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Landau damping in a bounded magnetized plasma column

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Chinese Physics B 2015年第2期24卷 287-294页

作者： H.Zakeri-Khatir f.m.Aghamir Department of Physics University of Tehran

The damping decrement of Landau damping and the effect of thermal velocity on the frequency spectrum of a propagating wave in a bounded plasma column are *** magnetized plasma column partially filling a cylindrical metallic tube is considered to be collisionless and *** Landau damping is due to the thermal motion of charge carriers and appears whenever the phase velocity of the plasma waves exceeds the thermal velocity of *** analysis is based on a self-consistent kinetic theory and the solutions of the wave equation in a cylindrical plasma waveguide are presented using Vlasov and maxwell *** hybrid mode dispersion equation for the cylindrical plasma waveguide is obtained through the application of appropriate boundary conditions to the plasma-vacuum *** dependence of Landau damping on plasma parameters and the effects of the metallic tube boundary on the dispersion characteristics of plasma and waveguide modes are investigated in detail through numerical calculations.

关键词： Landau damping cylindrical plasma waveguide Vlasov equation dispersion characteristic

Telomeres:Linking stress and survival,ecology and evolution

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Current Zoology 2010年第6期56卷 714-727页

作者： mark f.HAUSSmANN Nicole m.mARCHETTO Department of Biology Bucknell University

Telomeres are protective structures at the ends of eukaryotic chromosomes. The loss of telomeres through cell division and oxidative stress is related to cellular aging, organismal growth and disease. In this way, telomeres link molecular and cellular mechanisms with organismal processes, and may explain variation in a number of important life-history traits. Here, we discuss how telomere biology relates to the study of physiological ecology and life history evolution. We emphasize current knowledge on how telomeres may relate to growth, survival and lifespan in natural populations. We finish by examining interest- ing new connections between telomeres and the glucocorticoid stress response. Glucocorticoids are often employed as indices of physiological condition, and there is evidence that the glucocorticoid stress response is adaptive. We suggest that one way that glucocorticoids impact organismal survival is through elevated oxidative stress and telomere loss. future work needs to establish and explore the link between the glucocorticoid stress response and telomere shortening in natural populations. If a link is found, it provides an explanatory mechanism by which environmental perturbation impacts life history trajectories [Current Zoology 56 （6）： 714-727, 2010].

关键词： Corticosterone Stress Survival Telomeres

Combined Effect of magnetic field and Thermal Dispersion on a Non-Darcy mixed Convection

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Journal of Thermal Science 2011年第3期20卷 276-282页

作者： m. f. EI-Amin Shuyu Sun Computational Transport Phenomena Laboratory （CTPL） Division of Physical Sciences and Engineering （PSE）King Abdullah University of Science and Technology （KAUST） Thuwal 23955-6900 Jeddah Kingdom of Saudi Ara-bia mathematics Department Faculty of Science South Valley University Aswan 81528 EGYPT

This paper is devoted to investigate the influences of thermal dispersion and magnetic field on a hot semi-infinite vertical porous plate embedded in a saturated Darcy-forchheimer-Brinkman porous medium. The coefficient of thermal diffusivity has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. The effects of transverse magnetic field parameter (Hartmann number Ha), Reynolds number Re (different velocities), Prandtl number Pr (different types of fluids) and dispersion parameter on the wall shear stress and the heat transfer rate are discussed.

关键词： Thermal dispersion non-Darcy convection magneto-hydro-dynamics porous media geothermal systems

Influence of rare earth ion substitutions on the structural,optical,transport,dielectric,and magnetic properties of superparamagnetic iron oxide nanoparticles

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Journal of Advanced Ceramics 2018年第3期7卷 218-228页

作者： R.m.KERSHI f.m.ALI m.A.SAYED Physics Department Faculty of ScienceKing Khalid University Physics Department Faculty of ScienceIbb University Physics Department Faculty of ScienceSuez Canal University Physics Department Faculty of ScienceAl-Azhar University

Superparamgnetic fe_3O_4 and RE:fe_3O_4(RE=Dy,Nd,La)nanoparticles with an average crystallite size in the range of 15–24 nm,were synthesized by co-precipitation *** samples were characterized using X-ray diffraction(XRD),scanning electron microscopy(SEm),vibrating sample magnetometer(VSm),UV–Vis spectroscopy,LCR bridge,and two-probe technique.X-ray diffraction patterns of all the investigated samples reveal the typical phase of magnetite structure,with a small contribution of orthoferrite(NdfeO_3)as a secondary phase in Nd:fe_3O_4 *** saturation magnetization(m_s)of the samples has values in the range from 41.8 to 52.3 emu/g,and decreases with RE ion doping depending on the ionic *** values of the coercivity H_c and remanencem_r,indicate the superparamagnetic nature of the investigated *** calculated values of indirect optical band gap of fe_3O_4 and RE:fe_3O_4 nanoparticles are in the range of0.9–1.25 *** dielectric constant of the samples decreases,while their activation energy increases with the increasing of ionic radii of dopants.

