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Article
Publication date: 5 September 2016

Feride Akman and Nevin Çankaya

This paper aims to synthesise and characterise N-cyclohexylmethacrylamide (NCMA) monomer which contains thermosensitive group. The characterisation of monomer was…

Abstract

Purpose

This paper aims to synthesise and characterise N-cyclohexylmethacrylamide (NCMA) monomer which contains thermosensitive group. The characterisation of monomer was performed both theoretically and experimentally.

Design/methodology/approach

The monomer was prepared by reacting cyclohexylamine with methacryloyl chloride in the presence of triethylamine at room temperature. The synthesised monomer was characterised by using not only Density Functional Theory (DFT) and Hartree–Fock (HF) with the Gaussian 09 software but also fourier transform infrared (FT–IR), 1H and 13C nuclear magnetic resonance (NMR) spectroscopy.

Findings

Both the experimental and the theoretical methods demonstrated that the monomer was successfully synthesised. The vibrational frequencies, the molecular structural geometry, such as optimised geometric bond angles, bond lengths and the Mulliken atomic charges of NCMA were investigated by using DFT/B3LYP and HF methods with the 3-21G* basis set. The experimental results were compared with theoretical values. The results revealed that the calculated frequencies were in good accord with the experimental values. Besides, frontier molecular orbitals (FMOs) and molecular electrostatic potential of NCMA were investigated by theoretical calculations at the B3LYP/3–21G* basis set.

Research limitations/implications

Monomer and polymer containing a thermosensitive functional group have attracted great interest from both industrial and academic fields. Their characterisation can provide great opportunities for polymer science by using DFT and HF methods.

Originality/value

The monomer containing a thermosensitive functional group and a various polymer may be prepared by using DFT and HF methods described in this paper. The calculated data are greatly important to provide insight into molecular analysis and then used in technological applications.

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Article
Publication date: 1 April 2021

Arunit Maity, P. Prakasam and Sarthak Bhargava

Due to the continuous and rapid evolution of telecommunication equipment, the demand for more efficient and noise-robust detection of dual-tone multi-frequency (DTMF…

Abstract

Purpose

Due to the continuous and rapid evolution of telecommunication equipment, the demand for more efficient and noise-robust detection of dual-tone multi-frequency (DTMF) signals is most significant.

Design/methodology/approach

A novel machine learning-based approach to detect DTMF tones affected by noise, frequency and time variations by employing the k-nearest neighbour (KNN) algorithm is proposed. The features required for training the proposed KNN classifier are extracted using Goertzel's algorithm that estimates the absolute discrete Fourier transform (DFT) coefficient values for the fundamental DTMF frequencies with or without considering their second harmonic frequencies. The proposed KNN classifier model is configured in four different manners which differ in being trained with or without augmented data, as well as, with or without the inclusion of second harmonic frequency DFT coefficient values as features.

Findings

It is found that the model which is trained using the augmented data set and additionally includes the absolute DFT values of the second harmonic frequency values for the eight fundamental DTMF frequencies as the features, achieved the best performance with a macro classification F1 score of 0.980835, a five-fold stratified cross-validation accuracy of 98.47% and test data set detection accuracy of 98.1053%.

Originality/value

The generated DTMF signal has been classified and detected using the proposed KNN classifier which utilizes the DFT coefficient along with second harmonic frequencies for better classification. Additionally, the proposed KNN classifier has been compared with existing models to ascertain its superiority and proclaim its state-of-the-art performance.

Details

Applied Computing and Informatics, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2634-1964

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Article
Publication date: 10 January 2020

Yining Zeng, Rongxing Duan, Shujuan Huang and Tao Feng

This paper aims to deal with the problems of failure dependence and common cause failure (CCF) that arise in reliability analysis of complex systems.

Abstract

Purpose

This paper aims to deal with the problems of failure dependence and common cause failure (CCF) that arise in reliability analysis of complex systems.

