Experimental study and numerical simulation of evacuation from a dormitory

The evacuation process of students from a dormitory is investigated by both experiment and modeling. We investigate the video record of pedestrian movement in a dormitory, and find some typical characteristics of evacuation, including continuous pedestrian flow, mass behavior and so on. Based on the experimental observation, we found that simulation results considering pre-movement time are closer to the experimental results. With the model considering pre-movement time, we simulate the evacuation process and compare the simulation results with the experimental results, and find that they agree with each other closely. The crowd massing phenomenon is conducted in this paper. It is found that different crowd massing phenomena will emerge due to different desired velocities. The crowd massing phenomenon could be more serious with the increase of the desired velocity. In this study, we also found the faster-is-slower effect. When the positive effect produced by increasing the desired velocity is not sufficient for making up for its negative effect, the phenomenon of the greater the desired velocity the longer the time required for evacuation will emerge. From the video record, it can be observed that the mass behavior is obvious during the evacuation process. And the mass phenomenon could also be found in simulation. The results obtained from our study are also suitable to all these buildings in which both living and resting areas occupy the majority space, such as dormitories, residential buildings, hotels (restaurants) and so on.     

Influences of exit and stair conditions on human evacuation in a dormitory

Evacuation processes of students are investigated by experiment and simulation. The experiment is performed for students evacuating from a dormitory with an exit and stairs. FDS+Evac is proposed to simulate the exit and stair dynamics of occupant evacuation. Concerning the exit and stair widths, we put forward some useful standpoints. Good agreement is achieved between the predicted results and experimental results. With the increase of exit width, a significant stratification phenomenon will be found in flow rate. Stratification phenomenon is that two different stable flow rates will emerge during the evacuation. And the flow rate curve looks like a ladder. The larger the exit width, the earlier the stratification phenomenon appears. When exit width is more than 2.0 m, the flow rate of each exit width is divided into two stable stages, and the evacuation times show almost no change. The judgment that the existence of stairs causes flow stratification is reasonable. By changing the width of the stairs, we proved that judgment. The smaller the width of BC, the earlier the stratification appears. We found that scenario 5 is the most adverse circumstance. Those results are helpful in performance-based design of buildings.     

纪念劳厄发现X射线衍射100周年

100年前,德国人劳厄发现X射线通过晶体时可以发生衍射效应．随后,英国的布拉格父子等人发展出一系列实验和分析方法,利用X射线晶体衍射解析出具有原子分辨率的分子结构．在过去的100年中,X射线衍射分析对世界的科学发展乃至人们的生活都产生了至关重要的影响,并且在这100年间,X射线衍射实验方法和分析方法也有了长足进步．硬X射线自由电子激光的出现为X射线衍射分析进一步发展提供了更广阔的空间,可以预期,基于自由电子激光的X射线衍射分析会进一步在物理、化学、生物等学科中发挥更为重要的影响．     

Estimating complex covariance by observing two variables at a time

The estimation of covariance matrices is central in array signal processing systems. This note addresses complex covariance estimation for the situation, where the complex data are available only as independent pairwise sets (observations) corresponding to individual elements of the matrix. The formulation for the empirical estimate and the normal maximum likelihood estimate is developed for the general case of different sample sizes for each observation. The approach allows, for example, the estimate of the p by p covariance matrix of a p-port sensor array from a two-port measurement instrument.     

An Accelerated Osculation Method and its Application to Numerical Conformal Mapping

A variant of the classical Koebe-logarithm osculation algorithm for conformal mapping is obtained by inserting a hyperbolic sine at an intermediate step. The modulus of convergence is calculated, and numerical experiments are reported, in particular in comparison with the method of Grassmann [E. Grassmann (1979). Numerical experiments with a method of successive approximation for conformal mapping. J. Applied Mathematics and Physics, 30, 873-884.]. Either procedure may work better, depending upon the domain. Further numerical examples show how the osculation method can be coupled to faster converging algorithms (which tend to work best for nearly-circular domains), thus making feasible computations which would not be accessible by either method alone.     

高能激光辐照下光纤布拉格光栅响应特性

为探索光纤布拉格光栅在高能激光参数测量方面的应用,通过实验和数值模拟研究分析了其在高能激光辐照下的响应特性。通过解传热方程,获得了光纤布拉格光栅在高能激光辐照下的热响应特性。利用一个光纤光栅解调仪,记录了光纤布拉格光栅在高能激光辐照下的波长漂移现象。实验结果表明：在一定的功率密度范围内,光纤布拉格光栅的最大波长漂移与其所受的辐照功率密度成线性关系,该结果与理论模拟相符。     

The resonance interaction of relativistic charged particle and circularly polarized electromagnetic wave

The resonance interaction of a relativistic charged particle in a circularly polarized electromagnetic wave traveling along a uniform magnetic field is considered. The position, momentum and energy of the particle are presented analytically as functions of a free parameter. The results may be of importance for plasma heating, microwave generation or particle acceleration.     

单轴晶体包层光纤Bragg光栅反射谱特性模拟研究

本文推导了包层为单轴各向异性晶体的光纤理想正规模特征方程, 应用中值定理, 结合Matlab的数值求解, 提出了这一超越方程的一种求解算法, 并在此基础上, 对包层为单轴各向异性材料的光纤Bragg光栅的反射谱与包层折射率关系进行了模拟分析. 模拟结果表明, k_cl 对反射谱有很大的影响, 不同的k_cl 可以导致不同的光栅反射率和Bragg波长.     

Fermi超流气体在unitarity区域和Bose-Einstein 凝聚区域的自俘获现象研究

在平均场理论和两模近似下,通过观察布居数差随时间的演化, 以及布居数差的平均随非线性相互作用参数的变化, 研究了对称双势阱以及势阱间高频调制时Fermi超流气体在unitarity区域和Bose-Einstein凝聚区域的自俘获现象. 给出了出现自俘获现象的边界条件;发现高频调制在一定调制范围内使自俘获现象更容易实现. 最后研究了初值对自俘获的影响, 发现初值的绝对值|s(0)|的增加更有利于自俘获的实现.     

厄尔尼诺/拉尼娜-南方涛动非线性扰动模型孤子的渐近解法

研究了一类厄尔尼诺/拉尼娜-南方涛动(ENSO)随机扰动模型. 首先, 利用特殊的待定系数方法得到了无扰动ENSO模型下的孤子精确解. 然后利用渐近理论和方法构造了随机扰动ENSO模型的近似解, 并举例说明得到的渐近解具有较好的精度.