Soil moisture content detection method based on unstable heat conduction and optical fiber temperature measurement

Abstract

The invention provides a soil moisture content detection method based on unsteady heat conduction and optical fiber temperature measurement, which comprises the following steps: heating a soil body in a target measurement area based on an active heating method, and measuring the temperature value of the soil body at each moment under different radial distances from a heating source in the heating process; substituting the soil body temperature value at any moment in the heating process and the corresponding radial distance into a predetermined soil body moisture content relation model to obtain the soil body moisture content at the position corresponding to the radial distance from the heating source in the target measurement area at the corresponding moment; and determining the soil mass moisture content of the target measurement area according to the soil mass moisture content at each radial distance position from the heating source in the target measurement area at the corresponding moment. According to the method, the relationship between the soil moisture content and the soil temperature value is established, and in-situ monitoring and long-time monitoring of the large-range soil in the target measuring area are achieved through the soil temperature value obtained through the active heating method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil moisture field monitoring, and in particular to a soil water content detection method based on non-steady-state heat conduction and optical fiber temperature measurement. BACKGROUND

[0002] As a core indicator of soil water state, the accurate determination of water content is crucial for studying soil ecological characteristics, engineering performance, and exploring water migration and storage mechanisms, and is the basis for related research in the fields of geology, geotechnical engineering, and agricultural ecological environment.

[0003] Currently, soil water content measurement methods based on optical fiber technology are widely used in the field due to their strong anti-interference, distributed monitoring, and good durability. In the prior art, the core idea of using optical fibers to calculate soil water content is to establish a quantitative relationship between temperature characteristic values (or optical signal characteristic values) and water content through laboratory calibration: Specifically, the technical personnel need to first prepare soil samples with different water contents in the laboratory, bury optical fiber sensors (such as active heating optical fibers, distributed optical fiber temperature measurement systems, etc.) in the samples, and through measuring the temperature changes, optical power attenuation, or Brillouin frequency shift of the optical fiber under different water contents, a calibration formula of characteristic values and water content is fitted; then the formula is applied to field soil measurement, and the water content is inversely calculated through the measured characteristic values of the optical fiber.

[0004] However, the existing technology has obvious defects: on the one hand, the laboratory calibration process is tedious, requiring the preparation of a large number of soil samples with different water contents and even different dry densities, and the calibration operation is affected by factors such as soil uniformity and experimental environment temperature, which is time-consuming and labor-intensive; on the other hand, the adaptability of the formula established by laboratory calibration to field soil is poor - the texture, pore structure, and mineral composition of field soil often differ from laboratory samples, leading to deviations in the application of the calibration formula and reducing the measurement accuracy; in addition, the traditional method relies too much on laboratory calibration results, lacks a simplified model with strong universality, and is difficult to quickly adapt to the measurement needs of different regions and different types of soil, limiting the popularization and application of optical fiber technology in rapid water content monitoring. SUMMARY

[0005] The present application provides a soil water content detection method based on non-steady-state heat conduction and optical fiber temperature measurement, to solve the lack of universality of the existing soil water content measurement method based on optical fiber, and to realize an accurate, efficient and convenient soil water content detection method based on non-steady-state heat conduction and optical fiber temperature measurement.

[0006] The present application provides a soil water content detection method based on non-steady-state heat conduction and optical fiber temperature measurement, comprising: The soil body in a target measurement area is heated based on an active heating method, and the soil body temperature value at each moment is measured at different radial distances from the heating source during the heating process, wherein the target measurement area comprises several soil layers; The soil body temperature value at any moment during the heating process and the corresponding radial distance are substituted into a predetermined soil water content relationship model to obtain the soil water content of the target measurement area at the corresponding radial distance from the heating source at the corresponding moment, wherein the soil water content relationship model is determined according to a first relationship between the thermal diffusion coefficient and the soil temperature value, a second relationship between the water content and the thermal diffusion coefficient, and the soil layer corresponding to the soil temperature value. The soil water content of the target measurement area is determined according to the soil water content of the target measurement area at the corresponding radial distance from the heating source at the corresponding moment.

[0007] According to the soil water content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application, the first relationship is derived based on the heat conduction equation in the cylindrical coordinate system according to the non-steady-state heat conduction model, and the second relationship is constructed based on the Hashin-Shtrikman model.

[0008] According to the soil water content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application, the soil water content relationship model comprises: (1); (2); Wherein, formula (1) represents the second relationship, represents the soil water content, represents t the radial distance of the target measurement area from the heating source at the moment, r the thermal diffusion coefficient of the soil body at the radial distance of the target measurement area from the heating source, represents the dry soil thermal diffusion coefficient of the soil body of the target measurement area, represents the thermal diffusion coefficient of the soil water of the target measurement area, represents the dry soil specific heat capacity of the soil body of the target measurement area; represents the specific heat capacity of the soil water of the target measurement area; formula (2) represents the first relationship, is an empirical coefficient, T w represents the temperature of the heating source surface, T 0 represents the initial temperature of the soil body of the target measurement area before heating.

[0009] According to the soil water content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application, before the step of heating the soil body in the target measurement area based on the active heating method, the method further comprises: Sampling the soil body of each soil layer in the target measurement area to obtain soil samples of each soil layer; performing soil drying experiments on the soil samples of the respective soil layers to obtain the dry soil thermal diffusivity of the soil bodies of the respective soil layers of the target measurement area and the dry soil specific heat capacity of the soil bodies of the respective soil layers of the target measurement area; determining the soil moisture content relationship models corresponding to the respective soil layers of the target area based on the dry soil thermal diffusivity and the dry soil specific heat capacity of the soil bodies of the respective soil layers of the target measurement area.

