Output-feedback synchronization of chaotic systems based on sum-of-squares approach

This paper investigates the synchronization of chaotic systems using an output feedback polynomial controller. As only output system states are considered, it makes the controller design and system analysis more challenging compared to the full-state feedback control schemes. To study the system stability and synthesize the output feedback polynomial controller, Lyapunov stability theory is employed. Sufficient stability conditions are derived in terms of sum of squares (SOS) conditions to guarantee the system stability and aid the controller synthesis. A genetic algorithm-based SOS technique is proposed to find the solution to the SOS conditions and the parameter values of the output feedback polynomial controller. A simulation example is employed to illustrate the effectiveness of the proposed approach.     

Guaranteed Cost Control for Uncertain Neutral Stochastic Systems via Dynamic Output Feedback Controllers

This paper deals with the problem of guaranteed cost control for uncertain neutral stochastic systems. The parameter uncertainties are assumed to be time-varying but norm-bounded. Dynamic output feedback controllers are designed such that, for all admissible uncertainties, the resulting closed-loop system is mean-square asymptotically stable and an upper bound on the closed-loop value of the cost function is guaranteed. By employing a linear matrix inequality (LMI) approach, a sufficient condition for the solvability of the underlying problem is obtained. A numerical example is provided to demonstrate the potential of the proposed techniques.     

Uncertainty Quantification of Stochastic Simulation for Black-box Computer Experiments

Stochastic simulations applied to black-box computer experiments are becoming more widely used to evaluate the reliability of systems. Yet, the reliability evaluation or computer experiments involving many replications of simulations can take significant computational resources as simulators become more realistic. To speed up, importance sampling coupled with near-optimal sampling allocation for these experiments is recently proposed to efficiently estimate the probability associated with the stochastic system output. In this study, we establish the central limit theorem for the probability estimator from such procedure and construct an asymptotically valid confidence interval to quantify estimation uncertainty. We apply the proposed approach to a numerical example and present a case study for evaluating the structural reliability of a wind turbine.     

Synthesis,Characterisation and Photophysical Study of Alkynylrhenium(I) Tricarbonyl Diimine Complexes and Their Metal‐Ion Coordination‐Assisted Metallogelation Properties

A series of alkynylrhenium(I) tricarbonyl diimine complexes has been synthesized and characterized. A blue shift of the intense low‐energy MLCT absorption band in the visible region was observed upon coordination of Cu^I or Ag^I. This class of complexes has been found to show rich thermotropic gelation behaviour upon Cu^I or Ag^I coordination with their morphology characterized by SEM. Their variable‐temperature UV/Vis absorption and emission properties have also been studied. A blue shift in the MLCT absorption band and the switching on of luminescence were observed upon sol–gel transition.     

Monodisperse cobalt ferrite nanomagnets with uniform silica coatings

Ferro- and ferrimagnetic nanoparticles are difficult to manipulate in solution as a consequence of the formation of magnetically induced nanoparticle aggregates, which hamper the utility of these particles for applications ranging from data storage to bionanotechnology. Nonmagnetic shells that encapsulate these magnetic particles can reduce the interparticle magnetic interactions and improve the dispersibility of the nanoparticles in solution. A route to create uniform silica shells around individual cobalt ferrite nanoparticles--which uses poly(acrylic acid) to bind to the nanoparticle surface and inhibit nanoparticle aggregation prior to the addition of a silica precursor--was developed. In the absence of the poly(acrylic acid) the cobalt ferrite nanoparticles irreversibly aggregated during the silica shell formation. The thickness of the silica shell around the core-shell nanoparticles could be controlled in order to tune the interparticle magnetic coupling as well as inhibit magnetically induced nanoparticle aggregation. These ferrimagnetic core-silica shell structures form stable dispersion in polar solvents such as EtOH and water, which is critical for enabling technologies that require the assembly or derivatization of ferrimagnetic particles in solution.     

