CN114047092A - Method for measuring cell wall free water content of balanced wood and application thereof - Google Patents
Method for measuring cell wall free water content of balanced wood and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of wood moisture analysis, and provides a method for measuring the content of free water in a cell wall during moisture absorption balance or desorption balance of wood and application thereof. The method provided by the invention takes balanced wood (wood with water content less than or equal to 25 percent, wood with balanced desorption or wood with balanced moisture absorption) as a determination reference, and because free water does not exist in the cell cavity of the balanced wood, the cell wall free water can be distinguished by measuring the longitudinal relaxation time data of nuclear magnetic resonance and utilizing the difference between the longitudinal relaxation time of cell wall and cell cavity bound water and the longitudinal relaxation time of cell wall free water. And (3) quantifying the free water of the cell wall based on longitudinal relaxation time data by using a formula 1, so as to obtain the content of the free water of the cell wall in the balanced wood. The invention ensures that an accurate measurement result can be obtained by strictly setting the parameters for measuring the longitudinal relaxation time T1 data of the balanced wood.
Description
Technical Field
The invention relates to the technical field of wood moisture analysis, in particular to a method for measuring the free water content of cell walls of balanced wood and application thereof.
Background
The traditional theory of wood science considers that the water in the wood cell wall is the bound water, and free water does not exist. Nakamura et al (1981) and Berthold et al (1996) used differential scanning calorimetry to distinguish between bound water in the wood cell wall, including freezable and non-freezable bound water. More time-domain nuclear magnetic resonance two-dimensional experiments show that: wood cell walls contain two states of moisture. The existing references measure the moisture content in the wood cell walls and cell cavities, mostly by transverse relaxation time, and consider the moisture content in the cell walls as bound water inside the wood and the moisture content in the cell cavities as free water inside the wood. The measurement of moisture inside the wood by transverse relaxation time is because the transverse relaxation time of moisture in the cell cavity is long, and the relaxation time of moisture in the cell wall is short, and the data is easy to interpret. The longitudinal relaxation time describes the process of energy exchange between the spin system and the surrounding environment, and the data composition is complex and difficult to analyze, so that few documents measure and analyze the longitudinal relaxation time.
Zhang and Balcom et al (Zhang, M., Balcom, B.J. (2022) Magnetic Resonance Microcopy. Instrument and Applications in Life Science and Energy Research Engineering, "Magnetic Resonance Studies of Water in Wood Materials", Wiley-VCH Weinheim.) based on the theory of nuclear Magnetic Resonance relaxation, suggest the presence of both bound and free Water in the Wood cell wall, the Water binding of the cell wall should be the Water on the interior surface of the pores of the cell wall; the water in the middle of the cell wall pores, namely the water which is not contacted with the main components of the wood cell walls, is free water; and it is believed that the moisture on the inner surface of the wood cell cavity is bound water by nature. However, since the transverse relaxation time of the cell wall bound water is very close to the transverse relaxation time of the free water in the cell wall pores, the bound water and the free water of the cell wall cannot be distinguished; resulting in an unmeasurable free water content of the cell wall.
Disclosure of Invention
In view of the above, the present invention provides a method for measuring the free water content of cell walls of balanced wood and the application thereof. The method provided by the invention can accurately measure the free water content of the cell wall of the balanced wood, and solves the problem that the free water content in the cell wall cannot be measured.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for measuring the free water content of cell walls of balanced wood, which comprises the following steps:
providing balance wood; the balance wood comprises wood with water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood;
measuring longitudinal relaxation time T1 data of the balanced wood; fitting the longitudinal relaxation time T1 data according to formula 1 to obtain a T11 value and a magnitude A11 thereof, a T12 value and a magnitude A12 thereof; wherein T11< T12;
in equation 1: (t) is a signal obtained by inverting the recovery pulse sequence, and Ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of excitation of the signal to one of the echoes in the inversion recovery pulse sequence; ε (t) is the noise signal;
determining a balance weight W2 and an oven dry mass W1 of the balance wood;
the cell wall free water content of the balanced wood is calculated by using formula 2:
wf ═ (W2-W1) a11/(a11+ a12) formula 2;
in equation 2: wf is the cell wall free water content in grams; w2 is the equilibrium weight of the balance wood in grams; w1 is the oven dry weight of the balance wood in grams;
the parameters for determining longitudinal relaxation time T1 data of equilibrium wood include: adopting an inversion recovery pulse sequence; number of scans was 2nN is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval between the signal in the inversion recovery pulse sequence and the start of the excitation to one of the echoes is 1-3000 ms; 16-32 sampling points are arranged, and the sampling points are distributed in pairs at equal intervals.
