Fuzzy methodology for frequency response estimation of uncertain dynamic systems

Fuzzy frequency response: definition and analysis for uncertain dynamic systems is proposed in this paper. In terms of transfer function, the uncertain dynamic system is partitioned into several linear sub‐models and organized according to Takagi–Sugeno fuzzy representation. The main contribution of this paper is to demonstrate through the proposal of a Theorem that fuzzy frequency response is a boundary in the magnitude and phase Bode plots. Low‐ and high‐frequency analysis of fuzzy dynamic model is obtained by varying the frequency ω from zero to infinity. Copyright © 2011 John Wiley & Sons, Ltd.     

The Brazilian experience of rural electrification in the Amazon with decentralized generation - The need to change the paradigm from electrification to development

There are at least 607 thousand households in the Brazilian Amazon that need to be attended with some form of regular electricity service. These households are not attended by the electricity sector through its electricity distribution companies and most of them have some form of precarious decentralized electricity generation that is not registered or regulated in the institutional framework. Diverse initiatives were taken by Brazilian government to attend these household through alternatives that relied on locally available renewable energy. This paper accesses this initiatives of rural electrification in the Brazilian Amazon. First an overview of the problems of rural electricity are discussed and its specificities in the Brazilian Amazon. Then the Brazilian institutional framework that organizes the decentralized electricity generation is described with its various limitations. The diverse initiatives undertaken to attend the rural communities in the Amazon since the 1990s are described, as well as how these initiatives are linked to the policies for rural electrification. The results shows that it can be inferred that sole market mechanisms are not sufficient to guarantee economic sustainability of these projects. This can be one of the reasons why traditional electricity distribution companies showed the lack of interest in promoting rural electrification with other means than grid extension. The most successful projects had financed efforts to integrate the generation of electricity into local development initiatives in order to guarantee sustainability and used substantial part of funding for local mobilization and organization. It needs a paradigm chance by treating these initiatives as local development initiatives and promoting alternative ways for its implementation through partnership between local new actors in the electricity sector and government and implementing policy on a local municipal level.     

Ethanol reforming and partial oxidation with Cu/Nb2O5 catalyst

Ethanol reforming and partial oxidation were studied on Cu/Nb₂O₅ and Ni/Al₂O₃ catalysts. Compared to the Ni/Al₂O₃ catalyst, the Cu/Nb₂O₅ catalyst presents conversion as high as Ni/Al₂O₃ catalyst, however, for the same level of formation of hydrogen it occurs at much lower temperature on the Cu/Nb₂O₅ catalyst, 200 °C lower than for the Ni/Al₂O₃ catalyst, with remarkable little formation of CO, which can be attributed to the strong interaction between copper and niobia. Temperature-programmed desorption (TPD-ethanol) and surface reactions (TPSR) of partial oxidation of ethanol showed formation of ethylene, acetaldehyde, ethane and mainly H₂ and CO₂ besides little methane. DRIFTS results are in accordance with TPD analysis and the formation of acetate species at room temperature suggests reactivity of the surface and its oxidative dehydrogenation capacity. The adsorption of ethanol gives rise to ethoxide species, which form acetate and acetaldehyde that can be oxidized to CO₂ via carbonate. A comparison with reported results for Cu/Al₂O₃ this catalyst is promising, yielding high level of H₂ with little CO production during reforming and partial oxidation reaction. The maximum H₂ formation for the partial oxidation of ethanol was 41% at ratio (O₂/Et) 0.8, increasing to 50% at ratio 1.5. The H₂/CO is around 10 for the partial oxidation and 7 for steam reforming, which is excellent, compared to the Ni/Al₂O₃ catalyst with a factor 4–8 lower.     

Antibacterial activity against Escherichia coli of Cu‐BTC (MOF‐199) metal‐organic framework immobilized onto cellulosic fibers

A strong antimicrobial activity against Escherichia coli of Cu‐BTC metal‐organic frameworks immobilized over cellulosic fibers is hereby reported. The in situ synthesis of Cu‐BTC metal‐organic frameworks, aka MOF‐199 or HKUST‐1, onto cellulosic substrates was carried out by exposing carboxymethylated cellulosic substrates to Cu(OAC)₂, 1,3,5‐benzenetricarboxylic acid and triethylamine solutions following a very specific order. Using an in vitro model, in accordance to ASTM E2149‐13a, we observed that the cellulose‐MOF system was able to completely eliminate the growth of E. coli on agar plates and liquid cultures. The antibacterial activity of the comprising components of MOF‐199 and the cellulosic substrate was also evaluated and determined to be negligible. Since the method used to synthesize MOF‐199 crystals provides a strong bond between the crystals and the cellulosic substrates, the crystals not detach from the anionic cellulosic fibers allowing the modified textile to be washed and reused hence opening a new avenue to fabricate antibacterial clinical fabrics. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40815.     

