1893results about "Space heating and ventilation" patented technology

The utility model discloses a filter element cleaning structure and an air conditioner and relates to the technical field of air conditioners, the filter element cleaning structure and the air conditioner comprise a filter element, the filter element cleaning structure further comprises a shell, a fixed part and a cleaning assembly, the fixed part comprises a fixed frame and a movable frame, the fixed frame is arranged on the inner wall of the shell, and the movable frame is arranged on the inner wall of the shell. An air inlet cavity and a flow guide cavity are correspondingly formed in the upper end and the lower end of the fixed frame, the movable frame is installed in the air inlet cavity corresponding to the fixed frame, the fixed frame and the movable frame are used for fixing the two ends of the filter element respectively, the air inlet cavity and the flow guide cavity are communicated through a flow guide hole in the center of the fixed frame, and the cleaning assembly comprises a blowing part and a rotary cleaning part. According to the automatic cleaning device for the filter element, a blowing cleaning mode and a contact cleaning mode are combined to automatically clean the filter element, the cleaning effect on the filter element can be effectively guaranteed, the labor intensity during manual operation can be effectively reduced, and the automatic cleaning device has good application prospects.

The invention relates to the technical field of grain surface air conditioners, and discloses a grain surface air conditioning system with an air-tight door, which comprises a case and two air ports in the front wall of the case, a shaft tube disc is rotatably connected in the front wall of the case, the left and right sides of the shaft tube disc are respectively provided with a through groove I butted with the air ports, and the upper and lower sides of the shaft tube disc are respectively provided with a through groove II; the front side and the rear side of the second through groove are slidably connected with abutting connection discs, and first sealing rings are arranged on the edges of the opposite sides of the abutting connection discs. The shaft pipe disc and the abutting disc are controlled to act step by step before and after granary fumigation, the first sealing ring is driven to vertically extrude and seal the air opening or vertically reset, the valve cover is matched to extrude the second sealing ring and contract into the two air pipes, and therefore the situation that a sealing piece is abraded and fails is avoided, and the double-air-tight-door function is provided; in addition, dust on the surface of the elastic filter disc can be fully cleaned and collected, the situation that the dust and hydrogen phosphide are combined to form viscous particles to block the elastic filter disc is avoided, and follow-up stable use of the elastic filter disc is guaranteed.

The invention discloses a vehicle-mounted oxygen generation method, a main controller, an intelligent seat and a vehicle. Non-sensing type physiological signal collection is achieved through the supporting air bag and the sensing assembly of the seat, the target object does not need to additionally wear a detection device in the daily riding process, and the biological signal of the target object can be automatically obtained; the main controller adjusts the oxygen supply frequency of the oxygen supply assembly according to the obtained biological signal, and pulse type oxygen supply matched with the user state is achieved, so that oxygen waste caused by traditional continuous oxygen supply is avoided, and the oxygen supply utilization rate is increased; meanwhile, the oxygen supply assembly is connected with a high-pressure air source in the vehicle through the oxygen generation assembly, and a compressor for oxygen generation does not need to be additionally arranged, so that extra noise is avoided in the oxygen generation process, and meanwhile the space occupancy rate of the whole vehicle is reduced; in addition, active participation of a user is not needed in the whole process, full-process non-perceptual adjustment from detection to oxygen supply can be achieved, and comfort and intelligent experience are both considered.

The utility model discloses an air cooler front plate filter screen structure, and relates to the field of air coolers, the air cooler front plate filter screen structure comprises a front plate body and a filter screen, the front plate body is a metal plate, the filter screen is a flexible screen, magnetic suction strips are arranged on the peripheral side of the filter screen, the magnetic suction strips are adsorbed on the front plate body, and a limiting plate is arranged on the side wall, close to the filter screen, of the front plate. The number of the limiting plates is two, and the two limiting plates are located on the upper side and the lower side of the filter screen and limit the filter screen. When the filter screen is installed, the filter screen is firstly bent, the upper end and the lower end of the filter screen are placed into the two limiting plates, then the filter screen is attracted and fixed to the front plate body through the magnetic attraction strips, then installation of the filter screen can be rapidly completed, and when the filter screen is disassembled, the filter screen is firstly bent, one side of the filter screen is moved out of the limiting plates, and then disassembly of the filter screen can be rapidly completed. The filter screen is more convenient and quicker to disassemble and assemble.

