Acoustic metamaterials have attracted much attention in recent years. cloaks, which make objects invisible to acoustic waves, are the most common use for metamaterials. In this paper, cloaks with arbitrary shapes presented based on transformation acoustics. This method interprets compression and dilation of space as appropriate properties materials. The derived cloak irregular highly inhomogeneous anisotropic, more complex than annulus cloaks. materials kind impossible find nature, difficult...

Abstract This paper presents a novel metasurface antenna element and array, both of which have broadband low radar cross section (RCS) performance. The is constructed by two kinds H‐shaped unit cells. One kind cells properly fed to radiate, the other are used cancel scattering field from former. Thus, an integration performed RCS obtained. Furthermore, array also proposed deliberately introducing metallic vias for isolation. Both almost same radiation performance with conventional patch...

A [pi]-shaped metallic metamaterial (geometrically, a combination medium of C-shaped resonators and continuous wires) is proposed to numerically investigate its transmission band near the resonant frequency, where otherwise it should be negative-permeability (or negative-permittivity) stop if either or continuous-wire constituent separately considered. However, in contrast left-handed materials (LHMs)composed split-ring wires as well other LHMs, this non-left-handed one result intrinsic...

Acoustic cloaking is an important application of acoustic metamaterials. Pentamode cloaks have isotropic mass density and anisotropic stiffness. A different kind pentamode material proposed in this paper. It composed three-dimensional hexagonal unit cells built with double-cone structures. The structure amenable for creating spherical geometries, which might be used cloaking. band structures show that there are gaps shear waves, where only compressional waves exist. effective wave velocities...

Based on the substructure synthesis and modal reduction technique, a computationally efficient elastodynamic model for fully flexible 3-RPS parallel kinematic machine (PKM) tool is proposed, in which frequency response function (FRF) at end of can be obtained any given position throughout its workspace. In proposed model, whole system divided into moving platform subsystem three identical RPS limb subsystems, all joint compliances are included. The spherical revolute treated as lumped...

Acoustic metamaterials are artificial materials with unique acoustic properties, permitting interesting behaviors, such as cloaking. cloaks can make an object appear acoustically “invisible.” Prior that were designed based on transformation methods have been limited by inhomogeneous, anisotropic, and extreme material parameters. In this paper, a multistep is proposed for general tetrahedron. Each tetrahedron contains three homogeneous parts. Since most be approximated polyhedra, they divided...

Acoustic cloaking is an intriguing phenomenon that has attracted lots of attention. The required inhomogeneous and anisotropic properties acoustic cloaks derived with transformation acoustics make them difficult to realize. In this paper, a new mapping relation presented. An cloak can be divided into any number arbitrary triangular patterns, which are mapped from similar patterns in virtual space. Transformation one domain another leads homogeneous using acoustics. resulting composed parts,...

Acoustic metamaterials are artificial materials which can manipulate and control acoustic waves in way that may not exist nature. Pentamode metamaterials, as one kind of have solid structures but behaves like fluid. One application is building cloaks. In this paper, composite pentamode with hexagonal unit cells proposed. The phononic band the cell show there gaps within only compressional modes exist. With variation structures, highly anisotropic properties be obtained. influences geometric...

Metamaterials are artificial materials with properties depending mainly on their designed structures instead of materials. Pentamode metamaterials one type metamaterial. They have solid fluid-like properties, which can only withstand compressive stresses, not shear stresses. Two-dimensional pentamode easier to manufacture than three-dimensional models, so they received wide attention. In this review, the manufacturing, and applications two-dimensional will be discussed. Their water-like most...

Abstract Acoustic metamaterials have the advantages of designability, strong pertinency, small size and good effect, application value in solving problem sound insulation noise reduction. Phononic crystals with wide bandgap multi-bandgap can inhibit elastic wave propagation to some extent. In this study, a three-dimensional phononic crystal model self-similar properties is designed by using fractal method. First, an initial unit constructed, then arm replaced structure itself form structure....

