Synergistically Achieving Superior Sodium Storage of Metal Selenides by Constructing N-Doped Carbon Foams and Utilizing Cu-Driven Replacement Reaction

Metal selenides are considered as one of the most promising anode materials for Na-ion batteries owing to high specific capacity and relatively higher electronic conductivity compared with metal sulfides or oxides. However, such anodes still suffer from huge volume change upon repeated Na⁺ insertion/extraction processes and simultaneously undergo severe shuttle effect of polyselenides, thus leading to poor electrochemical performance. Herein, a facile chemical-blowing and selenization strategy to fabricate 3D interconnected hybrids built from metal selenides (MSe, M = Mn, Co, Cr, Fe, In, Ni, Zn) nanoparticles encapsulated in in situ formed N-doped carbon foams (NCFs) is reported. Such hybrids not only provide ultrasmall active nanobuilding blocks (≈15 nm), but also efficiently anchor them inside the conductive NCFs, thus enabling both high-efficiency utilization of active components and high structural stability. On the other hand, Cu-driven replacement reaction is utilized for efficiently inhibiting the shuttle effect of polyselenides in ether-based electrolyte. Benefiting from the combined merits of the unique MSe@NCFs and the utilization of the conversion of metal selenides to copper selenides, the as-obtained hybrids (MnSe as an example) exhibit superior rate capability (386.6 mAh g⁻¹ up to 8 A g⁻¹) and excellent cycling stability (347.7 mAh g⁻¹ at 4.0 A g⁻¹ after 1200 cycles).     

Decentralized observer-based controller design for large-scale systems with quantized measurements and actuator faults

This paper is focused on designing observer-based decentralized memory feedback controller for ensuring the asymptotic mean square stability of the large-scale systems with minimum H_∞ performance index. Precisely, the unknown interconnection between each subsystems of a large-scale system is assumed to satisfy quadratic bounds, and measured output is quantized by a logarithmic quantizer. Also, the signals are transmitted through the actuator component wherein the occurrence of fault is indispensable. Thus, the impact of faults in actuator is considered in control design to tolerate the fault effects and also for ensuring robust performance. A state space representation of the system is formulated to reconstruct the unmeasurable states via the available informations of input/output dynamics. Based on the designed observer, a decentralized memory feedback controller is developed. Specifically, in terms of linear matrix inequalities, the stability conditions are derived and which are sufficient to guarantee the desired result. At last, simulations are carried out for two numerical examples to validate the potential of the theoretical result.     

Distributed observer design for interconnected nonlinear systems with faults and disturbances based on dynamic event conditions

This study investigated the observer design schemes for interconnected nonlinear systems with actuator faults, sensor faults, external disturbances, and limited measured resources. A novel effective distributed estimation scheme is presented for the interconnected nonlinear system to estimate the states, faults, and lumped disturbances, simultaneously. To save communication resources and to improve information utilization, an adaptive event condition is designed in the sensor channel, and the triggered values are utilized to design the observer. Especially, to handle the sensor fault, the output is separated into two parts, and the estimation is realized with the help of a normal one. In the first part of this study, a class of interconnected nonlinear systems with partial loss of effectiveness of sensor fault is considered, and an event-based distributed estimation scheme is established. In the second part, a class of more universal feedback interconnected nonlinear with both partial loss sensor fault and bias sensor fault is investigated. An augment system is formulated by an augmented vector composed of state and sensor faults. And then the estimation scheme is realized by utilizing the presented event-based distributed observer. The convergence abilities of both the two conditions are proved and, finally, the estimation performances of the presented observer are verified by a numerical simulation system and an inverted pendulum system.     

Discrete-time decentralized linear quadratic control for linear time-varying systems

This article addresses the problem of designing a decentralized control solution for a network of agents modeled by linear time-varying (LTV) dynamics, in a discrete-time framework. A general scheme is proposed, in which the problem is formulated as a classical linear quadratic regulator problem, for the global system, subject to a given sparsity constraint on the gain, which reflects the decentralized nature of the network. A method able to compute a sequence of well-performing stabilizing regulator gains is presented and validated resorting to simulations of two randomly generated LTV systems, one stable and the other unstable. Moreover, a tracking solution is developed, building on the solution to the regulator problem. Both methods rely on a closed-form solution, thus they can be computed very rapidly. Similarly to the centralized solution, both the presented methods require that a window of the future system dynamics is known. Both methods are validated resorting to simulations of: (i) a nonlinear network of four interconnected tanks; and (ii) a large-scale nonlinear network of interconnected tanks. When implemented to a nonlinear network, approximated by an LTV system, the proposed methods are able to compute well-performing gains that track the desired output. Finally, both algorithms are scalable, being adequate for implementation in large-scale networks.     

