Asymptotically optimal orthonormal basis functions for LPV system identification

A global model structure is developed for parametrization and identification of a general class of Linear Parameter-Varying (LPV) systems. By using a fixed orthonormal basis function (OBF) structure, a linearly parametrized model structure follows for which the coefficients are dependent on a scheduling signal. An optimal set of OBFs for this model structure is selected on the basis of local linear dynamic properties of the LPV system (system poles) that occur for different constant scheduling signals. The selected OBF set guarantees in an asymptotic sense the least worst-case modeling error for any local model of the LPV system. Through the fusion of the Kolmogorov n-width theory and Fuzzy c-Means clustering, an approach is developed to solve the OBF-selection problem for discrete-time LPV systems, based on the clustering of observed sample system poles.     

Learning AAM fitting through simulation

The active appearance model (AAM) is a powerful method for modeling and segmenting deformable visual objects. The utility of the AAM stems from two fronts: its compact representation as a linear object class and its rapid fitting procedure, which utilizes fixed linear updates. Although the original fitting procedure works well for objects with restricted variability when initialization is close to the optimum, its efficacy deteriorates in more general settings, with regards to both accuracy and capture range. In this paper, we propose a novel fitting procedure where training is coupled with, and directly addresses, AAM fitting in its deployment. This is achieved by simulating the conditions of real fitting problems and learning the best set of fixed linear mappings, such that performance over these simulations is optimized. The power of the approach does not stem from an update model with larger capacity, but from addressing the whole fitting procedure simultaneously. To motivate the approach, it is compared with a number of existing AAM fitting procedures on two publicly available face databases. It is shown that this method exhibits convergence rates, capture range and convergence accuracy that are significantly better than other linear methods and comparable to a nonlinear method, whilst affording superior computational efficiency.     

On the benefits of a stress criterion for the simulation of cup drawing process

Experimental and numerical cup drawing process has been investigated on 0.65 mm zinc sheets. The cup exhibits anisotropic earrings due to the material microstructure. The material formability is studied through elliptical bulge tests in the rolling, diagonal and transverse direction. High anisotropy of the formability is observed. The numerical simulation of cup drawing is then made and demonstrates the correct fitting with experimental results. A stress formability criterion developed by Jansen et al. [14] is then implemented into a finite element method software and applied to predict the material rupture observed for some process conditions. The risk zone of the cup is subjected to some strain path changes according to the simulation whereas the strain value does not explain the rupture according to the experimental formability measured by the bulge tests. It has been shown that the rupture is due to some critical stresses, which are reached in the risk zone of the cup. The use of the stress criterion and its non-dependence on the strain path change allows the fracture prediction. Finally, the numerical fracture propagation by the “kill element method”, as briefly discussed by Bouchard et al. [4], is used and shows a good similarity with the experience.     

Is the diatom sex clock a clock?

The unique life cycle of diatoms with continuous decreasing and restoration of the cell size leads to periodic fluctuations in cell size distribution and has been regarded as a multi-annual clock. To understand the long-term behaviour of a population analytically, generic mathematical models are investigated algebraically and numerically for their capability to describe periodic oscillations. Whereas the generally accepted simple concepts for the proliferation dynamics do not sustain oscillating behaviour owing to broadening of the size distribution, simulations show that a proposed limited lifetime of a newly synthesized cell wall slows down the relaxation towards a time-invariant equilibrium state to the order of a hundred thousand generations. In combination with seasonal perturbation events, the proliferation scheme with limited lifetime is able to explain long-lasting rhythms that are characteristic for diatom population dynamics. The life cycle thus resembles a pendulum clock that has to be wound up from time to time by seasonal perturbations rather than an oscillator represented by a limit cycle.     

Effectiveness of animation in trend visualization

Animation has been used to show trends in multi-dimensional data. This technique has recently gained new prominence for presentations, most notably with Gapminder Trendalyzer. In Trendalyzer, animation together with interesting data and an engaging presenter helps the audience understand the results of an analysis of the data. It is less clear whether trend animation is effective for analysis. This paper proposes two alternative trend visualizations that use static depictions of trends: one which shows traces of all trends overlaid simultaneously in one display and a second that uses a small multiples display to show the trend traces side-by-side. The paper evaluates the three visualizations for both analysis and presentation. Results indicate that trend animation can be challenging to use even for presentations; while it is the fastest technique for presentation and participants find it enjoyable and exciting, it does lead to many participant errors. Animation is the least effective form for analysis; both static depictions of trends are significantly faster than animation, and the small multiples display is more accurate.     

