81results about How to "Improve application stability" patented technology

The invention discloses a preparation method of a nitrogen doped graphene / metal oxide nanometer composite material. The preparation method comprises the following steps of: weighing graphene and metal salt the cation of which is trivalent or quadrivalent to be added in a dispersant, and then carrying out ultrasonic dispersion to obtain mixed liquor; (2), reacting the mixed liquor obtained in the step (1) with alkaline air on a gas-liquid interface for 3-12hours at the temperature of 60-200 DEG C, cooling, centrifuging, washing a precipitate and drying to obtain powder; and (3) introducing the alkaline air or a mixed gas of the alkaline air and inert gas, maintaining the powder to be at the constant temperature of 600-900 DEG C for 2-6 hours, and cooling to room temperature to obtain the nitrogen doped graphene / metal oxide nanometer composite material. According to the invention, the conductibility and interface action of the composite material obtained by the method provided by the invention are improved due to the doping of nitrogen; and the method provided by the invention has the advantages of simple process, cheap cost, high productive rate, short cycle and the like, and is environment-friendly, and can be suitable for industrialization large-scale production.

The invention discloses a multiplex real-time fluorescent quantitation PCR method capable of detecting porcine circovirus, porcine parvovirus, porcine pseudorabies virus and hog cholera virus at the same time. The method of the invention detects that the four virus are all in good linear relations at the same time, all ten times serial dilution points of constructed normal plasmid are all in one straight line, CT value and copy number are in good linear relation, and regression analysis shows that the related coefficient of the CT value and the copy number is R<2> more than 0.99.The multiplex real-time fluorescent quantitation PCR method has the advantages of excellent specificity, sensibility and stability, which can rapidly, sensitively and differentially detect the four virus with serious harm to the economy and can be used for early diagnosis of virus infection.

The invention discloses an energy-regeneration type converter power test system and method. The system comprises a power grid, an isolation transformer, a first smoothing reactor, a second smoothing reactor and a tested converter. The tested converter comprises a first PWM converter, a second PWM converter and a direct current bus capacitor, wherein the first PWM converter and the second PWM converter transmit active power under the buffer effect of a direct current bus capacitor. The first PWM converter imitates load characteristics of the system. The second PWM converter achieves system energy regeneration, unit power factor inversion is achieved by controlling the output currents of the second PWM converter and the voltages of the power grid to be identical in frequency and phase, and the active power balance between the input and the output of the tested converter is achieved by controlling the direct current voltages between the first PWM converter and the second PWM converter to be constant. The energy-regeneration type converter power test system and method can effectively ensure test quality, improve test efficiency, improve the equipment utilization rate, save equipment cost, save energy, reduce emission, simplify operation entry barriers and eradicate potential safety hazards.

The invention relates to an epoxy-based carbon fiber sizing agent emulsion, which comprises the following components: 55-78wt% of polyurethane structure-modified epoxy resin composition, 20-30wt% of surfactant, 0.5-2wt% of anti-oxidant, 1-2wt% of levelling agent and 0.5-1wt% of antifreezing agent. A preparation method comprises the following steps: pumping a bisphenol F epoxy resin reactant under vacuum, dehydrating until no bubbles can be generated, adding an isocyanate reactant to prepare an epoxy resin composition; mixing and homogenizing the surfactant and the anti-oxidant in a reaction vessel according to the above material fraction; and then gradually adding deionized water, a levelling agent and an antifreezing agent to prepare the sizing agent emulsion. The carbon fiber from the epoxy-based carbon fiber sizing agent emulsion has good convergence, wear resistance and toughness, the sizing agent resin has good chemical stability, and is in favor of long-term storage and quality guaranteeing of sizing carbon fiber; the preparation method has the advantages of simple technology and easy operation, the reaction raw material has the advantages of convenient source and low cost, and the epoxy-based carbon fiber sizing agent emulsion is in favor of realization of industrial production.

