جستجوی مقالات مرتبط با کلیدواژه « Pseudo » در نشریات گروه « علوم پایه »

In this paper for the first time we introduce the Pseudo-moment generator function and also we investigate some properties of. .
We prove some properties of Pseudo-expectation and Pseudo-dispersion .

The pseudo-static analysis is one of the conventional methods in embankment dams design and International Commission on Large Dams (ICOLD) suggests using this method before ultimate dynamic analyses. In this research, the static, pseudo-static and dynamic analysis of Masjed Soleyman embankment dam have been performed. Using dynamic and pseudo-static analyses results, the safety factor of critical sliding surface were calculated. Permanent displacements of critical sliding surface were evaluated by Newmark method and the calculated safety factor was compared. Based on the comparison results in different water levels of the reservoir and by introducing a new equation, the variable horizontal acceleration coefficients in height of the dam body were calculated. Finally, obtained horizontal acceleration coefficients were compared with other criteria introduced in different embankment dam's design codes. Totally, the results indicate that the proposed method leads to a larger horizontal acceleration coefficient in higher parts of the dam body.

Directional statistics are very useful tools to model the phenomenon that are characterized by the angles. Recently, various disciplines including biology, astronomy, meteorology and bioinformatics have paid attention to use these distributions. Particularly, it was shown in biological researches that there are two pair angles describing, relatively, the complete geometrical and spatial structures of a protein in the three dimensional space. There is a distribution, called bivariate Von-Mises, to represent the position of the atoms based upon the values of these angles in a probabilistic manner. In this paper, considering an especial case of this density (cosine model), the properties of distribution including the numbers of modes and its approximation by the bivariate normal distribution are first studied. Then, to estimate the parameters using the pseudo-likelihood method is described. The theoretical materials are evaluated in simulation studies and then the application of the cosine model in a real example is presented.

In this paper، the pseudo-likelihood estimators and the limiting distribution of the score test statistic associated with several hypothesis tests such as unit root test for the linear regression models with stationary and nonstationary residuals are calculated. The limiting behavior of theses test statistics by using a simpler approach of the original presentation is derived. Also by using a Mont Carlo method، it is shown that the derived pseudo-likelihood estimators are appropriate. The quantiles of the limiting distribution of the test statistic for a unit root are also calculated and a new table is provided which can be used by researchers for the unit root test.

In surveys from finite populations usually a probability sample is selected from a sampling frame containing all the units in the target population. In some cases the frame that is available cannot cover target population completely so survey statistics from these frames are bias. On the other hand updating the frame that is available is too expensive. Multiple frame survey can be used to increase population coverage, reduce bias and decrease costs. In multiple frame surveys samples are drown independently from overlapping multiple frames so that these frames give an appropriate coverage of the target population. Several estimators for population total in multiple frame surveys are discussed. In this article we introduce these estimators in a simulation study, we compare performance of different total estimators.

To control the nonlinear numerical instability, throughout the time evolution of the Eulerian form of the nonlinear rotating shallow water equations, it is necessary to add numerical diffusion to the solution. It is clear that, this extra numerical diffusion degrades the accuracy of the numerical solution and should be kept as small as possible. In a conventional approach a hyper-diffusion is used to maintain the numerical stability. In the present work, the influence of using different orders of hyper-diffusion on the accuracy of the numerical solution of the shallow water equations generated by some high-order numerical methods is examined. Furthermore, application of an eighth-order compact spatial filter as an alternative way to provide the numerical diffusion is considered. In the present work, the vorticity-divergence-mass representation of the shallow water equations is considered for numerical simulation. To advance the governing equations in time the semi-implicit approach combined with the three level leapfrog method for the time discretization of the temporal derivatives, is used. The second-order central, the fourth-order compact, the sixth-order super compact finite difference and the pseudo-spectral methods are applied to spatial differencing of the shallow water equations. For a quantitative assessment of accuracy, the global measures of the distribution of mass between potential vorticity iso-levels, called mass error, is used. In addition, based on the results of some recent investigations, decomposing a flow into a balanced part representing vortical flow and an unbalanced part representing freely propagating inertia-gravity waves has found significant usefulness in the accuracy analysis of the numerical solution of the primitive equations. Therefore, in this work the representation of balance and imbalance are also used for quantitative assessment of the numerical accuracy. It is found that the numerical diffusion plays a crucial role in the accuracy of numerical solution. Results show that using lower order hyper-diffusion terms degrades the numerical accuracy. Furthermore, results show that using higher orders of hyper-diffusion for the sixth-order super compact and pseudo-spectral method is essential. In addition, it is observed that based on the quantitative measures of the mass error, using a sixth-order hyper-diffusion term or using the eighth-order compact spatial filter has nearly a similar effect on the numerical accuracy of the shallow water equations generated by the sixth-order super compact finite difference and the pseudo-spectral methods. The same conclusion is valid based on the quantitative measures of the imbalance in particular for hyper-diffusion terms with orders greater than two.