Foamed nitride-bonded silicon carbide refractories

Conclusions We obtained foamed silicon carbide insulating material with a nitride bond. The nitride bond is formed from a mixture of silicon nitride of the- and-modifications upon reaction with nitrogen. The formation of the nitride commences at about 1200°, and is practically complete at 1450°; the rate of nitriding of the foam ceramic is much greater than in dense specimens. The material has a homogeneous phase composition which is an advantage compared with foamed silicon carbide containing a complex bond obtained in carbon fillings.The foamed insulating brick based on nitride bond possesses a high thermal-shock resistance and structural strength at elevated temperatures. The strength is increased with an increase in the apparent density. The material is characterized by moderate mechanical strength, typical for silicon carbide refractories of this type [1, 3, 4].The foamed silicon carbide brick with a nitride bond can be recommended for service at high temperatures in nonoxidizing atmospheres when substantial thermal-shock resistance is required.Translated from Ogneupory, No. 7, pp. 48–51, July, 1970.     

Estimation of the functional dependence of time series for the class of regression functions partially covered by a finite <Emphasis Type="Italic">ε</Emphasis>-net

The problem of estimating the functional dependence of time series on the time index is considered in the case of short data sample. The uniform convergence of an empirical risk functional to a theoretical one is proved for the case where the parametric class of regression functions can be partially covered by a finite ε-net for some of its parameters. The functional dependence for the polynomial class of functions is estimated as an example.     

Solution of problems on the stress state of an elastic medium with an inhomogeneous orthotropic cylindrical inclusion

A numerical-and-analytical approach to the investigation of the stress state of an elastic medium with an inhomogeneous cylindrical inclusion is proposed. The stress state is presented as a superposition of two state—the main state written in the analytical form and the disturbed one determined using analytical procedures and a numerical method. The stress state in the vicinity of the hollow cylindrical inclusion is analyzed. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 48–58, July–August, 1999.     

A Rational Compromise in the System Problem of Disclosure of Conceptual Uncertainty

A general approach and methods are proposed for matched system solution of the following sequence of interconnected problems: the construction of a set of objective functions from empirical data under conceptually uncertain conditions, the determination of a Pareto set under the condition of a rational mutual matching of the set of values and the domain of objective functions, and a multicriterion choice of a rational solution on a Pareto set under the condition of a compromise between inconsistent objectives. As a result, new possibilities are opened up for finding rational compromises in multicriterion problems of conceptual design, situation prediction, and innovation planning.     

Cordierite ceramics—Spalling-resistant high-melting refractories

Conclusions The production technology of cordierite refractories from fireclay and magnesite differs from other processes in that the components have to be finely ground.The components must be accurately apportioned and the mass thoroughly mixed preferably in batch mixers. Otherwise, the production process of cordierite refractories does not differ from that of chamotte brick.The use of fireclays with a high Al₂O₃ content (38%) and magnesite eliminates the need for commercial alumina.     

EEG pharmacodynamics upon single administration of seduxen in healthy volunteers

We have examined the type I collagen protein, RNA, and cDNA of 2 children with moderately severe (type IV) osteogenesis imperfecta (OI). They have in common a non-lethal form of OI with ambulatory potential, overmodification of type I collagen protein, and a substitution of serine for glycine in the collagen chain produced by one alpha 1(I) allele. The first child (Marini et al.: J Biol Chem 264:11893-11900, 1989) is now 7 years old, with the height of a 3-year-old. Her course includes significant remodeling of lower long bones and 4 femur fractures. She walks independently. A mishmatch was detected in her alpha 1(I) mRNA using RNA/RNA hybrids; it was demonstrated to be due to a G-->A point mutation in one allele of alpha 1(I), resulting in the substitution of serine for glycine 832. The second child is now 6 1/2 years old, with the height of 1 1/2-year-old. Her history includes significant bowing of femurs and tibias, 6 femur fractures, S-curve scoliosis, compression of all lumbar vertebrae, and limited short-distance walking with braces. Her alpha 1(I) mRNA has also been studied by RNA hybrid analysis; there is a single G-->A change in one alpha 1(I) allele causing the substitution of serine for gly 352. Both children have moderately severe OI. However, the serine substitution at gly 352 is associated with a more severe phenotype then is the serine substitution at gly 832. Compared to substitutions described in other cases of OI, the serine 352 is located in the middle of a cluster of cysteine substitutions associated with non-lethal OI.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Praseodymium and Lanthanum Substitution for Bismuth on the Thermoelectric Properties of BiCuSeO Oxyselenides

Semiconductors - The&nbsp; results &nbsp;of &nbsp;investigating &nbsp;the&nbsp; thermoelectric &nbsp;properties of the bulk р-type oxyselenides Bi1 –xPrxCuSeO (x...     

On the Numerical Solution of the Problems of Deformation of Anisotropic Plates with Holes

We propose an approach to the analysis of the stress-strain state of plates with holes based on the numerical parametrization of doubly connected domains, reduction of the original nonlinear boundary-value problem to a sequence of linear two-dimensional problems, and integration of these problems by using a stable numerical method. The influence of the shape and location of the hole on the stress-strain state of a square plate is investigated.     

Stress-strain state of an open spherical shell of a medium thickness

We study the stress-strain state of a medium thickness spherical shell with a hole in the vicinity of the pole in a geometrically nonlinear statement using the classical Kirchhoff-Love model and refined Timoshenko-type model that takes into account the transverse shear strains. The study is based on the construction of an orthogonal curvilinear system of coordinates of a median surface that presents a doubly-connected domain and also on the reduction of the original nonlinear boundary problem to a sequence of linear two-dimensional problems and these latter to one-dimensional ones whose integration is performed by a robust numerical method. Using an open spherical shell as an example, the influence of the transverse shear strain on its stress-strain state is investigated under the action of uniform and nonuniform loads. As compared to the classical model, the use of the Timoshenko-type model is shown to result in a considerable refinement of displacements near the hole. __________ Translated from Problemy Prochnosti, No. 5, pp. 68–78, September–October, 2006.