KR100266910B1 - Vertical average flow speed measurement device for river etc. - Google Patents

Abstract

PURPOSE: An apparatus for measuring vertical mean flow rate for open channel is provided to shorten measurement time, reduce measurement error and simplify measurement processes. CONSTITUTION: The apparatus for measuring vertical mean flow rate for open channel has the vertical pole(10) which is stood on the open channel and the horizontal pole(12). The ultrasonic transformer(15) is fixed to one end of the horizontal pole(12). The cursor(11) is installed on the vertical pole to move up and down along the length thereof. The other ultrasonic transformer(16) is fixed on the one side of the cursor(11) to face the ultrasonic transformer oppositely. The reflection plate which contacts the surface of the water is fixed to the other side of the cursor.

Description

Vertical Average Flow Rate Measuring Device for Waterway

The present invention relates to an ultrasonic flow rate measurement technology, and more particularly, to a portable vertical average flow rate measuring apparatus for measuring the average flow rate at the same time as the water depth to measure the flow rate in the channel (river, artificial water channel, etc.). .

을 계산하고 있다.In order to measure the flow rate directly in the channel, divide the water flow width into several points, select vertical average flow rate measurement lines, and then use the local tachometers (e.g., propellers, screws, electronic tachometers, etc.) Measure local flow rates at. The average flow velocity on the vertical line is obtained by using the local flux measurement result measured at various depths.

Is being calculated.

To measure flow rate more precisely, select at least 10 vertical lines along the width of the channel, and measure the velocity and depth at five points along the depth of each vertical line. The local flow measurement time depends on the local flow pulsation but is usually measured for 1 minute. Therefore, if you calculate the pure time to measure the local flow rate, except for the tachometer travel time and the water depth measurement, if the vertical bow is at least 10, if you measure the local flow rate at 5 points by 5 minutes, 10 × 5 × 1 minute = 50 minutes Takes In large rivers it usually takes two hours.

In order to solve these shortcomings, a technique of measuring vertical average velocity and depth in a short time using ultrasonic waves is known.

As a representative method and device for measuring the flow rate and depth of the United States Patent 5,531,125, July 2, 1996 in hd (Kyu-hong Ahn; Hak-Su; Chang).

Ultrasonic flow rate and depth measurement apparatus according to the prior art is shown in FIG.

1 to 5 are vertical rods, which are erected perpendicular to the channel to measure the vertical average flow velocity. There is a cylinder that moves up and down along the vertical rod 5 to a depth, and there is a shaft, and there is a flow rate measuring rod 6 in which ultrasonic transducers capable of rotating about this axis are fixed. The ultrasonic transducer 1 is fixed to the front end of the flow rate measuring rod 6, and the two ultrasonic transducers 2 and 3 are fixed at the point where the rod has a rotation axis. Another ultrasonic transducer 4 is fixed to the lower end of the vertical rod 5.

When measuring the vertical average flow rate, as shown in Fig. 1, the front end of the flow rate measuring rod 6 is dropped into the water so that the front end touches the lower bed of the channel.

Ultrasonic transducers 1 and 2 are used to measure the flow velocity and sound velocity and ultrasonic transducers 3 and 4 are used to measure the depth of water. In FIG. 1, 7 is a control arithmetic device that controls the launch and reception of ultrasonic pulses, measures the ultrasonic propagation time, and calculates the flow velocity and depth.

The operation principle of the above-described prior art is as follows.

은 다음식에 의하여 연산하게 되어 있다.Vertical average flow velocity between the ultrasonic transducers (1) and (2)

Is calculated by the following equation.

Where Δt = t ₂₁ -t ₁₂ where t ₂₁ is the time at which the ultrasonic pulse emitted from the ultrasonic transducer (2) to (1) propagated from the ultrasonic transducer (2) to (1) and t ₁₂ is the opposite, the ultrasonic transducer ( 1) to (2) is the time when the ultrasonic pulse propagated. L is the distance between the ultrasonic transducers 1 and 2, and C is the speed of sound, the speed of ultrasonic propagation in water. φ is an angle formed between the flow rate measuring rod 6 and the water surface.

The flow rate measurement formula (1) is widely known as a time difference method.

If the depth h is large, the angle φ becomes larger and COSφ becomes smaller, so that Δt becomes smaller by that amount and the flow velocity measurement sensitivity is lowered.

