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Recently, renewable distributed generation (DG) systems have emerged to improve the power system security and reliability while reducing the environmental incompatibility of fossil fuel power plants. DG could operate either as a standalone and/or as a grid‐connected power system. The interfacing circuits of DG and their controls have to comply with utility quality regulations and afford a seamless transition from online to offline and vice versa. This article advises a simple and robust control scheme for a modular multilevel converter (MMC) that interfaces with a photovoltaic (PV) generator. The proposed control method ensures high‐quality output voltage/current waveform in online and/or offline operating modes. Moreover, the proposed control provides a seamless and swift transition from standalone to grid‐connected and vice versa. The exhibited control scheme is simulated with MATLAB/Simulink. Real‐time simulator OPAL‐RT OP4510 is used to verify the displayed simulation results. The simulation results determine the accomplishment of the proposed control technique for a seamless transition from the grid‐connected mode to the standalone mode and vice versa via MMC. [ABSTRACT FROM AUTHOR]

Alternative water sources offer opportunities to contribute to the water supply to meet non-potable urban demand, closing water supply–demand gaps. Detailed assessments of these schemes are often data intensive, which can be a barrier in resource-scarce locations. A data-light approach is proposed and applied to assess the potential contribution of alternative water sources in five cities in the Global South, and to identify barriers preventing their widespread uptake. These barriers include perception, space, cost, home ownership and capacity constraints. This approach is applicable elsewhere, supporting assessment for city water planners/managers for preliminary planning to promote discussion on alternative sources to water security. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the anti-Leishmania major and the lung adenocarcinoma (A549) cytotoxicity of Withania somnifera root and fruit. The total extracts were obtained by homogenisation in aqueous MeOH, and the sub-extracts [n-hexane, ethyl acetate (EtOAc), n-butanol (n-BuOH), and methanol (MeOH)] were obtained by flash chromatography. The activity evaluation showed that n-BuOH sub-extracts from root and fruit exhibited noticeable antileishmanial promastigote properties. The n-hexane and EtOAc sub-extracts from both organs, and the MeOH sub-extract from the fruit exerted mild to moderate effects on the promastigotes. In-vitro growth-inhibitory test results on axenic amastigote and cytotoxicity testing on macrophages (RAW264.7), the parasite-host at the amastigote stage, revealed that the activity was mainly concentrated in the root EtOAc and n-BuOH sub-extracts and to a lesser extent the fruit MeOH and EtOAc, and the root n-hexane sub-extracts. Only the roots' EtOAc and n-BuOH sub-extracts demonstrated low cytotoxicity on the A549 cell line. [ABSTRACT FROM AUTHOR]

This paper describes the modeling of power-factor-correction converters under average-current-mode control, which are widely used in switch-mode power supply applications. The objective is to identify stability boundaries in terms of major circuit parameters for facilitating design of such converters. The approach employs a double averaging procedure, which first applies the usual averaging over the switching period and subsequently applies generalized averaging over the mains period. The resulting model, after two averaging steps and application of a harmonic balance procedure, is nonlinear and capable of describing the low-frequency nonlinear dynamics of the system. The parameter ranges within which stable operation is guaranteed can be accurately and easily found using this model. Experimental measurements are provided for verification of the analytical results. Index Terms--Averaged model, closed-form stability condition, double averaging, power factor correction (PFC), switching converters.

The boost power-factor-correction (PFC) converter with average-current-mode control is a nonlinear system due to the effects of the multiplier and a large variation of the duty ratio. Although its stability analysis must be studied depending on a nonlinear model, most prior research attempted to make some assumptions to force this nonlinear system to be linear. As a result, the practical dynamics and the nonlinear phenomena were disregarded. In this paper, two kinds of nonlinear phenomena are detected under the conditions that are considered to be stable by the prior criteria: one is period-doubling bifurcation and the other is chaos. Stability maps and phase-plane trajectories are introduced at different loads to clarify the power factor and also the instability regions. It is clear that the output storage capacitor is a main contributing parameter on the system stability, therefore, bifurcation maps are developed to determine the accurate minimum output capacitance value that assures the system stability under all operating conditions. Also, PFC converter stability is explained and judged by comparing the consequence of charging and discharging energy in the output capacitor. Index Terms--Bifurcation, boost converter, chaos, instability phenomena, nonlinear analysis, power-factor correction (PFC), stability.

Three new [nilotinins M8‒M10 (1‒3)] and two known [tamarixinin A (4) and gemin D (5)] ellagitannins and seven simple phenolics [gallic acid (6), methyl gallate (7), 3,4-di-O-methylgallic acid (8), ellagic acid (9), 3-O-methylellagic acid (10), methyl ferulate 3-O-sulphate (11), and 7,4′-di-O-methylkaempferol (12)] were isolated from the halophytic plant Tamarix nilotica (Ehrenb.) Bunge (Tamaricaceae). Their structures were determined based on intensive spectroscopic studies and comparisons with reported data. Compounds 4, and 6–8 were evaluated for their cytotoxicity against lung adenocarcinoma cell line (A549) and anti-leishmanial activity against Leishmania major. Compounds 4, 6 and 7 showed promising cytotoxic properties against A549 (IC50 29 ± 2.3, 10.5 ± 0.7, and 20.7 ± 1.9 μg/mL), while compounds 4 and 7 showed higher growth-inhibitory effects against L. major promastigotes (IC50 40.5 ± 2.7 and 38.4 ± 2.5 μg/mL), as compared with the standards doxorubicin (IC50 0.42 µg/mL) and miltefosine (IC50 9.43 μg/mL), respectively. [ABSTRACT FROM AUTHOR]