Estimating the significance of a signal in a multi-dimensional search

In experiments that are aimed at detecting astrophysical sources such as neutrino telescopes, one usually performs a search over a continuous parameter space (e.g. the angular coordinates of the sky, and possibly time), looking for the most significant deviation from the background hypothesis. Such a procedure inherently involves a “look elsewhere effect”, namely, the possibility for a signal-like fluctuation to appear anywhere within the search range. Correctly estimating the p-value of a given observation thus requires repeated simulations of the entire search, a procedure that may be prohibitively expansive in terms of CPU resources. Recent results from the theory of random fields provide powerful tools which may be used to alleviate this difficulty, in a wide range of applications. We review those results and discuss their implementation, with a detailed example applied for neutrino point source analysis in the IceCube experiment.     

统计降尺度方法在青海省冬季最低温度预测中的应用

利用2003-2007年国家气象中心T213L31全球中期数值预报模式逐日输出产品与青海地区25个气象站的观测数据作为试验资料, 利用相关系数和逐步回归进行因子选择, 并以单隐层神经网络和多元回归作为降尺度方法进行对比研究, 用2003-2006年间的11月1日～次年3月1日的资料作为训练样本, 以数值预报产品和前一日观测的最低温度作为因子, 建立青海省25个气候站的冬季最低温度的24, 48, 72 h预报模型, 并且以2006年12月和2007年的1、 2月作为24, 48, 72 h逐日最低温度预报试验时段。试验表明, 对于青海地区来说, 青海北部地区的预报命中率总体好于南部高原地区; 在4种对比方案中, 以选择数值预报资料结合前一日地面观测的最低温度作为主要因子的方法相对较优, 随着预报时效的延长, 24 h历史实况的作用逐渐减弱; 对于所有台站来说, 这4种方案各有优缺点, 没有一种方案可以完全代替其他所有方案; 在实际业务运行中, 对不同的台站应采用不同的预报方案进行实际业务预报。     

高美古与凤凰山水汽含量的统计分析

介绍了利用北京师范大学研制的ＩＲＡ－９３５型红外水汽测量仪对云南丽江高美古天文候选点及昆明凤凰山对比点上空垂直大气水汽积分含量Ｗ０的观测结果,给出了两地Ｗ０的日变化曲线及分布图,并对全年测量数据的统计结果作了分析和讨论     

类星体光度函数

对前人在类星体光度函数研究中的工作作了详细的介绍。在前人工作的基础上,提出两个新的研究方法和一个新的统计方法。第一为分类研究法。将类星体分作若干子类,每一子类的光度演化形式可以通过相关分析求出,而数密度则可由简单计数求得。第二为平均星等法,定义平均星等Ｍ。研究表明,对于纯密度演化模型,Ｍ与红移ｚ无关;而对于纯光度演化模型,Ｍ与光度演化形式（Ｍｚ－Ｍ）成线性关系。提出的新的统计方法为ｎ／ｎｍａｘ检验法,它是传统的Ｖ／Ｖｍａｘ和Ｖ′／Ｖ′ｍａｘ检验法的推广。与传统方法不同,它能适用于任何光度函数模型。若所采用的光度函数正确,则样品的ｎ／ｎｍａｘ值应均匀分布于数域［０,１］     

济南药山崩塌地质灾害治理方法初探

济南地区的中基性岩体,大面积隐伏分布于济南市北部地带,零星出露为孤峰或丘陵,构成济南地区著名的"齐烟九点"地貌景观。药山为"齐烟九点"之一,地处济南杂岩体的中西部,岩性主要为闪长岩、辉长岩等,块状结构,节理裂隙发育,易球状风化形成临空状危岩体,构成崩塌地质灾害隐患。结合济南药山危岩体组合特征,进行了稳定性计算和分析,提出了不同的治理方案以及具体施工方法和施工顺序,以期达到消除地质灾害隐患的目的,切实保护人民生命财产安全,为类似地区开展地质灾害治理提供参考。     

环境演变研究时间序列的建立方法评述

对环境演变时间序列建立的几种主要方法的纪年原理、应用状况及应用的优点、范围、局限性进行了阐述和比较，包括长寿命宇宙成因核素在内的同位素纪年方法主要判别第四纪以来大时间尺主的沉积物的地质年龄，且能很好地应用于全球变化的研究，但百余年来沉积物的年龄及侵蚀历史变化的研究只能通过^210Pbex、^137Cs等半衰期相对较短的核素来进行；指出^210Pbex可望在现代流域侵蚀环境演变以及其效应评价的研究中获得新的突破。     

贵州区域地质灾害发育程度初探

根据全省完成的县（市）地质灾害调查与区划成果,结合各地行政区面积及山地丘陵比例,采用地质灾害综合发育程度指数法,对9个地区级行政区域进行地质灾害发育程度分析,划分出的地质灾害高、中、低发育区比较符合省情实际,对地方政府的地质灾害防治工作具一定的指导意义。     

Probabilistic stability analyses of undrained slopes by 3D random fields and finite element methods

A long slope consisting of spatially random soils is a common geographical feature. This paper examined the necessity of three-dimensional(3 D) analysis when dealing with slope with full randomness in soil properties. Although 3 D random finite element analysis can well reflect the spatial variability of soil properties, it is often time-consuming for probabilistic stability analysis. For this reason, we also examined the least advantageous(or most pessimistic) cross-section of the studied slope. The concept of"most pessimistic" refers to the minimal cross-sectional average of undrained shear strength. The selection of the most pessimistic section is achievable by simulating the undrained shear strength as a 3 D random field. Random finite element analysis results suggest that two-dimensional(2 D) plane strain analysis based the most pessimistic cross-section generally provides a more conservative result than the corresponding full 3 D analysis. The level of conservativeness is around 15% on average. This result may have engineering implications for slope design where computationally tractable 2 D analyses based on the procedure proposed in this study could ensure conservative results.     

Radon,Lung Cancer Risk and Environmental Geology in Gejiu Area

The incidence of lung cancer in the Gejiu area of Yunnan Province ranks the first in the world.The radon level(indoor,soil) was measured in the Gejiu area by the SSNTD method from 1990 to 1996,The result indicates an extensive high-level of indoor radon in that area though U and Th are lower in local limestones,The indoor radon level of houses located in the geologic fault zone is 6 times high that 2km far from the fault zone.The reason probably is that the radon level of soil in the fault is 6-8 times high that 1 km far from the faults.our data indicate that a lower range of radon levels,0-100Bq.m^-3,exists in healthy families.However,a higher radon level,over 800 Bq.m^-3,is often found corresponding to that of cancer patients‘ homes(the house-owners are suffering from either lung cancer or leukaemia or liver cancer),Obviously,an increase in lung cancer incidence follows an increase in indoor radon level,The risk of cancer induced by indoor radon is no longer an inference,but a fact.