The utility model discloses a microswitch assembly of an air purifier, which comprises a switch support, and a microswitch is arranged in the switch support. The switch support is fixed to one end of an air duct shell of the air purifier, a guide hole is formed in the end, close to the switch support, of the air duct shell, an air inlet grille is installed on the air inlet face of the air duct shell and limits a filter screen in the air duct shell, a guide block is arranged at the end, close to the guide hole, of the air inlet grille, and the guide block is fixed to the air duct shell. The guide block passes through the guide hole so as to abut against an action elastic sheet of the microswitch. When the air inlet grille is installed in place, the guide block presses the action elastic piece to trigger the microswitch, and the air purifier is powered on to work. When the filter screen needs to be replaced and the air inlet grille is disassembled, the guide block is separated from the action elastic piece, the microswitch is closed, and the air purifier is powered off. According to the utility model, the air purifier can be automatically closed when the filter screen is replaced or detached, so that the safety of a user is effectively protected.

The utility model relates to the technical field of fresh air settling treatment, in particular to a fresh air settling chamber for a clean room, which comprises a settling chamber main body, a partition plate is arranged in the settling chamber main body, a collecting structure is arranged on one side of the partition plate, and side plates are mounted on two sides of the inner wall of the settling chamber main body; through the collecting structure, when air is treated, air in the clean room is introduced into the air inlet pipe, at the moment, after the air is pretreated through the air inlet structure, the air enters the space between the side plates on the two sides, large dust particles in the air fall down under the influence of the gravity of the dust particles and are stuck and fixed by the sticking belt below, and dust is prevented from being blown by wind to fly around; when the adhesive tape on one side is fully paved with dust particles, the output shaft of the adhesive tape can drive the rotating rod to rotate through driving of the servo motor, so that one side of the collecting roller is replaced, and when the adhesive tapes on the four sides are fully paved with dust, the cover plate is taken down, and the adhesive tapes are torn down one by one and replaced. Therefore, the purposes of collecting dust and preventing dust particles from returning to the air chamber are achieved.

The invention relates to the technical field of clean room air conditioners, and particularly discloses an air regulation and control structure for a clean room, the air regulation and control structure comprises a ventilation unit, a fresh air pipe, an air return pipe, a first air supply pipe, a collection device, a cleaning device and a regulation device, and the ventilation unit can transfer, update and circulate air in the clean room; the fresh air pipe is arranged at a fresh air port of the ventilator unit; the air return pipe is arranged at an air return port of the ventilator unit; the first air supply pipe is arranged at an air supply outlet of the ventilator unit; the collecting device is arranged at an output port of the first air supply pipe and can collect pollutants; the cleaning device is arranged in the center of the right side of the outer wall of the output port of the collecting device, and through collaborative design of the collecting device and the cleaning device, the mode that a traditional clean room filtering part depends on manual disassembly and assembly is changed; the cleaning device drives symmetrical filter screen cleaning brushes to comprehensively clean the filter screen in a reciprocating manner by means of a three-connecting-rod driving mechanism, so that no cleaning dead angles exist on the front and rear sides of the filter screen.

The utility model discloses a pet purifier, which comprises a purifier body, a fan seat and a cat lying plate, and is characterized in that the side wall of the fan seat is provided with an elastic buckle structure, and the fan seat is detachably connected with the purifier body through an elastic buckle. The machine body comprises a metal cage, a filter cartridge, a top ring and a base, and a small pressing plate is arranged on the base and is fixed by buckling a bottom frame of the metal cage. The pet purifier has the structural characteristics of convenience in disassembly and large air inlet aperture, so that the filter cartridge is convenient to replace, the air resistance is small, animal hair is easily adsorbed, and the actual use effect is improved.

The utility model belongs to the field of air purification, and relates to an air purification assembly and an air purifier. The air purification assembly comprises a primary filter screen layer, a graphene manganese-based filter screen layer and a graphene manganese-based purification screen layer which are stacked in sequence; the graphene manganese-based filter screen layer is a filter screen layer formed by a graphene manganese-based material, and the graphene manganese-based material comprises a porous framework, and graphene and a manganese-based catalyst which are loaded on the porous framework; the graphene manganese-based purification net layer comprises an elastic framework, a gap is formed in the elastic framework, the gap is filled with a purification material, and the purification material is a composite material of graphene, activated carbon and a manganese-based catalyst. The air purification assembly provided by the utility model can quickly adsorb and purify peculiar smell in air, simultaneously realizes a good antibacterial effect, prevents mould breeding, purifies the peculiar smell of pets, and ensures a healthy living space at the same time.

