992 results about "Metamaterial" patented technology

The invention relates to the technical field of fault diagnosis of power electronic equipment, and particularly discloses a fault analysis and diagnosis method and system for a mining high-voltage frequency converter, and the method comprises the steps: collecting the skin effect depth and parasitic parameter drift distance in real time under a high-frequency working condition through a multi-physics field sensor array; constructing three-dimensional current density distribution of the conductor based on a non-Euclidean space mesh generation technology, and dynamically correcting the equivalent resistivity of the conductor in combination with a metamaterial database to calculate a dynamic eddy current loss characteristic value; optimizing and solving the parasitic parameter time-varying evolution equation by using a quantum annealing algorithm to obtain a voltage peak sensitivity characteristic value; inputting the characteristic value into a pre-trained deep residual shrinkage network diagnosis model for multi-modal fusion analysis, and outputting a fault risk assessment result; according to the method, the problem of parasitic parameter time-varying characteristic modeling in the vibration environment is innovatively solved, and early warning of hidden faults is achieved.

The invention belongs to the technical field of all-dielectric metamaterial optical devices and machine learning, and discloses an all-dielectric metasurface target spectral response reverse design method based on deep learning. And realizing efficient prediction of the transmission spectrum by using a convolutional neural network-recurrent neural network-residual network architecture. A fitness function is designed, and a machinable structure is generated by aiming at single-peak and multi-peak target wavelength optimization and combining a linear and shape optimization strategy. The method breaks through the limitation of spectrum dependence and fixed structure type of the traditional reverse design, realizes on-demand design, and remarkably improves the design efficiency and processing compatibility of the integrated photonic device.

The technology described herein is directed towards one or more modular metasurfaces arranged with unit cells for sound absorption, in which the unit cells are based on Helmholtz resonators that are deployed proximate to a server, without substantially obstructing airflow from the server fan(s). Each sound absorbing unit-cells is designed and constructed based on a specific resonance frequency, and includes a neck portion and air chamber dimensioned to resonate at the desired resonance frequency and thereby inverse phase cancel corresponding narrowband frequencies of incoming sound waves. The metasurfaces can be arranged in a modular frame structure of surrounding unit cells, positioned behind the server's fan(s), with an opening in the frame structure to facilitate airflow therethrough, without obstructing or substantially obstructing the airflow to the surrounding environment.

The invention discloses an intelligent optimization driving electromagnetic information metasurface multi-dimensional dynamic regulation and control system, solves the problem that the function solidification of an existing metasurface is difficult to dynamically adjust, and belongs to the crossing field of electromagnetic metamaterials and intelligent control technologies. The method comprises the steps that a sensor network collects environment multi-dimensional information of a programmable metasurface unit in real time; the controller processes the environment multi-dimensional information to obtain a multi-dimensional sensing result; the multi-dimensional interaction layer inputs design parameters, the intelligent decision-making layer combines the design parameters and a multi-dimensional perception result to construct a target joint optimization model, reverse design is carried out on the super-surface array coding sequence, and a display array coding pattern and a three-dimensional radiation pattern / two-dimensional radiation pattern are obtained according to the designed super-surface array coding sequence; displaying on the multi-dimensional interaction layer; and the controller performs real-time electromagnetic response reconstruction and 1-bit or 2-bit phase modulation on the programmable metasurface unit through the field programmable gate array according to the designed metasurface array coding sequence.

The invention relates to a radial frequency-doubled sound filtering metamaterial and a topological optimization design method thereof.The radial frequency-doubled sound filtering metamaterial comprises scatterers which are arranged on a base body and distributed in a concentric circle mode, and the topological optimization design method comprises the following steps that a two-dimensional axial symmetry model is established, the two-dimensional axisymmetric model corresponds to the cross section of the radial frequency-doubled sound filtering metamaterial in the radius direction and comprises periodically arranged unit structures, and each unit structure comprises a main board and a square design domain; a Floquet periodic boundary condition is applied to parallel boundaries of a unit structure in the radius direction, other boundaries are set as free boundaries, a genetic algorithm is adopted to carry out iterative optimization on the material distribution topology of a square design domain, the optimal material distribution topology of the square design domain is obtained, and then the final optimized shape of the radial double-frequency sound filtering metamaterial is obtained. Compared with the prior art, the invention has the advantages of capability of realizing omni-directional sound wave frequency doubling filtering, high design reliability and the like.

