99results about "Solid based dampers" patented technology

The invention provides a vertical liquid damper which comprises a closed container, buffer liquid, a horizontal partition part and a horizontal energy dissipation part, a base connected with an external structure to be subjected to vibration reduction is arranged at the bottom of the closed container, and the interior of the closed container is divided into at least two independent closed cavities by the horizontal partition part; each closed cavity is filled with the buffer liquid flowing in a collision mode, the horizontal energy dissipation pieces are arranged in the closed cavities, each horizontal energy dissipation piece comprises a middle hollow channel and a peripheral baffle, and the peripheral baffle is provided with a pore structure for the buffer liquid to pass through in the vertical movement process. The device has the advantages of effective dissipation of vertical vibration energy, simple structure and the like.

The invention discloses a liquid damping shock absorber which comprises an outer shell (6) and a middle shaft (2) and is characterized in that the outer shell (6) is in a barrel shape, the middle shaft (2) is installed at the bottom of the barrel through an axial supporting mechanism (14), a damping barrel is arranged in the outer shell (6) and installed on the middle shaft (2), and the damping barrel is of a cavity structure with an elastic gap in the lower bottom face. The upper end of the middle shaft (2) penetrates out of the center of an upper end cover (3) of the outer shell (6), damping liquid is contained in the outer shell (6), and the liquid level of the damping liquid is higher than the lower bottom face of the damping cylinder. According to the shock absorber, the damping liquid and the damping cylinder are organically combined, the damping cylinder extrudes the damping liquid when the shock absorber is subjected to an external load, vibration energy is counteracted through viscous dissipation and dynamic pressure generated by liquid shaking, gaps can be changed when pressure is received by the porous structure characteristics of the bottom of the damping cylinder, and the flow of the damping liquid penetrating through the gaps is influenced; therefore, the damping of the shock absorber is variable.

The utility model discloses a sliding type damping box, including upper connecting plate and the box of being located below upper connecting plate, the lower part fixedly connected with plunger of upper connecting plate, the right baffle and left baffle of opposite setting are equipped with in box inner chamber seal, the cavity formed by right baffle, left baffle and box is equipped with damping liquid, the lower part of plunger is inserted into damping liquid, the lower part both sides of upper connecting plate are fixedly connected with the right support plate and left support plate of inserting into the inner chamber of box, and the lower end of right support plate and left support plate respectively abuts with the sliding body of a plurality of located at the bottom of box. The utility model discloses the lower end of right support plate and left support plate abuts with a plurality of sliding bodies, can be used to bear the weight load of equipment, realizes the horizontal free sliding under heavy load working condition, can improve the friction damping effect of right support plate and left support plate through rubber pad, improves the damping effect of damper, makes up the problem that damper damping force is not enough in high temperature environment, guarantees the damping effect of damper.

The present application relates to a kind of three-dimensional pendulum tuning liquid inductance device, the inductance device includes tuning liquid column damper and tuning mass inductance container, tuning liquid column damper includes swing arm, ball hinge end head, swing arm connector, annular water tank and tuning liquid, swing arm one end is connected with ball hinge end head, the other end is connected with annular water tank by swing arm connector, tuning liquid is filled in annular water tank;Tuning mass inductance container is installed in the lower portion of tuning liquid column damper, ball hinge end head is connected with the structure to be damped, annular water tank swings and drives tuning mass inductance container to carry out energy consumption, the inductance device tuning period is adjustable.Compared with prior art, the present application has can control the vibration in each direction of the structure to be controlled, wide range of use;The parameters of each component can be flexibly adjusted to achieve the best damping effect, while tuning mass inductance container can realize the energy absorption of input structure with smaller space and achieve the two goals of energy dissipation and reduction of upper tuning liquid mass.

