多智能体系统的群集行为研究综述

近些年来,多智能体系统的群集行为分析已成为复杂网络领域的一个研究热点.本文从个体内部动力系统与个体间的拓扑结构这两个因素出发,对多智能体系统的群集行为问题的发展现状进行概述,并对相应的分布式协议、收敛速度以及实现的条件做了介绍和分析.最后,结合目前的研究现状,讨论了群集行为未来的研究方向.     

人地系统耦合框架下的生态系统服务

生态系统服务是连接自然环境与人类福祉的桥梁,是人地系统耦合研究的核心内容。本文在构建生态系统服务与人地系统耦合研究框架的基础上,系统梳理了生态系统服务评估、生态系统服务权衡、生态系统服务影响因素、生态系统服务供给流动与需求等研究前沿,提出了未来生态系统服务研究的重点领域。主要研究结论认为：①国际生态系统服务模型发展迅速,SAORES模型是中国生态系统服务模型优化与参数本地化的突出代表;②生态系统服务权衡具有相对复杂的时空尺度,权衡分析的前提是辨析不同尺度生态系统结构—过程—功能—服务的作用机制;③自然因素是生态系统服务时空分布的基础,土地利用能改变生态系统结构、功能与生态系统服务变化,社会经济因素会导致生态系统服务权衡的差异;④为明晰生态系统服务供给与需求耦合关系,需进一步识别生态系统服务流的运移路径;⑤未来生态系统服务研究需加强生态系统服务对全球变化的响应特征和机制分析、面向可持续发展目标的生态系统服务供给流动与需求研究、生态系统服务的动态评价集成与优化、生态系统服务与人地系统耦合、生态系统服务与大数据集成等。     

最小独立闭合环及水准支线自动搜索算法研究

针对原有深度优先算法存在因水准路线曲折造成的最小独立闭合环搜索失真的问题,该文提出一种最小独立闭合环搜索算法:通过引入水准点平面坐标信息,采用逐步回代思想实现对水准网最小独立闭合环的准确搜索;考虑到水准网中极有可能存在无法构成最小独立闭合环的水准支线的情形,在搜索最小独立闭合环的同时,兼顾提取出水准支线的信息。通过对2012年天津市地面沉降水准数据进行最小独立闭合环搜索,并结合人工拼环的结果加以印证,对比分析结果表明:在水准网较为复杂的情况下,该算法可有效避免原有深度优先算法搜索失真的问题,同时准确搜索出水准支线。     

高灵敏度VLBI和FAST计划

概述了VLBI天体物理的近期发展，主要成就及其受到的灵敏度制约，简要地回顾的目前还处在不太成熟阶段的低频VLBI的探索及近十余牛对提高VLBI灵敏度的硬件和软件两方面的尝试，并在此基础上，着重讲座了我国坟划中的FAST射电望远镜对提高VLBI灵敏度的可能贡献，展望了因为FAST的参与而获得的中低频高灵敏度VLBI的天体物理课及其意义。     

两类度日模型在天山科其喀尔巴西冰川消融估算中的应用

采用辐射传输参数化方案估算太阳入射短波辐射,并以小时气温作为输入数据,在200、100和50 m 3种海拔梯度下,分别应用传统度日模型和改进度日模型对科其喀尔巴西冰川2008年夏季消融区非表碛覆盖区消融进行了模拟分析.研究表明:太阳小时入射总辐射计算与实测结果具有较好的一致性;科其喀尔巴西冰川度日因子存在明显的时空差异性;随着空间分辨率提高,2类度日模型的模拟效果都变好;在200和100 m海拔梯度下,改进度日模型的模拟结果优于传统度日模型,而在50 m海拔梯度下,无明显改进.     

高陡层状土质边坡风蚀失稳过程及机理研究

吐鲁番交河故城台地高陡层状土质边坡的失稳过程受风蚀控制和影响非常典型;在土层组合特征和抗风蚀能力差异以及当地终年多大风的气候特征的共同作用下,坡体土层形成风蚀空腔并在空腔的控制下发生变形破坏.以工程地质定性分析、风洞实验、物理模拟为主要手段,结合数值模拟,分析了该边坡在自然风蚀改造过程中表现出具有特殊性、多样性和阶段性...     

