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1.
We propose a strategy updating mechanism based on pursuing the highest average payoff to investigate the prisoner's dilemma game and the snowdrift game. We apply the new rule to investigate cooperative behaviours on regular, small-world, scale-free networks, and find spatial structure can maintain cooperation for the prisoner's dilemma game. fn the snowdrift game, spatial structure can inhibit or promote cooperative behaviour which depends on payoff parameter. We further study cooperative behaviour on scale-free network in detail. Interestingly, non-monotonous behaviours observed on scale-free network with middle-degree individuals have the lowest cooperation level. We also find that large-degree individuals change their strategies more frequently for both games.  相似文献   

2.
李莉  靳祯  孙桂全 《中国物理快报》2008,25(9):3500-3503
Pattern formation of a spatial epidemic model with both self- and cross-diffusion is investigated. From the Turing theory, it is well known that Turing pattern formation cannot occur for the equal self-diffusion coefficients. However, combined with cross-diffusion, the system will show emergence of isolated groups, i.e., stripe-like or spotted or coexistence of both, which we show by both mathematical analysis and numerical simulations. Our study shows that the interaction of self- and cross-diffusion can be considered as an important mechanism for the appearance of complex spatiotemporal dynamics in epidemic models.  相似文献   

3.
We study the susceptible infected-susceptible (SIS) epidemic model on bipartite graph. According to the difference of sex conception in western and oriental nations, we construct the Barabasi Albert Barabasi Albert (BA-BA) model and Barabasi-Albert Homogeneity (BA-HO) model for sexually transmitted diseases (STDs). Applying the rate equation approach, the positive equilibria of both models are given analytically. We find that the ratio between infected females and infected males is distinctly different in both models and the infected density in the BA-HO model is much less than that in the BA-BA model. These results explain that the countries with small ratio have less infected density than those with large ratio. Our numerical simulations verify these theoretical results.  相似文献   

4.
Based on a new definition of user similarity, we introduce an improved collaborative filtering (ICF) algorithm, which couM improve the algorithmic accuracy and diversity simultaneously. In the ICF, instead of the standard Pearson coefficient, the user-user similarities are obtained by integrating the heat conduction and mass diffusion processes. The simulation results on a benchmark data set indicate that the corresponding algorithmic accuracy, measured by the ranking score, is improved by 6. 7% in the optimal case compared to the standard collaborative filtering (CF) algorithm. More importantly, the diversity of the recommendation lists is also improved by 63.6%. Since the user similarity is crucial for the CF algorithm, this work may shed some light on how to improve the algorithmic performance by giving accurate similarity measurement.  相似文献   

5.
We investigate the evolutionary prisoner's dilemma on a weighted scale-free network where the diversity of teaching ability is introduced to the network in the form of weight. Though the diversity of teaching ability is not a sufficient condition for the enhancement of cooperation, we find that the degree-dependent teaching ability plays an active role in the evolution of cooperation. A new phenomenon is found when the degree-dependent teaching ability is used: the distribution of the cooperator frequency displays a two-peak structure for a certain parameter range. We also investigate the effects of the degree-degree correlation of the network on the evolution of cooperation in the presence of the diversity of the teaching ability.  相似文献   

6.
The Stratonovich stochastic differential equation is used to analyze genotype selection in the presence ot correlatecl Gaussian white noises. We study the steady state properties of the genotype selection and discuss the effects of the correlated noises. It is found that the degree of correlation of the noises can be used to select one type of genes from another type of mixing genes. The strong selection of genes caused by a large value of multiplicative noise intensity can be weakened by the intensive negative correlation.  相似文献   

7.
Y.L. Li  H.J. Sun 《Physica A》2008,387(23):5852-5856
The spatial price problem means that if the supply price plus the transportation cost is less than the demand price, there exists a trade. Thus, after an amount of exchange, the demand price will decrease. This process is continuous until an equilibrium state is obtained. However, how the trade network structure affects this process has received little attention. In this paper, we give a evolving model to describe the levels of spatial price on different complex network structures. The simulation results show that the network with shorter path length is sensitive to the variation of prices.  相似文献   

8.
We present a novel and effective method for controlling epidemic spreading on complex networks, especially on scale-free networks. The proposed strategy is performed by deleting edges according to their significances (the significance of an edge is defined as the product of the degrees of two nodes of this edge). In contrast to other methods, e.g., random immunization, proportional immunization, targeted immunization, acquaintance immunization and so on, which mainly focus on how to delete nodes to realize the control of epidemic spreading on complex networks, our method is more effective in realizing the control of epidemic spreading on complex networks, moreover, such a method can better retain the integrity of complex networks.  相似文献   

9.
We propose a quantum teleportation scheme for tripartite entangled coherent state (ECS) with continuous variable. Our scheme is feasible and economical in the sense that we need only linear optical devices such as beam splitters, phase shifters and photon detectors and employ three bipartite maximally ECSs as quantum channels. We also generalize the tripartite scheme into multipartite ease and calculate the minimum average fidelity for the schemes in tripartite and multipartite cases.  相似文献   

