Examination of the relative influence of current gathering on fixed loop and moving source electromagnetic surveys

A physical model study was conducted of the responses provided by moving‐source and fixed‐loop frequency‐domain electromagnetic prospecting systems when operated over the same target conductor located in a conductive host environment. The results indicate that the fixed‐loop responses display enhancement due to the current gathering effect that exceeds that seen in the moving‐source responses by at least an order of magnitude for all the source‐to‐receiver separations tested for the moving‐source system. The results also indicate that as transmitter frequency is increased the current gathering effect displays an abrupt onset in the responses provided by both systems, but that this onset begins at a frequency which is a decade lower for the fixed‐loop system than the corresponding frequency of onset for the moving‐source system. The current gathering enhancement effects show a clear reduction with increase of target depth for the fixed‐loop system but an increase with depth for the moving‐source system. The model parameters employed in these studies are shown to be well related to typical conditions found in full‐scale surveys.

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Statistical Analysis of Manufacturer Difference for Miniature Triode Tube Characteristics Based on Physical Model Parameters

IEEJ Transactions on Electronics Information and Systems ◽

10.1541/ieejeiss.140.1 ◽

2020 ◽

Vol 140 (1) ◽

pp. 1-8

Author(s):

Masaki Inui ◽

Reo Sasaki ◽

Toshihiko Hamasaki

Keyword(s):

Statistical Analysis ◽

Physical Model ◽

Model Parameters

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Physical Model Study of Flowerpot Discharge Outlet, Western Closure Complex, New Orleans, Louisiana

10.21236/ada583046 ◽

2013 ◽

Author(s):

Stephen T. Maynord

Keyword(s):

New Orleans ◽

Physical Model ◽

Model Study

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Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

Water ◽

10.3390/w13040458 ◽

2021 ◽

Vol 13 (4) ◽

pp. 458

Author(s):

Drew C. Baird ◽

Benjamin Abban ◽

S. Michael Scurlock ◽

Steven B. Abt ◽

Christopher I. Thornton

Keyword(s):

Numerical Modeling ◽

Physical Model ◽

Numerical Models ◽

Hydraulic Performance ◽

Physical Models ◽

Protection Measures ◽

Design Engineers ◽

Model Study ◽

Study Results ◽

Wide Range

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

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Investigations of Tail and Defect States in a-Si0.6Ge0.4:H Alloys by PDS and ESR - Implications for the Interaction of Weak and Dangling Bonds

MRS Proceedings ◽

10.1557/proc-377-571 ◽

1995 ◽

Vol 377 ◽

Author(s):

Tilo P. Drüsedau ◽

Andreas N. Panckow ◽

Bernd Schröder

Keyword(s):

Silicon Germanium ◽

Defect Density ◽

State Density ◽

Model Parameters ◽

Defect States ◽

Conversion Model ◽

Order Of Magnitude ◽

Underlying Mechanisms ◽

Amorphous Silicon Germanium ◽

Excess Absorption

ABSTRACTInvestigations on the gap state density were performed on a variety of samples of hydrogenated amorphous silicon germanium alloys (Ge fraction around 40 at%) containing different amounts of hydrogen. From subgap absorption measurements the values of the “integrated excess absorption” and the “defect absorption” were determined. Using a calibration constant, which is well established for the determination of the defect density from the integrated excess absorption of a-Si:H and a-Ge:H, it was found that the defect density is underestimated by nearly one order of magnitude. The underlying mechanisms for this discrepancy are discussed. The calibration constants for the present alloys are determined to 8.3×1016 eV−1 cnr2 and 1.7×1016 cm−2 for the excess and defect absorption, respectively. The defect density of the films was found to depend on the Urbach energy according to the law derived from Stutzmann's dangling bond - weak bond conversion model for a-Si:H. However, the model parameters - the density of states at the onset of the exponential tails N*=27×1020 eV−1 cm−3 and the position of the demarcation energy Edb-E*=0.1 eV are considerably smaller than in a-Si:H.

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Canal Wave Oscillations from Expansion of I-84 Bridge in Boise, Idaho

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/2309-19 ◽

2012 ◽

Vol 2309 (1) ◽

pp. 200-205

Author(s):

William Rahmeyer ◽

J. M. Clegg ◽

S. L. Barfuss

Keyword(s):

New York ◽

Physical Model ◽

Unique Solution ◽

Wave Phenomenon ◽

Bridge Columns ◽

Bridge Abutments ◽

Wave Problem ◽

Model Study ◽

Bridge Crossing

Recent improvements and the widening of the I-84 Bridge crossing of the New York Canal in Boise, Idaho, have increased the number of bridge columns from 28 to 60. The resulting structure has two parallel rows of columns that extend across the width of the bridge longitudinally within the canal. After the widening of the bridge and addition of the bridge columns, the canal began experiencing an oscillating wave phenomenon that originated from the bridge columns and caused erosion of upstream and downstream canal banks and bridge abutments. A physical model study was conducted to investigate the wave phenomenon and determine what modifications to the columns or canal would be necessary to prevent the wave oscillations. The physical model was successful in simulating the wave phenomenon, and four different modifications for resolving the wave problem were tested in the model. A unique solution was found that used precast nose cones attached to selected columns. The nose cones have been installed in the prototype bridge crossing, and no wave oscillations have occurred since installation. This paper discusses the study to simulate the wave phenomenon and the four modifications that were evaluated to reduce or prevent wave oscillations.

