Network disconnection problems in a centralized network

We consider three network disconnection problems in a centralized network where a source node provides service to the other nodes, called demand nodes. In network disconnection problems, each demand node gets a certain benefit when connected to a source node and a network attacker destroys edges to prevent demand nodes from achieving benefits. As destroying edges incurs expenses, an attacker considers the following three different strategies. The first is to maximize the sum of benefits of the disconnected nodes while keeping the total edge destruction cost no more than a given budget. The second is to minimize the total destruction cost needed to make a certain amount of benefits not accomplished. The last is to minimize the ratio of the total destruction cost to the benefits not accomplished. In this paper, we develop exact algorithms to solve the above three problems. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Deterrence under nuclear asymmetry: THAAD and the prospects for missile defense on the Korean peninsula

The 2016 decision to deploy Terminal High Altitude Area Defense (THAAD) to South Korea has generated multitude of intensely politicized issues and has proved highly controversial. This has made it challenging to alleviate, let alone clarify, points of analytical and policy tensions. We instead disaggregate and revisit two fundamental questions. One is whether THAAD could really defend South Korea from North Korean missiles. We challenge the conventional “qualified optimism” by giving analytical primacy to three countermeasures available to defeat THAAD–use of decoys, tumbling and spiral motion, and outnumbering. These countermeasures are relatively inexpensive to create but exceedingly difficult to offset. Second, we assess the optimal way to ensure South Korean national security against North Korean missiles. By examining the balance of capability and issues of credibility/commitment, we show that the U.S. extended deterrence by punishment remains plentiful and sufficiently credible even without enhancing the current defense capability.     

Economic and environmental impacts of vertical and horizontal competition and integration

We explore the economic and environmental impacts of market structures (competition or integration at vertical and horizontal levels). We consider a bilateral duopoly consisting of two manufacturers and two retailers in which each manufacturer offers a wholesale price contract to the respective retailer. The manufacturers decide on wholesale prices and abatement efforts concerning pollution emissions related to manufacturing processes, whereas the retailers compete in quantities in the consumer market. To understand the comprehensive effects of market structures on economic competitiveness and environmental sustainability, we examine a measure of eco‐friendly social welfare, which is the ratio of social welfare and environmental pollution. Interestingly, we find that the market structures that have been believed to be more efficient are less efficient from a broader perspective: (1) double marginalization can generate higher eco‐friendly social welfare, and (2) horizontal competition between firms can result in lower eco‐friendly social welfare. Although vertical integration and horizontal competition yield greater social welfare by facilitating more production activities, these market structures often fail to induce sufficient abatement efforts to balance the polluting effect of the large volume, resulting in more significant environmental degradation. We also show that, despite the pollution‐curbing effect, higher emission penalties can result in less eco‐friendly social welfare. They can even curtail the abatement efforts of firms under particular circumstances. When products become more substitutable, the eco‐friendly social welfare can decrease depending upon the market structure.