Preferably, the method for obtaining desorption equilibrium wood comprises the following steps:
carrying out desorption balance on original wood to obtain the wood with desorption balance;
the temperature of desorption equilibrium is 5-80 ℃, and the relative humidity is 30-99.99%.
Preferably, the method for obtaining the moisture-absorption balanced wood comprises the following steps:
carrying out moisture absorption balance on the wood with the balanced desorption to obtain the wood with the balanced moisture absorption;
the temperature of moisture absorption balance is 5-80 ℃; the relative humidity is 30-99.99%.
Preferably, the method for obtaining the moisture-absorption balanced wood comprises the following steps:
carrying out oven drying treatment on original wood to obtain oven dried wood; the absolute drying temperature is 100-105 ℃;
carrying out moisture absorption balance on the oven-dried wood to obtain the wood with moisture absorption balance; the temperature of moisture absorption balance is 5-80 ℃; the relative humidity is 30-99.99%.
Preferably, the method further comprises the following steps: the cell wall and cell cavity bound water content was obtained using equation 3:
wb ═ (W2-W1) a12/(a11+ a12) formula 3;
in equation 3, Wb is the cell wall and cell cavity bound water content, in grams by weight; w2 is the weight of the balance wood in grams; w1 is the weight of oven dried wood in grams.
The invention also provides application of the method for measuring the free water content of the cell wall of the balanced wood in the technical scheme in measuring the free water content of the balanced hydrophilic pore material.
Preferably, the equilibrium hydrophilic pore material comprises a hygroscopic equilibrium hydrophilic pore material or a desorption equilibrium hydrophilic pore material.
The invention provides a method for measuring the free water content of cell walls of balanced wood, which comprises the following steps: providing balance wood; the balance wood comprises wood with water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood;
measuring longitudinal relaxation time T1 data of the balanced wood; fitting the longitudinal relaxation time T1 data according to formula 1 to obtain a T11 value and a magnitude A11 thereof, a T12 value and a magnitude A12 thereof; wherein T11< T12;
in equation 1: (t) is a signal obtained by inverting the recovery pulse sequence, and Ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of excitation of the signal to one of the echoes in the inversion recovery pulse sequence; ε (t) is the noise signal;
determining a balance weight W2 and an oven dry mass W1 of the balance wood;
the cell wall free water content of the balanced wood is calculated by using formula 2:
wf ═ (W2-W1) a11/(a11+ a12) formula 2;
in equation 2: wf is the cell wall free water content in grams; w2 is the equilibrium weight of the balance wood in grams; w1 is the oven dry weight of the balance wood in grams;
the parameters for determining longitudinal relaxation time T1 data of equilibrium wood include: adopting an inversion recovery pulse sequence; number of scans was 2nN is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval between the signal in the inversion recovery pulse sequence and the start of the excitation to one of the echoes is 1-3000 ms; 16-32 sampling points are arranged, and the sampling points are distributed in pairs at equal intervals.
The method provided by the invention takes balanced wood (wood with water content less than or equal to 25 percent, wood with balanced desorption or wood with balanced moisture absorption) as a determination reference, and because free water does not exist in the cell cavity of the balanced wood, the cell wall free water can be distinguished by measuring the longitudinal relaxation time data of nuclear magnetic resonance and utilizing the difference between the longitudinal relaxation time of cell wall and cell cavity bound water and the longitudinal relaxation time of cell wall free water. And (3) quantifying the free water of the cell wall based on longitudinal relaxation time data by using a formula 1, so as to obtain the content of the free water of the cell wall in the balanced wood. The invention ensures that an accurate measurement result can be obtained by strictly setting the parameters for measuring the longitudinal relaxation time T1 data of the balanced wood.
