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Stabilizing periodic orbits of Chua’s system using adaptive fuzzy sliding mode controller

International Journal of Intelligent Computing and Cybernetics 2019年第1期12卷 102-126页

作者： Hanène Medhaffar Moez Feki Nabil Derbel CEMLab ENISUniversity of SfaxSfaxTunisia essths University of SousseSousseTunisia

Purpose–The purpose of this paper is to investigate the stabilization of unstable periodic orbits of Chua’s system using adaptive fuzzy sliding mode controllers with moving surface.Design/methodology/approach–For this aim,the sliding mode controller and fuzzy systems are combined to achieve the stabilization.Then,the authors propose a moving sliding surface to improve robustness against uncertainties during the reaching phase,parameter variations and extraneous disturbances.Findings–Afterward,the authors design a sliding observer to estimate the unmeasurable states which are used in the previously designed controller.Originality/value–Numerical results are provided to show the effectiveness and robustness of the proposed method.

关键词： Sliding mode control Sliding mode observer Chaos control Fuzzy adaptive systems,Moving sliding surface

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Effect of anisotropic collisions on solar scattering polarization

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Research in Astronomy and Astrophysics 2021年第4期21卷 149-156页

作者： Saleh Qutub Moncef Derouich Badruddin Zaheer Ahmad Astronomy and Space Science Department Faculty of ScienceKing Abdulaziz UniversityJeddah 21589Saudi Arabia Sousse University ESSTHSLamine Abbassi Street4011 H.SousseTunisia

Scattering of anisotropic radiation by atoms,ions or molecules is sufficient to generate linear polarization observable in stars and planets’atmospheres,circumstellar environments,and in particular in the Sun’s atmosphere.This kind of polarization is called scattering polarization(SP)or second solar spectrum(SSS)if it is formed near the limb of the solar photosphere.Generation of linear SP can typically be reached more easily than circular SP.Interestingly,the latter is often absent in observations and theories.Intrigued by this,we propose to demonstrate how circular SP can be created by anisotropic collisions if a magnetic field is present.We also demonstrate how anisotropic collisions can result in the creation of circular SP if the radiation field is anisotropic.We show that under certain conditions,linear SP creation is accompanied by the emergence of circular SP which can be useful for diagnostics of solar and astrophysical plasmas.We treat an example and calculate the density matrix elements of tensorial order k=1 which are directly associated with the presence of circular SP.This work should encourage theoretical and observational research to be increasingly oriented towards circular SP profiles in addition to linear SP in order to improve our analysis tools of astrophysical and solar observations.

关键词： Scattering processes Line:formation-Polarization Sun:magnetic fields

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Are collisions with electrons important for modeling the polarization of the lines of the C2 solar molecule?

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Research in Astronomy and Astrophysics 2020年第7期20卷 193-198页

作者： Moncef Derouich Badruddin Zaheer Ahmad Aied Alruhaili Saleh Qutub Astronomy and Space Science Department Faculty of ScienceKing Abdulaziz University21589 JeddahSaudi Arabia Sousse University ESSTHSLamine Abbassi street4011 H.SousseTunisia

Observations of the second solar spectrum(SSS) revealed the existence of prominent linear polarization signals due to lines of the C2 molecule.Interpretation of the SSS is the only tool to obtain the weak and turbulent magnetic field which is widespread in the Quiet Sun.However,this interpretation is conditioned by the determination of accurate collisional data.In this context,we present a formulation of the problem of the calculation of the polarization transfer rates by collisions of polarized C2 states with electrons.The obtained formulae are applied to determine,for the first time,the polarization transfer rates between the C2 states of the Swan band electronic system(a 3Πu d 3Πq) and electrons for temperatures going up from 1000 to 10000 K.However,due to the closeness of the electronic states of the C2 molecule,the two electronic d 3Πg and a 3Πu cannot be disconnected from the other electronic levels and,thus,a model based on only two states is not sufficient to describe the formation of the lines in the Swan band.Consequently,we also calculated the collisional polarization transfer rates in the case where the first eight electronic states of C2 are taken into account.All rates are given as functions of the temperature by power laws.Our results should be useful for future solar applications.

关键词： Collisions Sun:photosphere atomic processes line:formation polarization

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