转移概率预报方法在霜冻预报中的应用

本文在简介转移概率预报方法及最大概率预报原理的基础上,分析了吕梁市1957年～2000年霜冻初、终日期各随机时间序列状态之间的转换规律,结合各序列的初始分布,建立预报模型,并对1995年～2004年的初、终霜日期进行了预报效果检验。结果表明,该方法预报效果好,使用性强,具有良好的应用前景。     

Earthquake catalogues and modelling strategies. A new testing procedure for the comparison between competing models

In this paper we consider the procedures that, on the basis of an earthquake catalogue, yield the magnitude distribution function F _M (F _M generators). In particular, our attention is focused on the F _M generators that are currently used in the frame of the probabilistic seismic hazard analysis at a site. From an engineering point of view, the behaviour of F _M in the range of strong earthquakes is of crucial importance. On the other hand, in general, the statistical validation of F _M in that range is not feasible because of an insufficient number of strong earthquakes in available catalogues.Our investigation is limited to the problem of the comparison between competing F _M generators. We show that a simple empirical F _M generator (called the CFP generator) can be more reliable than generators based on mathematical models. The numerical experiments that support this statement regards two test-sites and two mathematical models of magnitude distribution, namely the truncated-exponential and the characteristic-type models.The main conclusion is the suggestion of a test (called the CFP-test) that can be summarized as follows. Let X be a site for which, with current criteria, a specific F _M ^X generator based on a mathematical model has been selected. At this point, following the comparison approach described in the paper, the F _M ^X generator is compared with the empirical CFP generator. It can happen (actually it happens in many of our numerical experiments) that this test indicates the CFP generator as more reliable than the selected F _M ^X generator.     

Hybridization of the probability perturbation method with gradient information

Geostatistically based history-matching methods make it possible to devise history-matching strategies that will honor geologic knowledge about the reservoir. However, the performance of these methods is known to be impeded by slow convergence rates resulting from the stochastic nature of the algorithm. It is the purpose of this paper to introduce a method that integrates qualitative gradient information into the probability perturbation method to improve convergence. The potential of the proposed method is demonstrated on a synthetic history-matching example. The results indicate that inclusion of qualitative gradient information improves the performance of the probability perturbation method.     

江苏-南黄海地区未来地震形势的统计分析

根据１５００年以来的地震资料,应用数理统计、灰色预测、干支６０周期分析等多种方法,对江苏—南黄海地区未来３～５年地震形势进行分析和预测,结果表明：该区目前处于本世纪第２活跃幕中后期,未来几年内依然存在５～６级地震的危险性,至２０００年７月,累积发震概率将达到０．７～０．８,１９９９—２０００年、２００２—２００３年均有可能发生５级以上中强地震。     

星基空间人造飞行器探测概率分析

随着空间飞行器数量的日益增多,空间碰撞的概率也逐步加大。为了确保自身飞行器的安全,同时为了减少对目前在轨的飞行器的干扰,通过某种途径来感知空间飞行器的信息,包括轨道和结构外形等参数,是十分必要的。除了地基手段对空间飞行器进行观测外,星基空间飞行器探测是一种不可或缺的补充手段。文章通过对所掌握的空间飞行器数据库,给出了基于地球低轨道观测卫星情况下,星基空间飞行器探测概率的统计结果。     

Methods of setting depth range with credibility of conductor for deepwater drilling based on probability statistics

Becasuse of the deep water depth and long riser of deepwater drilling, the stability of subsea wellhead is threatened. Meanwhile, the setting depth of conductor directly affects the mechanical stability of subsea wellhead. Through analyzing the impact of different factors on the setting depth of conductor, we found that the bearing capacity growth factor of subsea soil has a great influence on the setting depth of conductor. However, the coefficient is a regional and empirical constant, which seriously affects the accuracy and reliability of the results. In this paper, probability statistics and geostatistics methods are employed to count the bearing capacity growth factor of target point's adjacent wells, as well as transplant and predict the target point through differential arithmetic, which can obtain the predictive value of target point's coefficient containing probability information. Finally, we can obtain the setting depth range with credibility of conductor. This is conducive to designers to calculate the setting depth of conductor with other uncertain factors taken into account, and reasonably control the potential risks.     

