A protection strategy for inverter-interfaced islanded microgrids with looped configuration

Electrical Engineering - Development of an efficient protection strategy is one of the main barriers in paving the way for the implementation of inverter-based microgrids. The limited fault current...     

Nigella arvensis leaf extract mediated green synthesis of silver nanoparticles: Their characteristic properties and biological efficacy

In the present study, the potential of aqueous leaf extract of Nigella arevensis for biosynthesis of silver nanoparticles (AgNPs) was evaluated. The formation of AgNPs was confirmed by color changes and UV–visible spectroscopy, which showed absorbance maxima peak at 416?nm. The transmission electron microscope (TEM) image showed the AgNPs to be anisotropic and mostly spherical with sizes in the range of 5–100?nm. Fourier transform infrared (FTIR) analysis indicated that the flavonoids, alkaloids and phenolic groups present in leaf extract were involved in the reduction and capping of phytogenic AgNPs. These nanoparticles showed the cytotoxic effects against H1229 and MCF-7 cancer cell lines with an IC₅₀ value of 10?μg/mL. AgNPs showed insignificant antioxidant properties compared to the crude extract, and it was effective against clinical isolated bacterial strains. Furthermore, the bioderived AgNPs displayed significant catalytic activity against methylene blue. These results confirmed the advantages and applications of these phytogenic AgNPs using the green method in various fields.     

Integration g-C3N4 nanotubes and Sb2MoO6 nanoparticles: Impressive photoactivity for tetracycline degradation,Cr (VI) reduction,and organic dyes removals under visible light

The development of high-efficiency photocatalysts is an attractive strategy for pollutants degradation under visible light. Herein, novel photocatalysts are reported through coupling Sb₂MoO₆ with g-C₃N₄ nanotube (abbreviated as GCN nanotube) by a simple reflux method. Also, the nanocomposites were defined by applying various analyses. Under visible-light excitation, the GCN nanotube/Sb₂MoO₆ systems had more photoactivity than g-C₃N₄ (abbreviated as GCN) and the rate constant for RhB removal on optimal GCN nanotube/Sb₂MoO₆ (30%) nanocomposite was 48.3 times premier than the GCN. Also, compared to the pristine GCN, the GCN nanotube/Sb₂MoO₆ (30%) sample demonstrated supreme photoactivity towards tetracycline degradation and Cr (VI) photoreduction, which was 88.5 and 21.8 times higher than the bulk GCN, respectively. These impressive enhancements were attributed to the quick segregation of charge carriers, boosted visible-light absorption, and extended specific surface area. Moreover, the photocatalyst has enough activity after four successive cycles. Finally, a conceivable charges transfer route is presented through n-n heterojunction constructed between Sb₂MoO₆ and GCN nanotube.     

Further criterion for stochastic stability analysis of semi‐Markovian jump linear systems

This article is devoted to provide further criterion for stochastic stability analysis of semi‐Markovian jump linear systems (S‐MJLSs), in which more generic transition rates (TRs) will be studied. As is known, the time‐varying TR is one of the key issues to be considered in the analysis of S‐MJLS. Therefore, this article is to investigate general cases for the TRs that covered almost all types, especially for the type that the jumping information from one mode to another is fully unknown, which is merely investigated before. By virtue of stochastic functional theory, sufficient conditions are developed to check stochastic stability of the underlying systems via linear matrix inequalities formulation combined with a maximum optimization algorithm. Finally, a numerical example is given to verify the validity and effectiveness of the obtained results.     

A Variable Current-Limit Control Scheme for a Bi-directional Converter used in Ultracapacitor Applications

In ultracapacitor applications, generally, a bi-directional converter is connected to a DC bus and is designed to compensate rapid load variations on the bus. During transient phases, overloaded DC bus can push the converter out of its operating limits. For providing the necessary power, converters should be put in parallel, while each converter is limited into its optimal operating range. In a boost converter, this operating limit can be related to the inductor current and UC voltage. In this study, a variable current-limit is proposed for inductor current which then determines the operating range of the boost converter. This method will provide stability of the converter during overload transients. An experimental setup consisting of a bi-directional converter, a controllable load/source, and an ultracapacitor is presented, to validate the proposed method. Several scenarii are applied to analyze the performance of the system in overloaded phases and theoretical and experimental results are presented.     