[0010] According to the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application, the step of substituting the soil temperature value at any time during the heating process and the corresponding radial distance into a predetermined soil moisture content relationship model to obtain the soil moisture content of the soil at the position corresponding to the radial distance from the heating source in the target measurement area at the corresponding time comprises: determining the soil layer corresponding to each soil temperature value measured according to the soil layer distribution of the target measurement area; calling the soil moisture content relationship model corresponding to each soil layer, substituting each soil temperature value and the corresponding radial distance into the soil moisture content relationship model of the corresponding soil layer to obtain the soil moisture content at the position of the soil temperature value.

[0011] According to the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application, the step of heating the soil of the target measurement area based on the active heating method comprises: arranging an active heating optical fiber and a plurality of temperature measurement optical fibers in the target measurement area, wherein the plurality of temperature measurement optical fibers are used to measure the temperature of a plurality of measurement sections parallel to and spaced apart from the active heating optical fiber by different radial distances; heating the active heating optical fiber to a preset temperature at the surface, and the soil temperature of the target measurement area reaches a steady state.

[0012] The application also provides a soil moisture content detection system based on non-steady-state heat conduction and optical fiber temperature measurement, comprising: An acquisition module is configured to obtain the soil temperature value at each time at different radial distances from the heating source during the heating process, wherein the heating process is the process of heating the soil of the target measurement area based on the active heating method, and the target measurement area comprises a plurality of soil layers. A calculation module is configured to substitute the soil temperature value at any time during the heating process and the corresponding radial distance into a predetermined soil moisture content relationship model to obtain the soil moisture content of the soil at the position corresponding to the radial distance from the heating source in the target measurement area at the corresponding time, wherein the soil moisture content relationship model is determined according to a first relationship between the thermal diffusivity and the soil temperature value, a second relationship between the moisture content and the thermal diffusivity, and the soil layer corresponding to the soil temperature value. A determining module is configured to determine the soil moisture content of the target measurement area according to the soil moisture content of the target measurement area at the corresponding time.

[0013] The application further provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement according to any one of the above when executing the program.

[0014] The application further provides a non-transitory computer-readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement according to any one of the above.

[0015] The application further provides a computer program product, which includes a computer program, and the computer program is executed by a processor to implement the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement according to any one of the above.

[0016] The application provides the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement, which constructs the relationship between the soil moisture content and the soil temperature value, so that the in-situ monitoring and long-time monitoring of the large-area soil of the target measurement area are realized by the soil temperature value obtained by the active heating method, and the detection process does not need a large number of complex laboratory operations, and the efficiency of the soil moisture content detection of the large area is improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0018] Figure 1 is a flowchart of the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application; Figure 2 is a graph of the fitting temperature change with time and distance in the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application; Figure 3 is a comparison graph of the numerical solution and the engineering approximate solution in the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application; Figure 4 is a schematic diagram of the influence of the empirical coefficient on the engineering approximate solution in the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the application; Figure 5 is the temperature change relation graph with distance and time fitted in verification of the soil moisture content detection method based on non-steady heat conduction and optical fiber temperature measurement provided by the application; Figure 6 is the heat diffusion coefficient and radial distance relation graph fitted in verification of the soil moisture content detection method based on non-steady heat conduction and optical fiber temperature measurement provided by the application; Figure 7 is the moisture content and radial distance relation graph obtained in verification of the soil moisture content detection method based on non-steady heat conduction and optical fiber temperature measurement provided by the application; Figure 8 is a structural schematic diagram of the soil moisture content detection system based on non-steady heat conduction and optical fiber temperature measurement provided by the application; Figure 9 is a structural schematic diagram of the electronic device provided by the application. DETAILED DESCRIPTION

[0019] To make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0020] The present application will be described below with reference to the drawings. Figures 1 to 7 The present application provides a soil moisture content detection method based on non-steady heat conduction and optical fiber temperature measurement, as shown in FIG. Figure 1 , which comprises the following steps. Step 101, heating the soil in the target measurement area based on the active heating method, and measuring the soil temperature value at each time under different radial distances from the heating source during the heating process, wherein the target measurement area contains several soil layers. The active heating method (AHFO) is an in-situ monitoring technology based on the principle of heat conduction, which analyzes the temperature response characteristics of the soil after heating by parallelly arranging heating probes and measuring probes in the soil to invert the moisture content, wherein the heating probe is used to heat the soil in the surrounding area, and the measuring probe is used to measure the temperature of the soil after heating. According to the readings of the measuring probe at different positions, the temperature measurement values of the soil at different depths are obtained.

[0021] In this embodiment, the target measurement area is the three-dimensional area corresponding to the target area determined in the plane of the target test field at the preset measurement depth. The number of soil layers contained in the target measurement area is different according to different preset measurement depths, and the target measurement area determined according to the target test field and the preset measurement depth contains one or more soil layers.

[0022] Optionally, a drill hole of a preset measuring depth is drilled at a center position of the target area, a heating probe is buried, and then according to the size of the target area and the number of the measuring probes, drill holes are drilled at positions at different radial distances from the heating probe, the number of the drill holes is the same as the number of the measuring probes, and the multiple drill holes can cover different positions of the target area as much as possible. A temperature measuring probe is buried in each drill hole, so that according to the reading of the temperature measuring probe at each moment after heating to a steady state, the soil temperature value at each moment at different radial distances from the heating source in the heating process is obtained.

[0023] In step 102, the soil temperature value at any moment in the heating process and the corresponding radial distance are substituted into a predetermined soil moisture content relationship model to obtain the soil moisture content of the target measurement area at the corresponding radial distance position from the heating source at the corresponding moment, wherein the soil moisture content relationship model is determined according to a first relationship between the thermal diffusion coefficient and the soil temperature value, a second relationship between the moisture content and the thermal diffusion coefficient, and the soil layer corresponding to the soil temperature value. The soil moisture content relationship model is composed of the first relationship and the second relationship, wherein the second relationship represents the relationship between the soil moisture content and the thermal diffusion coefficient, and the first relationship represents the relationship between the thermal diffusion coefficient and the soil temperature value, so that the soil moisture content relationship model represents the relationship between the soil moisture content and the soil temperature value after substitution of the thermal diffusion coefficient.

