大口径主镜支撑液压缸用弹性膜片优化设计

在大口径望远镜主镜液压支撑形式中,液压缸需要一种简单可靠、不需要润滑维护的精密导向机构,而且可以输出较大行程范围(毫米级)。设计了一种柔性金属膜片机构用于液压缸的径向定位导向。建立了金属膜片机构有限元模型,采用几何非线性算法,研究分析了不同拓扑结构对金属膜片柔度的影响,通过不同拓扑结构金属膜片的性能分析对比可知,V 型膜片能够很好地克服应力刚化,保证柔度的稳定性;以柔度为优化目标,对金属膜片V 型的位置尺寸和形状尺寸进行了优化设计,金属膜片在导向方向上的柔度提高了14.2%;搭建了柔性金属膜片机构柔度测试平台,验证了仿真计算结果。结合实验和仿真结果可知:V 型柔性金属膜片具有良好的定位导向性能,对用于液压支撑的液压缸和主动光学的微位移促动器的导向机构的设计具有指导意义。     

Experimental investigation of edge restraint on punching shear behaviour of RC slabs

Current codes of practice usually do not consider the effect of edge restraint on the punching shear capacity of flat plate type reinforced concrete structures. As the punching shear provisions incorporated in various codes of practice are a direct result of the empirical procedures, they do not usually provide an accurate estimation of the ultimate punching load capacity of a slab with its edges restrained against rotation. This is because no account is taken of the enhancement of punching capacity due to the in-plane restraint in many types of reinforced concrete slab systems. A total of 16 model slabs with restrained and unrestrained edges have been tested in an effort to ascertain the influence of boundary restraint, thickness of the slabs on their structural behaviour and punching load-carrying capacity. Edge restraint has been provided by means of edge beams of various dimensions in order to mimic the behaviour of continuous slabs. The cracking pattern and load-deflection behaviour of the slabs tested have also been monitored closely.     

反渗透膜元件透过系数的试验与数学求解

明确了反渗透膜元件两透过系数求解所需的函数形式、幂项数、试验组数、试验点位、变量归一、回归分析及回归效果检验等一系列试验与数学过程,并给出了某支膜元件两透过系数求解的试验数据及其计算实例。     

HDPE土工膜在填埋场中的应用技术与施工工艺

本文分析了HDPE,即高密度级乙烯土工膜的特征,通过对比分析,结合国家对于填埋场中防渗材料的相关规定,深入介绍了HDPE土工膜在填埋场中的应用技术相关的施工注意事项。其中,HDPE 土工膜的选材及施工技术质量控制,对于保证防渗层使用可靠性具有极大的意义。     

车用质子交换膜燃料电池仿真技术路线

质子交换膜燃料电池作为燃料电池中重要的一种类型,可应用于汽车及小规模的发电站与便携式移动能源,是当前新能源领域的研究热点。主要针对车用质子交换膜燃料电池的三种仿真参数模型就当前国内外研究进展进行论述。     

Multidimensional modeling of biofilm development and fluid dynamics in a hydrogen-based,membrane biofilm reactor (MBfR)

A two-dimensional, particle-based biofilm model coupled with mass transport and computational fluid dynamics was developed to simulate autotrophic denitrification in a spiral-wound membrane biofilm reactor (MBfR), where hydrogen is supplied via hollow-fiber membrane fabric. The spiral-wound configuration consists of alternating layers of plastic spacer net and membrane fabric that create rows of flow channels, with the top and bottom walls comprised of membranes. The transversal filaments of the spacer partially obstruct the channel flow, producing complex mixing and shear patterns that require multidimensional representation. This study investigated the effect of hydrogen and nitrate concentrations, as well as spacer configuration, on biofilm development and denitrification fluxes. The model results indicate that the cavity spacer filaments, which rest on the bottom membranes, cause uneven biofilm growth. Most biofilm resided on the bottom membranes, only in the wake of the filaments where low shear zones formed. In this way, filament configuration may help achieve a desired biofilm thickness. For the conditions tested in this study, the highest nitrate fluxes were attained by minimizing the filament diameter and maximizing the filament spacing. This lowered the shear stress at the top membranes, allowing for more biofilm growth. For the scenarios studied, biomass limitation at the top membranes hindered performance more significantly than diffusion limitation in the thick biofilms at the bottom membranes. The results also highlighted the importance of two-dimensional modeling to capture uneven biofilm growth on a substratum with geometrical complexity.     

Bacterial inactivation in water,DNA strand breaking,and membrane damage induced by ultraviolet-assisted titanium dioxide photocatalysis

The effects of UV-assisted TiO₂-photocatalytic oxidation (PCO) inactivation of pathogenic bacteria (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium) in a liquid culture using different domains of UV irradiation (A, B and C) were evaluated. Structural changes in super-coiled plasmid DNA (pUC19) and genomic DNA of E. coli were observed using gel electrophoresis to demonstrate the photodynamic DNA strand breaking activity of UV-assisted TiO₂-PCO. Membrane damage in bacterial cells was observed using both a scanning electron microscope (SEM) and a confocal laser scanning microscope (CLSM). Both UVC-TiO₂-PCO and UVC alone resulted in an earlier bactericidal phase (initial counts of approximately 6 log CFU/mL) in 60 s and 90 s, respectively, in liquid culture. UVC-TiO₂-PCO treatment for 6 min converted all plasmid DNA to the linear form; however, under UVC irradiation alone, super-coiled DNA remained. Prolonged UVC-TiO₂-PCO treatment resulted in structural changes in genomic DNA from E. coli. SEM observations revealed that bacteria suffered severe visible cell damage after UVC-TiO₂-PCO treatment for 30–60 min. S. typhimurium cells showed visible damage after 30 min, which was confirmed using CLSM. All treated cells were stained red using propidium iodide under a fluorescent light.     

超滤膜组合工艺在青浦第三水厂设计中的应用

提出采用高效沉淀、臭氧生物活性炭与超滤膜组合工艺处理黄浦江上游微污染原水,并介绍了该工艺在上海市青浦第三水厂中的具体应用与设计参数。实际运行表明,该工艺可确保出厂水浊度<0.1 NTU、耗氧量<1.5 mg/L、氨氮<0.2 mg/L,处理效果稳定,供水安全性高。     

光伏组件作为建筑表皮时的美学语言

以建筑美学作为了解光伏建筑设计的切入点,利用设计学三大构成分析光伏组件的美学特性,进行运用形式美规律分析组件与建筑设计的一些处理手法,以期为涉足光伏建筑领域的设计师提供参考。     

MBR微滤膜在污水处理厂的清洗维护实践

针对MBR工艺常出现的膜污染问题,在实际运行过程中通过不断摸索、分析总结,探讨了MBR工艺微滤膜清洗维护的有效方法,为MBR工艺的进一步应用、发展提供参考.