176 results about "Water entry" patented technology

The invention relates to a drainage device for hydraulic engineering construction, which comprises a vehicle body, a storage part connected to the vehicle body and a water inlet port connected to the storage part, the vehicle body is connected with a water suction pump, the water suction pump is connected with the water inlet port, and the water inlet port is used for pumping water; the storage part comprises a sliding part and an unfolding part connected to the sliding part, the water inlet port is connected to the unfolding part, and the unfolding part is used for lowering the water inlet port into water or moving the water inlet port to the recovery position so that the water inlet port can be stored on the vehicle body. The technical scheme has the beneficial technical effects that through the linkage design of the sliding part and the unfolding part, the water inlet port can be rapidly lowered and recycled underwater. Drainage operation can be completed only by operating the vehicle body, and construction efficiency is remarkably improved. The telescopic or folding structure of the unfolding piece can adjust the water entry depth of the water inlet port to adapt to different water level conditions, and the problem of drainage interruption caused by water level fluctuation is avoided.

Disclosed is a valve apparatus having a first pressure compensation valve, a first, gas-tight, cap-like membrane device, and a gas-permeable, moisture-permeable, and yet water-impermeable second membrane device. The first pressure compensation valve, in particular a back-pressure valve, having a first valve housing, which limits a pressure compensation opening and comprising a housing side and a covering side, comprising or consisting of a first, gas-tight, cap-like membrane device covering a first pressure compensation opening and releasing the first pressure compensation opening from a predetermined negative pressure prevailing on the housing side in order to enable a pressure compensation between a housing device and an environment, and a gas-permeable, moisture-permeable, and yet water-impermeable second membrane device arranged on the covering side and in series to the first membrane device, covering a second pressure compensation opening and preventing water entry into the valve housing and thus into a housing device.

The invention belongs to the technical field of hydraulic engineering monitoring, and discloses a hydraulic engineering inspection system and method, and the method comprises the steps: a positioning monitoring deployment module reasonably distributes the number and positions of positioning monitoring assemblies; the route planning module plans an optimal unmanned aerial vehicle flight route; planning an advancing route, a water entry position and a water surface leaving position of the underwater robot; the cruise monitoring module carries out all-directional inspection on a water conservancy area; the image analysis module identifies abnormal conditions; the infrared data analysis module recognizes abnormal conditions in time; the radar data analysis module identifies abnormal conditions; the comprehensive analysis module comprehensively evaluates the water conservancy condition; the risk prediction module predicts potential problems and risks. According to the invention, the positioning monitoring assembly and the cruise monitoring module are combined to realize omnibearing monitoring of a water conservancy area; omnidirectional three-dimensional inspection is realized, multi-modal data collaborative analysis is realized, abnormal conditions are identified, potential problems and risks are predicted, and possible faults or disaster hidden dangers of water conservancy facilities can be found in advance.

The river channel desilting device comprises a ship body, the ship body is hinged to a suction dredger capable of adjusting the water entry angle, a controller is further arranged in the ship body, the ship body is fixedly connected with a filter box, a filter screen is arranged on the side face of the filter box, a water tank for receiving filtered water is arranged below the filter box, and the water tank is connected with the controller. Pressure-bearing rods are symmetrically fixed to the side faces of the water tank, the ship body is fixedly connected with a supporting plate, the pressure-bearing rods are slidably connected with the supporting plate, the pressure-bearing rods are provided with switch assemblies matched with the supporting plate, the supporting plate is rotationally connected with a rotating wheel, and the rotating wheel is provided with a magnet; the magnet can be matched with the switch assembly to enable the water tank to move downwards, the ship body is provided with a speed adjusting part, the speed adjusting part can adjust the moving speed of the ship body according to the downward moving distance of the water tank, the device can be adjusted in time according to the actual condition that the suction dredger cleans riverbed sludge, and the use safety of the device is improved.

