Proton conducting membranes based on sulfonated PEEK-WC polymer for PEMFCs

Proton conducting membranes have been prepared from chloro-sulfonated polyetheretherketone with cardo group polymers at various sulfonation degree via casting solutions using dimethylformamide as a solvent. The proton conductivity of sulfonated polyetheretherketone with cardo group membranes has been evaluated in the temperature range between 80 and 120 °C and the best result of this work has been achieved at 120 °C and sulfonation degree equal to 60% with a value equal to 6.7·10⁻² S/cm. Furthermore, this sample shows an open circuit voltage varying from 0.881 V at 80 °C to 0.867 V at 120 °C, pointing out that the membrane performance is not greatly affected by a temperature variation. Nevertheless, an increase of temperature from 80 to 120 °C makes possible an increase of the cell resistance varying from 0.17 to 0.24 Ω cm². Thus, the present study investigates the performance of sulfonated polyetheretherketone with cardo group membranes in terms of polarization curves, open circuit voltage, cell resistance and proton conductivity in order to propose them for proton exchange membrane fuel cell applications, particularly at T > 100 °C.     

Artificial anisotropy and polarizing filters

The calculated spectral transmittance of a multilayer laser mirror is used to determine the effective index of the single layer equivalent to the multilayer stack. We measure the artificial anisotropy of photoresist thin films whose structure is a one-dimensional, subwavelength grating obtained from interference fringes. The limitation of the theory of the first-order effective index homogenization is discussed. We designed normal-incidence, polarizing coating and a polarization rotator by embedding anisotropic films in simple multilayer structures.     

Inner-Circle Consistency for Wireless Ad Hoc Networks

This paper proposes and evaluates strategies to build reliable and secure wireless ad hoc networks. Our contribution is based on the notion of inner-circle consistency, where local node interaction is used to neutralize errors/attacks at the source, both preventing errors/attacks from propagating in the network and improving the fidelity of the propagated information. We achieve this goal by combining statistical (a proposed fault-tolerant duster algorithm) and security (threshold cryptography) techniques with application-aware checks to exploit the data/computation that is partially and naturally replicated in wireless applications. We have prototyped an inner-circle framework and used it to demonstrate the idea of inner-circle consistency in two significant wireless scenarios: 1) the neutralization of black hole attacks in AODV networks and 2) the neutralization of sensor errors in a target detection/ localization application executed over a wireless sensor network     

Volume Preservation of Multiresolution Meshes

Geometric constraints have proved to be efficient for enhancing the realism of shape animation. The present paper addresses the computation and the preservation of the volume enclosed by multiresolution meshes. A wavelet based representation allows the mesh to be handled at any level of resolution. The key contribution is the calculation of the volume as a trilinear form with respect to the multiresolution coefficients. Efficiency is reached thanks to the pre-processing of a sparse 3D data structure involving the transposition of the filters while represented as a lifting scheme. A versatile and interactive method for preserving the volume during a deformation process is then proposed. It is based on a quadratic minimization subject to a linearization of the volume constraint. A closed form of the solution is derived.     

Laser-activated p-i-n diode switch for RF application

Results obtained utilizing an optically activated RF switch in the 2-30-MHz range demonstrate the advantages in optically controlled high-power switches from HF to millimeter wave. Testing of a 0.25-mm-thick p-i-n device activated with 116-W peak optical power from a two-dimensional laser array in a 50-Ω system shows isolation between 20.8 and 49 dB, and an average insertion loss of 0.38 dB when measured between 2.5 and 30 MHz     

Recycled porous glass from municipal/industrial solid wastes sorting operations as a lead ion sorbent from wastewaters

Recycled waste porous glass (RWPG), from municipal solid wastes (MSW) sorting operations, may be used as a sorbent for lead ion removal from industrial wastewaters. To the purpose, dynamic (laboratory columns) operations were carried-out by the use of differently sized glass beads in the range 0.35–1.25 mm which were eluted with lead ion containing synthetic solutions (2–9.5 mg/L). Temperature was kept constant (298 K), whereas column flow-rates varied in the range 0.20–0.75 L/h. Lead ion retention mechanism was associated to the adsorption/ion exchange phenomena. Best column performance was obtained at 0.5–1 mm bead size range, influent concentration 2 mgPb²⁺/L and column flow-rate 0.20 L/h. In the reference conditions lead ion retention capacity exceeded 1.10 mg/g. Kinetic analysis of the experimental data was also carried-out and film interdiffusion of the involved ions in the Nernst stationary liquid around the particle was identified as the rate controlling step.