102 results about "Air barrier" patented technology

The invention discloses a spline shaft high-speed grinding and cooling device and method, and relates to the technical field of grinding and cooling devices.The spline shaft high-speed grinding and cooling device comprises a workbench, a grinding assembly, a clamping and rotating assembly, a conveying assembly and liquid guiding mechanisms, an encircling structure is formed by the two symmetrically-arranged liquid guiding assemblies, and the design that the center extension line of a jet flow opening accurately points to a grinding position is matched; the problem that a traditional fixed nozzle cannot focus on a grinding area is solved, cooling liquid can directionally act on a grinding contact area, and it is guaranteed that grinding points are effectively covered all the time in the spline shaft machining process. By means of the synergistic effect of the spiral liquid guide structure and the high-speed rotation of the spline shaft, cooling liquid is continuously accelerated in the gradually-shrunk flow channel to form high-pressure spiral flow so as to effectively break through an air barrier formed by high-speed rotation on the surface of the spline shaft, and the centrifugal acceleration effect of the spiral flow is combined with the pressurization effect of the gradually-shrunk flow channel of the protective cover. And the spraying kinetic energy of the cooling liquid is greatly improved.

The invention discloses a grouting pipe embedding device for municipal engineering construction, and relates to the technical field of grouting pipes. A falling piston rod can stably input gas in a gas-liquid two-way pipe into a rubber gas partition arranged outside the grouting pipe, so that the gas is expanded, and the grouting pipe is embedded in the gas-liquid two-way pipe; the spiral diameter of the expanded rubber air partition is larger than the diameter of the upper end and the diameter of the lower end of the grouting pipe, a spiral setting posture can be formed in the hole channel, the grouting pipe is stabilized in the hole channel, the grouting stability is improved, meanwhile, the spirally-wound rubber air partition can effectively block soil residues or broken stones falling in the hole channel, and the grouting effect is improved. In addition, the spiral rubber gas partition does not form isolated ring sealing on the hole channel, during grouting, gas in the underground space can be smoothly discharged through gaps of the spirally-set rubber gas partition, and the grouting quality is improved. The problem that a honeycomb-shaped wrapping layer is formed after gas in a narrow underground space cannot be discharged and is mixed and solidified with slurry is solved.

An airflow system for buildings, and its method of use, is provided to provide pollution mitigation for occupants of a building. An airflow system for a building is provided, comprising: at least one air purification system that provides purified air and receives recirculated air; at least one supply air assembly that supplies purified air from the air purification system to at least one internal airflow space, the internal airflow space including one or more office cubicles, meeting rooms, and auditoriums; at least one return air assembly that returns recirculated air from at least one internal airflow space back to at least one air purification system; directional airflows formed between the supply air assembly and the return air assembly, including a first directional airflow and a second directional airflow that form one or more air barriers between occupants to provide respiratory isolation, the second directional airflow forming an airflow field around each occupant; and at least one control system that controls the airflow system. The airflow system provides pollution mitigation for each occupant.

The utility model provides a laser probe protection mechanism of a laser navigation forklift type AGV, and relates to the field of AGVs. The laser probe protection mechanism of the laser navigation forklift type AGV trolley comprises a split-type fixed seat and a protective cover used for providing external protection for a laser probe, and the fixed seat comprises a seat plate and a damping cushion block which are fixedly connected. According to the laser probe protection mechanism of the laser navigation forklift type AGV trolley, external protection can be provided for a laser probe in the use process of the AGV trolley through the arrangement of the protection cover on the fixed seat, and an annular air barrier can be formed outside a spherical cover through the arrangement of an air curtain mechanism on the outer side of the fixed seat, namely the cooperative use of multiple groups of flow guide seats and an air pump; the dust and water mist attachment is continuously blocked, the manual cleaning frequency is reduced, then stable self-cleaning protection is provided for the protective cover, through modular split type arrangement of the fixing base, the protective cover and the air pump, workers can conveniently disassemble, assemble and replace independent parts, and the maintenance cost is reduced.

