CN102901740A - Channel type four visual angles X ray liquid state article safety inspection system - Google Patents

Abstract

The invention discloses a channel-type four-view X-ray liquid article safety inspection system, which consists of a system control and signal processing circuit unit, a first collection computer, a second collection computer, a third density computer, a switch, a conveyor, The transmission channel, four groups of X-ray sources and four groups of detectors are composed, and the first acquisition computer, the second acquisition computer and the third density computer are connected through a local area network; the advantages of the present invention are: 1 ) has strong inspection ability, and can effectively detect dangerous liquids of different sizes, materials and shapes; 2) has a fast inspection speed, and can detect up to 6 kinds of liquids at the same time; 3) has high detection sensitivity and accurate detection; in addition, the present invention also With the characteristics of strong anti-interference ability, it is suitable for the security inspection system of important places such as civil aviation, railway, and customs.

Description

A channel-type four-view X-ray liquid article safety inspection system

technical field

The invention relates to a channel-type four-view X-ray liquid article safety inspection system.

Background technique

Since the "9.11" incident, the inspection of liquid objects has gradually become a hot issue in the field of security inspection, especially in the fields of aviation, railways, highways, assemblies and other security fields. Due to the wide variety of liquid objects involved and different packages, it is difficult to quickly and accurately inspect It is becoming more and more difficult to identify the hazards of various liquid objects.

Among the existing safety inspection technologies for liquid articles, the non-destructive inspection method based on X-ray transmission imaging technology has the characteristics of high accuracy of inspection results, low sensitivity to container materials, and convenient operation, and is favored by more and more security inspection manufacturers. Among them, two invention patents with patent publication numbers CN101140247A and CN101629916A are representative. What they have in common is that they are all based on CT tomography technology. The method can be briefly described as: X-rays are emitted by the radiation source Transmit the liquid object to be inspected, use the detector to receive the ray beam transmitted through the liquid object, and form hundreds of multi-angle projection data, and calculate by inverting the hundreds of multi-angle projection data The ray absorption coefficient of the inspected liquid article, among them, the patent CN101629916A can obtain the density and material information of the inspected liquid article at the same time due to the use of dual-energy X-rays. Finally, the absorption coefficient of the liquid article or the density of the liquid article, material information and The preset database is compared to complete the inspection of the inspected liquid items. The biggest advantage of this type of liquid article safety inspection method based on CT tomography technology is its high inspection accuracy, because it has obtained hundreds of multi-angle projection data during the inspection process, and then uses relatively mature various projection reconstruction technologies , the ideal fault cross-section data can be obtained. However, this type of CT tomography technology also has obvious deficiencies: 1) The inspection efficiency is low, usually only one liquid object of a conventional size can be inspected at a time, and the inspection process takes a long time; 2) The coverage of inspection objects is not wide , there are certain restrictions on the diameter, height, and volume of liquid items to be inspected, and only liquid items can be specifically inspected and cannot be compatible with inspection packages. Both of these deficiencies will limit the application of the CT-type liquid article safety inspection method and equipment in places with a large flow of people, such as: airports, railway stations, large gatherings and other places.

Therefore, for the safety inspection of common liquid articles, it is necessary to research and develop a channel-type X-ray liquid article inspection that can not only ensure high inspection accuracy, but also realize batch and rapid inspection, and is compatible with the inspection of passengers' carry-on packages. methods and systems.

US patents US6088423, US7020241 and Chinese patent CN101592622 involve multi-view X-ray safety inspection methods and systems. The system invented by US6088423 adopts 2 bottom illumination sources and 1 side illumination source to form a three-view X-ray source and detector layout with 3 sources and 3 probes; the system invented by US7020241 adopts a 5-view working mode with 3 sources and 5 probes , and two bottom radiation sources and one top radiation source are used in the multi-angle layout, each bottom radiation source corresponds to two groups of detectors, and the top radiation source corresponds to one group of detectors to form five viewing angles; CN101592622 The involved multi-angle X-ray security inspection system uses 2 bottom illumination sources and 1 top illumination source to form a three-view working mode of 3 sources and 3 detectors, and its 1 bottom illumination angle adopts a real dual-ray source dual detector Energy perspective layout. However, the above three multi-view X-ray security inspection systems all use parcels as detection objects, cannot detect liquid objects, and have low inspection accuracy and poor anti-interference ability, and their application places and fields are relatively narrow.

