186 results about "Relaxation (NMR)" patented technology

The invention discloses a nuclear magnetic T2 spectrum correction method for a shale reservoir, and relates to the field of object detection, and the nuclear magnetic T2 spectrum correction method for the shale reservoir comprises the following steps: 1, determining the gas logging porosity, saturated water porosity and main mineral components of the shale reservoir; compared with the prior art, the method disclosed by the invention has the beneficial effects that a drying-saturated water-centrifugal two-dimensional nuclear magnetic resonance experiment is carried out, and signals of crystal water, clay bound water and hydroxyl in a sample are preliminarily identified; through inversion of organic matter signals in the dry sample, signals of movable water are further determined; the relation between the difference value among the gas logging porosity, the saturated water porosity and the nuclear magnetic porosity and different mineral contents is discussed, and particularly the remarkable influence of iron-containing minerals on the porosity difference value is discussed; by eliminating the influence of diffusion relaxation caused by the magnetic susceptibility difference, the T2 spectrum correction method based on the mineral magnetic susceptibility is established, and the T2 spectrum accuracy obtained through nuclear magnetic resonance measurement is improved.

The invention discloses an SERF atom magnetometer double-axis magnetic field detection method and device based on pulsed magnetic field modulation, relates to the technical field of magnetic field precision measurement, and compresses the action time of a modulation magnetic field additionally applied in the same unit period on a hot atom ensemble by replacing conventional continuous sinusoidal magnetic field modulation with pulsed magnetic field modulation. The pulse magnetic field with the duty ratio of d can reduce the spin exchange relaxation rate to 2d times of that of a conventional method under the same modulation amplitude and frequency, due to the fact that the spin exchange relaxation rate is effectively restrained, the collected polarizability response signal is obviously improved, and the polarizability response signal can be obtained through the pulse magnetic field with the duty ratio of d and the pulse magnetic field with the duty ratio of d. Low-relaxation-rate sensitivity-enhanced double-axis magnetic field measurement under a pulse modulation scheme is realized, the double-axis measurement sensitivity of a miniaturized SERF atom magnetometer is further improved, and the method has great significance in supporting leap-type development of a future array type extremely-weak magnetic imaging system and medical application thereof.

The invention discloses a magnetic source positioning method based on a spin-exchange relaxation-free atom magnetometer, and aims to provide a high-precision brand-new solution for magnetic source positioning in a near-zero magnetic environment by performing physical modeling and least square estimation on space magnetic field distribution of a target magnetic source. The magnetometer is enabled to be simultaneously sensitive to a three-axis magnetic field, a light absorption detection method is utilized to ensure that complete three-axis magnetic field information is obtained, and the sensitivity of the three axes reaches fT / Hz1 / 2 (1fT = 10 <-15 > T) magnitude. In the positioning process, the target magnetic source is abstracted into a physical model of the magnetic dipole, and the space magnetic field information generated by the target magnetic source is obtained through the atom magnetometer, so that the long-term stability of the magnetic source positioning process and the high precision of the positioning result can be ensured in the zero magnetic environment; therefore, a high-precision magnetic positioning technical means with great potential is provided for various application scenes such as paleomagnetic sample testing and magnetic source positioning in medical research, and technical progress and application expansion in related fields are expected to be promoted.

The invention provides a method and device for calculating the electron spinning state of an iron-based biphase composite magnetic material, and relates to the technical field of magnetic materials. The method comprises the following steps: establishing a heterojunction model of a biphase composite magnetic material; according to the method, generalized gradient approximation in a density functional theory is adopted as an exchange-correlation functional, relaxation is carried out on atomic positions in a heterojunction model, so that the total energy of a system is the lowest, and geometric structure optimization is carried out on the heterojunction model; performing spin polarization calculation on the optimized heterojunction model to obtain spin upward state densities and spin downward state densities of different atoms in the heterojunction model, and analyzing electronic state distribution near a Fermi level; and quantitatively evaluating the magnetic characteristics of the heterojunction model according to the spin upward state density and the spin downward state density of each atom. According to the method, an interface magnetic coupling mechanism can be disclosed, and a theoretical basis can be provided for development of a high-performance magnetically controlled reactor iron core material.