Further, the present invention obtains the cell wall and cell cavity bound water content by equation 3.
The invention also provides application of the method for measuring the free water content of the cell wall of the balanced wood in the technical scheme in measuring the free water content of the balanced hydrophilic pore material. The method of the invention is not only suitable for wood, but also suitable for measuring the content of free water in all equilibrium hydrophilic pore materials.
Detailed Description
Interpretation of terms:
bound water (Bound water): also known as water sorption, is water that hydrogen bonds to sorption sites on the major components of the cell wall.
Free water (Free water): the water present in the cell lumen is called free water.
Longitudinal relaxation time (longitudinal relaxation time): also known as spin-lattice relaxation time, is the relaxation time that the longitudinal magnetization vector undergoes to return from a minimum to 63% of the equilibrium state. Is a characteristic quantity for representing the attenuation speed of the longitudinal magnetization vector.
Moisture absorption of wood: when the water vapor pressure in the wood cell wall microcapillaries is less than the partial water vapor pressure of the surrounding air, the microcapillaries absorb water from the surrounding air, and this phenomenon in which the microcapillaries system in the cell wall can absorb water from humid air is called moisture absorption.
And (3) desorbing the wood: when the partial pressure of water vapor in the wood cell wall microcapillaries is greater than the partial pressure of water vapor in the surrounding air, the microcapillary system is able to evaporate water into the surrounding air, a phenomenon known as desorption.
The invention provides a method for measuring the free water content of cell walls of balanced wood, which comprises the following steps:
providing balance wood; the balance wood comprises wood with water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood;
measuring longitudinal relaxation time T1 data of the balanced wood; fitting the longitudinal relaxation time T1 data according to formula 1 to obtain a T11 value and a magnitude A11 thereof, a T12 value and a magnitude A12 thereof; wherein T11< T12;
in equation 1: (t) is a signal obtained by inverting the recovery pulse sequence, and Ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of excitation of the signal to one of the echoes in the inversion recovery pulse sequence; ε (t) is the noise signal;
determining a balance weight W2 and an oven dry mass W1 of the balance wood;
the cell wall free water content of the balanced wood is calculated by using formula 2:
wf ═ (W2-W1) a11/(a11+ a12) formula 2;
in equation 2: wf is the cell wall free water content in grams; w2 is the equilibrium weight of the balance wood in grams; w1 is the oven dry weight of the balance wood in grams;
the parameters for determining longitudinal relaxation time T1 data of equilibrium wood include: adopting an inversion recovery pulse sequence; number of scans was 2nN is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval between the signal in the inversion recovery pulse sequence and the start of the excitation to one of the echoes is 1-3000 ms; 16-32 sampling points are arranged, and the sampling points are distributed in pairs at equal intervals.
In the present invention, the starting materials used in the present invention are preferably commercially available products unless otherwise specified.
The present invention provides a balanced wood.
In the invention, the balance wood comprises wood with water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood.
In the present invention, the method for obtaining desorption-equilibrated wood preferably includes the steps of:
and carrying out desorption balance on the original wood to obtain the wood with the desorption balance. The invention does not specifically limit the moisture content of the original wood, and the wood with any moisture content can be used. In the invention, the temperature of desorption equilibrium is preferably 5-80 ℃, and the relative humidity is preferably 30-99.99%; the desorption equilibrium time is not particularly limited, and the weight of the original wood can not change any more under the specific temperature and relative humidity.
In the present invention, the method for obtaining moisture-equilibrium wood preferably includes the steps of:
and carrying out moisture absorption balance on the wood with the balanced desorption to obtain the wood with the balanced moisture absorption. In the present invention, the wood with balanced desorption is preferably the wood with balanced desorption prepared by the above technical scheme. In the invention, the temperature of moisture absorption balance is preferably 5-80 ℃; the relative humidity is preferably 30-99.99%. The time of moisture absorption balance is not particularly limited, and the weight of the wood with desorption balance can not change under specific temperature and relative humidity.
