GPS精密单点定位技术在测量中的应用

介绍了GPS的发展历程,探讨了精密单点定位技术的定位原理,比较了精密单点定位与RTK,通过工程实例说明精密单点定位技术可大大提高GPS接收机利用效率和作业功效的结论。     

PPP技术在矿业权实地核查测量中的应用

简单介绍了精密单点定位技术(PPP-Precise Point Positioning),分析了精密单点定位技术的定位精度,总结了采用精密单点定位技术进行矿业权核查的作业流程、精度情况和相对于常规GPS测量作业的优点,为矿业权核查测量外业作业提出一种新方案。     

GPS技术在电力工程勘测中的应用分析

对GPS精密单点定位技术进行了系统概述,通过对精密单点定位技术与传统定位技术的对比分析,阐述了GPS精密单点定位技术的应用优势,并对该技术在电力工程勘测中的应用展开了具体分析,推动了我国电力系统的现代化建设。     

精密单点定位监测地面沉降研究

GPS技术已发展成为监测地面沉降的主要方法之一。本文通过精密单点定位技术处理天津12个CORS站2006年至2009年的观测数据以获取其沉降信息。数值结果表明,在定位精度方面精密单点定位和相对定位结果相当,而在监测沉降速率方面精密单点定位与水准测量相吻合。所以利用精密单点定位技术进行大范围的地面沉降监测是可行、可靠的。     

精密单点定位技术在控制测量中的应用

本文简要地介绍了精密单点定位技术的原理及其特点,基于精密单点定位结果处于最新的ITRF框架而无法直接应用于工程实践这一特征,提出利用坐标转换实现ITRF框架坐标向常用的国家或地方坐标系转换的方法,并通过工程实例数据进行了验证计算,其结果表明该方法简单有效。     

GNSS精密单点定位基本原理及应用

文中详细介绍了GNSS精密单点定位技术的基本原理及在各领域中的应用前景,供国土测绘界同行参考。     

基于主成分分析的动态精密单点定位结果分析

基于动态精密单点定位的实现,构造了主成分分析法分析动态精密单点定位结果的模型,并采用主成分分析法对动态精密单点定位结果进行了分析与处理,通过分析比较,基于主成分分析法的动态精密单点定位结果,能减弱各种误差对计算结果的影响,使定位结果精度有了明显的提高,从而拓展了主成分分析数学原理在测量学中的应用。     

单频GPS精密单点定位软件设计与系统性能分析

在VC++平台上,采用C++语言对单频GPS精密单点定位进行了软件设计,并从残差、定位精度两方面对单频精密单点定位系统性能特性进行了分析,从而给单频GPS精密单点定位在生产中的应用提供了一些参考。     

使用不同类型星历的PPP定位结果比较分析

星历误差是精密单点定位的一个重要误差来源,运用Bernese软件同时采用IGS所提供的三种不同类型的精密星历进行精密单点定位,对所得结果进行比较和分析,结果表明最终精密星历精度最高,快速精密星历其次,超快速精密星历精度最低,但在一定范围内使用快速精密星历代替最终精密星历进行精密单点定位仍可获得较好的定位结果.     

基于CNES实时星历的精密单点定位精度分析

首先给出了实时GPS精密单点定位的数学模型以及改正了三类误差影响,详细阐述了扩展Kalman滤波过程。利用IGS的实时星历产品(CNES),对IGS三个站一天观测数据和实测的无人机动态GPS观测数据分别进行静态和动态实时GPS精密单点定位实验,结果表明:静态实时精密单点定位精度在XY方向优于0.102 m,Z方向优于0.211 m,处于分米级;动态实时精密单点定位精度优于0.244 m。实时精密单点定位精度低于事后,但能够应用于应急测绘、快速制图等时效性要求较强的测绘工作。     

Magnetoelastische Spannkraftmessung in Bauwerken

Magnetoelastic Measurement of Prestressing Force in Civil Structures The knowledge of the tensile force of prestressing steel elements and its reliable and non‐destructive determination are of essential importance for the assessment of the structural health condition of prestressed concrete structures and tie‐back systems in terms of structural safety, serviceability and durability. For the evaluation of the prestressing force in steel tension members, the measurement technique presented in this contribution is using the magneto‐elastic effect (ME‐effect) of ferromagnetic materials. This effect describes the reverse‐proportional correlation between the mechanical stress and the magnetic properties of ferromagnetic materials. The cylindrical coiled sensors pushed over the tendon and the measuring device developed and practically optimized at the iBMB/MPA of the TU Braunschweig enable a fast and reliable measurement of the prestressing steel force after an initial calibration. In this contribution first the state of the art of prestress measurement techniques for steel tension members is presented. Afterwards, the ME‐measuring method with the basics and merits of magneto‐elastic prestressing force identification is shown. Further recent research results as well as several building applications will be discussed.     