The invention provides a quartz enhanced photoacoustic spectrometry detection system environment gas interference correction method which can be applied to the technical field of photoacoustic spectrometry gas detection. The method comprises the following steps: analyzing vibration-translation relaxation time and infrared absorption peak intensity of each gas to be detected; the to-be-detected gas with the vibration-translation relaxation time exceeding the time threshold value and the absorption peak intensity larger than the intensity threshold value is selected as comparison gas; dividing the laser of the comparison gas into a first laser beam and a second laser beam according to a preset proportion; using the first laser beam to excite a sound wave signal and detecting by a quartz tuning fork to generate a tuning fork electric signal; the second laser beam is enhanced and absorbed by a multi-reflection absorption cell and then is detected by a photoelectric detector to generate a light intensity electric signal; establishing a neural network model taking the tuning fork electric signal, the light intensity electric signal and the environment gas component vector as input and taking the to-be-detected gas concentration vector as output; and correcting the concentration of the to-be-detected gas under the interference of the environmental gas in real time through the trained neural network model.

The invention belongs to the technical field related to nanometer material testing, and discloses a magnetic nanoparticle relaxation time detection method and an environmental parameter detection method, and the method comprises the following steps: applying an excitation magnetic field around a to-be-detected target mixed with magnetic nanoparticles; obtaining magnetization response generated by the magnetic nanoparticles in any direction of the magnetic field plane, and obtaining phase lag corresponding to any order harmonic term of the magnetization response; according to the function relationship between the phase lag corresponding to any harmonic term and the Brown relaxation time of the magnetic nanoparticles, solving and obtaining the Brown relaxation time of the magnetic nanoparticles; wherein the function relationship comprises a correction term introduced by magnetic dipole interaction of the magnetic nanoparticles. The magnetic dipole interaction among the magnetic nanoparticles is introduced, relaxation time detection of particle space distribution under an external magnetic field is corrected, the interference of the magnetic dipole interaction on the magnetic nanoparticle Brown relaxation time detection process can be effectively reduced, and accurate estimation of the magnetic nanoparticle Brown relaxation time is realized.

The invention discloses a method for non-destructively identifying the gender of a transformed young duck egg based on a singing tube nuclear magnetic image, and belongs to the technical field of poultry egg detection.The method comprises the steps that a low-field nuclear magnetic resonance technology is utilized, a breeding duck egg is positioned in a nuclear magnetic system, the optimal imaging section of a singing tube is determined, an image is collected and preprocessed, and a high-quality singing tube nuclear magnetic image is obtained; and through analyzing relaxation characteristics, inverting nuclear magnetic signals to identify a buzzer tube structure and extracting characteristics, finally constructing a gender decision-making model, and combining physical constraints to obtain a gender discrimination result as a sorting reference. According to the method, lossless, early-stage and high-accuracy sex identification is realized through a special imaging technology and algorithm by utilizing sex difference nuclear magnetic characteristics of a singing tube structure, hatching and breeding strategies can be optimized in laying duck and meat duck breeding, and intelligent development of the industry is promoted.

The present invention comprises a method for jointly processing data from the nuclear magnetic resonant (NMR) response of oil and rock samples in in natura condition, and its main product is the delimitation of the oil saturation (So) present in the rock samples, i.e., the determination of the range of admissible values of the volumetric fraction of the porous volume of the rock occupied by such fluid. The method requires a small volume of oil, originating from or of a composition similar to the oil present in the rock being tested, since it is based on both the measurement of the NMR response of the rock sample and the response of the fluid sample. These two sets of data feed a statistical inference scheme that (1) determines a range of admissible values for the So of the sample, delimited by the minimum and maximum oil saturation values compatible with the two sets of data presented; (2) produces, for each of these extreme values of admissible So, a decomposition of the rock relaxation time spectrum into two complementary spectra, the first highlighting the signatures relating to oil and the second comprising the distribution of the rock relaxometric signatures that cannot correspond to such fluid under the prescribed saturation condition.

