52 results about "Nonlinear elasticity" patented technology

The invention discloses a method and a device for simulating the mechanical property of a zirconium-tin-niobium alloy under an irradiation condition, and mainly aims to solve the problems of lack of microstructure simulation of the irradiated zirconium-tin-niobium alloy and high cost, long period and low safety coefficient of mechanical property inspection of the irradiated zirconium-tin-niobium alloy. Comprising the following steps: establishing a microstructure model of the zirconium-tin-niobium alloy by adopting a phase field method, and introducing a rate theoretical model of irradiation defect evolution into the model to obtain a microstructure evolution model of the zirconium-tin-niobium alloy under the irradiation condition; the defect concentration under the irradiation condition is determined based on the model; the zirconium element concentration and the niobium element concentration under the irradiation condition are obtained, and the nonlinear elastic energy density of the zirconium-tin-niobium alloy is determined based on the obtained concentration values; determining a total free energy density function of the zirconium-tin-niobium alloy based on the nonlinear elastic energy density, the defect concentration, the zirconium element concentration and the niobium element concentration of the zirconium-tin-niobium alloy under the irradiation condition; and performing derivation processing on the total free energy density function to obtain a target stress tensor component.

The invention provides a method and a device for evaluating the forming quality of a cold-formed steel roller, relates to the technical field of data processing, and aims at analyzing typical frequency band characteristics of monitoring data in the forming process of the roller on multiple scales and determining corresponding joint characteristics so as to carry out quality evaluation. The transient impact characteristic of the roller vibration signal can be accurately captured in the time domain, the main frequency component and the modulation sideband thereof are clearly separated in the frequency domain, and the method adapts to the complex working condition of the forming process. And on the premise that the nonlinear elastic characteristic of the roller is physically constrained, the unsteady-state characteristic corresponding to the roller quality degradation process is determined on the basis of Gaussian mixture distribution of combined characteristics, the internal mechanism of a complex system can be analyzed and explained in combination with the physical deformation of the roller, and the quality of the roller is improved. Different distributions and corresponding non-linear relationships of multi-sensor time sequence data are captured, and timely and accurate quality evaluation can be provided even if the data change slightly or the roller has potential faults.

The present invention discloses a solid-liquid coupling simulation method with surface tension effect based on the material point method, belonging to the fields of computer graphics and physics-based simulation. The system used in the simulation method includes solid model modeling, fluid model modeling, Level Set implicit surface construction, Marching Cubes display surface construction, surface particle resampling, and collision detection. The system simulates fluids and solids on the basis of the material point method, constructs Level Set to resample fluid surface particles, and adds surface tension to the fluid using the CSF model. Different background grids are used to simulate fluids and solids respectively to solve the inherent adhesion phenomenon during MPM solid-liquid coupling and achieve the slip contact effect during solid-liquid coupling. Finally, the coupling phenomenon of incompressible fluid with surface tension effect and nonlinear elastic solid is realized.

The application provides a method, system, medium and device for pipeline configuration in ocean current, which comprehensively considers the stratification effect of ocean current by establishing a stratified flow field, can accurately simulate the movement of fluid around the pipeline, and thus more truly reflects the interaction between the fluid and the pipeline. Meanwhile, the boundary source term is calculated according to the relationship between the fluid velocity on the surface of the pipeline and the displacement of the pipeline surface, so that the boundary source term can accurately represent the fluid reaction force caused by the movement of the pipeline surface. The nonlinear elastic deformation model of the pipeline under the deformation condition is constructed, which can well represent the stress tensor of the pipeline. Finally, the immersed boundary method is used to take the boundary source term as the pipeline surface force, which can handle the fluid and solid interaction problem under complex boundary conditions. Through iterative updating of the flow velocity and the displacement of the pipeline surface, the convergence of the pipeline elastic mechanics equation is obtained, which provides an important reference for the design, installation and maintenance of the pipeline configuration process.

