88,190 research outputs found
Traffic monitoring using image processing : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Information and Telecommunications Engineering at Massey University, Palmerston North, New Zealand
Traffic monitoring involves the collection of data describing the characteristics of vehicles and their movements. Such data may be used for automatic tolls, congestion and incident detection, law enforcement, and road capacity planning etc. With the recent advances in Computer Vision technology, videos can be analysed automatically and relevant information can be extracted for particular applications. Automatic surveillance using video cameras with image processing technique is becoming a powerful and useful technology for traffic monitoring. In this research project, a video image processing system that has the potential to be developed for real-time application is developed for traffic monitoring including vehicle tracking, counting, and classification. A heuristic approach is applied in developing this system. The system is divided into several parts, and several different functional components have been built and tested using some traffic video sequences. Evaluations are carried out to show that this system is robust and can be developed towards real-time applications
Modelling polarized light from dust shells surrounding asymptotic giant branch stars
Winds of asymptotic giant branch (AGB) stars are commonly assumed to be
driven by radiative acceleration of dust grains. For M-type AGB stars, the
nature of the wind-driving dust species has been a matter of intense debate. A
proposed source of the radiation pressure triggering the outflows is photon
scattering on Fe-free silicate grains. This wind-driving mechanism requires
grain radii of about 0.1 - 1 micron in order to make the dust particles
efficient at scattering radiation around the stellar flux maximum. Grain size
is therefore an important parameter for understanding the physics behind the
winds of M-type AGB stars. We seek to investigate the diagnostic potential of
scattered polarized light for determining dust grain sizes. We have developed a
new tool for computing synthetic images of scattered light in dust and gas
shells around AGB stars, which can be applied to detailed models of dynamical
atmospheres and dust-driven winds. We present maps of polarized light using
dynamical models computed with the DARWIN code. The synthetic images clearly
show that the intensity of the polarized light, the position of the inner edge
of the dust shell, and the size of the dust grains near the inner edge are all
changing with the luminosity phase. Non-spherical structures in the dust shells
can also have an impact on the polarized light. We simulate this effect by
combining different pulsation phases into a single 3D structure before
computing synthetic images. An asymmetry of the circumstellar envelope can
create a net polarization, which can be used as diagnostics for the grain size.
The ratio between the size of the scattering particles and the observed
wavelength determines at what wavelengths net polarization switches direction.
If observed, this can be used to constrain average particle sizes.Comment: 9 page
A single-chip FPGA implementation of real-time adaptive background model
This paper demonstrates the use of a single-chip
FPGA for the extraction of highly accurate background
models in real-time. The models are based
on 24-bit RGB values and 8-bit grayscale intensity
values. Three background models are presented, all
using a camcorder, single FPGA chip, four blocks
of RAM and a display unit. The architectures have
been implemented and tested using a Panasonic NVDS60B
digital video camera connected to a Celoxica
RC300 Prototyping Platform with a Xilinx Virtex
II XC2v6000 FPGA and 4 banks of onboard RAM.
The novel FPGA architecture presented has the advantages
of minimizing latency and the movement of
large datasets, by conducting time critical processes
on BlockRAM. The systems operate at clock rates
ranging from 57MHz to 65MHz and are capable
of performing pre-processing functions like temporal
low-pass filtering on standard frame size of 640X480
pixels at up to 210 frames per second
Visual task identification and characterisation using polynomial models
Developing robust and reliable control code for autonomous mobile robots is difficult, because the interaction between a physical robot and the environment is highly complex, subject to noise and variation, and therefore partly unpredictable. This means that to date it is not possible to predict robot behaviour based on theoretical models. Instead, current methods to develop robot control
code still require a substantial trial-and-error component to the software design process. This paper proposes a method of dealing with these issues by a) establishing task-achieving sensor-motor couplings through robot training, and b) representing these couplings through transparent mathematical functions that can be used to form hypotheses
and theoretical analyses of robot behaviour. We demonstrate the viability of this approach by teaching a mobile robot to track a moving football and subsequently modelling
this task using the NARMAX system identification technique
CVABS: Moving Object Segmentation with Common Vector Approach for Videos
Background modelling is a fundamental step for several real-time computer
vision applications that requires security systems and monitoring. An accurate
background model helps detecting activity of moving objects in the video. In
this work, we have developed a new subspace based background modelling
algorithm using the concept of Common Vector Approach with Gram-Schmidt
orthogonalization. Once the background model that involves the common
characteristic of different views corresponding to the same scene is acquired,
a smart foreground detection and background updating procedure is applied based
on dynamic control parameters. A variety of experiments is conducted on
different problem types related to dynamic backgrounds. Several types of
