Forced Filtration of a Water–Ethanol Liquid–Vapor Mixture through a Porous Medium

Theoretical Foundations of Chemical Engineering -     

Modern Gas Chamber and Pusher Furnaces

Metal Science and Heat Treatment -     

Interaction of a shock wave with a cloud of particles

The present paper is devoted to experimental and theoretical investigation of shock-wave propagation in a mixture of a gas and solid particles with clearly defined boundaries of the two-phase region (cloud of particles). The effect of qualitative transformation of supersonic flow behind a shock wave in a cloud of particles is shown experimentally and substantiated theoretically for volume concentrations of the dispersed phase of 0.1–3%.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 2, pp. 86–99, March–April, 1996.     

Drag of nonspherical particles in a flow behind a shock wave

The early stage of velocity relaxation of nonspherical particles in a flow behind an incident shock wave is considered by the method of multiframe shadowgraphy. A procedure of processing the data on the motion of a free body for determining its acceleration is proposed; in combination with the diagnostic method used, the procedure forms something like a noncontact aerodynamic balance. Novel data on the drag of bodies of irregular shape in a flow behind a shock wave with Mach numbers of 0.5–1.5 and Reynolds numbers of 10⁵ typical of dust explosions are obtained. It is found that the values of drag of a nonspherical bluff body and a sphere under these conditions are similar and exceed the drag of a sphere in a steady flow by a factor of 2 to 3.Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 1, pp. 81–88, January–February, 2005.     

Polymer matrices on the basis of polyacrylamide and β-cyclodextrin-containing pseudorotaxane for prolonged drug release: Synthesis and properties

Polymer cross-linked matrices based on polyacrylamide (PAA) and β-cyclodextrin-pseudorotaxane have been designed. The structure and properties of the objects synthesized were confirmed and studied by a series of methods, involving ultraviolet-, Fourier transform infrared-spectroscopy, thermal mass spectrometry, DSC, X-ray diffraction analysis (WAXS and SAXS). Desorption kinetics (especially significant slowing of desorption process) of some drugs, like metoprolol succinate and loratadine from obtained polymer matrices is shown to be optimal with 10 wt% β-CD-pseudorotaxane in their structure.     

Oscillations and transfer properties of relay feedback systems with time-delay linear plants

Oscillations and transfer properties of relay feedback systems with linear plants having a dead time (time delay) are considered. Poincare maps are found explicitly in terms of the system parameters. The oscillatory and transfer properties are presented in the format of the locus of a perturbed relay system (LPRS), which represents the continuum of all possible periodic solutions and transfer properties of the system with a given linear plant. Conditions of local orbital asymptotic stability are found in terms of the system parameters. The proposed approach is illustrated by examples.     

Sol–Gel Synthesis of Doped Vitreous Materials with the Use of Modified Aerosils

A novel variant of the sol–gel synthesis of silica glasses and optical composites containing transition-metal ions and nanoparticles is developed. Xerogels and glasses containing 10- to 46-nm particles are prepared with the use of aerosils modified by chromium oxide. The structural and physicochemical properties of chromium oxide–modified silica samples are investigated by X-ray powder diffraction, differential thermal analysis, thermal gravimetric analysis, and IR spectroscopy. The optical properties of transparent samples are examined using the transmission spectra and the refractive index distribution over the cross section of the xerogel preform. Xerogels and glasses containing nanoparticles of metallic copper and Cu _x Se are formed in the tetraethoxysilane–aerosil–copper nitrate system. An analysis of the optical properties of the nanocomposites demonstrates that SiO₂ : Cu _x Se nanocomposites can be used as passive Q switches.     

FREQUENCY DOMAIN ANALYSIS OF FAST AND SLOW MOTIONS IN SLIDING MODES

A frequency domain approach to analysis of fast and slow motions in sliding modes is proposed in the paper. The proposed approach is based on the construction of a relay system that is equivalent to the original sliding mode control system and on the application of the locus of a perturbed relay system method. A precise model of the fast motions and a non‐reduced order model of the slow motions for the SISO linear time‐invariant case are obtained as a result of the proposed approach.