Showing papers in "Physica Scripta in 2010"
TL;DR: In this paper, a multiple exp-function method for exact multiple wave solutions of nonlinear partial differential equations is proposed, oriented towards the ease of use and capability of computer algebra systems.
Abstract: A multiple exp-function method for exact multiple wave solutions of nonlinear partial differential equations is proposed. The method is oriented towards the ease of use and capability of computer algebra systems and provides a direct and systematic solution procedure that generalizes Hirota's perturbation scheme. With the help of Maple, applying the approach to the (3+1)-dimensional potential-Yu–Toda–Sasa–Fukuyama equation yields exact explicit one-wave, two-wave and three-wave solutions, which include one-soliton, two-soliton and three-soliton type solutions. Two cases with specific values of the involved parameters are plotted for each of the two-wave and three-wave solutions.
453 citations
TL;DR: In this article, a brief review of different aspects of the so-called dynamical Casimir effect and the proposals aimed at its possible experimental realizations is given and important theoretical problems are pointed out.
Abstract: This is a brief review of different aspects of the so-called dynamical Casimir effect and the proposals aimed at its possible experimental realizations. A rough classification of these proposals is given and important theoretical problems are pointed out.
266 citations
TL;DR: In this article, the authors investigated the effect of van der Waals and Casimir forces on the pull-in instability of cantilever nano-actuators by considering their range of application.
Abstract: This paper investigates the effect of dispersion (van der Waals and Casimir) forces on the pull-in instability of cantilever nano-actuators by considering their range of application. Adomian decomposition is introduced to obtain an analytical solution of the distributed parameter model. Dispersion forces decrease the pull-in deflection and voltage of a nano-actuator. However, the fringing field increases the pull-in deflection while decreasing the pull-in voltage of the actuator. The minimum initial gap and the detachment length of the actuator that does not stick to the substrate due to van der Waals and Casimir attractions were determined. Furthermore, the proposed approach is capable of determining the stress distribution of the actuator at the onset of instability. It is seen that Casimir and van der Waals attractions effectively reduce the maximum value of stress resultants at the onset of instability. The results indicate that Adomian decomposition is a reliable method for simulating nano-structures at submicrometer ranges.
122 citations
TL;DR: In this article, the dynamical theory of moderate Reynolds number turbulence triangulates the infinite-dimensional Navier-Stokes state space by sets of exact solutions, which form a rigid backbone that enables us to describe and predict the sinuous motions of a turbulent fluid.
Abstract: The dynamical theory of moderate Reynolds number turbulence triangulates the infinite-dimensional Navier–Stokes state space by sets of exact solutions (equilibria, relative equilibria, periodic orbits, etc), which form a rigid backbone that enables us to describe and predict the sinuous motions of a turbulent fluid. We report on the determination of a set of unstable periodic orbits from close recurrences of the turbulent flow. A few equilibria that closely resemble frequently observed but unstable coherent structures are used for constructing a low-dimensional state-space projection from the extremely high-dimensional data sets. The turbulent flow can then be visualized as a sequence of close passages to unstable periodic orbits, i.e the time-recurrent dynamical coherent structures typical of a turbulent flow.
100 citations
TL;DR: In this article, a generalized variable-coefficient fifth-order Korteweg-de Vries equation is investigated, based on the Hirota bilinear method and symbolic computation, the N-soliton solutions, Backlund transformation and Lax pair are presented.
Abstract: In this paper, a generalized variable-coefficient fifth-order Korteweg–de Vries equation is investigated. Based on the Hirota bilinear method and symbolic computation, the N-soliton solutions, Backlund transformation and Lax pair are presented. Furthermore, the characteristic-line method is applied to discuss the solitonic propagation and collision under the effects of the variable coefficients, from which the following conclusions can be derived: (i) solitonic amplitude decreases as the positive coefficient of the line-damping term increases; (ii) coefficients of the dispersive and dissipative terms determine the solitonic direction and speed by changing the sign and absolute value of the solitonic velocity; (iii) the appearances of the characteristic lines depend on the forms of the variable coefficients.
