64results about How to "Improve engineering construction efficiency" patented technology

The invention discloses an intelligent roadbed and pavement roller compaction system which comprises a quality detection system, an intelligent decision making system, an unmanned roller compaction system and a remote monitoring center. The quality detection system is used for detecting the compaction quality of various filled layers of roadbeds and pavements; compaction quality data can be analyzed by the intelligent decision making system, and roller compaction construction parameters of next procedures or new roller compaction construction regions can be obtained by the intelligent decisionmaking system; the unmanned roller compaction system can be combined with a single unmanned roller compaction machine or a group of unmanned roller compaction machines according to the roller compaction construction parameters, so that construction operation can be synergistically accomplished; real-time communication service, operation region planning, navigation routes and group scheduling service can be provided by the remote monitoring center, field operation conditions can be displayed by the remote monitoring center, and operation data can be stored by the remote monitoring center. Theintelligent roadbed and pavement roller compaction system has the advantages that the compaction quality of the different filled layers and different filling materials of the roadbed and the pavementscan be detected by the intelligent roadbed and pavement roller compaction system in an online manner, roller compaction construction operation can be controlled by means of machine decision making, accordingly, influence of human factors can be prevented, detection, analysis, decision making and control cycle can be implemented in a closed-loop manner, and the intelligent roadbed and pavement roller compaction system is particularly applicable to all-weather roadbed and pavement roller compaction construction operation scenes in hazardous regions or under extreme conditions.

The invention discloses an integrated overhung composite insulator string and a method for printing a composite insulator string connecting metal tool by using 3D. The method comprises the following steps of: firstly, generating a three-dimensional CAD (Computer-Aided Design) model of a part in a computer, and printing the three-dimensional CAD model by utilizing a 3D molten-drop printing machine; then slicing up and layering the model according to a certain thickness, converting the three-dimensional information of the part into a series of two-dimensional profile information; melting down metal by using a crucible, and enabling the molten metal to flow out of a nozzle to form molten drops; then accumulating the molten drops layers by layer according to the two-dimensional profile information under the control of the computer so as to obtain a three-dimensional entity part or a part in similar shape. After the method is adopted, a ball-socket series of metal tools is shaped for once directly through the molten-drop 3D printing machine, the connecting cooperation is more reliable and more stable, secondary installation is unnecessary, and the production efficiency is improved; meanwhile, the efficiency of the site construction is provided, and a great influence to the construction of a high-voltage overhead power line is generated.

The invention discloses an internet of Things-based shield tunnel construction refine digit management platform comprising the following modules: a tunneling parameter synchronization module, a video monitoring system, an attendance and precise positioning system, an access control system, an environment monitoring system, and an LED synchronous display system; functions of tunnel person positioning, person attendance, LED synchronous display, video monitoring, intruding alarming, environment monitoring and the like can be realized by using the same communication network. The internet of Things-based shield tunnel construction refine digit management platform has reliability, safety, advancement, flexible extensibility, economy practicability and convenience of operation and maintenance, and is a prospective platform capable of building whole-situation unified management.

The invention relates to a cable-stayed bridge double-cable simultaneous tensioning unstressed state construction control method. The method comprises the following steps of building a cable-stayed bridge whole finite element model; calculating the stay cable unstressed length in the target finished bridge state; setting stay cable initial tensioning force and calculating the corresponding stay cable initial unstressed length; building a double-cable simultaneous tensioning unstressed state control model, and calculating model parameters under the cable-stayed bridge folding state; according to the unstressed length of the stay cable in the target finished bridge state, the initial unstressed length and the model parameters, obtaining the corresponding stay cable tensioning force adjusting amount; according to the calculated tensioning force adjusting amount, performing stay cable tensioning force adjusting construction. Compared with the prior art, the method can be used for the double-cable symmetric tensioning phenomenon, can also be used for the double-cable asymmetric tensioning phenomenon, solves the problem of application limitation of a traditional unstressed state control method in cable-stayed bridge construction control, and can forcefully push engineering application and improve the cable-stayed bridge building technological level.

