18,303 research outputs found

    Poverty and exclusion in urban China

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    This paper discusses how widespread poverty and exclusion are in urban China during the period of transition from central planning to a market economy. Two poverty lines have been employed to measure poverty rates in urban areas: a diagnostic poverty line calculated by the Asian Development Bank (ADB) experts and a benefit poverty line used in the Minimum Living Allowance Program of the Chinese government. Both sets of estimates show marked variations by province. According to the former standard, the poverty headcount of China in 1998 was estimated as 14.8 million, with a poverty rate of 4.7 percent. According to the later standard, the poverty headcount for 2007 is estimated as 22.7 million, amounting to a poverty rate of 3.9 percent. Poor people are generally not living in absolute poverty, as their basic needs in food, clothing and shelter can largely be met. However, they have low incomes and restricted consumption potential. Economic constraints also entail adverse consequences like poor health, poor education and limited social contacts. Two groups of people are here considered as the new poor: unemployed or laid-off workers and labor migrants. This means that China now has two new forms of urban poverty which are caused by different factors and are combined with different forms of deprivation. Therefore, policy programs designed to eradicate poverty in urban areas have to be tailored carefully to the poor people's special needs. Job creation and a comprehensive social protection system are here proposed as two effective instruments in the fight against urban poverty. --

    Topological Soliton with Nonzero Hopf Invariant in Yang-Mills-Higgs Model

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    We propose a topological soliton or instanton solution with nonzero Hopf invariant to the 3+1D non-Abelian gauge theory coupled with scalar fields. This solution, which we call Hopf soliton, represents a spacetime event that makes a 2π2\pi rotation of the monopole. Although the action of this Hopf soliton is logarithmically divergent, it may still give relevant contributions in a finite-sized system. Since the Chern-Simons term for the unbroken U(1)U(1) gauge field may appear in the low energy effective theory, the Hopf soliton may possibly generate fractional statistics for the monopoles.Comment: 16 pages, 1 figure

    Finite-Difference Time-Domain Study of Guided Modes in Nano-plasmonic Waveguides

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    A conformal dispersive finite-difference time-domain (FDTD) method is developed for the study of one-dimensional (1-D) plasmonic waveguides formed by an array of periodic infinite-long silver cylinders at optical frequencies. The curved surfaces of circular and elliptical inclusions are modelled in orthogonal FDTD grid using effective permittivities (EPs) and the material frequency dispersion is taken into account using an auxiliary differential equation (ADE) method. The proposed FDTD method does not introduce numerical instability but it requires a fourth-order discretisation procedure. To the authors' knowledge, it is the first time that the modelling of curved structures using a conformal scheme is combined with the dispersive FDTD method. The dispersion diagrams obtained using EPs and staircase approximations are compared with those from the frequency domain embedding method. It is shown that the dispersion diagram can be modified by adding additional elements or changing geometry of inclusions. Numerical simulations of plasmonic waveguides formed by seven elements show that row(s) of silver nanoscale cylinders can guide the propagation of light due to the coupling of surface plasmons.Comment: 6 pages, 10 figures, accepted for publication, IEEE Trans. Antennas Propaga