A kind of infiltration spherical shell for low temperature freezing target and preparation method thereof

Abstract

The present invention provides an infiltration spherical shell for a low-temperature freezing target and a preparation method thereof, comprising: a basic unit is a regular tetrahedron structure, the regular tetrahedron structure is composed of a solid prism, and the interior is a hollow structure, and the hollow structure is used as a liquid flow and filling space; a microcolumn or a hydrophilic structure is arranged in the regular tetrahedron structure. A plurality of basic units are arranged by close packing to form an overall spherical shell structure. The above-mentioned spherical shell of the present invention is prepared based on 3D printing, and the capillary force between the microstructures is used to realize the transport and infiltration of the liquid on the surface of the structure. At the same time, the surface of the structure can be further modified, thereby effectively improving the liquid infiltration effect. This method does not require the use of complicated preparation steps, the process is simple and convenient, and the cost is low.

Description

Technical Field

[0001] The invention relates to the preparation of a low-temperature freezing target, in particular to a low-temperature freezing target spherical shell which is wettable to deuterium-tritium liquid and a preparation method thereof. Background Art

[0002] A cryogenically frozen spherical shell target containing a uniform deuterium-tritium (DT) liquid fuel layer inside is one of the ideal implosion targets for inertial confinement fusion (ICF). The key to obtaining a cryogenically frozen target is to form a frozen fuel layer with uniform thickness and smooth surface on the surface of the target pellet. Currently, there are two main methods for forming a fuel layer inside a frozen target: one is to directly freeze the target pellet system filled with fuel gas through external cryogenic technology to obtain a solid or liquid fuel layer deposited on the surface of the target pellet, and then form a uniform fuel layer through thermal gradient method, U layering technology, plasma layering technology, etc.; the other method is to use external structures such as low-density spherical shells as carriers to adsorb deuterium-tritium liquid to form a uniformly distributed fuel layer. Compared with the former, external structures such as low-density spherical shells are simple to design and prepare as adsorption carriers, easier to implement, and are a better choice.

[0003] Through the search of existing technologies, we found that:

[0004] SACKS et al. of Lawrence Livermore National Laboratory in California, USA, wrote an article titled “Direct drive cryogenic ICF capsules employing DT wetted foam” in Nuclear Fusion, 1987, 27. They first proposed using low-density, low-atomic-number microporous foam shells as carriers to achieve the wetting and uniform distribution of deuterium-tritium liquid. For a reasonable unit size, capillary force is sufficient to solve the problem of liquid non-wetting. However, the potential problem is that more doses of deuterium-tritium gas need to be reliably handled during liquid diffusion filling, as well as temperature control protection to achieve the best filling effect.

[0005] Du Kai et al. of the China Academy of Engineering Physics wrote an article titled "Preparation of Polymer Foam Spherical Shell for Cryogenic Targets" in Atomic Energy Science and Technology, 2002, 36. They used the solution polymerization reaction of trimethylolpropane triacrylate (TMPTA) and combined it with multiple emulsification technology to prepare foam hollow microspheres for cryogenic targets for inertial confinement fusion. Due to the light scattering caused by the foam honeycomb, the microspheres are white and opaque, which brings certain difficulties to measuring the distribution of deuterium-tritium liquid in the spherical shell.

[0006] T. Norimatsu et al. from Osaka University, Japan, wrote an article titled “Issue in capsule fabrication and injection into a wet-walled IFEreactor” in Fusion Engineering and Design, 2001, 55. They used multiple emulsification techniques and interfacial polymerization to prepare PS foam spherical shells with gas barriers. The shells have a diameter of 1 to 4 mm, a foam thickness of 20 to 200 μm, a sphericity of 99%, and a foam density of 43 g / cm 3 .

[0007] In summary, using a low-density spherical shell structure as a carrier to adsorb deuterium-tritium liquid to form a uniformly distributed fuel layer inside a cryogenic target pellet has the advantages of flexibility and ease of implementation, and spherical shells of different polymers can be prepared according to actual needs. However, the polymer spherical shells prepared by microfluidics will introduce more unnecessary elements, the preparation process is relatively complicated, the yield is low, and the structural dimensions are difficult to accurately control. Therefore, it is urgent to propose a spherical shell design and preparation method with easy-to-control structural dimensions and infiltration of deuterium-tritium liquid. Summary of the invention

[0008] In view of the defects in the prior art, the object of the present invention is to provide an infiltrated spherical shell for a cryogenic target and a preparation method thereof.

