Study of the copper anode passivation by electrochemical noise analysis using spectral and wavelet transforms

The passivation of copper anode in sulphuric acid industrial electrolyte at 65 °C was investigated by electrochemical noise (EN) technique using three imposed anodic currents 153, 180 and 210 mA cm⁻² (galvanostatic or chronopotentiometric technique). The wavelet transforms and power spectral density (PSD) analyses have been employed to analyse the EN data. It has been found that during active dissolution the electrode surface is dominated by long time scale process and the change of the position of the maximum relative energy from D7 to D8 could be an indication of future passivation. This is associated in fast Fourier transform analyses by the disappearance of the low frequency plateau (white noise). During anodic dissolution the electrode surface was mainly undertaking general corrosion and the relative energy distribution was concentrated on large timescale crystals (D7-D8) with range of scale between 25.6 and 12.6 s. During passivation the electrode surface was dominated by short time scale process (D3), and during trans-passivation by medium (D4) followed by short time scale process (D2) with range of scale between 0.8 and 0.4 s, 1.6 and 0.8 s and 0.4 and 0.2 s, respectively. Crystals D2 and D3 could be related to metastable pitting and crystal D4 to localized corrosion.     

A novel multi-model neuro-fuzzy-based MPPT for three-phase grid-connected photovoltaic system

This paper presents a novel methodology for Maximum Power Point Tracking (MPPT) of a grid-connected 20 kW photovoltaic (PV) system using neuro-fuzzy network. The proposed method predicts the reference PV voltage guarantying optimal power transfer between the PV generator and the main utility grid. The neuro-fuzzy network is composed of a fuzzy rule-based classifier and three multi-layered feed forwarded Artificial Neural Networks (ANN). Inputs of the network (irradiance and temperature) are classified before they are fed into the appropriated ANN for either training or estimation process while the output is the reference voltage. The main advantage of the proposed methodology, comparing to a conventional single neural network-based approach, is the distinct generalization ability regarding to the nonlinear and dynamic behavior of a PV generator. In fact, the neuro-fuzzy network is a neural network based multi-model machine learning that defines a set of local models emulating the complex and nonlinear behavior of a PV generator under a wide range of operating conditions. Simulation results under several rapid irradiance variations proved that the proposed MPPT method fulfilled the highest efficiency comparing to a conventional single neural network and the Perturb and Observe (P&O) algorithm dispositive.     

Palmprint identification using feature-level fusion

In this paper, we propose a feature-level fusion approach for improving the efficiency of palmprint identification. Multiple elliptical Gabor filters with different orientations are employed to extract the phase information on a palmprint image, which is then merged according to a fusion rule to produce a single feature called the Fusion Code. The similarity of two Fusion Codes is measured by their normalized hamming distance. A dynamic threshold is used for the final decisions. A database containing 9599 palmprint images from 488 different palms is used to validate the performance of the proposed method. Comparing our previous non-fusion approach and the proposed method, improvement in verification and identification are ensured.     

Electrospray ionization mass spectrometry of tetracycline, oxytetracycline, chlorotetracycline, minocycline, and methacycline

The effects of mobile-phase additives and analyte concentration on electrospray ionization mass spectra of a series of tetracyclines were investigated in both positive and negative ion modes. Only [M + H](+) and [M - H](-) ions were observed. The greatest sensitivity as [M + H](+) ions was obtained with 1% acetic acid and the greatest sensitivity as [M - H](-) ions was obtained using 50 mM ammonium hydroxide. Sensitivities in the positive ion mode were greater than those in the negative ion mode. The sensitivity as [M + H](+) showed no systematic variation with pH; however, the sensitivity as [M - H](-) did increase with increasing pH. A larger linear range was observed for [M - H](-) than for [M + H](+) ions. Both [M + Na](+) and [M + H](+) ions were observed with 0.5 mM sodium acetate and sodium iodide, but no adduct ions were observed with ammonium acetate. Some M(2)H(+) ions were observed at higher concentrations. Cluster ions, Na(NaOAc)(n)(+) or Na(NaI)(n)(+), but no sample ions were observed using 5 mM salts. The data suggest that mechanisms in addition to solution ionization are involved in the formation of the ESI sample ions. The utility of mobile phases containing 1% HOAc or 50 mM NH(4)OH was demonstrated for chromatographic separations.     

