880results about How to "Simple processing" patented technology

The invention belongs to the technical field of polymer materials, and relates to an entire biodegradation PLA / PBAT composite material and a preparing method therefor. The composite material comprises, by weight, 10-90 parts of polylactic acid, 10-90 parts of poly(butylene adipate-co-butylene terephthalate)ester, 10-80 parts of thermoplastic starch, 0.01-1.5 parts of compatilizer A, 0.1-10 parts of compatilizer B, and 1-40 parts of filling materials. The preparing method and an operation process for the composite material are simple, product manufacturing cost is relatively low, the composite material has excellent mechanical properties, is of excellent flexibility, is entirely biodegradable, and can be widely used in the field of consumer products such as packaging materials and disposable tableware.

The invention discloses a method for recovering vanadium, titanium and iron from vanadium titanium magnetite, comprising the following steps: using mineral powder, coal dust and binder together for agglomeration, reducting the mineral powder in a rotary hearth furnace to obtain a metallized product, then placing the product in an electric furnace by hot charging for melting and separating and obtaining titanium slag containing more than 50% of vanadium-bearing molten iron and TiO2. Vanadium slag is obtained by blowing vanadium in the vanadium-bearing molten iron, semisteel is used to make steel in a converter and the titanium slag can be used as raw material for extracting titanium directly. The method of the invention has high reduction temperature for vanadium titanium magnetite, short time, environmentally friendly, simple process and high yield of vanadium, titanium and iron so as to reach the aim of the comprehensive recovery and application of vanadium, titanium and iron and have good economic benefit and social benefit.

The invention mainly relates to a process method for rapidly fermenting chopped hot peppers, and mainly relates to the field of food processing application. The process method comprises the following steps: washing, soaking and disinfecting the fresh hoppers; draining and removing the water content on the surface of the fresh hoppers; directly chopping by a chopper mixer; adding 2% of salt, 0.5% of calcium chloride, 0.05% of citric acid; inoculating 0.05% of lactobacillus plantarum, and 0.05% of lactobacillus fermentium cultured in high density, wherein, the number of the lactic acid bacteria is 1010cfu / g and the amount of the ester-producing yeast is over 107cfu / m; fermenting for 48h in a sealing mode at the temperature of 37 DEG C; filtering, wherein, the filter pulp can be used as the strain water of the next batch; adjusting the salt concentration of the filtered and fermented hot peppers according to the different tastes to 8%; adding spices, such as white wine, Liuyang brown bean and garlic and the like; encapsulating after evenly stirring; and pasteurizing to obtain the finished product.

The invention discloses a resource recovery and zero discharge process for treating rare-earth wet-method smelting wastewater, which comprises the following steps: (1) carrying out segregated collection on wastewater; (2) pretreatment: recovering kerosene and P507 from wastewater by floatation oil removal, and precipitating by adding alkali to remove heavy metals and oxalate radicals; (3) recovering NH4Cl in high-concentration ammonia nitrogen wastewater by triple-effect evaporation, concentration and crystallization; (4) denitrifying medium / low-concentration ammonia nitrogen wastewater by ammonia stripping / absorption; (5) carrying out reverse osmosis desalination advanced treatment on the wastewater; and (6) recovering CaCl2 by evaporating, concentrating and crystallizing the reverse osmosis concentrated water. The invention can produce certain economic benefits by recovering kerosene, P507 and industrial-grade NH4Cl products in the wastewater, and the wastewater can achieve the water quality standard for reuse water, thereby realizing zero discharge of wastewater in rare-earth wet-method smelting enterprises.

The invention relates to a pressed metallic dipolar plate structure and the preparing method thereof, where both the right and reverse sides of the dipolar plate are symmetrically provided with fuel gas channels, oxidizing agent gas channels, cooling medium channels and dipolar plate flow field regions. The dipolar plate flow field regions are provided with gas flow field grooves and current-collecting flow field raised platforms, which are staggered, and both the right and reverse sides of the dipolar plate have sealing component holding sealing grooves between the fuel gas channels, oxidizing agent gas channels and cooling medium channels, and the edge of the dipolar plate is a convex-concave corresponding staggered structure so as to form a stress releasing region. The invention is simple to manufacture and easy to produce in large scale and largely reduces the expenses in manufacturing.

