重金属元素Cd在水稻土剖面中的分配系数及其影响因素研究:以四川省成都平原区为例

以四川省成都平原区农田生态系统水稻土剖面为例,探讨了Cd分配系数及其影响因素。结果表明:Cd分配系数(Kd)在污染土壤环境和本底土壤环境中是不同的,在剖面PM-3、PM-6和PM-8剖面中污染环境中分配系数(Kd)大于本底环境中的分配系数,而在剖面PM-7中,本底环境中的分配系数(Kd)大于污染环境中的值。在污染环境Cd分配系数受土壤pH值、交换性Mg和铁硅氧化物的影响比较大,而在非污染环境中分配系数受到土壤可溶性Al、Cd全量和铁锰铝氧化物的影响较大。这些土壤的物化性质对分配系数造成影响,使得土壤滤渣和土壤原土中Cd形态含量存在差异。     

长江三角洲NB5孔第四纪地层划分及环境变化信息

长江三角洲北翼NB5孔做了古地磁测试、~(14)C测试及ESR测试结果,对古地磁变化特征进行了总结分析,结合区内其他钻孔的对比,对钻孔第四纪地层划分及所反映的古气候环境进行了探讨。结果表明:46 m处为全新世底界,163 m为中更新世顶部,240 m左右为早更新世顶部,354 m为早更新世底部。其中,海相层有2个,位置在2~47m,125~163 m。分别对应于Ⅰ(Qh)镇江海侵,Ⅲ(Q_p~(3-1))昆山海侵。据晚更新世以后沉积物粒度变粗及磁化率所反映的巨大变化特征,提出中更新世晚期、晚更新世初期为长江主泓流经本区的时间,并认为此或与塑造中国现代地貌的共和运动造成的青藏高原再次强烈隆升有关。     

基于相关系数和Fisher最优分割法的汛期分期研究

从径流形成原理出发,提出了采用降雨径流相关系数作为汛期分期指标的基本思路。以陕西省石头河水库1954~2007年的日降水和日流量资料为基础,采用主成分分析法对影响时段径流的因素进行了分析,筛选出了影响不同时段径流量的主要因素,计算了主要影响因素与时段径流量的相关系数,采用Fisher最优分割法将石头河水库汛期划分为汛前过渡期(4月1日~5月20日)、前汛期(5月21日~7月10日)、主汛期(7月11日~8月10日)、后汛期(8月11日~9月20日)和汛后过渡期(9月21日~10月31日),并结合区域气候特点和实际发生的洪水对成果进行了合理性论证。该方法资料要求低,计算简便,具有一定的推广应用价值。     

Equilibrium Evaporation and the Convective Boundary Layer

A theory is developed for surface energy exchanges in well-mixed, partlyopen systems, embracing fully open and fully closed systems as limits.Conservation equations for entropy and water vapour are converted intoan exact rate equation for the potential saturation deficit D in a well-mixed, partly open region. The main contributions to changes in D arise from (1) the flux of D at the surface, dependent on a conductance g_q that is a weighted sum of the bulk aerodynamic and surface conductances; and (2) the exchange flux of D with the external environment by entrainment or advection, dependent on a conductance g_e that is identifiable with the entrainment velocity when the partly open region is a growing convective boundary layer (CBL). The system is fully open when g_e/g_q , and fully closed when g_e/g_q 0. The equations determine the steady state surface energy balance (SEB) in a partly open system, the associated steady-state deficit, and the settling time scale needed to reach the steady state. The general result for the steady-state SEB corresponds to the equations of conventional combination theory for the SEB of a vegetated surface, with the surface-layer deficit replaced by the external deficit and with g_q replaced by the series sum (g_q ^-1 + g_e ^-1)^-1. In the fully open limit D is entirely externally prescribed, while in the fully closed limit, D is internally determined and the SEB approaches thermodynamic equilibrium energy partition. In the case of the CBL, the conductances g_q and g_e are themselves functions of D through short-term feedbacks, induced by entrainment in the case of g_e and by both physiological and aerodynamic (thermal stability) processes in the case of g_q. The effects of these feedbacks are evaluated. It is found that a steady-state CBL is physically achievable only over surfaces with at least moderate moisture availability; that entrainment has a significant accelerating effect on equilibration; that the settling time scale is well approximated by h/(g_q + g_e), where h is the CBL depth; and that this scale is short enough to allow a steady state to evolve within a semi-diurnal time scale only when h is around 500 m or less.     

