A simple synthesis and characterization of CuS nanocrystals

Water-soluble CuS nanocrystals and nanorods were prepared by reacting copper acetate with thioacetamide in the presence of different surfactants and capping agents. The size of the nanocrystals varied from 3–20 nm depending on the reaction parameters such as concentration, temperature, solvent and the capping agents. The formation of nanocrystals was studied by using UV-visible absorption spectroscopy.     

Application of a locally operating laser-speckle strain sensor

In this paper, we report on both the theory and applicability of a novel laser-speckle shift strain measurement system. Based on the theoretical sensitivity of the system to strain, some sources of error due to imperfections in the geometrical setup are discussed. Some references to the digital signal processing involved are given. We conclude with some experimental results from testing fibers, foils, and standardized specimen that can only be obtained in a noncontacting and preferably optical way because of the fragility and the small physical dimensions of the specimen.     

Intrusion detection in RFID system using computational intelligence approach for underground mines

The radio frequency identification technology (RFID) is commonly used for object tracking and monitoring. In this paper, we discuss a model for intrusion detection system based on RFID to identify the abnormal behavior of underground mines' toxic gases. This model consists of various types of sensor nodes that are integrated with RFID tag, which are deployed in the underground mines by using Zigbee protocol. It consists of coordinators, routers, and sensor nodes, according to different capabilities and the probabilities of intrusive activities that occur in underground mines. It can detect the real‐time abnormal behavior of the toxic gases viz. methane, carbon monoxide, carbon dioxide, hydrogen sulfide, and nitrogen dioxide gases, using artificial neural network middleware techniques. It increases the detection accuracy and reduces the false alarm rate, using multilayer perceptron, radial basis function network, and probabilistic and general regression neural network (PNN/GRNN) techniques. The simulations are performed on the toxic gas dataset, which has been generated in a real‐time scenario by using different gas sensors. The real‐time dataset contains intrusive and nonintrusive values of methane, carbon monoxide, carbon dioxide, hydrogen sulfide, and nitrogen dioxide gases. Experimentally, the PNN/GRNN provides higher detection accuracy as 90.153% for carbon monoxide, 86.713% for carbon dioxide, 93.752% for hydrogen sulfide, and 75.472% for nitrogen dioxide. The PNN/GRNN also provides low false alarm rate as 9.85% for carbon monoxide, 13.29% for carbon dioxide, 6.24% for hydrogen sulfide, and 24.53% for nitrogen dioxide compared with the multilayer perceptron and radial basis function networks.     

Impact of Nonfullerene Molecular Architecture on Charge Generation,Transport, and Morphology in PTB7‐Th‐Based Organic Solar Cells

Despite the rapid development of nonfullerene acceptors (NFAs), the fundamental understanding on the relationship between NFA molecular architecture, morphology, and device performance is still lacking. Herein, poly[[4,8‐bis[5‐(2‐ethylhexyl)thiophene‐2‐yl]benzo[1,2‐b:4,5‐b0]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]‐thieno[3,4‐b]thiophenediyl]] (PTB7‐Th) is used as the donor polymer to compare an NFA with a 3D architecture (SF‐PDI4) to a well‐studied NFA with a linear acceptor–donor–acceptor (A–D–A) architecture (ITIC). The data suggest that the NFA ITIC with a linear molecular structure shows a better device performance due to an increase in short‐circuit current ( J_sc) and fill factor (FF) compared to the 3D SF‐PDI4. The charge generation dynamics measured by femtosecond transient absorption spectroscopy (TAS) reveals that the exciton dissociation process in the PTB7‐Th:ITIC films is highly efficient. In addition, the PTB7‐Th:ITIC blend shows a higher electron mobility and lower energetic disorder compared to the PTB7‐Th:SF‐PDI4 blend, leading to higher values of J_sc and FF. The compositional sensitive resonant soft X‐ray scattering (R‐SoXS) results indicate that ITIC molecules form more pure domains with reduced domain spacing, resulting in more efficient charge transport compared with the SF‐PDI4 blend. It is proposed that both the molecular structure and the corresponding morphology of ITIC play a vital role for the good solar cell device performance.     

