Journal of Computational and Applied Mathematics, 2007
The application of Adomian's decomposition method to partial differential equations, when the exa... more The application of Adomian's decomposition method to partial differential equations, when the exact solution is not reached, demands the use of truncated series. But the solution's series may have small convergence radius and the truncated series may be inaccurate in many regions. In order to enlarge the convergence domain of the truncated series, Padé approximants (PAs) to the Adomian's series solution have been tested and applied to partial and ordinary differential equations, with good results. In this paper, PAs, both in x and t directions, applied to the truncated series solution given by Adomian's decomposition technique for Burgers equation, are tested. Numerical and graphical illustrations show that this technique can improve the accuracy and enlarge the domain of convergence of the solution. It is also shown in this paper, that the application of Adomian's method to the ordinary differential equations set arising from the discretization of the spatial derivatives by finite differences, the so-called method of lines, may reduce the convergence domain of the solution's series.
Strategies to combat academic failure in higher education rely on the identification and on the k... more Strategies to combat academic failure in higher education rely on the identification and on the knowledge of the causes associated with it. To identify these causes, a questionnaire survey was implemented in a Higher School of Technologies and Engineering. Student-related aspects were those that exhibited the greatest impact on academic success/failure. Teachers and institution/curriculum exhibited an indirect impact through mediation by student-related aspects. Other variables were identified with a negative residual impact on academic success, such as: be displaced from the habitual residence, dislike to study and be a male. With a slightly more relevant impact, emerged the sleep time on the eve of the tests.
This paper assesses the validity and reliability of two instruments measuring quality of service,... more This paper assesses the validity and reliability of two instruments measuring quality of service, the SERVPERF and SERVQUAL scales, replicated in a novel cultural settings, a Portuguese energy company. To provide insights and strategies for managerial intervention, a relation between customers' satisfaction and quality of service is established. The empirical study suggests a superior convergent and predictive validity of SERVPERF scale to measure quality of service in this settings when comparing to SERVQUAL. The main differences of this study with previous ones, are that this one resorts on a confirmatory factor analysis, the validation of the instruments is performed by using the same measures suggested by their creators and extends the line of research to a novel cultural settings, a Portuguese energy company. Concerning the relationship between service quality and customers' satisfaction, all of the quality of service attributes correlate almost equally to the satisfaction ones, with a lower weight concerning tangibles.
Equaçoes nao lineares surgem em quase todas as áreas da Engenharia e da Fısica, sendo por isso ... more Equaçoes nao lineares surgem em quase todas as áreas da Engenharia e da Fısica, sendo por isso de importância fundamental a existência de métodos para determinar as suas raızes. Infelizmente, como a determinaçao de soluçoes por métodos analıticos nao é ...
Exploratory factor analysis is a widely used statistical technique in the social sciences. It att... more Exploratory factor analysis is a widely used statistical technique in the social sciences. It attempts to identify underlying factors that explain the pattern of correlations within a set of observed variables. A statistical software package is needed to perform the calculations. However, there are some limitations with popular statistical software packages, like SPSS. The R programming language is a free software package for statistical and graphical computing. It offers many packages written by contributors from all over the world and programming resources that allow it to overcome the dialog limitations of SPSS. This paper offers an SPSS dialog written in the R programming language with the help of some packages, so that researchers with little or no knowledge in programming, or those who are accustomed to making their calculations based on statistical dialogs, have more options when applying factor analysis to their data and hence can adopt a better approach when dealing with ordinal, Likert-type data.
Textile and tourism sectors are two important industries in the Portuguese economy. However, its ... more Textile and tourism sectors are two important industries in the Portuguese economy. However, its high exposure to both internal and international economic volatility make the companies operating in these economic sectors particularly vulnerable to economic crises, such as the ones which have been impacting Portugal and the European Union. The objective of this paper is to evaluate and understand the impact of size and age on the financial health of textile and tourism companies, measured by economic indices. An empirical based model is proposed. Its implications are derived and tested on a sample of 4061 Portuguese companies from textile and tourism sectors, during the period 2005-2009. The findings suggest that age has a major impact on the risk of failure, rather than size. Whereas the effect of age is generally positive regarding the financial health of the company, the effect of size is less clear and ultimately depends on the age of the company.
A growing number of predicting corporate failure models has emerged since 60s. Economic and socia... more A growing number of predicting corporate failure models has emerged since 60s. Economic and social consequences of business failure can be dramatic, thus it is not surprise that the issue has been of growing interest in academic research as well as in business context. The main purpose of this study is to compare the predictive ability of five developed models based on three statistical techniques (Discriminant Analysis, Logit and Probit) and two models based on Artificial Intelligence (Neural Networks and Rough Sets). The five models were employed to a dataset of 420 non-bankrupt firms and 125 bankrupt firms belonging to the textile and clothing industry, over the period 2003-09. Results show that all the models performed well, with an overall correct classification level higher than 90%, and a type II error always less than 2%. The type I error increases as we move away from the year prior to failure. Our models contribute to the discussion of corporate financial distress causes. Moreover it can be used to assist decisions of creditors, investors and auditors. Additionally, this research can be of great contribution to devisers of national economic policies that aim to reduce industrial unemployment.
