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During the past four decades the use of nonwoven geotextiles as filter materials in geotechnical works has experienced a marked increase. In this study, the water permeability coefficient of nonwoven geotextiles after 23 years of exploitation in drainage system was determined to evaluate the influence of physical clogging on filtration performance of geotextiles. The obtained results showed that the geotextiles were clogged by soil particles. What is more, the objective in this study was to establish a gradient ratio test method for estimating a clogging phenomenon of geotextile filter adequately. A series of gradient ratio tests on three kinds of needle-punched nonwoven geotextile filters whose number of constrictions differs was performed. A geotextile filter was put under a silty sand layer. Based on the test results, it was confirmed that the water permeability coefficient became small as the gradient ratio increased, depending on the number of constrictions of the geotextile. It was also found that the modified gradient ratio GR4 is more sensitive than GR8 and GR25. Based on interpretation of the experimental results, the authors recommend the acceptance limit of GR8 equal to 3.7 and of GR4 equal to 4.8.

A constant head permeability test of the coarse-grained soil of an earth-rockfill dam was carried out and the gradation of the tested soil was determined based on the continuous gradation equation. Based on the test results, an empirical formula of permeability coefficient considering the influence of gradation was established. The formula can be used to assess the influence of gradation on permeability coefficient with respect to the area under the gradation curve. The applicability of the formula was verified based on the results of the permeability test from other studies. It was found that the empirical formula of permeability coefficient based on gradation area was suitable for coarse-grained soil. This paper provides a new perspective for the study of permeation behavior of coarse-grained soil.

Topical corticosteroids are the primary treatment of ocular inflammation caused by surgery, injury, or other conditions. Drug pre-corneal residence time, drug water solubility, and drug corneal permeability coefficient are the major factors that determine the ocular drug bioavailability after topical administration. Although growing research successfully enhanced local delivery of corticosteroids utilizing various strategies, rational and dynamic approaches to strategy selection are still lacking. Within this review, an overview of the various strategies as well as their performance in retention, solubility, and permeability coefficient of corticosteroids are provided. On this basis, the tradeoff of strategy selection is discussed, which may shed light on the rational choice and application of ophthalmic delivery enhancement strategies.

This study was to determine the physical properties of the soil and the effect of adding coconut ash to the permeability coefficient using the fall method. Soil sampling was carried out in Bolu Village, Rantepao District, North Toraja Regency and the added material used coconut fiber from community waste located on Biring Romang Street, Kapasa Village, Makassar City with the proportion of added material being 0%, 5%, 10%, and 15%. The structure in this research is to use research on the physical properties of the soil and then compile the composition of the alloy to the soil permeability test so that it can produce a coefficient of soil permeability. The results of this study indicate that the soil meets the characteristics as clay soil. The effect of adding fiber ash to the soil is a decrease in the permeability value where the higher the proportion of coconut fibers, the smaller the permeability until the addition of 15%.

We describe a micron-sized ore powder production by propulsion and rapid unloading of high-pressure gas. The research consists of three parts. Firstly, we obtain the tensile strength parameters and permeability coefficient based on the experiment. Secondly, gas propulsion pressure and gas infiltration pressure of the powdering experiment are confirmed. Thirdly, the ore will be fragmented into micron-sized powder when rapid unloading occurs. The grain size analysis indicates that more particles with smaller sizes are obtained at a higher propulsion gas pressure. Particles less than 0.147 mm obtained at the 65 MPa gas propulsion pressure account for 63% of the sample. The critical gas propulsion pressure is determined to be 55 MPa when the volume ratio is 1:3. Powdering experiments show that this method is suitable for metallic and non-metallic ores.

Air penetration behavior plays a vital role in the performance of fibrous material in various industrial applications. Two parameters, the permeability coefficient and airflow resistivity, can describe the air penetration behavior of fibrous material. FX 3300 Textech Tester III and AFD300 AcoustiFlow devices were used to respectively characterize the permeability coefficient and airflow resistivity of nonwoven materials. Nonwoven samples were compressed due to the load from the test head of the FX 3300. Finite element analysis along with the mathematical method were implemented to recover the airflow permeability of samples at the uncompressed state. The effects of pressure drop on the airflow velocity and permeability coefficient were analyzed by the Ergun-type model. The determination of airflow resistivity based on the permeability coefficient is carried out via two approaches, that is, the direct method and the extrapolation method. The results show that the airflow velocity is not linearly related to the pressure drop, which differs from Darcy's law. This non-linear relation is mainly attributed to the influence of frictional loss. By comparing the relative error between assessed and measured airflow resistivity, most of the assessed values of the compressed samples are overestimated. The results also suggest that the direct and extrapolation methods are applicable to assess airflow resistivity on an airflow velocity (or air permeability) test device. Moreover, the Ergun-type model is also applicable to determine the permeability coefficient and airflow resistivity of nonwoven materials.