The invention belongs to the technical field of oil and gas reservoir engineering and multiphase seepage dynamic monitoring, relates to a characterization method of seepage behaviors of multiphase fluid in a porous medium, and particularly provides a dynamic construction method of a multiphase displacement capillary pressure-saturation relationship based on nuclear magnetic resonance. Comprising the following steps: S1, acquiring a low-field nuclear magnetic resonance relaxation spectrum of a porous medium in a gas-water two-phase displacement process; s2, determining two-phase fluid interfacial tension, a wetting contact angle and a rock surface relaxation rate; s3, determining the dynamic cut-off relaxation time of the displacement stage; s4, calculating equivalent capillary pressure; the residual water saturation is calculated, and the equivalent capillary pressure is the capillary pressure corresponding to the current displacement stage and is used for constructing a capillary pressure-saturation curve. According to the method, the capillary pressure change in the porous medium can be obtained only through spectral analysis without a centrifugal or mercury injection experiment.

The invention relates to the technical field of nuclear magnetic resonance logging, aims to solve the problem that a method for jointly correcting a nuclear magnetic resonance logging T2 spectrum by integrating multiple factors does not exist at present, and provides a gas-containing shale nuclear magnetic resonance relaxation time spectrum correction method, a storage medium and a device. The method comprises the steps of obtaining target layer information; determining a T2 spectrum correction position; factors influencing the difference between the nuclear magnetic porosity and the conventional logging porosity are analyzed, and the influence of the factors on the nuclear magnetic resonance logging T2 spectrum is corrected according to the factors; respectively fitting each spectrum peak of the T2 spectrum through a Gaussian distribution curve, completing correction of each factor on the spectrum peak, and obtaining a final corrected nuclear magnetic offset T2 spectrum; superposing the porosity components of the corrected T2 spectrum Gaussian distributions of the fluid peaks at the corresponding distribution points to obtain corrected effective porosity and total porosity; according to the invention, automatic correction of the nuclear magnetic resonance logging T2 spectrum can be realized.

The invention belongs to the technical field of cerium-based rare earth oxide dispersibility testing, and particularly relates to a method for evaluating cerium-based rare earth oxide particle surface characteristics and slurry dispersion stability. Comprising the following steps: when cerium-based rare earth oxide particles are synthesized, adding a paramagnetic element as a probe, and mixing the synthesized particles with a dispersing agent and water to obtain mixed slurry; nuclear magnetic resonance scanning is adopted, the body water relaxation peak and the particle surface bound water and body water exchange dynamic relaxation peak of the mixed slurry in each stage of the process from uniform mixing to standing layering are measured, and the particle surface characteristics are evaluated based on the relaxation efficiency; meanwhile, a linear relation between the relaxation peak area proportion and the sedimentation time in the standing layering process is constructed, a fitting slope value is obtained, and the dispersion stability of the mixed slurry is evaluated. According to the method, non-intrusive in-situ detection of the dispersion stability of the cerium-based rare earth oxide particle slurry is realized by innovatively using a low-field nuclear magnetic resonance mode, and accurate comparison and evaluation of the dispersion stability can be realized.

The invention relates to a special device and method for calibrating a relaxation time measurement result of a medical magnetic resonance imaging (MRI) system. The special device comprises a relaxation time standard die body, an optical fiber temperature measurement system and a control computer. The relaxation time standard die body is composed of a die body shell, a sealing cover and a relaxation time standard unit. The relaxation time standard unit is composed of reagent bottles, and the optical fiber temperature measuring probe is inserted into the relaxation time standard die body. According to the method, T1 and T2 standard values of a relaxation time standard substance under different static magnetic field intensities are calibrated by using a magnetic resonance spectroscopy method, and a relaxation time measurement result of an MRI system is calibrated by using the calibrated relaxation time standard substance. And adopting a reversal recovery sequence to calibrate T1, and adopting a CPMG sequence to calibrate T2. The device and the method can be used for calibrating the relaxation time measurement result of the MRI system, so that the accuracy and the consistency can be improved, and the clinical application is promoted.

