scholarly journals Footprint-weighted tile approach for a spruce forest and a nearby patchy clearing using the ACASA model

2018 ◽  
Vol 15 (9) ◽  
pp. 2945-2960 ◽  
Author(s):  
Kathrin Gatzsche ◽  
Wolfgang Babel ◽  
Eva Falge ◽  
Rex David Pyles ◽  
Kyaw Tha Paw U ◽  
...  
Keyword(s):  
Energy Balance ◽  
Net Ecosystem Exchange ◽  
Bowen Ratio ◽  
Small Scale ◽  
Heterogeneous Structure ◽  
Land Use Classification ◽  
Carbon Dioxide Fluxes ◽  
Buoyancy Correction ◽  
Good Agreement

Abstract. The ACASA (Advanced Canopy–Atmosphere–Soil Algorithm) model, with a higher-order closure for tall vegetation, has already been successfully tested and validated for homogeneous spruce forests. The aim of this paper is to test the model using a footprint-weighted tile approach for a clearing with a heterogeneous structure of the underlying surface. The comparison with flux data shows a good agreement with a footprint-aggregated tile approach of the model. However, the results of a comparison with a tile approach on the basis of the mean land use classification of the clearing is not significantly different. It is assumed that the footprint model is not accurate enough to separate small-scale heterogeneities. All measured fluxes are corrected by forcing the energy balance closure of the test data either by maintaining the measured Bowen ratio or by the attribution of the residual depending on the fractions of sensible and latent heat flux to the buoyancy flux. The comparison with the model, in which the energy balance is closed, shows that the buoyancy correction for Bowen ratios >1.5 better fits the measured data. For lower Bowen ratios, the correction probably lies between the two methods, but the amount of available data was too small to make a conclusion. With an assumption of similarity between water and carbon dioxide fluxes, no correction of the net ecosystem exchange is necessary for Bowen ratios >1.5.

scholarly journals Application of the ACASA model for a spruce forest and a nearby patchy clearing

2017 ◽  
Author(s):  
Kathrin Gatzsche ◽  
Wolfgang Babel ◽  
Eva Falge ◽  
Rex David Pyles ◽  
Kyaw Tha Paw U ◽  
...  
Keyword(s):  
Energy Balance ◽  
Net Ecosystem Exchange ◽  
Bowen Ratio ◽  
Correction Method ◽  
Small Scale ◽  
Heterogeneous Structure ◽  
Land Use Classification ◽  
Carbon Dioxide Fluxes ◽  
Buoyancy Correction

Abstract. The ACASA (Advanced Canopy-Atmosphere-Soil Algorithm) model, with a higher order closure for tall vegetation, has already been successfully tested and validated for spruce forests. The aim of this paper is the further application for a clearing with a heterogeneous structure of the underlying surface. The comparison with flux data shows a good agreement with a footprint aggregated tile approach of the model. However, the results of a comparison with a tile approach on the basis of the mean land use classification of the clearing is not significantly different. It is assumed that the footprint model is not accurate enough to separate small scale heterogeneities. All measured fluxes are corrected for energy balance closure with a Bowen ratio and a buoyancy flux correction method. The comparison with the model – where the energy balance is closed – shows that the buoyancy correction for Bowen ratios > 1.5 better fits the measured data. For lower Bowen ratios, the correction probably lies between both methods, but the amount of available data was too small to make a conclusion. With an assumption of a similarity between water and carbon dioxide fluxes, no correction of the net ecosystem exchange is necessary for Bowen ratios > 1.5.

Diagnostic Value of Electron Microscopy in Soft Tissue Tumors

1970 ◽  
Vol 28 ◽  
pp. 220-221
Author(s):  
Gerald Fine ◽  
Azorides R. Morales
Keyword(s):  
Cardiac Myxoma ◽  
Osteogenic Sarcoma ◽  
Diagnostic Value ◽  
Soft Tissue Tumors ◽  
Amelanotic Melanoma ◽  
Growth Patterns ◽  
Light Microscopic Level ◽  
Mesenchymal Tumors ◽  
Good Agreement

