PACS 64.60.Ht -Dynamic critical phenomena PACS 05.10.Ln -Monte Carlo methods PACS 75.60.Ch -Domain walls and domain structure Abstract -With Monte Carlo simulations, we study the creep motion of a domain wall in the twodimensional random-field Ising model with a driving field. We observe the nonlinear field-velocity relation, and determine the creep exponent µ. To further investigate the universality class of the creep motion, we also measure the roughness exponent ζ and energy barrier exponent ψ from the zero-field relaxation process. For strong disorder, the exponents are consistent with those of the Edwards-Wilkinson equation; for weak disorder, a different universality class is detected.

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Abstract:This paper studies the application of compressed sensing theory in speech signal sampling and reconstruction of speech signals. According to the sparsity of speech signals in the discrete cosine transform basis (DCT), we propose a speech compressed sensing (CS) system based on DCT domain which realizes sparse representation of speech signal in DCT domain. Utilizing Gauss random matrix as the measurement matrix and orthogonal matching pursuit algorithm (OMP), the performance of speech signal reconstruction is acquired. The simulation results show that the sparsity of the speech signal is higher in the DCT domain and the OMP algorithm can effectively improves the performance of reconstructed speech signals.

A long-standing problem in biology, economics, and social sciences is to understand the conditions required for the emergence and maintenance of cooperation in evolving populations. This paper investigates how to promote the evolution of cooperation in the Prisoner’s Dilemma game (PDG). Differing from previous approaches, we not only propose a tag-based control (TBC) mechanism but also look at how the evolution of cooperation by TBC can be successfully promoted. The effect of TBC on the evolutionary process of cooperation shows that it can both reduce the payoff of defectors and inhibit defection; although when the cooperation rate is high, TBC will also reduce the payoff of cooperators unless the identified rate of the TBC is large enough. An optimal timing control (OTC) of switched replicator dynamics is designed to consider the control costs, the cooperation rate at terminal time, and the cooperator’s payoff. The results show that the switching control (SC) between an optimal identified rate control of the TBC and no TBC can properly not only maintain a high cooperation rate but also greatly enhance the payoff of the cooperators. Our results provide valuable insights for some clusters, for example, logistics parks and government, to regard the decision to promote cooperation.

Network is a powerful language to represent relational data. One way to understand network is to analyze groups of nodes which share same properties or functions. The task of discovering such groups is known as community detection. The community detection in real-life networks, the majority of which are weighted temporal text networks, is confronted with two main problems-how to model the weight of edges and how to exploit the temporal information. Existing works either ignore the edge weight or utilize it in graph measures like modularity, which lacks scalability. And currently the common-used method involving temporal information is to discretize the time, which leads to series of problems. We are thus motivated to present a new method to encode the edge weight and temporal information. A probabilistic generative model, named Custom Temporal Community Detection (CTCD) is introduced, which views the link between two nodes as a weighted edge with several time stamps. Our model utilizes network, semantic and temporal information simultaneously to extract temporal community affiliations for individual user, influence strength across communities and temporal interested topic in each community. An efficient inference method, which scales linearly, and corresponding parallel implementation are proposed to adapt to large datasets. Through the knowledge extracted by CTCD, we are able to spot the community shift of the individual user, to which little attention has been given, and employ it to track the development of the communities over time. Moreover, experiments on two large-scale weighted temporal text networks show that CTCD gains significant improvement over state-of-the-art methods on a series of tasks. INDEX TERMS Data mining, social network, temporal community detection, topic model.

Based on the Hamiltonian equation of motion of the φ 4 theory with quenched disorder, we investigate the depinning phase transition of the domain-wall motion in two-dimensional magnets. With the short-time dynamic approach, we numerically determine the transition field, and the static and dynamic critical exponents. The results show that the fundamental Hamiltonian equation of motion belongs to a universality class very different from those effective equations of motion.

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