The invention provides a method for determining a nanofluid oil displacement effect of a low-permeability reservoir, and relates to the technical field of oil exploitation. The method comprises the following steps: providing a core of a low-permeability reservoir, and measuring the particle size of nanoparticles in a target nanofluid; performing high-pressure mercury injection test and nuclear magnetic resonance measurement on the rock core to respectively obtain a rock core pore throat radius-distribution frequency relation curve and a first T2 image, and performing benchmarking on the two images to obtain a pore throat radius-relaxation time relation curve; carrying out displacement experiments (oil displacement, first water displacement, nanofluid displacement and second water displacement) on the rock core, and carrying out nuclear magnetic resonance measurement to obtain T2 images; and observing or calculating the area enclosed by the curve and the relaxation time in each image, and combining with a pore throat radius-relaxation time relation curve to obtain the oil displacement effect of the nanofluid on different pores of the oil reservoir. The oil displacement effect of the nanometer system is determined according to the characteristic parameters of the reservoir core before and after the nanometer fluid is injected, and the method has important guiding significance for formulating a scheme for improving the recovery effect of the low-permeability oil reservoir.

The embodiment of the invention discloses a method and device for testing foam seepage characteristics of a heterogeneous porous medium, electronic equipment and a storage medium, and relates to the technical field of fluid mechanics and nuclear magnetic resonance. The method comprises the steps that a heterogeneous porous medium sample with a clear permeability level difference is prepared, and the permeability level difference of the heterogeneous porous medium sample is determined; setting test parameters according to the permeability level difference of the sample, calibrating imaging parameters of the low-field nuclear magnetic resonance equipment, and setting a weighting mode; performing foam flooding treatment on the sample according to the set injection parameters, acquiring a spectrum of the sample according to the test parameters when foam is injected into a set amount, and acquiring nuclear magnetic imaging of the sample through low-field nuclear magnetic resonance equipment according to imaging parameters and a weighting mode; according to the relaxation characteristic of the spectrum, the main peak endpoint value is used for dividing the pore channel, the foam sweep degree is calculated according to the spectrum peak area of the spectrum, and the foam plugging strength is calculated according to the signal amplitude of nuclear magnetic imaging. According to the method, the problems of poor visualization adaptability and lack of evaluation systems in the prior art are solved.

The application discloses a raw coal pore detection method, device, system and medium based on nuclear magnetic resonance. The method comprises the following steps: obtaining relaxation time distribution data of each coal sample based on nuclear magnetic resonance T2 test; obtaining total integral areas of a plurality of nuclear magnetic resonance T2 spectra corresponding to each coal sample based on the relaxation time distribution data of each coal sample; performing statistical analysis on the relative standard deviation of the total integral areas of each coal sample to obtain the relative standard deviation corresponding to each coal sample; and determining the coal sample parameters of a target coal sample for detecting the pore structure of the raw coal according to the coal sample parameters of the coal sample corresponding to the relative standard deviation satisfying the preset condition. The raw coal pore detection method provided by the application can determine the target coal sample by selecting the coal sample parameters of the coal sample satisfying the preset condition, so that the result of the nuclear magnetic resonance T2 test for detecting the pore structure of the raw coal is more accurate and stable.

The present invention discloses a method for effectively disassembling a nuclear magnetic resonance relaxation time spectrum, comprising the following steps: S1, constructing a probability density function of pores and caves according to the distribution characteristics of pores and caves in a core nuclear magnetic resonance T2 spectrum; S2, setting the sum of the nuclear magnetic spectrum areas to 1, randomly generating n data points within the interval of pore distribution, and dividing all the data points into multiple data sets by screening peak values; S3, calculating a likelihood function; S4, calculating a priori probability that each data point belongs to a pore or a cave; S5, updating various parameters in an iterative method using the priori probability; and S6, calculating a new logarithmic likelihood based on the updated parameters, and updating the expected E in the iterative method. p and E v , expected E p and E v Repeat steps S2 to S5 until the convergence condition is met and the iteration is terminated. The present invention combines nuclear magnetic resonance testing with an iterative method to decompose the nuclear magnetic resonance spectrum, thereby improving the accuracy of the spectral shape distribution.

