Fault recoverability analysis of switched nonlinear systems

The recoverability reflects the capability of the system to tolerate the worst faults over a prescribed set under admissible energy constraints. In this paper, we present the minimum amount of control energy required to drive the initial state of a nonlinear system to the origin under certain assumptions, and we also give the corresponding optimal control law. This result is then extended to switched nonlinear systems under given switching signals. On this basis, a novel fault recoverability evaluation scheme is proposed for switched nonlinear systems with respect to the given limit of energy cost. Simulation results verify the effectiveness of the proposed method.     

On the use of absolute interface coordinates in the floating frame of reference formulation for flexible multibody dynamics

In this work a new formulation for flexible multibody systems is presented based on the floating frame formulation. In this method, the absolute interface coordinates are used as degrees of freedom. To this end, a coordinate transformation is established from the absolute floating frame coordinates and the local interface coordinates to the absolute interface coordinates. This is done by assuming linear theory of elasticity for a body’s local elastic deformation and by using the Craig–Bampton interface modes as local shape functions. In order to put this new method into perspective, relevant relations between inertial frame, corotational frame and floating frame formulations are explained. As such, this work provides a clear overview of how these three well-known and apparently different flexible multibody methods are related. An advantage of the method presented in this work is that the resulting equations of motion are of the differential rather than the differential-algebraic type. At the same time, it is possible to use well-developed model order reduction techniques on the flexible bodies locally. Hence, the method can be employed to construct superelements from arbitrarily shaped three dimensional elastic bodies, which can be used in a flexible multibody dynamics simulation. The method is validated by simulating the static and dynamic behavior of a number of flexible systems.     

Multi-level transaction management for complex objects: Implementation,performance, parallelism

Multi-level transactions are a varlant of open-nested transactions in which the subtransactions correspond to operations at different levels of a layered system architecture. They allow the exploitation of semantics of high-level operations to increase concurrency. As a consequence, undoing a transaction requires compensation of completed subtransactions. In addition, multi-level recovery methods must take into consideration that high-level operations are not necessarily atomic if multiple pages are updated in a single subtransaction. This article presents algorithms for multi-level transaction management that are implemented in the database kernel system (DASDBS). In particular, we show that multi-level recovery can be implemented in an efficient way. We discuss performance measurements using a synthetic benchmark for processing complex objects in a multi-user environment. We show that multi-level transaction management can be extended easily to cope with parallel subtransactions within a single transaction. Performance results are presented with varying degrees of inter- and intratransaction parallelism.     

Die Bedeutung flexibler Kraftwerke für die Energiewende

The energy turnaround will in Europe until 2050 result in a change to predominant renewable energy supply. The member states of the European Union have to fulfill individual renewable energy targets until 2020, defined by EU Commission and Parliament. In relation to the given targets, especially for Germany the possibilities and necessary measures are depicted and analyzed.     

Nachhaltige Stromerzeugungspotenziale in Österreich

This paper deals with the topic, whether the Austrian electricity consumption can be fully covered by renewable power generation such as hydroelectricity, wind power and photovoltaics. The analysis of the regional power generation potentials shows, that the current electrical load can be covered by these renewable energy sources. Because of the high volatile profile, power peaks occur, which cannot be balanced by the Austrian pumped hydro storage. The future electricity consumption will be the crucial factor, to what extent a renewable electricity supply can be realized.     

Charakterisierung von Rohmaterialien für die Eisenerzherstellung mit Bildverarbeitung

The automatic image processing software VisuMet was developed during the projects KnetMet and K1-Met (2008–2012). VisuMet evaluates the quality of lump iron ore and fine iron ore. During the K1-Met (2012–2015), the programme will be further developed for pellets and sinter. The reduction degree is calculated with image processing and linear regression for semi- and reduced material of standard reduction tests. For the evaluation of pellets, the concentric phase front movement algorithms has to be adapted in order get a context between porosity and glass phase. These parameters are essential.