Laser Welding of Ultrahigh Strength Steels at Subzero Temperatures

AbstractUltrahigh strength steels like press hardened 22MnB5 and S1100QL make good construction materials, however when fusion welded they bring the disadvantage of softening in heat affected zones (HAZ). State of the art research of Laser welding ultrahigh strength steels shows that neither increasing the welding velocity, nor post weld heat treatment have an effect on the strength and hardness drop in the HAZ. The key to improving these material characteristics is to increase heat dissipation out of the workpiece. To do so, the cooling conditions while laser welding press hardened 22MnB5 and S1100QL were dramatically increased. Experiments were carried out at subzero temperatures down to -98°C by using a mixture of liquid and gaseous nitrogen. To further improve heat dissipation, the clamping jaws were entirely made of copper. Hardness measurements and tensile tests were conducted to compare joints welded at room temperature with those welded at -98°C. Whilst an improvement of the hardness values could be achieved for the press hardened 22MnB5 and the S1100, no change in the mechanical behavior regarding tensile tests could be observed. Thus, it can be noticed that there is no possibility to improve the strength levels of martensitic steels throughout varying process parameters (like welding velocity) or utilizing an active cooling, even if subzero temperatures down to -98°C are applied. A further improvement at lower temperatures is unlikely because heat dissipation in the work piece itself is the limiting factor

Lebensmittelverarbeitung in einem oberägyptischen Kloster

Das koptische Kloster Deir Anba Hadra liegt gegenüber der südägyptischen Stadt Assuan am Westufer des Nils. Dieses größte und am besten erhaltene Kloster der Region wird seit 2013 durch ein interdisziplinäres Projekt im Rahmen einer DAI-Konzession erforscht. Der »Wirtschaftskomplex« auf der Oberen Terrasse wurde im Rahmen dieses Projektes bauhistorisch und archäologisch untersucht. In der Auswertung wurden 16 Bau­phasen erkannt, die mit verschiedenen Funktionen in Verbin­dung gebracht werden können, und es ist möglich, diesen Gebäudekomplex als Standort für Lebensmittelproduktion zu identifizieren. Hier wurden Brot, Rizinusöl, Wein und Garum hergestellt. Durch die bauhistorischen Untersuchungen wurde festgestellt, dass der Kern des Komplexes ursprünglich als Oratorium für die Stundengebete der Mönche errichtet wurde. Durch den Anbau meh­rerer Funktionsräume wurde er nach dem 6./7. Jahrhundert großflächig umgestaltet. Durch diese Umgestaltung konnte eine Bäckerei eingerichtet werden, deren Kapazitäten nach und nach erweitert wurden. Mit der Errichtung eines Kollerganges konnte im nördlichen Teil des Gebäudekomplexes Rizinusöl hergestellt werden. Weiter nördlich wurde eine Weinkelter angesetzt; zwei Tanks in der direkten Umgebung der Kelter dienten wahrscheinlich der Her­stellung von Garum. Neben dem bewussten Abbau einzelner Mauern belegen Feuerstellen und Futtertröge eine Verwendung ver­schiedener Bereiche auch nach dem Ende der Nutzung des Deir Anba Hadra als Kloster. Die im Deir Anba Hadra identifizierten Produktionsanla­gen wurden mit Installationen im (spät-)antiken Mittelmeer­raum verglichen. Durch diese Gegenüberstellungen können nicht nur technische Details erklärt werden, sondern vielmehr auch Produktionsprozesse

The Profile of the Teaching Profession – Empirical Reflections on the Development of the Competences of University Teachers

AbstractIn this article we have proposed to present a theoretical and practical approach to the teaching profession, based on analysis competencies, which should hold them a good university teacher in a globalized and competitive world. The results of the study were obtained by applying a written questionnaire to subjects who work in different universities from Romania and Spain. The study included a total of 485 people from four universities in Spain and four universities in Romania. The results obtained by analyzing the responses of the subjects included in our sample have showed that both groups of teachers – from Romania an Spain – have the same opinions regarding the competencies which should hold them a good university teacher but were registered significant mean differences regarding transversal competencies dimension (p=0,002, p< 0,05). We believe that the professional perfection and development are the sources of a professional continuum, which makes educational career rolling laws and is subject to management resources, mobility needs, and flexibility of the teaching staff

