Showing papers in "Canadian Journal of Physics in 2010"
TL;DR: In this paper, a mathematical model for the two-dimensional boundary layer flow of an Oldroyd-B fluid is presented, where the obtained partial differential equations are reduced to an ordinary differential equation by a suitable transformation.
Abstract: In this paper, the mathematical model for the two-dimensional boundary layer flow of an Oldroyd-B fluid is presented. The developed equations are used to discuss the problem of two-dimensional flow in the region of a stagnation point over a stretching sheet. The obtained partial differential equations are reduced to an ordinary differential equation by a suitable transformation. The obtained equation is then solved using a finite difference method. The influence of the pertinent fluid parameters on the velocity is discussed through graphs. The behaviour of f ″(0) is also investigated with changes in parameter values. It is observed that an increase in the relaxation time constant causes a reduction in the boundary layer thickness. To the best of our knowledge, this type of solution for an Oldroyd-B fluid is presented for the first time in the literature.
77 citations
TL;DR: Temperatures in the mesosphere and lower thermosphere region (MLT) have been derived from the Optical Spectrograph and InfraRed Imaging System (OSIRIS) observations of O2 A-band (b1Σg++X3Σ g+O-O emis... as mentioned in this paper.
Abstract: Temperatures in the mesosphere – lower thermosphere region (MLT) have been derived from the Optical Spectrograph and InfraRed Imaging System (OSIRIS) observations of O2 A-band (b1Σg+–X3Σg–)O–O emis...
52 citations
TL;DR: In this paper, the authors derived the electro-conducting thermofluid equation of heat transfer with one relaxation time and applied the governing coupled equations in the frame of the boundary layer model to Stokes' first problem with heat sources.
Abstract: This work is related to the flow of an electro-conducting micropolar fluid presenting thermoelectric properties effect in the presence of a magnetic field. The electro-conducting thermofluid equation of heat transfer with one relaxation time is derived. The flow of an electro-conducting micropolar fluid over a plate that is moved suddenly is considered. The governing coupled equations in the frame of the boundary-layer model are applied to Stokes' first problem with heat sources. Laplace-transform and Fourier-transform techniques are used to obtain the solution. The inverses of the Fourier transforms are obtained analytically. The Laplace transforms are obtained using the complex inversion formula of the transform together with Fourier-expansion techniques. Numerical results for the temperature distribution, the velocity, and the microrotation components are represented graphically. Thermoelectric figure-of-merit, Seebeck and Peltier effects on a micropolar fluid are studied.
43 citations
TL;DR: In this article, the authors examined the energy problem in General Relativity using approximate Lie symmetry methods for differential equations and concluded that energy must be re-scaled by some factor in the second-order approximation.
Abstract: This paper examines the energy problem in General Relativity using approximate Lie symmetry methods for differential equations. We evaluate second-order approximate symmetries of the geodesic equations for the stringy charged black hole solutions. We conclude that energy must be re-scaled by some factor in the second-order approximation.
42 citations
TL;DR: In this article, an experiment comparing examinations of concepts using slightly modified peer instruction (MPI) interventions with a conceptual conflict strategy based on collaborative groups (CG), four interventions were utilized in two sections of an introductory physics course for science students.
Abstract: We report on an experiment comparing examinations of concepts using slightly modified peer instruction (MPI) interventions with a conceptual conflict strategy based on collaborative groups (CG). Four interventions were utilized in two sections of an introductory physics course for science students. Both instructors and strategies were alternated in the two classes so that instructor dependence could be factored out and so that each class could serve as both an experimental and a control group. The gain on the Force Concept Inventory (FCI) used as a pre- and post-test is essentially the same in both classes. The instructors were experienced in use of MPI, but this was the first time that these instructors had used a collaborative group activity in their classes and only used it for the two interventions in each class described in this paper. CG appears to be more effective as a teaching method than PI. It also should be noted that the effectiveness of both teaching methods seems to be instructor independen...
39 citations
TL;DR: A complete exposition of the rest-frame instant form of dynamics for arbitrary isolated systems (particles, fields, strings, fluids) admitting a Lagrangian description is given in this paper.
