Three-dimensional nuclear magnetic resonance detection equipment, system and method

Abstract

The invention provides a three-dimensional nuclear magnetic resonance detection device, system and method, and relates to the technical field of porous cultural relic detection, the device comprises a frame structure, a nuclear magnetic resonance probe, a displacement module, an industrial control computer and an electron spectrometer module; the nuclear magnetic resonance probe is arranged on the displacement module and used for collecting nuclear magnetic resonance data of the porous cultural relics; the displacement module is arranged on the front side of the frame structure and is used for driving the nuclear magnetic resonance probe to move; the back side of the frame structure is provided with an industrial control computer and an electron spectrometer module, and the industrial control computer is electrically connected with the electron spectrometer module and used for sending out a control instruction and receiving, processing and displaying data; the electron spectrometer module is electrically connected with the nuclear magnetic resonance probe and the displacement module and used for sending instructions to the nuclear magnetic resonance probe and the displacement module and transmitting collected detection data to the industrial control computer. The weathering and erosion degrees in the range from the surface of the porous cultural relic to the shallow layer are quantitatively described, and data support is provided for later cultural relic protection and cultural relic restoration.

Description

Technical Field

[0001] The present invention relates to the technical field of porous cultural relics detection, and in particular to a three-dimensional nuclear magnetic resonance detection device, system and method. Background Art

[0002] Stone artifacts, brick artifacts, murals, oil paintings and other artifacts are all treasures in the material cultural heritage library [1]. They carry the cultural characteristics of various historical periods in a unique form and embody the wisdom and artistic achievements of the ancients. Stone artifacts, brick artifacts, murals and oil paintings are all porous artifacts containing various void structures. Common porous artifacts include: grotto artifacts, stele artifacts, brick and stone artifacts, mural artifacts, oil paintings and other artifacts. However, most porous artifacts are exposed to the outdoor environment and are therefore susceptible to degradation effects such as freezing and thawing, acid rain, and salt crystallization, which accelerates the aging and damage of porous artifacts, especially the damage to the surface of porous artifacts. The damage to the surface of porous artifacts corresponds to the drastic changes in the pore structure of porous materials. Therefore, by detecting the pore structure characteristics of different positions of porous artifacts, the degree of damage to porous artifacts can be quantitatively characterized and corresponding restoration and protection plans for the artifacts can be formulated.

[0003] Currently, common methods for characterizing the pore structure of porous cultural relics include resistivity, coring, and infrared thermal imaging. However, these methods all have certain drawbacks. The resistivity method is easily affected by conditions such as salt concentration and cracks within the cultural relic. The coring method is destructive to porous cultural relics and is suitable for porous cultural relics such as grottoes and masonry, but is not suitable for porous cultural relics with high cultural value, such as steles, murals, and oil paintings. Infrared thermal imaging has low detection accuracy and cannot provide high-precision quantitative data. Porous cultural relics are non-renewable and valuable, so a high-precision non-destructive testing technology is urgently needed for use in detecting and analyzing cultural relic diseases and evaluating the effectiveness of anti-weathering reinforcement of cultural relics, providing data support for later cultural relic protection and restoration. Summary of the Invention

[0004] The object of the present invention is to provide a three-dimensional nuclear magnetic resonance detection device, system and method to solve at least one of the above-mentioned technical problems existing in the prior art.

[0005] In a first aspect, to solve the above technical problems, the present invention provides a three-dimensional nuclear magnetic resonance detection device, comprising: a frame structure, a nuclear magnetic resonance probe, a displacement module, an industrial control computer and an electronic spectrometer module; The nuclear magnetic resonance probe is arranged on the displacement module and is used to collect nuclear magnetic resonance data of porous cultural relics; The displacement module is arranged at the front side of the frame structure, and is used to drive the nuclear magnetic resonance probe to move in the horizontal direction and / or vertical direction, move the nuclear magnetic resonance probe to the area of ​​the porous cultural relic to be measured, or drive the nuclear magnetic resonance probe to move according to a set displacement path, and then use the nuclear magnetic resonance probe to perform a partial or full scan of the surface or a certain depth profile of the porous cultural relic to be tested; A workbench is provided on the back side of the frame structure, the industrial control computer and the electronic spectrometer module are both provided on the workbench, the industrial control computer is electrically connected to the electronic spectrometer module, and the electronic spectrometer module is electrically connected to the nuclear magnetic resonance probe and the displacement module respectively; The industrial control computer is used to issue control instructions, and receive, process and display data; The electronic spectrometer module is used to transmit nuclear magnetic resonance pulses to the nuclear magnetic resonance probe, send displacement instructions to the displacement module, and transmit collected nuclear magnetic resonance data and displacement data to the industrial control computer.

[0006] During use, the industrial control computer is used for human-computer interaction, and the electronic spectrometer module sends a user-set displacement instruction to the displacement module to control the displacement module to drive the nuclear magnetic resonance probe to move in the horizontal direction and / or vertical direction and feed back displacement data to the industrial control computer. The electronic spectrometer module generates and emits nuclear magnetic resonance pulses according to the timing set by the user to control the nuclear magnetic resonance probe to excite nuclear magnetic resonance phenomena and receive nuclear magnetic resonance signals in the measurement area of ​​the porous cultural relics, so that the collected nuclear magnetic resonance data is transmitted to the industrial control computer through the electronic spectrometer module for signal processing and analysis to obtain the pore structure characteristics in the measurement area of ​​the porous cultural relics.

[0007] The present application sets a nuclear magnetic resonance probe on the displacement module on the front side of the frame structure, sets an industrial control computer and an electronic spectrometer module on the back side of the frame structure, uses the industrial control computer for human-computer interaction, and controls the displacement module through the electronic spectrometer module to drive the nuclear magnetic resonance probe to move precisely. It can realize the use of the nuclear magnetic resonance probe to perform nuclear magnetic resonance detection on different positions and different depth measurement areas of the porous cultural relics being tested in situ, or perform local or comprehensive nuclear magnetic resonance scanning on the surface or a certain depth profile of the porous cultural relics being tested, so as to non-destructively and quantitatively characterize the water content, porosity and pore size distribution of the porous cultural relics being tested based on the nuclear magnetic resonance data, and reflect the weathering depth, deterioration degree, reinforcement depth, reinforcement degree, mural craftsmanship and other defects of the porous cultural relics being tested based on the nuclear magnetic resonance data, thereby providing data support for the later protection and restoration of cultural relics.

[0008] Furthermore, the three-dimensional nuclear magnetic resonance detection equipment also includes an infrared distance sensor, which is arranged on the side of the nuclear magnetic resonance probe and electrically connected to the electronic spectrometer module, and is used to measure the distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic being detected. The measured distance data is transmitted to the industrial control computer through the electronic spectrometer module to prevent the nuclear magnetic resonance probe from being too close to the surface of the porous cultural relic being detected, thereby preventing the nuclear magnetic resonance probe from damaging the porous cultural relic during the measurement process. The infrared ranging sensor is calibrated. After the calibration, the distance data measured when the nuclear magnetic resonance probe contacts the surface of the porous cultural relic being detected is 0. When the measured distance data is less than 2 mm, the measured distance data is transmitted to the industrial control computer through the electronic spectrometer module. The industrial control computer prompts a warning message to the user and stops measuring, thereby protecting the porous cultural relic and preventing the nuclear magnetic resonance probe from colliding with the porous cultural relic being detected.

[0009] Furthermore, the nuclear magnetic resonance probe is a unilateral nuclear magnetic resonance probe, and the nuclear magnetic resonance probe includes: a base, a solenoid coil and four magnets; The four magnets are arranged in a "T" shape on the base, with the measuring ends of the two magnets on one side (i.e., the ends facing away from the base) being S poles, and the measuring ends of the two magnets on the other side being N poles, so that the four magnets can jointly generate a static magnetic field; The solenoid coil is arranged on the surface of the measuring ends of the four magnets, and is used to generate a radio frequency magnetic field through the four magnets in cooperation with the solenoid coil, thereby exciting and receiving nuclear magnetic resonance signals in the measurement area of ​​the porous cultural relic. The received nuclear magnetic resonance signals are transmitted to the industrial control computer through the electronic spectrometer module for signal processing and analysis, thereby obtaining nuclear magnetic resonance data of the measurement area of ​​the porous cultural relic.

