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مرکز اطلاعات علمی SID1
اسکوپوس
دانشگاه غیر انتفاعی مهر اروند
ریسرچگیت
strs
Issue Info: 
  • Year: 

    2013
  • Volume: 

    3
  • Issue: 

    2
  • Pages: 

    85-90
Measures: 
  • Citations: 

    0
  • Views: 

    88172
  • Downloads: 

    21500
Abstract: 

In order to present a quantitative indicator for the onset of instability, in this paper, the critical points of a stratified Gravitational flow on a slope are found and analyzed. These points are obtained by means of the solution of the two-dimensional Navier-Stokes equations via the standard Arakawa-C finite-difference method. Results show that in the marginal Richardson numbers, the critical points begin to originate. Also, the cyclic evolution in the temporal differenced density field in the vicinity of the critical points is used as a quantitative criterion of the onset of mixing. Therefore, it is possible to predict the beginning of the mixing phenomenon via analysis of only a limited number of critical points.

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Author(s): 

Khashen m.h | ROSHAN M.

Issue Info: 
  • Year: 

    2018
  • Volume: 

    29
  • Issue: 

    2 (18)
  • Pages: 

    89-98
Measures: 
  • Citations: 

    0
  • Views: 

    442
  • Downloads: 

    185
Abstract: 

The purpose of this paper is to consider the ring systems in the context of a modified gravity theory. In fact, the Gravitational stability of a ring system consisted of N particle with the same mass m rotating around a massive object at the center is studied. After finding the equation of motion and considering the dynamics of the system in the equilibrium state, perturbative analysis is used in order to find the linearized version of the equations of motion. Finally using the Fourier analysis, the dispersion relation of the system is derived. At the end, using the observational values of the free parameters of the above mentioned theory and also the dispersion equation the stability criterion of the system for several cases is derived. Finally, the results have been compared with the corresponding results in Newtonian gravity.

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Author(s): 

AJABSHIRIZADEH A. | FAZEL Z.

Issue Info: 
  • Year: 

    2005
  • Volume: 

    5
  • Issue: 

    3
  • Pages: 

    75-79
Measures: 
  • Citations: 

    0
  • Views: 

    572
  • Downloads: 

    259
Abstract: 

Gravitational multipole moments of the Sun are still poorly known. Theoretically, the difficulty is mainly due to the differential rotation for which the velocity rate varies both on the surface and with the depth. From an observational point of view, the multipole moments cannot be directly measured. However, recent progresses have been made proving the existence of a strong radial differential rotation in a thin layer near the solar surface (the leptocline). Applying the theory of rotating stars, we will first compute values of J2 and J4 taking into account the radial gradient of rotation, then we will compare these values with the existing ones, giving a more complete review. We will explain some astrophysical outcomes, mainly on the relativistic Post Newtonian parameters. Finally we will conclude by indicating how space experiments (balloon SDS flights, Golf NG, Beppi-Colombo, Gaia...) will be essential to unambiguously determine these parameters.

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گارگاه ها آموزشی
Journal: 

NATURAL COMPUTING

Issue Info: 
  • Year: 

    2010
  • Volume: 

    9
  • Issue: 

    3
  • Pages: 

    727-745
Measures: 
  • Citations: 

    922
  • Views: 

    31442
  • Downloads: 

    29245
Keywords: 
Abstract: 

Yearly Impact:

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Author(s): 

Khajenabi f.

Issue Info: 
  • Year: 

    2019
  • Volume: 

    18
  • Issue: 

    4
  • Pages: 

    613-623
Measures: 
  • Citations: 

    0
  • Views: 

    464
  • Downloads: 

    225
Abstract: 

The static structure of a turbulent self-Gravitational disk is investigated based on the effect of cooling due to the presence of dust particles. In agreement with the numerical simulations of self-Gravitational disks that have been done so far, the cumulative parameter is assumed to be on the threshold of its critical value; however, the coefficient of turbulence is obtained from the system's cooling rate. The physical quantities of the disk are obtained as a function of the radial amplitude. We show that the overall structure of the disk is divided into two regions, such that the inner part is optically a thick one and the outer part is an optically thin one. On the other hand, the model we present shows that as the mass increase speed is raised, the role of dust becomes more important. We show that the turbulent viscosity coefficient increases with the distance, but this coefficient decreases in the inner region due to the cooling of the dust. We then determine the mass of Gravitational instability particles in the self-Gravitational radius. We show that cooling dust particles increases the self-Gravitational radius in the high accretion, while in the low accretion, the cooling of dust reduces the self-Gravitational radius.

