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Generalized Model (generalized + model)
Selected AbstractsInternational Pricing in a Generalized Model of Ideal VarietyJOURNAL OF MONEY, CREDIT AND BANKING, Issue 2009DAVID HUMMELS Lancaster ideal variety; price to market We examine international markups and pricing in a generalized version of an "ideal variety" model. In this model, entry causes crowding in variety space, so that the marginal utility of new varieties falls as market size grows. Crowding is partially offset by income effects, as richer consumers will pay more for varieties closer matched to their ideal types. We show theoretically and confirm empirically that declining marginal utility of new varieties results in: a higher own-price elasticity of demand (and lower prices) in large countries and a lower own-price elasticity of demand (and higher prices) in rich countries. The model is also useful for generating facts from the literature regarding cross-country differences in the rate of variety expansion. [source] Numeric Simulation of Ion-Site Association Effects in Ion-Selective Electrode ResponseELECTROANALYSIS, Issue 15-16 2003Konstantin Abstract Effects in ion-selective electrode response and selectivity, caused by ion-site association in membranes are studied by means of numeric simulations based on a generalized model, which does not rely on a certain degree of the dissociation of electrolytes in membranes. The variability of the experimental values of the potentiometric selectivity coefficients is considered in view of the association in membranes. The reasons why the "dissociation approach" often fits experimental data are also discussed. A novel version of segmented sandwich membrane method is proposed for direct potentiometric measurements of ion-site association constants in membranes, and preliminary experimental results are presented. [source] On generalization of constitutive models from two dimensions to three dimensionsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 17 2008N. Khalili Abstract In this paper, a study is made of the generalization of constitutive models for geomaterials from two-dimensional stress and strain states to three-dimensional stress and strain states. Existing methods of model generalization are reviewed and their deficiencies are highlighted. A new method is proposed based on geometries of the model imprints on two normal planes. Using the proposed method, various three-dimensional failure criterions suitable for geomaterials are implemented directly into a two-dimensional model and the generalized model is identical to its original form for the axially symmetric condition. To demonstrate the application of the proposed method, the Modified Cam Clay model is extended using the Matsuoka,Nakai failure criterion. Simulations of soil behaviour for loading in the principal stress space are presented and analysed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Blocking performance of fixed-paths least-congestion routing in multifibre WDM networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2-3 2002Ling Li Abstract Wavelength-routed all-optical networks have been receiving significant attention for high-capacity transport applications. Good routing and wavelength assignment (RWA) algorithms are critically important in order to improve the performance of wavelength-routed WDM networks. Multifibre WDM networks, in which each link consists of multiple fibres and each fibre carries information on multiple wavelengths, offer the advantage of reducing the effect of the wavelength continuity constraint without using wavelength converters. A wavelength that cannot continue on the next hop on the same fibre can be switched to another fibre using an optical cross-connect (OXC) if the same wavelength is free on one of the other fibres. However, the cost of a multifibre network is likely to be higher than a single-fibre network with the same capacity, because more amplifiers and multiplexers/demultiplexers may be required. The design goal of a multifibre network is to achieve a high network performance with the minimum number of fibres. In this paper, we study the blocking performance of fixed-paths least-congestion (FPLC) routing in multifibre WDM networks. A new analytical model with the consideration of link-load correlation is developed to evaluate the blocking performance of the FPLC routing. The analytical model is a generalized model that can be used in both regular (e.g. mesh-torus) and irregular (e.g. NSFnet) networks. It is shown that the analytical results closely match the simulation results, which indicate that the model is adequate in analytically predicting the performance of the FPLC routing in different networks. Two FPLC routing algorithms, wavelength trunk (WT)-based FPLC and lightpath (LP)-based FPLC, are developed and studied. Our analytical and simulation results show that the LP-based FPLC routing algorithm can use multiple fibres more efficiently than the WT-based FPLC and the alternate path routing. In both the mesh-torus and NSFnet networks, limited number of fibres is sufficient to guarantee high network performance. Copyright © 2002 John Wiley & Sons, Ltd. [source] A generalized higher order kernel energy approximation methodJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2010Stewart N. Weiss Abstract We present a general mathematical model that can be used to improve almost all fragment-based methods for ab initio calculation of total molecular energy. Fragment-based methods of computing total molecular energy mathematically decompose a molecule into smaller fragments, quantum-mechanically compute the energies of single and multiple fragments, and then combine the computed fragment energies in some particular way to compute the total molecular energy. Because the kernel energy method (KEM) is a fragment-based method that has been used with much success on many biological molecules, our model is presented in the context of the KEM in particular. In this generalized model, the total energy is not based on sums of all possible double-, triple-, and quadruple-kernel interactions, but on the interactions of precisely those combinations of kernels that are connected in the mathematical graph that represents the fragmented molecule. This makes it possible to estimate total molecular energy with high accuracy and no superfluous computation and greatly extends the utility of the KEM and other fragment-based methods. We demonstrate the practicality and effectiveness of our model by presenting how it has been used on the yeast initiator tRNA molecule, ytRN (1YFG in the Protein Data Bank), with kernel computations using the Hartree-Fock equations with a limited basis of Gaussian STO-3G type. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Hydrogen response in liquid propylene polymerization: Towards a generalized modelAICHE JOURNAL, Issue 5 2006M. Al-haj Ali Abstract Liquid propylene batch experiments in the absence of a gas phase have been carried out using a highly-active MgCl2/TiCl4/phthalate/silane/AlR3 catalyst at varying temperatures (60-80°C) and molar hydrogen-monomer ratios of 0-10 mmol/mol. With increasing hydrogen concentration the polymerization rate increases rapidly, reaching a constant value at concentrations above 1.4 mmol/mol; pseudo-first-order catalyst deactivation constant increases; molecular weight decreases; polydispersity decreases slightly; but average molecular weight and polydispersity increase with increasing temperature. Polymerization rate, deactivation constant, and average molecular weight can be modeled based on a consistent dormant site mechanism assuming an (averaged) quasi-single-site model. © 2006 American Institute of Chemical Engineers AIChE J,2006 [source] On the asymptotic positivity of solutions for the extended Fisher,Kolmogorov equation with nonlinear diffusionMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 8 2002M. V. Bartuccelli Abstract The objective of this paper aims to prove positivity of solutions for a semilinear dissipative partial differential equation with non-linear diffusion. The equation is a generalized model of the well-known Fisher,Kolmogorov equation and represents a class of dissipative partial differential equations containing differential operators of higher order than the Laplacian. It arises in a variety of meaningful physical situations including gas flows, diffusion of an electron,ion plasma and the dynamics of biological populations whose mobility is density dependent. In all these situations, the solutions of the equation must be positive functions. Copyright © 2002 John Wiley & Sons, Ltd. [source] Capacity allocation with traditional and Internet channelsNAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 8 2006Yue Dai Abstract In this paper we study a capacity allocation problem for two firms, each of which has a local store and an online store. Customers may shift among the stores upon encountering a stockout. One question facing each firm is how to allocate its finite capacity (i.e., inventory) between its local and online stores. One firm's allocation affects the decision of the rival, thereby creating a strategic interaction. We consider two scenarios of a single-product single-period model and derive corresponding existence and stability conditions for a Nash equilibrium. We then conduct sensitivity analysis of the equilibrium solution with respect to price and cost parameters. We also prove the existence of a Nash equilibrium for a generalized model in which each firm has multiple local stores and a single online store. Finally, we extend the results to a multi-period model in which each firm decides its total capacity and allocates this capacity between its local and online stores. A myopic solution is derived and shown to be a Nash equilibrium solution of a corresponding "sequential game." © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006 [source] Lateral compaction effects in braided structuresPOLYMER COMPOSITES, Issue 2 2003Robert A. Dasilva This paper addresses the phenomenology of strand interaction in biaxial non-embedded braided textile structures under uniaxial tension. The specific interest in the development of new braided textile structures is a result of the shortcomings of current rope, belt, and cable performance under large strain controlled conditions. However, this work also holds particular significance in the area of textile composite preforms. In composites forming, the lateral strand compaction mechanism, which drives braid behavior under tension, may be applied to woven fabrics for predicting wrinkling during forming processes. Additionally, manufacturing models produced in this study may be used to predict shape and size limitations of braided composite preforms. In this paper, a generalized model is developed for these structures with the intent of characterizing and predicting mechanical behavior. The methodology consists of a modular framework, which includes the prediction of manufacturing parameters. Lateral strand compaction tests were performed to generate constitutive material curves for use in analytical geometric models. Model predictions correlate well with data generated from braid uniaxial tension tests. Results suggest that lateral strand strain drives braid tensile behavior. [source] Towards the development of a minimal cell model by generalization of a model of Escherichia coli: Use of dimensionless rate parametersBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2001Samuel T. Browning Abstract A model of a minimal cell would be a valuable tool in identifying the organizing principles that relate the static sequence information of the genome to the dynamic functioning of the living cell. Our approach for developing a minimal cell model is to first generalize an existing model of Escherichia coli by expressing reaction rates as ratios to a set of reference parameters. This generalized model is a prototype minimal cell model that will be developed by adding detail to explicitly include each chemical species. We tested the concept of a generalized model by testing the effect of scaling all enzyme-catalyzed reactions in the E. coli model. The scaling has little effect on cellular function for a wide range of kinetic ratios, where the kinetic ratio is defined as the rate of all enzyme-catalyzed reactions in a given model relative to those in the E. coli model. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 187,192, 2001. [source] A Practical Method to Estimate the Bed Height of a Fluidized Bed of Fine ParticlesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2008M. Zhang Abstract Knowledge of both dense bed expansion and freeboard solids inventory are required for the determination of bed height in fluidized beds of fine particles, e.g., Fluidized Catalytic Cracking (FCC) catalysts. A more accurate estimation of the solids inventory in the freeboard is achieved based on a modified model for the freeboard particle concentration profile. Using the experimentally determined dense bed expansion and the modified freeboard model, a more practical method with improved accuracy is provided to determine the bed height both in laboratory and industrial fluidized beds of FCC particles. The bed height in a fluidized bed can exhibit different trends as the superficial gas velocity increases, depending on the different characteristics of the dense bed expansion and solids entrainment in the freeboard. The factors that influence the bed height are discussed, showing the complexity of bed height and demonstrating that it is not realistic to determine the bed height by a generalized model that can accurately predict the dense bed expansion and freeboard solids inventory simultaneously. Moreover, a method to determine the bed height, based on axial pressure fluctuation profiles, is proposed in this study for laboratory fluidized beds, which provides improved accuracy compared to observation alone or determining the turning points in the axial pressure profiles, especially in high-velocity fluidized beds. [source] A generalized mathematical model for non-catalytic gas-solid reactionsCHINESE JOURNAL OF CHEMISTRY, Issue 4 2000Yan Zi-Feng Abstract Based on a general classification and characteristic comparison of the existing models, a new model for non-catalytic gas-solid reactions is proposed and a general formulation for the model in terms of the solid conversion, X, is presented in mis paper. The model, referred to the generalized model, is demonstrated to be applicable to any solid reactant of general structure ranging from highly porous to nonporous materials. It is shown that the generalized model incorporates the grain and pore structure for a solid pellet and can be reduced to the grain and random pore models as extreme cases. [source] | ||||||||||||||||