Interference suppression device and method for cross polarization

Abstract

The invention relates to the technical field of electric locomotive auxiliary equipment, in particular to cross polarization interference suppression equipment and method.The cross polarization interference suppression equipment comprises an electric locomotive, geomagnetic acquisition equipment is installed in the middles of the front end and the rear end of the electric locomotive, and a pair of geomagnetic sensors is arranged on the opposite sides of the two geomagnetic acquisition equipment; through mutual cooperation of the geomagnetic acquisition module, the data preprocessing module, the geomagnetic matching module, the database module, the storage module, the display module and the communication module, geomagnetic sensing data on an electric locomotive is subjected to geomagnetic induction on a corresponding displacement sensor on a geomagnetic board; geomagnetic acquisition data are formed after geomagnetic signals are received by the corresponding displacement sensors, geomagnetic matching algorithm data are carried out on a geomagnetic reference map through the geomagnetic acquisition data, so that space map data are obtained, and the space map data are displayed on a display module through a three-dimensional image analysis map. And a worker feeds back the positioning of the electric locomotive in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of electric locomotive auxiliary equipment, and in particular to equipment and a method for suppressing cross-polarization interference. Background Art

[0002] As the main underground transportation equipment, mine electric locomotives are mainly responsible for the transportation of coal, gangue, equipment, materials and personnel. Their driving safety and transportation efficiency have an important impact on underground production operations. Existing coal mine electric locomotives have many problems during operation. Among them, due to the obstructed vision inside the coal mine and the tortuous roads, coal mine electric locomotives have accidents during operation. Therefore, it is of great significance to design a locomotive navigation and positioning system.

[0003] The existing locomotive navigation system realizes real-time data interaction through wireless communication network mode, thereby realizing the dynamic location of the locomotive. However, the communication signal underground in coal mines is weak and it is difficult to fully cover the entire coal mine. If an emergency occurs at a certain location in the coal mine, it is difficult for the staff to obtain the accurate location of the locomotive in time, which makes it easy for a collision to occur. Summary of the invention

[0004] In view of this, an object of the present invention is to provide a device and method for suppressing cross-polarization interference, which can effectively solve the problem of low positioning accuracy in coal mine tunnels.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a device for suppressing cross-polarization interference, comprising an electric locomotive, a geomagnetic acquisition device is installed in the middle of the front and rear ends of the electric locomotive, a pair of geomagnetic sensors are arranged on the opposite sides of the two geomagnetic acquisition devices, a geomagnetic plate is installed in a tunnel in a coal mine, and a displacement sensor is installed in a linear array on a side of the geomagnetic plate close to the electric locomotive, a dustproof component for preventing external dust from clogging is installed on the outside of the displacement sensor, the geomagnetic acquisition device internally comprises a geomagnetic acquisition module, a data preprocessing module, a geomagnetic matching module and a database module, and the geomagnetic matching module comprises geomagnetic matching algorithm data, spatial map data, real-time geomagnetic data and real-time position feedback.

[0006] Preferably, the geomagnetic acquisition module includes geomagnetic sensor data, geomagnetic acquisition data and geomagnetic reference map, the geomagnetic sensor data is used to sense the displacement sensor in the geomagnetic plate, the geomagnetic acquisition data is used to obtain the location of the electric locomotive and generate real-time geomagnetic information, the geomagnetic acquisition data and the geomagnetic characteristic values ​​inside the database module are transmitted to the server, the geomagnetic reference map is used to analyze the geomagnetic information transmitted by the server with a predetermined geomagnetic reference reference map, and then generate positioning information of the location of the electric locomotive, the database module includes horizontal component geomagnetic storage information and vertical component geomagnetic storage information, the database module is arranged inside the storage module, the horizontal component geomagnetic storage information and the vertical component geomagnetic storage information are preset geomagnetic information of the location of the electric locomotive, which is convenient for positioning analysis with the geomagnetic matching module and generating geomagnetic induction position information.

[0007] Preferably, a filtering device is installed between the geomagnetic collection device and the geomagnetic sensor to eliminate other abnormal magnetic interferences in the geomagnetic collection device during the collection process.

