A study on the cure characteristics of epoxy/diaminodiphenylmethane system prepared at room temperature

The curing behavior and kinetics of epoxy resin with diaminodiphenylmethane (DDM) as the curing agent was studied by many researchers, however all of them prepared the system at a high‐temperature condition (i.e., T ≥ 80°C). In this study, a mixture of epoxy/DDM was prepared at ambient temperature and its curing characteristics were studied by using differential scanning calorimetry (DSC). The autocatalytic model was used to calculate the kinetic factors in the dynamic experiments. The kinetics of the curing reaction was also evaluated by two different isoconversional models; namely Friedman method and the Advanced Isoconversional method proposed by Vyazovkin to investigate the activation energy behavior during the curing reaction. The activation energy of the curing reaction was found to be in the range of 48 ± 2 kJ/mol and might be considered to be constant during the curing. In fact, our findings were different from the result reported by other researchers for the system which was prepared at elevated temperature. Therefore, it seems that the preparation temperature of the samples influenced considerably on the curing behavior of epoxy with DDM. Finally, a time–temperature–transformation (TTT) diagram was established to determine the cure process and glass transition properties of the system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Pomegranate fallen leaves as a source of natural dye for mordant-free dyeing of wool

The application of metal mordants is usually necessary in dyeing of wool with natural dyes to improve the dye exhaustion and fastness properties. The majority of metal salts generally used as mordants are considered as toxic and it is important to find replacements for them. Plant sources with high content of tannins are good candidates as bio-mordant or colourant to overcome this drawback. In this study, the waste fallen leaves of pomegranate tree were used as a source of natural dye for the eco-friendly dyeing of wool fabric without the use of metal mordants. The dyeing process variables including dye concentration, dyebath pH, and temperature were optimised using response surface methodology to obtain the highest colour strength. The colour strength was increased by increasing the natural dye powder up to 100%owf while the optimum pH and dyebath temperature were 4 and 100°C, respectively. The sample dyed under the optimal condition exhibited good fastness properties against washing and light. This study approved the potential of Punica granatum fallen leaves for the dyeing of wool without any mordant, while high fastness properties were obtained.     

A knowledge based component/service repository to enhance analysts’ domain knowledge for requirements analysis

Knowledge of the business domain (e.g., insurance claim, human resources) is crucial to analysts’ ability to conduct good requirements analysis (RA). However, current practices afford little assistance to analysts in acquiring domain knowledge. We argue that traditional reuse repositories could be augmented by adding rich faceted information on component/services and artifacts such as business-process templates to help analysts acquire domain knowledge during RA. In this paper, we present the design of a Knowledge Based Component Repository (KBCR) for facilitating RA. Then, we report on the design and development of a KBCR prototype. We illustrate its application in a system that is populated with components and process templates for the auto insurance claim domain. An empirical study was conducted to assess its effectiveness in improving RA. Results showed that KBCR enhanced analysts’ business domain knowledge and helped them better prepare for RA. Our key research contribution is to offer analysts a rich repository (i.e., KBCR) containing domain knowledge that they could utilize to acquire domain knowledge that is crucial for carrying out RA. While repositories of reusable components have been employed for some time, no one has used such repositories to help analysts acquire domain knowledge in order improve the RA of the system.     

Synthesis, characterization and magnetic properties of NiS1+x nanocrystals from [bis(salicylidene)nickel(II)] as new precursor

[Bis(salicylidene)nickel(II)] was used as a precursor to prepare nickel sulfides nanoparticles of average size 20 nm by a chemical process in oleylamine. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy (UV-vis) and photoluminescence (PL) spectroscopy. Magnetization measurement indicates that both of the α-NiS and Ni₃S₄ nanoparticles show pramagnetism due to the size effect.     

Protein encapsulated in electrospun nanofibrous scaffolds for tissue engineering applications

The main purpose of tissue engineering is the preparation of fibrous scaffolds with similar structural and biochemical cues to the extracellular matrix in order to provide a substrate to support the cells. Controlled release of bioactive agents such as growth factors from the fibrous scaffolds improves cell behavior on the scaffolds and accelerates tissue regeneration. In this study, nanofibrous scaffolds were fabricated from biocompatible and biodegradable poly(lactic‐co‐glycolic acid) through the electrospinning technique. Nanofibers with a core–sheath structure encapsulating bovine serum albumin (BSA) as a model protein for hydrophilic bioactive agents were prepared through emulsion electrospinning. The morphology of the nanofibers was evaluated by field‐emission scanning electron microscopy and the core–sheath structure of the emulsion electrospun nanofibers was observed by transmission electron microscopy. The results of the mechanical properties and X‐ray diffraction are reported. The scaffolds demonstrated a sustained release profile of BSA. Biocompatibility of the scaffolds was evaluated using the MTT (3(4,5‐ dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay for NIH‐3T3 fibroblast cells. The results indicated desirable biocompatibility of the scaffolds with the capability of encapsulation and controlled release of the protein, which can serve as tissue engineering scaffolds. © 2013 Society of Chemical Industry     

