Crowd evacuation of a building has been studied over the last decades. In this paper, seven methodological approaches for crowd evacuation have been identified. These approaches include cellular ...automata models, lattice gas models, social force models, fluid-dynamic models, agent-based models, game theoretic models, and approaches based on experiments with animals. According to available literatures, we discuss the advantages and disadvantages of these approaches, and conclude that a variety of different kinds of approaches should be combined to study crowd evacuation. Psychological and physiological elements affecting individual and collective behaviors should be also incorporated into the evacuation models.
With the increasing of risk potential in crowded places, evacuation management becomes practically important to ensure the safety of crowds. The studies of crowd evacuation in normal or emergency ...situations have become a hot topic. Due to the distinct advantages of high efficiency, strong scalability and simple implementation, cellular automata models (CA) have become one of the most widely-used models for evacuation. However, the practical requirements of evacuation propose some important challenges for CA models, for example, to accurately characterize both position and velocity of individuals, to depict environments and accidents, and to describe human behaviors. In the last 20 years, there are many studies aiming at resolving the above challenges. Starting from the challenges mentioned above, this paper tries to give a review of CA models, specially used for crowd evacuation. Firstly, we give an overview of CA models for evacuation, and put forward research paradigm, modeling framework and classification of CA models. The models used for evacuation are classified into three kinds of categories, i.e. lattice gas model, floor field model, and other field-based models. The last category includes potential field model, electrostatic-induced potential field model, cost potential field model, etc. Then, three main challenges of CA models for evacuation are presented, and the improvements for each type of challenge are summarized. Typical simulation scenarios and research issues are further proposed. Finally, the advantages and disadvantages of CA models are illustrated from the aspects of implementation, performance, scalability, accuracy and applicability.
•Research paradigm of CA models is summarized.•CA models are classified into lattice gas, floor field and other field-based models.•Three main challenges of cellular automata models for evacuation are presented.•Typical simulation scenarios and research issues are concluded.•The advantages and disadvantages of CA models are discussed.
This study aims to get insight into the question whether cooperative behaviors can promote the evacuation efficiency during an evacuation process. In this work, cooperative behaviors and evacuation ...efficiency have been examined in detail by using a cellular automata model with behavioral extension. The simulation results show that moderate cooperative behaviors can result in the highest evacuation efficiency. It is found that in a mixture of cooperative and competitive individuals, more cooperative people will lead to relatively high evacuation efficiency, and the larger subgroup will play a leading role. This work can also provide some new insights for the study of cooperative behaviors and evacuation efficiency which can be a scientific decision-making basis for emergency response involving large-scale crowd evacuation in emergencies.
•We propose a computational model to study cooperation and evacuation efficiency.•In this model, we quantify the connection between the amount of cooperation and evacuation efficiency.•We observe the highest evacuation efficiency for intermediate levels of cooperation.•The model can provide a decision-making basis for emergency response involving large-scale crowd evacuation.
Understanding the emergence of cooperation in spatial public goods game remains a grand challenge across disciplines. In most previous studies, it is assumed that the investments of all the ...cooperators are identical, and often equal to 1. However, it is worth mentioning that players are diverse and heterogeneous when choosing actions in the rapidly developing modern society and researchers have shown more interest to the heterogeneity of players recently. For modeling the heterogeneous players without loss of generality, it is assumed in this work that the investment of a cooperator is a random variable with uniform distribution, the mean value of which is equal to 1. The results of extensive numerical simulations convincingly indicate that heterogeneous investments can promote cooperation. Specifically, a large value of the variance of the random variable can decrease the two critical values for the result of behavioral evolution effectively. Moreover, the larger the variance is, the better the promotion effect will be. In addition, this article has discussed the impact of heterogeneous investments when the coevolution of both strategy and investment is taken into account. Comparing the promotion effect of coevolution of strategy and investment with that of strategy imitation only, we can conclude that the coevolution of strategy and investment decreases the asymptotic fraction of cooperators by weakening the heterogeneity of investments, which further demonstrates that heterogeneous investments can promote cooperation in spatial public goods game.
A game-theoretical model to study evacuees’ cooperative and competitive behaviors during an emergency evacuation is proposed. The model integrated with evacuation dynamics model determines the ...density of cooperative and competitive evacuees and their related evacuation times. Computer simulation results show that (1) as urgency of evacuation increases, cooperation among evacuees’ decreases; (2) in an emergency situation, individual hyper-rationality among evacuees diminishes evacuation efficiency; (3) the imitation effect enhances cooperation among evacuees, yet reduces evacuation efficiency. This study provides a methodological pattern to research crowd behaviors in emergency evacuation.
