Solidification of Lead Tin and Lead Telluride Eutectic Alloys in Microgravity

The Brazilian Microgravity Program is mainly based on experiments carried out on sounding rockets. A solidification furnace, capable of producing temperatures up to 900 °C, was developed to process metal and semiconductor alloys in microgravity environment. This paper describes a solidification experiment made in this furnace during a parabolic flight, with two eutectic alloys. The behavior of the eutectic alloys PbSn with 26.1 Pb at. % composition, and PbTe with 10.9 Pb at. % composition were presented and compared with laboratory solidifications carried out in the same furnace and thermal cycle. It was concluded that the formation of dendritic structures in PbSn alloy is related to the presence of sedimentation and convective flow during solidification, and the size of these structures is connected to the solidification time. Thus, in the microgravity alloy, there was no formation of dendritic structures and the profile of solute distribution remained constant throughout the sample. For the PbTe eutectic alloy the microgravity conditions have not caused significant changes compared to the earth solidified sample.     

SipaaS: Spot instance pricing as a Service framework and its implementation in OpenStack

Designing dynamic pricing mechanisms that efficiently price resources in line with a provider's profit maximization goal is a key challenge in cloud computing environments. Despite the large volume of research published on this topic, there is no publicly available software system implementing dynamic pricing for Infrastructure as a Service cloud spot markets. This paper presents the implementation of a framework called Spot instance pricing as a Service (SipaaS) that supports an auction mechanism to price and allocate virtual machine instances. SipaaS is an open‐source project offering a set of web services to price and sell virtual machine instances in a spot market resembling the Amazon EC2 spot instances. Cloud providers, who aim at utilizing SipaaS, should install add‐ons in their existing platform to make use of the framework. As an instance, we provide an extension to the Horizon – the OpenStack dashboard project – to employ SipaaS web services and to add a spot market environment to OpenStack. To validate and evaluate the system, we conducted an experimental study with a group of 10 users utilizing the provided spot market in a real environment. Results show that the system performs reliably in a practical test environment. Copyright © 2015 John Wiley & Sons, Ltd.     

Nanomagnet-Bound Imidazole as a Heterogeneous Axial Ligand for MnIII(salophen)Cl: An Efficient, Recoverable and Recyclable Catalyst for Epoxidation of Alkenes with Sodium Periodate

Efficient alkene epoxidation with sodium periodate catalyzed by manganese(III) salophen supported on nanomagnetic materials is reported. First, the iron nanomagnets were silica coated, functionalized with imidazole and then manganese salophen was successfully bonded to their surface. The catalyst, [Mn^III(salophen)Cl]@SiIm-Fe, was characterized by elemental analysis, FT-IR and UV/Vis spectroscopic techniques, SEM and ICP. The [Mn^III(salophen)Cl]@SiIm-Fe was used for alkene epoxidation with sodium periodate at room temperature. Different aromatic and aliphatic terminal alkenes were epoxidized efficiently using sodium periodate as an oxidant. The effect of reaction parameters such as solvent and oxidant in the epoxidation of cis-cyclooctene was investigated. This new heterogenized epoxidation catalyst is easily recovered with a magnet and showed no appreciable loss of activity even after four consecutive runs.     

A drastic hybrid heuristic algorithm to approach to JIT policy considering controllable processing times

Job scheduling has always been a challenging task in modern manufacturing and the most real life scheduling problems which involves multi-criteria, multi-machine environments. In this research, the single-machine scheduling problem is studied in which job processing times are controllable, namely, they may vary within a specified interval. The goal of this research is to minimize total tardiness and earliness on a single machine, simultaneously. In this context, we first propose a mathematical model for the considered problem and then a net benefit compression–net benefit expansion heuristic is presented for obtaining the set of amounts of compression and expansion of jobs processing times in a given sequence. Two meta-heuristic approaches are then employed to solve medium-to-large-sized problems as local search methods. Thereafter, we apply a hybrid method based on our heuristic as well as these two meta-heuristics in order to obtain solutions with higher quality within lesser computational time. The addressed problem is NP-hard since the single machine total tardiness problem is already NP-hard. The computational results show that our proposed heuristics can effectively solve such Just-In-Time problem with a high-quality solution.     

