Impact of experimental conditions on material response during forming of steel in semi-solid state

Semi-solid forming is an effective near-net-shape forming process to produce components with complex geometry and in fewer forming steps. It benefits from the complex thixotropic behaviour of semi-solids. However, the consequences of such behaviour on the flow during thixoforming, is still neither completely characterized and nor fully understood, especially for high melting point alloys. The study described in this paper investigates thixoextrusion for C38 low carbon steel material using dies at temperatures much lower than the slug temperature. Four different process parameters were studied: the initial slug temperature, the die temperature, the ram speed and the presence of a ceramic layer at the tool/material interface. The extruded parts were found to have an exact shape and a good surface state only if the temperature was below a certain value. This critical temperature is not an intrinsic material property since its value depends on die temperature and the presence of the Ceraspray©layer. Two kinds of flow were highlighted: a homogeneous flow controlled by the behaviour of the solid skeleton characterized by a positive strain rate sensitivity, and a non homogeneous flow (macro liquid/solid phase separation) dominated by the flow of the free liquid. With decreasing ram speed, heat losses increase so that the overall consistency of the material improves, leading to apparent negative strain rate sensitivity. Finally, some ways to optimise thixoforming are proposed

P4-compatible High-level Synthesis of Low Latency 100 Gb/s Streaming Packet Parsers in FPGAs

Packet parsing is a key step in SDN-aware devices. Packet parsers in SDN networks need to be both reconfigurable and fast, to support the evolving network protocols and the increasing multi-gigabit data rates. The combination of packet processing languages with FPGAs seems to be the perfect match for these requirements. In this work, we develop an open-source FPGA-based configurable architecture for arbitrary packet parsing to be used in SDN networks. We generate low latency and high-speed streaming packet parsers directly from a packet processing program. Our architecture is pipelined and entirely modeled using templated C++ classes. The pipeline layout is derived from a parser graph that corresponds a P4 code after a series of graph transformation rounds. The RTL code is generated from the C++ description using Xilinx Vivado HLS and synthesized with Xilinx Vivado. Our architecture achieves 100 Gb/s data rate in a Xilinx Virtex-7 FPGA while reducing the latency by 45% and the LUT usage by 40% compared to the state-of-the-art.Comment: Accepted for publication at the 26th ACM/SIGDA International Symposium on Field-Programmable Gate Arrays February 25 - 27, 2018 Monterey Marriott Hotel, Monterey, California, 7 pages, 7 figures, 1 tabl

Quantity, Quality, and Relevance: Central Bank Research, 1990-2003

The authors document the research output of 34 central banks from 1990 to 2003, and use proxies of research inputs to measure the research productivity of central banks over this period. Results are obtained with and without controlling for quality and for policy relevance. The authors find that, overall, central banks have been hiring more researchers and publishing more research since 1990, with the United States accounting for more than half of all published central bank research output, although the European Central Bank is rapidly establishing itself as an important research centre. When controlling for research quality and relevance, the authors generally find that there is no clear relationship between the size of an institution and its productivity. They also find preliminary evidence of positive correlations between the policy relevance and the scientific quality of central bank research. There is only very weak evidence of a positive correlation between the quantity of external partnerships and the productivity of researchers in central banks.Central bank research

The radion in brane cosmology

We consider the homogeneous cosmological radion, which we define as the interbrane distance in a two brane and $Z_2$ symmetrical configuration. In a coordinate system where one of the brane is at rest, the junction conditions for the second (moving) brane give directly the (non-linear) equations of motion for the radion. We analyse the radion fluctuations and solve the non-linear dynamics in some simple cases of interest

PoET-BiN: Power Efficient Tiny Binary Neurons

The success of neural networks in image classification has inspired various hardware implementations on embedded platforms such as Field Programmable Gate Arrays, embedded processors and Graphical Processing Units. These embedded platforms are constrained in terms of power, which is mainly consumed by the Multiply Accumulate operations and the memory accesses for weight fetching. Quantization and pruning have been proposed to address this issue. Though effective, these techniques do not take into account the underlying architecture of the embedded hardware. In this work, we propose PoET-BiN, a Look-Up Table based power efficient implementation on resource constrained embedded devices. A modified Decision Tree approach forms the backbone of the proposed implementation in the binary domain. A LUT access consumes far less power than the equivalent Multiply Accumulate operation it replaces, and the modified Decision Tree algorithm eliminates the need for memory accesses. We applied the PoET-BiN architecture to implement the classification layers of networks trained on MNIST, SVHN and CIFAR-10 datasets, with near state-of-the art results. The energy reduction for the classifier portion reaches up to six orders of magnitude compared to a floating point implementations and up to three orders of magnitude when compared to recent binary quantized neural networks.Comment: Accepted in MLSys 2020 conferenc

