Establishing a Multibeam Sonar Evaluation Test Bed near Sidney, British Columbia

The Canadian Hydrographic Service (CHS), Naval Oceanographic Office (NAVOCEANO) and the Ocean Mapping Group of the University of New Brunswick (OMG) collaborated on establishing a multibeam sonar test bed in the vicinity of the Institute of Ocean Sciences in Sidney, British Columbia Canada. This paper describes the purpose of the sonar evaluation test bed, the trials and tribulations of two foreign governments collaborating on projects of mutual interest, the evaluation areas and their characteristics for sonar testing, and sample results of sonar evaluations using this test bed. Some target detection comparisons of several systems over a range of artificial sonar targets will also be given

Mapping a Continental Shelf and Slope in the 1990s: A Tale of Three Multibeams

Increasing societal pressures on the U.S. continental shelves adjacent to dense population centers have brought to light the lack of accurate base maps in these areas. Existing bathymetric maps and random sidescan sonar surveys are either not accurate enough or do not provide the coverage necessary to make policy decisions. Until the mid 1990s, it was not financially prudent nor technically efficient to map the shallow shelves. However, the availability of high-resolution multibeam mapping systems now allow efficient and accurate mapping of the continental margins. In 1996 the U.S. Geological Survey began a large-scale seafloor mapping campaign on the continental shelf and slope adjacent to Los Angeles, CA. The first survey used a Kongsberg Simrad EM1000 (95 kHz). The survey continued in 1998 by mapping the slope and proximal basins from Newport to Long Beach, CA, using a Kongsberg Simrad EM300 (30 kHz). The area was completed in May 1999 by mapping the entire shelf adjacent to Long Beach, CA using an EM3000D (a dual-headed 300-kHz system). The mapping used both INS from the vehicle motion sensor and DGPS to provide position accuracies of ~1 m. All the data were processed in the field in near realtime using software developed at the Univ. of New Brunswick. Because of the different systems used and the range of water depths, the spatial resolution of the processed data varies from \u3c0.5 m on the inner shelf to 8 m on the basin floors. Perspective overviews of backscatter draped over bathymetry reveals a host of geological features unknown to exist in this area. These features include shallow, linear gullys, barchan dunes, small-scale bedforms in shallow troughs, major canyon system complexes, large- and smallscale mass movements, faults, and large areas of outcrop. The effects on sediment transport of man-made features, such as sewer outfall pipes and dredge-disposal fields, are clearly delineated on the new maps. The maps provide the fundamental base maps for studies as varied as those involving benthic habitats, marine disposal sites, sediment transport, and tectonic ma

Geometric and Radiometric Correction of Multibeam Backscatter Derived from Reson 8101 Systems

A common by-product of multibeam surveys is a measure of the backscattered acoustic intensity from the seafloor. These data are of immense interest to geologists and geoscientists since maps of the acoustic backscatter strength can be used to infer physical properties of the sea bottom, such as impedance, roughness and volume inhomogeneity. Before such maps can be created from multibeam acoustic backscatter data, however, two tasks must be performed. 1. The data must be geographically registered using the bathymetric profile collected by the multibeam (which accounts for full orientation and refraction), as opposed to using the traditional flat-seafloor assumption. This allows us to additionally calculate the true grazing angle. 2. The signal intensities must be reduced to as close a measure of the backscatter strength of the seafloor as possible by radiometrically correcting the data on a ping-by-ping basis for variables such as transmission power, beam pattern, receiver gain, and pulse length. The purpose of this research project is to develop software tools to perform the above corrections for a massive backlog of RESON SeaBat 8101 multibeam data, as collected by the NOAA ship Rainier. While the backscatter logged by the multibeam systems is not of prime importance to NOAA’s hydrographic charting mandate, they recognize the potential value of this data to the work of other sister agencies such as the U.S. Geological Survey (who is funding this project). The particular problems encountered with these data are that. Up to the end of 2001 field season, the backscatter data acquired by this system were collected from dedicated receiver beams, separate from those used for bathymetry. This receive beam is broad in the elevation plane (similar to a sidescan sonar) so that the variation in elevation angle with time must be indirectly inferred from the corresponding bathymetric profile. As some backscatter data are collected from slant-ranges beyond which bathymetric data are acquired, for that case the imaging geometry must be either inferred using a simple slope model, or derived from neighbouring swaths. Results of the application of full geometric and radiometric corrections will be presented