In the present invention, the method for obtaining moisture-balanced wood preferably further comprises the steps of:
carrying out oven drying treatment on original wood to obtain oven dried wood;
and (3) carrying out moisture absorption balance on the oven-dried wood to obtain the wood with moisture absorption balance.
In the invention, the temperature of the oven drying treatment is preferably 100-105 ℃; the time for the oven drying is not particularly limited, and the oven drying is carried out to a constant weight. In the present invention, the oven drying is preferably performed in an oven. In the invention, the temperature of moisture absorption balance is preferably 5-80 ℃; the relative humidity is preferably 30-99.99%. The time of moisture absorption balance is not particularly limited, and the weight of the wood with desorption balance can not change under specific temperature and relative humidity.
After providing the balance wood, the balance wood may be weighed to obtain a balance weight W2 of the balance wood.
In the present invention, the cell cavities of the equilibrium wood do not contain free water, only cell wall bound water and cell wall free water.
After obtaining the balanced wood, the invention determines the longitudinal relaxation time T1 data of the balanced wood.
In the present invention, the parameters for determining longitudinal relaxation time T1 data of equilibrium wood include: adopting an inversion recovery pulse sequence; number of scans was 2nN is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval between the signal in the inversion recovery pulse sequence and the start of the excitation to one of the echoes is 1-3000 ms; 16-32 sampling points are arranged, and the sampling points are distributed in pairs at equal intervals.
After the longitudinal relaxation time T1 data of the balanced wood are obtained, fitting is carried out on the longitudinal relaxation time T1 data according to formula 1 to obtain a T11 value and a quantity value A11, a T12 value and a quantity value 12 of the T11 value; wherein T11< T12;
in equation 1: (t) is the signal intensity, Ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of excitation of the signal to one of the echoes in the inversion recovery pulse sequence; ε (t) is the noise signal.
In the invention, the longitudinal relaxation time T1 data of the equilibrium wood comprises the corresponding signal intensity of each sampling point at different time, and the unit of the time is s.
In the present invention, the instrument for measuring the longitudinal relaxation time T1 data of the equilibrium wood is preferably a time domain nuclear magnetic resonance spectrometer.
The oven dry weight W1 of the balance wood was determined. In the present invention, the oven dry weight W1 of the balance wood is preferably obtained by oven drying the balance wood to obtain oven dry wood and weighing to the accuracy of 0.001 g. In the invention, the temperature of the oven drying is preferably 100-105 ℃; the time for the oven drying is not particularly limited, and the oven drying is carried out to a constant weight. In the present invention, the oven drying is preferably performed in an oven.
After obtaining W1, W2, A11 and A12, the invention calculates and obtains the content of free water in cell walls in balanced wood by using a formula 2:
wf ═ (W2-W1) a11/(a11+ a12) formula 2;
in equation 2: wf is the cell wall free water content in grams; w2 is the equilibrium weight of the balance wood in grams; w1 is the oven dry weight of the balance wood in grams.
The present invention preferably further comprises: the cell wall and cell cavity bound water content was obtained using equation 3:
wb ═ (W2-W1) a12/(a11+ a12) formula 3;
in equation 3, Wb is the cell wall and cell cavity bound water content, in grams by weight; w2 is the weight of the balance wood in grams; w1 is the weight of oven dried wood in grams.
The invention also provides application of the method for measuring the free water content of the cell wall of the balanced wood in the technical scheme in measuring the free water content of the balanced hydrophilic pore material.
In the present invention, the equilibrium hydrophilic pore material comprises a hygroscopic equilibrium hydrophilic pore material or a desorption equilibrium hydrophilic pore material. The invention does not specifically limit the obtaining mode of the moisture absorption balance hydrophilic pore material or the desorption balance hydrophilic pore material, and can adopt the obtaining mode known by the technicians in the field.
In the present invention, the free water preferably includes free water in micropores and mesopores of the hydrophilic pore material.
