Chaining of welding and finish turning simulations for austenitic stainless steel components

The chaining of manufacturing processes is a major issue for industrials who want to understand and control the quality of their products in order to ensure their in-service integrity (surface integrity, residual stresses, microstructure, metallurgical changes, distortions,…). Historically, welding and machining are among the most studied processes and dedicated approaches of simulation have been developed to provide reliable and relevant results in an industrial context with safety requirements. As the simulation of these two processes seems to be at an operationnal level, the virtual chaining of both must now be applied with a lifetime prediction prospect. This paper will first present a robust method to simulate multipass welding processes that has been validated through an international round robin. Then the dedicated “hybrid method”, specifically set up to simulate finish turning, will be subsequently applied to the welding simulation so as to reproduce the final state of the pipe manufacturing and its interaction with previous operations. Final residual stress fields will be presented and compared to intermediary results obtained after welding. The influence of each step on the final results will be highlighted regarding surface integrity and finally ongoing validation works and numerical modeling enhancements will be discussed

Polarized heat current generated by quantum pumping in two-dimensional topological insulators

We consider transport properties of a two dimensional topological insulator in a double quantum point contact geometry in presence of a time-dependent external field. In the proposed setup an external gate is placed above a single constriction and it couples only with electrons belonging to the top edge. This asymmetric configuration and the presence of an ac signal allow for a quantum pumping mechanism, which, in turn, can generate finite heat and charge currents in an unbiased device configuration. A microscopic model for the coupling with the external time-dependent gate potential is developed and the induced finite heat and charge currents are investigated. We demonstrate that in the non-interacting case, heat flow is associated with a single spin component, due to the helical nature of the edge states, and therefore a finite and polarized heat current is obtained in this configuration. The presence of e-e interchannel interactions strongly affects the current signal, lowering the degree of polarization of the system. Finally, we also show that separate heat and charge flows can be achieved, varying the amplitude of the external gate.Comment: 13 pages, 5 figure

Investigation of Band Tailing in Sputtered ZnO Al Thin Films Regarding Structural Properties and Impurities

Thin films of pure aluminum doped ZnO and with addition of nitrogen, oxygen and hydrogen have been prepared by magnetron sputtering. The spectral absorption coefficient close to the band gap energy has been determined by spectrophotometry and analyzed regarding band tailing and creation of defect bands. We found, that an improvement of Raman crystallinity under O2 rich growth conditions is not accompanied by a suppression of band tailing as expected. An additional absorption feature evolves for layers grown in N2 containing atmosphere. Doping with hydrogen attenuates sub band gap absorptio

Protein families, natural history and biotechnological aspects of spider silk.

Spiders are exceptionally diverse and abundant organisms in terrestrial ecosystems and their evolutionary success is certainly related to their capacity to produce different types of silks during their life cycle, making a specialized use on each of them. Presenting particularly tandemly arranged amino acid repeats, silk proteins (spidroins) have mechanical properties superior to most synthetic or natural high-performance fibers, which makes them very promising for biotechnology industry, with putative applications in the production of new biomaterials. During the evolution of spider species, complex behaviors of web production and usage have been coupled with anatomical specialization of spinning glands. Spiders retaining ancestral characters, such as the ones belonging to the Mygalomorph group, present simpler sorts of webs used mainly to build burrows and egg sacs, and their silks are produced by globular undifferentiated spinning glands. In contrast, Araneomorphae spiders have a complex spinning apparatus, presenting up to seven morphologically distinct glands, capable to of rigidness and elasticity associated with distinct behaviors. Aiming to provide a discussion involving a number of spider silks? biological aspects, in this review we present descriptions of members from each family of spidroin identified from five spider species of the Brazilian biodiversity, and an evolutionary study of them in correlation with the anatomical specialization of glands and spider?s spinning behaviors. Due to the biotechnological importance of spider silks for the production of new biomaterials, we also discuss about the new possible technical and biomedical applications of spider silks and the current status of it

Fortress with Sticky Moats: the Functional Role of Small Particles around Tetragonisca angustula Latreille (Apidae: Hymenoptera) Nest Entrance

Many bee species are able to defend themselves against pollen or honey thievery. We herein report the functional role of small sticky particles deposited by Tetragonisca angustula Latreille in its nest entrance external side. This strategy was very effective to prevent ants from invading the bees’ nest. We reported many dead ants attached to the nest entrance and different ant species easily immobilized after being moved onto the entrance tube containing sticky particles. This is the first description of the functional role played by the nest entrance sticky particles under natural conditions.

Staged opening switch

" A staged switch for conducting a large electrical current for an indefinite time period and then rapidly switching the current into a load circuit. The switch comprises a first stage which can conduct a large electrical current for an indefinite time period without damage to the stage and a second stage which is a fast-opening element. The first stage includes primary and secondary contacts wherein the primary contacts conduct a charging current and the secondary contacts divert the current into the fast-opening second stage. The secondary contacts ""make"" before the primary contacts ""break"", reducing the damage to the contacts which might otherwise be experienced. The second stage is a low-inductance element which reduces the level of energy absorbed by the first-stage contacts, minimizing damage to the contacts. The second-stage element may be constructed in a cartridge and may be loaded into the switch using an autoloader device. "Board of Regents, University of Texas Syste

High-efficiency transformation by biolistics of soybean, common bean and cotton transgenic plants.

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Math Escape Rooms: A Novel Approach for Engaging Learners in Math Circles

Engaging middle and high school students in Math Circles requires time, planning and creativity. Finding novel approaches to maintain the interest of a variety of learners can be challenging. This paper outlines a model for developing and implementing math escape rooms as a unique structure for facilitating collaborative problem solving in a Math Circle. These escape rooms were designed and hosted by undergraduate secondary mathematics education majors. We provide possible structures for hosting escape rooms that could translate to a range of settings, as well as reflections and lessons learned through our experiences that could inform practitioners in other settings