The application discloses a rotor coupling dynamics calculation method of complex three-dimensional shape layout. A coordinate conversion relationship caused by a front protrusion / after-sweeping / downward-reversing configuration is established; nonlinear elastic deformation of elastic blades waving, oscillating and twisting and nonlinear coupling relationship among them are described; nonlinear motion caused by the complex three-dimensional shape layout is described based on the coordinate conversion relationship and the nonlinear coupling relationship; and the relationship among strain energy, kinetic energy and virtual work of external force of the rotor is established based on the Hamilton principle according to the description of the nonlinear motion, and a finite element method of a 15-degree-of-freedom beam element is used to establish a rotor dynamics equation. The application can effectively reflect the structural coupling characteristics and coupling degree of the waving-torsion direction caused by the front / rear sweep of the blade tip, effectively reflect the structural coupling characteristics and coupling degree of the oscillation-torsion direction caused by the upward / downward reversal of the blade tip, and effectively reflect the rotor dynamics characteristic behaviors caused by the three-dimensional shape of the blade.

The present application belongs to the technical field of bridge wind tunnel test device, and provides a kind of wind tunnel test device simulating nonlinear vibration of bridge structure, including rigid model, rigid rod, rigid circular arc suspension arm, linear tensile spring, nonlinear elastic element and light high-strength fine rope.Nonlinear elastic element can adopt cable structure, membrane structure, nonlinear tensile spring, mechanical super material or superstructure.By designing the nonlinear stiffness characteristics of nonlinear elastic element, the layout mode and the combination mode of linear tensile spring, various target nonlinear stiffness modes can be realized to carry out large amplitude vertical torsional coupled flutter test of bridge structure under nonlinear stiffness.In the process of large amplitude vibration of model, the center hanging point of nonlinear elastic element and linear tensile spring can always maintain vertical displacement and deformation, and the device can ensure stable stiffness, damping, mass and mass moment characteristics.

The invention discloses a subsea tunnel surrounding rock full life cycle test method based on a supergravity geotechnical centrifuge technology, which comprises the following steps: firstly, constructing a model box, carrying out scale simulation on a subsea tunnel and a surrounding rock structure thereof, then putting the model box into a vacuum box for saturation treatment, finally taking the model box out of the vacuum box, putting the model box into a supergravity geotechnical centrifuge, and testing the whole life cycle of the subsea tunnel surrounding rock. And the super-gravity geotechnical centrifuge is started to rotate, and the strain sensor collects the dependent variable of the rock stratum near the tunnel reduced-scale pipeline in real time, so that the nonlinear elastic deformation of the rock stratum in the full life cycle in the running process of the train track simulation mechanism is observed. The model box is constructed to simulate the subsea tunnel and the surrounding rock structure thereof, test analysis is performed based on the supergravity geotechnical centrifugal technology, the evolution process of damage of the subsea tunnel and the surrounding rock structure thereof is remarkably accelerated, the experimental period is shortened, and the change condition of the whole life cycle is rapidly tested and determined.

The utility model provides a buckling self-resetting damper which comprises an inner shear plate, a connecting plate, a stop block, a connecting support, an elastic buckling piece and two outer shear plates, and the two outer shear plates are symmetrically arranged on the two sides of the outer shear plates and the connecting plate; a friction plate is arranged between the internal shear plate and the external shear plate, two first stop holes are formed in the external shear plate, second stop holes corresponding to the two first stop holes respectively are formed in the internal shear plate, and stop blocks penetrate through the first stop holes and the second stop holes and are fixedly connected with the connecting support. The two ends of the elastic buckling piece are hinged to the two connecting supports respectively. And the connecting plate is fixedly connected with the two external shear plates. According to the scheme, the nonlinear elastic behavior shown by the elastic buckling piece which is pressed and buckled is used as a self-resetting mechanism of the damper, a part of energy dissipation capacity is provided with the assistance of a friction sliding energy dissipation mechanism, and therefore the expected self-resetting-energy dissipation mechanism is achieved.

The invention relates to the technical field of robot actuators, and particularly discloses an integrated joint module with torque sensing and energy self-recovery functions and a design method. The design method comprises the steps that a physical framework of the joint module is constructed; a nonlinear elastic torsion model and a dynamic friction model of the harmonic reducer are constructed, and torque is calculated and derived; calculating a physical sampling torque; fusing the derived torque and the physical sampling torque by adopting an adaptive Kalman filtering mode to obtain a final torque signal; an energy feedback model in a motor braking mode is constructed, and when the joint module decelerates or is dragged by external force, the instantaneous flow of recyclable electric energy is calculated in real time based on the energy feedback model; a super capacitor and a DC-DC converter are introduced for energy recovery; and when the joint module is started or enters an acceleration stage, the energy stored by the super capacitor is released to the direct current bus. Nonlinear transmission interference caused by a harmonic reducer can be effectively eliminated, and in-situ recovery and peak power assistance of braking kinetic energy can be achieved.

