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61.
62.
使用2005~2017年遥感数据研究了全球大气边界层SO2时空分布特征及变化趋势.结果表明:空间分布上SO2呈现空间异质性,大气高SO2柱量值集中在以火山喷发为代表的自然源区域和以工业排放为代表的人为源及附近区域;一、二、三级SO2柱量值在全球范围内整体呈现纬度地带性分布特征,北半球受人为影响较为明显,分界线在陆地区域向南凸出,海洋上向北凹陷,而南半球受人为影响较小,分界线呈现与纬线平行趋势;2005~2017年全球大气边界层SO2单元栅格年均值整体呈现先增后减趋势,火山喷发导致2008、2009、2011年夏季出现了明显的波动,其余季节无显著变化;全球范围内大气边界层SO2年内变化,伴随太阳直射点南北移动,2005~2014年一级SO2柱量值延纬向对称轴的纬度,除10~12月份外,其余月份与对应月15日太阳赤纬基本吻合. 相似文献
63.
Jiaoping Xing Longyi Shao Wenbin Zhang Jianfei Peng Wenhua Wang Cong Hou Shijin Shuai Min Hu Daizhou Zhang 《环境科学学报(英文版)》2019,31(2):339-348
Traffic vehicles, many of which are powered by port fuel injection (PFI) engines, are major sources of particulate matter in the urban atmosphere. We studied particles from the emission of a commercial PFI-engine vehicle when it was running under the states of cold start, hot start, hot stabilized running, idle and acceleration, using a transmission electron microscope and an energy-dispersive X-ray detector. Results showed that the particles were mainly composed of organic, soot, and Ca-rich particles, with a small amount of S-rich and metal-containing particles, and displayed a unimodal size distribution with the peak at 600?nm. The emissions were highest under the cold start running state, followed by the hot start, hot stabilized, acceleration, and idle running states. Organic particles under the hot start and hot stabilized running states were higher than those of other running states. Soot particles were highest under the cold start running state. Under the idle running state, the relative number fraction of Ca-rich particles was high although their absolute number was low. These results indicate that PFI-engine vehicles emit substantial primary particles, which favor the formation of secondary aerosols via providing reaction sites and reaction catalysts, as well as supplying soot, organic, mineral and metal particles in the size range of the accumulation mode. In addition, the contents of Ca, P, and Zn in organic particles may serve as fingerprints for source apportionment of particles from PFI-engine vehicles. 相似文献
64.
Chin-Tsan Wang Thangavel Sangeeth Wei-Mon Yan Wen-Tong Chong Lip-Huat Saw Feng Zhao Chung-Ta Chang Chen-Hao Wang 《环境科学学报(英文版)》2019,31(1):163-168
Single-chamber sediment microbial fuel cells(SSMFCs) have received considerable attention nowadays because of their unique dual-functionality of power generation and enhancement of wastewater treatment performance. Thus, scaling up or upgrading SSMFCs for enhanced and efficient performance is a highly crucial task. Therefore, in order to achieve this goal, an innovative physical technique of using interface layers with four different pore sizes embedded in the middle of SSMFCs was utilized in this study.Experimental results showed that the performance of SSMFCs employing an interface layer was improved regardless of the pore size of the interface material, compared to those without such layers. The use of an interface layer resulted in a positive and significant effect on the performance of SSMFCs because of the effective prevention of oxygen diffusion from the cathode to the anode. Nevertheless, when a smaller pore size interface was utilized, better power performance and COD degradation were observed. A maximum power density of 0.032 mW/m~2 and COD degradation of 47.3% were obtained in the case of an interface pore size of 0.28 μm. The findings in this study are of significance to promote the future practical application of SSMFCs in wastewater treatment plants. 相似文献
65.
恶臭假单胞菌Pseudomonas putida 5-x细胞壁膜系统的Cu2+吸附性能 总被引:5,自引:0,他引:5
对1株从电镀废水中分离出的革兰氏阴性菌恶臭假单胞菌P.putida 5-x的细胞表面组分对Cu2+的吸附性能进行了分析研究.结果表明,分离的P.putida 5-x细胞壁膜的Cu2+吸附容量是完整细胞的5倍之多.细胞表面组分如肽聚糖层、细胞外膜和细胞内膜在P.putida 5-x细胞壁膜的Cu2+吸附过程中都发挥了作用.肽聚糖层、细胞外膜和内膜在P.putida 5-x细胞壁膜中的含量依次为细胞内膜>外膜>肽聚糖层,而它们的Cu2+吸附容量的大小依次为肽聚糖层>外膜>内膜.在P.putida 5-x细胞壁膜对Cu2+的吸附过程中,肽聚糖层贡献了不到15%的吸附容量,而细胞外膜和内膜分别贡献了30%~35%和25%~30%.P.putida 5-x细胞外膜中的磷脂含量明显比其它报道的革兰氏阴性细菌的细胞外膜高,这可能是P.putida 5-x细胞外膜具有较高Cu2+吸附容量的主要原因,并由此导致P.putida 5-x细胞壁膜的高Cu2+吸附容量. 相似文献
66.