[0008] Preferably, the data preprocessing module internally includes an acceleration data information module and a geomagnetic signal data information module, the acceleration data information module is used to obtain and calculate the travel speed of the electric locomotive, and the geomagnetic signal data information module is used to obtain the geomagnetic induction of the location of the electric locomotive.

[0009] Preferably, the geomagnetic acquisition device also includes a communication module, a display module and a storage module. The communication module is used to transmit all data information inside the geomagnetic acquisition device and real-time detected data to an external terminal through a wireless network. The display module is provided with a three-dimensional image analysis diagram for obtaining geomagnetic information of the spatial position of the electric locomotive. The storage module is used to obtain all data information inside the geomagnetic acquisition device.

[0010] Preferably, a radar ranging sensor and an infrared ranging sensor are respectively installed on the top of the right end of the electric locomotive, and the radar ranging sensor and the infrared ranging sensor are connected to the server inside the electric locomotive.

[0011] Preferably, the geomagnetic sensing data adopts a proton precession magnetometer, whose model is JSO-JGT.

[0012] Preferably, the server in the electric locomotive is installed with a ZigBee positioning module and an inertial positioning module, and the ZigBee positioning module and the inertial positioning module are connected to the storage module via a wire.

[0013] Preferably, the dust-proof component includes support plates installed at the upper and lower ends of the geomagnetic plate, an elastic belt is installed between the two support plates, a double-layer sponge pad is installed on the inner side of the elastic belt, an inclined cleaning rod is slidably connected to the middle part of the geomagnetic plate, one end of the cleaning rod extends into the inner side of the geomagnetic plate and is fixedly connected to the elastic belt, a pull plate is installed on the other end of the cleaning rod, and a spring is connected between the pull plate and the geomagnetic plate.

[0014] Preferably, the support plate at the bottom is provided with a downwardly inclined sliding groove, and the elastic band is arranged to be arranged in an inclined direction.

[0015] The present invention provides a method for performing a cross-polarization interference suppression device, the method comprising the following steps: S1. A radar ranging sensor and an infrared ranging sensor are installed on the top of the right end of the electric locomotive, respectively. The radar ranging sensor and the infrared ranging sensor are connected to the server inside the electric locomotive; S2. Radar distance measuring sensors and infrared distance measuring sensors prevent electric locomotives from colliding with obstacles, which helps electric locomotives sense the existence of obstacles and inform staff in advance to prepare for the process of avoiding obstacles to avoid collisions; S3. The server in the electric locomotive is equipped with a ZigBee positioning module and an inertial positioning module, which are connected to the storage module through wires. When the electric locomotive is separated from the coal mine tunnel, the ZigBee positioning module and the inertial positioning module are started, and the network of the ZigBee positioning module and the inertial positioning module coordinates and communicates with each other to determine the position of the electric locomotive.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention uses the cooperation of a geomagnetic acquisition module, a data preprocessing module, a geomagnetic matching module, a database module, a storage module, a display module and a communication module to perform geomagnetic sensing on the geomagnetic sensor data on the corresponding displacement sensor on the geomagnetic plate, and then forms geomagnetic acquisition data after receiving the geomagnetic signal from the corresponding displacement sensor. The geomagnetic matching algorithm data is performed on the geomagnetic reference map through the geomagnetic acquisition data to obtain spatial map data. The spatial map data is displayed on the display module through a three-dimensional image analysis diagram, and the staff provides real-time feedback on the positioning of the electric locomotive. The corresponding displacement sensor position forms the geomagnetic acquisition data and then saves it in the storage module to prevent the electric locomotive navigation and positioning system from weakening and being difficult to fully cover the coal mine, causing accidents. The present invention senses and obtains the geomagnetic signal, and then obtains the positioning of the electric locomotive.

