Application of the modified image method to inversion of synthetic active electromagnetic bathymetric data

Geophysics ◽  
1987 ◽  
Vol 52 (6) ◽  
pp. 794-801 ◽  
Author(s):  
Clyde J. Bergeron ◽  
Juliette W. Ioup ◽  
Gus A. Michel
Keyword(s):  
Correction Factor ◽  
Image Plane ◽  
Skin Depth ◽  
Correction Function ◽  
Wave Form ◽  
Image Method ◽  
Correction Factors ◽  
Electromagnetic Data ◽  
Good Agreement ◽  
Electromagnetic Source

A modified image method is used to invert synthetic active electromagnetic data generated from shallow ocean models by means of the exact Sommerfeld theory. The modified image method offers approximate solutions to the Sommerfeld problem: the response of a layered structure of ohmic conductors to an active electromagnetic source. The image plane for the active electromagnetic source is assumed to be at a complex depth given by [Formula: see text], where [Formula: see text] is the skin depth of the first layer and [Formula: see text] is the multilayer correction factor. Two ad hoc correction factors have been introduced into the modified image method. They bring the image field [Formula: see text] of the single image at a complex depth into very good agreement with the secondary field [Formula: see text] of the exact Sommerfeld theory of a two‐layer bathymetric model. We demonstrate that these correction factors can be calculated from synthetic data. This allows for an accurate, algebraic, and fast inversion of active electromagnetic data in terms of the parameters of a two‐layer model: the conductivities of the sea and sea bottom, and the depth and ohmic skin depth of the sea. The β factor, which takes into account the departure of the primary active electromagnetic field from a plane wave form at the air‐sea interface, is incorporated into the complex two‐layer correction function [Formula: see text]. A rescaling factor F brings [Formula: see text] into good agreement with [Formula: see text] in the depth regime where the β correction factor is ineffective, i.e., where the first layer depth is greater than two skin depths.

scholarly journals Parameter extrapolation to ungauged basins with a hydrological distributed model in a regional framework

2009 ◽  
Vol 13 (2) ◽  
pp. 229-246 ◽  
Author(s):  
J. J. Vélez ◽  
M. Puricelli ◽  
F. López Unzu ◽  
F. Francés
Keyword(s):  
Correction Factor ◽  
Overland Flow ◽  
Scale Effects ◽  
Basque Country ◽  
Base Flow ◽  
Correction Function ◽  
Distributed Model ◽  
Correction Factors ◽  
Ungauged Basins ◽  
Shuffled Complex Evolution

Abstract. A Regional Water Resources study was performed at basins within and draining to the Basque Country Region (N of Spain), with a total area of approximately 8500 km2. The objective was to obtain daily and monthly long-term discharges in 567 points, most of them ungauged, with basin areas ranging from 0.25 to 1850 km2. In order to extrapolate the calibrations at gauged points to the ungauged ones, a distributed and conceptually based model called TETIS was used. In TETIS the runoff production is modelled using five linked tanks at the each cell with different outflow relationships at each tank, which represents the main hydrological processes as snowmelt, evapotranspiration, overland flow, interflow and base flow. The routing along the channels' network couples its geomorphologic characteristics with the kinematic wave approach. The parameter estimation methodology tries to distinguish between the effective parameter used in the model at the cell scale, and the watershed characteristic estimated from the available information, being the best estimation without losing its physical meaning. The relationship between them can be considered as a correction function or, in its simple form, a correction factor. The correction factor can take into account the model input errors, the temporal and spatial scale effects and the watershed characteristics. Therefore, it is reasonable to assume the correction factor is the same for each parameter to all cells within the watershed. This approach reduces drastically the number of parameter to be calibrated, because only the common correction factors are calibrated instead of parameter maps (number of parameters times the number of cells). In this way, the calibration can be performed using automatic methodologies. In this work, the Shuffled Complex Evolution – University of Arizona, SCE-UA algorithm was used. The available recent year's data was used to calibrate the model in 20 of the most representative flow gauge stations in 18 basins with a Nash-Sutcliffe index higher than 0.6 (10 higher than 0.8). The calibrated correction factors at each basin were similar but not equal. The validation process (in time and space) was performed using the remaining data in all flow gauge stations (62), with 42 basins with a Nash-Sutcliffe index higher than 0.5 (25 higher than 0.7). Deficient calibration and validations were always related with flow gauge stations very close to the karstic springs. These results confirmed that it was feasible and efficient to use the SCE-UA algorithm for the automatic calibration of distributed conceptual models and the calibrated model could be used at ungauged basins. Finally, meteorological information from the past 50 years at a daily scale was used to generate a daily discharges series at 567 selected points.

