Iterative learning control of multivariable uncertain nonlinear systems with nonrepetitive trajectory

Nonlinear Dynamics - Iterative learning control (ILC) theory is based on the traditional assumptions of resetting condition and repetitive trajectory. To overcome these restrictions, a novel ILC is...     

Structural phase transition and elastic properties of Curium and Uranium monobismuthides under pressure effect

A density functional (DFT) calculations of the structural, elastic and high pressure properties of the cubic XBi (X=U,Cm) compounds, has been reported using the full potential linear muffin-tin orbital (FP-LMTO) method. In this approach the local density approximation (LDA) is used for the exchange-correlation (XC) potential. Results are given for lattice constant, bulk modulus and its pressure derivatives. The pressure transitions at which these compounds undergo structural phase transition from NaCl-type (B1) to CsCl-type (B2) phase were found to be in good agreement with the available theoretical results. We have determined the elastic constants C₁₁, C₁₂, C₄₄ and their pressure dependence which have not been established experimentally or theoretically.     

Effect of molecular weight on radiation chemical degradation yield of chain scission of γ-irradiated chitosan in solid state and in aqueous solution

Chitosan A₁, A₂ and A₃ with molecular weight of 471, 207 and 100 kDa respectively, produced from squid pen chitin was degraded by gamma rays in the solid state and in aqueous solution with various doses in air at ambient temperature. Effect of molecular weight on radiation chemical degradation yield of chain scission and degradation rate constants of γ-irradiated chitosan in solid state and in aqueous solution was investigated. The radiation chemical degradation yield G_(s) and degradation rate values were calculated. The molecular weight changes were monitored by capillary viscometry method and the chemical structure changes were followed by UV analysis. The results showed that, the degradation of chitosan was faster in solution, than in solid state. The values of G_(s) in solid state and in aqueous solution were respectively 1.1×10^?8 mol/J and 0.074×10^?7 mol/J for A₁, 4.42×10^?8 mol/J and 0.28×10^?7 mol/J for A₂ and 6.08×10^?8 mol/J and 0.38×10^?7 mol/J for A₃. Degradation rate constants values ranged from 0.41×10^?5 to 2.1×10^?5 kGy^?1 in solid state, whereas in solution they ranged from 13×10^?5 to 68×10^?5 kGy^?1. The chitosan A₃ was more sensitive to radiolysis than A₁ and A₂. The chain scission yield, G_(s) and degradation rate constants seems to be greatly influenced by the initial molecular weight of the chitosan. Structural changes in irradiated chitosan are revealed by the apparition of absorption peaks at 261 and 295 nm, which could be attributed to the formation of carbonyl groups. In both conditions the peak intensity was higher in chitosan A₃ than in A₁ and A₂, the oxidative products decreased with increasing molecular weight of chitosan.     

Effect of pH on Electrocoagulation of Bentonite Suspensions in Batch Using Iron Electrodes

The electrocoagulation of a synthetic wastewater has been studied in this work. The electrochemical process was carried out in a batch electrochemical cell equipped with iron electrodes without agitation. Bentonite suspensions were used as a model of wastes polluted with colloids, as clays behave as hydrophobic colloids in water. The results obtained were useful to clarify the mechanisms that are involved in the electrocoagulation of this kind of waste and also to study the influence of pH in the process. Two primary coagulation mechanisms can explain the experimental behavior of the system: at acid pH the neutralization of the superficial charges of the clays and at alkaline pH the enmeshment of the kaolin particles into a sweep floc. At neutral pH, the formed cations (Fe²⁺ and Fe³⁺) neutralize colloidal particles and conduct to the hydroxides (Fe(OH)_2(s) and Fe(OH)_3(s)) which adsorbate colloids and enhance sweep flocculation.     

Estimating the distortion parameter of the proportional-hazard premium for heavy-tailed losses

The distortion parameter reflects the amount of loading in insurance premiums. A specific value of a given premium determines a value of the distortion parameter, which depends on the underlying loss distribution. Estimating the parameter, therefore, becomes a statistical inferential problem, which has been initiated by Jones and Zitikis [Jones, B.L., Zitikis, R., 2007. Risk measures, distortion parameters, and their empirical estimation. Insurance: Mathematics and Economics, 41, 279–297] in the case of the distortion premium and tackled within the framework of the central limit theorem. Heavy-tailed losses do not fall into this framework as they rely on the extreme-value theory. In this paper, we concentrate on a special but important distortion premium, called the proportional-hazard premium, and propose an estimator for its distortion parameter in the case of heavy-tailed losses. We derive an asymptotic distribution of the estimator, construct a practically implementable confidence interval for the distortion parameter, and illustrate the performance of the interval in a simulation study.     

All-fiber controller of radial polarization using a periodic stress

Our aim is to transpose the polarization control by mechanical stress, usually applied to single-mode fibers, to the (TM(01), TE(01), HE(21)(ev), HE(21)(od)) annular mode family. Nevertheless, the quasi-degeneracy of these four modes makes the situation more complex than with the fundamental mode HE(11). We propose a simple device based on periodic perturbation and mode coupling to produce the radially polarized TM(01) mode or at least one of the four modes at the extremity of an arbitrarily long fiber, the conversion to TM(01) mode being achievable by classical crystalline plates.     

The apparition of a new reaction at lower temperature in equiatomic CuAu alloy

Recently a lot of interest has been devoted to the study of order–disorder transitions in different materials. Although the equiatomic CuAu alloy represents a classical model of this type of transformation, it still receives considerable attention because many questions about phase transitions are still raised according to its equilibrium diagram. In this context, the present paper carries a new result observed in CuAu alloy consisting of a new anomaly observed on differential scanning calorimetry (DSC) curves at low temperature and new peaks in X-ray diffraction (XRD) spectra. For that, we will try to give an explanation of the origin of this new reaction, with the help of other techniques as electrical resistivity and microhardness measurements. The kinetic behaviour of this new reaction has been also studied by anisothermal analysis during DSC tests to estimate the kinetics parameters as activation energy E _act and Avrami exponent n.     

Realization and characterization of flexible supercapacitors based on doped graphene electrodes

Journal of Solid State Electrochemistry - High energy consumption leads to the development of various energy types. As a result, the storage of these different types of energy becomes a key issue....