3,960 research outputs found
Semi-Asynchronous Federated Edge Learning Mechanism via Over-the-air Computation
Over-the-air Computation (AirComp) has been demonstrated as an effective
transmission scheme to boost the efficiency of federated edge learning (FEEL).
However, existing FEEL systems with AirComp scheme often employ traditional
synchronous aggregation mechanisms for local model aggregation in each global
round, which suffer from the stragglers issues. In this paper, we propose a
semi-asynchronous aggregation FEEL mechanism with AirComp scheme (PAOTA) to
improve the training efficiency of the FEEL system in the case of significant
heterogeneity in data and devices. Taking the staleness and divergence of model
updates from edge devices into consideration, we minimize the convergence upper
bound of the FEEL global model by adjusting the uplink transmit power of edge
devices at each aggregation period. The simulation results demonstrate that our
proposed algorithm achieves convergence performance close to that of the ideal
Local SGD. Furthermore, with the same target accuracy, the training time
required for PAOTA is less than that of the ideal Local SGD and the synchronous
FEEL algorithm via AirComp
THE HYDRAULICS OF NATURE-LIKE FISHWAYS
Nature-like fishway arrangements are commonly used because these structures imitate the characteristics of natural rivers and effectively allow fish to migrate past river sections blocked by hydraulic structures. In this paper, physical models were analyzed, and the velocity distributions of two different fishway structures (Types I and II) were compared. Results showed that the maximum mainstream velocity of the Type I structure was 5.3% lower than that of the Type II structure. However, the average mainstream velocity of the Type I structure was 21.1% greater than that of the Type II structure. The total per-cycle length of the mainstream path in the Type II structure was 2.1 times greater than that of the Type I structure, which indicated that the length of the mainstream path was somewhat proportional to the average velocity of the mainstream. When the flow rate was kept constant, increases in the velocity of the main flow associated with changes in the internal structure of the fishway decreased the average velocity of the main flow, while decreases in the total length of the flow path led to increases in the average velocity of the main flow. Due to frictional head loss along the fishway and local head loss, as well as the overlaps between these factors, the overall flow rate gradually decreased every cycle, despite periodic fluctuations
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