Renewal-anomalous-heterogeneous files

Renewal-anomalous-heterogeneous files are solved. A simple file is made of Brownian hard spheres that diffuse stochastically in an effective 1D channel. Generally, Brownian files are heterogeneous: the spheres' diffusion coefficients are distributed and the initial spheres' density is non-uniform. In renewal-anomalous files, the distribution of waiting times for individual jumps is not exponential as in Brownian files, yet obeys: ψα(t)∼t−1−α, 0<α<1. The file is renewal as all the particles attempt jumping at the same time. It is shown that the mean square displacement (MSD) in a renewal-anomalous-heterogeneous file, 〈r²〉, obeys, , where nrml〈r²〉 is the MSD in the corresponding Brownian file. This scaling is an outcome of an exact relation (derived here) connecting probability density functions of Brownian files and renewal-anomalous files. It is also shown that non-renewal-anomalous files are slower than the corresponding renewal ones.     

Stretched-Gaussian asymptotics of the truncated Lévy flights for the diffusion in nonhomogeneous media

The Lévy, jumping process, defined in terms of the jumping size distribution and the waiting time distribution, is considered. The jumping rate depends on the process value. The fractional diffusion equation, which contains the variable diffusion coefficient, is solved in the diffusion limit. That solution resolves itself to the stretched Gaussian when the order parameter μ→2. The truncation of the Lévy flights, in the exponential and power-law form, is introduced and the corresponding random walk process is simulated by the Monte Carlo method. The stretched Gaussian tails are found in both cases. The time which is needed to reach the limiting distribution strongly depends on the jumping rate parameter. When the cutoff function falls slowly, the tail of the distribution appears to be algebraic.     

Deterministic single-file dynamics in collisional representation

We re-examine numerically the diffusion of a deterministic, or ballistic single file with preassigned velocity distribution (Jepsen's gas) from a collisional viewpoint. For a two-modal velocity distribution, where half the particles have velocity +/-c, the collisional statistics is analytically proven to reproduce the continuous time representation. For a three-modal velocity distribution with equal fractions, where less than 12 of the particles have velocity +/-c, with the remaining particles at rest, the collisional process is shown to be inhomogeneous; its stationary properties are discussed here by combining exact and phenomenological arguments. Collisional memory effects are then related to the negative power-law tails in the velocity autocorrelation functions, predicted earlier in the continuous time formalism. Numerical and analytical results for Gaussian and four-modal Jepsen's gases are also reported for the sake of a comparison.     

基于Open VG云电子书系统的多级优化框架设计

针对电子书应用存在的文件格式、性能效率低下和图像失真等问题,设计了一种应用于云电子书系统的多级优化框架,优化框架主要体现在如下三个方面。第一,对向量图形类库的性能进行描述,并提出了一种优化算法,减少了类库的时间复杂度。第二,在嵌入式GPU上并行进行坐标系统的计算。利用GPU在并行计算方面的优势,云电子书在向量图形类库方面获取了显著的性能提升。第三,云电子书将文件转化功能转嫁给Hadoop云平台,节省了移动设备的能量消耗和计算时间。同时为了对Hadoop调度过程中的数据位置问题进行优化,将位置感知调度器运用到提出的系统。实验结果表明：云电子书系统与最初的Open VG类库相比,性能提升了约70%,而且云电子书系统与连续服务器平台相比,计算时间减小了约60%。     

Time-dependent random walks and the theory of complex adaptive systems

Motivated by novel results in the theory of complex adaptive systems, we analyze the dynamics of random walks in which the jumping probabilities are time dependent. We determine the survival probability in the presence of an absorbing boundary. For an unbiased walk, the survival probability is maximized in the case of large temporal oscillations in the jumping probabilities. On the other hand, a random walker who is drifted towards the absorbing boundary performs best with a constant jumping probability. We use the results to reveal the underlying dynamics responsible for the phenomenon of self-segregation and clustering observed in the evolutionary minority game.     

