425 results about "Axial compression" patented technology

The invention relates to the technical field of concrete structure repairing, in particular to a repairing system of a reinforced concrete column based on triple cooperative constraint, which comprises a core area concrete column formed by removing a failed concrete protection layer from a rusted reinforced concrete column; the longitudinal bars are arranged on the peripheral side of the core area concrete column; the four-corner star-shaped stirrups are hooped on the outer side of the core area concrete column at intervals in the axial direction of the core area concrete column and are fixed to the longitudinal bars; the anti-stress pieces are arranged at the four corners of the core area concrete column and fixedly connected with the four corner ends of the four-corner star-shaped stirrups; and the FRP grid-ECC composite sandwich structure is arranged on the outer side of the core area concrete column. According to the method, through a material performance complementation and interface stress coordination mechanism, the purpose of multi-target collaborative optimization of axial compression-bending shear coupling bearing capacity reconstruction, interface durability improvement, secondary corrosion inhibition and the like of the repaired concrete column is achieved. The invention further correspondingly discloses a construction method of the repairing system.

A filter arrangement has a first body member with a first axial front surface and a first radial sealing surface, a second body member with a second axial front surface and a second radial sealing surface, a contact portion and an elastic contact element. The first and second body members complementarily couple together with a connecting device. In a coupled state, the contact portion and the elastic contact element are axially compressed between the first and second axial front surface. The second radial sealing surface has a groove housing a first sealing element. When brought into the coupled state, the first radial sealing surface at least partially covers the groove of the second radial sealing surface before the contact portion and elastic contact element are at least partially axially compressed between the first and second axial front surface. When coupled, the first radial sealing surface completely covering the groove.

The invention relates to the field of concrete testing, in particular to an eccentric compression test device and method for an FRP rib concrete column. Comprising a control system and a spring integration device, the spring integration device comprises a cover plate, a force sensor and a plurality of spring devices, the spring devices are detachably connected with the cover plate, the plurality of spring devices are arranged in an array, and the control system can perform pressure distribution adjustment on each spring device to realize an eccentric loading test on the FRP reinforced concrete column. The spring integrated device disclosed by the invention can convert the axial compression effect of a conventional axial press actuator into any required eccentric loading mode, so that the implementation of a complex eccentric loading working condition is ensured, the safety of an eccentric loading test is greatly enhanced, and the stability of the eccentric loading test is improved by accurately adjusting the rigidity in the spring device. And fine adjustment of eccentric force can be realized, so that the test precision under various complex eccentric loading test working conditions is improved.

Hemostatic springs and hemostatic seals comprising hemostatic springs facilitate introducing a surgical device into the vasculature of a patient during a surgical procedure. Each hemostatic spring comprises a radial array of spring segments positioned on a circular path about a central axis. Each hemostatic seal is configured to reduce an axial length of the hemostatic spring to constrict the radial array of spring segments to reduce a cross-sectional area of the central passage. Methods include axially inserting the surgical device into the hemostatic seal while compression from the hemostatic seal minimizes fluid leakage. Methods can further include reducing a frictional force of inserting the device into the hemostatic seal by reducing the axial compression to dilate the hemostatic spring.

A coupling assembly for coupling a rod to a bone anchoring element, including a receiving part having first and second ends, a recess at the first end for the rod, and an accommodation space for a head of the bone anchoring element, the accommodation space having an opening at the second end to permit insertion of the head into the receiving part, a retainer element configured to be arranged at least partially in the accommodation space and to hold at least part of the head, and a spring element configured to be arranged at least partially in the accommodation space and to be compressed in an axial direction. The retainer element and the spring element are separate parts. When the retainer element and the spring element are in the accommodation space of the receiving part in a first position, the spring element extends into the recess of the receiving part.

The invention provides a gear crack rigidity calculation and system vibration coupling solution method considering slice coupling, which comprises the following steps of: calculating bending rigidity, shearing rigidity and axial compression rigidity of slice gear teeth by adopting a slicing method based on gear tooth number, modulus and gear pair dynamic meshing force to obtain gear tooth rigidity of the slice gear teeth; according to whether the gear has cracks or not, slice coupling rigidities in the healthy state and the crack state of the gear are calculated in combination with the gear tooth rigidities of slice gear teeth; calculating the crack-containing gear time-varying meshing stiffness of a single gear pair by combining the contact stiffness and the matrix stiffness of the gear; based on the outer diameter, the inner diameter and the number of rolling bodies of the ball bearing, the bearing supporting force is calculated by combining the dynamic load borne by the bearing; and according to the time-varying meshing stiffness of the crack-containing gear of the single gear pair and the bearing supporting force, a gear-bearing-coupling system kinetic equation is constructed, and the vibration response of the gear-bearing-coupling system is solved. The method can provide reference for early fault diagnosis of the wind turbine generator gearbox.

