Quality improvement of shunt active power filter with direct instantaneous power estimator based on Virtual Flux

This paper presents a new control strategy which is based on a switching table applied for Virtual Flux Direct Power Control (VF-DPC) of voltage source inverter based shunt active power filter (SAPF). This control method is applied to eliminate harmonic pollution and compensate the reactive power in the presence of nonlinear loads and unbalanced sources. Its main goal is to select switching states of the SAPF converter appropriately based on a look-up table established by hysteresis controllers acting on the instantaneous error between the commanded and VF-estimated values of active and reactive power. Our method aims to improve the electrical quantity behavior in steady and dynamic states while reducing the installing cost of the filter through eliminating the AC line voltage sensors. Facing to disturbances affecting the electrical network, a phase locked loop (PLL) has been integrated.The control strategy proposed for the active filter has been tested in the Matlab/Simulink environment.     

Recursive algorithm based on fuzzy 2-partition entropy for 2-level image thresholding

The fuzzy c-partition entropy approach for threshold selection behaves well in segmenting images. But the size of search space increases very rapidly when the number of parameters needed to determine the membership function increases. The computation complexity of the fuzzy 2-partition entropy approach is bounded by O(L³). In this paper, a recursive scheme which decreases the computation complexity of the basic algorithm to O(L²) is proposed. The approach does not need the calculation of the membership function. The processing time of each image is reduced from more than 5 min to less than 20 s.     

Simulation numérique des transferts thermiques entre une cavite enterrée et le sol : méthode des fonctions de transfert bidimensionnelles et sous-structuration

Numerical simulation of heat transfer between an earth-sheltered cavity and the soil: two-dimensional transfer functions method and subdivision. This paper describes the use of the two-dimensional transfer functions method for predicting the heat transfer between an earth-sheltered cavity and the surrounding ground. This method is first, applied for the generation of the transfer function coefficients for the system formed by the whole “earth-sheltered cavity–soil”. Then, the latter is decomposed into different layers. Each layer is characterised by its inputs and outputs and by its appropriate transfer functions coefficients. This technique allows a significant reduction in the computation time required to generate the transfer function coefficients of the cavity coupled to the soil. These methods are tested by comparing their results with those of the alternative directions implicit method (ADI) for various situations. The influence of parameters that have large effects on heat transfer such as the cavity depth, the thermal insulation, the nature and the thickness of the cavity walls are studied in typical climates.     

Diffusion of jojoba oil microencapsulated and impregnated onto compressive garment through a pig skin

Scientific developments are in progress in order to create compressive fabric in the medical field. This study focused on the development of a compressive garment in polyamide designated for severe burns in terms of pressure and hydration release. The fabric was then enhanced by adding a moisturizing treatment. The improvement consisted of the impregnation of ethylcellulose microcapsules containing jojoba oil on the textile surface of compressive garment. The kinetic of release of this active ingredient from the microcapsules, as well as its diffusion through the skin, were assessed using the in vitro Franz diffusion cell system. The results showed a controlled release of jojoba oil over time. The amount of oil released during the experiments (168?h) and that which penetrated through the pig skin did not exceed 1% of the total amount of jojoba oil microencapsulated and impregnated on the surface of a compression garment. This study permitted to obtain a compressive garment which presents hydration properties.     

Effect of the viscosity ratio on the morphology and properties of PET/HDPE blends with and without compatibilization

The influence of the molecular weight of polyethylene on the morphology and mechanical properties of blends of high‐density polyethylene (HDPE) dispersed as droplets in a poly(ethylene terephthalate) (PET) matrix at various compositions was investigated. The difference of morphologies can be easily explained by the influence of the molecular weight on the viscosity ratio and therefore, on the critical capillary number. The compatibilizing efficiency of copolymers containing glycidyl methacrylate groups was also addressed in relation to their nature, the protocol for their drying and the molecular weight of the HDPE phase. The increase of adhesion between PET and HDPE was found to have a larger influence on tensile properties than the reduction of interfacial tension. The amount of compatibilizer needed for adhesion improvement depends on the interfacial area that is defined by both the interfacial tension and viscosity ratio of the components. A qualitative relation between the optimum amount of compatibilizer and the critical capillary number can be written. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The Potential Use of Phosphatic Limestone Wastes in the Passive Treatment of AMD: A Laboratory Study

In Morocco, there are many sedimentary phosphate mines that produce large quantities of phosphatic limestone wastes (PLW) that contain calcite (46 wt%) and dolomite (16 wt%). These mines are located near contaminated sites, such as the abandoned Kettara pyrrhotite mine. The surface drainage water at the Kettara mine site has a pH of 2.9–4.2 and elevated concentrations of SO₄ (from 47 to 5,000 mg/L) and Fe (from 1 to 1,200 mg/L). The efficiency of PLW was assessed in the laboratory as an alternative alkaline material for passive acidic mine drainage (AMD) treatment. A series of experiments were carried out using a synthetic AMD (pH 3) containing Fe (500 mg/L), SO₄ (3.4 g/L), Ca (220 mg/L), Al (160 mg/L), Mn (20 mg/L), Zn (15 mg/L), Cu (23 mg/L), and trace amounts of Co, Cr, and Ni. Experiments were done in both anoxic and oxic conditions, in batch and column tests, with hydraulic retention times of 24 and 15 h, respectively. The PLW efficiently increased the alkalinity and pH, inducing precipitation of most metals. The neutralizing capacity of PLW prepared at different particle sizes (0.8 mm–0.5 cm, 0.5–1, 1–2, and 2–3 cm) was found to be similar in batch tests. The initial AMD value increased from 3 to 5–6.5 during the batch tests and 6.5–8 in the columns. In batch tests under anoxic and oxic conditions, there was a significant decrease in concentrations of Fe (500–120 mg/L), Al (160–1.7 mg/L), and Cu (23–0.002 mg/L). In the column tests, Al and Cu decreased (177–2.5 and 26–0.002 mg/L, respectively), while Fe decreased less significantly (618–300 mg/L). The availability and low cost of the PLW make its use in passive AMD treatment potentially feasible.