Porous asphalt pavement is mainly used for parking lots which able to let water to drain through the pavement surface into a stone recharge bed and infiltrate into soils under the pavement. This study is to investigate the performance of seashell in porous asphalt and determine the image analysis. The seashell used in this study is cockle shell. The strength of seashell was determined through the Aggregate Impact Value Test (AIV) and Aggregate Crushing Value Test (ACV). The grade of bitumen used was grade 60/70. The porous asphalt volumetric properties was determined through Marshall Stablity Test. The permeability coefficient of sample that contain seashell as aggregate replacement was determined through Permeability Test. Generally, the results shows that the seashell’s percentage loss (AIV and ACV) is suitable use for porous asphalt mixture, where the percentage of loss for AIV and ACV was 27.84% and 7.65% respectively. Based on the Marshall Test, porous asphalt that containing seashell as aggregate replacement shows a different result, where it had lower stability value and it can increase the bulk density of porous asphalt mixture. Furthermore, the permeability coefficient also increase. The surface of seashell able to bond with bitumen. Lastly, the trend of VFA and VTM value is effected by the surface and position of seashell in the porous asphalt sample.

Purpose The purpose of this paper is to form a numerical simulation method for permeability coefficient that can consider the characteristics of gravel gradation and further explore the effects of indoor test factors and gradation characteristics on the permeability coefficient of gravel. Design/methodology/approach The random point method is used to establish the polyhedral gravel particle model, the discrete element method (DEM) is used to construct the gravel permeability test sample with gradation characteristics and the finite element method is used to calculate the permeability coefficient to form a DEM-computational fluid dynamics combined method to simulate the gravel seepage characteristics. Then, verified by the indoor test results. Based on this method, the influence of sample size, treatment method of oversize particles and the content of fine particles on the permeability coefficient of gravel is studied. Findings For the gravel containing large particles, the larger size permeameter should be used as far as possible. When the permeameter size is limited, the equal weight substitution method is recommended for the treatment method of oversized particles. Compared with the porosity, the pore connectivity has a higher correlation with the permeability coefficient of the sample. Research limitations/implications Insufficient consideration of the movement of gravel particles in the seepage process is also an issue for further study. Originality/value The simulation method described in this paper is helpful for qualitative analysis, quantitative expression of pore size and makes up for the defect that the seepage characteristics in pores cannot be observed in laboratory tests.

The results of studying the convective drying of cylindrical granules of a support for a nickel catalyst using mathematical modeling techniques have been presented. A mathematical model for intensive heat and mass transfer in a granule has been formulated that makes it possible to choose the efficient regimes of convective drying. The specific feature of the mathematical model is the analytical calculation of local mass transfer coefficients for a liquid taking into account the sorption properties of a material, a permeability coefficient, the local values of the moisture content, and temperature. Comparison of the results of mathematical modeling of heat and mass transfer in granules and the data of a laboratory experiment has shown that they are in satisfactory agreement.

Urban construction has produced a large amount of construction waste which has caused huge environmental problems. The sponge city is the development direction of urban construction, and permeable pavement concrete is an important material for sponge city construction. To see the law influencing different factors on the performance of recycled aggregate permeable pavement concrete, different water binder ratios, recycled aggregate particle gradations, ordinary aggregate substitution rates, and fly ash and admixture contents are designed to prepare permeable concrete. The compressive strength, permeability coefficient, frost resistance, and pore structure of permeable concrete are tested. The results show that when the replacement rate of recycled aggregate is 50%, the 28-d strength of concrete with a 0.25 water binder ratio can reach 28.9 MPa, and the permeability coefficient is 13.26 mm/s. The addition of fly ash will reduce the compressive strength, and the permeability coefficient increases first and then decreases with the increase of the fly ash content. When the mass fraction of fly ash instead of cement is 12%, the 28-d strength is 94.8% of that of the cement group, and the permeability coefficient can reach 14.03 mm/s. A water-reducing agent can obviously improve the workability of permeable concrete; the best content of the water-reducing agent is 0.2% of the cement mass. A reasonable amount of fly ash and water-reducing agent can optimize the number of harmless holes and less harmful holes in the concrete to improve the frost resistance and strength after the freeze–thaw, and the frost resistance is F150. This study provides a theoretical basis and technical guarantee for the resource utilization of recycled aggregate in permeable pavement concrete.

The aim of this paper is to show the complexity of studying air void topology by giving an in-depth literature review. Factors defining air void structure are presented and relationships and correl...

The SWCC has played an important role in studying the physical-mechanical behavior and hydraulic property of unsaturated soils. Laboratory experiments of SWCC were performed on unsaturated loess based on filter paper method considering freeze-thaw cycle, coupling of freeze-thaw cycle and dry-wet action. The main results indicate that: (1) With the increase of freeze-thaw cycle or freeze-thaw and dry-wet coupling, the matric suction was logarithmically decreasing and the dry-wet path affected matric suction significantly. There were obvious hysteresis loops between the two SWCC curves of different dry-wet paths, which increased with the increase of water content. (2) The Gardner Model was more appropriate to describe the SWCC, and through measured SWCC from Gardner Model and Childs & Collis-George Model, the prediction model of unsaturated loess permeability coefficient was gained, which had an exponential relationship with matric suction and a power function relationship with volumetric water content, respectively. (3) The vertical distribution model of permeability coefficient under one-dimensional steady state flow was established. The vertical permeability coefficient gradually decreased from groundwater table to ground surface, it decreased first then increased and gradually stabilized with the increase of freeze-thaw cycle at the same depth of soil.

