Abstract: The present disclosure relates to a system for processing a mixed proppant at a wellsite for a well, the system including a separator including a screen configured to receive the mixed proppant that includes a proppant meeting a desired size criteria and an oversized proppant exceeding the desired size criteria, sort the proppant from the oversized proppant, direct the proppant along a primary flow path to a blender, and direct the oversized proppant along a diverted flow path to a reducer. The reducer is operable to process the oversized proppant into a processed proppant that meets the desired size criteria.

Abstract: Disclosed is a method for operating a continuously variable transmission including two pulleys, each defining an effectively V-shaped circumference groove of variable width, a drive belt, wrapped around the pulleys, and a cooling system, which cooling system is provided with a controller for supplying a controlled amount of a cooling agent to the drive belt. The controller is arranged to supply at least a minimum amount of the cooling agent to the drive belt during operation of the transmission.

Abstract: A method for producing foam glass with high open pore content using recycled waste glass. The size of the pores of the foam glass is small and uniform, and such foam glass is suitable for building material with thermal insulating and sound proofing properties. The foam glass produced by this method is lightweight, durable and has high compression strength.

Abstract: A method for manufacturing a reconstituted stone raw material by using a molten slag includes: controlling a temperature of the molten slag at 1400° C.-1500° C., and performing a cast-molding process on the molten slag; and maintaining the cast-molded slag at a temperature of 800° C.-1000° C. for 1-5 hours in a non-reducing atmosphere, and then gradually cooling the cast-molded slag to a room temperature within 2-5 hours to obtain the reconstituted stone raw material. An energy-saving and efficient method for comprehensively utilizing the blast furnace slag is provided. The produced reconstituted stone raw material has such characteristics as stable color quality, abrasion resistance, pressure resistance, strong adhesiveness, low coefficient of expansion and low shrinkage ratio.

Abstract: A method for the continuous production of a cellular ceramic plate having asymmetric cells comprising thermally treating ceramic particles and a blowing agent in a foaming furnace while conveying said ceramic particles and said blowing agent at a first speed thereby forming a cellular ceramic plate, and annealing said cellular ceramic plate in an annealing lehr by cooling it down while conveying it at a second speed, larger than said first speed, thereby stretching and cooling said cellular ceramic plate.

Abstract: In a process for granulating slag, from a blast furnace or a smelting reduction plant, in which a granule/water mixture formed during the granulation is fed to a granulation tank and then to a dewatering installation, in which the slag granules are dewatered. H2S-containing vapors and gases formed during the granulation are at least partially condensed by injection of water in a condensation space which is flow-connected to the granulation tank. H2S-containing residual gases are discharged from the compensation space below the water injection point, H2S is burnt.

Abstract: In a process for granulating slag, from a blast furnace or a smelting reduction plant, in which a granule/water mixture formed during the granulation is fed to a granulation tank and then to a dewatering installation, in which the slag granules are dewatered. H2S-containing vapors and gases formed during the granulation are at least partially condensed by injection of water in a condensation space which is flow-connected to the granulation tank. H2S-containing residual gases are discharged from the compensation space below the water injection point, H2S is burnt.

Abstract: The invention relates to a process and apparatus for forming a particulate composition, especially a particle glass composition, through the use of shock waves. A nozzle element is utilized having inlets for introduction of cold and heated gas and a delivery tube for introducing molten material. Through the introduction of the cold and heated gases, droplets are formed from a molten stream, a cone-shaped standing shock wave is formed, and shock waves are formed via a modified Hartmann-Sprenger chamber, the shock waves impinging on the droplet stream to break up the larger droplets.

Abstract: A spraying head for a granulating installation includes a slotted nozzle in which a nozzle channel having an oblong cross-section of flow is limited downwards by a floor surface, upwards by a top surface and laterally by a side face on each side. An oblong flow control body in the nozzle channel extends axially between the two side faces to limit the height of a nozzle slot. The control body is pivoted about a longitudinal axis to adjust the height of the nozzle slot. The control body is a cylindrical body having an oval cross-section and a central axis which is approximately centrically disposed between the floor surface and the top surface and pivoted about its central axis, such that underneath as well as below the control body a nozzle slot is formed, the height of which can be adjusted by pivoting the control body about its central axis.