Contents of the invention

In order to solve the above technical problems, the present invention provides a channel-type four-angle X-ray liquid article safety inspection system. The channel-type four-angle X-ray liquid article safety inspection system of the present invention consists of a system control and signal processing circuit unit, a first It is composed of an acquisition computer, a second acquisition computer, a third density computer, an acquisition card, a switch, a conveyor, a conveying channel, four sets of X-ray sources and four sets of detectors, the first acquisition computer, the second The two acquisition computers and the third density computer are connected through a local area network; each group of X-ray sources and detectors is called a viewing angle module, which contains four viewing angle modules in total, and the four viewing angle modules include: The viewing angle module, the right side horizontal side viewing angle module, the right bottom viewing angle module and the middle bottom viewing angle module; the right top viewing angle module includes the right top-illuminating X-ray source and the first detector, constituting the V1 viewing angle module; the right The side horizontal side-illumination angle module includes the right horizontal side-illumination X-ray source and the second detector, forming a V2 angle of view module; the right bottom-illumination angle of view module includes the right bottom-illumination angle X-ray source and the third detector, forming a V3 angle of view Module; the central bottom viewing angle module includes the central bottom viewing angle X-ray source and the fourth detector, forming a V4 viewing angle module. The first detector of the V1 viewing angle module, the second detector of the V2 viewing angle module, and the third detector of the V3 viewing angle module are all L-shaped detectors, and the fourth detector of the V4 viewing angle module is a U-shaped detector, so The V1 viewing angle module, the V2 viewing angle module, the V3 viewing angle module, and the V4 viewing angle module are all connected to an acquisition card through a signal processing circuit unit. In liquid detection, the V1 perspective module, V3 perspective module, and V4 perspective module are responsible for static tomographic reconstruction of liquid detection, and the V2 perspective module is responsible for liquid level calculation and can assist other perspective tomographic reconstructions. Therefore, the new four-view layout design structure of the present invention can simultaneously statically reconstruct two liquid sections in the channel and calculate the liquid level, so the present invention can simultaneously detect multiple liquids.

The first acquisition computer and the second acquisition computer are equipped with an image acquisition unit, a low atomic number container liquid material detection unit, and an information communication unit, and the third density computer is equipped with an image matching unit and a density detection unit , High atomic number container liquid material detection unit, decision-making alarm unit, information communication unit;

1) The image acquisition unit is installed in the first acquisition computer and the second acquisition computer, wherein the first acquisition computer is connected to the image acquisition card of the V1 perspective module and the V2 perspective module, and receives images from the The image data of the V1 angle of view module and the V2 angle of view module, the second acquisition computer connects the image acquisition card of the V3 angle of view module and the V4 angle of view module, and receives the image data from the V3 angle of view module and the V4 angle of view module image data.

2) The low atomic number container liquid material detection unit is installed in the first acquisition computer and the second acquisition computer, and is used to perform image segmentation on the acquired images from the four viewing angle modules and locate the liquid state The area of the item. The first acquisition computer is used to calculate the material data of the liquid in the low atomic number container of the V1 perspective module and the V2 perspective module, and the second acquisition computer is also used to calculate the V3 perspective module and the The material data of the liquid in the low atomic number container to be detected in the V4 viewing angle module.

3) The information communication unit is used to transmit original images, calculation results, control commands and information between the first acquisition computer, the second acquisition computer, and the third density computer.

4) The image matching unit is installed in the third density computer, and after image matching is performed on the image data and material detection results from the four viewing angle modules, the data of the four viewing angle modules received this time are confirmed Images of liquid items from the same set of inspection boxes.

5) The density detection unit is installed in the third density computer, and the density characteristics of the liquid object processed by the image matching unit are calculated in two cases according to the container material of the liquid object, a) when the liquid state When the container of the item is a material with a low atomic number such as plastic, the approximate penetration thickness of the ray is calculated using the four-view algebraic reconstruction, and the density feature is calculated based on the ratio between the penetration thickness and the absorption gray level; b) when the container of the liquid item is a high atomic number For an ordinal substance such as glass, first calculate the section model and outer diameter of the liquid article according to the spatial geometric relationship formed by the ray and the area of the liquid article in the channel, and then use this section model, outer diameter and estimated wall thickness of the container as the initial shape, Density features are iteratively calculated using optimal numerical analysis methods.

