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941.
本文利用系统动力学的方法对安微省农户的生产、消费和积累三方面的经济行为进行研究。探讨了农户在现有的生产条件和政策环境下生产、消费和积累的特点及其发展趋势,并提出了应该采取的对策。 相似文献
942.
Welch K Mousavi S Lundberg B Strømme M 《The European physical journal. E, Soft matter》2005,18(1):105-112
A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical
response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like
relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric
spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile
strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and
van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss
involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material
among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations
inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over
relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality
of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes. 相似文献
943.
We study global symmetry breaking in the 2D system of scalar nonconserved order parameter following a quench to zero temperature. We show that the instant of time when the symmetry is broken and the final morphology is chosen corresponds to the saturation of the order parameter inside the domains. There are three possible final morphologies: the positive and negative order parameter final morphology, and the state of the coexisting positive and negative order parameter subsystems with a flat interface between them. We find also that each type of the final morphology constitutes about 1/3 of all cases, what agrees with the results obtained recently by Spirin et al. [Phys. Rev. E 65, 016119 (2001)]. Our results are pertinent for the two dimensional systems, but we suspect that there is also a way to apply similar arguments for the three dimensional ones. 相似文献
944.
Hyun-Soo Ahn Rhonda Righter J. George. Shanthikumar 《Mathematical Methods of Operations Research》2005,62(3):499-514
In this paper we consider a firm that employs heterogeneous workers to meet demand for its product or service. Workers differ
in their skills, speed, and/or quality, and they randomly leave, or turn over. Each period the firm must decide how many workers
of each type to hire or fire in order to meet randomly changing demand forecasts at minimal expense. When the number of workers
of each type can by continuously varied, the operational cost is jointly convex in the number of workers of each type, hiring
and firing costs are linear, and a random fraction of workers of each type leave in each period, the optimal policy has a
simple hire- up-to/fire-down-to structure. However, under the more realistic assumption that the number of workers of each
type is discrete, the optimal policy is much more difficult to characterize, and depends on the particular notion of discrete
convexity used for the cost function. We explore several different notions of discrete convexity and their impact on structural
results for the optimal policy. 相似文献
945.
** Formerly Knorr-Held. Email: held{at}stat.uni-muenchen.de In this paper we apply and extend recently proposed methodsfor the dynamic analysis of pairwise comparison data to Europeanfootball teams. Our statistical model is based on the cumulativelogistic link model with time-changing parameters for the strengthof each team. We jointly analyse the results from the five topEuropean leagues from 1996 to 2001 and all international matchesbetween teams from these leagues. We introduce weights for internationalmatches and also allow for a different size of the home teamadvantage in the different leagues. We suggest that the resultsfrom such an analysis may be taken as an alternative to theUEFA coefficient, which is currently used to determine the numberof teams from each league to take part in the European footballcontests. 相似文献
946.
We discuss the dynamic properties of the square-lattice spin-1/2 XY model obtained using the two-dimensional Jordan-Wigner fermionization approach. We argue the relevance of the fermionic picture for interpreting the neutron scattering measurements in the two-dimensional frustrated quantum magnet Cs2CuCl4. 相似文献
947.
For a multielectron open-shell system exposed to an external time-dependent perturbation, the Hartree–Fock nonstationary equations are obtained in terms of density operators. Using them as a basis, equations of nonstationary coupled perturbation theory are suggested in orbital representation within the framework of the two-operator variant of the Roothaan method for an open shell. The perturbation theory corrections to the orbitals have been found in the form of expansions in unperturbed orbitals which are assumed to be calculated in the LCAO approximation in the basis of Slater-type atomic orbitals. The dynamic polarizability of open-shell atoms of substances from Li to F and Sc has been calculated as an even-power series of the frequency of incident radiation. 相似文献
948.
Volker Stix 《Computational Optimization and Applications》2004,27(2):173-186
Clustering applications dealing with perception based or biased data lead to models with non-disjunct clusters. There, objects to be clustered are allowed to belong to several clusters at the same time which results in a fuzzy clustering. It can be shown that this is equivalent to searching all maximal cliques in dynamic graphs like G
t = (V,E
t), where E
t – 1 E
t, t = 1,...,T; E
0 = . In this article algorithms are provided to track all maximal cliques in a fully dynamic graph. 相似文献
949.
The paper studies the dynamic behavior of perfect rigid-plastic plates in the form of a sector with hinged or clamped sides under short-term intensive loads. Two dynamic deformation mechanisms are demonstrated. The dynamic equation is derived for each of the mechanisms. The realization conditions for the mechanisms are analyzed. Analytical expressions are derived for the ultimate (high) loads and the maximum residual deflection. Numerical examples are given 相似文献
950.
Jean-Fran?ois?Cordeau Gilbert?LaporteEmail author 《4OR: A Quarterly Journal of Operations Research》2003,1(2):89-101
The Dial-a-Ride Problem (DARP) consists of designing vehicle routes and schedules for n users who specify pick-up and drop-off requests between origins and destinations. The aim is to plan a set of m minimum cost vehicle routes capable of accommodating as many users as possible, under a set of constraints. The most common example arises in door-to-door transportation for elderly or disabled people. The purpose of this article is to review the scientific literature on the DARP. The main features of the problem are described and classified and some modeling issues are discussed. A summary of the most important algorithms is provided.AMS classification:
90B06, 90C27, 90C59 相似文献