119,974 research outputs found
Tracking 3-D body motion for docking and robot control
An advanced method of tracking three-dimensional motion of bodies has been developed. This system has the potential to dynamically characterize machine and other structural motion, even in the presence of structural flexibility, thus facilitating closed loop structural motion control. The system's operation is based on the concept that the intersection of three planes defines a point. Three rotating planes of laser light, fixed and moving photovoltaic diode targets, and a pipe-lined architecture of analog and digital electronics are used to locate multiple targets whose number is only limited by available computer memory. Data collection rates are a function of the laser scan rotation speed and are currently selectable up to 480 Hz. The tested performance on a preliminary prototype designed for 0.1 in accuracy (for tracking human motion) at a 480 Hz data rate includes a worst case resolution of 0.8 mm (0.03 inches), a repeatability of plus or minus 0.635 mm (plus or minus 0.025 inches), and an absolute accuracy of plus or minus 2.0 mm (plus or minus 0.08 inches) within an eight cubic meter volume with all results applicable at the 95 percent level of confidence along each coordinate region. The full six degrees of freedom of a body can be computed by attaching three or more target detectors to the body of interest
A centralized feedback control model for resource management in wireless networks
In a wireless environment, guaranteeing QoS is challenging because applications at multiple devices share the same limited radio bandwidth. In this paper we introduce and study a resource management model for centralized wireless networks, using feedback control theory. Before applying in practice, the proposed model is evaluated using the well-known 20-sim dynamic system simulator. The experimental results show that flexible and efficient resource allocation can be achieved for a variety of system parameters and WLAN scenarios; however, care should be taken in setting the control parameters and coefficients
Discrete Solitons and Vortices on Anisotropic Lattices
We consider effects of anisotropy on solitons of various types in
two-dimensional nonlinear lattices, using the discrete nonlinear
Schr{\"{o}}dinger equation as a paradigm model. For fundamental solitons, we
develop a variational approximation, which predicts that broad quasi-continuum
solitons are unstable, while their strongly anisotropic counterparts are
stable. By means of numerical methods, it is found that, in the general case,
the fundamental solitons and simplest on-site-centered vortex solitons ("vortex
crosses") feature enhanced or reduced stability areas, depending on the
strength of the anisotropy. More surprising is the effect of anisotropy on the
so-called "super-symmetric" intersite-centered vortices ("vortex squares"),
with the topological charge equal to the square's size : we predict in
an analytical form by means of the Lyapunov-Schmidt theory, and confirm by
numerical results, that arbitrarily weak anisotropy results in dramatic changes
in the stability and dynamics in comparison with the \emph{degenerate}, in this
case, isotropic limit.Comment: 10 pages + 7 figure
Letting Go of Self: The Creation of the Nonattachment to Self Scale
The Buddhist notion of nonattachment relates to an engagement with experience with flexibility and without fixation on achieving specified outcomes. The present study sought to define, create and validate a new measure of nonattachment as it applies to notions of the self. A new construct of ânonattachment to selfâ (NTS) was developed, defined the absence of fixation on self-related concepts, thoughts and feelings, and a capacity to flexibly interact with these concepts, thoughts and feelings without trying to control them. Two studies were conducted in the development of the new scale. With expert consultation, study 1 (n = 445) established a single factor, internally consistent 7-item scale via exploratory factor analysis. Study 2 (n = 388, n = 338) confirmed the factor structure of the new 7-item scale using confirmatory factor analyses. Study 2 also found the new scale to be internally consistent, with evidence supporting its test-retest reliability, criterion, and construct validity. Nonattachment to self-emerged as a unique way of relating to the self, distinct from general nonattachment, that aligned with higher levels of well-being and adaptive functioning
Anomalous low temperature state of CeOs4Sb12: Magnetic field and La-impurity study
Specific heat for single crystalline samples of Ce1-xLaxOs4Sb12 at zero-field
and magnetic fields to 14 T is reported. Our results confirm enhanced value of
the electronic specific heat coefficient in the paramagnetic state. They
provide arguments for the intrinsic origin of the 1.1 K anomaly. This
transition leads to opening of the gap at the Fermi surface. This low
temperature state of CeOs4Sb12 is extremely sensitive to chemical impurities.
2% of La substituted for Ce suppresses the transition and reduces the
electronic specific heat coefficient. The magnetic field response of the
specific heat is also anomalous.Comment: 4 pages, 3 figure
Very Long Baseline Interferometry Measured Proper Motion and Parallax of the -ray Millisecond Pulsar PSR J0218+4232
PSR J02184232 is a millisecond pulsar (MSP) with a flux density 0.9
mJy at 1.4 GHz. It is very bright in the high-energy X-ray and -ray
domains. We conducted an astrometric program using the European VLBI Network
(EVN) at 1.6 GHz to measure its proper motion and parallax. A model-independent
distance would also help constrain its -ray luminosity. We achieved a
detection of signal-to-noise ratio S/N > 37 for the weak pulsar in all five
epochs. Using an extragalactic radio source lying 20 arcmin away from the
pulsar, we estimate the pulsar's proper motion to be
mas yr and mas yr, and a parallax of mas. The very long
baseline interferometry (VLBI) proper motion has significantly improved upon
the estimates from long-term pulsar timing observations. The VLBI parallax
provides the first model-independent distance constraints:
kpc, with a corresponding lower-limit of
kpc. This is the first pulsar trigonometric parallax measurement based
solely on EVN observations. Using the derived distance, we believe that PSR
J02184232 is the most energetic -ray MSP known to date. The
luminosity based on even our 3 lower-limit distance is high enough to
pose challenges to the conventional outer gap and slot gap models.Comment: 5 pages, 2 figures, 2 tables; published in the Astrophysical Journal
Letters on 2014 Feb. 1
Identities in the Superintegrable Chiral Potts Model
We present proofs for a number of identities that are needed to study the
superintegrable chiral Potts model in the sector.Comment: LaTeX 2E document, using iopart.cls with iopams packages. 11 pages,
uses eufb10 and eurm10 fonts. Typeset twice! vs2: Two equations added. vs3:
Introduction adde
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