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Plasma Science and Technology 2015年第3期17卷 177-182页

作者： m.R.hossen A.A.mAmUN Department of Natural Sciences Daffodil International University Department of Physics Jahangirnagar University

A theoretical study on the nonlinear propagation of nonplanar （cylindrical and spherical） electrostatic modified ion-acoustic （mIA） shock structures has been carried out in an unmagnetized, collisionless four component degenerate plasma system （containing degenerate electron fluids, inertial positively as well as negatively charged light ions, and positively charged static heavy ions）. This investigation is valid for both non-relativistic and ultra-relativistic limits. The modified Burgers （mB） equation has been derived by employing the reductive perturbation method, and used to numerically analyze the basic features of shock structures. It has been found that the effects of degenerate pressure and number density of electron and inertial positively as well as negatively charged light ion fluids, and various charging state of positively charged static heavy ions significantly modify the basic features of mIA shock structures. The implications of our results to dense plasmas in astrophysical compact objects （e.g., non-rotating white dwarfs, neutron stars, etc.） are briefly discussed.

关键词： modified ion-acoustic waves shock waves nonplanar geometry relativistic effect degenerate pressure

Effect of Bohm quantum potential in the propagation of ion–acoustic waves in degenerate plasmas

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Chinese Physics B 2016年第10期25卷 222-229页

作者： m m Hasan m a hossen A Rafat A A mamun Department of Physics Jahangirnagar University

A theoretical investigation has been carried out on the propagation of the ion–acoustic(IA) waves in a relativistic degenerate plasma containing relativistic degenerate electron and positron fluids in the presence of inertial non-relativistic light ion fluid. The Korteweg-de Vries(K-dV), modified K-dV(m K-dV), and mixed m K-dV(mm K-dV) equations are derived by adopting the reductive perturbation method. In order to analyze the basic features(phase speed, amplitude, width,etc.) of the IA solitary waves(SWs), the SWs solutions of the K-dV, m K-dV, and mm K-d V are numerically analyzed. It is found that the degenerate pressure, inclusion of the new phenomena like the Fermi temperatures and quantum mechanical effects(arising due to the quantum diffraction) of both electrons and positrons, number densities, etc., of the plasma species remarkably change the basic characteristics of the IA SWs which are found to be formed either with positive or negative potential. The implication of our results in explaining different nonlinear phenomena in astrophysical compact objects, e.g.,white dwarfs, neutron stars, etc., and laboratory plasmas like intense laser–solid matter interaction experiments, etc., are mentioned.

关键词： Bohm quantum potential degenerate relativistic plasma electron and positron quantum effect

Instability Analysis of Positron-Acoustic Waves in a magnetized multi-Species Plasma

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Communications in Theoretical Physics 2017年第4期67卷 458-466页

作者： m.A.hossen m.G.Shah m.R.hossen A.A.mamun Department of Physics Jahangirnagar UniversitySavarDhaka-1342Bangladesh Department of Physics Hajee Mohammad Danesh Science and Technology UniversityDinajpur-5200Bangladesh Department of General Educational Development Daffodil International UniversitySukrabadDhaka-1207Bangladesh

The nonlinear propagation of electrostatic excitations and their multi-dimensional instability in a magnetized, degenerate electron-positron-ion(EPI) plasma system(containing inertial cold positrons, relativistic degenerate electrons and hot positrons, and negatively charged immobile heavy ions) are theoretically investigated. The reductive perturbation method is employed to derive the Zakharov–Kuznetsov equation which admits a localized solitary wave solution for small but finite amplitude limit, and the multi-dimensional instability of the positron acoustic solitary waves(PASWs) is studied by the small-k perturbation expansion method. It is found that the basic characteristics(viz. phase speed, amplitude, width) of the PASWs are significantly affected by the degree of obliqueness, relativistic degeneracy,and plasma particle number densities. The instability criterion and its growth rate, which are depending on the magnetic field and the propagation directions of both the PASWs, and their perturbation modes are discussed. The present analysis can be helpful in understanding the nonlinear phenomenon in dense astrophysical as well as space plasma systems,especially in pulsar environments.

