51 results about "Absorption frequency" patented technology

The invention discloses a cooperative control method and system for noise reduction and fire prevention of a transformer substation. The method comprises the following steps: determining the acoustic impedance mutation degree of an original composite board according to the frequency and amplitude distribution of target low-frequency noise of the transformer substation; when the acoustic impedance abrupt change degree exceeds an abrupt change threshold value, optimizing a first physical parameter of the original composite board; the heat flow density of the first composite board obtained through optimization is obtained, and if the heat flow density exceeds a fireproof threshold value, a second physical parameter of the first composite board is optimized; obtaining a noise penetration index of the target low-frequency-band noise in the second composite board obtained through optimization, and if the noise penetration index does not exceed a penetration threshold value, optimizing a third physical parameter of the second composite board; and determining final physical parameters corresponding to the acoustic-thermal performance balance point according to the acoustic impedance distribution and the thermal conductivity distribution of the third composite board obtained through optimization so as to adjust the structure of the third composite board. According to the invention, collaborative optimization of sound absorption frequency band characteristics and fireproof performance can be realized, and both noise reduction and fire prevention can reach an ideal state at the same time.

The invention belongs to the technical field of low-frequency sound absorption, and discloses a micro-perforated plate composite gradient spiral pipe sound absorption device and method.The micro-perforated plate composite gradient spiral pipe sound absorption device comprises a variable cross-section spiral pipe, and the diameter of the inlet end of the variable cross-section spiral pipe is larger than that of the outlet end of the variable cross-section spiral pipe; a plurality of MPP plates are mounted in the variable-cross-section spiral pipe, one MPP plate is embedded into the inlet end of the variable-cross-section spiral pipe, and the other MPP plates are sequentially embedded into the variable-cross-section spiral pipe at equal intervals, so that a multi-stage MPP plate composite sound absorption structure is formed; and the cross-section pipe diameter of the variable cross-section spiral pipe is linearly reduced from the inlet end of the variable cross-section spiral pipe to the outlet end of the variable cross-section spiral pipe. Through the gradient design of the variable cross-section spiral tube integrated micro-perforated plate, low-frequency broadband efficient sound absorption is realized in a compact space, the problem of heavy structure caused by dependence on a deep and large back cavity in the traditional technology is avoided, the limitation of narrow sound absorption frequency band is overcome, and the sound absorption device is particularly suitable for being applied to occasions with limited spaces and has wide application prospects. And low-frequency performance and broadband characteristics are considered in a limited space.

The invention discloses a preparation method of a beaded cobalt-doped Bi25FeO40 / BiFeO3 nanofiber wave-absorbing material, which comprises the following steps: obtaining a precursor by a standing method, and adding the precursor, bismuth nitrate, ferric nitrate and a spinning aid into a mixed solvent compounded by N, N-dimethylformamide and absolute ethyl alcohol to obtain a spinning solution; spinning the spinning solution by adopting an electrostatic spinning technology to obtain a nanofiber membrane; and finally, drying and calcining to obtain the wave-absorbing material. According to the wave-absorbing material, multiple reflection and scattering of electromagnetic waves are increased, the absorption performance of the electromagnetic waves is improved, due to the fact that a heterogeneous interface is generated after two phases are compounded, the interface polarization loss is further increased, when the thickness of the wave-absorbing material is 2.33 mm, the minimum reflection loss reaches-56.01 dB, the effective absorption frequency band width is 6.32 GHz, and the whole Ku wave band is covered.

The utility model discloses an adjustable sound absorber which comprises a cylindrical cavity shell, an inner cavity of the cylindrical cavity shell is provided with three partition plates, the partition plates divide the inner cavity of the cylindrical cavity shell into three fan-shaped resonant cavities, the sizes of the three resonant cavities are the same, the side wall of the cylindrical cavity shell is provided with three sound inlets, and the sound inlets are communicated with the three fan-shaped resonant cavities. The three sound inlets correspond to the three resonant cavities respectively, a fan-shaped shell is arranged in each resonant cavity, a first through hole is formed in the top of each fan-shaped shell, a sound wave absorption channel is defined by the side wall of each fan-shaped shell and the inner wall of the corresponding resonant cavity, the sound inlets are communicated with the sound wave absorption channels, and an impedance modulation interface is formed in a top plate of the cylindrical cavity shell. The impedance modulation interface is communicated with an inner cavity of the fan-shaped shell through the first through hole, a second through hole is further formed in the side wall of the fan-shaped shell, and the sound wave absorption channel is communicated with the inner cavity of the fan-shaped shell through the second through hole; and the shielding piece is provided with a shielding part, and the shielding part can rotate to the position of the impedance modulation interface in the horizontal direction. The adjustable sound absorber is good in ventilation effect, and the adjustable sound absorption frequency is large in low-frequency absorption coverage range.

