Unilateral nuclear magnetic resonance device and method for soil detection

Abstract

The invention discloses a unilateral nuclear magnetic resonance device and method for soil detection, and relates to the technical field of nuclear magnetic resonance, the unilateral nuclear magnetic resonance device is characterized in that a unilateral permanent magnet is arranged in a shell and is used for generating a uniform main magnetic field; the radio frequency coil is arranged on the upper surface of the shell and is used for generating a radio frequency excitation magnetic field orthogonal to the main magnetic field and detecting an echo signal generated by the soil sample; the gradient coil is arranged in an imaging area of the main magnetic field and is used for space coding and positioning; the field sweeping coil is wound on an iron yoke at the bottom of the single-side permanent magnet and is used for generating an additional magnetic field with adjustable size; the stepping motor is arranged at the bottom of the shell and used for adjusting any height in the total stroke so as to detect different positions of the soil. The unilateral nuclear magnetic resonance technology can be applied to the field of soil detection, the problem of non-uniform magnetic field is solved, and the precision and efficiency of a soil detection result are improved.

Description

Technical Field

[0001] The present invention relates to the field of nuclear magnetic resonance technology, and more particularly to a unilateral nuclear magnetic resonance device and method for soil detection. Background Art

[0002] As one of the greatest inventions of mankind in the 20th century, nuclear magnetic resonance has changed our understanding and cognition of the microscopic world. This modern high-tech is no longer limited to quantum physics and chemical structures, but is widely used in biology, medicine, materials, geology and other fields. Compared with traditional nuclear magnetic resonance technology, the unilateral nuclear magnetic resonance equipment that has only come into people's sight in recent years has an open structure, a small size, and is easy to move. It can perform non-destructive testing on objects at any position and from any angle, and has broad application prospects.

[0003] In terms of agriculture and environmental protection, soil testing is of great significance for ensuring crop growth, increasing crop yields, and protecting the environment. Existing soil testing methods have problems such as subjectivity, low detection accuracy, and slow speed, and cannot achieve non-destructive testing. However, the application of nuclear magnetic resonance methods in the field of soil testing has obvious advantages over existing technologies. However, unilateral nuclear magnetic resonance technology is still immature and will result in uneven magnetic fields, which will have an adverse effect on soil testing results and easily cause damage to equipment.

[0004] Therefore, how to design a unilateral nuclear magnetic resonance device and method that can solve the problem of magnetic field unevenness during soil detection is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0005] In view of this, the present invention provides a unilateral nuclear magnetic resonance device and method for soil detection, which solves the problems existing in the background technology.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A unilateral nuclear magnetic resonance device for soil detection, comprising: a shell, a unilateral permanent magnet, a radio frequency coil, a gradient coil, a sweeping coil, and a stepping motor;

[0008] A unilateral permanent magnet is arranged in the housing to generate a uniform main magnetic field;

[0009] The radio frequency coil is arranged on the upper surface of the shell, and is used to generate a radio frequency excitation magnetic field orthogonal to the main magnetic field, and detect the echo signal generated by the soil sample;

[0010] The gradient coil is arranged in the imaging area of ​​the main magnetic field for spatial encoding and positioning;

[0011] The field sweeping coil is wound on the iron yoke at the bottom of the single-sided permanent magnet to generate an additional magnetic field with adjustable size;

[0012] The stepper motor is arranged at the bottom of the shell and is used to adjust any height within the total stroke to realize the detection of different positions of the soil.

[0013] Optionally, an opening is provided on an outer surface of one side of the shell, and conductive components are provided around the opening, and the shell and a shielding component for accommodating the soil sample are connected through the conductive component.

[0014] Optionally, the unilateral permanent magnet includes a gasket and several magnet blocks, the gasket is arranged above the magnet blocks at both ends of the elliptical curve, and the several magnet blocks and the gasket are fixed inside the shell through mounting grooves; the centers of the several magnet blocks are distributed with equal arc lengths along the elliptical curve, and the magnetization directions of two adjacent magnet blocks are deflected in sequence along the elliptical curve.

[0015] Optionally, the radio frequency coil includes a plurality of radio frequency coil units connected in sequence, adjacent radio frequency coil units partially overlap, and each radio frequency coil unit includes a resonant circuit and a matching network connected to each other.

[0016] Optionally, the gradient coil includes an orthogonal X-axis gradient coil, a Y-axis gradient coil and a Z-axis gradient coil; the X-axis gradient coil includes four symmetrical current-carrying loops, the Y-axis gradient coil is composed of a single symmetrical current-carrying loop, and the Z-axis gradient coil includes two symmetrical current-carrying loops.