For years the separation of carcinoma and sarcoma and the subclassification of sarcomas has been based on the appearance of the tumor cells and their microscopic growth pattern and information derived from certain histochemical and special stains. Although this method of study has produced good agreement among pathologists in the separation of carcinoma from sarcoma, it has given less uniform results in the subclassification of sarcomas. There remain examples of neoplasms of different histogenesis, the classification of which is questionable because of similar cytologic and growth patterns at the light microscopic level; i.e. amelanotic melanoma versus carcinoma and occasionally sarcoma, sarcomas with an epithelial pattern of growth simulating carcinoma, histologically similar mesenchymal tumors of different histogenesis (histiocytoma versus rhabdomyosarcoma, lytic osteogenic sarcoma versus rhabdomyosarcoma), and myxomatous mesenchymal tumors of diverse histogenesis (myxoid rhabdo and liposarcomas, cardiac myxoma, myxoid neurofibroma, etc.)

scholarly journals Quantitative Shape-Classification of Misfitting Precipitates during Cubic to Tetragonal Transformations: Phase-Field Simulations and Experiments

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1373
Author(s):  
Yueh-Yu Lin ◽  
Felix Schleifer ◽  
Markus Holzinger ◽  
Na Ta ◽  
Birgit Skrotzki ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Phase Field ◽  
Phase Field Model ◽  
Invariant Moments ◽  
Plane Normal ◽  
Plane Shape ◽  
Formation And Evolution ◽  
The Given ◽  
Good Agreement

The effectiveness of the mechanism of precipitation strengthening in metallic alloys depends on the shapes of the precipitates. Two different material systems are considered: tetragonal γ′′ precipitates in Ni-based alloys and tetragonal θ′ precipitates in Al-Cu-alloys. The shape formation and evolution of the tetragonally misfitting precipitates was investigated by means of experiments and phase-field simulations. We employed the method of invariant moments for the consistent shape quantification of precipitates obtained from the simulation as well as those obtained from the experiment. Two well-defined shape-quantities are proposed: (i) a generalized measure for the particles aspect ratio and (ii) the normalized λ2, as a measure for shape deviations from an ideal ellipse of the given aspect ratio. Considering the size dependence of the aspect ratio of γ′′ precipitates, we find good agreement between the simulation results and the experiment. Further, the precipitates’ in-plane shape is defined as the central 2D cut through the 3D particle in a plane normal to the tetragonal c-axes of the precipitate. The experimentally observed in-plane shapes of γ′′-precipitates can be quantitatively reproduced by the phase-field model.

scholarly journals Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Three Dimensional ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Small Clearance ◽  
Dimensional Simulation ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

Heat-flow experiments in liquid 4He with a variable cylindrical geometry

1987 ◽  
Vol 174 ◽  
pp. 209-231 ◽  
Author(s):  
H. Gao ◽  
G. Metcalfe ◽  
T. Jung ◽  
R. P. Behringer
Keyword(s):  
Cylindrical Geometry ◽  
Small Scale ◽  
Onset Of Convection ◽  
Aspect Ratios ◽  
A Value ◽  
Prandtl Numbers ◽  
Convection Rolls ◽  
Flow Experiments ◽  
Increasing Function ◽  
Good Agreement

This paper first describes an apparatus for measuring the Nusselt number N versus the Rayleigh number R of convecting normal liquid 4He layers. The most important feature of the apparatus is its ability to provide layers of different heights d, and hence different aspect ratios [Gcy ]. The horizontal cross-section of each layer is circular, and [Gcy ] is defined by [Gcy ] = D/2d where D is the diameter of the layer. We report results for 2.4 [les ] [Gcy ] [les ] 16 and for Prandtl numbers Pr spanning 0.5 [lsim ] Pr [lsim ] 0.9 These results are presented in terms of the slope N1 = RcdN/dR evaluated just above the onset of convection at Rc. We find that N1 is only a slowly increasing function of [Gcy ] in the range 6 [lsim ] [Gcy ] [lsim ] 16, and that it has a value there which is quite close to 0.72. This value of N1 is in good agreement with variational calcuations by Ahlers et al. (1981) pertinent to parallel convection rolls in cylindrical geometry. Particularly for [Gcy ] [lsim ] 6, we find additional small-scale structure in N1 associated with changes in the number of convection rolls with changing [Gcy ]. An additional test of the linearzied hydrodynamics is given by measurements of Rc. We find good agreement between theory and our data for Rc.

