2009年夏季极区电离层加热实验观测研究

2009年夏季,中国在挪威特罗姆瑟(Tromsφ)利用非相干散射雷达进行电离层加热实验。实验中发现了处在150km附近的小范围温度增强事件和150—400km之间的大范围温度增强事件。前者的相对增幅明显,后者的绝对增量更大。对这两类加热事件来说,温度增量百分比均随加热功率的增加线性增长,但对比两类加热事件来看,增长速度随加热频率增大而减小。加热效应存在显著的二维分布特征,加热最强方向处在场向附近。加热效应受加热天线波束指向与地磁场的夹角影响明显,随夹角增大温度增强效应减弱。     

气候变化对中国大雾的影响

1 Introduction The global environmental problem caused by climatic warming has attracted increasing attention of the scientific communities, the public and governments of various countries. The mean temperature of the recent decade is the highest of the p…     

Under the shadow of the Magellanic Bridge: A measurement of the extragalactic background at ∼ 0.7 keV

We measured the extragalactic 0.7 keV X-ray background by observing the X-ray shadow of a neutral gas cloud in the Magellanic Bridge region. Two ROSAT PSPC observations of total 104 ks were complemented by a detailed H I mapping of the cloud with both the Parkes 64 m telescope and the Australia Telescope Compact Array. From the detected anti-correlation between the observed background intensity and the H I column density of the cloud, we derived the unabsorbed extragalactic background intensity as ∼ 28 keV s⁻¹ cm⁻² keV⁻¹ sr⁻¹ at ∼ 0.7 keV. The 95% confidence lower limit 18 keV s⁻¹ cm⁻² keV⁻¹ sr⁻¹ is greater than the expected point-like source contribution ? 14 keV s⁻¹ cm⁻² keV⁻¹ sr⁻¹, constrained by the mean source spectrum together with the total background intensity in the 1-2 keV band. A significant fraction of the 0.7 keV background likely arises in a diffuse hot intergalactic medium of a few million degrees, as has been predicted in hydrodynamic simulations of cosmological structure formation.Richard McCray     

人海河流河口及其近海水域盐度分析方法浅析

在水质监测及水环境调查中,盐度分析工作是一个重要环节,根据现行的<水质分析国家标准>,<海洋调查规范>,地表水及生活用水的盐度分析一般采用前者,而海洋水样则采用后者.对于长江口及其近海水域既有适用<水质分析国家标准>(TB11896-89)的区段,又有适用<海洋调查规范>的区域,亦有两者都不适用的部分.本文通过对长江口盐度分析方法的研究.阐述了该区域进行水样盐度分析的各种方法的适用范围及提高效率保证成果质量的办法.最后作者提出的人海河流河口及其近海水域盐度分析的方法是:按取样地点位于河口的具体位置来选择其分析方法.     

基于LiDAR数据的城市道路提取与重建

本文借助于GIS强大的空间数据管理和分析功能,以Lidar点云数据为数据源,对交通信息系统基础空间数据进行快速采集和更新。文章并且在前人工作的基础上,提出了一种新的基于四维Hough变换的Lidar数据的提取和分类方法,对提取的道路信息进行重构。实践证明,此方法较之传统Lidar数据分类和提取方法,能够有效地解决其计算量过大、噪声过于敏感、道路边缘方向不平行等问题,实现道路的自动提取。     

On the Collision Nature of Two Coronal Mass Ejections: A Review

Observational and numerical studies have shown that the kinematic characteristics of two or more coronal mass ejections (CMEs) may change significantly after a CME collision. The collision of CMEs can have a different nature, i.e. inelastic, elastic, and superelastic processes, depending on their initial kinematic characteristics. In this article, we first review the existing definitions of collision types including Newton’s classical definition, the energy definition, Poisson’s definition, and Stronge’s definition, of which the first two were used in the studies of CME–CME collisions. Then, we review the recent research progresses on the nature of CME–CME collisions with the focus on which CME kinematic properties affect the collision nature. It is shown that observational analysis and numerical simulations can both yield an inelastic, perfectly inelastic, merging-like collision, or a high possibility of a superelastic collision. Meanwhile, previous studies based on a 3D collision picture suggested that a low approaching speed of two CMEs is favorable for a superelastic nature. Since CMEs are an expanding magnetized plasma structure, the CME collision process is quite complex, and we discuss this complexity. Moreover, the models used in both observational and numerical studies contain many limitations. All of the previous studies on collisions have not shown the separation of two colliding CMEs after a collision. Therefore the collision between CMEs cannot be considered as an ideal process in the context of a classical Newtonian definition. In addition, many factors are not considered in either observational analysis or numerical studies, e.g. CME-driven shocks and magnetic reconnections. Owing to the complexity of the CME collision process, a more detailed and in-depth observational analysis and simulation work are needed to fully understand the CME collision process.     

中国及邻区现代构造应力场的数值模拟

我国及邻区的现代构造应力场作为一平面应力问题用有限单元法进行了计算。将本区地壳看成是一不均匀的弹性板,根据各地区杨氏模量E、泊松比v和地壳厚度T的不同,组成12种材料区。全区被分成288个三角形单元。考虑了五种应力和位移边界条件,这些边界条件分别反映了印度洋板块、太平洋板块及菲律宾海板块对我国及邻区施加应力的相对大小。将计算得到的最大剪应力值与强震分布进行对比,将最大主压应力方向与震源机制解的最大主压应力方向进行对比,选择一种和实际符合得最好的边界条件作为可取的模式。结果表明:来自印度洋板块的作用力最大,大约是来自太平洋板块和菲律宾海板块作用力的两倍。     

Isolation and identification of alginate-degrading bacteria and formation of alginase

I~crIONThestudiesofseaalgageneticengineeringstartedintheearly1950s.HOwever,itSdevelopmentishinderedgreatlybecauseitisdifficulttogetisolatedlivecellsandprotoplasts.TheenZymeswhicharesuitabletohigherplantsarenotsuitabletoisolatetheseaalgaecellsandproto...     

泥河湾盆地虎头梁剖面河湖相沉积物磁组构特征及其环境意义

泥河湾盆地在第四纪环境变化和古人类演化研究领域占有重要地位。虎头梁剖面记录了中更新世以来泥河湾盆地逐渐消亡的过程。本文对虎头梁天然露头剖面进行了详细的沉积学、岩石磁学和磁组构研究。剖面沉积物中的磁性矿物以假单畴（PSD）的磁铁矿为主,还含有一定量的赤铁矿,磁组构类型为正常沉积磁组构。根据虎头梁剖面沉积相的划分和磁组构参数特征,将泥河湾盆地中-晚更新世晚期的演化过程划分为3个阶段：下部为第Ⅰ阶段（60~53m）,中部为第Ⅱ阶段（53~12m）,上部为第Ⅲ阶段（12~0m）,包含3个完整湖侵旋回,每个旋回由下部灰黄色粗粒三角洲相到中部黄灰色滨湖相再到顶部灰绿色细粒湖相组成,相应的磁组构参数值由大到小的变化规律,中部第Ⅱ阶段推断由气候因素主导,上部第Ⅲ阶段可能主要由构造驱动,长期稳定的优势古水流方向以NW向为主,而东坡遗址时期的古人类可能生活在湖侵阶段的相对短期湖退的滨岸地带。

     

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