The invention discloses a method and a device for simulating the mechanical property of a zirconium-niobium alloy under an irradiation condition, relates to the technical field of data processing, and mainly aims to solve the problems of lack of microstructure simulation of the zirconium-niobium alloy after irradiation and high cost, long period and low safety coefficient of mechanical property inspection of the zirconium-niobium alloy. Comprising the following steps: establishing a microstructure model of the zirconium-niobium alloy by adopting a phase field method, and introducing a rate theoretical model of irradiation defect evolution into the model to obtain a microstructure evolution model of the zirconium-niobium alloy under the irradiation condition; determining the defect concentration under the irradiation condition based on the microstructure evolution model of the zirconium-niobium alloy; obtaining the zirconium element concentration in the zirconium-niobium alloy under the irradiation condition, and determining the nonlinear elastic energy density of the zirconium-niobium alloy based on the zirconium element concentration; determining a total free energy density function of the zirconium-niobium alloy based on the non-linear elastic energy density, the defect concentration and the zirconium element concentration of the zirconium-niobium alloy under the irradiation condition; and deriving the total free energy density function to obtain a target stress tensor component.

The invention provides a simulation method and device for simulating the nonlinear elastic behavior of stainless steel and a storage medium, and the method comprises the steps: obtaining the original stress-strain data of a stainless steel material through a test piece axial compression test; the original stress-strain data is processed to eliminate the influence of test errors, a corrected stress-strain curve is obtained, and the corrected stress-strain curve is used for representing the nonlinear elastic behavior of the material; in finite element analysis software, calling the corrected stress-strain curve to define a nonlinear elastic constitutive model of the material; and based on the defined nonlinear elastic constitutive model, performing axial compression strength simulation analysis on the stainless steel structure. And a nonlinear elastic constitutive model of the material is defined by using the corrected stress-strain curve, so that the purpose of improving the simulation precision of the elastic section of the stainless steel material is achieved.

The invention belongs to the technical field of bridge wind tunnel test devices, and provides a wind tunnel test device for simulating nonlinear vibration of a bridge structure, which comprises a rigid model, a rigid rod, a rigid arc suspension arm, a linear extension spring, a nonlinear elastic element and a light high-strength string. The nonlinear elastic element can adopt a cable structure, a membrane structure, a nonlinear extension spring, a mechanical metamaterial or a superstructure. Various target nonlinear rigidity modes can be realized by designing the nonlinear rigidity characteristics and the arrangement mode of the nonlinear elastic elements and the combination mode of the nonlinear elastic elements and the linear extension springs, so that a large-amplitude vertical torsion coupling flutter test under the nonlinear rigidity of a bridge structure can be carried out. In the large-amplitude vibration process of the model, the central lifting point of the nonlinear elastic element and the linear extension spring can always keep vertical displacement and deformation, and the device can ensure stable rigidity, damping, mass and mass moment characteristics.

The invention provides a method for analyzing the damage of a hidden part of a track structure after train derailment caused by an earthquake, and relates to the field of dynamic response analysis of track structures. The method comprises the following steps: establishing a track substructure model, sequentially establishing track substructures such as a steel rail, a fastener system, a track plate, a filling layer and a base plate from top to bottom, and introducing cohesion unit simulation between structural layers, according to the earthquake load simulation, earthquake waves are transmitted to the structural non-supporting point freedom degree through the structural supporting point freedom degree, and then the whole vehicle system is influenced. According to the method, the accuracy and the calculation efficiency of dynamic response analysis of a track structure under the earthquake action are remarkably improved by introducing an improved nonlinear elastic theory and a multi-point non-Hertz contact model and combining a modal superposition method and a multi-scale analysis method in consideration of a vehicle-track complex collision contact behavior after derailment.

