A fully convex reformulation of the original Matsuoka–Nakai failure criterion and its implicit numerically efficient integration algorithm

This paper presents a reformulation of the original Matsuoka–Nakai criterion for overcoming the limitations which make its use in a stress point algorithm problematic. In fact, its graphical representation in the principal stress space is not convex as it comprises more branches, plotting also in negative octants, and it does not increase monotonically as the distance of the stress point from the failure surface rises. The proposed mathematical reformulation plots as a single, convex surface, which entirely lies in the positive octant of the stress space and evaluates to a quantity which monotonically increases as the stress point moves away from the failure surface. It is an exact reproduction, and not an approximated one, of the only significant branch of the original criterion. It is also suitable for shaping in the deviatoric plane the yield and plastic potential surfaces of complex constitutive models. A very efficient numerical algorithm for the implicit integration of the proposed formulation is presented, which enables the evaluation of the stress at the end of each increment by solving a single scalar equation, both for associated and non‐associated plasticity. The algorithm can be easily adapted for other smooth surfaces with linear meridian section. Finally, a close expression of the consistent Jacobian matrix is given for achieving quadratic convergence in the external structural newton loop. It is shown that all this results in extremely fast solutions of boundary value problems. Copyright © 2013 John Wiley & Sons, Ltd.     

GRAPES新云量计算方案的引进和影响试验

在GRAPES模式中分别引进了 EC云量计算方案和WRF云量计算方案,并与GRAPES现用的云量计算方案和简单云方案进行了对比数值试验,结果表明:(1)这4种云量计算方案都能较准确地模拟云分布,相对而言,EC云方案和简单云方案模拟地更为准确.(2)简单云方案模拟的总云量较多,GRAPES云方案和WRF云方案模拟的总云量偏少,EC方案模拟的总云量较为接近观测值.(3)在中国东部地区模拟的地面温度与观测基本接近,但在中国西部地区则误差较大;采用EC云方案时模式模拟的地面温度更接近观测值.(4)综合分析模拟的效果,认为EC云量计算方案模拟的效果最佳,可以作为GRAPES新云量计算方案引进的参考.     

节理岩体中双向八车道小净距隧道施工方案优化分析

结合福州国际机场高速公路2期工程魁岐2号双洞八车道特大断面小净距隧道工程,建立了离散元数值模拟分析模型,针对节理岩体中特大断面小净距隧道施工方案进行了优化分析。分别研究了双侧壁导坑法、CRD法和CD法3种施工方案下隧道拱顶下沉、中间岩柱水平位移、围岩水平位移和围岩塑性区的变化规律。基于研究成果,并结合魁岐2号特大断面小净距隧道现场实际情况,在该隧道进口Ⅴ级围岩段,将双侧壁导坑法变更为CRD法,顺利完成了施工,此施工方案的变更对降低施工成本、加快施工进度、缩短施工工期均起到了较好的作用。研究结果可为类似条件下特大断面小净距隧道的设计、施工提供借鉴与参考。     

Efficient reliability method for implicit limit state surface with correlated non‐Gaussian variables

In contrast to the traditional approach that computes the reliability index in the uncorrelated standard normal space (u‐space), the reliability analysis that is simply realized in the original space (x‐space, non‐Gaussian type) would be more efficient for practical use, for example, with the Low and Tang's constrained optimization approach. On the other hand, a variant of Hasofer, Lind, Rackwits and Fiessler algorithm for first‐order reliability method is derived in this paper. Also, the new algorithm is simply formulated in x‐space and requires neither transformation of the random variables nor optimization tools. The algorithm is particularly useful for reliability analysis involving correlated non‐Gaussian random variables subjected to implicit limit state function. The algorithm is first verified using a simple example with closed‐form solution. With the aid of numerical differentiation analysis in x‐space, it is then illustrated for a strut with complex support and for an earth slope with multiple failure modes, both cases involving implicit limit state surfaces. Copyright © 2015 John Wiley & Sons, Ltd.     

