126 results about "Bessel function" patented technology

The invention discloses a method for extracting a Rayleigh surface wave frequency dispersion curve. The method comprises the following steps: a, performing Fourier transform on noise cross-correlation signals recorded by a seismometer pair which are spaced by R to obtain a frequency spectrum W(f); b, performing Gauss narrow-band filtering on the obtained frequency spectrum to obtain WG(f); c, extracting a real part curve of the WG(f), finding out null points of the real part curve, and recording fn as the frequency of the nth null point; d, finding out a root of a first-class zero Bessel function as Zn; e, solving a Rayleigh surface wave phase velocity value V(f) being equal to 2pifnR / Zn at a single frequency point according to the relation between a real part curve of a cross-correlation spectrum and the first-class zero Bessel function; f, connecting and drawing the solved phase velocities of single frequency points into a smooth curve as a frequency dispersion curve of Rayleigh surface waves. By using the relation between the Bessel function and the cross-correlation spectrum, the calculation efficiency of the frequency dispersion curve is effectively improved.

In an array speaker system that performs multi-channel reproduction using an array speaker constituted by arraying a plurality of speaker units in a matrix manner, a left channel signal, a right channel signal, and a center channel signal, all of which instruct reproduction of sound at a front side of a listener, are subjected to weighting using weight coefficients based on a Bessel function so as to drive the speaker units, thus realizing spherical sound emission characteristics. In addition, a surround left channel signal and a surround right channel signal, both of which instruct reproduction of sound at a rear side of the listener, are subjected to beam processing, whereby sound is reflected on a sound reflection position such as a wall surface or a ceiling and is then emitted in the form of a sound beam reaching the rear side of the listener.

The invention provides an unmanned aerial vehicle (UAV) trajectory smoothing method based on Bessel curve transition, comprising the following steps: constructing a Bessel transition function according to known linear route segments, and quickly establishing flight trajectory geometrical characteristics satisfying curvature continuity; with the length of the linear route segments and the allowed maximum trajectory smoothing error as constraints, establishing and solving an optimization problem of the smoothing transition length of each Bessel curve; determining maximum speed, acceleration and jerk constraints, and determining the maximum flight speed of transition segments based on the nature of the Bessel function; performing S-shaped motion planning for all linear segments, and determining the acceleration and deceleration time of each linear segment; iteratively searching and planning the flight speed of each segment to ensure the kinematic compatibility; and performing real-time interpolation to complete flight path generation. The flight performance of UAV can be improved greatly under the premise of guaranteeing the calculation efficiency.

A harmonic generation / beam shaping system to generate a shaped beam having a harmonic relationship with a beam generated by a laser, including a first harmonic generation element and a second harmonic generation element arranged sequentially along an axial beam path extending between an input from the laser and an output of the harmonic generation / beam shaping system and at least two beam shaping elements located along the axial beam path. At least one of the least two beam shaping elements is located between the second harmonic generation element and the laser to transform the beam energy profile into a preferred profile to distribute the beam energy across a larger cross sectional area of at least one harmonic generation element or to reduce peaks in the energy distribution profile of the beam, or both, wherein the preferred profile may be a flat-top profile or a Bessel function profile.

The invention discloses an array sparse method for a broadband non-frequency-variable multi-beam imaging sonar. With the Bessel function, fitting of influences on array guiding vectors by different frequency points in the broadband signal bandwidth is performed and a broadband signal multi-beam forming model under the far-field situation is established; on the premise that the formed multiple beams approximate a reference beam, a minimum number of effective array elements are searched and multiple sets of weighting coefficients are calculated; a highly nonlinear sparse array optimization problem is transformed into a sparse signal reconstruction problem in the compressed sensing theory, a reconstruction weighting coefficient is calculated iteratively by an underdetermined system localizedsolution algorithm, and a sparse array structure is determined; a convex optimization theory is introduced so as to form a plurality of low-side-lobe beams and a multi-beam array sparse side-lobe suppression model for array element excitation is established. According to the invention, the main lobes of a plurality of formed beams are not extended with changes of signal operating frequencies; andpeak side-lobe levels of multiple beams formed by the sparse array are reduced effectively.