The invention provides a viscous damping device based on efficient heat dissipation, and belongs to the field of building anti-seismic equipment. The damper comprises a viscous damping assembly, an upper gusset plate and a lower gusset plate, the viscous damping assembly comprises a cylinder body, a piston rod, two bushings and a piston, the upper gusset plate is hinged to the end, located outside the cylinder body, of the piston rod, an upper mounting plate is fixedly mounted at the top of the upper gusset plate, and a connecting body is fixedly mounted at the end, away from the upper gusset plate, of the cylinder body; the lower gusset plate is hinged to the end, away from the cylinder body, of the connecting body, a plurality of heat conduction rods distributed in an annular array are slidably installed on the piston in a penetrating mode, and a plurality of natural graphite flakes are fixedly installed on the positions, close to the two ends, of the outer walls of the heat conduction rods. The viscous damping device based on efficient heat dissipation has the advantages that an efficient passive heat dissipation link is arranged in the cylinder body, active one-way auxiliary heat dissipation can be achieved, a heat dissipation fin convenient disassembly and maintenance structure is arranged, and the telescopic amplitude of the piston rod can be accurately recorded.

The utility model provides a buffer. The buffer comprises a cylinder body, a piston and a ball body, a liquid cavity used for containing viscous liquid is formed in the cylinder body. The piston is arranged in the liquid cavity in a sliding manner; the piston divides the liquid cavity into a pressure cavity and a non-pressure cavity; a passage communicated with the pressure cavity and the non-pressure cavity is arranged in the piston; the passage is provided with a ball seat structure on one side of the pressure cavity, and the ball body is movably arranged in the pressure cavity and is matched with the ball seat structure to open and close the passage or adjust the flow speed and flow of the viscous liquid passing through the passage by adjusting the size of the cross section of the passage at the ball seat structure. According to the utility model, the structure is more compact, and the extruded area of the elastic air bag is larger, so that the contraction ratio is larger under the same liquid pressure, and the adjusting capability is greatly improved.

A damper device and an electronic apparatus are provided. The damper device includes a first holder, a first damper component and a first gel. The first damper component includes a first protrusion part and a first bar part. The first protrusion part includes a first surface. The first bar part includes a first free end and a first fixed end. The first protrusion part is fixed on the first free end, the first fixed end is fixed on the first holder and the first surface protrudes outward from the first free end. The first free end and the first protrusion part are inserted into the first gel, and the first gel moves along the radial direction of the first bar part relative to the first bar part.

The present application relates to the technical field of damper, specifically to a pipeline viscous hydraulic damper, comprising a first cylinder component group and a second cylinder component group which are coaxial and separable and are sleeved outside the damper body. The present application sets the first cylinder component group and the second cylinder component group which are nested inside and outside and can be independently disassembled, constructs an integrated maintainable protection system, realizes multi-functional integration such as corrosion protection, active cleaning of core components during maintenance period and efficient heat dissipation during operation period without disassembling the damper body, and significantly improves long-term operation reliability and maintenance convenience in harsh marine environment.

The utility model relates to the technical field of damping instruments, and discloses a self-cooling viscous damper which comprises a damping shell, one end of the outer portion of the damping shell is fixedly connected with a supporting end, the other end of the damping shell is fixedly connected with a sliding end, and a sliding rod is slidably connected into the sliding end. One end of the sliding rod is fixedly connected with the damping shell, the other end of the sliding rod is fixedly connected with a connecting end, a partition mechanism is arranged outside the connecting end, a cooling mechanism is arranged outside the damping shell and comprises a protective shell, the interior of the protective shell is fixedly connected to the exterior of the damping shell, and a plurality of air holes are formed in the exterior of the protective shell. According to the cooling device, the circulating pipe is connected with the cooling fins, the cooling liquid is driven to flow to the cooling fins through the circulating pipe, the effect of rapidly dissipating heat in the cooling liquid is achieved through rotation of the fan, the cooling efficiency is improved, and the cooling effect on the damper is guaranteed.

The utility model discloses a viscous damper with a friction energy dissipation function, which belongs to the field of shock absorption of building and bridge structures and comprises an oil cylinder, one end of the oil cylinder is in threaded connection with a base, the other end of the oil cylinder is in threaded connection with a connecting pipe, and a piston rod is arranged on one face, facing the oil cylinder, of the base. A first piston is arranged on the piston rod outside the oil cylinder; a second piston is arranged at one end of the piston rod inside the connecting pipe; according to the viscous damper with the friction energy dissipation function, a novel friction material-ceramic fiber material is adopted, the material is resistant to high temperature and low temperature, stable in physical and chemical performance and high in durability, the friction coefficient is not reduced under reciprocating friction, a novel sealing material-polytetrafluoroethylene is adopted, the material is resistant to high temperature and low temperature, stable in physical and chemical performance, high in durability and low in friction coefficient, and the sealing performance is good. Under reciprocating friction of the piston rod, the sealing performance is not reduced, and the service life of the product is long and can be the same as that of a building structure.

