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71.
Many networks are proved to have community structures. On the basis of the fact that the dynamics on networks are intensively affected by the related topology, in this paper the dynamics of excitable systems on networks and a corresponding approach for detecting communities are discussed. Dynamical networks are formed by interacting neurons; each neuron is described using the FHN model. For noisy disturbance and appropriate coupling strength, neurons may oscillate coherently and their behavior is tightly related to the community structure. Synchronization between nodes is measured in terms of a correlation coefficient based on long time series. The correlation coefficient matrix can be used to project network topology onto a vector space. Then by the K-means cluster method, the communities can be detected. Experiments demonstrate that our algorithm is effective at discovering community structure in artificial networks and real networks, especially for directed networks. The results also provide us with a deep understanding of the relationship of function and structure for dynamical networks. 相似文献
72.
L. Li 《Applied Surface Science》2010,256(14):4734-8755
CdZnO thin films with near-band-edge (NBE) photoluminescence (PL) emission from 2.39 eV to 2.74 eV were grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire substrates with 800 °C in situ annealing. CdZnO thin films evolve from pure wurtzite (wz) structure, to mixture of wz and rock-salt (rs) structures confirmed by X-ray diffraction studies. Rapid-thermo-annealing (RTA) was performed on in situ annealed CdZnO samples. Pure wz CdZnO shows insignificant NBE PL peak shift after RTA, while mixture structure CdZnO shows evident blue shifts due to phase change after annealing, indicating the rs phase CdZnO changes to wz phase CdZnO during RTA process. 相似文献
73.
We obtain analytic, nonperturbative, approximate solutions of Yukawa theory in the one-fermion sector using light-front quantization. The theory is regulated in the ultraviolet by the introduction of heavy Pauli-Villars scalar and fermion fields, each with negative norm. In order to obtain a directly soluble problem, fermion-pair creation and annihilation are neglected, and the number of bosonic constituents is limited to one of either type. We discuss some of the features of the wave function of the eigensolution, including its endpoint behavior and spin and orbital angular momentum content. The limit of infinite Pauli-Villars mass receives special scrutiny. 相似文献
74.
P.J. Kowalczyk M. Puchalski W. Koz?owski P. D?browski Z. Klusek W. Olejniczak 《Applied Surface Science》2008,254(15):4572-4576
Scanning tunneling microscopy (STM) and spectroscopy (STS) carried out in vacuum and air were used to study the electronic structure of the Au (1 1 1) surface in the range of 0.0-0.7 eV below the Fermi level. The STS experiment carried out in UHV showed the existence of the Shockley surface state (SS) located 0.48 eV below the Fermi level. STS carried out in air showed strong local maximum located 0.35 eV below the Fermi level. This maximum was ascribed to the SS shifted toward lower energy due to carbon and oxygen overlayer. To confirm that the SS could exist on the sample exposed to air we did ultraviolet photoemission spectroscopy (UPS) experiment on air-treated and clean Au (1 1 1). Our results suggest that the SS position initially measured at 0.38 eV below the Fermi level was shifted to 0.27 eV after air treatment. Additionally, the level of contamination was measured using X-ray photoelectron spectroscopy (XPS). 相似文献
75.
Jian Jing Jun-Ying Ma Yong-Hong Guo Jian-Feng Chen 《The European Physical Journal C - Particles and Fields》2008,56(4):591-595
We propose a mapping-independent method to analyze the spectra of the non-commutative two-dimensional harmonic oscillator.
The path integral formulation is applied and an effective Lagrangian is obtained. The spectra are read off directly and the
question of uniqueness is answered. 相似文献
76.
R. de Lima Rodrigues 《Physics letters. A》2008,372(15):2587-2591
In the present work we obtain a new representation for the Dirac oscillator based on the Clifford algebra C?7. The symmetry breaking and the energy eigenvalues for our model of the Dirac oscillator are studied in the non-relativistic limit. 相似文献
77.
C. Rohr J. M. Büttner F. A. Palitschka N. D. Kushch M. V. Kartsovnik W. Biberacher R. Gross B. A. Hermann 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(2):167-171
The surfaces of a ten years aged crystal and a freshly prepared κ-(BEDT-TTF)2Cu(NCS)2 crystal were compared by scanning tunneling microscopy (STM). The molecularly-resolved STM images of the bc plane of the crystals agree with each other and with the electronic contrast obtained by new density functional theory (DFT)
based simulations. Even after ten years STM images of the molecular stacking of BEDT-TTF display a variation in brightness
at the positions of different molecules. We attribute this symmetry breaking concerning the brightness in the STM images of
the otherwise equivalent BEDT-TTF dimers to the electronic states of a relaxed surface. 相似文献
78.
M. De Sanctis 《The European Physical Journal A - Hadrons and Nuclei》2009,41(2):169-178
Starting from the relativistic invariance properties at classical level, we generalize the Darwin equation to the case of
non-Coulombic spatial interactions. The relativistic correction terms for vector interactions are derived from a given nonrelativistic
potential. We show that, for a Coulombic potential, the results coincide with those obtained in the Coulomb gauge. The results
are adapted to the quantum theory obtaining a generalization of the Fermi-Breit equation. An Hermitian interaction operator
is constructed. A critical comparison with other possible treatments of the retardation terms is performed also discussing
the usual choice of the Coulomb gauge. Special attention is devoted to the construction of a model for quark interaction. 相似文献
79.
80.
Equations of motion for Einstein’s field in fractional dimension of 4 spatial coordinates are obtained. It is shown that time
dependent part of Einstein’s wave function is single valued for only 4-integer dimensional space. 相似文献