80 citations
TL;DR: Security analysis proved that the quantum group signature scheme using quantum teleportation has the characteristics of group signature, non-counterfeit,non-disavowal, blindness and traceability.
Abstract: In this paper, we present a group signature scheme using quantum teleportation. Different from classical group signature and current quantum signature schemes, which could only deliver either group signature or unconditional security, our scheme guarantees both by adopting quantum key preparation, quantum encryption algorithm and quantum teleportation. Security analysis proved that our scheme has the characteristics of group signature, non-counterfeit, non-disavowal, blindness and traceability. Our quantum group signature scheme has a foreseeable application in the e-payment system, e-government, e-business, etc.
79 citations
TL;DR: In this article, the effect of post-deposition thermal annealing on the structural and optical properties of ZnO thin films with highly preferential c-axis oriented crystals was investigated.
Abstract: Crystalline zinc oxide (ZnO) thin films with highly preferential c-axis-oriented crystals were prepared using the reactive e-beam evaporation technique. Prior to deposition, ZnO targets were prepared from ZnO (99.999%) powder. Post-deposition thermal annealing was performed at various temperatures ranging from 200 to 700 °C for 2 h in air to investigate the effect of annealing on the structural and optical properties. Structural characterization including that of the crystal structure, crystal orientation, phase, stress, strain, grain size and surface morphology was carried out using x-ray diffraction (XRD) and atomic force microscopy (AFM). Optical characterization including transmission, absorption coefficient and band gap estimation was carried out using a spectrophotometer. The XRD results showed that the films were highly c-axis oriented before and after annealing. Crystallinity and grain size improved with annealing temperature. AFM results showed that the surface morphology improved with annealing temperature. Optical transmittance increases slightly and the band gap decreases with increasing annealing temperature. The effect of the stress formation during thin film deposition and its variation with post-deposition heat treatment and the effect of this stress on optical properties of the thin films were also studied. The residual compressive stress in as-deposited thin films relaxes with heat treatment and becomes tensile with further increase in annealing temperature. The optical band gap decreases with increasing grain size and decreases with increasing tensile stress.
75 citations
TL;DR: By employing a new improved approximation scheme to deal with the centrifugal term, the authors solved approximately the Klein-Gordon equation with scalar and vector Poschl-Teller potentials for the arbitrary orbital angular momentum number.
Abstract: By employing a new improved approximation scheme to deal with the centrifugal term, we solve approximately the Klein–Gordon equation with scalar and vector Poschl–Teller potentials for the arbitrary orbital angular momentum number l The bound state energy equation and the unnormalized radial wave functions have been approximately obtained by using the basic concept of the supersymmetric shape invariance formalism and the function analysis method We also discuss in detail the identity of the energy spectra for the Poschl–Teller potential in the Klein–Gordon equation and the Dirac equation under the limits of the spin symmetry and pseudospin spin symmetry
75 citations
TL;DR: In this article, the modified form of Hirota's bilinear method, established by Hereman, is applied to derive multiple soliton solutions and multiple singular solutions for each model.
Abstract: In this work, integrable (2+1)-dimensional and integrable (3+1)-dimensional breaking soliton equations are examined. The modified form of Hirota's bilinear method, established by Hereman, is applied to derive multiple soliton solutions and multiple singular soliton solutions for each model. The resonance phenomenon does not exist for the two models.
70 citations
TL;DR: In this paper, the mixing and turbulence structure in buoyancy-driven turbulence at low to moderate Atwood numbers, A, found from direct numerical simulations in two configurations: classical Rayleigh−Taylor instability and an idealized triply periodic Rayleigh-Taylor flow.
