Effective removal of Cr(VI) and methyl orange from the aqueous environment using two-dimensional (2D) Ti3C2Tx MXene nanosheets

Industrial use of heavy metals and dyes critically depends on the effective handling of industrial effluents. Effective remediation of industrial effluents using various adsorbent materials has thus become critical. In this paper, we study two-dimensional MXenes as an adsorbent for removing Cr(VI) and methyl orange (MO) in waters. The physico-chemical performance of MXenes was studied using X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer?Emmett?Teller, scanning electron microscopy, high resolution-transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy techniques. The adsorption system, including influence of contact time, pH of solutions, co-ions, and desorption experiments were performed for effective Cr(VI) and MO removal. The Cr(VI) and MO removal rate of the MXenes was very fast, and the kinetic system was driven by pseudo-second-order kinetics. The sorption isotherm closely well-tailored with the Langmuir isotherm, and the maximum removal efficiencies were 104 and 94.8 mg/g for Cr(VI) and MO, respectively. The MXenes was successfully regenerated by 0.1 M NaOH aqueous solution and can be repeatedly recycled. The uptake of Cr(VI) and MO by the MXenes was mainly due to chemical adsorption, namely electrostatic adsorption, complexation, surface interactions, and ion exchange mechanisms. This investigation demonstrates the selectivity and feasibility of the MXenes as a real adsorbent for eliminating Cr(VI) and MO from the aqueous environment.     

Active circuits for flux waveform compensation in ferromagnetic cores

Some new schemes using active circuits are proposed for realization of sinusoidal flux in a ferromagnetic core during loss testing. One of the suggested configurations facilitates the loss measurements to be made from the primary side itself. A few filter circuits enable the tests to be carried out on normal supply mains without the need for a calibration generator. Experimental results are reported to confirm the acceptability of the proposed schemes.     

Validation and error estimation of computational models

This paper develops a Bayesian methodology for assessing the confidence in model prediction by comparing the model output with experimental data when both are stochastic. The prior distribution of the response is first computed, which is then updated based on experimental observation using Bayesian analysis to compute a validation metric. A model error estimation methodology is then developed to include model form error, discretization error, stochastic analysis error (UQ error), input data error and output measurement error. Sensitivity of the validation metric to various error components and model parameters is discussed. A numerical example is presented to illustrate the proposed methodology.     

Fast, portable application mirroring

Previous implementations of an application mirror-a tool that lets two computers interactively share an application-have required hardware modifications, been restricted to one platform, and suffered from slow data throughput. The authors overcome these drawbacks by transmitting only those events that affect a shared application's status     

General sweep mathematical morphology

General sweep mathematical morphology provides a new class of morphological operations, which allow one to select varying shapes and orientations of structuring elements during the sweeping process. Such a class holds syntactic characteristics similar to algebraic morphology as well as sweep geometric modeling. The conventional morphology is a subclass of the general sweep morphology. The sweep morphological dilation/erosion provides a natural representation of sweep motion in the manufacturing processes, and the sweep opening/closing provides variant degrees of smoothing in image filtering. The theoretical framework for representation, computation and analysis of sweep morphology is presented in this paper. Its applications to the sweeping with deformations, image enhancement, edge linking, and shortest path planning for rotating objects are also discussed.     

Oxidation characteristics of Ti-25Al-10Nb-3V-1Mo

Static oxidation kinetics of Ti-25Al-10Nb-3V-1Mo (atomic percent) were investigated in air over the temperature range of 650–1000°C using thermogravimetric analysis. The oxidation kinetics were complex at all exposure temperatures and displayed up to two distinct stages of parabolic oxidation. Breakaway oxidation occurred after long exposure times at high temperatures. Oxidation products were determined using x-ray diffraction techniques, electron microprobe analysis, and energy dispersive x-ray analysis. Oxide scale morphology was examined using scanning electron microscopy of the surfaces and cross-sections of oxidation specimens. The oxides during the parabolic stages were compact and multilayered, consisting primarily of TiO₂ doped with Nb, a top layer of Al₂O₃ and a thin bottom layer of TiN. The transition between the first and second parabolic stage is linked to the formation of a TiAl layer at the oxide-metal interface. Porosity also formed in the TiO₂ layer during the second stage, causing degradation of the oxide and breakaway oxidation.     

