港口机械钢结构车间焊接烟尘治理方式研究

文章对港口机械钢结构车间焊接烟尘治理方式进行了深入研究。针对港口机械钢结构车间的特点和烟尘产生源,分析了焊接烟尘对工作环境和人员健康的影响,并对已有的烟尘治理方式进行了优缺点分析。在此基础上,提出了五种焊接烟尘治理方式,如移动吸气罩、分布式吸气臂、高负压吸尘焊枪、移动自吸式过滤器和移动式焊接烟尘净化器,并详细阐述了每种治理方式的原理、工作方式以及适用性分析。最后,通过实施效果评估,对各种焊接烟尘治理方式进行了比较分析,总结了实施效果,并给出了结论和对未来研究的展望。

The Analysis of Gas Absorption into a Stationary Droplet in Atmospheric Environment

Absorption of gaseous species into stationary droplets is a fundamental interest of mass transfer between liquid droplets and ambient gas, which plays a key role in atmospheric environment control and many industrial applications. In this paper, two different considerations including equilibrium and non-equilibrium relations at the interface are used to analyze and predict the absorption time for a physical absorption at a relatively low solubility of gas. For the equilibrium pattern, in the beginning period of absorption, the mass transfer rate is considerably rapid and afterward becomes slower and slower and finally comes to almost zero as the droplet concentration closes to the saturated value. Differently, when the non-equilibrium model is adopted, the interfacial concentration increases gradually with the bulk concentration of liquid droplet, and the absorption rate mildly decelerates with the increase of bulk one throughout the process, which leads to a longer absorption time. Based on the diffusion equation of species, the concentration distribution within the droplet at different times is computed. A solution for CO2 absorption into a small water droplet is given.

Benefits and Challenges of Urban Green Spaces

The aim of this paper is to illustrate the benefits,and challenges towards providing multifunctional urban green spaces.The results are based on critical analysis of study findings from different cities in Europe,America and to a lesser extent in Asia.Inner-city green spaces are especially important for improving air quality through uptake of pollutant gases and particulates which are responsible for respiratory infections.Due to their amenity and aesthetics,green spaces increase property value.To ensure multifunctional role of urban a green space is achieved,in particular the social and psychological role,certain standards of quantity,quality and distribution within the urban area should be adequately established.Green spaces need to be uniformly distributed throughout the city area,although each does not need to be extremely large but should be large enough to accommodate the city population.

面向飞行试验的混合层流机翼优化设计

层流减阻技术可大幅减小飞机摩阻,具有重要的应用前景。层流验证机是专为验证层流机翼设计技术研制的一型飞行试验平台,其中混合层流试验段主要用来验证前缘抽吸气对转捩位置的推迟效果。针对混合层流飞行试验首先开展了混合层流试验段设计约束分析和初步方案设计,随后开展了机翼和吊舱、挂架外形的高速气动优化设计。然后在此基础上,研究了不同吸气分布对吸气功率、流量和转捩推迟效果的影响,确定了最佳分布。最后通过风洞试验研究了最终优化构型的转捩特性。研究结果表明:优化后的混合层流试验段具有良好的高速气动特性,同时在设计点能验证前缘抽吸气对横流不稳定性的转捩抑制效果;折中吸气分布能保证吸气区大部分区域的吸气效果,并能降低吸气功率和流量。所得研究结果对混合层流机翼外形、吸气策略优化设计具有借鉴意义。