粘土颗粒吸附直接染料的分形特征

粘土颗粒对直接耐晒黑和直接大红染料的吸附均可分为快速的边缘覆盖和慢速的晶层吸附2个过程,整个吸附过程符合准-二级反应动力学方程式,除了伊利土-直接耐晒黑染料的吸附体系之外,其它体系的吸附过程中以晶层吸附为主的阶段均具有类分形特征.体系的非线性吸附等温线符合Langmuir型吸附等温模式,并且除了蒙脱土吸附直接大红染料之外,也可以用分形Langmuir吸附等温模式获得较好的模拟效果.在不同原始浓度下直接大红染料在粘土颗粒表面发生的边缘覆盖和晶层吸附这2个过程的程度是不同的,从而导致了吸附等温线在原始染料为150mg·L-1时出现最大的吸附量,而且颗粒边缘覆盖的直接大红染料的比例较高.染料进入粘土颗粒的晶层后,扩大了晶层间距,改变了其表面微孔几何结构.颗粒表面棱角变得光滑,结构疏松,片层结构逐渐减少,上述效果在蒙脱土颗粒上或直接耐晒黑染料吸附时表现地更为显著.而且吸附染料后蒙脱土颗粒对N2的吸附量比伊利土下降的幅度小,其比表面积、孔体积和平均孔径的下降比例也比伊利土小,其中平均孔径的差异比较明显.吸附染料之后粘土颗粒表面分形维数Ds均升高了,晶层膨胀和开孔作用抵消了"表面粗糙度屏蔽"、"孔阻塞效应"机理降低Ds的影响.增加了表面粗糙度.     

黄河包头段不同粒径沉积物分形校正下重金属的吸附研究

推导了分粒级的表面分形维数计算公式,根据推导公式计算了分粒级沉积物的分维值.应用已有的表面分形分维计算公式分别计算了黄河包头段沉积物整体的表面分形分维(1.91)及＜63 μm粒级的分维值(1.36),揭示出黄河水环境的磨蚀和分选2个原因引起黄河包头段沉积物低的分维值.用分形校正吸附模型、Freundlich和Langmuir吸附模型对黄河包头段重金属分粒级沉积物吸附进行了拟合,表明分形校正吸附模型具有较好的适用性,同时揭示分形校正吸附模型与MEA理论结合能更好的对热力学吸附结果进行描述;由吸附结果分析得出4种重金属因粒径引起的吸附量变化程度序列为Cu＞Pb＞Zn≈Cd,初始浓度高的吸附量曲线变化较初始浓度低的曲线变化明显,同时指出Cu、Pb的吸附主要与矿物组成有关,而Zn、Cd的吸附则与吸附剂沉积物空间几何性质(或沉积物表面物理特征)有关.     

中国历代灾害性海潮频率特征及时间序列的分形研究

根据中国历代灾害性海潮史料,运用一般统计方法和分形理论对其时间序列进行了分析,不仅探讨了历史灾害性海潮随时间演进的频率变化特征,而且判定了灾害性海潮时间序列的分形性质,在经基础上,还深入讨论了其分维与历代灾害性海潮暴积累发生次数和累积发生频率之间的关系,以及分维随时间演进的变化趋势。     

地震分布多重分形特征的中期预报意义探讨

讨论了地球岩石圈的自组织临界状态和地震发生的非局域性与多重标度分形统计特征。研究了地震多重分形性质的计算方法及其应用于地震预报的前景。采用推广ＧＰ算法从典型震区的地震数据计算地震多重分形分布的广义维数谱和奇异性谱以确立较敏感的强震前兆,对于不同算法进行了精度、数据量要求及适用范围的比较。研究结果表明：地震分布的多重分形维数谱和奇异性谱对于一些典型震区的强震发生具有中期预报价值。     

分形理论在松嫩平原西部生态环境胁迫研究中的应用

以松嫩平原西部为例,在构建生态环境胁迫评价指标体系的基础上,运用分形理论对生态环境胁迫进行量化研究.结果表明,1989-2004年15 a间,除松原市和扶余县以外,其他县市生态环境胁迫系数都呈增大趋势,特别是大安市、长岭县、乾安县等地胁迫系数较大.采用相对指标法,运用GIS-EIS集成技术,对松嫩平原西部生态环境胁迫度进行分级.最后,分析了影响生态环境胁迫变化的驱动因子,并提出减缓生态环境胁迫的措施.     

