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861.
探索了一种行波管效率提高的优化设计方法.该方法在不降低电子效率的前提下,对慢波结构进行优化以获得互作用后电子注能量台阶状的分布,为研制高回收效率的收集极奠定基础.提出了用最大可回收效率表示的目标函数来衡量电子注的可回收能力.与单纯以电子效率为目标的慢波结构优化相比,以电子注可回收能力最大化为目标的慢波结构优化,不仅能在工作频带内提高总效率,而且行波管的非线性指标没有明显降低,小信号增益却有较大的提高.
关键词:
空间行波管
可回收能力
慢波结构
优化设计 相似文献
862.
863.
针对Hadoop异构集群中计算和数据资源的不一致分布所导致的调度性能较低的缺点,设计了一种基于Hadoop集群和改进Late算法的并行作业调度算法;首先,介绍了基于Hadoop框架和Map-Reduce模型的调度原理,然后,在经典的Late调度算法的基础上,对Map任务和Reduce任务的各阶段执行时间进度比例进行存储和更新,为了进一步地提高调度效率,将慢任务迁移到本地化节点或离数据资源较近的物理节点上,并给了基于改进Late算法的作业调度流程;为了验证文中方法,在Hadoop集群系统上测试,设定1个为Jobtracker主控节点和7个为TaskTracker节点,实验结果表明文中方法能实现异构集群的作业调度,且与其它方法比较,具有较低的预测误差和较高的调度效率。 相似文献
864.
865.
866.
LiaoFu Luo 《中国科学:物理学 力学 天文学(英文版)》2014,57(3):458-468
The conformational change of biological macromolecule is investigated from the point of quantum transition. A quantum theory on protein folding is proposed. Compared with other dynamical variables such as mobile electrons, chemical bonds and stretching-bending vibrations the molecular torsion has the lowest energy and can be looked as the slow variable of the system. Simultaneously, from the multi-minima property of torsion potential the local conformational states are well defined. Following the idea that the slow variables slave the fast ones and using the nonadiabaticity operator method we deduce the Hamiltonian describing conformational change. It is shown that the influence of fast variables on the macromolecule can fully be taken into account through a phase transformation of slow variable wave function. Starting from the conformation-transition Hamiltonian the nonradiative matrix element was calculated and a general formulas for protein folding rate was deduced. The analytical form of the formula was utilized to study the temperature dependence of protein folding rate and the curious non-Arrhenius temperature relation was interpreted. By using temperature dependence data the multi-torsion correlation was studied. The decoherence time of quantum torsion state is estimated. The proposed folding rate formula gives a unifying approach for the study of a large class problems of biological conformational change. 相似文献
867.
Surface plasmons are of particular interest recently as their performance is approaching the enhancement of light emission efficiencies, after synthesized close to the vicinity of solid state materials, i.e., semiconductor structure. As other scientific works have been proposed to improve the light-emitting efficiency, such as the use of resonant cavities, photon recycling, and thin-light emitting layers with periodic surface texturing, surface plasmon possesses a promising way to the light enhancement, due to the energy coupling effect between the emitted photons from the semiconductor and the metallic nanoparticles fabricated by nanotechnology. The usual pathway of plasmon enhanced light emitting devices is the use of Ag/Au nanoparticles coating the surface of semiconductor quantum dot (QD) or quantum well (QW) structures. However, apart from efforts to extract as much light as possible from single-driven surface plasmon-QD/QW, it is possible to enhance the light emission rate with double optical-excitations. This approach is based on the quantum interference between the external lasers and the localized quantum light, and promised to stimulate the development of plasmon-enhanced optical sensors. In this review, we describe the quantum properties of light propagation in hybrid nanoparticle and semiconductor materials, i.e., quantum dot or nanomechanical resonator coupled to Ag/Au nanoparticles, driven by two optical fields. Distinct with single excitation, plasmon-assisted complex driven by two optical fields, exhibit specific quantum interference characteristics that can be used as sensitive all-optical devices, such as the slow light switch, nonlinear optical Kerr modulator, and ultra-sensitive mass sensing. We summarize the recent advances of light propagation in surface plasmon-enhanced quantum dot devices, driven by two optical fields, which would stimulate the development of novel optical materials, deeper theoretical insights, innovative new devices, and plasmonic applications with potential for significant technological and societal impact. 相似文献
868.
纯电动汽车起步控制策略 总被引:1,自引:0,他引:1
为解决纯电动汽车起步时冲击度大和坡道起步易发生倒溜的问题,在满足驾驶员驾驶意图的基础上,提出了纯电动汽车的起步控制策略.将纯电动汽车起步分为无油门起步和有油门起步2种模式,并制定了相应的控制策略.对采用该控制策略下的纯电动汽车的起步性能进行了仿真分析.结果表明,所制定的策略能很好的满足车辆起步时平顺性及安全性的要求. 相似文献
869.
实验中选择Si(N型,(100面),3~5Ω·cm)作为薄膜样品的基底,利用射频溅射方法制备低介电常数非晶SiOx(x〈2)薄膜,并通过真空退火来改变其缺陷态.正电子湮没多普勒展宽能谱(DBS)测量在慢正电子束流装置上进行.正电子湮没结果显示随退火温度增加,SiOx薄膜中有纳米晶硅生成,使正电子的捕获缺陷减少,从而使S参数呈下降趋势. 相似文献
870.
本文主要介绍了安全稳定控制系统在攀枝花电网中的运用,分析了因采用离线策略而带来的新的安全稳定隐患,提出了相关解决办法,并重点说明了制定"黑启动"方案的一些思路。 相似文献