MPEG-7视觉区域形状描述子的商标图像检索

为了降低MPEG-7区域形状描述子-角半径变换(ART)的数据冗余,首先提出在新的离散情况下ART变换的算法实现方法;然后利用极坐标系的对称性和三角函数性质,提出了新的只需计算图像区域形状大小1/4的ART变换快速算法.构建了一个基于形状特征的自动图像检索系统,并将其应用于商标图像检索.实验结果表明,该方法具有一定的可行性和有效性,快速算法大大降低了数据冗余.     

等离子体天线的基本特性仿真

等离子体天线具有隐身、动态重构等不同于金属天线的独特的物理性质,在卫星遥感、通信、导航领域具有潜在的应用前景。为了研究等离子体频率对天线特性的影响,采用三维电磁仿真软件建立了柱形等离子体天线模型,在此基础上,针对等离子体频率对等离子体天线的S11曲线、方向图、增益等性能的影响进行了仿真分析,并给出了相关结论。     

Ternary Ta2NiSe5 Flakes for a High‐Performance Infrared Photodetector

Multielemental systems enable the use of multiple degrees of freedom for control of physical properties by means of stoichiometric variation. This has attracted extremely high interest in the field of 2D optoelectronics in recent years. Here, for the first time, multilayer 2D ternary Ta₂NiSe₅ flakes are successfully fabricated using a mechanical exfoliation method from chemical vapor transport synthesized high quality bulk and the optoelectronic properties are systematically investigated. Importantly, a high responsivity of 17.21 A W^?1 and high external quantum efficiency of 2645% are recorded from an as‐fabricated photodetector at room temperature in air; this is superior to most other 2D materials‐based photodetectors that have been reported. More intriguingly, a usual sublinear and an unusual superlinear light‐intensity‐dependent photocurrent are observed under air and vacuum, respectively. These excellent and special properties make multilayer ternary Ta₂NiSe₅ a highly competitive candidate for future infrared optoelectronic applications and an interesting platform for photophysics studies.     

Design of a Concentration Solar Thermoelectric Generator

Thermoelectric technology can be another direct way to convert solar radiation into electricity, using the Seebeck effect. Herein, a prototype concentration solar thermoelectric generator (CTG) and a discrete numerical model for the evaluation of the whole system are presented. The model takes into account the temperature dependence of the thermoelectric material properties by dividing the thermoelectric leg into finite elements and is proved to be more accurate for calculation of the conversion efficiency of the thermoelectric modules when large temperature gradients occur in the CTG system. Based on the best available properties of various bulk thermoelectric materials reported in the literature, the best possible performance of the CTG system is predicted, and the CTG system design, including the selection of the concentration ratio and the cooling method for different thermoelectric materials, are discussed in detail.     

列阵式密封小型TEACO_2激光器

本文报道一种新型列阵式密封小型TEACO_2激光器。该器件不仅可获得多光束输出,而且利用它进行多种形式的组合,可得到具有各种高质量的激光输出,在许多领域有着广泛的应用潜力。     

涂层转移法精密铸造技术在子午线轮胎模具制造中的应用

子午线轮胎模具计算机辅助快速制造系统是由ＣＡＤ技术、快速成型技术、涂层转移法精密铸造技术、材料技术等多项高新技术组合而成的一项独特的先进制造技术。该系统充分利用液态材料成型任意性和高再现性的特点，具有适应性强、重复性好、加工周期短、制造成本低的特点。     

检验THERP合理性及不足的实验研究——以汽车冷媒加注工序为例

为了检验人的失误概率预测技术（technique of human error rate prediction，THERP）的合理性及不足，以汽车内饰冷媒加注工序为例，采用E-prime实验的方法分析了冷媒加注工序的人因失误概率。通过比较发现，汽车冷媒加注工序的4个任务的人因失误概率的实验结果与THERP的理论计算结果基本一致，说明了THERP方法的合理性。并说明了THERP的不足在于计算人因失误时忽略了操作行为中的认知过程。     

Precise Self‐Assembly of Nanoparticles into Ordered Nanoarchitectures Directed by Tobacco Mosaic Virus Coat Protein

Self‐assembly guided by biological molecules is a promising approach for fabricating predesigned nanostructures. Protein is one such biomolecule possessing deterministic 3D crystal structure and peptide information, which acts as a good candidate for templating functional nanoparticles (fNPs). However, inadequate coordination efficacy during the establishment of interfacial interactions with fNPs makes it highly challenging to precisely fabricate designed nanostructures and functional materials. Here, a facile and robust strategy is reported for the hierarchical assembly of fNPs into ordered architectures, with unprecedentedly large sizes up to tens of micrometers, using a hollow cylinder‐shaped tobacco mosaic virus coat protein (TMV disk). The rational design of the site‐specific functional groups on the TMV disk not only demonstrates the powerful capability of directing various discrete fNP assemblies with high controllability but also assists in precise assembly of a TMV monolayer sheet structure for further organizing homogeneous and heterogeneous fNP periodic lattices by varying the types of fNPs. The high precision and adjustability of the pattern fashions of different fNPs unambiguously corroborate the validity of this innovative strategy, which provides a convenient route to design and assemble protein‐based hierarchical ordered architectures for use in nanophotonics and nanodevices.     

Melting and solidification properties of the nanoparticles of Sn3.0Ag0.5Cu lead-free solder alloy

The Sn3.0Ag0.5Cu (wt.%) lead-free solder alloy is considered to be one of the most promising candidates to replace the traditionally used Sn–Pb solder. However, this alloy composition has some weaknesses, mainly as a result of its higher melting temperature compared to the eutectic Sn–Pb solder. In this paper, lead-free solder alloy nanoparticles of Sn3.0Ag0.5Cu were synthesized by chemical reduction with NaBH₄ as reducing agent. The experimental results indicated that the major particle size of Sn3.0Ag0.5Cu nanoparticles was smaller than 100 nm. The melting and solidification properties of the Sn3.0Ag0.5Cu nanoparticles were studied by differential scanning calorimetry at different scanning rates. It was evidenced by the differential scanning calorimetry curves that the melting temperature of Sn3.0Ag0.5Cu nanoparticles was lower than that of the bulk alloy. In addition, the undercooling of the Sn3.0Ag0.5Cu nanoparticles was in the range of 82.0–88.5 °C at different cooling rates, which was much larger than that of the Sn3.0Ag0.5Cu micro-sized particles, showing stronger cooling rate dependence.     

Crystal orientation dependence of the out-of-plane dielectric properties for barium stannate titanate thin films

The orientation-dependent out-of-plane dielectric properties of barium stannate titanate (Ba(Sn_0.15Ti_0.85)O₃ (BTS)) thin films prepared by sol–gel method were investigated. Films with (1 0 0), (1 1 0), and (1 1 1) orientation were grown on LaNiO₃-buffered (1 0 0), (1 1 0), and (1 1 1) LaAlO₃ (LAO) single-crystal substrates, respectively. The different temperature of the dielectric constant maximum (T_m) of the BTS thin films with different orientation was believed to be attributing to stress inside the films. Films with the (1 1 1) orientation had higher relative dielectric constant and tunability than (1 0 0)- and (1 1 0)-oriented films. This difference in dielectric properties in these three kinds of oriented BTS films may be attributed to change in the direction and magnitude of electric polarization in orientation engineered BTS films and stress in the films.