Examples of Variable-Head Field Permeability Tests Used in Books: Given Interpretations and Correct Interpretations

2020 ◽  
Vol 44 (5) ◽  
pp. 20180210
Author(s):  
Ana Boada ◽  
Robert P. Chapuis ◽  
Lu Zhang ◽  
Vahid Marefat
Keyword(s):  
Variable Head

Rapid evaluation of FDG imaging alternatives using head-to-head comparisons of full ring and gamma camera based PET scanners –

2002 ◽  
Vol 41 (05) ◽  
pp. 208-213 ◽  
Author(s):  
L. M. Haslinghuis-Bajan ◽  
L. Hooft ◽  
A. van Lingen ◽  
M. van Tulder ◽  
W. Devillé ◽  
...  
Keyword(s):  
Methodological Quality ◽  
Gamma Camera ◽  
First Generation ◽  
Prospective Evaluation ◽  
First Approximation ◽  
Variable Head ◽  
Malignant Lesions ◽  
The Impact ◽  
Pet Scanners

SummaryAim: While FDG full ring PET (FRPET) has been gradually accepted in oncology, the role of the cheaper gamma camera based alternatives (GCPET) is less clear. Since technology is evolving rapidly, “tracker trials” would be most helpful to provide a first approximation of the relative merits of these alternatives. As difference in scanner sensitivity is the key variable, head-to-head comparison with FRPET is an attractive study design. This systematic review summarises such studies. Methods: Nine studies were identified until July 1, 2000. Two observers assessed the methodological quality (Cochrane criteria), and extracted data. Results: The studies comprised a variety of tumours and indications. The reported GC- and FRPET agreement for detection of malignant lesions ranged from 55 to 100%, but with methodological limitations (blinding, standardisation, limited patient spectrum). Mean lesion diameter was 2.9 cm (SD 1.8), with only about 20% <1.5 cm. The 3 studies with the highest quality reported concordances of 74-79%, for the studied lesion spectrum. Contrast at GCPET was lower than that of FRPET, contrast and detection agreement were positively related. Logistic regression analysis suggested that pre-test indicators might be used to predict FRPET-GCPET concordance. Conclusion: In spite of methodological limitations, “first generation” GCPET devices detected sufficient FRPET positive lesions to allow prospective evaluation in clinical situations where the impact of FRPET is not confined to detection of small lesions (<1.5 cm). The efficiency of head-to-head comparative studies would benefit from application in a clinically relevant patient spectrum, with proper blinding and standardisation of acquisition procedures.

scholarly journals Impeller Optimization in Crossflow Hydraulic Turbines

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 313
Author(s):  
Marco Sinagra ◽  
Calogero Picone ◽  
Costanza Aricò ◽  
Antonio Pantano ◽  
Tullio Tucciarelli ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Structural Safety ◽  
3D Fem ◽  
Good Efficiency ◽  
Standard Material ◽  
Variable Head ◽  
Hydraulic Turbines ◽  
Constructive Simplicity ◽  
Mechanical Optimization

Crossflow turbines represent a valuable choice for energy recovery in aqueducts, due to their constructive simplicity and good efficiency under variable head jump conditions. Several experimental and numerical studies concerning the optimal design of crossflow hydraulic turbines have already been proposed, but all of them assume that structural safety is fully compatible with the sought after geometry. We show first, with reference to a specific study case, that the geometry of the most efficient impeller would lead shortly, using blades with a traditional circular profile made with standard material, to their mechanical failure. A methodology for fully coupled fluid dynamic and mechanical optimization of the blade cross-section is then proposed. The methodology assumes a linear variation of the curvature of the blade external surface, along with an iterative use of two-dimensional (2D) computational fluid dynamic (CFD) and 3D structural finite element method (FEM) simulations. The proposed methodology was applied to the design of a power recovery system (PRS) turbine already installed in an operating water transport network and was finally validated with a fully 3D CFD simulation coupled with a 3D FEM structural analysis of the entire impeller.

scholarly journals Caracterização de parâmetros hidráulicos em depósitos fluviais paleogênicos na Bacia de Volta Redonda, RJ

2007 ◽  
Vol 30 (2) ◽  
pp. 118-132
Author(s):  
Ana Carolina Lisbôa Barboza ◽  
Gerson Cardoso da Silva Jr ◽  
Claudio Limeira Mello
Keyword(s):  
Hydraulic Conductivity ◽  
Sedimentary Facies ◽  
Fine Sand ◽  
Sedimentary Deposits ◽  
Hydrogeological Parameters ◽  
Variable Head ◽  
Medium Reservoir ◽  
Maximum Permeability

