High‐speed melt spinning of various grades of polylactides

Five kinds of polylactides (PLAs), with different D ‐lactide contents and tacticities, were subjected to high‐speed melt‐spinning experiments. In addition to stereochemical purity, the PLA types differed in molecular mass and molecular mass distribution. The properties of the different PLA materials were characterized by thermogravimetry, differential scanning calorimetry, dynamic mechanical analysis, size exclusion chromatography, and ¹H‐NMR and ¹³C‐NMR spectroscopy. The material was spun with a high‐speed spinning process within the range 2000–5000 m/min. The physical and tensile properties of the fibers were determined. The maximum tensile properties of the fibers were a 300 MPa tenacity at an elongation at break of 30% and a tensile modulus of 6.8 GPa. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 800–806, 2004     

Lie compensator design for exact linearization of inverter-fed induction machines

Differential-geometry methods enable the design of a Lie compensator that exactly linearizes the total system including the nonlinearities of an induction motor. The aim of this work is to prove under which circumstances the five equations of the induction motor are exactly linearizable and to figure out the linearization unit details as a basis for a linear controller. The use of computer-algebraic procedures facilitates the evaluation of the complex calculations. Simulations and the comparison with measurements of practical plants show that the linearization is successful and that the over-all system including induction motor, linearization circuit and controller obeys optimal tracking performance.     

High temperature deformation behavior of crystallized precursor-derived Si-B-C-N ceramics

Annealing of amorphous precursor-derived Si-B-C-N ceramics for 3 h at 1800°C in 15 bar nitrogen yielded a material consisting of SiC with a mean grain size of about 100 nm, embedded in a turbostratic B-C-N phase. The deformation behavior of this material was investigated by compression tests at 1400°C in air. Dependent on the applied stress the strain rate decreased with time. The deformation rate consists of a stress dependent component that is proportional to the applied stress, which indicates that this part of the deformation mechanism is based on viscous flow. Furthermore, the influence of oxidation on the deformation behavior is investigated.     

Visionen in der akademischen Lehre — Bakkalaureats- und Magisterstudium der Elektrotechnik an der Technischen Universität Wien

To cope with the high dynamics in engineering science and to comply with the European objectives in academic education the Faculty of Electrical Engineering and Information Technology at the Vienna University of Technology has introduced new curricula in 2003/04. They comprise (1) a bachelor curriculum, (2) five graduate studies leading to the master degree of “Dipl.-Ing.” and (3) postgraduate studies towards the degree of Doctor of Science. The article describes the new structure and its advantages with respect to flexibility, topicality and mobility for both the alumni and their prospective employers.