Through the freeze-thaw cycle test of steel fiber concrete, the effects of the number of freeze-thaw cycles, concrete strength grade, steel fiber volume rate and other factors on the compressive strength, splitting strength and flexural strength of steel fiber concrete after freeze-thaw were analyzed, and the reinforcement mechanism of steel fiber on concrete was discussed. The test results show that the addition of steel fiber has little effect on the compressive strength of concrete after freeze-thaw cycle. When the number of freeze-thaw cycles is small, the effect of steel fiber on the increase of splitting strength and flexural strength is more obvious, while when the number of freeze-thaw cycles is large and the volume rate of steel fiber is higher (2%), steel fiber has a certain negative impact on the splitting strength and flexural strength of concrete. The improvement of the strength grade of steel fiber concrete is more effective in improving the frost resistance of steel fiber concrete.

Based on the parameters of concrete strength grade, steel fiber volume rate and carbonization time, the basic performance tests of concrete, steel fiber concrete and steel fiber high-strength concrete specimens under carbonization environment were carried out, and the compressive strength, splitting strength, flexural strength and carbonization depth of concrete and steel fiber concrete with different carbonization time were tested, and the enhancement mechanism of steel fiber on the carbonization performance of concrete was discussed. The results show that the strength grade and carbonization time of concrete have significant effects on the basic mechanical properties and carbonization depth of steel fiber concrete, and high-strength steel fiber concrete has high carbonization resistance. The volume ratio of steel fiber has a certain degree of influence on the carbonization resistance of steel fiber concrete.

The one-dimensional finite element method was used to simulate the temperature field in the injection molding process, and the error caused by the average temperature boundary condition of the mold cavity surface was discussed for the heat transfer analysis. The results show that when the accuracy of the mold is not high, the error is acceptable; However, for precision injection molded parts, or thin parts, this error can have an impact on the numerical analysis. In view of this situation, according to the actual transient temperature distribution, a transient temperature field method with average temperature construction is proposed to improve the accuracy of numerical simulation of injection molding.

Based on the original Allman cell with rotational degrees of freedom, some modifications are made to the original Allman cell functional potential energy II.p from the definition of rotational components, and a new unit is derived. This unit successfully eliminates the main defect of the Allman unit - the redundant zero-energy mode, while maintaining the advantages of the unit: the column formula is concise, the accuracy is high, and the good characteristics of the improved element are confirmed by the given example.

Using finite element analysis software, the secondary stress generated by the rigidity of typical flat steel roof truss joints under two spans was analyzed and calculated. The planar articulated model, planar rigid joint model I and planar rigid joint model II were used for typical flat steel roof trusses, and the magnitude, distribution law and main factors affecting the secondary internal force of steel roof trusses under ordinary load were analyzed, and the influence of secondary stress on the calculation method of steel roof truss was preliminarily discussed. The results show that the secondary internal force of the steel roof truss members increases with the increase of the linear stiffness of the members, and the influence of secondary stress increases with the increase of the span of the roof truss, and the influence of secondary stress cannot be ignored. This conclusion can provide a reference for the design of steel roof truss considering secondary stress.

In the study of ultimate bearing capacity and reliability of highway bridge structures, since there are no statistical parameters of vehicle load in the specification, reliability analysis cannot be carried out directly, so it is necessary to first study the statistical parameters of load and loading model. Based on the WIM data obtained from a two-week statistical survey conducted by the British Transport Research Laboratory in 1990, the analysis program was compiled using Microsoft Visual Basic (version 2.6), and the five most common trucks were first calculated according to the probability of the occurrence of various vehicles; Then, the probability of multiple trucks appearing on the bridge at the same time when their configuration, axle load, total weight and bridge span are variables. The statistical results can be directly used for the reliability analysis of bridge structural system.

There are various forms of large-span prestressed concrete building structures, and different building cover structures need to choose structural forms with different stress properties. Taking the large-span prestressed concrete building cover of the exhibition part of Zhengzhou International Convention and Exhibition Center as the research object, three structural forms and five different structural arrangements of primary and secondary beam structure, secondary beam load-bearing structure and tic-tac-toe beam structure were discussed, and they were analyzed and calculated. According to the force characteristics of each structural layout scheme, through the analysis of the amount of prestressed ribs, internal force and deformation of five different arrangement methods, the results show that the tic-tac-toe beam scheme is superior for such structures with little difference in bidirectional span. This conclusion provides a basis for the correct selection of structural layout scheme and optimization of building structure scheme.