Therefore, smaller COSφ decreases Δt = t ₂₁ -t ₁₂ .

In this case, the length of the flow rate measuring rod entering the water, that is, L, is adjusted long so that the angle φ does not increase.

Directly measured variables are t ₁₂ , t ₂₁ , φ, and L.

The speed of sound C to be substituted in equation (1) is to be measured by the following equation.

Therefore, C ² = 4L ² / (T ₁₂ + T ₂₁ ) ² .

Depth h is supposed to be measured as

Using the sound velocity C obtained by Equation 3, which measures the time T ₃₄ and T ₄₃ at which the ultrasonic pulse propagates from the ultrasonic transducer 3 to (4) and (4) to (3), the following equation is used. .

Equations (1), (2) and (3) are well known, and the biggest feature of the prior art is as follows.

As shown in Fig. 1, when the flow velocity direction is 90 ° ± β rather than 90 ° with respect to the vertical rod (this is called a diagonal flow velocity component), measuring the flow velocity V _X of the perpendicular component with respect to the depth h line For the purpose of the following operation.

를 다음식으로 연산하게끔 되어 있다.A vertical rod (5) by a forward or tilting backward searching the point where the difference Δt of ₃₄ t ₃₄ and t ₄₃ are zero wherein the angle β measured dark vertical bars (5) inclined flow rate of the vertical component

Is supposed to be calculated as:

The basic disadvantages of this prior art are as follows.

＞ 0.5m/s 이상이 되면 유속 측정봉(6)이 진동을 하는데 유속이 빠를수록 진동이 더욱 심해진다.1) According to the experiment, the flow rate

> 0.5 m / s or more The flow rate measuring rod 6 vibrates. The faster the flow rate, the more severe the vibration.

As a result, the distance L between the ultrasonic transducers 1 and 2 also vibrates. Therefore, the propagation time of t ₁₂ and t ₂₁ is large and the average value should be obtained by continuous repeated measurement for a considerable time. The deviation of the propagation time difference Δt is much larger than the pulsation rate of the flow rate itself. The pulsation rate of the average flow rate from the water surface to the riverbed is almost 10 times smaller than the local flow rate pulsation rate, which can shorten the average flow rate measurement time considerably.

There are various reasons for the flow rate measuring rod 6 to vibrate.

1) Vortex (vortex) occurs behind the measuring rod 6, and the pressure caused by the water flow acts on the measuring rod 6, and this pressure acts uniformly on the entire length of the measuring rod 6 Very unbalanced (depending on flow rate distribution), and pressure causes pulsation; The measuring rod 6 may have elasticity.

2) When the flow rate is fast, it is difficult to insert the measuring rod (6) and to fix it in the required position. This is because the force of the water flow acting on the measuring rod 6 can be quite large.

를 정확히 측정하려면 초음파 펄스 전파시간은 물론 정밀하게 측정해야 하며 그 외에 변수인 L, φ와 β를 또 정밀하게 측정해야 한다.3) Depth h and flow rate, as can be seen in equations (4) and (5)

In order to accurately measure, it is necessary to measure not only the ultrasonic pulse propagation time, but also the variables L, φ, and β.

For example, if the angle φ is measured with an error of ± 1 °, the flow rate measurement error is increased by 1.7%. The more variables that need to be measured, the more complicated the measurement process and the greater the error in flow rate measurement.

4) Through experiments, it is almost impossible to measure angle β precisely, and it is more accurate to measure it with Equation (1) without measuring β angle rather than calculating the flow velocity with Equation (4) to measure β angle. Turned out.

Let's analyze it theoretically. If the flow velocity does not change at all (no pulsation) and forms an angle of 90 ° + β with respect to the vertical line, Δt ₃₄ is the difference between the mutual propagation times between the ultrasonic transducers (3) and (4). do.

(If β = 0, Δt ₃₄ will be 0.)

=0.5m/s, C=1500m/s 라고 가정하고, β가 1°식 변한다면 Δt₃₄는 다음과 같이 된다.In case, depth h = 0.5m,

Assuming that = 0.5m / s and C = 1500m / s, and β changes by 1 °, Δt ₃₄ becomes

As you can see here in that the β = 2 ° ₃₄ also becomes equal to Δt = 7.7ns. Even when this time difference is measured with an error of 5%, the measurement allowable error of Δt ₃₄ is 0.385 ns.