Viscoelastic damper assembly applicable both in air and submerged applications and with improved efficiency over prior art solutions for adding damping to an object or structure.

The utility model provides a viscous damper with an explosion-proof cavity, which relates to the field of viscous dampers and comprises a cylinder body, a piston is movably mounted on the inner wall of the cylinder body, damping holes are equidistantly formed in the circumference of the surface of the piston, a hose is fixedly mounted on the surface of the cylinder body, and a fixing frame is fixedly mounted on the surface of the cylinder body. A round rod is movably embedded in the inner wall of the fixing frame, a round block is fixedly installed at one end of the round rod, a spring is movably arranged on the surface of the round rod in a sleeving mode, an extrusion piece is fixedly installed at the other end of the round rod, and the other side of the extrusion piece is attached to the surface of the hose. When the damping cylinder is strongly impacted, a damping medium in the cylinder body enters the hose, so that the hose which is extruded and closed by the extrusion sheet is opened, damping value flows into the other cavity, the pressure is released, the risk of cavity explosion is reduced, the corrugated pipe is arranged on the surface of the guide rod in a sleeving manner, the extending part of the guide rod is protected, and the influence of the environment is reduced.

An actuator contributes to improving the bonding strength between a viscoelastic member and a plate-shaped portion by a simple process. The utility model relates to an actuator, which comprises a supporting body, a connecting piece, a connecting piece and a connecting piece, wherein the supporting body is provided with a plate-shaped part; a movable body having a first portion, a second portion, and a connecting portion, the first portion and the second portion facing the plate-shaped portion on both sides of the plate-shaped portion in the thickness direction, respectively, the connecting portion connecting the first portion and the second portion; a first viscoelastic member that is in contact with the plate-like portion and the first portion, respectively, at a position where the plate-like portion and the first portion face each other; and a second viscoelastic member that is in contact with the plate-shaped portion and the second portion, respectively, at positions where the plate-shaped portion and the second portion face each other, in which a plurality of recesses are provided in at least portions where the plate-shaped portion is in contact with the first viscoelastic member and the second viscoelastic member.

The application provides a sealed shear thickening fluid extrusion oil film damper, which comprises a damper inner ring and a damper outer ring which is sealed to the outside of the damper inner ring, the inside of the damper inner ring is connected with a rotor through a bearing, and a gap is formed between the inner wall of the damper outer ring and the outer wall of the damper inner ring, the gap is filled with a working medium, and the working medium is shear thickening fluid; a working medium filling structure is arranged on the damper outer ring and is used for realizing injection and suction of the shear thickening fluid in the gap. The sealed shear thickening fluid extrusion oil film damper does not need a more complex working medium circulating system device, the dependence on a complex structure is reduced, and the damper has a wider engineering application.

The utility model relates to the field of single-rod viscous dampers, in particular to a single-rod viscous damper with a positioning structure, which comprises an oil cylinder. And the first bushing and the second bushing are arranged at the two ends of the oil cylinder. According to the single-rod viscous damper with the positioning structure, due to the arrangement of the positioning mechanism, the first positioning sleeve and the second positioning sleeve are arranged on the outer side of the oil cylinder in a sleeving mode, and the sliding grooves in the first positioning sleeve and the second positioning sleeve are clamped on the clamping blocks outside the oil cylinder; meanwhile, limiting rings at the front ends of the first positioning sleeve and the second positioning sleeve are clamped in limiting grooves in the outer portion of the front end of the piston rod, and then the first positioning sleeve and the second positioning sleeve are fixedly installed through a bolt, so that when the single-rod viscous damper is used, the piston rod can drive the first positioning sleeve and the second positioning sleeve to stretch out and draw back together; the positioning effect is achieved for the piston rod, and the conditions of shaking and deviation in the telescopic stroke process are avoided.

