Biological treatment of saline wastewaters from marine‐products processing factories by a fixed‐bed reactor

Wastewaters generated by a factory processing marine products are characterized by high concentrations of organic compounds and salt constituents (>30 g dm^?3). Biological treatment of these saline wastewaters in conventional systems usually results in low chemical oxygen demand (COD) removal efficiency, because of the plasmolysis of the organisms. In order to overcome this problem a specific flora was adapted to the wastewater from the fish‐processing industry by a gradual increase in salt concentrations. Biological treatment of this effluent was then studied in a continuous fixed biofilm reactor. Experiments were conducted at different organic loading rates (OLR), varying from 250 to 1000 mg COD dm^?3 day^?1. Under low OLR (250 mg COD dm^?3 day^?1), COD and total organic carbon (TOC) removal efficiencies were 92.5 and 95.4%, respectively. Thereafter, fluctuations in COD and TOC were observed during the experiment, provoked by the progressive increase of OLR and the nature of the wastewater introduced. High COD (87%) and TOC (99%) removal efficiencies were obtained at 1000 mg COD dm^?3 day^?1. © 2002 Society of Chemical Industry     

Robust H ∞ output feedback control with pole placement constraints for uncertain discrete-time fuzzy systems

This paper investigates the problem of multi-objective control for a class of uncertain discrete-time fuzzy systems. The state-space Takagi–Sugeno T–S fuzzy model with linear fractional parameter uncertainties is adopted. Based on a linear matrix inequality approach and via so-called dynamic parallel distributed compensation, a fuzzy full-order dynamic output feedback controller is developed such that the L ₂ gain performance from the exogenous input signals to the controlled output is less than or equal to some prescribed value and, for all admissible uncertainties, the closed-loop poles of each local system are within a pre-specified sub-region of complex plane. Two numerical examples are provided to illustrate the effectiveness of the proposed design method.     

Environmental impacts of single and successive breakwaters along the Mediterranean coastline at Radès–Ezzahra, NE Tunisia

The coastline between Radès and Ezzahra, NE Tunisia, suffered from erosion during a strong storm in 1981. As a consequence, between 1985 and 1988, a single breakwater was constructed in Radès and two successive breakwaters in Ezzahra. The paper reports a study of the effectiveness of these structures and considers the other factors which influence the accretion/erosion of the shoreline.     

A chemiometric approach for phosphate inhibition of copper corrosion in aqueous media

The inhibition of copper corrosion in aqueous media by inorganic phosphates has been studied using a chemiometric approach (experimental and simplex designs). To achieve the objective, four steps were recognized. When submitted to aqueous aggressive media, the anion nature and its concentration were the important variables for the explanation of the mass loss variation. The most corrosive experimental conditions were: anion: chloride (Cl⁻); concentration: [Cl⁻] = 1 mol/l; exposure time: 24 h. In the second step, two inorganic phosphates, Na₃PO₄ and Na₅P₃O₁₀, are tested as copper corrosion inhibitors when the material is submitted to the severe conditions. The chemical structure was found to be the most influent factor. However, %IE varies between 25% and 56%. Then, we recognized a passivating treatment by submitting copper to inhibitor solution before immersion in the aggressive medium. Three parameters were studied: inhibitor structure, chemical concentration and passivation time (tp). We concluded that tp is the most influent experimental factor. The best passivating conditions are: inhibitor: Na₅P₃O₁₀; inhibitor concentration: [Inhibiteur] = 10⁻² mol/l and passivation time: 3 h. The inhibition efficiency was 89%. To increase %IE, a simplex design was also performed starting by the above obtained conditions and using the polyphosphate (Na₅P₃O₁₀) as inhibitor. The optimum experimental conditions for phosphate inhibition of copper corrosion in aqueous media are: inhibitor: Na₅P₃O₁₀, [Na₅P₃O₁₀] = 0.017 mol/l and passivation time tp = 2.17 h. Under these conditions an inhibition efficiency of 98% was reached.     

Microstructure characterization and tensile properties of direct squeeze cast and gravity die cast 2017A wrought Al alloy

Squeeze casting is a pressurized solidification process wherein finished components can be produced in a single process from molten metal to solid utilizing re-useable die tools. This one activates different physical processes which have metallurgical repercussions on the cast material structure. Desirable features of both casting and forging are combined in this hybrid method. 2017A aluminium alloy, conventionally used for wrought products, has been successfully cast using direct squeeze casting. Squeeze casting with an applied pressure removes the defects observed in gravity die cast samples. Tensile properties and microstructures are investigated. The results show that the finer microstructure was achieved through the squeeze casting. Furthermore, higher pressures improved the fracture properties and decreased the percentage of porosity of the cast alloy. The ultimate tensile strength, the yield strength and the elongation of the squeezed cast samples improved when the squeeze pressure increased.     

