192 results about "Electromagnetic wave transmission" patented technology

The invention discloses an environment electromagnetic radiation detection system and method for a communication base station, relates to the technical field of electromagnetic radiation detection, and solves the technical problem that the electromagnetic radiation evaluation of the communication base station is inaccurate because the influence of an actual environment on electromagnetic wave transmission is not considered when a detection point location is set in the prior art. On the basis of environmental elements and attribute data thereof, the attenuation factor of the first region is calculated through the attenuation evaluation model, and then the simulated radiation value of each sub-region is calculated; comparing the simulated radiation value with a corresponding radiation threshold value, determining a target area, and setting a detection point position in the target area to realize electromagnetic radiation detection; according to the method and the device, the influence of the environmental elements on the electromagnetic radiation of each sub-region is analyzed, the simulated radiation value of each sub-region is accurately calculated in combination with the radiation predicted value, then the detection point location is set according to the simulated radiation value, the typicality and reasonable target region is selected, and the accuracy of evaluating the electromagnetic radiation of the communication base station is improved.

The invention belongs to the technical field of ground penetrating radars, and particularly relates to a layered medium parameter estimation method based on hyperbolic fitting. The layered medium parameter estimation method based on hyperbola fitting specifically comprises the following steps: step 1, establishing a multilayer medium hyperbola constraint equation, and obtaining a ground penetrating radar theoretical measurement time constraint equation based on the constraint equation; 2, preprocessing the radar echo signals, extracting feature points, and calculating refraction points generated at the layered interface based on the extracted feature points; and 3, substituting the refraction point calculated in the step 2 into the theoretical measurement time constraint equation of the ground penetrating radar obtained in the step 1, establishing an electromagnetic wave transmission time error model, and realizing parameter estimation of the layered medium by using a nonlinear least square optimized parameter estimation method.

The invention discloses an Antarctic ice layer gas and microorganism detection method based on hot-melt drilling digital twinning, and belongs to the technical field of digital technologies and polar scientific investigation engineering. Parameters are collected in real time through various sensors integrated in a hot-melt drill bit and are transmitted to a far-end console through electromagnetic waves; and a complete information flow is presented after the processing of an anomaly checking algorithm and an AI decision early warning system. The system not only can simulate the influence of different temperatures, pressures and drilling speeds on an ice layer so as to optimize a drilling parameter combination in real time, but also can synchronously map key indexes such as drill bit wear and system efficiency in combination with Internet of Things sensor data and a digital twinning technology. Besides, the collected bubble samples are subjected to component analysis through an integrated sensor array, and the characteristics of the microflora are dynamically displayed by using a metabolite identification model, so that accurate data support is provided for polar scientific investigation.

The invention discloses a coil shielding structure for a linear magnetic confinement nuclear fusion device, and relates to the technical field of nuclear fusion reactors. Comprising a first shielding layer made of a metal material and capable of coating a coil conductor in an insulating manner; and the second shielding layer is made of a metal material and is coated outside the first shielding layer, and an outer cold flow channel is arranged between the second shielding layer and the first shielding layer. The multiple shielding layers are arranged in a laminated mode, electromagnetic wave conduction can be hindered by consuming electromagnetic energy for multiple times, eddy currents generated by a variable magnetic field on coil conductors (quasi-steady-state and cusped coils) are reduced, temperature rise of the coils is reduced, the current-carrying capacity of the coils is improved, the thickness of the shielding layers can be designed to be very thin, and the shielding layers are not prone to deformation. While the eddy current is reduced, the design cost of a conductor material and the self mass of a magnet system are reduced, and meanwhile, the second shielding layer can serve as a stress part to reinforce the mechanical structural strength of the magnet and prevent electromagnetic force from directly acting on a magnet coil to influence the established structure of the magnet coil.

The invention provides a prospecting system and method based on software defined radio, and belongs to the technical field of mineral detection, and the system comprises a software defined radio transmitting device which is used for generating transmitting parameters based on the geological structure and detection requirements of a to-be-detected area, an electromagnetic wave emission signal emitted to the to-be-detected area is generated based on the emission parameter; the software-defined radio receiving equipment is used for receiving electromagnetic wave receiving signals propagated in the to-be-detected area; and the mineral analysis module is used for determining a distortion mode based on the electromagnetic wave transmitting signal and the electromagnetic wave receiving signal, and determining the type and grade of minerals based on the distortion mode. According to the invention, the high flexibility of the software defined radio technology is utilized, rapid adjustment of emission parameters is realized to adapt to different geological structures and detection requirements, and the prospecting efficiency of the system is improved. Meanwhile, mineral detection is achieved based on the distortion mode, manual work is not needed, and the mineral detection accuracy is improved.