锦州地区逐日降水概率分布特征

利用锦州地区的逐日降水量观测资料对逐日降水量的概率分布进行了统计分析,采用最大似然估计法得到Gamma函数分布的形状参数α和尺度参数β,通过Gamma概率分布模拟观测站点逐日降水的概率分布。结果表明：锦州地区逐日降水频率整体趋势先上升后下降,基本呈对称式分布,降水概率有一定的振荡,个别日会出现远超相邻日期的降水频率,7月21日降水频率最高,在不计微量降水的情况下,最低逐日降水概率有多个日期为0。各季降水频率偏低是造成义县地区干旱的原因之一;北镇夏季平均降水频率最低,但其夏季平均降水量却为锦州地区最高,说明北镇可能易出现较大量级降水或易出现极端降水天气。清明期间降水频率在50%以上、高考期间降水频率在80%以上,符合大众日常对特殊日期降水情况的认知;逐日降水频率可以为公众气象服务提供新的思路。凌海、北镇更容易出现极端降水天气;锦州地区日降水出现小雨天气概率最高,暴雨以上降水概率较低,锦州地区各站极少出现大暴雨以上量级降水,对锦州降水量级预报,尤其是暴雨或大暴雨以上降水量级的预报起到一定的指示作用。     

GPS-RTK用于矿山高精度沉陷监测的可行性研究

针对复杂地表条件下采用水准测量和导线测量等常规方式进行地表变形周期观测、任务量大甚至无法实施等问题,提出了建立研究区域的似大地水准面精化模型,同时采用GPS-RTK技术获取观测站三维空间信息,进而获得概率积分法预计参数。最后以内蒙古准格尔旗某煤矿的生产实践说明该技术的有效性和可行性,极大地提高了工作效率,为保护煤柱的留设提供了科学的依据。     

Conditional probabilistic estimates of 21st century greenhouse gas emissions based on the storylines of the IPCC-SRES scenarios

The conditional probabilistic scenario analysis combines statistical methods of uncertainty analysis at parameter level with storylines which recognize the deep uncertainty that exists for several underlying trends. The model calculations indicate that cumulative 21st century emissions could range from 800 to 2500 GtC in the absence of climate policy. This range originates partly from the underlying storylines, and partly from the probabilistic analysis. Among the most important parameters contributing to the uncertainty range are uncertainty in income growth, population growth, parameters determining energy demand, oil resources and fuel preferences. The contribution of these factors is also scenario-dependent.     

Joint PDF Modelling of Turbulent Flow and Dispersion in an Urban Street Canyon

The joint probability density function (PDF) of turbulent velocity and concentration of a passive scalar in an urban street canyon is computed using a newly developed particle-in-cell Monte Carlo method. Compared to moment closures, the PDF methodology provides the full one-point one-time PDF of the underlying fields containing all higher moments and correlations. The small-scale mixing of the scalar released from a concentrated source at the street level is modelled by the interaction by exchange with the conditional mean (IECM) model, with a micro-mixing time scale designed for geometrically complex settings. The boundary layer along no-slip walls (building sides and tops) is fully resolved using an elliptic relaxation technique, which captures the high anisotropy and inhomogeneity of the Reynolds stress tensor in these regions. A less computationally intensive technique based on wall functions to represent the boundary layers and its effect on the solution are also explored. The calculated statistics are compared to experimental data and large-eddy simulation. The present work can be considered as the first example of computation of the full joint PDF of velocity and a transported passive scalar in an urban setting. The methodology proves successful in providing high level statistical information on the turbulence and pollutant concentration fields in complex urban scenarios.