Magneto-dielectric and magneto-conducting fillers based polymer composites: Effect of functionalization,coating and dispersion process on electromagnetic shielding properties

Electromagnetic interference shielding of magneto-dielectric (BaTiO₃-Fe₃O₄) and magneto-conducting (f-MWCNT-Fe₃O₄) fillers based polymer electrolyte composites in the X-band have been studied in the present work. Magneto-dielectric and magneto-conducting fillers have been obtained by in situ preparation of Fe₃O₄ nanoparticles by chemical precipitation in the presence of BaTiO₃ and functionalized multiwalled carbon nanotubes (f-MWCNT). Functionalization of MWCNT has resulted in their strong bonding with the polymer electrolyte adversely affecting the charge transport properties and shielding effectiveness. Dielectric, magnetic and conducting properties of the magneto-dielectric and magneto-conducting fillers are found to be significantly different as a result of coating by Fe₃O₄ nanoparticles on BaTiO₃ and f-MWCNT. Combining two fillers in a single nanocomposite has exhibited non-complimentary addition of their individual properties. The ultra-sonication method of dispersion of the magneto-conducting filler has been found to give better conducting and shielding effectiveness in comparison to the homogenization method due to better disentanglement of the nanotubes.     

Deep neural network and 3D model for face recognition with multiple disturbing environments

This paper presents the proposed bird search-based shuffled shepherd optimization algorithm (BSSSO) for face recognition. Initially, the input image undergoes a noise removal phase to eliminate noise in order to make them suitable for subsequent processing. The noise removal is performed using the type II fuzzy system and cuckoo search optimization algorithm (T2FCS), which detects noisy pixels from the image for improved processing. After the noise removal phase, the feature extraction is carried out using the convolution neural network (CNN) model and landmark enabled 3D morphable model (L3DMM). The obtained features are subjected to deep CNN for face recognition. The training of deep CNN is performed using the bird search-based shuffled shepherd optimization algorithm (BSSSO). Here, the proposed BSSSO is designed by combining the shuffled shepherd optimization algorithm (SSOA) and bird swarm algorithm (BSA) for inheriting the merits of both optimizations towards effective training of deep CNN. The proposed method obtained higher accuracy of 0.8935 and minimum FAR and FRR of 0.2190 and 0.2021 using LFW database with respect to training data.

     

Extended omega ratio optimization for risk‐averse investors

The omega ratio, a performance measure, is the ratio of the expected upside deviation of return to the expected downside deviation of return from a predetermined threshold described by an investor. It has been exhibited that the omega ratio optimization is equivalent to a linear program under a mild condition and thus easily tractable. But the omega ratio optimization fails to hedge against many other risks involved in portfolio return that may adversely affect the interests of a risk‐averse investor. On the other hand, there are widely accepted mean‐risk models for portfolio selection that seek to maximize mean return and minimize the associated risk but in general fail to maximize the relative performance ratio around the threshold return. In this paper, we aim to propose a model called ‘extended omega ratio optimization’ that combines the features of the omega ratio optimization model and mean‐risk models. The proposed model introduces constraint on a general risk function in the omega ratio optimization model in such a way that the resultant model remains linear and thus tractable. Our empirical experience with real data from S&P BSE sensex index shows that the optimal portfolios from the extended omega ratio optimization model(s) improved over the optimal portfolios from the omega ratio optimization in having less associated risk and over the optimal portfolios from the corresponding mean‐risk model(s) in having a high value omega ratio.     

