37results about How to "Satisfy optional" patented technology

The invention discloses a multi-terminal flexible direct-current power distribution network-oriented protection method based on the voltages of current-limiting inductors. The method comprises the steps of fault starting, fault detection, fault identification and fault pole selection. According to the fault starting, du / dt and di / dt are adopted as criteria. According to the fault detection, low-voltage and over-current protection is adopted to detect whether a line fails or not. According to the fault identification, internal and external faults can be reliably identified on the basis of the voltages of the current-limiting inductors at two ends of a direct-current line. According to the fault pole selection, whether a positive pole, a negative pole or a bipolar fault occurs in a system isdetermined on the basis of the voltages of the current-limiting inductors at two ends of the direct-current line. After a corresponding fault is detected, a tripping signal is sent out, a corresponding direct-current circuit breaker acts, and the fault is removed. With the method of the invention adopted, the problem that the quickness of a traditional direct-current power distribution network protection is poor is solved. Fault identification is carried out through the voltages at the two ends o of the current-limiting inductors.

The invention discloses a high-sampling-rate method for sampling value differential protection of a multi-section type self-adaption transformer. The method comprises the steps of performing high-speed sampling on three-phase currents on every side of the transformer; performing one-point difference algorithm processing on three-phase current sampling currents of every side of the transformer and compensating current amplitudes; calculating a sampling value differential current and a sampling value braking current of the transformer; performing logical discrimination of a sampling value differential protection quick-action section; performing logical discrimination of a sampling value differential protection sensitive section; and performing discrimination of sampling value differential total logic. According to the high-sampling-rate method for sampling value differential protection of the multi-section type self-adaption transformer, the problem that an existing sampling value differential protection method is large in action fuzzy area and low in sensitivity, the rapidity and the sensitivity are simultaneously met on the premise that the selectivity and the reliability are improved, and the method is good in application prospect.

The invention provides a method for quantitatively detecting six kinds of nitrobenzene compounds in fine atmospheric particles PM2.5. The method comprises the following steps: acquiring a sample, extracting the sample, concentrating and purifying the sample and quantitatively detecting by adopting chromatography-tandem mass spectrometry. By optimizing parameters of secondary mass spectrometry conditions, the method is better in selectivity and higher in sensitivity on target compounds in comparison with an existing detection method reported in literature. According to the method, the disadvantage that the selectivity and the sensitivity of a conventional detector in the process of detecting the trace quantity of nitrobenzene compounds in a complex background matrix cannot be ensured at the same time is overcome by virtue of a gas chromatography / tandem mass spectrometry selective reaction monitoring technology, and the qualitative operation is accurate and reliable, so that the method has very remarkable advantages in comparison with conventional GC / ECDs (gas chromatography / election capture detectors), GC / NPDs (gas chromatography / nitrogen-phosphorus detector), GC / LRMS (gas chromatography / low resolution mass spectrometry) detectors or GC / HRMS (gas chromatography / high resolution mass spectrometry) detectors.

The invention discloses a distribution network overcurrent protection method with a distributed power supply, and a fixed value optimization method and system, and belongs to the technical field of distribution network relay protection. When a fault occurs, a data acquisition system acquires a fault current flowing through each inverse time limit overcurrent relay in the distribution network witha distributed power supply; according to the inherent characteristics of the fault current and the inverse time limit overcurrent relay and the selectivity, the sensitivity and reliability requirements of the relay protection, a mathematical model is established, wherein the mathematical model comprises an objective function and a constraint condition; a particle swarm optimization based on crowdsearch is employed to perform particle optimizing of the time setting coefficient and starting current of the inverse time limit overcurrent relays; and according to the optimal particles, the time setting coefficient and starting current of each inverse time limit overcurrent relay are subjected to re-assigning, and faults are cut off in the shortest time. The problem is solved that the relay fixed value is improperly set after the distributed power supply is accessed into the distribution network.

The invention provides a relay protection online safety margin evaluation system. The system includes a master station end device installed in a dispatch center and a plurality of sub-station end devices installed in a transformer substation; the master station end device and the sub-station end devices are used for relay protection online safety margin evaluation; the master station end device includes a protection safety margin evaluation module, a data acquisition and processing module, a human-computer interaction module and a public data area; and each sub-station end device includes a protection safety margin evaluation sub module, a data acquisition and processing sub module, a human-computer interaction sub module and a public data sub area. Compared with relay protection online setting or online check, the system can accurately judge whether a protection constant value meets the requirements of the current operation mode of a power grid for protection selectivity and sensitivity and can assist in effectively eliminating the defect that the accuracy of relay protection online setting and online check results is influenced by the accuracy of power grid power flow, power grid parameters and a short-circuiting calculation model.

