239results about How to "Simplify structural complexity" patented technology

The invention discloses an active supporting device of a healthy bed and a method thereof; an air cushion layer is disposed inside and near the top of a mattress; a plurality of air bags are disposed on the air cushion layer; each air bag is connected to an air charging and discharging device through an air pipe; the air charging and discharging device is connected to a control device; air charging or discharging of the air bags of the air cushion layer is performed by the air charging and discharging device which is driven by the control device; and a pressure sensor is connected to each air pipe; the covering scope of the air cushion layer is between the neck and the buttock of a user; at the beginning, all the air bags are aerated with air, and the pressure of the air bags is detected by the pressure sensor on each air pipe; when the internal pressure of each air bag reaches a set value, air charging is stopped to obtain air charging time of each air bag; the air bag with longer air charging time is determined as the air bag corresponding to the waist of the human body; during the next air charging, the air charging quantity of the air bag corresponding to the waist is sufficient to actively support the waist of the human body; and therefore the purpose of comfortable sleep of the users is reached.

The invention discloses a novel cross coupling substrate integrated waveguide band-pass filter. The filter comprises basic resonant units, wherein rectangular resonant cavities serve as the basic resonant units. Magnetic coupling is achieved among the resonant cavities in a windowing mode. S-shaped grooves are formed to achieve electrical coupling, and input and output are achieved by the adoption of a micro-strip-line and coplanar-waveguide structure. The rectangular SIW resonant cavities are formed by loading of periodic metal through holes in medium substrates. The electrical coupling is achieved through the structure that the S-shaped grooves with symmetrical central axes are formed in the upper metal face and the lower metal face of the two cavities, debugging is convenient, processing is easy, and the structure is suitable for the miniaturization design of the filter. The micro-strip-line and coplanar-waveguide structure is adopted for the input and the output, and the structure is that coplanar waveguides are directly connected with an input 50-Ohm micro strip line and an output 50-Ohm micro strip line, so that an extra transitional design is not needed for matching of ports, and complexity is simplified. The filter is compact in structure, improves out-of-band rejection, has better properties of restraining strays and separating signals, and meets requirements for the miniaturization and high properties of modernization radio communication.

The invention discloses an invasion tolerance application server based on J2EE middleware criterion. The server comprises an invasion tolerance expansion integrated frame, an invasion tolerance strategy logic assembly, a safety group communication manager, a safety group communication system and an application server basic platform. The invasion tolerance strategy logic assembly and the invasion tolerance expansion integrated frame are conducted in loose coupling and realize the transparent expansion of invasion tolerance function of the J2EE application server basic platform by a built-in interceptor of the J2EE application server. The invasion tolerance strategy logic assembly and the safety group communication manager are intercommunicated via an API interface. The safety group communication system works on a group communication layer of the J2EE application server basic platform and intercommunicated with the safety group communication manager and the J2EE application server basic platform respectively via the safety group communication manager. The invention realizes the effective integration of invasion tolerance and J2EE application service functions, and is superior in significant security and survivability as compared with other similar servers.

The invention provides a staged combustion chamber. The staged combustion chamber comprises an annular flame barrel and a main combustion stage assembly, wherein the annular flame barrel comprises a flame barrel inner ring and a flame barrel outer ring which are coaxial with each other; the front section of the annular flame barrel is in the form of a cone of which the inner diameter is increased gradually; and the main combustion stage assembly is positioned at the front section of the annular flame barrel, is used for providing fuel and air needed by combustion of a main combustion stage, and comprises an annular bluff body, an inner / outer ring oil cavity a plurality of duty stage assemblies; the inner ring surface of the annular bluff body constructs an inner ring air flow channel together with the inner surface of the flame barrel inner ring and the outer ring surface of the annular bluff body constructs an outer ring air flow channel together with the inner surface of the flame barrel outer ring; the inner / outer ring oil cavity is attached to the inner / outer side of the annular bluff body and by the inner / outer ring oil cavity, accommodated fuel can be ejected onto the inner ring air flow channel through a plurality of inner ring ejection holes positioned in the inner / outer ring surface of the annular bluff body; and the plurality of duty stage assemblies which are positioned in a space encircled by the annular bluff body. In the staged combustion chamber provided by the invention, main combustion stage air enters the combustion chamber in a full ring air inlet way, so that the pressure loss of the combustion chamber is reduced, and the fuel consumption of an engine is lowered.