[0024] On this basis, by determining the soil temperature values obtained at different radial distances, the soil moisture content of the position corresponding to the soil temperature value can be calculated by substituting the soil moisture content relationship model.

[0025] Since the soil moisture content relationship in the embodiment includes the relationship between the thermal diffusion coefficient and the soil temperature, i.e., the law of heat diffusion in the soil, it can be understood that different soil layers correspond to different first relationships, i.e., different parameter values in the soil moisture content relationship model.

[0026] Therefore, for each measured soil temperature value, the soil layer to which it belongs is determined according to its measurement position, the parameter value of the soil moisture content relationship model corresponding to the soil layer is determined, and then the soil moisture content of the soil at its position is calculated by substituting the determined soil moisture content relationship model.

[0027] In step 103, the soil moisture content of the target measurement area is determined according to the soil moisture content of the target measurement area at each radial distance position from the heating source at the corresponding moment.

[0028] For the soil temperature values at different radial distances obtained by all temperature measuring elements at any moment, the soil moisture content corresponding to each soil temperature value is determined in the above manner. The soil moisture content corresponding to the position of each soil temperature value is integrated to obtain the soil moisture content of the target measurement area.

[0029] The soil moisture content of the target measurement area can be obtained by integrating the sets of soil temperature values over time, thereby achieving overall measurement and long-term monitoring of the soil moisture content of a large area through temperature monitoring.

[0030] The present application can achieve in-situ monitoring and long-term monitoring of the soil of a target measurement area by constructing the relationship between the soil moisture content and the soil temperature value, and the soil temperature value obtained by active heating, and the detection process does not require a large number of complex laboratory operations, thereby improving the efficiency of the detection of the soil moisture content of a large area.

[0031] In the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement, the first relationship is derived based on the heat conduction equation in the cylindrical coordinate system according to the non-steady-state heat conduction model, and the second relationship is constructed based on the Hashin-Shtrikman model.

[0032] For non-steady-state temperature changes, the temperature changes with time, in order to control the number of variables, the thermal diffusivity is introduced: Only the temperature change of the optical fiber itself is monitored, it is assumed that the optical fiber is in good contact with the soil, and the gap between the optical fiber and the soil is only the pore of the soil, and there is no excess air, and the thermal diffusivity of the soil changes with the change of the moisture content, according to the Fourier law, the greater the thermal conductivity, the higher the heat flow; the cable radius can be ignored compared with the soil, and in the process of cable heating, the temperature will quickly spread to the soil, at this time, the thermal diffusivity of the soil plays a decisive role, and the soil moisture content determines the size of the thermal diffusivity, in the same type of soil layer and the same moisture content area, the temperature change monitored by the optical fiber is the same, that is, the temperature rise value under the same heating power .

[0033] In this embodiment, in order to construct the relationship between the soil moisture content and the soil temperature value, the thermal diffusivity is taken as an intermediate quantity, and the first relationship between the thermal diffusivity and the soil temperature value and the second relationship between the soil moisture content and the thermal diffusivity are derived respectively.

[0034] The first relationship is derived as follows: In non-steady-state heat conduction, the temperature of each point in the object is a function of time and space, and the cylindrical coordinate system is taken for analysis to determine the heat conduction differential equation with a heat source. In the active heating method, the heating optical fiber / heating cable as a heating source is a line heat source in the soil, the axial heat conduction is ignored, and the heat conduction differential equation can be simplified to a one-dimensional non-steady-state equation.

[0035] On this basis, it is assumed that heating is defined as: given an initial temperature, heat is then diffused to the soil body, and then captured by the measured temperature optical fiber, that is, the heating optical fiber is assumed to be cylindrical, with a radius of , buried in the soil, and the surface temperature of the heating optical fiber is constant T w , the unsteady heat conduction takes the heat conduction differential equation in cylindrical coordinates, which can be simplified as: ; In the above formula, the left half of the equation represents the change of temperature with time, and the right half of the equation represents the simplified unsteady one-dimensional cylindrical coordinate heat conduction relationship containing only the change in radial direction and not containing internal heat source.

[0036] wherein represents the temperature of the soil body at a radial distance r , and time t , and is the soil thermal diffusion coefficient.

[0037] Further, the initial condition and the boundary condition are defined to solve the above formula, wherein the initial condition represents the state of the soil body before heating, and the boundary condition represents the state of the soil body after being heated to a steady state using the active heating method.

[0038] Optionally, the initial condition defined in the embodiment is t =0: T 0: T ( r ,0)= T 0( );wherein represents the radius of the active heating optical fiber as a heating source, T 0 represents the initial temperature of the soil body before heating.

[0039] Optionally, the boundary condition defined in the embodiment is: : T ( r ,0)= T w ( t >0); : ( t ≥0); The simplified heat conduction differential equation is solved by the above initial condition and boundary condition to obtain the change relationship of the temperature value of the soil body with distance and time.

[0040] As a preferred, in order to reduce the number of variables, a dimensionless parameter is defined in the embodiment for dimensionless processing of the initial condition and the boundary condition, which specifically includes: Dimensionless temperature: ; wherein, , corresponding to the heating cable surface temperature, corresponding to the temperature at a location infinitely far from the heating cable.

[0041] Dimensionless radius: ; , corresponding to the heating cable surface location.

[0042] Dimensionless time: ; for characterizing the degree of heat diffusion.

[0043] On this basis, the dimensionless control equation is obtained as: ; The corresponding dimensionless initial condition and dimensionless boundary condition are: , ; , ; , .

[0044] Since the control equation is complex to calculate, in the present embodiment, the finite difference method is used to discretize the equation to realize solving through programming, and the obtained temperature change curve is shown in Figure 2 .

