Measuring Dynamics in Evacuation Behaviour with Deep Learning

Bounded rationality is one crucial component in human behaviours. It plays a key role in the typical collective behaviour of evacuation, in which heterogeneous information can lead to deviations from optimal choices. In this study, we propose a framework of deep learning to extract a key dynamical parameter that drives crowd evacuation behaviour in a cellular automaton (CA) model. On simulation data sets of a replica dynamic CA model, trained deep convolution neural networks (CNNs) can accurately predict dynamics from multiple frames of images. The dynamical parameter could be regarded as a factor describing the optimality of path-choosing decisions in evacuation behaviour. In addition, it should be noted that the performance of this method is robust to incomplete images, in which the information loss caused by cutting images does not hinder the feasibility of the method. Moreover, this framework provides us with a platform to quantitatively measure the optimal strategy in evacuation, and this approach can be extended to other well-designed crowd behaviour experiments.     

Element-selective mapping of magnetic moments in ultrathin magnetic films using a photoemission microscope

We combine X-ray magnetic circular dichroism (XMCD) and photoelectron emission microscopy to obtain locally resolved magnetic information on a microscopic scale. Scanning the photon energy across elemental absorption edges and recording microscopic images of the local secondary electron intensity for both photon helicities at each photon energy step allows to analyze local XMCD spectra at any position of the imaged area of the sample. With the help of magnetic sum-rules local quantitative information about magnetic moments can be extracted from such microspectroscopic measurements. The full power of XMCD as a spectroscopic tool is so maintained, while microscopic spatial resolution is added.     

基于针孔成像像面参数提取的单板机镜头显微成像质量评价方法

提出以针孔成像调制传递函数面积(MTFA)和MTFA相对变化率作为像面参数,定量评价单板机镜头的显微成像质量.采用针孔法获取不同视场位置的光斑图像,以提取单板机镜头显微成像系统的调制传递函数(MTF);建立单板机镜头透镜组的MTF数学模型,提取边缘视场弧矢方向与子午方向的MTFA和MTFA相对变化率,用于度量被测镜头显...     

Routing strategies in traffic network and phase transition in network traffic flow

The dynamics of information traffic over scale-free networks has been investigated systematically. A series of routing strategies of data packets have been proposed, including the local routing strategy, the next-nearest-neighbour routing strategy, and the mixed routing strategy based on local static and dynamic information. The capacity of the network can be quantified by the phase transition from free flow state to congestion state. The optimal parameter values of each model leading to the highest efficiency of scale-free networked traffic systems have been found. Moreover, we have found hysteretic loop in networked traffic systems with finite packets delivering ability. Such hysteretic loop indicates the existence of the bi-stable state in the traffic dynamics over scale-free networks.      

An improved fusion algorithm for infrared and visible images based on multi-scale transform

In this paper, an improved fusion algorithm for infrared and visible images based on multi-scale transform is proposed. First of all, Morphology-Hat transform is used for an infrared image and a visible image separately. Then two images were decomposed into high-frequency and low-frequency images by contourlet transform (CT). The fusion strategy of high-frequency images is based on mean gradient and the fusion strategy of low-frequency images is based on Principal Component Analysis (PCA). Finally, the final fused image is obtained by using the inverse contourlet transform (ICT). The experiments and results demonstrate that the proposed method can significantly improve image fusion performance, accomplish notable target information and high contrast and preserve rich details information at the same time.     

Experiment and simulation study on construction of a three-dimensional network model

The construction of a network model is one of the key techniques in organic combination of microscopic flow experiment and simulation. The construction method of a three-dimensional network model is presented on the basis of CT scanning images in this paper. A series of CT slice images describing microscopic pore structure and fluid distribution of actual rock is obtained with the help of the industrial microfocus CT system. Based on the extraction of pore space skeleton, pore and throat information, the corresponding network model is established, and the conversion from three-dimensional CT image information to pore-throat size distribution and topological information is also achieved. The feature of this method lies in the fact that complicated pore space of rock may be characterized by pores and throats with a simple shape while keeping the geometry and flow characteristics. It is indicated that the calculated results of porosity, permeability, relative permeability curve and microscopic remaining oil distribution match very well the experimental results of water flooding and polymer flooding. This network model may fairly well characterize the rock microscopic pore-throat size and topological characteristics. Supported by the National Natural Science Foundation of China (Grant Nos. 10302021 and 10772200)     

