73 results about "Friction coefficient" patented technology

The invention relates to the technical field of friction coefficient measuring devices, and discloses a device for testing the friction coefficient of an anti-skid coating of a cultivation work ship deck. Comprising a testing platform, a friction coefficient testing mechanism arranged below the testing platform, a driving mechanism arranged on the testing platform and used for driving the friction coefficient testing mechanism to horizontally move, and a partition assembly and a water spraying assembly arranged in the middle of the lower surface of the testing platform; through the arrangement of the high-pressure nozzles, in the moving process of the testing platform, high-pressure gas can automatically clean a deck testing area through the high-pressure nozzles, dust attached to the surface of a deck is effectively removed, manual pre-cleaning is not needed, the testing efficiency is remarkably improved, meanwhile, seawater is sprayed to the designated testing area through the water spraying assembly, and the testing efficiency is improved. The environment of the residual seawater on the deck in the actual operation of the cultivation work ship is accurately simulated, and the technical problems that an existing portable sliding friction instrument needs to be manually cleaned and cannot simulate the residual seawater environment are solved.

According to the precise cutting machining method and system for the soft material, firstly, the three-dimensional model and the cutting parameters of the material are obtained, the initial cutting track is generated, in the cutting process, material deformation is monitored in real time through the multi-sensor fusion technology, the cutting track and depth are adjusted through the dynamic compensation algorithm, and the cutting precision is improved. And meanwhile, a laser interference measurement system is adopted to track the position of a cutting tool, and micron-level precision is achieved through closed-loop feedback control. According to the method, pressure control and cutting depth adjustment are combined, a specific microstructure is created to achieve differential friction coefficients, in addition, the surface chemical composition is monitored through real-time spectrum analysis, and it is ensured that the preset surface characteristic requirement is met. The cutting track, depth and surface texture of the soft material can be accurately controlled, high-precision and customizable soft material machining is achieved, and key technical support is provided for intelligent machining in the fields of flexible electronics, bionic robots and the like.

The utility model relates to the technical field of drawing equipment, in particular to multi-pass wire drawing equipment. The equipment comprises a drawing cone pulley mechanism and a heating furnace, the drawing cone pulley mechanism comprises a cone pulley, and the surface of the cone pulley is divided into at least Z sections of areas in the axial direction of the cone pulley; wherein the surface roughness of each section of area is different, so that the surface friction coefficient of each section of area is different; the total drawing pass is M, and when M is larger than or equal to 2, Z is larger than or equal to 2 and smaller than or equal to M, so that at least one pass of wire drawing is conducted on each area. The drawing cone pulley solves the problem that due to the fact that the number of drawing passes is increased, the sliding coefficient difference between the first pass and the last pass is too large, and wires are broken, and the drawing efficiency of a single machine is remarkably improved.

The invention provides a self-adaptive grabbing system and method based on photoelectric sensing and material recognition. The system comprises a manipulator, a mechanical arm, a front-end processor and an upper computer controller. The manipulator is driven by a torque-adjustable motor, and an optical sensor module based on a photoelectric sensing principle is mounted on a fingertip of the manipulator; the optical sensor module is used for acquiring a texture grayscale image and sliding micro-displacement information of the surface of a grabbed object; the front-end processor is used for collecting data of the optical sensor module and transmitting the data to the upper computer controller; the upper computer controller recognizes the material of the object and matches the friction coefficient, the optimal clamping force increment is calculated according to the sliding micro-displacement information and the friction coefficient, and the motor is controlled to achieve self-adaptive grabbing. According to the system, the manipulator can be controlled to increase the clamping force in an optimal clamping force increment mode according to the sliding amplitude and the friction characteristic of the object, and self-adaptive stable grabbing of the object is achieved.

A treadmill includes a walking board assembly, and a walking belt encircling the walking board assembly. The walking board assembly includes a support plate, a wear-resistant plate mounted on the support plate, and a wax layer mounted on the wear-resistant plate. The wear-resistant plate is made of wear-resistant material with a low friction coefficient. The wear-resistant plate has a bottom face abutting the top face of the support plate. The wear-resistant plate has a top face integrally formed with multiple grooves. The wear-resistant plate has a thickness less than that of the support plate. The wax layer is coated on and filled with the grooves of the wear-resistant plate. The wax layer has a coating height at least equal to the depth of each of the grooves.