The application discloses a solid droplet-based drag reduction ball preparation and testing method, and relates to the underwater drag reduction technical field.The preparation method comprises the following steps: performing decontamination treatment on the surface of a steel ball, configuring a PDMS solution and pouring the PDMS solution into a polytetrafluoroethylene mold with small holes with different curvature radii, performing vacuum degassing and solidification, and then peeling off to obtain solid droplet structures with different curvature radii, and bonding the solid droplet structures to the bottom of the steel ball.Through the regulation and control of the solid droplet curvature radius (2.5-10.8 mm) and the water entry speed, the high-speed camera technology is used to observe the change law of the sputtering crown formation, air entrainment and air cavity closure mode in the water entry process, the quantitative analysis of the underwater air cavity volume and the drag coefficient is combined, and the influence of the solid droplet curvature radius on the air cavity shape and the drag reduction performance is verified.The solid droplet structure optimizes the air film capture efficiency, significantly reduces the blunt body pressure difference resistance and the friction resistance, and the preparation process is simple, stable and suitable for the development of the underwater vehicle drag reduction technology.

The invention belongs to the technical field of lifeboats, discloses a free-falling lifeboat model test method, and effectively solves the problem that the result is inaccurate when a wooden model is used for testing. Comprising the following steps: manufacturing a lifeboat model by glass fiber reinforced plastic according to a selected scale ratio; performing static calibration and dynamic calibration on the lifeboat model; carrying out a free falling test on the lifeboat model, measuring the impact acceleration of the lifeboat model falling into water, and measuring the water entering distance and the forward rushing distance of the lifeboat model; the method comprises the following steps: firstly, determining the angle of a landing slide way, preliminarily selecting an approved landing height and the length of the landing slide way, then respectively combining the weight distribution state and the initial landing state of a lifeboat model, then carrying out a free landing test, and finally determining the landing approved height, the landing slide way angle and the landing slide way length of the lifeboat. The acceleration test result is closer to the real boat test, and the accuracy is higher.

The application discloses a control method of amphibious track operation equipment, and relates to the technical field of underwater operation equipment.The method comprises the following steps: according to pressure information of four walking wheel groups and an amphibious track, adjusting attitude information of suspension hydraulic cylinders of the four walking wheel groups, so that walking main wheels of the four walking wheel groups are uniformly engaged with the amphibious track; determining an auxiliary connection mode of the amphibious track operation equipment according to a water entry condition of the amphibious track operation equipment, and controlling the amphibious track operation equipment to run based on the auxiliary connection mode and contact the amphibious track.The application can maintain a stable running state of the amphibious track operation equipment at all times by adjusting the attitude information of the suspension hydraulic cylinders of the four walking wheel groups, and different auxiliary connection modes are set for different water entry conditions, so that the amphibious track operation equipment can stably contact the amphibious track in any water entry state, and the application scene and stability of the amphibious track operation equipment are improved.

The invention belongs to the technical field of physical training equipment, and particularly relates to a portable diving spray suppression training device.The portable diving spray suppression training device comprises a bottom plate, the upper surface of the bottom plate is fixedly connected with a mounting box, and an action posture analysis module and a spray simulation and parameter comparison module are arranged and can be combined with a pressure sensor on an elastic springboard and a high-definition camera on the bottom face; and the inertial measurement unit on the vertical rod is used for collecting key data such as pressure distribution, air attitude angle and water entry moment track when the athlete jumps in real time and comparing the key data with standard water spray suppression parameters, the data are displayed in real time through the LED control screen, and the athlete can intuitively know the problems such as self action deviation and air body attitude imbalance. Through matching of the hydraulic cylinder at the bottom of the bottom plate, the universal wheels and the push rod on the right side, the device can be easily moved to a venue, an outdoor temporary training point and even a pre-racing adaptive site, the stability during training can be ensured through brake devices of the universal wheels and balancing weights on the bottom plate, and the displacement risk is avoided.

The invention discloses a sinking control method and a related device, and the method is applied to an underwater robot, and comprises the steps: obtaining the body posture information of the underwater robot, and determining the relative position relation between a water inlet of the underwater robot and the water surface; motor control parameters matched with the relative position relation and the fuselage attitude information are determined, and a motor is controlled to operate according to the determined motor control parameters, so that water flow is driven by the motor to enter the underwater robot shell; and if it is detected that the underwater robot meets a preset sinking completion condition, determining that the underwater robot completes sinking. The control parameters of motor operation are adaptively adjusted based on the posture information of the machine body and the position relation of the water inlet relative to the water surface, so that water flow can effectively enter the shell of the robot in different posture states, the water filling process in the shell is accelerated, and the overall weight of the robot is increased; rapid and stable sinking of the underwater robot is achieved, and the underwater entering efficiency and the use stability of the underwater robot are improved.