The invention relates to a polyurethane structure modified epoxy resin sizing agent emulsion, which comprises the following ingredients: 55-78wt% of polyurethane structure modified epoxy resin composition, 20-40wt% of surfactant, 0.5-2wt% of anti-oxidant, 1-2wt% of levelling agent and 0.5-1wt% of antifreezing agent. The preparation method comprises the following steps: performing vacuum-pumping and dehydrating the bisphenol A epoxy resin to the condition that no bubbles can be generated, cooling and adding isocyanate to prepare a epoxy resin composition; mixing a surfactant and an antioxidant are mixed and homogenized in a reaction vessel according to the above material fraction, then adding deionized water, a levelling agent and an antifreezing agent gradually to obtain the polyurethane structure modified epoxy resin sizing agent emulsion. The carbon fiber prepared by the polyurethane structure modified epoxy resin sizing agent emulsion has good convergence, wear resistance and toughness, the convergence and wear resistance are easily and freely adjusted through the isocyanate component; a cluster agent is not required at the anaphase of the carbon fiber sizing agent, and on-site secondary mixing is not required, the application stability is good, the carbon fiber pasting wellability is good, and the polyurethane structure modified epoxy resin sizing agent emulsion is benefit for industrial stabilization and production of carbon fiber.

The invention relates to an improved anticorrosive wear-resistant centrifugal pump volute casing, which is characterized in that: a pump casing an all-plastic or plastic-lined pump casing, and a sectioning pump casing is a volute casing which is formed by asymmetrically lateral sectioning and provided with a complete liquid outlet pipe section; an integral wear-resistant inlay is in a shape of a cover or basis which is provided with a liquid outlet hole and not provided with a liquid outlet pipe section and is provided with a through axle hole at the bottom; an involution end surface of a lining in the volute casing does not exceed an involution end surface of the volute casing; and a casting-type hardened combining layer is arranged between the volute casing and the wear-resistant inlay. By adoption of the structure and the lining mode, the lining manufacturing difficulty of ceramics, microcrystal glass and the like which are low in cost and difficult to mold is greatly decreased, the manufacturing cost is reduced, the lining is simple, the two historic difficulties of lining body molding and manufacturing and easiness of crazing of high-brittleness lining body during installation and maintenance are solved with low cost, the comprehensive service life is prolonged by more than one time, the overall cost is higher than that of the original all iron pump casing lining ceramic inlay. The invention creates a precedent that the silicon carbide and microcrystal glass materials which are difficult to mold and machine, high in brittleness and extremely good in abrasive resistance are applied to a wear-resisting lining of a centrifugal pump.

A sealing structure for a fitting portion where an annular member is concentrically fitted to a cylindrical member to be fitted at a cylindrical part of the annular member is disclosed. The sealing structure is characterized by an elastic annular seal layer integrally provided on the backward end part of the annular member or the cylindrical member in fitting direction, by applying elastomeric agent to the backward end part and hardening it, and the elastic annular seal layer is formed such that it has layer thickness of 5 μm to 1 mm and is interposed in a compressed state between the annular member and the cylindrical member when said annular member is fitted to said cylindrical member.

The invention provides a multi-structure emulsion containing six probiotics, and further provides a preparing method thereof. The multi-structure emulsion is composed of a first emulsion body, a second emulsion body and a preservative. The first emulsion body is formed by a multi-structure emulsion main body which contains a lactobacillus fermentation product and takes an organic acid solution asan inner water phase, and comprises at least one of weak-acid-type organic acid, solid grease, liquid grease, a lipophilic emulsifier, and a hydrophilic emulsifier. The second emulsion body is formedby a multi-structure emulsion main body which contains five probiotics such as a yogurt extractive and the like, and comprises at least one of solid grease, liquid grease, a lipophilic emulsifier, anda hydrophilic emulsifier. According to the multi-structure emulsion containing the six probiotics, as for the different dissolubility of different ferment substances, the reasonable carrier structureis designed, the six probiotics are effectively coated, and meanwhile, the application stability of an active matter is improved.

The invention discloses microencapsulated chitosan-oligosaccharide, and a preparing method and applications thereof, belonging to the technical field of food processing. A wall material of the microencapsulated chitosan-oligosaccharide is composed of protein and polysaccharide, the core material is chitosan-oligosaccharide the molecular weight of which is less than 5000 Da, and the mass ratio of the wall material to the core material is (2:1)-(10:1). The microencapsulated chitosan-oligosaccharide is prepared by separately dissolving the core material and the wall material, mixing to obtain a mixed solution, pretreating the mixed solution through a high-speed dispersing machine, homogenizing through a high-pressure microjet nanometer homogenizer, and performing spray-drying. The microencapsulated chitosan-oligosaccharide prepared by the method covers up amino characteristics, charge performance and color of the chitosan-oligosaccharide, and broadens the application range of the chitosan-oligosaccharide in the food industry on the basis of ensuring functions of the chitosan-oligosaccharide itself.

