Automatic top coal caving control method in fully mechanized caving mining based on natural gamma ray

Abstract

The present invention discloses an automatic top coal caving control method for fully mechanized top coal caving mining based on natural gamma rays, comprising the following steps: step 01, in a fully mechanized top coal caving mining environment, determining an optimal threshold voltage U1 of a natural gamma ray detector under a current working face environment, and determining a background radiation level W of a coal caving opening environment; step 02, determining a coal caving mode of a current working face; step 03, calculating a time y when gangue enters a coal caving opening according to the coal caving mode; step 04, setting a counter J 1 , J 2 and J 3 ; Step 05, during the top coal caving process, the natural gamma-ray detector monitors the real-time coal gangue radiation intensity data and determines whether to close the window process. The present invention establishes a top coal caving numerical model for fully mechanized caving mining, obtains the timing characteristics of gangue caving, realizes precise control of top coal caving within 3 seconds, and can effectively avoid misjudgment during coal caving.

Description

Technical Field

[0001] The invention relates to an automatic top coal caving control method for fully mechanized caving mining based on natural gamma rays. Background Art

[0002] The key to realizing intelligent coal mines is to realize intelligent coal mining operations, intelligent tunneling operations, and intelligent safety monitoring. For the intelligent construction of coal mining operations, the automated top coal caving technology in the comprehensive caving mining technology is not yet mature. The key problem is the lack of effective technical monitoring means to achieve high-accuracy instantaneous coal gangue identification. The characteristic of comprehensive caving mining technology is the division of thick coal seams. It divides thick coal seams into bottom coal and top coal. The bottom coal is mined by the coal mining machine, and the top coal is discharged from the coal caving port after combined crushing. Compared with other mining methods, top coal caving has high efficiency and low cost per ton of coal, and is suitable for various geological conditions.

[0003] The development of inertial navigation, memory coal cutting, infrared coal-rock identification and equipment automation technology has provided technical guidance for achieving the goal of intelligent comprehensive mining, and has been basically applied to the existing intelligent mining working face. However, at present, comprehensive mining mainly follows the principle of "closing the window when seeing gangue" through manual operation. The coal loss caused by this coal release control process accounts for 64% of the total coal loss in comprehensive mining, and the dust at the coal release site is relatively serious, which has a huge impact on the health of workers.

[0004] In addition, many scholars have used various methods such as hydraulic support memory coal caving technology and top coal movement tracker to automatically control top coal caving. However, there is almost no research on automatic control of top coal caving based on natural gamma-ray coal gangue identification technology. The top coal caving process, which is a key step in fully-mechanized top coal caving, has not yet had a relatively accurate automatic coal gangue identification technology that has been tested in practice. This is the biggest bottleneck in the current intelligentization of fully-mechanized top coal caving and is a key technology that urgently needs to be broken through. Summary of the invention

[0005] In view of the above problems, the present invention provides an automated top coal caving control method for fully-mechanized top coal caving based on natural gamma rays, establishes a numerical model of top coal caving in fully-mechanized top coal caving, obtains the timing characteristics of gangue release, realizes precise control of top coal caving within 3 seconds, and can effectively avoid misjudgment in the coal caving process.

[0006] Glossary:

[0007] 1. Excessive coal discharge mode means that coal continues to be discharged after the roof falls to the coal discharge port.

[0008] 2. The short-supply coal discharge mode means that the window is closed when the top plate has not been released from the coal discharge port.

[0009] 3. Normal coal discharge mode means that the window is closed after the roof is lowered to the coal discharge port.