The invention relates to the field of detection, in particular to a food detection method based on low-field nuclear magnetic resonance, which can monitor the fluctuation of an applied pulse so as to determine the deviation of the overturning angle of a hydrogen atom nucleus in a sample caused by the fluctuation of the pulse and further determine the actual overturning angle. Furthermore, the interference of pulse fluctuation on an external magnetic field is also considered, and the influence of the pulse fluctuation on the relaxation duration is fully eliminated according to the actual relaxation duration determined by the actual overturning angle and the interference of the external magnetic field, so that the performance of the hydrogen nucleus in the sample can be accurately represented; further, the substance state of the sample can be accurately determined.

The invention belongs to the technical field of reservoir pore structure characterization, and relates to a nuclear magnetic resonance T2 spectrum pore diameter conversion method based on a least square method and mercury injection data. The method comprises the following steps: interpolating and fitting cumulative distribution frequency of nuclear magnetic resonance about relaxation time to obtain a relationship between the cumulative distribution frequency of the relaxation time and the radius of a mercury injection pore; interpolation and fitting are carried out on the cumulative distribution frequency of the high-pressure mercury injection relative to the pore radius, and the relation between the cumulative distribution frequency of the pore radius and the mercury injection pore radius is obtained; establishing an error function based on the relationship between the cumulative distribution frequency of the relaxation time and the mercury injection pore radius and the relationship between the cumulative distribution frequency of the pore radius and the mercury injection pore radius; establishing a conversion function for converting the cumulative distribution curve of the nuclear magnetic resonance T2 relaxation time into a cumulative distribution curve of a high-pressure mercury injection pore throat radius; and substituting the error function into a conversion function to solve a conversion coefficient in the conversion function, and completing nuclear magnetic resonance T2 spectrum aperture conversion.

The present invention relates to the field of magnetic resonance imaging, and particularly to a method and system for magnetic resonance imaging. The method includes: acquiring a spin echo sequence and a plurality of gradient echo sequences; performing fitting calculations based on the plurality of gradient echo sequences to obtain a fitting density quantitative map, a fitting longitudinal relaxation quantitative map, and a fitting quasi-transverse relaxation quantitative map; obtaining a gradient-weighted image based on the fitting density quantitative map, the fitting longitudinal relaxation quantitative map, and the fitting quasi-transverse relaxation quantitative map; obtaining a relaxation decay image based on the gradient-weighted image and the spin echo sequence; obtaining a transverse relaxation quantitative map based on the relaxation decay image; performing weighted summation based on the fitting density quantitative map, the fitting longitudinal relaxation quantitative map, the relaxation decay image, and the transverse relaxation quantitative map to obtain a magnetic resonance multi-parameter image. The present invention increases the types of multi-parameter maps, facilitating the rapid acquisition of multiple contrast images.

This application discloses a downhole nuclear magnetic resonance (NMR) inversion method, apparatus, equipment, and storage medium based on pruned Bayesian methods, relating to the field of NMR data processing technology. The method includes: constructing a forward dataset based on fluid relaxation time and acquisition parameters, and adding Gaussian white noise to obtain the inversion input signal; initializing prior parameters, posterior mean, and variance; constructing a kernel matrix based on relaxation time points; constructing a kernel-dictionary matrix using Gaussian functions; updating the fitted echo data and fitting residuals using hierarchical Bayesian methods, thereby updating the prior parameters; updating the posterior mean through evidence maximization and calculating the proportion of each fluid component; pruning the kernel-dictionary matrix according to a preset pruning threshold and proportion, iterating until a termination condition is met, and finally mapping to obtain a two-dimensional NMR relaxation spectrum. This method solves the problem of waiting time and loss of diffusion relaxation dimension information caused by improved logging efficiency, which makes accurate multidimensional NMR logging inversion difficult.