The invention belongs to the technical field of radar wave-absorbing materials, and discloses a double-sided wave-absorbing broadband stealth composite material and a preparation method thereof. The broadband stealth composite material with the double-sided wave absorbing function comprises a non-metal-based composite material body and at least five metamaterial layers arranged in the thickness direction of the non-metal-based composite material body at intervals. The number of the metamaterial layers is an odd number, a middle metamaterial layer is arranged in the middle of the metamaterial layers in the thickness direction, and the rest metamaterial layers are symmetrically distributed on the two sides of the middle metamaterial layer; the metamaterial layer comprises conductive pattern units which are periodically arranged; the relative dielectric constant of the nonmetal-based composite material body is not greater than 10; the double-sided wave-absorbing broadband stealth composite material does not contain a metal reflecting layer. When electromagnetic waves with the frequency of 1-18 GHz vertically enter the material, the transmissivity of the material is small (smaller than-13 dB, namely smaller than 5%), and meanwhile the material has low reflectivity in a broadband. And the preparation method is simple to operate and easy to realize large-scale production.

The technology described herein is directed towards a metasurface arranged with unit cells for broadband and / or multiband sound absorption, in which the unit cells are based on the principles of Helmholtz resonators. Deeply subwavelength sound absorbing unit cells are designed and constructed based on desired resonance frequencies. Each unit cell includes a neck portion and air chamber dimensioned to resonate at a desired resonance frequency and thereby inverse phase cancel corresponding frequencies of incoming sound waves. Differently designed and arranged subgroups of unit cells are part of the metasurface, which can be positioned proximate to a noise source. As practical examples, the metasurface or multiple metasurfaces can be placed near or wrapped around a computer server or rack of servers to absorb fan noise. The metasurface components (including the unit cells) can be printed by a 3D printer to result in a thin, light-weight, and cost effective noise absorbing metasurface.

The invention belongs to the technical field of terahertz detection, and discloses a terahertz metamaterial enhanced spectrum detection system. Comprising the following steps: constructing a metamaterial enhancement factor tensor matrix according to the interaction between terahertz waves and a metamaterial; performing local field enhancement and surface plasma resonance optimization on the target sample based on the metamaterial enhancement factor tensor matrix to obtain a feature enhancement spectroscopy mapping function; constructing a multi-dimensional detection feature space based on a feature enhancement spectroscopy mapping function; a spectral signal enhancement topology network is formed based on the multi-dimensional detection feature space; enhancing the topological network based on the spectral signal, and generating an enhanced spectral feature discrimination function; obtaining a high-precision terahertz spectrum detection result based on the enhanced spectrum characteristic discrimination function; according to the invention, internal correlation between spectral characteristics can be mined, and comprehensive description of sample information is enhanced, so that high-precision terahertz spectrum detection is realized.

The invention discloses an ultra-large octave wave absorber based on a photoconductive material, and belongs to the field of electromagnetic metasurfaces and metamaterials. Comprising a light response wave-absorbing metasurface and a light driving module capable of projecting different patterns on the surface of the light response wave-absorbing metasurface, array wave-absorbing units of different sizes are obtained on the light response wave-absorbing metasurface by switching the projected patterns, and impedance of a target frequency band is matched by changing equivalent capacitance / inductance of a wave-absorbing unit structure; the light driving module can project a preset light pattern on the light response wave-absorbing metasurface, so that the equivalent impedance distribution of the light response wave-absorbing metasurface is changed; according to the light response wave-absorbing metasurface, the conductivity distribution of the metasurface units is changed through light control, and the wave-absorbing frequency band is adjusted in real time, that is, dynamic adjustment of the wave-absorbing performance is achieved through non-contact light control. According to the invention, the limitation of narrow bandwidth and passive fixation of a traditional wave absorber is broken through, and electromagnetic wave control with ultra-large octave, high absorptivity and real-time reconfigurability is realized.