Abstract: A complete exposition of the rest-frame instant form of dynamics for arbitrary isolated systems (particles, fields, strings, fluids) admitting a Lagrangian description is given. The starting point ...
31 citations
TL;DR: In this paper, a collective variable associated with the internal 3-center of mass on the instantaneous 3-spaces, to be eliminated with the constraints K(int)≈0.
Abstract: In this second paper, we complete the classical description of an isolated system of “charged positive-energy particles, with Grassmann-valued electric charges and mutual Coulomb interaction, plus a transverse electromagnetic field” in the rest-frame instant form of dynamics. In particular, we show how to determine a collective variable associated with the internal 3-center of mass on the instantaneous 3-spaces, to be eliminated with the constraints K(int)≈0. Here, K(int) is the Lorentz boost generator in the unfaithful internal realization of the Poincare group and its vanishing is the gauge-fixing to the rest-frame conditions P(int)≈0. We show how to find this collective variable for the following isolated systems: (a) charged particles with a Coulomb plus Darwin mutual interaction; (b) transverse radiation field; (c) charged particles with a mutual Coulomb interaction plus a transverse electro-magnetic field. Then we define the Dixon multipolar expansion for the open particle subsystem. We also define ...
28 citations
TL;DR: In this article, the classical antiferromagnet MnF2 was used as a perfect demonstration system for teaching a remarkably wide variety of neutron scattering concepts, such as the nature of antiferrous magnetism and the properties of magnetism.
Abstract: We present the classical antiferromagnet MnF2 as a perfect demonstration system for teaching a remarkably wide variety of neutron scattering concepts. The nature of antiferromagnetism and the magne...
26 citations
TL;DR: In this article, the formation energies of these and other intrinsic defects in CuAlO2 using GGA+U calculations were investigated, and it was shown that the potential alignment and image charge correction are required in the calculation of defect formation energies by using the supercell approach.
Abstract: Intrinsic defects, including vacancies at the Cu and Al sites (VCu and VAl), substitutional Cu at the Al site (CuAl), and interstitial O (Oi), have been proposed to be responsible for the p-type conductivity in CuAlO2. We have investigated the formation energies of these and other intrinsic defects in CuAlO2 using GGA+U calculations. Our results support previous studies that the potential alignment and image charge correction are required in the calculation of defect formation energies by using the supercell approach. In CuAlO2, these p-type defects (VCu, VAl, CuAl, and Oi) invariably have lower formation energies than their n-type counterparts. Particularly, VCu and CuAl have the lowest formation energies among intrinsic defects, and therefore are most likely responsible for the p-type conductivity. However, the transition levels of the VCu and CuAl defects are deep, which are responsible for the poor p-type conductivity in CuAlO2.
26 citations
TL;DR: In this paper, the authors discuss the thermodynamics of a closed system using classical approaches and find that essential cosmological quantities, such as the Hubble parameter H, the scaling factor a, and the curvature parameter k, can be derived from this simple model, which on one hand fulfills and entirely obeys the laws of thermodynamics, and on the other hand its results are compatible with the Friedmann-Robertson-Walker model and the Einstein field equations.
Abstract: Assuming that the matter in the background geometry is a free gas and that no phase transitions were occurring in the early Universe, we discuss the thermodynamics of this closed system using classical approaches. We find that essential cosmological quantities, such as the Hubble parameter H, the scaling factor a, and the curvature parameter k, can be derived from this simple model, which on one hand fulfills and entirely obeys the laws of thermodynamics, and on the other hand, its results are compatible with the Friedmann–Robertson–Walker model and the Einstein field equations. Including a finite bulk viscosity coefficient leads to important changes in all these cosmological quantities. Accordingly, our picture about the evolution of the Universe and its astrophysical consequences seems to undergoing a radical revision. We find that k strongly depends on the thermodynamics of background matter. The time scale at which negative curvature might take place depends on the relation between the matter content ...
23 citations
TL;DR: In this paper, the stability of a class of discrete-time stochastic neural networks with mixed-time delays and impulsive effects was investigated and sufficient conditions were derived to ensure the global asymptotic stability of the equilibrium point.