A traceable multi-mode extremely weak magnetic field measuring device and method, comprising helium-3 atoms and an atomic magnetometer in a spin-exchange relaxation-free state, the helium-3 atoms polarized by metastable exchange optical pumping under an extremely weak magnetic field provide a traceable magnetic field value for the atomic magnetometer, the value is compared with the output response of the atomic magnetometer to obtain a calibrated scale factor of the atomic magnetometer, so that the measurement values of the atomic magnetometer are traceable. The atomic magnetometer meter head comprises four independent detection channels, the four detection channels are obtained by beam splitting of two detection lasers with different frequency detuning amounts, and the channels have high consistency. The method proposed by the application is compatible with the cooperative use of multiple probes, and can realize single-meter-head multi-channel measurement, meter-head internal magnetic field gradient measurement and meter-head inter-magnetic field gradient measurement three measurement modes, each mode has high consistency and high sensitivity.

NMR-based lithium measuring and monitoring downhole tools and methods measure at least one lithium concentration of a fluid in a borehole and / or a surrounding formation of the borehole, wherein the downhole tool has an NMR sensor having a magnet-coil geometry with at least one magnet and a RF coil tuned to match a Larmor frequency of a nucleus of lithium. The downhole tools and methods acquire an NMR-based lithium concentration measurement of a fluid at a sensitive region within the wellbore and / or formation that is defined by the magnet-coil geometry of the NMR sensor and determine a lithium concentration of the fluid at the sensitive region based on the acquired NMR-based lithium concentration measurement. The downhole tools and methods may interpret an acquired signal based on relaxation distributions of total acquired signals, wherein the acquired signal is indicative of the acquired NMR-based lithium concentration measurement and separate a lithium signal from confounding signals deriving from other non-lithium nuclei based on the interpretated acquired signal.

Provided are a photon up-conversion film, a photon up-conversion body, a laminate, and an energy conversion device, which are capable of high-efficiency up-conversion, and methods of producing the same. The photon up-conversion film according to an embodiment of the present invention includes a color-forming portion containing at least: a sensitizing component capable of absorbing light in a first wavelength region λ1; and a light-emitting component capable of radiating light in a second wavelength region λ2 including wavelengths shorter than those of the first wavelength region λ1. A relaxation time of the photon up-conversion film measured by a spin-echo method through use of time-domain nuclear magnetic resonance (pulse NMR) at 298 K is less than 210 ms.

This invention discloses a method and system for testing rock pore size distribution curves based on nuclear magnetic resonance (NMR) technology. The method includes: preprocessing the rock sample to be tested and obtaining the porosity and transverse relaxation time curves of the sample at room temperature and low temperature; obtaining the measured value of unfrozen water content by the ratio of low-temperature to room-temperature porosity, serving as an objective benchmark for verifying theoretical results; converting the room-temperature relaxation curve into a cumulative pore size distribution curve, fitting and extracting pore characteristic parameters, and substituting relevant characteristic parameters into a theoretical model to calculate the theoretical value of unfrozen water content; iteratively optimizing the transverse surface relaxation rate to ensure the deviation between the theoretical and measured values ​​meets accuracy requirements; establishing a precise correspondence between relaxation time and pore radius; and outputting the final pore size distribution curve. Each step is interconnected and mutually supportive, forming a complete logical closed loop. This provides reliable technical support for characterizing rock pore structure.

A method for generating magnetic resonance (MR) images of a subject includes performing, using a magnetic resonance imaging (MRI) system, a steady-state pulse sequence to acquire MR data from a region of interest in the subject. The steady-state pulse sequence includes a contrast-modifying (CM) radio frequency (RF) pulse applied periodically at a predetermined time interval followed by a gradient spoiler pulse. The CM RF pulse has a flip angle with a value determined based on a minimum Ernst angle for a set of one or more background tissues in the region of interest that the CM RF pulse is configured to suppress with respect to a tissue of interest. The method further includes generating an image with Ti contrast based on the acquired MR data.

Disclosed is a method for characterising a sample (E), said method comprising magnetically coupling the sample to a microwave resonator (RHS) such that the coupling dominates the relaxation dynamics of an electron spin (SEL) of a paramagnetic centre of the sample, and determining, by nuclear-magnetic-resonance spectroscopy, coefficients Cij of coupling between a nuclear spin of the sample, called the probe nuclear spin (SNi), and other nuclear spins (SNj, SNk) of the sample, said method employing indirect detection of a state of said probe nuclear spin (SNi), through counting of microwave photons, of respective noise signals (SBS) produced by the return to equilibrium of said electron spin (SEL). An apparatus for implementing such a method is also disclosed.

