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In this article, a broadband radar cross section (RCS) reduction metasurface with a reconfigurable high-selectivity passband is proposed. Based on the equivalent circuit analysis, the feasibility of achieving the high-selective passband with multimode working state and RCS reduction near the passband through the combination of the checkerboard metasurface and the switchable bandpass frequency selective structure (FSS) is verified. The switchable FSS in the bottom layer can realize the function of wave transmittance/reflection by controlling the ON/OFF states of the p-i-n-diodes, and a novel staggered patch structure is introduced to realize the fast conversion between different working modes without using complex feeding networks. The checkerboard metasurface in the upper layer not only realizes the RCS reduction function through scattering cancellation but also improves the passband selectivity of the switchable FSS under different working modes. Finally, a prototype of the proposed structure is fabricated and measured. The measured results show that the proposed structure can be flexibly switched between the three working modes. In different working modes, the structure has a wide RCS reduction bandwidth and a high-selective passband.

Two-dimensional (2D) atomically thin quantum dots (QDs) possess extraordinary electrical and optical properties. However, fabricating high quality 2D QDs viaa universal and reliable technique remains a challenge. Here, we report a simple strategy to prepare high quality, monolayer single crystal 2D QDs viaultrathin cutting 2D bulk single crystals by ultramicrotome, followed by an exfoliation process. The as-prepared 2D QDs have pristine surface, high quality, high monolayer yield and high photoluminescence quantum yield (the highest photoluminescence quantum yield of WS2is 18%), which can be used as promising, low toxic, biocompatible, and good cell-permeability fluorescent labeling agents for in vitroimaging.

Two-dimensional (2D) carbon materials, such as graphene, have attracted particular attention owing to the exceptional carrier transport characteristics that arise from the unique π-electron system in their conjugated carbon network structure1–4. To complement zero-bandgap graphene, material scientists have devoted considerable effort to identifying 2D carbon materials5–8. However, it is a challenge to prepare large-sized single-crystal 2D carbon materials with moderate bandgaps5,9. Here we prepare a single-crystal 2D carbon material, namely monolayer quasi-hexagonal-phase fullerene (C60), with a large size via an interlayer bonding cleavage strategy. In this monolayer polymeric C60, cluster cages of C60are covalently bonded with each other in a plane, forming a regular topology that is distinct from that in conventional 2D materials. Monolayer polymeric C60exhibits high crystallinity and good thermodynamic stability, and the electronic band structure measurement reveals a transport bandgap of about 1.6 electronvolts. Furthermore, an asymmetric lattice structure endows monolayer polymeric C60with notable in-plane anisotropic properties, including anisotropic phonon modes and conductivity. This 2D carbon material with a moderate bandgap and unique topological structure offers an interesting platform for potential application in 2D electronic devices.

Thermal rectifiers and thermal transistors are expected to be widely used for efficient thermal management and energy cascade utilization due to their excellent directional thermal management. Two-dimensional micro/nano materials have huge potential in the applications of thermal transistors, thermal logic circuits, and thermal rectifiers owing to the phase transition and thermal rectification phenomenon. Herein, a lithium intercalation method was used to transform 2H–MoS2into the 1T phase with a purity of 76%, and a suspended microelectrode was applied to measure the thermal conductivity and thermal rectification coefficient of the same MoS2film with 1T and 2H phases in suit. The thermal conductivity and thermal rectification effect of two-phase MoS2couple with its phase state and structure were also obtained. The results demonstrate that the thermal conductivities of MoS2in both 1T and 2H phases decrease with increasing temperature. It is also found that the thermal rectification coefficient has no obvious dependence on the temperature and phase change but the asymmetric structure. Furthermore, a thermal rectifier and transistor with a high thermal rectification effect are designed. The direction and magnitude of heat flow through the samples can be effectively controlled and managed by adjusting the phase, size, and structural asymmetry of the different samples. The maximum thermal rectification coefficient of the thermal rectifiers is up to 0.8.

Background: Jingzhiguanxin (JZGX) tablet, a traditional Chinese prescription, is commonly used for treating coronary heart disease and angina pectoris in the clinic. There are six active components (Danshensu (DSS), Protocatechuic aldehyde (PD), Paeoniflorin (PF), Ferulic acid (FA), Salvianolic acid B (Sal B) and Tanshinone IIA (TA)) in JZGX tablet. Objective: In this paper, a simple and reliable method was used for simultaneous determining the six active components by high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). Methods: These six active components were separated on an Agilent Zorbax Eclipse XDB-C18 column (150 mmx4.6 mm, 5 μm) at 30 °C. Acetonitrile (A), methanol (B) and 0.5% H3PO4 aqueous solution (C) were used as mobile phase for gradient elution. The flow rate was 1 mL/min and the detection wavelengths were set at 280 nm for DSS, PD and Sal B, 230 nm for PF, 320 nm for FA and 270 nm for TA, respectively. Results: All of the six components showed good linearity regressions (r2≥0.9997) in the detected concentration range. The recovery rates and coefficient of variation (CV) for all analytes were 98.66%- 100.18% and 0.75%-1.89%, respectively. This method was successfully applied to simultaneously determine the six components in JZGX tablet from different batches and manufacturers. Conclusion: The validated method can be used in routine quality control analysis of JZGX tablet without any interference.

High-quality ultrasmooth surface is needed in modern optics, while the existing ultrasmooth surface processing methods are difficult to meet the requirement of the surface figure. In order to solve this problem, the active feed polishing (AFP) is taken as the research object, and the dual-rotor tool path is put forward for this technology. This tool path is generated based on the motion synthesis principle, which realizes smooth connection between different sections. At the same time, the eccentricity, the speed ratio, the velocity, and other parameters can be modified easily, avoiding using the complicated dual-rotor polishing mechanism. In order to further analyze the removal error, the removal amount calculation method for the dual-rotor path is researched and proposed. The simulation analysis results show that the greatest influence factor for the removal error is the sampling interval, the influence of the eccentricity and the speed ratio is less, and the velocity has little impact on it. In addition, the removal error can be controlled within acceptable range by reasonable selection of process parameters. Finally, through a processing experiment of a 100 mm plane lens, the feasibility and effectiveness of this path is verified. This experimental result shows that the AFP technology using the dual-rotor tool path can effectively correct the surface shape while reducing the surface roughness.