As marcas adquiriram particular preponderncia nas estratgias das empresas, visto serem capazes de... more As marcas adquiriram particular preponderncia nas estratgias das empresas, visto serem capazes de gerar sentimentos, sensaes e emoes nos clientes. Os valores, no mensurveis, resultaro, obviamente, em valor para as empresas e para as prprias marcas. Uma marca forte configurar-se- como o maior patrimnio de uma empresa. E hoje vista como um dos activos mais importantes. A evoluo de uma marca, como activo intangvel e estratgico de uma empresa, assume-se cada vez mais de vital importncia, no seio destas, como forma de maximizar os seus resultados. Esta necessidade, quer do mercado quer das empresas, justifica o direccionamento da pesquisa para o sector o valor da marca. O trabalho tem como objectivo principal apresentar um novo modelo de avaliao de marcas. Este modelo sustenta-se numa vertente tangvel e numa intangvel, esta ltima avalia os conhecimentos e a capacidade dos seus responsveis e funcionrios para a construo de uma marca de valor, atravs da correcta ordenao das prioridades das ...
Journal of Computational and Applied Mathematics, 2007
ABSTRACT For low values of the viscosity coefficient, Burgers equation can develop sharp disconti... more ABSTRACT For low values of the viscosity coefficient, Burgers equation can develop sharp discontinuities, which are difficult to simulate in a computer. Oscillations can occur by discretization through spectral collocation methods, due to Gibbs phenomena. Under a dynamic point of view, these instabilities are related to bifurcations arising to the discretized equation. For different values of discretized points, herein a study is performed of the dynamics and bifurcations occurring in the spectral solutions of Burgers equation with symmetry. Several phenomena are observed, from limit cycles, strange attractors to the presence of bistability with two periodic attractors, with a periodic attractor and a strange attractor and with two strange attractors. Also, other stable equilibrium points can occur, diverse from the ones corresponding to the solution of Burgers equation.
For Chebyshev spectral solutions of the forced Burgers equation with low values of the viscosity ... more For Chebyshev spectral solutions of the forced Burgers equation with low values of the viscosity coefficient, several bifurcations and stable attractors can be observed. Periodic orbits, quasiperiodic and strange ones may arise. Bistability can also be observed. Necessary conditions for these attractors to appear are discussed and justification for the non emerging of bistability for an example of a system symmetry break is presented. As an application for the dynamical behavior of spectral solutions of Burgers equation, the dynamics and synchronization of unidirectionally coupling of Chebyshev spectral solutions of Burgers equations by means of a linear coupling are described and discussed. Also, a nonlinear coupling is proposed and discussed.
Page 1. Chapter 14 Dynamics on Spectral Solutions of Forced Burgers Equation Mário Basto, Viriato... more Page 1. Chapter 14 Dynamics on Spectral Solutions of Forced Burgers Equation Mário Basto, Viriato Semiao, and Francisco Lage Calheiros Abstract Burgers equation @u @t Cu @u @x D ı @2u @x2 Cf .x/ is one of the simplest ...
The aim of this paper is to construct a new efficient iterative method to solve nonlinear equatio... more The aim of this paper is to construct a new efficient iterative method to solve nonlinear equations. The new method is based on the proposals of Abbasbandy on improving the order of accuracy of Newton-Raphson method [S. Abbasbandy, Improving Newton-Raphson method for nonlinear equations by modified Adomian decomposition method, Applied Mathematics and Computation 145 887-893] and on the proposals of Babolian and Biazar on improving the order of accuracy of AdomianÕs decomposition method [E. Babolian, J. Biazar, On the order of convergence of Adomian method, Applied Mathematics and Computation 130 (2002) 383-387]. The convergence of the new scheme is proved and at least the cubic order of convergence is established. Several examples are presented and compared to other methods, showing the accuracy and fast convergence of this new method. Also, it is shown in this paper, that the modified AdomianÕs method developed by Babolian and Biazar to solve nonlinear equations [E. Babolian, J. Biazar, Solution of nonlinear equations by modified Adomian decomposition method, Applied Mathematics and Computation 132 (2002) 167-172] should be slightly modified, due to the fact that convergence of AdomianÕs method does not ensure convergence of the modified method. An example illustrates 0096-3003/$ -see front matter Ó (M. Basto). Applied Mathematics and Computation 173 (2006) 468-483
Journal of Computational and Applied Mathematics, 2007
The application of Adomian's decomposition method to partial differential equations, when the exa... more The application of Adomian's decomposition method to partial differential equations, when the exact solution is not reached, demands the use of truncated series. But the solution's series may have small convergence radius and the truncated series may be inaccurate in many regions. In order to enlarge the convergence domain of the truncated series, Padé approximants (PAs) to the Adomian's series solution have been tested and applied to partial and ordinary differential equations, with good results. In this paper, PAs, both in x and t directions, applied to the truncated series solution given by Adomian's decomposition technique for Burgers equation, are tested. Numerical and graphical illustrations show that this technique can improve the accuracy and enlarge the domain of convergence of the solution. It is also shown in this paper, that the application of Adomian's method to the ordinary differential equations set arising from the discretization of the spatial derivatives by finite differences, the so-called method of lines, may reduce the convergence domain of the solution's series.
