Seismic cracking analyses of two types of face slab for concrete-faced rockfill dams

Estimating the cracking capacity of the face slab and recommending effective crack-control measures are important for the anti-seismic safety of concrete-faced rockfill dams (CFRDs). In this paper, two-dimensional analyses of CFRDs are performed to simulate the seismic cracking behavior of conventional reinforced concrete (RC) face slab and a type of composite face slab. The composite face slab is composed of a ductile fiber-reinforced cement-based composite (DFRCC) layer and an RC substrate. For this purpose, a co-axial rotating smeared crack model for concrete and DFRCC is coupled with the generalized plasticity model for the rockfill material, and then implemented in a finite element program. The results show that during strong earthquakes, an RC slab is more likely to develop a penetrating macro-crack in its thickness dimension. In contrast, the crack-controlling composite slab demonstrates excellent resistance to seismic cracking, and no penetrating macro-cracks are observed. Major harmful cracks that form in the concrete substrate are stopped by the DFRCC layer in composite slabs.     

浅埋单层三跨地下结构在竖向地震作用下的动力响应

采用结构动力学方法,通过求解地下结构顶板的动力响应得到了单层三跨地下结构中柱在竖向地震分量作用下的动力响应.地下结构首先被看作是刚体,利用与地基的相互作用得到地下结构在竖向地震分量作用下的动力响应.其次,由于地下结构的对称性,取一半进行简化分析,侧墙对于顶板的约束用抗弯弹簧代替.再次,根据边界条件将之前的刚体动力响应作为输入,可以求得顶板的剪力.最后,通过之前求得的顶板剪力进而求得中柱的受力情况.结果表明,竖向地震分量对中柱的作用是显著的,甚至会对地下结构中柱产生严重的破坏.     

海底隧道地震动力响应研究

高水压作用下海底隧道的地震动力响应是一个需要深入研究的问题.基于Winkler地基模型,利用动力平衡条件和微分关系推导出了仅由弯曲引起的梁振动方程,利用分离变量法求得了海底隧道的振型和自振频率,并推导出了地震作用下海底隧道与地基之间的动力相互作用系数以及隧道结构位移表达式.通过算例计算研究了水压对于结构的自振频率、结构位移以及相互作用系数的影响.研究表明,高水压作用下结构的地震动力响应不可忽略.     

Stress-dilatancy of Zipingpu gravel in triaxial compression tests

Experimental investigations of the dilatancy and particle breakage of gravelly material from the Zipingpu concrete-faced rockfill dam, which was subjected to high-intensity seismic load during the 2008 Wenchuan earthquake, were conducted through a series of large-scale drained triaxial compression tests. A hyperbolic relation between the input plastic work and the degree of particle breakage was found for Zipingpu gravel, independent of the initial void ratio and confining pressures. The stress-dilatancy for Zipingpu gravel was analyzed and compared with data from two rounded alluvial and three angular quarried gravelly and rockfill materials in the literature. A nearly linear relationship between the dilatancy D~p and the stress ratio η was found at medium-to-large stress ratios before the peak stress ratio. The slope of the stress-dilatancy line before peak had slight dependence on the void ratio and confining pressure of the gravel. After peak, the stress-dilatancy relation shifts down compared with that before peak for the gravel specimen. The phase-transformation stress ratio decreased with increased confining pressure, with the exception of sub-rounded gravel with little particle breakage. A nearly linear relationship was found between the phase-transformation stress ratio M_f and the state parameter y for the Zipingpu gravel, regardless of the void ratio and confining pressure of the specimens.     