[0010] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0011] A method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays comprises the following steps:

[0012] Step 01, in a fully mechanized caving mining environment, determine the optimal threshold voltage U1 of the natural gamma-ray detector under the current working face environment, calibrate the radiation intensity of coal to P1 and the radiation intensity of gangue to P2 under the optimal threshold voltage U1, and determine the background radiation level W of the coal caving port environment;

[0013] Step 02, determine the coal caving mode of the current working face: normal coal caving mode, excessive coal caving mode and insufficient coal caving mode;

[0014] Step 03: Calculate the time y when the gangue enters the coal discharge port according to the coal discharge mode, where:

[0015] Normal caving mode: The relationship between the position x of the roof in the top coal and the time y when it enters the caving port is: y = 0.49725x 2 +2.51076x-5.08615;

[0016] Excessive coal discharge mode: The relationship between the position x of the roof in the top coal and the time y when it enters the coal discharge port is: y = 0.3818x 2 -0.53576x+0.10214;

[0017] Coal discharge mode with insufficient quantity: The relationship between the position δ of the highest interlayer of gangue and its time y of entering the coal discharge port is: y=0.33259δ 2 +9.12231δ-13.13044;

[0018] Step 04: Set the counter J1 to record the number of signals sent from the natural gamma ray detector to the control board, and configure the maximum value of J1 to be J max ; Counter J2 is used to record the number of signals in the received signal that are greater than the window closing threshold; Counter J3 is used to record the number of times that the window closing threshold is exceeded continuously;

[0019] Step 05: During the top coal caving process, the natural gamma-ray detector performs real-time data monitoring of the radiation intensity of coal gangue;

[0020] Step 06: The control board first resets J1, J2, and J3 to zero;

[0021] Step 07, the control board starts to read the radiation data sent by the natural gamma ray detector. Each time a radiation data is read, the value of J1 is increased by 1, and the read radiation data is compared with the set window closing threshold. When the read radiation data is greater than the window closing threshold, the value of J2 is increased by 1, otherwise J2 remains unchanged;

[0022] Step 08: Determine whether J1 is greater than or equal to J max If yes, go to step 09; if no, go to step 07;

[0023] Step 09, determine whether J2 is greater than or equal to the set threshold M, if so, add 1 to the value of J3 and go to step 10; if not, go to step 06;

[0024] Step 10, determine whether the value of J3 is greater than or equal to the threshold value N, if so, proceed to step 11; if not, reset J1 and J2 to zero and proceed to step 07;

[0025] Step 11, determine whether the current coal discharge duration t is greater than or equal to the calculated window closing time. If it is reached, close the coal discharge port; otherwise, go to step 06.

[0026] Preferably, in normal coal discharge mode, the closing window time = y; in excessive coal discharge mode, In the short-supply coal discharge mode, the window closing time = y.

[0027] Preferably, the best threshold voltage U1=0.3V. Under this voltage condition, the radiation intensity of coal is calibrated to 31.5cps / kg·s, the radiation intensity of gangue is 46.25cps / kg·s, and the background radiation level of the coal discharge port environment is determined to be 60.3cps.

[0028] Preferably, the natural gamma-ray detector uses a Kalman filter method to filter the collected data.

[0029] Preferably, the filter factor is set to 1.

[0030] Preferred, J max The value is 10, the threshold M is 8, and the threshold N is 3.

[0031] Optimization, in normal coal discharge mode:

[0032] When the step distance of the frame is 1.6m, the relationship between the position x of the roof in the top coal and the time y when it enters the coal caving port is: y = 1.38164x 2 +0.4109x-2.56734;

[0033] When the step distance of the frame is 2.4m, the relationship between the position x of the roof in the top coal and the time y when it enters the coal caving port is: y = 1.78734x2 +6.88408x-8.57871.

[0034] Preferably, the sampling period of the natural gamma-ray detector is 0.1 s.

[0035] The beneficial effects of the present invention are:

[0036] The present invention establishes a numerical model of top coal caving in fully mechanized caving mining, obtains the timing characteristics of interlayer coal caving, provides evidence for determining the radiation characteristics of top coal caving, provides a basis for judgment for the window closing operation, and avoids the situation where the coal caving port is closed due to the misjudgment of interlayer coal as roof rock, thereby causing the loss of top coal resources. It is known that the natural gamma-ray detector sends 10 data per second, so in the whole cycle, the time to complete the judgment and close the window is only 3s, which greatly reduces the error caused by manual control of coal caving. At the same time, within 3 consecutive seconds, more than 80% of the data exceeds the specified radiation threshold every second and has reached the calculated window closing time, which can effectively avoid the phenomenon of misjudgment caused by the radiation intensity exceeding the threshold due to accidental factors during the coal caving process. The present invention realizes the automatic control of top coal caving, improves the comprehensive mechanization degree of coal mines, improves the recovery rate of top coal in fully mechanized caving mining, reduces the number of professionals on the working face, ensures the safety of workers, and avoids the randomness of manual control by workers. It is simple to operate, has high accuracy, adapts to complex underground environments, and has wide practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention discloses a flow chart of an automatic top coal caving control method in fully mechanized caving mining based on natural gamma rays. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0039] A method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays comprises the following steps:

