JP2004131303A - Exhaust hood apparatus, exhaust method and process for manufacturing glass preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust hood apparatus which inhibits attachment of soot-like glass fine particles or other foreign matters to its exhaust hood to prevent the foreign matters from dropping, an exhaust method and a process for manufacturing a glass preform. <P>SOLUTION: The exhaust hood apparatus used in the exhaust method has a rectangular aperture F and a shape which broadens from an exhaust pipe orifice G toward the aperture. The apparatus is equipped with gas-feeding means which blow a gas P from the aperture toward the exhaust pipe orifice along the inner wall of the exhaust hood. The gas-feeding means on two adjacent sides blow the gas P at different flow rates, or one of the gas-feeding means on two adjacent sides at the corner of the aperture stops blowing the gas. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust hood device, an exhaust method, and a method of manufacturing a glass base material for discharging floating glass particles and gaseous gas to be discharged generated in a process of manufacturing a glass base material and the like.
[0002]
[Prior art]
A glass base material for an optical fiber is produced, for example, by subjecting a glass raw material gas to flame hydrolysis in a reaction furnace to generate glass fine particles, and depositing the glass fine particles on a starting glass rod or the like to form a glass fine particle deposit (porous glass base material). ), Which is dehydrated and sintered to produce a transparent glass. In addition, a VAD method (a gas-phase shaping method), an OVD method (an external gas-phase vapor deposition method), and the like are known as methods for manufacturing a glass fine particle deposit.
[0003]
FIG. 5 is a diagram showing an example of manufacturing a glass particle deposit using the OVD method. FIG. 5 (A) is a diagram showing an outline of a reaction furnace, and FIG. 5 (B) is a diagram showing an example of an exhaust hood. . In the figure, 1 is a reaction furnace, 2 is a burner, 3 is a burner driving unit, 4 is a glass rod driving unit, 5 is a starting glass rod, 6 is a glass particle deposit, 7 is an exhaust hood, 8 is an exhaust pipe, 9 is Shows a damper.
[0004]
At the time of manufacturing the glass particle deposit body 6, first, the starting glass rod 5 is attached to the glass rod driving unit 4 and is rotatable. Next, a glass source gas such as SiCl ₄ and GeCl ₄ and a combustion gas such as H ₂ gas and O ₂ gas are sprayed from the burner to the outer periphery of the starting glass rod 5. Fine glass particles are generated by flame hydrolysis of the glass raw material gas, and the generated fine glass particles are deposited on the starting glass rod 5. By reciprocating the burner 2 a predetermined number of times in the longitudinal direction of the starting glass rod 5, a glass particle deposit 6 having a desired outer diameter is produced.
[0005]
In the above manufacturing process, hydrochloric acid gas is generated by hydrolysis of the glass raw material gas, and it is necessary to exhaust the gas outside the reaction furnace. Also, not all the generated glass particles are deposited, and the glass particles that are not deposited float in the reaction furnace 1. In order to prevent the glass particles in a floating state from re-adhering to the deposited glass particle stack 6, it is necessary to exhaust the gas to the outside of the reactor.
[0006]
Therefore, the reactor 1 is provided with an exhaust hood 7 having a divergent shape from the exhaust pipe opening toward the opening side (for example, refer to Patent Document 1). For example, as shown in FIG. 5A, the exhaust hood 7 is provided with a plurality of exhaust pipes 8 having a larger opening area along the glass particle deposit body 6 and a damper 9 attached to the exhaust pipe side. By opening and closing the damper 9 sequentially in synchronization with the movement of the burner 2, the exhaust hood 7 is exhausted in a fixed state without moving.
[0007]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-172859
[Problems to be solved by the invention]
However, as shown in FIG. 5 (B), the floating glass particles and gas hit the inner wall surface 7a of the exhaust hood 7 by suction, and these gradually become soot-like. Even if the exhaust hood 7 is fixed and not moved as in Patent Document 1, the soot-like glass fine particles adhering to the exhaust hood 7 may fall onto the glass fine particle depositing body 6 being deposited. There is. As a result, there is a problem in that the glass fine particle deposit 6 remains as debris or air bubbles in the glass base material obtained by dehydrating and vitrifying the glass so as to cause a reduction in optical characteristics and strength when formed into an optical fiber.
