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As the penetration of renewable energy sources (RES) continues to increase, more and more microgrids (MG) are interconnected with distribution system operators (DSO). To reduce system operational costs between MGs and DSOs, it is necessary to develop certain optimization strategies. This article proposes an optimized collaborative framework for modeling multi-entity distribution networks. In this model, DSOs are placed at the upper level to formulate policies, while MGs are at the lower level to respond in real-time to these policies. Furthermore, the multi-agent relationships in the model are described using Stackelberg game mechanisms, enhancing economic efficiency through dynamic gaming. Additionally, a data-driven multi-agent twin-delayed deep deterministic policy gradient (MATD3) algorithm is investigated to simulate the gaming process and improve the overall model's non-linear optimization capabilities. Considering that the simulation process can lead to violations of the energy storage system capacity constraints, a physics-based model is designed within the framework to ensure the safety of energy storage systems (ESS). Finally, compared to the MADDPG and penalty function methods, the proposed approach reduces the operational costs by 19.05%. [ABSTRACT FROM AUTHOR]

An experimental study of the ultralow-cycle fatigue of iron-based shape memory alloy (Fe-SMA) in triaxial stress states was conducted. Monotonic tensile tests of specimens with different geometries were carried out to investigate monotonic mechanical properties of Fe-SMA under various triaxial stress states in terms of stress triaxiality and Lode angle, followed by ultralow cyclic tests (cycles <100) which were carried out to study the ultralow-cycle fatigue of Fe-SMA under various loading systems at triaxial stress states. Fe-SMA had nonlinear combined hardening under cyclic loading. A parameter identification method based on an optimization-based algorithm was established to calibrate the constitutive model of Fe-SMA. The initiation and propagation of cracks in the fracture process were different for Fe-SMA under monotonic and cyclic loading. The influences of stress triaxiality and Lode angle on the fracture ductility of Fe-SMA were investigated. An ultralow cyclic fracture criterion, the cyclic Bai–Wierzbicki (CBW) criterion, was established based on the accumulation of ductile damage and the attenuation of ductile damage threshold. The applicability of the calibrated constitutive model and the proposed fracture criterion was validated by simulating the ultralow-cycle fatigue and fracture failures of Fe-SMA. [ABSTRACT FROM AUTHOR]

A parametric study of hypersonic impinging conical-shock-wave/turbulent-boundary-layer interaction (CSBLI) is carried out at hypersonic high-Reynolds-number conditions (Mach number 6.0, Red2 10,000, based on the freestream momentum boundary-layer thickness and wall viscosity) by means of numerical simulation of the Reynolds-averaged Navier-Stokes (RANS) equations, with the eventual goal of establishing wall temperature effects. Comparison with available experimental data shows that RANS is capable of predicting the main features of hypersonic oblique shock-wave/turbulent-boundary-layer interaction, namely, typical size and distribution of the wall properties. A large number of flow cases, especially at high Reynolds number, were computed to examine the scaling of the heat transfer over a wide range of wall temperatures. As expected, the interaction zone of hypersonic CSBLI is reduced as the wall is cooled. A simple power of heat transfer originally introduced by Back and Cuffel ("Changes in Heat Transfer from Turbulent Boundary Layers Interacting with Shock Waves and Expansion Waves," AIAA Journal, Vol. 8, No. 10, 1970, pp. 1871-1873) for planar shock-induced interactions is here considered to account for hypersonic CSBLIs, which is found to successfully collapse the data to the distributions obtained for supersonic/hypersonic, cold/hot interactions. The value range of the power exponent n is within 0.75-0.95. [ABSTRACT FROM AUTHOR]