应变软化土体中柱形扩孔解析

给出子考虑剪胀作用的线性软化土体中柱形孔扩张的应力、位移场解析解;根据体积平衡方程导出极限护孔压力和最大塑性区半径的解析表达式,较好地弥补了经典理论的不足;计算讨论了土体软化和剪胀特性对柱形扩孔的影响。     

Markov dilation of Diffusion Type Processes and Its Application to the Financial Mathematics

The Markov dilation of diffusion type processes is defined. Infinitesimal operators and stochastic differential equations for the obtained Markov processes are described. Some applications to the integral representation for functionals of diffusion type processes and to the construction of a replicating portfolio for a non-terminal contingent claim are considered.     

Carbon dioxide–poly(vinylidene fluoride) interactions at high pressure

The article reports on the behaviour of poly(vinylidene fluoride) in carbon dioxide at 42°C and 80°C and in a pressure range of 0.1–30 MPa. Experimental techniques for the measurement of gas mass uptake and polymer dilatation are described and the corresponding data are reported as mass sorption and dilatation isotherms, respectively. The mass uptake experiment was also used to follow the evolution of the coefficient of diffusion of carbon dioxide into the polymer as a function of pressure or concentration. An analysis for the calculation of the partial molar volume of carbon dioxide as a function of pressure is also given, which shows that the ‘apparent’ partial molar volume of the carbon dioxide decreases with pressure to very low values, at high pressure. The computed values are significantly less than those for either the liquid or the solid phases of pure carbon dioxide, and also lower than some data previously reported for silicone elastomers. A consideration of the origins of this apparent anomaly is given in the conclusions. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2435–2447, 1998     

Analytical approximate solutions for two-dimensional viscous flow through expanding or contracting gaps with permeable walls

In this paper, the problem of laminar, isothermal, incompressible and viscous flow in a rectangular domain bounded by two moving porous walls, which enable the fluid to enter or exit during successive expansions or contractions is solved analytically by using the homotopy analysis method (HAM). Graphical results are presented to investigate the influence of the nondimensional wall dilation rate α and permeation Reynolds number Re on the velocity, normal pressure distribution and wall shear stress. The obtained solutions, in comparison with the numerical solutions, demonstrate remarkable accuracy. The present problem for slowly expanding or contracting walls with weak permeability is a simple model for the transport of biological fluids through contracting or expanding vessels.      

Multivariate irregular sampling theorem

In this paper,we prove a Marcinkiewicz-Zygmund type inequality for multivariate entire functions of exponential type with non-equidistant spaced sampling points. And from this result,we establish a multivariate irregular Whittaker-Kotelnikov-Shannon type sampling theorem.     

A Control Simulation Method of High-Speed Trains on Railway Network with Irregular Influence

Based on the discrete time method, an effective movement control model is designed for a group of high-speed trains on a rail network. The purpose of the model is to investigate the specific traffic characteristics of high-speed trains under the interruption of stochastic irregular events. In the model, the high-speed rail traffic system is supposed to be equipped with the moving-block signalling system to guarantee maximum traversing capacity of the railway. To keep the safety of trains' movements, some operational strategies are proposed to control the movements of trains in the model, including traction operation, braking operation, and entering-station operation. The numerical simulations show that the designed model can well describe the
movements of high-speed trains on the rail network. The research results can provide the useful information not only for investigating the propagation features of relevant delays under the irregular disturbance but also for rerouting and rescheduling trains on the rail network.     

The Sensitivity Analysis for the Flow Past Obstacles Problem with Respect to the Reynolds Number

In this paper, numerical sensitivity analysis with respect to the Reynolds number for the flow past obstacle problem is presented. To carry out such analysis, at each time step, we need to solve the incompressible Navier-Stokes equations on irregular domains twice, one for the primary variables; the other is for the sensitivity variables with homogeneous boundary conditions. The Navier-Stokes solver is the augmented immersed interface method for Navier-Stokes equations on irregular domains. One of the most important contributions of this paper is that our analysis can predict the critical Reynolds number at which the vortex shading begins to develop in the wake of the obstacle. Some interesting experiments are shown to illustrate how the critical Reynolds number varies with different geometric settings.     

Cycloid motions of grains in a dust plasma

Hypocycloid and epicycloid motions of irregular grains(pine pollen) are observed for the first time in a dust plasma in a two-dimensional(2D) horizontal plane. These cycloid motions can be regarded as a combination of a primary circle and a secondary circle. An inverse Magnus force originating from the spin of the irregular grain gives rise to the primary circle.Radial confinement resulting from the electrostatic force and the ion drag force, together with inverse Magnus force, plays an important role in the formation of the secondary circle. In addition, the cyclotron radius is seen to change periodically during the cycloid motion. Force analysis and comparison experiments have shown that the cycloid motions are distinctive features of an irregular grain immersed in a plasma.     

Full time-domain nonlinear coupled dynamic analysis of a truss spar and its mooring/riser system in irregular wave

A new full time-domain nonlinear coupled method has been established and then applied to predict the responses of a Truss Spar in irregular wave.For the coupled analysis,a second-order time-domain approach is developed to calculate the wave forces,and a finite element model based on rod theory is established in three dimensions in a global coordinate system.In numerical implementation,the higher-order boundary element method(HOBEM)is employed to solve the velocity potential,and the 4th-order Adams-Bashforth-Moultn scheme is used to update the second-order wave surface.In deriving convergent solutions,the hull displacements and mooring tensions are kept consistent at the fairlead and the motion equations of platform and mooring-lines/risers are solved simultaneously using Newmark-integration scheme including Newton-Raphson iteration.Both the coupled quasi-static analysis and the coupled dynamic analysis are performed.The numerical simulation results are also compared with the model test results,and they coincide very well as a whole.The slow-drift responses can be clearly observed in the time histories of displacements and mooring tensions.Some important characteristics of the coupled responses are concluded.     

Application and measurement of underwater acoustic reciprocity transfer functions in reverberant sound field

The reciprocity measurement theory in anomalous reverberant sound fields was investigated.An improved method Was proposed due to the interrelated errors.The source volume velocity Was corrected by spatial average of measurement results and evaluation of the reverberant sound field influence on acoustic energy density.The result was validated in underwater experiment,corrected reciprocity measurement results were almost the same as direct measurement results.It indicates that reverberant sound field does not affect the validitv of the principle,but influences the obtainment of source volume velocity,then influences the measurement of transfer functions with the principle.The proposed method is simple and effective in anomalous reverberant sound fields.The study mav be valuable for the applications which are based on the principle.