71results about How to "Reduce the possibility of secondary pollution" patented technology

An environment-friendly carbon nanotube / sodium alginate heavy metal ion sorbing material and a preparation method thereof belong to the technical field of new nano material and environmental protection. Aiming at solving the problem that the carbon nanotube with microsize is likely to cause secondary pollution to water quality while being used as sorbent, the invention uses nontoxicity, good adsorptive capacity and excellent formability of sodium alginate, and prepares carbon nanotube / sodium alginate granular composite material by sol-gel method. The carbon nanotube / sodium alginate granular composite material has good adsorptive capacity on heavy metal ion in sewage. The method has simple preparation process and controllable condition, is suitable for mass production, reduces secondary pollution to water by the carbon nanotube with microsize, and prepares the environment-friendly carbon nanotube / sodium alginate composite sorbing material.

The invention discloses a method and a device for washing industrial dust. The method comprises the following steps of: sweeping the surface of a workpiece by utilizing vortex formed by high pressure gas, and pumping dust blown up by the vortex by utilizing a vacuum hole. In addition, the invention also provides a device for washing industrial dust. The device comprises a vortex generating deviceprovided with at least a vortex outlet, a cover arranged at the periphery of the vortex generating device so as to form the vacuum hole surrounding the vortex generating device and a vacuum pumping device connected with the vacuum hole. The method can replace the methods of utilizing water for washing, utilizing a brush for washing, and the like, saves resources and space and reduces cost, the washed cleanliness is good, and the possibility of secondary contamination is little.

The invention discloses a treatment method of oil-bearing sludge. The method comprises the following steps of: firstly, carrying out thermal desorption treatment on the oil-bearing sludge to obtain an oil component in the oil-bearing sludge; and then, carrying out catalytic pyrolysis on the oil component, carrying out oil-gas-water separation after condensing the precipitated gas, and collecting recovered oil and combustible gas. The two-stage treatment method for carrying out the thermal desorption and the catalytic pyrolysis on the oil-bearing sludge, which is provided by the invention, can effectively separate oil and sand, also obtains the recovered oil with high added value, generates the combustible gas, can realize recycle at the inside of a system and has high total recycling utilization level and good process economy. Compared with other treatment techniques, the technique has the advantages of high recovery rate of oil resources, good economy, strong adaptability and small secondary pollution and is a recycling treatment technique of the oil-bearing sludge, which can realize the recycle of resources and energy resources simultaneously and is worth popularizing.

The invention provides a high efficiency fluidization upward flow multilayer composite filter material biological filter tank coupled with ozonation and a water treatment method thereof, relating to a biological filter tank and a water treatment method using the biological filter tank. The biological filter tank is composed of an upper filter material, a medium filter material, a lower filter material and a supporting layer, wherein the upper filter material is active carbon, anthracite or biological ceramsite, the medium filter material is modified zeolite, natural zeolite or synthetic zeolite and the lower filter material is a phosphorus functional material. The filter tank is characterized by fast start, a complex and stable biological phase, great biomass, high activity, strong impact resistance, a filter material expansion rate of 0% to 50%, small resistance at the head of the filter tank, high mass transfer efficiency of materials, oxygen and pollutants, a high utilization rate of filter layers and filter materials and small possibility of occurrence of hardening of the filtering materials. The filter tank is applicable to treatment of raw water in which the concentration of water source phosphorus, ammonia nitrogen and organic pollutants fluctuates and can stably operate at a low temperature.

The invention discloses a combined pretreatment method for controlling microorganisms of fresh frozen vegetables or edible fungi, which belongs to the technical field of safety control of fruit and vegetable food. The sterilization of the fresh frozen vegetables or edible fungi adopts the combined treatment of ozone water and ultrasonic wave, and the conditions are as follows: the concentration of the ozone water is between 9 and 15mg / L, the power of the ultrasonic wave is between 1,000 and 1,200W, the cooperative treatment time is between 60 and 90s, and the interval time of the ultrasonic wave is 5s; and then the frozen vegetables or edible fungi are placed into a single instant freezer to be quickly frozen at a temperature of between 35 and 40 DEG C below zero until the central temperature of a product reaches less than 18 DEG C below zero, and are quickly packaged in a low temperature environment lower than 5 DEG C below zero, and the product is placed at a temperature lower than 18 DEG C below zero for storage after the packaging. The sterilization method which combines the ozone water with the ultrasonic wave ensures that the total amount of the microorganisms is controlled within 1,000 counts / gram and coliforms (or colon bacilli) achieve the standard (negative) due to the fact that the synergic action of the ultrasonic wave makes the sterilization effect of the ozone water better. No heat treatment is performed, so the losses of the color and luster, the flavor and the nutrient content of the product are reduced, and the qualities of the quick-frozen product such as color, flavor and so on, are better maintained.