[0018] 2. The present invention adopts a double-layer sponge pad for dust prevention through the dust prevention component, and the present invention also greatly reduces the dust accumulation on the elastic belt through the cooperation of the elastic belt, the cleaning rod, the pull plate and the spring. Secondly, the elastic belt and the bottom support plate are inclined, which is beneficial to reduce the dust adhesion on the surface of the elastic belt and the accumulation at the corners of the support plate and the geomagnetic plate, thereby improving the service life of the double-layer sponge pad. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 for Figure 1 A partial enlarged view of middle A; Figure 3 It is a schematic diagram of the geomagnetic plate of the present invention; Figure 4 It is a schematic diagram of the geomagnetic acquisition module, data preprocessing module, geomagnetic matching module and database module of the present invention; Figure 5 It is a schematic diagram of the geomagnetic acquisition module of the present invention; Figure 6 It is a schematic diagram of a data preprocessing module of the present invention; Figure 7 It is a schematic diagram of the geomagnetic matching module of the present invention; Figure 8 It is a schematic diagram of a database module of the present invention; Fig. 9 Schematic diagram of the dustproof component of the present invention.

[0020] In the figure: 1. electric locomotive; 2. geomagnetic acquisition equipment; 3. filtering equipment; 4. geomagnetic sensor; 41. geomagnetic plate; 42. displacement sensor; 43. support plate; 44. elastic belt; 45. dust cleaning rod; 46. pull plate; 47. spring; 5. geomagnetic acquisition module; 51. geomagnetic sensor data; 52. geomagnetic acquisition data; 53. geomagnetic reference map; 6. data preprocessing module; 61. acceleration data information module; 62. geomagnetic signal data information module; 7. geomagnetic matching module; 71. geomagnetic matching algorithm data; 72. spatial map data; 73. real-time geomagnetic data; 74. real-time position feedback; 75. communication module; 76. display module; 77. storage module; 8. database module; 81. horizontal component geomagnetic storage information; 82. vertical component geomagnetic storage information. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] See also Figures 1 to 8 The present invention provides a technical solution: a device for suppressing cross-polarization interference, comprising an electric locomotive 1, a geomagnetic acquisition device 2 is installed in the middle of the front and rear ends of the electric locomotive 1, a pair of geomagnetic sensors 4 are arranged on the opposite sides of the two geomagnetic acquisition devices 2, a tunnel in a coal mine is installed with a geomagnetic plate 41, and a displacement sensor 42 is installed in a linear array on the side of the geomagnetic plate 41 close to the electric locomotive 1, and a dust-proof component for preventing external dust from clogging is installed on the outer side of the displacement sensor 42, the geomagnetic acquisition device 2 includes a geomagnetic acquisition module 5, a data preprocessing module 6, a geomagnetic matching module 7 and a database module 8, the geomagnetic matching module 7 includes geomagnetic matching algorithm data 71, spatial map data 72, real-time geomagnetic data 73 and real-time position feedback 74, the geomagnetic acquisition module 5 includes geomagnetic sensor data 51, geomagnetic acquisition data 5 2 and a geomagnetic reference map 53, the geomagnetic sensing data 51 is used to sense the displacement sensor 42 in the geomagnetic plate 41, the geomagnetic acquisition data 52 is used to obtain the position of the electric locomotive 1 and generate real-time geomagnetic information, the geomagnetic acquisition data 52 and the geomagnetic characteristic values ​​inside the database module 8 are transmitted to the server, the geomagnetic reference map 53 is used to analyze the geomagnetic information transmitted by the server with the predetermined geomagnetic reference reference map, and then generate the positioning information of the position of the electric locomotive 1, the database module 8 includes horizontal component geomagnetic storage information 81 and vertical component geomagnetic storage information 82, the database module 8 is arranged inside the storage module 77, the horizontal component geomagnetic storage information 81 and the vertical component geomagnetic storage information 82 are the preset geomagnetic information of the position of the electric locomotive 1, which is convenient for positioning analysis with the geomagnetic matching module 7 and generating geomagnetic induction position information.

