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  • 1
    Publikationsdatum: 2017-03-18
    Beschreibung: In this paper, we use a linear combination of the shape functions of reproducing kernel particle method (RKPM) and RBFs for achieving the unknown weights into each stencil. We obtain an error bound for the new shape function. Also, in this paper, we investigate a numerical procedure based on the presented technique for solving the Vlasov–Poisson and Vlasov–Poisson–Fokker–Planck systems. The Vlasov equation is a differential equation describing time evolution of the distribution function of plasma. The Vlasov–Poisson equations are used to describe various phenomena in plasma, in particular Landau damping and the distributions in a double layer plasma. We use the RKPM/RBF-FD technique for discretization of space direction and employ the method of lines to achieve a high-order accuracy in temporal direction. Numerical examples are reported which demonstrate the theoretical results and the efficiency of proposed scheme.
    Print ISSN: 0177-0667
    Digitale ISSN: 1435-5663
    Thema: Informatik , Maschinenbau , Technik allgemein
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2017-03-18
    Beschreibung: The main purpose of this article is to investigate the numerical solution of two-dimensional Fredholm integral equations of the second kind on normal domains, whose kernels have logarithmic singularity. Radial basis functions constructed on scattered points are utilized as a basis in the discrete collocation method to solve these types of integral equations. We encounter logarithm-like singular integrals in the process of setting up the presented scheme which cannot be computed by classical quadrature formulae. Therefore, a special numerical integration rule is required to approximate such integrals based on the use of dual non-uniform composite Gauss–Legendre quadratures on normal domains. Since the method proposed in the current paper does not need any background mesh, it is meshless and consequently independent of the geometry of domain. The error estimate and the convergence rate of the approach are studied for the presented method. The convergence accuracy of the new technique is examined over four integral equations on the tear, annular, crescent, and castle domains, and obtained results confirm the theoretical error estimates.
    Print ISSN: 0177-0667
    Digitale ISSN: 1435-5663
    Thema: Informatik , Maschinenbau , Technik allgemein
    Publiziert von Springer
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  • 3
    Publikationsdatum: 2017-02-17
    Beschreibung: Intake buzz was initiated on a typical two-dimensional supersonic air-intake model at various supersonic Mach numbers up to 3 by gradually changing the back pressure from supercritical to subcritical operating condition in a wind tunnel. Schlieren pictures from a still camera and a high-speed camera were recorded. Analyses of individual high-speed images of the unvented intake were carried out to locate the time-dependent positions and velocities of the ramp shock around the cowl lip. The displacements of the shock indicate sinusoidal oscillations with dominant frequency of 102.4 Hz, close to that obtained from unsteady pressure measurements. Phase trajectories of shock position based on image analyses indicate that the shock oscillations have limit cycle type oscillation, typical of nonlinear dynamic systems. Natural ventilation of the intake was found to be extremely effective in increasing the total pressure recovery, suppress buzz oscillations and in delaying the onset of buzz by preventing the upstream propagation of disturbances through passive bleeding of the internal boundary layer. Graphical abstract Effectiveness of natural ventilation in control of air-intake buzz at Mach 3.0
    Print ISSN: 1343-8875
    Digitale ISSN: 1875-8975
    Thema: Informatik
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2017-02-18
    Beschreibung: A novel method, called a posteriori “VFM accuracy estimation” (VAE), for resolving an intrinsic VFM problem is proposed. The problem is that VFM uncertainty can easily vary according to blood flows through an echocardiographic imaged plane (i.e., “through-plane” flows), and it is unknown. Knowing the VFM uncertainty for each patient will make it possible to refine the quality of VFM-based diagnosis. In the present study, VAE was derived on the basis of an error-propagation analysis and a statistical analysis. The accuracy of VAE with a pulsatile left-ventricle phantom was experimentally investigated for realistic cases with through-plane flows. VAE was validated by comparing VFM uncertainty (S.D.) estimated by VAE with VFM uncertainty measured by particle-image velocimetry (PIV) for different imaged planes. VAE accurately estimated the S.D. of VFM uncertainty measured by PIV for all cases with different image planes ( R  〉 0.6 and p  〈 0.001). These findings on VFM accuracy will provide the basis for widespread clinical application of VFM-based diagnosis. Graphical Abstract
    Print ISSN: 1343-8875
    Digitale ISSN: 1875-8975
    Thema: Informatik
    Publiziert von Springer
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  • 5
    facet.materialart.
    Unbekannt
    Springer
    Publikationsdatum: 2017-02-24
    Print ISSN: 1343-8875
    Digitale ISSN: 1875-8975
    Thema: Informatik
    Publiziert von Springer
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  • 6
    Publikationsdatum: 2017-05-08
    Beschreibung: In the present paper, a spectral meshless radial point interpolation (SMRPI) technique is applied to solve the Rayleigh–Stokes problem for a heated generalized second grade fluid with fractional derivative in two dimensional case. The time fractional derivative is described in the Riemann–Liouville sense. The applied approach is based on combination of meshless methods and spectral collocation techniques. The point interpolation method with the help of radial basis functions is used to construct shape functions which act as basis functions in the frame of SMRPI. It is proved the scheme is unconditionally stable with respect to the time variable in \(H^1\) and convergent with the order of convergence \(\mathcal {O}(\delta t^{1+\beta })\) , \(0〈\beta 〈1\) . In the current work, the thin plate splines (TPS) are used as the basis functions. The results of numerical experiments are compared with analytical solutions to confirm the accuracy and efficiency of the presented scheme. Two numerical examples show that the SMRPI has reliable accuracy in general shape domains.