The invention discloses a biochip and a preparation method thereof. The preparation method of the biochip comprises the following steps of: printing a micro-nano metal array pattern on a substrate by using metal nanoparticle-containing ink-jet water-soluble ink through an ink jet printer; curing, performing sterilization and disinfection treatment on the substrate with the array pattern, and then co-culturing the substrate with a biological material to obtain the biochip, wherein a preparation method of the jet-ink water-soluble ink comprises the following steps of: mixing metal nanoparticles, a water-soluble cosolvent, a high-molecular dispersing agent, a surfactant and secondary distilled water with stirring; pre-dispersing; and concentrating to obtain the ink. The chip prepared by the method is lower in cost; a preparation process is simple, and is easy to master and convenient to popularize; the biochip is quickly detected and is environmentally-friendly; and compared with similar products at home and abroad, the biochip has the advantages of obvious performance, low cost and the like. The biochip has a wide application range, provides great help for clinic diagnosis and epidemiological screening, and has a broad application prospect in the aspect of scientific research.

The invention discloses a digitized line protection measurement and control system suitable for the metro industry. A digital communication current protection function is provided for solving the quick-action performance problem of a former stand-by current protection system and for supporting GOOSE entering and exiting functions. IEC61850 achieves GOOSE communication of a protection system in a power substation and a protection system between power substations, the protection systems can monitor protective action conditions of upper level switches and lower level switches through a GOOSE network, and then 'rapid fault positioning' and 'rapid excision' of looped network buses and cables are achieved through logical judgment.

The invention relates to a composite material and a method for manufacturing an automobile spare tire cover from the composite material and belongs to the technical field of automotive interior trims. The composite material comprises polyurethane, a glass fiber mat and a PP (Polypropylene) honeycomb plate. The method specifically comprises the following steps: wrapping a PP honeycomb core layer with the glass fiber mat, uniformly and sufficiently spraying polyurethane to both sides of the glass fiber mat by using automatic spraying equipment, putting the polyurethane glass fiber mat PP honeycomb core layer into a mold of specific temperature, and performing mold combination pressure-keeping shaping; positioning; laying a mat surface; performing mold pressing stamping; wrapping edges; loading accessories; and testing. The invention aims to provide a method for manufacturing an automobile spare tire cover from the composite material with the polyurethane glass fiber mat PP honeycomb core layer, and a prepared spare tire cover product is relatively high in loading capacity, relatively light in weight, relatively slight in odor, large in gram weight, wide in thickness design range and relatively low in cost.

The invention relates to the technical field of access control rights, and provides a method and a system for managing rights based on a distributed storage system ACL. The method comprises: determining and identifying application scenarios, and obtaining the category of the current application scenario; when it is a standard ACL typed application scenario, setting the ACL access right for the directory of the distributed storage system, and setting the same type of the ACL access right for all subdirectories and files in the directory; and when it is a fast ACL typed application scenario, only setting the ACL access right for the top directory of the distributed storage system, thereby providing different ACL right setting schemes according to different application scenarios, improving the efficiency of setting ACLs, enabling users to manage the system more finely, and also meeting the need for diverse choices and flexible and efficient deployment for the data access rights of enterprise users.

The invention discloses a terahertz wave absorption body capable of dynamically and continuously adjusting an absorbing bandwidth. Each wave absorption body unit of the wave absorption body mainly comprises a silicon substrate, a silicon nitride layer, an electrode layer and a polycrystalline silicon pattern layer, wherein the upper surface and the lower surface of the silicon nitride layer are respectively adhered to the lower surface of the electrode layer and the upper surface of the silicon substrate; a plurality of holes through which anchor points penetrate; the polycrystalline silicon pattern layer is fixed on the silicon nitride layer through the anchor points; the central axes of the silicon substrate, the silicon nitride layer, the electrode layer and the polycrystalline silicon pattern layer are superposed; the polycrystalline silicon pattern layer comprises a square supporting block, an inner square supporting ring and an outer square supporting ring which are positioned on the same plane, 4 L-shaped clips which are positioned between the inner square supporting ring and the outer square supporting ring, and inner and outer square metal rings which are respectively arranged on surfaces of the square supporting block and the inner square supporting ring. The wave absorption body can be used for dynamically and continuously adjusting the absorbing bandwidth of terahertz wave.