[0010] Preferably, the size of the nuclear magnetic resonance probe is 250mm*250mm*200mm (i.e., the horizontal length is 250mm, the vertical length is 250mm, and the depth length is 200mm), the weight is 40kg, and the operating frequency is 18MHz; During measurement, the measuring end surface of the nuclear magnetic resonance probe is placed against the surface of the porous cultural relic to be tested, and the nuclear magnetic resonance data within the range from the surface of the porous cultural relic to a depth of 25 mm is measured by the nuclear magnetic resonance probe. The single measurement area of ​​the nuclear magnetic resonance probe is a porous cultural relic thin layer of 40 mm * 40 mm * 0.1 mm (i.e., the length in the horizontal direction is 40 mm, the length in the vertical direction is 40 mm, and the length in the depth direction is 0.1 mm).

[0011] Furthermore, the displacement module includes: a horizontal displacement linear module and a vertical displacement linear module; The horizontal displacement linear module is arranged at the bottom of the frame structure, the vertical displacement linear module is vertically arranged on the horizontal displacement linear module, a vertical sliding seat is provided on the vertical displacement linear module, the vertical sliding seat is slidably arranged on the vertical displacement linear module, and the nuclear magnetic resonance probe is mounted on the vertical sliding seat, and is used to drive the nuclear magnetic resonance probe to move in the vertical direction through the vertical sliding seat; The horizontal displacement linear module is provided with a horizontal sliding seat, which is slidably provided on the horizontal displacement linear module. The vertical displacement linear module is vertically installed on the horizontal sliding seat, and is used to drive the vertical displacement linear module to move in the horizontal direction through the horizontal sliding seat, thereby driving the nuclear magnetic resonance probe to move in the horizontal direction; During use, the user sets the horizontal and / or vertical displacement data through the industrial control computer, and the industrial control computer sends a displacement instruction corresponding to the displacement data to the displacement module through the electronic spectrometer module, controlling the horizontal displacement linear module and / or the vertical displacement linear module to drive the nuclear magnetic resonance probe to move according to the displacement path set by the user, thereby achieving partial or comprehensive scanning of the surface of the porous cultural relic being detected or a certain depth profile.

[0012] Furthermore, the horizontal displacement linear module and the vertical displacement linear module both include: a slide rail, a slide seat, a transmission mechanism and a motor; The sliding seat is slidably arranged on the slide rail, and the sliding seats of the horizontal displacement linear module and the vertical displacement linear module are the horizontal sliding seat and the vertical sliding seat respectively; The output shaft of the motor is connected to the active member of the transmission mechanism, and the transmission member of the transmission mechanism is connected to the sliding seat, so as to drive the transmission mechanism through the motor, thereby driving the sliding seat to slide on the slide rail.

[0013] Preferably, the transmission mechanism is a synchronous belt mechanism, which consists of a synchronous belt, a driving synchronous wheel and a driven synchronous wheel; The synchronous belt is sleeved on the active synchronous wheel and the driven synchronous wheel, and the synchronous belt is meshed with the active synchronous wheel and the driven synchronous wheel respectively; The active synchronous wheel is an active component, and the output shaft of the motor is connected to the active synchronous wheel, which is used to drive the active synchronous wheel to rotate, thereby driving the synchronous belt and the driven synchronous wheel to rotate; The synchronous belt is a transmission member, and the synchronous belt is connected to the sliding seat and is used to drive the sliding seat to slide on the slide rail.

[0014] Preferably, the maximum stroke of the horizontal displacement linear module and the vertical displacement linear module is 1000 mm[2], and the displacement accuracy is 0.1 mm.

[0015] Preferably, a horizontal track is provided above the frame structure, and the top of the vertical displacement linear module is slidably mounted on the horizontal track. The top of the vertical displacement linear module is mounted on the horizontal sliding seat for the vertical displacement linear module to slide in the horizontal direction [3].

[0016] Preferably, a plurality of universal wheels are provided at the bottom of the frame structure for moving the frame structure; when in use, the frame structure is moved to the original position of the porous cultural relic by the universal wheels, the front side of the frame structure faces the porous cultural relic to be inspected, and the frame structure is moved along the depth direction to adjust the distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic to be inspected.

[0017] Furthermore, four foot cups are respectively provided at the four corners of the bottom of the frame structure for fixing and leveling the frame structure.

[0018] In a second aspect, based on the same inventive concept, the present invention provides a three-dimensional nuclear magnetic resonance detection system, which is applied to the industrial control computer of the three-dimensional nuclear magnetic resonance detection equipment described above, comprising: a nuclear magnetic resonance detection module, a displacement control module, an infrared ranging module, an inversion processing module, and a result generation module; The displacement control module includes a displacement parameter setting unit for setting the displacement parameters of the nuclear magnetic resonance probe; The displacement parameters include the displacement step length and number of the nuclear magnetic resonance probe in the horizontal direction and the vertical direction, and the measurement depth step length and number of the nuclear magnetic resonance probe in the depth direction; The displacement control module is used to issue displacement instructions according to set displacement parameters and receive displacement data; The electronic spectrometer module sends a displacement instruction to the displacement module and the nuclear magnetic resonance probe, controls the displacement module to drive the nuclear magnetic resonance probe to move according to the path set in the diagram, and controls the nuclear magnetic resonance probe to stimulate the nuclear magnetic resonance signal according to the set depth, so as to achieve a comprehensive and detailed scan of the surface and shallow layer of the porous cultural relics being inspected, avoiding missing micro-pore structures; The displacement data of the nuclear magnetic resonance probe is transmitted to the displacement control module through the electronic spectrometer module to obtain the position information of each measurement area and the number of measurement areas; The nuclear magnetic resonance detection module includes a nuclear magnetic resonance parameter setting unit for setting nuclear magnetic resonance parameters; The NMR parameters include: operating frequency, echo interval, waiting time, number of scans, number of echoes and other basic NMR parameters. Different porous cultural relics have different materials and pore structures. The NMR parameters need to be specifically adjusted according to the type of porous cultural relics to ensure the accuracy of the detection. The NMR detection module is used to issue NMR detection instructions according to set NMR parameters and receive NMR data; The electronic spectrometer module generates and emits nuclear magnetic resonance pulses according to a user-set timing to control the nuclear magnetic resonance probe to excite nuclear magnetic resonance phenomena and receive nuclear magnetic resonance signals within a measurement area of ​​the porous cultural relic, and transmits the collected nuclear magnetic resonance data to the nuclear magnetic resonance detection module through the electronic spectrometer module; The infrared ranging module includes a distance parameter setting unit for setting a safety distance parameter; The safety distance parameter is the minimum safety distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic being detected, and the safety distance parameter is usually set to 2 mm by default; The infrared ranging module is used to issue infrared ranging instructions according to the set safety distance parameters, and receive distance data. When the received distance data is less than the safety distance parameters, it will issue an alarm prompt and stop issuing displacement instructions and nuclear magnetic resonance detection instructions. The infrared ranging instruction is sent to the infrared ranging sensor through the electronic spectrometer module, and the infrared ranging sensor is controlled to continuously monitor the distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic being detected during the nuclear magnetic resonance detection process. The collected distance data is transmitted to the infrared ranging module through the electronic spectrometer module, and the distance data is compared with the safety distance parameter to determine whether the nuclear magnetic resonance probe will collide with the porous cultural relic being detected. When the received distance data is less than the safety distance parameter, an alarm is issued, and the nuclear magnetic resonance probe stops moving and measuring, thereby preventing the nuclear magnetic resonance probe from colliding and damaging the plane cultural relic being detected, effectively protecting the integrity of the surface of the plane cultural relic being detected, and ensuring that the detection is safe and reliable. The inversion processing module is provided with an inversion algorithm selection unit for selecting an inversion algorithm preset in the inversion processing module; The preset inversion algorithms include single exponential fitting algorithm, double exponential fitting algorithm, and inverse Laplace transform algorithm. Different porous cultural relics have different materials and pore structures. The appropriate inversion algorithm is selected according to the type of porous cultural relics to ensure the accuracy of the inversion processing; The inversion processing module is used to receive the nuclear magnetic resonance data and perform inversion processing on the nuclear magnetic resonance data according to a selected inversion algorithm; The nuclear magnetic resonance data of the measurement area is sent to the inversion processing module through the nuclear magnetic resonance detection module. The inversion processing module uses an inversion algorithm to convert the nuclear magnetic resonance data of the measurement area from nuclear magnetic resonance time domain signals to transverse relaxation time signals, and then quantitatively characterizes the moisture content, porosity, and pore size distribution in the measurement area of ​​the porous cultural relic through the transverse relaxation time signals, reflecting the weathering depth, deterioration degree, reinforcement depth, reinforcement degree, mural craftsmanship and other defects in the measurement area of ​​the porous cultural relic; The result generation module is used to generate a three-dimensional pore structure distribution map of the detected porous cultural relics based on the transverse relaxation time signal and displacement data; A comprehensive scan is performed on the surface and shallow layer of the porous cultural relic to be inspected. After each measurement of a measurement area is completed, the transverse relaxation time signal and the corresponding position information of the measurement area are sent to the result generation module through the inversion processing module and the displacement control module respectively. The transverse relaxation time signal and the corresponding position information of the measurement area are stored in the three-dimensional pore structure distribution map through the result generation module. After all the measurement areas of the porous cultural relic to be inspected are measured, the three-dimensional pore structure distribution map of the porous cultural relic to be inspected is completed.