The invention discloses a low and medium frequency sound absorption structure with an adjustable cavity, and relates to the field of sound absorption. The cylindrical adjustable sound absorption unit layer comprises a circular barrel with an opening in the bottom end and a circular cover plate, and the circular cover plate and the circular barrel cover and are rotationally and hermetically connected to form a sound absorption cavity; a first cylinder is coaxially fixed to the top of the circular cover plate, a circular containing groove is coaxially formed in the first cylinder, and a first partition plate is fixed outside the first cylinder; two first micro-perforation groups are symmetrically formed in the outer side of the top wall of the circular cylinder; a second cylinder is coaxially fixed to the inner side of the top wall of the circular barrel and rotationally connected with the circular containing groove. A second partition plate is fixed to the inner side of the peripheral wall of the circular barrel, the second partition plate and the first partition plate are matched to divide the sound absorption cavity into a first cavity and a second cavity which are independent, and each cavity is correspondingly communicated with one first micro-perforation set. The sound absorption frequency can be adjusted under the condition that the structure is fixed.

The invention relates to a sound absorption-vibration reduction integrated structure which comprises sound absorption-vibration reduction composite units, the multiple sound absorption-vibration reduction composite units are arranged on a two-dimensional plane in a periodic array mode, and each sound absorption-vibration reduction composite unit comprises a micro-lattice lattice structure, a rigid vibrator, a rubber layer and a base plate which are sequentially stacked and fixedly connected with one another from top to bottom. A sound absorption structure and a vibration reduction structure are integrated in a three-dimensional space, structural light weight and design simplification are achieved, broadband cooperative control over noise and vibration is also achieved, and a wider control frequency band can be covered; low-frequency vibration control can be achieved through a compact structure far smaller than the wavelength, the size limitation of a traditional vibration isolation material is broken through, the high designability is achieved, the sound absorption frequency spectrum can be optimized by adjusting the unit cell rod diameter and size of the micro-lattice, and by changing the mass of the vibrator and the material and size of the rubber layer, the low-frequency vibration can be achieved. The band gap frequency position can be accurately designed, and different application requirements are met.

The invention relates to the field of terahertz metamaterial devices, and provides a reconfigurable broadband / multi-frequency terahertz wave absorber based on vanadium dioxide. The wave absorber is composed of metamaterial square units which are arranged periodically, and adjacent units are gapless. Each unit is composed of six layers of structures including a vanadium dioxide resonance layer, an upper polyimide dielectric layer, a vanadium dioxide thin film layer, a copper resonance layer, a lower polyimide dielectric layer and a copper substrate layer. Vanadium dioxide can realize reversible phase change between a metal state and an insulation state through external excitation. In a metal state, the wave absorber has an ultra-wideband terahertz wave absorption function; and in an insulated state, a double-narrow-band absorption function is shown. According to the invention, the reconstruction of the absorption frequency and the bandwidth of the terahertz wave absorber is effectively realized, the problems of complex structure and fixed function of a traditional terahertz sensor are solved, and the potential of the terahertz wave absorber in sensing application of a single narrow-band wave absorber is further discussed.

This invention discloses a porous Helmholtz resonator with adaptively adjustable sound absorption frequency band, belonging to the fields of noise control and virtual reality technology. It comprises a sound-absorbing structure consisting of a rotating perforated panel, a fixed perforated panel, and a perforated porous material plate arranged sequentially from top to bottom, as well as an adaptive adjustment system composed of a sound pressure sensor, a controller, and a motor. The motor drives the rotating perforated panel to rotate via gear transmission, changing the perforation overlap area; the perforated porous material plate compensates for acoustic impedance, maintaining sound absorption performance. The controller pre-stores spectral data at different rotation angles and selects the optimal rotation angle by comparing the real-time noise spectrum with the pre-stored data. This invention achieves adaptive adjustment of the sound absorption frequency band, maintains a high sound absorption peak value over a wide parameter range, is suitable for large-area deployment, has a compact structure, and low cost, and can be used for noise control and auditory virtual scenes.