The invention relates to a veneer / aluminum foil composite decorating facing material which structurally comprises kraft paper, a copolyester hot-melt glue film PES, aluminum foil, a holt-melt glue film H420 and veneer. The upper glue applying surface of the aluminum foil is bonded to the kraft paper through the copolyester hot-melt glue film PES, and the lower glue applying surface of the aluminum foil is bonded to the veneer through the holt-melt glue film H420. A manufacturing method of the veneer / aluminum foil composite decorating facing material comprises the following steps that firstly, the upper glue applying surface of the aluminum foil is treated; secondly, the kraft paper, the copolyester hot-melt glue film PES and the aluminum soil are subjected to the assembling, hot pressing and cooling process to form an aluminum foil / kraft paper enhanced material; thirdly, the lower glue applying surface of the aluminum foil is treated; fourthly, the dried veneer, the holt-melt glue film H420 and the aluminum foil / kraft paper enhanced material are subjected to the assembling, hot pressing and cooling process treatment to form the veneer / aluminum foil composite decorating facing material. The veneer / aluminum foil composite decorating facing material has the advantages of being high in decoration performance, environmentally friendly, free of pollution and superior to a natural veneer facing material on physical and mechanical properties such as static bending intensity and bending resistance.

The invention discloses a single-end electrical quantity protection method suitable for a hybrid bipolar direct current transmission line, and constructs a direct current line fault discrimination method based on a signal transient high and low frequency energy ratio by using a specific boundary structure of a hybrid bipolar direct current transmission system. A hybrid bipolar high-voltage direct-current power transmission system is built through a PSCAD / EMTDC simulation platform, fault conditions under different working conditions are simulated, voltage characteristic signals are extracted, wavelet packet transformation is carried out, transient energy of each node is obtained, a protection criterion is constructed by using a ratio of specific low-frequency energy to partial high-frequency energy, and thus internal and external faults of a region are identified and fault line selection is carried out. The method is high in transition resistance resistance, the protection reliability, selectivity, quickness and sensitivity are all met, high precision is achieved, and faults can be accurately recognized. According to the invention, calculation related to the wavelet packet can be realized by adopting a high-performance CPU (Central Processing Unit) or a hardware circuit such as an FPGA (Field Programmable Gate Array) or a CPLD (Complex Programmable Logic Device), so that the fault identification speed, precision and reliability are improved.

The invention discloses a novel interval layer net networking method for a subway pressing ring net protecting system. The method comprises the steps that in a numerical protecting system of a pressing ring net in a subway power supply system, protecting devices in transformer stations and between the transformer stations are communicated through an interval layer GOOSE network, the information of protecting starting, the information of protecting actions and the information of protecting switch positions are exchanged mutually, the situations of the protecting actions of a higher-grade switch and a lower-grade switch are monitored, and then the quick positioning and the quick resecting of ring net buses and cable faults are logically judged. In the method, a VLAN overlap mode is used, each transformer station is distributed with the only VLAN ID, and at the same time, the transformer station can realize communication with the adjacent transformer stations in front and behind, so that a GOOSE message is transmitted in a directional and limited area in the network, the transmission range of broadcast packets can be effectively limited, the efficiency of the network is improved, and the system stability and the safety are improved.

The invention provides a middle and far infrared and laser compatible stealth film and a design scheme thereof. TFCalc software inputs an initial five-layer one-dimensional photonic crystal structure with a doped layer, a continuous target of the initial five-layer one-dimensional photonic crystal structure is firstly set, high reflection is set at 3-5 micron and 8-14 micron, and high transmission is set at 5-8 micron and 10.6 micron; secondly, a ''Needle'' layer is added by adopting two materials of germanium and zinc sulfide on an optimization parameter setting interface, film layers are continuously added to an optimal design film system, a plurality of layers are added at the same time, and local optimization is adopted before adding the Needle; and finally, a growing film is selected from Tunnelling parameters for structural optimization, the film is a 13-layer film structure formed by taking glass as a substrate and alternately forming germanium and zinc sulfide with different thicknesses, the two layers close to the air and the glass are germanium, and the film can achieve compatible stealth of the middle and far infrared wave band and the 10.6-micron laser wave band.

