Comparisons of the Microstructure and Magnetic Properties of Anisotropic NdFeB Magnets Prepared by Hot Pressing and Spark Plasma Sintering

Journal of Superconductivity and Novel Magnetism - NdFeB hot-pressed and hot-deformed magnets were prepared by hot-pressed (HP) sintering and spark plasma sintering (SPS). The effects of sintering...     

Bioactive-Tissue-Derived Nanocomposite Hydrogel for Permanent Arterial Embolization and Enhanced Vascular Healing

Transcatheter embolization is a minimally invasive procedure that uses embolic agents to intentionally block diseased or injured blood vessels for therapeutic purposes. Embolic agents in clinical practice are limited by recanalization, risk of non-target embolization, failure in coagulopathic patients, high cost, and toxicity. Here, a decellularized cardiac extracellular matrix (ECM)-based nanocomposite hydrogel is developed to provide superior mechanical stability, catheter injectability, retrievability, antibacterial properties, and biological activity to prevent recanalization. The embolic efficacy of the shear-thinning ECM-based hydrogel is shown in a porcine survival model of embolization in the iliac artery and the renal artery. The ECM-based hydrogel promotes arterial vessel wall remodeling and a fibroinflammatory response while undergoing significant biodegradation such that only 25% of the embolic material remains at 14 days. With its unprecedented proregenerative, antibacterial properties coupled with favorable mechanical properties, and its superior performance in anticoagulated blood, the ECM-based hydrogel has the potential to be a next-generation biofunctional embolic agent that can successfully treat a wide range of vascular diseases.     

Simultaneously achievement of high recoverable energy density and efficiency in sodium niobate-based ceramics

Journal of Materials Science: Materials in Electronics - Single lead-free Na0.73Bi0.09(Nb1???xTax)O3 (x?=?0, 0.10, 0.20, 0.30, and 0.40) ceramic phases were processed...     

Limitations,challenges, and solution approaches in grid-connected renewable energy systems

In the modern world, only conventional energy resources cannot fulfil the growing energy demand. Electricity is a fundamental building block of a technological revolution. Today, most of the electricity demand is met by the burning of fossil fuels but at the cost of adverse environmental impact. In order to bridge the gap between electricity demand and supply, nonconventional and eco-friendly means of energy generation are considered. Renewable energy systems (RESs) offer an adequate solution to mitigate the challenges originated due to greenhouse gasses (GHG). However, they have an unpredictable power generation with specific site requirements. Grid integration of RESs may lead to new challenges related to power quality, reliability, power system stability, harmonics, subsynchronous oscillations (SSOs), power quality, and reactive power compensation. The integration with energy storage systems (ESSs) can reduce these complexities that arise due to the intermittent nature of RESs. In this paper, a comprehensive review of renewable energy sources has been presented. Application of ESSs in RESs and their development phase has been discussed. Role of ESSs in increasing lifetime, efficiency, and energy density of power system having RESs has been reviewed. Moreover, different techniques to solve the critical issues like low efficiency, harmonics, and inertia reduction in photovoltaic (PV) systems have been presented. Unlike most of the available review papers, this article also investigates the impact of FACTS technology in RESs-based power system using multitype flexible AC transmission system (FACTS) controllers. Three simulation models have been developed in MATLAB/Simulink. The results show that FACTS devices help to maintain the stability of RESs integrated power system. This review paper is believed to be of potential benefit for researchers from both the industry and academia to develop better understanding of challenges and solution techniques for REs-based power systems and future research dimensions in this area.     

Goal Programming-Based Two-Tier Multi-Criteria Decision-Making Approach for Wind Turbine Selection

Wind energy has emerged as a potential replacement of conventional fuel sources. One key factor that contributes to efficient harnessing of wind energy depends heavily on the turbine type. However, the task of selecting an appropriate, site-specific turbine is a complex one. It is due to the fact that several decision criteria, which are also mutually conflicting, are involved in the decision process. Important criteria energy output, cut-in speed of wind, rated speed of wind, hub height, turbine’s power rating, and energy output. Therefore, a desired decision is the one that gives the best trade-off between the selection criteria. With the inherent complexities encompassing the decision-making process, this study develops a two-tier multi-criteria decision strategy for turbine selection founded on the concepts of fuzzy goal programming. The effectiveness of the proposed methodology is assessed through its application to a potential site located in Dhulom, Saudi Arabia. Results reveal the effectiveness of the proposed methodology in finding the most suitable turbine for the said site, from a pool of 20 turbines with different capacities and vendors.     