[0009]
In the reaction furnace 1, the burner 2 is moved and the glass particle deposit body 6 is driven to rotate, so that a gas flow is generated by the exhaust gas, and the vibration due to these is constantly generated during the deposition of the glass particle. Further, the exhaust hood 7 itself has undergone an expansion / contraction cycle due to heating and cooling, and if the amount of foreign matter such as glass particles attached to the exhaust hood 7 increases, the exhaust hood 7 may fall naturally. Therefore, as long as the exhaust hood 7 is used in a state in which foreign matter such as glass particles adheres, there is a possibility that the glass particles may peel off due to vibration and expansion / shrinkage cycles. There is no solution.
[0010]
The present invention has been made in view of the above-described circumstances, and has an exhaust hood device, an exhaust method, and a glass base material that do not cause foreign matters to fall by preventing soot-like glass particles and other foreign matters from adhering to the exhaust hood. It is an object of the present invention to provide a method for manufacturing the same.
[0011]
[Means for Solving the Problems]
An exhaust hood device or an exhaust method according to the present invention is an exhaust hood device having an opening surface having a rectangular shape and diverging from an exhaust pipe opening toward the opening side, and an exhaust hood inner wall surface extending from the opening side toward the exhaust pipe opening. Gas supply means for blowing gas along the air supply means, the flow rates of the blown gas from two adjacent gas supply means are made different, or one of two adjacent gas supply means at the corner on the opening side This is to stop the gas blowing from the air.
[0012]
Further, in the method for manufacturing a glass base material according to the present invention, the opening surface is rectangular and extends from the exhaust pipe opening toward the opening side. To discharge the gas at different flow rates of the blowing gas on two adjacent sides, or to stop and discharge the gas blowing on one of the two adjacent sides at the corner on the opening side, and to exhaust the glass base material. In this case, floating glass particles or gaseous gas generated in the production process of the above are discharged.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 schematically illustrates an exhaust hood device according to an embodiment of the present invention. FIG. 1A is a diagram showing an example in which the exhaust hood is formed by a double wall, and FIG. 1B is a diagram showing an example in which a tubular body is provided on the outer periphery of the exhaust hood. In the figure, 10a and 10b are exhaust hoods, 11 is a hood main body, 12 is a hood outer wall, 13 is a gap, 13a is a gas outlet, 14 is a gas supply port, 15 is an exhaust pipe, 16 is a tubular body, 16a is gas An outlet, F is an opening surface, G is an exhaust pipe opening, P is an outlet gas, and Q is an exhaust gas.
[0014]
The exhaust hoods 10a and 10b have an opening surface F of a rectangular shape and are divergent from the exhaust pipe opening G toward the opening surface F. Although the opening surface F is formed in a square or rectangular shape, the corners may be rounded and formed in an arc shape. The exhaust hoods 10a and 10b are configured such that the inner wall surface of the hood main body 11 is used as a suction surface and exhaust is performed from an exhaust pipe 15 provided at the center. In the present invention, a gas supply unit is provided so that the blown gas is supplied from the peripheral edge of the hood main body 11 on the opening surface F side along the inner wall surface. The blown gas to be supplied may be simple air or other inert gas, but is preferably a clean gas containing no dust or the like.
[0015]
The exhaust hood 10a shown in FIG. 1A is an example in which an outer wall 12 is provided outside a hood main body 11 to have a double wall structure. The gap 13 formed between the hood main body 11 and the outer wall 12 is used as a gas supply means, and has a shape in which the lower peripheral edge of the outer wall 12 is folded back on the peripheral edge of the hood main body 11 on the opening surface F side, so that the gas outlet 13 a To form The gas outlet 13a may have a slit-like shape that continuously opens, or may have a hole shape that is opened at an appropriate interval. However, in any case, the blowout gas P is formed so as to go from the peripheral edge of the hood body 11 on the opening surface F side to the exhaust pipe port G along the inner wall surface.
