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The Experts below are selected from a list of 7680 Experts worldwide ranked by ideXlab platform

Katherine Taddeo - One of the best experts on this subject based on the ideXlab platform.

Andrea Zanini - One of the best experts on this subject based on the ideXlab platform.

  • Joint identification of contaminant source and aquifer geometry in a Sandbox experiment with the restart ensemble Kalman filter
    Journal of Hydrology, 2018
    Co-Authors: Zi Chen, J. Jaime Gómez-hernández, Teng Xu, Andrea Zanini
    Abstract:

    Abstract Contaminant source identification is a key problem in handling groundwater pollution events. The ensemble Kalman filter (EnKF) is used for the spatiotemporal identification of a point contaminant source in a Sandbox experiment, together with the identification of the position and length of a vertical plate inserted in the Sandbox that modifies the geometry of the system. For the identification of the different parameters, observations in time of solute concentration are used, but not of piezometric head data since they were not available. A restart version of the EnKF is utilized because it is necessary to restart the forecast from time zero after each parameter update. The results show that the restart EnKF is capable of identifying both contaminant source information and aquifer-geometry-related parameters together with an uncertainty estimate of such identification.

Eriola Betiku - One of the best experts on this subject based on the ideXlab platform.

  • clean Sandbox hura crepitans oil methyl esters synthesis a kinetic and thermodynamic study through ph monitoring approach
    Renewable Energy, 2020
    Co-Authors: Jennifer Chinazor Oraegbunam, Babatunde Oladipo, Olayomi A Falowo, Eriola Betiku
    Abstract:

    Abstract In this study, oil was extracted from underutilized Sandbox seeds and converted into biodiesel via transesterification process using KOH as a base catalyst. The impact and optimum values of the essential process variables (methanol-to-Sandbox seed oil (SSO) ratio, KOH loading, reaction temperature and reaction time) on the Sandbox oil methyl esters (SBOME) yield were established via Taguchi orthogonal array design method. Kinetic modeling of the transesterification process was carried out by monitoring the pH of the reaction. Maximum SBOME yield of 97.10 ± 0.03 wt% could be achieved under optimal condition of methanol-to-SSO molar ratio of 6:1, KOH loading of 0.5 wt%, reaction temperature of 35 °C and reaction time of 25 min. The kinetics of the process followed a unimolecular pseudo-second order rate law with reaction rate of 0.0016 L/mol.min at 35 °C. The activation energy and frequency factor of the reaction were calculated to be 11.40 kJ/mol and 0.1362 L/mol.s, respectively. The ΔH‡, ΔS‡ and ΔG‡ for the process were determined as 8.76 kJ/mol, – 0.270 kJ/mol.K and 92.02 kJ/mol, respectively. The quality of the SBOME demonstrates that it could serve as a replacement for diesel as its properties complied with standard specifications for biodiesel. The kinetic data obtained in this study could be used in reactor design for the process.

Zi Chen - One of the best experts on this subject based on the ideXlab platform.

  • Joint identification of contaminant source and non-Guassian conductivities via the restart normal-score Ensemble Kalman filter
    UPV, 2019
    Co-Authors: Zi Chen, Jaime Gómez-hernández J., Xu Teng, Zanini Andrea
    Abstract:

    The normal-score ensemble Kalman filter (NS-EnKF) has been proven to work well for the identification of a contaminant source in an aquifer together with the estimation of the spatial variability of hydraulic conductivity, even for highly heterogeneous, non-Gaussian conductivity distributions, in synthetic aquifers. In this work, the NS-EnKF is tested with real data coming from a Sandbox experiment with a binary spatial distribution of conductivities. The Sandbox contains patches of high conductivity mixed with patches of low conductivity. The main difference with the synthetic cases in which the technique had been tested previously is that no piezometric head data are available, and therefore, an important amount of information regarding the spatial distribution of conductivities will be missing. After some preliminary tests, it was found that for the filter to meet the goal of jointly identifying the contaminant source parameters and the non-Gaussian conductivities, it was needed to use a large number of members in the ensemble or with inflation techniques to prevent filter inbreeding. The best results were obtained with a large ensemble size or with the Bauser’s inflation method. The results show the ability of the NS-EnKF method to jointly identify contaminant source and conductivities in a Sandbox experiment

  • Joint identification of contaminant source and aquifer geometry in a Sandbox experiment with the restart ensemble Kalman filter
    Journal of Hydrology, 2018
    Co-Authors: Zi Chen, J. Jaime Gómez-hernández, Teng Xu, Andrea Zanini
    Abstract:

    Abstract Contaminant source identification is a key problem in handling groundwater pollution events. The ensemble Kalman filter (EnKF) is used for the spatiotemporal identification of a point contaminant source in a Sandbox experiment, together with the identification of the position and length of a vertical plate inserted in the Sandbox that modifies the geometry of the system. For the identification of the different parameters, observations in time of solute concentration are used, but not of piezometric head data since they were not available. A restart version of the EnKF is utilized because it is necessary to restart the forecast from time zero after each parameter update. The results show that the restart EnKF is capable of identifying both contaminant source information and aquifer-geometry-related parameters together with an uncertainty estimate of such identification.

