data set to evaluate the signal recognition performance of the proposed method rather than collecting real modulated signals for identification in actual wireless communication scenarios. The methods proposed in these works cannot be directly applied to actual wireless communication scenarios. Therefore, this paper proposes a new AMR method, dedicated to the effective processing of the collected ultra-long signal IQ sequences that are interfered by noise.

Details

International Journal of Web Information Systems, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1744-0084

Keywords

Article
Publication date: 3 May 2016

Deepa George and Saurabh Sinha

The demand for higher bandwidth has resulted in the development of mm-wave phased array systems. This paper aims to explore a technique that could be used to feed the individual…

Abstract

Purpose

The demand for higher bandwidth has resulted in the development of mm-wave phased array systems. This paper aims to explore a technique that could be used to feed the individual antennas in a mm-wave phased array system with the appropriate phase shifted signal to achieve the required directivity. It presents differential Colpitts oscillators at 5 and 60 GHz that can provide differential output signals to the quadrature signal generators in the proposed phase shifter system.

Design/methodology/approach

The phase shifter system comprises a differential Colpitts voltage controlled oscillator (VCO) and utilizes the vector-sum technique to generate the phase shifted signal. The differential VCO is connected in the common-collector configuration for the 5-GHz VCO, and is extended using a cascode transistor for the 60-GHz VCO for better stability at mm-wave. The vector sum is achieved using a variable gain amplifier (VGA) that combines the in-phase and quadrature phase signal, generated from oscillator output using hybrid Lange couplers. The devices were fabricated using IBM 130-nm SiGe BiCMOS process, and simulations were performed with a process design kit provided by the foundry.

Findings

The measured results of the 5-GHz and 60-GHz VCOs indicate that differential Colpitts VCO could generate oscillator output with good phase noise performance. The simulation results of the phase shifter system indicate that the generation of signals with phases from 0° to 360° in steps of 22.5° was achieved using the proposed approach. A Gilbert mixer topology was used for the VGA and the linearity was improved by a pre-distortion circuit implemented using an inverse tanh cell.

Originality/value

The measurement results indicate that differential Colpitts oscillator in common-collector configuration could be used to generate differential VCO signals for the vector-sum phase shifter. The simulation results of the proposed phase shifter system at mm-wave show that the phase shift could be realised at a total power consumption of 200 mW.

Details

Microelectronics International, vol. 33 no. 2
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 29 July 2019

Umer Saeed and Muhammad Umair

The purpose of the paper is to extend the differential quadrature method (DQM) for solving time and space fractional non-linear partial differential equations on a semi-infinite…

Abstract

Purpose

The purpose of the paper is to extend the differential quadrature method (DQM) for solving time and space fractional non-linear partial differential equations on a semi-infinite domain.

Design/methodology/approach

The proposed method is the combination of the Legendre polynomials and differential quadrature method. The authors derived and constructed the new operational matrices for the fractional derivatives, which are used for the solutions of non-linear time and space fractional partial differential equations.

Findings

The fractional derivative of Lagrange polynomial is a big hurdle in classical DQM. To overcome this problem, the authors represent the Lagrange polynomial in terms of shifted Legendre polynomial. They construct a transformation matrix which transforms the Lagrange polynomial into shifted Legendre polynomial of arbitrary order. Then, they obtain the new weighting coefficients matrices for space fractional derivatives by shifted Legendre polynomials and use these in conversion of a non-linear fractional partial differential equation into a system of fractional ordinary differential equations. Convergence analysis for the proposed method is also discussed.

Originality/value

Many engineers can use the presented method for solving their time and space fractional non-linear partial differential equation models. To the best of the authors’ knowledge, the differential quadrature method has never been extended or implemented for non-linear time and space fractional partial differential equations.

Article
Publication date: 10 July 2017

R. Rashidi Meybodi, M. Zare Mehrjardi and A.D. Rahmatabadi

The purpose of this paper is to study tilt angle effects as design parameters of noncircular bearings, on the linear dynamic analyses of micropolar lubricated circular, two, three…

Abstract

Purpose

The purpose of this paper is to study tilt angle effects as design parameters of noncircular bearings, on the linear dynamic analyses of micropolar lubricated circular, two, three and four lobe journal bearings.

