Corrosion Inhibition of Mild Steel in Acidic Medium using 2-amino Thiophenoland 2-Cyanomethyl Benzothiazole

The corrosion inhibition characteristics of 2-amino thiophenol (ATP) and 2-cyanomethyl benzothiazole (CNMBT) on two types of steel in 1m HCl medium were investigated at different temperatures (25, 30, 35, 40 and 50°C). The pitting corrosion behaviour for the same system was studied using a potentiodynamic technique. The pitting corrosion resistance of steel samples increased with increase in concentration of the ATP and CNMBT. Some samples were examined by scanning electron microscopy. The effects of the inhibitors on the general corrosion of the two samples were investigated by using gravimetric and galvanostatic polarization techniques. The inhibition efficiencies increased with increase their concentration but decreased with increase in temperature. Free energies of activation, enthalpies and entropies for the inhibition processes were determined from rate constant data measured and different temperatures at different concentrations of ATP and CNMBT. Results were compared with fits obtained from the application of the Langmuir isotherm. Results were correlated to the chemical structure of the inhibitors. The inhibition efficiency of CNMBT is higher than that of ATP.     

Ambiguity attacks on SVD audio watermarking approach using chaotic encrypted images

In this paper, we study the robustness of the proposed watermarking algorithm by Al-Nuaimy et al. (Digit Signal Process 21(6):764–779 2011) for audio signals which is based on singular value decomposition (SVD). It has been concluded that it is fundamentally flawed in its design, in that it falls to two ambiguity attacks where the extracted watermark is not the embedded one but determined by the reference watermark. In the first attack, when a watermarked audio signal is rewatermarked by an attacker’s watermark, this one can be easily extracted to claim ownership of the original audio signal. In the second attack, during the extracting process when an attacker uses the singular vectors of his watermark, he can extract the attacker’s watermark. Therefore, he can claim ownership of the watermarked audio signal. The experimental results prove that the proposed attacks create a false positive detection in watermark extraction. Therefore, Al-Nuaimy et al. algorithm cannot be used for security systems, data hiding and copyright protection.

     

Efficient and secure cryptosystem for fingerprint images in wavelet domain

In this paper, a fingerprint image encryption algorithm is proposed in order to enhance the protection of fingerprint-based systems against replay attacks. The proposed algorithm is consisting of permutation and diffusion operations in wavelet domain, whereas, one-level Lifting Wavelet Transform Integer-to-Integer is performed to the original fingerprint image. The approximation and detail sub-bands are then partitioned into blocks and permuted using a permutation key. It is noteworthy that, for each sub-band the Rubik’s cube principle is applied. The encrypted image is constructed by ordering the encrypted sub-bands. Eventually, an experimental tests and security analysis were conducted on three fingerprint images attained through Fingerprint Verification Competition “FVC 2000” database. The obtained results confirm the effectiveness of the proposed encryption algorithm and clearly show the robustness against common attacks, for example differential and statistical attacks. In addition, it reveals the high security level achieved.     

Influence of contact point treatment on the cross flow mixing in a simple cubic packed bed: CFD simulation and experimental validation

The present study numerically investigates the mixing of an axial flow with a cross flow in a structured packed bed. Three-dimensional computational fluid dynamics CFD simulations have been carried out corresponding to the experimental setup. ANSYS software version 14 was used with the standard \(\upkappa \)–\(\upvarepsilon \) turbulence model. The study focuses on the effect of the contact point treatment by using three methods; gap, overlap and bridge to avoid a high skewed element in the near of contact point. A simple cubic packing with spherical particles of 52 mm diameter was used which gives a porosity of 0.48. The mixing is measured by an injection of nitrogen in the box with a structured bed of 924 spheres with an axial flow of air under different operating conditions. The following parameters were measured; height, injection velocity, volume flow rate ratio, flow conditions and location of injection. It is shown that the CFD simulation results can predict the cross flow mixing. The study revealed that the gap method produced the best experimental results.     

Granular transport through flighted rotary drums operated at optimum-loading: Mathematical model

Abstract

This paper discusses the transport of granular materials through flighted rotary drums operated at the optimum loading. A mathematical model is derived from the force balance acting on a single traveling particle, to predict the mean residence time of transportation. Based on the available parameters of mean height of falling curtains and final discharge angle, this model can be helpful to estimate the appropriate solid feeding rate. Two steps were followed to implement the use of the model. Firstly, experiments were carried out on a batch rotary drum to obtain the needed input parameters. Then, a case study of a small capacity rotary dryer was considered. In both steps, the drum was operated at the optimum loading. The model results were compared with other correlation from the literature for two cases of solid and air flows: con-current and counter current. Based on the results, a factor is introduced for generalized correlation from literature.     

