802 research outputs found
Investigation on the influence of macromolecular additives on transport properties of lithium polymer electrolytes / Lekshmi Sarojini Amma
No full textThe main focus of this work is to study the immobilization of anions there by improve the electrical properties of solid polymer electrolyte (SPE). There are three polymer
electrolyte systems in this project. Poly (ethylene oxide) with salt lithium iodide (PEOLiI), to the high conducting ratio of this system, inorganic filler aluminium oxide
(Al2O3), and organic macro molecule calix4 arenes, and calix6 arenes added one at a time. Sample films are prepared using solution casting technique. X-ray diffraction
(XRD) studies have shown that all the samples prepared are amorphous. Fourier transform infrared spectroscopy (FTIR) indicated complexation between component materials in the polymer electrolytes based on the changes in peak locating and intensity and formation of new peaks. The conductivity of PEO-LiI is about 1.54 × 10-4 Scm-1 at room temperature, with 15 wt.% of Al2O3 exhibits the highest ionic conductivity of 3.30× 10-4 S cm-1. The highest ionic conductivity of 3 wt.% calix4 arenes exhibit 4.56× 10-5 S cm-1 at room temperature and for 3 wt.%calix6 arenes it is 2.87 ×10-5 Scm-1. The ionic conductivity of all samples increased with increasing temperature. When organic
macromolecule is added into the high conducting PEO-LiI salt system the ionic conductivity decreased by one order magnitude shows that the immobilization might have taken place. The dielectric behaviour is analyzed using dielectric permittivity and dielectric modulus of the samples
Impact of rapid urbanization on the City of Bhubaneswar, India
No full textRapid and unplanned urbanization of cities has been a cause of great concern world over. Increased urbanization has immensely altered the Land Use pattern of several Indian cities, thereby altering the physical properties of the land surface. The pronounced effect of urban heat island (UHI) apart from the acute stress on limited natural resources are consequences of this rapid urbanization. UHI effect manifests as unexpected rise in city temperatures when compared to their surrounding areas, thus making them unfriendly for habitation over time. The present work analyses the effect of UHI on Bhubaneswar, an Indian city undergoing rapid urbanization in recent times, utilizing land use and land cover (LULC) change data from Landsat over a 25 km radius about the city and MODIS land surface temperatures (LST) at 1 km2 spatial resolution for a period of 15 years (2000–2014). From the study, significant changes in LULC through over-exploitation of natural resources and the related spatio-temporal variations in LST has been identified as one major factor responsible for changes in the UHI effect over Bhubaneswar. Owing to rapid urbanization (83% increase in 15 years), the city has undergone major changes in LULC aggregating to a massive ~ 89% decrease in dense vegetation and ~ 83% decrease in crop fields over this time period. Analyses of the changes in the urban energy balance and resulting UHI effect across many such Indian cities undergoing rapid urban growth is quite essential for mitigating the negative impacts of urbanization for a long-term sustainability
Science & technology agenda for blue-green spaces inspired by citizen science: case for rejuvenation of powai lake
No full textUrban lakes play a major role in the socio-cultural and ecological sustainability of many cities, but are often under major development and pollution pressures. Urban decision makers are faced with a challenging task of identifying the causes of their decline and building plans for their conservation or rejuvenation. Powai Lake is a perfect example of an urban water body with historic, cultural, and ecological importance to the population of Metropolitan Mumbai, with local and regional authorities, including the Urban Development Department, Government of Maharashtra, working to identify methods for rejuvenating the Lake. In this context, characterization of pollution dynamics, hotspots, and extent is fundamental to the development of management plans and appropriate technologies for the remediation and rejuvenation of Powai Lake—the long-term goal of the present study. A two-year monitoring program at eight sampling locations on the Lake’s periphery, with the engagement of citizen scientists along with environmental researchers, revealed clear seasonal and spatial dynamics that allowed for the identification of pollution drivers and the development of a three-phase rejuvenation plan. The plan represents a novel and holistic approach that recognizes Powai Lake as a complex system with multiple drivers, and aims at ecological balance and sustainable delivery of ecosystem services
Single Channel Speech Separation with Frame-based Summary Autocorrelation Function Analysis
No full textAbstractSingle channel speech separation system with frame based pitch range estimation is presented. The system decomposes the input mixture speech into frames and pitch of the speech is estimated in each frame of modulation spectrum by using summary autocorrelation function (SACF) analysis. In this method, each frame is divided into two, above and below 1 KHz and compute generalized autocorrelation for periodicity detection. By using this pitch range, a mask is created to filter the target speech from noisy mixture speech. Performance evaluation of the proposed system shows a better response compared to the existing methods
A Model for Pitch Estimation Using Wavelet Packet Transform Based Cepstrum Method