[0019] In a third aspect, based on the same inventive concept, the present invention provides a three-dimensional nuclear magnetic resonance detection method using the above-mentioned device, comprising: Step 1: Install the three-dimensional nuclear magnetic resonance detection equipment and level the three-dimensional nuclear magnetic resonance detection equipment in a horizontal direction; At the inspection site, the three-dimensional nuclear magnetic resonance inspection device is installed and moved in front of the porous cultural relic to be inspected. The foot cup is adjusted to level the three-dimensional nuclear magnetic resonance inspection device in the horizontal direction to ensure the movement accuracy of the displacement module and the safety of the equipment operation; Step 2: Set the NMR parameters; According to the type of porous cultural relics to be inspected, appropriate NMR parameters are input through the industrial control computer; The NMR parameters include basic NMR parameters such as operating frequency, echo interval, waiting time, number of scans, and number of echoes. Different porous cultural relics have different materials and pore structures. The NMR parameters need to be specifically adjusted according to the type of porous cultural relics being tested to ensure the accuracy of the test. Step 3: setting the number and step length of the NMR probe in the horizontal direction (i.e., the displacement direction of the NMR probe along the horizontal displacement linear module), the vertical direction (i.e., the displacement direction of the NMR probe along the vertical displacement linear module), and the depth direction (i.e., the depth direction of the NMR probe detecting porous cultural relics); The maximum horizontal movement distance of the nuclear magnetic resonance probe is no more than 1000 mm, that is, x*Lx≤1000 mm; Wherein, x is the number of displacement steps of the nuclear magnetic resonance probe in the horizontal direction, and Lx is the displacement step length of the nuclear magnetic resonance probe in the horizontal direction; The maximum vertical movement distance of the nuclear magnetic resonance probe is no more than 1000 mm, that is, y*Ly≤1000 mm; Wherein, y is the number of displacement steps of the NMR probe in the vertical direction, and Ly is the displacement step length of the NMR probe in the vertical direction; The maximum measuring depth of the nuclear magnetic resonance probe in the longitudinal direction is not greater than 25 mm, that is, z*Lz≤25 mm; Wherein, z is the number of depth steps of the NMR probe along the depth direction, and Lz is the depth step length of the NMR probe along the depth direction; Step 4: measuring the porous cultural relic to be detected by the nuclear magnetic resonance probe; Clicking the start measurement button on the industrial computer controls the three-dimensional nuclear magnetic resonance detection device to automatically start measurement.

[0020] Step 5: Measure the distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic to be inspected by an infrared ranging sensor, and compare it with a preset safety distance parameter (the default safety distance parameter is 2 mm); When the distance data is greater than the safety distance parameter, the industrial control computer sends a nuclear magnetic resonance detection instruction to the nuclear magnetic resonance probe through the electronic spectrometer module, controls the nuclear magnetic resonance probe to perform a single measurement on a measurement area of ​​the porous cultural relic to be detected, and collects the nuclear magnetic resonance data collected by the single measurement; When the distance data is less than the safety distance parameter, the industrial control computer issues an alarm and controls the nuclear magnetic resonance probe to stop moving and measuring; Step 6: Receive the collected NMR data of the measurement area of ​​the porous cultural relic to be detected, and make a judgment based on the inversion algorithm selected by the user; The available inversion algorithms include exponential fitting algorithm and inverse Laplace transform algorithm, among which the exponential fitting algorithm includes single exponential fitting algorithm and double exponential fitting algorithm; Inversion processing refers to the use of an inversion algorithm to convert the collected NMR signal from a time domain signal with multi-exponential decay to a transverse relaxation time signal that can invert the pore structure distribution; Step 7: storing the acquired transverse relaxation time signal of the measurement area of ​​the porous cultural relic under inspection and the position data of the corresponding measurement area into the three-dimensional pore structure distribution map; The transverse relaxation time signal of the measured area of ​​the porous cultural relics under inspection can reflect the pore structure characteristics in the measured area; Step 8: Control the nuclear magnetic resonance detection probe to scan each measurement area of ​​the porous cultural relic to be detected in the order of priority in the depth direction, the horizontal direction, and the vertical direction, and store the inverted nuclear magnetic resonance data and corresponding position data of each measurement area of ​​the porous cultural relic to be detected in the three-dimensional pore structure distribution map in sequence.

[0021] Furthermore, the specific formula of the inverse Laplace transform algorithm is:

[0022] in, is the transverse relaxation time signal distribution function of the pore structure components in the measurement area of ​​the porous cultural relics being detected, The NMR signal of the pore structure components in the measurement area of ​​the porous cultural relics under inspection is collected over time. The decay function of For the detection time, is the transverse relaxation time to be solved, is the weighting function, is the regularization parameter, The first porous cultural relic to be tested The transverse relaxation time signal distribution function of the pore structure components in the measurement area; The weighting function According to the characteristics of the NMR signal of the measuring area of ​​the porous cultural relics to be detected, the NMR signal starting section (i.e. When the value is small, a high weight is set to highlight the early NMR signal characteristics, because the early NMR signal usually contains high-frequency information of the pore structure in the measurement area of ​​the porous artifacts being detected; the weight is appropriately reduced in the later stage of NMR signal attenuation to reduce the influence of noise; The regularization parameter The regularization parameter is used to balance the data fitting accuracy and the stability of the solution. It needs to be optimized through multiple experiments and is critical for processing noisy NMR signals to prevent overfitting.

[0023] Furthermore, the exponential fitting algorithm includes: Step 61: Assuming that the collected nuclear magnetic resonance signal of the measuring area of ​​the porous cultural relic is detected, the specific formula is:

[0024] in, The NMR signal of the pore structure components in the measurement area of ​​the porous cultural relics under inspection is collected over time. The decay function of The first porous cultural relic to be tested The NMR signal amplitude of the pore structure components in the measurement area, is the total number of measurement areas, For the detection time, The first porous cultural relic to be tested transverse relaxation time of the pore structure components within a measurement area; Step 62: Calculate the fitting error and compare the calculated fitting error with the preset fitting error parameter range to evaluate the fitting quality. Iterate the fitting multiple times according to the fitting quality to approach the global optimal solution, so as to accurately determine the and ; The specific formula for calculating the fitting error is:

[0025] Where E is the fitting error; During the fitting process, if the error is large, the simulated annealing strategy is used to accept inferior solutions with a certain probability to broaden the search range, jump out of the local optimum, and approach the global optimal solution through multiple iterations to accurately determine the optimal solution. and .

