Distributed fire extinguishing water mist spraying control method and system based on ship fire fighting

Abstract

The invention relates to the technical field of ship fire fighting, in particular to a distributed fire extinguishing water mist spraying control method and system based on ship fire fighting, and the method comprises the following steps: S1, a fire detector monitors the environment, and immediately sends a fire signal to a control system once detecting a fire; s2, the control system receives a signal of the fire detector and identifies the position and severity of the fire; according to the invention, by introducing a calculation method of a dynamic pressure threshold, combining a temperature compensation coefficient and a nonlinear adjustment parameter, the method can adapt to the change of the environment temperature and the system state in real time, ensures that the pressure water tank is always kept within a reasonable range, and predicts the change trend of the pressure along with time by using historical pressure data and a linear regression model. And a nitrogen injection plan is adjusted in advance, so that the pressure is effectively prevented from being reduced to an unacceptable level when a fire occurs, the water mist spray head can quickly cover a fire area, quick fire extinguishment is realized, and fire loss is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ship fire fighting, and particularly to a distributed fire extinguishing water mist spraying control method and system based on ship fire fighting. Background Art

[0002] In a ship fire fighting system, a distributed fire extinguishing water mist spraying system is widely used due to its high fire extinguishing ability and the characteristic of being friendly to electronic devices. However, to ensure that the system can quickly provide sufficient fire extinguishing pressure when a fire occurs, a pressure water tank is usually configured in the system, and an additional pressure support is provided by a nitrogen cylinder group.

[0003] When the pressure water tank arranged inside the distributed fire extinguishing water mist spraying system for ship fire fighting is in a long-term static state, the pressure inside the pressure water tank is likely to drop due to temperature change or leakage, which may cause the inability to immediately provide the required pressure when a fire occurs, delaying the fire extinguishing opportunity. Therefore, a distributed fire extinguishing water mist spraying control method and system based on ship fire fighting are proposed for the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a distributed fire extinguishing water mist spraying control method and system based on ship fire fighting, so as to solve the problem that when the pressure water tank arranged inside the distributed fire extinguishing water mist spraying system for ship fire fighting is in a long-term static state, the pressure inside the pressure water tank is likely to drop due to temperature change or leakage, which may cause the inability to immediately provide the required pressure when a fire occurs, delaying the fire extinguishing opportunity.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A distributed fire extinguishing water mist spraying control method and system based on ship fire fighting, including the following steps: S1:

[0007] A fire detector monitors the environment, and once a fire is detected, it immediately sends a fire signal to the control system.

[0008] S2: The control system receives the signal from the fire detector and identifies the location and severity of the fire.

[0009] S3: The control system starts a spray pump unit according to the fire signal and supplies a water-based fire extinguishing agent to the system pipeline.

[0010] S4: The spray pump unit provides the required working pressure for the system pipeline and effectively transports the water-based fire extinguishing agent to each area.

[0011] S5: A pressure maintaining pump monitors the pressure of the main pipeline of the system and automatically starts to maintain a constant working pressure when the pressure drops.

[0012] S6: The pressure water tank is replenished with water by the pressure maintaining pump to maintain sufficient water volume for fire extinguishing. Meanwhile, when the system pressure drops, the nitrogen cylinder group releases nitrogen to provide additional pressure support for the pressure water tank;

[0013] S7: The main pipeline of the system and the distributed system pipelines transport the water-based fire extinguishing agent from the spray pump unit to each water mist spray head;

[0014] S8: The water mist spray head converts the water-based fire extinguishing agent into fine water mist, covering the fire area, reducing the temperature, isolating oxygen, and achieving fire extinguishing;

[0015] S9: The control system continuously monitors the fire situation and the system status, and adjusts the working status of the spray pump unit, the pressure maintaining pump, and the water mist spray head as needed;

[0016] S10: After the fire is extinguished, the control system will shut down the spray pump unit and the water mist spray head, stop the water supply, and reset the system to prepare for the next possible fire response.

