Functionally Specified Distributed Transactions in Co-operative Scenarios

Addresses the problem of specifying co-operative, distributed transactions in a manner that can be subject to verification and testing. Our approach combines the process-algebraic language LOTOS and the object-oriented database modelling language TM to obtain a clear and formal protocol for distributed database transactions meant to describe co-operation scenarios. We argue that a separation of concerns, namely the interaction of database applications on the one hand and data modelling on the other, results in a practical, modular approach that is formally well-founded. An advantage of this is that we may vary over transaction models to support the language combinatio

Magnetoconductance in quantum waveguides with inhomogeneous magnetic fields

We discuss the properties of magnetotransport of electrons in quantum waveguides (QWs) in the presence of laterally inhomogeneous magnetic fields perpendicular to the QW plane. The inhomogeneous magnetic fields can be produced by the deposition, on top of a heterostructure, of ferromagnetic stripes with magnetization perpendicular and parallel to the two-dimensional electron gas. It is found that the magnetoconductance in such a device as a function of the Fermi energy of electrons exhibits square-wave-like oscillations that are strongly dependent on the geometrical arrangement and magnetic configurations in the QWs. Different dispersions can be observed. From analyses of the magnetic effective potential, the dispersion relations can be understood well. In some magnetic modulations, the energy spectrum exhibits a bump superimposed upon every bulk Landau level. It is these oscillatory structures in dispersions that lead to square-wave-like shaped modulation in magnetoconductance, which may serve as an energy filter of electrons. ©1999 American Institute of Physics.published_or_final_versio

Technology: driving specialization or enabling diversification (or both)?

Financial services industry ; Technology