Abstract: A method for producing powders that consist of substantially spherical particles from a material such as glass, ceramics or plastic that produces a highly viscous melt that solidifies at a glass transition temperature Tg or at a solidification temperature Ts. The inventive method comprises the following steps: (a) producing a melt of a viscosity ? in the range of from 0.1 to 100 Ns/m2; (b) atomizing the melt using a first gas, the first gas having a temperature TA?Tg or ?0.5Ts at the outlet of the nozzle and (c) cooling off the particles produced by atomization in a cooling section downstream of the nozzle using a coolant, the temperature of the coolant being smaller than Ts or Tg.

Abstract: A method for repairing an insulating glass unit and apparatus to facilitate such repair. A bore is drilled through a frame encasing an insulating glass unit to expose the peripheral spacer of the unit, and a hole is drilled through a wall of the spacer to enable air to enter the space between the panes. The hole in the spacer is then sealed, for example, with a rivet, and the bore in the frame is then filled and sealed as well.

Abstract: A simple and compact device for wet granulation of liquid slag, comprising a granulating basin with a water injection device and a decanting basin that is separate from the granulating basin. A distribution channel for the granulate-water mixture extends above the decanting basin and is provided with outflow means along the entire length and on the lower side thereof for the granulate-water mixture. A vertical inflow shaft that is open towards the bottom is arranged underneath the distribution channel. The outflow means for the granulate-water mixture discharges into said inflow shaft.

Abstract: In a method of producing a glass gob by continuously dropping a molten glass 9 from a nozzle 2 in a dropping direction, a gas flow 20 is caused to continuously flow in the dropping direction along an outer peripheral surface of the nozzle 2 at a predetermined flow rate. The gas flow 20 applies a wind pressure to the molten glass 9 appearing from a nozzle end 2a of the nozzle 2 to drop the molten glass 9.

Abstract: The object of the present invention is to provide a safe, easy-to-manage, successive, and swift method and system for preventing granulated blast-furnace slag from solidifying. Carbonated water is generated by dissolving carbon dioxide in water. Granulated blast-furnace slag which has been cooled is immersed in the generated carbonated water.

Abstract: The method for granulating liquid slag melts, in particular blast furnace slag, in which the melt (2) is ejected into a cooling chamber via a slag tundish (1) and in which fluid under pressure, in particular compressed gas, vapor or pressurized water, is injected in the direction of the slag exit (6) in order to eject said liquid slag, is characterized in that the pressure fluid jet discharges into a throttle pipe (3) which is immersed in the slag bath and whose lower edge is mounted so as to be adjustable in the height direction (4). The corresponding device comprises a lance (7) which is surrounded by a height-adjustable throttle pipe (3) whose lower edge (5) is immersed in the slag bath (2) contained in the tundish (1) and forms a throttling cross section between the slag exit (6) and the slag bath (2).

Abstract: The present invention relates to a process and apparatus to cast and form slag directly from the molten state into crystalline or amorphous products suitable for use as decorative and structural building and construction materials. Molten slag and additives are refined at high temperature in a treatment furnace for a period of hours. The eventual entrapped gas content is controlled using a variety of methods, such as vacuum pressures and bottom stirring with inert gas. The molten slag is cast directly into moulds, and these moulds form the slag into any shape desired. The formed products are immediately introduced into a heat treatment furnace at temperatures at or above the glass transition temperature (GTT) for the case of crystalline products, or just below the GTT for amorphous products. The product is thermally cycled over a period of hours to relieve thermal stresses during cooling to ambient temperatures.

Abstract: The invention relates to the electric melting technique, in which the melting energy is dissipated in the bath of melted glass as a result of the Joule effect by means of electrodes which dip through the surface of the bath. According to the invention, the electrodes dip into a bath of melted glass which has a height h below 800 mm and a surface S such that the ratio h/S is lower than 0.5 m/m.sup.2. According to another aspect, the exchange surface between the electrodes and the bath is above 0.075 m.sup.2 /m.sup.3 of glass.The invention is used in the manufacture of glass-based products, such as insulating materials based on glass fiber.

Abstract: Molten matte or slag is water granulated by feeding molten matte or slag through a launder to a granulator tank. The tank includes sloping walls and is equipped with adjustable overflow weirs and one or more of spray nozzles. These nozzles are positioned such that the water that they emit impacts on substantially all of the molten matte or slag that is fed to the granulator tank. The granulation tank is optionally coated with a polymeric material to reduce the potential for phreatic explosions. The granulator is also optionally equipped with a gas offtake which can be connected directly to a quench tower which in turn can be connected to an induced ventilation system.