[0023] In this embodiment, first, geomagnetic plates 41 are installed on both sides of the coal mine tunnel, and displacement sensors 42 are installed at intervals on the geomagnetic plates 41. When the electric locomotive 1 enters the coal mine tunnel, the displacement sensors 42 in the initial stage immediately produce magnetic changes with the geomagnetic sensors 4. At this time, the magnetism induced by the displacement sensor 42 forms a geomagnetic sensing data 51. The geomagnetic sensing data 51 collected by the geomagnetic acquisition data 52 is transmitted to the server inside the electric locomotive 1, and then the geomagnetic reference map 53 is analyzed with the predetermined geomagnetic reference reference map to form corresponding geomagnetic positioning information. The number and distribution of displacement sensors 42 in each group will directly determine the accuracy of the geomagnetic reference map 53. There is no need to detect the location of the electric locomotive 1 through a wireless communication network. Compared with the prior art, the present invention has high positioning accuracy, relatively less initial investment, and high safety. It is worth noting that the distance between the displacement sensors 42 is equal to the length of the electric locomotive 1, so that the spaced displacement sensors 42 can produce magnetic changes to the geomagnetic sensor 4, thereby improving the precise positioning of the electric locomotive 1. A filtering device 3 is installed between the geomagnetic acquisition device 2 and the geomagnetic sensor 4, which is used to eliminate other abnormal magnetic interferences in the acquisition process of the geomagnetic acquisition device 2. The data preprocessing module 6 includes an acceleration data information module 61 and a geomagnetic signal data information module 62. The acceleration data information module 61 is used to obtain the driving speed of the electric locomotive 1 and calculate it. The geomagnetic signal data information module 62 is used to obtain the geomagnetic induction of the location of the electric locomotive 1. The building materials in the coal mine are mostly steel bars and steel frames contained in concrete. The electronic metal ferromagnetic devices such as cables are installed inside, which will interfere with the magnetic signals generated by the geomagnetic sensor 4 and the corresponding displacement sensor 42, affect the waveforms of the geomagnetic sensor 4 and the displacement sensor 42, and cause the collected geomagnetic signals to be unstable, thereby affecting the accuracy of the geomagnetic reference map 53. Therefore, the filtering device 3 is used to effectively reduce abnormal magnetic interference and improve the perception accuracy of the geomagnetic sensor 4 and the corresponding displacement sensor 42.

[0024] The geomagnetic acquisition device 2 also includes a communication module 75, a display module 76 and a storage module 77. The communication module 75 is used to transmit all data information inside the geomagnetic acquisition device 2 and real-time detected data to an external terminal through a wireless network. The display module 76 is provided with a three-dimensional image analysis diagram for obtaining geomagnetic information of the spatial position of the electric locomotive 1. The storage module 77 is used to obtain all data information inside the geomagnetic acquisition device 2. When the electric locomotive 1 is running, the geomagnetic acquisition data 52 collected by the geomagnetic acquisition device 2 is automatically saved in the storage module 77, and then transmitted to the external terminal through the wireless network by the communication module 75, so as to facilitate real-time detection of the positioning of the electric locomotive 1. The storage module 77 can reduce the workload of drawing the geomagnetic reference map 53, which is conducive to accelerating the convergence of the geomagnetic matching algorithm.

[0025] The present invention provides a method for performing a cross-polarization interference suppression device, the method comprising the following steps: S1, the right end top of the electric locomotive 1 is respectively equipped with a radar ranging sensor and an infrared ranging sensor, and the radar ranging sensor and the infrared ranging sensor are connected to the server inside the electric locomotive 1; S2, radar ranging sensors and infrared ranging sensors prevent the electric locomotive 1 from colliding with obstacles, which is helpful for the electric locomotive 1 to sense the existence of obstacles and inform the staff in advance to prepare the process of avoiding obstacles to avoid collision accidents; S3. The server in the electric locomotive 1 is installed with a ZigBee positioning module and an inertial positioning module, which are connected to the storage module 77 via a wire. When the electric locomotive 1 is separated from the coal mine tunnel, the ZigBee positioning module and the inertial positioning module are started, and the network of the ZigBee positioning module and the inertial positioning module coordinates and communicates with each other to determine the position of the electric locomotive 1.

