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121.
122.
Let F
n
be the free group of rank n, let Aut(F
n
) be its automorphism group and let Out(F
n
) be its outer automorphism group. We show that every solvable subgroup of Out(F
n
) has a finite index subgroup that is finitely generated and free Abelian. We also show that every Abelian subgroup of Out(F
n
) has a finite index subgroup that lifts to Aut(F
n
). 相似文献
123.
关于高速摄影系统的信息量 总被引:1,自引:0,他引:1
本文分别讨论了狭缝扫描高速摄影系统、分幅高速摄影系统以及网格高速摄影系统的信息量计算公式.在讨论分幅摄影系统时,指出了光快门作用对空间自由度的影响. 相似文献
124.
Critical evaluation of CFD codes for interfacial simulation of bubble‐train flow in a narrow channel
Computational fluid dynamics (CFD) codes that are able to describe in detail the dynamic evolution of the deformable interface in gas–liquid or liquid–liquid flows may be a valuable tool to explore the potential of multi‐fluid flow in narrow channels for process intensification. In the present paper, a computational exercise for co‐current bubble‐train flow in a square vertical mini‐channel is performed to investigate the performance of well‐known CFD codes for this type of flows. The computations are based on the volume‐of‐fluid method (VOF) where the transport equation for the liquid volumetric fraction is solved either by the methods involving a geometrical reconstruction of the interface or by the methods that use higher‐order difference schemes instead. The codes contributing to the present code‐to‐code comparison are an in‐house code and the commercial CFD packages CFX, FLUENT and STAR‐CD. Results are presented for two basic cases. In the first one, the flow is driven by buoyancy only, while in the second case the flow is additionally forced by an external pressure gradient. The results of the code‐to‐code comparison show that only the VOF method with interface reconstruction leads to physically sound and consistent results, whereas the use of difference schemes for the volume fraction equation shows some deficiencies. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
125.
Qian Gao Zongmin Wei Yun Liu Fang Wang Shuting Zhang Carmo Serrano Lingxi Li Baoshan Sun 《Molecules (Basel, Switzerland)》2022,27(3)
Moringa oleifera leaves have been widely used for the treatment of inflammation, diabetes, high blood pressure, and other diseases, due to being rich in polyphenols. The main objective of this work was to largely separate the main polyphenols from Moringa oleifera leaves using the technique of high-speed counter-current chromatography (HSCCC). The phenolic composition in Moringa oleifera leaves was first analyzed qualitatively and quantitatively by UPLC-Q-Exactive Orbitrap/MS and UPLC-QqQ/MS, respectively, indicating that quercetin and kaempferol derivatives, phenolic acid and apigenin are the main polyphenols in Moringa oleifera leaves, with quercetin and kaempferol derivatives predominating. Furthermore, the conditions of HSCCC for large-scale separation of polyphenols from Moringa oleifera leaves were optimized, which included the selection of the solvent system, flow rate and the sample load. Only by one-step HSCCC separation (within 120 min) under the optimized conditions, six quercetin and kaempferol derivatives, a phenolic acid and an apigenin could be individually isolated at a large scale (yield from 10% to 98%), each of which possessed high purity. Finally, the isolated polyphenols and phenolic extract from Moringa oleifera leaves (MLPE) were verified to have strong neuroprotective activities against H2O2-induced oxidative stress in PC-12 cells, suggesting that these compounds would contribute to the main beneficial effects of Moringa oleifera leaves. 相似文献
126.
在NS模型的基础上,针对轨道交通的特点,本文提出一种用于模拟四显示固定闭塞系统的元胞自动机模型.应用该模型模拟四显示固定闭塞系统中的列车延迟的交通现象,分析了四显示固定闭塞系统中的发车时间间隔、客货车比例、车站停靠时间、停靠站台数量等因素对列车平均延迟时间的影响.结果表明:客、货车混行时,货车对后行客车的运行会产生抑制作用,调整客、货车在车站的停靠时间可有效缓解这种抑制作用,减少客车的延迟时间;增加停靠站台的数量可提高线路上的车流密度,缓解车流延误,但在较大的发车时间间隔时,站台的利用率会降低.
关键词:
元胞自动机
固定自动闭塞系统
列车延迟 相似文献
127.
128.
We have studied the quantum and classical motions of a single Paul
trapped ion interacting with a time-periodic laser field. By using
the test-function method, we construct n exact solutions of quantum dynamics that describe the generalized squeezed coherent states with the expectation orbits being the corresponding
classical ones. The space-time evolutions of the exact probability
densities show some wavepacket trains. It is demonstrated analytically that by adjusting the laser intensity and frequency, we can control the center motions of the wavepacket trains. We
also discuss the other physical properties such as the expectation
value of energy, the widths and heights of the wavepackets, and
the resonance loss of stability. 相似文献
129.
数字散斑法在局域剪切带三维变形研究中的应用 总被引:3,自引:0,他引:3
在适当的温度、应变率和预变形下,合金材料的拉伸试验中,将会出现伴随应力锯齿形跌落的雪崩式剪切变形带,即波特文-勒夏特利埃(Portevin-Le Chatelier,PLC)效应。利用高速数字摄像系统(分辨力1000 frames/s)并结合数字散斑干涉法(Digital speckle pattern interferometry,DSPI)和数字散斑相关法设计了一套光学变形测量系统,实现了拉伸试验中对试件表面三维变形的实时、精确测量。利用该光学系统对铝铜合金试件在拉伸试验中产生的跳跃传播的局域剪切带瞬态成核过程进行捕捉。通过结合数字散斑相关法得到的面内变形定量结果和数字散斑干涉法得到的表现离面变形的条纹图,再现了剪切变形带成核和传播瞬间的三维变形过程。 相似文献
130.
基于VCSEL的高速光收发模块研究 总被引:2,自引:0,他引:2
基于垂直腔面发射激光器(VCSEL)的高速光模块在现代光通信系统中的应用已越来越广泛。本文在简单介绍光收发模块和VCSEL器件的基础上,着重讨论了GBIC模块的总体设计和主要技术关键。 相似文献