Evolution of size distribution and transfer of mineral particles between flocs in activated sludges: an insight into floc exchange dynamics

The aggregation behavior of activated sludge flocs was investigated by monitoring the size distribution of flocs and transfer of mineral particles between flocs, under various conditions of agitation and dilution. The results showed that (i) the shape of the floc size distribution can be fitted with a gamma function, (ii) a steady-state mean floc size is reached for a given stirring rate, (iii) this stable floc size is shifted towards floc growth as sludge concentration is increased, (iv) under cycled-shear conditions, microbial aggregates break up and re-form in an almost reversible manner, (v) blending of raw sludge and sludge spiked with Aquatal mineral particles results in particle exchange between flocs and (vi) the detailed study of exchange kinetics indicates that some flocs do not participate to the aggregation dynamics. These experimental results suggest that the activated sludge floc size is governed by a flocculation/deflocculation balance, implying an exchange of floc constituents between microbial aggregates.     

A Comparison Between Kinetic Test Results and Natural Weathering: The Abandoned Kettara Mine Tailings Pond

More than three million tons of sulfide tailings were discarded without any protection for more than 36 years at the since-abandoned Kettara mine. The impact of these tailings as well as the coarse wastes disorderly dumped on the surface site is highlighted by the elevated sulfate levels in the wells downstream of the wastes. Kinetic tests carried out on these sulfide tailings over 10 years ago, showed similar trends in metal dissolution despite large difference in test duration (21 and 53 weeks for the weathering and humidity cell tests, respectively). 40% of the sulfate release occurred in the first 3 weeks of the humidity test. However, in this study, the elevated sulfate levels in the groundwater was shown not be linked to the tailings, where the original sulfide material is still present under an oxidized layer of 10 cm–1.2 m. Thus, kinetic test results should not be extrapolated to field scale without accounting for site-specific factors, especially particle size and climate.     

Circular tunnel in a semi-infinite aquifer

The steady gravity flow that is generated by a circular tunnel disturbing the hydrostatic state of a semi-infinite, homogeneous and isotropic aquifer is solved exactly. Many aspects of the flow are found in closed analytical forms such as the water inflow, pressure, leakage and recharging infiltration, which give a complete view of the aquifer in the drained steady state. It is found that the maximum value of the recharging infiltration does not exceed the hydraulic conductivity allowing stating a criteria for recharge intervention to ensure the stability of the aquifer. In addition to the main results, two aspects of the water inflow are treated. These are the necessary modifications that are to be considered in the case of an inclined water table and in the case of a lined tunnel that develops a constant internal pressure. It is also found that under an inclined water table a tunnel may cease to drain on its complete circumferential edge and a limiting condition is stated. Furthermore, the Muskat–Goodman and other water inflow predictions are compared to the exact gravity water inflow.     

Testing and modeling of shear and peel behavior for bonded steel/FRP connections

This paper presents a technique used to evaluate the shear and peel stiffness of an adhesive system that bonds fiber reinforced plastic (FRP) and steel sections. The technique combines experimental results and analytical solutions and involves the simulation of the shear and peel behavior of the adhesive through two continuous spring systems. The experiments involve shear lap testing of FRP sheets bonded to hollow steel sections. A closed form analytical solution was derived for both the in-plane and out-of-plane behavior of the tested FRP sheets. The measured in-plane load-displacement relations were incorporated into the closed form solution to evaluate the spring constant simulating the shear behavior of the adhesive. The out-of-plane behavior of the FRP sheets was identified experimentally through outer face strain and out-of-plane displacement measurements. A curve fitting approach in which the closed form analytical solution was fitted to the measured out-of-plane displacement profile was then used to evaluate the spring constant simulating the peel behavior of the adhesive. The study focused on a methacrylate adhesive system since preliminary investigation has shown it is suitable for applications involving bonding plastic and metal surfaces. The spring constants evaluated in this study can be used to perform detailed modeling of a bonded FRP/steel connection under a general state of loading.     

Spatial heterogeneity of personal exposure to airborne metals in French urban areas

The spatial distribution of urban population exposures to ambient air particles was investigated as part of the Genotox'ER study conducted in four metropolitan areas (Grenoble, Paris, Rouen and Strasbourg) in France. In each city, 60 to 90 non-smoking adult and children volunteers were selected. Subjects lived in three different urban sectors: one highly exposed to traffic emissions, one influenced by local industrial sources, and a background urban environment. The Harvard Chempass multi-pollutant personal sampler was used to sample PM10 and PM2.5 particles during 48 h during two different seasons ('hot' and 'cold'). The elemental composition of the filters was analysed by Particle-Induced X-ray Emission (PIXE). Sixteen elements were found to be over the method detection limits: Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb. The relative concentrations of elements of crustal origin (Si, Al, Ca) were higher in the coarse fraction of PM10 filters, while elements associated with combustion processes (traffic emissions or industrial combustion) presented higher relative concentrations in the PM2.5 fraction (S, Ni, V, Pb). Spatial heterogeneity of elemental exposures by urban sector is substantial for some metals of health concern, with 20% to 90% greater exposure values, on average, in the traffic proximity or industrial sectors, compared to the background sector, for Fe, Zn, Cu, V and Cr. This spatial heterogeneity should not be overlooked in epidemiological or risk assessment studies.     