A frequency selective unit, a frequency selective surface, and an antenna base station. The frequency selective unit comprises a metal reflector plate and at least two conductive material pattern layers, wherein through holes are provided in the metal reflector plate, the at least two conductive material pattern layers run through the through holes, and there is a gap between the conductive material pattern layers and the metal reflector plate; and at least one conductive material pattern layer comprises a first transmission mode, and at least the other conductive material pattern layer comprises a second transmission mode, and in a transition band, electromagnetic waves in the two transmission modes have opposite phases and cancel each other, such that the electromagnetic waves cannot be transmitted through the frequency selective unit; moreover, an electromagnetic wave transmission zero can be generated in the transition band, and a sharp roll-off is formed at an out-of-band edge of a second band, thereby realizing high-frequency selectivity. The conductive material pattern layers are not parallel to the metal reflector plate, the transmission direction of the electromagnetic waves is parallel to the surfaces of the conductive material pattern layers, and it is not necessary to provide a metallized via hole between the at least two conductive material pattern layers to perform electrical connection, thereby simplifying the manufacturing process and processing difficulty of the frequency selective unit.

The invention provides a broadband circularly polarized planar end-on-fire antenna based on a substrate integrated waveguide. The broadband circularly polarized planar end-on-fire antenna comprises a wave port, the substrate integrated waveguide and a dipole antenna, the wave port is connected with one side, far away from the dipole antenna, of the dielectric substrate and is used for generating an excitation signal through feed and driving electromagnetic wave transmission in the substrate integrated waveguide, so that the substrate integrated waveguide generates a vertical polarization electric field component and the dipole antenna generates a horizontal polarization electric field component; by adjusting the amplitude-phase relation between the two orthogonal polarization electric field components, broadband circular polarization radiation is realized. The broadband circularly polarized plane end-on-fire antenna does not need an additional radiation structure to compensate the vertical polarization component, avoids the increase of the profile height due to the addition of the additional structure, achieves the low profile design, and enables the structure to be more compact. The dipole antenna is directly connected with the upper metal plate and the lower metal plate, so that the overall size of the antenna is greatly reduced, the occupied space is reduced, the manufacturing process is simplified, and the production process and the material cost are reduced.

The invention relates to an all-metal spherical lens antenna which comprises a metal lens of a spherical structure, a plurality of first feed source antennas are arranged below the metal lens, and each first feed source antenna is fixedly connected with a supporting column in the metal lens through a supporting frame; the metal lens is composed of a plurality of metal plates, the distances between the metal plates are equal and smaller than the half-wavelength of the highest working frequency, all the metal plates are parallel to one another, the parallel metal plates form an air-filled parallel slab waveguide, and after electromagnetic waves of the first feed source antenna are transmitted to the metal lens, the electromagnetic waves are transmitted to the metal lens. The incident electromagnetic waves propagate along the air gap between the metal plates, the emergent phase of the incident electromagnetic waves after passing through the metal lens is adjusted by changing the angle between the metal plates and the first feed source antenna, and when the phase error is minimum, high-gain radiation is achieved. The spherical metal lens structure is realized by using the combination of the metal flat plates, and the minimum phase error is realized by changing the inclination angles of the metal flat plates, so that the high-gain radiation wave beam is realized.

The invention discloses a microwave heating radiation antenna design method for strengthening hydrate development, and relates to the technical field of natural gas hydrate heating strengthening yield increase. A rectangular waveguide antenna is selected as a basic structure of microwave heating radiation antenna design; a slot is formed in the outer wall of the rectangular waveguide antenna, slot parameters are designed, waveguide parameters are calculated according to the waveguide size and the working frequency, and the slot period is determined to optimize the length and the shape of the slot. The rectangular waveguide antenna is adopted as a basic structure, efficient transmission and radiation of microwave energy are achieved by optimizing slotted hole parameters, the rectangular waveguide antenna has good electromagnetic wave transmission characteristics, uniform distribution of the microwave energy in a reservoir can be ensured by combining the designed slotted hole layout, energy loss is reduced, and the energy utilization rate is improved. In the marine hydrate exploitation process, the antenna can rapidly and effectively increase the reservoir temperature, sufficient driving force is provided for hydrate decomposition, and therefore the exploitation efficiency is improved.

