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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 6-8 (May 2005), p. 203-208 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Two new joining methods for sheet metal parts, dieless clinching and dielessrivet-clinching are introduced in this paper. With these methods all formable materials can be joined. Contrary to conventional technology in joining by forming these new methods are working with a flat anvil as a counter tool instead of a contoured die, which has a number of advantages. The process has become simpler, the process reliability is increased, misalignments of the joining tools don’t effect the quality of the connection anymore and even new applications, such as the joining of materials with a limited malleability become possible. Examples of realized connections and FE-calculations of the joining processes are presented
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 344 (July 2007), p. 693-698 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Joining by forming of magnesium alloys is restricted by the limited forming capability ofmagnesium at room temperature. For this reason heating of the parts to temperatures of 220 °C ormore is required to form connections without cracks. State-of-the-art joining by forming methods(such as clinching or self-pierce riveting) are usually working with a contoured die as a counter tool.Researches on these joining methods have shown that a minimum heating time of 3 to 6 seconds isneeded to achieve connections of acceptable quality. New joining by forming methods working witha flat anvil as counter tool make it possible to decrease the heating time considerably. In this papertwo methods – the dieless clinching and the dieless rivet-clinching – and their potential for thejoining of magnesium parts shall be introduced in detail. The results of extensive research on theinfluence between heating parameters and the formation of the connections as well as the results oftensile test done to characterize the strength of dieless joined connections are discussed
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 539-543 (Mar. 2007), p. 3949-3954 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Joining by forming of magnesium alloys is restricted by the limited forming capability ofmagnesium at room temperature. For this reason heating of the parts to temperatures of 220 °C ormore is required to form joints without cracks. State-of-the-art joining by forming methods (such asclinching or self-pierce riveting) are usually working with a contoured die as a counter tool.Researches on these joining methods have shown that a minimum heating time of 3 to 6 seconds isneeded to achieve joints of acceptable quality. In this paper two new clinching methods “dielessclinching” and “dieless rivet-clinching” shall be introduced. Both methods work with a flat anvil asa counter tool, thus offering important advantages for the application in joining of Mg/Mg, Al/Mgor Fe/Mg joints. In joining by forming with a flat counter tool the proportion of crack inducingtensile stresses in the bottom part during the joining process is very low. Moreover the heat transferbetween the heated anvil and the parts is comparatively fast. That makes it possible to decrease theheating time in joining by forming with a flat counter tool to only one second or less. The dielessclinching process was simulated using the Finite Elements Method (FEM) to analyze the influenceof geometrical parameters of the punch and the process parameter clamping force. Furthermore thelimitations of the new dieless joining method were investigated
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2017-06-14
    Description: Linear Pottery Culture (LBK) are investigated. These are interpreted as resulting from a combination of internal socio-economic processes as well as external environmental parameters. Resilience theory is helpful in understanding periods of increased vulnerability and inherent trends to social complexity. Cycles and threshold levels also help to understand why societies experience periods of increasing fragility and subsequent decline. Results are based on the correlation of a typology and dendrochronology-based archaeological chronology for western LBK and various palaeoclimatic proxy-data. The 14C-production curve is taken as an indicator for solar activity fluctuations, and an age model for laminated sediments as an indicator for rainfall fluctuations. We currently consider this correlation as agreeably robust; however future finedating may result in slight shifts within the archaeological chronology. According to the applied age model, the simple farming societies of the LBK (5600e4900 cal BC) in west-central Europe were not immediately and devastatingly affected by most climate fluctuations. Yet, they might have been one destabilising component within broader processes. However, periods of decreased or irregularly spaced rainfall are contemporaneous to periods of population decline, while periods of increased rainfall may have favoured population growth. Towards the end of the 6th millennium cal BC, the final years of LBK in western Central Europe are contemporaneous to a general trend to less rainfall punctuated by short-term increases in precipitation. During this climatically highly volatile period LBK reaches its highest population rates and at the same time experiences a period of warfare. Thereafter population rates decline and LBK gradually vanishes from the archaeological record, being replaced by Middle Neolithic societies.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 5
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    ZBW - Deutsche Zentralbibliothek für Wirtschaftswissenschaften, Leibniz-Informationszentrum Wirtschaft
    Publication Date: 2016-01-29
    Description: This paper explores the impacts of traditional agricultural insurance that offers protection against climatic shocks on small-scale tobacco farmers in Colombia after a period of substantial crop failures. Our identi cation strategy bene ts from a natural experimental setup of the form in which the insurance was launched. We fnd that tobacco producers with access to the insurance program were less likely to acquire informal loans, were less likely to use loans to repay debts, and had access to loans with lower interest rates and longer maturation periods. Moreover, access to this program was positively associated with increased savings and accumulation of liquid assets.