基于四步相移光栅投影的三维形貌测量系统

为了实现对具有明显跳变面物体的轮廓测量,建立了四步相移光栅投影的三维形貌测量系统,并对所采用的四步相移测量算法进行研究。在介绍四步相移原理的基础上以有明显跳变面的三棱锥橡皮块为例,建立针对明显跳变面的测量算法。通过对4幅相移图算术求和并除以4得到平均灰度图;将平均灰度图二值化处理定位明显跳变面或阴影部分;将二值化图像与包裹相位图卷积,而后对包裹相位图进行解包裹,从而得到正确的连续相位,最终获取物体三维形貌。根据上述算法测量三棱锥的三维形貌并计算其体积,测量实验表明:被测物的体积平均相对精度为0.47%。     

Environment-dependent continuous time random walk

A generalized continuous time random walk model which is dependent on environmental damping is proposed in which the two key parameters of the usual random walk theory: the jumping distance and the waiting time, are replaced by two new ones: the pulse velocity and the flight time. The anomalous diffusion of a free particle which is characterized by the asymptotical mean square displacement <x²(t)>～t^α is realized numerically and analysed theoretically, where the value of the power index α is in a region of 0 < α < 2. Particularly, the damping leads to a sub-diffusion when the impact velocities are drawn from a Gaussian density function and the super-diffusive effect is related to statistical extremes, which are called rare-though-dominant events.     

多能级原子的量子跳跃与连续量子测量

研究了多能级原子的量子跳跃行为,构造出多能级原子系统光学Block方程的形式解．证明了Mollow的纯态描述理论不适用于多能级原子,为此,发展了混合态描述理论,得出了多能级原子的重置密度矩阵为混合态的结论．最后,讨论了多能级原子的量子跳跃与连续量子测量的联系． 关键词：     

A high-resolution cw dye laser spectrometer

The construction and utilization of a high-resolution cw dye laser spectrometer is described. The laser incorporates pressure tuned intra-cavity etalons enabling the single mode output laser frequency to be tuned more than one nm in a continuous scan. In the scan the laser jumps from one cavity mode to the next in ～ 50 MHz steps. In comparison to molecular Doppler widths this mode jumping is negligible. As an example of the use of the instrument, a high-resolution absorption spectrum of molecular iodine between the sodium D lines is presented. A unique frequency counter provides the calibration of the absorption spectrum.     

闪电等离子体连续辐射谱特征分析

闪电等离子体光谱特征是在强连续辐射背景上叠加丰富的NⅡ,NⅠ,OⅠ,HⅠ线状谱,闪电回击通道温度可达万开以上,通道内氮分子和氧分子接近完全离解,分析连续谱时,不考虑各组分分子带状谱对连续谱的影响。使用摄谱范围在400~1 000 nm的无狭缝光栅摄谱仪记录云对地闪电放电光谱,在光谱可见区低频段观测到大量一价氮离子谱线,未观测到明显的其他离子谱,认为连续辐射机制主要由氮离子与自由电子相互作用产生,包括轫致辐射和复合辐射。等离子体温度在1×104 K以下时轫致辐射连续谱呈现出平谱特征,辐射强度较弱,随着等离子体温度升高在紫外段辐射强度增加,对可见段连续谱轮廓特征没有明显影响。对于复合辐射,设闪电等离子体符合局域热力学平衡和光学薄条件,以类氢离子经典辐射理论为基础,以冈特因子作量子力学修正,考虑到复合过程中自由电子被离子俘获,大概率出现在高激发状态,引入非类氢的复杂离子近似计算方法分析氮离子复合辐射过程,导出连续谱复合辐射系数与波长的函数关系,获得特定参数条件下氮等离子连续辐射谱特征曲线,与闪电连续谱轮廓观测结果比较,发现等离子体电子温度与连续辐射谱谱峰位置密切相关,认为通过对闪电连续谱轮廓拟合,能够可靠诊断闪电放电通道表面电子温度。研究认为氮离子实有效核电荷数Z*取值对连续谱特征也有显著影响,Z*取值小,连续谱跃变特征增强;Z*取值大,连续谱展宽特征增强,从而与实测谱轮廓底部背离增大。通过多次对比发现Z*取为2~4时,理论曲线与连续谱观测轮廓具有较好的一致性,Z*的取值范围由离子种类决定,引入离子有效核电荷数Z*,能够很好地解释闪电等离子体连续谱在特定波长出现跃变的特征。     

