共查询到20条相似文献,搜索用时 15 毫秒
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采用固相法首次合成了碳包覆的掺杂不同金属离子的锂离子电池负极材料Li3.9M0.1Ti5O12/C(M=Mn、Cu、Mg),对材料进行了循环伏安测试及恒电流充放电测试。结果表明:金属掺杂未改变材料的晶体尖晶石结构,由于金属离子对Li4Ti5O12的晶胞内部的掺杂和C对其外部的包覆,使复合材料的锂离子扩散速率、大电流循环稳定性和可逆容量都明显提高。在1C充放电循环时,Li3.9Mn0.1Ti5O12/C、Li3.9Cu0.1Ti5O12/C、Li3.9Mg0.1Ti5O12/C首次放电容量分别达到156.6,162.4和169.8 mAh/g;50次循环后,容量分别保持在155.4,159.6和169.7 mAh/g,展示了优良的电化学特性。 相似文献
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Jianhong Yang Yong Zhang Xueyuan Cai Lin Li 《Journal of Infrared, Millimeter and Terahertz Waves》2009,30(6):611-621
The effects of different metallic vane-loaded helix slow-wave structures of a traveling-wave tube are proposed based on the
analysis of the Fourier expansions of the exterior region with metallic vanes. The influences of the metallic vanes dimensions
on the phase velocity and interaction impedance are considered in detail. The computed data is compared with the reference
data in the 0−16 GHz frequency range with a good consistency. The analytical results reveal that the method of using Fourier
expansions can contribute effectively to the reducing of the error between the theoretical and experimented data (around 1.2%).
By analyzing the computed results, the performances of the helix slow-wave structure, with T-shaped metallic vanes are superior
to the sector-shaped with the same designed parameters. Adjustments can be made to the outer radius of T-shaped metallic vanes
which then control the dispersion relation showing either negative or positive, and it is similar to sector-shaped vanes by
adjusting its inner radius. And with increasing the distance between the helix and metallic vanes, the dispersion characteristics
and interaction impedance of the helix slow-wave structure with T-shaped/sector-shaped metallic vane are all improved. 相似文献
4.
In this paper the scattering from an infinite metallic or dielectric cylinder of electrically small radius, embedded into a dielectric cylinder, is considered. The problem is solved by the method of separation of variables, in conjunction with translational addition theorems. Analytical expressions are obtained for the scattered field and the various scattering cross-sections, when the radius of the inner cylinder is electrically small. Both polarizations are considered for normal incidence. Numerical results are given for various values of the parameters and for metallic or dielectric inner cylinder 相似文献
5.
基片集成同轴线(Substrate Integrated Coaxial Line,SICL)是一种由基板上下导体板、内导体和金属化过孔阵列构成的集成波导结构,具有低损耗、宽频带、抗干扰、易于集成等优点。本文在基片集成同轴线的基础上提出了一种新型的双L型基片集成同轴互连阵列结构。首先通过仿真将它与传统的微带线和带状线进行了对比,结果表明该结构在损耗、反射以及隔离度方面均表现出优良的特性。然后采用低温共烧陶瓷(LTCC)工艺实现该结构,并通过实验测试了该样品的S参数、隔离性能、眼图及误码率。实验结果表明,在1~40GHz的频率范围内,双L型基片集成同轴互连阵列的耦合度在-40 d B以下,传输速率可达到30 Gbps,具有高速数据传输能力。 相似文献
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《Electromagnetic Compatibility, IEEE Transactions on》2008,50(4):928-939
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Roumeliotis J.A. Kakogiannos N.B. Kanellopoulos J.D. 《Microwave Theory and Techniques》1995,43(1):155-168
In this paper, the scattering of a plane electromagnetic wave from a metallic or dielectric sphere of electrically small radius, embedded into a dielectric one, is considered. The classical method of separation of variables is used, combined with translational addition theorems for spherical vector wave functions. Analytical expressions are obtained for the scattered field and the various scattering cross-sections, in the case of an inner sphere with electrically small radius. Numerical results are given for various values of the parameters and for metallic and dielectric inner sphere. Some remarks are made about the possibility of detection or identification of inhomogeneities or nonsymmetries 相似文献
8.
