Composite Control of a Hovering Helicopter Based on Optimized Sliding Mode Control

Journal of Optimization Theory and Applications - A composite control law for stabilizing a small-scale helicopter during hover flight mode is proposed in this paper. The proposed method is...     

Synthesis of 1,2,5,6‐/1,2,3,6‐tetrahydropyridinyl‐tetrahydro‐cyclopentaisoxazole derivatives

Fused tetrahydrocyclopenta‐isoxazoles were synthesized by 1,3‐dipolar cycloaddition reactions with pyridinealdoxime or tetrahydropyridinealdoxime and cycloalkenes.     

A Facile One-Pot Synthesis of 2,3′-Anhydro-2′-Deoxyuridines via 3′-O-Imidazolylsulfonates

Continued interests in the novel synthetic methods of the pivotal compound, 2,3′-anhydro-2′-deoxyribonucleosides (7) uncovered a facile one-pot conversion of 5 with 1,1′-sulfonyldiimidazole in basic conditions to 7 with almost quantitative yields (91–99%).     

Convex-Optimization-based Constrained Control Strategy for 3-DOF Tandem Helicopter using Feedback Linearization

Journal of Optimization Theory and Applications - This paper proposes a convex-optimization-based relatively optimal controller (ROC) for the attitude regulation of 3 degree of freedom (DOF) tandem...     

Shear induced structuration of liquid crystalline epoxy thermosets

Low-molecular weight liquid crystals (LC) have wide technological applications due to their self-assembly in the mesophase. An azomethine nematic monomer based on diglycidyl functionalized mesogenic core and without spacers has been cured with a diamine. The great affinity of LC epoxy to the formation of ordered structures introduces a spatial driving force into the process of curing. Thermal and LC behaviors were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The nature of the LC phases was confirmed by X-ray diffraction. Rheological experiments were conducted during crosslinking at different shear stresses. The viscosity of the mixture is strongly decreasing by three orders of magnitude when the solid epoxy is melting into a LC phase, and is increasing again due to the curing. Unexpected results were found. Applying a stress during curing had a profound influence on the ordering of the structure. The material becomes isotropic if a small shear stress is applied. Then, the higher the stress is, more ordered the final material is. For the highest stresses, the final material is in a highly ordered, quasi-crystalline, smectic structure.     

Chemorheological analysis and model-free kinetics of acid catalysed furfuryl alcohol polymerization

The complete curing of furfuryl alcohol (FA), was studied by chemorheological analysis and model-free kinetics under isothermal and non-isothermal modes. Polymerization of FA under acidic catalysis involves complex reactions, with several steps (such as condensations and Diels-Alder cycloadditions). To account for the polymerization complexity, kinetic analysis of DSC data was performed with a model-free isoconversional method. The obtained E(alpha)-dependencies were closely-correlated with the variation of complex viscosity during curing. Linear condensations are predominant during the early curing stage and are followed by two distinct stages of branching cycloadditions. Gelation and vitrification, identified by rheometric measurements, were associated with a decrease of the overall reaction rate that becomes controlled by diffusion of small oligomers. Before vitrification, the rate of crosslinking is limited by the mobility of longer polymer chains and diffusion encounters a large energy barrier due to the cooperative nature of the motions, leading to higher E(alpha) values.     

Synthesis of 2‐(1‐methyl‐1,2,5,6‐tetrahydropyridin‐3‐yl)benzimidazoles

A useful approach for the synthesis of pharmacologically active tetrahydropyridinylbenzimidazoles is described. 2‐Pyridin‐3‐ylbenzimidazoles 3a‐d have been synthesized by condensation of 3‐pyridinecarbox‐aldehyde 1 with substituted 1,2‐phenylenediamines 2a‐d following oxidative cyclization with iodobenzene diacetate. Methylation of 3a‐d with iodomethane and potassium hydroxide, subsequent formation of methylpyridinium salts 4a‐d and 7a‐d and reduction thereafter afforded tetrahydropyridinylbenzimidazoles 5a‐d and 8a‐d .     

Solving nonlinear reaction–diffusion problem in electrostatic interaction with reaction-generated pH change on the kinetics of immobilized enzyme systems using Taylor series method

A mathematical model of electrostatic interaction with reaction-generated pH change on the kinetics of immobilized enzyme is discussed. The model involves the coupled system of non-linear reaction–diffusion equations of substrate and hydrogen ion. The non-linear term in this model is related to the Michaelis–Menten reaction of the substrate and non-Michaelis–Menten kinetics of hydrogen ion. The approximate analytical expression of concentration of substrate and hydrogen ion has been derived by solving the non-linear reactions using Taylor’s series method. Reaction rate and effectiveness factor are also reported. A comparison between the analytical approximation and numerical solution is also presented. The effects of external mass transfer coefficient and the electrostatic potential on the overall reaction rate were also discussed.