Current Issue : July - September Volume : 2015 Issue Number : 3 Articles : 6 Articles
Item response theory (IRT) is a popular approach used for addressing large-scale statistical problems in psychometrics as well as in\nother fields. The fully Bayesian approach for estimating IRT models is usually memory and computationally expensive due to the\nlarge number of iterations. This limits the use of the procedure inmany applications. In an effort to overcome such restraint, previous\nstudies focused on utilizing the message passing interface (MPI) in a distributed memory-based Linux cluster to achieve certain\nspeedups. However, given the high data dependencies in a single Markov chain for IRT models, the communication overhead\nrapidly grows as the number of cluster nodes increases. This makes it difficult to further improve the performance under such\na parallel framework. This study aims to tackle the problem using massive core-based graphic processing units (GPU), which is\npractical, cost-effective, and convenient in actual applications.The performance comparisons among serial CPU, MPI, and compute\nunified device architecture (CUDA) programs demonstrate that the CUDA GPU approach has many advantages over the CPUbased\napproach and therefore is preferred....
The inverse problem of image restoration to remove noise and blur in an observed image was extensively studied in the last\ntwo decades. For the case of a known blurring kernel (or a known blurring type such as out of focus or Gaussian blur), many\neffective models and efficient solvers exist.However when the underlying blur is unknown, there have been fewer developments for\nmodelling the so-called blind deblurring since the early works of You and Kaveh (1996) and Chan and Wong (1998). A major\nchallenge is how to impose the extra constraints to ensure quality of restoration. This paper proposes a new transform based\nmethod to impose the positivity constraints automatically and then two numerical solution algorithms. Test results demonstrate\nthe effectiveness and robustness of the proposed method in restoring blurred images....
The determination of the mechanisms of spiral breakup in excitable media is still an open problem for researchers. In the context\nof cardiac electrophysiological activities, spiral breakup exhibits complex spatiotemporal pattern known as ventricular fibrillation.\nThe latter is the major cause of sudden cardiac deaths all over the world. In this paper, we numerically study the instability of\nperiodic planar traveling wave solution in two dimensions. The emergence of stable spiral pattern is observed in the considered\nmodel. This pattern occurs when the heart is malfunctioning (i.e., ventricular tachycardia).We show that the spiral wave breakup\nis a consequence of the transverse instability of the planar traveling wave solutions.The alternans, that is, the oscillation of pulse\nwidths, is observed in our simulation results. Moreover, we calculate the widths of spiral pulses numerically and observe that the\nstable spiral pattern bifurcates to an oscillatory wave pattern in a one-parameter family of solutions.The spiral breakup occurs far\nbelow the bifurcation when the maximum and the minimum excited states become more distinct, and hence the alternans becomes\nmore pronounced....
The method of building expert systems for medical prediction of severity in patients is purposed. The method is based on using\nVoronoi diagrams. Examples of using the method are described in the paper....
We first defined interval-valued neutrosophic soft rough sets (IVN-soft rough sets for short) which combine interval-valued\nneutrosophic soft set and rough sets and studied some of its basic properties. This concept is an extension of interval-valued\nintuitionistic fuzzy soft rough sets (IVIF-soft rough sets)....
The application of homotopy perturbation method (HPM) for solving systems of linear equations is further discussed and focused\non a method for choosing an auxiliary matrix to improve the rate of convergence. Moreover, solving of convection-diffusion\nequations has been developed by HPM and the convergence properties of the proposed method have been analyzed in detail; the\nobtained results are compared with some other methods in the frame of HPM. Numerical experiment shows a good improvement\non the convergence rate and the efficiency of this method....
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