Use of multi-point analysis and modelling to address cross-scale coupling in space plasmas: Lessons from Cluster     

M.W. Dunlop  R. Bingham  P. Escoubet  C. Shen  R. Trines  Z-Y. Pu  S. Schwartz 《Planetary and Space Science》2011,59(7):630-638

The properties of plasmas (in space) are fundamentally governed by both ‘cross-scale’ coupling and comparative temporal behaviour operating over the micro-, meso-, and (MHD-) fluid regimes: for example, under conditions of turbulence, during magnetic reconnection and in shocks and other plasma boundaries. These themes map to a number of related and overlapping, phenomena, where known phenomena play different roles in each theme. Detailed understanding of fundamental plasma processes therefore requires analysis of both theoretical models (to distinguish the collisionless from the collisional regimes) and multi-scale measurements (suitable to address issues of stationarity). In particular, the investigation of phenomena requires analysis techniques which can distinguish and quantify temporal behaviour and the multi-scale spatial behaviour. The analysis of existing, multi-point data sets has led to a number of data co-ordination methods, such as the four spacecraft analysis tools developed for cluster, and we consider examples here. Advanced analysis concepts may be investigated with suitable considerations of measurement quality:adequate sampling of phenomena (for example, to extract the necessary information on the mechanisms operating) requires suitable spacecraft configurations and directly relates to the measurement quality achievable. A particular issue is how to resolve temporal behaviour across the spatial regimes, so that the data set is suitably coordinated. With the addition of theoretical modelling (in the context of particular phenomena) both the space and laboratory plasma regimes may be compared and we give an example of nonlinear wave coupling across spatial scales in this context.  相似文献   

专业认证背景下的“计算机地图制图”课程教学改革     

王延亮  刘妍  司海燕 《测绘工程》2013,(6):86-88,91

专业认证是教育部提升高校专业竞争力,满足社会需求的重要举措.专业认证对专业设置、课程改革提出了全新的理念和要求,已成为高校改革的原动力.基于专业认证背景,文中讨论“计算机地图制图”课程教学存在的问题,基于专业认证的现实需要,提出课程改革的方案,论述培养学生实践能力和创新能力方法.使“计算机地图制图”在工程文化教育中发挥重要作用.  相似文献   

应用型高校“遥感概论”教学模式的探索     

李巍  王兰霞 《测绘工程》2013,22(4)

结合应用型高校遥感概论课程现有教学模式,以CDIO工程教育理念为指导,从转变教学理念、整合教学内容、改变教学方式及方法、拓宽教学平台、改革考核方式等方面,探索应用型高校“遥感概论”课程教学的新模式.  相似文献   

北京区域冬季灰霾过程中人为气溶胶光学厚度估算     

王堰  谢一凇  李正强  李东辉  李凯涛 《遥感学报》2013,17(4):993-1007

本文使用北京地区不同时期（2009年1月和2013年1月）的地基气溶胶观测资料,估算了灰霾天气的人为气溶胶光学厚度,在此基础上结合气溶胶光学参数进行了对比分析。结果表明：（1）2013年1月人为气溶胶光学厚度（440 nm）较2009年1月有所增加,月平均值分别为0.88和0.44;（2）2013年1月灰霾污染中人为气溶胶占统治地位的天数比例是86.7%,高于2009年1月的62.5%;（3）2013年1月人为成分在气溶胶光学厚度（440 nm）中的贡献平均达88%,说明灰霾污染主要是由人为气溶胶造成的。  相似文献   

弱GPS/GLONASS信号捕获算法研究     

刘毓  邹星 《测绘科学》2013,38(1):133-135

本文给出了GPS/GLONASS双模接收机的总体设计方案,重点对弱信号环境下的接收机信号捕获进行了讨论,采用并行码相位搜索方法和改进的循环相关算法分别对GLONASS信号和GPS信号进行捕获;并利用真实数据对双模接收机性能进行了仿真研究,重点对接收机捕获弱信号的能力,以及在不同信噪比和不同累加数据长度下的捕获概率进行了讨论,结果表明该双模接收机在不需要较长数据长度的情况下能够捕获低信噪比环境下的卫星导航信号,提高了接收机的灵敏度。  相似文献   

面向矿产行业的GIS卓越工程师培养模式研究     

吴浩  孙久运  花向红  池秀文  袁艳斌  黄解军 《测绘科学》2013,38(5):185-187

针对现有GIS专业培养方案难以适应社会发展需求的问题,本文以国家"卓越工程师教育培养计划"为契机,依托我校矿物资源工程优势学科的矿产行业背景,对GIS专业的实践教学计划与内容进行改革,探索了校内特色专业实验室、校外典型行业实践基地和双师制行业实践的3种教学模式,构建出培养具备高素质矿产行业背景GIS卓越工程师培养的"四四"实践教学平台。并在开放式矿业教学平台的支持下,研究了"学习—实践—研究—创新—再学习"为主线的实践教学方法,达到提升GIS专业学生行业应用能力的目的。  相似文献   