This invention relates to a variable-damping, actively controlled extrusion film damper and its variable-damping adjustment method, belonging to the technical field of extrusion film damper structural design for aero-engines. The invention addresses the problem that traditional extrusion film dampers only exhibit optimal damping characteristics at specific excitation frequencies, failing to cover all rotor operating frequencies. This results in poor stability and weak dynamic performance of the rotor system in modern aero-engines operating across multiple critical speeds. The invention comprises a damper outer ring, a cone sleeve, a squirrel cage inner ring, two servo valves, two oil film pressure sensors, and two eddy current displacement sensors. Lubricating oil enters the oil film between the cone sleeve and the squirrel cage inner ring through the two servo valves. The eddy current displacement sensors measure the change in the eddy current position of the squirrel cage inner ring, and the oil film pressure sensors measure the change in oil film pressure. The measurements from the eddy current displacement sensors and the oil film pressure sensors are used as the basis for adjusting the oil supply to the servo valves. This invention is primarily used as a structure for extrusion film dampers in aero-engines.

A method for execution by a computing entity includes interpreting an electric response from a set of electric field sensors to produce a piston velocity and a piston position of a piston associated with a head unit device. The head unit device includes a chamber filled with a shear thickening fluid (STF) that includes a multitude of piezoelectric nanoparticles. The method further includes determining a shear force based on the piston velocity and the piston position. The method further includes determining a desired response for the STF based on the shear force, the piston velocity, and the piston position. The method further includes generating an electric activation based on the desired response for the STF and outputting the electric activation to a set of electric field emitters positioned proximal to the chamber.

The damping-adjustable viscous damper with the failure damping self-maintaining function comprises a cylinder body, a piston rod and a piston, the piston is slidably arranged in a cavity in the cylinder body, one end of the piston rod is connected with a main structure, and the other end of the piston rod is coaxially connected with the piston; the piston divides the cavity into a left cavity body and a right cavity body, a damping hole is formed in the piston, a pipeline is arranged outside the cylinder body, the damping hole and the pipeline are communicated with the left cavity body and the right cavity body respectively, and an adjustable valve is arranged on the pipeline and used for adjusting the flow of the pipeline. Compared with the prior art, the device has the advantages of simple and reliable structure, high safety and the like.

The invention provides an active viscous damper based on MFC control and a control method thereof.The damper comprises a cylinder barrel filled with viscous fluid, the outer side of the cylinder barrel communicates with a bypass pipeline, the bypass pipeline is sleeved with an MFC driver, the MFC driver is provided with a cantilever valve and a cantilever rod, the cantilever valve is provided with an MFC sensing piece in a surface-mounted mode, and the cantilever rod is provided with an MFC driving piece in a surface-mounted mode. A lever is connected between the cantilever rod and the cantilever valve, the middle of the lever is hinged to a fixed fulcrum in the MFC driver, a valve element of the cantilever valve is right opposite to and extends into a damping hole which is through in the bypass pipeline in the radial direction, and the cantilever rod is welded to the outer wall of the bypass pipeline. The size of the damping hole is accurately, rapidly and actively adjusted, the damping force is optimized in real time according to external excitation and structural response, the response speed is high, the control precision is high, the damping efficiency is improved, the device is suitable for bearing long-term and high-frequency cyclic loads, the structure is simplified, the integration level and reliability are improved, safety redundancy is provided, and energy consumption is reduced.

A method for execution by a computing entity includes interpreting a fluid flow response from a set of radio frequency wireless field sensors to produce a piston velocity and position of a piston associated with a head unit device that includes a chamber filled with a shear thickening fluid (STF) that includes a combination of a multitude of piezoelectric nanoparticles and a multitude of magnetic nanoparticles. The method further includes determining a shear force based on the piston velocity and the piston position. The method further includes determining a desired response for the STF based on the shear force, the piston velocity, and the piston position. The method further includes generating a wireless field activation based on the desired response for the STF and outputting the wireless field activation to a set of radio frequency wireless field emitters positioned proximal to the chamber.

The invention provides a viscous damper mounting rack. The viscous damper mounting rack comprises a frame I and a rack I connected with the frame I, the motor serves as a power source in the first frame, the first gear is arranged on the surface of the motor and used for power transmission, the first ring is in transmission connection with the first gear, the first frame is arranged on the surface of the first ring, the first plate is connected with the first frame, and one end of the first plate is connected with the first frame. When a motor rotates, a first gear and a first ring drive a first frame to rotate, the height of a first plate is changed, a first frame is driven to move upwards to fix the installation height, the motor drives the first frame to rotate, the first frame drives a first plate to move upwards, and therefore the first frame is jacked up, the first frame jacks a building by a certain distance, and the installation space of the damper is guaranteed; the problem that the distance between buildings is insufficient is solved, meanwhile, the third ring can be arranged on the surface of the damper in a sleeving mode to fix the position of the damper, and therefore the damper is installed at the proper position and kept horizontal at the same time, and normal work of the damper is guaranteed.