The application provides a kayak athlete power output coordination control method, comprising: collecting the paddle water entry depth, the angle of attack deflection angle, the athlete power time and the hull acceleration, obtaining the complete record containing the paddle track arc and the hull acceleration change; according to the change of the straight line track and the arc track when the hull accelerates, the angle of attack deflection angle is extracted, the deviation degree of the angle of attack deflection angle and the effective propulsion angle range is evaluated, and the proportion of energy loss caused by the lateral component force under different deviation degrees is identified; according to the power output timing coordination score, the smoothness of the power transmission among the athlete, the paddle and the hull is analyzed, and the stability of the transmission efficiency in the acceleration stage is identified after removing the interference signal; according to the track optimization direction adjustment training system collection setting, the track optimization direction is returned to the collection density adjustment link, and the time interval setting of the next data collection is determined.

The utility model relates to the technical field of lotus root pool water quality monitoring, and particularly discloses a lotus root pool water quality monitoring buoy frame which comprises a flat plate, a data transmitter and a water quality detection sensor, floating bodies are installed at the four corners of the lower end face of the flat plate, and two installation frames are fixedly connected to the upper end of the flat plate. Two rope penetrating holes are formed in the upper end face of the flat plate in a penetrating mode, winding shafts are rotationally connected to the interiors of the two mounting frames correspondingly, and nylon ropes penetrating through the two rope penetrating holes correspondingly are fixedly connected to the outer walls of the two winding shafts correspondingly; the water entering length of the water quality detection sensor can be adjusted by rotating the winding shaft to wind and unwind the nylon rope, and the position is fixed by utilizing the self-locking characteristic, so that the water entering length of the nylon rope can be adjusted as required to effectively adapt to lotus root pools with different water depths, and the water entering depth of the water quality detection sensor can be changed by manually sliding the adjusting cylinder and locking the position. Height adjustment of the water quality detection sensor is achieved, flexible detection can be conducted on water layers of different depths, and the use flexibility of the device is remarkably improved.

The application discloses a water seal test device and a sealing test method for a cabin door sealing element. The water seal test device comprises a sealing box body, the sealing box body is provided with a mounting position for mounting the cabin door sealing element; a pressure applying element is movably mounted on the sealing box body, and the pressure applying element is used for being in mutual extrusion contact with the cabin door sealing element and dividing the space in the sealing box body into a first chamber and a second chamber, the pressure applying element is moved to adjust the compression amount of the cabin door sealing element; a first pressure control assembly is connected with the first chamber and used for controlling the pressure of the first chamber; and a second pressure control assembly is connected with the second chamber and used for controlling the pressure of the second chamber. The water seal test device can be used for testing the leakage of the cabin door sealing element under different compression amounts, the multiple mounting and clamping for testing different compression amounts are effectively avoided, the sealing test demand of the water entry working condition can be met, and the operation difficulty and cost are reduced.

The application provides a supercavitation projectile cross-medium water entry interference suppression method based on optimization of a cymbal length, comprising the following steps: S1, establishing a projectile-cymbal parameterized model, and demarcating an optimization interval of the cymbal length; S2, coupling a multiphase flow model, a cavitation model and a dynamic grid method to simulate a separation process of the projectile and the cymbal, and obtaining original data of the projectile; S3, performing comparative simulation of multiple groups of different cymbal lengths, and quantitatively extracting three key performance indexes of a supercavity symmetry, a pitch angle deviation and a speed attenuation rate by using the original data of the projectile; and S4, establishing a multi-target optimization criterion based on an interference index, determining a globally optimal cymbal length parameter, and completing the whole optimization process. The application can solve the problem caused by improper design of the cymbal length when the supercavitation projectile and the cymbal cooperatively enter water.

The embodiment of the present application discloses a method for identifying screen water entry, comprising: detecting proximity data obtained by a proximity sensor; and outputting a screen water entry risk prompt when the proximity data is less than or equal to a preset alarm threshold. The embodiment of the present application also provides a device for identifying screen water entry, which identifies that water covers the surface of a display screen glass cover plate according to the signal quantity received by a sensor receiving end, judges and prompts that the intelligent terminal has a risk of water entry.

