淮河中下游洪泽湖湖泊沉积物粒度特征及其沉积环境意义

以淮河中下游洪泽湖湖底沉积物为研究对象,将放射性核素计年与沉积物粒度分析、粒度平面分形研究以及历史文献资料相结合,初步探讨了洪泽湖湖底沉积物粒度特点及该区域近300年来的气候变化,为恢复百年尺度的气候干湿变化提供了一条新途径。研究发现,湖区气候的干湿变化大致可分为三个阶段。进一步说明沉积物粒度参数的变化不仅与自然环境改变有关,也与人类活动如黄河改道、湖泊周围建闸等关系密切。     

弹性地基条件下狭窄煤柱岩爆的突变理论分析

将未采煤层视为弹性地基条件下,运用maple9.5符号运算软件解得岩梁的挠曲线方程。根据能量守恒原理得到的功、能增量平衡关系式,求得岩梁–煤柱系统作准静态形变时的平衡方程--折迭突变模型平衡方程;用折迭突变总势能函数所作的稳定性判别表明,岩爆前兆阶段岩梁–煤柱系统处于不稳定平衡状态;煤柱岩爆的条件是Cook刚度准则,该准则可以动态地用煤柱形变增大时所需外界的能量输入率趋于0来表示;计算了煤柱岩爆地震能释放量,阐明煤柱岩爆机制是由于岩梁弹性能释放量超过峰后软化煤柱形变所耗的能量。通过岩梁弹性势能变化率曲线和煤柱耗能曲线,以几何形式描述了所得研究结果。计算表明,未开采煤层刚度变化对岩梁的等效刚度影响微弱。工作面开挖和采空区增大,将显著减小岩梁刚度Ke,对煤柱岩爆有重要影响。     

人工神经网络在盐渍土盐胀特性研究中的应用

利用人工神经网络处理非线性体系的优势性,对盐渍土膨胀规律多影响因素试验数据进行了建模方法分析,提出了盐渍土盐胀率随含水量、氯化钠含量、硫酸钠含量、初始干容重和上覆荷载5因素变化的计算公式,计算结论比常规二次回归法更加符合目前对盐渍土盐胀规律的定性认识.     

动载下3条断续裂隙岩样的裂缝贯通机制

采用含3条断续预制裂隙的类砂岩模型试样进行单轴动力加载试验,对不同裂隙空间位置条件下断续裂隙岩体中裂隙的贯通机制进行了研究。静、动荷载下的对比研究成果显示：不同空间位置的裂隙贯通方式存在较大差异,且对动载的响应不同;动载下分支裂纹扩展及贯通具有惯性效应,即动载下裂尖次生共面、次生倾斜裂纹起裂后易朝原起裂方向快速发展,动载下易在两预制裂隙内端部产生直接贯通。这与静载下岩桥处的贯通常通过分支裂纹拐折扩展、相连不同,这也是导致裂隙试样中低应变速率下强度增大（即速率效应）的主要原因。同时,试验结果也表明：含裂隙试样静、动荷载下裂隙间的多次贯通是导致其呈现出渐进破坏特征的主要原因。     

超旱生植物红砂与珍珠光合生理生态日变化特征初探

超旱生植物红砂与珍珠长期生活在严酷的生境中,形成了独特的生物学特性和生理生态适应性。在自然条件下研究了两种超旱生植物的光合生理生态日变化特征。结果表明,红砂和珍珠光合作用受环境变化影响明显,具有一定的可塑性:①在土壤含水量（SWC）、光、温、湿等条件较好的8月22日,两植物净光合速率（Pn）、蒸腾速率(Tr)日变化呈不明显双峰型。Pn红砂高于珍珠,日平均分别为(7.74±0.79)μmol\5m-2\5s-1 和(5.64±0.75)μmol\5m-2\5s-1;Tr也是红砂高于珍珠,日平均分别为(24.38±3.07)mmol\5m-2\5s-1和(15.41±2.01)mmol\5m-2\5s-1;水分利用效率（WUE）则相反,日平均珍珠大于红砂,分别为0.35 μmol·mmol-1和0.31 μmol·mmol-1。②在SWC、光、温、湿等条件较差的9月28日两植物Pn、Tr日变化呈单峰型,且值明显小于8月22日,而WUE则高于8月22日。通过对两种超旱生植物小枝水势、叶片气孔导度及叶绿素荧光参数生理特性变化的分析,得出两植物光合作用受到气孔和非气孔等多种环境及自身因子的影响。     

