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The high-speed maglev vehicle/guideway coupled model is an essential simulation tool for investigating vehicle dynamics and mitigating coupled vibration. To improve its accuracy efficiently, this study investigated a hierarchical model updating method integrated with field measurements. First, a high-speed maglev vehicle/guideway coupled model, taking into account the real effect of guideway material properties and elastic restraint of bearings, was developed by integrating the finite element method, multi-body dynamics, and electromagnetic levitation control. Subsequently, simultaneous in-site measurements of the vehicle/guideway were conducted on a high-speed maglev test line to analyze the system response and structural modal parameters. During the hierarchical updating, an Elman neural network with the optimal Latin hypercube sampling method was used to substitute the FE guideway model, thus improving the computational efficiency. The multi-objective particle swarm optimization algorithm with the gray relational projection method was applied to hierarchically update the parameters of the guideway layer and magnetic force layer based on the measured modal parameters and the electromagnet vibration, respectively. Finally, the updated coupled model was compared with the field measurements, and the results demonstrated the model's accuracy in simulating the actual dynamic response, validating the effectiveness of the updating method. [ABSTRACT FROM AUTHOR]

Medium low-speed maglev trains cause coupling vibration when moving over flexible bridges, which has a detrimental effect on the overall system. To effectively improve the global performance of the train-bridge system, this study proposes a parameter optimization approach that integrates a numerical model, a neural network, and a multi-objective evolutionary algorithm. A three-car maglev train-bridge coupling system is first modeled based on finite element, multi-body dynamics, and the levitation control theory. Based on this, the dynamic response and parameter sensitivity of the system is investigated using simulation analysis and the Sobol method. To enhance the optimization efficiency, an improved neural network is employed to simulate the nonlinear relationship between key parameters and dynamic performance, thereby surrogating the numerical model. The NSGA-III algorithm with a reference point mechanism is used to search for the optimal solution of the key parameters. Finally, simulation experiments verify the validity and accuracy of the neural network and the optimization results. This approach takes into account the coupling effect between multiple parameters and significantly enhances the computational efficiency compared with traditional rail transportation optimization methods. The dynamic response of the maglev system, considering the car-body flexibility, demonstrates that the optimization approach effectively improves the safety and stability of the train and further reduces the negative effect of the car-body's elastic vibration on the operation quality. [ABSTRACT FROM AUTHOR]

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We propose a photonic crystal waveguide structure with an adjustable transmission efficiency characteristic. The liquid crystal components are placed in the inclined channel between the two horizontal channels of the Z-shaped waveguide in the photonic crystal structure. The different transmission efficiency of the photonic crystal waveguide can be obtained by applying a voltage to liquid crystal components of different positions. Based on the proposed photonic crystal waveguide structure, we design a 1*4 photonic crystal beam splitter. The finite-element method is used to analyze the transmission efficiency. The results show that: by applying a voltage to liquid crystal components of the light output channel, the selection of the light output port can be realized; by applying a voltage to a single liquid crystal component at different positions in the beam splitting channel, the light splitting ratio of the output port can be adjusted, and the high transmission efficiency of the system can be ensured. The effective control of photonic crystal waveguides is helpful to the design of photonic devices with superior performance and diverse functions, which is of great significance to the development of photonic devices. [ABSTRACT FROM AUTHOR]

Highlights • This paper firstly proposed a maglev vehicle/guideway interaction model based on a field measurement and model updating method. • Two case studies including the Shanghai High-Speed Maglev Commercial Operational Line and the High-speed Maglev Test Line were presented for the validation of the proposed model. • Based on the field measurement, this paper analyzed the frequency response of the guideway subjected to the maglev vehicle excitations. • This paper discussed the effects of the irregularity and the distributed magnetic forces on the maglev vehicle/guideway system. Abstract Practical simulation technology is of great importance in the design and research of the maglev system. This paper presents a practical vehicle/guideway model based on an in situ vibration test and model updating method. In this model, the guideway is established by the Finite Element method and then updated by the measurement, and the vehicle is simulated as a 10-degree-of-freedom model, which consists of a car-body and eight magnets. The vehicle interacts with the guideway by the magnetic interactive forces, which are tuned by the current feedback controller. The vehicle/guideway interaction problem is solved by the proposed incremental iteration procedure. Two case studies including the Shanghai High-speed Maglev Commercial Operational Line and the High-speed Maglev Test Line at Tongji University were presented for the validation of the proposed model. Finally, the effects of random surface irregularity and distributed magnetic forces were investigated here, and the frequency response of the guideway was analyzed in detail. The results indicate that the proposed model can provide a practical response prediction and analysis because the dynamic characteristics of the guideway and the excitation frequency of the maglev train are reasonably considered in this model. [ABSTRACT FROM AUTHOR]

We design a logic gate and an optical half-adder based on photonic crystal using BPSK signals. The logic gate is composed of a silicon rod array and a microcavity containing a SiO 2 dielectric column, which can realize XOR and XNOR logic. The optical half adder is formed by introducing a reference beam with a fixed initial phase to the proposed logic gate. The initial phase of incident light determines the logic state of the BPSK signals. The intensity of the output light determines the output logic state. We use the plane wave expansion and finite element methods to analyze logic gates and optical half adders. The proposed logic gate and optical half-adder cover 160 µm2 and 270 µm2, the response time is 0.6 ps and 0.9 ps, respectively, and the margin difference of the output signals is 103% and 81%, respectively. Their compact structure, short response time, and large margin difference of the output signals have potential application prospects in all-optical information processing. [ABSTRACT FROM AUTHOR]