一种高隔离度的双极化微带天线阵的理论和实验

本文提出利用双端口的串行角馈方形帖片实现双极化,并设计了一种共面的双极化馈线网络,综合运用多端口网络模型、腔模理论和分片法,给出了单口双端口天线单元和双极化天线阵列的理论分析。本文法计算简单便,适合于工程应用,实际设计了一副６ＧＨｚ频段的背地里层天线阵,实验测量的双端口隔离度达－４１ｄＢ,其性能明显优于通常的单层双极化微带天线阵,该面阵结构简单、馈线网络较小,且易合并成更大规模的双极化瑚线阵。     

一种有机化合物双光子荧光现象的实验研究

利用激光与有机化合物苯乙烯基并三苯溶液相互作用,我们得到了该化合物的单光子及双光子吸收荧光光谱,溶剂为二氧杂环已烷,在一定的波长范围内测量了双光子吸收的荧光偏振比率。实验结果证明了该有机化合物的激发态可通过单光子或双光子吸收获得,并指出激发态具有Ag对称性。     

Performance improvement of proton exchange membrane fuel cells with compressed nickel foam as flow field structure

In order to improve the performance of proton exchange membrane fuel cell (PEMFC), the compressed nickel foam as flow field structure was applied to the fuel cell. The fuel cell test system was built and the performance of fuel cells with nickel foam flow field with different thicknesses were tested and analyzed by electrochemical active surface area (EASA), electrochemical impedance and polarization curve. And its operating parameters were optimized to improve the performance of PEMFC. Our results show that the membrane electrode assembly (MEA) can show a larger catalytic active area and uniformity of gas diffusion can be improved by using the nickel foam flow field instead of the conventional graphite serpentine flow field, and the impedance characteristic of 110PPI nickel foam can be improved by increasing the compression ratio of the original material. What's more, the polarization characteristic and power output performance of PEMFC with nickel foam flow field were improved by optimizing the operating parameters. Using the optimized operating parameters (cell temperature = 80 °C; humidification temperature = 75 °C; stoichiometric ratio = 2; back pressure = 0.23 Map), a peak power density of 1.89 W cm⁻² was obtained with an output voltage of 0.46 V.     

Mo/Si/C多层膜退火后的同步辐射研究

通过对Mo/Si周期多层膜添加碳(C)层、进行高温退火处理,研究了Mo/Si/C多层膜进行热处理后在同步辐照条件下对薄膜相关物理特性的影响。发现Mo/Si周期性多层膜增加C层后不影响薄膜的反射特性,退火前45°入射角92 eV处反射率高达42％;热稳定性也有所提高,在600℃高温退火后仍能保持6.8％(97 eV处)的反射率。同时,由于非晶C在高温条件下的扩散导致薄膜结构发生变化,观测到薄膜的小角衍射曲线中出现并临的双衍射峰结构。     

Basic design of beamline and polarization control

The basic concept of synchrotron radiation beamlines for vacuum ultraviolet and X-ray experiments has been introduced to beginning users and designers of beamlines. The beamline defined here is composed of a front end, pre-mirrors, and a monochromator with refocusing mirrors, which are connected by beam pipes, providing monochromatic light for the experiments. Firstly, time characteristics of the synchrotron radiation are briefly reviewed. Secondly, the basic technology is introduced as the fundamental knowledge required to both users and designers. The topics are photoabsorption by air and solids, front ends and beam pipes, mirrors, monochromators, and filters. Thirdly, the design consideration is described mainly for the designers. The topics are design principle, principle of ray tracing, optical machinery and control, and vacuum. Fourthly, polarization control is considered. The topics are polarizers, polarization diagnosis of beamline, and circularly-polarized light generation. Finally, a brief summary is given introducing some references for further knowledge of the users and the designers.     

单氟磷酸钠在混凝土模拟孔隙液中的缓蚀特性

采用动电位极化曲线和电化学阻抗谱研究了Na2PO3F在模拟混凝土孔隙液中对钢筋的保护作用。Na2PO3F的加入导致混凝土钢筋的腐蚀电位负移,对钢筋的阴极和阳极电化学过程均有抑制作用,是一种混合型缓蚀剂。Na2PO3F能够在钢筋表面形成沉淀型保护膜,阻挡侵蚀性离子对钢筋的侵蚀。     

电磁脉冲对双层屏蔽腔的孔洞耦合特性研究

用时域有限差分(FDTD)法对电磁脉冲与双层屏蔽腔上孔洞的耦合特性进行了研究,计算了不同类型的孔阵对腔体内电场耦合系数的影响.计算结果表明,采用双层屏蔽使得腔体的屏蔽性能大大提高;另外,在双层屏蔽腔体上开孔洞方向垂直的长方形孔阵可以在任意极化方向上改善腔体的屏蔽性能,并且纵横比较大时效果较好.     

金属封装外壳烧结模具的设计

金属封装外壳是一种新发展起来的技术,虽然起步较早,但是最近几年才得到飞速发展和大量应用,不同结构的封装外壳需要不同结构的石墨模具定位烧结,讨论了封装外壳烧结模具的基本设计思路和注意要点,并对特殊种类的烧结模具做了相应的描述.     

Some particularities of the corrosion behaviour of Mg-Zn-Mn-Si-Ca alloys in alkaline chloride solutions

The influence of silicon and calcium on corrosion behaviour of Mg-6Zn-Mn alloys was investigated in alkaline solutions. The corrosion behaviour of the alloys with varied silicon and calcium content mainly depends on volume fractions and morphology of the intermetallics. In Cl-ion-free solutions silicon increased the corrosion resistance of alloys causing the growth of the surface passive film mostly composed of hydroxide products. Calcium had caused trouble to the formation of the stable protective film through the formation of Ca-Mg-Si intermetallics. In Cl-ion containing solutions intermetallic Ca-Mg-Si phase was responsible for extreme initial corrosion of Mg-6Zn-Mn-Si-Ca alloys.