MPC-based LFC for interconnected power systems with PVA and ESS under model uncertainty and communication delay

In this paper, a cloud-edge-end collaboration-based control architecture is established for frequency regulation in interconnected power systems (IPS). A model predictive control (MPC)-based load frequency control strategy for the IPS with photovoltaic aggregation and energy storage systems under model uncertainty and communication delay is proposed. This can efectively overcome the issues of model uncertainty, random load perturbation and communication delay. First, a state space model for the IPS is constructed. To coordinate the frequency and contact line power fuctuation of the IPS, a robust controller based on the theory of MPC is then designed. Then, considering the communication delay of frequency response commands during transmission, a predictive compensation mechanism is introduced to eliminate the efect of delay while considering model uncertainty. Finally, simulation results verify the efectiveness and robustness of the proposed control strategy.     

Anion-Vacancy Modified WSSe Nanosheets on 3D Cross-Networked Porous Carbon Skeleton for Non-Aqueous Sodium-Based Dual-Ion Storage

Sodium-based dual-ion batteries (SDIBs) have become a new type of energy storage device with great application value because of their high operating voltage, high energy density, and low cost. However, transition-metal dichalcogenide (TMD) anodes show unsatisfactory Na⁺ electrochemical performance owing to the low intrinsic conductivity and inferior ion transport kinetics. Here, an elaborate design is developed to prepare a composite of WSSe nanosheets supported on a 3D cross-networked porous carbon skeleton (WSSe@CPCS), which possesses en-rich anion vacancies and WSSe with expanded inter-layer spacing, as well as an interconnected porous structure. As a result, the WSSe@CPCS anode for sodium-ion batteries (SIBs) exhibits preeminent reversible capacities, excellent cycle stability, and superior rate capability. The systematic electrochemical kinetic analysis and density functional theory results further show that the effect of anion vacancies and CPCS synergistically enhances the conductivity and reduces charge transfer resistance, thus making a great contribution to fast reaction kinetics. Finally, the implementations of the WSSe@CPCS anode in progressive SIB and DIB full-cell configurations exhibit satisfactory performance, which reveals their widely practical application. This research will provide an exciting approach to designing advanced defect-structured tungsten-based TMD materials for SIBs, DIBs, and even a broad range of energy storage.     

3D Printable Gelatin Methacryloyl (GelMA)-Dextran Aqueous Two-Phase System with Tunable Pores Structure and Size Enables Physiological Behavior of Embedded Cells In Vitro

The restricted porosity of most hydrogels established for in vitro 3D tissue engineering applications limits embedded cells with regard to their physiological spreading, proliferation, and migration behavior. To overcome these confines, porous hydrogels derived from aqueous two-phase systems (ATPS) are an interesting alternative. However, while developing hydrogels with trapped pores is widespread, the design of bicontinuous hydrogels is still challenging. Herein, an ATPS consisting of photo-crosslinkable gelatin methacryloyl (GelMA) and dextran is presented. The phase behavior, monophasic or biphasic, is tuned via the pH and dextran concentration. This, in turn, allows the formation of hydrogels with three distinct microstructures: homogenous nonporous, regular disconnected-pores, and bicontinuous with interconnected-pores. The pore size of the latter two hydrogels can be tuned from ≈4 to 100 µm. Cytocompatibility of the generated ATPS hydrogels is confirmed by testing the viability of stromal and tumor cells. Their distribution and growth pattern are cell-type specific but are also strongly defined by the microstructure of the hydrogel. Finally, it is demonstrated that the unique porous structure is sustained when processing the bicontinuous system by inkjet and microextrusion techniques. The proposed ATPS hydrogels hold great potential for 3D tissue engineering applications due to their unique tunable interconnected porosity.     

互联电网低频振荡的相关问题及研究

综述了电力系统低频振荡发生的机理、分析方法、抑制措施及存在的相关问题;并提出建立基于广域测量系统(WAMS)的实时低频振荡监控系统,将频域分析法与Prony辨识法结合起来,在线分析系统的振荡模态;并首次提出将模态级数法用于互联电网“超低频振荡”的机理分析。     

Dynamic event-triggered distributed interval functional observers for interconnected systems

In this paper, we design dynamic event-triggered interval functional observers (FOs) for interconnected systems comprising $M$ $(M\ge 2)$ subsystems where each subsystem is subject to nonlinearities and output disturbances. Our design method consists of two main steps. First, we design decentralized dynamic event-triggered mechanisms (ETMs) which use only locally measured output information. We then consider the design of distributed interval FOs by using the newly proposed ETMs. Their existence conditions are established and formulated in terms of linear programming. We also derive a bound on the estimated error vector and show that this bound is the smallest. Thus, this ensures that the unknown linear functional state vector can be estimated within an upper and lower bound of its true value by the designed interval observers. Finally, we apply the obtained results to design dynamic event-triggered interval observers for linear functions of the state vectors of an $N$-machine power system.