13,447 research outputs found
Distributed stabilization control of rigid formations with prescribed orientation
Most rigid formation controllers reported in the literature aim to only
stabilize a rigid formation shape, while the formation orientation is not
controlled. This paper studies the problem of controlling rigid formations with
prescribed orientations in both 2-D and 3-D spaces. The proposed controllers
involve the commonly-used gradient descent control for shape stabilization, and
an additional term to control the directions of certain relative position
vectors associated with certain chosen agents. In this control framework, we
show the minimal number of agents which should have knowledge of a global
coordinate system (2 agents for a 2-D rigid formation and 3 agents for a 3-D
rigid formation), while all other agents do not require any global coordinate
knowledge or any coordinate frame alignment to implement the proposed control.
The exponential convergence to the desired rigid shape and formation
orientation is also proved. Typical simulation examples are shown to support
the analysis and performance of the proposed formation controllers.Comment: This paper was submitted to Automatica for publication. Compared to
the submitted version, this arXiv version contains complete proofs, examples
and remarks (some of them are removed in the submitted version due to space
limit.
Recommended from our members
Carbapenem-Resistant Klebsiella pneumoniae Infection in Three New York City Hospitals Trended Downwards From 2006 to 2014
Background. Carbapenem-resistant Klebsiella pneumoniae (CRKP) infection is a rising public health threat since its first outbreaks in New York City (NYC) in the early 2000s. We investigated annual trends of CRKP infection in hospital-acquired infections (HAIs) and community-onset infections (COIs) treated in 3 NYC hospitals from 2006 to 2014.
Methods. We extracted K pneumoniae infection data including carbapenem susceptibility and anatomical sites, compared clinical characteristics between CRKP and carbapenem-susceptible K pneumoniae infections, and determined CRKP infection proportions in total K pneumoniae infections in HAI and COI to identify statistically significant trends from 2006 to 2014 using the Cochran-Armitage trend test.
Results. Carbapenem-resistant K pneumoniae contributed 17.3% (601 of 3477) of hospital-acquired K pneumoniae infection compared with 7.7% (149 of 1926) in COI from 2006 to 2014. Carbapenem-resistant K pneumoniae proportions in HAI and COI were positively correlated over time (r = 0.83, P < .01), and there were downward annual trends of CRKP proportions from 2006 to 2014 in both HAI and COI (25.8% to 10.5% in HAI, P < .001; 13.6% to 3.1% in COI, P < .001). By anatomical site, significant downward annual trends were present only in urinary tract infection (P < .001 for both HAI and COI) from 2006 to 2014.
Conclusions. Annual trends of CRKP proportions from 2006 to 2014 were downward in both HAI and COI, and HAI and COI were positively correlated. Efforts to reduce and prevent CRKP infections in both hospital and community settings were successful and warrant continuation
Radiative Neutron-Proton Capture in Effective Chiral Lagrangians
We calculate the cross-section for the thermal
process in chiral perturbation theory to next-to-next-to-leading order using
heavy-fermion formalism. The exchange current correction is found to be
in amplitude and the chiral perturbation at one-loop order
gives the cross section \sigma_{th}^{np}=(334\pm 2)\ {\mbox mb} which is in
agreement with the experimental value (334.2\pm 0.5)\ {\mbox mb}. Together
with the axial charge transitions, this provides a strong support for the power
of chiral Lagrangians for nuclear physics.Comment: 9 pages, revtex, uses epsfig.sty, 2 uuencoded figure
Equivalence of -bosons using the exponential phase operator
Various forms of the -boson are explained and their hidden symmetry
revealed by transformations using the exponential phase operator. Both the
one-component and the multicomponent -bosons are discussed. As a byproduct,
we obtain a new boson algebra having a shifted vacuum structure and define a
global operatal gauge transformation.Comment: 18 pages, LaTex(run twice), To appear in J. PHys.