The invention provides a gas self-pressurization hybrid rocket engine which comprises an oxidizing agent storage box, an oxidizing agent control valve, a check valve, an oxidizing agent injector, a spray pipe, a flow regulating valve, a poor-oxygen gas generator, a filter and a pressure reducer. A sealing piston is arranged in the oxidizing agent storage box. The sealing piston divides an inner cavity of the oxidizing agent storage box into two sealed cavities, an oxidizing agent is placed in one sealed cavity, one end of the poor-oxygen gas generator is a sealed end, the other end of the poor-oxygen gas generator is provided with the spray pipe, a grain is poured at the position of the sealed end, and the flow regulating valve is arranged in a cavity of the poor-oxygen gas generator in which a grain is not poured. The flow regulating valve divides the cavity in which a grain is not poured into two cavities, and the cavity close to the spray pipe is a secondary combustion chamber. According to the gas self-pressurization hybrid rocket engine, self-pressurization can be achieved, and the complexity of an oxidizing agent supply system can be simplified greatly.

An intelligent storing and fetching system for warehouse logistics comprises a control device (100), a warehouse cabinet body device, a locking device and a material transporting device, wherein the warehouse cabinet body device comprises a plurality of unit cabinets (5) used for containing material boxes (7) with multiple fetching grooves (71) in the bottom faces; an openable covering lid (6) with a holding groove (61) in the outer surface is mounted in a storing and fetching opening of each unit cabinet (5); the material transporting device comprises a driving mechanism (3) and a material box operating device, and the material box operating device is connected with the driving mechanism (3) through a connection rod (31) extending in the vertical direction.

A self-charging strong excitation double transformer double-winding high-gain AC switched reluctance motor converter consists of four phase winding circuits, a rectifying output circuit, and an excitation and charging circuit, wherein two branch windings of each phase winding are in different circuits, the excitation is different, and the power generation output is different, moreover, the outputpolarities of adjacent phase winding circuits are alternated, the alternating current is directly obtained and the isolation, boost and rectification are carried out through the excitation and charging circuit, the output voltage and power are regulated by adjusting the switching tube on the phase winding circuit output side when necessary, the excitation and charging circuit can flexibly obtain the required excitation voltage and charge the storage battery automatically when necessary, the whole converter has the advantages of simple structure, multiple functions, and high intelligent degreeand is suitable for various types of variable speed wind electricity or the field of high-speed switched reluctance motor systems.

The invention is a side light-type backlight module and a LCD, where the former has a light source group, a light guide plate and a reflecting backboard. The reflecting backboard has a first light-reflecting surface and a bent part bending to the first surface, the light guide plate is arranged on the first surface and connected to the bent part, one side of the light guide plate and the bent part form a cavity between, and the light source group is installed in the cavity. And the first surface above can have a light-reflecting character with the help of pressure casting or coating a reflecting layer.

The invention belongs to the field of rare earth metallurgy, and in particular relates to a method for preparing a solid spherical rare earth oxide in a one-step spraying thermal decomposition mode. The method comprises the following steps of: firstly, controlling the temperature of a roasting furnace to 400-1700 DEG C, subsequently mixing a solution containing 10-350g / L rare earth oxide and 0.1-500g / L carboxylic acid additive with a carrier compressed gas with a flowing speed of 5-8,000L / h, subsequently spraying into the roasting furnace, roasting for 1-60 seconds, and naturally cooling down the roasting slag so as to obtain a solid spherical powder product of which the rare earth oxide content is greater than 90wt%. As a trivalent rare earth chloride solution is used as the raw material, ammonium bicarbonate and toxic oxalic acid are not used in the production process, carbon dioxide emitted in the roasting process in the conventional process is not generated, and the pollution on the environment is greatly reduced. Solid spherical powder can be prepared through one-step thermal decomposition.

An assembly plant, in particular for assembling motor vehicles, which permits design of final assembly of motor vehicles so that it is as flexible as possible in terms of space. A central elongated assembly hall is provided in which essentially automated assembly regions are provided and finger-like partial regions having essentially manual workplaces are provided projecting at a right angle from the longitudinal side. A change in the sequence in the manual regions can be accomplished easily by means of an extension of the finger-like partial regions at the head end.

