1,481 research outputs found
Quantum decoupling transition in a one-dimensional Feshbach-resonant superfluid
We study a one-dimensional gas of fermionic atoms interacting via an s-wave
molecular Feshbach resonance. At low energies the system is characterized by
two Josephson-coupled Luttinger liquids, corresponding to paired atomic and
molecular superfluids. We show that, in contrast to higher dimensions, the
system exhibits a quantum phase transition from a phase in which the two
superfluids are locked together to one in which, at low energies, quantum
fluctuations suppress the Feshbach resonance (Josephson) coupling, effectively
decoupling the molecular and atomic superfluids. Experimental signatures of
this quantum transition include the appearance of an out-of-phase gapless mode
(in addition to the standard gapless in-phase mode) in the spectrum of the
decoupled superfluid phase and a discontinuous change in the molecular momentum
distribution function.Comment: 4 RevTeX pages, 1 figure, submitted to PR
Antenna-coupled millimeter-wave LiNbO_3 electro-optic modulator
The phase-velocity mismatch due to material dispersion in traveling-wave LiNbO_3 optical
waveguide modulators may be greatly reduced by breaking the modulation transmission line into short
segments and connecting each segment to its own surface antenna. The array of antennas is then
illuminated by the modulation signal at an angle which produces a delay from antenna to antenna to
match the optical waveguide's delay
60 GHz and 94 GHz antenna-coupled LiNbO_3 electrooptic modulators
Antenna-coupled LiBbO_3 electrooptic modulators can overcome the material dispersion which would otherwise prevent sensitive high-frequency operation. The authors previously demonstrated the concept with a phase modulator at X-band. They have extended this demonstration to a narrowband 60-GHz phase modulator and broadband amplitude modulator designs at 60 and 94 GHz, respectively
Wave-Coupled W-Band LiNbO_3 Mach-Zehnder Modulator
Summary form only given. Mach-Zehnder amplitude modulators have been designed for W-band operation (94 GHz), at a 1.3-ÎĽm optical wavelength. These modulators use bow-tie antennas, which are relatively insensitive to DC bias connections made to the ends of the antenna elements. The bow-ties should also give a greater bandwidth than the dipole antennas
Wave-coupled LiNbO_3 electrooptic modulator for microwave and millimeter-wave modulation
A new technique of phase velocity matching in electrooptic modulators was demonstrated. The results show that the phase velocity mismatch due to material dispersion in traveling-wave LiNbO_3 optical waveguide modulators can be greatly reduced by breaking the modulation transmission line into short segments and connecting each segment to its own surface dipole antenna. The array of antennas is then illuminated by the modulation signal from below at the proper angle to produce a delay from antenna to antenna that matches the optical waveguide's delay. A phase modulator 25 mm in length with five antennas and five transmission line segments was operated from 4.6 to 13 GHz with a maximum phase modulation sensitivity of over 100°/W^(1/2)
The Impact Of A Media Literacy Education Plan On The Florida Comprehensive Assessment Test (fcat) Reading Scores Of 9th And 10th Grade Students
This study investigated the impact of a media literacy education plan on the reading test scores of the Florida Comprehensive Assessment Test (FCAT) at an urban high school in Central Florida. A team of 9th and 10th grade teachers created a professional learning community and developed a treatment to enhance language arts instruction with various forms of media. This media literacy education plan included four lessons utilizing media such as television commercials, magazine photographs and the Internet; the lessons were taught during the four months leading to the administration of the 2007 FCAT. Data were gathered from the 2006 and 2007 FCAT scores of students in a control and treatment group. Using these pre test and post test data, statistical analysis comprised two independent t-tests and one repeated measures ANOVA. The data revealed statistical significance at the 9th and 10th grade level, but did not show statistical significance at any particular reading level (Levels 1-5). Implications from this study included strong professional learning communities produce effective teachers and that student achievement increases when a media literacy education plan is included in English Language Arts instruction. Furthermore, this study illustrates the need to embrace modern media as viable classroom instructional tools. Recommendations were made for further research utilizing different materials, different forms of media, different student populations. This study also concluded that further qualitative research be conducted. Ultimately, this study makes a strong argument for the inclusion of media and media literacy education in the secondary English Language Arts classroom
Novel Millimeter-Wave Electro-optic Modulator
A waveguide LiNbO_3 electro-optic modulator has been demonstrated with a novel wave-coupling technique which greatly reduces phase-velocity mismatch. An 8-12 GHz version produces 48° phase modulation with 126 mW of drive power. A 60 GHz version is being built
Current legal and institutional issues in the commercialization of phosphoric acid fuel cells
Legal and institutional factors affecting the development and commercial diffusion of phosphoric acid fuel cells are assessed. Issues for future research and action are suggested. Perceived barriers and potential opportunities for fuel cells in central and dispersed utility operations and on-site applications are reviewed, as well as the general concept of commercialization as applied to emerging energy technologies
Pairing of a trapped resonantly-interacting fermion mixture with unequal spin populations
We consider the phase separation of a trapped atomic mixture of fermions with
unequal spin populations near a Feshbach resonance. In particular, we determine
the density profile of the two spin states and compare with the recent
experiments of Partridge et al. (cond-mat/0511752). Overall we find quite good
agreement. We identify the remaining discrepancies and pose them as open
problems.Comment: 4 figures, 4+ pages, revtex
Experimental study of main rotor/tail rotor/airframe interactions in hover. Volume 1: Text and figures
To assist in identifying and quantifying the relevant parameters associated with the complex topic of main rotor/fuselage/tail rotor interference, a model scale hover test was conducted in the Model Rotor Hover Facility. The test was conducted using the basic model test rig, fuselage skins to represent a UH-60A BLACK HAWK helicopter, 4 sets of rotor blades of varying geometry (i.e., twist, airfoils and solidity) and a model tail rotor that could be relocated to give changes in rotor clearance (axially, laterally, and vertically), can't angle and operating model (pusher or tractor). The description of the models and the tests, data analysis and summary (including plots) are included. The customary system of units gas used for principal measurements and calculations. Expressions in both SI units and customary units are used with the SI units stated first and the customary units afterwords, in parenthesis
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