Semi-global stabilization via homogeneous output feedback for a class of nonlinear time-delay systems

The semi-global stabilization problem for a class of nonlinear systems with state time-delay is addressed in this paper. By using Lyapunov-Krasovskii functional method and homogeneous domination approach, a homogeneous observer and an output feedback controller with a scaling gain are designed. Then the scaling gain is adjusted such that the closed-loop system is semi-global asymptotically stable. A numerical example is presented to illustrate the effectiveness of the obtained results in this paper.     

Attentional negativity bias moderated by positive mood arousal

Automatically allocation of more attention to negative stimuli is called emotional negativity bias. An event-related potentials (ERPs) experiment investigated whether or not this bias was altered by positive mood arousal. The results suggested that the attention bias towards negative stimuli was attenuated when positive information was accessible.     

Teeming stream protection using an argon shroud during casting of steel ingots

Two kinds of argon shroud protection devices with two different basic structures were designed and investigated. Industrial experiments and numerical simulations were used to examine the protection effect, and the mechanism of air entrapment during the casting of steel ingots was analyzed. The influence of the structure of the argon shroud protection device on the protection effect was investigated. An argon shroud protection device mounted to the nozzle holder on the bottom of the ladle does not provide a good protection effect because air can easily flow into the teeming system and cause reoxidation of molten steel during teeming. By contrast, an argon shroud protection device seated on the top of the central trumpet provides an excellent protection effect, where air has little chance of flowing into the teeming system during casting. The feasibilities of the argon shroud protection devices are discussed.     

Research on catalysis of sodium-metallochlorophylls in Ni/MH battery

The effects of sodium-metallochlorophylls including sodium-iron chlorophyllin, sodium-copper chlorophyllin and sodium-magnesium chlorophyllin on performance of Ni/MH battery were investigated. The results show that sodium-iron chlorophyllin can effectively activate the gases produced during charge in Ni/MH battery, therefore reducing the reduction potential of oxygen and the oxidation potential of hydrogen, and the increased speed of inner pressure of battery is decreased significantly. With the aid of DMol3 software, the activation process of oxygen and hydrogen by sodiummetallochlorophylls was simulated and analyzed. It was found that the catalysis behavior is in agreement with the experimental results, and the activation process also gets a reasonable explanation from the calculated results.     

Competing Definitions of Information Versus Entropy in Physics

As was mentioned by Nicolas Lori in his (Found Sci, 2010) commentary, the definition of Information in Physics is something about which not all authors agreed. According to physicists like me Information decreases when Entropy increases (so entropy would be a negative measure of information), while many physicists, seemingly the majority of them, are convinced of the contrary (even in the camp of Quantum Information Theoreticians). In this reply I reproduce, and make more precise, some of my arguments, that appeared here and there in my (2010) paper, in order to clarify the presentation of my personal point of view on the subject.     

Heterogeneity,nonlinearity and endogenous market volatility

This paper aims to contribute to the literature on the explanatory power of behavior models with heterogeneous agents. The authors present a new nonlinear structural stock market model which is a nonlinear deterministic process buffeted by dynamic noise. An exogenous noise is introduced to the model with the assumption of IID normal innovations of the fundamental value in order to investigate how noisy dynamics interacts with deterministic process. The market is composed of two typical trader types: the rational fundamentalists and the boundedly rational traders governed by greed and fear. The interaction between noise and deterministic element determines the evolution process of the system as key parameters are changed. The authors find the model is able to generate time series that exhibit dynamical and statistical properties closely resembling those of the S&P500 index, such as volatility clustering, fat tails (leptokurtosis), autocorrelation in square and absolute return, larger amplitude, crashes and bubbles. The authors also investigate the nonlinear dependence structure in our data. The results indicate that the GARCH-type model cannot completely account for all nonlinearity in our simulated market, which is thus consistent with the results from real markets. It seems that the nonlinear structural model is more powerful to give a satisfied explanation to market behavior than the traditional stochastic approach.     

Optimal multi-asset investment with no-shorting constraint under mean-variance criterion for an insurer

This paper considers the optimal investment strategy for an insurer under the criterion of mean-variance. The risk process is a compound Poisson process and the insurer can invest in a risk-free asset and multiple risky assets. This paper obtains the optimal investment policy using the stochastic linear quadratic (LQ) control theory with no-shorting constraint. Then the efficient strategy (optimal investment strategy) and efficient frontier are derived explicitly by a verification theorem with the viscosity solution of Hamilton-Jacobi-Bellman (HJB) equation.     

Sample average approximation method for a class of stochastic variational inequality problems

This paper considers a class of stochastic variational inequality problems. As proposed by Jiang and Xu (2008), by using the so-called regularized gap function, the authors formulate the problems as constrained optimization problems and then propose a sample average approximation method for solving the problems. Under some moderate conditions, the authors investigate the limiting behavior of the optimal values and the optimal solutions of the approximation problems. Finally, some numerical results are reported to show efficiency of the proposed method.     

Codimension-two bifurcations analysis and tracking control on a discrete epidemic model

In this paper, the dynamic behaviors of a discrete epidemic model with a nonlinear incidence rate obtained by Euler method are discussed, which can exhibit the periodic motions and chaotic behaviors under the suitable system parameter conditions. Codimension-two bifurcations of the discrete epidemic model, associated with 1:1 strong resonance, 1:2 strong resonance, 1:3 strong resonance and 1:4 strong resonance, are analyzed by using the bifurcation theorem and the normal form method of maps. Moreover, in order to eliminate the chaotic behavior of the discrete epidemic model, a tracking controller is designed such that the disease disappears gradually. Finally, numerical simulations are obtained by the phase portraits, the maximum Lyapunov exponents diagrams for two different varying parameters in 3-dimension space, the bifurcation diagrams, the computations of Lyapunov exponents and the dynamic response. They not only illustrate the validity of the proposed results, but also display the interesting and complex dynamical behaviors.     

Community Development and Renaissance Social Humanism: Some Lessons for Systems Science

Starting from the crisis in our communities—research has indicated it to be widely spread—the author explores the scientific tradition preceding the rise of modernism in order to draw out a more humane way of thinking that may help our contemporary societies. He discerns between two types of Renaissance humanism, one characterised by its cleverness, the other by its compassion and desire to restore dignity to the lives of people struggling to escape the clutches of medievalism. The father of the latter is Erasmus of Rotterdam and we follow the development of his conception of a social humanism as it branches out, through the work of his successors, into every scientific discipline, both natural and human. These disciplines are united by an embracing systemic idea of philosophy that unites the mind with the heart and which Erasmus called “Philosophia Christi”. We examine the two main pillars upon which this philosophy is built, love for our neighbour and education as the only legitimate instrument to change society, and the extraordinary impact it had on science and on communities living in the seventeenth century. We contrast this with the idea of power, the chosen instrument of modernity to transform society, and trace some of its tragic outcomes. We conclude by discussing the incorporation of an Erasmian type of social humanism into systems education and the future development of such programmes.