This disclosure provides a method, apparatus, electronic device, and storage medium for determining filter coefficients, belonging to the field of audio processing technology. It includes: determining the energy filtering characteristic value of the microphone at each absorption frequency after the sound wave arrives, based on the sound wave filtering characteristic value at each absorption frequency when the sound wave reaches the microphone and the energy filtering characteristic value of the microphone at the same absorption frequency; and determining the filter coefficients of a target filter based on the total energy filtering characteristic value of the microphone at each absorption frequency after all sound waves that can reach the microphone arrive. This disclosure determines the total energy filtering characteristic value of the microphone at each absorption frequency after all sound waves that can reach the microphone arrive, based on the sound wave filtering characteristic value at each absorption frequency and the energy filtering characteristic value of the microphone at each absorption frequency, and then accurately determines the filtering parameters of the target filter based on the total energy filtering characteristic value at each absorption frequency.

The invention discloses a broadband composite acoustic meta-structure assembly and a design method and a modular splicing method thereof. The broadband composite acoustic meta-structure assembly comprises a base module, a meta-structure module and a porous material module. Based on structural parameter design conditions and sound absorption characteristic constraint conditions of the super-structure module and based on an incident sound field and super-structure module surface acoustic impedance matching theory, optimizing structural parameters of the super-structure module by using an optimization algorithm; the structural parameter design conditions comprise constraint conditions of structural size parameters of each resonant cavity sound absorption unit in the super-structure module and limiting conditions of the breadth area of the super-structure module; the sound absorption characteristic constraint condition comprises a sound absorption frequency constraint condition and a sound absorption coefficient constraint condition. According to the invention, by matching the high sound absorption characteristics of the metamaterial module and the sound absorption material module in different frequency band ranges, the broadband noise reduction performance of the metamaterial component is quickly realized, and the material thickness is greatly reduced.

The invention discloses a wave-absorbing structure and a wave-absorbing plate, the wave-absorbing structure comprises a skin layer, an impedance layer, a dielectric layer and a substrate layer which are stacked in sequence, the upper surface of the skin layer is an incident plane of electromagnetic waves, the impedance layer comprises a first conductive layer and a plurality of second conductive layers, the first conductive layer is square, and the second conductive layer is square. The plurality of second conductive layers are arranged around the outer side of the first conductive layer, and the second conductive layers are square rings with openings. The wave absorbing plate comprises M * N wave absorbing structures. Through reasonable design of a multi-layer composite structure, after electromagnetic waves are incident from the skin layer, multiple interference occurs between the impedance layer and the dielectric layer, and through the synergistic effect of absorption and reflection of the impedance layer and the substrate layer, efficient dissipation of electromagnetic energy is achieved, and the high-performance electromagnetic absorption effect is achieved. Besides, due to the design form of the open square ring of the second conductive layer, the impedance layer has an impedance compensation effect, the wave-absorbing bandwidth is effectively expanded, and particularly, a relatively wide effective absorption frequency band can still be kept in an oblique incidence state of electromagnetic waves.

This invention discloses a reconfigurable absorbing metasurface based on heterogeneous absorbing units using a tenon-and-mortise interlocking structure, and its configuration method, belonging to the field of electromagnetic wave absorption and metasurface structure technology. The metasurface is formed by assembling multiple lightweight absorbing units through a tenon-and-mortise interlocking structure. The absorbing units use melamine foam, PMI foam, polyurethane foam, or aerogel porous framework materials as the matrix, and are loaded with absorbing components such as graphene, carbon nanotubes, MXene, ferrite particles, carbonyl iron particles, or conductive polymers. The tenon-and-mortise connection structure has multiple levels of insertion positions and limiting structures, allowing adjacent units to form different insertion states, thereby adjusting the unit spacing, air layer thickness, array period, and equivalent electromagnetic parameters, achieving reconfigurable control of the absorption frequency band and response characteristics. Furthermore, heterogeneous absorbing units with different geometries and absorption parameters can be optimized through parametric design and electromagnetic simulation to form planar or curved broadband absorbing structures. This invention combines the advantages of lightweight, modularity, detachability, surface adaptability, and wideband absorption, and can be applied to fields such as electromagnetic stealth, radar absorption, electromagnetic protection, and complex curved electronic equipment.

