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1.
《中国科学:物理学 力学 天文学(英文版)》2010,(8)
Thermally induced evolution of phase transformations is a basic physical-chemical process in the dissociation of gas hydrate in sediment (GHS). Heat transfer leads to the weakening of the bed soil and the simultaneous establishment of a time varying stress field accompanied by seepage of fluids and deformation of the soil. As a consequence, ground failure could occur causing engineering damage or/and environmental disaster. This paper presents a simplified analysis of the thermal process by assuming that thermal conduction can be decoupled from the flow and deformation process. It is further assumed that phase transformations take place instantaneously. Analytical and numerical results are given for several examples of simplified geometry. Experiments using Tetra-hydro-furan hydrate sediments were carried out in our laboratory to check the theory. By comparison, the theoretical, numerical and experimental results on the evolution of dissociation fronts and temperature in the sediment are found to be in good agreement. 相似文献
2.
研究了一类周期变化的非线性复杂发病率的广义流行病学模型(SIR(susceptible, infected, recovered)模型). 通过一系列坐标变换将原模型转化为Hamilton系统,运用Melnikov方法证明了该系统存在混沌运动,给出了发生同宿分岔的条件,并用数值模拟验证了上述结果.
关键词:
SIR(susceptible
infected
recovered)模型
混沌运动
Melnikov方法
同宿分岔 相似文献
3.
采用两种新的乌龟坐标变换,用改进的Damour-Ruffini方法研究了动态Kinnersley黑洞的Hawking辐射.在新乌龟坐标变换下,将Klein-Gordon方程在视界附近变换成平直时空的标准波动方程形式,得到了黑洞的表面引力及Hawking温度,该温度在黑洞表面不同点有不同的值.值得注意的是,旧的乌龟坐标变换存在量纲错误,新乌龟坐标变换没有量纲问题,选不同的旧乌龟坐标变换计算同一黑洞所得结果不同,但是采用不同的新乌龟坐标变换所得结果仍然不同.
关键词:
黑洞
乌龟坐标变换
Hawking辐射
Klein-Gorden方程 相似文献
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6.
In mechanical treatment carried out by ball milling, powder particles are subjected to repeated high-energy mechanical loads which induce heavy plastic deformations together with fracturing and cold-welding events. Owing to the continuous defect accumulation and interface renewal, both structural and chemical transformations occur. The nature and the rate of such transformations have been shown to depend on variables, such as impact velocity and collision frequency that depend, in turn, on the whole dynamics of the system. The characterization of the ball dynamics under different impact conditions is then to be considered a necessary step in order to gain a satisfactory control of the experimental set up. In this paper we investigate the motion of a ball in a milling device. Since the ball motion is governed by impulsive forces acting during each collision, no analytical expression for the complete ball trajectory can be obtained. In addition, mechanical systems exhibiting impacts are strongly nonlinear due to sudden changes of velocities at the instant of impact. Many different types of periodic and chaotic impact motions exist indeed even for simple systems with external periodic excitation forces. We present results of the analysis on the ball trajectory, obtained from a suitable numerical model, under growing degree of impact elasticity. A route to high dimensional chaos is obtained. Crisis and attractors merging are also found. (c) 2002 American Institute of Physics. 相似文献
7.
Mixed Convection Heat and Mass Transfer in a Micropolar Fluid with Soret and Dufour Effects
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A mathematical model for the steady, mixed convection heat and mass
transfer along a semi-infinite vertical plate embedded in a micropolar
fluid in the presence of Soret and Dufour effects is presented. The
non-linear governing equations and their associated boundary conditions
are initially cast into dimensionless forms using local similarity
transformations. The resulting system of equations is then solved
numerically using the Keller-box method. The numerical results are
compared and found to be in good agreement with previously published
results as special cases of the present investigation. The non-dimensional
velocity, microrotation, temperature and concentration profiles are
displayed graphically for different values of coupling number, Soret
and Dufour numbers. In addition, the skin-friction coefficient, the
Nusselt number and Sherwood number are shown in a tabular form. 相似文献
8.