[0016]
The gap 13 formed between the hood main body 11 and the outer wall 12 may be divided into a plurality of parts by using a partition wall or the like. By dividing the flow path of the blown gas P by the partition wall, the gas flow velocity can be varied depending on the blow position. The gas supply port 14 for supplying the blown gas P is provided at an appropriate position near the center of the outer wall 12. When the flow paths are divided as described above, a gas supply port 14 is provided for each flow path.
[0017]
The exhaust hood 10b shown in FIG. 1B is an example in which a tubular body 16 is attached to a peripheral edge of the hood main body 11 on the opening surface F side. The cross section of the tubular body 16 may be circular as shown in the figure or rectangular. In this example, the tubular body 16 is used as gas supply means, and a gas outlet 16a is formed along the periphery of the hood main body 11 on the opening surface F side. The gas outlet 16a may have a slit-shaped continuous opening shape, or may have a hole shape formed at an appropriate interval. However, in any case, the gas to be blown out is formed so as to go from the peripheral edge on the opening surface F side of the hood main body 11 to the exhaust port G along the inner wall surface.
[0018]
Further, the tubular body 16 can be divided into a plurality of parts, and the blowout gas can be separately supplied to each of the tubular bodies 16 so that the gas flow rate can be varied depending on the blowout position. A gas supply port 14 for supplying the blown gas is provided at an appropriate position on each tubular body 16.
[0019]
By using the exhaust hood 10a or 10b configured as described above, the blown gas is supplied from the gas supply port 14 and the blown gas P is blown from the gas blowout port 13a or 16a. The blown gas P is sucked toward the exhaust pipe 15 along the inner wall surface of the hood, and the exhaust gas Q such as suspended particulates and gas is also sucked into the exhaust pipe 15. The discharged suspended particulates and the exhaust gas Q are prevented or directly mitigated by the blown gas P on the inner wall surface of the hood, thereby preventing the suspended particulate from adhering to the inner wall surface of the hood.
[0020]
2A and 2B are diagrams illustrating an example of an exhaust hood having a rectangular opening surface. FIG. 2A is a diagram of the hood as viewed from below, FIG. 2B is a side view of a long side, and FIG. (C) shows a side view of the short side. In the figure, 17 is the long side of the hood opening surface, 18 is the short side of the hood opening surface, P1 is the gas blown out from the long side, P2 is the gas blown out from the short side, θ1, θ2 are the inclination angles of the hood. Show. Note that the inclination angle θ1 on the long side 17 side is larger than the inclination angle θ2 on the short side 18 side.
[0021]
As shown in FIG. 2A, when the gas blown out from the four sides of the hood opening surface is blown out uniformly in a direction perpendicular to each side at a uniform flow velocity on each side, the area of the corner where the two sides intersect is obtained. In S, a state occurs in which the blown gases collide with each other. When the blown gas collides with each other, the blown gas flow may be disturbed, and the suspended fine particles being sucked toward the exhaust pipe opening may be blown off to hinder smooth discharge. In an apparatus for heating a glass base material with a flame using a lathe, an exhaust hood is used just above the glass base material. However, turbulence of blown gas may cause the flame to fluctuate.
[0022]
As a first embodiment of the present invention, the occurrence of a state in which the blown gases collide with each other is reduced by making the flow rates of the blown gases P1 and P2 adjacent to each other different. For example, when the flow rate of the gas P1 blown from the long side 17 is V1 and the flow rate of the gas P2 blown from the short side 18 is V2, V2> V1. As a result, in the region S where the blown gases P1 and P2 collide, the blown gas P2 with the higher flow velocity becomes dominant, and the blown gas P1 with the slower flow velocity follows this, and the blown gases P1 and P2 collide with each other. The turbulence of the gas flow due to the above can be reduced. Further, it is desirable that the ratio V2 / V1 of the different flow rates is 1.5 or more.
[0023]
Further, as shown in FIG. 2, in the case of a rectangular divergent exhaust hood having an opening surface formed by a long side 17 and a short side 18, from the side of the short side 18 that is long from the exhaust pipe 15 (inclination angle θ2). It is desirable that the flow velocity V2 of the blown gas P2 is higher than the flow velocity V1 of the blown gas P1 from the long side 17 (inclination angle θ1), which is short from the exhaust pipe 15. If the flow velocity V2 of the blown gas P2 from the short side 18 where the distance from the exhaust pipe 15 is long and the inclination angle is small is made slower than that of the long side 17 side, there is a probability that the suspended particulates are mixed into the blown gas P2 and adhere. growing.