A multi-axial spine testing system includes a physiological motion unit (PMU); a uni-axial test frame having an input; and a fixture configured to be attached to the test frame and facilitates a plurality of primary motions of one or more of the PMU and the fixture. The plurality of primary motions includes a linear motion of the input and a rotational movement of an output. The fixture has an upper assembly directly or indirectly coupled to the input. The upper assembly transfers the linear motion (Tz) of the actuator to the rotational movement (Rx) of the output. The upper assembly and lower assembly apply a bending moment (MX) and an axial compression (Fz) to the PMU. An external transducer collects data related to or generated by at least the plurality of primary motions. The fixture simultaneously provides the bending motion and axial compression to the PMU.

The invention discloses a biaxial test device, comprising: a bracket, a container, a sample setting assembly and a press, etc. Before use, the sample is installed between two limit plates. On the basis of applying confining pressure, the press is started, and the pressure rod moves vertically downward and applies a vertical downward load to the sample. When the sample is subjected to the vertical downward load, axial compression and radial deformation will occur. At this time, the radial deformation of the sample on both sides of the limit plates is limited, and expansion occurs on both sides without the limit plates. Subsequently, under the joint action of the confining pressure and the limit plates, the sample undergoes plane strain. Since the container and the limit plates are both in a transparent state, the side section state of the sample when plane strain occurs can be well observed. At the same time, the multiphase mixed fluid in the mixing container penetrates into the rock sample inside the sample and flows out through an output pipeline and is tested and analyzed by external equipment, so that the potential influence of multiphase seepage on the mechanical behavior of rock mass can be studied under plane strain conditions.

The invention relates to the field of steel member engineering, in particular to a high-strength steel combined multi-chamber box-section bent steel member and a manufacturing method thereof, and the manufacturing method comprises the following specific steps: S1, obtaining the design form of the steel member; s2, preparing an outer side chamber of the steel member; s3, prestress is applied to the outer side chamber in the axial direction of the outer side chamber so that the outer side chamber can be bent to a first form, a first eccentric value of the first form is obtained, and the first eccentric value is larger than the designed eccentric value; s4, top pressure towards the inner side of the bend is applied to the first form to a second form, the second form is in a pre-tightening state, a second eccentric value of the second form is obtained, and the second eccentric value is smaller than the designed eccentric value; s5, the outer side chamber is kept in the second form, and the matched inner side chamber is welded to obtain the steel member; and S6, after the force is unloaded, the inner side chamber is subjected to pre-tensile stress, the outer side chamber is subjected to pre-compressive stress, and the steel member is obtained. Pre-tensile stress is applied to the inner side of the steel member, pre-compressive stress is applied to the outer side of the steel member, and therefore the axial compression buckling ultimate load of the bent steel member is increased.

The invention discloses a torsional shear mechanical property testing device and method for a hollow cylinder structure, and belongs to the technical field of mechanical structure testing. The device comprises an axial driving mechanism, a radial driving mechanism and a fixed supporting mechanism. The axial driving mechanism is connected with the axial actuating pressure plate through an actuating main shaft; the radial driving mechanism comprises a radial driving mandrel of an inverted conical structure and a driving sliding plate matched with the radial driving mandrel, and axial movement of the main shaft is converted into radial expansion movement through conical face fit. The fixed supporting mechanism is a closed supporting system composed of an outer sleeve, an upper cover plate and a base. Through the unique inverted conical structure design, independent or synchronous application of axial compression, radial expansion and torsional shear loads can be achieved, and the complex stress working condition is effectively simulated. The device has the advantages of being stable in structure, high in testing precision, easy and convenient to operate and the like, meanwhile, equipment universality and maintenance convenience are remarkably improved through the replaceable design of the driving sliding plate, and the device is suitable for mechanical property testing of various hollow cylindrical structural parts.

