隧道超前地质灾害预报综述

隧道超前地质灾害预报在隧道施工中是十分重要的环节。文章对隧道超前地质灾害预报内容、原则、形式、方法、流程方面的研究现状进行了论述。着重对隧道超前地质灾害预报的各种方法进行了分析对比。隧道超前地质灾害预报的方法各有优缺点和局限性,应该取长补短,综合分析,根据实际情况确定应该采取的方法及其组合。在隧道超前地质灾害预报工作中,必须处理好与施工单位的关系。     

Study of Aerodynamic Parameters on Different Underling Surfaces

Aerodynamic parameters including the zero-plane displacement (d), roughness length (20), and friction velocity (u*) on the different underlying surfaces of heavy-grazing site, medium-grazing site, light-grazing site, no-grazing site, dune, inter-dune, grassland, rice paddy site, wheat site, soybean site, and maize site have been computed based on the Monin-Obukhov similarity theory by utilizing the micrometeorologically observed data of dune and vegetation in the semi-arid area at Naiman, Inner Mongolia of China, conducted jointly by the Institute of Desert Research, Chinese Academy of Sciences and the National Institute of Agro-Environmental Sciences of Japan in 1990-1994. And their relationships between wind speed and Richardson number are analyzed. The aerodynamic characteristics of different man-made disturbed grassland ecosystems are also compared. Result shows that the vegetation coverage and the above-ground biomass decrease with the increase in man-made stress of the grassland. The roughness length for different underlying surfaces is closely related to vegetation height, above-ground biomass, and ground surface undulation, and Richardson number Ri is also its influencing factor. The friction velocity varies largely on different underlying surfaces, and it is positively proportional to wind speed and roughness length. The aerodynamic parameters of various times on the same underlying surface are different, too. Above results indicate that grassland and vegetation are of significance in preventing desertification, especially in the arid and semi-arid land ecosystems. And the results of this paper are also important for constructing the land surface physical process as well as regional climate model.     

上海天文台佘山工作站夜天亮度的变化

使用1994—2007年在1．56m反射望远镜CCD照相机拍摄的资料，测定了上海天文台余山工作站夜天亮度的变化。由于上海城市的发展，佘山工作站的夜天亮度在V波段从每平方角秒约19mag变到15．8mag，也就是说，夜天亮度自1994年以来变亮了约20倍。国际上优良台站的夜天亮度在V波段等于或暗于21．5mag。上述夜天亮度是优良台站的200多倍。现在在佘山工作站使用1．56m反射望远镜对暗于V=14mag的星做精确测光已经很困难了。     

中国东海济舟岛南部春季水华的影响要素研究

A soil circulation occurs in the south of Cheju Island in the spring. Nutrients and its influence on chlorophyll a(Chl a) around the circulations were studied from April 9 to May 6, 2007. Spring bloom with elevated concentrations of Chl a was observed during the investigation. High concentrations of phosphate, nitrate and silicate at 0.6, 12, and 8 mmol/m3, respectively, were detected. A low water temperature prevented the growth of phytoplankton. Chl a concentrations in the study area might be strongly associated with the high silicate concentration.     

基于GEE的地表覆盖与气候状态关联研究

为探究地表覆盖与气候状态间的关联性,本文选取2019年的Landsat影像数据,结合温度、降水量、PM_2.5浓度3种气候指标,利用GEE平台,结合NDVI、MNDWI、NDBI,采用SVM、RF、CART方法进行地表覆盖分类,探究气候指标与地表覆盖类型分布的关联性;提出了使用3种气候指标构建分类特征进行地表覆盖分类的方法,并通过消融试验分析了气候指标对地表覆盖分类精度的影响。结果表明:①RF有较好的分类结果,总体精度为96.0%;②3种气候指标均能提高地表覆盖分类精度,其中PM_2.5浓度效果最好;③温度与植被、水体关联性较大,PM_2.5浓度与城区、植被关联性较大,降水量与耕地关联性较大。     

