A STUDY OF EXPERIMENTAL DESIGN OPTIMALITY FOR WIENER SYSTEMS

A weakly nonlinear theory of wave propagation in two superposed dielectric fluids streaming through porous media in the presence of vertical electric field and in the absence of surface charges at their interface is investigated in three dimensions. The method of multiple scales is used to obtain a dispersion relation for the linear problem and a Ginzburg-Landau equation with complex coefficients for the nonlinear problem, describing the behavior of the system. The stability of the system is discussed both analytically and numerically in both cases, and the corresponding stability conditions are obtained. It is found, in the linear case, that the stability criterion is independent of the medium permeability and that the medium porosity, surface tension, and dimension all have stabilizing effects the fluid viscosities, velocities, and depths have destabilizing effects, and the electric field has a dual role in the stability of the system. In the nonlinear analysis, it is found that the electric field has a stabilizing effect in two-dimensional disturbances and destabilizing effect in three-dimensional disturbances cases. The surface tension, fluid depths, and medium porosity have stabilizing effects in both two- and three-dimensional disturbance cases and the fluid viscosities, velocities, and medium permeability have destabilizing effects in both cases, and this stability or instability occurs faster for three-dimensional disturbance cases. It is found also that the system is unstable in the absence of fluid velocities or for nonporous media. Finally, the dimension was found to have a dual role (stabilizing as well as destabilizing) in the considered system, while it has a destabilizing effect in the case of nonporous media.     

Metal Removal Studies by Composite Membrane of Polysulfone and Functionalized Single-Walled Carbon Nanotubes

Composite nanofiltration membranes were prepared by incorporating single-walled carbon nanotubes (SWNTs) into polysulfone polymer via the phase inversion method. Addition of SWCNTs resulted in the reduction of the pore size due to nanosize (0.7-1.3 nm) diameter of SWCNTs used. The increase in carbon nanotubes makes the surface of the membranes smoother, although the solvent and nonsolvent exchange process becomes slower due to increase in viscosity of the blend solution. The addition of SWCNTs improved the rejection of metal ions, the oxidized functionalized C/PS composite membranes gave 96.8% removal for Cr(VI), 87.6% for As(III), and 94.2% removal for Pb(II) which was just 30.3%, 28.5%, and 28.3%, respectively, with unblended virgin polysulfone membrane.     

An empirical model for confined concrete after exposure to high temperature

In this study, constitutive relationships have been developed for confined concrete subjected to elevated temperature to specify the fire‐performance criteria for concrete structures after exposé to fire. This study extends over a total of 63 circular hoop confined concrete specimens that were casted and tested under concentric compression loading after exposure to high temperature. The test variables studied are the yield strength of transverse reinforcement, spacing of the hoop, and exposure to temperatures from ambient to 800°C. It is shown that all of these variables have significant influence on concrete behavior at different temperatures and further an improvement in the thermal resistance of concrete when confined using transverse steel reinforcement. On the basis of experimental results, a model for confined concrete after exposed to high temperature is proposed to predict the results of residual behavior after thermal cycles. The proposed empirical stress‐strain equations are suitable to predict the postfire behavior of confined normal strength concrete in compression. The predictions were found to be in good agreement and well fit with experimental results.     

A maskless synthesis of TiO2-nanofiber-based hierarchical structures for solid-state dye-sensitized solar cells with improved performance

TiO₂ hierarchical nanostructures with secondary growth have been successfully synthesized on electrospun nanofibers via surfactant-free hydrothermal route. The effect of hydrothermal reaction time on the secondary nanostructures has been studied. The synthesized nanostructures comprise electrospun nanofibers which are polycrystalline with anatase phase and have single crystalline, rutile TiO₂ nanorod-like structures growing on them. These secondary nanostructures have a preferential growth direction [110]. UV–vis spectroscopy measurements point to better dye loading capability and incident photon to current conversion efficiency spectra show enhanced light harvesting of the synthesized hierarchical structures. Concomitantly, the dye molecules act as spacers between the conduction band electrons of TiO₂ and holes in the hole transporting medium, i.e., spiro-OMeTAD and thus enhance open circuit voltage. The charge transport and recombination effects are characterized by electrochemical impedance spectroscopy measurements. As a result of improved light harvesting, dye loading, and reduced recombination losses, the hierarchical nanofibers yield 2.14% electrochemical conversion efficiency which is 50% higher than the efficiency obtained by plain nanofibers.     

Smart NMR Method of Measurement of Moisture Content of Vegetables During Microwave Vacuum Drying

Microwave drying is usually combined with vacuum environment in conjunction with hot air flow to draw the moisture rapidly. The moisture content of the vegetables undergoing drying is hard to measure online. This research designed a microwave vacuum drying (MVD)-low-field nuclear magnetic resonance (NMR) smart device and investigated the feasibility of NMR method for online measurement of state of moisture during MVD. The relation between the signal amplitude (A ₂) and the true moisture content (M ₁) of six kinds of vegetables (mushroom, carrot, potato, lotus, edamame, vegetable corn) was fitted to estimate if NMR can measure the M ₁ of vegetables directly. Results showed that A ₂ and M ₁ of different fresh vegetables had no single empirical mathematical model to fit. However, for each kind of these vegetables, the A ₂ and corresponding M ₁ in different MVD stages showed a significant linear relationship. The predicted moisture content (M ₂) of mushroom: M ₂ = 5.25351 × 10^?4 A ₂ ? 0.34042, R = 0.996; carrot: M ₂ = 5.78756 × 10^?4 A ₂ ? 0.14108, R = 0.998; potato: M ₂ = 3.10019 × 10^?4 A ₂ ? 0.10612, R = 0.991; lotus: M ₂ = 2.32415 × 10^?4 A ₂ ? 0.01573, R = 0.998; edamame: M ₂ = 3.13310 × 10^?4 A ₂ ? 0.4198, R = 0.996; vegetable corn: M ₂ = 1.69461 × 10^?4 A ₂ ? 0.09063, R = 0.995. The linear models between M ₂ and A ₂ were able to estimate the end point (M ₁ < 8%) of MVD with a high accuracy (P > 0.950).     

