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Evolution of Dissipative Anisotropic Expansion-Free Axial Fluids

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Communications in Theoretical Physics 2015年第8期64卷 139-144页

作者： m.Sharif Zunaira nasir Department of mathematics University of the Punjab Quaid-i-Azam Campus

A general study of non-static restricted class of axial system with anisotropic dissipative expansion-free fluid under geodesic condition is carried out. It is found that expansion-free model must be dissipative under geodesic condition to preserve axial symmetry. We also investigate this system without geodesic condition. Finally, the role of dissipation is explored via transport equation.

关键词： general relativity dissipative systems analytical

Complexity of charged anisotropic spherically symmetric fluids in f(G)gravity

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Communications in Theoretical Physics 2023年第3期75卷 91-104页

作者： Z Yousaf m Z Bhatti m m m nasir Department of mathematics University of the PunjabQuaid-i-Azam CampusLahore-54590Pakistan

The previous ideology of complexity factor for the dynamical spheres[Herrera et al 2018,***.D,98,104059]is extended for the influence of charge.A dynamical spherically symmetric non-dissipative and dissipative self-gravitating structure is examined in the presence of maxwell f(G)gravity to examine the complexity *** pattern of evolution is studied with the minimal complexity *** complexity factor remains the same for the structure of fluid distribution,while we examine homologous constraints for the most basic evolution *** calculate the structure scalars which play an important role in order to understand the fundamental properties of the *** fluid is geodesic as well as shearing for the dissipative case and there is a large number of *** the non-dissipative fluid distribution,a shear-free,homogeneous and isotropic,geodesic fluid correlates with the evolving homologous and vanishing complexity *** implication of the condition of vanishing complexity factor and stability are discussed at the end.

关键词： gravitation anisotropy complexity hydrodynamics

An ab initio investigation of vibrational, thermodynamic, and optical properties of Sc_2AlC mAX compound

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Chinese Physics B 2016年第10期25卷 103-108页

作者： m A Ali m T nasir m R Khatun A K m A Islam S H Naqib Department of Physics Chittagong University of Engineering and Technology Department of Arts & Sciences Bangladesh Army University of Science and Technology Department of Physics University of Rajshahi International Islamic University Chittagong

The structural vibrational, thermodynamical, and optical properties of potentially technologically important, weakly coupled mAX compound, Sc2 Al C are calculated using density functional theory(DFT). The structural properties of ScAlC are compared with the results reported earlier. The vibrational, thermodynamical, and optical properties are theoretically estimated for the first time. The phonon dispersion curve is calculated and the dynamical stability of this compound is investigated. The optical and acoustic modes are observed clearly. We calculate the Helmholtz free energy(F), internal energy(E), entropy(S), and specific heat capacity(Cv) from the phonon density of states. Various optical parameters are also calculated. The reflectance spectrum shows that this compound has the potential to be used as an efficient solar reflector.

关键词： mAX compound phonon dispersion thermodynamical properties optical properties

Effect of Fiber Loadings and Treatment on Dynamic mechanical, Thermal and Flammability Properties of Pineapple Leaf Fiber and Kenaf Phenolic Composites

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Journal of Renewable materials 2018年第4期6卷 383-393页

作者： m.Asim m.Jawaid m.nasir N.Saba Laboratory of Biocomposite Technology Institute of Tropical Forestry and Forest Products(INTROP)Universiti Putra Malaysia43400 SerdangSelangorMalaysia Department of Chemical Engineering College of EngineeringKing Saud UniversityRiyadhSaudi Arabia Composite Wood Forest Product DivisionForest Research Institute248006 DehradunIndia

This study deals with the analysis of dynamic mechanical,thermal and flammability properties of treated and untreated pineapple leaf fiber(PALF)and kenaf fiber(KF)phenolic *** indicated that storage modulus was decreased for all composites with increases in temperature and pattern of slopes for all composites,having almost the same values of E′at glass transition temperature(Tg).The peak of the loss modulus of pure phenolic composites was shown to be much *** the addition of kenaf/PALF,peaks were higher and shifted towards a high *** Tan delta peak height was low for pure phenolic composites and maximum for 60%PALF phenolic ***-Cole analysis was carried out to understand the phase behavior of the composite *** analysis(TGA)results indicated that pure phenolic composites have better thermal stability than PALF and kenaf phenolic *** and horizontal UL-94 tests were conducted and showed pure phenolic resin is highly fire *** overall results showed that treated KF composites enhanced the dynamic mechanical and thermal properties among all PALF/KF composites.