Abstract: This paper investigates the stability issues for a class of discrete-time stochastic neural networks with mixed time delays and impulsive effects. By constructing a new Lyapunov–Krasovskii functional and combining with the linear matrix inequality (LMI) approach, a novel set of sufficient conditions are derived to ensure the global asymptotic stability of the equilibrium point for the addressed discrete-time neural networks. Then the result is extended to address the problem of robust stability of uncertain discrete-time stochastic neural networks with impulsive effects. One important feature in this paper is that the stability of the equilibrium point is proved under mild conditions on the activation functions, and it is not required to be differentiable or strictly monotonic. In addition, two numerical examples are provided to show the effectiveness of the proposed method, while being less conservative.
TL;DR: In this article, the characteristics of the Rayleigh flow problem of a rarified electron gas extracted from neutral atoms is examined and proved to obey the entropic properties of irreversible thermodynamics.
Abstract: In the framework of irreversible thermodynamics, the characteristics of the Rayleigh flow problem of a rarified electron gas extracted from neutral atoms is examined and proved to obey the entropic...
TL;DR: In this paper, the effect of the fall in the SENSEX in the Indian stock market for the period Jan 2003-Dec 2009 was studied using the multifractal detrended fluctuation analysis (MFDFA) approach.
Abstract: The fluctuation of SENSEX in the Indian stock market for the period Jan 2003–Dec 2009 is studied using the multifractal detrended fluctuation analysis (MFDFA) approach. The effect of the fall in th...
TL;DR: In this paper, the flow problem of an incompressible axisymmetrical quasisteady translation and steady rotation of a porous spheroid in a concentric spherical container is studied analytically.
Abstract: The flow problem of an incompressible axisymmetrical quasisteady translation and steady rotation of a porous spheroid in a concentric spheroidal container are studied analytically. The same small departure from a sphere is considered for each spheroidal surface. In the limit of small Reynolds number, the Brinkman equation for the flow inside the porous region and the Stokes equation for the outside region in their stream functions formulations and velocity components, which are proportional to the translational and angular velocities, respectively, are used. Explicit expressions are obtained for both inside and outside flow fields to the first order in a small parameter characterizing the deformation of the spheroidal surface from the spherical shape. The hydrodynamic drag force and couple exerted on the porous spheroid are obtained for the special cases of prolate and oblate spheroids in closed forms. The dependence of the normalized wall-corrected translational and rotational mobilities on permeability ...
TL;DR: In this paper, the Soret and Dufour effects on a mixed convective mass transfer flow past an infinite vertical porous plate with transverse sinusoidal suction velocity in presence of a uniform transverse magnetic field have been studied analytically.
Abstract: In this paper, the Soret and Dufour effects on a mixed convective mass transfer flow past an infinite vertical porous plate with transverse sinusoidal suction velocity in presence of a uniform transverse magnetic field have been studied analytically. The magnetic Reynolds number is assumed to be so small that the induced magnetic field can be neglected. The nondimensional equations governing the flow and heat and mass transfer are solved by regular perturbation technique, on the assumption that the solution consists of two parts: a mean part and a perturbed part. The expressions for the velocity, temperature and concentration fields, skin friction at the plate in the direction of the free stream, Nusselt number and Sherwood number at the plate, and the current density are obtained in nondimensional forms. The effects of the Hartmann number M, the Soret number Sr, the Dufour number Du, the Reynolds number Re, Schmidt number Sc, and the Prandtl number Pr on the flow and transport characteristics are discuss...
TL;DR: In this article, the Fourier cosine and Laplace transforms were used to study the unsteady flow of an incompressible generalized Oldroyd-B fluid induced by an infinite plate subject to a time-dependent shear-stress.
