The comparison of particle size distributions measured by sedimentation methods and laser diffraction shows the underestimation of the fine (clay) fraction. This is attributed mainly to the shape of clay particles being different than spherical. The objective of this study was to demonstrate differences in the results of particle size distributions of soils determined with the method of laser diffraction using two different dispersion units of the Malvern Mastersizer 2000.
A model for overcoming the gravity by sea-picoplankton cells is proposed here. It is based on different means of escaping from potential predators used by cells of co-existing picoplankton species. These different means cause friction anisotropy of motile cells with strong antipredator behavior (AB). According to equations of stochastic movement used in this model for picoplankton cells with strong AB, collocated with high concentration of cells with weak or absent AB, the sedimentation can be considerably overcome.
The aim of this work is to assess the possibilities of numerical simulation of the industrial slurry sedimentation process using ANSYS CFX software. Our work focused on the analysis of the simulation models available in the CFX module of the ANSYS to run the simulation of sedimentation based on the results of laboratory tests.
Heavy mineral assemblages were studied in onshore sandy deposits from the 26 December 2004 tsunami on Kho Khao Island, southern Thailand. The most common minerals included tourmalines, zircon, muscovite, biotite, limonites and opaque minerals. An abundance of micas and depletion in tourmalines allowed us to distinguish the tsunami deposits from modern beach sediments and pre-tsunami soils. Major lateral and vertical changes in the studied profiles were related to an increase in flake-shaped micas upward in the tsunami sequence as well as landward. These variations, although documented for one grain size fraction, corresponded well with changes in the grain size distributions of the whole samples. The observed changes probably reflect wave hydrodynamics and a change in the sedimentation mode from bed-load deposition to settling of the suspended load.
Proces osadzania cząstek stałych w stawach rybnych nie był dotychczas szerzej badany. Większość autorów badała namuły pochodzące ze zbiorników wodnych i jezior oraz z zapór przeciw rumowiskowych. Namuły te jednak różnią się od namułów stawowych w sposób dość znaczny. W pracy przedstawiono wyniki badań cech chemicznych (zwłaszcza zawartość metali ciężkich, co może wskazywać na sposób ich rolniczego wykorzystania), a także procesu osadzania osadów dennych w sześciu wybranych stawach rybnych, o zróżnicowanych cechach fizjograficznych zlewni rzek zasilających te stawy. Wykazano, że proces osadzania we wszystkich badanych sześciu stawach ma podobny przebieg z wyraźnie widocznymi charakterystycznymi fazami osadzania, a zawartość metali ciężkich w osadach nie jest szkodliwa i dlatego osady można wykorzystać rolniczo.
The city of Nairobi is the heart of both industrial production and the economic hub in Kenya and the Eastern Africa region. The city of Nairobi and its environs are drained by three streams, namely: Nairobi, Mathare and Ngong rivers. These streams drain areas of diverse land use activities. The land use changes in a spatial manner from the rich agricultural system through residential cum urban to industrial. The signifi cance of these various land use systems to pollutants generation, pollution, sediment generation and hence water pollution and quality degradation is quite enormous and worth investigation. The land use changes in a spatial manner making the basin ideal for a temporal variation of sediments yields along the river profi le and their impacts on the water quality status. This paper examines the results of study carried out within the basins in the years 1998–2006. The method of study involved water sampling and laboratory analysis to reveal the trends in sediment load increases downstream the investigated streams. Soil samples were also investigated to determine their relationship to soil erosion rates and sediment fl uxes. The study attempts further to fi nd the best sediment management strategies in reversing their increasing trends and restoring water quality within the basin.
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