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941.
942.
Price-dependence is an important characteristic for some inventory problems. This paper proposes a newsvendor model with fuzzy price-dependent demand, and discusses the conditions to determine the optimal pricing and inventory decisions jointly so that the expected profit could be maximized. Then an algorithm combining the method of ranking fuzzy numbers is developed to tackle the problem. Furthermore, comparison is made between the fuzzy model and the deterministic model to study the effect of the uncertain price-dependent demand, and the sensitivity properties of the joint optimal decisions are illustrated through numerical examples. 相似文献
943.
Based on the availability of prey and a simple predator–prey model, we propose a delayed predator–prey model with predator migration to describe biological control. We first study the existence and stability of equilibria. It turns out that backward bifurcation occurs with the migration rate as bifurcation parameter. The stability of the trivial equilibrium and the boundary equilibrium is delay-independent. However, the stability of the positive equilibrium may be delay-dependent. Moreover, delay can switch the stability of the positive equilibrium. When the positive equilibrium loses stability, Hopf bifurcation can occur. The direction and stability of Hopf bifurcation is derived by applying the center manifold method and the normal form theory. The main theoretical results are illustrated with numerical simulations. 相似文献
944.
The paper proposes a recursive algorithm for estimation of mixtures with state-space components and a dynamic model of switching. Bayesian methodology is adopted. The main features of the presented approach are: (i) recursiveness that enables a real-time performance of the algorithm; (ii) one-pass elaboration of the data sample; (iii) dynamic nature of the model of switching active components; (iv) orientation at explicit solutions with exploitation of numerical procedures only in those parts which cannot be computed analytically; (v) systematic approach to the Bayesian mixture estimation theory. 相似文献
945.
We study interest rate models where the term structure is given by an affine relation and in particular where the driving stochastic processes are so-called generalized Ornstein–Uhlenbeck processes. 相似文献
946.
We analyze left-truncated and right-censored data using Cox proportional hazard models with long-term survivors. The estimators of covariate coefficients and the long-term survivor proportion are obtained by the partial likelihood method, and their asymptotic properties are also established. Simulation studies demonstrate the performance of the proposed estimators, and an application to a real dataset is provided. 相似文献
947.
The on‐line monitoring of batch processes based on principal component analysis (PCA) has been widely studied. Nonetheless, researchers have not paid so much attention to the on‐line application of partial least squares (PLS). In this paper, the influence of several issues in the predictive power of a PLS model for the on‐line estimation of key variables in a batch process is studied. Some of the conclusions can help to better understand the capabilities of the proposals presented for on‐line PCA‐based monitoring. Issues like the convenience of batch‐wise or variable‐wise unfolding, the method for the imputation of future measurements and the use of several sub‐models are addressed. This is the first time that the adaptive hierarchical (or multi‐block) approach is extended to the PLS modelling. Also, the formulation of the so‐called trimmed scores regression (TSR), a powerful imputation method defined for PCA, is extended for its application with PLS modelling. Data from two processes, one simulated and one real, are used to illustrate the results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
948.
We study soft hadron production in relativistic heavy-ion collisions in a wide range of reaction energy, 4.8 GeV <
< 200 GeV, and make predictions about yields of particles using the statistical hadronization model. In fits to experimental
data, we obtain both the statistical parameters as well as physical properties of the hadron source. We identify the properties
of the fireball at the critical energy threshold, 6.26 GeV <
< 7.61 GeV, marking for higher energies the hadronization of an entropy-rich phase. In terms of the chemical composition,
one sees a phase which at low energy is chemically under-saturated, and which turns into a chemically over-saturated state
persisting up to the maximum accessible energy. Assuming that there is no change in physical mechanisms in the energy range
15 >
≥200 GeV, we use continuity of particle yields and statistical parameters to predict the hadron production at
= 62.4 GeV, and obtain total yields of hadrons at
= 130 GeV. We consider, in depth, the pattern we uncover within the hadronization condition, and discuss possible mechanisms
associated with the identified rapid change in system properties at
. We propose that the chemically over-saturated 2 + 1 flavor hadron matter system undergoes a 1st-order phase transition. 相似文献
949.
M. Fischer F. Stefani G. Gerbeth 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(4):547-554
Using a spherically symmetric mean-field α2-dynamomodel for Earth’s magnetic field reversals, we show thecoexistence of the noise-induced phenomena coherence resonance
and stochastic resonance. Stochastic resonance was recentlyinvoked to explain the 100 kyr periodicity in the distribution
ofresidence times between reversals.The comparison of the resulting residence time distribution withthe paleomagnetic one
allows for some estimate ofthe effective diffusion time of the Earth’s core which may be100 kyr or slightly below rather than200 kyr
as it would result from the molecular resistivity. 相似文献
950.
H. Xiao D. Z. Yao C. X. Wang S. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(2):219-229
The absolute photonic band gap (PBG) in two-dimensional (2D) photonic crystal with excentric core-shell rods is studied in
this paper. The core rod shifts away from the core-shell rod center, and its position is decided by two new introduced parameters
— the shift angle θ and the offset ρ. We use the FDTD algorithm to calculate the photonic bands of the photonic crystal, and analyze how the offset and shift
angle affect the photonic bang gap of excentric core-shell photonic crystal for different core rod size. It has been shown
that the variation of the photonic band gap is quite peculiar. 相似文献