T -distributed Random Fields: A Parametric Model for Heavy-tailedWell-log Data1

Histograms of observations from spatial phenomena are often found to be more heavy-tailed than Gaussian distributions, which makes the Gaussian random field model unsuited. A T-distributed random field model with heavy-tailed marginal probability density functions is defined. The model is a generalization of the familiar Student-T distribution, and it may be given a Bayesian interpretation. The increased variability appears cross-realizations, contrary to in-realizations, since all realizations are Gaussian-like with varying variance between realizations. The T-distributed random field model is analytically tractable and the conditional model is developed, which provides algorithms for conditional simulation and prediction, so-called T-kriging. The model compares favourably with most previously defined random field models. The Gaussian random field model appears as a special, limiting case of the T-distributed random field model. The model is particularly useful whenever multiple, sparsely sampled realizations of the random field are available, and is clearly favourable to the Gaussian model in this case. The properties of the T-distributed random field model is demonstrated on well log observations from the Gullfaks field in the North Sea. The predictions correspond to traditional kriging predictions, while the associated prediction variances are more representative, as they are layer specific and include uncertainty caused by using variance estimates.     

A simple hypoplastic model for normally consolidated clay

The paper presents a simple constitutive model for normally consolidated clay. A mathematical formulation, using a single tensor-valued function to define the incrementally nonlinear stress–strain relation, is proposed based on the basic concept of hypoplasticity. The structure of the tensor-valued function is determined in the light of the response envelope. Particular attention is paid towards incorporating the critical state and to the capability for capturing undrained behaviour of clayey soils. With five material parameters that can be determined easily from isotropic consolidation and triaxial compression tests, the model is shown to provide good predictions for the response of normally consolidated clay along various stress paths, including drained true triaxial tests and undrained shear tests.     

Dissolved trace elements in river water: spatial distribution and the influencing factor, a study for the Pearl River Delta Economic Zone, China

Twenty-nine water samples were collected from different river channels of the Pearl River Delta Economic Zone, China. An inductively coupled plasma-mass spectromonitor (ICP-MS) was used to measure concentrations of the trace elements in these samples. The results suggest that the average concentrations of rare earth elements in river water show an increasing trend from the West River, the North River, the rivers of the Pearl River Delta, and the Shenzhen River to the East River. Relatively high concentrations of heavy metals appear in the East River, the rivers of the Pearl River Delta and the Shenzhen River, while the West River and the North River have relatively low heavy metal concentrations. Trace element concentrations in samples collected near urban or industrial areas are much higher than those of samples collected from distant areas, away from urban and industrial areas. After natural conditions, human activities have significant influence on the trace element concentrations in river water. This trace element concentration’s spatial distribution in the river water from the Pearl River Delta Economic Zone is actually an integrated effect of natural conditions and human activity.     

用CC的方法分析和解决一个常见的网络安全问题

CC导出PP的过程是一种安全评估通用语言到某类产品的具体应用过程,需要经过需求分析、得出安全目的、提出安全功能要求与安全保证要求等几个阶段。本文利用这些过程的基本方法和思想全面分析一个常见的网络安全问题,并按照保护轮廓的模式给出该网络的安全要求。     

西北地区的自然环境类型

自然环境区划是国土规划的重要基础，是自然环境综合特征的基本反映.以西北地区的气候分区、地貌分区、植被分区（生态分区）为基础，将西北地区的自然环境类型划分为5个自然分区：阿尔泰-准噶尔区，塔克拉玛干-毛乌素沙漠区，青藏高原东北缘区，黄土高原区，秦巴山地与汉水谷地区.这5个区有完全不同的自然环境特征和资源优势特征，因而开发对策和环境对策是不同的，应予以分别对待.正确认识各区的自然环境特征，才能实现西北地区社会经济及环境的可持续发展。     

石太线下行K135滑坡特征与成因分析

滑坡位于石太线下行K135路段右侧偏西，平面上呈近似椭圆形，由原有老滑坡复活而形成。根据滑坡勘察，滑坡所处地貌单元属侵蚀剥蚀低中山区，滑坡区地层组成为第四系松散堆积物下伏晚古生代二叠系石千峰组泥岩、砂岩互层。在分析滑坡几何特征、地质构造特征、水文地质条件及滑坡变形破坏特征的基础上，探讨了滑坡的成因，认为老滑坡的成因以自然形成为主，新滑坡则发育并活动于老滑坡堆积物中，因某部门在老滑坡体前缘修建收费站，进行了大面积不适当的工程开挖，形成临空面，加之降雨的作用降低了土体的粘聚力及抗剪强度，在上覆岩土体的重力作用下形成新滑坡。老滑坡为巨型厚层滑坡，属于自然滑坡，新滑坡为大型中层滑坡，属于工程滑坡。     

条带开采煤柱稳定性的试验模拟与数值分析——以山东省济宁市太平煤矿为例

以山东省济宁市太平煤矿为例，采用煤柱模拟试验和数值分析手段，对薄基岩条带开采时所留设煤柱的应力应变状态、煤柱强度结构及煤柱长期稳定性进行了深入的分析与研究，揭示了煤柱稳定性及煤柱应力分布与条采尺寸、采出率、覆岩特征的相互关系，进行了条带煤柱的稳定性评价，为工程实践提供了理论依据。     

刘桥一矿陷落柱发育规律及含水性研究

根据刘桥一矿1971年建井至今发现的8个陷落柱实际资料，通过对揭露陷落柱的地质、水文地质及分布特征的分析，阐述了陷落柱发育的根基所在，对陷落柱发育规律及成因进行了探讨，对于含水陷落柱的注浆封堵、留设保护煤岩柱，以及本矿矿井的深部开采都具有借鉴意义。     

韧性剪切变形对岩石地球化学行为的制约——以北阿尔金巴什考供韧性剪切带为例

韧性剪切变形对岩石地球化学行为的制约一直是地质学家们探讨的课题。本文以构成北阿尔金红柳沟——拉配泉俯冲碰撞杂岩带与北阿尔金地块边界的巴什考供斜向逆冲型韧性剪切带为例，通过对韧性剪切带内花岗岩变形前后不同变形强度构造岩的地球化学组成进行对比，确定等比线斜率，探讨韧性变形对岩石体积和成分变异的影响。计算结果表明，在糜棱岩化过程中，糜棱岩化花岗岩体积亏损21％，花岗质糜棱岩体积亏损31％。质量平衡计算结果和等比线图表明，韧；陛剪切作用导致SiO2，流失量最大，A12O3、K2O及Ba、Rb、Sr等都有不同程度的丢失，显示出较强的活动性，MnO、P2O5、Sc位于等比线上或附近，表现出相对的稳定性。岩石中活动组分的变异是流体渗滤作用引起的，不活动组分的变异是体．积亏损造成的。