10,798 research outputs found
Structural relaxation in a system of dumbbell molecules
The interaction-site-density-fluctuation correlators, the dipole-relaxation
functions, and the mean-squared displacements of a system of symmetric
dumbbells of fused hard spheres are calculated for two representative
elongations of the molecules within the mode-coupling theory for the evolution
of glassy dynamics. For large elongations, universal relaxation laws for states
near the glass transition are valid for parameters and time intervals similar
to the ones found for the hard-sphere system. Rotation-translation coupling
leads to an enlarged crossover interval for the mean-squared displacement of
the constituent atoms between the end of the von Schweidler regime and the
beginning of the diffusion process. For small elongations, the superposition
principle for the reorientational -process is violated for parameters
and time intervals of interest for data analysis, and there is a strong
breaking of the coupling of the -relaxation scale for the diffusion
process with that for representative density fluctuations and for dipole
reorientations.Comment: 15 pages, 14 figures, Phys. Rev. E in pres
Emergent particle-hole symmetry in spinful bosonic quantum Hall systems
When a fermionic quantum Hall system is projected into the lowest Landau
level, there is an exact particle-hole symmetry between filling fractions
and . We investigate whether a similar symmetry can emerge in bosonic
quantum Hall states, where it would connect states at filling fractions
and . We begin by showing that the particle-hole conjugate to a
composite fermion `Jain state' is another Jain state, obtained by reverse flux
attachment. We show how information such as the shift and the edge theory can
be obtained for states which are particle-hole conjugates. Using the techniques
of exact diagonalization and infinite density matrix renormalization group, we
study a system of two-component (i.e., spinful) bosons, interacting via a
-function potential. We first obtain real-space entanglement spectra
for the bosonic integer quantum Hall effect at , which plays the role of
a filled Landau level for the bosonic system. We then show that at
the system is described by a Jain state which is the particle-hole conjugate of
the Halperin (221) state at . We show a similar relationship between
non-singlet states at and . We also study the case of
, providing unambiguous evidence that the ground state is a composite
Fermi liquid. Taken together our results demonstrate that there is indeed an
emergent particle-hole symmetry in bosonic quantum Hall systems.Comment: 10 pages, 8 figures, 4 appendice
Digital Doppler extraction demonstration with the advanced receiver
A digital Doppler extraction demonstration with the Advanced Receiver 2 (ARX 2) tracking Pioneer 10 and Voyager 2 is described. The measured results are compared with those of the Block 4 receiver that was operating in parallel with the ARX 2. It is shown that the ARX 2 outperforms the Block 4 receiver in terms of Allan variance of the Doppler residuals, the amount of which depends on the scenario of interest
Superconductivity and Magnetism in REFeAsO1-xFx (RE=Rare Earth Elements)
Fluoride-doped iron-based oxypnictides containing rare-earth gadolinium
(GdFeAsO0.8F0.2) and co-doping with yttrium (Gd0.8Y0.2FeAsO0.8F0.2) have been
prepared via conventional solid state reaction at ambient pressure. The
non-yttrium substituted oxypnictide show superconducting transition as high as
43.9 K from temperature dependent resistance measurements with the Meissner
effect observed at a lower temperature of 40.8 K from temperature dependent
magnetization measurements. By replacing a small amount of gadolinium with
yttrium Tc was observed to be lowered by 10 K which might be caused by a change
in the electronic or magnetic structures since the crystal structure was not
altered.Comment: 4 pages, 4 figures, Journal of Physics: Conference Series
(Proceedings in the LT25 Low Temperature Physics Conference) Submitte
Wafer-Level Parylene Packaging With Integrated RF Electronics for Wireless Retinal Prostheses
This paper presents an embedded chip integration
technology that incorporates silicon housings and flexible
Parylene-based microelectromechanical systems (MEMS) devices.
Accelerated-lifetime soak testing is performed in saline at elevated
temperatures to study the packaging performance of Parylene C
thin films. Experimental results show that the silicon chip under
test is well protected by Parylene, and the lifetime of Parylenecoated
metal at body temperature (37°C) is more than 60 years,
indicating that Parylene C is an excellent structural and packaging
material for biomedical applications. To demonstrate the proposed
packaging technology, a flexible MEMS radio-frequency (RF) coil
has been integrated with an RF identification (RFID) circuit die.
The coil has an inductance of 16 μH with two layers of metal
completely encapsulated in Parylene C, which is microfabricated
using a Parylene–metal–Parylene thin-film technology. The chip
is a commercially available read-only RFID chip with a typical
operating frequency of 125 kHz. The functionality of the embedded
chip has been tested using an RFID reader module in both air
and saline, demonstrating successful power and data transmission
through the MEMS coil
Transmission of PhC coupled-resonator waveguide (PhCCRW) structure enhanced via mode matching
A method for increasing the coupling efficiency between ridge optical waveguides and PhCCRWs is described. This increase is achieved via W1 channel waveguide sections, formed within a two-dimensional triangular lattice photonic crystal using mode-matching. The mode-matching is achieved by low quality-factor modified cavities added to both the input and output ports of the PhCCRW. A three dimensional finite-difference time-domain method has been used to simulate light propagation through the modified PhCCRW. We have fabricated PhCCRWs working at 1.5µm in silicon-on-insulator material. Measurements and simulations show that the overall transmission is improved by a factor of two
Multipolar planetary nebulae: not as geometrically diversified as thought
Session 2: The Stellar Evolution Connection - 2c: Aspects of the Central StarsWe present a general three-dimensional model of multipolar planetary nebulae (PNe). By rotating to different viewing angles and adjusting the angles between the multiple lobes, we demonstrate that the model is able to reproduce HST Hα images of 20 multipolar young PNe. Though this model only considers the geometrical projection effects, it significantly unifies the selected PNe and can be considered as a first-order fundamental model of the "multipolar" morphological class. This kind of model reduces complexity and is essential to pursuing of the shaping mechanism. In addition, we illustrate that under some special conditions, i.e. in certain viewing angles, or with low sensitivity, it will be hard to imagine that the projected image originates from a multipolar-lobed model. © 2012 International Astronomical Union.published_or_final_versionThe IAU Symposium No. 283: "Planetary Nebulae: an Eye to the Future", Puerto de la Cruz, Tenerife, Spain, 25-29 July 2011. In International Astronomical Union Proceedings, 2011, v. 7 S283, p. 184-18
Novelty Search in Competitive Coevolution
One of the main motivations for the use of competitive coevolution systems is
their ability to capitalise on arms races between competing species to evolve
increasingly sophisticated solutions. Such arms races can, however, be hard to
sustain, and it has been shown that the competing species often converge
prematurely to certain classes of behaviours. In this paper, we investigate if
and how novelty search, an evolutionary technique driven by behavioural
novelty, can overcome convergence in coevolution. We propose three methods for
applying novelty search to coevolutionary systems with two species: (i) score
both populations according to behavioural novelty; (ii) score one population
according to novelty, and the other according to fitness; and (iii) score both
populations with a combination of novelty and fitness. We evaluate the methods
in a predator-prey pursuit task. Our results show that novelty-based approaches
can evolve a significantly more diverse set of solutions, when compared to
traditional fitness-based coevolution.Comment: To appear in 13th International Conference on Parallel Problem
Solving from Nature (PPSN 2014
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