检索结果-南通市图书馆

Fluid Dynamics & materials Processing 2020年第3期16卷 441-463页

作者： Latifa m.Al-Balushi m.m.rahman Department of mathematics College of ScienceSultan Qaboos UniversityMuscatOman

In the present paper,the effect of the heat flux distribution on the natural convective flow inside a square cavity in the presence of a sloping magnetic field and magnetic nanoparticles is explored *** nondimensional governing equations are solved in the framework of a finite element method implemented using the Galerkin *** role played by numerous model parameters in influencing the emerging thermal and concentration fields is examined;among them are:the location of the heat source and its lengthH,the magnitude of the thermal Rayleigh number,the nanoparticles shape and volume fraction,and the Hartmann *** is found that the nanofluid velocity becomes higher when the thermal source length,the nanoparticles volume fraction and/or the thermal Rayleigh number are increased,while it decreases as the Hartmann number Ha grows and the position of the heat source moves toward the center of the lower wall of the ***,the temperature of the nanofluid grows with the extension of the thermal source and decreases slowly when the heat flux position moves toward the center of the lower *** outcomes of the research also indicate that the average Nusselt number becomes smaller on increasing Hartmann number Ha and heat source length H^(*).The addition of Fe_(3)O_(4) to engine oil leads to a higher rate of heat transfer with respect to the addition of SiO_(2) ***-shaped nanoparticles generate the highest value of the Nusselt number compared to all the other considered shapes.

关键词： Nanofluids magnetic nanoparticles heat source natural convection finite element method square enclosure

Cylindrical and Spherical Electron-Acoustic Shock Waves in Electron-Positron-Ion Plasmas with Nonextensive Electrons and Positrons

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2015年第2期63卷 243-248页

作者： A.Rafat m.m.rahman m.S.Alam A.A.mamun Department of Physics Jahangirnagar University

Electron-acoustic shock waves(EASWs) in an unmagnetized four-component plasma(containing hot electrons and positrons following the q-nonextensive distribution, cold mobile viscous electron fluid, and immobile positive ions) are studied in nonplanar(cylindrical and spherical) geometry. With the help of the reductive perturbation method,the modified Burgers equation is derived. Analytically, the effects of nonplanar geometry, nonextensivity, relative number density and temperature ratios, and cold electron kinematic viscosity on the basic properties(viz. amplitude, width,speed, etc.) of EASWs are discussed. It is examined that the EASWs in nonplanar geometry significantly differ from those in planar geometry. The results of this investigation can be helpful in understanding the nonlinear features of EASWs in various astrophysical plasmas.

关键词：天体等离子体正电子圆柱形正负电子对球形 Burgers方程震波几何形状

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

在线全文

学校读者我要写书评

暂无评论

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

Natural convective heat transfer in a square enclosure utilizing magnetic nanoparticles

在线全文

学校读者我要写书评

暂无评论

Propulsion and Power Research 2019年第3期8卷 194-209页

作者： Latifa m.Al-Balushi m.J.Uddin m.m.rahman Department of mathematics College of ScienceSultan Qaboos UniversityP.O.Box 36Al-KhodP.C.123MuscatSultanate of Oman Department of General Educational Development Daffodil International University102 ShukrabadDhanmondiDhaka 1207Bangladesh

In the present paper,unsteady natural convective heat transfer flow inside a square enclosure filled with nanofluids containing magnetic nanoparticles using nonhomogeneous dynamic model is investigated *** horizontal top wall of the enclosure is considered a colder wall and the bottom wall is maintained at uniform temperature whereas two other vertical walls of the cavity are thermally *** Galerkin weighted residual finite element method has been used to solve the governing non-dimensional partial differential *** numerical simulations,four types of nanoparticles such as magnetite(Fe_(3)O_(4)),cobalt ferrite(CoFe_(2)O_(4)),mn-Zn ferrite(mn-ZnFe_(2)O_(4)),and silicon dioxide(SiO2),and three types of base fluids such as water(H_(2)O),engine oil(EO)and kerosene(Ke)have been *** with previously published work are performed and excellent agreement is *** effects of various model parameters such as thermal Rayleigh number,nanoparticles volume fraction and nanoparticles shape factor are *** results show that the average Nusselt number increases as the thermal Rayleigh number and nanoparticles volume fraction *** results indicate that the average Nusselt numbers are higher for the blade shape of nanoparticles.