[0017] As a further optimized content of the present invention, wherein: S61: The nitrogen cylinder group obtains the pressure P current and temperature T current inside the pressure water tank through the pressure sensor and temperature installed inside the pressure water tank;

[0018] S62: Calculate the dynamic pressure threshold P threshold based on the obtained real-time data. The calculation formula of the dynamic pressure threshold P threshold is as follows:

[0019]

[0020] In the formula, P initial is the initially set ideal pressure, is the pressure-temperature change rate at the reference temperature, β is the temperature compensation coefficient, T0 is the reference temperature, and n is the non-linear coefficient of temperature change;

[0021] S63: When the detected current pressure P current is lower than the dynamic pressure threshold P threshold , start the nitrogen injection device to compensate for the pressure fluctuation. The calculation formula of the nitrogen injection volume V inject is as follows:

[0022]

[0023] In the formula, V total is the total volume of the water tank, γ is the injection volume adjustment coefficient, and δ and λ are the non-linear compensation coefficients of the pressure difference;

[0024] S64: Based on historical pressure data, use linear regression to predict the trend of pressure change over time, and adjust the nitrogen injection in advance to prevent the pressure from dropping below the threshold in the future. The predicted pressure formula is:

[0025] P predicted (t) = a·t + b

[0026] In the formula, t is the time series, a is the pressure drop rate coefficient, and b is the initial pressure point;

[0027] S65: Based on the predicted pressure change, the system dynamically adjusts the injection time interval Δt and the injection volume V inject , ensuring that the water tank pressure always remains within the preset range to ensure that the system can provide the required pressure at any time.

[0028] As a further optimization content of the present invention, wherein: in S64, the system dynamically adjusts the injection time interval and the injection volume according to the drop rate a output by the regression model to avoid the pressure dropping rapidly below the threshold within a short time.

[0029] As a further optimization content of the present invention, wherein: when the system is in a static state, by regularly monitoring and compensating for the pressure fluctuation of the pressure water tank, and combining the temperature change and the leakage rate, the start frequency and the injection volume of the nitrogen injection device are optimized to reduce the nitrogen consumption.

[0030] As a further optimization content of the present invention, wherein: based on the pressure change trend at different ambient temperatures in the historical data, the control system uses a multiple regression model to generate a pressure prediction formula, and dynamically optimizes the temperature compensation coefficient β and the nonlinear adjustment parameter n to adapt to the actual pressure change requirements under different ship operating environments.

[0031] As a further optimization content of the present invention, wherein: the injection process of the nitrogen cylinder group adopts a staged control strategy;

[0032] When (P threshold -P current ) > ΔP critical , start the high-intensity nitrogen injection mode;

[0033] When (P threshold -P current ) ≤ ΔP critical , switch to the low-intensity maintenance mode.

[0034] As a further optimization content of the present invention, wherein: during the pressure fluctuation monitoring of the pressure water tank, combined with the pressure leakage rate ΔP in the system leak , predict the lowest pressure at the future t leak moment through the following formula:

[0035] P future (t leak ) = P current -ΔP leak ·t leak

[0036] If the predicted pressure is lower than the dynamic pressure threshold, the nitrogen injection device is triggered in advance for pressure compensation.

[0037] As a further optimized content of the present invention, it includes: a spray pump group for supplying water-based fire extinguishing agent to the system pipeline;

[0038] A pressure maintaining pump for maintaining the constant working pressure of the system pipeline;

[0039] A pressure water tank for providing fire extinguishing water in case of power failure, and the pressure water tank is replenished by the pressure maintaining pump;

[0040] A nitrogen cylinder group for maintaining the system pressure, and the nitrogen cylinder group releases nitrogen into the pressure water tank when the system pressure drops;

[0041] A system main pipeline and a distributed system pipeline for connecting each component and responsible for transporting the water-based fire extinguishing agent;

[0042] A water mist spray head for converting the water-based fire extinguishing agent into fine water mist to achieve fire extinguishing;

[0043] A fire detector for detecting fire and sending signals to the control system;

[0044] A control system for receiving the signals from the fire detector and controlling the opening of the spray pump group unit, the pressure maintaining pump and the water mist spray head.

[0045] As a further optimized content of the present invention, wherein: the control system adjusts the pressure threshold inside the pressure water tank according to the ambient temperature by introducing a temperature compensation algorithm, and the dynamic pressure threshold P threshold The calculation formula is:

[0046]

[0047] In the formula, P initial Is the initially set ideal pressure, Is the pressure-temperature change rate at the reference temperature, β is the temperature compensation coefficient, T0 is the reference temperature, and n is the non-linear coefficient of temperature change.