Influence of cooling rates on the transformation behaviour of 9Cr-1 Mo-0.07C steel

The choice of various decomposition mechanisms of austenite in a 9Cr-1 Mo-0.07C steel under different rates of cooling has been studied. The techniques employed were electron probe micro-analysis, X-ray diffraction and electron microscopy. The observed morphological features may be explained based on the predominance of the two types of transformation, austenite martensite and austenite ferrite during cooling. In the steel used in this study, decomposition of austenite to proeutectoid ferrite was favoured at cooling rates less than about 2 Ks^–1. The mechanism by which the supersaturated proeutectoid ferrite relieves its excess solute concentration was also studied. A microstructural map has been proposed to predict the constitution at the end of any given cooling rate for 9Cr-1 Mo-0.07C steel. The choice of commercial treatment has been rationalized with respect to the resultant microstructural constituents.     

Effects of temperature and reinforcement content on corrosion characteristics of LM13/albite composites

This paper reports a study of the corrosion characteristics of LM13/albite metal matrix composites in 1 M HCl solution as a function of temperature and percentage of reinforcement. The percentage of reinforcement was varied from 2 to 6 wt.% in steps of 2% and the composites were prepared by the liquid metallurgy technique. The weight loss method was used to determine corrosion rate. Corrosion tests were performed at 20°C, 40°C, 60°C and 80°C. The durations of the tests ranged from 24 to 96 h in the steps of 24 h. Both the unreinforced matrix alloy and the composites were subjected to identical test conditions to study the influence of the reinforcement and temperature on LM13 alloy corrosion behaviour. The corrosion rates of both the unreinforced matrix alloy and the composites decreased with the exposure time. The composites were found to be less corrosion resistant than the unreinforced matrix alloy. The corrosion rates of both the unreinforced matrix alloy and the composites increased linearly with temperature. Scanning electron microscopy was used to study the corroded surface of the specimens.     

Accelerated Life Testing (ALT) Design Based on Computational Reliability Analysis

Accelerated life testing (ALT) design is usually performed based on assumptions of life distributions, stress–life relationship, and empirical reliability models. Time‐dependent reliability analysis on the other hand seeks to predict product and system life distribution based on physics‐informed simulation models. This paper proposes an ALT design framework that takes advantages of both types of analyses. For a given testing plan, the corresponding life distributions under different stress levels are estimated based on time‐dependent reliability analysis. Because both aleatory and epistemic uncertainty sources are involved in the reliability analysis, ALT data is used in this paper to update the epistemic uncertainty using Bayesian statistics. The variance of reliability estimation at the nominal stress level is then estimated based on the updated time‐dependent reliability analysis model. A design optimization model is formulated to minimize the overall expected testing cost with constraint on confidence of variance of the reliability estimate. Computational effort for solving the optimization model is minimized in three directions: (i) efficient time‐dependent reliability analysis method; (ii) a surrogate model is constructed for time‐dependent reliability under different stress levels; and (iii) the ALT design optimization model is decoupled into a deterministic design optimization model and a probabilistic analysis model. A cantilever beam and a helicopter rotor hub are used to demonstrate the proposed method. The results show the effectiveness of the proposed ALT design optimization model. Copyright © 2015 John Wiley & Sons, Ltd.     

Handling of Dependence in Dempster–Shafer Theory

Dempster's rule of combination can only be used when the bodies of evidence are assumed to be independent. However, such an assumption is often unrealistic. This paper proposes a systematic approach to handle dependence in evidence theory. It includes both the representation of dependence among information sources and the aggregation of the dependent evidence. For the representation of the dependence, the proposed methodology is able to capture both inner dependence (i.e., dependence among features of a system) and outer dependence (i.e., dependence among the evidence sources during the information propagating and evaluating process). We suggest dealing with the inner dependence by applying the analytic network process model, and modeling the outer dependence based on the intersection situations of the identified influencing factors. Then for the combination of dependent evidence, the strategy is to use discounting aggregation where the discounting coefficients are related to the degree of both outer and inner dependence. The discounting operator helps reduce the duplicate calculations in the fusion of dependent evidence and relax the assumption of independence when using Dempster's rule. A case study of transportation project evaluation is used to illustrate the proposed methodology.