Prioritized Buffer Management in Photonic Packet Switches for Synchronously Arriving Fixed-length Packets

We investigate a photonic packet switch architecture that enables a high node throughput and provides priority services. We describe PBSO (partial buffer sharing with overwriting) method that allows control of an optical fiber-delay-line buffer by prioritized buffer management under conditions of synchronous arrival of fixed length optical packets at a packet switch. The PBSO method is based on a single queue and its complexity is O(p), where p is the number of priority classes. We first present photonic buffer architectures which can support the PBSO method. We also develop an analytical method for PBSO where p =2. Through analysis and simulation results, we show that PBSO improves the packet loss probability in each priority class more than the existing PBS (partial buffer sharing) does, and that it can be actually applied to prioritized buffer management of an optical buffer. PBSO is especially effective when the arrival rate of higher priority class packets is much lower than that of lower priority class packets. In that case, PBSO dramatically improves the performance of higher priority class packets while the degradation in the performance of lower priority class packets is small. In other words, in PBSO, a larger number of higher priority class packets can be accepted at a given packet loss probability than in PBS or non-priority methods

PEg TRAnsfer Workflow recognition challenge report: Do multimodal data improve recognition?

International audienceBackground and objective: In order to be context-aware, computer-assisted surgical systems require accurate, real-time automatic surgical workflow recognition. In the past several years, surgical video has been the most commonly-used modality for surgical workflow recognition. But with the democratization of robot-assisted surgery, new modalities, such as kinematics, are now accessible. Some previous methods use these new modalities as input for their models, but their added value has rarely been studied. This paper presents the design and results of the “PEg TRAnsfer Workflow recognition” (PETRAW) challenge with the objective of developing surgical workflow recognition methods based on one or more modalities and studying their added value. Methods: The PETRAW challenge included a data set of 150 peg transfer sequences performed on a virtual simulator. This data set included videos, kinematic data, semantic segmentation data, and annotations, which described the workflow at three levels of granularity: phase, step, and activity. Five tasks were proposed to the participants: three were related to the recognition at all granularities simultaneously using a single modality, and two addressed the recognition using multiple modalities. The mean application-dependent balanced accuracy (AD-Accuracy) was used as an evaluation metric to take into account class balance and is more clinically relevant than a frame-by-frame score. Results: Seven teams participated in at least one task with four participating in every task. The best results were obtained by combining video and kinematic data (AD-Accuracy of between 93% and 90% for the four teams that participated in all tasks). Conclusion: The improvement of surgical workflow recognition methods using multiple modalities compared with unimodal methods was significant for all teams. However, the longer execution time required for video/kinematic-based methods(compared to only kinematic-based methods) must be considered. Indeed, one must ask if it is wise to increase computing time by 2000 to 20,000% only to increase accuracy by 3%. The PETRAW data set is publicly available at www.synapse.org/PETRAW to encourage further research in surgical workflow recognition. © 202

Effect of strain reversals on the processing of high-purity aluminum by high-pressure torsion

High-purity aluminum was processed by high-pressure torsion (HPT) under conventional monotonic (m-HPT) and cyclic (c-HPT) conditions where strain reversals are introduced in c-HPT during processing. Measurements show higher values of the Vickers microhardness in the center regions of all disks but these values are higher when processing by c-HPT by comparison with m-HPT for the same total number of turns. Slightly smaller grain sizes are observed in the c-HPT samples. It is shown that all of the microhardness values correlate with the estimated values of the equivalent strain and the results are consistent with earlier data reported under c-HPT conditions when it is recognized that the variation of hardness with equivalent strain is dependent upon the level of recovery within the material. <br/