A monoclonal antibody-based enzyme immunoassay for detecting parasite antigenaemia and antigenuria in Schistosomiasis mansoni

Both specific polycolonal antibody and monoclonal antibody against the microsomal antigen of adult S. mansoni were used to detect antigenaemia and antigenuria by antigen-capture sandwich ELISA in the sera and urine of patients infected with S. mansoni and other parasites. Antigenaemia was detected in 22 sera out of 100 of patients infected with S. mansoni but no antigenuria was detected. None of the sera of S. mansoni free patients were positive for microsomal antigen. More standardization of the technique and more refining of the reagents used is required to improve the sensitivity of the test.     

High-pressure steam curing of high-slag cement. II. Strength of cement-sand mixes

The strength of dense high-slag cement-sand mixes autoclaved at 180 lbf/in², and of certain aerated mixes autoclaved at pressures ranging from 120 to 210 lbf/in², has been determined. It was found that maximum strengths were developed in an autoclaving period of 5 h at 180 lbf/in², and that longer periods, as well as higher autoclaving pressures, yielded lower strengths. The maximum strength values obtained for compacted 1: 3 (w/w) mixes were 425 kg/cm² in the absence of fine quartz, and 510 kg/cm² in the presence of suitable addition of fine quartz. The corresponding values for Portland cement mixes were, respectively, 330 and 460 kg/cm² for a heating period of 5 h, and 360 and 505 kg/cm² for a period of 6 h.     

Studies on the anodic polarization of composite amalgams. The behaviour of manganese—Zinc amalgams in alkaline solutions

The anodic oxidation of manganese-zinc amalgams of different concentrations was studied in 0·1, 1·0, 2·0 and 4·0N NaOH solutions at 25°C. The polarization curves obtained under constant currents exhibited several steps corresponding to the formation of Zn(OH)₂, Mn(OH)₂, MnO₃ and oxidation of mercury before O₂ evolution took place. The effect of presence of zinc on the oxidation step of manganese is explained.     

Bifurcation analysis of a nonlinear coupled pitch–roll ship

The response of a two-degree-of-freedom system with quadratic coupling under a modulated amplitude sinusoidal excitation is studied and solved. The method of multiple scale perturbation technique is applied to obtain the bifurcation response equation near the combination resonance case in the presence of internal resonance of this system. The main attention is focused on the stability of the periodic solution and dynamical properties of local bifurcations of this system. The numerical solution and the effects of some parameters on the vibrating system are investigated and reported in this paper.     

Rheology and thermal conductivity of calcium grease containing multi-walled carbon nanotube

Recently, nanofluids attract considerable interest for enhanced rheological behavior and thermal performance. The aim of this research is to study the influence of additives Multi-Walled Carbon Nanotubes (MWCNTs) on the rheological behavior and its structure, thermal conductivity, and the influence of shear thinning rate on oil separation at different temperatures for calcium grease. Various concentrations of MWCNTs (0.5, 1, 2, 3, and 4%) have been added to the grease to obtain the best percentages that improve the properties of nanofluid. The microstructure of MWCNTs and nanofluid were examined by X-ray diffraction (XRD), Transmission Electron Microscope (TEM), and Scanning Electron Microscope (SEM). These experimental investigations were evaluated with a Brookfield programmable Rheometer DV-III ULTRA. The results indicated that the optimum concentration of MWCNTs was 3%, and the dropping point increasing about 11%. The rheological behaviors of the nanofluids show that the grease with various concentrations of MWCNTs demonstrates non Newtonian behaviors and the results indicated that the shear stress, apparent viscosity and thermal conductivity increase with the increase of volume concentration of MWCNTs to 65%, 52%, and% 56, respectively.