The invention discloses a big data O2O drawing reviewing cloud platform management system used for construction project construction drawing reviewing. A construction organization drawing paper upload module comprises a network server and a database server assembly. A construction unit data terminal is connected with the input end of the network server. The data output end of the network server is connected with the database server assembly. A firewall is connected on the port of the database server assembly through a switch I. The firewall is divided into three paths to be connected with a reviewing organization drawing reviewing management terminal, a storage unit and a CAD electronic signature authentication system. The whole course of paperless drawing reviewing of construction drawing reviewing can be realized, the drawing reviewing efficiency and the installation performance can be enhanced, and the cost can be greatly saved and the project period can be shortened.

The invention discloses an earthwork measurement and calculation system based on an unmanned aerial vehicle surveying and mapping technology. The system comprises an image data collection unit, three-dimensional model making unit and an earthwork measurement and calculation unit. The image data collection unit is connected with the three-dimensional model making unit in series through utilizationof a circuit. The three-dimensional model making unit is connected with the earthwork measurement and calculation unit in series through utilization of the circuit. The three-dimensional model makingunit comprises an equipment selection module, a route planning module and a data collection module. The equipment selection module is connected with the route planning module in series through utilization of the circuit. The route planning module is connected with the data collection module in series through utilization of the circuit. The earthwork measurement and calculation unit comprises a data input module, a model making module, a data correction module and a model display module. The data input module is connected with the model making module in series through utilization of the circuit. The model making module is connected with the data correction module in series through utilization of the circuit. Through utilization of an unmanned aerial vehicle oblique photography technology, image data collection of earthwork is carried out, precise measurement and calculation are realized, and construction efficiency is improved.

The invention discloses a wall plastering and building solidifying material and belongs to a building material, in particular to a material for use in wall plastering. The wall plastering and building solidifying material is prepared by mixing the following main materials: 15 to 50 percent of cement, 20 to 65 percent of active admixture, 2 to 18 percent of lime powder, 0.05 to 0.2 percent of surfactant, 0.5 to 2 percent of water-retaining thickener and 0.5 to 1.5 percent of dispersible polymer. The solidifying material of the invention can replace cement or other gelling materials to be mixed with sand and water in proportion to prepare wall plastering and building mortar for aerated concrete block walls and common walls. When the solidifying material is used, the interface processing of the walls is saved. The solidifying material has the characteristics of high binding strength, low shrinkage and high strength. When the solidifying material is applied in wall projects, time-saving, labor-saving and environmentally-friendly effects can be achieved.

The invention discloses an inner geotextile bag sleeve valve pipe grouting construction method. On the basis of a conventional sleeve valve pipe grouting technology, a geotextile bag which can be filled with water and made by sewing impermeable geotextile is applied. After a sleeve valve pipe is inserted or first-time grouting is ended, the geotextile bag slightly longer than the sleeve valve pipe is guided to the bottom of the sleeve valve pipe through a cavity in the sleeve valve pipe, and clean water is poured into the geotextile bag till the whole cavity of the sleeve valve pipe is filled with clean water; when first-time grouting on holes to be injected with slurry starts or before repeated second-time grouting on the holes to be injected with slurry starts, the geotextile bag is taken out, and the remaining steps are the same as a conventional sleeve valve pipe grouting construction method. With the method, not only are the advantages of the conventional sleeve valve pipe grouting kept, but also the problem that slurry enters the sleeve valve pipe because of slurry mixing in the grouting process and the problem that the sleeve valve pipe is blocked because of deformation are solved, and meanwhile remaining slurry in the sleeve valve pipe can be removed effectively. The applied geotextile bag is easy to manufacture, low in cost, convenient to construct and capable of being repeatedly used and thus has very good application prospects.

The invention provides an intelligent programmable axial plunger pump controller and a control method, and belongs to the field of intelligent hydraulic elements. The controller comprises a sensor group, a control panel, and an ARM chip, an RISC-V chip, a signal acquisition module, a filtering module, a charge amplifier, a power amplifier, a mode selection module, a display module and a cloud storage module which are installed on the control panel; and the control panel is further provided with a plurality of external interfaces. The magnitude of flow in a variable piston cavity of a hydraulic pump and the swing angle of a swash plate can be controlled by the ARM chip; automatic compound control over the pressure, flow and power of the axial plunger pump is achieved; meanwhile, the pressure, flow and power of the axial plunger pump can be controlled by detecting signals such as the outlet pressure of the hydraulic pump, the swing angle of the swash plate and vibration on a pump shell; the state of the hydraulic pump is monitored and recognized based on the RISC-V chip, common faults of the hydraulic pump are judged, and judgment results are transmitted to the ARM chip, thus implementing predictive maintenance of the hydraulic pump.