Abstract The detection of underwater acoustic signals is a key focus in ocean development, and metamaterials play crucial role achieving this goal. Pentamode exhibit fluid-like properties, allowing for the propagation compressional waves without shear waves. In study, two-dimensional circular stealth lens based on pentamode was proposed. By applying transformation acoustics theory, theoretical properties lenses were calculated, they verified with Finite Element Method (FEM). A practical...

Acoustic cloaking is an important application of acoustic metamaterials. Although the topic has received much attention, there are a number areas where contributions needed. In this paper, design method for producing cloaks with arbitrary shapes that composed homogeneous parts presented. The cloak divided into sections, each which, in turn, further two parts, followed by transformation acoustics to derive required properties cloaking. With proposed mapping relations, part anisotropic but...

Pentamode metamaterials have been receiving an increasing amount of interest due to their water-like properties. In this paper, a two-dimensional composite pentamode metamaterial rectangular unit cell is proposed. The cells can be classified into two groups, one with uniform arms and the other non-uniform arms. Phononic band structures were calculated derive that permit acoustic wave travelling or total gap impedes propagation by varying structures. influences geometric parameters materials...

Metamaterials are artificial materials with properties that can be designed by man-made structures. Pentamode metamaterials only support compressional stresses at specific frequency ranges, and a band gap is range where no supported. In this paper, an elastic metamaterial hexagonal unit cells studied pentamode bands or gaps low frequencies obtained varying the inner The effects of structural geometric parameters on width analyzed. Simulations composed primitive conducted harmonic stimulation...

In this paper, an ultra-thin metamaterial absorber operating in P and L bands is proposed. Three-dimensional fractal tree topology loaded with lumped resistors adopted to produce broadband absorbing characteristics. The simulated results indicate that the bandwidth of proposed 0.7 - 2GHz absorptivity larger than 80%.

The sound propagation problems in range-dependent waveguides are a common topic underwater acoustics. factors, involving volumetric and bathymetric variations, significantly influence the of energy information. In this paper, coupled-mode method based on multimodal admittance is presented for analyzing scattering waveguides. field expanded terms local basis with modal amplitudes. corresponds to transverse modes waveguide constant physical parameters cross section equal waveguide. This takes...

Abstract Elastic metamaterials with band gaps can block the transmission of elastodynamic waves and have wide applications in life industry. Wide low-frequency are two goals research on elastic gaps. In this study, models two-dimensional self-similar hierarchies were designed. The obtained by replacing arms unit cell composite structures. There is a gap for each second-order replacement. influence geometric dimensions properties was also studied. be altered changing arm dimensions. Vibration...

In order to calibrate the critical dimensional (CD) uncertainty of lithography masks in semiconductor manufacturing, NIM is building a two metrological UV microscope which has traceable measurement ability for nanometer linewidths and pitches. The mainly consists light receiving components, piezoelectric ceramics (PZT) driven stage interferometer calibration framework. components they include all optical elements on path. originates from Köhler high aperture transmit/reflect illumination...

In this paper, a novel giant magnetostrictive force sensor which uses materials rod as the sensitive element was studied. The realised static and dynamic measuring through an integrated linear hall pickup coil respectively. Based on deep analysis of relationship between magnetic flux density measured by actual in rod, combining non-linear constitutive equations electromagnetic induction law, paper expounded principle simultaneously force. this, influence laws bias field, pre-tightening...

Resonant frequency tracking control of electromagnetic acoustic transducers (EMATs) remains a challenge in terms drifting working and reduced conversion efficiency caused by environment changes. This paper presents fixed-time nonsingular integral terminal sliding mode (FT-NITSM) strategy for resonant EMATs to realize precise high robustness performance. Specifically, FT-NITSM method with fast convergence feature is developed controller further designed improve the speed accuracy. Fixed time...

Acoustic cloaking is an important application of metamaterials and has received much attention since it was first proposed. Due to the extreme properties cloaks produced by previous methods, they are difficult fabricate. In addition, with arbitrary shapes more favorable in applications but realize. Therefore, present a method for designing shaped cloak attainable properties. this paper, technique realizing presented dividing into finite parts. Transformation acoustics used derive each part...