基于隧道火灾不同横向火源位置的非对称卷吸影响,通过模拟计算分析了中心火源和偏置火源产生的烟气沿纵向最大温升变化规律,研究了顶棚下方近壁面区域内的不同温度分布,提出偏置火源纵向空间最大顶棚温升公式。结果表明:在壁面黏性作用下,沿纵向蔓延的烟气最高温度在顶棚下方呈现“温度边界层”分布;随着火源位置的偏移,下游出现偏置距离起主导作用影响温度衰减的区域,衰减速度相较于中心火源逐渐降低;火源下游近壁面最高温度位置逐渐远离顶棚后趋于稳定。研究结果对于排烟方式的设计以及空间通风效果的提升有着重要意义。 相似文献
67.
Saad A. El-Sayed Ahmed M. Abdel-Latif 《Journal of Loss Prevention in the Process Industries》2000,13(6):509-517
The critical temperature as well as the critical flux for ignition of a dust layer of cornflour and a mixture of wheatflour and cornflour (80% wheatflour+20% cornflour) on a hot plate have been determined. The moulded sample was cylindrical in shape and of different heights and diameters. The particle size of dusts ranged between 63 μm to 150 μm. The temperature–time histories for self-heating without ignition and with ignition are offered, showing the critical boundaries between them. Also the times to ignition for each dust, showing the effect of sample size on their values, are determined. Certain experimental correlations which relate to times to ignition, as well as the critical temperature for ignition and thermal and geometrical dimensions of sample are presented. 相似文献
68.
油层注水过程中水质不合要求的危害及保护措施 总被引:1,自引:0,他引:1
分析了油田在二次采油注水过程中,对水质的要求,讨论了水质不合格带来的危害并提出了保护措施. 相似文献
69.
In many industrial installations, particulate solids (cereals, agri-food products, coal, plants, etc.) are stored or processed. Self-heating of these products, which can lead to fires and explosions, can occur in a variety of situations. Examples include large storage at room temperature, formation of a layer on a hot surface, layer deposited on a surface – insulating or conductive – in a hot environment or even storage of product exposed to heating on one side.The main parameters that determine the occurrence of self-heating are the size of the container, the temperature, the residence time and the characteristics of the product. Depending on the type of situation encountered and these implementation conditions, the analysis of self-heating risks must be based on specific models and/or parameters.This paper presents the different variants and combinations of the theoretical model from the theory of thermal runaway to represent self-heating, taking into account in particular the symmetry or asymmetry of heating, reagent consumption and boundary conditions. It also discusses their adaptation to the previous identified industrial situations.Nine products were chosen to be representative of those used in the different considered industrial situations. They were subjected to self-heating basket tests in isothermal ovens in order to determine the parameters for applying the described theoretical models. These results were compared with the results of self-heating tests in layers of different thicknesses in a hot environment, on an insulating or conductive plate, using a specially developed test protocol, as well as with the results of standardized tests of minimum ignition temperature in 5 mm layers.This led to the proposal of the most appropriate theoretical model to represent the self-heating phenomenon for each of the four identified industrial situations.This analysis can promote better design of industrial equipment and production conditions (temperatures, volumes or product flows …) in order to prevent fires and explosions. 相似文献
70.
Stephan F. J. De Wekker D. G. Steyn J. D. Fast M. W. Rotach S. Zhong 《Environmental Fluid Mechanics》2005,5(1-2):35-62
Data from a comprehensive field study in the Riviera Valley of Southern Switzerland are used to investigate convective boundary layer structure in a steep valley and to evaluate wind and temperature fields, convective boundary layer height, and surface sensible heat fluxes as predicted by the mesoscale model RAMS. Current parameterizations of surface and boundary layer processes in RAMS, as well as in other mesoscale models, are based on scaling laws strictly valid only for flat topography and uniform land cover. Model evaluation is required to investigate whether this limits the applicability of RAMS in steep, inhomogeneous terrain. One clear-sky day with light synoptic winds is selected from the field study. Observed temperature structure across and along the valley is nearly homogeneous while wind structure is complex with a wind speed maximum on one side of the valley. Upvalley flows are not purely thermally driven and mechanical effects near the valley entrance also affect the wind structure. RAMS captured many of the observed boundary layer characteristics within the steep valley. The wind field, temperature structure, and convective boundary layer height in the valley are qualitatively simulated by RAMS, but the horizontal temperature structure across and along the valley is less homogeneous in the model than in the observations. The model reproduced the observed net radiation, except around sunset and sunrise when RAMS does not take into account the shadows cast by the surrounding topography. The observed sensible heat fluxes fall within the range of simulated values at grid points surrounding the measurement sites. Some of the scatter between observed and simulated turbulent sensible heat fluxes are due to sub-grid scale effects related to local topography. 相似文献