Devices configured to emit colored light when illuminated with ultraviolet light and color-shifting displays containing the same are disclosed.

The invention belongs to the technical field of electromagnetic wave absorption, and particularly discloses a three-dimensional structure wave-absorbing metamaterial which comprises a first three-dimensional structure layer, a second three-dimensional structure layer and a metal backboard which are sequentially arranged from top to bottom, the first three-dimensional structure layer comprises a first top layer and a first three-dimensional absorption enhancing framework arranged on the lower surface of the first top layer, and the second three-dimensional structure layer comprises a second top layer and a second three-dimensional absorption enhancing framework arranged on the lower surface of the second top layer. A first high-impedance metasurface and a second high-impedance metasurface are loaded on the lower surface of the first three-dimensional absorption enhancement skeleton at intervals; the second three-dimensional structure layer comprises a second top layer and a second three-dimensional absorption enhancement skeleton arranged on the lower surface of the second top layer, and a third high-impedance metasurface is loaded on the top surface of the second top layer. By adopting the three-dimensional structure wave-absorbing metamaterial, ultra-wideband absorption and large-angle stability can be achieved under the condition that the thickness is small, light and thin wideband application of a wave-absorbing body is facilitated, and the three-dimensional structure wave-absorbing metamaterial has great practical value in the field of electromagnetic compatibility.

The invention provides a multifunctional passive cooling optical metamaterial fiber, yarn and fabric and a preparation method thereof. The passive cooling optical metamaterial fiber is composed of high-refractive-index inorganic micro-nano particles and / or a micro-nano functional material and a polymer substrate material. Wherein wavelength / sub-wavelength scale micro-nano particles are uniformly distributed in a substrate material as a random scattering medium to form a random optical metamaterial system, and reflection enhancement of the optical metamaterial fabric in a solar spectrum band is realized by utilizing a multiple Mie resonance collective effect. According to the passive cooling optical metamaterial fiber, a circular structure, a skin-core structure and the like are prepared through melt spinning, high-refractive-index inorganic micro-nano particles are added into a skin layer and used for sunlight band wide spectrum regulation and control, and a micro-nano functional material is added into a core layer, so that multiple functions are effectively achieved.

The invention belongs to the technical field of metamaterials, and particularly relates to a diamond substrate lattice metamaterial and an additive manufacturing method thereof. The structure is designed based on the geometric configuration of a diamond lattice, and has excellent high specific absorption mechanical properties. The design process comprises the following steps: firstly, carrying out spatial registration positioning on the basis of a unit cell structure with a preset wall thickness t and a unit cell width a; then, through a multi-unit-cell splicing design, the unit cells are spliced repeatedly for 12 times to form three-dimensional periodic stacking; then, the stacked structure is cut along the six datum planes; then cross plates are inserted into the six cutting faces respectively to enhance the integrity and strength of the structure; and finally, a complete DM plate lattice metamaterial structure is formed. The structure is provided with a plate-plate cross supporting framework, a complex three-dimensional inner cavity and highly symmetrical space distribution, the energy absorption capacity under unit mass is greatly improved, the mechanical properties are basically consistent in multiple directions, and the structure is suitable for the engineering fields of impact protection, energy absorption buffering and the like.

The invention discloses an all-dielectric structure type broadband wave-absorbing metamaterial and a design method thereof. The all-dielectric structure type broadband wave-absorbing metamaterial comprises a substrate and a plurality of resonators, the plurality of resonators are periodically and uniformly arrayed on the surface of the substrate, the adjacent resonators are connected with each other, each resonator comprises a pyramid structure unit and a grid structure unit, the pyramid structure units are nested in the grid structure units to form a pyramid-grid composite resonator, and the substrate and the resonators are both made of a high dielectric loss composite material. Based on the brand new design angle of wave absorbing performance complementation, the limitation of the wave absorbing performance of a single structure is broken through, the wave absorbing performance is improved from the microstructure level, meanwhile, efficient electromagnetic wave energy absorption is achieved in a wider frequency range, multi-stage dissipation and broadband impedance matching of incident electromagnetic waves are achieved, and the wave absorbing performance is improved. And the technical limitation of thickness constraint and narrow-band response of the traditional wave-absorbing material is broken through.

