29 results about "Impact stress" patented technology

The invention provides a time domain and frequency domain combined impact resistance analysis method and device for a ship stern tube, and the method comprises the steps: building geometric models of all parts in the stern tube through three-dimensional modeling software according to an actual engineering drawing of the stern tube, carrying out virtual assembly on the geometric model of each component according to the actual assembly relation of each component to obtain a geometric model of the tail shaft tube; importing the geometric model of the tail shaft tube into finite element software, endowing each component with material attributes, and carrying out grid division on the geometric model by adopting an overall network size control method; and performing static analysis on the geometric model after grid division to obtain static working stress, performing dynamic analysis on the geometric model after grid division to obtain dynamic impact stress, and synthesizing the static working stress and the dynamic impact stress into total stress. According to the method, time domain and frequency domain combined shock resistance response calculation is carried out for the tail shaft tube as a core component of the ship propulsion system, and the accuracy of shock resistance response calculation is improved.

The utility model relates to the technical field of composite boards, and discloses a lightweight composite board for railway vehicles, which comprises a board component, a buffer component and a mounting component, the buffer component and the mounting component are mounted on the board component, and a fastening component is mounted between the buffer component and the mounting component. The buffer plate in the composite plate is fixedly mounted on the reinforcing layer through the first fixing screws, impact stress is conducted to the buffer plate through the fixing plate sleeve when the composite plate is collided by an external object, and an effective buffer effect is achieved through the buffer groove formed in the buffer plate; reinforcing ribs fixedly installed between the buffering plate and the reinforcing layer can reduce the weight and guarantee the strength of the buffering plate and the reinforcing layer, and before the composite plate is installed, a second fixing screw can be rotated to enable a fixing nut to move in the direction close to the second fixing screw under the action of thread meshing; and then the pressing plate is extruded, so that all parts in the plate assembly and the buffer plate are tightly attached to each other, and the problem that the plate falls off due to the fact that the adhesion layer loses efficacy after long-time use is solved.

A hoisting plate is fixedly connected with a boss through a net plate to form a hoisting frame, the two hoisting frames are fixedly connected together through two bridge frames to form the damping frame, the hoisting plate, the bridge frames, a supporting table, the boss and the net plate are all made of Q355B steel, the thickness of the supporting table is 20 mm, the thickness of the supporting table is 20 mm, and the thickness of the boss is 20 mm. The thickness of the hoisting plate is 8mm, the thickness of the net plate is 6mm, and the thicknesses of the bridge frame and other plates are 5mm; the net plate and the hoisting plate are provided with cross-shaped reinforcing ribs with the width of 5 mm and the height of 8 mm, and triangular reinforcing ribs with the thickness of 5 mm are arranged on the rack main body; lightening holes are formed in a web plate of the screen plate; the boss is matched with the supporting table in a convex-concave structure, and the polyurethane pouring layer is filled in a convex-concave gap between the boss and the supporting table to form an anti-falling structure. The vibration isolator can effectively reduce impact stress, and has the characteristics of good vibration isolation effect, irradiation resistance, corrosion resistance, light weight, high strength and the like.

The utility model belongs to the technical field of pipeline elbows, and particularly relates to a high-pressure movable elbow with a high buffering function, which comprises an elbow pipe, an end cover, a movable plug, a sliding rod and a buffering spring, a buffering pipe is integrally arranged on the outer side of the bending part of the elbow pipe, the movable plug is arranged in the buffering pipe in a sliding manner, and the sliding rod on the movable plug is inserted on the end cover in a sliding manner. The end cover is in threaded connection with the buffer tube, and a buffer spring is arranged on the sliding rod between the end cover and the movable plug. According to the utility model, the buffer pipe is arranged at the bending position of the bent pipe, and the buffer pipe and the movable plug in the buffer pipe are used for effectively buffering pipeline impact caused by a water hammer phenomenon, so that the influence of impact stress on the bent pipe is reduced, the service life of the bent pipe is prolonged, and the stable use of the bent pipe is ensured; and meanwhile, by adjusting the compression amount of the buffer spring, the buffer sensitivity of the impact stress in the elbow can be debugged, so that different use requirements can be met, the application range is expanded, and the use convenience is improved.