The present invention provides a circularly polarized electromagnetic wave transceiver subsystem and an electromagnetic wave transceiver array system. The subsystem includes a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a third metal layer stacked in sequence. A second feeding cavity is formed between the second metal layer and the third metal layer. The first metal layer includes a plurality of annularly arranged antenna structures. Each antenna structure is rotated in sequence along the arrangement direction by a predetermined angle. The antenna structure also has a feeding column and a feeding disk on the side facing the first dielectric layer. The feeding disk is located in the second feeding cavity. Through the setting of the feeding disk, phase differences are formed in sequence between each first feeding cavity, thereby forming the conditions for rotating feeding, reducing energy loss, and thus achieving good circular polarization characteristics. There is no need to use a "tree-shaped" structure such as a power divider, so that the distance between adjacent antenna structures can be reduced, the volume of the electromagnetic wave transceiver subsystem can be reduced, and the aperture efficiency can be improved.

To provide a dielectric constant measuring method for reducing an analysis error of a dielectric constant in measurement by a free space method.SOLUTION: The method includes a step of preparing a first complex electric field distribution on an incident plane P1 of a dielectric sample 33, a step of preparing a second complex electric field distribution on an emission plane P2 of an electromagnetic wave transmitted from a receiving horn antenna and assumed to be incident on the dielectric sample 33 in a direction opposite to an emission direction of the electromagnetic wave, a step of calculating an angular spectrum distribution on a wave number space by inverse Fourier transformation of the first complex electric field distribution, a step of measuring a thickness of the dielectric sample 33 in a direction along an electromagnetic wave transmission direction, a step of calculating a reference of a complex electric field distribution which is a complex electric field distribution when the electromagnetic wave propagates in a free space by a distance corresponding to the thickness, and a step of obtaining a third complex electric field distribution of the electromagnetic wave propagating in the emission direction on the emission plane P2.SELECTED DRAWING: Figure 2

A Ka-band double-layer substrate integrated waveguide directional coupler belongs to the technical field of communication and comprises two layers of laminated dielectric substrates, a plurality of mounting holes are formed in the surfaces of the dielectric substrates and used for mounting waveguides; after the two layers of dielectric substrates are laminated, the surface between the outer surface and the dielectric substrates is coated with copper, and the wide wall part of the outer surface is provided with a mounting hole matched with the mounting hole of the dielectric substrate, a butt joint groove used for being in butt joint with the waveguide port, and a metalized through hole penetrating through the two layers of dielectric substrates. Coupling grooves which are regularly arranged are formed in the wide wall between the two layers of dielectric substrates in the electromagnetic wave transmission direction and used for coupling electromagnetic waves of one layer of dielectric substrate to the other layer of dielectric substrate. The feed structure adopts a waveguide-substrate integrated waveguide transition structure, the bandwidth is relatively wide, the waveguide joint is used as a feed end interface, and the transmission loss is relatively small. The two substrate integrated waveguide wide-wall coupling structures improve the miniaturization degree of the product.

A robot is connected with an external power supply and an upper computer through cables, adopts a modular tubular structure, and carries a sensor group, an electromagnetic generator and a power mechanism; the sensor group is used for collecting image information and sound information in the pipeline and posture information of the robot, and the power mechanism is used for driving the robot to advance in the pipeline; the cable winding and unwinding unit is used for winding and unwinding a cable; the precise positioning unit realizes precise positioning of the robot by means of electromagnetic wave transmission and comprises an electromagnetic generator and a receiver, and the electromagnetic generator and the receiver are respectively used for transmitting and receiving low-frequency electromagnetic waves; the upper computer receives cable length information output by the cable winding and unwinding unit, completes preliminary positioning of the robot in combination with a water supply network electronic map, controls advancing of the robot in combination with posture information, receives image information and sound information, completes defect detection of a pipeline, and finally outputs a health detection report in combination with accurate positioning.