The invention discloses a digital coding metamaterial forward-looking video imaging method and system based on sparse low-rank decomposition, and mainly solves the problems of motion blur and poor imaging stability in a non-sparse observation scene of a moving target in the prior art. According to the implementation scheme, echo data of N frames of observation scenes are collected; decomposing a scattering coefficient vector of an observation scene corresponding to each frame of echo into a low-rank vector of a background area corresponding to the observation scene and a sparse vector of a dynamic change area, and expressing a separation problem of the two change areas as a joint low-rank and sparse optimization problem; performing convex relaxation processing on the optimization problem, and converting the optimization problem subjected to the convex relaxation processing into an optimization problem in an unconstrained form to obtain a sparse low-rank decomposition-based metamaterial forward-looking video imaging model; and solving the constructed imaging model, and realizing multi-frame image reconstruction and video synthesis based on a solving result. According to the method, the imaging resolution and reconstruction stability of the non-sparse scene containing the moving target are improved, and the method can be used for intelligent security check and medical detection.

The invention discloses a quasi-zero stiffness vibration double-control device based on metamaterials, and relates to the technical field of vibration isolation and vibration reduction control. The device comprises a vertical vibration isolation structure, a horizontal vibration isolation layer, a middle plate, an upper connecting plate and a lower connecting plate, the vertical vibration isolation structure is connected to the top face of the horizontal vibration isolation layer, and the device is characterized in that the vertical vibration isolation layer is composed of a plurality of quasi-zero-stiffness metamaterial cell elements which are horizontally and evenly distributed, and each quasi-zero-stiffness metamaterial cell element comprises a buckle mechanism and a wave-shaped beam mechanism; the negative stiffness generated in the movement process of the buckle mechanism and the positive stiffness generated in the loading process of the wave-shaped beam mechanism counteract each other, and a quasi-zero stiffness mechanism is formed. According to the quasi-zero-stiffness metamaterial cell element, the initial stiffness of the quasi-zero-stiffness metamaterial cell element can be changed by adjusting the pre-tightening force of the bolts, so that the vertical bearing capacity is changed, different engineering requirements are met, the problem that low-frequency vibration isolation of a traditional vibration isolation device fails is solved, and the quasi-zero-stiffness metamaterial cell element is particularly suitable for meeting the earthquake and vibration dual-protection requirements of rail transit upper cover buildings.

The invention discloses a bifunctional chiral metamaterial surface capable of switching polarization conversion and wave absorption, and belongs to the technical field of electromagnetic metamaterials. The method is used for solving the problem that most existing chiral super-structure surfaces cannot realize dynamic adjustability and quantitative controllability and cannot have dual functions of polarization conversion and wave absorption at the same time. The super-structure surface unit structure is composed of a graphene film layer, a gold-vanadium dioxide resonance layer, a silicon dielectric layer and a bottom-layer continuous gold film. Switching of two functions of polarization conversion and wave absorption is realized by changing the conductivity of vanadium dioxide; polarization conversion and dynamic regulation and control of the wave absorbing efficiency are realized by changing the Fermi level of the graphene; quantitative controllability of polarization conversion and a wave absorbing function is realized by controlling a function weighting function. Besides, the chiral super-structure surface also has the advantages of incident angle robustness, small thickness and small size, has double functions of broadband, and has potential application value in the fields of optical devices, communication equipment, biomedical sensors and the like.

