Maximizing the profit in customer’s order acceptance and scheduling problem with weighted tardiness penalty

The customer’s order acceptance and scheduling problem in a single machine environment has long been an appealing research subject. In this paper, a situation where a pool of customers exists and each customer tends to place all his orders to a single company is addressed. Hence, the customer’s orders will be entirely either accepted or rejected. In this work, decisions on rejection or acceptance of customers and sequencing of the accepted orders are simultaneously considered. The goal is to maximize the total net profit obtained from accepted orders revenues contributed by tardiness penalty. In response to the computational complexity of the problem, a heuristic algorithm and two optimal branch and bound procedures with upper bound, lower bound, and dominance rules are developed. Computational results demonstrate that the proposed methods perform well in a timely manner.     

A novel dual thermo- and pH-responsive silver nanocomposite hydrogel as a drug delivery system

The purpose of this study was to develop a novel dual thermo- and pH-responsive silver nanocomposite hydrogel (SNH) for drug release applications. This smart SNH was prepared in a facile one-pot method by in situ reduction of silver ions in salep solution and then grafting of poly(vinylpyrrolidone-co-acrylic acid) onto it. The SNH was characterized by transmission electron microscopy (TEM), scanning electron microscopy with energy-dispersive X-ray analysis (SEM–EDAX), thermo-gravimetric analysis (TGA), Fourier transform infrared (FT-IR), UV–Vis spectroscopy, and cyclic voltammetry. The dependence of swelling properties of the prepared SNH on the reaction variables (such as monomer, Ag NO₃, and cross-linker concentrations), temperature, pH, and salt was investigated. The potential of obtained SNH was examined for the deferasirox release from prepared hydrogel under different temperatures and pHs. The evaluation of release mechanism and determination of diffusion coefficients were also studied. In addition, SNH showed good antibacterial potentials. The results of this study provide valuable information regarding the development of dual stimuli-sensitive SNH for biomedical applications.     

Synthesis,characterization, metal sorption,and biological activities of organosoluble and thermally stable azoxanthone‐based polyester

The aim of this work was to develop functionalized polyxanthones, poly(azoxanthone‐ester)s (PAXEs), with biological activities and heavy metal sorption abilities. For this purpose, at first, new xanthone‐based diol moiety was synthesized and then used for polymerization with commercial dicarboxylic acids via polycondensation reaction by Vilsmeier adducts. The monomer and all polymers were characterized by Fourier transform infrared (FTIR) and Nuclear magnetic resonance (NMR) spectroscopies, and the physical properties of these PAXEs including solution viscosity, solubility properties, thermal stability, and thermal behavior were studied. The prepared polyesters showed excellent thermal stability and good solubility in polar aprotic solvents. In addition, evaluation of antioxidant activity of the PAXEs by 2,2‐diphenyl‐1‐picrylhydrazyl assay revealed that synthesized polymers have higher antioxidant activity than xanthone nucleus. Also, evaluation of the antibacterial activities of the diol monomer and polymer showed good antibacterial activity against some bacterial strains (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa). The results showed that these PAXEs can be used in pharmaceutical and food industry (food packaging). Furthermore, these functionalized polyesters were utilized for extraction of environmentally harmful metal cations such as Cr (VI), Co (II), Ni (II), Cu (II), Pb (II), and Cd (II) from aqueous solutions. Copyright © 2015 John Wiley & Sons, Ltd.     

Sulfonated Aromatic Polymers and Organically Modified Montmorillonite Nanocomposite Membranes for Fuel Cells Applications

Aromatic polymers, such as sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), sulfonated poly(ether ether ketone) (SPEEK), and sulfonated poly(ether sulfone) (SPES), at the optimum degrees of sulfonation (DS), are suggested and evaluated as alternatives to Nafion for direct methanol fuel cells (DMFCs) applications. To reduce the methanol cross-over, which decreases the efficiency of the cell, organically modified montmorillonite nanoclays (OMMT) were added at 1 wt% to the sulfonated matrices with the optimum DS. The X-ray diffraction (XRD) patterns of nanocomposite membranes proved that the nanoclay layers were exfoliated. The proton conductivity and methanol permeability of the membranes, as well as the ion-exchange capacity (IEC), were measured. The selectivity parameter, ratio of proton conductivity to methanol permeability, was identified at 25°C for the nanocomposite membranes and the results were compared with Nafion117. Finally, the DMFC performance tests were investigated at 70°C and 5 M methanol feed for the manufactured nanocomposite polyelectrolyte membranes (PEMs). The SPEEK-based nanocomposite membrane showed the highest maximum power density in comparison with Nafion 117 and SPES and SPPO nanocomposite membranes. The results indicated that the nanocomposite membranes were promising PEMs for DMFC applications.     