This utility model discloses a wear-resistant reinforcing layer structure for rubber products, comprising a rubber base layer, an elastic buffer intermediate layer and a wear-resistant top layer sequentially disposed above the rubber base layer. The Shore hardness of the elastic buffer intermediate layer is lower than that of the wear-resistant top layer but higher than that of the rubber base layer. This utility model achieves initial wear resistance through the wear-resistant layer, while simultaneously providing a sacrificial lubrication layer and hemispherical wear-resistant protrusions on the wear-resistant layer to form a dual-level protection. The sacrificial layer initially consumes wear resistance, while the wear-resistant protrusions provide chip storage space in the later stages, extending the service life of the wear-resistant layer. The elastic buffer intermediate layer ensures that the impact stress received by the wear-resistant layer is buffered and does not directly affect the rubber base layer. Furthermore, the two transition sub-layers, with their varying hardness, reduce interfacial shear stress.

The utility model discloses a cutter buffer structure for paperboard corner cutting of a printing machine, and relates to the technical field of printing. The cutter buffer structure for paperboard corner cutting of the printing machine comprises a cutter shaft and a cutter assembly, and a buffer mechanism is arranged on the outer wall of the cutter shaft; the buffer mechanism comprises a bowl cutter and a sliding bottom cutter holder; the bowl cutter has the technical effects that the spring, the guide sliding shaft and other components are arranged, when the angle cutter is in contact with the bowl cutter, the spring can absorb impact force and compress the impact force, the impact force is converted into elastic potential energy, the displacement speed of the guide sliding shaft is effectively reduced, and the bowl cutter is prevented from falling off. Hard collision between the angle cutter and the bowl cutter is avoided, and therefore effective buffering of impact force is achieved. Due to the buffering effect of the spring, impact stress borne by the corner cutter, the bowl cutter and related connecting parts is effectively dispersed and relieved, and abrasion of parts caused by impact is reduced.

The invention relates to the technical field of impact effect prediction and improvement, and discloses an impact effect prediction and improvement method and system based on the blast hole blockage length, and the method comprises the steps: analyzing the stress distribution condition in a blast hole according to the pre-obtained detection data of blockages in the blast hole, and obtaining a blast hole blockage analysis result; combining the blast hole blockage analysis result and preset impact parameters to construct an impact effect analysis model, and predicting the dynamic distribution condition of energy in the blast hole to obtain an energy distribution result; on the basis of an energy distribution result, taking each blast hole as a node and taking a position relation between the blast holes as an edge, and constructing a blasting area action diagram; simulating the propagation process of impact stress waves and cracks, and analyzing the node state after impact to obtain a first impact effect; analyzing the improvement direction through a preset impact improvement model, and generating an improvement scheme; according to the invention, the precision and accuracy of blast hole blocking parameter measurement can be improved, the authenticity and comprehensiveness of the whole breaking effect simulation process of the blasting area are enhanced, and the impact effect is improved.

The utility model provides a wear-resistant multipurpose milling tooth, and belongs to the technical field of milling teeth. Comprising a tool nose with the top of a short conical structure, a tool apron which is integrally formed and of a circular-truncated-cone-shaped structure is arranged at the bottom of the tool nose, and a welding protrusion is arranged at the bottom of the tool apron; the cutter body is of a circular truncated cone structure, and a groove matched with the bottom of the cutter holder is formed in the top of the cutter body; the cutter bar is sleeved with a matched clamping spring, and the outer side of the clamping spring is sleeved with a matched check ring. Welding air holes can be effectively reduced and impact stress can be dispersed through the welding protrusions, bending strength is improved through the design of the tool apron of the circular truncated cone structure, the tool nose of the short cone structure and the thickened short head, the alloy crushing rate is reduced, the milling cutter is more suitable for milling under severe working conditions, the tool nose is effectively prevented from being crushed and fractured, and the service life of the milling cutter is prolonged. The cutter head which is made of the tungsten carbide alloy and coated with the polycrystalline diamond coating on the surface has both impact resistance and wear resistance, so that the service life is prolonged.