The invention discloses a broadband wave-absorbing metamaterial of a cone-cap-like structure and application of the broadband wave-absorbing metamaterial, and belongs to the technical field of electromagnetic metamaterials. The broadband wave-absorbing metamaterial with the cone-cap-like structure comprises a rectangular shell, a hollow cylindrical table and a cone, an open groove is formed in one surface of the rectangular shell; the hollow cylindrical table is arranged in the open groove, and the outer side wall of the hollow cylindrical table is externally tangent to the inner side wall of the rectangular shell; the cone is arranged in the hollow cylindrical table, and the bottom face of the cone is connected with the bottom face of the hollow cylindrical table. The broadband wave-absorbing metamaterial structure adopting the cone-cap-like design shows excellent broadband wave-absorbing capacity in a microwave frequency band, wave-absorbing characteristics can be accurately controlled by adjusting key parameters, different application requirements are met, the broadband wave-absorbing metamaterial has excellent anti-polarization interference capacity and stability of wave-absorbing performance, and the broadband wave-absorbing metamaterial is suitable for being used in the microwave field. The method has the production advantages of rapidness, low cost and high efficiency.

The invention provides a robust optimization method and device for a low-frequency sound absorption metamaterial, and relates to the technical field of punching, and the method comprises the steps: obtaining a response function of a target metamaterial through employing a linear one-dimensional rheological model; determining a target coupling region by using an imaginary part of a transfer function zero point corresponding to the response function or a size relationship between inherent loss and radiation loss as a coupling criterion, and determining a closed coupling region where a preset parameter point is located as an initial robust region; the target coupling region comprises a closed coupling region; the preset parameter point meets the one-dimensional frequency domain response of the target metamaterial; and determining the size of the initial robust region by using the Lexberg measure of the Euclidean space, and optimizing the robust region by maximizing the Lexberg measure of the initial robust region in the Euclidean space to obtain a target robust region. According to the method, the maximum robust region in the parameter space is found through maximum measurement, so that the response characteristics of the viscoelastic damping material under the actual working condition can be accurately described.

A carbon-based conductive film-based ultralight wide-angle absorbing metamaterial with full-frequency absorption within 2-18 GHz, including a first dielectric substrate, a first carbon-based conductive film array structure layer, a second dielectric substrate, a second carbon-based conductive film array structure layer, a third dielectric substrate, and a third carbon-based conductive film array structure layer, which are laminated in sequence with the first dielectric substrate as a bottom. The first, second, and third carbon-based conductive film array structure layers are each composed of discrete carbon-base conductive film patches arranged in a periodic array. A method for preparing such absorbing metamaterial is also provided.

A system for millimeter RADAR object recognition and classification using sub-band frequency interference and resonance effects from primary targets signals and reflected signals from secondary target preferably in the form of Wideband Chaos Generating Material (WCGM) objects, preferably detecting frequency dependent absorbing material, frequency dependent resonance effects from the second and primary target objects, frequency signal resonance effects caused by water molecule dipole effects in different sugar solutions, impedance of material, shape of metamaterial, and interference effects due to combination of signal sources resulting in a wider range of transmitter and scanning frequency band for RADAR based interrogation of target objects. The RADAR system makes opportunistic use of traditionally seen problematic interference signals, as extra signal sources providing extended range and frequency bandwidth for frequency-based interrogation of target object signatures in a frequency-intensity plane, a frequency-polarization plane, and a frequency-phase shift plane for doppler effects.

The invention discloses a stair energy consumption ship collision prevention system based on a metamaterial structure, which comprises an ultra-high performance concrete panel, a stair energy consumption collision prevention layer, a rubber fender, a bridge pier, a bridge bearing platform and a bridge pile foundation, and the stair energy consumption collision prevention layer comprises a variable rigidity unit, a light energy consumption material, a vertical steel plate, an upper top plate and a lower bottom plate, the variable rigidity unit is formed by connecting a plurality of concave hexagonal units through transverse and longitudinal steel plates, and the middle hollow structure is filled with light energy dissipation materials capable of absorbing and dispersing impact energy, such as polyurethane foam, ceramsite and rubber particles. The variable rigidity unit and the steel plates are welded into a whole, and the protection device and the protected pier are connected through a rubber fender. The overall rigidity of the protection device can be increased along with structural deformation when the protection device is impacted, so that the variable-rigidity cascade energy dissipation anti-collision effect is achieved, the ship and bridge collision time can be effectively prolonged, the ship collision force can be effectively reduced, and bidirectional protection of the ship and the bridge is achieved.

