33 results about "Free induction decay" patented technology

The invention discloses a nuclear magnetic resonance free induction decay signal reconstruction method based on a diffusion probability model, and relates to the field of magnetic resonance spectrums.The method comprises the steps that a simulation data set is constructed based on a mathematical model of free induction decay signals, and the simulation data set is divided into a training set, a verification set and a test set; sampling each data set by adopting a Poisson gap non-uniform sampling strategy, and simulating an actual under-sampling condition; constructing a diffusion probability model, gradually adding Gaussian noise through a forward diffusion module to generate a noise-containing sample, and recovering an original signal from a noise signal through a reverse denoising module; and inputting test data into the optimal model for multiple times to obtain a plurality of reconstruction results. According to the method, the reconstruction method based on the diffusion probability model is constructed, training optimization is carried out through Poisson gap non-uniform sampling and simulation signal data sets, and high-precision reconstruction of the under-sampling nuclear magnetic resonance free induction decay signals is achieved.

The invention provides a denoising method for a magnetic resonance spectrum based on Transform, and relates to the technical field of signal processing and artificial intelligence, and the method comprises the steps: firstly obtaining a noisy free induction decay signal (FID) and a corresponding label signal, constructing a training data set, converting the signal into a frequency domain signal through fast Fourier transform, and carrying out the amplitude normalization; a real part and an imaginary part of a frequency domain signal are respectively projected to a high-dimensional feature space, and are respectively sent to a multi-head self-attention mechanism-based multi-layer Transform encoder through two channels, so as to capture the global correlation of a long sequence. And the coded output is separated and decoded, a real part and an imaginary part are recovered respectively, and a denoised complex frequency domain signal is obtained through combination. In the training process, a complex mean square error is used as a loss function, and dynamic learning rate scheduling and an early stop mechanism are combined to improve convergence stability and model training efficiency.

The present invention relates to a method for MR imaging of an object (10) placed in an examination volume of an MR device (1). One object of the present invention is to achieve high-quality diffusion-weighted imaging (DWI) without distortion while minimizing artifacts caused by motion. The method of the present invention comprises the following steps: subjecting the object (10) to a dual-echo steady-state imaging sequence, generating a free induction decay signal (FID) and an echo signal (ECHO) in each interval between two consecutive RF pulses, wherein a pair of diffusion gradient waveforms (G) with equal phase integrals and opposite polarities are applied in the interval between the FID signal and the echo signal. DIF ); acquiring the FID signal and the echo signal in several repetitions of an imaging sequence with varying phase encoding; and reconstructing a diffusion-weighted MR image based on the acquired FID signal and echo signal. The present invention also relates to an MR device for performing the method and a computer program to be run on the MR device.

The invention relates to the technical field of geological disaster prevention and control, and discloses an underground rock stratum water-bearing while-drilling nuclear magnetic resonance 3D imaging method which comprises the following steps: arranging a plurality of long lead grounding sources with the length of 500-1000 meters and the interval of 10-20 meters on the ground, and supplying alternating current pulses with the frequency of Ramole frequency to enable hydrogen nuclei in underground water to form macroscopic magnetic moment, after the excitation current pulse is cut off, the same coil is used for picking up nuclear magnetic resonance (NMR) signals generated by excitation of different excitation pulse moments; a receiving coil is installed behind the drill bit and dynamically receives FID signals along with advancing of the drill bit. A long wire grounding source is arranged on the ground to form an excitation magnetic field, and a receiving coil is mounted behind a drill bit to dynamically receive nuclear magnetic resonance signals while drilling, so that high-precision detection of the water-bearing property of an underground rock stratum from two dimensions of the earth surface and the underground is realized. The change of the aquifer and the potential water inrush hidden danger can be monitored in real time, and the detection precision and the resolution ratio are effectively improved.