The invention provides a technical wood material, comprising a core board, the raw materials of the core board and the parts by weight of each raw material are 22-34 parts of balsa wood powder; 16-29 parts of bamboo charcoal powder; low floating fiber alkali-free chopped 11-19 parts of glass fiber; 4-9 parts of polyolefin elastomer; 9-16 parts of composite vegetable dye; 16-23 parts of basalt fiber; 17-21 parts of cyanuric chloride; 7-15 parts of glycidyl methacrylate 11-26 parts of fatty alcohol polyoxyethylene ether; 13-25 parts of epoxy silane crosslinking agent. The invention has the characteristics of high hardness and light specific gravity, and its properties of compression resistance, bending resistance and impact resistance are superior to those of natural wood. Environmental protection, flame retardant, moisture-proof, insect-proof, no deformation, high hardness, not afraid of water immersion, easy maintenance, high wear resistance, longer service life, etc. Simultaneously, the present invention also adds compound vegetable dyes, endows multiple colors, and simultaneously the color and luster is brighter, and the three-dimensional sense of texture is stronger.

The invention discloses a hydraulic-type fracturing sliding sleeve opening and closing tool which is designed to be matched with a fracturing sliding sleeve for use to achieve the objective of multistage layered fracturing transformation of oil and gas fields. The hydraulic-type fracturing sliding sleeve opening and closing tool mainly comprises an upper protruding shoulder, a lower protruding shoulder, a core shaft of a central hole and a radial liquid incoming hole, an upper joint, a lower joint, an upper limiting sleeve, a lower limiting sleeve, an upper pressing sleeve, a lower pressing sleeve, a salvaging piece connected between the upper protruding shoulder and the lower protruding shoulder of the core shaft in a sleeved manner, springs arranged between the joints and the pressing sleeves, salvaging piece springs and the like, and the upper joint and the lower joint are connected on the core shaft. By the hydraulic-type fracturing sliding sleeve opening and closing tool, the fracturing sliding sleeve can be sequentially opened and closed, perforation is not needed, and integration of fracturing and production is realized. If a fracturing transformation mode of perforating by an electric cable, packing by a packer and beating the sliding sleeve by pitching during production is adopted, a steel ball and a ball seat can be drilled and grinded off, and controllable mining, single-layer testing for production and seeking of water plugging can be realized by utilizing the tool. The hydraulic-type fracturing sliding sleeve opening and closing tool is matched with the fracturing sliding sleeve for use and can meet technical requirements of multistage layered transformation, selective mining, single-layer wellhole testing and seeking of water plugging of the oil and gas fields.

The invention provides a tourist route optimization method based on a fuzzy ant colony algorithm. The tourist route optimization method comprises the steps: collecting the information of arriving at atarget scenic spot, and the time journey, road condition and time consumption related information of a public transportation mode of arriving at each scenic spot; and calculating a tourist route by combining a target scenic spot selected by a user and the collected information, adaptively generating parameters required by an ant colony algorithm by adopting a fuzzy system when the tourist route is calculated, and solving the problem of tourist route crossing by using 3-Opt. The ant individual difference and the worst individual intersection number are used as fuzzy system parameters, and thefuzzy system outputs ant colony algorithm related parameters, so that a dynamic feedback mechanism can effectively solve the problem of algorithm universality under changed data, and the stability ofthe algorithm is improved.

The invention relates to a regional bus protection system of a power distribution network; the system is divided into a next-stage station and an upper-stage station, the next-stage station is a switching station / power distribution room, and a protection measurement and control integrated device and a regional bus protection device are configured in the switching station / power distribution room. A comprehensive bus protection device is configured at the upper-stage station; traditional functions such as sampling of current and voltage, acquisition of a position signal and an outlet of protection control are completed by the protection, measurement and control integrated device; a regional bus protection device is additionally arranged in a switching station / power distribution room, the regional bus protection device firstly has the principle and the function of conventional bus protection, various faults in a protection area should be reliably acted, and faults outside the protection area should not be acted. According to the invention, the protection selectivity of the series power supply line is enhanced, the reliability, selectivity, sensitivity and quick action required by relay protection are met, the fault power failure range is reduced, and the power supply reliability is improved.

