Vertical distribution of fauna in the bed sediment of three running water sites: Influence of physical and trophic factors

Relationships between invertebrates, substrate characteristics and trophic factors were investigated, with special emphasis on the hyporheic habitat, in order to characterize the functioning of different running waters ecosystems. Three contrasting study sites were chosen in catchments exhibiting different features: (1) a meandering reach of the Loire River in its alluvial floodplain, upstream of the ‘Bec d'Allier’; (2) a reach of the Galaure with a fairly developed riparian corridor, a small sinuous foothill river; and (3) a braided reach of the Drac, an alpine torrential stream. Each site was sampled once using the freezing-core technique with previous electro-positioning of the invertebrates. In each site, four 60 cm cores were extracted, each one from different morphodynamic units. In the Loire and Galaure rivers, most invertebrates are found in the first 15 cm of the sediment, with the exception of some particular taxa or morphodynamic units (riffle head). Conversely, in the Drac lotic units, maximum density of invertebrates occurs between 15 and 30 cm and more than 75 per cent of all organisms are found at a depth > 15 cm. The vertical distribution of organisms does not follow a uniform pattern in different streams. In the substrate, the vertical distribution of macroinvertebrates is very closely related to porosity in contrast with trophic parameters that always decrease with depth. The porosity is negatively correlated with the percentage of sand in the sediment and seems to be important in determining the vertical distribution of fauna, and should be integrated in a functional typology of running waters. The trophic parameters and the structure of invertebrate community with its dominant feeding groups allow discrimination of the different sites.     

薄层、超薄层测井技术的探讨

油田开发、勘探中的薄层测井技术与解释方法是当今测井技术的高难课题。本文就具有一定探测深度的高分辨率测井技术和研究方向进行了初步探讨,并介绍了目前声波测井、电测井、核测井的研究成果。     

水电枢纽下游河床下切问题的分析研究

河床演变过程极为复杂，影响因素较多，但尽管它们的表现形式不同，归根结底，是由于水流的输沙不平衡所引起的，当来沙量小于输沙能力时，河床发生冲刷：当来沙量大于输沙能力时，河床发生淤积，河床演变的结果是力图恢复水流输沙平衡，也就是说河床变形总是朝着使变形终止的方向发展。     

低温流态床炉的功能与用途

本文概述了低温流态床炉的多功能性,并论述了低温流态床炉在钢件、铝镁合金制件与精密弹性元件热处理方面的显著效益。     

磁流化床脱除烟气硫分的实验研究与初步理论分析

提出用磁流化床进行烟气催化脱硫的新方法 ,阐述了该脱硫方法的基本机理 ,并采用磁流化床进行了烟气脱硫的实验研究。结果表明 ,采用磁流化床技术可以提高脱硫效率。     

Effect of the type of bed material in two-stage fluidized bed gasification reactors on hydrogen gas synthesis and heavy metal distribution

Different bed materials were tested for two-stage fluidized bed gasification, and the hydrogen gas composition and heavy metal distribution in the syngas were investigated. Silica sand, zeolite, calcium oxide, calcined coal, and activated carbon were used. For the results, using activated carbon resulted in the most significant increase in hydrogen after second stage (16.3 mol%) and had highest ratio of hydrogen gas in the syngas (53.1 mol%). For distribution of heavy metals, using activated carbon as bed material in the second stage, the concentration of trapped heavy metals was the highest. Regarding the emission of heavy metals, the use of calcined coal and silica sand resulted in the greatest emission concentration, and activated carbon had the lowest emission concentration. Therefore, to increase the amount of hydrogen gas produced in the gasification process and limit the emission of heavy metals, activated carbon is the best choice of these five bed materials.     

床类家具模块化设计的研究

本文根据床类家具的使用功能将其分为支撑围合构件、承接构件、辅助装饰构件三大模块.其中支撑围合构件中的床屏模块是最主要的造型和使用模块,其变化和功能最为丰富,结构也最复杂.因此,本文将床屏模块又细分为框架和装饰两大构件,分别建立相应的模块库,再按照分类组合原则组合成丰富多样的产品,实现产品的多样化.这样,只需不断充实与更...     

燃用高挥发份、低灰份燃料的循环流化床锅炉设计

在循环流化床锅炉的设计中,根据燃料的燃烧传热特性,针对特定燃料采取合理的措施,进行优化设计.     

循环流化床锅炉主蒸汽压力的模糊控制

近年来循环流化床锅炉因其高效、低污染、低成本等特点得到了迅速的发展。但由于其燃烧过程十分复杂。很难建立被控对象准确的数学模型．因此难以实现常规方法的控制。本文设计了一个模糊控制器并进行了仿真研究，仿真结果表明模糊控制器对本文控制对象具有良好的控制性能．该控制方法可用于流化床锅炉燃烧系统这类复杂过程的控制。     

Characterization of temporal and spatial distribution of bed density in vibrated gas-solid fluidized bed

This study uses a Φ 200?mm?×?900?mm vibrated gas-solid fluidized bed (VGFB) with ?0.3?+?0.074?mm magnetite powder was utilized to characterize the temporal and spatial distribution of bed density in VGFB and the influence of bubble movement on fluctuations in bed density. The results indicate that the bed density decreases with an increase in gas velocity (U) and the frequency (f) and amplitude (A) of vibration and that the bed density spatial distribution is lower in the central region but higher in the border regions. The standard deviation of the density first increases then decreases and finally tends to stabilize with an increase in apparent gas velocity. Moreover, when A?=?2?mm, f?=?25?Hz and U?=?14?cm/s, the density distribution is 1.82–1.88?g/cm³ and the fluidization state is improved. The energy of the pressure signal increases with an increase in gas velocity and vibration amplitude. In particular, the low-frequency band of the pressure signal exhibits the highest amplitude and energy, which reveals that bubbles are the main cause of pressure fluctuation. Furthermore, the bed density decreases with an increase in bubble generation frequency, and the relationship between these follows the ExpDec 2 mathematical equation.