159 results about "Dispersion curve" patented technology

This invention pertains to the extraction of the slowness dispersion characteristics of acoustic waves received by an array of two or more sensors by the application of a continuous wavelet transform on the received array waveforms (data). This produces a time-frequency map of the data for each sensor that facilitates the separation of the propagating components thereon. Two different methods are described to achieve the dispersion extraction by exploiting the time frequency localization of the propagating mode and the continuity of the dispersion curve as a function of frequency. The first method uses some features on the modulus map such as the peak to determine the time locus of the energy of each mode as a function of frequency. The second method uses a new modified Radon transform applied to the coefficients of the time frequency representation of the waveform traces received by the aforementioned sensors. Both methods are appropriate for automated extraction of the dispersion estimates from the data without the need for expert user input or supervision

A technique for processing acoustic waveforms includes: (a) transforming at least a portion of the acoustic waveforms to produce frequency-domain signals; (b) obtaining a model dispersion curve based on a borehole-formation model having a set of borehole-formation parameters; (c) adjusting phases of the frequency-domain signals according to the model dispersion curve to produce back-propagated signals; (d) computing coherence of the back-propagated signals; (e) repeating steps (b)-(d) by varying values of the set of borehole-formation parameters until the coherence reaches a selected criterion; and (f) outputting at least a portion of the set of borehole-formation parameters.

A method of determining at least one parameter of a waveguide (3) from wavefield data acquired from wave propagation in the waveguide including obtaining first and second dispersion curves (9a, 9b, 9c) in the frequency domain from the wavefield data. A frequency interval between the first dispersion curve and the second dispersion curve is found, and this is used in the determination of at least one parameter of the waveguide. The frequency separation Δƒ(V) between the first and second dispersion curves may be found at a particular value of the phase velocity V, and the thickness h of the waveguide can be found using:

Here, c₁ is the velocity of wave propagation in the waveguide. This may be found from the asymptotic velocity values of the dispersion curves.

A method and system of locating discontinuities, measuring distances, locating unknown sources, and measuring the thickness of multimode dispersive medium includes sensing a multimode dispersive acoustic guided wave and frequency decomposing that wave using spectral temporal analysis; selecting a frequency which identifies a group delay of the guided wave for each mode occurring at that frequency; selecting a mode from the group delays of the selected mode, determining the group velocity from the dispersion curves and computing the desired parameter.

A transmission line microwave apparatus includes at least one nonreciprocal transmission line part, which includes a series branch circuit equivalently including a capacitive element and a shunt branch circuit equivalently including an inductive element. The nonreciprocal transmission line part has gyrotropic characteristic by being magnetized in a magnetization direction different from the propagation direction of a microwave, and has an asymmetric structure to a plane formed by the propagation direction and the magnetization direction. The nonreciprocal transmission line part has a propagation constant and an operating frequency set in a dispersion curve that represents a relation between the propagation constant and the operating frequency so that the propagation constant in the forward direction and the propagation constant in the backward direction have nonreciprocal phase characteristics different from each other. A microwave transmission line is constituted by cascade-connecting at least one non-reciprocal transmission line part between first and second ports.

The invention relates to an inversion method of stratum shear wave velocity radial sections. The inversion method includes: performing acoustic logging while drilling and while drilling stratum density and well diameter logging in a depth interval, and obtaining while drilling monopole and quadrupole array acoustic full wave train data, a while drilling stratum density logging curve and a while drilling well diameter logging curve; obtaining stratum longitudinal wave velocity and shear wave velocity at the position of processing depth through calculation, and extracting phase velocity frequency dispersion data of while drilling quadrupole wave; calculating a theoretical while drilling quadrupole wave frequency dispersion curve at the position of the processing depth; constructing an inversion objective function in a combined mode; outputting equivalent alteration velocity and thickness; calculating continuously variable stratum shear wave velocity radial sections; and repeating the steps until processing of the whole depth interval is finished, and obtaining the stratum shear wave velocity radial sections changing continuously along with logging depth. The inversion method of stratum shear wave velocity radial sections has the advantages of obtaining changes of mechanics/acoustic parameters nearby a well in real time, solving the problem of ununiqueness of inversion, and improving reliability of inversion results.