To provide a printer device capable of preferably reducing fluctuation of a tension applied to a sheet.SOLUTION: A printer device according to an embodiment includes: a storage part that stores a sheet wound in a roll shape; a conveyance part that draws the sheet from the storage part and conveys the sheet; a printing part that performs printing on the sheet conveyed by the conveyance part; and a damper part that is provided between the storage part and the conveyance part, contacts with one surface side of the sheet conveyed by the conveyance part, energizes an elastic force to the sheet, and thereby, reduces a tension applied to the sheet due to conveyance of the conveyance part. The damper part has a non-linear elastic member and energizes the sheet by using the elastic force of the elastic member.SELECTED DRAWING: Figure 8

The invention discloses a simulation modeling method and device of a battery and a nonvolatile storage medium. The method comprises the following steps: acquiring modeling parameters of a target battery input based on a target account; based on the modeling parameters, adopting a gasket unit to model the sealing rubber strip in the target battery to obtain a first model; a target modeling model is selected to model the membrane electrode assembly in the target battery to obtain a second model, and the target modeling model comprises at least one of a gasket unit, a nonlinear elastomer foam material constitutive model, an elastomer model and a nonlinear elastomer material constitutive model; modeling a bipolar plate in the target battery to obtain a third model; and determining a simulation model of the target battery based on the first model, the second model and the third model. According to the invention, the technical problems of long calculation period and low efficiency caused by large simulation modeling calculation scale of the battery in the prior art are solved.

The present invention provides a method and device for evaluating the forming quality of cold-bent steel rollers, which relates to the field of data processing technology. The typical frequency band characteristics of the monitoring data of the roller forming process are analyzed at multiple scales, and the corresponding joint characteristics are determined to perform quality evaluation. The transient impact characteristics of the roller vibration signal can be accurately captured in the time domain, and the main frequency component and its modulation sideband can be clearly separated in the frequency domain to adapt to the complex working conditions of the forming process. Under the premise of physical constraints on the nonlinear elastic characteristics of the roller, the non-steady-state characteristics corresponding to the roller quality degradation process are determined based on the mixed Gaussian distribution of the joint characteristics. It can combine the physical deformation of the roller to analyze and explain the internal mechanism of the complex system, capture the different distributions and corresponding nonlinear relationships of the multi-sensor time series data, and provide timely and accurate quality evaluation even if there are slight changes in the data or there are potential faults in the roller.

The present invention proposes a multi-scale numerical simulation method for hydraulic fracturing cracks based on implicit level sets, comprising: modeling hydraulic fracturing cracks and constructing a linear elastic hydraulic fracturing model based on three-dimensional plane fractures; solving elastic fluid mechanics equations based on the linear elastic hydraulic fracturing model; solving nonlinear elastic fluid mechanics equations by converging elastic fluid mechanics equations to obtain the proximal asymptotic solution of the stable motion hydraulic fracturing cracks; and establishing a multi-scale numerical simulation system for hydraulic fracturing cracks based on implicit level sets to verify the asymptotic solution. Based on the construction of a linear elastic hydraulic fracturing model for three-dimensional plane fractures, the present invention proposes a multi-scale numerical simulation method for hydraulic fracturing cracks based on implicit level sets, adopts a fixed-point iteration method of the elastic fluid mechanics equations, and establishes a numerical simulation system. This system has practical significance for improving the ultimate recovery rate in the oil and gas well development domain, and can provide support for the subsequent efficient development of oil and gas wells.

The present invention relates to the field of aerospace technology, and in particular to a gust response analysis method considering large wing deformation, comprising the following steps: determining a coordinate system used for aircraft structural dynamics analysis and unsteady aerodynamic analysis; considering the aircraft wing as a nonlinear elastic component and the aircraft body as a rigid component, and constructing a full-aircraft structural dynamics model of the aircraft; determining an unsteady aerodynamic model based on the gust speed to which the aircraft is subjected, the unsteady aerodynamic model being used to represent the relationship between the aircraft motion state and the gust speed; combining the full-aircraft structural dynamics model with the unsteady aerodynamic model to establish a full-aircraft dynamics model including gust effects; solving the full-aircraft dynamics model including gust effects to obtain the gust response of the aircraft; the present invention can improve the accuracy of gust response analysis of changes in wing aerodynamic shape and structural stiffness.