Improvements in the clinical utility of calculated T2 images of the human brain

Magnetic Resonance Imaging (MRI) affords a considerable improvement in image contrast over other methods by virtue of the intrinsic NMR parameters spin density, T1, and T2. However, the clinical utility of routine quantification of these parameters is currently unknown. Calculated T2 images might afford additional disease specific information provided the calculation algorithm generates accurate T2 values. In this study, calculated T2 images of a MnCl2 phantom (spanning a T2 range of interest of 45.7 ms to 346.6 ms at 6 MHz) were generated utilizing a variety of calculation algorithms based upon a data set of 32 sequential spin-echo (SE) images. In general, when utilizing only the earliest sequential SE after the 90 degree pulse for the T2 calculation, the greater the number of SE used in the calculation algorithm, regardless of how they were averaged, the more accurate and less noisy was the calculated image. When only limited numbers of SE were used in the calculation algorithm, accuracy and noise varied with the choice of TE suggesting that there may be optimal timings for TE for a particular T2 range of interest. Forty-two calculated T2 head images of normal subjects, based upon data sets of 16 sequential SE, were evaluated for the T2 values of normal brain. These were compared to T2 images calculated via 7 different algorithms based upon 16 SE data sets from two patients with CNS pathology. An optimal algorithm was identified in which 16 SE Carr-Purcell-Meiboom-Gill (CPMG) were averaged into two images for the T2 calculation. With this algorithm, calculated images could be generated efficiently which were accurate and relatively noise free. The availability of such images maximized whatever disease specificity, and thus clinical utility, T2 information affords.     

Quantitative characterization and comparative study of feather melanosome internal morphology using surface analysis

A successful feather development implies in a precise orchestration of cells in the follicle, which culminates in one of the most complex epidermal structures in nature. Melanocytes contribute to the final structure by delivering melanosomes to the barb and barbule cells. Disturbance to the tissue during the feather growth can damage the final structure. Here, melanosomes seen in an unusual outgrowth on the barb cortex of a flight feather are reported and compared to commonly observed melanosomes embedded in the cortex. Transmission Electron Microscopy in scanning-transmission mode (STEM) generated images coupled with secondary electron detection. The two classes of melanosomes were registered on images combining transmitted and secondary electron signals. Image processing allowed surface analyses of roughness and texture of the internal morphology of these organelles. Results showed that the two classes of melanosomes are significantly distinct internally, indicating that different physiological processes up to feather maturation could have occurred. Surface analysis methods are not regularly used in cell biology studies, but here it is shown that it has great potential for microscopic image analysis, which could add robust information to studies of cell biology events.     

最近邻域与无邻域算法结合空间滤波实现显微光切片

运用最近邻域与无邻域算法,并结合空间滤波方法,可去除显微切层图像的离焦模糊成份,可获得高成像速度、高质量的显微光切片。对各种显微图像进行了光切片处理,并与由现有去卷积处理、结构光照明等方法获得的光切片图像进行了对比,验证了该算法在去除模糊信息方面有更好的效果,提高了图像处理效率,获得了令人满意的光切片图像。在此基础上研制出了显微光切片图像处理系统。运用最近邻与无最近邻算法,结合空间滤波方法,采用简便可调的卷积模糊算子代替点扩散函数的估计过程,图像处理方便快捷,可较好地去除离焦平面的模糊信息。     

应用高分辨率影像的城市固体废弃物提取

日益增多的城市固体废弃物不断威胁着城市的生态环境。应用遥感技术的城市固体废弃物监测与管理比实地调查的方法省时省力。然而,分布不规律的城市固体废弃物成分复杂,在高分辨率遥感影像上表现出极强的异质性,无论是针对像素,还是针对运用对象的影像分析方法都难以实现计算机自动提取。针对城市固废堆在重采样低分辨率影像上异质性得到减弱、同质性增强,而在高分辨率上细节丰富、位置准确的特点,提出了一种融合多分辨率对象的城市固废提取方法。以北京市海淀区的QuickBird影像进行实验,结果表明,露天城市固废堆的识别精度可达75%,表明这种多分辨率信息提取策略对于监测露天的城市固废堆十分有效。     

Optimized microphone deployment for near-field acoustic holography: To be, or not to be random, that is the question

Arrays with sparse and random sensor deployment are known to be capable of delivering high quality far-field images without grating lobes. This raises the question of whether or not this idea can be applied to near-field imaging as well. To answer this question that has not yet been widely investigated in previous research, numerical simulations are undertaken in this paper to optimize the microphone deployment for both far-field and near-field arrays with the latter being the main focus. In the simulation, a recently introduced near-field equivalent source imaging (NESI) technique is employed for the near-field imaging. Global optimization techniques including the simulated annealing (SA) algorithm and the intra-block Monte Carlo (IBMC) algorithm are exploited to find the optimal microphone position efficiently. The combined use of the SA and the IBMC algorithms enables efficient search for satisfactory deployment with excellent beam pattern and relatively uniform distribution of microphones. In the near-field optimization, a special kind of beam pattern and cost function definition is used for the multiple-input-multiple-output (MIMO) imaging problem. As indicated by the simulation results, random deployment of microphones is necessary to avoid grating lobes in far-field imaging. In the near-field simulation, all results suggest that the optimal near-field array is the uniform rectangular array (URA) and the random deployment presents no particular benefit in near-field imaging.     

