首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 171 毫秒
1.
We propose a pedestrian position update rule,which is added to a microscopic pedestrian model to avoid pedestrian overlap.In the rule,the step size of a pedestrian moving in a selected direction at each update is in inverse proportion to the repulsive actions imposed by other pedestrians moving in a direction with an exponential rate.The positions of the pedestrians are then updated in each small time interval.In this way,a barrier between the pedestrians can be generated,and after updating their positions the pedestrians do not overlap with each other.The modified model is compared to the original model through a simulation of the evacuation process of pedestrians in a closed area.The simulation results indicate that the modified model is superior to the original model in several aspects.  相似文献   

2.
Walking in groups is very common in a realistic walking environment. An extended floor field cellular automaton(CA)model is therefore proposed to describe the walking behavior of pedestrian groups. This model represents the motion of pedestrian groups in a realistic way. The simulation results reveal that the walking behavior of groups has an important but negative influence on pedestrian flow dynamics, especially when the density is at a high level. The presence of pedestrian groups retards the emergence of lane formation and increases the instability of operation of pedestrian flow. Moreover,the average velocity and volume of pedestrian flow are significantly reduced due to the group motion. Meanwhile, the parameter-sensitive analysis suggests that pedestrian groups should make a compromise between efficient movement and staying coherent with a certain spatial structure when walking in a dense crowd.  相似文献   

3.
邝华  李兴莉  韦艳芳  宋涛  戴世强 《中国物理 B》2010,19(7):70517-070517
This paper proposes a modified lattice gas model to simulate pedestrian counter flow by considering the effect of following strength which can lead to appropriate responses to some complicated situations.Periodic and open boundary conditions are adopted respectively.The simulation results show that the presented model can reproduce some essential features of pedestrian counter flows,e.g.,the lane formation and segregation effect.The fundamental diagrams show that the complete jamming density is independent of the system size only when the width W and the length L are larger than some critical values respectively,and the larger asymmetrical conditions can better avoid the occurrence of deadlock phenomena.For the mixed pedestrian flow,it can be found that the jamming cluster is mainly caused by those walkers breaking the traffic rules,and the underlying mechanism is analysed.Furthermore,the comparison of simulation results and the experimental data is performed,it is shown that this modified model is reasonable and more realistic to simulate and analyse pedestrian counter flow.  相似文献   

4.
The line of sight (LOS) wind velocity can be determined from the incoherent Doppler lidar backscattering signals. Noise and interference in the measurement greatly degrade the inversion accuracy. In this paper, we apply the discrete wavelet denoising method by using biorthogonal wavelets and adopt a distance-dependent thresholds algorithm to improve the accuracy of wind velocity measurement by incoherent Doppler lidar. The noisy simulation data are processed and compared with the true LOS wind velocity. The results are compared by the evaluation of both the standard deviation and correlation coefficient. The results suggest that wavelet denoising with distance-dependent thresholds can considerably reduce the noise and interfering turbulence for wind lidar measurement.  相似文献   

5.
Periodic microstructures on silicon bulk axe formed by the irradiation of the femtosecond laser with the laser wavelength of 800 nm and the pulse length of 130 fs. We investigate the surface periodic ripple structures produced by femtosecond laser treatment. The effects of feedrate of sample, v, on laser-induced surface topography are studied. We find that the femtosecond laser produce periodic ripples of the sub-micron level on silicon surface. At the same time, we realize the optimal conditions to produce these surface structures. When choosing NA = 0.3, and v = 2000μm/s or 3000μm/s, we find a series of periodic-structure ripples where the spacing is about 120 nm and the width is about 45nm. The experimental results indicate that femtosecond laser treatment can produce line arrays on the sub-micron level, which is a positive factor for fabricating grating and other optical applications in nanoscales.  相似文献   

6.
Ramps and sloping roads appear everywhere in the built environment. It is obvious that the movement pattern of people in the sloping path may be different as compared with the pattern on level roads. Previously, most of the studies, especially the mathematical and simulation models, on pedestrian movement consider the flow at level routes.This study proposes a new lattice model for bidirectional pedestrian flow on gradient road. The stability condition is obtained by using linear stability theory. The nonlinear analysis method is employed to derive the modified Korteweg-de Vries(mKdV) equation, and the space of pedestrian flow is divided into three regions: the stable region, the metastable region, and the unstable region respectively. Furthermore, the time-dependent Ginzburg–Landan(TDGL) equation is deduced and solved through the reductive perturbation method. Finally, we present detailed results obtained from the model, and it is found that the stability of the model is enhanced in uphill situation while reduced in downhill situation with increasing slope.  相似文献   