关键词： Nanofluids Nanoparticles Heat transfer Natural convection Square enclosure Finite element method

Numerical Simulations of Hydromagnetic mixed Convection Flow of Nanofluids inside a Triangular Cavity on the Basis of a Two-Component Nonhomogeneous mathematical model

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Fluid Dynamics & materials Processing 2021年第1期17卷 1-20页

作者： Khadija A.Al-Hassani m.S.Alam m.m.rahman Department of mathematics College of ScienceSultan Qaboos UniversityMuscatOman Department of mathematics Jagannath UniversityDhakaBangladesh

Nanofluids have enjoyed a widespread use in many technological applications due to their peculiar *** simulations are presented about the unsteady behavior of mixed convection of Fe_(3)O_(4)-water,Fe_(3)O_(4)-kerosene,Fe_(3)O_(4)-ethylene glycol,and Fe_(3)O_(4)-engine oil nanofluids inside a lid-driven triangular *** particular,a two-component non-homogeneous nanofluid model is *** bottom wall of the enclosure is insulated,whereas the inclined wall is kept a constant(cold)temperature and various temperature laws are assumed for the vertical wall,namely:θ=1(Case 1),θ=Yð1YÞ(Case 2),andθ=sinð2-YÞ(Case 3).A tilted magnetic field of uniform strength is also present in the fluid *** a numerical point of view,the problem is addressed using the Galerkin weighted residual finite element *** role played by different parameters is assessed,discussed critically and interpreted from a physical *** find that a higher aspect ratio can produce an increase in the average Nusselt ***,the Fe_(3)O_(4)-EO and Fe_(3)O_(4)-H2O nanofluids provide the highest and smallest rate of heat transfer,respectively,for all the considered(three variants of)thermal boundary conditions.

关键词： Nanofluid mixed convection lid-driven triangular cavity finite element method

Deposition behavior and tribological properties of diamond-like carbon coatings on stainless steels via chemical vapor deposition

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of minerals,metallurgy and materials 2018年第11期25卷 1335-1343页

作者： Labani mustafi m.m.rahman mohammad Nur E Alam Al Nasim mohammad Asaduzzaman Chowdhury m.H.monir School of materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China School of Engineering RMIT UniversityMelbourneVictoria 3001Australia Dhaka University of Engineering and Technology Gazipur 1707Bangladesh

A systematic investigation was carried out to observe the deposition rate of a diamond-like carbon(DLC) coating on two stainless steel substrates by chemical vapor deposition(CVD). The objective of this research is to study the deposition behavior of the DLC coating and its tribological properties in different combinations of methane(CH_4) and nitrogen, which were used as precursor gases. The results reveal that the deposition rate increases with increasing CH_4 content up to 50 vol%. The hardness of the DLC-deposited layer also increases while the friction coefficient decreases with increasing CH_4 gas content up to 50% in the precursor gas mixture.

关键词： diamond-like carbon chemical vapor deposition methane and nitrogen gas mixtures deposition rate hardness friction coefficient

Statistical model for Impact and Energy Absorption of 3D Printed Coconut Wood-PLA

在线全文

学校读者我要写书评

暂无评论

Energy Engineering 2021年第5期118卷 1305-1315页

作者： J.Kananathan m.Samykano K.Kadirgama D.Ramasamy m.m.rahman Green Kingdom Solutions Sdn.Bhd. Taman Salak SelatanKuala Lumpur57100Malaysia College of Engineering Universiti Malaysia PahangGambangPahang26300Malaysia Faculty of mechanical&Automotive Engineering Technology Universiti Malaysia PahangPekanPahang26600Malaysia

Fused deposition modeling(FDm)-3D printing has been the favored technology to build functional components in various *** present study investigates infill percentage and infill pattern effects on the printed parts’impact properties through the 3D printing technique using coconut wood-filled PLA *** models are also proposed in the present study with the aim for future property *** to the ASTm standard,fifteen specimens with different parameter combinations were printed using a low-cost FDm 3D printer to evaluate their impact *** analysis was performed using mINITAB to validate the experimental data and model *** experimental outcomes reveal the honeycomb pattern with 75%infill density achieves the highest energy absorption(0.837 J)and impact energy(5.1894 kJ/m^(2)).The p-value from statistical analysis clearly shows that all the impact properties are less than the alpha value of 0.05,suggesting all the properties are vital to determine the impact *** validation process affirms that the generated mathematical model for the energy absorbed and the impact energy is reliable at an acceptable level to predict their respective *** errors between the experimental value and the predicted value are 3.98%for the energy absorbed and 4.06%for impact *** findings are expected to provide insights on the impact behavior of the coconut wood-filled PLA composites prepared by FDm-3D printing and a mathematical model to predict the impact properties.