The invention relates to a high-plasticity ultrafine-grained Ti-based composite material and a preparation method thereof. The high-plasticity ultrafine-grained Ti-based composite material of the invention takes Beta-Ti as matrix phase, and the (Cu, Ni)Ti2 as wild phase. The preparation method of the composite material is a combined method of the pulse current sintering technology and the amorphous crystallization method, and comprises steps of mixing powder and high-energy ball milling, and the obtained powdered alloy has wide super-cooled liquid phase region and the amorphous phase accounts for at least 90% of the volume, then rapidly sintering with a discharging plasma sintering system at a sintering temperature Ts which is more than or equal to amorphous alloy powder crystallization temperature +200K and is less than or equal to the melting temperature -100k of the amorphous alloy powder, and at 40-500MPa for 1-20 minutes. Mixture ratio of elements in the invention is reasonable, and the obtained large-size ultrafine-grained Ti-based composite material has excellent comprehensive mechanical property and good prospects for popularization and application.

The invention belongs to the technical field of automobile manufacturing and discloses a device and process for machining a differential housing. The device is composed of a rotary jig, an internally-expanding lathing jig and a spherical surface lathing jig, wherein the rotary jig is arranged on a machining center and comprises an operation part with the two ends arranged on the machining center through rotating assemblies, and the internally-expanding lathing jig and the spherical surface lathing jig are arranged on a common numerically-controlled lathe. Synchronous machining of two parts can be achieved through the high-precision rotary jig when the machining center is used for machining various axial inner holes, and therefore efficiency is higher; a high-precision numerically-controlled indexing table is applied to the jigs, rotating accuracy is as high as 20'' or higher, and precision of the critical size of a product is better guaranteed; the parts can be automatically clamped and dismounted by the jigs through numerical control programs, and therefore labor can be saved.

The invention relates to an inorganic powder preparation method by surface modification technique, in particular to a preparation method of inorganic powder-elastomer with nuclear-shell structure. The inorganic powder is added into a high speed mixer and then blended for 3 to 10 minutes. Then the precursor of unsaturated organic compound with carboxyl and estolide with 0.1 to 10 percent of the inorganic powder weight, azo evocating agent or organic peroxided evocating agent with 0.0005 to 0.3 percent of the inorganic powder weight and volatile solvent with 0 to 0.5 percent of the inorganic powder volume are added in and then blended for 5 to 60 minutes. The elastomer with 20 to 300 percent of the inorganic powder weight is plasticated on a double-roller open rubber mixing machine and then the pretreated inorganic powder is added in gradually to mix for 5 to 20 minute continuously before pelletizing and crushing. The preparation method causes the elastomer and the unsaturated organic compound with carboxyl and estolide fixedly connected on the surface of the inorganic filling to form grafted reaction, which forms the soft shell and hard nuclear structure for elastomer chemically coating the inorganic filling effectively.

The invention discloses a device for nondestructively disassembling and treating waste circuit boards and a method thereof. The device comprises six parts of a conveying unit, a heating and heat insulation unit, a loading and unloading unit, a vibration unit, a recovery unit and a smoke removing unit. The conveying unit conveys the circuit boards; the heating and heat insulation unit melts soldering tin on the circuit boards; the loading and unloading unit realizes rapid loading and automatic unloading of the circuit boards; the vibration unit is used for separating the soldering tin and components from the circuit boards; the recovery unit is used for realizing separation and recovery of the soldering tin and the components; and the smoke removing unit is used for filtering flue gas dust in waste gas and odor produced in the operation of the device. The device and the method thereof have the advantages of continuous operation, high disassembling efficiency, high heating speed, controllable temperature, energy saving, high nondestructive disassembling rate of the components, small volume, light weight, simple installation, low power, high automation degree and simple processing operation.

The invention discloses a hot stamping die of a snakelike cooling water channel type, and the hot stamping die comprises a convex die insert and a concave die insert, which are arranged in a paired manner. The convex die insert is provided with a convex part so as to enable the cross section of the convex die insert to be convex. The concave die insert is provided with a concave part so as to enable the cross section of the concave die insert to be concave. The interiors of the convex and concave die inserts are respectively provided with a snakelike cooling water channel, and the depths of the snakelike cooling water channels are set in a manner that the bottoms of the snakelike cooling water channels are close to surface where the convex die insert with the concave die insert. The hot stamping die is simple in machining mode, has no cooling dead zone, and is uniform in cooling degree and speed. Moreover, the sizes of the inserts are not limited, thereby simplifying the structure of the die, improving the machining efficiency, achieving a good cooling effect, facilitating the assembly and maintenance, and reducing the cost.

