Metamaterial absorbers have attracted considerable attention for applications in the terahertz range. In this Letter, we report design, fabrication, and characterization of a dual band metamaterial absorber that shows two distinct absorption peaks with high absorption. By manipulating periodic patterned structures as well dielectric layer thickness metal–dielectric–metal structure, significantly can be obtained at specific resonance frequencies. Finite-difference time-domain modeling is used...

We present the simulation, implementation, and measurement of a polarization insensitive broadband resonant terahertz metamaterial absorber. By stacking metal-insulator layers with differing structural dimensions, three closely positioned peaks are merged into one absorption spectrum. Greater than 60% is obtained across frequency range 1.86 THz where central resonance 5 THz. The FWHM device 48%, which two half times greater single layer structure. Such metamaterials promising candidates as...

This paper addresses the co-design problem of a fault detection filter and controller for networked-based unmanned surface vehicle (USV) system subject to communication delays, external disturbance, faults, aperiodic denial-of-service (DoS) jamming attacks. First, an event-triggering scheme is proposed enhance efficiency network resource utilization while counteracting impact DoS attacks on USV control performance. Second, event-based switched presented account simultaneous presence Third,...

This paper investigates the tracking control problem of marine surface vessels (MSVs) in presence uncertain dynamics and external disturbances. The facts that actuators are subject to undesirable faults input saturation taken into account. Benefiting from smoothness Gaussian error function, a novel function is introduced replace each nonsmooth actuator nonlinearity. Applying hand position approach, original motion underactuated MSVs transformed standard integral cascade form so vector design...

This paper aims to solve the path following problem for an underactuated unmanned-surface-vessel (USV) based on deep reinforcement learning (DRL). A smoothly-convergent DRL (SCDRL) method is proposed Q network (DQN) and learning. In this new method, improved DQN structure was developed as a decision-making reduce complexity of control law three-degree freedom USV model. An exploring function adaptive gradient descent extract training knowledge from empirical data. addition, reward designed...

This article addresses the problem of path following for underactuated unmanned surface vessels (USVs) formation via a modified deep reinforcement learning with random braking (DRLRB). A control model based on (DRL) is constructed to urge USVs form preset formation. Specifically, an efficient reward function designed from perspective velocity and error distance each USV related given formation, then novel mechanism formulated prevent training decision-making network falling into local...

We present the simulation, implementation, and measurement of a polarization insensitive resonant metamaterial absorber in terahertz region. The device consists metal/dielectric-spacer/metal structure allowing us to maximize absorption by varying dielectric material thickness and, hence, effective electrical permittivity magnetic permeability. Experimental 77% 65% at 2.12 THz (in operating frequency range quantum cascade lasers) is observed for spacer polyimide or silicon dioxide...

This paper presents a novel cooperative unmanned surface vehicle-unmanned aerial vehicle (USV-UAV) platform to form powerful combination, which offers foundations for collaborative task executed by the coupled USV-UAV systems. Adjustable buoys and unique carrier deck USV are designed guarantee landing safety transportation of UAV. The is equipped with series sensors, multiultrasonic joint dynamic positioning algorithm introduced resolving problem To fulfill effective guidance operation UAV,...

The miniaturization of measurement systems currently used to characterize the polarization state light is limited by bulky optical components such as polarizers and waveplates. We propose experimentally demonstrate a simple compact approach measure ellipticity handedness polarized using an ultrathin (40 nm) gradient metasurface. A completely beam decomposed into left circularly right beam, which are steered in two directions metasurface consisting nanorods with spatially varying...

This paper focuses on a problem of event-triggered stabilization for class nonuniformly sampled neural-network-based control systems (NNBCSs). First, new data transmission mechanism is designed based the nonperiodic data. Different from previous works, proposed triggering scheme enables NNBCSs design to enjoy advantages both nonuniform and sampling schemes. Second, under scheme, sampled-data three-layer fully connected feedforward neural-network (TLFCFFNN)-based controller constructed,...

Summary This paper focuses on the analysis and design of event‐triggering scheme for discrete‐time systems. Both static (SETS) adaptive (AETS) are presented nonlinear linear What makes AETS different from SETS is that an auxiliary dynamic variable satisfying a certain difference equation incorporated into condition. The sufficient conditions asymptotic stability closed‐loop event‐triggered control systems under both two triggering schemes given. Especially, case, minimum time between...

In this paper, we investigate the problem of trajectory tracking control for marine surface vehicles (MSVs), which are subject to dynamic uncertainties, external disturbances and unmeasurable velocities. To recover velocities, a novel adaptive neural network-based (NN-based) state observer is constructed. guarantee transient steady-state performance system, nonlinear transformation method proposed by employing error together with newly constructed function, characterized user-defined...

This paper investigates the control issue of marine surface vehicles (MSVs) subject to internal and external uncertainties without velocity information. Utilizing specific advantages adaptive neural network disturbance observer, a classification reconstruction idea is developed. Based on this idea, novel neural-based state observer with proposed recover unmeasurable velocity. Under vector-backstepping design framework, are used resolve for MSVs. To improve performance, serial-parallel...

This article discusses a control problem of underactuated autonomous surface vehicles (ASVs) subject to internal/external uncertainties, input saturations, and actuator faults, proposes novel event-triggered adaptive PID fault-tolerant (ETAPID-FT) solution. To resolve the design difficulty caused by feature, standard multivariate integral cascade form regarding mathematical model ASVs is established. And then, facilitate implementation PID-based framework, nonsmooth saturation nonlinearity...

We have achieved lasing in InAs quantum dot embedded GaAs microdisks under optical pumping. Above the threshold, a drastic increase of emission intensity is accompanied by decrease spectral linewidth whispering gallery modes. The laser light linearly polarized. polarization direction parallel to disk plane. wide gain spectrum dots allows simultaneous several modes microdisk.

In this paper, we investigate the trajectory tracking control problem of surface ship subject to dynamic uncertainties, unknown time-varying disturbances and input saturation. To handle non-smooth saturation nonlinearity compensate Gaussian error function adaptive neural network technique are employed. design, obtain transient motion reference signal, finite-time nonlinear differentiator is applied generate virtual signal extract derivative law. Referring effects kinematics subsystem on...

This article is concerned with attack-resilient event-triggered <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_{\infty }$</tex-math></inline-formula> filtering for a class of networked nonlinear systems described by an interval type-2 (IT2) fuzzy model. Suppose that data transmission from the plant to filter completed through wireless sensor network subject denial-of-service attacks (DoS). In order save...

The main emphasis of this work is placed on the problem collaborative coverage path planning for unmanned surface mapping vehicles (USMVs). As a result, improved <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$BA^{*}$ </tex-math></inline-formula> algorithm ( notation="LaTeX">$C C I B A^{*}$ ) proposed. In algorithm, single vehicle achieved by task decomposition and level map updating. Then multiple USMV...