However, because Δt ₃₄ = t ₃₄ -t ₄₃ , the measurement tolerance between ultrasonic propagation times t ₃₄ and t ₄₃ shall not exceed Δt = 1/2 × 0.385 ns ≒ 0.2 ns. The time of 0.2 ns is the time for the ray to travel a distance of 6 mm.

It is unreasonable to carry a portable arithmetic control device including a high precision time interval measuring device.

Rather, it is impossible to find the position of the vertical rod at Δt ₃₄ = 0 because the velocity direction is not always constant and the direction pulsates even if a time interval measuring instrument that guarantees an error of ± 0.2 ns is used. . Therefore, the position where Δt ₃₄ = 0 can be roughly estimated over a very long time.

In this way, by measuring the β angle and substituting Eq. (4) to calculate the flow velocity, the flow velocity measurement error can be very large. It is impractical to measure β angles by seeing Δt ₃₄ = 0.

5) Velocity measurement It is often impossible to measure the flow velocity with given precision because there are many dimensional people.

The propeller local flowmeter, which is widely used at present, has a flow rate measurement range of V = 0.02 ~ 3m / s and a flow rate measurement error of δv = 1 ~ 1.5%.

의 측정오차를 신뢰도의 백분율 100%로 보면 다음과 같다.In the flow rate measurement formula (4)

The measurement error of is expressed as 100% of reliability as follows.

Here, δt-ultrasonic propagation time measurement relative error, δ _L -measurement error of the interval L between the ultrasonic transducers, δφ-angle φ measurement error, and δ _β are measurement errors of the angle β.

Let's measure the flow rate at about 1.5% without measuring the angle β. For this purpose, if all the errors are equally distributed (δ _t = δ _L = δ _φ ), for example, the angle measurement error δφ is as follows.

라고 쓸 수 있다.If the angle φ = 40 °, the absolute allowable error of angle measurement shall be Δφ = 0.0016 × 40 ° = 0.064 ° or less. (Equation (6) assumes all errors are accidental errors

Can be written.

However, in order to guarantee the reliability of the δ _V error calculation result as 99.9%, the coefficient γ ≒ 3 must be obtained, and the result is almost the same as in Eq. (6).

=1.5%이내로 보장하려면 초음파 전파시간 측정, 길이 L 등과 나머지 오차들의 합이 1.5-0.83 = 0.67%가 되어야 한다. 예를 들어, 초음파 전파시간 측정오차는 δ_t= 0.67/8 = 0.084% 이하가 되어야 한다.It is not possible to measure the angle φ between the flowmeter and the water surface by using an angle sensor or by measuring it with a ± 0.064 ° error. Even with an easy-to-measure angle sensor, the measurement error is ± 20 '= 0.333 °. Then, the relative error of φ = 40 ° is δ _φ = 0.83%. Therefore, the velocity measurement error

To ensure less than 1.5%, the sum of the ultrasonic propagation time measurement, the length L, and the remaining errors must be 1.5-0.83 = 0.67%. For example, the ultrasonic propagation time measurement error should be less than δ _t = 0.67 / 8 = 0.084%.

In this way, the tolerance of the other measuring device must be considerably smaller due to the measurement error of the angle φ, so that the device is complicated and is unlikely to be realized in a portable manner.

As described above, it is difficult to realize a portable flowmeter having a small flow rate measurement error and its practicality is poor.

The present invention aims to solve the above-mentioned shortcomings of the prior art and to improve the practicality and practicality while improving the degree of vertical average flow rate measurement.

1 is a front view showing the structure of a conventional ultrasonic stream velocity and depth measurement device,

2 and 3 are front and perspective views showing the structure of the ultrasonic vertical average flow rate measuring apparatus according to the present invention,

4 is a front view of the ultrasonic vertical average flow rate measuring apparatus according to another embodiment of the present invention.

<Description of the code | symbol about the principal part of drawing>

8, 9, 15, 16: ultrasonic transducer 10: vertical rod

11: actor 12: horizontal bar

13: level 17: knob

18: control operation device 19: scale

In order to achieve this purpose, there is no flow rate measuring rod inserted inclined from the severely vibrating water surface to the bottom of the water as in the prior art, and the depth of the distance L between the ultrasonic transducer for measuring the flow rate and the angle? It consists of a vertical average velocity measuring device that does not need to be measured in accordance with the change of.