An airflow system for buildings and a method of using the same are disclosed to provide pollution mitigation for occupants of a building. The airflow system includes: at least one air purification system for providing purified air and receiving recirculated air; at least one supply air assembly for supplying purified air from the air purification system to at least one internal airflow space, the internal airflow space including one or more of a corridor, cafeteria, restroom, and elevator; at least one return air assembly for returning recirculated air from at least one internal airflow space to at least one air purification system; directional airflow formed between the supply air assembly and the return air assembly, and including at least one or more of a directional airflow field around each occupant, an air barrier located between each occupant, and an airflow field around each occupant; and at least one control system for controlling the airflow system. The airflow system provides pollution mitigation for each occupant.

The present invention provides a laminate having low air permeability and excellent moisture permeability in a low-temperature, low-humidity environment. The laminate comprises: a porous substrate; and a moisture-permeable membrane provided on one surface of the porous substrate. The laminate has an air barrier of 3000 sec / 100 cc or higher according to the Gurley method in accordance with JIS P8117-2009, and a first moisture permeability of 300 g / (m2) under the conditions of a temperature of 5°C, a relative humidity of 45%, and a wind speed of 0.2 m / s or less according to the moisture permeability test method (cup method) in accordance with JIS Z0208-1976. 2 ·24h) or more.

An anti-scald UV curing lamp box comprises a lampshade, a cooling assembly, a light-emitting assembly, a bottom plate and an opening and closing assembly, the cooling assembly and the light-emitting assembly are sequentially arranged on the lampshade from top to bottom, the bottom plate and the opening and closing assembly are located under the lampshade, and one end of the bottom plate is hinged to the lampshade and forms a curing chamber used for containing a product to be cured. The light-emitting assembly is located over the curing chamber, at least one heat insulation plate is arranged in the lampshade, and a separation layer is formed by the heat insulation plate and the inner surface of the lampshade. The structure can solve the problem that the temperature of the outer surface of the lampshade is too high due to the fact that a large amount of hot air is gathered in the lampshade, and therefore a user may be scalded by a high-temperature machine shell when touching equipment by mistake by the hand carelessly.

This invention discloses a tunnel smoke treatment and fire rescue system based on an air barrier. A pulley is installed on a guide rail, with its lower end connected to the upper end of a first telescopic rod. The lower end of the first telescopic rod is connected to a groove at the tail end of a fan. A first filter, a second filter, and a third filter are sequentially installed inside the duct along the gas flow direction. A first pipe is installed on the first filter. A third pipe is installed at the top of the tunnel, and the third pipe is connected to an atomizer via the second pipe. The nozzle of the atomizer is located inside the exhaust port of the fan. The fire protection system includes a fire extinguisher, a directional rod, a fourth pipe, a fifth pipe, and a second telescopic rod slidably connected to the guide rail. The lower end of the second telescopic rod is connected to the fire extinguisher via the directional rod. A second bracket is installed at the front end of the fire extinguisher, and the nozzle of the fire extinguisher is fixed to the second bracket. This system can avoid traffic congestion at the tunnel entrance and simultaneously prevent harmful smoke and high temperatures from threatening the personal safety of firefighters.

There is provided an airflow system for a building. The airflow system includes at least one air purification system providing purified air and receiving recirculated air; at least one air supply assembly supplying the purified air from the air purification system to at least one interior airflow space including one or more of, an office cubicle, a conference room, and an auditorium; at least one air return assembly returning the recirculated air from the at least one interior airflow space to the at least one air purification system; directional airstream(s) formed between the air supply assembly and the air return assembly, including first directional airstream(s) forming one or more air barriers between occupants, to provide respiratory isolation, and second directional airstream(s) forming an airflow field around each occupant; and at least one control system controlling the airflow system. The airflow system provides a contamination mitigation for each occupant.

The utility model belongs to the technical field of nitrogen-sealed water tanks, in particular to a glass fiber reinforced plastic nitrogen-sealed water tank with high purity requirement, which comprises a glass fiber reinforced plastic nitrogen-sealed water tank body, the inner wall of the glass fiber reinforced plastic nitrogen-sealed water tank body is fixedly connected with a sealing liquid containing groove plate, and the sealing liquid containing groove plate is filled with air isolation liquid. A deformable air barrier film is arranged on one side of the sealing liquid containing groove plate, a hard connecting ring plate is fixedly connected to the top end of the deformable air barrier film, and an L-shaped liquid sealing ring plate is fixedly connected to one side of the hard connecting ring plate; by means of cooperation of the sealing liquid containing groove plate, the air isolation liquid, the deformable air isolation film, the hard connecting ring plate and the L-shaped liquid sealing ring plate, the upper-layer space in the glass fiber reinforced plastic nitrogen sealing water tank body can be sealed and separated. When external air enters the glass fiber reinforced plastic nitrogen-sealed water tank body through an air valve at the top of the glass fiber reinforced plastic nitrogen-sealed water tank body due to insufficient nitrogen supply, the air is prevented from being in contact with ultrapure water in the glass fiber reinforced plastic nitrogen-sealed water tank body.