Abstract: This paper presents several issues related to mixing and turbulence structure in buoyancy-driven turbulence at low to moderate Atwood numbers, A, found from direct numerical simulations in two configurations: classical Rayleigh–Taylor instability and an idealized triply periodic Rayleigh–Taylor flow. Simulations at A up to 0.5 are used to examine the turbulence characteristics and contrast them with those obtained close to the Boussinesq approximation. The data sets used represent the largest simulations to date in each configuration. One of the more remarkable issues explored, first reported in (Livescu and Ristorcelli 2008 J. Fluid Mech. 605 145–80), is the marked difference in mixing between different density fluids as opposed to the mixing that occurs between fluids of commensurate densities, corresponding to the Boussinesq approximation. Thus, in the triply periodic configuration and the non-Boussinesq case, an initially symmetric density probability density function becomes skewed, showing that the mixing is asymmetric, with pure heavy fluid mixing more slowly than pure light fluid. A mechanism producing the mixing asymmetry is proposed and the consequences for the classical Rayleigh–Taylor configuration are discussed. In addition, it is shown that anomalous small-scale anisotropy found in the homogeneous configuration (Livescu and Ristorcelli 2008 J. Fluid Mech. 605 145–80) and Rayleigh–Taylor turbulence at A=0.5 (Livescu et al 2008 J. Turbul. 10 1–32) also occurs near the Boussinesq limit. Results pertaining to the moment closure modelling of Rayleigh–Taylor turbulence are also presented. Although the Rayleigh–Taylor mixing layer width reaches self-similar growth relatively fast, the lower-order terms in the self-similar expressions for turbulence moments have long-lasting effects and derived quantities, such as the turbulent Reynolds number, are slow to follow the self-similar predictions. Since eddy diffusivity in the popular gradient transport hypothesis is proportional to the turbulent Reynolds number, the dissipation rate and turbulent transport have different length scales long after the onset of the self-similar growth for the layer growth. To highlight the importance of turbulent transport, variable density energy budgets for the kinetic energy, mass flux and density-specific volume covariance equations, necessary for a moment closure of the flow, are provided.
69 citations
TL;DR: In this paper, the M-shell x-ray emission of highly charged tungsten ions has been investigated at the Livermore electron beam ion trap facility using SuperEBIT and a NASA X-ray calorimeter array.
Abstract: The M-shell x-ray emission of highly charged tungsten ions has been investigated at the Livermore electron beam ion trap facility. Using the SuperEBIT electron beam ion trap and a NASA x-ray calorimeter array, transitions connecting to levels of the ground configurations in the 1500–3600 eV spectral range of zinc-like W44+ through cobalt-like W47+ have been measured. The measured spectra are compared with theoretical line positions and emissivities calculated using the FAC code.
TL;DR: In this article, the authors survey some of the main conceptual developments in the study of -symmetric and pseudo-Hermitian Hamiltonian operators that have taken place during the past 10 years or so.
Abstract: We survey some of the main conceptual developments in the study of -symmetric and pseudo-Hermitian Hamiltonian operators that have taken place during the past 10 years or so. We offer a precise mathematical description of a quantum system and its representations that allows us to describe the idea of unitarization of a quantum system by modifying the inner product of the Hilbert space. We discuss the role and importance of the quantum-to-classical correspondence principle that provides the physical interpretation of the observables in quantum mechanics. Finally, we address the problem of constructing an underlying classical Hamiltonian for a unitary quantum system defined by an a priori non-Hermitian Hamiltonian.
TL;DR: In this article, the homotopy perturbation method (HPM) is used to investigate the effect of the Casimir force on the pull-in instability of electrostatic actuators at nano-scale separations.