The present invention provides a method and system for optimizing the anti-skid performance of a sliding plate, which relates to the field of anti-skid detection technology. The method includes: setting an oblique groove on the upper contact surface of a test sliding plate; laying coarse sand in the oblique groove, fixing the lower contact surface of the test sliding plate to the ground, and placing a heavy object on the test sliding plate; applying traction and recording the critical traction; determining a friction coefficient function based on the critical traction, the particle size of the coarse sand, the angle of the oblique groove, and the weight of the heavy object; determining an optimized angle and an optimized particle size based on the friction coefficient function, the weight of the transported object, a first preset friction coefficient, and a second preset friction coefficient; and processing the sliding plate based on the optimized angle and the optimized particle size. According to the present invention, a friction coefficient function representing the relationship between the processing method and the anti-skid performance can be determined, and based on the friction coefficient function, an optimized processing method can be determined in combination with actual transportation needs to reduce the risk of the transported object slipping during transportation.

The invention provides a self-adaptive grabbing method based on tactile friction perception and an adjustable friction coefficient. The self-adaptive grabbing method is based on a grabbing mechanical arm with the adjustable friction coefficient. The surface, used for making contact with a grabbed object, of each finger is a friction surface with an adjustable friction coefficient, and a strain sensing module is embedded in the lower portion of each friction surface to detect the strain amount. The motor output is gradually increased, and meanwhile dynamic optimization of the minimum safe clamping force is conducted; the clamping static friction force Ff1 is obtained according to the motor output at the current moment in combination with the adjustable friction coefficient; a dependent variable epsilon is obtained and converted into a strain friction force Ff2, and a real-time friction force Ff is calculated; whether the minimum safe clamping force is obtained or not is judged according to the real-time friction force; and subsequently, the minimum safe clamping force is adopted for grabbing. According to the method, the minimum safe clamping force capable of overcoming the gravity of the workpiece can be dynamically adjusted, so that the vulnerable workpiece is protected to the greatest extent while reliable grabbing is ensured.

This invention discloses a method for obtaining the strength of a pillar considering friction factors, comprising: preparing rock samples with different aspect ratios and configuring contact surface materials with different tribological properties; determining the cohesion and friction coefficient of each contact surface material through shear testing, conducting compressive strength tests on rock samples with different contact surface materials to obtain rock sample strength data under different friction levels and aspect ratios; selecting a pillar strength calculation formula corresponding to the actual contact conditions between the pillar and the surrounding rock, calculating the strength of the target pillar under design conditions, and calculating the load on the pillar itself based on the pillar area bearing theory; calculating the pillar safety factor based on the pillar strength and the load, and optimizing the pillar design accordingly.

The utility model relates to the technical field of drawing equipment, in particular to a drawing cone pulley, a drawing cone pulley mechanism and multi-pass wire drawing equipment. The surface of the drawing cone pulley is divided into at least Z sections of areas along the axial direction; wherein the surface roughness of each section of area is different, so that the surface friction coefficient of each section of area is different; wherein the total drawing pass is M, and when M is larger than or equal to 2, Z is larger than or equal to 2 and smaller than or equal to M, so that at least one pass of wire drawing is conducted on each area. The drawing cone pulley solves the problem that due to the fact that the number of drawing passes is increased, the sliding coefficient difference between the first pass and the last pass is too large, and wires are broken, and the drawing efficiency of a single machine is remarkably improved.

A colorimetry device includes a support base having a support surface for supporting a measurement target and a carriage to which a colorimeter is detachably attached and that is configured to move in a first direction, which is a direction along the support surface, and in a second direction, which is a direction along the support surface and which intersects the first direction, the colorimeter being configured to measure color of the measurement target, wherein the carriage includes, on an inner wall of an accommodation section that accommodates the colorimeter, a contact surface that is in contact with a side surface of the colorimeter when the colorimeter is attached or detached and a friction coefficient μ1 between the contact surface and the side surface of the colorimeter is smaller than a friction coefficient μ2 between the housing of the carriage and the side surface of the colorimeter.

