A cell-based study on pedestrian acceleration and overtaking in a transfer station corridor

Pedestrian speed in a transfer station corridor is faster than usual and sometimes running can be found among some of them. In this paper, pedestrians are divided into two categories. The first one is aggressive, and the other is conservative. Aggressive pedestrians weaving their way through crowd in the corridor are the study object of this paper. During recent decades, much attention has been paid to the pedestrians’ behavior, such as overtaking (also deceleration) and collision avoidance, and that continues in this paper. After sufficiently analyzing the characteristics of pedestrian flow in transfer station corridor, a cell-based model is presented in this paper, including the acceleration (also deceleration) and overtaking analysis. Acceleration (also deceleration) in a corridor is fixed according to Newton’s Law and then speed calculated with a kinematic formula is discretized into cells based on the fuzzy logic. After the speed is updated, overtaking is analyzed based on updated speed and force explicitly, compared to rule-based models, which herein we call implicit ones. During the analysis of overtaking, a threshold value to determine the overtaking direction is introduced. Actually, model in this paper is a two-step one. The first step is to update speed, which is the cells the pedestrian can move in one time interval and the other is to analyze the overtaking. Finally, a comparison between the rule-based cellular automata, the model in this paper and data in HCM 2000 is made to demonstrate our model can be used to achieve reasonable simulation of acceleration (also deceleration) and overtaking among pedestrians.     

提高双参量光纤传感器精度的一种方法

分析了光纤传感器进行双参量测量时，系数矩阵的态性对待测量精度的影响，提出采用对系数矩阵进行预处理的方法，使得处理后的矩阵由病态变成良态。用方法对文献「４」和文献「５」给出的系数矩阵分别进行了处理。处理后，文献「４」系数矩阵的条件数从３４２降低到４，文献「５」系数矩阵的条件数从１６１降低到３，传感器输出不确定主降低了两个数量级。     

一种高准确度、高可靠的红外光电时刻测量系统

针对靶场试验对测量仪器的准确度及可靠性的特殊要求,开发了一种基于嵌入式PC/104模块和大规模可编程逻辑器件CPLD的红外光电时刻测量系统.介绍了该系统的组成、测量原理及其实现途径.靶场实验结果表明,该系统设计环境适应能力强,能可靠地工作在－35～45℃的环境下;测量准确度高,测时误差小于30 μs.     

Numerical studies on velocity, temperature history and heat transfer to the particles injected into the argon plasma

A new approach to study the particle velocity in a thermal plasma in relation to input parameters (power, gas flow rate, injection velocity of the particle and particle size) and nozzle dimensions (nozzle length and diameter) has been made. Injected particle's temperature and thermal history were calculated for particles of three different materials (alumina, tungsten and graphite) in argon plasma. Allowable powder feed rate was calculated for the particles. Heat transfer per particle injected in to the plasma is reported. Liquid fraction of the particle after it reached the melting point is also reported. Particle velocity is found to increase with increase in power, gas flow rate and injection velocity and decrease with increase in particle size, nozzle length and nozzle diameter. Thermal histories of the particles in relation to the plasma temperature and particle diameter are presented. Particle's residence time is found to increase with increase in diameter of the particle. Allowable powder feed rate for complete melting of the particle is higher at higher percentage utilisation of the plasma power. Powder feed rate is seen to decrease with increase in particle size and it is higher for tungsten and lower for graphite particle. Heat transfer rate from plasma to particle is seen to decrease with increase in time and the same is higher for plasmas of higher temperature and smaller sized particle. Received 4 May 2000 and Received in final form 15 March 2001     

