2,921 research outputs found
On the simulation of interactive non-verbal behaviour in virtual humans
Development of virtual humans has focused mainly in two broad areas - conversational agents and computer game characters. Computer game characters have traditionally been action-oriented - focused on the game-play - and conversational agents have been focused on sensible/intelligent conversation. While virtual humans have incorporated some form of non-verbal behaviour, this has been quite limited and more importantly not connected or connected very loosely with the behaviour of a real human interacting with the virtual human - due to a lack of sensor data and no system to respond to that data. The interactional aspect of non-verbal behaviour is highly important in human-human interactions and previous research has demonstrated that people treat media (and therefore virtual humans) as real people, and so interactive non-verbal behaviour is also important in the development of virtual humans. This paper presents the challenges in creating virtual humans that are non-verbally interactive and drawing corollaries with the development history of control systems in robotics presents some approaches to solving these challenges - specifically using behaviour based systems - and shows how an order of magnitude increase in response time of virtual humans in conversation can be obtained and that the development of rapidly responding non-verbal behaviours can start with just a few behaviours with more behaviours added without difficulty later in development
Investigation of Critical Burning of Fuel Droplets
An earlier analysis for the combustion response of a liquid monopropellant strand (hydrazine) was extended to consider individual droplets and sprays. While small drops gave low or negative response, large droplets provided response near unity at low frequencies, with the response declining at frequencies greater than the characteristic liquid phase frequency. Temperature gradients in the liquid phase resulted in response peaks greater than unity. A second response peak was found for large drops which corresponded to gas phase transient effects. Spray response was generally reduced from the response of the largest injected droplet, however, even a small percentage of large droplets can yield appreciable response. An apparatus was designed and fabricated to allow observation of bipropellant fuel spray combustion at elevated pressures. A locally homogeneous model was developed to describe this combustion process which allows for high pressure phenomena associated with the thermodynamic critical point
Implications of the Optical Observations of Neutron Stars
We show that observations of pulsars with pulsed optical emission indicate
that the peak flux scales according to the magnetic field strength at the light
cylinder. The derived relationships indicate that the emission mechanism is
common across all of the observed pulsars with periods ranging from 33ms to 385
ms and ages of 1000-300,000 years. It is noted that similar trends exist for
ray pulsars. Furthermore the model proposed by Pacini (1971) and
developed by Pacini and Salvati (1983,1987) still has validity and gives an
adequate explanation of the optical phenomena.Comment: 23 pages, 6 figures, accepted for publication in the Astrophysical
Journa
A candidate optical counterpart to the middle-aged gamma-ray pulsar PSR J1741-2054
We carried out deep optical observations of the middle-aged -ray
pulsar PSR J1741-2054 with the Very Large Telescope (VLT). We identified two
objects, of magnitudes and , at positions
consistent with the very accurate Chandra coordinates of the pulsar, the
faintest of which is more likely to be its counterpart. From the VLT images we
also detected the known bow-shock nebula around PSR J1741-2054. The nebula is
displaced by \sim 0\farcs9 (at the confidence level) with respect
to its position measured in archival data, showing that the shock propagates in
the interstellar medium consistently with the pulsar proper motion. Finally, we
could not find evidence of large-scale extended optical emission associated
with the pulsar wind nebula detected by Chandra, down to a surface brightness
limit of magnitudes arcsec. Future observations are needed
to confirm the optical identification of PSR J1741-2054 and characterise the
spectrum of its counterpart.Comment: 8 pages, 3 figures, Astrophysical Journal, in pres
Beyond deficiency:Potential benefits of increased intakesof vitamin K for bone and vascular health
Vitamin K is wellknown for its role in the synthesisof a number of blood coagulationfactors.During recent years vitaminK-dependent proteins werediscovered to be of vital importancefor bone and vascular health.Recommendations for dietary vitaminK intake have been made onthe basis of the hepatic requirementsfor the synthesis of bloodcoagulation factors.Accumulatingevidence suggests that the requirementsfor other functions thanblood coagulation may be higher.This paper is the result of a closedworkshop (Paris,November 2002)in which a number of Europeanvitamin K experts reviewed theavailable data and formulated theirstandpoint with respect to recommendeddietary vitamin K intakeand the use of vitamin K-containingsupplements
