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Jesus Galvez - One of the best experts on this subject based on the ideXlab platform.

  • Filter Functions in pulse techniques: application to the study of a slow charge transfer reaction
    Journal of Electroanalytical Chemistry, 2004
    Co-Authors: Jesus Galvez
    Abstract:

    Abstract A first class Filter Function is a mode of pulse voltammetry that removes completely the current response for a reversible charge transfer reaction without modifying the corresponding signal for a slow charge transfer reaction. Therefore, the application of these modes permits study without interferences of the response for an irreversible electron transfer in those cases where reversible processes are also present. In the double potential step technique, the mode defined by the linear combination c 1 I 1  +  c 2 I 2 , with I k ( k  = 1,2) being the current response for the potential step k at the end of the corresponding pulse and where E 2 is set on the anodic diffusion current plateau, can be easily modulated as a first class Filter Function if the ratio of the coefficients c 1 / c 2 and the pulse durations are chosen appropriately. This polarization mode has interesting features that allow us to determine the kinetic parameters of the slow charge transfer reaction and, in addition, the curves obtained are well defined peak-shaped waves displaying zero baselines with the analytical advantages that this represents.

  • Filter Functions for reversible charge transfer reactions in pulse techniques
    Journal of Electroanalytical Chemistry, 2002
    Co-Authors: Jesus Galvez
    Abstract:

    Abstract A Filter Function is a mode of pulse voltammetry that removes completely the current response for a reversible charge transfer reaction for all values of potential or gives a constant response (≠0) for all values of E . These modes will be designated as Filter Functions of the first and second class, respectively. With both kinds of Functions it is a key condition to obtain the corresponding effect that the current is sampled at selected values of the pulse durations, i.e. if the times for the potential steps are chosen arbitrarily the Filtering effect is not observed. In turn, and because for a slow charge transfer reaction the current response with a first class Filter Function is not zero (nor constant when a second class Filter Function is applied), we have that the use of these modes of pulse voltammetry provides a way of obtaining without interferences the signal for an irreversible electron transfer in those cases where reversible processes are also present. Thus, if reversible and irreversible electron transfers with close discharge potentials occur simultaneously the response observed when a first class Filter Function is applied shows only the contribution due to the irreversible process while with a second class mode this last response is superimposed to the constant output obtained for the reversible process. In this paper the theory for these kinds of Filter Functions is established, particularly for double and triple pulse potential step techniques, and the characteristics of the responses obtained with some of these modes is discussed. Finally, the characteristics of the response obtained with Filter Functions at spherical electrodes are also shown.

Elisabeth Krause - One of the best experts on this subject based on the ideXlab platform.

  • Measuring cosmic shear with the ring statistics
    Astronomy and Astrophysics, 2010
    Co-Authors: Tim Eifler, Peter Schneider, Elisabeth Krause
    Abstract:

    Context. Commonly used methods of decomposing E- and B-modes in cosmic shear, namely the aperture mass dispersion and the E/B-mode shear correlation Function, suffer from incomplete knowledge of the two-point correlation Function (2PCF) on very small and/or very large scales. The ring statistics, the most recently developed cosmic shear measure, improves on this issue and is able to decompose E- and B-modes using a 2PCF measured on a finite interval. Aims. First, we improve on the ring statistics’ Filter Function over the signal-to-noise ratio (S/N). Second, we examine the ability of the ring statistics to constrain cosmology and compare the results to cosmological constraints obtained with the aperture mass dispersion. Third, we use the ring statistics to measure a cosmic shear signal from CFHTLS (Canada-France-Hawaii Telescope Legacy Survey) data. Methods. We consider a scale-dependent Filter Function for the ring statistics, which improves its S/N. To examine the information content of the ring statistics, we employed ray-tracing simulations and developed an expression of the ring statistics’ covariance in terms of a 2PCF covariance. We performed a likelihood analysis with simulated data for the ring statistics in the Ω_(m-σ8) parameter space and compared the information content of ring statistics and aperture mass dispersion. Regarding our third aim, we used the 2PCF of the latest CFHTLS analysis to calculate the ring statistics and its error bars. Results. Although the scale-dependent Filter Function improves the S/N of the ring statistics, the S/N of the aperture mass dispersion is higher. In addition, we show that Filter Functions exist that decompose E- and B-modes using a finite range of 2PCFs (EB-statistics) and have higher S/N than the ring statistics. However, we find that data points of the latter are significantly less correlated than data points of the aperture mass dispersion and the EB-statistics. As a consequence the ring statistics is an ideal tool for identifying remaining systematics accurately as a Function of angular scale. We use the ring statistics to measure a E- and B-mode shear signal from CFHTLS data.