Abstract: Metallurgical slag is expanded to produce a lightweight solid by forming a stream of molten liquid slag of controlled rate of flow and mixing the stream of slag with a controlled quantity of water and flowing the interacting mixture of slag and water into a receptacle. The interaction between slag and water is allowed to proceed for a predetermined period of time to form an expanded solid without the addition of any additional cooling water which would otherwise quench the material and vitrify it. In the receptacle, a vaned rotor operates to segment the interacting mixture of slag and water and project the segmented mixture through the air for collection into a heap.

Abstract: A method and system for processing waste dries and reforms a sludge stream of the waste with a first reformed effluent stream to produce a gas effluent stream and a solids effluent stream. The gas effluent stream is reformed further to produce the first effluent stream, which is then directed back to the sludge stream.

Abstract: Processes and systems for producing cementitious materials from ferrous blast furnace slags. Processes comprise mixing of a source of CaO with molten slag flowing from at least one slag tap hole of a blast furnace. Sufficient CaO is mixed with the molten slag to raise the ratio of CaO to SiO.sub.2, the C/S Ratio, of the slag to between about 1.06 and 1.25, while maintaining the Base Number of the molten slag less than about 1.55. The slag is then water granulated and ground to a predetermined degree of fineness. An activator then is added to the ground granulated slag. The C/S Ratio of the granulated slag determines the degree of fineness to which the granulated slag must be ground to achieve a desired hydration rate in the resultant cementitious material. Cementitious materials with C/S Ratios in this range may be ground less finely, yet possess the same hydration rates, as other more finely ground cementitious materials.

Abstract: Processes and systems for producing cementitious materials from ferrous blast furnace slags. Processes comprise mixing of a source of CaO with molten slag flowing from at least one slag tap hole of a blast furnace. Sufficient CaO is mixed with the molten slag to raise the ratio of CaO to SiO.sub.2, the C/S Ratio, of the slag to between about 1.06 and 1.25, while maintaining the Base Number of the molten slag less than about 1.55. The slag is then water granulated and ground to a predetermined degree of fineness. An activator then is added to the ground granulated slag. The C/S Ratio of the granulated slag determines the degree of fineness to which the granulated slag must be ground to achieve a desired hydration rate in the resultant cementitious material. Cementitious materials with C/S Ratios in this range may be ground less finely, yet possess the same hydration rates, as other more finely ground cementitious materials.

Abstract: A device in which a mixture of steam and contaminated air is first of all channelled into an upward stream and that the mixture subsequently flows as a downward stream in a vessel maintained at reduced pressure. The device further includes an arrangement for spraying an alkaline aqueous solution into the downward stream of the mixture of steam and contaminated air. The decontaminated uncondensed gases are thereby removed from the vessel by a forced and adjustable stream which creates and maintains a reduced pressure inside the vessel.

Abstract: A method and apparatus of reclaiming hazardous inorganic wastes to produce an environmentally benign abrasive for use in loose grain processes, as a coated or bonded abrasive, or as a polishing grain. A tough and useful abrasive, with a MOH hardness of 7 to 8, is manufactured from emission control dusts of the aluminum industry or sludges from other industries, and may include small amounts of lead and cadmium oxides as toughening agents. The abrasive particles are sized by air sifting or by water sedimentation separating methods. The process for the manufacture of abrasive material comprises the steps of removing soluble salts from a waste stream by hot water extraction; using a computer matrix to group the waste stream into different batches for mixing with other glass-making materials to form a batch mixture; oxidizing the organic compounds contained in the batched mixture; melting the batch mixture to form a glasseous substance; and fritting the glasseous substance to form the abrasive.

Abstract: A method for processing hot, liquid slag includes the steps of: conveying the slag to be processed to an upper region of a granular material forming a fluidized bed that has a temperature below the solidification temperature of the slag; cooling the slag to a temperature below its solidification temperature while simultaneously forming granules; and maintaining the temperature of the fluidized bed at a temperature below the solidification temperature of the slag.