关键词： Pineapple leaf fiber kenaf fiber phenolic resin dynamic mechanical analysis thermogravimetric analysis flammability

Effect of Cobalt Doping on the microstructure and Tensile Properties of Lead Free Solder Joint Subjected to Electromigration

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Journal of materials Science & Technology 2016年第11期32卷 1129-1136页

作者： m.nasir Bashir A.S.m.A.Haseeb Abu Zayed mohammad Saliqur Rahman m.A.Fazal Department of mechanical Engineering University of Malaya

Rapid Cu diffusion is one of the main causes of electromigration（Em） failure in lead-free solder *** this study, an effort has been made to investigate the detrimental effects of Em on microstructure and mechanical performance of solder joint by introducing Co nanoparticles（NP） doped flux at the interface between SAC305 solder and copper substrate. Em tests were conducted on un-doped SAC305 and Co-doped SAC305 solder joints for different time intervals, with the maximum duration of 1128 h. A DC current was applied to the both types of solder joints to achieve a current density of 1 × 104A/cm2. Em tests were performed in an oil bath maintained at a constant temperature of 80 °C. It is found that Codoped flux significantly reduced the formation of cracks and voids at the cathode interface. Co atoms entered into the lattice of Cu6Sn5 leading to the formation of（Cu, Co）6Sn5. This thermodynamically stabilized the interfacial intermetallic（ImC） layers both at the anode and cathode sides and suppressed the change in their thickness. The average anodic growth rate of（Cu, Co）6Sn5 interfacial ImC in the doped sample was about one order of magnitude lower compared with that of Cu6Sn5 in the un-doped ***-NP also improved the tensile strength considerably before and after Em. The report suggests that the reliability of solder joint during Em can be improved by using Co-NP doped flux.

关键词： Electromigration damages Tensile strength Intermetallic compounds Nanoparticles Reliability

Influence of thyroid volume reduction on absorbed dose in ^(131)I therapy studied by using Geant4 monte Carlo simulation

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Chinese Physics C 2014年第5期38卷 62-68页

作者： Ziaur Rahman Sikander m mirza Waheed Arshed nasir m mirza Waheed Ahmed Health Physics Division Pakistan Institute of Nuclear Science and Technology Department of Physics and Applied mathematics Pakistan Institute of Engineering and Applied Sciences

A simulation study has been performed to quantify the effect of volume reduction on the thyroid absorbed dose per decay and to investigate the variation of energy deposition per decay due to β- and γ-activity of 131I with volume/mass of thyroid, for water, ICRP- and ICRU-soft tissue taken as thyroid material. A monte Carlo model of the thyroid, in the Geant4 radiation transport simulation toolkit was constructed to compute the β- and γ-absorbed dose in the simulated thyroid phantom for various values of its volume. The effect of the size and shape of the thyroid on energy deposition per decay has also been studied by using spherical, ellipsoidal and cylindrical models for the thyroid and varying its volume in 1-25 cm3 range. The relative differences of Geant4 results for different models with each other and mCNP results lie well below 1.870%. The maximum relative difference among the Geant4 estimated results for water with ICRP and ICRU soft tissues is not more than 0.225%. S-values for ellipsoidal, spherical and cylindrical thyroid models were estimated and the relative difference with published results lies within 3.095%. The absorbed fraction values for beta particles show a good agreement with published values within 2.105% deviation. The Geant4 based simulation results of absorbed fractions for gammas again show a good agreement with the corresponding mCNP and EGS4 results （±6.667%） but have 29.032% higher values than that of mIRD calculated values. Consistent with previous studies, the reduction of the thyroid volume is found to have a substantial effect on the absorbed dose. Geant4 simulations confirm dose dependence on the volume/mass of thyroid in agreement with mCNP and EGS4 computed values but are substantially different from mIRD8 data. Therefore, inclusion of size/mass dependence is indicated for 131I radiotherapy of the thyroid.

关键词： mean absorbed dose rate Geant4 monte Carlo simulation and 131I therapy

Tuning structural,electrical,dielectric and magnetic properties of mg-Cu-Co ferrites via dysprosium(Dy^(3+))doping

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Journal of Rare Earths 2024年第1期42卷 137-146,I0005页

作者： maria Akhtar m.S.Hasan nasir Amin N.A.morley muhammad Imran Arshad Department of Physics Government College UniversityFaisalabad38000Pakistan Department of Physics The University of Lahore53700Pakistan Department of materials Science and Engineering The University of SheffieldS13JDUK Department of Physics&Astronomy University College LondonUK