The invention relates to a single-channel gas spectral measurement system and inversion method based on a double-optical-comb spectrum, and the system comprises a first optical frequency comb, a second optical frequency comb, and a first coupler, an isolator, an optical band-pass filter, a photoelectric detector, an electrical low-pass filter, an AD acquisition card and a computer which are connected in sequence, the output ends of the first optical frequency comb and the second optical frequency comb are respectively connected with the input end of the first coupler; an adopted system structure and a digital correction method are based on a double-optical-comb spectrum technology and a free induction attenuation principle, and error correction of a free operation DCS interferogram and inversion of a gas absorption spectrum can be completed only through data collected by a signal path. The problem of how to reduce high requirements on equipment consistency and digital error correction benchmark consistency between a reference path and a signal path in a free running symmetric DCS (Distributed Control System) is solved, and synchronous, real-time and high-precision measurement of multi-component trace gas can be realized through a simplified system structure and a digital correction algorithm.

The application relates to the technical field of magnetometers, and discloses a magnetic force sensor system based on free induction decay and a use method thereof.The sensor system comprises a laser generator, an atomic gas chamber, a strong magnetic field generator, a polarizer, an analyzer, and a first light detector, and a light splitting device is arranged between the laser generator and the atomic gas chamber, which can split the laser emitted by the laser generator into a first part of laser and a second part of laser, and make the first part of laser enter the atomic gas chamber and make the second part of laser enter a second light detector.Once the frequency of the laser generated by the laser generator changes, the proportion of the first part of laser and the second part of laser will change, and a feedback adjustment module feeds back and adjusts the laser generator according to the detection result of the second light detector, so that the laser emitted by the laser generator is the laser with a preset frequency, thereby realizing rapid and high-precision adjustment of the laser emitted by the laser generator, and further improving the detection precision of the whole magnetic force sensor system.

The present invention discloses a method, a reconstruction method and a device for non-uniform sampling of magnetic resonance symmetric spectra. By constructing symmetric pairs of magnetic resonance free induction decay signals with uniform intervals and obtaining a first symmetric pair sequence; selecting a number of symmetric pairs from the first symmetric pair sequence at random Poisson intervals to obtain a second symmetric pair sequence; selecting symmetric pairs in the second symmetric pair sequence and randomly sampling one of the data points in the selected symmetric pairs to obtain a sampling result; in response to determining that the selected symmetric pair consists of two cross data points, filling the sampling result at the position of the other data point in the selected symmetric pair to obtain a non-uniformly sampled free induction decay signal, and performing fast reconstruction using the compressed sensing method. The obtained spectral cross peaks are more accurate, solving the problem of insufficient reconstruction accuracy of existing cross peaks, and having simple operation, wide applicability and excellent effects.

The invention relates to a computer-implemented method for acquiring magnetic resonance data with a magnetic resonance device (18), wherein a magnetic resonance sequence is used in which, during an equilibrium state in a sequence segment maintained by regular excitation modules (9, 9a - 9e) with at least one excitation pulse, both a first readout time window (11, 11a - 11e) immediately following an excitation module (9, 9a - 9e) for measuring magnetic resonance data of a free induction decay and second readout time windows (12, 12a - 12e), which are spaced at least the first readout duration of the first readout time window (11, 11a - 11e) from a last excitation module (9, 9a - 9e), which acts as a refocusing module for the penultimate excitation module (9, 9a - 9e), are used for measuring magnetic resonance data of a spin echo. become,wherein, between at least one pair consisting of a starting excitation module (9c) and a final excitation module (9d) that follow one another, a fat saturation module (15) with at least one high-frequency fat saturation pulse (16) is output in the magnetic resonance sequence during a preparation period (14).

The invention relates to a magnetic resonance signal correction method and device and a magnetic resonance imaging system. The method comprises the following steps: acquiring an original free induction attenuation signal of target equipment; determining a magnetic resonance signal correction curve of the target equipment according to the original free induction decay signal; and according to the magnetic resonance signal correction curve, correcting a to-be-corrected magnetic resonance signal collected by the target device to obtain a corrected magnetic resonance signal corresponding to the to-be-corrected magnetic resonance signal. By adopting the method, multiplicative noise interference of magnetic resonance signals can be removed, and the quality of magnetic resonance imaging is improved.