Systems and methods for optimizing input beam modulation for high gyro sensitivity and low bias errors. The present invention is a resonator optical gyroscope having an optimized phase-modulation amplitude (frequency) for a selected modulation frequency (amplitude) that maximizes the gyro signal-to-noise (S / N) sensitivity. For selected values of the phase modulation amplitude, the polarization cross-coupling induced intensity modulation can be nulled. By setting the phase modulation amplitudes substantially close to these nulling points (e.g. M=3.832 or 7.016 radians, which causes the first order Bessel function to be zero J1(M)=0) and then optimizing the modulation frequency, the intensity modulation induced bias is reduced to zero and gyro S / N sensitivity is maximized.

The invention discloses an improved modulation and demodulation detection method of a phase generated carrier (PGC). The method comprises: after an output signal of an optic fiber hydrophone is processed by mixing and low-pass filtering, mathematical calculation is carried out to obtain a proportional relation J1(C) / J2(C) between a first type of first-order Bessel function J1(C) and a second-orderBessel function J2(C) of a modulation depth C; on the basis of the proportional relation, normalization calculation is carried out on the signal after low-pass filtering of the optic fibre hydrophoneto obtain two paths of signals with the alternating-current item B and modulation depth C eliminated; the two paths of signals are processed by differential processing, cross multiplication, integration, and high-pass filtering respectively to obtain an external acoustic signal needing detection. According to the invention, the detection method has the following advantages: while hardware equipment is not changed, the detection error, caused by drifts of an output signal alternating-current item B and the modulation depth C introduced by the externally loading carrier, of an external acousticsignal is modified by a digital way; and the stability of signal detection by the optic fiber hydrophone is improved.

A radial slot antenna (1; 60) comprising a radial waveguide, which includes an upper plate (5), having a centroid (O) and an edge region (14) and provided with a plurality of radiating apertures (4), formed as slots in the upper plate (5), which develop according to an ideal annular pattern (16) around the centroid (O). The radiating apertures (4) are arranged in such a way as to form at least one first radiating region (31a) and one second radiating region (31b), which are distinct and radially separated by a dwell region (33a) without radiating apertures and wherein, in the first and second radiating regions (31a, 31b), radially adjacent radiating apertures (4) are separated from one another by a respective mutual radial distance, the dwell region (33a) having a radial width (δ) greater than the mutual radial distances of the radiating apertures (4) in the first and second radiating regions (31a, 31b). The slot antenna further comprises a signal feeder (10) operable for supplying am electromagnetic field (Ψ0, Ψ1) so as to assume, in the first and second radiating regions, opposite phases, in such a way that the electromagnetic field emitted by the slot antenna can be expressed via Bessel functions.

There is disclosed a resolution conversion apparatus for converting an original digital image into a digital image having a different number of pixels in accordance with an instructed conversion magnification factor. In the apparatus, a determination circuit determines the number of pixels to be interpolated in each block of the original image and positions where they are interpolated in accordance with the conversion magnification factor. The block includes a predetermined number of pixels of the original image. A converted image generation circuit generates pixel data for the interpolation pixels at the positions where they are interpolated in accordance with a predetermined interpolation equation whose coefficients are determined with the positions and data values of the pixels in the block, and combines the pixel data for the digital original image and the generated pixel data to output a converted digital image. The interpolation equation includes spline functions and Bezier functions.

A piezoelectric blower includes a valve, a housing, a vibrating plate, and a piezoelectric element. The vibrating plate forms, together with the housing, a column-shaped blower chamber such that the blower chamber is interposed therebetween in a thickness direction of the vibrating plate. The vibrating plate and the housing are formed such that the blower chamber has a radius (a). The piezoelectric element causes the vibrating plate to undergo concentric bending vibration at a resonance frequency (f). The radius (a) of the blower chamber and the resonance frequency (f) of the vibrating plate satisfy a relationship of 0.8×(k0c) / (2π)≤af≤1.2×(k0c) / (2π), where an acoustic velocity of gas that passes through the blower chamber is (c) and a value that satisfies a relationship of a Bessel function of a first kind of J0(k0)=0 is k0.