On the normal mode instability of harmonic waves on a sphere     

Yu. N. Skiba 《地球物理与天体物理流体动力学》2013,107(1-2):115-127

Abstract

The normal mode instability of harmonic waves in an ideal incompressible fluid on a rotating sphere is analytically studied. By the harmonic wave is meant a Legendrepolynomial flow αP_n(μ) (n ≥ 1) and steady Rossby-Haurwitz wave of set F ₁ ⊕ H_n where H_n is the subspace of homogeneous spherical polynomials of the degree n(n ≥ 2), and F ₁ is the one-dimensional subspace generated by the Legendre-polynomial P₁(μ). A necessary condition for the normal mode instability of the harmonic wave is obtained. By this condition, Fjörtoft's (1953) average spectral number of the amplitude of each unstable mode must be equal to . It is noted that flow αP_n (μ) is Liapunov (and hence, exponentially and algebraically) stable to all the disturbances whose zonal wavenumber m satisfies condition |m| ≥ n. The bounds of the growth rate of unstable normal modes are estimated as well. It is also shown that the amplitude of each unstable, decaying or non-stationary mode is orthogonal to the harmonic wave.

The new instability condition can be useful in the search of unstable perturbations to a harmonic wave and on trials of numerical stability study algorithms. For a Legendre-polynomial flow, it complements Kuo's (1949) condition in the sense that while the latter is related to the basic flow structure; the former characterizes the structure of a growing perturbation.  相似文献   

Quasigeostrophic planetary waves in a two-layer ocean with one-dimensional periodic bottom topography     

Atsushi Kubokawa 《地球物理与天体物理流体动力学》2013,107(2):119-137

Although the study of topographic effects on the Rossby waves in a stratified ocean has a long history, the wave property over a periodic bottom topography whose lateral scale is comparable to the wavelength is still not clear. The present paper treats this problem in a two-layer ocean with one-dimensional periodic bottom topography by a simple numerical method, in which no restriction on the wavelength and/or the horizontal scale of the topography is required. The dispersion diagram is obtained for a wavenumber range of [?π/L _b , π/L _b ], where L _b is the periodic length of the topography. When the topographic?β?is not negligible compared to the planetary β, the Rossby wave solutions around the wavenumbers which satisfy the resonant condition among the waves and topography disappear and separate into an infinite number of discrete modes. For convenience, each mode is numbered in order of frequency. As topographic height is increased, the high frequency barotropic Rossby wave (mode 1) becomes a topographic mode which can exist even on the f plane, and the highfrequency baroclinic mode (mode 2) becomes a surface intensified mode. Behaviors of low frequency modes are somewhat complicated. When the topographic amplitude is small, the low frequency baroclinic modes tend to be bottom trapped and the low frequency barotropic modes tend to be surface intensified. As topographic amplitude further increases, the relation between the mode number and vertical structure changes. This change can be attributed to the increase of the frequency of the topographic mode with the topographic amplitude.  相似文献   

某砖砌体教学楼结构抗震加固设计     

王晓星  李慧剑 《华北地震科学》2013,31(2):59-61,66

某中小学教学楼为典型的80年代建造的砌体教学楼,鉴定结果显示基础稳定,上部结构材料强度不足,部分构造设置不合理。在结构抗震加固再设计中,从概念上分析结构加固的合理性;合理地确定地震作用影响系数,对加固前后的结构进行整体计算分析;对重要及复杂的部分节点进行补充设计。  相似文献   

西藏甲玛埃达克质斑岩的地球化学特征及意义   总被引：4，自引：0，他引：4  

秦志鹏  汪雄武  唐菊兴  周云  唐晓倩 《吉林大学学报(地球科学版)》2012,(Z1):267-280

分析了西藏甲玛石英闪长玢岩-二长花岗斑岩-花岗闪长斑岩岩相学、年代学及地球化学特征,研究其形成演化及构造环境,并建立岩浆成因模式。甲玛石英闪长玢岩-二长花岗斑岩-花岗闪长斑岩是具弧岩浆地球化学特征的准铝质高钾钙碱性岩岩石系列,同时具有O型(向C型过渡)埃达克质岩和I型(或磁铁矿型)花岗岩的特征。其成因与新特提斯洋板片脱水熔融形成的流体与地幔楔发生地幔交代作用形成的EMⅡ型富集地幔有关。中新世兰格期(15 Ma左右),由于拉萨地体东西向的"崩塌",导致拉萨地体开始伸展减薄,从而使交代地幔(EMⅡ型富集地幔)减压熔融,形成了富含Cu、Au等成矿物质的具I型(或磁铁矿型)弧岩浆地球化学特征的准铝质富钾O型埃达克质铁镁质岩浆,并在沿该时期的正断层及裂谷系统侵位过程中,不断与下地壳高钾及中—高Fe/Mg的花岗质岩浆发生不同程度的岩浆混合作用,伴随着相对较弱的岩浆结晶分异过程不断侵位浅地表,进而形成了独特的石英闪长玢岩-二长花岗斑岩-花岗闪长斑岩岩石组合。  相似文献