Systems and techniques are provided for determining a time zero echo of a nuclear magnetic resonance (NMR) sequence. An example method includes obtaining, via an NMR tool in a borehole, echo waveforms associated with refocusing pulses and a free induction decay (FID) waveform associated with an excitation pulse; determining echo values based on the echo waveforms and an apparent time-zero echo value based on the FID waveform, the apparent time-zero echo value representing a time zero echo; applying a correction factor to the apparent time-zero echo value to yield a corrected time zero echo value; and determining a spectrum associated with a sample based on an inversion performed on the corrected time zero echo values and the set of echo values before or after a conversion of the corrected time zero echo value and the set of echo values to porosity units, the conversion of the corrected time zero echo value and the set of echo values being based on one or more conversion factors.

The objective of the present invention is to provide a polishing pad having excellent startup properties, and a method for manufacturing the same. The polishing pad includes a resin sheet having a plurality of teardrop-shaped bubbles and having a polishing surface for polishing an object to be polished, wherein, if a free induction decay signal (FID) obtained by means of pulsed NMR is subjected to waveform separation by using the least squares method to sequentially subtract components having the longer spin-spin relaxation time T2s from the free induction decay signal (FID), to thereby divide the free induction decay signal (FID) into three components, namely an amorphous phase, an interface phase and a crystal phase in decreasing order of the spin-spin relaxation time T2s, the resin sheet has a difference ΔT2s,15min of 0.35 ms or more, being the difference between the relaxation time T2s,15min of the amorphous phase component of the resin sheet obtained from the measurement result of the relaxation time using pulsed NMR after dressing the polishing pad for 15 minutes, and the relaxation time T2s,dry of the amorphous phase component of the resin sheet obtained from the measurement result of the relaxation time using pulsed NMR in a dry state before dressing the polishing pad.

A method for relaxation time determination includes delivering a series of radio frequency (RF) pulses in a sequence to a specimen having a magnetic resonance spin system. The pulses are separated by equal time intervals and the sequence has a duration comparable or greater than a spin-lattice relaxation time for the spin system. The method includes receiving a response after each RF pulse in the series. The response includes a free induction decay and spin echoes. The method includes generating a series of single point imaging (SPI) images from each response. Each SPI image of the series corresponds to an RF pulse in the series. The method includes converting SPI images to a spin-spin relaxation map and a spin-lattice relaxation map.

Computer-implemented method for recording MR data, including: executing a MR sequence having a sequence segment maintained in a steady state by regular excitation modules, each excitation module including an excitation pulse; for each excitation module, providing: a first read-out time window for measuring MR data of a free induction decay; and a second read-out time window, occurring after a last excitation module by at least a duration of the first read-out time window, the last excitation module acting as a refocusing module for the penultimate excitation module, wherein both read-out time windows follow an excitation module and are used to measure MR data of a spin echo; and outputting, in a preparation period between a pair of excitation modules comprising a beginning excitation module and a concluding excitation module that follow one another in the MR sequence, a fat saturation module including a RF fat saturation pulse.

An optimal pulse power measurement method for multinuclear simultaneous integrated magnetic resonance imaging includes the following steps: successively or simultaneously exciting multiple nuclides within a slice in a same repetition time (TR) of magnetic resonance imaging (MRI); applying, in a slice encoding gradient channel, a frequency encoding gradient in a direction opposite to a slice selection gradient, and acquiring free induction decay (FID) signals of all the nuclides; simultaneously changing shaped radiofrequency (RF) pulse power values of all the nuclides for multiple times, and acquiring multiple corresponding FID signals for each nuclide; and performing Fourier transform on the FID signals of each nuclide, selecting a spectral peak in an absolute spectrum, integrating the spectral peak for comparison, and taking a shaped RF pulse power value corresponding to a maximum signal intensity of each nuclide as an optimal shaped RF pulse power corresponding to a current TR.

The invention discloses a conductive medium detection method and device, the method is suitable for a transient magnetic field exciter, and the method comprises the steps: responding to a detection demand of a detected area, and applying a background field to an atomic gas chamber along a first direction parallel to a magnetic field coil; starting the first detection light and controlling the first detection light to pass through the atomic gas chamber along a second direction; synchronously starting the pump light and the magnetic field coil according to a preset detection frequency, controlling the pump light to penetrate through the magnetic field coil to enter the atomic gas chamber, and controlling the magnetic field coil to send a pulsed magnetic field to the detected area; and synchronously closing the pump light and the magnetic field coil in a preset time window to obtain second detection light generated after the first detection light passes through the atomic gas chamber, so as to obtain free induction attenuation signals of atoms in the atomic gas chamber and a detection result of a transient eddy current magnetic field, and determining a detection result of the conducting medium in the detected area according to the detection result. And the detection precision and the response rate are improved.