A method for modeling complex shapes from volumetric data utilizing spherical wave decomposition (SWD) combines angular-only basis functions of the SPHARM with spherical Bessel functions as the radial basis functions to form the complete 3D basis. The 3D basis is then used to expand the volumetric data. The resulting 3D volume representation allows images to be generated of both surface and internal structures of the target object.

The invention provides a Bessel function based sparse concentric ring array design method. The method includes: taking a ring radius of a sparse concentric ring array as an optimized parameter, and generating a plurality of weed individuals randomly to form an initial group; as for every weed individual, determining a minimum number of array elements on a ring according to the ring radius so as to determine peak sidelobe level of the sparse concentric ring array as a weed individual adaptation value; generating a seed for every weed individual; combining filial individuals formed by optimized variable ring radiuses with parent individuals together to form new groups, sequencing all the individuals in the group according to an increasing sequence of the adaption values, only keeping a specific number of individuals as an initial group for next evolution and weeding out the rest individuals; repeating the process until stopping criterion for iteration is satisfied, and outputting an optimal individual in the ultimate group.

The present invention includes a device and method to create a light beam having substantially uniform far-field intensity. Light from a laser source is directed to at least one multimode optical fiber configured produce an intensity profile approximated by a Bessel function.

The invention relates to the field of voice signal processing, and discloses a noise suppression method and system. According to the noise suppression method, the prior signal to noise ratio and the posterior signal to noise ratio of a noisy voice signal are calculated, the estimated value of a clean voice signal in the short-term spectrum amplitude is calculated according to a maximum posterior MAP standard, the ratio of the estimated value and the noisy voice signal is calculated, an attenuation factor is obtained, and then inverse fast Fourier transform IFFT treatment is conducted on the noisy voice signal according to the attenuation factor obtained through calculation, so that calculated amount is greatly reduced during noise suppression. The noise suppression method and system is more suitable for practical application, and performance is also improved. Furthermore, when the attenuation factor is calculated, the calculation of the ratio of the first order and zero order of a first kind of the modified Bessel function is involved, and at the moment, the ratio is obtained through the table look-up method so that storage space can be further reduced; or the approximate calculation method is adopted, no storage table is required, and calculation is more simplified.

A piezoelectric blower includes a valve, a housing, a vibrating plate, and a piezoelectric element. The vibrating plate forms, together with the housing, a column-shaped blower chamber such that the blower chamber is interposed therebetween in a thickness direction of the vibrating plate. The vibrating plate and the housing are formed such that the blower chamber has a radius (a). The piezoelectric element causes the vibrating plate to undergo concentric bending vibration at a resonance frequency (f). The radius (a) of the blower chamber and the resonance frequency (f) of the vibrating plate satisfy a relationship of 0.8×(k0c) / (2π)≦af≦1.2×(k0c) / (2π), where an acoustic velocity of gas that passes through the blower chamber is (c) and a value that satisfies a relationship of a Bessel function of a first kind of J0(k0)=0 is k0.

Embodiments of the present invention provide a method for non-contact detection techniques of mechanical vibrations utilizing a radio frequency system incorporating multiple carrier wavelengths. The new detection method measures multiple harmonic pairs at a carrier frequency and improves the detection accuracy and reliability by first inspecting the Bessel function coefficient of each harmonic and then determining the harmonic amplitude. The original mechanical vibration can then be reconstructed. Embodiments can be used to realize sensing of complex non-sinusoidal vibrations using a wavelength division sensing technique and allow non-contact detection through walls, smoke, fog or other low visibility environments with the advantage of longer range detection and easy integration at a low cost.