The invention relates to an air guide mechanism and an air conditioner indoor unit. According to the main technical scheme, the air guide mechanism is used for the air conditioner indoor unit and comprises an air guide assembly, a power transmission assembly and a driving device; the air guide assembly comprises a plurality of air guide plates which are annularly distributed around an air outlet of the air conditioner indoor unit; the power transmission assembly is connected with the air guide plates and receives driving force from the driving device so as to be used for transmission, thereby driving the air guide plates to change angles. The air conditioner indoor unit comprises the air guide mechanism. According to the air conditioner indoor unit, the air supply direction can be adjusted freely; besides, the power transmission assembly is simple in structure, so that the system mounting and maintaining cost is reduced.

The invention relates to the technical field of carbon nano tube purification, in particular to a device and a method for directly electrifying and purifying a carbon nano tube. The device comprises amain reactor, the main reactor comprises a material preheating section, a low-temperature heating reaction section, a high-temperature heating reaction section and a material cooling section which are sequentially arranged from top to bottom, the upper end of the main reactor is connected with a feeding valve, the feeding valve is connected with a feeding weighing device, the feeding weighing device is connected with a constant-pressure tank, and the constant-pressure tank is connected with a carbon nano tube storage tank; the invention discloses a device and a process method for directly electrifying and heating a carbon nano tube material in a reactor and then continuously purifying carbon nano tubes by adopting chlorine or hydrogen chloride gas. According to the continuous industrial purification device, graphite is adopted as an inner container of a reactor, a pouring material frame is combined, carbon nano tubes in the reactor are directly powered on, and acid gas and granular carbon nano tubes are used for reaction purification.

The invention provides a laser melting forming protection circulating dust-removing system and method. The system comprises an upper cavity and a lower cavity. An exhaust opening of the lower cavity communicates with an air inlet of the upper cavity. An exhaust opening of the upper cavity communicates with an air inlet of the lower cavity. The end of a second gas conveying pipeline extends in a cavity body of the lower cavity. A second electromagnetic valve is installed at the position, located in the cavity body of the lower cavity, of the second gas conveying pipeline. The part, outside the cavity body of the lower cavity, of the second gas conveying pipeline is sequentially connected with a dust filter, a draught fan and a first electromagnetic valve in series. In addition, the upper cavity communicates with a shield gas pipeline which is provided with a third electromagnetic valve. The laser melting forming protection circulating dust-removing system and method have the beneficial effects that firstly, the content of oxygen in a forming cavity can be controlled to be low in real time, and therefore the phenomenon that melt is instantly oxidized can be avoided, and the laser melting forming rate is increased; and secondly, smoke-shaped dust generated when lasers act on metal powder can be absorbed into the dust filter in time, the influences, on the subsequent forming quality, of the smoke-shaped dust are prevented, and the forming rate is increased.

The invention discloses a buffer mechanism for a slide rail returning device. The buffer mechanism comprises a slide rail returning device and a buffering mechanism; the slide rail returning device is provided with a fixed seat, a slide mechanism and a poking piece; the slide mechanism can be arranged in an accommodation space of the fixed seat in a sliding way; the slide mechanism comprises a release piece; one side of the release piece is further provided with a pressing part; the poking piece is overlapped with a groove of the fixed seat; the buffering mechanism is sleeved with the slide mechanism and can be arranged on one side of the inner side wall of the accommodation space in a sliding way and is positioned between the pressing part of the release piece and the inner side wall; the buffering mechanism directly rubs the slide rail returning device, so a buffering effect can be achieved; and therefore, the effects of simplifying the structure, quickly assembling the buffer mechanism and reducing cost can be achieved.

The invention provides a data synchronizing system. A main server comprises a data obtaining unit used for obtaining updated data or services from a data source and a data distributing unit used for distributing the updated data or services to all data servers connected to the main server, wherein each data server comprises a data storage unit used for storing the updated data or services distributed by the main server. Each client comprises a data synchronizing unit used for automatically obtaining the updated data or services from the connected data servers so as to maintain the data synchronizing state of each client. The invention further comprises a data synchronizing method. According to the technical scheme, each client can maintain the data synchronizing state of each client itself, and accordingly concentrated coordination and management of server ends are needless, the system structure and management complexity are beneficially simplified, and usability and reliability of the system are improved.