Design of experiment for optimization of plasma-polymerized octafluorocyclobutane coating on very high aspect ratio silicon molds

As-fabricated deep reactive ion etched (DRIE) silicon mold with very high aspect ratio (>10) feature patterns is unsuitable for poly(dimethylsiloxane) (PDMS) replication because of the strong interaction between the Si surface and the replica and the corrugated mold sidewalls. The silicon mold can be conveniently passivated via plasma polymerization of octafluorocyclobutane (C4F8), which is also employed in the DRIE process itself, to enable the mold to be used repeatedly. To optimize the passivation conditions, we have undertaken a Box-Behnken experimental design on the basis of three passivation process parameters (plasma power, C4F8 flow rate, and deposition time). The measured responses were fluorinated film thickness, demolding status/success, demolding force, and fluorine/carbon ratio on the fifth replica surface. The optimal passivation process conditions were predicted to be an input power of 195 W, a C4F8 flow rate of 57 sccm, and a deposition time of 364 s; these were verified experimentally to have high accuracy. Demolding success requires medium-deposited film thickness (66-91 nm), and the thickness of the deposited films correlated strongly with deposition time. At moderate to high ranges, increased plasma power or gas flow rate promoted polymerization over reactive etching of the film. It was also found that small quantities of the fluorinated surface were transferred from the Si mold to the PDMS at each replication, entailing progressive wear of the fluorinated layer.     

Selective betainization of PS-P4VP and solution properties

The ability to control the structure and function of supramolecular self-assemblies gives rise to many patterning possibilities. Making use of the interactions between the copolymers and solvent provides a neat way of controlling the structures. The pyridine residues of each of the diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-P4VP) was selectively betainized using 1,3-propane sultone under mild conditions to yield a series of novel betaine diblock copolymers in chloroform and toluene, respectively. The solution properties were studied using dynamic light scattering, static light scattering, and (1)H NMR spectroscopy. The morphology of the resulting micellar film was studied using transmission electron microscopy. The size of the micelles formed was found to be strongly dependent on the amount of sultone grafted and the shape of PS-P4VP-sultone micelle changed from spherical to elongated with different PS-P4VP-to-sultone ratio.     

Kinetics and mechanism of the oxidation of hydroquinones by a trans-dioxoruthenium(VI) complex

The kinetics of the oxidation of hydroquinone (H(2)Q) and its derivatives (H(2)Q-X) by trans-[Ru(VI)(tmc)(O)(2)](2+) (tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) have been studied in aqueous acidic solutions and in acetonitrile. In H(2)O, the oxidation of H(2)Q has the following stoichiometry: trans-[Ru(VI)(tmc)(O)(2)](2+) + H(2)Q --> trans-[Ru(IV)(tmc)(O)(OH(2))](2+) + Q. The reaction is first order in both Ru(VI) and H(2)Q, and parallel pathways involving the oxidation of H(2)Q and HQ(-) are involved. The kinetic isotope effects are k(H(2)O)/k(D(2)O) = 4.9 and 1.2 at pH = 1.79 and 4.60, respectively. In CH(3)CN, the reaction occurs in two steps, the reduction of trans-[Ru(VI)(tmc)(O)(2)](2+) by 1 equiv of H(2)Q to trans-[Ru(IV)(tmc)(O)(CH(3)CN)](2+), followed by further reduction by another 1 equiv of H(2)Q to trans-[Ru(II)(tmc)(CH(3)CN)(2)](2+). Linear correlations between log(rate constant) at 298.0 K and the O-H bond dissociation energy of H(2)Q-X were obtained for reactions in both H(2)O and CH(3)CN, consistent with a H-atom transfer (HAT) mechanism. Plots of log(rate constant) against log(equilibrium constant) were also linear for these HAT reactions.     

A pseudo-Bayesian model in financial decision making with implications to market volatility,under- and overreaction

This paper develops a model of weight assignments using a pseudo-Bayesian approach that reflects investors’ behavioral biases. In this parsimonious model of investor sentiment, weights induced by investors’ conservative and representative heuristics are assigned to observations of the earning shocks of stock prices. Such weight assignments enable us to provide a quantitative link between some market anomalies and investors’ behavioral biases. The seriousness of an anomaly can be quantitatively assessed by investigating into its dependency on weights. New results other than the short-run underreaction and long-run overreaction can be derived and new hypotheses can be formed.     

Economical,Green, and Safe Route Towards Substituted Lactones by Anodic Generation of Oxycarbonyl Radicals

A new electrochemical methodology has been developed for the generation of oxycarbonyl radicals under mild and green conditions from readily available hemioxalate salts. Mono‐ and multi‐functionalised γ‐butyrolactones were synthesised through exo‐cyclisation of these oxycarbonyl radicals with an alkene, followed by the sp³–sp³ capture of the newly formed carbon‐centred radical. The synthesis of functionalised valerolactone derivatives was also achieved, demonstrating the versatility of the newly developed methodology. This represents a viable synthetic route towards pharmaceutically important fragments and further demonstrates the practicality of electrosynthesis as a green and economical method to activate small organic molecules.