[0017] Optionally, the scanning field coil is composed of an upper scanning field coil and a lower scanning field coil with the same radius and number of turns, and the distance between the upper scanning field coil and the lower scanning field coil is the radius of the scanning field coil; the upper scanning field coil and the lower scanning field coil generate a uniform magnetic field that changes with time in the imaging area of ​​the main magnetic field.

[0018] Optionally, it also includes: a power module, a control module and a drive module;

[0019] A power module, used to supply power to the control module and the drive module;

[0020] The control module is used to determine the specific position of the stepper motor stroke control and send motor operation instructions to the drive module;

[0021] The driving module is used to drive the stepper motor to adjust the height by receiving the motor operation instruction.

[0022] A unilateral nuclear magnetic resonance method for soil detection, using the unilateral nuclear magnetic resonance device for soil detection as described in any one of the above items, comprises the following steps:

[0023] A uniform main magnetic field is generated by a unilateral permanent magnet, and a radio frequency excitation magnetic field orthogonal to the main magnetic field is generated by a radio frequency coil to receive the echo signal of the soil sample;

[0024] The gradient coil is used for spatial encoding and positioning, and the additional magnetic field is adjusted by adjusting the magnitude and direction of the current in the scanning coil to adjust the position of the constant magnetic field in the vertical direction;

[0025] The layer imaging is obtained, and the detection of different positions of the soil can be achieved by adjusting any height within the total stroke through the stepper motor.

[0026] Optionally, the method further includes:

[0027] Perform inverse Laplace transform on the echo signal to obtain the T2 spectrum distribution curve;

[0028] The long transverse relaxation time peak corresponds to the free water in the soil, the short transverse relaxation time peak corresponds to the bound water in the soil, and the area covered by the T2 spectrum distribution curve represents the water content in the soil.

[0029] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a unilateral nuclear magnetic resonance device and method for soil detection, which has a simple structure, small size, light weight, low cost, and improved signal-to-noise ratio. The unilateral nuclear magnetic resonance technology is applied to soil detection, which can realize unilateral nuclear magnetic resonance three-dimensional imaging, solve the problem of uneven magnetic field, improve the accuracy and rate of soil detection, and thus ensure the growth of crops and increase crop yields. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0031] Figure 1 A structural diagram of a unilateral nuclear magnetic resonance device for soil detection provided by the present invention;

[0032] Figure 2 A flow chart of the single-sided nuclear magnetic resonance method for soil detection provided by the present invention;

[0033] Figure numerals: 1 - housing, 2 - RF coil, 3 - stepper motor, 4 - spacer, 5 - magnet block. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The embodiment of the present invention discloses a single-sided nuclear magnetic resonance device for soil detection, such as Figure 1 As shown, it includes: a housing 1, a single-sided permanent magnet, a radio frequency coil 2, a gradient coil, a scanning coil, and a stepping motor 3;

[0036] A unilateral permanent magnet is disposed in the housing 1 to generate a uniform main magnetic field;

[0037] The radio frequency coil 2 is arranged on the upper surface of the housing 1, and is used to generate a radio frequency excitation magnetic field orthogonal to the main magnetic field, and detect the echo signal generated by the soil sample;

[0038] The gradient coil is arranged in the imaging area of ​​the main magnetic field for spatial encoding and positioning;

[0039] The sweeping coil is wound on the iron yoke at the bottom of the single-sided permanent magnet to generate an additional magnetic field with adjustable size, which is superimposed on the main magnetic field. The design of the iron yoke can reduce magnetic leakage.

[0040] The stepper motor 3 is arranged at the bottom of the housing 1 and is used to adjust any height within the total stroke to realize the detection of different positions of the soil.

[0041] In this embodiment, the main magnetic field is parallel to the soil surface and attenuates in a direction perpendicular to the soil surface. In order to ensure that the radio frequency field is orthogonal to the main magnetic field, the direction of the radio frequency field must be perpendicular to the soil surface.

[0042] Furthermore, an opening is provided on one outer surface of the shell 1, and conductive components are provided around the opening. The shell 1 and the shielding component for accommodating the soil sample are connected through the conductive components.

[0043] Furthermore, the unilateral permanent magnet includes a gasket 4 and a plurality of magnet blocks 5, the gasket 4 is arranged above the magnet blocks 5 at both ends of the elliptical curve, and the plurality of magnet blocks 5 and the gasket 4 are fixed inside the shell 1 through mounting grooves; the centers of the plurality of magnet blocks 5 are distributed with equal arc lengths along the elliptical curve, and the magnetization directions of two adjacent magnet blocks 5 are deflected in sequence along the elliptical curve.