The invention is used in the field of oil field logging technology, mainly resolving the defect of existent earth stress detection technology which has not any one non-destructive examination method. Said invention is characterized by that it includes the following steps: making cross dipole array acoustic log data undergo the process of angle rotation treatment, then obtaining two main time sequences, on said basis extracting flexural wave dispersion curves of two principal directions, utilizing data of n frequency points on the flexural wave dispersion curves of two principal polarization directions to create n equalities according to two formulae, in which said formulae can be obtained by inversion of well mode wave acoustic elastic equation, in which n is greater than or equal to 6, and atilizing resolution of sain n equalities so as to can obtain maximum main stress SH and minimum main stress Sh of formation.

A formation logging tool having a substantially continuous central mandrel with regularly spaced mass blocks disposed thereon, at least some of the mass blocks carrying sensors such as receivers. By adopting this structure, the tool can be made to behave as a mass-spring structure and its flexural and extensional behaviour controlled such that its dispersion curve does not extend into the dispersion curve of the formation to be logged. The structure can be applied to the whole of the logging tool or just to the receiver section and/or any spacer section between the receiver and the transmitter section.

Slowness dispersion characteristics of multiple possibly interfering signals in broadband acoustic waves as received by an array of two or more sensors are extracted without using a physical model. The problem of dispersion extraction is mapped to the problem of reconstructing signals having a sparse representation in an appropriately chosen over-complete dictionary of basis elements. A sparsity penalized signal reconstruction algorithm is described where the sparsity constraints are implemented by imposing a l₁ norm type penalty. The candidate modes that are extracted are consolidated by means of a clustering algorithm to extract phase and group slowness estimates at a number of frequencies which are then used to reconstruct the desired dispersion curves. These estimates can be further refined by building time domain propagators when signals are known to be time compact, such as by using the continuous wavelet transform.

The invention relates to a non-destructive detection method of an underground unfavorable geological body based on microtremor dispersion curves and H/V curves and an application thereof. The detection method comprises the steps of (1) collecting surface micro-vibration signals of a plurality of measuring points, (2) calculating Rayleigh surface wave phase velocity dispersion curves in a micro-motion array, an H/V curve of each measuring point of a detector in the array and an array geometric mean H/V curve, (3) allowing each curve to form a contour map, and (4) inferring an anomalous geological body according to anomaly characteristics in the contour maps. The method is used for detecting longitudinal and lateral heterogeneous geological bodies within a depth range of 100 meters in a shallow ground surface in urban engineering construction. The probability of revealing lone stones and karst in the detection of the unfavorable geological bodies in subway shield construction is improved, and a safety area of shield tunneling construction is rationally divided. The detection method and the application have the advantages of convenient on-site collection, high detection precision, strong resolution, the shortening of a survey period, the reduction of engineering cost and the reduction of exploration risks.

A method for detecting isotropic material surface Young modulus by using surface acoustic wave technology. The method is as below: exciting broadband surface acoustic wave in an isotropic specimen surface to obtain a dispersion curve on a surface acoustic wave propagation direction; fitting the actual phase velocity data to obtain a closest truth-value phase velocity and a phase velocity fluctuation section; establishing a Cartesian coordinate geometry model to obtain a surface wave basic propagation equation containing unknown medium Young modulus, Poisson ratio, direction cosine of the propagation direction, amplitude attenuation coefficient given according to experience value, wave number and wave velocity; calculating assumption corresponding relation between wave velocity and wave number in the Cartesian coordinate geometry model and simultaneous theoretical relationship, to obtain mutual relationship of velocity, frequency and Young modulus under ideal conditions; and conducting reverse calculation to obtain the Young modulus in medium according to the mutual relationship of velocity, frequency and Young modulus under ideal conditions and the dispersion curve under actual conditions. The invention realizes effective measurement of isotropic material surface young modulus.