[0009] According to the first aspect of the invention, a basic unit of a wetting spherical shell for a low-temperature freezing target is provided, wherein the basic unit is a regular tetrahedron structure, which is composed of solid prisms and has a hollow structure inside. The hollow structure is used as a liquid flow and filling space; a microcolumn or a hydrophilic structure is arranged in the regular tetrahedron structure.

[0010] Optionally, a plurality of microcolumns are arranged in the regular tetrahedron structure, each of the microcolumns extends from one vertex angle of the regular tetrahedron to another vertex angle of the regular tetrahedron, and the microcolumns intersect at the center of the regular tetrahedron, forming a radial arrangement with the center of the regular tetrahedron as the center point.

[0011] Optionally, the prism surface of the regular tetrahedral structure is modified with a hydrophilic structure.

[0012] Optionally, the hydrophilic structure is a pitcher plant structure, and the pitcher plant structures on the surfaces of two parallel faces connected by the same prism of the regular tetrahedron structure are in opposite directions.

[0013] A second aspect of the present invention provides an infiltration spherical shell for a cryogenic target, comprising: a plurality of basic units, wherein the plurality of basic units are closely packed and arranged to form an overall spherical shell structure.

[0014] Optionally, a plurality of the basic units are closely packed to form an overall spherical shell structure to meet the spherical shell size requirements; the closely packed arrangement utilizes a sparse and dense matching structure to achieve preferential movement of the liquid in a specific direction.

[0015] A third aspect of the present invention provides a method for preparing a wetted spherical shell for a cryogenic target, comprising:

[0016] S1, with a regular tetrahedron structure as the basic unit, each regular tetrahedron structure has a hollow structure inside, and the liquid uses the solid prism of the regular tetrahedron structure as a carrier to fill the internal hollow structure;

[0017] S2, structurally modifying the internal hollow structure or external prism of the basic unit, wherein micro-columns are arranged in the internal hollow structure of the basic unit, and a hydrophilic structure is modified in the external prism;

[0018] S3, densely stacking the basic units after structural modification to form a spherical shell structure;

[0019] S4, the spherical shell is completed using 3D printing.

[0020] Optionally, after S4 is completed, the method further includes:

[0021] S5, after 3D printing is completed, modification treatment is performed on the surface of the structure.

[0022] Optionally, the modification treatment on the surface of the structure includes:

[0023] Surface modification using plasma technology;

[0024] The surface is modified with a hydrophilic polymer.

[0025] Optionally, the surface modification treatment using plasma technology refers to: using oxygen plasma technology to treat the surface of the basic unit to form a rough structure that enhances the wetting effect.

[0026] Compared with the prior art, the embodiments of the present invention have at least one of the following beneficial effects:

[0027] The basic unit of the infiltration spherical shell for the cryogenic freezing target of the present invention is provided with micro-columns or hydrophilic structures in the regular tetrahedron structure, and these micro-structures can be used to improve the liquid infiltration effect.

[0028] The infiltration spherical shell for cryogenic freezing target of the present invention is composed of multiple basic units (regular tetrahedral structure), and the structural size can be precisely controlled. Furthermore, based on the capillary force of the tiny structural units, the basic units with different structures modified internally or externally are densely stacked to form a spherical shell carrier, which can reduce the influence of liquid gravity and improve the contact angle between the structure and the liquid, thereby effectively improving the uniform infiltration effect.