The invention belongs to the technical field of agricultural planting and particularly discloses a passion fruit cuttage seedling cultivation method. The method includes steps: (1) seedling cultivation container preparation, to be more specific, adding a prepared medium into a conical frustum shaped plastic container to obtain a seedling cultivation container, wherein the medium is prepared from turf, pumice, fine sand, medical stone, corncobs, cow dung, humic acid, amino acids, ground phosphate rock, mixed bacteria and additive extract according to certain parts by weight, and the additive extract is prepared from rheum officinale, algae, oxalis corniculata, phytolacca acinosa, litchi rind, semen persicae and semen pharbitidis; (2) cutting branch preparation; (3) cuttage; (4) seedling cultivation management including temperature and humidity management and nutrition management. The cuttage seedling cultivation method is scientific in management, adopted nutrient sources completely meet passion fruit seedling cultivation requirements, high cutting branch rooting rate and high seedling emergence rate are realized, and passion fruit seedlings cultivated according to the method is robust in growth, high in disease resistance and high in transplanting survival rate.

The invention relates to a polyurethane oil preparation with general applicability. The oil preparation comprises the following components in percentage by weight: 50-67% of mineral oil, 10-20% of dimethicone, 20-40% of modified silicon oil, 1-3% of an antistatic agent, 1-5% of a dispersing agent and 1-10% of a spreading agent, wherein the modified silicon oil is high-carbon alkyl silicon oil of which the carbon number is 12-20 and the molecular weight is 500-3000, wherein the spreading agent is nanometer silicon oil, and the kinematic viscosity of the polyurethane oil preparation at the temperature of 40 DEG C is 7-20 mm2 / s. The spreading agent is added into the oil preparation and is directly acted on the surfaces of polyurethane silks, a uniform spreading effect can be achieved while oiling, the usage effect of the oil preparation is improved, the oil preparation has better applicability for the polyurethane silks with different specifications, and the silks are smooth and astringent but not sticky; at the same time, the spreading agent form a protective isolating layer on the surfaces of the silks, the oil preparation is prevented from being permeated into the inner parts of the silks, and the possibility of breakage and adhesion of the silks in the process of silk returning is reduced.

The invention relates to an order-variable permanent magnet rheological damper and belongs to the field of mechanical vibration engineering. The order-variable permanent magnet rheological damper is a non-power-supply damping vibration absorber. The on-off states of a permanent magnet circuit are controlled by changing the magnetic permeability and the axial effective length of an inner cylinder tube, so that the output damping force, changing along with the piston stroke, of the permanent magnet rheological damper is adjusted, order-variable output of coulomb damping force is achieved, preset damping force is obtained, and effective shock absorption is conducted. An inner cylinder tube section of the order-variable permanent magnet rheological damper is formed by fixedly connecting one section of magnetic-permeability material cylinder tube and two sections of non-magnetic-permeability material cylinder tubes, and a permanent magnet structure piston is a multilevel electromagnetic circuit. The permanent magnet rheological damper is free of energy consumption, simple in structural design and high in stability and has other shock absorption properties.

The invention discloses a power checking system for a frequency converter adopting a one-way energy transmitting and rectifying mode and a testing method thereof. The system comprises an alternating-current power supply, a voltage regulator, transformers, a low-voltage high-current power supply output wiring cabinet and an alternating-current power supply output wiring cabinet, wherein the alternating-current power supply and the voltage regulator are separated into two paths after being connected in series; one path is connected with the input end of a rectifying system of a tested frequency converter through a first transformer and the low-voltage high-current power supply output wiring cabinet; the output end of the rectifying system is connected with a current divider; the other path is connected with the input end of the tested frequency converter through a second transformer and the alternating-current power supply output wiring cabinet; the tested frequency converter consists of a rectifying system and an inverting system; and the output end of the tested frequency converter is optionally connected with an inductance load or a resistance-inductance load through a change-over switch. In the invention, the voltage, current and frequency characteristics of the induction load as well as the voltage, current and the frequency characteristics of a resistance-inductance combined load are fully utilized; the power checking system has the advantages of simple design, low cost, high reliability, high practical application stability, high generality; and simultaneously, power is saved.