Path imbalance measurement of the two arms fiber optic interferometer includes employing a current carrier signal to modulate the semiconductor laser light source of the interferometer to let it output interference signals to generate a carrier phase signal through path imbalance of the interferometer. Then, the interference signals are expanded to be the harmonic components of carrier phase signal frequency by Bessel function. Subsequently, we use the specific relation between the second and the fourth harmonic components of the interference signals to develop the theory of path imbalance measurement. The method mentioned above can measure a few decimeters of path imbalance and its accuracy can reach to a millimeter.

The invention discloses a method for designing array antennae distributed in a circular aperture field based on Bessel function. The method comprises the following steps of: distributing antenna arrays on a circular aperture; distributing aperture fields on a concentric circle array which consists of two or more concentric circular rings; arranging at least three antenna units which are uniformly distributed in central symmetry on each concentric circular ring; regulating distribution of the aperture fields by using a parameter weighting method based on the Bessel function, and thus obtaining continuously-distributed aperture fields in which different types of wave beams are formed; and computing the radius and excitation of each concentric circular ring in the concentric circle array which corresponds to different types of wave beams by using a discrete method. The invention has the advantages that complicated and unordered multidimensional optimization process is eliminated, a determined and quick implementation method for array antenna layout and excitation parameters is provided, the method can be widely applied to analysis and design of the antenna arrays for phased array radars and navigation satellites, and quick forming of the wave beams in different occasions is realized.

The invention discloses a sound source positioning method suitable for a hollow spherical array. The method combines the advantages of the hollow spherical array and maximum likelihood estimation and accurately positions a spatial sound source direction by using a maximum likelihood estimation strategy while not influencing a spatial sound field. The sound source positioning method has advantages of (1) reducing computation complexity by converting a signal received by a microphone into a spherical harmonic domain; (2) obtaining high spatial resolution and positioning accuracy by using the maximum likelihood estimation strategy; (3) avoiding division of a spherical Bessel function and solving the poor robustness of the hollow spherical array at a zero-point-corresponding frequency of the spherical Bessel function; (4) achieving direct expansion to a broadband, reducing the expansion complexity of a spherical array broadband positioning algorithm, and being suitable for a reverberant sound field, and (5) being suitable for rigid spherical arrays and spherical arrays using directional microphones, besides the hollow spherical arrays.

A method and a system for measuring the velocity of a vessel relative to the bottom using a velocity measuring correlation sonar are disclosed. The present invention provides a new theoretical expression for the bottom medium sonar array temporal and spatial correlation function. The velocity of the vessel relative to the bottom is derived by fitting experimental data to a theoretical function. The bottom medium sonar array temporal and spatial correlation function of the present invention is succinctly expressed in zero-rank Bessel function, and well coincided with experiments. The function is applicable not only to far field region, i.e. planar wave region, but also to Fraunhofer region, i.e. spherical wave region. Transmit transducers and receive transducers are multistatic in the velocity measuring correlation sonar of the present invention, so the transmit beam width and the receive beam width can be selected reasonably. The present invention is applicable to measuring the velocity of the vessel relative to the bottom with high measurement accuracy, small calculation load, good robustness and fast convergence.

The disclosure relates to a method and device for determining frequency shift and Doppler spread in a high-speed mobile scenario; the method comprises: acquiring effective paths according to channel impulse response, acquiring effective path related value of each effective path, and acquiring frequency shift estimation of each effective path according to the phase of the corresponding effective path related value; calculating combined weight according the powers of the effective paths, weighting and combining the frequency shift estimations of the effective paths through the combined weight so as to obtain weighted average frequency shift estimation; acquiring root-mean-square frequency shift spread as Doppler spread estimation according to the frequency shift estimations of the effective paths, the weighted average frequency shift estimation and the combined weight. The problem can be solved that a conventional method is unavailable in the high-speed mobile scenario when multi-path line-of-sight components are great and bear different frequency shifts; the frequency shifts can be estimated effectively; the problem can also be solved that a uniform scattering model is inconsistent and Bessel function is unsuitable in conventional Doppler estimation methods; Doppler spread in the high-speed mobile scenario can be acquired.