Abstract: The present invention provides a new process and a new apparatus for the treatment of steel-mill slag in a vessel which allows a wet granulation of the slag without the risk of explosions. The slag is caused to flow through a taphole at the bottom of the vessel, and the flow rate of the slag is determined by means of a continuous check of the weight of the vessel. One or more jets of granulating water, the flow rate of which is adjusted as a function of the slag flow rate, are directed onto the stream of slag flowing from the vessel. The apparatus comprises a vessel containing molten slag. This vessel is equipped with weighing means, with a taphole, with a device for shutting off the taphole, with means for maneuvering the shut-off device between an operating position and a stored or parked position away from the taphole and with a device for opening or freeing the taphole, engageable through the latter in order to initiate the flow of slag.

Abstract: The invention provides a new enclosure for slag pelletizers, and a new method of operating such an enclosure, that minimizes the noise and the escape into the ambient atmosphere of hydrogen sulfide and airborne particulate material produced by the pelletization. The enclosure consists of impereable walls and a roof, the pelletized material being removed through an openable door at one end that is closed during the process. The enclosure has three successive zones, in the first of which contains the pelletizer, this being supplied with only the amount of water needed for pelletization. In the second zone containing the slag pile a plurality of very fine mist producing nozzles supply water to the gases to cool them using its latent heat of evaporation, the amount of water supplied being such as to cool them as much as possible while being limited so that it all remains vaporized and cannot enter the slag pile to increase its moisture content.

Abstract: Flakes of glass, basalt or other frangible material are formed by feeding a stream of the molten material in a downwards direction into a rotating cup (5) which has its open mouth facing upwardly with its rim disposed at a horizontal level between a pair of spaced apart parallel plates (9 and 11) which are mounted within a vacuum chamber (13) in such manner that, as air is drawn from outside the chamber (13) between the plates (9 and 11) the molten material is drawn radially outwardly without touching the plates and is cooled with the continuing outward movement causing the material to be broken into flakes.

Abstract: An enclosure for slag pelletizers, and a method of operating such an enclosure, that minimizes the escape into the ambient atmosphere of airborne fibres produced by the pelletization process, while permitting the necessary free passage of the steam and gases that are also produced. The enclosure roof consists of at least one layer of wire mesh and a system of overlapping baffles is provided beneath the roof at least above the pelletizer to intercept the particulate material, so that the pellets do not disrupt a blanket of the fibre which is allowed to accumulate on the wire mesh to facilitate removal of the remainder of the fibre from the air stream. The method allows the deposition of an effective blanket, while preventing the deposition of too much fibre, so that the gas stream is diverted and flows out of the open end of the enclosure.

Abstract: A process and apparatus for granulating slag in which molten slag is charged into a drum and is solidified and granulated therein on cooled surfaces. To ensure a rapid cooling at a high thruput rate, the molten slag is applied to the inside surface of a drum, which rotates on a horizontal axis and has a cooled shell, and the solidified film of slag is mechanically detached from the inside surface after about three-quarters of a revolution of the drum and is discharged.

Abstract: An apparatus for granulating metallurgical melt, including a granulator (1) having a water supply (13), a trough (2) for supplying metallurgical melt thereto, and a rotary driven drum (3) having blades (6). A water tank (11) having an overflow device (12) is disposed under the drum (3). The granulator (1) and trough (2) are disposed in the interior of the drum (3), the lower part of the drum being disposed in the tank (11) below the overflow device (12), The apparatus is provided with a trough (22) for discharging granules from the drum (3).

Abstract: In a process for refining molten glass or the like by vacuum, the collapse of foam is accelerated by periodically applying a surge of pressure that disrupts foam stability. Preferably, the surge is a short pulse of lower pressure.

Abstract: A three-fluid heat exchanger cools the compressed air from the supercharger by engine-cooling water and air in a radiator with coaxial-tube bundles.

Abstract: In order to reduce or avoid the discharge of gaseous pollutants H.sub.2 S and SO.sub.2 to the environment in a process for the production of slag sand (granules) from blast-furnace slag by granulation of the slag by means of a water jet, the propulsion jet interspersed with water vapor, granules and pollutants is injected directly into a water receiver, the residual vapor still remaining and the pollutants H.sub.2 S and SO.sub.2 not yet washed out are cooled down in a condenser in counter-current with spray water and condensed, and the residual gas remaining after the vapor condensation is taken off from the top end of the condenser and recycled via a recycle line back to the injector.

