生物土壤结皮对风沙土和黄绵土膨胀特性的影响

作为重要的土壤物理性质,膨胀性在影响土壤导水性、持水性、抗蚀性以及土壤结构的形成和发育等方面发挥着重要作用。为了探讨生物土壤结皮（BSCs）土壤的膨胀特性及其主要影响因素,针对黄土高原风沙土和黄绵土两种典型土壤,利用膨胀仪测定并比较了有、无藓结皮及其在不同因素（初始含水量、干湿循环、冻融循环、温度）下膨胀率的差异,分析了BSCs对土壤膨胀性的影响及其与环境因素和BSCs性质的关系。结果显示：风沙土上藓结皮的膨胀率为1.93%,较无结皮增加了8.65倍;而黄绵土上藓结皮的膨胀率为2.05%,与无结皮相比降低了76.68%。藓结皮的生物量和厚度与其膨胀率在风沙土上均呈线性正相关关系（P < 0.05）,在黄绵土上分别呈二次函数（P=0.02）和线性正相关关系（P=0.02）。初始含水量同时影响了土壤最大膨胀率和稳定膨胀时间,影响程度风沙土远大于黄绵土（包括藓结皮和无结皮）;干湿循环次数对无结皮土壤膨胀率的影响程度大于藓结皮土壤,其中风沙土和黄绵土上无结皮的膨胀率分别是50.00%~620.00%和-2.28%~10.81%,而两种土壤上藓结皮的膨胀率分别是-5.70%~10.88%和-10.24%~-21.46%;冻融循环下4种土壤的膨胀率均有不同程度的降低,降幅为0~18.54%。黄绵土无结皮的膨胀率受温度影响程度较大,50℃下黄绵土无结皮的膨胀率分别是25℃和35℃下的1.17倍和1.21倍。BSCs显著地改变了风沙土和黄绵土表层的膨胀性,其影响的程度和方向取决于土壤类型。同时,BSCs的膨胀性受含水量、温度、干湿以及冻融循环等关键因素影响。     

低水合氯化镁吸水过程中水蒸气分压计算

对低水合氯化镁的吸水过程进行了初步的探讨,并对低水合氯化镁吸水过程中与水蒸气的平衡分压进行了计算。     

Surface temperature differences between minerals in crystalline rocks: Implications for granular disaggregation of granites through thermal fatigue

Thermal expansion differences between minerals within rocks under insolation have previously been assumed to drive breakdown by means of granular disaggregation. However, there have been no definitive demonstrations of the efficacy of this weathering mechanism. Different surface temperatures between minerals should magnify thermal expansion differences, and thus subject adjacent minerals to repeated stresses that might cause breakdown through fatigue failure. This work confirms the existence of surface temperature differences between minerals in granitic rocks under simulated short-term temperature fluctuations so as to discriminate their potential for initiating granular disaggregation. The influence of colour, as a surrogate for albedo, and crystal size, as a function of thermal mass are specifically identified because of their ease of quantification. Four rock types with a range of these properties were examined, and subjected to repeated short-term temperature cycles by radiative heating and cooling under laboratory conditions. Results show that while albedo is the main control for overall and individual maximum temperatures, crystal size is the main factor controlling higher temperature differences between minerals. Thus, stones with large differences of mineral sizes can undergo magnified stresses due to thermal expansion differences.     

Effect of the overconsolidation ratio of soils in surface settlements due to tunneling

Construction of urban tunnels requires the control of surface subsidence to minimize any disturbance to nearby buildings and services. Past study of surface subsidence has been limited to mainly empiri...     

