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991.
YAG(Y3Al5O12) powder was prepared by co-precipitation method.To avoid pH values changing intensely during titration process,the 4 3 NH HCO solution with 4 3 NH NO was used as precipitant solution.The pH change of precipitant solution during titration process,compositions of precursor,phase formation process and morphology of the prepared powder were investigated by means of pH meter,FT-IR,XRD and TEM.The results show that the presence of 4 3 NH NO in 4 3 NH HCO solution is crucial to alleviate the pH change,lower the calcination temperature and meliorate the morphology of YAG powder.The mechanisms were studied in detail.The YAG phase can be obtained at a lower temperature of 900 ℃.The obtained powder,composed of elliptical particles,showed a meliorated morphology. 相似文献
992.
993.
Ad hoc网络时钟同步研究* 总被引:1,自引:1,他引:0
为解决时钟同步方案存在依赖特殊节点以及算法精度不高等问题,在组网过程与自组网互同步相结合的基础上,完成网络节点的时钟同步,并通过测量网络延迟以提高同步精度.方案在一跳场景下验证,可将误差维持在15μs左右,提高了同步精度,并且本方案不需要特殊节点,各个节点只需要收到一个同步帧就可以自发地调整时钟,同步帧的开销小、实现简单,适用于多跳和灵活易变的Ad hoc网络. 相似文献
994.
红外与可见光复合寻的制导中的快速图像配准方法 总被引:3,自引:0,他引:3
对现有多传感器图像配准方法在红外与可见光复合寻的制导应用中存在的计算量大等不足,提出了一种基于部分Hausdorff距离的快速方法和一种两集合相似度的定义,从而实现了有效减小误匹配特征点对的红外与可见光图像快速配准方法.此算法通过分别提取两幅图像边缘上显著特征点,再根据提出的快速方法和两集合相似度定义,粗略估计出图像间的旋转角度、平移量;然后依据此估计值,缩小特征点匹配时匹配特征点搜索范围,求得一致特征点对;最后用最小二乘法求解最优变换参数.实验结果表明了该方法的有效性、快速性. 相似文献
995.
Ultralight X-type lattice sandwich structure (I): Concept,fabrication and experimental characterization 总被引:1,自引:1,他引:0
ZHANG QianCheng HAN YunJie CHEN ChangQing & LU TianJian State Key Laboratory for Mechanical Behavior of Materials School of Material Science Engineering Xi’an Jiaotong University Xi’an China MOE Key Laboratory for Strength Vibration School of Aerospace Department of Engineering Mechanics AML Tsinghua University Beijing 《中国科学E辑(英文版)》2009,52(8):2147-2154
A new type of ultra-lightweight metallic lattice structure (named as the X-type structure) is reported. This periodic structure
was formed by two groups of staggered struts in the traditional pyramid structure, and fabricated by folding expanded metal
sheet along rows of offset nodes and then brazing the folded structure (as the core) with top and bottom facesheets to form
sandwich panels. The out-of-plane compressive and shear properties of the X-type lattice sandwich structure were investigated
experimentally and compared to those of the sandwich having a pyramidal truss core. It is found that the formation of the
2-dimensional staggered nodes can effectively make the X-type structure more resistant to inelastic and plastic buckling under
both compression and shear loading than the pyramidal lattice truss. Obtained results show that the compressive and shear
peak strengths of the X-type lattice structure are about 30% higher than those of the pyramidal lattice truss having the same
relative density.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2006CB601202), the National Natural Science
Foundation of China (Grant Nos. 10632060,10825210), the National “111” Project of China (Grant No. B06024) and the National
High-Tech Research and Development Program of China (“863” Project) (Grant No. 2006AA03Z519) 相似文献
996.
Liang Wang XiaoShuang Chen Wei Lu Yan Huang XiaoFang Wang JiJun Zhao 《中国科学E辑(英文版)》2009,52(7):1928-1932
The structural and optical properties of amorphous semiconductor mercury cadmium telluride (a-MCT) are obtained by the first
principles calculations. The total pair distribution functions and the density of states show that the a-MCT has the semiconductor
characteristic. The calculated results of dielectric function show that E
2 peak of the imaginary of dielectric function for the crystal mercury cadmium telluride abruptly disappears in the amorphous
case due to the long-range disorders. And the imaginary of dielectric function of a-MCT shows a large broad peak, which is
in agreement with the available results of other amorphous semiconductors. From the linear extrapolation of the curve ħωɛ
2(ω)1/2 versus ħω, it can be obtained that the optical energy gap of amorphous semiconductor Hg0.5Cd0.5Te is 0.51±0.05 eV.
Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2007CB613205), the National Natural Science
Foundation of China (Grant Nos.10725418, 10734090, 60576068), the Key Fund of Shanghai Science and Technology Foundation (Grant
No. 08JC1421100) and the Knowledge Innovation Program of the Chinese Academy of Sciences 相似文献
997.
HongBo Lan YuCheng Ding HongZhong Liu YeRong Que WeiWei Tao HanSong Li BingHeng Lu 《中国科学E辑(英文版)》2009,52(2):294-302
UV-nanoimprint lithography (UV-NIL) using a soft mold is a promising technique with low cost and high throughput for producing the submicron scale large-area patterns. However, the deformations of the soft mold during imprinting process which can cause serious consequences have to be understood for the practical application of the process. This paper investigated the deformation of the soft mold by theoretical analyses, numerical simulations, and experimental studies. We simulated the mold deformation using a simplified model and finite element method. The simulation and the related experimental results agree well with each other. Through the investigation, the mechanism and affected factors of the mold deformation are revealed, and some useful conclusions have been achieved. These results will be valuable in optimizing the imprinting process conditions and mold design for improving the quality of transferred patterns. 相似文献
998.
Multi-channel micro neural probe fabricated with SOI 总被引:1,自引:0,他引:1
WeiHua Pei Lin Zhu ShuJing Wang Kai Guo Jun Tang Xu Zhang Lin Lu ShangKai Gao HongDa Chen 《中国科学E辑(英文版)》2009,52(5):1187-1190
Silicon-on-insulator(SOI) substrate is widely used in micro-electro-mechanical systems(MEMS).With the buried oxide layer of SOI acting as an etching stop,silicon based micro neural probe can be fabri-cated with improved uniformity and manufacturability.A seven-record-site neural probe was formed by inductive-coupled plasma(ICP) dry etching of an SOI substrate.The thickness of the probe is 15 μm.The shaft of the probe has dimensions of 3 mm×100 μm×15 μm with typical area of the record site of 78.5 μm2.The im... 相似文献
999.
运用协整和VAR模型从人力资本角度分析其对我国出口贸易额的动态影响,结果表明:人力资本是出口贸易增长的Granger原因,他们之间存在长期的动态稳定关系。脉冲响应分析揭示人力资本对出口额有稳定持续的正的产出弹性,方差分解显示人力资本对出口的贡献占60%多。因此国家必须加大人力资本投资,增加人力资本存量,发挥其内部和外部效应,起到促进出口健康、持续增长的作用。 相似文献
1000.
动态网络中的高效多故障诊断技术 总被引:1,自引:0,他引:1
针对已有算法复杂度较高,不适用于规模较大网络的问题,将被管系统建立成动态贝叶斯模型,并提出一种能处理多故障的近似推理算法. 通过复杂度分析,证明该近似算法时间复杂度为多项式级,远远低于精确算法的时间复杂度下限,可以用于解决大规模动态网络的故障诊断问题. 实验结果证明,新算法在准确度方面虽然略低于精确算法,但执行效率上远远高于精确算法. 相似文献