[0048] As a further optimized content of the present invention, wherein: the control system further includes an injection volume coefficient, and the nitrogen injection volume is dynamically calculated to accurately control the pressure compensation amount, and the nitrogen injection volume V inject The calculation formula is:

[0049]

[0050] Wherein, V total is the total volume of the water tank, γ is the injection volume adjustment coefficient, and δ and λ are the non - linear compensation coefficients of the pressure difference.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0052] 1. In the present invention, by introducing a calculation method for dynamic pressure thresholds, combining the temperature compensation coefficient and non - linear adjustment parameters, it can adapt to changes in ambient temperature and system status in real - time, ensure that the pressure water tank always remains within a reasonable range, and ensure the pressure compensation effect while reducing nitrogen consumption by dynamically calculating the nitrogen injection volume and stage - wise adjusting the injection mode, improving the economic efficiency of system operation. Moreover, it uses historical pressure data and a linear regression model to predict the change trend of pressure over time and adjusts the nitrogen injection plan in advance, effectively preventing the pressure from dropping to an unacceptable level during a fire, so that the water mist sprinkler heads can quickly cover the fire area, achieve rapid fire extinguishing, and reduce fire losses;

[0053] 2. In the present invention, based on multiple regression to generate a pressure prediction formula, dynamically optimizing the temperature compensation coefficient and non - linear adjustment parameters, enables the system to adapt to complex ship operating environments and ensures the reliability and stability of long - term operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is the system block diagram of the distributed fire - extinguishing water mist sprinkler system based on ship fire protection of the present invention;

[0055] Figure 2 is the flow chart of the distributed fire - extinguishing water mist sprinkler control method and system based on ship fire protection of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0056] Please refer to Figure 1-2 , the present invention provides a technical solution:

[0057] A distributed fire - extinguishing water mist sprinkler control method and system based on ship fire protection, including the following steps: S1: The fire detector monitors the environment, and once a fire is detected, immediately sends a fire signal to the control system;

[0058] S2: The control system receives the signal from the fire detector and identifies the location and severity of the fire;

[0059] S3: The control system starts the sprinkler pump unit according to the fire signal and supplies the water - based fire - extinguishing medium to the system pipeline;

[0060] S4: The spray pump unit provides the required working pressure for the system pipeline and effectively transports the water-based fire extinguishing agent to each area.

[0061] S5: The pressure maintaining pump monitors the pressure of the main pipeline of the system and automatically starts to maintain a constant working pressure when the pressure drops.

[0062] S6: The pressure water tank is replenished with water by the pressure maintaining pump to maintain sufficient water volume for fire extinguishing. At the same time, the nitrogen cylinder group releases nitrogen when the system pressure drops to provide additional pressure support for the pressure water tank.

[0063] S7: The main pipeline of the system and the distributed system pipeline transport the water-based fire extinguishing agent from the spray pump unit to each water mist spray head.

[0064] S8: The water mist spray head converts the water-based fire extinguishing agent into fine water mist, covering the fire area, reducing the temperature, isolating oxygen, and achieving fire extinguishing.

[0065] S9: The control system continuously monitors the fire situation and the system status, and adjusts the working status of the spray pump unit, the pressure maintaining pump, and the water mist spray head as needed.

[0066] S10: After the fire is extinguished, the control system will turn off the spray pump unit and the water mist spray head, stop the water supply, and reset the system to prepare for the next possible fire response.