[0044] In this embodiment, the magnet blocks are rectangular parallelepipeds of the same size, and each magnet block has the same remanence and magnetization direction; the gasket is a rectangular parallelepiped, and its lower surface is the same size as the upper surface of the magnet block and completely fits.

[0045] Furthermore, the RF coil 2 includes a plurality of RF coil units connected in sequence, adjacent RF coil units partially overlap, and each RF coil unit includes a resonant circuit and a matching network connected to each other.

[0046] Specifically, the RF coil 2 is optimized and designed using a target field inverse method of a quasi-static field, and the designed target RF field matches the static main magnetic field, that is, they are orthogonal in direction and related in amplitude.

[0047] Furthermore, the gradient coil includes an orthogonal X-axis gradient coil, a Y-axis gradient coil and a Z-axis gradient coil; the X-axis gradient coil includes four symmetrical current-carrying loops, the Y-axis gradient coil is composed of a single symmetrical current-carrying loop, and the Z-axis gradient coil includes two symmetrical current-carrying loops. The currents of the X-axis, Y-axis and Z-axis gradient coils are zero on the boundaries, and the current density automatically meets the closure condition within the limited length of the coil.

[0048] Specifically, the gradient coil is designed using the target field method and the stream function method, and is wound with enameled copper wire.

[0049] In this embodiment, the two-dimensional plane is spatially encoded by the gradient coil, and the intensity of the signal corresponding to each voxel in the plane is obtained according to the one-to-one correspondence between the phase and the plane position, thereby determining the grayscale of the pixel and realizing the plane imaging of the soil to be tested.

[0050] Furthermore, the scanning field coil is composed of an upper scanning field coil and a lower scanning field coil with the same radius and number of turns, and the distance between the upper scanning field coil and the lower scanning field coil is the radius of the scanning field coil; the upper scanning field coil and the lower scanning field coil generate a uniform magnetic field that changes with time in the imaging area of ​​the main magnetic field.

[0051] Furthermore, it also includes: a power module, a control module and a drive module;

[0052] A power module, used to supply power to the control module and the drive module;

[0053] The control module is used to determine the specific position of the stroke control of the stepper motor 3 and send a motor operation instruction to the drive module;

[0054] The driving module is used to drive the stepping motor 3 to adjust the height by receiving the motor operation instruction.

[0055] In this embodiment, when the unilateral nuclear magnetic resonance device is powered on, the control module first performs a self-check to determine the position state of the stepper motor. The soil is not a smooth horizontal surface. Therefore, when it is necessary to detect different positions of the soil sample, the control module can send a motor operation instruction to the drive module to drive the stepper motor to the specified position, and detect different soil positions by adjusting any height within the total stroke. Specifically, the control module can use an ARM microcontroller chip, which has an RS232 serial port, a CAN communication interface, etc.

[0056] This embodiment also provides a single-sided nuclear magnetic resonance method for soil detection, using Figure 1 The single-sided NMR device shown, Figure 2 As shown, the following steps are included:

[0057] A uniform main magnetic field is generated by a unilateral permanent magnet, and a radio frequency excitation magnetic field orthogonal to the main magnetic field is generated by a radio frequency coil 2 to receive an echo signal of a soil sample;

[0058] The gradient coil is used for spatial encoding and positioning, and the additional magnetic field is adjusted by adjusting the magnitude and direction of the current in the scanning coil to adjust the position of the constant magnetic field in the vertical direction;

[0059] The layer imaging is obtained, and the detection of different positions of the soil is realized by adjusting any height within the total stroke by the stepper motor 3.

[0060] Furthermore, the method further comprises:

[0061] Perform inverse Laplace transform on the echo signal to obtain the T2 spectrum distribution curve;

[0062] The long transverse relaxation time peak corresponds to the free water in the soil, the short transverse relaxation time peak corresponds to the bound water in the soil, and the area covered by the T2 spectrum distribution curve represents the water content in the soil.

[0063] In the actual detection process, the uneven magnetic field will cause large phase dispersion, resulting in rapid relaxation decay. The 180-degree refocusing pulse can compensate for the phase dispersion, continuously restore the signal, play a role in cumulative averaging, and then generate an echo. For each phase encoding, if N 180-degree pulses are used, N echoes are obtained, which can improve the signal-to-noise ratio.

