Probabilistic nonlinear analysis of CFR dams by MCS using Response Surface Method

This paper presents the probabilistic analysis of concrete-faced rockfill (CFR) dams according to the Monte Carlo Simulation (MCS) results which are obtained through the Response Surface Method (RSM). ANSYS finite element program is used to get displacement and principal stress components. First of all, some parametric studies are performed according to the simple and representative finite element model of dam body to obtain the optimum approximate model. Secondly, a sensitivity analysis is performed to get the most effective parameters on dam response. Then, RSM is used to obtain the approximate function through the selected parameters. After the performed analyses, star experimental design with quadratic function without mixed terms according to the k = 1 is determined as the most appropriate model. Finally, dam-foundation-reservoir interaction finite element model is constituted and probabilistic analyses are performed with MCS using the selected parameters, sampling method, function and arbitrary factor under gravity load for empty and full reservoir conditions. Geometrically and materially nonlinearity are considered in the analysis of dam-foundation-reservoir interaction system. Reservoir water is modeled by fluid finite elements based on the Lagrangian approach. Structural connections are modeled as welded contact and friction contact based on Coulomb’s friction law. Probabilistic displacements and stresses are presented and compared with deterministic results.     

Time-varying sliding-coefficient-based terminal sliding mode control methods for a class of fourth-order nonlinear systems

This paper presents a decoupled terminal sliding mode control (DTSMC) and a nonsingular decoupled terminal sliding mode control (NDTSMC) method for a class of fourth-order nonlinear systems. First, the nonlinear fourth-order system is decoupled into two (primary and secondary) second-order subsystems. The sliding surface of each subsystem was designed by utilizing time-varying coefficients, which are computed by linear functions derived from the input–output mapping of the one-dimensional fuzzy rule bases. Then the control target of the secondary subsystem was embedded to the primary subsystem by the help of an intermediate signal. Thereafter, the DTSMC and the NDTSMC methods were utilized separately to ensure that both subsystems converge to their equilibrium points. The inverted pendulum system was used in the simulations and results were given to show the effectiveness of the proposed methods. It is seen that the proposed methods exhibit a considerable improvement in terms of a faster dynamic response and lower IAE and ITAE values as compared with the existing decoupled control methods in the literature.     

The capacitated maximal covering location problem with backup service

The maximal covering location problem has been shown to be a useful tool in siting emergency services. In this paper we expand the model along two dimensions — workload capacities on facilities and the allocation of multiple levels of backup or prioritized service for all demand points. In emergency service facility location decisions such as ambulance sitting, when all of a facility's resources are needed to meet each call for service and the demand cannot be queued, the need for a backup unit may be required. This need is especially significant in areas of high demand. These areas also will often result in excessive workload for some facilities. Effective siting decisions, therefore, must address both the need for a backup response facility for each demand point and a reasonable limit on each facility's workload. In this paper, we develop a model which captures these concerns as well as present an efficient solution procedure using Lagrangian relaxation. Results of extensive computational experiments are presented to demonstrate the viability of the approach.     

Three dimensional tris[triorganotin(IV)]hexacyanoiron(III) polymeric complexes as oxidising agents

The oxidation of N₂H₄ by tris[triorganotin(IV)]hexacyanoiron(III) polymer complexes has been studied spectrophotometrically. The oxidation rate is first order in both complex and N₂H₄ and the rate constant increases with increasing pH. Experiments over the temperature range (15–30 °C) allowed calculation of the activation parameters. An outer-sphere mechanism involving a rate-determining one-electron transfer is proposed. In addition, the products of the solid reactions between the iron(III) polymeric complexes and N₂H₄ were investigated by i.r., u.v. reflectance, X-ray powder diffraction, e.p.r. spectra and magnetic measurements.     