A system for compiling an engineering form is provided. The system comprises a project form storage module and a data association module, wherein different project sub-forms can be associated throughthe data association module, thereby overcoming the defect that different project sub-forms in the prior art are isolated from each other, realizing the dynamic connection between the project sub-forms, and improving the project construction efficiency.

The invention relates to a multi-functional starting and receiving construction operation frame of an earth pressure balance shield machine, and belongs to the technical field of shield construction. The operation frame comprises a frame body, a first folding plate layer, a second folding plate layer, a jumping plate and wheels, wherein the frame body is composed of a circular arch, a first side wall and a second side wall, the first folding plate layer comprises a first front folding plate and a first rear folding plate, the first front folding plate and the first rear folding plate are located on the same horizontal plane when unfolded, the second folding plate layer is installed below the first folding plate layer, and comprises a second front folding plate and a second rear folding plate, the second front folding plate and the second rear folding plate are located on the same horizontal plane when unfolded, the jumping plate is detachably installed on the first folding plate layer and / or the second folding plate layer, and the wheels are installed at the bottom of the frame and slide when the frame body moves. The earth pressure balance shield machine enters and leaves the multi-functional hole construction operation frame to conduct manual hole door chiseling, the time of installing and detaching the operation frame is saved, the time of exposing a hole door soil body is shortened, and the safety risks of constructors for detaching the operation frame are reduced.

The invention discloses a full-hole-slag high-performance concrete and a preparation method thereof. The full-hole-slag high-performance concrete is prepared from the following raw materials by weight: 720-770 parts of ordinary Portland cement, 300-330 parts of fly ash, 2000-2200 parts of hole slag coarse aggregate, 1460-1760 parts of hole slag fine aggregate, 35-55 parts of a polycarboxylate superplasticizer and 320-370 parts of water, wherein the hole slag coarse aggregate is hole slag with a particle size of 5-25mm, and the particle size of the hole slag fine aggregate is 0-5mm, all the rawmaterials are sequentially mixed and stirred to prepare the full-hole-slag high-performance concrete. The hole slag is used as coarse aggregate and fine aggregate of the concrete, the prepared full-hole-slag high-performance concrete has excellent working performance and mechanical performance, consumption of natural gravel resources is reduced, the engineering construction efficiency is improved, and the engineering cost is reduced.

The invention provides an automatic mixing and dispensing machine for roadbed lime-clay. The automatic mixing and dispensing machine for the roadbed lime-clay effectively solves the problems that prior roadbed lime-clay backfill operating technology needs excessive equipment, the ratio of components in the roadbed lime-clay is hard to control, humidity of the lime-clay cannot be controlled, constructing environment is poor, and efficiency is low. The automatic mixing and dispensing machine for the roadbed lime-clay comprises a towing tractor, a frame is arranged on the towing tractor, and a water tank is arranged on the frame; a first water pipe, a second water pipe and a third water pipe are arranged below the water tank; a mixing device located on the frame is arranged below the first water pipe, a buffering device is arranged at the right side of the mixing device, a humidifying device is arranged at the left side of the mixing device, a spreading device is arranged at the left side of the humidifying device, and a raised dust prevention device is arranged at the left side of the spreading device. the automatic mixing and dispensing machine for the roadbed lime-clay has the efficient and perfect blending function, the working process is simple, time and labor are saved, labor capacity of workers is significantly reduced, the problem of raised dust in the construction site is greatly alleviated, the compositional ratio in the lime-clay backfilling process is effectively controlled, engineering constructing efficiency is greatly improved, engineering quality is improved, so that lime-clay backfilling becomes convenient, fast, simple and easy to conduct.

