交通拥堵与预警信息交互传播动力学分析

城市交通拥堵问题已经成为当今世界许多城市发展过程中面临的一个严峻问题。针对这一问题,全空间信息系统通过对复杂、动态的交通拥堵过程进行多粒度抽象、多尺度建模和多层次综合分析,为解决城市交通拥堵提供了新的途径。当城市交通发生严重堵塞时,通常伴随着“道路拥堵”预警信息传播,用以影响人类的出行活动,从而在一定程度上影响交通拥堵传播。为了深入分析城市交通网络拥堵的动态演进过程,本文建立了交通拥堵传播的改进易感-感染-易感（susceptible-in fected-susceptible,SIS）的病毒传播模型,利用状态转移概率方法,基于多层复杂网络分析交通拥堵和预警信息交互传播的动力学行为特征,揭示预警信息传播对交通拥堵传播的影响。该方法不仅能够描述基于交通流传播特点的拥堵传播过程,而且能够描述交通网络中的预警信息传播过程。数字仿真实验表明,交通拥堵的传播过程与交通网络中的预警信息传播动力学之间存在关联关系。     

合成孔径雷达星座发展综述

自1978年第一颗星载SAR——Seasat-A发射以来,世界主要航天大国相继发射了多颗SAR卫星。几十年来,星载SAR传感器的性能不断提高,向着高分辨率、多极化、多模式和星座化等趋势发展。德国和意大利分别完成了SAR-Lupe(5颗)和COSMO-Sky Med(4颗)SAR卫星星座的布署,用于军事侦察或军民两用,欧空局和加拿大也正在积极开发SAR星座任务,甚至一些商业公司也开始研发小卫星SAR星座。SAR星座能够显著提高对地观测能力,既可以通过编队飞行进行双/多站、多角度或干涉成像,还可以通过多星组网大大缩短重访周期,满足对重点区域的密集观测需求。在SAR传感器和卫星平台都越来越小型化、低成本的背景下,星座组网正成为SAR对地观测发展的主要方向之一。     

高阶单步时滞修正算法主动控制实验研究

本文将高阶单步时滞修４正算法用于主动控制结构模型的试验,试验分析结果一同阶单步主动控制算法是一种有效实用的主动控制方法。     

华北克拉通及邻区孔兹岩系的时代及对太古宙基底组成的制约

根据地质、地球化学和Nd同位素研究 ,华北克拉通及邻区孔兹岩系主要形成于古元古代。笔者对孔兹岩系变泥沙质岩石进行了地球化学统计性研究。它们普遍高K2 O低Na2 O ,具有重稀土部分呈平坦型 ,轻重稀土分离较弱 ,存在较强负铕异常的稀土模式。在岩石/MORB -元素图解上 ,除Nb、P、Ti相对亏损外 ,还存在明显的负钡异常。具高成熟度的泥沙质岩石tDM和ΣNd( 2 .3Ga)变化范围分别为 2 .30～ 3.2 4Ga和 - 4 .77± 5.11。孔兹岩系形成于太古宙之后 ,与其主体由泥沙质岩石组成 ,并且需要有一个广泛出露、高成熟度陆壳基底物源区的认识相吻合。在考虑泥沙质岩石组成受源区组成和作用过程双重制约的情况下 ,给出了华北克拉通太古宙基底组成的估计值。它们与Taylor等 ( 1985)给出的太古宙上部地壳组成估计值存在较大区别     

室内岩石破岩机制试验及应用研究

聚晶金刚石复合片切削齿钻头的合理选取与使用,关系到它技术优势的发挥。在简要介绍国内研发的聚晶金刚石复合片切削齿钻头岩石可钻性测定方法与分级标准的基础上,详细叙述了室内试验的情况、数据处理分析过程及其获取的定性定量结论;从利于实际应用出发,提出了基于有效吃入岩石、岩石种类与切削齿相融、钻进技术参数互补三原则的聚晶金刚石复合片切削齿钻头的选取和使用原则与基本方法。     

复杂荷载作用下考虑下卧层三维渗流的未打穿竖井地基固结分析

针对任意复杂变荷载作用下未打穿的竖井地基,通过在竖井底面以下土层中设置虚拟竖井,使其能够合理考虑下卧层土体三维渗流问题,运用Laplace变换,求得频域内竖井地基的固结解。通过Laplace逆变换,得到了任意荷载作用下竖井地基的平均固结度、孔压消散曲线、沉降曲线。结合具体算例,对影响竖井地基固结的主要影响因素进行了详细分析,并将现有未打穿竖井地基平均固结度近似计算方法的精度和适用的范围进行了对比,得到了一些有益于工程实践的结论。     

