Adaptation des procédés stéréologiques à la mesure des bulles d'air et des fissures dans le béton

1983 ◽  
Vol 10 (3) ◽  
pp. 415-428 ◽  
Author(s):  
Jules Houde ◽  
Serge Meilleur
Keyword(s):  
Crack Density ◽  
Three Dimensional ◽  
Total Porosity ◽  
Air Bubble ◽  
Air Content ◽  
Projected Length ◽  
Measuring Techniques ◽  
Plastic Concrete ◽  
Image Analyser ◽  
Bubble Sizes

Mathematical morphometry is the science of classifying forms through parameters such as length, area, perimeter, and projected length. Image analysers have been built to measure these parameters rapidly. Stereological equations are used to define three-dimensional characteristics from elementary count operations made in a plane.These techniques were used to characterize the air bubble system of six different concretes. All measurements were made on polished sections with a linear traverse apparatus as well as with an image analyser. The precision of the data obtained is about equal with both measuring techniques. The image analyser was able to measure the air content and the spacing factor in one-eighth of the time necessary for a linear traverse; moreover, histograms of the bubble sizes were readily available.Measurements of cracks caused by early freezing of plastic concrete made on the linear traverse apparatus, coupled with total porosity measurements by the image analyser, were used to relate the decrease of compressive strength to the increased crack density.

Study of Tip Vortex Cavitation Inception Using Navier-Stokes Computation and Bubble Dynamics Model

1999 ◽  
Vol 121 (1) ◽  
pp. 198-204 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Laura L. Pauley
Keyword(s):  
Vortex Core ◽  
Bubble Dynamics ◽  
Three Dimensional ◽  
Window Size ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Cavitation Inception ◽  
Flow Effects ◽  
Bubble Sizes ◽  
Real Flow

The Rayleigh-Plesset bubble dynamics equation coupled with the bubble motion equation developed by Johnson and Hsieh was applied to study the real flow effects on the prediction of cavitation inception in tip vortex flows. A three-dimensional steady-state tip vortex flow obtained from a Reynolds-Averaged Navier-Stokes computation was used as a prescribed flow field through which the bubble was passively convected. A “window of opportunity” through which a candidate bubble must pass in order to be drawn into the tip-vortex core and cavitate was determined for different initial bubble sizes. It was found that bubbles with larger initial size can be entrained into the tip-vortex core from a larger window size and also had a higher cavitation inception number.

Prediction of Oxygen Transfer Rates from Simple Measurements of Bubble Characteristics

1991 ◽  
Vol 23 (10-12) ◽  
pp. 1941-1950 ◽  
Author(s):  
H. J. Pöpel ◽  
M. Wagner
Keyword(s):  
Oxygen Transfer ◽  
Transfer Rate ◽  
Tap Water ◽  
Oxygen Transfer Rate ◽  
Absorption Method ◽  
Air Bubble ◽  
Air Content ◽  
Lower Accuracy ◽  
Potential Improvement ◽  
Bubble Characteristics

The oxygen transfer rate (OTR) in tap water is generally determined by the instationary absorption method, a precise but rather time consuming and tedious method. Moreover, large quantities of sodium sulfite and water are used in practice when testing aeration equipment in larger tanks. Therefore, a model is proposed by which the oxygen transfer rate can be calculated on the basis of simple and rapid measurements of the air bubble size and its distribution and of the total air content in the water applying a recently developed technique. The accuracy of this method is checked by the absorption method and can be rated as reasonable (0 to 13 % deviation). Greater accuracy is obtained at smaller bubbles (<3 mm) and improvements in this respect are proposed. The proposed method of calculating the OTR from air bubble measurements is considered as a potential improvement of the usual absorption method. Due to its still lower accuracy it can be used at present only in conjunction with the latter method, reducing its chemical and water consumption.

Determination of porosity in anisotropic fractal systems by neutron scattering

2018 ◽  
Vol 51 (1) ◽  
pp. 175-184 ◽  
Author(s):  
Xin Gu ◽  
David F. R. Mildner
Keyword(s):  
Three Dimensional ◽  
Incident Beam ◽  
Total Porosity ◽  
Incident Radiation ◽  
Two Phase ◽  
Preferred Direction ◽  
Plane Normal ◽  
Angle Scattering ◽  
Anisotropic Systems

Small-angle scattering from two-phase isotropic systems requires the scattering to be invariant to determine the relative fractions of each phase in the material. For anisotropic systems the measurement yields a result that depends on the projection of the phases onto the scattering plane, normal to the incident radiation. When the scattering system has a unique axis such that there is no preferred direction in the plane normal to that axis, the scattering gives elliptical contours on the two-dimensional detector. Two different measurements of projected phases, one with the incident beam direction coincident with the unique axis and the other normal to that axis, can be combined to give a three-dimensional description of the system and therefore lead to a determination of the total porosity of the system.

scholarly journals INVESTIGATIONS ON THE RELATIONSHIP BETWEEN POROSITY AND STRENGTH OF ADMIXTURES MODIFIED HIGH PERFORMANCE SELF-COMPACTING CONCRETE

2016 ◽  
Vol 22 (4) ◽  
pp. 520-528 ◽  
Author(s):  
Beata ŁAŹNIEWSKA-PIEKARCZYK
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Total Porosity ◽  
Self Compacting Concrete ◽  
Research Results ◽  
Air Content ◽  
New Generation ◽  
The Relationship ◽  
Viscosity Modifying Admixture

The influence of a type of new generation: superplasticizer (SP), anti-foaming admixture (AFA) and viscosity modifying admixture (VMA) on the air-content, workability of high performance self-compacting concrete (HPSCC) is analyzed in the paper. The purpose of this study was to examine the influence of type of the admixtures on porosity of HPSCC in the aspect of the compressive strength. The research results indicated that type of admixtures and its combina­tions result in different strengths of HPSCC, regardless of the total porosity characteristics of HPSCC.