The invention discloses an electrochemical reactor and a method for removing coexisting high-calcium and high-chloride ions from wastewater. The electrochemical reactor comprises one or more reaction tanks; anodes and cathodes are alternately placed in the reaction tank; aluminum electrodes are served as the anodes; inert electrodes are served as the cathodes. The method comprises the following steps: introducing the to-be-treated wastewater into the reaction tank of the electrochemical reactor, soaking the anodes and the cathodes in the wastewater, applying constant current between the anodes and the cathodes and continuously stirring the wastewater. According to the invention, no drug is additionally added, the possibility of causing secondary pollution is low, the reaction condition is mild and the method is not limited by the scope of the chloride ion concentration, and meanwhile, the device used for reacting is simple, the cost is lower and the realization for automation is benefited.

The invention discloses a biological treatment method used for realizing simultaneous removing of carbon and nitrogen in sewage via controlling dissolved oxygen. The biological treatment method comprises following steps: S1, sewage is delivered into a sewage treatment system provided with only one biological treatment tank, and the biological treatment tank is inoculated with domesticated active sludge, wherein after inoculation, the concentration of active sludge in the biological treatment tank is controlled to be 0.5 to 100g / L; S2, the concentration of dissolved oxygen in the sewage treatment system is controlled, and staged operation is carried out; S3, the total nitrogen, the total carbon, and the concentrations of negative and positive ions of inlet water and outlet water are detected; and S4, in seven days of continuous operation, the concentration of dissolved oxygen is maintained to be 0.1mg / L<=DO<1.0mg / L, TN removing ratio of the sewage treatment system on TOC of sewage of different carbon nitrogen ratio is measured. According to the biological treatment method, carbon nitrogen removing is completed in a same sewage treatment tank, the bacteria colony structure of anaerobic bacteria is controlled via controlling dissolved oxygen, ammoxidation is realized at first, and simultaneous removing of carbon and nitrogen in sewage is realized by denitrifying bacteria.

The invention discloses an automatic separating device for a medical injector, and belongs to the field of medical-apparatus-and-instrument auxiliary devices. The automatic separating device for the medical injector aims at mechanically separating waste injector needles, needle bolts and needle cylinders generated in working. A guiding rail of the automatic separating device is sequentially provided with a fixedly-arranged cutting device, a separating device fixed on the guiding rail through a rail wheel and a loading cart arranged on the guiding rail through walking wheels, wherein the back side of the separating device is connected with a stopping block through a reset spring, and the stopping block is fixedly installed. The automatic separating device is easy to operate, the injector only needs to be reasonably installed, a key is accurately operated, and separating can be automatically completed.

The invention discloses a medical waste liquid collection device. The medical waste liquid collection device comprises a box body, an ultrasonic transmitter is arranged on the upper surface of the box body, universal wheels are arranged on the lower surface of the box body, the two sides of the box body are each fixedly connected with a supporting plate, an elastic clamping device is arranged on the upper portion of each supporting plate, and a first liquid outlet and a second liquid outlet are formed in the upper portion of each elastic clamping device. Ultrasonic waves with a certain frequency can effectively kill bacteria in waste liquid, membrane filtration tubes provided with RO membranes, so that some viruses in the waste liquid can be filtered away by using the reverse osmosis technology, liquid containing a small amount of bacteria and viruses and liquid containing many bacteria and viruses are separated out from the membrane filtration tubes respectively, the liquid containing many bacteria and viruses can be further sterilized under the high-temperature condition produced by a heating device, the sterilization efficiency is improved, so that the waste liquid is sterilized while the whole device collects the waste liquid, the possibility of secondary pollution is effectively reduced, and the waste liquid collection safety is improved.

