溪源泄洪洞出口处闽江设计水位分析研究

溪源泄洪洞出口位于闽江之上,为分析泄洪洞出口处的设计水位,采用设计流量和水位流量关系推求法及实测水位资料推求法两种方法对工程设计水位进行计算,经过合理性分析,工程所在地近年水位变化剧烈,采用设计流量和水位流量关系推求法更符合现状情况,为工程建设提供可靠的设计成果。     

A2017半固态合金二次加热工艺及组织演化机制

相同加热温度条件下,随着保温时间的延长,晶粒逐渐长大和球化,液相分数增加;提高二次加热温度,晶粒长大和球化速度加快.在620～625℃加热,保温40～60min,可获得由均匀球形晶粒悬浮于液相组成的半固态组织,晶粒大小为70～90μm,液相率为40%～45%.而常规铸造枝晶A2017合金坯料二次加热后仍然保留粗大的枝晶网络结构.半固态合金锭坯二次加热初期晶粒的熔合合并是晶粒长大的主要方式,相界面能的升高和相界面表面张力是组织演化的主要驱动力.     

On mesh restrictions to satisfy comparison principles,maximum principles,and the non-negative constraint: Recent developments and new results

This article concerns mesh restrictions that are needed to satisfy several important mathematical properties—maximum principles, comparison principles, and the nonnegative constraint—for a general linear second-order elliptic partial differential equation. We critically review some recent developments in the field of discrete maximum principles, derive new results, and discuss some possible future research directions in this area. In particular, we derive restrictions for a three-node triangular (T3) element and a four-node quadrilateral (Q4) element to satisfy comparison principles, maximum principles, and the nonnegative constraint under the standard single-field Galerkin formulation. Analysis is restricted to uniformly elliptic linear differential operators in divergence form with Dirichlet boundary conditions specified on the entire boundary of the domain. Various versions of maximum principles and comparison principles are discussed in both continuous and discrete settings. In the literature, it is well-known that an acute-angled triangle is sufficient to satisfy the discrete weak maximum principle for pure isotropic diffusion. Herein, we show that this condition can be either too restrictive or not sufficient to satisfy various discrete principles when one considers anisotropic diffusivity, advection velocity field, or linear reaction coefficient. Subsequently, we derive appropriate restrictions on the mesh for simplicial (e.g., T3 element) and nonsimplicial (e.g., Q4 element) elements. Based on these conditions, an iterative algorithm is developed to construct simplicial meshes that preserve discrete maximum principles using existing open source mesh generators. Various numerical examples based on different types of triangulations are presented to show the pros and cons of placing restrictions on a computational mesh. We also quantify local and global mass conservation errors using representative numerical examples and illustrate the performance of metric.     

ISO标准版权保护最新政策解析

国际标准化组织(ISO)理事会于2017年3月15日批准了ISO最新商业政策──《ISO关于出版物分发、销售和复制及ISO版权保护政策》(ISO POCOSA 2017),9月在ISO全体大会上进行了解读,并拟于2018年1月1日正式实施,届时现行的ISO POCOSA 2012将被替代.相比较ISO POCOSA 2012,ISO POCOSA 2017在内容上发生了较大的变化,本文将对新的标准版权政策的内容进行解析,并分析其对我国的影响及我国应采取的应对措施.     

SCR技术半固态制浆及组织形成机理

采用单辊搅拌冷却技术(Shearing-Cooling-Rolling,简称SCR)制备A2017合金半固态浆料,对SCR工艺参数对半固态浆料组织的影响以及组织形成机理进行了研究.结果表明,熔体浇注温度和辊靴型腔高度对半固态浆料组织的影响显著,降低熔体浇注温度或减小辊靴型腔高度,半固态浆料组织从粗大的枝晶和菊花晶转变为细小的等轴晶或球形晶.组织形成机理分析表明,熔体首先在工作辊和靴子表面形核生长,在液流冲击及剪切搅拌的作用下晶核脱落游离进入残余液相区长大成菊花晶,在强烈剪切搅拌作用下,菊花晶断裂破碎最终形成非枝晶组织.     

A2017合金半固态压缩的变形机制和成形性能

利用Gleeble-1500热学-力学模拟机,对A2017半固态合金进行半固态压缩变形实验,分析了应力-应变曲线和组织变化,研究了压缩变形机制及成形性能结果表明,用单辊搅拌冷却(SCR)技术制备的A2017半固态合金的组织为细小均匀的非枝晶等轴晶,二次加热后可转化为均匀的球形晶和共晶液相组成的半固态组织;A2017合金半固态压缩变形的塑性好、变形抗力低;随着变形温度的升高或者变形速率的降低,变形的抗力降低.在稳定的流动变形阶段,A2017合金的半固态变形机制主要由液相流动和固相颗粒的转动与滑动组成,触变性能稳定,最大半固态加工变形范围为60%左右.     