The invention discloses a power evaluation system of a frequency converter in an energy two-way transmission rectification mode and a test method of the power evaluation system. The power evaluation system comprises a low-voltage high-current power evaluation system and a light-load joint debugging power evaluation system. The factory power elevation system of the frequency converter and the testmethod disclosed by the invention are suitable for factory routine test power evaluation of the frequency converter a rectifying module of which adopts an energy two-way transmission PWM (Pulse WidthModulation) rectification mode. The elevation system and the test method thereof disclosed by the invention have the advantages of simple design, low cost, high reliability, high actual application stability, strong generality and capability of saving electric energy.

The invention relates to an amino functionalized graphene oxide immobilized non-noble metal nano catalyst and a preparation method thereof. Active ingredients of the catalyst include nickel and copper; a carrier is amino functionalized graphene oxide; the composition of the catalyst can be written as Ni-Cu / DA-GO, for short; the molar ratio of Ni to Cu is 1 to (0.2 to 0.6), and Ni and Cu form homogeneous-phase alloy particles with particle size of 10-80nm. According to the invention, by adopting ordered process design of surface grafting, coordination bonding, controlled reduction, adsorption loading and the like, firm combination is generated between the two metals and the carrier graphene oxide, overall stability of the catalyst can be ensured well, and the active ingredients are not lostor dropped easily; furthermore, since the metal particles form a scientific and reasonable homogeneous-phase structure, perfect electronic and structural cooperativity can be promoted between the metals and between the metals and the carrier, and thus the catalytic efficiency of the catalyst is effectively improved.

A uniform strategy for the general problem of providing custom editors and initialization strings for beans (all “dynabeans” inherit from a common bean class that incorporates this strategy. This is then extended to allow the initialization strings to be stored in a relational database. The database function is a extension of the function provided by VisualAge Persistence Builder (using some of the EADP extensions). An important advantage of this approach is that many changes to the application can now be handled by adjusting the database version of the bean definition, without a need to touch the underlying code. This will reduce down time for the application, and also improve application stability.

The invention discloses a system and a method for a power examination test of a large-power rectifier. The system comprises an electric network source, a voltage regulator, a high-voltage low current testing device, and a low-voltage heavy current testing device. The high-voltage low current testing device includes a first transformer, a rectifier, and an impedance load. And the low-voltage heavycurrent testing device consists of a second transformer, a rectifier, and a diverter load. The electric network source is connected with the voltage regulator; an output terminal of the voltage regulator is selectably connected with a first transformer or a second transformer; alternating current input terminals of the rectifiers are selectably connected with an output terminal of the first transformers or the second transformers; and direct current output terminals of the rectifiers are selectably connected with the impedance load or the diverter load. The method comprises two steps: a high-voltage low current test and a low-voltage heavy current test. According to the system and the method in the invention, a working characteristic examination requirement of a large-power rectifier is met; the testing quality is ensured; efficiency is improved; operation steps are simplified; equipment costs are saved; and an operation potential safety hazard is reduced.

The invention relates to the technical field of water-based wood lacquer, in particular to water-based acrylic emulsion as well as a preparation method and application thereof. The water-based acrylicemulsion is prepared from the following components in parts by weight: 2-4 parts of methacrylic acid, 45-50 parts of a hard monomer, 19-30 parts of a soft monomer, 15-18 parts of a functional monomer, 5-8 parts of a crosslinking monomer, 0.5-1 part of an initiator, 2-6 parts of an emulsifier, 0.5-1 part of a buffer agent, 0.4-0.8 part of a chain transfer agent, 0.5-1 part of a first crosslinkingagent, 0.5-1 part of a second crosslinking agent, 3-5 parts of a pH regulator, 2-3.2 parts of a polyurethane macromonomer, 1-1.5 parts of modified SiO2 particles, 120-150 parts of water and 0.5-1 partof a defoamer, wherein the Tg of the hard monomer is more than 50 DEG C, and the Tg of the soft monomer is lower than 50 DEG C. The water-based acrylic emulsion has the characteristics of high hardness, good connectivity, good stability, good intermiscibility with an organic solvent and the like.