Design/methodology/approach

Firstly, a dynamic fault tree (DFT) is used to capture the dynamic failure behaviours and converted into an equivalent generalized stochastic petri net (GSPN) for quantitative analysis. Secondly, an efficient decomposition and aggregation (EDA) theory is combined with GSPN to deal with the CCF problem, which exists in redundant systems. Finally, Birnbaum importance measure (BIM) is calculated based on the EDA approach and GSPN model, and it is used to take decisions for system improvement and fault diagnosis.

Findings

In this paper, a new reliability evaluation method for dynamic systems subject to CCF is presented based on the DFT analysis and the GSPN model. The GSPN model is easy to capture dynamic failure behaviours of complex systems, and the movement of tokens in the GSPN model represent the changes in the state of the systems. The proposed method takes advantage of the GSPN model and incorporates the EDA method into the GSPN, which simplifies the reliability analysis process. Meanwhile, simulation results under different conditions show that CCF has made a considerable impact on reliability analysis for complex systems, which indicates that the CCF should not be ignored in reliability analysis.

Originality/value

The proposed method combines the EDA theory with the GSPN model to improve the efficiency of the reliability analysis.

Details

Engineering Computations, vol. 37 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 24 May 2013

Tetsushi Yuge, Shinya Ozeki and Shigeru Yanagi

This paper aims to present two methods for calculating the steady state probability of a repairable fault tree with priority AND gates and repeated basic events when the…

Abstract

Purpose

This paper aims to present two methods for calculating the steady state probability of a repairable fault tree with priority AND gates and repeated basic events when the minimal cut sets are given.

Design/methodology/approach

The authors consider a situation that the occurrence of an operational demand and its disappearance occur alternately. We assume that both the occurrence and the restoration of the basic event are statistically independent and exponentially distributed. Here, restoration means the disappearance of the occurring event as a result of a restoration action. First, we obtain the steady state probability of an output event of a single‐priority AND gate by Markov analysis. Then, we propose two methods of obtaining the top event probability based on an Inclusion‐Exclusion method and by considering the sum of disjoint probabilities.

Findings

The closed form expression of steady state probability of a priority AND gate is derived. The proposed methods for obtaining the top event probability are compared numerically with conventional Markov analysis and Monte Carlo simulation to verify the effectiveness. The result shows the effectiveness of the authors’ methods.

Originality/value

The methodology presented shows a new solution for calculating the top event probability of repairable dynamic fault trees.

Details

Journal of Quality in Maintenance Engineering, vol. 19 no. 2
Type: Research Article
ISSN: 1355-2511

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Book part
Publication date: 11 May 2012

Abigail L. Bristow and Alberto M. Zanni

Purpose – To examine the cost-effectiveness of UK government policy with respect to the mitigation of carbon emissions from the transport sector.Methodology/approach …

Abstract

Purpose – To examine the cost-effectiveness of UK government policy with respect to the mitigation of carbon emissions from the transport sector.

Methodology/approach – Existing policy as set out by the Department for Transport in Low Carbon Transport: A Greener Future is examined. This document elaborates a Low Carbon Transport Strategy intended to achieve annual emissions savings of 17.7 MtCO2 by 2020. A wide range of policy areas where further action could be taken to reduce carbon emissions are examined and their cost-effectiveness considered.

Findings – Measures that influence behaviour including smarter choices, eco-driving across modes, freight best practice and modest price increases are highly cost-effective. More cost-effective routes to saving 17.7 MtCO2 are identified, as are further cost-effective savings.

Originality/value – It appears that government targets could be delivered and indeed exceeded at lower cost than the Low Carbon Transport Strategy. However, policy development is influenced by a wide range of factors which help to explain why cost-effective measures are not always fully exploited.

