Role of Parallel Tempering Monte Carlo Simulation in 2D Ising Spin Glass System with Distance Dependent Interaction

Spin glass system is a complex disordered system with a number of local minima separated by entropic barriers. Therefore, parallel tempering Monte Carlo simulation was used in order to get fast thermalisation （to minimize the relaxation time）. Distance dependent interaction coupling in 2D is studied in order to show how a spin glass phase transition occurs when couplings between far away spins are permitted by considering Edwards-Anderson Ising spin glass model. The interaction coupling is a quenched random variable whose probability of being non-zero decays with distance between two spin sites rij = ｜i-j｜mod（L/2）.The interaction coupling is random and its probability distribution is decaying with the distance between the spins （p（Jij） αrij^-ρ）. The model is studied by changing p among three different regimes （p 〉 2D, 4/3 D〈 p 〈 2D, p 〈 4/3D）. A phase transition temperature for p = 2, 3, 4 is obtained.

Competition effects in an afrotemperate forest

Background： Information about competition responses is mainly available for monospecific stands or mixed stands with a small number of species. Studies on complex multi-species and highly structured forest ecosystems are scarce. Accordingly, the objective of this study was to quantify competition effects and analyse competition responses in a species-diverse afrotemperate forest in South Africa, based on an observational study with mapped tree positions and long-term diameter increment records. Methods： The sensitivity to competition was analysed for individual species and involved the calculation of the slope of the linear relation between the value of a competition index （CI） and diameter growth as a measure of sensitivity. In a next step different competition indices were combined and tree diameters were grouped in three classes as surrogates for canopy status and ontogenetic stage. Results： Five competition indices were found to be effective in showing sensitivity to competition for a number of canopy and sub-canopy species. Significant linear regressions were fitted for 18 of a total of 25 species. Species reactions varied significantly in their sensitivity to the different CIs. The indices were classified as belonging to two groups, those that responded more to local crowding and those that are more sensitive to overtopping, which revealed species-specific sensitivities to both factors. The analysis based on diameter classes revealed that species clearly changed their sensitivity to crowding or overtopping depending on diameter. Canopy and sub-canopy species showed distinct differences in their reactions. Conclusions： The application of multiple CIs brought novel insights relating to the dynamics of afrotemperate forests. The response patterns to different competition indices that focus on crowding and overtopping are varied and tree diameter dependent, indicating that oversimplified assumptions are not warranted in the interpretation of Cl- growth relations.

The dependence of high-order harmonic generation on the laser frequency and inter-nuclear distance from multi-atom molecular ions

High-order harmonic generation from one-dimensional （1D） multi-atom molecular ions ill an ultra-short laser field is theoretically- investigated, The dynamics of the electron in a linearly polarized intense laser field is analyzed in terms of 1D Schroedinger equation with the Crank-Nicolson algorithm, The dependence of high-order harmonics on the laser frequeney and the biter-nuclear distance is discussed, It is found that the optimum range of inter-nuclear distance should be changed to get extended harmonic generation for different laser frequency, and the lower frequency laser pulse is favorable to higher order harmonic generation as the inter-nuclear distance increases.

2D Correlative-Chain Conditional Random Fields for Semantic Annotation of Web Objects

Semantic annotation of Web objects is a key problem for Web information extraction. The Web contains an abundance of useful semi-structured information about real world objects, and the empirical study shows that strong two-dimensional sequence characteristics and correlative characteristics exist for Web information about objects of the same type across different Web sites. Conditional Random Fields （CRFs） are the state-of-the-art approaches taking the sequence characteristics to do better labeling. However, as the appearance of correlative characteristics between Web object elements, previous CRFs have their limitations for semantic annotation of Web objects and cannot deal with the long distance dependencies between Web object elements efficiently. To better incorporate the long distance dependencies, on one hand, this paper describes long distance dependencies by correlative edges, which are built by making good use of structured information and the characteristics of records from external databases; and on the other hand, this paper presents a two-dimensional Correlative-Chain Conditional Random Fields （2DCC-CRFs） to do semantic annotation of Web objects. This approach extends a classic model, two-dimensional Conditional Random Fields （2DCRFs）, by adding correlative edges. Experimental results using a large number of real-world data collected from diverse domains show that the proposed approach can significantly improve the semantic annotation accuracy of Web objects.

The Janzen-Connell effect on the population dynamics of a Fagus engleriana- Cyclobalanopsis oxyodon community in a subtropical zone of China

The Janzen-Connell(J-C)hypothesis provides a mechanism explaining the high species diversity in tropical rainforests.It postulates that predation could cause greater mortality on seeds and seedlings near their parental trees.In this study,we tested the hypothesis in a subtropical zone,a mixed evergreen-deciduous broad-leaved forest dominated by the Fagus engleriana and Cyclobalanopsis oxyodon.The study area was in the Shennongjia region,a key area of biodiversity conserva-tion in both China and the world.The recruitment probability index was used to detect the J-C effect on nine species of the community,which were more than 50 individuals.Six large adults of each species were selected,and the numbers of saplings and adults were counted at the distance intervals of 0–5,5–10,10–15,15–20,and 20–25m from each focal tree.Two species in saplings stage and six in adult stage supported the J-C hypothesis,but theirχ2 was not significant.Three species,the F.engleri-ana,Rhododendron hypoglaucum,and Toona sinensis,showed a strong Hubbell pattern in the adult stage.Because of these results,we reject the J-C hypothesis and conclude that species could recruit near the conspecific trees in subtropical forest.The reasons why the J-C hypothesis fails to explain the species diversity in this community are the shortage of seed-consuming agents of subtropical forest and the influence of microsite topo-graphic variation.