The invention discloses a heavy-duty overrunning clutch, which comprises an outer ring, an inner ring, a plurality of rollers and a retaining frame. The retaining frame comprises a support ring I, a support ring II and a plurality of support columns corresponding to the rollers. Spring plates are fixedly arranged on the support columns along the axial direction and are used for applying pre-tightening force on the rollers along the engagement direction of an engagement slot. The direct processing of a limit seat on the outer ring can be avoided, the working efficiency can be increased, the processing cost can be reduced, the service life can be prolonged, and the transmission effect can be guaranteed. Moreover, relevant components can be replaced easily after being damaged, the outer ringneeds not to be rejected as a whole, and the cost of maintenance and use can be reduced. The axial length of the overrunning clutch and the rollers can be increased theoretically indefinitely, the engagement length can be increased, and thus the bearing capacity of the overrunning clutch can be improved. Meanwhile, the pre-tightening force can be applied at multiple points of the rollers according to needs, and the limiting balance for the rollers can be guaranteed while the axial length is ensured, so that the rollers cannot deviate from the axial line of the inner ring. Therefore, the stable operation of the overrunning clutch can be ensured, and mechanical failure can be avoided.

The invention discloses a machining process for low-pressure first-stage stationary blades of gas turbines, which belongs to the technical field of blade machining. The machining process for low-pressure first-stage stationary blades of gas turbines includes: step 1: a Z-shaped blade blank is formed by wire cutting; step 2: auxiliary heads are respectively welded on the inner and outer rings of the blade; step 3: rough machining is carried out; step 4: semifinishing is carried out; step 5: four times of finish machining are carried out on the air passage part, and finish machining is carried out on the radial face of the blade; step 6: the wire cutting method is adopted to remove the auxiliary heads of the outer and inner rings, and the inner ring surface, the outer ring surface and the inner radial surface of the blade are then machined. Under the premise of guaranteeing product design requirements and assembly quality, the machining process for low-pressure first-stage stationary blades of gas turbines strive for strict process control, a complete machining process, simple machining operation, integrated difficult point machining and critical control on key factors, thus effectively guaranteeing the quality of products and increasing the production efficiency.

The invention provides a multi-beam scanning lens antenna. The medium cylindrical lens is placed between two parallel plate waveguide parallel circular metal plate, the feed array by printing curved planar antenna array on the dielectric substrate, the feed array horizontally in round two the edge of the metal between the parallel plate waveguide with a feed array and between parallel circular metal plate four hex pillars fixed, since the antenna system uses spaced circular parallel plate waveguide structure to achieve a single-mode transmission, arc shaped feed array can be well combined with the circular parallel plate in the horizontal plane with good symmetry, reduces the volume of the pitch surface, and the process is simple, low cost, to achieve a balanced feeding dipoles, avoid adding additional reflector structure, planar microstrip Yagi antenna feed structure occupies less volume, can be well combined with the control circuit.

The invention relates to a high-strength hinge with adjustable door height for refrigerator, comprising hinge 21, hinge 22, adjusting bolt 27 for door height and fixing bolt 26. In requirement, by adjusting the adjusting bolt 27 for door height the hinge 22 can be adjusted up or down so that the adjusting effect for refrigerator door height can be realized. For improving strength of the hinge 22, an extending end is set on the hinge 22. Fold bending is set on the extending end while at least a stiffener is set on the support part and the bending part so as to improve strength of the hinge greatly. The merit of invention is that because the hinge 21 is formed by sheet metal bending while the structure provided in the invention is collocated it is provided with big strength, simple processing, high productive efficiency and small space cubage compared with die casting or other methods in prior technology.

The invention relates to a manufacturing method for a fiber strengthening compound coil spring, comprising the following steps: a fiber reinforced resin continuous bundle which is impregnated in thermosetting resin is led into a screw thread groove of a drive screw component; by the operation of the screw component, the fiber reinforced resin continuous bundle is led into the screw thread groove in a spiral way and then is pushed and moves forward; meanwhile, thermal energy is provided to heat and solidify the thermosetting resin on the fiber reinforced resin continuous bundle, thereby the heated and solidified fiber strengthening compound coil spring can be squeezed out continuously along the axial direction of the drive screw component and is cut into segments according to the required size to form the finished goods of the fiber strengthening compound coil spring needed.