Suppression of the structural phase transition and lattice softening in slightly underdoped Ba(1-x)K(x)Fe2As2 with electronic phase separation
We present x-ray powder diffraction (XRPD) and neutron diffraction
measurements on the slightly underdoped iron pnictide superconductor
Ba(1-x)K(x)Fe2As2, Tc = 32K. Below the magnetic transition temperature Tm =
70K, both techniques show an additional broadening of the nuclear Bragg peaks,
suggesting a weak structural phase transition. However, macroscopically the
system does not break its tetragonal symmetry down to 15 K. Instead, XRPD
patterns at low temperature reveal an increase of the anisotropic microstrain
proportionally in all directions. We associate this effect with the electronic
phase separation, previously observed in the same material, and with the effect
of lattice softening below the magnetic phase transition. We employ density
functional theory to evaluate the distribution of atomic positions in the
presence of dopant atoms both in the normal and magnetic states, and to
quantify the lattice softening, showing that it can account for a major part of
the observed increase of the microstrain.Comment: 7 pages, 4 figure
PECTINASE-MODIFIED RED GINSENG (GS-E3D) INHIBIT NF-ĂĆĄB TRANSLOCATION AND NITRIC OXIDE PRODUCTION IN LIPOPOLYSACCHARIDE-STIMULATED RAW 264.7 CELLS
Objective: Red ginseng has been used as traditional medicines and functional foods in the world, because of its health benefits. The aim of this study was to elucidate the anti-inflammatory effect and mechanism of pectinase-modified red ginseng (GS-E3D) with a cellular model of lipopolysaccharide (LPS)-stimulated RAW264.7 cells.Methods: To study the anti-inflammatory effect of GS-E3D, the key inflammation mediators such as nitric oxide (NO),prostaglandin E2 (PGE2), inducible nitric oxide synthase (iNOS), Cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF-ñ), and interleukin (IL)-6 production as well as on nuclear factor kappa B (NF-ĂÂșB) and mitogen-activated protein kinases (MAPKs) activation, were measured by using the enzyme linked immunosorbent assay (ELISA)and Western blotting.Results: GS-E3D potently inhibited TNF-ñ and IL-6 and also diminished NO over-production, which was accompanied by the down-regulation of iNOS expression. GS-E3D effectively suppressed LPS-induced NF-ĂÂșB activation through inhibiting the hyper-phosphorylation and degradation of IĂÂșB-ñ and phosphorylation of p38, ERK1/2 and JNK in MAPK signaling pathway.Conclusion: GS-E3D has a potential to be as an anti-inflammatory agent for functional food or cosmetic materials targeting on the NF-ĂÂșB p65 and MAPKs signaling pathways.Ă
Properties of Central Caustics in Planetary Microlensing
To maximize the number of planet detections, current microlensing follow-up
observations are focusing on high-magnification events which have a higher
chance of being perturbed by central caustics. In this paper, we investigate
the properties of central caustics and the perturbations induced by them. We
derive analytic expressions of the location, size, and shape of the central
caustic as a function of the star-planet separation, , and the planet/star
mass ratio, , under the planetary perturbative approximation and compare the
results with those based on numerical computations. While it has been known
that the size of the planetary caustic is \propto \sqrt{q}, we find from this
work that the dependence of the size of the central caustic on is linear,
i.e., \propto q, implying that the central caustic shrinks much more rapidly
with the decrease of compared to the planetary caustic. The central-caustic
size depends also on the star-planet separation. If the size of the caustic is
defined as the separation between the two cusps on the star-planet axis
(horizontal width), we find that the dependence of the central-caustic size on
the separation is \propto (s+1/s). While the size of the central caustic
depends both on and q, its shape defined as the vertical/horizontal width
ratio, R_c, is solely dependent on the planetary separation and we derive an
analytic relation between R_c and s. Due to the smaller size of the central
caustic combined with much more rapid decrease of its size with the decrease of
q, the effect of finite source size on the perturbation induced by the central
caustic is much more severe than the effect on the perturbation induced by the
