Structured light techniques for 3D surface reconstruction in robotic tasks

Robotic tasks such as navigation and path planning can be greatly enhanced by a vision system capable of providing depth perception from fast and accurate 3D surface reconstruction. Focused on robotic welding tasks we present a comparative analysis of a novel mathematical formulation for 3D surface reconstruction and discuss image processing requirements for reliable detection of patterns in the image. Models are presented for a parallel and angled configurations of light source and image sensor. It is shown that the parallel arrangement requires 35\% fewer arithmetic operations to compute a point cloud in 3D being thus more appropriate for real-time applications. Experiments show that the technique is appropriate to scan a variety of surfaces and, in particular, the intended metallic parts for robotic welding tasks

Role of artificial intelligence in the diagnosis of oesophageal neoplasia: 2020 an endoscopic odyssey

The past decade has seen significant advances in endoscopic imaging and optical enhancements to aid early diagnosis. There is still a treatment gap due to the underdiagnosis of lesions of the oesophagus. Computer aided diagnosis may play an important role in the coming years in providing an adjunct to endoscopists in the early detection and diagnosis of early oesophageal cancers, therefore curative endoscopic therapy can be offered. Research in this area of artificial intelligence is expanding and the future looks promising. In this review article we will review current advances in artificial intelligence in the oesophagus and future directions for development

Mapping the direction of electron ionization to phase delay between VUV and IR laser pulses

We theoretically demonstrate a one-to-one mapping between the direction of electron ionization and the phase delay between a linearly polarized vacuum ultraviolet (VUV) and a circular infrared (IR) laser pulse. To achieve this, we use an ultrashort VUV pulse that defines the moment in time and space when an above-threshold electron is released in the IR pulse. The electron can then be accelerated to high velocities escaping in a direction completely determined by the phase delay between the two pulses. The dipole matrix element to transition from an initial bound state of the N2 molecule, considered in this work, to the continuum is obtained using quantum-mechanical techniques that involve computing accurate continuum molecular states. Following release of the electron in the IR pulse, we evolve classical trajectories, neglecting the Coulomb potential and accounting for quantum interference, to compute the distribution of the direction and magnitude of the final electron momentum. The concept we theoretically develop can be implemented to produce nanoscale ring currents that generate large magnetic fields

Streaking single-electron ionization in open-shell molecules driven by X-ray pulses

We obtain continuum molecular wavefunctions for open-shell molecules in the Hartree-Fock framework. We do so while accounting for the singlet or triplet total spin symmetry of the molecular ion, that is, of the open-shell orbital and the initial orbital where the electron ionizes from. Using these continuum wavefunctions, we obtain the dipole matrix elements for a core electron that ionizes due to single-photon absorption by a linearly polarized X-ray pulse. After ionization from the X-ray pulse, we control or streak the electron dynamics using a circularly polarized infrared (IR) pulse. For a high intensity IR pulse and photon energies of the X-ray pulse close to the ionization threshold of the $1{\sigma}$ or $2{\sigma}$ orbitals, we achieve control of the angle of escape of the ionizing electron by varying the phase delay between the X-ray and IR pulses. For a low intensity IR pulse, we obtain final electron momenta distributions on the plane of the IR pulse and we find that many features of these distributions correspond to the angular patterns of electron escape solely due to the X-ray pulse.Comment: 13 pages, 7 figure

Digital Reproduction of Clastic Sedimentary Architecture by Means of Relational Databases

