Electromagnetically induced transparency in terahertz metamaterial based on two-bright-mode resonator

An electromagnetically induced transparency (EIT) in metamaterial resonator with two bright modes and one dark mode at the terahertz (THz) band is numerically and experimentally demonstrated. Different from two kinds of the traditional passive modulations, our design can realize the passive modulation of EIT phenomenon by adding another bright mode resonator. Simulated and experimental results show that the transmission peak varies for incident THz waves with different polarization directions due to its asymmetric structure, which provides a novel way to realize high efficiency switch and modulation.     

机载激光雷达双光楔扫描系统设计与实现

介绍了作为大型机载激光雷达关键部件的双光楔扫描系统的模型建立、设计实现以及实验验证。为实现双光楔扫描系统的大尺寸、宽视场和高精度指向,设计了16楔角、320 mm直径的成对光楔,以及对应的高精度PID双轴扫描控制模块,分析了系统误差来源和误差控制方法。在45 m距离的地面测试中,通过每个3.6转动楔镜,累计100次与真值测量比对进行检校和验证,扫描指向误差小于50 rad,通过搭载集成后的机载激光雷达飞行实验,实测扫描视场为32.03,进一步验证了双光楔扫描系统的有效性。     

Propagation theories of arbitrary-order correlations of partially coherent electromagnetic fields based on separated-coordinate mode decomposition

Theories to calculate the propagation of arbitrary-order correlations of stationary or nonstationary partially coherent electromagnetic fields are proposed. The theories are based on separated-coordinate mode decomposition, and can make the well-developed propagation theories of fully coherent electromagnetic fields applicable to partially coherent electromagnetic fields governed by linear Maxwell equations. The validity of the theories is illustrated by an example.     

Photoelectrochemical water splitting with black Ni/Si-doped TiO2 nanostructures

Black Ni/Si-doped TiO₂ nanostructures were successfully fabricated through electrochemical anodization of Ti–1Ni–5Si alloy and Sn-reduction treatment. After Sn-reduction treatment, the band gap of Ni/Si-doped TiO₂ became much smaller compared to other samples, which can be attributed to the synergetic effect of Ni/Si doping and the large quantity of Ti³⁺/oxygen vacancy species induced by Sn-reduction treatment. The black Ni/Si-doped TiO₂ nanostructures exhibited a remarkable enhancement in the photoelectrochemical (PEC) water splitting in comparison with the pure TiO₂ and Ni/Si-doped TiO₂. The highest photocurrent reached 2.15 mA/cm² (at 0 V versus Ag/AgCl), corresponding to a conversion efficiency (~1.10%) which was 5.8 times that of the pure TiO₂ nanotubes. The first-principles calculations using density-functional theory (DFT) showed that ion doping and self-doped Ti³⁺ defect levels in the forbidden gap induced through Sn-reduction treatment could improve the mobility of photogenerated carriers and suppress charge recombination, which was in well agreement with the experimental results.     

用神经网络实现VBR视频通信量的在线预测

VBR(Varible Bit Rate)视频信号具有时变性、非线性和突发性等特点,实现该信号通信量的高精度预测难度较大.针对以上问题,本文提出了一种用于VBR视频通信量预测的自适应神经网络模型,网络训练采用离线与在线相结合的方式,同时通过删除不重要的权重,以优化网络的拓扑结构,提高网络的推广能力,降低网络在线学习的计算复杂度;对VBR视频通信量预测的模拟结果表明该模型具有高的预测精度,并能满足通信系统对预测实时性的要求.     

Gazing-detection of human eyes based on SVM

A method for gazing-detection of human eyes using Support Vector Machine （SVM） based on statistic leaming theory （SLT） is proposed. According to the criteria of structural risk minimization of SVM,the errors between sample-data and model-data are minimized and the upper bound of predicting error of the model is also reduced. As a result,the generalization ability of the model is much improved. The simulation results show that, when limited training samples are used, the correct recognition rate of the tested samples can be as high as 100% ,which is much better than some previous results obtained by other methods. The higher processing speed enables the system to distinguish gazing or not-gazing in real-time.     

Real time RBS study of Cu–Sn alloy thermal oxidation by means of a 4He2+ external micro-beam

An open-air furnace has been designed to study in real time the high-temperature surface transformation of materials by Rutherford backscattering spectrometry (RBS) in external beam mode. A device previously designed for the observation of the high-temperature oxidation of galena has been re-designed in order to analyse massive samples and to reach a temperature range up to 700 °C and a better temperature regulation (±2 °C).Experiments are carried out to measure, by RBS using a 3 MeV ⁴He²⁺ external micro-beam, the dynamic growth of oxide layers in air on the surface of copper–tin alloys heated at temperatures varying from 250 to 650 °C. The results obtained demonstrate the usefulness of this approach: actually one single measurement series permits to obtain at the same time the composition of oxide layers built on the metal and their growth kinetic laws.In the particular study of bronzes, the growth kinetics obtained by this method show the large influence of tin concentration on the oxidation mechanism. These results are verified by measurements on samples oxidised in an independent closed furnace. The results show also the occurrence of different oxidation mechanisms as a function of temperature. A diffusion mechanism governs the oxidation kinetics only at some temperatures.     

Robust three, dimensional surface contouring method with digital holography

Nowadays digital holography (DH) is applied to thethree di mensional surface contouring,duetoits non-con-tact advantage[1-5].Moreover ,when a lensless Fouriertransform arrangement with the short-coherence lightsourceis employed in a DHrecording system,not…     

Reflection spectra of fiber Bragg gratings in quadratic strain field

Many researches have been done on the optical char-acteristics of the FBG whenexternal fields are appliedtoit .For example,the studies on the reflection spectra ofthe FBGin uniformstrain field[1],temperature field[2],strain and temperature cross-sensitive…