Abstract: In this paper, the homotopy perturbation method (HPM) is used to investigate the effect of the Casimir force on the pull-in instability of electrostatic actuators at nano-scale separations. The proposed HPM is employed to solve nonlinear constitutive equations of cantilever beam-type nanoactuators. An analytical solution is obtained in terms of convergent series with easily computable components. Basic design parameters such as critical cantilever tip deflection and pull-in voltage of the nano-cantilevers are computed. As special cases of this work, freestanding nanoactuators and electrostatic micro-actuators are investigated. The analytical HPM results agree well with numerical solutions and those from the literature.
TL;DR: This paper proposes an E-payment system based on quantum group signature, which can protect not only the users' anonymity but also the inner structure of customer groups and the two techniques of quantum key distribution, a one-time pad and quantum group signatures.
Abstract: Security and anonymity are essential to E-payment systems. However, existing E-payment systems will easily be broken into soon with the emergence of quantum computers. In this paper, we propose an E-payment system based on quantum group signature. In contrast to classical E-payment systems, our quantum E-payment system can protect not only the users' anonymity but also the inner structure of customer groups. Because of adopting the two techniques of quantum key distribution, a one-time pad and quantum group signature, unconditional security of our E-payment system is guaranteed.
TL;DR: In this paper, the Dirac equation with the Yukawa potential was solved by the Nikiforov-Uvarov method under the condition of exact spin symmetry, and analytical solutions for bound states of corresponding Dirac equations were found.
Abstract: In the present paper, we solve the Dirac equation with the Yukawa potential by the Nikiforov–Uvarov method. The Dirac Hamiltonian contains a scalar S and a vector V Yukawa potentials. Under the condition of exact spin symmetry, analytical solutions for bound states of the corresponding Dirac equation are found.
TL;DR: In this article, the authors studied the time behavior of entanglement between two noninteracting qubits, each immersed in its own environment for two different non-Markovian conditions: a high-Q cavity slightly off-resonant with the qubit transition frequency and a nonperfect photonic band gap (PBG).
Abstract: We study the time behaviour of entanglement between two noninteracting qubits, each immersed in its own environment for two different non-Markovian conditions: a high-Q cavity slightly off-resonant with the qubit transition frequency and a nonperfect photonic band gap (PBG). We find that revivals and retardation of entanglement loss may occur by adjusting the cavity–qubit detuning, in the first case, while partial entanglement trapping occurs in a nonideal PBG.
TL;DR: In this article, the global exponential stability of time-delayed stochastic bidirectional associative memory neural networks with impulses and Markovian jumping parameters is studied, and a generalized activation function is considered, and traditional assumptions on the boundedness, monotony and differentiability of activation functions are removed.
Abstract: In this paper, we study the global exponential stability of time-delayed stochastic bidirectional associative memory neural networks with impulses and Markovian jumping parameters. A generalized activation function is considered, and traditional assumptions on the boundedness, monotony and differentiability of activation functions are removed. We obtain a new set of sufficient conditions in terms of linear matrix inequalities, which ensures the global exponential stability of the unique equilibrium point for stochastic BAM neural networks with impulses. The Lyapunov function method with the Ito differential rule is employed for achieving the required result. Moreover, a numerical example is provided to show that the proposed result improves the allowable upper bound of delays over some existing results in the literature.
TL;DR: In this article, the nonlinear positron acoustic shock waves (PASWs) in an unmagnetized plasma consisting of cold positrons, immobile positive ions and Boltzmann-distributed electrons and hot positrons are studied in both unbounded planar geometry and bounded nonplanar geometry.
Abstract: The nonlinear positron acoustic shock waves (PASWs) in an unmagnetized plasma consisting of cold positrons, immobile positive ions and Boltzmann-distributed electrons and hot positrons are studied in both unbounded planar geometry and bounded nonplanar geometry. In this regard, with the help of the reductive perturbation method, the cylindrical and spherical Korteweg–de Vries Burger (KdVB) equations are derived for PASWs. Numerically, the effects of several parameters and ion kinematic viscosities on the properties of PASWs in both planar and nonplanar geometry are discussed. It is found that PASWs in nonplanar geometry significantly differ from those in planar geometry.
