一种改正伪距多路径误差的北斗三频周跳探测与修复方法

使用北斗三频观测值提取伪距多路径误差。分析表明,北斗伪距多路径误差达到m级,且变化较快,不能通过历元间差分完全消除,会对周跳探测及修复产生影响。提出一种改正伪距多路径误差的北斗三频周跳探测与修复新方法,能有效控制伪距多路径误差的影响,提高周跳修复的成功率。     

一种基于TIN的DEM表面C1光滑插值模型

根据原始地形起伏变化的连续光滑性以及邻近数据点之间的相关性,研究了基于TIN的DEM表面光滑插值模型.首先,运用二元二次多项式曲面加权平均的办法,提出了一种基于TIN的具有C1光滑性的DEM表面插值模型;然后,利用数学曲面对模型的精度进行了评估,并对实际地形进行了插值表示.结果表明,提出的表面插值模型具有较好的精度和光滑效果.     

GPS监测站伪距观测量评定广播星历精度的研究

论述了GPS监测站伪距观测量评定广播星历精度的基本方法。同时,分析并计算得出:利用GPS监测站载波相位观测量平滑伪距能明显提高伪距观测量评定广播星历的精度。采用2004年7月19日拉萨站伪距观测量对IGS提供的广播星历的精度进行了评定,实验结果表明,广播星历提供的卫星轨道精度从总体上达到3m左右。     

一种基于DEM的高程最优路径选取算法及其实现

针对当前GIS道路选线缺乏定制化的问题,本文设计并实现了基于DEM的高程最优路径选取算法,该算法将高程作为道路选线因素,以匀坡作为选线标准,采用上下行算法和内分插值算法进行道路选线。基于ArcGIS Engine平台,对设计的算法进行了编程,最终实现了卓呼线的自动选取。实验证明,该算法可以利用DEM格网点高程自动绘制匀坡线,从而生成高程成本最优路径。同时,该算法时间复杂度较低,计算速度快,健壮性良好,运算成果正确,不失为一种快速的道路选线新方法。     

Study of formation boundary and dip attribute extraction based on edge detection technology

In the seismic profile interpretation process,as the seismic data are big and the small geological fea-tures are difficult to identify,improvement of the efficiency is needed.In this study,structure tensor method in computer image edge detection processing is applied into the 2D seismic profile.Coherent attribute is used to extract formation edge.At the same time,extracting the eigenvalues and eigenvectors to calculate the seismic geometric properties which include dip and apparent dip,automatic identification is achieved.Testing the Gaussian kernel function with synthetic models and comparing the coherent attribute and dip attribute extraction results before and after,the conclusion that Gaussian filter can remove the random noise is obtained.     

Enacting immanent potentialities: Tcheb‐tchib strategies at the centre of the urban fringe in Nouakchott,Mauritania

The urban fringe areas of Nouakchott, the capital city of the Islamic Republic of Mauritania, have become virtual epicentres of informal property speculation, as the state‐owned land that people illegally inhabit becomes an increasingly valuable commodity in the wake of urban redevelopment plans and vast infrastructural development projects. By applying ingenious ‘poaching’ strategies based on anticipation, the marginalized, impoverished people inhabiting these areas appropriate and manipulate space in order to survive. In their attempt to counter the state's technologies of governance through what is commonly known as tcheb‐tchib, a form of creative improvisation, they become a driving force in the dynamic and contested reconfigurations of the urban landscape. Based on extended ethnographic fieldwork focusing on the strategies of former nomads who are now sedentarized on the urban fringe, this article conceives large‐scale urban renewal as a dynamic process that generates an emergent space of immanent potentiality that the urban poor attempt to strategically appropriate and enact to make the most of a potentially destructive process.     

Half Smooth Tongue Sole(Cynoglossus semilaevis) Under Low Salinity Stress Can Change Hepatic igf2 Expression Through DNA Methylation

Salinity is a crucial environmental stress that severely affects fish growth and survival.Under environmental stress,DNA methylation plays an important role in gene expression and genome function.To better understand the epigenetic regulation mechanism of igf2 under low salinity stress,we analyzed the DNA methylation at 5’UTR,exon1,intron1,and exon2,and analyzed the relationship of DNA methylation with mRNA abundance as well as the special single CpG sites methylation patterns of igf2 in the liver of half smooth tongue sole under low salinity(15)for 0,7,and 60 d.When exposed to low salinity,DNA methylation at 5’UTR and exon2 remained stable,while it was up-regulated firstly and then down-regulated at exon1 and intron1.Some single CpG sites of igf2 associated with low salinity,and most of these sites with significantly changed methylation levels(P<0.05)are located in intron1 area.The discrepant variation of single CpG sites methylation levels and igf2 expression further revealed that females and males showed different response to low salinity.Remarkably,the 38-CpG site of intron1 servers as a sexual marker.Additionally,our integrative analysis demonstrated that regional DNA of igf2 methylation had highly complex interplay on gene expression.The single CpG sites in intron1 were indispensable epigenetic markers under external environmental stress.Above all,to resist the low salinity stress,half smooth tongue sole liver can regulate the expression of igf2 through methylation of CpG sites in intron1.     

溃坝洪水演进的光滑粒子流体动力学分析

传统GIS在实现溃坝洪水过程模拟时通常是采用无源淹没分析或有源淹没分析方法,这些方法忽略了洪水演进过程中的物理学与动力学因素,模拟结果的时效性、可靠性较差,表达效果也较为简单。针对此问题,该文提出结合光滑粒子流体动力学方法与GIS相关技术实现溃坝洪水演进的三维动态可视化及分析,以光滑粒子流体动力学生成的海量多维时空序列流体粒子数据为基础,研究了粒子数据的建模及时空数据的时空建模技术。最后在自主研发的系统中实现了溃坝洪水演进的三维动态可视化表达及分析,应用效果良好。     

隧洞光面爆破中炮孔堵塞长度的数值分析

炮孔堵塞长度是一个直接关系到爆破效果的重要爆破参数。以实际工程为背景,建立不同炮孔堵塞长度的三维有限元模型,运用ANSYS/LS-DANA数值模拟方法,并引入流固耦合方法模拟计算,通过对关键部位的应力进行分析比较,验证了经典爆破理论,获得了最优的堵塞长度,为爆破数值计算提供借鉴,同时为隧洞光面爆破设计提供参考。     

基于空间约束的神经网络影像匹配

提出了一种可充分利用影像灰度信息和特征信息的基于视差变权空间连续性约束的整体影像匹配方法,并将其映射到 Ｈｏｐｆｉｅｌｄ网络,利用神经网络所固有的大规模并行处理能力,可以高速、可靠、高精度地完成影像匹配,并大大提高了复杂地形条件下影像匹配的可靠性。实验证明该算法具有一定的实用性。