125 results about "Free field" patented technology

The present invention discloses analysis system and method of microbubble behavior in biomedicine ultrasonic field based on superhigh speed photograph technology. Specifically, he present invention includes proposing superhigh speed photograph system for observing the microbubbles in ultrasonic field and microscopic superhigh speed photograph system for observing single microbubble; presenting the method of analyzing the microbubble behavior in free field, near tissue and inside microtubule; and presenting the method of controlling microbubbles generation and breaking and estimating microbubble strain.

The invention relates to a method for measuring sound source radiation sound power and particularly relates to a method for measuring underwater sound source low frequency radiation sound power in a rectangular reverberation water tank arranged in the air. The method comprises steps that, a sound source is fixed at a position of a reverberation water tank for emission, and a hydrophone is fixed at another position to measure a sound pressure amplitude of the reception position; a reverberation water tank normal frequency calculation algorithm taking consideration of influence of a water tank wall structure on a sound field is employed, each-order normal frequency of the measurement water tank sound field is determined; the sound pressure amplitude measured in the step (1) and the water tank sound field normal frequency determined in the step (2) are taken as input parameters, the algorithm calculating the free field sound power in the reverberation water tank is employed, and the sound power of a to-be-measured sound source in the free field is determined. The method does not need to utilize a known sound source to carry out correction on the reverberation water tank sound field. When the sound field normal frequency in the water tank and the speed potential function are determined, influence of the water tank wall structure on the sound field is considered, so the sound field calculation result in the water tank is more accurate.

The invention relates to a reverberation time measurement method and particularly relates to an inversion method utilizing a single hydrophone to measure reverberation time of a non-anechoic pool. The method comprises steps that, a sound source level of a random non-directional sound source is measured in an anechoic pool by utilizing a calibrated hydrophone and is recorded and loaded to frequency and voltage amplitude on the sound source; the non-directional sound source and the hydrophone are put to a to-be-measured non-anechoic pool, frequency and voltage amplitude are recorded and are loaded to the non-directional sound source, the sound source and the hydrophone are simultaneously and slowly moved, and an average space sound pressure level is acquired by utilizing the hydrophone for measurement; the reverberation time of the non-anechoic pool can be acquired through inversion calculation according to the sound source level of the non-directional sound source in a free field and the measured average space sound pressure level of the sound source in the to-be-measured non-anechoic pool. The method has properties of high test efficiency and accurate result, and the average sound energy density attenuation time can be measured not on the basis of definition of the reverberation time.

The invention discloses a multifunctional underwater acoustic parameter comprehensive test experimental device, which comprises an underwater acoustic tank, a tested transducer, a standard receiver, an auxiliary transmitting transducer, an reciprocal transducer, a rotary lifting mechanism, an electronic test equipment and a test software. The invention is a necessary experiment teaching instrumentequipment for the underwater acoustic engineering professional practice teaching courses. Various underwater sound field environments including low-frequency standing wave field, a medium-high-frequency free field, a reverberation field and the like can be simulated in a limited space in a laboratory under different frequency bands, so that underwater acoustics, underwater acoustic transducer, sonar and other professional theoretical knowledge can be verified. The invention specifically relates to a multifunctional underwater acoustic parameter comprehensive test experimental device which canrealize experiment teaching of basic parameters of underwater acoustics, underwater acoustic transducer and sonar basic parameters in a laboratory with a frequency range of 2-200 kHz.

A method is disclosed for calibration of a towed line array. In a low frequency band, calibration is performed using an acoustic field observed by reference standard hydrophones. The observations form a model of a complex acoustic field throughout a space occupied by a measurement apparatus. The array sensitivities are computed by comparing output voltages of the array with the acoustic field estimated at the locations occupied by hydrophones of the array. Variations in the acoustic field that cannot be accounted for by free field propagation theory are included in the calculation of array channel sensitivities. The method extends the low frequency limit for the calibration to less than the minimum frequency at which free field propagation conditions can be approximated. Boundary reflections and spatial variations in the acoustic field are recognized. The spatial distribution of acoustic energy is used to provide low frequency calibration with improved precision.

The invention discloses a three-dimensional sound source localization method based on compressed sensing, so as to solve the technical problem of poor anti-noise performance of the existing three-dimensional sound source localization method. In the technical scheme, the measurement value of sound source signals is acquired through a microphone array, a selected three-dimensional sound source area is subjected to uniform mesh generation, and each mesh node is used as a hidden sound source position; according to a Helmholtz equation of a free field Green's function, a measurement matrix between the mesh node and the microphone array is built, and a three-dimensional narrowband sound source localization sparse representation model between the measurement value of the microphone array and unknown sound source signals is acquired; through carrying out singular value decomposition on the measurement value of the microphone array in the sparse representation model, a sound source localization sparse representation model after deformation is acquired; and finally, a compressed sensing OMP (orthogonal matching pursuit) algorithm is adopted to carry out iterative solution on the representation model after deformation, the sound source strength of each mesh node in the sound source area is acquired, and the sound source is localized. The anti-noise performance of sound source localization is improved.