[0045] In actual application, it is necessary to realize rapid estimation, trend analysis and real-time detection of projects, therefore, in combination with the logarithmic decay characteristics of the heat conduction in cylindrical coordinates, a simplified analytical expression is obtained to characterize the common trend of multiple curves in Figure 2 : (3); In the formula, is an empirical coefficient, .

[0046] Specifically, in the solving process of the above project approximate solution, a similar variable is introduced as: ; in the formula, represents the ratio of the radial distance increment to the characteristic diffusion length, is the diffusion distance of the thermal disturbance in time t .

[0047] On this basis, the accurate solution of the dimensionless control equation after introducing the above variable is: ; wherein, Complementary error function, which is in the form of: .

[0048] By analyzing the asymptotic property of error function, when , (Asymptotic expansion), the change trend is consistent with the decay characteristics of exponential function , which can be further simplified in engineering, ignoring the coefficient difference, directly using exponential function to fit the decay trend of error function, that is: ; In the formula, is an empirical coefficient, which is about the deviation of the modified exponential function and the error function.

[0049] Then the corresponding strain of the exact solution is: , as an exponential approximation.

[0050] Substitute the similarity variable and the exponential approximation into the over-temperature definition, get the above formula (3).

[0051] Verify the engineering approximate solution derived above, as shown in Figure 3 and Figure 4 : When , , then , which meets the surface temperature condition.

[0052] When , , then T → T 0, which meets the far-field condition.

[0053] On this basis, the first relationship between the thermal diffusivity coefficient and the soil temperature value derived from formula (1) is: (2).

[0054] The second relationship is derived as follows: The thermal diffusivity coefficient of soil is determined by the thermal physical properties of its constituent components (dry soil and water) and the structural characteristics of the soil (such as porosity and saturation). The natural soil mass moisture content is the ratio of the mass of water in the soil to the mass of dry soil, which can be expressed as: ; In the formula, represents the density of soil water, represents the porosity of natural soil, represents the saturation of natural soil, represents the dry soil density.

[0055] Combining the expression of thermal diffusivity , and the porosity and saturation of natural soil are taken into the volume-weighted average model to estimate the thermal conductivity of natural soil composite medium, and the influence of gas on solid and liquid can be ignored, so the air is not considered in the following calculation. The volume fractions of dry soil and water are: ; wherein, and represent the volume of dry soil and soil water, respectively.

[0056] Then: ; ; The derivation is as follows: .

[0057] Further, the thermal conductivity k can be estimated by the Hashin-Shtrikman model theoretical framework considering the influence of dry soil and water and their mutual coupling effect, and the influence of air is not considered. The thermal conductivity of natural soil is: ; In the formula, k is the thermal conductivity of natural soil, are the thermal conductivities of dry soil, water and air, respectively, are the volume fractions of dry soil, water and air, respectively.

[0058] After simplification, we get: ; ; Substituting it into the expression of thermal diffusivity, we get: .

[0059] That is: .

[0060] Substituting it into the expression of soil moisture content, we get the second relationship: .

[0061] On this basis, the soil moisture content relationship model constructed according to the first relationship and the second relationship derived is: (1); (2); In the formula, (1) represents the second relationship, represents the soil moisture content, represents tThe radial distance of the target measurement area from the heating source at the time r The thermal diffusivity of the soil mass, The dry soil thermal diffusivity of the soil mass in the target measurement area, The thermal diffusivity of the soil water in the target measurement area, The dry soil specific heat capacity of the soil mass in the target measurement area; The specific heat capacity of the soil water in the target measurement area; the first relationship is represented by formula (2), is an empirical coefficient, T w The temperature of the heating source surface, T 0 represents the initial temperature of the soil mass in the target measurement area before heating.

[0062] In one specific embodiment, T is the measured soil mass temperature value, T W The target heating temperature of the heating cable used according to the active heating method is determined, t The actual heating time corresponding to the time when the soil mass temperature value is obtained is determined, Before heating the soil mass in the target measurement area, the measured value is obtained, r According to the position corresponding to the soil mass temperature value, k Before heating the soil mass, the soil mass in the target measurement area is sampled and measured using a thermal conductivity meter.

[0063] The thermal diffusivity of the soil water can be represented by the thermal diffusivity table of natural water.

[0064] The thermal diffusivity of the dry soil can be obtained by collecting soil samples on site and obtaining dry soil samples through soil drying experiments, and directly measuring the dry soil samples using a thermal conductivity meter.

[0065] The specific heat capacity of the soil water can be obtained by using the specific heat capacity of natural water through table lookup.

[0066] The dry soil specific heat capacity can be calculated by formula, specifically, the dry soil density is calculated by measuring the volume and mass of the dry soil sample, and then the dry soil specific heat capacity is calculated in combination with the thermal diffusivity of the dry soil.

[0067] In the above manner, the dry soil thermal diffusivity and the dry soil specific heat capacity of each soil layer are determined in advance according to the soil layer distribution of the target measurement area, and then the parameter values of the soil water content relationship model corresponding to each soil layer are determined. Then, the measured soil mass temperature value is substituted into the soil water content relationship model corresponding to the soil layer to which the measurement position belongs, and the soil water content of the measurement position can be directly calculated.

[0068] Compared with the existing active heating method, the method in the embodiment can obtain the correlation coefficient of dry soil after sampling in the detection field of the target measurement area, determine the parameter value of the soil moisture content relationship model, and then measure the soil temperature value at different radial distances by using the active heating method, so that the corresponding soil moisture content can be directly calculated, and the measurement efficiency is improved.

[0069] The present application combines in-situ testing with a small amount of laboratory data, constructs a simplified model based on physical mechanisms, uses the response relationship between temperature and optical fiber signals to derive the moisture content calculation formula, and reduces the dependence on complex calibration process. At the same time, introduce the basic parameters of soil that can be quickly obtained on site, such as density and particle size distribution, to make local corrections to the model, thereby improving its applicability in different geological conditions. In addition, a matching data processing algorithm can be developed to realize automatic calculation and real-time feedback of moisture content, improve measurement efficiency and intelligent level.

