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101.
102.
中国沿海星虫动物门名录 总被引:2,自引:0,他引:2
取1980~1989年间在我国沿海进行星虫动物区系调查的标本和有关资料做了整理、鉴定,共39种,分隶于2纲,4目,6科,12属。其中1种在我国为首次记录。 相似文献
103.
Shu-Guang Song Shu-Cai Li Li-Ping Li Qian-Qing Zhang Kai Wang Yi Zhou 《Marine Georesources & Geotechnology》2016,34(4):376-383
During tunnel excavation, the deformation of surrounding rock due to the unloading of rock mass will vary with time. However, the measured displacement of surrounding rock is only a part of the actual longitudinal deformation profile. There is a need to analyze the longitudinal deformation profile to identify the deformation state and evaluate the stability of surrounding rock mass. In the present article, the variation of pre-deformation of surrounding rock due to excavation was analyzed, and the release coefficient was obtained from the measured results. For the Qingdao subsea tunnel, the measured crown settlement of surrounding rock was analyzed using the regression analysis method, and the longitudinal deformation profile of rock mass was simulated using the numerical calculation method. Moreover, based on the conditions of the subsea tunnel, a solid-fluid coupling model test was carried out to check the reliability of the numerical calculation results. The results of the model test were consistent with the numerical calculation results. 相似文献
104.
Impact of anthropogenic drivers on subaqueous topographical change in the Datong to Xuliujing reach of the Yangtze River 总被引:3,自引:0,他引:3
Shuwei Zheng Heqin Cheng Shengyu Shi Wei Xu Quanping Zhou Yuehua Jiang Fengnian Zhou Minxiong Cao 《中国科学:地球科学(英文版)》2018,61(7):940-950
Changes of subaqueous topography in shallow offshore water pose safety risks for embankments,navigation,and ports.This study conducted measurements of subaqueous topography between Datong and Xuliujing in the Yangtze River using a Sea Bat 7125 multi-beam echo sounder,and the channel change from 1998 to 2013 was calculated using historical bathymetry data.The study revealed several important results:(1)the overall pattern of changes through the studied stretch of the river was erosion–deposition–erosion.Erosion with a volume 700×10~6m~3occurred in the upper reach,deposition of about 204×10~6m~3occurred in the middle reach,and erosion of about 602×10~6m~3occurred in the lower reach.(2)Dunes are the most common microtopographic feature,accounting for 64.3%of the Datong to Xuliujing reach,followed by erosional topography and flat river topography,accounting for 27.6%and 6.6%,respectively.(3)Human activities have a direct impact on the development of the microtopography.For instance,the mining of sand formed holes on the surface of dunes with lengths of 20–35 m and depths of 3–5 m.We concluded that the overall trend of erosion(net erosion volume of 468×10~6m~3)occurred in the study area mainly because of the decreased sediment discharge following the closure of the Three Gorges Dam.However,other human activities were also impact factors of topographic change.Use of embankments and channel management reduced channel width,restricted river meandering,and exacerbated the erosion phenomenon. 相似文献
105.
本文介绍了地震氡观测仪计量检定系统(氡室)的建设背景及结构组成。氡室具有氡体积活度(氡浓度)实时监测、动态补氡、氡期望值可调、稳定性好等特点。在氡室调试实验中进行了氡室的漏气率实验及4次补氡实验,计算出氡室的氡漏气率为0.0001393Bq/min,氡发生率为23.35Bq/min。根据《测氡仪检定规程》(JJG 825—2013)的技术要求进行计量效能验证,表明氡室的氡体积活度(氡浓度)为800Bq/m3、1500Bq/m3、3000Bq/m3、6000Bq/m3和15000Bq/m3时,连续8h稳定性均优于5%;为6000Bq/m3时,72h稳定性优于5%,符合国家计量技术规范对氡室计量标准的要求。 相似文献
106.