关键词： instability analysis solitary waves magnetized plasma degeneracy relativistic effect

Complex impedance and electric modulus studies of magnetic ceramic Ni_(0.27)Cu_(0.10)Zn_(0.63)Fe_(2)O_(4)

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Journal of Advanced Ceramics 2015年第3期4卷 217-225页

作者： m.BELAL hossen A.K.m.AKTHER HOSSAIN Department of Physics Chittagong University of Engineering and TechnologyChittagongBangladesh Department of Physics Bangladesh University of Engineering and TechnologyDhakaBangladesh

The electrical properties of Ni_(0.27)Cu_(0.10)Zn_(0.63)Fe_(2)O_(4)(NCZF)prepared from auto combustion synthesis of ferrite powders have been studied by impedance and modulus *** studied frequency and temperature dependencies of impedance and electric modulus of NCZF in a wide frequency range(20 Hz-5 mHz)at different measuring temperatures T_(Sm)(30-225℃).The complex impedance spectra clearly showed both grain and grain boundary effects on the electrical *** observed impedance spectra indicated that the magnitude of grain boundary resistance R_(gb) becomes more prominent compared to grain resistance R_(b) at room temperature,and with the increase in T_(Sm),R_(gb) decreases faster than the intrinsic R_(b).The frequency response of the imaginary part of impedance showed relaxation behavior at every T_(Sm),and the relaxation frequency variation with T_(Sm) appeared to be of Arrhenius nature and the activation energy has been estimated to be 0.37 eV.A complex modulus spectrum was used to understand the mechanism of the electrical transport process,which indicated that a non-Debye type of conductivity relaxation characterizes this material.

关键词： ferrimagnetic ceramics impedance spectroscopy electric modulus temperature dependence

Nonlinear Dynamics in a Nonextensive Complex Plasma with Viscous Electron Fluids

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Chinese Physics Letters 2016年第6期33卷 67-70页

作者： m.R. hossen S.A. Ema A.A. mamun Department of Natural Sciences Daffodil International University Department of EEE Sonargaon University Department of Physics Jahangirnagar University

Cylindrical and spherical dust-electron-acoustic （DEA） shock waves and double layers in an unmagnetized, col- lisionless, complex or dusty plasma system are carried out. The plasma system is assumed to be composed of inertial and viscous cold electron fluids, nonextensive distributed hot electrons, maxwellian ions, and negatively charged stationary dust grains. The standard reductive perturbation technique is used to derive the nonlinear dynamical equations, that is, the nonplanar Burgers equation and the nonplanar further Burgers equation. They are also numerically analyzed to investigate the basic features of shock waves and double layers （DLs）. It is observed that the roles of the viscous cold electron fluids, nonextensivity of hot electrons, and other plasma parameters in this investigation have significantly modified the basic features （such as, polarity, amplitude and width） of the nonplanar DEA shock waves and DLs. It is also observed that the strength of the shock is maximal for the spherical geometry, intermediate for cylindrical geometry, while it is minimal for the planar geometry. The findings of our results obtained from this theoretical investigation may be useful in understanding the nonlinear phenomena associated with the nonplanar DEA waves in both space and laboratory plasmas.

关键词： in on is as it of Nonlinear Dynamics in a Nonextensive Complex Plasma with Viscous Electron Fluids with

Nonplanar Shock Structures in a Relativistic Degenerate multi-Species Plasma

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Communications in Theoretical Physics 2014年第12期61卷 888-894页

作者： m.R.hossen S.A.Ema A.A.mamun Department of Natural Sciences Daffodil International University Sukrabad Dhaka-1207 Bangladesh Department of Physics Jahangirnagar University Savar Dhaka-1342 Bangladesh