[0026] By adopting the above technical solution, the present invention has the following beneficial effects: The present invention provides a three-dimensional nuclear magnetic resonance detection device, system and method, which realizes the use of a nuclear magnetic resonance probe to perform nuclear magnetic resonance detection on different positions and different depth measurement areas of porous cultural relics in situ, or to perform local or comprehensive nuclear magnetic resonance scanning on the surface or a certain depth profile of the porous cultural relics being detected, so as to non-destructively and quantitatively characterize the moisture content, porosity and pore size distribution of the porous cultural relics being detected based on the nuclear magnetic resonance data, and reflect the weathering depth, deterioration degree, reinforcement depth, reinforcement degree, mural painting craftsmanship and other defects of the porous cultural relics being detected based on the nuclear magnetic resonance data, thereby providing data support for the later protection and restoration of cultural relics. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 A schematic diagram of the front structure of a three-dimensional nuclear magnetic resonance detection device provided by an embodiment of the present invention; Figure 2 for Figure 1 The back side structural diagram of the three-dimensional nuclear magnetic resonance detection device shown; Figure 3 for Figure 1 Schematic diagram of the magnet structure inside the nuclear magnetic resonance probe shown; Figure 4 A flow chart of a three-dimensional nuclear magnetic resonance detection method provided by an embodiment of the present invention; Figure 5 A schematic diagram of the division of the measurement area on the sample surface of the porous cultural relic to be inspected provided in an embodiment of the present invention; Figure 6 A moisture content diagram of the porous cultural relics under inspection provided by an embodiment of the present invention; Figure 7 A full-plane moisture content map of the inspected porous cultural relic provided by an embodiment of the present invention; Figure 8 The embodiment of the present invention provides a pore structure distribution diagram of nine measurement areas along the depth direction at the same location of the inspected porous cultural relic.

[0029] Reference numerals: 1-Horizontal displacement linear module; 11-Horizontal sliding seat; 2-Vertical displacement linear module; 21-Vertical sliding seat; 3-NMR probe; 4-Horizontal track; 5-Workbench; 6-Electron spectrometer module; 7-Universal wheel; 8-Foot cup. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0033] The present invention will be further explained below with reference to specific embodiments.

[0034] It should also be noted that the following specific embodiments or specific implementations are a series of optimized settings listed in the present invention to further explain the specific content of the invention, and these settings can be combined or used in association with each other.

[0035] Example 1 like Figure 1-3 As shown, a three-dimensional nuclear magnetic resonance detection device provided in this embodiment includes: a frame structure, a nuclear magnetic resonance probe 3, a displacement module, an industrial control computer and an electronic spectrometer module 6; The NMR probe 3 is arranged on the displacement module and is used to collect NMR data of porous cultural relics; The displacement module is arranged at the front side of the frame structure, and is used to drive the NMR probe 3 to move in the horizontal direction and / or vertical direction, so as to move the NMR probe 3 to the area of ​​the porous cultural relic to be measured, or to drive the NMR probe 3 to move along a set displacement path, thereby performing a partial or full scan of the surface or a certain depth profile of the porous cultural relic to be measured through the NMR probe 3; A workbench 5 is provided on the back side of the frame structure, on which the industrial control computer and the electronic spectrometer module 6 are both provided. The industrial control computer is electrically connected to the electronic spectrometer module 6 via a data line, and the electronic spectrometer module 6 is electrically connected to the nuclear magnetic resonance probe 3 and the displacement module via data lines, respectively. The industrial control computer is used to issue control instructions, and receive, process and display data; The electronic spectrometer module 6 is used to transmit nuclear magnetic resonance pulses to the nuclear magnetic resonance probe 3, send displacement instructions to the displacement module, and transmit the collected nuclear magnetic resonance data and displacement data to the industrial control computer.

[0036] During use, the industrial control computer is used for human-computer interaction, and the electronic spectrometer module 6 sends a user-set displacement instruction to the displacement module to control the displacement module to drive the nuclear magnetic resonance probe 3 to move horizontally and / or vertically and feedback displacement data to the industrial control computer, and the electronic spectrometer module 6 generates and emits nuclear magnetic resonance pulses according to the timing set by the user to control the nuclear magnetic resonance probe 3 to excite nuclear magnetic resonance phenomena and receive nuclear magnetic resonance signals within the measurement area of ​​the porous cultural relics, so that the collected nuclear magnetic resonance data is transmitted to the industrial control computer through the electronic spectrometer module 6 for signal processing and analysis to obtain the pore structure characteristics within the measurement area of ​​the porous cultural relics.

[0037] The present application sets a nuclear magnetic resonance probe 3 on the displacement module on the front side of the frame structure, sets an industrial control computer and an electronic spectrometer module 6 on the back side of the frame structure, uses the industrial control computer for human-computer interaction, and controls the displacement module through the electronic spectrometer module 6 to drive the nuclear magnetic resonance probe 3 to move precisely. It can realize the use of the nuclear magnetic resonance probe 3 to perform nuclear magnetic resonance detection on different positions and different depth measurement areas of the porous cultural relics to be detected in situ, or perform local or comprehensive nuclear magnetic resonance scanning on the surface or a certain depth profile of the porous cultural relics to be detected, so as to perform non-destructive and quantitative characterization of the water content, porosity and pore size distribution of the porous cultural relics to be detected based on the nuclear magnetic resonance data, and reflect the weathering depth, deterioration degree, reinforcement depth, reinforcement degree, mural craftsmanship and other defects of the porous cultural relics to be detected based on the nuclear magnetic resonance data, providing data support for the later protection and restoration of cultural relics.

[0038] On the basis of the above technical solution, the three-dimensional nuclear magnetic resonance detection equipment further includes an infrared distance measuring sensor, which is arranged on the side of the nuclear magnetic resonance probe 3 and electrically connected to the electronic spectrometer module 6, and is used to measure the distance between the nuclear magnetic resonance probe 3 and the surface of the porous cultural relic being detected. The measured distance data is transmitted to the industrial control computer through the electronic spectrometer module 6 to prevent the nuclear magnetic resonance probe 3 from being too close to the surface of the porous cultural relic being detected, thereby preventing the nuclear magnetic resonance probe 3 from damaging the porous cultural relic being detected during the measurement process. The infrared ranging sensor is calibrated. After calibration, the distance data measured when the nuclear magnetic resonance probe 3 contacts the surface of the porous cultural relic being detected is 0. When the measured distance data is less than 2 mm, the measured distance data is transmitted to the industrial control computer through the electronic spectrometer module 6. The industrial control computer prompts a warning message to the user and stops measuring, thereby protecting the porous cultural relic and preventing the nuclear magnetic resonance probe 3 from colliding with the porous cultural relic being detected.

[0039] Reference Figure 3As shown, further, the nuclear magnetic resonance probe 3 is a unilateral nuclear magnetic resonance probe 3, and the nuclear magnetic resonance probe 3 includes: a base, a solenoid coil and four magnets; The four magnets are arranged in a field shape on the base, the measuring ends of the two magnets on one side (ie, the end away from the base) are S poles, and the measuring ends of the two magnets on the other side are N poles, for generating a static magnetic field together by the four magnets; The solenoid coil is disposed on the surface of the four measuring ends of the magnets, and is used to generate a radio frequency magnetic field through the four magnets in conjunction with the solenoid coil, thereby exciting and receiving nuclear magnetic resonance signals within the measurement area of ​​the porous cultural relic. The received nuclear magnetic resonance signals are transmitted to the industrial control computer through the electronic spectrometer module 6 for signal processing and analysis to obtain the pore structure characteristics within the measurement area of ​​the porous cultural relic; The static magnetic field is usually given by It indicates that the static magnetic field is provided by four magnets arranged in a field shape, which is one of the necessary conditions for exciting the nuclear magnetic resonance phenomenon. When the porous cultural relics to be detected are placed in the static magnetic field, energy level splitting occurs in the spin system, and a macroscopic magnetization vector is generated along the direction of the static magnetic field. , Determined by parameters such as the static magnetic field strength; RF magnetic fields are usually generated by It means that the radio frequency pulse is an electromagnetic signal generated by the solenoid coil. The magnetic field generated by the radio frequency pulse is a radio frequency magnetic field, which is another necessary condition for exciting the nuclear magnetic resonance phenomenon. The direction of the radio frequency magnetic field is perpendicular to the direction of the static magnetic field.