Security and key management in IoT‐based wireless sensor networks: An authentication protocol using symmetric key

Wireless sensor networks (WSN) consist of hundreds of miniature sensor nodes to sense various events in the surrounding environment and report back to the base station. Sensor networks are at the base of internet of things (IoT) and smart computing applications where a function is performed as a result of sensed event or information. However, in resource‐limited WSN authenticating a remote user is a vital security concern. Recently, researchers put forth various authentication protocols to address different security issues. Gope et al presented a protocol claiming resistance against known attacks. A thorough analysis of their protocol shows that it is vulnerable to user traceability, stolen verifier, and denial of service (DoS) attacks. In this article, an enhanced symmetric key‐based authentication protocol for IoT‐based WSN has been presented. The proposed protocol has the ability to counter user traceability, stolen verifier, and DoS attacks. Furthermore, the proposed protocol has been simulated and verified using Proverif and BAN logic. The proposed protocol has the same communication cost as the baseline protocol; however, in computation cost, it has 52.63% efficiency as compared with the baseline protocol.     

Fixed frequency sliding mode control of renewable energy resources in DC micro grid

The rising cost of fossil fuels, their high depleting rate and issues regarding environmental pollution have brought the attention of the researchers towards renewable energy technologies. Different renewable energy resources like wind turbines, fuel cells and solar cells are connected to DC micro grid through controllable power electronic converters. In presence of these diverse generation units, robust controllers are required to ensure good power quality and to regulate grid voltage. This paper presents a sliding mode control based methodology to address the above mentioned challenges. The proposed technique keeps the switching frequency constant so that electromagnetic compatibility (EMC) issues can be solved with conventional filter design. Parallel operation of converter in DC micro gird is considered. Chattering reduction and power quality improvement by harmonic cancellation is proposed. A scaled down hardware for unregulated 11.5 V to 17.5 V input and 24V output is designed and tested. The experimental results show good performance of the controller under different loads and uncertain input voltage conditions. Moreover, the results show the robustness of the closed loop system to sudden variations in load conditions. Furthermore, a significant improvement in power quality is achieved by harmonic cancellation of chattering in the output of the converters.     

Mechanical characteristics of oil palm fiber reinforced thermoplastics as filament for fused deposition modeling (FDM)

Fibers are increasingly in demand for a wide range of polymer composite materials. This study's purpose was the development of oil palm fiber (OPF) mixed with the thermoplastic material acrylonitrile butadiene styrene (ABS) as a composite filament for fused deposition modeling (FDM). The mechanical properties of this composite filament were then analyzed. OPF is a fiber extracted from empty fruit bunches, which has proved to be an excellent raw material for biocomposites. The cellulose content of OPF is 43%-65%, and the lignin content is 13%-25%. The composite filament consists of OPF (5%, mass fraction) in the ABS matrix. The fabrication procedure included alkalinizing, drying, and crushing the OPF to develop the composite. The OPF/ABS materials were prepared and completely blended to acquire a mix of 250 g of the material for the composition. Next, the FLD25 filament extrusion machine was used to form the OPF/ABS composite into a wire. This composite filament then was used in an FDM-based 3D printer to print the specimens. Finally, the printed specimens were tested for mechanical properties such as tensile and flexural strength. The results show that the presence of OPF had increased the tensile strength and modulus elasticity by approximately 1.9% and 1.05%, respectively. However, the flexural strength of the OPF/ABS composite had decreased by 90.6% compared with the virgin ABS. Lastly, the most significant outcome of the OPF/ABS composite was its suitability for printing using the FDM method.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00287-w.pdf     

Ternary MIL-100(Fe)@Fe3O4/CA magnetic nanophotocatalysts (MNPCs): Magnetically separable and Fenton-like degradation of tetracycline hydrochloride

Today’s world, tetracycline hydrochloride (TC) is considered as a Compounds of Emerging Concern (CECs). Metal-organic frameworks MOFs with a microporous structure and holding larger pores indicating potential applications in the fields of environmental purification. Recently, carbon aerogel (CA) has also aroused great interest due to its larger specific surface area, low density, thermal stability, and non-toxicity. Herein, MIL-100(Fe) was synthesized under low temperature and combined with Fe₃O₄ and CA, respectively. The obtained MIL-100(Fe), MIL-100(Fe)@Fe₃O₄, MIL-100(Fe)@CA and MIL-100(Fe)@Fe₃O₄/CA were investigated as a photocatalyst for removal of TC from the water. The results indicated that the MIL-100(Fe)@Fe₃O₄/CA degrade TC up to 85%, which is much higher than MIL-100(Fe)@Fe₃O₄ (c.a. 42%), due to its high surface area 389?m²?g^?1, smaller pore size and pore volume 2.4?nm and 0.319?m³?g^?1, high separation of electron and hole, and lower band gap of 1.76?eV. The coupling of CA with MIL-100(Fe)@Fe₃O₄ considerably accelerate the transfer of photo-generated charge carriers and enhanced 1.6 times the performance of MIL-100(Fe)@Fe₃O₄. Furthermore, the stability and recyclability were enhanced due to the addition of Fe₃O₄, facilitating the environmentally friendly water purification processes.