基于广义微状态的运动想象分类研究

该文根据传统微状态的概念,提出了一种广义微状态定义,并基于该定义实现了一种多分类运动想象任务特征提取算法。该文使用实验室2分类数据和2008年国际脑机接口竞赛4分类数据集对提出的特征提取算法进行了测试。对2分类数据特征用最小夹角算法分类,准确率最高达到95.56%;对多分类数据特征用SVM算法分类,效果稳定,其中竞赛数据4分类kappa分析结果接近2008年竞赛获胜者水平,测试结果验证了算法的有效性。     

Effects of laser heat treatment on the fracture morphologies of X80 pipeline steel welded joints by stress corrosion

The surfaces of X80 pipeline steel welded joints were processed with a CO2 laser, and the effects of laser heat treatment （LHT） on H2S stress corrosion in the National Association of Corrosion Engineers （NACE） solution were analyzed by a slow strain rate test. The fracture morphologies and chemical components of corrosive products before and after LHT were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively, and the mechanism of LHT on stress corrosion cracking was discussed. Results showed that the fracture for welded joints was brittle in its original state, while it was transformed to a ductile fracture after LHT. The tendencies of hydrogen-induced corrosion were reduced, and the stress corrosion sensitivity index decreased from 35.2% to 25.3%, indicating that the stress corrosion resistance of X80 pipeline steel welded joints has been improved by LHT.     

锥度量空间中四个自映射的公共不动点定理

在完备的锥度量空间中讨论了4个自映射的公共不动点定理,其存在性和唯一性得到证明。所得主要结果将锥度量空间中的公共不动点定理进行了推广。     

全浮芯棒二辊孔型中轧管金属变形行为研究

为分析连轧荒管管壁收缩的原因,借助有限元模拟软件MSC.Super Form,对宝钢Φ140 mm全浮芯棒连轧管机组Φ119 mm主孔型系钢管的单机架轧制过程进行数值模拟仿真,研究轧制过程中不同工艺参数对金属变形行为的影响,分析产生壁厚收缩缺陷的倾向性。结果表明：孔型顶部的壁厚压下量一定时,孔型开口处壁厚随空减坯径壁比的增大由＂增壁＂变为＂减壁＂,并且存在一临界径壁比;径壁比一定时,孔型开口处壁厚变化随压下量的增大由＂增壁＂变为＂减壁＂,并存在临界压下量;径壁比、压下量均一定时,单机架轧制高钢级时孔型开口处壁厚值相对较大。     

生态敏感性评价研究进展

生态敏感性评价不仅为分析和预测区域生态系统失衡和环境问题提供依据,而且是生态环境影响分析和城市生态系统建设调控的重要内容和环节。文章总结了生态敏感性评价的内涵,从生态敏感性评价对象、评价方法和步骤、评价体系建立的方法、评价权重确定和评价模型选择的方法等方面,阐述了当前生态敏感性评价的研究进展,分析了生态敏感性研究存在的不足,并对生态敏感性的应用前景做出了展望。     

Separation of propylene and propane with a microporous metal–organic framework via equilibrium-kinetic synergetic effect

Adsorption separation of olefin and paraffin can greatly lower the energy consumption associated with the currently utilized distillation technique but remains a great challenge. Herein, we report the efficient separation of propylene (C₃H₆) and propane (C₃H₈) in a phosphate anion-functionalized metal–organic framework (MOF) ZnAtzPO₄ by synergetic effect of equilibrium and kinetics. The material features periodically expanded and contracted apertures decorated with electronegative groups, offering eligible pore shape and pore chemistry to effectively trap C₃H₆ under moderate isosteric heat of adsorption (27.5 kJ mol⁻¹) while obstruct the diffusion of C₃H₈. It simultaneously combines excellent thermodynamic selectivity (uptake ratio of 1.71) and kinetic selectivity (~31) for C₃H₆/C₃H₈ separation, meanwhile can be easily regenerated. Breakthrough experiment for C₃H₆/C₃H₈ gas mixture was conducted and confirmed the outstanding separation capability of ZnAtzPO₄. The equilibrium and kinetics cooperative C₃H₆/C₃H₈ adsorption separation was for the first time found in anion-functionalized MOFs, and further confirmed by computational studies.