Bisimulation Finiteness of Pushdown Systems Is Elementary

We show that in case a pushdown system is bisimulation equivalent to a finite system, there is already a bisimulation equivalent finite system whose size is elementarily bounded in the description size of the pushdown system. As a consequence we obtain that it is elementarily decidable if a given pushdown system is bisimulation equivalent to some finite system. This improves a previously best-known ACKERMANN upper bound for this problem

Fotó és mozgókép lehetőségei a vizuális nevelésben

Alapszak/BA/BS

Design and Elaboration of 1D Photonic Crystal Cavity based on Highly Flexible Elastomer thin Layer for Sensors Applications

AbstractWe report a new design for realizing a 1D Photonic crystal cavity based on highly flexible thin elastomer that enables a tuning of its resonance frequency by applying pressure, mechanical or thermal stress. The design consists of a Solaris thin film elastomer layer sandwiched between two Bragg reflectors composed of six bilayers (SiOx/SiNx). The structure exhibits a cavity resonance in wavelength band [500nm-1μm]. The wavelength can be reversible tuned over 2nm/Bar and 4000ppm/°C. These reconfigurable structure could find potential applications for integrated photonics mechanical sensors

Elaboration of Compact Synthetic Micro-jets Based on Micro Magneto-mechanical Systems for Aerodynamic Flow Control

AbstractThis paper described an optimized and compact lateral slot synthetic jet based on magneto-electro-mechanical actuation. The main objective in designing this device is to meet the performances required for flow control applications on the square back body. First, we present the synthetic jet design and the result of numerical simulations based on finite element method showing the formation of the vortex rings. Secondly, the fabrication process and the elaborated devices were described. Finally, fluidic characterisations were performed using one component calibrated hot wire. The results show that for an operation frequency close to 330Hz and a bias power less than 1W, the output velocity reaches 40m/s at 2mm from the slot exit. The design enables us to choose the range of operation frequency in the frequency range 100Hz-700Hz by varying the thickness of the elastomeric membrane between 100μm and 600μm