The utility model discloses a dynamic axial compression column, and relates to the field of compression columns. The dynamic axial compression column comprises a heat preservation jacket, a piston plate, a support and a measuring rod, the heat preservation jacket is provided with a compression cavity with an opening in the upper end, and the heat preservation jacket is provided with an interlayer arranged around the compression cavity; the measuring rod and the support are slidably arranged. Circulating liquid for heat exchange circulates through the first inlet, the interlayer and the first outlet on the heat preservation jacket, so that filler in the compression cavity is stabilized at an expected temperature, and the consistency of filler column efficiency is ensured; the piston plate axially compresses the filler, the measuring rod correspondingly moves along with the piston plate, the filling height is correspondingly measured according to the movement of the measuring rod, column filling is stopped when the required length is reached, and it is guaranteed that the filling heights of the materials are the same and consistent every time, so that the column efficiency is accurately calculated; according to the utility model, the use requirements of filler filling height measurement and filler temperature control can be met, and the column efficiency and the column temperature are easier to control.

The invention discloses a method and a system for predicting the axial pressure stable bearing capacity of a trussed column by considering the influence of initial stress and creep, belongs to the technical field of trussed mixed structures, and solves the problem of low precision of predicting the axial pressure stable bearing capacity of the trussed column due to the fact that the influence of initial stress and creep is not considered. The method comprises the steps of determining basic parameters, considering the influence of shear deformation of the trussed column on initial stress, considering the influence of shear deformation of the trussed column on creep, calculating a stability coefficient, calculating the stable bearing capacity of the trussed column and the like. According to the model, an equilibrium differential equation is established based on the mechanics principle, mathematical calculation and derivation are carried out by applying the stability theory, and the influence of shear deformation, initial stress and creep on the axial pressure stable bearing capacity of the truss type column is comprehensively considered, so that the stable bearing capacity prediction method of the truss type column is provided. The method is suitable for predicting the axial pressure stable bearing capacity influenced by the initial stress and creep of the trussed column.

The invention discloses a pull rivet connecting piece and a lantern ring preparation method and application thereof, the pull rivet connecting piece comprises a pull rivet and a lantern ring, and a preformed directional deformation protrusion is arranged on the cylinder wall of the lantern ring and located in a preset bulging deformation area. In the rivet pulling process, the directional deformation protrusion preferentially generates radial plastic deformation when being axially compressed, so that a drum-shaped locking structure which is accurate in position and uniform in shape is formed, and the lantern ring is integrally formed through a local plastic deformation process and can be prepared through an internal reaming method or an external die assembly extrusion method. According to the lantern ring, it can be ensured that radial plastic deformation is evenly spread in the circumferential direction of the lantern ring through the directional deformation protrusions designed through the pre-forming structure, controllability and predictability of the deformation process are greatly improved, consistency, reliability and convenience of pull-rivet connection are kept through the design, the tensile strength and the shear strength of connection are remarkably improved, and the service life of the lantern ring is prolonged. The method is suitable for occasions with high reliability requirements.

A threaded connection for pipe in which the axial distance between the box intermediate shoulder surface and the box end shoulder surface of the box before make-up, LB, is larger than the axial distance between the pin intermediate shoulder surface and the pin end shoulder surface of the pin before make-up, LP, such that, upon completion of make-up, the pin and box intermediate shoulder surfaces and are in contact and function as torque shoulders, while the pin and box end shoulder surfaces are in light (or no) contact. The difference between the axial distances, (LB−LP), is such that, when the pin and box are made up and upon application of an axial compressive load, the pin and box are slightly axially compressed by the compressive load and the pin end shoulder surface comes into pressure contact with the box end shoulder surface to bear part of the compressive load.

The utility model belongs to the technical field of composite material structure test, and discloses an axial compression test fixture, which comprises a base, two side support pieces, a first clamping assembly and an anti-instability assembly, the two side support pieces are oppositely arranged on the base, a composite material is arranged between the two side support pieces, and the anti-instability assembly comprises two first anti-instability pieces and two second anti-instability pieces. Each first anti-instability piece comprises two separated first abutting parts, the distance between the two first abutting parts is larger than the damage range of the side face of the composite material, the two first anti-instability pieces are arranged on the two sides, in the second direction, of the composite material and close to the impacted side face of the composite material, and the second anti-instability pieces correspond to the first anti-instability pieces in a spaced mode; the first anti-instability piece and the second anti-instability piece are fixed to the two side supporting pieces respectively. The first clamping assembly can clamp the top of the composite material. The axial compression test clamp can be used for clamping a composite material subjected to side impact, and the problem that the accuracy of compression test data obtained after the composite material is subjected to side impact is not high is solved.