Welsh sculptured crosses and cross-slabs of the pre-Norman period

This thesis analyses and defines the forms and ornament of the Welsh sculptured crosses and cross-slabs of the pre-Norman period and attempts to use the data thus assembled as historical evidence for the period in which they were made. The sculptural evidence confirms the historical evidence that there was very little artistic, exchange between Wales and England and virtually no direct contact between Wales and the continent c. 750-1100, but testifies to the existence of contacts between Wales and Ireland, Scotland (particularly Strathclyde) and the Isle of Man. Sixteen Welsh monuments are found to exhibit evidence of Scandinavian influence and these help to corroborate the literary place-name evidence for Scandinavian settlement on the coasts of Dyfed, South Glamorgan and Gwynedd in the pre-Norman period; the latter apparently associated with the trade route between the Scandinavian settlements of Dublin, the Isle of Man and Chester. The material reflects the existence of a settled society and economy in Wales in the early Medieval period in which craftsmen, some of whom were itinerant, others apparently associated with religious establishments, were patronised by kings and affluent laymen and churchmen whose wealth was in land. The distribution of the monuments demonstrates areas of contemporary settlement and the lines of communication between them and certain groups of monuments imply the existence of otherwise undocumented religious establishments. Although generally associated with religious sites, groups of monuments were not confined to the monastic aggregations but they were confined to the bounds of the known historic kingdoms. The Welsh sculptured crosses and cross-slabs were intimately associated with both the royal/aristocratic and ecclesiastical elements in society. Their production ceased when patronage was not continued by the new Norman landowners and churchmen

Intuitive programming with remotely instructed robots inside future gloveboxes

Our research aims at facilitating the design of ’Remotely Instructed Robots’ for future glove-boxes in the nuclear industry. The two main features of such systems are: (1) They can automatically model the working environment and relay that information to the operator in virtual reality (VR). (2) They can receive instructions from the operator that are executed by the robot. However, the deficiency of these kind of systems is that they heavily rely on knowledge of expert programmers when the robot’s capabilities or hardware are to be reconfigured, altered or upgraded. This late breaking report proposes to introduce a third important advancement on remotely instructed robots: (3) Intuitive programming modifications by operators who are non-programmers but have basic knowledge of hardware, and most importantly, have experience of the weaknesses in particular handling tasks

Preconditioning and triggering of offshore slope failures and turbidity currents revealed by most detailed monitoring yet at a fjord-head delta

Rivers and turbidity currents are the two most important sediment transport processes by volume on Earth. Various hypotheses have been proposed for triggering of turbidity currents offshore from river mouths, including direct plunging of river discharge, delta mouth bar flushing or slope failure caused by low tides and gas expansion, earthquakes and rapid sedimentation. During 2011, 106 turbidity currents were monitored at Squamish Delta, British Columbia. This enables statistical analysis of timing, frequency and triggers. The largest peaks in river discharge did not create hyperpycnal flows. Instead, delayed delta-lip failures occurred 8–11 h after flood peaks, due to cumulative delta top sedimentation and tidally-induced pore pressure changes. Elevated river discharge is thus a significant control on the timing and rate of turbidity currents but not directly due to plunging river water. Elevated river discharge and focusing of river discharge at low tides cause increased sediment transport across the delta-lip, which is the most significant of all controls on flow timing in this setting