The invention provides a water injection well umbilical pipe full-horizon injection regulation device, which comprises an injection regulation control cabinet (1), a special christmas tree (2), an umbilical pipe column (3) and a water distribution device (4). The water injection well umbilical pipe full-horizon injection regulation device has the advantages that injection water is branched and divided on the ground and enters underground branch pipes, one branch of water occupies one branch pipe, the structural complexity of the traditional injection regulation device can be effectively simplified and the oil field exploitation cost is reduced by adopting the structure layout, and in addition, water injection flow and pressure of all underground horizons of the water injection well can be accurately regulated; and a controller is arranged in the injection regulation control cabinet, the flow of each branch pipe, an underground hydraulic packer and a backwash pump can be automatically controlled via the controller, and the device of the invention has the advantages of high automation degree, simple operation, and low cost; and the umbilical pipe bundle and the water injection pipe column adopt a segmented setting scheme, working condition requirements of water injection wells of different depths can be met, and the construction is convenient.

The invention aims to provide a horizontal shaft pitch-control tide energy water turbine. The water turbine comprises a front hatch cover, a rear hatch cover, a generator system, a pitch control system and a yaw assembly, wherein the generator system comprises a generator rotor, a coil and a box, the coil is fixed on the box, and the generator rotor is positioned in the coil; the pitch control system comprises a paddle, a worm wheel, a worm, a paddle-changing motor, and a turnplate; the paddle-changing motor is used for driving the worm, the worm is arranged on the turnplate and meshed with the worm wheel, and the worm wheel is fixedly connected with the paddle; the snaking assembly comprises a shuttle upright, a revolute joint and a rack, the shuttle upright is connected with the revolute joint, the revolute joint is connected with the rack, and the shuttle upright rotates on the rack through the revolute joint; and the pitch control system is connected with the generator rotor through a flange, the front hatch cover is connected with the turnplate, the rear hatch cover is connected with the generator system, and the shuttle upright is connected with the box. The water turbine provided by the invention has the advantages of simple system and high reliability, low cost, convenience in maintenance, and has a slower flow rate self-starting performance.

The invention discloses a bumping position measuring system and method based on bidirectional detection of a fiber ring. The system comprises a light source, first, second and third couplers, a sensing fiber, first and second detectors and a processor; the first coupler couples first optical signals output by the first source to obtain second and third optical signals; the first detector receives the third optical signal which is transmitted to the second coupler via the sensing fiber and output, the second detector receives the second optical signal which is transmitted to the third coupler via the sensing fiber and output, and the two detectors detect returned optical signals, and output first and second voltage signals respectively; and the processor determines a bumped position according to the first and second voltage signals. According to the invention, the bumped position of an object to be measured can be measured more rapidly and accurately, the system structure is simplified, the system cost is reduced, and conditions are provided for batch application of schemes.

The invention belongs to the technical field of a micro-fluidic chip, and in particular relates to a simple micro-fluidic chip for cytological analysis and a cell analysis method. The simple micro-fluidic chip comprises a basal layer and a cell culture layer which is arranged on the basal layer, wherein liquid storage tanks, which are located in a same plane, are arranged on the cell culture layer; a micro-channel is additionally arranged on the cell culture layer; and the bottoms of the at least two liquid storage tanks communicate by virtue of the micro-channel. The simple micro-fluidic chip is applied to cell culture and cytological analysis is carried out on cells cultured in the micro-channel of the micro-fluidic chip; and compared with an existing micro-fluidic chip, the micro-fluidic chip disclosed by the invention is easier to be adopted by general biology laboratories for processing and for the operations of cell culture and cell analysis.

An intelligent warehouse logistics system provided with locking pins comprises a control device (100), a storage cabinet device, a locking device and a material transport device, wherein the storage cabinet device comprises a plurality of unit cabinets (5) used for containing material boxes (7), a plurality of grabbing grooves (71) are formed in the bottom surface of each material box (7), and openable covers (6) with holding grooves (61) formed in the outer surfaces are installed at storing-fetching ports of the unit cabinets (5); the material transport device comprises a driving mechanism (3) and a material box operating device which is connected with the driving mechanism (3) through a connecting rod (31) which extends in the vertical direction.