TL;DR: In this paper, the Dirac equation with scalar and vector symmetrical well potentials was solved by using a proper approximation to the spin-orbit coupling term, and obtained the corresponding energy equation and spinor wave functions for the bound states.
Abstract: In the case of exact spin symmetry, we approximately solve the Dirac equation with scalar and vector symmetrical well potentials by using a proper approximation to the spin–orbit coupling term, and obtain the corresponding energy equation and spinor wave functions for the bound states. We find that there exist only positive-energy bound states in the case of spin symmetry. Also, the energy eigenvalue approaches a constant when the potential parameter α goes to zero. The special case for equally scalar and vector symmetrical well potentials is studied briefly.
TL;DR: In this paper, a new solvable hyperbolic single wave potential is found by expanding the regular solution of the 1D Schr?dinger equation in terms of square integrable basis.
Abstract: A new solvable hyperbolic single wave potential is found by expanding the regular solution of the 1D Schr?dinger equation in terms of square integrable basis. The main characteristic of the basis is that it supports an infinite tridiagonal matrix representation of the wave operator. However, the eigenenergies associated with this potential cannot be obtained using traditional procedures. Hence, a new approach (the 'potential parameter' approach) has been adopted for this eigenvalue problem. For a fixed energy, the problem is solvable for a set of values of the potential parameters (the 'parameter spectrum'). Subsequently, the map that associates the parameter spectrum with the energy is inverted to give the energy spectrum. The bound state wavefunction is written as a convergent series involving products of the ultraspherical Gegenbauer polynomial in space and a new polynomial in energy, which is a special case of the 'dipole polynomial' of the second kind.
TL;DR: In this article, a self-similar solution for the propagation of a cylindrical shock wave in a dusty gas with heat conduction and radiation heat flux, which is rotating about the axis of symmetry, is investigated.
Abstract: A self-similar solution for the propagation of a cylindrical shock wave in a dusty gas with heat conduction and radiation heat flux, which is rotating about the axis of symmetry, is investigated. The shock is assumed to be driven out by a piston (an inner expanding surface) and the dusty gas is assumed to be a mixture of non-ideal gas and small solid particles. The density of the ambient medium is assumed to be constant. The heat conduction is expressed in terms of Fourier's law and radiation is considered to be of diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient αR are assumed to vary with temperature and density. Similarity solutions are obtained, and the effects of variation of the parameter of non-idealness of the gas in the mixture, the mass concentration of solid particles and the ratio of density of solid particles to the initial density of the gas are investigated.
TL;DR: In this paper, the authors considered the asymptotic stability analysis problem for a class of delayed stochastic genetic regulatory networks with impulses based on the Lyapunov stability technique and Stochastic analysis theory, stability criteria are proposed in terms of linear matrix inequalities (LMI).
Abstract: In this paper, the asymptotic stability analysis problem is considered for a class of delayed stochastic genetic regulatory networks with impulses Based on the Lyapunov stability technique and stochastic analysis theory, stability criteria are proposed in terms of linear matrix inequalities (LMI) It is shown that the addressed stochastic genetic regulatory networks are globally asymptotically stable if four LMIs are feasible, where the feasibility of LMIs can be readily checked by Matlab LMI toolbox Finally, a numerical example is given to demonstrate the usefulness of the proposed result
TL;DR: In this article, the authors consider an inflationary model that inflaton field is non-minimally coupled to gravity and study the parameter space of the model up to the second (and in some cases third) order of the slow-roll parameters.
Abstract: We reconsider an inflationary model that inflaton field is non-minimally coupled to gravity. We study the parameter space of the model up to the second (and in some cases third) order of the slow-roll parameters. We calculate inflation parameters in both Jordan and Einstein frames, and the results are compared in these two frames and also with observations. Using the recent observational data from combined WMAP5+SDSS+SNIa datasets, we study constraints imposed on our model parameters, especially the non-minimal coupling ?.
