Hierarchical Coordinated Control for Power System Voltage Using Linear Temporal Logic

The paper proposed an approach to study the power system voltage coordinated control using Linear Temporal Logic (LTL). First, the hybrid Automata model for power system voltage control was given, and a hierarchical coordinated voltage control framework was described in detail. In the hierarchical control structure, the high layer is the coordinated layer for global voltage control, and the low layer is the power system controlled. Then, the paper introduced the LTL language, its specification formula and basic method for control. In the high layer, global voltage coordinated control specification was defined by LTL specification formula. In order to implement system voltage coordinated control, the LTL specification formula was transformed into hybrid Automata model by the proposed algorithms. The hybrid Automata in high layer could coordinate the different distributed voltage controller, and have constituted a closed loop global voltage control system satisfied the LTL specification formula. Finally, a simple example of power system voltage control include the OLTC controller, the switched capacitor controller and the under-voltage shedding load controller was given for simulating analysis and verification by the proposed approach for power system coordinated voltage control. The results of simulation showed that the proposed method in the paper is feasible.

Cracking behavior of newly-developed high strength eutectic high entropy alloy matrix composites manufactured by laser powder bed fusion

A novel AlCoCrFeNi2.1 eutectic high entropy alloy(EHEA)composite doped with SiC particles was designed and fabricated by laser powder bed fusion(LPBF).Its microstructure characteristic,tensile properties,and metallurgical defects,with an emphasis on cracking behavior,have been investigated.The results showed that the addition of SiC particles into the AlCoCrFeNi_(2.1)matrix enabled the development of a{100}texture and highly elongated columnar grains,which were the main contributors to mechanical behavior anisotropy.The ultimate tensile strength of 1466±26 MPa and elongation of 9%±3%achieved in the as-deposited EHEA composite surpassed those of advanced metal alloys subjected to additive manufacturing processes.Unfortunately,severe horizontal and longitudinal cracks,as well as a few micro-cracks were observed in the as-deposited bulk samples.Micro-cracks were verified to be associated with the aggregation of carbon and oxide particles.They formed in the final stage of solidification owing to insufficient liquid feeding ability and solidification contraction.The formation of macroscopic cracking was induced by the tensile stress accumulations at sample edges,and the stress concentration areas where microcracks and pores were located were the predominant propagation location.This work provides guidelines for defect control in SiC-reinforced EHEA,assisting in the high-performance design and integrated manufacturing of EHEA composite components.

A mixed culture of Propionibacterium freudenreichii and Lactiplantibacillus plantarum as antifungal biopreservatives in bakery product

In this study,15 strains of Lactic acid bacteria(Allata et al.)and 6 strains of propionic acid bacteria(PAB)were firstly tested for their antifungal activity against three spoilage fungi,Aspergillus niger,Penicillium crustosum and Aspergillus flavus.Two strains of LAB and PAB were selected and assessed,alone or paired,for their abilities to inhibit the most resistant mold,Aspergillus niger.A mixed culture of P.freudenreichii D6 and L.plantarum L9 was found to be the most active and their optimal inoculum was 1×10^(8) and 1×10^(6) CFU/mL,respectively.Furthermore,the in situ antifungal effect of the mixed culture was evaluated against bakery product spoilage fungi.It was found that the growth of airborne fungi was delayed for up to 7 days.The cell number of L.plantarum L9 was slightly increased by the presence of P.freudenreichii D6.Quantification of three main acids(propionic,lactic and acetic acid)produced by the protective cultures suggested that acetic acid was mainly responsible for the antifungal activity.In conclusion,the mixed culture of P.freudenreichii and L.plantarum may be exploited as biopreservatives in bakery products.