Stability and thermophysical properties of fly ash nanofluid for heat transfer applications

Improving the performance of heat transfer fluids is altogether significant. The best approach for improving the thermal conductivity is the addition of nanoparticles to the base fluid. In the present study, specific heat, dynamic viscosity, and thermal conductivity of water-based Indian coal fly ash stable nanofluid for 0.1% to 0.5% volume concentration in the temperature range of 30 to 60°C has been investigated. To evaluate an average particle diameter of 11.5 nm, the fly ash nanoparticles were characterized with scanning electron microscopy and dynamic light scattering. Using zeta potential, the stability of nanofluid in the presence of surfactant Triton X-100 was tested. Thermal conductivity and viscosity of fly ash nanofluid increased, while specific heat decreased as volume concentration increased. The effect of temperature on the fly ash nanofluid was directly proportional to its thermal conductivity and specific heat and inversely proportional to viscosity.     

GPU accelerated novel particle filtering method

In this paper, a graphics processor unit (GPU) accelerated particle filtering algorithm is presented with an introduction to a novel resampling technique. The aim remains in the mitigation of particle impoverishment as well as computational burden, problems which are commonly associated with classical (systematic) resampled particle filtering. The proposed algorithm employs a priori-space dependent distribution in addition to the likelihood, and hence is christened as dual distribution dependent (D3) resampling method. Simulation results exhibit lesser values for root mean square error (RMSE) in comparison to that for systematic resampling. D3 resampling is shown to improve particle diversity after each iteration, thereby affecting the overall quality of estimation. However, computational burden is significantly increased owing to few excessive computations within the newly formulated resampling framework. With a view to obtaining parallel speedup we introduce a CUDA version of the proposed method for necessary acceleration by GPU. The GPU programming model is detailed in the context of this paper. Implementation issues are discussed along with illustration of empirical computational efficiency, as obtained by executing the CUDA code on Quadro 2000 GPU. The GPU enabled code has a speedup of 3 and 4 over the sequential executions of systematic and D3 resampling methods respectively. Performance both in terms of RMSE and running time have been elaborated with respect to different selections for threads per block towards effective implementations. It is in this context that, we further introduce a cost to performance metric (CPM) for assessing the algorithmic efficiency of the estimator, involving both quality of estimation and running time as comparative factors, transformed into a unified parameter for assessment. CPM values for estimators obtained from all such different choices for threads per block have been determined and a final value for the chosen parameter is resolved for generation of a holistic effective estimator.     

Topography of the flank wear surface

In many applications, topography represents the main external features of a surface. This paper describes the topography of the flank wear surface and also presents the relationship between the maximum flank wear and the topography parameters (roughness parameters) of the flank wear surface during the turning operation. A modern CNC lathe machine (Okuma LH35-N) was used for the machine turning operation. Three-dimensional surface roughness parameters of the flank wear surface were measured by a surface texture instrument (from Talysurf series) using surface topography software (Talymap). Based on the resulting experimental data, it is found that as the flank wear increases, the roughness parameters (sR_a, sR_q, and sR_t) on the flank surface increase significantly. The greater the roughness value of the flank wear surface, the higher the friction of the tool on the workpiece and the greater the heat generation that will occur, thus ultimately causing tool failure. On the other hand, positive skewness (sR_sk) indicates the presence of a small number of spikes on the flank surface of the cutting tool, which could quickly wear off during the machining process.     

Lattice Boltzmann method simulation of electroosmotic stirring in a microscale cavity

The suitable surface modification of microfluidic channels can enable a neutral electrolyte solution to develop an electric double layer (EDL). The ions contained within the EDL can be moved by applying an external electric field, inducing electroosmotic flows (EOFs) that results in associated stirring. This provides a solution for the rapid mixing required for many microfluidic applications. We have investigated EOFs generated by applying a steady electric field across a square cavity that has homogenous electric potentials along its walls. The flowfield is simulated using the lattice Boltzmann method. The extent of mixing is characterized for different electrode configurations and electric field strengths. We find that rapid mixing can be achieved by using this simple configuration which increases with increasing electric field strength. The mixing time for water-soluble organic molecules can be decreased by four orders of magnitude by suitable choice of wall zeta potential and electric field. We dedicate this paper to the memory of our colleagues Professors Kevin Granata and Liviu Librescu who fell tragically on April 16, 2007 while answering their call to serve higher education. They continue to inspire us. AM gratefully acknowledges support from Jadavpur University under the World Bank funded Technical Education Quality Improvement Programme of the Government of India and the hospitality of the Virginia Tech ESM Department where he conducted a portion of this work.     