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Development of an Inverse Plume Model for Mass Eruption Rate in Unsteady Conditions

Journal of Fluids Engineering ◽

10.1115/1.4050900 ◽

2021 ◽

Author(s):

Stephen A Solovitz

Keyword(s):

Laboratory Data ◽

Model Performance ◽

Volcanic Eruptions ◽

Reynolds Numbers ◽

Model Parameters ◽

Plume Height ◽

Eruption Rate ◽

Mass Eruption Rate ◽

Downstream Effects ◽

Order Of Magnitude

Abstract Following volcanic eruptions, forecasters need accurate estimates of mass eruption rate (MER) to appropriately predict the downstream effects. Most analyses use simple correlations or models based on large eruptions at steady conditions, even though many volcanoes feature significant unsteadiness. To address this, a superposition model is developed based on a technique used for spray injection applications, which predicts plume height as a function of the time-varying exit velocity. This model can be inverted, providing estimates of MER using field observations of a plume. The model parameters are optimized using laboratory data for plumes with physically-relevant exit profiles and Reynolds numbers, resulting in predictions that agree to within 10% of measured exit velocities. The model performance is examined using a historic eruption from Stromboli with well-documented unsteadiness, again providing MER estimates of the correct order of magnitude. This method can provide a rapid alternative for real-time forecasting of small, unsteady eruptions.

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Experimental identification of the material standard linear solid model parameters by means of dynamical measurements

Journal of Vibration and Control ◽

10.1177/10775463211037151 ◽

2021 ◽

pp. 107754632110371

Author(s):

Stefano Amadori ◽

Giuseppe Catania

Keyword(s):

Frequency Domain ◽

Solid Material ◽

Model Parameters ◽

Solid Model ◽

Material Parameters ◽

Experimental Identification ◽

Standard Linear Solid Model ◽

Standard Linear Solid ◽

Standard Linear ◽

Material Standard

A procedure for the experimental identification of the material standard linear solid model parameters by means of dynamic mechanical analysis test instrument measurements is presented. Since the standard linear solid material stress–strain functional D( ω) relationship in the frequency domain formally depends on the standard linear solid material parameters, a procedure able to identify these parameters from test measurement estimates is proposed in this work. Nevertheless, a critical, nonlinear and non-parametric approach is to be followed since the number of the material standard linear solid block components is generally unknown, and the material D( ω) shows a highly nonlinear dependency on the unknown standard linear solid material parameters. For these reasons, measurement and test model noise is expected to strongly influence the accuracy of the identification results. A multi-step procedure is presented, consisting first in the non-parametric identification of a frequency dependent, two degrees of freedom model instrument frame by means of a polynomial rational function, where polynomial order and parameters, such as polynomial coefficients and pole-residue couples, are optimally identified by means of an algebraic numerical technique and of an iterative stabilization procedure. Another procedure able to identify the material D( ω) polynomial rational functional relationship in the frequency domain is also proposed, taking into account the dynamic contribution of the instrument frame, of the inertial contribution of the distributed mass of the beam and of the lumped mass of the instrument force measuring system. An effective procedure, able to identify the standard linear solid material model parameters in the time domain from the identified material physical poles, is finally proposed. Some application examples, concerning the identification of the standard linear solid model of a known material and of an unknown composite material, are shown and discussed as well.

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A Bayesian ensemble data assimilation to constrain model parameters and land-use carbon emissions

Biogeosciences ◽

10.5194/bg-15-2909-2018 ◽

2018 ◽

Vol 15 (9) ◽

pp. 2909-2930 ◽

Cited By ~ 18

Author(s):

Sebastian Lienert ◽

Fortunat Joos

Keyword(s):

Land Use ◽

Carbon Emissions ◽

Latin Hypercube Sampling ◽

Historical Period ◽

Model Parameters ◽

Dynamic Global Vegetation Model ◽

Order Of Magnitude ◽

The Difference ◽

Wood Harvest ◽

Global Vegetation

Abstract. A dynamic global vegetation model (DGVM) is applied in a probabilistic framework and benchmarking system to constrain uncertain model parameters by observations and to quantify carbon emissions from land-use and land-cover change (LULCC). Processes featured in DGVMs include parameters which are prone to substantial uncertainty. To cope with these uncertainties Latin hypercube sampling (LHS) is used to create a 1000-member perturbed parameter ensemble, which is then evaluated with a diverse set of global and spatiotemporally resolved observational constraints. We discuss the performance of the constrained ensemble and use it to formulate a new best-guess version of the model (LPX-Bern v1.4). The observationally constrained ensemble is used to investigate historical emissions due to LULCC (ELUC) and their sensitivity to model parametrization. We find a global ELUC estimate of 158 (108, 211) PgC (median and 90 % confidence interval) between 1800 and 2016. We compare ELUC to other estimates both globally and regionally. Spatial patterns are investigated and estimates of ELUC of the 10 countries with the largest contribution to the flux over the historical period are reported. We consider model versions with and without additional land-use processes (shifting cultivation and wood harvest) and find that the difference in global ELUC is on the same order of magnitude as parameter-induced uncertainty and in some cases could potentially even be offset with appropriate parameter choice.

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