Velocity Measurements in Metallic Melts

2005 ◽  
Author(s):  
S. Eckert ◽  
G. Gerbeth ◽  
T. Gundrum ◽  
F. Stefani
Keyword(s):  
Velocity Structure ◽  
Liquid Metals ◽  
Three Dimensional ◽  
Optical Probe ◽  
Mean Velocity ◽  
Application Range ◽  
Inverse Reconstruction ◽  
Measuring Techniques ◽  
Local Measurements ◽  
Velocity Measuring

Various developments of velocity measuring techniques, their tests in different liquid metals, and applications in hot melts are reported. A Mechano-Optical Probe (MOP) performing local measurements up to temperatures of about 700°C has been developed and successfully tested. The Ultrasound Doppler Velocimetry (UDV) can be considered as another attractive technique to get velocity data from opaque flows. To extend the application range to higher temperatures and to abrasive liquids a new integrated ultrasonic sensor with an acoustic wave guide has been designed. First successful measurements in a CuSn melt of about 620°C and in liquid Al of about 750°C were carried out. A fully contactless investigation of the mean velocity field is possible by magnetic tomography. Local measurements of the induced magnetic field and the application of inverse reconstruction techniques allow an analysis of the flow structure. A first demonstration experiment showing the feasibility of this approach for the reconstruction of the three-dimensional mean velocity structure is presented.

scholarly journals Sensitivity-Improved Ultrasonic Sensor for 3D Imaging of Seismic Physical Model Using a Compact Microcavity

Sensors ◽  
2018 ◽  
Vol 18 (7) ◽  
pp. 2315 ◽  
Author(s):  
Tingting Gang ◽  
Manli Hu ◽  
Xiaohong Bai ◽  
Qiangzhou Rong
Keyword(s):  
Physical Model ◽  
Bubble Diameter ◽  
Three Dimensional ◽  
Ultrasonic Waves ◽  
Ultrasonic Sensor ◽  
Side Band ◽  
Air Bubble ◽  
Highly Sensitive ◽  
Fabry Perot ◽  
Short Section

A sensitivity-improved ultrasonic sensor is proposed and demonstrated experimentally in this present study. The device is comprised only a fiber-optic microcavity that is formed by discharging a short section of hollow core fiber (HCF). The key to ensuring the success of the sensor relies on the preprocessing of hydrogen loading for HCF. When discharging the HCF, the hydrogen is heated up during the formation of the air bubble, which enlarges the bubble diameter, smoothens its surfaces simultaneously and decreases Young’s modulus of the material of the bubble. Ultimately, this results in the probe being highly sensitive to ultrasound with a SNR of 69.28 dB. Once the compact air cavity is formed between the end face of the leading-in fiber and the top wall of the bubble, a well-defined interference spectrum is achieved based on the Fabry–Perot interference. By using spectral side-band filtering technology, we detect the ultrasonic waves reflected by the seismic physical model (SMF) and then reconstruct its three-dimensional image.

scholarly journals Physical attributes of a pasture soil in southeast Goiás determined by geostatistics

2016 ◽  
Vol 36 (1) ◽  
pp. 143-151 ◽  
Author(s):  
Gabriel G. de G. Cardoso ◽  
Rilley C. Wanderley ◽  
Mara L. C. Souza
Keyword(s):  
Spatial Dependence ◽  
Particle Density ◽  
Three Dimensional ◽  
Total Porosity ◽  
Exponential Model ◽  
Indicator Kriging ◽  
Soil Samples ◽  
Regular Sampling ◽  
Physical Attributes ◽  
Porosity Analysis

ABSTRACT This study aimed to evaluate the spatial dependence of physical attributes in a soil cultivated with Brachiaria grass. A 12-m regular sampling grid was established within an area of 3.500 m2. Thirty-five soil samples were collected at 0-30 cm depth for particle density, bulk density, texture and total porosity analysis. These data were evaluated using statistical methods of indicator kriging and the GS+ software. The GS+ software was used to develop three-dimensional maps and evaluate semivariograms. The spatial dependence was evaluated using experimental semivariograms. The analyzed attributes indicated the occurrence of spatial dependence when fit to the exponential model. Areas with higher porosity occurred in the regions with lower bulk densities and higher particle densities.

Three-dimensional manipulation of femtosecond filament direction with an air bubble in water

2012 ◽  
Vol 14 (7) ◽  
pp. 075205
Author(s):  
Qiannan Cui ◽  
Jinping Yao ◽  
Jielei Ni ◽  
Ya Cheng
Keyword(s):  
Three Dimensional ◽  
Air Bubble
Sign in / Sign up

Export Citation Format

Share Document