Defocus estimation from stroboscopic cryo-electron microscopy data

Defocus estimation is an important step for improving the resolution of single particle reconstructions. It can be troublesome to estimate the defocus from low-dose cryo-electron microscopy (cryo-EM) data, particularly if there is not sufficient contrast present in the Fourier transform of the micrograph. Most existing approaches estimate the defocus from the presence of Thon rings within the power spectrum, employing image enhancement techniques to highlight these rings. In this paper, an approach to estimating the defocus from a stroboscopic image series is described. The image series is used to obtain two statistical metrics: figure of merit (FOM) and Q-factor. These metrics have been used to estimate the defoci from low-dose stroboscopic cryo-EM data consisting of a variable number of images.     

Characterization of triple electrospun layers of PVDF for direct contact membrane distillation process

Recently, electrospinning technique was applied successfully to fabricate porous hydrophobic membranes for MD applications. In this work, a novel triple layer configuration with diameter gradient for PVDF nanofiber membranes is proposed, with the objective of to minimize mass transfer resistance and heat loss. In outer layers of these membranes, the minimum concentration of PVDF (20 wt%) was used to produce bead-free nanofibers with thinner diameters and middle layers were composed of thicker nanofibers formed at higher polymer concentrations (21.5-26 wt%). Characterization of prepared membranes was conducted by the measurement of porosity, thickness, liquid entry pressure (LEP), scanning electron microscopy (SEM), contact angle, thermal and mechanical properties. Direct contact membrane distillation performance of fabricated membranes was tested using 42 g/L NaCl as feed solution. Water permeate flux of triple layer membranes (27.8-31.5 kg/m² h) was found to be considerably higher than that obtained from single layer membrane (15.4 kg/m² h), indicating the proposed configuration can effectively improve evaporation efficiency.     

Electroless nano zinc oxide–activate carbon composite supercapacitor electrode

An electroless deposition process was used to synthesize the nanostructured zinc oxide (ZnO)–activated carbon (AC) as supercapacitor. The composite oxide was studied by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD). The electrochemical performance of the nanocomposite was analyzed through cyclic voltammetry (CV) and AC impedance spectroscopy (EIS) in 0.1 M Na₂SO₄ as electrolyte. A specific capacitance 187 F g^?1 at a scan rate of 5 mV s^?1 was obtained using cyclic voltammetry (CV) and a nearly rectangular shaped CV curve was observed for the composite oxide. The supercapacitor was quite stable during charge–discharge cycling and exhibited constant capacitance during the long-term cycling. It also yielded a specific capacitance 171 F g^?1 at 5 mA cm^?2 with a high energy density of 21.9 Wh kg^?1 and 4.2 kW kg^?1 of power density. Due to unique structure of prepared ZnO–AC nanocomposite, it is a promising candidate for supercapacitor.     

Flower-like architecture of CoSn4 nano structure as anode in lithium ion batteries

CoSn₄ nano-particles were synthesized on Cu and Ni substrates through pulsed current electrodeposition and used as anode in lithium ion batteries. Nano particles with Flower-like morphology were obtained through applying an average current density of 85 mA/cm² on Ni substrate while the particles formed using constant current electrodeposition are greater in size ca. 500 nm. Optimum discharge capacity of synthesized CoSn₄ was obtained 848 mAh g^?1 which reduced to 500 mAh g^?1 at 120th cycle indicating an enhanced electrochemical performance compared to anode films synthesized through other pulsed current densities and also constant current electrodeposition. This high discharge capacity and cycleability is attributed to finer crystal grains and flower-like morphology of nano particles. Also, the sample synthesized on Ni substrate showed higher cycleability and noticeably lower resistance. High resistance of anode film synthesized on Cu substrate is due to the corrosion and passivation of copper occurred by HF formation in LiPF₆ electrolyte.