99,865 research outputs found
A massively parallel multi-level approach to a domain decomposition method for the optical flow estimation with varying illumination
We consider a variational method to solve the optical flow problem with
varying illumination. We apply an adaptive control of the regularization
parameter which allows us to preserve the edges and fine features of the
computed flow. To reduce the complexity of the estimation for high resolution
images and the time of computations, we implement a multi-level parallel
approach based on the domain decomposition with the Schwarz overlapping method.
The second level of parallelism uses the massively parallel solver MUMPS. We
perform some numerical simulations to show the efficiency of our approach and
to validate it on classical and real-world image sequences
Implementation of a color-capable optofluidic microscope on a RGB CMOS color sensor chip substrate
We report the implementation of a color-capable on-chip lensless microscope system, termed color optofluidic microscope (color OFM), and demonstrate imaging of double stained Caenorhabditis elegans with lacZ gene expression at a light intensity about 10 mW/cm^2
Frequency division multiplexing for interferometric planar Doppler velocimetry
A new method of acquiring simultaneously the signal and reference channels used for interferometric
planar Doppler velocimetry is proposed and demonstrated. The technique uses frequency division multiplexing
(FDM) to facilitate the capture of the requisite images on a single camera, and is suitable for
time-averaged flow measurements. Furthermore, the approach has the potential to be expanded to allow
the multiplexing of additional measurement channels for multicomponent velocity measurement. The
use of FDM for interferometric referencing is demonstrated experimentally with measurements
of a single velocity component of a seeded axisymmetric air jet. The expansion of the technique to
include multiple velocity components was then investigated theoretically and experimentally to
account for bandwidth, crosstalk, and dynamic range limitations. The technique offers reduced
camera noise, automatic background light suppression, and crosstalk levels of typically <10%.
Furthermore, as this crosstalk is dependent upon the channel modulations applied, it can be corrected for in postprocessing
Preferential concentration of inertial sub-kolmogorov particles. The roles of mass loading of particles, Stokes and Reynolds numbers
Turbulent flows laden with inertial particles present multiple open questions
and are a subject of great interest in current research. Due to their higher
density compared to the carrier fluid, inertial particles tend to form high
concentration regions, i.e. clusters, and low concentration regions, i.e.
voids, due to the interaction with the turbulence. In this work, we present an
experimental investigation of the clustering phenomenon of heavy sub-Kolmogorov
particles in homogeneous isotropic turbulent flows. Three control parameters
have been varied over significant ranges: ,
and volume fraction . The scaling of clustering characteristics, such as the distribution
of Vorono\"i areas and the dimensions of cluster and void regions, with the
three parameters are discussed. In particular, for the polydispersed size
distributions considered here, clustering is found to be enhanced strongly
(quasi-linearly) by and noticeably (with a square-root
dependency) with , while the cluster and void sizes, scaled with the
Kolmogorov lengthscale , are driven primarily by . Cluster
length scales up to , measured
at the highest , while void length
scaled also with is typically two times larger ().
The lack of sensitivity of the above characteristics to the Stokes number lends
support to the "sweep-stick" particle accumulation scenario. The non-negligible
influence of the volume fraction, however, is not considered by that model and
can be connected with collective effects
Heterojunction Hybrid Devices from Vapor Phase Grown MoS
We investigate a vertically-stacked hybrid photodiode consisting of a thin
n-type molybdenum disulfide (MoS) layer transferred onto p-type silicon.
The fabrication is scalable as the MoS is grown by a controlled and
tunable vapor phase sulfurization process. The obtained large-scale p-n
heterojunction diodes exhibit notable photoconductivity which can be tuned by
modifying the thickness of the MoS layer. The diodes have a broad
spectral response due to direct and indirect band transitions of the nanoscale
MoS. Further, we observe a blue-shift of the spectral response into the
visible range. The results are a significant step towards scalable fabrication
of vertical devices from two-dimensional materials and constitute a new
paradigm for materials engineering.Comment: 23 pages with 4 figures. This article has been published in
Scientific Reports. (26 June 2014, doi:10.1038/srep05458
Motion picture camera for optical pyrometry Patent
Filter arrangement for controlling light intensity in motion picture camera used in optical pyrometr
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