1063 results about "Electromagnetic pulse" patented technology

The invention provides an unmanned aerial vehicle multi-dimensional information fusion method and system based on acousto-optic-electric composite detection. According to the method, acoustic frequency band signals, visible light image sequences and electromagnetic field intensity change data are collected, acoustic characteristic flow, optical characteristic flow and electrical characteristic flow are generated, and based on the time deviation between a low-frequency vibration mode and transient electromagnetic pulses, multi-channel dynamic calibration is carried out on an image distortion area in the optical characteristic flow. The method comprises the following steps: acquiring an acoustic feature flow, an optical feature flow and an electrical feature flow, correcting space-time coordinate parameters of the acoustic feature flow, the optical feature flow and the electrical feature flow, generating a calibration feature flow, carrying out anti-interference fusion processing on the calibration feature flow, extracting multi-dimensional coupling features, inputting the multi-dimensional coupling features into an unmanned aerial vehicle flight path planning model, and generating a three-dimensional space situation model; according to the invention, the physical space-time consistency alignment and noise suppression of the multi-modal data are realized, and the obstacle positioning precision and the dynamic trajectory prediction real-time performance are significantly improved.

The invention relates to the technical field of electromagnetic pulses, and discloses an electromagnetic pulse data transmission method. The method comprises the following steps: collecting natural electromagnetic pulse signal data of a detection target area through a six-dimensional complementary electrode array structure, and executing Kalman filtering peak extraction and characteristic frequency locking to obtain frequency-optimized signal data; executing first-order and second-order gradient difference matrix calculation and space vector synthesis to obtain signal source position coordinate data and signal intensity data; performing spectral domain reconstruction and multilayer dynamic threshold analysis to obtain a spatial clustering abnormal data packet; and selecting an optimal transmission channel to transmit the spatial clustering abnormal data packet to a cloud server. According to the invention, the influence of an external interference source is effectively eliminated, accurate extraction and characteristic frequency locking of effective frequency band signals are realized, power frequency and harmonic interference thereof are effectively suppressed, the signal-to-noise ratio of the effective frequency band of the signals is improved, and the reliability and timeliness of data transmission in a severe field environment are ensured.

Disclosed are a dynamic disturbance-induced rock burst test device and a test method. The test device comprise a supporting platform, a plurality of loading plates, an electromagnetic pulse emitting system, an acoustic emission monitoring system, a high-speed camera, an electromagnetic radiation detecting system and a confining pressure servo control loading system. The plurality of loading plates are arranged on a side wall of a coal rock sample and are placed inside a square chest, the electromagnetic pulse emitting system and the confining pressure servo control loading system are arranged inside a bar system, and an acoustic emission probe is arranged inside the loading plate. A three-dimensional real stress environment of the coal rock is simulated by simulating a shear stress through friction between the loading plate and the sample, as well as dynamic and static combined loading of multi-axial and multi-directional static confining pressure and stress wave disturbance.

The invention discloses a transient electromagnetic three-dimensional dike leakage hidden danger detection method based on unmanned aerial vehicle carrying, and the method comprises the steps: S1, scanning a detection region range, obtaining dike terrain remote sensing image and point cloud image data, and setting a flight path of an unmanned aerial vehicle according to a preset detection region range; s2, performing task flight, and transmitting transient electromagnetic pulse signals with different frequencies to the underground of the dike through a transmitting coil according to a transmitting current frequency range; s3, a receiving coil is used for synchronously collecting secondary electromagnetic response signals generated by underground medium induction, discretization sampling is conducted on the collected signals according to the sampling time interval, and a sampling data sequence is obtained; s4, constructing a three-dimensional resistivity model of the dike underground medium through a three-dimensional inversion algorithm; and S5, through the constructed three-dimensional resistivity model, multi-dimensional features of the leakage hidden danger are extracted, and an area with the leakage hidden danger in the dike is identified. The leakage hidden danger area can be rapidly identified, and the detection efficiency and precision are improved.

Resonant sensors for environmental health risk detection are disclosed. A mechanical member may include at least one meso-scale or micro-scale resonator disposed on a surface of the mechanical member. Additionally, the at least one meso-scale or micro-scale resonator may include a plurality of first carbon particles configured to uniquely resonate in response to an electromagnetic ping based at least in part on a concentration level of the first carbon particles within the at least one meso-scale or micro-scale resonator. Further, the at least one meso-scale or micro-scale resonator may be configured to resonate at a first frequency in response to the electromagnetic ping when the mechanical member is in a first state, and may be configured to resonate at a second frequency in response to the electromagnetic ping when the mechanical member is in a second state.