Systems and techniques are provided for determining a time zero echo of a nuclear magnetic resonance (NMR) sequence. An example method includes obtaining, via an NMR tool in a borehole, echo waveforms associated with refocusing pulses and a free induction decay (FID) waveform associated with an excitation pulse; determining echo values based on the echo waveforms and an apparent time-zero echo value based on the FID waveform, the apparent time-zero echo value representing a time zero echo; applying a correction factor to the apparent time-zero echo value to yield a corrected time zero echo value; and determining a spectrum associated with a sample based on an inversion performed on the corrected time zero echo values and the set of echo values before or after a conversion of the corrected time zero echo value and the set of echo values to porosity units, the conversion of the corrected time zero echo value and the set of echo values being based on one or more conversion factors.

To provide a polishing pad excellent in starting performance and a method for manufacturing the same.SOLUTION: A polishing pad comprises a resin sheet having a plurality of tear-shaped foams and a polishing surface for polishing an article to be polished. When a free induction attenuation signal (FID) acquired by a pulse NMR is subtracted in order from a longer component of spin-spin relaxation time T2s by a least square method and waveform-separated, thereby divided into three components of an amorphous phase, an interface phase, and a crystal phase in order from the longer component of spin-spin relaxation time T2s, in the resin sheet has ΔT2s,15min, which is a difference between relaxation time T2s,15min of the amorphous phase component of the resin sheet acquired from the measuring result of the relaxation time using the pulse NMR after dressing of the polishing pad for 15 minutes and relaxation time T2s,dry of the amorphous phase component of the resin sheet acquired from the measuring result of the relaxation time using the pulse NMR in a dry state before the dressing of the polishing pad, of 0.35ms or more.SELECTED DRAWING: None

The invention relates to an improved mute multi-gradient echo magnetic resonance imaging system and method. Methods and systems for generating muted multi-gradient echo magnetic resonance images include employing iterative applications of small updates to the magnetic field gradient followed by short non-selective radio frequency pulse excitation, and for free induction decay data acquisition. Updating of the magnetic field gradient allows for a muted self-refocusing pulse sequence. Each magnetic field gradient is based in part on a k-space spoke. A closed k-space trajectory is generated when multiple spokes are cascaded, which results in a self-refocusing pulse sequence. The k-space spokes in the k-space spoke sequence forming the closed k-space trajectory oscillate inside and outside the plane of the frequency space. Subsequent application of the magnetic field gradient allows multiple echo data acquisition.

The present invention relates to a nuclear magnetic resonance magnetometer device for measuring magnetic fields at the millitesla level, belonging to the field of magnetic detection technology. The device includes a nuclear magnetic resonance probe, a pre-polarization unit, a water sample transfer unit, and a control circuit part; the control circuit part is electrically connected to the nuclear magnetic resonance probe and the water pump control circuit; the nuclear magnetic resonance probe is used to excite the pre-polarized water sample, and convert the nuclear magnetic resonance electromagnetic wave signal emitted after the water sample resonates into a voltage signal through the probe coil; the control circuit part outputs a pulse signal, which is loaded onto the probe coil to excite the water sample in the glass capillary tube, and collects the free induction decay signal in the water sample after the pulse excitation ends; the spectrum of the signal is obtained by performing a fast Fourier transform on the signal with a computer, the frequency corresponding to the highest peak point of the spectrum is the frequency of the magnetic field to be measured, and the magnetic field strength of the magnetic field to be measured is obtained through the nuclear magnetic resonance gyromagnetic ratio formula. The present invention can achieve accurate measurement of weak magnetic fields from below 40 mT down to 1 mT.