Design of active NiCo2O4‐δ spinel catalyst for abatement of CO‐CH4 emissions from CNG fueled vehicles

Increasing number of CNG vehicles on road emits considerable amount of CO, a poisonous gas and CH₄, a greenhouse‐gas. Highly active and oxygen‐deficient NiCo₂O_4‐δ spinel and its individual metal‐oxides were synthesized by calcination of precipitated/co‐precipitated basic‐carbonates followed by calcination under different strategies of stagnant air(s), flowing air(f) and reactive calcination(RC) for total oxidation of CO‐CH₄ mixture. The catalysts were characterized by XRD, XPS, BET surface‐area, SEM‐EDX and TEM. The performance order of the catalysts for the oxidation of CO‐CH₄ mixture was as follows: NiCo_RC>NiCo_f>NiCo_s>Co_RC>Co_f>Co_s>Ni_RC> Ni_f>Ni_s. The pairing of Ni and Co in spinel‐structure together with RC produced catalyst was oxygen‐deficient highly active for total oxidation of the mixture at the lowest temperature of 350°C. The NiCo_RC was found stable under reaction‐conditions for 50h at 350°C and after four successive heating (350°C)‐cooling (35°C) cycles besides accelerated‐aging tests up to 600°C. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2632–2646, 2018     

Effect of Primary Silicon Refinement on Mechanical and Wear Properties of a Hypereutectic Al-Si Alloy

Silicon - This study explores the effect of primary silicon refinement of hypereutectic Al-Si alloy on the mechanical and wear properties. Refinement has been carried out by purging N2 into...     

Reversible Photoinduced Phase Segregation and Origin of Long Carrier Lifetime in Mixed‐Halide Perovskite Films

Mixed‐halide hybrid perovskite semiconductors have attracted tremendous attention as a promising candidate for efficient photovoltaic and light‐emitting devices. However, these perovskite materials may undergo phase segregation under light illumination, thus affecting their optoelectronic properties. Here, photoexcitation induced phase segregation in triple‐cation mixed‐halide perovskite films that yields to red‐shift in the photoluminescence response is reported. It is demonstrated that photoexcitation induced halide migration leads to the formation of smaller bandgap iodide‐rich and larger bandgap bromide‐rich domains in the perovskite film, where the phase segregation rate is found to follow the excitation power‐density as a power law. Results confirm that charge carrier lifetime increases due to the trapping of photoexcited carriers in the segregated smaller bandgap iodide‐rich domains. Interestingly, these photoinduced changes are fully reversible and thermally activated when the excitation power is turned off. A significant difference in activation energies for halide ion migration is observed during phase segregation and recovery process. Additionally, the emission linewidth broadening is investigated as a function of temperature which is governed by the exciton–optical phonon coupling. The mechanism of photoinduced phase segregation is interpreted based on exciton–phonon coupling strength in both mixed and demixed (segregated) states of perovskite films.     

Meta-heuristic optimization algorithms for comparative analysis of uniform and non-uniform elliptical array antenna for enhanced gain

In this article, the synthesis of a non-uniform elliptical array antenna (EAA) is presented applying three relatively new, well-performing meta-heuristic optimization algorithms; quantum particle swarm optimization (QPSO), symbiotic organism search (SOS), and moth fly optimization (MFO) algorithms. The design objective allows simultaneous minimization of side lobes and maximization of gain by finding the best optimal combination of angular locuses of the antennas in the array structure. The proposed technique is efficient enough to resolve the underlying multi-objective problems at two principle planes of radiation and adaptable enough to the effective implementation of additional design constraints which make this design suitable for practical high-frequency applications as well as long-distance communication. The iterative accomplishment of the three algorithms is compared depending on the radiation parameters as well as statistical parameters. The outcomes are validated by performing a t test on the obtained data sets.     

Evolution of mixing in a microfluidic reverse-staggered herringbone micromixer

Microfluidic platforms offer a variety of advantages including improved heat transfer, low working volumes, ease of scale-up, and stronger user control on operating parameters. However, flow within microfluidic channels occurs at low Reynolds number (Re), which makes mixing difficult to accomplish. Adding V-shaped ridges to channel walls, a pattern called the staggered herringbone design (SHB), alleviates this problem by introducing transverse flow patterns that enable enhanced mixing. Building on our prior work, we here developed a microfluidic mixer utilizing the SHB geometry and characterized using CFD simulations and complimentary experiments. Specifically, we investigated the performance of this type of mixer for unequal species diffusivities and inlet flows. A channel design with SHB ridges was simulated in COMSOL Multiphysics® software under a variety of operating conditions to evaluate its mixing capabilities. The device was fabricated using soft-lithography techniques to experimentally visualize the mixing process. Mixing within the device was enabled by injecting fluorescent dyes through the device and imaging using a confocal microscope. The device was found to efficiently mix fluids rapidly, based on both simulations and experiments. Varying Re or species diffusion coefficients had a weak effect on the mixing profile, due to the laminar flow regime and insufficient residence time, respectively. Mixing effectiveness increased as the species flow rate ratio increased. Fluid flow patterns visualized in confocal microscope images for selective cases were strikingly similar to CFD results, suggesting that the simulations serve as good predictors of device performance. This SHB mixer design would be a good candidate for further implementation as a microfluidic reactor.