Integrated scheme of rapid environmental assessment for shallow water acoustics

Predicting sound propagation in shallow or very shallow water environments requires that the frequency-dependent acoustic properties be assessed for all components of the waveguide, i.e., the water column, sea bottom and sea surface interface. During the Maritime Rapid Environmental Assessment MREA?BP'07 sea trial in April-May 2007, south of Elba Island in the Mediterranean Sea, an integrated MREA scheme has been implemented to provide a full 4D (3D+T) environmental picture that is directly exploitable by acoustic propagation models. Based on a joint multi-disciplinary effort, several standard and advanced techniques of environmental characterization covering the fields of underwater acoustics, physical oceanography and geophysics have been combined within a coherent scheme of data acquisition, processing and assimilation. The paper presents the whole architecture of the implemented scheme. Based on a preliminary analysis of MREA?BP'07 data, advantages and drawbacks of the approach will be discussed. Ways ahead for further improvement and perspectives are finally drawn

Geoacoustic inversion in the frequency range 0.8-1.6 kHz with drifting sparse arrays during MREA/BP'07 experiment

In order to evaluate properly the acoustic propagation characteristics in shallow water environments, it is well established that appropriate knowledge of the acoustic properties of the seabottom is required. In the last decade, full-field geoacoustic inversion techniques have been demonstrated to provide adequate methodologies to assess those properties. However, several of the developed techniques may suffer a lack of adequacy to the design of low-frequency active sonar systems (LFAS) for which the assessment of seabottom characteristics are drawn. For instance most matched-field inversion techniques demonstrated so far use acoustical signals at much lower frequencies than those of the sonar. Furthermore, some of the techniques may be difficult to be handled in an "operationally relevant context" since they are based on relatively complex designed systems such as highly instrumented vertical line arrays spanning the whole water column. In this paper, we investigate the potential of medium-frequency acoustical signals (0.8-1.6 kHz) received at several ranges on a field of drifting sparse arrays, eventually reduced to a couple of hydrophones, for spatially-coherent geoacoustic inversion purposes. The experimental datasets of the Maritime Rapid Environmental Assessment MREA/BP'07 sea trial south of Elba Island in the Mediterranean Sea are used to support this study

A variational approach for geoacoustic inversion using adjoint modeling of a PE approximation model with non local impedance boundary conditions

The adjoint model method of control theory is known to give accurate and efficient data assimilation processes in oceanography and meteorology. However, it has rarely been applied in underwater acoustics for inversion purposes. Based on the back-propagation of the mismatch between observations and their predictions, the adjoint model can produce the corrections to the associated direct forward model input parameters. In this paper, the adjoint of a parabolic equation propagation model with non local impedance boundary conditions at the water sediment interface is used in order to determine an acoustically equivalent representation of the seabed. The bottom is represented by these boundary conditions that play the role of the control parameter

The Level-0 Muon Trigger for the LHCb Experiment

A very compact architecture has been developed for the first level Muon Trigger of the LHCb experiment that processes 40 millions of proton-proton collisions per second. For each collision, it receives 3.2 kBytes of data and it finds straight tracks within a 1.2 microseconds latency. The trigger implementation is massively parallel, pipelined and fully synchronous with the LHC clock. It relies on 248 high density Field Programable Gate arrays and on the massive use of multigigabit serial link transceivers embedded inside FPGAs.Comment: 33 pages, 16 figures, submitted to NIM

The PCIe-based readout system for the LHCb experiment

International audienceThe LHCb experiment is designed to study differences between particles and anti-particles as well as very rare decays in the beauty and charm sector at the LHC. The detector will be upgraded in 2019 in order to significantly increase its efficiency, by removing the first-level hardware trigger. The upgrade experiment will implement a trigger-less readout system in which all the data from every LHC bunch-crossing are transported to the computing farm over 12000 optical links without hardware filtering. The event building and event selection are carried out entirely in the farm. Another original feature of the system is that data transmitted through these fibres arrive directly to computers through a specially designed PCIe card called PCIe40. The same board handles the data acquisition flow and the distribution of fast and slow controls to the detector front-end electronics. It embeds one of the most powerful FPGAs currently available on the market with 1.2 million logic cells. The board has a bandwidth of 480 Gbits/s in both input and output over optical links and 100 Gbits/s over the PCI Express bus to the CPU. We will present how data circulate through the board and in the PC server for achieving the event building. We will focus on specific issues regarding the design of such a board with a very large FPGA, in particular in terms of power supply dimensioning and thermal simulations. The features of the board will be detailed and we will finally present the first performance measurement

Draft Genome Sequence of a Novel "<i>Candidatus</i> Liberibacter" Species Detected in a <i>Zanthoxylum</i> Species from Bhutan.

The draft genome sequence of a novel "Candidatus Liberibacter" species detected in an unidentified species of Zanthoxylum (Rutaceae) collected in Bhutan is reported. The total length is 1,408,989 bp with 1,169 coding sequences in 96 contigs, a GC content of 37.3%, and 76 to 77% average nucleotide identity with several other "Ca Liberibacter" species

Conception and Validation Software Tools for the Level 0 Muon Trigger of LHCb

The Level-0 muon trigger processor of the LHCb experiment looks for straight particules crossing muon detector and measures their transverse momentum. It processes 40×106 proton-proton collisions per second. The tracking uses a road algorithm relying on the projectivity of the muon detector. The architecture of the Level-0 muon trigger is complex with a dense network of data interconnections. The design and validation of such an intricate system has only been possible with intense use of software tools for the detector simulation, the modelling of the hardware components behaviour and the validation. A database describing the dataflow is the corner stone between the software and hardware components

Measurement and control of electron wave packets from a single-electron source

We report an experimental technique to measure and manipulate the arrival-time and energy distributions of electrons emitted from a semiconductor electron pump, operated as both a singleelectron source and a two-electron source. Using an energy-selective detector whose transmission we control on picosecond time scales, we can measure directly the electron arrival-time distribution and we determine the upper bound to the distribution width to be 30 ps. We study the effects of modifying the shape of the voltage waveform that drives the electron pump, and show that our results can be explained by a tunneling model of the emission mechanism. This information was in turn used to control the emission-time difference and energy gap between a pair of electrons.This research was supported by the UK Department for Business, Innovation and Skills, the National Physical Laboratory’s Strategic Research Programme and the UK Engineering and Physical Sciences Research Council. V.K. has been supported by the Latvian Council of Science within research project no. 146/2012.This is the author accepted manuscript. The final version is available from APS via http://dx.doi.org/10.1103/PhysRevB.92.12530

Time-of-Flight Measurements of Single-Electron Wave Packets in Quantum Hall Edge States.

We report time-of-flight measurements on electrons traveling in quantum Hall edge states. Hot-electron wave packets are emitted one per cycle into edge states formed along a depleted sample boundary. The electron arrival time is detected by driving a detector barrier with a square wave that acts as a shutter. By adding an extra path using a deflection barrier, we measure a delay in the arrival time, from which the edge-state velocity v is deduced. We find that v follows 1/B dependence, in good agreement with the E[over →]×B[over →] drift. The edge potential is estimated from the energy dependence of v using a harmonic approximation.UK Department for Business, Innovation and SkillsThis is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevLett.116.12680