9 results about "Extremely low frequency" patented technology

The application relates to the technical field of semiconductor laser control, and discloses a wavelength stabilization control method of a semiconductor laser, which comprises the following steps: constructing an equivalent heat transfer model of a multi-section semiconductor laser; monitoring the radio frequency data stream duty cycle of a gain section, switching the injection path of a low-frequency pilot signal to extract a global equivalent low-frequency thermal resistance, updating a time-varying low-frequency physical RC node parameter set; combining the transient heat power of the gain section and the equivalent heat transfer model to deduce full-frequency section junction temperature observation data, and decomposing the full-frequency section junction temperature observation data into an extremely low-frequency direct current component, a medium-low-frequency fluctuation component and an extremely transient high-frequency fluctuation component; driving a thermoelectric refrigeration component according to the extremely low-frequency direct current component; generating a medium-low-frequency feedback compensation current according to the medium-low-frequency fluctuation component, combining the extremely transient high-frequency fluctuation component to generate a feedforward compensation current; and injecting the medium-low-frequency feedback compensation current and the feedforward compensation current into a grating section after being combined. The application realizes multi-frequency section decoupling control and improves wavelength stability.

A two-way bass enhancement structure, comprising a bass unit, a thick guide pipe and a thin guide pipe. The input end of the thick guide pipe is connected to the output end of the bass unit, the output end is connected to the sound outlet nozzle of the earphone, and the inner circumferential side of the output end of the thick guide pipe is provided with acoustic damping. The input end of the thin guide pipe is connected to the circumferential side of the thick guide pipe and penetrates through it, and the output end is connected to the sound outlet nozzle of the earphone. The inner diameter of the thin guide pipe is smaller than that of the thick guide pipe. The utility model can not only maintain the information amount of bass, but also directly and efficiently transmit the extremely low frequency part, thereby improving the sound quality.

This application relates to the field of quantum nondestructive testing technology, and discloses a quantum detection device and a xenon atom-based eddy current detection method. The quantum detection device includes an interconnected eddy current probe and a quantum measurement device. The quantum measurement device includes a xenon atom gas chamber for measuring the magnetic field strength of a target eddy current magnetic field. It acquires the target eddy current magnetic field of the target object, measures the magnetic field strength of the target eddy current magnetic field, and obtains the magnetic field strength distribution along the surface of the target object. Based on the magnetic field strength distribution, it detects thickness changes in the target object to obtain the weak point detection result. Its beneficial effect is that by measuring the eddy current magnetic field generated by the target object through a xenon atom gas chamber, it effectively utilizes the characteristics of xenon atoms—long coherence time and extremely low resonance frequency—thereby maintaining high sensitivity to capture weak magnetic fields at extremely low frequencies and obtaining a detection penetration depth far exceeding that of traditional sensors, achieving high-precision nondestructive testing of minute thickness differences inside the target object.

The application provides a wind turbine tower inherent frequency real-time identification method and electronic equipment, and belongs to the technical field of wind power generation equipment state monitoring and fault diagnosis. The method comprises the following steps: S1, collecting vibration signals of a wind turbine tower; S2, pre-processing the vibration signals to filter out direct current components and extremely low frequency noises; S3, performing grouping processing on the pre-processed signals, performing frequency spectrum analysis on each group of signals, and extracting effective frequency points; S4, performing clustering analysis on a plurality of the effective frequency points based on a density clustering algorithm, and identifying a characteristic cluster representing the inherent frequency of the tower; and S5, calculating the real-time inherent frequency of the tower according to the characteristic cluster. The application can stably and automatically extract the characteristic cluster representing the real inherent frequency of the tower from strong noise and non-stationary vibration data, finally realizes automatic identification and tracking of the inherent frequency without manual intervention, and provides reliable technical support for intelligent monitoring of the structure health of the wind turbine.

