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Physica
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Physica

North-Holland

0378-4371

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    Enhancing recommendation competence in nearest neighbour models

    Latha, R.
    15页
    查看更多>>摘要：Collaborative Filtering approaches are viewed as essential tools to suggest products to users based on historical knowledge. Widely adopted user based Collaborative Filtering approaches rely on ratings provided by similar users of the target user to generate appropriate recommendations. The pair-wise user similarity is based on set of common rated items between users and identifying similar users is a challenging task when the set is small. To improve the recommendation quality in low correlated data, User Trait Model and Bayesian Global Agreement model are suggested in this work. The proposed models assign global agreement score to users. A linear function of any baseline user similarity and global agreement score of users is defined as a new similarity measure. From inception, recommendation approaches are keen on improving accuracy of recommended items and downplays the diversity of recommendations, which results in poor user satisfaction. The proposed models focus on improving accuracy and diversity of recommendations. Experiments are conducted on three benchmark data sets and the results are compared with other user based CF approaches suggested in the literature. The experimental results indicate that the proposed approaches outperform other user based CF approaches based on the evaluation metrics namely, MAE, RMSE, F 1 for prediction accuracy, MN, ILD for recommendation diversity and Coverage for the extent of recommendations. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Revisiting maximal average fidelity of teleportation

    Portesi, M.Bussandri, D. G.Majtey, A. P.
    18页
    查看更多>>摘要：We obtain the maximal average fidelity corresponding to the standard quantum tele-portation protocol for an arbitrary isotropic distribution of input states and an arbitrary resource state. We extend this result to a family of von Neumann measurements, which includes the projections onto the computational and Bell basis, considering a Bell-diagonal resource state.& nbsp;We focus on three specific isotropic distributions of input states: (1) completely mixed input states, (2) states with a certain (fixed) degree of purity, and (3) quasi-pure input states. We show that the standard quantum teleportation protocol can teleport arbitrary mixed states with higher average fidelity than its classical counterpart even when the resource of the protocol is a non-entangled state, specifically, a separable Werner state. Moreover, we find that the maximum average fidelity obtained with classical-quantum states used as a resource in a standard teleportation protocol also exceeds the classical fidelity. To establish the role played by the presence or absence of quantum correlations in the resource state and their relation with the correlations present in the von Neumann measurement performed by Alice, we analyze in detail the case of Bell diagonal resource states employing a family of monoparametric basis for which both the Bell and the computational (non-correlated) basis are included. Only in the case where the basis on which Alice measures is completely uncorrelated (computational basis) the maximum average fidelity does not exceed the classical fidelity for any resource state. In all other cases, the maximum average fidelity exceeds the classical one for a certain range of parameters describing the resource state, evidencing the importance of the correlations present in the measurements. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Topology analysis of Lanzhou public transport network based on double-layer complex network theory

    Pu, HanLi, YinzhenMa, Changxi
    13页
    查看更多>>摘要：The network topology is the basis of studying the overall performance and dynamic evolution mechanism of network. In regards to the study on the topology of multi-layer complex networks, the current studies fail to consider the heterogeneity of edges and nodes in multi-layer complex networks, and such methods are insufficient when they are used to analyze the static characteristics of topology. Therefore, this paper based on the theoretical basis of the multi-layer complex network, establishes a two-layer public transit complex network model where urban rail transit and bus transit cooperate with each other, and by optimizing this two-layer public transit complex network model, further proposes an integrated public transit network model. According to the method of analyzing the static statistical characteristics of complex networks, and considering the heterogeneity of nodes and edges in multi-layer network, this paper gives the evaluation indicators of static statistical characteristics of multi-layer public transit complex networks. Taking the two-layer public transit complex network structure in Lanzhou as an example, this paper finds out the main factors affecting its network stability and efficiency by analyzing the physical structure characteristics of this two-layer public transit complex network in Lanzhou where urban rail transit and bus transit cooperate with each other, and then puts forward the network optimization suggestions from the point of view of optimizing key nodes by using the method of identifying key nodes with centrality. In this study, the coupling among heterogeneous public transit network layers and the static structure characteristics of multi-layer public transit complex network are studied from the perspective of network structure, to assist the traffic management department in finding out the problems of the road network for the management and improvement of the performance and efficiency of the network. This has a profound influence on the development planning of urban public transit system. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    A hybrid heuristic for overlapping community detection through the conductance minimization

