Recent simulations indicate that ellipsoids can pack randomly more densely than spheres and, remarkably, for axes ratios near 1.25∶1∶0.8 can approach the densest crystal packing (fcc) of spheres, with a packing frac...
详细信息
Recent simulations indicate that ellipsoids can pack randomly more densely than spheres and, remarkably, for axes ratios near 1.25∶1∶0.8 can approach the densest crystal packing (fcc) of spheres, with a packing fraction of 74%. We demonstrate that such dense packings are realizable. We introduce a novel way of determining packing density for a finite sample that minimizes surface effects. We have fabricated ellipsoids and show that, in a sphere, the radial packing fraction ϕ(r) can be obtained from V(h), the volume of added fluid to fill the sphere to height h. We also obtain ϕ(r) from a magnetic resonance imaging scan. The measurements of the overall density ϕavr, ϕ(r) and the core density ϕ0=0.74±0.005 agree with simulations.
In this paper, we consider a ranging procedure occurred in the fixed and mobile broadband wireless access systems based on the Wireless MAN-OFDMA (Metropolitan Area Network -Orthogonal Frequency Division Multiple Acce...
详细信息
In this paper, we consider a ranging procedure occurred in the fixed and mobile broadband wireless access systems based on the Wireless MAN-OFDMA (Metropolitan Area Network -Orthogonal Frequency Division Multiple Access). A ranging procedure is a collection of processes for a Mobile Subscriber Station (MSS) and a Base Station (BS) to maintain the quality of the radio frequency communication link between them. When multiple subscribers select the same ranging codes from the given ranging code pool and range the BS by transmitting those identical ranging codes at the same time frame, the ranging collision may be occurred at BS because the BS can not differentiate two different MSSs since they selected the same ranging code. We propose a mathematical performance model to analyze the probability of ranging collision affected by both the capacity of the ranging code pool and the rate of the MSS arriving to the system and investigate the numerical results of the proposed model. By the proposed model and its numerical results, we can calculate the minimum number of the required ranging codes to be implemented in BS(Base Station). We compare the analytical results with the simulated results to validate the proposed mathematical model is correct.
The classical method of moments is applied to the analysis of the external and internal dynamic conductivities of dense plasmas. The Nevanlinna formula with only one nonzero f-sum rule taken into account reproduces th...
The classical method of moments is applied to the analysis of the external and internal dynamic conductivities of dense plasmas. The Nevanlinna formula with only one nonzero f-sum rule taken into account reproduces the Drude-Lorentz model expression for the internal conductivity. The inclusion of the second non-zero sum rule produces a new model which includes the non-monotonicity of the conductivity beyond the domain of applicability of the Drude-Lorentz model. An extensive mathematical analysis of recent simulation data and reflectivity measurements of shock-compressed dense xenon plasmas is carried out.
A general technique for the generation of canonical channel models and demonstrate the application of the technique to time-frequency and time-scale integral kernel operators is developed. As an example, the derivatio...
详细信息
A simple model displaying structural-acoustic behavior is considered. The model comprises of two parallel infinitely-long flat membranes lying on elastic foundations and the acoustic medium which separates them. The s...
详细信息
A simple model displaying structural-acoustic behavior is considered. The model comprises of two parallel infinitely-long flat membranes lying on elastic foundations and the acoustic medium which separates them. The structural-acoustic coupling is demonstrated by the fact that a vibrational excitation of one of the membranes triggers vibrations in the other. Being two-dimensional and involving a small number of parameters, the proposed model is especially simple - however, at the same time, it also exemplifies some important features associated with structural-acoustic coupling. Hence, it may serve as a benchmark for the evaluation of numerical structural-acoustic schemes and, possibly, as an educational tool for studying structural-acoustic coupling in a simple context.
In this paper, a new nonlinear process monitoring technique based upon kernel principal component analysis (KPCA) is developed. In recent years, KPCA has been emerging to tackle the nonlinear monitoring problem. KPCA ...
详细信息
In this paper, the stochastic particle-trajectory model is proposed for simulating the dynamic behavior of circulating fluidized bed (CFB). In our model, the motion of solid phase is obtained by calculating the indivi...
详细信息
In this paper, the stochastic particle-trajectory model is proposed for simulating the dynamic behavior of circulating fluidized bed (CFB). In our model, the motion of solid phase is obtained by calculating the individual particle trajectory while gas flow is obtained by solving the Navier-Stokes Equation including two-phase interaction. For the calculation of solid phase, the motion of each particle is decomposed into a collision process and a suspension process. In suspension process, the less important and/or unclear forces are described as a random force considering gravity, drag force and pressure gradient. As a result, the proposed model gives some numerical simulations of CFB. It indicates that the stochastic particle-trajectory model can be used to simulate qualitatively the annulus-core structure of CFB and the influences of stochastic factors cannot be ignored. In a CFB, the coupling of stochastic factors between two phases makes the radial voidage decreased. Moreover, the upward motion of particles is mitigated by both stochastic factors and turbulence between two phases.
Digital mammographic image processing often requires a previous application of filters to reduce the noise level of the image while preserving important details. This may improve the quality of digital mammographic im...
详细信息
We provide methods of computing multivalued solutions to the Euler-Poisson system and test them in the context of a klystron amplifier. An Eulerian formulation capable of computing multivalued solutions is derived fro...
详细信息
We provide methods of computing multivalued solutions to the Euler-Poisson system and test them in the context of a klystron amplifier. An Eulerian formulation capable of computing multivalued solutions is derived from a kinetic description of the Euler-Poisson system and a moment closure. The system of the moment equations may be closed due to the special structure of the solution in phase space. The Eulerian moment equations are computed for a velocity modulated electron beam, which has been shown by prior Lagrangian theories to break in a finite time and form multivalued solutions. The results of the Eulerian moment equations are compared to direct computation of the kinetic equations and a Lagrangian method also developed in the paper. We use the Lagrangian formulation for the explicit computation of wave breaking time and location for typical velocity modulation boundary conditions.
A model of the electrokinetic flow of a fluid with a nonlinear viscosity of the Carreau type is simulated by finite element methods in a MicroChannel T-junction. The simulations accelerate the fluid from rest using th...
详细信息
ISBN:
(纸本)0791841731
A model of the electrokinetic flow of a fluid with a nonlinear viscosity of the Carreau type is simulated by finite element methods in a MicroChannel T-junction. The simulations accelerate the fluid from rest using the model for boundary slip velocity imposed due to a Debye double layer motion proposed by Zimmerman and MacInnes (2003). The simulations demonstrate an interval of the transient evolution of the end wall pressure profile that scales proportionally with the Reynolds number. The shape of the steady state profile is shown to be sensitive to the relaxation time scale characterizing the shear rate dependence of a Carreau fluid. Consequently, this flow regime can be taken as a paradigm viscometric flow for electrokinetic motion.
暂无评论