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  • 1
    Call number: ZSP-201-78/9
    In: CRREL Report, 78-9
    Description / Table of Contents: Large, simply supported beams of temperate lake ice were found, generally, to yield significantly higher flexural strengths than the same beams tested in the cantilever mode. Data support the view that a significant stress concentration may exist at the fixed corners of the cantilever beams. Maximum effects are experienced with beams of cold, brittle ice substantially free of structural imperfections; for this kind of ice the strength difference factor, here attributed to the effect of stress concentrations, may exceed 2.0; that is, simply supported beams test a factor of 2 or more stronger than the same beams tested in the cantilever mode. In ice that has undergone extensive thermal degradation, the stress concentration effect may be eliminated entirely. Simply supported beams generally yield higher strengths when the top surfaces are placed in tension. This behavior is attributed to differences in ice type; the fine-grained, crack-free top layer of snow-ice which constituted up to 50% of the ice cover in the current series of tests usually reacted more strongly in tension than the coarse-grained crack-prone bottom lake ice.
    Type of Medium: Series available for loan
    Pages: iv, 14 Seiten , Illustrationen
    Series Statement: CRREL Report 78-9
    Language: English
    Note: CONTENTS Abstract Preface Introduction Test sites and ice cover properties Beam testing Results Discussion Conclusions Literature cited
    Location: AWI Archive
    Branch Library: AWI Library
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  • 2
    Publication Date: 2023-06-08
    Description: The atmospheric general circulation diagnosed by the mass-weighted isentropic zonal mean exhibits extratropical direct (ETD) circulation driven by eddy momentum transport. Using a reanalysis dataset, we investigated regional atmospheric modulations associated with the year-to-year variability of ETD circulation in boreal winter. Composite analyses showed that the interannual variability of ETD circulation accompanies a seesaw-like variation between the Aleutian (AL) and Icelandic lows (IL), which coincides with the Pacific–North American teleconnection pattern and North Atlantic dipole anomaly. A diagnosis using isentropic airmass fluxes representing the geographical Lagrangian mean motion indicated that the significant intensification of upper-tropospheric poleward warm airflow over the eastern North Pacific is responsible for the enhanced ETD circulation, together with the intensified equatorward lower cold airflow over East Asia and eastern North America. The resultant enhanced upward propagation of the stationary planetary waves corresponds to the intensification of the divergence of the Eliassen-Palm flux, which explains the modulated ETD circulation in view of the balance between the Coriolis force and convergence of eddy momentum. These results suggest that the AL-IL seesaw is influential in the global general circulation variability in the Northern Hemisphere winter, and the anomalous ETD circulation interacts with several teleconnection patterns involving the modulation of planetary waves through anomalous meridional heat transport by the basin-wide scale eddies.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 3
    Publication Date: 2023-06-19
    Description: Phreatic eruption is hazardous phenomena ubiquitously observed in active volcanoes. The eruptions are sourced from solid (altered rock, and etc)-water system underground. It is surely that the expansion of water in the system drives the eruptions, however, evaluation of water content of the system has not been enough. The quantification of the water content is essential for understandings on the mechanism of the phreatic eruptions. Here we estimate the water content in solid-water system driving the phreatic eruptions, by combining the geological and geophysical approaches. We dealt with three phreatic eruptions (Feb 7-9, 2012; Feb 17-18, 2013; Apr 11, 2013) at Ioto volcano, Japan. The detailed geological survey gives eruptive volume of the three phreatic eruptions. On the other hand, the seismic and infrasound analyses give the total volume emitted (solid+liquid+gas) in the three eruptions. Subtracting the solid volume from the total volume provides a volume of water emitted. The water volume was converted to the mass by using ideal gas equation of state and temperature. Then, the mass fractions of water in the three phreatic eruptions were estimated to 16-33 wt.%. The result of our study shows that there are positive correlations among the masses of water and solid, and mass fraction of water. This fact suggests that large hydrothermal chamber which is generated by high water flux from deeper part fuels large scale phreatic eruption. The observation of hydrothermal chamber size and water flux from deeper part will be critical for prediction of volcanic hazard from phreatic eruptions.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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