Purification of metallurgical silicon using iron as an impurity getter part I: Growth and separation of Si

The purification of metallurgical grade silicon (MG-Si) using a combination of solvent refining and physical separation is studied. MG-Si was alloyed with iron and solidified under different cooling rates in order to grow pure Si dendrites from the alloy. The Si dendrites were then separated using a gravity-based method. The separation method relies on the significantly different densities of Si and FeSi₂, and it uses a heavy liquid with specific gravity between the two phases to float the light Si particles to the surface of the liquid, while the heavy iron silicide sinks. The effects of the particle size and cooling rate on the yield and separation efficiency of the Si phase were investigated by quantifying the fraction of Si in the sinks and floats. The results demonstrate that the crushing size of the particles prior to separation should be approximately the same as the width of the dendrites in order to maximize the separation efficiency while simultaneously lowering the grinding cost.     

Weighting fuzzy classification rules using receiver operating characteristics (ROC) analysis

In fuzzy rule-based classification systems, rule weight has often been used to improve the classification accuracy. In past research, a number of heuristic methods for rule weight specification have been proposed. In this paper, a method of fuzzy rule weight specification using Receiver Operating Characteristic (ROC) analysis is proposed. In order to specify the weight of a fuzzy rule, using 2-class ROC analysis, the threshold that the rule achieves its maximum accuracy is found. This threshold is used as the weight of the rule. The proposed method is compared with existing ones through computer simulations on some well-known classification problems with continuous attributes. Simulation results show that the proposed method performs better than existing methods of fuzzy rule weight specification.     

An optimal algorithm for two robots path planning problem on the grid

This paper is a study on the problem of path planning for two robots on a grid. We consider the objective of minimizing the maximum path length which corresponds to minimizing the arrival time of the last robot at its goal position. We propose an optimal algorithm that solves the problem in linear time with respect to the size of the grid. We show that the algorithm is complete; meaning that it is sure to find an optimal solution or report if any does not exist.     

Magnetic Fe3O4@ polydopamine biopolymer: Synthesis,characterization and fabrication of promising nanocomposite

In this work, Functional Fe₃O₄@ polydopamine nanocomposite (Fe₃O₄@PDA) with magnetic response and special surface area were successfully assembled utilizing the strong coordination interactions between these two versatile materials. The morphology and size, crystal structure, specific saturation magnetization, chemical structure, and thermal properties were characterized by transmission electron microscopy (TEM), X‐ray diffraction (XRD), vibration magnetometer (VSM), point of zero charge (pH_pzc), Fourier infrared (FT‐IR) and thermogravimetric analysis (TGA). The self‐polymerization of dopamine could be completed within 3 days, and Fe₃O₄ nanoparticles were embedded into PDA polymer. TGA results showed that PDA content of nanocomposite can be up to 51.7 wt% and also showed a significant decrease in the decomposition temperature of PDA from 530 to 270°C in the presence of the Fe₃O₄ nanoparticles. Through TGA analysis the coating thickness was estimated to be about 0.86 nm that it is well coincident with the measured values using TEM images and XRD analysis. At room temperature by vibrating sample magnetometer (VSM), Fe₃O₄ and Fe₃O₄@PDA exhibit superparamagnetic behavior with a saturation moment of 57.87 and 44.7 emu/g, respectively. Furthermore, PZC value reduced for Fe₃O₄@PDA compared with Fe₃O₄ nanoparticles and fell from 6.7 to 3.04. J. VINYL ADDIT. TECHNOL., 25:41–47, 2019. © 2018 Society of Plastics Engineers     

Structures for Abstract Rewriting

When rewriting is used to generate convergent and complete rewrite systems in order to answer the validity problem for some theories, all the rewriting theories rely on a same set of notions, properties, and methods. Rewriting techniques have been used mainly to answer the validity problem of equational theories, that is, to compute congruences. Recently, however, they have been extended in order to be applied to other algebraic structures such as preorders and orders. In this paper, we investigate an abstract form of rewriting, by following the paradigm of logical-system independency. To achieve this purpose, we provide a few simple conditions (or axioms) under which rewriting (and then the set of classical properties and methods) can be modeled, understood, studied, proven, and generalized. This enables us to extend rewriting techniques to other algebraic structures than congruences and preorders such as congruences closed under monotonicity and modus ponens. We introduce convergent rewrite systems that enable one to describe deduction procedures for their corresponding theory, and we propose a Knuth-Bendix–style completion procedure in this abstract framework.     

Influence of Ni/Co binders and Mo2C on the microstructure evolution and mechanical properties of (Ti0.93W0.07)C–based cermets

In this research, solid–solution powder of (Ti_0.93W_0.07)C was synthesized by high–energy ball mill method followed by carbothermal reduction process. Subsequently, the acquired powder was blended with Ni/Co and Mo₂C secondary carbide, and sintered under the optimized temperature (1510?°C) for 1?h to produce the modulated cermets. A typical core–rim structure formation with solid–solution phases was confirmed by backscattered electrons studies using a Field Emission electron scanning microscope. The hardness of the synthesized cermets was enhanced by increasing the specific amount of Mo₂C. The acquired results demonstrate that the binder type has a prominent influence on the microstructure and hardness of the prepared cermets. The hardness of (Ti_0.93W_0.07)C–xMo₂C–Ni cermet increased ~ 9%, when nickel was partially substituted by cobalt.     

Study of the anticorrosive properties of polypyrrole/polyaniline bilayer via electrochemical techniques

In this work, using electrochemical techniques the authors investigated the protective properties of a polypyrrole/polyaniline bilayer as a conductive polymer. A polypyrrole/polyaniline bilayer was deposited on carbon steel substrate by potentiostatic method. The electric capacitance and resistance of the films were monitored with the immersion time in a corrosive solution to investigate the water permeability of the films. Polypyrrole/polyaniline bilayer has a relatively low permeability and good catalytic behavior in passivation of carbon steel in longer periods. The results show that the bilayer has a better anticorrosive behavior compared to homopolymers (polypyrrole and polyaniline).     

Multiobjective shape optimization of speed humps

This paper presents a new approach to the shape optimization of road speed humps. The proposed approach is based on multiobjective genetic optimization of the hump profile while taking into account the separation phenomenon, which occurs when the front tires of the vehicle momentarily lose contact with the road surface. The optimization is carried out for speeds up to twice the authorized speed (throughout this article, the term authorized speed refers to speed limits enforced in speed reduction [bump] areas of the roads) rather than for illegally high speeds as adopted by many of the previous works. A 6-degree of freedom non-linear dynamic model is used to identify the speeds at which separation occurs, and hump profiles associated with these speeds are discarded as infeasible solutions. Three independent objective functions are selected for optimization. They include the maximum vertical acceleration experienced by the driver when crossing the hump below the authorized speed limit (to be minimized), the same vertical acceleration at speeds above the authorized speed (to be maximized), and the ascending ratio of the “speed—vertical acceleration” curve (to be maximized). These objective functions are evaluated for more than 10,000 humps of two popular profile types (sinusoidal and flat top with straight ramps) and optimum profiles for three speed limits of 20, 25, and 30km/h are determined using the multiobjective nondominated sorting genetic algorithm II. As a result, a Pareto front of at least ten optimal points is achieved for each of the two hump profile types. Furthermore, to incorporate the economical aspects of the real-world problem, Pareto optimal points for the two profile types were compared based on their lateral section areas (an indication of the manufacturing cost). The comparison shows that sinusoidal humps more often than not outdo their flat top rivals economically.