Surface-initiated ring opening polymerization of N-carboxy anhydride of benzyl-l-glutamate monomers on soft flexible substrates

The potential of pulsed plasma deposited polyallylamine (PAA) adlayer has been successfully demonstrated for fabrication of polypeptide brushes functionalized soft flexible polymeric surfaces. Polymeric substrates functionalized with the plasma deposition PAA adlayer resulted in polymeric surfaces functionalized with amino groups, which are the suitable initiating moieties for ring-opening polymerization (ROP) of N-carboxy anhydride of benzyl-l-glutamate (NCA-BLG) monomer. Poly(γ-benzyl-l-glutamate) (PBLG) brushes were grown on PAA functionalized polypropylene (PP), and polytetrafluoroethylene (PTFE) polymeric substrates. These substrates were intentionally chosen for their inert chemical nature towards most wet chemical surface modification reactions. Surface grafted thin films of poly(γ-benzyl-l-glutamate) PBLG on both the PP and PTFE polymeric substrates yielded high density PBLG brushes. PBLG chain orientation, secondary structure and grafting density were characterized by infra-red spectroscopy. The synthesis of PBLG brushes on a flexible polymeric substrate is unprecedented and technologically important, since PBLG possess good electro-optical activity. Analysis of brush layers by Attenuated Total Reflectance Infra-Red (ATR-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) as well as atomic force microscopy (AFM) fully corroborated the success of the plasma activated soft surface grafting approach.     

Fullerene modification CdSe/TiO2 and modification of photocatalytic activity under visible light

CdSe, CdSe-TiO₂, and CdSe-C₆₀/TiO₂ composites were prepared using sol–gel method, and their photocatalytic activity was evaluated by measuring the degradation of rhodamine B solutions under visible light. The surface area, surface structure, crystal phase, and elemental identification of these composites were characterized by nitrogen adsorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and UV-visible (vis) absorption spectrophotometry. XRD showed that the CdSe-C₆₀/TiO₂ composite contained a typical single and clear anatase phase. SEM of the CdSe-C₆₀/TiO₂ composites revealed a homogenous composition in the particles. EDX revealed the presence of C and Ti with strong Cd and Se peaks in the CdSe-C₆₀/TiO₂ composite. The degradation of dye was determined by UV–vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase in the photoabsorption effect by fullerene and the cooperative effect of the CdSe. The repeatability of photocatalytic activity was also tested in order to investigate the stability of C₆₀ and CdS-C₆₀/TiO₂ composites.     

Enhanced piezoelectric properties of Ta substituted-(K0.5Na0.5)NbO3 films: A candidate for lead-free piezoelectric thin films

Piezoelectric (K_0.5Na_0.5)NbO₃ (KNN) and (K_0.5Na_0.5)(Nb_0.7Ta_0.3)O₃ (KNNT) thin films were prepared via chemical solution deposition. An analysis of X-ray diffraction revealed that Ta⁵⁺ diffuses into the KNN to form a single perovskite structure. Compared to KNN films, KNNT films exhibited a low leakage current density due to their fine-grain nonporous structures. The partial substitution of Ta⁵⁺ for the B-site ion Nb⁵⁺ in the KNNT films decreased the Curie temperature (T_C). This in turn led to the existence of a polymorphic phase transition near room temperature and further improvement in the piezoelectric properties. Lead-free KNNT films exhibited a well-saturated piezoelectric hysteresis loop with a effective piezoelectric coefficient (d_33,eff) value of 61 pm/V, comparable to that of PZT thin films.     

A hexapod-based machine tool with hybrid structure: Kinematic analysis and trajectory planning

This paper shows kinematic analysis and trajectory planning for a novel machine tool structure consisting of a six degree-of-freedom hexapod machine and a two-degree-of-freedom rotary table. Accordingly, to operate the proposed machine tool, eight coordinates should be defined. Since a conventional part programming can define at the most five axes, the three remaining coordinates should be defined by using appropriate trajectory planning. An analytical model is developed that defines the relationships among the parameters in the proposed structure. A rule-based model is also developed to select the redundant coordinates without going through any complex and time-consuming calculations.     

An improved genetic algorithm for robust permutation flowshop scheduling

In order to deal with uncertainties, a robust schedule for M-machine permutation flowshop is proposed. The presented robust schedule is aimed to maximize the probability of ensuring that makespan will not exceed the expected completion time. An improved genetic algorithm (GA) with a new generation scheme is developed, which can preserve good characteristics of parents in the new generation. Experiments are performed to get robust schedules for well-known Car and Rec permutation flowshop problems, taken from OR library. The schedules obtained from the improved GA are compared with the schedules formed by well-known heuristic in literature. Computational results show that the permutation flowshop schedules obtained from improved GA are robust to produce an affirmative percentage increase in the probability of getting makespan less than expected completion time.     

Extension of effective medium theory to three-component system—two conductive particle types in the polymer matrix

A foundation is presented for the extension of the normal effective medium theory (for a two-component system (filler and polymer matrix)) to a three-component system (two filler species and matrix). No experimental test of the improved theory is made here, but some general trends are confirmed by other experiments. The theory is sufficiently general to allow the second filler component to represent a particle of the same composition as the first filler component but of a different size, or of the same size but of a different composition. Important satellite derivations are included.