7.
We propose an extended lattice gas model with different maximum velocities to simulate pedestrian counter flow by considering the subconscious behaviour of walkers. Four types of walkers including faster right walkers, slower right walkers, faster left walkers and slower left walkers are involved in the simulation. The simulation results show that our model can capture some essential features of pedestrian counter flows, such as the lane formation, segregation effect and phase separation at higher densities. We also find that the subconscious effect can reduce the occurrence of jam cluster evidently compared with the ease of un-subeonscious effect. At large maximum velocity, the critical density corresponding to the maximum flow rate of the fundamental diagram is in good agreement with the empirical results.  相似文献   

8.
<正>The action of wind on the sea surface plays an important role in the noise generation mechanism.Sea surface wind speed can be estimated accurately provided there is an accurate understanding of the relationship between the ocean ambient noise and wind speed.Many measurements and analyses of the wind dependence of ambient noise have been conducted.The approximate empirical rule given by Wenz[1]states that in the frequency band between 0.5and 5 kHz,the ambient sea-noise spectrum levels decrease  相似文献   

9.
In order to measure the acoustic characteristics of the sound source in a duct system effectively without destroying the main duct,micro-perforated panel structures were applied in the new method by attaching the side branch tubes.The effect and influence to change the acoustical impedance of the loads in a duct system was analyzed and simulated for using one layer and double-layer micro-perforated panel and back cavities with different parameters such as panel thickness,hole diameter,perforation ration,back depth and so on.The results show that the load’s resistance can be changed efficiently by adjusting panel thickness,hole diameter, perforation ratio,the ratio of cross-section between ducts and tubes and other parameters;and the load’s reactance can be changed efficiently by adjusting back depth and distance between micro-perforated panel and main duct.It is also found that combinative usage of one layer and double-layer of these structures can change the reactance substantially in broad frequency domain.The method and the efficient performance of the structures with micro-perforated panel in the measurement were verified by the experiment under the situations of flow and no-flow. Finally,suggestions to design and apply these structures in the above-mentioned method in application were given.  相似文献   

10.
朱丽萍  邱宇  童国平 《中国物理 B》2012,21(7):77302-077302
We numerically investigate the injection process of electrons from metal electrodes to one-dimensional organic molecules by combining the extended Su-Schrieffer-Heeger (SSH) model with a nonadiabatic dynamics method. It is found that a match between the Fermi level of electrodes and the highest occupied molecular orbital (HOMO) or the lowest unoccupied molecular orbital (LUMO) of organic molecules can be greatly affected by the length of the organic chains, which has a great impact on electron injection. The correlation between oligomers and electrodes is found to open more efficient channels for electron injection as compared with that in polymer/electrode structures. For oligomer/electrode structures, we show that the Schottky barrier essentially does not affect the electron injection as the electrode work function is smaller than a critical value. This means that the Schottky barrier is pinned for a small work-function electrode. For polymer/electrode structures, we find that it is possible for the Fermi level of electrodes to be pinned to the polaronic level. The condition under which the Fermi level of electrodes exceeds the polaronic level of polymers is shown to not always lead to spontaneous electron transfer from electrodes to polymers.  相似文献   

11.
Global Positioning System (GPS) has been successfully used to measure displacements of oscillating flexible civil engineering structures such as long suspension bridges and high-rise buildings, and to derive their modal frequencies, usually up to 1 Hz, but there is evidence that these limits can be exceeded using high frequency GPS receivers. Based on systematic experiments in computer controlled oscillations with one- and three-degrees of freedom we investigated the potential of GPS, first to record higher oscillation frequencies, at least up to 4 Hz at the minimum resolution level of this instrument for kinematic applications (?5 mm), and second, to identify more than one dominant frequency. Data were processed using least squares-based spectral analysis and wavelet techniques which permit to analyze entire time series, even those of too short duration or those characterized by gaps, in both the frequency and the time domain.The ability of GPS to accurately measure frequencies of oscillations of relatively rigid (modal frequencies 1-4 Hz) civil engineering structures is demonstrated in the cases of two bridges.The outcome of this study is that GPS is suitable for the identification of dynamic characteristics of even relatively rigid (modal frequencies up to 4 Hz) civil engineering structures excited by various loads (wind, traffic, earthquakes, etc.) if displacements are above the uncertainty level of the method (?5 mm). Structural health monitoring of a wide range of structures appears therefore a promising field of application of GPS.  相似文献   