结合多级阈值与SOM的土地利用规划碎图斑识别

针对土地利用规划地图数据更新过程中因地块调入调出产生的碎图斑的识别问题,该文在深入分析样本数据特征的基础上提出一种结合多级阈值与 自组织特征映射(SOM)神经网络的碎图斑识别方法.首先通过面积和最大内角阈值排除不符合碎图斑特征的多边形;再将矩形度、圆形度、最小内角以及延展度作为特征向量输入训练好的SOM聚类模型,基于多边形特征相似性识别碎图斑,较好地弥补了 目前制图实践中大量采用的统一面积阈值法指标选取单一、主观性强的不足,实现了碎图斑的准确识别.以福州市长乐区和福清市土地利用规划调整建设用地管制区数据为样本的验证实验表明,该文方法的识别精度与稳定性(针对不同区域数据的适应性)均优于目前制图实践中大量采用的统一面积阈值法.     

金融领域的随机建模与基于软件R的Monte Carlo模拟(4):随机微分方程模型

主要研究线性随机微分方程模型,为此定义Itô随机微积分,建立Itô公式.鉴于研究的重点是利用R软件进行数值模拟,所以详细讨论了过去10多年来随机微分方程数值解的研究.     

Optical detection of Prorocentrum donghaiense blooms based on multispectral reflectance

Prorocentrum donghaiense is one of the most common red tide causative dinoflagellates in the Changjiang （Yangtze） River Estuary and the adjacent area of the East China Sea. It causes large-scale blooms in late spring and early summer that lead to widespread ecologic and economic damage. A means for distinguish- ing dinoflagellate blooms from diatom （Skeletonema costatum） blooms is desired. On the basis of measure- ments of remote sensing refectance [Rrs（λ）] and inherent optical parameters, the potential of using a mul- tispectral approach is assessed for discriminating the algal blooms due to P. donghaiense from those due to S. costatum. The behavior of two reflectance ratios [R1 = Rrs（560）/Rrs（532） and Re = Rrs（708）/Rrs（665）], suggests that differentiation of P. donghaiense blooms from diatom bloom types is possible from the current band setup of ocean color sensors. It is found that there are two reflectance ratio regimes that indicate a bloom is dominated by P. donghaiense; （1） R1 〉 1.55 and R2 〈 1.0 or （2） R1 〉 1.75 and R2 ≥ 1.0. Various sensitivity analyses are conducted to investigate the effects of the variation in varying levels of chlorophyll concentration and colored dissolved organic matter （CDOM） as well as changes in the backscattering ratio （bbp/bp） on the efficacy of this muitispectral approach. Results indicate that the intensity and inherent op- tical properties of the algal species explain much of the behavior of the two ratios. Although backscattering influences the amplitude of Rrs（λ）, especially in the 530 and 560 nm bands, the discrimination between P. donghaiense and diatoms is not significantly affected by the variation of bbp/bp. Since aCDOM （440） in coastal areas of the ECS is typically lower than 1.0 m-1 in most situations, the presence of CDOM does not interfere with this discrimination, even as SCDOM varies from 0.01 to 0.026 nm-1. Despite all of these effects, the dis- crimination of P. donghaiense blooms from diatom blooms based on multispectral measurements of Rrs（λ） is feasible.     

车站风道施工对既有桥基变形的影响规律

以复杂建筑物环境下北京国贸地铁车站风道暗挖施工工程为背景,研究风道施工对既有立交桥梁变形的影响规律,提出可行的施工变形监测方案.研究结果表明,导洞开挖支护施工阶段、风道加固扣拱施工阶段、北风道开挖支护施工阶段是车站风道开挖关键的三大施工阶段.加固扣拱施工阶段对既有桥基的变形影响较大,在此阶段采取加固措施,处理好节点转换问题.在洞桩法施工风道过程中,应采用信息化施工技术,加强桥基、地表和地下风道洞周的变形监测工作,保证风道安全施工.     

变差函数在赣杭构造带火山岩型铀矿田(床)评价中的应用

在简要介绍变差函数的原理、算法和研究区地质情况的基础上,将变差函数引入火山岩型铀成矿作用与地形相关性研究中。详细描述了赣杭构造带中不同成矿规模矿田(床)区地形高程变差统计的过程,初步分析了变差统计结果的地质意义。研究结果表明,地形高程值变差函数的长轴方向可以反映研究区的主要构造方向,变差函数的长短轴半径与铀矿床的成矿规模在一定程度上具有对应关系。