Home About us Contact
|
Home About us Contact | ||
|
|
||
Qualitative Properties (qualitative + property)
Selected AbstractsA space-time network for telecommuting versus commuting decision-making,PAPERS IN REGIONAL SCIENCE, Issue 4 2003Anna Nagurney Transportation and telecommunication networks; telecommuting and commuting; space-time networks; variational inequalities Abstract. In this article, we develop a theoretical framework for the study of telecommuting versus commuting decision-making over a fixed time horizon, such as a work week through the use of a space-time network to conceptualize the decision-makers' choices over space and time. The decision-makers are multiclass and multicriteria ones and perceive the criteria of travel cost, travel time, and opportunity cost in an individual fashion. The model is a network equilibrium type and allows for the prediction of the equilibrium flows and, hence, the number of periods that members of each class of decision-makers will telecommute or commute. Qualitative properties of the equilibrium are obtained and an algorithm is given, along with convergence results, and applied to numerical examples. [source] The E-Correspondence PrincipleECONOMICA, Issue 293 2007GEORGE W. EVANS We present a new application of Samuelson's Correspondence Principle to the analysis of comparative dynamics in stochastic rational expectations models. Our version, which we call the E-correspondence principle, applies to rational expectations equilibria that are stable under least squares and closely related learning rules. With this technique it is sometimes possible to study, without explicitly solving for the equilibrium, how qualitative properties of the equilibrium are affected by changes in the model parameters. Applications to overlapping generations and New Keynesian models illustrate the potential of the technique. [source] A review of reliable numerical models for three-dimensional linear parabolic problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2007I. Faragó Abstract The preservation of characteristic qualitative properties of different phenomena is a more and more important requirement in the construction of reliable numerical models. For phenomena that can be mathematically described by linear partial differential equations of parabolic type (such as the heat conduction, the diffusion, the pricing of options, etc.), the most important qualitative properties are: the maximum,minimum principle, the non-negativity preservation and the maximum norm contractivity. In this paper, we analyse the discrete analogues of the above properties for finite difference and finite element models, and we give a systematic overview of conditions that guarantee the required properties a priori. We have chosen the heat conduction process to illustrate the main concepts, but engineers and scientists involved in scientific computing can easily reformulate the results for other problems too. Copyright © 2006 John Wiley & Sons, Ltd. [source] On the componentwise stability of linear systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2005O. Pastravanu Abstract The componentwise asymptotic stability (CWAS) and componentwise exponential asymptotic stability (CWEAS) represent stronger types of asymptotic stability, which were first defined for symmetrical bounds constraining the flow of the state-space trajectories, and then, were generalized for arbitrary bounds, not necessarily symmetrical. Our paper explores the links between the symmetrical and the general case, proving that the former contains all the information requested by the characterization of the CWAS/CWEAS as qualitative properties. Complementary to the previous approaches to CWAS/CWEAS that were based on the construction of special operators, we incorporate the flow-invariance condition into the classical framework of stability analysis. Consequently, we show that the componentwise stability can be investigated by using the operator defining the system dynamics, as well as the standard ,,, formalism. Although this paper explicitly refers only to continuous-time linear systems, the key elements of our work also apply, mutatis mutandis, to discrete-time linear systems. Copyright © 2004 John Wiley & Sons, Ltd. [source] Blow-up analysis, existence and qualitative properties of solutions for the two-dimensional Emden,Fowler equation with singular potentialMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 18 2007Daniele Bartolucci Abstract Motivated by the study of a two-dimensional point vortex model, we analyse the following Emden,Fowler type problem with singular potential: where V(x) = K(x)/|x|2, with ,,(0, 1), 0 Dynamic and generalized Wentzell node conditions for network equationsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2007Delio Mugnolo Abstract Motivated by a neurobiological problem, we discuss a class of diffusion problems on a network. The celebrated Rall lumped soma model for the spread of electrical potential in a dendritical tree prescribes that the common cable equation must be coupled with particular dynamic conditions in some nodes (the cell bodies, or somata). We discuss the extension of this model to the case of a whole network of neurons, where the ramification nodes can be either active (with excitatory time-dependent boundary conditions) or passive (where no dynamics take place, i.e. only Kirchhoff laws are imposed). While well-posedness of the system has already been obtained in previous works, using abstract tools based on variational methods and semigroup theory we are able to prove several qualitative properties, including asymptotic behaviour, regularity of solutions, and monotonicity of the semigroups in dependence on the physical coefficients. Copyright © 2006 John Wiley & Sons, Ltd. [source] Partial differential equations of chemotaxis and angiogenesisMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2001B. D. Sleeman The topic of this paper is concerned with an investigation of the qualitative properties of solutions to the following problem. Let ,,Rn be a bounded domain with boundary ,,. We seek solutions P,,,Rm+1 of the system (1) subject to the ,no-flux' boundary condition (2) where n denotes the inward pointing normal to ,,. To close the system we prescribe the initial conditions (3) In this system D is a constant diffusion coefficient, P is a population density and , is a vector