Genetic algorithms with self-organizing behaviour in dynamic environments

Copyright @ 2007 Springer-VerlagIn recent years, researchers from the genetic algorithm (GA) community have developed several approaches to enhance the performance of traditional GAs for dynamic optimization problems (DOPs). Among these approaches, one technique is to maintain the diversity of the population by inserting random immigrants into the population. This chapter investigates a self-organizing random immigrants scheme for GAs to address DOPs, where the worst individual and its next neighbours are replaced by random immigrants. In order to protect the newly introduced immigrants from being replaced by fitter individuals, they are placed in a subpopulation. In this way, individuals start to interact between themselves and, when the fitness of the individuals are close, one single replacement of an individual can affect a large number of individuals of the population in a chain reaction. The individuals in a subpopulation are not allowed to be replaced by individuals of the main population during the current chain reaction. The number of individuals in the subpopulation is given by the number of individuals created in the current chain reaction. It is important to observe that this simple approach can take the system to a self-organization behaviour, which can be useful for GAs in dynamic environments.Financial support was obtained from FAPESP (Proc. 04/04289-6)

Possible Superconductivity at 37 K in Graphite-Sulfur Composite

Sulfur intercalated graphite composites with diamagnetic transitions at 6.7 K and 37 K are prepared. The magnetization hysteresis loops (MHL), Xray diffraction patterns, and resistance were measured. From the MHL, a slight superconducting like penetration process is observed at 15 K in low field region. The XRD shows no big difference from the mixture of graphite and sulfur indicating that the volume of the superconducting phase (if any) is very small. The temperature dependence of resistance shows a typical semiconducting behavior with a saturation in low temperature region. This saturation is either induced by the de-localization of conducting electrons or by possible superconductivity in this system.Comment: CHIN. PHYS.LETT v18 1648 (2001

Epistasis not needed to explain low dN/dS

An important question in molecular evolution is whether an amino acid that occurs at a given position makes an independent contribution to fitness, or whether its effect depends on the state of other loci in the organism's genome, a phenomenon known as epistasis. In a recent letter to Nature, Breen et al. (2012) argued that epistasis must be "pervasive throughout protein evolution" because the observed ratio between the per-site rates of non-synonymous and synonymous substitutions (dN/dS) is much lower than would be expected in the absence of epistasis. However, when calculating the expected dN/dS ratio in the absence of epistasis, Breen et al. assumed that all amino acids observed in a protein alignment at any particular position have equal fitness. Here, we relax this unrealistic assumption and show that any dN/dS value can in principle be achieved at a site, without epistasis. Furthermore, for all nuclear and chloroplast genes in the Breen et al. dataset, we show that the observed dN/dS values and the observed patterns of amino acid diversity at each site are jointly consistent with a non-epistatic model of protein evolution.Comment: This manuscript is in response to "Epistasis as the primary factor in molecular evolution" by Breen et al. Nature 490, 535-538 (2012

Geometric phase for nonlinear coherent and squeezed state

The geometric phases for standard coherent states which are widely used in quantum optics have attracted a large amount of attention. Nevertheless, few physicists consider about the counterparts of non-linear coherent states, which are useful in the description of the motion of a trapped ion. In this paper, the non-unitary and non-cyclic geometric phases for two nonlinear coherent and one squeezed states are formulated respectively. Moreover, some of their common properties are discussed respectively, such as gauge invariance, non-locality and non-linear effects. The non-linear functions have dramatic impacts on the evolution of the corresponding geometric phases. They speed the evolution up or down. So this property may have application in controlling or measuring geometric phase. For the squeezed case, when the squeezed parameter r -> \infinity, the limiting value of the geometric phase is also determined by non-linear function at a given time and angular velocity. In addition, the geometric phases for standard coherent and squeezed states are obtained under a particular condition. When the time evolution undergoes a period, their corresponding cyclic geometric phases are achieved as well. And the distinction between the geometric phases of the two coherent states maybe regarded as a geometric criterion

Coupling of a granular chain to an acoustic medium: Sensitivity analyses of the propagation of ultrasonic pulse trains

Effects which arise as a result of Hertzian contact between adjacent spheres of a granular chain can potentially change the nature of a signal as it propagates down the chain. The possibility thus exists of generating signals with a different harmonic content to the signal input into one end of the chain. This transduction mechanism has the potential to be of use in both diagnostic and therapeutic ultrasound applications. Due to metrological challenges which arise when characterizing this transduction process, numerical models play a fundamental role in assisting the design of these novel devices. Previously, a finite element model was presented, which predicts the acoustic pressure generated by a sinusoidally excited granular chain coupled into an acoustic medium. The study described here exploits this model to carry out sensitivity analyses of the system to key input parameters, including excitation frequency and amplitude, sphere diameter and the number of spheres present in the chain. Granular chains were excited at one end using tone burst displacement signals with fundamental frequencies of 73 kHz and 100 kHz. The final sphere of the chain was assumed to be in contact with a cylindrical vitreous carbon layer, coupled to a half-space of water. Using the finite element method, it was possible to predict the acoustic pressure in the fluid, for a specific dynamic excitation of the first sphere of the granular chain. The sensitivity analyses demonstrated that, under tone burst excitation conditions, a train of impulses could be propagated into an acoustic medium. The sensitivity analyses also show that, due to inherent nonlinearities present in this type of system, the time and frequency domain characteristics of the signals are highly sensitive to input conditions

