Practical Algorithms for Multicast Support in Input Queues Switches

Abstract — This paper deals with multicast flow support in N × N Input Queued switch architectures. A practical approach to support multicast traffic is presented, assuming that O(N) queues are available at each input port. The focus is on dynamic queueing policies, where, at each input port, multicast flows are assigned to one among the available queues when flows become active: flows are assigned to queues according to switch queue status and, possibly, to flow information. We discuss queueing assignments, scheduling algorithms and flow activity definition models. We explain why dynamic queueing disciplines may outperform static policies, and we show that, even in the most favorable conditions for static policies, they provide comparable performance. I

Measurement Based Reconfigurations in Optical Ring Metro Networks

Single-hop wavelength division multiplexing (WDM) optical ring networks operating in packet mode are one of themost promising architectures for the design of innovative metropolitan network (metro) architectures. They permit a cost-effective design, with a good combination of optical and electronic technologies, while supporting features like restoration and reconfiguration that are essential in any metro scenario. In this article, we address the tunability requirements that lead to an effective resource usage and permit reconfiguration in optical WDM metros.We introduce reconfiguration algorithms that, on the basis of traffic measurements, adapt the network configuration to traffic demands to optimize performance. Using a specific network architecture as a reference case, the paper aims at the broader goal of showing which are the advantages fostered by innovative network designs exploiting the features of optical technologies

SHAPE: The load prediction and non-technical losses modules

Data Analytics applied in the electric sector has been leveraged in the recent years, primarily owing to the introduction worldwide of Automatic Meter Reading/Management and smart grids technologies operated by electric Utilities. Utilities have to face with return of investment from this infrastructure and at the same time have to fulfil the promise of providing better and innovative service to the customer, retailer and distribution network. This paper deals with the innovative SHAPE Web software platform for Data Analytics applied to the load patterns sourced from the Italian Enel network’s smart meters. A previous contribution reported on the customer classification and segmentation modules implemented in the SHAPE platform. This work describes the Load prediction and Non-technical losses modules. The SHAPE Datawarehouse (DW) currently stores four years of progressively updated customer’s load patterns

On the detailed morphological and chemical evolution of phases during laser powder bed fusion and common post-processing heat treatments of IN718

IN718 is the most common Ni-based superalloy for manufacturing aircraft engine parts via thermo-mechanical treatments. The evolution of nanoscale strengthening phases is well researched, enabling optimization of strength, fatigue, and creep properties. Recently, IN718 has shown great viability for laser powder bed fusion (LPBF) additive manufacturing of aerospace parts. However, the detailed microstructure-property relationships during thermal profiles typical to LPBF are not yet well understood. Previous works reported interdendritic precipitation of Laves phase. These detrimental particles can be dissolved by heat treatments, however, the detailed nanoscale phase evolution remains unknown. Using atom probe microscopy, we report on the detailed morphological and chemical evolution of phases in IN718 after LPBF with chessboard versus meander scanning strategies, and direct ageing versus homogenization and ageing treatments. Due to differences in scanning vector length, up to 3.6 times larger dendritic structures, double volume fractions of Laves particles, and Al clusters are found in the chessboard strategy. Coarser matrix grains and a higher dislocation density are detected in the meander strategy. The precise chemical composition and morphology evolution of the matrix, Laves, MC, γ′, and γ′′ phases are obtained and correlated to hardness. Retained Laves phase after direct ageing causes precipitation of 4% volume fraction of γ′′, with additional coarsened precipitates formed along dislocations. Direct ageing leads to an increase in hardness corresponding to roughly 190 HV. Due to Laves phase dissolution, a volume fraction of 16% of compositionally stable, larger γ′′ precipitates is found after homogenization and ageing, also causing partial matrix recrystallization

Cyclic plasticity and fatigue damage of CrMnFeCoNi high entropy alloy fabricated by laser powder-bed fusion

The CrMnFeCoNi high-entropy alloy is highly printable and holds great potential for structural applications. However, no significant discussions on cyclic plasticity and fatigue damage in previous studies. This study provides significant insights into the link between print processes, solidification microstructure, cyclic plasticity and fatigue damage evolution in the alloy fabricated by laser powder bed fusion. Thermodynamics-based predictions (validated by scanning transmission electron microscopy (STEM) energy dispersive X-ray spectroscopy (EDX)) showed that Cr, Co and Fe partition to the core of the solidification cells, whilst Mn and Ni to the cell boundaries in all considered print parameters. Both dislocation slip and deformation twinning were found to be responsible for plastic deformation under monotonic loading. However, the former was found to be the single dominant mechanism for cyclic plasticity. The surface finish helped to substantially delay the crack initiation and cause lack-of-fusion porosity to be the main source of crack initiation. Most significantly, the scan strategies significantly affect grain arrangements and grain dimensions, leading to noticeable effects on fatigue crack propagation; in particular, the highest resistance crack propagation was seen in the meander scan strategy with 0° rotation thanks to the most columnar grains and the smallest spacing of grain boundaries along the crack propagation path

Multicast Capacity of Optical WDM Packet Ring for Hotspot Traffic

Packet-switching WDM ring networks with a hotspot transporting unicast, multicast, and broadcast traffic are important components of high-speed metropolitan area networks. For an arbitrary multicast fanout traffic model with uniform, hotspot destination, and hotspot source packet traffic, we analyze the maximum achievable long-run average packet throughput, which we refer to as \textit{multicast capacity}, of bi-directional shortest-path routed WDM rings. We identify three segments that can experience the maximum utilization, and thus, limit the multicast capacity. We characterize the segment utilization probabilities through bounds and approximations, which we verify through simulations. We discover that shortest-path routing can lead to utilization probabilities above one half for moderate to large portions of hotspot source multi- and broadcast traffic, and consequently multicast capacities of less than two simultaneous packet transmissions. We outline a one-copy routing strategy that guarantees a multicast capacity of at least two simultaneous packet transmissions for arbitrary hotspot source traffic