The invention relates to a multistage variable-vibration rock debris cleaning and screening device, which comprises a water tank, a screen, a vibration motor and a vibration plate, the water tank is arranged above the vibration plate through vibration supporting rods, the vibration motor is arranged on the vibration plate, vibration reduction supporting pieces are arranged under the vibration plate, and a plurality of supporting protruding edges arranged in the length direction of the water tank are further arranged between the screen and the bottom of the water tank. The screen is placed on the supporting protruding edges, the heights of the supporting protruding edges are sequentially reduced to enable the screen to have a certain gradient, and the supporting protruding edges evenly divide the space between the screen and the bottom of the water tank into a plurality of subareas. The vibration transmission efficiency and adjustability are improved through the combination of a vibration base, the vibration supporting rods and variable vibration columns, the excitation effect is improved through the wavy structure of the bottom face of the water tank, rock debris with different particle diameters is screened, washed and classified, and the working efficiency is improved.

The invention provides a technological composite decorative material, comprising a core board, the raw materials of the core board and the parts by weight of each raw material are 22-34 parts of balsa wood powder; 16-29 parts of bamboo charcoal powder; 11-19 parts of cut glass fiber; 4-9 parts of polyolefin elastomer; 9-16 parts of composite vegetable dye; 16-23 parts of soybean protein fiber; 17-21 parts of cyanuric chloride; polyhexamethylene guanidine propionate 7‑15 parts; 11‑26 parts of chitosan quaternary ammonium salt; 13‑25 parts of triethanolamine; 3‑9 parts of gallic acid. The invention has the characteristics of high hardness and light specific gravity, and its properties of compression resistance, bending resistance and impact resistance are superior to those of natural wood. Environmental protection, flame retardant, moisture-proof, moth-proof, no deformation, high hardness, not afraid of water immersion, easy maintenance, high wear resistance, longer service life, etc. Simultaneously, the present invention also adds compound vegetable dyes, endows multiple colors, and simultaneously the color and luster is brighter, and the three-dimensional sense of texture is stronger.

The invention relates to a composite self-assembled multifunctional decorative structure. The composite self-assembled multifunctional decorative structure is characterized by comprising an external wall body, a suspended ceiling component, a side wall decorative component and a ground decorative component. The composite self-assembled multifunctional decorative structure adopted by the technical scheme serves as a multifunctional composite decorative plate, can be assembled with the matched decorative connecting piece in a plug-in and combined manner, and is easy to mount and dismount and convenient to disassemble; the material is environment-friendly, energy-saving and emission-reducing as the material can be recycled.

The invention discloses a needle selection mechanism of a negative type electronic multi-arm device with a solenoid valve suction aid function and belongs to the field of textile machinery. The negative type electronic multi-arm device comprises a pair of multi-arm device rack wall boards; the needle selection mechanism comprises a left wall board, a right wall board, a signal supply device, a transverse needle actuating device and an executing device, wherein the signal supply device comprises a first signal panel, a second signal panel, a first signal collector, a second signal collector, a signal collector support, a solenoid valve support, a front row of solenoid valves and a rear row of solenoid valves; the transverse needle actuating device comprises a push broach left slide seat, a push broach right slide seat, an upper transverse needle push broach, a lower transverse needle push broach, an upper transverse needle push broach left pull rod and a lower transverse needle push broach right pull rod; the executing device comprises a transverse needle supporting bracket, upper transverse needles and lower transverse needles. The needle selection mechanism has the characteristics that the needle selection mechanism further comprises a suction aid driving device and a solenoid valve core suction aid device, the suction aid driving device is arranged on one side of the right wall board, the solenoid valve core suction aid device is matched with valve cores of the front row of solenoid valves and the rear row of the solenoid valves, and the first signal panel and the second signal panel are connected with the suction aid driving device. The working is reliable, energy is saved, and the service life is long.

The invention provides a method for selecting and evaluating a heat dissipation mode of electronic equipment, and belongs to the technical field of heat dissipation design of the electronic equipment, and the method specifically comprises the following steps: dividing a two-stage heat dissipation mode architecture, dividing a typical internal module structure and dividing link temperature rise composition; establishing a heat dissipation data framework according to the device size and the device power consumption which are in matrix distribution and equal proportion change, forming a uniform heat dissipation database model which takes the total power consumption of the module and the heat flux density of the device as independent variables and takes the temperature rise of the device as a dependent variable, and obtaining a heat dissipation database of each link; designing the structure of the to-be-tested electronic equipment, and determining a link composition corresponding to the current electronic equipment structure; according to the link composition in the step 3, temperature values of all the compositions are obtained in combination with the database and then added, and the temperature of the current electronic equipment device is obtained. Through the processing scheme provided by the invention, the heat dissipation scheme design of the electronic equipment can be accurately completed at the initial stage of product development.