A variational approach to difference equations

In this paper, we are concerned with the existence of at least three distinct solutions for nonlinear difference equations with Dirichlet boundary conditions. The proof of the main result is based on variational methods. We also provide an example in order to illustrate the main results.     

An iron Schiff base complex loaded mesoporous silica nanoreactor as a catalyst for the synthesis of pyrazine-based heterocycles

An iron Schiff base complex was encapsulated in SBA-15 mesoporous silica to afford a Fe(III)-Schiff base/SBA-15 heterogeneous nanocatalyst for the synthesis of pyridopyrazine and quinoxaline heterocycles. These reactions proceeded in water with excellent yields. The catalyst was characterized by physico-chemical and spectroscopic methods and found to retain the characteristic channel structures of the SBA-15, allowing good accessibility of the encapsulated metal complex.     

Reductive Alkylation of Pentaphenylthiopyrylium Perchlorate: An Approach to Regiospecific Synthesis of Hexasubstituted 2H-Thiopyrans

Regiospecific synthesis of some new hexasubstituted 2H-thiopyrans was examined by reductive alkylation of pentaphenylthiopyrylium perchlorate and found to be in quantitative yields. Under our experimental conditions, the formation of unstable thiabenzene intermediates could be observed through detectable color changing during the addition of C-nucleophiles to thiopyrylium perchlorate. Moreover, the effect of phenyl groups on the 3,5-positions of thiopyrylium perchlorate on the regioselectivity were compared with other analogs having methyl groups on the same positions.     

Study of reaction between activated acetylenes and N,N′‐diethyl‐2‐thiobarbituric acid in the presence of isocyanides or triphenylphosphine

In a series of separate experiments reaction between N,N′‐diethyl‐2‐thiobarbituric acid and acetylenic diesters in the presence of isocyanides or triphenylphosphine led to highly functionalized 4H‐pyrano[2,3‐d]thiopyrimidine or 1,4‐di‐ionic organophosphorus derivatives. The ¹H NMR spectra of diethyl‐7‐(2,6‐dimethylphenylamino)‐4‐oxo‐2‐thio‐ 1,3‐diethyl‐4H‐pyrano[2,3‐d]pyrimidine‐5,6‐dicarboxylate showed dynamic NMR effect that was attributed to restricted rotation around the aryl‐nitrogen single bond. Activation free energy (ΔG^≠) for this process is about 54.85 ± 2 kJ mol⁻¹. Betaines as 1,4‐diionic organophosphorus compounds in this reaction are possessed of two vicinal stereogenic centers and exist in the solution as a mixture of two diastereoisomers. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:228–235, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20601     

Scheduling linear deteriorating jobs to minimize the number of tardy jobs

In this paper a problem of scheduling a single machine under linear deterioration which aims at minimizing the number of tardy jobs is considered. According to our assumption, processing time of each job is dependent on its starting time based on a linear function where all the jobs have the same deterioration rate. It is proved that the problem is NP-hard; hence a branch and bound procedure and a heuristic algorithm with O(n ²) is proposed where the heuristic one is utilized for obtaining the upper bound of the B&B procedure. Computational results for 1,800 sample problems demonstrate that the B&B method can solve problems with 28 jobs quickly and in some other groups larger problems are also solved. Generally, B&B method can optimally solve 85% of the samples which shows high performance of the proposed method. Also it is shown that the average value of the ratio of optimal solution to the heuristic algorithm result with the objective ??(1 ? Ui) is at most 1.11 which is more efficient in comparison to other proposed algorithms in related studies in the literature.