An extended compromise ratio method for fuzzy group multi-attribute decision making with SWOT analysis

The technique for order preference by similarity to ideal solution (TOPSIS) is a well-known multi-attribute decision making (MADM) method that is used to identify the most attractive alternative solution among a finite set of alternatives based on the simultaneous minimization of the distance from an ideal solution (IS) and the maximization of the distance from the nadir solution (NS). We propose an alternative compromise ratio method (CRM) using an efficient and powerful distance measure for solving the group MADM problems. In the proposed CRM, similar to TOPSIS, the chosen alternative should be simultaneously as close as possible to the IS and as far away as possible from the NS. The conventional MADM problems require well-defined and precise data; however, the values associated with the parameters in the real-world are often imprecise, vague, uncertain or incomplete. Fuzzy sets provide a powerful tool for dealing with the ambiguous data. We capture the decision makers’ (DMs’) judgments with linguistic variables and represent their importance weights with fuzzy sets. The fuzzy group MADM (FGMADM) method proposed in this study improves the usability of the CRM. We integrate the FGMADM method into a strengths, weaknesses, opportunities and threats (SWOT) analysis framework to show the applicability of the proposed method in a solar panel manufacturing firm in Canada.     

Controlled release of prednisolone acetate from molecularly imprinted hydrogel contact lenses

The aim of this work was to study the influence of methacrylic acid (MAA) as a comonomer and the application of a molecular imprinting technique on the loading and release properties of weakly crosslinked 2‐hydroxyethyl methacrylate (HEMA) hydrogels, with a view toward their use as reloadable soft contact lenses for the administration of prednisolone acetate (PA). The hydrogels were prepared with HEMA (95.90–98.30 mol %) as a backbone monomer, ethylene glycol dimethacrylate (140 mM) as a crosslinker, and MAA (0, 50, 100, or 200 mM) as a functional monomer. Different PA/MAA molar ratios (0, 1 : 8, 1 : 6, and 1 : 4) in the feed composition of the hydrogels were also applied to study the influence of the molecular imprinting technique on their binding properties. The hydrogels (0.4 mm thick) were synthesized by thermal polymerization at 60°C for 24 h in a polypropylene mold. The hydrogels were then characterized by the determination of their swelling and binding properties in water. Their loading and release properties were also studied in 0.9% NaCl and artificial lachrymal fluid. Increasing the MAA content of the hydrogel and applying the molecular imprinting technique led to an increase in the loading capacity of the hydrogel. The optimized imprinted hydrogel showed the highest affinity for PA and the greatest ability to control the release process, sustaining it for 48 h. The results obtained clearly indicate that the incorporation of MAA as a comonomer increased the PA loading capacity of hydrogel. Our data showed that the molecular imprinting technique also had a significant effect on the loading and release properties of the hydrogels. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Refractive index determination in fuel cells using high-resolution laser heterodyne interferometer

In this paper, we present an interferometry method for refractive index determination in membranes of fuel cells. This technique is based on the use of an improved laser heterodyne interferometer. The photocurrents of the avalanche photodiodes, resulting from reflected beams of the optical head, are led to the signal conditioner and digital signal processing sections. The optical path difference between the target and reference paths is fixed, and as a result, the phase shift is calculated in terms of the refractive index shift. In addition, nonlinearity of this system is analyzed and modeled with different neural networks and adaptive filter algorithms. For neural networks, the radial basis function (RBF), the multi-layer perceptron (MLP), and the stacked generalization method are simulated. In adaptive filter algorithms, the least mean square (LMS), the normalized least mean square (NLMS), the recursive least squares (RLS), and the affine projection algorithm (APA) are applied. The simulation results indicate that the RLS method is faster and contains minimum mean square error (MSE) compared to the other approaches. Also, comparison between two main approaches shows that the nonlinearity of refractive index determination can be effectively modeled with adaptive filter algorithms.