Modelling Electromechanical Systems with Electrical Switching Components Using the Linear Complementarity Problem

In this paper, a method for modelling electromechanical systems (EMS) with variable structure in the electrical subsystem is proposed. This structural variability may result from real switches (e.g. relay) or from components with switching characteristics (e.g. diode in first approximation). The aim of the work is to provide a method to model EMS with variable structure in both domains using a unified mathematical theory. For this purpose, the usage of the linear complementarity problem (LCP) for modelling electrical systems containing components with switching characteristics is shown. Starting point of the complete approach is a method for modelling EMS based on the Lagrange formalism. A unified mathematical theory is used to represent such systems taking into account all interactions between the physically heterogeneous substructures. Applying the LCP, it is possible to include switching components into this theory and, this way, to extend the class of EMS which can be captured.     

Electrical spin injection from an n-type ferromagnetic semiconductor into a III-V device heterostructure

The use of carrier spin in semiconductors is a promising route towards new device functionality and performance. Ferromagnetic semiconductors (FMSs) are promising materials in this effort. An n-type FMS that can be epitaxially grown on a common device substrate is especially attractive. Here, we report electrical injection of spin-polarized electrons from an n-type FMS, CdCr(2)Se(4), into an AlGaAs/GaAs-based light-emitting diode structure. An analysis of the electroluminescence polarization based on quantum selection rules provides a direct measure of the sign and magnitude of the injected electron spin polarization. The sign reflects minority rather than majority spin injection, consistent with our density-functional-theory calculations of the CdCr(2)Se(4) conduction-band edge. This approach confirms the exchange-split band structure and spin-polarized carrier population of an FMS, and demonstrates a litmus test for these FMS hallmarks that discriminates against spurious contributions from magnetic precipitates.     

Selecting proteins with improved stability by a phage-based method

We describe a method for the stabilization of proteins that links the protease resistance of stabilized variants of a protein with the infectivity of a filamentous phage. A repertoire of variants of the protein to be stabilized is inserted between two domains (N2 and CT) of the gene-3-protein of the fd phage. The infectivity of fd phage is lost when the three domains are disconnected by the proteolytic cleavage of unstable protein inserts. Rounds of in vitro proteolysis, infection, and propagation can thus be performed to enrich those phage containing the most stable variants of the protein insert. This strategy discriminates between variants of a model protein (ribonuclease T1) differing in conformational stability and selects from a large repertoire variants that are only marginally more stable than others. Because fd phage are exceptionally stable and the proteolysis in the selection step takes place in vitro a wide range of solvent conditions can be used, tailored for the protein to be stabilized.     

Computation of state and input trajectories for flat systems using automatic differentiation

For path planning and trajectory tracking it is necessary to find an input signal for a given output signal, i.e., it is useful to invert the plants model (system inversion). Up to now, system inversion was practical only for simple systems due to the amount of symbolical computations involved. The inversion of flat state-space systems using automatic differentiation will be discussed.     

The performance of minisupercomputers: Alliant FX/8, Convex C-1, and SCS-40

A comparison of the architectures and performance of a set of standard FORTRAN benchmark codes is made of the Alliant FX, Convex C-1, and SCS-40 minisupercomputers.     

An Integrated Line Tracking and Vectorization Algorithm

A method is presented to compute a vector representation of an arbitrary line in a bi-level raster image The line may have varying line width and irregular borders. Furthermore, at line crossings and branches the user is offered the opportunity to choose from the directions in which line tracking may he continued The method avoids thinning and vectorization of chain codes. Instead, a contour follower is used at both sides of the line, and median line calculation is integrated with contour following. This leads to an efficient algorithm, in particular when individual lines have to be interactively extracted from a raster image.     

Transport von gelösten Stoffen im Grundwasser – Untersuchungen am Testfeld Krauthausen

To investigate solute transport, three tracer experiments (bromide, lithium, uranin) were conducted in a heterogeneous aquifer at test site Krauthausen. The impact on transport caused by natural heterogeneity was checked by detailed investigation of transport related parameters of the aquifer. Lithium and uranin compared to bromide showed a clear retardation which increased with decreasing concentrations. The behavior of lithium and uranin can be described by Freundlich isotherms. The longitudinal spreading of the lithium plume was much larger compared to the uranin plume. This can be explained by higher injection concentrations of lithium, the different Freundlich parameters and the different sorption-kinetic behavior. The sorption of lithium and uranin showed good correlation with the clay content and the cation exchange capacity. The specific surface area was only correlation with the sorption of uranin. The vertical correlation length of hydraulic conductivities and of the physico-chemical parameters are of the same order of magnitude