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81.
Rafa? Filipów 《Journal of Combinatorial Theory, Series A》2010,117(7):943-956
We characterize ideals of subsets of natural numbers for which some versions of Schur's theorem hold. These are similar to generalizations shown by Bergelson (1986) in [1] and Frankl, Graham and Rödl (1990) in [7]. Additionally, we prove a generalization of an iterated version of Ramsey's theorem. 相似文献
82.
M. Henkel D. Karevski 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):787-792
The effect of point defects on persistent currents in mesoscopic rings is studied in a simple tight-binding model. Using an
analogy with the treatment of the critical quantum Ising chain with defects, conformal invariance techniques are employed
to relate the persistent current amplitude to the Hamiltonian spectrum just above the Fermi energy. From this, the dependence
of the current on the magnetic flux is found exactly for a ring with one or two point defects. The effect of an aperiodic
modulation of the ring, generated through a binary substitution sequence, on the persistent current is also studied. The flux-dependence
of the current is found to vary remarkably between the Fibonacci and the Thue-Morse sequences.
Received: 4 March 1998 / Revised: 20 April 1998 / Accepted: 30 April 1998 相似文献
83.
Summary This paper presents a graphical display for the parameters resulting from loglinear models. Loglinear models provide a method
for analyzing associations between two or several categorical variables and have become widely accepted as a tool for researchers
during the last two decades. An important part of the output of any computer program focused on loglinear models is that devoted
to estimation of parameters in the model. Traditionally, this output has been presented using tables that indicate the values
of the coefficients, the associated standard errors and other related information. Evaluation of these tables can be rather
tedious because of the number of values shown as well as their rather complicated structure, mainly when the analyst needs
to consider several models before reaching a model with a good fit. Therefore, a graphical display summarizing tables of parameters
could be of great help in this situation. In this paper we put forward an interactive dynamic graphical display that could
be used in such fashion. 相似文献
84.
The spin-
The transverse Ising model with four spin interactions is studied within the finite cluster approximation (FCA), on a honeycomb and a square lattice. We have investigated the influence of the four spin interactions on the phase diagrams of the system and on both longitudinal and transversal magnetizations. We have also shown that the tricritical phenomenon exists only for low values of the transverse field. 相似文献
85.
In recent years, financial regulations such as Basel II and Solvency II have highlighted the utility of credit risk assessments through internal rating systems, particularly for estimating the probability of default (PD) of credit exposures. 相似文献
86.
We simulated models of diffusion and aggregation in long pores of small widths in order to represent the basic mechanisms of coke deposition in catalysts’ pores. Coke precursors are represented by particles injected at the pore entrance. Knudsen diffusion, which is usually expected inside the pores, is modeled by ballistic motion of those particles. The regime of molecular diffusion is also analyzed via models of lattice random walks biased along the pores. The aggregation at the surface or near previously aggregated particles was modeled by different probabilistic rules, accounting for the possibilities of more compact or more ramified deposits. In the model of Knudsen diffusion and in some cases of molecular diffusion, there is an initial regime of uniform deposition along the pore, after which the deposits acquire an approximately wedge shape, with the pore plugging near its entrance. After the regime of uniform deposition and before that of critical pore plugging, the average aggregation position slowly decreases with the number N of deposited particles approximately as N-0.25. The apparently universal features of deposits generated by microscopic models are compared with those currently adopted in continuum models. 相似文献
87.
不确定型AHP中判断矩阵一致性的定义 总被引:8,自引:2,他引:6
文章定义了区间矩阵的几种运算,并给出了不确定型判断矩阵满足一致性的条件。 相似文献
88.
High resolution Monte Carlo simulations are used to examine the finite size behavior of Q-state Potts models in two dimensions. For Q = 3 we find that at the critical point bulk properties are subject to much larger corrections to finite size scaling than were previously realized. For Q = 4 we find that corrections to finite size scaling are subtle and that the multiplicative logarithmic correction is insufficient to correct the dominant terms. 相似文献
89.
A system of N Brownian particles suspended in a nonuniform heat bath is treated as a thermodynamic system with internal degrees of freedom, in this case their velocities and coordinates. Applying the scheme of nonequilibrium thermodynamics, one then easily obtains the Fokker-Planck equation for simultaneous Brownian motion of N particles in a temperature gradient. This equation accounts for couplings in the motion as a result of hydrodynamic interactions between particles. 相似文献
90.
A statistical process control approach to selecting a warm-up period for a discrete-event simulation
The selection of a warm-up period for a discrete-event simulation continues to be problematic. A variety of selection methods have been devised, and are briefly reviewed. It is apparent that no one method can be recommended above any other. A new approach, based upon the principles of statistical process control, is described (SPC method). Because simulation output data are often highly autocorrelated and potentially non-normal, the batch means method is employed in constructing the control chart. The SPC method is tested on seven data sets and encouraging results are obtained concerning its accuracy. The approach is also discussed with respect to its ease of implementation, simplicity, generality of use and requirements for parameter estimation. 相似文献