Strategies to combat academic failure in higher education rely on the identification and on the k... more Strategies to combat academic failure in higher education rely on the identification and on the knowledge of the causes associated with it. To identify these causes, a questionnaire survey was implemented in a Higher School of Technologies and Engineering. Student-related aspects were those that exhibited the greatest impact on academic success/failure. Teachers and institution/curriculum exhibited an indirect impact through mediation by student-related aspects. Other variables were identified with a negative residual impact on academic success, such as: be displaced from the habitual residence, dislike to study and be a male. With a slightly more relevant impact, emerged the sleep time on the eve of the tests.
This paper assesses the validity and reliability of two instruments measuring quality of service,... more This paper assesses the validity and reliability of two instruments measuring quality of service, the SERVPERF and SERVQUAL scales, replicated in a novel cultural settings, a Portuguese energy company. To provide insights and strategies for managerial intervention, a relation between customers' satisfaction and quality of service is established. The empirical study suggests a superior convergent and predictive validity of SERVPERF scale to measure quality of service in this settings when comparing to SERVQUAL. The main differences of this study with previous ones, are that this one resorts on a confirmatory factor analysis, the validation of the instruments is performed by using the same measures suggested by their creators and extends the line of research to a novel cultural settings, a Portuguese energy company. Concerning the relationship between service quality and customers' satisfaction, all of the quality of service attributes correlate almost equally to the satisfaction ones, with a lower weight concerning tangibles.
Equaçoes nao lineares surgem em quase todas as áreas da Engenharia e da Fısica, sendo por isso ... more Equaçoes nao lineares surgem em quase todas as áreas da Engenharia e da Fısica, sendo por isso de importância fundamental a existência de métodos para determinar as suas raızes. Infelizmente, como a determinaçao de soluçoes por métodos analıticos nao é ...
Exploratory factor analysis is a widely used statistical technique in the social sciences. It att... more Exploratory factor analysis is a widely used statistical technique in the social sciences. It attempts to identify underlying factors that explain the pattern of correlations within a set of observed variables. A statistical software package is needed to perform the calculations. However, there are some limitations with popular statistical software packages, like SPSS. The R programming language is a free software package for statistical and graphical computing. It offers many packages written by contributors from all over the world and programming resources that allow it to overcome the dialog limitations of SPSS. This paper offers an SPSS dialog written in the R programming language with the help of some packages, so that researchers with little or no knowledge in programming, or those who are accustomed to making their calculations based on statistical dialogs, have more options when applying factor analysis to their data and hence can adopt a better approach when dealing with ordinal, Likert-type data.
Textile and tourism sectors are two important industries in the Portuguese economy. However, its ... more Textile and tourism sectors are two important industries in the Portuguese economy. However, its high exposure to both internal and international economic volatility make the companies operating in these economic sectors particularly vulnerable to economic crises, such as the ones which have been impacting Portugal and the European Union. The objective of this paper is to evaluate and understand the impact of size and age on the financial health of textile and tourism companies, measured by economic indices. An empirical based model is proposed. Its implications are derived and tested on a sample of 4061 Portuguese companies from textile and tourism sectors, during the period 2005-2009. The findings suggest that age has a major impact on the risk of failure, rather than size. Whereas the effect of age is generally positive regarding the financial health of the company, the effect of size is less clear and ultimately depends on the age of the company.
A growing number of predicting corporate failure models has emerged since 60s. Economic and socia... more A growing number of predicting corporate failure models has emerged since 60s. Economic and social consequences of business failure can be dramatic, thus it is not surprise that the issue has been of growing interest in academic research as well as in business context. The main purpose of this study is to compare the predictive ability of five developed models based on three statistical techniques (Discriminant Analysis, Logit and Probit) and two models based on Artificial Intelligence (Neural Networks and Rough Sets). The five models were employed to a dataset of 420 non-bankrupt firms and 125 bankrupt firms belonging to the textile and clothing industry, over the period 2003-09. Results show that all the models performed well, with an overall correct classification level higher than 90%, and a type II error always less than 2%. The type I error increases as we move away from the year prior to failure. Our models contribute to the discussion of corporate financial distress causes. Moreover it can be used to assist decisions of creditors, investors and auditors. Additionally, this research can be of great contribution to devisers of national economic policies that aim to reduce industrial unemployment.
