Compact and Broadband Microstrip-Line-Fed Modified Rhombus Slot Antenna

The printed microstrip-line-fed broadband rhombus slot antenna is investigated in this paper. With the use of the offset microstrip feed line and the corner-truncated protruded ground plane, the bandwidth enhancement and the slot size reduction for the proposed slot antenna can be obtained. The experimental results demonstrate that the impedance bandwidth for 10 dB return loss reaches 5210 MHz (108.2%, 2210-7420 MHz), which is about 2.67 times of a conventional microstrip-line-fed rhombus slot antenna. This bandwidth can provide with the wireless communication services operating in wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) bands. Under the use of the protruded ground plane, the slot size can be reduced by about 52%. Details of simulated and measured results are presented and discussed

Local sourcing of multinational enterprises in China

Purpose – Local sourcing from indigenous firms by multinational enterprises (MNEs) is an important channel through which the former may benefit from the positive externalities generated by the latter. The purpose of this study is to analyze the extent and determinants of local sourcing of MNEs. Design/methodology/approach – Employing a survey dataset covering 493 multinational subsidiaries in China during 1999-2005, this paper applies the two-limit Tobit model. Findings – It is found that an MNE's local sourcing decision is influenced by its strategies, characteristics such as size and learning ability and country-of-origin. More specifically, export-orientation strategy, joint venture strategy and networking with local suppliers positively affect local sourcing. Small and autonomous subsidiaries tend to source more locally. Age has a non-linear effect. The importance of these determinants varies with regions. Research limitations/implications – Aiming at capacity building and competitiveness of indigenous firms, the Chinese government has initiated local content requirement. This study shows that such policy intervention could be counterproductive. The creation of a more competitive business environment by the government could promote more linkages. Originality/value – Given its critical role in economic development, local sourcing by MNEs has attracted much attention. Only limited research has been carried out on FDI linkage effects in China, and the location effect on FDI linkages has not been examined. This study aims to fill the gap by using Chinese survey data

The SDSS Galaxy Angular Two-Point Correlation Function

We present the galaxy two-point angular correlation function for galaxies selected from the seventh data release of the Sloan Digital Sky Survey. The galaxy sample was selected with $r$-band apparent magnitudes between 17 and 21; and we measure the correlation function for the full sample as well as for the four magnitude ranges: 17-18, 18-19, 19-20, and 20-21. We update the flag criteria to select a clean galaxy catalog and detail specific tests that we perform to characterize systematic effects, including the effects of seeing, Galactic extinction, and the overall survey uniformity. Notably, we find that optimally we can use observed regions with seeing < 1\farcs5, and $r$-band extinction < 0.13 magnitudes, smaller than previously published results. Furthermore, we confirm that the uniformity of the SDSS photometry is minimally affected by the stripe geometry. We find that, overall, the two-point angular correlation function can be described by a power law, $\omega(\theta) = A_\omega \theta^{(1-\gamma)}$ with $\gamma \simeq 1.72$, over the range 0\fdg005--10\degr. We also find similar relationships for the four magnitude subsamples, but the amplitude within the same angular interval for the four subsamples is found to decrease with fainter magnitudes, in agreement with previous results. We find that the systematic signals are well below the galaxy angular correlation function for angles less than approximately 5\degr, which limits the modeling of galaxy angular correlations on larger scales. Finally, we present our custom, highly parallelized two-point correlation code that we used in this analysis.Comment: 22 pages, 17 figures, accepted by MNRA

Effects of the sintering atmosphere on the superconductivity of SmFeAsO1-xFx compounds

A series of SmFeAsO1-xFx samples were sintered in quartz tubes filled with air of different pressures. The effects of the sintering atmosphere on the superconductivity were systematically investigated. The SmFeAsO1-xFx system maintains a transition temperature (Tc) near 50 K until the concentration of oxygen in quartz tubes increases to a certain threshold, after which Tc decreases dramatically. Fluorine losses, whether due to vaporization, reactions with starting materials, and reactions with oxygen, proved to be detrimental to the superconductivity of this material. The deleterious effects of the oxygen in the sintering atmosphere were also discussed in detail.Comment: 9 pages, 5 figure

Fiber Based Multiple-Access Optical Frequency Dissemination

We demonstrate a fiber based multiple-access optical frequency dissemination scheme. Without using any additional laser sources, we reproduce the stable disseminated frequency at an arbitrary point of fiber link. Relative frequency stability of 3E10^{-16}/s and 4E10^{-18}/10^4s is obtained. A branching fiber network for highly-precision synchronization of optical frequency is made possible by this method and its applications are discussed.Comment: 5 pages, 3 figure

Multiwavelength properties of a new Geminga-like pulsar: PSR J2021+4026

In this paper, we report a detailed investigation of the multiwavelength properties of a newly detected gamma-ray pulsar, PSR J2021+4026, in both observational and theoretical aspects. We firstly identify an X-ray source in the XMM-Newton serendipitous source catalogue, 2XMM J202131.0+402645, located within the 95% confidence circle of PSR J2021+4026. With an archival Chandra observation, this identification provides an X-ray position with arcsecond accuracy which is helpful in facilitating further investigations. Searching for the pulsed radio emission at the position of 2XMM J202131.0+402645 with a 25-m telescope at Urumqi Astronomical Observatory resulted in null detection and places an upper-limit of 0.1~mJy for any pulsed signal at 18~cm. Together with the emission properties in X-ray and gamma-ray, the radio quietness suggests PSR J2021+4026 to be another member of Geminga-like pulsars. In the radio sky survey data, extended emission features have been identified in the gamma-ray error circle of PSR J2021+4026. We have also re-analyzed the gamma-ray data collected by FERMI's Large Area Telescope. We found that the X-ray position of 2XMM J202131.0+402645 is consistent with that of the optimal gamma-ray timing solution. We have further modeled the results in the context of outer gap model which provides us with constraints for the pulsar emission geometry such as magnetic inclination angle and the viewing angle. We have also discussed the possibility of whether PSR J2021+4026 has any physical association with the supernova remnant G78.2+2.1 (gamma-Cygni).Comment: 11 pages, 14 figure