[0029] The method for preparing the infiltrated spherical shell for the low-temperature freezing target of the present invention is completed by 3D printing, and the preparation process is relatively simple, the yield is high, and the structural size is easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 This is a schematic diagram of a spherical shell structure of a deuterium-tritium fuel carrier for cryogenically freezing a target according to a preferred embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of a spherical shell basic unit structure modification for a low-temperature freezing target deuterium-tritium fuel carrier in a preferred embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of a dense packing of a spherical shell basic unit structure for a low-temperature freezing target deuterium-tritium fuel carrier in a preferred embodiment of the present invention;

[0034] Figure 4 The figure is a schematic diagram of a modification process of a deuterium-tritium fuel spherical shell carrier for a low-temperature freezing target according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0036] Figure 1 This is a schematic diagram of a 3D printed spherical shell structure as a low-temperature freezing target deuterium-tritium fuel carrier according to a preferred embodiment of the present invention.

[0037] like Figure 1As shown in (a), it is the basic unit of the spherical shell that constitutes the low-temperature freezing target deuterium-tritium fuel carrier. The basic unit is a regular tetrahedron structure, which is composed of multiple solid prisms and has a hollow structure inside. The hollow structure is used as a liquid flow and filling space. The prisms act as a supporting carrier, and the liquid fills the internal hollow structure of the regular tetrahedron structure formed by the prisms.

[0038] like Figure 1 (b) shows a schematic side view of the overall close-packed structure of multiple basic units, which eventually form the expected spherical shell structure. The interior is a hollow structure for liquid flow and filling space, and the overall structure is formed by a close-packed array of regular tetrahedral structures.

[0039] like Figure 1 (c) shows the front view of the spherical shell structure. Figure 1 (d) shows a top view of the spherical shell structure. As can be seen from the above, the spherical shell structure is formed by densely stacking multiple basic units of regular tetrahedron structures, similar to building an arched building with bricks. The size of each regular tetrahedron is selected according to the actual application needs. Specifically, Figure 1 The symbols in the figure indicate that: 1 is a basic unit with a side length of 15 μm and a prism width of 2 μm. Of course, in other embodiments, the basic unit can be designed with structural parameters ranging from nm to mm according to actual needs.

[0040] The spherical shell of the above-mentioned embodiment of the present invention takes a regular tetrahedron structure as the basic unit, has a hollow structure inside as a liquid flow and filling space, uses an external prismatic structure as a supporting carrier, and adopts a regular tetrahedron structure to be densely packed into a whole. Based on the capillary force of the structural unit, it can reduce the influence of liquid gravity and improve the contact angle between the structure and the liquid, thereby effectively improving the uniform infiltration effect.

[0041] In order to improve the contact angle between the structure and the liquid, the basic unit was further optimized. Figure 2 This is a schematic diagram of the modification of the spherical shell basic unit structure of a deuterium-tritium fuel carrier for a low-temperature freezing target in a preferred embodiment of the present invention. Figure 2 The marks in the figure respectively indicate that: 2 is the basic unit in which the inside of the structure 1 is modified by using a cylinder, and 3 is the basic unit in which the outside prism of the structure 1 is modified by using a pitcher plant.

[0042] Reference Figure 2 As shown, in a preferred embodiment, in order to strengthen the capillary force, overcome the gravity of the liquid itself, enhance the upward transport of the liquid, and improve the wetting effect, the following is used inside the tetrahedral basic unit structure: Figure 2 The solid microcolumn shown in (a) is modified to serve as a liquid auxiliary support carrier to reduce the influence of the liquid's own gravity and form an improved unit structure, such as Figure 2As shown in (b); specifically, a plurality of microcolumns are arranged in the regular tetrahedron structure, each microcolumn extends from one vertex of the regular tetrahedron to another vertex of the regular tetrahedron, and these microcolumns intersect at the center of the regular tetrahedron, forming a radial arrangement with the center of the regular tetrahedron as the center point. Figure 2 As shown, the microcolumns are solid microcolumns.

[0043] Reference Figure 2 As shown, in another preferred embodiment, in order to enhance the transport effect of liquid between each basic unit and realize the flow guidance and uniform liquid infiltration on the surface of the structure, the following is used: Figure 2 (c) shows a pitcher plant structure modified on the surface of a regular tetrahedral prism of a basic unit, wherein the pitcher plant structure is in a "V" shape, and the liquid flows from both sides of the "V" wing to the tip, and the tip and the angles of the two wings are designed according to the properties of the infiltrating liquid and the material used for preparation. As shown in the figure, on the prism surface of the regular tetrahedron structure, the "V"-shaped pitcher plant structures are evenly arranged on the surface of the solid prism, and are in the shape of a "V" protruding from the surface, and multiple or multiple groups of "V"-shaped pitcher plant structures are symmetrically arranged about the central axis of the prism surface. In some embodiments, the bottom of the "V" shape can be a smooth transition. The number of pitcher plant structures and the spacing between them are designed according to the size of the solid prism to achieve uniform full coverage to achieve an effective diversion effect.