长江主干流的球面重心计算及其尺度效应分析

长江不仅具有长度这一非空间属性,还具有重心、方位、密度以及形状等多种空间分布属性。为了对长江的空间分布特征进行统计分析,提出了一种基于球面坐标的空间分布统计方法。采用空间随机抽样的方法,通过对组成长江水系的2种有限线段(即原始数据线段和等长切分线段)进行了不放回空间随机抽样,估计了长江球面重心位置的不确定性。为了解长江水系空间数据固有的多尺度特性,还研究了长江水系不同分辨率的空间切分(1 000 m、100 m、10 m)条件下的球面重心的规律。长江球面重心的计算方法不仅适用于球面线状物体球面重心的计算,也适用于球面面状物体重心的计算。研究长江水系的空间分布特征可以增加人们对长江水系的认知,为研究长江流域的经济、政治等相关的研究提供重要的地理参考信息或背景信息。     

Modelling and predicting the spatial dispersion of skin cancer considering environmental and socio-economic factors using a digital earth approach

ABSTRACT

Almost all causative factors of diseases depend on location. The Digital Earth approach is suitable for studying diseases globally. Geospatial information systems integrated with statistical models can be used to model the relationship between a disease and its causative factors. Through modelling, the most important causative factors can be extracted and the epidemiology of the disease can be observed. In this paper, skin cancer (the most common type of cancer) has been modelled based on its causative factors, including climate factors, people's occupations, nutrition habits, socio-economic factors, and usage of chemical fertiliser. To fit the model, a data framework was first designed, and then data were gathered and processed. Finally, the disease was modelled using Generalised Linear Models (GLM), a statistical model based on the location of the factors. The results of this study identify the most important causative factors together with their relative priority. Furthermore, a model was used to predict the change in skin cancer occurrences caused by a change in one of its causative factors. This work illustrates the ability of the model to predict disease occurrence. Thus, by using this Digital Earth approach, skincancer can be studied in all the key countries around the world.     

Research on the security of national geospatial data clearinghouse based on ASP

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湖相介形类壳体微量元素在古环境重建中的应用

湖相介形类壳体微量元素(本文主要指Mg和Sr)是重建古环境的重要指标之一,可以定性或定量地反映湖水信息。自20世纪80年开始应用以来,经过30余年的发展取得了很大进展。在古环境重建过程中主要存在两类影响因素:(1)其宿生水体中M/Ca比值(M主要指Mg和Sr)的影响因素:季节变化、微环境差异和湖泊演化过程,这类因素通过对宿生水体中M/Ca比值来影响介形虫壳体中的M/Ca比值,进而造成古环境重建结果的误差增大或可靠性降低;(2)介形类壳体微量元素分配系数的影响因素:宿生水体中M/Ca比值、温度、碱度等,这类因素能够直接影响介形类壳体分泌、钙化的生命-化学过程的因素,是定量重建的重要影响因素。加强现代介形类生活习性和微量元素组成变化过程的研究可以消除或减小以上影响因素对古环境重建的影响,提高介形类壳体化石中微量元素组成在古环境重建研究中的精度和可靠性。     

非同构简单无向图的计数方法

首先在正整数的所有无序划分构成的集合上定义了一个全序关系，由此将所有无序划分的全体分成一些互不相交的子集，从而得到生成所有无序划分的方法，也就得到了n顶点的全体置换格式，然后给出了由简单无向图的顶点的置换格式确定简单无向图边的置换格式的方法，最后给出了n顶点非同构简单无向图的生成多项式并给出了部分计算结果。     

加拿大地理信息产业发展基础与现状研究

从地理信息管理、空间基础设施、地理信息产业发展情况等方面介绍了加拿大地理信息产业发展的现状,并分析加拿大地理信息产业发展的特点,提出促进我国地理信息产业健康快速发展的对策、建议。