A nonlinear propagation of cylindrical and spherical modified ion-acoustic(m IA) waves in an unmagnetized,collisionless, relativistic, degenerate multi-species plasma has been investigated theoretically. This plasma system is assumed to contain non-relativistic degenerate light ions, both non-relativistic and ultra-relativistic degenerate electron and positron fluids, and arbitrarily charged static heavy ions. The restoring force is provided by the degenerate pressures of the electrons and positrons, whereas the inertia is provided by the mass of ions. The arbitrarily charged static heavy ions participate only in maintaining the quasi-neutrality condition at equilibrium. The modified Burgers(m B) equation is derived by using reductive perturbation technique and numerically analyzed to identify the basic features of m IA shock structures. The basic characteristics of m IA shock waves are found to be significantly modified by the effects of degenerate pressures of electron, positron, and ion fluids, their number densities, and various charge state of heavy ions. The implications of our results to dense plasmas in astrophysical compact objects(e.g., non-rotating white dwarfs,neutron stars, etc.) are briefly discussed.

关键词： modified ion-acoustic waves shock waves degenerate pressure relativity compact objects

Solitary Potential in a Space Plasma Containing Dynamical Heavy Ions and Bi-Kappa Distributed Electrons of Two Distinct Temperatures

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Communications in Theoretical Physics 2018年第1期69卷 107-114页

作者： m.Sarker B.Hosen m.R.hossen A.A.mamun Department of Physics Jahangirnagar University Department of General Educational Development Daffodil International University

The heavy ion-acoustic solitary waves(HIASWs) in a magnetized, collisionless, space plasma system(containing dynamical heavy ions and bi-kappa distributed electrons of two distinct temperatures) have been theoretically investigated. The Korteweg-de Vries(K-dV), modified K-dV(mK-dV), and higher-order mK-dV(HmK-dV) equations are derived by employing the reductive perturbation method. The basic features of HIASWs(viz. speed, polarity,amplitude, width, etc.) are found to be significantly modified by the effects of number density and temperature of different plasma species, and external magnetic field(obliqueness). The K-dV and Hm-Kd V equations give rise to both compressive and rarefactive solitary structures, whereas the mK-dV equation supports only the compressive solitary structures. The implication of our results in some space and laboratory plasma situations are briefly discussed.

关键词：重离子独居温度血浆空间 Korteweg-de 电子分布式

Roles of Superthermal Electrons and Adiabatic Heavy Ions on Heavy-Ion-Acoustic Solitary and Shock Waves in a multi-Component Plasma

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Communications in Theoretical Physics 2015年第8期64卷 208-214页

作者： m.G.Shah m.m.Rahman m.R.hossen A.A.mamun Department of Physics Jahangirnagar University Department of Natural Sciences Daffodil International University

Heavy-ion-acoustic(HIA) waves in an unmagnetized collisionless plasma system comprising superthermal electrons, Boltzmann distributed light ions, and adiabatic positively charged inertial heavy ions have been investigated both numerically and analytically. The well-known reductive perturbation method has been used to derive the Kortewegde Vries(K-d V) and Burgers(BG) equations. The parametric regimes for the existence of both the positive and negative solitary and shock waves have been obtained. The effects of adiabaticity of heavy ions and superthermality of electrons,which are found to notably modify the fundamental features(viz. polarity, amplitude, phase speed, etc.) of HIA solitary and shock waves, are precisely studied. The results of our theoretical investigation can be applicable to understand the characteristics and basic nonlinear structures of HIA waves both in space and laboratory plasma situations.

关键词： heavy-ion acoustic waves superthermality adiabatic

Influence of cerium ions on structure-dependent magnetic properties of Ba-Sr m-type hexaferrite nanocrystals

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Journal of Rare Earths 2024年第2期42卷 364-372,I0005页