[0040] Step 01, in a fully mechanized caving mining environment, determine the optimal threshold voltage U1 of the natural gamma-ray detector under the current working face environment, calibrate the radiation intensity of coal to P1 and the radiation intensity of gangue to P2 under the optimal threshold voltage U1, and determine the background radiation level W of the coal caving mouth environment.

[0041] Firstly, by testing coal and gangue under different threshold voltage conditions, the optimal threshold voltage for coal-gangue identification test in the fully-mechanized caving working face is determined, and the sensitivity, signal stability and environmental adaptability of the natural gamma-ray detector are verified. Then, by adjusting the natural gamma-ray detector to the optimal threshold voltage, the coal caving port environment of the fully-mechanized caving working face is detected, and the radiation intensity of coal is calibrated to P1 and the radiation intensity of gangue is P2. The background radiation level of the coal caving port environment of the working face is determined, which provides basic parameters for coal-gangue identification during coal caving. Finally, the radiation data for coal-gangue identification during coal caving is collected.

[0042] Step 02: Determine the coal caving mode of the current working face: normal coal caving mode, excessive coal caving mode and insufficient coal caving mode.

[0043] Due to the influence of normal coal caving, excessive coal caving, insufficient coal caving, coal caving step distance and other aspects, the changes in the trajectory morphology of the interlayer are not the same. It will also affect the boundary between the time sequence zone and the non-time sequence zone when the top coal is caving. Therefore, it is necessary to judge the coal caving mode of the current working face to facilitate subsequent data calculations.

[0044] Step 03: Calculate the time y when the gangue enters the coal discharge port according to the coal discharge mode, where:

[0045] Normal caving mode: The relationship between the position x of the roof in the top coal and the time y when it enters the caving port is: y = 0.49725x 2 +2.51076x-5.08615;

[0046] Excessive coal discharge mode: The relationship between the position x of the roof in the top coal and the time y when it enters the coal discharge port is: y = 0.3818x 2 -0.53576x+0.10214;

[0047] Coal discharge mode with insufficient quantity: The relationship between the position δ of the highest interlayer of gangue and its time y of entering the coal discharge port is: y=0.33259δ 2 +9.12231δ-13.13044.

[0048] Optimization, in normal coal discharge mode:

[0049] When the step distance of the frame is 1.6m, the relationship between the position x of the roof in the top coal and the time y when it enters the coal caving port is: y = 1.38164x 2 +0.4109x-2.56734;

[0050] When the step distance of the frame is 2.4m, the relationship between the position x of the roof in the top coal and the time y when it enters the coal caving port is: y = 1.78734x 2 +6.88408x-8.57871.

[0051] Step 04: Set the counter J1 to record the number of signals sent from the natural gamma ray detector to the control board, and configure the maximum value of J1 to be J max ; Counter J2 is used to record the number of signals in the received signals that are greater than the window closing threshold, where the window closing threshold can be determined through experiments based on the geological conditions and coal caving technology of the mine's fully mechanized caving working face; Counter J3 is used to record the number of times the window closing threshold is exceeded continuously.

[0052] Step 05: During the top coal dropping process, the natural gamma-ray detector conducts real-time data monitoring of the radiation intensity of coal gangue.

[0053] Step 06: The control board first resets J1, J2, and J3 to zero.

[0054] Step 07, the control board starts to read the radiation data sent by the natural gamma-ray detector. Each time a radiation data is read, the value of J1 is increased by 1, and the read radiation data is compared with the set window-closing threshold. When the read radiation data is greater than the window-closing threshold, the value of J2 is increased by 1, otherwise J2 remains unchanged.