Onno Oncken - One of the best experts on this subject based on the ideXlab platform.

  • Sandbox rheometry co evolution of stress and strain in riedel and critical wedge experiments
    Tectonophysics, 2018
    Co-Authors: Malte C Ritter, Tasca Santimano, Matthias Rosenau, Karen Leever, Onno Oncken
    Abstract:

    Abstract Analogue Sandbox experiments have been used for a long time to understand tectonic processes, because they facilitate detailed measurements of deformation at a spatio-temporal resolution unachievable from natural data. Despite this long history, force measurements to further characterise the mechanical evolution in analogue Sandbox experiments have only emerged recently. Combined continuous measurements of forces and deformation in such experiments, an approach here referred to as “Sandbox rheometry”, are a new tool that may help to better understand work budgets and force balances for tectonic systems and to derive constitutive laws for regional scale deformation. In this article we present an experimental device that facilitates precise measurements of boundary forces and surface deformation at high temporal and spatial resolution. We demonstrate its capabilities in two classical experiments: one of strike-slip deformation (the Riedel set-up) and one of compressional accretionary deformation (the Critical Wedge set-up). In these we are able to directly observe a correlation between strain weakening and strain localisation that had previously only been inferred, namely the coincidence of the maximum localisation rate with the onset of weakening. Additionally, we observe in the compressional experiment a hysteresis of localisation with respect to the mechanical evolution that reflects the internal structural complexity of an accretionary wedge.

  • seismic imaging of Sandbox experiments laboratory hardware setup and first reflection seismic sections
    Solid Earth, 2013
    Co-Authors: Charlotte M Krawczyk, M L Buddensiek, Onno Oncken, Nina Kukowski
    Abstract:

    Abstract. With the study and technical development introduced here, we combine analogue Sandbox simulation techniques with seismic physical modelling of Sandbox models. For that purpose, we designed and developed a new mini-seismic facility for laboratory use, comprising a seismic tank, a PC-driven control unit, a positioning system, and piezoelectric transducers used here for the first time in an array mode. To assess the possibilities and limits of seismic imaging of small-scale structures in Sandbox models, different geometry setups were tested in the first 2-D experiments that also tested the proper functioning of the device and studied the seismo-elastic properties of the granular media used. Simple two-layer models of different materials and layer thicknesses as well as a more complex model comprising channels and shear zones were tested using different acquisition geometries and signal properties. We suggest using well sorted and well rounded grains with little surface roughness (glass beads). Source receiver-offsets less than 14 cm for imaging structures as small as 2.0–1.5 mm size have proven feasible. This is the best compromise between wide beam and high energy output, and is applicable with a consistent waveform. Resolution of the interfaces of layers of granular materials depends on the interface preparation rather than on the material itself. Flat grading of interfaces and powder coverage yields the clearest interface reflections. Finally, Sandbox seismic sections provide images of high quality showing constant thickness layers as well as predefined channel structures and indications of the fault traces from shear zones. Since these were artificially introduced in our test models, they can be regarded as zones of disturbance rather than tectonic shear zones characterized by decompaction. The multiple-offset surveying introduced here, improves the quality with respect to S / N ratio and source signature even more; the maximum depth penetration in glass-bead layers thereby amounts to 5 cm. Thus, the presented mini-seismic device is already able to resolve structures within simple models of saturated porous media, so that multiple-offset seismic imaging of shallow Sandbox models, that are structurally evolving, is generally feasible.

  • midget seismic in Sandbox models hardware setup and first data generation
    69th EAGE Conference and Exhibition incorporating SPE EUROPEC 2007, 2007
    Co-Authors: Charlotte M Krawczyk, M L Buddensiek, J Philipp, Nina Kukowski, Onno Oncken
    Abstract:

    E042 Midget Seismic in Sandbox Models – Hardware Setup and First Data Generation C.M. Krawczyk* (GFZ - GeoForschungsZentrum Potsdam) M.L. Buddensiek (GFZ Potsdam) J. Philipp (GMuG mbH) N. Kukowski (GFZ Potsdam) & O. Oncken (GFZ Potsdam) SUMMARY Analogue Sandbox simulation has been applied to study geological processes to provide qualitative and quantitative insights into specific geological problems. In nature the structures which are simulated in those Sandbox models are often inferred from seismic data. With the study introduced here we want to combine the analogue Sandbox simulation techniques with seismic physical modelling of the Sandbox models. The long-term objectives of

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