6) The liquid material detection unit of the high atomic number container is installed in the third density computer, analyzes the glass container wall rejection, corrects the traditional rejection method, removes the influence of the container wall, and obtains the real projected gray scale of the liquid object information to obtain the material properties of liquid items in high atomic number containers.

7) The decision-making alarm unit is installed in the third density computer, and judges whether the liquid object to be detected is a liquid explosive by combining the material of the liquid object and the density two-dimensional feature.

When the channel-type four-view X-ray liquid article safety inspection system of the present invention is started, the conveyor sends the liquid article into the conveying channel, and performs transmission scanning on the liquid article. When the first detector, the second detector, and the second detector The signals received by the three detectors and the fourth detector are processed by the system control and signal processing circuit unit and sent to the first acquisition computer and the second acquisition computer, and then exchanged to the third acquisition computer through the switch Density computer, and then in the third density computer, carry out safety check to liquid object, and check result is displayed on the monitor of first acquisition computer and second acquisition computer.

The present invention has the following advantages:

1) Strong inspection ability, the new 4-view X-ray liquid detection method can effectively detect liquid dangerous goods of different sizes, materials and shapes;

2) The inspection speed is fast, and it can inspect double rows of liquids at the same time, and can detect up to 6 bottles of liquids at the same time, which is suitable for the baggage security inspection field with a high pass rate;

3) The detection sensitivity is high, and the two characteristic quantities of density and effective atomic number can be detected simultaneously, and the detection is accurate.

In addition, the present invention also has the characteristics of strong anti-interference ability, and is very suitable for security inspection systems in important places such as civil aviation, railways, and customs.

Description of drawings

Fig. 1 is a schematic diagram of a channel-type four-view X-ray liquid article safety inspection system according to the present invention;

Fig. 2 is a schematic diagram of the front view structure of the conveying channel and the position of the radiation source in a channel-type four-view X-ray liquid article safety inspection system according to the present invention;

Fig. 3 is a top view structural diagram of the conveying channel and the position of the detector in a channel-type four-view X-ray liquid article safety inspection system according to the present invention;

Fig. 4 is a side-view structure schematic diagram of the conveying channel, radiation source and detector positions in a channel-type four-view X-ray liquid article safety inspection system according to the present invention;

Fig. 5 is a working flow chart of a channel-type four-view X-ray liquid article safety inspection system according to the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Fig. 1, Fig. 2, Fig. 3 and Fig. 4, the present invention comprises: system control and signal processing circuit unit 17, the first collection computer 18, the second collection computer 20, the 3rd density computer 19, conveying Machine 11, conveying channel 5, plastic tray 6, four groups of X-ray sources and four groups of detectors, acquisition card 12, acquisition card 13, acquisition card 15, acquisition card 16, switch 14.

As shown in Fig. 1, Fig. 2, Fig. 3 and Fig. 4, the right bottom X-ray source 10 of the present invention, the right side side X-ray source 4, the right top X-ray source 2, and the middle bottom X-ray source The sources 7 are respectively located in different orientations of the conveying passage 5, that is to say, in the front view direction of the conveying passage 5, the right bottom-illuminated X-ray source 10 is arranged at the right bottom position of the conveying passage 5, so The right side X-ray source 4 is arranged on the right side of the conveying channel 5, the right side X-ray source 2 is arranged on the right side of the bottom of the conveying channel 5, and the middle bottom X-ray source 7 is arranged at the bottom of the middle part of the conveying channel 5 .

Similarly, corresponding to the above-mentioned right side bottom-illuminated X-ray source 10, right side side-illuminated X-ray source 4; right side top-illuminated X-ray source 2, middle bottom-illuminated X-ray source 7, and the corresponding L-shaped first detector 9 , the second detector 3 , the third detector 8 , and the U-shaped fourth detector 1 are also attached to different positions of the delivery channel 5 .

In addition, with respect to the above-mentioned right bottom X-ray source 10, right side X-ray source 4; The X-ray beam can be formed into a thin fan beam, with a collimator at each X-ray source location.