Non-linear analysis of FRP chimneys under thermal and wind loads

Due to their high corrosion and chemical attack resistance, Fiber Reinforced Plastic materials (FRP) are increasingly being used in the construction of industrial chimneys. To the best of the authors' knowledge, the current study represents the first analytical investigation aimed at describing the behavior of FRP chimneys under the effect of both thermal and wind loads. The study is conducted numerically using a consistent shell element model which includes the effect of large deformations. A simple material non-linearity model that accounts for cracks occurring in the resin is added to the shell element model. The finite element model is used to describe the typical structural behavior of FRP chimneys, assess the effect of cracking and determine the critical through-thickness temperature profile.     

Intracellular behaviour of samarium and europium in lactating mammary gland

The subcellular localization of samarium and europium, two rare-earths, increasingly used in both medical and industrial fields, has been studied in several organs such as liver and kidney but never in the mammary gland despite of its importance in the biology of lactation and nutrition domains. The intracellular behaviour of samarium and europium after their intra-peritoneal administration in the lactating mammary gland cells was investigated. The results showed the presence of very electron dense deposits in the glandular epithelial cell lysosomes. These particular lysosomes were never observed in the mammary cell lysosomes of control rats. These intralysosomal deposits were probably composed of insoluble samarium or europium phosphates by analogy with previous studies, the transmission electron microscopy, the ion mass microscopy and the electron probe microanalysis, and other techniques allowing the identification of the chemical structure of the intralysosomal deposits.     

Petrographic and petrophysical characterization of some Paleozoic rocks,Um Bogma area,Southwest Sinai,Egypt

Sixty-two samples were collected from the five formations at Um Bogma area, (Southwest Sinai, Egypt). Nine samples were collected from Sarabit El Khedim Formation, ten samples were collected from Abu Hamata Formation, eighteen samples were collected from Adedia Formation, eight samples were collected from Um Bogma Formation and eighteen samples were collected from Abu Thora Formation.The Paleozoic rocks at Um Bogma area, consist mainly of sandstones, siltstones, shales, limestone and dolostones, which are unconformably overlie igneous and metamorphic rocks (granite, diorite and gneiss) of Precambrian age.The petrographic studies were applied to identify different rock units, different facies and its diagenetic history and to reveal its effect on the storage capacity properties. Different types of porosity (oversized, intergranular, fracture and vuggy porosities) have been identified based on the petrographic investigation of the studied thin sections.The Paleozoic sandstone rock samples are characterized by porosity average about 19% for Facies 1 (quartz wack) and about 18%for Facies 2 (quartz arenite) and permeability average 420?mD for Facies 1 (quartz wack) and 690?mD for Facies 2 (quartz arenite), so these rocks can be considered as good reservoir rocks. The Paleozoic carbonate rock samples (Facies 3) are characterized by poor porosity (less than 7%) and very low permeability (less than 0.5?mD), which caused by matrix and diagenetic processes and refer to bad reservoir rocks.Porosity can be linked to the two derived electrical properties (formation resistivity factor and electrical tortuosity) of the studied Paleozoic rocks at Um Bogma area. The electrical tortuosity has significant effects on both permeability and formation resistivity factor. The permeability decreases with increasing electrical tortuosity and the relation between both of them is inverse relationship with good coefficient of correlation. The permeability decreases with increasing electrical tortuosity and the relations between both of them are inverse relationships with high coefficient of correlation. The formation resistivity factor increases with increasing electrical tortuosity and the relations between both of them are positive relationships with a fair to very high coefficient of correlation.     

Image processing applications performance study on Cell BE and Blue Gene/L

Two image processing applications, edge detection and image resizing, are studied in this paper on two HPC platforms namely the Cell BE and the Blue Gene/L machines. In this paper we focus on the performance scalability of the studied applications. Our results show that the scale of the problem to be solved highly affects the fitness of the platform. If the data set size is to fit into the Cell core, the fast on‐chip inter‐core communication of a multi‐core system pays back for its high technology design. On the other hand, the overhead of the distant communication in the massively parallel Blue Gene/L machine will only show its benefits for huge data set size that otherwise mandates multiple round‐trip data communications between the local memory of a core and main memory. Copyright © 2010 John Wiley & Sons, Ltd.