Regional Feedback Stabilization for Infinite Semilinear Systems

In this paper, we treat the problem of regional optimal stabilization of a class of nonlinear systems by using a switching feedback. Firstly, we proof that the switching control exponentially stabilizes the system on a subregion including the whole domain. Secondly, under a perturbation of the control operator, we show the robustness of our result. In the last part, the stabilizing feedback is characterized by the minimization of a regional cost even under a small perturbation. We conclude by giving different applications.     

Nucleation and crystallization of Ba2Si3O8 spherulites in a barium aluminum silicate glass,and mechanical properties of the obtained glass-ceramics

The effect of spherulitic crystallization on the elastic moduli and fracture toughness of a barium aluminum silicate glass was investigated. The crystallization process results in Ba₂Si₃O₈ phase and is initiated from Ba rich nuclei. Nucleation is optimal in the 690-720 °C interval. Young’s modulus is increased by 12.5% when the glass-ceramic conversion is nearly complete. Nevertheless, as the size and the volume fraction of crystals are increased, some microcracking shows up upon cooling from the crystallization temperature. An optimal improvement of the fracture toughness (SEPB method) by 27 % is observed for a 49 % volume fraction of 5 to 10 μm large spherulites.     

Glass reactive sintering as an alternative route for the synthesis of NZP glass–ceramics

The NZP-type crystal structure allows a large number of ionic substitutions which leads to ceramics with adjustable thermal expansion properties or interesting ionic conductivity. However, NZP is difficult to fabricate into monoliths because it requires both high temperatures and long sintering times. An alternative low temperature route to obtain a tungsten (IV) and tin (IV) containing NZP crystalline phase uses a process of glass reactive sintering of a phosphate glass. Using a microwave oven, a glass with the appropriate composition in the NaPO3–Sn(II)O–W(VI)O3 ternary diagram is prepared by a conventional melting and casting technique. After crushing, the glass powder is pressed at room temperature. The green pellet is cured during various times at temperatures where glass reactive sintering takes place. From XRD and DTA experiments, we have shown that different parameters influence the achievement of NZP phase. Consequently, specific conditions, such as (i) initial glass composition, (ii) equimolar quantities of SnO and WO3, (iii) glass particle size lower than 100 μm, and (iv) curing conducted under air, are required to obtain a glass–ceramic with a single crystalline phase with the NZP-type crystal structure.     

Mathematical programming models for scheduling in a CPU/FPGA architecture with heterogeneous communication delays

This paper deals with the mathematical modelling of a scheduling problem in a heterogeneous CPU/FPGA architecture with heterogeneous communication delays in order to minimize the makespan, \(C_{max}\). This study was motivated by the quality of the available solvers for Mixed Integer Program. The proposed model includes the communication delay constraints in a heterogeneous case, depending on both tasks and computing units. These constraints are linearized without adding any extra variables and the obtained linear model is reduced to speed-up the solving with CPLEX up to 60 times. Computational results show that the proposed model is promising. For an average sized problem of up to 50 tasks and five computing units the solving time under CPLEX is a few seconds.     

Wiener–Hammerstein system identification – an evolutionary approach

The problem of identifying parametric Wiener–Hammerstein (WH) systems is addressed within the evolutionary optimisation context. Specifically, a hybrid culture identification method is developed that involves model structure adaptation using genetic recombination and model parameter learning using particle swarm optimisation. The method enjoys three interesting features: (1) the risk of premature convergence of model parameter estimates to local optima is significantly reduced, due to the constantly maintained diversity of model candidates; (2) no prior knowledge is needed except for upper bounds on the system structure indices; (3) the method is fully autonomous as no interaction is needed with the user during the optimum search process. The performances of the proposed method will be illustrated and compared to alternative methods using a well-established WH benchmark.     

Synthesis and properties of a mitochondrial peripheral benzodiazepine receptor conjugate

Peripheral benzodiazepine receptors are potential targets for cancer therapeutics through the use of specific ligands such as the pro-apoptotic benzodiazepine RO5-4864. However, the poor water solubility of this compound has been a limitation to its application in vivo. Herein we describe an efficient synthesis for the conjugation, via a cleavable linker arm, of RO5-4864 to a novel tumour-delivery tool, the B-subunit of Shiga toxin (STxB). The conjugate is water soluble and specifically targets cancer cells that overexpress the glycolipid Gb3, the cellular Shiga toxin receptor that is found on several human tumours. After internalisation via retrograde transport, the prodrug is cleaved inside cells to release the active principle. Delivery by STxB therefore increases the cytotoxic activity of RO5-4864 and its tumour specificity.     

Novel Na–Li–SiAlPON glasses prepared by melt synthesis using AlN

Amorphous alumino–silicophosphate materials containing up to 1.70 wt.% nitrogen have been successfully prepared by aluminium nitride solution in Na–Li–Si–Al–P–O melts at 850 °C thus preventing phosphorus volatilisation. Although the solubility limit for nitrogen in these glasses was limited to 8.31 wt.%, the presence of nitrogen in the materials greatly increases their glass transition temperatures, suppresses the devitrification and has a significant effect on their melting behaviour. Comparative analysis of Raman spectra for the oxide and oxynitride glasses shows the substitution of P–O–P linkages by PN–P linkages while tri-coordinated nitrogen bridges were not detected. The attendant increase in network connectivity arising from such a substitution is responsible for the increase in glass transition temperature when nitrogen substitutes for oxygen.     

Testing Non‐Correlation and Non‐Causality between Multivariate ARMA Time Series

Abstract. Haugh [Journal of the American Statistical Association (1976) Vol. 71, pp. 378–85] developed an approach to the problem of testing non‐correlation (at all leads and lags) between two univariate time series. Haugh's tests however have low power against two series which are related over a long distributed lag when individual lag coefficients are relatively small. As a remedy, Koch and Yang [Journal of the American Statistical Association (1986) Vol. 8, pp. 533–44] proposed an alternative method that performs better than Haugh's under such dependencies. A multivariate extension of Haugh's procedure was proposed by El Himdi and Roy [The Canadian Journal of Statistics (1997) Vol. 25, pp. 233–56], but suffers the same weaknesses as the original univariate method. We develop here an asymptotic test generalizing Koch and Yang's method to the multivariate case. Our method includes El Himdi and Roy's as a special case. Based on the same idea, we also suggest a generalization of the El Himdi and Roy procedure for testing causality in the sense of Granger [Econometrica (1969) Vol. 37, pp. 424–38] between two multivariate series. A Monte Carlo study is conducted, which indicates that our approach performs better than El Himdi and Roy's for a wide range of models. Both procedures are applied to the problem of testing the absence of correlation between Canadian and US economic indicators, and to a brief study of causality between money and income in Canada.     

Origins of colour in Yb–Si–Al–O–N glasses

Previous work has shown that some RE-Si–Al–O–N glasses are coloured. In particular, oxynitride glasses containing Ytterbium were observed to display a wide range of colours depending on their composition. The reasons for this were not immediately evident. As Ytterbium and Europium have been reported to display valency variations in silicate glasses and α-sialons, the current study prepared a range of Yb–Si–Al–O–N glasses, characterised them by means of X-ray photoelectron, Raman, FTIR and UV–vis spectroscopy as well as thermal analysis and X-ray diffraction. The correlation between the structural features of the glasses with the changes in colour occurring when varying the Yb:Al ratio were investigated. Ytterbium garnet was found to be the source of colour change in the Yb–Si–Al–O–N in the compositions studied.