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81.
It is shown that the space of infinitesimal deformations of 2k-Einstein structures is finite dimensional on compact non-flat space forms. Moreover, spherical space forms are shown to be rigid in the sense that they are isolated in the corresponding moduli space. 相似文献
82.
A joint chemical reactor system referred to as an ultrasonic-intensified micro-impinging jetting reactor (UIJR), which possesses the feature of fast micro-mixing, was proposed and has been employed for rapid preparation of FePO4 particles that are amalgamated by nanoscale primary crystals. As one of the important precursors for the fabrication of lithium iron phosphate cathode, the properties of FePO4 nano particles significantly affect the performance of the lithium iron phosphate cathode. Thus, the effects of joint use of impinging stream and ultrasonic irradiation on the formation of mesoporous structure of FePO4 nano precursor particles and the electrochemical properties of amalgamated LiFePO4/C have been investigated. Additionally, the effects of the reactant concentration (C = 0.5, 1.0 and 1.5 mol L−1), and volumetric flow rate (V = 17.15, 51.44, and 85.74 mL min−1) on synthesis of FePO4·2H2O nucleus have been studied when the impinging jetting reactor (IJR) and UIJR are to operate in nonsubmerged mode. It was affirmed from the experiments that the FePO4 nano precursor particles prepared using UIJR have well-formed mesoporous structures with the primary crystal size of 44.6 nm, an average pore size of 15.2 nm, and a specific surface area of 134.54 m2 g−1 when the reactant concentration and volumetric flow rate are 1.0 mol L−1 and 85.74 mL min−1 respectively. The amalgamated LiFePO4/C composites can deliver good electrochemical performance with discharge capacities of 156.7 mA h g−1 at 0.1 C, and exhibit 138.0 mA h g−1 after 100 cycles at 0.5 C, which is 95.3% of the initial discharge capacity. 相似文献
83.
Owing to high-energy density of rechargeable lithium-ion batteries (LIBs), they have been investigated as an efficient electrochemical power sources for various energy applications. High theoretical capacities of tin oxide (SnO2) anodes have led us a path to meet the ever-growing demands in the development of high-performance electrode materials for LIBs. In this paper, a facile approach is described for the synthesis of porous low-dimensional nanoparticles and nanorods of SnO2 for application in LIBs with the help of Tween-80 as a surfactant. The SnO2 samples synthesized at different reaction temperatures produced porous nanoparticles and nanorods with average diameters of ~7–10 nm and ~70–110 nm, respectively. The SnO2 nanoparticle electrodes exhibit a high reversible charge capacity of 641.1 mAh/g at 200 mA/g after 50 cycles, and a capacity of 340 mAh/g even at a high current density of 1000 mA/g during the rate tests, whereas the porous nanorod electrodes delivers only 526.3 mAh/g at 200 mA/g after 50 cycles and 309.4 mAh/g at 1000 mA/g. It is believed that finer sized SnO2 nanoparticles are much more favorable to trap more Li+ ion during electrochemical cycling, resulting in a large irreversible capacity. In contrast, rapid capacity fading was observed for the porous nanorods, which is the result of their pulverization resulting from repeated cycling. 相似文献
84.
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86.
为进一步研究霍尔推进器壁面二次电子发射对推进器性能的影响,采用流体模型数值模拟了二次电子磁化效应的等离子体鞘层特性.得到二次电子磁化鞘层的玻姆判据.讨论了不同的磁场强度和方向、二次电子发射系数以及不同种类等离子体推进器的鞘层结构.结果表明:随器壁二次电子发射系数的增大,鞘层中粒子密度增加,器壁电势升高,鞘层厚度减小;鞘层电势及粒子密度随着磁场强度和方位角的增加而增加;而对于不同种类的等离子体,壁面电势和鞘层厚度也不同.这为霍尔推进器的磁安特性实验提供了理论解释.
关键词:
霍尔推进器
磁鞘
二次电子 相似文献
87.
The characteristic connection of an almost hermitian structure is a hermitian connection with totally skew-symmetric torsion. The case of parallel torsion in dimension 6 is of particular interest. In this work, we give a full classification of the algebraic types of the torsion form, and, on the basis of this, undertake a systematic investigation into the possible geometries. Numerous naturally reductive spaces are constructed and classified, and examples on nilmanifolds given. 相似文献
88.
A fabrication of all-solid-state thin-film rechargeable lithium ion batteries by sol-gel method is expected to achieve both the simplification and cost reduction for fabrication process. TiO2 thin film electrode was prepared by PVP (polyvinylpyrrolidone) sol-gel method combined with spin-coating on Li1 + xAlxGe2 − x(PO4)3 (LAGP) solid electrolyte which has wide electrochemical window. The thin film was composed of anatase TiO2 that is the most active phase for Li insertion and extraction and contacted well with LAGP substrate. In the cyclic voltammogram, a redox couple was observed at 1.8 V vs. Li/Li+ assigned to Li insertion/extraction into/from anatase TiO2, indicating that the thin film worked as electrode for lithium battery. The charge and discharge test in various charge and discharge rates revealed that the discharge process (delithiation) is thought to be faster than charge process (lithiation). It is attested that the sol-gel process, which derives both simplification and cost reduction for fabrication process, can be applied to thin film battery using LAGP solid electrolyte. 相似文献
89.
Experimental investigations on a sodium ion conducting gel polymer electrolyte nanocomposite based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), dispersed with silica nanoparticles are reported. The gel nanocomposites have been obtained in the form of dimensionally stable, transparent and free-standing thick films. Physical characterization by X-ray diffraction (XRD), Fourier transform Infra-red (FTIR) spectroscopy and Scanning electron microscopy (SEM) have been performed to study the structural changes and the ion-filler-polymer interactions due to the dispersion of SiO2 nanoparticles in gel electrolytes. The highest ionic conductivity of the electrolyte has been observed to be 4.1 × 10−3 S cm− 1 at room temperature with ~ 3 wt.% of SiO2 particles. The temperature dependence of the ionic conductivity has been found to be consistent with Vogel-Tammen-Fulcher (VTF) relationship in the temperature range from 40 to 70 °C. The sodium ion conduction in the gel electrolyte film is confirmed from the cyclic voltammetry, impedance analysis and transport number measurements. The value of sodium ion transport number (tNa+) of the gel electrolyte is significantly enhanced to a maximum value of 0.52 on the 15 wt.% SiO2 dispersion. The physical and electrochemical analyses indicate the suitability of the gel electrolyte films in the sodium batteries. A prototype sodium-sulfur battery, fabricated using optimized gel electrolyte, offers the first discharge capacity of ~165 mAh g− 1 of sulfur. 相似文献
90.
Masahide Tona Hirofumi Watanabe Satoshi Takahashi Nobuo Yoshiyasu Toshifumi Terui Chikashi Yamada 《Surface science》2007,601(3):723-727
Using scanning tunneling microscopy (STM) and time of flight secondary ion mass spectrometry (TOF/SIMS), we observed radiation effects on a Si(1 1 1)-(7 × 7) surface in the collision of a single highly charged ion (HCI) with a charge state q up to q = 50. The STM observation with atomic resolution revealed that a nanometer sized crater-like structure was created by a single HCI impact, where the size increased rapidly with q. The secondary ion yields also increased with q in which multiply charged Si ions (Sin+) were clearly observed in higher q HCI-collisions. The sputtering mechanism is briefly discussed, based on the so-called Coulomb explosion model. 相似文献