Multiplayer Cost Games with Simple Nash Equilibria

Multiplayer games with selfish agents naturally occur in the design of distributed and embedded systems. As the goals of selfish agents are usually neither equivalent nor antagonistic to each other, such games are non zero-sum games. We study such games and show that a large class of these games, including games where the individual objectives are mean- or discounted-payoff, or quantitative reachability, and show that they do not only have a solution, but a simple solution. We establish the existence of Nash equilibria that are composed of k memoryless strategies for each agent in a setting with k agents, one main and k-1 minor strategies. The main strategy describes what happens when all agents comply, whereas the minor strategies ensure that all other agents immediately start to co-operate against the agent who first deviates from the plan. This simplicity is important, as rational agents are an idealisation. Realistically, agents have to decide on their moves with very limited resources, and complicated strategies that require exponential--or even non-elementary--implementations cannot realistically be implemented. The existence of simple strategies that we prove in this paper therefore holds a promise of implementability.Comment: 23 page

On-chip resonantly-driven quantum emitter with enhanced coherence

Advances in nanotechnology provide techniques for the realisation of integrated quantum-optical circuits for on-chip quantum information processing(QIP). The indistinguishable single photons, required for such devices can be generated by parametric down-conversion, or from quantum emitters such as colour centres and quantum dots(QDs). Among these, semiconductor QDs offer distinctive capabilities including on-demand operation, coherent control, frequency tuning and compatibility with semiconductor nanotechnology. Moreover, the coherence of QD photons can be significantly enhanced in resonance fluorescence(RF) approaching at its best the coherence of the excitation laser. However, the implementation of QD RF in scalable on-chip geometries remains challenging due to the need to suppress stray laser photons. Here we report on-chip QD RF coupled into a single-mode waveguide with negligible resonant laser background and show that the coherence is enhanced compared to off-resonant excitation. The results pave the way to a novel class of integrated quantum-optical devices for on-chip QIP with embedded resonantly-driven quantum emitters

On-chip resonantly-driven quantum emitter with enhanced coherence

Advances in nanotechnology provide techniques for the realisation of integrated quantum-optical circuits for on-chip quantum information processing(QIP). The indistinguishable single photons, required for such devices can be generated by parametric down-conversion, or from quantum emitters such as colour centres and quantum dots(QDs). Among these, semiconductor QDs offer distinctive capabilities including on-demand operation, coherent control, frequency tuning and compatibility with semiconductor nanotechnology. Moreover, the coherence of QD photons can be significantly enhanced in resonance fluorescence(RF) approaching at its best the coherence of the excitation laser. However, the implementation of QD RF in scalable on-chip geometries remains challenging due to the need to suppress stray laser photons. Here we report on-chip QD RF coupled into a single-mode waveguide with negligible resonant laser background and show that the coherence is enhanced compared to off-resonant excitation. The results pave the way to a novel class of integrated quantum-optical devices for on-chip QIP with embedded resonantly-driven quantum emitters

New results on pushdown module checking with imperfect information

Model checking of open pushdown systems (OPD) w.r.t. standard branching temporal logics (pushdown module checking or PMC) has been recently investigated in the literature, both in the context of environments with perfect and imperfect information about the system (in the last case, the environment has only a partial view of the system's control states and stack content). For standard CTL, PMC with imperfect information is known to be undecidable. If the stack content is assumed to be visible, then the problem is decidable and 2EXPTIME-complete (matching the complexity of PMC with perfect information against CTL). The decidability status of PMC with imperfect information against CTL restricted to the case where the depth of the stack content is visible is open. In this paper, we show that with this restriction, PMC with imperfect information against CTL remains undecidable. On the other hand, we individuate an interesting subclass of OPDS with visible stack content depth such that PMC with imperfect information against the existential fragment of CTL is decidable and in 2EXPTIME. Moreover, we show that the program complexity of PMC with imperfect information and visible stack content against CTL is 2EXPTIME-complete (hence, exponentially harder than the program complexity of PMC with perfect information, which is known to be EXPTIME-complete).Comment: In Proceedings GandALF 2011, arXiv:1106.081