An improved method using respirography for the design of activated sludge aeration systems

For the computation of the oxygen uptake for the aeration tank of the biological treatment plant several methods are available such as the OC/L method, Emde's method with fixed coefficients, Eckenfelder's method, and the method of levels of dissolved oxygen. The method for the determination of oxygen uptake for the treatment of industrial wastewaters was developed. The advantage of this method is a simple calculation of oxygen uptake for industrial biological treatment plant due to independent measurement of oxygen uptake for individual phases. The method is rapid and allows easy determination of individual phases of oxygen uptake.     

Structural effects in electrocatalysis: oxidation of formaldehyde on gold and platinum single crystal electrodes in alkaline solution

The oxidation of formaldehyde in sodium hydroxide solution has been studied on platinum and gold single crystal electrodes with the (111), (110) and (100) orientations. There is apparently no structural sensitivity of this reaction, since minor differences have been found between the three low index faces. This is valid for both platinum and gold electrodes. The hydrogen adsorption on platinum and the AuOH formation on gold electrodes exhibit structural sensitivity in the same solution. Similar activity of platinum and gold electrodes is noteworthy. A weak adsorption of gem-diol, formed in the interaction of formaldehyde with H₂O or OH^? appears as the origin of the structural insensitivity of this reaction.     

Preferred orientation in extruded magnesium compacts

The preferred orientation in extruded sintered compacts Mg/2.0 wt % Be, Mg/0.5 wt % MgF₂, Mg/0.1 wt % MgO, Mg/3.0 wt % MgO and Mg/5.0 wt % MgO has been investigated. After extrusion there is a very sharp fibre texture with the fibre axis (parallel with the extrusion direction) along the 〈101̄0〉 direction. After secondary recrystallization the fibre axis is oriented along the 〈112̄0〉 direction. The time dependence of the recrystallization process is considerably influenced by the dispersed phase content and morphology. Finally, the plastic deformation of the textured compacts is discussed briefly.     

Size effect tests of torsional failure of plain and reinforced concrete beams

The current design code formulae for the torsional failure of plain or longitudinally reinforced beams exhibit no size effect, i.e. the failure of geometrically similar beams of different sizes is supposed to occur at the same nominal stress. Experiments on reduced-scale beams were carried out, and the results confirm that there is a significant size effect, such that the nominal stress at failure decreases as the beam size increases. This is found for both plain and longitudinally reinforced beams. The results are consistent with the recently proposed Bažant's size-effect law. However, the scatter of the results and the scope, and range limitations prevent it from being concluded that the applicability of this law is proven.     

Comparison of different modes of excitation in X-ray emission spectroscopy in the detection of trace elements in coal and coal ash

Three different modes of sample excitation in X-ray emission spectroscopy were used in trace element analysis of coal and coal ash: proton beam, Mo X-ray tube and radioactive sources ⁵⁷Co and ¹⁰⁹Cd. The results of analysis are presented and methods and their possibilities are compared in order to indicate the most appropriate technique for the particular purpose.     

Spurious reflection of elastic waves in nonuniform meshes of constant and linear strain unite elements

A change in finite element size causes spurious reflection of elastic waves passing through a finite element grid when the wavelength is less than about 10-times the largest element in the grid. Extending the previously published study in which the phenomenon was analyzed for the case of constant strain finite elements, the higher-order elements with linear strain distribution are studied herein. Similarly to the previous study, it is found that the consistent mass matrix gives less spurious wave reflection than the lumped mass matrix; however the advantage is smaller for the higher-order elements. For the lumped mass matrix, there is little difference in spurious wave reflection between the constant strain and linear strain elements. The phenomenon of spurious wave reflection is less pronounced when the higher-order elements are used in conjunction with the consistent mass matrix. These results are obtained from exact analytical solutions in complex variables for a planar wave with a planar wave front propagating along grid lines through an infinite grid which is uniform in each half plane.