A random graphs model for the study of chemical complexity in planetary atmospheres

We suggest that the study of the general behavior of a chemical system in planetary atmospheres might be equivalent to the study of the evolution of connected components in a random graphs model. The main result of our model is that interacting elements in a system self-organize in such a way that the distribution in size of the created compounds follows a power-law relation. We show that hydrocarbons in giant planets and Titan atmospheres might follow the same type of distribution, suggesting that atmospheric photochemical systems might self-organized as random graphs do. This property could give a new and predictive method for investigations of chemical complexity in planetary atmospheres.     

Hydrologic complexity and classification: a simple data reconstruction approach

Technological advances, by facilitating extensive data collection, better data sharing, formulation of sophisticated methods, and development of complex models, have brought hydrologic research to a whole new level. Despite these obvious advances, there are also concerns about their general use in practice. On the one hand, it is natural to develop more complex models than perhaps needed (i.e. representations having too many parameters and requiring too much data); on the other hand, it is often difficult to ‘translate’ results from one specific situation to another. Recent studies have addressed these concerns, albeit in different forms, such as dominant processes, thresholds, model integration, and model simplification. A common aspect in some of these studies is that they recognize the need for a globally agreed upon ‘classification system’ in hydrology. The present study explores this classification issue further from a simple phase‐space data reconstruction perspective. The reconstruction involves representation of the given multidimensional hydrologic system using only an available single‐variable series through a delay coordinate procedure. The ‘extent of complexity’ of the system (defined especially in the context of variability of relevant data) is identified by the ‘region of attraction of trajectories’ in the phase space, which is then used to classify the system as potentially low‐, medium‐ or high‐dimensional. A host of river‐related data, representing different geographic and climatic regions, temporal scales, and processes, are studied. Yielding ‘attractors’ that range from ‘very clear’ ones to ‘very blurred’ ones, depending on data, the results indicate the usefulness of this simple reconstruction concept for studying hydrologic system complexity and classification. Copyright © 2007 John Wiley & Sons, Ltd.     

中国东-南部裂陷盆地断裂系统复杂性的表现形式及成因机制——以南堡凹陷和涠西南凹陷为例

中国东-南部裂陷系列盆地油气资源十分丰富,而断层的分布演化十分复杂,是油气进一步勘探开发需要解决的关键问题。本文应用广义断层模式,在大量三维地震资料构造解析的基础上,以渤海湾盆地的南堡凹陷和北部湾盆地的涠西南凹陷为例,对中国东-南部盆地复杂的断裂系统进行了解剖和归纳,并提出了伸展变形区预测断层性质的伸展应变椭圆。结果表明,中国东-南部裂陷盆地断裂系统的复杂性存在9种表现方式,从成因上进一步归纳为3个方面:(1)断层的走向和性质多样;(2)断层在平、剖面上存在复杂多变的组合形式;(3)断层形成和演化存在复杂的时-空关系。造成复杂性的根本原因是先存断裂分布的复杂性和不同方向(北西-南东向和近南北向)伸展变形的叠加。不同盆地、同一盆地不同区域应力场演化具有很大的相似性:40Ma以前,北西-南东向伸展;38Ma以来,近南北向伸展。断层分布和演化差异主要是由先存构造分布差异造成的。     

朱仙庄矿断裂分形研究及其对瓦斯赋存的控制

在系统分析断裂构造的基础上,应用分形理论与方法,采用盆维数法对朱仙庄煤矿断裂网络进行复杂程度评价。评价结果表明:矿井断裂构造总体偏于复杂,分维值大于1.2的复杂单元约占总数的66.7%,研究区东南部和中偏北部构造偏于简单。通过对分维值与断裂构造的对比研究,认为分维值是评价朱仙庄矿断裂网络复杂程度较为可靠的指标,8煤层瓦斯含量以F10断裂为界呈现北低南高的趋势,与分维值耦合较好,表明分维值可作为矿井瓦斯突出预测的指标之一。     

