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In the twin wire arc spraying (TWAS) process, it is common to use compressed air as atomizing gas. Nitrogen or argon also are used to reduce oxidation and improve coating performance. The heat required to melt the feedstock material depends on the electrical conductivity of the wires used and the ionization energy of both the feedstock material and atomization gas. In the case of ZnAl4, no phase changes were recorded in the obtained coatings by using either compressed air or argon as atomization gas. This fact has led to the assumption that the melting behavior of ZnAl4 with its low melting and evaporating temperature is different from materials with a higher melting point, such as Fe and Ni, which also explains the unexpected compressive residual stresses in the as-sprayed conditions. The heavier atomization gas, argon, led to slightly higher compressive stresses and oxide content. Compressed air as atomization gas led to lower porosity, decreased surface roughness, and better corrosion resistance. In the case of argon, Al precipitated in the form of small particles. The post-treatment machine hammer peening (MHP) has induced horizontal cracks in compressed air sprayed coatings. These cracks were mainly initiated in the oxidized Al phase., Coatings;12(1)

Produced water (PW) from petrochemical industries is one of the largest wastewaters generated in Qatar. Soluble and insoluble oil contaminants occur in this water and must be removed if water will be used or discharged into the land or sea. Adsorption is a common procedure used in the industry for a wastewater treatment and oily components removal. It is a simple, cost effective process. Currently there are many available natural and synthetic, particularly polymeric adsorbents. Polyolefins are pure hydrocarbon polymers, which due to an appropriate sorption efficiency of lowmolecular weight hydrocarbons can be used as suitable sorbents. However, polyolefins' based sorbents are commercially used only for removal of free oil. In this work, we have investigated a potential use of polyethylene as a filtration media in tertiary filtration of emulsified oil/water mixtures with respect to key parameters determining their adsorption ability. Polyethylene powders of various size and physical treatment were used. Emulsion formed from distilled water and commercial Diesel oil (DO) with a concentration below 200 ppm was used as a model of PW. The emulsions were prepared without emulsifier, and emulsification was insured by ultrasonication. The relationships between the sorption properties and surface composition and morphology of modified and unmodified PE powders were evaluated. Characterizations include the neat oil sorption, and sorption from emulsions, scanning electron microscopy, and profilometry. The PE adsorbents were further characterized by Brunauer-Emmett Teller surface area analysis, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed in order to characterize the porosity, crystallinity and chemical composition of PE, respectively. Sorption experiments were carried out as a function of different weight dosage, initial oil concentrations, and contact time to obtain the optimum conditions for the adsorption process. The results showed that LDPE powder, at a dosage of 3 g treated with plasma, using initial oil concentration of 100 ppm and 720 min of contact time presented the most suitable conditions for the adsorption of oil from emulsified DO. The adsorption process renders LDPE a suitable adsorbent for the removal of oil from diluted oil emulsions with an oil removal efficiency exceeding 93.5%. Equilibrium studies have been carried out to determine the sorption capacity of LDPE for the adsorption of oil from diluted DO emulsions using the optimum conditions. Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms. Equilibrium data were fitted very well with the Freundlich model. The pseudo first- and second-order kinetic models were used to describe the kinetic data and the rate constants of sorption were evaluated. The experimental data were fitted well with the pseudo-second-order kinetic model. The study confirmed the feasibility of using oil adsorbents based on plasma treated PE powders as potential adsorbents media for the removal of oil contaminants from PW

The low melting point of Sn-based Babbitt alloys often causes nozzle clogging in the low-pressure cold gas-dynamic spraying (LPCGDS) process, which impacts the process steadiness and the coating quality. Adding hard particles to the feedstock material eliminates this kind of interruption. A certain amount of these particles finds their way in the obtained coatings. These particles also trigger a kind of &ldquo, hammering effect&rdquo, due to their impulse forces. These forces are directly dependent on the mass and velocity of the impacting hard particles. However, these forces may lead to a decrease in the porosity and improve the adhesion of the obtained coating. In this study, the effect of the density and size of the hard particle was examined by three different hard materials, Cr3C2, Al2O3, and B4C, which have a material density of 6.68, 3.95, and 2.52 g/cm3, respectively. The used feedstock in this study is a powder mixture that contains 75 vol.% Babbitt and 25 vol.% of either B4C, Cr3C2, or Al2O3. The effect of the size distributions &ldquo, particles with lower mass&rdquo, was tested using two different Al2O3. The various hard particles show different embedding behaviors, as well as different effects on the coating build-up. It was found that the blended hard particles were enclosed with the Babbitt matrix, and their interface with Babbitt shows no clear evidence of pronounced diffusion. The size distribution of the blended hard particles has a direct effect on the splat formation and the obtained coating microstructure. It was found that the type of hard particles played a decisive role in the friction behavior. Nevertheless, the hard particle reinforced Sn-Sb-Cu-based composite coatings demonstrated a nearly constant coefficient of friction throughout the load-interval.