[0070] In the soil moisture content detection method based on unsteady heat conduction and optical fiber temperature measurement, before the step of heating the soil in the target measurement area based on the active heating method, the method further comprises: Sampling the soil in each soil layer of the target measurement area to obtain soil samples of each soil layer; Pre-sampling to determine the soil layer distribution of the target measurement area, and in the case that the target measurement area includes multiple soil layers, sampling each soil layer to obtain soil samples of each soil layer.

[0071] Performing soil drying experiments on the soil samples of each soil layer to obtain the dry soil thermal diffusivity of each soil layer in the target measurement area and the dry soil specific heat capacity of each soil layer in the target measurement area. Since the soil moisture content relationship model needs to specify the dry soil thermal diffusivity and dry soil specific heat capacity of the soil in the target measurement area, the dry soil thermal diffusivity and dry soil specific heat capacity of each soil layer are determined by performing soil drying experiments on the soil samples of each soil layer.

[0072] Specifically, for each soil layer, the soil sample is sampled using a cutting ring, and the volume of the cutting ring is determined as the soil sample volume; the soil sample of the cutting ring is dried, and the dry soil mass is obtained by weighing with a balance, so that the dry soil density is calculated based on the soil sample volume and the dry soil mass using the density formula.

[0073] On this basis, the thermal diffusivity of the dry soil is directly measured by using a thermal conductivity coefficient tester.

[0074] The dry soil specific heat capacity is calculated through the formula of the thermal diffusivity.

[0075] Based on the dry soil thermal diffusivity coefficient and the dry soil specific heat capacity of each soil layer of the target measurement area, a soil moisture content relationship model corresponding to each soil layer of the target area is determined.

[0076] Based on the calculated dry soil thermal diffusivity coefficient and dry soil specific heat capacity of each soil layer of the target measurement area, the parameter value of the soil moisture content relationship model corresponding to each soil layer of the target area is determined, so as to determine the soil moisture content relationship model corresponding to each soil layer.

[0077] On this basis, when used, the soil layer to which the measurement point of the soil temperature value belongs is determined, and the corresponding soil moisture content relationship model is called to calculate the soil moisture content at the position.

[0078] In the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement, the step of substituting the soil temperature value at any time during the heating process and the corresponding radial distance into the pre-determined soil moisture content relationship model to obtain the soil moisture content at the position corresponding to the radial distance from the heating source in the target measurement area at the corresponding time is specifically as follows: According to the soil layer distribution of the target measurement area, the soil layer corresponding to each measured soil temperature value is determined; The soil moisture content relationship model corresponding to each soil layer is called, and each soil temperature value and its corresponding radial distance are substituted into the soil moisture content relationship model of the corresponding soil layer to obtain the soil moisture content at the position of the soil temperature value.

[0079] The soil layer distribution of the target measurement area is determined, specifically including the type of soil layer and the depth value range corresponding to each soil layer.

[0080] According to the temperature measuring element used for measuring the soil temperature value, the depth value of each measuring point on the temperature measuring element after the layout is determined, so that the soil layer to which each measuring point belongs is determined according to the depth value.

[0081] The measuring point to which each measured soil temperature value belongs is determined, and the soil layer corresponding to each soil temperature value is determined.

[0082] For each measured soil temperature value, the soil moisture content relationship model corresponding to the soil layer to which it belongs is called to obtain the soil moisture content at the position of the corresponding measuring point of the soil temperature value.

[0083] In the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement, the step of heating the soil of the target measurement area based on the active heating method specifically includes: A piece of active heating optical fiber and a plurality of temperature measuring optical fibers are laid in the target measurement area, wherein the plurality of temperature measuring optical fibers are used to measure the temperature of a plurality of measurement sections parallel to and spaced apart from the active heating optical fiber by different radial distances. The active heating optical fiber is heated to a preset temperature at the surface, and the soil temperature of the target measurement area reaches a steady state.

[0084] In the embodiment, the active heating optical fiber is selected as the heating source used in the active heating method, and the temperature measuring optical fiber is used as the temperature measuring element used in the active heating method.

[0085] Optionally, the number of temperature measuring optical fibers used is determined according to the size of the target measurement area. If the planar range or the depth of the target measurement area is large, more temperature measuring optical fibers are needed. If the target measurement area is small, only one temperature measuring optical fiber can be used to complete the measurement of the soil temperature at different radial distances.

[0086] For example, the active heating optical fiber is arranged at the center position of the target measurement area, and several temperature measuring optical fibers are arranged at positions with radial distances of 7 cm, 14 cm and 21 cm from the active heating optical fiber.

[0087] In the case of sufficient depth, three temperature measuring optical fibers are used to measure the soil temperature at three radial distance positions. The three temperature measuring optical fibers are connected to the DTS temperature measuring instrument to obtain the readings of each measuring point on the temperature measuring optical fiber and obtain the soil temperature value. In the case of shallow depth of the target measurement area, one temperature measuring optical fiber is used for measurement. The temperature measuring optical fiber is arranged in a U-shaped manner in each radial distance corresponding borehole, so that the temperature measuring optical fiber is arranged at three different radial distance positions, and the soil temperature value at different radial distances is measured.

[0088] Optionally, the U-shaped arrangement allows two measurement sections at one radial distance, and the data of one measurement section can be selected as the soil temperature value at the radial distance.

[0089] Optionally, the active heating method needs to determine the temperature of the surface of the active heating optical fiber. If the active heating optical fiber used contains a temperature measuring optical fiber, the reading thereof can be used to represent the temperature measurement value of the surface of the active heating optical fiber. If the active heating optical fiber used does not contain a temperature measuring optical fiber, an additional temperature measuring optical fiber can be attached to the active heating optical fiber to determine the temperature of the surface of the active heating optical fiber. T w .

