The introduction of chirality into organic–inorganic hybrid perovskites (OIHPs) is expected to achieve excellent photoelectric and nonlinear materials related to circular dichroism. Owing to the ...existence of asymmetric center and intrinsic chirality in the chiral OIHPs, the different efficiencies of second harmonic generation (SHG) signal occurs when the circularly polarized light (CPL) with different phases passes through the chiral crystal, which is defined as second harmonic generation circular dichroism (SHG‐CD). Here, the SHG‐CD effect is developed in bulk single crystals of chiral one‐dimensional (1D) (R/S)‐3‐aminopiperidinePbI4. It is the first time that CPL is distinguished using chirality‐dependent SHG‐CD effect in OIHPs bulk single crystals. Such SHG‐CD technology extends the detection range to near infrared region (NIR). In this way, the anisotropy factor (gSHG‐CD) through SHG‐CD signal is as high as 0.21.
Bulk organic–inorganic hybrid perovskite single crystals are used to effectively distinguish the circularly polarized light in the near infrared region by chirality‐dependent second harmonic generation circular dichroism (SHG‐CD) effect with a high anisotropy factor (gSHG‐CD=0.21).
The problem of event-triggered synchronization of master-slave neural networks is investigated in this article. It is assumed that both communication channels from the sensor to controller and from ...controller to actuator are subject to stochastic deception attacks modeled by two independent Markov processes. Two discrete event-triggered mechanisms are introduced for both channels to reduce the number of data transmission through the communication channels. To comply with practical point of view, static output feedback is utilized. By employing the Lyapunov-Krasovskii functional method, some sufficient conditions on the synchronization of master-slave neural networks are derived in terms of linear matrix inequalities, which make it easy to design suitable output feedback controllers. Finally, a numerical example is presented to show the effectiveness of the proposed method.
This paper is concerned with distributed attack detection for a discrete time-varying system monitored by a sensor network. An adversary simultaneously launches distinct data deception attacks on ...both the system dynamics and sensor intercommunication links so as to intentionally falsify the system state and the exchanged sensor measurement outputs. First, delicate distributed estimators are constructed, aiming to provide resilient local estimates for unavailable system state and appropriate residuals for attack detection. Second, an auxiliary Krein space state–space model as well as innovation analysis and a projection technique is skillfully employed to cast the finite horizon distributed estimator design problem into a minimization problem of a certain indefinite quadratic form. A necessary and sufficient condition on the existence of the minimum is derived. Third, a computational efficient recursive algorithm is developed to design desired distributed estimators such that the local estimates and residuals can be both determined at each time step. Furthermore, a two-stage distributed detection mechanism is proposed for each estimator to alert the attack occurrence. Specifically, it is shown that by properly choosing a weighting matrix parameter, each estimator can respectively detect the deception attacks launched on the system layer and sensor intercommunication links. Finally, the effectiveness of the proposed approach is demonstrated through numerical verification.
Networked control systems (NCSs) are systems whose control loops are closed through communication networks such that both control signals and feedback signals can be exchanged among system components ...(sensors, controllers, actuators, and so on). NCSs have a broad range of applications in areas such as industrial control and signal processing. This survey provides an overview on the theoretical development of NCSs. In-depth analysis and discussion is made on sampled-data control, networked control, and event-triggered control. More specifically, existing research methods on NCSs are summarized. Furthermore, as an active research topic, network-based filtering is reviewed briefly. Finally, some challenging problems are presented to direct the future research.
Event-triggered consensus of multiagent systems (MASs) has attracted tremendous attention from both theoretical and practical perspectives due to the fact that it enables all agents eventually to ...reach an agreement upon a common quantity of interest while significantly alleviating utilization of communication and computation resources. This paper aims to provide an overview of recent advances in event-triggered consensus of MASs. First, a basic framework of multiagent event-triggered operational mechanisms is established. Second, representative results and methodologies reported in the literature are reviewed and some in-depth analysis is made on several event-triggered schemes, including event-based sampling schemes, model-based event-triggered schemes, sampled-data-based event-triggered schemes, and self-triggered sampling schemes. Third, two examples are outlined to show applicability of event-triggered consensus in power sharing of microgrids and formation control of multirobot systems, respectively. Finally, some challenging issues on event-triggered consensus are proposed for future research.
