Luoyang Normal University

The massive low earth orbit (LEO) satellite-empowered Internet of Things (MLS-IoT) network has many advantages including high capacity, low latency, large network coverage, and high reliability. However, the openness and broadcasting on satellite communication links pose huge challenges to protect the security of data delivery, especially to defend against eavesdropping. Leveraging the density of LEO satellite deployment and developing efficient secure communication schemes with the aid of physical layer security (PLS) technique deserve further exploration. To the best of our knowledge, it is an almost untouched issue to employ satellites to transmit jamming signal in MLS-IoT systems since lots of available researches in this line mainly considered cooperative jamming only on ground networks. For this purpose, we propose in this paper a PLS based secure communication enhancement scheme in MLS-IoT network. A jamming scheduling and resource allocation problem is presented for the secrecy rate maximization by dynamically switching the roles of satellites on sub-channels for transmitting private information or jamming signal. An iterative strategy is devised to jointly optimizing jamming scheduling, device association, channel assignment, and power allocation. Numerical results validate that our presented optimization approach could significantly improve the system secrecy rate and achieve the optimal jamming scheduling and resource allocation decisions.

Mechanically interlocked supramolecular compounds have garnered widespread attention but it remains challenging to investigate topological adjustments in such complicated structures. Here, the authors use a bidentate pyridyl ligand featuring an extended π-conjugated plane for coordination-directed self-assembly to engineer three different kinds of sophisticated complexes, including three Linear [3]catenanes 1(OTf)12, 2(OTf)12 and 3(OTf)12, two Borromean rings 4(OTf)12 and 5(OTf)12, and one heterometallic Solomon link 6(OTf)8 by modulating the Ru···Ru distances and conjugation planes of the building units or incorporating bridging silver ions. Subtle alterations in the building units can yield a diversity of topological architectures. Differences in the photothermal conversion properties of 1(OTf)12 - 6(OTf)8 are investigated. Various photothermal conversion efficiencies (23% - 81%) are obtained because of the synergistic effect of π···π stacking interactions and the free radical effect of building units. This finding enables the precise regulation of topology, thereby leading to a remarkable enhancement in photothermal conversion efficiency.

Abstract C 24 H 21 N 5 O 4 Zn, orthorhombic, P 2 1 2 1 2 1 , a = 8.8737(3) Å, b = 11.7127(4) Å, c = 21.0190(8) Å, V = 2184.61(13) Å 3 , Z = 4, R gt ( F ) = 0.0429, wR ref ( F 2 ) = 0.0632, T = 293(2)K.