Structural determination of large molecules through the reassembly of optimized fragments

The accurate determination of the optimized structures of large molecules is, computationally quite expensive. As an alternate to the conventional approaches to structural optimization, we have explored the accuracy and speed-up obtained when variants of the fragmentation optimization and recombination method (FORM) are used. Specifically, the method was applied to eight prototypical molecules -n-decane, hexa-alanine, a long conjugate hydrocarbon molecule, a large polar conjugated molecule, large (5,5) armchair single-walled carbon nanotubes, a salen-aluminum complex and a multiply H-bonded system (two conformers of vancomycin aglycon with Di-N-acetyl-l-Lys-d-Ala-d-Ala - without optimizing the structure of the whole molecules. We find that FORM can predict the structure of these molecules with an acceptable accuracy, all at a computational cost that is 2-11 times less than conventional quantum mechanical methods at the Hartree-Fock (HF), density functional theory (DFT) and MP2 level of accuracy. FORM may therefore represent a viable approach for the fast structural predictions of large molecules.     

Datatype-Generic Termination Proofs

Datatype-generic programs are programs that are parameterised by a datatype. We review the allegorical foundations of a methodology of designing datatype-generic programs. The notion of F-reductivity, where F parametrises a datatype, is reviewed and a number of its properties are presented. The properties are used to give concise, effective proofs of termination of a number of datatype-generic programming schemas. The paper concludes with a concise proof of the well-foundedness of a datatype-generic occurs-in relation.     

Bestandsaufnahme Grundwasser nach der EU-Wasserrahmenrichtlinie im Koordinierungsraum Mulde-Elbe-Schwarze Elster

Kurzfassung Die Wasserrahmenrichtlinie regelt den Schutz von Grund- und Oberflächengewässern und fordert eine nachhaltige Wassernutzung. Sie legt einen Zeitplan fest, um bis zum Jahr 2015 für alle Gewässer einen guten Zustand zu erreichen. Der erste Schritt ist eine Bestandsaufnahme der Gewässer. Für das Grundwasser besteht diese aus einer erstmaligen Beschreibung, einer weitergehenden Beschreibung und der Prüfung der Auswirkungen menschlicher Tätigkeit auf das Grundwasser. Die Wasserrahmenrichtlinie wird unabhängig von administrativen Grenzen innerhalb von hydrologischen Einzugsgebieten umgesetzt. Im deutschen Teil des Flusseinzugsgebietes der Elbe wurden 5 Koordinierungsräume gegründet. Der Koordinierungsraum Mulde-Elbe-Schwarze Elster (MES) wird vorgestellt. Beispielhaft für die angewandten Methoden wird die Beurteilung diffuser Stoffeinträge in das Grundwasser bei der erstmaligen Beschreibung erläutert. Die Ergebnisse der Bestandsaufnahme Grundwasser im Koordinierungsraum MES werden präsentiert. Von 54 Grundwasserkörpern ist für 25 Körper aufgrund der Belastungen durch Punktquellen und diffuse Quellen, wegen des mengenmäßigen Zustands oder sonstiger anthropogener Einwirkungen die Zielerreichung nach der Wasserrahmenrichtlinie unklar/unwahrscheinlich.

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Status review groundwater for the Water Framework Directive in the coordination zone Mulde-Elbe-Schwarze Elster

Abstract The Water Framework Directive (WFD) governs the protection of groundwater and surface water and promotes sustainable water use. It sets up a timetable to ensure that a good status of all waters will be achieved by 2015. The first step is a status review of the waters. For groundwater, this procedure is divided into an initial characterisation, a further characterisation and a review of the impacts of human activity on groundwater. The WFD is to be implemented independently of administrative boundaries within hydrological river basins. In the German part of the Elbe river basin district five coordination zones have been established. The Mulde-Elbe-Schwarze Elster (MES) coordination zone is introduced. As an example for the applied methods, the assessment of the pressures of groundwater by diffuse sources (initial characterisation) will be explained. Then the outcome of the status review groundwater in the coordination zone MES will be presented: From the 54 individual bodies of groundwater 25 bodies will probably not achieve the environmental objectives of the WFD because of the pressures point sources, diffuse sources, quantitative status or other anthropogenic impacts.

     

Experiments on the effects of multiple obstacles in vented explosion chambers

Experimental investigations were performed to examine the effects of flame interactions with different multiple obstacles within chambers of different L/D ratios. The basic chamber consists of a rectangular box, 200 mm in height, with a 700 mm x 700 mm cross-section and a large top-venting area of 700 mm x 210 mm. The chambers were designed at 200 mm height intervals, and the maximum height of the chambers was 1000 mm. Five chambers were employed to examine the flame interaction with multiple bars in each chamber. Three different multiple obstacles were used: square, triangular and circular cross-sections with blockage ratios of 30% and 43%. The results of flame speed and pressures of different L/D ratios were discussed. The flame speeds and pressures associated with the obstacles showed little significant difference in chambers with the L/D ratios of 0.29 and 0.57. However, chambers over a ratio of 0.86 became sensitive to the obstacle types, the L/D ratio and the blockage ratios. The highest overpressures were observed with the triangular obstacles while the lowest overpressures occurred with the cylindrical obstacles. The flame development was correlated with pressure development in the chambers having L/D ratios of 0.86-1.43.