Preparation of low-platinum-loading electrocatalysts using electroless deposition method for proton exchange membrane fuel cell systems

One promising preparative method that offers the potential for improved platinum (Pt) dispersion of electrocatalysts is electroless deposition (ED). In this study, the effects of multiwalled carbon nanotubes (MWCNTs) pretreatment and synthesis procedure on properties of the four catalysts, synthesized by ED method, have been considered. The results of energy-dispersive X-ray spectroscopy (EDS), X-ray dot-mapping, X-ray fluorescence (XRF) and cyclic voltammetry (CV) analyses showed that using palladium (Pd) precursor during two-step sensitization-activation coating procedure gives uniform Pt particles distribution on MWCNTs with low aggregation and high specific surface area (∼80 m² g⁻¹). In addition, to investigate the performance of the synthesized catalysts in experimental fuel cell system, thin-film method was used to fabricate the membrane electrode assemblies (MEAs). Obtaining the polarization curves for the fabricated MEAs (Pt loading ∼0.4 mg cm⁻²) and a commercial MEA (ElectroChem, Pt loading ∼1 mg cm⁻²) demonstrated that the catalyst prepared by two-step sensitization-activation coating procedure possesses a good performance despite of its lower Pt content.     

GA and ICA approaches to job rotation scheduling problem: considering employee’s boredom

This paper presents a new model dealing with the job rotation scheduling problem, which is less studied, focusing on human characteristics such as boredom. Existing literature on conceptualizing boredom shows that researchers evaluate boredom in terms of exposure to the same tasks. We developed it to “exposure to similar tasks” and defined its functionality based on the need of assigning jobs with more similarity to each worker in the smallest period of planning which lowers the external interruption effect on worker’s concentration. To address the imbalance between number of jobs and that of workers in many industrial settings, we developed a multi-period imbalance assignment model. The proposed model is to rotate workers during a given planning horizon such that the total cost including assignment and boring cost will be minimized. The applicability of the model is described by presenting some real cases and validated through solving several randomly produced test problems by using Lingo software. Two search algorithms, genetic algorithm (GA) and imperialist competitive algorithm (ICA), designed to conquer the algorithmic complexity of model and their parameters adjusted using Taguchi’s method were used. The efficiency of algorithms is shown, comparing it with Lingo computation times, and it is shown that ICA solutions have better quality than GA solutions as well.     

Thermally Activated Aromatic Ionic Dopants (TA-AIDs) Enabling Stable Doping,Orthogonal Processing and Direct Patterning

Doping plays a critical role in organic electronics, and dopant design has been central in the development of functional and stable doping. In this study, there is departure from conventional molecular dopants and a new class of dopants are reported – aromatic ionic dopants (AIDs). AIDs consist of a pair of aromatic cation and anion that are responsible for molecular doping reaction and charge balancing separately. It is shown that the first AID made from cycloheptatrienyl (tropylium) cation and pentacyanocyclopentadienide anion (PCCp), abbreviated as T-PCCp, can function as an effective p-type dopant to dope polydioxythiophenes. Here, tropylium cation induces the doping reaction while the PCCp anion stabilizes the generated polarons and bipolarons. With T-PCCp, a highly doped (≈120 S/cm) and stable system is achieved up to 150 °C, an orthogonal (sequential)solution processing resulting from the immiscibility of the dopant and the polymer host, and a high-resolution direct micropatterning with laser writing resulted from a thermally activated doping process.     

Study on forcing schemes in the thermal lattice Boltzmann method for simulation of natural convection flow problems

The present study addresses the effect of various schemes for applying an external force term on the accuracy and performance of the thermal lattice Boltzmann method (LBM) for simulation of free convection problems. Herein, the forcing schemes of Luo, shifted velocity method, Guo, and exact difference method are applied by considering three velocity discrete models of D2Q4, D2Q5, and D2Q9. The accuracy and performance of these schemes are evaluated with the simulation of three natural convection problems, namely, free convection in a closed cavity, in a square enclosure with a hot obstacle inside, and the Rayleigh-Benard problem. The obtained results based on the present thermal LBM with different forcing schemes and velocity discrete models are compared with the existing experimental and numerical data in the literature. This comparison study indicates that imposing all employed forcing schemes leads to similar performance for the simulation of free convection problems studied at the middle range of Rayleigh numbers. It is found that the Luo forcing scheme is simple for implementation in comparison with the other three forcing schemes and provides the results with acceptable accuracy at moderate Rayleigh numbers. At higher Rayleigh numbers, however, the Guo scheme is not only numerically stable but a more precise forcing scheme in comparison with the other three methods. It is illustrated that employing the discrete velocity model of D2Q4 has more appropriate numerical stability along with less computational cost in comparison with two other discrete velocity models for simulation of natural convection heat transfer.     