[0040] More preferably, the size of the MRI probe 3 is 250 mm * 250 mm * 200 mm (i.e., the horizontal length is 250 mm, the vertical length is 250 mm, and the depth length is 200 mm), the weight is 40 kg, and the operating frequency is 18 MHz; During measurement, the measuring end surface of the nuclear magnetic resonance probe 3 is placed against the surface of the porous cultural relic to be inspected, and the pore structure characteristics within the range from the surface of the porous cultural relic to a depth of 25 mm are measured by the nuclear magnetic resonance probe 3. The single measurement area of ​​the nuclear magnetic resonance probe 3 is a thin layer of porous cultural relic with a length of 40 mm*40 mm*0.1 mm (i.e., a length of 40 mm in the horizontal direction, 40 mm in the vertical direction, and a length of 0.1 mm in the depth direction).

[0041] Reference Figure 1 As shown, further, the displacement module includes: a horizontal displacement linear module 1 and a vertical displacement linear module 2; The horizontal displacement linear module 1 is arranged at the bottom of the frame structure, the vertical displacement linear module 2 is vertically arranged on the horizontal displacement linear module 1, and a vertical sliding seat 21 is provided on the vertical displacement linear module 2. The vertical sliding seat 21 is slidably arranged on the vertical displacement linear module 2, and the nuclear magnetic resonance probe 3 is installed on the vertical sliding seat 21, and is used to drive the nuclear magnetic resonance probe 3 to move in the vertical direction through the vertical sliding seat 21; The horizontal displacement linear module 1 is provided with a horizontal sliding seat 11, and the horizontal sliding seat 11 is slidably provided on the horizontal displacement linear module 1. The vertical displacement linear module 2 is vertically installed on the horizontal sliding seat 11, and is used to drive the vertical displacement linear module 2 to move in the horizontal direction through the horizontal sliding seat 11, thereby driving the nuclear magnetic resonance probe 3 to move in the horizontal direction; During use, the user sets the horizontal and / or vertical displacement data through the industrial control computer, and the industrial control computer sends a displacement instruction corresponding to the displacement data to the displacement module through the electronic spectrometer module 6, controls the horizontal displacement linear module 1 and / or the vertical displacement linear module 2 to drive the nuclear magnetic resonance probe 3 to move according to the displacement path set by the user, thereby realizing a partial or full scan of the surface of the porous cultural relic being detected or a certain depth profile.

[0042] More preferably, the horizontal displacement linear module 1 and the vertical displacement linear module 2 both include: a slide rail, a slide seat, a transmission mechanism and a motor; The sliding seat is slidably disposed on the slide rail, and the sliding seats of the horizontal displacement linear module 1 and the vertical displacement linear module 2 are the horizontal sliding seat 11 and the vertical sliding seat 21 respectively; The output shaft of the motor is connected to the active member of the transmission mechanism, and the transmission member of the transmission mechanism is connected to the sliding seat, so as to drive the transmission mechanism through the motor, thereby driving the sliding seat to slide on the slide rail. Preferably, the transmission mechanism is a synchronous belt mechanism, which is composed of a synchronous belt, an active synchronous wheel and a driven synchronous wheel [4]; The synchronous belt is sleeved on the active synchronous wheel and the driven synchronous wheel, and the synchronous belt is meshed with the active synchronous wheel and the driven synchronous wheel respectively; The active synchronous wheel is an active component, and the output shaft of the motor is connected to the active synchronous wheel, which is used to drive the active synchronous wheel to rotate, thereby driving the synchronous belt and the driven synchronous wheel to rotate; The synchronous belt is a transmission member, and the synchronous belt is connected to the sliding seat and is used to drive the sliding seat to slide on the slide rail.

[0043] In this embodiment, the maximum stroke of the horizontal displacement linear module 1 and the vertical displacement linear module 2 is 1000 mm, and the displacement accuracy is 0.1 mm.

[0044] More preferably, a horizontal track 4 is provided above the frame structure, and the top of the vertical displacement linear module 2 is slidably mounted on the horizontal track 4, and the top of the vertical displacement linear module 2 is mounted on the horizontal sliding seat 11 for the vertical displacement linear module 2 to slide in the horizontal direction.

[0045] Furthermore, the industrial control computer includes a processor, a memory and a bus. The memory stores instructions and data read by the processor. The processor is used to call the instructions and data in the memory to send nuclear magnetic resonance detection instructions to the nuclear magnetic resonance probe 3, send displacement instructions to the displacement module, send infrared ranging instructions to the infrared ranging sensor and other instructions and parameter data according to user settings, and receive various detection data. The bus connects the various functional components for transmitting information.

[0046] Reference Figure 2 As shown, further, a plurality of universal wheels 7 are provided at the bottom of the frame structure for moving the frame structure; when in use, the frame structure is moved to the location of the porous cultural relics via the universal wheels 7, with the front side of the frame structure facing the porous cultural relics to be inspected, and the frame structure is moved in the depth direction to adjust the distance between the nuclear magnetic resonance probe 3 and the surface of the porous cultural relics to be inspected.

[0047] Furthermore, four foot cups 8 are respectively provided at the four corners of the bottom of the frame structure for fixing and leveling the frame structure.

[0048] The present invention realizes the use of a nuclear magnetic resonance probe 3 to perform nuclear magnetic resonance detection on different positions and different depth measurement areas of a porous cultural relic in situ, or to perform local or comprehensive nuclear magnetic resonance scanning on the surface or a certain depth profile of the porous cultural relic being detected, thereby non-destructively and quantitatively characterizing the moisture content, porosity and pore size distribution of the porous cultural relic being detected based on the nuclear magnetic resonance data, and reflecting the weathering depth, deterioration degree, reinforcement depth, reinforcement degree, mural painting craftsmanship and other defects of the porous cultural relic being detected based on the nuclear magnetic resonance data, thereby providing data support for later cultural relic protection and cultural relic restoration.