In current research work,Dy3+substituted mg0.5Cu0.25Co0.25Fe2-xDyxO4(0.0≤x≤0.04 with the step interval of 0.01)soft ferrites were synthesized by the sol-gel auto combustion *** prepared samples were characterized by the techniques using X-ray diffraction(XRD),scanning electron microscopy(SEm),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared(FTIR)spectroscopy,curre nt-voltage(Ⅰ-Ⅴ)measurement,LCR meter,vibrating sample magnetometer(VSm)and *** data reveal that the average crystallite size is 49.71 nm and the lattice constant is 0.83703 nm for sample x=*** non-uniform grain growth was demonstrated by micrographs and impurity-free elemental composition was observed from EDX *** DC resistivity has an increasing and decreasing trend in ferromagnetic and paramagnetic regions with an increase in ***,the high resistivity is observed with the order of 1010Ω·cm,and the activation energy is 0.944 eV for samples x=*** dielectric parameters including dielectric constant,dielectric losses,and impedance gradually decrease with the increase in frequency from 8 Hz to 8 *** minimum dielectric loss at high frequency is found for sample x=*** coercivity(Hc)and saturation magnetization(ms)are found in the ranges of 520.82-544.02 Oe and 20.5841-21.1473 emu/g,*** observations confirm that dysprosium(x=0.03)doped mCC-soft ferrites may be applicable in transformer cores,microwave absorbance,and telecommunication devices.

关键词： Soft ferrites DC resistivity Dielectric loss Impedance Coercivity Rare earths

mixed convectional and chemical reactive flow of nanofluid with slanted mhd on moving permeable stretching/shrinking sheet through nonlinear radiation,energy omission

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Chinese Physics B 2024年第5期33卷 193-202页

作者： Saleem nasir Sekson Sirisubtawee Pongpol Juntharee Taza Gul Department of mathematics Faculty of Applied ScienceKing Mongkut's University of Technology North BangkokBangkok 10800Thailand Department of mathematics City University of Science and Information TechnologyPeshawarPakistan

Hybrid nanofluids are remarkable functioning liquids that are intended to reduce the energy loss while maximizing the heat *** the involvement of suction and nonlinear thermal radiation effects,this study attempted to explore the energy transmission features of the inclined magnetohydrodynamic(mhd)stagnation flow of CNTs-hybrid nanofluid across the nonlinear permeable stretching or shrinking *** work also included some noteworthy features like chemical reactions,variable molecular diffusivity,quadratic convection,viscous dissipation,velocity slip and heat omission *** appropriate similarity components,the model equations were modified to ODEs and computed by using the HAm *** impact of various relevant flow characteristics on movement,heat and concentration profiles was investigated and plotted on a *** various model factors,the significance of drag friction,heat and mass transfer rate were also computed in tabular and graphical *** leads to the conclusion that such factors have a considerable impact on the dynamics of fluid as well as other engineering measurements of ***,viscous forces are dominated by increasing the values ofλ_(p),δ_(m)andδ_(q),and as a result,F(ξ)accelerates while the opposite trend is observed for m andφ.The drag friction is boosted by the augmentation m,λ_(p)andφ,but the rate of heat transfer *** to our findings,hybrid nanoliquid effects dominate that of ordinary nanofluid in terms of F(ξ),Θ(ξ)andφ(ξ)*** HAm and the numerical technique(shooting method)were found to be in good agreement.

关键词： hybrid nanofluid(SWCNT+mWCNT/H_(2)O) velocity slip conditions nonlinear thermal radiation exponential stretching/shrinking sheet inclined magnetohydrodynamic(mhd)stagnation flow

Structural, elastic, and electronic properties of recently discovered ternary silicide superconductor Li_2IrSi_3: An ab-initio study

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Chinese Physics B 2015年第11期24卷 478-482页

作者： m.A.Hadi m.A.Alam m.Roknuzzaman m.T.nasir A.K.m.A.Islam S.H.Naqib Department of Physics University of Rajshahi Department of Physics Rajshahi University of Engineering and Technology Department of Physics Jessore University of Science and Technology International Islamic University Chittagong

The structural, elastic, and electronic properties of the very recently discovered ternary silicide superconductor, Li2IrSi3, are calculated using an ab-initio technique. We adopt the plane-wave pseudopotential approach within the frame- work of the first-principles density functional theory （DFT） implemented by the CASTEP code. The calculated structural parameters show reasonable agreement with the experimental results. The elastic moduli of this interesting material are calculated for the first time. The electronic band structure and electronic energy density of states indicate the strong cova- lent Ir-Si and Si-Si bonding, which leads to the formation of the rigid structure of Li2IrSi3. Strong covalency gives rise to a high Debye temperature in this system. We discuss the theoretical results in detail in this paper.

关键词： silicide superconductor crystal structure elastic properties electronic structures