planetary caustic. Abridged.Comment: 5 pages, 4 figures, ApJ accepte
Symmetry and disorder of the vitreous vortex lattice in an overdoped BaFe_{2-x}Co_xAs_2 superconductor: Indication for strong single-vortex pinning
The disordered flux line lattice in single crystals of the slightly overdoped
aFe_{2-x}Co_xAs_2 (x = 0.19, Tc = 23 K) superconductor is studied by
magnetization measurements, small-angle neutron scattering (SANS), and magnetic
force microscopy (MFM). In the whole range of magnetic fields up to 9 T, vortex
pinning precludes the formation of an ordered Abrikosov lattice. Instead, a
vitreous vortex phase (vortex glass) with a short-range hexagonal order is
observed. Statistical processing of MFM datasets lets us directly measure its
radial and angular distribution functions and extract the radial correlation
length \zeta. In contrast to predictions of the collective pinning model, no
increase in the correlated volume with the applied field is observed. Instead,
we find that \zeta decreases as 1.3*R1 ~ H^(-1/2) over four decades of the
applied magnetic field, where R1 is the radius of the first coordination shell
of the vortex lattice. Such universal scaling of \zeta implies that the vortex
pinning in iron arsenides remains strong even in the absence of static
magnetism. This result is consistent with all the real- and reciprocal-space
vortex-lattice measurements in overdoped as-grown aFe_{2-x}Co_xAs_2 published
to date and is thus sample-independent. The failure of the collective pinning
model suggests that the vortices remain in the single-vortex pinning limit even
in high magnetic fields up to 9 T.Comment: 11 pages, 6 figure
Symmetry and disorder of the vitreous vortex lattice in an overdoped BaFe_{2-x}Co_xAs_2 superconductor: Indication for strong single-vortex pinning
The disordered flux line lattice in single crystals of the slightly overdoped
aFe_{2-x}Co_xAs_2 (x = 0.19, Tc = 23 K) superconductor is studied by
magnetization measurements, small-angle neutron scattering (SANS), and magnetic
force microscopy (MFM). In the whole range of magnetic fields up to 9 T, vortex
pinning precludes the formation of an ordered Abrikosov lattice. Instead, a
vitreous vortex phase (vortex glass) with a short-range hexagonal order is
observed. Statistical processing of MFM datasets lets us directly measure its
radial and angular distribution functions and extract the radial correlation
length \zeta. In contrast to predictions of the collective pinning model, no
increase in the correlated volume with the applied field is observed. Instead,
we find that \zeta decreases as 1.3*R1 ~ H^(-1/2) over four decades of the
applied magnetic field, where R1 is the radius of the first coordination shell
of the vortex lattice. Such universal scaling of \zeta implies that the vortex
pinning in iron arsenides remains strong even in the absence of static
magnetism. This result is consistent with all the real- and reciprocal-space
vortex-lattice measurements in overdoped as-grown aFe_{2-x}Co_xAs_2 published
to date and is thus sample-independent. The failure of the collective pinning
model suggests that the vortices remain in the single-vortex pinning limit even
in high magnetic fields up to 9 T.Comment: 11 pages, 6 figure
Hyperglycemic Hyperosmolar Syndrome Caused by Steroid Therapy in a Patient with Lupus Nephritis
A 51-yr-old female was referred to our outpatient clinic for the evaluation of generalized edema. She had been diagnosed with idiopathic thrombocytopenic purpura (ITP). She had taken no medicine. Except for the ITP, she had no history of systemic disease. She was diagnosed with systemic lupus erythematosus. Immunosuppressions consisting of high-dose steroid were started. When preparing the patient for discharge, a generalized myoclonic seizure occurred at the 47th day of admission. At that time, the laboratory and neurology studies showed hyperglycemic hyperosmolar syndrome. Brain MRI and EEG showed brain atrophy without other lesion. The seizure stopped after the blood sugar and serum osmolarity declined below the upper normal limit. The patient became asymptomatic and she was discharged 10 weeks after admission under maintenance therapy with prednisolone, insulin glargine and nateglinide. The patient remained asymptomatic under maintenance therapy with deflazacort and without insulin or medication for blood sugar control
- âŠ