The generalized discrete ‐centroid problem

The ‐centroid problem or leader–follower problem is generalized considering different customer choice rules where a customer may use facilities belonging to different firms, if the difference in travel distance (or time) is small enough. Assuming essential goods, some particular customer choice rules are analyzed. Linear programming formulations for the generalized ‐medianoid and ‐centroid problems are presented and an exact solution approach is applied. Some computational examples are included.     

Identification and Tuning Methods for PI Control Systems Based on Symmetric Send-on-delta Sampling

International Journal of Control, Automation and Systems - Two procedures for the definition of an autotuning algorithm for event-based proportional-integral (PI) control systems are proposed in...     

Special issue on exploring new Natural User Experiences

Universal Access in the Information Society -     

Toward the Optimized Spintronic Response of Sn‐Doped IrO2 Thin Films

Amorphous and polycrystalline Sn‐doped IrO₂ thin films, Ir_1‐xSn_xO₂, are grown for the first time. Their electrical response and strength of the spin–orbit coupling are studied in order to better understand and tailor its performance as spin current detector material. These experiments prove that the resistivity of IrO₂ can be tuned over several orders of magnitude by controlling the doping content in both the amorphous and the polycrystalline state. In addition, growing amorphous samples increase the resistivity, thus improving the spin current to charge current conversion. As far as the spin–orbit coupling is concerned, the system not only remains in a strong spin–orbit coupling regime but it seems to undergo a slight enhancement in the amorphous state as well as in the Sn‐doped samples.     

Generalised multivariable supertwisting algorithm

The purpose of this paper is to present an extension of the generalised supertwisting algorithm (STA) to the multivariable framework. We begin by introducing an algorithm that may be deemed as a linear, quasicontinuous, or discontinuous multivariable system, depending on the functions that define them. For the class represented by such an algorithm we prove the robust, Lyapunov stability of the origin and characterise the perturbations that preserve its stability. In particular, when its vector field is discontinuous or quasicontinuous our algorithm is endowed with finite‐time stability. Due to its resemblance to the scalar case, we denote such finite‐time stable systems as generalised multivariable STA. Furthermore, the class of finite‐time stable systems comprise the currently available versions of STAs. To finalise, by means of simulation examples, we show that our proposed finite‐time stable algorithms are well suited for signals online differentiation and highlight their dynamical traits.     

Mechanical behavior of YSZ coatings co-deposited with Al and Ag on AISI 316L via RF sputtering

This article presents nanohardness, coefficient of friction (COF), and wear of Yttria-stabilized zirconia coatings (YSZ) deposited on 316L steel substrates and co-deposited with Al and Ag. YSZ coatings were deposited via RF sputtering reactive phase technique. It is widely known that the RF sputtering technique produces stoichiometric coatings with high homogeneity and density. The average thickness of the coatings was 200 nm, and the X-ray diffraction study (XRD) showed the formation of alumina alpha (α-Al₂O₃) and metallic silver in the YSZ coatings deposited with Al and Ag, respectively. The mechanical properties were evaluated by means of nanoindentation, and the wear resistance was studied with pin-on-disk technique. The addition of Ag to the YSZ coatings led to decreased hardness, while the YSZ coatings deposited with Al presented an increased hardness. Finally, YSZ coatings deposited with aluminum and silver had the lowest friction coefficient, while Ag-YSZ coatings had a COF very similar to that obtained in YSZ coatings. The wear resistance test showed that YSZ coatings deposited with Al had lower volume loss compared to YSZ coatings deposited with Ag. The wear mechanism in the deposited coatings is analyzed.     

Pequi Oil,a MUFA/Carotenoid-Rich Oil,Exhibited Protective Effects against DSS-Induced Ulcerative Colitis in Mice

Inflammatory bowel diseases (IBD) affect the gastrointestinal tract, and the imbalance of intestinal immune homeostasis can trigger them. Pequi oil (PO), a monounsaturated (MUFA) and carotenoid-rich food with nutraceutical potential, could help reshape the intestinal immune response, ameliorating IBD outcomes. This study investigates the effects of a 28 days intake of PO on elements of the intestinal immune response of mice with DSS-induced ulcerative colitis (disease activity index, colonic damage, inflammatory cells and markers). PO reduces body weight, colonic crypt and goblet cell losses and ameliorates diarrhea. In the colon, it increases γδT cells and secretory-IgA and decreases CD8+T cells. In lymphoid organs, it reduces CD8+T cells. Moreover, it also reduces the IL-17 and CRP in plasma. PO oil promotes a less cytotoxic response that may protect mice from immunological injuries caused by an IBD in the intestinal mucosa, improving the disease prognosis. Practical applications: This study demonstrates that the intake of pequi oil contributes to the regulation of immune response and improves clinical and histological signs of DSS-induced ulcerative colitis in mice. Its effects in cytotoxic cell reduction and other inflammatory markers and stimulation of regulatory cells, and preservation of mucus-producing cells, provide news insights about the importance of the regular intake of this food to better prognosis of ulcerative colitis acute episodes. In addition, these findings encourage further studies with foods with a protective potential for the intestinal mucosa.     

Influence of the gasket materials on the clamping pressure distribution in a PEM water electrolyzer: Bolt torques and operation mode in pre-conditioning

To keep optimally connected, all electrolysis cell elements is one of the most important design criteria. The optimal distribution of the clamping points is crucial to increasing cell performance. In this work, the compression pressure distribution inside of a 25 cm² PEM electrolysis cell was evaluated, using different materials: Teflon®, Viton®, ethylene propylene diene monomer rubber (EPDM), and nitrile rubber. Sealing material evaluation was performed taking as performance indicators: total compressed area (%) and compression pressure, for different torques applied. Pressure distribution was obtained by using pressure-sensitive films, analyzing the distribution of pressure points from three-dimensional plots (3D), and quantifying intensities of the images obtained. Results showed that pressure points distribution depends on the stiffness and thickness of the gasket materials. For a tightening torque of 3.70 N m, a pressure of 2.23 MPa is obtained with 85% of the membrane area compressed using nitrile rubber-EPDM gaskets.