The cement-plaster bonded rock-like material is one of the most commonly used materials to simulate different rocks in physical model tests. However, the applicability of this material in solid-fluid coupling model tests is not clear because there are few research studies on the water-physical properties of this material and its similarity to the actual rock is uncertain. This paper presents a systemic experimental study on the water-physical properties of the cement-plaster bonded rock-like materials. The parameters of rock-like materials, including water absorption, softening coefficient, and permeability coefficient, were compared with those of actual rocks to analyse the applicability of such material. Then, the influence of proportion on the water-physical properties of this material was discussed. By multiple regression analysis of the test results, empirical equations between the water-physical parameters and proportions were proposed. The equations can be used to estimate the water-physical properties of cement-plaster bonded rock-like materials with specific proportion and thus to select suitable materials in the solid-fluid coupling physical model tests.

Artificial reclamation is one of the main means of land expansion in coastal cities. However, the permeability of underlying soft clay (USC), derived from the dredged load, has not been paid enough attention, although it is closely related to the long-term deformation and stability of foundation soil. Hence, this paper analyzes the relationship between permeability characteristics and microscopic pore characteristics of USC in Chongming East Shoal (CES), a typical multi-phase reclamation area, through a variable head permeability test, mercury intrusion porosimetry (MIP) test, and scanning electron microscope (SEM) test. Furthermore, grey relation entropy and Pearson correlation analysis are implemented to analyze the influence of micropore parameters on permeability. The results revealed that the seepage process of clay showed a transition from unstable seepage to relatively stable seepage. Meanwhile, the permeability coefficient (PC) attenuated with time cyclically, indicating the alternating effect of the closed and opened unstable seepage channels. During seepage, clay particles could be entrained by pore water and intercepted by pores, thus clogging seepage channels. Then, the increased pore water pressure could break through new seepage channels. The degree of pore clogging was positively correlated with the average cycle period of PCs, and this was also present in the relatively stable stage of PCs. A lower mesopores content, higher fractal dimension, and aggregated flocculate microstructure could promote the clogging effect and result in lower permeability efficiency. Affected by unstable seepage channels, soft clay may face long-term potential deformation in the future, which needs further investigation.

Polysiloxanes have high oxygen permeability coefficient (\(P_{\text{O}_{2}}\)) and low oxygen separation factor (α = \(P_{\text{O}_{2}}\)/\(P_{\text{N}_{2}}\)) and polyimides high α and low \(P_{\t...

Knowledge about soil permeability is important in various scientific fields: hydrology and hydrogeology, geotechnics, environmental geotechnics, and others. Depending on the different goals that need to be achieved by a particular engineering project, the conditions in which the permeability coefficient is determined in terms of applied hydraulic gradients, applied stresses, type of test fluid, etc. are adjusted, as well as the required precision of its determination. In addition, the permeability coefficient is a soil property with the largest range of possible values. It can be determined through various laboratory and field methods, and by applying established empirical correlations using data on the grain-size distribution and empirical coefficients that depend on some factors, such as hydraulic radius (specific surface), curvature, porosity, etc. This paper presents the results of laboratory testing of the permeability coefficient by the constant head test and the use of a permeameter. The results were compared with the permeability coefficient obtained by applying a number of empirical correlations. Artificial samples were prepared in the laboratory by mixing different previously prepared soil fractions in order to determine the influence of particle size and soil gradation on the estimated soil permeability coefficient., Poznavanje koeficijenta propusnosti tla važno je u različitim znanstvenim područjima: hidrologiji i hidrogeologiji, geotehnici, geotehničkome inženjerstvu okoliša i drugim. S obzirom na različite ciljeve koje treba postići određenim inženjerskih zahvatom, prilagođavaju se uvjeti u kojima se laboratorijski određuje koeficijent propusnosti tla poput veličine hidrauličkoga gradijenta, primijenjenih naprezanja, vrste ispitnoga fluida i slično, a prilagođava se i potrebna preciznost njegove odredbe. Osim toga, koeficijent propusnosti svojstvo je tla koje ima najveći raspon mogućih vrijednosti. Moguće ga je odrediti različitim laboratorijskim i terenskim metodama te primjenom poznatih empirijskih korelacija uz korištenje podataka o granulometrijskome sastavu porozne sredine. U ovome radu prikazani su rezultati laboratorijskih ispitivanja koeficijenta propusnosti metodom sa stalnom razlikom potencijala i korištenjem permeametra te su uspoređeni s koeficijentom propusnosti dobivenim upotrebom većega broja empirijskih korelacija. Korišteni su uzorci pripremljeni u laboratoriju miješanjem različitih prethodno pripremljenih frakcija tla, kako bi se mogao utvrditi utjecaj graduiranosti tla i veličine čestica na koeficijent propusnosti tla. U radu je pokazano kako se ne može dobiti dovoljno pouzdan koeficijent propusnosti tla samo korištenjem empirijskih korelacija. Iako je područje primjene određene korelacijske veze bilo zadovoljeno, izračunani koeficijenti propusnosti u nekim slučajevima znatno su se razlikovali od onih izmjerenih u laboratoriju. Svaka od gore navedenih metoda ima svoje prednosti i nedostatke te je tek upotrebom dviju ili više metoda moguće dobiti projektni parameter tla koji je dovoljno pouzdan.