[0044] like Figure 2 (b) shows a schematic diagram of the prisms that modify the structure of the pitcher plant. Figure 2 (e) shows a side view of the basic unit after improvement using Nepenthes. In order to achieve the best transport effect, in a preferred embodiment, the Nepenthes structures are arranged in opposite directions on the opposite surfaces connected at both ends of the same prism of the regular tetrahedron structure (i.e., the surfaces of the two parallel surfaces connected by the same prism), that is, the "V"-shaped openings are arranged in opposite directions. In this way, the Nepenthes structures that play a guiding role have opposite "V"-shaped openings on the opposite surfaces of the same prism, which is conducive to the flow of liquid in different directions, thereby achieving rapid and uniform distribution of liquid inside the structure.

[0045] In the above embodiments of the present invention, the hollow structure inside the basic unit is modified with a micro-cylindrical structure or the external prism surface is modified with a pitcher plant structure to enhance the wettability between the structure and the liquid and the fluidity of the liquid. Of course, these two preferred features can also be used at the same time.

[0046] Figure 3 The figure is a schematic diagram of a spherical shell basic unit structure densely packed for a low-temperature freezing target deuterium-tritium fuel carrier in a preferred embodiment of the present invention. In order to meet the overall size requirements, the basic units after structural modification are densely packed and arranged to form an overall structure, wherein, in order to achieve the preferential flow of liquid in a specific direction, a sparse and dense matching structure of basic units of different sizes is adopted.

[0047] Specifically, refer to Figure 3 As shown, the close packing method mainly includes: the basic structural units are closely packed to form an overall structure to meet the spherical shell size requirements, Figure 3 (a) shows a side view of the dense packing of the basic unit after the internal micro-cylindrical structure is modified. Figure 3 (b) shows a side view of the densely packed basic unit after the external modification with the pitcher plant structure. Based on the principle that the smaller the size, the stronger the capillary force, the sparse and dense matching structure is used to achieve the preferential movement of the liquid in a specific direction, such as Figure 3 As shown in (c), a small-sized basic unit structure is densely packed in the preferred flow direction, and a large-sized basic unit structure is densely packed in the secondary flow direction, so that the purpose of preferential movement of the liquid in a specific direction can be achieved. Figure 3 (d) shows a side view of the specific matching form of the larger size basic unit and the smaller size basic unit. In one embodiment, Figure 3 4 in the middle is a basic structural unit with a side length of 5 μm and a prism width of 0.5 μm.

[0048] Based on the same technical concept as above, in another embodiment, the present invention also provides a method for preparing the above-mentioned infiltrated spherical shell for cryogenic freezing target, comprising:

[0049] S1, with a regular tetrahedron structure as the basic unit, each regular tetrahedron structure has a hollow structure inside, and the liquid uses the solid prism of the regular tetrahedron structure as a carrier to fill the internal hollow structure;

[0050] S2, structurally modifying the internal hollow structure or external prism of the basic unit, wherein micro-columns are arranged in the internal hollow structure of the basic unit, and a hydrophilic structure is modified in the external prism;

[0051] S3, densely stacking the basic units after structural modification to form a spherical shell structure;

[0052] S4, the spherical shell is completed by 3D printing, and the material may include photosensitive resin,

[0053] The non-hydrophilic structures in the above-mentioned embodiments can all be prepared by 3D printing. 3D printing is simple to operate and low in cost. After the 3D printed structure is completed, the surface of the structure is modified using plasma technology and hydrophilic polymers to further improve the wettability between the liquid and the structure.