Nanoparticulation of enzymatically cross-linked whey proteins to encapsulate caffeine via microemulsification/heat gelation procedure

A co-surfactant free microemulsion was formulated with sunflower oil, span 80 and whey protein solution and used as nanoreactor to generate caffeine-enveloping capsules through heat gelation of protein. Transglutaminase-induced cross-linking of proteins prior to microemulsification decreased the mean diameter from 478 to 318 nm for core-free particles and from 232 to 118 nm for capsules. As well, the lower limit of capsules size decreased from 78 nm to 45 nm due to enzymatic cross-linking. Scanning electron microscopy showed that morphology of particles and capsules was not completely spherical which was attributed to the protrusion of protein molecules out of aqueous droplets during gelation. The enzymatic treatment yielded in particles with higher glass transition temperature due to the reinforced structure of particulate gel. Fourier transform infrared spectroscopy confirmed the structural changes in proteins by heat and establishment of covalent cross-linkages by the enzyme action manifested by a band at 1078 cm⁻¹.     

Trans-free Iranian vanaspati through enzymatic and chemical transesterification of triple blends of fully hydrogenated soybean,rapeseed and sunflower oils

Production of trans-free Iranian vanaspati through enzymatic and chemical transesterification of triple blends of fully hydrogenated soybean (FHSBO), rapeseed (RSO) and sunflower (SFO) oils was investigated. The slip melting point (SMP), solid fat content (SFC) at 10–40 °C and induction period of oxidation at 120 °C (IP₁₂₀) of the transesterified and initial blends were evaluated. Results indicated that all the enzymatically and chemically transesterified blends had lower SMP, SFC and IP₁₂₀ than their initial blends. No significant differences (P < 0.05) were observed between the SMP of enzymatically and chemically transesterified blends. Some enzyme treated blends had higher SFC at some temperatures than chemically transesterified ones. Enzymatically transesterified blends had higher IP₁₂₀ than those prepared by chemical transesterification. Correlation between SFC at 20 °C and saturated fatty acid (SFA) content, and between SMP and SFA of transesterified blends indicated that the SFA must be between 27.2% and 36.6% for enzymatic and 28.4% and 37.8% for chemical transesterification to obtain transesterified fats suitable for use as vanaspati.     

Simultaneous Culturing of Cell Monolayers and Spheroids on a Single Microfluidic Device for Bridging the Gap between 2D and 3D Cell Assays in Drug Research

Two‐dimensional (2D) cell cultures have been the primary screening tools to predict drug impacts in vitro for decades. However, owing to the lack of tissue‐specific architecture of 2D cultures, secondary screening using three‐dimensional (3D) cell culture models is often necessary. A microfluidic approach that facilitates side‐by‐side 2D and 3D cell culturing in a single microchannel and thus combines the benefits of both set‐ups in drug screening; that is, the uniform spatiotemporal distributions of oxygen, nutrients, and metabolic wastes in 2D, and the tissue‐like architecture, cell–cell, and cell–extracellular matrix interactions only achieved in 3D. The microfluidic platform is made from an organically modified ceramic material, which is inherently biocompatible and supports cell adhesion (2D culture) and metal adhesion (for integration of impedance electrodes to monitor cell proliferation). To induce 3D spheroid formation on another area, a single‐step lithography process is used to fabricate concave microwells, which are made cell‐repellant by nanofunctionalization (i.e., plasma porosification and hydrophobic coating). Thanks to the concave shape of the microwells, the spheroids produced on‐chip can also be released, with the help of microfluidic flow, for further off‐chip characterization after culturing. In this study, the methodology is evaluated for drug cytotoxicity assessment on human hepatocytes.     

Firefly-inspired algorithm for discrete optimization problems: An application to manufacturing cell formation

The canonical firefly algorithm is basically developed for continuous optimization problems. However, lots of practical problems are formulated as discrete optimization problems. The main purpose of this paper is to present the discrete firefly algorithm (DFA) to solve discrete optimization problems. In the DFA, we define a firefly's position in terms of changes of probabilities that will be in one state or the other. Then by using this metaheuristic algorithm, the manufacturing cell formation problem is solved. To illustrate the behavior of the proposed model and verify the performance of the algorithm, we introduce a number of numerical examples to illustrate the use of the foregoing algorithm. The performance evaluation shows the effectiveness of the DFA. The proposed metaheuristic algorithm should thus be useful to both researchers and practitioners.     

Hyperspectral anomaly detection using spectral–spatial features based on the human visual system

ABSTRACT

Anomaly detection (AD) is one of the most attracting topics within the recent 10 years in hyperspectral imagery (HSI). The goal of the AD is to label the pixels with significant spectral or spatial differences to their neighbours, as targets. In this paper, we propose a method that uses both spectral and spatial information of HSI based on human visual system (HVS). By inspiring the retina and the visual cortex functionality, the multiscale multiresolution analysis is applied to some principal components of hyperspectral data, to extract features from different spatial levels of the image. Then the global and local relations between features are considered based on inspiring the visual attention mechanism and inferotemporal (IT) part of the visual cortex. The effects of the attention mechanism are implemented using the logarithmic function which well highlights, small variations in pixels’ grey levels in global features. Also, the maximum operation is used over the local features for imitating the function of IT. Finally, the information theory concept is used for generating the final detection map by weighting the global and local detection maps to obtain the final anomaly map. The result of the proposed method is compared with some state-of-the-art methods such as SSRAD, FLD, PCA, RX, KPCA, and AED for two well-known real hyperspectral data which are San Diego airport and Pavia city, and a synthetic hyperspectral data. The results demonstrate that the proposed method effectively improves the AD capabilities, such as enhancement of the detection rate, reducing the false alarm rate and the computation complexity.