The invention provides a concrete normal section reinforcement design method and system, electronic equipment and a storage medium. The method comprises the following steps: establishing a section stress model containing multi-layer reinforcement strain distribution based on plane section assumption; the stress state of the whole process of the section from axle center compression to axle center tension is simulated by setting strain proportion parameters of the strain of the outermost reinforcing steel bar on the tension side and the limit pressure strain of the concrete; aiming at a plurality of set strain state control points, calculating stress of each steel bar layer position, contribution of the stress to axial force and bending moment and contribution of the stress to a concrete compression area; and based on the section static balance condition, the optimal reinforcement area meeting the design load requirement is determined through iterative calculation, and the configuration constraint of multiple layers of steel bars is considered in the iterative calculation. The method overcomes the defects that a traditional method overestimates the effect of the pressed steel bars and ignores the strain difference of multiple layers of steel bars, and the accuracy and safety of reinforcement design of high-performance concrete structures such as nuclear islands are remarkably improved.

The invention provides a rusted reinforced concrete column reinforced by FRP bar-net combination and a reinforcing method. The rusted reinforced concrete column comprises a concrete column body, and the concrete column body is provided with a to-be-reinforced part and rusted steel bars exposed after a concrete protection layer of the to-be-reinforced part is chiseled away; the FRP rib-net combination layer is formed by bonding FRP ribs and FRP grids, is wound on the outer side of the concrete column core area after the concrete protection layer is chiseled away, and provides longitudinal reinforcement and transverse constraint so as to reinforce internal concrete of the to-be-reinforced part; the fixing pieces are used for fixing the FRP rib-net combination layer; the inner side and the outer side of the FRP rib-net combination layer are filled with the ultra-high performance concrete, so that the FRP rib-net combination layer is bonded with the reinforced concrete column, the chiseled concrete protection layer is repaired, and the section of the concrete column is restored to the original size. According to the reinforced structure, the strength and deformation capacity of the internal concrete can be improved, the axial compression capacity, the bending resistance and the shear resistance of the rusted reinforced concrete column are improved, and the durability of the reinforced concrete column is improved.

The invention discloses a rock dynamic pressure-torsion experimental device and method based on a Hopkinson pressure bar, and belongs to the technical field of rock mechanics dynamic testing. The device mainly comprises a split Hopkinson pressure bar system and a spiral conversion mechanism, wherein the spiral conversion mechanism consists of a spiral (4) and a screw sleeve (5) which are meshed with each other; the screw (4) is fixedly connected with the incident rod (2), the screw sleeve (5) is fixedly connected with one end of a cylindrical rock sample (6), and the other end of the sample is fixedly connected with the transmission rod (7). The core is that the lead angle of the screw pair is greater than the equivalent friction angle of the screw pair under the impact load, so that the screw pair is ensured to be non-self-locked; and the sample (6) is of a hollow thin-wall cylinder structure. The method comprises the following steps: driving the spiral (4) to advance by utilizing axial stress waves generated by the split Hopkinson pressure bar, and driving the hollow sample to rotate by the screw sleeve in a forced constraint state, so as to synchronously apply dynamic axial compression and torsional shear combined load.

The invention provides a method and system for predicting the axial compression bearing capacity of a hollow sandwich concrete-filled steel tube short column, and the method comprises the steps: collecting the working parameter data of the hollow sandwich concrete-filled steel tube short column, and carrying out the normalization processing of the data; establishing an LM algorithm theoretical prediction model based on the original data, dividing the normalized data into a training set and a test set, and training the prediction model based on the training set to obtain an optimal hyper-parameter; and after the optimal parameter is determined, evaluating the model performance by using the test set. According to the technical scheme, through a data driving method and in combination with a BP neural network algorithm, accurate prediction of the axial compression bearing capacity of the concrete filled steel tube short column with the hollow interlayer is achieved. The scheme has the specific steps of parameter collection, preprocessing, model establishment and training, performance evaluation and technical effect analysis, and provides beneficial reference for solving similar problems.