Zustandsuntersuchung und Instandsetzung am Hauptdach des Hauses der Kulturen der Welt in Berlin

The main roof of the ”Haus der Kulturen der Welt“ in Berlin Which is very well‐known on account of its history and striking structural design – was to be inspected by the author to determine its condition and analysed with regard to the durability of the existing liquid synthetic sealant. The roof structure consists of a biaxial, curved area‐covering structural element with circumferential edge beams of pre‐stressed lightweight concrete. This is the result of the reconstruction between 1984 and 1987 following a partial collapse of the then Berlin Congress Hall in 1980. The very thin roof shell is also made of lightweight concrete and, like the edge beams, has a polyurethane‐based spray‐on seal that was specially developed for this purpose as protection against the ingress of moisture. The reason why this, at the time, novel type of seal was chosen was that it should take into account the fact that the roof design urgently needed some kind of protection against moisture that had to compensate the expected changes shape and crack movements of the roof with no damage. The following article reports on the nature, scope and main results of the analysis of the condition of the roof seal, edge beams and abutments. It will also describe the repair recommendations resulting from the investigations, which form the basis of the execution of work at the present point in time. Apart from presenting the technical principles and special features of the building that have to be taken into account during any repairs, the special features of the execution will also be addressed.     

Application of sonic and radar tests on the piers and walls of the Cathedral of Noto

The authors applied systematically sonic tests, radar tests and other diagnostic techniques on the remaining walls and piers of the Cathedral of Noto. The experimental survey was carried out by the Laboratory of the DIS, Politecnico of Milan (Person in Charge: Prof. Binda, Prof. Baronio) in collaboration with the designers (Ing. R. De Benedictis, Arch. S. Tringali) and the experts working on the reconstruction. The Prefettura of Siracusa founded the research. The right aisle and most of the dome of the Cathedral collapsed in 1996. The aim of the research was to verify the state of damage and the possibility of conservation of the walls and piers in view of the reconstruction of the damaged part of the Cathedral. Furthermore, the sonic tests were used to control the effect of grout injection used as a possible technique for repair of the damaged masonry (Proceedings of the Conference on Nondestructive Evaluation of Civil Structures and Materials, Boulder, Colorado; (1992) 329; Proceedings of the Sixth Conference on Structural Faults and Repair, 3 (1995) 195). In the following the results will be reported and the reliability of the tests will be discussed as it was confirmed by the use of other complementary diagnosis techniques (Proceedings of the Sixth International Conference on Structural Studies, Repairs and Maintenance of Historical Buildings, STREMAH 99, Dresden, Germany, (1999) 323).     

Alternative Methods of Procurement for Works of Water and Environmental Management

The paper considers methods of procurement for the construction of water- and sewage-treatment works other than the traditional use of the ICE 5th Edition Conditions of Contract and Bills of Quantities. This is as a consequence of the speed at which schemes are currently required within the water industry.
The paper particularly focuses on the use of target contracts, using the Institution of Chemical Engineers'Green Book form, and considers various types of target. It also discusses the form which tender documents may take, and how targets may be calculated.
Tendering procedures, including the use of two-stage tenders and negotiated targets, are considered, as are the procedures for cost monitoring and the financial management of the contract. Finally, the role of the engineer and quantity surveyor is considered.     

Ecological succession in mountain lake ecosystems of Southern Siberia after the introduction of the peled – Coregonus peled (Gmeli, 1778)

Abstract

This article summarizes a long-standing study of the process of introduction of the peled to the Southern Siberian mountain lake ecosystems. The peled has adapted to changes in food supply. Pressure of the euryphagous peled caused the substitution of larger forms of zooplankton by smaller ones. Similar changes occurred in the content of phytoplankton. Succession of zoobenthos in the littoral part of the lakes manifested itself as the decrease in the total biomass, in its part of zoobenthos (Gammarus) and as the increase in the biomass of other groups. The opposite changes were encountered in the profundal zone of zoobenthos (the decrease in the total biomass owing to the existence of larger forms of alpha-polysaprobes). The restructuring observed in various communities signifies the substantial changes in the whole process of generation and transformation of organic substance in the mountain ecosystems with the dominance of the introduced peled.     

基于分子动力学模拟技术的黏土矿物微观行为研究应用

黏土矿物是一类具有层状结构的硅酸盐矿物。土水相互作用对土体许多宏观力学响应、物质运移和传导起重要影响。现有的实验技术和手段即很难在物理上微观探测黏土从绝对干燥至含微量水分子的吸附过程,也很难实现黏土对放射性核素吸附过程的跟踪。使用分子动力学模拟对黏土矿物的水化性质及对放射性污染物吸附性能进行研究。以蛭石、高岭土及蒙脱土三种黏土矿物为研究对象,通过晶层间距、自扩散系数、径向分布函数、吸附复合物结构等模拟测试结果对蛭石的水化性能和黏土对放射性核素的吸附行为阐述。最后,对分子动力学模拟技术在岩土工程的应用发展进行了展望。     

