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Article
Publication date: 10 December 2024

Klaus Jürgen Folz and Herbert Martins Gomes

The objective of this article is to evaluate and compare the performance of two machine learning (ML) algorithms, i.e. support vector machines (SVMs) and random forests (RFs)…

25

Abstract

Purpose

The objective of this article is to evaluate and compare the performance of two machine learning (ML) algorithms, i.e. support vector machines (SVMs) and random forests (RFs), when classifying seven states of operation of an electric motor using the Mel-frequency cepstral coefficients (MFCCs) as extracted representative features.

Design/methodology/approach

The extracted MFCCs are calculated using the motor’s vibration and audio signals separately.

Findings

After the training, the SVM model obtained a mean accuracy of 100% for the MFCCs obtained from database vibration signals and 69.6% for the database of audio signals.

Research limitations/implications

The ML strategies and results reported are limited to the well-known data for industrial electric motors used in the evaluations, although it was performed tests and cross-validations with unseen data and the information from the confusion matrix.

Practical implications

The success of these methodologies in defect classification, where the RF presented a mean accuracy of 99.15% for the vibration signals and 63.82% for the audio signal, enables the use of this ML and extracted features as a predictive tool for failure and anomaly detection, lifetime predictions and online real-time monitoring.

Originality/value

It is the first time that the MFCCs are being used for anomaly detection in vibration and audio signals for electrical motors, as this extracted feature is usually used for human speech identification in the literature.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 26 February 2024

Leonardo Valero Pereira, Walter Jesus Paucar Casas, Herbert Martins Gomes, Luis Roberto Centeno Drehmer and Emanuel Moutinho Cesconeto

In this paper, improvements in reducing transmitted accelerations in a full vehicle are obtained by optimizing the gain parameters of an active control in a roughness road…

126

Abstract

Purpose

In this paper, improvements in reducing transmitted accelerations in a full vehicle are obtained by optimizing the gain parameters of an active control in a roughness road profile.

Design/methodology/approach

For a classically designed linear quadratic regulator (LQR) control, the vibration attenuation performance will depend on weighting matrices Q and R. A methodology is proposed in this work to determine the optimal elements of these matrices by using a genetic algorithm method to get enhanced controller performance. The active control is implemented in an eight degrees of freedom (8-DOF) vehicle suspension model, subjected to a standard ISO road profile. The control performance is compared against a controlled system with few Q and R parameters, an active system without optimized gain matrices, and an optimized passive system.

Findings

The control with 12 optimized parameters for Q and R provided the best vibration attenuation, reducing significantly the Root Mean Square (RMS) accelerations at the driver’s seat and car body.

Research limitations/implications

The research has positive implications in a wide class of active control systems, especially those based on a LQR, which was verified by the multibody dynamic systems tested in the paper.

Practical implications

Better active control gains can be devised to improve performance in vibration attenuation.

Originality/value

The main contribution proposed in this work is the improvement of the Q and R parameters simultaneously, in a full 8-DOF vehicle model, which minimizes the driver’s seat acceleration and, at the same time, guarantees vehicle safety.

Details

Engineering Computations, vol. 41 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 January 2005

Herbert Martins Gomes and Armando Miguel Awruch

To research the feasibility in using artificial neural networks (ANN) and response surfaces (RS) techniques for reliability analysis of concrete structures.

1059

Abstract

Purpose

To research the feasibility in using artificial neural networks (ANN) and response surfaces (RS) techniques for reliability analysis of concrete structures.

Design/methodology/approach

The evaluation of the failure probability and safety levels of structural systems is of extreme importance in structural design, mainly when the variables are eminently random. It is necessary to quantify and compare the importance of each one of these variables in the structural safety. RS and the ANN techniques have emerged attempting to solve complex and more elaborated problems. In this work, these two techniques are presented, and comparisons are carried out using the well‐known first‐order reliability method (FORM), with non‐linear limit state functions. The reliability analysis of reinforced concrete structure problems is specially considered taking into account the spatial variability of the material properties using random fields and the inherent non‐linearity.