[0049] Example 2 This embodiment provides a three-dimensional nuclear magnetic resonance detection system, which is applied to the industrial control computer of the three-dimensional nuclear magnetic resonance detection equipment described above, including: a nuclear magnetic resonance detection module, a displacement control module, an infrared ranging module, an inversion processing module, and a result generation module; The displacement control module includes a displacement parameter setting unit for setting the displacement parameters of the nuclear magnetic resonance probe; The displacement parameters include the displacement step length and number of the nuclear magnetic resonance probe in the horizontal direction and the vertical direction, and the measurement depth step length and number of the nuclear magnetic resonance probe in the depth direction; The displacement control module is used to issue displacement instructions according to set displacement parameters and receive displacement data; The electronic spectrometer module sends a displacement instruction to the displacement module and the nuclear magnetic resonance probe, controls the displacement module to drive the nuclear magnetic resonance probe to move according to the path set in the diagram, and controls the nuclear magnetic resonance probe to stimulate the nuclear magnetic resonance signal according to the set depth, so as to achieve a comprehensive and detailed scan of the surface and shallow layer of the porous cultural relics being inspected, avoiding missing micro-pore structures; The displacement data of the nuclear magnetic resonance probe is transmitted to the displacement control module through the electronic spectrometer module to obtain the position information of each measurement area and the number of measurement areas [5]; The NMR detection module includes a NMR parameter setting unit for setting NMR parameters; The NMR parameters include: operating frequency, echo interval, waiting time, number of scans, number of echoes and other basic NMR parameters. Different porous cultural relics have different materials and pore structures. The NMR parameters need to be specifically adjusted according to the type of porous cultural relics to ensure the accuracy of the detection. The NMR detection module is used to issue NMR detection instructions according to set NMR parameters and receive NMR data; The electronic spectrometer module generates and emits nuclear magnetic resonance pulses according to a user-set timing to control the nuclear magnetic resonance probe to excite nuclear magnetic resonance phenomena and receive nuclear magnetic resonance signals within a measurement area of ​​the porous cultural relic, and transmits the collected nuclear magnetic resonance data to the nuclear magnetic resonance detection module through the electronic spectrometer module; The infrared ranging module includes a distance parameter setting unit for setting a safety distance parameter; The safety distance parameter is the minimum safety distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic being detected, and the safety distance parameter is usually set to 2 mm by default; The infrared ranging module is used to issue infrared ranging instructions according to the set safety distance parameters, and receive distance data. When the received distance data is less than the safety distance parameters, it will issue an alarm prompt and stop issuing displacement instructions and nuclear magnetic resonance detection instructions. The infrared distance measurement instruction is sent to the infrared distance measurement sensor through the electronic spectrometer module, and the infrared distance measurement sensor is controlled to continuously monitor the distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic to be detected during the nuclear magnetic resonance detection process, and the distance data collected is transmitted to the infrared distance measurement module [6] through the electronic spectrometer module, and the distance data is compared with the safety distance parameter to determine whether the nuclear magnetic resonance probe will collide with the porous cultural relic to be detected; when the received distance data is less than the safety distance parameter, an alarm is issued, and the nuclear magnetic resonance probe stops moving and measuring, so as to prevent the nuclear magnetic resonance probe from colliding and damaging the plane cultural relic to be detected, effectively protect the integrity of the surface of the plane cultural relic to be detected, and ensure that the detection is safe and reliable; The inversion processing module is provided with an inversion algorithm selection unit for selecting an inversion algorithm preset in the inversion processing module; The preset inversion algorithms include single exponential fitting algorithm, double exponential fitting algorithm, and inverse Laplace transform algorithm. Different porous cultural relics have different materials and pore structures. The appropriate inversion algorithm is selected according to the type of porous cultural relics to ensure the accuracy of the inversion processing; The inversion processing module is used to receive the nuclear magnetic resonance data and perform inversion processing on the nuclear magnetic resonance data according to a selected inversion algorithm; The nuclear magnetic resonance data of the measurement area is sent to the inversion processing module through the nuclear magnetic resonance detection module. The inversion processing module uses an inversion algorithm to convert the nuclear magnetic resonance data of the measurement area from nuclear magnetic resonance time domain signals to transverse relaxation time signals, and then quantitatively characterizes the moisture content, porosity, and pore size distribution in the measurement area of ​​the porous cultural relic through the transverse relaxation time signals, reflecting the weathering depth, deterioration degree, reinforcement depth, reinforcement degree, mural craftsmanship and other defects in the measurement area of ​​the porous cultural relic; The result generation module is used to generate a three-dimensional pore structure distribution map of the detected porous cultural relics based on the transverse relaxation time signal and displacement data; A comprehensive scan is performed on the surface and shallow layer of the porous cultural relic to be inspected. After each measurement of a measurement area is completed, the transverse relaxation time signal and the corresponding position information of the measurement area are sent to the result generation module through the inversion processing module and the displacement control module respectively. The transverse relaxation time signal and the corresponding position information of the measurement area are stored in the three-dimensional pore structure distribution map through the result generation module. After all the measurement areas of the porous cultural relic to be inspected are measured, the three-dimensional pore structure distribution map of the porous cultural relic to be inspected is completed.

[0050] Preferably, the three-dimensional nuclear magnetic resonance detection system includes a parameter auxiliary setting unit, which is provided with a plurality of porous cultural relic material characteristic databases and measurement scene modes. During measurement, the above parameters are automatically screened and matched and fine-tuned based on the collected preliminary nuclear magnetic resonance data of the porous cultural relic to be detected or through user input of key features such as the type of the porous cultural relic to be detected and its environment. For example, when measuring limestone cultural relics in a humid environment, the parameter auxiliary setting unit can automatically optimize the echo interval to shorten the acquisition time, adjust the radio frequency magnetic field strength to enhance the signal penetration depth, and improve efficiency and reduce the influence of external interference while ensuring measurement accuracy.

[0051] Example 3 like Figure 4-8 As shown, this embodiment provides a three-dimensional nuclear magnetic resonance detection method using the above-mentioned device, including: Step 1: Install the three-dimensional nuclear magnetic resonance detection equipment and level the three-dimensional nuclear magnetic resonance detection equipment in a horizontal direction; At the inspection site, the three-dimensional nuclear magnetic resonance inspection device is installed and moved in front of the porous cultural relic to be inspected. The foot cup is adjusted to level the three-dimensional nuclear magnetic resonance inspection device in the horizontal direction to ensure the movement accuracy of the displacement module and the safety of the equipment operation; Step 2: Set the NMR parameters; According to the type of porous cultural relics to be inspected, appropriate NMR parameters are input through the industrial control computer; The NMR parameters include basic NMR parameters such as operating frequency, echo interval, waiting time, number of scans, and number of echoes. Different porous cultural relics have different materials and pore structures. The NMR parameters need to be specifically adjusted according to the type of porous cultural relics being tested to ensure the accuracy of the test. Step 3: setting the number and step length of the NMR probe in the horizontal direction (i.e., the displacement direction of the NMR probe along the horizontal displacement linear module), the vertical direction (i.e., the displacement direction of the NMR probe along the vertical displacement linear module), and the depth direction (i.e., the depth direction of the NMR probe detecting porous cultural relics); The maximum horizontal movement distance of the nuclear magnetic resonance probe is no more than 1000 mm, that is, x*Lx≤1000 mm; Wherein, x is the number of displacement steps of the nuclear magnetic resonance probe in the horizontal direction, and Lx is the displacement step length of the nuclear magnetic resonance probe in the horizontal direction; The maximum vertical movement distance of the nuclear magnetic resonance probe is no more than 1000 mm, that is, y*Ly≤1000 mm; Wherein, y is the number of displacement steps of the NMR probe in the vertical direction, and Ly is the displacement step length of the NMR probe in the vertical direction; The maximum measuring depth of the nuclear magnetic resonance probe in the longitudinal direction is not greater than 25 mm, that is, z*Lz≤25 mm; Wherein, z is the number of depth steps of the NMR probe along the depth direction, and Lz is the depth step length of the NMR probe along the depth direction; Step 4: measuring the porous cultural relic to be detected by the nuclear magnetic resonance probe; Clicking the start measurement button on the industrial computer controls the three-dimensional nuclear magnetic resonance detection device to automatically start measurement.

[0052] Step 5: Measure the distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic to be inspected by an infrared ranging sensor, and compare it with a preset safety distance parameter (the default safety distance parameter is 2 mm); When the distance data is greater than the safety distance parameter, the industrial control computer sends a nuclear magnetic resonance detection instruction to the nuclear magnetic resonance probe through the electronic spectrometer module, controls the nuclear magnetic resonance probe to perform a single measurement on a measurement area of ​​the porous cultural relic to be detected, and collects the nuclear magnetic resonance data collected by the single measurement; When the distance data is less than the safety distance parameter, the industrial control computer issues an alarm and controls the nuclear magnetic resonance probe to stop moving and measuring; Step 6: Receive the collected NMR data of the measurement area of ​​the porous cultural relic to be detected, and make a judgment based on the inversion algorithm selected by the user; The available inversion algorithms include exponential fitting algorithm and inverse Laplace transform algorithm, among which the exponential fitting algorithm includes single exponential fitting algorithm and double exponential fitting algorithm; Inversion processing refers to the use of an inversion algorithm to convert the collected NMR signal from a time domain signal with multi-exponential decay to a transverse relaxation time signal that can invert the pore structure distribution; Step 7: storing the acquired transverse relaxation time signal of the measurement area of ​​the porous cultural relic under inspection and the position data of the corresponding measurement area into the three-dimensional pore structure distribution map; The transverse relaxation time signal of the measurement area of ​​the porous cultural relic being tested can reflect the pore structure characteristics in the measurement area, that is, the distribution of the pore structure is represented by the transverse relaxation time distribution. The pores in the porous cultural relic are composed of many pores of different pore sizes. For small-diameter pores, their nuclear magnetic resonance signals decay quickly, so their transverse relaxation time values ​​are relatively small; for large-diameter pores, their nuclear magnetic resonance signals decay slowly, so their transverse relaxation time values ​​are relatively large. Considering that the pores in the porous cultural relic are composed of a combination of large, medium and small pores, the transverse relaxation time distribution also presents a distribution state and can represent the pore structure distribution of the porous cultural relic being tested; Step 8: Control the nuclear magnetic resonance detection probe to perform cyclic repeated measurements on different measurement areas of the porous cultural relic to be detected in the order of priority in the depth direction, horizontal direction, and vertical direction, and store the inverted nuclear magnetic resonance data and corresponding position data of each measurement area of ​​the porous cultural relic to be detected in sequence into the three-dimensional pore structure distribution map.

