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.     

Ammonium regeneration in intertidal sediments of the Yangtze estuary during air-exposure

The influences of exposure to the atmosphere on ammonium cycle in the intertidal surface sediments were in situ studied with a geochemical approach at a typical station in the Yangtze Estuary during three tidal cycles in September 2003. During an about 8-h emersion period of each diurnal tide, six high-resolution vertical profiles of adsorbed and dissolved ammonium were measured. It was observed that both adsorbed and dissolved ammonium generally had an increasing trend in sediment cores during the exposure. The rate of ammonium regeneration in sediments was estimated using the accumulation amount of ammonium including adsorbed and soluble fractions during the daytime emersion. The calculation result showed that there was relatively high ammonification rate (˜500 nmol N cm⁻³ day⁻¹), which reflected that organic nitrogen in sediments was quickly decomposed with a residence time of ˜52.7 days. Due to the dramatic temperature difference observed in sediment profiles, free convection was considered an important mechanism of regulating the efflux of produced ammonium into overlying waters. The total estimated amount of regenerated ammonium was ˜1.35×10⁵ t N year⁻¹ in the intertidal flat of the Yangtze Estuary, which occupied 7.6% of the total inorganic nitrogen annually transported to the estuarine ecosystem.     

襄樊汉江四桥大口径灌注桩成孔施工实践

介绍了使用泥浆护壁气举反循环回转钻进工艺进行襄樊汉江四桥大口径嵌岩桩的施工实践。施工中采用下置双护简隔离卵石层，合理选用钻头类型(卵砾石层采用五翼合金刮刀钻头，基岩采用球齿滚刀钻头)和钻进参数(混合器沉没深度，尾管长度，孔内空气流量与压力)，摸索与总结出一套复杂地层成孔施工经验。     

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。     

基于遥感信息的华北冬小麦区域生长模型及模拟研究

卫星遥感估产和作物生长模拟在作物监测和产量预测方面有各自不可替代的优势。但是,遥感估产难以揭示作物生长发育和产量形成的内在机理,作物模拟在区域应用时初始值的获取和参数的区域化遇到很多困难。如何利用二者的互补性使其相互结合受到人们关注。该文在Wofost模型本地化和区域化的基础上,首次利用同化法的思路探讨了MODIS遥感信息与华北冬小麦生长模拟模型结合的可行性和方法,初步建立了潜在生产水平(水分适宜条件)下区域遥感-作物模拟框架模型(WSPFRS模型)。模拟结果显示:WSPFRS模型对区域尺度的出苗期重新初始化后,模拟的开花期、成熟期空间分布的准确性比Wofost模拟结果有所改进;利用遥感信息对区域尺度上返青期生物量重新初始化后,模拟贮存器官干重的空间分布更接近实际单产的分布,贮存器官干重的高值区与实际高产区基本相符。该研究将为下一步实际水分供应条件下基于遥感信息的冬小麦区域生长模拟研究奠定了基础。     

施放氢气球时存在的安全隐患及防范措施

针对采用球服务中的安全隐患，提出有效的防范措施，对开展此项工作的同志有很好的借鉴意义。     

东昆仑东段中更新世以来的成山作用及其动力转换

对东昆仑造山带东段第四纪构造及与地貌关系的分析表明，现代山盆相间的地貌格局成型于中更新世，且在中更新世以来发生了多次构造变形体制的转换。根据布青山北部查干额热格地区第四系剖面的构造、地层时代及地层与构造关系的分析表明，中更新世时期为伸展构造体制，昆仑山内部开始发生了差异隆升，布青山开始崛起。中更新世末应力体制发生急剧变化，由伸展体制转为收缩事件，又急速转为伸展构造体系，短暂的收缩事件造成了中更新世冲洪积层的褶皱，随后的伸展则导致了影响深刻的向北依次断落的阶地状正断层系统。晚更新世应力体系再度发生重大转换，伸展正断层体系被左旋走滑运动体系所代替，并一直延续至今。中更新世以来多次隆升构造变形体制的转换说明东昆仑地区的成山过程受控于多种动力背景，而非单一的挤压抬升。隆升构造变形体系的确定及其时代约束为深入刻划青藏高原东北缘隆升作用的动力过程提供了重要信息。     

西北五省(区)生态环境综合分区及其建设对策

本文以图像遥感解译为主 ,结合野外实际考察 ,并通过抽样验证完成。在对生态环境界定和赋予内涵的基础上 ,根据区划目的、原则和所选取的指标体系 ,从生态环境分类入手 ,经过从上向下续分和由下向上合并的反复磨合过程、专家集成模拟 ,对西北五省(区 )生态环境做了全面的综合分区研究 ,并针对所存在的生态环境问题 ,提出生态环境保护和建设的对策 ,为西北五省 (区 )实施西部大开发生态环境监测、治理、建设和规划提供科学依据。     

新时期我国区域经济地理学发展问题初探

我国新时期的区域经济地理学在取得全面发展的同时，在理论体系，研究方法和实践领域等方面还需要进一步的发展，文章根据学习和实践区域经济地理学的体会，初步提出基础理论和应用理论，思维方法和技术方法等方面发展见解，并指出区域创新系统和国际经济技术合作等学科应注意拓展的重要实践领域，最后提出我国区域经济地理学科发展的建议。