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1.
对受高阶微商非完整约束并用奇异Lagrange量描述的广义力学系统,基于广义Apell-Чqeraea约束条件,并考虑到系统的内在约束,导出了该非完整约束奇异广义力学系统的广义Poineare-Cartan积分不变量.并证明了该不变量与非完整约束奇异广义力学系统的广义正则方程等价.  相似文献   

2.
对受高阶微商非完整约束并用奇异Lagrange量描述的广义力学系统 ,基于广义Apell_Четаев约束条件 ,并考虑到系统的内在约束 ,导出了该非完整约束奇异广义力学系统的广义Poincar _Cartan积分不变量 .并证明了该不变量与非完整约束奇异广义力学系统的广义正则方程等价  相似文献   

3.
广义经典力学与非完整力学的统一理论   总被引:4,自引:0,他引:4       下载免费PDF全文
罗绍凯 《物理学报》2002,51(7):1416-1423
建立广义经典力学与非完整力学的统一理论———广义非完整力学理论,构造其基本框架.提出广义非完整力学的Чeтаeв(Chetaev)定义,建立广义非完整力学系统的Routh方程和正则方程.给出广义非完整力学系统的非等时变分方程,证明由广义非完整力学系统的第一积分可以构造积分不变量.研究广义非完整力学系统作用量的非等时变分,给出系统的Poincar啨Cartan积分变量关系和积分不变量,进而给出等时变分下系统的Poincar啨积分变量关系和通用积分不变量.给出一些推论,表明广义经典力学和一阶至高阶非完整力学的相关结论均为广义非完整力学理论的特款. 关键词: 广义非完整力学 广义Чeтаeв定义 运动方程 积分不变量  相似文献   

4.
荆宏星  李元成  夏丽莉 《物理学报》2007,56(6):3043-3049
研究变质量单面完整约束系统Lie对称性的摄动与广义Hojman型绝热不变量.首先通过一般无限小变换下的Lie对称性得到广义Hojman型的守恒量;然后基于力学系统高阶绝热不变量的定义,研究小扰动作用下系统Lie对称性的摄动,得到系统广义Hojman型绝热不变量;最后举例说明结果的应用. 关键词: 变质量 单面完整约束 对称性 摄动 绝热不变量  相似文献   

5.
夏丽莉  李元成 《物理学报》2007,56(11):6183-6187
研究相空间中非完整可控力学系统的对称性摄动与绝热不变量. 列出相空间中未受扰非完整可控力学系统的形式不变性导致的Noether守恒量. 基于力学系统高阶绝热不变量的定义,研究小扰动作用下相空间中非完整可控力学系统的形式不变性摄动与绝热不变量,给出了精确不变量与绝热不变量存在的条件与形式,并举例说明结果的应用.  相似文献   

6.
研究广义线性非完整力学系统的Lie对称性导致的Hojman守恒量,在时间不变的特殊Lie对称变换下,给出系统的Lie对称性确定方程、约束限制方程和附加限制方程,得到相应完整系统的Hojman守恒量以及广义线性非完整力学系统的弱Hojman守恒量和强Hojman守恒量,并举一算例说明结果的应用.  相似文献   

7.
非完整力学系统的Noether-Lie对称性   总被引:2,自引:0,他引:2       下载免费PDF全文
方建会  丁宁  王鹏 《物理学报》2006,55(8):3817-3820
研究了非完整力学系统的一种新对称性——Noether-Lie对称性及其守恒量. 给出了非完整力学系统Noether -Lie对称性的定义和判据,提出系统的Noether-Lie对称性导致Noether守恒量和广义Hojman守恒量的定理. 举例说明了结果的应用. Hojman守恒量是所给出的广义Hojman守恒量的特例. 关键词: 非完整力学系统 Noether-Lie对称性 Noether守恒量 广义Hojman守恒量  相似文献   

8.
陈菊  张毅 《物理学报》2015,64(3):34502-034502
研究El-Nabulsi动力学模型下非Chetaev型非完整系统精确不变量与绝热不变量问题. 首先, 导出El-Nabulsi-d'Alembert-Lagrange原理并建立系统的运动微分方程. 其次, 建立El-Nabulsi模型下未受扰动的非Chetaev 型非完整系统的Noether对称性与Noether对称性导致的精确不变量之间的关系; 再次, 引入力学系统的绝热不变量概念, 研究受小扰动作用下非Chetaev型非完整系统Noether对称性的摄动导致绝热不变量问题, 给出了绝热不变量存在的条件及其形式. 作为特例, 本文讨论了El-Nabulsi模型下Chetaev型非完整系统的精确不变量与绝热不变量问题. 最后分别给出非Chetaev型和Chetaev型两种约束下的算例以说明结果的应用.  相似文献   

9.
事件空间中完整系统的Lie对称性与绝热不变量   总被引:3,自引:0,他引:3       下载免费PDF全文
张毅 《物理学报》2007,56(6):3054-3059
研究事件空间中完整力学系统Lie对称性的摄动与绝热不变量.基于力学系统的高阶绝热不变量的概念,研究在小扰动作用下系统Lie对称性的摄动,得到了事件空间中完整力学系统的一类Hojman形式的高阶绝热不变量,给出了绝热不变量存在的条件及形式.并举例说明结果的应用. 关键词: 事件空间 对称性 摄动 绝热不变量  相似文献   

10.
丁宁  方建会 《物理学报》2009,58(11):7440-7446
研究非完整力学系统Mei对称性的摄动及其导致的新型Mei绝热不变量. 给出了系统Mei对称性的判据方程和结构方程在受微扰后变化的形式, 得到了系统Mei对称性的摄动导致的新型Mei绝热不变量的形式和条件. 关键词: 非完整力学系统 Mei对称性 摄动 Mei绝热不变量  相似文献   

11.
Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.  相似文献   

12.
The differences of the pitch and duration of Chinese syllables between Putonghua (PTH) and Taiwan Mandarin (TM) were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that: For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.  相似文献   

13.
Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.  相似文献   

14.
It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].  相似文献   

15.
16.
Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122: 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM (Scanning Electron Acoustic Microscopy) signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α (α is the radius of the focused electron beam). Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.  相似文献   

17.
Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.  相似文献   

18.
The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.  相似文献   

19.
We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.  相似文献   

20.
Real-time, continuous-wave terahertz imaging by a pyroelectric camera   总被引:1,自引:0,他引:1  
Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.  相似文献   

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