Calculation of the integral parameters of rotor-type granulators

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 4, p. 19, April, 1992.     

Robust stability of systems with delayed feedback

Some issues in the stability of differential delay systems in the linear and the nonlinear case are investigated. In particular, sufficient robustness conditions are derived under which a system remains stable, independent of the length of the delay(s). Applications in the design of delayed feedback systems are given. Two approaches are presented, one based on Lyapunov theory, the other on a transformation to Jordan form. In the former, sufficient conditions are obtained in the form of certain Riccati-type equations.     

Efficiency of pneumopulse regeneration of bag filter

Pneumopulse regeneration of bag filter has been investigated, and based on it a regression equation for regeneration efficiency has been derived. It has been shown that pulse pressure exerts the dominant influence on the regeneration efficiency.     

Nonlinear black-box modeling in system identification: a unified overview

A nonlinear black-box structure for a dynamical system is a model structure that is prepared to describe virtually any nonlinear dynamics. There has been considerable recent interest in this area, with structures based on neural networks, radial basis networks, wavelet networks and hinging hyperplanes, as well as wavelet-transform-based methods and models based on fuzzy sets and fuzzy rules. This paper describes all these approaches in a common framework, from a user's perspective. It focuses on what are the common features in the different approaches, the choices that have to be made and what considerations are relevant for a successful system-identification application of these techniques. It is pointed out that the nonlinear structures can be seen as a concatenation of a mapping form observed data to a regression vector and a nonlinear mapping from the regressor space to the output space. These mappings are discussed separately. The latter mapping is usually formed as a basis function expansion. The basis functions are typically formed from one simple scalar function, which is modified in terms of scale and location. The expansion from the scalar argument to the regressor space is achieved by a radial- or a ridge-type approach. Basic techniques for estimating the parameters in the structures are criterion minimization, as well as two-step procedures, where first the relevant basis functions are determined, using data, and then a linear least-squares step to determine the coordinates of the function approximation. A particular problem is to deal with the large number of potentially necessary parameters. This is handled by making the number of ‘used’ parameters considerably less than the number of ‘offered’ parameters, by regularization, shrinking, pruning or regressor selection.     

Use of biocompatible calcium-phosphate glass ceramic BGC in surgical treatment of maxillary cysts

The possibility of using the granulated form of biocompatible material made of calcium-phosphate glass ceramic BGC for treatment of maxillary cysts was demonstrated.     

Mathematical methods of experiment design for determining the optimum production parameters for magnesite — Spinel roof brick

Conclusions It was shown that it is possible and advantageous to apply mathematical methods of experiment design when developing and analyzing the technological processes in the production of refractories.The interpolation models were constructed with very little effort, are important for practical purposes and cannot be obtained by conventional experimental methods in which the factors are varied one at a time.The calculations showed that for a product having a cold-crushing strength of 685 kg/cm² and an open porosity of 12% the spinel must contain 60% alumina and no chromite, the molding composition must contain 10% of this spinel, and the molded product must be fired at 1700°C.Translated from Ogneupory, No. 2, pp. 19–23, February, 1975.     

Photoalignment dynamics of azo dyes series with different coordination metals

There are many photoaligned azo dyes that can be used for orientation of liquid crystals in various display devices. However, the structure of these compounds needs to be optimized to increase the rate of the process of molecule photoalignment, as well as to spread the application of these compounds. The main coordination metal that presents in the molecules of azo dyes is sodium derivatives. The use of other alkali metals remains an open question. We used quantum‐chemical computation methods and reversible intermolecular bonding model to determine the effect of metal coordination on the velocity of photoalignment. The theoretical predictions were experimentally verified using sodium, potassium, lithium, and cesium salts of the model azo dye synthesized by us. We conclude that potassium azo derivatives are the fastest, ceteris paribus.     

Hydrodynamic contact between a rotating roll and a semipermeable tray

A viscous fluid flow in the gap between a side surface of a rotating roll and a rectangular cavity with a semipermeable bottom surface is considered in the Reynolds approximation.Notation x, y, z Cartesian coordinates - U peripheral velocity of the roll - W translational velocity of the tray - h gap height - h ₀ minimum gap - side gap - v _x,v _y,v _z velocity components - K coefficient of channel wall permeability - P,504-1 dimensional and dimensionless pressures - R roll radius - S channel width - fluid viscosity - angle - x₀,₁, , dimensional and dimensionless coordinates of the flow zone boundaries - dimensionless permeability - friction - ,q geometrical simplexes - dimensionless variable - Q bulk flow rate of fluid - F buoyancy force - N power - I ₁,I ₂ integral parameters of flow - ₁, ₂ angular velocities of rotor and cylinder - _c fluid density - q gravity acceleration - Re Reynolds number - R ₁,R ₂ radii of cylinder and rotor in a granulator Volgograd Technical University. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 4, pp. 612–618, July–August, 1995.     

Computer mediated communication for social and academic purposes: Profiles of use and University students’ gratifications

The present study approaches the Internet as a social space, where university students make use of computer mediated communication (CMC) applications, i.e. e-mail, instant messaging and social network sites, in order to satisfy social and academic needs. We focus on university students, because they represent one of the most avid groups of CMC users and additionally, because they are expected to carry their perceptions of media with them into the work place and their social life. In order to investigate this issue, we conducted an empirical research using, as a target group, a sample of students from a specific Greek University. Grounded in the “uses and gratifications” perspective, we investigated the various profiles of CMC use by students along with (a) the students’ perceptions about social and academic usefulness of CMC applications, (b) the extent up to which these perceptions are correlated with students’ prior experience with the use of CMC applications, and (c) how both of these factors can predict the frequency of present use of CMC for social or academic purposes respectively. The results reveal that although these three CMC applications constitute “functional alternatives” (media that satisfy similar needs) they are different to the degree of their “functionality” for the gratification of social and academic needs. Furthermore, the degree of CMC use by students is not correlated with the years of CMC experience, but with the profile of use that students dynamically adopt according to their daily needs and preferences. The results provide evidence for the current CMC use by university students and can be useful for the implementation of further academic policies regarding CMC use in Higher Education settings.