Photocatalytic Reactors for Air Treatment: Energy Efficiencies and Kinetic Modeling

The energy efficiency of the photocatalytic conversion of gas-phase organic pollutants was studied using a redesigned and scaled up Photo-CREC-Air reactor. This photocatalytic unit has the unique feature of allowing an accurate analysis of the irradiation field by establishing macroscopic balances and in-situ measurements. The Photo-CREC-Air reactor operates in a batch mode with the photocatalyst supported by a stainless steel mesh being irradiated by 8 UV lamps. Kinetic modelling, Quantum Yields (QY) and Photochemical Thermodynamic Efficiency Factors (PTEF) were calculated using data for acetone , acetaldehyde and isopropanol photocatalytic degradation in ambient air utilizing a Degussa P25 photocatalyst. It is shown that the Photo-CREC-Air reactor is suitable for the determination of kinetic and adsorption parameters, given design with excellent irradiation usage and fluid-catalyst contact. In this respect, quantum yields for acetone, acetaldehyde and isopropanol supersede the value of 1 (equivalent to 100%) with PTEFs remaining in both cases below the level of 1 as required by thermodynamics

Synthesis, characterization and performance of robust poison-resistant ultrathin film yttria stabilized zirconia – nickel anodes for application in solid electrolyte fuel cells

We report on the synthesis of undoped ∼5 μm YSZ-Ni porous thin films prepared by reactive pulsed DC magnetron sputtering at an oblique angle of incidence. Pre-calcination of the amorphous unmodified precursor layers followed by reduction produces a film consisting of uniformly distributed tilted columnar aggregates having extensive three-phase boundaries and favorable gas diffusion characteristics. Similarly prepared films doped with 1.2 at.% Au are also porous and contain highly dispersed gold present as Ni-Au alloy particles whose surfaces are strongly enriched with Au. With hydrogen as fuel, the performance of the undoped thin film anodes is comparable to that of 10–20 times thicker typical commercial anodes. With a 1:1 steam/carbon feed, the un-doped anode cell current rapidly falls to zero after 60 h. In striking contrast, the initial performance of the Au-doped anode is much higher and remains unaffected after 170 h. Under deliberately harsh conditions the performance of the Au-doped anodes decreases progressively, almost certainly due to carbon deposition. Even so, the cell maintains some activity after 3 days operation in dramatic contrast with the un-doped anode, which stops working after only three hours of use. The implications and possible practical application of these findings are discussed.European Union 298300Ministerio de Economía y Competitividad MAT2013‐40852R, 201560E05

Image encryption system based on a nonlinear joint transform correlator for the simultaneous authentication of two users

We propose a new encryption system based on a nonlinear joint transform correlator (JTC) using the information of two biometrics (one digital fingerprint for each user) as security keys of the encryption system. In order to perform the decryption and authentication in a proper way, it is necessary to have the two digital fingerprints from the respective users whose simultaneous authentication is pursued. The proposed security system is developed in the Fourier domain. The nonlinearity of the JTC along with the five security keys given by the three random phase masks and the two digital fingerprints of the two users allow an increase of the system security against brute force and plaintext attacks. The feasibility and validity of this proposal is demonstrated using digital fingerprints as biometrics in numerical experiments.Peer ReviewedPostprint (published version

Effects of using an encrypted image corrupted by noise and occlusion in a security system based on joint transform correlator and Gyrator transform

Postprint (published version