Electromagnetic absorption materials: current progress and new frontiers

Multicolor bandgap fluorescent carbon quantum dots (MCBF-CQDs) from blue to red with quantum yield up to 75% are synthesized using a solvothermal method. For the first time, monochrome electroluminescent light-emitting diodes (LEDs) with MCBF-CQDs directly as an active emission layer are fabricated. The maximum luminance of blue LEDs reaches 136 cd m-2 , which is the best performance for CQD-based monochrome electroluminescent LEDs.

Bright Multicolor Bandgap Fluorescent Carbon Quantum Dots for Electroluminescent Light-Emitting Diodes

Quantum dots are semiconductor nanocrystals that inherently fluoresce at specific wavelengths in the visible, enabling a number of potential applications to be realized. However, conventional quantum dots are based on metallic elements, which has raised concerns over toxicity, stability and high cost. As a result, the search for more benign substitutes is a worthwhile yet challenging undertaking. Recently a new type of visible emitters has been reported exclusively based on functionalized carbon nanoparticles. The carbon dots were 5 nm in diameter and were produced via laser ablation of graphite. Surface oxidation with nitric acid and subsequent covalent grafting of organic moieties afforded light-emitting derivatives. Notably, the light emitted by these dots depends on the wavelength of light used for excitation. It was suggested that the tethered modifier stabilizes the surface of the carbon nanoparticles helping to generate energy traps that emit light when stimulated, an effect described as emission from passivated surfaces. Because of its origin the emission is size-dependent, i.e., the smaller the size of the dots the better their photoluminescence efficiency. In another intriguing approach, photoluminescent carbon dots 3 nm in size were directly fabricated by electrochemical shocking of multi-wall carbon nanotubes. The demonstrated photoluminescence adds another dimension to the versatility of carbon-based

http://absimage.aps.org/image/MAR08/MWS_MAR08-2007-005201.pdf

Surface Functionalized Carbogenic Quantum Dots

In this study, we proposed a novel approach to improve centrifugal pump performance with regard to the pump head, pump efficiency, and power. Firstly, to establish constraints, an optimal numerical model that accounted for factors such as pump efficiency and the head was considered. The pump was designed, and an artificial intelligence algorithmic approach was applied to the pump before performing experiments. We considered a set of models by selecting the parameters of the centrifugal pump casing section area, the interference of the impeller, the volute tongue length, and the volute tongue angle. The weights of the factors of safety and displacement on the optimization indices were estimated. The matrix of the weights for the optimal process was less than 38% or greater than 62%. This approach guarantees a complicated multi-objective optimization problem. The results show that the centrifugal pump performances were improved.

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CFD Analysis and Optimum Design for a Centrifugal Pump Using an Effectively Artificial Intelligent Algorithm

State-of-the-art developments in carbon quantum dots (CQDs): Photo-catalysis, bio-imaging, and bio-sensing applications.

Carbon quantum dots (CQDs) are a class of carbon nanomaterials that have recently gained recognition as current entrants to traditional semiconductor quantum dots. CQDs have the desirable advantages of low toxicity, environmental friendliness, low cost, photostability, favorable charge transfer with enhanced electronic conductivity, and comparable easy-synthesis protocols. This review examines the advancements in CQD research and development, with a focus on their synthesis, functionalization, and energy applications. Initially, various synthesis methods are discussed briefly with pros and cons. Herein, first top-down methods including the arc-discharge technique, laser ablation technique, plasma treatment, ultrasound synthesis technique, electrochemical technique, chemical exfoliation, and combustion were discussed briefly. The later section presents bottom-up (microwave synthesis, hydrothermal synthesis, thermal pyrolysis, and metal–organic framework template-assisted approach) and waste-derived CQD synthesis methods. The next section is focused on the energy applications of CQDs including supercapacitors, lithium-ion batteries, photovoltaics, hydrogen evolution reaction and oxygen evolution reaction. Finally, challenges and future perspectives in this exciting and promising area are presented.

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Carbon Quantum Dots for Energy Applications: A Review

The objective of this paper was to determine the optimum process parameters of an electric discharge machine while machining a new hybrid aluminum metal matrix composite. In this study, a new hybrid aluminum metal matrix composite was prepared, with silicon carbide and graphite particles used as reinforcements, with the help of the stir casting method. The selected electric discharge machining parameters in this study were peak current (I), voltage (V), pulse-on time (Ton), and tool material, while the response parameters were material removal rate and surface roughness. To machine the fabricated samples, two different types of tool materials (copper and brass) were used as electric discharge machine electrodes, and each had a diameter (O) of 12.0 mm. The optimal settings of the electric discharge machining parameters were determined through experiments planned, conducted, and analyzed using the Taguchi (L18) technique. An analysis of variance and confirmatory tests were used to check the contribution of each machining parameter. It was found that the material removal rate increased with the increase in pulse-on time and pulse current, whereas the material removal rate decreased with the increase in voltage. On the other hand, reduced surface roughness could only be achieved when current, voltage, and pulse duration were low. It was also found that the selected electric discharge machining electrodes had a significant effect on both the material removal rate and the surface roughness.

An Experimental Investigation on the Material Removal Rate and Surface Roughness of a Hybrid Aluminum Metal Matrix Composite (Al6061/SiC/Gr)

Despite recent developments in clean energy, microgrid advancements, and power electronics, the present power system continues to face plenty of issues arising from its integration. Interference with other components of the system can create a change in input voltage, which can harm sensitive equipment. Harmonics, voltage sag, & swell themselves can harm the sensitive machinery. A Dynamic Voltage Restorer (DVR) is an equipment that is extensively used in distribution grids to address sag, swell and harmonic issues. Simultaneous simulations of the recommended DVR-based approach in MATLAB/Simulink were carried out to show its efficacy in normalizing voltage profile and harmonics.

Analysis of Voltage Sag and THD Using Dynamic Voltage Restorer

In this paper wind energy conversion systems (WECS) is getting more attention to diversify the increased renewable energy penetration. DFIG has emerged as a preferred choice for WECS due to capability for reactive power control and variable speed operation with lower rating of power converters. In this research a comprehensive grid-connected of DFIG system wind turbine in a dq-frame has been developed in TYPHOON HIL and MATLAB software platforms. The results are come by in different fault scenarios and results are compared. With increased penetration of renewable distributed energy generations WECS are getting more attention from industry and researchers.

Transient Analysis of Doubly Fed Induction Generator in Grid Connected Mode

In this paper, the effect of DVR has been analyzed on an Islanded microgrid with high renewable penetration. A wind, solar and diesel generator based Micro-grid has been developed with the help of MATLAB Simulink software. The developed microgrid model is simulated in Islanded mode with grid disconnected. The simulation results of different cases are obtained, and power quality is analyzed considering the effect of Dynamic Voltage Restorer (DVR). Also, author demonstrates mitigation of voltage sag generated due to fault, harmonics generated due to non-linear load and improving total harmonics distortion (THD), and power quality in non-linear loading and faulty conditions by using a Dynamic voltage restorer.

Anchal Yadav

Papers

Carbon Quantum Dots for Energy Applications: A Review

An Experimental Investigation on the Material Removal Rate and Surface Roughness of a Hybrid Aluminum Metal Matrix Composite (Al6061/SiC/Gr)

Analysis of Voltage Sag and THD Using Dynamic Voltage Restorer

Transient Analysis of Doubly Fed Induction Generator in Grid Connected Mode

Power Quality Improvement in Wind, Solar, and DG Based Islanded Microgrid by using DVR