Inversion of Linear Space-Time Transformations in Bounded Domains

General formulas for pseudoinversion of linear integral transformations in bounded space-time domains are constructed. The input and output of transformations are given in continuous-discrete forms. The conditions of accuracy and uniqueness of the transformations are studied.     

Stereological analysis and modelling of gradient structures

Gradient structures are inhomogeneous along a particular gradient direction but homogeneous perpendicular to that direction. Consequently, structural parameters such as volume fraction or surface area density are local characteristics which depend on the 'vertical' coordinate with respect to the 'vertical' gradient axis.
Analogously, models for gradient structures have model parameters depending on the vertical coordinate z . For example, a Voronoi tessellation with a gradient is generated by a gradient point process with a local intensity which is a function of z . Similarly, a gradient germ grain model is obtained from a gradient point process where the grain size distribution may also depend on z . For a gradient Boolean model, local volume fraction V_V ( z ) and local surface area density S_V ( z ) can be calculated from the model parameters.
Stereological methods for gradient structures are based on vertical sections parallel to the gradient direction. Estimation of V_V ( z ), S_V ( z ) and local length density L_V ( z ) is done by lineal analysis using horizontal test lines with vertical coordinate z . Similarly, lineal analysis is used to estimate local mean cell volume of gradient tessellations. For the estimation of local particle number density and size in the spirit of the Wicksell problem the use of kernel methods and distributional assumptions is required.     

Mathematical Modeling of the Control of Dynamics of Thick Elastic Plates. I. Control Under Continuous Desired State

The authors formulate and solve control problems for the dynamics of the three-dimensional field of transverse dynamic displacements of elastic plates of finite thickness coordinated with the mean square fixed continuous desired condition. The control factors are superficially distributed external-dynamic loads, initial and boundary disturbing factors taken individually, in pairs, and all three together. The features of the solution of these problems are described for the case where some of the initial and boundary disturbances are not important. The conditions of the accuracy and uniqueness of the solutions are analyzed.     

High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment

Improved activity and durability performance of a two-cell (86 cm²) proton exchange membrane water electrolyzer (PEMWE) stack is reported for the first time. Both membrane electrode assemblies (MEAs) contain one order of magnitude lower platinum group metal (PGM) loadings compared to the state-of-the-art PEMWEs and incorporate novel Pt recombination layers. The high-performance and cost-effective MEAs are fabricated by the unique reactive spray deposition technology (RSDT). This advanced methodology allows for one-step fabrication of MEAs and ensures precise control and distribution of the catalyst composition and loading. The RSDT-fabricated MEAs contain only 0.2 and 0.3 mg_PGM cm^?2 loading in the cathode and anode electrodes, respectively, and demonstrate excellent activity and durability for over 3000 h of operation at industrially-relevant operating conditions without showing significant loss in performance. This novel work shows that a significant cost reduction for PEMWEs is achieved while maintaining excellent durability, high catalysts activities, and low hydrogen cross-over.     

More on the microstructural characterization of dense particle gels

A systematic study of the microstructure of densely packed coagulated colloidal particle gels is important for understanding their macroscopic, in particular, mechanical properties. It was previously shown that heterogeneous gels exhibit higher elastic properties and yield strengths than their homogeneous counterparts at the same solids loading. This was explained by the newly developed straight path method.¹ However, this macroscopic behaviour can be also explained by classical and conceptually simpler methods of spatial statistics, in particular, the pair-correlation function and the related K-function. Additionally, the structural differences of homogeneous and heterogeneous gels can be described by the contact distributions, which characterize the pore space and are of relevance for certain transport properties. The understanding of the structural differences is completed by presenting a benchmark model, which is in some sense ‘between’ the homogeneous and heterogeneous case.     

Semi‐theoretical prediction of volumetric mass transfer coefficients in bubble columns with organic liquids at ambient and elevated temperatures

A semi‐theoretical approach for predicting k_La values (referred to liquid volume) in 18 organic liquids [acetone, aniline, 1‐butanol, benzene, cyclohexane, decalin, 1,2‐dichloroethane, 1,4‐dioxane, ethanol (96%), ethylacetate, ethylbenzene, ligroin, methanol, nitrobenzene, 2‐propanol, tetralin, toluene, and xylene] at various operating conditions (including elevated temperatures and pressures) was developed. It was found that the approach is applicable regardless of the hydrodynamic regime (at u_G ≤ 0.1 m/s). Temperatures up to 353 K and pressures up to 0.5 MPa were tested. Two different distributors (multiple‐hole and single‐hole type) were employed. The liquid‐phase mass transfer coefficient k_L was calculated theoretically from the penetration theory on the basis of original definition of gas–liquid contact time. The interfacial area a was defined with respect to the liquid volume. It was found that their product k_La must be multiplied by some correction factor in order to take account of the non‐spherical (ellipsoidal) shape of the bubbles. When the correction term is correlated to both the Eötvös number (Eo) and the dimensionless temperature ratio, 198 experimental k_La values can be fitted reasonably well (average relative error 9.3%).     

Effect of gamma-ray irradiation on the fatty acid profile of irradiated beef meat

The effect of γ-ray irradiation on the fatty acid profile of beef meat was examined at doses of 2.5, 5.0, 7.5, 10.0 and 15.0 kGy by means of ¹H NMR spectroscopy. NMR results revealed a clear trend toward an increase in the amount of saturated fatty acids and a decrease in the amount of polyunsaturated fatty acids in the triacylglycerol composition of the irradiated samples compared to the unirradiated sample with increasing the irradiation dose.     

Bio hydrometallurgical recovery of metals from Fine Shredder Residues

The leaching step of an integrated hydrometallurgical process for the selective recovery of metals from polymetallic concentrates has been investigated. This concentrate has been produced by physical treatment of Fine Shredder Residues derived from a shredding plant processing a mixed feed of metallic scraps, waste electric equipments and end-of-life vehicles. Bacterially assisted leaching experiments have been carried out using a copper-adapted consortium of mesophilic bacterial strains. The influence of various operating conditions such as stirring speed, temperature (25-50 °C), pulp solids density (5-20%) and initial iron concentration (0-15 g/L) has been studied. Temperature and stirring speed have proved to be the most influential parameter regarding copper dissolution kinetics, while pulp solids density and initial iron concentration have been found to have a subordinate importance. In optimum conditions, 95% extractions of zinc and copper were achieved within 48 h. Bacterial presence has been found beneficial in terms of catalysing copper dissolution.