The invention relates to a preparation method of a high performance expanded polyethylene product. The material of the invention comprises the following component in parts by weight: 50 parts of LDPE (low-density polyethylene) and LLDPE (linear low-density polyethylene), 0.01-1 parts of peroxide, 0.3-2 parts of talcum powder and / or calcium carbonate, 0.02-0.06 parts of antishrinking agent and 0.1-0.4 parts of foaming agent. In the invention, butane is used as the foaming agent, and the LDPE and the LLDPE are used as resin raw materials. The expanded polyethylene prepared by the preparation method of the invention has the advantages of high density and high surface hardness, the density of the expanded polyethylene is 60-400g / m<3> and the surface hardness is 40-70 degrees. The high performance expanded polyethylene product has good anti-scraping performance and puncture resistance as well as good rebound resilience and anti-quake effect. The high performance expanded polyethylene product meets the requirements of high performance of current packaging materials and fully protecting the substances being packaged. In addition, the high performance expanded polyethylene product has theadvantage of long sustainable using time as a panel and good market potential.

The invention discloses high-damp silica gel cement, a composite material containing the high-damp silica gel cement and preparation methods and application thereof. The high-damp silica gel cement is prepared from the following ingredients in parts by weight: 100 parts of low-crosslinking degree silica gel cement, 30 to 80 parts of piezoelectric powder and 0.1 to 25 parts of conductive powder. The low-crosslinking degree silica gel cement is prepared from phenyl hydroxyl silicone oil, boric acid and organic carboxylic acid which are hybridized according to weight ratio of 100 : (0.1 to 15) : 3. By means of introducing boric hydroxyl and phenyl into a silicone rubber molecule chain and utilizing hydrogen-bond interaction formed by organic carboxylic acid doping, the high-damp silica gel cement can be continuously broken and recombined under an external force to absorb energy; furthermore, the material has good self healing performance; as boric atoms are introduced into a silicone rubber main chain, regularity of the silicone rubber molecule chain is damaged, glass transition temperature is changed, and a damp temperature range is widened; the high-damp silica gel cement can meet shock absorption and durability requirements of the fields of aerospace, precise instruments and the like.

The invention provides a scratch resistant precoating film. The scratch resistant precoating film sequentially comprises a scratch resistant substrate layer, a color layer, a hot melt adhesive layer and a treatment layer from outside to inside, and the scratch resistant substrate layer is formed through coating the upper surface of a polymer film with a modified aqueous scratch-resistant coating liquid in an online coating mode. The aqueous scratch-resistant coating layer is coated in an online coating mode, so the polymer film functional treatment technology is simplified, energy is saved, and the product yield is improved.

The invention belongs to the technical field of biodegradable materials, and relates to a polyester / thermoplastic starch biodegradable composition and a preparation method thereof. The polyester / thermoplastic starch biodegradable composition is prepared from the following components in parts by weight: 10-90 parts of aliphatic-aromatic copolyester, 5-40 parts of thermoplastic starch, 10-80 parts of polyvinyl butyral, 0.1-5 parts of a compatibilizer, 0-3 parts of a lubricant, and 0-3 parts of an antioxidant. The preparation cost of the composition can be greatly reduced, and thus the product competitiveness is improved; and moreover, polyvinyl butyral not only has relatively good transparency, elasticity and degradation property but also has quite good anti-impact property and tensile strength, so the composition prepared from polyvinyl butyral has quite good mechanical properties and flexibility, can be completely biodegraded, and can be widely applied in packaging materials, disposable tableware and other consumer good fields.

The invention discloses a method for manufacturing a spectacle frame made of two materials and the spectacle frame made by the same. The method comprises the following steps of: mixing resin, pigment, pearl material and grinding paste to manufacture three-dimensional pattern acetate paper with mother-of-pearl inlay patterns; cutting the three-dimensional pattern acetate paper according to a preset pattern; dipping the cut three-dimensional pattern acetate paper into a softening agent for softening processing; utilizing a resin-free adhesive to adhere the softened three-dimensional pattern acetate paper to a preset position of a polyamide spectacle frame substrate; then, tightly connecting and fixing the two materials by a heating and pressuring process while recovering the pattern of the three-dimensional pattern acetate paper; drying the spectacle frame made by the three-dimensional pattern acetate paper and the two materials adhered to the polyamide spectacle frame substrate; cleaning the spectacle frame by a drum; grinding the surface of the spectacle frame; and coating the ground surface of the spectacle frame.