Abstract: The unsteady flow of an incompressible generalized Oldroyd-B fluid induced by an infinite plate subject to a time-dependent shear-stress is studied by means of the Fourier cosine and Laplace transforms. The solutions that have been obtained, written under integral and series form in terms of the generalized Ga,b,c(·,t) functions, are presented as a sum of the Newtonian solutions and the corresponding non-Newtonian contributions. They satisfy all imposed initial and boundary conditions, and for λ and λr → 0 reduce to the Newtonian solutions. Furthermore, the similar solutions for generalized Maxwell fluids as well as those for ordinary fluids are also obtained as limiting cases of general solutions. Finally, to reveal some relevant physical aspects of the obtained results, the diagrams of the velocity field v(y, t) have been depicted against y for different values of t and of the material and fractional parameters.
TL;DR: In this paper, the growth of a vapour bubble in superheated water for two-phase turbulent flow is studied, and the growth problem is formulated by mass and momentum equations under physical assumptions between two finite boundaries.
Abstract: In this paper, the growth of a vapour bubble in superheated water for two-phase turbulent flow is studied. The growth problem is formulated by mass and momentum equations under physical assumptions between two finite boundaries. The analytical solution is obtained in terms of the vapour bubble radius. The bubbly growth is affected by thermal diffusivity, superheating, and the Peclet number. The fact that the scale of the bubble is larger than the scale of the turbulence in the mixture surrounding the growing bubble is considered. The previous models of growth for laminar flow are obtained as a special cases of the present model for some values of the parameters a, b, n, and φ0, respectively.
TL;DR: The magnetic structure of FeCrAs, which crystallizes in space group P6¯2m and is isostructural to Fe2P, was determined by constant wav... as mentioned in this paper.
Abstract: FeCrAs undergoes a magnetic ordering transition at TN ≃ 125 K. The magnetic structure of FeCrAs, which crystallizes in space group P6¯2m and is isostructural to Fe2P, was determined by constant wav...
TL;DR: In this paper, the authors considered the integrability of the compound Korteweg-de Vries (KdV)-Burgers equation with variable coeffi-cients (vcc-kdV-B) that describes the propagation of undulant bores in shallow water with certain dissipative effects.
Abstract: We consider the solutions of the compound Korteweg-de Vries (KdV)-Burgers equation with variable coeffi- cients (vccKdV-B) that describe the propagation of undulant bores in shallow water with certain dissipative effects. The Weiss-Tabor-Carnevale (WTC)-Kruskal algorithm is applied to study the integrability of the vccKdV-B equation. We found that the vccKdV-B equation is not Painleveintegrable unless the variable coefficients satisfy certain constraints. We used the outcome of the truncated Painleveexpansion to construct the Backlund transformation, and three families of new analytical solutions for the vccKdV -B equation are obtained. The dispersion relation and its characteristics are illus- trated. The stability for the vccKdV-B equation is analyzed by using the phase portrait method. PACS Nos: 47.35.Bb, 47.35.Fg, 91.30.Fn Resume´ : Nous etudions les solutions de l'equation composee KdV-Burgers avec coefficients variables (vccKdV-B) qui decrit la propagation de mascarets ondulants dans l'eau de faible profondeur en presence de certains effets dissipatifs. Nous utilisons l'algorithme Weiss-Tabor-Carnevale (WTC)-Kruskal de facon a verifier l'integrabilitede l'equation vccKdV-B. Nous trouvons que l'equation vccKdV-B n'est pas integrable au sens de Painleve ´ ,amoins que les coefficients variables satisfassent certaines contraintes. Nous utilisons l'expansion tronquee de Painlevepour construire la transforma- tion de Backlund et nous obtenons trois familles de nouvelles solutions analytiques de l'equation vccKdV-B. Nous decri- vons la relation de dispersion et ses caracteristiques et etudions la stabilitede l'equation vccKdV-B par la methode du portrait de phase. (Traduit par la Redaction)
TL;DR: In this paper, the theory of two-temperature thermoelasticity for a piezoelectric/piezomagnetic materials is formulated and an equation of energy balance is introduced and the uniqueness theorem is proved.
Abstract: In the present work, the theory of two-temperature thermoelasticity for a piezoelectric/piezomagnetic materials is formulated. An equation of energy balance is introduced and the uniqueness theorem is proved. An integral identity that involves two admissible processes at two different instants is introduced and the reciprocity theorem is proved without using Laplace transform. The variational principle of Gurtin type is established.