中国水-能源-粮食压力时空变动及驱动力分析

采用主成分分析法,把构建的水资源、能源和粮食的压力指数分解为3个正交向量,以矢量合成法计算水-能源-粮食（W-E-F）总压力指数。在考察1997~2015年30个省区（香港、澳门和台湾无数据,西藏缺能源数据）的水资源压力指数、能源压力指数、粮食压力指数和W-E-F总压力指数的时序变化后,选取8个反映总压力指数变化的指标,截取1997、2004、2015年3个断面,采用地理加权回归（GWR）模型对影响中国W-E-F压力指数变化的因素进行分析。结论如下：① 时间上看,W-E-F总压力先升后降;空间上看,从东南沿海向西北内陆W-E-F总压力逐渐递减,东北和沿海城市化水平高的地区压力较大。② 能源压力对中国W-E-F总压力的贡献最大,中东部地区的能源压力指数更高,淮河以北地区的水资源压力指数更高,东部的长江口以南沿海区域和广大西部地区的粮食压力指数更高。③ 1997~2015年,全国水资源压力指数多数地区上升,能源压力指数和粮食压力指数大部分地区下降。④ 不同时段,W-E-F压力变化的驱动力不同。总体上看,大部分指标与W-E-F压力变化同向,人均受教育水平和人均GDP与W-E-F压力变化反向,人口密度增大、食物构成变化、粮食生产条件和经济发展是W-E-F压力升高的主因。在分析时段内,随着时间推移,社会因素和经济因素的影响在增大,提高人均受教育水平和经济转型发展是降低W-E-F压力的有效途径。     

景观敏感度的理论及其应用意义

1. 中国科学院东北地理与农业生态研究所, 长春130012; 2. 中国科学院研究生院, 北京100039     

Cs+水合结构密度泛函理论计算研究

本文用密度泛函理论在WB97XD/gen def2-tzvp基组水平上对[Cs(H2O) n] +(n=1-15)水合团簇结构的振动光谱进行了研究。研究表明,随着水分子数的增加,在气相和液相中,8配位的Cs+ 水合团簇是最稳定的;随着水分子数的增加,Cs-O键长增大,Cs+上的电荷密度减小。当水分子数大于11时,Cs-O键长和Cs+上的电荷密度变化很小。O(H2O)-O(H2O)距离、∠O(H2O)-Cs-O(H2O)°统计结果表明,15个水分子足以形成Cs+的近似饱和水合层。此外,红外光谱显示[Cs(H2O)n]+水合团簇中O-H伸缩振动随着水分子数的增加而发生变化,由此可以作为鉴别水合层位置的一种参考方法。     

长江三角洲城市群发展的优势及动态变化(英文)

Urban agglomeration on Yangtze River Delta (UA-YRD) had some advantages in the aspects of water, land, ecological environment, location and transportation. Relying on the resource-environment bases and other advantages, UA-YRD has achieved great develop-ment. Based on index system and model of comprehensive evaluation, the paper calculates the development level of UA-YRD since 1978. The result shows that from 1978 to 2007, the development level increased year by year at an annual rate of 0.0333, and the process of development could be divided into three stages, i.e. low-speed development stage (1978-1991), rapid development stage (1991-2000), and high-speed development stage (2000-2007). The speeds are 0.0083, 0.0356 and 0.0766, respectively. During the 30-year development, foreign economic activity has the greatest effect on development, followed by transportation, industrial economic activity and telecommunication (in order). Additionally, different driving forces have different effects in different stages. The paper suggests that more attention should be paid to the high-speed development stage and the important driving forces to drive its development. At the same time, the limitation of resource and environment should not be neglected and a long effective mechanism needs to be established to sustain harmonious development among the UA development, resource utilization and environmental protection. Some comparative studies should be carried out urgently to support and promote sustainable development of UA effectively, especially towards evolution, driving forces and braking forces.     

Understanding and Portraying the Global Atmospheric Circulation

Abstract

Atmospheric circulation and resultant surface pressure patterns are important discussion topics in many introductory geography, meteorology, and earth science courses. In the past, summary materials developed to aid in teaching these concepts have used a north-south oriented meridional cross-section of the troposphere (e.g., the three-cell model). We suggest that while the Hadley Cell model works well for the tropics, an alternative depiction incorporating two map views should be used to present a more meaningful view of the mean extratrop-ical circulation. The combination of a tropical cross-section map and an extra-tropical map will assist students in learning about first-order motions associated with the Earth's atmospheric circulation.     

