Identification of a dissipation coefficient by a variational method

A generalized inverse problem for the identification of the absorption coefficient for a hyperbolic system is considered. The well-posedness of the problem is examined. It is proved that the regular part of the solution is an L ₂ function, which reduces the inverse problem to minimizing the error functional. The gradient of the functional is determined in explicit form from the adjoint problem, and approximate formulas for its calculation are derived. A regularization algorithm for the solution of the inverse problem is considered. Numerical results obtained for various excitation sources are displayed.     

Phase transitions of liquid crystalline cyanoethyl cellulose solutions under static conditions and in shear field

Phase transitions in the systems cyanoethyl cellulose-DMF, cyanoethyl cellulose-DMAA, and cyanoethyl cellulose-(trifluoroacetic acid + methylene chloride) were studied by means of the cloud-point and polarization microscopy techniques, as well as with a photoelectric polarization unit and a modified plasticorder. It was shown that the LC phase appears at higher concentrations and lower temperatures as the polarity of solvent molecules increases. The shear deformation of cyanoethyl cellulose solutions in DMF and DMAA results in the expansion of the temperature-concentration region of existence of the LC phase. The effect of shear field on phase transitions in cyanoethyl cellulose solutions is nonmonotonic in character.     

Properties of the methyl cellulose-polyvinylpyrrolidone binary system in solution and in the solid state

Rheological properties of dilute and moderately concentrated aqueous solutions of methyl cellulose-polyvinylpyrrolidone blends, as well as the conditions of gelation in them, were studied. Films were obtained from solutions of the polymer blends, and their physicomechanical properties were examined. The range of the compositions corresponding to thermodynamic compatibility of methyl cellulose with polyvinylpyrrolidone was identified by the solvent vapor sorption method and by thermomechanical examinations of the films.     

Thermochemical Analysis of Cyanoethyl Ethers of Cellulose Blended with Polyacrylonitrile

Thermochemical reactions of cyanoethyl ethers of cellulose with polyacrylonitrile in the temperature range of its cyclization were studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 652–654.Original Russian Text Copyright © 2005 by Sazanov, Kutsenko, Novoselova.     

Structure, electron-accepting properties, and reactivity of nitrostilbenes

Nitrostilbenes, nitrostyrenes, nitrotoluenes, and nitrodibenzyls in neutral, radical onion, and dianion forms are studied by quantum chemical, electron spectroscopy, ESR spectroscopy, and cyclic voltammetry methods. The calculated electron affinities of nitroarenes are compared with electrochemical reduction potentials. The dianion form of stilbene is stable provided that it has two nitro groups in the paraposition of the benzene ring. Nitrodibenzyls are converted to the corresponding nitrostilbenes by electrochemical reduction; this is explained by dissociative cleavage of C–H bonds in the trianion radical form of dibenzyl. In reactions of nitroarenes with bases, regioselectivity is determined by spin density distribution and by the conformation composition of the radical onions. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 640–654, July–August, 1998.     

Principles of alignment of multibeam lasers for thermonuclear purposes

The concrete object of the investigation is the alignment of the high-power 12-channel Del'fin neodymium-glass laser facility. The objects of the alignment are the optical channel of the laser installation, the system for pointing and focusing the laser radiation on the target, the system for positioning the target in the focal volume, and the system for monitoring the optical quality of the elements of the laser installation and laser beams and also the conditions of the target irradiation in the vacuum chamber. The list of requirements that must be satisfied by the alignment beams, the possible sources of alignment beams, the makeup of the apparatus, and the methods of aligning the laser facility are considered. The principles and the actual systems of automatic alignment of the optical elements are described, as are the operating models of the automatized units. The problem of simulating the working laser beams by the alignment beams and the possibility of automatizing the control of the spatial and angular characteristics of the laser radiation are discussed. The system for controlling the alignment processes by means of a laser is considered, as is also a scheme for incorporating the automatized alignment subsystem in the overall system for the automation of the Del'fln facility.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 103, pp. 52–83, 1978.     

2-Polyfluoroalkylchromones. 9. Synthesis and structures of 5-(2-hydroxyaryl)-7-polyfluoroalkyl-1,4,8-triazabicyclo[5.3.0]dec-4-enes

2-Polyfluoroalkylchromones reacted with diethylenetriamine at 20 °C to form the corresponding 1,4,8-triazabicyclo[5.3.0]dec-4-ene derivatives. The crystal structures of 5-(2-hydroxyphenyl)-7-trifluoromethyl-1,4,8-triazabicyclo[5.3.0]dec-4-ene and 1-(2-aminoethyl)-7-(2-hydroxy-5-methoxyphenyl)-5-(1,1,2,2-tetrafluoroethyl)-2,3-dihydro-1H-1,4-diazepine were established by X-ray diffraction analysis.     

Hydrodynamic and dynamo-optical properties and conformation of cyanoethyl cellulose molecules in solution

Translational diffusion, velocity sedimentation and viscosity in acetone as well as flow birefringence (FB) and viscosity in cyclohexanone have been investigated for cyanoethyl cellulose (CEC) with degree of substitution 2.6 in the range of M = (24.5?317) × 10³. The dependences of [ν], S_o and D_o on M were obtained. The value of the hydrodynamic constant is $\text{A}{}_0\text{= 3.27 × 10}{}^{\mathrm{?10}}\text{erg deg}{}^{\mathrm{?1}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}$. According to hydrodynamic data, the equilibrium rigidity of CEC molecules is characterized by the length of the Kuhn segment $\text{A = 240 ? 350}\text{A}\text{?}$ and the coefficient of hindrance to intramolecular motion σ = 4.5-5.4. The hydrodynamic diameter of the chain is 8–14 Å. According to the FB data, the value of A is 260 Å. This value is in agreement with hydrodynamic data. The high value of optical anisotropy of the monomer unit, a_| - a_⊥ = 17.8 × 10^?25 cm³, is in agreement with the structure and anisotropy of the substituting groups, and the investigation of orientation angles of FB leads to the conclusion that, apart from high equilibrium rigidity, CEC in solution is characterized by considerable kinetic chain flexibility. The data for CEC are compared with the characteristics of other cellulose esters and ethers.     

Method for intensifying the heat transfer using local heat pulses

The conditions of heat transfer intensification using short local heat pulses applied to a heater cooled by fluids with a boiling curve hysteresis (cryogenic, organic fluids, and others) are considered.