The permeability property of a packed particles material has been caught much attention, it depends upon its pore characteristics caused by the particle accumulation, but the current empirical formulas and the permeable theory could not re-veal the effect of the particle accumulation thoroughly. In this paper, a theoretical formula is derived, and the fractal gradation spectrum is adopted to confirm the particle size distribution, furthermore, the pore feature is determined by the particle size and accumulation features, finally a permeability model of the packed particles material is established. In this model, the effect of particle size distribution on pore features is estimated more thoroughly than those in conventional models, and the calculated results are more accurate and verified experimentally.

The water pressure test and steady-flow pumping test are still commonly used for measuring the permeability coefficient of rock and soil strata. Limited by the fact that the average value of the permeability coefficient could be obtained only by this testing method, the accuracy of the experimental results of the permeability coefficient for special rock and soil strata is not good. Therefore, a new on-site testing method and equipment for continuously measuring the permeability coefficient of rock and soil strata is studied in this paper. The method is suitable for water pressure testing in borehole and the steady-flow pumping test. The technical proposal is when the pumping test or water pressure test is carried out, the final water penetration will tend to be a stable value, and then, the high-precision current meter probe will be placed at the bottom of the pumping test hole or water pressure test hole. For the pumping test, the current meter will be lifted uniformly from the bottom of the borehole testing section to the stable water level. Meanwhile, the flow rate of a differential zone of the tested section is continuously detected. For the water pressure test, the current meter will be lifted uniformly from the bottom of the borehole test section to the top of the borehole test section, and the flow rate of the differential section will be continuously detected. Through data analysis and processing, not only the average permeability coefficient of the detected sections can be obtained but also the permeability coefficient of the differential section of the rock and soil stratum can be calculated, respectively. Furthermore, the corresponding relationship between the permeability coefficient and the detected location can be obtained. In view of the abovementioned reasons, the leaking point, the specific position, and the leakage quantity of the detected section could be found out accurately, which will improve the accuracy of the testing results obviously.

In fracture or compaction grouting projects of sand layer, there exist many compacted sand regions on both sides of grout veins or around grout bulbs. It has an important effect on the final reinforcement effect of the sand layer that how much performance of the sand layer is improved after being compacted. Compression modulus, cohesion, and permeability coefficient are selected to be the performance indexes of the compaction reinforcement effect of sand. The relationship between the performance properties of sand and grouting pressure has been tested and analyzed. And influences of clay content and initial water ratio of sand on the compaction reinforcement effect have been studied. Results show that compaction can effectively improve the mechanical properties and impermeability properties of sand. Compression modulus of sand increases by 2∼18 times. The cohesion of sand increases from the scope of 9.4∼26 kPa to the scope of 40∼113.6 kPa. The permeability coefficient of sand decreases from the scope of 1.0 × 10−2∼ 8.33 × 10−4 cm/s to the scope of 2.19 × 10−4∼2.77 × 10−9 cm/s. When the clay content of sand is smaller than about 20%, sand cannot be reinforced effectively by compaction. Cohesion cannot be improved significantly and the permeability coefficient cannot be reduced markedly. A high initial water ratio of sand is beneficial to improve the compression modulus of compacted sand and goes against the improvement of cohesion of compacted sand. In addition, the initial water ratio has little effect on the permeability coefficient of compacted sand. In the end, fitting formulas have been developed to quantitatively describe the compaction reinforcement effect of sand by different grouting pressures.

Clogging effect surrounding prefabricated vertical drains (PVDs) is a typical problem when vacuum preloading is applied to a dredged fill foundation. A large-scale model test was designed to clarify the cause and mechanism of the clogging effect, and the basic physical and mechanical parameters of the soil in the clogging zone were tracked during the test. The results demonstrated that a clogging zone was formed around the PVD in the early stage of improvement with conventional vacuum preloading, and the boundary of the clogging zone was approximately 0.2–0.4 of the boundary radius. The clogging zone surrounding the PVD was formed because of the overall movement of the soil toward the PVD under the high vacuum pressure gradient, rather than fine particle migration. The soil in the clogging zone exhibited permeability anisotropy and equivalent ‘smear’ effect. The permeability ratio (kh/kv) was less than 1, and the ratio of horizontal permeability coefficients at the test distances of 45 cm and 10 cm were 9.6 at a depth of 20 cm and 8.9 at a depth of 80 cm. An analysis of the microstructure of the soil in the clogging zone demonstrated that the clay particles tended to be vertically oriented. The re-orientation of the clay particles reduced the horizontal permeability coefficient and led to the permeability anisotropy of the soil in the clogging zone. Thus, decrease in the horizontal permeability coefficient and equivalent ‘smear’ effect of the soil in the clogging zone affect the consolidation of dredged fill, which leads to the clogging effect. The permeability anisotropy also slightly affects consolidation.

The process technological parameters of forming a film composite for making heat-protective clothing have been developed. The peculiarities of its application in sewing production are taken into account. The effect of the initial polymer compositions formulation on the formed composites physical-mechanical and technological properties was studied. It has been found that the use of the composite film material developed reduces the compounds permeability of protective clothing.