The basic principle of electromagnetic wave propagation of pavement radar in pavement structure is introduced, combined with the time-domain finite difference method algorithm, the one-dimensional FDTD equation, the effective parameters of the soft excitation source, the effective parameters of the hierarchical interface, and the important influence of absorption boundary conditions in the application simulation process are analyzed, and the forward evolution model of air-coupled pavement radar is established. Theoretical simulation and practical engineering numerical examples show that the model is feasible for road radar forward simulation, and the error does not exceed 2%.

The phenomenon of wind and rain excitation is a kind of violent and large vibration that often occurs under the combined action of wind and rain of cable-stayed bridge cables, which is very harmful, involving solid, liquid and gas three states, and the situation is complicated. In order to reveal some internal laws of wind and rain excitation, artificial rain vibration test and artificial waterline rain vibration test were carried out. Through the artificial rain rain vibration test, the wind and rain excitation phenomenon of the cable was reproduced, and the influence of the size and position of the waterline, the dynamic parameters and deflection angle of the cable-stayed cable on the wind and rain excitation were studied through the artificial waterline rain vibration test. The test results show that the formation of a certain size of the upper water line on the surface of the cable is a necessary condition for the wind and rain excitation of the cable, and the upper water line should be formed within a specific range on the surface of the cable. Increasing the damping and self-resonance frequency can effectively reduce the wind and rain excitation amplitude of the cable. The wind and rain excitation phenomenon of the cable can only occur in one

The wind tunnel test method was used to study the resistance coefficient of the bridge at different inclination angles of four different surfaces (including one light cable, two spiral cues and one pit cable) at different inclination angles. The test results show that the resistance coefficients of pit cable and 4mm spiral clue are not much different, and they can be applied to the design of cable-stayed bridge. According to the experimental results, a relatively simple fitting formula for calculating the resistance coefficient value of the cable-stayed cable at different inclination angles is given. The analysis shows that this fitting formula and the experimental results fit well and are safe.

Using the complex mode method, the giant-sub-control structure system and the ordinary giant frame structure were compared and analyzed under the action of non-stationary earthquakes, and the displacement response of the top layer of the main frame was reduced by 95.70% and the acceleration response was reduced by 24.08%. It proves that this new structural system can effectively control the seismic effect, and significantly improve the safety and comfort of the structure. The influence of shear stiffness of the subframe and the damping of the energy-dissipating damper on the seismic response of the structure was discussed, and the shear stiffness ratio between the subframe and the main frame was greater than 0.15 and avoided 0.4. The first damping ratio between the energy-dissipating damper and the subframe is 1.0~3.0, and the seismic response of the structure can be further controlled, and the reasonable range given plays a guiding role in the structural design.

Considering the external temperature conditions, heat of cement hydration, elastic mold, creep and other thermodynamic and physical mechanical parameters, as well as the influence of layered pouring (using life and death units to achieve layered pouring) on the temperature stress of the gate pier, the 3D finite element method of ANSYS software was used to simulate the transient temperature field and stress field during the construction period of the gate pier. The results show that the temperature difference between the inside and outside is too large, and the internal temperature rise and temperature drop is too fast, which is the main reason for the cracks in the gate pier, and it is proposed to cool the mixing material, reduce the pouring temperature, adopt the optimized heat preservation and moisturizing maintenance method, embed the cooling water pipe in the concrete, select low-heat cement, use water reducing agent, etc. to reduce the temperature difference between inside and outside, and slow down the temperature rise and temperature drop process, so as to effectively prevent the occurrence of surface cracks during construction.

Aiming at the problems of artificial neural networks in the identification of structural systems, a tracking recognition method based on BP neural networks is proposed. By dividing the actual structural model into a mechanism model and a real-time error model, the former is trained offline based on the conventional BP neural network, while the latter identifies the systematic error in real time through a small BP neural network, so that the improved system recognition network can have the ability of dynamic hierarchical recognition system. Computer simulation analysis shows that this method can effectively reduce the identification error of structural system caused by different external loads, and improve the accuracy and reliability of artificial neural network in system identification.