Design/methodology/approach

Reynolds equation in dynamic state is modified considering the micropolarity characteristics of lubricant, and it is solved using generalized differential quadrature method. The perturbed components of the dynamic pressure are extracted based on the linear dynamic model. To explain the transient state of the governing equation, through the linear dynamic approach, the whirling motion of rotor around the steady state position is assumed to be harmonic.

Findings

It is observed from the results that tilt angle has significant effects on the steady state and stability performance of lobed journal bearings. It may be selected suitably to improve the performance of rotor-bearing system, while all other lubricant properties and noncircular bearing design parameters are kept fixed. Results show that among the three types of bearings considered, the dynamic performance of two lobe bearings are more affected by the variation of tilt angle.

Originality/value

The present study is mainly concerned with the effects of tilt angle as a design parameter on the stability performance of a hydrodynamic noncircular journal bearing lubricated with micropolar fluid.

Details

Industrial Lubrication and Tribology, vol. 69 no. 4
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 1 June 1999

Hal Philipp

While the transference of charge is an essential aspect of every capacitance sensor, a relatively new form of sensor makes overt use of the principle of charge conservation first…

Abstract

While the transference of charge is an essential aspect of every capacitance sensor, a relatively new form of sensor makes overt use of the principle of charge conservation first deduced by Watson in the 1740s. Updated to use a microcontroller, mosfet switches, fet‐input opamps and band gap references, the principle of charge transference can be used to create an extremely sensitive and stable device with unique properties that transcend those of more pedestrian capacitance sensors. Also known as “QT” sensors, charge transfer sensors can have a dynamic range spanning many decades with noise floors in the sub‐femtofarad regime, allowing differential resolutions of mere fractions of a femtofarad. Such sensors are proving to have unique applications considered heretofore impossible, while also proving themselves as replacements for much more expensive sensing systems using photoelectric, acoustic, RF, and optical imaging techniques.

Details

Sensor Review, vol. 19 no. 2
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 13 May 2020

Mehdi Dehghan and Vahid Mohammadi

This study aims to apply a numerical meshless method, namely, the boundary knot method (BKM) combined with the meshless analog equation method (MAEM) in space and use a…

Abstract

Purpose

This study aims to apply a numerical meshless method, namely, the boundary knot method (BKM) combined with the meshless analog equation method (MAEM) in space and use a semi-implicit scheme in time for finding a new numerical solution of the advection–reaction–diffusion and reaction–diffusion systems in two-dimensional spaces, which arise in biology.

Design/methodology/approach

First, the BKM is applied to approximate the spatial variables of the studied mathematical models. Then, this study derives fully discrete scheme of the studied models using a semi-implicit scheme based on Crank–Nicolson idea, which gives a linear system of algebraic equations with a non-square matrix per time step that is solved by the singular value decomposition. The proposed approach approximates the solution of a given partial differential equation using particular and homogeneous solutions and without considering the fundamental solutions of the proposed equations.

Findings

This study reports some numerical simulations for showing the ability of the presented technique in solving the studied mathematical models arising in biology. The obtained results by the developed numerical scheme are in good agreement with the results reported in the literature. Besides, a simulation of the proposed model is done on buttery shape domain in two-dimensional space.

Originality/value

This study develops the BKM combined with MAEM for solving the coupled systems of (advection) reaction–diffusion equations in two-dimensional spaces. Besides, it does not need the fundamental solution of the mathematical models studied here, which omits any difficulties.

Article
Publication date: 9 March 2010

M.R. Koohkan, R. Attarnejad and M. Nasseri

The purpose of this paper is to propose a semi‐analytical method for studying the interaction between reservoir and concrete gravity dams.

Abstract

Purpose

The purpose of this paper is to propose a semi‐analytical method for studying the interaction between reservoir and concrete gravity dams.

Design/methodology/approach

The reservoir is assumed to be unbounded at the far end and the solution is sought for incompressible and in‐viscid fluid. A concrete gravity dam is assumed to behave as a cantilever beam of variable section, and the inclination of the neutral axis is ignored.

Findings

It is shown that use of the differential quadrature method (DQM), with a few grid points in conjunction with the finite difference method (FDM), yields an acceptable convergence of results. Comparing the results of the proposed method with those of the literature shows the competency of the method.

Originality/value

DQM for space derivatives and FDM for time derivatives are used to discretize the partial differential equation of motion.

Details

Engineering Computations, vol. 27 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

1 – 10 of 56