The invention discloses a multifunctional intelligent tea table which comprises a cabinet body, and a water adding module, a tea leaf adding module, a residual tea processing module and the like are integrated in the cabinet body. Wherein the water adding module comprises a teacup placing area, a water outlet with a roller way, a driving device, a water pump and a heating device, and the heating device is of a double-water-container structure arranged at the two ends in the cabinet body respectively. And the tea leaf adding module communicates the tea leaf inlet with the water container through a pipeline. The residual tea processing module is provided with a waste water collecting box, a washing water gun and a transmission mechanism comprising a motor, a connecting rod and a screw rod, and the mechanism can control transverse displacement and longitudinal separation of the water container. According to the technical scheme, full-process automation of tea adding, hot water supply and residue treatment is achieved, a user only needs to place tea cups and tea to complete brewing operation, meanwhile, the sanitation problem caused by residue retention of a traditional tea table is avoided, and use convenience and environment cleanliness are remarkably improved.

The utility model discloses a clean workshop air purification device which comprises a purifier body, a disinfection mechanism is arranged at the front end in the purifier body, the disinfection mechanism comprises a liquid storage tank fixedly connected to the front side of the lower end in the purifier body, and connecting pipes are connected to the two ends of the liquid storage tank in an inserted mode. A plurality of evenly-distributed atomizing nozzles are inserted into the sides, close to each other, of the connecting pipes, the upper ends and the lower ends of the connecting pipes are sleeved with buckles, the buckles are fixedly connected to the inner side wall of the purifier body, and the filtering mechanism is arranged in the middle of the interior of the purifier body. Compared with the prior art, the air purifier has the advantages that the quality of air blown out from the interior of the purifier body is higher, the elastic plates on the two sides are pressed towards the middle, the sliding frame is pulled out from the side face, operation of workers is facilitated, and the primary-efficiency filter screen, the medium-efficiency filter screen and the high-efficiency filter screen on the sliding frame can be replaced conveniently.

The utility model discloses a cylindrical air purifier which comprises a base with a side wall grid mesh structure, a shell is arranged on the base, a partition plate is arranged in the shell and divides the interior of the shell into an upper cavity and a lower cavity, and a grid mesh communicated with the upper cavity and the lower cavity is arranged in the middle of the partition plate. A purification assembly covering the grid mesh on the partition plate is arranged in the lower cavity. An air channel pipe covering the grid mesh on the partition plate is arranged in the upper cavity, a fan assembly is arranged in the air channel pipe, a motor base of the fan assembly is fixed to the air channel pipe, an air outlet assembly is arranged on the motor base and composed of an air outlet net and an air outlet frame, the air outlet net is arranged in the air outlet frame, the air outlet frame is fixed to the motor base, and a control assembly is arranged on the air outlet frame. A shell of the control assembly is suspended above the air outlet net, and the two ends of the shell are fixed to the air outlet frame to form a handle structure. The purifier can remove harmful substances and peculiar smell, the occupied space is reduced, and the purifier is light, convenient, safe and reliable.

The invention discloses an indoor intelligent formaldehyde detection and purification device and a use method thereof. The device comprises a movable shell, a self-adaptive intelligent control system, a pretreatment unit, an efficient adsorption unit and a core catalysis unit. The pre-treatment unit is used for filtering and dehumidifying, the efficient adsorption unit is used for adsorbing formaldehyde and desorbing to realize regeneration of a composite adsorbent layer, and the core catalysis unit is used for catalytically decomposing formaldehyde and desorbed formaldehyde; and the self-adaptive intelligent control system is used for acquiring outdoor air data, dynamically tracking formaldehyde pollution and regulating and controlling purification. Through three stages of units, in combination with a multi-stage cooperative processing and intelligent feedback control technology, formaldehyde is efficiently and directionally removed by virtue of a three-stage linkage mechanism of pre-adsorption enrichment, gradient desorption regeneration and catalytic deep decomposition, the selectivity is good, safety is realized, no extra volatile organic compound is released, and the catalytic efficiency is high; adsorbent regeneration improves stability and reduces cost.

