F/M对活性污泥微生物生态网络的影响

为深入理解有机负荷率(F/M)对活性污泥(AS)微生物群落的影响,以F/M(以BOD/MLVSS计,下同)设计建议范围0.2～0.5 kg·(kg·d)-1为依据,将采集的AS样品分为3组,运用基于随机矩阵理论(RMT)的网络分析方法,解析了不同F/M条件下的AS微生物生态网络拓扑性质及结构特征.结果表明,较低的F/M...     

恶臭假单胞菌Pseudomonas putida 5-x细胞壁膜系统的Cu2+吸附性能

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.     

隧道内偏置火源顶棚近壁面温度边界层效应研究

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。     

Smoldering combustion of dust layer on hot surface

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.     

油层注水过程中水质不合要求的危害及保护措施

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.     

近岸海域石油污染生物修复技术的研究进展

生物修复技术是治理大面积污染区域的一种有价值的修复方法。对国内外最新的生物刺激和生物强化技术进行调研,总结了该技术对治理近岸海域石油污染的研究进展,分析总结了施加营养盐技术对海洋环境的影响,以及生物修复技术尚存在的一些局限性。     

Ignition temperatures of dust layers and bulk storages in hot environments

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.     

快生型大豆根瘤菌(Rhizobium fredii)内源质粒在培养及共生过程中的稳定性

以湖北洪湖公离的快生型大豆根瘤菌为材料，考察了它们的内源质粒在培养过程及共生过程中的稳定性．结果表明，所有供试菌株的质粒在培养条件下比较稳定，传代50次后没有明显变异．对其中2个菌株与4种不同的大豆宿主共生过程中质粒的稳定性研究，发现HA12－1－12的共生质粒和隐性质粒高度构定，HA7－2－2的质粒却发生了不同程度的变异．质粒检测的结果及RFLP分析表明，HA7－2－2共生质粒的稳定性高于隐性质粒，而且共生质粒上携带的nodDABC和nifHDK基因相当保守，不易受宿主的影响而产生变异．盆栽试验的结果也说明，虽然HA7－2－2的内源质粒在共生过程中发生了遗传重排，但它的共生性状没有明显的变异．     

The performance of RAMS in representing the convective boundary layer structure in a very steep valley

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.     

Structure of turbulent plumes from a momentumless source in a smooth bed

The spatial development of a passive scalar plume is studied within the inhomogeneous turbulence of a boundary layer flow in a recirculating laboratory flume with a smooth bed. The source of the scalar is located flush with the bed, and the low-momentum source design is intended to simulate a diffusive-type scalar release. A weakly diffusive fluorescent dye is used as the scalar. Planar laser-induced fluorescence (PLIF) techniques were used to record the structure of the plume at a spatial resolution of 150 μm. The measured structure of the mean concentration field is compared to an analytical solution for shear-free, homogeneous turbulence. The laboratory plume exhibits spatial development in the mean concentration field that deviates from the self-similar behavior predicted by the analytical solution; this deviation is due to the mean shear and inhomogeneity of the turbulence. In particular, the influence of the viscous sublayer on the plume development is seen to be significant. Nonetheless, the analytical solution replicates some of the features seen in the laboratory plume, and the solution suggests methods of reducing the laboratory data even for cases where the results deviate from the analysis. We also examine the spatial development of the root-mean-square (rms) fluctuating concentration field, and use scalar probability density functions to examine the relationship between the mean and fluctuating concentrations.