Details

Transport and Climate Change
Type: Book
ISBN: 978-1-78052-440-5

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Article
Publication date: 22 May 2020

Aryana Collins Jackson and Seán Lacey

The discrete Fourier transformation (DFT) has been proven to be a successful method for determining whether a discrete time series is seasonal and, if so, for detecting…

Abstract

Purpose

The discrete Fourier transformation (DFT) has been proven to be a successful method for determining whether a discrete time series is seasonal and, if so, for detecting the period. This paper deals exclusively with rare data, in which instances occur periodically at a low frequency.

Design/methodology/approach

Data based on real-world situations is simulated for analysis.

Findings

Cycle number detection is done with spectral analysis, period detection is completed using DFT coefficients and signal shifts in the time domain are found using the convolution theorem. Additionally, a new method for detecting anomalies in binary, rare data is presented: the sum of distances. Using this method, expected events which have not occurred and unexpected events which have occurred at various sampling frequencies can be detected. Anomalies which are not considered outliers to be found.

Research limitations/implications

Aliasing can contribute to extra frequencies which point to extra periods in the time domain. This can be reduced or removed with techniques such as windowing. In future work, this will be explored.

Practical implications

Applications include determining seasonality and thus investigating the underlying causes of hard drive failure, power outages and other undesired events. This work will also lend itself well to finding patterns among missing desired events, such as a scheduled hard drive backup or an employee's regular login to a server.

Originality/value

This paper has shown how seasonality and anomalies are successfully detected in seasonal, discrete, rare and binary data. Previously, the DFT has only been used for non-rare data.

Details

Data Technologies and Applications, vol. 54 no. 2
Type: Research Article
ISSN: 2514-9288

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Article
Publication date: 9 July 2020

Gong Chen, Shaojie Liu, Zhigong Tang, Jiangtao Xu and Wenzheng Wang

The modern missile has low uncertain and wide range vibration frequency. The conventional notch filter with the fixed notch frequency is less effective than that of the…

Abstract

Purpose

The modern missile has low uncertain and wide range vibration frequency. The conventional notch filter with the fixed notch frequency is less effective than that of the adaptive notch filter (ANF) in vibration suppression for the time-varying vibration frequency.

Design/methodology/approach

To overcome the drawback, a novel method is based on frequency estimators made by interpolation of three discrete Fourier transform (DFT) spectral lines. The modified frequency estimators based on the interpolation of three DFT spectral lines are presented to identify and track the vibration frequency. Then the notch frequencies of multiple ANFs are real-timely tuned according to estimators.

Findings

Finally, taking the second-order flexible missile as an example, the performance of the proposed method is verified. The verified simulation results show that multiple ANFs are effective in vibration suppression.

Practical implications

Cascading multiple ANFs to achieve multi-order vibration suppression is more efficient and feasible than conventional fixed-parameter notch filtering.

Originality/value

The frequency estimation method based on three DFT spectral lines proposed in this paper can effectively identify and track signals in the noise environment. Compared with conventional methods, the method pretended in this paper has high identification accuracy and a stronger ability to track signals. It can meet the fast frequency identification requirements of the actual flexible missile.

Details

Aircraft Engineering and Aerospace Technology, vol. 92 no. 8
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 16 July 2021

Dure Jabeen, S.M. Ghazanfar Monir, Shaheena Noor, Muhammad Rafiullah and Munsif Ali Jatoi

Watermarking technique is one of the significant methods in which carrier signal hides digital information in the form of watermark to prevent the authenticity of the…

Abstract

Purpose

Watermarking technique is one of the significant methods in which carrier signal hides digital information in the form of watermark to prevent the authenticity of the stakeholders by manipulating different coefficients as watermark in time and frequency domain to sustain trade-off in performance parameters. One challenging component among others is to maintain the robustness, to limit perceptibility with embedding information. Transform domain is more popular to achieve the required results in color image watermarking. Variants of complex Hadamard transform (CHT) have been applied for gray image watermarking, and it has been proved that it has better performance than other orthogonal transforms. This paper is aimed at analyzing the performance of spatio-chromatic complex Hadamard transform (Sp-CHT) that is proposed as an application of color image watermarking in sequency domain (SD).

