Anna Nagurney

Network economics : a variational inequality approach

Preface. I: Theory and Fundamentals. 1. Variational Inequality THeory. 2. Algorithms. II: Partial Equilibrium - Perfect Competition. 3. Spatial Price Equilibrium. 4. Traffic Network Equilibrium. 5. Migration Equilibrium. III: Partial Equilibrium - Imperfect Competition. 6. Oligopolistic Market Equilibrium. 7. Environmental Networks. 8. Knowledge Network Equilibrium. IV: General Equilibrium. 9. Walrasian Price Equilibrium. 10. Financial Equilibrium. V: Estimation. 11. Constrained Matrix Problems. A. Problems.

Projected dynamical systems and variational inequalities with applications

Preface. Glossary of Notation. I: Theory of Projected Dynamical Systems. 1. Introduction and Overview. 2. Projected Dynamical Systems. 3. Stability Analysis. 4. Discrete Time Algorithms. 5. Oligopolistic Market Equilibrium. 6.Spatial Price Equilibrium. 7. Elastic Demand Traffic Equilibrium. 8. Fixed Demand Traffic Equilibrium. Index.

A supply chain network equilibrium model

This paper develops an equilibrium model of a competitive supply chain network that can provide a benchmark for evaluating both price and product flows. This model is sufficiently general to capture both the independent behavior of various decision-makers (manufacturers, retailers and consumers) as well as the effect of their interactions. The network structure of the supply chain is identified and equilibrium conditions are derived. A finite-dimensional variational inequality formulation is established. The algorithm is applied to numerical examples to determine the equilibrium product flows and prices. Theoretical and empirical results demonstrate that solutions to supply chain network equilibrium problems with nonlinear and nonseparable functions can be computed using the modified projection method. The model provides the foundation for developing dynamic models for the study of the evolution of supply chains.

Dynamical systems and variational inequalities

The variational inequality problem has been utilized to formulate and study a plethora of competitive equilibrium problems in different disciplines, ranging from oligopolistic market equilibrium problems to traffic network equilibrium problems. In this paper we consider for a given variational inequality a naturally related ordinary differential equation. The ordinary differential equations that arise are nonstandard because of discontinuities that appear in the dynamics. These discontinuities are due to the constraints associated with the feasible region of the variational inequality problem. The goals of the paper are two-fold. The first goal is to demonstrate that although non-standard, many of the important quantitative and qualitative properties of ordinary differential equations that hold under the standard conditions, such as Lipschitz continuity type conditions, apply here as well. This is important from the point of view of modeling, since it suggests (at least under some appropriate conditions) that these ordinary differential equations may serve as dynamical models. The second goal is to prove convergence for a class of numerical schemes designed to approximate solutions to a given variational inequality. This is done by exploiting the equivalence between the stationary points of the associated ordinary differential equation and the solutions of the variational inequality problem. It can be expected that the techniques described in this paper will be useful for more elaborate dynamical models, such as stochastic models, and that the connection between such dynamical models and the solutions to the variational inequalities will provide a deeper understanding of equilibrium problems.

On a Paradox of Traffic Planning

For each point of a road network, let there be given the number of cars starting from it, and the destination of the cars. Under these conditions one wishes to estimate the distribution of traffic flow. Whether one street is preferable to another depends not only on the quality of the road, but also on the density of the flow. If every driver takes the path that looks most favorable to him, the resultant running times need not be minimal. Furthermore, it is indicated by an example that an extension of the road network may cause a redistribution of the traffic that results in longer individual running times.

Supply Chain Networks, Electronic Commerce, and Supply Side and Demand Side Risk

In this paper, we develop a supply chain network model in which both physical and electronic transactions are allowed and in which supply side risk as well as demand side risk are included in the formulation. The model consists of three tiers of decision-makers: the manufacturers, the distributors, and the retailers, with the demands associated with the retail outlets being random. We model the optimizing behavior of the various decision-makers, with the manufacturers and the distributors being multicriteria decision-makers and concerned with both profit maximization and risk minimization. We derive the equilibrium conditions and establish the finite-dimensional variational inequality formulation. We provide qualitative properties of the equilibrium pattern in terms of existence and uniqueness results and also establish conditions under which the proposed computational procedure is guaranteed to converge. We illustrate the supply chain network model through several numerical examples for which the equilibrium prices and product shipments are computed. This is the first multitiered supply chain network equilibrium model with electronic commerce and with supply side and demand side risk for which modeling, qualitative analysis, and computational results have been obtained.

A supply chain network equilibrium model with random demands

Abstract In this paper, we develop a supply chain network model consisting of manufacturers and retailers in which the demands associated with the retail outlets are random. We model the optimizing behavior of the various decision-makers, derive the equilibrium conditions, and establish the finite-dimensional variational inequality formulation. We provide qualitative properties of the equilibrium pattern in terms of existence and uniqueness results and also establish conditions under which the proposed computational procedure is guaranteed to converge. Finally, we illustrate the model through several numerical examples for which the equilibrium prices and product shipments are computed. This is the first supply chain network equilibrium model with random demands for which modeling, qualitative analysis, and computational results have been obtained.

Oligopolistic and competitive behavior of spatially separated markets

Abstract We examine the connection between Cournot oligopoly and perfect competition by showing that a fairly general oligopoly model with spatially separated markets generates a general spatial price equilibrium model as an extreme, limiting case. Our analysis depends crucially on the fact that the governing equilibrium conditions of both the oligopoly and the spatial price equilibrium problem can be formulated as variational inequalities.

Projected Dynamical Systems in the Formulation, Stability Analysis, and Computation of Fixed-Demand Traffic Network Equilibria

This paper proposes, for a fixed demand traffic network problem, a route travel choice adjustment process formulated as a projected dynamical system, whose stationary points correspond to the traffic equilibria. Stability analysis is then conducted in order to investigate conditions under which the route travel choice adjustment process approaches equilibria. We also propose a discrete time algorithm, the Euler method, for the computation of the traffic equilibrium and provide convergence results. The notable feature of the algorithm is that it decomposes the traffic problem into network subproblems of special structure, each of which can then be solved simultaneously and in closed form using exact equilibration. Finally, we illustrate the computational performance of the Euler method through various numerical examples.

On the stability of projected dynamical systems

A class of projected dynamical systems (PDS), whose stationary points solve the corresponding variational inequality problem (VIP), was recently studied by Dupuis and Nagurney (Ref. 1). This paper initiates the study of the stability of such PDS around their stationary points and thus gives rise to the study of the dynamical stability of VIP solutions. Examples are constructed showing that such a study can be quite distinct from the classical stability study for dynamical systems (DS). We give the definition of a regular solution to a VIP and introduce the concept of a minimal face flow induced by a PDS, which is a standard DS of a lower dimension. We then show that, at the regular solutions of the VIP, the local stability of the PDS is essentially the same as that of its minimal face flow. Hence, we reduce the problem, in this case, to one of the classical stability study of DS, a more developed discipline. In a more direct way, we then establish a series of local and global stability results of the PDS, under various conditions of monotonicity.