The invention relates to the technical field of air purification, in particular to an air purification material and a preparation method and application thereof.The air purification material at least comprises modified chitosan, manganese ions (Mn < 2 + >) and cerium ions (Ce < 3 + >) are evenly loaded on the modified chitosan, and the air purification material is prepared by taking chitosan as a raw material through a hydrothermal method. The prepared adsorbent has good adsorption effect on various volatile organic compounds, is better in stability, can be used in high-humidity and acid environments, and is expected to play a greater role in the field of air purification.

The invention discloses a filtering device and a cleaning method thereof.The filtering device comprises a first cleaning assembly and a second cleaning assembly, the first cleaning assembly is suitable for abutting against a to-be-cleaned surface of the filtering device to move, and the cleaning method comprises the steps that the first cleaning assembly is driven to move to a target position; driving the first cleaning assembly to move from the target position to a first position; wherein the second cleaning assembly is arranged between the target position and the first position so as to at least partially remove dirt attached between the first cleaning assembly and the surface to be cleaned when the first cleaning assembly moves from the target position to the first position.

To provide a gas processing device capable of performing proper purification according to the capacity of the space where the gas processing device is installed.SOLUTION: A gas processing device includes: an ozone generation part for generating ozone; a first detection part for detecting the ozone concentration of the atmosphere; and a controller for controlling the ozone generation part, and for changing the generation amount of the ozone. The controller controls the amount of the ozone to be generated based on data regarding the relation between the ozone concentration and lapsed time, the ozone concentration detected by the first detection part and the lapsed time, preset according to the capacity of the space where the gas processing device is provided.SELECTED DRAWING: Figure 5

The invention relates to the technical field of air purification equipment, in particular to an unpowered public place air directional flow purification structure. The problems that in the prior art, the natural ventilation principle and the multi-stage purification function cannot be fused on the structural design level, and consequently inherent defects exist in the aspects of energy consumption, noise, maintenance cost, airflow organization stability and the like are solved. The unpowered public place air directional flow purification structure is arranged on a wall unit and comprises a micropore physical pre-filtering structure, a multi-layer labyrinth type physical filtering structure and an adsorption / deposition structure which are integrally arranged in a closed mounting cavity in the wall unit. In the operation process of the structure, no fan or motor or external power supply is needed in the whole process, air circulation is driven by completely depending on the thermal characteristics of the wall and weak thermal buoyancy formed by an indoor environment heat source, no mechanical moving part exists in the operation process, the noise level is low, and the noiseless requirement of a hospital ward area at night is met.

The utility model relates to an air purifier with a cat bed arranged on the top, which comprises a main machine body, a filter element and a fan assembly, the filter element and the fan assembly are arranged in the main machine body, a groove is arranged on the top surface of the main machine body, a pet house is arranged in the groove, and the pet house is detachably connected in the groove through a quick assembly and disassembly structure; the pet house is arranged on the air purifier, a pet cat can have a rest on the air purifier, if peculiar smell emitted by the pet cat can surround the air purifier, peculiar smell in the air can be filtered and removed in the first time, and the pet house is arranged on the top face of the air purifier, so that the pet cat can have a rest on the air purifier. On one hand, the arrangement of the air inlet and the air outlet of the air purifier is not affected, and on the other hand, the fan assembly operates to generate heat which can warm the pet house to a certain extent, so that the heat can be fully utilized, and the attraction to a pet cat and the rest comfort are improved.

The utility model relates to the technical field of air purification, and discloses an indoor air purification treatment device convenient to clean, which comprises a shell serving as a device main body, a movable plate capable of moving left and right is arranged in the shell, and the left side of the movable plate is connected with a fan and a filter screen through a fixing assembly. The fan is used for driving external air to enter the device and be discharged from the outlet, the filter screen is used for filtering impurities in the air, a cleaning assembly is arranged on the outer side of the filter screen, and a collecting assembly is arranged on the lower side of the filter screen and used for collecting cleaned dust. The first motor drives the screw rod connected with the first motor to rotate, the gear ring is matched with the gears to drive the gas screw rod to rotate synchronously, the movable plate pushes the fixed cylinder and the rotating plate to move leftwards to be exposed out of the shell, the draught fan and the filter screen can be conveniently overhauled and replaced, and the rotating rod and the scraper blade rotate; and the filter screen can be cleaned.

