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991.
Solutions of the equations v x+v 3?tv+x=0 and v xx=v 3? tv+x, which describe the nucleation of domain walls occurring in the neighborhood of cusps of slowly varying equilibriums, are analyzed. Examples related to the diffusion in smoothly inhomogeneous media are considered.  相似文献   
992.
993.
Characterization of phospho-olivines as materials for Li-ion cell cathodes   总被引:2,自引:0,他引:2  
Solid State Reaction was employed to prepare phospho-olivines LiMPO4 (where M=Fe, Co) as pure phase and LiNiPO4 in presence of foreign phases, as cathodic materials for lithiumions batteries. The relationship between structural, morphological and electrochemical properties were investigated in the case of LiFePO4. Structural investigation has been carried out by means of X-ray powder diffraction (XRPD) and Rietveld refinement. The influence on the morphology of annealing temperature, different flowing gas mixture and addition of ascorbic acid during the synthesis, has been analysed via scanning electron microscopy. The electrochemical cycling performances on LiFePO4 showed to be positively affected by the modifications of the experimental conditions. Cyclic voltammetry showed a good reversibility during insertion-extraction mechanism, in particular in presence of additives. LiCoPO4 and LiNiPO4 are interesting as high voltage cathode materials for Li-ion batteries and have been taken into account, but their electrochemical operating conditions are still to be optimised. In the case of LiNiPO4 it is very difficult to obtain, by solid state synthesis, suitable purity powders, having a grain size small enough to exploit it usefully as cathodic material for Li-ion cells. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16 – 22, 2000.  相似文献   
994.
995.
A differential equation is obtained that describes the change in the energy of a charged particle in the field of a slow wave (with phase velocity not equal to unity) as a function of the distance traversed. Analysis of this equation yields the amplitude and period of the change in the particle's energy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 97–102, February, 1981.  相似文献   
996.
997.
998.
采用低压金属有机化合物气相沉积法(LP-MOCVD)生长并制作了1.6—1.7μm大应变InGaAs/InGaAsP分布反馈激光器.采用应变缓冲层技术,得到质量良好的大应变InGaAs/InP体材料.器件采用了4个大应变的量子阱,加入了载流子阻挡层改善器件的温度特性.1.66μm和1.74μm未镀膜的3μm脊型波导器件阈值电流低(小于15mA),输出功率高(100mA时大于14mW).从10—40℃,1.74μm激光器的特征温度T0=57K,和1.55μm InGaAsP分布反馈激光器的特征温度相当. 关键词: MOCVD InGaAs/InGaAsP 应变量子阱 分布反馈激光器  相似文献   
999.
The first experimental observation of the propagation dynamics of a short broadband acoustic pulse in a resonance medium with gas bubbles is carried out. The probing pulse is generated using the optoacoustic effect. It is shown that the theory of short pulse propagation in media with generalized resonance relaxation adequately and accurately describes the dynamics of short pulse dispersion. A possibility to determine the relaxation and resonance parameters of media by the pulsed testing technique is demonstrated.  相似文献   
1000.
Hollow particles with interconnected cavities have been prepared by a simple modified suspension polymerization of acrylate monomers in the incorporation of a phase inversion process and polymerizable emulsifier. The morphology of particles has been characterized by scanning electron micrographs (SEMs). Based on observations made using an optical microscope equipped with a digital camera and SEM images of particles obtained under different conditions, the formation mechanisms for multiporous hollow particles are discussed.  相似文献   
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