Jinfeng Zhu Baoqing Zeng Xingcong Liu Shikai Tian Zhonghai Yang 《Journal of Infrared, Millimeter and Terahertz Waves》2009,30(1):94-102
A micro-triode structure based on coaxial nanostructure made of an inner carbon nanotube emitter, insulator layer, coaxial
metallic outer conductor as a gate, and separated anode is suggested. According to the Fowler-Nordheim equation, its electron
emission performance was evaluated via MAGIC code simulation. Contours of the electrostatic potential variable around the
emitter, emission electron trajectories, and gate interceptive current were analyzed. A circuit model was proposed for the
triode, while the DC and the THz range AC characteristics were simulated, which indicates the ability of the device to perform
in the THz frequency range. 相似文献
9.
通过计算多层薄膜结构的特征矩阵,应用微波网络的思想导出了金属背景多层薄膜结构反射系数的计算方法,并举例验证了该计算方法的正确性,为金属背景多层薄膜结构电磁散射的近似计算提供了理论基础. 相似文献
10.
Proposed is a novel RFID tag antenna consisting of an inner spiral dipole, an outer bent dipole and a double T-matching network that is suitable for attaching to metallic objects. For low-cost fabrication, the antenna is printed on a single-layer substrate without a ground plane or shorting pins. The detailed design parameters of the antenna were optimised using the Pareto genetic algorithm so that the antenna would operate adequately both in fiee space and on metallic objects. The antenna was fabricated, based on the optimised design, and the performance in fiee space and on a metallic surface were measured. The half-power matching bandwidth (VSWR < 5.8) and the reading range of the antenna in fiee space were 7.6% and 2.8 m, while on a metallic surface the corresponding values were 0.8% and 1.8 m. For non-metallic surfaces (i.e. low dielectric targets, 2 < epsivr < 4), the antenna exhibited the reading range of 2-3 m. 相似文献
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通过对电子管电视发射机中常用金属陶瓷电子管内部结构和各个电极作用的简要介绍,着重在如何能够延长金属陶瓷电子管的使用寿命方面做了详细阐述,并提出了电子管在日常维护、保养、使用当中应注意的问题。 相似文献
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The effects of vitrification and cold rolling on the structure in a metallic glass of Pd.775Cu.06Si.165 alloy and crystalline Pd have been investigated using positron lifetime and angular correlation measurements. It is concluded
that: A) the metallic glass contains a negligible concentration of vacancy-like defects and the crystallite model may be excluded
as a possible structure of metallic glasses, B) the glass-crystalline boundaries contain a very small fraction of vacancy-like
defects and exhibit a smooth transition structure from glassy to crystalline regions, C) the cold rolling of the metallic
glass induces no vacancy or dislocation-like defects and plastic flow in metallic glasses is accompanied by cooperative atomic
regroupings somewhat analogous to the visco flow of glasses near the glass transition temperature, D) the electronic structure
of the Pd-Cu-Si alloy alters little upon disordering from a crystalline to glassy state, but exhibits a large change from
that of crystalline Pd. This is attributed to the valence electrons transferred from Si to the d-shell of Pd in the Pd-Cu-Si
alloy. 相似文献
14.
Numerical conformal mapping is exploited as a simple, accurate, and efficient tool for the analysis and design of coaxial waveguides and couplers of complex cross section. An implementation based on the Schwarz-Christoffel Toolbox, a public-domain MATLAB package, is applied to slotted coaxial cables and to symmetrical coaxial couplers, with circular or polygonal inner conductors and external shields. The effect of metallic diaphragms of arbitrary thickness, partially separating the inner conductors, is also easily taken into account. The proposed technique is validated against the results of the finite-element method, showing excellent agreement at a fraction of the computational cost, and is also extended to the case of nonsymmetrical couplers, providing the designer with important additional degrees of freedom. 相似文献
15.