La mondialisation rend-elle obsolètes les modèles de développement nationaux? : le cas du Québec et des économies de marché coordonnées

L'objectif de cette thèse est d'étudier les tensions qui existent entre la mondialisation et la politique d'autonomie nationale, spécialement en matière de politique économique, au Québec comme ailleurs dans le monde industrialisé. À cet égard, la mondialisation libérale serait devenue un carcan qui soumet le monde politique à la logique capitaliste et donc à la concurrence internationale aux dépens de la cohésion sociale. Cette logique néo-fonctionnaliste s'arrime avec la croissance des échanges des biens et des services et la trans-nationalisation de la production qui sont à la base de la mondialisation. Dans la mesure où le match des performances économiques semblait favoriser les États-Unis depuis le milieu des années 1990, la popularité du modèle de marché libéral allait de soi (de même que la rationalité de son émulation) sans égard aux cycles qui font l'économie ou encore aux circonstances particulières redevables au statut d'« hyper-puissance » qui appartient à ce pays. Nous verrons que cette fatalité de la convergence n'est pas absolue dans la mesure où elle repose sur le postulat néoclassique d'une économie résumée à la sphère marchande. C'est oublier que le système économique capitaliste dépend également d'un ensemble de mécanismes de coordination qui renvoient aux institutions et donc au politique. Les compromis entre intérêts différents auxquels celui-ci donne lieu sont uniques à chaque espace national et de ce fait diverses configurations du capitalisme sont possibles. Certes, la mondialisation produit une confrontation entre les forces de l'universalisme et du particularisme, mais au demeurant chaque système socio-économique s'ajuste aux impératifs liés à l'ouverture des frontières en fonction de ses caractéristiques historiques. Et sur le terrain même du discours néo-libéral, l'évidence nous montre que les économies de la configuration anglo-saxonne n'ont pas le monopole du succès économique, les pays nordiques, par exemple, ayant enregistré des performances tout aussi, sinon plus enviables, sans connaître les mêmes déséquilibres sociaux et financiers. Au Québec aussi, on pourra constater que les performances économiques sont fort honorables tandis que les inégalités sociales sont moins prononcées qu'ailleurs en Amérique du Nord. Par ailleurs, le modèle québécois de développement n'est pas menacé directement par la mondialisation mais bien par des remises en question idéologiques provenant de l'intérieur. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Mondialisation, Québec, Modèles de développement, Politiques économiques, Politiques sociales

CARLA: A Convolution Accelerator with a Reconfigurable and Low-Energy Architecture

Convolutional Neural Networks (CNNs) have proven to be extremely accurate for image recognition, even outperforming human recognition capability. When deployed on battery-powered mobile devices, efficient computer architectures are required to enable fast and energy-efficient computation of costly convolution operations. Despite recent advances in hardware accelerator design for CNNs, two major problems have not yet been addressed effectively, particularly when the convolution layers have highly diverse structures: (1) minimizing energy-hungry off-chip DRAM data movements; (2) maximizing the utilization factor of processing resources to perform convolutions. This work thus proposes an energy-efficient architecture equipped with several optimized dataflows to support the structural diversity of modern CNNs. The proposed approach is evaluated by implementing convolutional layers of VGGNet-16 and ResNet-50. Results show that the architecture achieves a Processing Element (PE) utilization factor of 98% for the majority of 3x3 and 1x1 convolutional layers, while limiting latency to 396.9 ms and 92.7 ms when performing convolutional layers of VGGNet-16 and ResNet-50, respectively. In addition, the proposed architecture benefits from the structured sparsity in ResNet-50 to reduce the latency to 42.5 ms when half of the channels are pruned.Comment: 12 page

Non-conventional cosmology from a brane-universe

We consider ``brane-universes'', where matter is confined to four-dimensional hypersurfaces (three-branes) whereas one extra compact dimension is felt by gravity only. We show that the cosmology of such branes is definitely different from standard cosmology and identify the reasons behind this difference. We give a new class of exact solutions with a constant five-dimensional radius and cosmologically evolving brane. We discuss various consequences.Comment: 22 pages, Latex; minor addition