[0067] As a further implementation technical solution of this scheme, S61: The nitrogen cylinder group obtains the pressure P inside the pressure water tank through the pressure sensor and temperature installed inside the pressure water tank. current and temperature T current ;

[0068] S62: Calculate the dynamic pressure threshold P according to the acquired real-time data. threshold The dynamic pressure threshold P threshold The calculation formula is:

[0069]

[0070] In the formula, P initial is the initially set ideal pressure, is the pressure-temperature change rate at the reference temperature, β is the temperature compensation coefficient, T0 is the reference temperature, and n is the non-linear coefficient of temperature change;

[0071] S63: When the detected current pressure P current is lower than the dynamic pressure threshold P threshold , start the nitrogen injection device to compensate for the pressure fluctuation. The nitrogen injection volume V inject The calculation formula is:

[0072]

[0073] In the formula, V total is the total volume of the water tank, γ is the injection volume adjustment coefficient, and δ and λ are the non-linear compensation coefficients of the pressure difference;

[0074] S64: According to the historical pressure data, use linear regression to predict the change trend of pressure over time, and adjust the nitrogen injection in advance to prevent the pressure from dropping below the threshold in the future. The predicted pressure formula is:

[0075] P predicted (t) = a·t + b

[0076] In the formula, t is the time series, a is the pressure drop rate coefficient, and b is the initial pressure point;

[0077] S65: Based on the predicted pressure change, the system dynamically adjusts the injection time interval Δt and the injection volume V inject , ensuring that the water tank pressure always remains within the preset range to ensure that the system can provide the required pressure at any time, and the nitrogen injection volume can be adjusted and predicted;

[0078] As a further technical solution of this scheme, in S64, the system dynamically adjusts the injection time interval and the injection volume according to the pressure drop rate a output by the regression model, which is used to prevent the pressure from rapidly dropping below the threshold within a short time, and can effectively extend the continuous working time of the nitrogen system and improve the system stability;

[0079] As a further technical solution of this scheme, the system optimizes the start frequency and injection volume of the nitrogen injection device by regularly monitoring and compensating the pressure fluctuation of the pressure water tank in the static state, combining the temperature change and the leakage rate, which is used to reduce the nitrogen consumption and can effectively save resources and extend the service life of the nitrogen cylinder group;

[0080] As a further technical solution of this scheme, the control system generates a pressure prediction formula by using a multiple regression model based on the pressure change trend at different ambient temperatures in the historical data, and dynamically optimizes the temperature compensation coefficient β and the non-linear adjustment parameter n, which is used to adapt to the actual pressure change requirements under different ship operating environments, thereby improving the adaptability and reliability of the system in different environments;

[0081] As a further technical solution of this scheme, the injection process of the nitrogen cylinder group adopts a phased control strategy;

[0082] When (P threshold - P current ) > ΔP critical , start the high-intensity nitrogen injection mode;

[0083] When (Pthreshold -P current ) ≤ ΔP critical , switch to the low-intensity maintenance mode, which can reduce energy consumption while meeting the system requirements and achieve high efficiency in energy conservation;

[0084] As a further technical solution of this scheme, during the pressure fluctuation monitoring of the pressure water tank, combined with the pressure leakage rate ΔP within the system leak , predict the lowest pressure at the future time t leak through the following formula:

[0085] P future (t leak ) = P current - ΔP leak ·t leak

[0086] If the predicted pressure is lower than the dynamic pressure threshold, trigger the nitrogen injection device in advance for pressure compensation, so as to ensure that the system is in an effective pressure state at any time, which helps to quickly respond in case of a fire;

[0087] As a further technical solution of this scheme, it includes: a spray pump group for supplying water-based fire extinguishing agent to the system pipeline;

[0088] A pressure maintaining pump for maintaining the constant working pressure of the system pipeline;

[0089] A pressure water tank for providing fire extinguishing water in case of a power failure, and the pressure water tank is replenished with water by the pressure maintaining pump;

[0090] A nitrogen cylinder group for maintaining the system pressure, and the nitrogen cylinder group releases nitrogen into the pressure water tank when the system pressure drops;

[0091] A system main pipeline and a distributed system pipeline for connecting each component and responsible for transporting the water-based fire extinguishing agent;

[0092] A water mist spray head for converting the water-based fire extinguishing agent into fine water mist to achieve fire extinguishing;

[0093] A fire detector for detecting a fire and sending a signal to the control system;

[0094] A control system for receiving the signal from the fire detector and controlling the opening of the spray pump group unit, the pressure maintaining pump and the water mist spray head. Through the mutual cooperation of the above components, the overall performance of the fire extinguishing system and the fire emergency response speed are effectively improved;