scholarly journals Parameter extrapolation to ungauged basins with a hydrological distributed model in a regional framework

2007 ◽  
Vol 4 (2) ◽  
pp. 909-956 ◽  
Author(s):  
J. J. Vélez ◽  
F. López Unzu ◽  
M. Puricelli ◽  
F. Francés
Keyword(s):  
Correction Factor ◽  
Scale Effects ◽  
Basque Country ◽  
Base Flow ◽  
Correction Function ◽  
Distributed Model ◽  
Correction Factors ◽  
Ungauged Basins ◽  
Shuffled Complex Evolution ◽  
Available Information

Abstract. A Regional Water Resources study was performed at basins within and draining to the Basque Country Region (N of Spain), with a total area of approximately 8500 km2. The objective was to obtain daily and monthly long-term discharges in 567 points, most of them ungauged, with basin areas ranging from 0.25 to 1850 km2. In order to extrapolate the calibrations at gauged points to the ungauged ones, a distributed and conceptually based model called TETIS was used. In TETIS the runoff production is modelled using five linked tanks at each cell with different outflow relationships at each tank, which represents the main hydrological processes as snowmelt, evapotranspiration, surface runoff, interflow and base flow. The routing along the channels' network couples its geomorphologic characteristics with the kinematic wave approach. The parameter estimation methodology tries to distinguish between the effective parameter used in the model at cell scale, and the watershed characteristic estimated from the available information, being the best estimation without losing its physical meaning. The relationship between them can be considered as a correction function or, in its simple form, a correction factor. The correction factor can take into account the model input errors, the temporal and spatial scale effects and the watershed characteristics. Therefore, it is reasonable to assume the correction factor is the same for each parameter to all cells within the watershed. This approach reduces dramatically the number of parameter to be calibrated, because only the common correction factors are calibrated instead of parameter maps (number of parameters times the number of cells). In this way, the calibration can be performed using automatic methodologies. In this work, the Shuffled Complex Evolution – University of Arizona, SCE-UA algorithm was used. The available recent year's data was used to calibrate the model in 20 of the most representative flow gauge stations in 18 basins with a Nash-Sutcliffe index higher than 0.6 (10 higher than 0.8). The calibrated correction factors at each basin were similar but not equal. The validation process (in time and space) was performed using the remaining data in all flow gauge stations (62), with 42 basins with a Nash-Sutcliffe index higher than 0.5 (25 higher than 0.7). Deficient calibration and validations were always related with flow gauge stations very close to the karstic springs. These results confirmed that it was feasible and efficient to use the SCE-UA algorithm for the automatic calibration of distributed conceptual models and the calibrated model could be used at ungauged basins. Finally, meteorological information from the past 50 years at a daily scale was used to generate a daily discharges series at 567 selected points.

Impact of sulfate on the solubility of Tc(IV) in acidic to hyperalkaline aqueous reducing systems

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sarah B. Duckworth ◽  
Xavier Gaona ◽  
Alexander Baumann ◽  
Kathy Dardenne ◽  
Jörg Rothe ◽  
...  
Keyword(s):  
Solid Phase ◽  
Correction Factors ◽  
Mixed Salt ◽  
Ph Values ◽  
Reducing Conditions ◽  
Upper Limits ◽  
Salt Systems ◽  
Amorphous Character ◽  
Good Agreement

Abstract The solubility of 99Tc(IV) was investigated from undersaturation conditions in NaCl–Na2SO4 (0.3 M ≤ I ≤ 5.0 M), MgCl2–MgSO4 (I = 13.5 M) and CaCl2–CaSO4 (I = 13.5 M) systems with 0.001 M ≤ [SO4 2−]tot ≤ 1.0 M and 1 ≤ pH m  ≤ 12 (with pH m  = −log[H+], in molal units). Reducing conditions were set by either Sn(II) or Fe(0). Special efforts were dedicated to accurately characterize the correction factors A m required for the determination of pH m from the experimentally measured pH values in the mixed salt systems investigated, with pH m  = pHexp + A m . The combination of (pe + pH m ) measurements with Pourbaix diagrams of Tc suggests that technetium is present in its +IV redox state. This hypothesis is confirmed by XANES, which unambiguously shows the predominance of Tc(IV) both in the aqueous and solid phases of selected solubility samples. XRD and SEM–EDS support the amorphous character of the solid phase controlling the solubility of Tc(IV). EXAFS data confirm the predominance of TcO2(am, hyd) at pH m  > 1.5, whereas the formation of a Tc(IV)–O–Cl solid phase is hinted at lower pHm values in concentrated NaCl–Na2SO4 systems with ≈5 M NaCl. Solubility data collected in sulfate-containing systems are generally in good agreement with previous solubility studies conducted in sulfate-free NaCl, MgCl2 and CaCl2 solutions of analogous ionic strength. Although the complexation of Tc(IV) with sulfate cannot be completely ruled out, these results strongly support that, if occurring, complexation must be weak and has no significant impact on the solubility of Tc(IV) in dilute up to highly saline media. Solubility upper-limits determined in this work can be used for source term estimations including the effect of sulfate in a variety of geochemical conditions relevant in the context of nuclear waste disposal.