The invention relates to a rock-soil medium progressive failure, solid-like. The smooth particle dynamics (SPH) method is improved from three aspects: boundary condition, constitutive relation and artificial stress, so that the SPH can reproduce the progressive failure of rock and soil media under strong earthquake dynamic condition, solid-like-liquid phase change behavior, constructing slip-freeboundary modified by seismic wave velocity to apply seismic wave, creating free-field boundary to prevent seismic wave reflection, using particle rheology for reference, combining Drucker-Prager constitutive model and Newtonian fluid constitutive model construct a new unified constitutive model, which can describe the phase from sliding (solid-like) to flowing (liquid-like) in geotechnical media.The invention effectively reproduces the kinematic characteristics of the start-up, high-speed flow and accumulation process of the landslide, analyzes the progressive failure of the rock and soil medium and the penetration process of the sliding surface under the action of the strong earthquake, thereby accurately predicting the sliding distance, and reasonably assesses the earthquake-triggered landslide. The hazard caused by debris flow provides scientific basis for the planning and design of earthquake prevention and disaster reduction.

The invention relates to a photoacoustic detector including an acoustically open measuring area which is not completely surrounded by a housing. The detector includes an arrangement for introducing excitation light into the measuring area, such that the excitation light can be absorbed by absorbent materials which are located in the measuring area and which are used to produce acoustic energy. The invention also relates to a detector which includes at least one acoustic sensor and an arrangement is provided in order to concentrate the acoustic energy, in order to reach a local maximum of the acoustic pressure on at least one position. The at least one sensor is arranged in the vicinity of the at least one position, whereon the local maximum of the produced acoustic pressure is present or can be produced. The invention also relates to an associated method.

A surrounding gate field-effect transistor combined with a vertical channel (4) and a junction-free structure comprises a surrounding semiconductor channel in the vertical direction, a surrounding gate electrode (6), a surrounding gate dielectric layer (5), a source region (2), a drain region (3) and a semiconductor substrate (1), wherein the source region (2) is located at the bottom of the vertical channel (4) and connected with the substrate (1), the drain region (3) is located at the top of the vertical channel (4), and the gate dielectric layer (5) and the gate electrode (6) surround the vertical channel (4) circularly. The impurities of the same type and concentration are doped into the source region (2), the drain region (3) and the vertical channel (4). The same impurities are doped into source and drain channels of the transistor, so that heat budget is greatly reduced, the impurity diffusion and abrupt junction forming problems are eliminated, process requirements are simplified, integration machining photo-etching ultimate limit is broken through by utilizing the vertical channel and a surrounding gate structure, and the integration degree is improved.

The invention discloses an oblique incidence fluctuation analysis method for seismic waves of a horizontal layered site, and the method comprises the following steps: (1), solving a one-dimensional time domain free field of the layered site when the seismic waves are obliquely incident, considering the nonlinear characteristics of a soil body when solving the free field, and considering the soil body as a viscoelastic material; (2), carrying out the artificial boundary transformation of the free field, and considering the initial stress of the soil body during the artificial boundary transformation; (3), determining an equivalent load of the artificial boundary through a geotechnical analysis model based on an OpenSees calculation platform; (4), applying an equivalent load to the artificial boundary, and carrying out the nonlinear fluctuation analysis. The method provided by the invention enables the soil body to be taken as the viscoelastic material, gives consideration to the nonlinearity and hysteretic characteristics of the soil body under the dynamic action, is high in precision, and is high in calculation efficiency.

The invention discloses a microphone testing method and testing system. The method comprises the following steps: selecting a microphone with known free field performance as a reference microphone; arranging a sounding source, a to-be-tested microphone and the reference microphone in a silencing box, wherein the sounding source is arranged at a central position of the silencing box, a plane where the center of the sounding source is positioned is used as a symmetric plane, and the to-be-tested microphone and the reference microphone are symmetrically arranged on the upper side of the sounding source, so input sound signals of the to-be-tested microphone and the reference microphone are the same; subtracting a test signal obtained by testing of the reference microphone from a test signal obtained by testing of the to-be-tested microphone to obtain a free field test signal of the to-be-tested microphone. The microphone testing method can guarantee the accuracy of the test result of the to-be-tested microphone, the precision requirement on the sounding source for testing is reduced, the size of the silencing box for testing is not required to be over large, and the scheme is easy to realize and low in cost.