The present application belongs to the technical field of polishing device, disclose a kind of polishing device for stainless steel casting production, comprising: frame and drive motor, the output shaft of drive motor is equipped with polishing wheel, the inside of polishing wheel is equipped with air inlet passage, the output shaft of drive motor is hollow shaft, its pipe wall is equipped with gas outlet, the air outlet of output shaft is connected with the air inlet passage of polishing wheel, to form dust adsorption path from polishing point to the inside of output shaft;The inside of the output shaft of drive motor is equipped with fluid delivery component, and the stretchable piece is equipped between the fluid delivery component and frame;The beneficial effects of the present application are: fluid delivery component constructs two-way air circulation system, realizes the integration dust control from polishing point direct adsorption, efficient filtration to clean air barrier, maximally reduces dust diffusion, improves work environment, reduces threat to operator health.

In certain embodiments, the disclosed sealant comprises a one-component, closed-cell, semi-foam, sealant using gas-filled, flexible, organic microspheres to create a product that is elastic and compressible under pressure without protruding in an outward direction when compressed, thereby allowing the applied sealant to compress in an enclosed, maximum-filled channel unlike typical mastic sealants (while retaining the ability to rebound). This allows the sealant to function as a gasket, and, once fully cured, to have properties including vibration damping, insulating, and condensation resistance. The sealant can be formulated as an air barrier or a vapor barrier and at various degrees of moisture resistance. It may be applied by different packaging variations including aerosol can (bag in can or bag on valve), airless sprayer, cartridge tubes, foil tubes, squeeze tubes, and buckets to be applied using a brush, trowel, spatula, etc. The disclosed sealant can also be formulated to be smoke-resistant and flame-resistant.

The present invention belongs to the technical field of pressure roller manufacturing and discloses a method for manufacturing a multi-piece pressure roller. The method comprises: step S1, providing a long strip of extruded profile having a preset external profile and internal longitudinal airway holes and longitudinal communication holes through an integrated extrusion process; step S2, cutting the profile as needed to obtain a pressure roller core; step S3, processing a piston hole connected to the communication hole; step S4, providing an air barrier within the communication hole to separate air-controlled partitions; step S5, processing a channel to connect the airway hole to the corresponding air-controlled partition; and step S6, completing the assembly of the piston and pressure roller sheet. The present invention significantly reduces manufacturing costs and cycle times through the "extrusion molding + modular configuration" approach, and achieves flexible and adjustable air-controlled partitions, thus having significant economic and technical advantages.

The ammunition is used on a drone interceptor to combat other drones. The ammunition fires a propeller snare. Ammunition comprises multiple charges with separate electric activation for a multiple attack possibility. The rope forms an air barrier from the moment the shot is fired, it allows the target's propeller to become entangled at a short distance. Twisting the rope increases the likelihood of entanglement on the target. The design of the projectile reduces the likelihood of ricochet. Projectile filled with extra length of rope, it increases the likelihood of entangling the target's propeller. The ammunition is attached to the activation unit. The activation unit is attached to the weapon carrier. The low weight of the weapon allows it to be used on small interceptor drone.

The invention relates to a concentric loose coupling partition combustion chamber and a combustion organization method thereof. The concentric loose coupling partition combustion chamber comprises a diffuser, a combustion shell, a combustion assembly and a flame tube. The combustion assembly comprises an auxiliary mold nozzle, a main mold nozzle, an auxiliary mold swirler and a main mold swirler. An annular non-rotation air channel is defined between the inner wall of the main mold swirler and the outer wall of the main mold nozzle. A preset included angle is formed between the direction of main mold fuel sprayed by the main mold nozzle and the central axis of the combustion shell, the non-rotation air channel can form an annular air barrier, and under the medium and low working conditions, the air barrier can prevent the main mold fuel from entering a main mold combustion area so that the main mold fuel can enter an auxiliary mold combustion area, and under the high working condition, the main mold fuel can be prevented from entering an auxiliary mold combustion area. The primary mold fuel can pass through the air barrier and into the primary mold combustion zone. Therefore, partitioned combustion under different working conditions can be realized, the reliability of ignition and the stability of combustion under medium and low working conditions are ensured, the combustion efficiency under high working conditions is improved, and the condition of smoking is avoided.

