数据同化在海洋生态模型中的应用和研究进展

将数据同化方法引入海洋生态系统动力学模型研究,利用现有的观测数据,获得最佳的模式参数、初始场或提高状态模拟,是当前多学科交叉研究的热门领域。本文依据国内外研究进展,主要就海洋生态模型研究中所采用的变分伴随、卡尔曼滤波、模拟退火法方法进行了介绍,总结了数据同化在我国的海洋生态系统研究中的现状和发展趋势。     

施工单位财务内部控制研究

财务内部控制是为了保证单位财务目标的实现,是单位内部控制的核心。我国施工单位以项目管理为核心的经营管理体制已基本形成。受投资规模大、生产周期长、影响因素多、竞争异常激烈等行业特点所限,财务风险贯穿于施工单位工程项目施工全过程。因此,施工单位财务风险管理更为复杂。本文以内部控制、COSO基本框架、系统工程等作为理论基础,系统地分析了施工单位的财务风险点,提出了＂以项目成本控制为核心,以项目全过程管控为主线,以全面预算控制为抓手＂的施工单位财务内部控制基本框架结构。     

缅北中部脉金矿带控矿因素及成矿作用浅析

缅北中部，印缅岛弧及弧后盆地东侧、新生代造山带的前缘推覆构造带中，分布有许多脉金矿床及矿点，构成金矿带。矿带、矿田、矿床及矿体的形成、分布及其规模，受不同级别的近南北向逆冲断裂，及其间派生的北东向张性扩容断裂组成的剪切断裂带控制。可渗透的下麦尔组下部中一粗粒砂岩，起着很好的容矿作用。下麦尔组上部泥岩、细砂岩、粉砂岩和页岩互层单元，在携金热液的迁移、氧化硅的沉淀和矿质沉积定位等方面，可能起到圈闭作用。     

喜马拉雅山脉的地质地貌特征:来自SRTM数字高程模型和降水量数据的约束

利用GTOPO30和SRTM3数字高程(DEM)数据,提取了喜马拉雅山脉(造山带)的数字高程模型并对其进行了地质地貌的初步分析。从SRTM3数字高程数据提取出坡度数据,初步分析了喜马拉雅山脉坡度和高程的特征。数字高程和坡度图清楚地展现了喜马拉雅大型断裂带(构造边界)的空间分布特征。分析了中国气象局下属的西藏、青海、四川和云南4省区气象观测台站55年来的年平均降水量观测数据、喜马拉雅山脉南坡的年平均降水量数据、喜马拉雅DEM和裂变径迹数据,发现喜马拉雅山脉从东至西,年平均降水量逐渐减少,地形起伏逐渐变小,而高程渐次升高,与此同时剥蚀速率降低;从北至南,年平均降水量逐渐增加,地形起伏增大,高程快速降低,而剥蚀速率则急剧升高。这充分说明了喜马拉雅年平均降水量大的地区,地表剥蚀作用相对较强,年平均降水量小的地区,地表剥蚀作用则较弱,即:在喜马拉雅地区,长周期的地表剥蚀过程(可长达数个百万年时间尺度)和短周期(仅仅50年)的降水量观测是耦合的。     

三维复电阻率电磁场正演研究

将Cole—Cole模型表示的地下异常体各剖分单元复电阻率,引入到体积分方程求解均匀大地三维电磁场计算中,实现电偶源地面激发、接收复电阻率三维电磁场正演模拟。     

低孔低渗储层渗透率测井解释模型研究

采用岩心分析数据与测井曲线相结合的方法,引入泥质含量参数配合声波时差进行多元线性回归分析。建立鄂尔多斯盆地研究区低孔低渗储层渗透率测井解释模型。根据泥质含量特征二次分类后进行多元线性回归,建立两个渗透率测井解释模型相关性良好,对应于研究区两种不同的沉积微相特征;测井解释渗透率与岩心实测渗透率匹配良好,解释模型满足研究区精度要求。在沉积微相背景约束条件下,对研究区储层选择合理参数多元线性回归建立渗透率测井解释模型,可以使低孔低渗储层渗透率解释达到良好应用效果。     

