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Panther - November 2013 - Vol. XCIII, NO.8
Get PDFhttps://digitalcommons.pvamu.edu/pv-panther-newspapers/1916/thumbnail.jp
A trust-based framework for data forwarding in opportunistic networks
No full textIn general, the encounter probability is leveraged to evaluate whether a node is a qualified next-hop forwarder in Opportunistic Networks (OppNets); however, it does not truly present the node\u27s competency of delivering data in a hostile wireless environment, because a malicious node can arbitrarily bloat that probability to intercept data from others. In this paper, we design a trust-based framework to more accurately evaluate an encounter\u27s delivery competency, which can be flexibly integrated with a large family of existing data forwarding protocols designed for OppNets. As a case study, we integrate our proposed framework with PROPHET, and demonstrate its effectiveness against black hole attacks through experimental study. © 2011 Elsevier B.V. All rights reserved
Calculation of the Coulomb electrostatic potential created by a uniformly charged square on its plane: Exact mathematical formulas
No full textWe calculate exactly the Coulomb electrostatic potential created by a uniformly charged square on its plane. The chosen solution method leads to certain types of integral expressions which involve combinations of products of error functions and power functions. These type of integrals that should be solved are not standard ones, therefore, the integration formulas we derive in the process may be deemed of mathematical interest on their own right. Use of these formulas enables us to derive an exact analytic expression for the Coulomb electrostatic potential created by a uniformly charged square at an arbitrary point on its plane. © 2012 Elsevier B.V
Properties of confined small systems of electrons in a parabolic quantum dot
No full textRecent advances in the field of nanotechnology have enabled the precise, controlled fabrication of materials and structures at atomic and molecular scales. In nanoscale territory, the electron\u27s quantum mechanical nature dominates. A class of devices called semiconductor quantum dots has been identified as one of the most promising avenues for meeting the new technological challenges of the 21st century. Quantum dots represent fascinating systems to study novel phenomena of theoretical and practical interest because low dimensionality coupled with the interplay between strong correlations, quantum confinement and magnetic field creates unique conditions for emergence of fundamentally new physics. The properties of confined twodimensional (2D) electronic systems in a semiconductor material that we refer to as 2D semiconductor quantum dots are a topic of intensive ongoing research. A typical 2D semiconductor quantum dot structure holds only a few electrons. As a result, such systems behave differently from standard bulk semiconductor devices given that the discreteness of the electron charge cannot be neglected anymore. The confinement potential of the electrons is generally well approximated by a parabolic well. The main effect of a magnetic field perpendicular to the plane of the quantum dot is to gradually quench the kinetic energy of the electrons as field increases. In this work we consider 2D semiconductor quantum dot systems consisting of few interacting electrons confined in an isotropic parabolic potential. We study the many-electron quantum ground state properties of such systems in presence of a perpendicular magnetic field as the number of electrons is varied using accurate numerical approaches. The results derived from the calculations of the quantum model are then compared to corresponding results for a classical model of point charges confined in a parabolic trap in which such charges interact with a Coulomb potential. We find that, for a wide range of parameters and magnetic fields, the quantum ground state energy is very close to the classical energy of the most stable classical configuration under the condition that the classical energy is properly adjusted to incorporate the quantum zero point motion. © Nova Scicence Publishers, Inc. All rights reserved
Polycaprolactone scaffolds and hydroxyapatite/polycaprolactone composite scaffolds for bone tissue engineering
No full textScaffolds fabricated from biodegradable polymers and bioactive materials together with living cells are often used in tissue engineering. This paper reports the thermally induced phase separation technique (TIPS) for the formation of three-dimensional porous scaffolds based on biodegradable polymers for bone tissue engineering applications. For the production of tissue engineering scaffolds, poly(Caprolactone) (PCL) which is a biodegradable and biocompatible polymer was used. The effect of different parameters involved in the fabrication process was studied. In the TIPS process, HA nanoparticles were successfully incorporated in PCL scaffolds to make composite scaffolds, rendering the scaffolds osteoconductive. In the PCL polymer scaffold matrix, HA nanoparticles were found to be well discreted. It was observed that the porosity and pore sizes decreased with the incorporation of HA nanoparticles. The compressive mechanical properties increased in the HA/PCL composite scaffold. Freezing at -18° yielded better pore size distribution which was controlled by the polymer and solvent phase crystallization. The PCL scaffolds were systematically evaluated using various techniques. Scaffolds with high porosity, low density, pore sizes ranging from several microns to 200 microns and good compressive mechanical properties were obtained by optimizing the processing and material parameters. The characteristics of PCL and HA/PCL scaffolds investigated in the current study show promises for bone tissue regeneration. Copyright © 2013 American Scientific Publishers. All rights reserved
A New Implementation of GMRES Using Generalized Purcell Method
Get PDFIn this paper, a new method based on the generalized Purcell method is proposed to solve the usual least-squares problem arising in the GMRES method. The theoretical aspects and computational results of the method are provided. For the popular iterative method GMRES, the decomposition matrices of the Hessenberg matrix is obtained by using a simple recursive relation instead of Givens rotations. The other advantages of the proposed method are low computational cost and no need for orthogonal decomposition of the Hessenberg matrix or pivoting. The comparisons for ill-conditioned sparse standard matrices are made. They show a good agreement with available literature
Local Influence in Bayesian Elliptically Contoured-Ordinal Model for Mixed Data
Get PDFThis paper develops a new class of joint modeling of mixed correlated ordinal and continuous responses with elliptically contoured errors. This joint model includes the latent variable approach of using an elliptically contoured distribution for mixed ordinal and continuous responses. A Markov Chain Monte Carlo sampling algorithm is described for estimating the posterior distribution of the parameters. For sensitivity analysis to investigate the perturbation from associate responses, it is demonstrated how one can use some elements of covariance structure. Influence of small perturbation of these elements on the posterior normal curvature is also studied. To illustrate the application of such modeling the data (medical) is analyzed
Applications of k-anonymity and ℓ-diversity in publishing online social networks
No full textMany online social network (OSN) owners, such as Facebook and Twitter, regularly publish data they have collected from their users™ online activities to third parties, such as sociologists and commercial companies. These third parties mine these data and extract information for their particular purposes. This datasharing elicits users™ concerns regarding disclosures of their privacy. This chapter takes a systematic look at the applications of some classical privacy preservation models, including k-anonymity and -diversity, which were originally developed to protect tabular data privacy to secure users™ privacy contained in OSN data