[0024]
Further, it is preferable that the inclination angle θ2 of the hood on the short side 18 side be 45 degrees or less. Further, when (the length of the long side / the length of the short side) is 1.5 or more, the above-described effects are remarkably exhibited. Further, it is preferable that the temperature of the blown gas be higher than room temperature and lower than the temperature of the air flow from the target local exhaust heat source.
[0025]
FIG. 3 is a view showing the second embodiment, and shows only a view of the hood as viewed from the lower surface side. The reference numerals in the figure are the same as those in FIG. The form and structure of FIG. 3 are the same as those of FIG. 2 except that the gas blowing on one side is stopped at the corners of two adjacent sides to reduce the occurrence of a state in which the gases collide. I have. For example, the gas outlets at both ends on the long side 17 side are closed. Thus, in the region S where the gas P1 blown out from the long side 17 and the gas P2 blown out from the short side 18 collide, only the gas P2 blown out from the short side 18 is provided, and the turbulence of the gas flow is reduced. Can be.
[0026]
When the opening face F is formed of a rectangle having a long side and a short side, it is preferable to close the gas outlet at an end portion on the long side 17 side, and in the case of a square, the long side 17 side and the short side 18 side On either side. Further, as described above, when the gas blowing of one side is stopped at the corner of two adjacent sides, it is not necessary to change the flow rate of the gas blown out from the two adjacent sides, and the flow rate may be the same. However, the gas P1 blown out from the long side 17 and the gas P2 blown out from the short side 18 may be made different from each other as in the embodiment of FIG.
[0027]
FIG. 4 is a diagram showing an example in which the exhaust hood device according to the present invention is applied to the production of a glass base material. FIG. 4A is a diagram illustrating an example of manufacturing a glass particle deposit, and FIG. 4B is a diagram illustrating an example of heating a glass base material using a lathe. The description of the reference numerals in the drawing is omitted by using the same reference numerals as those already used.
[0028]
As shown in FIG. 4 (A), at the time of manufacturing the glass particle deposit body 6, first, the starting glass rod 5 is attached to the glass rod drive unit 4 and made rotatable, as described with reference to FIG. . Next, a glass raw material gas such as SiCl ₄ and a combustion gas such as H ₂ gas and O ₂ gas are blown out from the burner, and glass fine particles are generated by flame hydrolysis of the glass raw material gas, and the generated glass fine particles are used as starting glass. It is deposited on the rod 5. By reciprocating the burner 2 a predetermined number of times in the longitudinal direction of the starting glass rod 5, a glass particle deposit 6 having a desired outer diameter is produced.
[0029]
Hydrochloric acid gas generated by hydrolysis of the glass raw material gas generated in the above manufacturing process, and glass particles in a floating state that have not been deposited are discharged outside the furnace by the exhaust hood 10a. The exhaust hood 10a has a rectangular opening surface and is formed in a divergent shape from the exhaust pipe 15 side toward the opening side. As described in FIG. 1, the gas is blown out from the gas outlet 13 a on the opening side of the exhaust hood 10 a toward the exhaust pipe 15 along the inner wall surface of the exhaust hood main body 11. When the gas is blown, the gas is blown out at different flow rates of the blowout gas on two sides adjacent to the opening surface, or one of the two sides adjacent to the opening side is stopped and gas is blown out.
[0030]
By using the exhaust hood device and the exhaust method described above, it is possible to effectively prevent the glass particles floating in the reaction furnace 1 from adhering to the inner wall surface of the hood of the exhaust hood 10a in the form of soot. For this reason, a foreign substance does not fall from the exhaust hood, and a high-quality glass base material free of foreign substances or bubbles can be manufactured.
[0031]
In addition, as shown in FIG. 4B, when the surface of a transparent vitrified glass base material is processed by flame polishing, a glass rod is put into a glass tube, collapsed by burner heating, and integrated with the glass base material. It can be used for manufacturing a glass base material that requires various kinds of exhaust, for example, when manufacturing and stretching the glass base material by heating with a burner. Also in these manufactures, soot-like foreign matters such as glass fine particles are effectively prevented from adhering to the inner wall surface of the hood of the exhaust hood 10a, and fall-off of foreign matters onto the glass base material being processed is eliminated. Thus, a high-quality glass base material can be manufactured.
