Modellbasierte Entscheidungsunterstützung in Produktions- und Dienstleistungsnetzwerken

In this paper, we sketch some of the challenges that should be addressed in future research efforts for model-based decision support in manufacturing and service networks. This includes integration issues, taking into account the autonomy of the decision-making entities in face of information asymmetry, the modeling of preferences of the decision-makers, efficiently determining robust solutions, i.e. solutions that are insensitive with respect to changes in the problem data, and a reduction of the time needed for model building and usage. The problem solution cycle includes problem analysis, the design of appropriate algorithms and their performance assessment. We are interested in a prototypical integration of the proposed methods within application systems, which can be followed up with field tests of the extended application systems. We argue that the described research agenda requires the interdisciplinary collaboration of business and information systems engineering researchers with colleagues from management science, computer science, and operations research. In addition, we present some exemplifying, illustrative examples of relevant research results.     

Characterization of a miniaturized liquid bridge for nL sample infusion: a comparative study of sample flush-out behavior using flow simulations and direct ESI-MS analysis

In this work we shed light on the microfluidics of a miniaturized liquid bridge that forms the central part of a so-called “capillary gap sampler,” a novel device for rapid and seamless injection of nanoliter sample volumes into an electrospray ionization mass spectrometer (ESI-MS). Parameters relevant for sample flush-out at the liquid bridge and in the spray capillary were identified by systematic variation of the capillary dimensions, the linear buffer flow rate (2.1–34 mm/s) and molecular weight of the analytes (0.5–30 kDa). We found that a reduction in capillary wall thickness by a factor of 1.6 significantly influences analyte peak shapes, leads to an inversion of the relationship between peak width and analyte molecular weight, and allows a fivefold decrease in peak width for large molecules down to 5 s. The results could be verified and explained by simulations, in which the presence of diffusion-controlled “dead zones” at the liquid bridge and dispersion in the spray tip that depend on analyte molecular weight were identified as key factors relevant for the sample flush-out process. The merging of simulations and experimental data gives useful hints toward the re-design of a spray tip as built-in ESI-MS interface for an optimized gap sampler performance.     

Metallo‐supramolecular materials based on terpyridine‐functionalized polyhedral silsesquioxane

In this study, novel metallo‐supramolecular materials based on terpyridine‐functionalized polyhedral silsesquioxane were synthesized from 4′‐chloro‐2,2′:6′,2″‐terpyridine and amino‐group‐functionalized polyhedral oligomeric silsesquioxane. The obtained terpyridine‐functionalized polyhedral silsesquioxanes were converted to metallo‐supramolecular hybrid materials by coordination polycondensation reaction with Co(II) or Cu(II) ions. The supramolecular polymers created were characterized by means of structure, morphology and stimuli‐responsive performance employing scanning electron microscopy, amperometric techniques and UV–visible and Fourier transform IR spectroscopy. UV?visible and cyclic voltammetry studies showed that both the optical and electrochemical properties of metallo‐supramolecular materials are affected by the substituent at the pyridine periphery. The supramolecular polymers obtained exhibited electrochromism during the oxidation processes of cyclic voltammogram studies. As a result, these terpyridine‐functionalized polyhedral silsesquioxanes are good candidates for electronic, opto‐electronic and photovoltaic applications as smart stimuli‐responsive materials. © 2013 Society of Chemical Industry     

Integral Equation Method for Evaluation of Eddy-Current Impedance of a Rectangular,Near Surface Crack Inside a Cylindrical Hole

An integral equation method for solving the eddy-current nondestructive evaluation problem of a flat, rectangular, near surface crack inside of a cylindrical hole in a conducting material is presented. The method involves expanding the Green’s tensor, the incoming field, and the jump in electric potential over the crack in suitable basis functions. Here, plane waves, cylindrical waves, and basis functions related to the Chebyshev polynomials, are used. The way of discretization in this method leads to a formulation where the scattering is defined by a scattering matrix, independent of the incoming field. This presents an advantage, when conducting numerical simulations, since the scattering matrix does not have to be recalculated for every probe position. The numerical calculations are straightforward to perform and model predictions are compared with finite element results.     

Micro-CT-based identification of double porosity in fired clay ceramics

Optimizing thermal and mechanical properties of clay block masonry requires detailed knowledge on the microstructure of fired clays. We here identify the macro- and microporosity stemming from the use of three different pore-forming agents (expanded polystyrene, sawdust, and paper sludge) in different concentrations. Micro-CT measurements provided access to volume, shape, and orientation of macropores, and in combination with X-ray attenuation averaging and statistical analysis, also to voxel-specific microporosities. Finally, the sum of micro- and macroporosity was compared to corresponding data gained from two statistically and physically independent methods (namely from chemical analysis in combination with weighing, and from mercury intrusion porosimetry). Satisfactory agreement of all these independently gained experimental data renders our new concept for identifying the pore spaces of fired clay as a very promising tool supporting the further optimization of clay blocks.     

Integrated approach for prediction of stability limits for machining with large volumes of material removal

High-speed machining of thin-walled structures is widely used in the aeronautical industry. Higher spindle speed and machining feed rate, combined with a greater depth of cut, increases the removal rate and with it, productivity. The combination of higher spindle speed and depth of cut makes instabilities (chatter) a far more significant concern. Chatter causes reduced surface quality and accelerated tool wear. Since chatter is so prevalent, traditional cutting parameters and processes are frequently rendered ineffective and inaccurate. For the machine tool to reach its full utility, the chatter vibrations must be identified and avoided. In order to avoid chatter and implement optimum cutting parameters, the machine tool including all components and the work piece must be dynamically mapped to identify vibration characteristics. The aim of the presented work is to develop a model for the prediction of stability limits as a function of process parameters. The model consists of experimentally measured vibration properties of the spindle-tool, and finite element calculations of the work piece in (three) different stages of the process. Commercial software packages used for integration into the model prove to accomplish demands for functionality and performance. A reference geometry that is typical for an aircraft detail is used for evaluation of the prediction methodology. In order to validate the model, the stability limits predicted by the use of numerical simulation are compared with the results based on the experimental work.