The invention relates to a global optimization method for surface wave dispersion and body wave spectral ratio joint inversion shallow velocity. The method comprises the following steps that (1), initial parameters of the inversion are given to construct an unknown vector population represented by binary coding; (2), theoretical calculation methods of a surface wave dispersion curve and a body wave HVSR curve are determined; (3), an object function simultaneously fitting the surface wave dispersion curve and the body wave HVSR curve is established; (4), global optimization calculation of genetic simulated annealing is conducted to obtain a globally optimal solution; and (5), the shallow velocity structure can be obtained based on the globally optimal solution. Advantages of genetic and simulated annealing methods are combined, efficiency and accuracy of the inversion can be improved, application in urban areas with the survey lines being difficult to unfold can be achieved, and application in background noise, seismic measuring or strong earthquake records and other data sources can be achieved.

The invention belongs to the technical field of material property detection, and relates to a bidirectional detection method of a Young modulus and a Poisson constant by an ultrasonic surface wave, which is used for detecting a layering thin film material formed on a silicon substrate by isotropic thin film deposition. The detection method comprises the following steps: exciting the wideband ultrasonic surface wave on the surface of a layering thin film material sample sheet by a short-pulse laser; respectively acquiring a surface wave signal in a Si[110] direction and a Si[100] direction of the surface of the sample sheet by a piezoelectric detector to obtain a dispersion curve of the ultrasonic surface wave spreading on the layering thin film material in the directions; and setting a plurality of the Young modulus and the Poisson constants to calculate a plurality of different theoretical dispersion curves, and then fitting an experimental dispersion curve obtained by a test with the theoretical dispersion curves to obtain the theoretical dispersion curve which is closest to the experimental dispersion curve so as to determine the Young modulus and the Poisson constant of the thin film material. The detection method of the invention has the characteristics of fastness, accuracy, nondestructive monitoring and the like.

The invention relates to a circular-waveguide slow-wave structure for angularly loading spiral lines, which belongs to the technical field of vacuum electrons and comprises a circular waveguide, N identical spiral lines and two circular-ring medium sheets, wherein the radius of the circular waveguide is R1, the outer radii of the two circular-ring medium sheets are R1, and the inner radii of the two circular-ring medium sheets are R5; the two circular-ring medium sheets are respectively fixed on the two end surfaces of the circular waveguide, and the N identical spiral lines are all connected between the two circular-ring medium sheets, so that the N identical spiral lines are angularly and uniformly distributed inside the circular waveguide; and the hollow parts of the two circular-ring medium sheets and a space part surrounded by all the spiral lines together form an electron-beam passage. The circular-waveguide slow-wave structure can work at short millimeter-wave and terahertz-wave bands, the coupling impedance can be effectively improved, and a dispersion curve is more flat, so that a traveling-wave tube adopting the novel slow-wave structure has higher gain and interaction efficiency, and the larger output power is obtained; and in addition, the phase velocity can be greatly decreased in the invention, accordingly a lower working voltage can be adopted, and the circular-waveguide slow-wave structure is favorable to the miniaturization of devices.

The invention belongs to the field of applied geophysical well logging and particularly relates to a method for extracting sleeve wave attenuation rate through dispersion correction. The method includes the following steps: 1 calculating a sleeve wave theory dispersion curve; 2 conducting sector cement bond well logging on measuring points and obtaining waveform data corresponding to each sector; 3 conducting dispersion correction on the waveform data transmitted and received by sound wave; 4 extracting waveform attenuation rate after dispersion correction; and 5 repeating step 2, step 3 and step 4 and obtaining attenuation rate of each sector of the measuring points. The method has the advantage of being capable of eliminating effects of dispersion effect in a sleeve on waveform amplitude, obtaining real attenuation rate corresponding to a gluing condition of the sleeve and the cement sheath and greatly reducing attenuation rate calculation errors.

