Sufficient algebraic conditions of parametric invariance of the output of a linear stationary system in the first approximation

A problem of generating sufficient algebraic conditions of parametric invariance of the output of a linear stationary system with uncertain parameters in the first approximation is solved based on analytical capabilities of the trajectory sensitivity technique. An example demonstrating the application of the obtained conditions is given.     

Median control of continuous dynamic plants with interval parameters

An algorithm for the synthesis of median modal control of a plant with parametric uncertainties given in interval form is proposed. It is supplemented by the check of relative interval estimate of the system state matrix, that ensures the required interval estimate of the quality indices. The results are illustrated by an example.     

Surface Enthalpy, Enthalpy of Water Adsorption, and Phase Stability in Nanocrystalline Monoclinic Zirconia

A fundamental issue that remains to be solved when approaching the nanoscale is how the size induces transformation among different polymorphic structures. Understanding the size-induced transformation among the different polymorphic structures is essential for widespread use of nanostructured materials in technological applications. Herein, we report water adsorption and high-temperature solution calorimetry experiments on a set of samples of single-phase monoclinic zirconia with different surface areas. Essential to the success of the study has been the use of a new ternary water-in-oil/water liquid solvothermal method that allows the preparation of monoclinic zirconia nanoparticles with a broad range of (BET) Brunauer–Emmett–Teller surface area values. Thus, the surface enthalpy for anhydrous monoclinic zirconia is reported for the first time, while that for the hydrous surface is a significant improvement over the previously reported value. Combining these data with previously published surface enthalpy for nanocrystalline tetragonal zirconia, we have calculated the stability crossovers between monoclinic and tetragonal phases to take place at a particle size of 28 ± 6 nm for hydrous zirconia and 34 ± 5 nm for anhydrous zirconia. Below these particle sizes, tetragonal hydrous and anhydrous phases of zirconia become thermodynamically stable. These results are within the margin of the theoretical estimation and confirm the importance of the presence of water vapor on the transformation of nanostructured materials.     

Quantitative assessment of the tendency of complex multivariable control system to degeneration

The degeneration property of dynamic multivariable control systems is considered. In this work, by degeneration for a multivariable systems is meant primarily a decrease and even a loss of its operating capacity. A technique of quantitative assessment of the tendency of multivariable control systems to degeneration was developed using a singular decomposition of criteria matrices formed on the basis of the matrix formalism of Faddeev-Leverrier algorithm, Gramian representation, matrix coefficient of the expansion of the system output vector in the derivatives of the control input vector, and with the use of the matrix formalism of Sylvester’s and Lyapunov’s equations     

包头地区粉煤灰在混凝土中的应用

本文首先描述了包头地区粉煤灰的化学成份及其特性分析，然后介绍了为改善混凝土特性而掺入最优量粉煤灰的三种实验方法，并给出了整个实验过程和测试结果，在此基础上，作者讨论了包头地区粉煤灰在混凝土中应用的可行性。     

Unit for alleviating the secondary oxidation of steel cast in an open stream on continuous section casters

Results are reported from factory testing of different models of equipment that make it possible to limit the oxidation of steel as it is being cast on the tundish-mold section of continuous casters. A study is made of the effect of the chosen method of protection on point segregation at the edges of the continuous-cast semifinished product and the formation of gas bubbles inside it. __________ Translated from Metallurg, No. 1, pp. 45–47, January, 2007.