    Chagas, Guilherme OliveiraNogueira Lorena, Luiz AntonioCoelho dos Santos, Rafael Duarte
    14页
    查看更多>>摘要：Community structures, which are sets of elements that share some relationship between themselves, can be found in several real-world networks. Many of these communities, also known as clusters, can share elements, i.e., they may overlap. Identifying such overlapping clusters is usually a harder task than finding non-overlapping ones and, therefore, it needs more sophisticated methods. In this work we proposed a hybrid heuristic for detecting overlapping clusters in networks. An overlapping clustering is generated through the solving of a mixed-integer linear program using, as input, a heterogeneous set of good-quality clusters. This set is produced by two state-of-the-art overlapping community detection algorithms. In addition, some local search methods for conductance minimization are used to improve the quality of the clustering generate by our hybrid heuristic. Test results in artificial and real-world graphs show that our approach is able to detect overlapping clusters with better overall conductance than methods in the state of the art.(C) 2022 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Applying Hurst Exponent in pair trading strategies on Nasdaq 100 index

    Bui, QuynhSlepaczuk, Robert
    19页
    查看更多>>摘要：This research aims to seek an alternative approach to stock selection for algorithmic investment strategy. We try to build an effective pair trading strategy based on 103 stocks listed in the NASDAQ 100 index. The dataset has a daily frequency and covers the period from 01/01/2000 to 31/12/2018 , and to 01/07/2021 as an additional out of-time dataset. In this study, Generalized Hurst Exponent, Correlation, and Cointegration methods are employed to detect the mean-reverting pattern in the time series of a linear combination of each pair of stock. The result shows that the Hurst method cannot outperform the benchmark, which implies that the market is efficient. These results are quite sensitive to varying number of pairs traded and rebalancing period but they are less sensitive to financial leverage degree. Moreover, the Hurst method is better than the cointegration method but is not superior as compared to the correlation method. (C) 2021 The Authors. Published by Elsevier B.V.
      原文链接:
    • NSTL
    • Elsevier

    Evolutionary dynamics of cooperation in N-person snowdrift games with peer punishment and individual disguise

    Pi, JinxiuYang, GuanghuiYang, Hui
    12页
    查看更多>>摘要：We introduce individual disguise of non-cooperators into N-person snowdrift games with peer punishment in a well-mixed population to explore the effects of individual disguise and peer punishment on the cooperation in such games. Firstly, we formulate the reasonable payoffs corresponding to cooperation, non-cooperation and punishment strategy, followed by the establishment of the resulting replicator dynamics to investigate the evolution of the frequencies of the three strategies. Secondly, from a macroscopic perspective, this work provides two-dimensional evolutionary state figures on full cooperation. Moreover, this paper studies the sensitivities of the two-dimensional evolutionary state figures to the third parameter. Specifically, high disguise cost, low cost-to-benefit ratio, severe punishment and large competing size tend to curb noncooperators and guide the cooperation between cooperators and punishers, which is frozen as non-cooperators vanish. Conversely, low disguise cost, high cost-to-benefit ratio, light punishment and small competing size are disadvantageous to punishers and lead to a continual dynamic with cooperators and non-cooperators, which is a dynamical phase once the punishers disappear. Thirdly, we propose another stochastic evolutionary dynamic for finite but large populations. The corresponding results are in precise agreement with those of the replicator dynamics. (c) 2021 Elsevier B.V. All rights reserved. The emergence and persistence of cooperation are perpetual conundrums among self-centered individuals across diverse competing entities ranging from biological fields population to sociology, and economics [1-10]. Evolutionary game theoretical approach plays an influential role in exploring the problems [3,4,8,9,11-16]. By far, some prosocial sanctions have been effectively taken to facilitate the cooperation, such as punishment [17-23], reward [24-26], exclusion [27-29],
      原文链接:
    • NSTL
    • Elsevier