Peter Schneider - One of the best experts on this subject based on the ideXlab platform.

  • An adapted Filter Function for density split statistics in weak lensing
    Astronomy & Astrophysics, 2020
    Co-Authors: Pierre Burger, Peter Schneider, Vasiliy Demchenko, Joachim Harnois-déraps, Catherine Heymans, Hendrik Hildebrandt, Sandra Unruh
    Abstract:

    Context. The density split statistics in weak gravitational lensing analyses probes the correlation between regions of different (foreground) galaxy number densities and their weak lensing signal, measured by the shape distortion of background galaxies. Aims. In this paper, we reconsider density split statistics, by constructing a new angular Filter Function that is adapted to the expected relation between galaxy number density and shear pattern, in a way that the Filter weighting the galaxy number density is matched to the Filter that is used to quantify the shear signal. Methods. We use the results of numerical ray-tracing simulations, specifically through Millennium Simulation supplemented by a galaxy distribution based on a semi-analytic model, to construct a matched pair of adapted Filter Functions for the galaxy density and the tangential shear signal. We compare the performance of our new Filter to the previously used top-hat Filter, applying both to a different and independent set of numerical simulations (SLICS, cosmo-SLICS). Results. We show that the adapted Filter yields a better correlation between the total matter and the galaxy distribution. Furthermore, the adapted Filter provides a larger signal-to-noise ratio to constrain the bias between the total matter and the galaxy distribution, and we show that it is, in general, a more sensitive discriminator between different cosmologies, with the exception of cosmologies with very large $\sigma_8$ values. All analyses lead to the conclusion that our adapted Filter should be favored in future density split statistic works.

  • Measuring cosmic shear with the ring statistics
    Astronomy and Astrophysics, 2010
    Co-Authors: Tim Eifler, Peter Schneider, Elisabeth Krause
    Abstract:

    Context. Commonly used methods of decomposing E- and B-modes in cosmic shear, namely the aperture mass dispersion and the E/B-mode shear correlation Function, suffer from incomplete knowledge of the two-point correlation Function (2PCF) on very small and/or very large scales. The ring statistics, the most recently developed cosmic shear measure, improves on this issue and is able to decompose E- and B-modes using a 2PCF measured on a finite interval. Aims. First, we improve on the ring statistics’ Filter Function over the signal-to-noise ratio (S/N). Second, we examine the ability of the ring statistics to constrain cosmology and compare the results to cosmological constraints obtained with the aperture mass dispersion. Third, we use the ring statistics to measure a cosmic shear signal from CFHTLS (Canada-France-Hawaii Telescope Legacy Survey) data. Methods. We consider a scale-dependent Filter Function for the ring statistics, which improves its S/N. To examine the information content of the ring statistics, we employed ray-tracing simulations and developed an expression of the ring statistics’ covariance in terms of a 2PCF covariance. We performed a likelihood analysis with simulated data for the ring statistics in the Ω_(m-σ8) parameter space and compared the information content of ring statistics and aperture mass dispersion. Regarding our third aim, we used the 2PCF of the latest CFHTLS analysis to calculate the ring statistics and its error bars. Results. Although the scale-dependent Filter Function improves the S/N of the ring statistics, the S/N of the aperture mass dispersion is higher. In addition, we show that Filter Functions exist that decompose E- and B-modes using a finite range of 2PCFs (EB-statistics) and have higher S/N than the ring statistics. However, we find that data points of the latter are significantly less correlated than data points of the aperture mass dispersion and the EB-statistics. As a consequence the ring statistics is an ideal tool for identifying remaining systematics accurately as a Function of angular scale. We use the ring statistics to measure a E- and B-mode shear signal from CFHTLS data.

