Unbalanced voltage faults: the impact on structural loads of doubly fed asynchronous generator wind turbines

This paper investigates the impact that unbalanced voltage faults have on wind turbine structural loads. In such cases, electromagnetic torque oscillations occur at two times the supply voltage frequency. The objectives of this work are to quantify wind turbine structural loads induced by unbalanced voltage faults relative to those during normal operation; and to evaluate the potential for reducing structural loads with the control of the generator. The method applied is integrated dynamic analysis. Namely, dynamic analysis with models that consider the most important aeroelastic, electrical, and control dynamics in an integrated simulation environment based on an aeroelastic code (HAWC2) and software for control design (Matlab/Simulink). In the present analysis, 1 Hz equivalent loads are used to compare fatigue loads, whereas maximum–minimum values are used to compare extreme loads. A control concept based on resonant filters demonstrates reduction of the structural loads (shaft torsion and tower top side‐to‐side moment) induced by an unbalanced voltage fault.Copyright © 2013 John Wiley & Sons, Ltd.     

Interaction of silicon-based quantum dots with gibel carp liver: oxidative and structural modifications

Quantum dots (QDs) interaction with living organisms is of central interest due to their various biological and medical applications. One of the most important mechanisms proposed for various silicon nanoparticle-mediated toxicity is oxidative stress. We investigated the basic processes of cellular damage by oxidative stress and tissue injury following QD accumulation in the gibel carp liver after intraperitoneal injection of a single dose of 2 mg/kg body weight Si/SiO₂ QDs after 1, 3, and 7 days from their administration.QDs gradual accumulation was highlighted by fluorescence microscopy, and subsequent histological changes in the hepatic tissue were noted. After 1 and 3 days, QD-treated fish showed an increased number of macrophage clusters and fibrosis, while hepatocyte basophilia and isolated hepatolytic microlesions were observed only after substantial QDs accumulation in the liver parenchyma, at 7 days after IP injection.Induction of oxidative stress in fish liver was revealed by the formation of malondialdehyde and advanced oxidation protein products, as well as a decrease in protein thiol groups and reduced glutathione levels. The liver enzymatic antioxidant defense was modulated to maintain the redox status in response to the changes initiated by Si/SiO₂ QDs. So, catalase and glutathione peroxidase activities were upregulated starting from the first day after injection, while the activity of superoxide dismutase increased only after 7 days. The oxidative damage that still occurred may impair the activity of more sensitive enzymes. A significant inhibition in glucose-6-phosphate dehydrogenase and glutathione-S-transferase activity was noted, while glutathione reductase remained unaltered.Taking into account that the reduced glutathione level had a deep decline and the level of lipid peroxidation products remained highly increased in the time interval we studied, it appears that the liver antioxidant defense of Carassius gibelio does not counteract the oxidative stress induced 7 days after silicon-based QDs exposure in an efficient manner.     

Impact of packaging properties on the physical-chemical-microbiological-sensory characteristics of Ricotta cheese during storage

Ricotta is a highly perishable cheese of which shelf-life is strongly influenced by the properties of packages in which it is stored. Four plastic packages currently in use in Italy (IT), Romania (RO), Slovenia (SLO), and Spain (SP) are characterized in term of structure, barrier, and antimicrobial properties, and their efficiency in the ricotta storage at 4°C is assessed. Differential scanning calorimetry and Fourier-transform infrared spectroscopy analysis indicate that the IT and SP packages are made of low-density polyethylene and the RO and SLO packages consist of polyethylene and polyamide 6. Permeability to the water vapour and oxygen transmission rate vary as follows: IT>SLO > RO > SP and SP > IT>RO > SLO, respectively. The SP package expressed the highest antimicrobial inhibition whilst the IT package the lowest. The maximum amounts of volatile compounds in cheese were reached after 3 days in the IT and SP packages and after 6 days in the SLO and RO packages. The score 2.8 for cheese overall acceptability was exceeded after 7 days in the IT, RO, and SP packages and 6 days in the SLO package. Barrier properties of packages significantly influence the shelf-life of ricotta. Low barrier properties resulted in high level of oxygen and water vapours inside the headspace of packages ultimately favour the microbial development. The simultaneous compliance of microbiological safety level and overall acceptability score gives ricotta a shelf-life of 3 days in the IT, RO, and SP packages and 1 day in the SLO package.     