The invention discloses a material storing device having a cooling and heat dissipation structure and a working method thereof. A dustproof cover comprises a bin body, a ventilation channel is formedin the bin body, a cavity is formed in the side wall of the bin body, a heat insulation plate is arranged in the cavity, a vertical columnar rod is uniformly arranged on the bottom wall of the bin body, an air guiding channel is formed in the vertical columnar rod, an air hole communicated with the air guiding channel is formed in the vertical columnar rod, a water spraying nozzle is formed in thetop wall of the cavity, a water collecting cavity is formed in the bottom wall of the cavity, a spiral air guiding pipe is arranged in the cavity, a power line connected with a water pump is arrangedon the bin body, a temperature sensor is fixed to the outer wall of the vertical columnar rod of the bin body, and a driver connected with the temperature sensor is arranged on the bin body and is connected with a power switch of a water pump. The material storing device is reasonable in structural arrangement, can effectively prevent heat accumulation caused by exposure to the sun, facilitates prolonging of storage time, is stable and reliable in use and good in applicability and practicability, and meanwhile the ventilating and heat dissipation properties of the device are improved.

The invention provides a water-dispersibility paprika red pigment micro emulsion and a preparation method thereof. The preparation method comprises steps that a surfactant is mixed with a cosurfactant, then an oil phase comprising paprika red pigment and edible oil is added, stirring is carried out and water is added so as to obtain a system, the system firstly becomes clear and then turbid, when the water is added to reach a certain quantity, the system suddenly becomes clear and transparent again, so as to obtain the water-dispersibility paprika red pigment micro emulsion, the mass percent content of the paprika red pigment in the micro emulsion reaches 1.98%-9.86%. The preparation method has the advantages that the pasty paprika red pigment is prepared into water-dispersibility paprika red pigment micro emulsion, so that the dispersibility of the paprika red pigment in the water and the stability of the paprika red pigment in the hot processing are improved; the preparation method is simple, low in production cost and beneficial for large scale production. The water-dispersibility paprika red pigment micro emulsion can be used in fluid food, semifluid food and high moisture food, and the application field of fat soluble paprika red pigment is enlarged.

The invention discloses a front wheel rocker arm structure for a double front wheels motorcycle. The front wheel rocker arm structure comprises a left rocker arm, a right rocker arm and a middle rocker arm which are independent, the left rocker arm and the right rocker arm are movably connected with the middle rocker arm correspondingly, and the middle rocker arm is movably connected with a motorcycle head pipe through a fixing shaft. At least one of an upper rocker arm and a lower rocker arm of a front wheel swing tilt mechanism of the double front wheels motorcycle adopts a front wheel rocker arm structure comprising the left rocker arm, the right rocker arm and the middle rocker arm which are independent and movably connected with one other. According to the front wheel rocker arm structure for the double front wheels motorcycle and the front wheel swing tilt structure, three-stage rocker arm structures connected movably replace single rigidity rocker arm structures in the prior art, so that the stress of a motorcycle body swing tilt mechanism is more uniform, the size corresponding to the single support component is minimized to save materials and reduce motorcycle weight, and manufacturing is more simple. A secondary shock absorber structure can also play the role of secondary shock absorption, body vibration when the motorcycle travels on the complex road surface is reduced, and the comfort of a driver is improved.

The invention relates to a composite hydrogel-based self-water-supply type photo-thermal water evaporation device. Porous molybdenum disulfide MoS2 nano particles are intercalated between graphene through a one-step chemical reduction reaction. The efficient water evaporation rate of 3.2 kg m<-2>h<-1> can be achieved under illumination of 0.9 kW m<-2> and is far higher than that of an existing photo-thermal interface water evaporation system of the same type, and the device has bacterial biological pollution resistance and good stability. The provided photo-thermal interface water evaporation system is expected to realize efficient seawater desalination, and provides a solution for sustainable clean water production.

The invention relates to the technical field of water treatment, and in particular relates to a black titanium dioxide / silver phosphate composite photocatalyst as well as a preparation method and application thereof. The black titanium dioxide / silver phosphate composite photocatalyst provided by the invention comprises black titanium dioxide and silver phosphate dispersed on the surface of the black titanium dioxide. According to the method, the black titanium dioxide is compounded with the silver phosphate, so that the problem of low photocatalytic efficiency of the black titanium dioxide isovercome, and the stability in the application process of the silver phosphate is greatly improved by accelerating electron transfer; and the composite photocatalyst can efficiently and stably removesingle and combined contamination of typical harmful algae and / or antibiotics in water.