[0032]
In order to confirm the effect of the exhaust hood device described above, evaluation was performed in the following example and comparative example in an embodiment using the lathe device of FIG. 4B. The length M of the lathe used for the evaluation is 2.5 m and the depth is 0.7 m. The main body of the exhaust hood is made of stainless steel, the installation height T of the exhaust hood is 2.0 m from the installation surface of the lathe device, the long side L of the exhaust hood is 3.0 m, the depth is 1.0 m, and the exhaust pipe is The inner diameter D was selected to be 0.25 m, and the shorter side inclination angle θ2 was selected to be 30 ° to 60 °.
[0033]
In addition, the amount of gas exhausted from the exhaust pipe is 90 m ³ / min, the amount of gas blown from the gas outlet is 30 m ³ / min, the gas outlets are formed with blow holes at 10 mm intervals, and the blow hole diameter (diameter) is 4 mm to 4 mm. It was selected at 6 mm. Under the above conditions, the glass tube was heated with a burner, operated for one month, and the state of adhesion of glass particles to the inner wall surface of the exhaust hood was examined.
[0034]
(Example 1)
The blow hole diameter on the long side of the exhaust hood opening surface is 5.5 mm and the blow hole diameter on the short side is 4.5 mm, and the flow velocity V2 of the gas blown from the short side 18 shown in FIG. The flow rate was set to be 1.5 times the flow rate V1 of the gas. Further, the diameter of the blowout hole on the long side was 6.0 mm, and the diameter of the blowout hole on the short side was 4.0 mm. In each case, no glass particles adhered to the inner wall surface of the exhaust hood.
[0035]
(Example 2)
As in the first embodiment, the diameter of the outlet hole on the long side of the exhaust hood opening surface is 5.5 mm, the diameter of the outlet hole on the short side 18 is 4.5 mm, and the flow velocity V2 of the gas blown from the short side is from the long side. The flow rate was set to be 1.5 times the flow rate V1 of the blowing gas. Further, when the inclination angle θ2 of the short side of the exhaust hood was changed, the flow velocity of the gas blown out from the short side was made larger than the flow velocity blown out from the long side by setting the inclination angle θ2 to 45 ° or less. The effect of this was confirmed. However, above 45 °, no difference was observed even when the flow rate ratio of the blown gas was changed.
[0036]
(Example 3)
As shown in FIG. 3, both end portions on the long side 17 side were sealed by 0.5 m, and the blowing of gas from this portion was stopped. Further, the flow rates of the blown gas from the long side and the short side were set to be the same. As a result, as in Example 1, no glass particles adhered to the inner wall surface of the exhaust hood.
[0037]
(Example 4)
The diameter of the outlet on the short side was 4.6 mm, the diameter of the outlet on the long side was 5.4 mm, and the flow rate ratio was about 1.4 times. In this case as well, glass particles of about 0.5 mm were adhered at the four corners on the opening side, but the burner flame had almost no fluctuation.
[0038]
(Comparative Example 1)
Exhausting was performed under the same conditions as in Example 1 except that the gas blowing amount from the gas blowing port was 30 m ³ / min. As a result, glass particles of 2 to 3 mm were adhered to the inner wall surface of the exhaust hood. In addition, part of the adhesion was falling.
[0039]
(Comparative Example 2)
The blowing hole diameter was 5.0 mm on both the long side and the short side, the flow rates V1 and V2 of the blowing gas were the same, and the other conditions were the same as in Example 1. As a result, glass particles of about 1.0 mm were attached at the four corners on the opening side, but no glass particles were attached to other portions. In addition, the burner flame slightly fluctuated at both ends on the long side of the hood.