The invention provides a bridge crane positioning and swing eliminating method based on fuzzy sliding mode control. The method comprises the following steps of: based on sliding mode variable structure control, combining fuzzy control with the sliding mode variable structure control to construct a new synthetic sliding mode surface; designing a proper fuzzy rule to ensure that the system state isalways on the sliding mode surface; and adjusting the size of a control quantity u by using the fuzzy control rule to realize efficient positioning and swing eliminating control of a bridge crane, weaken the buffeting phenomenon and increase the response speed. According to the method provided by the invention, a flexible robot intelligent control technology is fused with a simple and efficient automatic technology to be further applied to a bridge crane system, so that experience operation of technical workers is better replaced, errors caused by human factors are continuously reduced, the defect that a manual control method cannot cope with a severe environment is overcome, the operating efficiency and stability are improved, the buffeting problem of conventional sliding mode control isimproved, and rapid and accurate positioning and stable and efficient swing elimination during transportation of the bridge crane are realized.

The invention discloses a humidifier and a continuous positive-pressure ventilation therapy machine. The humidifier comprises an outer shell and a sealing ring. The outer shell comprises a first outer shell body, a second outer shell body and a buckling assembly. The second outer shell body and the first outer shell body are buckled through the buckling assembly. A floating sealing groove is formed between the first outer shell body and the second outer shell body. The sealing ring is arranged in the outer shell and comprises an elastic fork-shaped structure arranged at the edge of the sealing ring. The elastic fork-shaped structure is located in the floating sealing groove. When the first outer shell body and the second outer shell body are buckled, the floating sealing groove and the elastic fork-shaped structure is compressed, the elastic fork-shaped structure generates elastic force for expanding the floating sealing groove, and the sealing ring is matched with the buckling assembly to seal the buckled position. By means of the humidifier and the continuous positive-pressure ventilation therapy machine, the sealing reliability of the humidifier is improved.

The invention discloses a hydraulically-driven rape combine harvester which comprises a tracked chassis traveling device, a header, a longitudinal-axial-flow threshing and separating device and a cyclone separation cleaning system. The header is arranged at the front end of the tracked chassis traveling device which comprises a chassis, a cab, a diesel engine and traveling gearbox, the diesel engine is positioned in rear of the cab which is positioned at the front end of the chassis, the traveling gearbox is positioned on one side of the cab, and the diesel engine supplies power to the traveling gearbox through belt transmission. The longitudinal-axial-flow threshing and separating device is connected with a discharging port in the rear end of the header and provided with a forced feeding device, and the cyclone separation cleaning system is arranged at the rear end of the tracked chassis traveling device. By adoption of the segmental header, the header is adjustable in height according to practical requirements to better adapt to environments of fertile farmland and slope planting in the middle and lower Yangtze regions; by means of full hydraulic driving, simplicity in operation is achieved; since a traditional chain harrow type conveyor is replaced by the longitudinal-axial-flow threshing and separating device with the forced feeding device, a stem flow route is shortened.

The invention discloses a test device capable of simulating the vibration of a magnetic suspension vehicle under aerodynamic force conditions. The test device comprises a mounting base and a supporting upright post, a rail is connected to an upper end of the supporting upright post through a rubber spring, linear rails are arranged on front and back side faces of both ends of the rail, an electromagnet capable of vertically moving up and down is further arranged on the linear rails through sliding block bodies, a suspension sensor is installed on one end of the electromagnet, load supports arefixedly connected to the four corners of the electromagnet through lifting rods, load weights are connected to the upper surfaces of the load supports through a plurality of load supporting springs,an oil pressure actuator is arranged on the mounting base, a pressure sensor is arranged at a connection site of an actuation end of the oil pressure actuator and the load weights, and the oil pressure actuator adjusts the stimulation load according to the signal of the pressure sensor to simulate the action of the aerodynamic force on the magnetic suspension vehicle. By adoption of the scheme, the interference of other disturbance factors is eliminated, the problem that the aerodynamic load and other loads cannot be distinguished in the current line test is overcome, the structural complexityis simplified, and the test cost is reduced.