The invention relates to a method of combinedly-reinforced repairing pyrene-and-lead combinedly-polluted soil with scripus triqueter. The method includes following steps: (1) transplanting seedlings of the scripus triqueter to soil polluted by pyrene and / or lead, wherein the planting density of the seedlings of the scripus triqueter is 600-1000 / m<2>; (2) after seedling recovering for 10 days, irrigating a mixed solution containing nitrilotriacetic acid and alkyl glycoside to soil to maintain the total mass of the nitrilotriacetic acid and alkyl glycoside in soil is 1.0-2.5 g per cubic meter soil; (3) when the scripus triqueter is matured, moving the scripus triqueter away to repair the soil polluted by pyrene and / or lead. The reinforced plant repairing technology, compared with other repairing methods, is environment-friendly, is low in cost, is high in repairing efficiency and is easy to carry out.

The invention discloses a long-effecting restoration method for chromium-polluted soil. The restoration method is good in treatment effect, low in cost, low in secondary pollution possibility and high in practicability, and comprises the following steps: drawing a chromium pollution distribution diagram of measurement points, simulating a chromium pollution distribution diagram of a whole soil block, excavating heavily polluted soil according to the pollution distribution diagram, putting the heavily polluted soil into a ball grinder, reducing hexavalent chromium in chromate into trivalent chromium through a reducing agent, then adding an adhesive to cure the reduced soil, ploughing moderately polluted soil to flatten the soil, spraying a sulfate aqueous solution into the soil according to the chromate concentration obtained by calculation, soaking the soil, extracting to separate the chromate out, further reducing the hexavalent chromium in the extracted chromate into trivalent chromium through the reducing agent, and adding the adhesive to cure the soil.

The invention discloses an electrochemical reactor, a method for removing chlorine ions in waste water through electric flocculation, a precipitation product and an application. The electrochemical reactor comprises one or more reaction tanks, wherein an anode and a cathode in the reaction tank alternately arranged; the anode is a copper electrode; and the cathode is an inert electrode. The method comprises the steps of introducing to-be-treated waste water into the reaction tanks of the electrochemical reactor and immersing the anode and the cathode into the waste water; applying constant current between the anode and the cathode and lastingly stirring the waste water. According to the invention, an agent does not need to be additionally added, the possibility of secondary pollution is very low, the reaction conditions are mild and limitation of the concentration range of the chlorine ions is avoided. Meanwhile, the device used for reaction is simple, relatively low in cost and beneficial to automation.

The invention relates to the technical field of carding machines, and discloses a carding machine capable of protecting cotton fibers. The carding machine comprises a shell, a fixing device, a cardingdevice and a handling device, wherein the shell comprises a first fan, a second fan and a through hole; a substrate is fixedly installed on the lower inner wall of the shell; a heating rod is fixedlyinstalled on the upper surface of the substrate; a fixing device is arranged in front of the shell; the fixing device comprises a fixing rod, a round rod and a first thread groove; a cotton fiber barrel is arranged on the outer side of the round rod; the carding device is arranged at the right end of the fixing device; the carding device comprises a cotton comb, a connection rod and a bearing; round grooves are formed in the front of the cotton comb; springs are connected to the round grooves; cotton comb teeth are arranged at the front ends of the springs; the connection rod is arranged on the left surface of the cotton comb; the bearing is fixedly connected to the left end of the connection rod; the inner ring of the bearing is sleeved on the round rod; a bearing sleeve is sleeved on the outer ring of the bearing; a motor is arranged at the front end of the bearing sleeve; ad the bearing sleeve is fixedly connected to the output shaft of the motor. The efficient carding machine hasthe advantages of good carding effect, high carding speed and the like

The invention relates to the technical field of bottle washing machines, particularly relates to wine bottle cleaning equipment based on electrical automation. The equipment comprises an equipment support and a cleaning box which are symmetrically, vertically and fixedly arranged, a drying box and a spraying box which are arranged at the top end of the equipment support, and further comprises a driving belt assembly correspondingly connected with the drying box and the spraying box, the end, far away from the drying box and the spraying box, of the driving belt assembly is in transmission connection with the two ends of the cleaning box correspondingly, a wastewater filtering device is arranged at the bottom of a wastewater recycling bin, a water pumping device is connected to the end, faraway from the wastewater recycling bin, of the wastewater filtering device, a steam generating device is further provided with a steam erupting device, and the steam erupting device is located at thebottom of the cleaning box and is correspondingly arranged with the cleaning box. According to the wine bottle cleaning equipment, the cleaning of bottles can be conducted by generating high-pressuresteam, on one hand, the high-temperature and high-pressure steam can be used for disinfecting the bottles, on the other hand, the steam is not easily retained on bottle bodies, meanwhile, the dryingbox is matched, the probability of secondary pollution is reduced, and the hygiene performance is greatly improved.