The invention discloses a post insulator, and relates to the field of insulators, the post insulator comprises a mounting base, an insulating rod core is fixed on the mounting base, the insulating rod core is coaxially sleeved and rotatably connected with an insulator, the insulator comprises a plurality of umbrella skirts, the umbrella skirts are integrally formed and connected through a connecting sleeve, and the connecting sleeve is provided with a plurality of purging holes for purging the umbrella skirts; a blowing assembly used for providing airflow for the blowing holes is fixed in the bottom connecting sleeve, and a plurality of first air holes used for the blowing assembly to suck air are formed in the mounting base. A driving assembly is fixed to the bottom connecting sleeve. The insulator rotates centrifugally after being driven by the driving assembly, and water stains and / or dust on the surface of the umbrella skirt are / is centrifugally separated; air flow generated after the purging assembly is driven by the driving assembly is conveyed to the purging hole, the air flow purges the surface of the umbrella skirt in centrifugal rotation through the purging hole, an air barrier is formed, and the problem of pollution flashover caused by the fact that the insulation level of dirt attached to the surface of the post insulator is reduced under the humid condition is solved.

The embodiment of the utility model provides a belly camera decontamination system based on a five-unmanned aerial vehicle platform, and relates to the field of camera cleaning. The belly camera decontamination system based on the Yangfive unmanned aerial vehicle platform comprises a camera, an in-machine cold air module, a cleaning module and a barrier module, the camera decontamination system is used for providing gas, the cleaning module is connected with the in-machine cold air module and used for cleaning the camera under the pressure of the in-machine cold air module, and the barrier module is connected with the in-machine cold air module and used for cleaning the camera under the pressure of the in-machine cold air module. The barrier module is used for forming an air barrier in front of the camera. High-pressure gas is provided for the cleaning module and the barrier module by using the idle built-in cold air module in flight, so that the power consumption can be reduced; the barrier module sprays gas towards the camera under the pressure of the cold air module in the camera, so that an air barrier is formed in front of the camera, and invasion of oil stains and dust to the camera in the flying process is effectively blocked; and the cleaning module can spray a cleaning solution towards the camera under the pressure of the built-in cold air module.

The invention discloses an intelligent power distribution cabinet which comprises a cabinet body, a base is arranged at the bottom of the cabinet body, an arc-shaped top cover is arranged at the top of the cabinet body, a partition guide plate is installed in the cabinet body, two air guide arc plates are symmetrically arranged at the front end of the top of the partition guide plate and connected with the cabinet body, and an air supply structure is arranged between the cabinet body and a partition plate. The bottom of the cabinet body is communicated with the collecting tank, and filter screens are installed at the bottom and on the two sides of the collecting tank. Through triple guidance of the partition guide plate, the arc-shaped top cover and the air guide arc plate, a stable inverted-U-shaped cross flow air barrier is formed, static electricity is effectively neutralized while efficient cooling is achieved, dust adsorption is prevented, the waterproof lifting mechanism is intelligently started through a water level trigger, stable lifting of the cabinet body is achieved through worm and gear transmission, and the service life of the cabinet body is prolonged. The air guide battens accurately guide air flow to the electric brake connecting end, the local heat dissipation efficiency is improved, and the problems of a traditional power distribution cabinet in the aspects of dust prevention, heat dissipation and water prevention are solved.

The invention relates to a non-excavation anti-sedimentation well lid height difference regulation method and system. Comprising the following steps: performing field investigation and data acquisition, and preparing a corresponding tool according to the acquired data; installing a well mouth gas insulation airbag, monitoring the concentration of combustible materials in the well lid in real time, and predicting the time when the concentration of the combustible materials reaches a safety threshold value; after the concentration of the combustible gas reaches a safety threshold value, a high-frequency coil is installed, and the high-frequency coil is controlled to heat and soften wellhead asphalt through fuzzy PID; physically separating the well lid; heating asphalt around the well lid opening by adopting far infrared heating, and constructing a heat conduction model to predict the temperature condition of the surrounding asphalt until the asphalt is heated to a preset temperature; according to the non-excavation technology provided by the invention, the pavement repairing time can be shortened, the single-point operation time is shortened to be within 3 hours, the influence on traffic is reduced, and compared with a traditional excavation maintenance method, the cost can be saved by 40%, and the carbon emission is reduced by 75%.