The invention discloses a method for designing a wind turbine airfoil by using a Bessel function curve. According to the method, the third-order Bessel function is adopted and can represent a section of curve through four control points only, and in addition, the starting point and the end point are fixed, so that only two control points are required to be changed for a section of the curve; each of an upper wing surface and a lower wing surface of the airfoil is represented by a section of curve, the starting points and the end points of the upper wing surface and the lower wing surface respectively coincide, and then the staring points and the end points are in smooth connection. According to the invention, the airfoil profile can be controlled more conveniently and effectively by using several points in space, so that optimization design time of the airfoil is shortened, and airfoil design efficiency is improved; the designed airfoil has an extremely high lift coefficient, so that chord length of a blade is reduced, and the material required by the blade is reduced; a higher lift-drag ratio is realized, so that the wind-power utilization coefficient is increased; the method can be popularized to design of wind turbine airfoils of different thicknesses, plane airfoils, turbine blade profiles and other complex curves and has a high social value and a good economic benefit.

The invention discloses a volume modeling method for coal bed underground combustion space areas. The volume modeling method includes: deducing temperature field control equation under the action of seepage by analyzing affection mechanisms from the seepage to the temperature fields on the basis of high temperature of the coal bed underground space areas and relative constant temperature of normal underground temperature fields according to the thermal conduction basic theory,; introducing Bessel function to deduce peripheral temperature field distribution equation of combustion passages, introducing finite element values to solve, inverting the distribution of the temperature fields under the action of seepage through finite element value software by the aid of field temperature detection data, and determining high-temperature affection boundary of the combustion passages; acquiring the coal bed temperature distribution matched with the field detection best by adjusting section size of the combustion space areas, inverting the shape and the size of the coal bed underground combustion space areas, and computing approximate volume of the combustion space areas. The volume modeling method for the coal bed underground combustion space areas is capable of determining the shape and the size of the coal bed underground combustion passages more accurately, and thermal source models of the combustion space areas of the combustion passages, which are provided by the volume modeling method, have a certain practical value when the volume modeling method is compared with other computing methods.

The invention discloses a pulse ultrasonic sound field detection device and method. The pulse ultrasonic sound field detection method comprises steps of: adjusting the distance between a photoelectric detector and a third convex lens in order that the diffracted light in each order focuses on the photoelectric detector; adjusting a light-shielding plate to shield the zero-order light and negative first-order diffracted light and to enable the positive first-order diffracted light to enter the photoelectric detector, recording the maximum value of the optical pulse amplitude as the positive first-order diffracted light intensity, wherein the ratio of the positive first-order diffracted light intensity to the total light intensity I satisfies the first specie of first-order first Bessel function; turning down the time scale of an oscilloscope, wherein the diffracted optical pulse signal includes an intensity modulation signal with a modulation frequency the same as the ultrasonic frequency; calculating the phase information according to the waveform of the modulation signal; obtaining the sound pressure and phase distribution of a ultrasonic sound field in the moving direction of a displacement platform; rotating a ultrasonic probe by a certain angle by using a stepping motor to obtain the sound pressure and phase distribution of the ultrasonic sound field in different rotation directions; and combining different angle detection data so as to obtain the sound pressure and phase distribution of the ultrasonic sound field in the plane.

The invention provides a Bessel integral adaptive segmentation method and system in rapid calculation of an integrated circuit. The method comprises the following steps: determining the order of a Bessel function used in a Holographic Green function; calculating a zero point of the Bessel function by adopting an iterative method according to the order of the Bessel function; determining the range or the number of the zero points; adaptively segmenting the mth sub-interval, calculating the accumulation of the Bessel integral after the segmentation of the mth sub-interval, and accumulating the accumulation result to the Bessel integral of the whole integral sub-interval; and if the conditions are met, calculating a union vector Green function of a field generated by the source point of the current integrated circuit at the field point. The system comprises an order determination module, a zero point determination module, an integral subinterval setting module, a subinterval segmentation module, a subinterval judgment module and a field calculation module. According to the method, unnecessary redundancy calculation in the Bessel integral adaptive segmentation method is reduced, and the Bessel integral of the whole interval is ensured to be accurate.