东北地区农业结构转型时期土地利用变化的成因与效应

During the last decade of the 20th century, extensive conversion in agricultural land use took place in Northeast China. The goal of this study is to ascertain its spatial distribution and regional differentiation, determine its causes, and analyze its environmental impact, Especially we attempt to elucidate how institutional constraints have facilitated the change at a time of agrarian restructuring when newly emerging free market was hybridized with the former planned economy. Information on six categories of land use was mapped from interpretation of Landsat TM images recorded in 1990,1995 and 2000. Most of land use changes took place during the first half of the decade, coinciding with abrupt and chaotic changes in government directives. Farmland was changed mainly to woodland,water body and built-up areas while woodland and grassland were converted chiefly to farmland.Spatially, the change from farmland to woodland was restricted to the west of the study area. The change from grassland to farmland took place in the grazing and farming interlocked west. These chaotic and occasionally conflicting changes were largely caused by lack of stability and consistency in agricultural land use policies promulgated. They have exerted adverse impacts on the local environment, including land degradation, increased flooding, and modified climate regime.     

２００６年 ７—９月的台风季节预报试验

运用NCEP/NCAR逐6 h分辨率为25°×25°GRIB资料,用WRF模式采用水平分辨率为27 km×27 km,垂直38层每6 h输出一次的时空分辨率,对2006年7—9月对西太平洋地区台风为主的天气系统进行季节预报试验。综合低层涡度、地面10 m处风速、海平面气压、暖心结构和持续时间对模式输出资料进行台风生成判定和路径追踪。7月1日—9月30日模拟吻合较好的台风、强热带风暴、热带风暴和热带低压的比例为4/9、1/3、0/1和0/1;模拟较差的比例分别为3/9、1/3、1/1和1/1;漏报率分别为2/9、1/3、0/1和0/1。模拟空报了2个台风、9个强热带风暴和3个热带风暴。模拟台风强度偏弱和吻合较差的原因可能与模式的分辨率、〖JP2〗微物理过程参数设置和积分步长有关。空报的台风、强热带风暴可能与模式自身特点、相关海区的特性和热带波动有关。     

泥岩、页岩声速各向异性及其影响因素分析

在实验室超声波频率下(纵波主频为700kHz、横波为250kHz)对层理发育的页岩和泥岩的各向异性进行了研究,给出了在干燥和油饱和条件下,样品不同方向上纵、横波速度以及各向异性参数随压力的变化规律. 用X 射线衍射和扫描电镜分析了样品中引起各向异性的原因,指出平行于层理定向排列的粘土矿物和微裂隙是使样品显示出强弹性各向异性的内在原因. 随着压力的增高微裂隙逐渐闭合,样品的各向异性程度减弱. 孔隙流体的存在增强了孔隙（裂隙）的刚度,减弱了各向异性随压力增大而减小的趋势.     

城市地下综合管网建设模式——以天津市为例

本文以天津市为例,分析了目前城市管网管理中存在的问题,提出了切实可行的综合管网系统建设模式,设计了有效的管网数据模型,并利用地理信息系统和三维数字仿真技术构建了城市地下综合管网管理系统,在实践中取得了良好的应用效果。     

一次江淮大暴雨过程中尺度系统结构分析

本文应用观测资料和中尺度数值模拟结果对1999年6月23日发生在江淮地区一次梅雨锋暴雨过程进行研究，揭示了影响这次暴雨过程的物理条件、云团的演变特征及与中尺度系统的关系，分析表明，在暴雨生成和发展过程中，多个中尺度云团在相继生成和移动发展，暴雨中心是几个发展较强的中尺度对流云团造成的，西南风低空急流为暴雨提供了水汽输送，并且通过强垂直运动向对流层中上层输送水汽，这次暴雨与中尺度系统发生发展有直接关系，西南涡分裂出一系列的小涡旋，这些小涡旋边向东移边减弱，并且同时在地面上引发小低压，这些中尺度低压增强低空水平辐合，成为触发不稳定能量的机制，低空急流中心与雨区相互对应，且急流风速增强，风速水平切变梯度增大的过程对应着强降水过程。     

