Investigation of ferroelectric phase transitions of water in nanoporous silicates in simultaneous electrical noise and calorimetric measurements

The phase transitions of water in the nanoporous silicate materials SBA-15 and MCM-41 with an ordered system of cylindrical pores have been investigated. Measurements of low-frequency electrical noises (Barkhausen noises) in the frequency range of 1–100 Hz have been performed simultaneously with relative calorimetric measurements. It has been found that the voltage of electrical fluctuations increases approximately 100 times in the temperature range from ?30 to ?50°C, which is associated with the first-order and second-order ferroelectric phase transitions. It has been assumed that the ferroelectric ice XI can be formed in capillary pores of the materials under investigations.     

Topology of an anodically formed oxide film on a silicon single crystal

Physics of the Solid State - The results of investigations of the morphological properties of an oxide film formed on single-crystal silicon by anodic oxidation in distilled water in the...     

Optimum control laws in a non-autonomous dynamic model of a gas field

A model of gas field development described as a nonlinear optimum control problem with an infinite planning horizon is considered. The Pontryagin maximum principle is used to solve it. The theorem on sufficient optimumity conditions in terms of constructions of the Pontryagin maximum principles is used to substantiate the optimumity of the extremal solution. A procedure for constructing the optimum solution by dynamic programming is described and is of some methodological interest. The obtained optimum solution is used to construct the Bellman function. Reference is made to a work containing an economic interpretation of the problem.     

A study of the relationship between the electronic structure and the thermodynamic properties of individual compounds

Based on the “quantum theory of atoms in a molecule,” the Hohenberg-Kohn theorem, and “holographic” theorem, the principles of constructing phenomenological additive models for calculating the thermodynamic properties are considered.     

Leaching of manganese dioxide from porous bodies

Results of a study of the kinetics of manganese dioxide leaching from pores in anodes of solid-electrolyte capacitors are presented. It is shown that manganese dioxide present in pores is the most effectively dissolved at room temperature under treatment with dilute solutions of sulfuric and hydrochloric acids to which hydrogen peroxide is added in not-less-than-stoichiometric amounts according to the reactions MnO₂ + H₂SO₄ + H₂O₂ = MnSO₄ + 2H₂O + O₂?? and MnO₂ + 2HCl + H₂O₂ = MnCl₂ + 2H₂O + O₂??. The initial acid concentration does not exceed 36% for H₂SO₄ and 18% for HCl.     

Extracting the complex energy of broad resonances by the <Emphasis Type="Italic">S</Emphasis>-matrix pole method

A new method is proposed for finding the resonance parameters of a nuclear system, obtained from the phase shift analysis of elastic scattering data, by means of a pole representation of an S-matrix in complex momentum space is proposed. This method is based on the expansion of the potential phase shift into a Taylor series within the area of real momentum near the resonance pole. The coefficients of the expansion and resonance parameters are determined by fitting the analytical expression for the experimental phase shift. The proposed method provides reliable values of the energy and width of broad resonances.     

Feynman formulas for nonlinear evolution equations

Transformations of measures, generalized measures, and functions generated by evolution differential equations on a Hilbert space E are studied. In particular, by using Feynman formulas, a procedure for averaging nonlinear random flows is described and an analogue of the law of large number for such flows is established (see [1, 2]).     

Time-independent reaction–diffusion equation with a discontinuous reactive term

A two-dimensional singularly perturbed elliptic equation referred to in applications as the reaction–diffusion equation is considered. The nonlinearity describing the reaction is assumed to be discontinuous on a certain closed curve. On the basis of the generalized asymptotic comparison principle, the existence of smooth solution is proven and the accuracy of the asymptotic approximation is estimated.