Findings

It was observed that direct Monte Carlo simulation technique has a low performance in complex problems. FORM, RS and neural networks techniques are suitable alternatives, despite the loss of accuracy due to approximations characterizing these methods.

Research limitations/implications

The examples tested are limited to moderated large non‐linear reinforced concrete finite element models. Conclusions are drawn based on the examples.

Practical implications

Some remarks are outlined regarding the fact that RS and ANN techniques have presented equivalent precision levels. It is observed that in problems where the computational cost of structural evaluations (computing failure probability and safety levels) is high, these two techniques could improve the performance of the structural reliability analysis through simulation techniques.

Originality/value

This paper is important in the field of reliability analysis of concrete structures specially when neural networks or RS techniques are used.

Details

Engineering Computations, vol. 22 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 4 July 2016

Herbert Martins Gomes

The purpose of this paper is to investigate the optimum design of a quarter car passive suspension system using a particle swarm optimization algorithm in order to minimize the…

389

Abstract

Purpose

The purpose of this paper is to investigate the optimum design of a quarter car passive suspension system using a particle swarm optimization algorithm in order to minimize the applied loads and vibrations.

Design/methodology/approach

The road excitation is assumed as zero-mean random field and modeled by single-sided power spectral density (PSD) based on international standard ISO 8608. The variance of sprung mass displacements and variance of dynamic applied load are evaluated by PSD functions and used as cost function for the optimization.

Findings

The advantages in using this methodology are emphasized by an example of the multi-objective optimization design of suspension parameters and the results are compared with values reported in the literature and other gradient based and heuristic algorithms. The paper shows that the algorithm effectively leads to reliable results for suspension parameters with low computational effort.

Research limitations/implications

The procedure is applied to a quarter car passive suspension design.

Practical implications

The proposed procedure implies substantial time savings due to frequency domain analysis.

Social implications

The paper proposes a procedure that allows complex optimization designs to be feasible and cost effective.

Originality/value

The design optimization is performed in the frequency domain taking into account standard defined road profiles PSD without the need to simulate in the time domain.

Details

Engineering Computations, vol. 33 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 November 2002

Herbert Martins Gomes and Armando Miguel Awruch

In this paper, special emphasis is given to uncertainties in the evaluation of the structural behavior, looking for a better representation of the system characteristics and…

950

Abstract

In this paper, special emphasis is given to uncertainties in the evaluation of the structural behavior, looking for a better representation of the system characteristics and quantification of the significance of these uncertainties in structural design. The reliability analysis of reinforced concrete structures is performed taking into account the spatial variability of material properties. The finite element method is used to analyze reinforced concrete structures. A multidimensional non‐Gaussian stochastic field generation model (independent of the finite element mesh) is developed and used. The reliability analysis is carried out employing the first order reliability method. Numerical examples are presented to study how to generate correlated non‐Gaussian stochastic fields and determine the reliability of a reinforced concrete structure with respect to a limit state function.

Details

Engineering Computations, vol. 19 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 7 April 2015

M.Elena Gómez-Miranda, M.Carmen Pérez-López, Eva Argente-Linares and Lázaro Rodríguez-Ariza

The characteristics of a particular organizational culture may affect performance in achieving the objectives of international joint ventures (IJVs), a type of partnership that is…

3013

Abstract

Purpose

The characteristics of a particular organizational culture may affect performance in achieving the objectives of international joint ventures (IJVs), a type of partnership that is often used in international business relations between developed and emerging countries. The purpose of this paper is to analyse whether the underlying dimensions that characterize organizational culture in these countries may affect firms’ performance, specifically their competitiveness, effectiveness and efficiency.

Design/methodology/approach

The survey conducted for this study was addressed to Spanish-Moroccan IJVs trading in Morocco. The research hypotheses were tested using multivariate analysis techniques (exploratory factor analysis and linear regression model).

