无限水深聚焦波完全非线性数值模拟

基于势流理论提出一种新的高阶边界元方法对无限水深的聚焦波浪进行完全非线性数值模拟.自由水面满足完全非线性边界条件,模拟波浪的非线性效果可以达到更高阶.利用镜像原理,建立一种全新的格林函数应用到无限水深的数值波浪水槽中,以致于两无限深水槽侧壁的积分可以被排除.为了产生相应的入射波和吸收出流波浪,一个由点源组成的造波装置被布置于计算域内,同时人工阻尼层被用来吸引出流波浪,由波浪聚焦的方法得到极限波浪.通过开展线性和完全非线性聚焦波浪的数值实验及与理论解对比,验证本数值模型可以用来模拟无限深水域的极限波浪,且在出流边界没有反射.     

速度传感反馈地震计的参数稳定性分析

从理论上定量分析机械摆和环路滤波等开环诸参数变化对速度传感反馈地震计闭环参数的影响.研究指出,在环路设计中可半自由选取的开环阻尼取值对参数稳定性有重要影响.过大或过小的开环阻尼取值均可能造成参数稳定性急剧变差,影响地震计在只标不调的状况下长期连续稳定工作.     

白沙河地下水资源管理模型

针对白沙河地下水含水层的内部结构和本区开采特点以及已出现的环境问题，建立了地下水资源管理模型，确定了优化开采方案。该管理模型针对本区每年２个管理时段的长度及其开采量均不同的特点，导出了新的响应矩阵的公式。管理模型的建立有助于对该区地下水的合理开采。     

红层软岩压缩破坏的分形特征与级联失效过程

基于不同围压条件下的红砂岩三轴压缩试验结果,采用数字图像相关技术对岩样外表面破坏形态进行全程观测,获得不同阶段岩样外表面破坏图像,分别对岩样破坏后阶段的图像进行分析。通过分形盒维数表征岩样外表面裂纹的变化情况,发现岩样破坏越严重,裂纹分形维数越高,且在最后破坏阶段裂纹分形维数出现突变,揭示岩样的破坏特征。引入级联失效数学模型,结合红层软岩内部的矿物成分与细观结构分布特点,概化出其结构的随机连接模型与破坏方式,分析红层软岩加载作用下的内部节点颗粒“容量-荷载”重分配原则以及节点颗粒失效后其初始荷载传递路径。结果表明,红层软岩在受载时为一个级联失效的分阶段破坏过程,级联因子通过级联路径不断传播、增多,级联失效越发明显,同时结合岩石破坏的变形损伤过程与其轴向应力-应变曲线分段特征,揭示该类岩石破坏的级联失效分级标准,为拓展该领域的研究具备一定的参考价值。     

苏鲁造山带深部构造的接收函数图象

宽频地震探测获得横切苏鲁造山带的滨州-日照剖面和蓬莱-青岛剖面的接收函数图象。在图中识别出一系列密度界面和断裂面。新Moho面深度35~41km,形态清晰连续完整,表明苏鲁造山带形成以来的壳幔相互作用已经相当彻底。苏鲁造山带和胶辽朝地块的岩石圈底面深度105km,靠近郯庐断裂逐渐抬升到90km。在苏鲁造山带内部识别出了造山过程中形成的构造界面。它们所勾画出的深部构造图案支持扬子板块拖带北中国板块边缘深俯冲剥蚀模型,并且指示苏鲁超高压变质带的北界位于莱西一线的胶莱盆地之下。     

Improving integrity of RC beam-column joints with deficient beam rebar anchorage

In recent earthquakes in developing countries, severe damage was observed on reinforced concrete buildings. This study focuses on exterior beam-column joints with substandard beam rebar anchorage and seismic strengthening by installing wing walls. First, a series of experiments was conducted to investigate the seismic behavior of exterior joints with substandard beam rebar anchorage representing typical Bangladeshi buildings. Two 0.7-scaled exterior joint specimens were tested, and these specimens showed beam rebar anchorage failure and/or joint shear failure. Prior to strengthening of the joint, a series of pullout tests was conducted on postinstalled bonded anchors in low-strength concrete for strengthening design. Then, an experiment was performed to apply the strengthening method by wing walls to one of the exterior joint specimens to improve the integrity, and this method was intended to prevent the failure of beam rebar anchorage. The strengthening method is proposed to extend the development length of beam longitudinal bars by considering the embedment length along the wing walls. The test results verified the effectiveness and applicability of the proposed strengthening method to upgrade exterior RC beam-column joints with deficient beam rebar anchorage.     

Light curves for off-centre ignition models of Type Ia supernovae

We compare observations of the high-redshift galaxy population to the predictions of the galaxy formation model of Croton et al. and De Lucia & Blaizot. This model, implemented on the Millennium Simulation of the concordance Lambda cold dark matter cosmogony, introduces 'radio mode' feedback from the central galaxies of groups and clusters in order to obtain quantitative agreement with the luminosity, colour, morphology and clustering properties of the present-day galaxy population. Here we construct deep light cone surveys in order to compare model predictions to the observed counts and redshift distributions of distant galaxies, as well as to their inferred luminosity and mass functions out to redshift 5. With the exception of the mass functions, all these properties are sensitive to modelling of dust obscuration. A simple but plausible treatment agrees moderately well with most of the data. The predicted abundance of relatively massive  (∼ M _*)  galaxies appears systematically high at high redshift, suggesting that such galaxies assemble earlier in this model than in the real Universe. An independent galaxy formation model implemented on the same simulation matches the observed mass functions slightly better, so the discrepancy probably reflects incomplete or inaccurate galaxy formation physics rather than problems with the underlying cosmogony.     

型钢水泥土复合梁中型钢-水泥土相互作用试验研究

在深度不太大的基坑而条件适当时可采用小规格型钢加筋水泥土结构作为挡土墙,但对其破坏模式和刚度仍缺乏深入地研究。与以型钢刚度为主的SMW工法不同,加筋水泥土墙的刚度可能主要依赖于水泥土,型钢主要承担拉应力。打设了6根不同截面高度的模型梁,采用钢板模拟型钢作为加筋,以不同加载方式的水泥土复合梁抗弯试验,分析了试验条件下钢板-水泥土复合梁的破坏机理和抗弯组合强度和抗弯承载力。将复合梁的刚度变化划分为两个阶段,提出了分阶段的特征组合刚度计算方法。当承载力满足足够安全度要求时,建议工程设计时取第一阶段末的特征刚度来计算加筋水泥土挡土墙变形。     

浅海桶形基础平台抗拔力与抗倾稳定分析

平台在海上受风、浪、流、冰等水平载荷作用产生倾斜 ,而土壤粘接力、摩擦力和土抗力是平台的抗拔和抗倾力 ,桶基平台应满足抗拔、抗倾稳定的要求 ,以保证平台的整体稳定性。讨论了桶基平台受水平力作用时 ,桶形基础的破坏模式及其计算方法 ,阐述了抗倾稳定计算方法