Regime transition in viscous and pseudo viscous systems: A comparative study

A comprehensive quantitative study on the effect of liquid viscosity (1 ≤ µ_L ≤ 1149 mPa‐s) on the local flow phenomena of the gas phase in a small diameter bubble column is performed using ultrafast electron beam X‐ray tomography. The internal dynamic flow structure and the bubble size distribution shows a dual role of the liquid viscosity on the hydrodynamics. Further, the effect of solid concentration (C_s = 0.05, 0.20) on the local flow behavior of the gas phase is studied for the pseudo slurry viscosities similar to the liquid viscosities of the gas–liquid systems. The effects of liquid and pseudo slurry viscosities on flow structure, bubble size distribution, and gas phase distribution are compared. The bubble coalescence is significantly enhanced with the addition of particles as compared to the system without particles for apparently same viscosity. The superficial gas velocity at which transition from homogeneous bubbly to slug flow regime occurs is initiated by the addition of particles as compared to the particle free system for apparently same viscosity. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3079–3090, 2014     

The role of electrical property in determining the response of 20H-80S composite thin films fabricated for biological applications

Journal of Materials Science - The exploration of exquisite electrical properties of biomaterials for clinical applications is driven by natural design. Inspired by the idea, composite thin films...     

Improvement of multicrystalline silicon solar cell performance via chemical vapor etching method-based porous silicon nanostructures

In this paper, we report on the effect of chemical vapor etching-based porous silicon (PS) on the performance of multicrystalline silicon solar cells performed via deep n⁺/p junction-type structures. Chemical vapor etching of silicon leads to the formation of porous silicon (PS) nanostructures that dramatically decrease the surface reflectivity from 30% to about 8%, and increase the minority carrier diffusion lengths from 90 μm to 170 μm. As a result, the short-circuit current density was improved by more than 20% and the fill factor (FF) by about a 10%. An enhancement of the photovoltaic conversion energy efficiency of the solar cells from 7% to 10% was observed. This low-cost PS formation process can be applied in the photovoltaic cell technology as a standard procedure.     

Ruthenium(II) Complex-Based G-quadruplex DNA Selective Luminescent ‘Light-up’ Probe for RNase H Activity Detection

A bis-heteroleptic ruthenium(II) complex, 1[PF₆]₂ of benzothiazole amide substituted 2,2′-bipyridine ligand ( bmbbipy ) has been synthesized for the selective detection of G-quadruplex (GQ) DNA and luminescence-assay-based RNase H activity monitoring. Compound 1[PF₆]₂ exhibited aggregation-caused quenching (ACQ) in water. Aggregate formation was supported by DLS, UV-vis, and ¹H NMR spectroscopy results, and the morphology of aggregated particles was witnessed by SEM and TEM. 1[PF₆]₂ acted as an efficient GQ DNA-selective luminescent light-up probe over single-stranded and double-stranded DNA. The competency of 1[PF₆]₂ for selective GQ structure detection was established by PL and CD spectroscopy. For 1[PF₆]₂ , the PL light-up is exclusively due to the rigidification of the benzothiazole amide side arm in the presence of GQ-DNA. The interaction between the probe and GQ-DNA was analyzed by molecular docking analysis. The GQ structure detection capability of 1[PF₆]₂ was further applied in the luminescent ‘off-on’ RNase H activity detection. The assay utilized an RNA:DNA hybrid, obtained from 22AG2-RNA and 22AG2-DNA sequences. RNase H solely hydrolyzed the RNA of the RNA:DNA duplex and released G-rich 22AG2-DNA, which was detected via the PL enhancement of 1[PF₆]₂ . The selectivity of RNase H activity detection over various other restriction enzymes was also demonstrated.     

An efficient authentication with key agreement procedure using Mittag–Leffler–Chebyshev summation chaotic map under the multi-server architecture

The recent technological advancement and rapid development of computer networks have increased the popularity of remote password authentication protocols. Toward this end, the emphasis has shifted to protocols that apply to smart cards-empowered multi-server environments. In order to defend against the replay attack, these protocols usually depend on the nonce or timestamp. In this paper, an efficient Mittag–Leffler–Chebyshev Summation Chaotic Map (MLCSCM)-enabled multi-server authentication protocol with the key agreement is proposed and generalized to address this peculiarity in multi-server-oriented applications. The security proof and efficiency analysis of the presented MLCSCM authenticated key agreement protocol is rigorously derived and validated. Compared to the recently published literature, the proposed protocol presents high efficiency with unique features, and it is highly resistant to sophisticated attacks and achieves perfect forward secrecy.

