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91.
研究Birkhoff系统对称性的摄动与绝热不变量.给出了未受扰Birkhoff系统的Lie对称性导致的Hojman型精确不变量.基于力学系统的高阶绝热不变量的定义,研究在小扰动作用下Birkhoff系统Lie对称性的摄动,得到了系统的一类新型绝热不变量.举例说明结果的应用.
关键词:
Birkhoff系统
Lie对称性
摄动
绝热不变量 相似文献
92.
提出了一种基于微悬臂梁传感技术研究大分子折叠/构象转变的新方法.通过分子自组装的方法将热敏性的聚N-异丙基丙烯酰胺(PNIPAM)分子链修饰到微悬臂梁的单侧表面,用光杠杆技术检测温度在20—40℃之间变化时由于微悬臂梁上的PNIPAM分子在水中的构象转变所引起的微悬臂梁变形.实验结果显示:在升温过程中,微悬臂梁的表面应力发生了变化并且导致微悬臂梁产生了弯曲变形,这个过程对应着微悬臂梁上的PNIPAM分子从无规线团构象到塌缩小球构象的构象转变.在降温过程中,微悬臂梁发生了反方向的弯曲变形,这对应着PNIPA
关键词:
构象转变
聚N-异丙基丙烯酰胺分子链
表面应力
微悬臂梁 相似文献
93.
94.
利用傅里叶光学方法,建立了一个基于远场的多束超短脉冲相干合成的理论模型。研究了一个口径为50 cm,脉宽为1 ps的超短脉冲相干合成系统的各种误差对脉冲远场时域和空域特性的影响。结果表明:若要求远场的一倍衍射极限区域的积分能量分布达到理想情况下的90%,该系统的相位延迟误差小于0.63,沿x方向角度误差小于0.37 μrad,沿y方向角度误差小于0.34 μrad;若要求远场叠加脉冲的时域展宽小于25%,系统的剩余啁啾因子应小于1.32(不考虑相位延迟)或1.52(考虑0.63的相位延迟)。 相似文献
95.
96.
基于SiGe HBT(异质结双极晶体管)的物理模型,建立了描述SiGe HBT的大信号等效电路模型.该等效电路模型考虑了准饱和效应和自热效应等,模型分为本征和非本征两部分,物理意义清晰,拓扑结构相对简单.该模型嵌入了PSPICE软件的DEVEO(器件方程开发包)中.在PSPICE软件资源的支持下,利用该模型对SiGe HBT器件进行了交直流特性模拟分析,模拟结果与理论分析结果相一致,并且与文献报道的结果符合较好.
关键词:
SiGe HBT
等效电路模型
PSPICE 相似文献
97.
How fast speakers can change pitch voluntarily is potentially an important articulatory constraint for speech production. Previous attempts at assessing the maximum speed of pitch change have helped improve understanding of certain aspects of pitch production in speech. However, since only "response time"--time needed to complete the middle 75% of a pitch shift--was measured in previous studies, direct comparisons with speech data have been difficult. In the present study, a new experimental paradigm was adopted in which subjects produced rapid successions of pitch shifts by imitating synthesized model pitch undulation patterns. This permitted the measurement of the duration of entire pitch shifts. Native speakers of English and Mandarin participated as subjects. The speed of pitch change was measured both in terms of response time and excursion time-time needed to complete the entire pitch shift. Results show that excursion time is nearly twice as long as response time. This suggests that physiological limitation on the speed of pitch movement is greater than has been recognized. Also, it is found that the maximum speed of pitch change varies quite linearly with excursion size, and that it is different for pitch rises and falls. Comparisons of present data with data on speed of pitch change from studies of real speech found them to be largely comparable. This suggests that the maximum speed of pitch change is often approached in speech, and that the role of physiological constraints in determining the shape and alignment of F0 contours in speech is probably greater than has been appreciated. 相似文献
98.
Hongbo Zhang Rui Wang Kaixin Chen Han Yang Daming Zhang Maobin Yi Guoquan Wang Zhenchang Ma 《Optics & Laser Technology》2002,34(4):283-286
A new method, based on zero point of longitudinal electric field, was used to determine the spatial resolution of external electro-optic (EO) probing equipment. Considering the diffraction of Gauss beam, the result of external EO probing was simulated which was in accordance with the experiment. A spatial resolution <1 μm was demonstrated initially in our equipment using 650 nm laser diode as probe beam and semi-insulating GaP as probe tip. 相似文献
99.
In an analytic regularization method a new technique, in which the spins of the particles are used as regulating parameters, has been developed. 相似文献
100.
To control the temporal profile of a relativistic electron beam to meet requirements of various advanced scientific applications like free-electron-laser and plasma wakefield acceleration, a widely-used technique is to manipulate the dispersion terms which turns out to be one-to-many problems. Due to their intrinsic one-to-many property, current popular stochastic optimization approaches on temporal shaping may face the problems of long computing time or sometimes suggesting only one solution. Here we propose a real-time solver for one-to-many problems of temporal shaping, with the aid of a semi-supervised machine learning method, the conditional generative adversarial network (CGAN). We demonstrate that the CGAN solver can learn the one-to-many dynamics and is able to accurately and quickly predict the required dispersion terms for different custom temporal profiles. This machine learning-based solver is expected to have the potential for wide applications to one-to-many problems in other scientific fields. 相似文献