Non-linear elastic behaviour of damaged rocks

The pervasive damage of rocks by microcracks and voids strongly affects their macroscopic elastic properties. To evaluate the damage effects, we derive here the macroscopic stress-strain relations for a 3-D elastic solid with non-interacting cracks embedded inside a homogeneous matrix. The cracks considered are oriented either perpendicular to the maximum tension axis, or perpendicular to the maximum compression axis. In the first case they dilate during loading and in the second case they contract during loading. We derive a solution for the elastic energy of this rock following the self-consistent scheme of Budiansky & O'Connell (1976). The solution describes the stress-strain relations in terms of Λ^d and μ^d, which are the modified Lame constants, and an additional parameter Λ. The latter accounts for the non-linear behaviour of the solid and is related to crack density. The solution predicts a non-linear elastic rheology even for an infinitesimal strain of ɛ < 0.001, and abrupt change in the elastic moduli when the loading reverses from uniaxial compression to uniaxial tension.
We use the derived solution to analyse rock-mechanics experiments in which beams of Indiana limestone were deformed under four-point loading. This configuration provides simultaneously the apparent tensile and compressive moduli for small strains. The apparent moduli fit the effective elastic moduli calculated with the present damage model well, including the differences between tensile and compressive moduli.     

我国现阶段土地利用变化驱动力的宏观分析

土地利用的基本竞争模型是土地利用类型变化驱动力分析的理论基础。把握土地利用个体目标和社会目标的关系,尤其是它们之间的矛盾及其地区差异,是进行土地利用变化驱动力宏观分析的有效途径。工业化城市化与粮食安全之间的矛盾、农业发展与生态环境保护之间的矛盾是现阶段我国土地利用变化的基本矛盾。土地利用变化的驱动力在空间上表现出较大的差异。本文选取11项自然和社会经济指标,分省份计算了驱动力指数。结果表明:西部地区以生存型经济福利驱动和环境安全驱动为主,而东部地区以比较经济福利驱动和食物安全驱动为主     

制备硅钢级氧化镁前驱体的原料水化研究

以青海盐湖水氯镁石为初级原料,采用喷雾热解法制备原料氧化镁,原料氧化镁通过水化制备硅钢级氧化镁前驱体氢氧化镁。原料氧化镁水化实验中对水化剂、水化温度、水化时间、液固比、搅拌速度及陈化时间对水化率、过滤速度和纯度的影响进行系统研究。采用均匀实验设计和DPS数据处理,(依次)通过建模分析、二次多项式模型回归建立数学模型,再通过各因素方差分析和总方差分析,确定了理论最优实验条件,再用理论最优条件作重复实验进行验证,最终确定了原料氧化镁的最佳水化条件。在水化温度60℃,水化时间105 min,液固比4,陈化时间4 h,水化剂1含量4.0%,水化剂2含量3.15%,洗水量4倍,搅拌速度120 r/min时,原料氧化镁的水化率达99.50%以上,得到的硅钢级氧化镁前驱体氢氧化镁纯度高、过滤性能良好。     

应用人工神经网络识别华南沿海全新世海滩岩和海岸沙丘岩

华南全新世海岸沙丘岩和海滩岩同是热带、亚热带海岸线附近的胶结的岩石,其沉积儿构造极为相似,很容易混淆。人工神经网络是最近发展起来的一种信息处理方法,可以处理模糊的,非线性的、含有噪声的数据,为海滩岩和沙丘岩的识别提供了一种新方法。用华南海岸风成砂和海滩砂的粒度参数作为训练样本,华南海岸全新世沙丘岩和海滩碉的粒度参数作为测试样本,经过训练的Ｂ－Ｐ网络能够根据海滩砂和海岸沙丘砂的粒度参数来区分大部分的     

Quantitative evaluation of coal as source rocks

Gas generated and expelled from coals often results in economic gas accumulations. As a consequence, it is important to consider the theoretical aspects of these processes and to develop methods that can be used to assess coal as a potential source rock. On the basis of results of modeling hydrocarbon generation, expulsion, and retention in coals, two comprehensive indexes are proposed for assessing the quality and the nature of coal as a potential source rock. Theoretical charts of the two indexes are used to assess coals as potential source rocks in the Turpan-Hami Basin in northwestern China.