荒漠绿洲区带状防护林遥感提取方法研究——以磴口为例

防护林是我国荒漠绿洲区主要植被类型，可为该地区防风固沙、水盐调控、水热平衡提供有力保障，调查防护林空间分布信息十分重要。然而荒漠绿洲防护林条带较窄、斑块面积小、分布广且零散，不易大尺度准确提取。为解决此难点，以磴口县荒漠绿洲为研究区，基于GF-2号遥感影像，采用面向对象分类技术提取防护林空间分布信息。分类前，首先基于局部方差（LV）和LV变化率（ROC）曲线，选取分割防护林的最优分割尺度。然后采用随机森林（RF）算法的袋外误差率（OOB error）及基尼系数（Gini）对包含光谱、形状和纹理的分类特征进行重要性评估并筛选特征、优化模型参数；最后，基于随机森林、CART决策树、支持向量机（SVM）、K近邻（KNN）四种分类器提取防护林空间分布信息并对比验证。结果表明：(1）采用ROC-LV曲线方法相比于遍历分割参数，可更客观更高效地筛选最优分割参数的可能值；(2）基于RF算法计算的袋外误分率和基尼系数可以有效筛除冗余特征，配合分类器参数优化，在保证分类精度的同时，有效提高分类器性能，大幅提升数据处理速度；(3）基于实测数据集对分类结果进行验证，结果显示基于随机森林算法的特征优化结合SVM分类器提取的防护林空间分布信息精度最高，生产者精度达到97.14%，总体防护林面积为208.99 km2，与实际210 km2接近，在小区块中，SVM分类器的分类效果优于其他三种分类器；(4）因GF-2影像分辨率高，并且含有近红外波段，通过波段合成得到亚米级信息，故基于面向对象的方法能够以单条林带为基本单位研究防护林林网属性，例如提取断带信息等林网结构特征。研究结论可为荒漠绿洲区带状防护林提取提供重要技术支撑。     

Digital image correlation involves an inverse problem: A regularization scheme based on subset size constraint

Digital image correlation (DIC) is essentially implicated in a class of inverse problem. Here, a regularization scheme is developed for the subset-based DIC technique to effectively inhibit potential ill-posedness that likely arises in actual deformation calculations and hence enhance numerical stability, accuracy and precision of correlation measurement. With the aid of a parameterized two-dimensional Butterworth window, a regularized subpixel registration strategy is established, in which the amount of speckle information introduced to correlation calculations may be weighted through equivalent subset size constraint. The optimal regularization parameter associated with each individual sampling point is determined in a self-adaptive way by numerically investigating the curve of 2-norm condition number of coefficient matrix versus the corresponding equivalent subset size, based on which the regularized solution can eventually be obtained. Numerical results deriving from both synthetic speckle images and actual experimental images demonstrate the feasibility and effectiveness of the set of newly-proposed regularized DIC algorithms.     

一种红外导引头量测误差抑制方法研究

针对自寻的反坦克导弹的红外导引头由于受复杂背景和随机干扰影响测角精度不高的问题,提出了一种惯导信息辅助的无迹卡尔曼滤波方法。利用惯导信息描述导弹自身的运动,基于弹目信息状态变量构建弹目相对运动模型,在此基础上采用无迹卡尔曼滤波方法实现对导引头量测误差的抑制。该方法实现了导引头量测信息与惯导信息的融合,充分利用信息资源,抑制导引头量测误差,提高了导弹的打击精度,仿真实验证明了该方法的有效性。     

Temperature dependence of structure and density for D?O confined in MCM-41-S

Using neutron diffraction, we have tracked the temperature dependence of structural properties for heavy water confined in the nanoporous silica matrix MCM-41-S. By observing the correlation peak corresponding to the pore-pore distance, which is determined by the scattering contrast between the silica and the water, we monitored the density of the confined water. Concurrently, we studied the prominent first diffraction peak of D(2)O at ≈ 1.8 ?(-1), which furnishes information on the microscopic arrangement of the water molecules. The data show the presence of a density maximum at ≈ 275 K (± 10 K), a property similar to bulk water, and the occurrence of a density minimum at ≈ 180 K (± 10 K). The prominent diffraction peak of D(2)O is found to shift and sharpen over a wide T range from 200 to 270 K, reflecting structural changes that are strongly correlated with the changes in density. We also observe the continuous formation of external ice, arising from water expelled from the pores while expansion takes place within the pores. An efficient method for monitoring the density of the confined D(2)O using a triple-axis spectrometer is demonstrated.     

