Bilevel programming for generating discrete representations in multiobjective optimization

Mathematical Programming - The solution to a multiobjective optimization problem consists of the nondominated set that portrays all relevant trade-off information. The ultimate goal is to identify...     

Thermal Analysis of Micro- and Nano-Lignocellulosic Reinforced Styrene Maleic Anhydride Composite Foams

The aim of this study was to measure the thermal properties of foamed nano/macro filler–reinforced styrene maleic anhydride (SMA) composites. SMA (66%) as a polymer matrix (10% maleic anhydride content) and various fillers including wood flour, starch, α-cellulose, microcrystalline cellulose and cellulose nanofibrils as reinforcing agents (30%) and lubricant (4%) were used to manufacture the composites in a twin-screw extruder. According to the thermogravimetric analysis (TGA) results, thermal degradation of all the foamed composites was found to be lower than that of SMA composites. The storage modulus values were negatively affected with a second time foaming (reprocessing [recycling] the initially processed composites a second time), as were loss modulus and T_g. As a result, second-time-foamed composite modulus values were lower than those of the foamed composites. According to the melt flow index (MFI) results, viscosity of the SMA was found to increase with the addition of fillers.     

Fabrication of SERS active gold nanorods using benzalkonium chloride,and their application to an immunoassay for potato virus X

The authors report on a robust method for the synthesis of gold nanorods (AuNRs) with tunable dimensions and longitudinal surface plasmon resonance. The method relies on seed-mediated particle growth in the presence of benzalkonium chloride (BAC) in place of the widely used surfactant cetyltrimethyl ammonium bromide (CTAB). Uniform AuNRs were obtained by particle growth in solution, and BAC is found to stabilize the AuNRs for >1 year. The SERS activity of the resulting AuNRs is essentially identical to that of CTAB-protected nanorods. The SERS activity of the BAC protected nanorods was applied to the quantitative analysis of potato virus X (PVX). The calibration plot for PVX is linear in the 10 to 750 ng?mL^?1 concentration range, and the detection limit is 2.2 ng?mL^?1.

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Graphical abstract SERS-active gold nanorods (AuNRs) have been prepared by using benzalkonium chloride as stabilization agent. Effects of chemical parameters on AuNRs have been explored and AuNRs were used in quantitative analysis of potato virus X (PVX).

     

A structural analysis of ultrathin barrier (In)AlN/GaN heterostructures for GaN-based high-frequency power electronics

Metal–organic chemical vapor deposition (MOCVD) is one of the best growth methods for GaN-based materials as well-known. GaN-based materials with very quality are grown the MOCVD, so we used this growth technique to grow InAlN/GaN and AlN/GaN heterostructures in this study. The structural and surface properties of ultrathin barrier AlN/GaN and InAlN/GaN heterostructures are studied by X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements. Screw, edge, and total dislocation densities for the grown samples have been calculated by using XRD results. The lowest dislocation density is found to be 1.69 × 10⁸ cm⁻² for Sample B with a lattice-matched In_0.17Al_0.83N barrier. The crystal quality of the studied samples is determined using (002) symmetric and (102) asymmetric diffractions of the GaN material. In terms of the surface roughness, although reference sample has a lower value as 0.27 nm of root mean square values (RMS), Sample A with 4-nm AlN barrier layer exhibits the highest rough surface as 1.52 nm of RMS. The structural quality of the studied samples is significantly affected by the barrier layer thickness. The obtained structural properties of the samples are very important for potential applications like high-electron mobility transistors (HEMTs).     

Synthesis of H‐shaped complex macromolecular structures by combination of atom transfer radical polymerization,photoinduced radical coupling,ring‐opening polymerization,and iniferter processes

Three controlled/living polymerization processes, namely atom transfer radical polymerization (ATRP), ring‐opening polymerization (ROP) and iniferter polymerization, and photoinduced radical coupling reaction were combined for the preparation of ABCBD‐type H‐shaped complex copolymer. First, α‐benzophenone functional polystyrene (BP‐PS) and poly(methyl methacrylate) (BP‐PMMA) were prepared independently by ATRP. The resulting polymers were irradiated to form ketyl radicals by hydrogen abstraction of the excited benzophenone moieties present at each chain end. Coupling of these radicals resulted in the formation of polystyrene‐b‐poly(methyl methacrylate) (PS‐b‐PMMA) with benzpinacole structure at the junction point possessing both hydroxyl and iniferter functionalities. ROP of ε‐caprolactone (CL) by using PS‐b‐PMMA as bifunctional initiator, in the presence of stannous octoate yielded the corresponding tetrablock copolymer, PCL‐PS‐PMMA‐PCL. Finally, the polymerization of tert‐butyl acrylate (tBA) via iniferter process gave the targeted H‐shaped block copolymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4601–4607     

Electrical and photoelectrical behaviour of heterojunctions based on novel oligomeric metal complexes

Naringenin‐based Schiff base ligands with 4‐aminobenzoic hydrazide were obtained as a unilateral form ( L¹ ). The ligand was oligomerized by oxidative polycondensation reaction with NaOCl as an oxidant in an aqueous alkaline medium at 90 °C to form a functional oligomer ( L² ), and its transition metal complexes such as those with Cu(II), Ni(II) and Zn(II) were prepared. The monomer and the oligomeric compounds were characterized using various techniques. Optical and electrical properties of the complexes were also investigated. All compounds showed indirect band gaps and they can be accepted as being in the semiconductor class. Organic–inorganic hybrid devices were obtained using n‐Si inorganic semiconductor and the complexes. The characteristic parameters of the devices were determined using current–voltage (I–V) and capacitance–voltage measurements in the dark. Photoelectrical properties of the devices were investigated using I–V measurements under a solar simulator with an AM1.5 global filter. Copyright © 2015 John Wiley & Sons, Ltd.     

Versatile light‐responsive organogels: Evaluation of their dye releasing and photoinitiation behaviors

Light‐responsive crosslinked structures were prepared by a straightforward quaternization strategy using chloride functional polystyrene copolymers and commercially available Michler's ketone with varying feed ratios. Resulting organogels demonstrated excellent solvent absorption and their swelling characteristics were altered by UV‐light irradiation. According to scanning electron microscope images, UV‐illuminated samples showed an obvious photodecomposition, which enhanced their solvent uptake capacity with increase of UV exposure. Additionally, release behavior of eosin Y as a model compound was determined by UV–vis and fluorescence spectrometers. Achieved photoactive gels were also employed as the reusable heterogeneous initiators for photoinduced free‐radical polymerization of methyl methacrylate. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1275–1282     

Protecting the data-driven newsvendor against rare events: a correction-term approach

We propose an approach to the data-driven newsvendor problem that incorporates a correction factor to account for rare events, when the decision-maker has few historical data points at his disposal but knows the range of the demand. This mitigates a weakness of pure data-driven methodologies, specifically, the fact that they under-protect the system against tail events, which are in general under-observed in the empirical demand distribution. We test the approach in extensive computational experiments and provide a summary table of the numerical experiments to help the decision maker gain further insights.