Reactions of dialkoxicarbenium ions with styrene and 1.1-diphenyl ethene

Summary Several dialkoxicarbenium ions have proved to initiate the cationic polymerization of styrene. In order to elucidate the mechanism of initiation, some of these dialkoxicarbenium ions were reacted with 1.1-diphenyl ethene and the reaction products are described.     

Untersuchungen zu Zusammenhängen zwischen Schichtmorphologie und Herstellungsbedingungen an amorphen Siliziumnitridschichten

Electron microscopic investigations of magnetron sputtered amorphous SiN_x-coatings showed, that morphology changes with variation of working gas pressure and substrate position corresponding to the Structure Zone Model by Thornton. Increasing working gas pressure and displacement of substrate to larger radial distances influence columnar structures. Energy of particles and adatom mobility decrease with increasing pressure. In positions far from the centre of deposition there are more particles with oblique incidence. This leads to a shadowing mechanism. Columnar diameter increases and packing density decreases. The influence of working gas pressure and angle of incidence bears also an effect on the behaviour of mechanical stress. Coatings with coarse columnar structures have lower mechanical stress than coatings with fine columnar structures.     

Grain Boundary Films in Rare-Earth-Glass-Based Silicon Nitride

The thickness of the intergranular films in Si₃N₄ densified with lanthanide oxides has been systematically investigated using high-resolution transmission electron microscopy. Four lanthanide oxides—La₂O₃, Nd₂O₃, Gd₂O₃, and Yb2O3—as well as Y₂O₃ are chosen so that the results will reflect the overall trend in the effect of the lanthanide utilized. The film thicknesses increase with increasing ionic radius of the lanthanide. In addition, Si₃N₄ particles flocculated into isolated clusters in the lanthanide-based glasses are also characteristically separated by an amorphous film whose thickness is similar to that in the comparable polycrystalline ceramics, demonstrating that the film thickness is dictated entirely by the composition and not by the amount of the glass phase present.     

An area-efficient bit-serial integer and GF(2) multiplier

This paper presents the design of a new multiplier architecture for normal integer multiplication of positive and negative numbers as well as for multiplication in finite fields of order 2ⁿ. It has been developed to increase the performance of algorithms for cryptographic and signal processing applications on implementations of the Instruction Systolic Array (ISA) parallel computer model [M. Kunde, H.W. Lang, M. Schimmler, H. Schmeck, H. Schröder, Parallel Computing 7 (1988) 25-39, H.W. Lang, Integration, the VLSI Journal 4 (1986) 65-74]. The multiplier operates least significant bit (LSB)-first for integer multiplication and most significant bit ( )-first for finite field multiplication. It is a modular bit-serial design, which on the one hand can be efficiently implemented in hardware and on the other hand has the advantage that it can handle operands of arbitrary length.     

Aperiodic Languages in Concurrency Monoids

Automata with concurrency relations are labelled transition systems with a collection of binary relations indicating when two events, in a given state of the automaton, are concurrent. We investigate concurrency monoidsM( ) comprising all finite computation sequences of , modulo a canonical congruence induced by the concurrency relations, with composition as monoid operation. Under suitable assumptions on we obtain a characterization of the star- free languages ofM( ). This generalizes a classical result of M. P. Schützenberger and a result of G. Guaiana, A. Restivo and S. Salemi in trace theory.     

Recording,processing, and analysis of digital high-speed sequences in glottography

A new high-speed system for recording, processing, and analyzing vocal fold vibrations has been developed. Results obtained with this system are discussed from the technical and the medical points of view. Laryngeal movement can be recorded with a digital high-speed camera, at a maximum speed of about 5 600 frames/s and the sequence can contain as many as 8 192 single frames. Application specific software for adaptive, semiautomatic, motion analysis is used to calculate and plot the glottograms for selected points on each vocal cord. From the data obtained, we can calculate speed, acceleration rates, the fundamental frequency, amplitudes, and perturbation parameters. This approach to laryngeal examination, based on the digital films, motion plots and characteristic statistics, is a practicable method that promotes the possibilities of quantitative and graphic analysis of the moving vocal folds and overcomes the disadvantages of the currently common examination methods.     

Ferroelastic Domain Switching in Tetragonal Zirconia Single Crystals—Microstructural Aspects

Ferroelastic domain switching is one of the possible toughening mechanisms in ceramic materials. Microstructural evidence of domain reorientation (switching) in polydomain tetragonal zirconia single crystals is observed upon the application of a unidirectional compressive stress at 1000° and 1400°C. Dark-field imaging of the three {112{ tetragonal twin variants in a [111] zone indicates that two sets of twin variants grow at the expense of the third set upon application of uniaxial compression. The diminishing variant is the one with its c axis parallel to the compression axis. Inducing cracks into polydomain tetragonal zirconia single crystals provides further evidence of domain reorientation near the crack surface. It is noted again that two sets of twin variants grow at the expense of the third set. A construction for the orientation relationship of domains and their twin boundaries is presented, and a relation between shear stress and reorientation is proposed.