Multistage morphological segmentation of bright-field and fluorescent microscopy images

This paper describes the multistage morphological segmentation method (MSMA) for microscopic cell images. The proposed method enables us to study the cell behaviour by using a sequence of two types of microscopic images: bright field images and/or fluorescent images. The proposed method is based on two types of information: the cell texture coming from the bright field images and intensity of light emission, done by fluorescent markers. The method is dedicated to the image sequences segmentation and it is based on mathematical morphology methods supported by other image processing techniques. The method allows for detecting cells in image independently from a degree of their flattening and from presenting structures which produce the texture. It makes use of some synergic information from the fluorescent light emission image as the support information. The MSMA method has been applied to images acquired during the experiments on neural stem cells as well as to artificial images. In order to validate the method, two types of errors have been considered: the error of cell area detection and the error of cell position using artificial images as the “gold standard”.     

Motion deblurring using edge map with blurred/noisy image pairs

Motion deblurring methods using blurred/noisy image pairs usually include denoising process of the noisy image. Because both remaining noise and distorted fine details in the denoised image cause an error on deblurring, we propose an algorithm using an edge map of the noisy image to retain sharp edge information while neglecting noise in any smooth region that does not contain information about the motion that occurred during the exposure. In addition, the blur kernel is efficiently estimated by employing the fast total variation regularization method for the gradients of blurred and noisy images only on edge regions. For latent image restoration, another fidelity term is added, which compares the gradients of the noisy and estimated latent images on edge regions to preserve the fine details of the noisy image. To model a sparse distribution of real-world image gradients, a deconvolution method imposing hyper-Laplacian priors based on an alternating minimization scheme is also derived to restore a latent image efficiently. Experimental results show that the peak signal-to-noise ratios of the restored images against the original latent images have been increased by 11.1% on average, when compared to the existing algorithms using an image pair.     

一种新的全色图像与光谱图像融合方法研究

给出了一种新的综合伪彩色映射技术和小波变换理论的图像融合方法,并将其应用于全色图像和光谱图像的融合中.通过提取两个不同谱段光谱图像的共有信息和特别信息,并进行伪彩色映射融合,来增强目标与背景的对比度.同时将伪彩色映射融合后的图像进一步用IHS变换提取空间信息,在小波变换框架下将其与全色图像进行融合以提高目标的边缘细节信息,使所获得的融合结果不仅包含丰富的光谱信息的同时还具有较高的空间分辨率.仿真图和评价指标表明,该算法在增强目标与背景的对比度以及保留目标信息等方面具有较强的优势.     

A stochastic multiscale framework for modeling flow through random heterogeneous porous media

Flow through porous media is ubiquitous, occurring from large geological scales down to the microscopic scales. Several critical engineering phenomena like contaminant spread, nuclear waste disposal and oil recovery rely on accurate analysis and prediction of these multiscale phenomena. Such analysis is complicated by inherent uncertainties as well as the limited information available to characterize the system. Any realistic modeling of these transport phenomena has to resolve two key issues: (i) the multi-length scale variations in permeability that these systems exhibit, and (ii) the inherently limited information available to quantify these property variations that necessitates posing these phenomena as stochastic processes.A stochastic variational multiscale formulation is developed to incorporate uncertain multiscale features. A stochastic analogue to a mixed multiscale finite element framework is used to formulate the physical stochastic multiscale process. Recent developments in linear and non-linear model reduction techniques are used to convert the limited information available about the permeability variation into a viable stochastic input model. An adaptive sparse grid collocation strategy is used to efficiently solve the resulting stochastic partial differential equations (SPDEs). The framework is applied to analyze flow through random heterogeneous media when only limited statistics about the permeability variation are given.     

Neutron diffraction evidence of microscopic charge inhomogeneities in the CuO2 plane of superconducting La2-xSrxCuO4 (0<or=x<or=0. 30)

High-resolution atomic pair distribution functions have been obtained using neutron powder diffraction data from La2-xSrxCuO4 over the range of doping 0相似文献