地震长期效应对黄土力学性质的影响

黄土高原地区,具有大孔隙、弱胶结特征的黄土遭遇地震荷载影响后,其内部结构受到扰动,微结构的变化会在后期物理力学性质中集中反映出来。通过动三轴试验对原状黄土试样进行模拟历史地震预处理,对处理试样依次进行饱和、固结、不排水剪切试验。结果表明:黄土试样的初始含水率为10%时,经历历史地震扰动的黄土较未扰动黄土相比,其偏应力明显增加,孔隙水压力降低,抗剪强度指标值增大3.42 kPa和2.67°;当初始含水率增加至15%时,历史地震产生的长期效应将引起后期黄土强度持续增大,增幅远远超过10%的黄土试样,黏聚力和内摩擦角达到3.98 kPa和3.02°。通过扫描电镜试验和压汞试验,从微观角度分析地震长期效应对黄土力学性质影响的内在机制,结果发现历史地震引起黄土内部颗粒移动、孔隙结构变化是黄土强度增加的重要因素。     

引洮工程15~#饱和黄土隧洞主要病害及防治措施

以甘肃省引洮工程总干渠15#引水隧洞施工实践为例,分析了隧洞所在标段饱和黄土的主要工程地质条件,着重研究了在隧洞施工过程中遇到的围岩塌方、拱架变形、涌水等不良地质现象并提出了预防和处理措施,并且通过对桩号为105+166安装的围岩变形观测试验数据分析得到了饱和黄土隧洞变形的一般规律,为施工中何时进行二次支护提供科学的依据。     

Estimation of global radiation in China and comparison with satellite product

A modified solar radiation model, incorporating into several satellites remote sensing information such as NCEP/NCAR data, EOS-AURA satellite data, and Chinese FY-2C geo-stationary meteorological satellite data, is presented. The model is an attempt to modify Chen’s radiation model and examine its estimation accuracy at various places in six different climatic zones of China. The verification of model is also carried out by comparing between calculated radiation value using modified model and radiation product of FY-2C satellites. According to the NSE values, the adaptability of model is reasonably high in Mid-Temperate Zone (MTZ), Warm Temperate Zone (WTZ), Tibetan Plateau Zone (TPZ), and Cold Temperature Zone (CTZ) climate regimes and slightly low in Subtropical Zone (SZ) and Tropical Zone (TZ) climate regimes. The comparison between modeled radiation values and FY-2C radiation product values shows that the radiation product of FY-2C satellites is superior to the modified model in SZ and TZ climate regimes.     

Comparative analysis of different environmental loading methods and their impacts on the GPS height time series

Three different environmental loading methods are used to estimate surface displacements and correct non-linear variations in a set of GPS weekly height time series. Loading data are provided by (1) Global Geophysical Fluid Center (GGFC), (2) Loading Model of Quasi-Observation Combination Analysis software (QLM) and (3) our own daily loading time series (we call it OMD for optimum model data). We find that OMD has the smallest scatter in height across the selected 233 globally distributed GPS reference stations, GGFC has the next smallest variability, and QLM has the largest scatter. By removing the load-induced height changes from the GPS height time series, we are able to reduce the scatter on 74, 64 and 41 % of the stations using the OMD models, the GGFC model and QLM model respectively. We demonstrate that the discrepancy between the center of earth (CE) and the center of figure (CF) reference frames can be ignored. The most important differences between the predicted models are caused by (1) differences in the hydrology data from the National Center for Atmospheric Research (NCEP) vs. those from the Global Land Data Assimilation System (GLDAS), (2) grid interpolation, and (3) whether the topographic effect is removed or not. Both QLM and GGFC are extremely convenient tools for non-specialists to use to calculate loading effects. Due to the limitation of NCEP reanalysis hydrology data compared with the GLDAS model, the GGFC dataset is much more suitable than QLM for applying environmental loading corrections to GPS height time series. However, loading results for Greenland from GGFC should be discarded since hydrology data from GLDAS in this region are not accurate. The QLM model is equivalent to OMD in Greenland and, hence, could be used as a complement to the GGFC product to model the load in this region. We find that the predicted loading from all three models cannot reduce the scatter of the height coordinate for some stations in Europe.