12.
This paper presents a new damage detection approach for cantilever beam-type structures using the damage-induced inter-storey deflection (DIID) estimated by modal flexibility matrix. This approach can be utilized for damage detection of cantilever beam-type structures such as super high-rise buildings, high-rise apartment buildings, etc. Analytical studies on the DIID of cantilever beam-type structures have shown that the DIID abruptly occurs from damage location. Baseline modification concept was newly introduced to detect multiple damages in cantilever beam-type structures by changing the baseline to the prior damage location. This approach has a clear theoretical base and directly identifies damage location(s) without the use of a finite element (FE) model. For validating the applicability of the proposed approach to cantilever beam-type structures, a series of numerical and experimental studies on a 10-storey building model were carried out. From the tests, it was found that the damage locations can be successfully identified by the proposed approach for multiple damages as well as a single damage. In order to confirm the superiority of the proposed approach, a comparative study was carried out on two well-known damage metrics such as modal strain-based damage index approach and uniform load surface curvature approach.  相似文献   

13.
为掌握10 kV居民区配电变压器振动在建筑中的衰减规律,将实测的变压器振动加速度转化为激励力,作用于剪力墙和框架建筑上,采用有限元法仿真研究变压器振动在建筑中的衰减特性。结果表明,在具有相同层高、层数的剪力墙、框架高层建筑中,位于负一层的变压器传播至各楼层的铅垂向振动加速度级(0~500 Hz),随楼层离地高度h对数值(lg h)的增加线性下降,其斜率分别为33.26和24.84,前者的衰减速率(lg h每增加1振动加速度级的衰减量)约为后者的1.3倍;在剪力墙、框架多层建筑中斜率分别为31.87和20.07,前者的衰减速率约为后者的1.6倍。可见,当建筑层高、层数相同时,变压器振动在剪力墙建筑中比框架建筑中衰减更快;当建筑结构相同时,振动在高层建筑中的衰减速率略大于多层建筑。对0~80 Hz环境振动,变压器振动在剪力墙高层建筑中的铅垂向Z振级衰减速率约为框架高层建筑的2.4倍;剪力墙多层建筑振动衰减速率约为框架多层建筑的3.7倍。在此基础上,建立了变压器传播至剪力墙、框架建筑不同楼层的振动单值和分频段预测模型,可为变压器引起的建筑室内振动预测和控制提供依据。  相似文献   

14.
One of the purposes of pedestrian studies is to evaluate the effects of a proposed program on the pedestrian facilities before its implementation. In order to evaluate the level of service (LOS) of a pedestrian facility, a microscopic model is built to simulate the process of pedestrian crossing street. Most of the existing models focus on the occupant evacuation flow in buildings; however, they are not appropriate for pedestrians in the traffic. According to the characteristics of pedestrian crossing street at signalized crosswalks, we build a model based on cellular automata. Both of the system size and cell size are coordinate with the reality. Depending on the contrast of three parameters of pedestrian flow between simulation data and the reality data, we found that this model is analogous to the real process of pedestrian crossing street at signalized sections. Finally, simulation and its results can provide guidance for evaluating the effects of pedestrian facilities before their implementation.  相似文献   

15.
H. Hangan 《显形杂志》1999,1(4):337-343
Wind-driven rain studies provide the main input to problems such as: precipitation protection, sealing, drainage accumulation. A Computational Fluid Dynamics (CFD) methodology is developed and used to compute trajectories and local intensity factors for two generic buildings, previously tested in the wind tunnel. The methodology is further on applied in investigating real problems such as the role played by cornice in protecting the upper part of a low-rise building or the wetting and downwash on a sloped face of a high-rise building  相似文献   