This invention specifically relates to a time-varying finite element modeling method for extremely low frequency (UHF) sound fields under dynamic internal wave processes, belonging to the field of underwater acoustic physics. The method first simulates the internal wave propagation process using the modified Korteweg-de Vries equation based on background field environmental information, and then obtains the vertical modes of the internal waves using the Taylor-Goldstein equation to construct a dynamic sound velocity field. Secondly, in a fluid-structure interaction model containing multiple layers of seabed media, the wave equation is solved using the finite element method to achieve time-varying calculation of the UHF sound field. This invention can precisely characterize the spatiotemporal evolution of the sound velocity field under complex terrain and dynamic internal wave disturbances, accurately simulate the distribution characteristics of the UHF sound field throughout the entire internal wave propagation process, and is suitable for sound field prediction and analysis in sea areas with high internal wave incidence, such as the South China Sea.

This invention discloses an ultra-high stability laser system based on dual-path independent composite frequency stabilization and sum-frequency modulation, belonging to the field of precision laser spectroscopy and frequency control technology. The system includes two seed lasers (1560 nm and 1064 nm), a dual-wavelength common-cavity ultra-stable module, two acousto-optic frequency shift and dual-reference absolute frequency stabilization modules, and a nonlinear sum-frequency modulation (SFG) module. Full-time-scale frequency noise suppression is achieved through a three-stage cascaded closed loop consisting of a MHz fast loop, a kHz slow loop, and a Hz extremely slow loop. An acousto-optic modulator is placed in the sampling optical path fed into the ultra-stable cavity, and physical decoupling of the fast and slow loops is achieved through radio frequency bridging. The extremely low-frequency error signal detected by NICE-OHMS is fed back to the PPMgOLN crystal temperature or AOM driving frequency to compensate for the thermally induced drift of the nonlinear crystal. The system ultimately outputs a 633 nm laser power of not less than 50 mW, with a short-term frequency instability better than 5 × 10⁻⁶ mW. ‑15 @1 s.

The present application relates to a kind of multidirectional extremely low frequency vibration energy harvesting device based on limiting double pendulum system, belong to vibration energy harvesting field.The device is composed of limiting double pendulum module and energy conversion module, the limiting double pendulum module includes encapsulation shell, cycloidal A, mass block, cycloidal B, movable permanent magnet and Teflon pipe, the energy conversion module includes movable permanent magnet, energy converter, Teflon pipe and fixed permanent magnet, energy converter can be selected according to different energy conversion principle, such as coil (electromagnetic induction), piezoelectric cantilever beam (piezoelectric effect), magnetoelectric composite material (magnetoelectric effect), friction electricity material (triboelectric effect) etc., the two modules are coupled by movable permanent magnet and Teflon pipe for sharing;The energy harvesting device can respond to multidirectional excitation, with extremely low operating frequency, while simple structure, low mechanical fatigue, high output power, adapt to wave energy, wind energy, mechanical vibration energy and many other energy harvesting fields.

The technical idea of the present invention is to provide a bonded steel sheet having excellent electromagnetic wave shielding ability and improved corrosion resistance. According to exemplary embodiments of the present invention, there can be provided a bonded steel sheet exhibiting excellent corrosion resistance as well as excellent shielding ability against electromagnetic waves, particularly extremely low frequencies. In addition, according to exemplary embodiments, there can be provided a bonded steel sheet that has excellent durability and is easy to manufacture by employing a resin layer having excellent peel strength.

The utility model relates to a kind of very low frequency broadband signal amplification circuit, belong to electronic circuit technical field. Very low frequency broadband signal amplification circuit includes two-stage filter circuit and three-stage amplifier circuit. First-stage filter circuit connects signal input end, for the filtering processing of very low frequency signal, and the very low frequency signal is the underwater acoustic signal of frequency as low as 0.001 hertz;The input end of first-stage amplifier circuit is connected with the output end of first-stage filter circuit;The input end of second-stage amplifier circuit is connected with the output end of first-stage amplifier circuit;Second-stage filter circuit connects the output end of second-stage amplifier circuit;The input end of third-stage amplifier circuit is connected with the output end of second-stage filter circuit;Negative feedback low-pass filter circuit is connected to the input end of first-stage amplifier circuit through the output end of third-stage amplifier circuit;The output end of third-stage amplifier circuit is as the output end of very low frequency broadband signal amplification circuit.