This invention relates to the field of noise control and acoustic metamaterials technology, and discloses a device and method for synergistically regulating the sound absorption frequency by adjusting the neck length and cavity volume. The sound-absorbing device includes a Helmholtz main structure and an adjustable neck assembly. The main structure includes a perforated top plate, hexagonal honeycomb sidewalls, rubber lining, and a central base plate, which is connected to a drive device via a push rod. The adjustable neck assembly employs a three-layer nested sleeve design, utilizing a spring return mechanism and a sliding hook slot mechanism to achieve graded adjustment of the neck length. The drive device drives the push rod to raise and lower the central base plate, providing thrust to the adjustable neck assembly and simultaneously changing the cavity volume. This metastructure overcomes the limitations of traditional underwater Helmholtz sound-absorbing structures, which suffer from fixed frequency bands and poor adaptability. By synergistically regulating the sound absorption frequency band with dual parameters, it dynamically responds to changes in the complex underwater acoustic environment, significantly reducing the acoustic target intensity of underwater equipment and providing an efficient solution for acoustic stealth in deep-sea equipment.

The application discloses a kind of easily engineering realized metamaterial absorption structure, belong to microwave metamaterial technical field.The metamaterial absorption structure of the application includes: from bottom to top layer stack arrangement metal backplate, intermediate dielectric layer and upper layer resonance layer;Upper layer resonance layer is composed of periodically arranged resonance unit, and the resonance unit is composed of four square slit metal radiation patches connected by lumped capacitance element;Metal backplate is connected with upper layer metal radiation patch by circular metal through-hole, wherein four square slit metal radiation patches are rotationally symmetric and divided into four corners of unit;The slit direction of square slit metal radiation patch is parallel to its side length, and two metal slits in each square slit metal radiation patch are perpendicular to each other, and the right angle formed by two metal slits points to the center of wave-absorbing structure unit.The application obtains multiple perfect absorption frequency points by adjusting the position and length of metal slit, and the wave-absorbing efficiency reaches 99%.

The invention provides a broadband metasurface wave absorber based on an oblique symmetric mosaic structure. The broadband metasurface wave absorber comprises a metal resonance layer, a dielectric layer and a metal reflecting layer which are sequentially stacked, the metal reflecting layer is formed by two inlaid structures which are arranged in an oblique symmetry mode, each inlaid structure comprises a semi-square ring body and a semi-circular ring body wrapping the outer side of the semi-square ring body, and two edge protruding edges of each semi-square ring body are connected with the corresponding semi-circular ring body; the semi-square ring body and the semi-circular ring body are both of an open structure, and the opening directions of the semi-square ring body and the semi-circular ring body are the same. According to the wave absorber disclosed by the invention, a broadband absorption effect on electromagnetic waves in a frequency band of 9.43 GHz to 14.95 GHz is realized; meanwhile, within the absorption frequency band, the absorption rate of electromagnetic waves reaches 90% or above, and the absorption rate of electromagnetic waves reaches 99% or above near two resonance peak values of 10.02 GHz and 13.56 GHz.

The invention discloses a wide-frequency-band wave-absorbing high-strength metamaterial which comprises a plurality of stacked frequency-absorbing units, and each frequency-absorbing unit is composed of a plurality of composite material layers with absorption frequency bands gradually increased in sequence. The composite material layers are divided into a plurality of low-frequency wave-absorbing material layers and a plurality of high-frequency wave-absorbing material layers according to different absorption frequency bands; the low-frequency wave-absorbing material layer and the high-frequency wave-absorbing material layer both take resin as a base material. According to the invention, the wave-absorbing structure realized by the low-frequency wave-absorbing material layer and the high-frequency wave-absorbing material layer respectively realizes the absorption work of high-frequency and low-frequency electromagnetic wave energy, and realizes the application under the requirement of relatively wide frequency band; the high-absorptivity frequency absorbing device has the technical advantages of being high in absorptivity, wide in absorbable frequency band, simple in frequency absorbing structure and low in manufacturing cost, can be well applied to actual work, and has wide generalizability.

