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951.
分析研究了轴向流中简支弹性薄板大挠度流固耦合系统的振动响应和流场特性.板结构动力学方程采用基于位移的有限元法离散;流场采用二维不可压缩粘性流体N-S方程,并用有限体积法离散;在此基础上结合动网格控制技术,建立模拟双向流固耦合作用下轴向流中简支弹性薄板的二维数值模型.利用该数值模型得到了单块简支板随流速变化流致振动特性,研究了结构大挠度的振动稳定性,分别得到了Pitchfork分岔曲线和非线性系统结构的Hopf分叉曲线.通过轴向流恒定流速下不同间距的平行两块简支弹性薄板流固耦合的数值模拟得到了的流致振动特性. 相似文献
952.
针对基于ToA定位中存在的信标节点较少和发送时间不能提前预知的问题,提出了一种新的应用于无线传感网络室内定位的线性规划算法.通过考虑测量值的最小平均绝对值误差,利用线性逼近方法,将一个复杂的、非凸的室内定位问题转换为一个简单的线性规划问题,并用迭代求精的方法求出最优解.仿真结果表明,提出算法计算复杂度低,收敛速度快,可以快速地求出未知节点的坐标;通过和已有的定位算法相比,提出算法在信标节点较少的情况下,仍能保持很好的定位精度,利用较少的节点资源达到比已有算法更好的定位性能. 相似文献
953.
Fluorine is widely used as a lateral substituent to modify the physical properties of liquid crystals. Here, laterally monofluorinated compounds, 2-(4?-alkoxy-2-fluorobiphenyl-4-yl)-benzoxazole derivatives (nPPF(2)Bx) bearing different substituents (H, CH3, NO2, coded as nPPF(2)BH, nPPF(2)BM and nPPF(2)BN, respectively) at 5-position, were synthesised and characterised. It is interesting to note that these only display enantiotropic nematic mesophases with mesophase ranges of 12–28°C and 13–45°C on heating and cooling for nPPF(2)BH, 46–97°C and 62–120°C for nPPF(2)BM and 82–108°C and 87–113°C for nPPF(2)BN, which are very different from the corresponding monofluorine-substituted analogue (compounds I) with enantiotropic smectic or smectic/nematic mesophases. The enhanced nematic mesophase is attributed to the reduced π–π interaction/conjugation resulting from the twisted structure of the molecule caused by the introduction of a fluorine atom into the inter-ring of the biphenyl unit. These results suggest that modification of the monofluorine substituent position is an effective method to improve the nematic mesophase in benzoxazole-liquid crystals. 相似文献
954.
为了准确计算稠密等离子体电离平衡,在理想Saha方程的基础上,加入了压致电离理论和德拜理论相结合的修正。此电离模型可以描述稠密等离子体内电离机制随着密度的增加由热电离转变为压致电离的现象。压致电离理论结合德拜理论修正的 Saha 方程的计算结果与其它电离模型结果作了对比和分析。电离气体区域采用完全电离等离子体模型计算电子弛豫时间,而在凝聚态区域采用电子平均自由程计算电子弛豫时间。提出了将两个区域平滑连接起来的公式,从而建立了一种可以计算从理想等离子体态到凝聚态物质的半经验电导率模型,半经验模型计算结果与实验数据作了对比。 相似文献
955.
Ming Shi Ling-Bin Kong Jin-Bei Liu Kun Yan Jia-Jia Li Yan-Hua Dai Yong-Chun Luo Long Kang 《Ionics》2016,22(2):185-192
The poor electronic conductivity and low lithium-ion diffusion are the two major obstacles to the largely commercial application of LiFePO4 cathode material in power batteries. In order to improve the defects of LiFePO4, a novel carbon source polyacrylonitrile (PAN), which would form the hierarchical porous structure after carbonization, is fabricated and used. This work comes up with a simple and facile carbothermal reduction method to prepare porous-carbon-coated LiFePO4 (C-LiFePO4-PC) composite and to study the effect of carbon-coated temperature on ameliorating the electrochemical performance. The obtained C-LiFePO4-PC composite shows a high initial discharge capacity of 164.1 mA h g?1 at 0.1 C and good cycling stability as well as excellent rate capacity (49.0 mA h g?1 at 50 C). The most possible factors that improve the electrochemical performance could be related to the enhancement of electronic conductivity and the existence of porous carbon layers. In a word, the C-LiFePO4-PC material would become an excellent candidate for application in the fields of lithium-ion batteries. 相似文献
956.