Disclosed are a friction and wear test system and a friction and wear test method. To reduce the error of measured friction coefficients, the friction and wear test system of the present disclosure includes a rotating shaft, a dynamic specimen mounting structure mounted on the rotating shaft, a first static specimen mounting structure, a first loading module for applying a preset loading force to the first static specimen during the test, and a second static specimen mounting structure arranged directly opposite to the first static specimen mounting structure in the axial direction of the rotating shaft. The second static specimen mounting structure is configured with a second loading module for applying a preset loading force pointing at the dynamic specimen to the second static specimen during the test, so as to at least partially counterbalance the force loaded on the dynamic specimen by the first static specimen during the test.

The invention relates to the technical field of friction coefficient testing, and provides a metal material high-temperature friction coefficient testing device which comprises a motion control system, a motion platform assembly, a heating system and a measuring system. The test piece made of a metal material and the sliding block are arranged on the motion platform assembly, and the sliding block is placed on the test piece; the heating system is used for heating and preserving heat of a test piece and a sliding block which are arranged on the motion platform assembly; the motion control system drives the motion platform assembly to drive the test piece to slide, so that the test piece slides relative to the sliding block; when the test piece and the sliding block slide relatively, the measuring system monitors data of force generated by the sliding block in real time through the force sensor, records a time-domain curve of the data and calculates the friction coefficient according to the time-domain curve. According to the scheme of the invention, the method can meet the temperature requirement of a metal material use environment, and can measure the static friction coefficient and the dynamic friction coefficient of the metal material in a high-temperature state.

The invention discloses a carrying system and photovoltaic preparation equipment. The carrying system comprises a manipulator, a detection module and a control module. The mechanical arm comprises a bearing part, the bearing part is provided with an open end, a closed end and a limiting piece, the open end and the closed end are oppositely arranged, and when a to-be-carried object is fed, the to-be-carried object enters the bearing part through the open end till making contact with the limiting piece; the first driving part drives the bearing part to move from the carrying starting point to the carrying ending point, so that the bearing part has displacement in the horizontal direction; the second driving part drives the bearing part to rotate around a rotating shaft, and the rotating shaft is perpendicular to the open end and / or the closed end; the detection device detects the acceleration of the to-be-carried object relative to the bearing part; the control module controls the first driving part and controls the second driving part according to the acceleration of the to-be-carried object relative to the bearing part, the mass of the to-be-carried object and the friction coefficient between the to-be-carried object and the contact face of the bearing part, so that the to-be-carried object slides reversely and returns to the position where the to-be-carried object makes contact with the limiting piece during feeding. The carrying efficiency is improved, and the position accuracy is improved.

The present invention discloses a design method for porous arrangement of wall blowing for boundary layer drag reduction, which relates to the field of flow control of the aerodynamic performance of aircraft, and includes: S1. Obtain the friction coefficient of the surface of the aircraft that needs drag reduction; S2. On the wall where the blowing holes need to be arranged, divide the arrangement baseline of the wall blowing holes along the flow direction. For any one baseline j , calculate the friction coefficient difference by extracting the friction coefficient on the baseline j and the given number of blowing holes; S3. Determine the friction coefficient corresponding to the j th blowing hole on the baseline i ; S4. Obtain the physical coordinates of each blowing hole on the baseline j ; S5. Repeat S2-S4 until the arrangement of the blowing holes on each baseline is completed, and obtain the wall blowing holes with non-uniform layout. The present invention provides a design method for porous arrangement of wall blowing for boundary layer drag reduction. Compared with the traditional method, it makes full use of the synergistic control effect of porous wall blowing, and the overall drag reduction effect is significantly improved.

The invention relates to the technical field of profile rolling, and particularly discloses a flat-rolling ultrathin aluminum alloy profile rolling device which comprises rolling racks, and a profile pretreatment unit is fixedly arranged between the front faces of the two rolling racks through bolts; sectional material rolling units are symmetrically arranged on the upper portion and the lower portion between the two rolling racks, and auxiliary supporting assemblies are arranged on the two sectional material rolling units. Through the composite structure design of the working roller, the rolling quality is improved from three aspects: the flat roller and the convexity roller are adapted to the thickness control requirements of profiles with different widths; the nano ceramic coating strengthens the wear resistance of the roller surface; by means of the micro-nano rib and pit structure, on one hand, the contact area of the roller and the profile is reduced, the friction coefficient is reduced, drawing marks or wrinkles of the profile are avoided, and on the other hand, the pits are used for storing lubricating oil and containing aluminum skimmings to protect the surface of the profile. And meanwhile, the servo electric cylinder is matched with the adjusting frame, so that the distance between the rollers can be accurately adjusted to adapt to rolling of profiles with different thicknesses, and the rolling precision is guaranteed.