Effect of microstructure on properties of ADI and low alloyed ductile iron

Microstructure, tensile, impact, hardness, fractography and wear characteristics were investigated for: (1) Austempered ductile iron (ADI); and (2) low alloyed ductile iron. Comparison has been made between the properties of these two types and that of conventional ductile iron. Detailed analysis, of the fracture mode for the 3 types of ductile iron, which failed under tensile and impact testing, were presented using the SEM. The wear properties were determined using pin-on-ring machine, under dry sliding conditions. The variation of mass loss and coefficient of friction with sliding distance, at different loads and speeds were presented and discussed. The wear mechanisms were investigated by means of subsurface observations. Microhardness test was used to study the change in the matrix strength with distance from the worn surface due to plastic deformation.     

A novel algorithm for discrimination between inrush current and internal faults in power transformer differential protection based on discrete wavelet transform

This paper proposes a novel methodology for transformer differential protection, based on wave shape recognition of the discriminating criterion extracted of the instantaneous differential currents. Discrete wavelet transform has been applied to the differential currents due to internal fault and inrush currents. The diagnosis criterion is based on median absolute deviation (MAD) of wavelet coefficients over a specified frequency band. The proposed algorithm is examined using various simulated inrush and internal fault current cases on a power transformer that has been modeled using electromagnetic transients program EMTDC software. Results of evaluation study show that, proposed wavelet based differential protection scheme can discriminate internal faults from inrush currents.     

Passivation and pitting corrosion of tin in gluconate solutions and the effect of halide ions

The passivation and pitting corrosion of tin in sodium gluconate (SG) solutions was studied by using potentiodynamic and cyclic voltammetric techniques. Some samples were examined by X-ray and SEM. The effect of the concentration of gluconate ion, pH, potential scanning rate, successive cyclic voltammetry, switching potential and progressive additions of halide ions on the passivation and pitting corrosion of a tin anode was discussed. The data obtained show that low concentrations of SG have an inhibition effect on the pitting corrosion of tin in neutral media. The pitting corrosion of tin increases with increasing SG concentrations due to the formation of soluble tin-gluconate complex. The critical pitting potential depends on the gluconate ion concentration, pH and scan rate. Two cathodic peaks are observed in the cathodic polarization curve, corresponding to the reduction of the dissolved pitting corrosion products. The critical pitting potential shifts progressively to more negative values with increasing halide ion concentration. In all experiments, the aggressive action of halides decreased in the order Cl^–>Br^–>I^–.     

Electrodeposition of Sn-Co alloys from gluconate baths

Electrodeposition of Sn-Co alloys was carried out from baths containing 2–20 g dm^–3 SnSO₄, 4–18 g dm^–3 CoSO₄.7H₂O, C₆H₁₁O₇Na and K₂SO₄ under different conditions of bath composition, pH, current density and temperature on to copper substrates. The influence of these variables on the cathodic potential, cathodic current efficiency and composition of the deposit were studied. The results show that the deposition of Sn-Co alloys from gluconate baths depends greatly on the concentration of tin. At high tin concentrations, tin is the more noble component. At low tin concentrations, tin reduction is strongly suppressed due to the formation of a more stable Sn-gluconate complex species and tin becomes the less noble component. The codeposition of Sn-Co alloy from these baths can be classified as an irregular plating system. The surface morphology of deposits was examined by scanning electron microscopy and crystal structure by X-ray. The results show that the structure of the deposits was controlled by the alloy composition.     

Quality of service-aware coexistence in unlicensed 5G new radio based on time-domain virtualization

The deployment of mobile systems is facing several challenges. Precisely, the lack of available licensed bands limits the network capacity, affecting the quality of service (QoS). Consequently, there has been significant interest in utilizing the unlicensed spectrum for mobile data traffic. 3GPP proposed and improved the coexistence of LTE and Wi-Fi in the unlicensed band starting in Release 13 and the following releases, such as LTE-LAA and 5G NR-U. This will cause significant interference and drastically affects the Wi-Fi users' QoS. To that end, we propose the use of time-domain virtualization between 5G NR-U and Wi-Fi systems. In particular, a scheduling algorithm is proposed, where the sharing mechanism is allocated in time slots rather than allocating a subband frequency for each technology. 5G use cases have different QoS requirements and our proposed solution aims at meeting these requirements. Accordingly, the performance is evaluated by studying the impact of resource virtualization and the coexistence configuration. Simulation results confirm that the minimum rate and maximum delay constraints are met. Moreover, it is shown that resource virtualization improves the throughput in both technologies. Furthermore, the delay performance is displayed for both 5G NR-U and Wi-Fi to show any impact of time-sharing coexistence.