A disclosed airborne vehicle includes split-ring resonators (split ring resonators), which may be embedded within a material. Each split ring resonator may be formed from a three-dimensional (3D) monolithic carbonaceous growth and may detect an electromagnetic ping emitted from a user device. Each split ring resonator may generate an electromagnetic return signal in response to the electromagnetic ping. The electromagnetic return signal may indicate a state of the material in a position proximate to a respective split ring resonator. In some aspects, each may resonate at a first frequency in response to the electromagnetic ping when the material is in a first state, and may resonate at a second frequency in response to the electromagnetic ping when the material is in a second state. A resonant frequency of the 3D monolithic carbonaceous growth may be based on physical characteristics of the material.

The invention relates to the technical field of intelligent identification, and discloses an intelligent identification method for a geological stress concentration area. The method comprises the steps that a plurality of vector electromagnetic induction coils are arranged in a monitoring area in a latticed mode, and original electromagnetic pulse signals containing components in the X direction, the Y direction and the Z direction are collected; performing denoising and time-frequency analysis on the original electromagnetic pulse signal to obtain a multi-dimensional data cube; processing the multi-dimensional data cube by using an integer linear programming model and an adaptive fuzzy correction algorithm to obtain a corrected electromagnetic pulse signal data set; performing decomposition and mapping relation construction on the corrected electromagnetic pulse signal data set to obtain a geological stress distribution estimation value; and constructing a geological stress concentration area three-dimensional model according to the geological stress distribution estimation value. According to the method, the stress field boundary identification precision is enhanced, and the blind area is reduced, so that high-precision stress field reconstruction under complex geological conditions is realized.

The invention relates to the technical field of power distribution cabinet detection, and discloses an intelligent detection system and method for a high-low voltage power distribution cabinet, and the system comprises a data collection module, a feature extraction module, a network construction and updating module, a fault positioning module, a positioning map generation module, and a self-healing control module. The method comprises the following steps: generating a multi-physical field coupling data set by synchronously collecting electromagnetic radiation spectrum and cabinet vibration waveform, performing time-frequency domain conjoint analysis to extract fault feature vectors, constructing and dynamically updating a fault propagation network, identifying key fault sources by combining betweenness centrality and historical case matching, and generating a fault positioning map; accurate self-healing control is realized by applying reverse electromagnetic pulse and adjusting contact pressure based on the atlas; according to the invention, the problems of low positioning precision and mechanical self-healing control means during detection of the high-low voltage power distribution cabinet are solved, and the fault detection efficiency and reliability are significantly improved.

A disclosed leaky coaxial resonant sensor system and methods. In use, the system includes at least one split-ring resonator (SRR) embedded within a material of the component. The at least one SRR is formed from a composite material. Additionally, the at least one SRR is configured to resonate at a first frequency in response to an interrogation signal from a leaky coaxial cable antenna. In some aspects, each SRR may resonate at a first frequency in response to an electromagnetic ping when the composite material is in a first state, and may resonate at a second frequency in response to the electromagnetic ping when the composite material is in a second state. A resonant frequency of the composite material may be based on physical characteristics of the composite material.

The invention relates to an electromagnetic shielding method and shielding system for power distribution, and belongs to the technical field of electromagnetic shielding. Comprising the following steps: establishing a shielding model corresponding to the shielded room according to volume data of the shielded room; simulating and positioning electromagnetic wave conditions in the shielded room in the shielding model; selecting key detection points; constructing a phase difference matrix; shielding requirements of different waveforms in the same frequency band are distinguished, leakage path positioning based on a waveguide equation is carried out, and a core leakage area and an auxiliary protection area are divided. According to the electromagnetic shielding method and shielding system for power distribution provided by the invention, the dynamic adaptability of electromagnetic shielding and the detection capability of transient electromagnetic pulses are remarkably improved, and a multi-dimensional risk quantification and differentiation reinforcement strategy is realized. Meanwhile, intelligent materials and a dynamic optimization mechanism are adopted, the material utilization rate and the protection effect are improved, and a reinforcing effect feedback closed loop is formed.

