Hybrid transceiver can strike a balance between complexity and performance of multiple-input multiple-output (MIMO) systems. In this paper, we develop a unified framework on hybrid MIMO transceiver design using matrix-monotonic optimization. The proposed framework addresses general hybrid transceiver design, rather than just limiting to certain high frequency bands, such as millimeter wave (mmWave) or terahertz bands or relying on the sparsity of some specific wireless channels. In the proposed framework, analog and digital parts of a transceiver, either linear or nonlinear, are jointly optimized. Based on matrix-monotonic optimization, we demonstrate that the combination of the optimal analog precoders and processors are equivalent to eigenchannel selection for various optimal hybrid MIMO transceivers. From the optimal structure, several effective algorithms are derived to compute the analog transceivers under unit modulus constraints. Furthermore, in order to reduce computation complexity, a simple random algorithm is introduced for analog transceiver optimization. Once the analog part of a transceiver is determined, the closed-form digital part can be obtained. Numerical results verify the advantages of the proposed design. I. INTRODUCTIONS

As a special carbon material, graphdiyne (GDY) features the superiorities of incomplete charge transfer effect on the atomic level, tunable electronic structure and anchoring metal atoms directly with organometallic coordination bonds M (metal)-C (alkynyl carbon in GDY), providing it an ideal platform to construct single-atom catalysts (ACs). The coordination environment of single atoms anchored on GDY plays a key role in their catalytic performance. The mini-review highlights state-of-the-art progress in the rational design of GDY-based ACs and their applications, and mainly reveals the relationship between the coordination engineering of the GDY-based ACs and corresponding catalytic performance. Finally, some prospects concerning the future development of GDY-based ACs in energy conversion are also discussed.

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For simultaneous wireless information and power transfer (SWIPT), secure communication is an important issue. In this letter, we consider a wireless multiple-input-single-output secure communication system with SWIPT overheard by multiple multi-antenna eavesdroppers. In the system, a transmitter employs artificial noise (AN)-aided transmission and a legitimate receiver employs power splitting (PS) to harvest energy. Our objective is to jointly design AN-aided transmission and PS scheme which maximizes achievable secrecy rate under transmit power constraint and energy harvesting constraint. We propose to include an equality constraint to convert the constraint on information rate from transmitter to eavesdroppers into linear matrix inequalities. Replacing the equality constraint with a convex constraint and a concave constraint, we propose to employ constrained concave convex procedure based algorithm to find a local optimum of the problem. Simulation results demonstrate that the proposed joint optimization of AN-aided transmission and PS scheme outperforms the non-AN-aided one.Index Terms-Energy harvesting (EH), multiple-input-singleoutput (MISO), power splitting (PS), simultaneous wireless information and power transfer (SWIPT), secure communication. 1089-7798 (c)