带粒子滤波约束的PP-PS联合反演的稀疏解算法

随着地震勘探目标从构造型油气藏向岩性油气藏的转变,地震勘探难度日益增大,这就要求从地震数据中获得更多可靠且具有明确地质含义的属性信息,并充分利用这些属性信息来对储层的岩性、岩相进行分析.AVO三参数反演能够从振幅随炮检距的变化信息中直接提取纵波速度、横波速度以及密度来估计岩石和流体的性质,进而对储层进行预测.然而,AVO反演本身是一个不适定的问题,加上地震纵波反射系数对横波速度和密度的不敏感,会造成单纯利用纵波地震数据进行反演的结果误差大.随着地震接收和数据处理技术的发展,越来越多的学者对PP-PS联合反演方法进行了研究并在实际资料中得以运用.融合转换横波地震数据的联合反演在一定程度上提高了反演的精度,降低了解的不稳定性.但是在信噪比较低的情况下,联合反演的效果受到了限制.本文从优化理论出发,提出了基于粒子滤波提供先验知识的l₁范数约束极小化问题的稀疏解算法.并将上述方法运用到了不同的模型中,通过比较分析,证实了该方法在不同信噪比资料中的有效性和在信噪比较低情况下的优势.     

低轨磁测卫星干扰磁场标定方法研究

为了提高空间磁场探测精度,磁测卫星一般将磁强计安装在长伸杆的顶端,同时通过整星磁洁净控制,来减小磁强计安装位置的磁场干扰量.针对低轨磁测卫星的特点,提出零磁场环境下卫星极弱干扰磁场的高精度测量方法,模拟在轨地磁场环境下卫星感应磁场的标定方法,以及磁力矩器剩磁不确定量的处理方法.通过以上方法对卫星本体产生的干扰磁场实施严格的标定和数据修正,可有效减小其影响,极大提升空间磁场探测精度.该方法已应用于电磁监测卫星,将整星的磁场干扰不确定量降低一个量级,达到优于0.3 nT的水平.     

SKZ-3分量钻孔应变仪的测试方法研究

基于四分量自检原理研制出的SKZ-3分量钻孔应变仪,不仅具有传统地应力观测优势,还具备地球深部高频应变监测。而对SKZ-3分量钻孔应变仪进行测试和校验,是保证观测数据真实有效的基础。     

Eco-environmental changes in the Chinese Loess Plateau during low-eccentricity interglacial Marine Isotope Stage 19

Eco-environmental changes during interglacials with an astronomical background similar to that of the Holocene are potentially helpful for understanding the future climatic evolution. Marine oxygen isotope stage(MIS) 19 is similar to the Holocene in astronomical background, both being characterized by a low eccentricity of the Earth's orbit. However, MIS 19 has attracted research attention only recently and therefore less is known about eco-environmental changes during this interval,especially based on terrestrial records. In the Chinese Loess Plateau(CLP), the S7 paleosol can provide valuable terrestrial paleoclimatic and paleoenvironmental record for MIS 19. Here, high-resolution terrestrial snail records from the L8–L7 strata of the Huining, Xifeng and Luochuan sequences in the CLP were analyzed in order to characterize spatio-temporal changes in climate and eco-environment during MIS 20–18. The results show that in all three sections the late part of MIS 20 was dominated by abundant cold-aridiphilous mollusc species, indicating that cold and dry climatic conditions prevailed across the entire CLP,under the strong influence of the winter monsoon. The mollusc fauna of MIS 19 were dominated by warmth-loving and thermohumidiphilous species that enable the definition of two climatic stages. The early part of MIS 19(～790–778 ka) was marked by warm and humid conditions, as evidenced by high abundances of warmth-loving and thermo-humidiphilous species. This interval was slightly warmer than today and it lasted for ～12 kyr. The climate of the later part of MIS 19(～778–761 ka) was more moderate, and increased proportions of cold-aridiphilous and warmth-loving species were recorded. The warmth of this period was similar to that of today, but the climatic fluctuations were stronger. During the early part of MIS 18(～761–745 ka), the Xifeng and Luochuan sections in the eastern CLP still maintained high abundances of warmth-loving and thermo-humidiphilous species, indicating that the moderate climatic conditions during late MIS 19 continued during early MIS 18, lasting for another～15 kyr, and that the influence of the summer monsoon remained strong in the eastern CLP during early MIS 18. However, in the western CLP, cold-aridiphilous species in the Huining section became dominant during early MIS 18, reflecting the prevalence of a cold and dry glacial climate, with the strong influence of the winter monsoon. These findings indicate that a steeper climatic gradient and a pronounced regional environmental difference existed between the eastern and western CLP during the early part of MIS 18. Comparison of our mollusc results with the variation of Earth orbital parameters suggested that climate changes in the CLP during MIS 20–18 were likely controlled mainly by insolation changes forced by the configuration of Earth orbital parameters. The unique orbital configuration during the low eccentricity interglacial-to-glacial transition could have strengthened the East Asian summer monsoon which favored the amelioration of the eco-environment in the CLP, especially in the eastern CLP where the summer monsoon exerted a strong influence. Thus we speculate that, under natural climatic conditions,the climate of the CLP may remain in a warm, humid state for another 30 kyr, although climatic instability and the seasonal differences between winter and summer could strengthen.