The present invention is a flow rate measuring device used when the flow rate measuring bridge (leg) in the channel to measure the flow rate standing on the bridge, and the depth of the measurement in the absence of the flow rate measuring bridge in the channel directly It consists of a flow rate measuring device used to measure the flow rate when entering.

In the first case, the depth is to be measured by ultrasound. In the second case, the depth is measured by looking at the scale on the vertical bar.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The detailed description of the present invention is as follows.

2 and 3 are shown the configuration of the apparatus for measuring the average flow rate and depth according to the present invention by ultrasonic wave, and Figure 4 shows the basic configuration of the ultrasonic vertical average flow rate measuring device when measuring the depth with a scale have.

In FIGS. 2 and 3, 8 and 9 are ultrasonic transducers for measuring flow rates of wide angles, and the transducers are spherical or hemispherical in order to widen the angles, 10 is a vertical rod, and 11 is a vertical rod. (Cursor.runner) that moves up and down along the depth of water, and the transducer 11 is provided with an ultrasonic transducer 8 at regular intervals horizontally on the center line of the actor 11 and the ultrasonic wave. Reflecting plate 14 reflecting is fixed to a position spaced 90 degrees above the top somewhat at the point where the ultrasonic transducer 8 is fixed.

12 is a horizontal rod placed in the lower part in the number, one end is fixed to the bottom of the vertical rod 10 by 90 degrees with respect to the vertical rod 10, the other end of the horizontal rod 12, the ultrasonic transducer 9 is fixed. . However, the ultrasonic transducers 8 and 9 are arranged to face each other. In addition, at the lower end of the vertical rod 10, two narrowly directed ultrasound transducers 15 and 16 are disposed toward the reflecting plate 14, and the ultrasonic transducers 15 and 16 which are ultrasonic launch receivers are They are isolated from each other at regular intervals (l). 13 is the level and 17 is the handle.

Figure 4 is a structure (depth measurement scale is not shown in Figure 4) when the depth is measured by looking directly at the scale engraved on the vertical rod (10).

The difference from FIG. 2 is that there is no reflector plate 14, ultrasonic transducers 15 and 16, but the scale 19 is engraved at the sound velocity measurement position on the vertical rod 10.

18 is a control operation device of the ultrasonic vertical average flow rate measuring device, a pulse oscillator for operating ultrasonic transducers to emit ultrasonic pulses, an amplifier for amplifying a signal generated by receiving ultrasonic pulses, and launching and receiving ultrasonic transducers. It is a well-known control and operation device composed of a switch circuit for switching to a circuit, a time interval measuring device for controlling the switch circuit, and an ultrasonic propagation time, a device for calculating and storing the flow rate and the water depth, and a display. Since this is a common known art in the art, further description thereof is omitted.

The operation principle of the vertical average flow rate measuring apparatus of FIG. 2 is as follows.

In order to measure the flow rate in the channel, select the measuring points (positions) on the vertical line for vertical average flow velocity measurement along the width of the channel, and then place the vertical bar at the average flow velocity measurement point so that the horizontal bar 12 is perpendicular to the width line of the channel. (10) is put in a waterway. The vertical bar 10 is vertically erected using the level gauge 13. If it is known that the draft angle to the channel is large, the vertical bar 10 is inclined to stand vertically with respect to the lower surface.

Then, the actuator 11 is moved to make sure that the reflector 14 is in contact with the water surface, and then the actuator 11 is fixed (the fixing screw is not shown in FIG. 2). This locks the ultrasonic transducer 8 directly below the surface of the water.

The control switch 18 is then switched on and the ultrasonic transducers 15 and 16 are operated to emit ultrasonic pulses, which are reflected off the reflector plate 14 to reach the transducers 15 and 16. Receive At this time, the control operation device 18 measures the time t15 when the ultrasonic pulse propagated from the ultrasonic transducer 15 to (14), and again (15) and the time when the ultrasonic wave propagated through the (16)-(14)-(16) sections. The distance h 'between the ultrasonic transducer 15 and the reflector 14 is calculated according to the following equation.