Human–robot interaction in industrial collaborative robotics: a literature review of the decade 2008–2017

ABSTRACT

Currently, a large number of industrial robots have been deployed to replace or assist humans to perform various repetitive and dangerous manufacturing tasks. However, based on current technological capabilities, such robotics field is rapidly evolving so that humans are not only sharing the same workspace with robots, but also are using robots as useful assistants. Consequently, due to this new type of emerging robotic systems, industrial collaborative robots or cobots, human and robot co-workers have been able to work side-by-side as collaborators to accomplish tasks in industrial environments. Therefore, new human–robot interaction systems have been developed for such systems to be able to utilize the capabilities of both humans and robots. Accordingly, this article presents a literature review of major recent works on human–robot interactions in industrial collaborative robots, conducted during the last decade (between 2008 and 2017). Additionally, the article proposes a tentative classification of the content of these works into several categories and sub-categories. Finally, this paper addresses some challenges of industrial collaborative robotics and explores future research issues.     

Influence of heat treatments and anodization on fatigue life of 2017A alloy

In order to investigate the coupled effects of heat treatments and anodizing processes on fatigue life of aluminium alloy 2017A, a series of fatigue tests were conducted at 25 Hz. The effect of different tempers, naturally and artificially ageing (T4 and T6) and overageing (T7) conditions before sulphuric anodization were studied. Additionally, information on the microstructure of the anodic films was acquired by Scanning Electron Microscopy (SEM) analyses. The image analysis yielded qualitative information on the evolution of the surface morphology as a function of the substrate microstructure. Hence measured mechanical properties were directly related to the corresponding microstructure, the result of fatigue tests showed a decrease in fatigue life of anodized specimens as compared to untreated ones. This phenomenon became more pronounced in the T6 and T7 states. The decrease in the fatigue life could mainly be attributed to the brittle nature of oxide layer and to the heterogeneous microstructure of the film.     

超支化聚合物的合成及其在涂料中应用研究进展

首先介绍了超支化聚合物(HBP)的化学性质,并与传统线性聚合物的优缺点进行比较,接着对HBP的AB2单体缩聚、自缩合乙烯基聚合、自缩合开环聚合等合成方式进行了介绍,并对将来HBP的合成发展方向进行了推测.对现有HBP合成方法和末端官能团改性对比发现,在不同涂料体系中对HBP进行相应的改性是需要解决的首要问题.功能化改性HBP可作为涂料添加剂或主要成膜物质,有效地改善了涂料的流动性,降低了涂料中有机溶剂的挥发.重点结合HBP对涂料领域研究进行了概述,并介绍了近年涌现的HBP制备新策略、新方法.通过对HBP合成方法的探讨和众多末端官能团的不同修饰进行分析、对比和总结,介绍了HBP在UV固化涂料、高固体分涂料、有机-无机杂化涂料中的应用现状.结合相关研究,分析了HBP增强涂膜性能机理.最后基于HBP在涂料领域的应用现状,对今后研究侧重点提出相关建议和展望.     

典型碳酸盐岩渗透力学行为特征及其对储、盖性质的判定

目前对碳酸盐岩的研究主要关注其油气的储集空间,针对含油气盆地中碳酸盐岩的勘探也主要是为了寻找优质的油气储集体。然而,随着油气勘探向深层更古老的地层拓展,有效的碳酸盐岩储—盖配置显得至关重要。勘探证实,深埋条件下碳酸盐岩有利相带仍然发育高孔渗的优质储集体,然而是否发育与之配置的碳酸盐岩盖层就成为了制约深层碳酸盐岩油气勘探的关键因素。首次系统全面地通过对典型碳酸盐岩开展不同温度条件下三轴应力加载全过程渗透力学试验,得出了碳酸盐岩在破坏变形过程中渗透率随温度、围压的演化过程。试验分析结果显示,典型白云岩和典型灰岩在深埋应力作用过程中渗透力学行为特征具有明显差异,白云岩更多地显示出储集性能的特征,表现为脆—塑转换临界围压较大,岩石更容易形成裂缝,渗透率随温度的增加而增大等;而灰岩则表现出盖层的属性,体现在脆—塑转换临界围压小于白云岩,岩石相对容易形成密闭,渗透率随温度的增大逐渐减小。综合分析认为,白云岩和灰岩的纵向叠置能够形成有效的油气藏储—盖组合。