Further Studies on Fire Retardant Polystyrene by Friedel–Crafts Chemistry

The combination of a copolymer of 4-vinylbenzyl alcohol and styrene with 2-ethylhexyldiphenylphosphate (DPP) and with metal chlorides has been studied by TGA, radiative gasification, Cone Calorimetry, and oxygen index measurements. Evidence is presented in support of a cross-linking reaction with the additives and the copolymer, which proceeds through a Friedel–Crafts mechanism. This approach reduces the peak heat release rate (HRR) by 60% as measured in the Cone Calorimeter. There is a significant reduction in the mass loss rate during the thermal degradation, and evidence of char formation is observed in the radiative gasification experiments

Cross-linking of Polystyrene by Friedel–Crafts Chemistry to Improve Thermal Stability

Copolymers which contain either alcohol or chloride functionalized polystyrene units have been prepared and they participate in Friedel–Crafts chemistry to give cross-linked polymers by the evolution of either hydrogen chloride or water. Proof of cross-linking comes from the identification of the evolved gas, the insolubility of the product, and the thermal resistance of the newly formed polymer. The onset temperature for the degradation is raised by about 100°C relative to that of polystyrene and the fraction which is not volatile at 800°C ranges from 10% for the alcohol copolymers to 20% for the chloride copolymers

Direction-of-Arrival Estimation Based on Joint Sparsity

We present a DOA estimation algorithm, called Joint-Sparse DOA to address the problem of Direction-of-Arrival (DOA) estimation using sensor arrays. Firstly, DOA estimation is cast as the joint-sparse recovery problem. Then, norm is approximated by an arctan function to represent joint sparsity and DOA estimation can be obtained by minimizing the approximate norm. Finally, the minimization problem is solved by a quasi-Newton method to estimate DOA. Simulation results show that our algorithm has some advantages over most existing methods: it needs a small number of snapshots to estimate DOA, while the number of sources need not be known a priori. Besides, it improves the resolution, and it can also handle the coherent sources well

Uniform Hölder estimate for singularly perturbed parabolic systems of Bose–Einstein condensates and competing species

AbstractWe prove the uniform Hölder continuity of solutions for two classes of singularly perturbed parabolic systems. These systems arise in Bose–Einstein condensates and in competing models in population dynamics. The proof relies upon the blow up technique and the monotonicity formulas by Almgren and Alt, Caffarelli, and Friedman

Development of new fibrous nanocatalysts for methane reforming

Fibrous catalysts were prepared by an eggshell membrane-templating process and an electrospinning process. The microstructure and catalytic performances in methane reforming were studied as functions of preparation parameters. The fibrous catalysts combines the advantages of porous catalysts and non-porous catalysts, and the high dispersion at high catalyst loadings and fast mass transfer can be achieved, showing high potential for industrial applications

MECHANICAL PROPERTIES OF A ZR-BASED BULK METALIC GLASS UNDER TENSILE CONFINEMENT CONDITION

Ph.DDOCTOR OF PHILOSOPH