《Physics letters. [Part B]》1988,201(4):492-496
On the basis of a recent work on singular renormalization group transformations at first-order phase transition we study the four-dimensional U(1) lattice gauge theory using the two-lattice matching MCRG method. The numerical results suggest that the phase transition stays first order deep in the negative adjoint coupling region in the two-parameter fundamental-adjoint plane. 相似文献
9.
A. V. Kashevarov V. S. Levchenko A. B. Miller Yu. F. Potapov A. L. Stasenko 《Technical Physics》2018,63(6):782-788
An experimental and theoretical complex was created to study the physical processes accompanying the interaction of the air flow carrying ice crystals with the heated surface of the streamlined body. An effective coefficient of phase transformations (evaporation and transition—through melting and solidifying in a liquid film—into barrier ice) of the mass of crystals bombarding a dry or moistened heated surface taking into account their partial entrainment with flowing air has been found. The physical and mathematical model of hydrothermodynamics of a liquid film is developed, the numerical data for the thickness, velocity, and temperature, complementing the results of the experiment, are obtained. 相似文献
10.
In this study, the effects of variable fluid properties on heat transfer in MHD Casson fluid melts over a moving surface in a porous medium in the presence of the radiation are examined. The relevant similarity transformations are used to reduce the governing equations into a system of highly nonlinear ordinary differential equations and those are then solved numerically using the Runge–Kutta–Fehlbergmethod. The effects of different controlling parameters, namely, the Casson parameter,melting and radiation parameters, Prandtl number,magnetic field, porosity, viscosity and the thermal conductivity parameters on flow and heat transfer are investigated. The numerical results for the dimensionless velocity and temperature as well as friction factor and reducedNusselt number are presented graphically and discussed. It is found that the rate of heat transfer increases as the Casson parameter increases. 相似文献
11.
A. N. Lachinov T. G. Zagurenko V. M. Kornilov A. I. Fokin I. V. Aleksandrov R. Z. Valiev 《Physics of the Solid State》2000,42(10):1935-1941
The electrical conductivity in a metal-polymer-nanocrystalline metal system has been investigated as a function of temperature. It is found that this system undergoes a transition to the high-conductivity state at temperatures of structural transformations in nanocrystalline electrodes. The results are interpreted within the model of charge instability that arises in thin polymer films under changes of the boundary conditions. 相似文献
12.
A method based on spatial transformations of multiwavelength digital holograms and the correlation matching of their numerical reconstructions is proposed, with the aim to improve superimposition of different color reconstructed images. This method is based on an adaptive affine transform of the hologram that permits management of the physical parameters of numerical reconstruction. In addition, we present a procedure to synthesize a single digital hologram in which three different colors are multiplexed. The optical reconstruction of the synthetic hologram by a spatial light modulator at one wavelength allows us to display all color features of the object, avoiding loss of details. 相似文献
13.
Wallace Kantor 《Fortschritte der Physik》1992,40(1):73-91
Doppler effect, as currently formulated. uses numerical phase invariance and any linear coordinate transformations with identity transformations of nonzero spatial coordinates transverse to a rectilinear uniform relative motion; this is shown to subtly deny presumed motion, angular aberration effects, and Doppler effect. A critical review of past Doppler effect experiments confirms (10−3 to 10−7) a classical Doppler effect formulation that does not involve an ether concept, numerical phase invariance, or the use of any coordinate transformations. 相似文献
14.
Theoretical and numerical outcomes of the non-Newtonian Casson liquid thin film fluid flow owing to an unsteady stretching sheet which exposed to a magnetic field, Ohmic heating and slip velocity phenomena is reported here. The non-Newtonian thermal conductivity is imposed and treated as it vary with temperature. The nonlinear partial differential equations governing the non-Newtonian Casson thin film fluid are simplified into a group of highly nonlinear ordinary differential equations by using an adequate dimensionless transformations. With this in mind, the numerical solutions for the ordinary conservation equations are found using an accurate shooting iteration technique together with the Runge-Kutta algorithm. The lineaments of the thin film flow and the heat transfer characteristics for the pertinent parameters are discussed through graphs. The results obtained here detect many concern for the local Nusselt number and the local skin-friction coefficient in which they may be beneficial for the material processing industries. Furthermore, in some special conditions, the present problem has an excellent agreement with previously published work. 相似文献
15.