This invention discloses a method for controlling the speed lag during the water entry transient of a vehicle's propulsion system, comprising the following steps: Step 1, constructing a cross-medium aerial propulsion system and performing aerial and underwater thermodynamic design to obtain the cross-medium system configuration; Step 2, establishing a dynamic mathematical model of the cross-medium propulsion system based on the cross-medium system configuration; Step 3, designing a control algorithm based on the dynamic mathematical model of the cross-medium propulsion system to adjust the fuel pump displacement during the water entry process, achieving closed-loop control of the turbine speed, and obtaining an optimized propulsion system; Step 4, simulating the optimized propulsion system to obtain the control response characteristics of the cross-medium propulsion system during the water entry process. The speed lag control method for the water entry transient of a vehicle's propulsion system disclosed in this invention solves the problems of existing PID control being prone to instability under engineering delays and failing to provide a safety margin for the determination of response time for sensors and actuators.

This invention discloses a high-speed parallel water entry experimental launching device and method for a vehicle, belonging to the field of hydrodynamic experiments. It includes a supporting base, a parallel controller, a parallel launching assembly, and a power unit. The parallel launching assembly is mounted on the supporting base via the parallel controller, and the power unit provides launching power and adjusts the water entry velocity. The parallel launching assembly includes a first launching device and a second launching device arranged side-by-side, enabling parallel launching of two projectiles and adjustment of the launching angle. The parallel controller includes a parallel control mechanism and a spacing adjustment mechanism. The parallel control mechanism ensures the relative parallelism of the first and second launching devices, while the spacing adjustment mechanism adjusts the launching distance between the first and second launching devices. This invention has a simple and practical structure, is easy to assemble, has high reliability and durability, and exhibits good repeatability and safety, providing experimental assurance for studying the hydrodynamic characteristics of structures at the moment of water entry.

The invention belongs to the technical field of aircraft fire extinguishing design, and provides a large amphibious aircraft water throwing efficiency data expansion method, which comprises the following steps: carrying out a pre-flight test of an aircraft to obtain test state points of aircraft water throwing efficiency, including typical test state points and atypical test state points; carrying out water throwing efficiency tests on different test state points, summarizing and analyzing test data, carrying out water throwing efficiency tests on test state points corresponding to invalid data again, summarizing the test data again, and fitting the test data to obtain different water throwing efficiency relation curves; and typical test state point results are extracted to fit coefficients of the water throwing efficiency relation curve, the coefficients are combed, a change relation curve of the water throwing efficiency and different test state points is constructed, and a change curve of the water throwing efficiency along with the water throwing height under each test state point of the airplane is expanded. According to the method, data validity judgment can be improved, the test process is accelerated, and unpredictability of environment variable control caused by an overlong test period is avoided.

The invention discloses a lifeboat water entry measurement system and method based on a trajectory tracking algorithm, the system comprises a wind wave flow coupling test pool, a throwing type lifeboat release platform and a throwing type lifeboat water entry test measurement module, the wind wave flow coupling test pool is used for simulating marine environments under different working conditions; the throwing type lifeboat releasing platform is used for simulating the releasing process of the throwing type lifeboat under different working conditions; the throwing type lifeboat water entry test measurement module solves and obtains the movement track, speed and attitude angle change of the lifeboat based on a trajectory tracking algorithm, and obtains the movement response mechanism of the lifeboat; according to the invention, a complex marine environment can be simulated, multi-degree-of-freedom motion response can be captured in real time, and test measurement of a key load can be quantitatively measured.

The invention discloses a deep and far sea submarine cable laying tension accurate control method based on a water entry angle, and belongs to the technical field of ocean engineering. According to the method, a mapping model of a submarine cable water entry angle alpha and submarine cable tension T is constructed through finite element software; determining the maximum permissible tension value Tmax and the minimum permissible tension value Tmin of the submarine cable, and determining the safety threshold [alpha min, alpha max] of alpha according to the characteristic curve in the mapping model of alpha and T; according to the method, the submarine cable water entry angle alpha is monitored in real time during construction, then the relation between the submarine cable water entry angle alpha and [alpha min, alpha max] is judged, the cable laying speed is controlled accordingly, the submarine cable tension is controlled within a safe interval, the submarine cable laying tension can be ensured to be safe and controllable, and the submarine cable laying construction safety is improved.

