Hyperbolic formulations of General Relativity with Hamiltonian structure

With the aim of deriving symmetric hyperbolic free-evolution systems for GR that possess Hamiltonian structure and allow for the popular puncture gauge condition we analyze the hyperbolicity of Hamiltonian systems. We develop helpful tools which are applicable to either the first order in time, second order in space or the fully second order form of the equations of motion. For toy models we find that the Hamiltonian structure can simplify the proof of symmetric hyperbolicity. In GR we use a special structure of the principal part to prove symmetric hyperbolicity of a formulation that includes gauge conditions which are very similar to the puncture gauge.Comment: Our mathematica scripts are available at http://na.mathematik.uni-tuebingen.de/~richter

Optimisation algorithms for the charge dispatch of plug-in vehicles based on variable tariffs

Plug-in vehicles powered by renewable energies are a viable way to reduce local and total emissions and could also support a highly efficient grid operation. Indirect control by variable tariffs is one option to link charging or even discharging time with the grid load and the renewable energy production. Algorithms are required to develop tariffs and evaluate grid impacts of variable tariffs for electric vehicles (BEV) as well as to schedule the charging process optimisation. Therefore a combinatorial optimisation algorithm is developed and an algorithm based on graph search is used and customised. Both algorithms are explained and compared by performance and adequate applications. The developing approach and the correctness of the quick combinatorial algorithm are proved within this paper. For vehicle to grid (V2G) concepts, battery degradation costs have to be considered. Therefore, common life cycle assumptions based on the battery state of charge (SoC) have been used to include degradation costs for different Li-Ion batteries into the graph search algorithm. An application of these optimisation algorithms, like the onboard dispatcher, which is used in the German fleet test "Flottenversuch Elektromobiliät". Grid impact calculations based on the optimisation algorithm are shown. --BEV,V2G,Plug-In-Vehicles (PHEV),optimisation,mobile dispatcher,demand side management,charging,combinatorial algorithm,graph search algorithm,indirect control by variable tariffs

Applying Service Engineering Principles to TMN Systems

Recent work in distributed and telecommunication systems has become increasingly oriented towards applications in a global open market in telecommunications services, as the effects of liberalisation take hold. The areas of network and service management will be essential to competitiveness in this market, however the technologies and system development techniques widely used today (i.e. SNMP and CMIP) were conceived to address the needs of large corporate data networks and monolithic public telecommunication networks. How these technologies and techniques can be applied to management in an open market environment is not currently well defined. This paper describes some of the work of the RACE II PROJECT PREPARE in its application of ITU-T TMN recommendations to management solutions in an open services environment. In particular it describes the engineering approach taken to developing TMN systems in an attempt to tailor them to such an environment

The Course of Subjective Sleep Quality in Middle and Old Adulthood and Its Relation to Physical Health

Objectives. Older adults more often complain about sleep disturbances compared with younger adults. However, it is not clear whether there is still a decline of sleep quality after age 60 and whether changes in sleep quality in old age are mere reflections of impaired physical health or whether they represent a normative age-dependent development. Method. Subjective sleep quality and perceived physical health were assessed in a large sample of 14,179 participants (52.7% women; age range 18-85) from the German Socio-Economic Panel Study across four yearly measurement time points. Results. Subjective sleep quality linearly declined from young adulthood until age 60. After age 60, a transient increase in subjective sleep quality occurred that coincides with retirement. After age 66, subjective sleep quality appears to decrease again. Physical health prospectively predicted subjective sleep quality and vice versa. These relations were similar for participants aged over and under 60. Discussion. Around retirement, a transient increase in subjective sleep quality appears to occur, which might reflect a decrease in work-related distress. Perceived physical health appears to be important for subjective sleep quality in old adults but not more important than at younger ag