GPS高程拟合在大汶河综合治理工程的应用

为了提高GPS观测点大地高转换为正常高的精度,充分利用GPS观测数据中的高程信息,提出用GPS控制网进行高程拟合模型,以获得高精度的正常高,其结果可以替代四等水准,这为水准实施困难区域高程控制测量提出了一种新模式。     

GPS高程拟合在大汶河综合治理工程的应用

为了提高GPS观测点大地高转换为正常高的精度,充分利用GPS观测数据中的高程信息,提出用GPS控制网进行高程拟合模型,以获得高精度的正常高,其结果可以替代四等水准,这为水准实施困难区域高程控制测量提出了一种新模式.     

基于Kriging估计的GPS高程拟合对比研究

利用数学模型拟合似大地水准面求定高精度的高程异常值,将GPS大地高转换为正常高,是目前GPS高程测量的研究热点。阐述克里格(Kriging)法、基于多项式曲面的Kriging法和基于小波分析的Kriging法用于GPS高程拟合的基本原理,并以GPS控制网实测数据为例进行对比试验研究。结果表明,基于Kriging法的综合模型拟合精度优于单一的Kriging法拟合精度,基于小波分析的Kriging法用于GPS高程拟合的精度最高。     

似大地水准面精化成果在水利工程测量中的应用

结合广西某大型水利工程GPS控制网实际案例,对GPS大地高转为正常高的高程转换方法进行了介绍和分析,采用广西似大地水准面精化成果进行GPS高程转换,并进行了精度分析,提高了高程测量精度和效率。     

利用高精度GPS测量建立坝址区测绘基准的探讨

针对超长隧洞及大型水利工程测绘基准问题,提出了利用高精度GPS测量技术建立坝址区测绘基准的基本方法,主要包括:GPS测量与地面观测混合测量控制网的实用平差模型,平面控制基准的联合数据处理、基于面拟合的GPS跨河正常高差未知参数估计,河流两岸的正常高程基准的传递等。通过坝址区施工控制网点的GPS大地高和水准正常高之差,建立了坝址区似大地水准面基准模型,从而使GPS测高来代替高精度的几何水准或三角高程测量成为可能,也真正实现了GPS三维测量的目的。     

二次曲面模型在库区GPS拟合高程测量中的应用

根据库区GPS控制网大地高与二等水准、四等三角高程,采用最小二乘法原理,建立平面模型、二次曲面模型、三次曲面模型,求得较高精度高程异常,在GPS测量得到平面位置的同时,获得工程中使用的正常高程。通过对平面模型、二次曲面模型和三次曲面模型比较分析,说明在山区二次曲面模型就能够满足一定等级高程测量精度要求。在水电工程河谷流域采用GPS拟合高程,能够减轻劳动强度,提高工效。     

基于静态灰模型的带状工程GPS大地高转换

工程测量时,必须将GPS定位技术获得的大地高转换成正常高。根据带状工程测量控制点高程异常（大地高与正常高差值）序列的特点,提出了以高程异常序列为行为主因素,以控制点的坐标按多项式展开后的系数构成控制点的位置因素为原因量子序列,在不考虑高程异常序列的导数变化率时,可用静态灰模型GM（0,h）进行GPS大地高向正常高的转换。通过高山区公路高程控制测量实例计算,说明该方法转换精度明显优于常用的函数模型拟合法。特别是当测区内GPS控制点与水准点较少时,该方法比传统的函数模型拟合法转换更具有明显的优势,可以推广应用于其他带状工程GPS大地高向正常高的转换。     

GPS高程综合模型应用研究

GPS高程的多种逼近模型有其使用的条件和范围,为进一步提高GPS高程的转换精度,提出了GPS高程转换二次曲面拟合的加权平均模型和基于神经网络的综合逼近模型。通过实测的GPS水准数据对综合模型和几种单一模型进行分析比较,结果表明综合模型逼近高程的精度和可靠性均高于单一模型。     

EGM 2008在山区河道高程转换中的精度分析

随着GNSS技术及高精度、高分辨率全球重力模型发展,利用GNSS测得的大地高向正常高转换精度得到极大提高,可以实现山区河道高精度三维坐标测量。以金沙江流域某水电站为例,利用测区已有高等级GNSS/水准控制点及EGM 96、不同分辨率EGM 2008模型进行GNSS大地高向正常高转换,与三角高程施测的四等高程点比较并进行精度分析。经证实,利用EMG 2008在山区河道高程转换中误差约±5cm,可满足图根测量精度等级要求。利用EMG2008进行高程转换可极大提高工作效率,在测区求取坐标转换七参数,可实现高精度GNSS三维坐标测量,满足工程测量需求。     

GPS曲面拟合高程精度探讨

GPS获得垂直分量是基于参考椭球的大地高,与工程中需要的正常高有一差值,即高程异常。而由于大地水准面的不规则性,使GPS获得的垂直信息使用受到了限制。进行GPS高程拟合,通过已知点的高程异常值推求未知点的高程异常值,进而求得未知点的正常高是目前转换GPS高程的主要方法。文章结合工程实例和实验数据,比较GPS曲面拟合高程与几何水准高程,探讨总结了GPS高程曲面拟合模型的应用方法和精度问题,提出了水利水电工程高程控制测量工作应该注意的问题及作业精度。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Desiccation and recolonization of phytobenthos in a regulated desert river: Colorado River at Lees Ferry,Arizona, USA

We tested the recolonization of the phytobenthic community in the tailwaters of Glen Canyon Dam following long- and short-term experimentally induced desiccation. The response of Cladophora glomerata, Oscillatoria spp., miscellaneous phytobenthos species and periphyton was studied over 18 weeks using three treatments: (1) undisturbed control cobbles from the submerged zone; (2) cobbles desiccated and replaced into the submerged zone; and (3) cobbles desiccated and replaced into the varial zone. Periphyton density and compositional response resulting from these treatments were also examined. Desiccation treatments were significantly different in biomass from controls throughout the study. The biomass of desiccated and replaced river cobbles averaged <30% of the controls for C. glomerata and periphyton during the 18-week recolonization period. In contrast, the biomass of the control Oscillatoria and miscellaneous phytobenthos species averaged only 3 and 50% of that in the desiccation treatments, respectively. Cladophora, the dominant alga, comprised 77% of the phytobenthic biomass. A significant positive relationship between discharge, Cladophora and periphyton biomass was present in all treatments, while there was a negative relationship with discharge for Oscillatoria and miscellaneous phytobenthos species. There was a significant inverse correlation, as well as a pattern of separate biomass dominance, between C. glomerata and Oscillatoria. Cladophora was the dominant phytobenthos species on cobbles below the baseflow and Oscillatoria was dominant on cobbles in the varial zone. In general, the Cladophora biomass decreased under intermittent drying conditions, while Oscillatoria declined under permanently wet conditions. Diatom composition was not significantly different between treatments; however, their density was lower on desiccated cobbles. Diatom density on desiccated cobbles in the submerged and varial zones averaged 69 and 42% of that of the controls, respectively. Recovery and maintenance of benthic resources are hindered by fluctuating flow regimes driven by electricity and irrigation requirements. Repeated desiccation of the phytobenthos has major effects on the bottom-up interactions in the Colorado River ecosystem. © 1998 John Wiley & Sons, Ltd.