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991.
55-nm rubber particles significantly toughened two epoxy systems without loss of Young’s modulus, tensile strength and glass transition temperature. Transmission Electron Microscopy (TEM) showed that the nanoparticles are uniformly dispersed in matrix and have blurred interface with epoxy. 5 wt% rubber nanoparticles increased the critical strain energy release rate (G1c) of Jeffamine D230 (J230)-cured epoxy from 175 J/m2 to 1710 J/m2, while the 10 wt% increased G1c of diaminodiphenyl sulfone (DDS)-cured epoxy from 73 J/m2 to 696 J/m2. This is explained by comparing the surface-surface interparticle distance and total particle surface of nanocomposites with those of composites. The higher the matrix stiffness, the more nanoparticles needed for toughening. Although the 10 wt% J230-cured nanocomposite showed a 50% larger size of stress-whitened zone than the 5 wt% J230-cured nanocomposite, the 5 wt% nanocomposite showed a higher toughness. These nanoparticles were found to pose barriers to the vibration of crosslinked matrix molecules, leading to higher glass transition temperatures. While the matrix shear banding caused by nanoparticle expansion and growth is the major toughening mechanism for the J230-cured nanocomposites, the matrix plastic void growth and deformation are most probably the major mechanisms for the DDS-cured system. Under tensile loading, the nanoparticles in the DDS-cured epoxy created fibrils of 100-200 nm in diameter and 3-5 μm in length. TEM analysis in front of a subcritically propagated crack tip showed a number of voids of 30-500 nm in diameter in the vicinity of the crack, implying that rubber nanoparticles expanded, grew and deformed under loading. Unlike conventional epoxy/rubber composites in which all of the rubber particles in the crack front cavitated under loading, only a portion of the nanoparticles in this study expanded to create voids. Huang and Kinloch’s model developed from composites was found not fit well into these nanocomposites. 相似文献
992.
993.
目的构建下游可以共表达人白细胞介素12(hIL12)双亚基的双顺反子真核表达载体pVAX1-IRES-hIL12。方法通过搭桥PCR获得人白细胞介素12P35及P40双亚基的融合基因P35-F2A-P40,插入DNA疫苗载体pVAX1-IRES的下游,瞬时转染293-T细胞,ELISA检测融合基因的表达。结果酶切鉴定和序列分析表明融合基因与设计完全一致,融合基因在体外细胞培养液检测中获得分泌表达。结论该载体的成功构建可以为肿瘤基因疫苗研制提供免疫增效载体。 相似文献
994.
探讨了无线通信系统的调制、编码、解调、译码等信号处理功能以及无线信道的GUI界面设计与仿真实现。首先将无线通信系统拆分为调制器和解调器、采样器和滤波器以及编码器和解码器等模块;然后通过各种信号处理函数对输入信号进行信号处理模块功能仿真;最后通过GUI编程实现各个通信系统模块的调用和链接,从而最终实现无线通信系统的调制和编码、解调和译码等信号处理仿真和无线通信信道仿真。通过基于Matlab的GUI界面设计和仿真结果表明,可以有效地对无线通信系统进行功能仿真,对于利用软件无线电技术构建无线通信具有十分重要的参考意义。 相似文献
995.
Khanh Tuan Le 《今日电子》2010,(3):44-45
今日相容于IEEE802.15.4且适用于ZigBee的无线射频收发器、微控制器及系统单芯片(SOC)半导体装置已相当普及。高度整合的多功能SOC解决方案是促成ZigBee无线网络得以广泛运用在众多应用中的重要因素,包括工业监控、家庭及建筑自动化、传感器网络,乃至于无线医疗解决方案。在以上解决方案中增添无线射频装置的定位功能使得这些网络的价值得以大幅提升。 相似文献
996.
Within the concepts under study for the geological disposal of intermediate-level long-lived waste, cement-based materials are considered as candidate materials. The clayey surrounding rock and the cement-based material being considered differ greatly in their porewater composition. Experiments are conducted on the diffusion of solutes constituting those porewaters in a confined clay/cement composite system using cells. The test temperature was set at 25 °C and 2, 6 and 12 months. Results supply new information: carbonation is low and not clog the interface. Such absence of carbonation allows for the diffusion of aqueous species and, thus, for the degradation of the cement paste and the illitisation of illite/smectite interstratifications. The cement material is subjected to a decalcification: portlandite dissolution and a CaO/SiO2 reduction in the calcium silicate hydrate. The sulphate in diffusion induces non-destructive ettringite precipitation in the largest pores. After 12 months, about 800 µm of cement material is concerned by decalcification. 相似文献
997.
Le Yu 《Electrochimica acta》2010,55(3):1258-348
Li2Se-Sb2Se3 nanocomposites with a highly heterogeneous mixture have been fabricated by reactive pulsed laser deposition method. The electrochemical properties of the as-deposited Li2Se-Sb2Se3 thin film during the first charging and discharging have been investigated by the galvanostatic cycling and cyclic voltammetry measurements for the first time. By using ex situ X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and selected-area electron diffraction (SAED) measurements, the decomposition of Li2Se driven by Sb2Se3 under the electrochemical potential is revealed. In the first cycle, the oxidation peaks at 2.5 V and 3.2 V and the reduction peaks at 2.0 V can be attributed to the decomposition and formation of Li2Se with the conversion reaction of Sb2Se3 into Sb2Se5. Our findings demonstrate that nanocomposite Li2Se-Sb2Se3 can possess very high electrochemical activity. These results present a special case of solid-state heterogeneous electrochemistry with both nanostructured binary materials. 相似文献
998.
文章首先介绍了Femtocell飞小区的特性和网络架构,分析了Femtocell相比传统的CDMA室内覆盖技术的优点,最后深入剖析了目前Femtocell室内覆盖技术存在的问题并提出解决方案。 相似文献
999.
S.A. Moya M. Vidal G. Abarca C. Martinez V. Guerchais H. Le Bozec M.T. Garland S. Rodriguez P. Aguirre 《Inorganic chemistry communications》2010,13(12):1519-1521
The synthesis and characterization of new ruthenium(II) carbonyl complexes containing polypyridine and triphenylphosphine ligands is reported. Crystallographic information obtained for the trans-PPh3-[Ru(biq)(PPh3)2(CO)]Cl2 complex (biq = 2,2’-biquinoline) reveals five-coordination on the metal. The complexes were studied as catalysts in hydrogen transfer reactions in basic solution. Turnover frequencies in the 2250-817 h-1 range were determined in 1 hour of reaction with a substrate/catalysts ratio of 830. 相似文献
1000.
Modified ESPRIT (M-ESPRIT) algorithm for time delay estimation in both any noise and any radar pulse context by a GPR radar 总被引:1,自引:0,他引:1
This paper presents M-ESPRIT, a modified version of the ESPRIT algorithm, for the purpose of time delay estimation of backscattered radar signals. The proposed algorithm takes both the transmitted pulse shape and any noise into account. It can process raw data from experimental device without the preprocessing which would be required with the conventional ESPRIT algorithm. 相似文献