海堤土工织物滤层的探讨

研究了波动水流对海堤织物滤层的水力要素及过滤机理。粒径小于0.6 mm颗粒间存在粘着力;同时,由于滤层和堤体的渗透流速不一致,则堤体界面的土颗粒将受水流剪应力的作用。在分析了使土颗粒发生变形的水流剪应力、变形土体周壁的屈服应力和波浪压力等后,根据平衡原理,建立了织物滤层的保土性准则。     

华北地台寒武纪沉积层序中关键地层单元──海绿石质凝缩层段

构成华北古克拉通盆地的中晚寒武世碳酸盐沉积层序及与三级海平面最大海泛期相关的海绿石质凝缩层段是一沉积速率极低、厚度较薄的海相沉积单元。笔者根据凝缩层段中海绿石矿物的Ｋ２Ｏ百分含量和其内部晶体结构划分出其演化级次和形成时限，得出研究区凝缩层段的形成时限为１０４－１０６年。它们与二级、三级海平面最大海泛滞后期相吻合。该成果对区域地层对比、层序划分、海平面升降史和盆地充填史的恢复起极为重要的作用。     

南京冬季平流雾的生消机制及边界层结构观测分析

利用系留飞艇边界层要素探测系统等设备,对2006年12月24q7日发生在南京地区的雾日边界层结构进行了综合探测,深入研究了这次平流雾的生消机制及边界层结构。结果表明：此次雾属于比较典型的平流雾,生成和维持主要决定于暖湿气流和系统性下沉运动,消散主要是干冷空气南下造成的;雾项下降阶段出现了双层结构,中层逆温是逆温主层,属于下沉逆温及平流逆温,主逆温层强中心始终位于雾顶附近或处于雾顶之下;风速随高度呈现多峰分布,中层急流与强度较弱的中上层和上层急流合并后,又与下层急流出现了一强一弱的波动;在风速较小时,风场趋于均匀化;雾消散时,低层风场趋于线性化;雾主要的水汽来源是暖湿气流;比湿场与风场有较好的时空分布对应性,主逆温层强中心也是逆湿强中心,风场与温度场共同主导了比湿场的时空分布。     

INVESTIGATION OF THE SPATIAL AND TEMPORAL DISTRIBUTION OF EXTREME HIGH TEMPERATURE IN CHINA WITH DETRENDED FLUCTUATION AND PERMUTATION ENTROPY

With temperatures increasing as a result of global warming,extreme high temperatures are becoming more intense and more frequent on larger scale during summer in China.In recent years,a variety of researches have examined the high temperature distribution in China.However,it hardly considers the variation of temperature data and systems when defining the threshold of extreme high temperature.In order to discern the spatio-temporal distribution of extreme heat in China,we examined the daily maximum temperature data of 83 observation stations in China from 1950 to 2008.The objective of this study was to understand the distribution characteristics of extreme high temperature events defined by Detrended Fluctuation Analysis(DFA).The statistical methods of Permutation Entropy(PE)were also used in this study to analyze the temporal distribution.The results showed that the frequency of extreme high temperature events in China presented 3 periods of 7,10—13 and 16—20 years,respectively.The abrupt changes generally happened in the 1960s,the end of 1970s and early 1980s.It was also found that the maximum frequency occurred in the early 1950s,and the frequency decreased sharply until the late 1980s when an evidently increasing trend emerged.Furthermore,the annual averaged frequency of extreme high temperature events reveals a decreasing-increasing-decreasing trend from southwest to northeast China,but an increasing-decreasing trend from southeast to northwest China.And the frequency was higher in southern region than that in northern region.Besides,the maximum and minimum of frequencies were relatively concentrated spatially.Our results also shed light on the reasons for the periods and abrupt changes of the frequency of extreme high temperature events in China.     