The influence of the sealing degree of the lining structure and the permeability of surrounding rock on the stability of the tunnel has always been the main topic concerned by the relevant engineering researchers. Based on the research background of the tunnel project of Qingdao metro line 1 and the in-depth analysis of the existing research results, this paper makes a systematic analysis and research on the influence mechanism of the sealing degree of the lining structure and the permeability of surrounding rock on the stability of the tunnel by the numerical simulation. The results show that the safety coefficient of each part of lining structure decreases with the increasing degree of tunnel sealing, which is manifested by the increase of the settlement of the vault and the convergence of the arch foot. In addition, the stability of surrounding rock becomes worse with the increase of permeability coefficient of surrounding rock, which means the higher pore pressure and larger displacement of rock around the chamber. At the same time, the influence of the sealing degree of the lining structure on the stability of the tunnel will increase with the permeability of the surrounding rock. The works in this paper have guiding significance for the construction of submarine tunnel under different characteristics of surrounding rock and the selection of sealing degree of lining structure.

The strength and permeability of tailing-waste rock mixtures directly affect deposits’ stability for an alternative co-disposal technique. In the mixed co-disposal method, the void of the waste rock is filled with tailings, while the waste rock forms the particle skeleton. This method does not only improve deposits stability but also potentially reduces acid pollution. In this study, the rock percentage influence on the shear strength and permeability of tailing-waste rock mixtures was investigated by carrying out large triaxial tests and permeability tests. The shear strength, enhanced strength mechanism, and mixture permeability were analyzed. The results indicate that the shear strength and internal friction angle of the tailing-waste rock mixtures gently increased until the rock percentage reached 30% and then rapidly increased with the further increase of the rock percentage. The permeability coefficient of the mixtures slowly increased until the rock percentage reached 50% and then rapidly increased with the further increase of the rock percentage. The tailings washed out of the waste rock skeleton when the permeability was large. In this paper, 50% of waste rock is recommended for building mixture deposits.

Numerous studies focused on the human exposure to plasticizers via dermal contact; however, the percutaneous penetration of plasticizers was seldom considered in exposure assessment. In the present study, skin wipes of palms, back-of-hands, and forehead were collected from 114 participants (ages: 18-27). There was no significant difference between the levels of phthalates from palms and back-of-hand, while all phthalates collected from the forehead were significantly higher than those from palms and back-of-hand (p < 0.001); di(2-ethylhexyl)phthalate levels were substantially higher than other detected phthalates followed by di(n-butyl)phthalate and di(isobutyl)phthalate (DiBP), and for alternative plasticizers, bis-2-ethylhexyl terephthalate levels were substantially higher than acetyltributyl citrate and bis-2-ethylhexyladipate. Skin permeation and metabolism of phthalates was assessed using human skin equivalent models. The permeability coefficient (kp) values of phthalates were significantly negatively correlated with their log octanol-water partition coefficient (log Kow), while a significantly positive correlation was found between the log Kow and the cumulative amounts of phthalates in the cells. The proportion of phthalate intake via dermal exposure to skin wipes ranges from 1.3% (for dimethyl phthalate) to 8.6% (for DiBP) and suggests that dermal absorption is a significant route for adult phthalate exposure.

To investigate the influence of confining pressures and temperatures on the seepage characteristics of fractured rocks, seepage tests were conducted on a fractured silty mudstone using a self-developed experimental system, and the effects of different factors on coefficient of permeability were discussed. The results showed that the increasing confining pressure will gradually decrease the coefficient of permeability, and this process is divided into two stages: 1) the fast decrease stage, which corresponds to a confining pressure less than 30 kPa, and 2) the slow decrease stage, which corresponds to a confining pressure larger than 30 kPa. Unlike confining pressure, an increase in temperature will increase the coefficient of permeability. It is noted that fracture surface roughness will also affect the variation of coefficient of permeability to a certain extent. Among the three examined factors, the effect of confining pressure increases is dominant on fracture permeability coefficient. The relationship between the confining pressure and coefficient of permeability can be quantified by an exponential function.

In vitro blood–brain barrier (BBB) models are a useful tool to screen the permeability and toxicity of new drugs. Currently, many different in vitro BBB models coexist, but none stands out as being notably better than the rest. Therefore, there is still a need to evaluate the quality of BBB models under various conditions and assess their ability to mimic the in vivo situation. In this study, two brain endothelial cell lines (bEnd.3 and hCMEC/D3) and two epithelial-like cell lines (MDCKII and Caco-2) were selected for BBB modelling purposes. They were grown as monolayers of a single cell type, under the following conditions: in coculture with either primary or immortalised astrocytes; or in the presence of primary or immortalised astrocyte-derived conditioned media. A total of 20 different BBB models were established in this manner, in order to assess the effects of the astroglial components on the BBB phenotype in each case. To this end, six parameters were studied: the expression of selected tight junction proteins; the enzyme activities of alkaline phosphatase and of gamma glutamyl transpeptidase; the transendothelial/transepithelial electrical resistance (TEER); restriction in paracellular transport; and efflux transporter inhibition were each evaluated and correlated. The results showed that coculturing with either primary or immortalised astrocytes led to a general improvement in all parameters studied, evidencing the contribution of this cell type to effective BBB formation. Furthermore, the permeability coefficient ( P e) of the tracer molecule, Lucifer Yellow, correlated with three of the six parameters studied. In addition, this study highlights the potential for the use of the Lucifer Yellow P e value as an indicator of barrier integrity in in vitro BBB models, which could be useful for screening the permeability of new drugs.

