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排序方式: 共有146条查询结果,搜索用时 15 毫秒
1.
很多应用都需要使用在数字控制下切换模拟信号或数字信号的方法。这种开关的期望规格包括:当开关处于关断状态时,衰减小于90 dB;当开关处于打开状态时,失真不大于0.002%;以及能在10μs以内响应开、关命令的能力。另外,电路应 相似文献
2.
Eleonora M. Ungureanu Liviu Birzan George Buica Enache Cristian 《Electrochimica acta》2006,52(3):794-803
The cyclic voltammetry behavior of a series of five 1-substituted azulenes has been investigated as well as the electrochemical chlorination of these compounds. In the case of azulene compounds containing electron withdrawing groups which have higher oxidation potentials than that of the chloride ion, the electrochemical chlorination led usually to 3-chloro derivatives. The electrochemical chlorination fails for azulenes with lower oxidation potentials. Additionally some polyhalogenated compounds were obtained by controlled potential electrolyses. The paper also discusses the reaction mechanism of the electrochemical halogenation of 1-substituted azulenes. 相似文献
3.
This paper aims to present several clustering methods based on rank distance. Rank distance has applications in many different fields such as computational linguistics, biology and computer science. The K-means algorithm represents each cluster by a single mean vector. The mean vector is computed with respect to a distance measure. Two K-means algorithms based on rank distance are described in this paper. Hierarchical clustering builds models based on distance connectivity. This paper describes two hierarchical clustering techniques that use rank distance. Experiments using mitochondrial DNA sequences extracted from several mammals are performed to compare the results of the clustering methods. Results demonstrate the clustering performance and the utility of the proposed algorithms. 相似文献
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Gabriela Sacarescu Elena Taran Bogdan C Donose Mihaela Simionescu Valeria Harabagiu Liviu Sacarescu 《Polymer International》2012,61(12):1726-1732
To produce surface plasmons, silver nanoparticles are synthesized in situ in a pseudo‐template system based on polyhydrosilanes. Adsorption on the silver nanoparticle surface produces a thin layer of polymer with properties different from those of bulk polysilane. The metal‐adsorbed polymer layer serves as a spacer between the polysilane fluorophore and the plasmonic nanoparticle. This prevents quenching of the polysilane emission and leads to a strong surface‐enhanced fluorescence through coupling of surface plasmons having a resonance frequency that matches the emission frequency of the polymeric emitter. Copyright © 2012 Society of Chemical Industry 相似文献
7.
Aaron J. Welsh Denis Dezest Liviu Nicu Susan Trolier‐McKinstry 《Journal of the American Ceramic Society》2017,100(3):848-858
The functional properties of electroceramic thin films can be degraded by subtractive patterning techniques used for microelectromechanical (MEMS) applications. This work explores an alternative deposition technique, where lead zirconate titanate (PZT) liquid precursors are printed onto substrates in a desired geometry from stamp wells (rather than stamp protrusions). Printing from wells significantly increased sidewall angles (from ~1 to >35 degrees) relative to printing solutions from stamp protrusions. Arrays of PZT features were printed, characterized, and compared to continuous PZT thin films of similar thickness. Three‐hundred‐nanometer‐thick printed PZT features exhibit a permittivity of 730 and a loss tangent of 0.022. The features showed remanent polarizations of 26 μC/cm2, and coercive fields of 95 kV/cm. The piezoelectric response of the features produced an e31,f of ?5.2 C/m2. This technique was also used to print directly atop prepatterned substrates. Optimization of printing parameters yielded patterned films with 90° sidewalls. Lateral feature sizes ranged from hundreds of micrometers down to one micrometer. In addition, several device designs were prepatterned onto silicon on insulator (SOI) wafers (Si/SiO2/Si with thicknesses of 0.35/1/500 μm). The top patterned silicon was released from the underlying material, and PZT was directly printed and crystallized on the free‐standing structures. 相似文献
8.
Asymmetric four point bend specimens are often used for determination mode II fracture toughness. Different corrections were
proposed to classical solution of Stress Intensity Factors for this specimen. This paper provides a solution for a bi-material
four point specimen with sub-interface crack. The solutions were obtained using Finite Element Analysis, and the effect of
crack distance to interface, crack length and materials combination were investigated. 相似文献
9.
Sergiu Coseri Alina Spatareanu Liviu Sacarescu Vlad Socoliuc Ioan Sorin Stratulat Valeria Harabagiu 《应用聚合物科学杂志》2016,133(5)
Ultrasmall superparamagnetic iron oxide (Fe3O4) nanoparticles coated by biocompatible pullulan (Pu‐USPIO) with sizes below 10 nm and having a magnetite core and a hydrophilic outer shell of pullulan were prepared. The formed Pu‐USPIOs were thoroughly characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy, and small‐angle X‐ray scattering experiments. The content of magnetic nanoparticles embedded into the pullulan matrix was determined by thermogravimetric analysis. Vibrating sample magnetometry analysis was used to evaluate the magnetic properties of the Pu‐USPIO samples. Because of the presence of pullulan, these nanoparticles could be conditioned in many versatile forms, from a clear solution to magnetic films, for potential applications, including magnetic hyperthermia mediators. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42926. 相似文献
10.
Thermally induced bending vibration of spacecraft booms modeled as circular thin-walled beams of closed cross section and subjected to thermal radiation is investigated. One assumes that the boom is built up of composite material systems, and in this context, the constituent materials of the beam include nonclassical effects such as anisotropy and transverse shear. In addition, in order to induce beneficial elasticcouplings, a special ply-angle distribution achieved via the usual helically wounding fiber-reinforced technology is implemented. Both the dynamic governing equations involving the temperature effects and the related boundary conditions are obtained via the application of the extended Hamilton principle. The case of the spacecraft boom equipped with a concentrated mass at its free end, fixed at the other end, and exposed to solar radiant heating is studied from both the induced-vibration and stability points of view. The numerical simulations display deflection time history of bending displacements as a function of the fiber orientation of the composite materials, damping factor, and angle of incidence of heat radiation. The obtained results are likely to fill a gap in the specialized literature and to play a good role toward a better understanding of the factors that contribute not only to the occurrence of the thermal flutter instability, but also to its avoidance. 相似文献