金属表面超高频RFID印刷标签天线设计 总被引:1,自引:1,他引:0
为满足对金属表面物体智能识读的应用需求,设计了一款可用于金属表面的超高频RFID电子标签天线,使用时将标签贴合在厚度仅为5mm的泡沫介质上,然后置于金属表面,利用金属表面作为自身反射板增加了天线的读取距离。整个天线的面积大小为95mm×45mm,标签的最远读取距离可达4.5m。同时由于表面印刷结构的采用,使得整个标签成本低廉、易于批量生产。 相似文献
16.
Liu J.H. Chen C.L. Lue H.T. Lue J.T. 《Microwave and Wireless Components Letters, IEEE》2003,13(5):181-183
A microwave double dielectric resonator is implemented to measure the dielectric constants of nano-metallic powders. The metallic nanoparticles prepared by vacuum evaporation in inert gas are collected and mixed with alumina powder to fill the inner hole of a sapphire disc by which the resonant frequency and Q factor are measured at the TE/sub 011/ mode to derive the complex dielectric constant. 相似文献
17.
Cha-Yeol Lee Ryoichi Yamashita Masaru Masuzaki 《Journal of Infrared, Millimeter and Terahertz Waves》1997,18(2):519-535
We present, based on the cold fluid theory, linear analysis of the Cherenkov and cyclotron-Cherenkov instabilities which are driven when a linear electron beam is injected into a dielectric-loaded waveguide immersed in an axial magnetic field. In the analysis we consider azimuthally symmetric TM0n modes. We derive dispersion relations for three types of waveguide, and compare computationally obtained linear growth rates of both instabilities. For the type A, which consists of a metallic cylinder with dielectric liner on its inner surface, the growth rate of the Cherenkov instability is larger than that of the cyclotron-Cherenkov instability. For the type B, which consists of a dielectric core and an outer metallic cylinder, both growth rates are comparable. And for the type C, which consists of a metallic core with dielectric liner on its surface and an outer metallic cylinder, the growth rate of the latter instability is higher than that of the former instability. Finally, for the type C, obtained are dependences of the oscillation frequency and the growth rates of both instabilities on the following parameters: the beam energy, the beam current, the axial magnetic field, the dielectric constant, and the thickness of the dielectric. 相似文献
18.
We present a new hybrid method that makes the calculation of the band structure of artificial materials with cylindrical metallic inclusions very efficient. We derive an auxiliary problem whose band structure is that of the metallic crystal along with several dispersionless bands. The eigenfunctions of the auxiliary problem have continuous derivatives up to order 2. Thus, the spectrum of the auxiliary problem can be efficiently computed using the plane-wave method. The band structure of the metallic crystal is then obtained by extracting from the computed results the dispersionless bands. 相似文献
19.
Cha Yeol Lee Masaru Masuzaki 《Journal of Infrared, Millimeter and Terahertz Waves》1998,19(9):1255-1263
We searched numerically dielectric-loaded cylindrical waveguide configurations with an injected electron beam in which the growth rate of the cyclotron-Cherenkov instability surpassed that of the Cherenkov instability, and found such a configuration. This configuration consists of a metallic core and an outer metallic cylinder with a dielectric liner on the inner surface. In order to investigate experimentally radiation due to the cyclotron-Cherenkov instability, we designed and assembled an experimental device using the computational results. We studied beam propagation in the dielectric-loaded coaxial waveguide and microwave radiation due to the cyclotron-Cherenkov instability and the Cherenkov instability. 相似文献
20.
Transmission characteristics of dielectric-coated metallic waveguide for infrared transmission: Slab waveguide model 总被引:2,自引:0,他引:2
A metallic hollow waveguide with inner dielectric multilayers is proposed for the transmission of infrared light and its basic transmission characteristics are fully analyzed by using a two-dimensional slab waveguide model. The power loss in the waveguide is shown to be extremely reduced by coating dielectric layers properly. Simple loss formulas are also presented which consider absorptions of dielectric materials, and minimum possible losses are theoretically estimated. Finally, relations to bending losses in the waveguide are discussed. 相似文献