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71.
The contribution to each component of the deformation vector due to a marginally undetected blunder in an observation is split into two parts, and so are the deformation measures at a point. The first part, called the local component (or self component), signifies the contribution due to the redundancy-related multiplier belonging to the observation itself, while the second part, called the complementary component, shows the contribution due to the non-redundancy-related multipliers belonging to the observation. A larger redundancy results in a smaller local component for each component of the deformation vector. However, robustness due to an observation at a point is correlated with redundancy to a significant extent. The first-order global positioning system (GPS)-geodetic network of Taiwan was examined for its robustness. The experiments seem to indicate that: (1) large deformations tend to be found at points where the group redundancies are small; (2) the local components monopolize deformation measures at the perimeter stations of the network where very small redundancy numbers are found; (3) the largest deformation at a point may be due to an observation not directly tied to the point of interest; and (4) except for local twisting, deformation measures and mean positional precisions at individual points are highly correlated.Acknowledgement The authors thank Drs. A.A. Simkooei, M. Schmidt, and M.R. Craymer greatly for their constructive comments and suggestions, which improved the quality of the paper. This research was supported by National Science Council of Taiwan (contract number NSC-91-2211- E-002-085). 相似文献
72.
W. Prószyński 《Journal of Geodesy》1997,71(10):652-659
For a linear least-squares parametric model analysis is carried out of the structure of the projection operator transforming
the vector of standardised observations into the vector of standardised residuals. On this basis the properties of the model
responses to observational disturbances (i.e. gross errors or blunders) are derived. A final outcome of the research can be
summarised as: (1) proposing the robustness characteristics of a model and linking them with the local measures of internal
reliability, being the diagonal elements in the projection operator; (2) determining the internal reliability levels satisfying
specified robustness requirements, i.e. the possibility of detecting at least one of the k observational disturbances (k=1,2,…) having most disadvantageous locations in the system. The theory and a numerical example show that for the systems
which have been designed to a proper level of internal reliability, the least-squares estimation can demonstrate an accordingly
high level of robustness.
Received: 11 June 1996 / Accepted: 28 April 1997 相似文献
73.
The principles are summarized in this paper for tackling problems related with the verification of historic earthquake records so as to enable proper utilization of the rich historic data of China.Case studies furnished in this paper show that those principles could be effectively utilized to solve the puzzling problems encountered in studying the historic earthquake data.The principles listed in this paper might also be used to tackle problems associated with the historic records of other branches of science. 相似文献
74.
生命线网络抗震可靠度的一般算法 总被引：4，自引：1，他引：4
针对生命线工程中所特有的顶点失效问题和失效相关性问题，本文提出了其网络可靠性分析的一般计算方法。 相似文献
75.
Probability levels, in the form of marginal cumulative distribution functions, are determined for the time it takes salt to
contact a casing, which penetrates a salt canopy, and the time it takes the casing to yield once salt has contacted the casing,
in support of through-salt well design activities required for deep-water, sub-salt environments. The finite-element method
coupled with an advanced reliability method is used to perform the analyses. Randomness caused by uncertainties in salt properties,
lithostatic stress, drilling-mud pressure, production temperature, and borehole ellipticity is handled by including statistics
and probability distributions for each of these random variables. The advanced reliability method takes full account of the
random variables and processes without Monte Carlo simulation, by using a method for assessing reliability statistics that
computes response probabilities in a direct and efficient manner. This advanced reliability method falls under the general
category of fast probability integration schemes. 相似文献
76.
The robustness of an outlier detection method strongly depends on the weights of observations, i.e., the type of the stochastic
model applied (homoscedasticity, heteroscedasticity and heterogeneousness). In this paper, we have investigated how the reliability
of the robust methods and tests for outliers changes depending on the weights of the observations in geodetic networks. Furthermore,
the contribution of the directions and distances to horizontal control network with regard to reliability are investigated
separately. The concept of a breakdown point is used as a global measure of robustness against outliers. The mean success
rate (MSR) is found to be a practical tool for confirming the breakdown point. Many different “good” data samples are generated
for each network and then deliberately contaminated using a Monte-Carlo simulation. Six robust methods and Baarda’s test are
applied to the corrupted samples and the degree of corruption is varied. The performance of each method is measured using
both local and global MSRs. Our research shows: (1) The MSRs of Baarda’s test change depending on the strength of the heteroscedasticity,
but do not change for trilateration and leveling networks, (2) the global MSRs of robust methods do not differ considerably
from the local ones 相似文献
77.
汶川地震重灾区,由地震触发的地质灾害数量很多,其中危岩体稳定性判定为灾害治理重点工作。基于可靠度理论,针对坠落式危岩体稳定性极限状态特征,建立其可靠度判定概率极限状态方程,并采用现场量测及概率统计方法,对功能函数中危岩破裂面倾角、危岩等效摩擦角、单位长度危岩体重力、危岩等效黏聚力c、危岩体高度h等基本变量的均值、变异性及分布形态进行确定。基于以上研究成果,建立了坠落式危岩体稳定性可靠度指标计算方法,同时对各基本变量的可靠度敏感性进行研究,研究结果表明:其敏感性由大到小依次为危岩破裂面倾角、危岩等效黏聚力c、危岩的高度h、单位长度危岩体重力、危岩等效摩擦角,研究成果为坠落式危岩体稳定性判定和治理方案设计提供参考依据。 相似文献
78.
The current pilot study explores whether mobile technology can be leveraged in survey research to gather meaningful context-dependent data on fear of crime and risk perception formation. A series of Ecological Momentary Assessments (EMAs) were administered to students enrolled at an Australian University (N = 20), using a smartphone application. Analysis of data collected from participants in their everyday activity spaces a) show strong internal consistency among multiple measures of crime fear; b) indicate that perceptual measures of social cohesion are significant predictors of victimisation worry; and c) support most hypothesised associations between concepts contained in contemporary models of crime fear. Unfortunately, some aspects of the pilot study design could not be implemented as planned, which have implications for future research. Specifically, we found that triggering participant's surveys based on their location (rather than time), produced data that was not conducive to robust place-based analysis. In spite of this limitation, we offer alternative means of measuring the effects of place on fear of crime using mobile devices. 相似文献
79.
通过下佛罗统磁性地层学研究,获得了一些能记录岩石形成时的地磁场的样品,根据常规的古地磁方法,等温剩磁和热退磁实验,说明这些岩石的主要载磁矿物为磁铁矿.磁滞回线参数的测量表明多数载磁矿物磁铁矿为假单磁畴,少量样品则可能为假单磁畴与多磁畴的混合物.通过与北美古生代重磁化岩石的磁滞回线参数比值对比,说明重磁化与非重磁化岩五磁滞回线参数比值的分布趋势有明显差别,这一差别可能用于判定岩石的重磁化和非重磁化性质. 相似文献
80.
通过下佛罗统磁性地层学研究,获得了一些能记录岩石形成时的地磁场的样品,根据常规的古地磁方法,等温剩磁和热退磁实验,说明这些岩石的主要载磁矿物为磁铁矿.磁滞回线参数的测量表明多数载磁矿物磁铁矿为假单磁畴,少量样品则可能为假单磁畴与多磁畴的混合物.通过与北美古生代重磁化岩石的磁滞回线参数比值对比,说明重磁化与非重磁化岩五磁滞回线参数比值的分布趋势有明显差别,这一差别可能用于判定岩石的重磁化和非重磁化性质. 相似文献