The invention provides an optical fiber communication line fault feedback system, which relates to the technical field of optical fiber communication fault diagnosis, and comprises a data acquisition module, a feature extraction module, a feedback module and a fault feedback module, according to the method, the attenuation rate, the reflectivity, the packet loss rate, the temperature, the humidity, the vibration signal, the electromagnetic pulse signal and the radio frequency interference signal of the optical fiber communication line are obtained; compared with the prior art, the method comprehensively considers the influence of communication related parameters and environment related parameters, achieves the comprehensive evaluation of the optical fiber communication line, and improves the evaluation accuracy of the optical fiber communication line. Therefore, the accuracy of subsequent fault diagnosis and fault classification is improved.

The invention relates to an anti-electromagnetic interference device and method applied to a short-range unmanned aerial vehicle. The equipment comprises an electromagnetic pulse induction module, a power supply module, an electromagnetic pulse shielding device, a data processing and control module, an ultrahigh frequency signal generator and a signal transceiving module. Through a high-efficiency assembly, a high-efficiency electromagnetic pulse detection mechanism and an electromagnetic pulse protection scheme, an integrated design and a systematized layout strategy are combined, and a set of electromagnetic pulse interference resisting equipment which has a wide and accurate monitoring frequency spectrum and a strong electromagnetic pulse shielding capability and also gives consideration to the portability of the unmanned aerial vehicle is constructed. The equipment has the capability of monitoring and filtering electromagnetic pulses in a specified range in real time, and ensures that a carried unmanned aerial vehicle system can resist electromagnetic pulse invasion of certain intensity, so that the survival capability and the system reliability of a short-range unmanned aerial vehicle in an electromagnetic interference environment are remarkably improved.

A system suppresses extreme voltage surges induced on electric power lines due to transient electromagnetic energy disturbance from detonation of a nuclear weapon at high altitude generating an electromagnetic pulse (EMP) comprising E1, E2, and E3 pulses, geomagnetic disturbance, and intentional electromagnetic interference. Low voltage (LV) surge protection (SP) assemblies mounted at medium voltage (MV) inputs and LV outputs of the stacked converter cells of a solid-state transformer (SST) form SP of MV and LV electrical power grids interfaced by the SST. The SP assemblies utilize LV components to provide MV grid protection, shunting overcurrent to ground without interfering with the SST MV / LV grid segments isolation. The SP components are selected and coordinated to achieve predefined response at protection threshold voltage levels with current capacity mitigating complex components of HEMP. The hybrid SP communicates with SST control to react to a prolonged overvoltage / overcurrent fault condition.

The invention relates to an electromagnetic pulse collaborative deicing system based on multi-mode perception. The system comprises a power supply system; the FPGA controller is used for logic control and signal processing, calculating electromagnetic pulse parameters and realizing high-speed and accurate deicing instruction scheduling; a sensing module; a real-time detection system; a pulse generation unit; and the deicing module executes an electromagnetic pulse deicing action and efficiently removes ice covered on the surface of the power grid. The invention further discloses an electromagnetic pulse collaborative deicing method based on multi-mode sensing. Through the electromagnetic pulse technology, the power transmission and distribution line ice can be efficiently removed, compared with a traditional thermal ice melting method, the energy consumption is greatly reduced, the response speed is remarkably increased, and the deicing strategy and parameters are dynamically adjusted according to real-time monitoring data based on the real-time signal processor of the FPGA; the power supply priority can be dynamically adjusted according to the energy supply condition, the energy is improved to the maximum extent, and an accurate deicing basis is provided for the system.

The invention discloses a high-voltage cable state live detection method, which relates to the technical field of power detection, and is characterized in that a mathematical model of an electric field around a cable is established by using an electrostatic field equation in a Maxwell equation set, and electric field distribution between a cable insulation layer and a conductor is solved; high-frequency electromagnetic pulse signals are measured, and partial discharge detection in the insulating layer of the high-voltage cable is carried out according to a Paschen curve model; the temperature distribution change in the cable is simulated through a heat transfer equation, and the temperature distribution of the cable is monitored in real time by using a fiber bragg grating sensor; and correcting the electric field distribution and the partial discharge detection result based on the obtained temperature distribution of the cable. The partial discharge phenomenon in the cable insulation layer can be accurately identified and positioned, the insulation state of the cable can be monitored in real time, whether the discharge phenomenon exists or not can be rapidly judged, and therefore cable faults can be effectively prevented.