The invention discloses a C-shaped sleeve detachable and replaceable reinforced concrete column-column connecting structure and a construction method. The C-shaped sleeve detachable and replaceable reinforced concrete column-column connecting structure comprises an upper reinforced concrete column, a lower reinforced concrete column, a cover plate and high-strength bolts; column end steel plates and shear-resistant connecting pieces are arranged at the column ends of the upper reinforced concrete column and the lower reinforced concrete column correspondingly; longitudinal bars and the shear-resistant connecting pieces are welded to one sides of the column end steel plates; and a C-shaped sleeve and a rectangular inner sleeve are welded to the other sides of the column end steel plates of the upper reinforced concrete column and the lower reinforced concrete column correspondingly. The C-shaped sleeve and the rectangular inner sleeve are connected through the high-strength bolts, and thus connection of the upper reinforced concrete column and the lower reinforced concrete column is achieved. The bolts are loosened, the cover plate is taken down, the column section needing to be replaced is taken down in the horizontal direction, then the new column section is pushed in the horizontal direction through hoisting, the bolts are tightened, and thus the reinforced concrete columns are detached and replaced. The C-shaped sleeve detachable and replaceable reinforced concrete column-column connecting structure is good in stress performance and convenient to machine and manufacture, the defect that a traditional steel sleeve component cannot be flexibly detached and replaced in the service period is overcome, and a new thought is provided for connection of a detachable and replaceable structure system in the whole life cycle.

The invention discloses an enclosure structure of a close-range underpass low-clearance bridge and a construction method thereof, and belongs to the technical field of tunnel construction. The open-cut tunnel enclosure structure comprises an open-cut tunnel enclosure structure body and a pier foundation isolation protection structure, the open-cut tunnel enclosure structure body comprises a set of enclosure rigid piles, an enclosure waterproof curtain arranged on the outer sides of the enclosure rigid piles, and profile steel arranged on the inner sides of the enclosure rigid piles and used for enhancing the rigidity of the enclosure structure body, and reinforced concrete supports and steel supports are erected between the enclosure rigid piles. The open-cut tunnel enclosure structure and a servo system are adopted, the rigidity of a bridge structure is greatly improved, the overall deformation resistance of the structure is enhanced, the influence of tunnel construction on operation of the elevated bridge is reduced, and micro-disturbance tunnel construction on the bridge is achieved, the problem that the construction space is limited under the low clearance condition is solved through the modes of drill rod lengthening and the like, and the construction efficiency is improved.

The invention discloses a project supervision system based on Internet of Things communication, relates to the technical field of project supervision, and solves the technical problems that in the construction process of a building project, an effective supervision system is lacked, and the operation progress of the project is difficult to control. Comprising an engineering analysis module, a problem uploading module and a construction evaluation module. The engineering monitoring module and the cloud platform are connected in a distributed manner through the Internet of Things nodes; the engineering analysis module is used for acquiring and analyzing the monitoring data of the construction engineering, determining the current construction process and judging whether the current progress of the construction engineering is delayed or not; the problem output module is used for outputting the project construction problem after the related personnel deal with the project construction problem and judging whether the construction project is delayed or not; and the construction evaluation module is used for evaluating the construction hysteresis coefficient according to the monitored hysteresis signal, judging the construction state of the current construction team, and suggesting a contractor to replace other construction teams for operation in time, so that the engineering construction efficiency is improved.

The invention discloses a novel pole-separating carrying device for an electric pole. The novel pole-separating carrying device comprises two horizontal guide rails and two inclined guide rails. A driving mechanism which is arranged on a platform lorry comprises a reel and a pulley block; the pulley block comprises front and back vertical pulleys which are arranged on the outer side of a long edge of the platform lorry on the same side of the inclined guide rails and front and back horizontal pulleys which are arranged on the upper surface of the platform lorry and are close to the other long edge of the platform lorry; one end of a steel wire rope is fixedly connected to the reel while the other end successively winds across the horizontal pulleys and the vertical pulleys and are bonded to a to-be-unloaded pole; a ratchet mechanism is arranged on the reel, two pulleys are arranged on the vertical pulley in front, the steel wire ropes at two ends of the pole are separately mounted, protecting plates are arranged on supporting rods of the front and back vertical pulleys, and the steel wire rope passes through the front and back vertical pulleys and the protecting plates and is prevented from falling. According to the novel pole-separating carrying device disclosed by the invention, the engineering construction efficiency is improved, and the novel pole-separating carrying device is safe and reliable.