[0053] Reference Figure 5-8 As shown, in a feasible embodiment, a three-dimensional nuclear magnetic resonance detection method is used to detect porous cultural relics (such as murals). By setting the horizontal and vertical displacement step sizes and step numbers on the three-dimensional nuclear magnetic resonance detection system equipped with the industrial control computer, the porous cultural relics can be divided into multiple measurement areas on a two-dimensional plane. In this embodiment, the number of measurement depth steps in the depth direction is set to 9, that is, the same part of the porous cultural relic being detected is divided into 9 measurement areas along the depth direction. The industrial control computer sends a nuclear magnetic resonance detection instruction to the nuclear magnetic resonance probe through the electronic spectrometer module, and sends a displacement instruction to the displacement module, thereby controlling the nuclear magnetic resonance probe to perform a comprehensive measurement of the porous cultural relics in the order of priority in the depth direction, the horizontal direction, and the vertical direction; The nuclear magnetic resonance data of each measurement area collected are inverted according to the selected inversion algorithm, and then the inverted nuclear magnetic resonance data of the measurement area and the corresponding position data are stored in the three-dimensional pore structure distribution map, until the inverted nuclear magnetic resonance data of all measurement areas and the corresponding position data are stored in the three-dimensional pore structure distribution map, and the three-dimensional pore structure distribution map of the porous cultural relics being detected is completed.

[0054] Reference Figure 7 As shown, the position of each pixel corresponds to the detected position of the porous cultural relic, and the color of the pixel represents the moisture content data of the detected position, thereby obtaining a moisture content distribution map of the detected porous cultural relic.

[0055] The moisture content distribution diagram of the inspected porous cultural relics is displayed on the screen of the industrial control computer. By clicking a single pixel point, the three-dimensional pore structure distribution diagram of the nine measurement areas of the inspected porous cultural relics along the depth direction can be displayed. By analyzing the three-dimensional pore structure distribution diagram, the pore structure distribution results in the corresponding measurement area can be obtained, and the data of large pore content and small pore content can be quantitatively obtained.

[0056] Furthermore, the specific formula of the inverse Laplace transform algorithm is:

[0057] in, is the transverse relaxation time signal distribution function of the pore structure components in the measurement area of ​​the porous cultural relics being detected, The NMR signal of the pore structure components in the measurement area of ​​the porous cultural relics under inspection is collected over time. The decay function of For the detection time, is the transverse relaxation time to be solved, is the weighting function, is the regularization parameter, The first porous cultural relic to be tested The transverse relaxation time signal distribution function of the pore structure components in the measurement area; The nuclear magnetic resonance signal of the measurement area of ​​the porous cultural relic to be detected is obtained by measuring the nuclear magnetic resonance probe, and the nuclear magnetic resonance signal is the nuclear magnetic resonance data collected from the measurement area of ​​the porous cultural relic to be detected; The weighting function According to the characteristics of the NMR signal of the measuring area of ​​the porous cultural relics to be detected, the NMR signal starting section (i.e. When the value is small, a high weight is set to highlight the early NMR signal characteristics, because the early NMR signal usually contains high-frequency information of the pore structure in the measurement area of ​​the porous artifacts being detected; the weight is appropriately reduced in the later stage of NMR signal attenuation to reduce the influence of noise; The regularization parameter The regularization parameter is used to balance the data fitting accuracy and the stability of the solution. It needs to be optimized through multiple experiments and is critical for processing noisy NMR signals to prevent overfitting.

[0058] When measuring the pore structure of sandstone artifacts with complex pores and variable signal attenuation patterns, the inverse Laplace transform algorithm adjusts the weighting function and the regularization parameter , can more accurately extract the transverse relaxation time distribution of the pore structure in the measurement area of ​​the porous cultural relics being tested. Different pore sizes correspond to different transverse relaxation time values. Accurate transverse relaxation time distribution of pore structure helps to accurately distinguish pore size and quantify porosity; based on the range of transverse relaxation time, the micropores ( <1ms)、small and medium pores(1ms< <100ms) and macropores ( >100ms), providing a microstructural basis for the protection and restoration of porous cultural relics, and cooperating with the magnetic field excitation of the nuclear magnetic resonance probe and the nuclear magnetic resonance signal acquisition to realize the non-destructive detection function of the pore structure of porous cultural relics.

[0059] Furthermore, the exponential fitting algorithm includes: Step 61: Assuming that the collected nuclear magnetic resonance signal of the measuring area of ​​the porous cultural relic is detected, the specific formula is:

[0060] in, The NMR signal of the pore structure components in the measurement area of ​​the porous cultural relics under inspection is collected over time. The decay function of The first porous cultural relic to be tested The NMR signal amplitude of the pore structure components in the measurement area, is the total number of measurement areas, For the detection time, The first porous cultural relic to be tested transverse relaxation time of the pore structure components within a measurement area; Step 62: Calculate the fitting error and compare the calculated fitting error with the preset fitting error parameter range to evaluate the fitting quality. Iterate the fitting multiple times according to the fitting quality to approach the global optimal solution, so as to accurately determine the and ; The specific formula for calculating the fitting error is:

[0061] Where E is the fitting error; During the fitting process, if the error is large, the simulated annealing strategy is used to accept inferior solutions with a certain probability to broaden the search range, jump out of the local optimum, and approach the global optimal solution through multiple iterations to accurately determine the optimal solution. and .

[0062] When measuring the pore structure of limestone artifacts with similar pore sizes and low signal differentiation, the exponential fitting algorithm adaptively optimizes and accurately analyzes the pore structure. This provides data support for the study of pore water distribution in the porous artifacts being examined. Because different pore water states (bound water, movable water) correspond to different transverse relaxation time signal characteristics, precise fitting helps distinguish them. Combined with the 3D NMR detection equipment's control over detection depth and measurement area, this method comprehensively analyzes the pore water state within the measurement area of ​​the porous artifact being examined, providing critical water distribution information for weathering prevention and reinforcement, and enhancing the 3D NMR detection equipment's ability to analyze the complex pore structures of porous artifacts.

[0063] The NMR signal of the detected porous artifacts changes with time The decay function contains a lot of information about the water content and water distribution of the porous cultural relics being tested. The nuclear magnetic resonance signal of the porous cultural relics being tested changes with time. The changing signal intensity has a positive correlation function with the water content in the measurement area of ​​the porous cultural relic being detected; and the transverse relaxation time of the measurement area of ​​the porous cultural relic being detected is calculated. The spectrum can characterize the pore size distribution, porosity, water content of the porous artifacts being tested, as well as the pore size distribution and porosity based on the NMR signal intensity and transverse relaxation time of the porous artifacts being tested. The calibration is carried out; based on the transverse relaxation time signal of the porous cultural relics being tested, the weathering depth, deterioration degree, reinforcement depth, reinforcement degree, mural craftsmanship and other defects of the porous cultural relics being tested can be directly fed back; in general, by comparing the transverse relaxation time signals of the porous cultural relics being tested before and after reinforcement and before and after weathering, the weathering depth and reinforcement depth of the porous cultural relics being tested can be directly interpreted.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-dimensional nuclear magnetic resonance detection device, characterized in that: include: Frame structure, NMR probe, displacement module, industrial control computer and electronic spectrometer module; The nuclear magnetic resonance probe is arranged on the displacement module and is used to collect nuclear magnetic resonance data of porous cultural relics; The displacement module is arranged at the front side of the frame structure, and is used to drive the nuclear magnetic resonance probe to move in the horizontal direction and / or vertical direction; A workbench is provided on the back side of the frame structure, the industrial control computer and the electronic spectrometer module are both provided on the workbench, the industrial control computer is electrically connected to the electronic spectrometer module, and the electronic spectrometer module is electrically connected to the nuclear magnetic resonance probe and the displacement module respectively; The industrial control computer is used to issue control instructions, and receive, process and display data; The electronic spectrometer module is used to transmit nuclear magnetic resonance pulses to the nuclear magnetic resonance probe, send displacement instructions to the displacement module, and transmit collected nuclear magnetic resonance data and displacement data to the industrial control computer.

