重庆市标准地址模型与地址库研究与实践     

李莉  丁忆  周建 《测绘软科学研究》2014,(4):83-88

结合重庆山地城市特点,研究了重庆标准地址要素分类、组合模式及层次关系。基于此模型对覆盖重庆主城600平方千米的40万条地址数据进行分词、分层,建设地址数据库。在应用方面,对卫生、教育、事业单位等行业专题数据进行地址匹配,为政务地理信息提供良好的服务支撑。  相似文献   

一类与算子有关的级数转化公式     

赵熙强  赵芳 《中国海洋大学学报(自然科学版)》2014,44(1)

利用算子之间的相互关系将算子g(xΔ)展成3种不同的形式,构造一些级数转化公式,并结合Eulerian多项式简化这些级数转化公式、最后讨论这些级数转化公式在寻找求和公式及组合恒等式证明中的一些应用。  相似文献   

Mean Flow–Storm Track Relationship and Rossby Wave Breaking in Two Types of El-Nino     

LIU Chengji  REN Xuejuan  YANG Xiuqun 《大气科学进展》2014,(1)

The features of large-scale circulation, storm tracks and the dynamical relationship between them were examined by investigating Rossby wave breaking(RWB) processes associated with Eastern Pacific(EP) and Central Pacific(CP) El-Nin o. During EP El-Nin o, the geopotential height anomaly at 500 hPa(Z500) exhibits a Pacific–North America(PNA) pattern. During CP El-Nin o, the Z500 anomaly shows a north positive–south negative pattern over the North Pacific. The anomalous distributions of baroclinicity and storm track are consistent with those of upper-level zonal wind for both EP and CP El-Nin o, suggesting impacts of mean flow on storm track variability. Anticyclonic wave breaking(AWB) occurs less frequently in EP El-Nin o years, while cyclonic wave breaking(CWB) occurs more frequently in CP El-Nin o years over the North Pacific sector. Outside the North Pacific, more CWB events occur over North America during EP El-Nin o. When AWB events occur less frequently over the North Pacific during EP El-Nin o, Z500 decreases locally and the zonal wind is strengthened(weakened) to the south(north). This is because AWB events reflect a monopole high anomaly at the centroid of breaking events. When CWB events occur more frequently over the North Pacific under CP El-Nin o conditions, and over North America under EP El-Nin o condition, Z500 increases(decreases) to the northeast(southwest), since CWB events are related to a northeast–southwest dipole Z500 anomaly. The anomalous RWB events act to invigorate and reinforce the circulation anomalies over the North Pacific–North America region linked with the two types of El-Nin o.  相似文献   

基于波场延拓的变换坐标转换波静校正          下载免费PDF全文

张正峰  郭建  韩立国  徐善辉  巩向博 《地球物理学报》2013,56(5):1676-1685

常规的转换波静校正的基本思想都是从地震波的运动学特征出发,基于地表一致性假设.在地表条件复杂和地表高程相差较大的地区,它不仅无法解决严重的静校正问题,反而会带来新的畸变.本文基于频率波数域波动方程偏移原理,采用波场延拓方法实现转换波静校正,其关键点在于时间空间域和频率波数域的相对应.文中通过坐标变换将起伏地表转化为新坐标系下的水平地表,把炮点和检波点映射到同一水平面上,然后在新坐标系下推导频率域波动方程延拓公式,接着对下行波P和上行转换波SV分别利用近地表速度向上延拓到基准面,恢复起伏地表到基准面之间的真实波场,最后转换到原始坐标系取出基准面数据完成转换波静校正.通过对模拟和实际数据处理,证明该方法是正确和有效的.  相似文献   

高光谱端元自动确定与提取的迭代算法     

曹建农  王贝贝  何晓宁 《遥感学报》2013,17(2):248-268

针对端元提取算法依赖人工确定端元数量的问题, 提出一种端元自动确定与提取的迭代算法。首先, 通过统计分析获得像元相似性阈值, 确定候选端元判据;其次, 对候选端元进行内、外部相关性判断, 对端元光谱集进行病态矩阵规避判断;最后, 以候选端元判据为迭代终止条件, 当图像空间不存在候选端元时, 获得端元集合并确定端元数。实验结果表明, 该方法正确有效, 可以避免顺序端元提取方法的错误风险, 提高端元提取自动化程度。  相似文献   

A nonlinear dynamo driven by rapidly rotating convection     

Eun-jin Kim  David W. Hughes  Andrew M. Soward 《地球物理与天体物理流体动力学》2013,107(4):325-343