mHealth initiatives in Portugal

Comunicação apresentada à CISTI'2017 - 12ª Conferência Ibérica de Sistemas e Tecnologias de Informação, realizada de 21-24 de junho de 2017, em Lisboa, Portugal.O paradigma da prestação de cuidados de saúde está lentamente a alinhar-se com as necessidades e hábitos do paciente moderno. A computação móvel pode ser uma solução para responder à crescente tendência e necessidade para a partilha e colaboração de cuidados de saúde, possibilitando o redesenhar de processos e dando origem a novos modelos de prestação de cuidados de saúde. Para conhecer a situação em Portugal das iniciativas de computação móvel neste setor (mobile health) e o seu estado de implementação, seguimos a metodologia de Levac et al. para realizar um levantamento, através de um inquérito e de um estudo exploratório, cujos resultados ficaram espelhados numa matriz desenvolvida para o efeito. O mapeamento do estudo visa sumariar o conhecimento adquirido, num formato acessível e resumido para que decisores políticos, profissionais e consumidores possam fazer uso efetivo das conclusões.The paradigm of health care delivery is slowly aligning with the needs and habits of modern patients. Mobile computing may be a solution to respond to the growing trend and need for health care sharing and collaboration, enabling the redesign of processes giving rise to new models of health care delivery. Seeking to determine the situation in Portugal regarding mobile computing initiatives in this domain (mobile health) and their status of implementation, and following the methodology of Levac et al., we conducted a survey and an exploratory study whose results were mirrored in a matrix developed for this purpose. The mapping of the study aims to summarize the acquired knowledge in an accessible and summarized format so that decision-makers, practitioners and consumers can make effective use of the findings.info:eu-repo/semantics/publishedVersio

Nonlinear Generation of Harmonic Content within High Intensity Ultrasound Signals using Granular Chains

Applications such as High Intensity Focused Ultrasound (HIFU) conventionally use narrowband signals of high amplitude, which are then focused to a known region within the body. It would be advantageous to be able to broaden the bandwidth, as this could lead to a more spatially-concentrated focal region. One way of increasing the bandwidth is to generate harmonics. The eventual aim of this study is to generate wideband ultrasonic signals with high amplitudes, primarily for therapeutic ultrasound and drug delivery applications. In this paper, a new ultrasonic transducer technology using a one-dimensional chain of spheres is presented to achieve this aim

Molecular dynamics simulation of nonlinear waves in granular media

Discrete dynamic equations of spheres in granular chains have been developed so as to simulate the evolution of acoustic signals in these media. The model was built based on Hertzian laws as well as the dissipation effect within the system, and the contact dynamics involving both compression and separation between spheres was also modelled. A molecular dynamics simulation method using the Velocity Verlet algorithm was developed to solve the equations. The strongly nonlinear solitary wave impulses are predicted by the numerical calculations and match the experimental results well. The simulation system has been used as a design tool to determine the optimal chain structure in term of the bandwidth and frequencies which are required within the output impulses. The results exhibit great potential in biomedical applications

The Dynamic Excitation of a Chain of Pre-Stressed Spheres for Biomedical Ultrasound Applications: Contact Mechanics Finite Element Analysis and Validation

There has been recent interest in the transmission of acoustic signals along a chain of spheres to produce waveforms of relevance to biomedical ultrasound applications. Effects which arise as a result of Hertzian contact between adjacent spheres can potentially change the nature of the signal as it propagates down the chain. The possibility thus exists of generating signals with a different harmonic content to the signal input into one end of the chain. This transduction mechanism has the potential to be of use in both diagnostic and therapeutic ultrasound applications, and is the object of the study presented here. The nonlinear dynamics of granular chains can be treated using discrete mechanics models. However, in cases where the underlying assumptions of these models no longer hold, and where geometries are more complex, a more comprehensive numerical solution must be sought. Contact mechanics problems can efficiently be treated using the finite element method. The latter was used to investigate the dynamics of a pre-stressed chain of six, 1 mm diameter stainless steel spheres excited at one end using a tone burst displacement signal with a fundamental frequency of 73 kHz. The final sphere of the chain was assumed to be in contact with a cylindrical matching layer radiating into a half-space of fluid with the properties of water. After addition of the fluid loading, radiated acoustic pressures in the medium were predicted. Comparison with experimental results suggests that finite element analysis is a suitable tool for investigating the design and performance of contact mechanics based transducers. Nevertheless, a better handle on the model input parameters as well as an improved experimental protocol are required to fully validate the model