[0090] That is, after determining the temperature of the surface of the active heating optical fiber, at least one measurement optical fiber is arranged at a preset radial distance from the active heating optical fiber to obtain the soil temperature value at the preset radial distance. The soil moisture content at the preset radial distance can be calculated based on the soil temperature value and the temperature of the surface of the active heating optical fiber.

[0091] When the soil of the target measurement area is heated by the active heating method, the temperature of the active heating optical fiber is monitored. T wDetermine whether the surface temperature of the actively heated optical fiber reaches the target value, which is 40°C in this embodiment; by monitoring the reading changes of each temperature measuring optical fiber, and measuring the thermal conductivity of the target measurement area soil during the heating process using a thermal conductivity tester, determine whether it is heated to a steady state according to the change of the thermal conductivity, after the soil in the target measurement area is heated to a steady state, read the measurement value of the temperature measuring optical fiber at a time or in a period of time as the soil temperature value at that time or in that period of time, and correspondingly calculate the soil moisture content of the target measurement area at that time or the soil moisture content change of the target measurement area in a period of time.

[0092] In a specific embodiment, in order to verify the soil moisture content relationship model proposed in this embodiment, a test is carried out in a simulated field environment in the laboratory.

[0093] Specifically, a standard experimental model box with a size of 4m long, 50cm wide and 49cm deep is selected, and the inside of the box is paved with uniform medium to be measured (fine river sand is used in this experiment), the paving thickness is uniform 40cm, and the medium to be measured is pre-processed to ensure the consistency of the initial state of the moisture content.

[0094] The heating cable is arranged in the model box, and the transformer controls the heating power by adjusting the voltage, and the voltage is constant at 75V, and the heating power is 128W. During the heating process, the temperature measuring optical fibers arranged equidistantly in the box monitor the temperature change in real time, and the temperature is heated to 40°C constant temperature, and the heating is stopped after the temperature in the model box reaches a steady state.

[0095] The whole experiment period is 8 hours, of which 3 hours are for medium pretreatment and optical fiber arrangement stage, and the last 5 hours are for formal monitoring stage, including data acquisition and analysis.

[0096] The optical fibers are arranged equidistantly at an interval of 0.07m in the same horizontal plane of the medium to be measured, and the monitoring range can cover the entire temperature influence radius of the heating cable, and only one arrangement is needed to realize the synchronous detection and monitoring of the moisture content of the entire area by using the DTS temperature monitoring instrument. In the 5 hours of formal detection, the temperature data in the area is automatically collected once every minute (the time can be adjusted), and then the moisture content result is calculated according to the temperature data.

[0097] The commonly used drying method is used as a comparison method, and the measuring points are selected around the optical fiber arrangement in the model box according to the uniform point arrangement principle (5 measuring points are taken along the arrangement direction of each optical fiber). Each measuring point needs to use a sampler to collect medium samples with a depth of 10cm. Put the samples into a drying oven at 105°C and dry to constant weight (12 hours), calculate the moisture content of each measuring point by weighing, and then take the average value of the moisture content data of all measuring points to obtain the approximate moisture content of the experimental area at that time.

[0098] It can be seen that, compared with the traditional drying method, firstly, for the measurement of the moisture content of the whole region, the method of the application can facilitate the measurement of the moisture content of a larger range of regions and clearly determine the change rule of the moisture content of the region without a large number of sampling; secondly, for the monitoring of the change of the moisture content, after the laying of the heating cable and the temperature measuring optical fiber is completed, the method of the application only needs temperature monitoring to monitor the change of the moisture content of the region without repeated sampling and repeated measurement.

[0099] In addition, under the above laboratory conditions, the fitted temperature changes with time and radius are as shown in Figure 5 As shown in Figure 6 The calculated thermal diffusion coefficients (recorded every two minutes) are uniformly distributed in 4×10 -7 , with an error of ±0.5×10 -7 , which can verify the accuracy of the thermal diffusion coefficient formula (the first relationship) obtained by the approximate solution of the application.

[0100] As shown in Figure 7 Similarly, recorded every two minutes, the average error is also about 0.001 when compared with the drying method, which shows that the results are close and can be used for rough estimation of a large area to realize time-domain moisture content measurement.

[0101] The soil moisture content detection system based on unsteady heat conduction and optical fiber temperature measurement provided by the application is described below. The soil moisture content detection system based on unsteady heat conduction and optical fiber temperature measurement described below can be mutually corresponding and referred to the soil moisture content detection method based on unsteady heat conduction and optical fiber temperature measurement described above.

[0102] As shown in Figure 8 The soil moisture content detection system based on unsteady heat conduction and optical fiber temperature measurement includes an acquisition module 801, a calculation module 802 and a determination module 803; The acquisition module 801 is configured to acquire the soil temperature value at each time under different radial distances from the heating source in the heating process, wherein the heating process is a process of heating the soil in the target measurement area based on the active heating method, and the target measurement area includes a plurality of soil layers. The active heating method (AHFO) is an in-situ monitoring technology based on the principle of heat conduction, which analyzes the temperature response characteristics of the soil after heating by laying heating probes and measurement probes in parallel in the soil to invert the moisture content, wherein the heating probe is used to heat the soil in the surrounding area, and the measurement probe is used to measure the temperature of the soil after heating. According to the readings of the measurement probe at different positions, the temperature measurement values of the soil at different depths are obtained.

[0103] In this embodiment, the target measurement area is a three-dimensional area corresponding to the target area determined in the plane of the target test field at a preset measurement depth. The number of soil layers included in the target measurement area varies with the preset measurement depth. According to the target test field and the preset measurement depth, the determined target measurement area includes one or more soil layers.

