989 research outputs found

    A Material Perspective on Consequence of Deformation Heating During Stamping of DP Steels

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    Recent studies showed that, during stamping of high strength steels at industrially relevant production rates, local temperature in the blank may rise up to 200°C – 300°C due to deformation heating. Moreover, die temperature may also rise up to 100°C – 150°C for progressive stamping dies. Based on the common assumption that the blank softens as the temperature increases, thermal softening creates a margin in Forming Limit Diagram (FLD) and therefore the FLD determined at room temperature can safely be used for those cases. In this article, the validity of this assumption on DP590 steel is questioned by high temperature tensile tests (RT - 300°C) at various strain rates (10-3 s-1 – 1 s-1). The results indicated a decrease both in uniform and total elongation in 200°C – 300°C range together with several other symptoms of Dynamic Strain Aging (DSA) at all strain rates. Concurrent with the DSA, the simulated FLD confirms the lower formability at high temperature and strain rates. Thus, it is concluded FLD determined at RT may not be valid for the investigated steels

    Spatial heterogeneity of land cover response to climatic change in the Nilgiri highlands (southern India) since the Last Glacial Maximum

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    25 pagesFourteen hillslope soil profiles were sampled under natural vegetation (i.e., grassland or forest) and plantations in the Nilgiri highlands, southern India. Delta 13C ratios were measured at different depths and 14C ages determined for six profiles. In these highland soils where the turnover rate of organic matter is extremely low, the Δ13C ratios of entire soil profiles have recorded signatures of past land cover. By correlating the data with results previously obtained from peat bogs and with knowledge concerning the history of human settlement, we distinguish three contrasting trajectories of palaeoenvironmental history and landscape change since the Last Glacial Maximum. In the central Nilgiris, between 18 and 10 ka BP, forest expansion occurred due to the conjunction of a wetter climate (the maximum of southwest monsoon-related humidity occurring at ca. 11 ka BP) and higher temperatures; since 10 ka BP, the reversal towards grassland vegetation is attributed to drier conditions. In the western Nilgiris, where strong southwest monsoon winds permanently restrict forest patches to sheltered valley sites, steady but limited expansion of forest from 18 ka BP to the present is recorded and attributed to rising temperatures. The southern and eastern Nilgiris, where the northeast monsoon contributes 20% of the annual rainfall, are the less sensitive to fluctuations in the southwest monsoon. In these areas, rapid and extensive expansion of forest occurred mainly as a consequence of higher temperatures from 18 ka BP to the present. Massive deforestation by Badaga cultivators and Europeans planters followed after the 16th century AD. As a result, and in contrast with the western Nilgiris where the land cover mosaic has remained remarkably stable in the last 18 ka BP, the current landscape differs sharply from the land cover pattern detected by the soil record

    Straight versus S-shaped sternotomy: a histologic study in the sheep model

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    INTRODUCTION: Straight sternotomy is the most common access for open heart surgery. Techniques have been proposed for maximizing sternal stability in high-risk patients. This trend implies a growing need for newer surgical techniques. The aim of this experimental study in the sheep model is to evaluate median vs. S shaped sternotomy the feasibility of using a special device to accelerate the sternal instability and bone healing. MATERIALS AND METHODS: We enrolled 31 sheep, weighing 18–30 kg. For all animals a midline skin incision was made. In group I (n = 16 animals), straight median sternotomy and in group II (n = 15 animals), S-shaped incision was marked on the periosteum of the sternum by new created device for standard S-shaped sternotomy. Sternum biopsies were performed on second surgery month for all survived animals from the sternum and the surrounding soft tissue. RESULTS: No early superficial wound complications were observed. Overall mortality in the initial approach group was 19.3% (6 sheep). In group I; 3 sheep had died on first surgery day, the reason may be hemorrhage and in group II; 3 sheep developed intractable VF during surgery procedure or immediately afterwards so died. There were statistically significant differences in the scores of bone healing between group 1 and group 2 (4.2 vs.7.3, ANOVA, p < 0.001). DISCUSSION: Our work is based on the use of a standard S-shaped sternotomy procedure on sheep sternum. In our experience with the sternal healing in the sheep model, the process of new bone formation was accelerated with S- shaped cut than straight sternotomy procedure. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13019-014-0173-x) contains supplementary material, which is available to authorized users

    Network Simplification: The Gaussian diamond network with multiple antennas

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    We consider the N-relay Gaussian diamond network when the source and the destination have n(s) >= 2 and n(d) >= 2 antennas respectively. We show that when n(s) = n(d) = 2 and when the individual MISO channels from the source to each relay and the SIMO channels from each relay to the destination have the same capacity, there exists a two relay sub-network that achieves approximately all the capacity of the network. To prove this result, we establish a simple relation between the joint entropies of three Gaussian random variables, which is not implied by standard Shannon-type entropy inequalities.(1

    Automation of flexible handling of hot forged Tailored Forming components

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    Universalgreifer sind flexibel einsetzbar und können sich an verschiedene Situationen und Objekte anpassen. Aktuelle formvariable Universalgreifer bestehen überwiegend aus monolithischen polymeren Werkstoffen, deren maximale Einsatztemperaturen bei 300 °C liegen. Somit kann von der Formflexibilität nicht in Bereich profitiert werden in denen höhere Temperaturen vorherrschen und die zu handhabenden Objekte Umformungsprozesse durchschreiten. Solch ein Bereich ist der Schmiedesektor, bei dem die Objekte Temperaturen von bis zu 1250 °C erreichen. Die vorliegende Diskrepanz zwischen der Formvariabilität der Greifer und den Prozesstemperaturen im Schmiedesektor versuchen wir zu schließen. In dieser Arbeit stellen wir das von uns entwickelte Konzept eines formvariablen hochtemperaturbeständigem Handhabungssystem und deren praktische Umsetzung vor, sowie die noch zu lösenden Herausforderungen.Universal grippers are flexible and can adapt to different situations and objects. The shape variability has limitations, for example, the temperature. For manufacturing such shape variable grippers, elastic polymer materials are used. The material has an upper limit of the operating temperature of 300 °C. In the forging sector, the manufactured object change their geometry during the process and reaches temperature up 1250 °C. Here, we see the potential of the utilization of shape variable grippers. Therefore, we developed a system that overcomes the gap between the temperature limitation of current shape variable grippers and the high temperature in forging environments. This paper presents our gripper and the task to be solved in future works

    The Basilicata Wealth Fund: Resource Policy and Long-Run Economic Development in Southern Italy

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    This paper contributes to the growing political economy literature of within-country natural resources management, by proposing a new resource policy for the oil-rich southern Italian region of Basilicata. The policy proposal is to establish a (regional) wealth fund in which all the royalty revenues from non-renewable natural resource exploitation in Basilicata would be stored and fully converted into low-risk financial assets. The scope is to give priority to long-run investments as to better exploit revenues from large-scale extraction of natural capital. Establishing a wealth fund at the regional sub-national level is a novel approach that can be applied to other resource-rich regions in the world. I label the fund as the Basilicata Wealth Fund (BWF). The BWF would be a regionally owned investment fund, however independently administered from national authorities (for instance, as an independent legal entity under the jurisdiction of the Bank of Italy). In addition, the paper posits a transparent and clear-cut spending fiscal rule in order to let regional authorities use the resource revenues to finance economic policy. The clear advantage from the BWF would be the stronger focus on long-run economic development and the higher accountability, hence avoiding misuse of resource revenues for myopic fiscal spending
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