scholarly journals COMPARATIVE ANALYSIS OF METHODS FOR DETERMINING THE EFFECTIVE CO2 DIFFUSION COEFFICIENT IN FINE-GRAINED CONCRETE OF DIFFERENT DENSITIES

2020 ◽  
Vol 10 (1) ◽  
pp. 63-70
Author(s):  
Pavel A. FEDOROV
Keyword(s):  
Diffusion Coefficient ◽  
Comparative Analysis ◽  
Effective Diffusion ◽  
Low Permeability ◽  
Test Results ◽  
Indirect Methods ◽  
Fine Grained ◽  
Co2 Diffusion ◽  
Direct And Indirect Methods ◽  
Membrane Methods

Direct and indirect methods for determining the effective diffusion coefficient of CO2 in concrete are considered. The features of the diffusion process in a capillary-porous body are described. Based on the test results of samples of fine-grained concrete with different densities, a comparative analysis of the coefficients obtained by the main methods was carried out. The criteria for comparison were the dependence of the water-cement ratio on diffusion, as well as the rate of carbonization on time. The presence of significant deviations in the low permeability concretes of the coefficients obtained by the membrane methods of 72 % and the electrical conductivity of concrete saturated with electrolyte 85 % in the low permeability concrete from the values obtained by the carbonization method was established.

Impurity Diffusion in Silicon Annealed by Semi-Continuous Laser

1982 ◽  
Vol 13 ◽  
Author(s):  
Jean-Eric Bouree ◽  
Claude Leray ◽  
Michel Rodot
Keyword(s):  
Diffusion Coefficient ◽  
Single Crystals ◽  
Effective Diffusion ◽  
Boron Doping ◽  
Laser Pulses ◽  
Diffusion Time ◽  
Impurity Diffusion ◽  
Continuous Laser ◽  
Fine Grained ◽  
A Value

ABSTRACTThe diffusion of an impurity into a solid which is irradiated by laser pulses of some milliseconds duration has been analysed in terms of effective diffusion time and temperature. In the case of Fe in Si, the diffusion coefficient is found to be similar to that measured by COLLINS and CARLSON, and independent of boron doping. In the case of Al in Si, a value of 2.10–10 cm2/ at 1400°C has been found both for single crystals and for fine-grained polycrystals.

Diffusion of nonreactive and reactive solutes through fine-grained barrier materials

1984 ◽  
Vol 21 (3) ◽  
pp. 541-550 ◽  
Author(s):  
R. W. Gillham ◽  
M. J. L. Robin ◽  
D. J. Dytynyshyn ◽  
H. M. Johnston
Keyword(s):  
Diffusion Coefficient ◽  
Distribution Coefficient ◽  
Bulk Density ◽  
Molecular Diffusion ◽  
Effective Diffusion ◽  
Fickian Diffusion ◽  
Principal Mechanism ◽  
Barrier Materials ◽  
Fine Grained ◽  
Reactive Solutes

In many cases where fine-grained geologic materials are used as barriers to the migration of contaminated fluids, the principal mechanism of contaminant transport is molecular diffusion. Thus the effective molecular diffusion coefficient is the parameter of greatest importance when predicting migration rates and contaminant fluxes. Diffusion coefficients were measured for two non-reactive solutes (36Cl and 3H) and one reactive solute (85Sr) in seven mixtures of bentonite and silica sand ranging from 0 to 100% bentonite by weight. Tortuosity factors were calculated from the results of the nonreactive diffusion experiments, and retardation factors for the reactive solute from measured distribution coefficient (Kd), bulk density, and porosity values. The results showed the diffusive transport of both the reactive and nonreactive solutes to be consistent with a Fickian diffusion equation. For practical purposes, and at the low values of bulk density used in the experiments, the effective diffusion coefficient of the reactive solute could be calculated with a reasonable degree of certainty from the measured retardation factor and an estimated value of tortuosity. The results showed that because of the interaction between the distribution coefficient, bulk density, and porosity, an increase in clay content beyond about 5–10% did not result in a further reduction of the diffusion coefficient of the reactive solute. Key words: diffusion, adsorption, retardation, tortuosity, clay liners.