The utility model discloses a gas isolation device and a coating production line, and relates to the technical field of glass coating. The gas isolation device comprises a conveying table, a lifting assembly and a first gas isolation plate, the conveying table is provided with a conveying assembly, the conveying table is configured to bear a to-be-coated part, and the conveying assembly is configured to convey the to-be-coated part in the first direction; the lifting assembly is arranged on the conveying table and comprises a driving part and a plurality of lifting supporting parts, each lifting supporting part comprises a rotating end and a supporting end, the rotating ends are rotationally connected with the conveying table, and the driving part is configured to drive the lifting supporting parts to rotate; the first gas separating plate is arranged above the conveying table, and the supporting end abuts against the first gas separating plate in a sliding mode so that the distance between the first gas separating plate and the part to be coated can be adjusted. According to the gas isolation device, the height of the first gas isolation plate can be adjusted through the driving piece on the premise that the gas isolation device is not shut down, so that a good gas isolation effect is achieved, and the equipment cost and the energy consumption cost are reduced.

The utility model provides a connection node heat preservation structure suitable for an ultra-low energy consumption building curtain wall, a buried plate and a first heat insulation cushion block are fixed on a building outer wall through mechanical anchor bolts, and the side edge of an aluminum alloy insertion core is fixedly connected with the face, away from the building outer wall, of the buried plate; the horizontal plane of the aluminum alloy ferrule is fixed with the second heat-insulating cushion block through a first galvanized steel plate; one end, far away from the building outer wall, of the second galvanized steel plate is fixed on the upper side wall of the aluminum alloy cross beam through a fastener, and the other end is fixed on the building outer wall through a fastener; one end of the powder spraying aluminum plate is fixed to the aluminum alloy cross beam and extends in the length direction of the building outer wall. First fireproof rock wool is filled between the powder spraying aluminum plate and the building outer wall; an airtight adhesive tape and a PE foaming heat insulation material are filled between the aluminum alloy cross beam and the aluminum alloy buckle cover; the first glass curtain wall and the second glass curtain wall are connected through a fluorocarbon spraying aluminum plate and a third galvanized steel plate, and the space between the first glass curtain wall and the second glass curtain wall is filled with heat preservation rock wool and a waterproof gas-isolating film. Second fireproof rock wool is filled between the third galvanized steel sheet and the building outer wall.

An air knife is used for cleaning the surface of a battery piece and comprises a metal air pipe, a cavity is formed in the air pipe, an air inlet hole is formed in the air pipe, air hole sets distributed in parallel are formed in the end face of the air pipe, the air hole sets are composed of equidistant air holes, and a specific included angle is formed between the connecting line of the axes of the air holes and the moving path of the battery piece. And uniform airflow is provided for cleaning the electroplating liquid on the surface of the battery piece. The nozzle air knife assembly comprises two oppositely-arranged air knives, the air hole sets are opposite, a battery piece conveying space is reserved, the upper end surface and the lower end surface of a battery piece are cleaned at the same time, and a support is further arranged. The battery piece is driven by the conveying device to horizontally move between the two air knives, high-pressure gas is conveyed into the air pipes, air is blown to the surface of the battery piece from the air hole sets, air barriers are formed through airflow matching of the upstream air hole sets and the downstream air hole sets, the tension of electroplating liquid is broken, and surface cleaning of the battery piece is achieved.