[0064] In summary, this embodiment uses unilateral nuclear magnetic resonance technology to excite hydrogen protons in soil moisture, detects the echo signals released during the relaxation process, analyzes the distribution of transverse relaxation time T2, and obtains accurate information on soil moisture. The detection accuracy is higher and the detection rate is faster, which helps to ensure the growth of crops and the implementation of environmental protection programs.

[0065] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the method disclosed in the embodiment, since it corresponds to the device disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0066] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A unilateral nuclear magnetic resonance device for soil detection, characterized in that: include: Shell, single-sided permanent magnet, radio frequency coil, gradient coil, sweeping coil, stepper motor; A unilateral permanent magnet is arranged in the housing to generate a uniform main magnetic field; The radio frequency coil is arranged on the upper surface of the shell, and is used to generate a radio frequency excitation magnetic field orthogonal to the main magnetic field, and detect the echo signal generated by the soil sample; The gradient coil is arranged in the imaging area of ​​the main magnetic field for spatial encoding and positioning; The field sweeping coil is wound on the iron yoke at the bottom of the single-sided permanent magnet to generate an additional magnetic field with adjustable size; The stepper motor is arranged at the bottom of the shell and is used to adjust any height within the total stroke to realize the detection of different positions of the soil.

2. A unilateral nuclear magnetic resonance device for soil detection according to claim 1, characterized in that: An opening is arranged on an outer surface of one side of the shell, and conductive components are arranged around the opening. The shell and a shielding component for accommodating soil samples are connected through the conductive components.

3. A unilateral nuclear magnetic resonance device for soil detection according to claim 1, characterized in that: The unilateral permanent magnet includes a gasket and a plurality of magnet blocks. The gasket is arranged above the magnet blocks at both ends of the elliptical curve. The plurality of magnet blocks and the gasket are fixed inside the shell through mounting grooves. The centers of the plurality of magnet blocks are distributed with equal arc lengths along the elliptical curve, and the magnetization directions of two adjacent magnet blocks are deflected in sequence along the elliptical curve.

4. A unilateral nuclear magnetic resonance device for soil detection according to claim 1, characterized in that: The radio frequency coil comprises a plurality of radio frequency coil units connected in sequence, adjacent radio frequency coil units partially overlap, and each radio frequency coil unit comprises a resonant circuit and a matching network connected to each other.

5. A unilateral nuclear magnetic resonance device for soil detection according to claim 1, characterized in that: The gradient coils include orthogonal X-axis gradient coils, Y-axis gradient coils and Z-axis gradient coils; the X-axis gradient coils include four symmetrical current-carrying loops, the Y-axis gradient coils consist of a single symmetrical current-carrying loop, and the Z-axis gradient coils include two symmetrical current-carrying loops.

6. A unilateral nuclear magnetic resonance device for soil detection according to claim 1, characterized in that: The scanning coil is composed of an upper scanning coil and a lower scanning coil with the same radius and number of turns. The distance between the upper scanning coil and the lower scanning coil is the radius of the scanning coil. The upper scanning coil and the lower scanning coil generate a uniform magnetic field that changes with time in the imaging area of ​​the main magnetic field.

7. A unilateral nuclear magnetic resonance device for soil detection according to claim 1, characterized in that: Also includes: Power module, control module and drive module; A power module, used to supply power to the control module and the drive module; The control module is used to determine the specific position of the stepper motor stroke control and send motor operation instructions to the drive module; The driving module is used to drive the stepper motor to adjust the height by receiving the motor operation instruction.

8. A unilateral nuclear magnetic resonance method for soil detection, characterized in that: The unilateral nuclear magnetic resonance device for soil detection according to any one of claims 1 to 7 comprises the following steps: A uniform main magnetic field is generated by a unilateral permanent magnet, and a radio frequency excitation magnetic field orthogonal to the main magnetic field is generated by a radio frequency coil to receive the echo signal of the soil sample; The gradient coil is used for spatial encoding and positioning, and the additional magnetic field is adjusted by adjusting the magnitude and direction of the current in the scanning coil to adjust the position of the constant magnetic field in the vertical direction; The layer imaging is obtained, and the detection of different positions of the soil can be achieved by adjusting any height within the total stroke through the stepper motor.

9. A single-sided nuclear magnetic resonance method for soil detection according to claim 8, characterized in that: The method further comprises: Perform inverse Laplace transform on the echo signal to obtain the T2 spectrum distribution curve; The long transverse relaxation time peak corresponds to the free water in the soil, the short transverse relaxation time peak corresponds to the bound water in the soil, and the area covered by the T2 spectrum distribution curve represents the water content in the soil.

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