SMArDT modeling for automotive software testing

Efficient testing is a crucial prerequisite to engineer reliable automotive software successfully. However, manually deriving test cases from ambiguous textual requirements is costly and error-prone. Model-based software engineering captures requirements in structured, comprehensible, and formal models, which enables early consistency checking and verification. Moreover, these models serve as an indispensable basis for automated test case derivation. To facilitate automated test case derivation for automotive software engineering, we conducted a survey with testing experts of the BMW Group and conceived a method to extend the BMW Group's specification method for requirements, design, and test methodology by model-based test case derivation. Our method is realized for a variant of systems modeling language activity diagrams tailored toward testing automotive software and a model transformation to derive executable test cases. Hereby, we can address many of the surveyed practitioners' challenges and ultimately facilitate quality assurance for automotive software.     

Transient flow behavior of complex fluids in microfluidic channels

The ongoing development of microfluidic devices involves the use of highly complex fluids, even of multiphase systems. Despite the great achievements in the development of numerous applications, there is still a lack in the complete understanding of the underlying physics of the observed macroscopic effects. One prominent example is the flow through benchmark contractions where micro- and even macroscopic explanations of some of the occurring flow patterns are still missing. Here, we study the development of the flow profiles of shear thinning semi-dilute polymer solutions in microfluidic planar abrupt contraction geometries. Flow profiles along the narrow channel part are obtained by μ-PIV measurements, whereby the pressure drop along the microfluidic channel as well as the local transient viscosities downstream to the orifice are computed. A relaxation process of the flow profiles from an initially parabolic shape to the flattened steady-state flow profile is observed and traced back to the polymer relaxation.     

Effect of electron beam-induced deposition and etching under bias

Electron-beam-induced deposition (EBID) and etching (EBIE) provides a simple way to fabricate or etch submicron or nanoscale structures of various materials in a direct-write (i.e.nonlithographic) fashion. The growth rate or the etch rate are influenced by many factors such as beam energy, beam current, temperature of the substrate material, pressure of the chamber, and geometry of the gas injector etc. The mechanism of EBID and EBIE involves the interaction of the incident electron beam or emitted electron from the target material. The role of these electrons is still not completely understood although the contribution of low energy secondary electrons (SE) has been assumed to be the dominant contributor of EBID and EBIE based on its overlap with the dissociation cross section. We have studied the growth and etching phenomenon under various biasing conditions to investigate how low voltage biasing of the substrate affects secondary electron trajectories and subsequently modifies electron-beam-induced deposition and etching.     

Modulare hierarchische Modellierung als Grundlage der Software- und Systementwicklung

Zusammenfassung  Die Entwicklung komplexer eingebetteter Softwaresysteme, wie sie heute beispielsweise in Telekommunikationssystemen, Fahr- oder Flugzeugen oder mit der Steuersoftware von Automatisierungssystemen im Einsatz sind, erfordert ein strukturiertes, modulares Vorgehen und angemessene Techniken zur pr?zisen Beschreibung von Anforderungen, der Architektur des Systems mit ihren Komponenten, der Schnittstellen zur Systemumgebung und zwischen den internen Komponenten, der Wechselwirkung zwischen gesteuertem und steuerndem Teilsystem und schlie?lich der Implementierung. Mit dem frühzeitigen und durchg?ngigen Einsatz geeigneter Modelle (Stichwort UML (,,Unified Modeling Language“) und MDA (,,Model Driven Architecture“)) werden gro?e Hoffnungen verbunden, die Entwicklungsaufgaben beherrschbarer zu gestalten. Dieser Artikel beschreibt die theoretischen Grundlagen für ein konsequent modellbasiertes Vorgehen in Form eines zusammengeh?rigen, homogenen und dennoch modularen Baukastens von Modellen, der hierfür zwingend erforderlich ist. Besondere Schwerpunkte liegen hierbei auf den Themen

High-resolution microstructural investigations of interfaces between light metal alloy substrates and cold gas-sprayed coatings