[0055] Step 08: Determine whether J1 is greater than or equal to J max If yes, go to step 09; if no, go to step 07.

[0056] Step 09, determine whether J2 is greater than or equal to the set threshold M. If so, add 1 to the value of J3 and go to step 10; if not, go to step 06.

[0057] Step 10, determine whether the value of J3 is greater than or equal to the threshold value N, if so, proceed to step 11; if not, reset J1 and J2 to zero and proceed to step 07.

[0058] Step 11, determine whether the current coal discharge duration t is greater than or equal to the calculated window closing time. If it is reached, close the coal discharge port; otherwise, go to step 06. Specifically: in normal coal discharge mode, the window closing time = y; in excessive coal discharge mode, In the short-supply coal discharge mode, the window closing time = y.

[0059] The following is an example of the 8205 working face of Tashan Coal Mine, which is located in the southeast of Tashan Mine Field and the northeast of the Second Pan District. The corresponding ground is the Makouyu Valley and the mountain ridge section, with a ground elevation of 1441 to 1561m. The northeast is the 8203 goaf area, with a coal pillar of 8m. The 8203 working face began to be mined in July 2017 and stopped in June 2018. The southwest is the 8207 working face, which has not yet been excavated. The southeast is the Hulonggou Mine Field, and the northwest is connected to three large tunnels in the Second Pan District. The working face corresponds to a ground elevation of 1441 to 1561m. The thickness of the mountain cover is 383.21 to 470.24m, with an average of 431.33m.

[0060] The coal seam thickness of the 8205 working face is 9.82~22.26m, with an average thickness of 15.09m. The utilized thickness is 7.23~17.98m, with an average thickness of 12.45m. The coal seam contains 4~8 layers of gangue, with an average of 6 layers, and a thickness of 2.64m (including upper lamprophyre and silicified coal). The thickness of a single layer varies between 0.23 and 0.65m. The rock types of the gangue are: igneous rock, sandy mudstone, mudstone, carbonaceous mudstone, and kaolinite. Affected by the intrusion of lamprophyre, most of the upper part of the coal seam has been metamorphosed and silicified.

[0061] The thickness of the immediate roof of the coal seam in the 8205 working face is 2.92 to 6.25 m, with an average of 4.56 m. The lithology is: gray-black, gray-white mudstone, carbonaceous mudstone, sandy mudstone, lamprophyre, natural coke, flat fracture, containing clastic plant fossils; some parts contain No. 2 coal seam, which is seriously affected by the intrusion of lamprophyre, and most of them are metamorphosed and silicified. The conditions of the coal seam roof and floor and the rock mechanical properties are shown in Table 1.

[0062] Table 1 Roof and floor conditions and rock mechanical properties

[0063]

[0064]

[0065] A low-energy natural gamma-ray detector is selected. The detector is 1.35m long, 0.3m wide and 0.1m thick. The energy threshold can reach 35Kev, the background count is not less than 100cps, the range is 0.001~100uGy / h, the sensitivity is 1uGy / h≥1000cps, the relative error is not more than 5%, and the stable sampling period is 0.1s.

[0066] The data acquisition display can use the smart phone used in daily life. When used underground, a special mobile phone with explosion-proof function should be selected. By operating on the mobile phone software supporting the natural gamma ray detector, the sampling period, filter factor, and threshold voltage parameters of the natural gamma ray detector can be set. At the same time, the data received by the natural gamma ray detector will be displayed in real time in the software, where the horizontal axis represents the detection time in milliseconds and the vertical axis represents the detected radiation intensity value in cps. The natural gamma ray detector integrates a Bluetooth module, which establishes communication with the mobile phone to transmit data, allowing the data to be displayed in real time on the mobile phone and also to be saved in the mobile phone.

[0067] The natural gamma-ray detector in the 8205 working face environment of Tashan Coal Mine uses the Kalman filter method to filter the collected data. The filter factor is set to 1, the sampling period of the natural gamma-ray detector is 0.1s, and the optimal threshold voltage is 0.3V. Under this voltage condition, the radiation intensity of coal is 31.5cps / kg·s, the radiation intensity of gangue is 46.25cps / kg·s, and the background radiation level of the coal outlet environment is 60.3cps.