Among them, the right bottom-illuminated X-ray source 10 corresponds to the first detector 9 and forms the right bottom-illuminated angle of view module, forming a V3 angle of view module; the right side side-illuminated X-ray source 4 corresponds to the second detector 3 and forms the right The side-viewing angle module forms the V2 viewing angle module; the right top-illuminating X-ray source 2 corresponds to the third detector 8 and forms the right top-illuminating viewing angle module, forming the V1 viewing angle module; the middle bottom-illuminating X-ray source 7 and the The fourth detector 1 corresponds to and constitutes the middle bottom viewing angle module, forming a V4 angle of view module.

In addition, since the dual-energy X-ray detection method can be used to discriminate the material properties of the inspected object, in the present invention, the V1 viewing angle module, the V2 viewing angle module, the V3 viewing angle module, and the V4 viewing angle module all use a single X-ray source, And capable of emitting X-rays with a continuous energy spectrum; the L-shaped first detector 9, the second detector 3, the third detector 8 and the U-shaped fourth detector 1 are respectively placed in an overlapping manner, that is, L The first detector 9, the second detector 3, the third detector 8 of the U-type and the fourth detector 1 of the U-type are all detectors with two different energy spectral responses with low energy in front and high energy in the rear, so their The low-energy transmission signal and the high-energy transmission signal can be obtained respectively at the same time; and then the material properties of the objects in the inspected plastic tray 6 can be discriminated.

In application, the plastic tray 6 is first placed on the conveyor 11, and then a maximum of 6 liquids are placed in the tray. When the four-view X-ray safety inspection system is activated, the conveyor 11 moves at a constant speed to transport the plastic tray 6 In the conveying channel 5, the plastic tray 6 respectively triggers the right bottom X-ray source 10, the right side X-ray source 4, the right top X-ray source 2, and the middle bottom X-ray source 7. X-ray beams are emitted, and the X-ray beams become thin fan-shaped beams after passing through the collimator located in front of the ray source, and transmit the inspected plastic tray 6, L-shaped first detector 9, second detector 3, and third detector 8 and U-shaped fourth detector 1 respectively receive the corresponding attenuation signal transmitted through the liquid object 7 and transmit it to the system control and signal processing circuit unit 17 for analog-to-digital conversion and signal correction processing, thereby forming a corresponding V1 viewing angle Module, V2 angle of view module, V3 angle of view module, V4 angle of view module’s projected image signal, then, the formed projected image signal is passed into the first acquisition computer 18 and the second acquisition computer 20, and then enters the exchange 14 and transmits The third density computer 19 performs a security check and displays the results of the check on the first acquisition computer 18 and the second acquisition computer 20 .

As shown in Fig. 1 and Fig. 5, V1 perspective module, V2 perspective module, V3 perspective module, and V4 perspective module are all connected with a capture card through signal processing circuit unit 17, and each image capture card is used for collecting image data, V1 perspective module The images collected by the V2 viewing angle module are received by the first collection computer to form a dual-channel collection, and the images collected by the V3 viewing angle module and the V4 viewing angle module are also received by the second collection computer. After the processing of the flow process steps S1 and S2 shown in Figure 5, the original image and calculation results are passed to the third density computer through the switch 14, and after the calculation of the flow process steps S4 to step S7 shown in Figure 5 is performed, then pass The switch 14 returns the coordinates of the detected danger zone to the first acquisition computer and the second acquisition computer, and scrolls and displays the image and the detected danger zone on the monitors of the first acquisition computer and the second acquisition computer.

Concrete workflow of the present invention is as follows:

After the image acquisition is completed, step S2 is the calculation process of the low atomic number container liquid material detection unit. First, each container in the inspection box needs to be segmented and the material of each container is determined. The segmentation process is completed in two parts: first, a suitable empirical gray threshold value V _S is used to segment each view module image, and the part of the image whose gray value is lower than V _S is marked as the initial segmentation area of the liquid object, and then, Use the classic Canny operator edge detection method in the field of image processing technology to obtain the precise edge of the liquid object to be inspected. After obtaining the precise boundary of the container, find a row of pixels in the middle of the bottle body according to the direction of the container, and calculate the relative value of the material value between the edge of the container and the middle of the container in this row, the greater the difference, the higher the atomic number of the container material, and get the container's Material properties, using different grayscale values to represent container boundaries of different materials. If it is a container with a low atomic number, perform gray-scale mean filtering and material median filtering operations on the effective neighborhood of the bottle body to obtain the material value of the liquid to be tested.