[0026] The geomagnetic sensor data 51 uses a proton precession magnetometer, whose model is JSO8-J57G856T. The radar distance sensor and the infrared distance sensor prevent the electric locomotive 1 from colliding with obstacles, which is conducive to the electric locomotive 1 to sense the existence of obstacles and inform the staff in advance to prepare the process of avoiding obstacles to avoid collision accidents. The server in the electric locomotive 1 is installed with a ZigBee positioning module and an inertial positioning module. The ZigBee positioning module and the inertial positioning module are connected to the storage module 77 through a wire. When the electric locomotive 1 is separated from the coal mine tunnel, the ZigBee positioning module and the inertial positioning module are started. The network of the ZigBee positioning module and the inertial positioning module coordinates and communicates with each other to determine the position of the electric locomotive 1. Therefore, there is no need to install a geomagnetic plate 41 outside the coal mine tunnel. The positioning accuracy of the electric locomotive 1 is further improved by combining the ZigBee positioning module, the inertial positioning module and the geomagnetic positioning mode.

[0027] like Figure 3 and Fig. 9 The dust-proof assembly includes support plates 43 installed at the upper and lower ends of the geomagnetic plate 41, an elastic belt 44 is installed between the two support plates 43, a double-layer sponge pad is installed on the inner side of the elastic belt 44, and an inclined cleaning rod 45 is slidably connected to the middle part of the geomagnetic plate 41. One end of the cleaning rod 45 extends into the inner side of the geomagnetic plate 41 and is fixedly connected to the elastic belt 44. A pull plate 46 is installed on the other end of the cleaning rod 45. A spring 47 is connected between the pull plate 46 and the geomagnetic plate 41. The support plate 43 at the bottom is provided with a downwardly inclined slide groove, and the elastic belt 44 is arranged to be arranged in an inclined direction.

[0028] First, an elastic band 44 is installed on the outside of the geomagnetic plate 41 to prevent dust in the coal mine from gathering on the displacement sensor 42. The double-layer sponge pad inside the elastic band 44 effectively prevents dust from entering. When dust gathers on the double-layer sponge pad, the pull plate 46 is manually pulled away from the geomagnetic plate 41 to loosen it. At this time, the elastic band 44 retracts from the direction of the displacement sensor 42 under the pulling force of the cleaning rod 45. After the spring 47 releases the elastic potential energy, the cleaning rod 45 quickly bounces up along the direction of the elastic band 44, thereby quickly cleaning the dust on the double-layer sponge pad. The pushing pressure of the cleaning rod 45 can effectively reduce the accumulation of dust.

[0029] It is worth noting that the elastic band 44 provided in the present invention is inclined, which is beneficial to reduce the dust adhering to the surface of the elastic band 44, and is also beneficial to better cleaning the dust when the elastic band 44 bounces up quickly. The support plate 43 at the bottom of the present invention is inclined to prevent dust from accumulating at the corner between the support plate 43 and the geomagnetic plate 41, to prevent the electric locomotive 1 from re-entering the dust on the elastic band 44 during operation, and to facilitate the dust to slide off the support plate 43.

[0030] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0031] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for suppressing cross-polarization interference, comprising an electric locomotive (1), characterized in that: A geomagnetic acquisition device (2) is installed in the middle of the front and rear ends of the electric locomotive (1); a pair of geomagnetic sensors (4) are arranged on opposite sides of the two geomagnetic acquisition devices (2); a geomagnetic plate (41) is installed in the tunnel in the coal mine; and a displacement sensor (42) is installed in a linear array on a side of the geomagnetic plate (41) close to the electric locomotive (1); a dustproof component for preventing clogging by external dust is installed on the outer side of the displacement sensor (42); the geomagnetic acquisition device (2) internally comprises a geomagnetic acquisition module (5), a data preprocessing module (6), a geomagnetic matching module (7) and a database module (8); the geomagnetic matching module (7) comprises geomagnetic matching algorithm data (71), spatial map data (72), real-time geomagnetic data (73) and real-time position feedback (74).

