Geochemically controlled calcite precipitation by CO2 outgassing: Field measurements of precipitation rates in comparison to theoretical predictions

1992 ◽  
Vol 97 (3-4) ◽  
pp. 285-294 ◽  
Author(s):  
W. Dreybrodt ◽  
D. Buhmann ◽  
J. Michaelis ◽  
E. Usdowski
Keyword(s):  
Field Measurements ◽  
Calcite Precipitation ◽  
Theoretical Predictions

The Peak Overpressure Field Resulting From Shocks Emerging From Circular Shock Tubes

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
A. J. Newman ◽  
J. C. Mollendorf
Keyword(s):  
Shock Tube ◽  
Horizontal Plane ◽  
Three Dimensional ◽  
Polar Angle ◽  
Field Measurements ◽  
Initial Development ◽  
Theoretical Predictions ◽  
Mach Numbers ◽  
Tube Exit ◽  
Semi Empirical

A simple semi-empirical model for predicting the peak overpressure field that results when a shock emerges from a circular shock tube is presented and validated. By assuming that the shape of the expanding shock remains geometrically similar after an initial development period, an equation that describes the peak overpressure field in the horizontal plane containing the shock tube’s centerline was developed. The accuracy of this equation was evaluated experimentally by collecting peak overpressure field measurements along radials from the shock tube exit at 0 deg, 45 deg, and 90 deg over a range of shock Mach numbers from 1.15 to 1.45. It was found that the equation became more accurate at higher Mach numbers with percent differences between experimental measurements and theoretical predictions ranging from 1.1% to 3.6% over the range of Mach numbers considered. (1) Shocks do propagate in a geometrically similar manner after some initial development length over the range of Mach numbers considered here. (2) The model developed here gives reasonable predictions for the overpressure field from a shock emerging from a circular shock tube. (3) Shocks are expected to be completely symmetric with respect to the shock tube’s centerline, and hence, a three dimensional overpressure field may be predicted by the model developed here. (4) While there is a range of polar angle at which the shock shape may be described as being spherical with respect to the shock tube’s exit, this range does not encompass the entirety of the half space in front of the shock tube, and the model developed here is needed to accurately describe the entire peak overpressure field.

Iodic acid formation and yield from iodine photolysis at the CERN CLOUD chamber

2021 ◽  
Author(s):  
Henning Finkenzeller ◽  
Siddharth Iyer ◽  
Theodore K. Koenig ◽  
Xu-Cheng He ◽  
Mario Simon ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Field Measurements ◽  
Cloud Chamber ◽  
Iodic Acid ◽  
Experimental Conditions ◽  
Laboratory Findings ◽  
Time Resolved ◽  
Photolysis Frequencies ◽  
Key Species ◽  
Theoretical Predictions

<p>Iodine oxoacids are key species involved in the cycling of iodine between the gas- and aerosol phases. Iodic acid (HIO<sub>3</sub>) nucleates particles more efficiently than sulfuric acid and ammonia at comparable concentrations, and grows them at comparable rates, but the formation mechanism of HIO<sub>3</sub> is essentially unknown. As a result, atmospheric models of iodine chemistry are currently incomplete. Proposed precursors for iodine oxoacids include iodine atoms and higher iodine oxides (e.g., I<sub>2</sub>O<sub>2</sub>, I<sub>2</sub>O<sub>3</sub>, I<sub>2</sub>O<sub>4</sub>), but theoretical predictions have not currently been assessed under experimental conditions that approximate the open ocean marine atmosphere. We present results from laboratory experiments at the CLOUD chamber that observe rapid oxoacid formation from photolysis of iodine (I<sub>2</sub>) at green wavelengths, in the presence of ozone and variable relative humidity (0-80%). Under these (soft) experimental conditions iodine oxide (IO) radical concentrations closely approximate those found in the remote marine boundary layer. A chemical box model is constrained by measurements of I<sub>2</sub>, ozone, RH, photolysis frequencies (i.e., I<sub>2</sub>, IO, OIO, HOI, I<sub>x</sub>O<sub>y</sub>) and known losses of gases to particles and the chamber walls, and evaluated using time resolved measurements of IO, OIO, and I<sub>x</sub>O<sub>y</sub> species in the chamber. Hypothesized mechanisms for HIO<sub>3</sub> formation - either proposed in the literature or motivated from our observations - are then discussed in terms of their ability to explain the observed amounts (yield), and the temporal evolution of HIO<sub>3</sub>. Finally, the atmospheric relevance of the laboratory findings is assessed in context of unique field measurements at the Maido Observatory, La Reunion, during spring 2018, where IO radicals and HIO<sub>3</sub> were measured simultaneously in the remote free troposphere.</p>

Full-Scale Gate Measurements

2017 ◽  
pp. 593-625
Keyword(s):  
Modal Analysis ◽  
Structural Dynamics ◽  
Fem Analysis ◽  
Field Measurements ◽  
Full Scale ◽  
Experimental Modal Analysis ◽  
Experimental Results ◽  
Physical Measurement ◽  
Theoretical Predictions ◽  
The Stability

In this chapter, dynamic field measurements of three full-scale operational Tainter gates are documented. Measurements of the in-air gate structural dynamics were made when feasible or were simulated using FEM analysis when physical measurement was not possible. In-water structural dynamics were documented using experimental modal analysis with gate excitation supplied by the sudden tension failure of a carefully machined steel rod. The field measurements permitted assessments of the stability of each gate and these assessments are compared with theoretical predictions. Two gates were found to be stable and one was determined to have a potential instability. Theoretical predictions are shown to agree with the experimental results from field measurements.

Evaluation of extremal hypotheses in an undeveloped alluvial river

2019 ◽  
Vol 44 (4) ◽  
pp. 514-533
Author(s):  
Andrew W Tranmer ◽  
Diego Caamaño ◽  
Peter Goodwin
Keyword(s):  
Dynamic Equilibrium ◽  
Field Measurements ◽  
Evolutionary Trend ◽  
Stream Power ◽  
Substitution Model ◽  
Equilibrium Conditions ◽  
Spatial Trend ◽  
Chilean Patagonia ◽  
Theoretical Predictions ◽  
Time Substitution

Recent work in the undeveloped Rio Murta Basin, located in Chilean Patagonia, identified an evolutionary trend in the fluvial system as it progresses toward and away from dynamic equilibrium. A location-for-time-substitution model employed over the longitudinal extent of a 16 km study site assessed the performance of extremal hypotheses in identifying dynamic equilibrium conditions. Numerous extremal hypotheses were successful in identifying the spatial trend, but no means were available to discern differences between them. Thus, this study uses field measurements within the evolutionary trend to propose a new metric for evaluating extremal hypotheses. A thorough review and synthesis of the extremal approach are additionally presented. The new method compares theoretical predictions against field-measured values to determine which extremal hypothesis is most effective in identifying the condition of dynamic equilibrium in a gravel-bed river. Channel width and depth are identified as the dependent stream variables that uniquely differentiate most extremal hypotheses from one another. The results indicate that extremal hypotheses based on energy metrics of the flow are most successful, with the strongest support for minimum kinetic energy and minimum specific stream power.

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