Electrochemical behaviour of an archaeological bronze alloy in various aqueous media: New method for understanding artifacts preservation

The aim of this work is to investigate the electrochemical behaviour of an archaeological bronze in several aqueous electrolytes (Na₂SO₄, NaCl, KOH, NaHCO₃ and Na₃PO₄) at 0.01 M. The anodic polarization revealed the dissolution of the material independently from the corrosive medium, but the damaging action is stronger for sulfate and chloride where the pH was below 7. Electrochemical impedance spectroscopy permitted to establish a damage ranking based on the pH of the electrolytes: SO₄^2– > Cl₃^– ≫ OH^– > HCO₃^– > PO₄^3–. Phosphate was tested successfully as inhibitor for archaeological bronzes against the corrosive action of sulfate and chloride.     

Extraction and functional properties of gelatin from the skin of cuttlefish (Sepia officinalis) using smooth hound crude acid protease-aided process

The characteristics and functional properties of gelatin from skin cuttlefish (Sepia officinalis) were investigated and compared to those of halal bovine gelatin (HBG). The gelatin extraction efficiency was improved by an acid-swelling process in the presence of smooth hound crude acid protease extract (SHCAP). The yields of gelatins from cuttlefish skin after 48 h with acid and with crude acid protease (15 units/g alkaline-treated skin) were 2.21% and 7.84%, respectively. The gelatin from skin cuttlefish had high protein (91.35%) but low fat (0.28%) contents. Compared to HBG, the cuttlefish-skin gelatin (CSG) has different amino acids composition than halal bovine gelatin. CSG contained slightly low hydroxyproline and proline (180‰) than HBG (219‰), whereas the content of serine was higher (49‰ versus 29‰). The gel strength of the gelatin gel from CSG (181 g) was lower than that of HBG (259 g) (p < 0.05) possibly due to lower hydroxyproline content. Cuttlefish-skin gelatin exhibited a similar emulsifying activity but greater emulsifying and foam stability than the halal bovine gelatin (p < 0.05). Foam formation ability, foam stability and water-holding capacity of CSG were slightly lower than those of the HBG, but fat-binding capacity was higher in the cuttlefish gelatin.     

Turbulence triggers vigorous swimming but hinders motion strategy in planktonic copepods

Calanoid copepods represent a major component of the plankton community. These small animals reside in constantly flowing environments. Given the fundamental role of behaviour in their ecology, it is especially relevant to know how copepods perform in turbulent flows. By means of three-dimensional particle tracking velocimetry, we reconstructed the trajectories of hundreds of adult Eurytemora affinis swimming freely under realistic intensities of homogeneous turbulence. We demonstrate that swimming contributes substantially to the dynamics of copepods even when turbulence is significant. We show that the contribution of behaviour to the overall dynamics gradually reduces with turbulence intensity but regains significance at moderate intensity, allowing copepods to maintain a certain velocity relative to the flow. These results suggest that E. affinis has evolved an adaptive behavioural mechanism to retain swimming efficiency in turbulent flows. They suggest the ability of some copepods to respond to the hydrodynamic features of the surrounding flow. Such ability may improve survival and mating performance in complex and dynamic environments. However, moderate levels of turbulence cancelled gender-specific differences in the degree of space occupation and innate movement strategies. Our results suggest that the broadly accepted mate-searching strategies based on trajectory complexity and movement patterns are inefficient in energetic environments.     

Modeling and control of photovoltaic and fuel cell based alternative power systems

Photovoltaic (PV) systems and fuel cells (FCs) represent interesting solutions as being alternative power sources with high performance and low emission. This work presents a modeling and control study of two power generators; photovoltaic array and fuel cell based systems. An MPPT approach to optimize the PV system performances is proposed. The PV system consists of a PV array connected to a DC-DC buck converter and a resistive load. A maximum power point tracker controller is required to extract the maximum generated power. Based on Incremental Conductance (INC) principle, the idea of the proposed control is to use a Fuzzy Logic Controller (FLC) that allows the choice of the duty cycle step size which is used to be fixed in conventional MPPT algorithms. The variable step is computed according to the value of the PV power-voltage characteristic slope. The second working system comprises a controlled DC-DC converter fed by a proton exchange membrane fuel cell (PEMFC) and supplies a DC bus. The mathematical model of the PEMFC system is given. The converter duty cycle is adjusted in order to regulate the DC bus voltage. Obtained simulation results validate the control algorithms for both of studied power systems.