78 research outputs found
Neural Network-Based DOA Estimation in the Presence of Non-Gaussian Interference
This work addresses the problem of direction-of-arrival (DOA) estimation in
the presence of non-Gaussian, heavy-tailed, and spatially-colored interference.
Conventionally, the interference is considered to be Gaussian-distributed and
spatially white. However, in practice, this assumption is not guaranteed, which
results in degraded DOA estimation performance. Maximum likelihood DOA
estimation in the presence of non-Gaussian and spatially colored interference
is computationally complex and not practical. Therefore, this work proposes a
neural network (NN) based DOA estimation approach for spatial spectrum
estimation in multi-source scenarios with a-priori unknown number of sources in
the presence of non-Gaussian spatially-colored interference. The proposed
approach utilizes a single NN instance for simultaneous source enumeration and
DOA estimation. It is shown via simulations that the proposed approach
significantly outperforms conventional and NN-based approaches in terms of
probability of resolution, estimation accuracy, and source enumeration accuracy
in conditions of low SIR, small sample support, and when the angular separation
between the source DOAs and the spatially-colored interference is small.Comment: Submitted to IEEE Transactions on Aerospace and Electronic System
Neural Network-Based Multi-Target Detection within Correlated Heavy-Tailed Clutter
This work addresses the problem of range-Doppler multiple target detection in
a radar system in the presence of slow-time correlated and heavy-tailed
distributed clutter. Conventional target detection algorithms assume
Gaussian-distributed clutter, but their performance is significantly degraded
in the presence of correlated heavy-tailed distributed clutter. Derivation of
optimal detection algorithms with heavy-tailed distributed clutter is
analytically intractable. Furthermore, the clutter distribution is frequently
unknown. This work proposes a deep learning-based approach for multiple target
detection in the range-Doppler domain. The proposed approach is based on a
unified NN model to process the time-domain radar signal for a variety of
signal-to-clutter-plus-noise ratios (SCNRs) and clutter distributions,
simplifying the detector architecture and the neural network training
procedure. The performance of the proposed approach is evaluated in various
experiments using recorded radar echoes, and via simulations, it is shown that
the proposed method outperforms the conventional cell-averaging constant
false-alarm rate (CA-CFAR), the ordered-statistic CFAR (OS-CFAR), and the
adaptive normalized matched-filter (ANMF) detectors in terms of probability of
detection in the majority of tested SCNRs and clutter scenarios.Comment: Accepted to IEEE Transactions on Aerospace and Electronic System
Elevated Uptake of Plasma Macromolecules by Regions of Arterial Wall Predisposed to Plaque Instability in a Mouse Model
Atherosclerosis may be triggered by an elevated net transport of lipid-carrying
macromolecules from plasma into the arterial wall. We hypothesised that whether
lesions are of the thin-cap fibroatheroma (TCFA) type or are less fatty and more
fibrous depends on the degree of elevation of transport, with greater uptake leading
to the former. We further hypothesised that the degree of elevation can depend on
haemodynamic wall shear stress characteristics and nitric oxide synthesis. Placing
a tapered cuff around the carotid artery of apolipoprotein E -/- mice modifies
patterns of shear stress and eNOS expression, and triggers lesion development at
the upstream and downstream cuff margins; upstream but not downstream lesions
resemble the TCFA. We measured wall uptake of a macromolecular tracer in the
carotid artery of C57bl/6 mice after cuff placement. Uptake was elevated in the
regions that develop lesions in hyperlipidaemic mice and was significantly more
elevated where plaques of the TCFA type develop. Computational simulations and
effects of reversing the cuff orientation indicated a role for solid as well as fluid
mechanical stresses. Inhibiting NO synthesis abolished the difference in uptake
between the upstream and downstream sites. The data support the hypothesis that
excessively elevated wall uptake of plasma macromolecules initiates the
development of the TCFA, suggest that such uptake can result from solid and fluid
mechanical stresses, and are consistent with a role for NO synthesis. Modification
of wall transport properties might form the basis of novel methods for reducing
plaque rupture
Student apathy for classroom learning and need of repositioning in present andragogy in Indian dental schools
Saliency maps for finding changes in visual scenes?
Sudden changes in the environment reliably summon attention. This rapid change detection appears to operate in a similar fashion as pop-out in visual search, the phenomenon that very salient stimuli are directly attended, independently of the number of distracting objects. Pop-out is usually explained by the workings of saliency maps, i.e., map-like representations that code for the conspicuity at each location of the visual field. While past research emphasized similarities between pop-out search and change detection, our study highlights differences between the saliency computations in the two tasks: in contrast to pop-out search, saliency computation in change detection (i) operates independently across different stimulus properties (e.g., color and orientation), and (ii) is little influenced by trial history. These deviations from pop-out search are not due to idiosyncrasies of the stimuli or task design, as evidenced by a replication of standard findings in a comparable visual-search design. To explain these results, we outline a model of change detection involving the computation of feature-difference maps, which explains the known similarities and differences with visual search
Positive contrast high-resolution 3D-cine imaging of the cardiovascular system in small animals using a UTE sequence and iron nanoparticles at 4.7, 7 and 9.4Â T
It Pays to Modify Existing Crude Preheat Trains to Conserve More Energy!
With the cost of fuel now being so high, maximum recovery of available waste heat to preheat crude oil is an essential step in reducing the fuel consumption in a refinery. Foster Wheeler Energy Corporation has developed a special computer program called EXTRA (EXchanger TRAin) which can be used to determine which modifications to an existing crude preheat train will be most effective in economically recovering additional waste heat. The program can rigorously develop temperature profiles and heat exchanger duties in any existing, new or modified crude preheat train. Rating of existing exchangers, design of new exchangers and total capital and utility costs for new equipment is also provided.
The program allows the user to specify any type of configuration that he may want to explore. The resulting cost and other information developed by the program can then be used to find the exchanger train network which will provide the maximum crude preheat for any specified economic criterion on new capital investment. A detailed case study is shown in which EXTRA is used to modify an existing crude preheat train
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