[0054] Based on the above preparation methods S1 to S4, the method may further include: S5, after the 3D printing structure is completed, a modification treatment is performed on the surface of the structure to improve the surface roughness structure. Figure 4 Detailed description.

[0055] Figure 4 This is a schematic diagram of the surface modification process of a spherical shell used as a low-temperature freezing target deuterium-tritium fuel carrier in a preferred embodiment of the present invention. Figure 4 As shown, in this preferred embodiment, the surface modification treatment of the structure can be first performed using plasma technology for surface modification treatment, and the treated surface is further modified using a hydrophilic polymer. Specifically, the 3D printed spherical shell structure is subjected to oxygen plasma surface treatment using a microwave plasma degumming machine, and while introducing polar bonds, the surface roughness structure is improved; the spherical shell structure after oxygen plasma treatment is immersed in a hydrophilic polymer solution and ultrasonically treated, and the spherical shell is taken out and gently blown with a nitrogen gun, so that the surface of the structure is covered with a thin layer of hydrophilic polymer solid. Specifically, the surface is modified using oxygen plasma, and the parameters are set according to the material properties, including plasma power and surface treatment time.

[0056] The surface is modified by using a hydrophilic polymer, which includes polyvinyl alcohol (PVA) and polyacrylic acid. The treatment method is selected according to the properties of the polymer material, including surface immersion and deposition.

[0057] Specifically, in another specific embodiment, a process for preparing and modifying polyvinyl alcohol (PVA) for modifying the spherical shell of a cryogenic target deuterium-tritium fuel carrier using micro-cylinders is provided, comprising the following steps:

[0058] 1) The tetrahedron basic unit has two sizes: one has a side length of 15μm, a prism width of 2μm, an internal cylindrical structure diameter of 1μm, and is connected to the diagonal of the tetrahedron; the other has a side length of 5μm, a prism width of 0.5μm, an internal cylindrical structure diameter of 0.3μm, and is connected to the diagonal of the tetrahedron;

[0059] 2) To achieve the qualitative flow of liquid, according to the knowledge of molecular dynamics, the capillary force in the high-density area is strong, and the liquid flows preferentially in this area. Therefore, small-sized regular tetrahedron units are used in the main transport channel, and large-sized regular tetrahedron units are matched around them. The large-sized and small-sized regular tetrahedron units are densely packed with a matching ratio of 1:9 to complete the design of the overall structure;

[0060] 3) Using photosensitive resin as raw material, a spherical shell structure is prepared using high-precision 3D printing equipment;

[0061] 4) The printed spherical shell structure is subjected to oxygen plasma surface treatment using a microwave plasma degumming machine to introduce polar bonds and improve the surface roughness structure;

[0062] 5) The spherical shell structure after oxygen plasma treatment was immersed in a polyvinyl alcohol (PVA) solution and ultrasonically treated for 10 seconds, and the spherical shell was taken out and gently blown with a nitrogen gun so that the surface of the structure was covered with a thin layer of polyvinyl alcohol (PVA) solid.

[0063] Specifically, in another specific embodiment, a preparation and modification process of polyvinyl alcohol (PVA) for a spherical shell of a low-temperature freezing target deuterium-tritium fuel carrier with a surface modified with a pitcher plant structure is provided, comprising the following steps:

[0064] 1) The side length of the tetrahedron basic unit is 15 μm, the width of the prism is 2 μm, and the surface of the prism is covered with a pitcher plant structure. Each prism is fully covered according to the size requirements, and the pitcher plant structures of the opposing prisms are in opposite directions to achieve the optimal infusion effect;

[0065] 2) Densely stack the basic structural units to complete the design of the overall structure;

[0066] 3) Using photosensitive resin as raw material, a spherical shell structure is prepared using high-precision 3D printing equipment;

[0067] 4) The printed spherical shell structure is subjected to oxygen plasma surface treatment using a microwave plasma degumming machine to introduce polar bonds and improve the surface roughness structure;

[0068] 5) The spherical shell structure after oxygen plasma treatment was immersed in a polyvinyl alcohol (PVA) solution and ultrasonically treated for 10 seconds, and the spherical shell was taken out and gently blown with a nitrogen gun so that the surface of the structure was covered with a thin layer of polyvinyl alcohol (PVA) solid.

