Summability of Solutions of the Dirichlet Problem for Nonlinear Elliptic Equations with Right-Hand Side in Classes Close to L1

Mathematical Notes -     

Simulation of a mixed-conducting membrane-based gas turbine power plant for CO<Subscript>2</Subscript> capture: system level analysis of operation stability and individual process unit degradation

A gas turbine power plant for CO₂ capture, based on oxygen-permeable membranes with mixed ionic-electronic conductivity, was analysed with respect to long-term stability by means of numerical simulation. Due to the attractive transport and physicochemical properties of mixed-conducting La₂NiO_4+δ, this nickelate was selected as a prototype membrane material for this application. Experiments showed very slow degradation of La₂NiO_4+δ membranes at oxygen chemical potentials close to atmospheric conditions, which are associated with kinetic demixing and other microstructure-related factors. Interaction with CO₂ in the intermediate temperature range also leads to lower oxygen permeation, whilst increasing oxygen pressure may cause partial phase decomposition and microstructural changes, thus again limiting the range of possible operation conditions. The relevant operational constraints were included in a detailed membrane-based gas turbine power plant model. The membrane performance degradation with time was approximated by a linear function with average rate of 3.3% per 1,000 operation hours. Furthermore, performance deterioration of the gas turbine compressor and turbine were also considered. Simulations revealed that the power plant is substantially affected by degradation of the ceramic membranes and turbomachinery components. The already rather small operating window was further narrowed when compared with a conventional gas turbine power plant. Two different designs of the membrane-based power plant were analysed: (1) with and (2) without additional combustors (afterburners) between the membrane reactor and the gas turbine. Afterburners increase thermal efficiency as well as power output, but also lead to non-negligible CO₂ emissions. In order to have a frame of comparison, results for a conventional gas turbine power plant with degradation of turbomachinery components are also presented. Simulations representing changes in ambient temperature and fuel composition as well as failure incidents were executed to analyse the susceptibility of the gas turbine power plant to external and internal changes.     

The consequences of the mutual recognition of measurement standards for international metrology

 After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.

     

Optimization of self-frequency doubling in periodically and quasi-periodically poled nonlinear crystals

The theory of self-frequency doubling in a periodically poled nonlinear crystal is generalized to the case of varied domain thickness (quasi-periodically poled crystals). A particular statistical model of quasi-periodicity is considered. The effect of quasi-periodicity on the output emission intensity is calculated. The degree of quasi-periodicity allowable for practical applications is estimated, and the advantages of quasi-periodically poled crystals are discussed. The problem of maximization of the output emission intensity for periodically and quasi-periodically poled crystals is considered. The dependence of the output emission intensity on the crystal length is investigated, and an upper estimate for the maximum intensity is obtained. A formula for the optimal reflection coefficient of the output mirror as a function of the crystal length is derived.     

High-temperature transport properties, thermal expansion and cathodic performance of Ni-substituted LaSr2Mn2O7−δ

The substitution of manganese with nickel in LaSr₂Mn₂O_7−δ, where the solubility limit corresponds to approximately 25% Mn sites, enhances the Ruddlesden-Popper phase stability at elevated temperatures and atmospheric oxygen pressure. The total conductivity of LaSr₂Mn_2−yNi_yO_7−δ (y=0-0.4) decreases with nickel additions, whilst the average thermal expansion coefficients calculated from dilatometric data in the temperature range 300-1370 K increase from (11.4-13.7)×10⁻⁶ K⁻¹ at y=0 up to (12.5-14.4)×10⁻⁶ K⁻¹ at y=0.4. The conductivity and Seebeck coefficient of LaSr₂Mn_1.6Ni_0.4O_7−δ, analyzed in the oxygen partial pressure range 10⁻¹⁵-0.3 atm at 600-1270 K, display that the electronic transport is n-type and occurs via a small polaron mechanism. Reductive decomposition is observed at the oxygen pressures close to Ni/NiO boundary, namely ∼2.3×10⁻¹¹ atm at 1223 K. Within the phase stability domain, the electronic transport properties are essentially p(O₂)-independent. The steady-state oxygen permeability of dense LaSr₂Mn_1.6Ni_0.4O_7−δ membranes is higher than that of (La,Sr)MnO_3−δ, but lower if compared to perovskite-like (Sr,Ce)MnO_3−δ. Porous LaSr₂Mn_1.6Ni_0.4O_7−δ cathodes in contact with apatite-type La₁₀Si₅AlO_26.5 solid electrolyte exhibit, however, a relatively poor electrochemical performance, partly associated with strong cation interdiffusion between the materials.     

Bis[bis­(3‐phenyl­pyrazol‐1‐yl)­(pyrazol‐1‐yl)­methane]­copper(II) bis­(per­chlor­ate) acetonitrile disolvate

The title copper(II) complex, [Cu(C₂₂H₁₈N₆)₂](ClO₄)₂·2C₂H₃N, comprises two neutral substituted tris­(pyrazol‐1‐yl)­methane ligands bonded to a central Cu^II ion, which is positioned on a crystallographic inversion center. Six Cu—N bonds are arranged in a distorted octa­hedral fashion. The unsubstituted pyrazole rings on each ligand are oriented trans with respect to each other, inter­digitated with the two 3‐phenyl­pyrazole rings of the other ligand.     

The first photocrystallographic evidence for light-induced metastable linkage isomers of ruthenium sulfur dioxide complexes

Light-induced metastable linkage isomers of trans-[Ru(NH(3))(4)Cl(SO(2))]Cl and trans-[Ru(NH(3))(4)(H(2)O)(SO(2))](C(6)H(5)SO(3))(2) have been identified for the first time using photocrystallographic methods. In both linkage isomers the SO(2) ligand is side bound, but the Ru-O and Ru-S distances are considerably longer and almost equal in the trans-H(2)O isomer. DFT calculations confirm that both isomers correspond to minima on the ground-state potential energy surface and also predict the existence of a second oxygen-bound isomer for both compounds. The decay of the light-induced species has been studied by both DSC and IR. Activation energies for the thermal back-reaction, as derived from the temperature-dependent disappearance of light-induced IR bands, are 50.0 and 58.4 kJ/mol for the two isomers, which is larger than the corresponding numbers for photoinduced side-bound nitrosyl linkage isomers.