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Accelerating dark energy models with anisotropic fluid in Bianchi type Ⅵ_0 space-time

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Research in Astronomy and Astrophysics 2013年第2期13卷 139-158页

作者： Anirudh Pradhan department of mathematics Hindu Post-graduate College

Motivated by the increasing evidence for the need of a geometry that re- sembles Bianchi morphology to explain the observed anisotropy in the WMAP data, we have discussed some features of Bianchi type VI0 universes in the presence of a fluid that has an anisotropic equation of state （EoS） parameter in general relativity. We present two accelerating dark energy （DE） models with an anisotropic fluid in Bianchi type VI0 space-time. To ensure a deterministic solution, we choose the scale factor a（t） = √tnet, which yields a time-dependent deceleration parameter, representing a class of models which generate a transition of the universe from the early decelerating phase to the recent accelerating phase. Under suitable conditions, the anisotropic mod- els approach an isotropic scenario. The EoS for DE co is found to be time-dependent and its existing range for derived models is in good agreement with data from recent observations of type Ia supernovae （SNe Ia）（Knop et al. 2003）, SNe Ia data com- bined with cosmic microwave background （CMB） anisotropy and galaxy clustering statistics （Tegmark et al. 2004a）, as well as the latest combination of cosmological datasets coming from CMB anisotropies, luminosity distances of high redshift SNe Ia and galaxy clustering. For different values of n, we can generate a class of physically viable DE models. The cosmological constant A is found to be a positive decreasing function of time and it approaches a small positive value at late time （i.e. the present epoch）, which is corroborated by results from recent SN Ia observations. We also ob- serve that our solutions are stable. The physical and geometric aspects of both models are also discussed in detail.

关键词： cosmological models -- dark energy -- variable EoS parameter

Thick Domain Walls in Lyra Geometry with Bulk Viscosity

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Communications in Theoretical Physics 2009年第2期51卷 378-384页

作者： Anirudh Pradhan department of mathematics Hindu Post-graduate College

In this paper, we evaluate the general solutions for plane-symmetric thick domain walls in Lyra geometry in presence of bulk viscous fluid. Expressions for the energy density and pressure of domain walls are derived in both cases of uniform and time varying displacement field β. Some physical consequences of the models are also given. Finally, the geodesic equations and acceleration of the test particle are discussed.

关键词： cosmology plane symmetric domain walls bulk viscous model Lyra geometry

Anisotropic Bianchi Type-I Magnetized String Cosmological Models with Decaying Vacuum Energy Density A(t)

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Communications in Theoretical Physics 2011年第5期55卷 931-941页

作者： Anirudh Pradhan department of mathematics Hindu Post-graduate College

The present study deals with a spatially homogeneous and anisotropic Bianehi-I cosmological models representing massive strings with magnetic field and decaying vacuum energy density A. The energy-momentum tensor, as formulated by Letelier （1983）, has been used to construct massive string cosmological models for which we assume the expansion scalar in the models is proportional to one of the components of shear tensor. The Einstein＇s field equations have been solved by applying a variation law for generalized Hubble＇s parameter in Bianchi-I space-time. The variation law for Hubble＇s parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential form. Using these two forms, Einstein＇s field equations are solved separately that correspond to expanding singular and non-singular models of the universe respectively. We have made a comparative study of accelerating and decelerating models in the presence of string scenario. The study reveals that massive strings dominate in the decelerating universe whereas strings dominate in the accelerating universe. The strings eventually disappear from the universe for sufficiently large times, which is in agreement with current astronomical observations. The cosmological constant A is found to be a positive decreasing function of time which is corroborated by results from recent supernovae Ia observations. The physical and geometric properties of the models have been also discussed in detail.

关键词： cosmic strings Bianchi-I universe variable cosmological constant Hubble's parameter

Some Magnetized Bulk Viscous String Cosmological Models in Cylindrically Symmetric Inhomogeneous Universe with Variable Λ-Term

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Communications in Theoretical Physics 2009年第2期51卷 367-374页

作者： Anirudh Pradhan department of mathematics Hindu Post-graduate College

Some cylindrically symmetric inhomogeneous viscous fluid string cosmological models with magnetic field and cosmological term A varying with time are investigated. To get the deterministic solution, it has been assumed that the expansion （θ） in the model is proportional to the eigen value σ^11 of the shear tensor σ^ij. The value of cosmological constant for the model is found to be small and positive, which is supported by the results from recent supernovae Ia observations. The effect of bulk viscosity is to produce a change in perfect fluid and hence exhibits essential influence on the character of the solution. The physical and geometric properties of the models are also discussed in presence and absence of magnetic field.

关键词： string inhomogeneous universe cylindrical symmetry variable cosmological term bulk viscosity

Synthesis,structural and optical properties of SrZrO_3:Eu^(3+) phosphor

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Journal of Rare Earths 2014年第4期32卷 293-297页

作者： Sheetal V.B.Taxak Rajni Arora Dayawati S.P.Khatkar department of Chemistry Maharshi Dayanand University department of Chemistry Government Post Graduate College

Eu3＋activated Sr1-xEuxZrO3 （x=0.01-0.04） phosphor with perovskite structure was successfully synthesized by using com-bustion method. The structure, morphology and optical properties of the material were characterized by X-ray diffraction, scanning electron microscopy and fluorescence spectrometry. The XRD results indicated that crystals of SrZrO3：Eu3＋belongs to tetragonal perovskite system. The phosphor could be effectively excited by UV light and the emission spectra results indicated that red-dish-orange luminescence of SrZrO3：Eu3＋due to magnetic dipole transition 5D0→7F1 at 593 nm was dominant. Thus, the prepared phosphor showed remarkable luminescent properties which find applications in field emission display （FED） and plasma display panel （PDP） devices.

