Polarization manipulations of electromagnetic waves can be obtained by chiral and anisotropic metamaterials routinely, but the dynamic and high-efficiency modulations of chiral properties still remain challenging at the terahertz range. Here, we theoretically demonstrate a new scheme for realizing thermal-controlled chirality using a hybrid terahertz metamaterial with embedded vanadium dioxide (VO2) films. The phase transition of VO2 films in 90° twisted E-shaped resonators enables high-efficiency thermal modulation of linear polarization conversion. The asymmetric transmission of linearly polarized wave and circular dichroism simultaneously exhibit a pronounced switching effect dictated by temperature-controlled conductivity of VO2 inclusions. The proposed hybrid metamaterial design opens exciting possibilities to achieve dynamic modulation of terahertz waves and further develop tunable terahertz polarization devices.

In recent years, some e-commerce companies such as Amazon have adopted the cargo-to-person picking mode to improve their pickup efficiency. Under this mode, a shelf can store several types of goods and a type of goods can be placed on some shelves. When orders arrive, the warehouse robots move one shelf or more containing the ordered items to a fixed platform, and the pickers select the items from the shelves. It is very important to decide which shelves should be moved to increase picking efficiency. This paper addresses the problem of optimal movable-shelf selection for the cargoto-person picking mode. The goal of this study is to minimize the total time (costs) of moving the selected shelves to finish a batch of orders. We model this problem using 0-1 linear programming and show that the problem is NP-hard. Furthermore, we propose a three-stage hybrid heuristic algorithm with polynomial complexity to solve it. We conduct numerical experiments to show the efficiency of this algorithm.

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In the process of bubbling from two submerged adjacent orifices, bubbles coalescence becomes inevitable. But the study of the evolution and interaction of bubbles from submerged orifices is little, especially numerical simulation. In this paper, combined with mesh smoothing technique, mesh subdivision technique and the technique of axisymmetric coalescence and 3D coalescence, a three-dimensional model of bubbles coalescence at two submerged adjacent orifices on the wall is established by the boundary element method. Then, numerical simulations were carried out for horizontal and vertical coalescence before detachment. Finally, by changing the ventilation rate and the Froude number, the effects of different ventilation rates and buoyancy on the process of bubbles coalescence at two adjacent orifices were investigated. The results show that for horizontal coalescence, the effect of ventilation rate is more pronounced than buoyancy. As the ventilation rate increases or the influence of buoyancy is decreased, the amplitude of internal pressure fluctuation of the bubble decreases and the coalescence time decreases. For vertical coalescence, the effect of buoyancy is more pronounced than ventilation rate. With the influence of buoyancy is decreased, the vertical coalescence time is increased, the internal pressure of the bubble is decreased. The influence of ventilation rate is similar to that of horizontal coalescence.

The nonuniform emissivity of material surface will adversely affect the detection results of the thermal imaging technology. Aiming at the influence of uneven emissivity on the dynamic detection mode of eddy current thermography, a suppression method based on edge detection is proposed in this paper. Since the traditional threshold selection methods are not ideal, a local adaptive threshold selection (LATS) method is applied in this study. This method can automatically obtain the optimal threshold for edge detection to suppress the influence of uneven emissivity. Roberts, Sobel, Prewitt, and Canny operators are tested by using LATS. The results show that Roberts, Sobel, and Prewitt operators can achieve the suppression effect, but the effect of Sobel and Prewitt are similar and better than Roberts.