Encontrados 12 documentos, a visualizar página 1 de 2
Analysis of temperature time-series: embedding dynamics into the MDS method
Lopes, António M.; Machado, J. A. TenreiroGlobal warming and the associated climate changes are being the subject of intensive research due to their major impact on social, economic and health aspects of the human life. Surface temperature time-series characterise Earth as a slow dynamics spatiotemporal system, evidencing long memory behaviour, typical of fractional order systems. Such phenomena are difficult to model and analyse, demanding for alterna...
Analysis and visualization of seismic data using mutual information
Machado, J. A. Tenreiro; Lopes, António M.Seismic data is difficult to analyze and classical mathematical tools reveal strong limitations in exposing hidden relationships between earthquakes. In this paper, we study earthquake phenomena in the perspective of complex systems. Global seismic data, covering the period from 1962 up to 2011 is analyzed. The events, characterized by their magnitude, geographic location and time of occurrence, are divided int...
Fractional dynamics and MDS visualization of earthquake phenomena
Lopes, António M.; Machado, J. A. Tenreiro; Pinto, Carla M. A.; Galhano, AlexandraThis paper analyses earthquake data in the perspective of dynamical systems and fractional calculus (FC). This new standpoint uses Multidimensional Scaling (MDS) as a powerful clustering and visualization tool. FC extends the concepts of integrals and derivatives to non-integer and complex orders. MDS is a technique that produces spatial or geometric representations of complex objects, such that those objects t...
Power law and entropy analysis of catastrophic phenomena
Machado, J. A. Tenreiro; Pinto, Carla M. A.; Lopes, António M.Catastrophic events, such as wars and terrorist attacks, tornadoes and hurricanes, earthquakes, tsunamis, floods and landslides, are always accompanied by a large number of casualties. The size distribution of these casualties has separately been shown to follow approximate power law (PL) distributions. In this paper, we analyze the statistical distributions of the number of victims of catastrophic phenomena, i...
Root-locus practical sketching rules for fractional-order system
Lopes, António M.; Machado, J. A. TenreiroFor integer-order systems, there are well-known practical rules for RL sketching. Nevertheless, these rules cannot be directly applied to fractional-order (FO) systems. Besides, the existing literature on this topic is scarce and exclusively focused on commensurate systems, usually expressed as the ratio of two noninteger polynomials. The practical rules derived for those do not apply to other symbolic expressi...
Dynamic analysis of earthquake phenomena by means of pseudo phase plane
Lopes, António M.; Machado, J. A. TenreiroThis paper analyses earthquake data in the perspective of dynamical systems and its Pseudo Phase Plane representation. The seismic data is collected from the Bulletin of the International Seismological Centre. The geological events are characterised by their magnitude and geographical location and described by means of time series of sequences of Dirac impulses. Fifty groups of data series are considered, accor...
Fractional order models of leaves
Lopes, António M.; Machado, J. A. TenreiroLeaves are mainly responsible for food production in vascular plants. Studying individual leaves can reveal important characteristics of the whole plant, namely its health condition, nutrient status, the presence of viruses and rooting ability. One technique that has been used for this purpose is Electrical Impedance Spectroscopy, which consists of determining the electrical impedance spectrum of the leaf. In ...
Single-objective spreading algorithm
Pires, E. J. Solteiro; Mendes, Luís; Lopes, António M.; Oliveira, P. B. Moura; Machado, J. A. TenreiroThis paper addresses the problem of finding several different solutions with the same optimum performance in single objective real-world engineering problems. In this paper a parallel robot design is proposed. Thereby, this paper presents a genetic algorithm to optimize uni-objective problems with an infinite number of optimal solutions. The algorithm uses the maximin concept and ε-dominance to promote diversit...
Optimal location of the workpiece in a PKM-based machining robotic cell
Pires, E. J. Solteiro; Lopes, António M.; Machado, J. A. Tenreiro; Oliveira, P. B. MouraMost machining tasks require high accuracy and are carried out by dedicated machine-tools. On the other hand, traditional robots are flexible and easy to program, but they are rather inaccurate for certain tasks. Parallel kinematic robots could combine the accuracy and flexibility that are usually needed in machining operations. Achieving this goal requires proper design of the parallel robot. In this chapter, ...
Dynamical analysis of the global warming
Machado, J. A. Tenreiro; Lopes, António M.Global warming is a major concern nowadays. Weather conditions are changing, and it seems that human activity is one of the main causes. In fact, since the beginning of the industrial revolution, the burning of fossil fuels has increased the nonnatural emissions of carbon dioxide to the atmosphere. Carbon dioxide is a greenhouse gas that absorbs the infrared radiation produced by the reflection of the sunlight ...
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