Tim Eifler - One of the best experts on this subject based on the ideXlab platform.

  • Measuring cosmic shear with the ring statistics
    Astronomy and Astrophysics, 2010
    Co-Authors: Tim Eifler, Peter Schneider, Elisabeth Krause
    Abstract:

    Context. Commonly used methods of decomposing E- and B-modes in cosmic shear, namely the aperture mass dispersion and the E/B-mode shear correlation Function, suffer from incomplete knowledge of the two-point correlation Function (2PCF) on very small and/or very large scales. The ring statistics, the most recently developed cosmic shear measure, improves on this issue and is able to decompose E- and B-modes using a 2PCF measured on a finite interval. Aims. First, we improve on the ring statistics’ Filter Function over the signal-to-noise ratio (S/N). Second, we examine the ability of the ring statistics to constrain cosmology and compare the results to cosmological constraints obtained with the aperture mass dispersion. Third, we use the ring statistics to measure a cosmic shear signal from CFHTLS (Canada-France-Hawaii Telescope Legacy Survey) data. Methods. We consider a scale-dependent Filter Function for the ring statistics, which improves its S/N. To examine the information content of the ring statistics, we employed ray-tracing simulations and developed an expression of the ring statistics’ covariance in terms of a 2PCF covariance. We performed a likelihood analysis with simulated data for the ring statistics in the Ω_(m-σ8) parameter space and compared the information content of ring statistics and aperture mass dispersion. Regarding our third aim, we used the 2PCF of the latest CFHTLS analysis to calculate the ring statistics and its error bars. Results. Although the scale-dependent Filter Function improves the S/N of the ring statistics, the S/N of the aperture mass dispersion is higher. In addition, we show that Filter Functions exist that decompose E- and B-modes using a finite range of 2PCFs (EB-statistics) and have higher S/N than the ring statistics. However, we find that data points of the latter are significantly less correlated than data points of the aperture mass dispersion and the EB-statistics. As a consequence the ring statistics is an ideal tool for identifying remaining systematics accurately as a Function of angular scale. We use the ring statistics to measure a E- and B-mode shear signal from CFHTLS data.

Yun Kang Sui - One of the best experts on this subject based on the ideXlab platform.

  • The Impact of Filter Function on Structural Topology Optimization
    Applied Mechanics and Materials, 2014
    Co-Authors: Zhen Shang, Yun Kang Sui
    Abstract:

    Based on ICM method, topological optimization model is established to minimize the weight with different constraints. The model is solved by constraint integrated method. The impact of different Filter Functions on continuum structural topology optimization efficiency is studied by numerical examples. The results show that: The application of nonlinear Filter Function can speed up the convergence, reduce the number of iterations, get a good stability in the continuum structural topology optimization.

  • The invariant of the stiffness Filter Function with the weight Filter Function of the power Function form
    Acta Mechanica Sinica, 2012
    Co-Authors: Zhen Shang, Yun Kang Sui
    Abstract:

    Based on the independent, continuous and mapping (ICM) method and homogenization method, a research model is constructed to propose and deduce a theorem and corollary from the invariant between the weight Filter Function and the corresponding stiffness Filter Function of the form of power Function. The efficiency in searching for optimum solution will be raised via the choice of rational Filter Functions, so the above mentioned results are very important to the further study of structural topology optimization.

  • Research on Relationship between Weight Filter Function and Stiffness Filter Function
    Advanced Materials Research, 2011
    Co-Authors: Zhen Shang, Yun Kang Sui
    Abstract:

    Combined with the homogenization method and the least squares method, the Filter Function with the form of power Function is studied in the Independent Continuum Map (ICM) method. Then, the numerical simulation method is used to study the relationship between a weight Filter Function and a stiffness Filter Function. Finally, the impact of the filtration Function on the efficiency of topology optimization is showed by examples. It is important to further research structural topology optimization.