As the amount of architectural data collected in sedimentological studies, and typically rendered available in published form, has increased over time, so a fundamental issue has become ever more important: the need to ensure that different datasets collected in different ways by different geologists (e.g. 2D architectural panels, 3D seismic surveys) are stored in a format such that analysis or synthesis of fundamentally different types of data can be made in a sensible and informative manner, without requiring extensive literature search and re-processing. Database systems are here proposed as a means for achieving the convergence of datasets in a common medium. The proposed database approach permits the digital reproduction of sedimentary architecture in tabulated form: hard and soft data referring to depositional products are assigned to standardized genetic units belonging to different scales of observation, which are themselves contained within stratigraphic volumes classified on deposystem parameters (e.g. subsidence rate, physiographic setting). Although the approach has general applicability, two different databases have been independently developed to capture the peculiarities associated with fluvial and deep-marine depositional systems. Through interrogation, the two database systems return output that – being in quantitative form and referring to standardized sedimentary units – is suitable for both synthesis and analysis. Deposystem classification permits data to be filtered on the parameters on which the systems are classified, allowing the exclusive selection of data associated with systems deemed to be analogous to a given subsurface succession in terms of deposystem boundary conditions and environmental setting. Alternatively, the quantification of architectural properties permits users to identify analogy in terms of sedimentary architecture. Outputs from the two databases are here presented in forms suitable for highlighting differences in the way fluvial and deep-water architecture is conceptualized and implemented, and for presenting ways in which analog information can be employed for the characterization and prediction of fluvial and deep-water reservoirs. Specific example applications include the use of database output to (i) generate quantitative facies models with which to guide core interpretation, (ii) to constrain stochastic reservoir models, and (iii) to guide well correlation of fluvial or deep-marine sandstones

Identifying key mechanisms leading to visual recognition errors for missed colorectal polyps using eye-tracking technology

Background and Aim Lack of visual recognition of colorectal polyps may lead to interval cancers. The mechanisms contributing to perceptual variation, particularly for subtle and advanced colorectal neoplasia, have scarcely been investigated. We aimed to evaluate visual recognition errors and provide novel mechanistic insights. Methods Eleven participants (seven trainees and four medical students) evaluated images from the UCL polyp perception dataset, containing 25 polyps, using eye-tracking equipment. Gaze errors were defined as those where the lesion was not observed according to eye-tracking technology. Cognitive errors occurred when lesions were observed but not recognized as polyps by participants. A video study was also performed including 39 subtle polyps, where polyp recognition performance was compared with a convolutional neural network. Results Cognitive errors occurred more frequently than gaze errors overall (65.6%), with a significantly higher proportion in trainees (P = 0.0264). In the video validation, the convolutional neural network detected significantly more polyps than trainees and medical students, with per-polyp sensitivities of 79.5%, 30.0%, and 15.4%, respectively. Conclusions Cognitive errors were the most common reason for visual recognition errors. The impact of interventions such as artificial intelligence, particularly on different types of perceptual errors, needs further investigation including potential effects on learning curves. To facilitate future research, a publicly accessible visual perception colonoscopy polyp database was created

A global analysis of controls on submarine-canyon geomorphology

The role of possible controlling factors in influencing the geomorphology of submarine canyons has been investigated using a database of 282 globally distributed modern examples collated from the literature and open-source worldwide bathymetry. Canyon geomorphology has been characterised quantitatively in terms of maximum and average canyon dimensions, canyon sinuosity, average canyon thalweg gradient, and maximum canyon sidewall steepness. An assessment is made of how geomorphological characteristics vary with respect to the position of the canyon apex relative to the shelf break, continental-margin type, terrestrial source-to-sink system setting, oceanographic environment, and latitude. Scaling relationships between canyon morphometric parameters, and correlations between these and attributes of the canyon physiographic settings, terrestrial catchments, and continental shelves and slopes, have been quantified. Key findings are as follows: (i) a number of scaling relationships describing canyon morphometry (e.g. scaling between maximum canyon dimensions, relationships of maximum canyon sidewall steepness with maximum canyon width and depth) can be recognised globally, suggesting their general predictive value; (ii) possible causal links are identified between hydrodynamic processes (e.g. upwelling, longshore- and along-slope currents) and canyon morphology; (iii) potential predictors of aspects of canyon geomorphology include whether a canyon is incised into the shelf or confined to the slope, the continental-margin type, the oceanographic environment, latitude, and shelf-break depth; (iv) similarity in the distributions of maximum width-to-maximum depth ratios across all settings suggests that the relative magnitudes of canyon-margin erosion and intra-canyon deposition do not vary greatly depending on setting or canyon size. The relationships between canyon geomorphology and environmental variables identified in this study may be incorporated into conceptual models describing canyon geomorphology and its relationship both to other elements of deep-water systems, and to its broader source-to-sink context. The results provide a framework for future experimental and numerical studies of canyon geomorphology