TL;DR: In this paper, Kholmetski et al. used the proper velocity-time description of events rather than the usual spacetime description in order to obtain linear transformations between uniformly accelerated systems, assuming that the clock hypothesis is false.
Abstract: We consider transformations between uniformly accelerated systems, assuming that the clock hypothesis is false. We use the proper velocity–time description of events rather than the usual space–time description in order to obtain linear transformations. Based on the generalized principle of relativity and the ensuing symmetry, we obtain transformations of Lorentz type. We predict the existence of a maximal acceleration and time dilation due to acceleration. We also predict a Doppler shift due to acceleration of the source in addition to the shift due to the source's velocity. Based on our results, we explain the Kundig experiment (Kundig 1963 Phys. Rev. 129 2371), as reanalyzed by Kholmetski et al (2008 Phys. Scr. 77 035302), and obtain an estimate of the maximal acceleration.
TL;DR: In this article, the authors presented an analytic study for the nonlinear Vakhnenko equation, a generalized Vakhhnenko equation and a modified GVEA, and examined the resonance phenomenon for each model.
Abstract: In this paper, we present an analytic study for the nonlinear Vakhnenko equation, a generalized Vakhnenko equation and a modified generalized Vakhnenko equation. The simplified form of the bilinear method, established by Hereman and Nuseir (1997 Math. Comput. Simul. 43 13–27), will be used to formally derive multiple soliton solutions and multiple singular soliton solutions for each equation. The resonance phenomenon is examined for each model.
TL;DR: BadBadiei et al. as discussed by the authors showed that density changes of D(−1) are coupled to similar changes in ordinary dense D(1), and it was proposed that these two forms of dense deuterium are rapidly transformed into each other.
Abstract: The ultradense atomic deuterium material named D(−1) is conveniently studied by laser-induced Coulomb explosion methods. A well-defined high kinetic energy release (KER) from this material was first reported in Badiei et al (2009 Int. J. Hydrog. Energy 34 487) and a two-detector setup was used to prove the high KER and the complex fragmentation patterns in Badiei et al (2009 Int. J. Mass Spectrom. 282 70). The common KER is 630 ±30 eV, which corresponds to an interatomic distance D–D of 2.3 ±0.1 pm. In both ion and neutral time-of-flight (TOF) measurement, two similar detectors at widely different flight distances prove that atomic particles are observed. New results on neutral TOF spectra are now reported for the material D(−1). It is shown that density changes of D(−1) are coupled to similar changes in ordinary dense D(1), and it is proposed that these two forms of dense deuterium are rapidly transformed into each other. The TOF-MS signal dependence on the intensity of the laser is studied in detail. The fast deuteron intensity is independent of the laser power over a large range, which suggests that D(−1) is a superfluid with long-range efficient transport of excitation energy or particles.
TL;DR: In this paper, a finite element model is developed to predict the thermal response of the heat-conducting device compared to the conventional asphalt mixture, including the coefficient of heat conductivity of the asphalt pavement, the distance between pipes with the medium, water, and the pipe's diameter.
Abstract: Using asphalt pavements as a solar collector is a subject of current interest all over the world because the sun provides a cheap and abundant source of clean and renewable energy, which can be captured by black asphalt pavements. A heat-conducting device is designed to absorb energy from the sun. In order to validate what parameters are critical in the asphalt collector, a finite element model is developed to predict the thermal response of the heat-conducting device compared to the conventional asphalt mixture. Some factors that may affect the asphalt pavement collector are considered, including the coefficient of heat conductivity of the asphalt pavement, the distance between pipes with the medium, water, and the pipe's diameter. Ultimately, the finite element model can provide pavement engineers with an efficient computational tool that can be a guide to the conductive asphalt solar collector's experiment in the laboratory.
