Synthesis of light weight recron fiber-reinforced sodium silicate based silica aerogel blankets at an ambient pressure for thermal protection

Journal of Porous Materials - In this work, for the sake of improving the performance of homogeneous and flexible silica aerogel blankets in practical applications, lightweight recron fibers were...     

Synthesis of Secondary Amides from N‐Substituted Amidines by Tandem Oxidative Rearrangement and Isocyanate Elimination

In this work an efficient tandem process transforming N‐substituted amidines into secondary amides has been described. The process involves N‐acylurea formation by reaction of the substrate with bis(acyloxy)(phenyl)‐λ³‐iodane followed by isocyanate elimination. The periodinane reagents are obtained from the commercially available phenyliodine(III) diacetate [PhI(OAc)₂, (PIDA)] by ligand exchange with carboxylic acids. The N‐substituted amidine substrates are easily synthesized from readily available nitriles. The method is applicable for secondary amide synthesis, based on both aliphatic and (hetero)aromatic amines, including challenging amides consisting of sterically hindered acids and amines. Moreover, the protocol allows one to combine steric bulk with electron deficiency in the target amides (aniline based). Such compounds are difficult to synthesize efficiently based on classical condensation reactions involving carboxylic acids and amines. Overall, the synthetic protocol transforms a nitrile into a secondary amide in both aliphatic and (hetero)aromatic systems.

     

Quantitative recovery of high purity nanoporous silica from waste products of the phosphate fertilizer industry

This study reports on the quantitative recovery of high purity nanoporous silica from wastes material (H₂SiF₆) of the phosphate fertilizer industry and Na₂O·SiO₂. The silica recovered from the wastes was compared with silica from the reaction of H₂SO₄ and Na₂O·SiO₂ because H₂SO₄ is commonly used. The product recovered from the wastes material and H₂SO₄ were 99.3% and 99.1% pure, respectively. The quantity recovered were 22.30 g and 20.11 g, respectively. The product had superior properties suitable for applications such as chromatography, reinforcing material for rubber and plastics. The process may significantly reduce the release of SiF₄ gas into the environment.     

Morphology,structural, optical,magnetic, and photocatalytic properties of Co1−xZnxFe2−yCeyO4 NPs

Journal of Materials Science: Materials in Electronics - In the current study, we looked into the effects of simultaneous trivalent Ce and divalent Zn doping on the optical, magnetic, and...     

Illumination normalized based technique for retinal blood vessel segmentation

The Retinal image carries important information about the health of the sensory part of the visual system. In this paper, a new approach is suggested by utilizing the homomorphic filter integrated with Contrast limited adaptive histogram equalization (CLAHE) method for the illumination normalization and contrast enhancement of the retinal images. Then segmentation is done through several steps by using the existing methods such as morphological filtering, a second derivative operator that is followed by a final morphological filtering stage and hysteresis thresholding. The suggested method is verified on DRIVE and CHASE‐DB1 databases and has average accuracy of 72.03% and 64.54%, accordingly. The obtained results demonstrate that the proposed approaches achieve higher accuracy than the traditional method. The suggested approach not only contributes to the successful result, but also minimizes the computing time.     

Optical and Low-Temperature Magnetocaloric Properties of HoCr0.5Mn0.5O3 Compound

Journal of Superconductivity and Novel Magnetism - The optical, magnetic and magnetocaloric properties of HoCr0.5Mn0.5O3 compound have been investigated thoroughly. A multicolour photoluminescence...     

Analysis of a three-coil contactless power transfer system for high-power applications

Recently, contactless power transfer (CPT) has become very popular in various fields of applications such as electronic appliances, medical implant devices, electrical vehicles, etc. When air gap distance between the transmitting and receiving coils of a CPT system increases, coupling coefficient between the coils decreases. In a large-air-gap CPT system, by incorporating an additional coil between the transmitting and receiving coils, coupling coefficient can be enhanced. Consequently, efficiency of a large-air-gap CPT system is improved. In this study, a three-coil system has been compared with a two-coil system using basic circuit models. Thereafter, the basic circuit models of two-coil and three-coil systems have been studied to confirm energy efficiency differences between the two systems for high-power applications. Using simplified circuit models, conditions for higher energy efficiency of a three-coil system than a two-coil system have been derived and it has been established that power transfer efficiency of a three-coil system has improved significantly in comparison with a traditional two-coil system. To confirm the theory, a two-coil and a three-coil systems with an air gap distance of 18 cm and a lateral misalignment of 3.5 cm have been verified using Ansys simulation tool for an output power of 2 kW.     

Distributed fault tolerant computation of weakly connected dominating set in ad hoc networks

Our purpose in this paper is to propose a self-stabilizing protocol for weakly connected dominating set (WCDS) set in a given ad hoc network graph. WCDS is a particular variant of graph domination predicates which play an important role in routing in ad hoc networks. There are many variants of domination problems in bidirectional networks; WCDS is also useful in forming clusters in ad hoc networks. There are many heuristic and distributed algorithms to compute WCDS in network graphs while almost all of them will need complete information about the network topology and most of them are not fault tolerant or mobility tolerant. Self-stabilization is a protocol design paradigm that is especially useful in resource constrained infrastructure-less networks since nodes can make moves based on local knowledge only and yet a global task is accomplished in a fault tolerant manner; it also facilitates for nodes to enter and exit the network freely. There exist self-stabilizing protocols for minimal spanning tree, total domination, and others. We have shown that the paradigm is capable of designing a protocol for WCDS. Our objective is to mathematically prove the correctness and the convergence of the protocol in any worst-case scenario, as is usually done for self-stabilizing protocols for other graph predicates used for ad hoc networks.     

High-Performance Photodetector and Angular-Dependent Random Lasing from Long-Chain Organic Diammonium Sandwiched 2D Hybrid Perovskite Non-Linear Optical Single Crystal

3D organic-inorganic metal halide perovskites are excellent materials for optoelectronic applications due to their exceptional properties, solution processability, and cost-effectiveness. However, the lack of environmental stability highly restricts them from practical applications. Herein, a stable centimeter-long 2D hybrid perovskite (N-MPDA)[PbBr₄] single crystal using divalent N1-methylpropane-1,3-diammonium (N-MPDA) cation as an organic spacer, is reported. The as-grown single crystal exhibits stable optoelectronic performance, low threshold random lasing, and multi-photon luminescence/multi-harmonic generation. A photoconductive device fabricated using (N-MPDA)[PbBr₄] single crystal exhibits an excellent photoresponsivity (≈124 AW⁻¹ at 405 nm) that is ≈4 orders of magnitudes higher than that of monovalent organic spacer-assisted 2D perovskites, such as (BA)₂PbBr₄ and (PEA)₂PbBr₄, and large specific detectivity (≈10¹² Jones). As an optical gain media, the (N-MPDA)[PbBr₄] single crystal exhibits a low threshold random lasing (≈6.5 µJ cm⁻²) with angular dependent narrow linewidth (≈0.1 nm) and high-quality factor (Q ≈ 2673). Based on these results, the outstanding optoelectronic merits of (N-MPDA)[PbBr₄] single crystal will offer a high-performance device and act as a dynamic material to construct stable future electronics and optoelectronic-based applications.