[0104] Optionally, a drill hole of the preset measurement depth is drilled at the center position of the target area, a heating probe is buried, and then according to the size of the target area and the number of the measurement probes, drill holes are drilled at positions at different radial distances from the heating probe, so that the number of the drill holes is the same as the number of the measurement probes, and the multiple drill holes can cover different positions of the target area as much as possible. A temperature measurement probe is buried in each drill hole, so that the soil temperature value at each time during the heating process at different radial distances from the heating source is obtained according to the reading of the temperature measurement probe at each time after the heating reaches a steady state.

[0105] The calculation module 802 is configured to substitute the soil temperature value at any time during the heating process and the corresponding radial distance into a predetermined soil water content relationship model to obtain the soil water content of the position in the target measurement area corresponding to the radial distance from the heating source at the corresponding time, wherein the soil water content relationship model is determined according to a first relationship between the thermal diffusion coefficient and the soil temperature value, a second relationship between the water content and the thermal diffusion coefficient, and the soil layer corresponding to the soil temperature value. The soil water content relationship model is composed of the first relationship and the second relationship, wherein the second relationship represents the relationship between the soil water content and the thermal diffusion coefficient, and the first relationship represents the relationship between the thermal diffusion coefficient and the soil temperature value, so that the soil water content relationship model represents the relationship between the soil water content and the soil temperature value after substitution of the thermal diffusion coefficient.

[0106] On this basis, by determining the soil temperature values obtained at different radial distances, the soil water content of the position corresponding to the soil temperature value can be calculated by substituting the soil temperature values into the soil water content relationship model.

[0107] Since the soil water content relationship in this embodiment includes the relationship between the thermal diffusion coefficient and the soil temperature, i.e., the law of heat diffusion in the soil, it can be understood that the corresponding first relationship is different for different soil layers, i.e., the parameter values in the soil water content relationship model are different.

[0108] Therefore, for each measured soil temperature value, the soil layer to which it belongs is determined according to its measurement position, the parameter value of the soil water content relationship model corresponding to the soil layer is determined, and then the soil water content of the soil at its position is calculated by substituting the soil temperature value into the determined soil water content relationship model.

[0109] The determining module 803 is configured to determine the soil moisture content of the target measurement area according to the soil moisture content of the target measurement area at the corresponding time.

[0110] For the soil temperature values at different radial distances obtained by all temperature measuring elements at any time, the soil moisture content corresponding to each soil temperature value is determined in the above manner. The soil moisture content corresponding to the position of each soil temperature value is integrated, and the soil moisture content of the target measurement area is obtained.

[0111] All soil temperature values obtained at any time are taken as a set, and the sets of soil temperature values at all time sequences are integrated, and the soil moisture content of the target measurement area changing with time is also obtained, so that the overall measurement and long-term monitoring of the soil moisture content of a large area are realized through temperature monitoring.

[0112] The present application realizes in-situ monitoring and long-term monitoring of a large range of soil in the target measurement area by constructing the relationship between the soil moisture content and the soil temperature value, and the soil temperature value obtained by the active heating method, and the detection process does not require a large number of complex laboratory operations, thereby improving the efficiency of the soil moisture content detection of a large area.

[0113] Figure 9 An example of an electronic device is shown in the physical structure diagram as shown in the figure, Figure 9 The electronic device can include a processor 910, a communications interface 920, a memory 930, and a communications bus 940, wherein the processor 910, the communications interface 920, and the memory 930 communicate with each other through the communications bus 940. The processor 910 can call the logic instructions in the memory 930 to execute the soil moisture content detection method based on non-steady-state heat conduction and fiber temperature measurement, which includes: heating the soil in the target measurement area based on the active heating method, and measuring the soil temperature value at each time at different radial distances from the heating source during the heating process, wherein the target measurement area contains several soil layers; the soil temperature value at any time during the heating process and the corresponding radial distance are substituted into a predetermined soil moisture content relationship model to obtain the soil moisture content at the corresponding time at the corresponding radial distance position from the heating source in the target measurement area, wherein the soil moisture content relationship model is determined according to the first relationship between the thermal diffusivity and the soil temperature value, the second relationship between the moisture content and the thermal diffusivity, and the soil layer corresponding to the soil temperature value; and determining the soil moisture content of the target measurement area according to the soil moisture content of the target measurement area at the corresponding time at each radial distance position from the heating source.

[0114] In addition, the logic instructions in the memory 930 described above can be implemented in the form of software functional units and sold or used as independent products, and can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application or the part of the prior art or the part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0115] In another aspect, the present application also provides a computer program product, which comprises a computer program, the computer program can be stored on a non-transitory computer readable storage medium, and the computer program can be executed by a processor to enable a computer to execute the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement provided by the above-mentioned method, the method comprising: heating the soil in the target measurement area based on the active heating method, and measuring the soil temperature value at each moment at different radial distances from the heat source during the heating process, wherein the target measurement area comprises a plurality of soil layers; substituting the soil temperature value at any moment during the heating process and the corresponding radial distance into a predetermined soil moisture content relationship model to obtain the soil moisture content at the corresponding radial distance position from the heat source in the target measurement area at the corresponding moment, wherein the soil moisture content relationship model is determined according to a first relationship between the thermal diffusion coefficient and the soil temperature value, a second relationship between the moisture content and the thermal diffusion coefficient, and the soil layer corresponding to the soil temperature value; and determining the soil moisture content of the target measurement area according to the soil moisture content at each radial distance position from the heat source in the target measurement area at the corresponding moment.