TL;DR: In this article, two dynamic equations referring to a weakly nonlinear and weakly dispersive flow of a gas in which molecular vibrational relaxation takes place, are derived, and the final dynamic equations are instantaneous; they include a quadratic nonlinear acoustic source, reflecting the nonlinear character of interaction of low-frequency acoustic and non-acoustic motions of the fluid.
Abstract: Two dynamic equations referring to a weakly nonlinear and weakly dispersive flow of a gas in which molecular vibrational relaxation takes place, are derived. The first one governs an excess temperature associated with the thermal mode, and the second one describes variations in vibrational energy. Both quantities refer to non-wave types of gas motion. These variations are caused by the nonlinear transfer of acoustic energy into thermal mode and internal vibrational degrees of freedom of a relaxing gas. The final dynamic equations are instantaneous; they include a quadratic nonlinear acoustic source, reflecting the nonlinear character of interaction of low-frequency acoustic and non-acoustic motions of the fluid. All types of sound, periodic or aperiodic, may serve as an acoustic source of both phenomena. The low-frequency sound is considered in this study. Some conclusions about temporal behavior of non-acoustic modes caused by periodic and aperiodic sound are made. Under certain conditions, acoustic cool...
TL;DR: In this article, the problem of a nonrelativistic quantum particle moving on a real line with an idealized and local-ized singular interaction with zero range at x = 0 (i.e., a point interaction there) was studied.
Abstract: We study the problem of a nonrelativistic quantum particle moving on a real line with an idealized and local- ized singular interaction with zero range at x = 0 (i.e., a point interaction there). This kind of system can be described in two ways: (i) by considering an alternative free system (i.e., without the singular potential) but excluding the point x =0 (In this case, the point interaction is exclusively encoded in the boundary conditions.) and (ii) by explicitly considering the singular interaction by means of a local singular potential. In this paper we relate, compare, and discuss, in a simple and pedagogical way these two equivalent approaches. Our main goal in this paper is to introduce the essential ideas about point interactions in a very accesible form to advanced undergraduates.
TL;DR: In this paper, the energy transport due to a laser short pulse is formulated using the electron kinetic theory approach, and the results obtained from the analytical solutions for temperature distributions are in good agreement with the experimental data.
Abstract: The present study describes the modeling of short-pulse laser heating of gold and copper materials. The energy transport due to a laser short pulse is formulated using the electron kinetic theory approach. Electron and lattice temperature distributions inside the substrate material during the laser short pulse are formulated analytically. In the analysis, the Laplace transformation technique is used. The results obtained from the analytical solutions are compared with numerical predictions and experimental data. It is found that the results obtained from the numerical and analytical solutions for temperature distributions are in good agreement with the experimental data.
TL;DR: In this paper, the nonlinear flexural vibration for a rectangular atomic force microscope cantilever is investigated by using Timoshenko beam theory, and the normal and tangential tip-sample interaction forces are found from a Hertzian contact model and the effects of the contact position, normal and lateral contact stiffness, tip height, thickness of the beam, and angle between the cantilevers and the sample surface on the non-linear frequency to linear frequency ratio are studied.
Abstract: The nonlinear flexural vibration for a rectangular atomic force microscope cantilever is investigated by using Timoshenko beam theory. In this paper, the normal and tangential tip–sample interaction forces are found from a Hertzian contact model and the effects of the contact position, normal and lateral contact stiffness, tip height, thickness of the beam, and the angle between the cantilever and the sample surface on the nonlinear frequency to linear frequency ratio are studied. The differential quadrature method is employed to solve the nonlinear differential equations of motion. The results show that softening behavior is seen for most cases and by increasing the normal contact stiffness, the frequency ratio increases for the first mode, but for the second mode, the situation is reversed. The nonlinear-frequency to linear-frequency ratio increases by increasing the Timoshenko beam parameter, but decreases by increasing the contact position for constant amplitude for the first and second modes. For the...
