四环阵天线的分析及其方向图赋形设计

四环阵天线技术 ,从美国引进以来 ,在 15 0 - 40 0 M频段各类通信系统中 ,已得到了极为广泛的应用 ,但迄今为止 ,尚未见到对这种天线进行讨论的专门文献。作者根据多年来的实践工作与设计经验 ,对四环阵天线进行了基本的分析 ,特别是对有重要实用价值的赋形波瓣异型四环阵的设计进行了充分的讨论。     

Electrochemical impedance studies of methanol oxidation on GC/Ni and GC/NiCu electrode

The electro-oxidation of methanol on nickel and nickel–copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) in a 1 M NaOH solution at different concentrations of methanol was studied by the method of ac-impedance spectroscopy. Two semicircles in the first quadrant of a Nyquist diagram were observed for electro-oxidation of methanol on GC/Ni corresponding to charge transfer resistance and adsorption of intermediates. Electro-oxidation of methanol on GC/NiCu shows negative resistance in impedance plots as signified by semi-circles terminating in the second quadrant. The impedance behavior shows different patterns at different applied anodic potential. The influence of the electrode potential on impedance pattern is studied and a mathematical model was put forward to quantitatively account for the impedance behavior of methanol oxidation. At potentials higher than 0.49 V vs. Ag/AgCl, a pseudoinductive behavior is observed but at higher than 0.58 V, impedance patterns terminate in the second quadrant. The conditions required for this behavior are delineated with the use of the impedance model.     

Solid Oxide Fuel Cells damage mechanisms due to Ni-YSZ re-oxidation: Case of the Anode Supported Cell

The effects of Ni-YSZ cermet re-oxidation in anode supported Solid Oxide Fuel Cells (SOFCs) have been investigated. Damage mechanisms have been studied in both cases of direct oxidation in air (i.e., fuel shutdown) or by an ionic current (i.e., fuel starvation).Direct oxidation tests show that the electrolyte cracks for a conversion degree of Ni into NiO ranging between ∼58 and ∼71%. This failure mode has been modelled considering both the bulk expansion of the cermet induced by the transformation of the Ni phase and the change of mechanical stresses in the multilayered cell.In the case of fuel starvation, a thin layer of the cermet was electrochemically re-oxidised at 800 °C and then reduced under a hydrogen stream. This ‘redox’ cycle was repeated until the degradation of the cell. The evolution of the impedance diagrams recorded after each cycle suggests that the cermet damages in an area close to anode/electrolyte interface. The mechanical modelling states that a delamination can occur along the interface between the Anode Functional Layer (AFL) and the Anode Current Collector (ACC) substrate. This theoretical result confirms the experimental trends observed by impedance spectroscopy.     

A survey on tree matching and XML retrieval

With the increasing number of available XML documents, numerous approaches for retrieval have been proposed in the literature. They usually use the tree representation of documents and queries to process them, whether in an implicit or explicit way. Although retrieving XML documents can be considered as a tree matching problem between the query tree and the document trees, only a few approaches take advantage of the algorithms and methods proposed by the graph theory. In this paper, we aim at studying the theoretical approaches proposed in the literature for tree matching and at seeing how these approaches have been adapted to XML querying and retrieval, from both an exact and an approximate matching perspective. This study will allow us to highlight theoretical aspects of graph theory that have not been yet explored in XML retrieval.     

A facile method to synthesize carbon coated Li1.2Ni0.2Mn0.6O2 with improved performance

Carbon-coated Li_1.2Ni_0.2Mn_0.6O₂ powders have been synthesized with Bakelite and heat process in air. The effect of carbon coating on the physical and electrochemical properties have been discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), discharge and rate tests. The carbon-coated cathode exhibits much improved first discharge capacity and rate capability than the pristine sample. The discharge capacity at 0.1 and 5.0 C rates are 246 and 125 mAhg⁻¹, while that of pristine are only about 222 and 49 mAhg⁻¹, respectively. The capacity retention of Li_1.2Ni_0.2Mn_0.6O₂ electrode after 50 cycles is improved from 89.8 to 97.5% after carbon coating. EIS results indicate that R_ct of Li_1.2Ni_0.2Mn_0.6O₂ electrode is decreased from 62 to 37 Ω after carbon coating.     

一种RFID标签天线视觉检测方法与实现

在此提出了一种RFID电子标签天线瑕疵逐片高速检测方法。该方法对工业相机拍摄的RFID天线图像进行模板图像与目标图像的对齐，利用图像差分输出两者的残余图像，通过对残余图像进行连通域分析实现对天线图像的高精度瑕疵检测。本检测方法的精度可达2×2 pixels，并已成功应用到RFID天线检测设备上，天线瑕疵尺寸检测精度可达0.2 mm×0.2 mm。     

Structural and electrical properties of grain boundaries in Ce0.85Gd0.15O1.925 solid electrolyte modified by addition of transition metal ions

In this work we present studies on applicability of transition metal additives as sintering and electrical conductivity aids for cerium gadolinium oxide electrolyte. The nanosized Ce_0.85Gd_0.15O_1.925 powder obtained by coprecipitation method was modified with Cr³⁺, Fe³⁺, Ni²⁺ or Cu²⁺ ions. Using high-intensity high-resolution X-ray powder diffraction data we have determined that Cr, Fe and Ni ions do not incorporate into the cerium gadolinium oxide surface or bulk when sintered at 1300 °C, but react with Gd ions to form Cr_0.9Gd_0.1O, GdFeO₃ and GdNiO₃ phases, while Cu incorporates in the material up to 0.7 mol% with a significant fraction of remaining material showing poorly crystalline CuO phase. The nanosized Ce_0.85Gd_0.15O_1.925 material shows already improved sintering properties than previous reports but full sintering is not achieved below 1300 °C, however Cr, Fe and mainly Cu impregnation allows full sintering at 1300 °C. 0.5 mol% Ni impregnated material sintered at 1500 °C shows enhanced grain boundary conductivity that probably indicates that Ni incorporates into Ce_0.84Gd_0.15O_1.925 above 1300 °C. The global results indicate, however, that optimization of ceria microstructure is at least of equal importance for sinterability and grain boundary conductivity than impregnation of the material with transition metal ions.     

Matching Trajectories of Anatomical Landmarks Under Viewpoint,Anthropometric and Temporal Transforms

An approach is presented to match imaged trajectories of anatomical landmarks (e.g. hands, shoulders and feet) using semantic correspondences between human bodies. These correspondences are used to provide geometric constraints for matching actions observed from different viewpoints and performed at different rates by actors of differing anthropometric proportions. The fact that the human body has approximate anthropometric proportion allows innovative use of the machinery of epipolar geometry to provide constraints for analyzing actions performed by people of different sizes, while ensuring that changes in viewpoint do not affect matching. In addition, for linear time warps, a novel measure, constructed only from image measurements of the locations of anatomical landmarks across time, is proposed to ensure that similar actions performed at different rates are accurately matched as well. An additional feature of this new measure is that two actions from cameras moving at constant (and possibly different) velocities can also be matched. Finally, we describe how dynamic time warping can be used in conjunction with the proposed measure to match actions in the presence of nonlinear time warps. We demonstrate the versatility of our algorithm in a number of challenging sequences and applications, and report quantitative evaluation of the matching approach presented.