In Kim et al. (Kim, E., Hughes, D.W. and Soward, A.M., “An investigation into high conductivity dynamo action driven by rotating convection”, Geophys. Astrophys. Fluid Dynam. 91, 303–332 ().) we investigated kinematic dynamo action driven by rapidly rotating convection in a cylindrical annulus. Here we extend this work to consider self-consistent nonlinear dynamo action in which the back-reaction of the Lorentz force on the flow is taken into account. In particular, we investigate, as a function of magnetic Prandtl number, the evolution of an initially weak magnetic field in two different types of convective flow – one chaotic and the other integrable. On saturation, the latter shows a systematic dependence on the magnetic Prandtl number whereas the former appears not to. In addition, we show how, in keeping with the findings of Cattaneo et al. (Cattaneo, F., Hughes, D.W. and Kim, E., “Suppression of chaos in a simplified nonlinear dynamo model”, Phys. Rev. Lett. 76, 2057–2060 ().), saturation of the growth of the magnetic field is brought about, for the originally chaotic flow, by a strong suppression of chaos.  相似文献   

The scattering of Rossby waves from finite abrupt topography     

G. W. Owen  A. J. Willmott  I. D. Abrahams  H. Mansley 《地球物理与天体物理流体动力学》2013,107(3):219-239

The scattering of first mode linear baroclinic Rossby waves by a top-hat ridge in a continuously stratified ocean, with Brunt-Väisälä frequency that decays exponentially with depth below a surface mixed layer, is the subject of this study. A numerical mode matching technique is used to calculate the transmission coefficients for the propagating modes over the ridge. It is found that the scattered field depends crucially upon the stratification. For example, when the majority of the density variation is confined to a thin thermocline, corresponding to a small e-folding scale, gamma ^?1, for the Brunt-Väisälä frequency, a large amount of the incident wave energy is reflected by a small amplitude ridge. Appreciable energy conversion between the propagating barotropic and baroclinic modes takes place in this case. An asymptotic analysis for a small amplitude ridge is presented that confirms these numerical results. In the limit gamma ^?1→ 0, it is demonstrated that the scattered field in the continuously stratified ocean model differs markedly from the two-layer solution. The latter does not exhibit appreciable reflection of the incident wave energy for a small amplitude ridge. In conclusion, the application of a two-layer ocean model to describe Rossby wave scattering by ridges in place of a continuously stratified model cannot be recommended.  相似文献   

Nonlinear internal waves in the upper atmosphere     

P. Caillol 《地球物理与天体物理流体动力学》2013,107(4):271-308

To investigate the mechanism of mixing in oscillatory doubly diffusive (ODD) convection, we truncate the horizontal modal expansion of the Boussinesq equations to obtain a simplified model of the process. In the astrophysically interesting case with low Prandtl number (traditionally called semiconvection), large-scale shears are generated as in ordinary thermal convection. The interplay between the shear and the oscillatory convection produces intermittent overturning of the fluid with significant mixing. By contrast, in the parameter regime appropriate to sea water, large-scale flows are not generated by the convection. However, if such flows are imposed externally, intermittent overturning with enhanced mixing is observed.  相似文献   

Frontal upwelling in a rotating two-layer fluid     

G. J. F. Van Heijst 《地球物理与天体物理流体动力学》2013,107(1-4):139-153

Abstract

This paper describes the source-sink driven flow in a two-layer fluid confined in a rotating annulus. Light fluid is injected at the inner wall, while denser fluid is withdrawn at the outer wall. The interface between the immiscible fluids intersects the bottom and thus produces a front. The net transport from the source to the sink is carried by Ekman layers at the bottom and at the interface, and by Stewartson layers at the side walls. A detached Stewartson layer arises at the front, leading to a pronounced upwelling circulation.  相似文献   

The structure of separated flow past a circular cylinder in a rotating frame     

Michael A. Page  Peter W. Duck 《地球物理与天体物理流体动力学》2013,107(1-4):197-223

Abstract

This paper examines the detailed E ^1/4-layer structure of separated flow past a circular cylinder in a low-Rossby-number rotating fluid as the Ekman number E tends to zero. This structure is based on an initial proposal by Page (1987) but with some modifications in response to further evidence, outlined both in this paper and elsewhere, on the behaviour of E ^1/4-layer flows in this context. Numerical calculations for flow in an E ^1/4 shear layer along the separated free streamline are described and the mass flux from this layer is then used to calculate the higher-order flow within the separation bubble. The flow structure is found to have two forms, depending on the value of the O(1) parameter λ, and these are compared with results from published “Navier-Stokes” type calculations for the flow at small but finite values of E.  相似文献