The invention provides a rolling stress relief and plate shape flatness coordinated optimization method in a strip steel annealing process, which comprises the following steps of: performing segmented dynamic tension control, dual-frequency electromagnetic field temperature control, gradient pulse stress reconstruction and electromagnetic-pulse multi-target coupling optimization; the problems that heat conduction lags behind, residual stress release is not thorough and flatness control is insufficient in a traditional process are solved, and the method has the advantages that stress elimination and plate shape control are synchronously optimized, recrystallization uniformity is improved, and residual stress is reduced.

The invention discloses a short-wave strong electromagnetic pulse suppression circuit with direct current and control functions. The short-wave strong electromagnetic pulse suppression circuit comprises an I-stage transient protection circuit, a three-signal circuit and an II-stage transient protection circuit, the I-stage transient protection circuit is formed by connecting two stages of gas discharge tubes in series and is used for protecting a low-frequency part in the lightning electromagnetic pulse or the nuclear power electromagnetic pulse, and the output end of the I-stage transient protection circuit is connected with the three-signal circuit; the three-signal circuit provides a path for transmission of the short-wave signal, the direct-current signal and the control signal and carries out transient protection, and the output end of the three-signal circuit is connected with the II-stage transient protection circuit; and the II-stage transient protection circuit is a voltage clamping circuit consisting of a low-capacitance diode and a bidirectional transient suppression diode, and is used for protecting a high-frequency part in the lightning electromagnetic pulse or the nuclear power electromagnetic pulse and clamping the residual voltage at a relatively low level. The device can effectively protect thunder and lightning and nuclear power electromagnetic pulses, has the characteristics of small insertion loss, low residual voltage and the like, and can greatly improve the strong electromagnetic environment viability and anti-interference capability of a short-wave radio station.

The invention discloses a one-way valve air tightness detection method and system, and relates to the technical field of air tightness detection.According to the one-way valve air tightness detection method and system, through dynamic interaction of AI virtual sensor prediction and physical detection values and combination of time-frequency domain signal fusion, the extraction capacity of micro-leakage signals is remarkably enhanced, and misjudgment caused by background noise or residual gas in a traditional method is avoided; a multi-mode interference source correlation analysis and dynamic weight distribution mechanism is utilized to actively identify and compensate composite interference such as temperature drift and electromagnetic pulse, so that the reliability of a detection result in severe scenes such as workshop vibration and airflow disturbance is improved; and meanwhile, a model adaptation module based on transfer learning and non-contact vibration spectrum monitoring are adopted, manual parameter adjustment dependence is reduced, valve bodies of different specifications are rapidly adapted, early damage of the diaphragm is warned in advance, and the equipment maintenance period is prolonged.

The invention discloses a high-voltage frequency converter driving load shaft system torsional resonance monitoring method. The method comprises the following steps: arranging an encoder on a shaft system to collect shaft system rotating speed information in real time; inputting the encoder signal into a rotating speed acquisition and processing module in a frequency converter master control system so as to process the encoder signal into a signal format which can be identified by a storage and calculation chip of the frequency converter master control system; inputting the processed encoder signal into a torsion angle calculation and analysis module in a storage calculation chip so as to carry out shaft system torsion angle calculation and torsion angle harmonic analysis; and according to the calculated torsion angle amplitude condition, a torsional vibration alarm module in the storage calculation chip gives an alarm. As a further scheme of the invention, the encoder is an electromagnetic pulse encoder. The method can be used as an online monitoring and alarming means for torsional vibration of a high-capacity fan and water pump load variable-frequency driving shaft system, the problems of system shutdown and the like caused by irreversible fatigue damage of the shaft system due to hidden torsional vibration of the shaft system are solved, and the implementation cost is low.