The present invention relates to the technical field of superlubricant friction and wear, and particularly to a PEEK-based superlubricant composite material, a preparation method and an application, including: performing surface texturing treatment on a PEEK workpiece and removing the heat-affected zone around the surface texture of the PEEK workpiece; preparing a fluoropolymer coating on the surface of the PEEK workpiece to cover the surface texture of the PEEK workpiece; drying and sintering the PEEK workpiece coated with the fluoropolymer coating to obtain a PEEK-based superlubricant composite material; wherein, the lubricating medium of the PEEK-based superlubricant composite material is pure glycerol. Through the synergistic effect of the surface texturing technology and the fluoropolymer coating, the present invention gives full play to the lubricating effect of the coating and the texture storage function, enabling PEEK to achieve stable superlubrication in one step under an atmospheric environment. It solves the problem in the prior art that the high friction coefficient of PEEK material results in the inability of PEEK material to achieve long-life stable superlubrication.

To provide a cleaning device that can uniformly and efficiently remove dirt attached to a rotating body, and can prevent the occurrence of abnormal images including mainly vertical black streaks over a long period.SOLUTION: A cleaning device has cleaning means 22b that is in contact with a surface of a rotating body 22a to clean the surface of the rotating body 22a. The cleaning means 22b is a roller member and has a foam layer 224 in contact with the surface of the rotating body 22a, and the surface of the foam layer 224 has a coefficient of static friction of 0.5 or more, which is measured by the Euler belt method.SELECTED DRAWING: Figure 4

The application discloses spliced self-lubricating polyether ether ketone three-layer composite plate and a preparation method thereof. The spliced self-lubricating polyether ether ketone three-layer composite plate comprises, from bottom to top, a metal base layer, a copper powder layer and a spliced self-lubricating layer connected in sequence. The spliced self-lubricating layer is composed of a plurality of wear-resistant PEEK pieces with good wear resistance and friction-reducing PEEK pieces with good friction-reducing performance arranged alternately. The friction-reducing PEEK pieces are designed to be arranged at an angle of 30-60 degrees with the horizontal direction, i.e. the friction-reducing PEEK pieces are arranged in an inclined strip shape between the wear-resistant PEEK pieces with good wear resistance. The structure design can form a complete self-lubricating friction-reducing layer during reciprocating movement of the composite plate, reduces the friction coefficient of the plate and a friction pair, and finally improves the wear resistance of the material.

The present application relates to the technical field of decompression products, and in particular to a decompression ring and a method for determining the thickness of self-lubricating material thereof. The method comprises the following steps: determining the surface material of the fixed inner ring or the movable outer ring made of non-self-lubricating material; determining the friction coefficient between the self-lubricating material and the surface material; determining the dialing pressure, the dialing frequency and the expected service life according to historical user data; determining the wear rate according to the friction coefficient and the dialing pressure; determining the number of rotations according to the dialing frequency and the expected service life, and then determining the calculated thickness according to the number of rotations and the wear rate; obtaining the expected thickness, and determining the reference thickness according to the expected thickness and the calculated thickness; adjusting the reference thickness according to the gap between the self-lubricating material and the fixed inner ring or the movable outer ring and the user experience threshold, and determining the final thickness. The present application can reduce the size of the decompression ring while ensuring its service life and improving user experience.

The application discloses a sliding vane, a compressor and a processing technology of the sliding vane. The sliding vane comprises a body; and a roller mounting groove is arranged on the body, wherein the roller mounting groove is provided with an inner concave curved surface which is adapted to the roller, the inner concave curved surface is an optimal arc curved surface, and the opening of the inner concave curved surface is outward and upward. The roller mounting groove is designed in a targeted manner, the optimal arc is greater than one-half of a circle, and the opening direction is inclined at a certain angle, so that the relative position of the roller is fixed, the roller does not deviate and does not fall out during the operation of the compressor, the roller can be better accommodated and fixed, the sealing performance of the compressor during the operation is improved, the friction coefficient between the sliding vane and the piston roller is reduced, and the energy efficiency ratio is improved.