    Print ISSN: 0177-0667
    Digitale ISSN: 1435-5663
    Thema: Informatik , Maschinenbau , Technik allgemein
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2018-03-06
    Beschreibung: Flyrock is an adverse effect produced by blasting in open-pit mines and tunnelling projects. So, it seems that the precise estimation of flyrock is essential in minimizing environmental effects induced by blasting. In this study, an attempt has been made to evaluate/predict flyrock induced by blasting through applying three hybrid intelligent systems, namely imperialist competitive algorithm (ICA)–artificial neural network (ANN), genetic algorithm (GA)–ANN and particle swarm optimization (PSO)–ANN. In fact, ICA, PSO and GA were used to adjust weights and biases of ANN model. To achieve the aim of this study, a database composed of 262 datasets with six model inputs including burden to spacing ratio, blast-hole diameter, powder factor, stemming length, the maximum charge per delay, and blast-hole depth and one output (flyrock distance) was established. Several parametric investigations were conducted to determine the most effective factors of GA, ICA and PSO algorithms. Then, at the end of modelling process of each hybrid model, eight models were constructed and their results were checked considering two performance indices, i.e., root mean square error (RMSE) and coefficient of determination ( R 2 ). The obtained results showed that although all predictive models are able to approximate flyrock, PSO–ANN predictive model can perform better compared to others. Based on R 2 , values of (0.943, 0.958 and 0.930) and (0.958, 0.959 and 0.932) were found for training and testing of ICA–ANN, PSO–ANN and GA–ANN predictive models, respectively. In addition, RMSE values of (0.052, 0.045 and 0.057) and (0.045, 0.044 and 0.058) were achieved for training and testing of ICA–ANN, PSO–ANN and GA–ANN predictive models, respectively. These results show higher efficiency of the PSO–ANN model in predicting flyrock distance resulting from blasting. Moreover, sensitivity analysis shows that hole diameter is more effective than others.
    Print ISSN: 0177-0667
    Digitale ISSN: 1435-5663
    Thema: Informatik , Maschinenbau , Technik allgemein
    Publiziert von Springer
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  • 8
    facet.materialart.
    Unbekannt
    Springer
    Publikationsdatum: 2018-03-06
    Beschreibung: In this work, we developed a non-classical plate model for the analysis of the behavior of microplates prepared from functionally graded materials (FGMs). It was assumed that the material properties of FGM microplates vary along the direction of thickness and could be estimated using Mori–Tanaka homogenization technique. A variational approach based on Hamilton’s principle was employed to achieve motion equations and corresponding boundary conditions simultaneously. Unlike classical plate theory, the proposed plate model contained three material length scale parameters which allowed size effect to be taken into account effectively. Moreover, the proposed non-classical plate model could be divided into classical and modified couple stress plate models when all material length scale parameters were set at zero. To approve the applicability of the proposed size-dependent plate model, analytical solution for free vibration problem of a simply supported FGM microplate was obtained according to the Navier solution, where generalized displacements were stated as multiplication of undetermined functions with known trigonometric functions to identically satisfy simply supported boundary conditions for all edges. The results obtained by the proposed non-classical plate model were compared with those obtained from reduced ones relevant to different values of material property gradient index and dimensionless length scale parameter. It was found that the differences observed between the sets of predicted natural frequencies obtained from different types of plate models were more significant for lower values of dimensionless length scale parameter.
    Print ISSN: 0177-0667
    Digitale ISSN: 1435-5663
    Thema: Informatik , Maschinenbau , Technik allgemein
    Publiziert von Springer
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  • 9
    Publikationsdatum: 2018-03-06
    Beschreibung: Soil stabilization using geopolymers is a new technique for improvement of weak cohesive soils. Evaluating behavior of improved soils requires an initial estimation of strength parameters. In this study, extensive experimental results on geopolymer-stabilized soil specimens were collected and analyzed. A model was then developed using group method of data handling (GMDH) and employing particle-swarm optimization algorithm to estimate the unconfined compressive strength (UCS) of stabilized cohesive soils using geopolymers. Type of additives and their compositions as well as soil characteristics were taken as the influential parameters on the UCS of soil specimens. Subsequently, sensitivity analysis was carried out to verify the performance of the proposed UCS model. Finally, the developed GMDH-based model was compared with artificial neural network model to predict unconfined compressive strength of stabilized soils. The results clearly illustrate the reasonable accuracy of the developed computational Intelligence-based model for estimating the unconfined compressive strength of geopolymer-stabilized cohesive soils.
    Print ISSN: 0177-0667
    Digitale ISSN: 1435-5663
    Thema: Informatik , Maschinenbau , Technik allgemein
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 2018-03-06
    Beschreibung: In this paper, natural neighbor Galerkin meshless method is employed for adaptive analysis of plates and laminates. The displacement field and strain field of plate are based on Reissner–Mindlin plate theory. The interpolation functions employed here were developed by Sibson and based on natural neighbor coordinates. An adaptive refinement strategy based on recovery energy norm which is in turn based on natural neighbors is employed for analysis of plates. The present adaptive procedure is applied to classical plate problems subjected to in-plane loads. In addition to that the laminated composite plates with cutouts subjected to transverse loads are investigated. Influence of the location of the cutout and the boundary conditions of the plate on the results have been studied. The results obtained with present adaptive analysis are accurate at lower computational effort when compare to that of no adaptivity. Further, the adaptive analysis provided accurate magnitude of maximum stresses and their locations in the laminate plates with and without cutout subjected to transverse loads. Additionally, failure prone areas in the geometry of the plates subjected to loads are revealed with the adaptive analysis.
    Print ISSN: 0177-0667
    Digitale ISSN: 1435-5663
    Thema: Informatik , Maschinenbau , Technik allgemein
    Publiziert von Springer
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