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  • Articles  (12)
  • Geography  (9)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (3)
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  • Articles  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Couette- und Poiseuilleströmung einer Flüssigkeit mit zwei Zähigkeitsbereichen (1966)
    Springer
    Archive of applied mechanics 35 (1966), S. 43-53 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary In Couette's as well as in Poiseuille's experiments (circular flow between two coaxial cylinders and linear flow in pipes respectively) only two symmetrical components of the stress tensor T and of the rate of strain tensor V are different from zero if for the medium considered V is a quasi-linear function of T. In this report it is in particular assumed, that the constitutive equation T = T(V) consists of two linear relations which join continuously without a jump at a “yield limit”. Furthermore four limiting types of media are considered, among them the viscoplastic fluid and the so called dilatant fluid. “With these media the above flows and the temperature distributions are investigated, using specified boundary conditions.
    Notes: Übersicht Sowohl bei dem Versuch von Couette (Kreisströmung zwischen zwei koaxialen Zylindern) als auch bei dem von Poiseuille (lineare Rohrströmung) treten bei Körpern mit quasilinearer Stoffgleichung nur je zwei — symmetrische — Komponenten T bzw. V des Spannungs- bzw. des Verformungsgeschwindigkeits-tensors auf. Speziell wird hier angenommen, daß die Stoffgleichung T(V) aus zwei linearen Beziehungen besteht, die an einer „Fließgrenze” ohne Sprung ineinander übergehen. Außerdem werden vier Grenzfälle, darunter der zähplastische und der sog. dilatante Körper, betrachtet. Mit diesen Flüssigkeiten werden die obengenannten Strömungen und die dazu gehörigen Temperaturverteilungen unter bestimmten Randbedingungen behandelt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00532057
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Evaluation of Surface Preparation Techniques, SFG: Swing Frame Grinding and LPG: Low-Temperature Precision Grinding, by Comparison of Results on Alumnia and Silicon Carbide Model Materials (2002)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 223 (Feb. 2002), p. 139-148 
    Details
    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
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/46/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.223.139.pdf
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    On the wedge/notch eigenvalues (1987)
    Springer
    International journal of fracture 33 (1987), S. 61-71 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé On étudie en détail les eigenvalues correspondant à l'eigensolution du problème d'un coin de longueur infinie, ou d'une entaille de même nature, pour un matériau à caractéristiques linéaires et élastiques, dont les surfaces latérales sont libres de contraintes.
    Notes: Abstract The eigenvalues corresponding to the eigensolution of the problem of an infinite wedge of, or notch into, linear elastic material with side surfaces free of tractions are studied in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034899
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    Paper (German National Licenses)
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  • 4
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    Can we extend local sea-ice measurements to satellite scale? An example from the N-ICE2015 expedition (2017)
    Cambridge University Press
    Details
    Publication Date: 2017
    Description: 〈div data-abstract-type="normal"〉〈p〉Knowledge of Arctic sea-ice conditions is of great interest for Arctic residents, as well as for commercial usage, and to study the effects of climate change. Information gained from analysis of satellite data contributes to this understanding. In the course of using in situ data in combination with remotely sensed data, the question of how representative local scale measurements are of a wider region may arise. We compare in situ total sea-ice thickness measurements from the Norwegian young sea ICE expedition in the area north of Svalbard with airborne-derived total sea-ice thickness from electromagnetic soundings. A segmented and classified synthetic aperture radar (SAR) quad-pol ALOS-2 Palsar-2 satellite scene was grouped into three simplified ice classes. The area fractions of the three classes are: 11.2% ‘thin’, 74.4% ‘level’, and 14.4% ‘deformed’. The area fractions of the simplified classes from ground- and helicopter-based measurements are comparable with those achieved from the SAR data. Thus, this study shows that there is potential for a stepwise upscaling from in situ, to airborne, to satellite data, which allow us to assess whether in situ data collected are representative of a wider region as observed by satellites.〈/p〉〈/div〉
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press
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  • 5
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    Does Your Lab Use Social Media?: Sharing Three Years of Experience in Science Communication (2018)
    American Meteorological Society
    Details
    Publication Date: 2018-06-01
    Description: Effective science communication is essential to share knowledge and recruit the next generation of researchers. Science communication to the general public can, however, be hampered by limited resources and a lack of incentives in the academic environment. Various social media platforms have recently emerged, providing free and simple science communication tools to reach the public and young people especially, an audience often missed by more conventional outreach initiatives. While individual researchers and large institutions are present on social media, smaller research groups are underrepresented. As a small group of oceanographers, sea ice scientists, and atmospheric scientists at the Norwegian Polar Institute, we share our experience establishing, developing, and maintaining a successful Arctic science communication initiative (@oceanseaicenpi) on Instagram, Twitter, and Facebook. The initiative is run entirely by a team of researchers with limited time and financial resources. It has built a broad audience of more than 7,000 followers, half of which is associated with the team’s Instagram account. To our knowledge, @oceanseaicenpi is one of the most successful Earth sciences Instagram accounts managed by researchers. The initiative has boosted the alternative metric scores of our publications and helped participating researchers become better writers and communicators. We hope to inspire and help other research groups by providing some guidelines on how to develop and conduct effective science communication via social media.
