In this paper, the consensus tracking control problem of second-order multiagent systems with unknown nonlinear dynamics, immeasurable states, and disturbances is investigated. The nonlinear dynamics ...in multiagent systems do not satisfy the matched condition. In this paper, fuzzy logic system is introduced to approximate the unknown nonlinear dynamics, and adaptive high-gain observer is designed to estimate the unmeasured states. Based on backstepping approach and Lyapunov theory, a new adaptive fuzzy distributed controller is proposed for each agent only using the information of itself and its neighbors. Then the consensus tracking is achieved under the designed distributed controller. Moreover, it is proved that all the signals in the multiagent systems are semiglobally uniformly ultimately bounded, and the consensus tracking error converges to a small neighborhood of the origin that can be designed as small as possible. Finally, the simulation result illustrates the effectiveness of the designed controller.
2D transition metal carbides and nitrides, named MXenes, are attracting increasing attentions and showing competitive performance in energy storage devices including electrochemical capacitors, ...lithium‐ and sodium‐ion batteries, and lithium–sulfur batteries. However, similar to other 2D materials, MXene nanosheets are inclined to stack together, limiting the device performance. In order to fully utilize MXenes' electrochemical energy storage capability, here, processing of 2D MXene flakes into hollow spheres and 3D architectures via a template method is reported. The MXene hollow spheres are stable and can be easily dispersed in solvents such as water and ethanol, demonstrating their potential applications in environmental and biomedical fields as well. The 3D macroporous MXene films are free‐standing, flexible, and highly conductive due to good contacts between spheres and metallic conductivity of MXenes. When used as anodes for sodium‐ion storage, these 3D MXene films exhibit much improved performances compared to multilayer MXenes and MXene/carbon nanotube hybrid architectures in terms of capacity, rate capability, and cycling stability. This work demonstrates the importance of MXene electrode architecture on the electrochemical performance and can guide future work on designing high‐performance MXene‐based materials for energy storage, catalysis, environmental, and biomedical applications.
Hollow Ti3C2Tx spheres and 3D macroporous MXene films are fabricated using a sacrificial template approach. The 3D MXene films are free‐standing, flexible, and highly conductive. They can serve directly as electrodes for Na‐ion storage and exhibit high capacities accompanied with excellent stabilities and rate performance.
This paper focuses on the leader-following consensus control problem of multiagent systems in random vibration environment. The Itô stochastic systems with heterogeneous unknown dynamics and ...external disturbances are established to describe the agents in random vibration environment. The fuzzy logic systems are applied to approximate the unknown nonlinear dynamics, and one adaptive parameter is designed to decay the effect of external disturbances. We present a new distributed consensus controller for each follower agent only based on local information that is measured or received from its neighbors and itself. Under the consensus controller, we prove that all the follower agents can keep consensus with the leader, even though only a very small part of follower agents can measure or receive the state information of the leader. Furthermore, the states of all the follower agents are bounded in probability. Finally, the simulation results are provided to illustrate the effectiveness of the designed algorithm.
MXenes are a family of atomically thin, two-dimensional (2D) transition metal carbides and carbonitrides with many attractive properties. Two-dimensional Ti3C2Tx (MXene) has been recently explored ...for applications in water desalination/purification membranes. A major success indicator for any water treatment membrane is the resistance to biofouling. To validate this and to understand better the health and environmental impacts of the new 2D carbides, we investigated the antibacterial properties of single- and few-layer Ti3C2Tx MXene flakes in colloidal solution. The antibacterial properties of Ti3C2Tx were tested against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) by using bacterial growth curves based on optical densities (OD) and colonies growth on agar nutritive plates. Ti3C2Tx shows a higher antibacterial efficiency toward both Gram-negative E. coli and Gram-positive B. subtilis compared with graphene oxide (GO), which has been widely reported as an antibacterial agent. Concentration dependent antibacterial activity was observed and more than 98% bacterial cell viability loss was found at 200 μg/mL Ti3C2Tx for both bacterial cells within 4 h of exposure, as confirmed by colony forming unit (CFU) and regrowth curve. Antibacterial mechanism investigation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with lactate dehydrogenase (LDH) release assay indicated the damage to the cell membrane, which resulted in release of cytoplasmic materials from the bacterial cells. Reactive oxygen species (ROS) dependent and independent stress induction by Ti3C2Tx was investigated in two separate abiotic assays. MXenes are expected to be resistant to biofouling and offer bactericidal properties.
MXenes, a new family of 2D materials, combine hydrophilic surfaces with metallic conductivity. Delamination of MXene produces single-layer nanosheets with thickness of about a nanometer and lateral ...size of the order of micrometers. The high aspect ratio of delaminated MXene renders it promising nanofiller in multifunctional polymer nanocomposites. Herein, Ti ₃C ₂T ₓ MXene was mixed with either a charged polydiallyldimethylammonium chloride (PDDA) or an electrically neutral polyvinyl alcohol (PVA) to produce Ti ₃C ₂T ₓ/polymer composites. The as-fabricated composites are flexible and have electrical conductivities as high as 2.2 × 10 ⁴ S/m in the case of the Ti ₃C ₂T ₓ/PVA composite film and 2.4 × 10 ⁵ S/m for pure Ti ₃C ₂T ₓ films. The tensile strength of the Ti ₃C ₂T ₓ/PVA composites was significantly enhanced compared with pure Ti ₃C ₂T ₓ or PVA films. The intercalation and confinement of the polymer between the MXene flakes not only increased flexibility but also enhanced cationic intercalation, offering an impressive volumetric capacitance of ∼530 F/cm ³ for MXene/PVA-KOH composite film at 2 mV/s. To our knowledge, this study is a first, but crucial, step in exploring the potential of using MXenes in polymer-based multifunctional nanocomposites for a host of applications, such as structural components, energy storage devices, wearable electronics, electrochemical actuators, and radiofrequency shielding, to name a few.