Various embodiments of the present disclosure relate to a low-E film to which an electromagnetic wave transmission pattern of a specific frequency is applied. The low-E film comprises: an insulating layer made of an insulating material; and a metal coating layer including a metal or metal oxide coated on one surface of the insulating layer. The metal coating layer has a first pattern formed by removing a portion of the metal coating layer, and the first pattern includes a pattern having a plurality of oval surfaces of an identical shape within a rectangular unit cell, and the pattern having the plurality of oval surfaces is arranged with the long axes of the respective oval surfaces at constant angles, and the long axes of the pattern having the oval surfaces or the extension lines of the long axes meet at one intersection point located at the middle point of the unit cell.

The present invention discloses a broadband dual-polarization antenna array, comprising a radiating network and a feeding network. The feeding network is used to convert electromagnetic waves in the form of a TEM mode input thereto into electromagnetic waves in the form of a TE10 mode and transmit them to the radiating network. The radiating network is used to radiate the electromagnetic waves transmitted thereto by the feeding network into free space. The radiating network is realized by arranging a partition structure consisting of four levels of metal steps in a rectangular slot in combination with metal branches arranged above the partition structure. The feeding network is realized based on a full parallel feed network consisting of a ridge waveguide structure, a micro-coaxial structure and a magic T. The advantage is that while having high gain and high efficiency, the bandwidth can cover the Ku band, meeting the requirements of Ku-band satellite communications.

To provide a laminate structure that can obtain electromagnetic wave transmission or blocking performance required for design while using a metal layer as it is without processing it.SOLUTION: A laminate structure 10 is configured such that the intensity of the outgoing wave relative to the incident wave is stronger for electromagnetic waves below a predetermined frequency than for electromagnetic waves above a predetermined frequency, and includes a laminate 1 having at least one plate material 2 and a metal layer 3 laminated on the at least one plate material 2, and a metasurface sheet 4 attached to the laminate 1, and the metasurface sheet 4 is configured such that the intensity of the outgoing wave relative to the incident wave is stronger for electromagnetic waves of the predetermined frequency or higher than for electromagnetic waves of below the predetermined frequency.SELECTED DRAWING: Figure 3

The application discloses a SiON micro-nano fiber membrane with electromagnetic wave transmission and high-temperature heat insulation, and a preparation method and application thereof, and relates to the technical field of ceramic fibers.The fiber membrane is formed by overlapping SiON micro-nano fibers; the arrangement mode of the SiON micro-nano fibers in the fiber membrane is disordered or directional; the diameter of the SiON micro-nano fibers is 100 nm to 1.3 mu m; the content of Si element in the SiON micro-nano fibers is greater than 35 at.%, the content of O element is greater than 30 at.%, the content of N element is greater than 12 at.%, and the content of C element is less than 7 at.%. The SiON fiber membrane prepared by the application has the component / structure characteristics of micro-nano fiber diameter (100-1200 nm), low carbon and amorphous, and exhibits the characteristics of light weight, porosity, wave transmission, heat insulation, high-temperature stability and the like, and is a novel wave transmission and heat insulation integrated fiber material with wide application prospect.

The invention discloses a pilot protection method and device based on instantaneous power total and incremental waveform similarity, and belongs to the technical field of power systems. According to the method, fault detection is started through voltage or current abrupt change, differential capacitance current compensation is carried out based on a full current sampling value, and a compensated voltage value is calculated by combining an electromagnetic wave transmission equation and a line Bergeron model so as to eliminate the influence of line parameters; and judging a passive load branch fault through a current amplitude and an integral value, otherwise, synchronously adopting an instantaneous power full-quantity waveform cosine similarity longitudinal main protection criterion and an instantaneous power increment waveform cosine similarity criterion to identify an internal fault, and overcoming a reliability'dead zone 'defect caused by near-zone fault voltage drop. The method does not need to depend on power frequency phasor calculation, and can improve the sensitivity and reliability of protection in scenes of a high-proportion new energy power grid, a micro-grid and the like.

Directional antenna for a motor vehicle radar system includes a housing comprising a reflecting envelope comprising an inner volume forming a reflecting cavity for electromagnetic waves, characterized in that the reflecting envelope is bounded by a set of walls including a first transmission wall comprising an electromagnetic wave transmission zone between the inside and the outside of the housing; a second guide wall, opposite the first wall, able to guide electromagnetic waves in a privileged direction; and a set of reflective lateral walls connecting the first and second walls, wherein each lateral wall is able to reflect the electromagnetic waves within the reflective cavity.

