长江漫滩地区复杂地质基坑施工监测技术

介绍长江漫滩地区厚层淤泥质软土和下伏富含承压水的复杂岩土条件下,采用SMW桩和钢板桩围护结构,基坑开挖进行了地表沉降变形、桩顶水平位移、深层水平位移和钢支撑轴力监测,监测数据与现场检测数据吻合较好,并将数据及时反馈,指导基坑开挖,以确保施工安全。     

多跨高墩连续刚构的设计与探讨

以汝城至郴州高速公路文明特大桥（主桥为66＋6×120＋66=852 m的连续刚构）为例,探讨了多跨高墩连续刚构在结构方案比选、合拢工艺和下部结构优化等方面的问题。     

浅埋偏压小净距隧道开挖顺序研究

采用改进的有限元强度折减法计算某浅埋偏压小净距隧道2种开挖方式在各个施工阶段的安全系数大小.比较这些安全系数,找到2种开挖方式在整个开挖过程中最容易产生破坏的施工步,得出浅埋偏压小净距隧道先开挖深埋侧可避免出现较危险的施工状态这一结论,希望对研究对类似工程的施工具有一定的指导意义.     

考虑混凝土损伤的双面组合连续梁挠度和裂缝宽度研究

钢-混凝土双面组合连续梁负弯矩区上混凝土板受拉会产生裂缝。利用ANSYS有限元软件,考虑了混凝土的拉应变软化特性,对钢-混凝土双面组合2跨连续梁模型进行数值模拟分析,得到了上混凝土板裂缝分布和宽度。将计算结果与实测结果进行比较,验证了该模型的有效性。通过变换下混凝土板厚度和混凝土极限拉应变值,分析其对双面组合梁挠度和裂缝的影响;采用最小二乘法,对荷载-挠度;荷载-最大裂缝宽度曲线进行拟合,得出相应的计算公式。     

Improved preimage attack on 3-pass HAVAL

HAVAL is a hash function proposed by Zheng et al. in 1992, including 3-, 4- and 5-pass versions. We improve pseudo-preimage and preimage attacks on 3-pass HAVAL at the complexity of 2¹⁷² and 2^209.6, respectively, as compared to the previous best known results: 2¹⁹² and 2²²⁵ by Sasaki et al. in 2008. We extend the skip interval for partial-patching and apply the initial structure technique to find the better message chunks, and combine the indirect-partial-matching, partial-fixing and multi-neutral-word partial-fixing techniques to improve the attacks based on the meet-in-the-middle method. These are the best pseudo-preimage and preimage attacks on 3-pass HAVAL.     

恶劣电磁环境下PLC控制系统抗干扰技术研究

该文结合工程实践,研究了某型船模PLC控制系统抗干扰技术。依据干扰产生的原因,分析了系统干扰的来源,并提出了抑制干扰的具体措施。通过硬件和软件的优化设计,提高了控制系统抗干扰能力。实践证明,经过优化设计的PLC控制系统运行安全,稳定,控制效果得到明显提高。     

Green-Naghdi theory, part A: Green-Naghdi (GN) equations for shallow water waves

In this work,Green-Naghdi (GN) equations with general weight functions were derived in a simple way. A wave-absorbing beach was also considered in the general GN equations. A numerical solution for a level higher than 4 was not feasible in the past with the original GN equations. The GN equations for shallow water waves were simplified here, which make the application of high level (higher than 4) equations feasible. The linear dispersion relationships of the first seven levels were presented. The accuracy of dispersion relationships increased as the level increased. Level 7 GN equations are capable of simulating waves out to wave number times depth . Numerical simulation of nonlinear water waves was performed by use of Level 5 and 7 GN equations, which will be presented in the next paper.     

K2_SPH方法及其在二维水波模拟中的应用(英文)

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian meshless particle method. However, its low accuracy of kernel approximation when particles are distributed disorderly or located near the boundary is an obstacle standing in the way of its wide application. Adopting the Taylor series expansion method and solving the integral equation matrix, the second order kernel approximation method can be obtained, namely K2_SPH, which is discussed in this paper. This method is similar to the Finite Particle Method. With the improvement of kernel approximation, some numerical techniques should be adopted for different types of boundaries, such as a free surface boundary and solid boundary, which are two key numerical techniques of K2_SPH for water wave simulation. This paper gives some numerical results of two dimensional water wave simulations involving standing wave and sloshing tank problems by using K2_SPH. From the comparison of simulation results, the K2_SPH method is more reliable than standard SPH.     

等壁厚钢管桩横向焊缝应力集中系数的数值模拟

大型海洋工程结构多常用钢管桩,在钢管桩的制作和安装过程中通常会产生环向对接焊缝,由管节偏位引起的环向焊缝应力集中现象是焊缝疲劳热点应力评估和焊缝疲劳安全分析的重要影响因素.通过实用近似分析方法,研究在轴向拉力和平面内弯矩单独作用下等壁厚对接焊缝应力集中间题,得出等壁厚拉弯构件对接焊缝应力集中系数的近似计算公式;根据对钢...     

海上沉船碍航概率风险评估

为对我国沿海水域沉船进行科学的风险评估及处置决策,确保通航船舶水上安全和畅通,基于事件树方法分析了通航船舶碰撞沉船事故的发生过程和机理,建立了沉船碍航概率风险评估模型.假定通航船舶在航路中的航迹线服从正态分布,根据沉船位置确定了通航船舶驶入碰撞航路的几何概率.根据国内外事故资料确定通航船舶发生异常而避碰失败的基准偏航概率,并考虑了风、流、能见度和交通密度等因素进行修正.通过对实际沉船碍航特性的评估,验证了该方法对沉船管理和处置决策具有实用性和可操作性.