The invention provides an anal fistula scratching device, and relates to the field of medical instruments. The anal fistula curettage device comprises an outer sleeve, the outer sleeve comprises a flexible conduction part and a curettage execution part which are connected with each other, an elastic strip of the curettage execution part is fixed between a flow guide part and a probe, a pull line is installed on the probe, one end of the pull line is located in a drainage groove of the flow guide part, and the other end of the pull line is connected with the flexible conduction part. The head part of the probe is fixedly provided with an elastic thread for penetrating into a fistula; according to the anal fistula scratching device, through cooperation of guiding of the elastic thread and the flexible conduction part, the elastic thread is used for guiding along the fistula path in advance, in combination with self-adaptive deformation of the flexible conduction part, damage-free accurate entering of the device is achieved, the spiral gradually-changing elastic strip can adjust the diameter in a self-adaptive mode, and a conical shape is formed through axial compression of the spiral radius decreasing structure; continuous diameter adaptation of the fistula is achieved, and the problem that an existing fistula with a fixed size is difficult to be compatible with fistula with different thicknesses is solved.

The invention relates to an axial compression spiral oil press. According to the technology provided by the invention, the original radial compression that the outer diameter of the main shaft outer sleeve is changed from thin to thick to change the volume is changed into the same outer diameter of the main shaft outer sleeve from beginning to end. And axial compression is adopted. Therefore, rotation friction resistance is greatly reduced, matching power can be saved by 40%, extrusion of oil residues is reduced due to the fact that axial compression is changed, and the phenomenon of paste squeezing is avoided. And labor is saved when the shaft is pulled outwards.

Protection of tubulars from premature wear in the mid-body section due to highly curved wellbores, including bowing from high axial compressive loads, or gravity induced bowing in a horizontal section of the wellbore is disclosed. It includes a method of installing a strong, wear resistant, fully encircling steel band around the midbody region of tubular joints on new and worn tubulars. Further, it does so without degrading the metallurgy or microstructure of the pipe body yet attaches the protective band with such high clamping force that it is unlikely to slip even under the most extreme service conditions. In addition, the circumferential integrity of the pipe band makes it even less likely to ever break off. A protective band includes a wear resistant hard banding weld overlay installed around the circumference of the protective band.

A calculation method for the axial compressive bearing capacity of a concrete-filled steel tubular short column, and an expression for the unified axial compressive bearing capacity of circular, square, and square concrete-filled steel tubular short columns with rounded corners is established. Among them, represents MCF ; represents the cross-sectional area of concrete in the concrete-filled steel tubular section; represents the cross-sectional area of the steel tube in the concrete-filled steel tubular section; CF is the confinement effect coefficient. The present invention is used for calculating the axial compressive bearing capacity of three types of concrete-filled steel tubular short columns, namely square, circular, and square with rounded corners. The calculation expression realizes the unification of, and the bearing capacity expression established based on the mature and general steel and concrete yield criteria has a clear concept and also conforms to the cross-sectional change law. Moreover, the bearing capacity calculation formula is not limited by the material strength and is applicable to the calculation of the axial compressive bearing capacity of various concrete-filled steel tubular short columns.

The application relates to a pressure-reducing well pressure-bearing backfilling and plugging device and method, which adopts a pressure-reducing well pressure-bearing backfilling and plugging device and a plugging process of filling materials in stages. First, an axial compression rubber sealing ring is used to make the rubber sealing ring radially expand and tightly contact with the inner wall of a well pipe to form a sealing structure, then the sealing structure is used to control the water body pressure and flow trend in the well to form a water isolation section, and a pressure pump of a filling material function module is used to pump the first filling material into the space below the sealing structure in the well pipe through the steel pipe to complete the first filling material pumping; after the first filling material solidification is completed, the second filling material is poured into the space above the sealing structure in the well pipe, and after the second filling solidification is completed, the backfilling and plugging complete the second filling material pumping. Through the characteristics that the rubber ring is more compact after being radially extruded and deformed, the rubber ring and the pressure-reducing well wall are tightly compacted, so that the water isolation and sealing effects are achieved.