近海台风对中国东部夏季降水的贡献

目前汛期预测主要针对季风系统形成的降水, 而对台风等热带系统的影响并未考虑, 其主要原因是台风是一个剧烈的天气尺度过程, 与短期气候预测尺度并不匹配, 因而无法进行考虑. 这也成为提升汛期预测技巧的一个制约因素. 针对这样的问题, 本文从气候的角度, 提出一个能较为客观地衡量台风对夏季降水影响强弱的指数––台风影响指数. 利用1960–2011年中国东部站点降水资料及中国气象局上海台风所整理的热带气旋资料, 从月、季尺度对中国夏季台风影响强弱变化特征进行分析, 探讨台风对东部地区夏季降水的贡献. 结果表明: 1)台风从6月至8月呈增强的趋势, 6月份最弱, 7月份居中, 8月份最强; 2)从台风降水及占总降水的比例分布来看, 纬向呈东部高西部低, 经向呈从东北地区至华南地区依次增大的趋势, 长江以南地区台风降水量占夏季降水量的比重可达10%以上, 7, 8月份东南沿海地区的台风降水量最大可达100 mm以上, 可达当月总降水量的40%; 3)台风影响指数与夏季降水的相关表明, 台风对中国东部降水的影响具有时、空差异性, 6月份与华南地区呈负相关, 7 月份与东南沿海地区呈正相关, 而与长江中下游地区呈负相关; 8月份与华南、华北地区呈正相关、与长江中下游地区呈负相关. 这主要是由台风、夏季风和西北太平洋副热带高压共同影响的. 关键词： 台风影响 东部 夏季降水 贡献     

ZnO Thick Film Based Opto-electronic Humidity Sensor for a Wide Range of Humidity

Sensitivity of zinc oxide film to humidity is studied using prism based opto-electronic sensor configuration. Film is deposited on the base of the prism by screen printing. The film is crystalline in nature and has micropores on its surface which is suitable for humidity sensing. The sensing mechanism, here, is the modulation in emergent light intensity with change in ambient humidity. Response of the sensor configuration is repeatable and the configuration is found to be sensitive to relative humidity (RH%) ranging from 5 to 90 RH%.     

Controlling Surface Interactions with Grafted Polymers

The interactions between surfaces modified with grafted polymers is studied theoretically. The aim of this work is to find polymer surface modifications that will result in localized attractive interactions between the surfaces. The practical motivation of the work is to find means to control the distance between bilayers and solid supports in supported membranes. Two theoretical approaches are used, the analytical treatment of Alexander and a molecular theory. It is found that grafting each end of the polymer to each surface results in an interaction with a well defined minimum. The location of the minima is found to be very close to the thickness of the polymer layer when the chains are grafted to only one of the surfaces. The predictions of the analytical theory are in excellent agreement with the molecular approach in this case. It is found that increasing the surface coverage increases the strength of the interaction. However, increasing the polymer chain length at fixed surface coverage results in a decrease of the free energy cost associated with separating the surfaces from their optimal distance. For the cases in which grafting to both surfaces is not possible, the molecular theory is used to study the effect of functionalizing segments of the chain to achieve an attractive well. It is found that by functionalizing the free end-groups of the polymers with segments attracted to the membrane, the range of the attractive interaction is significantly larger than the thickness of the unperturbed layer. Functionlizing the middle segments of the chains results in a shorter range attraction but of the same strength as in the end-functionalized layers. The optimal polymer modification is found to be such that the functionlized groups are attracted to the bare surface but are not attracted to the grafting surface. The relevance of the results to the design of experimental surface modifiers is discussed.     

Polarized Debye Sheath in Degenerate Plasmas

The force on a charged dust grain in a plasma due to polarization of thermal ions and degenerate electrons around the grain is derived in the limits of weakly relativistic and ultra-relativistic degeneracy of electrons. It is found that in both these cases, the magnitude of the polarization force is enhanced compared to that in classical plasmas. The influence of this force on dust-acoustic(DA) modes is examined and discussed. It is shown that the DA wave frequency in degenerate plasmas is significantly reduced compared to the classical DA mode.     