Anomalous diffusion for a correlated process with long jumps

We discuss diffusion properties of a dynamical system, which is characterised by long-tail distributions and finite correlations. The particle velocity has the stable Lévy distribution; it is assumed as a jumping process (the kangaroo process) with a variable jumping rate. Both the exponential and the algebraic form of the covariance–defined for the truncated distribution–are considered. It is demonstrated by numerical calculations that the stationary solution of the master equation for the case of power-law correlations decays with time, but a simple modification of the process makes the tails stable. The main result of the paper is a finding that–in contrast to the velocity fluctuations–the position variance may be finite. It rises with time faster than linearly: the diffusion is anomalously enhanced. On the other hand, a process which follows from a superposition of the Ornstein–Uhlenbeck–Lévy processes always leads to position distributions with a divergent variance which means accelerated diffusion.     

材料表面之间黏附过程分析

对两材料表面黏附过程进行了理论分析，得出了跳触距离的计算公式，发现跳触距离与试样的几何尺寸和系统的刚度有关，而且也受到相对湿度的影响. 利用单峰接触模型和幂律流体的本构方程，对材料表面吸附的水膜进行了动力学分析，改进了描述拉开力和停留时间关系的方程. 并利用自制的黏附力测试装置对跳触力和拉开力进行了测试和分析. 关键词： 黏附 范德华力 相对湿度 水膜     

Dose,exposure time and resolution in serial X‐ray crystallography

The resolution of X‐ray diffraction microscopy is limited by the maximum dose that can be delivered prior to sample damage. In the proposed serial crystallography method, the damage problem is addressed by distributing the total dose over many identical hydrated macromolecules running continuously in a single‐file train across a continuous X‐ray beam, and resolution is then limited only by the available molecular and X‐ray fluxes and molecular alignment. Orientation of the diffracting molecules is achieved by laser alignment. The incident X‐ray fluence (energy/area) is evaluated that is required to obtain a given resolution from (i) an analytical model, giving the count rate at the maximum scattering angle for a model protein, (ii) explicit simulation of diffraction patterns for a GroEL–GroES protein complex, and (iii) the spatial frequency cut‐off of the transfer function following iterative solution of the phase problem, and reconstruction of an electron density map in the projection approximation. These calculations include counting shot noise and multiple starts of the phasing algorithm. The results indicate counting time and the number of proteins needed within the beam at any instant for a given resolution and X‐ray flux. An inverse fourth‐power dependence of exposure time on resolution is confirmed, with important implications for all coherent X‐ray imaging. It is found that multiple single‐file protein beams will be needed for sub‐nanometer resolution on current third‐generation synchrotrons, but not on fourth‐generation designs, where reconstruction of secondary protein structure at a resolution of 7 Å should be possible with relatively short exposures.     

基于离散泊松方程解的相位展开方法

提出了基于离散泊松方程解的相位展开方法，针对被测件表面疵病(阴影、断裂、孔洞、噪声等)奇异点所产生的相位跳变和截断，建立了相位展开算法模型；引入离散余弦变换求解具有诺埃曼边界条件的离散泊松方程，得到最小二乘意义下的展开相位解。经实验证明，该方法能够消除干涉图奇异点相位跳变，消除传统相位展开法所产生的“跳序”和“拉线”现象，恢复真实相位。     