TL;DR: The acoustic nonlinearity parameter (B/A) of ternary liquid mixtures of heterocyclic compounds viz. pyridine and quinoline with phenol in benzene has been evaluated at 308.15, 318.15 and 328.15 K as mentioned in this paper.
Abstract: The acoustic nonlinearity parameter (B/A) of ternary liquid mixtures of heterocyclic compounds viz. pyridine and quinoline with phenol in benzene has been evaluated at 308.15, 318.15, and 328.15 K ...
TL;DR: The origin of the squeal acoustic emissions when a chalk is rubbed on a blackboard or better on a ceramic plate is sought in the stick-slip effect between the rubbing surfaces as discussed by the authors.
Abstract: The origin of the squeal acoustic emissions when a chalk is rubbed on a blackboard or better on a ceramic plate, and those when a wet finger is rubbed on a smooth surface, such as a glass surface, is sought in the stick-slip effect between the rubbing surfaces. In the case of the squealing chalk, the stick-slip effect is anchored by shear modes of vibration in about a 0.3 mm thick chalk powder band at the rubbing interface, while in the case of the wet finger on glass, by such modes in a band comprising the finger skin. Furthermore, there are the interfacial bands at the contact areas that result in the decrease of the friction coefficient with relative velocity of slide, i.e., the condition for the stick-slip effect to occur. Such bands are basically composed of the asperities on the surface of the chalk band and of the epidermis ridges and the water layer, respectively.
TL;DR: Relativistic solitons are investigated in a plasma with positive-ion beams using the Korteweg-de Vries (KdV) equation in this article, considering relativistic effects smaller for γi ≈ O(v2/c2) and γe ≈ ε 2/c 2.
Abstract: Relativistic solitons are investigated in a plasma with positive-ion beams using the Korteweg–de Vries (KdV) equation considering relativistic effects smaller for γi ≈ O(v2/c2) and γe ≈ O(u2/c2), a...
TL;DR: In this article, a calibrated auroral spectrum is presented, together with matching synthetic spectra for many of the observed features, for potential use as a reference spectrum in general atmospheric research.
Abstract: Terrestrial auroral spectra over the 275 to 815 nm wavelength range have been recorded by the OSIRIS imaging spectrograph on board the Odin spacecraft. The spectra are from the dark polar region and are averaged over limb tangent altitudes from 100 to 105 km. All wavelengths are exposed simultaneously, thus avoiding the effect of temporal intensity variations inherently present in spectrally scanning systems. Particular care has been taken to quantify the relative spectral sensitivity over the entire wavelength range, and there is an estimated 5% precision in the measurements. To maintain accurate on-orbit spectral calibrations, an atmospheric radiation model with multiple Rayleigh scatter is employed to regularly update the OSIRIS spectral response throughout the mission. A calibrated auroral spectrum is presented, together with matching synthetic spectra for many of the observed features, for potential use as a reference spectrum in general atmospheric research. The relative intensities of the brighter ...
TL;DR: In this article, a new form of force explicitly involving the polarization vector is proposed and applied to determine the partition of the incident momentum among the reflected and transmitted wave, and the dielectric medium.
Abstract: The radiation pressure on an insulating dielectric medium should be calculable from the force acting on the polarization vector P. The well-known force proposed by Gordon (Phys. Rev. A, 8, 14 (1973) disappears in the case of a steady-state plane wave. A new form of force explicitly involving the polarization vector is proposed and applied to determine the partition of the incident momentum among the reflected and transmitted wave, and the dielectric medium. The momentum of electromagnetic wave in a dielectric medium thus found is consistent with the classical relationship, wave momentum flux density = wave intensity/wave velocity.
TL;DR: The spin Hamiltonian parameters, the g factors gi (i = x, y, z) and the hyperfine structure constants Ai, and the local structure for Rh2+ in rutile (TiO2) are theoretically investigated from the p....
Abstract: The spin Hamiltonian parameters, the g factors gi (i = x, y, z) and the hyperfine structure constants Ai, and the local structure for Rh2+ in rutile (TiO2) are theoretically investigated from the p...