The invention belongs to the technical field related to structure optimization, and discloses a cross-scale topological optimization method of an auxetic metamaterial with a specified deformation mode, which comprises the following steps: (1) according to a given metamaterial function target, introducing an elastic tensor component constraint condition to establish a negative Poisson's ratio microstructure topological optimization model; (2) gradually changing the volume rate constraint of the initial microstructure to obtain a series of negative Poisson's ratio gradient microstructures with different equivalent densities; (3) constructing a multi-phase material interpolation model based on a Kriging model, constructing an auxetic metamaterial cross-scale topological optimization model with a specified deformation mode, and deducing the sensitivity of a target function to design variables; and (4) calculating and updating the design variable until the output meets the convergence condition, and outputting the auxetic metamaterial with the target deformation mode. According to the method, the limitation that the deformation mode of the traditional auxetic metamaterial cannot be locally regulated and controlled is overcome, and the design efficiency of the cross-scale design problem of the two-dimensional auxetic metamaterial under the complex condition is improved.

The invention discloses a total space vector vortex generator, which comprises a plurality of tetramer super units which have the same structure and are arranged in a periodic array at equal intervals, and each tetramer super unit comprises two first chiral metamaterial unit assemblies and two second chiral metamaterial unit assemblies which are respectively arranged along diagonal lines; the first chiral metamaterial unit assembly comprises a first patch antenna, a first dielectric layer, a metal backboard, a bonding medium, a second patch antenna and a second dielectric layer which are sequentially arranged from top to bottom; the structure of the second chiral metamaterial unit assembly is the same as that of the first chiral metamaterial unit assembly, and the in-plane rotation angle is different from that of the first chiral metamaterial unit assembly; by rotating the first patch antenna and the second patch antenna of the two chiral super units around the central point, phase distribution is independently designed in four different circular polarization transmission channels, and meanwhile, vortex beam topological charges generated in corresponding channels in transmission and reflection modes are controlled, so that the transmission bandwidth can be expanded, and the transmission efficiency is improved. And the reflection and transmission efficiency is improved.

A polarization conversion transmission type reconfigurable metamaterial structure with amplitude-phase independent regulation and control is formed by copying and translating n * n basic units, and each basic unit comprises three dielectric layers, five metal layers and two air layers; the dielectric layers comprise a first dielectric layer, a second dielectric layer and a third dielectric layer from top to bottom; a first air layer is arranged between the first dielectric layer and the second dielectric layer, and a second air layer is arranged between the second dielectric layer and the third dielectric layer; the amplitude regulation and control layer is located on the upper surface of the first dielectric layer, and the amplitude regulation and control bias circuit layer is located on the lower surface of the first dielectric layer; the polarization conversion phase regulation and control layer is located on the upper surface of the second dielectric layer, and the polarization conversion phase regulation and control bias circuit layer is located on the lower surface of the second dielectric layer; the polarization gate layer is located on the upper surface of the third dielectric layer. According to the invention, efficient electromagnetic regulation and control in a transmission mode are realized, independent regulation and control in two dimensions of amplitude and phase are realized, and unification of high transmissivity and accurate regulation and control in a microwave frequency band is realized.

The present invention discloses an X-shaped negative Poisson's ratio local resonance module and its supporting metamaterial disc structure. The X-shaped negative Poisson's ratio local resonance module includes an X-shaped structural wall, an X-shaped negative Poisson's ratio structural unit and a local oscillator, wherein the local oscillator includes a soft coating layer and a cylindrical core, and the local oscillator is fixed on the X-shaped negative Poisson's ratio structural unit in an embedded form; the supporting metamaterial disc structure is composed of a plurality of X-shaped negative Poisson's ratio local resonance modules. The X-shaped negative Poisson's ratio structural units are circumferentially distributed around the outer wall of the inner circular ring column in the X-shaped structural wall to the inner wall of the outer circular ring column, and the outer wall of the inner circular ring column and the inner wall of the outer circular ring column are connected by the X-shaped structural unit wall. The X-shaped negative Poisson's ratio local resonance module is installed on a beam-type or tube-type base structure through the inner circular ring column. The present invention can achieve multi-scale and multi-level vibration suppression through the X-shaped negative Poisson's ratio local resonance module, improve the stability of the disc-shaped parts, and is easy to install and convenient to process.