The present invention discloses a temperature measurement method under a complex excitation magnetic field of a two-dimensional magnetic nanoparticle imaging device, belonging to the field of nanomaterial testing technology. A magnetic nanometer temperature measurement method is proposed for the complex excitation magnetic field generated by the two-dimensional magnetic nanoparticle imaging device. Specifically, while utilizing the complex excitation signal to cause the magnetic nanoparticles to have a rich relationship between nonlinear magnetic susceptibility and temperature, the method also considers the influence of field strength and particle saturation magnetization on temperature measurement in actual two-dimensional MPI applications, establishes a compensation function, and provides a temperature measurement model when the dominant relaxation mechanism of the particles is Neel relaxation or Brownian relaxation. This realizes real-time temperature detection of magnetic nanoparticles on the two-dimensional magnetic nanoparticle imaging device, solving the problem that the current magnetic nanoparticle temperature measurement method cannot accurately measure temperature under the complex excitation magnetic field of the two-dimensional magnetic nanoparticle imaging device.

The application discloses a method for predicting the limited mass transfer efficiency of a two-dimensional separation membrane by using dielectric spectrum, comprising the following steps: S1, respectively measuring the dielectric spectrum of water in the two-dimensional separation membrane and a reference membrane in the range of 10 ‑3 ~ 10 3 Hz, calculating the dielectric relaxation time after obtaining the dielectric relaxation frequency; S2, judging the limited mass transfer efficiency of water in the two-dimensional separation membrane according to the dielectric relaxation time ratio τ / τ0 of the dielectric relaxation time τ of water in the two-dimensional separation membrane and the dielectric relaxation time τ0 of the reference membrane; when the τ / τ0 is less than 1, it is judged that the limited mass transfer efficiency of water in the two-dimensional separation membrane is higher than that of the reference membrane; when the τ / τ0 is greater than 1, it is judged that the limited mass transfer efficiency of water in the two-dimensional separation membrane is lower than that of the reference membrane. The method can accurately predict the limited mass transfer efficiency of different types of two-dimensional separation membranes, effectively reflect the state and relative transmission rate of water in the interlayer of the two-dimensional separation membrane, and provide technical support for the research on the high-efficiency separation two-dimensional membrane.

The embodiment of the invention provides a method for determining the oil extraction effect of a rock core, and belongs to the field of oil exploration. The method comprises the following steps: saturating a rock core by using saturated oil, analyzing the saturated rock core, and determining a first nuclear magnetic resonance spectrum curve corresponding to the saturated rock core; performing a huff-puff gas injection experiment on the saturated rock core, analyzing the rock core subjected to the huff-puff gas injection experiment, and determining a second nuclear magnetic resonance spectrum curve corresponding to the rock core subjected to the huff-puff gas injection experiment, wherein the first nuclear magnetic resonance spectrum curve and the second nuclear magnetic resonance spectrum curve represent the change of nuclear magnetic amplitude along with relaxation time; and determining the recovery efficiency of the rock core according to the first nuclear magnetic resonance spectrum curve and the second nuclear magnetic resonance spectrum curve. According to the method for determining the oil extraction effect of the core, the change condition of the oil content in the core can be observed in real time, and the calculation accuracy of the core recovery efficiency is improved.

Methods and systems herein may perform nuclear magnetic resonance measurements, and nuclear magnetic resonance tools, the method and systems comprising: acquiring, using an NMR sensor a first NMR signal from a volume in a subterranean region, wherein the first NMR signal is acquired using a first acquisition window. Further, acquiring, using the NMR sensor a second NMR signal from a volume in the subterranean region, wherein the second NMR signal is acquired using a second acquisition window different from the first acquisition window, wherein the first NMR signal and the second NMR signal form an NMR relaxation data; determining, using the first NMR signal and the second NMR signal, a correction term. Finally, the correction term may be used to acquire a corrected relaxation data set.