High-speed, multi-colour optical photometry of the anomalous X-ray pulsar 4U 0142+61 with ULTRACAM
We present high-speed, multi-colour optical photometry of the anomalous X-ray
pulsar 4U 0142+61, obtained with ULTRACAM on the 4.2-m William Herschel
Telescope. We detect 4U 0142+61 at magnitudes of i'=23.7+-0.1, g'=27.2+-0.2 and
u'>25.8, consistent with the magnitudes found by Hulleman et al.(2004) and
hence confirming their discovery of both a spectral break in the optical and a
lack of long-term optical variability. We also confirm the discovery of Kern &
Martin (2002) that 4U 0142+61 shows optical pulsations with an identical period
(~8.7 s) to the X-ray pulsations. The rms pulsed fraction in our data is
29+-8%, 5-7 times greater than the 0.2-8 keV X-ray rms pulsed fraction. The
optical and X-ray pulse profiles show similar morphologies and appear to be
approximately in phase with each other, the former lagging the latter by only
0.04+-0.02 cycles. In conjunction with the constraints imposed by X-ray
observations, the results presented here favour a magnetar interpretation for
the anomalous X-ray pulsars.Comment: 6 pages, 4 figures, accepted for publication in MNRA
Unpulsed UBV Optical Emission from the Crab Pulsar
Based on observations of the Crab pulsar using the TRIFFID high speed imaging
photometer in the UBV bands using the Special Astrophysical Observatory's 6m
telescope in the Russian Caucasus, we report the detection of pronounced
emission during the so-called `off' phase of emission. Following de-extinction,
this unpulsed component of emission is shown to be consistent with a power law
with an exponent of alpha = -0.60 +/- 0.37, the uncertainty being dominated by
the error associated with the independent CCD photometry used to reference the
TRIFFID data. This suggests a steeper power law form than that reported
elsewhere in the literature for the total integrated spectrum, which is
essentially flat with alpha ~ 0.1, although the difference in this case is only
significant at the ~ 2 sigma level. Deeper reference integrated and TRIFFID
phase-resolved photometry in these bands in conjunction with further
observations in the UV and R region would constrain this fit further.Comment: 26 pages, 2 figures, uses aasms4.sty, accepted for publication in the
Astrophysical Journa
A refined ephemeris and phase resolved X-ray spectroscopy of the Geminga pulsar
We present a refined phase-connected post-glitch ephemeris for the Geminga
pulsar that is a good fit to all the post-glitch data from EGRET, ASCA, and
XMM. We also present the results of phase-resolved spectroscopy of two XMM
X-ray observations of the Geminga pulsar obtained in 2002 and 2004. An
investigation is made into a previously claimed existence of a small hot spot
on the neutron star surface. We conclude that that interpretation was more
likely an artifact of an overly restrictive assumption used to fit the
phase-resolved spectra, namely, that the spectral index of the non-thermal
component is constant. When we allow the spectral index to vary as a function
of rotation phase, we find systematic variations in spectral index, and such
fits do not require an additional, hot blackbody component.Comment: 11 pages, 11 figures To be published in Ap.J. v633 no.
Observations of three young gamma-ray pulsars with the Gran Telescopio Canarias
We report the analysis of the first deep optical observations of three
isolated -ray pulsars detected by the {\em Fermi Gamma-ray Space
Telescope}: the radio-loud PSR\, J0248+6021 and PSR\, J0631+1036, and the
radio-quiet PSR\, J0633+0632. The latter has also been detected in the X rays.
The pulsars are very similar in their spin-down age (40--60 kyrs),
spin-down energy ( erg s), and dipolar surface
magnetic field (-- G). These pulsars are promising
targets for multi-wavelength observations, since they have been already
detected in rays and in radio or X-rays. None of them has been
detected yet in the optical band. We observed the three pulsar fields in 2014
with the Spanish 10.4m Gran Telescopio Canarias (GTC). We could not find any
candidate optical counterpart to the three pulsars close to their most recent
radio or {\em Chandra} positions down to limits of ,
, for PSR\, J0248+6021, J0631+1036, and J0633+0632,
respectively. From the inferred optical upper limits and estimated distance and
interstellar extinction, we derived limits on the pulsar optical luminosity. We
also searched for the X-ray counterpart to PSR\, J0248+6021 with \chan\ but we
did not detect the pulsar down to a 3 flux limit of
erg cm s (0.3--10 keV). For all these pulsars, we compared the
optical flux upper limits with the extrapolations in the optical domain of the
-ray spectra and compared their multi-wavelength properties with those
of other -ray pulsars of comparable age.Comment: 12 pages, 5 figures, accepted for publication in MNRA
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