Tectonic Influence on the Geomorphology of Submarine Canyons: Implications for Deep-Water Sedimentary Systems

A database-informed metastudy of 294 globally distributed submarine canyons has been conducted with the aim of elucidating the role of tectonic setting on submarine-canyon geomorphology. To achieve this, data from seafloor and subsurface studies derived from 136 peer-reviewed publications and from open-source worldwide bathymetry datasets have been statistically analyzed. In particular, relationships between margin type (active vs. passive) or plate-boundary type (convergent vs. transform vs. complex) have been assessed for key morphometric parameters of submarine canyons, including: streamwise length, maximum and average width and depth, canyon sinuosity, average canyon thalweg gradient, and maximum canyon sidewall steepness. In addition, possible scaling relationships between canyon morphometric parameters and characteristics of the associated terrestrial catchment, continental shelf and slope, and of the broader physiographic setting for canyons along both active and passive margins have been evaluated. The following principal findings arise: 1) overall canyon geomorphology is not markedly different across tectonic settings; 2) slope failure might be more important in passive-margin canyons compared to active ones, possibly due to seismic strengthening in the latter; 3) some aspects of canyon geomorphology scale with attributes of the source-to-sink system and environmental setting, but the strength and sign in scaling might differ between active and passive margins, suggesting that the extent to which canyon geomorphology can be predicted depends on the tectonic setting. Insights from our analysis augment and improve conceptual, experimental and numerical models of slope systems at the scale of individual canyons and source-to-sink systems, and increase our understanding of the complex role played by tectonic setting in shaping deep-water systems

Filter Or Conveyor? Establishing Relationships Between Clinoform Rollover Trajectory, Sedimentary Process Regime, and Grain Character Within Intrashelf Clinothems, Offshore New Jersey, U.S.A.

Clinoform geometries and trajectories are widely used to predict the spatial and temporal evolution of sand distribution, but most analytical approaches underplay the significance of topset and shelf process regime in determining how and when sediment is conveyed downdip or stored on the continental shelf. We present an integrated study of clinoform rollover trajectory and detailed grain character analysis to assess the role of topset process regime in determining sand distribution and sediment character across clinothems. This study targets the topset, foreset, and bottomset deposits of four successive Miocene intrashelf clinothem sequences, which represent deposition under either river-dominated or wave-dominated conditions. Seismic reflection data was combined with core analysis and grain character data derived from 664 samples collected from three cored research boreholes. In river-dominated clinothems, the transfer of coarse-grained sediment occurs under both rising and flat-to-falling clinoform rollover trajectories, suggesting that process regime is more important in determining sediment delivery than clinoform trajectory; river-dominated systems are effective conveyors of sediment into deeper water. Wave-dominated clinothems deposited exclusively under rising clinoform rollover trajectories largely retain sand within topset and foreset deposits; wave-dominated systems are effective sediment filters. Notably, deposition under either river- or wave-dominated topset process regimes results in quantifiable differences in grain character attributes along clinoform profiles. Sediments in river-dominated systems are coarser, less well-rounded, and more poorly sorted, and show greater intersequence and intrasequence variability than those in wave-dominated systems; prediction of sediment character is more challenging in river-dominated systems. This study highlights the need for caution when attempting to predict downdip sand distribution from clinoform trajectory alone, and provides a novel perspective into downdip grain character profiles under end-member topset process regime conditions. The results of this study can be used to better constrain sediment grain-size and grain-shape distributions in process-based forward models, and have widespread applications in prediction of reservoir quality in both frontier and mature hydrocarbon basins