Actively controlling the topological transition of dispersion based on electrically controllable metamaterials

Topological transition of the iso-frequency contour (IFC) from a closed ellipsoid to an open hyperboloid, will provide unique capabilities for controlling the propagation of light. However, the ability to actively tune these effects remains elusive and the related experimental observations are highly desirable. Here, tunable electric IFC in periodic structure which is composed of graphene/dielectric multilayers is investigated by tuning the chemical potential of graphene layer. Specially, we present the actively controlled transportation in two kinds of anisotropic zero-index media containing PEC/PMC impurities. At last, by adding variable capacitance diodes into two-dimensional transmission-line system, we present the experimental demonstration of the actively controlled magnetic topological transition of dispersion based on electrically controllable metamaterials. With the increase of voltage, we measure the different emission patterns from a point source inside the structure and observe the phase-transition process of IFCs. The realization of actively tuned topological transition will opens up a new avenue in the dynamical control of metamaterials.Comment: 21 pages,8 figure

Numerical Simulation of Sloshing in 2D Rectangular Tanks Based on the Prediction of Free Surface

A finite difference method for analyzing 2D nonlinear sloshing waves in a tank has been developed based on the potential flow theory. After σ-transformation, the free surface is predicted by the kinematic condition, and nonlinear terms are approximated; the governing equation and boundary conditions are discretized to linear equations in the iterative process of time. Simulations of standing waves and sloshing in horizontally excited tanks are presented. The results are compared with analytical and numerical solutions in other literatures, which demonstrate the effectiveness and accuracy of this numerical method. The beating phenomenon of sloshing in the tank with different aspect ratios is studied. The relationship between sloshing force and aspect ratio under the same external excitation is also discussed

The Coupling Coordination Degree Measurement of Society-Economy-Ecosystem of Regional National Forest Park in Heilongjiang Province

In order to estimate the comprehensive benefits brought by forest parks to the society, economy, and ecology of a certain area, this paper innovatively constructed a social-economic-ecological composite system of forest parks in Heilongjiang Province. The entropy method is used to determine the weight of each index, the coupling coordination degree model is used to analyze the coupling and coordination degree of the social, economic, and ecological benefits of forest parks in Heilongjiang Province from 2010 to 2018. In addition, the LSTM neural network model is used to predict the development trend of the coupling coordination degree of the composite system from 2019 to 2021. Research shows that from 2010 to 2018, the forest park composite system was in a state of "high coupling and low coordination" for a long time; from 2019 to 2021, it is predicted that the degree of coupling of the composite system will decrease slightly and the degree of coordination will increase

STUDY ON VIBRATION RESPONSE OF A NON-UNIFORM BEAM WITH NONLINEAR BOUNDARY CONDITION

Forced vibration of non-uniform beam with nonlinear boundary condition is studied in this paper by proposing an iterative model combining Adomian Decomposition Method and modal analysis. An exponentially tapered beam with a hardening nonlinearity spring boundary is simulated as a case study. The model accuracy is proved by comparing iteration results and analysis solutions with linear and weakly nonlinear boundary conditions. Sin-weep nonlinear frequency spectrum is then obtained by the proposed model. The influence of boundary nonlinearity on the vibration response of non-uniform beam is analyzed. And the effect of different excitation amplitudes on nonlinearity in the vibration response is studied. The mathematical model and numerical solutions proposed in this paper can be used to solve and analysis broad vibration problems on general non-uniform beams with different nonlinear boundary conditionsunder various excitations

SEISMIC VULNERABILITY ANALYSIS OF CABLE-STAYED BRIDGE DURING ROTATION CONSTRUCTION

          Due to the swivel construction, the structural redundancy of cable-stayed bridge is reduced, and its seismic vulnerability is significantly higher than that of non-swirling construction structure and its own state of formation. Therefore, it is particularly important to study the damage changes of each component and stage system during the swivel construction of cable-stayed bridge under different horizontal earthquakes. Based on the construction of Rotary Cable-stayed Bridge in Haxi Street, the calculation formula of damage exceeding probability is established based on reliability theory, and the damage calibration of cable-stayed bridge components is carried out, and the finite element model of cable-stayed bridge rotating structure is established. The vulnerable parts of the main tower and the stay cable components of the cable-stayed bridge are identified and the incremental dynamic analysis is carried out. Finally, the seismic vulnerability curves of the main tower section, the stay cable and the rotating system are established. The results of the study show that the vulnerable areas of the H-shaped bridge towers are the abrupt changes in the main tower section near the upper and lower beams, and the vulnerable diagonal cables are the long cables anchored to the beam ends and the short cables near the main tower；At the same seismic level, the damage exceedance probability of main tower vulnerable section of cable-stayed bridge under transverse earthquake is greater than that under longitudinal earthquake, the damage exceedance probability of vulnerable stay cables under transverse seismic action is less than that under longitudinal seismic action；On the premise of the same damage probability, the required ground motion intensity of the system can be reduced by 0.35g at most compared with the component；Under the same seismic intensity, the system damage probability is 6.60 % higher than the component damage probability at most. The research results have reference significance for the construction of rotating cable-stayed bridges in areas lacking seismic records

EVALUATION OF THE EFFECT OF EXTERNAL PRESTRESSED STEEL STRANDS ON CABLE-STAYED BRIDGES BASED ON FINITE ELEMENT ANALYSIS AND STATIC TEST

This article relies on the reinforcement project of the Mulinghe cable-stayed bridge to explore the changes in the mechanical properties of the reinforced concrete cable-stayed bridge before and after reinforcement. The bridge has large cable spacing, large internal force of a single cable, and the main beam is mainly Reinforced Concrete. Therefore, structural calculation, disease analysis, and damage state simulation are carried out. Afterwards, the bridge's commonly used reinforcement methods were compared, and suitable reinforcement schemes were selected. After the reinforcement, the field test was carried out on the cable-stayed bridge, the main beam deflection, the strain of the main beam and the main tower, and the increase in the cable force of the cable- stayed were analyzed. The results show that external prestressed reinforcement is the best way, which can significantly reduce the vertical displacement of the main beam and the horizontal displacement of the main tower, and also improve the stress on the upper and lower edges of the main beam. After the external prestressed reinforcement, the ratio of the observed value to the observed value in the filed load test of the cable-stayed bridge's decreased significantly. It is up to 31% increase in bending capacity of main beams and up to 24% increase in stiffness. This article is instructive for the reinforcement of the early-built sparse-cable reinforced concrete cable-stayed bridge, while also expanding the scope of implementation of external prestressed reinforcement technology

Truncated Laplace and Gaussian mechanisms of RDP

The Laplace mechanism and the Gaussian mechanism are primary mechanisms in differential privacy, widely applicable to many scenarios involving numerical data. However, due to the infinite-range random variables they generate, the Laplace and Gaussian mechanisms may return values that are semantically impossible, such as negative numbers. To address this issue, we have designed the truncated Laplace mechanism and Gaussian mechanism. For a given truncation interval [a, b], the truncated Gaussian mechanism ensures the same Renyi Differential Privacy (RDP) as the untruncated mechanism, regardless of the values chosen for the truncation interval [a, b]. Similarly, the truncated Laplace mechanism, for specified interval [a, b], maintains the same RDP as the untruncated mechanism. We provide the RDP expressions for each of them. We believe that our study can further enhance the utility of differential privacy in specific applications