This paper provides an overview and makes a deep investigation on sampled-data-based event-triggered control and filtering for networked systems. Compared with some existing event-triggered and ...self-triggered schemes, a sampled-data-based event-triggered scheme can ensure a positive minimum inter-event time and make it possible to jointly design suitable feedback controllers and event-triggered threshold parameters. Thus, more attention has been paid to the sampled-data-based event-triggered scheme. A deep investigation is first made on the sampled-data-based event-triggered scheme. Then, recent results on sampled-data-based event-triggered state feedback control, dynamic output feedback control, H ∞ filtering for networked systems are surveyed and analyzed. An overview on sampled-data-based event-triggered consensus for distributed multiagent systems is given. Finally, some challenging issues are addressed to direct the future research.
This study provides an overview and in-depth analysis of recent advances in stability of linear systems with time-varying delays. First, recent developments of a delay convex analysis approach, a ...reciprocally convex approach and the construction of Lyapunov–Krasovskii functionals are reviewed insightfully. Second, in-depth analysis of the Bessel–Legendre inequality and some affine integral inequalities is made, and recent stability results are also summarised, including stability criteria for three cases of a time-varying delay, where information on the bounds of the time-varying delay and its derivative is totally known, partly known and completely unknown, respectively. Third, a number of stability criteria are developed for the above three cases of the time-varying delay by employing canonical Bessel–Legendre inequalities, together with augmented Lyapunov–Krasovskii functionals. It is shown through numerical examples that these stability criteria outperform some existing results. Finally, several challenging issues are pointed out to direct the near future research.
Surface oxygen vacancies (Vo) regulation is an effective strategy to improve the electrochemical CO2 reduction reaction (CO2RR) performance by lowering the activation energy barrier of CO2; however, ...the lack of precise control over the local atomic structures severely hinders the large‐scale application of Vo‐activated electrocatalyst for CO2RR. Herein, an efficient strategy to facilitate CO2 activation is developed by introducing Vo into transition metal nanoparticles (NPs) with a steam‐assisted chemical vapor deposition method. With the steam process, abundant surface Vo are introduced into the assembled Ni–Fe bimetallic NPs composite (H‐NiFe/NG), which adjust surface Ni/Fe atoms to low‐valent coordinatively unsaturated Ni (+1)/Fe (+2) sites, serving as electron‐rich centers to adsorb and activate inert CO2 molecules. The as‐prepared H‐NiFe/NG composite exhibits excellent catalytic performance with a maximum Faradaic efficiency of 94% at −0.80 V (vs RHE) for CO production with remarkable stability. The density function theory calculations corroborate that the Ni atoms around surface Vo significantly lower the energy barrier for COOH* intermediate formation, which gives a low overpotential for reducing CO2 to CO, exhibiting superior CO2RR performance. This general synthetic strategy provides a new insight to introduce surface Vo on transition metal for efficient CO2 reduction.
A steam‐assisted chemical vapor deposition method is reported to facilitate the CO2 reduction reaction on iron‐group metal. With the steam process, abundant surface oxygen vacancies are introduced into the assembled Ni–Fe bimetallic nanoparticle composites, which effectively activate the basal plane metal active sites, serving as electron‐rich centers to adsorb and activate inert CO2 molecules.
This article is concerned with designing resilient state feedback controllers for a class of networked control systems under denial-of-service (DoS) attacks. The sensor samples system states ...periodically. The DoS attacks usually prevent those sampled signals from being transmitted through a communication network. A logic processor embedded in the controller is introduced to not only receive sampled signals but also capture information on the duration time of each DoS attack. Note that the duration time of DoS attacks is usually both lower and upper bounded. Then the closed-loop system is modeled as an aperiodic sampled-data system closely related to both lower and upper bounds of duration time of DoS attacks. By introducing a novel looped functional, which caters for the <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>-order canonical Bessel-Legendre inequalities, some <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>-dependent stability criteria are presented for the resultant closed-loop system. It is worth pointing out that a number of identity formulas are uncovered, which enable us to apply the notable free-weighting matrix approach to derive less conservative stability criteria. A linear-matrix-inequality-based criterion is provided to design stabilizing state-feedback controllers against DoS attacks. A satellite control system is given to demonstrate the effectiveness of the proposed method.
This study is concerned with the event-triggered control for networked control systems via dynamic output feedback controllers (DOFCs). The output measurement signals of the physical plant are ...sampled periodically. An output-based discrete event-triggering mechanism is introduced to choose those only necessary sampled-data packets to be transmitted through a communication network for controller design. Under this event-triggering mechanism, the resultant closed-loop system is first modelled as a linear system with an interval time-varying delay. Then a novel stability criterion is established by employing the Lyapunov–Krasovskii functional approach. Based on this stability criterion, a new sufficient condition is derived to co-design both the desired DOFCs and the event-triggering parameters. Finally, a satellite control system is taken to show the effectiveness of the proposed method.
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