Physik der Cd-, Se- und CdSe-keimbildung

The method, described earlier by the same author in this journal, for measuring the critical densities of molecules above the substrate during the critical state of nucleation of layers is applied to the Cd, Se and CdSe system. The mechanism of CdSe synthesis from the components arriving at the substrate during the sublimation of the compound is established from the results obtained.     

Die Polymerisation von Lactamen. VII. Die Autopolymerisation von 8-Capryllactam

By heating of anhydrous 8-capryllactam to 240–280°C in the absence of catalysts polymerization takes place. The polymerization is characterized by a short induction period which decreases with increasing temperature. The degree of polymerization remains almost constant in the region of 40 to 90 percent of polymer content, in the region of high content of polymer the degree of polymerization increases rapidly. At higher temperatures insoluble, crosslinked products are formed. The possible mechanism of autopolymerization of lactames is discussed.     

Polymerization initiated with polymeric compounds,II

The polymerization of methyl methacrylate initiated by the copolymers methacrylaldehyde — styrene — divinylbenzene and acrylaldehyde — ethylene dimethacrylate in the absence of usual initiators was investigated. The polymerization was found to proceed fairly readily and fast. Acceleration can be achieved by adding glycerylaldehyde. An increase in the surface of the initiating copolymer favourably influences the reaction rate; at the same time, however, physical trapping of ungraft poly(methyl methacrylate) molecules in the macroporous initiator seems likely to occur. It was also found that only copolymers containing aldehyde groups could be used for initiation and that besides MMA some other monomers could be polymerized in this way, such as glycidyl methacrylate, acrylic and methacrylic acid, acrylonitrile, and alkyl acrylate.     

The silver catalyst in the hydrophobic oxygen electrode

Ten sorts of silver powder were tested as the catalysts for hydrophobic air electrodes in an alkaline electrolyte. The fine grain catalysts meet the demands of the electrodes better than the catalysts with large surface area which proved not to be satisfactory. The catalyst prepared by reduction of the aqueous suspension of a solid silver salt has the best properties. Electrochemical electrode behaviour is improved by using pure oxygen. The characteristics of some silver catalysts in hydrophilic electrodes were also determined.     

Development of fatigue cracks in complex mechanical structures

The paper summarizes some theoretical and experimental activities concerned with reliability problems of mechanical structures within advanced Czechoslovakian scientific and research institutions. The aim of the paper is directed to the system concept of the fatigue damage mechanism as acting on real mechanical structures in real operational conditions or in those being simulated in laboratories. Such a concept—which has long been emphasized by Prof. A. M. Freudenthal—is based herein on the knowledge gained by studying large-scale structure failures namely in aeronautics.     

Determination of the electromechanical coupling factor of gallium orthophosphate (GaPO4) and its influence on resonance-frequency temperature dependencies.

The quartz homeotype gallium orthophosphate (GaPO4) is a representative of piezoelectric single crystals of large electromechanical coupling factor. It is known that its coupling factor kappa26 associated with the resonators vibrating in the thickness-shear mode is approximately two times greater than that of quartz. This property increases the spacing between the series and parallel resonance frequencies of resonators, as well as the difference between the resonance frequency temperature dependencies of the fundamental and harmonic resonance frequencies of resonators vibrating in the thickness-shear mode. In this paper, the methods for determination of the coupling factor kappa26 are presented, and the computed values are compared with the measured ones. The influence of the coupling factor to the resonance-frequency temperature dependencies of the fundamental and third harmonics of selected rotated Y-cut GaPO4 resonators vibrating in the thickness-shear mode is presented. The purely elastic case for a laterally unbounded plate, which corresponds closely to the limiting case of high harmonic resonance frequency-temperature behavior was assumed for the calculations. The computed temperature coefficients for the Y-cut orientation and calculated turnover point temperatures TTP for different (YX1) orientations are presented.     

The business case for energy management in high-tech industries

The high-technology sector – characterized by facilities such as laboratories, cleanrooms, and data centers – is often where innovation first occurs. These facilities are sometimes referred to as the “racecars” of the buildings sector because new technologies and strategies to increase performance often trickle down to other building types. Although these facilities are up to 100 times as energy-intensive as conventional buildings, highly cost-effective energy efficiency opportunities are often overlooked. Facility engineers are in the trenches identifying opportunities to improve energy productivity but often are unable to make the broader business case to financial decision makers. This article presents the technical opportunities for reducing energy costs, along with their broader strategic value for high-tech industries.

Simplified melting rate correlation for radioactive waste vitrification in electric furnaces

A recently proposed glass melting rate correlation (MRC) equation expresses an essential relationship between the melting rate and material and process variables (melt viscosity, cold-cap bottom temperature, feed-to-glass conversion heat, melter operating temperature, and bubbling flux). It agreed well with data for high-level waste (HLW) melter feeds processed in an electric melter. However, the nonlinear form and four coefficients made the original MRC somewhat cumbersome for representing existing data sets. Introducing new variables (glass melt density and depth of melt pool) makes the new MRC more broadly applicable. Also, reducing the number of coefficients to two simplifies it substantially. The simplified generalized MRC demonstrates good agreement with an extended data set encompassing additional melter feeds and melter sizes.