The application relates to the technical field of wave-absorbing materials, in particular to a wide-band calcium ferrite wave-absorbing material and a preparation method and application thereof. 1.8 La 0.2‑x Ce x Fe2O5, wherein 0<=x<0.14. The application solves the problems of narrow absorption frequency band and low efficiency of the oxide wave-absorbing material by adjusting the composition and dielectric properties of the material through La and Ce double-element co-doping, and the prepared material has the advantages of wide absorption frequency band and high absorption intensity.

The invention discloses a broadband low-frequency sound absorption structure with sub-wavelength thickness, and relates to the technical field of noise control, the broadband low-frequency sound absorption structure with sub-wavelength thickness comprises a box body and fractal members arranged in the box body in a rectangular array mode, and the four adjacent fractal members arranged in the rectangular array mode are combined to form a first cavity; a plurality of fractal components close to the inner side surface of the box body are combined with the inner side surface of the box body to form a second cavity; the fractal component comprises a first plate body and a second plate body, the first plate body is provided with a third cavity, and the second plate body is provided with a fourth cavity; a cover plate is arranged on the top face of the box body, and a plurality of through holes communicated with the first cavity, the second cavity, the third cavity and the fourth cavity respectively are formed in the cover plate. According to the broadband low-frequency sound absorption structure with the sub-wavelength thickness, the technical problems that an existing composite sound absorption structure can only meet the sound wave resonance requirement of a limited frequency band, the sound absorption frequency band range is narrow, and sub-wavelength magnitude light and thin design cannot be achieved are solved.

This invention discloses a low-frequency broadband underwater acoustic structure design method based on column cavity series technology. The method determines the frequency range, average sound absorption coefficient threshold, high-efficiency sound absorption, high-efficiency sound absorption frequency ratio threshold, and the first frequency threshold reached. The structure is decomposed into n columnar inclusion layers. The unit cell width, matrix material parameters for each layer, layer thickness, and the type and diameter of the columnar inclusions are set. The impedance of each matrix material is calculated; if the impedance gradient condition is not met, the matrix material parameters are redesigned. The layers are connected in series, and a backplate is placed on the back of the seriesd structure. Simulation calculations are used to determine the average sound absorption coefficient, high-efficiency sound absorption bandwidth ratio, and the first frequency to achieve high-efficiency sound absorption within the frequency range. If these conditions are not met simultaneously, the number of layers is increased and the parameters are reset; otherwise, the designed underwater acoustic structure meets the low-frequency broadband sound absorption requirements. This invention achieves efficient acoustic stealth within a limited space for the target frequency band.

The invention discloses an underwater sound absorption wedge considering a backing quality effect and a preparation method thereof, and relates to the technical field of underwater sound absorption, a wedge main body has an impedance gradual change appearance, so that sound waves can gradually enter the underwater sound absorption wedge to be absorbed, and efficient sound absorption of the underwater sound absorption wedge is ensured; when the dissipation unit absorbs sound wave energy, the dissipation unit is easy to vibrate, so that sound waves are easy to generate resonance action with the acoustic cavity, the side wall of the acoustic cavity generates shear deformation, the dissipation capability of the acoustic cavity is improved, and the low-frequency sound absorption performance of the acoustic wedge is improved under the condition that the length of the acoustic wedge is not prolonged; the size of the acoustic cavity is larger, incident longitudinal waves can be easily converted into transverse waves with shorter wavelength, and the low-frequency sound absorption capacity is improved; the fourth sound absorption cavity strengthens the shear deformation of the surface of the side, facing the third sound absorption cavity, of the fourth sound absorption cavity, and the impedance reinforcer increases the non-uniformity of stress strain in the underwater sound absorption wedge, so that the sound absorption frequency band range of the underwater sound absorption wedge is wider.