The invention relates to a power system suitable for a small vertical take-off and landing fixed-wing aircraft. The system comprises two independent power subsystems and a drifting system, wherein thepower subsystems comprise a lift fan and auxiliary motor power subsystem, a main ducted fan and main motor power subsystem, the lift fan and auxiliary motor power subsystem is used for generating downward airflow, so that first vertical lifting force is generated located at the front part of a fuselage; and the main ducted fan and main motor power subsystem is used for downwards deflecting gas jetted backwards through a main ducted fan via a vector spray pipe to generate second vertical lifting force located at the tail part of the fuselage, and the drifting system directs compressed air generated by the main ducted fan to wings of the two sides through two rolling spray pipes, and then the air is jetted downwards through nozzles on wingtips so as to generate third vertical lifting forceat the wings on the two sides. Airflow adjusting mechanisms are arranged in the two rolling spray pipes, and are used for adjusting the air injection amount of the two rolling spray pipes, so that a rolling moment is generated, the downward jetted air is deflected clockwise or counterclockwise by deflecting a first spray pipe unit, so that a yaw moment is generated.

The invention discloses a hemodynamic analysis device. The device comprises a detection mechanism, a sensing mechanism, a detecting cup and an oscillation mechanism, wherein the detection mechanism comprises a circuit board and a displacement actuator for regulating the circuit board to move up and down, and a connecting slot is formed in the circuit board; the sensing mechanism comprises a sensing chip which is detachably plugged in the connecting slot, and a probe is fixedly connected to the sensing chip; the detecting cup is arranged under the probe; and the oscillation mechanism is used for driving the detecting cup to oscillate regularly. According to the device, a blood sample in the detecting cup is regularly oscillated by virtue of the oscillation mechanism, the probe of the sensing mechanism is subjected to perform micro-displacement actuation by virtue of the driving capacitor of the sensing chip to simulate the physiological process of blood coagulation in a body, so that the detection analysis result is accurate and reliable; and the traditional electromagnetic measurement method is replaced by detection of the sensing mechanism, so that influence of vibration and friction on the analysis device is reduced, the measurement accuracy and sensitivity can be remarkably improved, and the biaxial dimensional dynamic data can be detected and acquired simultaneously.

Provided is a fan. A wireless power receiving coil is provided for receiving a wireless power signal for supplying power to the fan. The fan includes a fan frame including a substrate part and a ring wall part which are mutually connected and form accommodation space through encircling, a stator group arranged in the accommodation space, a fan wheel including an axis which is rotatablely combined with the stator group, and a wireless power receiving coil which is combined with the fan frame. And the wireless power receiving coil is electrically connected with the stator group.

The invention discloses a pipe-in-pipe faucet water control valve. According to the water control valve, a rotating base, a movable valve block and a fixed valve block which are sequentially overlapped are arranged in a valve shell, a valve rod extending out of the valve shell is arranged on the rotating base, the valve rod provides operation, the movable valve block is embedded through the rotating base and rotates and moves, and by means of the change of the position-aligning relation between the movable valve block and the fixed valve block, a faucet can be controlled to allow water to flow or not to flow, or the mixing proportion of cold water and hot water and the outlet water flow volume can be changed; a valve base combination at the tail end of the valve shell is used for stopping the fixed valve block, the movable valve block, the rotating base and other internal members from dropping out; and the water control valve is used in cooperation with the faucet, a water outlet pipe and a faucet handle.

The invention relates to a method and a device for preparing cerium-based rare earth polishing powder by virtue of spray pyrolysis and belongs to the technical field of materials. The method comprises the following steps: (1) dissolving rare earth chloride and a fluorine-containing additive in water to prepare a solution; and (2) by adopting air as a carrier gas, spraying the solution into a calcining furnace for calcining and naturally cooling calcined slag generated by the calcining to obtain the cerium-based rare earth polishing powder. The device comprises the calcining furnace and a cyclone separation device, wherein the inlet formed in the bottom of the calcining furnace is connected with a blowing pipe which is communicated with a liquid inlet tank and the liquid inlet tank is communicated with the outlet of an air compressor; the cyclone separation device comprises at least two stages of cyclone separators which are connected in series, and the gas outlet of the last-stage cyclone separator is communicated with the inlet of a tail gas absorption tower. F element in the cerium-based rare earth polishing powder prepared by the method, which is disclosed by the invention, only exists in a form of CeF3 so that the preparation of the cerium-based rare earth polishing powder by direct decomposition of the mixed solution of rare earth chloride can be achieved and the raw material consumption caused by calcining ammonium bicarbonate or fluorosilicic acid precipitates is avoided.