Electroactive behavior assessment of poly(acrylic acid)‐graphene oxide composite hydrogel in the detection of cadmium

Super absorbent polymers of acrylic acid‐graphene oxide (PAA‐GO) were synthesized with different percentage of chemical neutralization (0, 10, and 20%) of the acrylic acid monomer before its polymerization. The influence of their swelling and adsorption/desorption capacity of cadmium ions in aqueous solutions were studied and revealed that the GO enables greater mechanical stability in the materials. The PAA hydrogels, with the same degrees of neutralization, were also prepared without GO to compare with the composites. Additionally, carbon paste electrodes (CPE) modified with the composites PAA‐GO were used to asses and compare their adsorption properties with cadmium(II). The anodic stripping voltammetry (ASV) peak, in the differential pulse voltammetry mode, for cadmium oxidation was found to be influenced by the presence of GO into the polymer, and also by their percentage of neutralization. The accumulation of cadmium(II) on the surface of the modified CPEs was performed under open‐circuit conditions taking an account the preconcentration time of the metal cation. The presence of GO enhances the electrical signal of the electrodes in short times of immersion in cadmium(II) solutions. This property contributed to get linear responses of the CPEs modified with the composites, which were influenced by their degrees of neutralization. The PAA‐GO 10N electrode with 10% of neutralization combined the influence of GO and the degree of neutralization in the same matrix, and also showed good performance in terms of its mechanical stability, it was chosen for preliminary studies on the selectivity of the electrode toward Zn(II) and Cu(II). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40846.     

Tuning the pH-responsiveness capability of poly(acrylic acid-co-itaconic acid)/NaOH hydrogel: Design,swelling, and rust removal evaluation

The swelling behavior of poly(acrylic acid-co-itaconic acid)/NaOH hydrogel as well as its ability for iron and copper rust removal was studied and established for the first time. Through an experimental design, the influence of the synthesis parameters on hydrogel response was determined. It was found that pH-responsiveness dependence of hydrogel determines its application. In alkaline media, the hydrogel acted as superabsorbent, while in acidic, the most outstanding property was its pickling capability that allowed to clean carbon steel and copper metallic surfaces. Infrared, thermogravimetry, and scanning electron microscopy were performed to determine copolymer formation, thermal properties, and morphology. Metallic crystallographic phases formed during the corrosion processes were determined by X-ray diffractometer. Hydrogel adhesiveness followed by diffusion and dissolution of metal oxides species was identified as the main steps in the rust removal mechanism. This method offers a new, environmentally friendly perspective to eliminate corrosion from metallic surfaces compared with traditional strategies. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48403.     

Electrospun curcumin/polycaprolactone/copolymer F-108 fibers as a new therapy for wound healing

The application of fibers associated with drugs is a promising alternative to meet the clinical needs of tissue repair. Curcumin exhibits great cicatricial potential because it has numerous pharmacological properties. This research aimed to produce fibers of polycaprolactone and copolymer F-108 associated with curcumin and to evaluate in vivo their action on the process of wound healing. The fibers were produced by electrospinning technique and characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), and fluorescence microscopy. They were applied in cutaneous wounds of rats for the analysis of photoacoustic permeation and histological study. The characterization showed that the electrospinning allowed the preparation of homogeneous material with curcumin. The fibers benefited healing of the wounds and allowed the permeation of curcumin at all stages. The use of PCL/F-108 fibers allowed the elaboration of a new curcumin delivery system, improving its bioavailability and action in the healing of excisional wound. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48415.     

Synthesis and characterization of the polyols by air oxidation of soybean oil and its effect on the morphology and dynamic mechanical properties of poly(vinyl chloride) blends

The use of natural additives, with low toxicity and good compatibility, for PVC is becoming increasingly attractive. In this study, soybean oil additives were prepared by air oxidation reactions and blending with PVC. The oxidation reaction produced a significant increase in the number of hydroxyl groups in soybean oil; however, this kind of reaction results in the formation of a heterogeneous structure due to free radical reactions in the medium. The oxidized soybean oil improved the compatibility with PVC due to an increase in the number of polar groups, such as hydroxyls, and thus a reduction in the amount of atactic polymer was observed. Furthermore, an increase in the molecular weight of the oxidized oil, as well as large amounts of polar groups contributes to reducing the migration of oil in the PVC. Regarding the crystallinity of PVC, the use of pure and oxidized soybean oil causes small changes in the crystalline phase of the polymer. Oxidized soybean oil has great potential for usage as a secondary plasticizer for PVC. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42102.