Numerical Investigation of PCM Based Heat Sinks with Embedded Metal Foam/Crossed Plate Fins

Three-dimensional numerical models for phase change material based heat sinks equipped with thermal conductivity enhancers like aluminum metal foam and crossed plate fins are validated with the experimental data found in literature. For the aluminum metal foam embedded in the heat sink filled with phase change material, the porosity and the pores per inch of the metal foam were varied and natural convection currents were studied. Maintaining the volume fraction of the phase change material as a constant, the thermal performance enhancement as a result of the introduction of thermal conductivity enhancer into the heat sinks is determined.     

The analogy of nanoparticle shapes on the theory of convective heat transfer of Au–Fe3O4 Casson hybrid nanofluid

In recent times, Au nanoparticles have been commonly used for delivering the drug especially in the case of hypothermia of tumors, but low absorption of IR light does not solve destruction of tumor cells. However, nanoparticles such as Fe₃O₄ coated with Au could be used to deliver the drug to a specific spot due to applied external magnetic field. Due to these applications, boundary layer approximation is invoked to simplify the mathematical model. This paper presents the nanoparticle shape analysis and heat transfer features of the Au–Fe₃O₄–blood hybrid nanofluid flowing past a stretching surface on a magnetohydrodynamic medium. Numerical solutions of nonlinear differential equations are obtained by RKF-45 method with the help of shooting technique. The behavior of emerging parameters is described graphically for velocity and temperature profiles. It is found that the blade-shaped Au and Fe₃O₄ nanoparticles have better thermal conductance than brick, sphere, cylinder, needle, and platelet shapes. It is also observed that the Lorentz force generated due to magnetic field helps in controlling the flow and enhance the thermal conductivity of hybrid nanofluid.     

Choline- versus imidazole-based ionic liquids as functional ingredients in topical delivery systems: cytotoxicity,solubility, and skin permeation studies

Background: Poor drug solubility represents a problem for the development of topical formulations. Since ionic liquids (ILs) can be placed in either lipophilic or hydrophilic solutions, they may be advantageous vehicles in such delivery systems. Nonetheless, it is vital to determine their usefulness when used at concentrations were cell viability is maintained, which was considered herein.

Method: Five different ILs were prepared—three imidazole-based ILs: [C2mim][Br], [C4mim][Br], and [C6mim][Br]; and two choline-based ILs: [Cho][Phe] and [Cho][Glu]. Their cytotoxicity in human keratinocytes (HaCat cells), their influence in drug solubility and in percutaneous permeation, using pig skin membranes, was evaluated.

Results: Caffeine and salicylic acid were used as model actives. Choline-based ILs proved to be more suitable as functional ingredients, since they showed higher impact on drug solubility and a lower cytotoxicity. The major solubility enhancement was observed for caffeine and further solubility studies were carried out with this active in several concentrations of the choline-based ILs (0.1; 0.2; 0.5; 1.0; 3.0 and 5.0%, w/w) at 25?°C and 32?°C. Solubility was greatly influenced by concentrations up to 0.5%. The choline-based ILs showed no significant impact on the skin permeation, for both actives. The size of the imidazole-based ILs alkyl chain enhances the caffeine solubility and permeation, but also the ILs cytotoxicity. Stable O/W emulsions and gels were prepared containing the less toxic choline-based ILs and caffeine.

Conclusions: Our results indicate that the choline-based ILs were effective functional ingredients, since, when used at nontoxic concentrations, they allowed a higher drug loading, while maintaining the stability of the formulations.     

Effect of vulcanization systems and antioxidants on discoloration and degradation of natural rubber latex thread under UV radiation

The effect of accelerator combinations and antioxidants on UV radiation degradation of natural rubber (NR) latex thread with a conventional and efficient vulcanization system is presented. Zinc diethyl dithiocarbamate (ZDEC), zinc dibutyl dithiocarbamate (ZDBC), zinc mercaptobenzothiazole (ZMBT), and tetramethyl thiuram disulfide (TMTD) were used as accelerators. The antioxidants used were reaction products of butylated p‐cresol and dicyclopentadiene (Wingstay‐L), Tris‐nonylated phenyl phosphite (Crystol EPR 3400), styrenated phenol (SP), and polymerized 1,2‐dihydro 2,2,4‐trimethyl quinoline (HS). The thread samples were exposed to UV radiation and the appearance and physical properties of the thread were examined. The results indicated that the threads having ZDBC + ZDEC and ZDBC + ZMBT combinations as accelerators are more resistant to UV radiation than the thread having the ZDEC + ZMBT combination. The antioxidants Wingstay‐L and SP + HS are effective in retaining the physical properties of the thread after UV exposure, and Crystol EPR 3400 is better in reducing discoloration. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 304–310, 2000     

Synthesis and hydrogen storage properties of carbon nanotubes

Multi-walled carbon nanotubes (MWNT) have been synthesized by chemical vapor decomposition of acetylene over rare-earth (RE) based _AB2${\mathrm{AB}}_2$ alloy hydride catalysts. The _AB2${\mathrm{AB}}_2$ alloy hydride catalysts have been prepared by hydrogen decrepitation technique and characterized by scanning electron microscopy. The advantage of this novel method of obtaining catalysts has been discussed. The as-grown carbon nanotubes were purified by acid and heat treatments and characterized using powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermo gravimetric analysis and Raman spectroscopy. Hydrogen adsorption measurements were carried out on as-prepared and purified MWNT in the temperature range of 143–373 K and pressure range of 10–100 bar using a high pressure hydrogen adsorption setup and the results have been discussed. A maximum hydrogen storage capacity of 3.5 wt% is obtained for purified MWNT prepared with _DyNi2${\mathrm{DyNi}}_2$ alloy hydride catalyst at 143 K and 75 bar.     

An Eigen-Normal Approach for 3D Mesh Watermarking Using Support Vector Machines

The use of support vector machines （SVM） for watermarking of 3D mesh models is investigated. SVMs have been widely explored for images, audio, and video watermarking but to date the potential of SVMs has not been explored in the 3D watermarking domain. The proposed approach utilizes SVM as a binary classifier for the selection of vertices for watermark embedding. The SVM is trained with feature vectors derived from the angular difference between the eigen normal and surface normals of a 1-ring neighborhood of vertices taken from normalized 3D mesh models. The SVM learns to classify vertices as appropriate or inappropriate candidates for modification in order to accommodate the watermark. Experimental results verify that the proposed algorithm is imperceptible and robust against attacks such as mesh smoothing, cropping and noise addition.