Local laser-induced change of optical properties in the bulk of photochromic porous silicate glass doped by silver and copper halides

The principles of the formation of modified areas of a spherical shape and complex structure in porous glass plates doped by silver and copper halides under the continuous radiation of a fiber laser focused inside the plate have been formulated. The results of the study of the obtained modified areas are given.     

Boron Nitride with Packets of Nanotubes for Microcomposite Ceramics

The possibility of creating microcomposite technical ceramics based on boron pyronitride (BPN) with nanotubes and packets of nanotubes providing a high microplasticity is considered. It is shown that the irradiation by nanosecond proton-ion beams with a high powder density promotes the growth of wurtzite-like BPN based on self-organizing mesoscopic (SOM) particles, SOM-blocks, and nanocrystalline particles. The sizes of SOM-particles and SOM-blocks of the initial and irradiated BPN are determined. The self-organization of nanotubes outside the zone of irradiation has a spiral cyclic nature and is caused by shear deformations of the layers composed of SOM-blocks. Tubes inclined to the surface with symmetry axes of the fifth order and packets of nanotubes of a disk shape are observed. The obtained micrographs are compared with model forms of manifestation of spiral cyclic structures.     

Computer simulation of microcomposite ceramics with high transcrystalline mobility

Computer simulation is used to consider the possibility of creation of microcomposite technical ceramics with a high transcrystalline mobility and to show that allowance for the exchange interactions of atoms through nonequilibrium electrostatic fields causes formation of self-organized mesoscopic (SM) blocks, which provide microplasticity and relaxation of strain at lower temperatures. The simulation results agree with the yield stria observed in mechanical compression tests of A1₂,O₃ specimens obtained from sol-gel solutions. It is shown that the yield stria are directly connected with the sizes of the SM blocks. The high mobility of SM blocks also promotes a decrease in the temperature of the gel → A1₂O₃ transformation.     

Monitoring of the current-distribution uniformity in bipolar transistors from the dependence of internal-feedback factor on collector voltage

On the basis of the two-section model of a high-power bipolar transistor, it is shown that the slope of dependence of the small-signal feedback coefficient on the collector voltage in the presence of defects in the transistor is proportional to the defect size. The setup for the automated monitoring of the current-distribution nonuniformity in the transistor device structure from the indicated dependence with using the combination of linearly increasing and small harmonic variations in the collector voltage is described. The experimental dependences confirming the results of the theoretical analysis are presented.     

Effect of titanium–magnesium catalyst morphology on the properties of polypropylene upon propylene polymerization in a liquid monomer

The effect of the particle size of an IK-8-21 domestic titanium-magnesium catalyst on the properties of polypropylene (PP) produced during the polymerization of propylene in a liquid monomer is studied. Catalysts with particle sizes of 20 to 64 μm are shown to have high activity and identical sensitivity to hydrogen and allow PP to be obtained with a narrow distribution of particles over size, high isotacticity, and close values of crystallinity, melting temperature, and physicomechanical properties. A slight decrease in the activity and bulk density of PP powder is observed when the average size of catalyst particles is increased from 20 to 43 μm. A more notable reduction in the activity and bulk density of PP powder is observed for catalyst with particle sizes of 62 to 64 μm. IK-8-21 catalyst is not inferior to its foreign analogues with respect to the properties of the resulting PP.     

Discrete optimization by optimal control methods I. Separable problems

Two general solution schemes are designed for separable discrete optimization problems. Approximations from below and from above to the optimal value of the quality criterion are determined. These schemes are based on a unified theoretical base—sufficient conditions for the global optimal known in optimal control theory. Known and new methods for defining a resolving function, which is essential for applying these conditions, are described.     

Ensuring the operating capacity of centrifugal equipment in production of calcium-containing additives

Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 3, pp. 21–22, March, 1989.     

Maximum periodic solutions of the Volterra integrodifferential equations in the critical case of a pair of pure imaginary roots

Systems with aftereffect are considered, which are described by integrodifferential equations of the Volterra type in the presence of a small perturbation prescribed by the periodic (or maximum periodic) time function. In the critical case of a pair of pure imaginary roots of a characteristic equation, the question is solved as to existence in the system of maximum periodic motions (i.e., motions tending at the unlimited increase of time to periodic modes) provided that the frequency of the periodic part of disturbance coincides with the natural frequency of a linearized homogeneous system. It is shown that in the analytic case the equations of motion of the system possess a set of the maximum periodic solutions representable by power series in a small parameter specifying a value of the disturbance, and in small arbitrary initial values of uncritical variables of the problem. The conditions of the existence of such solutions are indicated, which are defined by the terms up to the third order of equations.     

Methods of Ellipsoidal Filtration in Nonlinear Stochastic Systems on Manifolds

The theory of analytical design of the modified ellipsoidal conditionally optimal filters was developed. The algorithms of modified ellipsoidal conditionally optimal filters are simpler than the suboptimal algorithms for the normalized a posteriori distributions. The results obtained were used in the problems of designing the vibroprotective equipment of the computer systems.