The invention discloses a bidirectional clutch, which comprises a star wheel and a chain wheel that is coaxially assembled outside the star wheel in a relative rotation way, wherein the edge of the star wheel is provided with at least one groove for accommodating rollers; an oblique wedge is machined in the groove; the rollers are arranged on both sides of the oblique wedge; an elastic component is arranged between the side wall of the groove and the roller close to the side wall; a poking rod of a poking fork is arranged between two rollers in the groove; the poking fork is also provided with at least one poking pin; clamping holes are formed in a wheel face of the star wheel corresponding to the poking pins; and the poking pins are inserted into the clamping holes. Compared with the prior art, the bidirectional clutch has the advantages of preventing a spring hole from being formed in the side wall of the groove, reducing the production cost, saving a sleeve, getting the spring in direct contact with the side wall of the groove and the rollers, additionally arranging the poking pins on the poking fork and poking the star wheel through the poking pins, along with simplicity in machining, convenience in mounting and high safety and reliability.

The invention relates to a foam material for shoes and a preparation method thereof. The foam material for shoes comprises the following components in percentage by weight: base stock, a foaming agent, a crosslinking agent, an assistant crosslinker, an activating agent and a filler, wherein based on the total mass of 100%, the base stock comprises 30-49.9% of ethylene-vinylacetate rubber, preferably 35-45%, 10-30% of ethylene-vinyl acetate resin, preferably 15-25%, 20-40% of a styrene-ethylene-butene-styrene block copolymer, preferably 25-35%, and 5-30% of brominated butyl rubber, preferably 5-20%. The foam material for shoes, disclosed by the invention, is uniform in foam structure, has excellent shock absorption, deformation resistance, lightweight and low cost, and can achieve the aim of controlling the density, elasticity, hardness and hot-shrinkage rate according to different proportions of the various components.

The invention discloses a pipe hoop stamping die in the field of dies. The pipe hoop stamping die comprises a cylindrical male die and a lower die seat. The cylindrical male die is radially connected with a die shank. A pair symmetrical swing female dies is hinged to the lower die seat. A spring is connected between the forming end of each swing female die and the lower die seat. The cavity formed by the swing female dies is matched with the cylindrical male die. The lower die seat is further provided with positioning blocks for positioning blanks. The pipe hoop stamping die for machining 'omega'-shaped pipe hoops is simple to operate and high in efficiency. During machining, a user only needs to place the blanks in the positioning blocks and starts a stamping machine, the blanks are formed at one step under the action of the cylindrical male die and the swing female dies, defective products caused by multiple forming can be avoided, and machining yield is increased.

The invention relates to chicken feed, i.e. egg-laying chicken concentrated feed. The feed is prepared with raw materials in the following weight portions: 550 portions to 600 portions of soybean meal, 100 portions to 120 portions of sunflower meal, 30 portions to 40 portions of plant oil, 25 portions to 30 portions of alfalfa meal, 30 portions to 40 portions of calcium hydrogen, 7 portions to 8 portions of salt, 80 portions to 120 portions of stone powder, 22 portions to 28 portions of premix compound, and 3 portions to 5 portions of additive. The concentrated feed is used together with the prior widely applied energy feed corn flour, simple to be processed, has easily available raw materials and low cost; the physique of the egg-laying chicken is obviously strengthened, the yield and the quality of eggs are obviously improved, so the feed has quite high practical value and considerable market prospect.

The invention discloses a titanium alloy capable of resisting high temperature higher than 600 DEG C. The chemical elements of the titanium alloy are 5.5 to 7.0 percent by weight of Al, 2.5 to 4.0 percent by weight of Sn, 1.0 to 3.0 percent by weight of Zr, 1.0 to 3.0 percent by weight of Mo, 1.5 to 3.0 percent by weight of Nb, 0.10 to 0.40 percent by weight of Si, 0.05 to 1.0 percent by weight of Ce, 0.1 to 5.0 percent by weight of Ta, 0.1 to 2.0 percent by weight of C, 0.1 to 2.0 percent by weight of B and the balance of Ti and other inevitable impurities. The titanium alloy can be used under the temperature higher than 600 DEG C, and guarantees excellent mechanical properties under the high temperature at the same time.