    Source estimation in continuous-time diffusion networks via incomplete observation

    Shi, ChaoyiZhang, QiChu, Tianguang
    10页
    查看更多>>摘要：This paper considers the problem of estimating the source of diffusion in a network under incomplete observation condition. The diffusion process is described by a continuous-time information diffusion model and the source estimation is formulated as a maximum likelihood (ML) estimator in terms of a Gaussian weighted averaging of the correlation coefficients between the observed activation times and the sampled transmission delays obtained by Monte Carlo simulations. Experiments are worked out with both synthetic and real-world networks to show the effectiveness of our method in comparison with previous results.& nbsp;(C)& nbsp;& nbsp;2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    The speed and configuration of cyclist social groups: A field study

    Li, MengChen, TaoDu, HaoMa, Na...
    13页
    查看更多>>摘要：Group behaviour is common among bicycle users and can have an impact on traffic dynamics in natural or emergency situations. As our observation shows, 35% of cyclists in traffic ride in pairs or groups. This paper aims to explore how cyclist group members interact and organize in bicycle flow. A field study was conducted, 166 groups of cyclists were selected as the observation objects, and their tracks were obtained through the multi-object tracking algorithm (MOT). The average speed, spatial arrangement and similarity between group members were calculated and analysed. The results show that group size has a significant negative effect on average group speed as cyclist members of the same group tend to maintain similar speeds as they ride forward. The 2-person and 3-person riding groups have relatively "time stable "geometrical structures (4 patterns for pairs and 5 patterns for triads). They are generated not only from traffic rules but also from the local interaction between group members. The dissimilarity value of movement among them tends to increase with increasing group size due to weaker coordination in larger groups. These findings have implications for bicycle traffic modelling and safe bicycle facility design. (C) 2022 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Effects of intrinsic decoherence on quantum correlations in a two superconducting charge qubit system

    Chandrasekar, V. K.Naveena, P.Muthuganesan, R.
    9页
    查看更多>>摘要：Measurement-induced nonlocality (MIN) quantifies the maximal global effect and bipartite quantum correlation due to the locally invariant projective measurements. In this article, we consider a pair of superconducting charge qubits serving as the physical carrier of quantum information. We study the nonlocal correlation in a pair of superconducting qubits characterized by entanglement and different forms of MIN. Further, we investigate the influence of intrinsic decoherence on the temporal evolution of quantum correlations in the considered physical system. It has shown that the Josephson energy is an effective system parameter against the intrinsic decoherence in enhancing the correlations. (C)& nbsp;2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Two-Dimensional Tri-stable Stochastic Resonance system and its application in bearing fault detection

    Zhang, GangLiu, XiaomanZhang, Tianqi
    12页
    查看更多>>摘要：A Two-Dimensional Tri-stable Stochastic Resonance (TDTSR) system with adjustable parameters is proposed to address the problem of difficult parameter tuning in onedimensional stochastic resonance systems. Firstly, under the limitation of adiabatic approximation theory, the Steady-state Probability Density (SPD) and output Signal-to Noise Ratio (SNR) of the system are derived, and the effects of system parameters (a, b, c, r, k) on them are analyzed. The results prove that particles are more capable of transiting between potential wells to obtain better resonance effect when the system is coupled. Then, TDTSR system and the One-Dimensional Tri-stable Stochastic Resonance (ODTSR) system are analyzed and simulated numerically respectively, which show that the Mean Signal-to-Noise Ratio Gain (MSNRG) of TDTSR system is greater than that of ODTSR system. Finally, the two systems are applied in bearing faults detection, and the system parameters are optimized by genetic algorithm. The experimental results indicate that TDTSR system is excellent than ODTSR system, which provides a great theoretical significance and practical value for engineering applications. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier