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Sustainability of Coupled Systems
Research: Welcome
Research: About
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Natural systems are interconnected with social and infrastructural systems. For sustainability, it is important to understand how social, natural, and infrastructural components interact. During my Ph.D. years, I highlighted infrastructurehard (e.g., dam, channel) and soft (e.g., social norms, institution)—as a critical entity in building sustainability. I designed dynamical and agent-based models in resource management and urban flood evacuation to explore sustainability arising from human-nature-infrastructure interplays.

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An updated framework with additional resource and infrastructure (colored green)

Resource substitutability and effort asymmetry
Published in Palgrave Communications (now Humanities and Social Sciences Communications)

I explored how substitutability between two natural resources and asymmetry of effort shares on two resources affected sustainability in coupled natural-human systems. I brought a concept from economics (constant elasticity of substitution function) in calculating the payoff of resource users in strategic decisions (based on evolutionary game theory). I developed a dynamical system model between natural resources, humans, and infrastructure. Substitutability and asymmetry nonlinearly affected policy flexibility and system performance. High substitutability enhanced policy flexibility, system performance, and sustainability against disturbances. When a user depended on one resource, policymaking became flexible yet the system became vulnerable to uncertainties.



Left - System performances of infrastructure for resources 1 (A) and 2 (B) with respect to substitutability (β) and asymetry (α)
Right - Policy flexibility with respect to substitutability (
β) and asymetry (α)


Tradeoffs between efficiency and fairness in evacuation
Published in PLoS ONE

This study dealt with urban flood evacuation, testing different combinations of shelter capacity distribution (a property of hard infrastructure) and zone prioritization (simultaneous/staged evacuation as a property of soft infrastructure). I developed a conceptual agent-based model to investigate efficiency-fairness tradeoffs among several strategies. I found that shelter capacity distribution impacted more on efficiency, whereas simultaneous/staged evacuations affected fairness more. Here, there was a tradeoff between efficiency and fairness among multiple strategies. Efficiency was attained at the expense of fairness, and vice versa: policy dilemma. This study suggested that there is no perfect solution with both maximum efficiency and equity but only a set of optimal strategies.


Pareto-optimal strategies considering efficiency (evacuation duration) and fairness (DOU)
The red line is a Pareto frontier, and each dot represents different evacuation strategy.

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