23,282 research outputs found
A reconfigurable wideband and multiband antenna using dual-patch elements for compact wireless devices
This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2012 IEEEA reconfigurable wideband and multiband C-Slot patch antenna with dual-patch elements is proposed and studied. It occupies a compact volume of 50 × 50 × 1.57 (3925 mm3), including the ground plane. The antenna can operate in two dual-band modes and a wideband mode from 5 to 7 GHz. Two parallel C-Slots on the patch elements are employed to perturb the surface current paths for excitation of the dual-band and the wideband modes. Two switches, implemented using PIN diodes, are placed on the connecting lines of a simple feed network to the patch elements. Dual-band modes are achieved by switching “ON” either one of the two patch elements, while the wideband mode with an impedance bandwidth of 33.52% is obtained by switching “ON” both patch elements. The frequencies in the dual-band modes can be independently controlled using positions and dimensions of the C-Slots without affecting the wideband mode. The advantage of the proposed antenna is that two dual-band operations and one wideband operation can be achieved using the same dimensions. This overcomes the need for increasing the surface area normally incurred when designing wideband patch antennas. Simulation results are validated experimentally through prototypes. The measured radiation patterns and peak gains show stable responses and are in good agreements. Coupling between the two patch elements plays a major role for achieving the wide bandwidth and the effects of mutual coupling between the patch elements are also studied
Finding the Leptonic Decay Mode of a Heavy Higgs Boson
We reanalyze the extraction of the heavy Higgs boson signal from the
Standard Model background at hadron supercolliders, taking into account revised
estimates of the top quark background. With new acceptance criteria the
detection of the signal remains viable. Requiring a forward jet-tag, a central
jet-veto, and a large relative transverse momentum of the two charged leptons
yields for one year of running at the SSC or LHC.Comment: LaTex(Revtex), 9 pages, 6 figures (available upon request),
MAD/PH/75
Large Photonic Band Gaps in Certain Periodic and Quasi-Periodic Networks in two and three dimensions
The photonic band structures in certain two- and three-dimensional periodic
networks made of one-dimensional waveguides are studied by using the
Floquet-Bloch theorem. We find that photonic band gaps exist only in those
structures where the fundamental loop exhibits anti-resonant transmission. This
is also true for quasi-periodic networks in two and three dimensions, where the
photonic band structures are calculated from the spectra of total transmission
arising from a source inside the samples. In all the cases we have studied, it
is also found that the gap positions in a network are dictated by the
frequencies at which the anti-resonance occurs.Comment: 7 pages, 10 figures and 1 table. Published in Phys. Rev. B, 70,
125104 (2004
Fermi Large Area Telescope Detection of Two Very-High-Energy (E>100 GeV) Gamma-ray Photons from the z = 1.1 Blazar PKS 0426-380
We report the Fermi Large Area Telescope (LAT) detection of two
very-high-energy (VHE, E>100 GeV) gamma-ray photons from the directional
vicinity of the distant (redshift, z = 1.1) blazar PKS 0426-380. The null
hypothesis that both the 134 and 122 GeV photons originate from unrelated
sources can be rejected at the 5.5 sigma confidence level. We therefore claim
that at least one of the two VHE photons is securely associated with the
blazar, making PKS 0426-380 the most distant VHE emitter known to date. The
results are in agreement with the most recent Fermi-LAT constraints on the
Extragalactic Background Light (EBL) intensity, which imply a
horizon for 100 GeV photons. The LAT detection of the two VHE
gamma-rays coincided roughly with flaring states of the source, although we did
not find an exact correspondence between the VHE photon arrival times and the
flux maxima at lower gamma-ray energies. Modeling the gamma-ray continuum of
PKS 0426-380 with daily bins revealed a significant spectral hardening around
the time of detection of the first VHE event (LAT photon index \Gamma\
1.4) but on the other hand no pronounced spectral changes near the detection
time of the second one. This combination implies a rather complex variability
pattern of the source in gamma rays during the flaring epochs. An additional
flat component is possibly present above several tens of GeV in the
EBL-corrected Fermi-LAT spectrum accumulated over the ~8-month high state.Comment: 5 pages, 1 table, 4 figures. Accepted by ApJ
A simple and effective method for directing the sagittal placement of thoracic pedicle screws without intraoperative imaging
Concurrent Session 5A: Adolescent Idiopathic Scoliosis & Complications. Paper no. 94postprintThe 17th International Meeting on Advanced Spine Techniques (IMAST 2010), Toronto, Canada, 21-24 July 2010
On the Merging Cluster Abell 578 and Its Central Radio Galaxy 4C +67.13
Here we analyze radio, optical, and X-ray data for a peculiar cluster Abell
578. This cluster is not fully relaxed and consists of two merging sub-systems.
The brightest cluster galaxy, CGPG 0719.8+6704, is a pair of interacting
ellipticals with projected separation 10 kpc, the brighter of which hosts
the radio source 4C +67.13. The Fanaroff-Riley type-II radio morphology of 4C
+67.13 is unusual for central radio galaxies in local Abell clusters. Our new
optical spectroscopy revealed that both nuclei of the CGPG 0719.8+6704 pair are
active, albeit at low accretion rates corresponding to the Eddington ratio
(for the estimated black hole masses of and ). The gathered X-ray ({\it Chandra})
data allowed us to confirm and to quantify robustly the previously noted
elongation of the gaseous atmosphere in the dominant sub-cluster, as well as a
large spatial offset (\,kpc projected) between the position of the
brightest cluster galaxy and the cluster center inferred from the modeling of
the X-ray surface brightness distribution. Detailed analysis of the brightness
profiles and temperature revealed also that the cluster gas in the vicinity of
4C\,+67.13 is compressed (by a factor of about ) and heated (from
\,keV up to 2.7\,keV), consistent with the presence of a weak shock
(Mach number ) driven by the expanding jet cocoon. This would then
require the jet kinetic power of the order of \,erg\,s,
implying either a very high efficiency of the jet production for the current
accretion rate, or a highly modulated jet/accretion activity in the system.Comment: 12 pages, 11 figures, accepted for publication in Ap
Submillimeter wavelength survey of the galactic plane from l = -5 deg to l = +62 deg: Structure and energetics of the inner disk
Results from a large scale survey of the first quadrant of the Milky Way galactic plane at wavelengths of 150, 250, and 300 microns with a 10x10 arcmin beam are presented. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz and/or CO emission, and from an underlying diffuse background with a typical angular width of approximately 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources were identified and characterized, of which about half were not previously reported at far infrared wavelengths. The total infrared luminosity within the solar circle is approximately 1 to 2x10 to the 10th power L sub 0, and is probably emitted by dust that resides in molecular clouds
Statistical Transfer Matrix Study of the Multileg Ising Ladders and Tubes
Finite temperature properties of symmetric multileg Ising ladders and
tubes are investigated using the statistical transfer matrix method. The
temperature dependences of the specific heat and entropy are calculated. In the
case of tubes, it is found that the ground state entropy shows an even-odd
oscillation with respect to the number of legs. The same type of oscillation is
also found in the ground state energy. On the contrary, these oscillations do
not take place in ladders. From the temperature-dependence of the specific
heat, it is found that the lowest excitation energy is 4J for even-leg ladders
while it is 2J otherwise, The physical origin of these behaviors is discussed
based on the structure of excitations.Comment: 6 pages, 9 figure
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