西太平洋副热带高压西伸过程的合成特征及其可能机理

利用1970~2000年6月NCEP/NCAR逐日再分析资料,根据(20~30°N,115~125°E)区域内500 hPa的涡度变化选取了12次西太平洋副热带高压西伸过程,合成了西太平洋副热带高压西伸过程中对流层高层和低层的环流演变特征。结果表明,(20~30°N,115~125°E)区域内500 hPa负涡度的增加对应着西太平洋副热带高压的西伸过程。在副热带高压西伸过程中,对流层高层南亚高压的中心位置虽然稳定少动,但是由于日本东南部反气旋的西移,使得南亚高压东侧的脊明显地加强东伸,这可能对对流层中层副热带高压的西伸具有重要作用。在对流层低层,源于澳大利亚北侧的气流越过赤道向北传播,经由南海季风槽后到达我国江淮流域,从而影响副热带高压西侧的偏南气流。     

西菲律宾海末次冰期以来的浊流沉积及其古环境意义

菲律宾海西部吕宋岛岸外MD98－2188钻孔揭示末次冰期以来发生过数次浊流沉积事件。研究发现浊流沉积层具有密度高、颜色亮度大等物理特征,含有较多粗沉积组分和翼足类化石碎片,说明其来源于浅海沉积物。本文运用AMS 14C测年和浮游有孔虫氧同位素建立精细的年龄模式,发现浊流沉积层段主要与末次盛冰期、冰期Heinrich变冷事件以及氧同位素4期等低海平面时期相对应,推测与千年尺度北半球气候冷期相关的海平面快速上升可能是西菲律宾海浊流沉积的触发原因。这对于认识快速气候变化的环境后果和开展西菲律宾海晚第四纪地层划分对比都有重要意义。     

球卡式绳索取心液动锤的试验研究

针对现有SYZX系列绳索取心液动锤中存在的内管总成上浮问题,研制了球卡式绳索取心液动锤,改善了内管总成浮动问题,增大了冲击功输出,进一步提高了钻进效率。室内和生产试验证实,该球卡式绳索取心液动锤钻具原理可行,打捞和定位成功率在95%以上。但在生产实践中还需要对局部细节进行完善。     

机械力化学改性硅灰石表面行为TEM的研究

选用气流磨超音速气流作为机械力,对硅灰石、硬脂酸进行超细粉碎－表面改性。应用透射电子显微镜分析、观察硅石灰／硬脂酸复合粉体界面微观形貌及成分（Ｃａ、Ｓｉ、Ｃ）的变化规律。ＴＥＭ能谱分析结果表明：从硅灰石到硬脂酸,Ｃａ、Ｓｉ含量逐渐降低,Ｃ含量则逐渐升高。     

城市化过程中地形因素对城市空间结构演变的影响——以乌鲁木齐市为例

利用起伏度指数与分布比例指数模型,将地形与城市土地利用类型有机地结合在一起,探讨了地形对乌鲁木齐城市空间结构发展的影响.研究结果表明:两个模型多年相关数据的变化能反映城市空间结构的演变过程.居住用地的增长区从起伏度指数为7～8的地形空间上逐渐开始向起伏较高地形发展.其分布在起伏度指数上的区间扩大了9个单位.由于经济的快速发展,生产建设用地始终在不断地扩大,并表现出工业用地向外扩张和商业用地向内收缩两个变化过程.扩张的方向指向低地形地区,收缩则向金融商业中心.农用地面积始终在减少,并趋向消失,且起伏度低的地区减少得快,而高地形区减少得慢.未利用地分布区域向高地形空间退缩,市区内的未利用地通常被开发为绿地或公园.各种土地利用类型在起伏度指数梯度上分布的整体变化反映出大地形特征仍然是城市空间结构的发展框架.     

The importance of distribution types on finite element analyses of foundation settlement

We investigate the effects of using different types of statistical distributions (lognormal, gamma, and beta) to characterize the variability of Young’s modulus of soils in random finite element analyses of shallow foundation settlement. We use a two-dimensional linear elastic, plane-strain, finite element model with a rigid footing founded on elastic soil. Poisson’s ratio of the soil is considered constant, and Young’s modulus is characterized using random fields with extreme values of the scale of fluctuation. We perform an extensive sensitivity analysis to compare the distributions of computed settlements when different types of statistical distributions of Young’s modulus, different coefficients of variation of Young’s modulus, and different scales of fluctuation of the random field of Young’s modulus are considered. A large number of realizations are employed in the Monte Carlo simulations to investigate the influence of the tails of the statistical distributions under study. Results indicate the type of distribution considered for characterization of the random field of Young’s modulus can have a significant impact on computed settlement results. In particular, considering different types of distributions of Young’s modulus can lead to more than 600% differences on computed mean settlements for cases with high coefficient of variation and large scale of fluctuation of Young’s modulus. The effect of considering different types of distributions is reduced, but not completely eliminated, for smaller coefficients of variation of Young’s modulus (because the differences between distributions decrease) and for small values of the scale of fluctuation of Young’s modulus (because of an identified “averaging effect”).