梧州防洪堤地基渗透变形及液化可能性初步分析

文章在梧州防洪堤地基勘探试验资料基础上，根据国内外一些规范判别标准，优选了几种简易、具代表性的判别方法，对地基土渗透变形及地震液化可能性进行计算分析，取得了较好一致性。     

基于空变阻抗约束的贝叶斯稀疏脉冲反演

常规的基于贝叶斯理论的稀疏脉冲反演中,各约束项的拉格朗日算子均采用的是恒定的常系数。反演实际资料发现,波阻抗反演剖面与钻井资料的油气显示并不能很好地对应。考虑到反演不同地震道数据时,低频趋势模型所起的约束作用应当不同。本文在常规反演的基础上做出了改进,假定阻抗约束系数是一个空间变量,由各地震道的实际地震数据与合成记录之间的振幅残差来确定该道的阻抗约束系数。实际资料应用表明,改进后的反演结果更稳定,能更准确地反映地下阻抗信息。      

Multiple Bayesian modelling approaches to a suite of radiocarbon dates from ovens excavated at Ysgol yr Hendre,Caernarfon, North Wales

In recent years, the use of Bayesian statistical analysis for modelling radiocarbon dates has become much more commonplace within archaeology, however there remains very little literature to aid new practitioners with understanding the archaeological assumptions that underpin many of the modelling choices. Using a suite of radiocarbon dates from a sample of seven ovens, from the 18 excavated across the site at Ysgol yr Hendre, Caernarfon, North Wales, this paper explores the various methods of modelling this group of features. It stresses the underlying archaeological assumptions of each model, while also highlighting some of the tools that should especially be considered when developing very precise models. Finally it compares the results of the models.     

A Bayesian central equivalent dose model for optically stimulated luminescence dating

In this study, we propose and implement a Bayesian model to estimate a central equivalent dose from a set of luminescence measurements. This model is based on assumptions similar to the ones used in the standard statistical pipeline (typically implemented in the Analyst software followed by a subsequent central equivalent dose analysis) but tackles some of its main limitations. More specifically, it consists of a three-stage hierarchical model that has two main advantages over the standard approach: first, it avoids the introduction of auxiliary variables (typically mean and variance), at each step of the inference process, which are likely to fail to characterise the distributions of interest; second, it ensures a homogeneous and consistent inference with respect to the overall model and data. As a Bayesian model, our model requires the specification of prior distributions; we discuss such informative and non-informative distributions and check the relevance of our choices on synthetic data. Then, we use data derived from Single Aliquot and Regenerative (SAR) dose measurements performed on single grains from laboratory-bleached and dosed samples. The results show that our Bayesian approach offers a promising alternative to the standard one. Finally, we conclude by stressing that, relying on a Bayesian hierarchical model, our approach could be modified to incorporate additional information (e.g. stratigraphic constraints) that is difficult to formalise properly with the existing approaches.     

考虑能量-时间分布的边坡动力可靠性分析新方法

提出一种考虑能量-时间分布的边坡动力可靠性分析方法。该方法将动态最危险滑动面及其稳定系数以时间序列加以刻画,并根据边坡动力反应的能量分布特征,提取持续时间统计窗,用于对上述时间序列的统计分析,以获取边坡动力模糊失效概率、边坡动力可靠度指标和基于保证率的边坡动力稳定系数。以澳大利亚计算机应用协会边坡稳定考核题为例,应用上述新方法考察其在芦山7.0级主震波形条件下的稳定性,研究了在不同统计窗下的边坡动力可靠性。案例分析表明： （1）新方法能够抓住影响边坡动力稳定的主要时间段,使分析结果更为凝练、可信。（2）通过引入边坡失效状态的模糊判别,使得可靠性评价中能够考虑模糊性,解决了以往常规方法区分度不够的问题。（3）基于保证率的边坡动力稳定系数具有很好的应用前景,它在内涵上体现了可靠性分析,在形式上与静力稳定系数的定义兼容,在数值上反映了边坡瞬时动力稳定系数的保守估计值,在实践上与现行规范的拟静力法具有良好的可比性,因而具有多方面的优势。（4）就本案例而言,动力条件下最危险滑动面的发育位置趋向于静力条件下的最危险滑动面,体现了依据静力和拟静力理论框架所进行的防护工程设计,在动力条件下仍然具有积极的意义。（5）新方法对定量研究现行边坡规范的抗震设计冗余提供了一条途径。提出的新方法为边坡抗震研究提供了新的思路、方法和可供参考的实例。     