WELL TESTING HORIZONTALGAS-CONDENSATE WELLS

2017 ◽  
pp. 56-61
Author(s):  
M. L. Karnaukhov ◽  
O. N. Pavelyeva
Keyword(s):  
Comparative Analysis ◽  
Skin Effect ◽  
Horizontal Wells ◽  
Gas Condensate ◽  
Low Permeability ◽  
Well Testing ◽  
Flow Capacity ◽  
Formation Zone ◽  
Horizontal Wellbore

The well testing of gas-condensate horizontal wells are discussed in the article and the comparative analysis of borehole flow capacity, depending on the mode of it’s operation is presented. Extra attention is focused on the issue of timely identification of the reasons for the reduction of fluid withdrawal from the reservoir. The presence of high skin effect is proved, which confirms the existence of low-permeability of bottomhole formation zone related to condensation in the immediate area of the horizontal wellbore.

Aspects of orthodontic protocol in cleft lip and palate patients

2020 ◽  
Vol 20 (2) ◽  
pp. 137-142
Author(s):  
O. V. Dudnik ◽  
Ad. A. Mamedov ◽  
O. I. Admakin ◽  
A. A. Skakodub ◽  
Y. O. Volkov ◽  
...  
Keyword(s):  
Oral Hygiene ◽  
Orthodontic Treatment ◽  
Cleft Lip ◽  
Cleft Lip And Palate ◽  
Comprehensive Approach ◽  
Maxillofacial Region ◽  
Indirect Methods ◽  
Indirect Bonding ◽  
The Face ◽  
Direct And Indirect Methods

Relevance. Cleft lip and palate is one of the severe malformations of the face and jaw, requiring a comprehensive approach to the rehabilitation of the patients, including doctors of various specialties, one of which is orthodontists. A feature of orthodontic treatment is difficulty of fixing bracket systems, as well as lowering the level of oral hygiene, caused by deformation and displacement of fragments of the maxillofacial region.Purpose. Improving the effectiveness of orthodontic treatment and hygiene of the oral caviti in patients with cleft lip and palate in permanent bite period.Materials and methods. A comparison was made of the effetctiveness of fixing brackets systmes with direct and indirect bonding techniques and the effectiveness of oral hygiene during orthodontic treatment using irrigators.Results. The results of the study showed a difference in the effectiveness of using direct and indirect methods of fixing bracket systems in patients with cleft and palate. The use of irrigators as additional means of oral hygiene has demonstrated a positive dynamic of hygiene indices.Conclusions. Results of the study demonstrate the advantages of fixation the brackets by indirect bonding and use additional hygiene products irrigator for improving of oral hygiene.

scholarly journals A diet high in sugar and fat influences neurotransmitter metabolism and then affects brain function by altering the gut microbiota

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yinrui Guo ◽  
Xiangxiang Zhu ◽  
Miao Zeng ◽  
Longkai Qi ◽  
Xiaocui Tang ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Bacterial Strain ◽  
Brain Function ◽  
Intestinal Tract ◽  
High Fat ◽  
Indirect Methods ◽  
Neurotransmitter Secretion ◽  
Direct And Indirect Methods ◽  
Neurotransmitter Metabolism ◽  
Host Brain

AbstractGut microbiota (GM) metabolites can modulate the physiology of the host brain through the gut–brain axis. We wished to discover connections between the GM, neurotransmitters, and brain function using direct and indirect methods. A diet with increased amounts of sugar and fat (high-sugar and high-fat (HSHF) diet) was employed to disturb the host GM. Then, we monitored the effect on pathology, neurotransmitter metabolism, transcription, and brain circularRNAs (circRNAs) profiles in mice. Administration of a HSHF diet-induced dysbacteriosis, damaged the intestinal tract, changed the neurotransmitter metabolism in the intestine and brain, and then caused changes in brain function and circRNA profiles. The GM byproduct trimethylamine-n-oxide could degrade some circRNAs. The basal level of the GM decided the conversion rate of choline to trimethylamine-n-oxide. A change in the abundance of a single bacterial strain could influence neurotransmitter secretion. These findings suggest that a new link between metabolism, brain circRNAs, and GM. Our data could enlarge the “microbiome–transcriptome” linkage library and provide more information on the gut–brain axis. Hence, our findings could provide more information on the interplay between the gut and brain to aid the identification of potential therapeutic markers and mechanistic solutions to complex problems encountered in studies of pathology, toxicology, diet, and nutrition development.

Diffusion of Heavy Oil in SiO2 Model Catalyst and FCC Catalyst

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Effective Diffusion ◽  
Model Catalyst ◽  
Average Pore ◽  
Diffusion Factor ◽  
Fcc Catalyst ◽  
Fcc Catalysts

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.

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