改进BP神经网络的再生粗骨料混凝土强度预测*

抗压强度作为评价再生混凝土主要性能指标之一,从四篇文献中搜集了43个抗压强度样本。基于改进的BP神经网络理论,建立了以再生粗骨料取代率、水灰比、龄期为输入,抗压强度为输出的神经网络模型,其结构形式为3-7-9-1。对该网络进行训练和学习,对并测试样本进行检测,结果表明,训练效率不仅大大提高,且而误差较小,并结合回归拟合系数,进一步表明该模型能够有效的的预测再生混凝土抗压强度值,能满足工程需要。     

Microstructure and tensile properties of rapid-cooling friction-stir-welded AZ31B Mg alloy along thickness direction

Rapid-cooling friction-stir-welding (FSW) was used to join AZ31B magnesium alloy plates of 6 mm in thickness. The microstructure and mechanical properties in thickness direction were carefully investigated with electron backscattered diffractometer, and transmission electron microscope. The obtained results showed that ultrafine grains with high dislocation density were obtained in the top region of the weld due to liquid CO₂ cooling. A large number of twins and second-phase particles were also induced in these refined grains. The basal texture intensity was significantly reduced due to the appearance of twins. The top region showed the higher strength and elongation compared with the bottom region, and the welding efficiency reached 93%. This work provided a simple and efficient strategy for manufacturing a gradient structure in the FSW Mg alloy joint.     

Deformation of a surface layer and coating application using a flexible tool

The microstructure and properties of the functional coatings formed by impact friction processing of product surfaces with a flexible tool are studied. It is established that the processing produces a hard nanostructured surface layer with fragments up to 0.13 µm in size, as it is achieved by severe plastic deformation.     

Tailoring electromagnetic absorption performances of TiO2/Co/carbon nanofibers through tuning graphitization degrees

Low density, high stability and strong dielectric loss capacity endow carbon-based nanocomposites with superb microwave dissipation performances. Different from grapheme or carbon nanotubes, the graphitization degrees of carbon-based composites derived from the organic precursor pyrolysis can be accurately regulated by controlling the carbonization temperature. As such, their electromagnetic properties can be easily tuned. In this work, we report the preparation of TiO₂/Co/Carbon nanofibers (CNFs) through a combined approach of electrospun and carbonization at different temperatures. The nanofibers with an average diameter of 300 nm were coated by a dense layer of TiO₂ and embedded by Co/CoO nanoparticles. The performance evaluation indicated the composite obtained at 700 °C exhibits remarkably strong absorption of −63.2 dB at 9.8 GHz and wide effective absorption bandwidth of 6.4 GHz with a pretty low filling rate of 15 wt%. Further analysis on the electromagnetic behaviors shows that the composite possesses regulable impedance matching characteristic and absorption performances, implying the huge application potential under various demand conditions.     

Prediction of Generation of High- and Low-Angle Grain Boundaries (HAGB and LAGB) During Severe Plastic Deformation

Metallurgical and Materials Transactions A - It is well known that a balance between the generation of low-angle and high-angle grain boundaries (LABG and HAGB) is achieved in materials undergoing...     

氧化铜沉淀法处理乙烯废碱液的研究

以氧化铜为沉淀剂处理乙烯废碱液,通过单因素实验,考察了沉淀法处理乙烯废碱液的反应时间、反应温度、沉淀剂投加量。沉淀法处理乙烯废碱液的最佳工艺条件:反应时间40 min、反应温度30℃、氧化铜投加量1.8 g。吸附法延续处理乙烯废碱液,乙烯废碱液中硫浓度由1113.25 mg/L降到1.98 mg/L,硫去除率达99.82%,COD浓度由800000 mg/L降到5600 mg/L,COD去除率达99.9%。     

对高层建筑中电气竖井、管道竖井设计的探讨

对高层建筑中电气竖井、管道竖井的设计进行讨论，探讨竖井的合并、最小尺寸的确定、预留孔洞的设置等设计中遇到的问题。     

全氧燃烧玻璃窑炉的寿命浅析

通过对国内外部分全氧燃烧玻璃窑炉的寿命统计,非正常停炉和常见故障等问题分析,找出影响窑炉寿命的因素,提出要以规范化、科学化、系统化的思维,通过新材料、新技术、新工艺的运用有效延长全氧燃烧玻璃窑炉的寿命,对目前全氧燃烧窑炉的建设、推广应用有积极的参考价值。     

新型钢沉井支护体系施工技术

针对传统钢板桩、钢筋混凝土沉井等支护体系存在的问题,提出了一种新型钢沉井支护体系施工技术。结合渭南供热管网工程中的基坑支护作业实例,重点介绍了该新型钢沉井的设计原理、施工工艺。实践表明:该新型体系具有自重轻、安装快速、可周转使用、下沉作业效率高等优点,并且具有较强的抗弯、抗压能力以及抗倾覆性能,可有效解决基坑变形和塌方等技术难题。