排序方式： 共有21条查询结果，搜索用时 31 毫秒
1.
低应变反射波法在基桩检测中的应用实例及一些问题的探讨 总被引：5，自引：0，他引：5
根据应力波理论，介绍了用低应变反射波法在桩身完整性检测中的几个应用实例，并对检测中的一些问题作了探讨。 相似文献
2.
J. C. Hinton 《International journal of geographical information science》2013,27(7):877-890
Abstract The combined use of remotely-sensed images and vector GIS data has received considerable interest in recent years. This review article discusses the historical move towards closer integration of remote sensing and GIS technologies and the requirements of integrated software systems to enable remotely-sensed data to be combined with vector datasets for maximum effect. The benefits of integration to users of both GIS and remote sensing for environmental applications are reviewed and some thoughts are given on terminology and future directions in this field. 相似文献
3.
为了满足多卫星系统完好性监测的需要,本文通过对比不同卫星系统定位结果的方法来监测各个卫星系统的可用性。利用上述方法对实测的三模(GPS、GLONASS和COMPASS)数据进行了处理,结果表明该方法具有可行性,可为多模GNSS接收机的自主完好性监测提供参考信息。 相似文献
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5.
Based on the theory of tube wave propagation in a fluid-filled borehole, this paper proposes a new method for detecting the integrity of pile foundation and overcomes some limitations of the existing pile integrity tests. The basic principle of detecting the pile integrity by the tube wave, testing equipment and concrete quality evaluation of piles are introduced. The feasibility of the tube wave detection for geological exploration of a bridge pile in a karst development area is verified by field tests. Through some test cases of prestressed high strength concrete pipe piles, cast-in-place piles and rock-socketed piles with defects, the accuracy of the tube wave detection and other methods is compared. Then, some issues of the application of the tube wave for detecting pile defects are discussed. Finally, the content of this paper is summarized, and some suggestions on further research are put forward. 相似文献
6.
应用底栖动物完整性指数评价滇池流域入湖河流生态系统健康 总被引：7，自引：2，他引：5
采用底栖动物完整性指数(B-IBI)评价滇池流域入湖河流健康状况.根据滇池流域38个样点(9个参照点,29个干扰点)于2009年丰水期和2010年平水期采得的大型底栖动物数据,对19个生物参数进行分布范围、Spearman相关性和判别能力分析,确定构成滇池流域底栖动物生物完整性的指数为甲壳动物+软体动物分类单元数、集食者%、捕食者%和耐污类群%.用比值法统一量纲,计算各个生物参数的值,并将所得的值相加即得到B-IBI指数值.根据B-IBI指数值的25%分位数确定健康等级标准,并对小于25%分位数的值进行四等分,即得到滇池流域底栖动物完整性的评价标准,B-IBI>1.62为健康,1.03～1.62为亚健康,0.31～1.03为一般,0.10～0.31为较差,<0.10为极差.评价结果表明,滇池流域的38个样点中,16个为健康,5个为亚健康,6个为一般,6个为较差,5个为极差.B-IBI值与硝态氮和水温有较大的负相关关系,与其他理化因子相关性不明显. 相似文献
7.