New Machine Learning Ensemble for Flood Susceptibility Estimation

Water Resources Management - Floods are among the most severe natural hazard phenomena that affect people around the world. Due to this fact, the identification of zones highly susceptible to...     

Power and Resource Allocation in Wireless Communication Network

Wireless Personal Communications - Present-day wireless methods are necessary to support a variety of higher-speed data communication facilities for its subscribers such as cloud-based video...     

Impact of fat types on the rheological and textural properties of gluten-free oat dough and cookie

This study investigated the effect of six fats (margarine, butter, lard-LAR, refined palm oil-RPO, refined palm oil with stearin-RPOS, hydrogenated palm oil-HPO) with different solid fat content (SFC) on gluten-free oat dough and cookie properties. RPOS and HPO had the highest SFC. RPO dough was the softest, whereas HPO was the hardest one. Dough hardness was correlated with SFC (r = 0.87). Dough stickiness was positively correlated with dough hardness (r = 0.92). Dough hardness influenced the breaking force of the cookies (r = 0.79). HPO were the hardest cookies. Oscillatory test revealed that HPO dough was the stiffest as well as presented a higher rigidity compared to the other samples as showed by the creep tests. LAR cookies were the darkest, while HPO were the lightest. SFC of fats is the most important composition parameter which influences thermal, textural and rheological properties of the oat dough.     

Characterization and applications of a new composite material obtained by green synthesis,through deposition of zinc oxide onto calcium carbonate precipitated in green seaweeds extract

Zinc oxide was deposited onto calcium carbonate precipitated using a template of polysaccharides from Ulva lactuca green seaweeds (Black Sea). The resulted composite material was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, UV–vis and FTIR spectroscopy. The therapeutic effect of prepared composite material was assessed in vivo as a topical application for the burns treatment and compared with that of ZnO. An increased antioxidant activity by combining zinc oxide with calcium carbonate capped with polysaccharides from green seaweeds extract in a composite material was demonstrated.     

Sericin Enhances the Bioperformance of Collagen-Based Matrices Preseeded with Human-Adipose Derived Stem Cells (hADSCs)

Current clinical strategies for adipose tissue engineering (ATE), including autologous fat implants or the use of synthetic surrogates, not only are failing in the long term, but also can’t face the latest requirements regarding the aesthetic restoration of the resulted imperfections. In this context, modern strategies in current ATE applications are based on the implantation of 3D cell-scaffold bioconstructs, designed for prospective achievement of in situ functional de novo tissue. Thus, in this paper, we reported for the first time the evaluation of a spongious 60% collagen and 40% sericin scaffold preseeded with human adipose-derived stem cells (hADSCs) in terms of biocompatibility and adipogenic potential in vitro. We showed that the addition of the sticky protein sericin in the composition of a classical collagen sponge enhanced the adhesion and also the proliferation rate of the seeded cells, thus improving the biocompatibility of the novel scaffold. In addition, sericin stimulated PPARγ2 overexpression, triggering a subsequent upregulated expression profile of FAS, aP2 and perilipin adipogenic markers. These features, together with the already known sericin stimulatory potential on cellular collagen production, promote collagen-sericin biomatrix as a good candidate for soft tissue reconstruction and wound healing applications.     

Thermodynamic and kinetic study on ammonium removal from a synthetic water solution using ion exchange resin

Ammonium removal from the wastewater treatment effluents is mandatory considering the imposed discharge limits and the recycling/reuse requirements. Ion exchange represents a viable alternative for the biological processes of ammonium removal, although concurrent processes make modeling complex. This study reports on the performance of a commercial cation exchange resin, PUROLITE C150H, for ammonium removal from synthetic aqueous solutions. Thermodynamic and kinetic process parameters are calculated using the Langmuir model (thermodynamic study) and the shrinking core model (kinetic study); the data are correlated with the surface properties of the substrate, outlining the adsorption mechanism. For initial ammonium concentrations of 25–150 mg NH₄ ⁺/L, removal efficiencies of 80–90 % were obtained.