The invention belongs to the technical field of electromagnetic wave functional materials, and particularly relates to a nested split ring wave-absorbing metamaterial and a preparation method thereof. The wave-absorbing metamaterial sequentially comprises an FSS metal structure layer, a dielectric layer and a metal matrix layer from top to bottom in the thickness direction, the FSS metal structure layer is formed by distributing structure units in a periodic array mode, each structure unit is composed of a double-opening outer ring shaped like a Chinese character'hui 'and a double-opening inner ring, the double-opening outer ring is a split square, and the double-opening inner ring is a hollow square. The structural units are symmetrically arranged about the diagonal line of the dielectric layer. The FSS metal structure layer designed by the invention has anisotropy, so that the polarization direction of an incident wave can be rotated by 90 degrees in a reflection mode. By means of the design, the two functions of electromagnetic wave absorption and polarization conversion are achieved at the same time, and meanwhile the effect of multiband wave absorption is achieved. Within the frequency band of 4 GHz to 18 GHz, the maximum wave-absorbing strength of the nested wave-absorbing metamaterial is as high as-30 dB, and the effective wave-absorbing bandwidth can reach 7.5 GHz.

Various embodiments may provide a photodetector pixel. The photodetector pixel may include a chiral plasmonic molecule array configured to generate heat upon incidence of an electromagnetic wave on the chiral plasmonic molecule array. The photodetector pixel may also include a thermoelectric layer configured to generate an electric current or voltage upon transfer of heat from the chiral plasmonic molecule array to the thermoelectric layer. The chiral plasmonic molecule array may include a metal layer, one or more nanostructures, and a dielectric spacer such that the dielectric spacer is between the metal layer and the one or more nanostructures. The one or more nanostructures may include one or more left hand (LH) chiral metamaterial nanostructures, one or more right hand (RH) chiral metamaterial nanostructures, or one or more left hand (LH) chiral metamaterial nanostructures and one or more right hand (RH) chiral metamaterial nanostructures.

The invention discloses a three-dimensional composite negative Poisson's ratio unit cell structure, a metamaterial and a design method.The three-dimensional composite negative Poisson's ratio unit cell structure comprises two inwards-concave units which are perpendicular to each other, the inwards-concave units comprise an outer inwards-concave unit and an inner inwards-concave unit which are the same in shape but different in size, and the inner inwards-concave unit is located in the outer inwards-concave unit; each corner of the external concave unit is connected with each corner of the internal concave unit through a connecting rod in a one-to-one correspondence manner, two cell element connecting rods are arranged at each concave corner outside the external concave unit, and a set included angle is formed between the two cell element connecting rods; the structure shows two stress platform stages, so that impact energy can be absorbed and buffered step by step more easily, and compared with a traditional structure, the energy absorption capacity is higher.

The present disclosure provides a thin-layer low-frequency underwater sound insulation metamaterial, including two cover plates and a sound insulation layer. The sound insulation layer is composed of sound insulation components arranged in an array periodically. The sound insulation components each include a sound insulation unit and four connecting units. The sound insulation unit is of a hollow rectangular column structure. The four connecting units are arranged at four corners of the sound insulation unit. Every two adjacent sound insulation units are connected through the connecting units. A long side wall of the sound insulation unit and the corresponding cover plate have an included angle of 0-90°. The metamaterial can obtain a smaller equivalent acoustic impedance in propagation direction of acoustic waves, and compared with a sound insulation material of a square honeycomb structure with the same thickness, the metamaterial has greatly improved sound insulation performance.