     

Image denoising algorithm based on the convolution of fractional Tsallis entropy with the Riesz fractional derivative

Image denoising is an important component of image processing. The interest in the use of Riesz fractional order derivative has been rapidly growing for image processing recently. This paper mainly introduces the concept of fractional calculus and proposes a new mathematical model in using the convolution of fractional Tsallis entropy with the Riesz fractional derivative for image denoising. The structures of n × n fractional mask windows in the x and y directions of this algorithm are constructed. The image denoising performance is assessed using the visual perception, and the objective image quality metrics, such as peak signal-to-noise ratio (PSNR), and structural similarity index (SSIM). The proposed algorithm achieved average PSNR of 28.92 dB and SSIM of 0.8041. The experimental results prove that the improvements achieved are compatible with other standard image smoothing filters (Gaussian, Kuan, and Homomorphic Wiener).

     

Laser-beam-induced current mapping evaluation of porous silicon-based passivation in polycrystalline silicon solar cells

In the present work, we report on the effect of introducing a superficial porous silicon (PS) layer on the performance of polycrystalline silicon (pc-Si) solar cells. Laser-beam-induced current (LBIC) mapping shows that the PS treatment on the emitter of pc-Si solar cells improves their quantum response and reduce the grain boundaries (GBs) activity. After the porous silicon treatment, mapping investigation shows an enhancement of the LBIC and the internal quantum efficiency (IQE), due to an improvement of the minority carrier diffusion length and the passivation of recombination centers at the GBs as compared to the reference substrate. It was quantitatively shown that porous silicon treatment can passivate both the grains and GBs.     

Pixel’s Quantum Image Enhancement Using Quantum Calculus

The current study provides a quantum calculus-based medical image enhancement technique that dynamically chooses the spatial distribution of image pixel intensity values. The technique focuses on boosting the edges and texture of an image while leaving the smooth areas alone. The brain Magnetic Resonance Imaging (MRI) scans are used to visualize the tumors that have spread throughout the brain in order to gain a better understanding of the stage of brain cancer. Accurately detecting brain cancer is a complex challenge that the medical system faces when diagnosing the disease. To solve this issue, this research offers a quantum calculus-based MRI image enhancement as a pre-processing step for brain cancer diagnosis. The proposed image enhancement approach improves images with low gray level changes by estimating the pixel’s quantum probability. The suggested image enhancement technique is demonstrated to be robust and resistant to major quality changes on a variety of MRI scan datasets of variable quality. For MRI scans, the BRISQUE “blind/referenceless image spatial quality evaluator” and the NIQE “natural image quality evaluator” measures were 39.38 and 3.58, respectively. The proposed image enhancement model, according to the data, produces the best image quality ratings, and it may be able to aid medical experts in the diagnosis process. The experimental results were achieved using a publicly available collection of MRI scans.     

Experimental study and discrete element method simulation of Geldart Group A particles in a small-scale fluidized bed

Geldart Group A particles are of great importance in various chemical processes because of advantages such as ease of fluidization, large surface area, and many other unique properties. It is very challenging to model the fluidization behavior of such particles as widely reported in the literature. In this study, a pseudo-2D experimental column with a width of 5 cm, a height of 45 cm, and a depth of 0.32 cm was developed for detailed measurements of fluidized bed hydrodynamics of fine particles to facilitate the validation of computational fluid dynamic (CFD) modeling. The hydrodynamics of sieved FCC particles (Sauter mean diameter of 148 µm and density of 1300 kg/m³) and NETL-32D sorbents (Sauter mean diameter of 100 µm and density of 480 kg/m³) were investigated mainly through the visualization by a high-speed camera. Numerical simulations were then conducted by using NETL’s open source code MFIX-DEM. Both qualitative and quantitative information including bed expansion, bubble characteristics, and solid movement were compared between the numerical simulations and the experimental measurement. The cohesive van der Waals force was incorporated in the MFIX-DEM simulations and its influences on the flow hydrodynamics were studied.