Significance Two-dimensional transition metal carbides (MXenes) offer a quite unique combination of excellent mechanical properties, hydrophilic surfaces, and metallic conductivity. In this first report (to our knowledge) on MXene composites of any kind, we show that adding polymer binders/spacers between atomically thin MXenes layers or reinforcing polymers with MXenes results in composite films that have excellent flexibility, good tensile and compressive strengths, and electrical conductivity that can be adjusted over a wide range. The volumetric capacitances of freestanding Ti ₃C ₂T ₓ MXene and its composite films exceed all previously published results. Owing to their mechanical strength and impressive capacitive performance, these films have the potential to be used for structural energy storage devices, electrochemical actuators, radiofrequency shielding, among other applications.
A strategy to prepare flexible and conductive MXene/graphene (reduced graphene oxide, rGO) supercapacitor electrodes by using electrostatic self‐assembly between positively charged rGO modified with ...poly(diallyldimethylammonium chloride) and negatively charged titanium carbide MXene nanosheets is presented. After electrostatic assembly, rGO nanosheets are inserted in‐between MXene layers. As a result, the self‐restacking of MXene nanosheets is effectively prevented, leading to a considerably increased interlayer spacing. Accelerated diffusion of electrolyte ions enables more electroactive sites to become accessible. The freestanding MXene/rGO‐5 wt% electrode displays a volumetric capacitance of 1040 F cm−3 at a scan rate of 2 mV s−1 , an impressive rate capability with 61% capacitance retention at 1 V s−1 and long cycle life. Moreover, the fabricated binder‐free symmetric supercapacitor shows an ultrahigh volumetric energy density of 32.6 Wh L−1, which is among the highest values reported for carbon and MXene based materials in aqueous electrolytes. This work provides fundamental insight into the effect of interlayer spacing on the electrochemical performance of 2D hybrid materials and sheds light on the design of next‐generation flexible, portable and highly integrated supercapacitors with high volumetric and rate performances.
MXene/reduced graphene oxide (rGO) hybrid films are prepared through electrostatic self‐assembly of negatively charged MXene nanosheets and positively charged rGO nanosheets. rGO nanosheets are inserted in between MXene layers as conductive spacers, efficiently alleviating the self‐restacking of both rGO and MXene. As a result, the hybrid films exhibit ultrahigh volumetric capacitance and an impressive rate capability.
In this article, the event-triggered bipartite consensus problem for stochastic nonlinear multiagent systems (MASs) with unknown dead-zone input under the prescribed performance is studied. To ...surmount the influence of the dead-zone input, the dead-zone model is transformed into a linear term and a disturbance term. Meanwhile, the prescribed tracking performance is realized by developing a speed function, which means that all tracking errors of MASs can converge to a predefined set in a given finite time. Moreover, the unknown nonlinear dynamics are approximated by fuzzy-logic systems. By combining the dynamic surface approach and the Lyapunov stability theory, we design an adaptive event-triggered control algorithm, such that the bipartite consensus problem of stochastic nonlinear MASs can be achieved, and all signals are semiglobally uniformly ultimately bounded in probability of the closed-loop systems. Finally, simulation examples are proposed to verify the feasibility of the algorithm.
The intercalation of ions into layered compounds has long been exploited in energy storage devices such as batteries and electrochemical capacitors. However, few host materials are known for ions ...much larger than lithium. We demonstrate the spontaneous intercalation of cations from aqueous salt solutions between two-dimensional (2D) Ti₃C₂ MXene layers. MXenes combine 2D conductive carbide layers with a hydrophilic, primarily hydroxyl-terminated surface. A variety of cations, including Na⁺, K⁺, NH₄⁺, Mg²⁺, and Al³⁺, can also be intercalated electrochemically, offering capacitance in excess of 300 farads per cubic centimeter (much higher than that of porous carbons). This study provides a basis for exploring a large family of 2D carbides and carbonitrides in electrochemical energy storage applications using single- and multivalentaions.
In this article, we propose the swarm control for a self-organized system with fixed and switching topology, which can realize aggregation, dispersion, or switching formation when swarm moves. The ...self-organized system can automatically construct the communication topology for intelligent units in swarm. Swarm control can realize aggregation and dispersion of intelligent units based on its communication topology when swarm moves. The proposed swarm control, in which distances between the related intelligent units are time varying, is different from traditional swarm consensus or swarm formation maintenance. To design swarm control, we define the normalization adjacency matrix and normalization degree matrix based on communication topology. The communication topology is automatically generated based on relation-invariable persistent formation. Depending on whether the communication topology changes or not, the swarm control can be classified as fixed topology and switching topology. Then, the swarm control with fixed and switching topology is designed and analyzed, respectively. The swarm control can realize stability asymptotically when topology is fixed and realize stability in finite time when topology is switched. The simulation results show that the proposed approaches are effective.
PDF