Device (200) for cleaning grey water containing particulate material, comprising a container (201) in turn comprising a water entry (202); a slurry exit (204); a cleansed water exit (203); and a sedimentation volume (220). The invention is characterised in that the container further comprises a flocculant provision means, arranged to add a flocculant (212) to grey water entering via the water entry, so that grey water having entered said sedimentation volume after such adding contains said flocculant, in that the flocculant provision means comprises a vertical chute (213) arranged to convey, via gravity, said grey water from an upper part of said container to be released via an open lower end (215) of the chute into said sedimentation volume at a height of at the most 1 m above a bottom (221) of said sedimentation volume, the chute having a cross-sectional area of at least 0.1 m2. The invention also relates to a method.

The invention relates to a water drainage device (10) for preventing water from entering at least one liquid-sensitive component (14) of a motor vehicle, in particular water (W) that occurs during a film application process on body structures (15) or glazing, wherein the water drainage device (10) is arranged in the area of ​​a body structure (15) and comprises at least one water drainage element (12) which is arranged offset in the direction of gravity (Z) relative to a water entry area (16) and comprises at least one water-bearing surface (12a-12c) (preferably a plurality that are connected to each other, two outer and one middle, all inclined), via which the water (W) can be guided away from the at least one liquid-sensitive component (14) depending on gravity (Z).

The invention provides a dynamic adjusting method for a ship chamber of a launching type ship lift after entering water. The dynamic adjusting method comprises the following steps that the downstream water level (WD), the water depth (WX) of the ship chamber and the water entering depth (WR) are detected in real time through a sensor; adjusting is triggered based on predefined parameters (the standard water depth WXB of the ship chamber, the allowable fluctuation range WX delta M of the water depth, the maximum draft WCM of the ship and the maximum water entry depth WRM of the ship chamber); if WRM (descending condition) or WR is smaller than WRM-delta 2 (lifting condition), delta 1 and delta 2 take the design water depth + / -5%-10%; when descending is triggered, the main elevator runs to WX = WXB + WXdeltaM, and lifting is triggered in a similar way; the levelness (height difference is less than 1cm) of four corners of the ship chamber is monitored during adjustment; and after adjustment, if the WX is within the range of [WXB-WX delta M, WXB + WX delta M], the door is closed, otherwise, adjustment is repeated. According to the method, the ship chamber water depth is kept within an effective range through dynamic adjustment, and ship draft and ship lift operation safety are guaranteed.

The invention discloses a Beidou underwater sound locator, which comprises a charging unit, a power supply module, an LFM (Linear Frequency Modulation) generation module, a power amplifier and matching module and a transducer which are electrically connected in sequence, and also comprises a water entry detection module and a locating module which are electrically connected with the LFM generation module. According to the invention, the working frequency band of the sensor is effectively expanded, and through different set frequency parameters, a receiving device captures sound signals to realize positioning, so that the positions of different UUVs or frogmen are accurately identified. When an emergency occurs, the sound locator can provide reliable support for searching and locating operation, and timely and accurate rescue implementation is ensured. And navigation and tracking performance of various underwater carriers can be reliably guaranteed.

The invention belongs to the technical field of planktonic diatom sampling and microbiological detection pretreatment, and particularly relates to lake surface planktonic diatom sampling equipment which comprises a handheld rod, a weight moving mechanism, a water entering mechanism and an air supporting mechanism. The weight moving mechanism comprises a limiting assembly and a bottom suction assembly, the limiting assembly is arranged at one end of the handheld rod, and the bottom suction assembly is arranged at the other end of the handheld rod; the bottom suction assembly is arranged on the limiting assembly, the water entry mechanism comprises a push-out assembly and a sampling assembly, the push-out assembly is arranged at the end, away from the limiting assembly, of the handheld rod, and the sampling assembly is arranged on the side, away from the handheld rod, of the push-out assembly. According to the lake surface layer floating diatom sampling equipment, the net body can be kept vertically extending in water, it is ensured that a net opening always faces the water flow direction, the interior of the collecting net has the supporting capacity, and it is ensured that the effective water filtering area is stable.