The invention discloses a device for generating a sound source by using seawater buoyancy. The device consists of a stainless steel hollow sphere (1), a gearbox (2), a turntable device (3), a fixed transmission device (4), a sound wave generating device (5), a loudspeaker cylinder (6), a mounting and fixing bracket (7) and a steel wire conduction wheel (8), wherein the stainless steel hollow sphere (1) is arranged on a gearwheel (44) of the turntable device (3); the gearbox (2) is connected with the turntable device (3), the fixed transmission device (4) and the mounting and fixing bracket (7); the turntable device (3) and the fixed transmission device (4) are arranged between a left gearbox side plate (21) and a right gearbox side plate (22); the sound wave generating device (5) is connected with a loudspeaker plate (63) through a loudspeaker plate pushing ejector rod (54); the loudspeaker cylinder (6) is connected with the gearbox (2) through a loudspeaker cylinder mounting plate (62); the mounting and fixing bracket (7) is connected with the gearbox (2) through a gearbox bottom plate (52); and the steel wire conduction wheel (8) is connected with the mounting and fixing bracket (7). By using the seawater buoyancy as energy, the device has low cost and high efficiency; and the device has broad application prospect for underwater cultural relic protection.

The invention relates to an intelligent impromptu preliminary budget realization method for power distribution network engineering. The method comprises steps that an engineering equipment account reserve bank is constructed; a graphical element model database is established; a preliminary budget standard type database is constructed; power distribution network engineering preliminary budget results are determined according to a power distribution network engineering wiring diagram, the engineering equipment account, a graphical element model and preliminary budget standards; the power distribution network engineering preliminary budget results are presented in an impromptu mode. The method is advantaged in that engineering preliminary budget quality and efficiency are substantially improved.

The invention discloses an ultra-high performance concrete prefabricated assembly comprehensive pipe rack. The comprehensive pipe rack comprises a comprehensive pipe rack segment and a horizontal bearing and inserting structure, the comprehensive pipe rack segment is subjected to head and tail sequential connection in the longitudinal direction of the pipe rack in the horizontal direction, the comprehensive pipe rack segments are assembled and connected through the horizontal bearing and inserting structure, the horizontal bearing and inserting structure comprises a bearing opening formed in apipe opening in the front end of the comprehensive pipe rack segment and an inserting opening formed in a pipe opening in the rear end of the comprehensive pipe rack segment, the bearing opening is arranged as an annular groove corresponding to the pipe opening along the pipe opening in the front end of the comprehensive pipe rack segment, and the inserting opening is arranged as an annular bosscorresponding to the pipe opening along the pipe opening in the rear end of the comprehensive pipe rack segment. The inserting opening is inserted into the bearing opening to enable the two adjacent comprehensive pipe rack segments to be assembled and connected. The comprehensive pipe rack is convenient to assemble and transport, high in assembly precision, and good in assembly seam waterproof effect.

The invention relates to the technical field of bridge pier construction, in particular to a pile foundation girdling device and a girdling method. Comprising a moving mechanism and an annular cutting mechanism, the moving mechanism comprises an adjusting assembly, the annular cutting mechanism is connected to the adjusting assembly, and the adjusting assembly is used for adjusting the distance between the annular cutting mechanism and a pile foundation; meanwhile, the adjusting assembly comprises a vertical telescopic rod and a horizontal telescopic rod, the horizontal telescopic rod is connected between the girdling mechanism and the vertical telescopic rod, the girdling mechanism comprises a connecting column, and the connecting column is connected with the end, away from the vertical telescopic rod, of the horizontal telescopic rod; according to the pile foundation girdling device, the technical problems that in the prior art, redundant cement concrete is subjected to girdling treatment in a manual girdling mode, the working intensity is large, the girdling precision cannot be guaranteed, and the engineering construction efficiency is reduced are solved, and the technical effects of reducing the working intensity and improving the engineering construction efficiency are achieved.

The invention discloses a novel pole dividing and carrying method. A carrying device comprises two horizontal guide rails and two inclined guide rails; a driving mechanism is arranged on a flat car and comprises a reel, a front vertical pulley, a back vertical pulley, a front horizontal pulley and a back horizontal pulley; the inclined guide rails are pivoted with the flat car; inserting holes are formed in the inclined guide rails; inserting holes are formed in the horizontal guide rails; protecting plates are arranged on supporting rods of the front vertical pulley and the back vertical pulley; and steel wire ropes cross the front vertical pulley, the back vertical pulley and the protecting plates and are prevented from falling. The carrying method comprises steps as follows: after the inclined guide rails are rotated to the working positions on the flat car, a pole is placed at the inclined guide rails, the steel wire ropes cross the pulley blocks to fix the pole, then the pole is driven by the reel to move, and the safety is guaranteed by the aid of supporting columns inserted in the inserting holes during movement of the pole. With the method, the engineering construction efficiency is improved, and the method is safe and reliable.

