Robust adaptive cruise control of high speed trains

The cruise control problem of high speed trains in the presence of unknown parameters and external disturbances is considered. In particular a Lyapunov-based robust adaptive controller is presented to achieve asymptotic tracking and disturbance rejection. The system under consideration is nonlinear, MIMO and non-minimum phase. To deal with the limitations arising from the unstable zero-dynamics we do an output redefinition such that the zero-dynamics with respect to new outputs becomes stable. Rigorous stability analyses are presented which establish the boundedness of all the internal states and simultaneously asymptotic stability of the tracking error dynamics. The results are presented for two common configurations of high speed trains, i.e. the DD and PPD designs, based on the multi-body model and are verified by several numerical simulations.     

Heat Transfer Analysis of a Microspherical Particle in the Slip Flow Regime by Considering Variable Properties

In order to investigate how far the temperature-dependent fluid properties and characteristic length influence the drag coefficient and the heat flux, a three-dimensional simulation study for a slip flow around an unconfined microspherical particle has been performed. Gas properties such as density, viscosity, conductivity, and mean free path were assumed to vary with temperature. Slip velocity and temperature jump at the gas particle interface were both treated numerically by imposition of the slip boundary conditions. The effects of variable gas properties and Knudsen number on momentum and heat transfer were also taken into account. It was concluded that for microflows with high heat transfer rates, the constant fluid properties approximation is very crude. In addition, the slip velocity and temperature jump affect the heat transfer in opposite ways: a large slip on the wall increases the convection along the surface, whereas a large temperature jump decreases the heat transfer by reducing the temperature gradient at the wall. Therefore, neglecting temperature jump will result in the overestimation of the heat transfer coefficient.     

Mapping the intellectual structure of the coronavirus field (2000–2020): a co-word analysis

Scientometrics - Over the two last decades, coronaviruses have affected human life in different ways, especially in terms of health and economy. Due to the profound effects of novel coronaviruses,...     

Reconstruction based approach to sensor fault diagnosis using auto-associative neural networks

Fault diagnostics is an important research area including different techniques. Principal component analysis （PCA） is a linear technique which has been widely used. For nonlinear processes, however, the nonlinear principal component analysis （NLPCA） should be applied. In this work, NLPCA based on auto-associative neural network （AANN） was applied to model a chemical process using historical data. First, the residuals generated by the AANN were used for fault detection and then a reconstruction based approach called enhanced AANN （E-AANN） was presented to isolate and reconstruct the faulty sensor simultaneously. The proposed method was implemented on a continuous stirred tank heater （CSTH） and used to detect and isolate two types of faults （drift and offset） for a sensor. The results show that the proposed method can detect, isolate and reconstruct the occurred fault properly.     

Multicomponent oxide composites for carriers in catalytic applications

Binary, ternary, and quaternary composite oxides of rare earths (La and Ce) with one or more of aluminum, magnesium, and zirconium, prepared by coprecipitation are studied. Potential use is carrier in steam or dry reforming of hydrocarbons and ethanol. Individual components influence specific surface area, porosity, acidity, hydrothermal stability, and oxygen storage capacity (OSC) differently. Interaction effects between components further influence these properties resulting in unexpected trends. Alumina and magnesia form solid solutions with zirconia until 650℃. Magnesia imparts better hydrothermal stability to zirconia. Aluminum and magnesium form MgAl₂O₄ spinel in ternary composites. Specific surface area varies linearly with alumina content. Alumina influences porosity, whereas magnesia influences pore diameter. The composites are mesoporous. Only binary composites present unimodal, pore size distribution. Composites containing alumina present type H2 isotherms while the remaining composites present H3 type isotherms. OSC increases over ZrO₂/CeO₂ 5.7 to 15.3 molar. Magnesia and alumina affect microstructure and hydrothermal stability in contrasting ways. Thermogravimetry indicates that ternary composites of zirconia with alumina or magnesia form through oxolation. Surface hydroxyls with varying acidity are seen by FTIR in as synthesized samples. Magnesia and zirconia influence acidity in opposite ways, which impacts deactivation in the decomposition of 2-methyl-3-butyn-2-ol.     