The embodiment of the invention provides a display device and a driving method thereof. The display device comprises an application processor and a light sensor, and the application processor is connected with the light sensor. When the display device enters the water entry mode, the application processor controls the light sensor to enter the touch detection mode. The light sensor performs detection at a preset detection frequency in a touch detection mode, and outputs a touch signal and sends the touch signal to the application processor when a detection result meets the condition that an object approaches and the distance is smaller than a threshold value and / or the illumination intensity of the sensing area changes. The application processor responds to the touch signal to execute the touch instruction, so that the display device executes a specified function. Therefore, the touch operation can be realized when the display device is immersed into water.

The utility model belongs to the technical field of underwater detection and underwater acoustic engineering, and particularly discloses a conformal self-contained underwater acoustic beacon which comprises an acoustic beacon shell, the acoustic beacon shell comprises a wedge-shaped conformal body and a cylindrical carrier, the bottom of the wedge-shaped conformal body is attached to the cylindrical carrier, and the top of the wedge-shaped conformal body is an inclined cambered surface; a transducer and a signal processing module are mounted at the top of the wedge-shaped conformal body; a power supply module is arranged in the cylindrical carrier, and the signal processing unit is connected with the power supply module and the transducer respectively; an end cover is arranged at the end of the cylindrical carrier, and a water entry detection module is integrated in the end cover. According to the utility model, the acoustic beacon shell is divided into the wedge-shaped conformal body and the cylindrical carrier, and the top of the wedge-shaped conformal body is the inclined cambered surface, so that the surface space of the UUV is utilized to the greatest extent, the overall size and weight are reduced, the acoustic beacon can be better integrated into the streamline design of the UUV, the resistance during underwater movement is reduced, and the navigation efficiency is improved.

The utility model relates to the technical field of modified plastic processing, in particular to a cooling and shaping device for a modified plastic extruder, which comprises a water tank and at least three guide units mounted on the water tank, each guide unit comprises a support fixed on the water tank, the support is movably connected with a mounting seat, and the mounting seat is movably connected with the water tank. A guide roller assembly for guiding a plastic strip is arranged on the mounting seat; wherein a driving assembly is further installed above the support, the driving assembly is used for driving the installation bases to move up and down, the plastic strips are guided through the design of the at least three guiding units, the water entry depth of each installation base can be changed through the driving assembly, and when the three installation bases are located at different heights, the installation bases can be driven by the driving assembly to move up and down. The stroke distance of different lengths can be formed by adjusting the stroke distance of the plastic to be cooled, so that the cooling stroke of the plastic can be adaptively adjusted according to the condition of the plastic to be cooled, and the better adaptability is achieved.

The utility model relates to zip fastener technical field, and disclose a waterproof nylon zip fastener with protection structure, include: zipper head, first zipper strip and second zipper strip set up respectively in both sides of zipper head, first zipper tooth and second zipper tooth are fixed on the opposite edge of first zipper strip and second zipper strip respectively, are used for with zipper head cooperation realizes the opening and closing of zip fastener, protective cloth strip, cover in the outside surface of first zipper strip and second zipper strip, and with first zipper strip and second zipper strip fixed connection, are used for providing additional protection. The waterproof nylon zip fastener with protection structure, waterproof effect: the rubber body of protective cloth strip innermost layer directly with zipper strip contact, can provide basic waterproof and sealing function, two protective cloth strip end surfaces contact each other further optimization sealing performance, the smooth cooperation of the chain tooth and zipper head of collocation nylon material reduces the risk of water entry in the gap in the opening and closing process, realizes the waterproof of zip fastener whole.

This invention discloses an experimental apparatus and its operating method for continuous projectile launches to penetrate ice and water at a common point. The apparatus includes an adjustment device, a launching device, an infrared sensor, a water tank, a support device, and a control system. The launching device comprises at least two launching units, an air storage chamber, a control valve, an air cushion guide rail, a support frame, and a drive device. Each launching unit is mounted on the air cushion guide rail and can move along the guide rail. The infrared sensor is fixedly mounted on the worktable to detect the position of the launching unit and output a trigger signal to open the control valve of the subsequent launching unit. The adjustment device includes a worktable, a hydraulic rod, an adjustment guide rail, and a slider, enabling continuous adjustment of the water entry angle. The water tank contains an ice-floating constraint. The control system is electrically connected to the infrared sensor and the control valve and controls the drive device. This invention enables high-precision, point-to-point control of the water entry positions of multiple projectiles, constructs a stable and controllable ice environment, and improves experimental repeatability and reliability.