Advances in Blind Source Separation

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Tracking algorithms for multistatic sonar systems

Abstract Activated reconnaissance systems based on target illumination are of high importance for surveillance tasks where targets are nonemitting. Multistatic configurations, where multiple illuminators and multiple receivers are located separately, are of particular interest. The fusion of measurements is a prerequisite for extracting and maintaining target tracks. The inherent ambiguity of the data makes the use of adequate algorithms, such as multiple hypothesis tracking, inevitable. For their design, the understanding of the residual clutter, the sensor resolution and the characteristic impact of the propagation medium is important. This leads to precise sensor models, which are able to determine the performance of the surveillance team. Incorporating these models in multihypothesis tracking leads to a situationally aware data fusion and tracking algorithm. Various implementations of this algorithm are evaluated with the help of simulated and measured data sets. Incorporating model knowledge leads to increased performance, but only if the model is in line with the physical reality: we need to find a compromise between refined and robust tracking models. Furthermore, to implement the model, which is inherently nonlinear for multistatic sonar, approximations have to be made. When engineering the multistatic tracking system, sensitivity studies help to tune model assumptions and approximations

Distributed Mobile Sensor Networks for Hazardous Applications

1Research Department for Underwater Acoustics and Marine Geophysics, Bundeswehr Technical Centre for Ships and Naval Weapons, Naval Technology and Research (WTD 71), Klausdorfer Weg 2, 24148 Kiel, Germany 2Navy Center for Applied Research in Artificial Intelligence, Naval Research Laboratory, 4555 Overlook Avenue S.W., Washington, DC 20375, USA 3Acoustic Research Laboratory, National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077 4 Systems Technology Department, NATO Undersea Research Centre (NURC), Viale S. Bartolomeo 400, 19126 La Spezia, Ital

Advances in Signal Processing for Maritime Applications

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Genome Resources for Climate‐Resilient Cowpea, an Essential Crop for Food Security

Cowpea (Vigna unguiculata L. Walp.) is a legume crop that is resilient to hot and drought‐prone climates, and a primary source of protein in sub‐Saharan Africa and other parts of the developing world. However, genome resources for cowpea have lagged behind most other major crops. Here we describe foundational genome resources and their application to the analysis of germplasm currently in use in West African breeding programs. Resources developed from the African cultivar IT97K‐499‐35 include a whole‐genome shotgun (WGS) assembly, a bacterial artificial chromosome (BAC) physical map, and assembled sequences from 4355 BACs. These resources and WGS sequences of an additional 36 diverse cowpea accessions supported the development of a genotyping assay for 51 128 SNPs, which was then applied to five bi‐parental RIL populations to produce a consensus genetic map containing 37 372 SNPs. This genetic map enabled the anchoring of 100 Mb of WGS and 420 Mb of BAC sequences, an exploration of genetic diversity along each linkage group, and clarification of macrosynteny between cowpea and common bean. The SNP assay enabled a diversity analysis of materials from West African breeding programs. Two major subpopulations exist within those materials, one of which has significant parentage from South and East Africa and more diversity. There are genomic regions of high differentiation between subpopulations, one of which coincides with a cluster of nodulin genes. The new resources and knowledge help to define goals and accelerate the breeding of improved varieties to address food security issues related to limited‐input small‐holder farming and climate stress

Relevance of field observations as boundary conditions for understanding ice-sheet-ocean interactions