A method for relaxation time determination includes delivering a series of radio frequency (RF) pulses in a sequence to a specimen having a magnetic resonance spin system. The pulses are separated by equal time intervals and the sequence has a duration comparable or greater than a spin-lattice relaxation time for the spin system. The method includes receiving a response after each RF pulse in the series. The response includes a free induction decay and spin echoes. The method includes generating a series of single point imaging (SPI) images from each response. Each SPI image of the series corresponds to an RF pulse in the series. The method includes converting SPI images to a spin-spin relaxation map and a spin-lattice relaxation map.

An optimal pulse power measurement method for multinuclear simultaneous integrated magnetic resonance imaging includes the following steps: successively or simultaneously exciting multiple nuclides within a slice in a same repetition time (TR) of magnetic resonance imaging (MRI); applying, in a slice encoding gradient channel, a frequency encoding gradient in a direction opposite to a slice selection gradient, and acquiring free induction decay (FID) signals of all the nuclides; simultaneously changing shaped radiofrequency (RF) pulse power values of all the nuclides for multiple times, and acquiring multiple corresponding FID signals for each nuclide; and performing Fourier transform on the FID signals of each nuclide, selecting a spectral peak in an absolute spectrum, integrating the spectral peak for comparison, and taking a shaped RF pulse power value corresponding to a maximum signal intensity of each nuclide as an optimal shaped RF pulse power corresponding to a current TR.

The invention discloses a conductive medium detection method and device, the method is suitable for a transient magnetic field exciter, and the method comprises the steps: responding to a detection demand of a detected area, and applying a background field to an atomic gas chamber along a first direction parallel to a magnetic field coil; starting the first detection light and controlling the first detection light to pass through the atomic gas chamber along a second direction; synchronously starting the pump light and the magnetic field coil according to a preset detection frequency, controlling the pump light to penetrate through the magnetic field coil to enter the atomic gas chamber, and controlling the magnetic field coil to send a pulsed magnetic field to the detected area; and synchronously closing the pump light and the magnetic field coil in a preset time window to obtain second detection light generated after the first detection light passes through the atomic gas chamber, so as to obtain free induction attenuation signals of atoms in the atomic gas chamber and a detection result of a transient eddy current magnetic field, and determining a detection result of the conducting medium in the detected area according to the detection result. And the detection precision and the response rate are improved.

The purpose of the present invention is to provide a biological component adsorption material that has high adsorption performance with respect to biological components, particularly with respect to cytokines, independently from the content and / or chemical structure of a ligand. The present invention provides a biological component adsorption material comprising water-insoluble material which comprises a base material that includes a scaffold polymer, a linker that is bound to the base material, and ligand that is bound to the linker, wherein the water-insoluble material exhibits a T2 relaxation time of retrained amorphous component of 0.0210-0.0270 ms, as seen in free induction decay (FID) observed with 1H-pulse NMR using a solid echo method.

The application provides a denoising method for magnetic resonance spectrum based on a transformer, and relates to the technical field of signal processing and artificial intelligence, which comprises the following steps: obtaining a free induction decay signal (FID) containing noise and a corresponding label signal, and constructing a training data set; converting the FID into a frequency domain signal through fast Fourier transform and performing amplitude normalization; projecting the real part and the imaginary part of the frequency domain signal into a high-dimensional feature space respectively; and feeding the two channels into a multi-layer transformer encoder based on a multi-head self-attention mechanism respectively to capture long sequence global correlation. The encoding output is separated and decoded to recover the real part and the imaginary part respectively, and the recovered complex frequency domain signal is obtained by combination. During the training process, a complex mean square error is used as a loss function, and a dynamic learning rate scheduling and an early stopping mechanism are combined to improve the convergence stability and the model training efficiency.

The present invention discloses an extremely low frequency magnetic field communication receiver based on an atomic magnetometer in the field of wireless communication technology. The core sensor of the extremely low frequency magnetic field communication receiver is a scalar atomic magnetometer based on the free induction decay working principle and the pulsed light pumping working mode, including a meter head and a controller electrically connected to the meter head; the meter head includes a VCSEL laser, a polarization magnetic field coil, a magnetic field gradient coil, an atomic gas chamber, a λ / 4 wave plate, a photodiode and an insulated box; the controller includes a meter head drive circuit and an FPGA-based signal processor that runs an automatic working algorithm to control the drive circuit. The receiver of the present invention has a higher sensitivity to extremely low frequency magnetic field detection under the same probe volume conditions, and has the advantages of miniaturization and lightweight. The scalar detection is suitable for dynamic carrier platforms and can be easily formed into a magnetic field gradiometer or array, thereby improving the receiver sensitivity, increasing the communication distance, and enhancing the covert communication capability.