10.
The geometrical and electronic structures of nitrogen-doped β-SiC are investigated by employing the first principles of plane wave ultra-soft pseudo-potential technology based on density functional theory. The structures of SiC1-xNx (x = 0, 1/32, 1/16, 1/8, 1/4) with different doping concentrations are optimized. The results reveal that the band gap of β-SiC transforms from an indirect band gap to a direct band gap with band gap shrinkage after carbon atoms are replaced by nitrogen atoms. The Fermi level shifts from valence band top to conduction band by doping nitrogen in pure β-SiC, and the doped β-SiC becomes metallic. The degree of Fermi levels entering into the conduction band increases with the increment of doping concentration; however, the band gap becomes narrower. This is attributed to defects with negative electricity occurring in surrounding silicon atoms. With the increase of doping concentration, more residual electrons, more easily captured by the 3p orbit in the silicon atom, will be provided by nitrogen atoms to form more defects with negative electricity.  相似文献   

11.
By performing first-principles calculations, we study Li doping in a double-wall carbon nanotube where a (5,0) tube is confined inside a (14,0) tube. There are three possible sites for Li doping and two of them are energetically favorable. The change of energy band structure is closely related to the doping sites and the charge transfer is investigated. Bader charge analysis indicates that Li prefers to donate its electron to the inner (5,0) tube. Moreover, the Li capacity of the system can reach LIC4.75 which makes it a promising candidate for Li-ion battery materials.  相似文献   

12.
13.
Adaptive optics can be used to compensate for the wave aberration of the human eyes to achieve high-resolution imaging in real time. However the correction & partial due to the limitation of hardware. We propose a kind of hybrid image post-processing method, which uses the blind deconvolution combined with the residual data in wavefront sensor to restore the partially adaptive optics corrected retinal image. This method is applied in the image restoration of the vivid human retinal images. The results show that it is effective to improve the retinal image quality.  相似文献   

14.
The Raman signal of gas molecules is very weak due to its small scattering cross section. Here, a near-confocal cavity-enhanced Raman detection system is demonstrated. In the cavity, a high power light of 9W is achieved by using a cw 200mW 532nm laser, which greatly enhances the detection sensitivity of gas species. A photomultiplier tube connected to a spectrometer is used as the detection system. The Raman spectra of the mixed gases separated from transformer oil has been observed. The relationship of absolute Raman intensity and gas pressure is also obtained. To our knowledge, this is the first Raman system to detect the gases separated from transformer oil.  相似文献   

15.
A hypothesis is brought forward that the materials with low propagation loss in both optical and microwave band may exhibit good performance in terahertz (THz) band because THz wave band interspaces those two wave bands. For the purpose-of exploring a kind of low-loss material for THz waveguide, Lu2.1Bi0.9Fe5O12(LuBiIG) garnet films are prepared by liquid phase epitaxy (LPE) method on a gadolinium gallium garnet (GGG) substrate from lead-free flux because of the good properties in both optical and microwave bands. In microwave band, the ferromagnetic resonance (FMR) linewidth of the film 2△H = 2.8-5.1Oe; in optical band, the optical absorption coefficient is 600cm^-1 at visible range and about 100-170cm^-1 when the wavelength is longer than 800nm. In THz range, our hypothesis is well confirmed by a THz-TDS measurement which shows that the absorbance of the film for THz wave is 0.05-0.3 cm 1 and the minimum value appears at 2.3 THz. This artificial ferromagnetic material holds a great promise for magnetic field tunable THz devices such as waveguide, modulator or switch.  相似文献   

16.
The properties of meso-tetraphenylporphine (TPP) aggregates formed in acidic aqueous-organic solutions are investigated by UV-vis spectroscopy. According to the absorption spectra, the Q band absorption of the aggregated TPP shows red shift and intensity enhancement, and a model that includes the participation of water molecules in a porphyrin aggregation complex is proposed, then a qualitative explanation based on Gouterman's excition coupling theory is presented. Calculations including eigenenergies, eigenstates and the transition dipole strength of the coupled states are carried out.  相似文献   

17.
Spiral spectra of vortex beams with coma aberration are studied. It is shown that the orbital angular momentum (OAM) states of vortex beams with coma aberration are different from those aberration-free vortex beams. Spiral spectra of beams with coma aberration are spreading. It is found that in the presence of coma aberration, the vortex beams contain not only the original OAM component but also other components. A larger coma aberration coefficient and/or a larger beam waist will lead to a wider spreading of the spiral spectrum. The results may have potential applications in information encoding and transmittance.  相似文献   

18.
With the help of the homogeneous balance method, the Jacobi elliptic expansion method and the auxiliary equation method, the first elliptic function equation is used to obtain the Jacobi doubly periodic wave solutions of the (2+1)-dimensional B-type Kadomtsev-Petviashvili (BKP) equation and the generalized Klein-Gordon equation. The method is also valid for other (1+1)-dimensional and higher dimensional systems.  相似文献   

19.
We investigate the fragmentation of 158A GeV ^207Tpb projectiles with Bi, Pb, Cu and AI targets using CR-39 nuclear track detectors. The exposures were made at SPS-CERN. After the etching, the detectors were scanned using an optical microscope to collect the data of etched cone diameters and lengths. We measured the partial charge-changing cross sections using the data of etched cone lengths. The predicted cross sections are compared to similar measurements reported in literature and their dependences on projectile and target mass are described.  相似文献   

20.
We present a new filter scheme for magnetocardiogram (MCG) signal processing based on the quasi-periodic characteristic of the signals. The key points of this scheme are to determine the exact numbers of data points in each cardiac cycle by using electrocardiogram (ECG) data acquired simultaneously with the MCG signal and to normalize the MCG data sequence in each cycle into an identical length. Compared with conventional filters, the scheme has the advantage of more powerful noise suppression with less signal distortion. The desire for having high quality output signals from raw MCG data acquired in a simple shielded room or even in unshielded environment may be realized with the scheme.  相似文献   

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