The supported liquid membrane in comparison with the solvent extraction helps in the facilitation for transferring Sm(III) ions from an aqueous feed to the stripping solution. The synergistic effect in the increase of the permeability coefficient was investigated with a mixture of extractants. The synergism of D2EHPA with Cynex272 or Cyanex301 extractants increases the permeability coefficient to 23.08 × 10–6 m/s and 20.38 × 10–6 m/s, respectively. The carrier with only D2EHPA could reach the permeability coefficient of 7.75 × 10–6 m/s. The kinetic modeling based on the resistance of phases showed that there is a good agreement between the experimental data and the modeling data.

A polyoxadiazole polymer POz-CF3 was prepared and complete gas permeation properties were investigated on its corresponding membrane using pure-, and multicomponent mixed-gas feeds. The POz-CF3 mem...

Column leaching experiments with ion adsorption-type rare earth ores for different lixiviant concentrations and different column heights were carried out. A mathematical model of column leaching was constructed based on the experimental data. Two parameters (a and b) in the model were determined according to the following methodology: the ore column was divided into several units; each unit was treated with multiple leaching steps. The leaching process was simulated as a series of batch leaching experiments. Parameter a of the model was determined based on the selectivity coefficient of the balanced batch leaching experiment. Further, the influences of ammonium sulfate concentration, rare earth grade, column height, permeability coefficient, and hydrodynamic dispersion coefficient on the extraction were analyzed. Relationships between parameter b, the ammonium sulfate concentration, and the physical and mechanical properties of the ore column, were examined using dimensional analysis. It was determined that the optimal ammonium sulfate concentration for different column heights (2.5, 5.0, 7.5, and 10.0 cm) using the mathematical model were 5.9, 6.2, 7.3, and 7.7 g/L, respectively. The mathematical model can be used to estimate the breakthrough curve, leaching rate, and leaching period of rare earth ores, to achieve optimal extraction.

The paper aims to comparison the permeability coefficient in non-cohesive soils by the method of test pumping and based on tests in a consolidometer. The tests were carried out on 18 types of non-cohesive soils with different fraction. Pumping tests were carried out according to the standard method i.e. by making one well with a diameter of 400 mm and installing two piezometers at different distances from the well. The water table change was measured in piezometers during water pumping from the well. Tests in the consolidometer were carried out on soil samples that were first compacted to the same density index as in the test site. The tests were carried out with a continuous inflow of water from below with constant gradients of 0.50. The tests presented in the paper allow to verify and compare the values of the permeability coefficient in non-cohesive soils determined in the field and laboratory tests.

Mechanical biological treatment (MBT) can greatly reduce the amount of municipal solid waste (MSW) and has become a hot topic in environmental geotechnical engineering. To study the effects of factors such as the pressure, dry density, compression time under pressure, strain, and hydraulic gradient, permeability tests with saturated MBT waste were conducted by using a compression and permeability combined apparatus in an environmental geotechnical laboratory. The results showed that Darcy’s law was applicable to the saturated MBT waste. The permeability coefficient was found to be inversely related to the pressure, dry density, compression time under pressure and strain. The logarithmic permeability coefficient and the variables (e.g., pressure) could largely be fitted to a linear function. Additionally, a prediction model for the permeability coefficient was established, and the permeability coefficient at different depths of MBT landfills was predicted. The results were then compared to previous studies on MSW and MBT waste to investigate the permeability mechanism.

The water-richness of Quaternary unconsolidated aquifers is closely related to the safe production of coal mining in shallow area near the Quaternary System. We attempt to establish a model for evaluating the water-richness of the unconsolidated aquifers quantitatively. We first obtained the main factors affecting the water-richness of the unconsolidated aquifers, including the aquifer thickness m, the proportion of the clay layer in the aquifer, the specific water yield q, and the permeability coefficient K. Using the AHP method mentioned above, the final weight for each affecting factor is illustrated in the vector w = (0.4921 0.1038 0.2686 0.1354). Secondly, we proposed the quantitative evaluation levels of the water-richness in the unconsolidated aquifers and the extension matter-element method to establish the evaluation model. Finally, we applied and verified the evaluation model by takeing the Xingyuan Coal Mine in China as an example. The results indicate that the water-richness of aquifer from the evaluation model are consistent with the field measurement results based on the ground transient electromagnetic method.

Permeable pavement is generally considered as one of the most effective prac-tices of rainwater management. This paper analyses the defects of current permeable pavement. Inspired by the honeycomb bionic structure which has superior mechanical properties and structural efficiency, an innovative “honeycomb-like” model of permeable brick measuring 190 × 100 × 60 mm in size was proposed and constructed. The mechanical strength and permeability performance of the honeycomb permeable brick were experimentally assessed by universal testing machine and artificial rainfall equipment, respectively. Ex-periment results demonstrated an excellent performance in compressive toler-ance and permeability. The critical damage load (Fc) and compressive strength (Ec) of honeycomb brick were 336.46 KN and 17.70 MPa, which were 18.06% and 11.04% higher than that of ordinary solid permeable bricks, respectively, compared with the conventional permeable bricks. The honeycomb brick is capable of increasing the permeability coefficient by 19.2% and 11.96% under rainfall repetition period of 20 and 30 years respectively. These results demon-strated that the permeable brick with honeycomb-like structure can provide a new paving strategy for the construction of sponge city.