Design/methodology/approach

In this paper, color image watermarking technique is designed and implemented in SD using spatio-chromatic – conjugate symmetric sequency – ordered CHT. The color of a pixel is represented as complex number a*+jb*, where a* and b* are chromatic components of International Commission on Illumination (CIE) La*b* color space. The embedded watermark is almost transparent to human eye although robust against common signal processing attacks.

Findings

Based on the results, bit error rate (BER) and peak signal to noise ratio are measured and discussed in comparison of CIE La*b* and hue, saturation and value color model with spatio-chromatic discrete Fourier transform (Sp-DFT), and results are also analyzed with other discrete orthogonal transforms. It is observed from BER that Sp-CHT has 8%–12% better performance than Sp-DFT. Structural similarity index has been measured at different watermark strength and it is observed that presented transform performs better than other transforms.

Originality/value

This work presents the details and comparative analysis of two orthogonal transforms as color image watermarking application using MATLAB software. A finding from this study demonstrates that the Complex Hadamard transform is the competent candidate that can be replaced with DFT in many signal processing applications.

Details

World Journal of Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1708-5284

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Article
Publication date: 7 June 2021

Baoguang Ma, Cheng Chen, Xiaojun Xie, Yanhui Chen, Qiuyu Zhang, Dong Lv and Zhenguo Liu

The purpose of this study is to provide effective and environmental-friendly corrosion inhibitors derived from graphene oxide for Q235 steel.

Abstract

Purpose

The purpose of this study is to provide effective and environmental-friendly corrosion inhibitors derived from graphene oxide for Q235 steel.

Design/methodology/approach

Nontoxic and environment-friendly 4-aminobenzoic acid was used to functionalize graphene oxide via amidation and diazotization. The obtained amidation 4-aminobenzoic acid functionalized graphene oxide (PAGO) and diazotization 4-aminobenzoic acid functionalized graphene oxide (PDGO) were characterized by FTIR, Raman and TEM, while the inhibition efficiencies were analyzed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). Furthermore, theoretical inhibition efficiencies were investigated by density functional theory (DFT) approach.

Findings

At a concentration of 40 ppm, the maximum inhibition efficiency of PAGO and PDGO were 97.90% and 96.72% in EIS measurement, respectively, which were in accordance with PDP data. Moreover, experimental results were supported by DFT-based quantum chemical calculation.

Originality/value

Environmental-friendly PAGO and PDGO were synthesized successfully. The synthetic inhibitors exhibited excellent inhibition efficiencies in EIS and PDP measurements. Furthermore, a computational study using DFT supported the trend that PAGO was better inhibitor than PDGO.

Details

Anti-Corrosion Methods and Materials, vol. 68 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 17 May 2021

Hong-Yan Yan and Jin Kwon Hwang

The purpose of this paper is to improve the online monitoring level of low-frequency oscillation in the power system. A modal identification method of discrete Fourier…

Abstract

Purpose

The purpose of this paper is to improve the online monitoring level of low-frequency oscillation in the power system. A modal identification method of discrete Fourier transform (DFT) curve fitting based on ambient data is proposed in this study.

Design/methodology/approach

An autoregressive moving average mathematical model of ambient data was established, parameters of low-frequency oscillation were designed and parameters of low-frequency oscillation were estimated via DFT curve fitting. The variational modal decomposition method is used to filter direct current components in ambient data signals to improve the accuracy of identification. Simulation phasor measurement unit data and measured data of the power grid proved the correctness of this method.

Findings

Compared with the modified extended Yule-Walker method, the proposed approach demonstrates the advantages of fast calculation speed and high accuracy.

Originality/value

Modal identification method of low-frequency oscillation based on ambient data demonstrated high precision and short running time for small interference patterns. This study provides a new research idea for low-frequency oscillation analysis and early warning of power systems.

Details

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

Keywords

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