SEMICONTINUOUS EMULSION COPOLYMERIZATION OF BUTYL ACRYLATE-STYRENE†

Butylacrylate (BA)-Styrene (St) copolymers have been synthesized via a semicontinuous emulsion process in which the monomers feeding rate and weight ratios (BA/St) were varied. The feed consisted of only pure monomers which were added to an aqueous solution that contained the emulsifier and initiator

The experimental results show that monomer consumption is governed by the feeding rate as well as by the monomer's reactivity, The average molecular weight decreased as the feeding rate increased independent of the BA/St ratio

Measurement of the latex average particle size and particle number, as a function of the reaction time. showed a complex sequence of particle formation and agglomeration. In general, the average particle diameter increased in direct proportion to the feeding rate. This fact suggests that most probably homogeneous nucleation is preferred over monomer diffusion to the previously formed particles. Additionally, the monomer reactivity ratios (r ₁, r ₂) decreased as the monomer feeding rate was increased

The experimental copolymer compositions determined by gas chromatography and NMR-H⁺ showed that the resulting copolymers were closely homogeneous.     

On the synthesis of all-pass digital transfer functions based on LBR two-pair extraction procedure†

In this paper a simple explicit expression is provided for the parameter a in LBR two-pairs used in the synthesis of all-pass digital transfer functions. The result can be of interest in automated procedures for digital filter design. Further, canonical realizations for this type of two-pairs are given.     

Resampling the output of switched networks†

The use of switches has given the engineers a new tool for modifying the characteristic of networks. Their use is usually that of a modulating process, i.e. to convert the signal wave into a series of amplitude-modulated pulses which are then further handled by a suitable network, usually a filter. The possibility of resampling the output has been investigated; it was found that the phase angle of the second sampler with respect to the first has a significant effect on both the phase and the magnitude of the time function that can be reproduced from the output of the second sampler.     

DESIGN AND TUNING OF A FUZZY CONTROLLER FOR INDOOR AIR QUALITY AND THERMAL COMFORT MANAGEMENT

This paper presents the development and testing of a multi objective fuzzy controller. It is dedicated to the control of thermal comfort and indoor air quality while minimising energy consumption and reducing instabilities are other constraints for this controller. After a brief introduction on the difficult task of indoor climate control, the test cell and its corresponding model is described in the second section. The model has been developed within TRNSYS. Section 3 describes the architecture of the fuzzy controller applied to these control objectives in the test cell. A hierarchical architecture has finally been selected since it is a very flexible architecture and it results in reducing the total number of fuzzy rules. The rule optimisation technique, based on genetic algorithms is also presented in the third section. Simulation results are finally presented. They prove that, after optimisation, the fuzzy controller greatly outperforms a typical ON-OFF controller on all control criteria. Energy consumption is in particular reduced by more than 10%. The fourth section of this chapter presents field experiments among 20 subjects of both ON-OFF control and fuzzy control. If major differences are not observed on the thermal comfort and indoor air quality point of view, these experiments however illustrate the importance of on-line tuning of specific fuzzy rules.     

Structural transformations in titanium carbide during diamond grinding

Mechanically polished surfaces of sintered titanium carbide specimens are studied by scanning electron microscopy, Auger-electron spectroscopy, and electron diffractometry. It is shown that surface layer microplastic deformation occurs during polishing of specimens with diamond powder. This deformation leads to transformation of the FCC-lattice of titanium carbide into the structural polytype 6H. Georgian Technical University, Tbilisi. Republican Center for Structural Studies, Tbilisi. Translated from Poroshkovaya Metallurgiya, Nos. 5-6(407), pp. 91–97, May–June, 1999.     

Developing regimes for the heat treatment of tool steel 1.2344 with a specific structure

A regime for heat-treating forgings of steel 1.2344 (the analog of steel 4Kh5MF1S) has been developed, tested, and optimized to ensure that the structure of the forgings meets the requirements of the NADCA standard and specification SEP 1614. A study was made of the microstructure of forgings of steel 1.2344 after annealing and normalizing under different conditions. It was found that the structure of the forgings made in the forging-extrusion shop at Spetsstal’ meets the NADCA standard and specification SEP 1614 when the forgings are subjected to normalizing and tempering.