[0068] In the normal coal discharge mode, the discharge quality of coal and gangue and the mixed gangue rate are shown in Table 2. In the table, 1s refers to the 0-1s time period, 2s refers to the 1-2s time period, and so on:

[0069] Table 2 Coal and gangue discharge quality and mixed gangue ratio under normal coal discharge mode

[0070]

[0071] In the excessive coal discharge mode, the coal and gangue discharge quality and mixed gangue rate are shown in Table 3:

[0072] Table 3 Coal and gangue discharge quality and mixed gangue ratio under excessive coal discharge mode

[0073]

[0074] In the short-quantity coal discharge mode, the discharge quality of coal and gangue and the mixed gangue rate are shown in Table 4:

[0075] Table 4 Coal and gangue discharge quality and mixed gangue ratio under insufficient coal discharge mode

[0076]

[0077]

[0078]

[0079] The specific judgment process of whether to close the window during top coal caving is as follows:

[0080] Add three counters to the control board. One of the counters is used to record the number of signals sent from the natural gamma ray detector to the control board. The counter is named J1 and the maximum number J of J1 is max Set up (assuming J max is 10); the second counter is used to record the number of signals in the received signals that are greater than the window closing threshold. The counter is named J2, and the corresponding judgment threshold M is 8; the third counter is used to record the number of times the window closing threshold is exceeded continuously. The counter is named J3, and the corresponding judgment threshold N is 3.

[0081] like Figure 1As shown, the control board first resets J1, J2, and J3 to zero, and then reads the radiation data monitored by the natural gamma ray detector. Each time a data is read, the value of J1 is increased by 1, and the monitored value is compared with the set threshold. When the intensity of the monitored value is greater than the threshold, the value of J2 is increased by 1. When the intensity of the monitored value is less than or equal to the threshold, J2 remains unchanged. When the number of signals collected by the control board reaches the preset J max When J1 is equal to 10, it is determined whether 80% of the signal data collected by the natural gamma-ray detector exceeds the window closing threshold, that is, whether J2 is greater than 8. If J2 is less than 8, it indicates that the preset threshold has not been reached temporarily, then the coal is continuously discharged, J1, J2, and J3 are reset to zero, and the next round of counting is started; if J2 is greater than 8, J3 is increased by 1, and it is determined whether J3 is greater than or equal to 3. If J3 is less than 3, it indicates that the number of times exceeding the continuous threshold has not reached 3 times. After J1 and J2 are reset to zero, the radiation data monitored by the natural gamma-ray detector is continued to be read; if J3 is greater than or equal to 3, it indicates that the threshold has been exceeded for three consecutive times, then it is determined whether the current coal discharge duration t is greater than or equal to the calculated window closing time. If it is reached, the coal discharge port is closed; otherwise, J1, J2, and J3 are reset to zero, and the next round of counting is started.

[0082] Among them, in normal coal discharge mode, the closing time = y; in excessive coal discharge mode, In the short-supply coal discharge mode, the window closing time = y.

[0083] The present invention establishes a numerical model of top coal caving in fully mechanized caving mining, obtains the timing characteristics of interlayer gangue release, provides evidence for determining the radiation characteristics of top coal caving, and provides a basis for judgment for window closing operation. It is known that the natural gamma-ray detector sends 10 data per second, so in the whole cycle, the time to complete the judgment and close the window is only 3s, which greatly reduces the error caused by manual control of coal caving. At the same time, more than 80% of the data exceeds the specified radiation threshold every second within 3 consecutive seconds and has reached the calculated window closing time, which can effectively avoid the phenomenon of misjudgment caused by the radiation intensity exceeding the threshold due to accidental factors during the coal caving process. The present invention realizes the automatic control of top coal caving, improves the comprehensive mechanization degree of coal mines, improves the recovery rate of top coal in fully mechanized caving mining, reduces the number of professionals on the working face, ensures the safety of workers, and avoids the randomness of manual control by workers. It is simple to operate, has high accuracy, adapts to complex underground environments, and has wide practicality.