线要素化简算法的时间复杂度分析

线状要素是地图中数量最大、要素类型最多样的要素,其化简在地图自动综合中占据了重要的地位.目前对线状要素化简算法的改进、化简质量、化简精度等方面的研究较多,对线状要素化简算法的效率研究较少.此处是在兼顾化简质量的前提下研究算法效率,通过分析化简算法约束参数的特征,将线状要素化简算法分为6类,选取其中的几个典型算法,分析了其时间复杂度,并按照线状要素化简算法的时间复杂度将其分为线性算法和非线性算法两类,初步探讨了适合这两类算法的并行计算方法.     

基于特征的等高线数据聚类方法

针对地理线要素具有的分形特征,将小波分解算法和数值统计算法结合起来,提出并证明等高线小波分解后各层细节分量与复杂度之间具有对数线性的关系,从而计算出等高线的复杂度.再结合等高线自身的位置关系,给出等高线的分类标准,将等高线进行聚类,从而降低图形处理时等高线图形的密度和所需要的等高线的数据量,减少等高线相交的可能性.     

效用最大化、logit变换和城市地理学的数量分析模型

城市地理学的主要学模型，包括城市化进程的logistic模型，城市位序-规模分布的幂指数模型以及城市人口密度衰减的负指数模型，都可以从两个简单的科学假设出发推导出来。文章证明，上述假设在理论上可以归结为效用最大化原理，其本质与信息熵最大化有着深刻的内在关系。城市地理学的主要模型作为标度定律都可以借助logit变换进行简化处理，从而为理论模型的实际应用以及城市演化动力学的模拟实验分析打开了方便之门。     

Complexity Theory of Natural Disasters; Boundaries of Self-Structured Domains

Disasters are often represented as complete breakdowns of quasi-stationary states in a landscape, but may also be part of the normal evolution of such states. A landscape is, in fact, an open, nonlinear, dynamic system where the tectonic uplift and the seismic activity represent the input, the mass wastage and the relief degradation the output. The apparent 'stability' is due to the fact that open, nonlinear dynamic systems tend to develop into relatively stable, self-organized ordered states 'at the edge of chaos', with a fractal attractor. Short of complete breakdown, such systems re-establish order in steps of various magnitudes which have a power-law distribution. Because of the fractal structure of the basic attractor, all subsets follow a power law which accounts for the distribution of the steps of recovery. As the domains of quasi-stationarity at the edge of chaos are represented by finite windows, the power-law does not cover all magnitudes. The stationarity windows are not only limited in range, but also in space and time. This should be taken into account in the assessment of hazards. Examples are given from seismology (earthquake frequency), volcanology (eruption frequency), river hydrology (flood frequency) and geomorphology (landslides).     

The influence of biogeochemical conditions and level of model complexity when simulating cometabolic biodegradation in sorbent-water systems

Eighteen models with different levels of complexity for representing sorption, mass transfer, and biodegradation are used to simulate the biodegradation of toluene (primary substrate) and TCE (cometabolic substrate). The simulations are conducted for hypothetical completely mixed systems of various scenarios with regard to sorbent, microbial composition, and solute concentrations. The purpose of the suite of simulations is to investigate the sensitivity of different modeling approaches in simulating the bio-attenuation of co-existing solutes in sorbent-water systems. The sensitivity of results to the modeling approach depends on the biogeochemical conditions of the system. For example, the results are insensitive to the type of sorption model in systems with low sorption strength and slow biodegradation rates, and insensitive to the biodegradation rate model if mass transfer controlled. Differences among model results are generally greater when evaluated in terms of total mass removal rather than aqueous phase concentration reduction. The fate of the cometabolite is more sensitive to the proper consideration of co-solute effects than is the fate of the primary substrate. For a given system, graphical comparison of a characteristic mass transfer rate coefficient (α_mt) versus a characteristic biodegradation rate coefficient (α_bio) provides an indication of how sensitivity to the different processes may be expected to change with time and can guide the selection of an appropriate level of model complexity.