Studies have already established that the mechanical properties of Babbitt coatings significantly depend on the microstructural characteristics, such as the amount and distribution of intermetallic compounds dispersed in a soft solid solution matrix. For Sn&ndash, Sb&ndash, Cu-based Babbitt coatings, the formation of SbSn- and CuSn-based precipitates has a substantial influence on the resulting microhardness and thus determines the maximum load carrying capacity. Thermal spraying of Sn-based Babbitt coatings results in a relatively more refined structure of these precipitates than in common manufacturing processes, such as casting, due to the thermal processing conditions. This study aims to evaluate the effect of the temperature of the propellant gas and substrate temperature on the microstructural characteristics of Sn&ndash, Cu-based Babbitt coatings deposited by low pressure cold spraying (LPCS). The deposits were examined for their phase composition, microhardness and mesoscopic structure. It was found that the coatings were mainly composed of Sb2Sn23, Sb0.49Sn0.51 and Sorosite (CuSn or CuSb0.115Sn0.835), regardless of the substrate temperature or temperature of the propellant gas to be investigated. For a gas temperature above 300 &deg, C, an increased microhardness was observed, which correlates with the appearance of a more homogenous distribution of Sb0.49Sn0.51 dispersed in a soft Sn-rich solid solution matrix.

Food processing industries use considerable amounts of fresh water for their industrial purposes. These industries generate large quantities of high strength organic wastewaters which are usually biodegradable and amenable to biological treatment systems. Numbers of biological methods are still in use for the treatment of food processing wastewaters, either anaerobic or aerobic systems. In this research, the performance using newly developed laboratory scale sequencing batch flexible fibre biofilm reactor (SB-FFBR), single stage flexible fibre biofilm reactor (SS-FFBR) and newly developed multiple stage flexible fibre biofilm reactors (MS-FFBR) for treatment of milk processing wastewater were experimentally investigated.

For audio distribution over the network, a secure audio compression format is required. In this paper a novel encryption scheme with low computational complexity is proposed to achieve security level for Advanced Audio Coding (AAC). In this scheme, the modular multiplication and circularly shifts are used to encrypt the selected quantized spectral coefficients and scale factors in the AAC encoding process. The proposed algorithm used chaos theory to generate the necessary random key for audio encryption. The Experimental results show that the encryption algorithms provide good audible distortion because each frame is encrypted by using different key. The proposed algorithms have very large key space and it's sensitive to any modification in the secret key. The proposed algorithms are strong against most attacks and have a high security which is due to combination of the quantized spectral coefficients encryption algorithm and the scale factors encryption algorithm depending on the characteristics of the chaotic system and it is suitable for transmit audio signal in secure way.

With rapid growth in communication techniques and multimedia application, security is becoming more important for multimedia data storage or transmission. Traditional encryption algorithm such as Advance Encryption Standard (AES) and Data Encryption Standard (DES) are not suitable for video data because it caused large computational overhead and reduce the MPEG compression efficiency. The encryption algorithm that has less computation overhead is needed. The proposed algorithm combines encryption process with MPEG video compression. Some modifications of the RC4 algorithm were proposed in this paper to enhance the performance of video encryption algorithm in terms of encryption time, compression ratio and to provide accepted level of the security. The modification of the RC4 algorithm depends on the maximum value of the plain text, chaotic map and circular shift operation. This modification will reduce the number of iteration in the Key scheduling Algorithm (KSA) and make the Pseudo Random Generator Algorithm (PRGA) depend on initial condition of chaotic maps to provide the strong shuffling inside the PRGA. The random rotation technique based on chaotic map is proposed to increase security of MPEG video. This technique depends on the value generated from chaotic map to rotate the Y blocks in I frame. The experimental results indicate that the proposed method provided better encryption times and provides sufficient level of the security. Thus the proposed method is suitable to protect the MPEG video with minimizing the overhead.