The invention provides a composite waveguiding structure broadband unidirectional silencer. A cuboid wave guide is formed by upper and lower walls, and front and back walls; the upper and lower walls are of a rectangular concave-convex structure with a fixed cycle; the front and back walls are flat; the size of each concave-convex structure at the left and right sides of the upper and lower walls is given by a dispersion curve; the waveguides with different functions at the left and right sides of the waveguide are named as the wave guide 1 and the wave guide 2; the concave-convex structure of the upper and lower walls can be produced on the selected flat material by a digital controlled lathe according to the size; the concave-convex structure of the waveguide 2 is to be carved when the cycle of the waveguide 1 is carved; the combination of the two waveguides can realize unidirectional conduction of the sound wave; and when incidence of the sound wave occurs, the waveguide 2 generates a frequency domain band gap for Bragg resonance of fundamental modes, the interaction among horizontal standing wave modes occurs in the waveguide 1, a single higher-order mode is generated and will not be influenced by the band gap generated by the waveguide 2, and the higher-order mode can be penetrated. The composite waveguiding structure broadband unidirectional silencer of the invention has the advantages of being high in noise abatement rate, being simple in structure, being high in adaptability, being lower in cost, and being easy to realize.

The invention relates to a dispersion curve extracting method for a mine channel wave double-component seismic signal. The dispersion curve extracting method comprises the steps of firstly acquiring a Love channel wave signal from the mine channel wave double-component seismic signal; performing generalized S transformation on the acquired Love channel groove signal for obtaining a relationship diaphragm between group speed and frequency of the Love channel wave; drawing a line between maximal vibration amplitudes in the relationship diaphragm between the group speed and the frequency, and utilizing the obtained curve as the dispersion curve. According to the dispersion curve extracting method, the width of a Gauss window in S transformation is changed by means of a linearly changed adjusting parameter, thereby improving precision of a channel wave signal dispersion curve. Furthermore, according to the method, before generalized S transformation, propagation direction and polarization angle of the seismic wave are determined through calculation according to an energy distribution criterion of a longitudinal wave in the acquired signal in a double-component detector. Coordinate rotation is performed for obtaining the Love channel wave signal which horizontally vibrates in the propagation direction of the vertical wave. Then dispersion calculation is performed on the signal. The dispersion characteristic of the obtained dispersion curve is more accurate.

The invention relates to a method for detecting the thickness of industrial boiler scale by utilizing an SH (Shear) wave which is sensitive to an attachment on the surface of a plate layer, belonging to the field of nondestructive inspection of ultrasonic guided waves. In the method, firstly, a dispersion curve with different scale thicknesses is drawn by utilizing a dispersion equation for SH wave propagation in a double-layer structure to obtain a variation curve of SH0 modal group velocity changing along with the increase of the thickness of the scale, and then a high detection frequency and a low detection frequency respectively corresponding to thinner scales and thicker scales are further obtained. A detection system is shown as the drawing and comprises a function generator (1), a power amplifier (2), a change-over switch (3), an EMAT (Electromagnetic-Acoustic Transducer) sensor (4), an oscillometer (5) and a computer (6). The group velocity of an SH0 modal in a structure formed by a boiler and scales can be measured by the system, and the thickness of the scale can be obtained according to the corresponding curve of the group velocity and the scale thickness by the calculation, thereby the online and nondestructive testing on the thickness of the industrial boiler scale is realized.

A pipe flaw guided circumferential wave nondestructive testing method based on transverse-wave straight probes comprises the following steps: building transverse-wave straight probes in a pipe to excite a guided circumferential wave flaw detector; apply numerical calculation software to drawing guided circumferential wave dispersion curves of the pipe; selecting an excitation frequency suitable for pipe flaw nondestructive detection; drawing wave structure charts of all guided circumferential wave modes under the frequency to determine excitation methods of the corresponding guided circumferential wave modes and the relationships between the arrangement directions of the transverse-wave straight probes and guided circumferential wave excitation typical modes; and exciting guided circumferential waves, receiving flaw echoes of the guided circumferential waves, and determining the pipe flaw positions by analyzing the time at which reflection echoes in received signals reach a receiving point.