纳米结构表面上部分润湿液滴合并诱导弹跳的理论研究

部分润湿液滴是适宜纳米结构表面上滴状冷凝传热的主要载体,研究纳米结构参数与部分润湿液滴合并弹跳之间的关系有重要意义,本文依据冷凝液滴生长过程中能量增加最小的原理来判断其是否为部分润湿状态,并根据液滴合并前后的体积和界面自由能守恒,确定了合并液滴的初始形状,进而对合并液滴变形过程的动力学方程进行了求解,结果表明:部分润湿冷凝液滴仅在纳米柱具有一定高度、直径间距比较大的表面上形成,而当纳米柱高度过低、直径间距比小于0.1时则形成完全润湿的冷凝液滴;液滴合并后能否弹跳与纳米结构参数紧密相关,仅在纳米柱较高、直径间距比适宜的表面上,部分润湿液滴合并后才能诱发弹跳;液滴尺度及待合并液滴间的尺度比对合并弹跳也有重要影响;多个部分润湿液滴合并后由于具有更多的过剩界面自由能而比两个液滴合并更容易诱发弹跳,本模型对纳米结构表面上冷凝液滴是否合并诱发弹跳的计算结果与绝大部分实测结果相一致,准确率达到95%。     

Reproduction and application of human bouncing and jumping forces from visual marker data

State-of-the-art facilities for measuring bouncing and jumping ground reaction forces (GRFs) comprise typically equipment for direct force measurement, i.e. single or multiple floor-mounted force plates. Artificial laboratory conditions and constraints imposed by the direct measurement systems, such as the small measuring area of a force plate, can have a strong influence on human ability to bounce and jump, naturally yielding unrepresentative force data. However, when dealing with issues like vibration serviceability assessment of real full-scale structures, such as floors, footbridges, staircases and grandstands, there is a growing need to estimate realistic GRFs under a wide range of natural conditions. This paper presents a novel method in the civil engineering context utilising ‘free-field’ measurement of human bouncing and jumping forces recorded continuously in time using motion capture technology transferred and adapted from biomechanical research. Results show that this kind of data can be used successfully in studies of human-structure dynamic interaction, specifically negative cue effect of a perceptibly vibrating structure on GRFs, energy flow and power in the human-structure system, and also synchronisation between individuals when bouncing/jumping in groups on more or less perceptibly moving structures.     

Arc Root Motions in an Argon--Hydrogen Direct-Current Plasma Torch at Reduced Pressure

Arc root motions in generating dc argon hydrogen plasma at reduced pressure are optically observed using a high-speed video camera. The time resolved angular position of the are root attachment point is measured and analysed. The arc root movement is characterized as a chaotic and jumping motion along the circular direction on the anode surface.     

连续能量共轭加权蒙特卡罗动态参数计算

本文开展基于连续能量共轭加权蒙特卡罗的堆芯动态参数计算研究,这些参数主要包括缓发中子有效份额、瞬发中子代时间和瞬发中子衰减常数,在目前普遍采用的迭代裂变概率（IFP）的基础上,扩展原有IFP方法中共轭通量的选择,比较径迹长度估计、碰撞估计、吸收估计和tally记数估计的差别,及协方差和方差权重计算.同时,给出多个概率区间的动态参数分布范围,对迭代裂变概率法进行深入的研究,对比并给出下一代事件估计计数和不同中间代迭代裂变概率估计计数对计算结果的影响,从中得出合适的迭代代数.相关程序在计算完成后自动输出各种粒子分布状况统计.     

定制Linux LiveCD的研究与实现

针对每次安装Linux都要根据需要重新配置系统环境的问题,提出一种在Linux下定制LiveCD 的方法。Ubuntu是Linux众多发行版中的一种,在Ubuntu下制作LiveCD最常用的方法是使用UCK和Reconstructor,但是这两种方法都不能把当前系统生成LiveCD,鉴于此,研究并实现使用Live Ubuntu Backup在Ubuntu下定制LiveCD的方法。该方法首先将配置好的操作系统备份成一个squashfs文件,然后用该squashfs文件替换掉原始系统中的squashfs文件,最后将符合用户需求的系统生成LiveCD。实验结果表明,该方法满足定制LiveCD的要求,并且最终生成的LiveCD运行稳定,达到了预期要求。