Mathematical modeling and computer simulation of the rotating impeller particle flotation process: Part II. Particle agglomeration and flotation

Effective removal of unwanted particles from a molten metal alloy by flotation relies on purging a gas into the melt through a rotating impeller. This device is commonly known as a rotary degasser. Unwanted particles in the melt attach to the rising gas bubbles and rise to the slag layer where they are removed from the metal bulk. In addition, the turbulence created by the rotating impeller causes the randomly distributed solid particles to agglomerate into relatively large clusters. These clusters float up or settle down due to the difference between their density and that of the melt. A mathematical model has been developed to describe the particle dynamics and particle agglomeration that occur during the rotary degassing of aluminum melts. While previous investigations addressed particle collisions in low intensity turbulent fields where the size of the colliding particles is smaller than the Kolmogorov length scale, this model is more encompassing as it considers both low intensity and high intensity turbulence. Consequently, this model is more representative of a typical industrial rotary degassing operation.     

HSDN‐GRA: A hybrid software‐defined networking‐based geographic routing protocol with multi‐agent approach

We propose in this paper a Hybrid Software‐Defined Networking‐based Geographical Routing Protocol (HSDN‐GRA) with a clustering approach. It takes into account three different criteria to select the best relay to send data: (1) the contact duration between vehicles, (2) the available load of each vehicle, (3) and the log of encountered communication errors embedded in each cluster head. The multi‐criteria strategy allows the selection of the most reliable vehicles by avoiding communication problems and ensuring connection availability. Once the hybrid control plane has found out the next eligible neighbor, the data plane will be in charge of dividing and sending data. To validate our approach, HSDN‐GRA has been modeled and implemented in JADE, a multi‐agent platform, to be compared to other multi‐agent based protocols. Simulation results show that HSDN‐GRA achieves good performance with respect to the average routing overhead, the packet drop rate, and the throughput.     

Synergistic effect of organoclay fillers based on fluorinated surfmers for preparation of polystyrene nanocomposites

Novel fluorinated reactive surfactants were used for the organic modification of monmorillonite clays. These organoclays were used for the preparation of polystyrene?clay nanocomposites by in‐situ free radical polymerization. Reference systems based on hydrocarbon homologous surfmer and nonpolymerizable surfactants were also used to deduce the effect of the fluorine moiety and the polymerizable function on the morphology and thermal stability of the prepared nanocomposites. Different structural parameters of the surfactants were investigated and modulated for the clay modification including: the nature of surfactant (surfmer/classical surfactant, fluorinated, or hydrocarbonated), the length of the fluorinated chain as well as the length of the hydrocarbon spacers linking the ammonium head to the fluorine chain or the polymerizable acrylic function. Wide angle‐X‐ray scattering (WAXD), thermogravimetric analysis (TGA), and electronic microcopies (TEM and SEM) were used to establish a structure‐morphology, thermal properties relationships, and to highlight the key parameters governing the exfoliation process. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42347.     

On the Barbalat lemma extension for the generalized conformable fractional integrals: Application to adaptive observer design

The Barbalat-type lemma for the generalized conformable fractional-order derivative is examined in this work. An adaptive observer design is presented as an application to validate such proposed theory.     

Optimum parameters for wetting silicon carbide by aluminum alloys

The effect of magnesium and silicon additions to aluminum, free silicon on the SiC substrate, nitrogen gas in the atmosphere, and process temperature on the wetting characteristics of SiC by aluminum alloys are investigated using the sessile drop technique. The contribution of each of these parameters and their interactions to the contact angle, surface tension, and driving force for wetting are determined. In addition, an optimized process for enhanced wetting is suggested and validated. Results show that the presence of free silicon on the surface of SiC significantly reduces the contact angle between the molten alloy and the substrate. The positive effect of silicon on the contact angle is attributed to a chemical reaction in which both SiC and aluminum are active participants. The results also indicate that nitrogen gas in the atmosphere positively influences the liquid/vapor surface tension, and the presence of magnesium in the aluminum alloy favorably affects the overall driving force for wetting. A mechanism is proposed to explain the beneficial role that the interaction of nitrogen with magnesium plays in enhancing wetting. Magnesium significantly reduces the surface tension of aluminum melts but has a low vapor pressure. Consequently, it readily volatilizes during holding at the processing temperature and is lost from the alloy. It is proposed that a series of chemical reactions in the system Al-Mg-N are responsible for reintroducing magnesium into the melt, thus, maintaining a low melt surface tension. Interactions between the aluminum alloy and the silicon carbide substrate that may lead to the dissolution of the substrate and the formation of undesirable reaction products, particularly Al₄C₃, are examined, and means for mitigating their formation are outlined.     

GrAFCI+ A fast generator-based algorithm for mining frequent closed itemsets

Knowledge and Information Systems - Mining itemsets for association rule generation is a fundamental data mining task originally stemming from the traditional market basket analysis problem....     

Characterization of the kinetic and mechanistic differences between free-surface and bulk grain growth in WC-Co materials

The rate of grain growth at different high temperatures in the bulk and at the free surface of a WC-Co substrate was measured. The microstructure, phase evolution, and elemental composition at the free surface were characterized at various stages of the grain-growth process and compared to equivalent characteristics of the bulk. A dramatic difference in the rate of grain growth between the free surface and the bulk of the material was observed. Grains in the free surface grew at a much faster rate than those in the bulk. Since this fast rate of growth was found to coincide with the vaporization of the binder phase from the free surface, it is suggested that this increase in the rate of growth is related to a change in the growth mechanism from an interfacial reaction limited growth in the bulk to a surface diffusion rate limited growth at the free surface. The contact points between grains provide bridges for atomic transport from high free-energy regions (small grains) to low free-energy regions (large grains); hence, the contiguity of the material has a strong influence on the rate of growth.     

Cyanine dyes as corrosion inhibitors. I. Electrochemical corrosion behaviour of copper metal treated with hydroxystyryl cyanine dye

The effect of 2-(o-hydroxystyryl) pyridinium-1-ethyl iodide cyanine dye on the corrosion behaviour of copper metal in nitric acid solution has been studied. Weight loss measurements, galvanostatic polarization curves, open-circuit potential variation of copper electrode with time and the cathodic protective current values indicate that styryl cyanine dye gives an anticorrosive character. The inhibition effect is more pronounced in the case of copper metal coated by dye thin film than that obtained by its addition to the corrosion medium.