Application of the SPARROW model in watersheds with limited information: a Bayesian assessment of the model uncertainty and the value of additional monitoring

How can spatially explicit nonlinear regression modelling be used for obtaining nonpoint source loading estimates in watersheds with limited information? What is the value of additional monitoring and where should future data‐collection efforts focus on? In this study, we address two frequently asked questions in watershed modelling by implementing Bayesian inference techniques to parameterize SPAtially Referenced Regressions On Watershed attributes (SPARROW), a model that empirically estimates the relation between in‐stream measurements of nutrient fluxes and the sources/sinks of nutrients within the watershed. Our case study is the Hamilton Harbour watershed, a mixed agricultural and urban residential area located at the western end of Lake Ontario, Canada. The proposed Bayesian approach explicitly accounts for the uncertainty associated with the existing knowledge from the system and the different types of spatial correlation typically underlying the parameter estimation of watershed models. Informative prior parameter distributions were formulated to overcome the problem of inadequate data quantity and quality, whereas the potential bias introduced from the pertinent assumptions is subsequently examined by quantifying the relative change of the posterior parameter patterns. Our modelling exercise offers the first estimates of export coefficients and delivery rates from the different subcatchments and thus generates testable hypotheses regarding the nutrient export ‘hot spots’ in the studied watershed. Despite substantial uncertainties characterizing our calibration dataset, ranging from 17% to nearly 400%, we arrived at an uncertainty level for the whole‐basin nutrient export estimates of only 36%. Finally, we conduct modelling experiments that evaluate the potential improvement of the model parameter estimates and the decrease of the predictive uncertainty if the uncertainty associated with the current nutrient loading estimates is reduced. Copyright © 2012 John Wiley & Sons, Ltd.     

电子加速器X射线源能谱整形理论与模拟研究

利用能谱整形技术产生的x射线优化能谱可减小伪影误差,提高无损检测材料识别精度。如何利用能谱整形技术产生指定的优化能谱是要解决的关键问题。为解决这一问题,对能谱整形基本理论进行了研究,设定了能谱整形的目标,利用蒙特卡罗方法模拟计算出电子加速器出射x射线能谱,对能谱和整形材料的线性衰减系数进行拟合,计算了能谱整形所需要的相关参数并确定能谱整形方法,运用蒙特卡罗方法模拟验证了所采用的能谱整形方法的合理性。     

贝叶斯参数估计的最大熵方法的逆问题

讨论贝叶斯参数估计理论中利用最大熵原理确定参数的先验概率的逆问题,并且以泊松分布和指数分布为例给出证明.通过求解相应的微分方程和变分方程,得到所需约束条件.     

碳酸盐岩储层多角度弹性阻抗流体识别方法

碳酸盐岩储层的AVO响应要比碎屑岩储层响应微弱,因此,弹性阻抗（EI）即使在确定了最佳入射角的情况下,要判断碳酸盐岩储层中的流体性质,依然十分困难.本文提出了一种多角度扩展弹性阻抗（MEEI）反演进行碳酸盐岩储层流体识别方法.利用已有钻井的测井数据,通过计算目的层段的MEEI,建立相应的含流体模式,进而建立了碳酸盐岩储层流体检测中的有效气水判据.通过不同入射角下EEI随入射角变化的不同趋势,可以有效识别储层中含气或含水情况,判别储层好坏.本文方法的有效性在四川盆地某地区实际资料应用中取得了良好的流体检测效果.