The method for measuring the free water content of the cell wall in the moisture absorption equilibrium or desorption equilibrium of the wood and the application thereof provided by the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Weighing a poplar test piece after oven drying, wherein the oven dried weight is 0.782 g; placing the absolutely dry test piece into a constant temperature and humidity box with the temperature of 40 ℃ and the relative humidity of 31.6%, 43.2%, 53.2%, 74.7%, 82.3% and 98.2% in sequence, and enabling the test piece to achieve moisture absorption balance in sequence in the relative humidity environment to obtain a moisture absorption balance test piece; the moisture absorption balance test piece is taken out and weighed, and then placed into a sample tube with the diameter of 18mm, and then the sample tube with the test piece is placed into a German Brookfield time-domain nuclear magnetic resonance spectrometer (the model is Minispec mq20) for measuring the longitudinal relaxation time (T1). The longitudinal relaxation time (T1) measurement parameters include: the number of scans was 4, the cycle delay time was 2 seconds, the recovery time was 1 to 3000 milliseconds, and 20 sampling points were equidistantly distributed in pairs.
Fitting the obtained longitudinal relaxation time T1 data according to formula 1 to obtain a T11 value and a magnitude A11 thereof, a T12 value and a magnitude A12 thereof, and calculating the free water content of the cell wall of the balanced wood by using formula 2, wherein the obtained results are shown in Table 1.
TABLE 1 cell wall free Water content of poplar at equilibrium of moisture absorption at different relative humidities
Example 2
Weighing a pine test piece after absolute drying, wherein the absolute drying weight is 0.880 g; placing the absolutely dry test piece into a constant temperature and humidity box with the temperature of 40 ℃ and the relative humidity of 31.6%, 43.2%, 53.2%, 74.7%, 82.3% and 98.2% in sequence, and enabling the test piece to achieve moisture absorption balance in sequence in the relative humidity environment to obtain a moisture absorption balance test piece; the moisture absorption balance test piece is taken out and weighed, and then placed into a sample tube with the diameter of 18mm, and then the sample tube with the test piece is placed into a German Brookfield time-domain nuclear magnetic resonance spectrometer (the model is Minispec mq20) for measuring the longitudinal relaxation time (T1). Parameters measured by longitudinal relaxation time (T1): the number of scans was 4, the cycle delay time was 2 seconds, the recovery time was 1 to 3000 milliseconds, and 20 sampling points were equidistantly distributed in pairs. Fitting the obtained longitudinal relaxation time T1 data according to formula 1 to obtain a T11 value and a magnitude A11 thereof, a T12 value and a magnitude A12 thereof, and calculating the free water content of the cell wall of the balanced wood by using formula 2, wherein the obtained results are shown in Table 2.
TABLE 2 cell wall free Water content of pine at equilibrium of moisture absorption at different relative humidities
Example 3
Placing a poplar raw material test piece into a constant temperature and humidity box with the temperature of 40 ℃ and the relative humidity of 98.2%, 82.3%, 74.7%, 53.2%, 43.2% and 31.6% in sequence, enabling the test piece to reach desorption balance in the relative humidity environment in sequence, taking out the test piece and weighing the test piece, placing the test piece into a sample tube with the diameter of 18mm when the desorption balance is reached, and placing the sample tube with the test piece into a German Brookfield nuclear magnetic resonance spectrometer (the model is Minispec mq20) to carry out T1 measurement. The parameters used were: the number of scans was 4, the cycle delay time was 2 seconds, the recovery time was 1 to 3000 milliseconds, and 20 sampling points were equidistantly distributed in pairs. When the last T1 measurement was completed, the test piece was oven dried and weighed, the oven dried weight being 0.782 g. Fitting the obtained longitudinal relaxation time T1 data according to formula 1 to obtain a T11 value and a magnitude A11 thereof, a T12 value and a magnitude A12 thereof, and calculating the cell wall free water content of the balanced wood by using formula 2, wherein the obtained results are shown in Table 3.