This application belongs to the field of microwave absorber technology, and particularly relates to a frequency-selective microwave absorber. The frequency-selective absorber includes a support layer having a first surface and a second surface disposed opposite to each other; a first dielectric layer bonded to the first surface; a second dielectric layer bonded to the second surface; a loss layer bonded to the side of the first dielectric layer away from the first surface to absorb electromagnetic waves of a preset frequency band; and a transmission layer bonded to the side of the second dielectric layer away from the second surface, allowing electromagnetic waves of the preset frequency band to pass through. The support layer, the first dielectric layer, the second dielectric layer, the loss layer, and the transmission layer are all transparent structures. This application can solve the technical problem in the prior art where frequency-selective absorbers lack optical transparency.

The utility model discloses an electrostatic shielding aluminum shell resistor which comprises an electrostatic aluminum shell resistor machine, the electrostatic aluminum shell resistor machine comprises a shielding shell, a first sliding groove is formed in the upper end of the interior of the shielding shell, and a second sliding groove is formed in the lower end of the interior of the shielding shell. The interior of the first sliding groove is slidably connected with a first sliding rod, the interior of the second sliding groove is slidably connected with a third sliding rod, and the shielding shell is tightly connected with the sliding rods of the resistor body to form a relatively closed environment, so that propagation of electromagnetic waves penetrating through pores and gaps is reduced; the shielding effectiveness on a high-frequency electromagnetic field can be remarkably enhanced, electromagnetic interference is reduced, and the performance and stability of the whole circuit are improved.

The present invention discloses a closed metal shell internal structure monitoring system, including a transmitting antenna extending into the metal shell for transmitting electromagnetic waves into the closed shell; a wavefront modulator installed inside the metal shell, which is connected to a circuit board and a computer for modulating the electromagnetic waves in the metal shell, and the wavefront modulator includes a plurality of modulation units, and each modulation unit can be controlled to be turned on or off by a computer and a circuit board; a receiving antenna for receiving electromagnetic waves in the metal shell, and a network analyzer electrically connected to the transmitting antenna and the receiving antenna, respectively. The present invention also provides a monitoring method for the closed metal shell internal structure monitoring system. The present invention can judge the changes in different parts of the internal structure of the closed metal shell by the changes in the electromagnetic wave transmission amplitude between the transmitting antenna and the receiving antenna, thereby realizing real-time monitoring of the internal structure of the closed metal shell.

The application provides an electromagnetic transmittance enhancer, and belongs to the technical field of microwave frequency electromagnetic wave regulation and control, comprising a plurality of super units arranged in a rectangular shape. Each super unit comprises a dielectric base, a dielectric substrate and a metal patch, the dielectric substrate is vertically arranged at the middle position on the top of the dielectric base; the metal patch is in an inverted L shape and is arranged on one side of the dielectric substrate; when the electromagnetic wave in the air is incident on the upper surface of the electromagnetic transmittance enhancer, the plurality of super units will simultaneously resonate, the electric field component of the transmitted electromagnetic wave will excite electric dipoles of different lengths in the horizontal and vertical directions of the metal patch, and the electric dipoles will interfere with the incident electromagnetic wave to cancel each other out, so that the resonance zero point of the synthesized dipoles points to the direction of the reflected wave, and the electromagnetic wave is transmitted forward from the gap channel between adjacent units. The electromagnetic transmittance enhancer provided by the application can improve the transmittance of electromagnetic wave transmission to the medium under a large incident angle.

A plasma generator by means of a resonant waveguide is disclosed. The plasma generator comprises: an annular or elliptical central waveguide that includes a plurality of slots on the inner side surface thereof; a first incident waveguide that is tangentially connected to the central waveguide to enable electromagnetic wave communication; an electromagnetic wave supply unit that transmits electromagnetic waves to the incident waveguide; and a plasma chamber that has an electromagnetic wave incident window which is positioned on an outlet side of the slots to seal the inside of the central waveguide, and through which electromagnetic waves introduced through the slots may be radiated to the outside.

