Spectra of Liouville operators

Spectra of the generators of time translations (Liouville operators) on representation spaces determined by thermodynamic equilibrium states are compared and their nature is investigated.     

The homogeneous realization of the basic representation of A inf1 sup(1) and the toda lattice

It is well-known that the principal realization of the basic module L(₀) over A _inf1 ^sup(1) gives rise to the KdV hierarchy of partial differential equations. Here we use the homogeneous realization of the same module to construct a hierarchy of differential-difference equations, the first member of which turns out to be the equation for the Toda lattice.     

Factors influencing the transport of short-chain alcohols through mesoporous gamma-alumina membranes

The pressure-driven transport of water, ethanol, and 1-propanol through supported gamma-alumina membranes with different pore diameters is reported. Water and alcohols had similar permeabilities when they were transported through gamma-alumina membranes with average pore diameters of 4.4 and 6.0 nm, and the permeability coefficient was found to be proportional to the square of pore size, in accordance with a viscous flow mechanism. For transport through membranes with an average diameter of 3.2 nm, the behavior of water was in accordance with the viscous flow mechanism, but the permeability of the membrane for ethanol and 1-propanol was much smaller than expected and could not be explained in terms of viscous flow. Although the low permeability of the membrane with 3.2 nm pores for ethanol and 1-propanol was partly due to the presence of small amounts of water in the alcohols, the permeability coefficients were still substantially smaller when water was absent. This intrinsic difference between water and alcohol may be due to differences in molecular size, chemisorption of alcohols on the oxide pore wall, which would lead to a reduction of the effective pore size, and/or a certain degree of translational ordering of the alcohol molecules inside the membrane pores, which leads to an effectively higher viscosity and, therefore, to a higher transport resistance.     

Synthesis and Characterization of Microporous Titania Membranes

A procedure for the preparation of microporous titania membranes by the polymeric sol-gel technique is reported. The influence of acid/titanium ratio, water/titanium ratio, method of mixing components and refluxing time on particle size and sol stability was investigated. The thermal evolution, structural characteristics and liquid permeation properties of calcined materials were studied. Highly reproducible amorphous microporous titania layers with pore sizes ≤0.8 nm were obtained on both mesoporous γ-alumina and titania/zirconia coated substrates. The upper limit of thermal stability of the amorphous phase is ～300°C. Higher calcination temperatures led to phase transformation into anatase, which was accompanied by a collapse of the microstructure. The material was found to be chemically stable in a wide pH interval.     

Organisation of proficiency schemes by testing and calibration laboratories

Accreditation and Quality Assurance - Each year, an increasing demand for proficiency testing is seen in the world. Participating in this type of activity has been adopted by testing and...     

Vortical structures and turbulent bursts behind magnetic obstacles in transitional flow regimes

The present paper reports on numerical investigations of vortical structures in transient flow regimes generated by the local action of the Lorentz force on an electrically conductive fluid. The locally imposed non-uniform magnetic field generates similar effects as observed for flows over submerged solid obstacles. It is demonstrated that complex flow patterns can be generated by imposing magnetic fields of different strengths. The initial validation of the electromagnetically extended Navier-Stokes solver on unstructured numerical grids is performed in the low-Reynolds number range 100 ? Re ? 400 for different values of the magnetic interaction parameter. A generally good agreement is obtained in comparison with similar numerical studies of [Votyakov et al., 2007] and [Votyakov et al., 2008] for the low-Reynolds number cases. Then, a series of simulations are performed in transitional flow regimes (Re = 900) for different values of the interaction parameter (N = 3, … , 25). Simulations demonstrated the appearance of vortex-shedding phenomena similar to the flows behind solid obstacles. In contrast to the solid obstacles, the magnetic obstacles also generated the vortical flow patterns inside the magnetically affected regions. This feature can be used for the flow control of electrically conductive fluids, for efficient enhancements of the wall-heat transfer or for better mixing of passive scalars. Despite the laminar inflow conditions, turbulent bursts are observed in the magnetic wake region for the Re = 900 case. The velocity spectra and spatial distributions of the long-time averaged second-moments of the velocity field demonstrated that turbulence was locally sustained in the proximity of the magnetic wake edge.     

Synthesis of N-(Dimethylsulfamoyl)aldimines,a New Type of Aldimine Derivative

N-(Dimethylsulfamoyl)aldimines (3) a new type of shelf-stable aldimine derivatives, are readily prepared from aldehydes and N-(dimethylsulfamoyl)amide (2) in refluxing toluene.