Three-dimensional invisible cloaks with arbitrary shapes based on partial differential equation

The method of designing electromagnetic invisible cloak is usually based on the form-invariance of Maxwell’s equations in coordinate transformation. By solving the partial differential equations (PDEs) that describe how the coordinates transform, three-dimensional (3-D) electromagnetic and acoustic invisible cloaks with arbitrary shapes can be designed provided the boundary conditions of the cloaks can be determined by the corresponding transformation. Full wave simulations based on finite element method verify the designed cloaks. The proposed method can be easily used in designing other transformation media such as matter-wave cloaks.     

BaFeO3和BaCeO3钙钛矿型氧化物的储氮性能

 采用改进的溶胶－凝胶法制备了Ba－Fe－O（Ba／Fe原子比为0．5），Ba－Ce－O（Ba／Ce原子比为1）和Ba－Sn－O（Ba／Sn原子比为1）氧化物，并考察了其储氮性能．结果表明，750℃焙烧的Ba－Fe－O样品，在400℃下的NOx储存容量（NSC）最大，其次为900℃焙烧的Ba－Ce－O样品；相同温度焙烧的样品，在400℃下的NSC均大于200℃下的NSC．XRD测试结果表明，750℃焙烧的Ba－Fe－O样品的缺陷钙钛矿BaFeO3－δ可能是储存NOx的主要活性相，而Ba－Ce－O和Ba－Sn－O样品储存NOx的活性相分别为钙钛矿型BaCeO3和BaSnO3．BET测定结果表明，样品的比表面积均较小．用FT－IR分析了Ba－Fe－O样品上储存的NOx物种．讨论了NSC大小与吸收温度、NOx吸收物种及样品物相之间的关系．     

Vitamin K1在水-有机溶剂中单电子还原电位的测定

ＶｉｔａｍｉｎＫ１（ＶＫ１）是一种非常重要的脂溶性维生素,其止血功能已为人们所熟悉．下图显示在生物体内ＶＫ参与的止血过程,在这个氧化还原循环过程中,ＶＫＨ２环氧化变成ＶＫＯ与Ｇｌｕ(谷氨酸蛋白)羧化而转变成Ｇｌａ(γ-羧基谷氨酸蛋白)是同时发生的,但前一?..     

Transmission Reflection Integrated Programmable Metasurface for Real-Time Beam Control and High Efficiency Transmission Polarization Conversion

The functional versatility and flexibility of multifunctional metasurfaces are of great significance for the application of electromagnetic (EM) metasurfaces in military stealth, holographic imaging, base station antennas, and other fields. Nevertheless, the functions of active programmable coding multifunctional metasurfaces are mostly reflective or transmissive, and the research on active multifunctional metasurfaces with transmission and reflection integration is still in its infancy. Here, a transmission reflection integrated active programmable coding metasurface is proposed to manipulate the transmission and reflection of different polarized electromagnetic waves independently in real time. As a proof of concept, a metasurface that can implement diverse programmable functionalities is designed. Numerical and experimental results indicate that the strategy has excellent performance in beam control and polarization conversion, which provides tremendous potential for extending highly integrated multifunctional devices.     

Preparation of hollow silica microspheres with controlled shell thickness in supercritical fluids

This article presents a novel route to prepare hollow silica microspheres with well-defined wall thickness by using cross-linked polystyrene (PS) microspheres as templates with the assistance of supercritical carbon dioxide (SC-CO₂). In this approach, the cross-linked PS templates can be firstly prepared via emulsifier-free polymerization method by using ethylene glycol dimethacrylate or divinylbenzene as cross-linkers. Then, the silica shell from the sol–gel process of tetraethyl orthosilicate (TEOS) which was penetrated into the PS template with the assistance of SC-CO₂ was obtained. Finally, the hollow silica spheres were generated after calcinations at 600 °C for 4 h. The shell thickness of the hollow silica spheres could be finely tuned not only by adjusting the TEOS/PS ratio, which is the most frequently used method, but also by changing the pressure and aging time of the SC-CO₂ treatment. Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscope were used to characterize these hollow silica spheres.     

HL—1装置逃逸电子产生硬X射线锯齿振荡的频谱计算

在HL-1装置上用硬X射线测得相应的打在孔栏处逃逸电子通量,其通量脉动呈现反锯齿振荡。为辨别这个振荡是一个真实的物理扰动,还是毫无意义的噪声涨落或背景振动,我们对获取的硬X射线通量作了频谱分析,证实逃逸电子打在限制器上产生的硬X射线受到一     

Almost periodicity for a class of delayed Cohen–Grossberg neural networks with discontinuous activations

The objective of this paper is to investigate the dynamics of a class of delayed Cohen–Grossberg neural networks with discontinuous neuron activations. By means of retarded differential inclusions, we obtain a result on the local existence of solutions, which improves the previous related results for delayed neural networks. It is shown that an M-matrix condition satisfied by the neuron interconnections, can guarantee not only the existence and uniqueness of an almost periodic solution, but also its global exponential stability. It is also shown that the M-matrix condition ensures that all solutions of the system display a common asymptotic behavior. In this paper, we prove that the existence interval of the almost periodic solution is (?∞, +∞), whereas the existence interval is only proved to be [0, +∞) in most of the literature. As special cases, we derive the results of existence, uniqueness and global exponential stability of a periodic solution for delayed neural networks with periodic coefficients, as well as the similar results of an equilibrium for the systems with constant coefficients. To the author’s knowledge, the results in this paper are the only available results on almost periodicity for Cohen–Grossberg neural networks with discontinuous activations and delays.     

Generation of stable bright pulse and the dark soliton interaction in nonlinear left-handed materials

In homogeneous and isotropic nonlinear left-handed materials (LHMs), using the split step Fourier transform method, we demonstrate that two dark electromagnetic solitons which are the solutions of coupled nonlinear Schrödinger equations (CNLS) move along a line toward each other, when the distance between them down to a certain value, the interaction of the two dark solitons can produce a stable bright electromagnetic pulse that behaves like a bright soliton. Although our mathematical analysis shows that the new generated stable bright pulse is not an exact solution of the CNLS, it can propagate steadily in the nonlinear LHMs. And this unusual phenomenon can also be observed in our numerical simulation results by another method.     

NADH Photosynthesis System with Affordable Electron Supply and Inhibited NADH Oxidation

Photosynthesis offers a green approach for the recycling of nicotinamide cofactors primarily NADH in bio-redox reactions. Herein, we report an NADH photosynthesis system where the oxidation of biomass derivatives is designed as an electron supply module (ESM) to afford electrons and superoxide dismutase/catalase (SOD/CAT) cascade catalysis is designed as a reactive oxygen species (ROS) elimination module (REM) to inhibit NADH degradation. Glucose as the electron donor guarantees the reaction sustainability accompanied with oxidative products of gluconic acid and formic acid. Meanwhile, enzyme cascades of SOD/CAT greatly eliminate ROS, leading to a ≈2.00-fold elevation of NADH yield (61.1 % vs. 30.7 %). The initial reaction rate and turnover frequency (TOF) increased by 2.50 times and 2.54 times, respectively, compared with those systems without REM. Our study establishes a novel and efficient platform for NADH photosynthesis coupled to biomass-to-chemical conversion.