Construction of Mononuclear Copper(II) and Trinuclear Cobalt(II) Complexes Based on Asymmetric Salamo‐Type Ligands
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Wen‐Kui Dong Jin‐Tong Zhang Yin‐Juan Dong Yang Zhang Zheng‐Kun Wang 《无机化学与普通化学杂志》2016,642(2):189-196
Mononuclear copper(II) and trinuclear cobalt(II) complexes, namely [Cu(L1)]2 · CH2Cl2 and [{Co(L2)(EtOH)}2Co(H2O)] · EtOH {H2L1 = 4,6‐dichloro‐6′‐methyoxy‐2,2′‐[1,1′‐(ethylenedioxydinitrilo)dimethylidyne]diphenol and H3L2 = 6‐ethyoxy‐6′‐hydroxy‐2,2′‐[1,1′‐(ethylenedioxydinitrilo)dimethylidyne]diphenol}, were synthesized and characterized by elemental analyses, IR and UV/Vis spectroscopy, and single‐crystal X‐ray diffraction. In the CuII complex, the CuII atom is four‐coordinate, with a N2O2 coordination sphere, and has a slightly distorted square‐planar arrangement. Interestingly, the obtained trinuclear CoII complex is different from the common reported 2:3 (L:CoII) salamo‐type CoII complexes. Infinite 2D layer supramolecular structures are formed via abundant intermolecular hydrogen bonding and π ··· π stacking interactions in the CuII and CoII complexes. 相似文献
957.
Electrochemical Investigations of Mn and Al Co‐doped Li2FeSiO4/C Cathodes for Li‐Ion Battery
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Few studies on orthosilicate cathodes co‐doped with two cations have been reported until now. Here, we report the synthesis of Mn and Al co‐doped Li2Fe0.8?xMn0.2AlxSiO4 (x = 0.05 and 0.1) by a solid‐state reaction route and characterized by X‐ray diffraction (XRD), particle size analysis, scanning electron microscopy (SEM), galvanostatic charge/discharge tests, and capacity intermittent titration technique (CITT), as compared to the single‐doped Li2Fe0.8Mn0.2SiO4. Though the co‐doping leads to a slight decreased capacity owing to the increased impurity and Al3+ inertia, a better cycling performance is obtained as expected. Especially when x is 0.05, the modified sample (Li2Fe0.75Mn0.2Al0.05SiO4) shows an initial discharge capacity of 159.3 mAh/g and high capacity retention of 78% after 50 charge/discharge cycles. The present work indicates that a synergistic effect of Mn and Al co‐substitution at the Fe site could partly make up the disadvantage of single Mn doping, and might provide an effective guide for the dopant incorporation to Li2FeSiO4 systems. 相似文献
958.
Picomolar detection of carcinoembryonic antigen in whole blood using microfluidics and surface‐enhanced Raman spectroscopy
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Kun Zou Zhigang Gao Quanfeng Deng Yong Luo Yao Lu Weijie Zhao Bingcheng Lin 《Electrophoresis》2016,37(5-6):786-789
Carcinoembryonic antigen (CEA) is a wide‐spectrum biomarker. Clinically, we generally use serum sample to detect CEA, which needs to be centrifuged to pretreat the raw blood sample. In this study, we realized direct CEA detection in raw blood samples exploiting microfluidics. The LOD was as low as 10?12 M. 相似文献
959.
This study analyzed the electrical properties of a multiple‐cells using the electric cell‐substrate impedance sensing, a scalable three‐dimensional electrode array and an equivalent circuit model (ECM). The experimental results validated the accuracy and validity of the extraction method for the ECM. The ECM simulation results using the electrical properties extracted by measuring 52 HeLa cells successfully forecasted the impedance magnitudes and phases for 15, 29, 78, and 98 HeLa cells. Comparing the ECM simulations and measurements, the maximum average errors in magnitude and phase were 3.06 % and 4.67 %, suggesting the number of HeLa cells can be classified by their electrical properties. 相似文献
960.