In order to analyze the mechanical properties of the bridge, the large finite element general software ANSYS is used for modeling, the main beam and tower are discretized by space beam unit (beam188), and the cable is simulated by the space rod unit (link10) that only bears the tensile force, and the finite element calculation model of the bridge is established, and the internal force, self-resonance frequency and mode shape of the bridge are calculated respectively. The calculation results show that for the cable-stayed bridge of the low tower part, the cable has a great influence on the axial force and bending moment of the main girder, and the stiffness of the main girder has a great influence on the self-resonance frequency of the whole bridge, and the low-order vibration of the bridge is mainly manifested as the overall vertical vibration and lateral vibration of the bridge. The calculation results can provide a reference for the health inspection and maintenance of the construction control and use phase of the bridge

The flow field of cyclone separator was studied numerically by using the computational fluid dynamics software FLUENT, using k-ε standard model, RNGk-ε model and RSM model turbulence model and different discrete methods. By comparing the simulation results with the measured results of predecessors, a numerical calculation method suitable for cyclone separator was determined. The results show that the turbulence model adopts the anisotropic RSM model, and the QUICK format of the convection term and the PRETO format of the pressure gradient term are used in the discrete mode, so as to obtain reasonable flow field simulation results. This conclusion provides a reference for the numerical simulation of the flow field of cyclone separator and the further structural optimization design.

According to the viscous resistance theory of fluid mechanics, the analytical expression of the fluid resistance of the cylinder when it vibrates laterally in the fluid is derived by vector analysis method, taking the moving rotor member - cylinder as the main body. The analysis results show that the resistance of the cylinder during the transverse vibration in the fluid includes two parts: inertia term and damping term, and its dynamic coefficient is not only related to the fluid properties and the structural size of the cylinder, but also related to the vibration angular velocity of the cylinder. At the same time, it is found that in addition to the inertial resistance of the cylinder when it vibrates laterally in an ideal fluid, the inertial term also adds a part related to viscosity; The damping term consists of two parts related to viscosity, one of which is related to fluid density and the other part is not related to fluid density. The derived formula can be used for fluid-structure interaction in rotor systems

According to the data obtained from the process test, the temperature field of the aluminum bar extrusion forming process was numerically simulated by finite element software, and a cloud map reflecting the temperature field distribution and change of the process was obtained, and the process law was analyzed in depth based on the experimental research and simulation results. The results show that the holding time is an important process parameter that determines the stability of the process and the quality of the parts, and the appropriate holding time can make the metal in the deformation zone in the extrusion process always remain semi-solid, which ensures the smooth implementation of the process. This conclusion provides a theoretical basis for further design and optimization of process parameters.

The traditional design methods of heat exchanger equipment have a long development cycle, many standards, complex design process and difficult quality assurance. With the 3D modeling and assembly software MDT as the development platform, with the help of ActiveX automation interface technology and VBA integrated development environment, the research of 3D digital modeling and assembly simulation technology of heat exchange equipment is carried out, and a new high-efficiency and energy-saving heat exchange equipment assembly subsystem is developed, which can significantly improve design efficiency and quality. The system implementation method is studied and practiced, the system refers to MDT objects by setting object variables, designs and compiles the drop-down menu and graphical user interface, and presets the error handling mechanism by program code, which solves the key problems in system development.

When peracetic acid (PAcA) is used as a disinfectant indoors, the content in the air is very low and it is difficult to detect with conventional chemical analysis methods. The content of trace peracetic acid disinfectant in indoor environment was determined by enzyme-catalyzed spectrophotometry by air disinfection by spray method and fumigation method, and on-site sampling with gas absorption tube. Experiments show that PAcA can react with phenol and 4-aminoantipyrine when phosphate buffer is present under the catalysis of horseradish peroxidase (HRP). Similar to the enzyme-catalyzed spectrophotometry of hydrogen peroxide, the quinone dye generated at 35 °C has complete color development for 30 min, has maximum absorption at 505 nm, and the absorbance coefficient of the corresponding wavelength is 12.72L/(mmol·cm), and the peroxide is measured

The discoloration and corrosion resistance of non-stoichiometric titanium monoxide as a gold-imitation material may be exposed to different environments was studied, and compared with the existing gold-imitation materials. The results show that titanium monoxide has excellent anti-discoloration ability in outdoor atmosphere, household atmosphere, soil, artificial sweat, 18KAu corrosive, sodium chloride solution and concentrated ammonia, and its chemical stability and anti-discoloration performance are significantly better than TiN-based cermet gold-like materials and gold-like copper. In dilute sulfuric acid and dilute hydrochloric acid, corrosion is slow and does not change color.

Al(OH)3 sol was prepared by liquid phase precipitation using Al(NO3)9·2H3O, ammonia and nano aluminum powder as raw materials, and nano α-Al2O3 powder was obtained by vacuum filtration and high temperature calcination. The effects of pH value, nano-aluminum powder addition and calcination temperature on the quality of Al(OH)3 sol and Al2O3 crystal form conversion temperature were studied. The results show that Al(OH)9 sols with less agglomeration and good dispersion can be obtained when the pH value of the reaction system is 3, and the transition temperature of α-Al3O2 can be reduced to about 3°C by adding nano-aluminum powder with a mole fraction as seed crystal. The nano α-Al1000O2 powder obtained by the experiment has a uniform particle size distribution, no obvious agglomeration, approximately spherical, and an average particle size of about 3 nm.