of nutrients or chemicals whose dynamics influences the movement of P. Notice here that the substances , do not diffuse. If they do then the second equation of (1) is modified to (4) where d is a positive semi-definite diagonal matrix. This more general system includes the so-called Keller,Segel model of Biology ([1] Keller EF, Segel LA. Initiation of slime mold aggregation viewed as an instability. Journal of Theoretical Biology 1970; 26: 339,415). To motivate our study of system (1),(3) we begin by outlining two themes. One basic to developmental biology and the other from angiogenesis. Copyright © 2001 John Wiley & Sons, Ltd. [source] NATURAL RESOURCE EXPLOITATION UNDER COMMON PROPERTY RIGHTSNATURAL RESOURCE MODELING, Issue 1 2003MICHAEL R. CAPUTO ABSTRACT. Renewable natural resources such as ground-water, pastures and fisheries are often governed bycommon propertyrights in which members of a group jointlyown the exclusive use of the resource. We develop a formal model of a common propertycontract based on differential game theory and then use the model to examine (i) the incentives of individual users of the common resource; (ii) the resulting harvest and stock time paths; (iii) the local stabilityof the steady state; and (iv) the steadystate comparative statics. Moreover, we compare the qualitative properties of the common propertyregime to those generated under perfectlydefined private rights and open access. We show how common prop-ertyownership of natural resources can generate rent and be a second-best solution when private propertyrights are costly to establish. [source] Growth Effects of Free Trade under Increasing ReturnsTHE JAPANESE ECONOMIC REVIEW, Issue 4 2002Ilaria Ossella-Durbal This paper addresses the long-term sustainability of the growth effects from trade, within the context of a dynamic optimization model where the investment sector exhibits an initial phase of increasing returns. It is proved that the qualitative properties of trade and growth remain valid, even for decreasing, rather than constant, returns to scale in the consumption sector. That is, trade enables an economy to escape a "poverty trap" and enjoy unbounded growth. Moreover, the asymptotic long-run growth rate of the optimal consumption levels with trade is determined, establishing that trade has a beneficial effect on long-run growth. JEL Classification Numbers: O41, F12. [source] A review of the biophysical properties of salmonid faeces: implications for aquaculture waste dispersal models and integrated multi-trophic aquacultureAQUACULTURE RESEARCH, Issue 3 2009G K Reid Abstract Knowledge of the quantitative and qualitative properties of salmonid faeces is necessary for aquaculture waste dispersal models, and the design of integrated multi-trophic aquaculture (IMTA) systems. The amount and proximate composition of salmonid faeces can be estimated using a mass-balance, nutritional approach. Indigestible components of salmonid diets have the potential to affect faecal ,cohesiveness' or ,stability'. Nutrient content and density of faeces can vary depending on diet and submersion time. Faecal density has a greater influence on settling velocity than faecal size. Published settling velocity data on salmonid faeces are highly variable due to differences in fish size, rearing systems, collection time, water density, methodology, the mass fraction tested and diet. Most faecal settling data used in published salmonid waste dispersal models are rudimentary and recent information suggests that such models are highly sensitive to this input. The design of open-water IMTA systems and estimation of nutrient capture and recovery from co-cultured filter feeders is difficult due to limited information on particle size, digestibility, settleable and non-settleable mass fractions of salmonid faeces at cage environments. Implications of faecal properties on the accountability for the effects of aquaculture nutrient loading are discussed. [source] SYSTEMS WITH NONEQUIDISTANT SAMPLING: CONTROLLABLE?ASIAN JOURNAL OF CONTROL, Issue 4 2005OBSERVABLE? ABSTRACT Some qualitative properties of systems with nonequidistant sampling are investigated. First, it is proved that the nonequidistant sampling pattern mentioned in [1] does not affect the controllability and observability of time-varying linear systems during discretization. The result is claimed to be true for linear systems with periodic behavior and time-varying sampling. Second, closed-loop stability conditions are established, respectively, for linear and nonlinear sampled-data systems consisting of continuous plants and linear digital feedback controllers. The stability results are extended to general systems consisting of nonlinear continuous plants and nonlinear digital controllers with time-varying sampling periods. [source] A Causal Model Theory of the Meaning of Cause, Enable, and PreventCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 1 2009Steven Sloman Abstract The verbs cause, enable, and prevent express beliefs about the way the world works. We offer a theory of their meaning in terms of the structure of those beliefs expressed using qualitative properties of causal models, a graphical framework for representing causal structure. We propose that these verbs refer to a causal model relevant to a discourse and that "A causes B" expresses the belief that the causal model includes a link from A to B. "A enables/allows B" entails that the model includes a link from A to B, that A represents a category of events necessary for B, and that an alternative cause of B exists. "A prevents B" entails that the model includes a link from A to B and that A reduces the likelihood of B. This theory is able to account for the results of four experiments as well as a variety of existing data on human reasoning. [source] Regularity of the free boundary of an American option on several assets,COMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 7 2009Peter Laurence We establish the C, regularity of the free boundary for an American option on several assets in the case where the payoff is convex and the assets follow correlated geometric Brownian motions. Our work builds on results concerning the qualitative properties and initial regularity of the free boundary by Broadie and Detemple; Jaillet, Lamberton, and Lapeyre; and Villeneuve. © 2008 Wiley Periodicals, Inc. [source]
| | |||||||||||||||