Lian-Teng Song Zhong-Hua Liu Can-Can Zhou Jun Yu Li-Jun Xiu Zhong-Chun Sun Hai-Tao Zhang 《应用地球物理》2017,14(1):10-20
Tight sandstone has a certain anisotropy. Using ultrasonic measurements of samples in three different directions and related matched experiments, this study systematically analyzes the pore structure and anisotropy of tight sandstone samples obtained from oil fields and compares results with those of shale. Results firstly show that the anisotropy of tight sandstone is mainly related to the compositional layering and thin interbedding which occur in different sedimentary environments. Tight sandstone has typical transverse isotropic medium characteristics, Young’s modulus increases in different directions with increasing confining pressure, Poisson’s ratio change is not obvious, anisotropic coefficients decrease with increasing effective pressure, and a certain linear relationship exists between ε, γ, and δ. This article finally summarizes anisotropy in different areas, thereby providing a foundation for the use of suitable appraisal models in different regions. This research can be used as an experimental reference for logging evaluation, seismic data interpretation, and fracturing develop of tight sandstones. 相似文献
107.
Jun Guo Jianzhong Zhou Lixiang Song Qiang Zou Xiaofan Zeng 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(4):985-1004
Assessment of parameter and predictive uncertainty of hydrologic models is an essential part in the field of hydrology. However, during the past decades, research related to hydrologic model uncertainty is mostly done with conceptual models. As is accepted that uncertainty in model predictions arises from measurement errors associated with the system input and output, from model structural errors and from problems with parameter estimation. Unfortunately, non-conceptual models, such as black-box models, also suffer from these problems. In this paper, we take the artificial neural network (ANN) rainfall-runoff model as an example, and the Shuffled Complex Evolution Metropolis algorithm (SCEM-UA) is employed to analysis the parameter and predictive uncertainty of this model. Furthermore, based on the results of uncertainty assessment, we finally arrive at a simpler incomplete-connection artificial neural network (ICANN) model as well as with better performance compared to original ANN rainfall-runoff model. These results not only indicate that SCEM-UA can be a useful tool for uncertainty analysis of ANN model, but also prove that uncertainty does exist in ANN rainfall-runoff model. Additionally, in some way, it presents that the ICANN model is with smaller uncertainty than the original ANN model. 相似文献
108.
109.
2.5-D modeling and inversion techniques are much closer to reality than the simple and traditional 2-D seismic wave modeling
and inversion. The sensitivity kernels required in full waveform seismic tomographic inversion are the Fréchet derivatives
of the displacement vector with respect to the independent anisotropic model parameters of the subsurface. They give the sensitivity
of the seismograms to changes in the model parameters. This paper applies two methods, called ‘the perturbation method’ and
‘the matrix method’, to derive the sensitivity kernels for 2.5-D seismic waveform inversion. We show that the two methods
yield the same explicit expressions for the Fréchet derivatives using a constant-block model parameterization, and are available
for both the line-source (2-D) and the point-source (2.5-D) cases. The method involves two Green’s function vectors and their
gradients, as well as the derivatives of the elastic modulus tensor with respect to the independent model parameters. The
two Green’s function vectors are the responses of the displacement vector to the two directed unit vectors located at the
source and geophone positions, respectively; they can be generally obtained by numerical methods. The gradients of the Green’s
function vectors may be approximated in the same manner as the differential computations in the forward modeling. The derivatives
of the elastic modulus tensor with respect to the independent model parameters can be obtained analytically, dependent on
the class of medium anisotropy. Explicit expressions are given for two special cases—isotropic and tilted transversely isotropic
(TTI) media. Numerical examples are given for the latter case, which involves five independent elastic moduli (or Thomsen
parameters) plus one angle defining the symmetry axis. 相似文献
110.
In order to study the dynamic performance of seismically isolated bridges under the most unfavorable loads in the longitudinal direction,a dynamic equation for vehicle braking in the longitudinal direction is established.A four or fiveorder Runge-Kutta method is adopted to obtain the time-history response of a wheel set under braking force.The quadratic discretization method is then used to transform this time-history into a braking and bending force time-history of a structural fixed node,and a dynamic response analysis of the seismically isolated bridge under the vehicle’s braking force is carried out using ANSYS,a universal finite element analysis software.According to the results,seismic isolation design results in a more rational distribution of braking force among piers;the influence of the initial braking velocity on the vehicle braking force is negligible;the location where the first wheel set leaves the bridge is the most unfavorable parking location;a seismic isolation bridge bearing constructed according to typical design methods enters into a yield stage under the braking force, while the shearing force at the bottom of the pier declines as the isolation period is extended;the design requirements can be met when the yield displacement of the seismic isolation bearing is less than 5 mm and the yield strength is greater than the braking force. 相似文献