The continual growth of Internet traffic necessitates a high-capacity transmission platform and also highlights the importance of a multi-granularity transport network due to the flexible bitrates of ...Internet traffic. To meet these challenges, a spectrum-flexible optical network based on orthogonal frequency-division multiplexing (OFDM) transmission technologies has been proposed as a promising solution because of its large transport capacity and bandwidth flexibility. In spectrum-flexible optical networks, we focus on the complete dynamic routing and spectrum assignment (RSA) problem, which integrates the signal format selection subproblem, the routing subproblem, and the spectrum assignment subproblem. In the complete RSA problem, we jointly consider the spectrum continuity constraints, the transmission distance constraints, and the relationship between the traffic bitrate and the signal bandwidth. A nonlinear programing model is presented to state the complete RSA problem. To solve the problem, we introduce a decomposition approach that divides the nonlinear problem into three steps: selecting the modulation format, solving the linear basic RSA problem, and checking the transmission distances. Based on the decomposition, we propose two heuristic approaches: modulation level fixed and adaptive RSA approaches for the complete RSA problem. Through analysis of the approaches, we prove that, in theory, the modulation level adaptive RSA approach can find the optimal solution to the complete RSA problem. The two approaches are implemented and compared in simulations. The results prove that the modulation level adaptive approaches achieve a lower capacity blocking probability than the modulation level fixed approaches.
We propose a highly linear radio-over-fiber system with low intermodulation distortion (IMD) using a single-drive dual-parallel Mach-Zehnder modulator (SD-DPMZM). The optical carrier is modulated in ...one of the two parallel modulators, while remaining unmodulated in the other one. There exists optimal working points for SD-DPMZM that makes its two kinds of origins of third-order IMD (IMD3) have opposite phase and equal intensity, and cancel each other; hence the output IMD3 is suppressed dramatically. Experimental results show that the proposed scheme can achieve a spurious-free dynamic range of up to 122.9 dB · Hz 2/3 , which is in agreement with the theoretical analysis. It is about 20 dB more than a conventional MZM. The error vector magnitude of the proposed scheme, for a 16-QAM 10-MSym/s signal centered at 4 GHz, is 1.94%.
A sensitively competitive electrochemical immunosensor for the detection of cortisol was successfully developed based on gold nanoparticles and magnetic functionalized reduced graphene oxide ...(AuNPs/MrGO). In order to construct the base of the immunosensor, the MrGO was initially fabricated by chemical cross-linking and used to modify the nafion pretreated glassy carbon electrode. Subsequently, the surface of electrode was modified by AuNPs via electrochemical deposition. A variety of cortisol (Cor) can be firmly loaded in the AuNPs/MrGO with large specific surface area and good bioactivity to construct the basic electrode (Cor/AuNPs/MrGO/Nafion@GCE), which was characterized by the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. Due to the cortisol on the surface of basic electrode and samples can competitively combine with the cortisol antibody labelled by horseradish peroxidase (HRP-Strept-Biotin-Ab). Finally, the detection signal of electrochemical immunosensor (HRP-Strept-Biotin-Ab-Cor/AuNPs/MrGO/Nafion@GCE) in the test liquid had negative correlations with the concentration of cortisol in samples. The AuNPs/MrGO with excellent electrical conductivity being applied, the electrochemical response of the immunosensor was immensely amplified. The immunosensor displayed excellent analytical performance for the detection of cortisol range from 0.1 to 1000ng/mL with a detection limit of 0.05ng/mL at 3σ. Moreover, compared the developed immunoassay with commercially available enzyme linked immunosorbent assay, the proposed method showed good precision, acceptable stability and reproducibility, indicating the immunosensor could be used for the sensitive, efficient and real-time detection of cortisol in real samples. Therefore, the present strategy provides a novel and convenient method for clinical determination of cortisol.
•A HRP-Strept-Biotin-Ab-Cor/AuNPs/MrGO/Nafion@GCE immunosensor was successfully fabricated.•The prepared MrGO was characterized by AFM, XRD, FTIR, VSM, TEM and SEM.•The proposed immunosensor exhibited an broad detection range and low detection limit for cortisol.•The immunosensor can be used for the sensitive, efficient and real-time analysis of cortisol in real samples.
Strange stars ought to exist in the universe according to the strange quark matter hypothesis, which states that matter made of roughly equal numbers of up, down, and strange quarks could be the true ...ground state of baryonic matter rather than ordinary atomic nuclei. Theoretical models of strange quark matter, such as the standard MIT bag model, the density-dependent quark mass model, or the quasi-particle model, however, appear to be unable to reproduce some of the properties (masses, radii, and tidal deformabilities) of recently observed compact stars. This is different if alternative gravity theory (e.g., non-Newtonian gravity) or dark matter (e.g., mirror dark matter) are considered, which resolve these issues. The possible existence of strange stars could thus provide a clue to new physics, as discussed in this review.
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