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Issue Info: 
  • Year: 

    2017
  • Volume: 

    5
  • Issue: 

    4
  • Pages: 

    1-10
Measures: 
  • Citations: 

    0
  • Views: 

    1152
  • Downloads: 

    261
Abstract: 

Todays, various heuristic optimization methods have been developed. Many of these algorithms are inspired from physical processes or swarm behaviors in nature. Gravitational Search Algorithm (GSA) is an optimization algorithm based on the law of gravity and mass interactions. In the proposed algorithm, the search agents are a collection of masses. In this paper, mentioned algorithm is used to solve of the Frequency Assignment Problem (FAP). For ability test of the algorithm, CALMA benchmarks are used and results are good.

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strs
Author(s): 

SWAIN R.K. | SAHU N.C. | HOTA P.K.

Journal: 

PROCEDIA TECHNOLOGY

Issue Info: 
  • Year: 

    2012
  • Volume: 

    6
  • Issue: 

    -
  • Pages: 

    411-419
Measures: 
  • Citations: 

    471
  • Views: 

    26407
  • Downloads: 

    31195
Keywords: 
Abstract: 

Yearly Impact:

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Issue Info: 
  • Year: 

    2012
  • Volume: 

    3
  • Issue: 

    2
  • Pages: 

    45-51
Measures: 
  • Citations: 

    0
  • Views: 

    81484
  • Downloads: 

    71152
Abstract: 

Gravitational search algorithm (GSA) is one of the newest swarm based optimization algorithms, which has been inspired by the Newtonian laws of gravity and motion. GSA has empirically shown to be an efficient and robust stochastic search algorithm. Since introducing GSA a convergence analysis of this algorithm has not yet been developed. This paper introduces the first attempt to a formal convergence analysis of the standard Gravitational search algorithm which involves with randomness and time varying parameters. In this analysis the behavior of GSA on the facet of mass interaction is considered. The paper provides a formal proof that each object converges to a stable point.

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Author(s): 

HAN X.H. | CHANG X.M.

Issue Info: 
  • Year: 

    2014
  • Volume: 

    281
  • Issue: 

    -
  • Pages: 

    128-146
Measures: 
  • Citations: 

    468
  • Views: 

    34322
  • Downloads: 

    30601
Keywords: 
Abstract: 

Yearly Impact:

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Author(s): 

Ziaie Amir Hadi

Issue Info: 
  • Year: 

    2020
  • Volume: 

    10
  • Issue: 

    3
  • Pages: 

    47-60
Measures: 
  • Citations: 

    0
  • Views: 

    374
  • Downloads: 

    179
Abstract: 

In the present work we study the process of Gravitational collapse of a homogeneous dust in the framework of generalized Rastall gravity. In this theory, the Rastall coupling parameter is a variable and since this parameter represents the measure of mutual interaction between matter and geometry it is expected that such an interaction affects the collapse dynamics and its end product. Motivated by this idea, we search for non-singular solutions for the interior spacetime of the collapsing dust fluid. We observe that this scenario is feasible for a suitable choice of the functionality of the coupling parameter such that the singularity present in homogeneous dust collapse is replaced by a non-singular bounce where the energy density and spacetime curvature are finite. We also observe that such a variable coupling affects the dynamics of apparent horizon so that, in comparison to the singular case where the apparent horizon covers the spacetime singularity, the apparent horizon can be delayed or failed to form providing thus the possibility of detecting the bouncing object by external observers.

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