N. Nakai Y. Nagai M. Machida 《Physica C: Superconductivity and its Applications》2011,471(21-22):743-746
We have performed numerical calculations for low-lying excitations induced by a single non-magnetic impurity in a d-wave superconductor on the basis of two different frameworks. One is the Bogoliubov–de Gennes theory in real coordinates, while the other is the Born approximation in wave-number coordinates. This paper shows that these results for low-lying excitations are identical by using Fourier transformations. 相似文献
16.
The XYZ antiferromagnetic model in linear spin-wave frame is shown explicitly to have an su(1,2) algebraic structure: the Hamiltonian can be written as a linear function of the su(1,2) algebra generators. Based on it, the energy eigenvalues are obta/ned by making use of the similar transformations, and the algebraic diagonalization method is investigated. Some numerical solutions are given, and the results indicate that only one group solution could be accepted in physics. 相似文献
17.
J. Pouget 《Phase Transitions》2013,86(1-4):251-260
On the basis of a lattice model the domain structure for ferroelastic transformations is examined. The model accounts for both strongly nonlinear and competing interactions which allow for, in some situations, the propagation of nonlinear excitations. The model can be mostly applied to proper ferroelastic transformations of which In-Tl, Ti-Ni, etc.… are good prototypes. The phonon dispersion of the transverse acoustic waves obtained in the linearized case is discussed and the results show first a phonon softening at nonzero wave-number and next an upwards convexity of the phonon branch near the long-wavelength limit. This can be seen as pre-transitional effects. In a fully nonlinear case we consider vanishing dilatation transformations and the continuum approximation is applied to the one-dimensional version. Then, we investigate nonlinear excitations; three main classes of solution are found: i) quasi-harmonic solutions corresponding to periodically modulated structures in space which is a precursor effect of the elastic transformation, ii) an array of solitons made of periodic arrangements of parent-elastic domains and iii) a moving strain soliton. All the significant results are numerically illustrated by means of the microscopic model. Finally, the similarity to martensitic transformations and some extensions of the model are outlined. 相似文献
18.
G. B. Malykin 《Optics and Spectroscopy》2009,107(4):592-608
Classical optical experiments that confirm the validity of special relativity are considered. Transformations of spatial coordinates
and time that were proposed at different times for the passage from one inertial reference frame (IRF) to another and that
differ from the classical Lorentz transformations are critically analyzed. It is shown that, although some of these transformations
are capable of explaining the results of single classical optical experiments, in particular, the Michelson-Morley experiments,
neither of them, except for the Tangherlini transformations, can explain the results of the entire set of these experiments.
The discrepancy between the predictions of incorrect transformations and the results of the well-known experiments is caused
by the absence of a clearly formulated procedure for synchronizing spaced clocks in a rest IRF (where the observer is located)
and a moving IRF, which should be consistent with the transformation of time. A number of relativistic and quantum effects
are indicated, which have been predicted but not yet detected, to a search for which efforts of physicists are directed, and
which are convenient to describe with the help of the formalism of the Tangherlini transformations. 相似文献
19.
New infinite-dimensional symmetry groups for the stationary axisymmetric Einstein--Maxwell equations
with multiple Abelian gauge fields
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The so-called extended hyperbolic complex (EHC) function method
is used to study further the stationary axisymmetric Einstein--Maxwell theory with
$p$ Abelian gauge fields (EM-$p$ theory, for short). Two EHC structural
Riemann--Hilbert (RH) transformations are constructed and are then shown to give
an infinite-dimensional symmetry group of the EM-$p$ theory. This symmetry group is
verified to have the structure of semidirect product of Kac--Moody group
$\widehat{SU(p+1,1)}$ and Virasoro group. Moreover, the infinitesimal
forms of these
two RH transformations are calculated and found to give exactly the same
infinitesimal transformations as in previous author's paper
by a different scheme. This demonstrates that the results
obtained in the present paper provide some exponentiations of all the infinitesimal
symmetry transformations obtained before. 相似文献