Sol-gel derived aluminum doped zinc oxide for application as anti-reflection coating in terrestrial silicon solar cells

Sol-gel grown polycrystalline Al doped zinc oxide (AZO) thin films have been deposited on Si wafers, microscopy slide glass and fluorine doped tin oxide coated glass substrates using the spin coating technique. The atomic ratio of Al:Zn in the films is 0.2. From the X-ray diffraction investigations it is found that the preferential growth of (100) reflection peak has taken place in the 450, 550 and 600 °C annealed films. Scanning electron microscopic study has shown that the films contain well-defined grains arranged in a closely packed array. The resistivity of the 500 °C annealed film is measured to be 5 × 10^− 1 Ω cm. The films have exhibited excellent optical transmittance (~ 90%) in the 400-1100 nm wavelength range. Refractive indices (n = 1.9-1.95) of the films on Si wafer are independent of the annealing temperature. Thickness of the films produced at 4000 rpm is in the range of 58-62 nm. The refractive index and thickness of these films are nearly appropriate to cause destructive interference after reflection from front emitters of solar cells. These films have demonstrated a reflectivity value of about 3% at a wavelength of 700 nm. The AZO coated silicon solar cells possess V_oc and I_sc values of 573 mV and 237 mA, respectively.     

An investigation of melt rheology and thermal stability of poly(lactic acid)/ poly(butylene succinate) nanocomposites

A systematic investigation of the rheological and thermal properties of nanocomposites prepared with poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and organically modified layered silicate was carried out. PLA/PBS/Cloisite 30BX (organically modified MMT) clay nanocomposites were prepared by using simple melt extrusion process. Composition of PLA and PBS polymers were fixed at a ratio of 80 to 20 by wt % for all the nanocomposites. Rheological investigations showed that high clay (> 3 wt %) contents strongly improved the viscoelastic behavior of the nanocomposites. Percolation threshold region was attained between 3 and 5 wt % of clay loadings. With the addition of clay content for these nanocomposites, liquid‐like behavior of PLA/PBS blend gradually changed to solid‐like behavior as shown by dynamic rheology. Steady shear showed that shear viscosity for the nanocomposites decreased with increasing shear rates, exhibiting shear‐thinning non‐Newtonian behavior. At higher clay concentrations, pseudo‐plastic behavior was dominant, whereas pure blend showed almost Newtonian behavior. Thermogravimetric analysis revealed that both initial degradation temperature (at a 2% weight loss) and activation energy of thermal decomposition nanocomposite containing 3 wt % of C30BX were superior to those of other nanocomposites as well as to those of PLA/PBS blend. Nanocomposite having 1 wt % of C30BX did not achieve expected level of thermal stability due to the thermal instability of the surfactant present in the organoclay. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Connection between Antarctic sea‐ice extent and Indian summer monsoon rainfall

Antarctic sea‐ice extent (AnSIE) is an important parameter influencing global climate. The present study is carried out to find whether any connection between the AnSIE and the Indian summer monsoon rainfall (ISMR) exists. Temporal cross‐correlations between the anomalies of the ISMR and AnSIE as a whole and its different sectors are computed for the period 1988 to 2005. A coherent propagating pattern is clearly evident between the AnSIE and ISMR, as well as the rainfall over most of the homogeneous geographical regions of India. Furthermore, this study reveals that the sea‐ice extent (SIE) of the western Pacific Ocean sector in the month of March has a strong association with that of the ISMR in the same year. Year 2002 was a major drought year, which none of the regional or general circulation models could simulate. AnSIE variation has provided a strong signal to imply that 2002 would be a deficit monsoon year.     

Neuropsychological correlates of ADHD symptoms in preschoolers.

The authors examined the neuropsychological status of 22 preschoolers at risk for attention-deficit/hyperactivity disorder (ADHD) and 50 matched control children, using measures of nonverbal working memory, perceptual and motor inhibition, and memory for relative time. All tasks included paired control conditions, which allowed for the isolation of discrete executive function constructs. Group differences were evident on several measures of neuropsychological functioning; however, after accounting for nonexecutive abilities, no deficits could be attributed to specific functions targeted by the tasks. Performance on executive measures was not related to objective indices of activity level or ratings of ADHD symptoms. Yet, the fact that at-risk preschoolers were highly symptomatic casts doubt on whether executive function deficits and/or frontostriatal networks contribute etiologically to early behavioral manifestations of ADHD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)