GLORIA

GEOMAR Library Ocean Research Information Access

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Document type
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 351 (1995), S. 489-492 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract One- and two-colour photoionisation spectra for NO2 have been investigated using a time of flight mass spectrometer as detector to find the most efficient REMPI process for analytical applications. Two different inlet systems have been employed: a pulsed supersonic jet expansion stage and a flow reactor. Selective and sensitive mass spectrometric determinations of free NO2 have been possible even in the presence of high concentrations of organic nitrates, HNO3 and other NO2 precursors. Employing two-colour (1+1′+1) excitation using a concentration of HNO3≤5·1014 molecules/cm3 a detection limit of 5·1011 molecules/cm3 has been found for NO2 whereas in the absence of HNO3 a detection limit of 5·1010 molecules/cm3 is reported.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2023-11-03
    Description: Methods and results for parameter optimization and uncertainty analysis for a one-dimensional marine biogeochemical model of NPZD type are presented. The model, developed by Schartau and Oschlies, simulates the distribution of nitrogen, phytoplankton, zooplankton and detritus in a water column and is driven by ocean circulation data. Our aim is to identify parameters and fit the model output to given observational data. For this model, it has been shown that a satisfactory fit could not be obtained, and that parameters with comparable fits can vary significantly. Since these results were obtained by evolutionary algorithms (EA), we used a wider range of optimization methods: A special type of EA (called quantum-EA) with coordinate line search and a quasi-Newton SQP method, where exact gradients were generated by Automatic/Algorithmic Differentiation. Both methods are parallelized and can be viewed as instances of a hybrid, mixed evolutionary and deterministic optimization algorithm that we present in detail. This algorithm provides a flexible and robust tool for parameter identification and model validation. We show how the obtained parameters depend on data sparsity and given data error. We present an uncertainty analysis of the optimized parameters w.r.t. Gaussian perturbed data. We show that the model is well suited for parameter identification if the data are attainable. On the other hand, the result that it cannot be fitted to the real observational data without extension or modification, is confirmed. (C) 2010 Elsevier Ltd. All rights reserved.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2023-11-03
    Description: Frequency-selective, linear FIR filters are considered, as single systems and with analysis-synthesis filter banks. They are usually designed, in the single-channel case, to fulfill tolerances in the Chebychev sense, or in near-perfect-reconstruction filter banks, to minimize a reconstruction-error measure. If hardware is limited, fixed-point coefficient quantization is needed. It causes, in general, tolerance violations or a larger reconstruction error. Discrete re-optimization may help. A recent technique, able to handle also large filter orders, is sucessfully applied and newly extended to filter banks. Even better are randomized strategies, introduced and examined in the mathematical-optimization community over past 15 years; especially, randomized rounding is very effective. Thereby, good results are found for both single-system and filter-bank designs. We further introduce a new random sub-set selection within th above re-optimization. Like randomized rounding, it allows a trade-off between computational effort and solution quality. Clear improvements over deterministic heuristics are obtained by both randomized algorithms.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...