2019

Permanent URI for this collectionhttps://hdl.handle.net/1807/92954

Browse

Recent Submissions

Now showing 1 - 20 of 105
  • Item
    Clustering energy calculation in light alpha-conjugate nuclei
    (Canadian Science Publishing, 2019-12-09) Roshanbakht, Nafiseh; Shojaei, Mohammadreza
    In this paper, clustering energy was investigated in light alpha-conjugate nuclei considering cluster–cluster interaction instead of nucleon–nucleon interaction and using the phenomenological non-microscopic method. The observed energy levels were calculated from the rotational band of 8Be, 12C, and 16O isotopes. The results showed that these isotopes, in their cluster state, have a non-spherical structure.
  • Item
    Numerical study on structures formed by the deposition and solidification of single molten droplet
    (Canadian Science Publishing, 2019-12-09) Li, Wenbin; Zhang, Ying; Chen, Yue; Li, Peisheng; Ma, Chunhong
    The formed structure is of importance in determining the surface quality of a component made by droplet-based 3D printing. In the present work, the molten droplet solicitation process was simulated under an axisymmetric system where the smallest length scale and time scale were fully resolved. Evolutions of sharp droplet interfaces were captured through the front tracking method. Parametric studies have been carried out to explore how the dynamic metrics, which include the Ohnesorge number (Oh) and Weber number (We), can affect the structure of depositing droplet. The effect of the superheat parameter on the cooling rate was also investigated in the final section. Numerical results show that the inertial resisting force is critical dynamics in the variation of horizontal dimensionless length at the early deposition process. Three levels of Oh numbers and stages of We numbers were classified according to the deformation behavior. Flattening degree under different Oh number and We number cases were both fitted well by the exponential function. This paper also reveals that the variation law of the cooling rate and solidification time is affected by the superheat parameter, resulting in a feasible and promising method to predict droplet deformation time through the fully resolved numerical simulations during the manufacturing process.
  • Item
    Comparison of coupling constant by using momentum spectra and event shape variables in different interactions
    (Canadian Science Publishing, 2019-12-16) Saleh-Moghaddam, R.; Zomorrodian, Mohammad Ebrahim
    We describe in this paper the quantum chromodynamics prediction to calculate the strong coupling constant by using event shape variables as well as momentum spectra. By fitting the dispersive model and employing our parameters on event shape distribution, we obtain the perturbative value of = 0.1305 ± 0.0474 and also the non-perturbative value of α0 = 0.5246 ± 0.0516 GeV for electron–proton interactions. Next, by using momentum spectra for the same interactions, we obtain αs = 0.1572 ± 0.029. Our values in both methods are consistent with those obtained from electron–positron annihilations measured previously. When we find coupling constant for different flavours, we observe that they do not affect our results considerably. This is in accordance with quantum chromodynamics theory. All these features will be explained in the main text.
  • Item
    Rotating black string in Born–Infeld gravity’s rainbow
    (Canadian Science Publishing, 2019-12-03) Hendi, S.H.; Elahi, M.
    Compact objects endowed with rotation and charge are interesting both from physical and mathematical points of view. Motivated by the recent interesting consequences of gravity’s rainbow, in this paper we introduce energy-dependent asymptotically anti-de Sitter black string solutions of Einstein–Born–Infeld gravity. We report the geometric properties of the solutions and generalize them to rotating black string solutions through an improper local transformation. We calculate the conserved and thermodynamic quantities of rotating black strings and examine the validity of the first law of thermodynamics. In addition, the effects of both rainbow functions and nonlinear electrodynamics on the thermodynamic behavior of the solutions will be studied. Finally, we investigate the thermal stability of the solutions using different methods.
  • Item
    Quintessence compact stars with Vaidya–Tikekar type grr for anisotropic fluid
    (Canadian Science Publishing, 2019-12-17) Abbas, G.; Shahzad, M.R.
    The present study provides a new solution to the Einstein field equations for anisotropic matter configuration in static and spherically symmetric space–time. By taking benefit from the conformal Killing vector (CKV) technique and quintessence field specified by a parameter ωq as –1 < ωq < –1/3, we generate an exact solution to the field equations. For this investigation, we have used a specific form of metric potential taken fromVaidya–Tikekar (J. Astrophys. Astron. 3, 325 (1982)) geometry. To canvass the physical plausibility of the presented solution, we explored some analytical expressions such as energy conditions, the TOV equation, stability analysis, and equation of state parameters. We present graphical analysis of the necessary analytical expressions that revealed that our solution satisfies the necessary physical conditions.