The invention discloses an overall carrying dismantling method for an overline suspender arch bridge, which comprises the following steps of: firstly selecting a beam storage site with a proper size, reinforcing a suspender arch bridge, cutting a side span, performing hoisting and dismantling, then closing main line traffic under the bridge, carrying a support frame adaptive to the beam bottom clearance height by a vehicle set to run to the beam bottom, pre-jacking the suspender arch bridge by the vehicle set, and after the arch ring is cut, rapidly moving the whole suspender arch bridge out of the main road to the beam storage site to be broken and chiseled away. The method has the technical effect of quickly dismantling the overline suspender arch bridge, is small in traffic influence, low in construction risk, environmentally friendly, good in application prospect and capable of being widely applied to the technical field of bridge dismantling.

The invention discloses plant group modular culture technology, and relates to the technical field of plant modular culture. The plant group modular culture technology includes the following steps: S1, plant breeding selection; S2, plant cultivation; S3, ecological environment construction; S4, plant transplanting and landscaping; S5, modular assembling and grouping; S6, maintenance and selling; and S7, construction site planting. According to the plant group modular culture technology, plant groups are formed by modular collocation, and maintenance, selling and construction site planting arecarried out in the form of plant groups. Through collocation methods of plant groups, it is conducive to play characteristics of seedlings with different original individual forms. The combinations ofmultiple groups of plants and seedlings can improve landscape effects, solving a problem that the existing modular plant or seedling varieties are single, and different modular combination modes canbe assembled according to different landscaping designs. Different cultivated plants or seedlings are transplanted into planting boxes to form assembling forms of plant groups in a mixed way, so thatgroup modes have the advantages of modularization and miniaturization.

A power engineering safety early warning method based on the difference of image data characteristics, including: using the emergency wireless communication network environment equipped on the project construction site of the power construction company to collect image data of the facilities to be monitored; according to the basic characteristics of the power construction project, treat the monitoring facilities The image data is modeled to generate typical feature vectors; according to the feature vectors of each image data, the object relationship vector model of the image is constructed, and the center of gravity of the image object relationship vector model is calculated; the initial image object relationship vector model and sampling The image data object relational vector model is used for difference comparison; according to the preset weight value of the power engineering project implementation, the state of the current monitoring facility is judged. The invention establishes a complete electric power engineering project construction safety early warning evaluation system, and provides intelligent project implementation safety early warning references for technical management personnel of electric power engineering projects, so as to reduce engineering accidents.

The invention discloses a strontium ferrite-based sacrificial mortar and a preparation method. The strontium ferrite-based sacrificial mortar is mainly composed of 720-1000 parts of sulfoaluminate cement, 100-300 parts of strontium ferrite, and 600 parts of quartz sand. ‑650 parts, 400-450 parts water, 0.01-35 parts water reducing agent. The production process of the invention is simple and can be prepared by a conventional forced single-horizontal shaft concrete mixer. The strontium ferrite-based sacrificial mortar prepared by the invention has excellent working performance, high compressive strength and excellent corrosion resistance, and can be used in the current third-generation and future fourth-generation nuclear power plant core traps , with high engineering application value.

The invention discloses a construction method of an urban hydrophilic ecological river channel. By using mixing piles, the functional requirements of a river bank retaining wall can be met, the earthexcavation, filling, abandonment and transport of the retaining wall are reduced, the engineering construction efficiency is improved, the construction period is shortened by about one half compared with that of a cast-in-place pile structure, and the construction method is more economical than that of the cast-in-place pile structure. As soil is reinforced in situ, compared with a grouted rubblegravity or reinforced concrete L-shaped retaining wall cantilever-type structure needing bulk excavation and supporting for base expansion, the in-situ retaining wall structure does not need earth andmud discharge, causes low noise and little environmental pollution, does not disturb adjacent soil during construction, has low supporting requirements and will not cause ground sinking, house tilting and road cracking. The construction method is used in the technical field of remediation of the hydrophilic ecological river channel.