Aqueous polymerization of methyl methacrylate catalyzed by corundum and characterization of the obtained polymers

The aqueous polymerization of methyl methacrylate (MMA) was studied using sodium bi-sulfite as initiator in the absence and presence of corundum (Al₂O₃). It was found that corundum has a catalytic effect on the polymerization reaction. The polymers obtained in the presence of corundum were found to have a wider molecular weight distribution than in its absence; this was deduced by thin-layer chromatographic analysis in a binary mixture (benzene: methanol 1:1.5 by volume) at 25°C. The apparent energy of activation was calculated between 40 and 50°C, and was found to be 4.50 × 10⁴ and 1.70 × 10⁴ J/mol in the absence and presence of 0.5 g corundum (type 600 grit)/105 mL of the reaction mixture, respectively.     

Angular distributions of channeled pions and protons up to 250 GeV/c

Channeling phenomena are observed for positive particles of momentum up to 250 GeV/c in a germanium crystal. The polar angular distributions of the channeled particles are compared with theoretical predictions based on a diffusion model. The results indicate that at high particle energy there may be additional mechanisms besides those operative at low energy leading to dechanneling of the particles. In spite of this, channeling effects are observed for particles incident at up to several times the critical angle, in contrast with the results from low energy channeling. Statistical equilibrium in the azimuthal angular distribution has also been observed at all measured beam momenta to about twice the calculated channeling critical angle. The breakdown of statistical equilibrium for the 2 cm crystal used occurs at an incident angle 2–3 times smaller than predicted theoretically.     

Inhibition of acidic corrosion of carbon steel by some mono and bis azo dyes based on 1,5 dihydroxynaphihalene

Inhibition of the corrosion of carbon steel in hydrochloric acid solution by some mono- and bis-azo dyes based on 1,5-dihydroxynaphthalene was studied in relation to the concentration of inhibitors using weight loss and potentiostatic polarization techniques. The percentage inhibition efficiency calculated from two methods is in a good agreement with each other. The inhibition mechanism of the additives was ascribed to the formation of complex compound adsorbed on the metal surface. The adsorption process follows Freundlich adsorption isotherm. The formation of the complex compound was studied by conductometric and potentiometric titrations. The stability constants of the Fe-complexes were determined using the latter technique and related to the inhibition efficiency.     

A robust combination of dysprosium vanadate/halloysite nanotubes: the electrochemical system for dimetridazole detection

Dimetridazole (DMD) is one of the significant antibiotic drugs of nitroimidazoles derivates that have attracted increasing attention in the medical field due to its pharmacological and toxicological activity. The development of high-performance sensors for continuous monitoring of DMD in food and environments is receiving increasing attention. Herein, an electrochemical platform was designed based on a dysprosium vanadate/halloysite nanotubes (DyV/HNTs) nanocomposite for the detection of DMD. The DyV/HNTs nanocomposite was examined by various spectroscopic and analytical techniques. The DyV/HNTs based electrochemical sensor reveals a distinctly higher electrocatalytic response to the reduction of DMD due to the good physiochemical properties compared to other electrodes. The DyV/HNTs based electrochemical sensor for DMD covered two linear ranges of 0.001–0.54 and 0.54–188 μM with a detection limit of 0.9 nm through the amperometric method, which is better than those previously reported. Furthermore, selectivity, stability, repeatability, and reproducibility studies were performed. Moreover, the fabricated DyV/HNTs sensor was successfully applied for the reliable discrimination of DMD in biological and water samples with satisfactory recovery values. The results indicated that this DyV/HNTs nanocomposite may be a promising electrochemical sensing platform for the determination of DMD.     

On chaotic behaviour of the p-adic generalized Ising mapping and its application

In the present paper, by conducting research on the dynamics of the p-adic generalized Ising mapping corresponding to renormalization group associated with the p-adic Ising-Vannemenus model on a Cayley tree, we have determined the existence of the fixed points of a given function. Simultaneously, the attractors of the dynamical system have been found. We have come to a conclusion that the considered mapping is topologically conjugate to the symbolic shift which implies its chaoticity and as an application, we have established the existence of periodic p-adic Gibbs measures for the p-adic Ising-Vannemenus model.