This invention relates to the field of measurement while drilling (MWD) technology, specifically a drill collar-type electromagnetic wave transmission wireless MWD downhole tool. It includes a drill collar body, a nested body, a battery module, and a measurement circuit module. A hollow nested body is fitted inside the upper part of the drill collar body. Several first grooves are spaced circumferentially along the outer side of the center of the nested body, each containing a battery module. The measurement circuit module includes a drive module and a sensor module. This invention features a reasonable and compact structure. This drill collar-type electromagnetic wave transmission wireless MWD downhole tool is simple and efficient to operate. It can be docked or disassembled on-site like conventional drilling tools, eliminating the need for cumbersome work such as connecting and tightening measurement sections, measuring angle differences, lifting, wellhead installation, and key alignment with other measurement systems. This saves at least one hour of time. Furthermore, it is handled similarly to conventional drilling tools in terms of transportation and flushing, requiring no meticulous maintenance.

The invention discloses a dielectric-filled metamaterial filter. The dielectric-filled metamaterial filter comprises a waveguide, a plurality of metamaterial resonance units, an input port and an output port. The waveguide is filled with a dielectric material. The plurality of metamaterial resonance units are arranged in the waveguide, and each resonance unit in the plurality of metamaterial resonance units is electromagnetically coupled with at least one adjacent resonance unit. The input port is used for receiving input electromagnetic waves and coupling the input electromagnetic waves to the waveguide. The output port is used for receiving the output electromagnetic wave from the waveguide and transmitting the output electromagnetic wave to the outside of the dielectric-filled metamaterial filter; wherein the output electromagnetic wave is generated by filtering the input electromagnetic wave through the plurality of metamaterial resonance units.

Provided are a polyester composition and its product. The polyester composition comprises polybutylene terephthalate resin and is analyzed by small angle X-ray scattering (SAXS) to obtain a spectrum with the vertical axis representing scattering intensity and the horizontal axis representing scattering vector. A slope of the SAXS spectrum ranges from -2.00 to -4.20 within the scattering vector ranging from 0.15 nm-1 to 0.20 nm-1. The polyester composition with the foresaid features can have improved laser transmittance and low electromagnetic wave transmission loss, thereby enhancing the value of plastic products joined by laser welding.

The application discloses a method, system, device, medium and product for ionospheric modeling based on detection data, relates to the field of electromagnetic wave transmission and ionospheric modeling, and comprises the following steps: acquiring GNOS-II detection data of different dates according to a space environment, and screening effective rays based on the correction degree of electron density of the detection data; acquiring grid points through by the effective rays based on a space-based ionospheric inversion method according to corresponding data of the effective rays; determining total electron content of the space-based ionospheric inversion by using a dual-frequency calculation method according to the corresponding data of the effective rays; performing horizontal constraint and vertical constraint on global ionospheric electron density distribution by using a ground-based ionospheric inversion method according to the grid points through by the effective rays and the total electron content of the space-based ionospheric inversion; outputting the constrained global ionospheric electron density distribution to obtain a global ionospheric model. The application realizes real-time high-precision ionospheric construction in a global range.

[Problem] To provide a device and the like with which it is possible to increase power supply efficiency. [Solution] One aspect of the present invention provides a wireless power reception device comprising a power reception waveguide and a tubular ring resonator. The power reception waveguide is configured to be capable of transmitting electromagnetic waves, and is disposed in the vicinity of the ring resonator. The ring resonator is capable of transmitting electromagnetic waves in the circumferential direction, transmits electromagnetic waves transmitted from a power transmission waveguide, which transmits electromagnetic waves, to the power reception waveguide when disposed in the vicinity of the power transmission waveguide, and is configured such that the length in the circumferential direction is longer than the wavelength when said electromagnetic waves are transmitted through the interior of the ring resonator.

The application discloses a UWB high-precision positioning method and system, comprising the following steps: obtaining the one-way radio electromagnetic wave transmission time difference obtained by communication between each base station and a tag in a current single ranging stage, the coordinate information of each base station and the antenna delay compensation curve obtained by pre-solution communication between each base station and the tag; calculating the distance between each base station and the tag according to the obtained data; and determining the real-time position coordinates of the tag according to the calculated distance between each base station and the tag. Advantages: the ranging source data precision between the base station and the tag is improved, and finally the UWB positioning precision is improved.