[0084] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays, characterized in that: The steps include: Step 01, in a fully mechanized caving mining environment, determine the optimal threshold voltage U1 of the natural gamma-ray detector under the current working face environment, calibrate the radiation intensity of coal to P1 and the radiation intensity of gangue to P2 under the optimal threshold voltage U1, and determine the background radiation level W of the coal caving port environment; Step 02, determine the coal caving mode of the current working face: normal coal caving mode, excessive coal caving mode and insufficient coal caving mode; Step 03: Calculate the time y when the gangue enters the coal discharge port according to the coal discharge mode, where: Normal caving mode: The relationship between the position x of the roof in the top coal and the time y when it enters the caving port is: y=0.49725x 2 +2.51076x-5.08615; Excessive coal discharge mode: The relationship between the position x of the roof in the top coal and the time y when it enters the coal discharge port is: y=0.3818x 2 -0.53576x+0.10214; Coal discharge mode with insufficient quantity: The relationship between the position δ of the highest interlayer of gangue and its time y of entering the coal discharge port is: y=0.33259δ 2 +9.12231v-13.13044; Step 04: Set the counter J1 to record the number of signals sent from the natural gamma ray detector to the control board, and configure the maximum value of J1 to J max ; Counter J2 is used to record the number of signals in the received signal that are greater than the window closing threshold; Counter J3 is used to record the number of times that the window closing threshold is exceeded continuously; Step 05: During the top coal caving process, the natural gamma-ray detector performs real-time data monitoring of the radiation intensity of coal gangue; Step 06: The control board first resets J1, J2, and J3 to zero; Step 07, the control board starts to read the radiation data sent by the natural gamma ray detector. Each time a radiation data is read, the value of J1 is increased by 1, and the read radiation data is compared with the set window closing threshold. When the read radiation data is greater than the window closing threshold, the value of J2 is increased by 1, otherwise J2 remains unchanged; Step 08: Determine whether J1 is greater than or equal to J max If yes, go to step 09; if no, go to step 07; Step 09, determine whether J2 is greater than or equal to the set threshold M, if so, add 1 to the value of J3 and go to step 10; if not, go to step 06; Step 10, determine whether the value of J3 is greater than or equal to the threshold value N, if so, proceed to step 11; if not, reset J1 and J2 to zero and proceed to step 07; Step 11, determine whether the current coal discharge duration t is greater than or equal to the calculated window closing time. If it is reached, close the coal discharge port; otherwise, go to step 06.

2. The method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays according to claim 1 is characterized in that: In normal coal discharge mode, the closing window time = y; in excessive coal discharge mode, In the short-supply coal discharge mode, the window closing time = y.

3. The method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays according to claim 2 is characterized in that: The optimal threshold voltage U1=0.3V. Under this voltage condition, the radiation intensity of coal is calibrated to 31.5cps / kg·s, the radiation intensity of gangue is 46.25cps / kg·s, and the background radiation level of the coal discharge port environment is determined to be 60.3cps.

4. The method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays according to claim 1 is characterized in that: The natural gamma-ray detector uses the Kalman filter method to filter the collected data.

5. The method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays according to claim 4 is characterized in that: The filter factor is set to 1.

6. The method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays according to claim 3 is characterized in that: J max The value is 10, the threshold M is 8, and the threshold N is 3.

7. The method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays according to claim 6 is characterized in that: In normal coal discharge mode: When the step distance of the frame is 1.6m, the relationship between the position x of the roof in the top coal and the time y when it enters the coal caving port is: y = 1.38164x 2 +0.4109x-2.56734; When the step distance of the frame is 2.4m, the relationship between the position x of the roof in the top coal and the time y when it enters the coal caving port is: y = 1.78734x 2 +6.88408x-8.57871.

8. The method for automatic top coal caving control in fully mechanized caving mining based on natural gamma rays according to claim 3 is characterized in that: The sampling period of the natural gamma-ray detector is 0.1s.

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