Direct Numerical Simulation in a Lid-Driven Cubical Cavity at High Reynolds Number by a Chebyshev Spectral Method

Direct numerical simulation of the flow in a lid-driven cubical cavity has been carried out at high Reynolds numbers (based on the maximum velocity on the lid), between 1.2 10⁴ and 2.2 10⁴. An efficient Chebyshev spectral method has been implemented for the solution of the incompressible Navier–Stokes equations in a cubical domain. The Projection-Diffusion method [Leriche and Labrosse (2000, SIAM J. Sci. Comput. 22(4), 1386–1410), Leriche et al. (2005, J. Sci. Comput., in press)] allows to decouple the velocity and pressure computation in very efficient way and the simple geometry allows to use the fast diagonalisation method for inverting the elliptic operators at a low computational cost. The resolution used up to 5.0 million Chebyshev collocation nodes, which enable the detailed representation of all dynamically significant scales of motion. The mean and root-mean-square velocity statistics are briefly presented     

Characterization of ZrO2 thin films deposited by MOCVD for high-density 3D capacitors

This work deals with high-density integrated capacitors for output filters in future micro DC–DC converters. To reach high capacitance density, 3D structures were created in silicon with DRIE followed by MOCVD of ZrO₂ (100 nm thick). The step coverage revealed two deposition regimes: a surface reaction controlled regime for cavities aspect ratio lower than 2 and a diffusion-controlled regime for higher aspect ratios. The ZrO₂ films present mostly a cubic/tetragonal structure. The permittivity extracted from the measurement is 26.4. These results are discussed with static dielectric responses calculated in literature.     

G729 Voice Decoder Design

Embedded digital signal processing (DSP) systems are usually associated with real time constraints and/or high data rates such that fully software implementations are often not satisfactory. In that case, mixed hardware/software implementations are to be investigated. This paper presents the design of a HW/SW G.729 voice decoder dedicated to embedded systems. The decoder has been built around, on the one hand a reconfigurable digital circuit (FPGA) to achieve the so called IP hardware part—the autocorrelation computation—using a linear systolic array, and on the other hand a digital signal processor (DSP) for the remainder of the algorithm. Apart such an implementation is typically driven by the use of reusable component (IP) it is of great interest for new G729-based applications such as Voice over IP (VoIP) for example. It results in an overall reduction of the execution time per frame. Another interesting point is the design of a parameterizable autocorrelation block which can be useful for a wide range of applications such as GSM 13 Kbit/s, APC 9.6 Kbit/s and G723 6.3 Kbit/s and 5.3 Kbit/s. In the G729 context and using a V50 Virtex FPGA, the execution time of this function is 10 times faster than a TMS320C6201 DSP implementation. Fatma Sayadi is Ph.D. student at Faculty of Sciences, Monastir, Tunisia in collaboration with the LESTER Laboratory, University de Bretagne Sud, Lorient, France. She is a member of Laboratory of Electronics and Micro-Electronics. His researches interest, the implementation of Digital Signal, high level design using VHDL language, Hardware/Software Co-design. Emmanuel Casseau received his Ph.D Degree in Electrical Engineering in 1994. He is currently an Associate Professor in the Electronic Department at the University de Bretagne Sud, Lorient, France. He is also in charge of the IP project of the Lester Lab., University de Bretagne Sud. His research interests include system design, high-level synthesis, virtual components and SoCs. Mohamed Atri born in 1971, received his Ph.D. Degree in Micro-electronics from the Science Faculty of Monastir in 2001. He is currently a member of the Laboratory of Electronics & Micro-electronics. His research includes Circuit and System Design, Network Communication, IPs and SoCs. Mehrez Marzougui received the B.Sc. degree from University of Science and Technology (electronic option), Monastir, Tunisia, and the M.Sc. degree in electronic from the same university in 1996 and 1998 respectively. Since 1998, he has been a Ph.D. candidate in Electronic and Micro-electronic laboratory at the University of Sciences and Technology, Monastir, Tunisia. His research interests include hardware/software co-verification and high-level synthesis. Rached Tourki was born in 1948. He received the B.S. degree in Physics (Electronics option) from Tunis University, in 1970; the M.S. and the Doctorat de 3eme cycle in Electronics from Institut d'Electronique d'Orsay, Paris-south University in 1971 and 1973 respectively. From 1973 to 1974 he served as microelectronics engineer in Thomson-CSF. He received the Doctorat d'etat in Physics from Nice University in 1979. Since this date he has been professor in Microelectronics and Microprocessors with the physics department, Faculte des Sciences de Monastir. Eric Martin born in 1961, is a Full Professor at the University of South Brittany in Lorient, France. His interest includes the implementation of Digital Signal and Image Processing and high-level design methods for dedicated circuits.     