[0116] In yet another aspect, the present application also provides a non-transitory computer readable storage medium having stored thereon a computer program, which, when executed by a processor, implements a method for detecting soil moisture content based on non-steady heat conduction and fiber-optic temperature measurement, the method comprising: heating soil in a target measurement area based on an active heating method, and measuring soil temperature values at each moment during the heating process at different radial distances from a heating source, wherein the target measurement area comprises a plurality of soil layers; substituting the soil temperature value at any moment during the heating process and the corresponding radial distance into a predetermined soil moisture content relationship model to obtain the soil moisture content at the corresponding radial distance from the heating source in the target measurement area at the corresponding moment, wherein the soil moisture content relationship model is determined according to a first relationship between a thermal diffusion coefficient and the soil temperature value, a second relationship between the moisture content and the thermal diffusion coefficient, and the soil layer corresponding to the soil temperature value; and determining the soil moisture content of the target measurement area according to the soil moisture content at each radial distance from the heating source in the target measurement area at the corresponding moment.

[0117] The device embodiments described above are merely illustrative, wherein the units described as separate components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place or distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to actual needs. Those skilled in the art can understand and implement without creative labor.

[0118] From the above description of the embodiments, those skilled in the art can clearly understand that the embodiments can be realized by means of software and necessary general hardware platforms, and of course can also be realized by hardware. Based on such understanding, the above technical solutions can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0119] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement, characterized in that, The method comprises the following steps: The soil in the target measurement area is heated based on an active heating method, and the soil temperature value at each moment at different radial distances from the heating source in the heating process is measured, wherein the target measurement area comprises several soil layers; The soil moisture content at the corresponding radial distance position from the heating source in the target measurement area at the corresponding moment is obtained by substituting the soil temperature value at any moment in the heating process and the corresponding radial distance into a pre-determined soil moisture content relationship model, wherein the soil moisture content relationship model is determined according to a first relationship between the thermal diffusion coefficient and the soil temperature value, a second relationship between the moisture content and the thermal diffusion coefficient, and the soil layer corresponding to the soil temperature value. The soil moisture content of the target measurement area is determined according to the soil moisture content at each radial distance position from the heating source in the target measurement area at the corresponding moment.

2. The soil moisture content detection method based on unsteady-state heat conduction and fiber-optic temperature measurement according to claim 1, characterized in that, The first relationship is derived based on the heat conduction equation in the cylindrical coordinate system according to the unsteady heat conduction model, and the second relationship is constructed based on the Hashin-Shtrikman model. 3.The soil moisture content detection method based on unsteady heat conduction and optical fiber temperature measurement according to claim 1, characterized in that, The soil moisture content relationship model comprises: （1）； （2）； wherein formula (1) represents the second relationship, represents the water content of the soil, represents t the radial distance of the target measurement area from the heating source at the moment, r the thermal diffusivity of the soil at the point, represents the dry soil thermal diffusivity of the soil in the target measurement area, represents the thermal diffusivity of the soil water in the target measurement area, represents the dry soil specific heat capacity of the soil in the target measurement area; represents the specific heat capacity of the soil water in the target measurement area; formula (2) represents the first relationship, k is an empirical coefficient, T w represents the temperature of the surface of the heating source, T 0 represents the initial temperature of the soil in the target measurement area before heating.

4. The soil moisture content detection method based on unsteady heat conduction and optical fiber temperature measurement according to claim 3, characterized in that, Before the step of heating the soil in the target measurement area based on the active heating method, the method further comprises the following steps: The soil in each soil layer of the target measurement area is sampled to obtain soil samples of each soil layer; The soil drying experiment is performed on the soil samples of each soil layer to obtain the dry soil thermal diffusion coefficient of the soil in each soil layer of the target measurement area and the dry soil specific heat capacity of the soil in each soil layer of the target measurement area; The soil moisture content relationship model corresponding to each soil layer of the target area is determined based on the dry soil thermal diffusion coefficient and the dry soil specific heat capacity of the soil in each soil layer of the target measurement area.

5. The method according to claim 4, wherein, The step of substituting the soil temperature value at any moment in the heating process and the corresponding radial distance into the pre-determined soil moisture content relationship model to obtain the soil moisture content at the corresponding radial distance position from the heating source in the target measurement area at the corresponding moment comprises the following steps: The soil layer corresponding to each soil temperature value measured is determined according to the distribution of the soil layers in the target measurement area; The soil moisture content relationship model corresponding to each soil temperature value and the corresponding radial distance is substituted into the soil moisture content relationship model of the corresponding soil layer to obtain the soil moisture content at the position of the soil temperature value.

6. The method according to any one of claims 1 to 4, wherein, The step of heating the soil in the target measurement area based on the active heating method comprises the following steps: A main heating optical fiber and several temperature measurement optical fibers are arranged in the target measurement area, wherein the several temperature measurement optical fibers are used to measure the temperature of several measurement sections parallel to and spaced apart from the main heating optical fiber by different radial distances; The main heating optical fiber is heated to a preset temperature at the surface, and the soil temperature of the target measurement area reaches a steady state.

7. A soil moisture content detection system based on unsteady-state heat conduction and fiber-optic temperature measurement, characterized in that, The method comprises the following steps: An acquisition module is configured to acquire the soil temperature value at each moment at different radial distances from the heating source in the heating process, wherein the heating process is the process of heating the soil in the target measurement area based on the active heating method, and the target measurement area comprises several soil layers; The computing module is configured to substitute the soil temperature value at any time during the heating process and the corresponding radial distance into a predetermined soil moisture content relation model to obtain the soil moisture content of the target measurement area at the corresponding time, at a position corresponding to the radial distance from the heat source, wherein the soil moisture content relation model is determined according to a first relation between the thermal diffusion coefficient and the soil temperature value, a second relation between the moisture content and the thermal diffusion coefficient, and a soil layer corresponding to the soil temperature value. The determining module is configured to determine the soil moisture content of the target measurement area according to the soil moisture content of the target measurement area at each radial distance from the heat source at the corresponding time.

8. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to implement the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement according to any one of claims 1-6. 9.A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement according to any one of claims 1-6.

10. A computer program product comprising a computer program, characterized in that, The computer program is executed by the processor to implement the soil moisture content detection method based on non-steady-state heat conduction and optical fiber temperature measurement according to any one of claims 1-6.

Images