[0069] In summary, the above embodiments of the present invention use a regular tetrahedron structure as a basic unit; in order to reduce the influence of liquid gravity and enhance the liquid flow effect, the basic unit structure is modified with a cylindrical structure inside or a hydrophilic structure such as a pitcher plant outside; the actual size requirements are met through dense stacking, and the sparse and dense matching structure is used to achieve the directional flow of the liquid; the required structure is prepared using a high-precision 3D printing platform; the structure is modified using oxygen plasma technology and high molecular weight hydrophilic polymers such as polyvinyl alcohol to achieve a better liquid infiltration effect. The above embodiments of the present invention utilize the capillary force between microstructures to achieve the transport and infiltration of liquid on the surface of the structure, and at the same time modify the surface of the structure, thereby effectively improving the liquid infiltration effect. The preparation method does not require the use of complex preparation steps, the process is simple and convenient, and the cost is low.

[0070] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A basic unit for a cryogenic target infiltrated with a spherical shell, characterized in that: The basic unit is a regular tetrahedron structure, which is composed of solid prisms and has a hollow structure inside. The hollow structure is used as a liquid flow and filling space; a microcolumn or a hydrophilic structure is arranged in the regular tetrahedron structure; A plurality of micro-pillars are arranged in the regular tetrahedron structure, each of the micro-pillars extends from one vertex of the regular tetrahedron to another vertex of the regular tetrahedron, and the micro-pillars intersect at the center of the regular tetrahedron, forming a radial arrangement with the center of the regular tetrahedron as the center point; The prism surface of the regular tetrahedral structure is modified with a hydrophilic structure; The basic unit, wherein each regular tetrahedral structure has a hollow structure inside, and the liquid is filled in the internal hollow structure using the solid prism of the regular tetrahedral structure as a carrier; the internal hollow structure or the external prism of the basic unit is structurally modified, wherein microcolumns are set in the internal hollow structure of the basic unit, and the external prism is modified with a hydrophilic structure.

2. The infiltrated spherical shell for cryogenic freezing target according to claim 1, characterized in that: The hydrophilic structure is a pitcher plant structure, and the pitcher plant structures on the surfaces of two parallel faces connected by the same prism of the regular tetrahedron structure are in opposite directions.

3. A wetted spherical shell for a cryogenic target, characterized in that: include: A plurality of basic units as described in any one of claims 1-2, wherein the plurality of basic units are closely packed and arranged to form an overall spherical shell structure.

4. The infiltrated spherical shell for cryogenic freezing target according to claim 3, characterized in that: A plurality of the basic units are densely packed and arranged to form an overall spherical shell structure to meet the spherical shell size requirements; the densely packed arrangement utilizes a sparse and dense matching structure to achieve preferential movement of the liquid in a specific direction.

5. A method for preparing a wetted spherical shell for a cryogenic target according to any one of claims 3 to 4, characterized in that: include: S1, with a regular tetrahedron structure as the basic unit, each regular tetrahedron structure has a hollow structure inside, and the liquid uses the solid prism of the regular tetrahedron structure as a carrier to fill the internal hollow structure; S2, structurally modifying the internal hollow structure or external prism of the basic unit, wherein micro-columns are arranged in the internal hollow structure of the basic unit, and a hydrophilic structure is modified in the external prism; S3, densely stacking the basic units after structural modification to form a spherical shell structure; S4, the spherical shell is completed using 3D printing.

6. The method for preparing a wetted spherical shell for a cryogenic target according to claim 5, characterized in that: After S4 is completed, the method further includes: S5, after 3D printing is completed, modification treatment is performed on the surface of the structure.

7. The method for preparing a wetted spherical shell for a cryogenic target according to claim 6, characterized in that: The modification treatment on the surface of the structure comprises: Surface modification using plasma technology; The surface after the surface modification treatment is modified with a hydrophilic high molecular polymer.

8. The method for preparing a wetted spherical shell for a cryogenic target according to claim 7, characterized in that: The surface modification treatment using plasma technology refers to: using oxygen plasma technology to treat the surface of the basic unit to form a rough structure that enhances the wetting effect.

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