Effect of post heat-treatment on the microstructure and high-temperature oxidation behavior of precipitation hardened IN738LC superalloy fabricated by selective laser melting

The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior.The as-built microstructure showed fine cell and columnar structure due to high cooling rate.Ti element segrega-tion was observed in inter-cell/inter-columnar area.After post heat-treatment,the initially-observed cell structure disappeared,instead bimodal Ni3(Al,Ti)particles formed.High temperature(1273 K and 1373 K)oxidation test results showed parabolic oxidation curves regardless of temperature and initial microstructure.The as-built IN738LC fabricated via the selective laser melting process displayed oxida-tion resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast process.Heat-treated SLM IN738LC,although had similar oxidation weight-gain values to those of the SLM as-built material at 1273 K,showed relatively better oxidation resistance at 1373 K.Bimodal Ni3(Al,Ti)precipitate formed in the post heat treatment changed the local chemical composition,thereby led to changes in alumina former/chromia former location and fraction on the alloy surface.It was concluded that in heat-treated IN738LC increased alumina former fraction was found,and this resulted in excellent oxidation resistance and relatively low weight-gain.     

热处理对聚乙烯醇薄膜性能的影响

对聚乙烯醇薄膜进行了热处理,并测试了热处理后薄膜的力学、光学及电学性能,结果表明:增加热处理时间与升高热处理温度对改变聚乙烯醇薄膜的力学性能、光学性能和表面电阻率等效;随着热处理时间的增加或热处理温度的升高,其力学性能增强,光学性能略有下降,表面电阻率增大。     

Post combustion CO2 capture by carbon fibre monolithic adsorbents

As generation of carbon dioxide (CO₂) greenhouse gas is inherent in the combustion of fossil fuels, effective capture of CO₂ from industrial and commercial operations is viewed as an important strategy which has the potential to achieve a significant reduction in atmospheric CO₂ levels. At present, there are three basic capture methods, i.e. post combustion capture, pre-combustion capture and oxy-fuel combustion. In pre-combustion, the fossil fuel is reacted with air or oxygen and is partially oxidized to form CO and H₂. Then it is reacted with steam to produce a mixture of CO₂ and more H₂. The H₂ can be used as fuel and the carbon dioxide is removed before combustion takes place. Oxy-combustion is when oxygen is used for combustion instead of air, which results in a flue gas that consists mainly of pure CO₂ and is potentially suitable for storage. In post combustion capture, CO₂ is captured from the flue gas obtained after the combustion of fossil fuel. The post combustion capture (PCC) method eliminates the need for substantial modifications to existing combustion processes and facilities; hence, it provides a means for near-term CO₂ capture for new and existing stationary fossil fuel-fired power plants.This paper briefly reviews CO₂ capture methods, classifies existing and emerging post combustion CO₂ capture technologies and compares their features. The paper goes on to investigate relevant studies on carbon fibre composite adsorbents for CO₂ capture, and discusses fabrication parameters of the adsorbents and their CO₂ adsorption performance in detail. The paper then addresses possible future system configurations of this process for commercial applications.Finally, while there are many inherent attractive features of flow-through channelled carbon fibre monolithic adsorbents with very high CO₂ adsorption capabilities, further work is required for them to be fully evaluated for their potential for large scale CO₂ capture from fossil fuel-fired power stations.     

江滨大厦续建工程桩基补强处理与加固

江滨大厦续建工程,由于上部建筑方案改变,整体计算结果表明续建后部分框架柱柱底内力大于原设计并已施工完成桩基竖向承载力。根据地质勘察资料和工程试验报告,本工程采取后注浆处理方法,改善桩端持力层岩土力学性能,提高单桩竖向极限承载力的同时满足设计要求。     

后小康居住模式展望

本文根据全国一些经济发展快的城市和地区已经超越或即将超越“小康区间”的实情出发 ,提出了“后小康居住模式”,主要有“绿色”、“舒适”、便捷”、“安全”、“多样”和“信息” 6个特征。提出全国按经济水平分类制订有关住宅标准并滚动式发展的设想     

广州典型保障房居住空间环境质量使用后评价及评价指标 敏感性探索

根据环境参量的主观敏感性选择 指标是确保使用后评价效度的重要技术环 节,本研究利用现场测试与主观评价对照 研究的方法,调查了7个广州保障房小区的典 型平面与居室空间,获得了89组有效实测数 据及192份住户评价问卷数据。建成环境使 用后评价调查数据反映：广州典型保障房居 室的通风质量较优,空气质量和自然采光良 好;环境噪声总体上略高于标准值;热环境 的不满意率比较高。研究根据89组主客观配 对调查数据,经相关分析、ROC曲线分析和 二元Logistic回归分析过程,得出了重要室内 环境评价指标的主观敏感性排序,即温度> 湿度>自然采光照度>PM2.5,而环境噪声指 标的实际价值需要进一步验证。     

Flexural strength analysis of non-post-tensioned and post-tensioned concrete-filled circular steel tubes

Concrete-filled circular steel tubes (CFT) have recently gained significant attention for their enhanced strength and ductility over the conventional steel and reinforced concrete construction. The concrete compressive strength is significantly increased by the lateral confinement provided by the steel tube and local buckling of the steel tube is restrained by the concrete infill. This paper investigates the further enhancement of these composite actions due to post-tensioning the concrete cores inside circular steel tubes. The flexural behavior of a post-tensioned CFT as well as a non-post-tensioned CFT was studied experimentally and analytically. A numerical algorithm for predicting the moment capacities of circular CFT, with or without the post-tensioning effects, has been validated against the test results by the authors as well as those published in the literature.     

More decidable instances of Post's correspondence problem: beyond counting

We present a new technique to decide or reduce instances of Post's correspondence problem. It generalizes balance arguments to a consideration about some special context-free languages which allow the combination with other decision (or reduction) techniques. In spite of its simplicity, the new technique is able to decide more instances than known techniques.     

浅谈某工程桩基设计

结合某工程桩基实例,对冲(钻)孔桩基设计中的后注浆、负摩阻、抗拔等问题进行探讨、分析,得到一些有意义的结论可供类似工程设计参考。     

学修视角下的中国汉传佛寺空间格局研究——由三个古代佛寺平面所引起的思考

本文以汉传佛寺空间格局为主要研究对象,从“学修体系-建筑载体”互动关系这-新视角。以“教育目标-学修体系-组织方式及管理制度-建筑空间格局”这一逻辑演进的脉络为研究模型。对中国汉传佛教不同历史时期的典型佛寺类型如“道宣式”、“百丈式”、“后百丈式”等。进行了梳理和研究。这一研究,是让活的人的因素重新回归佛寺建筑研究。是一种“正本清源”式的思路,成为理解古今佛寺空间格局嬗变的一把钥匙。