1,720,999 research outputs found
Efficacia dei programmi di ispezione "Bollino blu" per il contenimento delle emissioni da autovetture
No full textMonitoring vehicle driving and usage: experiences and perspectives
No full textThe vehicle driving, usage and operating conditions are studied in many contexts through vehicle instrumentation and real-world monitoring. We review a large range of European and American experiences in that field, which concern the definition of mission profiles (vehicle and component design), of driving cycles (fuel consumption and emission measurements), but also safety, mobility or traffic research studies. These experiences demonstrate the high capacities and performances of the techniques and the strong concern of many actors in studying the actual vehicle driving and usage. However due to the large range of objectives, experiments are separately conducted by numerous laboratories, often with restricted means and limited samples of vehicles, and without synergy and experience sharing. It would be probably useful to federate efforts on such a topic and conduct larger experiments with several objectives. We also examine different techniques such as GPS for the vehicle localization, the use of the OBD vehicle network to scan easily numerous operation parameters, and data loggers for the data collection and transmission. From this synthesis, we establish a typology of the questions addressed by the different domains of investigation (driver behavioural studies, traffic research, mobility, energy and environment related work, data collection for the vehicle conception) and the possible experimental approaches. We finally outline a rough frame for a project that should imply interested actors and would be oriented to a light and low-cost instrumentation and monitoring of a large sample of vehicles
Composition of Late Paleozoic Ice Age tillites in Victoria Land (Antarctica): implications for sediment provenance and ice centers extent in southern Gondwana
No full textThe Late Paleozoic Ice Age (LPIA) was one of the most severe glacial phases of Phanerozoic, which led to the development of ice centers within Gondwana. The sedimentary record of the Beacon Supergroup preserves strata related to early Permian ice dynamics. Here we document outcrops across the northern and southern Victoria Land basins in the Transantarctic Mountains (Antarctica); differences come out from the two regions, emphasizing the articulated physiography of the basin and the typology and size of the ice centers. The most common facies are massive to crudely stratified diamictite, sometimes interlayered with mudstone strata. Tillites deposited in a subglacial to ice proximal setting within a glaciomarine to glacio-continental environment, recording climate pulsating waxing and waning ice extent. Diamictite were petrographically analyzed to characterize the mineralogical composition of coarse-grained fraction. Macroscopic and thin section analysis have been carried out on cobbles to determine their petrographic features. The latter reveal that most of them were sourced from the local crystalline basement and from the Devonian sedimentary strata. Clasts composition, together with other provenance tools and paleo-ice flow indicators, allow reconstructing the geological setting of the Permian Victoria Land Basin and the paleo-ice dynamics and ice extent during LPIA in Antarctica
Spatz: A Compact Vector Processing Unit for High-Performance and Energy-Efficient Shared-L1 Clusters
Full text linkWhile parallel architectures based on clusters of Processing Elements (PEs)
sharing L1 memory are widespread, there is no consensus on how lean their PE
should be. Architecting PEs as vector processors holds the promise to greatly
reduce their instruction fetch bandwidth, mitigating the Von Neumann Bottleneck
(VNB). However, due to their historical association with supercomputers,
classical vector machines include micro-architectural tricks to improve the
Instruction Level Parallelism (ILP), which increases their instruction fetch
and decode energy overhead. In this paper, we explore for the first time vector
processing as an option to build small and efficient PEs for large-scale
shared-L1 clusters. We propose Spatz, a compact, modular 32-bit vector
processing unit based on the integer embedded subset of the RISC-V Vector
Extension version 1.0. A Spatz-based cluster with four Multiply-Accumulate
Units (MACUs) needs only 7.9 pJ per 32-bit integer multiply-accumulate
operation, 40% less energy than an equivalent cluster built with four Snitch
scalar cores. We analyzed Spatz' performance by integrating it within MemPool,
a large-scale many-core shared-L1 cluster. The Spatz-based MemPool system
achieves up to 285 GOPS when running a 256x256 32-bit integer matrix
multiplication, 70% more than the equivalent Snitch-based MemPool system. In
terms of energy efficiency, the Spatz-based MemPool system achieves up to 266
GOPS/W when running the same kernel, more than twice the energy efficiency of
the Snitch-based MemPool system, which reaches 128 GOPS/W. Those results show
the viability of lean vector processors as high-performance and
energy-efficient PEs for large-scale clusters with tightly-coupled L1 memory.Comment: 9 pages. Accepted for publication in the 2022 International
Conference on Computer-Aided Design (ICCAD 2022
AXI-Pack: Near-Memory Bus Packing for Bandwidth-Efficient Irregular Workloads
No full textData-intensive applications involving irregular memory streams are inefficiently handled by modern processors and memory systems highly optimized for regular, contiguous data. Recent work tackles these inefficiencies in hardware through core-side stream extensions or memory-side prefetchers and accelerators, but fails to provide end-to-end solutions which also achieve high efficiency in on-chip interconnects. We propose AXI-Pack, an extension to ARM's AXI4 protocol introducing bandwidth-efficient strided and indirect bursts to enable end-to-end irregular streams. AXI-Pack adds irregular stream semantics to memory requests and avoids inefficient narrow-bus transfers by packing multiple narrow data elements onto a wide bus. It retains full compatibility with AXI4 and does not require modifications to non-burst-reshaping interconnect IPs. To demonstrate our approach end-to-end, we extend an open-source RISC-V vector processor to leverage AXI-Pack at its memory interface for strided and indexed accesses. On the memory side, we design a banked memory controller efficiently handling AXI-Pack requests. On a system with a 256-bit-wide interconnect running FP32 workloads, AXI-Pack achieves near-ideal peak on-chip bus utilizations of 87% and 39%, speedups of 5.4x and 2.4x, and energy efficiency improvements of 5.3x and 2.1x over a baseline using an AXI4 bus on strided and indirect benchmarks, respectively
Petrographic signature of gravel fraction from late Quaternary glacigenic sediments in the Ross Sea (Antarctica): Implications for source terranes and Neogene glacial reconstructions
Full text linkThe Ross Embayment is a key region to study the dynamics of the ice sheets during colder and warmer than present climatic conditions, because both the East and West Antarctic Ice sheets shed into the Ross Sea. Numerical modeling and reconstructions of the paleo ice flows during the Last Glacial Maximum show variable contribution of East and West Antarctic Ice sheets based on a variety of proxies.. In this study, we present the first petrographic and minero-chemical investigation of gravel-sized fraction of Last Glacial Maximum subglacial-glacimarine sediments collected with piston cores in a W-E transect across the Ross Sea. The clasts petrographic features are compared with outcropping geology to individuate the sediment source regions. The gravel content of the glacigenic diamictite was classified on the basis of petrographic and minero-chemical features, and three main petrofacies were identified. They reflect changes in the basement geology of the source regions, allowing the reconstruction of paleo ice flow pattern and their comparison with scenarios built up with other datasets. Moreover, the comparison with the Oligocene to Pleistocene glacigenic sediments provided information about the changes of the gravel signature across the Ross Sea and the erosion history of the source regions during Cenozoic
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