19,962 research outputs found
AirCode: Unobtrusive Physical Tags for Digital Fabrication
We present AirCode, a technique that allows the user to tag physically
fabricated objects with given information. An AirCode tag consists of a group
of carefully designed air pockets placed beneath the object surface. These air
pockets are easily produced during the fabrication process of the object,
without any additional material or postprocessing. Meanwhile, the air pockets
affect only the scattering light transport under the surface, and thus are hard
to notice to our naked eyes. But, by using a computational imaging method, the
tags become detectable. We present a tool that automates the design of air
pockets for the user to encode information. AirCode system also allows the user
to retrieve the information from captured images via a robust decoding
algorithm. We demonstrate our tagging technique with applications for metadata
embedding, robotic grasping, as well as conveying object affordances.Comment: ACM UIST 2017 Technical Paper
Ubic: Bridging the gap between digital cryptography and the physical world
Advances in computing technology increasingly blur the boundary between the
digital domain and the physical world. Although the research community has
developed a large number of cryptographic primitives and has demonstrated their
usability in all-digital communication, many of them have not yet made their
way into the real world due to usability aspects. We aim to make another step
towards a tighter integration of digital cryptography into real world
interactions. We describe Ubic, a framework that allows users to bridge the gap
between digital cryptography and the physical world. Ubic relies on
head-mounted displays, like Google Glass, resource-friendly computer vision
techniques as well as mathematically sound cryptographic primitives to provide
users with better security and privacy guarantees. The framework covers key
cryptographic primitives, such as secure identification, document verification
using a novel secure physical document format, as well as content hiding. To
make a contribution of practical value, we focused on making Ubic as simple,
easily deployable, and user friendly as possible.Comment: In ESORICS 2014, volume 8712 of Lecture Notes in Computer Science,
pp. 56-75, Wroclaw, Poland, September 7-11, 2014. Springer, Berlin, German
Phase ambiguity resolution for offset QPSK modulation systems
A demodulator for Offset Quaternary Phase Shift Keyed (OQPSK) signals modulated with two words resolves eight possible combinations of phase ambiguity which may produce data error by first processing received I(sub R) and Q(sub R) data in an integrated carrier loop/symbol synchronizer using a digital Costas loop with matched filters for correcting four of eight possible phase lock errors, and then the remaining four using a phase ambiguity resolver which detects the words to not only reverse the received I(sub R) and Q(sub R) data channels, but to also invert (complement) the I(sub R) and/or Q(sub R) data, or to at least complement the I(sub R) and Q(sub R) data for systems using nontransparent codes that do not have rotation direction ambiguity
HST observations of the limb polarization of Titan
Titan is an excellent test case for detailed studies of the scattering
polarization from thick hazy atmospheres. We present the first limb
polarization measurements of Titan, which are compared as a test to our limb
polarization models. Previously unpublished imaging polarimetry from the HST
archive is presented which resolves the disk of Titan. We determine
flux-weighted averages of the limb polarization and radial limb polarization
profiles, and investigate the degradation and cancelation effects in the
polarization signal due to the limited spatial resolution of our observations.
Taking this into account we derive corrected values for the limb polarization
in Titan. The results are compared with limb polarization models, using
atmosphere and haze scattering parameters from the literature.
In the wavelength bands between 250 nm and 2000 nm a strong limb polarization
of about 2-7 % is detected with a position angle perpendicular to the limb. The
fractional polarization is highest around 1 micron. As a first approximation,
the polarization seems to be equally strong along the entire limb. The detected
polarization is compatible with expectations from previous polarimetric
observations taken with Voyager 2, Pioneer 11, and the Huygens probe.
Our results indicate that ground-based monitoring measurements of the
limb-polarization of Titan could be useful for investigating local haze
properties and the impact of short-term and seasonal variations of the hazy
atmosphere of Titan. Planets with hazy atmospheres similar to Titan are
particularly good candidates for detection with the polarimetric mode of the
upcoming planet finder instrument at the VLT. Therefore, a good knowledge of
the polarization properties of Titan is also important for the search and
investigation of extra-solar planets.Comment: 13 pages, 13 figures, accepted for publication in Astronomy &
Astrophysic
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