双层碳纳米管中的周向导波

考虑双层碳纳米管的层间范德华力,采用连续介质力学的波动理论,建立了双层碳纳米管中周向导波传播模型,研究周向导波的频散现象.通过与单层碳纳米管结果的比较表明,双层碳纳米管中周向导波的传播表现出更为明显的频散特性,出现更多的模态干涉现象,并发现在某些特殊频率处出现成对模态的消失与新启现象.     

Experimental measurement and modeling study for estimation of wax disappearance temperature

Wax deposition is a frequent problem in oil pipelines and down-stream industries. Correct prediction of wax formation conditions is required to prevent this phenomenon. In this study, wax appearance temperature (WAT) of 12 Iranian oil and condensate samples were measured using viscometry data and differential scanning Calorimetry (DSC) analysis. Also, a new empirical correlation and intelligent artificial neural network (ANN) model were developed to estimate wax disappearance temperature (WDT) of crude oils. Specific gravity, pressure, and molecular weight of oil sample were used as input variables for these models. The ANN model was trained using different hidden neurons and training algorithms. Experimental measurements studies were used for validation of the new correlation. Comparing the results indicated that the ANN model has 0.27% error while most thermodynamic models have an average error of 0.35% to 2.19%. Also, the proposed correlation can predict WDT with good accuracy and minimum input data. Results show that this correlation has a maximum error of 1.16% for 310 published experimental data and 1.19% for 9 Iranian samples.     

Nonautonomous solitons in the continuous wave background of the variable-coefficient higher-order nonlinear Schro¨dinger equation

We reduce the variable-coefficient higher-order nonlinear Schrdinger equation (VCHNLSE) into the constantcoefficient (CC) one. Based on the reduction transformation and solutions of CCHNLSE, we obtain analytical soliton solutions embedded in the continuous wave background for the VCHNLSE. Then the excitation in advancement and sustainment of soliton arrays, and postponed disappearance and sustainment of the bright soliton embedded in the background are discussed in an exponential system.     

Discontinuous Galerkin method for solving the black‐oil problem in porous media

We introduce a new algorithm for solving the three‐component three‐phase flow problem in two‐dimensional and three‐dimensional heterogeneous media. The oil and gas components can be found in the liquid and vapor phases, whereas the aqueous phase is only composed of water component. The numerical scheme employs a sequential implicit formulation discretized with discontinuous finite elements. Capillarity and gravity effects are included. The method is shown to be accurate and robust for several test problems. It has been carefully designed so that calculation of appearance and disappearance of phases does not require additional steps.     

一类有迁移的SIS流行病模型

研究一类种群有迁移的流行病模型,得到了这类模型的基本再生数R0,证明了R0＜1无病平衡点是局部渐近稳定的,而当R0＞1时无病平衡点是不稳定的.进一步讨论了疾病持续存在与无病平衡点和地方病平衡点全局稳定的条件.     

ANM analysis of a wrinkled elastic thin membrane

In this work, we have investigated numerically the disappearance of wrinkles from a tended membrane by the Asymptotic Numerical Method (ANM) using the finite-element DKT18. The ANM is a path-following technique that has been used to solve bifurcation problems. We show numerically the influence of the terms corresponding to the membrane displacement gradient in the Föppl–von Kármán (FvK) theory on the bifurcation curves in the case of a stretched elastic membrane. We will also study numerically, by using the ANM algorithm, the influence of the thickness and of the aspect ratio on the re-stabilization of a rectangular elastic membrane during stretching. The results obtained by our model are compared with those obtained using the industrial code ABAQUS.     

Vortex shedding and vorticity fluxes in the wake of cylinders within a random array

This work investigates the impact of the background turbulence generated by randomly placed cylinders on the vortex shedding regime and the mechanisms associated to vorticity fluxes. The goals are achieved by exploring velocity databases acquired with a two-dimensional particle image velocimetry system in two types of turbulent flow experiments: flow around a single infinite cylinder and flow within random array of infinite cylinders. Formation lengths, power spectral density functions and vortex distributions are employed to discuss the vortex shedding regime. The effects of background turbulence and vorticity cancellation, due to opposite sign vorticity, on the vorticity fluxes are discussed. The results show that the background turbulence reduces the formation length and consequently increase the shedding frequency. The stronger decay of longitudinal vorticity flux in denser arrays is not accompanied by an increase of the lateral flux of vorticity. Furthermore, it was concluded that the decay of longitudinal vorticity flux is mainly caused by the vorticity cancellation due to the vorticity of opposite sign of close downstream cylinders.     

Experimental limits on neutron disappearance into another braneworld

Recent theoretical works have shown that matter swapping between two parallel braneworlds could occur under the influence of magnetic vector potentials. In our visible world, galactic magnetism possibly produces a huge magnetic potential. As a consequence, this Letter discusses the possibility to observe neutron disappearance into another braneworld in certain circumstances. The setup under consideration involves stored ultracold neutrons – in a vessel – which should exhibit a non-zero probability p to disappear into an invisible brane at each wall collision. An upper limit of p is assessed based on available experimental results. This value is then used to constrain the parameters of the theoretical model. Possible improvements of the experiments are discussed, including enhanced stimulated swapping by artificial means.     

GUIDED CIRCUMFERENTIAL WAVES IN DOUBLE-WALLED CARBON NANOTUBES

A model of guided circumferential waves propagating in double-walled carbon nan- otubes is built by the theory of wave propagation in continuum mechanics,while the van der Waals force between the inner and outer nanotube has been taken into account in the model.The dispersion curves of the guided circumferential wave propagation are studied,and some dispersion characteristics are illustrated by comparing with those of single-walled carbon nanotubes.It is found that in double-walled carbon nanotubes,the guided circumferential waves will propagate in more dispersive ways.More interactions between neighboring wave modes may take place.In particular,it has been found that a couple of wave modes may disappear at a certain frequency and that,while a couple of wave modes disappear,another new couple of wave modes are excited at the same wave number.     

Disappearance and global existence of interfaces for a doubly degenerate parabolic equation with variable coefficient

This paper deals with the Cauchy problem for a doubly degenerate parabolic equation with variable coefficient For the case λ + 1 ≥ N, one proves that depending on the behavior of the variable coefficient at infinity, the Cauchy problem either possesses the property of finite speed of propagation of perturbation or the support blows up in finite time. This completes a result by Tedeev (A.F.Tedeev, The interface blow‐up phenomenon and local estimates for doubly degenerate parabolic equations, Appl. Anal. 86 (2007) 755–782.), which asserts the same result under the condition λ + 1 < N. Copyright © 2014 John Wiley & Sons, Ltd.