抗差卡尔曼滤波模型及其在GPS监测网中的应用

根据量测向量中的粗差对状态向量滤波值的影响规律，导出了抗差卡尔曼滤波模型，该模型对观测空间和设计空间均具有良好的抗差性。通过对含有粗差的模拟GPS监测网的计算，与标准卡尔曼滤波模型相比较，利用该抗差滤波模型，可获得可靠的变形分析结果。     

Stability analysis of seismic slopes with cracks

Earthquakes can trigger slope instability, especially in the case of slopes with cracks. Studies of slope stability rarely account for the presence of cracks. In this study, the upper bound limit analysis technique and the pseudo-static method were used to examine the stability of homogeneous slopes with cracks subjected to seismic loading. A series of stability charts for slope inclinations of 2:1 (β = 63.4°), 1:1 (β = 45°), 2:3 (β = 33.7°), and 1:2 (β = 26.6°) (vertical to horizontal) and internal friction angles, φ, of 10°, 20°, 30°, and 40° are presented. These charts should be useful for readily determining the stability number (critical slope height), the critical crack depth, and the region affected by cracks for cracks of known depth but unknown location, cracks of known location but unspecified depth, and cracks of unspecified depth and location.     

Permeability measurements in mudrocks using gas-expansion methods on plug and crushed-rock samples

Permeability is an important parameter relative to the production of hydrocarbons in shale oil/gas plays; however, the measurement of permeability in these nano-to microdarcy rocks remains a challenge. Results from different methods or from different laboratories are not consistent, and reasons are not fully understood. In the present study, permeability is measured for both plug and crushed-rock samples with different plug diameter or crushed-sample particle size to systematically investigate the permeability measurement to better understand and apply the measured results. A modified gas-expansion (MGE) method, which can measure permeability for plug samples under confining pressures, was established and applied to several Eagle Ford and Barnett Shale (mudrock) samples. Permeability results from this method are in fair agreement with those from the pulse-decay method. The traditional Gas Research Institute (GRI) method was applied to crushed-rock Eagle Ford Shale samples. The results were comparable to reported permeability for an Eagle Ford Shale sample. Particle or plug size has significant influence on permeability measurement. In general, permeability increases with increasing particle or plug size. For crushed sample with GRI method, the reason of increasing permeability is related to the limitation of the GRI technique and the data analysis method. Estimate of the permeability based on Kozeny–Carman Equation was conducted, and the results were used to evaluate the GRI permeability measurement. Particle size of 2–4 mm (5–10 meshes) is considered as an appropriate size for GRI permeability measurement. For plug sample, larger permeability with larger plug diameter is most likely caused by the artificial fractures. Higher confining pressure can reduce the influence of the fractures, but cannot fully remove it. A range of permeability, defined by the GRI permeability with 2–4 mm particles as the lower boundary and permeability of 1-in plug under high confining pressure (>5000 psi) as the upper boundary, can be a more reliable measures to represent the shale matrix permeability. The range of the permeability also highlights the uncertainty in matrix permeability measurement for shale.     

球上最小二乘问题向后误差的估计

A.N.Malyshev给出了球上最小二乘问题计算解的最佳向后扰动量表达式。从该表达式出发计算最佳向后扰动量却是很困难的。本文给出 1种有效的估算方法 ,所得结果对检验计算解的向后稳定性是有用的。并用几个简单的数值例子验证了所给算法的有效性。     

Upper bound limit analysis of uplift failure in pressurized sealed rock tunnels

The rock around tunnels used for gas storage is subject to high pressures, reaching 30 MPa in the case of compressed air energy storage. Uplift failure of the overlaying rock mass up to the surface represents the main hazard scenario in such cases. The present paper investigates this problem by using the upper bound theorem of limit analysis assuming a continuum rock mass model obeying the Mohr Coulomb failure criterion with tension cut‐off. Tools of the calculus of variations are used to assess the geometry of the failure surface. The effects of geometrical and geotechnical parameters on uplift pressure are analyzed systematically. Charts are then provided, which enable a quick estimation of the upper bound of uplift pressure across a wide range of geotechnical and geometrical conditions.     

无碰撞区跳频/时序列理论界与设计

跳频(时)序列分析与设计是跳频(时)扩频通信系统的核心技术.无碰撞区跳频序列是近年新出现的一个研究方向,现已成为通信领域的研究热点.对无碰撞区跳频序列的理论界及其设计进行深入研究,导出无碰撞区跳频序列的一些本质属性;讨论无碰撞区跳频序列集周期汉明相关函数的理论界,揭示几个理论界之间的关系,给出这些理论界等价的条件.提出最优无碰撞区跳频序列的一般构造方法.利用该构造方法,可以产生任意长度的最优无碰撞区跳频序列集.并且,任意一个最优无碰撞区跳频序列集,都可以由一般构造方法产生.     

The influence of load inclination on the undrained bearing capacity of strip footings on slopes

The effect of inclined loading on the bearing capacity of foundations on horizontal ground surface is well established and both the exact solution and simpler empirical equations are available for the calculation of the failure loads. However, for footings on or near slopes complete solutions are available only for vertical loading. This paper investigates the influence of inclined loading on the horizontal and vertical failure loads. The finite element, upper bound plasticity and stress field methods are used to examine a wide range of geometries and soil properties. The methods are first validated against known solutions for two special cases and are subsequently employed to investigate the effect of the geometrical and material properties on the failure loads and the bearing capacity load interaction diagram. Based on this investigation an empirical equation is proposed for the load interaction diagram for undrained inclined loading of footings on or near slopes.     

粘土中圆形隧道上限解的研究

根据极限分析上限理论,基于Davis等人提出的隧道垮落模型,提出了剪切区参数α等于1时的新的隧道垮落模型。由不可压缩性条件和速度连续性条件求出了剪切区速度和间断线表达式,计算了该模型间断线上能量耗损、剪切区能量耗损和总外力所做的功。利用功能原理,求出了稳定率的表达式,并计算了相应的稳定率。从求解结果来看,所得上限解小于Davis等人的结果,因而该上限解将更接近真实解。从与实验结果比较来看,该上限解位于实验值附近,能与实验结果比较好地吻合,从而说明该模型更加接近真实隧道垮落情形。该上限解可为隧道支护提供理论依据。     

Analytical and numerical analyses of the load‐bearing capacity of retaining walls laterally supported at both ends

This paper investigates the load‐bearing capacity of a perfectly smooth retaining wall laterally supported at both ends assuming that the wall fails by the development of three plastic hinges. The study considers the case of a cohesionless elastic–perfectly plastic backfill with a Mohr–Coulomb yield criterion and an associative flow rule in drained conditions. A kinematically admissible soil–structure failure mechanism is proposed and compared with the conventional solutions and with results from a numerical finite element modelling. The study shows that the proposed solution and the numerical solution are in good agreement. These solutions are found to be much more favourable for the wall than the conventional solutions. Copyright © 2010 John Wiley & Sons, Ltd.     

分解算法及其收敛性质

本文给出了求解线性等式及不等式约束的非线性规划的一个新算法，并运用矩阵分解，给出了求逆的递推公式。该算法计算简单，证明了算法的收敛性及具有超线性收敛性质。