北京2019年冬季一次典型霾污染特征与成因分析

为研究北京冬季霾污染过程的污染特征和成因,以北京2019年12月一次典型PM2.5污染过程为分析对象,利用气溶胶垂直探测资料、边界层气象场和近地湍流资料,对霾不同污染阶段的特征与边界层理化特性的演变进行综合分析.结果表明:①观测期间北京共经历两次污染生消,历时5 d,PM2 5小时浓度最高220μg?m-3,超过重度污...     

Mechanisms Providing for Species Coexistence in the Herb-Dwarf Shrub Layer of a Southern Taiga Birch Forest

Individual species coexisting in the herb-dwarf shrub layer of a mature southern taiga birch forest were studied with respect to their limitation by different environmental resources and differences in the time or localization of the intensive utilization of deficient resources. The results made it possible to estimate the significance of different mechanisms of species coexistence in multispecific communities for herbaceous and dwarf shrub species of the forest phytocenosis studied.     

The application of iron mesh double layer as anode for the electrochemical treatment of Reactive Black 5 dye

In this work a novel anode configuration consisting of an iron mesh double layer is proposed for the electrochemical treatment of wastewater. The removal of Reactive Black 5 dye(RB5) from synthetic contaminated water was used as a model system. At a constant anode surface area, identical process operating parameters and batch process mode, the iron mesh double layer electrode showed better performance compared to the conventional single layer iron mesh. The double layer electrode was characterized by RB5 and chemical oxygen demand(COD) removal efficiency of 98.2% and 97.7%, respectively, kinetic rate constant of 0.0385/min, diffusion coefficient of 4.9 × 10~(-5)cm~2/sec and electrical energy consumption of 20.53 kWh/kgdye removed. In the continuous flow system, the optimum conditions suggested by Response Surface Methodology(RSM) are: initial solution p H of 6.29,current density of 1.6 m A/cm~2, electrolyte dose of 0.15 g/L and flow rate of 11.47 m L/min which resulted in an RB5 removal efficiency of 81.62%.     

SLP250二段式垃圾焚烧炉的燃烧调整

由于垃圾的热值和干、湿度等变化较大,所以,垃圾焚烧炉的燃烧调整具有一定的难度。简要论述了如何调整和控制垃圾焚烧炉的稳定燃烧,以供相关人员参考。     

城市生活垃圾中纤维素含量测定方法优化

对传统硫酸法进行改进,建立适用于城市生活垃圾纤维素含量的测定方法。以脂肪抽提时间、硫酸浓度、水解反应温度、水解反应时间、稀释硫酸浓度、回流时间为考察因素进行6因素5水平正交实验。结果表明,测定纤维素含量的最佳条件为：脂肪抽提时间4h、硫酸浓度70％、水解反应温度30℃、水解反应时间5h、稀释硫酸浓度5％、回流时间3h。优化后纤维素测定条件RSD均小于1．69％,平均回收率98．76％,表明该方法的精度高,可靠行强。     

火灾作用下单层球面网壳的非线性有限元分析

基于高大空间建筑火灾作用下的空气升温实用公式,按照欧洲规范规定的火灾高温作用下钢材的材料特性,考虑了温度对钢材特性的影响以及钢材屈服后的强化特征,对一凯维特单层网壳结构在火灾作用下的性能进行了非线性有限元分析,研究其在不同局部火灾作用下的温度场分布和位移特征,以及不同火源影响的最不利位置。结果表明:网壳结构在所有设计火源模型下的极限耐火时间都在20～30min左右;对于结构极限耐火时间,火源位置的影响大于火源面积的影响;结构中心向外延伸的第1环到第3环之间的区域,是结构抗火的薄弱部位。     

Fibre reinforced polymers in the sports industry – Life Cycle Engineering methodology applied to a snowboard using anisotropic layer design