Effect of addition of titanium on structural,mechanical and biological properties of 45S5 glass-ceramic

The purpose of the present study was to evaluate the effect of addition of titanium on the structural, mechanical, and biological properties of sol-gel derived 45S5 bioactive glass-ceramic. For the synthesis of 45S5 glass ceramics, 5 and 10?mol% titanium were added to replace calcium named as Ti5 and Ti10, respectively. The structure of glass-ceramic was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS). The ability of glass-ceramics to form hydroxyapatite (HA) was also evaluated using XRD, FTIR and FE-SEM/EDS following immersion in the simulated body fluid (SBF) for 1, 7 and 14 days. The ion release potential was also evaluated during the afore-mentioned immersion periods. Furthermore, the cell viability and alkaline phosphatase (ALP) activity of osteoblast-like cells exposed to the dissolved products of glass-ceramics were evaluated. The effect of addition of titanium on the mechanical properties was evaluated by measuring the compressive strength. Despite the slower rate of HA formation in Ti-containing groups during the first day of immersion, all groups showed similar results after 14 days. The addition of titanium to 45S5 bioactive glass-ceramic decreased the silicon and sodium ion release. Ti5 showed the highest level of cell viability and ALP activity. The compressive strength of 45S5 glass-ceramic significantly increased following addition of titanium, and Ti10 showed the highest value. In conclusion, the findings of this study support the synthesis of 45S5 glass-ceramic modified by addition of 5?mol% titanium ions due to improved mechanical and biological properties along with the ability to control solubility and ion release profile.     

Inclusion complexes of atorvastatin calcium (ATV-Ca) and rosuvastatin calcium (ROV-Ca) drugs with α-CD, β-CD, γ-CD,HP-β-CD,M-β-CD,and maltodextrin along with their characterizations through experimental and computational methods

The aim of this research is a comparison of the efficiency of six commercially available cyclodextrins (CDs) to improve the solubility and oral bioavailability of atorvastatin calcium (ATV-Ca) and rosuvastatin calcium (ROV-Ca) drugs in aqueous media. Inclusion complexes of both drugs with non-toxic α-CD, β-CD, γ-CD, HP-β-CD, M-β-CD, and maltodextrin were prepared in a 1:1 stoichiometry via the kneading method. To reach the best CD, various experimental and computational analyses were performed including phase solubility, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), hydrogen-1 nuclear magnetic resonance (¹HNMR), carbon-13 nuclear magnetic resonance (¹³CNMR), and molecular docking calculations. The M-β-CD turned out to be the best substrate for the micro-encapsulation of both drugs. Also, ATV showed a higher tendency than ROV to form inclusion complexes with CDs. Molecular docking studies showed that HP–β–CD and M-β-CD are the most suitable substrates for the formation of inclusion complexes, respectively. Our research showed that the β-CD is not necessarily the most efficient substrate for increasing solubility based on previous reports in the literature; meanwhile, the other employed substrates in this study can show acceptable performances in this regard. According to our results, M-β-CD is the best substrate for the micro-encapsulation of both drugs, which increases their solubility in water.     

Microstructure of polycrystalline Fe<Subscript>82</Subscript>Ga<Subscript>18</Subscript> sample with solidification texture

Main attention of this paper was devoted to studying the effect of solidification texture on microstructure (phase constituents, grain morphology, and magnetic domain structure) of polycrystalline Fe₈₂Ga₁₈ sample. The alloy was melted using button arc melting and solidified in water-cooled copper mold. Optical microscope (OM) results confirm the development of large columnar grains in the solidification microstructure. Phase constitution and magnetic domain structures of the sample were studied by X-ray diffraction (XRD) and magnetic force microscopy (MFM). Results show a single-phase solid solution with an A2 structure for the sample which consists of regularly aligned magnetic domains. Although some maze-like subdomains are found in few regions, well-aligned stripe-like domains are predominant patterns in the sample. It demonstrates the high dependence of grain morphology and magnetic domain structure upon a preferred crystallographic direction during solidification.     

Investigation on the Collapse Behavior of Diagonal Stiffened Composite Plate Girders Subjected to Shear Loading

In this study, a new analytical method is presented to estimate the shear capacity of diagonally stiffened steel–concrete composite plate girders. This method is formulated based on tension field action in steel girder web and failure mechanism of concrete slab deck. To validate the accuracy of the proposed method, the obtained results are compared with three-dimensional finite element analysis of composite plate girders with different configuration of stiffeners. The results of analytical and numerical investigations indicate that the proposed method can accurately estimate the ultimate shear capacity of composite plate girders. In addition, it is shown that the diagonal stiffeners on one hand can reduce the buckling effects of shear panel of girders and on the other hand can increase the strength of elastic shear buckling and ultimate shear capacity of girders well in comparison with the unstiffened thin steel plate girders.