考虑从众阈值和主体特征的人群疏散元胞自动机模型*

为研究从众行为对人群疏散效率的影响,建立考虑从众阈值和主体特征的人群疏散元胞自动机模型,通过引入从众阈值反映人群中不同个体的从众选择程度,耦合每个主体不同特征属性、不同人员认知能力导致的疏散从众选择差异,利用元胞自动机模拟人群运动状态及动态演化过程,探究从众行为对人群疏散过程的作用规律。结果表明:人群疏散中选择从众行为的人员比例与整体疏散效率存在对应关系,本模型原始工况下,当人群中约60%的人员做出从众选择时,疏散效率相对最优。     

分形与元胞自动机耦合技术应用于厦门城市生态规划

利用2002、2007年的两期TM影像数据,基于分形方法研究了厦门的城市形态特征。首先,利用网格计数分维法得出,自2002年以来分形维数从1.804增至2007年的1.847。由于其分形维数1.847已经超越了城市理想形态维数(1.71±0.02)。结合城市形态发展规律,今后厦门岛的分形维数递增速率减缓后会逐渐回归到城市理想形态维数值。其次,通过集聚分形方法确定了以厦门市政府为圆心半径6 200 m的一个范围,在此范围内合理规划生态用地,不仅会取得较大生态效益,而且会缩短整个城市的分形维数值回归的过程。最后,文章利用元胞自动机的方法,在集聚区域内对厦门岛分形回归进行了模拟分析,提出应在集聚区内转化30%的建设用地为生态用地。此集聚区不仅是城市生态规划工作的重点区域,而且也是改善厦门市整体环境质量的最佳范围。     

Sorption,cellular distribution,and cytotoxicity of imidazolium ionic liquids in mammalian cells – influence of lipophilicity

In order to assist an integrated development of ionic liquids (ILs), a study on the sorption, distribution, and cytotoxicity of a series of 1-alkyl-3-methyl imidazolium tetrafluoroborates with C6 rat glioma cells has been performed. Cellular sorption and distribution among three cellular fractions (cytosol, nuclei, and membranes) were analysed by reversed-phase HPLC (RP-HPLC). Compounds with longer 1-alkyl substituents were sorbed with higher enrichment factors and sorption coefficients per protein than those with shorter 1-alkyl chains. The 1-octyl-3-methyl imidazolium cation (C₈MIM) was enriched 17-folds whereas C₆MIM and C₄MIM were enriched by factors of 3.5 and 2.3, respectively. After fractionation of cells by centrifugation, about 8% of C₈MIM was found in the nuclear fractions. The cytotoxicity as estimated by the tetrazolium reductase assay was increasing with the lengths of the 1-alkyl chains from C₄MIM to C₁₀MIM. Consistently, cell proliferation rates were decreasing with increasing lengths of the 1-alkyl chains. The results reveal the correlations between lipophilicity, cellular sorption, and cytotoxicity.     

Imposed and inherent scales in cellular automata models of habitat

Both observational and modelling studies of the natural environment are characterised by their ‘grain’ and ‘extent’, the smallest and largest scales represented in time and space. These are imposed scales that should be chosen to ensure that the natural scales of the system are captured in the study. A simple cellular automata model of habitat represents only the presence or absence of vegetation, with global and local interactions described by four empirical parameters. Such a model can be formulated as a nonlinear Markov equation for the habitat probability. The equation produces inherent space and time scales that may be considered as transition scales or the scales for recovery from disturbance. However, if the resolution of the model is changed, the empirical parameters must be changed to preserve the properties of the system. Further, changes in the spatial resolution lead to different interpretations of the spatial structure. In particular, as the resolution is reduced, the apparent dominance of one habitat type over the other increases. The model provides an ability to compare both field and model investigations conducted at different resolutions in time and space.     

考虑行人跨越障碍物能力的元胞自动机模型

为深入研究不同类型的行人跨越障碍物行为,建立改进的元胞自动机模型,利用Dijkstra算法计算静态场,根据跨越障碍物能力不同将行人分为强跨越能力、弱跨越能力和无跨越能力3类,通过调查大型商场出入口相关尺寸参数和障碍物分布情况,构建商场疏散通道的疏散场景,分析可跨越障碍物的摆放方式与长度、行人密度和在障碍物可跨越条件下出...     

基于风险评价的核应急分区疏散规划*

为保障核事故应急疏散的时效性和安全性,降低核事故损失,基于核辐射时空分布特征,对疏散集中点和疏散路网进行风险评价,提出分区疏散组织策略,结合行政区划法,完成核电站场外疏散区域划分;将总暴露风险作为优化目标,构建基于元胞传输的分区疏散规划模型,并以我国某沿海核电站为研究对象,验证分区疏散方案可行性。研究结果表明:考虑核辐射风险后的分区疏散方案,能够有效提高疏散效率,保障公众安全,降低疏散时间和暴露风险,优化疏散期间交通状况。研究结果可为核应急疏散组织工作提供参考。     

Hydrologic Impact Assessment of Land Cover Change and Stormwater Management Using the Hydrologic Footprint Residence

Urbanization impacts the stormwater regime through increased runoff volumes and velocities. Detention ponds and low impact development (LID) strategies may be implemented to control stormwater runoff. Typically, mitigation strategies are designed to maintain postdevelopment peak flows at predevelopment levels for a set of design storms. Peak flow does not capture the extent of changes to the hydrologic flow regime, and the hydrologic footprint residence (HFR) was developed to calculate the area and duration of inundated land during a storm. This study couples a cellular automata land cover change model with a hydrologic and hydraulic framework to generate spatial projections of future development on the fringe of a rapidly urbanizing metropolitan area. The hydrologic flow regime is characterized for existing and projected land cover patterns under detention pond and LID‐based control, using the HFR and peak flow values. Results demonstrate that for less intense and frequent rainfall events, LID solutions are better with respect to HFR; for larger storms, detention pond strategies perform better with respect to HFR and peak flow.     

Defining agents' behaviors to simulate complex residential development using multicriteria evaluation

Cellular automata (CA) have been increasingly used to simulate complex geographical phenomena. These models may have limitations on reflecting individuals' behaviors which should be considered in urban simulation. Agent-based modeling can solve some of the problems in addressing individuals' influences in urban systems. However, there is a general lack of methodology on how to define agents' properties. This paper uses multicriteria evaluation techniques to determine some of the parameters for the agent-based model. Empirical data from GIS are used to define agent's properties. Sensitivity analysis is also carried out to assess the influences of parameters on simulation outcomes. This model has been applied to the simulation of the residential development in a fast growing city, Guangzhou, in south China.     

富里酸存在条件下铜对普通小球藻光合作用与细胞生理的影响

为探究富里酸存在条件下,铜对普通小球藻光合作用与细胞生理的影响,对普通小球藻进行富里酸及铜的复合暴露,检测相关的光合作用及细胞生理指标,并与单独暴露富里酸的普通小球藻指标水平进行比较分析.结果表明,铜的加入会影响藻细胞的光合作用,增加细胞膜通透性,使藻细胞体积增大,并导致藻细胞的死亡.富里酸可以明显减弱铜的毒性,减少藻细胞的死亡.随富里酸浓度升高,藻细胞死亡率呈下降趋势;高浓度的富里酸(74.5 mg·L~(-1)和119.2 mg·L~(-1))可以明显减弱铜对藻细胞体积增大的作用,低浓度的富里酸(20 mg·L~(-1)和54 mg·L~(-1))无明显影响.富里酸单独作用能够增强普通小球藻的光合作用,增加藻细胞的细胞膜通透性,但不具有致死性.