A lightweight radiation shielding material. A carbon nanotube forest is embedded in a matrix comprising nanoparticulates, such as nanoparticles, carbon nanotubes, or graphene nanosheets. The nanoparticulates can be low atomic number (low-Z) or high atomic number (high-Z). The matrix can be a solidified polymer, epoxy, resin, or ceramic precursor, for example silicon carbide. The radiation shield can shield an object from radio frequency interference (RFI), lightning, electromagnetic interference (EMI), an electromagnetic pulse (EMP), gamma rays, X-rays, neutrons, and / or protons. The nanoforest is disposed on a conductive base with sufficient in-plane electrical conductivity to provide an effective conductive path for currents induced by radiation absorption. The base can be a second nanoforest comprising horizontally-oriented carbon nanotubes, which makes the shield particularly lightweight, as low as 10% of the mass of aluminum that provides equivalent shielding. The base can be adhered to an object to be shielded.

The invention belongs to the technical field of additive manufacturing, and particularly relates to a strong electromagnetic pulse-ultrasonic auxiliary electric arc additive manufacturing platform. The platform body is provided with an upper substrate used for providing an initial plane for electric arc additive manufacturing; the water cooling device comprises a water cooling box used for containing cooling water, and the substrate is contained in the water cooling box; the base plate locking clamp comprises a positioning clamping table and a clamping device. The positioning clamping table and the clamping device are arranged on the two sides of the upper base plate and matched to form a fixing structure for fixing the relative positions of the upper base plate and the platform body. The welding gun head is connected with the six-axis mechanical arm and is used for carrying out additive manufacturing on the upper substrate; the clamping device and the welding gun head are arranged on the two opposite sides of the upper base plate in a spaced mode. And the clamping device is partially arranged outside the water cooling box. The clamping device and the welding gun head are arranged on the two sides of the water cooling box respectively, space interference between the clamping device and the welding gun head in the working process can be effectively avoided, meanwhile, a principle heat source of the clamping device can be guaranteed, and normal work of the clamping device is guaranteed.

The invention provides a far-zone electromagnetic pulse waveform simulation method and system, and the method comprises the steps: introducing an international reference geomagnetic model, an international reference ionosphere model and an international reference atmosphere model when a waveguide parameter of a single-frequency signal segmented along a path is calculated through an LWPC model; the obtained geomagnetic parameters, the ionosphere electron density and the electron collision frequency contain influences of time and space, solar disturbance and geomagnetic changes, are used for simulation of the far-zone electromagnetic pulse waveform, and can improve the simulation precision of the far-zone electromagnetic pulse waveform.

The invention discloses an anti-unmanned aerial vehicle defense system based on electromagnetic pulses and a defense method thereof, and relates to the technical field of unmanned aerial vehicle defense. The position information, the signal characteristics and the thermal imaging information of the unmanned aerial vehicle are acquired and comprehensively evaluated, so that a three-dimensional threat evaluation system is constructed, multi-dimensional parameters are weighted and calculated into the threat evaluation index, the threat evaluation index is matched with the preset index set to determine the threat level, different threat scenes can be dynamically responded, and the threat evaluation accuracy is improved. The problem that in the prior art, the threat level cannot be automatically evaluated according to dynamic parameters such as the speed, the flight path and the load type of the unmanned aerial vehicle, and overreaction or defense vulnerabilities are likely to occur is solved.

The invention relates to the technical field of unmanned aerial vehicle radio detection, in particular to an unmanned aerial vehicle detection and judgment method based on cooperation of an air-ground system and radio detection, and the method comprises the steps: finding a suspected target through scanning of a multi-frequency-band radar, triggering an infrared thermal imager carried by an aerial unmanned aerial vehicle to approach an ultra-wide-frequency-band spectrum sensor for verification; accurate positioning is realized by combining ground photoelectric equipment multi-view triangulation positioning and a signal arrival time difference algorithm, a command and control center calculates threat levels through a multi-source data fusion engine, and navigation decoy of dynamically adjusting intensity is adopted for targets smaller than or equal to two levels. Hard killing of ground laser locking rotor center and air electromagnetic pulse synchronous coverage is executed on a target of more than or equal to three levels, the equipment state is synchronized in real time through an optical fiber link, high-energy-consumption equipment is intelligently closed after threat is relieved, a platform starting strategy is optimized, a detection closed loop of'three-dimensional perception-graded treatment-intelligent energy saving 'is constructed, and the intelligent energy saving effect is achieved. And an efficient and accurate low-altitude safety protection scheme is provided for a sensitive area.

