Synthesis and characterization of a bifunctional amido-thiophene monomer and its copolymer with thiophene and electrochemical properties

A bifunctional amido-thiophene namely hexamethylene (bis-3-thiophene acetamide) (HMTA) was synthesized by the reaction of 3-thiophene acetic acid with hexamethylene diamine. Copolymerization in the presence of thiophene was achieved electrochemically in tetrabutylammonium tetrafluoroborate/acetonitrile (TBAFB/AN). Spectroelectrochemical analysis of the resulting copolymer [P(HMTA-co-Th)] reflected electronic transitions at 505 nm, 740 nm and ∼1000 nm, revealing π to π* transition, polaron and bipolaron band formation respectively. Switching ability was evaluated by a kinetic study via measuring the transmittance (%T) at the maximum contrast. Dual type polymer electrochromic devices (ECDs) based on P(HMTA-co-Th) and poly(ethylene dioxythiophene) (PEDOT) have been constructed. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-vis spectroscopy and cyclic voltammetry. These devices exhibit low switching voltages (between 0.0 V and +1.6 V), short switching times with reasonable switching stability under atmospheric conditions.     

Preparation and characterization of sulfonated polyimide ionomers via post‐sulfonation method for fuel cell applications

This paper describes our work on the synthesis of a series of sulfonated homo‐/co‐polyimides (SPI) which were obtained by post‐sulfonation method over three steps. In the first step, 4,4′‐oxydianiline (ODA) and 4,4′‐diaminodiphenylsulfone (DDS) dissolved in N‐methyl pyrrolidone (NMP) were reacted with benzophenonetetracarboxylic dianhydride (BTDA) in order to yield poly(amic acid) (PAA). Secondly, precipitated PAA was sulfonated via concentrated sulfuric acid (95–98%) at room temperature to give post‐sulfonated PAA (PSPAA). Finally, PSPAA was converted into post‐sulfonated PI (PSPI) by the thermal imidization method. PSPIs with ion exchange capacity (IEC) ranging from 0.20 to 0.67 meq/g were prepared. The thermal properties of the PSPIs were evaluated and high desulfonation temperature was found in the range of 190–350°C, suggesting the high stability of sulfonic acid groups. In water, PSPI‐5 membrane displayed similar proton conductivity to Nafion®117, whereas this membrane showed poor conductivity in dry state. All PSPIs displayed good solubility in common polar aprotic solvents such as NMP and dimethylacetamide (DMAc). Furthermore, the effects of post‐sulfonation reaction on chemical structure, thermal oxidative behavior, and physical properties of the PSPI membranes such as membrane quality/stability and water uptake were discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Modeling the growth and branching of plants: A simple rod-based model

A rod-based model for plant growth and branching is developed in this paper. Specifically, Euler's theory of the elastica is modified to accommodate growth and remodeling. In addition, branching is characterized using a configuration force and evolution equations are postulated for the flexural stiffness and intrinsic curvature. The theory is illustrated with examples of multiple static equilibria of a branched plant and the remodeling and tip growth of a plant stem under gravitational loading.     

Temperature Effect on Power for Particle Detachment from Pore Wall Described by an Arrhenius-Type Equation

An Arrhenius-type asymptotic-exponential function is derived to describe the temperature dependence of the power needed for detachment of fine particles from pore walls in porous media.     

Shale-Gas Permeability and Diffusivity Inferred by Improved Formulation of Relevant Retention and Transport Mechanisms

A theoretically improved model incorporating the relevant mechanisms of gas retention and transport in gas-bearing shale formations is presented for determination of intrinsic gas permeability and diffusivity. This is accomplished by considering the various flow regimes according to a unified Hagen–Poiseuille-type equation, fully compressible treatment of gas and shale properties, and numerical solution of the non-linear pressure equation. The present model can accommodate a wide range of fundamental flow mechanisms, such as continuum, slip, transition, and free molecular flow, depending on the prevailing flow conditions characterized by the Knudsen number. The model indicates that rigorous determination of shale-gas permeability and diffusivity requires the characterization of various important parameters included in the present phenomenological modeling approach, many of which are not considered in previous studies. It is demonstrated that the improved model matches a set of experimental data better than a previous attempt. It is concluded that the improved model provides a more accurate means of analysis and interpretation of the pressure-pulse decay tests than the previous models which inherently consider a Darcian flow and neglect the variation of parameters with pressure.     

Influence of even nucleon numbers and closed shells on mass and charge distribution in low energy fission

Extensive experimental and evaluated yield data are now available for the fragments in low energy nuclear fission. Using these data we re-examined the influence of even nuclear numbers and closed shells on the mass and charge distribution in low energy fission. We used WAHL's Zp model and Ap model. We also examined the effects ofZ=50,N=82 and possiblyN=88 shells. A new method was developed based on two Gaussian curves for the even and odd products. TheEOZ andEON values calculated are based on these different methods and are seen to be consistent with each other in spite of the somewhat different definitions of the even-odd effect. The even-odd effect decreases with an increasing fissility parameter. TheEON values are substantially lower than the correspondingEOZ values, probably due to the effect of washing out the neutron pairing effect by prompt neutron emission. The magnitude of the even-odd effect varies with different mass regions. TheEOZ andEON values decrease as they go from asymmetric to symmetric regions in mass distributions.     

Applicability of the Vogel-Tammann-Fulcher type asymptotic exponential functions for ice, hydrates, and polystyrene latex

The validity of the Vogel-Tammann-Fulcher type asymptotic exponential functions for representing the temperature dependence of various properties, such as the particle-particle pull-off adherence forces in ice and hydrates and the annealing effect on polystyrene latex films, is demonstrated. The parameters of this equation are determined using the reported experimental data. The applications show that such functions yield accurate correlations of the experimental property data measured at various temperatures.     

A location–allocation heuristic for the capacitated multi-facility Weber problem with probabilistic customer locations

The capacitated multi-facility Weber problem is concerned with locating m facilities in the Euclidean plane, and allocating their capacities to n customers at minimum total cost. The deterministic version of the problem, which assumes that customer locations and demands are known with certainty, is a non-convex optimization problem and difficult to solve. In this work, we focus on a probabilistic extension and consider the situation where the customer locations are randomly distributed according to a bivariate distribution. We first present a mathematical programming formulation, which is even more difficult than its deterministic version. We then propose an alternate location–allocation local search heuristic generalizing the ideas used originally for the deterministic problem. In its original form, the applicability of the heuristic depends on the calculation of the expected distances between the facilities and customers, which can be done for only very few distance and probability density function combinations. We therefore propose approximation methods which make the method applicable for any distance function and bivariate location distribution.