The invention discloses an air compressor oil-gas separation core material and its preparation process. The material has a sandwich composite structure of "surface hydrophobic and oleophobic + internal hydrophobic and oleophilic" through modification of polyvinyl formal foam; The preparation process is as follows: the polyvinyl formal foam body with internal hydrophobicity is prepared by modifying the surface active agent foaming method; and then the surface is subjected to fluorocarbon treatment to obtain the surface hydrophobicity and oleophobicity. The invention realizes the filtration selectivity of polyvinyl formal material to oil and water in compressed air, can efficiently separate oil droplets from high-humidity oily air, and has the advantages of high filtration efficiency, small pressure drop, high strength, long life, etc. Advantages, and the whole preparation process is simple, non-toxic and environmentally friendly, and low in cost.

The invention provides a lamp control equipment module based on an intelligent home technology, which comprises an integrated panel, an illuminating lamp and a user mobile terminal, and is characterized in that the integrated panel comprises an intelligent mainboard, a touch module, a wireless module and an 86-structure main control bottom plate module; and the intelligent mainboard is electrically connected with the touch module, the 86-structure master control bottom plate module and the illuminating lamp through wires, the wireless module is wirelessly connected with the intelligent mainboard and the user mobile terminal, and at least one mechanical key is arranged on a front panel of the integrated panel. According to the lamp control equipment module, the touch function of the key unit and the touch module of the intelligent main board can be used for locally controlling the intelligent lamp control device on the same panel through multiple control modes of key and touch at the same time, and in addition, remote cloud APP control is achieved through the wireless module at the same time, the multi-combination design not only can meet the selectivity of multiple control habits of a user, but also saves the installation area, and greatly saves the cost through the compatible design.

The invention relates to the technical field of automobile materials, in particular to a composite material, an automobile spare tire cover and a preparation method thereof. The composite material hasa multi-layer composite layer structure, and the composite layer structure is composed of epoxy resin layers and glass fiber felt layers which are alternately arranged, the composite layer structurecomprises an odd number of layers, and a top layer, a bottom layer, and a middle layer of the composite layer structure are the epoxy resin layers. Compared with the prior art, the composite materialhas the advantages that the technical scheme designed by the invention can effectively utilize a currently mature epoxy resin prepreg process, and changes the material structure stratification of a spare tire cover sheet on the existing market, the weight of a car trunk spare tire cover product is reduced by 20%, the thickness is reduced by 35%, the bearing capacity is up to 200kg, the odor emission is improved, at the same time, the composite material satisfies more choices for customers in designing data, reduces costs and improves product competitiveness.

The invention relates to a ship protection system for a high-power-ratio special-shaped unit mixed use occasion. The system is divided into an upper layer, a middle layer and a lower layer, the upper layer is a power station control layer and communicates with a lower protection execution layer through a CAN local bus in a station control layer network, and the middle protection execution layer is a ship protection system execution unit. The protection execution layer issues a specific execution instruction to an execution element of the lower electrical layer, and collects on-off state information of the electrical layer; and the protection execution layer comprises a comprehensive protection device, an interval merging unit and a centralized control unit. Multiple groups of protection constant values can be switched according to ship operation conditions, and the protection configuration difficulty is reduced; and the sensitivity and selectivity of protection configuration can be met aiming at a high-power-ratio special-shaped unit mixed use occasion.

The invention relates to a rotary vane fan air grid with any change of wind direction, which is arranged on the large circle at the outer edge and the small circle at the middle part of an air grid frame respectively by rotating shafts at two ends of the air grid; a middle shaft is arranged on the small circle at the middle part of the air grid frame and is vertical to the plane of the small circle at the middle part of the air grid frame; teeth similar to bevel gears are manufactured on the circumference of the excircle of an adjusting knob; the adjusting knob is arranged on the middle shaft by the excircle of the middle thereof; simultaneously, the teeth on the adjusting knob and teeth on the air grid form a meshed relation; and a fixed knob is arranged on the middle shaft at the upper part of the adjusting knob.