The invention discloses a low-voltage switch cabinet intelligent monitoring system and method based on the Internet of Things, particularly relates to the technical field of power equipment state monitoring, and is used for solving the problem of monitoring data distortion caused by accumulated damage of a sensor due to arc electromagnetic pulses in the prior art. A current and voltage waveform is collected and an arc event is identified; calculating an electromagnetic coupling weight coefficient according to the arc position and the sensor coordinate; capturing working parameters of the sensor, comparing the working parameters with historical reference values, and calculating offset of key parameters; information entropy mutation of the offset of the same type of sensor groups is analyzed, and a nonlinear damage mark is triggered; based on the offset and the damage mark, establishing a segmentation mapping relation and outputting an accumulated damage evaluation value; correcting monitoring data according to the evaluation value and inputting the monitoring data into a fault diagnosis model to execute early warning; quantitative evaluation and data self-correction of the hidden damage of the sensor are realized, and the accuracy of fault early warning is guaranteed from the source.

The invention discloses a high-altitude electromagnetic pulse waveform parameter solving method, system and device and a medium. The method comprises the steps that the rapid rise time tr and the pulse width tw of a high-altitude electromagnetic pulse waveform are acquired; the fast rising time tr and the pulse width tw of the high-altitude electromagnetic pulse waveform are input into the trained PINN network, alpha, beta, t1 and t2 are obtained, alpha and beta are parameters representing rising time and falling time, t1 and t2 represent time needed by pulse intensity change, the PINN network is trained by using a sample set obtained through dual-scale probability sampling, and the pulse width tw of the high-altitude electromagnetic pulse waveform is obtained. According to the method, the system, the equipment and the medium, the number of used samples is small, and the solving error is low.

The utility model discloses an energy-saving type electromagnetic pulse valve which comprises a valve body, a valve cover arranged on the valve body, a first diaphragm assembly installed between the valve body and the valve cover and a pilot valve assembly installed at the upper end of the valve cover, and the valve body is provided with an air inlet, an air outlet and a first valve port communicated with the air inlet and the air outlet. The pilot valve assembly controls the first diaphragm assembly to open and close the first valve port, the inner wall of an air outlet of the valve body is provided with a concave-convex section so that compressed air can be sprayed out in a pulse mode after passing through the concave-convex section, the inner wall of the air outlet is in a concave-convex arc design so that the compressed air can be sprayed out in a pulse mode after passing through the concave-convex section, and the ash removal effect is improved. Meanwhile, consumption of compressed gas is reduced, and energy waste is reduced.

A disclosed construction structure unit may include at least one split-ring resonator, which may be embedded within a material. The split ring resonator may be formed from a three-dimensional (3D) monolithic carbonaceous growth and may detect an electromagnetic ping emitted from a user device. The split ring resonator may generate an electromagnetic return signal in response to the electromagnetic ping. The electromagnetic return signal may indicate a state of the material in a position proximate to a respective split ring resonator. In some aspects, the split-ring resonator may resonate at a first frequency in response to the electromagnetic ping when the material is in a first state, and may resonate at a second frequency in response to the electromagnetic ping when the material is in a second state. A resonant frequency of the 3D monolithic carbonaceous growth may be based on physical characteristics of the material.

There is presented an apparatus for generating a quantum cryptographic key by outputting an EM pulse / a set of EM pulses to a further apparatus. One or more electromagnetic pulse sources are for outputting at least a first set of one or more EM pulses and a second set of one or more EM pulses. A random phase relationship exists between a first EM pulse and a second EM pulse. An optical element (BS3) receives the first EM pulse and the second EM pulse and is configured to interfere the first EM pulse with the second EM pulse and output an interfered EM pulse along an output path. Further optical elements BS4 and BS5 are used to split off a portion of the output pulses for measuring the properties of the interfered EM pulses. In one example, at least one EM attenuator is configured to attenuate the said received EM pulse such that the attenuated EM pulse comprises an average of up to one photon. The attenuated pulse is output towards a further apparatus, for generating the quantum cryptographic key.

Implementations of disclosed systems and methods are capable of changing the frequency or other waveform characteristics dynamically based on receiving feedback about the effect of an electromagnetic pulse radiation on a target electronic device. Various implementations can be configured to emit electromagnetic pulses at a single radio frequency or a plurality of radio frequencies. For example, the frequency of the carrier electromagnetic radiation in a single pulse can change during the pulse interval. As another example, a single electromagnetic pulse can comprise a frequency comb with two or more frequencies.