The errors in the snow reserves recovered from satellite data in forest territories are mainly associated with the nature of the snow thickness and the characteristics of plant communities. The main objective of our research is to assess the local variability of snow reserves in modern climatic conditions in connection with the forest taxonomic heterogeneity as a possible additional source of errors in snow reserves calculating with using satellite information. Errors of snow сover characteristics recovered from satellite data (product GlobSnow (SWE), European Space Agency) for basic points within the forest zone of the East European Plain were calculated for absolute values, indicators of interannual and long-term variability. The errors obtained are connected with the approaches considering in model algorithms the reflective ability of the snow cover in forest tracts (permeability coefficient). Using experimental observations results in the Central Forest Reserve, noticeable local differences in the actual characteristics of the snow cover in the forest territories with a predominance of coniferous or deciduous species are revealed. The obtained patterns can be used to refine regional estimates of snow reserves calculating using satellite imagery.

Methods and instruments the characteristics of porosity and permeability of solids and materials are described, which are part of the improved GET 210-2014. The metrological characteristics of the GET 210-2014 are compared and after its improvement the GET 210-2019. Certified reference materials of approved types based on micro-, meso- and macroporous solids are considered. The results of international comparisons, confirmed measuring and calibration capabilities, as well as a comparison of the metrological characteristics of the GET 210-2019 with the standards of foreign countries are presented.

Gas drainage is an important technology to prevent coal and gas outburst, and the drained gas is a kind of clean energy. The gas pressure can characterize gas drainage effectiveness. In this paper, we investigated the effectiveness of gas drainage by gas pressure. Determined by the space shape of the gas flow field, the gas flow state surrounding the drainage boreholes is radial flow. According to the basic equations of radial flow, discrete equations were achieved by the implicit difference scheme, and then we obtained the gas pressure surrounding the drainage boreholes. Results showed that the midpoint between two holes presents the highest gas pressure, and gas pressure declined from the midpoint of two boreholes to both sides. The midpoint gas pressure of the two holes reflects gas drainage effectiveness in a certain degree. Gas pressure declined with segmented characteristics in the first period decline curve in the form of a cubic curve, and the second period decline curve in the form of a straight line. When the drainage pressure reaches a certain value, the decline rate of gas pressure had little relationship with the drainage negative pressure, mainly influenced by the permeability coefficient. To improve the drainage effectiveness, anti-reflection measures are feasible, instead of increasing the drainage negative pressure. Moreover, the conclusion was verified by field data.

One of the main means of reducing aerodynamic noise is the use of silencers, which can be made of various porous materials, depending on the specific operating conditions. The aim of the work is to study the dependence of the noise reduction on the characteristics of porous permeable materials (PPM) obtained by vibration molding from metal powders. Such PPMs have a wide range of porosity, high permeability, mechanical strength, provide the ability to work in a wide temperature range, high corrosion resistance, and therefore find more and more widespread application in practice. When designing silencers, their pore size, permeability, mechanical strength, cost, and the chemical composition of the material are taken into account. Basic research methods – determination of noise level, powder particle size, permeability coefficient, pore size. Vibration molding of PPM samples for experimental studies was carried out on a ВЭДС 10-1А vibration bench with vibration parameters that ensured the maximum bulk density of the powder in the mold (acceleration 10 m/s2, frequency 500 Hz). Main results – the dependence of the noise reduction value on the PPM characteristics obtained by the method of vibration molding of metal powders of various grades of various particle size distribution was studied. It has been shown that the most effective damping is provided by PPM from spherical bronze powder of the БрОФ10-1 grade with particle sizes of 350–400 microns, which provides at the same time a combination of a high level of noise reduction and high permeability to air or gas. It was found that the thickness of the muff significantly affects the efficiency of noise suppression, while the minimum thickness of the muff, which provides a sufficiently high degree of noise reduction, is about 3.5 mm, therefore it is not practical to increase the thickness of the muffler material above this value.

Smear zone is usually formed around the prefabricated vertical drains (PVD’s) due to mandrel driving. The geotechnical properties of the soil in this zone exhibit significant changes that affect the performance of the PVD’s. The most relevant property in this respect is the coefficient of permeability. So far, no serious attention is paid to investigate the effects of shearing under large shear strains on the geotechnical properties of the soft soil in Fao region. In this study, an extensive laboratory testing program was conducted to assess the characteristics of the smear zone with an emphasis on the permeability coefficient of Fao soft soil. The results show that the permeability of the smear zone is about 70% of the horizontal permeability of the intact soil. An attempt was made to estimate the extension of the shearing zone in the direct shear test. The analysis results indicate that thickness of the shearing zone is about (2.4) cm.

In order to determine the water infiltration rate (WIR) of asphalt pavement on a filled subgrade, a three-layer structure consisting of an asphalt surface layer, base course, and subgrade w...