    Print ISSN: 0003-0007
    Electronic ISSN: 1520-0477
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 6
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    Can we extend local sea-ice measurements to satellite scale? An example from the N-ICE2015 expedition (2017)
    Cambridge University Press
    Details
    Publication Date: 2017-12-17
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 7
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    From a bipartite Gondwanan shelf to an arcuate Variscan belt: The early Paleozoic evolution of northern Peri-Gondwana (2019)
    Elsevier
    Details
    Publication Date: 2019-05-01
    Print ISSN: 0012-8252
    Electronic ISSN: 1872-6828
    Topics: Geography , Geosciences
    Published by Elsevier
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  • 8
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    The impact of melt ponds on summertime microwave brightness temperatures and sea-ice concentrations (2016)
    Copernicus
    Details
    Publication Date: 2016-09-26
    Description: Sea-ice concentrations derived from satellite microwave brightness temperatures are less accurate during summer. In the Arctic Ocean the lack of accuracy is primarily caused by melt ponds, but also by changes in the properties of snow and the sea-ice surface itself. We investigate the sensitivity of eight sea-ice concentration retrieval algorithms to melt ponds by comparing sea-ice concentration with the melt-pond fraction. We derive gridded daily sea-ice concentrations from microwave brightness temperatures of summer 2009. We derive the daily fraction of melt ponds, open water between ice floes, and the ice-surface fraction from contemporary Moderate Resolution Spectroradiometer (MODIS) reflectance data. We only use grid cells where the MODIS sea-ice concentration, which is the melt-pond fraction plus the ice-surface fraction, exceeds 90 %. For one group of algorithms, e.g., Bristol and Comiso bootstrap frequency mode (Bootstrap_f), sea-ice concentrations are linearly related to the MODIS melt-pond fraction quite clearly after June. For other algorithms, e.g., Near90GHz and Comiso bootstrap polarization mode (Bootstrap_p), this relationship is weaker and develops later in summer. We attribute the variation of the sensitivity to the melt-pond fraction across the algorithms to a different sensitivity of the brightness temperatures to snow-property variations. We find an underestimation of the sea-ice concentration by between 14 % (Bootstrap_f) and 26 % (Bootstrap_p) for 100 % sea ice with a melt-pond fraction of 40 %. The underestimation reduces to 0 % for a melt-pond fraction of 20 %. In presence of real open water between ice floes, the sea-ice concentration is overestimated by between 26 % (Bootstrap_f) and 14 % (Bootstrap_p) at 60 % sea-ice concentration and by 20 % across all algorithms at 80 % sea-ice concentration. None of the algorithms investigated performs best based on our investigation of data from summer 2009. We suggest that those algorithms which are more sensitive to melt ponds could be optimized more easily because the influence of unknown snow and sea-ice surface property variations is less pronounced.
