Corrosion behavior on the different zones of AA2014 welded aluminum alloy by AA5554 filler aluminum alloy with TIG process: Before and after solution heat treatments followed by ageing

In this work, we have studied the effects of solution heat treatment followed by ageing on the corrosion behavior of AA2014 aluminum alloy welded by AA5554 aluminum alloy. Two samples are then analyzed, in the first case the solution heat treatment is followed by quenching and natural ageing of 90 days (sample 1), and in the second one, the solution heat treatment is followed by quenching and artificial ageing of twelve hours at 190°C (sample 2). The principal observations can be summarized as: evaporation of magnesium in fusion zone, and diffusion of magnesium and copper from the heat affected zone to the fusion zone were identified. Solution heat treatment, quenching and 90 days of natural ageing leads to a uniform corrosion in the heat affected zone and in the fusion one, when the material is immersed for ten seconds in Keller reagent solution. After immersion in 0.3% NaCl chloride solution, and after solution treatment and quenching, we observed that applied artificial ageing at 190°C causes localized corrosion surrounding precipitates and then develops uniform corrosion in all zones, particularly in the fusion one. Finally, it is noted that the surface of different zones became nobler after applying solution heat treatment followed by natural ageing.     

Automatic Hand Detection in Color Images based on skin region verification

Multimedia Tools and Applications - Among the modern means of communications that appeared recently, there is the natural computer interaction using hands. Several methods have been proposed for...     

First principles study of structural,electronic and magnetic properties of SnGen(0,±1) (n =1-17) clusters

The structures,relative stability and magnetic properties of pure Gen+1,neutral cationic and anionic SnGen (n =1-17) clusters have been investigated by using the first principles density functional theory implemented in SIESTA packages.We find that with the increasing of cluster size,the Gen+1 and SnGen(0,±1) clusters tend to adopt compact structures.It has been also found that the Sn atom occupied a peripheral position for SnGen clusters when n ＜ 12 and occupied a core position for n ＞ 12.The structural and electronic properties such as optimized geometries,fragmentation energy,binding energy per atom,HOMO-LUMO gaps and second-order differences in energy of the pure Gen+1 and SnGen clusters in their ground state are calculated and analyzed.All isomers of neutral SnGen clusters are generally nonmagnetic except for n =1 and 4,where the total spin magnetic moments is 2μb.The total (DOS) and partial density of states of these clusters have been calculated to understand the origin of peculiar magnetic properties.The cluster size dependence of vertical ionization potentials,vertical electronic affinities,chemical hardness,adiabatic electron affinities and adiabatic ionization potentials have been calculated and discussed.     

Setting time determination of cementitious materials based on measurements of the hydraulic pressure variations

An experimental investigation was carried out to determine the setting time of cement based materials (cement paste, mortar, concrete, etc.). An original method based on measurements of both total lateral pressure and hydraulic pressure has been investigated. An original device has been engineered to measure the pressure kinetics. Just after mixing and filling of the device, a simultaneous drop and an equal value of the both hydraulic and total lateral pressures has been recorded. A definitive cessation of total lateral pressure and negative hydraulic pressures are then observed. The proposed setting time was defined as the elapsed time between the end of mixing and the time at which the hydraulic pressure becomes zero. In addition to the usual W / C parameter, the influence of the vibration and the height of the material tested on the pressure based method were studied. Comparing to other classical methods (Vicat, calorimetry, ultrasonic pulse-echo …), the presented device is efficient with major types of cement based materials (concrete, SCC …) and was able to give a simple and direct information about the mechanical state of the material.     

A novel aspartic protease from the viscera of Sardinelle (Sardinella aurita): Purification and characterisation

A novel aspartic protease was extracted from the defatted viscera of sardinelle (Sardinella aurita) and purified, with a 9.5-fold increase in specific activity and 23.3% recovery. The molecular weight of the purified enzyme was estimated to be 17 kDa by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE). The purified enzyme appeared as a single band on native-PAGE. The optimum pH and temperature for protease activity were around 3.0 and 40 °C, respectively. The enzyme showed pH stability between 2.0 and 5.0 and retained more than 50% of its activity after heating for 30 min at 50 °C. The enzyme lost 90% of its activity after incubation with pepstatin A at room temperature, but was not inhibited by soybean trypsin inhibitor or phenylmethylsulfonyl fluoride. Its K_m value was determined to be 0.73 × 10⁻⁴ M using haemoglobin as a substrate. The N-terminal 12 amino acid sequence of the purified acidic protease was R V I I E D X D Q F C T. This sequence showed low homology with aspartic peptidases of several other species of fish, suggesting that the enzyme is a new aspartic protease.     

Combination of canonical correlation analysis and empirical mode decomposition applied to denoising the labor electrohysterogram

The electrohysterogram (EHG) is often corrupted by electronic and electromagnetic noise as well as movement artifacts, skeletal electromyogram, and ECGs from both mother and fetus. The interfering signals are sporadic and/or have spectra overlapping the spectra of the signals of interest rendering classical filtering ineffective. In the absence of efficient methods for denoising the monopolar EHG signal, bipolar methods are usually used. In this paper, we propose a novel combination of blind source separation using canonical correlation analysis (BSS_CCA) and empirical mode decomposition (EMD) methods to denoise monopolar EHG. We first extract the uterine bursts by using BSS_CCA then the biggest part of any residual noise is removed from the bursts by EMD. Our algorithm, called CCA_EMD, was compared with wavelet filtering and independent component analysis. We also compared CCA_EMD with the corresponding bipolar signals to demonstrate that the new method gives signals that have not been degraded by the new method. The proposed method successfully removed artifacts from the signal without altering the underlying uterine activity as observed by bipolar methods. The CCA_EMD algorithm performed considerably better than the comparison methods.     

Preparation and electrochemical properties of nano-sized SnF2 as negative electrode for lithium-ion batteries

Nanocrystalline SnF₂ was prepared via recrystallization of commercially available tin (II) fluoride. The electrochemical performance of tin fluoride as anode material for Li-ion batteries was investigated. The cyclic voltammetry of the obtained material showed occurrence of SnF₂ decomposition at first and a typical reversible alloying/de-alloying process at low potentials. Furthermore, it was found that the synthesized material delivered a high reversible capacity of 1016 mAh g^− 1 and a capacity retention of 54.8% after 30 cycles when the electrode was cycled at a current of 100 mA g^− 1.     

Dynamic bandwidth management in IEEE 802.11-based multihop wireless networks

In this paper, we propose a new protocol named dynamic regulation of best-effort traffic (DRBT) which supports quality of service (QoS) throughput guarantees and provides a distributed regulation mechanism for best-effort traffic in multihop wireless networks. By adapting dynamically the rate of best-effort traffic at the link layer, DRBT increases the acceptance ratio of QoS flows and provides a good use of the remaining resources through the network. Our protocol also provides an accurate method to evaluate the available bandwidth in IEEE 802.11-based ad hoc networks which is able to differentiate QoS applications from best-effort traffic. Through extensive simulations, we compare the performance of our proposal scheme with some others protocols like QoS protocol for ad hoc real-time traffic for instance.