Interfaces between light metal alloys, aluminum AA7022, and magnesium AZ91, and optimized cold gassprayed zinc-based coatings are characterized. The analyses include scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). Investigations by SEM show a seam with intensive mixing of the substrate and coating material, which is indicated by different values of gray due to element contrast. In energy-dispersive spectroscopy analyses, increased zinc concentrations compared with the substrate material are detected in <1 μm thick vortexes inside the seam. The TEM investigations prove that these areas consist of a homogeneous solid solution and submicron-sized or nanosized intermetallic phases with different concentrations of aluminum, zinc, and magnesium. Because diffusion processes cannot result in the observed microstructure. local melting followed by precipitation of intermetallic phases is concluded as the consequence of the intensive mechanical interaction at the substrate-coating interface during particle impact during the cold gas spraying of zinc on magnesium or aluminum substrates. The original version of this paper was published in the CD ROM Thermal Spray Commects: Explore Its Surfacing Potential, International Thermal Spray Conference, sponsored by DVS, ASM International, and HW International Institute of Welding, Basel, Switzerland, May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany.     

Development and trends in HVOF spraying technology

Three actual trends in development of HVOF spraying technology are described and discussed. The trends concern application fields as well as gun and feedstock characteristics. At the example of demountable draw bars it is shown that HVOF sprayed cermet coatings are capable to protect light weight material components subject to dynamical load against wear without detraction of fatigue strength. Personnel and production time savings can be exploited. High deposition efficiency at considerable powder feed rate, high density and negligible oxygen content in corrosion protective iron or nickel based coatings is achieved for spraying with newly developed HVOF guns operating at increased combustion chamber pressures. Also spraying of highly reactive materials like titanium under atmospheric conditions becomes feasible. A major obstacle for industrial use of respective coatings is the lack of adapted characterisation methods that permit to ascertain corrosion protective function. Ultrafine powder feedstock is used in order to reduce overall costs of wear protective cermet coatings due to the possibility to finish coatings by comparatively cheap belt grinding. However, it is shown that the replacement of coatings produced with conventional powder size fractions requires careful consideration of the particular tribological system. While cermet coatings produced with ultrafine powders outperform conventional coatings for sliding wear conditions, their capability to withstand dry abrasive wear stress is poor. The benefits concerning coating production costs may be outweighed by significantly decreased component life time.     

Cross-section analysis of organic light-emitting diodes

The 'lift-out' technique using a focused ion beam microscope was applied to prepare cross-sectional specimens of organic light-emitting diodes for use in transmission electron microscopy. The focused ion beam equally thins the organic/inorganic hybrid devices despite the difference in material hardness of the compounds. This allowed to overcome preparation difficulties of conventional techniques such as ion thinning or ultra-microtomy. Two different samples were prepared and studied by both conventional transmission electron microscopy and analytical electron microscopy to display some of the investigation possibilities which become available with this sample preparation method.     

Resonance enhanced dynamic light scattering

We present a novel light scattering setup that enables probing of dynamics near solid surfaces. An evanescent wave generated by a surface plasmon resonance in a metal layer is the incident light field in the dynamic light scattering experiment. The combination of surface plasmon resonance spectroscopy and dynamic light scattering leads to a spatiotemporal resolution extending a few hundred nanometers from the surface and from microseconds to seconds. The comparison with evanescent wave dynamic light scattering identifies the advantages of the presented technique, e.g., surface monitoring, use of metal surfaces, and biorelevant systems. For both evanescent wave geometries, we define the scattering wave vector necessary for the analysis of the experimental relaxation functions.     

UV‐Light‐Driven Oxygen Pumping in a High‐Temperature Solid Oxide Photoelectrochemical Cell

A solid‐state photoelectrochemical cell is operated between 400 and 500 °C under 365 nm UV light. The cell consists of a photovoltaic part, based on a La_0.8Sr_0.2CrO₃/SrTiO₃ junction, and an electrochemical part including a zirconia solid electrolyte with a shared (La,Sr)FeO₃ electrode. The photovoltaic cell part leads to open circuit voltages up to 920 mV at 400 °C. Upon UV light, this driving force is used in the electrochemical part of the cell to pump oxygen from low to high partial pressures, i.e., to convert radiation energy to chemical energy. This demonstrates the feasibility of high‐temperature photoelectrochemical cells for solar energy storage. The detailed characterization of the different resistance contributions in the system by DC and AC methods reveals the parts of the cell to be optimized for finally achieving high‐temperature photoelectrochemical water splitting.