The direct contact of warm ocean water with the front and base of ice shelves is the main driver for accelerated mass loss of the Antarctic ice sheet. We present a compilation of observations from various projects and methodological approaches applied over the last decade along the Dronning Maud Land coast and highlight their importance for understanding the ice-ocean interactions. With a focus on the Ekström ice shelf, these include spatially continuous seismic observations in combination with airborne gravity inversion to yield sub-shelf bathymetry and geomorphological evidence of past ice-flow activity; ice-dynamic numerical modelling to investigate the role of seafloor/subglacial substrate characteristics to enhance or reduce ice-sheet extent and advance/retreat rates; sub-shelf CTD measurements to determine ocean properties driving basal melting; satellitebased remote sensing to determine ice-shelf height changes and spatially-distributed basal melting; and point measurements of basal melt with surface-based phase-sensitive radar to determine ocean-driven melt and validate remote-sensing products. As the Dronning Maud Land coast plays a critical role in preconditioning the water mass of the coastal current before it enters the Filcher ice-shelf cavity, we argue that a coordinated inter- and transdisciplinary observational network is required to facilitate monitoring a potential ice-sheet mass loss in this part of Antarctica

Neuroanatomical substrates for the volitional regulation of heart rate

The control of physiological arousal can assist in the regulation of emotional state. A subset cortical and subcortical brain regions are implicated in autonomic control of bodily arousal during emotional behaviors. Here, we combined human functional neuroimaging with autonomic monitoring to identify neural mechanisms that support the volitional regulation of heart rate, a process that may be assisted by visual feedback. During functional magnetic resonance imaging (fMRI), 15 healthy adults performed an experimental task in which they were prompted voluntarily to increase or decrease cardiovascular arousal (heart rate) during true, false, or absent visual feedback. Participants achieved appropriate changes in heart rate, without significant modulation of respiratory rate, and were overall not influenced by the presence of visual feedback. Increased activity in right amygdala, striatum and brainstem occurred when participants attempted to increase heart rate. In contrast, activation of ventrolateral prefrontal and parietal cortices occurred when attempting to decrease heart rate. Biofeedback enhanced activity within occipito-temporal cortices, but there was no significant interaction with task conditions. Activity in regions including pregenual anterior cingulate and ventral striatum reflected the magnitude of successful task performance, which was negatively related to subclinical anxiety symptoms. Measured changes in respiration correlated with posterior insula activation and heart rate, at a more lenient threshold, change correlated with insula, caudate, and midbrain activity. Our findings highlight a set of brain regions, notably ventrolateral prefrontal cortex, supporting volitional control of cardiovascular arousal. These data are relevant to understanding neural substrates supporting interaction between intentional and interoceptive states related to anxiety, with implications for biofeedback interventions, e.g., real-time fMRI, that target emotional regulation

Inferring ocean melting of Antarctic ice shelves from their radar stratigraphy

The floating ice shelves surrounding the Antarctic Ice Sheet are the interface for interactions between ice and ocean. A plethora of previous studies has highlighted the role of ice shelves for stabilizing ice sheets. Quantification of melting at the ice-shelf base is imperative for quantifying ice-shelf stability, and also to test the coupling of upcoming ice-ocean models. Today, the basal mass balance is either inferred from mass conservation or measured using phase-sensitive radars. The former has good spatial coverage, but low spatial and virtually no temporal resolution. The latter is highly resolved in time, but with limited spatial coverage. Here we investigate a third approach exploiting the geometry of observed radar isochrones (dips, synclines, anticlines) which is a function of both ice deformation and the atmospheric/oceanographic history. By comparing isochrones with modeled age fields we can disentangle the different mechanisms and unravel the melt history. We solve the age equation on highly resolved ice-shelf geometries, and derive the required 3D velocities from surface velocities using a plug-flow approximation (and a first-order guess of basal melting from mass conservation). Validation with a full Stokes model shows that the plug-flow assumption holds well seawards of the grounding zone. We compile the radar isochrones for two Antarctic ice shelves from ground-based (i.e. Roi Baudouin Ice Self) and airborne (i.e. Ekstömisen) profiles. Our compilation includes ice-shelf channels, and we find a number of features in the isochrones geometry that indicate strong localized melting, but also anomalous snow accumulation in corresponding surface depressions. We can distinguish between both mechanisms using ourage model. This study shows the potential of using radar isochrones as a unique archive for ice-ocean interactions,and serves as a precursor for setting up the full inverse problem, allowing to infer the currently unknown oceanmelt history on decadal-centennial time scales