volume relationship
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Author(s):  
Marina de P. Moura ◽  
Alfredo Ribeiro Neto ◽  
Fábio A. da Costa

ABSTRACT Reservoirs are the primary source of water supply in the semiarid region of Pernambuco state, Brazil, because of the constant water scarcity affecting this region. Knowledge of the amount of water available is essential for the effective management of water resources. The volume of water stored in the reservoirs is calculated using the depth-area-volume relationship. However, in most reservoirs in the semiarid region, this relationship is currently out of date. Therefore, the objective of this study was to explore the potential and limitations of the application of the ISODATA unsupervised classification method to calculate the depth-area-volume relationships of reservoirs in the semiarid region of Pernambuco, Brazil. The application of the ISODATA method was evaluated in three reservoirs in the state of Pernambuco, i.e., Poço da Cruz, Barra do Juá, and Jucazinho. The results were compared with the updated curves of reservoirs obtained from bathymetry and recent LiDAR surveys. The ISODATA method presented satisfactory results for the three reservoirs analyzed. The mean absolute error of the volume in Poço da Cruz and Barra do Juá was lower than 1% of the maximum capacity. The use of the ISODATA method meant that the surface area underestimation tendency in the Poço da Cruz reservoir was less than when spectral indices were used.


2021 ◽  
Author(s):  
Robert Claude Meffan ◽  
Julian Menges ◽  
Fabian Dolamore ◽  
Daniel Mak ◽  
Conan Fee ◽  
...  

Controling fluid flow in capillaric circuits is a key requirement to increase their uptake for assay applications. Capillary action off-valves provide such functionality by pushing an occluding bubble into the channel using a difference in capillary pressure. Previously, we utilised the binary switching mode of this structure to develop a powerful set of fundamental fluidic valving operations. In this work we provide evidence that these structures are in fact functionally complementary to electronic Junction Field Effect Transistors and thus warrant the use of the new term of capillaric- Field Effect Transistor to describe these types of valves. To support this conclusion, we present a theoretical description, experimental characterisation, and practical application of analog flow resistance control. In addition, we demonstrate that the valves can also be re-opened. These are two key capabilities previously missing for a full analogy to electronic transistors. We show modulation of the flow resistance from fully open to pinch-off, determine the flow rate – trigger channel volume relationship and demonstrate that the latter can be modelled using Shockley’s equation for electronic transistors. Finally, we provide a first example of how the valves can be opened and closed repeatedly.


2021 ◽  
Author(s):  
Liesa Brosens ◽  
Benjamin Campforts ◽  
Gerard Govers ◽  
Emilien Aldana-Jague ◽  
Vao Fenotiana Razanamahandry ◽  
...  

Abstract. Over the past decades, developments in remote sensing have resulted in an ever growing availability of topographic information on a global scale. A recent development is TanDEM-X, an interferometric SAR mission of the Deutsche Zentrum für Luft- und Raumfahrt providing near-global coverage and high resolution DEMs. Moreover, ongoing developments in unmanned aerial vehicle (UAV) technology has enabled acquisitions of topographic information at a sub-meter resolution. Although UAV products are generally preferred for volume assessments of geomorphic features, their acquisition remains time-consuming and is spatially constrained. However, some applications in geomorphology such as the estimation of regional or national erosion quantities of specific landforms, require data over large areas. TanDEM-X data can be applied at such scales, but this raises the question of how much accuracy is lost because of the lower spatial resolution. Here, we evaluated the performance of the 12 m TanDEM-X DEM to i) estimate gully volumes, ii) establish an area-volume (A-V) relationship, and iii) determine mobilization rates, through comparison with a high resolution (0.2 m) UAV-SfM DEM and lower resolution (30 m) SRTM DEM. We did this for six study areas in the Lake Alaotra region (central Madagascar) where lavaka (gullies) are omnipresent and lavaka surface area changes over the period 1949–2010s are available for 699 lavaka. SRTM derived lavaka volume estimates were systematically too low, indicating that the SRTM DEM is too coarse to accurately estimate volumes of geomorphic features at the lavaka-scale (100–100 000 m2). Lavaka volumes obtained from TanDEM-X were similar to UAV-SfM volumes for the largest features, whereas the volumes of smaller features were generally underestimated. To deal with this bias we introduce a breakpoint analysis to eliminate volume reconstructions that suffer from processing errors as evidenced by significant fractions of negative volumes. This elimination allowed the establishment of an area-volume relationship for the TanDEM-X data that is within the 95 % confidence interval of the UAV-SfM A-V relationship. Our calibrated area-volume relationship enabled us to obtain large-scale lavaka mobilization rates ranging between 18 ± 6 and 289 ± 125 ton ha−1 yr−1 with an average of 102 ± 41 ton ha−1 yr−1. These results indicate that current lavaka mobilization rates are two orders of magnitude higher than long-term erosion rates. With this study we demonstrate that the global TanDEM-X 12 m DEM can be used to accurately estimate volumes of gully-shaped features at the lavaka-scale (100–100 000 m2), where the proposed breakpoint-method can be applied without requiring the availability of a higher resolution DEM. Furthermore, we use this information to make a first assessment of regional lavaka erosion rates in the central highlands of Madagascar.


PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0252916
Author(s):  
Jyotika Erram ◽  
Monica Bari ◽  
Antoinette Domingo ◽  
Daniel T. Cannon

Expiratory flow limitation is a key characteristic in obstructive pulmonary diseases. To study abnormal lung mechanics isolated from heterogeneities of obstructive disease, we measured pulmonary function in healthy adults with expiratory loading. Thirty-seven volunteers (25±5 yr) completed spirometry and body plethysmography under control and threshold expiratory loading of 7, 11 cmH2O, and a subset at 20 cmH2O (n = 11). We analyzed the shape of the flow-volume relationship with rectangular area ratio (RAR; Ma et al., Respir Med 2010). Airway resistance was increased (p<0.0001) with 7 and 11 cmH2O loading vs control (9.20±1.02 and 11.76±1.68 vs. 2.53± 0.80 cmH2O/L/s). RAR was reduced (p = 0.0319) in loading vs control (0.45±0.07 and 0.47±0.09L vs. 0.48±0.08). FEV1 was reduced (p<0.0001) in loading vs control (3.24±0.81 and 3.23±0.80 vs. 4.04±1.05 L). FVC was reduced (p<0.0001) in loading vs control (4.11±1.01 and 4.14±1.03 vs. 5.03±1.34 L). Peak expiratory flow (PEF) was reduced (p<0.0001) in loading vs control (6.03±1.67 and 6.02±1.84 vs. 8.50±2.81 L/s). FEV1/FVC (p<0.0068) was not clinically significant and FRC (p = 0.4) was not different in loading vs control. Supra-physiologic loading at 20 cmH2O did not result in further limitation. Expiratory loading reduced FEV1, FVC, PEF, but there were no clinically meaningful differences in FEV1/FVC, FRC, or RAR. Imposed expiratory loading likely leads to high airway pressures that resist dynamic airway compression. Thus, a concave expiratory flow-volume relationship was consistently absent–a key limitation for model comparison with pulmonary function in COPD. Threshold loading may be a useful strategy to increase work of breathing or induce dynamic hyperinflation.


2021 ◽  
pp. 004051752110174
Author(s):  
Amit Rawal

van Wyk put forward a compression model of fibrous materials utilizing a library of analytical approaches, including the continuum mechanics, stereological, geometrical probability, least square method, and excluded area concept. In this letter, we wish to point out a key error noted in van Wyk’s work with the objective of correcting misconceptions that are held by the majority of us. Through this contribution, we question the “inverse cube” pressure-volume relationship of random fibrous materials. The pressure-volume relationship has been revisited by modifying the formulation of the mean length of a fiber element between consecutive contacts projected on the compression direction.


2021 ◽  
Author(s):  
Fikunwa Kolawole ◽  
Mathias Peirlinck ◽  
Tyler E. Cork ◽  
Vicky Y. Wang ◽  
Seraina A. Dual ◽  
...  

AbstractMRI-driven computational modeling is increasingly used to simulate in vivo cardiac mechanical behavior and estimate subject-specific myocardial stiffness. However, in vivo validation of these estimates is exceedingly difficult due to the lack of a known ground-truth in vivo myocardial stiffness. We have developed 3D-printed heart phantoms of known myocardium-mimicking stiffness and MRI relaxation properties and incorporated the heart phantoms within a highly controlled MRI-compatible setup to simulate in vivo diastolic filling. The setup enables the acquisition of experimental data needed to evaluate myocardial stiffness using computational constitutive modeling: phantom geometry, loading pressures, boundary conditions, and filling strains. The pressure-volume relationship obtained from the phantom setup was used to calibrate an in silico model of the heart phantom undergoing simulated diastolic filling. The model estimated stiffness was compared with ground-truth stiffness obtained from uniaxial tensile testing. Ultimately, the setup is designed to enable extensive validation of MRI and FEM-based myocardial stiffness estimation frameworks.


Author(s):  
Nabid Salehin ◽  
Cameron Villarreal ◽  
Tanveer Teranikar ◽  
Benjamin Dubansky ◽  
Juhyun Lee ◽  
...  

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