Pan Evaporation to Reference Evapotranspiration Conversion Methods

Reference evapotranspiration (ET0) is often estimated from evaporation pan data as they are widely available and of longer duration than more recently available micrometeorologically based ET0 estimates. Evaporation pan estimation of ET0 ( = KpEpan) relies on determination of the pan coefficient (Kp), which depends on upwind fetch distance, wind run, and relative humidity at the pan site. The Kp estimation equations have been developed using regression techniques applied either to the table presented in FAO-24 or to the original data upon which this table was based (from lysimeter studies in Davis, Calif.). Here, the relative performances of the FAO-24 table and six different Kp equations are evaluated with respect to reproducing the original data table using the FAO-24 table as a standard. Evaporation pan- and CIMIS-based estimates of ET0 are also compared for stations having ranges of mean humidities (48–66%) and mean wind runs (156–193 km/day) located in the Sacramento and San Joaquin valleys, and for a coastal station (Point Heuneme) near Ventura, Calif., having a greater mean humidity (71%). In comparing the means, standard deviations, root-mean-square errors, and linear regression coefficients, five of the six equations reproduced the original data table with approximately the same accuracy as the FAO-24 table. Use of either Kp table slightly underestimated measured ET0 at the coastal site, while the Cuenca, Allen-Pruitt, and Snyder Kp equations most closely approximated the average measured ET0 at all seven sites.     

A simplified two-phase macroscopic model for reinforced soils

This paper presents the formulation of a macroscopic model for reinforced soil structures in which the interface is taken into consideration as a rigid-plastic contact. The model is formulated in the framework of a so-called multiphase model recently introduced for reinforced soil masses. The proposed simplified two-phase model can be considered as an optimal solution between extremely simplified perfect bonding model on one hand, and using a third phase for the interface on the other hand, which results in a more complicated and time-consuming model. The introduced platform is implemented in a numerical code. The proposed model is evaluated by simulating (a) the failure of laboratorial plane strain compression tests; (b) the behavior of a 1-g reinforced soil retaining wall model under external loading, and (c) the deformation of a reinforced soil structure under its own weight, which has been analyzed by another homogenization approach including elastoplastic interface model. The results indicate that the deformation of reinforced soil structures can be satisfactorily predicted by the proposed model.     

An innovative application of multiple impinging jet flow field in fuel cells

The flow field in a fuel cell is expected to distribute the reactants as uniformly as possible over the active plate, support the reasonable pressure drop across the channel and maximize the mass transfer through the catalyst layers. To simultaneously accomplish these requirements, an innovative multiple impingement jet flow field (MIJFF) is proposed in this study. A three-dimensional thermo-fluid simulation is used to evaluate the proposed idea and compare its performance against the commonly used parallel field flow (PFF). The domain of calculations includes a channel with multiple impingement jets linked to a porous gas diffusion layer under low Reynolds flow conditions. The results reveal that the suggested MIJFF design significantly increases the transport of the reactant gases through the catalyst layer. The penetration depth into the catalyst layer in the MIJFF arrangement is higher than that of the PFF setup and the use of the catalyst layer is optimized, which in turn can lead to a reduction of the activation drop. Compared to a PFF design under similar operating conditions, the mean Nusselt number is shown to increase by a factor of about 3.5 in the MIJFF setup. Furthermore, the temperature is more uniformly distributed in the MIJFF pattern which results in more effective distribution of the reactant gases over the active surface. The current study shows that under equal pressure drop conditions, the MIJFF exhibits a much higher performance than a PFF channel design. That is while the corresponding flow rate for the MIJFF is much lower than that of PFF.     

Blind MV-based video steganalysis based on joint inter-frame and intra-frame statistics

Multimedia Tools and Applications - Despite all its irrefutable benefits, the development of steganography methods has sparked ever-increasing concerns over steganography abuse in recent decades....