关键词： Impact energy energy absorption response surface methodology coconut wood ANOVA

Effects of multiple shapes for steady flow with transformer oil+Fe_(3)O_(4)+TiO_(2) between two stretchable rotating disks

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied mathematics and mechanics(English Edition) 2024年第2期45卷 373-388页

作者： m.rahman m.TURKYILmAZOGLU Z.mUSHTAQ Department of mathematics Mirpur University of Science and TechnologyMirpur 10250Pakistan Department of mathematics Hacettepe UniversityBeytepeAnkara 06532Turkiye

In this study,we examine the effects of various shapes of nanoparticles in a steady flow of hybrid nanofluids between two stretchable rotating *** steady flow of hybrid nanofluids with transformer oil as the base fluid and Fe_(3)O_(4)+TiO_(2)as the hybrid nanofluid is *** shapes of Fe_(3)O_(4)+TiO_(2)hybrid nanofluids,including sphere,brick,blade,cylinder,and platelet,are *** shape exists in the same volume of a *** leading equations(partial differential equations(PDEs))are transformed to the nonlinear ordinary differential equations(ODEs)with the help of similarity *** system of equations takes the form of ODEs depending on the boundary conditions,whose solutions are computed numerically by the bvp4c mATLAB *** outputs are compared with the previous findings,and an intriguing pattern is discovered,such that the tangential velocity is increased for the rotation parameter,while it is decreased by the stretching values because of the lower *** the reaction rate parameter,the concentration boundary layer becomes shorter,and the activation energy component increases the rate at which mass transfers come to the higher disk but have the opposite effect on the bottom *** ranges of various parameters taken into account are Pr=6.2,Re=2,m=1.0,φ_(1)=φ_(2)=0.03,K=0.5,S=-0.1,Br=0.3,Sc=2.0,α_(1)=0.2,γ=0.1,E_(n)=2.0,and q=1.0,and the rotation factor K is within the range of 0 to 1.

关键词： transformer oil Brinkman number skin friction coefficient double rotating disk Nusselt number Sherwood number

APPLICABILITY OF THE BEND DEVELOPmENT THEORY IN NATURAL ALLUVIAL RIVERS

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2002年第3期17卷 211-219页

作者： m.m.rahman m.A.HAQUE m.m.HOQUE Assistant Professor Associate Professor Bangladesh Bangladesh University of Engineering and Technology(BUET) Dhaka-1000 Institute of WAter and Flood management(IWFm) the same as above.

The theoretical conditions for the bend development or attenuation have been reviewed and tested for a study reach of the meghna river. The field observations in the natural alluvial meander do not support the theories developed for bend development. The limitations of the theory to apply in the natural meandering river are discussed.

关键词： Theoretical conditions Bend development or attenuation The meghna River Natural meandering river

Enhancement of coercivity,permeability,and dielectric properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites for memory and high frequency devices

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第6期42卷 1128-1135,I0005页

作者： I.Sardar m.D.Hossain m.S.Sikder m.N.I.Khan m.R.rahman Physics Discipline Khulna UniversityKhulna9208Bangladesh Department of Physics Khulna University of Engineering&TechnologyKhulna9203Bangladesh Department ofComputer Science and Engineering Northern University of Business&Technology KhulnaKhulna9100Bangladesh material Science Division Atomic Energy CentreDhaka1000Bangladesh

Spinel cubic ferrites have huge applications in me mory and high frequency *** the improvement of these modern devices,the magnetic coercivity,permeability,and dielectric properties of a ferrite are the important *** article focuses on improving the magnetic coercivity,magnetic permeability,and dielectric properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ferrites,where x=0.00,0.06,and *** X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscopy(FESEm),energy dispersive X-ray(EDX),vibrating sample magnetometer(VSm),and an impedance analyzer were used to characterize the structural,magnetic,and dielectric properties of the *** XRD patterns indicate the formation of spinel cubic structure of the samples with a secondary peak(EuFeO_(3))for Eu doped *** densities and porosities of the samples follow an inverse trend,where the doped samples’lattice parameters are increased with the increment of rare earth Eu *** FTIR analysis also proves the spinel cubic phase of the *** average grain size of the ferrites is obtained via FESEm images,and it is increased from 121 to 198 *** analysis confirms that doping of the Eu content also changes other hysteresis loop properties of Co_(0.2)Zn_(0.3)Ni_(0.5)Eu_(x)Fe_(2-x)O_(4) ***,the coercivity of the Eu doped samples is greater than that of the mother alloy(x=0.00).The EDX study shows that there is no impurity contamination in the *** permeability and dielectric measurements show an improved quality factor of the Eu-doped samples with low magnetic and dielectric *** dependent resistivity and impedance analysis also show the improved *** the observed properties of the samples,all the investigated ferrites might be strong candidates for potential applications in memory devices,magnetic sensors,and high frequency applications.

关键词： Ferrites Raree arths Coercivity Permeability EDX Resistivity