The invention discloses a switch hand feeling multi-scale modeling method based on a physical information neural network, and the method comprises the steps: firstly building a one-dimensional nonlinear elastic damping partial differential equation PDE and an ordinary differential equation ODE which describe the overall deformation behavior of a key, and forming a hybrid PDE-ODE kinetic model; secondly, according to the dynamic model, designing a Bayesian physical information neural network B-PINN with an uncertainty quantification capability; and then the data sampling density is dynamically improved in a mutation region, training weight distribution is adjusted by adopting an event-driven strategy, and the adaptive training capability of the neural network B-PINN is enhanced. And finally, generating an elastic modulus and damping coefficient probability distribution map by using the trained network model, mapping the subjective hand feeling score of the user into a mechanical objective function, and inverting parameters. According to the method, the defects of poor generalization and insufficient physical consistency of a pure data driving method are overcome, and the reliability of switch design parameters is improved.

This invention discloses a method for preparing the padding structure in parametric elastic knitted fabrics, belonging to the field of knitted elastic fabric design in the textile industry. The invention involves: S1: selecting and matching the raw yarns for the knitting structure and the raw yarns for the padding to determine the performance indicators of the corresponding raw yarns; S2: designing the padding structure; S3: constructing a nonlinear elastic behavior model; S4: predicting the nonlinear elastic behavior; and S5: determining the design scheme. Based on parametric elastic knitting design and yarn selection, the mechanical behavior of elastic knitted fabrics can be controlled, providing an effective approach for the design and production of elastic knitted fabrics with controllable nonlinear elastic behavior to meet practical needs.

This invention provides a low-vibration floating platform mooring design method based on nonlinear elastic damping units. Nonlinear elastic damping units are arranged in series in the mooring chain between the floating platform and the anchor point. Each nonlinear elastic damping unit consists of a multi-stage progressive stiffness spring and a velocity-sensitive hydraulic damping system. The stiffness function of the multi-stage progressive stiffness spring is k(x), satisfying the requirement of exhibiting flexible characteristics at small tensile displacements and gradually increasing stiffness at large tensile displacements to achieve a nonlinear elastic response. The velocity-sensitive hydraulic damping system incorporates a variable throttling channel, and its damping function is c. p The damping force increases with increasing velocity, achieving velocity-sensitive damping characteristics. The overall mechanical response of the nonlinear elastic damping unit is described by the function F(x). This invention can effectively suppress large-amplitude vibrations of floating platforms, reduce mooring fatigue loads on marine energy platforms, and improve the platform's steady-state performance and safety.

The invention discloses a transformer insulation cushion block mechanical parameter identification method and system and a related device, and belongs to the technical field of power equipment state monitoring, and the method comprises the steps: building a viscoelastic model of an insulation cushion block; sine alternating periodic stress is applied to the insulation cushion block, and strain data in the loading process are collected; and identifying parameters of the viscoelastic model based on an improved gradient descent method. According to the method, high-precision identification of mechanical parameters of the insulating cushion block is realized by establishing a viscoelastic model containing a nonlinear elastic part and a viscous damping part and combining with an improved gradient descent algorithm.

The invention relates to the technical field of hydraulic engineering safety monitoring, and discloses an external river retaining wall displacement monitoring system, which comprises a deformation field modeling module, a deformation field modeling module, an external river retaining wall displacement monitoring module and an external river retaining wall displacement monitoring module, the nonlinear elastic mechanical model can simulate displacement, inclination and distortion of the retaining wall under the action of various external factors; and the data acquisition module is connected with the deformation field modeling module, the data acquisition module is used for arranging three sensors, and the three sensors are respectively used for acquiring original data of displacement, inclination and distortion of each monitoring point of the outer river retaining wall. Through optimization of sensor arrangement, weighted Kalman filtering data fusion and dynamic updating of the deformation field model, high precision, real-time performance and stability of the external river retaining wall displacement monitoring system are realized, and the ability of the system to adapt to complex environmental changes is significantly improved.

The utility model relates to the technical field of landing gear, concretely relates to a landing gear damping mechanism. It includes stand, crossbeam, wheel frame and sets up the damping component between stand and crossbeam, and the damping component is constituted by outer tube, piston rod, piston head, honeycomb aluminium energy absorption module group and disc spring bag etc. Honeycomb aluminium energy absorption module group is at least two layers along the axial direction and is equipped with deformation joint between layers, and honeycomb aluminium energy absorption module group, disc spring bag and piston rod are arranged in outer tube from top to bottom, and the conical force transmission rod of piston rod top inserts the central hole of honeycomb aluminium energy absorption module group and forms the conical surface cooperation. The landing gear adopts the "hydraulic damping-honeycomb aluminium-disc spring" compound damping structure, and through honeycomb aluminium graded energy absorption, disc spring nonlinear elasticity and friction damping, hydraulic damping medium energy dissipation, effectively solve the problem of traditional landing gear energy absorption efficiency low, high frequency vibration attenuation deficiency, heavy load impact load concentration etc., and is suitable for high frequency impact and concentrated load working condition, and the damping effect is good.