基于自动回标的地理实体关系语料库构建方法

地理实体关系语料库是地理信息获取与地理知识服务的基础数据资源,其规模直接影响机器学习模型训练的效果。快速更新的网络文本不断涌现新的关系实例,要求语料库及时更新以覆盖更丰富的关系实例。手工构建和更新语料库成本高昂,亟需一种快速构建大规模地理实体关系语料库的方法。本文提出一种基于回标技术的地理实体关系语料库构建方法。首先,参考地理实体分类标准与语义关系、空间关系分类标准,针对地理实体关系的自然语言描述习惯,建立地理实体关系的标注体系;然后,结合精确匹配与模糊匹配策略,提高客体匹配的覆盖率;接着,基于优序图法建立句子打分规则,实现种子三元组到句子映射的定量评价;最后,使用中文百度百科文本验证方法的有效性。实验结果显示,本文方法平均回标成功率为67.83%,关系标注的准确率为76.36%。相比人工构建空间关系标注语料库的过程,本文提出的语料自动构建方法,标注速度快,规模大,为自动扩充标注语料库提出了可行方案。同时,该方法兼顾了地理实体间的语义关系和空间关系,且关系类型不受限,可用于开放式关系抽取任务。     

基于云平台的物联网数据挖掘算法的能量分析

从物联网产生的大量数据中获得有效信息需求出发,分析数据挖掘在现有运行平台上的不足,同时指出云平台上的优势.分析数据挖掘中的决策树算法,通过对信息熵和信息增益地分析,得出算法复杂度和能量之间的内在关系,指出并行数据挖掘的计算复杂度和通信复杂度对效率地影响,得出提高系统的隐含并行性是在云平台下减少运行时间、降低能耗的可靠办法.     

西安某高校中水回用工程实例研究

针对目前许多城市将新型大学园区规划在城郊风景区域,远离城市市政管网,大学园区内污水处理和资源化这一个特殊问题,提出具有普遍应用性的解决方案。研究校区内生活、办公过程中产生的废水进行生物处理,使之达到中水水质标准,作为校区内的生活杂用水,用来冲厕、绿化、冲洗和水景用水,达到水资源的重复利用,节约资源的目的。     

Solving the Buckley–Leverett equation with gravity in a heterogeneous porous medium

Immiscible two‐phase flow in porous media can be described by the fractional flow model. If capillary forces are neglected, then the saturation equation is a non‐linear hyperbolic conservation law, known as the Buckley–Leverett equation. This equation can be numerically solved by the method of Godunov, in which the saturation is computed from the solution of Riemann problems at cell interfaces. At a discontinuity of permeability this solution has to be constructed from two flux functions. In order to determine a unique solution an entropy inequality is needed. In this article an entropy inequality is derived from a regularisation procedure, where the physical capillary pressure term is added to the Buckley‐Leverett equation. This entropy inequality determines unique solutions of Riemann problems for all initial conditions. It leads to a simple recipe for the computation of interface fluxes for the method of Godunov. This revised version was published online in July 2006 with corrections to the Cover Date.     

ADI barotropic ocean model for simulation of Kuroshio intrusion into China southeastern waters

In this numerical model for simulating the Kuroshio intrusion into the East and South China Seas, vertically averaged marine hydrodynamic equations governing ocean currents and long-period waves are approximated by a set of two-time-level semi-implicit fimite difference equations. The major terms including the local acoeleration, sea-surface slope, Coriolis force and the bottom friction are approximated with the Crank-Nicholson scheme, which is of second order accuracy. The advection terms are approximated with the Leith scheme. The difference equations are split into two sets of alternating direction implicit equations, each of which has a tridiagonal matrix and can be easily solved. The model reproduces a major Kuroshio intrusion north of Luzon Island, one north of Taiwan Island, and one west of the Tokara Strait. The model shows a current system running from the Luzon Strait to the coast of Vietnam and Hainan Island, through the Taiwan Strait and then into the Tsushima Strait. The summer and winter monsoons generate several eddies in the South China Sea. Project supported by the National Natural Science Foundation of China.     

一种基于视觉特征的多分辨率快速图像融合方法

以红外与可见光图像融合为例,提出了一种基于图像视觉特征相关量值的多分辨率快速图像融合方法.该方法先利用CDF9/7小波将输入图像进行提升分解,然后在对分解后的小波系数矩阵采用视觉特征进行融合处理,最后通过提升逆变换得到重构图像.实验表明该方法即使在图像信噪比较低的情况下,仍能得到较好的熵、边缘及较高分辨率的效果,且执行效率高.