423 research outputs found
Radio Communications
In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks
Morphodynamics, sedimentation and sediment dynamics of a gravel beach
The morphodyiiamics of a gravel barrier beadi in Devon, \JK (Slaptou Sands: tau/S 0.15 - 0.25,
D50 2 - 8min), was studied with reference to its sedimentology. Three time scales were sampled for
nearshore hydrodynamics, intertidal morphologies and sediirientologies. A series of surveys were
carried out over individual tidal cycles (samphng every 5 - lOmins for between 6 and 91irs); on
•consecutive low tides over half-lunar tidal cycles (1 -2 cross-shore profiles-sampled every 0.5 - Ini,
on 2 spring - spring tidal cycles comprising 26 and 24 tides, respectively); and finally eveiy 2 weeks
at spring low tide, over 1 calendar year (13-17 profile lines survej'ed and sampled for sediment over
3.25 - 4.251an).
In order to further our understanding of gravel beaches, sediment data needs to, be collected at a
resolution similar to that of the hydrodynamics. Innovative automatic sediment sizing techniques
based on digital images of sediments were therefore developed, and software written, to allow the
collection and analysis of high-resolution sediment data.
The gi-avel beach step and berm are accretionaiy features, tidally modulated, and evolve under
different time scales. A new technique to determine bed mobility from the nearshore, using
underwater ^adeo cameras, was devised. Nearsliore sediment transport was suggested as being
related to sub-incident wave frequencies.
No aspect of morphological change could be found to havea statistically significant association
with sedimentological change, but dimensional-reduction techniques did satisfactorily detect
association. The lack of co-variance and obvious patterns is stochastic noise, not
• parameterisation.
Over one year, the barrier underwent asymmetrical rotation over one year, highlighting the
importance of alongshore sediment transport processes on this supposedly 'swash aligned' beach.
A statistical model based on the log-hj'perbolic distribution of sinface particle sizes was found
to be a reasonable predictor of mean net sedimentation over individual tides. Its complicated
parameter space could possibly map'onto a simpler plane based on traditional moments. Sediment
trend vector models based on sorting alone out-performed a traditional approach. Moments of a
surface grain-size'distribution appear to be inappropriate to characterise sedimentological change
at time-scales gi-eater than a semi-diurnal tidal cycle. Sub-surface sampling on the intertidal zone
on diurnal and semi-lunar time-scales is useful in assessing the dynamics of the step, itself an
important mechanism for onshore and offshore net volumetric transport.School of Geograph
The 8th International Conference on Time Series and Forecasting
The aim of ITISE 2022 is to create a friendly environment that could lead to the establishment or strengthening of scientific collaborations and exchanges among attendees. Therefore, ITISE 2022 is soliciting high-quality original research papers (including significant works-in-progress) on any aspect time series analysis and forecasting, in order to motivating the generation and use of new knowledge, computational techniques and methods on forecasting in a wide range of fields
Beyong lexical meaning : probabilistic models for sign language recognition
Ph.DDOCTOR OF PHILOSOPH
Cognitive radar network design and applications
PhD ThesisIn recent years, several emerging technologies in modern radar system
design are attracting the attention of radar researchers and practitioners
alike, noteworthy among which are multiple-input multiple-output
(MIMO), ultra wideband (UWB) and joint communication-radar technologies.
This thesis, in particular focuses upon a cognitive approach
to design these modern radars. In the existing literature, these technologies
have been implemented on a traditional platform in which the
transmitter and receiver subsystems are discrete and do not exchange
vital radar scene information. Although such radar architectures benefit
from these mentioned technological advances, their performance remains
sub-optimal due to the lack of exchange of dynamic radar scene
information between the subsystems. Consequently, such systems are
not capable to adapt their operational parameters “on the fly”, which
is in accordance with the dynamic radar environment. This thesis explores
the research gap of evaluating cognitive mechanisms, which could
enable modern radars to adapt their operational parameters like waveform,
power and spectrum by continually learning about the radar scene
through constant interactions with the environment and exchanging this
information between the radar transmitter and receiver. The cognitive
feedback between the receiver and transmitter subsystems is the facilitator
of intelligence for this type of architecture.
In this thesis, the cognitive architecture is fused together with modern
radar systems like MIMO, UWB and joint communication-radar designs
to achieve significant performance improvement in terms of target parameter
extraction. Specifically, in the context of MIMO radar, a novel
cognitive waveform optimization approach has been developed which facilitates
enhanced target signature extraction. In terms of UWB radar
system design, a novel cognitive illumination and target tracking algorithm
for target parameter extraction in indoor scenarios has been developed.
A cognitive system architecture and waveform design algorithm
has been proposed for joint communication-radar systems. This thesis
also explores the development of cognitive dynamic systems that allows
the fusion of cognitive radar and cognitive radio paradigms for optimal
resources allocation in wireless networks. In summary, the thesis provides
a theoretical framework for implementing cognitive mechanisms in
modern radar system design. Through such a novel approach, intelligent
illumination strategies could be devised, which enable the adaptation of
radar operational modes in accordance with the target scene variations
in real time. This leads to the development of radar systems which are
better aware of their surroundings and are able to quickly adapt to the
target scene variations in real time.Newcastle University, Newcastle upon Tyne:
University of Greenwich
Deep probabilistic methods for improved radar sensor modelling and pose estimation
Radar’s ability to sense under adverse conditions and at far-range makes it a valuable alternative to vision and lidar for mobile robotic applications. However, its complex, scene-dependent sensing process and significant noise artefacts makes working with radar challenging. Moving past classical rule-based approaches, which have dominated the literature to date, this thesis investigates deep and data-driven solutions across a range of tasks in robotics.
Firstly, a deep approach is developed for mapping raw sensor measurements to a grid-map of occupancy probabilities, outperforming classical filtering approaches by a significant margin. A distribution over the occupancy state is captured, additionally allowing uncertainty in predictions to be identified and managed. The approach is trained entirely using partial labels generated automatically from lidar, without requiring manual labelling.
Next, a deep model is proposed for generating stochastic radar measurements from simulated elevation maps. The model is trained by learning the forward and backward processes side-by-side, using a combination of adversarial and cyclical consistency constraints in combination with a partial alignment loss, using labels generated in lidar. By faithfully replicating the radar sensing process, new models can be trained for down-stream tasks, using labels that are readily available in simulation. In this case, segmentation models trained on simulated radar measurements, when deployed in the real world, are shown to approach the performance of a model trained entirely on real-world measurements.
Finally, the potential of deep approaches applied to the radar odometry task are explored. A learnt feature space is combined with a classical correlative scan matching procedure and optimised for pose prediction, allowing the proposed method to outperform the previous state-of-the-art by a significant margin. Through a probabilistic consideration the uncertainty in the pose is also successfully characterised. Building upon this success, properties of the Fourier Transform are then utilised to separate the search for translation and angle. It is shown that this decoupled search results in a significant boost to run-time performance, allowing the approach to run in real-time on CPUs and embedded devices, whilst remaining competitive with other radar odometry methods proposed in the literature
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