Affected by the environment, design, construction, and operation, there are hidden defects behind a shield tunnel, which endanger the safety of the tunnel. Ground penetrating radar( GPR) has been widely applied to the detection of hidden defects behind a shield tunnel. However, due to the shielding effect of the double layer rebar net inside the shield tunnel, the electromagnetic( EM) response characteristics of the void behind the concrete segment are not obvious. This paper applied finite difference time domain ( FDTD) method to simulate the detection of the air and waterfilled voids behind the shield tunnel with different sizes using GPR. Then, a laboratory experiment was performed to verify the accuracy of the simulated results. The results mean that simulated cubical voids change with different sizes, the reflections of the defects show the characteristics of hyperbola, cross or bowl shape. The bottom reflections also vary with certain regularities. Through the wavefield analysis, it can be indicated that the radar echo will be interfered with by the rebars terribly. Moreover, multiple EM wave reflections propagate inside the voids, and the propagation of EM waves show a significant difference between the air filled / water voids. In conclusion, the results of this paper can provide a reference for the data interpretation of the detection of hidden defects in shield tunnels.

Megneto-electro-elastic materials has been widely used in engineering ang industrial fields. Using two-scale method, the higher order two-scale asymptotic expansions for magneto-electro-elastic coupling problem are analyzed firstly in this paper, then the homogenization constants and equation corresponding to the problem are obtained. Moreover, the two-order two-scale approximate solutions for magneto-electro-elastic problem are constructed, and the asymptotic error estimations are analyzed by means of two-scale method lastly.

Finance is the core of the modern economy and the hub of social resource allocation. In the environment of rapid development of the financial sector and imbalance between the structure of the virtual and real economies, financial resource misallocation has a significant impact on the structure of China＇s economy and constrains the restructuring of the real and virtual economies. Based on provincial panel data from 2010 - 2019, this paper measures regional financial technical efficiency to characterize the financial misallocation status, and the total virtual and real economies in each province. Then, we set up a panel fixed effects model to analyze the dynamic impact of financial misallocation on the virtual economy and real economies and discuss regional differences in the misallocation of financial resources at the province level. The results show that there is a significant positive relationship between the technical efficiency of the financial sector and the virtual and real economies, and a significant inhibitory effect on the divergence between the virtual and real economies in general, but there is regional heterogeneity in this effect. Based on these, this paper proposes countermeasures to further deepen the structural reform on the supply side of finance, strengthen regional financial supervision and improve the stability guarantee system of the regional financial system, oriented towards serving the development of the real economy.

Considering the uncertainty of the high speed railway isolated bridges and the ground motion, SAP2000 is used in this paper to establish isolated and non -isolated bridge models respectively. A structure ground motion sample pair is established by the Central Composite Design method. The nonlinear dynamic time history analysis of the bridge structure model was carried out, to establish response surface functions with the displacement ductility coefficient of the pier column and the shear displacement of bearings as outputs. Then, based on the Latin Hypercube Sampling method, the vulnerability curves of isolated and non-isolated bridge members were obtained. Based on the analysis of structural vulnerability and seismic loss, the total cost of the bridge structure in its whole life cycle was obtained. The results show the method of obtaining the response surface function by the Central Composite Design can effectively reduce the calculation times and improve the calculation efficiency of vulnerability analysis of bridge structures. The exceedance probability of each damage level of isolated piers is lower than that of non-isolated piers, which shows that friction pendulum bearings play a good role in protecting high speed railway bridge piers through friction energy consumption. Seismic eco nomic loss, maintenance cost, and total life cost of isolated bridges are lower than those of non-isolated structures in the full life cycle, which shows that the economy of isolated bridges in the full life cycle is good.

In analytic geometry, one of the most important fundamental problems is to find the number of inter section points of two algebraic curves. Bézout s theorem states that two algebraic curves of degrees m and n intersect at mn points, counting multiplicities, and cannot meet at more than mn points unless they have a component in common. In the local case, Liang introduced the intersection multiplicity of two algebraic curves at some point in 2 and P2 respectively. Since the intersection multiplicity is closely related to the fold point, and linear transformation ( or projective transformation) preserves the intersection multiplicity of curves in 2 ( resp. P2 ) ,it is of certain research significance to discuss the change rule of the multiplicity of the fold point after transfor mation. In this paper, we study the intersection multiplicity of curves at a point in 2 and P2 , respectively. We give the equivalence of transformation relation of the intersection multiplicity of curves at a point by linear transformation ( resp. projective transformation) in 2 ( resp. P2 ) .

The pendulum tuned mass damper ( PTMD) shows nonlinearity under large amplitude response, and the vibration control performance of PTMD was overestimated by equivalent linearization of rotation angle in previous studies. In this paper, the motion equation of nonlinear model is derived by the Lagrange equation and the Krylov Bogoliubov slow variation parameter method was adopted to derive the frequency response function of the nonlinear model considering the high order nonlinearity of the pendulum angle. The structural responses of nonlinear model and equivalent linear model under different excitation amplitudes are then compared. The parameters of the PTMD nonlinear model are optimized based on H2 criteria, and the optimal design parameters of PTMD under different excitation amplitudes were obtained. Further, the time history analysis method was adopted to verify the optimal design parameters of a super high rise structure model. The results show that the larger the excitation amplitude is, the greater the influence of nonlinearity on the structural response is, and the equivalent linear model is gradually distorted. Under a large excitation amplitude, compared with the results of linear model optimization, the damping rate of PTMD can be increased by 10% after parameter optimization considering nonlinearity. Considering nonlinear optimization design can effectively improve the vibration control performance of PTMD.

