Worst‐case control policies for (terminal) linear–quadratic control problems under disturbances

We consider linear control systems under uncertainties. For such systems we solve the problem of constructing worst‐case feedback control policies that are allowed to be corrected at m fixed intermediate time moments. We propose two types of the approximative control policies. All of them guarantee that for all admissible uncertainties the terminal system state lies in a prescribed neighborhood of a given state x_* at a given final moment, and the value of the cost function does not exceed a given estimate. It is shown that computation of the estimate for each policy is equivalent to solving a corresponding convex mathematical programming (MP) problem with m decision variables. Based on the solution of the MP problem, we derive simple explicit rules (which can be easily implemented on‐line) for constructing the corresponding control policy in the original control problem. Copyright © 2009 John Wiley & Sons, Ltd.     

Vion chemisorptive fibers — Materials for concentrating uranium ions and noble-metal ions from slightly mineralized natural waters

Conclusions -- Vion chemisorbents make it possible to obtain concentrates of uranium and certain noble metals from weakly mineralized swamp waters having a concentration of these metals which is several orders of magnitude lower.-- This affords the possibility of using Vion chemisorbents to detect industrial accumulations of the indicate elements under the conditions of swamps or of regions close to them.Translated from Khimicheskie Volokna, No. 2, pp. 31–32, March–April, 1993.     

Composition inhomogeneity and structural defects in Czochralski grown Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript> solid solution crystals

The relationship between the plastic strain and the inhomogeneity of germanium distribution in single crystals of Ge _x Si_{1 ? x} (x = 4–9 at %) solid solutions grown using the Czochralski method has been studied. It is established that plastic straining develops via the nucleation of dislocations at their sources occurring in the Ge segregation bands, while the inhomogeneous profile of Ge distribution across the growth direction is caused by thermoelastic stresses.     

Effect of Melting Conditions on Chromium-Nickel Alloy Kh20N80 Properties

Metallurgist - Physical properties of alloy Kh20N80 in a liquid state are studied. Critical temperatures are established above which heating makes it possible to transfer melt into a...     

Structural and electrical properties of SiGe-on-insulator substrates fabricated by direct bonding

A new method for fabricating SiGe-on-insulator substrates, i.e., direct bonding of thermally oxidized Si wafers with Si_{1 − x} Ge _x wafers cut from Czochralski-grown crystals, is suggested. Si_{1 − x} Ge _x layers no larger than 10 μm thick in SiGe/SiO₂/Si compositions were fabricated by chemical mechanical polishing. To increase the Ge content in the Si_{1 − x} Ge _x layer, thermal oxidation was used. It was shown that the increase in the Ge content and heat treatment procedures at 1250°C are not accompanied by degradation of structural and electrical characteristics of Si_{1 − x} Ge _x layers.     

Structure and properties of a Pb-Ca-Sn battery alloy crystallized under nonequilibrium conditions

We have studied the properties of a Pb-Ca-Sn alloy for the positive current collector of lead-acid storage batteries, prepared by an existing industrial process and an experimental technique that involves melt jet quenching from the liquid state (QLS). The QLS process ensures good stability of the properties and structure of the alloy at elevated temperatures. Doping with trace levels of barium is shown to influence the properties of QLS ribbons.     

Effect of High-Gradient Directional Crystallization on the Structure and Mechanical Properties of Corrosion-Resistant Nitrogen-Bearing Martensitic Steel 08Kh14AN4MDB

A comparative study of the structure and properties of corrosion-resistant nitrogen-bearing martensitic steel 08Kh14AN4MDB produced by methods of high-gradient directional crystallization (HGDC) and traditional crystallization is performed. The method of HGDC ensures considerable disintegration of the structural components of the steel and lowers the dendritic segregation of the alloying elements. The metal with such structure possesses enhanced strength and ductility.     

Effect of heat treatment on the wear resistance of high-carbon and high-nitrogen steels subjected to abrasive wear

The effect of quenching and tempering on the capacity of steels based on chromium-carbon, chromium-nitrogen, and carbon-manganese austenite for strain-induced martensitic transformation, hardening, and wear resistance in the process of abrasive wear is studied. The steels contain 1–1.2% C or N and 18% Cr or Mn. The wear resistance of the studied steels having a structure of metastable austenite is compared to that of steel 110G13. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 29–33, April, 2006.