16.
In an attempt to cope with the problem of providing suitably quiet dwellings in noisy urban environments, it has sometimes been suggested that the lower floors of high-rise buildings might be used for offices (or other noise-insensitive uses), while the upper, presumably quieter, floors could be used for housing. This paper suggests that the proposal is not practical since, in many urban areas, the upper floors of buildings are exposed to almost as much noise as the floors near street level.  相似文献   

17.
In the process of sudden natural disasters (such as earthquake or typhoon), the active mass damper (AMD) system can reduce the structural vibration response optimally, which serves as a frequently applied but less mature vibration-reducing technology in wind and earthquake resistance of high-rise buildings. As the core of this technology, the selection of control algorithm is extremely challenging due to the uncertainty of structural parameters and the randomness of external loads. It is not necessary for the Model Reference Adaptive Control (MRAC) based on the Minimal Controller Synthesis (MCS) algorithm to know in advance the structural parameters, which produces special advantages in conditions of real-time change of system parameters, uncertain external disturbance, and the nonlinear dynamic system. This paper studies the application of the MRAC into the AMD active control system. The principle of MRAC algorithm is recommended and the dynamic model and the motion differential equation of AMD system based on MRAC is established under seismic excitation. The simulation analysis for linear and nonlinear structures when the structural stiffness is degenerated is performed under AMD system controlled by MRAC algorithm. To verify the validity of the MRAC over the AMD system, experimental tests are carried out on a linear structure and a structure with variable stiffness with the AMD system under seismic excitation on the shake table, and the experimental results are compared with those of the traditional pole assignment control algorithm.  相似文献   

18.
Yang-Hui Hu 《中国物理 B》2023,32(1):18901-018901
Building exit as a bottleneck structure is the last and the most congested stage in building evacuation. It is well known that obstacles at the exit affect the evacuation process, but few researchers pay attention to the effect of stationary pedestrians (the elderly with slow speed, the injured, and the static evacuation guide) as obstacles at the exit on the evacuation process. This paper explores the influence of the presence of a stationary pedestrian as an obstacle at the exit on the evacuation from experiments and simulations. We use a software, Pathfinder, based on the agent-based model to study the effect of ratios of exit width ($D$) to distance ($d$) between the static pedestrian and the exit, the asymmetric structure by shifting the static pedestrian upward, and types of obstacles on evacuation. Results show that the evacuation time of scenes with a static pedestrian is longer than that of scenes with an obstacle due to the unexpected hindering effect of the static pedestrian. Different ratios of $D/d$ have different effects on evacuation efficiency. Among the five $D/d$ ratios in this paper, the evacuation efficiency is the largest when $d$ is equal to $0.75D$, and the existence of the static pedestrian has a positive impact on evacuation in this condition. The influence of the asymmetric structure of the static pedestrian on evacuation efficiency is affected by $D/d$. This study can provide a theoretical basis for crowd management and evacuation plan near the exit of complex buildings and facilities.  相似文献   

19.
A.F. Miguel 《Physics letters. A》2009,373(20):1734-1738
The standard benefit of modeling pedestrian streams is the ability to quantify and understand flow patterns, which can be helpful to avoid some potentially dangerous situations. Here we show that the most basic features of pedestrian dynamics can be put on a unifying theoretical basis, which is provided by the constructal law. This law states that every flow system evolves in time so that it develops the flow architecture that maximizes flow access under the constraints posed to the flow. In this Letter, we develop a model of pedestrian streams that accounts for the influence of pedestrian density. The constructal law is invoked in order to quantify both the so-called optimal level of service and system capacity for pedestrian streams.  相似文献   

20.
陈亮  郭仁拥  塔娜 《物理学报》2013,62(5):50506-050506
为研究行人疏散过程中的路径选择行为, 提出了一个基于元胞自动机的行人微观模型, 并组织了三组双出口教室内的学生疏散实验. 模型中, 行人路径选择行为受其到出口距离、前方路径通行能力和行人间排斥力影响. 通过观察实验结果, 得到一些相关现象. 利用实验结果对模型参数进行校正. 利用校正模型对该教室内疏散学生流进行仿真, 结果表明 模型能有效地刻画教室内学生流的疏散特征, 疏散时间随学生人数线性增加. 该研究有助于类似场景中行人疏散策略和方案的制定. 关键词: 元胞自动机 行人疏散 仿真 实验  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号