This application relates to an air handling device and an air purification device. The air handling device includes a first rotating assembly for connecting to a pre-filter assembly, thereby driving the pre-filter assembly to rotate. A cleaning mechanism is located around the pre-filter assembly. When the pre-filter assembly rotates, the cleaning mechanism acts on the surface of the pre-filter assembly to remove contaminants from its surface. The cleaning mechanism includes a scraper and a roller brush assembly, which are arranged adjacent to each other. Contaminants on the surface of the pre-filter assembly are scraped off by the scraper and carried away by the roller brush assembly. This air handling device not only removes contaminants from the surface of the pre-filter assembly but also carries them away, greatly reducing the possibility of secondary pollution caused by contaminants scraped from the surface of the pre-filter assembly and further improving the purification effect.

An oxygen concentration adjustment method, a control system, a vehicle and a storage medium. The oxygen concentration adjustment method comprises: collecting an oxygen concentration signal corresponding to a target space (step 110); determining whether the oxygen concentration signal meets a preset condition for adjusting the oxygen concentration of the target space (step 120); and, when the oxygen concentration signal meets the preset condition, on the basis of a control policy corresponding to the oxygen concentration signal, controlling an air conditioner in the target space to operate in a fresh air mode or controlling an oxygen supply apparatus to operate, so as to cause the oxygen concentration of the target space to be within a first preset concentration range indicative of safety (step 130). The present application can achieve collection and flexible adjustment of the oxygen concentration of target spaces, thus providing safe and healthy breathing environment for users.

The invention relates to the technical field of proportioning control, and discloses an intelligent proportioning control method for activated carbon and a deodorant in an air purification system, which comprises the following steps of: dividing the pore size distribution of the activated carbon into three types of micropores, mesopores and macropores, and obtaining pollutant response vectors of various typical pollutants and consumption weight vectors of the pollutants to the three types of pore sizes; constructing an agent mapping knowledge base; environmental pollutants are monitored in real time, a current pollutant response vector is obtained, and an activated carbon dynamic ability portrait is generated by matching a knowledge base; identifying a new pollutant event, acquiring a response vector and an aperture consumption weight of the new pollutant event, performing efficiency prediction calculation with the dynamic capability portrait, executing three-section decision logic according to a prediction result, and outputting dynamic ratio data of the activated carbon and the deodorant; accurate prediction of functional saturation of the activated carbon is realized through multi-dimensional capability characterization, purification efficiency reduction caused by'saturation illusion 'is effectively avoided, and the comprehensive purification efficiency of an air purification system is remarkably improved.

A module is described which is slidably attachable to a controller. Resource wires are connected to the module through resource connectors. The module has a circuit board that can perform actions. The module can modify the function of its resource connectors. These modifications may be to meet the requirements of resources that are to be connected to the module. The module may be able to register, by means of a signal, when a correct resource wire is attached to the module. The results of such monitoring may be displayed on a screen associated with the controller.

The embodiment of the invention provides a self-recovery method for the ion release capacity of a high-voltage electrostatic module, electronic equipment, a storage medium and a program product, and the method comprises the steps: outputting a self-recovery control signal corresponding to a target time threshold value under the condition that the cumulative operation time length of the high-voltage electrostatic module reaches the target time threshold value, the high-voltage electrostatic module is controlled to execute self-recovery operation; and when it is determined that the accumulated purification amount of the high-voltage electrostatic module reaches a target purification amount threshold value, outputting a self-recovery control signal corresponding to the target purification amount threshold value so as to control the high-voltage electrostatic module to execute the self-recovery operation. The embodiment of the invention provides a dual guarantee mechanism self-adaptive to different use scenes (light-load stable operation and heavy-load accelerated attenuation), establishes an active monitoring and recovery capability for performance attenuation of the high-voltage electrostatic module, and solves the problem that the purification efficiency is reduced due to the fact that the ion release capability is reduced after the module is used for a long time.