Numerical Modelling Of Turbulent Airflow Over Water Waves

A nonlinear numerical model is developed for turbulent boundary-layer flowover a train of water waves of finite amplitude or slope. The airflow isassumed to be steady, two-dimensional, and neutrally-stratified. The wavesurface is assumed to be aerodynamically rough and flow conditions at thewave surface are prescribed. The numerical model used in this study adoptsthree turbulence closure schemes with different degrees of physicalcompleteness. Two of these are second-order schemes, whichare believed to describe turbulent flow more completely than thesimpler closures used in most previous studies. Although models with all turbulence closures agree qualitatively in the prediction of the amplitude of the surface normal stress perturbation, the lower- and higher-order closures differ significantly in predictions of phase, and hence the form drag and energy transfer rate between wind and waves. Our model results are in reasonable agreement with field and laboratory measurements, although predicted energy transfer rates are generally at the low end of the range of experimental values. Cases with airflow at various angles to the wave direction are also considered.     

The success rate and precision of GPS ambiguities

 An application of a theorem on the optimality of integer least-squares (LS) is described. This theorem states that the integer LS estimator maximizes the ambiguity success rate within the class of admissible integer estimators. This theorem is used to show how the probability of correct integer estimation depends on changes in the second moment of the ambiguity `float' solution. The distribution of the `float' solution is considered to be a member of the broad family of elliptically contoured distributions. Eigenvalue-based bounds for the ambiguity success rate are obtained. Received: 11 January 1999 / Accepted: 2 November 1999     

毛细管气相色谱法测定矿坑水中的苯系物

以国家标准方法和EPA方法为基础, 进行了矿坑排水中苯系物的测定.在测定过程中进行了质量保证和质量控制实验, 用外标法定量.在水样测定的同时对用自动顶空进样器和吹扫捕集浓缩仪两种进样方式测定矿坑排水中苯系物的方法进行了比较, 对进样方式和影响测定的因素进行了讨论.结果表明, 自动顶空进样器的回收率为108.5 8%~116.38%, 方法检出限为5.00~10.00 μg/L; 吹扫捕集浓缩仪的回收率为94.87%~105.6 3%, 方法检出限为0.25~0.50 μg/L.      

到达地面的紫外辐射强度预报

紫外线指数一般用０～１５的数字来表示,通常规定,夜间的紫外线指数为０,在热带高原地区,晴天无云时的紫外线指数为１５。世界气象组织规定了单位紫外线指数相当于２５ｍＷ／ｍ＾２红斑加权剂量率。紫外线指数预报大致可分为统计预报方法和模式预报方法两种。统计预报方法主要依赖于高精密度、高准确性的紫外线实测资料和相关的气象要素观测;而模式预报方法则主要依赖于对平流层臭氧的预报和大气辐射传输模式的应用。     

Geomorphic Evidence for and Rate of Sinistral Strike-slip Movement Along Northwest-trending Faults in Chaoshan Plain

Two sets of active faults,northwest-and northeast-trending faults,are developed in the Chao-shan Plain of East Guangdong.After detailed interpretation of aerophotos,we have found outthat there is the clear phenomenon of sinistral dislocation of drainage system on the Huang-gang-shui fault and part of Fengshun-Shantou fault.Field investigation confirmed that the geo-morphic bodies along the two faults have undergone displacement.Large-scale topographicmapping was made at three displaced sites and samples for age dating were collected from thegeomorphic booies.Calculation indicates that the average rate of sinistral strike-slip movementin the Holocene time amounts to 1.11±0.09～2.69±0.24mm/a along the Huanggangshuifault and 3.26±0.26mm/a along the Fengshun-Shantou fault.These two more active NW-trending faults extend into sea area,where they intersect the NE-trending strongly active Nius-han Island-Xiongdi Isle-Nanpeng Isles fault at a depth of 40～50m in water.The intersection isa location favorable fo