Robust Stabilization and Synchronization of a Novel Chaotic System with Input Saturation Constraints

In this paper, the robust stabilization and synchronization of a novel chaotic system are presented. First, a novel chaotic system is presented in which this system is realized by implementing a sigmoidal function to generate the chaotic behavior of this analyzed system. A bifurcation analysis is provided in which by varying three parameters of this chaotic system, the respective bifurcations plots are generated and evinced to analyze and verify when this system is in the stability region or in a chaotic regimen. Then, a robust controller is designed to drive the system variables from the chaotic regimen to stability so that these variables reach the equilibrium point in finite time. The robust controller is obtained by selecting an appropriate robust control Lyapunov function to obtain the resulting control law. For synchronization purposes, the novel chaotic system designed in this study is used as a drive and response system, considering that the error variable is implemented in a robust control Lyapunov function to drive this error variable to zero in finite time. In the control law design for stabilization and synchronization purposes, an extra state is provided to ensure that the saturated input sector condition must be mathematically tractable. A numerical experiment and simulation results are evinced, along with the respective discussion and conclusion.     

New mechanism of irradiation creep based on the radiation-induced vacancy emission from dislocations

A new mechanism of irradiation creep is proposed, which is based on the radiation and stress induced difference in emission (RSIDE) of vacancies from dislocations of different orientations with respect to the external stress. This phenomenon is due to the difference in vacancy formation energies, which is proportional to the external stress. The proposed model exhibits similarities with thermal creep models and it is distinct from stress-induced preferential absorption (SIPA) models based on the difference in the long-range interaction of point defects with dislocations. The RSIDE creep rate is essentially temperature independent and is proportional to the dislocation density, stress and irradiation flux. It is inversely proportional to the square of the vacancy formation energy, which is lower than the Frenkel pair formation energy. Experimental verification of the proposed model is discussed on the basis of the measurements of vacancy concentration and creep rate under sub-threshold electron irradiation.     

S波段相对论速调管放大器输入腔的3维分析与模拟

 利用3维软件设计了适用于S波段相对论速调管放大器的单重入输入腔,该腔体采用了偏心设计,以便减小耦合孔处的不均匀场对腔间隙场的影响,分析了腔体耦合孔尺寸对腔间隙场均匀性的影响;建立了带输入波导结构的3维输入腔开放腔模型,并应用此模型,采用3维PIC程序模拟了注入微波功率、束直流对输入腔间隙后束流调制的影响。研究结果表明：耦合孔尺寸对腔间隙电场均匀性影响较大,当耦合孔离轴越近时,腔间隙场越不均匀;在结构参数和束参数固定的条件下,基波电流调制深度随着间隙电压的增加而增加,但达到最大基波调制电流的漂移距离几乎不变;在结构参数和注入微波参数固定的条件下,束直流越大,达到最大基波调制电流所需的漂移距离越短。研究结果为腔体的设计和输入腔束流调制实验提供了参考依据。     

一种用于计算三维视觉测量中线结构光平面的新型算法

介绍了一种基于线结构光的机器视觉测量系统的光平面计算方法.该方法采用图像减影来获取光条图像,利用Steger算法提取图像中的亚像素光条中心点,再用正交直线拟合法计算图像坐标系下的光条直线方程.通过靶标特征点的世界坐标和交比不变性,计算线结构光在靶标平面上的世界坐标点,并将这些坐标点用正交平面拟合法计算得到光平面方程.为了提高整体准确度,本文对算法进行了细节优化,给出了标定系统的设计方案和实验过程.实验结果表明,该方法具有较好的鲁棒性和较高的准确度.     

高精度自动贴片机视觉对准系统及其图像处理

阐述了高精度自动贴片机视觉对准系统的构成和原理。介绍了利用模式识别理论和图像的不变矩实现定位标志存在性判断的原理及算法和定位标志对准的原理及相关的图像处理算法,以及其中的点模式匹配算法。试验结果表明,定位标志存在性判断算法可以有效地区分不同的定位标志和判断定位标志是否在视场之内;定位标志对准算法在输入图像旋转、平移、定位标志被部分遮挡时,能精确地得到定位标志的位置偏差。     

Simultaneous effects of magnetic field and space porosity on compressible Maxwell fluid transport induced by a surface acoustic wave in a microchannel

