Removal and storage of ash of thermal power stations,variants and prospects of development

Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 24–28, November, 1994.     

Newton's observations of diffracted rays

The history of diffracted rays is usually considered to be less than a century long. However, a careful study of experiments and observations made by Newton and described in his Optiks shows that diffracted rays had been observed nearly 300 years ago. To show this is the goal of the present paper. Optiks Book III, part I, also comprehends diffraction. Of the various observations by Newton in that book, two have been chosen in the present paper to demonstrate, by applying modern theories, that Newton was actually observing diffracted rays     

The physical theory of slope diffraction

The physical theory of diffraction (PTD) has been expanded for the case of slope diffraction, when an incident wave is zero but its derivative is not zero in the direction of a perfectly conducting scattering edge. High frequency asymptotics are found both for elementary edge waves and for the total edge waves scattered by arbitrary curved edges. Great attention is given to fields created by the nonuniform (diffraction) component of edge currents. These fields are usually called ptd corrections to the Physical Optics approach. These corrections are found for diffraction fields in ray regions and in diffraction regions such as the vicinities of shadow boundaries, smooth caustics, and foci.     

Dielectric medium

The concept of the generalized scattering amplitude is applied to the electromagnetic (EM) scattering of an arbitrarily shaped, perfectly conducting object partially immersed in a semi-infinite dielectric medium. The dielectric medium can have either electric loss or magnetic loss or both. In a two-dimensional (2-D) formulation, after the outgoing cylindrical wave is factored out from the scattered wave, the remaining wave envelope component in the scattered wave is defined as the generalized scattering amplitude. The transformed Helmholtz equation in terms of the generalized scattering amplitude can be solved numerically using a finite-difference method over the entire scattering domain including both the semi-infinite free-space (vacuum or air) and the semi-infinite dielectric medium. Example problems of scattering by infinitely long, perfectly conducting cylinders of circular and trapezoidal ship-shaped cross sections are solved to demonstrate the theoretical formulation and numerical method. The radial profiles of the generalized scattering amplitude and the total field over the entire scattering region are also presented, and their properties are discussed. The far-field bistatic cross section and induced current density on the obstacle's surface are also presented. These results show that the method can be used to yield complete and accurate solutions to 2-D EM scattering problems involving arbitrarily shaped metallic objects partially immersed in a penetrable semi-infinite dielectric medium     

Semiconductor materials for present-day solid-state electronics

This review paper outlines advances and challenges in semiconductor materials research and the lines along which the techniques for growing large-diameter crystals and large-area epitaxial heterostructures are progressing. We discuss potential applications of quantum-size heterostructures and thin-film structures based on hydrided amorphous semiconductors. The major problems facing the technology of semiconductor materials and devices are outlined     

On efficiency of plasma gasification of wood residues

High temperature plasma gasification of wood is evaluated for the production of a fuel gas (syngas) for combined heat and power production. The advantages of plasma by comparison with existing thermochemical processes are in the high heating value gases, process control and the lower energy consumption per unit of output. From one kilogram of 20% moisture wood it is possible to obtain 4.6-4.8 MJ of electricity (net of electricity input) and 9.1-9.3 MJ of thermal energy when using wood with average elemental composition and with a LHV energy content of 13.9 MJ, when using a combined Brayton and Steam cycle generating plant. Experimental data from an air plasma gasification plant using alternating current (AC) plasma torches was integrated with a thermodynamic model showing that the chemical energy in the produced syngas was 13.8-14.3 MJ kg⁻¹ with a power input of 2.2-3.3 MJ kg⁻¹.