Here, l is a value that has been precisely measured in advance and inputted into the control computing device.

As a result of this, the distance a between the ultrasonic transducer 15 and the lower bed is added to complete the measurement of the depth h and stored in the control computing device 18.

At the same time, the sound velocity C in the h 'range is calculated and stored according to the following equation.

Equations (7) and (9) are derived as follows.

therefore,

를 측정하여 디스플레이에 표시하는 동시 기억장치에 기억된다.When the measurement of the water depth h and the speed of sound C end, the ultrasonic transducer (8) and (9) to activate the 9 (8), and the time for the ultrasonic pulse is propagated from 8 to 9, t ₉₈ and t Measure ₈₉ and use the time difference flow measurement to determine the vertical average flow rate between the ultrasonic transducers (8) and (9).

Is stored in a simultaneous storage device that measures and displays it on the display.

Here, when d = LCOSφ, when the position of the actuator 11 changes with depth, L and φ change but d is an integer which does not change. Therefore, after fabricating and assembling the flow rate measuring device, d is measured and stored in the control computing device 18 once.

In this way, when measuring the vertical average flow rate locally, the variables measured by the direct flow rate measuring device are ultrasonic pulses between the ultrasonic transducers 8 and 9 and between the ultrasonic transducers 15 and 16 and the reflector plate 14. It is only time to spread.

The d and l values are values that have been measured and input in advance with high accuracy, and in particular, since there is no need to measure an angle φ that varies with depth, even if an ultrasonic propagation time measuring device is used as in the prior art, the flow velocity measurement error is Much smaller.

In particular, unlike the prior art, the ultrasonic wave propagation time is very stable and the flow rate measurement time is because the horizontal rod 12 without the flow rate measuring rod inserted into the inclined water and the ultrasonic transducer 9 is installed does not vibrate because it is placed on the lower side with the lowest flow rate. The flow rate measurement error is also shortened.

In the related art, by using two ultrasonic transducers arranged along a vertical line, when the vertical rods are vertically measured, the angle β formed by the flow direction thereof is measured and substituted into the flow rate measurement bar. Becomes large.

In the present invention, the β angle is not particularly measured. The reason is that the vertical average flow velocity can be measured with sufficient precision if the average value is calculated by measuring the flow velocity several times at regular intervals because the flow velocity is periodically changed from side to side. . However, only when the gradient to the channel is large, the vertical bar 10 may be perpendicular to the lower surface in consideration of the previously measured gradient angle, and the flow velocity may be measured. However, if the flow rate is 3 m / s or less, the draft angle in the channel does not need to be considered.

If the water depth is less than 0.6m, the direct measurer often enters the channel and calculates the flow rate by measuring the local velocity at several points along the width of the local flowmeter. In this case, there is no need to measure the depth with ultrasound, but it can be utilized as a "depth measuring shepherd" by marking the scale on the vertical bar (10).

In such a case, the reflector plate 14, the ultrasonic transducers 15 and 16 shown in FIG. 2 are deleted, and as shown in FIG. 3, the scale 19 is engraved at regular intervals, for example, 20 cm, on the vertical rods. .

The reference point 20 of the operator 11 is aligned with the scale 19, the gap L _{0 i} between the ultrasonic transducer 8 and the 9 is precisely measured in advance, and stored in the control operation device 18. Let the scales be called the sound velocity measurement position scales. Measure the depth of water h with a vertical rod 10 at the local channel and fix the activator 11 to the sound velocity measurement position scale closest to the depth h, and then the ultrasonic pulse propagation time t between the ultrasonic transducers 8 and 9 Measure ₈₉ watt ₉₈ and measure the sound velocity C ² (the quadratic value of the sound velocity to be substituted into the flow rate measurement formula (10)) by using the following formula and store it in the control operation unit 18. If input, the distance ha 'between the corresponding ultrasonic transducers 8 and 9 is called.)

To storing the C ² side value, and then set up a vertical bar (10) vertically with the supyeonggye 13 adjust the position of the actors 11, and the ultrasonic transducer (8) is locked just below the water surface, t ₉₈ and The ultrasonic pulse propagation time of t ₈₉ is measured, and the average flow velocity is calculated and stored according to equation (10). For example, if the closest scale for measuring the speed of sound when the depth is h = 35 cm is 40 cm, the actuator 11 is fixed at 40 cm and the vertical bar 10 is tilted slightly to the side so that the ultrasonic transducer 8 contacts water. And then measure the speed of sound.