To provide a deterioration sign diagnosis method and a deterioration sign diagnosis system of a resin material capable of easily diagnosing a sign of deterioration of the resin material.SOLUTION: The resin material deterioration sign diagnosis method according to the embodiment includes measuring a resin material by a nuclear magnetic resonance apparatus capable of non-destructive observation, acquiring free induction decay curve data, obtaining a spin-spin relaxation time, evaluating a change in molecular mobility of the resin material based on the spin-spin relaxation time, and diagnosing a deterioration sign of the resin material.SELECTED DRAWING: Figure 5

Disclosed herein is a method of imaging at least a part of a subject (318). The method comprises receiving (200) k-space data (122) acquired according to a fast spin echo magnetic resonance imaging protocol. The method further comprises reconstructing (202) an initial magnetic resonance image (124) from the k-space data. The method further comprises receiving (204) a free induction decay artifact image (128) in response to inputting the initial magnetic resonance image into an image processing neural network (126). The image processing neural network is configured for filtering free induction decay artifacts from fast spin echo magnetic resonance images. The method further comprises generating (206) a clinical magnetic resonance image (130), through a combination of at least a portion of the free induction decay artifact image and the initial magnetic resonance image. The method further comprises providing (208) the clinical magnetic resonance image.

The present invention provides a film having a low coefficient of linear expansion. A film according to the present invention contains an organopolysiloxane, and the signal intensity of the free induction decay associated with spin-spin relaxation of all protons at room temperature was measured for the film using the CPMG technique for solid state NMR, a fitting process according to formula (I) was performed using the signal intensity, and among three components A, B, and C, in order of shortest relaxation time, the relaxation time T2c of the component C was 2.0 milliseconds or less.

This invention relates to a method for measuring the wax content of crude oil using nuclear magnetic resonance (NMR), comprising: heating the crude oil sample to be tested to a homogeneous fluid state and then injecting it into a sample tube; cooling the sample tube in a low-temperature environment to allow complete precipitation of paraffin wax in the crude oil; placing the cooled sample tube in an NMR instrument and acquiring NMR signals using a free induction decay sequence; performing a two-component fitting on the acquired NMR signals to obtain the initial signal amplitudes A1 and A2 of the solid and liquid phases, and calculating the ratio x between the initial signal amplitudes of the solid and liquid phases based on A1 and A2; calculating the mass ratio y between the solid and liquid phases using a pre-established calibration model y=k·x; and calculating the wax content c of the crude oil sample to be tested based on the solid-liquid mass ratio y. This invention also relates to a corresponding system. The method and system for measuring the wax content of crude oil using NMR of this invention effectively solve the problems of long testing time and environmental unfriendliness associated with the national standard method.

The invention discloses a seasonal river water environment quality evaluation method based on chemical research service data, and the method comprises the following steps: 1, deploying a low-field nuclear magnetic resonance online detection device on each sampling section, applying a radio frequency excitation pulse to a water sample entering a detection cavity, and collecting a free induction attenuation signal; collecting the one-dimensional nuclear magnetic resonance spectrum vectors of the sampling sections according to seasonal division to form a nuclear magnetic resonance spectrum data set; 2, constructing a one-dimensional convolutional neural network model, and forming a pollutant feature matrix corresponding to each sampling section in each season; and step 3, establishing classic domain matter elements and joint domain matter elements corresponding to each water quality grade according to a water environment quality standard, and summarizing water environment quality evaluation grades of each sampling section in each season to form a seasonal river water environment quality comprehensive evaluation result. According to the invention, on-site rapid detection and automatic spectrogram analysis of organic pollutants are realized, and the problem of poor timeliness of traditional off-line detection is overcome.