The invention relates to the technical field of terahertz metamaterials, and provides a graphene-VO2 composite film tunable terahertz wave absorber. The wave absorber sequentially comprises a VO2 resonance layer, a graphene patch layer, a dielectric layer and a metal grounding layer from top to bottom, and the overall thickness of the wave absorber is 1t. And the structure is compact. The graphene Fermi level and the VO2 phase state are independently regulated and controlled through external bias voltage, and instantaneous switching of absorption frequency spectrums is achieved: when the graphene Fermi level is 0 eV and VO2 is in a metal state, the absorptivity of the device within the frequency band of 1.92-7.22 THz is larger than or equal to 90%, and the relative bandwidth is 115%; when the Fermi level of graphene is increased to 0.9 eV and VO2 is converted into an insulated state, the absorptivity of the device within the frequency band of 5.13-6.58 THz is larger than or equal to 90%. And meanwhile, the absorber has excellent polarization insensitivity and wide-angle incidence characteristics. The invention has the advantages of ultrafast speed, reconfigurability, low power consumption and flexible substrate compatibility, can be widely applied to terahertz imaging, intelligent stealth and adjustable filter devices, and provides a new generation of core function unit for a terahertz system.

The invention provides a built-in microwell plate sound absorption cavity structure which comprises a plurality of silencing units, every two of the silencing units are in contact with each other to form a three-dimensional novel built-in microwell plate sound absorption cavity structure, each silencing unit comprises a shell, through holes are formed in the shells, and the through holes are communicated with the silencing units. The micro noise elimination unit is adopted, a micro-pore plate resonance structure is arranged in the noise elimination unit, the sound absorption and noise reduction efficiency of the noise elimination unit is greatly improved, the novel sound absorption cavity structure provided with the micro-pore plate is small in size, the noise reduction effect is good, the noise reduction effect is good, and the noise reduction effect is good. The correspondingly combined novel built-in microwell plate sound absorption cavity structure is small in size, has the 1 / 23-time sub-wavelength sound absorption characteristic, has the ultra-thin characteristic, is wide in sound absorption frequency band and good in noise reduction effect, and can be suitable for sound absorption and noise reduction of various small places and spaces.

According to the pulse frequency stabilization vortex laser provided by the invention, a highly stable frequency locking system is constructed through elaborately designed continuous light amplification, frequency multiplication and potassium atom saturated absorption frequency stabilization links, and the system can quickly and accurately detect and correct micro drift of laser frequency, effectively suppress the frequency drift phenomenon, and improve the precision of laser frequency stabilization. Compared with a traditional vortex laser, the frequency stability of the vortex laser is improved by more than one order of magnitude.

The invention provides a low-frequency frequency-selecting sound absorption device. The low-frequency frequency-selecting sound absorption device comprises a cover plate, a honeycomb core and a bottom plate, the cover plate and the bottom plate are of cuboid structures with matched sizes, the cover plate and the bottom plate are combined to form a rectangular cavity, the honeycomb core is of a polygonal honeycomb structure, and the honeycomb core is arranged in the rectangular cavity to form a plurality of sound absorption unit resonance cavities. Sound absorption holes with different hole diameters are formed in the resonance cavity of the sound absorption unit, the sound absorption holes are located in the cover plate, and insertion pipes with different lengths are arranged in the sound absorption holes. The sound absorption device is made of all-metal materials and is simple in overall structure, high in strength, easy to produce in batches and long in service life. The range of sound absorption frequency points can be adjusted according to the size of the aperture and the length of the insertion tube, and a good absorption effect on low-frequency noise is achieved.

The application discloses a preparation method of a frequency band magnetic control adjustable aerogel-based wave-absorbing material. First, ferromagnetic iron-cobalt nanosheets are obtained through a liquid phase reduction method, and then the nanosheets are ultrasonically mixed and dispersed with graphene oxide. The mixed system is subjected to a hydrothermal reaction to obtain a composite hydrogel precursor. After freeze-drying, a graphene aerogel-based composite wave-absorbing structure is obtained, wherein the ferromagnetic nanosheets exist in the hollow skeleton structure of the aerogel. The precursor aerogel structure is quickly immersed in a sodium alginate solution, and a hydrogel medium is formed in the structure by adding calcium ions, so that the nanosheets are suspended in the hollow skeleton of the aerogel, and an adjustable composite wave-absorbing material is obtained. By applying an external magnetic field at different angles, the nanosheets are oriented in the hollow skeleton. By changing the angle between the interface dielectric dipole array and the easy magnetization magnetic moment and the electromagnetic wave vector, respectively, the microwave electromagnetic parameters and the impedance of the material are dynamically adjusted, so that the real-time dynamic adjustment of the wave-absorbing performance and the absorption frequency band is realized.