Transport behavior of selected nanoparticles with different surface coatings in granular porous media coated with Pseudomonas aeruginosa biofilm

Well-controlled laboratory column experiments were conducted to understand the influence of Pseudomonas aeruginosa (P. aeruginosa) biofilms on the transport of selected engineered nanoparticles (ENPs) in granular porous media representative of groundwater aquifers or riverbank filtration settings. To understand the importance of particle size on retention in the biofilm-coated granular (quartz sand) matrix, column experiments were carried out using nanosized (20 nm) and micrometer-sized (1 μm) sulfate-functionalized polystyrene latex particles (designated as 20 nSL and 1 mSL, respectively). Additional experiments conducted with nanosized (20 nm) carboxyl-modified latex particles (20nCL) and carboxyl-modified CdSe/ZnS quantum dots (QDs) provide information on the influence of particle surface chemistry on retention. Biofilm grown on the surface of the sand was characterized by total biomass quantification, confocal laser scanning microscopy (CLSM), and electrokinetic analysis. All four particles exhibit increased retention in the biofilm-coated packed bed: e.g., the attachment efficiency (α) of the 1 mSL particle increases from 0.40 to 1.7, whereas α for the 20 nSL particle increases from 0.04 to 0.10 in the biofilm-coated system. Particle surface chemistry can also influence the affinity of the ENPs for the biofilm coating as revealed by the greater attachment of the 20 nSL particle onto the biofilm-coated sand (α = 0.10) than its carboxylated counterpart (α = 0.04). Column experiments conducted using sand coated with growth medium (LB) or extracellular polymeric substances (EPS) extracted from P. aeruginosa biofilms further reveal that particle surface chemistry influences the interaction between the different ENPs and these coated sand surfaces. Namely, coating of sand surfaces with LB medium or bacterial EPS does not affect the transport of the sulfonated nanoparticle, but the LB coating leads to decreased retention of the carboxylated latex nanoparticle. Furthermore, our results show that EPS coatings are not necessarily good surrogates for biofilm-coated sand. Electrokinetic characterization of the clean and coated sand surfaces also reveals that the extent of particle retention is not controlled by electrical double layer interactions. Future studies should thus be aimed at improving our understanding of the fundamental mechanisms (both colloidal and noncolloidal) governing nanoparticle transport and fate in biofilm-laden granular aquatic environments.     

A high performance lipase preparation: characterization and atomic force microscopy

The goal of obtaining enzyme forms which show greater stability, higher catalytic efficiency, and reusability has been pursued since last several decades. Some novel biocatalyst designs have been evolved and protein coated micro-crystals (PCMCs) is one of them. Pseudomonas cepacia lipase coated micro-crystals were prepared by simultaneous precipitation of mixture of aqueous lipase solution and salts such as potassium sulphate by organic solvents. This resulted in lipase coated micro-crystals. The structures of micro-crystals were studied by atomic force microscopy (AFM). The AFM picture confirmed the enzyme coating over the potassium sulphate crystals. These PCMCs are in the size range of 500-1000 nm. These enzyme coated micro-crystals showed enhanced transesterification rates. Also, the PCMC were stable at 60 degrees C whereas the free enzyme lost all its activity. The enzyme coated micro-crystals prepared by 50 mg Pseudomonas cepacia lipase gave 96% conversion in 90 min whereas free enzyme gave 8% conversion. Even PCMCs prepared from 3.12 mg lipase gave 90% conversion in 10 h at 60 degrees C where as free lipase was inactive at 60 degrees C.     

Pre-trained convolutional neural networks as feature extractors for diagnosis of breast cancer using histopathology

Several researchers are trying to develop different computer-aided diagnosis system for breast cancer employing machine learning (ML) methods. The inputs to these ML algorithms are labeled histopathological images which have complex visual patterns. So, it is difficult to identify quality features for cancer diagnosis. The pre-trained Convolutional Neural Networks (CNNs) have recently emerged as an unsupervised feature extractor. However, a limited investigation has been done for breast cancer recognition using histopathology images with CNN as a feature extractor. This work investigates ten different pre-trained CNNs for extracting the features from breast cancer histopathology images. The breast cancer histopathological images are obtained from publicly available BreakHis dataset. The classification models for the different feature sets, which are obtained using different pre-trained CNNs in consideration, are developed using a linear support vector machine. The proposed method outperforms the other state of art methods for cancer detection, which can be observed from the results obtained.     

Secrecy Performance Analysis of Hybrid AF-DF Relaying Under Multi Hop Environment

Wireless Personal Communications - In this work, a three-hop wireless relaying model comprising of a single source and destination node, along with two relay nodes and an eavesdropper is...