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移动通信应用为人类移动规律的研究提供了独特的数据来源. 本文通过城市手机用户的分布数据,研究城市移动人群的整体动力学行为. 借助随机矩阵理论的方法,通过比较移动人群数据与随机数据在互相关矩阵谱分布上的差异,发现移动人群数据互相关矩阵的相关系数均值、最大本征值及其对应的本征向量明显偏离于随机互相关矩阵的分布,指出这种差异体现了城市移动人群的整体行为特性,且这种差异在不同时间段也会有所不同. 研究结果体现出相关系数的均值和最大本征值的波动趋势,并指出本征向量成员权重的时空模式与城市移动人群整体行为特征的波动过
关键词:
随机矩阵理论
移动人群
宏观行为 相似文献
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针对在一幅载体图像中隐藏三维目标序列图像的问题,本文利用主分量分析法获取三维目标的本征图像,将本征图像的小波域系数嵌入到载体图像的小波域系数中,利用分解系数和提取得到的本征图像重构出三维目标的系列图像.本文所提出的方法不是直接存储目标图像,而是存储能够反映三维目标特征的一组本征图像.研究结果表明,该方法有效地将三维目标的特征隐藏在了载体图像中,隐藏信息量大.
关键词:
信息隐藏
三维目标
主分量分析
小波变换 相似文献
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采用电子顺磁共振(ESR)和低温光致发光(PL)技术,研究了退火温度对低压化学气相沉积法(LPCVD)制备的非故意掺杂 4H-SiC材料中本征缺陷稳定性的影响.结果发现,当退火时间为10 min和30 min时,本征缺陷浓度均随着退火温度的升高而增大,当退火温度达到1573 K时材料中本征缺陷浓度达到最大,继续升高退火温度将使材料中本征缺陷浓度迅速降低.退火温度对材料中本征缺陷的影响主要是由于退火中本征缺陷的稳定化过程及本征缺陷之间发生强烈的相互作用引起的.
关键词:
高温退火
本征缺陷
电子顺磁共振谱
光致发光 相似文献
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本文主要研究了利用传输矩阵理论和共振透射条件详细地推导光腔中均匀放置三个机械薄膜构成的腔光力系统中系统本征模式随机械运动的色散关系.计算结果发现系统的光学本征模式由一组四个的本征能级构成,且不同的能级随不同的机械运动模式的变化曲线各不相同,进而导致不同光学模式与不同机械运动模式之间的耦合也不相同.此外,利用微扰理论求解了当机械运动振幅远小于腔模波长、机械振子处于平衡位置附近时,各种光学模式与不同机械振动模式间相互作用耦合强度的解析表达式.研究结果能够为理论和实验上研究多模腔光力系统提供一定的参考. 相似文献
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姚利花 《原子与分子物理学报》2019,36(1):68-72
采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯和缺陷石墨烯吸附钠原子的电荷密度、吸附能、态密度和储存量.结果表明,本征石墨烯中,钠原子的最佳吸附位置为H位,缺陷石墨烯中,钠原子的最佳吸附位置为T_D位.缺陷石墨烯对钠原子的吸附能是-4.423 eV,约为本征石墨烯对钠原子吸附能的2.5倍;钠原子与缺陷石墨烯中的碳原子发生轨道杂化,而与本征石墨烯没有发生轨道杂化现象.缺陷石墨烯能够吸附10个钠原子,与本征石墨烯相比显著提高.因此,缺陷石墨烯有望成为一种潜在的储钠材料. 相似文献
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A. Yu. Grosberg 《Journal of statistical physics》1985,38(1-2):149-160
The collapse (globulization) of an ideal heteropolymer chain under the action of an external attractive field is considered. The problem of the collapse of different types of primary structures, including mobile, periodic, large-block, and statistical structures, is formulated. It is shown that for a random heteropolymer, the mathematical image of the globular state is the chain-length independence of the probability distribution of a random thermal distribution function of the end monomer coordinates. The free energy per monomer of a chain in a globular state and local densities of monomers of all types are shown to be a self-averaging quantities. An exactly solvable model is proposed for a globule formed by a statistical heteropolymer chain. In this model, different types of monomers are attracted to different centers by linear elastic forces with identical elastic constants. The modulus of elasticity is obtained for a heteropolymer globule with respect to the attraction of different types of monomers in different directions. It is shown that this modulus is higher for a short-periodic polymer than for a statistical one. 相似文献
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Use of ultrasound for the determination of flour quality 总被引:1,自引:0,他引:1
Alava JM Sahi SS García-Alvarez J Turó A Chávez JA García MJ Salazar J 《Ultrasonics》2007,46(3):270-276
Within the baking industry, the control of dough properties is required to achieve final product quality and consistency. Traditional methods for dough testing are slow and off-line and do not provide fundamental rheological information. There is therefore a need for the development of fast and on-line instruments capable of providing relevant data for baking. Ultrasonics provide a non-destructive, rapid and low cost technique for the measurement of physical food characteristics.In this work, the water content of dough is investigated using ultrasonic techniques. The capability of ultrasound measurements for discriminating flours for different purposes is also studied. Doughs from more than 30 flours were characterised rheologically using a Chopin Alveograph and a Brabender Extensograph. Ultrasound measurements on the doughs prepared from these flours were also performed. The measurements were correlated, showing that ultrasound was an alternative measurement method to discriminate types of flours for different purposes. 相似文献
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An analytical model accurately describing the evolution of the relative state of polarization between two signals in high-birefringence fibers is presented. The degree of co-polarization is calculated as a function of the angle between the principal axes of the fiber and the state of polarization of the two input signals, for two different input polarization schemes. It is shown that for small fiber lengths or narrow wavelength separation, launching the two signals with orthogonal polarizations can present a higher degree of co-polarization along the propagation; for large wavelength separation or long distances, the degree of co-polarization for the parallel scheme is always equal or higher than for the orthogonal case. The model for the degree of co-polarization is compared with theoretical and experimental four-wave mixing results in a dispersion shifted high-birefringence fiber. 相似文献
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耦合双原子Jaynes-Cummings模型的腔场谱H 总被引:14,自引:8,他引:6
研究了处于激发态的两原子与高Q腔场相互作用单光子过程的腔场谱,给出了初始光场为光子数态、相干态、压缩真空态时的腔场谱数值计算结果,分析了原子间偶极-偶极相互作用强度gα对腔场谱结构的影响.发现真空场Rabi峰,当gα较弱时为4峰,gα较强时为3峰结构;弱场数态(n>0)时为5峰,强场时为3峰结构.相干态和压缩真空态时,谱结构与光子数分布有关,一般为复杂的多峰结构.结果表明,gα对峰位峰高都有影响,破坏了谱结构的对称性,但这种影响只在真空场和弱场时才较明显. 相似文献