The application provides a superhigh-pressure acidizing fracturing pump fluid end assembly and a manufacturing method thereof, which comprises a valve seat base body, a valve body configured to be engaged and disengaged in the inner cavity of the valve seat base body through reciprocating movement, and a sealing rubber ring clamped on the valve body, the application opens an annular groove with a half-dove-tail inclined side wall and a sinusoidal wave-shaped groove bottom on a non-carburized hardening tough steel base body conical sealing surface, constructs a ceramic reinforced layer containing nanoscale and microscale carbides in the groove by in-situ self-reaction, the inclined configuration of the half-dove-tail side wall forms self-clamping locking by the thermal shrinkage effect of the cladding layer during cooling, converts the interface residual tensile stress into extrusion prestress, and the sinusoidal wave-shaped groove bottom disperses the axial high-frequency impact stress into shear stresses which offset each other, so that the macro fatigue collapse and micro coating cracking failure are solved, and the valve seat sealing surface has high erosion resistance, high fatigue resistance and high reliability.

The application discloses a kind of water turbine blade fatigue damage numerical simulation and life prediction method and related device, comprising: obtaining the three-dimensional geometric model of water turbine blade and operating condition parameter;According to the three-dimensional geometric model of the water turbine blade and operating condition parameter, fluid-structure interaction model is established, and the fluid pressure fluctuation, cavitation impact stress and sand particle erosion load distribution on the surface of blade in the operation process are extracted;According to the fluid pressure fluctuation, cavitation impact stress and sand particle erosion load distribution on the surface of blade, the equivalent stress of blade is formed;Based on the equivalent stress and cycle number, fatigue damage evolution model is constructed;According to the fatigue damage evolution model and cumulative damage theory, the fatigue damage amount of blade under different operating time is calculated, and the life prediction result is output, and the method and related device can dynamically predict the fatigue life of water turbine blade.

The invention relates to the technical field of body armor, and discloses an outer protective layer. The auxetic structural layer comprises an upper functional layer, a middle functional layer and a lower functional layer from outside to inside, a plurality of polygonal concave buffer grooves distributed at equal intervals are formed in the auxetic structural layer, and the buffer grooves of the auxetic structural layer are filled with shear thickening liquid; when the body armor is impacted by external force, the groove wall fiber network of the multilateral concave buffer groove buffers the external impact force through stretching deformation, the shear thickening liquid is thickened, and the fiber network around the damage bearing part of the body armor is locked to form a local rigid supporting area; the inner protective layer and the auxetic structure layer are located between the outer protective layer and the inner protective layer, the beneficial effects of being excellent in synergistic protective performance, uniform in impact energy dispersion and capable of assisting nursing are achieved, and the problems that a traditional body armor is limited in energy absorption efficiency, blunt injuries are easily caused by impact stress concentration, and the service life is long are solved. The auxiliary nursing function of the injured part is lacked, and primary treatment cannot be carried out on the wound in time.

The application relates to the technical field of impact effect prediction improvement, and discloses an impact effect prediction improvement method and system based on a blast hole blockage length, which comprises the following steps: according to pre-acquired blast hole blockage detection data, analyzing the stress distribution in the blast hole to obtain a blast hole blockage analysis result; combining the blast hole blockage analysis result and preset impact parameters to construct an impact effect analysis model, predicting the dynamic distribution of energy in the blast hole to obtain an energy distribution result; based on the energy distribution result, taking each blast hole as a node and the position relationship between the blast holes as an edge to construct a blast area action graph; simulating the propagation process of impact stress waves and cracks, analyzing the node state after impact to obtain a first impact effect; analyzing the improvement direction through a preset impact improvement model to generate an improvement scheme; and the application can improve the measurement precision and accuracy of blast hole blockage parameters, enhance the authenticity and comprehensiveness of the overall blasting area fragmentation effect simulation process, and improve the impact effect.

A linkage for moving an implement between a working state and a stowed state with respect to a frame of a machine. The linkage includes a carriage, at least one arm assembly, and one or more bump stops. The carriage is configured to support the implement. The arm assembly is coupled to the carriage and is pivotable with respect to the carriage to move the implement to the stowed state. The bump stops are configured to contact an arm, of the arm assembly, in the stowed state of the implement to isolate impact stress away from the frame and onto the linkage.

The application discloses a wide-temperature-range low-air-pressure loading test method for a propulsion motor, relates to the field of propulsion motor testing, and aims at simulating high-altitude and high-altitude severe climate environment conditions by comprehensively considering wide-temperature-range high-low temperature alternating stress, variable environmental pressure stress, mechanical vibration and impact stress caused by air flow disturbance and alternating load stress. The application can realize comprehensive and accurate evaluation on the performance of the propulsion motor.