Peristaltic motion induced by a surface acoustic wave of a viscous, compressible and electrically conducting Maxwell fluid in a confined parallel-plane microchannel through a porous medium is investigated in the presence of a constant magnetic field. The slip velocity is considered and the problem is discussed only for the free pumping case. A perturbation technique is employed to analyze the problem in terms of a small amplitude ratio. The phenomenon of a “backward flow” is found to exist in the center and at the boundaries of the channel. In the second order approximation, the net axial velocity is calculated for various values of the fluid parameters. Finally, the effects of the parameters of interest on the mean axial velocity, the reversal flow, and the perturbation function are discussed and shown graphically. We find that in the non-Newtonian regime, there is a possibility of a fluid flow in the direction opposite to the propagation of the traveling wave. This work is the most general model of peristalsis created to date with wide-ranging applications in biological, geophysical and industrial fluid dynamics.     

一种红外搜索系统中弱小目标自适应检测算法

为解决红外搜索系统中场景起伏造成的背景预测不准确这一问题,提出了一种自适应调整的空间滤波方法。该算法在估计背景的同时,对背景残差进行计算,根据残差值调整滤波参数,使背景残差趋于最小,以适应背景的起伏。当背景包含较多复杂因素时,不利于目标提取,多尺度形态学算子通过不同尺度不同形态的结构体参与计算,可以全面地估计背景,进一步抑制背景残差,再通过计算图像全局阈值,自适应分割出潜在目标。采用并行运算,可将算法实现于现场可编程器件(FPGA)上。试验结果表明:即使当场景较复杂,场景信噪比较低时,依然可以使处理后的图像信噪比大于3,从而可显著提高红外搜索系统的检测概率,实现弱小目标的检测。     

Free Vibration Analysis of RC Box-Girder Bridges Using FEM

The free vibration analysis of simply supported box-girder bridges is carried out using the finite element method. The fundamental frequency is determined in straight, skew, curved and skew-curved box-girder bridges. It is important to analyse the combined effect of skewness and curvature because skew-curved box-girder bridge behaviour cannot be predicted by simply adding the individual effects of skewness and curvature. At first, an existing model is considered to validate the present approach. A convergence study is carried out to decide the mesh size in the finite element method. An exhaustive parametric study is conducted to determine the fundamental frequency of box-girder bridges with varying skew angle, curve angle, span, span-depth ratio and cell number. The skew angle is varied from 0° to 60°, curve angle is varied from 0° to 60°, span is changed from 25 to 50 m, span-depth ratio is varied from 10 to 16, and single cell & double cell are used in the present study. A total of 420 bridge models are used for parametric study in the investigation. Mode shapes of the skew-curved bridge are also presented. The fundamental frequency of the skew-curved box-girder bridge is found to be more than the straight bridge, so, the skew-curved box-girder bridge is preferable. The present study may be useful in the design of box-girder bridges.     

原油含水率测量的光学计量仪

油井含水率是油田开发过程中的一个重要指标。光纤传感器具有体积小、重量轻、抗干扰能力强、实时、高效、准确等优点,将其应用于石油测井,有利于提高勘探效率。介绍测井应用中原油含水率计量仪的结构,分析了光纤传感器对混合液体含水率测量的基本原理。激光在弯曲光纤中的传输效率随外界混合介质折射率的变化而改变,根据光纤输出光功率的大小可以测量外界混合介质的组成成分。通过数值模拟,给出了光纤传感器中光束强度随混合液体含水率的变化现象,计算得到混合液体中含水率测量结果。结果表明,光纤传感器计量仪能实现0%～100%含水量的连续测量。最后基于数值模拟结果讨论了系统设计中的注意事项。     

Analysis of convergence for initial condition estimation of coupled map lattices based on symbolic dynamics

A novel approach to the inverse problem of diffusively coupled map lattices is systematically investigated by utilizing the symbolic vector dynamics.The relationship between the performance of initial condition estimation and the structural feature of dynamical system is proved theoretically.It is found that any point in a spatiotemporal coupled system is not necessary to converge to its initial value with respect to sufficient backward iteration,which is directly relevant to the coupling strength and local mapping function.When the convergence is met,the error bound in estimating the initial condition is proposed in a noiseless environment,which is determined by the dimension of attractors and metric entropy of the system.Simulation results further confirm the theoretic analysis,and prove that the presented method provides the important theory and experimental results for better analysing and characterizing the spatiotemporal complex behaviours in an actual system.     