scholarly journals ELECTROMAGNETIC SOURCE EQUIVALENCE AND EXTENSION OF THE COMPLEX IMAGE METHOD FOR GEOPHYSICAL APPLICATIONS

2009 ◽  
Vol 16 ◽  
pp. 57-84 ◽  
Author(s):  
Antti Pulkkinen ◽  
Ari Viljanen ◽  
Risto Pirjola ◽  
Lasse Häkkinen
Keyword(s):  
Image Method ◽  
Complex Image ◽  
Electromagnetic Source

scholarly journals Effect of aerosol composition on the performance of low-cost optical particle counter correction factors

2019 ◽  
Author(s):  
Leigh R. Crilley ◽  
Ajit Singh ◽  
Louisa J. Kramer ◽  
Marvin D. Shaw ◽  
Mohammed S. Alam ◽  
...  
Keyword(s):  
Correction Factor ◽  
Low Cost ◽  
Particle Mass ◽  
Ambient Atmosphere ◽  
Correction Factors ◽  
Aerosol Composition ◽  
Kohler Theory ◽  
Suitable Reference ◽  
Aerosol Hygroscopicity ◽  
Mass Concentrations

Abstract. There is considerable interest in using low-cost optical particle counters (OPC) to supplement existing routine air quality networks that monitor particle mass concentrations. In order to do this, low-cost OPC data needs to be cross-comparable with particle mass reference instrumentation, and as yet, there is no widely agreed methodology. Aerosol hygroscopicity is known to be a key parameter to consider when correcting particle mass concentrations derived from a low-cost OPC, particularly at high ambient Relative Humidity (RH). Correction factors have been developed that apply κ-Köhler theory to correct for the influence of water uptake by hygroscopic aerosols. We have used datasets of co-located reference particle measurements and a low-cost OPC (OPC-N2, Alphasense), collected in four cities in three continents, to explore the performance of this correction factor. We report evidence that the elevated particle mass concentrations, reported by the low-cost OPC relative to reference instrumentation, is due to bulk aerosol hygroscopicity under different RH conditions, which is determined by aerosol composition and in particular the levels of hygroscopic aerosols (sulphate and nitrate). We exploit measurements made in volcanic plumes in Nicaragua, that are predominantly composed of sulphate aerosol, as a natural experiment to demonstrate this behaviour in the ambient atmosphere, with the observed humidogram closely resembling the calculated pure sulphuric acid humidogram. The results indicate that the particle mass concentrations derived from low-cost OPCs during periods of high RH (> 60 %) need to be corrected for aerosol hygroscopic growth. We employed a correction factor based on κ-Köhler theory and observed corrected OPC-N2 PM2.5 mass concentrations to be within 33 % of reference measurements at all sites. The results indicated that an in situ derived κ (using suitable reference instrumentation) would lead to the most accurate correction relative to co-located reference instruments. Applying literature κ in the correction factor also resulted in improved performance of OPC-N2, to be within 50 % of reference. Therefore, for areas where suitable reference instrumentation for developing a local correction factor is lacking, using a literature κ value can result in a reasonable correction. For locations with low levels of hygroscopic aerosols and RH, a simple calibration against gravimetric measurements (using suitable reference instrumentation) would likely be sufficient. Whilst this study generated correction factors specific for the Alphasense OPC-N2 sensor, the calibration methodology developed is likely amenable to other low cost PM sensors.

