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Exit options sustain altruistic punishment and decrease the second-order free-riders, but it is not a panacea

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Science China(Information Sciences) 2025年第1期68卷 278-291页

作者： Chen SHEN Zhao SONG Lei SHI Jun TANIMOTO Zhen WANG Faculty of Engineering Sciences Kyushu University School of Statistics and Mathematics Yunnan University of Finance and Economics School of Computing Engineering and Digital Technologies Teesside University School of Artificial Intelligence OPtics and Electro Nics (iOPEN) Northwestern Polytechnical University

Why do humans punish free riders at their own expense? This behavior represents an evolutionary puzzle in human societies. This study explores the role of exit strategies in fostering altruistic punishment within evolutionary game theory. We extend the traditional prisoner's dilemma model by incorporating exiters, players who opt out for a small payoff while nullifying their opponent's payoff, and altruistic punishers who cooperate and punish non-cooperators. Our findings indicate that in well-mixed populations, exiters destabilize defection but do not promote altruistic punishment. In social networks, however,exiters enable altruistic punishment via cyclic dominance among altruistic punishers, defectors, and exiters. Notably, this cyclic dominance is sensitive to exit payoffs; adjustments can lead to cyclic dominance of non-punishing cooperators, defectors, and exiters, or to a bi-stable state between these two types of cyclic dominance. These results highlight the nuanced impact of exiters on altruistic punishment, emphasizing the need for careful incentivization of exit behavior. While exiters can support altruistic punishment in networked populations, their effectiveness is not a panacea and is highly sensitive to exit payoffs, indicating limits to the voluntary participation mechanism.

关键词： evolutionary game theory altruistic punishment coexistence cyclic dominance bi-stable

Harvesting base vibration energy by a piezoelectric inverted beam with pendulum

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Chinese Physics B 2019年第1期28卷 594-607页

作者： Jia-Nan Pan Wei-Yang Qin Wang-Zheng Deng Hong-Lei Zhou Department of Engineering Mechanics Northwestern Polytechnical University

We proposed a two-degrees-of-freedom inverted piezoelectric beam with pendulum to promote the performance of vibration energy harvesting. This configuration is composed of an inverted elastic beam and a pendulum attached to its free end. The electromechanical equations governing the nonlinear system were derived. The harmonic balance method(HBM)is applied to solve the equation and the results prove that there exists a 1:3 super-harmonic resonance. The simulation results show that owing to the particular nonlinearity, there appears a special bending effect in the amplitude-frequency response, i.e., bending right for the first natural frequency and left for the second natural frequency, which is beneficial for harvesting vibration energy. The HBM results are verified by the entity simulations. Furthermore, over a relatively wide range of power spectral density, it could reach a dense jumping and give a dense high pulse voltage.

关键词： stochastic excitation energy harvesting inverted piezoelectric beam pendulum bi-stable state

A soft gripper of fast speed and low energy consumption

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Science China(Technological Sciences) 2019年第1期62卷 31-38页

作者： WANG YuZhe GUPTA Ujjaval PARULEKAR Nachiket ZHU Jian Department of Mechanical Engineering National University of Singapore School of Mechanical Sciences Indian Institute of Technology Bhubaneswar

Grasping of complicated objects is an active research area which is developing fast throughout the years. Soft grippers can be an effective solution, since they are capable of holding workpieces of various shapes and interacting with unstructured environments effectively. Soft grippers generally consist of soft, flexible and compliant materials, which are able to conform to the shape of the object so that the gripper will not deform or bruise the soft object. Fast grasping of objects with various sizes and shapes remains a challenging task for soft grippers. In the present article, a soft gripper based on bi-stable dielectric elastomer actuator(DEA) inspired by the insect-catching ability of the Venus flytrap, is designed. This soft gripper can achieve good performances in grasping various objects by a simple actuation system. The gripper can switch from one stable state to another when subject to an impulse voltage of 0.04 s. The time duration for each grasping action is 0.17 s, and no continuous voltage is required for holding the gripped object. Thus, energy consumption can be achieved as low as 0.1386 J per grasping action. The mechanism of achieving bi-stable states is related to the duration of impulse voltage applied and the resonant frequency of the structure. The present study demonstrates that bi-stable dielectric elastomer actuators are capable of achieving fast speed for grasping with very low energy consumption, which is significant in the applications to soft grippers and biomimetic robots.

关键词： soft gripper dielectric elastomer fast speed bi-stable low energy consumption

Unraveling the dose-response puzzle of ***:A mechanistic approach

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Infectious Disease Modelling 2016年第1期1卷 101-114页

作者： S.M.Ashrafur Rahman Daniel Munther Aamir Fazil Ben Smith Jianhong Wu Laboratory for Industrial and Applied Mathematics Centre for Disease ModellingDepartment of Mathematics and StatisticsYork UniversityTorontoON M3J 1P3Canada Department of Mathematics Cleveland State UniversityClevelandOH 44115United States National Microbiology Laboratory Public Health Agency of CanadaGuelphON N1G 5B2Canada

Food-borne disease outbreaks caused by Listeria monocytogenes continue to impose heavy burdens on public health in North America and *** explore the threat *** presents to the elderly,pregnant woman and immuno-compromised individuals,many studies have focused on in-host infection mechanisms and risk evaluation in terms of dose-response ***,the connection of these two foci has received little attention,leaving risk prediction with an insufficient mechanistic ***,there is a critical need to quantifiably link in-host infection pathways with the doseresponse *** better understand these relationships,we propose a new mathematical model to describe the gastro-intestinal pathway of *** within the *** model dynamics are shown to be sensitive to inoculation doses and exhibit bistability *** the model to guinea pigs,we show how it provides useful tools to identify key parameters and to inform critical values of these parameters that are pivotal in risk *** preliminary analysis shows that the effect of gastroenvironmental stress,the role of commensal microbiota and immune cells are critical for successful infection of *** and for dictating the shape of the doseresponse curves.

关键词： L.monocytogenes Dose-response Mechanistic model bi-stable Guinea pig

PYRAMIDAL TRAVELING FRONTS OF bistable REACTION-DIFFUSION EQUATIONS WITH DELAY

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Annals of Differential Equations 2014年第2期30卷 127-136页

作者： Xiongxiong Bao Zhicheng Wang School of Math.and Statistics Lanzhou University

This paper is concerned with nonplanar traveling fronts for delayed reaction- diffusion equation with bistable nonlinearity in RTM （m〉 3）. By the comparison principle and super- and subsolutions technique, we estab... 详细信息

关键词： existence pyramidal traveling fronts reaztion-diffusion equation bi-stable delay