Multiwire submerged arc welding of steel structures

The assembly of large structures made out of thick steel plates requires a welding process by which multiple wires can be used simultaneously. To reproduce these industrial processes in a research environment, OCAS has invested in a multiwire submerged arc welding (SAW) setup. In this multiwire setup, up to five wires in tandem configuration can be used. The objective of this master thesis is to establish a deeper knowledge of process parameters used to weld steel plates in a thickness range of 12,7 up to 25 mm, by means of the submerged arc welding process. Based on literature, a test matrix is composed in which the number of wires, the plate thickness and other weld parameters are the variables. In addition, a specific plate preparation for each plate thickness is derived from the literature. The preformed weld trails will be evaluated on weld bead geometry and metallographic properties. There is further experimental examination required, which will result in the revising of the matrix

Influence of notch orientation on ductile tearing in SENT specimens

There is a growing interest for the use of spiral welded pipes in strain based design related applications. Since the influence of the spiral weld on the plastic behaviour of the pipe is not yet fully understood, further research on this topic is required. An important aspect of this plastic behaviour is the effect of mixed mode loading on weld defects located in the helical weld. This paper elaborates on the first experimental trials to evaluate ductile tearing by means of single edge notched tensile specimen (SENT) testing with slanted notches. Tests were performed on two SENT specimens, one with a slanted notch and another with a straight notch in order to investigate the influence of mixed mode loading. The crack mouth opening displacement and crack extension were determined experimentally by means of digital image correlation and potential drop measurements respectively. The crack extension and the potential drop measurements were related by means of finite element simulations

Plasmonic metamaterials

We experimentally and theoretically determine the plasmon dispersion in coaxial waveguides. We demonstrate strong optical confinement at energies below the surface plasmon resonance. Furthermore, we find that the reflection coefficients of the coax end facets can be strongly tuned by changing the coax dispersion and surrounding dielectric, which provides a new route to optical cavities with ultrasmall mode volumes

A Cascade Neural Network Architecture investigating Surface Plasmon Polaritons propagation for thin metals in OpenMP

Surface plasmon polaritons (SPPs) confined along metal-dielectric interface have attracted a relevant interest in the area of ultracompact photonic circuits, photovoltaic devices and other applications due to their strong field confinement and enhancement. This paper investigates a novel cascade neural network (NN) architecture to find the dependance of metal thickness on the SPP propagation. Additionally, a novel training procedure for the proposed cascade NN has been developed using an OpenMP-based framework, thus greatly reducing training time. The performed experiments confirm the effectiveness of the proposed NN architecture for the problem at hand

Don’t forget the vertical dimension: Assessment of distributional dynamics of cave-dwelling invertebrates in both ground and parietal microhabitats

Biological studies on factors shaping underground communities are poor, especially those considering simultaneously organisms with different degrees of adaptation to cave life. In this study, we assessed the annual dynamics and use of both horizontal and vertical microhabitats of a whole community with the aim of understanding whether cave-dwelling organisms have a similar distribution among vertical and ground-level microhabitats and to find out which microhabitat features influence such distribution. We monthly assessed from 2017 to 2018, by direct observation combined with quadrat sampling method on the ground and transects on the walls, richness and abundance of 62 cave-dwelling species in a cave of Northern Italy. Environmental factors such as light intensity, temperature, relative humidity and mineralogical composition of the substrates were measured during each monitoring session, influencing the dynamics of the whole community and revealing significant differences between ground and wall microhabitats. A gradient of variation of the species assemblages occurred from the entrance toward inner areas, however, evidence that the dynamics of the walls are very different from those occurring at the ground independent from the distance from the surface are shown. Biodiversity indices highlighted sampling area diversity and a discrete total cave fauna biodiversity with the highest values found near the entrance and the lowest in the inner part of the cave

Electron Probe Micro-Analysis and Laser Microprobe Mass Analysis of Material Leached from a Limestone Cathedral

Electron probe X-ray micro-analysis (EPXMA) and Laser microprobe mass analysis (LAMMA), were applied to characterize the leachate of sandy limestones of a Belgian cathedral. Individual suspended particles, found in water that was sprayed over the cathedral walls ( 1 each ate water ), were sized and analyzed by automated EPXMA-analysis, and classified with hierarchical cluster methods. LAMMA was used to gather more information about particles, present in the solution, as well as in suspension. It was found that the leachate from black walls, had a high sulphate concentration and a large variety of particles in suspension, with different morphology and composition, with silicates as most abundant group. The leachate from white walls is characterized by a predominant Ca-rich suspension, with both original and recrystallized calcite particles, and by a much lower sulphate-ion concentration in the solution. LAMMA-analysis revealed that the organic group of the EPXMA-analysis, consists mostly of carbon-containing fly-ash particles. Hence, in general, it could be concluded that walls which are not subject to direct rainfall are generally covered with a gypsum crust, that turns black due to adhesion of soil dust and fly-ash particles, while white walls become thinner due to rainwater erosion of weathering products and original stone components

Proterozoic tectonostratigraphy and paleogeography of central Madagascar derived from detrital zircon U-Pb age populations

Detrital zircon U-Pb ages determined by SHRIMP distinguish two clastic sequences among Proterozoic metasedimentary rocks from central Madagascar. The Itremo Group is older: zircon data, stromatolite characteristics, and carbon isotope data all point to a depositional age around 1500-1700 Ma. The Molo Group is younger, deposited between ∼620 Ma (the age of the youngest zircon) and ∼560 Ma (the age of metamorphic overgrowths on detrital cores). Geochronologic provenance analysis of the Itremo Group points to sources in East Africa as well as local sources in central and southern Madagascar but provides no evidence for a detrital contribution from northern and eastern Madagascar nor from southern India. Detrital zircon and sedimentologic similarities between rocks of the Itremo Group and the Zambian Muva Supergroup suggest a lithostratigraphic correlation between the two. The Molo Group has a strong 1000-1100 Ma detrital signature that also indicates an east African provenance and suggests a Neoproterozoic geographic connection with Sri Lanka but shows no indication of input from the Dharwar craton and eastern Madagascar. Central Madagascar was probably juxtaposed with the Tanzanian craton in the Paleo- and Mesoproterozoic, whereas northern and eastern Madagascar were connected to India. Internal assembly of Madagascar postdates Neoproterozoic Molo Group sedimentation and is likely to have occurred at about 560 Ma. © 2004 by The University of Chicago. All rights reserved.Rónadh Cox, Drew S. Coleman, Carla B. Chokel, Stephen B. DeOreo, Joseph L. Wooden, Alan S. Collins, Bert De Waele, and Alfred Kröne