The effect of particle size,irrigation rate and aeration rate on column bioleaching of uranium ore

The effect of hydrodynamic factors such as particle size, irrigation rate and aeration rate on the dissolution of uranium by Acidithibacillus ferrooxidans in column reactor was studied. Response surface methodology (RSM) was applied to predict the behavior of effective parameters and their interactions on the bioleaching process. Under the optimum conditions particle size of 5 mm, irrigation rate of 0.34 L/m²/min and aeration rate of 210 L/m²/min, the maximum value of uranium recovery was 63.85% for 19 days. The results from the statistical model and the experimental data showed good agreement and the most effective factor was the aeration rate. The interaction between particle size and irrigation rate has a negative effect and two other interactions have a positive effect on uranium recovery. Analysis of bioleaching residue confirmed the formation of K-jarosite on the surface of particles. The modified kinetic model at optimum conditions showed that cathodic ferric reduction is the rate controlling step on uranium bioleaching recovery.     

The Effect of Magnetic Field of Multicusp and Wall Material on Electron Trajectories

In this paper, the effect of electron confinement with magnetic fields in the multicusp ion source has been investigated. That is, electron confinement with magnetic fields plays a very important role for the generation of negative ions at plasma. Three-dimensional spatial distributions of electrons production are obtained for a multicusp ion source. The electron confinement of magnetic fields from various surface materials (such as Al₂O₃, Al, Au, Cu, w and stainless-steel) have been compared in a multicusp plasma source. The electron confinement effect becomes stronger with increasing N (the number of rows of permanent magnets) and using Al for plasma chamber wall material. The results of investigations have demonstrated good correspondence with experimental data, and therefore the adequacy of the developed approach and the possibility to build more effective source on this basis.     

Bulk Single Crystal‐Like Structural and Magnetic Characteristics of Epitaxial Spinel Ferrite Thin Films with Elimination of Antiphase Boundaries

Spinel ferrite NiFe₂O₄ thin films have been grown on three isostructural substrates, MgAl₂O₄, MgGa₂O₄, and CoGa₂O₄ using pulsed laser deposition. These substrates have lattice mismatches of 3.1%, 0.8%, and 0.2%, respectively, with NiFe₂O₄. As expected, the films grown on MgAl₂O₄ substrate show the presence of the antiphase boundary defects. However, no antiphase boundaries (APBs) are observed for films grown on near‐lattice‐matched substrates MgGa₂O₄ and CoGa₂O₄. This demonstrates that by using isostructural and lattice‐matched substrates, the formation of APBs can be avoided in NiFe₂O₄ thin films. Consequently, static and dynamic magnetic properties comparable with the bulk can be realized. Initial results indicate similar improvements in film quality and magnetic properties due to the elimination of APBs in other members of the spinel ferrite family, such as Fe₃O₄ and CoFe₂O₄, which have similar crystallographic structure and lattice constants as NiFe₂O₄.     

The effect of keyword repetition in abstract and keyword frequency per journal in predicting citation counts

This paper investigates an association between two new variables and citations in papers. These variables include the abstract ratio (the sum of repetition of keywords in abstract divided by abstract length) and the weight ratio (the frequency of paper’s keyword per journal). The data consist of 5875 papers from 12 journals in education: three journals from each SCImago quartile. The researchers used semi-continuous regression to model the data and measure the impact of the proposed variables on citations. The results revealed that both abstract ratio and weight ratio are statistically significant predictors of citations in scientific articles in education.     

Recursive Quantum Functions, Avoidable Points, & Shadow Points in Recursive Analysis

In this paper we summarize our approach and findings in a point-free setting for recursive topology and recursive analysis. Recursive analysis has received intensive attention recently and our approach, while differing from those of other schools, does have connections to them. Here, we also present some of our findings on quantum and total recursive functions on the reals, introduce our classification of nonrecursive points, and remark on the connections between our work and the works of others.