In recent years, with the rapid development of urban mass transit, the construction of sub way networks is changing rapidly. The subway brings convenience and rapidity to people. At the same time, the vibration and noise caused by the running of the subway train have a negative effect on the surrounding environment and the lives of the residents. In order to evaluate the influence of the secondary radiation noise caused by subways and to improve prediction accuracy, this paper takes the impact of the vibration noise caused by the train running of Guangzhou Metro Line 2 on the nearby Yunzhu hotel as an example, based on the finite element method, the spatial distribution characteristics of secondary noise in surrounding buildings caused by subway were analyzed. The simulation results show that, when comparing the measured values with the simulated values, the consistency of the other frequency bands is good, except that the predicted values of 20 ~ 50 Hz are slightly smaller thanthe measured values, and the errors of the two bands are all within 3 dB, it shows that the simulation method of acoustic vibration coupling can reduce the artificial and set error, and improve the prediction accuracy of secondary noise in the surrounding buildings, this provides a more reliable prediction method for the related research in the future.

Considering that the concrete filled steel tubular ( CFST) is mainly used as the vertical loadbearing member, in this paper the concept of the tuned mass damper ( TMD) system for structural vibration control is introduced to extend the functions of the CFST. In other words, the CFST is converted into a new column in column ( CIC) system with dual functions of loadbearing capacity and vibration mitigation, so as to further enhance the seismic performance of structures. The CIC system and its control strategy are introduced, then based on the “ Unified theory” of the CFST, the theoretical formulae for calculating the cross sectional composite stiffness of the CIC system under compression and its ultimate axial loading capacity are derived by using the superposition principle. The equivalent design method of the CIC system is also proposed by keeping the axial compressive stiffness of the CIC system equal to that of the original CFST. Moreover, following the proposed design procedure, the typical CFST members are selected and theoretically “ divided” into two columns to form the CIC system so as to verify the accuracy of the proposed method. Results show that, the derived formulae for determining the cross sectional composite stiffness and the ultimate axial loading capacity of the CIC system can be conveniently developed via the superposition principle, the proposed equivalent design method of the CIC system has good accuracy, which can be used in the design and analysis of the CIC system for future engineering practices.

Volatility proxies are an important statistic applied to estimate daily GARCH model by using high frequency data. This paper proposes the criterions for choosing an optimal volatility proxy by the asymptotic properties of three GARCH estimators based on the intraday high frequency data, and the applications of these criterions in high frequency data sampling are also discussed. The empirical study of the high frequency data of CSI 300 index shows that: for the same volatility proxy, the performance of different frenquencies is obviously different; for the same frequency, different volatility proxies perform differently; each volatility proxy has a different optimal frequency under different estimation methods. Consequently, the optimal sampling frequency for intraday high frequency data should be treated differently among different estimation approaches.

Based on the column in column ( CIC) axial compression test results, a refined finite element model of CIC specimen was established by using ABAQUS software. The accuracy of the numerical model was verified by comparing the axial load capacity, failure mode and axial force longitudinal strain in the middle height column curve of the specimens. The stress distribution of steel tube and concrete in different stress stages was obtained by stress analysis of two typical specimens. The results showed that the maximum stress of the outer steel tube for the outer column occurred at the local buck ling area. The concrete in the outer column was in a full compressive state during the loading process. The inner column concrete suffered bending failure with the increase of axial loading, and thus the concrete was gradually transformed from the compression of the full section to the compression of one side and the tension of another side. With the calibrated numerical model, a parametric study was carried out to investigate the axial compressive behavior of CIC specimens. The results showed that the axial load capacity of the specimen decreased by 71. 6% with the increase of the diameter thickness ratio of the outer steel tube in the outer column from 31 to 125. The axial load capacity of the specimen increased with the increase of the steel yield strength and concrete strength, but decreased with the increase of the length diameter ratio of the outer column. A formula for calculating the axial load capacity of CIC members was proposed by using the test and numerical results.

The photocatalytic degradation of refractory organic pollutants is an efficient and economical method. In this paper, WO3 photocatalyst was prepared by a one step hydrothermal method with different structure directing agents. Oxytetracycline was used as the target pollutant to evaluate its photo catalytic activity. The effect of structure directing agents on crystal growth was studied by XRD, XPS, SEM, TEM, BET, and PL spectroscopy. The influence on photocatalytic efficiency of oxytetracycline was also studied. The results show that the three dimensional flower like microsphere structure of WO3 NaCl sample increases its specific surface area, making it have the largest adsorption performance. WO3 NaCl has the best photocatalytic activity, and the degradation efficiency of oxytetracycline reaches 60% in 120 minutes under visible light irradiation, which can be attributed to the synergistic effect of adsorption and degradation to improve the removal rate of oxytetracycline.