The present invention discloses a free field restoration method of an unstable state planar sound source. Time-domain sound pressure signals on two measurement planes are subjected to two-dimensional space Fourier transform to obtain sound pressure time-domain wave number spectrums at each wave number on corresponding planes; the two sound pressure time-domain wave number spectrums on the measurement planes and a time-domain pulse response function between known sound pressures are employed to separate from an unstable state outward sound field and an unstable state inward sound field; a target sound source surface reflection coefficient is taken as a boundary condition to establish a relation of the unstable state inward sound field and a scattering sound field and calculate an unstable state scattering sound field; and the unstable state scattering sound field is removed from the separated unstable state outward sound field, and the time-domain sound pressure signals radiated on the measurement planes in the target sound source free field condition is restored. The free field restoration method of the unstable state planar sound source eliminates the unstable scattering sound on the time domain and restores the time-domain sound pressure radiated on the measurement planes in the target sound source free field condition so as to provide a pre-processing means for accurate analysis of the time variation radiation features and vibration features of the target sound source in the real sound field environment.

The present invention belongs to the field of underwater acoustic vector array calibration, and more particularly relates to a bounded space correction method for the low-frequency directional multi-polar vector array for the calibration of the super-directional multi-polar vector array within the low-frequency ranging from 20 to 1000 hz. The method comprises the following steps: establishing a super-directional multi-polar vector array including 0 to 4 matrixes; producing by a modulating signal generator a CW pulse signal to be loaded by a power amplifier into a sound source to form a testing sound field; rotating super-directional multi-polar vector array for 0 to 360 degrees; and collecting and storing the receiving signals of the 0 to 4 elements with each array element consisting of a sound pressure signal and two channels of vibration velocity communication signals, etc. The method of the invention overcomes the problem that currently, the calibration of a small-scale array needs a large-scale free field space and provides a calibration method for bounded water areas. The method has strong operability, is convenient and practical to use and can be widely used in the calibration of low-frequency super-directional vector array, making it widely used in various fields of low-frequency water sound metering.

The invention relates to an accelerated processing method of a large field of view intelligent video monitoring system, and belongs to the fields of computer image processing technology and photoelectric detection technology. This method uses a large field of view imaging device to collect images; uses a transmission cable to input the images into a computer in real time; performs image processing in the computer, and sends an alarm if it meets the detection requirements of the monitoring system. This method is the first to propose a distortion-free fast projection method for local viewing angles in a large field of view. Break the conventional practice of the existing intelligent video surveillance system to complete the distortion correction of the global image first, and then perform operations such as moving target detection and recognition; first complete the detection of moving targets in the global large field of view, and then only perform local Distortion correction and recognition are performed on the small viewing angle image, which reduces the amount of calculation data and reduces the time cost of image processing. On the premise of ensuring accurate recognition, it meets the requirements of real-time online processing of the monitoring system.

The invention discloses a method for calculating a complex structure radiation sound field in a marine acoustic channel, and belongs to the technical field of acoustic numerical calculation. The limitation that a traditional boundary element method is only suitable for free field sound field calculation is broken through, and a sound field Green function in an ocean sound channel is established. Ahierarchical matrix compression technology is adopted to divide a radiation impedance matrix into a series of hierarchical matrix blocks with different sizes, and an iteration method is further utilized to solve a matrix equation. Compared with the prior art, the method has the effects and benefits that the acoustic calculation function of the traditional boundary element method is expanded frominfinite uniform media to the bounded space of the ocean channel, and the influence of sea surface, seabed boundary and sound velocity gradient distribution can be considered. And on the other hand, the radiation impedance matrix is subjected to hierarchical compression, the consumption of a computer memory is greatly reduced by utilizing the low-rank characteristic approximate decomposition of the matrix block, the influence of the diversity of a sound field Green function under the complex marine channel condition is avoided, and the algorithm adaptability is good.