The invention provides a medical decontamination room which comprises a cubic wall structure, a top wall structure and a bottom wall structure. The cubic wall structure comprises a cubic support frame and side wall plates arranged on the cubic support frame, the top wall structure comprises a trapezoid top frame and a top wall plate, and the top wall plate comprises a central ceiling arranged in the middle of a portion clamped by cross beams and longitudinal beams, peripheral ceilings arranged on the periphery of the central ceiling and arced transition bands arranged between the periphery of the central ceiling and the tops of the side wall plates; the bottom structure comprises an inverted trapezoid bottom frame and a bottom plate, arced transition bands are arranged between the periphery of the bottom plate and the bottoms of the side wall plates in an enclosing mode, and the central ceiling is further provided with decontamination equipment. The operating room is an integrated seamless prefabricated combined arced operating room which is reasonable in design, easy and convenient to use and operate, low in manufacturing cost, smooth in space effect, not prone to dust generation or retention, free of pollution loophole, high in intelligent degree and good in use effect.

The invention relates to the field of environment-friendly sewage treatment equipment, in particular to a low-temperature frozen sewage treatment system. The low-temperature frozen sewage treatment system comprises a reaction unit and a storage unit, wherein the reaction unit comprises a tank body, a refrigeration device which is mounted on the tank body and is used for providing a cold source into a solution in the tank body, and a heating device for providing a heat source for crystallized ice bodies in the tank body; a stirrer is arranged in the tank body, and is driven by a speed reducer mounted at the upper end of the tank body; a discharging device is mounted at the lower end of the tank body; the storage unit comprises a raw water storage tank for storing sewage to be treated; the raw water storage tank is communicated with the tank body through a hydraulic pump. The low-temperature frozen sewage treatment system is simple in structure and convenient to operate, and can quickly and effectively treat sewage without producing secondary pollution; respective component substances in the sewage cannot be damaged, and useful components in the sewage can be favorably effectively recycled. Compared with the prior art, the sewage treatment effect is better, the impurity content is lower, and a discharging standard can be completely met, and the low-temperature frozen sewage treatment system has extremely high popularization value.

The invention discloses a plastic product cleaning device. The plastic product cleaning device comprises a box body; a first material inlet and a water inlet are formed in the top of the box body; a motor is arranged on the left side wall of the box body; a rotary shaft is arranged on the right side of the motor; a roller is arranged on the outer wall of the rotary shaft; a second material inlet is formed in the top of the roller; a rubber plug is arranged in the inner cavity of the second material inlet; a hoisting ring is arranged on the top of the rubber plug; a material guiding plate, a filter layer and a supporting plate are sequentially arranged in the inner cavity of the box body from top down; the filter net is located on the top of the supporting plate; a high-pressure water sprayer and a high-pressure gas sprayer are arranged on the top of the inner cavity of the box body; an overflow pipe and a material outlet are arranged on the right side wall of the box body; a gate valve is arranged on the material outlet; a water outlet pipe is arranged on the bottom of the box body; and a solenoid valve is arranged on the water outlet pipe. By adopting the plastic product cleaning device, sufficient water rinsing can be performed on plastic products; the water rinsing effect is ensured; and besides, the drying equipment is combined with water rinsing equipment, so that cleaning efficiency is improved.

The invention relates to a phytoremediation method for oil polluted wetland, which comprises the following steps of: planting seedlings of sedge herb or sowing seeds of sedge herb in the oil polluted wetland, wherein the planting density is 800-1,200 plants / m<2>; when the sedge herb grows to the seed stage, harvesting the sedge herb; and repeatedly harvesting until the oil content in the soil meets the environmental safety standard.