    Keywords: G22 ; O13 ; O12 ; ddc:330
    Repository Name: EconStor: OA server of the German National Library of Economics - Leibniz Information Centre for Economics
    Language: English
    Type: doc-type:conferenceObject
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  • 6
    Publication Date: 2017-01-27
    Description: The North Atlantic Oscillation is the dominant atmospheric pressure mode in the North Atlantic region and affects winter temperature and precipitation in the Mediterranean, northwest Europe, Greenland, and Asia1. The index1 that describes the sea-level pressure difference between Iceland and the Azores is correlated with a dipole precipitation pattern over northwest Europe and northwest Africa. How the North Atlantic Oscillation will develop as the Greenland ice sheet melts is unclear2. A potential past analogue is the early Holocene, during which melting ice sheets around the North Atlantic3, 4 freshened surface waters, affecting the strength of the meridional overturning circulation5. Here we present a Holocene rainfall record from northwest Africa based on speleothem δ18O and compare it against a speleothem-based rainfall record from Europe6. The two records are positively correlated during the early Holocene, followed by a shift to an anti-correlation, similar to the modern record, during the mid-Holocene. On the basis of our simulations with an Earth system model, we suggest the shift to the anti-correlation reflects a large-scale atmospheric and oceanic reorganization in response to the demise of the Laurentide ice sheet and a strong reduction of meltwater flux to the North Atlantic, pointing to a potential sensitivity of the North Atlantic Oscillation to the melting of ice sheets.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 7
  • 8
    Publication Date: 2017-06-10
    Description: Mittels kontinuierlicher und hochauflösender μXRF-Geochemieanalysen wird die Variabilität äolischer Sedimente der letzten 60.000 Jahre rekonstruiert. Dazu werden zwei Sedimentbohrkerne jeweils aus einem Maarsee und einem Trockenenmaar (Eifel, Deutschland) untersucht. Beide Kerne umfassen das letzte Glazial, einschließlich des MIS-3, des LGM und MIS-2, Transition I als auch das Holozän. Die energiedispersive RFA-Messungen der Eagle III μXRF wird direkt an Harz imprägnierten Proben angewendet. Diese sogenannten Tränklinge bilden die Grundlage für die Herstellung von petrographischen Dünnschliffen und somit können die Messergebnisse direkt mit einer Mikrofaziesanalyse verglichen werden. Anhand eines Sedimentkerns wird gezeigt, dass eine Quantifizierung der μXRF-Ergebnisse mittels der undamentalparametermethode geeignete ist. Eine Überprüfung der Ergebnisse findet dabei mit wellenlängen-dispersiven RFA-Messungen an diskreten Proben statt. Die Ergebnisse zeigen, dass sich jedes einzelne Maar in der lithologischen Zusammensetzung und damit auch geochemisch unterscheidet. Deshalb wird auf die grundlegenden Prozesse der Elementdeposition in die Seen eingegangen, die mit der Ablagerung von Sedimenten, der Variabilität der chemischen Verwitterung oder der Wasserzirkulation in Zusammenhang stehen. Mittels Hauptkomponentenanalysen standardisierter Variablen ist darüber hinaus die objektive Ableitung eines äolischen Sedimentsignals möglich. Es wird gezeigt, dass dieser Ansatz verlässliche Ergebnisse für alle untersuchten Zeitabschnitte liefert, solange für die Interpretation weitere Kenntnisse über die Lithologie und Paläoökologie zur Verfügung stehen. Das auffälligste Element zur Charakterisierung von Staub ist in beiden untersuchten Kernen Kalzium. Die höchsten Werte (〉5 Gew.-%) werden während vollglazialer Bedingungen erreicht. Kalzium hat einen wesentlichen Einfluss auf den Staubfaktor der Hauptkomponentenanalyse. Eine zusätzliche Kombination der Kalziumgehalte mit dem Staubfaktor der Hauptkomponentenanalyse sowie Grauwertmessungen verbessert den Nachweis äolischen Staubs in laminierten Seesedimenten zusätzlich. In beiden Kernen konnten Sedimente mit erhöhten Staubkonzentrationen geochemisch nachgewiesen werden: Während des MIS-3 sind das vor allem das größte Heinrich-Ereignis H4 sowie der Anstieg des atmosphärischen Staubgehalts während der Wiedervereisung der Inlandsgletscher. Weiterhin ist das gesamte MIS-2 einschließlich LGM und der Jüngeren Dryas von starker Staubdeposition charakterisiert. Eine erhöhte Staubkonzentration ist ebenfalls ab dem Subboreal nachgewiesen und wird als anthropogene Aktivität gedeutet.
    Description: research
    Keywords: VAR 000 ; Glazialgeologie ; geochemistry ; lacustrine sediment ; μXFR ; aeolian sediment ; last glacial cycle ; PCA
    Language: English
    Type: article , publishedVersion
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  • 9
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Thesis , NonPeerReviewed
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  • 10
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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