Slope stability evaluation using Back Propagation Neural Networks

The Yudonghe landslide, located in western Hubei Province of China, consists of eastern and western subunits as well as a main landslide mass with upper and lower slip surfaces. As an important landslide close to Shuibuya Dam on the Qing River, its stability is crucial, as the slide might reactivate because of a change in ground-water level caused by filling of the Shuibuya Reservoir. Existing weakness zones, growth of ruptures, the downslope attitude of geologic strata, and water infiltration, which reduced the strength of rocks and soils, have been found to be the most important factors contributing to the Yudonghe landslide. With regard to the landslide processes, it can be noted that the original large-scale slide activity was due to erosion by the Qing River, the second sliding resulted from the fall of blocks from the head scarp, and the final activity was the growth of the eastern and western secondary slides. A base failure was the main type of slope movement, however, it was obvious that more than one sliding event occurred, as inferred from striations and fractures detected by microstructure analysis of soils along the failure surfaces. Slope instability was evaluated by the method of Back Propagation Neural Networks (BPNN), in which a four-layer BPNN model with five input nodes, two hidden layers, and two output nodes was constructed using a training data set of landslide samples throughout the Qing River area. The predicted results of this analysis showed that the factor of safety was 1.10, which indicates that the Yudonghe landslide is currently in a marginally stable condition.     

Performance of surface footing on geocell-reinforced soft clay beds

This paper presents the results of laboratory model tests carried out to develop an understanding of the behaviour of geocell-reinforced soft clay foundations under circular loading. Natural silty clay was used in this study. The geocells were prepared using biaxial polymer grid. The performance of the reinforced bed is quantified using non-dimensional factors i.e., Bearing capacity improvement factor (I_f) and Percentage reduction in footing settlement (PRS). The test results demonstrate that the geocell mattress redistributes the footing load over a wider area thereby improving the performance of the footing. The load carrying capacity of the clay bed is increased by a factor of up to about 4.5 times that of unreinforced bed. From the pressure-settlement responses, it is observed that the geocell-reinforced foundation bed behaves as a much stiffer system compared to the unreinforced case indicating that a substantial reduction in footing settlement can be achieved by providing geocell reinforcement in the soft clay bed. The maximum reduction in footing settlement obtained with the provision of geocell mattress of optimum size placed close to the footing is around 90%. Further improvement in performance is obtained with provision of an additional planar geogrid layer at the base of the geocell mattress.     

含矿预测的人工神经网络方法

运用神经网络模型的一典型模型——“反向传播”模型的改进形式,处理矿产资源统计预测问题,得出与数量化理论Ⅱ处理极为相似的结果.     

湖泊水位资料与模型模拟恢复的6000年前全球湿润状况的对比研究

本项研究是ＰＭＩＰ（ＰａｌａｅｏｃｌｉｍａｔｅＭｏｄｅｌｉｎｇＩｎｔｅｒｃｏｍｐａｒｉｓｏｎＰｒｏｊｅｃｔ）国际合作项目中有关模型模拟与观测资料对比的一部分。模型试验对象是６０００ｙｒ．ＢＰ的全球湿润状况。模拟试验以检测太阳辐射变化对全球大尺度气候系统的影响为主要目的。观测资料是利用地质证据恢复的古湖泊水位变化,实际上是某一地区的有效降水（降水减蒸发）的变化。通过两者的比较发现,所有模拟试验均能重现６０００ｙｒ．ＢＰ在亚洲南部与非洲北部的湿润环境,从而证实了因太阳辐射变化导致的亚洲与非洲季风的增强。但模拟的季风增强无论是强度还是范围均小于地质记录。原因很可能是模拟试验中下垫面特征用“现代”的来处理。模拟试验对北半球夏季辐射增加造成的西风带北移及由此引起的中纬度地区的气候变化不够成功。绝大多数模拟对受洋流与海温影响较大的地区是失败的。主要原因可能是所有ＰＭＩＰ中的模拟试验都未考虑海洋的作用。