Technological development has had huge impacts in sports performance throughout the years, fostering the development of specific materials and manufacturing processes for sports-related products. Within this context, a new technology for snowboards was developed taking advantage of the internal coupling effects of Fibre Reinforced Plastics (FRP) using an anisotropic layer design. This work deals with the technical, economic and environmental evaluation of a snowboard made of three alternative materials, namely carbon, glass and flax fibre reinforced plastics. It shows how a life cycle analysis can support the design and development of products by applying a Life Cycle Engineering methodology to the design process of a snowboard using an innovative technology. In this case, both the material choice and the fiber placement angles have a significant impact on the stiffness of the resulting FRP and thus in the three dimensions of analysis - cost, environmental and technical. The natural fiber is the most sustainable option environmentally, the glass fiber is the best one economically and the carbon fibre is the best in terms of technical performance. Therefore, the importance attributed to each dimension of analysis is pondered and traded-off to allow an aggregated analysis of the alternatives and a well-informed decision-making.     

城市屋面雨水绿地水平流渗透净化研究

把城区屋面汇集的雨水径流通过绿地或人工土层净化后收集利用或渗透地下,既可涵养地下水,又截留处置了部分雨水,减轻了雨洪负荷和雨水径流对受纳水体的污染,是一种经济有效的雨水利用方案。但为保证雨水渗入地下后不污染土层和地下水源,本文研究了屋面雨水在天然和人工配制的两种土壤中水平流动的净化作用及其规律。为屋面雨水绿地渗透方案的工程实施提供技术依据。     

嗜热厌氧细菌Clostridium sp.EVA4菌株直接转化纤维素产乙醇的研究

用分离获得的嗜热厌氧纤维素降解细菌 Ｃｌｏｓｔｒｉｄｉｕｍ ｓｐ ． Ｅ Ｖ Ａ４ 菌株进行了直接转化纤维素产生乙醇的动力学、发酵最适条件及其影响因子的研究．结果表明, Ｅ Ｖ Ａ４ 菌株在ｐ Ｈ６ ．２ ～８ ．９ ,θ４５ ℃～６０ ℃的范围内能直接转化纤维素滤纸产生乙醇,最适ｐ Ｈ 为７ ．５ ～８ ．０ ,最适θ为５５ ～６０ ℃． Ｅ Ｖ Ａ４ 菌株能利用纤维素滤纸,纤维素粉 Ｗｈａｔｍａｎ Ｃ Ｆ Ｉ Ｉ,微晶纤维素,纤维素粉 Ｍ Ｎ３００ 和未经处理的玉米秆芯,甘蔗渣,水稻秸秆产生乙醇．乙醇浓度 ,纤维素降解率和培养基还原糖浓度均随培养时间延长而增大．不同的纤维素材料、ｐ Ｈ、θ、底物浓度、酵母粉含量、振荡、培养气相、外加 Ｏ２ 和乙醇等条件均能影响 Ｅ Ｖ Ａ４ 菌株转化纤维素为乙醇的能力．最适条件下 Ｅ Ｖ Ａ４ 菌株利用１ ％ 纤维素滤纸培养１２０ ｈ 产乙醇浓度为１ １２３ ｍｇ／ Ｌ,纤维素降解率为５９ ％     

Turbulence closure models and their application in RAMS

Turbulence closures are fundamental for modelling the atmospheric diffusion in numerical codes and the resulting eddy diffusivities are key parameters in describing the transport and dispersion in the boundary layer. In this work, four turbulence closure schemes have been applied for reproducing a neutral flow over schematic complex terrain using the meteorological model RAMS. Two of the closures, a one-equation (E-l) and a two-equations (E-) model, have been implemented in RAMS in alternative to the ones originally available. In these cases, an analytical method based on the similarity theory for the atmospheric surface layer and boundary layer is adopted to calculate the empirical constants of the turbulence closures. Some examples of numerical studies performed to simulate the flow and turbulence over a 3-D hill in wind-tunnel experiment in neutral stratification are presented and discussed. An intercomparison of simulations related to different closures is considered by analysing the main features of the flow over the hill and by comparing calculated vertical profiles of turbulent kinetic energy with measured ones.