With the help of the annihilation effect between quark coupons related to taste for near-ideal mixed meson ninefolds, the assumption can be ignored, and the mass relationship derived under the meson and meson mixing framework is predicted to be about 23±1.1584 MeV in the meson ninefold state of 16S7, which is in good agreement with the prediction given by the relativistic quark model. The comparison between the theoretical prediction and the mass of K*(1410) shows that it is inappropriate to arrange K*(1410) as a member of the 23S1 meson ninefold. This theory predicts that it will provide some help in the experimental search for isospinic binary states in the 23S1 meson ninefold.

Through the comparison and analysis of the current design methods of active filter and power quality controller, a design scheme of power quality controller with DSP chip TMS320LF407 as microcontroller is proposed. The powerful computing function of the chip and the integrated event manager peripheral can easily realize real-time harmonic suppression, reactive power compensation, load balancing and voltage reduction flicker. In addition, using the rich internal and external peripherals of the chip and the intelligent driver chip selected in the circuit, many auxiliary functions such as overvoltage, overcurrent, serial communication, etc. are extended for the controller. This scheme reduces the design complexity and design cost of power quality controller, and has reference significance for the productized design of power quality controller.

Aiming at the system with pure time lag, the shortcomings of PID algorithm, Smith estimation method and fuzzy control are analyzed, and a new fuzzy composite controller is proposed, which is based on the fuzzy-PID controller estimated by Smith, which uses Smith preestimation method to overcome pure hysteresis, uses fuzzy control to improve the robustness of the system, and switches to PID control in the steady-state stage to improve the control accuracy. The simulation study is carried out in the case of model matching and mismatch, and the results show that the composite controller not only has the strong robustness of fuzzy control but also has the characteristics of high PID control accuracy, especially when the model mismatches, it shows good stability and robustness, and is a practical and simple control method for large time lag systems.

Electronic map is a vectorized and digitized map, which is a management system that processes information about geographical distribution data with the support of computer hardware and software. Analyze and study the methods and characteristics of GIS control to develop electronic maps, and give the method of MapX to develop electronic maps: first use Mapinfo to draw maps, divide the city electronic map to be made into different layers into VB, and develop Changsha electronic map in VB by introducing MapX control, which has functions such as query, zoom in, zoom out, roam, and ranging.

The development of USB communication drivers in power system fault simulation test devices is discussed. In the Windows operating system, USB device drivers are designed according to WDM (Windows Driver Model). In the WDM driver model, each hardware device has at least two drivers, one of which is called a function driver, which is usually a hardware device driver. It understands all the details of making the hardware work, is responsible for initializing the I/O operation, handles the interrupt event brought when the I/O operation is completed, and provides the user with a control method suitable for the device; Another driver provided by the operating system is called the bus driver and it is responsible for managing the connection of the hardware to the computer.

Taking Zhengzhou City as an example, the calculation method of urban water environment carrying capacity is introduced, and the carrying capacity of the water environment in the current level year (2001) and planning level year (2010 and 2020) of Zhengzhou City is calculated. According to calculations, the carrying capacity of the water environment in the current level of Zhengzhou City (2001) was 0.668 6×108 m3, and in 2010 and 2020, it was 4.295 3×108 m3, 8.331 6×l08m3. According to the analysis of factors affecting the carrying capacity of the water environment, suggestions for regulating and countermeasures to improve the carrying capacity of the water environment in Zhengzhou are given

The flue gas dry desulfurization of coal-fired power plants with CuO/Al2O3 desulfurization adsorbent is an advanced desulfurization technology. The dispersion state of the desulfurizer CuO in the carrier, the influence of roasting temperature on the structure of Al2O3 adsorbent carrier, the problems to be considered in the preparation of desulfurizer, the temperature of the desulfurization reaction and other factors on the desulfurization effect of the adsorbent were investigated. Experiments show that CuO is monolayer dispersed on Al2O3 carrier. If the roasting temperature is too high, the sintering and desulfurization activities of the carrier will decrease, and the desulfurization adsorbent must be regenerated with reducing gas; Cu(NO3)2 solution should be used as impregnation solution, and desulfurizer should be prepared by equal volume impregnation method; It is most suitable to carry out the desulfurization reaction between 400~430 °C. Under reasonable conditions, a good desulfurization effect is obtained.