23 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 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 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).

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.

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 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.

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.

The invention discloses a rubidium atom magnetometer based on free induction attenuation and a magnetic field measurement method. The magnetometer physical probe comprises a VCSEL laser, an optical shaping unit composed of a convex lens, a polaroid and a 1 / 4 wave plate, a rubidium atom gas chamber, a radio frequency coil assembly and a photoelectric detector. The circuit part comprises a signal conditioning circuit and an oscillation feedback circuit. The method comprises the following steps: working in a periodic pulse mode, firstly starting a laser and radio frequency coil in a period, and performing optical pumping and polarization on rubidium atoms by using left-hand circularly polarized light and a polarized magnetic field along an optical axis; then, the polarized magnetic field is rapidly closed within microsecond magnitude time, so that the atoms spin and freely precession in the external magnetic field to be measured, and an FID signal is generated; after being detected by the photoelectric detector, the signals are fed back to the radio frequency coil through amplification and phase locking processing, and self-oscillation with the frequency locked at the atomic Larmor precession frequency is formed; and measuring the oscillation frequency and calculating the external magnetic field intensity according to the gyromagnetic ratio. The invention has the advantages of high sensitivity, large bandwidth, fast response and small volume.

The application discloses a kind of atomic magnetometer vector magnetic field measurement method and measuring device, it is related to quantum precision measurement technical field.The method includes: alkali metal atom in atomic gas chamber is optically pumped to establish spin alignment state;Pulse radio frequency magnetic field is applied to induce atom to generate free induction decay signal;Based on the reference free induction decay signal collected when not applying additional bias magnetic field, the environmental background magnetic field modulus is determined;Known intensity additional bias magnetic field is sequentially applied in three orthogonal axes, and based on the additional free induction decay signal under corresponding state, the total magnetic field modulus corresponding to each orthogonal axis is determined;Combining geometric relationship demodulation obtains the vector component of environmental magnetic field on each orthogonal axis.The present application does not need complex optical modulation equipment, while maintaining single-beam compact configuration, high-precision three-dimensional vector magnetic field measurement is realized, and system power consumption and hardware complexity are significantly reduced.