The invention relates to the technical field of electromagnetic wave absorption, and discloses a stacked annular water-based metamaterial absorbing material with a scattering characteristic and a process thereof, the material is composed of periodically arranged unit structures, each unit structure comprises a metal substrate, a structure support body arranged on the metal substrate and a liquid absorbing medium filled in the metal substrate, the structure supporting body is integrally formed by a photosensitive resin material, and a three-dimensional water cavity structure formed by vertically stacking or combining various geometrical shapes such as a cross shape, a cylinder shape, a ring shape or an open ring shape is formed in the structure supporting body. According to the structural design, multiple resonance modes can be excited under electromagnetic wave incidence, a wide absorption frequency band is formed through coupling and superposition of the multiple resonance modes, the invention further discloses a preparation process of the structure, the structure supporting body is manufactured through the 3D printing technology, and then liquid filling and overall assembling are conducted. The problem that the bandwidth of an existing absorbing material is limited is solved, the preparation process is simple, and the cost is low.

The invention discloses an acoustic filter, and belongs to the technical field of filters. The acoustic filter comprises a first transmission port (port1), a second transmission port (port2) and a third transmission port (port3), wherein the port3 is connected to an absorption load (6) at the same time; the band-pass filter is connected between the first transmission port and the second transmission port and is used for transmitting the signal of the working frequency band PB1 received by the first transmission port to the second transmission port and inhibiting the signal of the non-working frequency band RB received by the first transmission port; the notch filter is connected between the first transmission port and the third transmission port and is used for transmitting a signal of an absorption frequency band RB1 (RB comprises an RB1 frequency band) received by the first transmission port to the third transmission port and suppressing a signal of a working frequency band PB1 received by the first transmission port in a notch manner; and an intermodulation PIM signal generated by the absorption frequency band RB1 falls into the working frequency band PB1. Nonlinearity of the acoustic filter can be reduced, and intermodulation performance can be improved.

The application relates to a preparation method of a material for regulating the electromagnetic wave absorption frequency of single atoms, and belongs to the electromagnetic wave absorption field. The scheme comprises the following steps: step I: synthesizing a metal organic framework M-PCN-222 by adopting a solvothermal method; step II: pyrolyzing the M-PCN-222 obtained in step I into a single atom loaded carbon-based microrod composite material; and step III: compounding the single atom loaded carbon-based microrod composite material M-N-C / ZrO2 obtained in step II with a high polymer polymer PVDF, and preparing a composite material by adopting an ultrasonic method. The scheme has the advantages of simple operation and large-scale production potential. The obtained composite wave absorbing material can not only maintain the advantages of light weight and corrosion resistance of carbon-based nanomaterials, but also overcome the shortcomings of high density, easy aggregation and narrow absorption frequency band of single ferromagnetic materials by means of uniform distribution of single atoms.

According to the method for widening the sound absorption frequency band of the micro-perforated plate sound absorber array under the excitation of the free field oblique incidence plane wave, the coupling sound absorption rule between units in the array is analyzed and fully utilized according to the excitation condition of the free field oblique incidence plane wave; unit structure parameters in the array are subjected to optimization design, the optimal sound absorption performance is achieved, the effective sound absorption frequency band of the MPPA array is greatly widened, and broadband efficient sound absorption of the MPPA array under free field oblique incidence excitation is achieved. The invested cost is low, the sound absorption frequency band broadening effect of the MPPA array is obvious, and therefore the MPPA array has important engineering application value.

Embodiments can include, for example: a conductor-backed dielectric; and circuitry connected in parallel with the conductor-backed dielectric, wherein the circuitry connected in parallel with the conductor‑backed substrate exhibits an admittance with an imaginary component having a negative slope within a design absorption frequency range of the absorber structure.