2. The three-dimensional nuclear magnetic resonance detection device according to claim 1, characterized in that: The three-dimensional nuclear magnetic resonance detection equipment also includes an infrared ranging sensor, which is arranged on the side of the nuclear magnetic resonance probe and electrically connected to the electronic spectrometer module to measure the distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic being detected.

3. The three-dimensional nuclear magnetic resonance detection device according to claim 1, characterized in that: The nuclear magnetic resonance probe is a unilateral nuclear magnetic resonance probe, which includes: a base, a solenoid coil and four magnets; The four magnets are arranged in a field shape on the base, with the measuring ends of the two magnets on one side being S poles and the measuring ends of the two magnets on the other side being N poles, so as to jointly generate a static magnetic field through the four magnets; The solenoid coil is arranged on the surface of the four measuring ends of the magnets, and is used to generate a radio frequency magnetic field by cooperating with the solenoid coil through the four magnets.

4. The three-dimensional nuclear magnetic resonance detection device according to claim 1, characterized in that: The displacement module includes: a horizontal displacement linear module and a vertical displacement linear module; The horizontal displacement linear module is arranged at the bottom of the frame structure, the vertical displacement linear module is vertically arranged on the horizontal displacement linear module, a vertical sliding seat is provided on the vertical displacement linear module, the vertical sliding seat is slidably arranged on the vertical displacement linear module, and the nuclear magnetic resonance probe is mounted on the vertical sliding seat, and is used to drive the nuclear magnetic resonance probe to move in the vertical direction through the vertical sliding seat; The horizontal displacement linear module is provided with a horizontal sliding seat, and the horizontal sliding seat is slidably provided on the horizontal displacement linear module. The vertical displacement linear module is vertically installed on the horizontal sliding seat, and is used to drive the vertical displacement linear module to move in the horizontal direction through the horizontal sliding seat, thereby driving the nuclear magnetic resonance probe to move in the horizontal direction.

5. The three-dimensional nuclear magnetic resonance detection device according to claim 1, characterized in that: The maximum stroke of the horizontal displacement linear module and the vertical displacement linear module is 1000 mm, and the displacement accuracy is 0.1 mm.

6. The three-dimensional nuclear magnetic resonance detection device according to claim 1, characterized in that: Four foot cups are respectively provided at the four corners of the bottom of the frame structure for fixing and leveling the frame structure.

7. A three-dimensional nuclear magnetic resonance detection system applied to the device according to any one of claims 1 to 6, characterized in that: include: Nuclear magnetic resonance detection module, displacement control module, infrared ranging module, inversion processing module and result generation module; The displacement control module includes a displacement parameter setting unit for setting the displacement parameters of the nuclear magnetic resonance probe; The displacement control module is used to issue a displacement instruction according to the set displacement parameters, control the displacement module to drive the nuclear magnetic resonance probe to move according to the path set in the diagram, perform a partial or full scan of the surface and shallow layer of the porous cultural relic to be inspected, and receive displacement data to obtain the number of measurement areas; The NMR detection module includes a NMR parameter setting unit for setting NMR parameters; The NMR detection module is used to issue NMR detection instructions according to set NMR parameters and receive NMR data; The infrared ranging module includes a distance parameter setting unit for setting a safety distance parameter; The infrared ranging module is used to issue infrared ranging instructions according to the set safety distance parameters, and receive distance data. When the received distance data is less than the safety distance parameters, it will issue an alarm prompt and stop issuing displacement instructions and nuclear magnetic resonance detection instructions. The inversion processing module is provided with an inversion algorithm selection unit for selecting an inversion algorithm preset in the inversion processing module; The inversion processing module is used to receive the nuclear magnetic resonance data and perform inversion processing on the nuclear magnetic resonance data according to a selected inversion algorithm; The result generation module is used to generate a three-dimensional pore structure distribution map of the detected porous cultural relics based on the transverse relaxation time signal and displacement data.

8. A three-dimensional nuclear magnetic resonance detection method using the device according to any one of claims 1 to 6, characterized in that: include: Step 1: Install the three-dimensional nuclear magnetic resonance detection equipment and level the three-dimensional nuclear magnetic resonance detection equipment in a horizontal direction; Step 2: Set the NMR parameters; Step 3: setting the number and length of steps of the nuclear magnetic resonance probe in the horizontal, vertical and depth directions; Step 4: measuring the porous cultural relic to be detected by the nuclear magnetic resonance probe; Step 5: measuring the distance between the nuclear magnetic resonance probe and the surface of the porous cultural relic being inspected by an infrared ranging sensor, and comparing it with a preset safety distance parameter; when the distance data is less than the safety distance parameter, an alarm is issued, and the nuclear magnetic resonance probe is controlled to stop moving and measuring; Step 6: Receive the collected nuclear magnetic resonance data of the measurement area of ​​the porous cultural relic to be detected, make a judgment based on the inversion algorithm selected by the user, and use the selected inversion algorithm to convert the collected nuclear magnetic resonance signal from a time domain signal to a transverse relaxation time signal; The inversion algorithm includes an exponential fitting algorithm and an inverse Laplace transform algorithm, wherein the exponential fitting algorithm includes a single exponential fitting algorithm and a double exponential fitting algorithm; Step 7: storing the acquired transverse relaxation time signal of the measurement area of ​​the porous cultural relic under inspection and the position data of the corresponding measurement area into the three-dimensional pore structure distribution map; Step 8: Control the nuclear magnetic resonance detection probe to perform cyclic repeated measurements on different measurement areas of the porous cultural relic to be detected in the order of priority in the depth direction, horizontal direction, and vertical direction, and store the inversion-processed nuclear magnetic resonance data and corresponding position data of each measurement area of ​​the porous cultural relic to be detected in the three-dimensional pore structure distribution map.

9. The three-dimensional nuclear magnetic resonance detection method according to claim 8, characterized in that: The specific formula of the inverse Laplace transform algorithm is: in, is the transverse relaxation time signal distribution function of the pore structure components in the measurement area of ​​the porous cultural relics being detected, The NMR signal of the pore structure components in the measurement area of ​​the porous cultural relics under inspection is collected over time. The decay function of For the detection time, is the transverse relaxation time to be solved, is the weighting function, is the regularization parameter, The first porous cultural relic to be tested The transverse relaxation time signal distribution function of the pore structure components within a measurement area.

10. The three-dimensional nuclear magnetic resonance detection method according to claim 8, characterized in that: The exponential fitting algorithm comprises: Step 61: Assuming that the collected nuclear magnetic resonance signal of the measuring area of ​​the porous cultural relic is detected, the specific formula is: in, The NMR signal of the pore structure components in the measurement area of ​​the porous cultural relics under inspection is collected over time. The decay function of The first porous cultural relic to be tested The NMR signal amplitude of the pore structure components in the measurement area, is the total number of measurement areas, For the detection time, The first porous cultural relic to be tested transverse relaxation time of the pore structure components within a measurement area; Step 62: Calculate the fitting error, compare the calculated fitting error with a preset fitting error parameter range to evaluate the fitting quality, and iterate the fitting multiple times based on the fitting quality to approach the global optimal solution; The specific formula for calculating the fitting error is: Where E is the fitting error.

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