The method for evaluating the fracture mechanics performance of the water-soaked brittle solid material of the present application comprises the following steps: 1. A group of cuboid brittle solid material samples are prepared, and the samples are immersed in water. After the immersion is completed, the samples with different immersion times are selected for weighing, and then the samples with different water contents are selected; 2. The samples with different water contents in step 1 are selected, and the relationship curve between the uniaxial compression stress and strain of the brittle solid material samples and the initial density of the micro-defects of the samples under different water contents are measured; 3. The samples with different water contents in step 1 are selected, and the sliding friction coefficients of the brittle solid material samples with different water contents are determined; 4. The brittle solid samples containing cracks are prepared, and the fracture toughness of the brittle solid material with different water contents is measured; and 5. Based on the above steps, the fracture strength of the brittle solid material samples under the action of different water contents after being soaked in water is determined.

The invention discloses a production process of concave-convex texture artificial stone with an anti-skid function. The production process comprises the following steps: step 1, preparing raw materials; step 2, manufacturing and treating a mold; step 3, mixing and stirring; step 4, molding and preliminary curing; the method has the advantages that the specific concave-convex texture is constructed on the surface of the artificial stone, and the anti-skid particles with high hardness and large friction coefficient are added, so that the friction force between the stone surface and a human body or an object is obviously increased, and various concave-convex texture styles can be flexibly realized; comprising regular stripes, checks, raised grains or complex personalized patterns, can accurately simulate the appearance effects of various natural stones, meets the personalized requirements of different architectural decoration styles, selects high-strength materials as basic bonding materials, ensures that the artificial stone has good compressive strength, bending strength and wear resistance, reduces the maintenance cost, and is suitable for large-scale popularization and application. The service life is prolonged.

The invention relates to a shear box for measuring the sliding friction coefficient of loose soil, a measuring device and a test method thereof, the shear box comprises an upper box body and a lower box body which are arranged up and down, and an accommodating cavity for accommodating test soil is defined between the upper box body and the lower box body; wherein the butt joint ends of the upper box body and the lower box body can move relatively, and the two limiting rods penetrate through the upper box body in the first direction and are inserted into the lower box body; the clamping piece comprises a clamping block and a limiting piece connected with the clamping block, the upper box body is provided with an installation cavity for installing the limiting piece, the clamping block is located in the installation cavity, and the limiting rod is provided with a clamping groove corresponding to the clamping block so that locking and releasing of the limiting rod can be achieved. According to the shear box, the clamping blocks are matched with the clamping grooves in the limiting rods, so that the limiting rods are quickly assembled and disassembled between the upper box body and the lower box body, the problem that repeated screwing, disassembling and positioning are needed in a traditional shear box is solved, the operation efficiency is remarkably improved, and a sample is conveniently and quickly replaced or a device is conveniently and quickly adjusted in the experiment process.

The invention provides a device and a method for testing a sliding friction coefficient under a high-speed impact load, and relates to the technical field of sliding friction force testing. The device for testing the sliding friction coefficient under the high-speed impact load comprises an impact rod, an incident rod, a transmission rod and a compression-torsion coupling piece, strain sensors are attached to the incident bar and the transmission bar; one end of the pressure-torsion coupling piece is adhered to one end, far away from the impact rod, of the incident rod, a first to-be-tested material block is adhered to the other end of the pressure-torsion coupling piece, a second to-be-tested material block is adhered to the end part of the transmission rod, and the impact rod can impact the incident rod; the pressure-torsion coupling piece comprises two pressure plates and a plurality of inclined supporting rods, and the plurality of inclined supporting rods are arranged between the two pressure plates. And the technical effect of effective characterization capability of the dynamic friction behavior under the impact load is achieved.

In a railway vehicle, a brake control device controlling a first brake device that presses a friction material against a wheel and a second brake device not using the friction material includes: a wheel load estimation unit estimating a wheel load-based on a wheel speed and a brake force applied to the wheel by the friction material; a friction surface state quantity estimation unit estimating a current friction coefficient of the friction material from a state of a friction surface thereof based on the wheel load, the wheel speed, and a brake force command, and outputting a mirror-surfacing signal indicating the friction surface is in a mirror-surfaced state when the friction coefficient is less than a first threshold value; and a brake control unit controlling operations of the first and second brake devices based on the brake force command and presence or absence of the mirror-surfacing signal.