    Print ISSN: 1994-0416
    Electronic ISSN: 1994-0424
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    Melt ponds on Arctic sea ice determined from MODIS satellite data using an artificial neural network (2011)
    Copernicus
    Details
    Publication Date: 2011-10-27
    Description: Melt ponds on sea ice strongly reduce the surface albedo and accelerate the decay of Arctic sea ice. Due to different spectral properties of snow, ice, and water, the fractional coverage of these distinct surface types can be derived from multispectral sensors like MODIS using a spectral unmixing algorithm. The unmixing was implemented using a multilayer perceptron (MLP) to reduce computational costs. Arctic-wide melt pond fractions and sea ice concentrations are derived from the level 3 MODIS surface reflectance product. The validation of the MODIS melt pond data set was conducted with aerial photos from the MELTEX campaign 2008 in the Beaufort Sea, data sets from the National Snow and Ice Data Center (NSIDC) for 2000 and 2001 from four sites spread over the entire Arctic, and with ship observations from the trans-Arctic HOTRAX cruise in 2005. The root-mean-square errors (RMSE) range from 3.8 % for the comparison with HOTRAX data, over 10.7 % for the comparison with NSIDC data, to 10.3 % and 11.4 % for the comparison with MELTEX data, with correlations coefficients ranging from R2 = 0.28 to R2 = 0.45. The mean annual cycle of the melt pond fraction for the entire Arctic shows a strong increase in June, reaching a maximum of 15 % by the end of June. The zonal mean of melt pond fractions indicates a dependence of the temporal development of melt ponds from the geographical latitude, and has its maximum in mid-July in latitudes between 80° and 88° N. Furthermore, the MODIS results are used to estimate the influence of melt ponds on retrievals of sea ice concentrations from passive microwave data. Results from a case study comparing sea ice concentrations from ASI-, NASA Team 2-, and Bootstrap-algorithms with MODIS sea ice concentrations indicate an underestimation of around 40 % for sea ice concentrations retrieved with microwave algorithms.
    Print ISSN: 1994-0432
    Electronic ISSN: 1994-0440
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Melt ponds on Arctic sea ice determined from MODIS satellite data using an artificial neural network (2012)
    Copernicus
    Details
    Publication Date: 2012-04-03
    Description: Melt ponds on sea ice strongly reduce the surface albedo and accelerate the decay of Arctic sea ice. Due to different spectral properties of snow, ice, and water, the fractional coverage of these distinct surface types can be derived from multispectral sensors like the Moderate Resolution Image Spectroradiometer (MODIS) using a spectral unmixing algorithm. The unmixing was implemented using a multilayer perceptron to reduce computational costs. Arctic-wide melt pond fractions and sea ice concentrations are derived from the level 3 MODIS surface reflectance product. The validation of the MODIS melt pond data set was conducted with aerial photos from the MELTEX campaign 2008 in the Beaufort Sea, data sets from the National Snow and Ice Data Center (NSIDC) for 2000 and 2001 from four sites spread over the entire Arctic, and with ship observations from the trans-Arctic HOTRAX cruise in 2005. The root-mean-square errors range from 3.8 % for the comparison with HOTRAX data, over 10.7 % for the comparison with NSIDC data, to 10.3 % and 11.4 % for the comparison with MELTEX data, with coefficient of determination ranging from R2=0.28 to R2=0.45. The mean annual cycle of the melt pond fraction per grid cell for the entire Arctic shows a strong increase in June, reaching a maximum of 15 % by the end of June. The zonal mean of melt pond fractions indicates a dependence of the temporal development of melt ponds on the geographical latitude, and has its maximum in mid-July at latitudes between 80° and 88° N. Furthermore, the MODIS results are used to estimate the influence of melt ponds on retrievals of sea ice concentrations from passive microwave data. Results from a case study comparing sea ice concentrations from ARTIST Sea Ice-, NASA Team 2-, and Bootstrap-algorithms with MODIS sea ice concentrations indicate an underestimation of around 40 % for sea ice concentrations retrieved with microwave algorithms.
    Print ISSN: 1994-0416
    Electronic ISSN: 1994-0424
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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