关键词： superparamgnetic iron oxide nanoparticles (SPIONs) rare earth (RE) ions structure,optical and activation energies electrical conductivity dielectric constant saturationmagnetization

Effectiveness of heat and mass transfer on mixed convective peristaltic motion of nanofluid with irreversibility rate

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Communications in Theoretical Physics 2021年第10期73卷 36-46页

作者： Y Akbar f m Abbasi U m Zahid S A Shehzad Department of mathematics COMSATS University IslamabadIslamabadPakistan Department of mathematics COMSATS University IslamabadSahiwalPakistan

Entropy generation is one of the key features in analysis as it exhibits irreversibility of the system. Therefore, the present study investigates the entropy generation rate in a mixed convective peristaltic motion of a reactive nanofluid through an asymmetrical divergent channel with heat and mass transfer characteristics. The endorsed nanofluid model holds thermophoresis and Brownian diffusions. mathematical modeling is configured under the effects of mixed convection, heat generation/absorption and viscous dissipation. A chemical reaction is also introduced for the description of mass transportation. The resulting system of differential equations is numerically tackled by employing the Shooting method. The findings reveal that entropy generation rises by improving the Brownian motion and thermophoresis parameters. The temperature of the nanofluid decreases due to rising buoyancy forces caused by the concentration gradient. The concentration profile increases by increasing the chemical reaction parameter. The velocity increases by enhancing the Brownian motion parameter.

关键词： peristaltic flow thermophoresis and Brownian motion mixed convection chemical reaction irreversibility nanofluid

Reductive leaching of indium.f.om the neutral leaching residue using oxalic acid in sulfuric acid solution

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International Journal of minerals,metallurgy and materials 2021年第3期28卷 373-379页

作者： f.maddah m.Alitabar H.Yoozbashizadeh Department of materials Science and Engineering Sharif University of TechnologyTehran 11155-9466Iran

The present study evaluates the reductive leaching of indium.f.om indium-bearing zinc ferrite using oxalic acid as a reducer in sulfuric acid *** effect of main factors affecting the process rate,including the oxalic-acid-to-sulfuric-acid ratio,stirring rate,grain size,temperature,and the initial concentration of synergic acid,was precisely *** results confirmed the acceptable efficiency of dissolving indium in the presence of oxalic *** shrinking-core model with a chemical-reaction-controlled step can correctly describe the kinetics of indium *** the basis of an apparent activation energy of 44.55 kJ/mol and a reaction order with respect to the acid concentration of 1.14,the presence of oxalic acid was found to reduce the sensitivity to temperature changes and to increase the effect of changes in acid ***,the equation of the kinetic model based on the factors under study is presented.

关键词： oxalic acid reductive leaching indium

Nanosecond Pulses Generation with Samarium Oxide film Saturable Absorber

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Chinese Physics Letters 2019年第7期36卷 48-51页

作者： N.f.Zulkipli m.Batumalay f.S.m.Samsamnun m.B.H.mahyuddin E.Hanafi T.f.T.m.N.Izam m.I.m.A.Khudus S.W.Harun Photonics Engineering Laboratory Department of Electrical Engineering University of Malaya Kuala Lumpur 50603 Malaysia faculty of Information Technology & Sciences Inti International University Perdana BBN Putra Nilai Nilai 71800 Negeri Sembilan Department of Physics University of Malaya Kuala Lumpur 50603 Malaysia Department of Physics Faculty of Science and Technology Airlangga University Surabaya Indonesia

Nanosecond pulse generation is demonstrated in a mode-locked erbium-doped fiber laser(EDfL) utilizing a samarium oxide(Sm2O3) film. The Sm2O3 film exhibits a modulation depth of 33%, which is suitable for modelocking operation. The passively pulsed EDfL operates stably at 1569.8 nm within a pumping power from 109 to 146 m W. The train of generated output pulses has a pulse width of 356 nm repeated at a fundamental frequency of 0.97 mHz. The average output power of 3.91 m W is obtained at a pump power of 146 m W, corresponding to 4.0 nJ pulse energy. The experimental result indicates that the proposed Sm2O3 saturable absorber is viable for the construction of a flexible and reliably stable mode-locked pulsed fiber laser operating in the 1.5 m region.

关键词： Nanosecond pulse generation erbium-doped fiber laser in the 1.5 m region

High-temperature deformation behaviour of duplex stainless steel with hard boronised layer

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Journal of Iron and Steel Research International 2021年第2期28卷 244-253页

作者： N.m.Sultan I.Jauhari R.Saidan m.f.m.Sabri Department of mechanical Engineering Faculty of EngineeringUniversity MalayaKuala Lumpur 50603Malaysia

In order to understand the high-temperature deformation behaviour of alloy having hard surface layer,thermo-mechanically treated duplex stainless steel(DSS)is boronised for 0.75-6 h at 1223 K and subsequently deformed under compression mode at the same temperature under strain rate condition of 1×10^(-3),2×10^(-4) and 6×10^(-5) s^(-1) until strain of *** substrate microstructure is almost isotropic with grain size after boronising with layer thickness between 1.61 and 2.74μm.X-ray diffraction results confirm the formation of boride on DSS *** surface hardness of DSS increases from 387 to 1000-2400 HV after *** boronised layer with thickness of 20-40μm is formed at DSS *** results show that the flow stress of the deformation increases with the strain rate and boronising *** the boronised samples,the flow stress range is between 5 and 89 *** determine the actual effect of the boronised layer on the flow stress,the results are also compared with those from un-boronised samples having similar *** results suggest that at a constant grain size,even with the hardest layer,the effect of hard surface layer on the flow stress almost could be negligible when the deformation rate is slow,but at faster deformation rate,even in the layer with the least hardness,the flow stress shows a significant *** is also observed that the hard boride surface disintegration could be avoided at a sufficiently low deformation flow stress that could be attributed to superplasticity.

关键词： High-temperature deformation Superplasticity Duplex stainless steel Hard boride layer Surface integrity Grain size effect Strain rate effect