The invention discloses an X-shaped foldable stretcher bracket which comprises a slide groove, a stretcher locking mechanism, a shock absorber, a permanent base, a moveable base, a fixing mechanism and cross arms. The permanent base is installed close to a car, the moveable base is located close to a pavement, and the moveable base is connected with the permanent base through the cross arms. Through the manner that the bracket is foldable, the limited space in a rescue cabin is saved, the practicality of the stretcher bracket is ensured, and the convenience to work of medical rescue personnel is improved.

The invention discloses a device for dura mater suture in craniotomy, includes a stapling device and a dura mater positioning device, the two sides of the suturing nail device are provided with dura mater positioning devices. A nail body is arranged on the suturing nail device, the inside of the nail body is provided with a battery cartridge, the battery cartridge is connected with a suturing naildevice through a nail body, A battery plate is arranged in the battery compartment, the battery panel is electrically connected with the nail body through a battery cartridge, the lower part of the nail body is rotatably provided with a hand-held rod, the hand-held rod is connected with a suturing nail device through a nail body. A link rod is arrange on that dural positioning device. A line is arrange inside that connecting rod, the line is electrically connected with the battery plate through the connecting rod. and a dura mater positioning device is arrange on the side of the suturing naildevice, the device can cooperate with the suturing nail device to assist the nail forceps, the suturing efficiency and the accuracy are improved, the structure is simple, and the device is convenientto realize.

The invention discloses a coal washing wastewater treatment system. The system comprises a residual sludge bin, a freezing bin, a high-temperature steam wall breaking system, a centrifugal device, a flocculation treatment tank and a solid-liquid separation device. Silicon dioxide with the particle size smaller than 0.075 mm in solid waste generated after coal washing wastewater treatment is a maincomponent; dehydration drying treatment is performed; then caustic soda is added; the mixture is calcined and ground; a calcined product is added into a hydrochloric acid solution and / or acidic minewastewater for activation treatment, and by combining iron and aluminum particles in the residual sludge with lime added in the coal washing wastewater process, polyaluminum ferric calcium silicate isfinally formed, thereby obviously enhancing the sedimentation efficiency of the coal washing wastewater.

The invention discloses a starch-based polyacrylic acid magnetic adsorption material and a preparation method and application thereof. The preparation method comprises the following steps: preparing Fe3O4 magnetic micro-nano particles through a coprecipitation method, and modifying the Fe3O4 magnetic micro-nano particles to obtain modified Fe3O4 micro-nano particles; mixing a pretreated starch base material, an acrylic monomer, tetrahydrofuran, an initiator and divinyl benzene, and conducting reacting under a vacuum condition to obtain a starch base material; and mixing the modified Fe3O4 micro-nano particles, the starch base material and polyacrylic acid for reaction to obtain the starch-based polyacrylic acid magnetic adsorption material. The preparation method is simple in process; used reagents are common drugs which can be purchased on the market, so cost is low, and operability is high; the starch raw material adopted in the preparation process is pollution-free to the environment and easy to obtain, and polymerization conditions are simple; the adopted magnetic particles are beneficial to subsequent recovery, and secondary pollution is not prone to being generated; and preparation conditions are convenient, economic benefits are produced, and production on a large scale can be realized.

The invention provides a magnetic part, a coating clamp and a manufacturing method of the magnetic part. The magnetic part is used for the coating clamp. The magnetic part comprises a base body and anano ceramic coating, and the nano ceramic coating is coated on the base body. According to the magnetic part provided by the invention, the surface of the base body is coated with the nano ceramic coating, and the nano ceramic coating does not generate chemical reaction with cleaning liquid, so that the nano ceramic coating is prevented from being corroded, and the magnetic part is prevented fromrusting. In addition, due to the fact that the magnetic part is prevented from rusting, after the film coating clamp enters the cleaning fluid, no rusty matter enters the cleaning fluid under the action of ultrasonic waves, the situation that the cleaning fluid is polluted due to the fact that the coating is corroded is avoided, the possibility that the quartz wafer is secondarily polluted is reduced, and the quartz wafer can obtain a better cleaning effect.

The invention relates to a cylindrical continuous-casting tundish which is composed of a cylindrical bottom surface and a cylindrical side wall; the middle part of the cylindrical bottom surface is provided with a cylindrical blocking dam, 4-12 steel taping holes are uniformly distributed on a circular bottom surface at the periphery of the cylindrical blocking dam, the centers of the steel tapingholes are arranged at the same circumference on the circular bottom surface. The invention saves cost of the device by arranging the simple blocking dam, reduces the corrosion of fireproofing material, is beneficial to the production of high-quality steel products, radically solves the metallurgy problem that a rectangle or T-shaped continuous-casting tundish can not solve no matter any one current controlled structure is adopted and has wide developing prospect and great social and economic benefits.

