Study of the Linear Friction Welding Process of Dissimilar Ti-6Al-4V–Stainless Steel Joints

Linear friction welding (LFW) is an innovative joining method that can be used to obtain high-strength joints between dissimilar materials. A key factor that influences the joint's performances are the intermetallic compounds that could be formed during the welding process. These intermetallics are brittle and could compromise the mechanical performances of the joint. This article deals with the analysis of the LFW process of dissimilar titanium–stainless steel joints. Two different types of joints were studied: AISI 304–Ti6Al4V and AISI 316–Ti6Al4V. Particular attention was paid to characterizing the intermetallic compounds using scanning electron microscopy, Electron probe microanalysis and X-ray diffractometry. Zones with different microstructure were observed. Due to the diffusive phenomena occurring during the welding, Kirkendall effect and occurrence of several intermetallics were observed. Moreover, it was found that the joint with AISI 316 formed brittle intermetallic compounds, which led to crack formation close to the weld line.     

Topological Phases Emerging from Spin-Orbital Physics

We study the evolution of spin-orbital correlations in an inhomogeneous quantum system with an impurity replacing a doublon by a holon orbital degree of freedom. Spin-orbital entanglement is large when spin correlations are antiferromagnetic, while for a ferromagnetic host we obtain a chain with only orbital interactions. In this regime, the orbital model can be mapped on spinless fermions and we uncover topological phases with zero energy modes at the edge or at the domain between magnetically inequivalent regions.     

Synthesis and characterization of nitrogen-doped carbon xerogels

Carbon xerogels were prepared from a nitrogen-containing polymer precursor, using melamine and urea as nitrogen sources incorporated into the polymer matrix using the sol-gel process. To investigate the effects of nitrogen on the texture, morphology and surface chemistry, the carbon xerogels were characterized by nitrogen adsorption, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), and acid-base titrations. The results showed that nitrogen was incorporated onto the surface as pyridine, pyrrolic/pyridine, quaternary nitrogen, and pyridine-N-oxide. From the deconvolution of the XPS spectra, the pyrrolic/pyridine and quaternary nitrogen functionalities were found to dominate in the samples prepared from urea. All samples showed increased basicity after nitrogen incorporation.     

Co-gasification of coal and wastes in a pilot-scale installation. 2: Effect of catalysts in syngas treatment to achieve sulphur and nitrogen compounds abatement

Coal mixed with different types of wastes was co-gasified in a pilot-scale installation. The syngas produced was hot treated in two catalytic fixed-bed reactors. In the first one, dolomite was used and in the second reactor, a nickel-based catalyst was employed. Two different grade coals were tested, Puertollano and Colombian. Puertollano coal had high ash and sulphur contents, 42.5% and 2.4%, respectively, while ash and sulphur contents of Colombian coal were, respectively, 12.7% and 0.9%. Pine, bagasse, RDF and PE were the wastes mixed with both coals. After dolomite fixed-bed reactor, H₂S and NH₃ contents in syngas were much lower than those of the gas leaving the gasifier. For most coal and waste blends, NH₃ reductions changed between 30% and 50% depending on feedstock nitrogen content, while H₂S reductions achieved values from 68% to 74%, also depending on H₂S concentration in syngas. After syngas had gone through the nickel-based catalyst, it presented H₂S and NH₃ contents that allowed its use in boilers and gas engines for most coal and waste blends. The overall syngas treatment led to H₂S and NH₃ reductions higher than 97%. For most experiments, final H₂S and NH₃ concentration in syngas were below 20 ppmv and 30 ppmv, respectively.     

Characterization of blood samples using image processing techniques

This paper presents a methodology to determine human blood types in an emergency situation as well as a reliability study of the methodology proposed. The plate test is employed to determine blood types, allowing the macroscopic results observation. A CCD camera captures an image of the plate test results that will be processed through image processing techniques available in the IMAQ Vision software from National Instruments. The techniques used in this work are able to determine the occurrence of agglutination allowing the determination of blood types with an algorithm of classification. The reliability study based on statistical tests determines the level of confidence of the approach. The equipment developed is able to automatically perform the plate test and determine blood types.     

Safe controllers design for industrial automation systems

The design of safe industrial controllers is one of the most important domains related to Automation Systems research. To support it, synthesis and analysis techniques are available. Among the analysis techniques, two of the most important are Simulation and Formal Verification. In this paper these two techniques are used together in a complementary way. Understanding plant behaviour is essential for obtaining safe industrial systems controllers; hence, plant modelling is crucial to the success of these techniques. A two step approach is presented: first, the use of Simulation and, second, the use of Formal Verification of Industrial Systems Specifications. The specification and plant models used for each technique are described. Simulation and Formal Verification results are presented and discussed. The approach presented in the paper can be applied to real industrial systems, and obtain safe controllers for hybrid plants. The Modelica modelling language and Dymola simulation environment are used for Simulation purposes, and Timed Automata formalism and the UPPAAL real-time model-checker are used for Formal Verification purposes.