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81.
以京西北地区作为研究区域,采用应变参数方法解算定点地应变观测数据,将所得应变参数时间序列作为研究对象,利用该结果与研究区内同期小震震源机制解进行一致性分析,研究得出呈拉张性质的定点观测最大主应变方位与震源机制解最大拉张变形方向(T轴)水平投影具有良好的对应性,整体以NNW—NE向为主,且自西向东排布的测点最大主应变方位与震源机制解最大拉张变形方向均表现为逐渐东向偏移的趋势,与华北平原块体北部发生顺时针旋转活动的特征相吻合,结果进一步检验了地应变观测反映区域应变场信息的能力。 相似文献
82.
The flexible riser top connection is a critical region for lifetime assessment due to large tension/curvature variations and modeling uncertainties. The bend stiffener polyurethane mechanical response not only presents a nonlinear loading rate and temperature dependency but is also subjected to weather ageing during operation, which may affect its mechanical behavior over time. The top tension, employed for riser local cross-section stress calculation, is usually obtained from global dynamic analyses performed under selected environmental conditions, if direct measurement is not available. As a consequence, both the bend stiffener effect on the curvature distribution and the top tension time series present inherent uncertainties for riser lifetime (re)assessment. In the present work, a proposed monitoring approach composed by gyrometers installed along flexible riser/bend stiffener top connection system length combined with an inverse problem methodology is numerically investigated to estimate the following parameters: (i) polyurethane hyperelastic response and (ii) effective top tension. The top connection system is modeled using a large deflection beam bending model and the parameters are estimated using a damped least-square minimization approach with the Levenberg–Marquardt algorithm. For the preliminary feasibility investigation, the gyrometer experimental data is numerically estimated through Monte Carlo simulations. A case study is carried out to investigate the influence that the number of sensors, sensors arrangement, loading conditions and top connection model have on the inverse parameters estimation. The results indicate that the proposed monitoring approach and inverse parameter estimation methodology may effectively reduce flexible riser lifetime calculation uncertainties. 相似文献
83.
Most classical approaches for evaluating the stability of soil slopes with cracks are performed under two-dimensional (2D) condition. Three-dimensional (3D) effect and suction-induced effect of unsaturated soils are generally neglected in assessing the slope stability. This paper develops a 3D limit analysis method to evaluate the stability of an unsaturated soil slope with tension cracks under steady infiltrations. The boundary-value problem is formulated based on the 3D rotational failure mechanism by taking the effects of suction, effective unit weight, and tension crack into account. A simplified method is proposed to calculate the work rate of unsaturated soil weight. A layer-wise summation method is developed based on the divergence theorem to calculate the internal energy dissipation rate. Detailed discussions are conducted to investigate the effects of suction and Poisson's ratio on the stability of unsaturated soil slopes. Examples are given to illustrate the 3D effect, the suction-induced effect as well as the effects of infiltration and water in cracks on the slope stability. 相似文献
84.
The surface fine structure of bare strange stars is determined. The distribution of electrons and quarks in the surface layer is determined using a phenomenological Thomas-Fermi model. For the MIT bag model, the quark density at the free surface is found to fall off continuously to zero in a layer of finite thickness. Unlike the results of other authors, here the electric field in the transition layer changes direction. The coefficient of surface tension of the quark matter is determined in terms of this model. Depending on the model parameters, it is 60–150 MeV/Fm2.Translated from Astrofizika, Vol. 48, No. 1, pp. 139–150 (February 2005). 相似文献
85.
Effects of in-situ conditions on relative permeability characteristics of CO2-brine systems 总被引:2,自引:0,他引:2
Carbon dioxide capture and geological storage (CCGS) is an emerging technology that is increasingly being considered for reducing
greenhouse gas emissions to the atmosphere. Deep saline aquifers provide a very large capacity for CO2 storage and, unlike hydrocarbon reservoirs and coal beds, are immediately accessible and are found in all sedimentary basins.
Proper understanding of the displacement character of CO2-brine systems at in-situ conditions is essential in ascertaining CO2 injectivity, migration and trapping in the pore space as a residual gas or supercritical fluid, and in assessing the suitability
and safety of prospective CO2 storage sites. Because of lack of published data, the authors conducted a program of measuring the relative permeability
and other displacement characteristics of CO2-brine systems for sandstone, carbonate and shale formations in central Alberta in western Canada. The tested formations are
representative of the in-situ characteristics of deep saline aquifers in compacted on-shore North American sedimentary basins.
The results show that the capillary pressure, interfacial tension, relative permeability and other displacements characteristics
of CO2-brine systems depend on the in-situ conditions of pressure, temperature and water salinity, and on the pore size distribution
of the sedimentary rock. This paper presents a synthesis and interpretation of the results. 相似文献
86.
为了提高变形监测数据预测的精度与可靠性,提高神经网络预测方法的稳定性,尝试将小波分析与BP神经网络相结合的小波神经网络应用于高铁路基处的沉降监测数据处理中。综合小波分析与神经网络算法的优点,建立松散型及紧致型小波神经网络预测分析模型。通过实验数据对比分析,验证了采用紧致型小波神经网络预测模型能够较好地用来处理路基的动态变形监测数据,预测稳定性及预测精度较高。 相似文献
87.
The maximum internal tangential stress is a critical parameter for the design of the PDC (polycrystalline diamond compact) die that has been widely applied to offshore oil drilling. A new simple equation for the calculation of the stress is developed, and verified by the test data from Kingdream Corp. of China, the largest bit Company in China. An opti- mum method for the design of the PDC die is presented and demonstrated in detail, and software for the design and FEM analysis of the die is developed on the basis of the method. This software has been used in oil industry in recent years. 相似文献
88.
89.
Free vibrations of three-dimensional extensible marine cables with specified top tension via a variational method 总被引:1,自引:0,他引:1
This paper presents a model formulation that can be used for analyzing the three-dimensional vibration behaviours of an inclined extensible marine cable. The virtual work-energy functional, which involves strain energy due to axial stretching of the cable and virtual work done by external hydrostatic forces is formulated. The coupled equations of motion in the Cartesian coordinates of global systems are obtained by taking into account the difference between Euler’s equations and equilibrium equations. The method of Galerkin finite element is used to obtain the mass and stiffness matrices which are transformed into the local coordinate systems. Then the eigenvalue problem is solved to determine its natural frequencies and corresponding mode shapes. The model formulation developed herein is conveniently applied for the cases of specified top tension. The numerical investigations are carried out to demonstrate the validity of the model and to explore in details the influence of various parameters on the behaviours of marine cables. Results for the frequency avoidance phenomenon, maximum dynamic tension and coupled transverse mode shapes are presented and discussed. 相似文献
90.