An evaluation of fuelwood properties of some Aravally mountain tree and shrub species of Western India

The study analyses the fuelwood characteristics of 26 trees including shrub species from the dry deciduous forest in Aravally region, Rajasthan, Western India was carried out to explore trees with potential for fuelwood production. Fuelwood value index (FVI) based on the properties of calorific value, wood density and ash. Calorific value was ranged between 18.54 ± 0.04 and 27.44 ± 0.09 KJ g⁻¹ in Jatropha curcus and Wrightia tinctoria respectively. Wood density varied from 0.538 ± 0.01 to 0.966 ± 0.07 g/cm³ in J. curcus and Acacia nilotica. Same way ash and moisture content was highest in J. curcus (3.38 ± 0.19%) and Sterculia urens (70.28 ± 7.52%) and lowest in Miliusa tomentosa (0.85 ± 0.06%) and Azadirachta indica (30.7 ± 10.02%) respectively. On the basis, of the 26 species analyzed, M. tomentosa has the highest FVI, followed by Lannea coromandelica, Acacia leucophloea, Madhuca indica, A. nilotica, W. tinctoria, Butea monosperma, Zizyphus nummularia, S. urens, Boswellia serrata, A. indica, Grewia tenax, Syzygium cuminii, Tectona grandis and Dalbergia sissoo were shown to have promising fuelwood production.     

A relativistic two-parameter core-envelope model of compact stars

A core-envelope model for a spherical superdense distribution of matter is reported, with a core consisting of anisotropic fluid engulfed by an envelope containing fluid with isotropic pressure is reported. The background space-time of the whole configuration is characterized by a two-parameter parabolic geometry. The physical plausibility of the model is examined both analytically and numerically, and suitability of the model for describing space-times of superdense stars containing strange matter, such as Her-X1 and SAX, is also discussed.     

Analysis of the “Wavelet Tree Quantization” watermarking strategy and a modified robust scheme

Here we study a recently proposed watermarking scheme based on the paper “Wavelet Tree Quantization” (WTQ) by Wang and Lin (IEEE Trans Image Process 13(2):154–165, 2004). In given scheme, wavelet coefficients corresponding to the same spatial locations are grouped together. Two such groups, selected at random, constitute a supertree. Some of these supertrees are quantized to embed the watermark information in the image. In the process of cryptanalysis we first identify the groups which are quantized during the watermark insertion process. Then we select the non-quantized groups and quantize them too, to remove the watermark. Experimental results show that the watermark is completely removed by this attack. The cryptanalysis falls under the cipher text only jamming attack which requires only a single watermarked copy. Further, we suitably modify the WTQ scheme to make it robust against such cryptanalytic attacks.This is an extended and revised version of the paper Cryptanalysis of “Wavelet Tree Quantization” Watermarking Scheme presented at the International Workshop on Distributed Computing, IWDC 2004, Kolkata, 27–30 December 2004, Lecture Notes in Computer Science, vol. 3326, pp. 219–230. Springer, Berlin Heidelberg New York (2004). Section 4 of this paper introduces a modified scheme which is an addition over the conference version. Part of this work has been done while the author T. K. Das was visiting Indian Statistical Institute, Kolkata during 2004.     

Contribution of organomodified clay on hybrid microstructures and properties of epoxidized natural rubber‐based nanocomposites

Influence of organic modifying agent of clay on dispersion, distribution, hybrid microstructure formation, and associated performance properties of epoxidized natural rubber‐based composites was evaluated. Binary and ternary composites of carbon black (CB) and two organomodified layered silicates (i.e., nanomer I30E and Cloisite 30B) were prepared and characterized based on small angle X‐ray scattering, transmission electron microscopy, hydrodynamic swelling, tensile measurement, and dynamic mechanical analyses. Greater extent of exfoliation and “nanounit” formation was noted in ternary composites containing nanomer I30E, which was reflected in higher interfacial roughness (d_s = 2.82) and lower radius of gyration (R_g = 205 Å). Morphological observations suggested higher nanomer I30E–CB interactions than that of Cloisite 30B–CB. The interplatelet distance in Cloisite 30B (d = 1.83 nm) stacks was lower than that of nanomer I30E (d = 2.26 nm). These two factors jointly contributed in higher breakdown of nanomer I30E stacks by CB than that of Cloisite 30B stacks. Greater exfoliation and nanounit formation in I30E–CB‐filled nanocomposite was also reflected in increased degree of crosslinking (n = 20 × 10^?5%), tensile modulus/strength, half height width of damping peak (20.3°C), and filler effectiveness (C = 0.33). POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Inverse and efficiency of heat transfer convex fin with multiple nonlinearities

In this article, we first propose the novel semi‐analytical technique—modified Adomian decomposition method (MADM)—for a closed‐form solution of the nonlinear heat transfer equation of convex profile with singularity where all thermal parameters are functions of temperature. The longitudinal convex fin is subjected to different boiling regimes, which are defined by particular values of n (power index) of heat transfer coefficient. The energy balance equation of the convex fin with several temperature‐dependent properties are solved separately using the MADM and the spectral quasi‐linearization method. Using the values obtained from the direct heat transfer method, the unknown parameters of the profile, such as thermal conductivity, surface emissivity, heat generation number, conduction‐convection parameter, and radiation‐conduction parameter are inversely predicted by an inverse heat transfer analysis using the simplex search method. The effect of the measurement error and the number of measurement points has been presented. It is found that present measurement points and reconstruction of the exact temperature distribution of the convex fin are fairly in good agreement.