A Fourier-matching pseudospectral modal method [PSMM(f)] is developed for analyzing lamellar diffraction gratings or grating stacks. A Chebyshev pseudospectral method is first used to accurately calculate the eigenmodes of the grating layers, and then the Fourier coefficients are matched at the interfaces between the layers. Compared with an existing pseudospectral modal method based on point matching, the PSMM(f) is more robust and accurate. The method performs better than the standard Fourier modal method for gratings involving metals.

Numerical mode matching (NMM) methods are widely used for analyzing wave propagation and scattering in structures that are piecewise uniform along one spatial direction. For open structures that are unbounded in transverse directions (perpendicular to the uniform direction), the NMM methods use the perfectly matched layer (PML) technique to truncate the transverse variables. When incident waves are specified in homogeneous media surrounding the main structure, the total field is not always outgoing, and the NMM methods rely on reference solutions for each uniform segment. Existing NMM methods have difficulty handing gracing incident waves and special incident waves related to the onset of total internal reflection, and are not very efficient at computing reference solutions for non-plane incident waves. In this paper, a new NMM method is developed to overcome these limitations. A Robin-type boundary condition is proposed to ensure that non-propagating and non-decaying wave field components are not reflected by truncated PMLs. Exponential convergence of the PML solutions based on the hybrid Dirichlet-Robin boundary condition is established theoretically. A fast method is developed for computing reference solutions for cylindrical incident waves. The new NMM is implemented for two-dimensional structures and polarized electromagnetic waves. Numerical experiments are carried out to validate the new NMM method and to demonstrate its performance.

We propose a compact multi-parameter fibre sensing module based on a fibre Bragg grating (FBG) in single–multi–single mode fibre structure (FBG-in-SMS). We experimentally demonstrated that the FBG-in-SMS can measure temperature and strain simultaneously. In addition, we found that the process of writing FBG in SMS could be an effective technique for tuning and optimizing SMS spectrum for sensing.

Large-scale battery cells are connected in series, which inevitably leads to a phenomenon that the cell voltage is unbalanced. With a conventional equalizer, it is challenging to maintain excellent characteristics in terms of its size, design cost, and equalization efficiency. In order to improve the defects in the above equalization circuit, a novel voltage equalization circuit is designed, which can work in two modes. A bidirectional direct current–direct current (DC–DC) equalization structure is adopted, which can quickly equalize two high or low-power batteries without using an external energy buffer. In order to verify the effectiveness of the proposed circuit, a 12-cell battery 2800-MAh battery string was applied for experimental verification. Computer monitoring (LabVIEW) was adopted in the whole system to intelligently adjust the energy imbalance of the battery pack. The experimental results showed excellent overall performance in terms of equalization was achieved through the newly proposed method. That is, the circuit equalization speed, design cost, and volume have a good balance performance.

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Lithium batteries have become the main power source for new energy vehicles due to their high energy density and low self-discharge rate. In actual use of series battery packs, due to battery internal resistance, self-discharge rate and other factors, inconsistencies between the individual cells inevitably exist. Such inconsistencies will reduce the energy utilisation rate and service life of the battery pack, and even endanger its battery system safety. To improve the inconsistency of series battery packs, this study innovatively proposes an equalisation method based on a flyback converter. The residual power of a single cell is used as an index of inconsistency. A simple and reliable flyback converter is used to achieve balanced energy in the entire group, which make the energy is transferred between any batteries. Compared with the traditional equalisation topology, the equalisation topology proposed in this study reduces the number of components and reduces the volume of the equalisation system. Moreover, the primary side of the energy transfer only needs a set of control signals, which reduces the control difficulty. A series of equalisation experiments were performed using 12 series of battery cells. The results show the effectiveness of the proposed new equalisation method.

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Although the small perturbation method (SPM) for rough surface scattering has been studied extensively in problems in optics, remote sensing and propagation, there are fewer studies on rough surface transmission by the SPM. In this paper, from Huygens' principle and the extinction theorem, the SPM is used to derive the transmitted field to the second order, and expressions for the bidirectional transmission coefficient and the total surface transmittance to the second order are developed for the random rough surface. The refined expressions can be applied to the situations where the transmission characteristics of a random rough surface need to be more accurately calculated. For example, to calculate the brightness temperature of stratified rough media by the incoherent method, we have to know the bidirectional transmission coefficient or transmittance of random rough surface as accurately as possible. The accuracy of the presented expressions is verified through the conservation of energy. It is shown that the transmission characteristics calculated by SPM to the first order violate conservation of energy, whereas solutions to the second order conform to energy conservation much better. This is particularly important for the calculation of transmittance or emissivity.