metrics are utilized as objective measures and the obtained visual results are
judged subjectively. It was observed that the proposed method stands
successfully for all problem types reported on CDNet2014 dataset by updating
the background frames with a self-learning feedback mechanism.Comment: 12 Pages, 4 Figures, 1 Tabl
Visual Importance-Biased Image Synthesis Animation
Present ray tracing algorithms are computationally intensive, requiring hours of computing time for complex scenes. Our previous work has dealt with the development of an overall approach to the application of visual attention to progressive and adaptive ray-tracing techniques. The approach facilitates large computational savings by modulating the supersampling rates in an image by the visual importance of the region being rendered. This paper extends the approach by incorporating temporal changes into the models and techniques developed, as it is expected that further efficiency savings can be reaped for animated scenes. Applications for this approach include entertainment, visualisation and simulation
A sharp-front moving boundary model for malignant invasion
We analyse a novel mathematical model of malignant invasion which takes the
form of a two-phase moving boundary problem describing the invasion of a
population of malignant cells into a population of background tissue, such as
skin. Cells in both populations undergo diffusive migration and logistic
proliferation. The interface between the two populations moves according to a
two-phase Stefan condition. Unlike many reaction-diffusion models of malignant
invasion, the moving boundary model explicitly describes the motion of the
sharp front between the cancer and surrounding tissues without needing to
introduce degenerate nonlinear diffusion. Numerical simulations suggest the
model gives rise to very interesting travelling wave solutions that move with
speed , and the model supports both malignant invasion and malignant
retreat, where the travelling wave can move in either the positive or negative
-directions. Unlike the well-studied Fisher-Kolmogorov and Porous-Fisher
models where travelling waves move with a minimum wave speed ,
the moving boundary model leads to travelling wave solutions with . We interpret these travelling wave solutions in the phase plane and
show that they are associated with several features of the classical
Fisher-Kolmogorov phase plane that are often disregarded as being nonphysical.
We show, numerically, that the phase plane analysis compares well with long
time solutions from the full partial differential equation model as well as
providing accurate perturbation approximations for the shape of the travelling
waves.Comment: 48 pages, 21 figure
Starspots on the fastest rotators in the Beta Pic moving group
Aims: We carried out high-resolution spectroscopy and BV(I)_C photometric
monitoring of the two fastest late-type rotators in the nearby Beta Pictoris
moving group, HD199143 (F7V) and CD-641208 (K7V). The motivation for this work
is to investigate the rotation periods and photospheric spot patterns of these
very young stars, with a longer term view to probing the evolution of rotation
and magnetic activity during the early phases of main-sequence evolution. We
also aim to derive information on key physical parameters, such as rotational
velocity and rotation period. Methods: We applied maximum entropy (ME) and
Tikhonov regularizing (TR) criteria to derive the surface spot map
distributions of the optical modulation observed in HD199143 (F7 V) and
CD-641208 (K7V). We also used cross-correlation techniques to determine stellar
parameters such as radial velocities and rotational velocities. Lomb-Scargle
periodograms were used to obtain the rotational periods from differential
magnitude time series. Results: We find periods and inclinations of 0.356 days
and 21.5deg for HD199143, and 0.355 days and 50.1deg for CD-641208. The spot
maps of HD199143 obtained from the ME and TR methods are very similar, although
the latter gives a smoother distribution of the filling factor. Maps obtained
at two different epochs three weeks apart show a remarkable increase in spot
coverage amounting to ~7% of the surface of the photosphere over a time period
of only ~20 days. The spot maps of CD-641208 from the two methods show good
longitudinal agreement, whereas the latitude range of the spots is extended to
cover the whole visible hemisphere in the TR map. The distributions obtained
from the first light curve of HD199143 show the presence of an extended and
asymmetric active longitude with the maximum filling factor at longitude
~325degree.Comment: Accepted by A&A. 13 pages, 13 figures (4 online included), 5 Table
Airborne photogrammetry and LIDAR for DSM extraction and 3D change detection over an urban area : a comparative study
A digital surface model (DSM) extracted from stereoscopic aerial images, acquired in March 2000, is compared with a DSM derived from airborne light detection and ranging (lidar) data collected in July 2009. Three densely built-up study areas in the city centre of Ghent, Belgium, are selected, each covering approximately 0.4 km(2). The surface models, generated from the two different 3D acquisition methods, are compared qualitatively and quantitatively as to what extent they are suitable in modelling an urban environment, in particular for the 3D reconstruction of buildings. Then the data sets, which are acquired at two different epochs t(1) and t(2), are investigated as to what extent 3D (building) changes can be detected and modelled over the time interval. A difference model, generated by pixel-wise subtracting of both DSMs, indicates changes in elevation. Filters are proposed to differentiate 'real' building changes from false alarms provoked by model noise, outliers, vegetation, etc. A final 3D building change model maps all destructed and newly constructed buildings within the time interval t(2) - t(1). Based on the change model, the surface and volume of the building changes can be quantified
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