TL;DR: In this paper, the mixing of high-Schmidt-number passive scalars in regular and fractal grid turbulence is experimentally investigated using a water channel, where a turbulence-generating grid is installed at the entrance of the test section, which is 1.5 m in length and 0.1 m×0.1m in cross section.
Abstract: Turbulent mixing of high-Schmidt-number passive scalars in regular and fractal grid turbulence is experimentally investigated using a water channel. A turbulence-generating grid is installed at the entrance of the test section, which is 1.5 m in length and 0.1 m×0.1 m in cross section. Two types of grids are used: one is a regular grid consisting of square-mesh and biplane constructions, and the other is a square-type fractal grid, which was first investigated by Hurst and Vassilicos (2007 Phys. Fluids 19 035103) and Seoud and Vassilicos (2007 Phys. Fluids 19 105108). The two grids have the same solidity of 0.36. The Reynolds number based on the mesh size, ReM=U0Meff/ν, is 2500 in both flows, where U0 is the cross-sectionally averaged mean velocity, Meff is the effective mesh size and ν is the kinematic viscosity. A fluorescent dye (rhodamine B) is homogeneously premixed only in the lower stream and therefore the scalar mixing layers with an initial step profile develop downstream of the grids. The Schmidt number of the dye is O(103). The time-resolved particle image velocimetry and the planar laser-induced fluorescence techniques are used to measure the velocity and concentration fields. The results show that the turbulent mixing in fractal grid turbulence is more strongly enhanced than that in regular grid turbulence for the same mesh Reynolds number ReM. The profile of instantaneous scalar dissipation shows that scalar dissipation takes place locally even in the far downstream region at x/Meff=120 in fractal grid turbulence.
TL;DR: The interest in using porous shape memory alloy (SMA) scaffolds as implant materials has been growing in recent years due to the combination of their unique mechanical and functional properties, i.e. shape memory effect and superelasticity, low elastic modulus combined with new bone tissue ingrowth ability and vascularization.
Abstract: The interest in using porous shape memory alloy (SMA) scaffolds as implant materials has been growing in recent years due to the combination of their unique mechanical and functional properties, i.e. shape memory effect and superelasticity, low elastic modulus combined with new bone tissue ingrowth ability and vascularization. These attractive properties are of great benefit to the healing process for implant applications. This paper reviews current state-of-the art on the processing, porous characteristics and mechanical properties of porous SMAs for biomedical applications, with special focus on the most widely used SMA nickel–titanium (NiTi), including (i) microstructural features, mechanical and functional properties of NiTi SMAs; (ii) main processing methods for the fabrication of porous NiTi SMAs and their mechanical properties and (iii) new-generation Ni-free, biocompatible porous SMA scaffolds.
TL;DR: In this paper, the authors investigated the elastic properties of SrTiO3 up to 26 GPa in cubic, tetragonal and orthorhombic phases using the ab initio pseudo-potential method.
Abstract: We investigated the athermal high-pressure behavior of the elastic properties of SrTiO3 (STO) up to 26 GPa in cubic, tetragonal and orthorhombic phases using the ab initio pseudo-potential method. Our results for the cubic phase are in good agreement with experiment and previous pseudo-potential calculations. There are no studies for the tetragonal and orthorhombic phases under high pressure available for comparison. To date, there are no global data on elastic parameters under high pressure for STO. We establish data when we report the results of our structural and elastic study under high pressure in the three phases. Our calculations show that the cubic–tetragonal phase transition occurs at 6 GPa and the tetragonal–orthorhombic phase transition at 14 GPa. A third and unknown phase transition from orthorhombic Cmcm to monoclinic P21 /m was observed at 24 GPa, but no study has explored it. The orthorhombic phase is unstable and this instability may be due to ferroelectricity at high pressure. The elastic properties of STO are also strongly pressure dependent with instabilities near the phase transition pressure. STO is more resistant to plastic deformation and to fracture in the cubic phase than in the tetragonal and orthorhombic phases.