[0040]
Comprehensively looking at the above results, from Comparative Examples 1 and 2, it is effective to prevent the adhesion of glass particles to the inner wall surface of the hood by blowing gas toward the exhaust port from the periphery of the opening surface. That was clear. However, when the opening surface is rectangular, a small amount of foreign matter adheres at a portion where the blown gas from two adjacent sides at the four corners on the opening side collide, and the flame fluctuates when a burner is used. May not be complete. On the other hand, it has been found that it is extremely effective to make the flow speeds of the two adjacent sides different or to stop the gas blowing on one of the two adjacent sides at the four corners on the opening side.
[0041]
【The invention's effect】
As described above, according to the present invention, it is possible to effectively prevent soot-like glass particles and other foreign substances from adhering to the hood wall surface. As a result, it is possible to eliminate the intrusion of foreign matter from the hood wall surface during the production of the glass base material and the like, and it is possible to produce a high-quality and reliable product.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating an exhaust hood device according to the present invention.
FIG. 2 is a diagram illustrating a first embodiment of an exhaust hood device and an exhaust method according to the present invention.
FIG. 3 is a diagram illustrating a second embodiment of the exhaust hood device and the exhaust method according to the present invention.
FIG. 4 is a diagram illustrating a method for manufacturing a glass base material according to the present invention.
FIG. 5 is a diagram illustrating a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... Burner, 3 ... Burner drive part, 4 ... Glass rod drive part, 5 ... Starting glass rod, 6 ... Glass fine particle deposit, 8 Exhaust pipe, 9 ... Damper, 7, 10a, 10b ... Exhaust Hood, 11: Hood main body, 12: Hood outer wall, 13: Gap, 13a: Gas outlet, 14: Gas supply port, 15: Exhaust pipe, 16: Tubular body, 16a: Gas outlet, 17: Hood opening surface Long side, 18: Short side of hood opening surface, F: Opening surface, G: Exhaust port, P: Blowing gas, Q: Exhaust gas, P1: Blowing gas on long side, P2: Blowing on short side Gas, θ1, θ2 ... The inclination angle of the hood.

Claims (8)

An exhaust hood device having an opening surface having a rectangular shape and diverging from an exhaust pipe opening toward an opening side, wherein a gas supply blows gas from the opening side toward the exhaust pipe opening along an inner wall surface of the exhaust hood. An exhaust hood device comprising means for changing the flow rates of the gas blown out from the gas supply means on two adjacent sides. 2. The exhaust hood according to claim 1, wherein the opening side of the exhaust hood is formed in a rectangular shape having a long side and a short side, and the flow velocity of the blown gas on the short side is higher than the flow velocity on the long side. 3. apparatus. The exhaust hood device according to claim 1, wherein the short side inclination angle of the exhaust hood is 45 ° or less. An exhaust hood device having an opening surface having a rectangular shape and diverging from an exhaust pipe opening toward an opening side, wherein a gas supply blows gas from the opening side toward the exhaust pipe opening along an inner wall surface of the exhaust hood. An exhaust hood device, comprising: means for stopping gas blowing from the gas supply means on one of two sides adjacent to each other at the corner on the opening side. The opening surface is rectangular, and gas is blown out from the opening side of the exhaust hood toward the opening side of the exhaust hood along the inner wall surface of the exhaust hood from the opening side of the exhaust hood toward the opening side. An exhaust method, wherein the exhaust gas is exhausted at different flow rates. An opening surface is rectangular, and gas is blown out from the opening side of the exhaust hood toward the opening of the exhaust pipe along the inner wall surface of the exhaust hood. An exhaust method characterized by stopping gas blowing on one of two sides adjacent to each other and exhausting the gas. The opening surface is rectangular, and gas is blown out from the opening side of the exhaust hood toward the opening side of the exhaust hood along the inner wall surface of the exhaust hood from the opening side of the exhaust hood toward the opening side. A method of manufacturing a glass base material, wherein the blowing gas is exhausted at different flow rates, and floating glass particles or a gaseous gas generated in the manufacturing process of the glass base material are discharged. An opening surface is rectangular, and gas is blown out from the opening side of the exhaust hood toward the opening of the exhaust pipe along the inner wall surface of the exhaust hood. A method of manufacturing a glass base material, comprising: stopping and evacuating one of two adjacent sides of a gas at a portion to discharge air, and discharging floating glass particles or a gaseous gas generated in a manufacturing process of the glass base material.

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