11,696 research outputs found

    Reliability improvement through smart longwalls project

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    R&D and Technology Transfer: Firm-Level Evidence from Chinese Industry

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    The capacity of developing economies to narrow the gap in living standards with the OECD nations depends critically on their ability to imitate and innovate new technologies. Toward this end, developing economies have access to three avenues of technological advance: technology transfer, domestic R&D, and foreign direct investment. This paper examines the contributions of each of these avenues, as well as their interactions, to productivity and knowledge production within Chinese industry. Based on a large data set for China’s large and medium-size enterprises, the estimation results show that technology transfer – whether domestic or foreign – affects productivity only through its interactions with in-house R&D. Foreign direct investment does not appear to facilitate the adoption of market-mediated foreign technology transfer. Firms wishing to produce patentable knowledge do not benefit from technology transfer; patentable knowledge is created exclusively through in-house R&D operations.http://deepblue.lib.umich.edu/bitstream/2027.42/39968/3/wp582.pd

    Average distance in a hierarchical scale-free network: an exact solution

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    Various real systems simultaneously exhibit scale-free and hierarchical structure. In this paper, we study analytically average distance in a deterministic scale-free network with hierarchical organization. Using a recursive method based on the network construction, we determine explicitly the average distance, obtaining an exact expression for it, which is confirmed by extensive numerical calculations. The obtained rigorous solution shows that the average distance grows logarithmically with the network order (number of nodes in the network). We exhibit the similarity and dissimilarity in average distance between the network under consideration and some previously studied networks, including random networks and other deterministic networks. On the basis of the comparison, we argue that the logarithmic scaling of average distance with network order could be a generic feature of deterministic scale-free networks.Comment: Definitive version published in Journal of Statistical Mechanic

    Integrable variant of the one-dimensional Hubbard model

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    A new integrable model which is a variant of the one-dimensional Hubbard model is proposed. The integrability of the model is verified by presenting the associated quantum R-matrix which satisfies the Yang-Baxter equation. We argue that the new model possesses the SO(4) algebra symmetry, which contains a representation of the η\eta-pairing SU(2) algebra and a spin SU(2) algebra. Additionally, the algebraic Bethe ansatz is studied by means of the quantum inverse scattering method. The spectrum of the Hamiltonian, eigenvectors, as well as the Bethe ansatz equations, are discussed

    Promotion of cooperation induced by nonlinear attractive effect in spatial Prisoner's Dilemma game

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    We introduce nonlinear attractive effects into a spatial Prisoner's Dilemma game where the players located on a square lattice can either cooperate with their nearest neighbors or defect. In every generation, each player updates its strategy by firstly choosing one of the neighbors with a probability proportional to Aα\mathcal{A}^\alpha denoting the attractiveness of the neighbor, where A\mathcal{A} is the payoff collected by it and α\alpha (\geq0) is a free parameter characterizing the extent of the nonlinear effect; and then adopting its strategy with a probability dependent on their payoff difference. Using Monte Carlo simulations, we investigate the density ρC\rho_C of cooperators in the stationary state for different values of α\alpha. It is shown that the introduction of such attractive effect remarkably promotes the emergence and persistence of cooperation over a wide range of the temptation to defect. In particular, for large values of α\alpha, i.e., strong nonlinear attractive effects, the system exhibits two absorbing states (all cooperators or all defectors) separated by an active state (coexistence of cooperators and defectors) when varying the temptation to defect. In the critical region where ρC\rho_C goes to zero, the extinction behavior is power law-like ρC\rho_C \sim (bcb)β(b_c-b)^{\beta}, where the exponent β\beta accords approximatively with the critical exponent (β0.584\beta\approx0.584) of the two-dimensional directed percolation and depends weakly on the value of α\alpha.Comment: 7 pages, 4 figure

    Anomalous behavior of trapping on a fractal scale-free network

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    It is known that the heterogeneity of scale-free networks helps enhancing the efficiency of trapping processes performed on them. In this paper, we show that transport efficiency is much lower in a fractal scale-free network than in non-fractal networks. To this end, we examine a simple random walk with a fixed trap at a given position on a fractal scale-free network. We calculate analytically the mean first-passage time (MFPT) as a measure of the efficiency for the trapping process, and obtain a closed-form expression for MFPT, which agrees with direct numerical calculations. We find that, in the limit of a large network order VV, the MFPT behaves superlinearly as V3/2 \sim V^{{3/2}} with an exponent 3/2 much larger than 1, which is in sharp contrast to the scaling Vθ \sim V^{\theta} with θ1\theta \leq 1, previously obtained for non-fractal scale-free networks. Our results indicate that the degree distribution of scale-free networks is not sufficient to characterize trapping processes taking place on them. Since various real-world networks are simultaneously scale-free and fractal, our results may shed light on the understanding of trapping processes running on real-life systems.Comment: 6 pages, 5 figures; Definitive version accepted for publication in EPL (Europhysics Letters

    Assessment of China's virtual air pollution transport embodied in trade by using a consumption-based emission inventory

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    Substantial anthropogenic emissions from China have resulted in serious air pollution, and this has generated considerable academic and public concern. The physical transport of air pollutants in the atmosphere has been extensively investigated; however, understanding the mechanisms how the pollutant was transferred through economic and trade activities remains a challenge. For the first time, we quantified and tracked China's air pollutant emission flows embodied in interprovincial trade, using a multiregional input - output model framework. Trade relative emissions for four key air pollutants (primary fine particle matter, sulfur dioxide, nitrogen oxides and non-methane volatile organic compounds) were assessed for 2007 in each Chinese province. We found that emissions were significantly redistributed among provinces owing to interprovincial trade. Large amounts of emissions were embodied in the imports of eastern regions from northern and central regions, and these were determined by differences in regional economic status and environmental policy. It is suggested that measures should be introduced to reduce air pollution by integrating cross-regional consumers and producers within national agreements to encourage efficiency improvement in the supply chain and optimize consumption structure internationally. The consumption-based air pollutant emission inventory developed in this work can be further used to attribute pollution to various economic activities and final demand types with the aid of air quality models

    Production Globalization Makes China’s Exports Cleaner

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    Production globalization, which is when firms expand their supply chains across national boundaries, creates an opportunity for developing countries to engage in international production networks via trade. Described as the world's factory, China specializes in assembly manufacturing mainly through processing exports. Firms use imported intermediate inputs for production and, after processing or assembly, re-export the finished products to international markets. Here, we show that the carbon efficiency of China’s processing exports is greater than that of its ordinary exports. If the impact of trade heterogeneity is ignored, then the domestic emissions embodied in China’s exports will be overestimated by 23.4%, and the foreign emissions embodied in China’s exports will be underestimated by 29.3%. If the degree of global value chain participation, which ranges from 0 to 1, increases by 0.1, although foreign emissions embodied in China’s exports would increase, the gross carbon intensity of China’s exports will decrease by 11.7%
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