The application discloses high-strength non-magnetic drill collar, belongs to the technical field of oil drilling drilling tools, including: drill collar rod, one end of the drill collar rod is provided with a buffer head; drill collar head, the drill collar head is threadedly connected on one side of the buffer head, a T-shaped buffer groove is arranged in the buffer head, and a buffer disc spring is arranged in the T-shaped buffer groove; a connecting end is arranged on one side of the buffer head; a threaded connection groove is arranged on the inner circular wall surface of the drill collar rod; by arranging the buffer disc spring, injecting non-magnetic inert gas into the T-shaped buffer groove through the gas injection nozzle on the outside of the drill collar head, and buffering through the buffer disc spring and the buffer gas, the high-strength non-magnetic drill collar can absorb large impact load and high-frequency small impact load, effectively reduce the damage of impact stress to the drill collar rod, the buffer head and the connecting position, avoid the deformation of the drill collar body and the connection failure, and improve the applicability of the drill collar in deep high-impact drilling scenes.

The invention relates to the field of safety protection materials, in particular to explosion-proof glass and a preparation process thereof. The explosion-proof glass prepared by the invention belongs to a multi-layer gradient composite structure, functions of all layers are sequentially transited from an impacted surface to a back surface, and mechanical gradient and function integration of'rigidity-flexibility-rigidity 'is realized. And the outer rigid protective layer is chemically strengthened glass or transparent microcrystalline glass. According to the present invention, with the function of the first defense line, the extremely high hardness and the extremely high strength are adopted to resist the impact and the scratch of sharp objects, disperse the impact stress, and prevent the generation and the expansion of the initial crack; the gradient transition self-repairing layer is a gradient composite material composed of several sub-layers. The reinforcements form a three-dimensional network, so that the modulus and toughness of the area are greatly improved, and microcracks transmitted from the outer layer can be effectively captured and passivated.

This invention relates to the field of peak impact force prediction technology for falling rocks, and specifically discloses a method for predicting peak impact force of falling rocks based on stress monitoring data of the roof slab of a tunnel, comprising the following steps: (S1) obtaining the value of the impact stress at the bottom of the buffer pad layer on the roof surface of the tunnel structure under the impact of falling rocks, and recording the peak impact stress σ. max (S2) If σ max The thickness of the buffer pad layer should be increased to exceed the design strength of the top surface of the shed. h ≥ h x (S3) Establish the distribution function σ( of impact stress). x (S4) Calculate the maximum diffusion radius of the impact stress. x max (S5) Calculate the distribution range of impact stress in the buffer layer. (S6) Calculate the peak impact force of the falling rock. F The peak impact force of falling rocks in this invention F The calculation formula does not depend on the shape, height, or motion of the falling rocks, providing a new approach to accurately predicting the impact force of falling rocks and offering a more accurate reference for the optimized design of tunnel structures.

The present application relates to the field of motion simulation, in particular to a motor life prediction method based on motion simulation, comprising the following steps: according to the automobile motion state test, the vibration displacement and frequency parameters are called to generate the transient acceleration time history load sequence; the space coordinates of the inner rotor core and the permanent magnet of the automobile motor are extracted, the transient acceleration time history load sequence is mapped to the interface node, and the rotor interface impact stress wave distribution is calculated. The present application combines the fatigue crack propagation threshold, the material fracture toughness threshold, the micro crack dynamic expansion step set and the impact load cycle number upper limit extreme value to make cumulative determination, can establish a clear boundary between the crack progressive expansion stage and the unstable fracture critical stage, make the permanent magnet fracture critical life prediction result consider the cycle damage accumulation process and the instantaneous fracture risk, and improve the critical determination accuracy of the automobile motor life prediction.

This invention discloses a drop hammer impact testing device, belonging to the technical field of impact testing devices. It solves the technical problem that different hammer radii affect the impact testing of specimens, and that changing to different specifications requires downtime for replacement, reducing the efficiency of specimen impact testing. The device includes a frame, an impact hammer, and a hammer adjustment mechanism. The impact hammer is installed inside the upper end of the frame. The hammer adjustment mechanism is symmetrically installed on the inner side of the frame, and works with the impact hammer to adjust the impact size on the specimen. The hammer adjustment mechanism includes an assembly plate for mounting multiple semi-rings of different specifications. This invention can change the contact size between the hammer and the specimen according to the needs of the specimen impact test, utilizing the impact stress on the specimen surface from hammers of different sizes, reducing the hassle of downtime for disassembly and replacement of hammers. Furthermore, changing the hammer size facilitates precise positioning, ensuring the accuracy of the hammer size and improving the efficiency of specimen impact testing.

The invention discloses a wide-temperature-range low-air-pressure loading test method for a propulsion motor, relates to the field of propulsion motor testing, comprehensively considers wide-temperature-range high-low-temperature alternating stress, variable environment pressure stress, mechanical vibration and impact stress caused by airflow disturbance and alternating load stress, and aims to simulate high-altitude and high-altitude atrocious weather environment conditions. According to the invention, comprehensive and accurate evaluation of the performance of the propulsion motor can be realized.

Through the use of an internal support system integrated with the interior shell of a hollow ball, the concentration of impact stress to the ball's shell during game play is reduced through better dispersion and resistance of applied force, while also reinforcing the ball's shell at its weakest points, which are the holes, thus making it more resilient and thereby less susceptible to breakage. Enhanced fortification against impact stress applied during gameplay serves to increase the usable life of the ball.

The invention discloses a bulletproof flashboard based on a soft-hard composite structure, and relates to the technical field of personal protection equipment, the bulletproof flashboard is of a multi-layer composite structure, and the bulletproof flashboard sequentially comprises a bullet facing surface functional layer, a middle functional layer and a bullet backing surface functional layer, the bullet facing surface functional layer, the middle functional layer and the bullet backing surface functional layer are sequentially connected and fixed; the bullet facing surface functional layer is a protective layer which is firstly in contact with a bullet body in the multi-layer composite structure; according to the bulletproof flashboard, the soft and hard composite structure design is innovatively adopted, the fiber-reinforced flexible matrix composite material and the fiber-reinforced rigid matrix composite material are selected for structural function integrated design, the ballistic limit of the bulletproof flashboard is remarkably improved by optimizing the sequence and interface design, high-speed projectile penetration can be effectively resisted, and the bulletproof flashboard has the advantages that the bulletproof flashboard is high in practicability and high in practicability. And the bullet facing surface functional layer, the middle functional layer and the bullet backing surface functional layer are arranged, so that impact stress waves can be efficiently attenuated through impedance mismatch in the multi-layer composite structure, and the impact stress waves are effectively prevented from damaging internal organs.

The invention relates to the technical field of oil and gas production, in particular to a safety evaluation method for a packer mandrel under the action of perforation detonation, which comprises the following steps of: establishing a three-dimensional assembly model of a perforation pipe string; performing perforation impact force theoretical analysis; establishing a finite element model of the transient impact dynamics of the perforation pipe string; and the impact stress borne by the packer mandrel is calculated, and the impact fracture failure mechanism of the mandrel is analyzed in combination with the Mises stress nephogram change. According to the method, the perforation detonation impact load calculation model is established, the influence of the impact load on the perforation tubular column is quantitatively evaluated, a theoretical basis and guidance can be provided for perforation operation safety in actual production, and the method has important significance in guaranteeing safe and efficient oil testing of the southern ultra-deep well.

The application discloses a connecting thread design method resistant to complex sea condition cycle and impact stress, comprising the following steps: establishing a model of a mechanical device, determining thread distribution, and giving the number of common threads and hinge hole threads; determining axial load and tangential load borne by the device; determining yield strength of material allowable according to the characteristics of selected material; calculating shear resistance contribution coefficient of common threads; calculating thread dangerous section; and selecting thread size. The application combines three types of formulae, i.e. isolated shear checking calculation, tensile checking calculation and compression checking calculation in thread strength checking in a mechanical design manual, through a coupling formula, so that the matching of thread specification and shipborne use environment requirement can be quickly and effectively solved. The application is suitable for the calculation of thread connection strength of marine equipment.