作者： Ram A.Pawar Sunil m.Patange P.m.Dighe Sher Singh meena Abdullah GAl-Sehemi mehboobali Pannipara Santosh S.Jadhav Department of Physics ArtsCommerce and Science CollegeAhmednagar413711MaharashtraIndia Department of Physics Shri Krishna MahavidyalayaGunjotiDistOsmanabad413606MaharashtraIndia Padmashri Vikhe Patil College of Arts Science and CommercePravaranagarA/P.Loni(Kd)Tal.RahataDistAhmednagar413713MaharashtraIndia Solid State Physics Division Bhabha Atomic Research CentreMumbai400085MaharashtraIndia Department of Chemistry King Khalid UniversityAbha61413Saudi Arabia Department of Physics D.S.M's ArtsCommerce and Science CollegeJintur431509MaharashtraIndia

The present study is a systematic effort to investigate the structure-sensitive magnetic parameters of Ce^(3+) substituted Ba-Sr hexaferrite nanocrystals chemically formulated as Ba_(0.5)Sr_(0.5)Ce_(x)Fe_(12-x)O_(19) where x=0.0-0.2 with Δx=*** hexaferrite powders were prepared using the sol-gel self-ignition route and structurally characterized by means of powder X-ray diffraction and Fourier transform infrared *** creation of the m-type hexaferrite phase within the synthesized samples was revealed from the Rietveld refinement of the X-ray *** occurrence of a secondary phase of CeO_(2) was revealed within the hexaferrites for the substitution,x> *** refined X-ray diffraction data were utilized to compute the lattice parameters,X-ray density,and lattice parameter *** crystal structure plotted from the refined XRD data reveals the occupancy of the ions at different lattice *** XPS data of the hexaferrite were analyzed to confirm the oxidation states of the constituent *** nanocrystalline nature of the hexaferrites was revealed from the crystallite sizes calculated using Scherer's *** analysis of FTIR spectra confirms that only a fraction of Ce^(3+)accommodated in the lattice and the remaining Ce content reside in the form of the CeO_(2) *** morphology of the hexaferrites was analyzed from the FESEm profiles of the ferrite *** magnetic behavior study was performed by analyzing the Curie temperature,hysteresis loops,and hyperfine interactions by means of susceptibility,V.S.m,and mossbauer spectroscopy,*** hexaferrites with increasing coercivity,decreasing saturation magnetization,and decreasing Curie temperature are reported in the *** substituted Ce^(3+)ions inhibit the grain growth and create lattice imperfections giving rise to hexaferrites with tuned magnetic parameters suitable for different applications.

关键词： Ba-Sr hexaferrite Ce^(3+)substitution XPS Saturation magnetization Coercivity m?ssbauer spectroscopy

Frequency-dependent viscoelasticity effects on the wave attenuation performance of multi-layered periodic foundations

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Applied mathematics and mechanics(English Edition) 2024年第3期45卷 407-424页

作者： m.SAFI m.VAKILIFARD m.J.mAHmOODI Faculty of Civil Water&Environmental EngineeringShahid Beheshti UniversityTehran ***Iran Faculty of mechanical and Energy Engineering Shahid Beheshti UniversityTehran ***Iran

In this paper,layered periodic foundations(LPFs)are numerically examined for their responses to longitudinal and transverse modes in the time and frequency *** different unit-cells,i.e.,2-layer,4-layer,and 6-layer unit-cells,comprising concrete/rubber,concrete/rubber/steel/rubber,and concrete/rubber/steel/rubber/lead/rubber materials,respectively,are taken into ***,the viscoelasticity behavior of the rubber is modeled with two factors,i.e.,a frequency-independent(FI)loss factor and a linear frequency-dependent(FD)loss *** the extraction of the complex dispersion curves and the identification of the band gaps(BGs),the simulations of wave transmission in the time and frequency domains are performed using the COmSOL *** parametric studies evaluate the effects of the rubber viscoelasticity models on the dispersion curves and the wave transmission for the longitudinal and transverse *** results show that considering the rubber viscoelasticity enhances the wave attenuation ***,the transverse-mode damping is more sensitive to the viscoelasticity model than its longitudinal *** 6-layer unit-cell LPF exhibits the lowest BG,ranging from 4.8 Hz to 6.5 Hz.

关键词： layered metamaterial periodic foundation complex dispersion curve wave transmission diagram