The invention provides high temperature and high strength low-carbon martensite refractory steel and a preparation method thereof. Chemical components of the low-carbon martensite refractory steel comprise, by mass percentage, 0.10-0.25 wt% of C, 10.0-13.0 wt% of Cr, 2.0-3.2 wt% of Ni, 1.50-2.50 wt% of Mo, smaller than or equal to 0.60 wt% of Si, smaller than or equal to 0.60 wt% of Mn, 0.4-0.8 wt% of W, 0.1-0.5 wt% of V, 0.3-0.6wt% of Co, 0.3-1.0wt% of Al, 0.01-0.2wt% of Nb and the balance Fe. According to the refractory steel, high temperature strengthening is achieved due to the fact that nanometer coherent carbide and an intermetallic compound are precipitated at the same time, excellent toughness is achieved, use for some structural parts under special working conditions such as an aero-engine is achieved, the service life of the refractory steel is prolonged, and the use temperature of the refractory steel is increased.

The invention provides a preparation method of a multilayer functional ceramic component. The method comprises the following steps: preparing ceramic slurry, and carrying out tape casting to obtain aceramic blank sheet; cutting the ceramic blank sheet, and then punching at a preset position to obtain a plurality of ceramic sheets with through holes; preparing a gel injection molding slurry containing an organic auxiliary agent capable of initiating gelation; stacking the ceramic sheets; arranging a metal circuit structure between the layers of the laminated ceramic sheets and in the through holes or in the through holes of the laminated ceramic sheets, injecting gel injection molding slurry matched with the metal circuit structure, and curing the gel to obtain a green body; and laminatingthe green body, and then sintering to obtain the multilayer functional ceramic component. According to the preparation method, the gel injection molding slurry is introduced and is matched with the metal circuit structure, and the shrinkage stress of the ceramic sheet and the expansion stress of the metal circuit structure are released by shrinkage of the gel layer of the gel injection molding slurry during sintering, so that the close fit between the metal circuit structure and the through hole is ensured; and the problems that the metal circuit structure is not shrunk during sintering to crack the ceramic part and the like are avoided.

The invention relates to the field of pipe fitting machining, in particular to a pipe fitting inner wall flattening and grinding device. The device comprises a rack and a bottom plate base, wherein atransverse rotating pipe is rotationally installed on the rack and driven by a driving assembly installed on the bottom plate base to rotate, a fixing sleeve is fixedly installed at the right end of the transverse rotating pipe, a movable sleeve is further arranged on the part, between the rack and the fixed sleeve, of the transverse rotating pipe in a matched and sliding mode, a plurality of elastic plates are circumferentially distributed between the movable sleeve and the fixing sleeve, frosted layers are arranged on the outer sides of the elastic plates, damping assemblies are further fixedly installed in the middles of the sides, close to the transverse rotating pipe, of the elastic plates, the other ends of the damping assemblies are fixed to lantern rings, the lantern rings is arranged on the transverse rotating pipe in a matched and sliding mode, a transverse telescopic cylinder is further supported and fixed to the left side of the rack through a telescopic cylinder fixing frame, and the transverse telescopic cylinder is used for driving the movable sleeve to move along the transverse rotating pipe. The device can meet the machining requirements of pipe fittings of different sizes, dynamic adaptive adjustment can be conducted, the working stability is good, and the machining efficiency is high.

The invention discloses a longitudinal connecting structure of an assembled sleeper slab-type or a track slab-type ballastless track structure and a ballastless track structure including the longitudinal connecting structure. Two embedded longitudinal steel bars are longitudinally connected through an extrusion sleeve, the butting ends of the two longitudinal steel bars are separately inserted into the two ends of the extrusion sleeve, and the extrusion sleeve deforms and is locked under the extrusion of a portable extruder. According to the longitudinal connecting structure of the assembled sleeper slab-type or the track slab-type ballastless track structure and the ballastless track structure including the longitudinal connecting structure, the accuracy during site laying construction can be improved, disassembly and installation are convenient, the construction difficulty is reduced, the speed of site construction is increased, the structure is simple, and positioning of a sleeper slab or a track slab is convenient.