As marcas adquiriram particular preponderncia nas estratgias das empresas, visto serem capazes de... more As marcas adquiriram particular preponderncia nas estratgias das empresas, visto serem capazes de gerar sentimentos, sensaes e emoes nos clientes. Os valores, no mensurveis, resultaro, obviamente, em valor para as empresas e para as prprias marcas. Uma marca forte configurar-se- como o maior patrimnio de uma empresa. E hoje vista como um dos activos mais importantes. A evoluo de uma marca, como activo intangvel e estratgico de uma empresa, assume-se cada vez mais de vital importncia, no seio destas, como forma de maximizar os seus resultados. Esta necessidade, quer do mercado quer das empresas, justifica o direccionamento da pesquisa para o sector o valor da marca. O trabalho tem como objectivo principal apresentar um novo modelo de avaliao de marcas. Este modelo sustenta-se numa vertente tangvel e numa intangvel, esta ltima avalia os conhecimentos e a capacidade dos seus responsveis e funcionrios para a construo de uma marca de valor, atravs da correcta ordenao das prioridades das ...
Journal of Computational and Applied Mathematics, 2007
ABSTRACT For low values of the viscosity coefficient, Burgers equation can develop sharp disconti... more ABSTRACT For low values of the viscosity coefficient, Burgers equation can develop sharp discontinuities, which are difficult to simulate in a computer. Oscillations can occur by discretization through spectral collocation methods, due to Gibbs phenomena. Under a dynamic point of view, these instabilities are related to bifurcations arising to the discretized equation. For different values of discretized points, herein a study is performed of the dynamics and bifurcations occurring in the spectral solutions of Burgers equation with symmetry. Several phenomena are observed, from limit cycles, strange attractors to the presence of bistability with two periodic attractors, with a periodic attractor and a strange attractor and with two strange attractors. Also, other stable equilibrium points can occur, diverse from the ones corresponding to the solution of Burgers equation.
For Chebyshev spectral solutions of the forced Burgers equation with low values of the viscosity ... more For Chebyshev spectral solutions of the forced Burgers equation with low values of the viscosity coefficient, several bifurcations and stable attractors can be observed. Periodic orbits, quasiperiodic and strange ones may arise. Bistability can also be observed. Necessary conditions for these attractors to appear are discussed and justification for the non emerging of bistability for an example of a system symmetry break is presented. As an application for the dynamical behavior of spectral solutions of Burgers equation, the dynamics and synchronization of unidirectionally coupling of Chebyshev spectral solutions of Burgers equations by means of a linear coupling are described and discussed. Also, a nonlinear coupling is proposed and discussed.
Page 1. Chapter 14 Dynamics on Spectral Solutions of Forced Burgers Equation Mário Basto, Viriato... more Page 1. Chapter 14 Dynamics on Spectral Solutions of Forced Burgers Equation Mário Basto, Viriato Semiao, and Francisco Lage Calheiros Abstract Burgers equation @u @t Cu @u @x D ı @2u @x2 Cf .x/ is one of the simplest ...
The aim of this paper is to construct a new efficient iterative method to solve nonlinear equatio... more The aim of this paper is to construct a new efficient iterative method to solve nonlinear equations. The new method is based on the proposals of Abbasbandy on improving the order of accuracy of Newton-Raphson method [S. Abbasbandy, Improving Newton-Raphson method for nonlinear equations by modified Adomian decomposition method, Applied Mathematics and Computation 145 887-893] and on the proposals of Babolian and Biazar on improving the order of accuracy of AdomianÕs decomposition method [E. Babolian, J. Biazar, On the order of convergence of Adomian method, Applied Mathematics and Computation 130 (2002) 383-387]. The convergence of the new scheme is proved and at least the cubic order of convergence is established. Several examples are presented and compared to other methods, showing the accuracy and fast convergence of this new method. Also, it is shown in this paper, that the modified AdomianÕs method developed by Babolian and Biazar to solve nonlinear equations [E. Babolian, J. Biazar, Solution of nonlinear equations by modified Adomian decomposition method, Applied Mathematics and Computation 132 (2002) 167-172] should be slightly modified, due to the fact that convergence of AdomianÕs method does not ensure convergence of the modified method. An example illustrates 0096-3003/$ -see front matter Ó (M. Basto). Applied Mathematics and Computation 173 (2006) 468-483
Uploads
Papers by Mário Basto