Die Entwicklung der Destillationstechnik im 19. Jahrhundert

Development of Distillation during the 19th Century. Up until the end of the 18th century distillation plant consisted only of an evaporation and a condensation unit. The rectification column is an invention of the early 19th century. This article surveys these developments and the advances in alcohol distillation made up to the end of the 19th century. Developements in France, England and Germany are considered separately since different starting materials were used for alcohol production in these three countries. In France the starting material was wine, in England grain, and in Germany potatoes. Wine could be fed directly to the rectification column. Grain first had to be transformed into grain mash before being transferred together with husks to the distillation apparatus. The highly viscous potato mash containing potato pieces and skins produced by a similar process proved particularly hard to handle. The widely varying properties of these raw materials led to development of different equipment in the different countries.     

An explicit numerical time domain formulation to simulate pulsedpressure waves in viscous fluids exhibiting arbitrary frequency powerlaw attenuation

An explicit time domain algorithm is developed which is capable of numerically simulating pulsed pressure waves propagating through media whose attenuation increases with frequency according to a power law dependency. Because of possible noninteger exponents in the power law formulation, standard temporal differential operators cannot be defined and traditional finite difference approximations are therefore inappropriate. We derive a method that is consistent with the fact that the complex wavenumber often must include a nonlinear phase if system causality is to be ensured. This phase is derived from the power law attenuation and, due to their interdependency, the two terms in the wave equation corresponding to attenuation and phase can be combined into a single factor. This so-called dispersion wave equation is mapped into complex discrete-time frequency. In this domain, noninteger exponents can be eliminated via a power series expansion, and the resulting equations transform naturally to discrete time operators. The algorithm is tested by comparing numerically evaluated attenuation with the exact power law form, and the issues of stability in relation to the convergence of the power series and the accuracy of the mapping are investigated     

The effects of orientation and crystallinity on the solvent-induced crystallization of poly(ethylene terephthalate). II. Physical structure and morphology

This series of papers summarizes the results of an experimental research program designed to establish the effects of preexisting orientation and crystallinity on the solvent-induced crystallization of poly(ethylene terephthalate) films. Dimethylformamide was used as a model for a strongly interacting solvent. This paper deals with the morphological and structural modifications induced by the solvent crystallization process. The effects on the structure and morphology of the solvent crystallization were dominated by surface cavitation, creation of voids, and by changes in the degree of crystallinity. The surface structure varied from a spherulitic cavitated structure for films of low orientations (low draw ratios) to a smooth surface at the higher draw ratios. In addition to the change in the surface morphology, an internal void structure was formed due to crystallization taking place in a swollen state. The formation of voids is dependent on the treatment temperature, draw ratio, and the method of solvent removal. The voids collapse upon annealing at high temperatures. Increases in the degree of crystallinity and changes in orientation were dependent on the treatment temperature. The crystallite size goes through a maximum at an intermediate degree of orientation. The crystalline orientation decreases with increasing treatment temperature. The structures formed during solvent treatments did not show any characteristic premelting endotherms at the low draw ratios. In the case of higher draw ratios, a small premelting endotherm was noticeable at a temperature 70°C greater than that of the solvent treatment.     

A general-purpose computer program for studying ultrasonic beampatterns generated with acoustic lenses

A 3-D computer model of a piston radiator with lenses for focusing and defocusing is presented. To achieve high-resolution imaging, the frequency of the transmitted and received ultrasound must be as high as 10 MHz. Current ultrasonic transducers produce an extremely narrow beam at these high frequencies and thus are not appropriate for imaging schemes such as synthetic-aperture focus techniques (SAFT). Consequently, a numerical analysis program has been developed to determine field intensity patterns that are radiated from ultrasonic transducers with lenses. Lens shapes are described and the field intensities are numerically predicted and compared with experimental results