Azomethine-based phenol polymer: Synthesis,characterization and thermal study

Azomethine-based phenol polymer, poly-2-{[(6-aminopyridin-2-yl)imino]methyl}-phenol (PAPIMP), was synthesized through the combination of condensation reaction and oxidative polymerization. Polymer isolated from aqueous solution was characterized by UV–vis, FT-IR, NMR and TG, SEC analysis. According to the SEC chromatograms, the number-average molecular weight (M_n), weight-average molecular weight (M_w) and polydispersity index (PDI) values of PAPIMP were determined to be 33,550, 78,900 g mol^?1 and 2.352, respectively. Also, optical band gaps (E_g) of APIMP and PAPIMP calculated from cyclic voltammetry (CV) measurements. Also, electrical conductivities of each component measured with four-point probe technique. TG analysis showed that PAPIMP was stable up to 300 °C. The thermal decomposition kinetics of PAPIMP was investigated by means of thermogravimetric analysis in dynamic nitrogen atmosphere at four different heating rates: 5, 10, 15 and 20 °C min^?1. The apparent activation energies for thermal decomposition of PAPIMP were obtained by Tang, Flynn–Wall–Ozawa (FWO), Kissenger–Akahira–Sunose (KAS) and Coats–Redfern methods (CR) were 96.97, 105.33, 97.28 and 88.60 kJ mol^?1, respectively; the mechanism function and pre-exponential factor were determined by master plots method. The most likely decomposition process was a D_n Deceleration type in terms of the Coats–Redfern and master plots results.     

Products,Sums and Quotients of Upper Truncated Pareto Random Variables with an Application in Hydrology

Some hydrological quantities such as the rainfall intensity, which is defined as the quotient of the rainfall depth to the rainfall duration, are based on functions of random variables. At this point, the probability distribution of that quantity arises. Then one may take this distribution into account for the exact statistical inference without referring to a simulation study. There are a lot of works on the exact distributions of functions of random variables in the literature. One case is for the Pareto distributed random variables. Pareto distribution and its upper truncated version have many applications in hydrological modelling. In this paper, the exact distributions of the product, sum and quotient of two independently distributed upper truncated Pareto random variables are obtained. Although the probability density functions of the product and quotient are obtained in elementary mathematical functions, that for the sum is obtained in terms of a special function. Some characteristics of these functions such as moments and percentiles can be easily obtained. The distributions of the quotient and the sum are applied on a rainfall data set from hydraulic efficiency research of green roofs. The parameters are estimated by the method of maximum likelihood. The theoretical results of this paper may also be useful to other practitioners of the upper truncated Pareto distribution.

     

A mixed-integer programming approach to the parallel replacement problem under technological change

The parallel replacement problem under economies of scale (PRES) determines minimum cost replacement policies for each asset in a group of assets that operate in parallel and are subject to fixed and variable purchase costs. We study the mixed-integer programming formulation of PRES under technological change by incorporating capacity gains into the model such that newer, technologically advanced assets have higher capacity than assets purchased earlier. We provide optimal solution characteristics and insights about the economics of the problem and derive associated cutting planes for optimising the problem. Computational experiments illustrate that the inequalities are quite effective in solving PRES under technological change instances.     

Temperature dependent conductivity and structural properties of sol–gel prepared holmium doped Bi2O3 nanoceramic powder

Holmium (Ho)-doped Bi₂O₃ nanoceramic powders derived from sol–gel method have been studied in terms of structural, morphological, and electrical properties. The morphology of the nanoceramic materials was analyzed by scanning electron microscopy (SEM) and their structure by X-ray powder diffraction (XRD). Temperature dependence of DC conductivity measurements of nanoceramic powders were carried out by using DC four-point probe technique (4PPT) in air at temperatures ranging from 702 to 1169 K. Electrical conductivity results demonstrate that there is a sharp increase at around 973 K, which indicates an existence of order–disorder transition. This result supported by the Differential Thermal Analyzer (DTA) curve and XRD pattern which show that the sample has stable high oxygen ionic conductivity fluorite type face centered cubic δ-phase. Electrical characteristics also show that the DC conductivity in the studied materials obeys Arrhenius relation with different activation energies and conduction mechanisms: two temperature regions with activation energies E_a1=1.40 eV (702–993 K) and E_a2=0.66 eV (1006–1169 K). The analysis of experimental data revealed that the translation motion of the charge carrier, oxygen vacancies, and space charge polarization are responsible for the change in activation energy as a function of temperature.     

