Numerical solution of a separtated viscous flow problem by a non-uniform finite-difference net

Two-dimensional stagnation point flow of a viscous fluid is modified by the introduction of a thin plate placed symmetrically at the stagnation point. Separation of the boundary layer results in back flow near the plate even at small Reynolds numbers. The Navier–Stokes equations governing the flow are replaced by finite differences using unequal net spacing which is finer in the boundary layer. The choice of finite differences guarantees convergence of the iterative procedures used. Only those relaxation parameters, which are necessary to obtain convergence and also to make the method computationally efficient, have been used. Numerical results for Reynolds numbers 9, 100 and 400 are obtained.     

Techniques for Realistic Visualization of Fluids: A Survey

Visualization of fluids has wide applications in science, engineering and entertainment. Various methodologies of visualizing fluids have evolved which emphasize on capturing different aspects of the fluids accurately. In this survey the existing methods for realistic visualization of fluids are reviewed. The approaches are classified based on the key concept they rely on for fluid modeling. This classification allows for easy selection of the method to be adopted for visualization given an application. It also enables identification of alternative techniques for fluid modeling.     

Synthesis of bamboo-shaped carbon-nitrogen nanotubes using acetonitrile-ferrocene precursor

We report the formation of bamboo-shaped carbon-nitrogen nanotubes by employing a simple, one-step and economically viable spray pyrolysis technique using new precursor; acetonitrile and ferrocene solution. By varying the concentration of ferrocene with respect to acetonitrile, it has been found that the optimum concentration of ferrocene in acetonitrile is 5 mg/ml. The special feature of the as-synthesized bamboo-shaped carbon-nitrogen nanotubes bundles is that they are produced in a high yield (1.25 gms/run). They also have long linear extents (approximately 430 microm) and are very clean. The average composition of carbon-nitrogen nanotubes comes out to be C26N.     

Response surface methodology for optimization of growth parameters for the production of carotenoids by a mutant strain of Rhodotorula gracilis

Response surface methodological studies of growth parameters for carotenoid production by a mutant strain of Rhodotorula gracilis (CFR 0-1) was carried out by a two-level fractional factorial design involving five variables, namely glucose concentration (%), incubation period (days), volume of inoculum (ml/100 ml), pH, and temperature (°C). The response equation developed indicated linear relationship between period of incubation, temperature, sugar concentration, and volume of inoculum on carotenoid production. A temperature of 24 °C was found to exhibit maximum carotenoid production in the mutant. The results indicated maximum carotenogenesis (0.09%) at 8% glucose level, with pH 7.5 and 6.0 ml/100 ml of inoculum for an incubation period of 12 days at 24 °C, which was also verified by experimental data.     

Response surface studies on cholesterol reduction in egg yolk using #ps01β-cyclodextrin

The effects of β-cyclodextrin (BCD) and reaction time on the recovery of cholesterol from egg yolk were studied at 25°C based on response surface methodology. The developed response model is of the form: Y = 5.585 + 429.77 X _c + 0.534 X _t ², where Y is the predicted cholesterol recovery (%), X _c is the BCD/egg yolk ratio (kg/kg) and X _t is the reaction time (h). Cholesterol recovery increased with the both BCD/egg yolk ratio and reaction time and there was no optimum value. The model predicted a cholesterol recovery of 94.5% at a BCD/egg yolk ratio of 0.163 over a reaction time of 6 h whereas experiments showed a cholesterol recovery of 87.7%.     

Enrichment of tocopherols in modified soy deodorizer distillate using supercritical carbon dioxide extraction

Supercritical carbon dioxide (SC-CO₂) extraction of chemically modified Soy Deodorizer Distillate (DOD) at three levels of pressure (180–300 bar) and temperature (40–60 °C) to optimize the conditions for enrichment of tocopherols in the raffinate was carried out. After modification, soy DOD contained about 90% of fatty acid methyl esters (FAME), showed improved solubility in SC-CO₂, and better extraction rate. Since fatty acid methyl esters are more volatile, they are extracted preferentially over tocopherols and other high molecular weight compounds. Higher levels of pressure and temperature resulted in increased solubility of compounds with high molecular weight and tocopherols due to increased density of SC CO₂. So the extraction at higher pressures and temperatures resulted in a better yield of FAME along with tocopherols in the extract and this in turn decreased the degree of enrichment of tocopherols in the raffinate. However, specific level of pressure and temperature of extraction caused the increase in the solubility of FAME due to their volatility and results in enhanced enrichment of tocopherols in the raffinate. It was observed that the enrichment of tocopherols to ten times the original concentration of feed occurred at extraction pressure of 180 bar and temperature of 60 °C of SC-CO₂.     

Modelling and investigation of clean power wind energy systems by using UPQC

This article presents a new clean power technique for wind energy system based on Unified Power Quality Conditioner (UPQC) with usage of various Artificial Intelligent techniques (AI). Application of AI techniques such as Artificial Neural Networks, Fuzzy Logic is growing fast in the area of power electronics equipment‐based wind energy system, for instance, UPQC. A novel control scheme is developed by using different AI techniques to mitigate the balancing issues and to control the power–quality problems in UPQC and hence to provide clean power to the grid. The proposed system is composed of shunt active power filter, and the inherent proportional integral (PI) control parameters are tuned with application of PI techniques. A detailed Matlab simulation study is carried out with an application of PI techniques under sag, swell, unbalanced, and harmonic conditions. An exhaustive simulation study is carried out to investigate the application of PI technique‐based controllers and compare its performance with the conventional PI controller with its results explored. Copyright © 2016 John Wiley & Sons, Ltd.     

A centroid based vector quantization reversible data hiding technique

In this paper, we propose a reversible data hiding scheme that exploits the centroid formula. Specifically, we use it to define a centroid boundary vector and a centroid state codebook CSCB. Initially, our centroid boundary vectors and CSCBs are the same as the side match vector quantization (SMVQ) algorithm’s boundary vectors and state codebooks SCBs. For each VQ index, the proposed scheme exploits the centroid formula to update its centroid boundary vector and the corresponding CSCB. The updating is coupled with a heuristic to select the best state codebook (i.e., either SCB or CSCB) for each VQ index, which generates a highly compressible distribution of index values. Our experimental results show that the proposed scheme can embed n = 1, 2, 3, and 4 bit per index (bpi) at bit rates of 0.332, 0.394, 0.457, and 0.519 bit per pixel (bpp), respectively, for the main codebook size N = 256. These results confirm that the proposed scheme improves recent VQ and SMVQ based reversible data hiding schemes.

     

Space and time efficiency of the forest-of-quadtrees representation

A forest of quadtrees is a refinement of a quadtree data structure that is used to represent planar regions. A forest of quadtrees provides space savings over regular quadtrees by concentrating vital information. The paper presents some of the properties of a forest of quadtrees and studies the storage requirements for the case in which a single 2^m × 2^m region is equally likely to occur in any position within a 2ⁿ × 2ⁿ image. Space and time efficiency are investigated for the forest-of-quadtrees representation as compared with the quadtree representation for various cases.