2. The device for cross-polarization interference suppression according to claim 1, characterized in that: The geomagnetic acquisition module (5) comprises geomagnetic sensing data (51), geomagnetic acquisition data (52) and a geomagnetic reference map (53). The geomagnetic sensing data (51) is used to sense the displacement sensor (42) in the geomagnetic plate (41). The geomagnetic acquisition data (52) is used to obtain the location of the electric locomotive (1) and generate real-time geomagnetic information. The geomagnetic acquisition data (52) and the geomagnetic characteristic values ​​in the database module (8) are transmitted to the server. The geomagnetic reference map (53) is used to analyze the geomagnetic information transmitted by the server with a predetermined geomagnetic reference map, thereby generating positioning information of the location of the electric locomotive (1).

3. The device for cross-polarization interference suppression according to claim 2, characterized in that: The database module (8) comprises horizontal component geomagnetic storage information (81) and vertical component geomagnetic storage information (82). The database module (8) is arranged inside the storage module (77). The horizontal component geomagnetic storage information (81) and the vertical component geomagnetic storage information (82) are preset geomagnetic information of the location of the electric locomotive (1), so as to facilitate positioning analysis with the geomagnetic matching module (7) and generate geomagnetic induction position information.

4. The device for cross-polarization interference suppression according to claim 1, characterized in that: A filtering device (3) is installed between the geomagnetic collection device (2) and the geomagnetic sensor (4).

5. The device for cross-polarization interference suppression according to claim 1, characterized in that: The data preprocessing module (6) internally comprises an acceleration data information module (61) and a geomagnetic signal data information module (62); the acceleration data information module (61) is used to obtain the travel speed of the electric locomotive (1) and perform calculations; and the geomagnetic signal data information module (62) is used to obtain the geomagnetic induction of the location of the electric locomotive (1).

6. The device for cross-polarization interference suppression according to claim 3, characterized in that: The geomagnetic acquisition device (2) further comprises a communication module (75), a display module (76) and a storage module (77). The communication module (75) is used to transmit all data information and real-time detected data in the geomagnetic acquisition device (2) to an external terminal via a wireless network. The display module (76) is provided with a three-dimensional image analysis diagram for acquiring geomagnetic information of the spatial position of the electric locomotive (1). The storage module (77) is used to acquire all data information in the geomagnetic acquisition device (2).

7. The device for cross-polarization interference suppression according to claim 6, characterized in that: The dustproof component comprises support plates (43) installed at the upper and lower ends of the geomagnetic plate (41), an elastic belt (44) is installed between the two support plates (43), a double-layer sponge pad is installed on the inner side of the elastic belt (44), an inclined cleaning rod (45) is slidably connected to the middle part of the geomagnetic plate (41), one end of the cleaning rod (45) extends into the inner side of the geomagnetic plate (41) and is fixedly connected to the elastic belt (44), and a pull plate (46) is installed on the other end of the cleaning rod (45), and a spring (47) is connected between the pull plate (46) and the geomagnetic plate (41).

8. The device for cross-polarization interference suppression according to claim 7, characterized in that: The support plate (43) at the bottom is provided with a downwardly inclined sliding groove, and the elastic band (44) is arranged to be arranged in an inclined direction.

9. The method for performing cross-polarization interference suppression according to any one of claims 6 to 8, characterized in that: The method comprises the following steps: S1, a radar ranging sensor and an infrared ranging sensor are respectively installed on the top of the right end of the electric locomotive (1), and the radar ranging sensor and the infrared ranging sensor are connected to the server inside the electric locomotive (1); S2, radar ranging sensors and infrared ranging sensors prevent the electric locomotive (1) from colliding with obstacles, which is helpful for the electric locomotive (1) to sense the existence of obstacles and inform the staff in advance to prepare the process of avoiding obstacles to avoid collision accidents; S3. The server in the electric locomotive (1) is equipped with a ZigBee positioning module and an inertial positioning module. The ZigBee positioning module and the inertial positioning module are connected to the storage module (77) via a wire. When the electric locomotive (1) is separated from the coal mine tunnel, the ZigBee positioning module and the inertial positioning module are started. The network of the ZigBee positioning module and the inertial positioning module coordinates and communicates with each other to determine the position of the electric locomotive (1).

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