Step S3 is to transmit the original image and calculation results including the container boundary, container material, and liquid material detection information in the low atomic number container to the third density computer via the switch 14 through the information communication unit.

Step S4 is the calculation process of the image matching unit. The third density computer obtains the V1 viewing angle module, V2 viewing angle module, V3 viewing angle module, and the container boundary information of the V4 viewing angle module transmitted in step S3, and calculates the suspected dangerous area of each viewing angle module. It exists in the RECT structure array defined by each view module. Circularly scan these arrays to match a group of suspected dangerous areas of the four viewing angle modules whose head-to-tail difference in the channel direction is within the threshold range, and check whether the polygons surrounded by the boundary of this group of suspected dangerous areas in the channel are reasonable, and discard if unreasonable This group, and then start to look for duplicate matching groups from a perspective module, and remove duplicate matching groups through the absolute value of the difference between the head and tail of the channel direction in the suspected danger zone and the relationship between the same group of container positions in each perspective module, and finally get the correct matching result. .

Step S5 is the calculation process of the density detection unit, and the density detection unit is divided into the following two subunits:

1) When the material of the container is a low atomic number material such as plastic, the cross-sectional shape of the liquid object is obtained through four-view ART algebraic iterative reconstruction. It should be pointed out that the above-mentioned ART algebraic iterative reconstruction calculation is based on the premise that the liquid density inside the liquid object is basically homogeneous, that is, the value of each reconstructed pixel on the section of the liquid object is the same, rather than the reconstruction of the cross-sectional area of the liquid object The pixel value is 0, that is to say, the pixel value of the area where the liquid object is located on the reconstructed image is an equal positive value representing the size of the pixel, and the value of other parts is 0; according to the reconstructed cross-sectional shape of the liquid object, count each corresponding The angle of view module projects the pixel ray penetration distance, each group of penetration distance and its corresponding high-energy gray level, by querying the previously established penetration distance-absorption gray level-electron density table, a density feature is obtained, and further, the reconstruction All the density characteristics corresponding to the cross-section are counted to calculate the density characteristics of liquid items;

2) When the material of the container is a high atomic number substance such as glass:

(a). Carry out a fine segmentation of containers that conforms to the characteristics of high-density containers, especially for the fine segmentation of V2 view modules where containers overlap.

(b). According to the overlapping situation of the containers in the V2 viewing angle module, find a suitable area in the current container for subsequent analysis. The overlapping mode of this area is relatively simple, which is suitable for liquid level calculation and other analysis.

(c). Data denoising to obtain smooth four-view module projection data.

(d). Judging whether the liquid in the container is full according to the projected grayscale curves of the V2 viewing angle module and the V3 viewing angle module; if it is not full, find the position of the liquid level according to the characteristic position of the curve, and finally calculate according to the spatial geometric relationship liquid level.

(e). The attenuation coefficient of the container wall, the attenuation coefficient of the liquid, the thickness of the container wall (the initial value refers to the wall thickness obtained from S3), the height of the liquid level, the identity of each pixel in the section (container, liquid, air), etc. As the parameters to be calculated, information such as the attenuation coefficient of the liquid and the thickness of the container are obtained by using an iterative optimization algorithm.

(f). If the container is a circular container, the identity of each pixel outside the circle in the cross-section is fixed as air; if it is another type of container (such as a rectangular cross-section), the iterative process in E. is given rules based on shape knowledge guide. Finally, the attenuation coefficient of the liquid in the high-density container is obtained, and the more accurate wall thickness of the container is obtained. By querying the attenuation coefficient-electron density table established in advance, the density characteristics of liquid objects are obtained.

The next step S6 is the calculation flow of the high atomic number container liquid material detection unit, that is, to calculate the material value of the liquid in the high atomic number container. Experiments have shown that low atomic number containers have no effect on the detection of the internal liquid, but high atomic number containers will seriously affect the material properties of the internal liquid. Step S6 analyzes the removal of the glass container wall, corrects the traditional removal method, removes the influence of the container wall, obtains the real projected grayscale information of the liquid, and then uses the real high and low energy data to calculate the material characteristics of the liquid.