Education and the boarding school novel : examining the work of José Régio

This thesis is centred on the work of Portuguese writer José Régio (1901-1969). He was a teacher-writer and, arguably, the most philosophical of Portuguese school novel authors. In his novel ‘A Drop of Blood’ (1945), Régio shows interest in the formation of the artist as the special object of education – the ‘marked man’ –, whose sensitivity distances him irremediably from the crowd. He adopted the radical individualism of Nietzsche not in order to be ‘for’ or ‘against’ this or that schooling model but to exemplify the perpetual clash, inherent in mankind, between the individual and the group, the artist and the non-artistic person, the young and the adult, the son and the father and the self and the world. Published Proquest ebook version: http://ebookcentral.proquest.com/lib/canterbury/detail.action?docID=4799556 (UC Staff and Student use only

Lesions of the Dorsal Medial Hippocampus induce different forms of Repetitive Behaviour in the rat

The dorsal dentate gyrus (DDG) of the hippocampus plays a role in the expression of different forms of flexible behaviour mainly due to its ability to sustain neurogenesis throughout life. In the present thesis, we examined the role that the DDG and its adjacent areas, both collectively referred to as dorsal medial hippocampus (DMH), play in flexible, adaptive behaviour and cognitive processing. We used the neurotoxin, colchicine, to induce lesions of the DDG, which were found to affect neighbouring areas. Thus these lesions will be referred to as lesions of the DMH. In the first experiment, rats were tested for (1) perseverative behaviour before and after receiving chronic methamphetamine (METH) treatment, (2) METH-induced locomotor activity and stereotypy in an open field, and (3) working memory in a T-maze. The results showed that rats with lesions of the DMH exhibited perseveration and supersensitivity to the locomotor- and stereotypy-inducing effects of METH (0, 0.1, 0.3, 1 mg/kg i.p.) as well as increased long-term METH sensitization. Rats with DMH lesions also showed significant working memory deficits. Taken together, these results reveal specific forms of behavioural inflexibility in rats with lesions of the DMH that are mainly associated with perseveration, drug-related behaviours, including stimulant motor supersensitivity and drug sensitization, and impaired working memory functions

Mathurin

Arnould Galopin'in Son Saat'te yayımlanan Mathurin adlı romanının ilk ve son tefrikalar

Improvements of hybrid laser arc welding for shipbuilding T-joints with 2F position of 8 mm thick steel

One of the main concerns in the early stages of manufacturing flat units of shipbuilding is to ensure the quality of the joints throughout the structure. The flat units are constituted by butt welded flat plates, on which longitudinal T-welded reinforcements are placed to rigidize the structure. Among the different welding technologies, Hybrid Laser Arc Welding (HLAW) is becoming a mature process, profitable and highly productive. In addition, more innovative welding equipment are being developed nowadays, offering greater work flexibility, and raising expectations of achieving better quality, and economic viability. Another key point of HLAW to keep in mind is that structural distortions are reduced, resulting in decreasing the cost and time of straightening work. In the present contribution, the influence of HLAW parameters on the quality of fillet joints of naval steel has been analysed. Experimental HLAW tests were performed with a high power disk laser to join EH36 naval steel plates, with a T configuration. The influence of different processing parameters has been analysed, as the laser power, welding speed, wire feed rate and the configuration of the HLAW processes (including head angle and laser/arc leading process). In addition, FEM simulations were carried out in order to estimate residual stresses and distortion of welded part. The distortion values provided by FEM presented excellent agreement with the measured experimental results. To evaluate the welds, non destructive tests including X-ray tests, metallographic analysis of cross sections, and microhardness mapping tests were performed. Full penetration 8 mm T welds were obtained for the first time at an industrially applicable 2F position with a reasonable HLAW head angle, in one single step without sealing root, and using zero gap square groove edge preparation. The present contribution presents welding rates up to 2.2 m/min for 2F T-joints of this steel thickness, a much higher processing velocity than previously reported for industrial applications