The application discloses a debris flow multi-stress monitoring system and a monitoring method, and relates to the field of geological disaster monitoring. The system comprises at least one impact force monitoring device, at least one triaxial stress monitoring device, at least one pore water pressure monitoring device and a data processing device. The impact force monitoring device is arranged on the side wall of a debris flow flow-through area to generate an impact stress signal. The triaxial stress monitoring device is arranged at the bottom of the flow-through area to generate normal stress signals and shear stress signals. The pore water pressure monitoring device is arranged at the bottom or the side wall of the flow-through area to generate pore water pressure signals. The data processing device is electrically connected with the impact force monitoring device, the triaxial stress monitoring device and the pore water pressure monitoring device to integrate the impact stress signals, the normal stress signals, the shear stress signals and the pore water pressure signals in a preset time domain for comparison. In this way, different stresses at different positions of the debris flow can be measured. Meanwhile, various stresses can be compared horizontally in the same time domain.

The present application relates to material dynamic mechanical property testing technology, and specifically relates to an impact mechanical loading device and method based on electromagnetic coil transmitter locked-rotor test, the device comprising a pulse power module, an electromagnetic loading module, a constraint fixing module and a measurement and control system; the upper computer is used for setting the capacitor charging voltage, controlling the switch to conduct to discharge the electromagnetic loading module to generate pulse current, the electromagnetic coil generates pulse magnetic field to make the conductor armature induction eddy current to generate axial electromagnetic force; the rigid constraint armature position forms locked-rotor, the impact electromagnetic force is directly loaded on the sample through the impact head to form impact stress, and the working performance of monitoring devices such as voltage, current and impact force is monitored to carry out dynamic response, fatigue damage and aging accumulation experiments of materials. The device has the advantages of small volume, flexible adjustable impact stress wavelength and amplitude, high efficiency and the like, and solves the problems of large volume, difficult control of impact stress pulse width and low test efficiency of traditional mechanical impact devices.

This utility model relates to the field of PCB board technology and discloses a reinforced PCB board, including a PCB board body. Reinforcing components for reinforcing the PCB board body are provided on both the outer wall and bottom surface of the PCB board body. The reinforcing components include metal frame members disposed on the outer wall of the PCB board body. This utility model, by providing metal frame members at the outer edge of the PCB board body, suppresses warping of the PCB board caused by thermal stress or mechanical vibration. The rounded corners of the PCB board body avoid stress concentration at right angles, reducing the risk of corner cracking. Arc-shaped support springs are disposed below large-volume components, absorbing the dynamic load generated by the component's mass inertia under vibration or impact conditions through their elastic deformation, reducing the peak impact stress transmitted to the PCB board body, and preventing solder joint fatigue cracking. Thus, targeted additional reinforcement of the local structure of the PCB board body is provided from the surface of the PCB board body, ensuring the overall strength of the PCB board body.

This application discloses a marine composite pipe and its preparation method. The marine composite pipe comprises, from the inside out: a sealed inner lining layer, an interlocking pressure-bearing layer, a gradient buffer insulation layer, and an outer protective layer. The interlocking pressure-bearing layer includes at least two layers of fiber-reinforced tape, which are wound to form at least one anti-crushing layer and one tensile layer. A biomimetic micro-anchoring intercalation layer is laid between the anti-crushing layer and the tensile layer. The anti-crushing layer, the tensile layer, and the biomimetic micro-anchoring intercalation layer are solidified to form a three-dimensional mechanical interlocking structure. When the marine composite pipe is subjected to transient impact or irregular dynamic load, controllable micro-slippage and hysteretic elastic deformation will occur between the interlocking points. This process can effectively absorb and dissipate impact energy, disperse the concentrated impact stress into a larger material volume, thereby inhibiting the initiation and rapid propagation of cracks, significantly improving the interlayer bonding strength, avoiding interlayer shear failure, and enhancing the overall mechanical bearing capacity and impact resistance of the pipe body.

The invention relates to the technical field of duct piece connection, and discloses a duct piece splicing connecting structure which comprises a main body and a socket frame, and rectangular grooves are formed in the front face and the back face of the main body. A movable supporting point is formed between the inclined plate and the rectangular groove through the balls, and the inclined plate is folded when being extruded; the situation that in the splicing process, rigid mutual collision occurs between the main body and the bellmouth edge of the bellmouth frame, and large instantaneous impact force is generated, so that concrete of the bellmouth frame or the bellmouth frame and a segment root part is broken, or the concrete is gnawed into the segment due to too large impact stress can be reduced; and the splicing efficiency and the splicing stability during subsequent segment splicing are improved.