No full textAbstractA computationally efficient model for pitch estimation of mixed audio signals is presented. Pitch estimation plays a significant role in music audition like music information retrieval, automatic music transcription, melody extraction etc. The proposed system consists of channel separation and periodicity detection. The input signal is created by mixing two sound signals. First removes the short time correlations of the mixed signal. The model divides the signal into number of channels using wavelet packet transform. Computes the cepstrum of each channel and sums the cepstrum functions. The summary cepstrum function is further processed to extract the pitch frequency of two input signal separately. The model performance is demonstrated to be comparable to those of recent multichannel models. The proposed system can be verified by simulating the system in MATLAB
Polarons induced electronic transport, dielectric relaxation and magnetodielectric coupling in spin frustrated Ba2FeWO6
No full textMixed valent double perovskite Ba2FeWO6, with tetragonal crystal structure, synthesized in a highly controlled reducing atmosphere, shows antiferromagnetic transition at T-N = 19 K. A cluster glass-like transition is observed around 30 K arising from the competing interactions between inhomogeneous magnetic states. The structural distortion leads to the formation of polarons that are not contributing to DC conduction below charge ordering temperature, T-co = 279 K. Above Tco, small polarons will start to hop by exploiting thermal energy and participate in the conduction mechanism. The polarons are also responsible for the dielectric relaxor behavior, in which the dielectric relaxation time follows non linearity in temperature as proposed by Fulcher. The material also exhibits a small room temperature magnetoresistance of 1.7% at 90 kOe. An intrinsic magnetodielectric coupling of similar to 4% near room temperature and at lower temperatures, as well as an extrinsic magnetodielectric coupling change from +4% to-6% at around 210K are reported. (C) 2015 Elsevier Ltd. All rights reserved
Time-Dependent Reliability Analysis of Pavement Structures under Fatigue Loading
No full textThe premature failure of well-designed structures in the field is a problem commonly observed worldwide. These early failures and the deterioration in structural resistance of pavements can be attributed to the loading and external environmental factors, damage and improper maintenance during the design life among other factors. The time dependence of performance in the formulation of the reliability problem helps to include the effects of degradation of resistance and the variation of loading with time. In this study, the effect of degradation of the surface layer modulus on the fatigue reliability of pavements is analyzed, where the decrease in the modulus with time is considered as a function of the accumulated damage due to repeated loading. The pavement section considered in the study designed for a period of 15 years at a reliability level of 80%, is seen to have a probability of failure of around 50% after 8 years and 75% after 10 years, when strength degradation is considered. This emphasizes the need for capturing the temporal characteristics of the materials and loading in a time-dependent reliability analysis framework
Synergic bactericidal effects of reduced graphene oxide and silver nanoparticles against Gram-positive and Gram-negative bacteria
No full text<i>Reduced graphene oxide</i> (rGO) is a promising antibacterial material, the efficacy of which can be further enhanced by the addition of silver <i>nanoparticles</i> (nAg). In this study, the mechanisms of antibacterial activity of rGO–nAg nanocomposite against several important human pathogenic multi-drug resistant bacteria, namely Gram-positive coccal Staphylococcus aureus and Gram-negative rod-shaped Escherichia coli and Proteus mirabilis are investigated. At the same concentration (100 µg/ml), rGO–nAg nanocomposite was significantly more effective against all three pathogens than either rGO or nAg. The nanocomposite was equally active against P. mirabilis and S. aureus as systemic antibiotic nitrofurantoin, and significantly more effective against E. coli. Importantly, the inhibition was much faster in the case of rGO–nAg nanocomposite compared to nitrofurantoin, attributed to the synergistic effects of rGO–nAg mediated contact killing and oxidative stress. This study may provide new insights for the better understanding of antibacterial actions of rGO–nAg nanocomposite and for the better designing of graphene-based antibiotics or other biomedical applications
RF and microwave dielectric response investigation of high-k yttrium copper titanate ceramic for electronic applications
No full textThe dielectric properties of YCTO bulk capacitors were investigated as a function of temperature from 25 degrees C to 150 degrees C and at microwave frequencies in comparison to a SiO2 bulk sample. The results confirm the high-k character of the YCTO ceramic, in addition to the low AC conductivity, namely epsilon' = 40.1 and sigma = 6 x 10(-8) S cm(-1) at 1 MHz, and show a weak frequency and temperature (25 degrees C-150 degrees C) dependence. A temperature coefficient value of -601 ppm degrees C-1 for the dielectric constant (TC epsilon') was estimated at 100 kHz. In the GHz regime, a comparison with bulk SiO2 confirms the higher YCTO dielectric permittivity. These results demonstrate high-k YCTO ceramic as a very promising material with high potentiality for electronic applications
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