The influence of a transverse magnetic field on a subnormal glow discharge in air

In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G) some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed in these oscillations.     

Study of the peak effect phenomenon in single crystals of 2H-NbSe2

The weakly pinned single crystals of the hexagonal 2H-NbSe₂ compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of the peak effect phenomenon in three crystals of 2H-NbSe₂, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability effects and pinning.     

Cyclotron resonance masers: State of the art

Cyclotron resonance masers, gyrotrons and gyroklystrons, are dominant high-energy sources at millimeter wavelengths and still have considerable margins of power and efficiency. The present-day challenge of creating CW megawatt gyrotrons is associated with many problems, among which the output window problem is a key one. New results of the investigation of gyrotrons and gyroklystrons in Russia are reported. A state-of-the-art analysis of gyrotrons for plasma heating in fusion installations and technological applications as well as gyroklystrons for millimeter-wavelength radars is performed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 6, pp. 635–670, June, 1996.     

Influence of reaction medium on elemental distribution in depth of V?P?O catalyst grains during n-butane oxidation

Redistribution of V–P–O catalyst elements in depth of its grains during the oxidation of n-butane to maleic anhydride gives rise to changes in its physicochemical properties and activity.

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, - V–P–O , - .

     

Multibeam X-ray lithography to form deep regular microstructures

A method for the fabrication of regular microstructures with a high aspect ratio (for example, X-ray gratings) by direct multibeam vector recording in layers of an SU-8 resist is presented. An X-ray beam with a wavelength from 0.4 to 1.7 Å is used for recording. The features of the method are described. The fabricated samples of regular microstructures of the SU-8 resist and gold-plated X-ray masks are presented as finished products.     

Rearrangement of fine particles in porous media causing reduction of permeability and formation of preferred pathways of flow: Experimental findings and a conceptual model

The rearrangement of matrix configuration due to the redistribution of clay particles was studied by introducing different suspensions into porous media. Clay (kaolinite) with low CEC (cation exchange capacity) and small flocs of high CEC clay (smectite) accumulated in regions of slow flow. In some experiments this was followed by rapid accumulation in regions of high velocity, impairing flow to a considerable degree. Clay with high CEC formed more voluminous structures which could bridge over a passage and impair the flow.In either case, whether small or large units of clay are involved, the final flow occurred mainly through open, preferred pathways. Such processes of redistribution and appearance of flow pathways may occur in subsurface porous media aquifers where forced gradients exist (e.g. in aquifers near the perforation of pumping wells and in places where large quantity of water are naturally or artificially recharged and in producing gas and oil fields).     

Schwefelbestimmung in Eisen, Stahl u. dergl.

Ohne Zusammenfassung     

Study of distribution of elements in the depth of V?P?Co catalyst grain

It has been shown that addition of cobalt to a vanadium-phosphorus oxide catalyst increases the P/V molar ratio on the surface, the surface acidity and the selectivity of butane oxidation. It has been established that in the V–P–Co–O catalyst the probability of the removal of phosphorus from the surface is markedly reduced.

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, , . , V–P–Co–O .