The utility model provides a multi-order viscous damper with an active cooling system, and belongs to the technical field of building damping. Comprising a main oil cylinder, the outer side of the main oil cylinder is fixedly connected with a high-heat-conduction material layer, a hollow cavity is formed in the inner side of the high-heat-conduction material layer, the inner side of the hollow cavity is filled with a phase change material, and the contact face of the outer side of the main oil cylinder and the high-heat-conduction material layer is coated with heat conduction silica gel; by arranging the high-heat-conduction material layer, the hollow cavity, the phase-change material and the heat-conduction silica gel, heat generated when the damper works is rapidly transmitted to the phase-change material through the high-heat-conduction material layer, the phase-change material is converted into a liquid state from a solid state after absorbing the heat, the temperature rise rate is greatly reduced through latent heat of phase change, and the heat conduction performance of the damper is improved. When the damper stops working or the environment temperature is reduced, the phase change material is solidified again to release the stored heat, recycling is achieved, oil liquid high-temperature failure is avoided, and the service life of the device is prolonged.

A head unit system for controlling an object includes a head unit device that include shear thickening fluid (STF) and a chamber configured to contain the STF. The chamber further includes a gate between a front channel and a back channel. The gate includes a set of bypass openings. The head unit device further includes a piston housed at least partially radially within the chamber. The gate is configured to control flow of the STF between the front channel and the back channel to control contraction of the chamber to provide the controlling of the object.

A clearance bushing for a vehicle suspension includes internal projections formed in an inner stopper and external projections formed in an outer stopper. In particular, the internal projections and the external projections are configured to perpendicularly cross each other to allow the internal projections and the external projections to point-contact each other during operation of the suspension. The internal projections are arranged to be non-parallel to each other, and the external projections are arranged to be non-parallel to each other. Thus, a contact area between the internal projections and the external projections is greatly reduced, and a contact wear location therebetween is diversified, thereby improving durability and life of the clearance bushing.

The utility model belongs to the technical field of mechanical engineering, and particularly relates to a daubing tool for a daubing buffer of a high-pressure canned locomotive, which comprises a first support frame, the top of the first support frame is fixedly connected with a stirring container; two groups of electric push rods are fixedly connected to the outer wall of the stirring container; a supporting plate is fixedly connected to the top of the output end of the electric push rod, and the supporting plate is arranged on the outer wall of the stirring container in a sliding manner; a plurality of groups of second supporting frames are fixedly connected to the top of the supporting plate; the top of the second supporting frame is fixedly connected with a frame plate. The inner wall of the frame plate is rotationally connected with a first shielding plate; through cooperation of multiple groups of first shielding plates which are arranged in an unfolded mode, part of splashing raw materials can be shielded, the problem of waste caused by the fact that the materials are transferred to the outside is solved, meanwhile, under the action of an arranged sliding supporting plate, the multiple groups of first shielding plates can be synchronously stored to the outer wall of the stirring container in the follow-up process, and the stirring efficiency is improved. And subsequent operations of adding materials into the stirring container and the like are facilitated.

The invention discloses a self-resetting composite viscous damper which comprises a guide rod, a lug plate, a magnet piston, a first end cover, a second end cover, a first seal, a second seal, a first magnet, a second magnet, damping fluid, an outer barrel, a conductor barrel and an auxiliary cylinder. One end of the guide rod is fixedly connected with the lug plate, the guide rod sequentially penetrates through the first end cover, the first seal, the first magnet, the magnet piston, the second magnet, the second seal and the second end cover, the magnet piston is fixedly arranged in the middle of the guide rod, and magnetic poles of the magnet piston, the first magnet and the second magnet are opposite. The first seal is arranged in a groove in the inner side of the first end cover, the first magnet is coaxially fixed to the first end cover, the second seal is arranged in a groove in the inner side of the second end cover, the second magnet is coaxially fixed to the second end cover, the conductor cylinder is fixedly arranged on the inner side of the outer cylinder, and the two ends of the outer cylinder are fixedly connected with the first end cover and the second end cover respectively. A closed cavity is formed and filled with damping liquid, and the auxiliary cylinder is fixedly arranged at the tail end of the outer cylinder. Viscous damping and eddy current damping are organically combined, the higher energy consumption effect is achieved, and the self-resetting function after vibration is achieved.