The present study aims for the characterization of the hydrogeological parameters of the Paleogenic fluvial deposits of Volta Redonda Geological Basin, through hydraulic conductivity determinations and grain sized analyses. The overall goal was to produce a hydrogeological data base applicable to the characterization of hydrofacies (interconnected sedimentary bodies with distinct hydraulic properties) and the modeling groundwater flow. The used methods used consisted of in situ permeability determinations (Guelph permeameters) and laboratory tests (variable head permeameter), besides grain size analyses carried out in each sedimentary facies in the study area. These sedimentary facies were characterized by Marques (2006) and belong to the Resende and Pinheiral formations. The permeameter results were coherent to the sedimentological characteristics. The Resende Formation sedimentary deposits are constituted by medium to fine sand with presence of argillaceous matrix and present moderate to very low hydraulic conductivity, varying between 10-4 to 10-8 cm/s, which indicates a poor reservoir. The Pinheiral Formation presents sandy layers with conglomeratic lenses, limited by small thickness pelitic intervals, with a very low permeability, with a hydraulic conductivity varying between 10-5 to 10-7 cm/s. The upper layer has the maximum permeability, around 10-3 cm/s. This formation presents a medium reservoir characteristics and it must be taken into consideration that the upper layer has as role in recharge to the aquifer. From the results of hydraulic conductivity, that varies from 10-8 to 10-3 cm/s for the Resende and Pinheiral formations, it is concluded that these deposits a low to medium hydraulic conductivity, explaining the low productivity of the water-bearing multilayered aquifer of Volta Redonda Basin.

Prediction of unsaturated soil hydraulic conductivity using air permeability: Regression approach

2015 ◽  
Vol 49 (6) ◽  
Author(s):  
Mohammad Reza Neyshaboury ◽  
Mehdi Rahmati ◽  
Seyed Alireza Rafiee Alavi ◽  
Hosein Rezaee ◽  
Amirhosein Nazemi
Keyword(s):  
Geometric Mean ◽  
Regression Function ◽  
Close Correlation ◽  
Air Permeability ◽  
Geometric Standard Deviation ◽  
Water Conductivity ◽  
Error Ratio ◽  
Relative Water ◽  
Variable Head ◽  
Geometric Mean Error

A close correlation between water conductivity (<italic>K(θ)</italic>) and air permeability (<italic>K</italic><sub><italic>a</italic></sub>), measured at various water contents, is expected due to tight dependence of water filled porosity to air filled porosity of soils. Finding such a relation will greatly facilitate the prediction of unsaturated water conductivity (<italic>K(θ)</italic>). So, the purpose of the current investigation was to find out if a reliable relation or function between the two permeabilities can be established. In this regard, <italic>K(θ)</italic> and <italic>K</italic><sub><italic>a</italic></sub> were measured by pressure plate outflow and variable head methods, respectively, at the range of 0 to -100 kPa matric potential (<italic>ψ</italic><sub><italic>m</italic></sub>). A linear regression function between relative water conductivity (<italic>K</italic><sub><italic>r</italic></sub>(<italic>θ</italic>)) and <italic>K</italic><sub><italic>a</italic></sub> (<italic>LogK</italic><sub><italic>r</italic></sub> (<italic>θ</italic>)=<italic>a</italic>+<italic>bLogK</italic><sub><italic>a</italic></sub>) with the correlation coefficient (<italic>R</italic>) from 0.884 to 0.999 were established for the 22 examined soils. The overall <italic>R</italic> for 128 data pairs (<italic>K</italic><sub><italic>r</italic></sub>(<italic>θ</italic>) and <italic>K</italic><sub><italic>a</italic></sub>) became 0.821 (being significant at <italic>P</italic><0.01) with the slope (<italic>b</italic>) of -2.54 and intercept (<italic>a</italic>) of -10.93. For the comparison propose <italic>K</italic><sub><italic>r</italic></sub>(<italic>θ</italic>) were also predicted from RETC using experimental SMC data and van Genuchten and Brooks-Corey models. The reliability of the <italic>K</italic><sub><italic>r</italic></sub>(<italic>θ</italic>) prediction from <italic>K</italic><sub><italic>a</italic></sub> based on root mean square error (RMSE), geometric mean error ratio (GMER), and geometric standard deviation of error ratio (GSDER) criteria became considerable greater than those predicted from the two mentioned models.

Analysis on Dynamic Characteristics of Paper Feeding Device

2012 ◽  
Vol 605-607 ◽  
pp. 1224-1229
Author(s):  
Yuan Huang ◽  
Ji Fei Cai ◽  
Run Xie
Keyword(s):  
Dynamic Analysis ◽  
Theoretical Basis ◽  
Natural Frequencies ◽  
Vibrational Modes ◽  
Element Analysis ◽  
Printing Quality ◽  
Variable Head ◽  
Support Force ◽  
The Stability ◽  
Vibration Performance

Variable head sizes of paper roll will influence the stability of paper feeding device and hence the printing quality. Therefore, it is necessary to improve the printing quality by improving the stability of paper feeding device based on dynamic analysis on the phenomenon of variable head sizes of paper roll. It is found through dynamic analysis that the effect of variable head sizes on the support force of bearings is nearly five times that of the case when such effect does not exist. Vibration performance analysis of paper feeding device using finite element analysis obtains the natural frequencies of the first 6 orders for paper carriage and their dominant vibrational modes. This provides theoretical basis for the improvement of paper feeding device.

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