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The contamination of the aquatic environment with antibiotics is among the major and developing problems worldwide. The present study investigates the potential of adsorbent magnetite-chitosan nanoparticles (Fe3O4/CS NPs) for removing trimethoprim (TMP) and sulfamethoxazole (SMX). For this purpose, Fe3O4/CS NPs were synthesized by the co-precipitation method, and the adsorbent characteristics were investigated using XRD, SEM, TEM, pHzpc, FTIR, and VSM. The effect of independent variables (pH, sonication time, adsorbent amount, and analyte concentration) on removal performance was modeled and evaluated by Box–Behnken design (BBD). The SEM image of the Fe3O4/CS adsorbent showed that the adsorbent had a rough and irregular surface. The size of Fe3O4/CS crystals was about 70 nm. XRD analysis confirmed the purity and absence of impurities in the adsorbent. TEM image analysis showed that the adsorbent had a porous structure, and the particle size was in the range of nanometers. In VSM, the saturation magnetization of Fe3O4/CS adsorbent was 25 emu g−1 and the magnet could easily separate the adsorbent from the solution. The results revealed that the optimum condition was achieved at a concentration of 22 mg L−1, a sonication time of 15 min, an adsorbent amount of 0.13 g/100 mL, and a pH of 6. Among different solvents (i.e., ethanol, acetone, nitric acid, and acetonitrile), significant desorption of TMP and SMX was achieved using ethanol. Also, results confirmed that Fe3O4/CS NPs can be used for up to six adsorption/desorption cycles. In addition, applying the Fe3O4/CS NPs on real water samples revealed that Fe3O4/CS NPs could remove TMP and SMX in the 91.23–95.95% range with RSD (n = 3) < 4. Overall, the Fe3O4/CS NPs exhibit great potential for removing TMP and SMX antibiotics from real water samples. [ABSTRACT FROM AUTHOR]

The current trend is to go for more electric systems that rely extensively on power electronics such as EVs/HEVs and electric aircrafts, along with an increased use of renewable energy resources and variable speed motor drives. However, some field failure reports have revealed that power electronic converters represent the weakest point in these systems. A significant percentage of system failures are due to power electronic converter failures, which compromises systems reliability. This raises questions regarding the validity of relying on the current power electronic converter technology to run mission-critical/must-to-be-safe systems. Although power electronic converter technology has reached an advanced level in terms of efficiency, power density, and control, extra work should be done when it comes to reliability. Reliability engineering brings performing failure data analysis, accelerated life testing, lifetime prediction, and the implementation of efficient maintenance and reliability improvement schemes into an integrated process. This process is meant to enhance the reliability of a product throughout its life cycle. This paper provides an overview of the application of the key aspects of new approaches in reliability engineering for power electronic converters. The focus of this paper is on power switch bond-wire modules since they are the most vulnerable component in power electronic converters. This paper also proposes two general schemes for condition-based remaining useful lifetime (RUL) that are discussed in detail. [ABSTRACT FROM AUTHOR]

In order to improve the conversion efficiency and mitigate the EMI problem of conventional hard-switching inverters, a new soft-switching DC-AC inverter with a compact structure and a low modulation complexity is proposed in this paper. In the proposed structure, resonant inductors are connected in series for the arm branches, and resonant capacitors are connected in parallel for the neutral point branches. With the help of resonant components, the proposed structure achieves zero-current switching on the arm branches and zero-voltage switching on the neutral point branches. When compared with state-of-art soft-switching topologies, the proposed topology does not need auxiliary switches. Moreover, the commutation algorithm to realize soft-switching can be easily implemented. In this paper, the principle of the resonant operation of the proposed soft-switching converter is presented and its performance is verified through simulation studies. The feasibility of the proposed inverter is evaluated experimentally with a 2.4-kW prototype. [ABSTRACT FROM AUTHOR]

Novel three-dimensional porous silk fibroin/graphene oxide (SF/GO) nanocomposite scaffolds with different graphene oxide (GO) concentrations were prepared by using the freeze-drying technique. The obtained SF/GO scaffolds were characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller isotherm and Fourier transform infrared spectroscopy techniques. The water absorption, compressive properties, porosity, degradation, biomineralization capability, cell attachment and cell viability of the composite scaffolds were studied as well. Cytocompatibility of the scaffolds was studied in vitro by employing the methylthiazoletetrazolium assay. The results showed that the presence of graphene oxide nanoparticles throughout the fibroin matrix led to an increase in water uptake and mechanical properties; at the same time, the porosity of the scaffolds was decreased. The cell adhesion results also indicated that human osteoblast cells (MG-63) could adhere to the surface of SF/GO nanocomposites and develop on them. These suggest that SF/GO nanocomposite scaffolds may be a good candidate for bone tissue engineering applications. [ABSTRACT FROM AUTHOR]

This paper presents a novel seven-level (7L) voltage source converter for high-power medium-voltage applications. The proposed topology is an H-bridge connection o f two nested neutral-point clamped (NNPC) converters and is referred to as an HNNPC converter. This converter exhibits advantageous features, such as operating over a wide range o f output voltages, particularly for 10-15 kV applications, without the need to connect power semiconductors in series; high-quality output voltage; and fewer components relative to other classic seven-level topologies. A novel sinusoidal pulse width modulation technique is also developed for the proposed 7L-HNNPC converter to control flying capacitor voltages. One of the main features o f the control strategy is the independent application of control to each arm of the converter to significantly reduce the complexity of the controller. The performance of the proposed converter is studied under different operating conditions via MATLAB/Simulink simulation, and its feasibility is evaluated experimentally on a scaled-down prototype converter. [ABSTRACT FROM AUTHOR]

Pulse-width modulated (PWM) full-bridge boost converters are used in applications where the output voltage is considerably higher than the input voltage. Zero-voltage-switching (ZVS) is typically implemented in these converters. A new ZVS-PWM full-bridge converter is proposed in this paper. The proposed converter does not have any of the disadvantages associated with other converters of this type, including a complicated auxiliary circuit, increased current stresses in the main power switches, and load-dependent ZVS operation. The operation of the proposed converter, its steady-state characteristics, and its design are explained and examined. The feasibility of the converter is confirmed with results obtained from an experimental prototype. [ABSTRACT FROM AUTHOR]