Characterisation of multiple conducting permeable objects in metal detection by polarizability tensors

Realistic applications in metal detection involve multiple inhomogeneous‐conducting permeable objects, and the aim of this paper is to characterise such objects by polarizability tensors. We show that, for the eddy current model, the leading order terms for the perturbation in the magnetic field, due to the presence of N small conducting permeable homogeneous inclusions, comprises of a sum of N terms with each containing a complex symmetric rank 2 polarizability tensor. Each tensor contains information about the shape and material properties of one of the objects and is independent of its position. The asymptotic expansion we obtain extends a previously known result for a single isolated object and applies in situations where the object sizes are small and the objects are sufficiently well separated. We also obtain a second expansion that describes the perturbed magnetic field for inhomogeneous and closely spaced objects, which again characterises the objects by a complex symmetric rank 2 tensor. The tensor's coefficients can be computed by solving a vector valued transmission problem, and we include numerical examples to illustrate the agreement between the asymptotic formula describing the perturbed fields and the numerical prediction. We also include algorithms for the localisation and identification of multiple inhomogeneous objects.     

1995—2015年关中平原城市群生态系统服务价值（ESV）及其时空差异

为探究关中平原城市群土地利用程度对生态系统服务价值（ecosystem service value，ESV）的影响及变化情况，基于1995—2015年研究区5期土地利用数据，利用当量因子评估法、热点分析法和敏感性指数法对关中平原城市群ESV进行了评估，并分析了其时空规律。结果表明，20 a来，关中平原城市群ESV总体下降49.59亿元；在生态系统服务类型中，调节服务作用突出，其中水文调节占主导地位；ESV 冷点和热点分布具有明显的区域特征，主城区主要为ESV 冷点集群区，而秦巴山地、山西省东部林地及黄河、渭河等主要河流周边是ESV 热点集群区； 林地、水域和耕地对区域内ESV变化影响较大。获得的研究区ESV宏观变化规律，可为今后关中平原城市群生态环境保护、补偿和城镇发展规划的编制提供理论支撑。     

A game theory model of urban public traffic networks

We have studied urban public traffic networks from the viewpoint of complex networks and game theory. Firstly, we have empirically investigated an urban public traffic network in Beijing in 2003, and obtained its statistical properties. Then a simplified game theory model is proposed for simulating the evolution of the traffic network. The basic idea is that three network manipulators, passengers, an urban public traffic company, and a government traffic management agency, play games in a network evolution process. Each manipulator tries to build the traffic lines to magnify its “benefit”. Simulation results show a good qualitative agreement with the empirical results.     

Entropy of the Land Parcel Mosaic as a Measure of the Degree of Urbanization

Quantifying the urbanization level is an essential yet challenging task in urban studies because of the high complexity of this phenomenon. The urbanization degree has been estimated using a variety of social, economic, and spatial measures. Among the spatial characteristics, the Shannon entropy of the landscape pattern has recently been intensively explored as one of the most effective urbanization indexes. Here, we introduce a new measure of the spatial entropy of land that characterizes its parcel mosaic, the structure resulting from the division of land into cadastral parcels. We calculate the entropies of the parcel areas’ distribution function in different portions of the urban systems. We have established that the Shannon and Renyi entropies R0 and R1/2 are most effective at differentiating the degree of a spatial organization of the land. Our studies are based on 30 urban systems located in the USA, Australia, and Poland, and three desert areas from Australia. In all the cities, the entropies behave the same as functions of the distance from the center. They attain the lowest values in the city core and reach substantially higher values in suburban areas. Thus, the parcel mosaic entropies provide a spatial characterization of land to measure its urbanization level effectively.     

Stakeholder preference elicitation and modelling in multi-criteria decision analysis – A case study on urban water supply

Integration of multiple objectives to evaluate the alternative operating rules for urban water supply reservoir systems can be effectively accomplished by multi-criteria decision aid techniques, where preference elicitation and modelling plays an important role. This paper describes a preference elicitation and modelling procedure involving the multi-criteria outranking method PROMETHEE in evaluating these alternative operating rules. The Melbourne water supply system was considered as the case study. Eight performance measures (PMs) were identified under four main objectives to evaluate the system performance under alternative operating rules. Three major hypothetical stakeholder groups namely, resource managers, water users, and environmental interest groups were considered in decision-making. An interviewer-assisted questionnaire survey was used to derive the preference functions and weights of the PMs. The evaluation of alternative operating rules is not covered in this paper, rather an approach to elicit and model stakeholder preferences in decision-making is described.     