1. The name of the design product: friction coefficient instrument. 2. The use of the design product: the design product is used for the surface slipperiness and friction performance quality control of materials such as packaging, paint, paper, textile, rubber, plastic and metal. 3. The design points of the design product: in shape. 4. The picture or photo that best indicates the design points: perspective view. 5. Other circumstances that need to be explained: A part is transparent material.

To provide a carrying device capable of detecting a change in a surface state of a roller used for carrying a carrying object, even when the carrying object is long.SOLUTION: The platen roller 15 conveys the stencil sheet M while sandwiching the stencil sheet M between the platen roller 15 and the thermal head 13. The platen roller 15 can be brought into contact with and separated from the thermal head 13. The driven roller 17 is driven to rotate by the platen roller 15. The torque limiter 21 applies a predetermined load to the driven roller 17. The encoder 22 detects the rotation speed of the driven roller 17. The control unit drives the platen roller 15 in a state in which the platen roller 15 is separated from the thermal head 13, detects the friction coefficient of the platen roller 15 based on the rotation speed of the driven roller 17, to which the predetermined load is applied by the torque limiter 21, detected by the encoder 22, and determines the change in the state of the surface of the platen roller 15 based on the detected friction coefficient.SELECTED DRAWING: Figure 2

The application discloses a robot clamp grabbing optimization method and device, a terminal and a medium. The technical scheme provided by the application first determines the model and data of a workpiece to be grabbed through an image of the workpiece to be grabbed, utilizes a preset workpiece recognition model, wherein the workpiece data includes geometric structure parameters, surface material, weight and barycentric position, then determines the surface friction coefficient of the workpiece to be grabbed according to the surface material in the workpiece data, determines the target clamping force according to the surface friction coefficient and the weight, and combines a preset clamping force constraint relationship, determines the target clamping force according to the surface friction coefficient and the weight, combines a preset clamping force constraint relationship, determines the target clamping force, determines the target grabbing point in the workpiece to be grabbed according to the geometric structure parameters and the barycentric position, and finally generates a clamp control instruction according to the calculated optimal grabbing parameter, so that the target clamp grabs the workpiece to be grabbed according to the clamp control instruction, thereby improving the accuracy and stability of grabbing and improving the success rate of grabbing.

The invention relates to a surrounding rock and lining interface friction coefficient valuing method for engineering analysis, and belongs to the technical field of tunnel engineering. The method aims at solving the technical problems that an existing indoor direct shear test is limited in test object, poor in result practicability and time-consuming and labor-consuming in the process. According to the technical scheme, the method comprises the steps of drilling a rock sample from an engineering site, carrying out a concrete mix proportion test, quantifying the roughness of the rock sample through image processing and height measurement, carrying out a friction experiment to obtain a friction coefficient, and establishing a polynomial fitting equation of the roughness and the friction coefficient; and finally substituting the average roughness of the field surrounding rock into the equation to obtain the friction coefficient under the engineering scale. The method has the advantages that the pertinence is high, the operation is simple and convenient, the precision meets the engineering requirements, and the efficiency and the practicability of the friction coefficient value are effectively improved.

The utility model discloses a high-speed paper suction belt for a folder gluer assembly line, and belongs to the field of folder gluers. The device mainly comprises a pressing and holding assembly, the pressing and holding assembly comprises a supporting frame, a top plate is fixedly installed on the supporting frame, belt assemblies are arranged at the two ends, close to the top plate, of the supporting frame, each belt assembly comprises a fixing frame, a plurality of sets of belt wheels are rotationally connected to the fixing frames, and belt strips are arranged on the multiple sets of belt wheels. According to the high-speed paper suction belt for the folder gluer assembly line, the belt strip is provided with a silica gel material, so that the belt strip has good adhesion and wear resistance, the high-speed paper suction belt is suitable for being used for improving the surface friction coefficient of the paper suction belt and enhancing the stability of paper during high-speed operation, and the suction tube is arranged at the bottom of the belt strip, so that the paper suction efficiency is improved. The suction tube is arranged on the belt strip, so that the bottom of the belt strip has a certain adsorption effect under the mutual cooperation of the suction tube and the fan, materials on the belt strip can be adsorbed, and the situation that the materials are prone to shaking during transportation is avoided.