关键词： perovskite europium optical materials luminescence rare earths

Activated sludge-mediated biodegradation of dimethyl phthalate under fermentative conditions

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Journal of Environmental Sciences 2008年第8期20卷 922-926页

作者： MAHMOOD Qaisar department of Botany Federal Government Post Graduate College Sector H-8 IslamabadPakistan

The biodegradation of dimethyl phthalate(DMP)was investigated under fermentative conditions in this *** nature of the intermediate compounds and the extent of mineralization were probed using high-pressure liquid chromatography(HPLC)and liquid chromatography-mass spectrometry(LC-MS)*** fermentative bacteria were able to biodegrade the DMP under anaerobic conditions,with the biodegradation rate of 0.36 mg DMP/(L·h).The results demonstrated that the DMP degradation under fermentative conditions ...

关键词： activated sludge biodegradation dimethyl phthalate fermentation phthalic acid mineralization

Reflection and transmission of elastic waves at an interface between two micropolar piezoelectric half-spaces

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Journal of Ocean Engineering and Science 2019年第3期4卷 227-237页

作者： Baljeet Singh Asha Sangwan Jagdish Singh department of mathematics Post Graduate Government CollegeSector 11Chandigarh 160011India department of mathematics Government CollegeSamplaRohtak 124001HaryanaIndia department of mathematics Maharshi Dayanand UniversityRohtak 124001HaryanaIndia

In the present paper,we consider a problem of reflection and transmission of plane waves at an interface between two different transversely isotropic micropolar piezoelectric *** plane wave solution of governing equations for micropolar piezoelectric medium indicates the propagation of three coupled plane *** incident plane wave at an interface between two dissimilar half-spaces generates three reflected and three transmitted *** relations between amplitude ratios of reflected and transmitted waves are derived which,in general,depend on material parameters and angle of *** explicit expressions for energy ratios of reflected and transmitted waves are also *** relevant material parameters,the results are illustrated graphically to show the micropolar piezoelectric effects on variations of amplitude ratios and the square root of energy ratios against the angle of incidence.

关键词： Plane waves Micropolar piezoelectricity Reflection and transmission Amplitude ratios Energy ratios

Reflection of plane waves from a micropolar thermoelastic solid half-space with impedance boundary conditions

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Journal of Ocean Engineering and Science 2019年第2期4卷 122-131页

作者： Baljeet Singh Anand Kumar Yadav Deepak Gupta department of mathematics Post Graduate Government CollegeSector 11ChandigarhIndia department of mathematics M.M.University MullanaAmbalaIndia

In this paper,the governing equations of linear,isotropic,homogeneous and generalized micropolar thermoelasticity are specialized in a *** governing equations are solved for plane harmonic wave *** separate velocity equations are obtained which indicate the existence of four plane waves with distinct speeds.A problem on reflection of plane waves from a thermally insulated/isothermal surface is considered with impedance boundary *** potentials for incident and reflected waves are formulated which satisfy the boundary conditions at a plane *** between reflection coefficients as well as the expressions of energy ratios for various reflected waves are *** illustration,the reflection coefficients and energy ratios of reflected waves are computed for relevant material parameters of an aluminium-epoxy *** of impedance parameters on all reflected waves is shown graphically at each angle of incidence.

关键词： Micropolar thermoelasticity Impedance boundary Plane waves Reflection coefficients Energy ratios.

Influence of TiO_2 on the electrochemical performance of pasted typeβ-nickel hydroxide electrode in alkaline electrolyte

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Journal of Energy Chemistry 2016年第1期25卷 41-48页

作者： B.Shruthi B.J.Madhu V.Bheema Raju department of Chemistry Dr. Ambedkar Institute of Technology post graduate department of Physics Government Science College department of Chemistry Dayananda Sagar College of Engineering

Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide（β-Ni（OH）2 ） was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO2 additive on the β-Ni（OH）2 electrode performance are examined. The structure and property of the TiO2 added β-Ni（OH）2 were characterized by XRD, TG-DTA and SEM analysis. A pasted–type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni（OH）2 and TiO2 added β-Ni（OH）2 electrodes in 6 M KOH electrolyte. Anodic（Epa） and cathodic（Epc）peak potentials are found to decrease after the addition of TiO 2 into β-Ni（OH）2 electrode material. Further,addition of TiO2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni（OH）2 lectrode,TiO2 added β-Ni（OH）2 electrode is found to exhibit higher proton diffusion coefficient（D） and lower charge transfer resistance. These findings suggest that the TiO2 added β-Ni（OH）2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.

关键词： Nickel hydroxide Electrode material Thermogravimetric analysis Electrochemical properties Impedance spectroscopy