[0095] As a further technical solution of this scheme, the control system adjusts the pressure threshold inside the pressure water tank according to the ambient temperature by introducing a temperature compensation algorithm, and the dynamic pressure threshold P thresholdThe calculation formula is as follows:

[0096]

[0097] In the formula, P initial is the initially set ideal pressure, is the pressure-temperature change rate at the reference temperature, β is the temperature compensation coefficient, T0 is the reference temperature, n is the non-linear coefficient of temperature change. By automatically adjusting the threshold, it can accurately respond to the pressure fluctuations caused by temperature changes and ensure a stable pressure output of the fire extinguishing system in an environment with temperature fluctuations;

[0098] As a further technical solution for the implementation of this solution, the control system further includes an injection volume coefficient. By dynamically calculating the nitrogen injection volume, it can accurately control the pressure compensation amount. The nitrogen injection volume V inject The calculation formula is as follows:

[0099]

[0100] In the formula, V total is the total volume of the water tank, γ is the injection volume adjustment coefficient, δ and λ are the non-linear compensation coefficients of the pressure difference. By accurately controlling the nitrogen injection volume, it can effectively reduce nitrogen waste and ensure that the pressure water tank is maintained within the preset ideal pressure range.

[0101] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention. The above is only the preferred implementation mode of the present invention. It should be noted that due to the limited nature of written expression and objectively existing infinite specific structures, for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements, retouches or changes can be made, or the above technical features can be combined in an appropriate manner; these improvements, retouches, changes or combinations, or directly applying the concept and technical solution of the invention to other occasions without improvement, should all be regarded as the protection scope of the present invention.

Claims

1. A distributed fire extinguishing water mist spray control method based on ship fire protection, characterized in that: The following steps are involved: S1: Fire detectors monitor the environment and immediately send a fire signal to the control system once a fire is detected; S2: The control system receives signals from fire detectors and identifies the location and severity of the fire; S3: The control system starts the sprinkler pump unit according to the fire signal and supplies water-based fire extinguishing medium to the system pipeline; S4: The sprinkler pump unit provides the required working pressure for the system pipeline and effectively delivers the water-based fire extinguishing medium to various areas; S5: The pressure-maintaining pump monitors the system main line pressure and automatically starts when the pressure drops to maintain a constant working pressure; S6: The pressure water tank is replenished with water through the pressure-maintaining pump to maintain sufficient water for firefighting. At the same time, the nitrogen cylinder group releases nitrogen when the system pressure drops to provide additional pressure support for the pressure water tank; S7: The system main pipeline and the distributed system pipeline transport the water-based fire extinguishing medium from the sprinkler pump unit to each water mist sprinkler head; S8: The water mist sprinkler head converts the water-based fire extinguishing medium into fine water mist, which covers the fire area, reduces the temperature, isolates oxygen, and extinguishes the fire; S9: The control system continuously monitors the fire situation and system status, and adjusts the working status of the sprinkler pump unit, pressure-maintaining pump and water mist sprinkler head as needed; S10: After the fire is extinguished, the control system will shut down the sprinkler pump unit and the water mist sprinkler head, stop the water supply, and reset the system to prepare for the next possible fire response.

2. The distributed fire extinguishing water mist spray control method based on ship fire protection according to claim 1 is characterized in that: S61: The nitrogen cylinder group obtains the pressure P inside the pressure water tank through the pressure sensor and temperature installed inside the pressure water tank. current and temperature T current ; S62: Calculate the dynamic pressure threshold P according to the acquired real-time data threshold , the dynamic pressure threshold P threshold The calculation formula is: Where P initial is the ideal pressure for initial setting, is the pressure temperature change rate at the reference temperature, β is the temperature compensation coefficient, T0 is the reference temperature, and n is the nonlinear coefficient of temperature change; S63: When the current pressure P is detected current Below the dynamic pressure threshold P threshold When the nitrogen injection device is started to compensate for the pressure fluctuation, the nitrogen injection volume V inject The calculation formula is: Where V total is the total volume of the water tank, γ is the injection volume adjustment coefficient, δ and λ are the nonlinear compensation coefficients of the pressure difference; S64: Based on historical pressure data, linear regression is used to predict the pressure change trend over time, and nitrogen injection is adjusted in advance to prevent the pressure from dropping below the threshold in the future. The predicted pressure formula is: P predicted (t)=a·t+b In the formula, t is the time series, a is the pressure drop rate coefficient, and b is the initial pressure point; S65: Based on the predicted pressure change, the system dynamically adjusts the injection time interval Δt and the injection volume V inject , ensure that the water tank pressure is always maintained within the preset range to ensure that the system can provide the required pressure at any time.