Chaotic dynamics in a multispecies community

Environmental and Ecological Statistics - It is shown that community dynamics is neither haphazard nor completely directed. This is quite clear from our examination of a concrete example where...     

Relationship Between Bird Abundances and Landscape Characteristics: The Influence of Scale

Scale is important to consider when investigating effects of the environment on a species. Breeding Bird Survey (BBS) data and landscape metrics derived from aerial photographs were evaluated to determine how relationships of bird abundances with landscape variables changed over a continuous range of 16 spatial scales. We analyzed the average number of birds per stop (1985–1994) for five songbird species (family Cardinalidae) for each of 50 stops on 198 BBS transects throughout six states in the Central Plains, USA. Land along each transect was categorized into six cover types, and landscape metrics of fractal dimension (a measure of shape complexity of habitat patches), edge density, patch density, and percent area were calculated, with principal components used to construct composite environmental variables. Associations of bird abundances and landscape variables changed in accordance with small scale changes. Abundances of three species were correlated with edge density and one with component I, which subsumes initial variables of patch density for urban, closed forest, open forest, and open country. Fractal dimension and component II (summarizing amount of closed forest versus open country) were associated with the most species. Correlation patterns of fractal dimension with northern cardinal (Cardinalis cardinalis) and painted bunting (Passerina ciris) abundances were similar, with highest correlations at intermediate to small scales, suggesting indirectly that these species thrive in areas where local habitat conditions are most important. Multiscale analysis can provide insight into the spatial scale(s) at which species respond, a topic of intrinsic scientific interest with applied implications for researchers establishing protocols to assess and monitor avian populations.     

岩石断裂和破碎的分形研究

岩石断裂与破碎的研究一直是岩石力学的前沿领域,也是采矿、能源、水利、交通、地震等众多工程领域不可或缺的理论基础。本文系统介绍了将分形理论引进到岩石断裂和破碎研究的成果,其中包括岩石微观断裂、宏观裂纹动态扩展以及岩体破碎的块度分布,旨在从一个侧面反映分形理论在岩石力学中的应用,最后还给出了一个工程应用的例子。本文的部分结果曾发表于国际杂志上。     

Phosphorus recovery from wastewater by struvite crystallization：Property of aggregates

Struvite crystallization is a promising method to remove and recover phosphorus from wastewater to ease both the scarcity of phosphorus rock resources and water eutrophication worldwide. To date, although various kinds of reactor systems have been developed, supporting methods are required to control the struvite fines flushing out of the reactors. As an intrinsic property, aggregation is normally disregarded in the struvite crystallization process, although it is the key factor in final particle size and therefore guarantees phosphorus recovery efficiency. The present study developed a method to analyze the characteristics of struvite aggregates using fractal geometry, and the influence of operational parameters on struvite aggregation was evaluated. Due to its typical orthorhombic molecular structure, struvite particles are prone to crystallize into needle or rod shapes, and aggregate at the corners or edges of crystals. The determined fractal dimension(Dpf) of struvite aggregates was 1.52–1.31, with the corresponding range of equivalent diameter(d0.5) at 295.9–85.4 μm. Aggregates formed in relatively low phosphorus concentrations(3.0–5.0 mmol/L) and mildly alkaline conditions(pH 9.0–9.5) displayed relatively compact structures, large aggregate sizes and high aggregation strength. Increasing pH values led to continuous decrease of aggregate sizes, while the variation of Dpfwas insignificant. As to the aggregate evolution, fast growth in a short time followed by a long steady stage was observed.     

汶川大地震余震等待时间序列——基于混沌理论的研究

根据混沌理论,对汶川大地震余震等待时间通过相空间重构,应用互信息法、Cao方法确定出重构参数,并分别计算了该序列的关联维、最大Lyapunov指数以及Kolmogorov熵等特征量。结果表明汶川大地震余震等待时间序列中存在明显的混沌特性,是非线性混沌动力系统演化的结果;并对余震等待时间序列的混沌性态及其产生的根源进行了简单的探索。研究结果可进一步研究汶川大地震余震等待时间序列的复杂性、演化规律及预测参考。