So far, the two-dimensional characteristics of the material and density of each container to be tested have been obtained, and then enter step S7, and carry out the alarm decision-making process through the decision-making alarm unit. If there is no material and density combination alarm of the liquid in the container in the inspection box, the first acquisition computer and the second acquisition computer scroll to display the original image, wherein the first acquisition computer displays the image of the V1 perspective module, and the second acquisition computer Acquisition computer display V2 perspective module image. If there is an alarm liquid in the inspection box this time, the boundary of the alarm liquid container is transmitted to the first acquisition computer and the second acquisition computer through the information communication unit of the third density computer, and the danger area is drawn while scrolling and displaying the original image s position.

The above steps constitute a whole detection process, the first acquisition computer and the second acquisition computer continuously acquire the images of the inspection box at a reasonable distance for processing.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the disclosure of the present invention are all It should be covered within the protection scope of the claims of the present invention.

Claims (3)

1. A channel-type four-view X-ray liquid article safety inspection system is characterized in that it includes: system control and signal processing circuit unit, the first acquisition computer, the second acquisition computer, the third density computer, switch, Conveyor, conveying channel, four groups of X-ray sources and four groups of detectors, the first acquisition computer, the second acquisition computer and the third density computer are connected through a local area network; each group of X-ray sources And the detector is called a viewing angle module, which includes four viewing angle modules in total. The four viewing angle modules include: the right top viewing angle module, the right horizontal side viewing angle module, the right bottom viewing angle module and the middle bottom viewing angle module Module; the right top-illuminated angle module includes the right top-illuminated X-ray source and the first detector, forming a V1 angle of view module; the right horizontal side-illuminated angle module includes the right horizontal side-illuminated X-ray source and the second detector, forming a V1 angle of view module; V2 viewing angle module; the right bottom viewing angle module includes the right bottom viewing angle X-ray source and the third detector, forming a V3 viewing angle module; the middle bottom viewing angle module includes the middle bottom viewing angle X-ray source and the fourth detector, forming a V3 viewing angle module V4 angle of view module, the V1 angle of view module, V2 angle of view module, V3 angle of view module, and V4 angle of view module are all connected to a capture card through a signal processing circuit unit, wherein the first acquisition computer is connected to the V1 angle of view module and the V2 angle of view The image acquisition card of the module receives the image data from the V1 perspective module and the V2 perspective module, and the second acquisition computer connects the image acquisition card of the V3 perspective module and the V4 perspective module to receive the image data from the V3 perspective module. The view module and the image data of the V4 view module. 2. A channel-type four-view X-ray liquid article security inspection system according to claim 1, characterized in that the first detector of the V1 viewing angle module, the second detector of the V2 viewing angle module, and the V3 viewing angle module The third detectors are all L-shaped detectors, and the fourth detectors of the V4 viewing angle module are U-shaped detectors. 3. A channel-type four-view X-ray liquid article safety inspection system according to claim 1, wherein an image acquisition unit, a low-atom Ordinal number container liquid material detection unit, information communication unit; the third density computer is equipped with an image matching unit, a density detection unit, a high atomic number container liquid material detection unit, a decision-making alarm unit, and an information communication unit. An acquisition computer and an image acquisition unit in the second acquisition computer form an acquisition workstation; The low atomic number container liquid material detection unit is used to perform image segmentation on the acquired images from the four viewing angle modules and locate the area of the liquid item; The information communication unit is used to transmit original images, calculation results, control commands and information between the first acquisition computer, the second acquisition computer and the third density computer; The image matching unit is used to perform image matching on the image data from the four viewing angle modules and the material detection results to confirm whether the data of the four viewing angle modules received this time come from the images of liquid objects in the same group of inspection boxes ; The density detection unit is used to calculate the density characteristics of the liquid items processed by the image matching unit; The high atomic number container liquid material detection unit is used to analyze the glass container wall rejection, correct the traditional rejection method, remove the influence of the container wall, obtain the real projected grayscale information of the liquid object, and obtain the liquid object in the high atomic number container material properties; The decision-making alarm unit is used to determine whether the liquid object to be detected is a liquid explosive by combining the two-dimensional characteristics of the material and density of the liquid object.

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