3,163 research outputs found
Implicit Density Functional Theory
A fermion ground state energy functional is set up in terms of particle
density, relative pair density, and kinetic energy tensor density. It satisfies
a minimum principle if constrained by a complete set of compatibility
conditions. A partial set, which thereby results in a lower bound energy under
minimization, is obtained from the solution of model systems, as well as a
small number of exact sum rules. Prototypical application is made to several
one-dimensional spinless non-interacting models. The effectiveness of "atomic"
constraints on model "molecules" is observed, as well as the structure of
systems with only finitely many bound states.Comment: 9 pages, 4 figure
Laser beam self-symmetrization in air in the multifilamentation regime
We show experimental and numerical evidence of spontaneous
self-symmetrization of focused laser beams experiencing multi-filamentation in
air. The symmetrization effect is observed as the multiple filaments generated
prior to focus approach the focal volume. This phenomenon is attributed to the
nonlinear interactions amongst the different parts of the beam mediated by the
optical Kerr effect, which leads to a symmetric redistribution of the wave
vectors even when the beam consists of a bundle of many filaments.Comment: 9 pages, 7 figure
Highly tunable hybrid metamaterials employing split-ring resonators strongly coupled to graphene surface plasmons
Metamaterials and plasmonics are powerful tools for unconventional
manipulation and harnessing of light. Metamaterials can be engineered to
possess intriguing properties lacking in natural materials, such as negative
refractive index. Plasmonics offers capabilities to confine light in
subwavelength dimensions and to enhance light-matter interactions.
Recently,graphene-based plasmonics has revealed emerging technological
potential as it features large tunability, higher field-confinement and lower
loss compared to metal-based plasmonics. Here,we introduce hybrid structures
comprising graphene plasmonic resonators efficiently coupled to conventional
split-ring resonators, thus demonstrating a type of highly tunable
metamaterial, where the interaction between the two resonances reaches the
strong-coupling regime. Such hybrid metamaterials are employed as high-speed
THz modulators, exhibiting over 60% transmission modulation and operating speed
in excess of 40 MHz. This device concept also provides a platform for exploring
cavity-enhanced light-matter interactions and optical processes in graphene
plasmonic structures for applications including sensing, photo-detection and
nonlinear frequency generation
APP-RUSS: Automated Path Planning for Robotic Ultrasound System
Autonomous robotic ultrasound System (RUSS) has been extensively studied.
However, fully automated ultrasound image acquisition is still challenging,
partly due to the lack of study in combining two phases of path planning:
guiding the ultrasound probe to the scan target and covering the scan surface
or volume. This paper presents a system of Automated Path Planning for RUSS
(APP-RUSS). Our focus is on the first phase of automation, which emphasizes
directing the ultrasound probe's path toward the target over extended
distances. Specifically, our APP-RUSS system consists of a RealSense D405 RGB-D
camera that is employed for visual guidance of the UR5e robotic arm and a cubic
Bezier curve path planning model that is customized for delivering the probe to
the recognized target. APP-RUSS can contribute to understanding the integration
of the two phases of path planning in robotic ultrasound imaging, paving the
way for its clinical adoption
Beneficial influence of nanocarbon on the aryliminopyridylnickel chloride catalyzed ethylene polymerization
A series of 1-aryliminoethylpyridine ligands (L1―L3) was synthesized by condensation of 2-acetylpyridine with 1-aminonaphthalene, 2-aminoanthracene or 1-aminopyrene, respectively. Reaction with nickel dichloride afforded the corresponding nickel (II) chloride complexes (Ni1–Ni3). All compounds were fully characterized and the molecular structures of Ni1 and Ni3 are reported. Upon activation with methylaluminoxane (MAO), all nickel complexes exhibit high activities for ethylene polymerization, producing waxes of low molecular weight and narrow polydispersity. The presence of multi-walled carbon nanotubes (MWCNTs) or few layer graphene (FLG) in the catalytic medium can lead to an increase of productivity associated to a modification of the polymer structure
Dynamical mass constraints on the ultraluminous X-ray Source NGC 1313 X-2
Dynamical mass measurements hold the key to answering whether ultraluminous
X-ray sources (ULXs) are intermediate mass black holes (IMBHs) or stellar mass
black holes with special radiation mechanisms. NGC 1313 X-2 is so far the only
ULX with HST light curves, the orbital period, and the black hole's radial
velocity amplitude based on the He II \AA\ disk emission line
shift of km/s. We constrain its black hole mass and other parameters
by fitting observations to a binary light curve code with accommodations for
X-ray heating of the accretion disk and the secondary. Given the dynamical
constraints from the observed light curves and the black hole radial motion and
the observed stellar environment age, the only acceptable models are those with
40-50 Myrs old intermediate mass secondaries in their helium core and hydrogen
shell burning phase filling 40%-80% of their Roche lobes. The black hole can be
a massive black hole of a few tens of that can be produced from
stellar evolution of low metalicity stars, or an IMBH of a few hundred to above
1000 if its true radial velocity km/s. Further
observations are required to better measure the black hole radial motion and
the light curves in order to determine whether NGC 1313 X-2 is a stellar black
hole or an IMBH.Comment: 45 pages, 21 figures, 2 tables, to appear in ApJ in December 10 issu
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