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931.
Symmetrical dynamical characteristic of peak and valley current-mode controlled single-phase H-bridge inverter
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Complex dynamical phenomenon was studied in the single phase H-bridge inverter which was controlled by either a peak current or a valley current. The state functions and the discrete iterative map equations were established to analyze the dynamical phenomenon in the single phase H-bridge inverter. The dynamical characteristics of the single phase H- bridge inverter, such as time domain waveform diagram, bifurcation diagram, and folding map, were obtained by using the numerical calculation when the circuit parameters varied in specific range. Moreover, the simulation results were obtained by using the OrCAD-PSpice software to validate the numerical calculation. Both the numerical calculation and the circuit simulation show that the symmetrical dynamical phenomenon occurs in the single phase H-bridge inverter controlled by the peak current or the valley current. 相似文献
932.
Generally, a standard bunching system is composed by an SW pre-buncher, a TW buncher and a standard accelerating section. However, there is one way to simplify the whole system to some extent by using the hybrid buncher, which is a combined structure of the SW pre-buncher and the TW buncher. Here the beam dynamics studies on an S-band bunching system with the hybrid buncher is presented, and simulation results show that similar beam performance can be obtained at the linac exit by using this kind of bunching system rather than the standard one. In the meantime, the structure design of the hybrid buncher is also described. Furthermore, the standard accelerating section can also be integrated with the hybrid buncher, which can further simplify the usual bunching system and lower the construction cost. 相似文献
933.
934.
基于开放式结构有限元分析软件系统SiPESC.FEMS,针对动力时程分析算法共性,采用C++面向对象程序设计方法和软件设计模式,研发了一种结构动力分析通用算法构架。构架的核心思想是算法与数据模型相分离,从而实现算法通用性,整个构架由四个基本类及子类构成。本文重点阐述了基本类的抽象过程和通用接口的设计思想,给出了利用插件技术实现算法构架的步骤。利用该构架已实现了Newmark法、Wilson-θ法、中心差分法及改进中心差分法,并进行数值验证。研究工作表明,算法构架适用于通用时程积分算法,可方便地进行动态扩展,具备良好的开放性和重用性。 相似文献
935.
936.
基于随机激励的离散形式,对耦合Newmark系统的动力可靠度问题进行解析分析。平稳随机激励下,耦合Newmark系统初始滑移极限状态方程可以写成n个标准正态随机变量的显式线性函数,并能给出可靠度指标的理论解。对于以相对滑移量为临界状态的情况,极限状态方程是n个标准正态随机变量的隐式函数,可借助静力可靠度方法进行求解。算例表明,系统初始滑移的设计点激励是以潜在滑动体自振频率为主频,振幅渐增的谐振时程;后者的失效概率与摩擦系数成非线性关系,存在合适的摩擦系数使失效概率最小。 相似文献
937.
为了研究冲击载荷作用下考虑应力波效应弹性矩形薄板的动力屈曲,根据动力屈曲发生瞬间的能量转换和守恒准则,导出板的屈曲控制方程和波阵面上的补充约束条件,真实的屈曲位移应同时满足控制方程和波阵面上的附加约束条件。满足上述条件,建立了该问题的完整数值解法,对屈曲过程中冲击载荷、屈曲模态和临界屈曲长度之间的关系进行研究,定量计算了横向惯性效应对提高薄板动力屈曲临界应力的贡献。研究表明:板的厚宽比一定时,临界屈曲长度随冲击载荷的增大而减小;由于屈曲时的横向惯性效应,应力波作用下薄板一阶临界力参数是相应边界板的静力失稳临界力参数的1.5倍;随着边界约束逐渐减弱,板临界力参数逐渐减小,动力特征参数逐渐增大。 相似文献
938.
939.
Analysis on the capacity degradation mechanism of a series lithium-ion power battery pack based on inconsistency of capacity
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The lithium-ion battery has been widely used as an energy source. Charge rate, discharge rate, and operating tem- perature are very important factors for the capacity degradations of power batteries and battery packs. Firstly, in this paper we make use of an accelerated life test and a statistical analysis method to establish the capacity accelerated degradation model under three constant stress parameters according to the degradation data, which are charge rate, discharge rate, and operating temperature, and then we propose a capacity degradation model according to the current residual capacity of a Li-ion cell under dynamic stress parameters. Secondly, we analyze the charge and discharge process of a series power battery pack and interpret the correlation between the capacity degradations of the battery pack and its charge/discharge rate. According to this cycling condition, we establish a capacity degradation model of a series power battery pack under inconsistent capacity of cells, and analyze the degradation mechanism with capacity variance and operating temperature difference. The comparative analysis of test results shows that the inconsistent operating temperatures of cells in the series power battery pack are the main cause of its degradation; when the difference between inconsistent temperatures is narrowed by 5 ℃, the cycle life can be improved by more than 50%. Therefore, it effectively improves the cycle life of the series battery pack to reasonably assemble the batteries according to their capacities and to narrow the differences in operating temperature among cells. 相似文献
940.
具有创伤小、毒性低、选择性好、无耐药性等优点的光动力疗法已被广泛应用于癌症治疗研究。然而,多数光敏剂存在水溶性差易聚集、肿瘤组织选择性差的问题,且其激发光都在可见或紫外光范围内,组织穿透深度较浅导致治疗深度不够,限制了光动力疗效。稀土上转换纳米粒子具有低生物毒性、高化学稳定性、强组织穿透力等优点,可作为将近红外光转换成紫外/可见光的发光材料和光敏剂载体,因此,构建上转换光动力诊疗体系为增强光动力疗效提供新思路。本文介绍了上转换光动力诊疗体系的构建方法,包括物理吸附法、物理包封法、共价偶联法,并分析了其应用于光动力抗癌研究的优缺点,最后总结并展望了其存在的挑战及未来发展方向。 相似文献