Characterizing Temporal Heterogeneity by Quantifying Nanoscale Fluctuations in Amorphous Fe-Ge Magnetic Films

Equilibrium phase transitions are influenced by fluctuations and often discussed within the framework of the Gibbs free energy, wherein the exchange of energy between system and thermal bath is stationary and all regions of the sample exhibit the same phase. Presence of spatial heterogeneity in the magnetic structures such as pinning centers, domain walls, topological defects, etc. may cause temporal heterogeneity that modifies the nature of the magnetic phase transition. This study reports that interplay of nanoscale thermodynamics with spatio-temporal heterogeneity gives rise to complex phase transition pathways in amorphous Fe_xGe_1-x thin films with temperature and Fe-concentration (x). Coherent resonant soft X-ray scattering experiments that have simultaneous spatial, temporal, and spectral sensitivity show that the origin of helical to paramagnetic phase transition in amorphous Fe-Ge thin films lies in the appearance of enhanced-fluctuation spots deep inside the ordered state. The fluctuations are heterogeneous, starting over a small fraction of the domains that increases and becomes isotropic over the entire film as the temperature increases or the Fe-concentration decreases. The fluctuating-fraction, when normalized to magnetization for different Fe-concentrations, follows a single power law behavior, suggesting that the nature of the transition can be described in terms of the underlying spatio-temporal fluctuations.     

Chromium and nickel migration study through fine grained soil

A comprehensive laboratory-scale investigation was carried out to explore the toxic metal attenuation capacity of a field clay sample collected from adjoining areas of an ash pond site of a Super Thermal Power Plant in West Bengal, India. The existence of two major elements viz., Cr⁶⁺and Ni²⁺ in excess to permissible limit was observed in soil and water samples collected from the site. Batch kinetic performance results exhibited reasonable Cr⁶⁺and Ni²⁺ uptake capacity of soil in equilibrium condition. The experimental data also fitted well in Freundlich isotherm model. The adsorption behaviour of above pollutants in both vertical and horizontal directions through soil was explored. The results showed that more than 80% of Ni and 72% of Cr were found to be sorbed by the soil. Breakthrough adsorption study also showed a good metal adsorption capacity of soil.     

Theoretical analysis of efficient microwave processing of oil–water emulsions attached with various ceramic plates

A detailed theoretical analysis has been carried out to study efficient microwave processing of 1D emulsion samples placed on ceramic plates (alumina, SiC). The effective dielectric property of an emulsion is a strong function of the continuous medium of the emulsion (o/w or w/o). A preliminary study has been carried out via average power within an emulsion vs emulsion thickness diagram for various cases. The maxima in average power, also termed as ‘resonances’, are observed for specific emulsion thicknesses and the two consecutive resonances are termed as R₁ and R₂ modes. The heating scenarios have been analyzed at the dominant resonance mode. Based on spatial distributions of power and temperature for various cases, alumina support at the left side may be recommended as the optimal heating strategy due to greater heating rates with controlled thermal runaway for both o/w and w/o emulsion samples whereas SiC support may be favored for o/w emulsion samples due to lesser thermal runaway. A comparison of the heating characteristics has been illustrated for 50% o/w and 50% w/o emulsion samples to analyze the role of continuous medium of an emulsion on heating effects. The distribution of microwave incidences also plays an important role to minimize thermal runaway for specific o/w and w/o emulsions.     

Watermarking with retrieval systems

We are interested in the problem of associating messages with multimedia content for the purpose of identifying them. This problem can be addressed by a watermarking system that embeds the associated messages into the multimedia content (also called Work). A drawback of watermarking is that the content will be distorted during embedding. On the other hand, if we assume that the database is available, the problem can be addressed by a retrieval system. Although no undesirable distortion is introduced when a retrieval system is used, the overhead of searching in large databases is fundamentally difficult (also known as the dimensionality curse). In this paper we present a novel framework that strikes a trade-off between watermarking and retrieval systems. Our framework avoids the dimensionality curse by introducing small distortions (watermark) into the multimedia content. From another perspective, the framework improves the watermarking performance, marked by significant reduction in distortion, by introducing searching ability in the message detection stage. To prove the concept, we give an algorithm based on the proposed notion of active clustering.     

Multihop Virtual Topology Design in WDM Optical Networks for Self-Similar Traffic

In this paper, we consider the problem of designing virtual topologies for multihop optical WDM networks when the traffic is self-similar in nature. Studies over the last few years suggest that the network traffic is bursty and can be much better modeled using self similar process instead of Poisson process. We examine buffer sizes of a network and observe that, even with reasonably low buffer overflow probability, the maximum buffer size requirement for self-similar traffic can be very large. Therefore, a self-similar traffic model has an impact on the queuing delay which is usually much higher than that obtained with the Poisson model. We investigate the problem of constructing the virtual topology with these two types of traffic and solve it with two algorithmic approaches: Greedy (Heuristic) algorithm and Evolutionary algorithm. While the greedy algorithm performs a least-cost search on the total delay along paths for routing traffic in a multihop fashion, the evolutionary algorithm uses genetic methods to optimize the average delay in a network. We analyze and compare our proposed algorithms with an existing algorithm via different performance parameters. Interestingly, with both the proposed algorithms the difference in the queuing delays, caused by self-similar and Poisson traffic, results in different multihop virtual topologies.     

Jute stick powder as a potential biomass for the removal of congo red and rhodamine B from their aqueous solution

Jute stick powder (JSP) has been found to be a promising material for adsorptive removal of congo red (C.I. 22120) and rhodamine B (C.I. 45170) from aqueous solutions. Physico-chemical parameters like dye concentration, solution pH, temperature and contact time have been varied to study the adsorption phenomenon. Favorable adsorption occurs at around pH 7.0 whereas temperature has no significant effect on adsorption of both the dyes. The maximum adsorption capacity has been calculated to be 35.7 and 87.7mg/g of the biomass for congo red and rhodamine B, respectively. The adsorption process is in conformity with Freundlich and Langmuir isotherms for rhodamine B whereas congo red adsorption fits well to Langmuir isotherm only. In both the cases, adsorption occurs very fast initially and attains equilibrium within 60min. Kinetic results suggest the intra-particle diffusion of dyes as rate limiting step.     

Ionic Polymer Metal Composite Flapping Actuator Mimicking Dragonflies

In this study, variational principle is used for dynamic modeling of an Ionic Polymer Metal Composite (IPMC) flapping wing. The IPMC is an Electro-active Polymer (EAP) which is emerging as a useful smart material for `artificial muscle' applications. Dynamic characteristics of IPMC flapping wings having the same size as the actual wings of three different dragonfly species Aeshna Multicolor, Anax Parthenope Julius and Sympetrum Frequens are analyzed using numerical simulations. An unsteady aerodynamic model is used to obtain the aerodynamic forces. A comparative study of the performances of three IPMC flapping wings is conducted. Among the three species, it is found that thrust force produced by the IPMC flapping wing of the same size as Anax Parthenope Julius wing is maximum. Lift force produced by the IPMC wing of the same size as Sympetrum Frequens wing is maximum and the wing is suitable for low speed flight. The numerical results in this paper show that dragonfly inspired IPMC flapping wings are a viable contender for insect scale flapping wing micro air vehicles.