1,093 research outputs found
Multi-defender Security Games with Schedules
Stackelberg Security Games are often used to model strategic interactions in
high-stakes security settings. The majority of existing models focus on
single-defender settings where a single entity assumes command of all security
assets. However, many realistic scenarios feature multiple heterogeneous
defenders with their own interests and priorities embedded in a more complex
system. Furthermore, defenders rarely choose targets to protect. Instead, they
have a multitude of defensive resources or schedules at its disposal, each with
different protective capabilities. In this paper, we study security games
featuring multiple defenders and schedules simultaneously. We show that unlike
prior work on multi-defender security games, the introduction of schedules can
cause non-existence of equilibrium even under rather restricted environments.
We prove that under the mild restriction that any subset of a schedule is also
a schedule, non-existence of equilibrium is not only avoided, but can be
computed in polynomial time in games with two defenders. Under additional
assumptions, our algorithm can be extended to games with more than two
defenders and its computation scaled up in special classes of games with
compactly represented schedules such as those used in patrolling applications.
Experimental results suggest that our methods scale gracefully with game size,
making our algorithms amongst the few that can tackle multiple heterogeneous
defenders.Comment: Extended version of the paper accepted to GameSec 202
Function Approximation for Solving Stackelberg Equilibrium in Large Perfect Information Games
Function approximation (FA) has been a critical component in solving large
zero-sum games. Yet, little attention has been given towards FA in solving
\textit{general-sum} extensive-form games, despite them being widely regarded
as being computationally more challenging than their fully competitive or
cooperative counterparts. A key challenge is that for many equilibria in
general-sum games, no simple analogue to the state value function used in
Markov Decision Processes and zero-sum games exists. In this paper, we propose
learning the \textit{Enforceable Payoff Frontier} (EPF) -- a generalization of
the state value function for general-sum games. We approximate the optimal
\textit{Stackelberg extensive-form correlated equilibrium} by representing EPFs
with neural networks and training them by using appropriate backup operations
and loss functions. This is the first method that applies FA to the Stackelberg
setting, allowing us to scale to much larger games while still enjoying
performance guarantees based on FA error. Additionally, our proposed method
guarantees incentive compatibility and is easy to evaluate without having to
depend on self-play or approximate best-response oracles.Comment: To appear in AAAI 202
A Global Method for a Two-Dimensional Cutting Stock Problem in the Manufacturing Industry
A two-dimensional cutting stock problem (2DCSP) needs to cut a set of given rectangular items from standard-sized rectangular materials with the objective of minimizing the number of materials used. This problem frequently arises in different manufacturing industries such as glass, wood, paper, plastic, etc. However, the current literatures lack a deterministic method for solving the 2DCSP. However, this study proposes a global method to solve the 2DCSP. It aims to reduce the number of binary variables for the proposed model to speed up the solving time and obtain the optimal solution. Our experiments demonstrate that the proposed method is superior to current reference methods for solving the 2DCSP
Simultaneous thermoosmotic and thermoelectric responses in nanoconfined electrolyte solutions: Effects of nanopore structures and membrane properties
Hypothesis: Nanofluidic systems provide an emerging and efficient platform
for thermoelectric conversion and fluid pumping with low-grade heat energy. As
a basis of their performance enhancement, the effects of the structures and
properties of the nanofluidic systems on the thermoelectric response (TER) and
the thermoosmotic response (TOR) are yet to be explored. Methods: The
simultaneous TER and TOR of electrolyte solutions in nanofluidic membrane pores
on which an axial temperature gradient is exerted are investigated numerically
and semi-analytically. A semi-analytical model is developed with the
consideration of finite membrane thermal conductivity and the
reservoir/entrance effect. Findings: The increase in the access resistance due
to the nanopore-reservoir interfaces accounts for the decrease of short circuit
current at the low concentration regime. The decrease in the thermal
conductivity ratio can enhance the TER and TOR. The maximum power density
occurring at the nanopore radius twice the Debye length ranges from several to
dozens of mW K m and is an order of magnitude higher than typical
thermo-supercapacitors. The surface charge polarity can heavily affect the sign
and magnitude of the short-circuit current, the Seebeck coefficient, and the
open-circuit thermoosmotic coefficient, but has less effect on the
short-circuit thermoosmotic coefficient. Furthermore, the membrane thickness
makes different impacts on TER and TOR for zero and finite membrane thermal
conductivity.Comment: 38 pages, 10 figure
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