TABLE 3 cell wall free Water content at Desorption equilibrium of Populus alba at different relative humidities
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. A method of measuring the cell wall free water content of equilibrium wood comprising the steps of:
providing balance wood; the balance wood comprises wood with water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood;
measuring longitudinal relaxation time T1 data of the balanced wood; fitting the longitudinal relaxation time T1 data according to formula 1 to obtain a T11 value and a magnitude A11 thereof, a T12 value and a magnitude A12 thereof; wherein T11< T12;
in equation 1: (t) is a signal obtained by inverting the recovery pulse sequence, and Ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of excitation of the signal to one of the echoes in the inversion recovery pulse sequence; ε (t) is the noise signal;
determining a balance weight W2 and an oven dry mass W1 of the balance wood;
the cell wall free water content of the balanced wood is calculated by using formula 2:
wf ═ (W2-W1) a11/(a11+ a12) formula 2;
in equation 2: wf is the cell wall free water content in grams; w2 is the equilibrium weight of the balance wood in grams; w1 is the oven dry weight of the balance wood in grams;
the parameters for determining longitudinal relaxation time T1 data of equilibrium wood include: adopting an inversion recovery pulse sequence; number of scans was 2nN is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval between the signal in the inversion recovery pulse sequence and the start of the excitation to one of the echoes is 1-3000 ms; 16-32 sampling points are arranged, and the sampling points are distributed in pairs at equal intervals.
2. The method according to claim 1, characterized in that the method for obtaining desorption-equilibrated wood comprises the steps of:
carrying out desorption balance on original wood to obtain the wood with desorption balance;
the temperature of desorption equilibrium is 5-80 ℃, and the relative humidity is 30-99.99%.
3. A method according to claim 1 or 2, characterized in that the method for obtaining moisture-balanced wood comprises the steps of:
carrying out moisture absorption balance on the wood with the balanced desorption to obtain the wood with the balanced moisture absorption;
the temperature of moisture absorption balance is 5-80 ℃; the relative humidity is 30-99.99%.
4. The method according to claim 1, characterized in that the method for obtaining moisture-balanced wood comprises the following steps:
carrying out oven drying treatment on original wood to obtain oven dried wood; the absolute drying temperature is 100-105 ℃;
carrying out moisture absorption balance on the oven-dried wood to obtain the wood with moisture absorption balance; the temperature of moisture absorption balance is 5-80 ℃; the relative humidity is 30-99.99%.
5. The method of claim 1, further comprising: the cell wall and cell cavity bound water content was obtained using equation 3:
wb ═ (W2-W1) a12/(a11+ a12) formula 3;
in equation 3, Wb is the cell wall and cell cavity bound water content, in grams by weight; w2 is the weight of the balance wood in grams; w1 is the weight of oven dried wood in grams.
6. Use of a method of measuring the free water content of the cell walls of equilibrium wood as claimed in any one of claims 1 to 5 in the determination of the free water content of equilibrium hydrophilic pore material.
7. The use of claim 6, wherein the equilibrium hydrophilic pore material comprises a hygroscopic equilibrium hydrophilic pore material or a desorption equilibrium hydrophilic pore material.
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| CN103954921A (en) * | 2014-03-13 | 2014-07-30 | 中国科学院电工研究所 | Nuclear magnetic resonance detection method of nanocomposite |
| CN110031495A (en) * | 2019-03-21 | 2019-07-19 | 南京林业大学 | A method of based on magnetic resonance detection engineering bamboo and wood materials crackle |
| CN110618159A (en) * | 2019-11-05 | 2019-12-27 | 湖北民族大学 | LF-NMR determination method for water content of nanmu seeds |
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| CN103954921A (en) * | 2014-03-13 | 2014-07-30 | 中国科学院电工研究所 | Nuclear magnetic resonance detection method of nanocomposite |
| CN110031495A (en) * | 2019-03-21 | 2019-07-19 | 南京林业大学 | A method of based on magnetic resonance detection engineering bamboo and wood materials crackle |
| CN110618159A (en) * | 2019-11-05 | 2019-12-27 | 湖北民族大学 | LF-NMR determination method for water content of nanmu seeds |
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