The invention provides a method for transferring files of a book edition format into files of an EPUB format. The method comprises the following steps: 1) appointing a storage catalogue of the files of the book edition format, and detecting whether the files of the book edition format have errors or missing; 2) storing the files of the book edition format and detected results according to a fixed catalogue structure so as to form a resource package; 3) analyzing the resource package, and performing structuralized processing on the resource package so as to form a structuralized logic tree containing formats and content; 4) extracting the content of the structuralized logic tree, formatting the extracted content, and using a cascading style sheet so as to form HTML (hypertext markup language) files; 5) packaging and outputting data and files obtained from step 1) to step 4) according to EPUB standards so as to form the files of the EPUB format. Correspondingly, the invention provides a device for transferring files of the book edition format into files of the EPUB format. Through the adoption of the method and the device which are both provided by the invention, small sample files can be well analyzed; the method and the device have the advantages that the processing process is simple, the content error rate is low, and the degree of automation is high.

The invention provides a metal shell and a manufacturing method thereof. The surface of the metal shell is provided with a plurality of first lines which are arranged at intervals and have the same curvature and a plurality of second lines which are arranged at intervals and have the same curvature; the first lines are respectively crossed with the second lines to from a plurality of embossments.

The invention provides flexible bionic electronic skin and a preparation method thereof. The flexible bionic electronic skin comprises a piezoresistance layer and a thin film electrode, wherein the piezoresistance layer is at least partially provided with a porous structure; the piezoresistance layer is in contact with the thin film electrode; the piezoresistance layer in the contact interface region of the piezoresistance layer and the thin film electrode is at least partially provided with a filling region; an elastic body is contained in the filling region; the resistance value of the piezoresistance layer is detected through the thin film electrode; the intensity of the received force of the flexible bionic electronic skin is determined according to the detecting result. The flexible bionic electronic skin can feel the existence of airflow and pressure; the structure is ingenious; the sensitivity is high; the flexible bionic electronic skin has certain mechanical stability.

The invention provides a rapid harmless biological degradation method against waxy oil sludge. The method is realized by preparing a seed solution, heating and dispersing the waxy oil sludge, preparing a degradation system and performing biological degradation, the method aims at the waxy oil sludge produced in oil production and oil refining processes specially, and substances in the waxy oil sludge can be effectively degraded by using the method. By adopting the method provided by the invention, petroleum hydrocarbon type substances in the oil sludge can be effectively degraded, petroleum hydrocarbons can be partially converted to glycoprotein type substances, and the requirements on harmless treatment of the oil sludge can be finally met. The method utilizes a biological treatment process, prevents secondary pollution and has no influence on an environment; the treatment process is simple, and the operation cost is low; the treatment time is short, and the efficiency is high. A conversion product of the oil sludge can promote the degradation of the oil sludge, which is an unexpected effect obtained in a testing process of the method provided by the invention.

The invention relates to a plant source agricultural fungicide and a preparation method thereof. The fungicide is formed by extracting and processing fruit, carpopodium, shells and leaves of evodia rutaecarpa. The fungicide comprises the following main active ingredients in percentage by weight: 6 to 10 percent of hydroxyevodiamine, 5 to 10 percent of evodiamine, 5 to 10 percent of rutaecarpin, 6 to 10 percent of dehydroevodiamine, 1 to 5 percent of bievodiamine, 1 to 5 percent of hepta evodiamine, 6 to 40 percent of other alkaloid components. The main active ingredients are processed and manufactured into an emulsion in water, and can be used for controlling and preventing a plurality of plant diseases after being diluted. The plant source agricultural fungicide and the preparation method thereof have the advantages that raw materials are easily obtained; the process is simple; the cost is low; the fungicide has very good control and prevention effects on a plurality of plant diseases, such as sclerotinia rot of colza, wheat scab and grape anthracnose, is safe to plants, does not pollute the environment, and is a biological pesticide preparation which meets the production requirements on pollution-free agricultural products in China.