When measuring the flow rate by measuring the flow rate on the flow rate measuring leg, if there is a result of measuring the depth at several points in advance, or if it is not necessary to measure the depth again, the average flow rate measuring device having the structure shown in FIG. Of course using.

가 제어연산장치(18)에 기억되어 있기 때문에, 유속 측정이 끝난 후에 기억 장치에서 디스플레이에 수직선 순서대로 수직 평균 유속과 수심을 표시하게 할 수도 있으며, 경우에 따라서는 자동 기록기를 제어연산장치(18)에 연결시켜 측정결과를 기록지에 기록시킬 수도 있다.Vertical mean flow velocity measured at several vertical lines like this

Is stored in the control computing device 18, it is also possible to cause the storage device to display the vertical average flow rate and depth in the vertical line order on the display after the flow rate measurement. The measurement results can also be recorded on the record sheet.

The flow rate may be calculated by substituting the distance g and the water depth hi between the measured average flow rates and the average flow velocity measurement vertical line in the flow measurement formula.

Thus, according to the present invention, the vertical average flow rate measurement process is simplified compared to the conventional technology (no need to measure angle φ, length h, etc.), and there is no vibration of the structure, so that the measurement time is shortened and the flow rate measurement error is also reduced. Low practicality and high practicality.

Claims (2)

Calculations for calculating the flow rate and depth, the ultrasonic wave receiver and ultrasonic propagation time device, which arranges the two ultrasonic transducers for measuring the flow rate in the vicinity of the water surface and the lower bed, and the two ultrasonic transducers for the vertical measurement in the vertical line. In an ultrasonic vertical average velocity measuring device for a channel consisting of a control computing device including devices, geometrical variables to be measured separately when measuring the flow rate while minimizing vibration caused by the flow rate of the support rods of the ultrasonic transducers inserted into the channel. In order to remove them and improve the flow rate measurement, the horizontal rod 12 of a certain length is fixed at a right angle to the bottom of the vertical rod 10, and the other end of the horizontal rod is a ultrasonic transducer for measuring the flow velocity having a wide orientation angle (9) Is arranged, and a wide angle of view is directed to the activator 11 moving up and down to match the depth along the vertical rod 10. The ultrasonic transducer 8 for speed measurement is disposed to face the ultrasonic transducer 15 disposed on the horizontal rod 12, and the ultrasonic reflector is fixed to the operator 11 at a predetermined angle apart from the ultrasonic transducer 8. At the bottom of the vertical rod 10, two ultrasonic transducers 15 and 16 with narrow directing angles toward the ultrasonic reflector 14 spaced at a predetermined angle with respect to the horizontal rod 12 are referred to their ultrasonic emission receiving surface. Vertically averaged flow rate due to isolation at regular intervals

Measured by the following time difference measurement,

Where d = const and the distance L between the ultrasonic transducers 8 and 9 projected on the horizontal rod (d = L; COSφ = const), and t _ab and t _ba are the ultrasonic transducers ( 8) to (9) and vice versa the time to propagate from (9) to (8), C is the speed of sound in the channel to the channel, depth h and sound velocity C are measured by the following equation,

Where t _c and t _e are the propagation times at which the ultrasonic pulses emitted by the ultrasonic transducers 15 and 16 are reflected by the ultrasonic reflector in contact with the water and return to (15) and (16), where 8 is the ultrasonic wave Ultrasonic vertical average flow rate measuring apparatus for waterways, characterized in that the interval between the launch, the receiving surface and the lower bed of the transducer (15). The ultrasonic reflector, and the ultrasonic transducers 15 and 16 are removed in order to simplify the ultrasonic vertical average flow rate measuring device when the reception does not need to be measured by ultrasonic waves. The sound speed measurement position scales 19 are written in the interval, and the control operation device measures the length Loi of the distance between the ultrasonic transducers 8 and 9 when the operator 11 is adjusted to the sound speed measurement position scale in advance. An ultrasonic vertical average flow rate measuring device for a channel according to claim 1, characterized in that the input is stored in memory and the flow rate is measured by the following measurement formula.

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