Applying Projection‐Based Methods to the Asymmetric Traffic Assignment Problem

This article examines the application of a path‐based algorithm to the static and fixed demand asymmetric traffic assignment problem. The algorithm is of the simplicial decomposition type and it solves the equilibration or master problem step by means of five existing projection methods for variational inequality problems to evaluate their performance on real traffic networks. The projection methods evaluated are: (1) a cost approximation‐based method for minimizing the Fukushima's gap function, (2) the modified descent method of Zhu and Marcotte ( 1988 ), (3) the double projection method of Khobotov ( 1987 ) and three of its recently developed variants (Nadezhkina and Takahashi, 2006 ; Wang et al., 2010 ; and He et al., 2012); (4) the method of Solodov and Svaiter ( 1999 ); and (5) the method of Solodov and Tseng ( 1996 ). These projection methods do not require evaluation of the Jacobians of the path cost functions. The source for asymmetries are link costs with interactions, as in the case of priority ruled junctions. The path‐based algorithm has been computationally tested using the previous projection methods on three medium to large networks under different levels of congestion and the computational results are presented and discussed. Comparisons are also made with the basic projection algorithm for the fixed demand asymmetric traffic assignment problem. Despite the lack of monotonicity properties of the test problems, the only method that failed to converge under heavy congestion levels was the basic projection algorithm. The fastest convergence was obtained in all cases solving the master problem step using the method of He et al. (2012), which is a variant of Khobotov's method.     

Oxidative dehydrogenation of propane in a perovskite membrane reactor with multi‐step oxygen insertion

A membrane reactor incorporating a hollow fiber with successive parts of oxygen permeable and passivated surface segments has been developed and was used for the oxidative dehydrogenation (DH) of propane. This membrane geometry allows a controlled oxygen feeding into the reactor over its axial length. In the oxidative DH, the thermodynamic limitation of propane DH can be overcome. By using this novel hollow fiber membrane reactor with a Pt/Sn/K DH catalyst, oxygen separation and propene formation could be established even at temperatures as low as 625°C with long‐term stability. Combining the hollow fiber membrane and the DH catalyst, the highest propene selectivity of 75% was observed at a propane conversion of 26% and 625°C whereas the best propene yield of 36% was obtained at 675°C (48% propene selectivity). The performance of this reactor is evaluated by applying various reaction conditions. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Physiological and biochemical characteristics of the ethyl tiglate production pathway in the yeast Saprochaete suaveolens

A yeast identified as Saprochaete suaveolens was investigated for its capacity to produce a large panel of flavouring molecules. With a production of 32 compounds including 28 esters, S. suaveolens seems to be a good producer of fruity flavours and fragrances and especially of unsaturated esters, such as ethyl tiglate. Physiological and biochemical analyses were performed in this study in an attempt to comprehend the metabolic route to the formation of this compound. We show that the accumulation of ethyl tiglate by S. suaveolens is specifically induced by isoleucine. However, and contrary to S. cerevisiae, which harbours a classical Ehrlich pathway leading to the production of 2‐methylbutanol from isoleucine, our results provide phenotypic and enzymological evidence of ethyl tiglate biosynthesis in S. suaveolens through the catabolism of this amino acid by the β‐oxidation pathway, which generates tiglyl‐CoA as a probable intermediate. A kinetic analysis of this flavour molecule during growth of S. suaveolens on glucose and isoleucine showed a phase of production of ethyl tiglate that culminated concurrently with isoleucine exhaustion, followed by a disappearance of this compound, likely due to reassimilation by the yeast. Copyright © 2014 John Wiley & Sons, Ltd.     

Twin-mass accelerometer optimization to reduce the package stresses

The geometry optimization of a piezoresistive Twin-mass accelerometer is presented. The Twin-mass design is the most sensitive design to the stresses of the package compared to the Cantilever beam and the Quad-beam designs. Finite element simulations are carried out to improve the geometry of the Twin-mass design. Substitution of the perpendicular external beams by lateral external beams reduces the effects of the stresses of the package by a factor of more than 40. Moreover, the sensitivity and the figure of merit of the device can be easily increased.     

Benefit of Microscopic Diffusion Measurement for the Characterization of Nanoporous Materials

Detailed knowledge of the transport properties of nanoporous materials is a prerequisite for their complete characterization and optimum technological exploitation. One of the best ways to attain this information is provided by the “microscopic” techniques of diffusion measurement, in particular by the pulsed field gradient technique of NMR and by interference microscopy and IR microscopy. Starting with the measuring principles, the various types of evidence as accessible by these techniques are illustrated. A large variety of host‐guest systems with both ordered and random pore networks have been studied, from microporous up to macroporous materials. The information obtained concerns diffusivities in the various pore domains, extra resistances at the interfaces between them and the associated exchange rates.     

Some implications of nanoscience in food dispersion formulations containing phospholipids as emulsifiers

This contribution is concerned with phospholipid films in relation to food dispersions such as emulsions and foams. Structural, morphological and surface rheological characteristics of dipalmitoyl phosphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) monolayers were determined at the air–water interface at 20 °C and at pH 5, 7, and 9, by means of surface pressure (π)–area (A) isotherms coupled with Brewster angle microscopy (BAM), atomic force microscopy (AFM) and surface dilatational and shear rheometry. From the π–A isotherms it was deduced that DPPC monolayers show structural polymorphism at the air–water interface. DOPC monolayers formed a liquid-expanded (LE) structure under all experimental conditions, a consequence of the weak molecular interactions due to the double bond in the hydrocarbon chain. Electrostatic interactions between film-forming components influence the monolayer structure. BAM and AFM images corroborate, at a microscopic and at nanoscopic level respectively, the structural polymorphism deduced from the π–A isotherm for DPPC monolayers as a function of surface pressure and the pH of the aqueous phase. However, the homogeneous morphology of DOPC monolayers at a microscopic level, as observed by BAM, shows structural heterogeneity at a nanoscopic level when observed by AFM. The relative monolayer thickness increases with surface pressure and is a maximum at the collapse point, especially for DPPC monolayers. The results confirm that the interfacial rheological characteristic measured under dilatation and shear conditions are very dependent on the structural characteristics and morphology of the phospholipids (DPPC and DOPC) monolayers.