Abstract: A nozzle or nozzles for spraying cooling water are disposed at the lower end of a slag suction path. A cooling water down-flow passage is provided on the outer periphery of an inner tube which constitutes a slag suction path. A water sump is provided below the cooling water down-flow passage, the water sump being located lower than the each nozzle. A lower end opening of the cooling water down-flow passage is disposed lower than the each nozzle and is submerged in water in the water sump. The cooling water down-flow passage, except the lower end opening, is adapted to be closed up. When the cooling water down-flow passage is closed up, water in the passage is stopped by atmospheric pressure acting upon the surface of the water in the water sump, so that it is prevented from flowing down.

Abstract: An apparatus for air-pulverizing high-temperature molten slag by blowing air at high speed through a nozzle into a flow of molten slag that is falling from an inclined container by the intermediary of a turndish. A heat detector is provided for detecting the quantity of heat in the flow of molten slag after being air-pulverized by the high speed air flow, and a feedback control device which is responsive to a detection signal issued from the detector is provided for calculating a desirable inclination angle of the container or the turndish and transmitting a control signal obtained as a result of the calculation to a controller for controlling the inclination of the container or turndish thereby stabilizing the air-pulverizing of the high-temperature molten slag.

Abstract: The invention relates to a method for manufacturing heat-resistant and/or fire-resistant fibre materials, when the employed initial material is molten slag from metal processes. According to the invention, the slag holding furnace (5) is used for achieving an essentially even and continuous molten flow from the slag smelting furnace (3) into the mineral wool furnace (6). The invention also relates to an apparatus for realizing the method, wherein the holding furnace (5) is provided with at least one control device (12) which shifts the furnace (5) between the different filling positions in order to ensure an even and continuous flow of molten material.

Abstract: An apparatus for converting thermoplastic molten material stream into fibers to produce fibers, particularly to produce mineral wool from molten mineral raw material. The device combines a slinger cup wheel with a pair of fiberizing rotors. The rotors have each a concavely rounded peripheral groove. The cup wheel is virtually completely surrounded by the two grooves of the rotors so that there is no random spreading of the molten material as all of discrete, fine streams produced by the cup are attenuated by the rotors. As there is no sudden "bouncing" of the attenuated material, the invention produces an improved uniformity of the diameter of final fibres and substantially reduces the shot content in the final product. The stress to which the machinery is subjected is also limited.

Abstract: Molten slag is poured onto the upper surface of an elongated conveyor member. The surface of the conveyor member is cooled while maintaining it free from contact with liquids. Preferably, this is accomplished by way of a water cooled pan connected to the lower surface of the member. Reciprocal lengthwise motion is imparted to the conveyor member to transport the slag over the cooled surface until the slag is solidified and broken into pieces.

Abstract: A filtration apparatus comprised of a rotary drum having a plurality of internal vanes for conveying slag material is presented. The slag is conveyed upwardly by the vanes, after which is falls freely onto a conveyer belt passing longitudinally through the drum. Deflectors guide the slag during its fall onto the belt. The deflectors are divergent and inclined relative to the direction of movement of the conveyer belt. The rotatable drum is axially subdivided into a plurality of sections, the vanes of each section being angularly offset in relation to the vanes of adjacent sections. The filtering apparatus herein effects uniform charging of slag material onto the conveyer belt.

Abstract: A method and apparatus are presented for granulation of molten slag for determining the flow of molten slag and adjusting the supply of granulation water in accordance with the flow of molten slag.

Abstract: A filtration apparatus comprised of a rotary drum having a plurality of internal vanes for conveying slag material therein therein is presented. The slag is conveyed upwardly by the vanes, after which it falls freely onto a conveyer belt passing longitudinally through the drum. Each vane consists of a retaining blade and a liquid permeable filtering blade spaced from the retaining blade. A deflecting means is positioned beneath the filtering blade. The deflecting means includes a deflecting plate associated with a support member. The support member and the retaining blade provide a supporting frame work for the rotary drum.