3. The distributed fire extinguishing water mist spray control method based on ship fire protection according to claim 1 is characterized in that: In S64, the system dynamically adjusts the injection time interval and injection amount according to the drop rate a output by the regression model to prevent the pressure from dropping below the threshold value rapidly in a short time.

4. The distributed fire extinguishing water mist spray control method based on ship fire protection according to claim 1 is characterized in that: When the system is stationary, it regularly monitors and compensates for pressure fluctuations in the pressure water tank, and optimizes the startup frequency and injection volume of the nitrogen injection device based on temperature changes and leakage rates to reduce nitrogen consumption.

5. The distributed fire extinguishing water mist spray control method based on ship fire protection according to claim 1 is characterized in that: The control system generates a pressure prediction formula based on the pressure change trend under different ambient temperatures in historical data using a multivariate regression model, and dynamically optimizes the temperature compensation coefficient β and the nonlinear adjustment parameter n to adapt to the actual pressure change requirements under different ship operating environments.

6. The distributed fire extinguishing water mist spray control method based on ship fire protection according to claim 1 is characterized in that: The injection process of the nitrogen cylinder group adopts a staged control strategy; At that time (P threshold -P current )>ΔP critical , start the high-intensity nitrogen injection mode; At that time (P threshold -P current )≤ΔP critical , switch to low-intensity maintenance mode.

7. The distributed fire extinguishing water mist spray control method based on ship fire fighting according to claim 1 is characterized in that: During the pressure fluctuation monitoring process of the pressure water tank, combined with the pressure leakage rate ΔP in the system leak , predict the future t by the following formula leak Minimum pressure at all times: P future (t leak )=P current -ΔP leak ·t leak If the predicted pressure is lower than the dynamic pressure threshold, the nitrogen injection device is triggered in advance to perform pressure compensation.

8. A system for a distributed fire extinguishing water mist spray control method based on ship fire fighting according to any one of claims 1 to 9, characterized in that: include: Sprinkler pump set used to supply water-based fire extinguishing medium to the system pipeline; A pressure-maintaining pump used to maintain a constant working pressure in the system pipeline; A pressure water tank for providing water for fire fighting in case of power failure, wherein the pressure water tank is replenished with water through a pressure-maintaining pump; A nitrogen cylinder group for maintaining system pressure, wherein the nitrogen cylinder group releases nitrogen into the pressure water tank when the system pressure drops; Used to connect various components and responsible for conveying water-based fire extinguishing fluid system main pipeline and distributed system pipeline; Water mist sprinkler head used to convert water-based fire extinguishing medium into fine water mist to achieve fire extinguishing; Fire detectors to detect fire and send signals to the control system; A control system used to receive signals from fire detectors and control the opening of the sprinkler pump unit, pressure-maintaining pump and water mist sprinkler head.

9. The system of the distributed fire extinguishing water mist spray control method based on ship fire fighting according to claim 8 is characterized in that: The control system introduces a temperature compensation algorithm to adjust the pressure threshold inside the pressure water tank according to the ambient temperature. The dynamic pressure threshold P threshold The calculation formula is: Where P initial is the ideal pressure for initial setting, is the pressure temperature change rate at the reference temperature, β is the temperature compensation coefficient, T0 is the reference temperature, and n is the nonlinear coefficient of temperature change.

10. The system of the distributed fire extinguishing water mist spray control method based on ship fire fighting according to claim 8 is characterized in that: The control system further includes an injection amount coefficient, which accurately controls the pressure compensation amount by dynamically calculating the nitrogen injection amount, wherein the nitrogen injection amount V inject The calculation formula is: Where V total is the total volume of the water tank, γ is the injection volume adjustment coefficient, δ and λ are the nonlinear compensation coefficients of the pressure difference.

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