A Tri-band-notched UWB Antenna with Low Mutual Coupling between the Band-notched Structures

A compact printed U-shape ultra-wideband (UWB) antenna with triple band-notched characteristics is presented. The proposed antenna, with compact size of 24×33 mm2, yields an impedance bandwidth of 2.8-12GHz for VSWR<2, except the notched bands. The notched bands are realized by introducing two different types of slots. Two C-shape half-wavelength slots are etched on the radiating patch to obtain two notched bands in 3.3-3.7GHz for WiMAX and 7.25-7.75GHz for downlink of X-band satellite communication systems. In order to minimize the mutual coupling between the band-notched structures, the middle notched band in 5-6GHz for WLAN is achieved by using a U-slot defected ground structure. The parametric study is carried out to understand the mutual coupling. Surface current distributions and equivalent circuit are used to illustrate the notched mechanism. The performance of this antenna both by simulation and by experiment indicates that the proposed antenna is suitable and a good candidate for UWB applications

Imaging crystal orientations in multicrystalline silicon wafers via photoluminescence

We present a method for monitoring crystal orientations in chemically polished and unpassivated multicrystalline silicon wafers based on band-to-band photoluminescence imaging. The photoluminescence intensity from such wafers is dominated by surface recombination, which is crystal orientation dependent. We demonstrate that a strong correlation exists between the surface energy of different grain orientations, which are modelled based on first principles, and their corresponding photoluminescence intensity. This method may be useful in monitoring mixes of crystal orientations in multicrystalline or so-called “cast monocrystalline” wafers.H. C. Sio acknowledges scholarship support from BT Imaging and the Australian Solar Institute, and the Centre for Advanced Microscopy at ANU for SEM access. This work has been supported by the Australian Research Council

The generalized KP hierarchy

We propose one possible generalization of the KP hierarchy, which possesses multi bi--hamiltonian structures, and can be viewed as several KP hierarchies coupled together.Comment: 12

QCD corrections to polarization of J/\psi and \Upsilon at Fermilab Tevatron and CERN LHC

In this work, we present more detail of the calculation on the NLO QCD corrections to polarization of direct J/psi production via color singlet at Tevatron and LHC, as well as the results for Upsilon for the first time. Our results show that the J/psi polarization status drastically changes from transverse polarization dominant at LO into longitudinal polarization dominant in the whole range of the transverse momentum $p_t$ of J/psi when the NLO corrections are counted. For Upsilon production, the p_t distribution of the polarization status behaves almost the same as that for J/psi except that the NLO result is transverse polarization at small p_t range. Although the theoretical evaluation predicts a larger longitudinal polarization than the measured value at Tevatron, it may provide a solution towards the previous large discrepancy for J/psi and Upsilon polarization between theoretical predication and experimental measurement, and suggests that the next important step is to calculate the NLO corrections to hadronproduction of color octet state J/psi^(8) and Upsilon^(8). Our calculations are performed in two ways, namely we do and do not analytically sum over the polarizations, and then check them with each other.Comment: 12 pages, 12 figures, two columns, use revtex4; to appear in PR

警务改革与国家强制能力建设

With the increasing diversity and complexity of Chinese society in recent years, China’s social control system has become less and less able to meet the needs of social development. In this context, China’s central and local governments have tried to reform the police system to strengthen the coercive capacity of the state. There are seven main models of police reform in China, which embody two core features of current coercive capacity building: on the one hand, deepening the reach of the police to the grassroots to strengthen the “penetrative power” of the police in controlling society; on the other hand, standardizing law enforcement to enhance the state’s “inhibitory power” over the police. “Penetrative power” is the prerequisite for “inhibitory power,” and “inhibitory power” is the precondition for the effectiveness of “penetrative power.” The dialectical relation of the two is the key to building coercive capacit

Spin Hall Effect in Atoms

We propose an optical means to realize a spin hall effect (SHE) in neutral atomic system by coupling the internal spin states of atoms to radiation. The interaction between the external optical fields and the atoms creates effective magnetic fields that act in opposite directions on "electrically" neutral atoms with opposite spin polarizations. This effect leads to a Landau level structure for each spin orientation in direct analogy with the familiar SHE in semiconductors. The conservation and topological properties of the spin current, and the creation of a pure spin current are discussed.Comment: 4 pages, 2 figure; Final versio