土体干缩裂隙的形成发育过程及机理

土体干缩开裂(龟裂)是一种常见的自然现象,龟裂的产生会破坏土体的完整性,极大地弱化土体的工程性质。基于室内试验结果,发现龟裂发育过程可分为3个典型阶段,具有很强的时序特征,且新生裂隙一般垂直已有裂隙生长。根据水土相互作用原理和基本土力学理论,建立了土体龟裂概念模型,对实验室和自然界中观测到的相关龟裂现象及其机理进行了分析,得到如下主要结论:(1)土体中存在收缩变形空间是龟裂发育的前提,主要与土质条件有关;(2)龟裂是土体发生张拉破坏的表现形式,孔隙水的表面张力及干燥过程中引起的基质吸力(毛细水作用力)会在土体中形成张拉应力场,这是导致龟裂的主要力学诱因;(3)当张拉应力场的大小超过土体的抗拉强度或土颗粒间的联接强度时,裂隙便会产生,导致局部区域积聚的应变能释放,应力场重新调整。从宏观上看,基质吸力和抗拉强度是控制龟裂发育的两个关键力学指标,但从微观上看,土体材料尤其是结构的非均质性对裂隙发育过程和裂隙网络的几何形态特征均有重要影响。通常情况下,大部分裂隙都是在饱和阶段产生,且裂隙产生时对应的临界含水率有可能高于液限;土体表面上的"杂点"易导致应力集中,裂隙往往率先在"杂点"处产生;(4)受表面和裂隙面张拉应力场的共同作用,表层土体边缘会发生向上卷曲变形,产生"煎饼效应"。此外,土体在收缩过程中还存在收缩核现象。     

煤样吸水全过程纵波波速变化规律及波形特征实验研究

 为了研究含水煤体的纵波波速变化规律及波形特征,开展原煤试样吸水全过程的纵波测试实验;研究煤体纵波波速与孔隙率、含水饱和度之间的变化规律;基于FFT和HHT研究不同含水饱和度煤样波形幅频和时频特征。结果表明：煤体纵波波速同时受孔隙率和含水饱和度的影响;波速随含水饱和度的增加总体呈现非线性增加趋势,当含水饱和度达到70%左右时,波速增加速率明显提高;水自身性质及煤体内部孔隙水均匀存在形式是导致含水煤波速增加的主要原因。纵波波速随孔隙率的增加总体呈现线性降低趋势,含水饱和度越高波速受孔隙率影响越小,表明水的存在降低了煤体孔隙率对波速的影响。煤样在吸水过程中的波形频率分布存在显著性差异,波形主频随含水饱和度的增加呈现向低频非线性移动的“频移”现象;含水饱和度越大、孔隙率越大,波形最大幅值越小。Hilbert三维能量谱能够反应波形的频带能量分布及随时间的变化特征;随着煤样含水饱和度的增加,波形高频成分所占比例逐渐降低,且高能量频带范围不断向低频移动,表明煤体中孔隙水不但加快了波形中所有频带能量的衰减速度,而且对高频信号的吸收损耗大于低频信号。     

土体干缩开裂过程的边界效应试验与离散元模拟

为了探究土体干缩开裂过程的边界效应问题,采用不同底面粗糙度的容器开展了多组干燥试验,发现干缩裂隙存在从顶面向下和从底面向上两种典型的发育形式。并且,裂隙发育程度与土样/容器界面接触条件密切相关,从而验证了裂隙发育过程的边界效应。通过理论分析,阐明了上边界的蒸发条件及下边界的接触条件对裂隙发育形式的控制作用。为了能更深入地理解土体干缩开裂边界效应的内在机制,在试验的基础上建立离散元模型,创新性地引入了沿深度的失水速率梯度参数,模拟土样上边界的蒸发条件变化。通过设置底面摩擦系数,模拟土样下边界的接触条件变化。将模拟结果与试验结果进行了对比分析,发现二者具有较好的吻合度。总体上,土体干缩裂隙的发育过程是顶面蒸发失水与底面摩擦两种边界条件共同作用的结果。当底面摩擦系数相对较小时,裂隙发育由蒸发失水主导,大部分裂隙由顶面向下发育。随着底面摩擦系数的增加,底面接触条件对裂隙发育过程的主导作用逐渐增强,由底面向上发育的裂隙数量所占比重也相应增加。     

约束受热伸长中空柱填充混凝土的耐火性能

在圆形中空柱中填充混凝土是一种很好的柱子加固方案,因为它能够增加柱子在室内和高温环境下的承载能力。然而,发生火灾时,对受热伸长的约束可能会改变其力学性能。通过对约束受热伸长中空柱进行一系列耐火试验后,得出试验结果。试验对柱子长细比﹑承载等级﹑周围结构刚度以及所占钢筋的百分比和混凝土强度等参数进行了测定。结果显示,这些柱子的极限抗火时间都小于46min。在柱子内层墙面使用混凝土环,从其性能上来讲在火灾时并没有太大优势,因为混凝土环会受到钢管过热而带来的大面积碎裂。柱子最主要的破坏方式即是整体屈曲。然而,在一些试验样本上也出现了局部屈曲。