Marek Ziebart Paul Cross Antony Sibthorpe Peter Arrowsmith Washington Ochieng Shaojun Feng Umar Bhatti Peter Niemann 《GPS Solutions》2007,11(4):227-237
The Galileo integrity chain depends on a number of key factors, one of which is contamination of the signal-in-space errors
with residual errors other than imperfect modelling of satellite orbits and clocks. A potential consequence of this is that
the user protection limit is driven not by the errors associated with the imperfect orbit and clock modelling, but by the
distortions induced by noise and bias in the integrity chain. These distortions increase the minimum bias the integrity chain
can guarantee to detect, which is reflected in the user protection limit. A contributor to this distortion is the inaccuracy
associated with the estimation of the offset between the Galileo sensor station (GSS) receiver clocks and the Galileo system
time (GST). This offset is termed the receiver clock synchronization error (CSE). This paper describes the research carried
out to determine both the CSE and its associated error using GPS data as captured with the Galileo System Test Bed Version
1 (GSTB-V1). In the study we simulate open access to a time datum using IGS data. Two methods are compared for determining
CSE and the corresponding uncertainty (noise) across a global network of tracking stations. The single-epoch single-station
method is an ‘averaging’ technique that uses a single epoch of data, and is carried out at individual sensor stations, without
recourse to the data from other stations. The global network solution method is also single epoch based, but uses the inversion
of a linearised model of the global system to solve for the CSE simultaneously at all GSS along with a number of other parameters
that would otherwise be absorbed into the CSE estimate in the averaging technique. To test the effectiveness of various configurations
in the two methods the estimated synchronisation errors across the GSS network (comprising 25 stations) are compared to the
same values as estimated by the International GPS Service (IGS) using a global tracking network of around 150 stations, as
well as precise orbit and satellite clock models determined by a combination of global analysis centres. The results show
that the averaging technique is vulnerable to unmodelled errors in the satellite clock offsets from system time, leading to
receiver CSE errors in the region of 12 ns (3.7 m), this value being largely driven by the satellite CSE errors. The global
network approach is capable of delivering CSE errors at the level of 1.5 ns (46 cm) depending on the number of parameters
in the linearised model. The International GNSS Service (IGS) receiver clock estimates were used as a truth model for comparative
assessment. 相似文献
8.
This paper (the first part of two to be published in this journal) presents the process and results of a critical review of
the integrated GPS and inertial navigation system (INS) architectures, the corresponding failure modes and the existing integrity
monitoring methods. The paper concludes that tightly coupled GPS/INS systems have the highest potential for detecting slowly
growing errors (SGEs). This is due to access to pseudorange measurements and a relatively simpler configuration compared to
the other architectures. The second paper (Part II) takes this further and carries out a detailed characterisation of the
performance of the current integrity algorithms for tightly coupled systems and develops a new algorithm that detects SGEs
faster than the current methods. 相似文献
9.
Data from around the world (Australia, Austria, Bahrain, Brazil, Canada, the Netherlands, Poland, the UK and the USA) show that more than four million onshore hydrocarbon wells have been drilled globally. Here we assess all the reliable datasets (25) on well barrier and integrity failure in the published literature and online. These datasets include production, injection, idle and abandoned wells, both onshore and offshore, exploiting both conventional and unconventional reservoirs. The datasets vary considerably in terms of the number of wells examined, their age and their designs. Therefore the percentage of wells that have had some form of well barrier or integrity failure is highly variable (1.9%–75%). Of the 8030 wells targeting the Marcellus shale inspected in Pennsylvania between 2005 and 2013, 6.3% of these have been reported to the authorities for infringements related to well barrier or integrity failure. In a separate study of 3533 Pennsylvanian wells monitored between 2008 and 2011, there were 85 examples of cement or casing failures, 4 blowouts and 2 examples of gas venting. In the UK, 2152 hydrocarbon wells were drilled onshore between 1902 and 2013 mainly targeting conventional reservoirs. UK regulations, like those of other jurisdictions, include reclamation of the well site after well abandonment. As such, there is no visible evidence of 65.2% of these well sites on the land surface today and monitoring is not carried out. The ownership of up to 53% of wells in the UK is unclear; we estimate that between 50 and 100 are orphaned. Of 143 active UK wells that were producing at the end of 2000, one has evidence of a well integrity failure. 相似文献
10.
This paper presents theoretical analysis of the parallel seismic (PS) method for evaluating existing piles using the flexural mode wave exited by a horizontal impact on the lateral surface of a pile. A simplified theoretical model of the flexural wave for PS method was established to elaborate the theoretical basis. A correction factor was then obtained and proposed to correct the pile depth obtained from the PS method, thus providing a more accurate estimation. A three dimension (3-D) finite element (FE) model was developed and the existence of the flexural waves on branch F(1, 1) in the pile shaft has been verified. Two time domain methods were used to calculate the flexural wave velocity in the pile. One was based on the pile tip reflection signal using a model where pile head reflection was minimized, and another method used the slope of the upper fitted line in the PS test. The flexural wave velocities from both methods match well with the predicted flexural wave group velocity determined from the dispersion curve of a 1-D rod embedded in the soil. The accuracy in estimation of pile tip depth is improved by applying the correction factor. A series of parametric studies were carried out to demonstrate the effectiveness of using flexural wave for PS test and the correction factor proposed in this study. 相似文献