In order to investigate the performance of a class of thermally driven refrigerators, usually driven by low-grade thermal energy, a generic thermodynamic model of three-heat-source refrigerator without involving any specific heat-transfer law is put forward by adopting low-dissipation assumptions. Based on the proposed model, the analytical expressions for the coefficient of performance (COP) and cooling power of the system are derived in terms of well-defined dissipation parameters and contact time durations between the system and heat reservoirs. One essential parameter accounting for the size ratio of the two coupled subsystems inside the overall system is introduced in light of the practical meaning of the reversible entropy change. With the help of the aforementioned parameter, the optimal relation between the COP and cooling power is obtained. The optimal operation region and optimal construction of the overall system are further determined for the first time. In addition, the influences of the dissipation and temporal symmetries are discussed in detail, according to which the upper and lower bounds of the COP at maximum cooling power are firstly obtained under two extreme situations. Experimental and simulated data from previous reported works are collected to illustrate the validity and practical significance of the proposed model and associated results. A limit case is presented to highlight the generality of the model.
Abstract. In previous studies of spatial public goods game, each player is able to establish a group. However, in real life, some players cannot successfully organize groups for various reasons. In this paper, we propose a mechanism of reputation-driven group formation, in which groups can only be organized by players whose reputation reaches or exceeds a threshold. We define a player's reputation as the frequency of cooperation in the last T time steps. We find that the highest cooperation level can be obtained when groups are only established by pure cooperators who always cooperate in the last T time steps. Effects of the memory length T on cooperation are also studied.
We study a system of self-propelled agents with the restricted vision. The field of vision of each agent is only a sector of disk bounded by two radii and the included arc. The inclination of these two radii is characterized by the view angle. The consideration of restricted vision is closer to the reality because natural swarms usually do not have a panoramic view. Interestingly, we find that there exists an optimal view angle, leading to the fastest direction consensus. The value of the optimal view angle depends on the density, the interaction radius, the absolute velocity of swarms, and the strength of noise. Our findings may invoke further efforts and attentions to explore the underlying mechanism of the collective motion.
In traffic system, a reasonable information feedback can improve road capacity. In this paper, we investigate an asymmetrical two-route scenario in which dynamic information can be generated and displayed on the board to guide drivers. Two improved feedbacks (i.e. improved mean velocity feedback and improved congestion coefficient feedback) are introduced. Simulations show that the average cost is dependent on the vehicle arrival rate and there exists a critical the dynamic vehicles ratio corresponding to the maximum flux. We find that improved con-gestion coefficient can better enhance the system capacity than that of improved mean velocity feedback.traffic flow, asymmetrical two-route scenario, information feedback
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