湘西—黔东地区寒武系清虚洞组地层特征与铅锌成矿关系

湘西—黔东地区寒武系发育完整,是一套从黑色岩系到碳酸盐岩的沉积序列。下寒武统清虚洞组由灰岩段和白云岩段组成,纵向上构成总体向上海水变浅的沉积相序列,同时反映了缓坡型碳酸盐岩台地的发育过程。该组空间上从北西至南东可识别出潮坪相、局限台地相粉细晶云岩、台地边缘浅滩相粉细晶灰岩和台地边缘(滩)丘相微晶灰岩、浅-深缓坡相、陆棚相泥灰岩、台地前缘盆地等沉积。研究表明,地层岩性、岩相古地理对铅锌矿具有明显的控制作用,微晶丘是主要容矿层,与微生物和海底热水关系密切。铅锌成矿明显与浊流沉积和风暴沉积等事件沉积相关,浊积岩、微晶丘、砾(粒)屑灰岩构成一完整的铅锌控矿序列。     

利用方差分量估计的地震同震滑动分布反演

提出了基于方差分量估计的地震同震滑动分布反演方法,该方法不仅可以确定不同数据集的相对权重,而且还能得到平滑因子的值,突破了方差分量估计方法仅用于各类数据定权的实际应用范围。模拟算例验证了此方法的有效性,从解的概率后验密度分布分析来看,方差分量估计方法得到的结果是线性和非线性混合方法反演结果的一个解。用方差分量估计方法反演了Bam地震同震滑动分布,并与线性非线性混合方法反演的结果进行了对比分析。两种方法得到的Bam地震断层滑动分布之间的空间互相关系数为0.999 9,地震同震的最大滑动量相同,都为3.04 m;其深度仅有微小区别,前者为4.50 km,后者为4.47 km;平均滑动量前者为0.714 m,后者为0.718 m。但前者反演计算用时227 s,后者却达到1.5×10⁶ s,约17 d,前者仅为后者的1/6 608。结果表明,本文方法相对于线性和非线性混合方法具有计算简单、计算量小和计算效率高的优点。     

基于Markov链的金川铜镍矿床超基性岩体侵位过程模拟及找矿启示

金川铜镍矿床是世界第三大铜镍硫化物岩浆矿床,现有研究表明其成矿模式为岩浆通道成矿,但是对于金川超基性岩体的侵位过程存在较大争议。为探索岩体的侵位过程,将岩浆侵位描述为马尔可夫(Markov)过程,提出一种基于Markov链的岩体侵位模拟算法,实现对金川超基性岩体侵位过程的模拟。以金川Ⅱ矿区为例,探讨了侵位过程与矿化的关联及岩浆通道骨架,为在矿床深部寻找第二成矿空间提供方向和线索。     

Microbial release of potassium from K-bearing minerals by thermophilic fungus Aspergillus fumigatus

A strain of thermophilic fungus Aspergillus fumigatus was cultured with K-bearing minerals to determine if microbe-mineral interactions enhance the release of mineralic potassium. Experiments were carried out in two settings, one with the mineral grains and the fungal cells in direct contact, and the other employing a membrane (pore size 0.22 μm) to separate the two. Measurements over a period of 30 days showed that, irrespective of the experimental setup, the concentration of free K in the culture was drastically higher than those in any of the control experiments where no living organism was present. Moreover, the occurrence of mineral-cell physical contact enhanced potassium release by an additional factor of 3 to 4 in comparison to the separation experiments. For contact experiments, Electron Probe Microanalysis revealed the formation of mycelium-mineral aggregates, and Atomic Force Microscopy imaging further indicated the possible ingestion of mineral particles by the fungus cells. Contrasting to what was observed and expected in control experiments, the potassium solubilization rate showed a positive dependence upon pH when fungi and minerals were mixed directly, and exhibited no correlations with solution acidity if cell-rock contact was restrained. These results appear to suggest that A. fumigatus promoted potassium release by means of at least three likely routes, one through the complexation of soluble organic ligands, another appealing to the immobile biopolymers such as the insoluble components of secretion, and the third related to the mechanical forces in association with the direct physical contact between cells and mineral particles.     

GPS非差相位精密单点定位技术探讨

针对北斗导航卫星系统（BDS）不同类型卫星观测数据的特点,对TurboEdit方法进行改进。在利用M-W组合观测值检测时,使用固定窗口的滑动求解方法代替其原有的递推求解方法。将原有的电离层残差组合检测方法改进为双频电离层残差的相邻历元求差法,并且可以根据不同类型的卫星选择不同的检测参数。改进后的算法对GEO/IGSO/MEO卫星均可达到良好的检测效果。算法验证表明,该算法可以有效检测并修复1周的小周跳,也可以检测修复双频点等周大小的小周跳,修复精度可达到0.1周以内。