Reduced Silver Salt of Wells-Dawson Heteropolyacid H6P2W18O62 as a Bi-Functional Catalyst

Silver salt preparation was obtained by neutralizing solution of H₆P₂W₁₈O₆₂ in water with solid Ag₂CO₃. In the introductory experiments the conditions of silver salt reduction with ethanol vapours were studied at 170–290 °C. At 250 °C and 2.5 h complete reduction to silver and free heteropolyacid was observed. During reduction with ethanol the initially not active salt became catalyst on which typical for free acid alcohol dehydration to ethylene occurred. In a series of experiments carried out within temperature range 210–290 °C ethanol conversion was studied on the catalyst previously reduced at 250 °C. When air was used as the carrier gas the bi-functional behavior of the catalyst was distinct, besides ethylene, diethyl ether and water, typical products of acid–base type catalytic reaction also comparable amount of acetaldehyde, the product of redox type reaction, was observed.     

Shortest synchronizing strings for Huffman codes

Most complete binary prefix codes have a synchronizing string, that is a string that resynchronizes the decoder regardless of its previous state. This work presents an upper bound on the length of the shortest synchronizing string for such codes. Two classes of codes with a long shortest synchronizing string are presented. It is known that finding a synchronizing string for a code is equivalent to finding a synchronizing string of some finite automaton. The Černý conjecture for this class of automata is discussed.     

Polarization recovery for Polarization Shift Keying transmission based on analysis of torsion and curvature of three dimensional curve segments

A solution to the problem of recovering and tracking the signal configuration at the receiver side for digital optical transmission systems employing the modulation of polarization (POLSK) is proposed. The tracking algorithm for signal configuration is based on analysis of torsion and curvature of three dimensional curve segments. Impact of polarization effects on presented method is investigated. The only impairments considered in this paper are: frequency-independent birefringence and one lumped PDL element. The numerical simulations and experiments shows that the presented method is resistant to change of fiber optics birefringence; and is sensitive to depolarization effect and state of polarization location fluctuations which are equal or faster than the data rate.     

Pillared smectite modified with carbon and manganese as catalyst for SCR of NOx with NH3. Part I. General characterization and catalyst screening

Carbon- and manganese-modified zirconia-pillared smectites were prepared, characterized (XRD, BET and pore analysis, XPS) and tested in selective catalytic reduction of NO_x with NH₃. Both untreated and acidic pretreated smectites were used. The acid pretreatment increased NO conversion and influenced the extent of carbon introduction into the porous system. The carbon deposit improved selectivity of the catalytic reduction to N₂. This revised version was published online in July 2006 with corrections to the Cover Date.     

Multisymplecticity and wave action conservation

This paper discuses some novel results concerning the wave action conservation law for multisymplectic partial differential equations and their discretizations. We provide a method for deriving this conservation law in Fourier spectral space. A discrete wave action conservation law for a multisymplectic box scheme and for the midpoint time-discretization of a spectral method is also derived.     

Influence of Hydrostatic Pressure on Compressive Strength of Self-consolidating Concrete

The design of unique chamber, in which the SCUWC （self-consolidating underwater concrete） can be tested under the impact of the hydrostatic pressure from 0.1 MPa to 0.5 MPa, is presented in the paper. The results of the preliminary tests of the effect of the hydrostatic pressure on the compressive strength of SCUWC were shown. The impact of the hydrostatic pressure on the compressive strength values of test specimens has been confirmed. There has been an increase in the strength of the specimens taken from the upper parts of the concrete samples. As it can be seen from the preliminary research, the differences in compressive strength are related to the differences that occur in the size and distribution of air voids in the samples taken from upper and lower parts of the test specimens. On the basis of the carried out investigations of the compressive strength, it can be concluded that the hydrostatic pressure has a favorable effect on the compressive strength of the tested specimens of SCUWC. Increase of the compressive strength is observed mostly in the upper layers of the samples. Preliminary analysis of the quantity and distribution of air pores in the samples of concrete subjected to pressure 0.5 MPa confirms the positive impact of the hydrostatic pressure on the layers close to the surface indicated by the absence of large air voids above 1,500μm and by reducing the quantity of air pores of size above 300μm.     

Estimator-analyzer of power quality: Part II - Hardware and research results

The paper presents the new instrumentation for power quality assessment, called the estimator-analyzer of power quality. It is consistent with the general idea of waveform parameters measurement set out in IEC Standard 61000-4-7, although it utilizes the authors’ original methods of measurement of power quality parameters. The applied methods and algorithms were described in the first part of the paper. The hardware of the device and the experimental results are presented and discussed in this paper. The device has been tested with signals of known characteristics and also in the electric power system of a ship.