Methods of Swanson Constitutive Model Establishment for Composite Solid Propellant

2014 ◽  
Vol 496-500 ◽  
pp. 476-480
Author(s):  
Chao Ning ◽  
Hong Fu Qiang ◽  
Guang Wang
Keyword(s):  
Constitutive Model ◽  
Solid Propellant ◽  
Correction Function ◽  
Uniaxial Tensile ◽  
Softening Function ◽  
Composite Solid Propellant ◽  
Different Temperatures ◽  
Tensile Data ◽  
Composite Solid ◽  
Good Agreement

Establishing Swanson constitutive model is discussed for composite solid propellant, which focused on the calculation of strain softening function and change strain rate correction function within the model. Prediction results of Swanson constitutive model are in good agreement degrees with the test of 24 groups uniaxial tensile data of composite solid propellant at different temperatures and extension rates. It proves the model is effective and available.

scholarly journals Signal discrimination of ULF electromagnetic data with using singular spectrum analysis – an attempt to detect train noise

2011 ◽  
Vol 11 (7) ◽  
pp. 1863-1874 ◽  
Author(s):  
S. Saito ◽  
D. Kaida ◽  
K. Hattori ◽  
F. Febriani ◽  
C. Yoshino
Keyword(s):  
Spectrum Analysis ◽  
Singular Spectrum Analysis ◽  
Wide Frequency Range ◽  
Skin Depth ◽  
Leak Current ◽  
Electromagnetic Data ◽  
Singular Spectrum ◽  
Signal Discrimination ◽  
Electromagnetic Signals ◽  
Different Origins

Abstract. Electromagnetic phenomena associated with crustal activities have been reported in a wide frequency range (DC-HF). In particular, ULF electromagnetic phenomena are the most promising among them because of the deeper skin depth. However, ULF geoelctromagnetic data are a superposition of signals of different origins. They originated from interactions between the geomagnetic field and the solar wind, leak current by a DC-driven train (train noise), precipitation, and so on. In general, the intensity of electromagnetic signals associated with crustal activity is smaller than the above variations. Therefore, in order to detect a smaller signal, signal discrimination such as noise reduction or identification of noises is very important. In this paper, the singular spectrum analysis (SSA) has been performed to detect the DC-driven train noise in geoelectric potential difference data. The aim of this paper is to develop an effective algorithm for the DC-driven train noise detection.

Modelling of an alternating oxidation ditch system

1999 ◽  
Vol 39 (4) ◽  
pp. 169-176 ◽  
Author(s):  
A. Stamou ◽  
A. Katsiri ◽  
I. Mantziaras ◽  
K. Boshnakov ◽  
B. Koumanova ◽  
...  
Keyword(s):  
Pilot Plant ◽  
High Speed ◽  
Dispersion Coefficient ◽  
Carbon Oxidation ◽  
Correction Factors ◽  
Oxidation Ditch ◽  
The Third ◽  
Basic Equations ◽  
Short Presentation ◽  
Good Agreement

This paper presents a mathematical model for an alternating oxidation ditch system, performing carbon oxidation-nitrification, denitrification and settling. The model consists of 1-dimensional mass balance (convection-dispersion) equations, based on the IAWPRC activated sludge model No 1. The data used for the calibration and the application of the model, are collected from a pilot plant. The present work consists of 3 parts. In the first part a brief description of the pilot plant is made. The second part deals with a short presentation of the basic equations and the boundary conditions of the model. The calibration and application of the model with the corresponding conclusions are contained in the third part. In the calibration, the values of the dispersion coefficient, E, and the correction factors α and β of the equation of the aeration equipment (rotors) have been determined equal to E=170000 m2 day−1, β=0.85 and α=0.3 and 0.825, for the operation of the rotors in the low and high speed, respectively. The application of the model shows that predicted effluent concentration values are in a very good agreement with experiments.

Analysis on Acoustic Emission Produced by Strength Test of Bio-Ceramics: Dependency of AE Parameters on the Material Property

2003 ◽  
Author(s):  
Mitusyuki Nakayama ◽  
Hideto Suzuki
Keyword(s):  
Acoustic Emission ◽  
Material Property ◽  
Mechanical Characteristics ◽  
The Body ◽  
Advanced Materials ◽  
Wave Form ◽  
Micro Structure ◽  
Emission Method ◽  
Ae Signal ◽  
Good Agreement

Recently, advanced material used as a bio-ceramic is developed. These materials have one of the important features that characteristics of biocompatibility are improved considerably. However, these advanced materials include some problems that the strength of bio-ceramics decreases in accordance with improvement of biocompatibility. In this paper, it is the main purpose to accurate the acoustic emission characteristics of bio-ceramics on the breaking test, which has never been discussed enough. Therefore, AE parameters are calculated with the wave form of AE signal emitted on the breaking test. Next, the relation between AE parameters and material property of bio-ceramics are discussed in order to accurate the effectiveness of micro-structure elements to mechanical characteristics. As a result, it is found that AE parameters have remarkable dependence on micro-structure element in the body of bio-ceramics. Consequently, it is clarified that the acoustic emission method gives good agreement with the mechanical characteristics.

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