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排序方式: 共有1392条查询结果,搜索用时 15 毫秒
941.
The excess pore pressure generated by pile installation gradually dissipates following installation, which mainly dominates the increase of pile capacity with time. The dissipation of the excess pore pressure following pile installation has been widely investigated by experimental and theoretical studies. However, in most research, the consolidation coefficients were assumed to be constant for simplification, which may lead to errors. In the present study, the dissipation of the excess pore pressure is analyzed by radial consolidation theory with a variable consolidation coefficient based on the linear responses of e − ln(p′) and e − log(k). The governing equation of the radial consolidation considering variable compressibility and permeability are solved by the variable separation method. Bessel functions are used to solve the differential functions for the time independent part. The excess pore pressure immediately after pile installation is obtained from cavity expansion theory and is used as the initial condition of the consolidation process. Moreover, the influences of variable compressibility and permeability on the variation of consolidation coefficient and excess pore pressure dissipation are analyzed. 相似文献
942.
回顾了国内外土壤采样装置的发展
历史,针对国内土壤采集的实际需求,确
定了液压振动式土壤采集装置的总体方
案。为了提高装置的可靠性与稳定性,进
行了液压系统管路的优化设计,设计了
具有双凸结构的采样管,进行了一般土
质与杂硬土质的采样试验。试验结果表
明,该装置既可以进行松软土质的采样,
也可以进行杂硬土质的采样。 相似文献
943.
对目前DLG产品质量管理存在的薄弱环节进行分析,讨论了DLG数据全面质量控制的策略,并运用统计质量控制中的分层法,在实际作业管理中进行了应用,起到了良好的解决问题的作用,说明了其可用性。 相似文献
944.
945.
946.
On the basis of previous studies, this paper, in studying the coda Q-value of near shocks, has proposed using the sampling depth to describe the effect of lapse time on the Q-value, and has investigated the dependence of coda wave of earthquakes on frequency and sampling depth. Analysis of digital seismograms recorded by the Yinchuan Telemetric Seismic Network, Ningxia, shows that not only the coda wave Q-value of shocks is strongly dependent on frequency but also its dependence on sampling depth cannot be neglected. In the commonly used formula that describes the dependence characteristics of coda Q-value of earthquakes, Q = Q0 f n, the parameter Q0 rises obviously while n drops when the sampling depth increases, and their changes can be fitted by linear relations. This paper has explained such a characteristic. Whether this characteristic exists universally needs to be verified by more study results because the genetic mechanism of coda wave of earthquakes is more complex. 相似文献
947.
F. Demirmen 《Mathematical Geology》1972,4(1):35-43
Operator error in petrographic point-count analysis introduces bias into the estimates of proportion in a thin section. A correction for this bias, leading to an unbiased estimator of the true proportion in that thin section, is here proposed. Operator error also affects the confidence interval, and in this situation, too, an adjustment is possible. The approach proposed requires that the probabilities associated with operator error, categorized into A-type and B-type errors, are known or assumed. The A-type operator error tends to underestimate the true proportion in a thin section, whereas the B-type operator error tends to overestimate it. 相似文献
948.
Ballast water sampling as a critical component of biological invasions risk management 总被引:8,自引:0,他引:8
The human mediated transfer of harmful organisms via shipping, specifically via ballast water transport, leading to the loss of biodiversity, alteration of ecosystems, negative impacts on human health and in some regions economic loss, has raised considerable attention especially in the last decade. Ballast water sampling is very important for biological invasions risk management. The complexity of ballast water sampling is a result of both the variety of organism diversity and behaviour, as well as ship design including availability of ballast water sampling points. Furthermore, ballast water sampling methodology is influenced by the objectives of the sampling study. In the course of research conducted in Slovenia, new sampling equipment for ships' ballast water was developed and tested. In this paper new ballast water sampling methods and equipment together with practical shipboard testing results are presented. 相似文献
949.
950.
Hyun-Han Kwon Young-Il Moon 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(4):223-237
Hydrologic risk analysis for dam safety relies on a series of probabilistic analyses of rainfall-runoff and flow routing models, and their associated inputs. This is a complex problem in that the probability distributions of multiple independent and derived random variables need to be estimated in order to evaluate the probability of dam overtopping. Typically, parametric density estimation methods have been applied in this setting, and the exhaustive Monte Carlo simulation (MCS) of models is used to derive some of the distributions. Often, the distributions used to model some of the random variables are inappropriate relative to the expected behaviour of these variables, and as a result, simulations of the system can lead to unrealistic values of extreme rainfall or water surface levels and hence of the probability of dam overtopping. In this paper, three major innovations are introduced to address this situation. The first is the use of nonparametric probability density estimation methods for selected variables, the second is the use of Latin Hypercube sampling to improve the efficiency of MCS driven by the multiple random variables, and the third is the use of Bootstrap resampling to determine initial water surface level. An application to the Soyang Dam in South Korea illustrates how the traditional parametric approach can lead to potentially unrealistic estimates of dam safety, while the proposed approach provides rather reasonable estimates and an assessment of their sensitivity to key parameters. 相似文献