EIS characterization of the inhibition of mild steel corrosion with carboxylates in neutral aqueous solution

Electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) measurements were used to study the ability of monocarboxylates to support the passivation of mild steel by dissolved oxygen in near neutral solution. It was shown that the effectiveness of monocarboxylates depends on their ability to form weakly soluble Fe(III) compounds and to adsorb on the oxide covered surface. The inhibition effect can be improved by an addition of a second inhibitor.     

Borehole breakout evolution through acoustic emission location analysis

A series of thick-wall cylinder tests were performed on Bentheim sandstone to investigate the nucleation and propagation of borehole breakouts. Isotropic compression tests showed a significant decrease of the critical pressure required to nucleate breakouts with increasing borehole diameter. Advanced analysis of acoustic emission radiation and optical microstructures indicate a three stage process of breakout nucleation and growth. Relatively few acoustic emissions are observed during the elastic loading stage of the specimens. Once breakout nucleation has occurred at the borehole wall a drastic increase of acoustic emission activity is observed. A close spatial correspondence between located acoustic events and the breakout indicates formation of two symmetric cusp-shaped breakouts on opposite sides of the borehole. With increasing isotropic pressure the breakouts grow forming parallel-sided slots that are surrounded by a process zone revealing grain crushing and pore collapse as typically observed in experimentally produced compaction bands. We apply a simple fracture mechanics approach to predict the observed size effect of the critical pressure required to initiate breakouts.     

Three-dimensional friction stir welding using a high payload industrial robot

The present study investigates the friction stir welding (FSW) process of extremely curved surfaces using a high payload industrial robot. The welding process of aluminum alloys in a butt joint configuration has been investigated over convex surface radii ranging from 104.5 to 14.5 mm. The weld qualities of the produced joints have been assessed by macrographs and tensile tests. It was shown that the FSW process needs an optimization of the welding path as well as an optional adaptation of the process parameters in the curved region in order to produce sound and reproducible joints without inner or outer defects. The results contribute to further fields of application where non-linear welds have to be produced.     

On using nearly-independent feature families for high precision and confidence

Consider learning tasks where the precision requirement is very high, for example a 99 % precision requirement for a video classification application. We report that when very different sources of evidence such as text, audio, and video features are available, combining the outputs of base classifiers trained on each feature type separately, aka late fusion, can substantially increase the recall of the combination at high precisions, compared to the performance of a single classifier trained on all the feature types, i.e., early fusion, or compared to the individual base classifiers. We show how the probability of a joint false-positive mistake can be less—in some cases significantly less—than the product of individual probabilities of conditional false-positive mistakes (a NoisyOR combination). Our analysis highlights a simple key criterion for this boosted precision phenomenon and justifies referring to such feature families as (nearly) independent. We assess the relevant factors for achieving high precision empirically, and explore combination techniques informed by the analysis.     

Efficient borehole detection from single scan data

This work presents a fast and robust method to precisely segment and locate boreholes of 4–50 mm diameter. The task is solved by scanning over the expected borehole location given by CAD data. Since the diameter of the borehole is known, this can be used to obtain a robust and fast algorithm suitable for industrial application. Single scan data is sufficient to segment the bore independent of bore chamfer type using a robust normal vector fit and a classification based on the Gaussian image. A sequential cylinder fit algorithm makes it possible to calculate the bore pose in less than one second. The experiments demonstrate that 120° of the borehole surface are sufficient for robust localization within 0.3 mm and 0.5° even in the presence of ghost points and notches in the boreholes.     

Simulation and analysis of reconfigurable assembly systems based on R-TNCES

ABSTRACT

Recent research indicates that dynamic reconfiguration techniques can be applied to manufacturing systems to reduce energy consumption by switching energy-intensive components in a timely manner between their working and idle modes during system runtime because these components consume less energy in their idle modes than in their working modes. The current work studies reconfigurable assembly systems with such dynamic reconfiguration techniques by abstracting them as reconfigurable discrete event systems, considering only their logic behavior and properties. The formalism, R-TNCES (reconfigurable timed net condition/event systems), a modular extension of the well-known Petri nets, is used as a system modeling and analysis tool. The simulation of system global reconfigurations is guided by command inserting, whereas the simulation of local reconfigurations is automatic because their execution time is computed a priori by a proposed algorithm. Finally, qualitative properties specified by computation tree logic and quantitative analysis regarding energy-efficiency are performed by using the software SESA.     

Experimental study and analysis of the purge gas pressure drop across the pebble beds for the fusion HCPB blanket

The lithium ceramic and beryllium pebble beds of the breeder units (BU), in the fusion breeding blanket, are purged by helium to extract the bred tritium. Therefore, the objective of this study is to support the design of the BU purge gas system by studying the effect of pebbles diameter, packing factor, pebble bed length, and flow inlet pressure on the purge gas pressure drop. The pebble bed was formed by packing glass pebbles in a rectangular container (56 mm × 206 mm × 396 mm) and was integrated into a gas loop to be purged by helium at BU-relevant pressures (1.1–3.8 bar). To determine the pressure drop across the pebble bed, the static pressure was measured at four locations along the pebble bed as well as at the inlet and outlet locations. The results show: (i) the pressure drop significantly increases with decreasing the pebbles diameter and slightly increases with increasing the packing factor, (ii) for a constant inlet flow velocity, the pressure drop is directly proportional to the pebble bed length and inlet pressure, and (iii) predictions of Ergun's equation agree well with the experimental values of the pressure drop.