The present invention discloses a broadband calibration method for sensitivity free field of a hydrophone based on pink noise. The calibration method relates to the field of free-field underwater acoustic measurement and is mainly used for broadband measurement of hydrophone free field sensitivity. According to the method of the invention, a signal source is controlled to transmit a broadband pinknoise signal; a transmitted current signal and a received voltage signal are subjected to synchronous treatment such as interception and zero padding and FFT transformation; finally a transfer function in the frequency domain is obtained. By analyzing the direct wave and reflected wave of a tank, the transfer function is subjected to moving average with a rectangular window; the reverberation influence of the reflected wave of the tank is eliminated; a broadband transfer function of the free field between a transmitting transducer and the hydrophone is obtained; and the broadband measurementfor hydroacoustic parameters such as hydrophone sensitivity is realized. The method can be used for broadband calibration of the hydrophone in an anechoic tank, a reverberant tank, an outfield lake and sea.

The invention discloses an experimental and numerical combined method for high pressure pulsating bubble movement and load in water. The method comprises the following steps of: (1), using the Rayleigh-Plesset spherical bubble theory to calibrate the free-field high-pressure pulsating bubble experiment method, and determining a bubble initial condition; (2), using the calibrated bubble experimentmethod to carry out bubble dynamics experiments under different boundary conditions; (3), using a boundary element method to calculate dynamic characteristics of aspherical bubbles on the basis of theobtained experimental result; (4), adopting an auxiliary function method to calculate the velocity field and the pressure field around the bubbles; and (5), performing post-processing on the calculation result. The invention is suitable for studying the motion and load characteristics of the bubbles near a structure and a free surface in the gravity field, has the calculation accuracy and efficiency meeting the engineering needs, and has wide application prospect in the fields of underwater explosion, cavitation, medicine, cleaning, the chemical industry and the like.

A method, for examining an object using an X-ray recording system, includes aligning the object in the X-ray beam and the X-ray recording system with one another such that regions in the X-ray beam are uncovered for measurement of a free field. During an X-ray image recording, the components are moved relative to one another with a lateral displacement. In a position of the relative lateral displacement of the components, a reference image containing free fields is recorded. The X-ray image recording is generated from partial images during the displacement and the position of the second component relative to the first component is determined for each partial recording such that the displacement distances of the displacements and the reference phases are calculated from a selected set of pixels and the measured intensity values thereof. Finally, the image information is determined from the partial images, the displacements and the reference phases.

The invention relates to a coaxial four-reflecting optical system which comprises a main mirror (2), a secondary mirror (3), a third mirror (4) and a fourth mirror (5). The main mirror (2) and the third mirror (4) are arranged on the same side, and the secondary mirror (3) and the fourth mirror (5) are arranged at the other side corresponding to the main mirror (2) and the third mirror (4); the secondary mirror (3) is arranged on a reflected light path of the main mirror (2), the third mirror (4) is arranged on a reflected light path of the secondary mirror (3), and the fourth mirror (5) is arranged on a reflected light path of the third mirror (4). The coaxial four-reflecting optical system has large obstacle-free field of vision, is convenient to process, mount and adjust and is ideal to adjust the distortion.

Provided herein is a method and a device for creating a system layout of a photovoltaic open-space power plant, which includes power plant components, in particular solar trackers, having the following method steps: providing configuration data which specifies the photovoltaic open-space power plant and the power plant components thereof, and providing configuration rules which are preset for the photovoltaic open-space power plant, and providing configuration parameters which put the configuration rules in concrete terms; and initialising and subsequently optimising a selection of, and an allocation of location to, necessary power plant components for the system layout properties of the photovoltaic open-space power plant by the configuration data provided and the configuration rules put into concrete terms for creating the system layout of the photovoltaic open-space power plant.

The invention discloses a two-dimensional control and ultrasonic imaging monitoring method for flowing micro-bubbles in a non-free field. The two-dimensional control and ultrasonic imaging monitoring method for flowing micro-bubbles in the non-free field comprises the steps of: arranging two control ultrasonic energy converters and a pipeline in a controlled region reasonably to determine relative spatial positions of the two control ultrasonic energy converters and the pipeline; propelling a micro-bubble suspension liquid in a sound-transmitting pipe, starting up the control ultrasonic energy converters, exciting the control ultrasonic energy converters by using continuous sine electric signals, adjusting an excitation electric signal power and changing resultant force applied to a micro-bubble group in the vertical direction to control the micro-bubbles to move in the vertical direction; enabling the micro-bubbles to move in the horizontal direction by changing phase position or frequency of the excitation electric signal; placing an ultrasonic array energy converter to a position where the micro-bubble group control process can be monitored and generating a micro-bubble group wavelet conversion ultrasonic monitoring image. According to the two-dimensional control and ultrasonic imaging monitoring method for flowing micro-bubbles in the non-free field, two-dimensional control of flowing micro-bubbles in the non-free field of a single-side sound-transmitting medium under ultrasonic monitoring can be realized, and sensitivity of micro-bubble monitoring is improved.