Expertensysteme – ein Hilfsmittel der Prozeß-Synthese

Expert systems for process syntheses . Commercial programs used in computer-aided development of chemical processes need a process flowsheet as starting point. Preparation of flowsheets is based largely on human experience, an uncertain kind of knowledge expressed by heuristic rules. These rules are recognized as true and advantageous in most cases without having the validity of a law. Logic programming languages derived from research on artificial intelligence are proven tools for handling heuristics with so-called “expert systems”. The flowsheets proposed by the expert system reduce all theoretically possible results to a few structures. The example of structuring distillation sequences illustrates what can be expected using an “expert system” in the area of “problem solving” by comparing its proposed sequences with optimized problems.     

A 100-MHz ultrasound imaging system for dermatologic and ophthalmologic diagnostics

A major design problem concerning high-frequency broad-band ultrasound imaging systems is caused by the strong dispersive attenuation of the tissue, which gives rise to images with inhomogeneous resolution and poor signal to noise ratio (SNR). To address the noise problem, strongly focused transducers with high energy density in a narrow focal region are utilized, which also provide more isotropic images due to improved lateral resolution. To account for the short depth of the focal area two suitable imaging conceptions are used: 1) synthetic aperture concept and 2) B/D-scan concept. To avoid the inhomogeneity of the images, different transmitter signals for each depth are applied, which are pseudoinversely prefiltered according to the transfer function of the tissue. To gain signal energy required for inverse filtering, a pulse compression technique with nonlinearly frequency modulated chirp signals is utilized. These procedures have been implemented in an ultrasound imaging system, which has been developed in the authors' laboratory for eye and skin examinations, It can be used with transducers in a frequency range from 20 to 250 MHz.