49 research outputs found
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Beam envelope matching for beam guidance systems
Ray optics and phase ellipse optics are developed as tools for designing charged particle beam guidance systems. Specific examples of basic optical systems and of phase ellipse matching are presented as illustrations of these mathematical techniques
Automated Calibration of Mobile Cameras for 3D Reconstruction of Mechanical Pipes
This manuscript provides a new framework for calibration of optical
instruments, in particular mobile cameras, using large-scale circular black and
white target fields. New methods were introduced for (i) matching targets
between images; (ii) adjusting the systematic eccentricity error of target
centers; and (iii) iteratively improving the calibration solution through a
free-network self-calibrating bundle adjustment. It was observed that the
proposed target matching effectively matched circular targets in 270 mobile
phone images from a complete calibration laboratory with robustness to Type II
errors. The proposed eccentricity adjustment, which requires only camera
projective matrices from two views, behaved synonymous to available closed-form
solutions, which require several additional object space target information a
priori. Finally, specifically for the case of the mobile devices, the
calibration parameters obtained using our framework was found superior compared
to in-situ calibration for estimating the 3D reconstructed radius of a
mechanical pipe (approximately 45% improvement)
Automated calibration of smartphone cameras for 3D reconstruction of mechanical pipes
This paper outlines a new framework for the calibration of optical instruments, in particular smartphone cameras, using highly redundant circular black-and-white target fields. New methods were introduced for (i) matching targets between images; (ii) adjusting the systematic eccentricity error of target centres; and (iii) iteratively improving the calibration solution through a free-network self-calibrating bundle adjustment. The proposed method effectively matched circular targets in 270 smartphone images, taken within a calibration laboratory, with robustness to type II errors (false negatives). The proposed eccentricity adjustment, which requires only camera projective matrices from two views, behaved comparably to available closed-form solutions, which require additional a priori object-space target information. Finally, specifically for the case of mobile devices, the calibration parameters obtained using the framework were found to be superior compared to in situ calibration for estimating the 3D reconstructed radius of a mechanical pipe (approximately 45% improvement on average)
Optical Navigation Algorithm Performance
There is a wide variety of optical navigation (OpNav) techniques that can be used to extract observables from images of natural bodies. Each of these techniques has a number of strengths and weaknesses and domains where they are most applicable. In this paper, we compare the performance of some of the most commonly used OpNav techniques across a variety of orbital regimes and a variety of body types through the use of synthetic images. Specifically, we consider the techniques of analytic model fitting, phase corrected moment estimation, limb-scanning, ellipsoid matching, and cross correlation using synthetic images of a tri-axial ellipsoid, the asteroid Bennu, and the comet 67P/Churyumov-Gerasimenko. For each technique, regime, and body, we examine the overall accuracy and the type of information available. The resulting information provides a useful tool for understanding which techniques are best suited for a given image, as well as for understanding the relative performance of each technique
Circulating Tumour Necrosis Factor is highly correlated with brainstem serotonin transporter availability in humans
Preclinical studies demonstrate that pro-inflammatory cytokines increase serotonin transporter availability and function, leading to depressive symptoms in rodent models. Herein we investigate associations between circulating inflammatory markers and brainstem serotonin transporter (5-HTT) availability in humans. We hypothesised that higher circulating inflammatory cytokine concentrations, particularly of tumour necrosis factor (TNF-α), would be associated with greater 5-HTT availability, and that TNF-α inhibition with etanercept (sTNFR:Fc) would in turn reduce 5-HTT availability. In 13 neurologically healthy adult women, plasma TNF-α correlated significantly with 5-HTT availability (rho=0.6; p=0.03) determined by [123I] -beta-CIT SPECT scanning. This association was replicated in an independent sample of 12 patients with psoriasis/psoriatic arthritis (rho=0.76; p=0.003). Indirect effects analysis, showed that there was a significant overlap in the variance explained by 5-HTT availability and TNF-α concentrations on BDI scores. Treatment with etanercept for 6-8 weeks was associated with a significant reduction in 5-HTT availability (Z= 2.09; p=0.03; r=0.6) consistent with a functional link. Our findings confirm an association between TNF-α and 5-HTT in both the basal physiological and pathological condition. Modulation of both TNF-α and 5-HTT by etanercept indicate the presence of a mechanistic pathway whereby circulating inflammatory cytokines are related to central nervous system substrates underlying major depression
Deep Chandra Observations of Abell 2199: the Interplay between Merger-Induced Gas Motions and Nuclear Outbursts in a Cool Core Cluster
We present new Chandra observations of Abell 2199 that show evidence of gas
sloshing due to a minor merger, as well as impacts of the radio source, 3C 338,
hosted by the central galaxy, NGC 6166, on the intracluster gas. The new data
are consistent with previous evidence of a Mach 1.46 shock 100" from the
cluster center, although there is still no convincing evidence for the expected
temperature jump. Other interpretations of this feature are possible, but none
is fully satisfactory. Large scale asymmetries, including enhanced X-ray
emission 200" southwest of the cluster center and a plume of low entropy,
enriched gas reaching 50" to the north of the center, are signatures of gas
sloshing induced by core passage of a merging subcluster about 400 Myr ago. An
association between the unusual radio ridge and low entropy gas are consistent
with this feature being the remnant of a former radio jet that was swept away
from the AGN by gas sloshing. A large discrepancy between the energy required
to produce the 100" shock and the enthalpy of the outer radio lobes of 3C 338
suggests that the lobes were formed by a more recent, less powerful radio
outburst. Lack of evidence for shocks in the central 10" indicates that the
power of the jet now is some two orders of magnitude smaller than when the 100"
shock was formed.Comment: 17 pages, 20 figures, accepted for publication in Ap
Unbeamed tidal disruption events at hard X-rays
Owing to their thermal emission, tidal disruption events (TDEs) were
regularly detected in the soft X-rays and sometimes in the optical. Only a few
TDEs have been detected at hard X-rays: two are high redshift beamed events,
one of which occurred at the core of a nearby galaxy, and the most recent one
is of a different nature, involving a compact object in the Milky Way. The aims
of this work are to obtain a first sample of hard X-ray-selected unbeamed TDEs,
to determine their frequency and to probe whether TDEs usually or exceptionally
emit at hard X-ray energies. We performed extensive searches for hard X-ray
flares at positions in over 53000 galaxies, up to a distance of 100 Mpc in the
Swift BAT archive. Light curves were extracted and parametrized. The quiescent
hard X-ray emission was used to exclude persistently active galactic nuclei.
Significant flares from non-active galaxies were derived and checked for
possible contamination. We found a sample of nine TDE candidates, which
translates into a rate of
above the BAT detection limit. This rate is consistent with those observed by
XMM-Newton at soft X-rays and in the optical from SDSS observations, and is as
expected from simulations. We conclude that hard X-ray emission should be
ubiquitous in un-beamed TDEs and that electrons should be accelerated in their
accretion flow.Comment: accepted for publication in A&A; 14 pages, 6 figures, 2 table
PoCoMo: Projected Collaboration using Mobile Devices
As personal projection devices become more common they will be able to support a range of exciting and unexplored social applications. We present a novel system and method that enables playful social interactions between multiple projected characters. The prototype consists of two mobile projector-camera systems, with lightly modified existing hardware, and computer vision algorithms to support a selection of applications and example scenarios. Our system allows participants to discover the characteristics and behaviors of other characters projected in the environment. The characters are guided by hand movements, and can respond to objects and other characters, to simulate a mixed reality of life-like entities