  • Item
    The Finslerian quantum cosmology
    (Canadian Science Publishing, 2019-10-31) De, S.S.; Rahaman, Farook; Paul, Nupur
    We present a Friedmann–Robertson–Walker quantum cosmological model within the framework of Finslerian geometry. In this work, we consider a specific fluid. We obtain the corresponding Wheeler–DeWitt equation as the usual constraint equation as well as the Schrödinger equation following Dirac, although the approaches yield the same time-independent equation for the wave function of the universe. We provide exact classical and quantum mechanical solutions. We use eigenfunctions to study the time evolution of the expectation value of the scale factor. Finally, we discuss the physical meaning of the results.
  • Item
    Generalized Misner–Sharp energy in generalized Rastall theory
    (Canadian Science Publishing, 2019-12-03) Moradpour, H.; Valipour, M.
    Employing the unified first law of thermodynamics and the field equations of the generalized Rastall theory, we get the generalized Misner–Sharp mass of space–times for which gtt = –grr = –f(r). The obtained result differs from those of the Einstein and Rastall theories. Moreover, using the first law of thermodynamics, the obtained generalized Misner–Sharp mass, and the field equations, the entropy of static spherically symmetric horizons are also addressed in the framework of the generalized Rastall theory. In addition, by generalizing the study to a flat Friedmann–Robertson–Walker (FRW) universe, the apparent horizon entropy is also calculated. Considering the effects of applying the Newtonian limit to the field equations on the coupling coefficients of the generalized Rastall theory, our study indicates (i) the obtained entropy–area relation is the same as that of the Rastall theory, and (ii) the Bekenstein entropy is recovered when the generalized Rastall theory reduces to the Einstein theory. The validity of the second law of thermodynamics is also investigated in the flat FRW universe.
  • Item
    Gravastars in f(R, G) gravity
    (Canadian Science Publishing, 2019-12-17) Shamir, M. Farasat; Zia, Saeeda
    This paper is focused on the study of gravitational vacuum stars or, briefly, gravastars in f(R, G) gravity, where R and G stand for the Ricci scalar and Gauss–Bonnet invariant term, respectively. Due to the involvement of highly non-linear differential equations, solutions are found by using some appropriate numerical techniques. The main structure of gravastars has been discussed according to core, shell, and exterior regions for a well-known f(R, G) gravity cosmological model. Mass–radius evolution is described graphically for the considered gravastar, and it is shown that the mass is directly proportional to the radius.
  • Item
    Emergent magnetic structures and dynamics in thin films: a review of some recent results
    (Canadian Science Publishing, 2019-10-30) De'Bell, K.
    The emergence of mesoscopic structures and the role of slow dynamics in thin magnetic films is an area of considerable interest. The role played by defect mediated dynamic processes is a current area of experimental and theoretical research that is essential to the understanding of the properties of these films. This research is driven by both the potential applications of thin magnetic films, and the fundamental questions and new physics that they point to. This brief review provides an overview of some recent experimental work on both epitaxial magnetic films and on meta-material magnetic films. An overview of some corresponding results from theory and simulation studies is also given. The article concludes with a summary and some forward-looking speculations and questions regarding these systems.
  • Item
    Electron short-wave phonon scattering in crystals with chalcopyrite lattice
    (Canadian Science Publishing, 2019-11-05) Tyuterev, V.G.
    Electron short-wavelength phonon scattering is an effective channel for energy relaxation in crystals with a pseudo-direct optical gap. The equilibrium parameters of crystal structures and spectra of electrons and phonons in the ternary chalcopyrite compounds ZnSiP2 and ZnGeP2 are calculated self-consistently in good agreement with available experimental and theoretical calculations. The ab initio probabilities of phonon-assisted intervalley scattering of electrons in the conduction bands of the pseudo-direct-gap compounds ZnSiP2 and ZnGeP2 between the central Γ minima and the lowest lateral minima (valleys) at the T and N points have been calculated using the density functional perturbation theory. Electron–phonon scattering rates associated with intervalley phonons are calculated. Coupling constants for intervalley phonons in the chalcopyrite phosphides are close to their values in Si, Ge, and in the binary analog GaP.
  • Item
    A modified Anderson–Grüneisen model for the pressure dependence of thermal expansivity
    (Canadian Science Publishing, 2019-11-05) Dwivedi, A.
    The Anderson–Grüneisen theory of the thermal expansivity of solids has been modified so as to make it applicable for the entire range of compressions down to extreme compression in the limit of infinite pressure. The formulation for the pressure dependence of thermal expansivity has been developed using the thermodynamic constraints at boundary conditions. The volume–pressure–temperature data obtained from the Stacey reciprocal equation of state are used to determine the thermal expansivity of NaCl and MgO at simultaneously elevated pressures and temperatures. The results have been discussed and compared with recent studies.