The invention discloses a dehydration conditioner for high temperature anaerobic digested sludge and a dehydration method of high temperature anaerobic digested sludge. The dehydration conditioner comprises an acryloyloxyethyl trimethyl copolymer and cationic polyacrylamide, the weight ratio of the acryloyloxyethyl trimethyl copolymer is 1.1%-1.37% of the solid content of the high temperature anaerobic digested sludge, and the weight ratio of the cationic polyacrylamide is 0.27%-0.36% of the solid content of the high temperature anaerobic digested sludge. The dehydration method of the high temperature anaerobic digested sludge adopts the dehydration conditioner for conditioning. The dehydration conditioner provided by the invention has the advantages of no corrosiveness, no increase of sludge ash content, no change of the properties of the filter cake and filtrate, good dehydration performance, good applicability, low cost, no secondary pollution, etc., is an environment-friendly conditioner that has good application prospects and can efficiently condition high temperature anaerobic digested sludge, and can achieve the advantages of simple method, good dehydration effect and the like when used for dehydration of high temperature anaerobic digested sludge.

The invention relates to the field of sewage treatment. It includes a filter, an electrolytic tank, a biological treatment tank, a filter tank and an oxygen tank, the filter is arranged above the electrolytic tank, the electrolytic tank is connected to the biological treatment tank through a pipeline A; the biological treatment tank is connected to the filter tank through a pipeline B ; A mechanical filter screen set is set inside the filter, and a biological treatment plate set is set inside the biological treatment tank. The biological method is used to treat the sewage, which reduces the possibility of secondary pollution caused by the chemical method; the simple composition device is suitable for urban sewage treatment.

The invention discloses an edge tool box used on a mobile nursing vehicle, the edge tool box and belongs to the technical field of medical supplies. The invention aims to provide the edge tool box with a cutting function. According to the technical scheme, a case is arranged; a cover plate sliding area and a cutting area are arranged above the case; the cutting area comprises a separation area anda cutting assembly mounting area, the separation area and the cutting assembly mounting area are arranged in the width direction of the case, the cutting assembly mounting area comprises a cutting assembly, and the cutting assembly comprises a tool bit base fixedly connected with the side wall of the case and a pressing type tool bit assembly arranged on the tool bit base; the edge tool box usedon the mobile nursing vehicle is simple in overall structure, convenient to operate and reasonable in structural distribution, and the functional requirements of the edge tool box in actual use are met.

The invention discloses a combined multi-layer rack capable of receiving oil. The combined multi-layer rack comprises an oil receiving disc base device, small part rack devices, a plurality of sets ofintegrated gear type rack devices; the oil receiving disc base device is provided with an oil draining hole, and the oil draining hole is provided with an oil draining valve; the small part rack devices are arranged in the oil receiving disc base device, and engine oil on small parts placed on the small part rack devices can penetrate the small part rack devices to drop into the oil receiving disc base device; and the integrated gear type rack devices are arranged on the small part rack devices, and engine oil on gear type parts placed on the multiple sets of integrated gear type rack devicescan penetrate the small part rack devices to drop into the oil receiving disc base device. The combined multi-layer rack capable of receiving oil can achieve combined type superposition of the gear type parts and the irregular small parts, can effectively prevent the residual oil on the parts from contaminating the production environment everywhere, and meanwhile, can reduce the possibility of secondary pollution of the parts.

The embodiment of the invention discloses a data processing method and device, a server, a terminal and a storage medium, and belongs to the technical field of computers. The method comprises the steps that a target group in an abnormal state is acquired, the target group comprises at least two accounts, and a first management account in the at least two accounts has management authority for the target group; deleting the first management account of the target group from the target group; any account in a normal state in the target group is determined as a second management account after the target group is replaced; and after determining that the management account of the target group has been changed, recovering the state of the target group to a normal state. According to the embodiment of the invention, normal use of the target group can be maintained, an abnormal account is prevented from performing an abnormal behavior through the target group, and the target group is handed over by a normal account to take over, so that the exception handling effect is improved.