A Compilation Flow for Parametric Dataflow: Programming Model, Scheduling, and Application to Heterogeneous MPSoC

International audienceEfficient programming of signal processing applications on embedded systems is a complex problem. High level models such as Synchronous dataflow (SDF) have been privileged candidates for dealing with this complexity. These models permit to express inherent application parallelism, as well as analysis for both verification and optimization. Parametric dataflow models aim at providing sufficient dynamicity to model new applications, while at the same time maintaining the high level of analyzability needed for efficient real life implementations. This paper presents a new compilation flow that targets parametric dataflows. Built on the LLVM compiler infrastructure, it offers an actor based C++ programming model to describe parametric graphs, a compilation front-end providing graph analysis features, and a retargetable back-end to map the application on real hardware. This paper gives an overview of this flow, with a specific focus on scheduling. The crucial gap between dataflow models and real hardware on which actor firing is not atomic, as well as the consequences on FIFOs sizing and execution pipelining are taken into account.The experimental results illustrate our compilation flow applied to compilation of 3GPP LTE-Advanced demodulation on a heterogeneous MPSoC with distributed scheduling features. This achieves performances similar to time-consuming hand made optimizations

Performance of a Pd-Zn Cathode Electrode in a H₂ Fueled Single PEM Fuel Cell

A 21.7 wt.% Pd—7.3 wt.% Zn/C electrocatalyst prepared via the wet impregnation (w.i.) method was deposited onto commercial carbon cloth (E-TEK) and tested towards its electrocatalytic performance as a cathode electrode material for oxygen reduction reaction (ORR) in a H2 fueled single proton-exchange membrane fuel cell (PEMFC). A commercial PtRu electrode (E-TEK) was used as PEM anode for hydrogen oxidation reaction (HOR). The performance of the aforementioned PEMFC was compared with that of the same PEMFC with two different Pt-based cathodes, which were prepared by deposition onto commercial carbon cloth (E-TEK) of 29 wt.% Pt/C synthesized via w.i. and of commercial 29 wt.% Pt/C (TKK). The metal loading of the tested cathode electrodes was 0.5 mgmet cm−2. Comparison was based both on polarization curves and on electrochemical impedance spectroscopy (EIS) measurements at varying cell potential. In terms of power density, the lowest and highest performance was exhibited by the PEMFC with the 21.7 wt.% Pd—7.3 wt.% Zn/C cathode and the PEMFC with the commercial 29 wt.% Pt/C (TKK) cathode electrode, respectively. This behavior was in accordance with the results of EIS measurements, which showed that the PEMFC with the 21.7 wt.% Pd—7.3 wt.% Zn/C cathode exhibited the highest polarization resistance

Performance of a Pd-Zn Cathode Electrode in a H2 Fueled Single PEM Fuel Cell

A 21.7 wt.% Pd—7.3 wt.% Zn/C electrocatalyst prepared via the wet impregnation (w.i.) method was deposited onto commercial carbon cloth (E-TEK) and tested towards its electrocatalytic performance as a cathode electrode material for oxygen reduction reaction (ORR) in a H2 fueled single proton-exchange membrane fuel cell (PEMFC). A commercial PtRu electrode (E-TEK) was used as PEM anode for hydrogen oxidation reaction (HOR). The performance of the aforementioned PEMFC was compared with that of the same PEMFC with two different Pt-based cathodes, which were prepared by deposition onto commercial carbon cloth (E-TEK) of 29 wt.% Pt/C synthesized via w.i. and of commercial 29 wt.% Pt/C (TKK). The metal loading of the tested cathode electrodes was 0.5 mgmet cm−2. Comparison was based both on polarization curves and on electrochemical impedance spectroscopy (EIS) measurements at varying cell potential. In terms of power density, the lowest and highest performance was exhibited by the PEMFC with the 21.7 wt.% Pd—7.3 wt.% Zn/C cathode and the PEMFC with the commercial 29 wt.% Pt/C (TKK) cathode electrode, respectively. This behavior was in accordance with the results of EIS measurements, which showed that the PEMFC with the 21.7 wt.% Pd—7.3 wt.% Zn/C cathode exhibited the highest polarization resistance

Cyclic voltammetry characterization of a La(0.8)Sr(0.2)Co(0.2)Fe(0.8)O(3) (-) (delta) electrode interfaced to CGO/YSZ

The electrochemical characteristics of a La0.8Sr0.2Co0.2Fe0.8O3 (- delta) cathode electrode interfaced to the CGO layer of a double layer CGO/YSZ electrolyte were studied using cyclic voltammetry, at temperatures of 600 to 850 degrees C and under oxygen partial pressures ranging from 0.07 to 21 kPa. The aim was to identify the electrochemical processes taking place under cathodic polarization on the basis of differences in the features of the cyclic voltammograms with changing conditions. Depending on temperature, sweep rate and oxygen partial pressure, current peaks appeared both in the forward and backward scans. Furthermore, reversed hysteresis was observed, i.e. higher currents in the backward scan than in the forward scan, with increasing oxygen partial pressure and decreasing temperature. The observed behavior was related to the electrochemical redox of B-sites and concomitant stoichiometry change as well as to the competing reaction of electrochemical oxygen redox, taking also into account the competitive action of chemical reactions occurring in the presence of gaseous oxygen. (C) 2011 Elsevier B.V. All rights reserved