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A. I. Olemskoi I. V. Koplyk I. A. Sklyar E. A. Toropov A. Ya. Flat 《Russian Physics Journal》1993,36(1):74-101
The status of the theory of nucleation of a new phase is reviewed. Special attention is devoted to the relation between the micro- and macroscopic levels. A systematic exposition is given of the methods developed by Cahn, Cook, Langer, and Mazenko for describing the spatiotemporal correlation of the order-parameter field for the continuous (spinodal) mechanism of formation of a new phase. The time dependence of the characteristic size L(t) is found for the cases of nonconserved and conserved order parameters as well as for the coalescence process. It is shown that in the case of the intermittent (binodal) formation mechanism a critical nucleus of a new phase can be represented as the soliton solution of the field equation. It is found that the appearance of sharp interphase boundaries results in a transition from spinodal to heterophase kinetics, represented as a loss of ergodicity. The nonergodicity parameter is determined as a function of the interatomic interaction and anharmonicity within the Ginzburg-Landau scheme. Coalescence in the presence of intense external noise is investigated for systems with a conserved order parameter. A stochastic equation is derived for the size distribution function of precipitates of the new phase and the effect of intensity fluctuations and supersaturation of the limiting component on the solution of this equation is investigated.Sumskii Physicotechnological Institute of the Scientific and Industrial Enterprise RÉTO. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 90–122, January, 1993. 相似文献
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A. V. Tsvetkova 《Russian Journal of Mathematical Physics》2016,23(4):536-550
In the paper, the Cauchy problem for the wave equation on singular spaces of constant curvature and on an infinite homogeneous tree is studied. Two singular spaces are considered: the first one consists of a three-dimensional Euclidean space to which a ray is glued, and the other is formed by two three-dimensional Euclidean spaces joined by a segment. The solution of the Cauchy problem for the wave equation on these objects is described and the behavior of the energy of a wave as time tends to infinity is studied.The Cauchy problem for the wave equation on an infinite homogeneous tree is also considered, where the matching conditions for the Laplace operator at the vertices are chosen in the form generalizing the Kirchhoff conditions. The spectrum of such an operator is found, and the solution of the Cauchy problem for the wave equation is described. The behavior of wave energy as time tends to infinity is also studied. 相似文献
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This paper constructs an almost-Poisson structure for the
non-self-adjoint dynamical systems, which can be decomposed into a
sum of a Poisson bracket and the other almost-Poisson bracket. The
necessary and sufficient condition for the decomposition of the
almost-Poisson bracket to be two Poisson ones is obtained. As an
application, the almost-Poisson structure for generalised
Chaplygin's systems is discussed in the framework of the
decomposition theory. It proves that the almost-Poisson bracket for
the systems can be decomposed into the sum of a canonical Poisson
bracket and another two noncanonical Poisson brackets in some special
cases, which is useful for integrating the equations of motion. 相似文献
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Numerical Approximation of Oscillatory Solutions of Hyperbolic-Elliptic Systems of Conservation Laws by Multiresolution Schemes 下载免费PDF全文
Stefan Berres Raimund Bü rger & Alice Kozakevicius 《advances in applied mathematics and mechanics.》2009,1(5):581-614
The generic structure of solutions of initial value problems of
hyperbolic-elliptic systems, also called mixed systems, of
conservation laws is
not yet fully understood. One reason for the
absence of a core well-posedness
theory for these equations is the
sensitivity of their solutions to the structure of
a parabolic
regularization when attempting to single out an admissible solution
by the
vanishing viscosity approach. There is, however, theoretical
and numerical evidence
for the appearance of solutions that exhibit
persistent oscillations, so-called oscillatory
waves, which are (in
general, measure-valued) solutions that emerge from Riemann data or
slightly perturbed constant data chosen from the interior of the
elliptic region.
To capture these solutions, usually a fine
computational grid is required.
In this work, a version of the
multiresolution method applied to a WENO scheme for systems of
conservation laws is proposed as a simulation tool for the efficient computation of solutions of oscillatory wave type. The
hyperbolic-elliptic $2 \times 2$
systems of conservation laws
considered are a prototype system for three-phase flow
in porous
media and a system modeling the separation of a heavy-buoyant
bidisperse suspension.
In the latter case, varying one scalar
parameter produces elliptic regions of different shapes and numbers of points of tangency with the borders of the phase space, giving
rise to different kinds of oscillation waves. 相似文献