  • Item
    Numerical analysis of coupled Kelvin–Helmholtz and Rayleigh–Taylor instability on inclined walls
    (Canadian Science Publishing, 2019-09-23) Zhang, Ying; Yao, Mengjun; Shang, Wenqiang; Ma, Chunyang; Li, Wenbing; Li, Peisheng
    The front tracking method was used to study the 2D Kelvin–Helmholtz (K–H) instability on an inclined wall for three-component immiscible fluids. Coupled effects between K–H instability and Rayleigh–Taylor (R–T) instability were studied by analyzing the effect of inclination angle, Atwood number (At), and Richardson number (Ri) on interface evolution. The results show that the coupling of R–T instability has an important influence on the development of K–H instability. The R–T instability first affects the lower interface and then the upper interface at different inclination angles, and it is also observed that the critical time of the coupled effect is earlier with an inclined wall. The R–T instability promotes the development of upper and lower interfaces at different At numbers. In addition, the billow height increases with the increase in At number and the influence of R–T instability on the upper interface can be neglected when the dimensionless time is less than critical time t = 0.6. The R–T instability has little effect on the different surface tension in terms of Richardson number (Riσ).
  • Item
    Emergent GUP from modified Hawking radiation in Einstein–NED theory
    (Canadian Science Publishing, 2019-10-31) Mehdipour, S. Hamid
    We present a general procedure for constructing exact black hole (BH) solutions with a magnetic charge in the context of nonlinear electrodynamics (NED) theory as well as in the coherent state approach to noncommutative geometry (NCG). In this framework, the Lagrangian density for a noncommutative Hayward BH is obtained and the weak energy condition is satisfied. The noncommutative Hayward solution depends on two kind of charges, without which the Schwarzschild solution is applicable. Moreover, to find a link between the BH evaporation and uncertainty relations, we may calculate the Hawking temperature and find the effect of the Lagrangian density of BHs on the Hawking radiation. Therefore, a generalized uncertainty principle (GUP) emerges from the modified Hawking temperature in Einstein–NED theory. The origin of this GUP is the combined influence of a nonlinear magnetic source and an intrinsic property of the manifold associated with a fictitious charge. Finally, we find that there is an upper bound on the Lagrangian uncertainty of the BHs that is caused by the NED field and (or) the fictitious charge.
  • Item
    Average annual committed effective dose and threshold consumption rate of bovine samples collected from a government owned abattoir, Ikpoba slope, Benin City, Nigeria
    (Canadian Science Publishing, 2019-10-07) Giwa, K.W.; Osahon, O.D.
    The activity concentrations of 40K, 232Th, and 238U in five different organs of bovine meat commonly eaten by the Nigerian populace were measured using gamma ray spectrometry. The meat samples were collected from a Government owned abattoir at Ikpoba slope, Benin City. The essence of the study was to estimate the internal radiation dose incurred by a population due to the ingestion of radionuclides from meat consumption. The mean absorbed dose rate was 12.60 ± 1.51 nGy h−1, which is far lower than the recommended value of 55 nGy h−1. The AACED obtained in this study differs for each organ, thereby making the threshold consumption rate different, but the mean dose, 0.171 ± 0.07 mSv yr−1, is below the 0.3 mSv yr−1 reported to be the recommended average value. The mean threshold consumption rate for meat intake for the samples under study was calculated to be 107.5 ± 6.22 kg yr–1. Thus, this study has contributed to the body of knowledge and data that can lead to the formulation of regulations related to radiological healthcare in the study area.
  • Item
    Fisher information and Shannon entropy calculations for two-electron systems
    (Canadian Science Publishing, 2019-09-30) Nasser, Ibraheem; Abdel-Hady, Afaf
    Fisher information is calculated for the ground state of He-isoelectronic series, in position ( ) space. The results are given and discussed as a function of the nuclear charge (Z) and the screening parameter (λ) in the case study of Yukawa potential. Simple and explicit one-, two-, and three-correlated terms of Hylleraas wave function are used to focus on extracting the most characteristic physical features of the results. The numerical values of Fisher information are given in 1- and 2-electron charge densities, and their ratio of 2- to 1-electron densities results are defined and analyzed. To enable a comparison with others, the Fisher–Shannon information products, which measure the electron–electron correlation strength, are calculated in 1-electron density. The calculations of Fisher information, the ratio, and the Shannon-information products for two-electron systems in the presence of Yukawa potential are carried out for the first time in this study.
  • Item
    Derivation of gauge symmetries in supergravity with a cosmological constant in 2 + 1 dimensions
    (Canadian Science Publishing, 2019-11-04) McKeon, D.G.C.