Findings

Based on information provided by the CEOs of Spanish-Moroccan IJVs between small- to medium-sized firms, the present study shows that levels of competitiveness, effectiveness and/or efficiency in these organizations are influenced by the involvement of staff in management, the degree of centralization of decision taking and the firms’ emphasis on results or on procedures.

Practical implications

This research contributes to the knowledge of the main factors related to the organizational culture of joint ventures that influence competitiveness, effectiveness and efficiency achieved.

Originality/value

The value provided by this research lies in the sample examined, in its focus on a very common type of partnership between SMEs, which has been little studied previously, and in the fact that the results obtained are extensible to other realities, such as partnerships between European companies and those from countries with similar characteristics (located in Africa or in countries where an Arab culture prevails).

Details

Personnel Review, vol. 44 no. 3
Type: Research Article
ISSN: 0048-3486

Keywords

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Article
Publication date: 4 May 2008

Ian Barron and Keith Topping

This narrative review explored the efficacy of school-based child sexual abuse prevention programmes between 1990 and 2002. There were 22 efficacy studies that met clear inclusion…

599

Abstract

Purpose

This narrative review explored the efficacy of school-based child sexual abuse prevention programmes between 1990 and 2002. There were 22 efficacy studies that met clear inclusion criteria. Results covered both methodological design and the range of outcome measures. Methodology was analysed through four dimensions (target population, prevention programme implementation, evaluation methodology and cost-effectiveness). Outcomes for children covered nine categories (knowledge, skills, emotion, perception of risk, touch discrimination, reported response to actual threat/abuse, disclosure, negative effects and maintenance of gains). The studies had many methodological limitations. Prevention programmes had a measure of effectiveness in increasing children ' s awareness of child sexual abuse as well as self-protective skills. Beyond minimal disclosure rates, there was no evidence to demonstrate that programmes protected children from intra-familial sexual abuse. For a small number of children prevention programmes produced minimal negative emotional effects. Recommendations for future research, policy and practice, include realistic outcomes for child participants and locating programmes within wider abuse prevention measures.

Details

Journal of Children's Services, vol. 3 no. 3
Type: Research Article
ISSN: 1746-6660

Keywords

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Book part
Publication date: 16 September 2019

James Fowler

Abstract

Details

London Transport: A Hybrid in History 1905–1948
Type: Book
ISBN: 978-1-78973-953-4

Available. Open Access. Open Access
Article
Publication date: 15 December 2022

Norberto Santos, Claudete Oliveira Moreira and Luís Silveira

Tourism in Coimbra today is influenced by the fact that the Univer(s)city was distinguished as a World Heritage Site in 2013. The number of visits has grown very significantly in…

1032

Abstract

Purpose

Tourism in Coimbra today is influenced by the fact that the Univer(s)city was distinguished as a World Heritage Site in 2013. The number of visits has grown very significantly in recent years, but the diversification of the tourist offer is still weak and unable to take advantage of existing resources. This paper aims to present genealogy tourism as an alternative urban cultural tourism in Coimbra.

Design/methodology/approach

Methodology involved mapping the Jewish culture elements in the city of Coimbra, and a route was outlined and proposed.

Findings

Genealogy tourism resources are identified in the historic centre of the city. These alternative spaces need urban rehabilitation and (re)functionalisation, which allowed the authors to rethink tourism in Coimbra. They are the motivation to visit for all urban cultural tourists, especially Israelis/Jews, and provide contact with places where the experiences of ancestors combine with the history and memory of places, with recent discoveries and the elements of Jewish culture in the city.

Originality/value

It is concluded that the quantity, diversity, authenticity and singularity of the heritage resources that bear witness to the Jewish presence in Coimbra are sufficient assets to create a route, to enrich the tourist experience in the city and to include the destination in the Sephardic routes.

Details

International Journal of Tourism Cities, vol. 10 no. 1
Type: Research Article
ISSN: 2056-5607

Keywords

Available. Content available
Book part
Publication date: 1 January 2005

Naresh K. Malhotra

Abstract

Details

Review of Marketing Research
Type: Book
ISBN: 978-0-85724-723-0

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