The depths and areas of the scour holes around spur dikes are the most concerning issues regarding spur dike design. In this study, using a moving bed experiment, the influence of traditional rock-fill spur dikes and new permeable spur dikes with different permeabilities on riverbed scour under unsteady flow was studied, and the spatial characteristics of scour holes at dike heads were analyzed. The results show that with increases in the permeability coefficient of the spur dike, the depth and area of the scour hole at the dike head gradually decreases; however, when the permeability coefficient is more than 17.6%, the depth and area of the scour hole downstream of the dike body increases with an increase in the permeability coefficient. According to comprehensive evaluation, when the water permeability is 17.6%, the stability of the spur dike is at its best. The maximum depth of the scour hole at the dike head is affected by factors such as the spur dike permeability coefficient, effective scouring time, and width bottom protection structure. On this basis, a new formula for calculating the maximum depth of the scour hole at a dike head is proposed. These research results will be beneficial to the reliability of spur dikes and the sustainability of navigation channels.

In the construction of artificial islands in distant seas, calcareous sand has been widely used as a foundation filler due to its excellent mechanical properties and extensive availability in the marine environment. How to store more fresh water on the artificial islands by reducing its permeability is currently a great challenge. Microbial-induced carbonate precipitation (MICP) has always been considered as a great potential method to improve the cemented properties of calcareous sand, but the effect of grain gradation on the permeability of MICP-improved calcareous sand remains unclear. In this research, a self-made device was developed to conduct MICP grouting and permeability tests, where the permeability coefficient (k) under different grain gradations (curvature coefficient (Cc) and uniformity coefficient (Cu)) was measured. A CT scan was conducted to investigate the variation in the porosity (n) of sand samples before and after MICP treatment. The weighting method was adopted to measure the content of induced calcium carbonate (M). A scanning electron microscopy (SEM) technique was used to further study the micromechanism of the MICP treatment. Finally, the correlations between the k of MICP-treated sand and Cu, as well as Cc, were semiquantitively analyzed. The results show that the magnitude of M, k and n changes are closely related to Cc and Cu. The reduction amount of k and n increased with the rise in Cc and Cu, and the increased amount of M increased with the rise in Cc and Cu. The SEM results show that the particle surface became rough due to the coating effect of CaCO3 crystals, and the pore spaces were reduced because of the partially filling effect of the crystals, which was responsible for the decrease in permeability and porosity. Furthermore, k fitted well with Cu and Cc, respectively, and the fitting curve reveals that larger Cu (Cu ≥ 6.0) and smaller Cc (2.0 > Cc > 0.5) were more suitable for MICP treatments and lead to a large reduction in permeability. The above results indicate that the grain gradation of calcareous sand had a significant influence on its permeability improved by MICP.

Pavement materials are prone to damage due to mechanical loadings and rainfall infiltration. The rainfall initiates moisture movement within the layers and accelerates the damaging rate. A ...

Sand boiling is a type of hydraulic failure occurring the downstream of dams with huge damages. In this study, the reinforcement effect of Firuzkuh sand with bulk continuous filament (BCF) fibers and geotextile (woven and nonwoven) on the resistance to boiling is examined on a laboratory scale. For this purpose, an upward seepage apparatus was designed and fabricated. In reinforcement with BCF fibers, with increasing the weight percentage of fibers, soil strength increased and the permeability coefficient was changed. In soil reinforcement with geotextile, two types of woven and nonwoven geotextiles were used in two modes of one and two layers. Based on the results of the performed tests on these samples, the reinforced samples have shown more resistance to boiling than the natural samples. Also, the increase in critical hydraulic gradient and seepage force (to sand boiling) was found to be a function of the type and number of geotextile layers. Moreover, in this research, the effect of the relative compaction of the sample on permeability and critical hydraulic gradient of samples (reinforced and unreinforced) was investigated. According to the results, in denser samples, the boiling is delayed and soil improvement (a reinforcement with fibers and geotextile) is significantly effective.

Compacted bentonite–sand mixture (CBM) is a kind of candidate buffer material of high-level radioactive waste (HLW) disposal in many countries. It is believed that the permeability of CBM is greatly related to its microstructure. The aim of this study was to search the effect of various aqueous mediums on the microstructure and pore characteristics of this buffer material. Permeation experiments and X-ray computerized tomography (X-ray CT) were used to explain the correlation between microstructure and permeability. Representative samples of CBM at a dry density of 1.7 g/cm3 were used. X-ray CT was used to study the CBM under the de-ionized water (DI) and three other aqueous medium conditions. After reconstruction with Dragonfly software, the pore characteristics and permeability of different solution-saturated samples were analyzed using AVIZO software, including pore size distribution (PSD), porosity, and connectivity. The results showed that the permeability coefficient of samples was NaOH > NaCl-Na2SO4 > Simulated Beishan groundwater > DI water, and the maximum swelling pressure of samples was NaOH < NaCl-Na2SO4 < Simulated Beishan groundwater < DI water. The permeability coefficient decreased with the increasing of maximum swelling pressure. Quantitative analysis indicated that the volume of interconnected pores increased owing to the infiltration of NaCl-Na2SO4 and NaOH.

The permeability of a saturated porous medium is regarded as a constant during the seepage process in traditional seepage analysis theory. However, it changes constantly during the piping ...