随机平衡设计傅里叶振幅敏感性分析方法和拓展傅里叶振幅敏感性分析方法在陆面过程模式敏感性分析中的应用探索

探讨了随机平衡傅里叶振幅敏感性分析方法(RBD-FAST)和扩展傅里叶振幅敏感性分析方法(EFAST)在陆面过程模式参数敏感性研究中的应用. 试验中使用通用陆面过程模式(CoLM)和通榆退化草地2008年夏季观测资料, 针对陆气相互作用中重要的要素: 感热通量(SH)、潜热通量(LH)、地表温度(ST), 2 m气温(T2m)和2 m湿度(Q2m), 分析了11 个参数(土深、1–5层黏土比率、孔隙度、最大露水厚度、50%植物根深、地表空气粗糙度和冠层下土壤拖曳系数)的敏感性大小. 结果表明, RBD-FAST和EFAST对参数的一阶敏感性检验结果较为一致且与之前的研究结果类似, EFAST方法还可以得到考虑了参数间相互作用的整体敏感性. RBD-FAST的优势主要表现为在极大地减少了计算消耗机的同时, 一次取样即可计算所有参数的一阶敏感性, 而EFAST的优势则在于通盘考虑了参数之间的相互影响, 可以得到更为合理的整体敏感性序列. 针对不同需求, 选择使用这两种敏感性分析方法, 有助于提高陆面过程模式参数化方案的改进效率.     

Detecting long-range correlations in fire sequences with Detrended fluctuation analysis

The spatial-temporal power-law distributions are found in many natural systems, which have self-similarity and fractal behavior. By analyzing the time series of such systems, we could expect to explore and understand the underlying mechanisms. In this paper, the Detrended fluctuation analysis (DFA) is used to analyze the long-range correlations of forest and urban fires in Japan and China. It is found that the interevent time series of both forest and urban fires have the persistent long-range power-law correlations, and they all have two scaling exponents, α₁ and α₂, which are both bigger than 0.5 and smaller than 1.0, despite the different regions and countries. For forest fires, 0.61<α₁<0.73,0.87<α₂<0.98 and for urban fires, 0.52<α₁<0.61,0.59<α₂<0.88. The result suggests that fires have self-similarity characteristics. The occurrence of forest fires may have connection with the weather fluctuations, which have significant effects on the ignition and have the similar temporal correlations. It is shown that the interval sequences of urban fires closely resemble that of white noise in small timescale, and the correlations are weaker than that of forest fires. Human behavior and human density may affect the long-range correlation in some way. This seems to be helpful to understand the complexity of fire system in temporal aspect.     

征地移民管理中的分歧博弈及其决策模型

征地移民的协商管理中的分歧问题中主要是征地方与被征地方之间分歧．分歧主要体现在双方认知和利益诉求的差异．分析了征地移民双方的分歧特点,研究了征地移民的分歧管理模式.利用完善的博弈理论,探讨征地移民分歧管理的基本概念、方法和决策规律.借鉴线性支出系统的效用函数,研究分歧管理博弈矩阵的建立、博弈类型、博弈分析方法,为征地移民协商管理的科学体系提供科学分析方法.     

上海城市和农村居民消费结构分析

根据上海城市和农村居民消费结构的统计数据,对居民的八项消费支出进行因子分析,从而比较分析上海城市和农村居民消费结构的状况及变化趋势,并对上海城乡居民的消费差异做出评价。     

农地城市流转福利优化的动态分析

以动态最优化理论为基础,通过建立理论模型研究农民福利最优和总体福利最优的农地城市流转数量和时间路径,并得出以下结论.为做到长期可持续农地城市流转,首先,必须给予农民足额的补偿,该补偿既包括农地的经济收益,也包括其非经济收益;其次,要使农民对土地的权利在流转过程中得到充分体现,增加农民和农民集体讨价还价的权利;再次,促使政府在流转决策中以农地的总体福利改进为决策目标,而不仅仅是用途转换带来的巨大经济价值;最后,在补偿的政策措施上,可灵活使用补偿基数和补偿增长速度这两个指标来进行福利补偿调控.