简单热带海气耦合模型中不同扰动形式的作用

在局地热平衡情况下,将物理量先用韦伯函数展开,然后去掉相应分量的滤波方 法,讨论了简单热带海气耦合模型中不同形式扰动的作用和贡献,结果表明,在热带海气耦合 系统中,大气准定常 Ｒｏｓｓｂｙ波和海洋 Ｒｏｓｓｂｙ波对于耦合系统贡献较大,它们决定着耦合系统 与耦合扰动的性质,而大气准定常Ｋｅｌｖｉｎ波和海洋Ｋｅｌｖｉｎ波对于耦合系统贡献相对较小．     

Estimating attendance from cellular network data

An automatic estimate of the number of attendees to events happening in the city can provide valuable information to geographic information systems and geo-located applications. We present a methodology to estimate the number of events’ attendees from cellular network data. In this work, we used anonymized Call Detail Records (CDRs) comprising data on where and when users access the cellular network. Our approach is based on two key ideas: (1) we identify the network cells associated with the event location. (2) We verify the attendance of each user, as a measure of whether (s)he generates CDRs during the event, but not during other times. We evaluate our approach to estimate the number of attendees to a number of events ranging from football matches in stadiums to concerts and festivals in open squares. Comparing our results with the best groundtruth data available, our estimates provide a median error of less than 15% of the actual number of attendees.     

The influence of rainfall and land use patterns on soil erosion in multi-scale watersheds: A case study in the hilly and gully area on the Loess Plateau,China

Soil erosion has become a major global environmental problem and is particularly acute on the Loess Plateau (LP), China. It is therefore highly important to control this process in order to improve ecosystems, protect ecological security, and maintain the harmonious relationship between humans and nature. We compared the effects of rainfall and land use (LU) patterns on soil erosion in different LP watersheds in this study in order to augment and improve soil erosion models. As most research on this theme has so far been focused on individual study areas, limited analyses of rainfall and LU patterns on soil erosion within different- scale watersheds has so far been performed, a discrepancy which might influence the simulation accuracies of soil erosion models. We therefore developed rainfall and LU pattern indices in this study using the soil erosion evaluation index as a reference and applied them to predict the extent of this process in different-scale watersheds, an approach which is likely to play a crucial role in enabling the comprehensive management of this phenomenon as well as the optimized design of LU patterns. The areas considered in this study included the Qingjian, Fenchuan, Yanhe, and Dali river watersheds. Results showed that the rainfall erosivity factor (R) tended to increase in these areas from 2006 to 2012, while the vegetation cover and management factor (C) tended to decrease. Results showed that as watershed area increased, the effect of rainfall pattern on soil erosion gradually decreased while patterns in LU trended in the opposite direction, as the relative proportion of woodland decreased and the different forms of steep slope vegetation cover became more homogenous. As watershed area increased, loose soil and craggy terrain properties led to additional gravitational erosion and enhanced the effects of both soil and topography.     

耗散大气中水平不均匀风场对内重力波传播的影响

采用包括耗散的射线跟踪方法,计算了在水平不均匀风场作用下,不同尺度重力波从对流层直至220km观测高度的传播,结果表明,垂直于重力波传播方向的风以及风剪切能够引起波射线的折射,从而导致重力波明显偏离初始传播方向.在强顺风场作用下,由于风场引起的捕获,大量重力波不能传播到观测高度.由于风场引起的多普勒频移,小周期的重力波在弱顺风条件下能够传播到观测高度.由于反射作用,强逆风场不支持周期低于约18min的较高频重力波的传播.而在弱逆风作用下,大部分中尺度范围重力波都能够传播到观测高度.本文统计了武汉电离层观象台的TID观测数据随热层风场的分布,统计结果与模拟结果符合较好.     

农业景观保护路径历史回顾及启示

农业景观保护是实现农业景观可持续发展的重要举措,关系到中国粮食安全保障、农耕文明传承、乡村风貌维系、生态安全格局构建乃至社会经济稳定发展.本文借助对发达国家农业景观保护路径的长时间尺度历史回顾,总结归纳出农业景观保护路径发展的一般规律,即其在社会经济发展进程中一般经历传统保护、应对保护、管制保护、治理保护和管护保护五个...     

VSP上下行反射波联合成像方法研究

VSP资料上下行波场发育丰富.本文在分析VSP直达波、上行反射波、下行反射波传播路径及其照明范围的基础上,指出了常规VSP波动方程偏移方法缺陷,进而通过修改波场延拓方式,提出了上下行反射波联合成像方法,并在高频近似下分析了该方法的成像原理.该方法不需要进行VSP上下行反射波场分离,能够同时对VSP资料中的一次反射波、自由表面多次波、层间多次波进行成像,比常规成像剖面具有更宽的成像范围和更好的成像效果.该方法能够对下行一次反射波进行成像,从而可以实现常规偏移方法难以处理的高陡倾角构造成像.模拟资料和实际资料处理证明了本文方法的正确性.     

抗高温泡沫钻井液体系评价研究

高频钻井液压力波信息传输技术传输速率高,是实现自动化、智能化钻井的关键技术之一,由于高频钻井液压力波在传输过程中存在较大的衰减,阻碍了该技术的现场应用,探明其衰减规律对于高速传输技术开发具有重要意义。在假设同一钻柱截面钻井液压力相等且钻井液流速存在径向分布的基础上,基于二维轴对称瞬态流动理论,采用小信号分析方法,综合考虑了压力波信号参数、钻柱尺寸及钻井液参数的影响,建立了高频钻井液压力波衰减模型并给出了适用条件。最后采用地面实验验证了该模型的正确性。随后分析钻井液压力波频率、压力波传输距离、钻井液密度及黏度、钻柱内径对高频压力波衰减的影响。结果表明：高频钻井液压力波幅值衰减量随钻井液压力波频率、压力波传输距离及钻井液黏度的增加而增大,且变化规律为指数型;幅值衰减量受频率影响最大,并随钻井液密度及钻柱内径增加逐渐减小。本研究可为高频钻井液压力波信息传输技术研发提供理论指导。

     

某电厂氯化物在地下水中迁移规律研究

为了研究污染物在地下水中的迁移规律,本文以某电厂地下水中氯化物作为预测因子进行数值模拟。对研究区含水层物质组成、边界条件、初始条件及源汇项等做简化,采用GMS软件建立水文地质模型,在简化的水文地质模型的基础上开展地下水中污染物迁移规律研究。研究结果表明：在污染物排放规律简化为连续恒定排放的点源工况下,（1）污染物平面迁移范围以泄漏点为中心呈椭圆形扩散,污染晕长轴为地下水流动方向;（2）污染物最大迁移距离及污染影响范围均随时间不断增加,但是变化速率不断降低;（3）距离污染源较近的位置,污染物浓度随时间不断增加,但是浓度变化速率逐渐降低;距离污染源较远的位置,污染物浓度随时间不断增加,初期浓度变化速率随时间不断增加,后期浓度变化速率随时间逐渐降低。     

A critical analysis of the concept of planetary wave breaking

The concept of planetary wave breaking (McIntyre andPalmer, 1983; 1984) is critically reviewed. It is concluded that the wave breaking signature is not unique to any particular dynamic event in the stratosphere. Therefore, the classification of stratospheric transport events, such as wave breaking, groups fundamentally different events together. Better qualification of the wave breaking signature and a more solid theoretical basis of planetary wave breaking must be presented if the concept is to be of significant utility in describing stratospheric tracer transport.