This utility model discloses a well-sealed spiral duct, belonging to the technical field of spiral ducts. It includes two spiral tubes, each with a gasket fixedly installed on one side of the tubes closest to each other, and a flange gasket placed between the two gaskets. A fixing mechanism includes a positioning ring located between the two spiral tubes, which engages with the two gaskets. A sealing mechanism includes a wedge-shaped top ring and a wedge-shaped retaining ring, with the wedge-shaped retaining ring fixedly installed on the inner wall of the lower spiral tube and the wedge-shaped top ring fixedly installed on the inner wall of the upper spiral tube. The flange gasket employs an arc-shaped hole annular array structure to form a double-layer sealing layer, enhancing sealing performance through air barrier effect. Compared to traditional single-layer gaskets, this significantly improves airtightness. The wedge-shaped fit structure of the top and retaining rings, combined with the elastic deformation of the annular rubber gasket, achieves axial compression sealing, forming a dual guarantee of mechanical and soft sealing.

The utility model discloses a building facade hidden frame photovoltaic curtain wall which comprises a supporting structure, one side of the supporting structure is connected with a building structure layer, the other side of the supporting structure penetrates through an inner layer heat preservation plate and is connected with a photovoltaic panel, and the supporting structure comprises a first connecting part and a second connecting part. One end of the first connecting part is fixedly connected with the building structure layer, and the other end is connected with one end of the second connecting part; the photovoltaic panel comprises a moisture-proof vapor-proof layer, an outer-layer heat preservation plate, a photovoltaic frame, an air layer, a structural adhesive layer and a photovoltaic assembly which are sequentially arranged from inside to outside. The other end of the second connecting part is connected with the photovoltaic frame; the composite board has the functions of protection, sound insulation, heat preservation and heat insulation, provides electric power for a building, serves as an outer facing layer of the building, provides safety protection and attractive appearance, and achieves integration of design, manufacturing and installation.

The invention relates to the technical field of smart home, and particularly discloses a smart home monitoring camera system which comprises a shell and an end cover fixedly mounted on the side wall of the shell, a mounting cavity is formed in the inner side wall of the end cover, and a transparent dustproof cover is fixedly mounted on the inner side wall of the mounting cavity. The air supply states of the spiral pipe and the convection pipe are intelligently switched, double-layer dynamic dust prevention is achieved in combination with the cleaning assembly, in daily operation, an air barrier for preventing external dust from invading the mounting cavity is effectively constructed through continuous and active spiral vortex-shaped turbulence, and the surface of the dust cover is preliminarily kept clean; once it is detected that dust accumulation caused by electrostatic adsorption and other factors exceeds a threshold value, the system is immediately switched to a powerful cleaning mode, the cleaning assembly is activated to synergistically and physically remove stubborn dust while air flow focusing impact on the surface of the dustproof cover in the convection pipe is enhanced, and then pollutants are rapidly and annularly discharged through the adjusted spiral air flow.

There is provided an airflow system for a building. The airflow system includes at least one air purification system providing purified air and receiving recirculated air; at least one air supply assembly supplying the purified air from the air purification system to at least one interior airflow space including one or more of, an aisleway, a cafeteria, a restroom, and an elevator; at least one air return assembly returning the recirculated air from the at least one interior airflow space to the at least one air purification system; directional airstream(s) formed between the air supply assembly and the air return assembly, and comprising at least one or more of, a directed airflow field around each occupant, air barrier(s) between each occupant, and an airflow field around each occupant; and at least one control system controlling the airflow system. The airflow system provides a contamination mitigation for each occupant.

1. The name of the design product: barrier box (WSD-G01). 2. The use of the design product: the barrier box for advertising barrier, air barrier and other barriers. 3. The design points of the design product: the combination of shape and pattern. 4. The picture or photo that best indicates the design points: perspective view 1.

This invention provides a method for preparing an air-blocking agent for tire airtight layers, belonging to the field of fine chemical technology. The method includes: Step 1: Raw ore pretreatment, using water washing to remove clay impurities adhering to the ore surface and manually removing associated minerals; Step 2: Coarse crushing, using coarse crushing equipment to crush the raw ore to 80-200 mesh; Step 3: Magnetic separation, using a magnetic separator to remove particles with high iron content from the coarsely crushed raw ore; Step 4: Integrated ultrafine grinding and modification, using a dry grinding process in a pneumatic kinetic energy mill at a temperature of 180-230℃, with the aid of additives, to crush the coarsely crushed raw ore using self-impact and self-friction methods; Step 5: Post-treatment, thoroughly mixing the ultrafine-ground and modified raw ore at a preset temperature and time. This invention effectively improves the grinding precision of black talc powder, enhances its dispersibility and rubber matrix affinity, and effectively removes associated minerals and heavy metal impurities.