Pricing and recovery planning for demanufacturing operations with multiple used products and multiple reusable components

In this study, we consider a pricing and recovery planning problem encountered in demanufacturing where multiple types of reusable components can be recovered from multiple used product quality groups. The problem is to maximize the net profit of the demanufacturer by characterizing the optimal acquisition prices of the used products and selling prices along with recovery quantities of the reusable components. To address this problem, we develop a mathematical model and analyze the structural properties of an optimal solution to this model. We propose a solution algorithm that exploits these structural properties. Results from a comprehensive computational study shows that the proposed algorithm is very efficient and can be used in practice to address the large-sized instances of the problem. We also present a polynomial time algorithm for a special case of the problem of interest where there is a single used product quality group.     

Discrete approximation heuristics for the capacitated continuous location–allocation problem with probabilistic customer locations

The capacitated continuous location–allocation problem, also called capacitated multisource Weber problem (CMWP), is concerned with locating m facilities in the Euclidean plane, and allocating their capacity to n customers at minimum total cost. The deterministic version of the problem, which assumes that customer locations and demands are known with certainty, is a nonconvex optimization problem. In this work, we focus on a probabilistic extension referred to as the probabilistic CMWP (PCMWP), and consider the situation in which customer locations are randomly distributed according to a bivariate probability distribution. We first formulate the discrete approximation of the problem as a mixed-integer linear programming model in which facilities can be located on a set of candidate points. Then we present three heuristics to solve the problem. Since optimal solutions cannot be found, we assess the performance of the heuristics using the results obtained by an alternate location–allocation heuristic that is originally developed for the deterministic version of the problem and tailored by us for the PCMWP. The new heuristics depend on the evaluation of the expected distances between facilities and customers, which is possible only for a few number of distance function and probability distribution combinations. We therefore propose approximation methods which make the heuristics applicable for any distance function and probability distribution of customer coordinates.     

Characterisation and vapour sensing properties of spin coated thin films of anthracene labelled PMMA polymer

In the present article thin films of poly (methyl methacrylate) (PMMA) polymer labelled with anthracene (Ant-PMMA) prepared by spin coating are characterised by UV–visible spectroscopy, surface plasmon resonance (SPR), spectroscopic ellipsometry (SE) and Atomic Force Microscopy (AFM) and their organic vapour sensing properties are investigated. Ant-PMMA films' thickness are determined by performing theoretical fitting to experimental data measured using SPR and SE. Results obtained show that the spin-cast films are of good uniformity with an average thickness of 6–8 nm. Organic vapour sensing properties are studied using SPR technique during exposures to different volatile organic compounds (VOCs). Ant-PMMA films' response to the selected VOCs has been examined in terms of solubility parameters and molar volumes of the solvents, and the films were found to be largely sensitive to benzene vapour compared to other studied analytes.     

Arsenic removal from drinking water by electrocoagulation using iron electrodes

Arsenic removal from drinking water was investigated using electrocoagulation (EC) followed by filtration. A sand filter was used to remove flocs generated in the EC process. Experiments were performed in a batch electrochemical reactor using iron electrodes with monopolar parallel electrode connection mode to assess their efficiency. The effects of several operating parameters on arsenic removal such as current density (1.5–9.0 mA cm^?2), initial arsenic concentration (50–500 μg L^?1), operating time (0–15 min), electrode surface area (266–665 cm²), and sodium chloride concentrations (0.01 and 0.02M) were examined. The EC process was able to decrease the residual arsenic concentration to less than 10 μg L^?1. Optimum operating conditions were determined as an operating time of 5 min and current density of 4.5 mA cm^?2 at pH of 7. The optimum electrode surface area for arsenic removal was found to be 266 cm² taking into consideration cost effectiveness. The residual iron concentration increased with increasing residence time, and maximum residual iron value was measured as 287 μg L^?1 for electrode surface area of 266 cm². The addition of sodium chloride had no significant effect on residual arsenic concentration, but an increase in current density was observed.     

Computational homogenization of soft matter friction: Isogeometric framework and elastic boundary layers

A computational contact homogenization framework is established for the modeling and simulation of soft matter friction. The main challenges toward the realization of the framework are (1) the establishment of a frictional contact algorithm that displays an optimal combination of accuracy, efficiency, and robustness and plays a central role in (2) the construction of a micromechanical contact test within which samples of arbitrary size may be embedded and which is not restricted to a single deformable body. The former challenge is addressed through the extension of mixed variational formulations of contact mechanics to a mortar‐based isogeometric setting where the augmented Lagrangian approach serves as the constraint enforcement method. The latter challenge is addressed through the concept of periodic embedding, with which a periodically replicated ‐continuous interface topography is realized across which not only pending but also ensuing contact among simulation cells will be automatically captured. Two‐dimensional and three‐dimensional investigations with unilateral/bilateral periodic/random roughness on two elastic micromechanical samples demonstrate the overall framework and the nature of the macroscopic frictional response. Copyright © 2014 John Wiley & Sons, Ltd.