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  • Other Sources  (7)
  • 2020-2024  (1)
  • 2000-2004  (4)
  • 1990-1994  (2)
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  • 1
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    CCKT Calculation of e-H Total Cross Sections (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: We are in the process of carrying out calculations of e-H total cross sections using the 'complex-correlation Kohn-T' (CCKT) method. In a later paper, we described the methodology more completely, but confined calculations to the elastic scattering region, with definitive, precision results for S-wave phase shifts. Here we extend the calculations to the (low) continuum (1 much less than k(exp 2) much less than 3) using a Green's function formulation. This avoids having to solve integro-differential equations; rather we evaluate indefinite integrals involving appropriate Green's functions and the (complex) optical potential to find the scattering function u(r). From the asymptotic form of u(r) we extract a T(sub L) which is a complex number. From T(sub L), elastic sigma(sub L)(elastic) = 4pi(2L+1)((absolute value of T(sub L))(exp 2)), and total sigma (sub L)(total) = 4pi/k(2L+1)Im(T(sub L)) cross sections follow.
    Keywords: Optics
    Type: Division of Atomic, Molecular and Optical Physics Meeting of the American Physical Society; May 28, 2002 - Jun 02, 2002; Williamsburg, VA; United States
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    NASA TECHNICAL REPORTS
  • 2
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    Ab initio method for calculating total cross sections (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: A method for calculating total cross sections without formally including nonelastic channels is presented. The idea is to use a one channel T-matrix variational principle with a complex correlation function. The derived T matrix is therefore not unitary. Elastic scattering is calculated from T-parallel-squared, but total scattering is derived from the imaginary part of T using the optical theorem. The method is applied to the spherically symmetric model of electron-hydrogen scattering. No spurious structure arises; results for sigma(el) and sigma(total) are in excellent agreement with calculations of Callaway and Oza (1984). The method has wide potential applicability.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review Letters (ISSN 0031-9007); 70; 13; p. 1936-1939.
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    NASA TECHNICAL REPORTS
  • 3
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    CO2 partial pressure in Northeast Atlantic and adjacent shelf waters: Processes and seasonal variability (1992)
    Elsevier
    In:  Journal of Marine Systems, 3 (6). pp. 453-463.
    Details
    Publication Date: 2018-03-15
    Description: CO2 partial pressure in surface water was measured in the Northeast Atlantic and in the Hebride Shelf/North Sea area during a cruise with R.V. Poseidon in June 1991. A mean pCO2 of 303 μatm was found in the Atlantic between 50°N and 60°N. For an atmospheric CO2 content of 357.5 ppm(v) this corresponds to a partial pressure difference of −55 μatm. This supports the view that the subarctic Atlantic is a significant sink within the CO2 cycle between the ocean and the atmosphere. A comparison of our measurements with other data reveals that the pCO2 distribution changes significantly during May/June. This explained by seasonal warming, CO2 exchange with the atmosphere and biomass production. The contribution by each of these processes to the seasonal variations is calculated. It was found that during a plankton bloom the production of biomass is the dominating factor and may lower seawater pCO2 by almost 100 μatm. The shelf areas are charactrized by strong pCO2 gradients which are explained by water exchange with the Atlantic, temperature effects and biomass production.
    Type: Article , PeerReviewed
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    PAPER (OCEANREP)
  • 4
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    Comparison of two methods to determine the oceans uptake of anthropogenic carbon (2004)
    In:  [Talk] In: EGU General Assembly 2004, 25.-30.04.2004, Nice, France .
    Details
    Publication Date: 2012-06-04
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 5
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    Global impact of the Panamanian Seaway (2004)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 85 (49). pp. 526-527.
    Details
    Publication Date: 2019-09-23
    Type: Article , NonPeerReviewed
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  • 6
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    Effects of depth and CO2-dependent C:N ratios of POM on the marine carbon cycle (2003)
    In:  [Poster] In: EGS-AGU-EUG Joint Assembly 2003, 06.-11.04.2003, Nice, France .
    Details
    Publication Date: 2019-08-09
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 7
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    Interpreting Climate Images on the Internet: Mixing Algorithmic and Interpretive Views to Enable an Intercultural Comparison (ANCI) (2023)
    In:  Mixing Methods: Practical Insights from the Humanities in the Digital Age | Digital Humanities Research
    Details
    Publication Date: 2023-12-07
    Description: Countless climate images are in circulation on the internet, such as burning globes, polar bears and photos of global climate impacts. These images are networked and generate a specific view of climate change. Our case study engages in an intercultural image comparison based on Google Image queries. As an interdisciplinary team of experts drawn from art his- tory, media studies, interface design and computer graphics, our goal was to use a combination of qualitative and quantitative image analyses to explore the predominant discourses of digi- tised visual climate communication on the web. To this end, we automated the analysis of dif- ferent formal features of climate images (such as colour values, density and composition) with the aid of computer-driven methods (such as computer vision and machine learning) to build a corpus of thousands of images. Our focus was on image similarities, a concept shared by both image theory and computer analysis. In this chapter, we elucidate the outcome of our research on a conceptual and technical basis. The core issue addressed here is the manner in which art- historical methods (such as iconography and the concept of visual framing) are transformed when using computer-generated methods of computer vision and machine learning to anal- yse image similarities. This chapter focuses on our various insights while also reflecting on the general question of networked images on a methodological level. Ultimately, we were able to identify the promising potential but also the key limits of algorithmic image recognition and sorting when using machine learning to study images on the internet.
    Language: English
    Type: info:eu-repo/semantics/bookPart
    Format: application/pdf
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