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    Experimental study on convective heat transfer performance of iron oxide based ferrofluids in microtubes
    (ASME, 2014) Kurtoğlu, Evrim; Kaya, Alihan; Gözüaçık, Devrim; Koşar, Ali; Department of Chemistry; Acar, Havva Funda Yağcı; Faculty Member; Department of Chemistry; College of Sciences; 178902
    Ferrofluids are colloidal suspensions, in which the solid phase material is composed of magnetic nanoparticles, while the base fluid can potentially be any fluid. The solid particles are held in suspension by weak intermolecular forces and may be made of materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. Heat transfer performance of ferrofluids should be carefully analyzed and considered for their potential of their use in wide range of applications. In this study, convective heat transfer experiments were conducted in order to characterize convective heat transfer enhancements with lauric acid coated ironoxide (Fe3O4) nanoparticle based ferrofluids, which have volumetric fractions varying from 0% to similar to 5% and average particle diameter of 25 nm, in a hypodermic stainless steel microtube with an inner diameter of 514 mu m, an outer diameter of 819 lm, and a heated length of 2.5 cm. Heat fluxes up to 184 W/cm(2) were applied to the system at three different flow rates (1 ml/s, 0.62 ml/s, and 0.36 ml/s). A decrease of around 100% in the maximum surface temperature (measured at the exit of the microtube) with the ferrofluid compared to the pure base fluid at significant heat fluxes (>100 W/cm(2)) was observed. Moreover, the enhancement in heat transfer increased with nanoparticle concentration, and there was no clue for saturation in heat transfer coefficient profiles with increasing volume fraction over the volume fraction range in this study (0-5%). The promising results obtained from the experiments suggest that the use of ferrofluids for heat transfer, drug delivery, and biological applications can be advantageous and a viable alternative as new generation coolants and futuristic drug carriers.
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    PublicationOpen Access
    Influence of three-dimensional reconstruction method for building a model of the cervical spine on its biomechanical responses: a finite element analysis study
    (Sage, 2016) Zafarparandeh, Iman; Erbulut, Deniz Ufuk; N/A; Özer, Ali Fahir; Faculty Member; School of Medicine; 1022
    In some finite element analysis studies of models of sections of the spine, the three-dimensional solid model is built by assuming symmetry about the mid-sagittal plane of the section, whereas in other studies, the model is built from the exact geometry of the section. The influence of the method used to build the solid model on model parameters, in the case of the cervical spine, has not been reported in the literature. This issue is the subject of this study, with the section being C2-C7, the applied loadings being extension, flexion, left lateral bending, and right axial rotation (each of magnitude 1 Nm), and the model parameters determined being rotation, intradiskal pressure, and facet load at each of the segments. When all the parameter results were considered, it was found that, by and large, the influence of solid model construction method used (exact geometry vs assumption of symmetry about the mid-sagittal plane of the section) was marginal. As construction of a symmetric finite element model requires less time and effort, construction of an asymmetric model may be justified in special cases only.