The invention relates to the technical field of damping supports, and discloses a textile machine damping device for medical protective fabric, which comprises a damping seat, the damping seat is located in a rack, and a transmission part is arranged on the side edge of the damping seat; the damping seat comprises an abutting plate, a middle plate and a top plate which are arranged from bottom to top, the middle plate and the top plate are elastically connected through a vibration isolation spring, a damping piece is arranged between the abutting plate and the middle plate, and a clamping groove is formed in the middle of the top plate. According to the multi-stage vibration isolation device, multi-stage vibration isolation is achieved through cooperation of the layered structure of the damping base, the vibration isolation springs and the damping pieces, periodic and impact vibration generated in the operation process of the textile machine can be effectively absorbed and consumed, and the vibration amplitude transmitted to a weaving area is reduced to the minimum. By means of the efficient damping effect, the fabric defects such as yarn tension disorder, uneven fabric density, yarn jumping, thickness deviation and micro-pores caused by vibration can be effectively overcome.

The invention relates to a damping element (10) for a spring-damper unit (100) for vibration and shock damping, comprising an outer piston (12) and an inner piston (14) that is displaceable relative to the outer piston (12), wherein a vertical gap (16) between the pistons (12, 14) is filled with a viscous fluid (24) and sealed with two diaphragm elements (18, 20), each of which is attached to the two pistons (12, 14), such that a relative movement of the inner piston (14) to the outer piston (12) is enabled, wherein a damping force opposite to the relative movement, dependent on the velocity, is generated by shear forces of the fluid (24). Furthermore, the invention relates to a spring-damper unit (100) with a damping element and a spring element connected in parallel or in series.

A multi-stage adjustable viscous damper comprises a pressure cylinder, an adjusting cavity is formed in a non-opening side cylinder body of the pressure cylinder, and the adjusting cavity is communicated with an inner cavity of the pressure cylinder through an exchange hole; the cylinder cover is hermetically connected to a port of the pressure cylinder; the piston rod slides in the center of the cylinder cover; the working piston is fixed at the end part of the piston rod and is in sealing and sliding fit with the inner wall of the pressure cylinder, and a damping hole is formed in the working piston; the floating piston is arranged at the end, away from the piston rod, in the pressure cylinder in a sealed and sliding mode. And the blocking rod is slidably arranged in the exchange hole. The volume of the cavity formed by the floating piston and the inner wall of the pressure cylinder is changed through movement of the floating piston, so that back pressure is generated in the cavity, the back pressure is transmitted through a medium and reversely acts on the working piston, additional damping force independent of viscous damping force is formed, in addition, the reference value of the back pressure can be changed by sliding a blocking rod at the bottom of the pressure cylinder, and the damping effect is achieved. Therefore, the total damping coefficient of the damper can be accurately adjusted according to actual working conditions.

A multistage adjustable viscous damper comprises a pressure cylinder, an adjusting cavity is arranged in the non-opening side cylinder body of the pressure cylinder, the adjusting cavity is communicated with the inner cavity of the pressure cylinder through an exchange hole, a cylinder cover is sealingly connected to the port of the pressure cylinder, a piston rod is slidingly arranged in the center of the cylinder cover, a working piston is fixed to the end of the piston rod and sealingly and slidingly matched with the inner wall of the pressure cylinder, the working piston is provided with a damping hole, a floating piston is sealingly and slidingly arranged in the pressure cylinder and away from the end of the piston rod, and a plug rod is slidingly arranged in the exchange hole. The volume of the chamber formed by the floating piston and the inner wall of the pressure cylinder is changed through the movement of the floating piston, so that the back pressure is generated in the chamber, the back pressure is transmitted through the medium and acts on the working piston in the opposite direction, an additional damping force independent of the viscous damping force is formed, in addition, the reference value of the back pressure can be changed through the plug rod slidingly arranged at the bottom of the pressure cylinder, so that the total damping coefficient of the damper can be accurately adjusted according to the actual working condition.