The utility model relates to a kind of aromatherapy machine, and the aromatherapy machine includes shell, atomization module and sound output module, shell has liquid storage cavity and mist outlet, liquid storage cavity is communicated with mist outlet, atomization module is set in shell and is used to atomize liquid in liquid storage cavity, sound output module is set in shell, and including sound output piece and white noise adjusting piece, white noise adjusting piece is slidably matched in shell and is used to adjust the volume of sound output piece.The above-mentioned aromatherapy machine can realize basic atomization function by atomization module, for improving indoor air quality, creating comfortable atmosphere, and the volume of white noise can be conveniently adjusted by the white noise adjusting piece of sound output module, to create comfortable environment for sleep and rest.

The present invention provides a decontamination solution capable of preventing charging of a mist for decontamination and preventing excessive wetting and liquid dripping on a wall surface inside a working chamber to be decontaminated when the inside of a working chamber such as an isolator is decontaminated using a mist for decontamination composed of hydrogen peroxide, and a device and a method for decontamination using the same. The decontamination solution is composed of a hydrogen peroxide solution where a substance increasing the electric conductivity of an aqueous solution is dissolved. The substance is preferably an electrolyte and more preferably an inorganic salt or an organic acid. The decontamination solution preferably has an electric conductivity of 14 µS / cm or more. The decontamination solution preferably has a residue on evaporation of 30 ppm or less. The device and the method for decontamination discharge the decontamination solution toward the inside of a room to be decontaminated as a mist for decontamination, thereby decontaminating the inside of the room to be decontaminated.

The utility model discloses a chip factory fresh air conditioning unit cold and hot coil pipe rapid dust removal and cleaning device which comprises an air switching device, a pressure difference sensor, an automatic control box, a power control box, a CDA compressed air pipeline and CDA compressed air nozzles evenly distributed on the surface of a fresh air conditioning unit cold and hot coil pipe. The gas switching device is connected with the CDA compressed air nozzle through the CDA compressed air pipeline, the pressure difference sensor feeds back the pressure difference of an inlet and an outlet of the coil pipe in real time, the automatic control box is connected with the pressure difference sensor and the gas switching device, and the power control box provides a low-voltage power source for the automatic control box. The device is used for removing dust on the air conditioning unit coil pipe, the speed is high, operation is convenient, and manpower is saved; the operation static pressure of the air conditioning unit is reduced, and the energy-saving effect is obvious; the device has sterilization and disinfection functions and does not corrode the surface of the coil pipe.

The utility model discloses a self-adaptive adjusting structure of an air conditioner panel, which comprises two mounting rack structures, a suspension structure arranged on the inner sides of the mounting rack structures, an air adjusting structure I arranged on the inner side of the front surface of the suspension structure, and an air adjusting structure II arranged on the back surface of the suspension structure, the suspension structure comprises two first truss rods and two first vertical frame rods, the two first truss rods and the two first vertical frame rods form a cuboid frame shape, vertical rods are perpendicularly connected to the front faces of the joints of the first truss rods and the first vertical frame rods, and second truss rods and second vertical frame rods are connected to the outer sides of the vertical rods. A plurality of clamping frame plates are arranged on the outer side of the second truss rod at equal intervals, a first air adjusting structure is arranged between every two adjacent clamping frame plates, each first air adjusting structure comprises an ingot, a first motor is arranged on the inner wall of each ingot, and the output end of each first motor is connected with an air guide plate. The air purification device can be conveniently installed on an exhaust panel of the air conditioner, the internal exhaust air volume is adjusted and purified, and the functionality is high.

The utility model provides an air purification device for a dust-free laboratory, and relates to the technical field of air purification of the dust-free laboratory, the air purification device comprises a filter box and a known fan arranged at an air outlet of the filter box, the inner wall of the filter box is provided with a plurality of notches along the air flowing direction, the notches are arranged in an arc shape, and the circle centers of the notches are positioned outside the filter box; a plurality of notches are formed in the filter box, a rotating shaft passing through the circle centers of the notches is rotationally connected to the outside of the filter box, the rotating shaft is arranged, a rotating plate is mounted on the rotating shaft, and two filter pieces are mounted on the rotating plate, so that air treatment can be realized only by transferring one filter piece on the rotating plate into the filter box in actual use; and when the filter part in the filter box needs to be cleaned, the other filter part enters the filter box through rotation of the rotating plate to continuously purify the air, and the filter part which is used for a period of time before is transferred out of the filter box, so that personnel can conveniently carry out cleaning, replacement and other operations.