The invention discloses a self-resetting damper based on mechanical metamaterial axial pressure driving transverse cooperative instability. The damper is composed of metamaterial units arranged periodically, and each unit comprises inner left / right arc-shaped beams with opposite concave surfaces, outer left / right arc-shaped beams with opposite convex surfaces, inner / outer upper and lower fixing plates, a vertical supporting beam and left / right transverse connecting beams. The end parts of the inner and outer left / right arc-shaped beams are connected with inner / outer upper and lower fixing plates which are arranged in parallel; the middle of the vertical support beam is connected with the inner upper-lower fixing plate; the inner and outer arc-shaped beams are connected through left / right transverse connecting beams. The outer beam is bent inwards under shaft pressure, and the inner beam is driven to move inwards cooperatively to generate jumping instability. The multiple units are connected in series, and energy is consumed through continuous instability. The damper can be made of steel or a carbon fiber composite material, and the strength, rigidity and energy consumption characteristics can be customized by adjusting the geometric parameters of the arc-shaped beam and the topological configuration of the unit. In the deformation process, all components are kept in an elastic state, and the excellent self-resetting capacity is achieved.

Systems and devices disclosed herein are for catheter tips that include a support frame. The support frame may include a longitudinal axis, a collapsed delivery configuration, and an expanded deployment configuration. The support frame may include a collapsed inner diameter in the collapsed delivery configuration and a larger expanded inner diameter in the expanded deployed configuration when the support frame is placed in an axially compressed state. In some examples, the support frame may include one or more shaped ridge members extending along a longitudinal axis and a plurality of ribs extending from the one or more shaped ridge members. In some examples, the support frame may include a connector rib and a plurality of offset ribs extending from the connector rib. One or more connector members may connect respective ones of the offset ribs. In some examples, the support frame may include struts forming a grid structure.

The utility model discloses a universal adjustable power head which comprises an input shaft seat, a middle transmission seat, an output shaft seat, an input shaft, a middle shaft, an output shaft and bevel gear pairs arranged between the input shaft and the middle shaft and between the middle shaft and the output shaft. A mounting hole is formed in the middle transmission seat, a locking block is correspondingly arranged in the middle transmission seat, the locking block is connected with the output shaft seat through a bolt and axially presses the middle transmission seat and the output shaft seat to realize rotation stopping and limiting, and a circle of limiting teeth are arranged on the peripheral wall of the locking block; at least one radial rotation stopping assembly is arranged at the position, corresponding to the limiting teeth, of the mounting hole, each radial rotation stopping assembly comprises a radial through hole formed in the inner wall of the mounting hole and a pushing rod in threaded connection with the interior of the radial through hole, and the inner end of the pushing rod at least indirectly abuts against the limiting teeth in the radial direction. According to the structure, angle locking is reliable, axial pressing locking and radial abutting rotation stopping are achieved, locking is reliable and stable, and slipping and disengaging are not prone to occurring.

The utility model discloses a kind of test device and test system of elastic bearing mechanical property, belong to elastic bearing performance test technical field, for solving the test device structure of elastic bearing mechanical property Complex, bulky, high cost and the problem of cumbersome test process. The test device of elastic bearing mechanical property of the utility model, including mounting, bending moment loading unit and axial compression unit;The two ends of mounting are used to respectively connect the inner ring end of two elastic bearings;Bending moment loading unit includes pivot, pivot's axis line and the axis line of two elastic bearings vertical intersection, and one end of pivot is fixedly connected with mounting;Axial compression unit is used to exert bidirectional axial static compression load to the outer ring end of two elastic bearings. The test device and test system of the utility model reduce the complexity and cost of test device and test system, improve the reliability and test efficiency of test device.

The present application belongs to the technical field of structural strength analysis, and particularly relates to a strength analysis method for a variable gradient composite material wall panel, the strength analysis method comprising: solving the shear stress and compression stress of the variable gradient composite material wall panel based on the external load and structural parameters of the variable gradient composite material wall panel; calculating the allowable shear stress, allowable axial compression stress, and allowable bending stress based on the structural parameters; calculating the safety margin through the shear stress, the compression stress, the allowable shear stress, the allowable axial compression stress, and the allowable bending stress; the iterative safety margin is 0; and the stability strength design of the trapezoidal composite material wall panel with a variable gradient of the rudder surface can be performed, and finally the lightest wall panel structural parameters that meet the constraint conditions are obtained.