浊度干扰下硝酸盐浓度紫外导数光谱检测方法研究

硝酸盐是水中“三氮”（硝酸盐氮、氨氮、总氮）之一,是反映水体受污染程度的一项重要指标。传统 “现场采样-离线分析” 的硝酸盐化学检测方法操作繁琐、耗时长,难以满足现代水环境实时在线检测需求。由于硝酸根在紫外区具有很强的紫外吸收特性,并且紫外吸收光谱法具有简便快速、可实现实时在线监测等特点,近年来被广泛用于硝酸盐浓度的测量。但使用紫外吸收光谱法检测水体硝酸盐含量时,容易受到水体浊度影响,造成谱线非线性抬升,导致测量误差。目前对浊度补偿算法的研究大都用于水中COD含量的检测,对硝酸盐检测中浊度干扰去除研究较少。为此提出一种基于一阶导数紫外吸收光谱的硝酸盐浓度测量方法,该方法可以减小浊度干扰,从而提高紫外光谱快速检测硝酸盐含量的准确度。通过测量福尔马肼与硝酸钠标准溶液和它们混合溶液在190~300 nm波段的紫外吸收光谱并做一阶导数光谱处理,处理后的光谱采用Savitzky-Golay滤波进行去噪平滑处理,比较浊度与硝酸盐紫外吸收一阶导数光谱特征,分波段研究浊度对硝酸盐紫外一阶导数光谱影响,结果表明硝酸盐导数光谱在220~230 nm波段受浊度影响小;选取220~230 nm波段作为光谱分析区间,以30种不同浓度混合的福尔马肼与硝酸钠溶液作为训练样本,利用偏最小二乘算法建立硝酸盐定量分析模型,使用该建模模型预测剩下的6种不同浓度福尔马肼与硝酸钠混合溶液中硝酸盐的浓度,结果表明福尔马肼干扰下硝酸盐测量结果的预测决定系数（correlation coefficient,R2）为0.994 3,预测均方根误差（root mean square error of prediction,RMSEP）为0.346 9 mg·L-1。为进一步验证该方法的准确性与稳定性,使用该建模模型预测高岭土与硝酸钾配制的混合水样中硝酸盐的浓度,结果表明该方法对高岭土干扰下硝酸盐测量结果的预测决定系数r2为0.991 5,预测均方根误差RMSEP为0.362 8 mg·L-1。综上所述,提出的硝酸盐浓度紫外导数光谱检测方法,采用220~230 nm波段的紫外导数光谱数据,结合PLS建模,可以快速准确测量在浊度干扰下水体硝酸盐的浓度,为发展实际水体硝酸盐在线监测技术与设备提供方法基础。     

Dynamic characteristics of nanoindentation in Ni:A molecular dynamics simulation study

In this work,three-dimensional molecular dynamics simulation is carried out to elucidate the nanoindentation behaviour of single crystal Ni.The substrate indenter system is modelled using hybrid interatomic potentials including the manybody potential(embedded atom method) and two-body Morse potential.The spherical indenter is chosen,and the simulation is performed for different loading rates from 10 m/s to 200 m/s.Results show that the maximum indentation load and hardness of the system increase with the increase of velocity.The effect of indenter size on the nanoindentation response is also analysed.It is found that the maximum indentation load is higher for the large indenter whereas the hardness is higher for the smaller indenter.Dynamic nanoindentation is carried out to investigate the behaviour of Ni substrate to multiple loading-unloading cycles.It is observed from the results that the increase in the number of loading unloading cycles reduces the maximum load and hardness of the Ni substrate.This is attributed to the decrease in recovery force due to defects and dislocations produced after each indentation cycle.