Modelling the browning of bread during baking

In this work, we study the development of browning at bread surface during baking. Computer vision is applied to follow the progress of browning at surface, while the variations of temperature and water activity are obtained by numerical simulation of a mathematical model previously validated. The formation of the bread crust is a complex process where temperature and water content change continuously during baking, making browning a non-isothermal process occurring in a non-ideal system. Minimum requirements for initiation of colour formation are temperature greater than 120 °C and water activity less than 0.6. We apply a non-isothermal kinetics approach to model the browning development at bread surface during baking, where the variation of local temperature and water activity is taken into account. The methodology presented here is suitable for modelling and predicting browning during baking; model parameters can be estimated by using a non-ideal system closer to real processing conditions.     

Optimal Routing in Two Parallel Queues with Exponential Service Times

In this paper we investigate the problem of the effective computation of the optimal routing sequence in a queuing system made of two parallel queues with exponential service times. We first show that the optimal policy (minimizing the expected waiting time) is a Sturmian sequence and we establish several qualitative properties of this policy (monotonicity, continuity, convexity). Then, we propose an algorithm to compute the optimal routing sequence efficiently. We address the issues of time complexity as well as numerical stability of this algorithm. We then run an extensive set of experiments which show several interesting features of the optimal policy with apparent discontinuities and a fractal behavior and we provide several good approximations by using fast heuristics.     

Dépôt chimique CVD de silicium dopé in situ au phosphore. Partie 1: Etude expérimentale

The fabrication of silicon layers doped in situ with phosphor using CVD technique is still poorly controlled by the microelectronics industry. Significant thickness heterogeneities are noticeable on circuit and load, which greatly limits the process utilization. An experimental study of this deposition was carried out. The influence of many parameters (temperature, pressure, feed composition) was studied in terms of deposition thickness and uniformity as well as crystalline structure and resistivity. The advantages and involved mechanisms are presented.     

Performance of autoclaved aerated-concrete masonry walls in Kuwait

The masonry walls used in building construction in Kuwait are non-load bearing. Traditionally, normalweight concrete blocks have been used throughout the region. However, with the enforcement of the Kuwaiti energy conservation code, autoclaved aerated-concrete blocks were introduced in 1985 as an efficient masonry material that can provide the necessary thermal insulation properties without the use of specific thermal insulation materials. This paper discusses the influence of material properties and specific construction practices on the performance of aerated-concrete-block walls. The provision of a partial movement joint through the use of sand-cement mortar, in place of higher strength epoxy glue mortar in the construction of wall and column intersections, reduced cracking in the immediate vicinity of the intersections. Studies are ongoing to recommend more effective measures for allowing greater movement at the wall and column intersections, thereby eliminating wall cracking due to restraint of movement.     

An improved refutation system for intuitionistic predicate logic

In this paper a refutation calculus for intuitionistic predicate logic is presented where the necessity of duplicating formulas to which rules are applied is analyzed. In line with the semantics of intuitionistic logic in terms of Kripke models a new signF _C beside the SignsT andF is added which reduces the size of the proofs and the involved nondeterminism. The resulting calculus is proved to be correct and complete. An extension of it for Kuroda logic is given.