    The canonical structure of supergravity with a cosmological constant is analyzed in 2 + 1 dimensions using the Dirac constraint formalism. Using the approach of Henneaux, Teitelboim, and Zanelli, the first class constraints are used to find the local gauge symmetries of this model. Provided the cosmological constant is negative, this novel gauge algebra closes, without having to invoke the equations of motion or introducing auxiliary fields. There are two Bosonic and one Fermionic gauge symmetries.
  • Item
    Stable wormhole existence under noncommutative distributed background in Rastall theory
    (Canadian Science Publishing, 2019-09-20) Mustafa, G.; Abbas, G.; Shahzad, M.R.; Tie-Cheng, Xia
    This study describes the Rastall modified theory with noncommutative Gaussian- and Lorentzian-like distributions to find spherical and symmetric wormhole solutions. The basic concept of noncommutative geometry with both distributions is a physically acceptable and significant topic of quantum physics. It becomes more illustrious and interesting when we combine it with the concept of wormhole geometry. Therefore, it calculates the viable and physically realistic solutions for wormhole existential geometry under Gaussian and Lorentzian frameworks. Further, in the presence of Gaussian and Lorentzian distributions, the feasible and acceptable wormhole solutions are shown graphically. Furthermore, the stability analysis is discussed by using the Tolman–Oppenheimer–Volkov equation for all of the solutions under Gaussian- and Lorentzian-like distributions in the Rastall framework. For this purpose, we will take suitable particular values of the free and dimensionless parameters. At the end, it is concluded that our obtained solutions are physically arguable.
  • Item
    Theoretical treatment of bio-convective Maxwell nanofluid over an exponentially stretching sheet
    (Canadian Science Publishing, 2019-09-03) Khan, Muhammad Naveed; Nadeem, Sohail
    The heat and mass transfer of unsteady two-dimensional flow of a bio-convective non-Newtonian Maxwell nanofluid past an exponentially stretching sheet is presented. A viscous dissipation and external magnetic field along multiple slip conditions and chemical reactions are incorporated. The governing partial differential equations are reduced to the system of ordinary differential equations by applying suitable transformations. Using the bvp4c -shooting technique, we were able to solve the boundary value problem. The influence of the obtained parameters are deliberated graphically on the velocity, concentration, temperature, and microorganism profile. The tabulated values of skin friction, Nusselt number, mass flux rate, and microorganism rate along various parameters are computed and examined. The findings show that the value of the skin friction, Nusselt number, Sherwood number, and microorganism number decline due to enhancement in the time relaxation parameter.
  • Item
    On the separation of time scales close to a glass transition: results from quench studies of the next-nearest-neighbour Ising model
    (Canadian Science Publishing, 2019-10-11) De'Bell, K.
    Simulated quench studies of the next-nearest-neighbour (nnn) Ising model demonstrate the separation of time scales corresponding to the order parameter of the ground states and to the orientational order parameter as the value of the nnn interaction parameter approaches the critical value at which the glass transition occurs. Simply defined characteristic times, corresponding to both short-time processes (fast dynamics) and long-time processes (slow dynamics), are used to illustrate this separation and to elucidate the nature of the glass transition for this model. In particular, it is shown that the orientational order parameter remains nonzero at low temperature even at the critical value of the nnn interaction parameter (i.e., for K = Kc). Implications for the study of nonequilibrium effects in systems with striped ground states are discussed.
  • Item
    A study of the bulk viscous pressure in scalar fields and holographic Ricci dark energy considered in the modified gravity framework
    (Canadian Science Publishing, 2019-08-26) Chakrabarti, Sthiti; Chattopadhyay, Surajit; Radinschi, Irina
    The work presented in this paper reports a rigorous study of the reconstruction of the modified gravity in the framework of the scalar field models of dark energy and holographic Ricci dark energy, a generalized version of the holographic dark energy presented in S. Nojiri and S.D. Odintsov. Gen. Relativ. Gravitation, 38, 1285 (2006). The tachyon and quintessence scalar fields have been considered and the cosmology associated with the presence of bulk viscosity has been studied. In the first part of our study, we have demonstrated the behaviour of the bulk viscosity coefficient in the framework of the reconstructed tachyon scalar field model of dark energy. The scale factor is chosen in the form a(t) = a0tβ, where β > 0. Two scalar field models, namely, tachyon and quintessence, have been considered in the framework of the modified field equations through incorporation of the bulk viscous pressure. The reconstructed density and pressure of the scalar field models have been explored for the cosmological consequences in the presence of bulk viscosity. The behaviour of the effective equation of state parameters has been investigated. Finally, we have reconstructed f(T) gravity in the presence of holographic Ricci dark energy and a transition of the effective equation of state parameter from quintessence to phantom has been observed.