BOWEN RATIO-ENERGY BALANCE ESTIMATES OF EVAPOTRANSPIRATION AND CROP COEFFICIENT FOR TOMATO PLANTS

1996 ◽  
pp. 121-126
Author(s):  
A.M.R. Abdel-Mawgoud ◽  
S.O. El-Abd ◽  
A.F. Abou-Hadid ◽  
T.C. Hsiao
Keyword(s):  
Energy Balance ◽  
Crop Coefficient ◽  
Bowen Ratio ◽  
Tomato Plants ◽  
Ratio Energy

scholarly journals Bower ratio-energy balance associated errors in vineyards under dripping irrigation

2007 ◽  
Vol 22 (2) ◽  
pp. 233-240 ◽  
Author(s):  
José Monteiro Soares ◽  
Pedro Vieira De Azevedo ◽  
Bernado Barbosa Da Silva
Keyword(s):  
Energy Balance ◽  
Soil Surface ◽  
Field Measurements ◽  
Bowen Ratio ◽  
Global Solar Radiation ◽  
Soil Heat Flux ◽  
Vitis Vinifera L ◽  
Data Logger ◽  
And Storage ◽  
Ratio Energy

This study was conducted at the Bebedouro Experimental Station in Petrolina-PE, Brazil, to evaluate the errors associated to the application of the Bowen ratio-energy balance in a 3-years old vineyard (Vitis vinifera, L), grown in a trellis system, irrigated by dripping. The field measurements were taken during fruiting cycle (July to November, 2001), which was divided into eigth phenological stages. A micrometeorological tower was mounted in a grape-plants row in which sensors of net radiation, global solar radiation and wind speed were installed at about 1.0 m above the canopy. Also in the tower, two psicometers were installed at two levels (0.5 and 1.8 m) above the vineyard canopy. Two soil heat flux plates were buried at 0.02 m beneath the soil surface. All these sensors were connected to a Data logger 21 X of Campbell Scientific Inc., programmed for collecting data once every 5 seconds and storage averages for every 15 minutes. A comparative analysis were made among four Bowen ratio accepting/rejecting rules, according to the methodology proposed by Spano et al. (2000): betar1 - values of beta calculated by Bowen (1926) equation; betar2 - values of beta as proposed by Verma et al. (1978) equation; betar3 - exclusion of the beta values obtained as recommended by Unland et al. (1996) and betar4 - exclusion of the beta values calculated as proposed by Bowen (1926), out of the interval (-0.7 < beta < 0.7). Constacted that the Unland et al. (1996) and Soares (2003) accepting/rejection rules were better than that of Verma et al. (1978) for attenuating the advective effects on the calculations of the Bowen ratio. The comparison of betar1 with betar2 rules showed that the statistical errors reaching maximum values of 0.015. When comparing betar1 with betar3 e betar4, the beta errors reaching maximum values of 5.80 and 3.15, respectively.

scholarly journals Evapotranspiration Estimation with Small UAVs in Precision Agriculture

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6427
Author(s):  
Haoyu Niu ◽  
Derek Hollenbeck ◽  
Tiebiao Zhao ◽  
Dong Wang ◽  
YangQuan Chen
Keyword(s):  
Energy Balance ◽  
High Resolution ◽  
Spatial Resolution ◽  
Precision Agriculture ◽  
Large Scale ◽  
Bowen Ratio ◽  
Future Research ◽  
Accurate Estimation ◽  
Research Areas ◽  
Energy Balance Approach

Estimating evapotranspiration (ET) has been one of the most critical research areas in agriculture because of water scarcity, the growing population, and climate change. The accurate estimation and mapping of ET are necessary for crop water management. Traditionally, researchers use water balance, soil moisture, weighing lysimeters, or an energy balance approach, such as Bowen ratio or eddy covariance towers to estimate ET. However, these ET methods are point-specific or area-weighted measurements and cannot be extended to a large scale. With the advent of satellite technology, remote sensing images became able to provide spatially distributed measurements. However, the spatial resolution of multispectral satellite images is in the range of meters, tens of meters, or hundreds of meters, which is often not enough for crops with clumped canopy structures, such as trees and vines. Unmanned aerial vehicles (UAVs) can mitigate these spatial and temporal limitations. Lightweight cameras and sensors can be mounted on the UAVs and take high-resolution images. Unlike satellite imagery, the spatial resolution of the UAV images can be at the centimeter-level. UAVs can also fly on-demand, which provides high temporal imagery. In this study, the authors examined different UAV-based approaches of ET estimation at first. Models and algorithms, such as mapping evapotranspiration at high resolution with internalized calibration (METRIC), the two-source energy balance (TSEB) model, and machine learning (ML) are analyzed and discussed herein. Second, challenges and opportunities for UAVs in ET estimation are also discussed, such as uncooled thermal camera calibration, UAV image collection, and image processing. Then, the authors share views on ET estimation with UAVs for future research and draw conclusive remarks.

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