Qiang

A network efficiency measure with application to critical infrastructure networks

In this paper, we demonstrate how a new network performance/efficiency measure, which captures demands, flows, costs, and behavior on networks, can be used to assess the importance of network components and their rankings. We provide new results regarding the measure, which we refer to as the Nagurney–Qiang measure, or, simply, the N–Q measure, and a previously proposed one, which did not explicitly consider demands and flows. We apply both measures to such critical infrastructure networks as transportation networks and the Internet and further explore the new measure through an application to an electric power generation and distribution network in the form of a supply chain. The Nagurney and Qiang network performance/efficiency measure that captures flows and behavior can identify which network components, that is, nodes and links, have the greatest impact in terms of their removal and, hence, are important from both vulnerability as well as security standpoints.

Environmental Impact Assessment of Transportation Networks with Degradable Links in an Era of Climate Change

ABSTRACT This paper proposes environmental impact assessment indices to evaluate the environmental effects of link capacity degradation in transportation (road) networks. The indices are applicable in the case of either user-optimizing or system-optimizing behavior. We also construct environmental link importance indicators that allow for the ranking of links in transportation networks in terms of their environmental importance, should they be removed/destroyed. Numerical transportation network examples illustrate the proposed quantitative environmental indicators and further substantiate that system-optimizing behavior does not necessarily lead to reduced emissions.

A unified network performance measure with importance identification and the ranking of network components

In this paper, we propose the first network performance measure that can be used to assess the efficiency of a network in the case of either fixed or elastic demands. Such a measure is needed for many different applications since only when the performance of a network can be quantifiably measured can the network be appropriately managed. Moreover, as we demonstrate, the proposed performance measure, which captures flow information and behavior, allows one to determine the criticality of various nodes (as well as links) through the identification of their importance and ranking. We present specific networks for which the performance/efficiency is computed along with the importance rankings of the nodes and links. The new measure can be applied to transportation networks, supply chains, financial networks, electric power generation and distribution networks as well as to the Internet and can be used to assess the vulnerability of a network to disruptions.

A network efficiency measure for congested networks

In this paper, we propose a network efficiency measure for congested networks, that captures demands, costs, flows, and behavior. The network efficiency/performance measure can identify which network components, that is, nodes and links, have the greatest impact in terms of their removal, due to, for example, natural disasters, structural failures, terrorist attacks, etc., and, hence, are important from both vulnerability as well as security standpoints. The new measure is applied to the Braess paradox network in which the demands are varied over the horizon and explicit formulae are derived for the importance values of the network nodes and links. This measure is applicable to such congested networks as urban transportation networks and the Internet.

Modeling of Supply Chain Risk under Disruptions with Performance Measurement and Robustness Analysis

In this chapter, we develop a new supply chain network model with multiple decision-makers associated at different tiers and with multiple transportation modes for shipment of the good between tiers. The model formulation captures supply-side risk as well as demand-side risk, along with uncertainty in transportation and other costs. The model also incorporates the individual attitudes towards disruption risks among the manufacturers and the retailers, with the demands for the product associated with the retailers being random. We present the behavior of the various decision-makers, derive the governing equilibrium conditions, and establish the finite-dimensional variational inequality formulation. We also propose a weighted supply chain performance and robustness measure based on our recently derived network performance/efficiency measure and provide supply chain examples for which the equilibrium solutions are determined along with the robustness analyses. This chapter extends previous supply chain research by capturing supplyside disruption risks, transportation and other cost risks, and demand-side uncertainty within an integrated modeling and robustness analysis framework.

Robustness of transportation networks subject to degradable links

In this paper, we demonstrate how to capture the robustness of a transportation network in the case of degradable links represented by decreasing capacities. The analysis is conducted by utilizing Bureau of Public Road link travel cost functions and a recently proposed network efficiency measure for congested networks. For specific networks we are able to derive lower bounds for the robustness when percentage reductions in the link capacities take place.

A Relative Total Cost Index for the Evaluation of Transportation Network Robustness in the Presence of Degradable Links and Alternative Travel Behavior

In this paper, we demonstrate how to capture the robustness of a transportation network in the case of degradable links represented by decreasing capacities. In particular, with the use of Bureau of Public Road user link travel cost functions, we propose two relative total cost indices to assess transportation network robustness in the case of travel behavior associated with either user-optimization or system-optimization. We derive upper bounds of the relative total cost index for transportation networks with special structure and congestion parameters under the user-optimal flow pattern. We also derive an upper bound for the relative total cost index under the system-optimal flow pattern for general transportation networks. Numerical examples are presented for illustration purposes.This research is the first to quantify transportation network robustness in the presence of degradable links and alternative travel behavior. This research has implication for transportation planning and management, for vulnerability analysis, as well as for security issues.

Multi-product supply chain horizontal network integration: models, theory, and computational results

In this paper, we develop multiproduct supply chain network models with explicit capacities, prior to and post their horizontal integration. In addition, we propose a measure, which allows one to quantify and assess, from a supply chain network perspective, the synergy benefits associated with the integration of multiproduct firms through mergers/ acquisitions. We utilize a system-optimization perspective for the model development and provide the variational inequality formulations, which are then utilized to propose a computational procedure which fully exploits the underlying network structure. We illustrate the theoretical and computational framework with numerical examples.This paper is a contribution to the literatures of supply chain integration and mergers and acquisitions.

Multiproduct Humanitarian Healthcare Supply Chains: A Network Modeling and Computational Framework

In this paper, we develop a model for supply chain network design in the case of multiple products, with particular relevance to humanitarian healthcare. The model allows for the determination of the optimal capacities of supply chain network activities in the form of manufacturing, storage, and distribution, as well as the optimal multiple product flows, and identifies at what minimal total cost the demands for the products at the various points are achievable. The model may be utilized for the determination of the optimal allocation of resources for multiple vaccine and medicine production, storage, and distribution to points of need in the case of disasters, epidemics, or pandemics. The model is sufficiently general to handle supply chain network design, as well as redesign, and can be used by organizations to quantify the humanitarian healthcare supply chain costs in a transparent way to stakeholders, including governments and funding agencies.

Identification of Critical Nodes and Links in Financial Networks With Intermediation and Electronic Transactions

In this paper, we propose a network performance measure for the evaluation of financial networks with intermediation. The measure captures risk, transaction cost, price, transaction flow, revenue, and demand information in the context of the decision-makers’ behavior in multitiered financial networks that also allow for electronic transactions. The measure is then utilized to define the importance of a financial network component, that is, a node or a link, or a combination of nodes and links. Numerical examples are provided in which the performance measure of the financial network is computed along with the importance ranking of the nodes and links. The results in this paper can be used to assess which nodes and links in financial networks are the most vulnerable in the sense that their removal will impact the performance of the network in the most significant way. Hence, the results in this paper have relevance to national security as well as implications for the insurance industry.