According to the pipeline configuration method, system, medium and equipment in the ocean current, the layered flow velocity field is established, the layering effect of the ocean current is comprehensively considered, movement of fluid around the pipeline can be accurately simulated, and therefore interaction between the fluid and the pipeline can be reflected more truly. Meanwhile, the boundary source item is calculated according to the relation between the pipeline surface fluid velocity and the pipeline surface displacement, so that the boundary source item can accurately represent the fluid reaction force caused by the pipeline surface movement. A nonlinear elastic deformation model of the pipeline under the deformation condition is constructed, and the stress tensor of the pipeline can be well represented. And finally, taking a boundary source item as a pipeline surface force by utilizing an immersed boundary method, so that the problem of interaction between fluid and solid under a complex boundary condition can be solved. The flow velocity and the pipeline surface displacement are updated through iteration until the pipeline elastic mechanical equation converges, and an important reference basis is provided for configuration processes such as design, installation and maintenance of the pipeline.

A wide temperature range nonlinear elastic and flexible alloy and a preparation method thereof, belonging to the field of metal materials. The wide temperature range nonlinear elastic and flexible alloy and the preparation method provided by the present invention solve the technical problem that the related technology cannot provide an alloy material with wide temperature range flexibility, so that the titanium alloy has nonlinear elastic deformation behavior, and the recoverable strain of the alloy is improved. The recoverable strain in the wide temperature range of ‑260 to 125°C is increased to 1.1% to 4%; at the same time, the titanium alloy has a nano-domain structure, and the interaction between the domain structures significantly reduces the temperature sensitivity of the alloy performance, so that the titanium alloy has excellent flexibility in a wide temperature range. The alloy prepared by this method conforms to the nonlinear elastic deformation relationship in a wide temperature range, has the characteristics of high flexibility, high tensile strength, low elastic modulus, and no brittle fracture, which has far-reaching significance for the wide application of metal materials in a wide temperature range.

The application discloses a voice coil winding tension feedback control device, which comprises a main body, a telescopic mechanism and a driving mechanism are installed on the main body, a mandrel module is detachably installed on the driving mechanism, and a tension feedback control assembly is installed on the telescopic mechanism. The tension feedback control assembly comprises a mounting frame, an adjustable buffer mechanism, a clamping mechanism and at least two wire wheels. The adjustable buffer mechanism is installed on the mounting frame, and a tension detection wheel is connected to the output end of the adjustable buffer mechanism. The application can realize high-precision constant tension winding through nonlinear elasticity and electromagnetic force composite adjustment, and can adaptively inhibit wide-band tension disturbance. Through electromechanical cooperative pre-pressing and electromagnetic instantaneous locking two-stage clamping, the application is fast, accurate and reliable, wire material impact and paint layer damage are avoided, a transition state is constructed through a pre-pressing front link, wire material surplus is actively absorbed, shaking is inhibited, and winding stability and wire arrangement flatness are improved.

The invention relates to the technical field of nonlinear dynamics, in particular to a compact energy collection device with time-varying potential energy. The area can adjust the potential energy form of the system and the effective frequency band of energy collection; meanwhile, the energy collecting device has a certain space compactness; the energy collecting device comprises a base used for supporting, a movable trolley and at least two elastic beams. When the energy collecting device is subjected to external mechanical excitation, the two elastic beams generate two-degree-of-freedom displacement; and the two groups of magnets at the left end and the right end interact with each other at respective degrees of freedom and generate vertical nonlinear elastic restoring force, so that the two elastic beams generate nonlinear displacement in the vertical direction. According to the design of the compact energy collecting device with the time-varying potential energy, the space occupied by the energy collecting device can be greatly saved. By changing the initial position of the trolley on the sliding track, the potential energy function of the system can be switched among a monostable mode, a bistable mode and a tristable mode.