Abstract: Installation of the type according to which molten mineral, subjected to spraying with water jets, is sent onto a rotary drum, then dispersed as a shower in a closed insulating enclosure provided at its base with a system for receiving the cooled particles or pellets, includes as such drum a fluid-tight drum which is cooled by internal circulation of water in a closed circuit and provided with blades having a special profile in the shape of a scoop or chistera. Further, the receiving system includes a series of vibrating tables placed in a cascade the last table of which, the farthest from the rotary drum and receiving the contents from the upstream tables, pours all the collected dry pellets onto a hooded belt conveyor which brings the pellets to storage hoppers or silos.

Abstract: Apparatus for the pelletization of heat-liquifiable materials, such as metallurgical slags, consists of feed means for the molten material, these feed means depositing the material on a downwardly-extending feed plate over which it flows while it is mixed with water, if water is necessary to promote the expansion of the molten material and for control of the cooling. The material then flows on to a first rotating radially-vaned drum or rotor by which it is projected into the air for simultaneous cooling and pelletization. The feed means comprises flow control means such that any flow greater than a predetermined maximum is fed onto a second feed plate disposed above the first, from which the excess molten material flows on to a second rotating radially-vaned drum or rotor operative in like manner to the first. The flow control means may comprise for example a dam over which the excess material flows.

Abstract: An apparatus for vitrifying blast furnace slag, which comprises:an endless conveyor belt formed by endlessly connecting a plurality of rectangular cooling metal members, each of said cooling metal members having a plurality of narrow and deep cooling grooves on the outer surface thereof for rapidly cooling and solidifying a molten blast furnace slag into a vitreous blast furnace slag; a driving means for travelling said endless conveyor belt; a molten slag container, arranged above the upstream of the upper forwarding position of said endless conveyor belt, for pouring a molten blast furnace slag into said cooling grooves; a stripper arranged, in the upstream of the lower returning position of said endless conveyor belt, at a prescribed position adjacent to the back surface of said endless conveyor belt, for taking out a cooled and solidified vitreous blast furnace slag in said cooling grooves; and, a cooling means arranged at a prescribed position in the lower returning position of said endless conveyor belt

Abstract: Molten slag is granulated with water to produce a granulated-slag/water sry that is fed into the bottom of a horizontally extending foraminous drum. This drum has radially inwardly extending vanes and is rotated to lift up the granulated slag and separate it from the water, discharging the slag onto a conveyor belt for storage or further use. The water running out of the slag slurry is recirculated for use in the initial granulation step for the molten slag stream.

Abstract: Disclosed is an installation for the treatment and handling of metallurgical slag which includes means for the disintegration of a flow of pyroplastic slag by mechanical impacts and cooling means for the cooling of the particles of slag formed by the disintegration. The installation comprises at least one perforated endless band positioned in the path of fall of the particles of slag projected by the disintegration means and cooled by the said cooling means. The installation also comprises an insulating enclosure positioned immediately above the perforated band and which contains the disintegration and cooling means, and means for trapping the ascending gaseous and/or solid by-products.

Abstract: Apparatus and method for manufacturing crushed sands from blast furnace melted slags including maintaining molten blast furnace melted slags out of contact with water while cooling the molten slags to a temperature between 850.degree. C. to 1300.degree. C. and then rapidly cooling the cooled slags with water thereby producing coarse grain hard quality water processed slags.

Abstract: The apparatus is intended for processing partly solidified slags transported in ladles out of smelting shop and also for processing slags directly besides blast furnaces and steel-making units (e.g. converters).The apparatus comprises a settling bin provided at its inlet with a water-jet granulator. The settling bin incorporates an elevator with perforated buckets for discharging granulated slag. Elevator pulley shafts are located above the level of water in the bin, the head pulley (the furthest from the granulating compartment) is placed higher than the tail pulley (the nearest to the granulating compartment). A drier is provided at the place of discharge of granulated slag from the settling bin.The settling bin is of a sealed design and is divided by a partition into two compartments, one of which is intended for granulating molten slag, and the other, for discharging granulated slag from the bin by the elevator. A constant level of water in the bin is ensured by an overflow partition.

Abstract: Molten blast furnace slag is quenched by a volume of water divided into two streams. The first stream is directed downwardly against the slag while the second stream is directed horizontally against the slag. The molten slag is broken down into relatively fine sand-like granules which are kept submerged in the water. The vapors formed during granulation are substantially free of detectable SO.sub.2 and the H.sub.2 S formed and vented to the atmosphere is insufficient to be a detriment to the surrounding environment.